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HomeMy WebLinkAboutFile Documents.506 E Main St.0054.2019 (41).ACBK Stormwater Management Facility Inspection and Maintenance (I&M) Plan for: Pitkin County Courthouse Remodel Located at: 506 E. Main Street, Suite 300, Aspen, CO 81611 Prepared for: Anderson Hallas Architects, PC 715 Fourteenth Street Golden, CO 80401 303-278-4378 Prepared by: Mason Talkington Martin/Martin, Inc. 0101 Fawcett Road, Suite 260, Avon, CO 81620 303-926-6007 August 13, 2019 Approved On This Date __________________ City Engineer Date Reference: This plan is adapted from Southeast Metro Stormwater Authority, OPERATION AND MAINTENANCE (O & M) MANUAL, and Town of Parker, Colorado, STORMWATER PERMANENT BEST MANAGEMENT PRACTICES (PBMP) LONG-TERM OPERATION AND MAINTENANCE MANUAL, October 2004 Reviewed by Engineering 09/05/2019 1:15:13 PM "It should be known that this review shall not relieve the applicant of their responsibility to comply with the requirements of the City of Aspen. The review and approval by the City is offered only to assist the applicant's understanding of the applicable Engineering requirements." The issuance of a permit based on construction documents and other data shall not prevent the City of Aspen from requiring the correction of errors in the construction documents and other data. 2 Stormwater Management Facility Inspection and Maintenance (I&M) Plan Table of Contents I. Compliance with Stormwater Facility Maintenance Requirements II. Inspection & Maintenance- Annual Reporting III. Preventative Measures to Reduce Maintenance Costs IV. Access and Easements V. Safety VI. Field Inspection Equipment VII. Inspecting Stormwater Management Facilities A. Inspection Procedures B. Inspection Report C. Verification of Inspection and Form Submittal VIII. Maintaining Stormwater Management Facilities A. Maintenance Categories B. Maintenance Personnel C. Maintenance Forms Appendices Appendix A - Maintenance Agreement Appendix B - Description of Stormwater Management Facilities Appendix C - Standard Maintenance Procedures for Permeable Pavement Systems and Proprietary Underground Treatment Devices Appendix D – Drainage Plan w/ Identified Stormwater Facility BMP Locations 3 Stormwater Management Facility Inspection and Maintenance (I&M) Plan I. Compliance with Stormwater Facility Maintenance Requirements All property owners are responsible for ensuring stormwater facilities installed on their property are properly maintained and function as designed. Pitkin County Courthouse may elect to assign many of the management and maintenance functions described in this plan to a third party. Pitkin County Courthouse is aware of their responsibilities regarding stormwater facility maintenance. Maintenance agreement(s) associated with this property are provided in Appendix A. II. Inspection & Maintenance – Annual Reporting Requirements for the inspection and maintenance of stormwater facilities, as well as reporting requirements are included in this Stormwater Management Facility Inspection and Maintenance (I&M) Plan. Verification that the Stormwater facilities have been properly inspected and maintained; submittal of the required Inspection and Maintenance Forms and Inspector qualifications shall be provided to the City of Aspen Engineering Department on an annual basis, or as coordinated with the City of Aspen during execution of the Stormwater Best Management Practices Operations and Maintenance Agreement. Copies of the Inspection and Maintenance forms for each of the stormwater facilities are located in Appendix D and E. A standard annual reporting form is provided in Appendix F. Each form shall be reviewed by the property owner or property manager and submitted to: City of Aspen Engineering Department 130 South Galena Street Aspen, Colorado 81611 III. Preventative Measures to Reduce Maintenance Costs The most effective way to maintain your water quality facility is to prevent the pollutants from entering the facility in the first place. Common pollutants include sediment, trash & debris, chemicals, dog wastes, runoff from stored materials, illicit discharges into the storm drainage system and many others. Pitkin County Courthouse’s maintenance program includes measures to address these potential contaminants. Depending on the storm water quality facilities installed on the site the maintenance program includes: • Educate property owners/residents to be aware of how their actions affect water quality, and how they can help reduce maintenance costs. • Keep properties, streets and gutters, and parking lots free of trash, debris, and lawn clippings. 4 • Ensure the proper disposal of hazardous wastes and chemicals. • Plan lawn care to minimize the use of chemicals and pesticides. • Sweep paved surfaces regularly and dispose the sweepings properly. • Be aware of automobiles leaking fluids. Use absorbents such as cat litter to soak up drippings – dispose of properly. • Re-vegetate disturbed and bare areas to maintain vegetative stabilization. • Clean out the upstream components of the storm drainage system, including inlets, storm sewers and outfalls. • Do not store materials outdoors (including landscaping materials) unless properly protected from runoff. IV. Access A Drainage Plan showing all stormwater management facility locations on the site has been prepared and is located in Appendix G. V. Safety Keep safety considerations at the forefront of inspection procedures at all times. Likely hazards should be anticipated and avoided. Pitkin County Courthouse personnel should never enter a confined space (outlet structure, manhole, etc.) without proper training or equipment. A confined space should never be entered without at least one additional person present and without using appropriate personal protection equipment. If a toxic or flammable substance is discovered, leave the immediate area and call 911. If any hazard is found within the facility area that poses an immediate threat to public safety, call 911. VI. Field Inspection Equipment Pitkin County Courthouse inspectors shall have the appropriate equipment to take to the field. This is to ensure the safety of the inspector and allow the inspections to be performed as efficiently as possible. Below is a list of the equipment that may be necessary to perform the inspections of all Stormwater Management Facilities: • Protective clothing and boots. • Safety equipment (vest, hard hat, confined space entry equipment). • Communication equipment. • Inspection and Maintenance Plan for the site including stormwater management facility location maps. • Clipboard. • Stormwater Facility Maintenance Inspection Forms (See Appendix D). 5 • Manhole Lid Remover • Shovel. Some of the items identified above need not be carried by the inspector (manhole lid remover, shovel, and confined space entry equipment). However, this equipment should be available in the vehicle driven to the site. VII. Inspecting Stormwater Management Facilities The quality of stormwater entering the waters of the state relies heavily on the proper operation and maintenance of permanent best management practices. Stormwater management facilities shall be periodically inspected to ensure they function as designed. The inspection will determine the appropriate maintenance required for the facility. A. Inspection Procedures All stormwater management facilities shall be inspected by a qualified individual at a minimum of once per year. See the City of Aspen Urban Runoff Management Plan for general guidelines for maintenance and inspection. Inspections will follow the inspection guidance found in the SOP for the specific type of facility. (Appendix C of this manual). B. Inspection Report Pitkin County Courthouse personnel or inspector conducting the inspection activities shall complete the appropriate inspection report for the specific facility. Inspection reports are located in Appendix D. The following information explains how to fill out the Inspection Forms: General Information This section identifies the facility location, person conducting the inspection, the date and time the facility was inspected, and approximate days since the last rainfall. Property classification is identified as single- family residential, multi-family residential, commercial, or other. The reason for the inspection is also identified on the form depending on the nature of the inspection. All facilities shall be inspected on an annual basis at a minimum. In addition, all facilities shall be inspected after a significant precipitation event to ensure the facility is draining appropriately and to identify any damage that occurred as a result of the increased runoff. 6 Inspection Scoring For each inspection item, a score must be given to identify the urgency of required maintenance. The scoring is as follows: 0 = No deficiencies identified. 1 = Monitor – Although maintenance may not be required at this time, a potential problem exists that will most likely need to be addressed in the future. This can include items like minor erosion, concrete cracks/spalling, or minor sediment accumulation. This item should be revisited at the next inspection. 2 = Routine Maintenance Required – Some inspection items can be addressed through the routine maintenance program (See SOP in Appendix C). This can include items like vegetation management or debris/trash removal. 