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s AL0 N ------ --- ENVIRONMENTAL CONSULTANTS _ 131 NORTH TUSTIN AVENUE.• SUITE 213 •TUSTIN,CAUF0 y 91 iU V �� )41 SIIOREFOIN'C COURT • SUITE )52 • 441ALA - F (510)CALIFOR5 94501 ��} u TEL:(Sl0)521-2441 • F,vc:61o)521-Y-0- TEL:(714)836-6632 • Fnx:(714)836-6642 i August 17, 2001 Public Health Services San Joaquin County Attn: Ms. Margaret Lagorio 304 East Weber Avenue, Third floor Stockton, California 95201 Subject: Work Plan for Offsite Groundwater Assessment and Monitoring Well Installation at Joe's Truck Stop, at 15600 South Harlan Road, Lathrop, California. Ms. Lagorio: Pursuant to your request,Avalon Environmental Consultants(Avalon) is pleased to submit this work plan to perform a Groundwater Assessment and Monitoring Well Installation at Joe's Truck Stop at 15600 South Harlan Road in Lathrop, County of San Joaquin, California. This investigation will consist of installing four groundwater monitoring wells, one on the subject property and three on a property adjacent and north/northeast of the subject property. The purpose of this investigation is to monitor levels of Methyl Tertiary Butyl Ether (MTBE) and other hydrocarbon contamination in the groundwater both on and offsite and to determine the limits of impact. The offsite impact was previously identified through groundwater grab samples collected by Avalon during a Phase II Site Assessment dated April 15, 2001. Elevated levels of MTBE as high as 2,600 parts per billion (ppb) were identified in the groundwater in borings located approximately 300 feet north/northeast of the subject property. Due to these elevated levels of MTBE, the county has requested that groundwater monitoring wells be installed in order to obtain repeatable data and determine the severity of the impact. This investigation will consist of drilling and sampling four groundwater monitoring wells onsite and offsite of the subject property. Three wells will be located on the adjacent property to the north, and one of the wells, which will test a deeper horizon, will be placed on the subject property downgrading to the former tank pit. Once monitoring well construction is complete, and the monitoring wells have been developed, the locations and top of casings will be surveyed by a State Licensed Land Surveyor. Once this is complete, the wells will be given one week to stabilize, prior to measuring and sampling. This will allow groundwater levels to stabilize, thereby giving accurate data. Soil and groundwater samples will be analyzed for Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA Modified 8015, Benzene, Toluene, Ethyl Benzene, and Xylenes (BTEX) by