20 May 2022 ACEC Virginia Hosts Tour of Cobbs Creek Reservoir
Koontz Bryant Johnson Williams, Inc. team members recently attended a tour of the Cobbs Creek Reservoir, which was hosted by the American Council of Engineering Companies (ACEC) of Virginia. The facility, located in Cumberland County near Columbia, VA, is an offline storage reservoir using the James River in a ‘catch and release’ fashion to augment Henrico County’s water supply. Currently, the County is permitted for a 35 MGD withdrawal at their Gaskins Road intake. This facility will add an additional 45 MGD to that capacity.
The dam is 4,850 feet long and 160 feet high, and includes 3,200,000 CY of zoned earth fill, 160-ft high reinforced concrete inlet/outlet tower, and two saddle dikes for the 1,100-acre reservoir to be later impounded. Seepage controls include a double row grout curtain in the rock foundation and a slag cement, cement-bentonite slurry wall in the overburden.
Extensive seepage modeling was performed to evaluate other rim conditions that could lead to seepage loss. This reservoir will be filled by pumping from the James River during high flows, and water will be released into the James River from the reservoir for flow augmentation during low flows.
The river intake and pump station have a design capacity of 150 MGD, and water will be conveyed between the river and reservoir via approximately 3,200 linear feet of 72-inch diameter pipe.
KBJW engineer Simon Mueller, geologist Ken Bannister, and intern Grace Bannister ended the day with a post tour networking event at Lickinghole Creek Craft Brewery in Goochland, VA. Grace, a personal friend of the brewery owner, left the event with a new KBJW client and potential wetlands work for them.
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KBJW geologist Ken Bannister & intern Grace Bannister visiting the new Cobbs Creek Reservoir in Cumberland County, VA.
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Engineer of Record explaining the design of Cobbs Creek Reservoir.
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Downstream toe of the Cobbs Creek Reservoir dam.
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Explaining the rapid drawdown system.
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Upstream face of the Cobbs Creek Reservoir dam.
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Explaining the filling system as KBJW engineer Simon Mueller listens in.
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Upstream face of the Cobbs Creek Reservoir dam showing filling structure. Water is delivered from the river to the top of the standing structure and spills out falling onto the chute below to be delivered to the reservoir pool. Existing Cobbs Creek is on the left side of photo and currently is piped under the dam, but will be filling it when the gate is closed.
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KBJW engineer, Simon Mueller, discusses the intake structure with its designer and the project’s overall engineer of record.
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Intake structure on the James River, which consists of two groups of four intakes, constructed as large screens, each capable of 25 MGD. Special construction prohibits intake of aquatic biota.
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Cobbs Creek Reservoir Pumphouse with intakes on the James River. The pumphouse is located above the 100 year flood, with all electronics above the 500 year flood.
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The final stop with networking at Lickinghole Creek Craft Brewery. The KBJW team enjoyed great beer and finished the evening with two new clients, including the Brewery.
