In January of 2017, the massive snowpack from a “hundred-year winter” was melting and threatening to flood low-lying areas in Sparks. And though the flooding wasn’t as bad as some predicted, significant damage was done to the diversion and intake structures at the Glendale Water Treatment Plant.
“The water moved an enormous amount of rock and dirt from the area around the intake,” said Andy Gebhardt, TMWA Director of Operations and Water Quality. “This hasn’t dramatically affected plant operations since, but the riverbed was hit hard, impacting both fish passage and recreational use. On top of that, erosion around the intake made repairs necessary to maintain structural integrity.”
When the diversion and intake structure were last rebuilt in 2010, the objective was to increase the operating capacity of the plant while also improving fish passage and navigability for
recreational users. Unfortunately, despite the great amount of thought, work and community input that were put into those improvements, the configuration was no match for the massive torrent of the 2017, spring runoff.
With the new rebuild, the focus was on maintaining capacity and retaining adequate passage for fish and recreational users while reinforcing the structure of the riverbed to be more resistant to extreme flows.
Using large boulders approximately 5 feet in diameter, a stair-step arrangement has been created to form a series of descending pools through which the river will flow. Tthe large boulders being used in channeling the river will be much more resistant to damage during extreme-flow situations.
“Fundamentally the diversion and shape of the riverbed should be the same as it was prior to the flood events,” said Ryan Dixon, TMWA Sr. Construction Engineer. “The difference is the larger materials used and their ability to
withstand heavy flooding. The boulders were interlocked to secure placement. This will protect the structure and help TMWA provide greater reliability to our customers by allowing us to divert water into the Glendale plant under a wide variety of river-flow scenarios.
“TMWA would like to acknowledge the outstanding work Granite Construction has done in executing our plan to rehabilitate the Glendale Diversion. We put a lot of emphasis at TMWA on quality, timeliness and managing costs; Granite
has been an excellent partner in all those categories.”
Work began on the diversion rehab in August and project completion is anticipated prior to the end of the year.