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TAB`' 1 - CHECKLIST OF REQUIRED C TA
<br /> 'FOR NO.FURTHECTION REQUESTS AT UNDERGt UND TANK SITES
<br /> Site game and Location: Sears Auto Center#1288, 5110 Pacific Avenue, Stockton, San Joaquin County
<br /> ETI 1. Distance to production wells for municipal, domestic, agriculture, A well receptor survey completed in January 2000 did
<br /> industry and other uses within 2000 feet of the site; not identify any water supply wells within 2,000 feet of
<br /> the site.
<br /> 3
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Seven USTs removed in
<br /> Y 2185, and three USTs
<br /> excavation contours and sample locations, boring and monitoring well elevation contours,
<br /> gradients, and nearby surface waters, buildings, streets, and subsurface utilities; removed in 6187. Site maps
<br /> are provided.
<br /> 0 3. Figures depicting lithology(cross section); Solis encountered during tank removal show clay and silt with minor
<br /> sand to 21 feet, the total depth investigated.
<br /> 4. Stockpiled soil was remediated off-site(quantity); Approximately 100 cubic yards of excavated soils were
<br /> aerated off-site in February 1985.
<br /> N
<br /> 5. Monitoring wags remaining on-site, fate; Groundwater,was not sampled, and monitoring wells were not installed.
<br /> �`~6`Tabulated results of all groundwater elevations-and-depths-to-water,•_Qepth_to water is—_.es . fed at.30 feet and the
<br /> groundwater flow direction is to the northeast.
<br /> �Y 7. Tabulated results of all sampling and analyses: . Maximum soil concentrations from UST and pipeline removal show
<br /> TPHd at 4.8 mg/kg and lead at 67 mg/kg. TPHg, BTEX, and MWE were
<br /> Detection limits for confirmation sampling non-detect at appropriate detection limits.
<br /> Lead analyses
<br /> Y 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, and both on-site and off-site: The lateral extent of contamination is
<br /> defined. The vertical extent of
<br /> Lateral and Y�J Vertical extent of soil contamination
<br /> contamination is defined to 21 feet.
<br /> N❑ Lateral and 0 Vertical extent of groundwater contamination
<br /> Groundwater was not encountered.
<br /> 9.Zone of influence calculated and assumptions used for subsurface Due to the limited extent of contamination, a
<br /> Qremediation system and the zone of capture attained for the soil and remediation system was not required at this
<br /> groundwater remediation system; site.
<br /> 10.Reports/informationyl71 Unauthorized Release Form N❑ QMRs
<br /> 0 Boring logsN❑ PAR ❑ FRP El
<br /> Other(Site Assessment Report and Request for Closure)
<br /> ED
<br /> 11.Best Available Technology(BAT) used or an explanation for not using BAT; Remove USTs, natural attenuation of
<br /> remaining contamination.
<br /> 12.Reasons why background wasfis Minor contamination remains in on-site soils. Further excavation is not cost
<br /> unattainable using BAT, - - Y'effective..Remaining contamination does not present a significant threat to
<br /> quality.
<br /> N� 13.Mass balance calculation of substance
<br /> A Based on the limited extent of contamination, a mass balance was not
<br /> treated versus that remaining;
<br /> required.
<br /> 14.Assumptions,parameters, calculations and model used in risk Based on the limited extent of contamination, a risk
<br /> assessments,and fate and transport modeling;
<br /> assessment was not required.
<br /> 0 15. Rationale why conditions remaining at site will not adversely Contamination is limited to on-site soils. Contamination
<br /> impact water quality, health, or other beneficial uses;and will naturally degrade.
<br /> By: Comments: The site is an active Sears Auto Center. Four 1,000-gallon oil USTs and three 90,000-gallon gasoline USTs
<br /> •`��� were removed from the site in February 1985. Tank pit soil samples were not collected. One 1,000-gallon waste oil UST
<br /> YltI and two 1,000-gallon oil USTs were removed in June 1987, tank pit soil samples were collected, and the County closed
<br /> these three USTs- In August 1994, UST piping and dispensers were removed, and soil contamination was identified in
<br /> Date: shallow soil samples. In!November 1999, six borings were completed to delineate the extent of site contamination, and
<br /> soil sampling shows diesel in one boring at 21 feet. Lead was identified in all six soil samples ranging from 37 to
<br /> Z�f 67 mg/kg, and is believed to be background concentrations for this area. Due to the limited extent of contamination and
<br /> the immobile nature of diesel, a groundwater investigation was not required. Based on the investigation completed to
<br /> date, Board staff concur with San Joaquin County's closure recommendation.
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