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Mr. James Nitzschke 0 - 2 - • 13 February 2008- <br /> about five feet bgs, and the cohesive soils were encountered below this depth. Therefore, <br /> Deere & Company should extend the soil borings at least until cohesive soils are encountered. <br /> Since there is limited data available regarding the distribution of constituents in soil, Deere & <br /> Company should also analyze soil samples from two and five feet below ground surface from <br /> each of the monitonng`well:bbrings for nitrate, ammonium and sulfate. <br /> The monitoring wells are proposed to be installed with five-foot screen intervals extending from <br /> the bottom of the boring to about two feet above the encountered water table, filter pack <br /> extending to two feet above the screen interval, a transition seal and finishing with at least two <br /> feet of annular seal extending to the surface. Since groundwater is found at six feet below <br /> ground surface, ERM needs to be cognizant of the minimum sealing depths required by San <br /> Joaquin County Environmental Health Department and there may not be sufficient vertical <br /> space to have the well screen extend above the water table. <br /> Summary <br /> Regional Water Board staff conditionally concur with the October 2007 Additional Site <br /> Characterization and Monitoring Well Installation Workplan. Deere & Company shall make the <br /> following changes and additions to the Work Plan: <br /> • Locate monitoring well MW-1 to the area between the Former Mixing Area and the western <br /> levee. <br /> • From each monitoring well boring, obtain soil samples from about two feet and five feet <br /> below ground surface and analyze the soil samples for nitrate, ammonium, and sulfate. <br /> • Be aware that groundwater will be encountered at a shallow depth, and be sure to provide <br /> sufficient distance above the well screen to provide the minimum well seal intervals. <br /> • Monitoring well installation shall be conducted to the satisfaction of San Joaquin County <br /> Environmental Health Department. <br /> • Notify Regional Water Board staff when a date for monitoring well installation is secured. <br /> Deere & Company intends to commence field work as soon as practically feasible. According <br /> to the schedule proposed in the Work Plan, Deere & Company will prepare a Report of <br /> Findings within about four months of the date of this letter. Therefore, we look forward to <br /> seeing the Report of Findings by 30 May 2008. <br /> Thank you for taking responsibility for the investigation and remediation of Lesco's Port of <br /> Stockton lease property. Regional Water Board staff look forward to working with Deere & <br /> Company to conclude its obligations to the Port of Stockton property. If you have any <br /> questions, you may contact me by telephone at (916) 464-4680, by email at <br /> aterrell�waterbo ds.ca. ov, or by postal mail at the letterhead address. <br /> AM TERRELL <br /> Private Sites Cleanup Unit <br /> Distribution List Attached <br />