ARCHIVED REPORTS XR0002752 - Laserfiche WebLink

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" Date: October 29,2001 Quarter: 3Q01 ARCO QUARTERLY GROUNDWATER MONITORING REPORT Facility No.: 4932 Address: 16 E. Harding Way,Stockton,CA ARCO Environmental Engineer: Paul Supple Consulting Co./Contact Person: SECORIRusty Benkosky Consultant Project No.: 077.43285.703 Primary Agency/Regulatory 1D No.: Sart Joaquin County Public Health Services(SJCPHS) Assembly Bill 681 Status: Property owned by ARCO WORK PERFORMED THIS QUARTER (Third Quarter - 2001): 1. Performed quarterly groundwater monitoring and sampling. 2. Prepared and submitted quarterly groundwater monitoring report. 3. Performed additional site assessment,including the installation of five groundwater monitoring wells,and the drilling of two soil borings. WORK PROPOSED FOR NEXT QUARTER (Fourth Quarter - 2001): i. Perform quarterly groundwater monitoring and sampling. 2. Prepare and submit quarterly groundwater monitoring report. 3. Prepare and submit report documenting additional site assessment. P P g QUARTERLY RESULTS SUMMARY Current Phase of Project: Monitoring Frequency of Groundwater Sampling: MW-1 through MW-9 and SVE-1 sampled quarterly Frequency of Groundwater Monitoring: Quarterly Is Free Product(FP)Present Onsite: Yes Current Remediation Techniques: Natural attenuation Approximate Depth to Groundwater: 263/4-28'12 ft Groundwater Flow and Gradient: Northeast @ 0.002 ft/ft DISCUSSION: Free product was present in MW-4 and SVE-1 at thicknesses of 0.02 ft and 0.01 ft,respectively.This is the first time that free product has been measured at the site. Total petroleum hydrocarbons as gasoline(TPHg) were reported in one of the eight wells sampled this quarter at a concentration of 200 ppb(MW-9). Benzene was reported in one of the eight wells at a concentration of 1.2 ppb(MW-9). Methyl tert-butyl ether(MtBE),analyzed using EPA Method 8260A,was reported in four of the eight wells at concentrations ranging from 2.2 ppb(MW-3)to 67,000 ppb(MW-6). Tert-amyl methyl ether{TAME) was reported in one of the eight wells at a concentration of 5.8 ppb(MW-1). 1,2- Dichloroethane(1,2-DCA) was reported in three of the eight wells at concentrations ranging from 3.8 ppb(MW-5)to 32 ppb(MW-1). Chemical concentrations are generally consistent with,or slightly lower than,historical data. Groundwater elevations across the site decreased by an average of 1.36 ft. Groundwater flow was to the northeast at an approximate gradient of 0.002 ft/ft,which is generally consistent with historical data.