SITE INFORMATION AND CORRESPONDENCE

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TAwLE 1 - CHECKLIST OF REQUIRED DATA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Former Unocal Station#5421, 7303 Pacific Ave., Stockton, San Joaquin Co. Y 1. Distance to production wells for municipal, domestic, agriculture, industry Municipal well located approx. 114-mile east(downgradient)of the site. Several and other uses within 2000 feet of the site; other wells located cross/up gradient. 0 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, See closure report. excavation contours and sample locations, boring and monitoring well elevation contours, gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Q 3. Figures depicting lithology(cross section), treatment system diagrams; Monitoring well borings and additional soil borings logs are included in various docs. EYD 4. Stockpiled soil remaining on-site or off-site disposal(quantity); approximately 3,180 cubic yards of soils was disposed of at three different landfilWhaz waste locations. a5. Monitoring wells remaining on-site, fate; 4 monitoring wells remain on-site.Destruction permit applications have been - submitted to SJCEHD for approval of well decommissioning. ^ 0 B. Tabulated results of all groundwater elevations and depths to water; All groundwater monitoring data was included in closure report. 7.Tabulated results of all sampling and analyses: Al!sampling results are present In the Closure Report, F Detection limits for confirmation sampling FN Lead analyses ID8. Concentration contours of contaminants found and those remaining in soil Soil contamination is well defined for both and groundwater, and both on-site and off--site: generations of tank excavations. The Y�Lateral andFYI Vertical extent of soil contamination lateral extent of groundwater impact is defined in relation to the first set of tanks; FN]Lateral and a Vertical extent of groundwater contamination however,is poorly def in rel to new tanks. 0 9.Zone of influence calculated and assumptions used for subsurface Soil overexcavation is the only remediation remediation system and the zone of capture attained for the soil and that was attempted at this site. groundwater remediation system; 0 10.Reports/information a Unauthorized Release Form FY-]QMRs(Dates) 1990- 1998 QWelland boring logs 0 PAR FRP Other(report name) Closure Report _YY -11.Best Available.:Technology.(BAT).used or an-explanation-for not using:BA-T,r giver--Ex used as the only remedial tech. NA 12.Reasons why background wash's unattainable using BAT; D13.Mass balance calculation of substance treated versus that remaining; Unknown mass remains in place in soils. No significant impact to groundwater presented. NA 14.Assumptions,parameters, calculations and model used in risk assessments, and fate and transport modeling; 0 15.Rationale why conditions remaining at site will not adversely Low,concentrations of contaminants were detected in I impact water quality, health, or other beneficial uses;and conf soil samples at approx.26'bgs. Historic high G W is at-35: Source is essentially removed NA 16.WET or TCLP results Sy., `"A„6 _ Comments:The information provided in the Closure report and by SJCEHD was evaluated in determining the site 1v klw status. Residual contamination remains in the soil at approximately 17'bgs. There is a low risk of impact to Date, groundwater from the UST activities at this site.Approximately 3,180 cubic yawls of contaminated soil were hauled + zb \°1\ from this site to landfills or haz waste disposal facilities.