Nicholson Construction says it was recently named general contractor by Grant County Public Utility District for remedial foundation drain work on its Priest Rapids and Wanapum dams.
Nicholson will focus on reconditioning foundation drains by core drilling 3.375-inch-diameter holes on both dams, which may be experiencing reduced flows or blocking by unknown materials or foreign objects, including calcium carbonate deposits.
The scope of work at Priest Rapids Dam includes drilling of 128 drain holes in the upstream gallery at the dam’s powerhouse and left bank fish facilities. Wanapum Dam will have 290 drain holes drilled in the upstream gallery.
Priest Rapids Dam impounds water for a 955.6-MW powerhouse, and Wanapum features a 1,092-MW powerhouse.
Other work scopes for the project included flow and pressure measurements on all drain holes and video inspection on selected holes.
The company has previously performed work for Grant County PUD, including post-tensioned anchor installation to repair a crack in Wanapum Dam’s spillway and investigative coring,for Priest Rapids Dam.
Nicholson’s portion of the work on Priest Rapids Dam will be completed by Dec. 31 and at Wanapum Dam in May 2020.
Nicholson has worked in the geotechnical construction industry for more than 60 years, offering expertise in the design and installation of deep foundation elements, earth retention systems and ground treatment solutions.