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S . Where borings are completed as groundwater monitoring wells, 2-inch ID schedule 40 PVC blank pipe will be used. Usual well screen selection will be 2 inch ID Schedule 40 PVC pipe with 0.020 inch machine slot. Sections.will be threaded and screwed together; glues will not be used. Screens will extend 3-5 feet above first encountered groundwater. The annulus of the perforated section will be packed with clean #3 or#4 Monterey Sand, Lonestar 2/12 Sand or equivalent, to a point about 2-feet above the screen interval. Final well design will be adjusted in the field to site specific subsurface conditions, and will be placed so as not to interconnect two possible aquifers. Screens will extend a nominal length above first encountered groundwater for floating product detection. A 1-2 foot thick bentonite seal will be placed on top of the sandpack. A cement annular seal which extends to the surface will be placed by tremie line from the bottom to top of the remaining annular space above the bentonite. I4 6 . The top of the well casing will be locked to prevent contamination and tampering. Above- grade or at-grade well completion will; depend upon the final well location. Above-grade ' completion will require a 6 inch diameter locking, steel protective casing and a Christy, or equivalent, traffic box and concrete pad. Monitoring Well Development I . Wells will be developed until the water is free of fine-grained sediments and/or until field measurements of pH, and electrical conductivity have stabilized. Approximately 3 to 10 well volumes of water will be removed during development of the well. Duration of development will be specific for each well and site aquifer conditions and continue until the water clears and sand content is minimal or ceases. Notes of development will be kept. 2 . Equipment inserted into the well during development will be decontaminated by washing or steam cleaning prior to and after its use. Development water will be collected in drums. Monitoring Well Sampling I . Depth to groundwater will be measured to the nearest 0.01 foot, and the well checked for presence of separate phase product. If present, the apparent thickness of the product will be measured. The well will not be sampled if separate phase product is present. 2. The standing well volume calculated, and usually between 3 to 10 well volumes will be purged from the well prior to sampling, depending on well performance according the USEPA sampling guidance document, since purge volumes are aquifer specific for each well. Measurements of conductivity, temperature and the pH of the water will be taken until parameters have stabilized to indicate that aquifer water is entering the well. the sampler will keep field notes for each well sampled. 3 . The groundwater samples will be collected using a Teflon Bailer. A field log will record sampling measurements and observations. parameters er A uifwhich will be Aquifer p measured are; pH, temperature and electrical conductivity. Aquifer.water is assumed to be entering the well when these parameters are measured within a 10% range. The sample will be collected when the well recovers to within 80% of the original depth to water measurement. 4 . The bailer will be thoroughly steam-cleaned or cleaned with soapy (TSP) water, rinsed with tap water, and finally rinsed with.deionized or distilled water prior to the collection of each sample. A separate clean bailer will be used to sample each individual well. Wright Environmental Services, Inc. rev. 6/2/94 Geoscience Protocols Page 3