Moses Lake, WA 98837, USA

Contractor hired to help with Wanapum Dam spillway pier evaluation

BEVERLY, Wash. – Grant PUD plans to work with contractor Kuney-Goebel JV and subcontractors to begin investigative drilling into Wanapum Dam spillway pier monolith No. 4 on Thursday. A fracture was discovered in the monolith on Feb. 27.

The precise-drilling project is expected to take about nine days to complete. It is part of an extensive evaluation being conducted on the structure to help determine the cause of the fracture and its geometry. Data from the examination will be used by a team of Grant PUD engineers, an independent board of consultants, and Federal Energy Regulatory Commission officials to determine the best way to repair the structure and possibly raise the elevation of the Wanapum reservoir to an intermediate level during the restoration phase.

No additional damage to the dam was found during a thorough inspection, other than some minor surface damage on spillways neighboring monolith No. 4.

To repair spillway pier No. 4, Grant PUD is exploring the possibility of using steel strand anchors that are drilled from the top of the dam through the concrete structure into bedrock. The steel strand anchors would be set into place with a specialized, high-strength grout. Data from the ongoing evaluation of the structure will help determine if this process would be an effective way to repair the spillway pier. The independent board of consultants and FERC will also evaluate the data and must approve any action before it is implemented by Grant PUD.

Along with the forensic evaluation of spillway pier No. 4, fish biologists, engineers, and stakeholders are developing plans to modify the fish ladders at Wanapum Dam. The modifications include installing a pumping system and creating temporary slides at the top of the fish ladders so returning adult salmon and steelhead can safely pass the dam and into the drawn-down reservoir.

Grant PUD is working with 11 irrigators who have land-use authorizations for surface-water withdrawals from the reservoir. The utility continues to work with Chelan PUD and other dam operators on the Columbia River, along with federal, state and local agencies, as well as tribes and other stakeholders impacted by the drawdown.

The Wanapum reservoir shoreline and boat launches remain temporarily closed to the public. Sections of the shoreline, including the riverbank and mud flats are extremely unstable and have proven to be a serious safety hazard. The Wanapum Lower Boat Launch, Wanapum Heritage Center and day-use park also remain closed. Grant PUD has posted signs informing the public of the shoreline closure and is actively monitoring the area. The utility has contracted with state and local law enforcement to patrol the reservoir shoreline on land and on the water. Also the Washington Department of Fish and Wildlife has closed their properties on the shoreline and has increased their patrol efforts.

Facilitating safe public recreation on the reservoir is one of Grant PUD’s goals as it moves forward in its response to the situation at Wanapum Dam. The utility has reopened public-access sites on the Priest Rapids reservoir, including the Priest Rapids Recreation Area at Desert Aire and the Buckshot Recreation and Wildlife Area. The Wanapum Dam Overlook is also open.

Grant PUD plans to work with river stakeholders to explore the possibility of moving up the timetable for scheduled modifications to the Kittitas County Boat Launch at Vantage and the Frenchman Coulee Boat Launch, and dredging of the Crescent Bar boating channel during the low-level reservoir conditions.

Grant PUD continues to meet customer electricity needs with its current power-supply portfolio. Wanapum Dam is generating about half of the electricity it would produce under normal river conditions.