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Home My WebLink AboutInformation Update.202001281 AGENDA INFORMATION UPDATE January 28, 2020 4:00 PM, INFORMATION ONLY UPDATE Climate Work Plan Update Conditional Water Rights Reports Review 2019 Traffic Counts 1 INFORMATION MEMORANDUM TO: Mayor Torre and City Council FROM: Ashley Perl, Climate Action Manager THRU: CJ Oliver, Environmental Health and Sustainability Director Phillip Supino, Community Development Director MEETING DATE:January 28, 2020 RE:Information Only: Climate Action Office Workplan Update Background: In 2004, the City of Aspen joined the world’s leading sustainable cities in establishing a Climate Action Office, then known as the Canary Initiative, to understand, measure and actively reduce the community’s greenhouse gas emissions and curb the disastrous effects of climate change. The office was first tasked with measuring Aspen’s environmental footprint, which it did through Aspen’s first greenhouse gas inventory. From there, the Canary Initiative created Aspen’s first Climate Action Plan (CAP)in 2006. Since then, the office has published four subsequent greenhouse gas inventories and an updated CAP. With this guiding document in place, the Aspen community pursued aggressive climate actions in the areas of transportation, energy supply, energy demand, and waste reduction over the last decade. Because of these robust actions, Aspen’s greenhouse gases have reduced 21% since 2004, and Aspen continues to pursue a 30% reduction by the end of 2020. Attachment A shows past City Council leadership in the area of climate action. Discussion: The 2018 -2020 Climate Action Plan (CAP)is the guiding document for the current work of the City of Aspen’s Climate Action Office.It identifies 42 actions that the City of Aspen and regional partners must accomplish to meet the community’s GHG emissions reduction goals of 30% by 2020 and 80% by 2050. In 2019, the City and community of Aspen made significant strides towards building a more sustainable community and reducing greenhouse gases (Attachment B). The Climate Action Office is planning for an even more impactful 2020. Below outlines a high-level workplan for 2020 for the Climate Action Office based on the direction of the Climate Action Plan and with the focus of achieving a 30% reduction by the end of the year. Ongoing Foundational Programs:These programs are key to the success of Aspen’s climate goals and will continue through 2020. o Energy Efficiency Programs.The City of Aspen and the Community Office for Resource Efficiency (CORE) offer energy efficiency services to the Aspen community. Energy efficiency is the backbone of reducing greenhouse gas emissions from buildings and adds important benefits, such as reduced utility bills and improved comfort and safety. City of Aspen and CORE programming includes:Home Energy Assessments,Commercial Energy Site Visits, rebates from Aspen Electric and CORE, the Income Qualified Program, the Small Lodge Energy Efficiency Program, and Contractor Trainings. o Water Conservation.Aspen has a responsibility to conserve and protect the regional water supply. Aspen,and the surrounding region,experienced a significant drought in 2018 that prompted the City to 2 Page 2 of 3 enact a Stage 2 Water Shortage for the first time. While 2018 was a particularly dry year, the drought underscores the need and importance of strong ongoing conservation efforts even during wetter years, like 2019. The Climate Action Office runs foundational water conservation programs that focus on outdoor water use. This program provides sprinkler efficiency assessments and retrofits to support homeowners, business owners, multifamily housing complexes, and City parks in conserving water. o State and National Climate Policy.Influencing state and federal policy is a necessary and effective way to advance City Council’s goals and to allow Aspen’s impact to extend beyond the city limits. Aspen’s participation in state climate policy matters is mainly conducted through CC4CA (Colorado Communities for Climate Action), a coalition of local governments across the state advocating for policies to protect Colorado’s climate for current and future generations. Federal policy engagement is mostly conducted through Aspen’s involvement in two national organizations: The Mountain Pact and Climate Mayors. o City of Aspen Department Support. Most of the Climate Action Office’s programming is intended to reduce community-wide greenhouse gas emissions. However, the City of Aspen has a responsibility to lead by example through reducing the impact of its government operations. This work includes a focus on energy reduction in City buildings, recycling and composting in all offices, reducing and offsetting the impact from employee travel and commuting, and increasing the efficiency of the City’s fleet. Each department is asked to set an annual goal to reduce greenhouse gas emissions, and the Climate Action Office supports employees and departments in doing all they can to reduce the impact of the organization through these goals and day-to-day work. Numerous departments have set goals to reduce waste or start composting in 2020. o Community Engagement.Much of Aspen’s success in reaching its greenhouse gas emissions targets relies on the actions and commitment of partners, organizations, businesses and individuals in the community. For this reason, the Climate Action Office maintains programming and support for the climate action programs at the Aspen School District and works with our partners to produce community events such as the upcoming 50th Anniversary of Earth Day and Imagine Climate month in March. o Regional Partnerships.To continue expanding Aspen’s impact,it is essential to work across the region and in new program areas. In 2020, the Climate Action Office will facilitate regional working groups in the following areas: Carbon Sequestration, Expanding Renewable Energy Supply, and Beneficial Building Electrification. 2020 Programs: These programs are identified in the CAP as key implementation items to continue addressing climate change and build upon the foundational programs listed above. o Building IQ.Building IQ is an initiative to help commercial and multi-family buildings save energy and water in a community-wide effort to keep the community, and planet, healthy and thriving. Buildings account for 58% of Aspen’s greenhouse gas emissions and Building IQ aims to reduce this by requiring that large buildings and municipally-owned buildings track energy and water use and take steps to reduce that use overtime. 2020 Approach: Building on the engagement and Council direction from 2019, staff will return to City Council with a benchmarking ordinance in late winter/spring 2020 for adoption of the first phase of the Building IQ regulations. Staff will then dive into deeper research and stakeholder engagement on an energy saving upgrades ordinance, the second component of the Building IQ initiative. Community engagement will continue to broaden to include an ever-greater diversity of Aspen’s buildings, 3 Page 3 of 3 including large and medium multifamily and commercial buildings, as well as workforce professionals and the community at large. In 2020, staff will offer support for privately-owned buildings to start benchmarking and work with City of Aspen building managers to benchmark all City-owned buildings. o EV Readiness. Electric Vehicle (EV) Readiness is a community priority outlined in the Aspen Community Electric Vehicle Plan (adopted by Aspen City Council in 2017) and in Aspen’s CAP. Especially when charged on a low-carbon electric grid like Aspen Electric, driving an EV significantly reduces GHG emissions and local air pollution, when compared with a gas-powered car. EVs have lower fuel costs, as electricity is less expensive than gasoline, and lower maintenance costs due to the absence of an internal combustion engine. In 2020, work will focus on supporting City of Aspen departments in EV purchasing and on the creation of a long-term plan for installing and incentivizing the growth of the vehicle charging network in Aspen. o Affordable Housing Upgrades.Energy efficiency improvements to Aspen’s affordable housing stock are designed to upgrade aging infrastructure, reduce energy use and greenhouse gas emissions, reduce utility bill costs, and improve tenant comfort and home health. In 2016, the City of Aspen partnered with CORE to perform energy efficiency upgrades at Burlingame Seasonal, Truscott, and Marolt Seasonal housing complexes. On average, the buildings upgraded saw a 17% reduction in total energy use and realized approximately $32,000 in utility bill savings. In 2020, the Asset department, Climate Action Office, and CORE will expand on this work by continuing to improve rental housing in Aspen. The final scope of this work will be available later this spring. Next Steps:Aspen continues to be a leader in the field of Climate Action, and the City of Aspen Climate Action Office strives to create innovative and impactful local programming that can also be replicable and scalable across the country. With continued support and leadership from City Council, the coming year will be no exception. The workplan above is currently funded, staffed and underway. City Council can expect an update from the Climate Action Office on these programs as they progress and additional info-only memos early this summer. City Council has provided clear direction to the Climate Action Office regarding their focus on aggressive pursuit of climate action and environmental sustainability. In 2019, City Council voiced unanimous support for the development of the next implementation step of the Climate Action Plan, which is the development and adoption of Building IQ. The Climate Action Office plans to return to City Council this spring with a Benchmarking Ordinance, the first phase of the Building IQ regulations. Attachments: Attachment A – City Council’s Historic Support of Climate Action Attachment B – 2019 Climate Action Program Successes 4 Attachment A: Aspen’s Action on Climate Change Aspen’s City Councils have long supported ambitious and effective action to both cut emissions and respond to the impacts of climate change. The following list is an overview of previous Council actions that have helped Aspen lead in the areas of climate action and sustainability. 1991:Adopted the 1986 Model Energy Code. 1996:Adopted the Aspen/ Pitkin Energy Conservation Code in 1996, Ordinance 3. 1999:Revised Aspen Energy Conservation Code to collect fees for the Renewable Energy Mitigation Program (REMP). The Community Office for Resource Efficiency (CORE)is founded. 2003:Adopted the Aspen / Pitkin Efficient Building Program. 2005:Formed the Canary Initiative (now known as the Climate Action Office) with the goal of aggressively reducing Aspen’s carbon footprint to protect the community’s future. 2005:Created the first Greenhouse Gas (GHG) Inventory for Aspen, measuring Aspen’s emissions from the year 2004. 2006: Published Climate Change and Aspen: An Assessment of Impacts and Potential Responses to understand how anticipated changes are likely to affect key sectors and ecosystems. 2007:Adopted the first Climate Action Plan, covering the years 2007 – 2009. This Plan specified GHG reduction goals of 30% below 2004 levels by 2020 and 80% below those levels by 2050. 2009:Revised REMP to include Commercial REMPand adopted the 2009 International Energy Conservation Code. 2012:Published an updated Aspen Area Community Plan that prioritized reductions in GHG emissions, energy use, and traffic congestion. 2004, 2007, 2011 and 2014: Published community–wide GHG inventories to better understand the Aspen community’s GHG sources, trends, and reduction opportunities. 2010:Expanded food waste composting operations (a GHG reduction action) in conjunction with Pitkin County through a grant from the State of Colorado. 2014:Published Climate Change and Aspen 2014: An Update on Impacts to Guide Resiliency Planning and Stakeholder Engagement detailing likely climate impacts and providing adaptation strategies in key sectors. 2014:Joined Climate Mayors, an association of United States mayors with the goal of reducing GHGs. The group represents 379 cities and nearly 20% of the U.S. population. 2015:Accomplished a key CAP goal of achieving 100% renewable electricity for Aspen Electric and directed staff to maintain a 100% renewable portfolio. 2015:Further expanded food waste composting program, which was officially named SCRAPS! 2016:Finalized a resilience strategy to prepare key sectors of the community for the unavoidable impacts of climate change. 2016:Adopted Resolution 11, Series 2016 urging the U.S. Congress to introduce and pass carbon fee and dividend legislation. 2016:Joined the Global Covenant of Mayors for Climate and Energy, an international alliance of local governments dedicated to reducing global scale emissions through local action. 5 2016-2019:Joined Colorado Communities for Climate Action (CC4CA), a coalition of local governments working to affect climate and energy policy at the state level. 2017:Launched the Compact of Colorado Communities to help build the necessary capacity for effective climate action in local governments throughout the state. 2017:Adopted “Top Nine Goals” for 2017–2019, two of which are directly tied to local climate action, goal number four (transforming the mobility landscape) and goal number seven (decreasing the carbon footprint of the community’s energy supplies). 2017:Adopted Aspen Community Electric Vehicle Readiness Plan and began implementation by installing public charging stations and providing EV education across Aspen. 2018:Adopted Aspen’s Climate Action Plan and re-committed to reducing GHG emissions 30% below the baseline by 2020 and 80% by 2050. 2018:Published the GHG Reduction Toolkit, which won a State of Colorado Award for Clean Energy Leadership. 2018 - 2019:Began implementing the Climate Action Plan. As of August 2019, 25 of 46 CAP actions were underway through 65 unique projects and programs. 2019:Released the 2017 Community-wide GHG Inventory, finding that the Aspen community had reduced its total GHG emissions 20.5% below 2004 levels. 2019:Adopted Resolution #114 in support of Energy Innovation and Carbon Dividend. 6 Attachment B:2019 Climate Action Office Program Accomplishments Energy Efficiency. In 2019, the City of Aspen continued to partner with the Community Office for Resource Efficiency to offer energy efficiency advising, rebates, and grants to Aspen’s residents and businesses. This included 37 home energy assessment and 18 commercial site visits. The Small Lodge Energy Efficiency Program (SLEEP) thrived in 2019 with site visits to all participating lodges. From these site visits, six lodges (Snow Queen, St Moritz, Shadow Mountain, Hearthstone, Aspen Mountain Lodge, and Prospector Condos) took advantage of funding for energy efficiency upgrades. Commercial energy efficiency rebates (including SLEEP lodges) in 2019 resulted in an estimated energy savings of 2,366,047 kBtus per year, which is equivalent to the energy use of approximately 18 homes or 33 passenger vehicles per year coming off the roads. Building IQ.In 2019, a Design Team of interdepartmental staff and partner organizations worked to design the Building IQ program. The team discussed the benchmarking component of Building IQ with Aspen City Council at work sessions on 8/27/19 and 12/9/19. Additionally, staff began targeted stakeholder engagement with representatives from Aspen’s largest buildings and a wide range of community organizations. This includes stakeholder steering committee meetings, one-on-one and small group conversations, and digital outreach. Numerous benchmarking test cases on both City-owned and privately- owned buildings are also underway. Water Conservation Sprinkler Efficiency Program.In 2019, the program assessed 45 large, privately owned commercial and residential properties, in addition to numerous City facilities, and installed water saving retrofits like high efficiency nozzles, Wi-Fi controllers, and rain sensors free of charge to the customer in 55% of those properties. Participants of the program, on average, have seen a 23% reduction in water use, resulting in the decrease of over 25,000 gallons of water per property during the summer season. Additionally, participants have experienced an approximately 30% reduction in water utility costs in the year following an assessment and/or retrofit. State and National Climate Policy.The 2019 state legislative session delivered significant climate action and renewable energy legislation that supports and enables Aspen’s local goals. This work, as well as work within the federal policy landscape, was supported by engagement from Aspen City Council, which included Councilmember Hauenstein’s participation in the Mountain Pact Fly In to D.C. to meet with members of congress, and the inclusion of climate action in Council’s adopted policy statement. City of Aspen Department Support. Each year, all City of Aspen departments set a goal to reduce greenhouse emissions within their operations or scope. In 2019, all departments accomplished their goals and contributed to Aspen’s reductions. Examples include: o All employees in nine departments successfully completed the ‘Staff Mobility Challenge’ which focused on smart transportation choices for commuting and job tasks. o The Utilities Department completed a comprehensive water audit. o New composting programs were started at Truscott, Aspen Country Inn, and Smuggler. o Significant energy efficiency upgrades were installed at Recreation Department facilities. 7 Community Engagement.The Building IQ project kicked-off in 2019 and focused heavily on listening to the community and building relationships with stakeholders. Over the course of 2019, the Building IQ team engaged with 65% of program participants (representatives from commercial buildings >20,000 square feet), convened 55% of program participants in 2 steering committee meetings, met with numerous community organizations, and the online engagement platform has seen 300 unique visitors since launched in August. Staff also met with High School and Middle School students throughout the year and built new relationships through events like the Climate Strike. Regional Partnerships and CAP.In 2019 the Climate Action Office convened a meeting of the Aspen Community Climate Action Advisory Committee, and asked attendees to re- commit to aggressive climate actions in their organizations. Also, City Council approved funding to bring all City of Aspen facilities that are served by Holy Cross Energy onto 100% renewable electricity, making all City of Aspen operations 100% renewable and strengthened the partnership with Holy Cross. Additionally, Holy Cross Energy received approval to construct a 5MW solar farm in Woody Creek, made possible in part because of the City of Aspen’s expressed public support of solar expansion in the region. Electric Vehicles.In 2019, a new public dual cord Level 2 EV charging station was installed on 1st Street, near the corner with Main Street. To date, seven (7) public EV charging stations have been installed in Aspen (see a map here). The City of Aspensponsors an annualregional EV Sales Event, which lowers the price of EVs at local dealerships. In 2019, a total of 50 all- electric and plug in hybrid vehicles were sold during the event. The City of Aspen Transportation Department also added a new electric vehicle to the CarToGo fleet and worked collaboratively with RFTA to add 8 electric buses to the fleet. Waste Reduction.Although waste reduction doesn’t fall directly under the Climate Action Office, staff works closely with colleagues to reduce waste in the community. Recycling and especially composting helps reduce greenhouse gas emissions and increased composting is a top priority listed in the Climate Action Plan. During 2019 there were several waste program achievements including: o Successfully changing the Rio Grande Recycle Center from a single stream collection facility to a targeted collections facility. The center now accepts yard waste on a year-round basis as well as expanded metals collection, glass and cardboard. o Compost collection in the city expanded with numerous new residential and business accounts. o Three new city departments added compost collection to their buildings (Parks, Red Mountain Grill, and Streets). o Paper bag sales at grocery stores have remained flat since 2017. o Significant improvement in waste diversion from large special events was realized, particularly at Ruggerfest and the Motherlode Volleyball Tournament. 8 1 MEMORANDUM TO:Mayor and City Council FROM: Raquel Flinker, Interim Utilities Portfolio Manager THROUGH:Tyler Christoff, Director of Utilities MEMO DATE:01/21/2020 MEETING DATE:01/28/2020 RE:Conditional Water Rights Reports Review SUMMARY: During the November 25, 2019 Work Session on the Aspen Water Integrated Resource Plan, Council requested a review of the water demand and storage options reports that were used as part of the conditional water rights discussions in 2017 and 2018. BACKGROUND:The City of Aspen operates a water utility that supplies customers both inside and outside the municipal boundary. The City is committed to operating a water system that is safe, legal and reliable. To this end, the City has developed an integrated water supply system. As part of this integrated water supply system, since 1965 the City has held and maintained conditional water rights for reservoirs on Maroon and Castle Creeks. Aspen now sees 23 fewer winter days than in the years before 1980. This trend is projected to continue and Aspen’s current water storage – our snowpack – will likely diminish. In addition, current storage infrastructure holds less than a day’s worth of City water demand; this means in an emergency, supplies are limited. In recognition of this scenario and the vital need to further develop its water storage, City Council passed Resolution #141, Series of 2016 on October 10, 2016 directing staff to pursue actions in four task areas: 1. File and pursue an application for finding of reasonable diligence in the development of the Castle and Maroon Creek conditional water rights; 2. Continue development and implementation of the City’s integrated water supply system; 3. Initiate a collaborative process to update the anticipated water supply and demand gap and evaluate existing and identify new alternatives to fill this gap; 4. Enhance and increase the City’s efforts to investigate alternative locations and sizing requirements of the Maroon Creek Reservoir and/or Castle Creek Reservoir. Below is the summary of key documents that were developed to address Council’s directive: 9 2 DOCUMENT SUMMARIES: 1. Aspen’s Water Future: Estimating the Number and Severity of Possible Future Water Shortages, Headwater Corporation, November 30, 2017 Headwaters Corporation developed a risk assessment tool to determine Aspen’s vulnerability associated with its water supply and demand. The results of this analysis determined the following levels of risk and vulnerability that are summarized in Table 1. Table 1: City of Aspen Water Shortage Probabilities During its July 11, 2017 Work Session, Council identified the 1/100 event as the appropriate level of risk for long-range water planning. The full content of this report is included in Attachment A. 2. Calculation of Storage Demand for the City of Aspen, Deere and Ault Consultants, November 20, 2017 Deere and Ault used the model developed by Headwaters in its vulnerability analysis and developed a reservoir operation model to convert the annual water shortage calculated for the 1/100 event into a storage amount. Based on their analysis, detailed in Attachment B, they concluded that the required storage capacity for the City of Aspen is approximately 8,800 AF. The full content of this report is included in Attachment B. 3. Storage Site Matrix, Deere and Ault Consultants Deere and Ault investigated potential storage locations in the Aspen area, but not located at the decreed sites for the Maroon Creek and Castle Creek Reservoir storage rights. They identified several sites that have suitable geology for in-situ and/or surface reservoirs. A rough estimate for sizes and costs is detailed in Attachment C. 10 3 A 63-acre site, known as the Woody Creek Parcel, was identified as a site with high reservoir potential and flexibility to accommodate a wide range of storage options, sizes and implementation timing. Council entered into a contract to purchase the Woody Creek Parcel and is currently engaged in a due diligence process to further study the site. The full content of this report is included in Attachment C 4. Reservoir Pre-Feasibility Woody Creek Parcel Memorandum, Deere and Ault Consultants, September 29, 2017 The Woody Creek Parcel was identified as a desirable site for future water storage. The benefits of this site include: The City could partner with the local gravel mining operation to improve the reclamation of the gravel pit site. The downstream location of the site facilitates relocation of storage rights from Maroon and Castle Creeks to a diversion point near the Woody Creek Parcel. Scalability provides planning flexibility. The layout and size of the site allow for design of water storage from around 350 acre-feet to a maximum of 8,000 acre-feet when combined with the existing Elam Gravel Pit site. ATTACHMENT A – Aspen’s Water Future: Estimating the Number and Severity of Possible Future Water Shortages, Headwaters Corporation. ATTACHMENT B – Calculation of Storage Demand for the City of Aspen, Deere and Ault Consultants ATTACHMENT C – Storage Site Matrix, Deere and Ault Consultants ATTACHMENT D – Reservoir Pre-Feasibility, Woody Creek Parcel Memorandum, Deere and Ault Consultants 11 1 Aspen’s Water Future: Estimating the Number and Severity of Possible Future Water Shortages November 30, 2017 Prepared by: 12 2 Contents Impact of Uncertainty on the Number and Severity of Future Water Shortages......................................... 