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Frontier Transportation B2350101A January 2, 1996 Page 7 (C57 Contractors License No. 506159) under the supervision of a Twining geologist. Soil samples will be collected in the boreholes drilled for the monitoring wells at 5-foot intervals commencing at a depth of 10 feet BSG. Soil samples will be observed in the field for the purpose of developing lithological logs and screened for evidence of PPCs with a photoionization detector (PID) consistent with our SOPS. Soil samples will be retained for chemical analysis only if field screening indicates the possible presence of PPCs in soils originating from the monitoring well boreholes. General practice requires that boreholes for groundwater monitoring well installation shall not pass through impacted soil into the groundwater surface. Therefore, during the drilling of the boreholes, should evidence of PPCs be encountered, drilling will be terminated and the borehole backfilled. A new location for the monitoring well will then be chosen further from the presumed source of the PPCs. The final depth of the soil borings will be determined by the depth at which groundwater is encountered. The boreholes will be advanced until they are approximately 15 feet below the groundwater surface. For the purposes of this work plan, the final depth of the boreholes for the groundwater monitoring wells is presumed to be approximately 35 feet BSG. The monitoring wells will be constructed of 24nch diameter schedule 40 PVC casing and screened over the bottom 20 feet of the well. Consistent with our SOPS, the well filter pack material consisting of appropriately-sized pre-washed sand will be placed in the annulus between the boring wall, from the bottom of the boring to approximately 2 feet abovethe top of the screen. After filter pack emplacement, preliminary development may be performed to provide a uniform filter pack about the casing. Above the filter pack, a 3- to 4-foot thick bentonite seal will be installed. The remainder of the well annulus is sealed with a 6-sack sand-cement, or cement grout slurry in one continuous operation from the bottom of the interval to be filled to the top. The grout will be emplaced through the hollow augers, which will extend to within 10 feet of the bentonite seal. The augers will be withdrawn from the boring in 10400t increments as the boring fills with grout. A monitoring well construction (proposed) schematic for the monitoring wells is presented as Drawing 5. A minimum of 48 hours after installation, the monitoring wells will be developed consistent with our SOPS to remove excess sediment and to settle the filter pack. Development will continue until the purged water is relatively sediment free, and measured field parameters (pH, electrical conductivity, and temperature) have stabilized. 4. 1.3 Level Survey: Following installation, the monitoring wells will be surveyed consistent with our SOPs to determine ground surface/wellhead elevations and locations. The survey data collected during this phase will be referenced to a United States Geological Survey