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r i MIMENTAL HEAL I it RMIT SFRVICE Working To Restore Nature .' '�_� ` �V f � PM I� � 6 GROUNDWATER MONITORING On July 28, August 30, and September 28, 1994, a RESNA technician measured the water levels in wells MW-1 through MW-5, well RW-1, and piezometer PZ-1. No floating product was noted in any site well. Groundwater monitoring data are summarized in Table 1. The depth to water measurements and the elevations of the well casings (Table 1) were used to evaluate the groundwater flow direction and gradient beneath the site (refer to attached Field Procedures). The average depth to groundwater beneath the site has increased by 1.53 feet during the third quarter of 1994.. The groundwater gradient magnitude and direction was generally consistent during the reporting period. The calculated gradients for July (0.006 ft/ft), August (0.006 ft/ft), and c/ September (0.006 ft/ft) are depicted on Plates 3, 4 and 5, respectively. Groundwater flow direction was to the northeast during the reporting period. The direction of groundwater flow has ranged from southeast to northeast since groundwater monitoring was initiated in December 1988. On September 28, 1994, groundwater samples were collected from wells MW-1 through MW- 5 for laboratory analyses. The field methods used are presented in Attachment 1. Field purge • logs are included in Attachment 2. Groundwater samples were analyzed by Sequoia Analytical for total purgeable petroleum hydrocarbons (equivalent to total petroleum hydrocarbons as gasoline [TPHg]) using Environmental Protection Agency (EPA) Method 503018015, total extractable petroleum hydrocarbons (equivalent to total petroleum hydrocarbons as diesel [TPHd]) using EPA Method 3510/8015 (modified for gasoline and diesel), and for benzene, toluene, ethylbenzene, and total xylene (BTEX) isomers using EPA Method 5030/8020 Copies of the laboratory reports and chain of custody documentation are included in Attachment 3. Results of laboratory analyses indicated dissolved TPHg was detected in the sample from well MW-i at 4,500 parts per billion (ppb). BTEX constituents were also detected in well MW-1, most notably benzene at 580 ppb. No TPHg or BTEX constituents were detected in any other well with the exception of well MW-2. Well MW-2 contained relatively low levels of BTEX BTEX constituents had not been detected in MW-2 since April of 1992. TPHd was detected in wells MW-1, MW-2, MW-4 and MW-5 at 590 ppb, 75 ppb, 52 ppb, and 280 ppb, respectively. The laboratory results of TPHd were reported as non-diesel mix. Dissolved TPHd and TPHg concentrations were below laboratory detection limits in monitoring well MW-3. Results of laboratory analyses are summarized in Table 2 • 38009-IOX3QSM doc 2