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Home My WebLink AboutSIGNED Notice of Approval_ACES_Hallam Lake Improvements Page | 1 NOTICE OF APPROVAL APPROVING A STREAM MARGIN EXEMPTION REVIEW TO IMPROVE DRAINAGE, FLOOD CONTROL, WATER CONTROL AND BANK STABILIZATION FOR THE PROPERTY COMMONLY KNOWN AS THE ASPEN CENTER FOR ENVIRONMENTALLY STUDIES, LEGALLY DESCRIBED AS ASPEN CENTER FOR ENVIRONMENTAL STUDIES SPECIALLY PLANNED AREA FINAL DEVELOPMENT PLAN, ACCORDING TO THE PLAT THEREOF RECORDED JANUARY 26, 2010 IN PLAT BOOK 93 AT PAGE 1 AND ACCORDING TO THE FIRST ADDENDUM RECORDED JULY 8, 2011 IN PLAT BOOK 97 AT PAGE 31. COUNTY OF PITKIN, STATE OF COLORADO. Parcel ID No. 2737-073-00-801 APPLICANT: Chris Lane, Aspen Center for Environmental Studies SUBJECT & SITE OF APPROVAL: Stream Margin Review Exemption at the Aspen Center for Environmental Studies. The Applicant is requesting to make several improvements to Hallam Lake related to drainage, flood control, water diversion, and bank stabilization. This application was reviewe d by Community Development, Engineering, and Parks. SUMMARY: The Aspen Center for environmental Studies (ACES) Hallam Lake Preserve is a 25.5-acre property, zoned Academic (A) with a Planned Development (PD) Overlay. ACES serves as an education center and nature preserve and is considered an important community asset. The property surrounds Hallam Lake and is adjacent to the Roaring Fork River. In the 1880’s, Hallam Lake was used for recreation, fisheries, and ice production. At the time, an earthen berm was constructed around the lake to stabilize the bank. Some maintenance was completed in the 1980’s, but a large portion of the berm remained untouched. Today, several segments of the berm are beginning to fail; many sections are less than one-foot thick and are at water level. The Applicant plans to improve bank stability by repairing the berm and replacing the outflow structure. To complete this work, the lake will be drained, and heavy machinery will be mobilized onsite. The lake and associated berm do not appear to be located within the Stream Margin Review Area of the Roaring Fork River, however, access to the construction site will encroach into the Stream Margin Review Area. The scope of work is eligible for consideration under the Exemption criteria associated with Stream Margin Review. Pursuant to Code Section 26.435.040.B.1, Exemptions, the Community Development Director may exempt the following type of development within the stream margin review area: 1. Construction of pedestrian or automobile bridges, public trails or structures for irrigation, drainage, flood control or water diversion, bank stabilization, provided plans and specifications are submitted Page | 2 to the City engineer demonstrating that the structure is engineered to prevent blockage of drainage channels during peak flows and the Community Development Director determines the proposed structure complies, to the extent practical, with the stream margin review standards. STAFF EVALUATION: To allow the exemption, the Community Development Director must find that the work complies, to the extent practical, with the following standards of 26.435.040.C. 1. It can be demonstrated that any proposed development which is in the Special Flood Hazard Area will not increase the base floo d elevation on the parcel proposed for development. This shall be demonstrated by an engineering study prepared by a professional engineer registered to practice in the State which shows that the base flood elevation will not be raised, including, but not limited to, proposing mitigation techniques on or off -site which compensate for any base flood elevation increase caused by the development; and 2. The adopted regulatory plans of the Open Space and Trails Board and the Roaring Fork River Greenway Plan are implemented in the proposed plan for development, to the greatest extent practicable. Areas of historic public use or access shall be dedicated via a recorded easement for public use. A fisherman's easement granting public fishing access within the high water boundaries of the river course shall be granted via a recorded "Fisherman's Easement;" and 3. There is no vegetation removed or damaged or slope grade changes (cut or fill) made outside of a specifically defined building envelope. A building envelope shall be designated by this review and said envelope shall be designated by this review and said envelope shall be recorded on a plat pursuant to Subsection 26.435.040.F.1; and 4. The proposed development does not pollute or interfere with the natural changes of the river, stream or other tributary, including erosion and/or sedimentation during construction. Increased on-site drainage shall be accommodated within the parcel to prevent entry into the river or onto its banks. Pools or hot tubs cannot be drained outside of the designated building envelope; and 5. Written notice is given to the Colorado Water Conservation Board prior to any alteration or relocation of a water course and a copy of said notice is submitted to the Federal Emergency Management Agency; and 6. A guarantee is provided in the event a water course is altered or relocated, that applies to the developer and his heirs, successors and assigns that ensures that the flood carrying capacity on the parcel is not diminished; and 7. Copies are provided of all necessary federal and state permits relating to work within the 100-year flood plain; and 8. There is no development other than approved native vegetation planting taking place below the top of slope or within fifteen (15) feet of the top of slope or the high waterline, whichever is most restrictive. This is an effort to protect the existing ripa rian vegetation and bank stability. New plantings (including trees, shrubs, flowers and grasses) outside of the designated building envelope on the river side shall be native riparian vegetation as approved by the City. A landscape plan will be submitted with all development applications. The top of slope and 100-year flood plain elevation of the Roaring Fork River shall be determined by the Stream Margin Map located in the Community Development Department and filed at the City Engineering Department; an d 9. All development outside the fifteen (15) foot setback from the top of slope does not exceed a height delineated by a line drawn at a forty-five (45) degree angle from ground level at the top of slope. Height shall be measured and determined by the Community Development Director using the definition for height set forth at Section 26.04.100 and method of calculating height set forth at Section 26.575.020 as shown in Figure "A"; and Page | 3 10. All exterior lighting is low and downcast with no light(s) directed toward the river or located down the slope and shall be in compliance with Section 26.575.150. A lighting plan will be submitted with all development applications; and 11. There has been accurate identification of wetlands and riparian zones. The application demonstrates that work is not occurring in the Special Flood Hazard Area and there will be no changes to base flood elevation and no alteration to a water course. There are approvals required from state and federal agencies that are underway and will be secured before the project commences. There is no permanent development associated with this project. All temporary access paths for equipment needed for the project will be protected to avoid erosion impacts and will be re -vegetated with native grasses. Tree replacement/mitigation and approval of the re-vegetation plan will occur through coordination with the City of Aspen Parks Department. DECISION: The Community Development Director determines that the request to improve drainage, flood control, water diversion and bank stabilization for Hallam Lake meets the requirements of a Stream Margin Review Exemption with the following conditions: 1. A tree removal permit shall be submitted prior to the removal of any trees. 2. Tree protection fencing is required at the LDA line as depicted in the plans associated with this approval (on file with the Park’s Department). 3. A 12” minimum mulch bedding separated a ¾” plywood must be placed on roadway into the project within the dripline of trees . 4. The entrance of vehicles into the area is limited to what is specifically needed to construct the project. APPROVED BY: _______________________________________ ________________________ Amy Simon Date Planning Director Attachments: Exhibit A – Application (On File) 8/12/2021