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i Project No 58080-06-02 January 5, 1995 ' Page 7 Distribution of Petroleum Hydrocarbons, MTBE and VOC's to Groundwater 1, Petroleum hydrocarbons reported as gasoline and also reported as"unidentified hydrocarbons within the diesel fuel range", in addition to MTBE and VOC's were detected in several of the onsite and ' offsite groundwater monitoring wells Petroleum hydrocarbons reported as "weathered gasoline" � were detected to offsite upgradient well MW-5 at a concentration of 250 ug/L and in onsite well MW-3 at 250 ug/L r ' Petroleum hydrocarbons reported as "unidentified hydrocarbons within the diesel fuel range" were detected in wells MW-1, MW-3, MW-4 and MW-5 at concentrations ranging from 52 to 190 ug/L / t The distribution of these diesel fuel range hydrocarbons in groundwater beneath and beyond the site extend be and upgrad�ent well MW-5 and both cross gradient wells MW-1 and MW-4 f`+ MTBE was detected in wells MW-1, MW-3 and MW-5 at concentrations ranging from 76 to 610 ug/L The highest concentration of MTBE was detected in upgradient well MW-5 at a concentration of 610 ug/L The distribution of MTBE extends beyond upgradtent well MW-5 and cross gradient well MW-1 One or more VOC's were detected in each of the groundwater monitoring wells with the compound specific concentrations ranging from the low parts-per-billion to a maximum concentration of 41 ug/L for DCA in well MW-5 Vapor Extraction Test Results of the VET indicate that well extraction flowrates ranging from 30 to 70 acfm with an effective radius of influence of 50 to 100 feet can be expected Data indicates that the maximum expected wellhead vacuum will not exceed approximately 30 - 50 inches of water column apor samples collected during the test are currently being analyzed 'for TPHg and BTEX m order to evaluate ;he expected mass removal rate for a soil vapor extraction system (VES) A minimum of 1 one vapor sample collected from vapor extraction well VW-6 will also be analyzed utilizing a gas chromatography/mass spectrometry "open scan"fusing EPA le,st Method 8240 in order to possibly identify the nature of the unidentified petroleum hydrocarbons repoe m soil I Based on pan effective radius of influence of 50 feet at a flowrate of 30 acfm, the six existing vapor extraction wells should provide vacuum influence for the onsite and offsite portions of the vadose 1 zone petroleum hydrocarbon plume CONCLUSIONS Based on Geocon's review of all soil and groundwater data acquired through November 1994, summarized below are conclusions regarding the distribution and possible sources of petroleum hydrocarbons and other organic chemicals beneath and in the vicinity of the subject site I I I 1 I i