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<br />5. Gently wmpact backfill with excavation machinery (i.e., backhce bucket) as <br />directed by the RESIDENT PROJECT REPRESENTATIVE in order to seat <br />rocks. <br />6. Where there is a water discharge from the adit to be backfilled, a 6-inch diameter <br />' drain pipe shall be placed at the bottom of the fill. The drain pipe shall be <br />covered with at least 6 inches of compacted fill prior to backfilling the adit. The <br />ends of the pipe must extend at least 5 feet beyond the edges of the fill. <br />C. Marking <br />1. Anew, 6-foot long, 3-inch I.D. (inside diameter), galvanized steel pipe shall be <br />installed in front of each backfilled feature. The lower 2 feet of pipe shall be set <br />' in concrete a minimum of 1-foot diameter and the upper 1-foot minimum, 2-foot <br />maximum, of the pipe shall extend above grade. Alternatively, a minimum 1-foot <br />diameter, 3/8-inch thick galvanized steel plate may be welded perpendicular to <br />1 the bottom end of the pipe in lieu of the concrete anchor. A brass cap shall be <br />grouted into the upper end of the pipe by the Subcontractor using anon-shrink <br />grout or adhesive, such a Moly Parabond, Pour Rock, or Kwik Crete. The <br />' Subcontractor may alternatively drill and grout a brass cap in undisturbed, <br />competent rock immediately adjacent to each backfilled feature. The brass caps <br />will be supplied by the RESIDENT PROJECT REPRESENTATIVE. <br />3.4 ROCK BULKHEAD SEAL CLOSURE <br />' A. Description <br />1. This work includes construction of a rock bulkhead seal in an adit or inclined <br />shaft as designated in these Specifications or as directed by the RESIDENT <br />PROJECT REPRESENTATIVE. <br />' B. Clearing and Grubbing <br />1. The foundation for the rock bulkhead seal must be to bedrock. The foundation <br />must be cleared of all unwnsolidated materials prior to construction of the seal. <br />If unwnsolidated material is in excess of 36 inches below the original excavated <br />level of the adit, the rock bulkhead seal must be constructed from 36 inches <br />' below the original excavated level to the adit roof. <br />C. Installation <br />t 1. The bulkh must be constructed of grouted durable native rock, a <br />mini f 30 inch in thickness. There shall be no spaces between the rock <br />b d th adit walls. Dry-stacking of rock is not permitted. <br />' 2. Cor~ shall be r rtioned and mixed to produce a minimum compressive <br />s ofd ~&P i t 28 days. <br />~`~ Cr9 <br />