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U.S. ARMY ENGINEER SACRAMENTO DISTRICT CORPS OF ENGINEERS DESIGN REVIEW COMMENTS Project: CA ARNG Site Investigations—Stockton AASF ❑ SITE DEV&GEO ❑ MECHANICAL ❑ SAFETY ❑ SYSTEMS ENG REVIEW Final Work Plan—Former USTs ❑ ENVIR PROT&UTIL ❑ MFG TECHNOLOGY ❑ ADV TECH ❑ VALUE ENG DATE 27 July 2007 ❑ ARCHITECTURAL 13 ELECTRICAL ❑ ESTIMATING ❑ OTHER 11 STRUCTURAL Marcus Pierce—RWOCB STRUCTURAL ❑ INST&CONTROLS 13 SPECIFICATIONS DRAWING NO. ITEM OR REFERENCE COMMENT ACTION General Comments It is unclear why the investigation proposed in the Work Plan is only focused on The Work Plan has been revised to include investigation the former 20,000-gallon underground storage tanks(USTs)that were used to of the area of the three former 5,000-gallon USTs.All of store aviation fuel. Section ES.3 indicates that three adjacent 5,000-gallon USTs the results from known previous investigations,as leaked and contaminated soil removed along with these tanks may have been documented in the Versar report,have already been placed back in the UST excavation pit.The Work Plan should be revised to incorporated into the previous version of the Work Plan. include investigation of the 5,000-gallon USTs and all associated piping and fuel dispensers,or CA ARNG needs to explain why the former 5,000-gallon USTs do not require further investigation. A summary of any previous investigations of the former 5,000-gallon USTs,piping,and fuel dispensers along with figures/tables depicting sample locations/results should be included in the work plan. If leakage from the former 5,000-gallon USTs or potential leakage from the former fuel dispensers and underground piping has not been adequately characterized,the Work Plan should be revised to include additional borings in these areas. CA ARNG should follow Tri-Regional Staff Recommendations on Preliminary Investigation and Evaluation of Underground Storage Tank Sites (2004)in conducting the investigation. Given that groundwater appears to flow north beneath the Army Aviation and Additional groundwater samples will be collected from Support Facility(AASF),the existing three monitoring wells(MW-I through borings to be located north of the former 5,000-gallon MW-3)are not located down gradient from the former 20,000-gallon USTs, USTs and fuel dispensers.. 5,000-gallon USTs,or the associated fuel dispensers and underground piping. Additional groundwater samples north of the former 5,000-gallon USTs and fuel dispensers are needed to delineate potential groundwater contamination. Regional Water Board Staff also recommends installing at least one monitoring well immediately north of all former UST and fuel dispensers to improve understanding of local groundwater flow. CESPK FORM 7 (Revised) PREVIOUS EDITIONS OF THIS FORM ARE OBSOLETE PAGE-1— OF-4- 15 F_4i_15 Apr 89