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23 June 1998 AGE-NC Project No. 96-0229 Page 3 of 5 • Between January 1995 and June 1998,twelve ground water monitoring/sampling events have been performed at the site to monitor dissolved petroleum hydrocarbon concentrations in ground water and to characterize ground water flow direction and gradient on the site. 3.0. SCOPE OF WORK This work plan addendum is for the advancement of four soil borings to provide additional vertical characterization of site lithology and vertical assessment of petroleum hydrocarbons. 3.1. DRILLING AND SAMPLING Each soil boring will be advanced utilizing a 25-ton truck-mounted cone penetrometer testing(CPT) drill rig equipped with 2-inch diameter hollow-stem rods. The drill rig will utilize a hydraulic ram to advance a cone penetrometer to the desired depth. Soil parameters such as cone bearing, sleeve friction, friction ration and pore water pressure will be measured as the cone penetrometer is advanced. Rinseate generated during drilling activities will be containerized in properly labeled D.O.T. 55-gallon drums, and stored on-site in an area lacking public access. Disposal alternatives will be evaluated at a later date based on laboratory results of rinseate. Following completion of CPT,a second soil boring will be located adjacent the CPT boring for soil sample collection. Based on CPT findings, discrete soil samples will be collected beginning at a depth of 20 feet bsg at 10-foot intervals or in areas of lithologic variation. Soil samples will be collected utilizing a 2-inch diameter piston soil sampling assembly loaded with pre-cleaned brass sleeves. Upon soil sample retrieval, a brass sleeve will be removed from the sampler. The ends of the brass sleeve will be immediately covered with Teflon or aluminum sheets, sealed with plastic end caps, secured with tape and immediately placed in a chilled container for transportation to a state-certified laboratory. Each sample sleeve will be labeled with the location, boring designation, depth,time, date and sampler's initials. During soil sampling activities, sample duplicates will be monitored for the presence of organic vapor using a photo-ionization detector(PID: Thermo Environmental 580A, 10.0 eV, calibrated to isobutylene) and described on boring logs using the Unified Soil Classification System (USCS). Proposed soil boring locations are illustrated on Figure 2.Following borehole advancement,portland cement(grout mix)will be utilized to backfill each borehole utilizing a tremie pipe. The PHS-EHD will be given the opportunity to inspect the grout mix prior to backfilling activities. Advanced GeoEnvirontnental,Inc.