3 Purpose ..................................................................................................................................................... 3 Definition of a Water Shortage ................................................................................................................. 4 Analytical Model ....................................................................................................................................... 4 Historical Streamflow ............................................................................................................................ 4 Hydrograph Modification Utility ........................................................................................................... 5 Operations Tool .................................................................................................................................... 5 Model Output ....................................................................................................................................... 6 Uncertainties Affecting Supply and Demand ............................................................................................ 6 Period of Record ................................................................................................................................... 6 Flow Adjustment Factors ...................................................................................................................... 8 Climate Change ..................................................................................................................................... 9 Demand ................................................................................................................................................... 13 Previous Water Demand Estimates and Water Production ............................................................... 13 Evapotranspiration Impacts ................................................................................................................ 16 Results of the Uncertainty Analysis ........................................................................................................ 17 Current Supply and Demand Conditions ............................................................................................ 17 Year 2065 Conditions With No Uncertainty ........................................................................................ 18 Year 2065 Conditions With Uncertainty ............................................................................................. 21 Sensitivity of the Results to Risk Assumptions .................................................................................... 25 Appendix A: Monte Carlo Simulation as a Tool for Assessing Supply and Demand Uncertainties ............ 26 What is Monte Carlo Simulation? ........................................................................................................... 26 The Benefit of Monte Carlo Simulation .................................................................................................. 26 Monte Carlo Simulation and Climate Change ......................................................................................... 27 Implementing Monte Carlo Simulation .................................................................................................. 27 Appendix B: Model Screenshots ................................................................................................................ 31 Appendix C: Service Area Map of the Aspen Water System ...................................................................... 39 13 3 Impact of Uncertainty on the Number and Severity of Future Water Shortages Purpose The City of Aspen water system is supplied in a “run-of-the-river” manner utilizing Castle and Maroon Creeks to meet municipal demands. This run-of-the-river characteristic means that as long as there is water in the creeks, Aspen has access to water. There is minimal water storage in the system, so if anything interrupts these supplies, whether it be long-term drought events induced by climate change, or short-term events such as floods or wildfires damaging critical infrastructure, the City’s water supply is at risk. In light of these increasing risks and growing demands, the City is assessing the adequacy and resiliency of their current water supplies and water infrastructure. An initial step in this assessment involves estimating the potential frequency and severity of water shortages to the Aspen water system over a range of possible future hydrological and demand conditions. This is based on a concern that existing water supply risks will significantly increase over time due to climate change’s impact on the timing and volume of flows in Castle and Maroon Creeks. This analysis estimates the frequency and severity of water shortages to the Aspen system assuming water supply and demand conditions anticipated for the year 2065. It assesses upon Castle Creek’s and Maroon Creek’s abilities to fully serve the City’s demands. At this point in time, it does not consider mitigating measures to prevent or minimize shortages, such as conservation beyond measures currently in effect, supplemental groundwater, or storage. The analysis focuses upon climate change’s potential impact on the timing and volume of creek flows, and its potential impact on evapotranspiration (ET) both upstream of the City’s water diversion points and on municipal irrigation water demands. In addition to the uncertainties of climate change, this analysis directly addresses other important uncertainties related to the volume of flow and to water demand. The analysis uses Monte Carlo simulation to examine the combined effects of these numerous uncertainties on the overall uncertainty behind the number and severity of potential water shortages.1 A characteristic of this method is that there is no single “correct” number of shortages or severity of shortage, the results are expressed in terms of probabilities, equivalently shown as frequency diagrams (histograms), percentiles, or cumulative probability functions. These metrics are more valuable than simple averages because they better describe the uncertainties and allow decision makers to decide how much risk they are willing to take. The following sections: • Describe what is meant by a water shortage for Aspen • Present and discuss an analytical spreadsheet-based model for estimating the number and severity of shortages 1 Monte Carlo simulation is discussed in Appendix A. 14 4 • Identify the uncertain variables most significantly impacting long-term supply and demand, and presents assumptions about their possible values • Present the results of the Monte Carlo simulation Definition of a Water Shortage A shortage occurs when combined flow at the City’s diversion points is insufficient to simultaneously meet City demand, deliveries to three irrigation ditches below the City’s Castle Creek diversion, and provide for instream flows. Since the City’s water rights are senior to the instream flow right, the City and irrigation ditches can deplete the creeks before experiencing their own shortage.2 Alternatively stated, this analysis assumes that instream flows are already gone when the City experiences a shortage. Analytical Model An analytical spreadsheet model of the City of Aspen’s raw water supply system was developed to identify possible shortages to municipal and industrial (M&I) or other demands. The model consists of two components: 1. Hydrograph modification tools for Castle Creek and Maroon Creek, 2. An operations tool that uses the streamflows output by the hydrograph tools to meet Aspen’s potable and non-potable water demands and identify any shortages. Based on the availability of historical streamflow data, the period of record for the model is Water Years (WY) 1970-1994 (October 1, 1969-September 30, 1994). The model simulations run on a weekly 3 time step. Historical Streamflow Daily historical gaged streamflows for Castle Creek 4 and Maroon Creek 5 above Aspen were the underlying input to the hydrograph tools. The USGS streamflow gages were located several miles upstream of the city’s raw water diversion structures, and therefore the historical data were not directly reflective of the water supply available to the city. Field measurements were used by Enartech (1994) to estimate multipliers which can be used to transform the gage measurements to flows at the municipal intakes.6 Values for the multipliers are input by the model user; the assumed values were 2.43 for Castle Creek and 1.27 for Maroon Creek, although other values can be entered within a specified range. These adjustments are used to account for intervening ungaged tributary inflows, return flows, and other reach gains and losses. The estimated daily streamflows at the municipal intakes were used to 2 It should be noted that the above definition may not reflect City policies that may be in effect when shortages occur, such as possible decisions on how to allocate limited supplies between instream flows and City-controlled irrigation demands on Castle Creek. 3 Daily and monthly models were also developed, but based on discussions with the City of Aspen, the project team agreed on a weekly time step to achieve a reasonable balance between computation time and data density. 4 USGS 09074800 Castle Creek above Aspen, CO 5 USGS 09075700 Maroon Creek above Aspen, CO 6 Enartech Inc. 1994. City of Aspen Evaluation of Raw Water Availability. October. 15 5 calculate a time series of weekly average streamflow during each year for the period of record. This time series was then condensed into a single hydrograph of average weekly flow. Hydrograph Modification Utility The model does not incorporate specific climate change scenarios, but instead allows the user to input and test modifications to the timing of the hydrograph peak and to the magnitude of the flows represented by the hydrograph. For the present analysis, it was assumed that under future conditions the peak flow week would occur earlier (a shift of 2 to 6 weeks depending on the model run) and that flows over the entire hydrograph could range from +10% to -50%. These modifications to peak timing and magnitude of flows were applied to adjust the hydrographs of average weekly flow. The same modification factors were used for both Castle Creek and Maroon Creek. The patterns of historical gaged streamflow on each creek were then used to distribute the modified average hydrographs to a pair of modified 25-year weekly streamflow time series for use in the operations tool. Operations Tool The operations tool starts with the modified weekly streamflows at the municipal intakes on Castle Creek and Maroon Creek as the water supply available to the City of Aspen, then applies a succession of potable and non-potable demands to identify potential shortages. Non-potable demands are considered first, including the city’s downstream irrigation demands on Castle Creek and the Herrick Ditch upstream of the City’s Maroon Creek diversion. 7 8 Remaining flows on the two creeks are then combined and used meet the City’s water demands, which are those that draw on Thomas Reservoir and are then met through the city’s distribution system; these include variable indoor, outdoor, and non-potable water uses. Modeled municipal water shortages, if they exist, are identified and quantified. Any water that is left is applied to meet instream flow (ISF) demands. The ISFs are junior water rights held by the Colorado Water Conservation Board for 12.0 cfs on Castle Creek9 and 14.0 cfs on Maroon Creek 10. Aspen is committed to an additional 1.3 cfs on Castle Creek, so a combined ISF flow rate of 27.3 cfs is used in the operations tool. Modeled ISF shortages are identified and quantified. Although the ISFs are decreed separately for the two creeks, the available supply, ISF demands, and potential shortages are evaluated as aggregate quantities in the model because the timing and amount of any shortage would be influenced by the city’s operational decisions regarding diversions from each creek into Thomas Reservoir. 7 The headgate for the Herrick Ditch is located upstream of the city’s Maroon Creek diversion structure, but as a gaged diversion, it is handled separately and is not a component of the factor used to transform flow from the USGS gage location to the municipal intake. 8Herrick Ditch diversions were assumed to be 16 cfs through the irrigation season ending in the second week of October, representing the most water Herrick Ditch used on a daily (or weekly) basis across an entire irrigation season in recent history. This occurred in 2003 and 2016. The portion of the Herrick water right senior to Aspen’s is 9.3 cfs. However, for purposes of this planning study, 16 cfs was assumed based on precedent. Reducing Herrick’s diversion to 9.3 cfs in the analysis would likely reduce the number of late season shortages. 9 Case No. W-2947, with appropriation date January 14, 1976 10 Case No. W-2945, with appropriation date January 14, 1976 16 6 Model Output Output from the model includes the frequency and magnitudes of M&I or ISF shortages. This information is used to generate figures illustrating the likelihood of a given shortage magnitude as well as plots that depict the timing and magnitude of ISF shortages on a grid representing the period of record. Appendix B shows screen shots of the model’s input and output tables, highlighting critical assumptions. Figure 1 illustrates the operational component of the model through a schematic diagram. Uncertainties Affecting Supply and Demand The analysis considers four areas of uncertainty: 1. Annual flow; Period of Record 2. Flow adjustment factors 3. Climate Change 4. Demand Period of Record The hydrologic period of record defines the uncertainty surrounding the volume and timing of flow from year to year. This study uses the period 1970 through 1994, corresponding to the years that gages were continuously active on each of the creeks. Since Aspen is run-of-the-river system with minimal storage, Figure 2 shows the estimated average monthly flows at the City’s diversion points for the two creeks during this period and their combined flows. This hydrologic period contains 1977, which is the driest year on record, and 1983 and 1984, representing very wet years in the Colorado River basin. It should be noted that dry years did not occur in succession during the 1970-94 period, like during the 1950’s.11 Nor does the data contain the years since 2000, when Colorado has experienced statistically significant higher average temperatures compared to 1970 through 1994. Also, since the period 1970 through 1994 mostly pre-dates the establishment of statistical trends showing warming in Colorado, any climate change-based impacts occurring between 1994 and the present are likely not reflected in the data. Extending the hydrological record to include the entire 1950 through present period would be desirable to better quantify the variability of flows, the frequency of critical years, and the possibility of successive critical years. However, for now, this analysis uses the 1970 through 1994 period with the above caveats. 11 Precipitation data and snowfall data from the Aspen Station indicate that all years but one between 1952 and 1958 had less total precipitation than 1977. The year 1953 had substantially less snowfall than the 1977 water year, but the remaining years had more snowfall than 1977. 17 7 Figure 1. Schematic of the Castle Creek and Maroon Creek Operational Model 18 8 Figure 2. Estimated monthly flows at Aspen’s Castle Creek and Maroon Creek diversions. Flow Adjustment Factors Stream gages used to measure flows over the period of record were located high in the Castle and Maroon Creek systems, above the City’s diversion points and with intervening, ungaged tributaries. As a result, adjustments had to be made to the gaged flows to approximate flows at the City’s diversions. For purposes of this analysis, the factors were estimated for each creek incorporating a least squares regression analysis that uses gaged flow as the independent variable and flow at the City diversion point as the dependent variable. For Castle Creek, an R-square of regression of 0.993 supports a flow adjustment factor of 2.43 for Castle Creek and an R-square of 0.996 supports a flow adjustment factor of 1.27 for Maroon Creek. Although the fit of the regression equation defining the factor is very good, the estimates are limited by a relatively small number of observations primarily taken in 1994. However, subsequent paired observations appeared to confirm these relationships. Also, despite, the good fit, there is still significant uncertainty around the factors, as measured by the standard error of the regressions. Figures 3 and 4 illustrate the uncertainty around the estimates of the flow adjustment factors for Castle Creek and Maroon Creek, respectively. In both cases, the uncertainty is assumed to be normally distributed, or bell-shaped, centering around their expected values. 0 200 400 600 800 1,000 1,200 Oct-69Jun-70Feb-71Oct-71Jun-72Feb-73Oct-73Jun-74Feb-75Oct-75Jun-76Feb-77Oct-77Jun-78Feb-79Oct-79Jun-80Feb-81Oct-81Jun-82Feb-83Oct-83Jun-84Feb-85Oct-85Jun-86Feb-87Oct-87Jun-88Feb-89Oct-89Jun-90Feb-91Oct-91Jun-92Feb-93Oct-93Jun-94cfsFlows in cfs Castle Creek Maroon Creek Castle Creek + Maroon Creek 19 9 Figure 3. Assumed uncertainty around the Castle Creek flow adjustment factor Figure 4. Assumed uncertainty around the Maroon Creek flow adjustment factor Climate Change An important component of this effort is to assess the possible impacts of climate change. A previous analysis by Wilson Water Group examined 5 climate change scenarios with varying levels of impact to flow patterns, ranging from about +9% to -19%, concluding that climate change would adversely affect 20 10 Aspen’s water supply, but not to a level requiring additional infrastructure, such as a storage reservoir.12 Since the development of these 5 climate change scenarios, there have been questions as to whether a wider range of impacts should now be considered, especially those based on the greater resolution provided by more recent research. It should be noted that much of this recent research has not yet been downscaled to a level readily applicable to Castle or Maroon Creeks, or the Roaring Fork Valley. Although various efforts are underway at the State and major water provider level to adapt this data at a basin level, it is not currently available.13 To best incorporate current climate change knowledge, this effort is working with the City’s climate change staff and their associates to incorporate recent data and plausible ranges of data into the current modeling framework. The potential impacts of climate change will remain highly uncertain, but the effort described below is an attempt to bracket the possible range of impacts for purposes of assessing the number and severity of possible future water shortages. More recent climate change research indicates that impacts to flows in the Colorado River and its tributaries may be much more severe than previously thought. Recent research suggests the following: “Recently published estimates of Colorado River flow sensitivity to temperature combined with a large number of recent climate model-based temperature projections indicate that continued business-as- usual warming will drive temperature-induced declines in river flow, conservatively −20% by midcentury and −35% by end-century, with support for losses exceeding −30% at midcentury and −55% at end- century. Precipitation increases may moderate these declines somewhat, but to date no such increases are evident and there is no model agreement on future precipitation changes. These results, combined with the increasing likelihood of prolonged drought in the river basin, suggest that future climate change impacts on the Colorado River flows will be much more serious than currently assumed, especially if substantial reductions in greenhouse gas emissions do not occur”.14 Climate change and its uncertain impacts will ultimately affect Castle and Maroon Creeks through the timing and quantity of their future flows. Snowmelt run-off will likely occur earlier in the year over time and the total volume of flow may or may not decline over time. These impacts will be reflected in their hydrographs that show flows over the course of a representative year, at a specific point in the basin. It should be noted that the existing hydrographs account for existing water use, or evapotranspiration (ET), based on current upstream land uses. With warming associated with climate change, upstream ET will likely increase and further impact the resulting hydrograph, regardless of the precipitation impacts. This increase in ET may also affect Aspen’s customers through an increase in outdoor water demand. To assess overall possible impacts of climate change to the hydrographs, a utility was embedded in the modeling framework which allows the user to specify changes to the hydrographs’ timing and shape. By 12 Wilson Water Group. 