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v 0 0 California Regional Water Quality Control Board Winston H. Hickox Secretaryfor Environmental Protection 7 November 2003 Mr. William Barber Central Valley Region Robert Schneider, Chair Sacramento Main Office Internet Address: http://www.swreb.ca.gov/—rwgcb5 3443 Routier Road, Suite A, Sacramento, California 95827-3003 Phone (916) 255-3000 • FAX (916) 255-3015 Group Environmental Management Company 4850 East 49th Street Cuyahoga Heights, Ohio 44125 NOV 1 0 2003 ENVIRONMENT HEALTH PERMIT/SERVICES d��.r:or, Gray Davis Governor WORK PLAN FOR MONITORING WELL INSTALLATION, BP/ APPLIED AEROSPACE STRUCTURES CORPORATION, STOCKTON, SAN JOAQUIN COUNTY Staff of the Central Valley Regional Water Quality Control Board (Regional Board) has reviewed the 23 October 2003 Work Plan for Monitoring Well Installation Offsite Southeast of MW -SR (Work Plan) for the BP/Applied Aerospace Structures Corporation (BP/AA) site in Stockton, submitted on your behalf by Parsons Engineering Sciences. Parsons submitted the Work Plan because trichloroethylene (TCE) pollution continues to be found seasonally in monitoring well MW -5R. Although BP/AA operates a groundwater extraction and treatment system, MW -5R is outside the capture zone. You previously conducted a soil gas survey to locate the source of the TCE. Because the soil gas survey was not able to locate the source of the TCE, you are proposing to install a well downgradient of MW -5R to define the extent of the plume. The Work Plan proposes to locate the new well about 300 feet southeast of MR -5R, based on the gradient measured during the fall when TCE is detected. However, the gradient during the spring months is known to shift to an easterly direction. If the TCE in the groundwater is migrating with groundwater flow, its course would also shift to the east during the spring. Therefore, the monitoring well should be placed midway within the are formed by the fall and spring gradient directions. The Work Plan is approved on the condition that a site map is submitted by 26 November 2003 showing a revised well location as discussed above. By 2 January 2004, please provide a report containing the results of the well construction and sampling. If you have any questions, you may contact me at (916) 255-3077 or by email at djuths; a rb5s.swrcb.ca.tov. GERALD J. DJUTH, P.E., C.E.G. Associate Engineering Geologist cc: Ms. Margaret Lagorio, San Joaquin County Public Health Services, Stockton Mr. Fred Kintzer, Parsons Engineering Science, Inc., Walnut Creek California Environmental Protection Agency 05 Recycles! Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can do to reduce demand and cut your energy costs, see our Website at http://www.swrcb.ca.gov/rwgcb5.