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Boyett Petroleum April 19, 2000 419 South Main Street, Manteca, California Page 2 Work Plan for Lateral Extent of Groundwater Contamination On October 5, 1998, WHF, Inc. (V4-IF) in conjunction with Fisch Environmental Exploration Services, a state licensed drilling contractor, completed two (2) vertical soil ' borings, SB-1 and SB-2, to a maximum depth of eighteen (18) feet near the fuel dispenser island. The data collected was utilized to evaluate the presence or absence of contamination in the shallow subsurface and groundwater underlying the fuel dispensers. Soil samples were taken from all borings at five (5) foot intervals for soil classification. Three (3) soil samples were selected from each boring at 4-6 feet, 9-11 feet, and 16 feet for laboratory analysis. One (1) groundwater sample was collected from the termination point at eighteen (18) feet for laboratory analysis. ' On August 27 and 30, 1999, WHF, Inc., in conjunction with Frontier Drilling, a state licensed drilling contractor, completed four (4) soil borings, that were converted to ' monitoring wells, to a depth of approximately 30' bgl (groundwater depth --18') to confirm the presence or absence of petroleum hydrocarbons and the vertical extent of the soil contamination in the unauthorized release area. The actual depth of the wells varied ' between 26.5' and 36.5'. The event provided data to evaluate the soil contamination at the dispenser island, and the extent of groundwater contamination underlying the site. The soil sample analysis indicated no detectable levels of Petroleum Hydrocarbons as Gasoline or BTXE in the eleven (11) soil samples collected from the borings/wells. The soil sample analysis indicated MTBE contamination is present in MW-1, MW-3, and M-4. Samples MW-1@20' and MW-1 a 30' contain MTBE contamination at concentrations of 150 ug/Kg and 65 ug/Kg, respectively. The sample MW-3@18'18' contains 200 ug/Kg of MTBE. Samples MW-4@10', MW-4@15', and MW-4@20' contain MTBE contamination at concentrations of 22 ug/Kg, 40 ug/Kg, and 45 ug/Kg, respectively. The groundwater sample analysis indicated that gasoline oxygenate contamination exists in the groundwater underlying this site. MTBE contamination is present in MW-1 at a concentration of 2,700 ug/L, MW-3 at a concentration of 5,700 ug/L, and in MW-4 at a ' concentration of 140 ug/L. Tertiary-Butanol is present in MW-1 at a level of 98 ug/L. TAME is present in MW-1 and MW-3 at levels of 7.7 ug/L and 16 ug/L, respectively. No other contaminant is present in the groundwater at significant levels. rQuarterly groundwater monitoring has been conducted at appropriate intervals since the monitoring well installation event in August, 1999. 3.0 Scope of Work This scope of work was developed to explore the lateral extent of groundwater contamination at Boyett Petroleum in Manteca, California. Soil contamination was not 1