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' Introduction <br />' The Fulton Lakes Reservoirs are located in Adams County, bounded by the South Platte River on <br />the South and East and McKay Road to the West. The site is located in Section 17, Township 2 <br />South, Range 67 West of the 6te Principal Meridian, as shown in Figure 1. Aggregate Industries <br />originally mined the site for sand and gravel resources. The reservoir will be a lined gravel pit <br />that is intended to be anon-jurisdictional structure. <br />This design report should be used in conjunction with the Construction Plans prepared by this <br />office to fulfill the requirements of the agreement between Aggregate Industries, City of <br />Thornton, and Arvada. Although the construction of the reservoir is non-jurisdictional, it is <br />being designed to standards that are similar to the rules and regulations used by the State <br />Engineer in the review of jurisdictional.dams. The structure does need to meet the requirements <br />for lined gravel pits as written by the State Engineer. <br />A slurry wall liner was installed around the perimeter of the entire Fulton Lakes pit in September <br />of 2000. This slurry wall was designed by Rocky Mountain Consultants, as a part of a design- <br />build contract for Hall Irwin Construction Company. The approved reclamation plan for this site <br />divides the pit boundary into two sepazate reservoirs. Consequently an interior dike was <br />designed to keep the reservoirs separate units that can be operated independently by Arvada and <br />Thornton. <br />The reservoir embankments are being returned to grade. No water storage is intended to be <br />above existing ground level. The proximity of the reservoir to the South Platte River presents a <br />unique situation where the reservoir will be inundated in a 100-year South Platte River flood. <br />Interior Dike Design Philosonh <br />The interior dike was designed to construct two reservoirs as independent units. The dike will be <br />approximately 2,600 feet long. This interior dike was designed as a zoned earth embankment <br />using a clay shale core as the impermeable zone and a random fill section consisting of <br />overburden to protect the core. All materials used in the construction of the dike will come from <br />on-site sources. Geotechnical testing of the clay shale and overburden were done to determine <br />their suitability for use in embanlnnent construction. <br />^ A slurry wall was considered as an alternate to the zoned design that was selected. However, <br />due to the need for a working area for slurry mixing, the top width would have to be <br />' approximately 80 feet wide. Therefore both reservoirs would lose significant water storage. <br />Consequently a zoned embankment was determined to be the best alternative. Zoned earth <br />construction will also provide a thicker impermeable zone as well as the ability to visually <br />construct a good keyway into bedrock. <br />The slurry wall continues azound the perimeter of the originally mined pits therefore it will be <br />necessary to tie the interior dike into the slurry wall on the ends. An intersecting slurry wall will <br />extend approximately two hundred (200) feet from each end of the dike and will be constructed <br />to tie-into the existing slurry wall. The location of the tie-in sluny wall will align with the key <br />trench that is proposed in the zoned earth dike. The slurry wall tie-in will need to meet the <br />