1400000062 Droz Creek Inundation Report

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DROZ CREEK DAM Emergency Action Plan, DAMID: 110234 Revised: January 10, 2014 Page 3 of 14 ESSENTIAL DAM INFORMATION Purpose The purpose of this EAP is to reduce the potential for loss of life and injury and to minimize property damage during an unusual or emergency event at DROZ CREEK Dam. Directions to the Dam Also see Location and Vicinity Maps. From Poncha Springs: Head south on US-285/Main Street for approximately 4.9 miles. Turn west onto CR-200/Marshall Pass Road for approximately 0.6 miles. Turn slight west onto unnamed street for approximately 0.4 miles. From Saguache: Head east on Gunnison Avenue/US-285 for approximately 35 miles. Turn west onto CR-200/Marshall Pass Road for approximately 0.6 miles. Turn slight west onto unnamed street for approximately 0.4 miles. Potentially Impacted Areas Also see Inundation Mapping and Summary of People/Structures at Greatest Risk In the event of a sunny day dam failure at Droz Creek Dam, it is anticipated that the four ponds immediately downstream of the dam, Smith Ponds Nos. 1, 2, 3, and 4 will be overtopped. Following the channel downstream, the flood water is expected to cross CR-200/Marshall Pass Road approximately 530 feet downstream from Smith Pond No. 4, and impact the residential structure located at 1055 County Road 200. The substation 800 feet downstream is also anticipated to be inundated. Following along the Poncha Creek, the flood water is projected to overtop the junction of CR-200/Marshall Pass Road and US-285, located approximately 0.75 miles downstream of the dam. Flood water will progress along Poncha Creek, and is expected to inundate two structures at approximately 1 mile downstream prior to flooding US-285 again approximately halfway between mile markers 121 and 122. At approximately 2.5 miles downstream, another residential structure will fall in the projected flood inundation area and another residential structure approximately 4.6 miles downstream is expected to also be impacted by floodwaters. From approximately 5.25 miles downstream to approximately 6.25 miles downstream, another 22 structures fall into the anticipated flood inundation zone. Beyond 6.25 miles downstream, the floodwaters are expected to no longer pose a significant threat to human life. A 1,500 foot stretch of US Highway 285 is anticipated to be inundated in the event of a breach starting approximately 0.5 miles north of Marshall Pass Road. The floodwave is expected to reach this location within approximately 45 minutes of breach initiation. Flows will reach a maximum depth of 2.5-ft and a maximum velocity of 6 ft/s.