3 = Immediate Repair Necessary – This item needs immediate attention because failure is imminent or has already occurred. This could include items such as structural failure of a feature (outlet works, forebay, etc), significant erosion, or significant sediment accumulation. This score should be given to an item that can significantly affect the function of the facility. N/A This is checked by an item that may not exist in a facility. Not all facilities have all of the features identified on the form (forebay, micro-pool, etc.). Inspection Summary/Additional Comments Additional explanations to inspection items, and observations about the facility not covered by the form, are recorded in this section. Overall Facility Rating An overall rating must be given for each facility inspected. The overall facility rating should correspond with the highest score (0, 1, 2, 3) given to any feature on the inspection form. C. Verification of Inspection and Form Submittal The Stormwater Management Facility Inspection Form provides a record of inspection of the facility. Inspection Forms for each facility type are provided in Appendix D. Verification of the inspection of the stormwater facilities, the facility inspection form(s), and Inspector Qualifications shall be provided to the City of Aspen on an annual basis. The verification and the inspection form(s) shall be reviewed and submitted by Pitkin County Courthouse or the property manager. 7 Refer to Section II of this manual regarding the annual reporting of inspections. VIII. Maintaining Stormwater Management Facilities Stormwater management facilities shall be properly maintained to ensure they operate correctly and provide the water quality treatment for which they were designed. Routine maintenance performed on a frequently scheduled basis, can help avoid more costly rehabilitative maintenance that results when facilities are not adequately maintained. A. Maintenance Categories Stormwater management facility maintenance programs are separated into three broad categories of work. These categories are based largely on the Urban Drainage and Flood Control District’s Maintenance Program for regional drainage facilities. The categories are separated based upon the magnitude and type of the maintenance activities performed. A description of each category follows: Routine Work The majority of this work consists of routine scheduled inspection of the onsite permanent BMP’s. If debris or trash is observed, it should be removed to ensure the effective performance of the devices. If sediment deposition is significant (over 75% of the water quality treatment unit storage capacity) it should be removed. Sediment observed at the outlet of the underground vault should also be removed if present. These activities normally will be performed at a minimum, once a year. Springtime is preferable because deposition of sand is most likely to occur during the winter. Removal of accumulated sediments, trash and debris is typically done with a vacuum truck, and can be accomplished without entering the facilities. These items can be completed without any prior correspondence with the City of Aspen; however, completed inspection and maintenance forms shall be submitted to the City of Aspen for each inspection and maintenance activity with the annual report. Restoration Work This work consists of a variety of isolated or small-scale maintenance and work needed to address operational problems. Most of this work can be completed by a small crew, with minor tools, and small equipment. If it is necessary to enter below grade stormwater structures, procedures for confined space access should be followed. The Pitkin County Courthouse shall correspond with the City of Aspen and submit completed maintenance forms to the City of Aspen for each maintenance activity. 8 Rehabilitation Work This work consists of large-scale maintenance and major improvements needed to address failures within the stormwater management facilities. This work requires consultation with the city of Aspen and may require an engineering design with construction plans to be prepared for review and approval. This work may also require more specialized maintenance equipment, surveying, construction permits or assistance through private contractors and consultants. If it is necessary to enter below grade stormwater structures, procedures for confined space access should be followed. If these items are needed the Pitkin County Courthouse shall correspond with the City of Aspen and submit completed maintenance forms to the City of Aspen for each maintenance activity. B. Maintenance Personnel Pitkin County Courthouse maintenance personnel shall be qualified to properly maintain stormwater management facilities. Inadequately trained personnel can cause additional problems resulting in additional maintenance costs. If it is necessary to enter below grade stormwater structures, procedures for confined space access should be followed and performed under the direction of personnel with appropriate training for entering and working in confined spaces. C. Maintenance Forms The Stormwater Management Facility Maintenance Form provides a record of maintenance activities. Maintenance Forms for each facility type are provided in Appendix E. Maintenance Forms shall be completed by the Pitkin County Courthouse’s contractor completing the required maintenance items. The form shall then be reviewed by the Pitkin County Courthouse or an authorized agent of the property owner and submitted on an annual basis to the City of Aspen. Refer to Section II of this manual regarding the annual reporting of inspections and maintenance activities performed. APPENDIX A MAINTENANCE AGREEMENT STORMWATER BEST MANAGEMENT PRACTICES OPERATIONS AND MAINTENANCE AGREEMENT City of Aspen, Colorado THIS AGREEMENT, made and entered into this Full Name of Owner) day of _, 20 , by and between (Insert hereinafter called the "Landowner", and the City of Aspen, Colorado, hereinafter called the "City". WITNESSETH WHEREAS, the Landowner is the owner of certain real property described as (Pitkin County tax Map/Parcel Identification Number) located at and as more fully as follows, to wit: also known as, , hereinafter called the "Property"; and WHEREAS, the Landowner is proceeding to build on and develop the property; and WHEREAS, the stormwater management BMP Operations and Maintenance Plan for the property identified herein has been approved by the City, herein after called the “Plan”, which is attached hereto as Appendix A and made part hereof, as approved by the City, provides for management of stormwater within the confines of the Property through the use of stormwater management or Best Management Practices (BMPs) facilities; and WHEREAS, the City and the Landowner, its successors and assigns, agree that the health, safety, and welfare of the residents of City of Aspen, Colorado and the maintenance of water quality require that on-site stormwater management/BMP facilities be constructed and maintained on the Property; and WHEREAS, the City requires, through implementation of the Plan from the Landowners dated and attached hereto, that on-site stormwater management/BMPs as shown on the Plan be adequately constructed, operated, and maintained by the Landowner, its successors and assigns. NOW, THEREFORE, in consideration of the foregoing premises, the mutual covenants contained herein, and the following terms and conditions, the parties hereto agree as follows: 1. Construction of BMP facility by Landowner. The on-site stormwater management/BMP facilities shall be constructed by the Landowner, its successors and assigns, in accordance with the plans and specifications approved by the City and identified in the Plan. 2. Duty of Operation and Maintenance of Facility. The Landowner, its successors and assigns, including any homeowners association, shall adequately operate, inspect, and maintain the stormwater management/BMP facilities as acceptable to the City and in accordance with the specific operation, inspection, and maintenance requirements noted in the Plan. Adequate operation and maintenance is herein defined as good working condition so that these facilities are performing their design functions. 3. Duty of Documentation. The Landowner, its successors and assigns, shall document inspections, maintenance, and repairs performed and provide said documentation to the City or its representatives upon request. 4. Right of Entry on Property. The Landowner, its successors and assigns, hereby grant permission to the City, its authorized agents and employees, to enter upon the Property at reasonable times and upon presentation of proper identification, and to inspect the stormwater management/BMP facilities whenever the City deems necessary. The purpose of inspection is to follow-up on suspected or reported deficiencies, to respond to citizen complaints, and/or to assure safe and proper functioning of the facilities. The City shall provide the Landowner, its successors and assigns, copies of the inspection findings and a directive with timeline to commence with the repairs if necessary. 5. Failure to Maintain. In the event the Landowner, its successors and assigns, fails to construct, operate and maintain the stormwater management/BMP facilities in good working condition acceptable to the City, the City, its authorized agents and employees, may enter upon the Property and take whatever action(s) deemed necessary to correct deficiencies identified in the inspection report and to charge the costs of such construction or repairs to the Landowner. It is expressly understood and agreed that the City is under no obligation to install, construct, or routinely maintain or repair said stormwater management/BMP facilities, and in no event shall this Agreement be construed to impose any such obligation on the City. 6. Reimbursement by Landowner. In the event the City pursuant to this Agreement, performs work of any nature, or expends any funds in performance of said work for labor, use of equipment, supplies, materials, and the like, the Landowner, its successors or assigns, shall reimburse the City upon demand, within thirty (30) days of receipt thereof for all actual costs incurred by the City hereunder. 7. Duty to Inspect by City. The City, its employees or representatives, shall inspect the stormwater management/BMP facilities at a minimum of once every three years to ensure their continued and adequate functioning. 