MOSES LAKE — Dealing with the problem of blue-green algae in Moses Lake is most likely going to be a “long term and expensive project.”

That was the conclusion of members of the Moses Lake Irrigation and Rehabilitation District, or MLIRD, during a special meeting on Thursday, Jan. 9, to talk about two possible options — using alum to remove some of the phosphorus from lake water and diverting additional Columbia River water to dilute the lake.

“This is 20 to 30 years, and we want to push the rock uphill,” said Jeff Foster, recently re-elected member of the MLIRD board. “This isn’t we need $1 million or $2 million this year. We need that every year for a while.”

“It’s a $10 million commitment over the next five years,” Foster added.

The board met to examine a couple of options to reduce the levels of phosphorus in the lake. Phosphorus is the primary nutrient promoting the blue-green algae blooms that have plagued the lake in the past few years.

When blue-green algae — actually a form of bacteria — die, they produce a toxin that can be harmful or even lethal to animals and humans.

Harvey Harper, the president and CEO of Florida-based Environmental Research and Design, an environmental consulting and engineering firm, told board members that he has designed over 60 alum-injection systems during his career as an engineer.

“We invented this in 1986,” Harper said. “We’ve built several systems similar to this.”

The first would involve injecting alum — aluminum salts that bond to the phosphorus — into the high-phosphorus water of Rocky Ford Creek before the creek empties into Moses Lake. Such a process would require about 5,000-6,000 gallons of alum per day and cost between $500,000 and $600,000 for five months of continuous treatment.

Such treatments, if sustained, could remove around 80 percent of the phosphorus from Rocky Ford Creek — which is naturally high in phosphorus to begin with — from 180 parts-per-billion to around 25-30 ppb.

Harper also said it would also require storage tanks, a pump house, a computer control system and a place to mix the alum into the water — probably at the dam on Rocky Ford Creek just north of where it meets the lake — since alum is heavier than water and without proper mixing, will simply sink to the bottom.

“And it won’t do what it’s designed to do,” he said.

Shannon Brattebo, an environmental engineer with Pasadena, California-based consultancy Tetra Tech, told board members that spraying a fairly large area of the surface of the Rocky Ford Arm of Moses Lake — say, 1,500 acres — and then letting that alum sink to the bottom, pulling out dissolved phosphorus as it sinks, would cost more but likely provide several years of remediation per treatment.

“This would cost $400,000 to $2.5 million (per treatment), depending on the dose of alum,” she said.

Both Brattebo and Harper said treating the lake with alum would still pose the problem of what to do with the flocculant — the phosphorus and aluminum compound formed by treatment.

“There’s no problem with leaving the flocculant on the bottom of the lake,” Harper said, noting that sediments with less phosphorus can improve the health of lake-bottom biomes.

However, injecting alum into Rocky Ford Creek would likely require a pond to allow the flocculant to settle before it’s sent out to Moses Lake, Harper said.

Peter Burgoon, a consulting engineer from Wenatchee, outlined a proposal to divert a portion of the water in the Quincy West Irrigation District’s canal system into Moses Lake through a feeder pipe from the W-20 canal, which was designed to deliver irrigation water to the Mae Valley area.

However, Burgoon said diverting even 50,000 acre-feet per year to dilute the water of Moses Lake would be costly and challenge the entire Columbia Basin Project’s water capacity.

The total capacity at peak irrigation season of the CBP canal system is 8,600 cubic feet per second — 4,600 through the West Canal and 4,000 through the East Low Canal, he said.

“At peak season, all of these flows are used,” Burgoon said. “All that flow is needed, and they actually have some deficit in the system at Royal City.”

Currently, Burgoon said the Royal City area is about 200-400 cfs short of water. Diverting water to dilute Moses Lake would require 150-300 cfs — depending on the amount of time the water is diverted.

Burgoon said the Bureau of Reclamation looked at the possibility of diverting water from the W-20 canal as an additional way of getting water to Potholes Reservoir through Moses Lake, and calculated the project would cost around $15 million.

If built today, he estimated the same project would cost around $27 million.

Harper said alum was the least expensive way of removing large amounts of phosphorus from lake and river water. But he also said there is no one shot, cheap solution, and board members agreed it will take time and effort to improve the quality of lake water.

“There are things you will have to do every year until you have a permanent solution,” he said.

The board made no decisions about the options that were presented, and it agreed to keep partners in the Moses Lake Watershed Council, which was established to deal with the algae problem, informed of its projects.

Charles H. Featherstone can be reached at cfeatherstone@columbiabasinherald.com.