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TAEs' E 1 - CHECKLIST OF REQUIRED19TA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Valley Showcase,913 West Fremont Street, Stockton, San Joaquin County
<br /> FTI 1. Distance to production wells for municipal, domestic, agriculture, No water supply wells were identified within 2,000 feet
<br /> industry and other uses within 2000 feet of the site; of the site.
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank Q systems, One 500-gallon UST was II?
<br /> excavation contours and sample removed ih February 1988.locations, boring and monitoring well elevation contours, .
<br /> gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Site maps are available in
<br /> the various reports.
<br /> 3. Figures depicting lithology(cross section), treatment system diagrams, Site lithology consists of silty clay and sandy
<br /> clay to 25 feet, the total depth investigated.
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<br /> 0 4. Stockpiled soil disposed off-site(quantity); Approximately 108 cubic yards of soil were disposed of at West Contra
<br /> Class 111 Landfill in May 1990.
<br /> 5. Monitoring wells remaining on-site fate; Five monitoring wells were installed for this investigation. The wells will be
<br /> Y properly destroyed pending site closure. i
<br /> 6. Tabulated results of all groundwater elevations and depths to water,, The depth to water varied from 8 to 15 feet, and the
<br /> groundwater flow direction is to the northeast.
<br /> 7.Tabulated results of all sampling and analyses` The maximum soil concentrations show TPHg at 1,300 mg/kg and
<br /> El Detection limits for confirmation sampling benzene at 4.1 mg/kg at 15 feet bgs. Groundwater contamination as
<br /> p g TPHg has decreased from a maximum of 98,600 pg/l In 3194 to a50 pg1l
<br /> Lead analyses in 5102. All constituents are currently non-detect in all wells.
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<br /> Y 8. Concentration contours of contaminants found and those remaining.in soil The extent of contamination is defined by ;
<br /> and groundwater, both on-site and off-site: on-site soil borings and on and'off--site
<br /> YM Latera!and RY Vertical extent of soil contamination monitoring wells.
<br /> Lateral and Vertical extent of groundwater contamination
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<br /> 9.Zone of influence calculated and assumptions used for subsurface Based on the limited exteht of
<br /> 0 remediation system and the zone of capture attained for the soil and contamination, an englneered remediation
<br /> groundwater remediation system; system was not warranted at this site:
<br /> 0 10.Reports/information El Unauthorized Release Form Y❑ QMRs(3/94 to 5/02)
<br /> '`' . Y❑ Boring logs 0 PAR, 0 FRP (NFAR Request& QMR, 7/02)
<br /> 11.Best Available Technology(BAT) used or an explanation for not using BAT. Remove US Ts and impacted soil; ORC
<br /> treatment, and natural attenuation.
<br /> -12.Reasons.why background wasps .�. _ Minor soil and groundwater contamination remains on-site at the former UST
<br /> r unattainable using BAT, areas and downgradient-of the former_USTarea ,T-
<br /> 0 13.Mass balance calculation of substance The consultant estimates that 42 pounds(7 gallons)of TPHg remains in site
<br /> treated versus that remaining, soils, and 0.33 pounds of TPHg remains in groundwater.
<br /> 0 14. Assumptions,parameters, calculations and model used in risk
<br /> assessments, and fate and transport modeling, A risk assessment was not required.
<br /> Y 15. Rationale why conditions remaining at site will not adversely Soil and groundwater contamination is limited in extent,
<br /> FEimpact water quality, health, or other beneficial uses;and results of groundwater monitoring show decreasing
<br /> trends,and contamination will continue to degrade. I
<br /> By: Comments: One 500-gallon gasoline UST was removed from the subject site in February 1988. Soil contamination was
<br /> MH identified in the tank pit soil samples, and visually impacted soils were excavated and disposed off-site. Multiple borings
<br /> were completed, and five monitoring wells were installed. Core monitoring wells have been monitored since March 1994,
<br /> Date: and site constituents show decreasing trends. MTBE was identified at a maximum of 0.80 pg4 in December 9999 at
<br /> MW-1;however, it has not been confirmed. As an additional remediation effort, an ORC sock was installed into
<br /> 14/29/02 monitoring well MW-2 from March 1999 to September 1999. Groundwater monitoring results for MW-2 continued to"
<br /> decline during this added remedial work. Based on the limited extent of contamination and the decreasing constituent
<br /> trends, Board staff concur with San Joaquin County's Closure Recommendation. f
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