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<br /> l TABLE 1 - CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES:. '
<br /> Site Name and Location: Regal #603,6425 Pacific Avenue, Stockton, San Joaquin County
<br /> 0 1. Distance to production wells for municipal, domestic, agriculture, industry A well receptor survey was completed in
<br /> and other uses within 2000 feet of the site; 1998. Three existing water supply wells
<br /> li::.; are within 2,000 feet of the site.
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Three 10,000-gallon gasoline '
<br /> excavation contours and sample locations, boring and monitoring well elevation contours,
<br /> USTs were removed and
<br /> gradients, and nearby surface waters, buildings,streets, and subsurface utilities; replaced in October 1988.
<br /> Site maps provided.
<br /> 3. Figures depicting litho/ogy(cross section), treatment system diagrams; Lithology figures show a shallow sand
<br /> aquifer overlain with silty clay sediments.
<br /> 0 4. Stockpiled soil remaining on-site or off-site disposal(quantity),, Excavated soils associated with the USTs were returned
<br /> to the tank pit.
<br /> Y 5. Monitoring wells remaining on-site, fate;
<br /> Thirteen monitoring wells remain on-site and off--site.
<br /> 6. Tabulated results of all groundwater elevations and depths to water Groundwater elevations vary from 33 to 60 feet bgs,
<br /> ; and groundwater flow is east/northeast.
<br /> FY 7. Tabulated results of all sampling and analyses: January 1999 maximum groundwater monitoring results in pg/I show
<br /> Detection limits for confirmation sampling TPHg at 5,400,benzene at 7, toluene at 55,ethyl benzene at 170,
<br /> xylenes at 1100, and MtBE at 16. Lead was identified at 12 mg/kg in
<br /> Lead analyses one overexcavation soil sample. 4
<br /> 0 ETIConcentration contours of contaminants found and those remaining in soil The vertical and lateral extent of
<br /> and groundwater, and both on-site and off-site: groundwater contamination has not been
<br /> Lateral and iiy Vertical extent of soil contamination defined. v
<br /> fk
<br /> Lateral and " I� Vertical extent of groundwater contamination
<br /> FI
<br /> 9.Zone of influence calculated and assumptions used for subsurface A SVE system operated from October 1991
<br /> remediation system and.the zone of capture attained for the soil and. to December 1998,and an air sparging
<br /> groundwater remediation system; system operated from December 1997 to
<br /> December 1998. i
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<br /> 0 10.Reports/information;�fyq Unauthorized Release Form QMRs(8/91 through 1/99) g-
<br /> f
<br /> ElWelland boring logs; QPAR 0 FRP Other(Overexcavation of Soils, 4/00)
<br /> c:
<br /> Y 11.Best Available Technology(BAT)used or an explanation for not using BAT,. Free product removal, followed by SVE and
<br /> Contamination remains in on-site soils;and the -
<br /> T1 12.Reasons why background was/is unattainable using BAT
<br /> e III. groundwater plume has extended off-site.
<br /> N� 13.Mass balance calculation
<br /> A mass balance completed In 1998 estimated 90ion of substance treated versus that remaining; pounds of TPHg and 1 pound of benzene
<br /> remaining in groundwater.
<br /> 14.Assumptions,parameters, calculations and model used in risk A RBCA evaluation was completed using the Tier 2
<br /> assessments, and fate and transport modeling; assessment.
<br /> YE15.Rationale why conditions remaining at site will not adversely Consultant states that 99% of the benzene,and 69%of
<br /> impact water quality, health, or other beneficial uses. the TPHg has been removed,and removal rates have
<br /> ,P decreased to asymptotic levels. However, the extent of
<br /> contamination in groundwater has not been defined.
<br /> By: Comments: Three USTs were removed and-replaced in 1988, and on-site remediation operated from 10/91 until 12/98.
<br /> TPHg is detected in downgradient monitoring wells MW-8 and MW-12 at concentrations higher than in on-site wells.
<br /> JJ�r�eKK77"- Benzene and MtBE concentrations are low. A well survey was completed, and three wells are within 2,000 feet of the
<br /> site. The closest,well is a 120-foot deep domestic well approximately 950 feet southeast of the site. City water is
<br /> Date: , supplied, and itis unknown if the domestic well is active. The extent of groundwater contamination beyond MW-12 has
<br /> not been defined: The on-site groundwater plume appears to be stable;however, the last groundwater monitoring was
<br /> completed in 1/99 after the SVE and air sparging systems were shut off. Based on information provided, San Joaquin
<br /> County's cfosure�'recommendation is not appropriate at this time.
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