2016. City of Aspen Water Supply Availability Study 2016 Update. June. It should be noted that the Wilson analysis assumed an operating supplemental groundwater system. 13 http://onlinelibrary.wiley.com/doi/10.1002/joc.4594/full 14 Udall, et al. http://onlinelibrary.wiley.com/doi/10.1002/2016WR019638/abstract, l 21 11 specifying variables related to the timing of peak flows and the impact to total flow volume, a wide range of possible impacts are considered. For purposes of incorporating this utility into the analysis, assumptions were made about the uncertainty of the timing and volume of flows. For timing, it was assumed that peak flows could occur anywhere from 2 to 6 weeks earlier by 2065, with equal probability, relative to the 1970 through 1996 data (Figure 5). Figure 5. The timing of peak run-off relative to 1970 through 1994, number of weeks earlier and the assumed probability for each week. The combined impact to flows in Castle and Maroon Creeks, and associated upstream ET, are assumed to range from +10% to -55% from the 1970-96 baseline levels. It was further assumed that the probable value is likely skewed towards the low side of this range, as shown in Figure 6. This results in a mode, or most likely value, near -35%. The assumption about skew is based on recent literature, such as that cited above, stating that impacts may be worse than previously thought. 22 12 Figure 6. Assumptions regarding the probability of flow and ET impacts to Castle and Maroon Creek flows resulting from climate change, relative to 1970 through 1994. Figure 7 illustrates the baseline hydrograph for Castle Creek and a modified hydrograph based on a single set of alternative assumptions about long-term timing and flow impacts associated with climate change. For this figure, it was assumed that peak runoff occurs 4 weeks earlier and flow is uniformly reduced by 35%, both relative to the period 1970 through 1994. Monte Carlo simulation will examine the probability-weighted range of possible timing and flow impacts, as represented by Figures 5 and 6. Figure 7. Example of Existing and Alternative Modified Hydrograph 23 13 Demand During the course of this analysis, it became apparent that a land use-based estimate of future water demand would be more useful than simple extrapolations of historical data. This is due to Aspen’s relatively high degree of land use control and limited remaining lands to develop. There is wide agreement that a land use approach is desirable and the City is currently taking steps to develop long- term land use maps that incorporate a water demand component. However, at this point in time, there is not a future land use map to base demand estimates upon or plans that can be readily translated to a map. As a result, this analysis uses existing data and previous analyses to develop a probable range of future demand. It should also be noted that the City of Aspen’s water system consists of the City itself, plus territory outside the City limits to the east and to the west, primarily along the Highway 82 corridor. In perspective, in 2010, the City was estimated to have permanent population of about 6,700, but the water service area had a permanent population of about 10,000. The City has land use controls over a major portion of the water service area but not the entirety. Pitkin County policies will also impact future demand growth. Overall, the City’s water service area population is estimated to grow to about 12,000 in 2025 and 13,500 in 2035, based on a 1.2% rate of planned population growth. It is likely that much of this growth, if it occurs, will target areas outside the City’s current boundaries with future land use requirements between the City and Pitkin County influencing future demands on the City’s water system. Previous Water Demand Estimates and Water Production The water demand portions of three previous studies have been evaluated with respect to their applicability to this analysis, as summarized in Table 1. As indicated above, full-time, or permanent, population within the City of Aspen was approximately 6,700 in 2010. It was estimated that Aspen Water served a permanent population of slightly over 10,000 within the Urban Growth Boundary (UGB) when extra-territorial service is included.15 An issue frequently brought-up while discussing the previous demand studies was the use of a compound population growth rate over a long period of time. For instance, a 1.2% population growth rate over 50 years applied to the City of Aspen would result in a 2065 population in the 12,000 to 13,000 range and a total service area population nearing 20,000, nearly doubling of current levels. These levels of population may be untenable to many Aspen area residents for quality of life reasons. Based on this, there is a probability that measures will be taken through the City’s and County’s land use processes to limit new single and multi-family housing development. The ultimate limit to these land uses is unknown, as is whether these limits might similarly apply to non-residential land uses, and how these limits might be allocated between the City and County. 15 Element Water Consulting and Water DM. 2015. Aspen Municipal Water Efficiency Plan. 24 14 Table 1. Summary of Previous Demand Studies Previous study Summary Estimated Demand Applicability Enartech, 1994 Examined a range of land use build-out scenarios; based on the most expansive, estimated total system buildout would be 19,800 Equivalent Capacity Units (ECU’s). There are currently about 17,300 ECU’s in the system. This implies that the service area can only growth another 15% to reach buildout. Build-out demand is estimated to be about 4,300 acre-feet per year, as estimated by Headwaters, based on a 15% increase from its current level; current annual demand at the water treatment plant is about 3,725 acre-feet; a proportional increase in the number of permanent residents would imply a buildout population of about 7,820 in the City and about 11,500 in the City and County combined. Data point in identifying the possible range of demand growth. It implies that demand would only grow a total of 15% above its current level. This growth could occur anytime over the 2017-2065 period, but implies a compound growth rate of 0.3%. Wilson Report, 2016 Estimated that demand at the water treatment plant would grow from its 2012 level at a baseline rate of 1.2% per year based on population growth trends. Alternative scenarios of slightly less than 1.2% and 1.8% were also examined. 2065 demand is estimated to be in the range of 6,300 acre-feet per year, as estimated by Headwaters; implied population for the City is over 12,100, a 77% increase over current levels; implied population for Aspen service area would be approximately 20,000. Data point in the range. The implied population of 20,000 in the Urban Growth Boundary in 2065 may be untenable to those supporting growth management. Water Efficiency Plan, 2015 Used same baseline demand growth rate as Wilson Report, 1.2%; examined passive and active conservation measures that reduce indoor and outdoor usage for certain customer classes. Period of analysis was 2016-2035. Essentially same baseline demand through 2035 as Wilson Report, with minor reductions due to passive water conservation. With active conservation and focus on outdoor irrigation, demand is reduced significantly, estimated to grow at a rate of 0.50% between 2015 and 2035. Since the study has a 20-year time horizon, whether the reduced growth in demand attributable to active conservation can be maintained past 2035 is not addressed. Aspen and regional land use plans This includes the Aspen Area Community Plan and Pitkin County’s West of Castle Creek and West of Maroon Creek Master Plans These documents discuss future development trends that would ultimately affect water demand within, or adjacent to, Aspen Water’s service area. Currently, there are no future land use maps to directly link future land uses to demand, although they will likely evolve in the near future. 25 15 By examining water demand on a customer class basis, such as single family residential, multi-family residential, commercial, and other types of usage, different rates of growth could be applied to different customer classes. In response to the above population concerns, the number of customers and associated demand for residential customer classes was assumed to grow at slower rate than for non- residential customer classes. For this analysis, it was assumed that the rates of growth in residential water usage and non-residential water usage are random variables with a range of possible outcomes. • Residential water usage is assumed to increase between 0.3% and 0.5%, corresponding to a 2065 Aspen permanent population ranging from about 7,800 to 8,800, or a service area population ranging from 11,600 to about 13,000. The distribution is assumed to be triangular, centering around 0.4%, as shown in Figure 8. • Non-residential water usage is assumed to increase over time at an annual rate of 1.2%, similar to the rate assumed in previous demand studies, but may vary between 0.8% to 2.0% to reflect uncertainties regarding future growth policies. This distribution is assumed to be slightly skewed to the low side of the range, indicating that it is more likely that non-residential growth will be below 1.2% than above this rate (Figure 9). Figure 8. Assumed growth rate for residential water service 26 16 Figure 9. Assumed growth rate for non-residential water service The above assumptions would result in a greater proportion of Aspen’s water being used for non- residential purposes. However, at this point, whether these non-residential uses are for commercial enterprises, industries, or extra-territorial service is not specified. Evapotranspiration Impacts Although the climate-change induced impacts to flow discussed above are intended to include the impacts of increased upstream ET, there will likely be additional ET-related impacts to Aspen’s future outdoor water usage and increased irrigation consumptive use along the three irrigation ditches on Castle Creek. The increase in ET would likely translate to an increase in municipal treated outdoor water demand but irrigation diversions are assumed to remain at their current levels due to water rights decrees. Research is still being conducted to estimate the possible ET impacts. However, to provide a placeholder until this research is complete, it is assumed that potential ET impacts may vary from 10% to 30%, with municipal treated outdoor irrigation increasing in the same proportion. It is assumed that the ET impacts are distributed in a triangular manner, centered at 20%, as shown in Figure 10. It is further assumed that ET impacts as applied to outdoor irrigation are correlated to climate change impacts. For instance, if streamflow impacts of climate change are highly adverse, ET impacts are also highly adverse. 27 17 Figure 10. Potential ET impacts to outdoor water usage. Results of the Uncertainty Analysis As previously stated, there is not a single result or set of results associated with this analysis. Results are expressed in probabilities. However, for presentation purposes, the adequacy of the Aspen water system to satisfy demands is discussed under three conditions: 1. Current supply and demand conditions 2. Assumed year 2065 conditions assuming the period of record and expected values for uncertain variables. Alternatively stated, no uncertainty is considered 3. Year 2065 conditions assuming the period of record and uncertainty with respect to flow uncertainty, utilizing Monte Carlo simulation Current Supply and Demand Conditions Under current water supply and demand conditions, and no climate change, there are no estimated shortages to the Aspen water system and very minor impacts to the instream flows (Figure 11). The impacts to instream flows primarily occur during simulated 1977 drought conditions. 28 18 Figure 11. Shortages associated with current supply and demand conditions. Year 2065 Conditions With No Uncertainty Other than the uncertainty associated with the hydrological period of record, Figure 12 shows possible shortages assuming year 2065 supply and demand conditions. This assumes that uncertain variables identified in previous sections, specifically flow adjustment factors, climate change, and demand variables are set at their expected values with no uncertainty. • Flow adjustment factors are fixed at 2.43 and 1.27 for Castle and Maroon Creeks, respectively. • Climate change is expected to move peak flows back by 4 weeks and reduce flows by 35% when ET impacts are considered, both compared to 1970-94 conditions • Residential water demand is expected to increase at an annual rate of 0.4% and non-residential water demand is expected to increase at an annual rate of 1.2%. - 20 40 60 80 100 120 140 160 1970197119721973197419751976197719781979198019811982198319841985198619871988198919901991199219931994Acre-feetHydrologic year Annual Shortages Annual shortage to Aspen Annual instream flow shortage 29 19 Figure 12. Estimated shortages for year 2065, no uncertainties considered. Figure 13 shows that instream flows are estimated to be adversely affected in nearly every year but the City’s supply is affected in just one, the 1977 hydrologic year. The impact to instream flows may be severe under the climate change and demand conditions assumed here, even without considering uncertainty. This is shown in Figure 14, which shows combined instream flow levels in Castle and Maroon Creeks. These combined flows should be 27.3 cfs or greater to ensure that minimums can be met for each creek.16 The impacts appear to be most severe during the fall months, but are also chronic during the winter months. 16 Negative values in Figure 13 should be interpreted as 0, or no instream flow. - 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 1970197119721973197419751976197719781979198019811982198319841985198619871988198919901991199219931994Acre-feetHydrologic year Annual Shortages Annual shortage to Aspen Annual instream flow shortage 30 20 Figure 13. Impact to Instream Flows with no Uncertainties Considered. 31 21 Year 2065 Conditions With Uncertainty The Monte Carlo simulation examined about 10,000 different, probability-weighted combinations of climate change, flow adjustment factors, and demand. Municipal Shortages In contrast to the “certain” case above, the presence of uncertainties associated with climate change, the flow adjustment factors, and demand reveals a significant probability that there may be more than just one shortage to the Aspen water system. Figure 14 shows the following probabilities in a cumulative manner: • The number of years with shortages to the City of Aspen over the 25-year hydrologic period of record • The number of years with shortages exceeding 100 acre-feet • The number of years with shortages exceeding 1,000 acre-feet For the first panel of Figure 14, the cumulative plot shows that with a probability of 0.80, or 80%, there are one or more shortages over the 25-year period of record; with a probability of 0.10, or 10%, there are 12 or more shortages over this period; and so on. For the second panel of Figure 14, the cumulative plot shows that with a probability in the range of 0.40 to 0.50, there will be one or more shortages of 100 acre-feet or more; with a probability of 0.10, or 10%, there are 5 or more shortages over 100 acre-feet during this period; and so on. The third panel shows that with something less than 5% probability, there may be several shortages greater than 1,000 acre-feet. 32 22 Figure 14. Summary of shortages to the City of Aspen municipal supply over the 1970-1994 hydrologic period of record (3 panels). ` 33 23 Table 2 summarizes these frequencies and severities of shortages in terms of probabilities. Table 2. Frequency and severity of shortages to the Aspen Water system. • With a probability of 0.002, or 1/500 odds, there may be as many as 22 shortages to Aspen’s water system over the 25-year hydrologic period of record, with 18 of those exceeding 100 acre- feet and 8 exceeding 1,000 acre-feet. • With a probability of .01, or 1/100, there may be as many as 19 shortages over the 25-year hydrologic period of record, with 15 exceeding 100 acre-feet, and 5 exceeding 1,000 acre-feet. This is the level of risk that many water supply managers plan for. • With a probability of 0.10, or 1/10 odds, there is still estimated to be 12 shortages over the 25- year hydrologic period of record, with 1 over 1,000 acre-feet. • At even odds, or 50-50, there may still be as many as 2 shortages over the 25-year hydrologic period of record, with 1 over 1,000 acre-feet. Instream Flows A shortage to the City of Aspen means that instream flows have been depleted. So, with whatever frequency municipal shortages are experienced, Castle and Maroon Creeks are dewatered at approximately the same frequency. To graphically illustrate this, Figure 15 shows instream flows for the 1 in 100 outcome from above, where the creeks are dewatered 19 years out of 25. The impact to the ecosystem is not estimated but would appear to be very severe. 34 24 Figure 15. Impact to Instream Flows with Uncertainty (1 in 100 occurrence). 35 25 Sensitivity of the Results to Risk Assumptions Figure 16 shows the contribution to variance attributable to the sources of uncertainty. Assumptions about climate change account for 70% of the overall uncertainty surrounding the number and severity of shortages, with assumptions about the flow adjustment factors and demand contributing 20% and 10% to the overall variability, respectively. This indicates that climate change may be the most effective area in which to develop better data. It is notable that demand plays a relatively small role in the overall variability, although it plays a more significant role in the severity of the shortage. Figure 16. Sensitivity of the results to risk assumptions. 36 26 Appendix A: Monte Carlo Simulation as a Tool for Assessing Supply and Demand Uncertainties What is Monte Carlo Simulation? Monte Carlo simulation performs risk analysis by building models of possible outcomes by substituting a range of values—a probability distribution—for any factor that has inherent uncertainty. It then calculates results over and over, each time using a different set of random values from the probability functions. Depending upon the number of uncertainties and the ranges specified for them, a Monte Carlo simulation could involve thousands or tens of thousands of recalculations before it is complete.17 For Aspen, factors containing inherent uncertainty include the flows of Castle Creek and Maroon Creek, how those flows are statistically adjusted at the City’s diversion points, the possible impact of climate change, and future municipal water demands. The results are estimates of the frequency and severity of potential future water shortages. This brief definition of Monte Carlo simulation will be further developed in subsequent sections. The Benefit of Monte Carlo Simulation The analysis contained in this document differs from Aspen’s previous analyses in how it deals with long- term water supply demand uncertainties, including potential future climate change impacts. Previous analysis followed a traditional path of defining a limited number of plausible supply and demand scenarios incorporating various combinations of these uncertainties and comparing the impacts of each. Although this type of scenario analysis is common, and is a useful starting point for planning, it is not without some shortcomings. • The number of scenarios are generally limited in number. For instance, the previous WWG analysis of Aspen’s water needs considered about 15 different combinations of climate change impacts and demand growth, with the assumptions underlying each appearing within reasonable bounds. Although reasonable, in general this scenario building leaves a lot to the analyst and doesn’t consider the full probable range of combinations of the uncertainties, especially those combinations that might have a low probability of occurring yet may have significant consequences to the water provider. • Unless otherwise noted, there are no insights about the probability of the outcomes. That is, the scenarios are often weighted the same because they are assumed to have the same probability of occurring. • A limited and unweighted range of possible outcomes is not useful for determining thresholds, or tipping points, where the risk of an action, or inaction becomes critical. 17 http://www.palisade.com/risk/monte_carlo_simulation.asp 37 27 In response to these shortcomings, combined with the substantial uncertainties associated with climate change, this analysis uses Monte Carlo simulation to consider a much wider range of assumptions and possible outcomes. The assumptions are probability-weighted in the sense that their underlying uncertainties are explicitly addressed and incorporated into the analysis. As a result, there is not a single point estimate of underlying water needs, or in Aspen’s case, the number of possible municipal water shortages over a 25-year period. Instead of a single outcome, or point estimate, the outcomes are expressed in terms of probabilities. As an example, the outcome could be: … “there is a 40% probability that there will no shortages over the 25-year period of analysis; there is a 10% probability that the City will experience shortages in 12 years or more and experience at least one shortage in excess of 1,000 acre-feet in 2 years out of 25; there is a 1% probability that there will be shortages in 15 years or more, with shortages in excess of 1,000 acre-feet in 4 years out of 25”. Although more complicated than simply asserting whether supplies are adequate or not over a limited range of assumptions, expressing results in terms of probabilities is a realistic format more useful for decision-making. It focuses discussion to where it belongs: the impacts of inherent risks and uncertainties, and the willingness of decision-makers to accept these risks or take measures to hedge against them. Monte Carlo Simulation and Climate Change An issue like climate change is well-matched for Monte Carlo simulation because little is certain about the potential climate change impacts to Castle Creek and Maroon Creek. Despite the attention given to the subject of climate change in municipal water supply planning, models adapting the results of larger climate change models to local basins are still under development for many Colorado basins and have inherent uncertainties of their own. Information to date reflects a degree of certainty that temperatures are rising and peak run-off dates are getting earlier in the year. Plant evapotranspiration (ET) rates appear to be increasing as a result of the higher temperatures. However, climate change’s potential impact to the long-term timing and volume of run-off remains highly uncertain. In response to these major uncertainties, including the uncertainties about the shape of the underlying probability distribution itself, available information was used to define the likely distributions around the timing of run-off, in terms of weeks relative to the period 1970-1994, and average weekly flows, also relative to 1970-1994. Discussion of this process is contained in the main body of this report. In combination with the other uncertain variables, Monte Carlo simulation was then used to assess a very wide range and large number of combinations of climate change-induced timing and flow combinations, approximately 10,000 different combinations, weighted by probability. The results of this process are also contained in the main body of this report, but it should be noted that sensitivity analysis associated with the Monte Carlo simulations indicated that the uncertainties of climate change was the major driver behind uncertainties in the number of possible shortages, much more so than demand uncertainties. Implementing Monte Carlo Simulation 38 28 Although the term Monte Carlo suggests a gaming application, this method of simulation has wide application and acceptance, including for water resources planning, financial planning, and energy exploration. The benefit of Monte Carlo simulation is its ability to simultaneously consider a large number of combinations and uncertainties, far more than the number considered in previous analyses. As a greater number of combinations are created through Monte Carlo simulations, a statistical picture begins to develop regarding the probability and severity of shortages over the hydrological period of record. That is, how often does demand exceed supply given these various combinations of uncertain supply, demand, and climate change values? How these combinations are “matched-up” depends on the assumptions made about the uncertain variables. Input values used in a Monte Carlo analysis are, in technical terms, probability-weighted because the analyst assigns probabilities to their frequency of occurrence. These probabilities describe how the variable might range around its estimated value. Some probabilities can be described with a normal, bell-shaped, distribution, meaning that it is equally likely that the value might fall below or above its estimated value. Figure A-1, below, is a depiction of a normal distribution for a hypothetical example. As can be seen, the distribution is symmetric around the expected value of 180 in this example. Figure A-1. Hypothetical Example of a “Normal” Statistical Distribution Figure A-2 illustrates an alternative depiction of this variable as having skewed characteristics. The mean is the same, 180, but there is a higher probability that the value is higher than 180 than below it. Alternatively stated, the distribution in Figure A-2 has a long tail, indicating that although the probability is small, a large impact is possible. 