ARCHIVED REPORTS XR0001072 - Laserfiche WebLink

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CAMBRIA RECOMMENDATIONS Wells MW-1 through MW-10 have been sampled quarterly since at least 1991 Groundwater collected from wells MW-1, MW-5, MW-6, and MW-10 have not contained detectable concentrations of petroleum hydrocarbons for several years, with the exception of anomalous toluene detections during the second quarter 2004 sampling event The groundwater data from wells MW-2, MW-3, and MW4 demonstrate a sigmfiee nt deceasing trend for several years Therefore, Cambria recommends that these wells be sampled annually during the second quarter Wells MW-7, MW-8, and MW-9 would continue to be sampled quarterly Note that there is also a significant decreasing trend in samples from well MW-7, but we recommend continued quarterly sampling of that well because it is downgradient of the presumed source area at the property boundary If SJCEHD concurs with this recommendation, Cambria will implement the revised sampling schedule beginning with the fourth quarter 2004 sampling event To further assess the lateral extent of petroleum constituents in groundwater, Cambria recommends drilling two CPT borings across Charter Way and two CPT borings on the Best Western property east-northeast of the subject site Depth-discrete groundwater samples would • be collected from these borings at approximate depths of 50, 75, and 90 fbg This will provide / additional lateral assessment data and assist in locating deep wells, if warranted Additionally, Cambria recommends advancing a CPT boring downgradient of MW-9 to assess the lateral extent of fuel oxygenates in shallow groundwater If SJCEHD concurs with these recommendations, Cambria will submit a worm plan detailing these activities 5 If you have any questions regarding the contents of this document, please call Aubrey Cool at (510)420-3336 Sincerely, Cambria Environmental Technology, Inc � ��r-, � © GEp% Aubrey K Cool, RG Project Geologist • NO 7659 RG 7659 LP 2Q' OF CXF�� 0778 4