SPOKANE — Spokane County is spending $2 million to fight scum.
Green, goopy, gross lake scum, that is.
The county commissioners plan to use $2.1 million to build a new system for combating algae blooms at Newman Lake. County taxpayers won’t be paying for it directly. The money is coming out of the $101 million Spokane County got through the American Rescue Plan, a stimulus bill Congress passed last year to help the country recover from the COVID-19 pandemic.
“This will impact the water quality of the lake for my kids and grandkids for generations to come,” said Karen Stebbins, chair of the Newman Lake Flood Control Zone District Advisory Board. “It’ll make the lake a much better place to recreate for Spokane County residents.”
Algae aren’t inherently bad. They’re essential for many aquatic ecosystems and form the base of lake food chains. For instance, algae feed zooplankton, which in turn feed fish.
But an overabundance of algae can wreak ecological and recreational havoc.
Algae flourish in warm, slow-moving, nutrient-rich waters, and algae blooms have become reliable, unwelcome summertime events in the Inland Northwest.
At their worst, the blooms create large mats of floating scum.
The goop presents an aesthetic problem. Not many people like swimming in oily, green, viscous water. It can be dangerous, too.
Algae blooms can blanket the top of a lake, depriving the plants below of life-giving sunlight. The algae decomposition process consumes large quantities of oxygen, which can leave fish gasping for air.
Blue-green algae — which is actually a photosynthesizing cyanobacteria — can make people sick if ingested. It can kill dogs if the animals drink too much of it or lick it off their fur. Regional health districts frequently issue blue-green algae warnings in late summer when blooms peak. The Spokane Regional Health District has issued warnings for Newman Lake five years in a row.
While algae blooms plague many Eastern Washington and North Idaho lakes, Newman Lake’s struggles are especially acute.
People are part of the problem.
The number of people living in the Newman Lake watershed has grown exponentially in the last 120 years. Roughly 17,000 people live there today.
Some of those residents fertilize their lawns, and some of that fertilizer runs off their property, eventually ending up in the lake. Plus, their homes rely on septic systems.
Aging septic systems can leach nutrients, such as phosphorus. That phosphorus trickles into creeks and flows into Newman Lake. A phosphorus-rich lake is algae heaven.
At 30 feet deep, being shallow doesn’t help Newman Lake either.
Shallow lakes tend to be warmer and more hospitable to algae. Their waters circulate better, too.
In spring and fall, winds blow over Newman Lake’s surface. Those gusts and breezes are enough to mix the waters.
The mixing introduces oxygen that’s critical for wildlife and plants, but it also disturbs the sediment on the lake floor. As the water kicks up the dirt, it releases phosphorus trapped at the bottom, and that becomes algae food.
To battle algae, Newman Lake’s defenders have to go to war against phosphorus. For the last 30 years, they’ve used two primary weapons — aluminum sulfate and oxygen.
Aluminum sulfate, often referred to as alum, is typically a benign chemical. It can be used to purify drinking water.
The Newman Lake flood control district in spring releases tens of thousands of gallons of alum into the lake. The alum binds with phosphorus and pulls it down to the lake floor where it stays, inert and useless to algae.
Pumping oxygen into the lake in summer helps reduce phosphorus too.
Newman Lake’s waters mix in spring and fall when winds churn the surface, but the waters become static in the heart of summer.
The calm lake becomes stratified, with layers of warm water above and cold ones below.
“They don’t mix because they’re different densities of water,” Spokane County Water Reclamation Engineer Ben Brattebo said.
Without mixing, oxygen on the lake bottom can’t be replenished. At the same time, decomposing plant matter uses much or all of the little oxygen available.
Those cold, oxygen-poor conditions cause a chemical reaction that releases phosphorus.
Pumping oxygen into the bottom of the lake can prevent that release.
“If you can keep a layer of oxygen on the bottom, it helps keep the phosphorus bound up,” Brattebo said. “Then, when the lake does mix again in the fall or the late summer, the phosphorus won’t be there for plants to grow.”
The new Newman Lake oxygenation system will suck oxygen out of the air, then pump it through a tube on the lake bottom with compressors. Stebbins said the 2,000-foot tube will be “like a soaker hose,” releasing oxygen bubbles that will float upward.
Stebbins said the old oxygenation and alum distribution system, installed in 1991 for $539,000, has failed.
The new one will use advanced technology but accomplish the same goal more efficiently.
None of these phosphorus reduction efforts comes cheap.
“It’s an intense treatment system that’s unusual in our area for one lake,” Brattebo said.
The Newman Lake flood control district has a $321,000 budget for 2022. About $50,000 of that is for flood control. The remaining $271,000 is for improving water quality, mostly through oxygenation and alum application.
Spokane County Commissioner Josh Kerns said he believes the oxygenation and alum project is a wise investment.
Newman Lake is Spokane County’s largest lake by surface area, he said. Anglers, kayakers and Jet Ski-ers flock to the area every summer.
“It gets a lot of use,” Kerns said. “Newman Lake is a community asset.”