39 29 Figure A-2. Hypothetical Example of a Non-Normal Skewed Statistical Distribution Variability in time series and cross-sectional data is often used to assist in developing these distributions, although informed judgment may also play a role when data is lacking. Many uncertainties in water planning are non-normal, or skewed, in nature because they are influenced by sometimes erratic weather patterns with periodic extreme events. Monte Carlo simulation is the best tool available for incorporating combinations of these skewed characteristics. Given assumptions about the uncertainties affecting a municipality’s water supply reliability and their statistical characteristics, what sort of output can be expected? Figure A-3 is an example of the type of output that Monte Carlo simulation can create. It shows a hypothetical output that summarizes the number of shortages over a 25-year period of record. As a result of variables that have non-normal distributions, the graphic shows that most of the time there are only 2 shortage years of the 25 considered. However, it is much more likely that there will be more shortages of this magnitude rather than fewer. There may be as many as 16 to 18. Again, the example is hypothetical, but this type of data tells decision makers that reliance upon averages and most likely values does not always paint the full picture. 40 30 Figure A-3. Example Monte Carlo Output for Hypothetical Example 41 31 Appendix B: Model Screenshots 42 32 Figure B-1. Screen shot of Maroon Creek assumptions: flow adjustments between the Maroon Creek gage and City diversion; adjustments for climate change. Note, green highlighted cells represent uncertain variables examined with Monte Carlo simulation 43 33 Figure B-2. Screen shot of Castle Creek assumptions: flow adjustments between the Castle Creek gage and City diversion; adjustments for climate change Note, green highlighted cells represent uncertain variables examined with Monte Carlo simulation User Interface Output Graphs Castle Creek at Aspen Diversion - WY 1970-1994 Properties of Average Weekly Hydrograph *52-week hydrograph *Leap year days excluded from calculations *December 24-31 treated as an 8-day week (arbitrary) Min Weekly Flow =23.6 cfs Max Weekly Flow =479.4 cfs Peak Week of Water Year =38 Dates of Peak Flow =18-Jun to 24-Jun User Inputs (1) Enter a multiplier ratio to translate flows at the upstream USGS stream gage to flows at the downstream municipal intake Gage Flow Ratio, Castle Creek =2.43 Example: Enartech 1994 assumed a ratio of 2.30 2.43 NOTE: If gage values are desired, enter a value of 1 (2) Enter value between -6 weeks (earlier peak) and +6 weeks (later peak) Peak Shift =-4 weeks OK! (3) Select Option from Pull-down Menu Below (Click yellow box and pull-down will appear) Flow Modification Options =Modify Entire Hydrograph (4) Enter percent flow modification as a decimal value between -1 and 1 Peak Modification Factor =-0.35 OK! (5) For Modify Peak Flow Only option enter a value between MIN = 23.6 cfs and MAX = 479.4 cfs. Peak Modification Threshold =50 cfs OK! 0.0 25.0 50.0 75.0 100.0 125.0 150.0 175.0 200.0 225.0 250.0 275.0 300.0 325.0 350.0 375.0 400.0 425.0 450.0 475.0 500.0 525.0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031323334353637383940414243444546474849505152Average Weekly Flow [cfs]Week of water year (starts October 1) Castle Creek at Aspen Diversion, Average Weekly Flow Water Year 1970- 1994 Average Weekly Hydrograph, WY 1970-1994 Modified Hydrograph 44 34 Figure B-3. Screen shot of operations routing component. 45 35 Figure B-4. Screen shot of Demand assumptions Note, green highlighted cells represent uncertain variables examined with Monte Carlo simulation 46 36 Figure B-5. Screen shot of shortage estimates with expected values for demand, flow adjustments, and climate change Note: Monte Carlo simulation examined about 10,000 different combinations of plausible demands, flow adjustment factors, and climate change impacts. The following graphic represents results from a single combination. WY Annual shortage to Aspen Annual instream flow shortage 1970 - 719 1971 - 215 1972 - 2,418 1973 - 1,466 1974 39 3,696 1975 - 1,971 1976 - 2,710 1977 1,922 7,994 1978 103 6,410 1979 - 3,569 1980 - 1,700 1981 - 4,023 1982 - 2,264 1983 - 176 1984 - 33 1985 - - 1986 - - 1987 - 500 1988 - 2,710 1989 - 2,804 1990 3 5,444 1991 - 2,446 1992 - 1,020 1993 - 292 1994 - 1,635 - 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 1970197119721973197419751976197719781979198019811982198319841985198619871988198919901991199219931994Acre-feetHydrologic year Annual Shortages Annual shortage to Aspen Annual instream flow shortage 47 37 Figure B-6. Screen shot of estimated impacts to instream flows with expected values for demand, flow adjustments, and climate change Note: Monte Carlo simulation examined about 10,000 different combinations of plausible demands, flow adjustment factors, and climate change impacts. The following graphic represents the results from a single combination. Number of years with M&I shortages 4 Number of years M&I shortage exceeds 100 acre-feet 2 Number of years M&I shortage exceeds 1000 acre-feet 1 CY Wk 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 WY Wk 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 1969 21 16 29 26 36 35 34 33 30 27 26 27 25 1970 27 27 28 27 24 24 24 25 25 28 31 34 39 56 77 ##################259 238 154 104 75 62 43 41 41 50 39 76 93 66 45 38 35 45 43 51 49 46 43 40 36 36 34 32 1971 29 30 31 30 31 30 29 28 28 26 28 34 51 77 ####################335 206 145 118 103 73 52 41 42 49 53 50 32 25 19 22 17 32 29 38 38 36 34 32 30 29 27 25 1972 25 27 27 26 25 24 24 24 25 27 32 42 56 82 ####################154 85 54 30 22 15 16 12 18 14 13 22 16 21 16 16 18 42 38 43 39 36 33 31 28 29 28 27 1973 26 29 24 23 23 21 20 18 20 22 23 29 38 55 76 98 ################168 272 170 134 110 77 66 67 56 48 40 35 31 21 17 19 13 26 24 34 33 31 30 28 26 27 25 26 1974 27 26 26 25 24 22 21 20 20 21 26 31 43 63 83 ##################249 136 79 39 40 32 22 21 18 8 1.7 4.2 1.2 0.8 -1.8 4.4 3.2 19 20 32 31 31 32 29 29 27 26 25 1975 26 23 23 24 23 23 23 21 22 25 24 31 35 55 72 96 ################133 159 277 251 211 119 85 65 63 46 34 32 31 24 16 15 13 27 25 35 34 33 31 28 27 27 26 26 1976 25 23 24 24 23 22 25 23 25 25 29 35 45 81 ####################112 88 78 49 41 31 29 20 20 18 14 12 8.6 7.7 14 17 12 24 21 30 28 26 25 23 23 23 22 22 1977 21 20 20 19 18 17 16 16 17 18 20 25 33 52 80 ################89 16 -11 -11 -19 -18 -14 -15 -15 -11 -8.4 -10 -7 -4.3 -9 -11 -6 -6.8 8 8 19 17 16 16 15 14 15 14 15 1978 15 16 15 15 15 14 15 15 15 17 18 24 31 48 70 93 ################289 218 140 128 121 74 52 31 30 16 11 14 10 7.3 3.7 5 1.7 16 17 26 26 26 25 23 21 22 22 20 1979 19 18 18 18 18 18 18 18 19 20 23 28 37 54 73 ##################214 264 212 164 164 146 95 76 90 56 38 32 20 15 13 14 11 26 25 34 35 32 28 26 25 23 22 23 1980 23 23 23 23 23 22 23 23 24 25 27 33 39 56 73 ##################345 237 169 121 86 69 55 43 49 37 34 35 43 25 20 22 18 33 30 39 38 35 33 32 31 31 30 30 1981 30 29 26 23 22 21 19 19 19 20 22 28 35 52 84 ##################94 50 35 23 16 13 6.1 4.9 10 4.5 5.8 14 14 8.6 5.8 8.3 7 23 20 32 30 28 27 25 23 23 20 15 1982 13 14 17 23 24 23 22 25 26 25 27 29 37 55 84 ##################227 221 177 140 141 150 127 84 89 64 49 49 48 53 55 52 41 52 45 50 46 41 39 37 34 33 31 28 1983 29 28 29 29 28 26 26 26 26 27 31 38 48 72 96 ##################357 323 246 224 178 141 162 153 122 93 83 65 39 31 26 30 26 40 37 47 45 42 40 37 35 34 31 33 1984 33 32 29 31 32 31 30 31 30 29 30 40 53 75 ####################420 390 334 325 239 229 164 125 140 127 106 87 67 62 56 56 50 58 55 60 57 56 53 49 49 48 46 47 1985 48 46 45 45 43 41 40 38 36 36 40 49 57 79 ####################424 232 208 166 142 113 97 85 68 52 48 58 52 51 41 40 42 49 46 55 53 49 48 46 43 39 38 37 1986 37 37 36 36 36 33 32 33 32 35 41 52 69 ######################362 247 266 161 138 111 81 75 80 92 78 65 67 53 54 50 45 56 51 59 54 50 47 43 42 39 37 35 1987 37 36 33 30 29 29 30 28 27 34 33 40 47 76 ####################173 97 79 55 48 59 56 57 51 58 33 31 19 17 14 16 14 29 28 41 38 33 30 29 27 25 29 27 1988 29 29 27 25 27 27 27 28 32 32 33 45 61 79 ####################151 98 58 23 13 12 22 14 14 14 12 11 17 16 13 14 9 21 18 29 28 29 29 26 24 25 25 24 1989 24 23 25 27 27 24 26 27 24 23 28 35 49 68 94 ##################178 112 108 76 44 70 52 34 34 17 9.3 12 9.3 11 9.4 12 6.5 19 17 26 25 25 25 23 23 21 20 18 1990 17 18 16 17 18 19 19 21 24 24 26 32 46 68 90 ##################193 127 79 57 28 20 12 6.1 16 7.2 3.6 7.8 0.7 8.9 6.2 15 13 26 24 33 32 29 28 25 25 29 22 22 1991 22 22 21 19 19 19 20 18 19 21 22 27 35 70 84 ##################247 138 128 93 72 54 42 31 29 18 18 26 35 27 18 26 18 29 26 36 35 34 34 32 31 28 29 27 1992 26 25 26 23 23 24 24 24 25 24 29 36 49 71 ####################161 118 95 83 58 62 37 43 38 39 39 33 19 24 21 20 16 29 28 39 38 35 33 30 30 29 29 30 1993 28 30 32 30 31 31 31 33 34 34 37 46 65 90 ####################408 328 228 239 167 135 130 120 99 86 71 69 56 43 33 31 31 44 39 48 45 43 40 37 35 32 29 32 1994 32 29 30 27 24 26 25 26 26 25 27 30 39 54 75 ##################239 118 72 40 28 25 25 21 26 15 13 25 13 12 9.2 Figure 13. Spells Plot - Periods when Combined Castle Creek + Maroon Creek Flow <=27.3 cfs after Meeting all but ISF Demands Apr May Jun Jul Aug Sep Oct Nov DecJanFebMar 48 38 49 39 Appendix C: Service Area Map of the Aspen Water System 50 600 S. Airport Road, Building A, Suite 205 Longmont, CO 80503 Phone: 303-651-1468 ● Fax: 303-651-1469 November 20, 2017 Ms. Margaret Medellin, P.E. Utilities Portfolio Manager City of Aspen Utilities 130 South Galena Street Aspen, Colorado 81611 Re: Calculation of Storage Demand for the City of Aspen Dear Ms. Medellin: The purpose of this letter is to present the findings and describe our analysis of the anticipated storage demand for the City of Aspen. This analysis was informed by simulated streamflow and water demand data developed by Headwaters Corporation (Headwaters). The data provided by Headwaters included adjusted streamflows based on recorded historical flows during the 1970 through 1994 period. The City’s water demand was based on previous projections for the year 2064. This analysis identified 1977 as the year with the most severe water shortage. While the entire period of data was simulated, the 1977 dry- year event, as affected by uncertainties identified by Headwaters, was found to be the determining factor for calculating storage demand. In addition, we analyzed consecutive dry year events in order to determine if such an occurrence would change the required storage volume. DATA AND ASSUMPTIONS This analysis utilized the water supply and demand data developed by Headwaters, and described in a draft report dated September 27, 2017, entitled, “Aspen’s Water Future: Estimating the Number and Severity of Potential Future Water Shortages.” In particular, we utilized the 1 in 100 probability dry-year event developed by Headwaters to inform the reservoir operations model. Because the details of the physical capacities and characteristics of potential storage infrastructure have not been fully developed, we made several assumptions about the performance and operating characteristics of the storage infrastructure. These assumptions included the following: 1. The storage vessel(s) will exhibit approximately 25 percent losses annually. These losses could be attributed to evaporation, plant transpiration, leakage, transportation losses, and other unforeseen losses. 2. The storage vessel(s) will be operated to maintain the maximum possible storage volume at all times. This assumption is not applicable to all water storage reservoirs, as factors such as seasonal water quality concerns, runoff management, and other considerations often dictate that less than full conditions are desirable for at least a portion of most years. Because these potential factors 51 November 20, 2017 Page 2 are unknown at this time, we assumed operations would maximize operational storage at all times. We compensated for the possibility that this might not occur by assuming an adequately large residual pool to accommodate alternative operations. 3. The residual pool that is left in the storage vessel(s) after the largest simulated drawdown of the storage volume was assumed to be one third of the reservoir capacity. This would allow for contents less than one hundred percent of the reservoir capacity at the initiation of all critical dry- year events. In addition, this would allow for events that would either be more severe than the anticipated hydrologic conditions, or would be compounded by other exacerbating factors. An example of one such factor would be that a portion of in-situ storage vessel contents is difficult to recover, and may not be available during extreme drawdown conditions. This would also allow for a conservation pool in any open reservoirs that would avoid the environmental and aesthetic impacts of a completely drained reservoir. 4. We assumed the water rights exercised to fill the storage vessel(s) would be senior to, and therefore would not be curtailed by, any downstream in-stream flow rights. This assumption is consistent with the exercise of Aspen’s conditional Castle Creek and Maroon Creek storage water rights. RESULTS Based on the data provided by Headwaters and the assumptions described above, we determined that the required storage capacity for the City of Aspen is approximately 8,800 acre-feet. This storage capacity is driven entirely by seasonal conditions, as even consecutive dry-year events provide enough snowmelt water supply to recover the necessary storage volume each year. The attached Figure 1 shows the simulated storage volume before, during, and after the critical dry-year event. Figure 2 shows the available storage inflows and necessary outflows before, during, and after the critical dry-year event. Please let me know if you have any questions, or would like to discuss this analysis. Sincerely, DEERE & AULT CONSULTANTS, INC. Jason M. Brothers, P.E. Associate/Project Manager U:\0687 City of Aspen\Water Resources Storage demand calculations\Aspen Storage Demand Letter.docx 52 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Reservoir Contents (Acre-Feet)Date Figure 1. Reservoir Operation Model 53 -500 0 500 1000 1500 2000 Acre-FeetFigure 2. Reservoir Inflows and Outflows Reservoir In (+)/Out (-) 54 Table 1 Site Cost Matrix Aspen In-Situ Storage Screening Study Site ID Site Name Foundation Geology Water Delivery Infrastructure (To/From) Area (acres) Perimeter (feet) Estimated Depth to Bedrock (feet) Estimated Slurry Wall Area (ft2) Unit Slurry Wall Construction Cost ($/ft2) Storage Cost per Acre-foot ($/AF) Estimated Water Delivery Cost ($250/foot) Water Delivery Cost per Acre- foot ($/AF) Estimated Project Cost* 1 North Star Preserve Precambrian Quartz Monzonite (granite)Augmented alluvial wells/ Pipeline to WTF 25.7 4943 100 509,129 $35.00 $32,400 2.3 2.3 $3,036,000 $5,520 $34,400,000 2 Moore Open Space Castle Creek Fault Zone: Overturned Triassic - Permian Sedimenary Rocks Merolt Ditch/ Pipeline to WTF 33.8 4951 85 435,688 $35.00 $27,700 0.8 0.8 $1,056,000 $1,920 $26,900,000 3A Castle Creek Fault Zone: Overturned Triassic - Permian Sedimenary Rocks 49.6 5936 85 650 522,368 $35.00 $18,283,000 1.0 3B Castle Creek Fault Zone: Overturned Triassic - Permian Sedimenary Rocks 75.0 9225 85 760 659,560 $35.00 $23,085,000 1.4 4 Zoline Open Space Mancos Shale and Possibly Castle Creek Fault Zone Augmented alluvial wells/ Pipeline to WTF 42.0 5921 85 521,048 $35.00 $28,100 1.8 1.8 $2,376,000 $3,655 $34,000,000 5A Mancos Shale 61.4 7757 50 400 426,635 $5.50 $2,346,000 2.6 5B Mancos Shale 58.2 6840 50 350 276,100 $5.50 $1,519,000 2.9 5C Mancos Shale 62.3 7305 50 300 309,650 $5.50 $1,703,000 3.3 5D Mancos Shale 67.7 8596 50 350 385,880 $5.50 $2,122,000 3.9 6A Mancos Shale 13.1 3819 50 100 210,045 $5.50 $1,155,000 5.4 6B Mancos Shale 11.8 3374 50 100 158,620 $5.50 $872,000 5.6 7 Woody Creek Mancos Shale Augmented alluvial wells, Salvation Canal/ Pipeline to WTF 45.0 6217 50 341,935 $5.50 $6,300 6.4 6.4 $8,448,000 $28,160 $17,000,000 8 Vagneur Gravel Pit Mancos Shale Augmented alluvial wells, Salvation Canal/ Pipeline to WTF 42.9 6794 50 373,670 $5.50 $10,100 6.8 6.8 $8,976,000 $8,976 $31,400,000 *Construction Costs rounded to nearest $100,000 and marked up by 65%: 10%Mobilization 5%Permitting 15%Engineering 5%Miscelaneous 30%Contingency Does not include land acquisition costs Aspen Golf Course Aspen Airport Cozy Point Ranch $2,027,000 $15,500,000200 $71,300,000 $21,200,0001,400 $17,820,000 $15,249,000 $7,392,000 $3,700 Estimated Storage Construction Cost $41,368,000 $7,690,000 $37,000 $1,848,000 $1,300 $5,500 $10,100 3.9 5.6 $5,148,000 $1,881,000 $10,055,000 650 300 1,000 $18,237,000 Merolt Ditch/ Pipeline to WTF Augmented alluvial wells, Spring Creek (?)/ Pipeline to WTF Augmented alluvial wells/ Pipeline to WTF Estimated Storage Volume Rounded to nearest 50 AF (Acre-feet) 550 550 1,400 1.4 Distance to WTF (miles) $29,500 55 600 S. Airport Road, Building A, Suite 205 Longmont, CO 80503 Phone: 303-651-1468 ● Fax: 303-651-1469 MEMORANDUM TO: Dave Hornbacher, Director, City of Aspen Utilities Margaret Medellin, Utilities Portfolio Manager FROM: Victor G. deWolfe, P.E., P.G. Don W. Deere, P.E. DATE: September 29, 2017 RE: Reservoir Pre-Feasibility, Woody Creek Parcel, McLain Flats, Pitkin County, Colorado; D&A Job No. CG-0687.003.00 INTRODUCTION This memorandum describes Deere & Ault Consultants’ (D&A) reservoir pre-feasibility study for a site consisting of two adjacent parcels of land on McLain Flats in Pitkin County, Colorado (Figure 1). The McLain Flats site includes a vacant property currently owned by the Woody Creek Development Company (aka, the Woody Creek Parcel, herein referred to as the WCDC parcel), for which the City of Aspen is currently under contract to purchase. The adjacent Vagneur gravel mine, owned by Elam Construction, could provide additional water storage. This site was identified as being a potential site for reservoir construction during an earlier site screening process. The pre-feasibility study included geotechnical investigations, a natural resources assessment (NRA), a site visit of the active Vagneur mine, preliminary geologic and geotechnical anal ysis, development of in-situ and gravel pit reservoir alternatives, and cost estimating. Four separate alternatives for water storage are presented in this memorandum. The alternatives include options that are built on the WCDC parcel alone to options that encompass both sites. The alternatives range in storage from a low of about 320 acre-feet for in-situ storage to a maximum reservoir of 8,000 acre-feet. SITE CONDITIONS The McLain Flats site is located in unincorporated Pitkin County in the Eastern One-Half of Section 16, Township 9 South, Range 85 West of the 6th Principal Meridian (Figure 1). The site is situated on a glacial outwash terrace about 150 feet above the Roaring Fork River. Upper River Road runs along the slope of the terrace about 50 feet above the river. The community of Woody Creek occupies a lower terrace northwest of the site. The topography of the terrace is generally flat on the top, exhibiting 1 to 2 percent slopes; and very steep on the sides with slopes up to 50 percent. 56 - 2 - The WCDC parcel considered for reservoir development by the City, occupies an area of about 55.7 acres on top of the terrace. A smaller parcel measuring 1.9 acres located along Upper River Road would also be acquired by the City (Figure 1). The WCDC parcel is currently a vacant sage brush meadow. Overhead electric transmission lines run along the edge of the terrace on the west side of the site. Smaller overhead electric lines cross the site as well. A high-pressure gas line runs beneath Raceway Drive along the eastern edge of the parcel. The Rio Grande Trail is a paved bicycle path on Pitkin County land that runs along the terrace about 30 feet below the top. A fiber optic line is buried beneath the bicycle path. A smaller gravel trail runs along the top of the terrace. The existing Vagneur Gravel Mine is situated on an adjacent parcel of land measuring about 104.4 acres. The mine consists of an open pit in the middle terrace (which has been partially filled in) and a benched quarry in the upper terrace. The mine operates a crusher to supply aggregate for industrial uses. GEOTECHNICAL CONDITIONS The geotechnical conditions at the site were investigated by conducting reconnaissance geologic mapping, drilling four borings, digging five test pits, and testing soil and rock in the laboratory. To support the investigation, we acquired 2-foot topographic contours from a LiDAR survey performed in 2016 for Pitkin County. The topography of the site is included along with the geologic map and locations of the geotechnical borings, test pits, and other sample sites on Figure 2. The geotechnical conditions of the site are characterized by deep glaciofluvial gravel, cobble, and boulder deposits overlying fractured Mancos Shale bedrock. A deep buried ancestral valley of the Roaring Fork River (paleochannel) appears to cut northerly through the WCDC property. The glaciofluvial outwash deposits were laid down during glacial melting events by large sustained floods. The resulting morphology is an ancestral valley buried by a series of three terraces, labelled as youngest through oldest, as shown on the map of Figure 2, and Profile A on Figure 3. The community of Woody Creek occupies the youngest outwash terrace (Qga) and the WCDC parcel occupies is the middle outwash terrace (Qgb). The Vagneur pit is located on the upper two terraces (Qgb and Qgc). The oldest terrace (Qgc) is capped by clayey eolian (windblown) deposits (Qe). The Mancos Shale (Km) is a Cretaceous aged rock that constitutes bedrock at the site and is the base of the buried valley. Glaciofluvial Outwash Deposits The glaciofluvial outwash deposits were observed during geologic mapping, geotechnical drilling, and test pit excavation. Summary logs of the geotechnical borings and test pits are included as Figure 4. Select samples were tested in a laboratory for index properties. Laboratory test data is shown by depth on the summary logs and tabulated on Table 1. The outwash deposits consist of layers of very densely compacted cobbles, gravel and boulders up to 7 feet in one-dimension. The cobbles consist primarily of sub-rounded granite or red sandstone. Due to the size of the particles in the outwash deposit, it is expected to have a very high permeability. 