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1 1� Wnght Enmronmental Seances,Inc A thin salty sand-to-sand and silt strata package that is interpreted as a related deeper portion of the A-aquifer occurs roughly between 70 and 75 feet These small deeper A-aquifer beds appear to extend under site and pinch out to the southeast under the Charter Way (see Figure 2) A water equilibration test in these strata suggested a similar degree of confinement as in the A-aquifer and these strata are interpreted as a portion of the A-aquifer Recent groundwater monitoring data show depths to groundwater occur about 40-43 feet (below ground surface) bgs depending upon the time of year and aquifer recharge and discharge Site groundwater flow contouring shows historically flow has been southeasterly CPT water equilibration tests indicate water levels at about 38 to 40 feet, similar to groundwater monitoring well observations It is possible that sandy bed in the vicinity of CPT- 01 and MW-2 may create a local stratigraphic conduit allowing some vertical leakage to deeper A-aquifer strata on the basis of closely spaced groundwater contour lines hooking around MW- 2 suggesting a possible vertical flow component in that vicinity An aquiclude separates the A- and B-aquifers The aquiclude below A-aquifer is interpreted as slightly leaky on the basis of site stratigraphy and overall contaminant occurrence The aquiclude appears as predominantly clayey silt with depth and contain some thin discontinuous sandy beds above about 100 to 110 feet It is assumed that some leakage might occur B-Ag u fifer . The B-aquifer laterally varies from sand to silty sand that appears to partially pinch out near CPT-05 where the sandy beds become interbedded with silt and clayey silt The largest deposit interpreted as channel occurs roughly under the site and extends under Charter Way until it thins and laterally grades into the clayey silt fnterbeds Currently there are no monitoring wells in the B-aquifer for potentrometric measurements CPT-05 water equilibration data indicates about 40 feet of head from water equilibration tests (test taken at about 115-120 feet A silt-to-clayey site aquiclude may at least partially underlie the B-aquifer however the underlying aquiclude extent was not fully mapped in this work 6.0 Dissolved Contaminant Extent and Movement Historic groundwater monitoring has shown the dissolved plume on-site mainly at Wells MW-2 and MW-3, with a groundwater flow direction to the east-southeast Well MW-4 in the most far down-gradient position has not shown contaminant presence since it was installed A vadose zone sandy bed occurs at about 28-35 feet under the site that appears nearly directly below the former underground tank location This area is interpreted to contain residual contaminant occurrence in area of proposed sod vapor extraction as Ramage had previously mapped Contaminants appear to have wicked into the sand, as well as overlying and underlying clayey silt strata Well MW-2 installed at this location has historically had the most elevated contaminant concentrations It is possible that residual contaminants may drain into the Upper A-aquifer at this location 5tefano's—CPT Report Page 5 of 11