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EEC Project No. 1082030 <br />ASCI - Tumpike Reservoir <br />May 5, 2008 <br />Page 14 <br />Earth Engineering Consultants, Inc. <br />activities should be field verified/approved by means of field density testing procedures and <br />visual observations. The approved liner material, when compacted to at least 95% of the <br />materials' maximum dry density should have a coefficient of permeability of 1 x 10-7 cm/sec <br />or slower. <br />Due to the relatively shallow depth to groundwater and/or perched groundwater on top of the <br />relatively impervious bedrock formation, a deepened core trench will be required to reduce <br />the potential for inflow into the pond. The deepened core trench should be excavated into <br />the underlying bedrock formation to an approximate depth of 10-feet below the bottom of the <br />reservoir or to "practical refusal" within the bedrock formation. The core trench should be <br />excavated by use of heavy-duty track mounted backhoe machinery capable of excavating <br />hard/competent bedrock having the characteristics of a SPT test of 50 blows per 4-inches or <br />less. The extended core trench should be approximately 8 to 12-feet in width, depending on <br />the type of machinery used and adequately sloped while excavating to the required level. <br />The trench should then be backfilled with an approved cohesive material having a falling <br />head coefficient of permeability of 1x10-7 cm/sec. or slower. <br />The deepened core trench should be backfilled with approved cohesive soils similarly as <br />described with the wetted perimeter recommendations in maximum 9-inch thick loose lifts, <br />adjusted in moisture and compacted to at least 95% of the materials' maximum dry density as <br />determined in accordance with ASTM Specification D-698. After completion of the deepened <br />core trench, the previous recommendations for constructing and installing the wetted perimeter <br />of the reservoir should be performed. We have provided a schematic cross-sectional view of <br />the deepened core trench and side slope embankments. <br />We believe the on-site overburden lean clay with sand and sandy lean clay soils as described <br />herein and analyzed as part of this assessment as well as the underlying bedrock, processed to <br />at least 2-inch minus particle size, could be used for low permeability earthen liner materials <br />as intended for the raw water storage pond. Consideration could also be given to using <br />portions of the non-cohesive overburden materials blended with bentonite. Additional <br />laboratory testing and analyses would be required.