8. Release of City. The Landowner, its executors, administrators, assigns, and other successors in interests, shall release the City, its employees and designated representatives from all damages, accidents, casualties, occurrences, or claims which might arise or be asserted against said City, employees, and representatives from the construction, presence, existence, operative or maintenance of the stormwater management/BMP facilities by the Landowner or City. In the event that a claim is asserted against the City, its elected officials, City Officers or employees, the City shall promptly notify the Landowner and the Landowner shall defend, at its own expense, any suit based on the claim. If any judgment or claims against the City’s employees or designated representatives shall be allowed, the Landowner shall pay all costs and expenses regarding said judgment or claim. 9. Recording of Agreement running with the Property. This Agreement shall be recorded in the real property records of Pitkin County, Colorado, and shall constitute a covenant running with the Property or land, and shall be binding on the Landowner, its administrators, executors, assigns, heirs and any other successors in interests, in perpetuity. IN WITNESS WHEREOF the undersigned have hereunto affixed their signatures as of the date first above written. LANDOWNER: By:_ Print Name: State of Colorado ) :ss County of Pitkin ) The foregoing Agreement was acknowledged before me this day of , 20_ , by . My Commission Expires: Notary Public THE CITY OF ASPEN: By:_ Print Name: State of Colorado ) :ss County of Pitkin ) The foregoing Agreement was acknowledged before me this day of , 20_ , by . My Commission Expires: Notary Public APPENDIX B DESCRIPTION OF STORMWATER MANAGEMENT FACILITIES City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-47 Rev 11/2014 8.5.1.4 Pervious Pavement (PP) Description Pervious Pavement (PP) covers a variety of stabilized surfaces that can be used for the movement and parking of vehicles (automobiles, trucks, construction equipment, etc.) and storage of materials and equipment. Pervious pavement differs from conventional pavement. It is designed to infiltrate stormwater runoff instead of shedding it off the surface. PP offers the advantage of decreasing the effective imperviousness of an urbanizing or redevelopment site, thereby reducing runoff and pollutant loads leaving the site. Pervious pavement can be designed with and without underdrains. Whenever underdrains are used, infiltrated water will behave similarly to interflow and will surface at much reduced rates over extended periods of time. All types of pervious pavement help to return stormwater runoff hydrology to more closely resemble pre-developed conditions. However, the actual consumptive use of water falling onto Figure 8.26 Modular block permeable pavement in this small parking lot allows runoff from roof downspout, promoting infiltration and reducing the overall storage volumes for the site. Figure 8.27 Modular block permeable pavement is used for an on-street parking lane on this residential street. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-48 Rev 11/2014 the ground is considerably less than under pre-developed conditions and for grass lawns in urban areas. The designer needs to consult with a geotechnical engineer as to the suitability of each type of pervious pavement for the loads and traffic it will support and carry, and the geologic conditions the pavement will rest upon. For modular block pavement and reinforced grass pavement, the WQCV can be provided by providing adequate aggregate depth to provide the storage required for the WQCV in the pore volume beneath the pavement. Because of the very limited net open area of a cobblestone block pavement, it is generally not feasible to attain enough infiltration to provide WQCV storage beneath the pavement. All of the types of pervious pavement discussed reduce effective imperviousness. The following sections describe three types of pervious pavement that may be used in Aspen. Porous concrete and asphalt are not allowed in Aspen, largely because of experience with failures of these types of pervious pavements in other parts of Colorado. Modular Block Pavement (MBP) This pavement consists of concrete block units with open surface voids laid on a gravel sub-grade with open surface voids. These voids occupy at least 20% of the total surface area that are filled with sand (ASTM C-33 sand fine concrete aggregate or mortar sand) or sandy loam turf that has at least 50% sand by weight in its volume. However, unless the pavement will be watered regularly (i.e., using a sprinkler system ) to keep the vegetation viable, concrete sand infill is the recommended material. Modular block pavement may be sloped or flat. Modular block pavement has been in use in United States since the mid-1970s. Although field data that quantify their long-term performance are somewhat limited, the data collected locally, and at other part of United States, and the episodic reports from Canada, Australia, Asia, and Europe, indicate that properly installed modular block pavements are reliable and have experienced few problems under a wide range of climates. Cobblestone Block Pavement (CBP) This pavement consists of concrete block units replicating the appearance of cobblestone that create open voids by beveling the corners of each block and/or wider spacing between the blocks. One of the commercial “cobblestone” products that meets this description is Eco-stone™ made by Pavestone Co®. These “cobblestones” are laid on a gravel sub-grade. The surface area has voids that occupy at least 8% of the total surface area and are filled with sand or stone per the manufacturer recommendation and compliance with PICP standards. Cobblestone block pavement may also be laid on a sloped or on a flat grade. This type of pavement has been in use since the 1980s. Field data that quantify the long-term performance of cobblestone block pavement are limited; however, the data and the episodic reports from other parts of the United States, Canada, Australia, Asia and Europe indicate that when properly installed, Cobblestone block pavement is reliable and has experienced few problems under a wide range of climates. Reinforced Grass Pavement (RGP) This is a stabilized grass surface intended for use in parking lots that experience intermittent use. Past experience has shown that RGP may not be suitable for heavy vehicles, especially those associated with critical services such as fire trucks. It has been shown to function well under wet-weather conditions and, when properly designed and installed, it will infiltrate rainwater at rates that equal or exceed the infiltration rates of NRCS Hydrologic Soil Group Type B soils. The grasses need to be mowed on a cycle that depends on the grass types and whether or not irrigation is used. Use of irrigated grasses should be considered for more actively-used parking lots. Another type of reinforced grass pavement design is based on the Federal Aviation Administration’s (FAA) recommendations for Aggregate Turf originally developed for use with light aircraft that do not exceed a gross load of 12,500 pounds. This design offers a very stable surface and has a relatively simple cross-section. When it is installed using good site preparation, compaction and the specified gravel-topsoil mix, it has functioned well on small general aviation airports for many years. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-49 Rev 11/2014 General Application Modular Block and Cobblestone Block Pavement Modular block pavements and cobblestone block pavements are best suited for use in low vehicle movement zones, such as roadway shoulders, driveways, parking strips and parking lots. Vehicle movement (i.e., not parking) lanes that lead up to one of these types of porous pavement parking pads may be better served, but not always, by solid asphalt or concrete pavement. The following are potential applications for these two types of porous pavement: • Low vehicle movement zones • Crossover/emergency stopping/parking lanes • Residential street parking lanes • Private and public building driveways • Maintenance roads and trails • Roadway shoulders and parking lanes • Emergency vehicle and fire access lanes • Low vehicle movement commercial and industrial parking lots, including driveways • Commercial/retail parking lots • Equipment storage areas Reinforced Grass Pavement Reinforced grass pavement is best used in overflow parking zones or in parking lots that experience occasional uses (e.g., once-a-week-used portions of church and football stadium parking lots), roadway shoulders, residential street parking lanes, and emergency vehicle access lanes. Vehicle movement lanes (i.e., not parking pads themselves) that lead up to one of these reinforced grass pavement surfaces need to be served by solid asphalt or concrete pavement. The following are potential applications for this type of porous pavement: • Crossover/emergency stopping/parking lanes • Roadway shoulders and parking lanes • Maintenance roads and trails • Commercial/retail parking lot overflow areas • Church parking areas more remote from buildings • Residential parking areas with light use. Advantages/Disadvantages Aside from the potential for high particulate pollutant removal and the removal of other constituents similar to what a sand filter would provide, pervious pavements can dramatically reduce the surface runoff from most rainstorms and snowmelt events and virtually eliminate surface runoff from smaller storms. These reductions in runoff volumes translate directly to proportional reductions in pollutant loads leaving the site. Its use can result in stormwater surface runoff conditions that approximate the predevelopment site conditions, something that can be used in selecting surface retention and infiltration parameters that are close to pre-developed conditions when using stormwater runoff hydrologic models. Even when underdrains are used, the response time of runoff is significantly delayed and approaches the characteristics of what hydrologists call interflow (flow that enters the subsurface via infiltration and then reemerges to the surface with a time delay). As a result, drainage and downstream flooding problems can be significantly reduced. These can translate in savings since the downstream facilities needed to address site runoff, such as WQCV, detention volumes and conveyance facilities can be smaller. For modular block and reinforced grass pavements, the WQCV can actually be provided in the aggregate pore space beneath the pavement surface. If aggregate is deep enough, flood control benefits (i.e. minor storm) may also be achieved. