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TAB 1 - CHECKLIST OF REQUfREDj TA j
<br /> {4 FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
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<br /> Site Name and Location: Beacon#27 (Cardlock 610),3300 Waterloo Road;Stockton, San Joaquin County
<br /> A well survey in 2002 shows two domestic water
<br /> 1. Distance to production wells for municipal, domestic,agriculture,EJ supply;wells located approximately 325 feet south and
<br /> industry and other uses within 2000 feet of the site;
<br /> 1200 feet southwest of the site.
<br /> p One 550-gallon waste oil UST was
<br /> 1 2. Site maps, to scale, of area impacted showing locations of former and existing tank g
<br /> systems, excavation contours and sample locations, boring and monitoring well ! removed in June olive Two
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and ,I 10,000-gallon gasoline,and one
<br /> { ;, 10,000-gallon diesel USTs were
<br /> subsurface utilities; removed in October 1993.
<br /> y
<br /> 3. Figures depicting lifhology(cross section), treatment system diagrams; Site lifoologconsists of clay,silt,sand andravel to 90 feet, the total depth investigated. .A
<br /> higher permeability zone lies between 55 and 65
<br /> feet below ground surface.
<br /> 4. Stockpiled soil disposed off--site (quantity); Approximately 900 cubic+yards of excavated soil was transported by
<br /> 111 Ben's Truck&Equip. Inc. to Red Bluff for aeration and disposal.
<br /> 1'_ 5. Monitoring wells
<br /> remaining on-site, fate; seven mdn!to ring wells=(MW-1-through MW-7)-and three vapor extractiah
<br /> wells(VE-1 through VE-3)have been�installed for this investigation. The
<br /> wells will be properly destroyed pending site closure.
<br /> 0 6. Tabulated results of all groundwater elevations and depths to water; The;depth ito water varied from 35 to 75 feet,and
<br /> the groundwater flow direction varied from south
<br /> (1987) to northwest(1999).
<br /> 0 7. Tabulated results of all sampling and analyses: Groundwater monitoring results in 9/99 were: 66 lig/L for TPHd,
<br /> <50 lig/L for TPHg, <0.5 pg/L for benzene,and<0.5 erg/L for MtBE.
<br /> i Detection limits for confirmation sampling Lead in soil was 12 mg/kg in 10/93.
<br /> HY Lead analyses
<br /> �., 0 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, both on-site and off-site: The extent of contamination is defined by
<br /> � Y® Latera!and �Y Vertical extent of soil contamination
<br /> on-site soil borings and monitoring wells.
<br /> Lateral and Vertical extent of groundwater contamination .M
<br /> Q9. Zone of influence calculated and assumptions used for subsurface "' Based on the limited extent of soil
<br /> # remediation system and the zone of capture attained for the soil and contamination, an engineered remediation
<br /> groundwater remediation system, system was not required at this site.
<br /> 10.Reports/information Y❑ Unauthorized Release Form Y❑ QMRs(3/87 to 4/87, 10/94 to 12(95, 3/99 and 9199)
<br /> Boring logs N❑ PAR FRP El (No FurtherActi`on Request Reports, 1/95 and 8/02)
<br /> 11.Best Available Technology(BAT)used or an explanation for not using BAT; Remove USTs and natural attenuation.
<br /> ETIDecreasing concentrations have been attained at all monitoring wells as a
<br /> 12.Reasons why background wasss g L
<br /> unattainable using BAT; Y _v.. result of excavation. Minor soil contamination remains on-site.
<br /> 13.Mass balance calculation of substance
<br /> In 1/95, the consultant estimated that 5 gallons of TPHg and 46 gallons of TPHd
<br /> treated versus that remaining, remain in shallow soils. Mass balance was not calculated for groundwater.
<br /> 0 14.Assumptions,parameters, calculations and model used in risk M
<br /> assessments, and fate and transport modeling,and A risk assessment was not required.
<br /> FY
<br /> 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent,and based on
<br /> f impact water quality, health, or other beneficial uses. nine sampling events, contamination is not continuing to
<br /> leach to groundwater. Groundwater monitoring shows a
<br /> decreashig trend in concentrations for all constituents.
<br /> By: Comments: Two 10,000-gallon gasoline and one 10,000-gallon diesel,USTs were removed from the subject site in 1/99.
<br /> + 3LB One 550-gallon waste oil tank was removed in 6/87. Soil contamination was identified at the gasoline/diesel USTs area.
<br /> Multiple borings and seven monitoring wells were completed to delineate andi',monitor contamination at this site. UST
<br /> Date: monitoring wells MW-1 through MW-4 were sampled from 3/87 to 9/99. MW-5 through MW-7 were sampled from 4/93 to
<br /> 9/99. In 9/99, maximum groundwater contaminant concentrations had,declined to 66 ug/L for TPHd, X50 ug/L for TPHg,
<br /> 3/20/03 <0.5 ug/L for benzene,and X0.5 ug/L for MtBE. After testing in 10/01,;resultsi'ishowed that the nearest domestic supply
<br /> well was not impacted by contaminants. Based on the minor soil contamination and the low level of TPHd in
<br /> groundwater, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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