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Technical Memorandum <br /> Phase 2 Sediment Pond Jurisdictional Dam Evaluation ■ <br /> NewFields Job No.475.0106.006 <br /> August 8,2016 <br /> Rule 4.2.5 "Dam" means a man-made barrier, together with appurtenant structures, <br /> constructed above the natural surface of the ground for the purpose of impounding water. <br /> Flood control and storm runoff detention dams are included. <br /> Rule 4.2.5.1 "Jurisdictional Size Dam" is a dam creating a reservoir with a capacity of more than <br /> 100 acre-feet, or creates a reservoir with a surface area in excess of 20 acres at the high-water <br /> line, or exceeds 10 feet in height measured vertically from the elevation of the lowest point of <br /> the natural surface of the ground where that point occurs along the longitudinal centerline of <br /> the dam up to the crest of the emergency spillway of the dam. For reservoirs created by <br /> excavation, or where the invert of the outlet conduit is placed below the surface of the natural <br /> ground at its lowest point beneath the dam, the jurisdictional height shall be measured from <br /> the invert of the outlet at the longitudinal centerline of the embankment or from the bottom of <br /> the excavation at the longitudinal centerline of the dam, whichever is greatest. Jurisdictional <br /> height is defined in Rule 4.2.19. The State Engineer shall have final authority over <br /> determination of the jurisdictional height of the dam. <br /> Rule 4.2.5.2 "Non-jurisdictional Size Dam" is a dam creating a reservoir with a capacity of 100 <br /> acre-feet or less and a surface are of 20 acres or less and with a height measured as defined in <br /> Rules 4.2.5.1 and 4.2.19 of 10 feet or less. Non-jurisdictional size dam are regulated and <br /> subject to the authority of the State Engineer consistent with sections 37-87-102 and 37-87-105 <br /> C.R.S. <br /> Rule 4.2.19 "Jurisdictional Height" means the vertical dimension measured from the elevation <br /> of the lowest point of the natural surface of the ground, or from the invert of the outlet pipe if <br /> excavated below the natural surface of the ground, whichever is lower, where the low point if <br /> occurs along the longitudinal centerline of the dam, up to the spillway crest of the emergency <br /> spillway. For existing dam, the jurisdictional height shall be measured by using the slope of <br /> downstream channel and the height if the dam at the downstream toe by extrapolating the <br /> measured height to the longitudinal centerline of the dam. The formula for determining the <br /> vertical height of the existing dam is h=hd-fb-(s*I); where h =jurisdictional height, hd = height of <br /> the dam from downstream toe, fb = freeboard, s = slope of the natural surface of the ground <br /> downstream of the dam, I = measured or computed horizontal distance between the <br /> downstream toe of the longitudinal centerline of the dam. The State Engineer shall have the <br /> final authority over determination of the height of the dam. (see Figure 2) <br /> Page 3 <br />