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<br />on map 8-1, conveys drainage under the main road to the confluence with outflow from <br />half-culvert O in the west collection ditch. The north end of the west collection ditch <br />AA-.4A depicted on mao 8-5 doesn't appear to be of the same ditch. TR 91-14 in <br />Volume 8 describes channel AA as being trapezoidal, with a top width of 8.42 feet, a <br />bottom width of 6 feet, a depth of .4 feet, side slopes of 3h:1v, and D50 riprap of 8" <br />diameter. Capacity is 34.69 cfs. Two 36-inch diameter CMP culverts, labeled N1 on <br />map 9-1, convey drainage from the west collection ditch under a refuse pile access <br />road. Volume 8 indicates that the minimum diameter needed for these culverts to pass <br />runoff from a 100-year, 24-hour event is 24". The west collection ditch just west of the <br />last culvert leading to the pond is shown with cross section JJ-JJ on map 8-1. Though <br />not illustrated, this cross section is described in volume 8 as trapezoidal with a top <br />width of 9.16', bottom width, 6', depth, .53 feet, side slopes of 3h:1 v, and D50 riprap 8" <br />in diameter. Capacity at this location is 37.66 cfs. CMP culvert O under the WRWDA <br />pond access road is a single 48-inch culvert, considerably larger than the 30" culvert <br />shown in volume 8 as needed to handle runoff from a 100-year, 24-hour event. The <br />WRWDA pond held water but was not discharging. <br />On the WRWDA's east side, drainage controls either convey runoff to the east <br />collection ditch into the WRWDA pond or into a natural drainage along the east side of <br />the pile and eventually into pond 3. Runoff from a small area about .45 acres in size at <br />the northeast end of the WRWDA would flow to the main drainage between the east <br />and west ridges into pond 3. Drainage from the pile south of this area flows to the east <br />collection ditch. Cross section MM-MM on map 8-1 for the north end of the east <br />collection ditch isn't illustrated, but volume 8 describes it as trapezoidal with a top width <br />of 3.36', bottom width, 2', depth of .23 feet, D50 riprap 8" in diameter, and side slopes <br />of 3h:1 v. Capacity is 3.49 cfs. In the area just north of its discharge into the WRWDA <br />pond, the east collection ditch is labeled on map 8-1 with cross section II-II. Though <br />not illustrated, this cross section is described in volume 8 as trapezoidal. It has a top <br />width of 4.05', a bottom width of 2', a depth of .34', side slopes of 3h:1 v; and D50 riprap <br />of 8" in diameter. Capacity is 3.49 cfs. The east underdrain conveys drainage into the <br />natural channel and to pond 3. The drain is to be at least 3' high, consisting of granular <br />material containing no more than 10 percent rock less than 1" in size and no rock larger <br />than 9", and extend at least 5' beyond the toe of the pile. Grade of the drain is <br />designed to be 5%, and the drain is to be wrapped in filter fabric. A toe bench least. <br />10' long and 45' wide was designed to be constructed at the toe of the waste pile in the <br />location of the east underdrain. The east underdrain and toe bench are shown on <br />Field measurements were taken to spot-check WRWDA's construction and were <br />approximate. Measurements taken were as follows: <br />A. Ditch on crushing and screening fill @ pt. near cross section EE-EE: <br />7 <br />f <br />