For more than a decade, the McCall water storage facility off of Deinhard Ln. has been leaking.
Treated effluent is making its way into the Payette River, upstream from the Cascade Reservoir. But water managers say the leak isn’t a direct cause of a harmful algae bloom on the reservoir this summer – or in years past.
A history of failed tests
The Payette Lakes Recreation Water and Sewer District has owned and operated the water storage facility for the past five years following a 2017 election that resulted in the City of McCall sewer systems being annexed into the district.
Water Quality Engineering Manager Valerie Greear, who works for the Idaho Department of Environmental Quality, says the storage pond repeatedly failed the leakage test well before it was acquired by PLRWSD.
The facility was first installed in 2003 and according to DEQ rules, wastewater lagoons must be tested when the system is first installed and every ten years. DEQ says the lagoon did not pass its initial test in 2003. This resulted in yearly testing, which the lagoon failed each year through 2011. The maximum allowed leakage is 0.125 inches per day or an eighth of an inch.
“The storage facility has been tested for leaks routinely and has failed to comply with the maximum allowable leakage rates,” an Environmental Monitoring Report from 2017 said.
After the regular failed tests, the operators of the storage pond asked DEQ if a different testing route could be explored. This led to an agreement between DEQ and the city to conduct environmental monitoring and study the effects of any leak on surface and groundwater.
“So in about 2013, they asked if they could stop doing this every year and take a different approach,” Greear said. “And that’s kind of the path we’ve been on ever since of trying to figure out whether this leaking has an impact on the environment.”
BoiseDev had multiple people reach out inquiring about the leak and questioning whether it was related to the harmful algae blooms in the Cascade Reservoir.
Where is the leak?
Because of the leak in the storage pond, water collected in the underdrain discharges to a drainage swale that DEQ says creates “wetland-like conditions,” which could then overflow to the North Fork Payette.
An underdrain is a drainage system that is installed under a road that collects, then transports subsurface water. This water also eventually makes its way to the Cascade Reservoir.
“The water collected in the underdrains includes leakage from the winter storage pond and groundwater. Cascade Reservoir is the “basin” of the watershed, catching the contributions of all the tributaries. So yes, that is where this water ultimately flows,” Greear said in an email. “The water also seeps into groundwater, and those impacts were also part of the focus of the 2017 Environmental Monitoring Report. Water stored in the winter storage pond has been treated and is beneficially used for irrigation under a Recycled Water Reuse Permit.”
Is the leak a cause for concern?
What are the ramifications of this leak? Greear says it’s important to understand that the leak is fully treated wastewater, not sewage. This means the wastewater has been through a treatment process to remove contaminants and converted into an effluent that can go back into the water cycle. In this case, the water is moved to the storage pond. Greear said farmers then use this water to irrigate land in the area.