SITE INFORMATION AND CORRESPONDENCE

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California Regional Water Qualityontrol Boar Central Valley Region a',l Robert Schneider,Chair ) Winston H.Hickox Gray Davis Secrelaryfor Sacramento Main Office Governor Environmental Internet Address: http://www.swrcb.ca.gov/—mgcb5 Protection 3443 Routier Road,Suite A,Sacramento,Califomia 95827-3003 _o Phone(916)255-3000•FAX(916)255-3015 TO: Cori L. Condon V r FROM: Marty Hartzell Senior Engineering Geologist Associates E-nggin�eering .}Geeolo'gii'st DATE: 29 March 2001 SIGNATURE: �aw;� �ffA�/rr�yvv UNDERGROUND STORAGE TANK CLOSURE, HERMAN& HELEN'S MARINA 15135 EIGHT MILE ROAD, STOCKTON, SAN JOA QUIN COUNTY San Joaquin County Environmental Health Division (County) referred Herman and Helen's Marina underground storage tank(UST) site to the Regional Board on 5 January 2001 due to the County's determination that MtBE contamination was originating from the above ground petroleum storage tanks, and not the former USTs. I reviewed the 2 October 2000 Soil and Groundwater Investigation and Sensitive Receptor Survey Report,and the 12 January 2001 Fourth Quarter 1000 Groundwater Monitoring Report (QMR)both submitted by Condor Earth Technologies, Incorporated(Condor) on behalf of Herman&Helen's Marina. Based on my review and discussions with the County,I concur with the County's determination. Herman&Helen's Marina is located on the Little Connection Slough off Eight Mile Road north of Stockton. The Little Connection Slough connects the Stockton Deep Water Channel in the south to the San Joaquin River via the Potato Slough in the north. Herman&Helens Marina has in the past, and currently supplies motor fuels for boating customers. The attached Figure 1 from Condors QMR shows a location map for the site. In October 1991, three USTs were removed from the site, and soil contamination was identified at 9 to 12 feet below ground surface (bgs) at the UST tank pits. From August 1995 to September 1996,three Hydropunce and five Geoprobe borings were completed to identify groundwater contamination, and in September 1997, four monitoring wells were subsequently installed. In September 2000, thirteen additional borings were completed to delineate the extent of groundwater contamination approximately 100 feet downgradient of the former USTs. The attached Figures 2 and 3 show site maps with boring locations for Herman &Helens Marina. The water level in the Little Connection Slough west of the levee and west of the former USTs averages 10 to 15 feet above ground surface east of the levee, and shallow groundwater flow at the site has been consistently to the southeast. As shown on Figures 2 and 3, shallow groundwater is intercepted by a drainage ditch, which directs water to the Island Drainage Channel, and is eventually pumped back into the Little Connection Slough. Groundwater monitoring has been conducted quarterly since September 1997. The maximum groundwater monitoring results in micrograms per liter(µg/l) for samples collected for the Fourth Quarter 2000 monitoring event on 13 December 2000, show TPHg at 670,benzene at 3.4, ethyl benzene at 4.2, total xylenes at 120, and MtBE at 14,000. Toluene was non-detect at<0.3 µg/l. Historically, TPHg, BTEX, and low MtBE (maximum California Environmental Protection Agency 0 Recycled 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 reduce demand and cut your energy costs,see our Web-site at http://www.swreb.ca.gov/rwgeb5