SITE INFORMATION AND CORRESPONDENCE_CASE 2

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TABtt 1 - CHECKLIST OF REQUIRED DATA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: Collegeville Market, 13521 Mariposa Road,Stockton, San Joaquin County 0 1. Distance to production wells for municipal, domestic, agriculture, Site is located southeast of Stockton with no public industry and other uses within 2000 feet of the site; wells within 2000 feet(USGS Stockton East Topographic Map). A sensitive receptor survey was not conducted. 0 2. Site maps, to scale, of area impacted showing locations of former and existing tank Soil contamination was reported systems, excavation contours and sample locations, boring and monitoring well under the dispenser island when elevation contours, gradients, and nearby surface waters, buildings, streets, and dispenser pans were upgraded in subsurface utilities, 5/02. 0 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of silt clay to 25 feet, the total depth investigated. FN 1 4. Stockpiled soil disposed off-site(quantity); No contaminated soil was removed. FN 5. Monitoring wells remaining on-site, fate; Monitoring wells were not required or installed. 6. Tabulated results of all groundwater elevations and depths to water,• The depth to water was estimated at 80 to 100 feet Regionally, groundwater flows towards the North. 0 7. Tabulated results of all sampling and analyses: Results of soil samples collected 2 feet below dispensers for dispenser pan upgrades(5/02);were:xylenes, 0.38 mg/kg;MtBE, Y Detection limits for confirmation sampling 12 mg/kg;and TBA, 25 mg/kg. On 11/02, one soil boring adjacent to Lead analyses dispenser reported non-detect for TPHg(<1 mg/kg), BTEX(<0.005 mg/kg),and MtBE(<0.005 mg/kg)at 10-and 20-foot depths. FN 1 8. Concentration contours of contaminants found and those remaining in soil and groundwater, both on-site and off-site: The dispenser pan upgrade soil samples Y® Lateral and ®Y Vertical extent of soil contamination and on-site soil boring define the extent of Lateral and Vertical extent of groundwater contamination contamination. FE 9. Zone of influence calculated and assumptions used for subsurface Based on the limited extent of soil remediation system and the zone of capture attained for the soil and contamination,an engineered remediation groundwater remediation system; system was not required at this site. Y� 10.Reports/information Y❑ Unauthorized Release Form q QMRs a Boring logs El PAR El FRP Y❑ Other Closure Summary Report Y� 11.Best Available Technology(BAT)used or an explanation for not using BAT, Natural attenuation. Q12.Reasons why background was/is unattainable using BAT, Minor soil contamination remains on-site. _ 0 13.Mass balance calculation of substance treated versus that remaining; Mass balance was not calculated for soil. 0 14.Assumptions,parameters, calculations and model used in risk A risk assessment was not required. assessments, and fate and transport modeling;and Y 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent,and is not impact water quality, health, or other beneficial uses. expected to reach groundwater. By: Comments: Soil contamination was observed and reported during dispenser pan upgrade at the subject site in 5/02. JLB Minor soil contamination was identified at the dispenser island area. One soil boring(11/02)did not reveal visible contamination at five-foot soil boring sample intervals to 25 feet bgs. Soil results from 10 and 20-foot depth samples Date: were ND. Depth to groundwater was estimated at 80 to 100 feet bgs. Based on the minor soil contamination and 5-24-04 minimal threat to water quality, Regional Board staff concur with San Joaquin County's Closure Recommendation.