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" 6.o 1.2 SITE DESCRIPTION The Federal Building is located in downtown Stockton, California (refer to Figure 1 - Site ,r Vicinity Map). The USTs were formerly located on the south side of the building in a planter. Figure 2 - Site Plan depicts the location and orientation of the subject site. The site is situated in a relatively flat area of Stockton. Boring logs from soil borings advanced on the site indicate that, generally, site soil consists of clayey silt to silt to a depth 25 feet below ground surface (bgs). Groundwater was not encountered in the soil borings. The local groundwater gradient is reported to be to the west, but has not been established at the site. 2.0 SUBSURFACE INVESTIGATION PLAN The following Work Plan has been developed to assess the extent of impacted soil associated with v the former USTs. A groundwater monitoring well will be installed, developed and sampled to investigate the possibility of hydrocarbon impacts to groundwater at the site. In addition, the proposed plan will also initiate implementation of a quarterly groundwater monitoring program. 2.1 PROPOSED SCOPE OF WORK The following is a description of the proposed scope of work which has been developed to further investigate soil and potential groundwater impacts, as per the request of the EHD. A site specific health and safety plan will be prepared prior to beginning the field work. All required permits will be obtained prior to the start of field work. In general, proposed field work will include the drilling of four (4) soil borings and installation of a groundwater monitoring well in one (1) of the soil borings. The soil borings will be advanced using a truck mounted hollow stem auger drill rig. Field work will also include collecting soil and groundwater samples and subsequent laboratory analyses as outlined below. One of the soil borings will be advanced at an angle to penetrate the side of the former excavation beneath the retaining wall at the north end of the excavation. The second soil boring will be advanced at an angle to penetrate the side of the former excavation beneath the transformer vault west of the excavation. The third soil boring will be advanced straight down at the former location of UST "A," near the south end of the excavation. These soil borings will be advanced to a depth of 30 feet bgs or until auger refusal is met. If evidence of hydrocarbon impacted soil is observed during drilling; staining, odor, and/or elevated photoionization detector (PID) readings; the soil borings will be extended until ten feet of soil which does not display evidence of hydrocarbon impact is encountered or until auger refusal is met. The final soil boring will be advanced near the location where the highest concentration of hydrocarbons were detected within the excavation. This soil boring will be advanced until groundwater is encountered or until the total depth of the boring is 60 feet bgs. Figure 3 is the Proposed Boring Location Diagram depicting 2403c.20\stockton.pin 2 r