57 - 3 - The drilling program encountered 90 feet of outwash and about 11 feet of Mancos Shale in Boring B-102. In B-102, groundwater was observed at 85 feet deep within the outwash deposits. A pair of nested monitoring wells were installed in B-102, with one screened in the shale and one in the outwash deposits. Both wells measure approximately the same pore water pressure, suggesting that the near surface fractured bedrock is in hydraulic connection with the alluvial groundwater in the cobbles. The well completion details are summarized on Figure 4. The other three borings encountered only dry glaciofluvial cobbles and boulders to 123 feet deep, the depth limit of the drilling program. The test pits were excavated up to 15 feet deep into the glaciofluvial outwash terrace Qgb. In general, the top 4 to 5 feet contains a silty deposit of cobbles and boulders, followed by a 3 to 4- foot layer of cobbles with caliche rinds and cement. Below about 9 feet deep, a cleaner gravel deposit was encountered. Gradation tests were performed on TP-8 bulk samples of the 3-inch minus fraction, the results of which are shown on Table 1 and Figure 4. During test pit excavation, we also estimated the maximum and median particle sizes encountered. Using the field observations in conjunction with the gradation data, we constructed gradation curves for the three layers encountered in TP-8. These curves are presented in Appendix A along with other laboratory test data. We also performed boulder counts in three test pits to help estimate the relative number of boulders with one-dimension equal to or greater than 2 feet within the volume of soil excavated. This estimate suggests that approximately 10 percent of the deposit is composed of boulders greater than or equal to 2 feet. Eolian Deposits The eolian deposits (Qe) are wind-blown deposits consisting of clay, silt and sand. They are located on top of the oldest glaciofluvial outwash terrace (Qgc) in the eastern part of the Elam parcel (Figure 2). The eolian soils are dry silty clays with medium stiffness and low plasticity. Based on the Unified Soils Classification System, the soils classify as lean clay (CL). These soils were sampled and tested in the laboratory for index and engineering properties to assess the soil’s suitability as dam core material. The samples were collected from a stockpile in the Vagneur Mine and from the in-place deposits at the top of the highwall. The laboratory testing indicates that the soils have more than 80 percent fines (passing the No. 200 sieve) and between 5 and 20 percent sand. A hydrometer test shows that most of the fine material is silt, although there is enough clay to yield Atterberg limits values that classify the soils as lean clay (CL). The Standard Proctor test performed on the eolian clays suggest the optimum moisture content is about 14.5 percent and the maximum dry density is about 113 pounds per cubic foot (pcf). These data indicate that the eolian clays would be suitable to use as core materials in a dam, but there is only a limited volume on-site. Mancos Shale The Mancos Shale is a Cretaceous age (± 78 to 112 million years old) rock deposited in a marine environment. In the Woody Creek quadrangle, it is described by Freeman (1972) to be a dark gray silty to sandy shale with frequent zones of concretions and minor bentonite beds. Overall the main body is about 4,750 feet thick and contains interbedded sandstone layers. The shale is known to have a low permeability which provides a satisfactory bottom seal for gravel pit 58 - 4 - reservoir construction. The shale is generally moderately strong with unconfined compressive strengths on the order of 7,000 pounds per square inch (psi) reported in the literature. The Mancos Shale was observed in outcrop and in core samples during the site investigations. The rock is dark grey to black, dense, thinly bedded, slickensided, fractured shale with local calc-silica concretions and interbeds. Boring B-102 was the only boring to encounter the Mancos Shale on the WCDC parcel. The rock was very difficult to core due to the frequent fractures and the calc-silica concretions, and 10 feet of poor quality core was retrieved in B-102. A piece of core tested in the laboratory indicates the rock has a specific gravity of 2.73, which is a dry density of 170 pcf (very dense). The Mancos outcrops as a steep slope in the road cut along Upper River Road following the southwest edge of the site (Figure 2). A package of northward dipping sandstone (Kms) beds was observed on the far south end of the site. However, further north along the road cut, the outcrop transitions to a southward dipping package of fractured shale beds with calc-silica concretions and concretionary beds. This structural orientation is the result of a west-to-east plunging syncline (Figure 2). Under the WCDC site, the bedding appears to be fairly uniform striking southwest and dipping 50 ̊ south. The Mancos Shale was also observed in outcrop along the lower highwall of the Vagneur Mine. In this area, groundwater seeps were observed from the glaciofluvial deposits above the outcrop (Figure 2), indicating that the shale has a very low permeability and acts as a groundwater barrier. Paleo Topography Because the shale was not encountered in three of the borings drilled 123 feet deep during geotechnical investigations, the depth of the bedrock beneath the site was evaluated using published geologic logs of State permitted wells in the vicinity. A total of 13 well logs were found in the area that provided an estimate to the top of bedrock. These data, in conjunction with our geologic mapping and interpretation, were used to build a contour map of the bedrock surface. This contour map, along with the pertinent data is presented as Figure 5. The contour map shows a deep paleochannel, or buried valley, of the ancestral Roaring Fork River beneath the site. The presence of the sandstone outcrop at the south end of the site suggests that this more resistant rock formed a knickpoint where the river sharply veered east and down-cut into the shale. Subsequent erosion through the Qgb terrace resulted in the current position of the Roaring Fork River and a ridge of bedrock between it and the paleochannel. This rendition of the bedrock surface at the site is in large part based on a well that was drilled in 1994 and encountered dry Mancos Shale at a depth of 200 feet. The location of this well is based on the permit documents, as well as inspection of 1991 versus 1999 aerial imagery of the site. Using 3D analytical techniques in GIS, a difference model was created between the topography and the bedrock surfaces to show the depth to bedrock contours at the site. This map is presented as Figure 6. 59 - 5 - Preliminary Slope Stability Preliminary slope stability analyses were conducted for the site using the geometry based on the bedrock elevation map and the topography. The primary stability analyses were conducted for the steep slopes leading towards the Roaring Fork River. Examples of these slopes are shown on the western edges of the profiles on Figure 3. The glaciofluvial outwash deposits are very strong soil deposits as they are dense, free draining, and made up of about 50 percent cobbles and boulders. We estimate that they have a frictional strength of the order of 50 ̊. They stand on natural slopes of 45 ̊. The Mancos Shale has variable shear strength properties highly dependent on bedding. The steep bedding orientation on-site is generally favorable for the stability of terrace slopes. Our preliminary analysis indicates that the northern one-half of the site is quite stable with the thick glaciofluvial deposits of the middle terrace (Qgb) fully buttressed by the lower terrace (Qgc). This is the case near the community of Woody Creek where very high factors of safety for stability were calculated. In the southern parts of the site, bedrock is higher and the overall terrace slope is higher. Additional investigations should be conducted in this area to verify adequate slope stability exists. ENVIRONMENTAL CONDITIONS An ecologist with ERO conducted a natural resources assessment (NRA) at the site during a visit in July 2017. The full report is provided as Appendix B. The assessment did not identify any wetland areas or potential federally threatened and endangered species habitat. However, if any work is planned to pump water directly out of the Roaring Fork River, a Nationwide 404 Permit will need to be acquired from the U.S. Army Corps of Engineers prior to any construction work in the riparian area. There is a potential for nesting raptors at the site, but initial construction activities can be planned to avoid the nesting season, or a nest survey could be conducted prior to beginning construction. Another issue that could affect open-water reservoir development at the property is the potential to increase the risk of bird/wildlife aircraft strike hazards because the reservoir could attract wildlife, especially flocks of water fowl. The site is situated within five miles of the Aspen/Pitkin County Airport. According to Section 4 of the Federal Aviation Administration’s (FAA) Advisory Circular No. 150/5200-33B, (Appendix C of the Aspen/Pitkin County Airport Wildlife Hazard Management Plan), any proposed land-use practice changes within five miles of an airport (aka the “General Zone”) would need to be reviewed by the FAA. As discussed in the NRA, in the context of water storage, mitigation techniques include, but are not limited to, the following: 1. Building an in-situ or underground storage vessel. This would eliminate the hazard by eliminating an open water surface that attracts wildlife. 60 - 6 - 2. Using a layer of floating bird deterrent balls or other covers. This mitigation is used for open storage vessels, and forms a floating cover on a reservoir that does not attract wildlife. This method also reduces evaporation, but would preclude recreational uses. 3. Implementing a wildlife hazard management plan in coordination with the airport’s plan. 4. Employing wildlife deterrent officers and trained dogs to patrol the reservoir and keep wildlife away. WATER STORAGE ALTERNATIVES The water storage alternative concepts developed include above grade storage (with small dams), below grade storage (all below site ground level) and in-situ storage (storage in voids of the gravel and cobbles). To realize any of these concepts requires a positive water cutoff within the highly permeable glaciofluvial outwash deposits. The positive cutoff methods we considered include deep cutoff walls (such as slurry walls), dams, slope liners, and geosynthetic liners. Cutoff walls, dam cores and slope liner cores require a foundation key into the Mancos Shale. The shale would act as a low permeability barrier and form the bottom of these reservoirs. Construction of deep cutoff walls is considered marginally feasible based on depths to bedrock exceeding 200 feet and the number of nested cobbles and very large boulders. Installation of geosynthetic liners, made of HDPE or PVC, appears to be geotechnically feasible at this site. Geosynthetic liners are versatile. They can form the positive cutoff for a dam slope or a cut slope, and can either be anchored to the shale or installed completely within the outwash where shale is too deep. Once the excavation slope is prepared, a bedding layer of silty sand material is typically placed. The geosynthetic liner is then installed on the bedding and buried by a filter layer of silty sand. The bedding and filter layers act to protect the liner and mitigate seepage in the event the liner is compromised. They also allow riprap to be safely placed on the liner. For the McLain Flats site, we developed four storage alternatives. These alternatives include both the WCDC and Elam parcels. The four alternatives are: 1. Alternative 1 – Three-Phase Reservoir Storage 2. Alternative 2 – Maximum Reservoir Storage 3. Alternative 3 – Two-Phase Reservoir Storage 4. Alternative 4 – Manufactured In-Situ Reservoir Storage We prepared a pre-feasibility level engineer’s opinion of costs for the four alternatives, and these values are itemized on Tables 2 through 5. All alternatives include gravity filling and gravity releasing to the Roaring Fork River. We assumed water delivery could be accomplished using a pipeline from existing ditch structures. We assumed a combined low level outlet pipe and Morning Glory spillway to the Roaring Fork River. Alternative 4 does not require a spillway because it is all in-situ storage, but it would still have the same type of outlet. Additionally, all engineer’s opinions of cost include 30 percent contingency. 61 - 7 - To use the Vagneur pit for water storage would require a revision to the mine’s reclamation plan and cessation of placing inert fill in the pit. The first three alternatives also involve some degree of mining at the WCDC parcel. We therefore assumed all excavation costs would be incurred by a miner. Mining the WCDC parcel would require the property to be permitted as a mine, or added to the existing Vagneur Mine permit. Alternative 1 – Three-Phase Reservoir Storage Alternative 1 is a phased project that could realize initial storage at the Vagneur Mine relatively quickly, possibly within a few years. This option also allows time to incorporate the WCDC parcel into the Vagneur mining permit. The layout of this concept is presented on Figure 7, and on the geologic profile on Figure 8. Phase 1 of this concept would be to impound water in the Vagneur gravel pit. Low asphalt cored dams would be constructed on the north and south ends of the vessel. HDPE geosynthetic liners would be installed on the cut slopes between the dams and anchored to the shale. The Mancos Shale appears to be more shallow in this area, which suggests it is feasible to use it as a foundation for the positive cutoff methods. Clay cores could also be built in the dams if enough material is available for borrow from the upper terrace stockpile or in-place eolian deposits. This reservoir would total approximately 1,000 acre-feet of storage. Phases 2 and 3 assume the WCDC parcel can be mined and reclaimed as open water storage. Phase 2 would be on the north end of the site, and include a 20-foot high dam to provide both above grade and below grade storage. The gravel pits would be cut at 3:1 (horizontal to vertical) slopes down to about elevation 7340 feet. The vessels would be completely lined with HDPE geosynthetic liners because the Mancos Shale is so deep. The HDPE liner would be anchored to the dam or to the ground surface at the top of the excavation. Mined material could be stockpiled on the south end of the site so that Phase 2 reservoir construction could continue independent of mining permit approval. The Phase 2 reservoir would realize approximately 700 acre-feet of storage. Once the mining permit is approved, the material stockpiled on the south end of the WCDC parcel could be processed and sold. With two reservoirs on line, construction of the third phase would begin in conjunction with mining operations. The Phase 3 reservoir would be constructed using HDPE geosynthetic liner as the positive cutoff, resulting in an additional 800 acre-feet of fully below grade storage. This project would involve mining approximately 3 million cubic yards of material, or about 4.5 million tons. Currently, most of the sand and gravel used for construction in Aspen is trucked from gravel pits in the Carbondale area. Thus, utilization of this local resource would reduce Aspen’s carbon footprint. National per-capita consumption of sand and gravel can be as high as 10 tons per year. 62 - 8 - Alternative 1 would provide a total of 2,500 acre-feet of storage at a cost of approximately $73 million, or about $29,000 per acre-foot of storage (Table 2). The fastest total completion of all three phases would be of the order of a decade. However, the phasing of this alternative provides flexibility for bringing these vessels on line as they are needed. Alternative 2 – Maximum Reservoir Storage Alternative 2 represents the maximum storage vessel that could be realized using both parcels. It is also, therefore, the longest-term solution to water storage. The maximum reservoir includes the construction of a 5,000-foot long dam, with a 60-foot maximum section, around the north side of the Vagneur parcel and along the west side of the WCDC parcel (Figure 9). The positive cutoff would be provided by an HDPE geosynthetic liner. The outwash would be mined at 2.5:1 (horizontal to vertical) slopes to bedrock. This would result in an excavation of about 11 million cubic yards (16.5 million tons) of gravel and cobbles. A gravity drain would be installed behind the liner on the east side of the reservoir to drain groundwater from behind the liner. The tunneled outlet and spillway would be located on the south end of the reservoir. All utilities, including the high-pressure gas line and multiple overhead electric lines running through each parcel, would have to be relocated. This alternative would provide approximately 8,000 acre- feet of total storage for about $81 million or about $10,000 per acre-foot of storage (Table 3). Alternative 3 – Two-Phase Reservoir Storage Alternative 3 is a variation of Alternative 1 that involves maximizing open water storage on the WCDC parcel with one reservoir, rather than building two smaller vessels (Figure 10). The first phase is the same as for Alternative 1: a 1,000 acre-foot reservoir in the Vagneur pit. The second phase of this alternative would be to build the same low dam as in Phase 2 of Alternative 1, but the excavation would be site-wide instead of leaving material between two cells. The excavation would be cut at 3:1 (horizontal to vertical) slopes down to approximately elevation 7300 feet producing approximately 3.9 million cubic yards (5.9 million tons) of gravel material. This reservoir would provide approximately 2,000 acre-feet of storage on the WCDC parcel compared to 1,500 acre-feet in Alternative 1. The total storage realized for this alternative would therefore be approximately 3,000 acre-feet and would cost approximately $74 million, or nearly $25,000 per acre-foot of storage (Table 4). Alternative 4 – Manufactured In-Situ Reservoir Storage Alternative 4 was developed as an alternative to open water storage. This concept involves manufacturing in-situ storage on the south one-half of the WCDC parcel, while the north one- half is used for material stockpiling and processing (Figure 11). This option essentially represents converting only the Phase 3 vessel of Alternative 1 to in-situ storage. Manufacturing in-situ storage would be accomplished by building the fully below grade geosynthetic lined vessel, then backfilling the reservoir with select large cobbles and boulders and storing water in the voids. To fill the vessel, an infiltration gallery consisting of 15,000 linear feet of 36-inch diameter slotted HDPE pipes bedded in gravel would be built near the 63 - 9 - surface. The infiltration gallery would be plumbed to the water supply system and buried up to grade. The outlet works would be tunneled to the Roaring Fork River. The outlet would be connected to a 9-foot diameter concrete collection gallery in the bottom of the reservoir. The gallery would run up one slope to a gate house to control releases. Using select coarse rock as backfill for the vessel would likely allow the manufactured porosity to be of the order of 40 percent. Therefore, such a vessel could provide up to about 320 acre-feet of storage. This alternative would cost approximately $48 million, which would be around $150,000 per acre-foot. This is a very high unit cost for reservoir construction due to the additional handling and processing of the material and the relatively low storage volume it allows. A variation of Alternative 4 could involve constructing two such in-situ vessels to double the storage. Unit costs would remain high for this variation. A further variation could involve a recharge facility on half of the site. In this case, another infiltration gallery could be constructed and used to recharge water to the Roaring Fork River to replace any out-of-priority depletions in lagged time. Having lagged return flow credits accreting to the river from the recharge facility could allow additional flexibility in operating the storage vessel. CONCLUSIONS This reservoir pre-feasibility investigation has resulted in the following conclusions: 1. Open water storage using geosynthetic liners is geotechnically feasible. 2. Slurry wall, or deep cutoff wall construction for in-situ storage, is considered marginally feasible because of the greater than 200-foot bedrock depth and numerous cobbles and boulders. 3. Alternative 1, a three-phase project, could potentially provide 1,000 acre-feet of storage within a few years, and eventually provide up to 2,500 acre feet for about $29,000 per acre-foot. 4. Alternative 2, the maximum storage alternative, could provide 8,000 acre-feet of storage at about $10,000 per acre-foot. 5. Alternative 3, a variation of Alternative 1, would be a two-phase project that could provide about 3,000 acre-feet of storage for roughly $25,000 per acre-foot. 6. Alternative 4, a manufactured in-situ storage vessel, could be constructed to provide approximately 320 acre-feet of storage for a unit cost of up to $150,000 per acre-foot. RECOMMENDATIONS Based on this pre-feasibility level investigation and its conclusions, we arrived at the following recommendations: 64 - 10 - 1. Pursue the potential for using both parcels for water storage. 2. Conduct feasibility level geotechnical analyses for both parcels. Before pursuing reservoir alternatives, the next steps include: - Drilling two deep rotosonic borings on the WCDC parcel to confirm depth to bedrock - Drilling several borings in the Vagneur gravel pit to assess the foundation conditions - Conduct more detailed slope stability analyses 3. Perform a water resources analysis to better understand how the McLain Flats site can be used to optimize the flexibility of the City’s water rights. 