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T*EALON VI RON M ENTAL CONSULTANTS 131 NORTH T UMN AVENUE• Sum 213 .TUSTIN,CALIFORNIA 92780 941SHOREPOINT Col T SUITE F121 •AL MMA,CAUFORNIA 94501 TEL:(714)8366632 • FAX:(714)836-6642 3Y 22 PH s` 1' 00 TEL:(510)521-2441 • Svc:(510)521-2607 May 18, 2000 Public Health Services San Joaquin County Attn: Ms. Carol Oz 304 East Weber Avenue, Third floor Stockton, California 95201 Subject: Work Plan for Groundwater Assessment and Monitoring Well Installation at Joe's Truck Stop, at 15600 South Harlan Road, Lathrop, California. Ms. Oz: Pursuant to your request, Avalon Environmental Consultants (Avalon) presents this work plan to perform further soil and groundwater Assessment at Joe's Truck Stop at 15600 South Harlan Road in Lathrop, County of San Joaquin, California. The additional investigation is prompted by a letter from Public Health Services San Joaquin County (PHSSJC) dated April 3, 2000, in which further characterization of the subject property was requested. This additional investigation will consist of performing additional testing both onsite and offsite with a geoprobe device. The purpose of this investigation is to determine, to the extent possible, the horizontal limits of Methyl Tertiary Butyl Ether (MTBE) and other hydrocarbon contamination in the groundwater at the subject property. Additionally, more detailed lithologic information near the area of impact, offsite to the northeast, and west, along existing utility trenches. The first quarter groundwater monitoring report showed levels of MTBE at a level of 1,800 ppb in MW-2 which is a well located to the northeast of the former tank pit. Levels of MTgc within the tank pit in well MW-1 were lower, 250 ppb. The second quarter groundwater monitoring showed a decrease in the well MW-2 from 1,800 ppb to 290 ppb and an increase in MW-1 from 250 ppb to 2,800 ppb. This investigation will consist of performing continuous cores collected from ten geoprobe borings placed near the area of impact, offsite to the northeast, and west, along existing utility trenches. Select soil samples will be analyzed for Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA Modified 8015, Benzene, Toluene, Ethyl Benzene, and Xylenes (BTEX) by EPA Method 8020, and for Oxygenated Compounds which will include Tertiary Butanol, MTBE, DIPE, ETBE, TAME and lead scavengers by EPA Method 8260. Select soil samples will be analyzed for porosity, permeability, bulk density, organic carbon, and moisture content as requested in the County's, April 3, 2000 directive.