Bigger culverts part of Pine Nut Creek solution

A rain gauge at the top of Pine Nut Creek recorded .96 inches of rain over six hours on Sept. 18, making it the wettest spot in the county from what is likely the last wet storm of the 2023-24 water year.

Typically, that much rain would send a torrent of water down Pine Nut Creek through Fish Springs, but dry conditions over the past four months likely kept that to a minimum.

It has been a decade since the nighttime Aug. 6 flash flood that sent debris and logs down the creek, after 1.75 inches of rain fell in 45 minutes in the Bison Fire burn scar.

While that might have been one of most serious instances where the drainage has endangered residents, the flooding from record snowfall from the New Year’s 2023 Tonopah low and another blast two months later spurred studies of the drainage.

A federally funded feasibility study examining the drainage completed last summer estimated that building a dam and several basins would cost $78 million, with just the dam accounting for just under a third of that cost.

On Thursday, Douglas County commissioners heard a presentation on a follow-up study conducted by J-U-B Engineering to drill down on the basins.

That study found four locations where culverts were undersized, Douglas County Flood Manager Courtney Walker said.

The study also identified sites for basins on county owned land at Mel and Myers along Fish Springs Road. Just the work on the basins would cost around $9 million.

According to the study, the culvert at Calle Pequeno, upstream of the others, only handles 38 percent of a 10-year flood, and if expanded could handle 91 percent. However, in a 25-year flood, that drops to 57 percent and 14 percent in a 100-year flood. A 100-year-flood indicates 1 in 100 odds of a certain size flood in any given year.

Flows at the site in a 100-year flood are 1,713 cubic feet per second while the two circular culverts can handle 80 cfs.

Pine Nut Creek drains 55 square miles of the Pine Nuts and according to a new model has a 100-year peak discharge of 4,360 cubic feet per second, which is more than Buckeye Creek to the north, which drains a larger area.

“This is great, but as always is subject to available funding,” Commissioner Mark Gardner said. “The question is whether the board would ever entertain spending the money if it weren’t from another source? It’s so frustrating. You can see a problem that’s kind of obvious, but you don’t have the financial resources to make that happen.”

Commissioner Sharla Hales said she felt the information is valuable to the county.

“It will help us focus on some things we can do that might help a little bit before we can do a comprehensive fix,” she said.