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wwrson seftakor, aim. -Uenswasmen eAoxoaoonp 2.2.2 Hydrogeologic Selling Subsurface investigations have been conducted at the Site from 1988 to present for the assessment of the lower and vertical extent of petroleum hydmcal"ns hgmriczlly released from former Site Opereftors. Soil beneath the She was coddled using hollow atom auger drill rigs and die lithulogy was described by a geologist haled on visual Observations. Boring lags were created for all 12 groundwater monitoring wells installed at the Site and from two deep soil borings (BH-13, and 1411-14). Soil bmings BH-1 through BB-12 were drilled to groundwater, ranging from 25 to 40 feet below ground surf (bgs), in Order to determine the extent of conmmbmtion prior to the excavation of impacted soil and were not Ingged For lithologic descriptions. Soil beneath the Silo is comprised of interconnected layers of sand, silt and day. "fhe Site is generally underlain by clay to a depth nfapproximately 14 feet bgs, silt to 18f tbgs and send to 48feet bgs. Silt and sand layerssepara d by clay ore located beneath the Site from 54 feet to 105 feet bgs. '1 h ve groundwater nines were encountered while drilling the deepest wall at the Site (MW-10). The shallow water table groundwater was is located in the upper wind layer. An intermediate water woe is located in a silt layer between 54 and 28 f bgs and is separated f the sand Loyd above by b-feet of clay. However the upper and intermediate groundwater zones ate contiguous at well MW-2 located down gradient from the Site. Me lower groundwater zone at MW-10 is located between 74 and 105 feet bgs and is separated from the Intermediate zone by 5 f of clay. The lower groundwater woe was not logged in boring Bill-14, htcatod 40f to the somhwest. The lower grouMwater zone appears to be semi-confined based on rising groundwater levels measured in the well shortly alter removing the well plug although the static water level in well MW-10 is similar to those in otter nearby wells. Groundwater elevations have historically ranged from approximately 25 reel bgs in 2011 to 50 ft in 1991. The initial wells (MW-I though MW-3) were installed in December 1988. Hermetic tine water bible subsequently dropped 15 feet and deeper Wells (MW4 through M W-S) were installed in August 1991. The water bible his rebounded 25 feet since I"I with small seasonal Budrrou0ns.