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• <br />n N • :ENMUNU <br />G. BRUWJH. <br />RECEIVED <br />U-4OVRNO <br />• <br />MArTHEvi ROO <br />RIOUE2 <br />-C.11A EORWater Boards �� 014 NVIAONMENTAL <br />PROTECTION <br />Central Valley Regional 1Nater Quality Control Board RONMENTALHEALTh� <br />PERMIT/SERVICES <br />21 April 2014 <br />Ralph Lee White <br />2201 East Eighth Street <br />Stockton, CA 95206 <br />Peter Bui & Kimberly Hoang <br />4004 Maddie Circle <br />Stockton, CA 95209 <br />WORK PLAN AND DOCUMENTS REVIEW FOR RALPH'S SQUARE, 2211 SOUTH AIRPORT <br />WAY, STOCKTON, SAN JOAQUIN COUNTY, RB CASE # 390995 <br />California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br />Board) staff reviewed the Groundwater Report - First Quarter 2014 (Report) and the Soil Vapor <br />Investigation Work Plan (Work Plan). The Report and the Work Plan were received as an email <br />attachment on 15 April 2014 and electronically in GeoTracker on 10 April 2014, respectively <br />from your consultant Advanced GeoEnvironmental, Inc. (AGE). <br />The Report provides the 4 March 2014 groundwater monitoring results of MW -1 through <br />MW -11. The data show methyl tert butyl ether (MTBE) concentrations have generally declined <br />from one to three orders of magnitude since the last complete round of sampling in October <br />2008, with the exception MW -5, which increased from 17,000 micrograms per Liter (ug/L) to <br />28,000 ug/L. The data show the MTBE plume has migrated at least 50', and is undefined to the <br />east. The MTBE plume is defined to the west by MW -1, to the north by MW -7 and MW -8, to the <br />south by MW -9, to the southeast by MW -10, and vertically in the source area by MW -11. <br />The San Joaquin County Environmental Health Department (SJCEHD) approved a work plan <br />for a groundwater investigation to define the downgradient extent of the plume in a letter dated <br />27 August 2009. In the Report, AGE proposed to complete the delayed investigation by <br />installing one soil boring (B-5) 80'to the east of the Ralph's Square building, which is about <br />60' east of the USTs pit. B-5 would be located about 20' east of a residence on Phelps Street. <br />AGE proposed to collect one grab groundwater sample from B-5. AGE recommended <br />submitting a new sensitive receptor survey, stating a water supply well has been confirmed in <br />City of Stockton Park to the northeast. <br />In the Work Plan, AGE proposed installation of five (5) soil vapor wells completed to five (5) feet <br />below ground surface (' bgs), one well in the underground storage tanks (USTs) pit and the <br />remaining four wells between the USTs pit and the Ralph's Square building, to evaluate the <br />threat from vapor intrusion. Two soil borings are proposed to be advanced to 10' bgs with soil <br />samples collected at 5' bgs and 10' bgs, one in the USTs pit and the second 20' to the northeast <br />near MW -2, to evaluate for a bio -attenuation zone. I concur with the tasks proposed in the Work <br />Plan with the conditions stated below. <br />KAnL E, LONOLEY SCE), P.E., CHAIR I PAMELA C. CREEDON P.E., SCEE, EXECUTIVE orrICER <br />11020 Sun Center Drive #200, Rancho Cordova, CA 95670 1 www.waterboards.ca.gov/centralvalley <br />=ra RECYCLED PAPER <br />