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Memo to Erica Crosby 3 March 22 2000 Reservoir Filling Past practices by the Division in permitting lined reservoirs included a requirement to provide bond sufficient to purchase enough water from a reliable source to fill the reservoir one time. Numerous gravel pits have been reclaimed or are proposed to be reclaimed as lined storage reservoirs since the passage of Senate Bill 120 in 1989. It has become clear that there is a great demand for lined storage in over appropriated basins and in particular the South Platte basin, so it is no longer a substantial concern to the Division that lined reservoirs will not be tilled and ptn to their intended beneficial use. In the worst case, virtually any reservoir could be filled eventually by using junior water rights in priority. For these reasons, the Division will not require bonding to fill the reservoirs. However, the Division will require a statement from [he applicant describing their plans for filling the reservoir. Slurry Wall Costs Slurry wall installation costs include geotechnical investigation and testing, design and quality control, mobilization and setup, excavation of regolith, excavation of the bedrock key, delivery of bentonite and water, mixing of slurry, mixing of soil/bentonite, backfilling of soil/bentonite, clean up and demobilization, and testing and quality assurance. Specialized equipment is required to excavate deep slurry trenches, and the cost of excavation increases dramatically for trenches deeper than 35 feet and/or if the bedrock into which the slurry wall will key is hard or otherwise difficult to excavate. Experience with slurry walls in Weld County and statements in the application indicate that the Ft. Lupton Sand and Gravel Mine slurry wall costs will not be substantially increased by depth to bedrock or by excessive difficulty excavating the key trench. The following slurry wall cost references are illustrative: • The U.S. Army Corps of Engineers installed slurry walls in an extensive levee improvement project in the Pocket area near Sacramento, California. These slurry walls were 30 feet deep with a reported unit installation cost of $5.00 per square foot. • The Federal Remediation Technologies Roundtable "Remediation Technologies Screening Matrix and Reference Guide" reports slurry wall installation costs of between $5.00 and $7.00 per square foot. • Environmental Protection Agency document EPA 542-R-98-005, "Evaluation of Subsurface Engineered Barriers at Waste Sites," August 1998 reports slurry wall installation costs of between $5.00 and $15.00 per square foot. The costs to install slurry walls at waste containment sites are higher than the costs to line clean water reservoirs using a slurry wall. This is partially due to the need [o conduct chemical compatibility testing and the higher degree of quality control used at waste containment sites. The applicant proposes a $3.00 per sq. ft. unit cost For slurry wall installation, and based on review of recent bids for slurry walls around gravel pits on the Front Range, this is believed to be appropriate. The slurry wall bond, whether it is for installation around the entire reservoir perimeter or is a 20 percent contingency bond as