Holding the line on phosphorus in Lake Whatcom - Salish Current
March 4, 2022
Holding the line on phosphorus in Lake Whatcom
Mallory Biggar

An aerial view of Lake Whatcom last July looking east toward Mount Baker demonstrates the lake’s popularity with residents and boaters. Since 1998, Whatcom County and the City of Bellingham have been tasked with reducing the amount of phosphorus in the lake to reduce pollution and preserve aquatic life. (Image: By Dicklyon – Own work, CC BY-SA 4.0)

March 4, 2022
Holding the line on phosphorus in Lake Whatcom
Mallory Biggar


Lake Whatcom is a recreational playground and residential gem: 5,000 acres nestled at the bottom of 56 square miles of drainage basin. It’s where people swim, fish and boat; where they walk, drive and live along — and where many of the county’s residents get their drinking water.

A map in the Lake Whatcom Watershed Annual Build-out Analysis Report 2022 shows vacant lots in pink, and protected and public lands in light and bright green.

In 1998, the lake was listed by the state as polluted because of increasing levels of phosphorus, a mineral that, among other things, stimulates plant growth. When those plants are lake algae and the phosphorus contributes to an overgrowth, the dying algae remove significant oxygen as they decompose, creating “dead zones” — areas devoid of aquatic life.

Phosphates, chemicals that contain phosphorus, are found in a number of household products, such as dishwasher detergents that soften hard water, and plant fertilizers. Phosphorus is washed by rains off lawns and lots down roadways to lakes and ponds, where it contributes to algae overgrowth.

After Lake Whatcom was listed as polluted, the lake’s managers — the City of Bellingham and Whatcom County — were required to develop and follow a plan to limit and reduce the amount of phosphorus entering the lake. This Total Maximum Daily Load (TMDL) is a measurable goal to hold the city and county accountable to reduce phosphorus by 2029. The Lake Whatcom Water and Sewer District is also contributing funds for tributary monitoring.

To mimic a forest

Urbanization, as indicated by water quality monitoring done by the Western Washington University Institute for Watershed Studies, is the greatest contributor of phosphorus in the lake, according to James Kardouni of the state Department of Ecology.

Updates as to how the county is meeting its goal will be presented at the Lake Whatcom Management Cooperative Management Program annual online meeting on March 23. The meeting will include a question-and-answer opportunity. 

“Development on the lake has to meet certain criteria, and the objective is to mimic a natural forest,” said Kardouni, who worked on the TMDL process. Ecology uses a model to predict what a natural forest would look like with absolutely no development. The goal, he said, is for 87% of the developed watershed to mimic a natural forest.

“If runoff is reduced to match forested conditions in 87% of the current developed area, Lake Whatcom will meet water quality standards for dissolved oxygen and phosphorus,” he said. 

Achieving the TMDL goal in phosphorus loading would allow the watershed to function as if only 2% of the drainage basin were developed.

In hard numbers, this means removing from runoff about 410 pounds of phosphorus per year over a 50-year period before it reaches the lake, per the TMDL. That was the plan’s original goal, but the city and the county will have an updated goal in 2023, depending on how much progress is being made.

A scene during construction of the Britton Road Retrofit project in the Silver Beach area, completed in 2010, shows infrastructure upgrades made to systems filtering runoff into the lake. (Photo courtesy City of Bellingham)

The 2020 Lake Whatcom Management Program reported that the amount of phosphorus entering the lake had been reduced by approximately 507 pounds per year.

Politics of protection

But development along the lake and in its drainage basin will continue and increased human activity will increase phosphorus loadings. The city and county have their own development codes which must be approved to meet the Department of Ecology’s TMDL standards, Kardouni said. “Ultimately, a lot of those decisions are not necessarily driven by science. It is interesting that development still occurs; it is certainly politically charged.”

There are three strategies to reduce phosphorus levels in the lake: technology, regulation and changing human behavior. Although phosphorus is problematic, Kardouni said that the city and county are doing their best to be proactive by improving stormwater treatment and homeowner incentive programs for residences on the lake.

