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EDMUN❑G.BROWN JR, jid a �OVERxDR CALIFORNIA ML THE pDRIGUEZ WaterBoards ENVIRONMENTAL PROTECTION Central Valley Regional Water Quality Control Board 21 December 2012 Mr. Roger Smith Glenn Springs Holdings, Inc. 5005 LBJ Freeway, Ste 1350 Dallas, TX 75244-6119 MONITORING WELL DESTRUCTIONS AND SOIL SAMPLING SCHEDULE, OXYCHEM STOCKTON, 1904 CHARTER WAY, SAN JOAQUIN COUNTY Staff of the California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) reviewed a 20 November 2012 email request from your consultant, Mr. Matt Sutton of The Source Group. Mr. Sutton requested that the annual soil sampling obligation be removed from the phytoremediation treatment procedures, and questioned why monitoring wells MW-3 and MW-4 were included in the monitoring schedule. This letter addresses these two inquiries. Monitoring Well Destructions A staff review of the file correspondence shows that MW-3 and MW-4 were installed for the purpose of evaluating the underground fuel tanks and were no longer a necessary component of the monitoring program. In a 5 August 2002 letter, Central Valley Water Board staff concurred with OxyChem's proposal to destroy them. In my 27 November 2012 telephone conversation with Mr. Sutton, he confirmed that the wells had not been destroyed. Staff review of the monitoring reports finds that intermediate monitoring wells MW-19, MW-22, and MW-24 have consistently been beyond the footprint of the shallow zone groundwater pollution, and are unlikely to provide useful data. Therefore, by 1 March 2013, please provide a workplan to destroy MW-3 and MW-4, and if desired, monitoring wells MW-19, MW-22, and MW-24. The wells shall be destroyed according to San Joaquin County regulations. Soil Sampling Schedule The phytoremediation treatment system was implemented in 2003 to remove nitrate from groundwater, uptake nitrogen from soil, and degrade pesticide and herbicide compounds. Soil sampling was initiated to monitor the effects of phytoremediation on soil constituents. Pursuant to a letter dated 22 January 2008 by Central Valley Water Board staff, OxyChem discontinued sampling for pesticides and herbicides, because the concentration of these compounds were below cleanup goals. OxyChem may be required to resample soil for organic constituents prior to considering the site for no further action. The fall 2011 sampling data show that nitrogen still exceeds cleanup goals in many locations. Therefore, OxyChem needs to continue sampling for nitrogen compounds. However, the KARL E. LGNGLEY SCD, P.E.,CHAIR I PAMELA C. CREEDON P.F., SCEE. EXECUTIVE OFFICER 1 102 0 Sun Center brie#201),Ranc he COrdova.CA 95670 1 www.w at er60 and 5.ca.govlce nt ralva I ley 4'RECv CLE❑PAPER