Dam Design, Rehabilitation, and Inspection

New Dam Design and Construction

New Cache La Poudre Irrigating Company, Weld County, Colorado

EA staff designed the Cornish Plains Reservoir to help The New Cache La Poudre Irrigating Company better control their down system water needs. The new zoned earth embankment dam is used as a storage and augmentation reservoir with a storage capacity of 3,500 acre-feet. EA staff completed the geotechnical investigation, material testing, design report, construction drawings, construction specifications, and construction permits as required by the Colorado State Engineer. EA staff also prepared all bid documents, coordinated the construction contract with the selected contractor, conducted the construction oversight, and certified that construction was completed to the construction specifications.

Existing Dam Rehabilitation

Henrylyn Irrigation District, Weld County, Colorado

EA managed the rehabilitation of Prospect Reservoir Dam. Prospect Reservoir Dam is a 45-foot-tall earthfill dam that impounds approximately 6,500 acre-feet of water. Upon investigation, EA determined that the dam face and outlet conduit were significantly deteriorated and required repair. EA staff conducted a feasibility study to determine the most cost efficient repair methods and provided all geotechnical investigations, hydrologic and hydraulic analysis, structural calculations, bid and construction drawings, specifications, and contract documents for the project. EA bid the project for the owner and provided all resident project inspection, QC testing, and contract administration during construction.

Demolition and Repair

Sanchez Ditch & Reservoir Company, Costilla County, Colorado

Located near the town of San Luis, Colorado, Sanchez Reservoir dam is a 135-foot-high earthfill dam which impounds 110,000 acre-feet of water. EA staff worked on this dam from 1992 through 2014. The outlet control gates in the gate tower were rehabilitated in 1997. Some gates were repaired, some replaced, and a new cone valve was installed at the bottom of the tower to regulate discharges. A new gate control system was also designed and implemented that allowed remote control of the system which can only be accessed by a gondola. The third phase began with a structural investigation of the outlet tunnel and tower. Our team concluded that to maintain the serviceability of the tower and outlet tunnel, modifications to the tower were needed and the tunnel would need to be reinforced with rebar and shotcrete. The repairs included removing the top 100 feet of the tower, installing a new gate control slab with hydraulically operated gates at the lower tower level, and lining the 8-foot x 10-foot outlet conduit with concrete and shotcrete.

New Dam Design and Construction

City of Greeley, Weld County, Colorado

EA designed a roller compacted concrete (RCC) dam for Peterson Reservoir to replace an existing earthfill dam constructed in the 1930s. original dam was removed and a 75 foot high RCC dam was constructed in approximately the same location as the earthfill dam. EA provided all geotechnical investigations, materials testing, RCC mix designs, and the structural design for the dam. EA also provided construction QC services and resident inspection during construction.

Brilliant Waterline Replacement

Colorado Division of Parks & Wildlife, Jefferson, Colorado

EA was the Engineer of Record for the design and construction services for rehabilitation and reconstruction of Davis Dams #2 and #3 at Staunton State Park. EA conducted all subsurface investigations and provided the geotechnical and structural design; the hydrologic and hydraulic design of the spillway and outlet works; and the construction inspection and quality assurance testing. The rehabilitation included the installation of an upstream seepage cutoff and clay face blanket; downstream seepage control with toe drains; new outlet works including new intake structure, control gate, conduit, and energy dissipater; and new spillways.


Outlet Improvements and Rehabilitation

Georgetown Lake, Georgetown Colorado

The Georgetown Lake Outlet Improvement project increased the outlet capacity of the Georgetown Lake dam. To solve the demand problems of the dam owners and downstream water users the outlet capacity was tripled by the addition of a crest gate. EA conducted an alternatives analysis of four different options; helped the owners select the preferred alternative; provided all construction drawings and specifications; inspected the outlet conduit and control gate; conducted all engineering analysis; and provided inspection and oversight during construction.


Lake Dorothy Spillway Rehabilitation

Las Animas County, Colorado

EA provided the design, bidding and construction management for the rehabilitation of the concrete ogee spillway for this dam, located in Las Animas County, Colorado. EA saved the owner approximately $137K in negotiations with the contractor, value engineering, and effective construction management. The cost savings allowed the owner to increase the scope for additional improvements and stay within their budget. Deliverables included design, construction plans, and specifications. Final as-built drawings were prepared for the concrete overlay of the spillway floor and a portion of the spillway wall; drains under the spillway floor and behind the spillway wall; valve vault lid with hatch doors; and wood vegetation removal. EA also developed plans to add a toe seepage collection swale for the ongoing monitoring of seepage.

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