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-50 Rev 11/2014 Another advantage that the use of pervious pavement offers is that creative selection by land planners and landscape architects of pervious pavement materials, patterns and colors can also provide aesthetic enhancements to what often are very mundane surfaces. Some types of pervious pavements may be snowmelted. The primary disadvantage of pervious pavements is that they cost more to install and maintain than conventional concrete or asphalt pavement. These added costs can be somewhat offset by the cost savings in the downsizing of on-site and downstream drainage systems and facilities such as detention basins, numbers of inlets, storm sewers and channels. Other disadvantages of pervious pavements can include uneven driving surfaces and potential inconvenience of walking on these types of surfaces in high heel shoes. Pervious pavements are not compatible with sanding activities. Snow plowing has the potential to damage many types of pervious pavements, and special plowing techniques may be necessary. Physical Site Suitability Pervious pavements can be installed even when free draining sub-soils are not present at the site by providing them with underdrains. An underdrain insures that the gravel sub-grade is drained when the sub-soils or site conditions do not allow infiltration. Not all types of pervious pavements may be suitable for heavy equipment/fire lane access. Applications of pervious pavements that are anticipated to experience heavy loads should be evaluated to assure that the pervious pavement is compatible with the intended use. In the case where the installation is located on top of expansive soils, the installation of an impermeable liner along with underdrains is strongly recommended. The liner is needed to prevent wetting the underlying expansive clays. In addition, pervious pavements installed over expansive soils should not be located adjacent to structure foundations in order to reduce the potential for damages to structures. An impermeable liner with underdrains shall be utilized anywhere pavers are installed immediately adjacent to a structure. The impermeable liner shall be installed along the foundation of the structure and extend a minimum of 10’ away from the structure walls. Liners and underdrains shall direct runoff away from the building foundation. A continuous impermeable liner with underdrains shall also be used whenever commercial or industrial sites may have activities, or processes, that could result in the storage and/or handling of toxic or caustic chemicals, fertilizers, petroleum products, fats, or greases. An impermeable liner has to be designed to prevent groundwater and soil contamination should such products or materials come into contact with stormwater and could infiltrate into the ground. If the site is expected to have contaminants mentioned above, the underdrains shall be directed or connected to runoff capture and treatment facilities. Construction Considerations The construction phase and staging is critical to producing PPS that are structurally sound and have good rates of stormwater infiltration into surface of the pavement and into the underlying sub-grade or underdrains. It is important to understand that permeable pavement systems are examples of high performance infrastructure that have two functions: a structural pavement and a stormwater management BMP. It is not sufficient to use the same construction practices for PPS as for conventional, non-porous pavement. Issues of concern that can affect the eventual performance of the PPS include but are not limited to the following:  Excessive compaction of the sub-grade and heavy equipment traffic over these surfaces.  Sediment loading from adjacent construction areas. Pervious pavements should be constructed as late in the phasing of a project as feasible, and if there are adjacent disturbed areas redundant erosion and sediment control measures should be provided (i.e. silt fence and wattles).  Proper gradation and installation of the fracture-faced aggregate and sand materials at City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-51 Rev 11/2014 various levels of the PPS cross section.  Proper use and installation of geotextiles and geogrids.  Impermeable geomembrane (liner) installation, seaming and liner penetrations.  Underdrain installation, including providing adequate slope and avoiding damage to the underdrain pipe.  Edge restraints for permeable interlocking concrete pavers and concrete grid pavement.  Achieving uniform gradation of aggregate and soils for reinforced turf type of pavements. Pollutant Removal and Effective Imperviousness Specific field data on the reductions of pollutant concentrations by various pervious pavements are very limited as of 2009. However, reductions in the concentrations of total suspended solids and associated constituents, such as metals, oils and greases appear to be relatively high. At the same time, the fact that all pervious pavements significantly reduce the average annual runoff volume makes them very effective in reducing pollutant loads reaching the receiving waters. Filtration of stormwater runoff through the sand and gravel of the modular block voids and entrapment in the gravel media are the primary removal mechanisms of pollutants. Adsorption and ion exchange that occur as stormwater travels through the underlying soils before the stormwater reaches groundwater are secondary removal mechanisms. When using pervious pavements, the site designer can take advantage of the fact that it reduces the effective surface runoff rates and volumes. Based on field testing and observations of modular block pavement by the Denver Urban Drainage and Flood Control District at a test site in Lakewood and other information gleaned from literature, interim recommendations for reducing total site imperviousness to effective imperviousness were developed. Because this represents the best currently available data, these guidelines have been adopted by Aspen. The use of these interim guidelines is recommended when planning stormwater quality and drainage facilities for new land development and redevelopment sites. These guidelines are summarized in Figure 8.28 and are called “interim” because they are based, in part, on limited amounts of short-term data and best professional judgment that considered the type of pavement, its long term maintenance needs, its sealing potential and its loss of void space volume over time. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-52 Rev 11/2014 Figure 8.28 Recommended Effective Percent Imperviousness for PPS (Based on the Ratio of the Impervious Area Tributary to Porous Pavement) The following notes apply to using Figure 8.28: 1. It is recommended that impervious areas be made to drain to pervious pavements where possible. Figure 8.28 shows the effective imperviousness values used for all paved area (impervious and pervious) in situations where impervious areas drain to pervious pavements. To calculate the ratio shown on the x-axis, divide the impervious area that drains to pervious pavement by the area that is pervious. For example if 500 ft2 of impervious area flows uniformly over 500 ft2 of pervious pavement the ratio in Figure 8.28 is 1.0. If modular block pavement is used without underdrains, the effective imperviousness for a ratio of impervious area to pervious pavement area of 1.0 would be approximately 25 percent according to Figure 8.28. The effective imperviousness, 25%, would apply to the entire 1000 ft2. 2. Use no more than two units of impervious area for each unit of PP. All impervious areas exceeding this ratio shall be treated as 100% impervious in hydrologic calculations, including runoff volumes. For example, the maximum amount of impervious area that could drain to a 500 ft2 pervious pavement area would be 1000 ft2. Any imperviousness beyond that should not be directed to the pervious pavement area or, if it must be directed to the pervious pavement area, it should be treated as 100 All PP’s (Except RGP) With Underdrains (Impervious Trib. Area)/(Pervious Pavement Area) City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-53 Rev 11/2014 percent impervious area in all calculations. 3. Whenever impervious areas cannot be made to run onto the pervious areas in a uniform sheet-flow fashion, identify individual areas and what ratios apply to each and then composite them treating each as a separate area. Cold Weather Considerations PPS have been applied in cold weather climates including the northeast, northern states in the Mid-West and even Canada. In cold climates PPS have an advantage of quicker melting of accumulated snow due to circulation of air beneath the surface. Potential challenges in cold climates include plugging from accumulated sediment (sanding) and freeze-thaw deterioration. These disadvantages can be minimized in the following ways:  PPS may not be used in areas that are sanded or in locations where adjacent tributary drainage areas are sanded.  Signage should be used for PPS to caution against sanding.  