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tb Mr Jeff Wong October 12, 2001 Page 2 of 4 level (MSL) Groundwater levels in shallow monitoring wells MWl through MW8 fell an average of 2 83 feet between May 2001 and August 2001 The groundwater elevation in well MW9B, which was completed in a deeper aquifer, fell 2 95 feet during the same period A potentiometnc surface map generated using the August 15, 2001 monitoring data is presented on Figure 2 The map indicates an apparent groundwater depression exists near well MW4, which suggests that the shallow aquifer is being influenced by pumping in the water supply well or that some vertical leakage of the shallow aquifer is occurring through the water supply well Groundwater monitoring data are summarized in Table 1 and field data sheets are included in Attachment A Monitoring wells MW2 through MW9B were purged of at least three well casing volumes prior to sampling The physical parameters of temperature, pH and electrical conductivity were measured during the purging process Samples were collected after the physical parameters stabilized and water levels in the wells recovered to 80% or more of their pre-purged levels Purged groundwater was contained in appropriately labeled DOT-approved 55-gallon drums in accordance with 49 CFR part 172 and 40 CFR part 262 The water was subsequently transported to Seaport Environmental's Redwood City, California facility for disposal Purge logs are included in Attachment A 2.2 Free Product Measurement and Recovery A Ground Zero technician measured and removed free product from well MW on August 31, September 7, September 13, September 21, and September 26, 2001 The thickness of measured product averaged 0 97 feet over that period Product thickness measured only 0 39 feet on September 26, 2001, however A total of approximately 23 gallons of product/water mixture was removed from well NMI by manually batting the product for temporary storage in a double-contained salvage drum As an interim remedial action, Ground Zero is actively bailing product from well MW 1 on a weekly basis Table 3 summarizes product thickness measurements and volume removed Field notes are included in Attachment B I 3.4 GROUNDWATER ANALYSES Groundwater samples were delivered under chain of custody protocol to Argon Laboratories (ELAP #2359) for analysis of TPHg by EPA method 8015M, BTEX by EPA method 8020, and oxygenated gasoline additives, EDB and 1,2-DCA, by EPA method 8260B No sample was collected from well MW 1 due to the presence of free product TPHg was detected in wells MW2, MW3, MW4, and MW7 at 2,700 parts per billion (ppb), 830 ppb, 1,400 ppb, and 75 ppb, respectively Benzene was detected in wells MW2, MW3, and MW7 at 230 ppb, 4 0 ppb and 0 8 ppb, respectively MTBE was detected in wells MW2, MW3, MW4 and MW6 at 7 0 ppb, 2,000 ppb, 32,000 ppb and 780 ppb, respectively Well MW8 contained low levels of toluene (0 7 ppb) and xylenes (1 1 ppb) No petroleum hydrocarbon constituents were detected in well MW No MTBE was detected in shallow monitoring wells MW5, MW7, or MW8 Deep well MW9B contained 0 6 ppb xylenes No other constituents of concern were detected in well MW9B Groundwater analytical results are summarized in Table 2 Laboratory reports and chain-of- G 1Data\GROUNDZF-\TUI.EBURG1Reports\QM \3QM2001 doc