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<br />SANTA MARIA DAM - 1 - July 11, 2013 <br />INUNDATION MAPPING REPORT <br />1.0 INTRODUCTION <br /> <br />Deere & Ault Consultants, Inc. (D&A) has prepared this Inundation Mapping Report at the request <br />of the Santa Maria Reservoir Company. This report documents the procedure of modeling a clear- <br />day breach of the dam at Santa Maria Reservoir and the development of the resulting inundation <br />maps downstream of the dam. The inundation maps will be used to update the existing Emergency <br />Action Plan (EAP) and to assist those involved with emergency preparedness planning and <br />response. The hydraulic models and inundation maps contained in this report were prepared using <br />the NAVD 88 vertical datum. The report and all associated models have been prepared in <br />accordance with the regulations and guidelines set forth by the Colorado Department of Natural <br />Resources, Division of Water Resources, Office of the State Engineer (SEO). <br /> <br />1.1 Location and Background <br /> <br />Santa Maria Dam is located in Mineral County approximately 10 miles southwest of the town of <br />Creede, Colorado in Section 16 of Township 41 North, Range 2 West of the New Mexico P.M. <br />Santa Maria Dam is an earthen compacted embankment that was constructed in 1911. It has a <br />height of approximately 90 feet at the dam centerline and a storage capacity of 43,823 acre-feet with <br />the water surface at the emergency spillway crest. <br /> <br /> <br />2.0 DAM BREACH ANALYSIS <br /> <br />2.1 Breach Parameter Estimation <br /> <br />The dam dimensions, emergency spillway crest elevation, and other relevant data were taken from <br />the following sources which are provided in Appendix A: <br /> <br /> 1911 construction plans for the Santa Maria Lake Project. Sheets used: Contour Map and <br />Plan of Dam, Typical Sections. <br /> 1990 “as-built” plan set: Santa Maria Dam Rehabilitation, by Hydro-Triad. Sheets used: 2 of <br />5, 3 of 5. <br /> Capacity table for Santa Maria Reservoir. <br /> <br />The average upstream and downstream embankment slopes were found on Sheet 3 of 5 of the 1990 <br />rehabilitation plans for Santa Maria Dam. The upstream and downstream slopes listed were 3:1 and <br />2:1 H:V, respectively. A dam crest width of 16 feet was taken from the Typical Sections sheet in <br />the 1911 plan set. <br /> <br />Both the 1911 and the 1990 plan sets use the same unknown vertical datum, but the capacity table <br />lists gage height. Unfortunately, there was not enough data available to directly convert between <br />the two datums. During a phone conversation between D&A and Colorado Dam Safety Engineer <br />Matt Gavin it was decided that gage height 93 was a reasonable estimate for the spillway crest <br />elevation because the capacity listed for gage height 93 on the Santa Maria capacity table was very