Achieving a well-drained sub-base is critical to avoid problems with freezing. Studies in the northeast have shown that PPS with at least 12 inches of sub-base material are more resistant to freeze-thaw damage. It may be feasible to install a snowmelt system beneath the surface of cobblestone block or modular block pavements; however, care should be taken to assure that the snowmelt tubing does not interfere with infiltration. Design Considerations Design criteria for pervious pavements vary depending on the wearing course. Volume 3 of the UDFCD Urban Storm Drainage Criteria Manual provides extensive guidance for all of the types of pervious pavements in this Manual. Because of the length of the UDFCD guidance (more than 80 pages) and the desire to keep the Aspen Manual streamlined, the following is provided as general guidance and criteria for pervious pavements. The designer should refer to the Denver Urban Storm Drainage Criteria Manual for detailed guidance, figures, etc. All pervious pavement designs in the City of Aspen should be checked against the most current version of Volume 3 of the UDFCD guidance since pervious pavement criteria are currently evolving. Modular Block and Cobblestone Block Pavements Figure 8.29 below shows one type of locally available modular block pervious pavement. There are other block patterns that may be used, provided they have at least 20 percent (≥ 40% preferred) of their surface area as open annular spaces. This is the minimum open surface area to be considered as modular block pavement. Figure 8.29 Modular Block Pavement City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-54 Rev 11/2014 Figure 8.30 is of a typical cobble block pervious pavement available locally. It has to have at least eight percent (8%) of its surface area as open annular spaces to qualify as cobblestone block pervious pavement. Figure 8.30 Cobblestone Block Pavement Figure 8.31 below shows typical cross-sections for modular block and cobblestone block pervious pavements. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-55 Rev 11/2014 Figure 8.31 Typical Pervious Pavement Cross Section City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-56 Rev 11/2014 Figure 8.32 Membrane Liner/Concrete Connection Detail City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-57 Rev 11/2014 Table PPS-1. Gradation Specifications for Class C Filter Material (Source: CDOT Table 703-7) Sieve Size Mass Percent Passing Square Mesh Sieves 19.0 mm (3/4”) 100 4.75 mm (No. 4) 60-100 300 μm (No. 50) 10-30 150 μm (No. 100) 0-10 75 μm (No. 200) 0-3 Table PPS-2. Dimensions for Slotted Pipe Pipe Diameter Slot Length1 Maximum Slot Width Slot Centers1 Open Area1 (per foot) 4” 1-1/16” 0.032” 0.413” 1.90 in2 6” 1-3/8” 0.032” 0.516” 1.98 in2 1 Some variation in these values is acceptable and is expected from various pipe manufacturers. Be aware that both increased slot length and decreased slot centers will be beneficial to hydraulics but detrimental to the structure of the pipe. Table PPS-3. Physical Requirements for Separator Fabric1 Property Class B Test Method Elongation <50%2 Elongation >50%2 Grab Strength, N (lbs) 800 (180) 510 (115) ASTM D 4632 Puncture Resistance, N (lbs) 310 (70) 180 (40) ASTM D 4833 Trapezoidal Tear Strength, N (lbs) 310 (70) 180 (40) ASTM D 4533 Apparent Opening Size, mm (US Sieve Size) AOS < 33 mm (US Sieve Size No. 50) ASTM D 4751 Permittivity, sec -1 0.02 default value, Must also be greater than that of soil ASTM D 4491 Permeability, cm/sec K fabric > k soil for all classes ASTM D 4491 Ultraviolet Degradation at 500 hours 50% strength retained for all classes ASTM D 4355 Table PPS-4. Physical Requirements for Geomembrane Property Thickness 0.76 mm (30 mil) Test Method Thickness, % Tolerance ±5 ASTM D 1593 Tensile Strength, kN/m (lbs/in) width 12.25 (70) ASTM D 882, Method B Modulus at 100% Elongation, kN/m (lbs/in) 5.25 (30) ASTM D 882, Method B Ultimate Elongation, % 350 ASTM D 882, Method A City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-58 Rev 11/2014 Tear Resistance, N (lbs) 38 (8.5) ASTM D 1004 Low Temperature Impact, °C (°F) -29 (-20) ASTM D 1790 Volatile loss, % max. 0.7 ASTM D 1203, Method A Pinholes, No. Per 8 m2 (No. per 10 sq. yds.) max. 1 N/A Bonded Seam Strength, % of tensile strength 80 N/A Reinforced Grass Pavement Figure 8.33 shows typical cross-sections and details for one type of reinforced grass pavement based on a product called Grasspave2™ by Invisible Structures, Inc. Other products that achieve the same end goal and structural stability are also available. Regardless of which brand of product is used, the manufacturer’s instructions should be closely followed except as called for differently in this Chapter. The typical section of an RGP design based on the Federal Aviation Administration’s (FAA) recommendations for Aggregate Turf is illustrated in Figure 8.34. The thickness is designed same as for asphalt pavement; however the design includes extra base course thickness for compensate in the carrying capacity of asphalt pavement sections. When designing and installing Aggregate Turf, it is critical that the sub-grade be adequately compacted, especially when the gravel and pavement is being placed on fill. Additional guidance is provided in Volume 3 of the Denver UDFCD Urban Storm Drainage Criteria Manual City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-59 Rev 11/2014 Figure 8.33 Typical Reinforced Grass Pervious Pavement Cross Section 10" MINIMUM OF COMPACTED SANDY GRAVEL ** Y X SUPPLIED BY MANUFACTURER A A VA 1. INSTALL GRASS TURF REINFORCING LAYER 2. DETAIL BASED ON INVISIBLE STRUCTURES, INC., ET AL DETAILS, BUT MODIFIED TO SUIT USDCM REQUIREMENTS. NOTES: A A AA Y ASTM C-33 CONCRETE SAND LEVELING COURSE TOP OF GRASS ROOT MASS1/4" ABOVE TOP OF RING 10" MINIMUM OF WELL COMPACTED SANDY GRAVEL **A 1" ASTM C- 33 CONCRETE SAND A GRASSPAVE Y X Y AA ** GREATER DEPTH OF PAVEMENT MAY BE REQUIRED BY PAVEMENT DESIGNER MIX OF 60% AASHTO #67 (CDOT SECT. 703 #67) AGGREGATE AND 40% ASTM C-33 SAND PER MANUFACTURER' S RECOMMENDATIONS INCLUDE MODIFICATIONS SHOWN ON THIS DRAWING. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-60 Rev 11/2014 Figure 8.34 Typical Aggregate Turf Reinforced Grass Pervious Pavement Cross Section Design Procedure and Criteria Modular Block Pervious Pavement 1. Select Blocks Select MBP that have 20% or more (40% preferred) of the surface area open. Follow Manufacturer’s installation instructions, except that Porous Pavement Infill and Base Course materials and dimensions specified in this section shall be strictly adhered to. 2. Infill materials and Leveling Course The MBP openings shall be filled with ASTM C-33 graded sand or very sandy loam and shall be placed on a one-inch thick leveling course of C-33 sand. 3. Base Course The Base Course shall be AASHTO No. 3 coarse aggregate; all fractured surfaces. For volume calculations assume 30 percent of total volume to be open pore space. Unless an underdrain is provided, at least 6-inches of the sub-grade underlying the Base Course shall be sandy and gravely material with no more than 10% clay fraction. 4. Impermeable Liner Under the Base Course When expansive or NRCS Type D soils are present, or potential for groundwater contamination exists, install an impermeable 30 mil thick, or heavier, liner on the bottom and sides of the basin under the pavement. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-61 Rev 11/2014 5. Membrane Installation Place by rolling membrane parallel to the contours starting at the most downstream part of the pavement. Provide a minimum of 18-inches of overlap between adjacent sheets. Bring up impermeable membrane to the top of perimeter walls. Attach membrane to perimeter walls with roofing tar or other adhesive or concrete anchors. Provide sufficient slack in the membranes to prevent stretching them when sand and/or rock is placed. Seal all joints of impermeable membrane to be totally leak free. 6. Perimeter Wall Recommend that a concrete perimeter wall be installed to confine the edges of the MBP block areas. 7. Contained Cells – Lateral Flow Barriers Install lateral-flow cut-off barriers using 30 mil, or thicker, PE or PVC membrane liner or concrete walls installed parallel to the contours (i.e., normal to the flow) to prevent flow of water downstream and then surfacing at the toe of the PP installation. Distance (L MAX ) between these cut-off barriers shall not exceed: O MAX S DL•=5.1 in which, L MAX = Maximum distance between cut off membrane normal to the flow (ft.), S O = Slope of the base course (ft/ft), D = Depth of gravel Base Course (ft). 8. Sub-drain System When the MBP is located on NRCS Type D soils, when the Type B or C soil sub-base is to be compacted for structural reasons, or when an impermeable membrane liner is needed, install a sub-drain system using Schedule 40 HDPE pipe. Locate each perforated pipe just upstream of the lateral-flow cut-off barrier. Do not exceed 20-foot spacing. Use a control orifice sized to drain the pore volume to empty each cell in 6-12 hours. 9. Design Area Ratio and Effective Imperviousness The design area ratio shall not exceed 2.0 (ratio = contributing impervious area divided by porous pavement area). In certain cases where the land use of the contributing drainage basin is known to carry low sediment levels, a slightly higher design area ratio may be permitted. The interim recommendations for the “Effective Imperviousness” are given in Figure 8.28 and may be used when sizing detention basins, WQCV and stormwater conveyance systems. Cobblestone Block Pervious Pavement 1. Select Blocks Select CBP blocks that have 8% or more of the surface area open. Follow Manufacturer’s installation instructions, except that Porous Pavement Infill and Base Course materials and dimensions specified in this section shall be strictly adhered to. 2. Infill materials and Leveling Course The CBP openings shall be filled with AASHTO No. 8 fractured aggregate and shall be placed on a one-inch thick leveling course of same No. 8 aggregate. 