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P R O C F. D U R 8 S Methodologiou and Conventiunn GENERAL PRACTICLS WITHIN A MULTIPLE AGENCY 1119HARCIIY U.S. Environmental Protection Agency standards serve an the foundation for all field sampling operations performed by our firm. The EPA SW 846 is thin primary publication from which procedures are derived, though there are s additional EPA sources such as training films and verbal communications, Sampling related to underground storage tanks and tank related threats to groundwater are governed by the California Water Resources Control Board and their Regional water Quality Control Boards. While some aspects of field and laboratory work may be delegated to the California Department of Health Services, the CWRCB and the nine Regional dater Quality Control Boards establish the general and specific criteria for �Ampiing performed in connection with underground storage tanks. This is done through the publication of guidance documents, the issuance of memoranda and verbal announcements. Other agencies, such as Air Pollution Control Districts, may require additional samplen, but these are usually in addition to samples required by the RWQCB. Local implementing agency (LIA) instpectors are frequently present during the tank removal phase of a project and either direct or request that J samples be taken according to RWQCB specifications. Additional samples may, and frequently are, taken at the request of the LIA inspector. Based on field conditions directly observable by the LIA inspector, our field personnel may be asked to collect samples that are tailored to the specific actuation and which the inspector judges will provide substantial Information about the: site. Quite often these directions or suggestions coincide with the sampling areas established by the RWQCB as the proper collection points for samples which will be used as the Primary Criteria for a Regulatory Agency Determination on whether additional exploration or remediation will be required at a particular site. Similarly, there are Instances when the LIA inspector's judgements do not coincide with Board specifications. Two common examples of this are ars follows: 1. A local implementing agency inspector notes that soil dug up from the l� correct RWQCB interface sampling point is relatively clean, but observes that there is quite obviously contaminated backfill underlying the center of the tank. The inspectordirects that the contaminated backfill should be taken instead of the.clean Interface soil so as to provide information about the "worst case" condWons within the tank pit. 2. The soil at the specified interlace sampling depth is found to be slightly contaminated, but touch leas no than the soil only a feu inches above. Noting Sampling Report 88057-G-1 Chevron 1918 SECTION TWO/page 7