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Quik Stop Market No. 132 July 11, 1991 Project No. 3-49132-31 Page 7 A. downward movement slowed by the clayey soil. Some of this water could flow laterally along the surface of this clayey soil and become localized in low areas. In logging the borings for MW-IR and NIVW-5, which were with in 3 feet of each other, attention was paid to the soil type and field estimated soil moisture content. In MW-IR, the static groundwater level was measured at 14.41 feet below the surface. During the drilling of this boring, a soil sample collected from 14 feet to 15-1/2 feet below the surface was observed as predominantly a fine to medium grained sand with some clay, both of which were moist (no free water was observed). This condition continued until a depth of about 17 feet, where groundwater was encountered. In MW-5, the static groundwater level was measured at 14.20 feet below the surface. During the drilling of this boring a soil sample collected from 15 feet to 16-1/2 feet be.ow the surface was also observed as predominantly a fine to medium grained sand with some sand, both of which were moist (no free water was observed). This condition again continued until at about 17 feet groundwater was encountered. Below this wei sand, a very stiff silty clay bed was encountered at between 13-1/2 and 19 feet, which was moist. The top of this clay bed was sRizcted as the bottom of the well casing for MW-5. In MW-IR, drilling was continued through this clay which was found to be 3 feet thick, beneath which a wet fine to medium grained sand was encountered. Drilling was continued 10 feet past the bottom of this clay bed, the bottom of which was selected as the top of the slotted section of this well. In both wells several water level measurements were obtained prior to well installation activities which revealed that the groundwater level was rising. Duret ;both development and sampling of these-two.wells (which were within 3.feet of4 each"other} the water level of the well not beteg.developed or:'purged was manttored t9detect;any�huctuations in the groundwater level; none.was detected This;observations supports the presence of two.water-bearing zonas. - Results of chemical analyses of water samples collected from MW-1R and MW-5 were markedly different. In MW 5,.TPHG, .benzene, and,,„xylenes were detected at, concentrations of 210.ppb, 3.4 ppb, and 2.1 ppb, respecttvel ,while'iri MW 1R tl esey corrip9gents..were not detected. i Chemical analysis of the groundwater samples reveal that the hydrocarbon components were not detected in monitoring wells MW-2, MW-3, MW-4 and MW-IR which monitor the shallow aquifer. However, petroleum hydrocarbons were detected in the sample from MW-5, indicating that contamination is limited to the perched aquifer. Figures 5 and 6 depict Exceltech's interpretation of the conditions under the site. The clay bed, which is shaded, acts as a confining layer and an aouitard. The wet sandy soil located near MW-1 above this clay bed represents a localized perched aquifer. Beneath the clay layer is the local shallow aquifer which is semi-confined to confined. As shown in the cross-sections, the borings for MW-2, MW-3,and MW-4 encountered this clayey layer at a much shallower depth. This clayey layer acts as a confining layer to the