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<br />e <br /> <br />. <br /> <br />. <br /> <br />DESIGN/BUILD ISSUES ASSOCIATED WITH STREAM RESTORATION PROJECTS: <br />BLUFF LAKE CASE STUDY <br />Ted Johnson, P.E. <br />Camp Dresser & McKee Inc. <br />1999 CASFM Conference, September 22 - 24,1999 <br /> <br />ABSTRACT <br /> <br />This paper is intended to provide insight into the design/build process as it relates to the restoration of a <br />stream highly impacted by urbanization of its watershed. The history of the project is given along with <br />constraints and opportunities provided by the design/build process. Several problems were encountered <br />that, although not necessarily caused by or resulting from design/build, posed challenges that were <br />creatively met by the design and construction teams working together through the entire project. <br /> <br />Background <br /> <br />Bluff Lake is the result of a Consent Decree between Sierra Club and City and County of Denver, ending a <br />lawsuit resulting from contamination of Sand Creek with ethylene glycol contaminated stormwater. <br />Denver agreed to construct an educational facility at Stapleton Airport that would be used by elementary <br />school students to learn about water quality, wetland, and riverine habitats. Bluff Lake is located in the <br />former airport operations area, but largely undeveloped. Historically, the site included a stock watering <br />pond (Bluff Lake), the Tollgate Creek/Sand Creek confluence, and Highline Canal. Later, the Tollgate <br />Creek outfall was moved upstream, Highline Canal was abandoned, water storage rights at the stock <br />watering pond were transferred to other locations, and the part of the site north of the Sand Creek channel <br />became a municipal refuse dump. Evidence of the dump was apparent when the project started - the <br />north side of the creek contained acres of bakelite batteries and telephone sets strewn about, oily bare <br />patches of ground, asbestos house siding, tires, and other debris. The Tollgate Creek outfall is no longer <br />evident, but the Highline Canal channel is still present on the site. <br /> <br />Site Description <br /> <br />The Bluff Lake property encompasses approximately 120 acres located south of the Denver County Jail at <br />Smith Road and Havana Street and north of the east-west Stapleton Airport runways. The lake itself is a <br />10-acre impoundment supplied by stormwater runoff from the neighborhood south of Stapleton operations <br />area and groundwater inflow. The lake is eutrophicating and slowly being encroached upon by cattail <br />wetlands to the east. Sand Creek runs somewhat diagonally through the property from southeast to <br />northwest. Upland Bluffs, that give the property its name, frame the site on the east and south. The north <br />side is adjacent to the County Jail and State Department of Corrections property. Havana Street is on the <br />west and the City of Aurora Wastewater Reuse Treatment Plant on the east. The Denver/Aurora <br />corporate boundary forms the east property line, while Havana and Moline streets form the west and south <br />boundaries. Although access was restricted during operation of the airport, the site was used <br />surreptitiously by bikers, off-road vehicles, and transients. Historically, the site contained great-horned <br />owls; several species of hawks, including Swainson's and red-tail; a deer herd of 5 to 10 individuals, <br />including a six-point buck; coyote and fox; several species of waterfowl, including herons and cormorants, <br />as well as geese and ducks; bull and garter snakes; beaver; muskrat; and wild dogs. Aquatic vertebrate <br />species include white sucker, plains killfish, fathead minnow, and creek chub. <br /> <br />Sand Creek, a major tributary of the South Platte River with a watershed area of 189 square miles and <br />headwaters in eastern Arapahoe County, runs through the site for approximately 3,600 feet. Historically, <br />the channel, up to several hundred feet wide, meandered at will through an alluvial floodplain <br />approximately a mile wide. The stream contained very little or no baseflow, and due to its tendency to <br />migrate laterally, there was also very little riparian vegetation, in particular, trees and shrubs. The historic <br />channel was very shallow and wide, exhibiting little or no diversity in aquatic habitat. Substrate material <br />