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Floating Dewatering & Filtration Systems Aid in Dam Renovations

Rain for Rent bypasses, dewaters, and filters 5,000 acre feet of lake-water to provide access to the surface of the dam for hydro-electric dam system renovations.

BACKGROUND

Plumas County, CA – An aging concrete arch dam, originally built in 1929, was scheduled for multiple large renovation projects, one of which included installation of a geomembrane liner on the upstream surface of the dam. Installation of the liner would reduce spalling from the head pressure acting to force water through the porous concrete structure, and mitigate related freeze/thaw damage. In order for the liner to be installed down to the bottom elevation of the dam, the lake would need to be dewatered and incoming waters would need to be diverted.

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OUTCOME

In order to help set the stage for these upgrades to be carried out, Rain for Rent designed and installed a series of bypass, dewatering, and filtration systems, each of which underwent on-site design evolutions to meet the needs of this complex, multi-faceted project:

  • 9CFS bypass system: 2 miles of 18-inch HDPE pipe was installed to bypass and maintain instream flows around Lower Bucks Lake and across the dam during the entirety of the project.
  • 130CFS dewatering system: A floating pump platform was constructed to hold the six 18-inch pump dewatering system and filtration system that drained the lake and decreased the water level by more than 65-feet to facilitate the liner installation and sediment removal from the dam abutment. A unique element of this was the design, application, and successful performance of custom-fabricated HDPE swing joints that allowed the barge to travel vertically 65+ feet while maintaining optimum cartesian positioning, and while operating only 130 linear feet from shore.
  • 10CFS filtration system: A stringent 3NTU discharge requirement for all dewatering operations was maintained via a passive sand media and bag filtration system which was later upgraded to an active treatment system with the addition of a BHR-P50 flocculant injection (in partnership with MC Environmental Services).

Rain for Rent’s system successfully pumped and treated 5,000 acre feet (roughly 1.8 billion gallons) while overcoming low level outlet elevation challenges, meeting NTU constraints and multiple environmental controls, and staying within project time restrictions despite having to evacuate the area for 3-weeks due to a complex of nearby wildfires.

CUSTOMER FEEDBACK

Jeff Jukkola, P.E., PG&E DeSabla Hydro Senior Civil Engineer shared, “I am specifically writing this letter in recognition of Rain for Rent… (Their) engineering and construction sensibility made (them) an absolute asset during the barge pump design – barge configuration, piping swivel joints, fuel lines, access, etc. – and countless in-flight changes while minimizing construction delays. …Regular communications to the Construction Foreman, Engineers and Project Managers kept us ahead of upcoming problems. The coordinated effort to demobilize in winter conditions saved the project capital and risk over the winter months. …Overall dedication to the project from start to finish was essential to the success of the project.”

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