Laserfiche WebLink
SOP No. 5.0 Monitoring Well Install <br />For boreholes that may need to be backfilled to a certain depth before well installation, clean <br />sand with a 3-foot bentonite seal will be added to fill the borehole to the depth desired for well <br />installation. Wax coated pellets may be used if the saturated water column in the borehole is <br />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 will calculate and record the volume of the filter pack, bentonite seal, and <br />grout required to fill the annular space based on the borehole size and casing size. The volume is <br />calculated by subtracting the volume of the casing (based on the outer diameter) from the volume <br />of the borehole using the equation: <br />V=n (rbZ-r,2)h <br />where: <br />V =volume (in feet 3) <br />rb = radius of borehole (in feet) <br />rc = 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 />n=p' (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 each grout lift. <br />Following well completion, the horizontal location of the monitoring well will be surveyed in <br />accordance with SOP 34.0, Surveying (GPS). The elevation of the ground surface and top of the <br />PVC casing (i.e., water level measuring point) will also be determined. A notch will be cut on <br />the north side of the PVC casing that will be used as a measuring point for water levels. <br />5.2.1.1 Casing and Screen Requirements <br />The casing requirements will be as follows (EPA 1990): <br />7/28/08 Page 4 of 10 R Squared Inc.