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J I ! f 4 a 1h y- ^"r J e i 05 May 1997 ! I � AGE-NC Project No 95-0139 ' Page 6 of 9 s" Since 1988, the depth to ground water at thersite has fluctuated from 9 5 to,12 6 feet bsg Ground " ' water flow direction has remained between N 2°E and N 39°W,consistent with regional trends YThe " gradient has varied from 0 0017 ft/ft to 0 0050 ft/ft Recent depth to,ground water information is 'j `summarized on-Table'4 Historical ground water'flow directions and gradients are summarized ori Table 5 k 0 In MWA, concentrations of TPH-g and TPH-d have ranged from less than the detection limit of 50 I' parts per billion (ppb) to 80,000 ppb, benzene has been detected at concentrations as high as 870 I I ppb y , 'In all other wells at the site, TPH-g, toluene, ethylbenzene and/or xylenes have been detected near the detection limits in six of 35 samples, benzene and,TPH-d have not been detected iii any samples , `-„ collected from MW-2, MW-3 or MW-4 TPH,as motor oil has not been detected in any water ! ' samples collected at the site Analytical results of all ground water samples collected at the site are summarized on Table 6 1 + r V 3 0. GROUND WATER MONITORING,'JANUARY�1997 r r 3 1 MONITORING WELL PURGE PROCEDURES I � J On 02 January 1997, arSolinst water level meter was used to measure the depth to water in each well relative to the top of the casing The relative ground water elevations and hydraulic gradient were ' determined from'these data (Table 4)!u r = F 7 = 3 I t After depth to ground water measurements, a submersible pump was used to remove standing water ' from each well Approximately six gallons (minimum of three well volumes)of water were removed from each well to,stabilize' temperature, pH and conductivity Ground water parameters were.t measured at two'gallon intervals using an ICM model 52200 water analyzer 4�t All purging equipment was decontaminated,by being washed in an'Alconox solution and rinsed�in ua water prior to purging "each` well Purged water' 'was stored in 55-gallon drums on-site ` rPhysicochemical data and field logs are included iri Appendix A r r i 3 2, + COLLECTION OF GROUND WATER SAMPLES 1 I Water samples were collected from each well using disposable plastic bailers The samples were : transferred mto'40 ml EPA-approved VOA vials'containing 0 5 ml of 18% hydrochloric acrd as a preservative and 1-inter amber bottles without preservative The sample containers,were labeled, , ! + > J l 1 4