Reservoir Outlet and Toe Drain Remediation
Henrylyn Irrigation District, Weld County, Colorado
Engineering Analytics staff was tasked with inspecting the outlet works and toe drain system at Horse Creek Reservoir in Weld County, Colorado. The investigation revealed that the outlet pipes and gates were in need of repair and a flume was needed in the channel to measure flows leaving the reservoir. EA staff provided geotechnical investigations, conducted hydrologic and hydraulic analyses, and provided bid, construction drawings, specifications, and contract documents for the project. In addition, EA staff also bid the project for the owner and provided resident project inspections, QC testing, and contract administration during construction.
Flood Channel Erosion Protection Design
Nebraska Public Power District, Holt County, Nebraska
Engineering Analytics staff designed improvements at a 2.4 MW power plant located on the Niobrara River in northern Nebraska. The plant, which has operated continuously since the 1930s, required improvements to the downstream channel and the power house spillway to maintain its operational status. In addition to the design improvements, EA staff also inspected and evaluated the condition of the dam’s outlet structure.
Dam Breach Inundation Mapping
Various Clients, Western United States
Engineering Analytics staff has performed dam breach inundation mapping for earthen embankment dams with heights of over 150 feet and reservoirs impounding from 16 acre-ft to 26,000 acre-ft. Our staff has performed analyses with distances of over 40 miles through municipalities and along highways and bridges. Our ability to work with existing topographic surveys and mapping help control costs for our clients. EA staff works closely with emergency management professionals to ensure that modeling results can be incorporated into emergency planning to aid in preventing the potential loss of life.
Diversion Dam Rehabilitation
Union Ditch Company, Weld County Colorado
The Union Ditch Diversion Dam, constructed in the early 1900s, was no longer functional for checking the river and controlling diversions to the Union Ditch. The diversion dam is approximately ten feet in height and 200 feet in length and provides for diversion of up to 175 cfs. EA provided geotechnical investigations and design; conducted hydrologic and hydraulic analysis; and provided structural design for the replacement diversion dam. EA also provided construction drawings, specifications, and contract documents for the project and provided the contract administration and resident inspection and quality control testing during construction. The new diversion dam structure includes a 40 foot Obermeyer gate with automatic controls, and the diversion structure into the ditch contains two 10 foot Obermeyer gates that are also remotely controlled.
Reservoir Feasibility Study
Dawson Ranch Company, Colfax County, New Mexico
Engineering Analytics staff performed a feasibility study for selection of off-stream dam sites. Maps were prepared outlining the ranch property and detailing the locations of eight potential dam sites and their areas of inundation. A preliminary design for an additional off-stream dam located east of the Vermejo River was designed with a conveyance pipeline to provide water to the reservoir. Cost estimates were prepared for the construction of the off-stream dam by comparing an earthfill construction with a roller compacted concrete method.
St. Vrain Creek Flood Damage Restoration
Boulder County, Colorado
Significant flooding and damage occurred along a 4‑mile stretch of St. Vrain Creek between the Town of Lyons and the Town of Hygiene in Boulder County in September 2013. Very heavy rains in the mountains west of Lyons created a 500-year flood event with flows of greater than 12,000 cfs in the creek.
Engineering Analytics was retained by Boulder County Parks and Open Space to provide design for repair of one embankment dam, two augmentation reservoirs, and seven embankment breaches along the creek. The overall project goal was to provide a design that met the requirements of the NRCS Emergency Watershed Protection Program and FEMA funding constraints. The design was prepared to mitigate the impacts of the 2013 flooding along the creek and to reduce the impact of future flooding on life and property, while restoring reservoir capacity and riparian and wildlife habitat throughout the reach.
Preliminary and final designs were prepared for the reservoirs including repair of an existing slurry wall, the 30 foot tall embankment, and replacement low level outlet works. The embankment breach repairs were designed to resist flood flows and reduce underseepage and internal erosion during flood flows. Embankments were founded on the undisturbed native soils below sediment and disturbed materials.