4. Conduct a risk assessment for potential wildlife hazards. LIMITATIONS This pre-feasibility level analysis is considered reasonable, given the data, time and budget available. It was performed using publicly available data and data obtained from field investigations. These data are limited, however, and therefore the results of the analysis must be considered approximate. Should additional data or information become available, D&A can analyze the information and to update the opinions provided in this memorandum. U:\0687 City Of Aspen\0687.003 Gravel Pit Reservoir Pre-Feasibility\Pre-Feasibility Memo\Reservoir Pre-Feasibility.Mem.Docx 65 TABLES 66 Upper Terrace 1'Qe - Eolian Grab 4.5 0.1 6.3 93.6 34 19 Lean clay (CL) Upper Terrace Stockpile 0'-1'Qe - Eolian Bulk 1.4 18.0 61.2 19.4 80.6 26 11 113.8 14.5 Lean clay with sand (CL) 0'-4'Qgb - Outwash Bulk 4.6 41.2 32.8 26.0 25 8 NA 4'-8.5'Qgb - Outwash Bulk 2.7 54.8 33.7 11.5 NA 12'-14'Qgb - Outwash Bulk 1.1 54.0 41.7 4.3 NA 33'Qgb - Outwash SPT 50.1 43.5 6.4 NA 91'Km - Mancos Shale SPT 10.6 48.4 23 8 NA 91'-101'Km - Mancos Shale NQ Core 56.8 21 7 NA 98'Km - Mancos Shale NQ Core 2.73 NA Road Cut 0'Km - Mancos Shale Bulk 11.8 28.5 59.7 22 4 NA * Table 1 Unit Sample Type Gravel (%) Gradation* Gravel Pit Reservoir Pre-Feasibility Summary Of Laboratory Test Results SAMPLE LOCATION Test Hole Sand (%) Depth (feet) September-2017 Plasticity Index (%) Natural Moisture Content (%) Gradation tests performed on glacial outwash deposits represent the fraction less than 3 inches for bulk samples and less than 1.5 inches for the SPT sample. Bulk samples of outwash had an estimated 50 percent of cobbles and boulders greater than 3 inches. Liquid Limit (%) Percent Passing No. 200 Sieve TP-8 Unified Soil Classification (Symbol) Hydrometer Silt (%) Clay (%) Standard Proctor Max Dry Density (Pcf) Optimum Moisture Content (%) Specific Gravity Atterberg Limits B-102 Page 1 of 1 67 TABLE 2 ENGINEER'S PRE-FEASIBILITY LEVEL OPINION OF COST WOODY CREEK GRAVEL PIT RESERVOIR 2,500 ACRE-FEET Quantity Unit Cost Extension 1 Phase 1 Mobilization (5%)1 LS 1,235,450$ 1,235,450$ 2 Phase 1 Reservoir (1,000 AF) a. Foundation Excavation 130,000 CY 10$ 1,300,000$ b. Foundation Preparation 1 LS 75,000$ 75,000$ c. Main Dam Rockfill (Zone 4)900,000 CY 6$ 5,400,000$ d. Asphalt Core (Zone 1)20,000 CY 125$ 2,500,000$ e. HDPE Liner 648,000 SF 3$ 1,944,000$ f. Graded Filter Zone & Bedding (Zones 2 & 3)123,000 CY 25$ 3,075,000$ g. Riprap/w Bedding 12,000 CY 45$ 540,000$ h. Concrete HDPE anchor slab 1,000 CY 800$ 800,000$ i. Grouting 1 LS 500,000$ 500,000$ j. Instrumentation & Electrical 1 LS 75,000$ 75,000$ Subtotal 16,209,000$ 3 Combined Outlet Works & Morning Glory Spillway 1500 LF 3,000$ 4,500,000$ 4 Water Delivery Infrastructure 1 LS 4,000,000$ 4,000,000$ 5 Phase 2 Mobilization (5%)1 LS 479,700$ 479,700$ 6 Phase 2 Reservoir (700 AF) a. Foundation Preparation 1 LS 75,000$ 75,000$ b. Main Dam Zone 65,000 CY 6$ 390,000$ c. HDPE Liner 943,000 SF 3$ 2,829,000$ d. Graded Filter Zone & Bedding 140,000 CY 25$ 3,500,000$ e. Riprap 6,000 CY 45$ 270,000$ f. Interconnect Pipeline 1,250 LF 2,000$ 2,500,000$ g. Instrumentation & Electrical 1 LS 30,000$ 30,000$ Subtotal 9,594,000$ 7 Phase 3 Mobilization (5%)1 LS 412,650$ 412,650$ 8 Phase 3 Reservoir (800 AF) a. Foundation Preparation 1 LS 75,000$ 75,000$ b. HDPE Liner 991,000 SF 3$ 2,973,000$ c. Graded Filter Zone & Bedding 147,000 CY 25$ 3,675,000$ d. Interconnect Pipeline 750 LF 2,000$ 1,500,000$ e. Instrumentation & Electrical 1 LS 30,000$ 30,000$ Subtotal 8,253,000$ Miscellaneous Unlisted Items @ 5%2,234,190$ Total Construction Items 44,683,800$ Engineering @ 15%6,703,000$ Permitting @ 10%4,468,000$ Subtotal 55,854,800$ Contingency @ 30%16,756,000$ ESTIMATED TOTAL (rounded to nearest $1,000,000)73,000,000$ 29,000$ Note: These costs do not include land acquisition costs or excavation costs. The latter are assumed to be incured by the miner. Construction Item Cost per Acre Foot (rounded to nearest $1,000) ALTERNATIVE 1 - THREE PHASED RESERVOIRS 68 TABLE 3 ENGINEER'S PRE-FEASIBILITY LEVEL OPINION OF COST WOODY CREEK GRAVEL PIT RESERVOIR ALTERNATIVE 2 - ULTIMATE RESERVOIR 8,000 ACRE-FEET Quantity Unit Cost Extension 1 Mobilization (5%)1 LS 2,267,250$ 2,267,250$ 2 Dam Embankments a. Foundation Preparation 1 LS 75,000$ 75,000$ b. Main Dam Zone 1,070,000 CY 6$ 6,420,000$ c. HDPE Liner 4,530,000 SF 3$ 13,590,000$ d. Graded Filter Zone & Bedding 671,000 CY 25$ 16,775,000$ e. Riprap 25,000 CY 45$ 1,125,000$ f. Gravity Drain 2,600 LF 100$ 260,000$ g. Instrumentation & Electrical 1 LS 100,000$ 100,000$ Subtotal 38,345,000$ 3 Combined Outlet Works & Morning Glory Spillway 1000 LF 3,000$ 3,000,000$ 4 Water Delivery Infrastructure 1 LS 4,000,000$ 4,000,000$ Miscellaneous Unlisted Items @ 5%2,380,613$ Total Construction Items 49,992,863$ Engineering @ 15%7,499,000$ Permitting @ 10%4,999,000$ Subtotal 62,490,863$ Contingency @ 30%18,747,000$ ESTIMATED TOTAL (rounded to nearest $1,000,000)81,000,000$ 10,000$ Note: These costs do not include land acquisition costs or excavation costs. The latter are assumed to be incured by the miner. Construction Item Cost per Acre Foot (rounded to nearest $1,000) 69 TABLE 4 ENGINEER'S PRE-FEASIBILITY LEVEL OPINION OF COST WOODY CREEK GRAVEL PIT RESERVOIR 3,000 ACRE-FEET Quantity Unit Cost Extension 1 Phase 1 Mobilization (5%)1 LS 1,235,450$ 1,235,450$ 2 Phase 1 Reservoir (1,000 AF) a. Foundation Excavation 130,000 CY 10$ 1,300,000$ b. Foundation Preparation 1 LS 75,000$ 75,000$ c. Main Dam Rockfill (Zone 4)900,000 CY 6$ 5,400,000$ d. Asphalt Core (Zone 1)20,000 CY 125$ 2,500,000$ e. HDPE Liner 648,000 SF 3$ 1,944,000$ f. Graded Filter Zone & Bedding (Zones 2 & 3)123,000 CY 25$ 3,075,000$ g. Riprap/w Bedding 12,000 CY 45$ 540,000$ h. Concrete HDPE anchor slab 1,000 CY 800$ 800,000$ i. Grouting 1 LS 500,000$ 500,000$ j. Instrumentation & Electrical 1 LS 75,000$ 75,000$ Subtotal 16,209,000$ 3 Combined Outlet Works & Morning Glory Spillway 1500 LF 3,000$ 4,500,000$ 4 Water Delivery Infrastructure 1 LS 4,000,000$ 4,000,000$ 5 Phase 2 Mobilization (5%)1 LS 923,090$ 923,090$ 6 Phase 2 Reservoir (2,000 AF) a. Foundation Preparation 1 LS 75,000$ 75,000$ b. Main Dam Zone 64,800 CY 6$ 388,800$ c. HDPE Liner 1,962,000 SF 3$ 5,886,000$ d. Graded Filter Zone & Bedding 290,700 CY 25$ 7,267,500$ e. Riprap 29,100 CY 45$ 1,309,500$ f. Gravity Drain 2,600 LF 100$ 260,000$ g. Interconnect Pipeline 1,600 LF 2,000$ 3,200,000$ h. Instrumentation & Electrical 1 LS 75,000$ 75,000$ Subtotal 18,461,800$ Miscellaneous Unlisted Items @ 5%2,266,467$ Total Construction Items 45,329,340$ Engineering @ 15%6,799,000$ Permitting @ 10%4,533,000$ Subtotal 56,661,340$ Contingency @ 30%16,998,000$ ESTIMATED TOTAL (rounded to nearest $1,000,000)74,000,000$ 25,000$ Note: These costs do not include land acquisition costs or excavation costs. The latter are assumed to be incured by the miner. ALTERNATIVE 3 - TWO PHASED RESERVOIRS Construction Item Cost per Acre Foot (rounded to nearest $1,000) 70 TABLE 5 ENGINEER'S PRE-FEASIBILITY LEVEL OPINION OF COST WOODY CREEK GRAVEL PIT RESERVOIR 320 ACRE-FEET Quantity Unit Cost Extension 1 Mobilization (5%)1 LS 1,494,580$ 1,494,580$ 2 Manufactured In-Situ Reservoir (400 AF) a. Excavation, processing, stockpiling and backfilling 1,290,400 CY 9$ 11,613,600$ b. Foundation Preparation 1 LS 75,000$ 75,000$ c. HDPE Liner 991,000 SF 3$ 2,973,000$ d. Graded Filter Zone & Bedding 146,800 CY 25$ 3,670,000$ e. Infiltration Piping (36" slotted HDPE)15,000 LF 180$ 2,700,000$ f. Gravity Drain 2,600 LF 100$ 260,000$ g. Concrete Collection Gallery (9' dia.)750 LF 2,000$ 1,500,000$ h. Combined Outlet Works & Morning Glory Spillway 1000 LF 3,000$ 3,000,000$ i. Instrumentation & Electrical 1 LS 100,000$ 100,000$ Subtotal 25,891,600$ 3 Water Delivery Infrastructure 1 LS 4,000,000$ 4,000,000$ Miscellaneous Unlisted Items @ 5%1,569,309$ Total Construction Items 31,386,180$ Engineering @ 15%4,708,000$ Permitting @ 3%942,000$ Subtotal 37,036,180$ Contingency @ 30%11,111,000$ ESTIMATED TOTAL (rounded to nearest $1,000,000)48,000,000$ 150,000$ Note: These costs do not include land acquisition costs. ALTERNATIVE 4 - MANUFACTURED IN-SITU RESERVOIR Construction Item Cost per Acre Foot (rounded to nearest $1,000) 71 FIGURES 72 M C L A IN F L A T S M C L A IN F L A T S Woody Creek Development Co.(WCDC Parcel)55.7 Acres Elam Construction(Vagneur Gravel Mine)104.4 Acres W O O D Y C R E E KWOODY C R E E K U p p e r R iv e r R o a d H ig h w a y 8 2 1.9 Acres A s p e n (~6 m ile s ) G le n w o o d S p r in g s (~3 5 m ile s )21 16 22 15 16 9 15 10 Woody CreekR oaringForkR i v e r Brush Creek Salvation Ca n al Salvat ion Canal Legend State Highway 82 Streams Salvation Canal McLain Flats Reservoir Parcels Section Lines ¥0 800 1,600Feet MCLAIN FLATS STORAGE PROJECT FIGURE NO.1 DATE:SCALE: Site Location Map 1 inch=800 feetSEPTEMBER 2017 JOB NO. 0687.003.00 U:\0687 City of Aspen\0687.003 Gravel Pit Reservoir Pre-Feasibility\GIS\Figure 1 - Site Location Map.mxd Thursday, September 28, 2017 09:39 AMTownship 9 South, Range 85 West (6th P.M.)Parcel Data from Pitkin CountyAerial Photo from NAIP (2015) C o l o r a d o I n d e x M a pColorado I n d e x M a p Woody CreekPitkin County, COWater Division 5 C olorado R iver73 Mo ooÂÂÂÂÂo")")")")")!A!A!A!AEER oaring Fork R iverUpper River Road W O O D Y C R E E KWOODY C R E E K U p p er R iver R o ad R io G ran d e T railH ig h w a y 8 2 M C L A IN F L A T S M C L A IN F L A T S Q g bQgb Woody CreekPROFILE APROFI LE BQ g bQgb Q g aQga Q a lQal Q g cQgc Q g bQgb Q eQe Q g aQga Q a lQal Q a lQal Q a lQal Q fQf Q fQf K mKm Q fQf Q g cQgc Q g aQga Q fQf Q eQe Q eQe Q g aQga Q g bQgbKmKm Q a lQal K m sKms K mKm 7340 73507 3 6 073707 3 8 0 73907 4 0 0 7 4 1 0 7 4 2 0 7 4 3 0 7 4 4 0 74507460 7 4 7 0 7 4 8 0 7 4 9 07500 7 5 1 0 7 5 2 0 7 5 3 0 7 5 4 0 75507560 7 3 3 0 7570 7 5 8 0 7 3 2 0 73107 5 9 0 73007600 7290 7 6 1 0 7620 7 2 8 0 7630 7640 73807 4 3 07480 7350 7370 748075407410 74107360 7520737074207590 74 70 7450732073707340 7 3 5 0 743075007410 74707420742073207 4 0 07400 75007 4 2 0 7 4 1 0741074507490 7310 7480 7 4 6 0 750075307380748074807 4 2 0 7390 739074407 3 3 0 7 4 1 07470 7 3 7 0 75007380 7 4 8 0 73707350 7 4 5 0 7360 7400 73607490 745074 20 74607480746074907490 74807310 742074907 3 4 0 7 4 4 0 75107 3 7 0 7 4 5 0 7360748073107390 752073207380 749074307 4 7 07370 7490 7520 7480 74307450 7570 74107480 7 5 0 0 7 4 3 0 73307480737073407 3 2 0 7410 74307420735073607340 744074807480 75307340738073907 3 5 0 7 3 6 0 74307340735075007400743074907500 65 27 81 6862 58 5147 27 TP-8 TP-7 TP-6 TP-1 Seeps B-101(O) B-103(O) B-104(O) B-102(O, C, P) Km Roadcut Sample Upper TerraceQe Sample Upper Terrace StockpileQe Sample MCLAIN FLATS STORAGE PROJECT FIGURE NO.2 DATE:SCALE: Geologic Map 1 inch=400 feetSEPTEMBER 2017 JOB NO. 0687.003.00 U:\0687 City of Aspen\0687.003 Gravel Pit Reservoir Pre-Feasibility\GIS\Figure 2 - Gelogic Map.mxd Thursday, September 28, 2017 09:37 AMLegend Geotechnical Site Investigations !A Borings (O = Odex, C = Core, P = Piezometer) ")Test Pits Other Sample Locations EGroundwater Seeps oStrike and Dip of Bedding ÂStrike and Dip of Joint M Approximate Syncline Axis Arrow indicates direction of plunge Geology (Contacts Approximate) Qal - Alluvial Deposits Qf - Fan Deposits Qe - Eolian Deposits Qga - Glacial Outwash Terrace A Qgb - Glacial Outwash Terrace B Qgc - Glacial Outwash Terrace C Km - Mancos Shale Kms - Mancos Sandstone Water¥0 400 800Feet Geologic Profiles are shown on Figure 3.Geology after Freeman, 1972LiDAR Topography from Pitkin County (2016), C.I. = 2' 74 ELEVATION (FT) ELEVATION (FT)STATION (FT)720073007400750072007300740075000+002+004+006+008+0010+0012+0014+0016+0018+0020+0022+00MANCOS SHALEUPPER RIVERROADAPPROXBEDROCKSURFACEROARINGFORK RIVEREXISTINGGROUNDOUTWASH DEPOSITSQgbQalWESTEASTAPPROX GROUNDWATERSURFACEELEVATION (FT) ELEVATION (FT)STATION (FT)Terraces PROFILE71007200730074007500760077007800710072007300740075007600770078000+002+004+006+008+0010+0012+0014+0016+0018+0020+0022+0024+0026+0028+0029+43EXISTINGGROUNDB-102EL=7423.0(OFFSET 0.7)ROARING FORKRIVERELAM PROPERTYWCDC PROPERTYELAM PROPERTYPITKINCOUNTYPROPERTYWCDCPROPERTYPRIVATEPROPERTYBEND IN SECTION MANCOS SHALEQgaQalQgbQgcWESTEASTAPPROX BEDROCKSURFACEAPPROX GROUNDWATERSURFACEQeDATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTGEOLOGIC PROFILES A AND B3JOB NO. 0687.003.00SEPTEMBER 2017100 0200 SCALE IN FEETGEOLOGIC PROFILEB100 0200 SCALE IN FEETGEOLOGIC PROFILEA75 74107420743074007390732073807370735073407330ELEVATION (FT)7360BH-102101'BH-104BH-101123'BH-103123'===EL=7430N:1526448E:2608447EL=7454N:1525112E:2608490EL=7470.3N:1524099E:2608400EL=7455.5N:1524846E:26079537470744074507460907/25/177/28/17663DRY 7/27/17123'4DRY 7/28/17273453591071156575805101550/3"30/0"50/4"50/7"50/2"50/3"100/014/073/0100/074/05101551015510151411141010101210101074107420743074007390732073807370735073407330ELEVATION (FT)7360DRY7470744074507460-20056.8LL21PI72====-20048.4LL23PI8MC10.6SpG = 2.73===-2006.4G50.1S43.57/28/172NESTEDWELLDETAILGROUNDWATER LEVER ENCOUNTERED DURING DRILLINGAPPROXIMATE DEPTH OF GEOLOGIC CONTACT7/28/176350/7"STANDARD PENETRATION TEST BLOW COUNT. NUMBER("N" VALUE) INDICATES THE NUMBER OF BLOWS OF A 140LB. HAMMER FREE FALLING 30 INCHES REQUIRED TODRIVE THE SPLIT SPOON SAMPLER 1 FOOT OR THEINDICATED INTERVAL.101'DEPTH OF BORING OR TEST PIT (FT)SUMMARY LOGS LEGEND:1.EXPLORATORY BORINGS WERE DRILLED BETWEEN JULY 24 AND JULY 28, 2017 USING A TRACK-MOUNTED CME 850DRILL RIG. BORINGS WERE DRILLED WITH ODEX AND NQ CORING TECHNIQUES.2.EXPLORATORY TEST PITS WERE EXCAVATED JULY 25, 2017 USING A LINK BELT 225 TRACK MOUNTED EXCAVATOR.TEST PITS 3, 4, AND 5 INTENTIONALLY OMITTED.3.LINES BETWEEN MATERIALS REPRESENT APPROXIMATE BOUNDARIES BETWEEN TYPES AND TRANSITIONS MAY BEGRADUAL.4.GROUNDWATER LEVELS WERE MEASURED AT THE TIME OF DRILLING OR DATE INDICATED. GROUNDWATER LEVELSMAY FLUCTUATE SEASONALLY.5.ELEVATIONS ARE BASED ON A 2016 LIDAR SURVEY FROM PITKIN COUNTY, RELATIVE TO THE NAVD88 VERTICALDATUM.6.COORDINATES ARE RELATIVE TO THE NAD 83 HORIZONTAL DATUM PROJECTED IN THE COLORADO STATE PLANECENTRAL ZONE COORDINATE SYSTEM, UNITS IN FEET.7.LAB TESTING: MC=% MOISTURE CONTENT G=% GRAVEL BY WEIGHTS=% SAND BY WEIGHT-200=% BY WEIGHT PASSING THE #200 SIEVE (FINES) SILT=%SILT CLAY=%CLAYLL=LIQUID LIMITPI=PLASTICITY INDEX MDD=MAXIMUM DRY DENSITY (PCF) OMC=OPTIMUM MOISTURE CONTENT (%) SpG=SPECIFIC GRAVITY8.TWO ONE-INCH PVC OPEN STANDPIPE PIEZOMETERS ARE NESTED IN BORING B-102. THE WELLS WERE COMPLETEDUSING 10-SLOT SCREEN, 10/20 FILTER SAND AND TIME-RELEASE BENTONITE SEALS. THE SURFACE COMPLETIONCONSISTS OF A LOCKING 4-INCH STICK-UP STEEL WELL BOX IN A CONCRETE PAD.NOTES:105TP-1814'TP-28.515'TP-61115'TP-7715'DEPTH (FT)EL=7470.0N:1524122E:2608404EL=7455.6N:1524841E:2607954EL=7457.8N:1525069E:2608485EL=7448.4N:1525473E:260876902015TP-8415'8.5EL=7437.5N:1526068E:260853842461425SAND & GRAVEL: COBBLEY, TRACE SILT , LOCAL BOULDERS, WELL GRADED, COARSEGRAINED SAND, DENSE TO VERY DENSE, DRY TO SLIGHTLY MOIST, RED BROWN TOGRAY.CLAY, SILTY, MEDIUM, DRY, RED-BROWN, LOW TO MODERATE PLASTICITY, LOCALROOTS PRESENT (CL).COBBLES, GRAVELLY TO BOULDERY WITH SAND AND LOCAL SILT, VERY DENSE, DRYTO WET, WHITE, GRAY, PINK-BROWN, LOCALLY CONTAINS BOULDERS UP TO 6'-7'DIAMETER, CALCAREOUS, LOCAL CALICHE RINDS & CEMENT. RED SANDSTONE ANDLIGHT GRAY GRANITE ARE MOST COMMON COBBLES.SHALE: HARD (SOILS), MODERATELY STRONG, MOIST TO WET, DARK GRAY TO BLACK,FRACTURED, LOW TO MODERATELY PLASTIC, VERY THINLY BEDDED, SLIGHTLYWEATHERED TO FRESH NEAR BEDROCK/SAND AND GRAVEL CONTACT, LOCALLYCONTAINS CALC-SILICA CONCRETIONS AND LENSES. BEDDING DIPS 45° TO 55° TO THESOUTH.7/28/17GROUNDWATER LEVER MEASURED ON DATE INDICATED5101510ODEX DRILLING RATE IN MINUTES PER 5 FOOT RUN.RUNS OF 10 MINUTES OR LONGER ARE NOTED.100/014/073/0100/074/0CORE INTERVAL SHOWING RECOVERY (%) AND RQD (%) ROCKQUALITY DESIGNATION (RQD) IS THE RATIO (%) OF THECUMULATIVE LENGTH OF THE SOLID ROCK CORE = 4 INCHESTO LENGTH OF THE CORE RUN.105DEPTH (FT)02015105UPPER TERRACE10'STOCKPILE8'DEPTH (FT)EL=7545.0N:1526528E:2609578EL=7442N:1526728E:2609004020153105DEPTH (FT)02015ROAD CUT12'EL=7370N:1524475E:26076667UPPER TERRACEGRAVEL, SANDY, SILTY, COBBLY , WITH BOULDERS UP TO 5' IN DIAMETER, DRY,BROWN TO RED BROWN, LOW PLASTICITY, LOCAL ROOTS PRESENT.DRYDRYDRY===-20093.6G0.1S6.3=MC4.5=LL34=PI19===-20080.6G1.4S18=LL26=PI11=MDD113.8=OMC14.5=SILT61.2=CLAY19.4===-20059.7G11.8S28.5=LL22=PI4===-2004.3G54.0S41.7=MC1.1===-20011.5G54.8S33.7=MC2.7===-20026G41.2S32.8=MC4.6EOLIAN DEPOSITS:GLACIOFLUVIAL OUTWASH DEPOSITS:MANCOS SHALE:==PI8LL25INTERVAL SEALEDWITH BENTONITEMONITORING WELLSCREENED INTERVALBORING LOGS10 SCALE IN FEET020 TEST PIT LOGS5 SCALE IN FEET010 DATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTSUMMARY LOGS OF EXPLORATORY BORINGS & TEST PITS4JOB NO. 0687.003.00SEPTEMBER 2017WELLDETAIL76 !A!A!A!AR oaring Fork R iverU p p e r R iv e r R o a d R io G ra n d e T ra ilW O O D Y C R E E KWOODY C R E E K H ig h w a y 8 2 Roaring Fork Roaring Fork PaleochannelPaleochannelWoody Creek7360 7380 7320 7300728 07400 72607420 724072207 3 4 0 7200744073407340 73407 3 5 0 73707 3 8 0 7360 7 3 9 0 7 4 0 0 7 4 1 0 74207 4 3 0 7 4 4 0 7 4 5 0 7 4 6 0 7 4 7 0 7 4 8 0 7 4 9 07500 7 5 1 0 7 5 2 0 7 5 3 0 7 5 4 0 73307 5 5 0 7 3 2 0 7 5 6 0 7310 7 5 7 0 73007 5 8 0 7 5 9 0 7290 7 6 0 0 7280 7 6 1 0 7 6 2 0 7270 748073807 4 0 0 741073807380 74007310 74707490 7 4 8 0 7420743074 20 7350 7310 74507 3 9 0 73707 4 2 0 7280 73007410 74307470748073807500748074207360 7 4 1 0 7570 74807 3 9 0 75007 3 3 0750073407470 73907480 7 5 3 0 73607 4 3 0 7 4 6 0 75207380732074007390 7 4 9 0 74507 4 3 0 73407460740074107400 744074007 4 5 0 742074607420751074807 4 9 0 7410732074807 3 5 0 73007420 74907 3 7 0 74407 4 2 0 7340749074507370737073807480 7 3 0 0 754073107440 7 3 6 0 73507 3 3 0 74307 3 8 0 750074207490 7370733074807 3 5 0 74407 4 5 0 7 4 8 0 7520 731073207480 7 3 7 0 7270 74307430 742073507 4 1 0 7 3 5 07370 73607 4 6 0 7280 7480 7 4 8 0 7360 7360 73907480 7 3 7 0 7 4 3 0 7 3 4 0 74207 3 5 0 7450 7400 7 3 7 0 75007340 7362 7366 736773697369 7374 7345 7279 7338 7323 7353 7249 72517429 7282 7412 B-101(O) B-103(O) B-104(O) B-102(O, C, P) MCLAIN FLATS STORAGE PROJECT FIGURE NO.5 DATE:SCALE: Bedrock Contour Map 1 inch=400 feetSEPTEMBER 2017 JOB NO. 0687.003.00 U:\0687 City of Aspen\0687.003 Gravel Pit Reservoir Pre-Feasibility\GIS\Figure 5 - Bedrock Contour Map.mxd Thursday, September 28, 2017 09:36 AMLegend 2017 Geotechnical Borings !A Borings (O = Odex, C = Core, P = Piezometer) Bedrock Elevation Data (Approximate) Bedrock Elevation Contours (C.I. = 20 feet) Approximate Outcrop Location Inferred Location Bedrock ElevationHigh : 7440 Low : 7200¥0 400 800Feet Aerial Imagery from Pitkin County (2014)LiDAR Topography from Pitkin County (2016), C.I. = 10' 77 !A!A!A!AR oaring Fork R iverU p p e r R iv e r R o a d R io G ra n d e T ra ilW O O D Y C R E E KWOODY C R E E K H ig h w a y 8 2 Roaring Fork Roaring Fork PaleochannelPaleochannelWoody Creek806 0 1 0 040 12014016020 1 8 0 2000 0 4 040 16 0 4 0 20 1 2 0 1206 0 14020 4 0 1 2 0 601001 2 0 8 0 100060 201 0 0 80 20 1 4 00 60020120100160 120 12060100140140201401 4 0 40 1 4 0 806 0 1408 0 12014000 2 0 1 4 0 1401600 10080208040 040100180 40 1201401001 2 0 801 2 0 1 2 0 201 0 0 40 4 0120 160100401206 0 1602000 00 00 0 90 30 28 39 82 61 41 28 40 200 117 B-101(O) B-103(O) B-104(O) B-102(O, C, P) MCLAIN FLATS STORAGE PROJECT FIGURE NO.6 DATE:SCALE: Bedrock Depth Isopach Map 1 inch=400 feetSEPTEMBER 2017 JOB NO. 0687.003.00 U:\0687 City of Aspen\0687.003 Gravel Pit Reservoir Pre-Feasibility\GIS\Figure 6 - Bedrock Depth Isopach Map.mxd Thursday, September 28, 2017 09:37 AMLegend 2017 Geotechnical Borings !A Borings (O = Odex, C = Core, P = Piezometer) Bedrock Depth Data (Approximate) Depth to Bedrock Isopachs (feet) Bedrock Depth (feet)High : 224 Low : 0¥0 400 800Feet Aerial Imagery from Pitkin County (2014)LiDAR Topography from Pitkin County (2016), C.I. = 10' 78 B-101B-102B-103B-104TP-1TP-2TP-6TP-7TP-80SCALE IN FEET300150NWL=7452NWL=7444NWL=7431ROARINGFORKRIVER WOODY CREEKUPPER RIVER ROADRIO GRANDE TRAILVAGNEURGRAVELMINEASPHALTCORE DAMPHASE 11,000 afPHASE 2700 afPHASE 3800 afWOODY CREEKPROPERTYLINESDAMASPHALTCORE DAMTUNNELED OUTLET &SPILLWAY TO ROARINGFORK RIVER25201510507460732073407360738074007420744001002003004005006007008009001,0001,10074607320734073607380740074207440AREA (AC)CAPACITY (AF)ELEVATION (FT)ELEVATION (FT)PH1 AREA (AC)PH1 CAPACITY (AF)PH2 CAP (AF)PH3 CAP (AF)PH2 AREA (AC)PH3 AREA (AC)HWL=7431HWL=7444HWL=7452UPPER RIVER ROAD DATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTALTERNATIVE 1 - THREE-PHASE RESERVOIR STORAGE7JOB NO. 0687.003.00SEPTEMBER 2017L I T T LE TEXASNOTES:OVERHEAD ELECTRICHIGH PRESSURE GAS LINEFIBER OPTIC CABLECINTERCONNECTPIPELINEINTERCONNECTPIPELINE79 ELEVATION (FT) ELEVATION (FT)STATION (FT)7200730074007500760077007200730074007500760077000+005+0010+0015+0020+0025+0030+0035+0040+0045+0050+0052+00HDPE LINEREXISTINGGROUNDSOUTHNORTHAPPROXBEDROCKSURFACEMANCOS SHALEOUTWASH DEPOSITSEL=7435ASPHALTCORE DAMB-104EL=7449.0(OFFSET 19.5)B-101EL=7465.0(OFFSET 156.5)B-102EL=7423.0(OFFSET 264.1)EL=7448PHASE 2NWL=7444PHASE 3NWL=7452VAGNEUR MINEPHASE 1NWL=7431EL=7435UPPERRIVERROADBEND IN SECTION BEND IN SECTIONINTERCONNECT PIPELINESAPPROX GROUNDWATER SURFACEHDPEGEOSYNTHETICLINERFILTER / BEDDINGZONES312'2'OUTWASH DEPOSITSNWL=74313131ZONE 3COARSE TRANSITIONCREST EL=743518" RIPRAPZONE 2FINE TRANSITIONZONE 4ROCKFILLZONE 13' WIDEASPHALTCORESHALE BEDROCKZONE 402001005 010 SCALE IN FEETGEOSYNTHETIC LINER DETAILNTSPHASE 1 ASPHALT CORE DAM TYPICAL DETAIL0400200Vertical Scale (Feet)Horizontal Scale (Feet)GEOLOGIC PROFILEDATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTALTERNATIVE 1 PROFILE & DETAILS8JOB NO. 0687.003.00SEPTEMBER 2017C80 B-101TP-1B-102B-103B-104TP-2TP-6TP-7TP-80SCALE IN FEET300150NWL=7451FILL WITHDIKEROARINGFORKRIVER WOODY CREEKUPPER RIVER ROADRIO GRANDE TRAILTUNNELED OUTLET &SPILLWAY TOROARING FORK RIVERPROPERTYLINESAREACAPACITY HWL=7451010002000300040005000600070008000CAPACITY (AF)90000102030405060708090100AREA (AC)7250ELEVATION (FT)73007350740074507250ELEVATION (FT)7300735074007450UPPER RIVER ROAD L I T T LE TEXAS DATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTALTERNATIVE 2 - MAXIMUM RESERVOIR STORAGE9JOB NO. 0687.003.00SEPTEMBER 2017MAXIMUM RESERVOIR8,000 afNOTES:OVERHEAD ELECTRICHIGH PRESSURE GAS LINEFIBER OPTIC CABLEDAM81 B-102B-103B-104TP-2TP-6TP-7TP-8B-101TP-10SCALE IN FEET300150NWL=7444NWL=7431ROARINGFORKRIVER WOODY CREEKUPPER RIVER ROADRIO GRANDE TRAILVAGNEURGRAVELMINEPHASE 11,000 afPHASE 22,000 afWOODYCRE E KASPHALTCORE DAMPROPERTYLINESASPHALTCORE DAMTUNNELED OUTLET &SPILLWAY TO ROARINGFORK RIVER72500ELEVATION (FT)0AREA (AC)500100015002000250073007350740074507250ELEVATION (FT)73007350740074501020304050HWL=7444CAPACITYAREACAPACITY (AF)PHASE 1 CAPACITY CURVESSHOWN ON FIGURE 6.NOTES:OVERHEAD ELECTRICHIGH PRESSURE GAS LINEFIBER OPTIC CABLEDATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTALTERNATIVE 3 - TWO-PHASE RESERVOIR STORAGE10JOB NO. 0687.003.00SEPTEMBER 2017UPPER RIVER ROAD L I T T LE TEXASINTERCONNECTPIPILINE DAM82 B-101B-102B-103B-104TP-1TP-2TP-6TP-7TP-8ELEVATION (FT) ELEVATION (FT)STATION (FT)720073007400750072007300740075000+002+004+006+008+0010+0012+0014+0016+0018+0020+0022+00MANCOS SHALEUPPER RIVERROAD9'Ø CONCRETECOLLECTIONGALLERYWESTEASTEXISTINGGROUNDNWL=745236"Ø INFILTRATIONGALLERY (TYP)GATEHOUSEAPPROXBEDROCKSURFACEHDPE LINER31ROARINGFORK RIVERBACKFILLTO GRADETUNNELEDOUTLETOUTWASH DEPOSITSQalAPPROX GW LEVEL0SCALE IN FEET300150NWL=7452ROARINGFORKRIVER UPPER RIVER ROADRIO GRANDE TRAILVAGNEURGRAVELMINEWOODY CREEKPROPERTYLINESTUNNELED OUTLET TOROARING FORK RIVERUPPER RIVER ROADDATE:SCALE:FIGURE NO.AS NOTEDMCLAIN FLATS STORAGE PROJECTALTERNATIVE 4MANUFACTURED IN-SITU RESERVOIR STORAGE11JOB NO. 0687.003.00SEPTEMBER 2017L I T T LE TEXAS NOTES:OVERHEAD ELECTRICHIGH PRESSURE GAS LINEFIBER OPTIC CABLE100 0200 SCALE IN FEETGEOLOGIC PROFILEMATERIALPROCESSINGANDSTOCKPILEAREABBGATEHOUSE83 APPENDIX A LABORATORY TEST RESULTS 84 TP-8, 0'-4' TP-8, 4'-8.5' TP-8, 12'-14' Estimated Gradation for the Glaciofluvial Outwash Deposits 85 86 87 88 89 90 91 92 93 APPENDIX B NATURAL RESOURCES ASSESSMENT 94 Consultants in Natural Resources and the Environment Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado Prepared for— Deere & Ault Consultants, Inc. 600 South Airport Road, Suite A-205 Longmont, Colorado 80503 Prepared by— ERO Resources Corporation 1842 Clarkson Street Denver, Colorado 80218 (303) 830-1188 ERO Project #6941 September 26, 2017 Denver • Durango • Hotchkiss • Idaho www.eroresources.com 95 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 i ERO Resources Corporation Contents Executive Summary ................................................................................................................ ii Introduction .......................................................................................................................... 