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Fuller Mobile Home Park 36S Fast Louuse Avenue, Lathrop, California September 6, 1994 Phase HAdditional Site Characterization Page. S 3.2 Well Construction All materials used in Well construction will be thoroughly cleaned prior to introduction into the bo�rng. A Bentonite or cement and Bentonite grout will be placed at the bottom of the boring as necessary. After the seal has been allowed to set long_enough to support the weight of the casing, a 2- inch diameter well casing (stainless steel or PVC)with end cap and factory perforations for placement in the saturated zone (taking irtc account seasonal variation) will be placed in the boring. The screen and filter pack sizes will be as noted in the well construction drawing. The casing and end caps will be threaded or joined by stainless steel screws; no PVC cement will be used. The filter pack will extend two feet above the .. perforated zone. A Bentonite seal two to three feet thick will be placed in the annular space above the�'filter pack follov�ed by a cement grout io the surface. Seal and. filter pack elevations may change based on the underlying geology (Figure 4). 3.3 Well Development and Sampling The well will be developed until the well water appears clear of sediment, or until an appropriate numberi� of well volumes (based upon the judgment of the responsible professional) have been evacuated. The water produced during well development will be containerized and left on-site in 55-gallon drums, or other suitable containers for disposal as hazardous waste if deemed necessary upon receipt of laboratory results. Disposal will be the responsibility of the client unless l' other arrangements have�.been made. The wells will be allowed to stabilize for twenty-four (24) hours prior to sampling. � All soil and ground water samples will be properly labeled with date collected, project number, sample coordinator, and sample identification. Field records will document the above information and other significant data, such asInames of on- site personnel, sampling:�inethods, date and time of sampling, the number of well volumes removed before`Sampling, preservatives added (if any), and any filtration performed on samples. The samples will be re i frigerated immediately for delivery to the laboratory and will under no circumstancesbe opened by anyone other than laboratory .personnel. Chain of Custody records�will be maintained at all times (Figure 5). , 3.4 Soil Sampling' All soil sampling equipment will be thoroughly steam-cleaned before and between sampling to prevent cress contamination. Relatively undisturbed soil samples will be taken at intervals of hot more than 5 feet in-order to. evaluate the subsurface materials, however, tl is llsampling interval may be waived in saturated sands in which sample recovery islnot possible_ � I .