The Red Rock Hydroelectric Project (RRHP) is located at the Red Rock Presa on the Des Moines River, approximately 3.8 miles southwest of the Pella, IA in Marion County Iowa, approximately 45 miles southeast of Des Moines, Iowa, and approximately 143 miles above the confluence of the Des Moines River with the Mississippi River.

The U.S. Army Corps of Engineers (USACE) constructed Red Rock Dam between 1960 and 1969 to impound Lake Red Rock for flood control, recreational, and fish and wildlife purposes. The presa, reservoir, and adjacent land are federally owned and operated by the Rock Island District of the USACE. The RRHP has been constructed immediately adjacent to the left (northeast) side of the dam’s existing concrete aliviadero.

Red Rock Dam is a composite earthfill and concrete presa de gravedad with an overall length of 6,260 ft, an embankment base width of about 655 ft, and a height of 110 ft. The dam’s center section is comprised of a concrete ojiva spillway with five Tainter puertas and fourteen bottom outlet conduits. Marion County Highway T15 (Highway T15) traverses the length of the dam along the crest.

The dam consists of two earthfill segments with a combined length of 5,676 ft, which are linked by a concrete gravity section that contains the dam’s outlet works and spillway. On each side of the spillway is a non-overflow concrete gravity section that extends into the adjoining embankment. Large concrete gravity sections are located on each side of the spillway structure. The concrete gravity section on the northeast side, where the hydro project is located, consists of three non-overflow monoliths and one spillway transition monolith.

The concrete ogee spillway is 241 feet long and fitted with five Tainter crest gates. Fourteen bottom outlet conduits are located within the spillway structure. Each outlet discharges below minimum tailwater to a hydraulic jump-type stilling basin measuring 241 feet wide and 213.5 feet long. Baffle blocks in the stilling basin are in two rows (staggered), each 12 feet high, 16 feet long, 8 feet wide, and spaced 10 feet apart in each row.

RRHP consists of a concrete intake structure, two tuberías forzadas, a concrete central eléctrica, 69 kV subestación, transmission line, and utilities. The concrete intake structure used to bring water into the project, is founded on concrete pilings and consists of trash racks, emergency closure gates, stoplogs for maintenance purposes, and associated equipment. The emergency closure gates are designed to fail closed under all conditions, including loss of power to the intake structure.

Two penstocks route water from the intake structure through the dam to the powerhouse. Each compuerta is entirely buried underground and penetrates two of the concrete monoliths of the original dam. Each penstock incudes a vent shaft located near the intake structure, otherwise access to the penstocks can only be achieved through the powerhouse.

The concrete powerhouse is founded on bedrock and contains two vertical Kaplan turbine generators and associated equipment. The multi-level building includes all equipment necessary to transfer energy from flowing water to electrical energy. Plant and Unit Control systems are located in the powerhouse and control all aspects of water flow through the project and power generation.

Operation of RRHP is coordinated with the USACE to ensure compliance with the Federal Energy Regulatory Commission (FERC) issued license and related project plans. The USACE controls the timing and quantity of water released through Red Rock Dam and coordinates those releases with project staff located in Sioux Falls, SD. Water can be released through the project, and/or through existing dam infrastructure controlled by the USACE.

Archivos:

• Red Rock Project – Certification Application 2021
• US Fish and Wildlife Service Comments – Red Rock Application 2022
• IDNR Comments – Red Rock