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si �Y Mr Jeffrey Wong Page 3 of 7 San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) in a letter dated August 16, 1999 directed the responsible party to conduct a subsurface investigation Ground Zero prepared a workplan dated October 13, 1999 on behalf of the Ferraiolos and submitted the report to PHS/EHD for approval PHS/EHD approved on November 30, 1999 2.3 Investigations Undertaken In accordance with the approved workplan, soil bonngs were advanced at the subject site to investigate the lateral and vertical extent of residual soil contamination, as well as the potential impact to groundwater Due to evidence of impact within the saturated zone, PHS/EHD directed the installation of a monitoring well Subsequently, boring SB 1 was converted into a groundwater monitoring well Soil boring and monitoring well locations are depicted on Figure 3 3.0 INVESTIGATIVE PROCEDURES 3.1 Drilling and Sampling On February 22 and 23, 2000 eight borings were advanced at the site to investigate the extent of contamination Spectrum Exploration advanced the borings under the supervision of field geologist Sean Garvey and project manager Gregory Stahl, a California Registered Geologist Mr Jeffery Wong PHS/EHD conducted the site inspection and observed field activities Boring SB 1 was advanced to a depth of approximately 80 feet below ground surface (bgs) in the vicinity of the former tank pit, and converted into groundwater monitoring well MW 1 Boring SB2 was advanced approximately 9 feet north-northeast of MW1 to a depth of approximately 30 feet bgs Boring SB3 was initially advanced approximately 15 feet north of MW1, however, due to apparent hydrocarbon odors at this location, three subsequent steps outs were drilled Apparent hydrocarbons odors were noted at each The final location of SB3 was approximately 45 feet south west of MW1 SB4 was advanced approximately 31 feet south southwest of MW1, and boring SB5 was advanced approximately 35 feet east of MW 1 Boring logs and well construction details are included in Attachment A Soil samples were collected at 5-foot intervals using an 18-inch long core sampler lined with new 2-inch diameter brass sleeves, affording soil identification and subjective evaluation for contamination A flame ionization detector (FID) was used to monitor the presence of volatile organic compounds in the soil Due to a malfunctioning of the FID on the second day of drilling screening of soil samples for contamination on that day was solely by olfactory and visual indications After collection, the samples were sealed, labeled, and immediately placed in an iced cooler and transported to Argon under chain of custody protocol Soil sample selection was based on field observations and screening results Groundwater was first found in boring SB 1 at a depth of approximately 50 feet bgs Subsequent measurements indicated that the water level had apparently stabilized datalgrounze\ha ryslsumrpt doe