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Work Plan—PEA Page 6 Former Haley Flying Service GPE Project 474.2 crop dusting operations was sufficient justification to maintain the listing, even though the fire that triggered the listing was acknowledged to have been at another location. The DTSC has required that a PEA be completed before a letter requiring "no further action" can be issued. The owner of the property recently entered the DTSC's Voluntary Cleanup Program (VCP), and this Work Plan is intended to propose steps to complete an adequate PEA describing the soil and groundwater conditions as they relate to past crop dusting operations as well as the surface spill reported by San Joaquin County, and to assess the possible risks to public health. 1.4 Potential Problem It does not appear that any soil or groundwater samples have ever been collected to determine whether past operations on the property might have impacted the soil or groundwater with organo-chlorine pesticides or other contaminants. The only samples ever collected were confirmation soil samples taken in connection with the 1990 removal of a 1,000-gallon regular unleaded gasoline tank and a 5,000-gallon aviation fuel tank (see Section 1.2 for details). The area of most concern is the past use of the pesticide loading onto aircraft and the use of the washout pit. These installations raise concerns regarding possible releases that might have impacted the soil. A secondary issue is the possibility that the reported spill of two drums of waste water/oil/diesel in the area in front of the westerly hangar may have impacted the soil. The Conceptual Site Model Diagram (next page) provides a summary of the potential contaminant pathways and receptors. 1.5 Scope of Work This Work Plan describes a series of shallow soil samples that will be collected and tested for the possible presence of organo-chlorine, organo-phosphate, and N-Methyl Carbamate, pesticides; and chlorinated and triazine herbicides. Samples will be collected from all parts of the parcel, but will be concentrated in the area of the building complex, and especially the washout pit and aircraft-loading apron. In addition, two Geo-Probe soil borings will be installed to collect groundwater samples at points near the washout pit. These groundwater samples will also be tested for the pesticide and herbicide groups mentioned. One sample from the apron in front of the westerly hangar will also be tested for the presence of Volatile Organic Compounds (VOC's) and total extractible petroleum hydrocarbons (TEPH). Upon completion of the data collection phase, the laboratory analytical results will be evaluated and an assessment made regarding the potential for possible endangerment to the public health. 2937 Veneman Avenue, Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 Modesto, Ca 95356 Fax: (209) 569-0295