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Clayton Group Services The groundwater sampling procedures and equipment are dependent on the objectives of the sampling program, the design of the monitoring well, the contaminants of interest, etc. A groundwater sampling plan should be developed prior to sampling based on the reasons for sampling which define the sampling method, quantity of water to be collected, preservation techniques, and health and safety concerns, if any. In all cases, the ultimate goal is to obtain a groundwater sample representative of water present in the aquifer. In this sense, the sampling process can be divided into three steps: well flushing, sample withdrawal, and field preparation of samples. Sampling of groundwater shall follow ASTM standards, Designation: D 4448 - 85a (Reapproved 1992) - Standard Guide for Sampling Groundwater Monitoring Wells. By reference, these standards are incorporated into these Standard Operating Procedures. The California Water Quality Control Board - Los Angeles Region (CRWQCB-LA) (Interim Site Assessment & Cleanup Guidebook, May 1996) recommends that water sampling not take place until at least seven (7) days following well development. 1. Groundwater Sampling Plan - Because groundwater sampling protocol is dependent on the objectives in taking water samples, a site-specific sampling plan should be prepared and reviewed prior to sampling to include: • Objectives of sampling and analyses; • Location and access to wells, including any special equipment and keys; • Number, frequency, and quantity of water to be collected; • Health and Safety concerns; • Sampling protocol; — well purging procedure and equipment, — sample depths, — sample collection equipment (bailers, pump, etc.), — QA/QC controls, • Sample containers and treatment (including preservatives, if any);