Laserfiche WebLink
Gary A. Reents -2- 24 February 1989 <br /> 3, Hydrogeologic Interpretation <br /> A. One aquifer underlies the facility from water table to at least 450 feet <br /> BGS, <br /> B. Consists of discontinuous lenses of sand , gravelly sand , silty sand, <br /> clayey silt, silty clay, and clay, <br /> C. Logs indicate sandiest layer between 80 to 200 feet BGS. <br /> D. H&A divided the aquifer into four (4) hydrostratigraphic subunits based on <br /> lithologic and hydraulic properties. <br /> E. The four (4) hydrostratigraphic subunits were depicited on three (3) <br /> lithological and three (3) geophysical cross-sections. Two (2) cross- <br /> sections were oriented parallel to the plume, the remaining cross-section <br /> was oriented perpendicular to the plume, <br /> F. The uppermost subunit, the "shallow zone", extends form the water table to <br /> about 80 feet BGS . This submit consists primarily of electrically <br /> conductive sediments (silts and clays) . <br /> G. Underlying the shallow zone is the "1DO-foot sand" , occurring between <br /> approximately 80 to 120 feet BGS . The thickness of this unit varies from <br /> 5 feet at the South yard to 30 feet approximately 3500 feet downgradient, <br /> This unit consists of electrically resistive sediments ( sands) . <br /> H. Underlying the 100-foot sand layer is the "intermediate zone" , occurring <br /> between 110 to 150 feet BGS. This zone consists of highly resistive <br /> sediments (sand and gravel ) . Thickness varies from 30 to 50 feet . This <br /> unit and the overlying 100-foot sand layer are separated by approximateiy <br /> 60 feet of electrically conductive sediments (silts and clays) at the <br /> south yard. However, this fine-grained layer thins downgradient (to the <br /> south) and pinches out about 2500 feet downgradient , <br /> I . Underlying the intermediate zone is the "deep zone" , occurring between 170 <br /> to 200 feet BGS. This zone extends to at least 450 feet BGS and consists <br /> c, alternating layers of resistive and conductive sediments ( interbedded <br /> sands, silts and clays) . <br /> 4, Flow Patterns and Hydraulic Heads (December 1988) <br /> A. A ground water mound, within the shallow zone, has formed under the north <br /> yard. <br /> B. Shallow zone ground water micration is south to southwest with a hydraulic <br /> gradientyof 0,0006 (contour map provided) , <br />