ARCHIVED REPORTS_XR0004411 - Laserfiche WebLink

Home Browse Search

EXECUTIVE SUMMARY • Upgradient Environmental Consultants visited the Valley Motors dealership on February 19 to measure water depths and collect groundwater samples from the four on-site monitor well 3 The depth to groundwater has risen one foot since the last monitoring in October, and measurements indicate that groundwater continues to flow to the east The data indicate that the gradient is steeper in the northern part of the site near VM-4 than in the southern part of the site near VM-3 The difference appears to be related to the permeability of the water-bearing zone hi the north low- permeability clay near the ground surface forms a slight confining layer, causing the static water surface to be slightly deeper than in the southern part of the site After measuring the depth to groundwater,the wells were purged with a submersible grou adwater pump and water samples were collected with disposable Teflon bailers, poured into 40-m1 vials and preserved for laboratory analysis The samples were analyzed for TPH-gasoline using EPA method 602, for BTEX using EPA method 8020, and for five oxygenates using EPA method 8240B After declining in October 1998, gasoline-range hydrocarbon concentrations rose sharply in VM-1, while BTEX concentrations continued to decline to their lowest levels since monitoring began in 1995 Concentrations of all analytes continued to decline in VM-2, and benzene is the only BTEX compound detected in this well The laboratory noted that the gasoline chromatograms from both wells differ from the gasoline standard, and that two non-gasoline peaks were strong contributors to the concentrations reported These peaks may represent solvent compounds, several of which have been detected in these wells in the past Samples from VM-3 and VM-4 did not contain detectable concentrations of gasoline Benzene, toluene, and xylene were detected very near the reporting limit in VM-4 None of the well, contained detectable concentrations of any of the oxygenates Previously, MTBE had been detected on once occasion in VM-1 and TBA had been reported on one occasion in VM-4 These niay have been laboratory errors (carryover from previously analyzed samples from another site) In addition to groundwater monitoring, two other issues were addressed during the first quarter On January 12, a meeting was held at the offices of the San Joaquin County Environmental Health Division to discuss the issue of the removal of a small underground storage tank from the sidewalk along Main Street PHS/EHD requested Valley Motors to submit a tank closure permit and pay delinquent fees Valley Motors informed PHS/EHD that prior to April 1998 the existence if the tank was unknown and that because the tank is located in the public sidewalk,the City of Stockton is responsible for its removal Valley Motors was instructed to inform the City in writing, and the issue was tabled pending a response from the City Also during the first quarter, Upgradient Environmental submitted a Soil Remediation Plan to PHS/EHD for review The purpose of the SRP was to present the rationale and methodology for interim remediation of the site in the second quarter of 1999 PHS/EHD reviewed the SRF in early March Due to the volume of soil proposed for excavation, PHS/EHD concluded that the 'State UST Fund would not approve the costs associated with the proposed methodology Therefore, PHS/EHD did not approve the SRP • 1