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' ENVIRONMENTAL SCIENCE & ENGINEERING, INC_ CONCORD,CALIFORNIA OFFICE STANDARD OPERATING PROCEDURE NO.Z FOR MONITORING WELL INSTAL A TION AND DEVELOPMENT PAGE X Environmental Science & Enemeeri Inc- (ESE) typically installs ground-water momtoring wells is unconsolidated sediments drilled using a truck-mounted hollow-stem auger drill rig. The design and installation of all monitoring wells is performed and supervised by an experienced ESE geologist. FWire A-TVical FSE Monitoring Weil Construction Diagram(attached)graphically splays a typical FSE well completion. Prior to the construction of the well,the portion of the borahoia that penetrates a lower Confining layer(if any) is filled with bentonite pellets.The monitoring well is thea constructed by inserting polyviuykhlodde(PVC)pipe through the center of the hollow stem augers. The AX-(Wa-cadng)is fastened together byjoining the factory threaded ' pipe ends. ESE IW=illy uses two-inch or fourinch diameter pipe for ground-water monitoring wolfs. The diameter of the borehole is typically Vetches greater than that of the diameter of the va-casiag but is at least four-inches greater than that of the well casing. 11= lowcrnhost portion of the well-casing will be factory perforated QWwally having slot widths of OD10-inch or 0=04ach). Mic slotted portion of the well-casing will emend from the bottom of the boring up to approrimatdY fivrrfeet above the ooccurence of ground water. A PVC dip or threaded cap will be placed at the bottom end of the well-usin&and a locking expandable well cap will be placed over the top (or surface) cad of the w611-casing. A sand pack (typically No. 2/12 or No. 3 Monterey sand)will W placed in the borehole annulus,from the bottom of the wa-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 bentoake pellets will thea be hydrated with ' three to four-g~+llons of potable water, to protect the sand pack from intrusion during the placement of the sanitary seal. The sanitary seal(gr-out)will Consist of either neat oemea%a neat cement and beatonitc powder m<uture(eontaiaing no more than 5%bentonite),or a nkat cement and sand mixture,(containing no more than ' a 2:1 sand to Cement ratio). If, the grout seal 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,thea the grout mixture;will W b vn&d into the boring from the top of the bentonite seal using either a hose„pipe or the hollow6stera augers,which serve as a tremic. . The well will be protected at the surface by a water tight utnTity boxes The utility box WZ be set into the grout I mixture so that it is lass than 0.1-foot above grade,to p=VCnt the collodion:of su&(r-water at the weft head. If the well is set within the public right of way,then the utility boot will be Department of Transportation(DOT) traffic rated, and the top of the boat WM 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 place with a grout mbcture and will emend one to taro-feet above ground surface. All wrli eomrpWoa details will be recorded by the ESE geologist on the geologic boring logy. tSubsequent 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 devdopmtent will be performed using merging,balling and ov+erpump ng techniques. Surging is performed by raising and kwwing a surge block through the water ' column within the slotted int mal 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 duo to displacement and vacuum caused by the movement of the surge blocs Bailing is performed by lowering a bailer to the bottom of the well and ' gently bouncing the bailer off of tine well cad cap,thea removing the fall bailer and repeating the procedure. This will bring any material(soft.or PVC fragments)that may have accumulated in the well into suspension for removal. Overpum&g 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 casings Effective well development will settle the sand pack 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 tho 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 forcip objects(PVC fragments) from the well casing. no FSE geologist or