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<br />foot high embankment. The limited capacity of the two culverts will <br />restrict any major storm runoff and create 200 acre-feet of temporary <br />detention ponding behind the embankment. An excavation on either side <br />of the railroad embankment creates additional ponding capacity before <br />any flow is dischqrged through the two pipe culverts. Rating of the ponding <br />I <br /> <br />volume below the inverts of the pipes has shown that essentially no storm <br />water will emit from sub-basin A3 with 100 year recurrence interval preci- <br />pitation. <br /> <br />The second main drainageway crossing is located approximately 1000 <br />feet west of Hyde (on the swale from sub-basin AB). The drainage flows <br />are car~ied through the embankment (approximately 12 feet high) in 4 unit <br />box culverts each with approximately 600 square feet of opening. No <br />significant routing effect will occur on the flood hydrograph discharge <br /> <br />throu~h ~his box culvert. <br />The other two drainageway crossings by the railroad embankment are <br />just west of the Town of Yuma in Section 20, T2N, R4BW. The upstream <br />or westernmost of these embankments is approximately fifteen feet high, <br />but the water would only pond to a depth of approximately 10 feet over <br /> <br />the invert of the two culvert pipes. The two cast iron culvert pipes <br /> <br />are 24 inch diameter and 30 inch diameter and are set at the natural ground <br /> <br />surface level. An excavation has created an additional ponding depth of <br /> <br />nearly four feet below the pipe inverts. The storage behind this embankment <br />before overflow is 400 acre-feet, and the overflow is to the east along the <br />railroad track. <br /> <br />-5- <br /> <br />~. ~ <br />