County council member Todd Donovan said that the county could do more to decrease pollution by using county funds to acquire property in the watershed and reduce residential development. Around 40 houses per year are built in the drainage basin, but stopping development is not a simple process, he said. 

“It’s politically very fraught to down-zone places and basically tell people they have fewer development rights,” Donovan said. “This is county, and the county is not like the city in terms of people agreeing on progressive politics. It’s occasionally a conservative, pro-developer majority, or four-three [council vote] split. It would be very difficult to get four votes to say ‘no more lawns’ or ‘you can’t build a house’.”

The Britton Road stormwater treatment pond conversion project targets phosphorus and other pollutants. Reducing phosphorus entering the lake remains a high priority for maintaining lake water quality. (Photo courtesy City of Bellingham)

Donovan said that having a better understanding of how phosphorus gets into the water and why it pollutes the lake is the key to better water quality. 

“We are always looking forward to better data, and we’re spending a fair amount of money to better understand how [water pollution] works, and what is best to invest in for phosphorus reduction,” Donovan said. “We know more about our ability to actually calculate the benefits of a particular projects and how much they reduce.”

Acquistions and incentives

City of Bellingham efforts, said Clare Fogelsong, environmental policy manager, include taxpayer-funded property acquisitions and stormwater projects such as the Britton Pond retrofit and Park Place Stormwater Facility Rebuild to remove phosphorus. The city and the county together offer a Homeowner’s Incentive Program which reimburses residents who landscape with native grasses and plants and install underground pollution filters.

New projects like the Geneva Bioretention Pilot Program would improve water quality by using a newly developed soil to reduce phosphorus. Bioretention soil mixes, 60% sand and 40% compost, both filter stormwater and control water flow. Donovan said that the county has a five-year plan for projects like this and funding comes from the county’s stormwater utility and the countywide flood tax.

Monitoring by the Institute for Watershed Studies shows that chlorophyll, an indicator for algae growth, has been leveling off over time, but not decreasing, Fogelsong said. Polluted runoff is not easily addressed, he said, because Lake Whatcom has been a multipurpose watershed for the better part of a century, and it would be difficult to change that solely through government policies. 

“The potential development left is just a fraction of what has already occurred,” he said. “To stop development would be a real challenge and I’m not sure that we would move the dial of preventing phosphorus getting into the lake all that much.”

Residences already are built around the lake, said Fogelsong. According to the 2022 Lake Whatcom Watershed Build-out report, there are a total of 7,224 existing dwelling units, and many are on the shoreline.

“The challenge is how to have people understand their individual actions.,” said Fogelsong. To help them understand, the city provides best yard practice guidance and advises residents to avoid using fertilizers, pesticides and herbicides. The city has also prohibited use of phosphorus-containing fertilizers, mulches and soil amendments in the Lake Whatcom watershed.

Legacy impacts

Ander Russell, program director of local environmental group RE Sources, said that the issues plaguing Lake Whatcom extend beyond any single issue and will affect future generations.

“Actions taken create a legacy,” Russell said. “No matter how much good we’re doing now, whatever bad was done in the past, it has this legacy impact. We’re dealing with these legacy impacts [and they] create a lot of challenges for Lake Whatcom.”

The most pressing threat Lake Whatcom faces is not the substances in the water themselves, but the contributing factors which introduce them to the lake, Russell said.

“Whether we’re talking about a timber sale or we’re talking about aquatic invasive species, or we’re talking about protecting land, [we need to] really think about the whole suite of challenges facing the lake at any given time,” Russell said. “Those things need to be considered when we’re making decisions, certainly when we’re planning for future uses of the lake.”

Despite these concerns, Fogelsong still has hope. The flow of phosphorus into the lake for now isn’t getting worse. However, more people will bring more polluted runoff and the challenge will be to make the lake cleaner.

“I think we’re doing a good job,” he said. “I think we’ve identified the ways we can improve, and I think over time, we’ll turn this around.”

— Reported by Mallory Biggar

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