3. Base Course The Base Course shall be AASHTO No. 67 coarse aggregate; all fractured surfaces. For volume calculations assume 30 percent of total volume to be open pore space. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-62 Rev 11/2014 4. Impermeable Liner Under Bottom Sand Layer When expansive or NRCS Type D soils are present, or potential for groundwater contamination exists, install an impermeable 30 mil thick, or heavier, liner on the bottom and sides of the basin under the pavement. 5. Membrane Installation Place by rolling membrane parallel to the contours starting at the most downstream part of the pavement. Provide a minimum of 18-inches of overlap between adjacent sheets. Bring up impermeable membrane to the top of perimeter walls. Attach membrane and fabric to perimeter walls with roofing tar or other adhesive or concrete anchors. Provide sufficient slack in the membranes to prevent stretching them when sand and/or rock is placed. Seal all joints of impermeable membrane to be totally leak free. 6. Perimeter Wall Recommend that a concrete perimeter wall be installed to confine the edges of the MBP or CBP block areas. 7. Contained Cells – Lateral Flow Barriers Install lateral-flow cut-off barriers using 30 mil, or thicker, PE or PVC membrane liner or concrete walls installed parallel to the contours (i.e., normal to the flow) to prevent flow of water downstream and then surfacing at the toe of the PP installation. Distance (L MAX ) between these cut-off barriers shall not exceed: O MAX S DL•=5.1 in which, L MAX = Maximum distance between cut off membrane normal to the flow (ft.), S O = Slope of the base course (ft/ft), D = Depth of gravel Base Course (ft). 8. Sub-drain System When the CBP is located on NRCS Type D soils, when the Type B or C soil sub-base is to be compacted for structural reasons, or when an impermeable membrane liner is needed, install a sub-drain system using Schedule 40 HDPE pipe. Locate each perforated pipe just upstream of the lateral-flow cut- off barrier. Do not exceed 20-foot spacing. Use a control orifice sized to drain the pore volume of empty each cell in 6-12 hours 9. Design Area Ratio and Effective Imperviousness The design area ratio shall not exceed 2.0 (ratio = contributing impervious area divide by porous pavement area). In certain cases where the land use of the contributing drainage basin is known to carry low sediment levels, a slightly higher design area ratio may be permitted. The interim recommendations for the “Effective Imperviousness” are given in Figure 8.28 and may be used when sizing detention basins, WQCV and stormwater conveyance systems. Reinforced Grass Pavement 1. Select Type of RGP to be Used Select which type of RGP will be used. The two types that are described in this Manual are Reinforced Grass, as illustrated in Figure 8.33 and Aggregate Turf, as illustrated in Figure 8.34. 2. Base Course for Provide the required Base Course of AASHTO No. 67 (CDOT Section 703) coarse aggregate for the Reinforced Grass type of RGP as called for in Figure City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-63 Rev 11/2014 Reinforced Grass 8.33. The aggregate shall have all fractured surfaces. No Base Course is required for Aggregate Turf. 3. Impermeable Membrane Under the Base Course For Reinforced Grass type of RGP, and when expansive or NRCS Type D soils are present, or potential for groundwater contamination exists, install an impermeable 30 mil thick, or heavier, liner on the bottom and sides of the basin under the pavement. 4. Membrane Installation Place by rolling impermeable membrane parallel to the contours starting at the most downstream part of the pavement. Provide a minimum of 18-inches of overlap between adjacent sheets. Bring up impermeable membrane to the top of perimeter walls. Attach membrane to perimeter walls with roofing tar or other adhesive or concrete anchors. Provide sufficient slack in the membranes to prevent stretching them when sand and/or rock is placed. Seal all joints of impermeable membrane to be totally leak free. 5. Design Area Ratio and Effective Imperviousness The design area ratio shall not exceed 2.0 (ratio = contributing impervious area divide by porous pavement area). In certain cases where the land use of the contributing drainage basin is known to carry low sediment levels, a slightly higher design area ratio may be permitted. The interim recommendations for the “Effective Imperviousness” are given in Figure 8.28 and may be used when sizing detention basins, WQCV and stormwater conveyance systems. Construction/Installation The construction phase is very critical in having a successful pervious pavement installation. Successful PP installations are structurally sound and have good rates of stormwater infiltration into surface of the pavement and into the underlying sub-base or underdrains. It is not sufficient to use the same construction practices for pervious pavement as for conventional, non-porous pavement. Issues of concern are excessive compaction of the sub-grade and heavy equipment traffic over these surfaces, proper gradation and installation of the gravel and sand materials at various levels of the pervious pavement section, proper use and installation of geotextile and impermeable liner membranes, edge restraints for modular block types of pervious pavements, achieving uniform gradation of gravels and soils for reinforced turf type of pavements and other issues that can affect the eventual performance of the pervious pavement. Sub-grade When the native soils in the sub-grade are suitable for infiltration (i.e., NRCS Hydrologic Group A, B and C), it is important maintain their infiltration capacities as much as possible. When the sub-base is deliberately compacted to provide greater pavement stability or is inadvertently compacted by construction equipment traffic over them, infiltration capacity will be significantly reduced. To prevent the latter, it is crucial that heavy construction equipment, especially rubber-tired machinery, be kept off the sub-grade. This will require the use of light track equipment, delivery of gravels via conveyors, delivery of concrete via extended chutes (not conveyors) or lift pour buckets, and stopping all work when the sub- grade is wet or thawing. When compaction of the sub-grade is needed for structural support of the pavement that will carry or park vehicular traffic, an underdrain system may be needed to compensate for the loss of infiltration capacity. This will be the case if the sub-grade soils have significant fractions of silt or clay and are not granular in nature (e.g., not Type A or B). City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-64 Rev 11/2014 Compaction of the sub-grade is recommended for sites where the pavement will be placed on top of fill. Unless the fill is composed of predominantly granular materials, the engineer needs to plan for underdrains for all PP types except Aggregate Turf, which essentially duplicates natural grass surfaces. Preventing Clogging from Excess Sediment It is common to install pavement before all site work such as landscaping and finishing of buildings is completed. As a result, sediment loads from construction and landscaping activities after the pervious pavement is installed can be very high. It crucial to protect all surfaces of the pervious pavement from runoff and sediment deposits until all construction activities are completed and the areas tributary to the pervious pavement are fully stabilized. Regardless of the type of pervious pavement being used, the highest priority during construction has to be to prevent sediment from entering the base course and the surface of pervious pavement. The following practices will help to keep the pervious pavement form being clogged during these construction periods: • Keep muddy equipment and materials away from the pervious pavement area • Install silt fences and temporary swales to divert water away from the pervious pavement area • Cover the surfaces with heavy flexible impermeable membrane whenever construction activities threaten to deposit sediment onto the pervious pavement area Base Course Each lift shall not exceed 6-inches and shall be compacted by using a 10-ton, or heavier, vibrating steel drum roller. Make at least four passes with the roller, with the initial passes made while vibrating the roller and the final one to two passes without vibration. If the design calls for an upper layer of the Base Course, install it using the same layer thicknesses and compaction requirements described above. Follow-up the installation of the uppermost layer of the Base Course by installing the specified geotextile fabric on top of it. The leveling course or porous pavement, as required by the plans, is then applied over the uppermost geotextile fabric. When a sand leveling course is called for in the plans, compact it using the drum roller before laying the paver units on top of it. If the top of the Base Course, sand filter layer or the leveling course layers are disturbed and not uniform, they shall be re-leveled and re-compacted. The top of each layer below the leveling course shall uniform and will not deviate more than +1/2-inch when a 10 foot straight edge is laid on its surface. The top of the leveling course shall not deviate more than +3/8-inch in 10 feet. Modular Block and Cobblestone Block Installation Place the paver blocks tightly against each other on top of the compacted sand leveling course. Before compacting the pavers into place, cut and place paver units to tightly fill spaces between adjacent pavers and the restraining wall at the edges. Compact the installed paver blocks initially using a plate compactor that exerts a minimum of 5,000 lbs/ft2 when using 4-inch thick pavers and a minimum of 6,800 lbs/ft2 when using pavers thicker than 4-inches. After initial compaction, fill the paver openings and joints to the top with ASTM C-33 sand and compact again. If the sand or gravel infill drops more than 1/8 inch below the top of the paver block, add more sand and re-compact. Remove excess sand or gravel by broom sweeping the surfaces. Paver installation can be done by hand or using mechanical equipment specially designed for this type of work. If the latter is used, follow the requirements and procedures provided in the ICPT (1998) Technical Specification 11 – Mechanized Installation of Interlocking Concrete Pavements. Reinforced Grass Pavement Installation For the Reinforced Grass type of installations adhere strictly to the recommendations of the manufacturer for the installation of this pavement. