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• Soil samples were collected from several soil gas borings (A2-SG1, A3-SG1, A3-SG2, A3-SG3, A3-SG5, B1-SG1, D2-SG1 and E1-SG1) based on the observance of potentially impacted materials; and • Groundwater Monitoring Well TW-5 was constructed using 0.010-inch slotted screen and Lonestar #2/12 sand for the filter pack based on observations made in the field. The original plan was to construct the well with 0.020-inch slotted screen and Lonestar #3 sand, but due to geologic conditions, the finer screen and filter pack were necessary. 3.4 HEALTH AND SAFETY MONITORING Health and safety monitoring, using a PID, was administered during the drilling and sampling conducted as part of the implementation of the RI/SSI. Although VOCs were identified in headspace readings conducted on soil samples, there were no detections above action levels in the breathing zone of the on-site workers. Concentrations of VOCs in the breathing zone ranged from 0.0 ppmv to a maximum of 1.8 ppmv. The results of the monitoring were recorded in the boring logs provided in Appendix E. 3.5 DISPOSAL OF INVESTIGATION DERIVED WASTE In the process of collecting environmental samples during the proposed field sampling program, different types of potentially contaminated investigation-derived wastes (IDW) were generated and include the following: • Used personal protective equipment(PPE); • Disposable sampling equipment; • Soil cuttings; • Well development and purging fluids; and • Decontamination fluids. The USEPA's National Contingency Plan requires that management of IDW comply with all applicable or relevant and appropriate requirements to the extent practicable. The sampling plan will follow the Office of Emergency and Remedial Response Directive 9345.3-02 dated May 1991, which provides the guidance for the management of IDW. In addition, other legal and practical considerations that may affect the handling of IDW were considered. Listed below are the procedures that were followed for handling the IDW: • Used PPE and disposable equipment was double bagged and placed in a municipal refuse dumpster. These wastes are not considered hazardous and can be sent to a municipal landfill. Any PPE and disposable equipment that was disposed and could still be reused was rendered inoperable before disposal in the refuse dumpster. • Decontamination/development/purge water was placed in Department of Transportation approved 55-gallon drums and sealed. The drums were identified with labels stating "Caution: Potentially Hazardous Substance — Pending Analysis". In addition, the label identified the address of the Site; the source of its contents (i.e., soil boring numbers, sample depths, etc.); the contents of the drum(i.e., soil, groundwater, etc.); and a notation PARSONS 30 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010