2012-08-31_REVISION - M1980244 - Laserfiche WebLink

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CC &V Reply: AMEC provides the following as confirmation of the 48 -inch diameter HDPE SDR11 riser pipe to support itself given the number ofperforations at the bottom. The proposed pumpback tube has following characteristics: • 48" Diameter HDPE SDR 17 • Pumpback tube is 27.5' feet tall. • DR 17 has a wall thickness of 2.284" • Pipe circumference is 143.6" • Proposed perforations are located in the bottom 7 feet of the pipe. • Diameter ofperforation is .5", and there are 24 holes per row, spaced 3" apart. • The compressive strength of HDPE is 11,150 psi • Weight of 48" Diameter SD17 pipe is 1751b /ft Surface area through the pipe — through a perforation row is: 143.6" x 2.284" — (2 x.252 x & x 24 = 327.6 sq inches Allowable strength is: 327.6 sq inches * 11,150 psi = 3,652,740 pounds Weight of the pipe is: 27.5'x175 lb/ft = 4,812.5lbs Therefore: there is a safety factor of 759 against the 48 -inch diameter HDPE SDR11 riser pipe crushing under its own weight. A320 — Please confirm the 50 -foot wide material at a 1% slope in Detail J is GCL. CC &V Reply: CC& V provides Attachment 4, which includes labeling of the GCL on drawing A320 in Detail J that confirms 50 foot wide GCL material at a I% slope. A500 — a) Note 5: Inclusion of the tick mark (') after the 4 is confusing, in that it suggests a 4 -foot Precon Impact Baffle. Please either remove the single quotation marks or use double quotation marks in order to avoid confusion over the proposed size of the appurtenant structure. Also, note the proper spelling of baffle. b) The current proposed location of the emergency spillway subjects the 211:1V slope to overtopping flows and will lead to significant erosion of this slope. Please move the emergency spillway to the northeast corner of the proposed sediment pond and armor the outfall to at least the contact with native ground. This will lead to a somewhat flatter gradient (at the contact) as well as a more defined channel to convey overtopping flows under this temporary condition. DRMS Response: Finally, the Division notes we have not received a response to the Geotechnical Preliminary Adequacy Review, dated August 2, 2012. CC &V Reply: CC &V provides Attachment 4, which is a revised drawing A500 to reflect removal of the tick mark () in Note 5, and relocation of the emergency spillway to the northeast corner of the proposed sediment pond that will include armoring the outfall to at least the contact with native ground