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SOP No. 5.0 Monitoring Well Installation <br />Bentonite pellets, chips or suitable alternative materials may be used if the saturated water <br />column in the borehole is greater than 50 feet. <br />The annular space between the well string and the borehole wall will be filled with a filter pack <br />(adjacent to the well screen), a bentonite seal, and casing grout. As the annular space is being <br />filled, the well string will be centered and suspended such that it does not rest on the bottom of <br />the hole. At least two stainless steel centralizers will be used if the well is deeper than 50 feet — <br />one at the bottom of the well screen and one at the top of the well screen. For deep bedrock <br />wells, additional centralizers will be attached to the riser casing at 100 foot intervals and one near <br />the top of the well string. <br />The field geologist and or the driller will calculate and record the volume of the filter pack, <br />bentonite seal, and grout required to fill the annular space based on the borehole size and casing <br />size. The volume is calculated by subtracting the volume of the casing (based on the outer <br />diameter) from the volume of the borehole using the equation: <br />V = A(rb 2 - ] 4 c 2 A <br />where: <br />V = volume (in feet <br />rb = radius of borehole (in feet) <br />= radius of casing (in feet) <br />h = height (in feet) between the top and bottom of the material (filter pack, <br />bentonite, or grout). <br />7C = 1) (3.14) <br />Measurements made during filling of the annular space will be performed to the nearest 0.1 foot <br />below ground surface (bgs) and will consist of the following: <br />• Total depth of borehole at the completion of drilling <br />• Total depth of the open borehole before the start of well construction <br />• Lengths of the end cap, screen sections, riser blank sections, and stickup of well above <br />ground surface <br />• The depth to the top of the filter pack, top of the bentonite seal, and the top of the grout. <br />Following well completion, the horizontal location of the monitoring well will be surveyed in <br />accordance with SOP No. 35.0, Surveying (Land and GPS). The elevation of the ground surface <br />and top of the PVC casing (i.e., water level measuring point) will also be determined. A notch <br />will be cut on the north side of the PVC casing that will be used as a measuring point for water <br />levels. <br />7/28/08 <br />5 -4 R Incorporated <br />