C150259 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I Water Demands and Water Rie:hts There are 19,176.84 acres in the Bijou District with rights to divert up to 575 cfs from the South Platte River under an original river call of May 18, 1905. Bijou has a storage decree for 37,710 acre feet plus refill. The official name on the decree is the Bijou Irrigation District with their water being diverted down the Empire Reservoir Inlet Ditch. As mentioned before, Bijou has had an average annual diversion of 50,970 acre-feet for all water diverted into Empire Reservoir. Yearly diversions for Bijou would be considered fairly inconsistent. Variations in these numbers correspond to the amount of rainfall during the irrigation season and overall demand placed on the reservoir by its district members. More rainfall in a certain year meant that less water had to be diverted out of the reservoir in that year and therefore less water had to be diverted into the reservoir in the following year and vice-versa. Analvsis of Alternatives Three alternatives for the slope protection of the Empire Reservoir East Embankment were studied. These options included the following: soil cement, articulating concrete blocks, and traditional riprap. Of the three alternatives the traditional riprap was selected and is discussed in more detail in the following section. Below is a short description of the other two alternatives that were studied for this project. Soil Cement Soil cement is commonly used as a means of slope protection in areas lacking a nearby supply of good quality rock riprap. Due to the distance of Empire reservoir from rock quarries located in the foothills this option was examined as an alternative for slope protection. Soil tests were performed on soils located within the reservoir to determine if they were suitable for using as soil cement. All tests showed that borrow materials were sands or silty sands with no plasticity, which is ideal for using as soil cement. Based on the soils tests it was assumed that 250 Ib of cement would be needed per cubic yard to provide an adequate strength for the soil cement mixture. It was further assumed that the material would be placed in horizontal lifts 6 inches thick and 8 feet wide, which results in a thickness of 2.5 feet when measured perpendicular to the embankment. The soil cement would extend from the toe of the embankment to the top of the dam crest. Due to the relatively smooth nature of the constructed soil cement the amount of wave run-up would be higher than for riprap slope protection. It was calculated that the amount of wave run-up would still be less than the amount of freeboard, 7 feet, at Empire Reservoir. This option was compared to riprap and articulating blocks on a cost per square foot basis. Articulating Concrete Blocks Articulating concrete blocks have been increasing in popularity as a form of slope protection. This type of slope protection consists of precast concrete blocks which are placed atop a layer of gravel bounded above and below by a geosynthetic fabric. It was determined that a 70L block manufactured by ARMORTECQP would be sufficient to resist the wave action at Empire Reservoir. Similar to the soil Empire Reservoir East Embankment Dam, Water Division 1 DAMID 010728 Page 2