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STANDARD OPERATING PROCEDURES Groundwater Monitoring Well or Extraction Well Installation and Development WELL INSTALLATION The bore holes for monitoring or extraction wells (wells) are drilled using a truck mounted hollow-stem auger drill rig The diameter of the borehole is a minimum four inches larger than the outside diameter of the well casing when installing the well screen (DWR Publication 74-81) The hollow-stem auger provides minimal interruption of drilling, and permits soil sampling at desired depths All wells are installed by state licensed drillers The wells are cased with threaded, factory slotted or blank Schedule 40 PVC plastic The perforated interval consists of slotted casing, generally 0 020 inch wide by 1 5 inch long slot size, with 42 slots per linear foot of pipe A threaded PVC cap is fastened to the bottom of the casing Centering devices may be fastened to the casing to assure even distribution of filter material and grout within the bore hole annulus The well casing is thoroughly washed and steam cleaned prior to installation After setting the casing i de the hollow stem, sand or gravel filter mates ial is poured into the ann r space to fill from the bottom of the boring to one foot above the slotted interval A 1 - 2 foot thick bentonite plug is placed above the filter material to prevent the grout from infiltrating down into the filter material Neat cement, containing about 5% bentonite, is then tiemied into the annular space from the top of the bentonite plug to the surface A lockable PVC cap is placed on each well head Traffic rated flush mounted steel covers are installed around well heads for wells in paved areas, while steel stove pipes are usually set over well heads in landscaped areas WELL DEVELOPMENT After installation, the wells are thoroughly developed to remove residual drilling materials from the well bore, and to improve well performance by removing any fine material in the filter pack that can pass from the native material into the well Well development is performed is performed in accordance with California Regional Water Quality Control Board (RWQCB) procedures described in the Leaking Underground Fuel Tank (LUFT) Field Manual, the Tri-Regional Board Staff Recommendations for Preliminary Evaluation and Investigation of Underground . Tank Sites, and local regulatory guidelines Parker Environmental Services 4185 Rialto Court Pittsburg CA 94565-6116 Phone (510) 439-1024 Fax (510) 439-2566