Ty Ziegler, P.E., HDR Engineering, Inc., Charlotte, North Carolina
Abstract:
The Dillsboro Hydroelectric Project (Project) was originally constructed in 1909 on the Tuckasegee River in the Town of Dillsboro in southwestern North Carolina. The Project supplied power to businesses and a few commercial customers in the nearby Town of Sylva. The original wooden dam and powerhouse facilities were first modernized in the 1930s and again in 1958. The Project had an installed capacity of 225 kilowatts and included a 12-foot-high, 310-foot-long concrete masonry dam impounding a 15-acre reservoir.
Duke Power Company, a predecessor of Duke Energy Carolinas, LLC (Duke Energy) acquired the Project when it purchased Nantahala Power and Light Company in 1988. The Project was licensed by the Federal Energy Regulatory Commission (FERC) as No. 2602 on July 17, 1980, with an expiration date of July 31, 2005. In 2004, Duke Energy filed an application to surrender the Project license and remove the dam and powerhouse as part of a Settlement Agreement addressing continued operation of Duke Energy's other nearby hydroelectric projects. Removal of the dam provided mitigation for fish passage and minimum instream flows at these other projects. Removal of the dam allowed full aquatic and recreational access to an additional 9.5 miles of river and restored 4,220 feet of the impounded Tuckasegee River to its original condition.
While the Settlement Agreement was signed by Duke Energy and the majority of the stakeholders, including all of the pertinent state and federal agencies, local communities immediately challenged the surrender application which tied up the removal process for several years. FERC ultimately issued a surrender order on April 22, 2008.
The surrender order marked a major milestone, however the ultimate removal of the Project works presented additional regulatory, environmental, and engineering challenges. Before the dam and powerhouse were removed, several environmental conditions needed to be addressed and local, state, and federal permit authorizations were required. One challenge was the presence of several populations of federally and North Carolina endangered Appalachian elktoe mussels immediately downstream of the dam. Before the dam was removed, approval from the US Fish and Wildlife Service was required to relocate the mussels to a suitable upstream site. The Section 401 Water Quality Certification also required dredging a significant amount of sediment impounded by the dam. In addition, FERC required several dam removal and demolition licensing conditions including the preparation of a demolition plan, a public safety plan, a quality control and inspection program, and a site restoration plan.
Biography:
Mr. Ziegler has 24 years of experience in analyzing and resolving environmental issues at fossil, nuclear, and hydroelectric stations. As an Environmental and Regulatory Manager for HDR's Charlotte, North Carolina office, Mr. Ziegler supervises a diverse team of environmental scientists and engineers, regulatory specialists, and Geographical Information System specialists who are dedicated to serving the environmental, regulatory, and permitting needs of clients in the electric utility industry. His experience has enabled him to develop solutions to help manage and, in many cases, alleviate power plant operational constraints. The focus of his work has been in developing and using hydrologic, hydraulic, water quality, and thermal models to predict the effects of modifying fossil, nuclear, and hydroelectric station operations.
This work has involved development and implementation of study plans, results analyses, strategy development, and interacting with local, state, and federal resource and regulatory agencies. His experience has been particularly valuable in Federal Energy Regulatory Commission instream flow and water quality relicensing studies at hydroelectric stations and in obtaining Clean Water Act Section 401/404 permits and National Pollution Discharge Elimination System permits for power plants.