SITE INFORMATION AND CORRESPONDENCE

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TABL - CHECKLIST OF REQUIRED DA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES E ite Name and Location: M&M Automotive, 60 East 10`x'Street, Tracy, San Joaquin County r 1. Distance to production wells for municipal, domestic, agriculture, Nine water supply wells are within 2,000 feet of the industry and other uses within 2000 feet of the site; former USTs. The nearest downgradient well is 1,900 feet northeast of the site. 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Two USTs,were removed in excavation contours and sample locations, boring and monitoring well elevation contours, November 1991. Site maps gradients, and nearby surface waters, buildings, streets, and subsurface utilities; provided. Y� 3. Figures depicting lithology(cross section), treatment system diagrams; Boring logs and cross-sections show silty clay to 14 feet, and silty sand to 32 feet, the total depth explored. 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 170 cubic yards of excavated soil was disposed at Forward Landfill in Manteca. 5. Monitoring wells remaining on-site, fate; Three monitoring wells exist onsite. The wells will be properly destroyed pending site closure. i Y 6. Tabulated results of all groundwater elevations and depths to water; Groundwater levels varied from 8 to 12 feet below ground surface, and flow is to the northeast i4 0 7. Tabulated results of all sampling and analyses: Groundwater monitoring results for the Third Quarter 2000 are non- FIDetection fruits for confirmation sampling deteci for all constituents including MTBE at acceptable detection limits. MW-1 which had high concentrations of TPHg and BTEX was ©Lead analyses destroyed in April 2000 during an over excavation. The remaining three wells have shown minor detections since December 1994. 8. Concentration;contours of contaminants found and those remaining in soil and groundwater, and both on-site and off-site: The lateral and vertical extent of soil ' Lateral and Vertical extent of soil contamination contamination has been defined. The ' Lateral and Vertical extent of groundwater contamination vertical extent of groundwater contamination has been defined to 32 feet. 9. Zone of influence calculated and assumptions used for subsurface Remediation consisted of soil excavation ri remediation system and the zone of capture attained for the soil and to 10 feet Approximately 170 cubic yards groundwater remediation system; of contaminated soils were disposed off site at Forward Landfill. 0 10.Reports/information 19 Unauthorized Release Form 0 QMRs 171 I Boring logs 0 PAR N❑ FRP Other(Site Closure Report, 12/2000) Excavate contaminated soils { 11.Best Available.'Technology(BAT) used or an explanation for not using BAT,' , and dispose off-site. i - -=92.-J4easonswhybackground was7is- � Contamination.;remains.in-soiland-groundwater. .F.urthe_rexnot .---.----- "'� 0 unattainable using BAT; cost effective. The groundwater contamination is limited in extent, and remaining concentrations do not present a significant threat to water quality. 13.Mass balance:calculation of substance treated versus that remaining; The mass balance shows that 56%of contaminated soil has been removed. 14.Assumptions,parameters, calculations and model used in risk Based on the limited extent of groundwater assessments, and fate and transport modeling; contamination,a risk assessment was not required. 15. Rationale why conditions remaining at site will not adversely Remaining contamination is limited in extent Y� impact waterquality, health, or other beneficial uses;and ' Contamination will naturally degrade. By: Comment's: Two gasoline USTs(a 285-gallon and a 550-gallon) were removed from the site in November 1991. Soil . contamination was identified, and multiple borings and four monitoring wells were installed. Three wells have been monitored.quarterly since December 1994, and only MW-1 located in the former UST tank pit showed confirmed concentrations of TPHg and BTEX. (MW-1 was destroyed during over excavation activities in April 1999.) MW-4 was Date: installed in August 1997, and has only shown irregular detections of TPHg. An over excavation in April 1999 removed approximately 170 cubic yards of contaminated soils. Quarterly monitoring results show the remaining contamination is 3i o limited in extent. The site is covered with asphalt and concrete, which should limit further leaching of contaminants into ? the groundwater. Based on the site investigation completed to date, Board staff concur with San Joaquin County's i closure recommendation. ! T