ARCHIVED REPORTS XR0011650 - Laserfiche WebLink

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i Lk` R KLEINFELDER 4 TPH-G was detected in GP-12, GP-13 and GP-15 covering an area approximately 120 feet west and 100 feet south from the intersection of Country Club Boulevard and ' Mission Road Trace concentrations of total xylenes were detected in five of the pushprobe locations (GP-12 through GP-16) Total xylenes and the requested analytes (See Section 3 3) were not detected in groundwater from the three eastern-most ' pushprobes along Country Club Boulevard (GP-9, GP-10 and GP-11) Total lead was detected in all fifteen groundwater samples collected in the two areas ranging from 0 24 to 13 mg/1 These total lead concentrations exceed the State and Federal Primary MCL of 0 015mg/l However these concentrations do not exceed the City's limit of 2 0 mg/l 5 In the event of dewatering operations in the Mission and Pershing Site Areas, it is likely that groundwater contamination from adjacent sites may cause an increase in contaminant concentrations in groundwater or introduce contaminants not detected in this assessment At least two sites were identified south of the proposed pipeline routing near the Mission ' Site Area (1876 Country Club and 1850 to 1856 Country Club) Two sites were also identified north of the pipeline routing in the Pershing Site Area (1403 and 1267 Country Club) Additionally, extensive pumping may also affect the size and location of the ' existing and adjacent groundwater plumes from these sites, potentially causing increased remediation costs and liability ' 6 The additional geotechnical considerations for the proposed project are detailed in a separate report Based on the conclusions noted above, the following recommendations are being made A It is anticipated that dewatering in the Mission Area will require treatment of ' groundwater prior to discharge to the sanitary sewer It is estimated remedial efforts will take approximately two to six weeks for set up prior to discharging water Efforts should ' be made to reduce the amount of dewatering discharge in this area as to reduce remedial costs I � ' B Although no significant groundwater contamination was detected at the Pershing Site Area, groundwater contamination could conceivably be encountered at a later date Efforts should be made to reduce the amount of dewatering discharge so as to reduce or ' eliminate the risk of impacting the adjacent Tosco/Former BP and former Shell plume It is suggested that as a precaution, discharge not be made to a surface water body or the storm drain system C Removal of sediment and fines within the trench {assuming a trench dewatering system} is essential in the remedial design to limit costs Above ground filter control can be ' costly and contaminants typically absorb to suspended sediment and fines, which may be more difficult to effectively remove in an above ground filtration system (especially at high flow rates) The signatories of this report should be consulted as part of planning tthe dewatering sediment control methodology 28699101 /ST03R793 Page 14 of 16 Copyright 2003,Kleinfelder,Inc July 21,2003 I