|
IL
<br /> �,. TAIT E 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: JH Simpson Company,4025 Coronado Avenue,Stockton,San Joaquin County
<br /> N 1. Distance to production wells for municipal, domestic, agriculture, industry A well survey was not conducted. The County
<br /> and other uses within 2000 feet of the site; indicates that drinking water wells or surface
<br /> waters are not affected by site conditions.
<br /> 0 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, In 1996,one 2,000-gallon
<br /> gasoexcavation co.Ontours and sample locations,boring and monitoring well elevation contours, from the tank was removed
<br /> p g g from the site.
<br /> gradients, and nearby surface waters, buildings,streets, and subsurface utilities;
<br /> 0 3. Figures depicting lithology(cross section), treatment system diagrams;
<br /> 4. Stockpiled soil remaining on-site or off-site disposal(quantity); An unspecified amount of excavated soil was returned to the
<br /> tank excavation.
<br /> FTJ 5. Monitoring wells remaining on-site, fate; One monitoring well was installed. The well will be decommissioned pending site
<br /> closure.
<br /> 6. Tabulated results of all groundwater elevations and depths to water,• Groundwater elevations varied from 43 to 75 feet bgs,and
<br /> groundwater flow Is northerly.
<br /> 0 7.Tabulated results of all sampling and analyses: in 1996,using EPA Method 8020, up to 1,000.Ug/kg of MISE was detected in soil
<br /> from the tank excavation. In 1998,a grab water sample collected during a soil
<br /> Y❑Detection limits for confirmation sampling vapor survey revealed low levels of TPHg and TEX. In 1998,soil borings SB-1
<br /> RILead analyses and SB-2(later converted to well MW-1)were drilled 10 to 11'bgs,respectively.
<br /> No contaminants were detected in soil samples below seven feet. During the
<br /> August 1999 sampling event,DIPS at 0.69.Ugil was the only constituent
<br /> detected In the water sample. MtBE was not detected using EPA Method 8260.
<br /> y 8. Concentration contours of contaminants found and those remaining in soil
<br /> and groundwater, and both on-site and off-site:
<br /> Y❑ Lateral and q Vertical extent of soil contamination
<br /> Fwi Lateral and FW-1 Vertical extent of groundwater contamination
<br /> 9.Zone of influence calculated and assumptions used for subsurface The site map shows the limits of the tank
<br /> remediation system and the zone of capture attained for the soil and excavations.
<br /> groundwater remediation system,
<br /> 10.Reports/information 0 Unauthorized Release Form FT� QMRs(Dates)2/93— 10/99
<br /> EY Welland boring logs EiPAR Ei FRP q Other(report name)January 14,2000 Closure Summary
<br /> 11.Best Available Technology(BAT)used or an explanation for not using BAT; The tank,dispensers,and piping were removed
<br /> from the site.
<br /> lt� 12.Reasons why background was/is unattainable using BAT,' The remaining hydrocarbons require time to naturally attenuate.
<br /> N7 13.Mass balance calculation of substance treated versus that remaining,
<br /> NE 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; Comments:in 1996,one UST was removed from the site. Using EPA Method 8020,elevated levels of MtBE were detected in soil
<br /> l1 samples following the removal of the tank. However,because Method 8020 was used,the County speculates this initial MtBE
<br /> a e: detection could have been a'false positive': in 1998,soil vapor samples revealed elevated levels of petroleum constituents. A grab
<br /> )))' water sample collected during the vapor survey showed minor concentrations of TPHg and TEX. In 1998, one soil boring(SB-1)
<br /> was installed in the former tank excavation, whereas another boring(SB-2)was drilled midway between the former tank location and
<br /> 7.� dispensers. No contaminants were detected in samples from SB-1. Soil samples from SB-2 revealed TPHg and TEX but not below
<br /> rrlr five feet. In 1998,traces of ethyl benzene and xylenes were detected in groundwater samples,and a trace amount of DIPS was
<br /> detected in 1999. MtBE was not detected after the initial detection. Based on the absences of MtBE in soil and groundwater
<br /> samples and the minor contamination remaining in the subsurface,staff concurs with San Joaquin County closure recommendation.
<br />
|