Laserfiche WebLink
65 and 70 feet and subsequently stabilized at a depth of <br /> approximately 68 feet. In an earlier letter to Mr. Ed Gotelli, <br />' dated December 11, 1992 , the PHS/EHD reported that seasonal high <br /> groundwater (1986) at this site was estimated to be between 45 and <br /> 50 feet. <br />' 2 . 4 Initial Assessment and Drilling <br />' On 9 October 19921 a soil boring was installed in the center of the <br /> gasoline tank cavity (Boring #1; see Figure 2) . This boring was <br /> advanced to a depth of 60 feet. Samples were collected at five-foot <br /> intervals and analyzed for total petroleum hydrocarbons (TPH as <br />' gasoline) and volatile aromatics (BTE&X) . <br /> TPH as gas was detected in samples BI -20 (93 ug/g) , B1-30 (6, 100 <br /> gg/g) and B1-40 (13 Mcg/g) . Benzene, toluene and xylene were <br /> detected in all analyzed samples except B1--60, at levels ranging <br /> from 0. 007 pg/g (xylene, B1-50) to 520 gg/g (toluene and xylene, <br /> B1-30) . Ethylbenzene was detected in samples B1-20 (3 . 5 gg/g) , Bl- <br /> 30 (170 mg/g) and B1-40 (0 . 37 pg/g) . The results were described in <br /> the Soil Boring Installation report dated 16 November 1992 , <br /> prepared by GeoAudit. <br /> 2 . 5 Monitorng Well installation <br /> On 9 and 10 March 1993 , three soil borings were drilled to a depth <br /> of 77 feet. Samples were collected at five-foot intervals and <br /> selected samples anaylzed for TPH as gasoline and BTE&X. The <br /> borings were completed as groundwater monitoring wells (MW-1 <br />' through MW-3) . A benzene concentration of 0 . 0079 mg/kg was detected <br /> at a depth of 45 feet in M7-2 , dust south of the tank pit. <br /> 2 . 6 Groundwater Monitoring <br /> On 17 March 1993 , the casing elevations were surveyed, the water <br /> I level in each well was measured, each well was purged and samples <br /> were collected. The hydraulic gradient was determined to be 0. 0073 <br /> ft/ft directed S 70 W. Benzene and Xylene were detected at <br /> concentrations of 3 . 7 gg/l and 1 . 1 µg/l in monitoring well MW-2 . <br /> Both concentrations are only slightly above the detection limits of <br /> 0. 30 gg/L and 0. 50 gg/L. <br /> 3. 0 PROCEDURES <br /> I 3. 1 Purge Procedures <br /> The second monitoring event was conducted on June 24 , 1993 . A <br /> Solinist water level meter was used to measure the depth to <br /> groundwater in the three monitoring wells. After water levels were <br /> measured, a representative of Del-Tech Geotechnical used a 2" <br /> Grundfos Stainless Steel Pump to purge approximately 10 to 12 <br /> 2 <br />