Cobbs Creek in Cumberland County will be dammed to form a new drinking water reservoir for Henrico, Powhatan, Goochland and Cumberland counties
Source: US Geological Survey (USGS), Lakeside Village 7.5x7.5 topographic map (2013, Revision 1)
After the 2002 drought, the state required all localities to develop long-range water supply plans. Cumberland County started planning a new reservoir on Cobbs Creek in Cumberland County, then arranged with Henrico County to purchase the land and build the new water storage system. Powhatan County and Goochland County were also recruited to share costs and water, so Cobbs Creek Reservoir became a regional water supply project.
Two dams, one 150' high and the other 35' high, will block flow of the creek. Runoff from the Cobbs Creek watershed behind the high dams will not be sufficient to provide a reliable water source; the watershed is too small. Instead, when the James River is at high flow during the winter, excess river water (up to 150 million gallons/day) will be pumped uphill into the Cobbs Creek Reservoir. Dam construction will be completed in 2019, but it will take two years to fill the 1,100-acre reservoir.1
the planned Cobbs Creek Reservoir requires two dams (shown in green), including one 35' high to block potential overflow on the western edge
Source: Henrico County, Cobbs Creek Reservoir Map
A larger dam on the James River itself, creating a new lake on the main stem, would provide more water storage - but a new dam blocking the primary channel of a major river is no longer a viable option. Such a dam would would flood wetlands, farmland, and historical resources, as well as interfere with fish migration. Tapping the James River only at high flow times will ensure that withdrawals will not reduce water flow below the minimums required for fish during periods of drought.
No water treatment plant is planned for the Cobbs Creek Reservoir, and the water stored in the reservoir will not be delivered to Henrico County's existing water treatment plant via pipeline. Instead, up to 47 million gallons/day of water will be released from the reservoir during periods of high demand. The released water will augment the natural flow in the James River and provide wildlife benefits. Henrico plans to withdraw 30 million gallons/day at its raw water intake near Boshers Dam. Cumberland County will withdraw up to 7 million gallons/day, and Powhatan will withdraw up to 10 million gallons/day, at sites to be determined later.2
Cobbs Creek, at the location for the reservoir, is a small stream in Cumberland County
Source: Virginia Section: American Water Works Association 2011 conference, Reservoir Development for Sustainable River Management - Cobbs Creek Reservoir
Combining the requirements from multiple counties will result in one large 1,100-acre reservoir ("one of the largest, if not the largest, municipally owned reservoir in Virginia") that will flood 31 acres of wetlands and 15 miles of streams. If separate jurisdictions had chosen to build multiple small reservoirs on different tributary streams, riparian zones on multiple streams would have been impacted. The wetlands and riparian zone of Cobbs Creek will be drowned by the new reservoir, but consolidating requirements will result in a higher dam that will flood more acres of upland forests - rather than multiple strips of wetlands and riparian areas on multiple tributaries.3
The counties were required to mitigate the environmental impacts of the project, and the mitigation strategy was controversial because 75% of it was based on adding additional legal protection to streams in Cumberland State Forest. That state-owned forest was already being managed to meet environmental objectives.
The counties claimed they were offsetting the impacts of flooding the Cobbs Creek watershed by putting $9.8 million into a Virginia Department of Forestry stream mitigation fund, highlighting that the state forest was not required by the Chesapeake Bay Preservation Act to maintain 100-foot riparian buffers. Cumberland State Forest is located in Cumberland County, outside the Tidewater counties subject to the act, but for over 50 years the state has maintained protected buffers in the forest twice the width required for reservoir "mitigation."
the Cobbs Creek Reservoir will require relocating oil pipelines and electrical transmission lines
Source: Cumberland County Online GIS System
Owners of private weland mitigation banks had hoped that mitigation would require the counties to purchase "credits," which were available from the creation of new wetlands and preservation of other streams. Henrico County did purchase credits for the project's 31 acres of wetland impacts and 25% of the required stream preservation credits, but prohibited bidders from publicly opposing the mitigation plan. A member of the House of Delegates from Cumberland County stated his opposition clearly:4
No site for a water reservoir is "perfect." Flooding the Cobbs Creek watershed required relocating existing high-voltage electrical transmission powerlines. Relocation was also required for the two Colonial pipelines that transported over 100 million gallons/day of refined petroleum products from refineries on the Gulf Coast to customers near New York City. Relocation costs exceeded $50 million, a substantial percentage of the reservoirs total $280 million cost.5
planned Cobbs Creek Reservoir, in Cumberland County
Source: Reservoir Development for Sustainable River Management - Cobbs Creek Reservoir