ARCHIVED REPORTS XR0002730 - Laserfiche WebLink

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3 S IEC0R �"° QUARTERLY RESULTS SUMMARY Current Phase of Protect Monitoring/Remediation Frequency of Groundwater Sampling MW-1 through MW-11, EW-1 through EW-7, DMW-1 through DMW-3, and SVE-1 Sampled Quarterly Frequency of Groundwater Monitoring Quarterly Is Free Product(FP) Present Onsite No Current Remediation Techniques SVE/GWE (onsite), Batch Extraction (offsite), Ozone TPHg removed this quarter(Ibs) 246 (SVE), 1 (GWE) MtBE removed this quarter(Ibs) 3 (SVE), 1 5 (GWE) TPHg removed - cumulative (Ibs) _24,170 3 (SVE + GWE) _ MtBE removed-cumulative (Ills) 2,010 6 (SVE + GWE) Groundwater extracted this quarter 208,580 (GWE), 9,250 (Batch Extraction) Cumulative groundwater extracted 1,263,300 (GWE), 121,740 (Batch Extraction) _ Approximate Depth to Groundwater 32 57-35 78 ft Groundwater Flow and Gradient Shallow- Regional Flow Northeasterly @ 0 008 ft/ft Locally radially inward toward well MW-6 ' Intermidiate- Northeast @ 0 004 ft1 t ' DISCUSSION: During the first quarter 2005, remediation and sampling activities included the following methods Groundwater was extracted through extraction well EW-1 using a submersible pump installed in the well Groundwater anid—s-oil vapor were extracted simultaneously using high vacuum equipm-e nected to wells MW-4 and EW-7 Wells MW-4W 11 EW-6 and EW-7 were sampled at the remediation system manifold because they are connecte the system via underground-reenching Groundwater-batcfi ' extractions were performed on offsite wells EW-2, EW-3, EW-4, and EW-5 Quarterly groundwater samples were collected once the batch extractions were completed Groundwater sample fie idsLilq sheets were inadvertently not completed for wells EW-1 through EW-6 and are not included in this report Review of historical groundwater analytical da a indicates thacentrations reported during the current quarter are consistent with historical concentrations Chemical concentrations beneath and in the vicinity of the ARCO site were generally consistent with historical data excluding well DMW-3 DMW-3 was re-sampled on March 28, 2005, and concentrations were consistent with historical data Using resampling results for DWM-3, total petroleum hydrocarbons as gasoline (TPHg) were reported in twelve of the twenty wells sampled this quarter at concentrations ranging from 210 ppb (EW-3) to 7,300 ppb (EW-2) Benzene was reported in two of the twenty wells at a maximum concentration of 4 5 ppb (DMW-2) Methyl tertiary butyl ether (MtBE), analyzed using EPA Method 8260B, was reported in fifteen of the twenty ' wells at concentrations ranging from 062 ppb (DMW-1) to 15,000 ppb (EW4 ) 1,2-Dichloroethane (1,2- DCA) was reported in seven of the wells analyzed at concentrations ranging from 1 0 ppb (DMW-3) to 34 ppb (MW-5) Tertiary butyl alcohol (TBA) was reported in two of the wells at a maximum concentration at 8000 ppb (DMW-3) Toluene, ethyl-benzene, and total xylenes were reported in MW-4 at concentrations of ' 6 8 ppb, 2 0 ppb, and 27 ppb, respectively Toluene and total xylenes were reported in DMW-2 at concentrations of 1 7 ppb and 2 5 ppb, respectively Toluene and total xylenes were reported in DMW-3 at concentrations of 0 95 ppb and 1 1 ppb, respectively Decreases in concentrations of petroleum hydrocarbons, MtBE and/or TBA continue to be observed in several of the site wells as a result of remedial I system operation Groundwater flow within the shallow water-bearing zone was regionally to the northeast at a hydraulic gradient of 0 005 ft/ft, and local variations near batchg extraction wells EW-2, EW-4, and EW-5 Groundwater flow within the intermediate water-bearing zone was to the northeast at an approximate � A 1BP-ARCO149321QMRs12005110MR05 doe k r w