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r,41M n Mr Martin Harris April 27,2004 Page 4 of 7 l 2.7 Well Development and Groundwater Sampling A Ground Zero technician developed the new wells and collected groundwater samples on January 23, 2004 Water levels were monitored prior to well development Each new well was developed by surging, bailing and pumping until turbidity was minimized The temperature, pH, and electrical conductivity of the purged water were measured during well development and were allowed to stabilize prior to collecting a groundwater sample Groundwater purged from the wells was placed into DOT approved 55-gallon drums, which were eventually transported off-site for disposal/recycling Groundwater samples were collected from each well after the physical parameters stabilized and the water in the well recovered to at least 80% of pre-purged levels Samples were placed in an ice chest at a temperature of 4° Centigrade and submitted to Argon under chain of custody protocol The samples were analyzed for the presence of TPHg, BTEX, and oxygenated gasoline additives, including 1,2-DCA and EDB Field development/purge logs are included in Attachment C To determine the groundwater elevation, the static depth to groundwater was measured in each well and subtracted from the surveyed wellhead elevation The potentiometric surface ranged from • 18 00 feet above mean sea level (msl) in well MW7 to 18 14 feet above msl in wells MW2 and MW4 Groundwater flowed in a westerly direction with a hydraulic gradient of approximately 0 001 ft/ft, or approximately 5 6 ft/mi Due to an apparent groundwater elevation anomaly, the data from well MW7 was omitted from the calculation Groundwater elevations are summarized in Table 1 A potentiometric surface map generated using the January 23, 2004 well monitoring data is depicted on Figure 3 Groundwater monitoring and purge logs are included in Attachment C 3.0 RESULTS 3.1 Subsurface Conditions CPT methods were used to classify soil from the ground surface to a depth of approximately 35 feet bgs in boring CPT1 Traditional soil logging methods were used to classify the soil in bonngs MWS, MW6, and MW7 to a depth of 19 feet bgs The lithology observed in borings MW5 through MW7 correlated well with the CPT data Shallow soil beneath the site consists of sandy soil (SW, SW-SM, and SW-SC) from the ground surface to approximately 11-12 feet bgs, silt (ML) and clay (CL) from approximately 11-12 feet bgs to approximately 16 feet bgs, and poorly graded sand (SP) to well graded sand (SW) from approximately 16 feet bgs to approximately 17 5-19 feet bgs, which corresponds to the bottom of borings MW5 through MW7 Accurate soil classification was not possible in boring MW6 beyond 12 feet bgs due to heaving sands Groundze/souzah�,portsAVELLRPT2b doc