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15 April 2003 AGE-NC Project No. 02-0950 Page 4 of 10 samples are found utilizing an organic vapor meter(OVM)equipped with a photo-ionization detector (PID: Thermo Environmental 580A, 10.0eV [or equivalent], calibrated to isobutylene). The total depth and proposed location of the soil boring may be modified due to field observations. The proposed soil boring location is presented on Figure 2. In addition,AGE proposes to advance three pilot soil borings to approximately 35 feet bsg to install groundwater monitoring wells(MW-1 through MW-3);the total depth of each pilot boring may vary according to hydrogeologic/geologic information obtained during the initial soil boring investigation and drilling conditions.Based on known ground water contamination encountered at the site to date, AGE proposes to advance the pilot borings in the following locations (Figure 2): • Between 15 and 20 feet south (down-gradient) of the former UST area; • Between 15 and 20 feet west (down-gradient) of the former UST area; and V • Between 20 to 25 feet east-northeast(up-gradient) of the former UST area . 3.2.1. Soil and Ground Water Collection and Analyses As the borings are advanced,soil samples will be collected at 5-foot intervals beginning at 5 feet bsg and extending to the total soil boring depth. In addition, grab ground water samples will be taken at first encountered ground water and again at total depth of the vertical-assessment boring B4.Field procedures for advancement of the soil boring and collection of soil and groundwater samples are presented in Section 4.1. The grab ground water samples from B4 and selected soil samples from the four soil borings will be submitted for laboratory analysis. AGE proposes to discontinue sampling for volatile organic compounds (VOC's)specifically the following fuel additives: tertiary butanol(TBA),di-isopropyl ether (DIPE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and methyl tertiary- butyl ether (MTBE), in any future work at the site. The five VOC's of concern have not been detected at or above laboratory detection levels in any of the soil or groundwater samples associated with the tank removal and the preliminary site investigation. If the EHD concurs with this request, selected samples will be analyzed by a State of California Department of Health Services (DHS)- certified laboratory for the following constituents: V • TPH-g and TPH-d in accordance with EPA Method 8015 Modified; • Benzene, toluene, ethyl-benzene and total xylenes (BTEX) and the lead scavengers 1,2-dibromoethane (EDB) and 1,2-dichloroethane (1,2-DCA) in accordance with EPA Method 8260 Modified; and • Total lead in accordance with EPA Method 6010B. r Advanced GeoEnvironmental,Inc. 6.i