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Manteca Unified School District Subsurface Soil &Groundwater Invgation backfilled with Bentonite and cement. Borings into the saturated zone will be drilled to a maximum of 20 feet beneath the top of the aquifer being explored. Any perching layers encountered will be investigated to a maximum thickness of 5 feet and will be backfilled with cement slurry, after a Bentonite seal has been placed. If a deeper aquifer is to be investigated, conductor casing will first be grouted into place to seal off the upper aquifer(s), in series, if necessary, and drilling will proceed through the conductor casing after the grout has been allowed to set properly. If evidence of contamination is noted during the drilling, the drilling will be halted until the responsible professional determines the advisability of deeper drilling. Upon termination, the borings into the saturated zone will be completed as monitoring wells and backfilled with concrete grout, after a Bentonite seal has been placed. The borings for the monitoring wells will be of a diameter at least 4 inches greater than the 2-inch diameter of the well casing to be used. The cuttings from the drilling operation will be containerized on-site during drilling for proper disposition. The proper method of disposal will be dependent upon results of laboratory analysis. This disposal will be the responsibility of the client unless other arrangements are made. 2.2 Well Construction All materials used in well construction will be thoroughly cleaned prior to introduction into the boring. 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 (PVC) with end cap and factory perforations for placement in the saturated zone (taking into 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 2- to 3-feet thick will be placed in the annular space above the filter pack followed by a cement grout to the surface. Seal and filter pack elevations may change based on the underlying geology. 2.3 Well Development and Sampling The well will be developed until the well water appears clear of sediment, or until an appropriate number of well volumes (based upon the judgment of the responsible professional) have been evacuated. The water produced during well development will be contained and disposed of by the driller. The wells will be allowed to stabilize for twenty-four (24) hours prior to sampling. All soil and groundwater samples will be properly labeled with date collected, project number, sample coordinator, and sample identification. Field records will 4