SITE INFORMATION AND CORRESPONDENCE

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it TABLE 1 - CHECKLIST OF REQUIRED DADA , FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Gemelos-Paladine Mileage Center,2421 Holly Drive,Tracy,San Joaquin County 1. Distance to production wells for municipal, domestic, agriculture, A well receptor survey identified one domestic well industry and other uses within 2000 feet of the site; and one irrigation well within 2,000 feet of the site. Y 2. Site maps, to scale, of area impacted showing locations of farmer and existing tank systems, Site maps are provided in excavation contours and sample locations, boring and monitoring well elevation contours, the various reports. Two gradients, and nearby surface waters, buildings, streets, and subsurface utilities; 10,000-gallon gasoline USTs were removed in April 1988. k 3. Figures depicting lifhology(cross section), treatment system diagrams; Boring logs show clay to 15 feet with minor lenses of sand and silty sand. 0 Y 4. Stockpiled soil dis Dosed off-site(quantify); Approximately 120 cubic yards of soil was excavated at the time of UST removal. The disposition of the soil was not presented. Q5. Monitoring wells remaining on-site, fate; Three monitoring wells remain on-site. The wells will be properly destroyed pending site closure. 6. Tabulated results of all groundwater elevations and depths to water, Groundwater levels varied from 6 to 8 feet below ground surface,and flow is to the north/northwest G 7.Tabulated results of all sampling and analyses: Samples collected in July 2001 show TPHg at 270 pg/i and benzene at FY ih 1.3 pg/1 in only one of the three monitoring wells on-site. Al!other 0 Defection limits'f`or confirmation sampling constituents including MtBE and other fuel oxygenates are non-detect ©Lead analyses ;I at acceptable detection limits. Groundwater samples analyzed in July 2001,reported lead at<5 pg/l. Y 8. Concentration contours of contaminants found and those remaining in soil The extent of soil contamination has been and groundwater, and both on-site and off-site: defined Based on the limited soil Lateral and i YY Vertical extent of soil contamination contamination and the low concentrations ❑ Lateral and ❑ Vertical extent of groundwater contamination of TPHg and benzene,a "zero"line of definition in groundwater was not required. 9.Zone of influence calculated and assumptions used for subsurface Based on the limited contamination,site Qremediation system and the zone of capture attained for the soil and remediation beyond soil excavation and groundwater remediation system; disposal was not required. FTJ 10.Reports/information E] Unauthorized Release Form y❑ QMRs(7/96, 9/97, 11/98, 3/00, and 7/01) 0 Boring logs PAR FRP Other(Closure Summary Report and Addendum) Y� 11.Best Available Technology(BAT) used or an explanation for not using BAT; The UST and contaminated soils were removed. - -0Y 12.Reasons wh:back round warms Minor groundwater contamination remains near the former tank pit area. The -== =y g—~ --w s_ 'contaniir:adon is limited In'extent,-and does not presenta-slgnirrcant`throbt to unattainable using BA`T, water quality. Y� 13.Mass balance calculation of substance The consultant estimates that approximately 1.7 pounds of TPHg remains in treated versus that re Irl aining; groundwater at the site. 14.Assumptions,parameters, calculations and model used in risk Based on the limited groundwater contamination and the remaining mass, a risk assessment was not required. assessments,and fate and transport modeling; Y� 15. Rationale why co aditions remaining of site will not adversely Remaining contamination is limited in extent impact wafer quality, health, or other beneficial uses;and Contamination will naturally degrade. By: Comments: The site is a former retail gasoline fueling center. Two 10,000-gallon gasoline USTs were removed in MH April 1988. Four soil borings were completed in July 1996, and minor soil contamination was identified in one boring at ten feet. Three of the borings were converted to monitoring wells, and the wells have been monitored five times since July 1996. TPHg, the only constituent with repeatable results, shows a stable trend over the five sampling events. Only Date: one of the three monitoring wells on-site show detections of TPHg and benzene. Groundwater samples analyzed for fuel 12/26/01 oxygenates and additives using EPA Method 8260E were non-detect at acceptable detection limits. The well receptor survey completed in April 2001 identified one domestic well and one irrigation well within 2,000 feet of the site. The remaining contamination in groundwater is limited in extent, and will naturally degrade. Based on the site investigation and activities completed to date, Board staff concur with San Joaquin County's closure recommendation. r F� E