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APPENDIX C <br /> Once the hollow stem augers have been advanced to the desired depth for monitoring well installation, the <br /> depth to the bottom of the hole will be measured inside the augers to ensure that it is free of slough. The <br /> monitoring well casing will then be lowered into the hollow stem augers and the annular space between the <br /> borehole and screened portion of the well will be backfilled with sand pack as the augers are withdrawn. <br /> The sand pack (determined by sieve analysis of representative soil samples) will extend to approximately <br /> two feet above the top of the screened section. A two-foot-thick bentonite seal will be placed on top of the <br /> sand pack. The remaining annular space will be backfilled to the surface with a cement grout. The <br /> monitoring wells will be finished with a water-tight, steel, locking street box set into concrete. A removable <br /> PVC cap will be placed over the end of the well casing inside the street box cover. The monitoring wells <br /> will be developed with a surge block followed by bailing to remove the fines. Figure C-1 shows a typical <br /> monitoring well installation. <br /> 462891/42/PPU26 C-1 <br />