ARCHIVED REPORTS_XR0007887 - Laserfiche WebLink

Home Browse Search

Ms Mary Meays Page 3 April 13, 1994 5A) are nondetect for gasoline and gasoline constituents Tidal fluctuations as a result of the proximity of the Stockton Deep Water Channel do influence the ground water gradient at the site, but the ground water flow direction has been generally consistent Also, no significant migration of chemicals in ground water has been observed over time, and the extent of hydrocarbons in ground water at Site 2 has been relatively stable over time GROUND WATER REMEDIATION The selected ground water remedial alternative, as described in the Final Remediation Plan involved the extraction of a fixed volume of hydrocarbon- containing ground water from each site using the existing monitoring wells Given the limited extent of the hydrocarbons in ground water at both sites, this strategy was employed to remove the bulk of the chemicals in ground water at each site Natural degradation of any residual hydrocarbons would thus be expedited Between December 7, 1993 and January 12, 1994 (a total of 13 days), approximately 4,000 gallons of water was extracted from each site (8,000 gallons total) using a submersible pump Because of the low permeability soils at both sites, the extraction rate was limited to an approximate range between 12 and 16 gallons per minute At Site 1, ground water was extracted from monitoring wells MW-4 (approximately 1,000 gallons) and MW-5 (approximately 3,000 gallons), and at Site 2, ground water was extracted from monitoring well MW-1A The extracted water was pumped into Baker tanks for temporary storage and subsequently transported via vacuum trucks to the City of Stockton Publicly-Owned Treatment Works (POTW) for direct discharge Prior to discharge, samples were collected from each tank and analyzed for volatile organic compounds and metals as required by the POTW Discharge of the extracted water was authorized by the City of Stockton POTW in a letter addressed to Mr Larry Williams dated January 21, 1994 GROUND WATER MONITORING Following the extraction of a fixed-volume of ground water from each site, all of the monitoring wells were sampled to measure the effectiveness of the extraction program Samples were collected from all 10 site monitoring wells (wells MW-1 through MW-5 at Site 1 and wells MW-1A through MW-5A at Site 2) on January 27 and 28, 1994 All samples were analyzed for TPH as gasoline (EPA Method 8015- Modified) and for BTEX (EPA Method 8020) These results, along with all of the historic monitoring well results for both sites, are summarized in Tables 1 and 2 for Sites 1 and 2, respectively The analytical data sheets for the January 27 and 28, 1994 samples are also attached The most recent monitoring well data results show a significant reduction in concentrations of TPH and BTEX compounds in ground water at both sites At Site 1, the concentration of TPH detected in ground water in MW-5 decreased from 3 mg/l (parts per million or ppm) in April 1993 to 0 88 ppm in January 1994