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TABLE I -CHECKLIST OF REQUIRED DAMO
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND UND TANK SITES
<br /> Site Name and Location: Piedmont Lumber,7777 West Eleventh Street,Tracy,San Joaquin County
<br /> Y 1.Distance to production welts for municipal,domestic,agriculture,industry domestic wells were reported woIn
<br /> and other uses within 2000 feet of the site, 2,000 feet of the site. The nearest well appears
<br /> to be approximately 250 feet norE mW of the
<br /> site. An on-site well was sampled and destroyed
<br /> In 1998. Sample results were non-detect
<br /> 2.Site maps, to scale, of area impacted showing locations of former and existing tank systems, In July 1996,one 350-gallon
<br /> excavation co.Ontours and sample locations,boring and monitoring well elevation contours, gasoline UST was removed
<br /> gradients,and nearby surface waters,buildings,streets,and subsurface utilities; from the site.
<br /> 3.Figures depicting lith No treatment system was used. Site lithology is
<br /> /9 g ology(cross section),treatment system diagrams; depicted in the well boring logs.
<br /> F 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Impacted soil was removed from the tank pit and aerated. After
<br /> one year,the pit was backfilled with clean soil.
<br /> I S.Monitoring wells remainbg on-site, fate; Four momftdng walls were InsbBad San J"q&W-County hau f proposed
<br /> decommissioning these wells pending the Regional Board's concurrence with the
<br /> closure recommendation.
<br /> PY 6. Tabulated results of all groundwater elevations and depths to water, Groundwater elevations varied between 6.5 and 10 feet
<br /> bgs,with a north/northwesterly flow direction.
<br /> El 7.Tabulated results of all sampling and analyses: In 1996,TPHg at 4„300 mg/kg,TPHd at 870 mg/kg,BTEX at 567.5 mg/kg
<br /> (cumulative)were the maximum constituent concentrations detected In soil
<br /> El Detection limits for confirmation sampling samples from beneath the former UST. In 1997,four groundwater monitoring
<br /> =Lead analyses wells were Installed at the site. Contaminants were detected In water samples
<br /> from each well. The latest groundwater monitoring data(Mach 1999)only
<br /> show contamination in wells,A1W-2 and MW-BT,where AftBE was detected at
<br /> 4.3 pgll and BEX at 7.6 pg/►,respectively.
<br /> ❑Y 8.Concentration contours of contaminants found and those remaining,in soil
<br /> and groundwater, and both on-site and off-site:
<br /> Lateral and Y❑ Vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 0 9.Zone of influence calculated and assumptions used for subsurface No subsurface remediation system was used at
<br /> remediation system and the zone of capture attained for the soil and this site. Impacted sol►was removed from the
<br /> groundwater remediation system; former tank pit
<br /> a10.Reports/information 19 Unauthorized Release Form EjMRs(Dates)November 1997—March 1999
<br /> a Well and boring logs IDPAR FRP El Other(report name)May 10, 1999 Closure Report
<br /> 11.Best Available Technology(BA 7)used or an explanation for not using BAT, The leak source(hnp was removed from 0e
<br /> site.
<br /> 12.Reasons why background wasrs unattainable using BAT; The remaining contaminants require time to degrade.
<br /> • E] 13.Mass balance calculation of substance treated versus that remaining; An estimated 439 pounds of TPHg and 5.8 pounds of
<br /> BEX remain in the soil. Negligible contamination,
<br /> Including WOE,remains in groundwater at the alta.
<br /> 14.Assumptions,parameters,calculations and model used in risk
<br /> assessments,and fate and transport modeling,
<br /> 15.Rationale why conditions remaining at site will not adversely
<br /> impact water quality,health,or other beneficial uses;and
<br /> 16.WET or TCLP results
<br /> By. (J Comments: In 1996,elevated levels of TPH9, TPHd,and BTEX were detected in native soil below the fo mer UST. An unspecified
<br /> U amount of soil was removed from the tank pit and aerated. In 1997,four monitoring wells were installed on site. Although
<br /> Date: contaminants were detected in each well,their concentrations generally declined over time. The latest groundwater mondo»ng data
<br /> (Manch 1999)show contamination in two wells. MtBE at 4.31/954 was detected in MW-2,and low levels of BEX were found in
<br /> MW-BT. Twenty domestic wells were reported within 2,000 feet of the site. The nearest off-site well appears to be approximately
<br /> 250 feet northeast of the site. Details about this well have not been provided in the closure report However,San Joaquin County
<br /> indicates in their closure summary that no drinking water wells are affected by conditions at the site. Based on the low
<br /> concentrations of remaining contaminants,staff concurs with San Joaquin County closure recommendation.
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