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Extended Plume Definition:-7500 W 11th St., Tracy,CA. Page 14 4.8.1 Hydraulic Conductivity of Strata Based on pump tests that SJC had conducted in similar strata at other locations in Tracy, it • was estimated that the clays and silty clays beneath the 7500 West Eleventh Street site had a horizontal hydraulic conductivity on the order of 10-4 to 10-6 cm./sec., while the silts and L sands have a horizontal permeability in the range of 10-1 to 10-2 cm./sec. (The San Joaquin Company Inc. 1994). The accuracy of that estimate was confirmed by analyses of contaminant transport parameters based on site-specific observations of MTBE migration at Lthe Navarra Site (The San Joaquin Company Inc. 2002c, Sec. 7.3.2.3). To further quantify the low-permeability characteristics of the surficial clays and deeper clay strata that serve to isolate the near-surface aquifer from the atmosphere and the separate deeper aquifers from each other, on April 19, 2004, a sample of clay soil was recovered at a depth of 7.5 ft. from the boring drilled for floating product Monitoring Well MWFP-4 in a LShelby Tube sampling tool. That sample was transported to Fugro West, Inc.'s laboratory in Hayward, California, where its hydraulic conductivity in a vertical orientation was measured L in a constant-head permeability testing apparatus. The vertical permeability was found to be 10.8 x 10-7 cm/sec. A copy of the laboratory certificate of analysis for that permeability test is presented in Appendix D. 4.9 Well Development On April 28 and 29, 2004, the new groundwater-quality monitoring wells were developed by pumping and surging and by bailing a minimum of 10 well volumes from each. The development water was staged at the well-head on-site in 55-gal., closed-top, steel drums. As the drums were filled, they were transported to the 7500 West Eleventh Street property and held until the results of analysis from the wells were available. When data was available on the concentrations of analytes of concern in samples recovered from the newly installed groundwater-quality monitoring wells, drums that contained clean water were emptied by decanting them onto the Navarra property. Drums containing water affected by hydrocarbons were emptied into a 1,100 gallon, polyethylene holding tank located on the 7500 West Eleventh Street property where it will be held. until it is economically feasible to ship the contents off-site for disposal at a permitted recycling facility. 4.10 Groundwater-quality Monitoring After the new groundwater-quality monitoring wells were installed and developed they were used together with the existing wells at the site to establish a new, expanded groundwater monitoring program. In order to comply with the SJCEHD-directed monitoring schedule for the site, given the greatly-expanding well array, the sampling round had to be conducted in two parts, which required a total of three days. On April 21 and 22, 2004, groundwater f sampling was performed in the pre-existing wells MW-1 through MW-12 and MW-3A,MW- 3B and MW-12A. The sampling from the newly-installed groundwater-quality monitoring > wells MW-13 through MW-19 wasconducted on April 30. However, to ensure that the SJC