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-65 Rev 11/2014 Maintenance Tables 8.8 through 8.10 outline maintenance recommendations for pervious pavements. Table 8.8 Maintenance Recommendations for Modular Block Pervious Pavement Required Action Maintenance Objective and Action Frequency of Action Debris and litter removal Accumulated material should be removed as a source control measure. Routine – As needed. Sod maintenance If sandy loam turf is used, provide lawn care, irrigation system, and inlay depth maintenance as needed. Routine – As dictated by inspection. Inspection Inspect representative areas of surface filter sand or sandy loam turf for accumulation of sediment or poor infiltration. Routine and during a storm event to ensure that water is not bypassing these surfaces on frequent basis by not infiltrating into the pavement. Rehabilitating sand infill surface To remove fine sediment from the top of the sand and restore its infiltrating capacity. Routine – Sweep the surface annually and, if need be, replace lost sand infill to bring its surface to be ¼ below the adjacent blocks. Replacement of Surface Filter Layer Remove, dispose, and replace surface filter media by pulling out turf plugs or vacuuming out sand media from the blocks. Replace with fresh ASTM C-33 sand or sandy loam turf plugs, as appropriate. Non-routine – When it becomes evident that runoff does not rapidly infiltrate into the surface. May be as often as every two year or as little as every 5 to 10 years. Replace modular block pavement Restore the pavement surface. Remove and replace the modular pavement blocks, the sand leveling course under the blocks and the infill media when the pavement Surface shows significant deterioration. Non-routine – When it becomes evident that the modular blocks have deteriorated significantly. Expect replacement every 10 to 15 years dependent on use and traffic. Table 8.9 Maintenance Recommendations for Cobblestone Block Pervious Pavement Required Action Maintenance Objective and Action Frequency of Action Debris and litter removal Accumulated material should be removed as a source control measure. Routine – As needed. Inspection Inspect representative areas of surface filter fine gravel infill for accumulation of sediment and poor infiltration. Routine and during a storm events to ensure that stormwater is infiltrating and not bypassing the pavement surface on frequent basis. Rehabilitating fine grave infill surface To remove fine sediment and trash accumulations from the top of the gravel and restore its infiltrating capacity. Routine – Vacuum sweep the as indicated by inspection and if need be replace lost or clogged gravel infill to bring its surface to be ¼ below the adjacent blocks. Replace cobble block pavement Restore the pavement surface. Remove and replace the cobble pavement blocks, the leveling course under the blocks, the infill media, gravel base and geotextile materials when the pavement surface shows Non-routine – When it becomes evident that the modular blocks have deteriorated significantly and the underlying gravels have accumulated much sediment and/or when the geotextile fabrics underneath it are clogged. Expect replacement every 10 City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-66 Rev 11/2014 significant deterioration or when the pavement no longer infiltrates stormwater at rates that are acceptable. to 25 years dependent on use and traffic. Table 8.10 Maintenance Recommendations for Reinforced Grass Pervious Pavement Required Action Maintenance Objective and Action Frequency of Action Debris and litter removal Accumulated material should be removed as a source control measure. Routine – As needed. Inspection Inspect all surface areas for healthy grass growth, areas of dead grass, tire rutting, surface erosion, accumulation of sediment and slow infiltration. Routine and during a storm events to ensure that water is infiltrating and not bypassing the pavement’s surface on frequent basis. Repair sod surface To repair worn out or damaged sod with sod grown in very sandy loam type soils. Routine – As needed. Repairs may be needed as often as every year. Repair and replacement of sod Major repair of damaged and aged sod. Remove and replace, as needed the sod layer to maintain a healthy vegetative cover or when sod layer builds up significant amount of silt (i.e., >1.5 inches) above the originally installed surface layer. Non-routine – When it becomes evident that many parts of the sod has deteriorated or when runoff does not rapidly infiltrate into the surface. Major replacement of sod may be as little as every 10 to 25 years. 8.5.1.5 Green Roofs (GR) Figures 8.35 and 8.36 Two local examples of green roofs are pictured above. These roofs have a significant impact on stormwater runoff and are aesthetically pleasing while providing extra insulation for homes. A wide variety of plants can be used on green roofs. These plants help reduce the impervious area of roofs to nearly zero in some cases. City of Aspen Urban Runoff Management Plan Chapter 8 – Water Quality 8-121 Rev 11/2014 8.5.4.3 Proprietary Underground Treatment Devices Proprietary underground treatment devices are allowable in Aspen as long as they meet the treatment objectives described in Section 8.4 (90 percent removal of total suspended solids 60 microns and coarser for 80 percent of runoff events on an annual basis). It is the responsibility of the applicant to provide documentation that the BMP will meet this criterion. The City reserves the right to not accept any proprietary BMP proposed. Documentation of performance must meet the following criteria: 1. Testing must consist of field data collected in substantial compliance with the Technology Acceptance and Reciprocity Partnership (TARP). Laboratory studies will not be considered. Information on the TARP program can be found in several locations on the internet including http://www.dep.state.pa.us/dep/deputate/pollprev/techservices/tarp/. 2. Data collected in environments similar to Aspen (i.e. high-mountain, cold climates). Data from other climates may be considered; however, the City may deem data collected in dissimilar locations (e.g. Florida) unacceptable. Many studies have been conducted over the past decade to document the performance of proprietary BMPs. Sources of data that may be used to support using a proprietary BMP include the following: • International Stormwater BMP Database (www.bmpdatabase.org). • University of Massachusetts Amherst Stormwater Technologies Clearinghouse (www.mastep.net). Other data sources may also be acceptable, provided they meet the documentation criteria above. Maintenance of any underground BMP, proprietary or not, is of utmost importance. For proprietary BMPs, manufacturers’ recommended maintenance shall be followed. Where frequency of inspection and maintenance activities vary from the requirements described above for dry wells, the stricter (more frequent) schedule shall be followed. APPENDIX C STANDARD MAINTENANCE PROCEDURES FOR PERMEABLE PAVEMENT SYSTEMS AND PROPRIETARY UNDERGROUND TREAMENT DEVICES Chapter 6 BMP Maintenance November 2010 Urban Drainage and Flood Control District 6-15 Urban Storm Drainage Criteria Manual Volume 3 Photograph 6-4. This broom sweeper will only remove debris from the pavement surface. Broom sweepers are not designed to remove solids from the void space of a permeable pavement. Use a vacuum or regenerative air sweeper to help maintain or restore infiltration through the wearing course. 10.3 Aquatic Plant Harvesting Harvesting plants will permanently remove nutrients from the system although removal of vegetation can also resuspend sediment and leave areas susceptible to erosion. For this reason, UDFCD does not recommend harvesting vegetation as routine maintenance. However, aquatic plant harvesting can be performed if desired to maintain volume or eliminate nuisances related to overgrowth of vegetation. When this is the case, perform this activity during the dry season (November to February). This can be performed manually or with specialized machinery. If a reduction in cattails is desired, harvest them annually, especially in areas of new growth. Cut them at the base of the plant just below the waterline, or slowly pull the shoot out from the base. Cattail removal should be done during late summer to deprive the roots of food and reduce their ability to survive winter. 10.4 Sediment Removal If the channel becomes overgrown with plants and sediment, it may need to be graded back to the original design and revegetated. The frequency of this activity is dependent on the site characteristics and should not be more than once every 10 to 20 years. 