Forest Hills Metropolitan District Storage Pond Development

The new storage ponds would be used for Water Augmentation purposes (releasing water from the ponds back into the Bear Creek watershed for use by water users downstream with senior water rights to enable the District to continue to draw water from its wells) and secondly as a water source in the event of a forest fire. The importance of constructing new storage ponds has increased in importance due to heightened concerns regarding droughts. The District has Conditional Rights to build these four ponds, which together could have water rights to hold up to 13 acre-feet. The purpose of our involvement was to perform technical analysis, water capacity estimate, feasibility study, design, cost estimate, and draft application for building up to four additional water augmentation ponds within the Districts territory. The following deliverables were requested:1. The project background information including the users and the overall project goals.2. A comprehensive review of the water rights available to the District and a technical feasibility study for building one to four new ponds.3. A comprehensive field evaluation drainage basin, existing ground cover, subgrade, ditches, and culverts. 4. Design for each of the four detention ponds including the proposed construction sequence, pond liners, water input sources, pond water capacity, outlet works including water flow back into the watershed, flood protection, erosion control, landscaping, and costs.5. A draft application for construction that could be submitted to the State Engineer.As part of our investigation, we performed a site visit on January 29 and also met with Mr. Laves to obtain the background on the FHMD storage ponds. We also MoreInformationHere. This report contains our findings, conclusions, and recommendations. We thank you for this opportunity and experience, and we hope that our work will aid FHMD in its goal to create storage ponds for all its needs.Project BackgroundPurposeJurisdictions Having AuthorityApplicable Building CodesFindingsRecommendations1. Sealing the ponda. Clay blanketsPond areas lacking sufficient amount of clay are highly susceptible to excessive seepage. Pond areas can be sealed by clay blankets to prevent seepage. The clay blankets are placed on pond areas where Water is to be impounded as well as the upstream slope of the embankment. (USDA Ponds 63) Minimum clay blanket requires 20 percent clay and to reduce cost, clay can be obtained from borrow areas close to the ponds. The minimum compacted thickness is 12 inches for all depths of water under 10 feet. Increase this thickness by 2 inches for each foot of water over 10 feet and above. (USDA Ponds 63) Clay blankets are constructed similar to earth embankments and are spread uniformly over pond areas in layers of 6 to 8 inches and each layer should be compacted completely, under optimum moisture conditions. The clay blankets should be protected against cracking by covering a layer of 12 to 16 inches of gravel and rock riprap around areas where water flow in the pond is concentrated.