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ENVIRONMENTAL SCIENCE & ENGINEERING, INC. CONCORD, CALIFORNIA OFFICE STANDARD OPERATING PROCEDURE NO.2 FOR MONITORING WELL INSTALLATION AND DEVELOPMENT PAGE 1 Environmental Science & Engineering, Inc. (FSE) typically installs ground-water monitoring wells in unconsolidated sediments drilled using a truckmounted hollow-stem.auger drill rig. The design and installation of all monitoring wells is performed and supervised by an experienced ESE geologist. Figure A-Typical ESE Monitoring Well Construction Diagram (attached)graphically displays a typical ESE well completion. Prior to the construction of the well,the portion of the borehole that penetrates a lower confining layer (if any) is filled with bentonite pellets. The monitoring well is then constructed by inserting polyvinylchloride(PVC)pipe through the center of the hollow stem augers. The pipe(well-casing)is fastened together by joining the factory threaded pipe ends. ESE typically uses two-inch or four-inch diameter pipe for ground-water monitoring wells. The diameter of the borehole is typically 5-inches greater than that of the diameter of the well-casing,but is at least four-inches greater than that of the well casing. The lowermost portion of the well-casing will be factory perforated(typically having slot widths of 0 010-inch or 0.020-inch). The slotted portion of the well-casing will ' extend from the bottom of the boring up to approximately five-feet above the occurrence of ground water. A PVC slip or threaded cap will be placed at the bottom end of the well-casing,and a locking expandable well cap will be placed over the top (or surface) end of the well-casing. A sand pack (typically No. 2/12 or No. 3 ' Monterey sand)will be placed in the borehole annulus,from the bottom of the well-casing up to one to two-feet above the top of the slotted portion,by pouring the clean sand through the hollow stem augers. One to two-feet of bentonite pellets will be placed on top of the sand pack. The bentonite pellets will then be hydrated with three to four-gallons of potable water, to protect the sand pack from intrusion during the placement of the sanitary seal. The sanitary seal(grout)will consist of either neat cement, a neat cement and bentonite powder mixture(containing no more than 5%bentonite),or a neat cement and sand mixture(containing no more than a 2;1 sand to cement ratio). if, the grout seat is to be greater than 30-feet in depth or if standing water is present in the boring on top of the bentonite pellet seal,then the grout mixture will be tremied into the boring from the top of the bentonite seal using either a hose,pipe or the hollow-stem augers,which serve as a tremie. • The well will be protected at the surface by a water tight utility box. The utility box will be set into the grout mixture so that it is less than 0.1-foot above grade,to prevent the collection of surface water at the well head. If the well is set within the public right of way,then the utility box will be Department of Transportation(DOT) traffic rated, and the top of the box will be set flush to grade. If the well is constructed in a vacant field a brightly painted metal standpipe may be used to protect the well from traffic. If a standpipe is used,it will be ' held in plate with a grout mixture and will extend one to two-feet above ground surface. All well completion details will be recorded by the ESE geologist on the geologic boring logs. ' Subsequent to the solidification of the sanitary seal of the well (a minimum of 72 hours), the new well will be developed by an ESE geologist or field technician. Well development will be performed using surging,bail and overpumping techniques. Surging is performed by raising and lowering a surge block through the water column within the slotted interval of the well casing. The surge block utilized has a diameter just smaller than ' that of the well casing,thus, forcing water flow through the sand pack due to displacement and vacuum caused by the movement of the surge block. Bailing is performed by lowering a bailer to the bottom of the well and gently bouncing the bailer off of the well end cap, then removing the full bailer and repeating the procedure. ' This will bring any material(soil or PVC fragments) that may have accumulated in the well into suspension for removal. Overpumping is performed by lowering a submersible pump to the bottom of each well and pumping at the highest sustainable rate without completely evacuating the well casing. Effective well development will settle the sand park surrounding the well-casing,which will improve the filtering properties of the sand pack and allow water to flow more easily through the sand pack;improve the communication between the aquifer and the well by aiding the removal of any smearing of fine sediments along the borehole penetrating the aquifer, and, remove fine sediments and any foreign objects (PVC fragments) from the well casing. The ESE geologist or