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GROUNDWATER SAMPLING . Prior to collecting a sample of groundwater from a well, the well will be purged by removing three or more well volumes of water, using either a pump or a bailer. A well volume is defined as the amount of groundwater in the well casing The pH and electrical conductivity of the water will be measured periodically during the purging The groundwater sample will be obtained with a teflon or polyethylene disposable bailer equipped with a bottom-emptying device To release water from the bailer with minimal aeration, the protrusion on the bottom-emptying device actuates the bottom check valve and regulates the flow into the sample bottle The sample bottle will be obtained precleaned from the analytical laboratory, and it will be specific with respect to size and material to the type of analysis to be performed The bottle will be carefully filled to the very top, in order to create a positive meniscus, and sealed with a teflon-lined cap (septa) These precautions aid in eliminating air from the sample The sample will be visually inspected to ensure that no air bubbles remain within. Depending on the type of chemical analysis required, samples will be preserved with acid and/or they are cooled to 4 degrees Celsius Samples then will be labeled, stored, and transported in cooled ice chests to the analytical laboratory within the permissible holding time SAMPLE HANDLING Samples are handled during collection and shipment in such a way as to ensure maximum sample quality and integrity. All samples will be collected by experienced Brown and Caldwell field personnel. The samples will be collected in containers that are appropriate to the sample material and the required analyses All containers will have been precleaned by the analytical laboratory or the container manufacturer or decontaminated prior to use by washing in laboratory-grade detergent, rinsing with tap water, and then rinsing with deionized water All sampling equipment will be decontaminated prior to and between use by washing in laboratory-grade detergent, rinsing with tap water, and then rinsing with deionized water. Each sample container will have a label affixed in the field that identifies the date and time of sample collection, name of sampler, fob number, and a unique sample number. This information will be recorded on the boring log or in the field records. Samples are stored and shipped to the laboratory in a cooled chest Only analytical laboratories certified by the California Department of Health Services will be used. A chain-of-custody form will be used to record possession of samples from the time of collection to the time of arrival at the laboratory The sample-control officer at the laboratory will verify sample integrity and confirm that they were collected in the proper containers, preserved correctly, and that there is an adequate volume for analysis If these conditions are met, the samples will be assigned a unique log number for identification throughout analysis and reporting The log number will be recorded on the chain-of-custody form and in the log • book maintained at the analytical laboratory The sample description, date received, client's name, and other relevant information will also be recorded 264UREPORTS\2640-01 WP