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<br />i <br />"I <br /> <br />'J <br /> <br />" <br /> <br />V. PLAN OF DEVELOPMENT (preliminary) <br /> <br />A. Physical <br /> <br />The Hyannis Peak Dam is proposed to be an 80-foot <br />high earth or rockfill embankment which will impound a- <br />bout 2000 acre-feet of water in a narrow valley (see <br />Sheet 3). The dam as presently envisioned will utilize <br />a natural spillway adjacent to the east abutment. This <br />will reduce construction costs significantly in addition <br />to ensuring the integrity of the dam. Access will most <br />likely be gained via a 12 ft. to 16 ft. roadway, approx- <br />imately 7000 feet in length, paralleling the present <br />Hyannis Peak pack trail. The reservoir will inundate <br />an area of 65 acres of National Forest land to provide <br />valuable irrigation water for hay and pasture production <br />and the potential for an outstanding recreation site. <br /> <br />B. Geologic Investigations <br /> <br />See Appendix Q report, entitled "Preliminary Geologic <br />Investigation of the Hyannis Peak Reservoir Site, Jackson <br />County, Colorado", October, 1981, by Greg D. Sherman. <br /> <br />I <br />, , <br /> <br />" ~1 <br />, <br />, , <br /> <br />C. Design <br />1. Foundation <br /> <br />The existing overburden material beneath the embank~ <br />ment will be excavated to bedrock and any significant <br />joints in the bedrock will be treated to prevent the <br />loss of embankment materials. A grout curtain will <br />be provided in the foundation to reduce seepage <br />through the abutment rock. The grout curtain was <br />assumed to consist of a concrete grout cap and thirtv- <br />five 50~foot deep grout holes drilled every 10 feet . <br />along the aam centerline (more geologic information needed). <br /> <br />Embankment <br /> <br />2. <br /> <br />':., <br /> <br />The most economical design is a rockfill dam with an <br />impervious core. The impervious core will be made <br />up of the sandy clay and clayey sand materials avail- <br />able in the reservoir area. A filter zone is requir- <br />ed between the fine grained soils in the impervious <br />core and the coarse grained material in the external <br />rockfill zone to prevent the fine grained soils from <br />sifting into the spaces of the coarser material. , <br />This filter material is a very well graded material <br />with the attributes of both the fine and coarse zones. <br />Concrete sand has been shown to be the most reliable <br />filter material regardless of the gradation of the <br />fine material it is place in contact with. If ade- <br />quate filter material is not available at the site, <br /> <br />'"-:; <br />;: ,~ <br /> <br />,.;'1 <br /> <br />,,':i <br /> <br />-23- <br />