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3.7 Water Drain Valves <br />At each bulkhead, a 2" stainless steel ball valve was placed as the primary <br />shutoff mechanism, with an ancillary 1"ball valve to allow a pressure gauge <br />reading to be taken. <br />y;. <br />ti' <br />- `~ `~~. <br />f C~ _. A`r <br />&,~"': <~ <br />`:~~ ~ , <br />~r <br />• Figure 11: Typical drain valve assembly <br />3.8 Decant risers <br />Each of the bulkhead drain pipes included dual vertical decant risers on the inby <br />(wet) side, to prevent clogging of the drain pipe in the event that it becomes <br />desirable to drain water from behind the bulkhead in the future. <br />These inlets were constructed of 4-inch Schedule 40 PVC pipe, connected to the <br />2-inch diameter stainless steel pipe via ells and reducers, and secured to the <br />bulkhead form beams. The pipes were slotted with 1/8 inch kerf width slots, on <br />'/2 inch centers, to provide filtration of water passing into the drain line. <br />3.9 Completed adit bulkheads <br />Inspection of the bulkheads after the front forms were stripped showed a good <br />homogenous pour, with no areas of aggregate separation, voids or other defects. <br />. The concrete was in very tight contact with the rock on all sides. <br />14 <br />