The West Wash Dam in old northwest Reno is out of compliance and the city of Reno is in the process of getting it in working order. The dam is located near Wyoming Avenue north of Kings Row and protects about 30,000 homes from flooding in the Peavine Mountain watershed.
The second public meeting for the West Wash Dam Rehabilitation Project was Tuesday evening and gave residents more information about the project and the chance to ask questions. The project wouldn’t start construction until 2025 if everything goes as planned and would most likely be finished in 2028.
“This operation would reduce our required operations and maintenance, it will minimize impacts to surrounding residents, it increases the flood protection to downstream residents, and it will bring the West Wash Dam into compliance,” said Alex Stodtmeister, the hydraulic and hydrologic modeling lead with engineering firm DOWL.
The earthen dam was constructed in 1960 and given an evaluated life expectancy of 50 years. After assessing the dam, it is now classified as “High Hazard” by the Nevada Division of Water Resources, which means if there was a breach of the dam there would be the possibility of a reasonable loss of life.
Those who spoke about the project said the dam has held up well during past significant storm events and that a breach would only occur during flooding events larger than the area has seen in the past.
One type of theoretical storm engineers use as a model is called a Probable Maximum Precipitation Event or PMP. A PMP is a type of storm that would cause the most precipitation physically possible in an area and that can also be considered a worst-case scenario. This gives engineers a theoretical maximum so they know what their dams and waterways need to be able to endure.
This should not be used as a probable storm that could affect the area at any time in the near future.
The preferred plan was chosen by taking 13 original ideas and narrowing them down to five that would be the best fit. They were then ranked with points to determine both the most cost-effective and operational plan.
The current plan would cost about $23 million and would result in the least amount of change to the area. Other options included buying and demolishing up to 664 properties to clear the path of any floodwater so that it could flow into the Truckee River unimpeded.
Specifics of the plan would include raising the dam by five feet and widening the auxiliary spillway to the original 80 feet. This would bring the dam into compliance with Natural Resources Conservation Service requirements and would prevent flooding from occurring, outside of a 500-year event.
Corrections: This story has been updated to correct DOWL engineer Alex Stodtmeister’s name and that the auxiliary spillway will be widened, not the principal one.
