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�r a <br /> • A S S O C I A T E 5 I N C <br /> results of groundwater samples are summarized in Table 2 and laboratory data sheets are <br /> contained in Attachment 2 <br /> GROUNDWATER FLOW DIRECTION <br /> Water level measurements were collected from wells MW1 through MW3 on June 1, 1999 <br /> Water levels ranged from 19 38 to 19 76 feet below the tops of the well casings elevation, <br /> representing an average decrease in the water table elevation of approximately 0 19 feet since <br /> January 1999 The water level data were used to develop the groundwater elevation contour map <br /> (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost <br /> aquifer beneath the site flowed towards the southwest The average hydraulic gradient on June 1, <br /> 1999 was calculated to be 0 0006 ft/ft or approximately 3 ft/mile A summary of groundwater <br /> monitoring data is presented in Table 1 <br /> ADDITIONAL SITE ACTIVITIES <br /> On May 27, 1999, ATC personnel supervised the transport and disposal of approximately 330 <br /> gallons of purge water stored on site Prior to the purge water disposal, analytical data was <br /> supplied to Clearwater Environmental to profile the purge water for the appropriate disposal <br /> . method Clearwater pumped the 330 gallons of purge water into a vacuum truck and transported <br /> the purge water to Alviso, California where it was recycled by Alviso Independent Oil Copies of <br /> the non-hazardous waste manifests are included in Attachment 3 <br /> CONCLUSIONS <br /> Concentrations from wells MW1 and MW2 remain consistent with the results from the previous <br /> sampling event The direction of groundwater flow is consistent with the previous event <br /> Groundwater elevations have decreased slightly since January 1999 <br /> RECOMMENDATIONS <br /> Based on the results of the second quarter 1999 monitoring episode, we recommend the <br /> following <br /> • Install two additional groundwater monitoring wells south-southeast and southwest of <br /> well MW1 to define the lateral extent of TPHd impacted groundwater <br /> • Conduct a Remedial Investigation/Feasibility Study (RI/FS) immediately following the <br /> installation, development, and sampling of the two additional groundwater momtonng <br /> wells The RI/FS should include a 24-hour groundwater pumping test <br /> • <br /> w 1130991quar11y12gr-1999 doc 3 <br />