ARCHIVED REPORTS XR0007779 - Laserfiche WebLink

Home Browse Search

'i 24 August 1995 AGE-NC-95-0142 ' Page 2 of 6 t 2 4 INSTALLATION OF GROUND WATER MONITORING WELLS I , On 9 and 10 February 1994, three ground water morutonng wells (MW-1, MW-2 and MW-3)were installed at the site by CET The wells were installed to depths of 60 feet using 20 feet of 4-inch ' diameter slotted PVC casing - Soil samples collected during installation of the monitoring wells were analyzed for total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) and volatile aromatics (benzene, toluene, ethyl benzene and xylenes BTE&X) TPH-g, TPH-d and BTE&X were not detected in`soil ' samples from MW-I or MW-2 However, TPH-g and BTE&X were detected in soil samples from MW-3 at concentrations up to 8 2 parts per million (ppm) ' Ground water samples were collected from wells MW-1, MW-2 and MW-3 on 22 February 1994 TPH-g was detected in MW-3 at 48,000 parts per billion(ppb) BTE&X were detected in each well at concentrations ranging from 1 2 ppb (toluene, MW-2) to 13,000 ppb (benzene, MW-3) ' Installation and sampling of the ground water morutonng wells was summarized in the "Soil and Ground Water Investigation Report" dated 19 March 1994, prepared by CET The wells were sampled a second time on 24 October 1994 by Roger Foote Associates (RFA) TPH- g was detected in MW-3 at 12,000 ppb, BTE&X were detected in wells MW-2 and MW-3 at concentrations up to 8,800 ppb Results of the sampling were summarized in a "Quarterly Monitoring Report" prepared by RFA, dated 14 November 1994 In' November 1994,RFA installed one additional monitoring well at the site (MW-4) No petroleum hydrocarbons were detected to soil samples collected dieing installation RFA collected ground water samples from MW-4 on 6 December 1994 No TPH or BTE&X were detected in the initial sample However, because a slight odor was noted during sampling, the PHS-EHD requested that the well be re-sampled Therefore, RFA re-sampled the well on 22 December 1994 Concentrations of toluene(0-31 ppb) and xylenes (0 74 ppb) were present in the re-sample just above detection limits (0 3 ppb and 0 6 ppb, respectively) 3.0. PROCEDURES r 3 1 MONITORING WELL PURGE PROCEDURES On 23 May 1995, a So"water level was used to measure the depth to ground water,in four wells The relative piezometric level in each well and hydraulic gradient were determine from these data ' points(Table 1) Each monitoring well was then purged of approximately 10 to 40 gallons of water (a minimum of 3 well volumes), using a PVC and stainless steel submersible pump Temperature, pH, and conductivity were measure at ten-gallon intervals (one-gallon interval for MW4) using an ICM