SITE INFORMATION AND CORRESPONDENCE

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0 • 3.0 IN SITU GROUNDWATER SAMPLING In-situ groundwater sampling will be conducted as a screening investigation to assess the potential presence of impacts to groundwater beneath the site. The number and location of groundwater sampling points will be based on the results of the soil vapor survey discussed in Section 2.0. However,at this time,it is anticipated that up to 10 groundwater samples,designated HP-1 through HP-10,will be collected at the approximate locations shown on the attached figure. At each location an in situ groundwater sample will be collected at first encountered water estimated to be between 30 to 50 feet below ground surface. In situ groundwater samples will be collected using TEG's STRATAPROBE direct displacement multi-media sampling system. Soil samples can be obtained as discrete samples in stainless steel or brass sleeves. Water samples can be obtained from a 1 inch hole through a stainless steel screen using a bailer or peristaltic pump. Soil samples will be collected at a minimum of every 5 feet for lithologic description and to estimate the depth to first water. The use of a Direct Displacement System virtually eliminates waste and cuttings associated with a drilling program. TEG uses a standard Screen Point Sampler method for discrete groundwater sampling in most soil conditions. The assembled Screen Point Sampler is 1.0 inch O.D. X 36-inch overall length. This sampler features a 19-inch screen encased in a perforated stainless sleeve. The device is also useful for measurement of piezometric levels. The assembled Screen Point Sampler threads onto the leading end of the probe rod and is driven into the subsurface using a STRATAPROBE machine. Additional probe rods are connected in succession to advance the sampler to depth. While the Screen Point Sampler is being driven to the desired sampling depth, it is kept seated by O-ring connections at critical locations on the assembly. When the desired sampling depth is reached, the sampler is pulled up about 2 feet which disengages the expendable drive point and creates an open borehole from which to sample. The inner core, which consists of a stainless steel wire screen inside of a perforated stainless steel sleeve, is then pushed out into the borehole and water is allowed to enter the sampler and connected probe rods. After collection of the in situ groundwater sample the hole will be grouted to the ground surface using the tremie method with a cement/bentonite grout. Ground water samples will be recovered by pumping or bailing of water collected in the open sampler. Alternately,tubing from the surface may be used to recover samples using a peristaltic pump or a vacuum source. The pore size of the screen is .0057 inches (145 mm). Samples will be placed into containers supplied by TEG and analyzed immediately by the mobile laboratory. Samples will be analyzed for TPH,BTEX and HVOCs. The in situ groundwater sampling program will be supervised by a Heritage Environmental California registered geologist. 4.0 PREPARATION OF REPORT After completion of the investigation,a report will be prepared that will include: • a discussion of the field methods used for the soil vapor survey and in situ groundwater sampling program; • a map showing the location of soil survey and m situ groundwater sampling points; and • results of chemical testing.