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I 27 October 2008 AGE-NC Project No. 97-0301 Page 2 of 3 v ;' >V 0.1 be safe. Though located within a roadway, AGE maintains the highest of safety �4 �� 1 ' records; we have installed numerous borings and wells within major roadways — - including California State Highways — with no incidents. Furthermore, EHD has already approved the drilling of CPT boring P- 10 in the South El Dorado Street turn C? �. ` (' �v ora lane in July 2001 . The proposed monitoring well area on South El Dorado Street is k �r�p , not considered to be located on a high volume traffic road, as specified bythe County of San Joaquin. Furthermore, prior to conducting anyfield work on El Dorado Street, an updated traffic safety control plan would have to be approved by the San Joaquin County Public Works Department. P yr 3 . EHD Comment: Instead, the EBD recommends relocating the monitoring well south of MW-9 on the west side of South El Dorado Street, and installing another monitoring well down gradient ofMW-9 on the east side of South El Dorado Street. AGE response: We disagree with the EHD assessment that another monitoring well is necessary down gradient of MW-9. Ground water flow direction at this site has been documented to be east-northeast. Relative to well MW-9, well MW- 11 is or already situated east-northeast of well MW-9 (i.e. down gradient). Furthermore, based on the low hydrocarbon concentrations encountered at well MW-9A, and because down gradient well MW- 11 samples have repeatedlyreported as non-detect, AGE believes that installing an additional well down gradient of well MW-9 is neither cost effective nor warranted. W 4 . EHD comment: Also, the EDH believes a monitoring well is needed down gradient of MW-10 on the east site of El Dorado Street to laterally define the 1, 2- dichloroehtane (1,2-DCA) plume. AGE response: At this time, AGE disagrees with this EHD recommendation. 1 ,2- DCA has been reported from MW40A (35 - 45 feet) and MW-10B (65 - 75 feet) at Ie low concentrations on nine (9) occasions and has been reported as non-detect (ND) n_nine_(9)_occasions AGE_has interprietedxhe data_to_suggestfhat_welLMW-101s b G located at or near the margins of the dissolved plume. Additionally, the 1 ,2-DCA �s I concentrations have remained relatively stable, suggesting the plume is stable. tl tµ r S, r Because this site is progressing towards remediation, it is reasonable to assume that 0the 1 ,2-DCA plume will recess back towards the site or degrade towards "1VD" once remediation as been initiated. Therefore, AGE does not believe installation of an nt_,`'lfd additional well down gradient from MW- 10 is warranted at this time. Advanced GeoEnvironmental, ire.