|
sent By: Rwoc9; 2553439
<br /> May-5-60?0:44; Page 3/3 i
<br /> TAl._.c 'I - CHECKLIST-OF REQUIRED ,�ATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES ?
<br /> Site Name and Location: Charlie's Day'and Night Lock Service,706 N..Eldorado Street,Stockton,San Joaquin County
<br /> 1. Distance to production wells for municipal, domestic,agriculture, A well survey in 2001 showed three municipal wells
<br /> industry and other uses within 2000 feet of the site; 'located approximately 500 to 1800 feet crossgradlent
<br /> of the site. All municipal wells Kaye been closed.'Two
<br /> domestic wells located 2,000 feet crossgradlent. One
<br /> domestic well is located 1,700 fleet upgradfent
<br /> 2. Site maps,to scale, of area lmpacfed showing locations of former andexisting tank Two 4,000 gallon gasoline US Ts
<br /> systems, Excavation contours and sample locations,boring and monitoring well elevation were removed in June 1991.
<br /> contours,gradients,and nearby surface waters, buildings, streets, and subsurface ut itles; piping was removed in August
<br /> 1998.
<br /> 0 3. Figures depicting llthology(cross section), treatment system diagrams; Site oconsists f silt and clay, with
<br /> discontintinuou&lenses of sand to 60 feet,the total
<br /> depth Investigated.
<br /> 0 4. Stockpiled soil disposed off-site(quantity), Consultant reported the.excavated soil was redistributed onto adjacent
<br /> lot east of site. i
<br /> Y Q 5.Monitoring wells remaining on-site,fate; Five monitoring wells have been installed for this Investigation. The wells(MW-1 through MW-5)will be property destroyed pending site closure_
<br /> - i
<br /> 0 6. Tabulated results of al!groundwater elevations and depths to water,• The depth to water varied from 21 to 24 feet,and
<br /> the groundwater flow direction varied from norih to
<br /> northeast
<br /> Q 7.Tabulated results of all sampling and analyses: Groundwater monitoring results'la 5/02 were 230 pg/L for TPHo,4 pg/L
<br /> for benzene,and 2.1 pg/L for MtBE. Groundwater monitoring results In
<br /> ®Y Detection limits for confirmation sampling 8/02 were 0.771rg/L for 1,2-DCA. Lead In soil at 1.5 feet below fuel f
<br /> Lead analyses dispenser was 330 mg/kg. No other lead samples were taken.
<br /> 8. Concentration contours of contaminants found and those remaining in soil The extent of contamination is defined by
<br /> 0a d groundwater, both on-site and off.-site: on-site soil borings and monitoring wells.
<br /> MLateral and � vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<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 remedlation system; system was not required at this site.
<br /> 10.Reports/information Q Unauthorized Release Form QMRs(10197 to 10/99)
<br /> C
<br /> Boring logs El PAR FRP (Additional Site Assessment Report, 3/02)
<br /> 11.Best Available Technology(BAT)used or an explanation for not using BAT; Remove USTs,natural attenuation.
<br /> 12.Reasons why background was/is Decreasing concentrations have been attained at all monitoring wells. Minor '
<br /> unattainable using BAT; soil contamination remains on-site.
<br /> An estimate of contaminant mass was not required,due to declining
<br /> 13.Mass balance calculation of substance concentration trends In groundwater.
<br /> treated versus that remaining;
<br /> 14.Assumptions,parameters, calculations and model used in risk A risk assessment was not required,
<br /> assessments, and fate and transport ihodeling;and
<br /> 15.Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent,and based on
<br /> impact water quality, health, or other beneficial uses. twelve sampling events, contamination Is not continuing
<br /> to leach to groundwater. Groundwater monitoring
<br /> shows a decreasing trend in concentrations.
<br /> By: Comments: Two 4,000-gallon gasoline US Ts were removed from the subject site in June 1997. Piping and a dispenser
<br /> lLl3 island were removed in August 1998. Soil contamination was identified of the UST area and dispenser island. Multiple
<br /> borings and five monitoring wells were completed to delineate and monitor contamination at this site: Additional borings
<br /> Date: and grab sampling was completed in 2002. Monitoring well maximum groundwater concentrations declined to 230 pg/L
<br /> for TPHg,4 pg/L for benzene,and 2.1 pg/L for ABE in 2002. 1,2-DCA was Identified only once in 2002 at a
<br /> 1121103 concentration slightly above water quality objectives. Based on the limited extent of soil contamination and decreasing
<br /> contaminant concentrations in groundwater,board staff concur with San Joaquin County's Closure Recommendation.
<br />
|