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HomeMy WebLinkAboutCITY OF FORT COLLINS UTILITY SERVICE CENTER MODIFICATION OF A STANDARD - 16 90E - SUBMITTAL DOCUMENTS - ROUND 1 - WETLANDS DOCUMENTSu WETLAND IMPACTS AND MITIGATIONS For THE CITY OF FORT COLLINS SERVICE CENTER STORAGE YARD EXPANSION PROJECT Prepared by City of Fort Collins Utilities Department 700 Wood Street Fort Collins, Colorado July, 2002 INTRODUCTION The City of Fort Collins is planning an expansion of its Utilities Department Service Center storage yard at 700 Wood Street. Proposed work will include overlot grading with stormwater, paving, and landscape improvements. In general, the yard will be expanded to the south across an abandoned railway spur and field. A new stormwater swage and landscaped berm will be installed along the north side of Elm Street. A large stormwater drainage pipeline will be installed across the existing yard and will exit the northeast corner of the facility into a newly constructed stormwater quality pond. EXISTING ENVIRONMENTAL CONDITIONS The project site is on the northeast comer of Wood Street and Elm Street (Drawing 1). Two areas currently not under pavement are affected by the new construction. Immediately south of the existing facility is a triangular field covered by a variety of grass and weed species, including smooth brome, crested wheat, bindweed, sweetclover, thistle, and knapweed. The field is bordered on the north by an abandoned railway spur line (immediately south of the existing paved yard) and by Elm Street on the south. A large berm, a soils stockpile from a previous facility upgrade, occupies the west end of the field. A drainage swale, constructed in the last expansion of the Utilities facility, crosses from southwest to northeast, approximately dividing the site in two. This swale culminates in a small pond just south of the existing railroad spur (Drawing 4). A wetland has developed along the swale and around the pond. Primary species present include arrowhead, cattail, meadow fescue, three square, willow, cottonwood, and Russian olive. At the northeast corner of the existing yard are wetland and upland areas which are a part of the Poudre river corridor (Drawing 2). The primary wetland species are cattail, Nebraska sedge, reed canary grass, softstem bulrush, horsetail, and milkweed, with willows along the southern fringe. The upland area immediately north of the wetland is remnant shortgrass prairie with buffalo grass, blue grama, western wheat, prickly pear cactus, and rose, all being overrun with spreading infestations of non=native smooth brome and cheatgrass PROJECT IMPACTS TO WETLAND AREAS Wetlands in the project area were delineated in April, 2002 by a qualified environmental specialist with the Fort Collins Utilities. Areas delineated were discussed with a U. S. Army Corps of Engineers (COE) representative in a site visit in late April. At that time, it was determined that the wetlands in the swale and around the pond on the south side of the existing facility are not-COE jurisdictional. No 404 permit or COE mitigation is required for this wetland. Project plans indicate this wetland area will be completely filled during construction. 0 The wetland areas northeast of the existing facility are connected directly to the Poudre River, and are COE jurisdictional. A stormwater quality pond is proposed here, and a 404 permit will be obtained prior to any construction. Since both wetland areas fall under the wetland provisions of the City of Fort Collins Land Use Code, any -impacts must be mitigated per City specifications at a 2 to 1 ratio. Project Wetland Impacts/Mitigations: Location Area Impacted Required Mitigation (Acres) (Acres) New Yard Area (Pavement) South 0.20 0.40 of Existing Facility Stormwater Quality Pond Northeast 0.20 0.40 of Existing Facility (COE 404 Permit Required) Totals 0.40 Acres 0.80 Acres WETLAND MITIGATION, UPLAND REVEGETATION A portion of the upland area north of the proposed stormwater quality pond will be excavated to an elevation consistent with the existing wetland (Drawing 3). This will provide a mitigation area contiguous with the existing wetland with ample hydrology to support wetland plant species. The hydric soils and wetland plant materials displaced during the construction of the proposed stormwater quality pond and the filling of the wetland south of the existing facility will be distributed in the bottom of the excavations to provide for rapid establishment of the wetlands there. The entire disturbed area will be enhanced with deciduous native trees and shrubs. In addition, willow cuttings will be placed into the toe of the new water quality pond and upland area next spring to provide more overstorey wildlife habitat than currently exists. Specific plantings are shown on the Landscape Plan. The newly created wetland area will be 1.3 acres in size, exceeding the required mitigation acreage by 0.50 acres. Topsoil from the upland area excavated for the wetland mitigation will be stockpiled separately. This material, containing native plant seed and propagules, will be spread on the completed stormwater quality pond embankments. In addition, the embankments will be seeded with a native mix of western wheat, blue grama, buffalo grass, and sideoats grama.