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Odic Environmental Page 2 of 4 southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys,respectively. The Modesto, Riverbank and Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500-square-mile San Joaquin Valley Ground Water Basin. Perched aquifers are found in shallow unconsolidated alluvium. A property located approximately 650 feet to the west of the site (26090 Thornton Road)reports depth to ground water ranging from approximately 2.83 feet to 17.08 feet below the tops of the well casings (Advanced GeoEnvironmental,August 2009). Scope of Work A geophysical survey will be conducted to identify the septic tank and leach field location and also identify subsurface utilities in the proposed drilling area. A total of four soil borings are proposed. One borings will be drilled at the septic tank and soil samples will be collected for potential laboratory analysis at depths of 5, 10, and 15 feet. If groundwater is encountered, a groundwater sample will be collected from this boring. Two borings will be drilled at the septic leach field to depths of 10 feet,with soil samples collected for potential laboratory analysis at depths of 3, 5, and 10 feet. One soil boring will be drilled at the area of visual surface staining northeast of the building,with soil samples collected at depth of 3,5,and 10 feet for potential laboratory analysis. Soil boring locations will be based on the results of the geophysical survey. The attached Figure 2 illustrates the preliminary soil boring locations. Pre-drilling Activities • Perform Site Visit to verify existing conditions and pre-mark boring locations and notify Underground Service Alert(USA)of the intent to excavate or drill and use standard care to avoid potential damage to subsurface utilities. • A Site-specific Health and Safety Plan(Level D Health&Safety according to OSHA CFR 1910.120, will be prepared. • Submit a Drilling Permit Application to the San Joaquin County Environmental Health Department Field Investigation • A full access push probe rig with a licensed operator will be mobilized to the site to complete the proposed scope of drilling and sampling activities.All down-hole sampling equipment will be cleaned before starting a soil boring,with a non-phosphate detergent and water before each use. • Odic will backfill each boring with a bentonite slurry or approved method of backfilling per the San Joaquin County requirements. Each borehole will be abandoned/filled with bentonite,and restored to pre-drilling condition via applying patching materials. • Collect soil samples at 5-foot intervals,or at significant changes in lithology.Attempt to collect the lowermost sample at or immediately above the groundwater level if groundwater is encountered during drilling. • If groundwater is encountered grab samples may be collected down hole(either through the drive rods or temporary installed 1-inch PVC well screen)using a peristaltic pump and disposal polyvinyl tubing under low flow conditions. • Monitor the headspace of each sample for the presence of volatile organic compounds using a photo- ionization detector(PID)or flame-ionization detector(FID). • The soil boring will be logged using the Unified Soils Classification System under the supervision of ODIC's State Professional Geologist(PG)or Registered Professional Engineer.