11.0 Permeable Pavement Systems The key maintenance objective for any permeable pavement system is to know when runoff is no longer rapidly infiltrating into the surface, which is typically due to void spaces becoming clogged and requiring sediment removal. This section identifies key maintenance considerations for various types of permeable pavement BMPs. 11.1 Inspection Inspect pavement condition and observe infiltration at least annually, either during a rain event or with a garden hose to ensure that water infiltrates into the surface. Video, photographs, or notes can be helpful in measuring loss of infiltration over time. Systematic measurement of surface infiltration of pervious concrete, Permeable Interlocking Concrete Pavers (PICP), concrete grid pavement, and porous asphalt 1 1 Porous asphalt is considered a provisional treatment BMP pending performance testing in Colorado and is not included in this manual at the present time. can be accomplished using ASTM C1701 Standard Test Method for Infiltration Rate of In Place Pervious Concrete. BMP Maintenance Chapter 6 6-16 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 11.2 Debris Removal, Sweeping, and Vacuuming • All Pavements: Debris should be removed, routinely, as a source control measure. Typically, sites that require frequent sweeping already plan for this activity as part of their ongoing maintenance program. For example, a grocery store may sweep weekly or monthly. Depending on the season, city streets also may have a monthly plan for sweeping. This is frequently performed with a broom sweeper such as the one shown in Photo 6-4. Although this type of sweeper can be effective at removing solids and debris from the surface, it will not remove solids from the void space of a permeable pavement. Use a vacuum or regenerative air sweeper to help maintain or restore infiltration. If the pavement has not been properly maintained, a vacuum sweeper will likely be needed. • PICP, Concrete Grid Pavements (with aggregate infill), Pervious Concrete, and Porous Asphalt1: Use a regenerative air or vacuum sweeper after any significant site work (e.g., landscaping) and approximately twice per year to maintain infiltration rates. This should be done on a warm dry day for best results. Do not use water with the sweeper. The frequency is site specific and inspections of the pavement may show that biannual vacuuming is more frequent than necessary. After vacuuming PICP and Concrete Grid Pavers, replace infill aggregate as needed. 11.3 Snow Removal In general, permeable pavements do not form ice to the same extent as conventional pavements. Additionally, conventional liquid treatments (deicers) will not stay at the surface of a permeable pavement as needed for the treatment to be effective. Sand should not be applied to a permeable pavement as it can reduce infiltration. Plowing is the recommended snow removal process. Conventional plowing operations should not cause damage to the pavements.  PICP and Concrete Grid: Deicers may be used on PICP and grid pavers; however, it may not be effective for the reason stated above. Sand should not be used. If sand is accidently used, use a vacuum sweeper to remove the sand. Mechanical snow and ice removal should be used.  Pervious Concrete: Do not use liquid or solid deicers or sand on pervious concrete. Deicers can damage the concrete and sand will reduce infiltration. Mechanical snow and ice removal should be used.  Porous Asphalt2 11.4 Full and Partial Replacement of the Pavement or Infill Material : Use liquid or solid deicers sparingly; mechanical snow and ice removal is preferred. Do not apply sand to porous asphalt.  PICP and Concrete Grid: Concrete pavers, when installed correctly, should have a long service life. If a repair is required, it is frequently due to poor placement of the paver blocks. Follow industry guidelines for installation and replacement after underground repairs. If surface is completely clogged and rendering a minimal surface infiltration rate, restoration of surface infiltration can be achieved by removing the first ½ to 1 inch of soiled aggregate infill 2 Porous asphalt is considered a provisional treatment BMP pending performance testing in Colorado and is not included in this manual at the present time. Chapter 6 BMP Maintenance November 2010 Urban Drainage and Flood Control District 6-17 Urban Storm Drainage Criteria Manual Volume 3 material with a vacuum sweeper. After cleaning, the openings in the PICP will need to be refilled with clean aggregate infill materials. Replacement of the infill is best accomplished with push brooms.  Porous Gravel: Remove and replace areas of excessive wear or reduced infiltration as needed. The frequency is dependent on site characteristics including site uses, vegetation, and materials.  Pervious Concrete: Partial replacement of pervious concrete should be avoided. If clogged, power washing or power blowing should be attempted prior to partial replacement because saw cutting will cause raveling of the concrete. Any patches should extend to existing isolated joints. Conventional concrete may be used in patches, provided that 90 percent of the original pervious surface is maintained.  Reinforced Grass: Remove and replace the sod cover as needed to maintain a healthy vegetative cover or when the sod layer accumulates significant amount of sediment (i.e., >1.5 inches). Maintenance and routine repairs should be performed annually, with sod replacement approximately every 10 to 25 years. When replacing sod, use a high infiltration variety such as sod grown in sandy loam.  Porous Asphalt3 12.0 Underground BMPs : Conventional asphalt may be used in patches, provided that 90 percent of the original permeable surface is maintained. Maintenance requirements of underground BMPs can vary greatly depending on the type of BMP. Frequent inspections (approximately every three months) are recommended in the first two years in order to determine the appropriate interval of maintenance for a given BMP. This section provides general recommendations for assorted underground BMPs. For proprietary devices, the manufacturer should provide detailed maintenance requirements specific for the BMP. 12.1 Inspection  All Underground BMPs: Inspect underground BMPs at least quarterly for the first two years of operation and then twice a year for the life of the BMP, if a reduced inspection schedule is warranted based on the initial two years. Specifically look for debris that could cause the structure to bypass water quality flows. Strong odors may also indicate that the facility is not draining properly. Inspection should be performed by a person who is familiar with the operation and configuration of the BMP.  Inlet Inserts: Inspect inlet inserts frequently; at a minimum, inspect after every storm event exceeding 0.6 inches. Removal of flow blocking debris is critical for flood control. 12.2 Debris Removal, Cartridge Replacement, and Vacuuming  All Underground BMPs: Follow the manufacturer's recommended maintenance requirements and remove any flow blocking debris as soon as possible following inspection. 3 Porous asphalt is considered a provisional treatment BMP pending performance testing in Colorado and is not included in this manual at the present time. CDS® Inspection and Maintenance Guide ENGINEERED SOLUTIONS Maintenance The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill should be cleaned out immediately. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be power washed to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. CDS Diameter Distance from Water Surface Sediment Model to Top of Sediment Pile Storage Capacity ft m ft m yd3 m3 CDS2015-4 4 1.2 3.0 0.9 0.9 0.7 CDS2015 5 1.5 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.1 1.3 1.0 CDS2025 5 1.5 4.0 1.2 1.3 1.0 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3030 6 1.8 4.6 1.4 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 8 2.4 4.6 1.4 5.6 4.3 CDS4040 8 2.4 5.7 1.7 5.6 4.3 CDS4045 8 2.4 6.2 1.9 5.6 4.3 CDS5640 10 3.0 6.3 1.9 8.7 6.7 CDS5653 10 3.0 7.7 2.3 8.7 6.7 CDS5668 10 3.0 9.3 2.8 8.7 6.7 CDS5678 10 3.0 10.3 3.1 8.7 6.7 Table 1: CDS Maintenance Indicators and Sediment Storage Capacities 800.925.5240 www.ContechES.com Support • Drawings and specifications are available at www.contechstormwater.com. • Site-specific design support is available from our engineers. ©2014 Contech Engineered Solutions LLC Contech Engineered Solutions LLC provides site solutions for the civil engineering industry. Contech’s portfolio includes bridges, drainage, sanitary sewer, stormwater, earth stabilization and wastewater treament products. For information, visit www.ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS AN EXPRESSED WARRANTY OR AN IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. SEE THE CONTECH STANDARD CONDITION OF SALES (VIEWABLE AT WWW.CONTECHES.COM/ COS) FOR MORE INFORMATION. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; 7,517,450 related foreign patents or other patents pending. cdsMaintenance 11/14 ENGINEERED SOLUTIONS CDS Inspection & Maintenance Log CDS Model: Location: Water Floatable Describe Maintenance Date depth to Layer Maintenance Personnel Comments sediment 1 Thickness 2 Performed —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— —————————————————————————————————————————————————————————— 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note: to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately. APPENDIX D DRAINAGE PLAN W/ IDENTIFIED STORMWATER FACILITY LOCATIONS 4" 4"4" 8" 4" 4" 24" 4" 4" 16" 17" 7" 19" 4" 4" 4" 24" 20" 4" 9" 9" 9" 8" 12" 11" 4 4.2 4.1 Project Number Date Drawn by Checked by Anderson Hallas Architects, PC ARCHITECTURE HISTORIC PRESERVATION COPYRIGHT 2018 ANY UNAUTHORIZED USE OF THESE DOCUMENTS IS PROHIBITED WITHOUT THE WRITTEN CONSENT OF: ANDERSON HALLAS ARCHITECTS, P.C. PLANNING Issue 715 FOURTEENTH STREET GOLDEN, COLORADO 80401 (303) 278-4378 FAX (303) 278-0521 Scale AS NOTED DR A W I N G L O C A T I O N : H: \ M C 1 7 . 1 4 3 5 - P i t k i n C o u n t y C o u r t h o u s e \ E N G \ D R A I N A G E \ D W G \ D r a i n a g e M a p . d w g PL O T D A T E : Tu e s d a y , J u n e 1 1 , 2 0 1 9 3: 4 4 P M L A S T S A V E D B Y : MT A L K I N G T O N PI T K I N C O U N T Y CO U R T H O U S E R E M O D E L PI T K I N C O U N T Y , C O REJ LML 50 6 E M a i n S t S t e 3 0 0 , A s p e n , C O 8 1 6 1 1 No.Description Date 811 MARTIN/MARTIN C O N S U L T I N G E N G I N E E R S 0101 FAWCETT ROAD, SUITE 260, AVON, COLORADO 81620 970.926.6007 MARTINMARTIN.COM 2017910 04/03/19 PERMIT DRAINAGE MAP D1 1 GRASS PAVERS, TYP. PERMEABLE PAVERS, TYP.