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G¢ological Technic inn. Page 4 Additional Site Characterization Work Plan Project No.724.2 March 15,2005 Although soil and groundwater contamination has been documented at depths greater than 100 feet, GTI believes that these occurrences are drilling artifacts. This theory is supported by the rapid attenuation of contaminant concentrations in well MW-101 after it was installed. This well is screened from 92 - 97 feet bgs and has contained low to trace levels of BTEX and TPH-G for the last five years. 2.1 Cone Penetrometer Testing (CPT) Cone penetrometer testing (CPT) uses specialized technology to determine subsurface lithology. It consists of using a large truck to apply massive force to drive a cone at the head of rods through the subsurface. Friction, pore water pressure and tip resistance are measured as the cone moves downward and these values can be correlated to determine the type of soil present. GTI proposes to utilize the services of Gregg Drilling & Testing Inc. (Gregg) of Martinez, California to perform the CPT boreholes. Gregg has 20 — 25 ton trucks that can achieve the target depths of 100 feet below grade surface (bgs). In addition, Gregg has sampling devices that can be used to collect depth discrete soil and groundwater samples from the boreholes. Data on CPT technology provided by Gregg is included in Appendix C. Soil boring permits will be secured as necessary and the local regulatory agency will be notified 48 hours prior to commencing work. The subsurface will be cleared of underground utilities by notifying Underground Service Alert. In each boring location two boreholes will be advanced. The first borehole will be installed to determine subsurface lithology, and the second to obtain soil and groundwater samples. The need for two holes in each location is designed to alleviate the necessity of repeated removal and re-insertion of the rods, and changing the cone/sampler fixtures during sampling. 2.1.1 Soil Sampling Soil sample depths will be targeted to complete the site conceptual model illustrating the lateral and vertical extent,of the soil plume at the site. A soil sample from the capillary fringe in each CPT borehole shall be submitted for laboratory analysis at a minimum. Gregg will utilize a piston type soil sampler to obtain samples at depths to be determined in the field. The sampler is attached to the end of the drill rods and then advanced to the targeted depth. When the targeted depth is achieved, the rods are retracted 12 — 18 inches to allow the cone to slide upward into the hollow core of the sampler. The rods are then advanced downward to allow soil to fill the now empty core. A description and schematic of the process is included in Appendix C.