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r- <br /> BP Oil Company Y <br /> Page 2 <br /> A replacement monitoring well for MWI should be installed. MWs should be <br /> appropriately screened and total screen length should not exceed 20 feet. MWs screened <br /> to intersect current water level must be installed. Additional MWs may need to be <br /> installed to define the lateral extent of contamination_ Asp reviously stated in the April <br /> 1999 PHS/EHD letter, it may be necessary to install wells screened in different intervals. <br /> If different casing diameter sizes are proposed for MWs (as in the IWP);'provide <br /> information for why this is necessary. <br /> In the IWP reference was made to slug tests that were performed on MWs 1, 2 and S. <br /> Provide these test results to PHS/EHD and show all calculations for determining how the <br /> groundwater velocity was derived. <br /> Provide a rose gradient diagram showing historical groundwater gradient for the site. <br /> Identify the lithological section of the aquifer that the rose gradient diagram represents. <br /> Submit a Work Plan that will investigate-the lateral and vertical extent of contamination <br /> at this site to PHS/EHD by AuRust 16. 1999. Contact Carol Oz, Senior REHS at <br /> (209)468-3440 if you have questions regarding this letter. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Carol Oz, Senior REHS Margaret Lagorio, RE <br /> Site Mitigation unit IV Supervisor <br /> cc: Mark List-CVRWQCB <br /> Khaled Rahman-Cambria <br /> Dave Camille-Tosco <br />