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Carbonton Dam removal: A 6th Anniversary Look Back

Hard Hat News, 2006. Demolition of the Carbonton Dam, by Gwen Laird Pernie

In the Central Piedmont Region of North Carolina an effort is underway to restore 10-miles of the Deep River, a tributary to the Cape Fear River Basin. The river has been environmentally damaged for the past 200 years, when the first dam was built at Carbonton to power a mill on the riverbank. This $8.2 million dam-removal project, the largest ever of its kind in North Carolina, is also the first dam removal in the state to be done primarily for mitigation purposes. This project is the culmination of a five-year planning effort by Restoration Systems, LLC, of Raleigh, NC (owner of the dam) to re-establish the native aquatic ecology of the Cape Fear River Basin to gain “mitigation credits” under the North Carolina Ecosystem Enhancement Program. It was planned and is being implemented in close coordination with multiple county, state, and federal regulatory agencies. The dam is a former hydropower generating facility that is licensed under the Federal Regulatory Energy Commission. Site contractor for the project is Backwater Environmental of Pittsboro, NC, a subsidiary of Osborne Company General Contractors of Eden, NC. Osborne will handle the physical demolition and heavy work of the project, while Backwater will handle the earthmoving, grading, site restoration, and softer work. Restoration Systems retained Milone & MacBroom Inc. (MMI), of Cheshire, Connecticut and Greenville, South Carolina to investigate the existing dam and assist with agency permitting, and to design the removal strategy, prepare construction documents, and handle inspection during demolition. MMI is also designing a future public recreation park that will occupy the south riverbank at the dam site. According to Ken Kloeber, branch office manager of MMI’s southeastern regional office in Greenville, the most challenging aspect of the project was to design a dam removal sequence and methodology that will get heavy equipment in and out of the river quickly. “The challenge is to minimize the exposure of the removal operations on the Deep River system and the aquatic critters that this entire project will benefit,” Kloeber explained. “We wanted to avoid short term effects while accomplishing the greater good in the long term.” “An additional challenge was that much of the planning involved working with and getting approval from many county, state, and federal agencies–sometimes with overlapping authorities–on a fast-track schedule,” Kloeber continued. “Hydropower dam demolitions involving FERC approval typically take years in the planning and design stage. With the owner, contractor, and agencies cooperating, this one took a matter of months.” “Every dam removal is unique because no two are constructed the same,” Kloeber said. “We had to first evaluate and understand the structural components of the spillway and the powerhouse before designing the demolition methodology and sequence. It’s typically easiest to demolish dams in reverse order of their construction sequence.” “The planning of the particular project has been especially interesting because we were able to locate original 1921 construction photos of the powerhouse and spillway in their de-watered state, which gave us insight into how the facility was constructed,” Kloeber stated. “It literally painted a picture of what was hidden under the water, and allowed us to anticipate in order to save time.” “Typically, dam removals involve starts and stops as structures are uncovered and new situations need to be assessed, Kloeber said. “Having the right information and evaluations of the structures up front has allowed this demolition to proceed very smoothly. To the credit of Restoration Systems, the owners recognized the need for adequate investigations right away, and they provided us the resources to make that happen.” “Because of its age and type of construction, the Carbonton Dam is eligible for the National Register of Historic Places,” stated Kloeber. “So, Restoration Systems has taken extra care to preserve the history of the structures.”

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Repopulation of Deep River with endangered fish — confirmed.

We were excited to see a (rather dry but) important report summary confirming the ecological success of Restoration Systems’ 2006 Carbonton Dam removal project.  The successful re-population of the Deep River and Carbonton Dam impoundment by the threatened Cape Fear Shiner was documented by The Catena Group under contract to Restoration Systems and reported nationwide in a 2007 article that ran on the AP wire.  A careful reading of the article, however, reveals that not everyone was totally convinced the Cape Fear Shiner was rebounding due to Restoration Systems’ removal of the dam:

State officials are still awaiting the company’s annual report, documenting the endangered shiner’s return. But as a sign of improving water quality and nature revived, it is welcome news, said Tad Boggs of the state’s ecosystem enhancement program.

Assuming it’s accurate, it represents a win-win situation for what our program is designed to do,” said Boggs, whose agency has supervised about 700 such projects statewide since its creation four years ago.

“Assuming it’s accurate”??!!  Well, rest assured, it’s accurate.  The project has been under independent evaluation by the N.C. Wildlife Resources Commission, the N.C. Museum of Natural Sciences and N.C. State University since the removal was completed in 2006.  According to an annual report submitted by the NCWRC to the U.S. Fish and Wildlife Service we’ve managed to repopulate the river with a fish that was nearly extinct.  Our independent monitoring confirmed this success some time ago, as was reported, but it is nice to see it further memorialized.  There were no Cape Fear Shiner.  Now there are. Enjoy.

Cape Fear shiner (Notropis mekistocholas) [federal – endangered]: Staff have been evaluating the effects of removing the Carbonton Dam on the Cape Fear shiner. The NCWRC, North Carolina State University (NCSU), and the Museum of Natural Sciences have continued a multi-year study of the effects of removing the Carbonton Dam. The dam was located on the Deep River (upper Cape Fear River Basin) along the Chatham/Lee County line near Hwy 42. The objectives of this study are to determine the short- and long-term effects of dam removal on freshwater mussels and fishes by pre- and post-removal monitoring of their abundance and diversity within the tailrace, impoundment, and at reference sites. Changes in fish populations are being quantified to document any downstream impacts as well as recovery of riverine fauna within the former impoundment. So far, we have captured a total of 43 species of fish, including the Cape Fear shiner. Our sampling has documented the Cape Fear Shiner at all sites including the former impoundment. Consultants contracted by the NCWRC have completed a final report on the current distribution of Cape Fear shiner in the Cape Fear River Basin. Cape Fear shiner populations appear to be stable. Individuals were also collected in the Haw and mainstem Cape Fear Rivers for the first time in several years. The final report was prepared and is available for review in the Section 6 project files in Raleigh. — From 2009 Annual Performance Report on Endangered Species, Submitted to the U.S. Fish and Wildlife Service  to the N.C. Wildlife Resource Commission