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I I I I I I I I I I I I I I I I I I I maintenance than a riprapped shoreline. The entire dam would be constructed from on-site materials to eliminate the haul costs associated with select materials. The downstream toe ofthe dam would be constructed from the sand and gravel alluvium excavated for the key trench. A toe drain will likely be required to address seepage issues both through the dam as well as protecting neighboring properties. The embankment would use the clay overburden that overlays the entire property. The proposed reservoir design is based on not excavating into the ground more than 2 feet. The remaining clays in the reservoir bottom would be scarified and re-compacted to form an impermeable liner and keep the reservoir bottom relatively leak free. This property has an underlying sand and gravel valley fill alluvium that is part of the old South Platte River stream channel. This alluvium is highly permeable. If it is penetrated by reservoir construction, it will create a leaky bottom in the reservoir that will not effectively hold water. The shallow depth of construction will also eliminate groundwater pressure against the bottom of the reservoir that could compromise the integrity of a liner when the reservoir water level is drawn down. C. Project Goals The primary goal of the reservoir project is to divert and store water during times of available flow from the South Platte River. An off stream reservoir site would allow strategic releases to increase flows in the river during periods of low flow within the river call requirements. This re- regulation of flows in the South Platte River is intended to increase flows in the river to insure increased periods of compliance with the State water right administration and compact provisions. II. Project Parameters A. Site Hydrology The proposed size of the impoundment will make this structure a jurisdictional dam regulated by the State Engineer. The designation as a jurisdictional dam will require addressing such issues as dam hazard classification and probable maximum flood criteria. The location of the project is adjacent to the town of Ovid and will require additional information to determine hazard classification. The flood criteria for the South Platte River would likely show in a hazard classification evaluation that failure of this structure during a PMP event would have minimal impacts downstream. The reservoir site is off channel and therefore does not intercept any major drainage basin. The proposed design using a ring dike will prohibit any upstream drainage from entering the reservoir. The upstream drainage will be routed around the perimeter of the reservoir and returned to the South Platte River. This will greatly reduce the size requirements for the spillway, which will result in construction cost savings. B. Water Diversions/Delivery The Peterson Ditch is a left bank diversion from the South Platte River that passes to the north of the proposed reservoir site. The Peterson Ditch has the option of diverting flows directly from the river or being supplied from three high capacity wells owned by GASP, which are located near the diversion structure. The Peterson Ditch is owned and operated by the Julesburg Irrigation District. A new reservoir turnout structure will be constructed in the ditch to divert water from the ditch into the reservoir. This structure would have a capacity in the range of 20 to 40 cfs depending on final project configuration. It is anticipated that a carriage charge will be 6