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c TABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Caltrans Stockton Yard Maintenance, 1604 B St.,Stockton, San Joaquin County(RB#390708)
<br /> y 1. Distance to production wells for municipal,domestic, A 2013 sensitive receptor survey reported nineteen water
<br /> agriculture, industry and other uses within 2000 feet of supply wells within 2,000'of the Site. The nearest wells are
<br /> the site. 850'southeast,900'northeast and 980'northeast,
<br /> respectively. The supply wells are not threatened by the
<br /> -Petroleum hydrocarbon release.
<br /> Y 2. Site maps,to scale, of area impacted showing In 5188, one 500-gallon kerosene UST was removed.In 12189,
<br /> locations of any former and existing tank systems, one 1,500 gallon diesel and one 10,000-gallon gasoline USTs
<br /> excavation contours and sample locations, boring and were removed. In 9193, one 115-gallon diesel UST was
<br /> monitoring well elevation contours,gradients,and removed. Site maps and figures showing tank locations,
<br /> nearby surface waters, buildings,streets,and area of excavations,buildings and residual pollutants were
<br /> subsurface utilities; provided in investigation reports.
<br /> Y 3. Figures depicting lithology (cross Site lithology consists of clay,silt and sand to 80', the total depth investigated.
<br /> section),treatments stem diagrams; All figures were provided in the investigation reports.
<br /> Y 4.Stockpiled soil remaining on-site Approximately 2.9 tons of soil was excavated and transported to TPS
<br /> or off-site disposal (quantity); Technologies,Inc. in Adelanto. Consultant did not estimate mass of TPH
<br /> removed by excavation.
<br /> y5. Monitoring wells remaining on-site, Eighteen(18)monitoring(MW-1 through MW-18)and six remediation (VW-1,
<br /> ate; VW-2,AS-1,and OW-1 through OW-3)wells will be properly destroyed prior to
<br /> closure.
<br /> 6.Tabulated results of all groundwater Tabulated data was provided in reports indicating depth to groundwater ranged
<br /> elevations and depths to water; from 34'bgs to 68'bgs. Groundwater flow varied from east to southeast.
<br /> Groundwater gradient varied from 0.0007 fJft to 0.0012 ft/ft.
<br /> 7.Tabulated results of all sampling All data was adequately tabulated in various reports.
<br /> and analyses:
<br /> Y❑ Detection limits for
<br /> confirmation sampling
<br /> QY Lead analyses
<br /> Ly J 8. Concentration contours of contaminants found and those remaining in The horizontal extent of the petroleum
<br /> soil and groundwater,and both on-site and off-site: pollution remains onsite. Vertical extent
<br /> was delineated by non-detect results at
<br /> ElLateral and Vertical extent of soil contamination MW-1 (groundwater levels decreased 20'
<br /> Lateral and Vertical extent of groundwater contamination since 1993).
<br /> 9.Zone of influence calculated and assumptions used for subsurface SVE demonstrated a radius of influence at
<br /> remediation system and the zone of capture attained for the soil and 20'.
<br /> groundwater remediation system;
<br /> 10.Reports/information ❑Y Unauthorized Release Form FY QMRs(58)4-92 to 8-12
<br /> FY] Well and boring logs PAR 0 FRP FYI Other Site Conceptual Model,1 -09;
<br /> Request for Closure, 9-13
<br /> Y
<br /> —,,-Best Available Technology(BAT) used or Leak was stopped by removing tanks. Soil vapor extraction, air
<br /> an explanation for not usingBAT; sparging and ozone injection were implemented as the BAT.
<br /> Y 12. Reasons why background was/is not Contaminant concentrations are declining naturally and background is
<br /> mable using BAT; predicted to be restored in 29 years.
<br /> Y13.Mass balance calculation of substance Consultant estimates residual TPH mass in soil as 1,184 lbs. (179 gal.)
<br /> treated versus that remaining; and TPH mass in groundwater as 5.25 lbs. (0.8 gal.).
<br /> Y 14. Assumptions, parameters, calculations Site is an active fueling station that is exempt from LTCP vapor
<br /> and model used in risk assessments, and fate intrusion limits. Consultant states site does not represent a significant
<br /> and transport modeling; environmental or health risk.
<br /> 15. Rationale why conditions remaining at Groundwater pollution is reportedly confined to the property limits.
<br /> site will not adversely impact water quality, Land use(commercial)is not expected to change in the foreseeable
<br /> Y
<br /> health,or other beneficial uses; and future. WQOs are predicted to be reached by 2043- Groundwater plume
<br /> is stable and slowly decreasing in concentration.
<br /> By. JLB Comments: Multiple USTs were removed from the-site.Soil pollution presents a minimal threat to human
<br /> health and groundwater pollution is predicted to be restored in 29 years. Based on the stable and declining
<br /> Date: concentrations in groundwater, no foreseeable changes in future land use(commercial), and minimal risks
<br /> 4/15/2014 from soil vapor and soil, Regional Board staff concur with San Joaquin County's Closure recommendation.
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