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%We *./ TETRA TECH, INC. well screen and decontaminated pump, as described below. Actual field conditions and professional judgment will determine the groundwater sample method used in the field. 1) Care must be taken to monitor any volume of water injected into the boring. Injected water must be removed prior to collecting a groundwater sample to ensure samples are representative of actual aquifer conditions. 2) Advance casing to a depth that allows the temporary well screen and pump to be lowered far enough to submerge the pump intake(i.e.,approximately 5 feet into the saturated zone). 3) Lower a clean, screened well casing into the borehole casing. Ensure the screen reaches the bottom of the borehole casing. 4) Lower the pump to the screen. 5) Calculate the volume of water to be purged. At a minimum, ensure three well volumes, the volume of water injected into the boring, and an additional 10 percent are purged from the well before sampling. 6) Tum pump on and begin purging. Calculate the purge rate and, based on the volume of water to be purged,the purge time. 7) After purging the appropriate volume of water, collect the groundwater sample from the pump discharge tubing. 8) If aquifer production is adequate, measure the groundwater temperature, pH, conductivity, turbidity, dissolved oxygen content, and oxidation-reduction potential using an YSI multi-probe meter (a flow-through cell attached to the YSI multi-probe meter may also be used to measure these parameters). 9) Turn off the pump. Remove the pump and the temporary well screen. Decontaminate the pump and,if it's not disposable,the discharge tubing. 4.4 SAMPLING PLAN 4.4.1 Sampling Locations A total of six borings will be advanced to groundwater (Figure 3-1). These borings are located on the southern portion of the Site. Field personnel will collect a minimum of one groundwater and one soil sample from each boring. One passive soil gas sample will also be collected in the vicinity of each of the six the boring locations. See Section 3.7 for a detailed description of the sample design. Appropriate sample containers,volumes, preservation, and holding times are listed in Table 4-1. Passive soil gas samples will be collected with AGI Universal Samplers (Appendix Q. The samples planned to be collected during this field effort are summarized in Table 4-2. Page 4.2 Sampling Effort Work Plan Tracy Mansfield Property