1 Project Area Description ........................................................................................................ 1 Wetlands and Waters of the U.S. ............................................................................................ 4 Background ...................................................................................................................................... 4 Site Conditions and Regulations ...................................................................................................... 5 Threatened, Endangered, and Candidate Species .................................................................... 5 Colorado River Endangered Fish Species ......................................................................................... 7 Other Species of Concern ....................................................................................................... 8 Raptors and Migratory Birds ............................................................................................................ 8 Other Wildlife ........................................................................................................................ 9 Bird/wildlife Aircraft Strike Hazard ........................................................................................ 9 Potential Regulatory Reviews ........................................................................................................ 11 Conclusions ......................................................................................................................... 12 References ........................................................................................................................... 12 Tables Table 1. Federally threatened, endangered, and candidate species potentially found in Pitkin County or potentially affected by projects in Pitkin County. .......................................... 6 Figures Figure 1. Vicinity Map ...................................................................................................................... 2 Figure 2. Existing Conditions ............................................................................................................ 3 Figure 3. Wildlife Zones and Attractions ........................................................................................ 10 Appendix Appendix A Photo Log 96 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 ii ERO Resources Corporation Executive Summary Deere & Ault Consultants, Inc. (D&A) retained ERO Resources Corporation (ERO) to provide a natural resources assessment for the Proposed Reservoir site in Pitkin County, Colorado (project area; Figure 1). The project area is on a terrace above the Roaring Fork River and the small community of Woody Creek. The purpose of this report is to provide an assessment of natural resources that would present a possible fatal flaw that would jeopardize the proposed project. ERO assessed the project area for potential wetlands and waters of the U.S., threatened and endangered species, and general wildlife use. Below is a summary of the resources found at the project area and recommendations or future actions necessary based on the current site conditions and federal, state, and local regulations. The natural resources and associated regulations described in this report are valid as of the date of this report and may be relied upon for the specific use for which it was prepared by ERO under contract to D&A. Because of their dynamic nature, site conditions and regulations should be reconfirmed by a qualified consultant before relying on this report for a use other than that for which ERO was contracted and if a significant amount of time has passed between the date of this report and project activities. Wetlands and Other Waters of the U.S. – No wetlands or other waters of the U.S. occur within the project area. If activities are limited to the project area and no other wetlands or waters of the U.S. would be directly affected by the proposed project, no action is necessary to comply with the Clean Water Act. Threatened and Endangered Species – The project area does not contain habitat for any federally listed threatened or endangered species, although if depletions (changes in the volume and timing of flow) to streams within the Colorado River basin would occur, consultation with the U.S. Fish and Wildlife Service would be required to determine impacts on four Colorado River endangered fish species. Migratory Birds – The sagebrush shrubland within the project area is nesting habitat for several species of migratory birds. No bird nests were observed during the 2017 site visit; however, an extensive nest survey was not conducted. ERO recommends removing vegetation outside of the active breeding season. If the project schedule does not allow for vegetation to be removed outside of the breeding season, a nest survey should be conducted within one week of activities that would disturb vegetation to ensure that no active nests are destroyed or nesting birds are harmed by project activities. Bird/Wildlife Aircraft Strike Hazard – The project area is within the General Zone (5-mile buffer) around the Aspen-Pitkin County Airport. Because the proposed reservoir could be an attractant to wildlife, especially water fowl, the Federal Aviation Administration would likely review the project and may have some concerns. Mitigation options may be available. Additional analysis may be needed to model the direct and indirect effects of the proposed reservoir on bird concentrations and to determine possible movements based on other attractants. Because Pitkin County 1041 approval may be needed, coordination with the county is recommended early in the process to determine the airport’s concerns and recommendations. Conclusion – Compliance with the Clean Water Act and the Endangered Species Act would not present a fatal flaw that would jeopardize the project. The proximity of the project area to the Aspen-Pitkin County Airport would present some challenges and would require coordination with Pitkin County and the airport’s Wildlife Coordinator to determine the concerns and potential mitigation strategies. 97 ERO Project #6941 1 ERO Resources Corporation Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado September 26, 2017 Introduction Deere & Ault Consultants, Inc. (D&A) retained ERO Resources Corporation (ERO) to provide a natural resources assessment for the Proposed Reservoir site in Pitkin County, Colorado (project area; Figure 1). The proposed reservoir would be to the east of the Roaring Fork River near the small community of Woody Creek. The purpose of this report is to provide an assessment of natural resource issues that may be considered fatal flaws by regulatory agencies and that would jeopardize the proposed reservoir project. On July 20, 2017, Leigh Rouse, an ecologist with ERO, assessed the project area for natural resources (2017 site visit). During this assessment, activities included a review of potential wetlands and other waters of the U.S. (streams, ponds, lakes, and some ditches); identification of potential federally threatened and endangered species habitat; and identification of other natural resources in the project area. This report provides information on existing site conditions and resources, as well as current regulatory guidelines related to those resources. ERO assumes the landowner would be responsible for obtaining all federal, state, and local permits for construction of the project. The natural resources and associated regulations described in this report are valid as of the date of this report and may be relied upon for the specific use for which it was prepared by ERO under contract to D&A. Because of their dynamic nature, site conditions and regulations should be reconfirmed by a qualified consultant before relying on this report for a use other than that for which ERO was contracted or if a significant amount of time has passed between the date of this report and project activities. Project Area Description The project area is in Section 16, Township 9 South, Range 85 West of the 6th Principal Meridian in Pitkin County, Colorado (Figure 1). The UTM coordinates for the approximate center of the project area are 337539mE, 4348130mN, Zone 13 North. The longitude/latitude of the project area is 106.883213°W/39.267297°N. The elevation of the project area is approximately 7,445 feet above sea level. Photos of the project area are in Appendix A. The project area is east of Woody Creek, a small community within the Roaring Fork Valley, and sits on a terrace above the Roaring Fork River, a perennial tributary to the Colorado River. State Highway 82 generally parallels the west side of the Roaring Fork River while the Upper River Road occurs between the river and the project area (Figure 2). Raceway Road creates the southeast boundary of the site and 98 Project Area Prepared for: Deere & Ault File: 6941 Figure 1.mxd (GS) September 26, 2017 ± Figure 1 Vicinity Map Proposed Reservoir Site Portions of this document include intellectual property of ESRI and its licensors and are used herein under license. Copyright © 2016 ESRI and its licensors. All rights reserved. 0 1,500750Feet LocationPath: P:\6900 Projects\6941 Buckeye Reservoir\Maps\6941 Figure 1.mxdSection 16, T9S, R85W; 6th PM UTM NAD 83: Zone 13N; 337539mE, 4348130mN Longitude 106.883213°W, Latitude 39.267297°N USGS Woody Creek, CO Quadrangle Pitkin County, Colorado 99 Upper Ri ver Roa d Hi ghway82R o arin g F ork R i v e r RacewayRoadWestLo w er B ellwinkleRoad Rio G ra n d e Trail 1.9-acre Parcel 55.7-acre Parcel Gravel Mine RaceTrack Prepared for: Deere & Ault File: 6941 Figure 2.mxd (GS) September 26, 2017 ± Figure 2 Existing Conditions Proposed Reservoir Site 0 500250FeetPath: P:\6900 Projects\6941 Buckeye Reservoir\Maps\6941 Figure 2.mxdImage Source: Google Earth©, April 2015 Project Area Boundary 100 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 4 ERO Resources Corporation provides access to a racetrack and shooting range east of the project area. A gravel mine is northeast of the project area. The main 55.7-acre parcel is on the upper terrace (Photo 1) and a secondary 1.9-acre parcel is on a steep bank that slopes toward the Woody Creek community, northwest of the project area (Photo 2). On the west side of the project area, two trails parallel the project area – the Rio Grande Trail is paved and the smaller trail east of the Rio Grande Trail is crusher fines. Powerlines cut through the western part of the project area (Photo 3). Occasionally, large boulders occur in mounds throughout the project area along with other disturbed soil mounds. Along the Roaring Fork River, the riparian corridor is dominated by narrowleaf cottonwood (Populus angustifolia) and blue spruce (Picea pungens) (Photo 4). The vegetation within the project area is dominated by sagebrush (Artemisia tridentata). Other species present include bitterbrush (Purshia tridentata), rabbitbrush (Chrysothamnus sp.), serviceberry (Amelanchier sp.), snowberry (Symphoricarpos sp.), Oregon grape (Berberis repens), and juniper (Juniperus sp.). Patches of scrub oak (Quercus gambelii) occur along the trails and the west property boundary. Forbs and grasses consist of Kentucky bluegrass (Poa pratensis), smooth brome (Bromus inermis), squirreltail (Elymus elymoides), fringed sage (Artemisia frigida), wild buckwheat (Eriogonum sp.), and pussytoes (Antennaria sp.). Wetlands and Waters of the U.S. Background The Clean Water Act (CWA) protects the physical, biological, and chemical quality of waters of the U.S. The U.S. Army Corps of Engineers’ (Corps) Regulatory Program administers and enforces Section 404 of the CWA. Under Section 404, a Corps permit is required for the discharge of dredged or fill material into wetlands and other waters of the U.S. In 2007, the Corps issued guidance in response to the Supreme Court ruling in the consolidated cases of Rapanos v. United States and Carabell v. U.S. Army Corps of Engineers (Rapanos) stating that the Corps considers traditionally navigable waters (TNWs), wetlands adjacent to a TNW, and tributaries to TNWs that are relatively permanent waters (RPWs) and their abutting wetlands to be jurisdictional waters. Other wetlands and waters that are not TNWs or RPWs will require a significant nexus evaluation to determine their jurisdiction. A significant nexus evaluation assesses the flow characteristics and functions of a tributary and its adjacent wetlands to determine if they significantly affect the chemical, physical, or biological integrity of downstream TNWs. On May 31, 2016, the U.S. Supreme Court concluded that approved jurisdictional determinations are judicially reviewable under the Administration Procedure Act and, therefore, can be appealed in court. The Corps has recommended that requests for both approved and preliminary jurisdictional determinations be done using guidance outlined in Regulatory Guidance Letter (RGL) 16-01 and that a jurisdictional form request be completed (Corps 2016). The Corps has indicated that jurisdictional determinations associated with a Section 404 CWA Permit request will preside over stand-alone 101 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 5 ERO Resources Corporation jurisdictional determination requests. While ERO may provide its opinion on the likely jurisdictional status of wetlands and waters, the Corps makes the final determination. Site Conditions and Regulations ERO assessed the project area for potential isolated wetlands, jurisdictional wetlands, and other waters of the U.S. (streams, ponds, lakes, and some ditches). The project area is entirely sagebrush-dominated upland, and no wetlands or other waters subject to Corps’ jurisdiction are present. Because no jurisdictional waters of the U.S. are present in the project area that would be directly impacted by project activities, no action is necessary to comply with the CWA. Other actions that may be part of the proposed project (e.g., construction of a diversion structure) and that would affect a jurisdictional water of the U.S. would require coordination with the Corps to determine compliance with the CWA. Threatened, Endangered, and Candidate Species ERO assessed the project area for potential habitat for threatened, endangered, and candidate species under the Endangered Species Act (ESA). Federally threatened and endangered species are protected under the ESA of 1973, as amended (16 U.S.C. 1531 et seq.). Significant adverse effects on a federally listed species or its habitat require consultation with the U.S. Fish and Wildlife Service (Service) under Section 7 or 10 of the ESA. The Service lists several threatened and endangered species with potential habitat in Pitkin County, or that would be potentially affected by projects in Pitkin County (Table 1). 102 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 6 ERO Resources Corporation Table 1. Federally threatened, endangered, and candidate species potentially found in Pitkin County or potentially affected by projects in Pitkin County. Common Name Scientific Name Status* Habitat Habitat Present Mammals Canada lynx Lynx canadensis T Climax boreal forest with a dense understory of thickets and windfalls No North American wolverine Gulo gulo luscus PT Boreal forests and cold areas that receive enough winter precipitation to reliably maintain deep persistent snow No Birds Mexican spotted owl Strix occidentalis T Closed canopy forests in steep canyons No Yellow-billed cuckoo Coccyzus americanus T Wooded habitat with dense cover and water nearby No Fish Bonytail chub** Gila elegans E Backwaters with rocky or muddy bottoms and flowing pools No habitat; affected by depletions within the Colorado River basin Colorado pikeminnow** Ptychocheilus lucius E Deep, fast-flowing rivers; prefer large turbid pools found in the main river and its tributaries No habitat; affected by depletions within the Colorado River basin Greenback cutthroat trout Oncorhynchus clarki stomias T Cold, clear, gravel headwater streams and mountain lakes No Humpback chub** Gila cypha E Variety of habitats ranging from pools with turbulent to little or no current; substrates of silt, sand, boulder, and bedrock; and depth ranging from 1 to 15 meters No habitat; affected by depletions within the Colorado River basin Razorback sucker** Xyrauchen texanus E Large rivers, in water 4 to 10 feet deep; adults are associated with areas of strong current and backwaters No habitat; affected by depletions within the Colorado River basin Plants Ute ladies’-tresses orchid Spiranthes diluvialis T Moist to wet alluvial meadows, floodplains of perennial streams, and around springs and lakes below 6,500 feet in elevation No Insects Uncompahgre fritillary butterfly Boloria acrocnema E Associated with large patches of snow willow above 3,780 meters in elevation No *T = Federally Threatened Species, E = Federally Endangered Species; PT = Proposed Threatened. **Water depletions in the Colorado River may affect the species and/or critical habitat in downstream reaches in other counties. Source: Service 2017. The proposed project would not directly affect the Canada lynx, North American wolverine, Mexican spotted owl, yellow-billed cuckoo, greenback cutthroat trout, Ute ladies’-tresses orchid, or Uncompahgre fritillary butterfly because of the lack of habitat in the project area. The riparian corridor along the Roaring Fork River is habitat for the yellow-billed cuckoo. Because the proposed project would not directly affect the riparian habitat and the site is on a terrace not directly abutting the river, 103 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 7 ERO Resources Corporation there would not be a direct effects on yellow-billed cuckoo habitat. The project would not result in any direct impacts on federally threatened and endangered species. Colorado River Endangered Fish Species The Roaring Fork River is a tributary to the Colorado River, which is habitat for four endangered Colorado River fish species – bonytail chub, Colorado pikeminnow, humpback chub, and razorback sucker. An action that causes a change in the volume or timing of flow is considered a depletion. Water diverted from the Roaring Fork River or any other tributary to the Colorado River would cause depletions to the Colorado River that would adversely affect the Colorado River fish species. If a project- related action, such as constructing a diversion structure, would require Section 404 authorization, the action would create a federal nexus and depletions to the Roaring Fork River would require consultation with the Service. Typically, the lead federal agency (i.e., the Corps for 404 authorization) would consult with the Service under Section 7 of the ESA. The Section 7 consultation process typically consists of a biological assessment (BA) provided by the Corps (or other lead federal agency) to the Service describing the effects on listed species and designated critical habitat and proposed mitigation for the impacts. The Service responds to the BA with a biological opinion (BO) providing its opinion on the effects and prescribing the required mitigation to avoid jeopardizing the continued existence of a federally listed species or adverse modification of designated critical habitat (reasonable and prudent alternatives or measures). The BO’s reasonable and prudent alternatives are included as special conditions in any permit issued by the Corps. In 1999, the Service issued a Programmatic BO with specific elements to implement the Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin (Recovery Program) (Service 1999). The Recovery Program is a mechanism to consult with the Service and for the regulated public to benefit from existing mitigation measures. When consulting on projects, the Service would determine if progress toward recovery has been sufficient for the Recovery Program to serve as a reasonable and prudent alternative or measure. The Service also would consider whether the probability of success of the Recovery Program is compromised as a result of the project or the cumulative effect of depletions. The Service would consider Recovery Program and non-Program actions throughout the basin in evaluating the sufficiency of the program to serve as a reasonable and prudent alternative or measure for the project. The Service would assess the sufficiency of Recovery Program actions in proportion to the potential impacts of a proposed federal action. That is, the smaller the impact of a federal action, the lower the level of actions by the Recovery Program or others needed to avoid jeopardy or destruction or adverse modification of critical habitat. The Service only consults on and tracks depletions associated with a federal action. If the proposed project would not trigger a federal nexus, consultation with the Service on the Colorado River endangered fish species would not be necessary. 