2018-07-02_PERMIT FILE - M2017013

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Earth Engineering Consultants,LLC EEC Project No. 1122096 Signal Reser<moir Improvements August 5,2015 Page 13 As mentioned above, to control and intercept potential seepage along the downstream slope a toe-drain will be installed. EEC has perform a filter analysis for the sand and gravel encasement material associated with the toe-drain. Please refer to the grain-size distribution analyses included in Appendix C of this report. General Geotechnical Considerations The primary purpose of our field explorations, laboratory evaluation/testing and engineering analyses was to determine the feasibility of deepening/modifying the existing Signal Reservoir to allow for an increased storage capacity, possibly excavating to depths of approximately 20-plus feet below existing site grades. The pond's embankments/wetted perimeter should consist of a homogeneous cohesive material constructed with relatively impervious clay and/or bedrock material having a coefficient of permeability, (k-value) of 1x10-7 cm/sec or slower when compacted to at least 95% of standard Proctor density (ASTM Specification D698). We understand the on-site overburden soils and the underlying bedrock materials will be utilized. The excavation phase of this project has not been determined, (i.e., the slope at which the deepening will occur either near vertical or 2:1, or possibly even 3:1), however we suggest the proposed upper portions of the reservoir embankments be constructed on minimum 3:1 (horizontal: vertical) around the perimeter. Steeper and/or near vertical slopes may be possible at greater depths within the bedrock formation. The design of wave and slope protection for the deepened reservoir is beyond the scope of subsurface exploration study and should be reviewed during the final design stages. Earthen Liner/Wetted Perimeter Improvements Groundwater and/or the initial presence of a water surface as previously discussed was encountered within five (5) reservoir and/or existing dam related soil borings at approximate depths of 22 to 38-feet below existing site grades. We understand initial concepts are to over- excavate the existing reservoir to depths of 20-feet or more to accommodate the increased storage capacity. To minimize the potential for groundwater fluctuations to impact and/or enter the "re-configured" reservoir, we suggest the bottom of the pond have a minimum separation of 3-feet above the maximum anticipate rise in groundwater and/or a minimum 3-foot layer, as part of the wetted perimeter improvements, of approved cohesive material should be placed and compacted along the bottom of the reservoir. As we understand a 90-day water balance/seepage analysis will not be required for the proposed Signal Reservoir improvements.