104 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 8 ERO Resources Corporation Other Species of Concern Raptors and Migratory Birds Migratory birds, as well as their eggs and nests, are protected under the Migratory Bird Treaty Act (MBTA). The MBTA does not contain any prohibition that applies to the destruction of a bird nest alone (without birds or eggs), provided that no possession occurs during the destruction. While destruction of a nest by itself is not prohibited under the MBTA, nest destruction that results in the unpermitted take of migratory birds or their eggs is illegal and fully prosecutable under the MBTA (Migratory Bird Permit Memorandum, Service (2003)). The regulatory definition of a take means to pursue, hunt, shoot, wound, kill, trap, capture, or collect; or attempt to pursue, hunt, shoot, wound, kill, trap, capture, or collect. Under the MBTA, the Service may issue nest depredation permits, which allow a permittee to remove an active nest. The Service, however, issues few permits and only under specific circumstances, usually related to human health and safety. Obtaining a nest depredation permit is unlikely and involves a process that takes from 8 to 12 weeks. The best way to avoid a violation of the MBTA is to remove vegetation outside of the active breeding season, which typically falls between March and August, depending on the species. Most MBTA enforcement actions are the result of a concerned member of the community reporting a violation. Habitat and Recommendations Sagebrush shrublands are nesting habitat for several bird species including Brewer’s sparrow, vesper sparrow, grasshopper sparrow, western meadowlark, horned lark, and loggerhead shrike. Generally, the nesting season in the Intermountain West is from April through August. No bird nests were observed in the project area during the 2017 site visit; however, a full nest survey was not conducted. The best way to avoid affecting nesting migratory birds is to remove vegetation outside of the active breeding season. If the project schedule does not allow vegetation removal outside of the breeding season, a nest survey should be conducted within a week prior to any vegetation-disturbing activity so that any active nest can be avoided until the birds, including fledglings, have left the nest to avoid a “take” under the MBTA. If active nests are found during surveys, any work that would destroy the nests or cause a bird to abandon eggs or chicks cannot be conducted until the birds have left the nests. There is no process for removing nests during the nonbreeding season; however, nests may not be collected under MBTA regulations. Although the proposed project would not affect the riparian corridor along the Roaring Fork River, it provides nesting habitat for a variety of birds including raptors. A few raptor species such as bald eagles, great horned owls, and red-tailed hawks can nest as early as December (eagles) or late February (owls and red-tailed hawks). Colorado Parks and Wildlife (CPW) has recommended setbacks from active raptor nests; the distance depends on the species. Prior to any land disturbance activity, a nest survey should be conducted in the riparian corridor adjacent to the project area to determine if any setbacks from an active nest are needed during the breeding season. CPW allows some changes in the setbacks depending on the circumstances, such as if birds are nesting in a highly disturbed area. 105 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 9 ERO Resources Corporation Other Wildlife The sagebrush habitat provides habitat for many of Colorado’s wildlife species including mule deer; elk; mountain lion; many small mammals (cottontail rabbit, jack rabbit, pocket gopher, striped skunk, red fox, coyote, and deer mouse); and reptiles (gartersnake, smooth green snake, and gopher snake). According to the Natural Diversity Information Source, the project area is within the overall range for elk, mule deer, and mountain lion and in summer range for mule deer (CPW 2017). The proposed project may displace some species but would not likely affect overall populations. The proposed reservoir may benefit some water fowl and other aquatic species. Bird/wildlife Aircraft Strike Hazard The proposed reservoir could be an attractant to water fowl, especially in the spring during migration. Birds that could be potentially attracted to open water in the Roaring Fork Valley are: gulls, geese, ducks, herons, and some raptors. Large mammals such as mule deer and elk may also use the proposed reservoir as a water source. The Aspen-Pitkin County Airport is about 2 miles to the south of the study area (Figure 3). The airport is approximately 7,820 feet in elevation. The mountain setting of the airport and the surrounding grasslands, shrublands, forests, and open water features create different types of habitat for many species of wildlife. The Federal Aviation Administration (FAA) determined that the Aspen-Pitkin County Airport has a high level of risk associated with wildlife collisions with aircraft, which creates a safety hazard for flights into and out of Aspen-Pitkin County Airport. The factors that primarily contribute to wildlife/aircraft strike risk include bird flight heights, aircraft flight patterns and heights, wildlife habitat affinities, and the location of wildlife attractants near aircraft movement areas. The FAA issued regulations (14 CFR 139.337) that require certified airports to conduct a wildlife hazard assessment if wildlife potentially have access to flight patterns and are capable of causing collisions. Because of the high wildlife hazards, the FAA required Aspen-Pitkin County Airport to conduct a Wildlife Hazard Assessment and as a result of determining a high level of risk, required the airport to prepare a Wildlife Hazard Management Plan (Mead & Hunt, Inc. 2012). As part of the airport’s wildlife management, a Wildlife Coordinator is appointed and assists with implementing the management protocols. The FAA developed Advisory Circular 150/5200-33A to provide guidance for land uses on airport property and in the surrounding area that could potentially attract wildlife hazardous to aircraft (U.S. Department of Transportation 2004). The FAA recommends maintaining a separation distance of 5,000 feet between airport ground movement areas and wildlife attractants for piston-powered aircraft, 10,000 feet for turbine-powered aircraft (Critical Zone), and 5 miles between wildlife attractants and approach, departure, or circling airspace (General Zone; Figure 3). Potential land uses that could attract wildlife that pose a risk to aircraft safety include wetlands or open water, landfills, livestock and agriculture fields, golf courses, or landscaped parks (Cleary and Dolbeer 2005). 106 Hi ghway82WoodyCreek Aspen - Pitkin County Airport WildcatReservoir MaroftReservoir Roari ng Fork River Pitkin CountySanitary Landfill SnowmassGolf Course City ofAspen SnowmassResort Prepared for: Deere & Ault File: 6941 Figure 3.mxd (GS) September 26, 2017 ± Figure 3 Wildlife Zones and Attractions Proposed Reservoir Site 0 8,0004,000 FeetPath: P:\6900 Projects\6941 Buckeye Reservoir\Maps\6941 Figure 3.mxdImage Source: USDA FSA, September 2015 Aspen-Pitkin County Airport Runway Critical Zone (Aspen Airport 10,000-Foot Buffer) General Zone (Aspen Airport 5-Mile Buffer) Project Area Boundary 107 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 11 ERO Resources Corporation Under Section 4 of Advisory Circular 150/5200-33A, the FAA discourages the development of facilities that would be located within the 5,000/10,000-foot criteria. For projects outside the 5,000/10,000-foot criteria, but within 5 statute miles of the airport’s aircraft movement areas, FAA may review proposed land use changes to determine if such changes present potential wildlife hazards to aircraft operations. The FAA may discourage the development if it shows that the area or proposed land use change supports wildlife species that are hazardous to aircraft. According to FAA (2017), there have been 42 documented bird strikes since August 2007 at the Aspen- Pitkin County Airport. About 28 percent of the strikes were identified as mountain bluebirds. Other birds involved in collisions were identified as magpie, American pipit, blue jay, western sandpiper, American crow, great horned owl, killdeer, horned lark, red-tailed hawk, and sparrow. The proposed reservoir would not be an important part of the preferred habitat of these species; however, water fowl species may be attracted to the proposed reservoir. The proposed reservoir is outside of the Critical Zone but within the General Zone. Some of the other attractants to wildlife within the General Zone include the Roaring Fork River and riparian corridor, Pitkin County Sanitary Landfill, Snowmass Golf Course, Wildcat Reservoir, and the many acres of natural habitat (Figure 3). Movements from the proposed reservoir to some of these features could potentially be through the flightpath. If the proposed reservoir is determined to be a hazard by the airport’s Wildlife Coordinator, options to deter wildlife use of the proposed reservoir could include: • Steep, unvegetated banks • Liners • Netting • Floating balls • Floating covers • Underground storage • Trained dogs to deter birds and other wildlife from using the reservoir Often times, using multiple methods can be the most effective. Additionally, the owners of the proposed reservoir would likely be expected to prepare and implement a Wildlife Management Plan to comply with the airport requirements. Birds using the reservoir would still be protected under the MBTA, and a permit from the Colorado Parks and Wildlife would be required for a lethal take. Potential Regulatory Reviews Clean Water Act 404 Authorization If the proposed project would require the placement of dredged or fill material into a water of the U.S. subject to Corps jurisdiction, Section 404 authorization would be required. Depending on the impacts of the project on waters of the U.S. (which are unknown at this time), the project could be authorized under a Nationwide or an Individual permit. Nationwide permits are issued when the impacts are under a specified threshold of impact for the specific activity, and no public review is completed. Individual 108 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 12 ERO Resources Corporation Permits are for impacts above a certain threshold but that do not cause significant overall adverse effects on resources. For an Individual permit, typically there is a 30-day public comment period during which the Corps could receive comments from the public, state agencies, and/or federal agencies. The Corps may receive comments on the proximity of the project area to the airport and would allow the applicant to respond. The Corps would likely not deny a permit because of the proximity of the proposed reservoir to the airport but would instead defer to local or county regulations to rule on the increased hazards or may require mitigation measures as a permit condition. Pitkin County Areas and Activities of State Interest As part of its Land Use Code, Pitkin County has a review process codified as the Areas and Activities of State Interest Act, or more popularly known as the 1041 Act. Pitkin County may require a review of the proposed reservoir because it involves the site selection and construction of a major facility of a public utility and because it is near the Aspen-Pitkin County Airport. For a project to proceed, the County would issue either a permit or a Finding of No Significant Impact determination. The County would likely defer to FAA recommendations and may require a wildlife management plan and mitigation to offset potential hazards of the proposed reservoir in order to issue a permit. Early coordination with the County is recommended. Additional analysis may be needed to model the direct and indirect effects of the proposed reservoir on bird concentrations and to determine possible movements based on other attractants. Conclusions The sagebrush-dominated project area provides habitat for many wildlife, plant, and invertebrate species, but none that are protected under the ESA. No wetlands or other waters of the U.S. would be directly affected by the proposed project. Coordination with regulatory agencies, such as the Corps or Service, may be required if the mechanism for providing water for the project would impact a jurisdictional water of the U.S. Depletions from the Colorado River basin would require consultation with the Service on the Colorado River endangered fish species. The proximity of the proposed reservoir to the Aspen-Pitkin County Airport could attract some birds that may increase the risk of collision with aircraft. Coordination with Pitkin County early in the process would help determine its concerns and possible management recommendations to comply with airport requirements. References Cleary, E.C. and R.A. Dolbeer. 2005. Wildlife Hazard Management at Airports: A Manual for Airport Personnel. USDA National Wildlife Research Center – Staff Publications. 133. Available at: http://digitalcommons.unl.edu/icwdm_usdanwrc/133. Colorado Parks and Wildlife. 2017. CPW Wildlife Shapefile Download. Species Activity Data Collection. Redlands, CA: ESRI. Available at: http://www.arcgis.com/home/group.html?owner=rsacco&title=Colorado%20Parks%20and%20Wi ldlife%20-%20Species%20Activity%20Data. 109 Natural Resources Assessment Proposed Reservoir Site Pitkin County, Colorado ERO Project #6941 13 ERO Resources Corporation Federal Aviation Administration (FAA). 2017. FAA Wildlife Strike Database. Available at: https://wildlife.faa.gov/database.aspx Mead & Hunt, Inc. 2012. Aspen/Pitkin County Airport Wildlife Hazard Management Plan. Prepared for Aspen-Pitkin County Airport. U.S. Army Corps of Engineers (Corps). 2016. Regulatory Guidance Letter 16-01. http://www.usace.army.mil/Portals/2/docs/civilworks/RGLS/rgl_6-01_app1-2.pdf?ver=2016-11-01- 091706-840. Last accessed April 10, 2017. U.S. Fish and Wildlife Service (Service). 1999. Final Programmatic Biological Opinion for Bureau of Reclamation’s Operations and Depletions, Other Depletions, and Funding and Implementation of the Recovery Program Actions in the Upper Colorado River above the Confluence with the Gunnison River. U.S. Fish and Wildlife Service (Service). 2003. Migratory Bird Permit Memorandum. April 15. U.S. Fish and Wildlife Service (Service). 2017. Information for Planning and Conservation (IPaC). https://ecos.fws.gov/ipac/. Last accessed April 10, 2017. 110 ERO Project #6941 ERO Resources Corporation Appendix A Photo Log 111 PROPOSED RESERVOIR SITE JULY 20, 2017 PHOTO LOG Photo 1 ‐ The 55.7‐acre parcel on the terrace above the Roaring Fork River. Photo 2 ‐ The 1.9‐acre parcel on a steep bank. 112 PROPOSED RESERVOIR SITE JULY 20, 2017 PHOTO LOG Photo 3 ‐ Powerlines on the west side of the project area paralleling a small trail. Photo 4 ‐ The riparian corridor along the Roaring Fork River. 113 INFORMATION ONLY-MEMORANDUM TO:Mayor and City Council FROM:John D. Krueger, Director of Transportation THROUGH:Scott Miller, Assistant City Manager Trish Aragon, PE, City Engineer MEETING DATE:January 28, 2020 RE:Information Only: 2019 Traffic Count Update SUMMARY: Attached for your review are the traffic counts coming in and out of townon SH 82 taken at the Castle Creek Bridgefor 2019. The counts are compared to the 1993 target year, 2018, and prior years. The City of Aspen’s goal is to keep Average Annual Daily Traffic (AADT) levels at or below the 1993 target levels. This goal has been accomplished for the last twenty years through our award-winning Transportation Demand Management (TDM) program which includes paid parking, increased mass transit, BRT, free local transit, the Downtowner micro transit service, bike sharing, a carshare program, free carpool parking and more. BACKGROUND The City of Aspen has maintained traffic counters to track the daily traffic coming into and out of Aspen since 1999. The counts are round trip (in and out of Aspen). The permanent counter is between Cemetery Lane and the Castle Creek Bridge on SH 82. The monthly counts from 1993 and were established in the FEIS for the ETA ROD as target counts. The annual average monthly average of 23,675 is the key number and was adopted by the community as the target – not to exceed. It was also adopted in the AACP as a community target. Some months have been higher or lower than the 1993 levels but, annual average has remained lower than the 1993 target for twenty years. This is due to the many measures and programs undertaken over the years including: expanded transit, BRT, paid parking, Car Share, Bike Share, Car-pooling, employer outreach, the Downtowner, expansion of the Brush Creek Park N Ride, SH 82 bus lanes, etc. The annual traffic count chart shows the history of the traffic counts since 1999. The highest traffic counts were in 2004 and 2005. Traffic volumes dipped in 2008 – 2010 with the recession and then began trending back upward in 2011-2015. Counts peaked again in 2015 and then have decreased through 2019. The bridge construction project in 2018 greatly impacted the counts as the construction detours routed traffic away from the counters. In 2019 traffic counts are up from 2018 but slightly down from 2017. 114 The monthly chart shows that July and August are the heaviest months with the July 4th week the heaviest week of the year. The highest day ever was July 3, 2003 when counts exceeded 33,000 back in 2003. The hourly charts show the hourly average traffic counts inbound and outbound compared to the S-curves free flowing level (800/hour with little or no delays or congestion). The month of May is below this level for most of the day except for an hour or so in the morning and afternoon. The hourly chart for July shows the hourly counts above the S-curve capacity inbound and outbound for most of the day. That is why there are delays and congestion at 1pm during the day. Traffic increases early in the morning and does not come back down until about 6pm. Back in 2004/05 hourly peak volumes were as high as 1100-1200 vehicles per hour resulting in long delays on Main Street and gridlock on streets in the West end and Power Plant Road. DISCUSSION: TRAFFIC COUNT COMPARISONS: 2019 Year to Date Compared to 1993 Target Levels The 2019 traffic counts (AADT) for the year were below the 1993 target levels by 10.9%. The counts in every month in 2019 so far have been below the 1993 levels. 2019 Year to Date Compared to 2018 The 2019 traffic counts (AADT) for the year were up over 2018 by 7.%. This was mainly due to the Castle Creek and Hallam Street construction project that occurred. Traffic counts for 2019 when compared to themore normal yearof 2017 were down -4.4%. In general traffic counts have been trending downward since 2015. 2019 HIGHLIGHTS Over 7 million vehicle trips in and out of town 2019 highest month = July = 26,083 2019 highest winter month = March = 21,792 2019 lowest month = Nov = 16,805 Busiest day of 2019 = July 3 = 29,106 Busiest Week of 2019 – July 4 th week Highest hourly count = July 3 at 2pm = 2138 in and out Busiest hour inbound annually = 8-9am Busiest hour outbound annually = 4-5pm Attachments: Monthly Traffic Counts 115 MONTHLY 1993 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2019 %2019 % AADT vs 1993 vs 1993 vs 2018 vs 2018 JAN 23,800 22,701 22,504 22,827 22,945 22,837 23,816 24,398 20,588 23,387 22,584 21,745 21,254 21,994 22,607 23,859 22,956 23,415 23,649 22,766 22,418 21,262 -2,538 -10.7%-1,156 -5.2% FEB 24,300 23,638 23,910 23,932 23,207 23,694 23,400 24,162 22,356 23,000 22,449 21,131 20,730 21,376 21,684 22,077 22,405 22,804 22,825 23,486 21,871 21,717 -2,583 -10.6%-154 -0.7% MAR 24,800 25,574 24,590 24,752 23,822 23,812 25,417 25,892 23,618 23,927 23,171 21,967 23,852 22,384 22,436 22,742 23,432 24,285 23,648 23,405 22,650 21,792 -3,008 -12.1%-858 -3.8% APR 18,800 19,734 20,270 19,443 19,900 19,789 18,921 19,420 18,264 18,993 18,882 19,177 18,405 no data 17,134 17,425 17,883 19,163 18,098 17,781 14,528 18,519 -281 -1.5%3,991 27.5% MAY 19,300 18,538 19,944 18,929 19,310 18,837 18,924 19,021 18,051 18,530 17,813 17,392 17,878 17,874 19,077 17,662 17,396 17,208 18,037 17,985 11,294 17,443 -1,857 -9.6%6,149 54.4% JUN 26,200 25,408 25,126 23,719 23,618 25,003 25,650 25,097 22,552 23,940 23,279 22,877 22,701 22,724 25,124 22,966 23,884 24,993 24,501 23,986 21,218 23,259 -2,941 -11.2%2,041 9.6% JUL 28,600 26,579 27,873 27,325 28,777 29,285 29,278 29,544 26,165 27,193 26,187 25,950 26,538 25,849 26,245 26,785 27,286 27,825 26,549 26,489 25,979 26,083 -2,517 -8.8%104 0.4% AUG 28,600 25,142 27,375 26,237 27,497 27,391 27,952 27,998 24,233 26,171 24,375 23,374 24,763 24,755 25,077 26,141 25,081 25,621 25,857 25,193 24,690 24,831 -3,769 -13.2%141 0.6% SEPT 24,000 23,294 21,964 21,763 22,396 22,231 23,879 23,796 no data*22,068 21,151 no data*21,901 21,590 21,080 21,428 22,033 23,207 23,325 23,246 17,474 22,170 -1,830 -7.6%4,696 26.9% OCT 20,500 20,038 20,511 19,921 19,969 19,866 20,521 20,371 no data*19,576 19,640 no data*18,350 18,189 18,873 19,024 19,519 20,497 19,772 19,823 14,307 17,782 -2,718 -13.3%3,475 24.3% NOV 20,000 no data*18,643 18,430 no data*18,220 19,652 18,892 no data*19,076 17,930 no data*17,853 17,531 18,910 no data no data 17,390 17,790 17,910 16,431 16,805 -3,195 -16.0%374 2.3% DEC 25,200 24,743 22,847 22,394 no data*22,880 24,882 22,449 22,567 21,983 21,038 20,376 21,986 23,049 24,788 no data no data 22,524 22,298 22,905 22,066 21,597 -3,603 -14.3%-469 -2.1% ANNUAL MONTHLY TOTAL 284,100 255,389 275,557 269,672 231,441 273,845 282,292 281,040 198,394 267,844 258,499 193,989 256,211 237,315 263,035 220,109 221,875 268,932 266,349 264,975 234,926 253,260 -30,840 -10.9%18,334 7.8% ANNUAL MONTHLY AVERAGE 23,675 23,217 22,963 22,473 23,144 22,820 23,524 23,420 22,044 22,320 21,542 21,554 21,351 21,574 21,920 22,011 22,188 22,411 22,196 22,081 19,577 21,105 -2,570 -10.9%1,528 7.8% The numbers highlighted in yellow mean monthly traffic counts exceeded the 1993 levels The numbers highlighted in blue mean that monthly traffic counts exceeded the 2018 levels The numbers highlighted in orange mean that the monthy traffic counts were impacted by the Castle Creek Bridge project and detours 116 23,217 22,963 22,473 23,144 22,820 23,524 23,420 22,044 22,320 21,542 21,554 21,351 21,574 21,92022,011 22,188 22,411 22,19622,081 19,577 21,105 19,000 19,500 20,000 20,500 21,000 21,500 22,000 22,500 23,000 23,500 24,000 199920002001200220032004200520062007200820092010201120122013201420152016201720182019Annual AADT 1999 -2019 AADT 1999-2019 1993 COMMUNITY GOAL 117 JAN FEB MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC 1993 Community Goal 23,800 24,300 24,800 18,800 19,300 26,200 28,600 28,600 24,000 20,500 20,000 25,200 2017 22,766 23,486 23,405 17,781 17,985 23,986 26,489 25,193 23,246 19,823 17,910 22,905 2018 22,418 21,871 22,650 14,528 11,294 21,218 25,979 24,690 17,474 14,307 16,431 22,066 2019 21,262 21,717 21,792 18,519 17,443 23,259 26,083 24,831 22,170 17,782 16,805 21,597 11,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 19,000 20,000 21,000 22,000 23,000 24,000 25,000 26,000 27,000 28,000 29,000 30,000 MONTHLY TRAFFIC COUNT COMPARISON 1993, 2017, 2018, 2019 YTD 1993 Community Goal 2017 2018 2019 118 12:00 AM 1:00 AM 2:00 AM 3:00 AM 4:00 AM 5:00 AM 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM 6:00 PM 7:00 PM 8:00 PM 9:00 PM 10:00 PM 11:00 PM INBOUND 22 15 10 5 17 52 304 737 907 815 714 689 674 615 586 643 574 529 398 305 209 145 96 50 OUTBOUND 41 24 20 8 12 35 110 322 396 471 547 641 691 694 742 855 892 821 494 334 259 212 156 95 S-CURVES FREE FLOW 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 - 100 200 300 400 500 600 700 800 900 1,000 1,100 MAY 2017 AVERAGE HOURLY TRAFFIC COUNTS INBOUND OUTBOUND 119 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM INBOUND 45 30 16 12 33 136 485 882 1,009 1,053 1,045 1,032 1,022 987 952 977 873 850 680 517 409 301 186 84 OUTBOUND 245 139 89 29 23 81 181 361 588 675 755 844 918 928 969 947 900 856 828 635 522 520 423 266 S-CURVES FREE FLOW 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 800 0 100 200 300 400 500 600 700 800 900 1,000 1,100 JULY 2019 AVERAGE HOURLY TRAFFIC COUNTS INBOUND OUTBOUND S-CURVES FREE FLOW 120 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 12:00 AM 2019 290 170 105 41 56 217 665 1244 1597 1728 1800 1877 1939 1915 1921 1924 1773 1706 1508 1152 930 821 609 351 1993 200 175 25 10 25 125 575 1375 1900 1850 1825 1900 2050 1900 1875 2000 2100 2000 1800 1300 1000 975 825 425 S-CURVES FREE FLOW 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 1600 0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 HOURLY ROUNDTRIP 1993 V 2019 2019 1993 121