Lake Ketchum Restoration

newburstgold50_png Public Hearing on Lake Ketchum Restoration Service Charge

Public Hearing for Proposed Lake Ketchum Restoration Service Charge

In person or Online via Zoom

Wednesday, August 16th at 10:30 AM

In Person:

8th Floor Henry M. Jackson Room

Drewel Building (Administration East)

3000 Rockefeller Avenue

Everett, Washington 98201


Zoom Webinar Link:

Dial in: (253) 215 8782 or (301) 715 8592

Meeting ID: 948 4685 0772

The Snohomish County Council will hold a PUBLIC HEARING on Ordinance No. 23-072 that would renew a service charge on properties around Lake Ketchum for the purpose of managing and controlling blue-green and toxic algae blooms and phosphorus pollution in Lake Ketchum.

If approved, the service charge would be changed as follows:

Rate Category

Annual Service Charge

Lake Front

((170.00)) $200.00 per parcel of real property abutting the shoreline of Lake Ketchum

Shared Lakefront

(($35.00)) $40.00 per parcel of real property with an undivided ownership interest in lake front real property used for common beach access

View included parcels on the interactive Ketchum Service Charge Area Map and read the notification letter and FAQ mailed to affected ratepayers.

The County Council will take public testimony on the proposed service charges at the hearing on August 16th.  You can review the draft ordinance on the Council’s web site at by choosing the “Public Hearings/Meetings Calendar” and then clicking on the ordinance listed for the August 16th public hearing date.  

The funding proposal put forth in this ordinance was brought forward by the Lake Ketchum Shores Improvement Club. In their spring 2023 meeting, the club voted on the proposed fees. The vote was unanimous with 18 members in attendance. 

Read below to learn more about the history of the project, its impact on the lake and more detailed costs and funding information.

Lake Ketchum is a 26-acre public lake located in northwest Snohomish County two miles north of the City of Stanwood. The lake supports swimming, fishing, boating, aesthetic enjoyment, and wildlife habitat. Historically, it was the drinking water supply for the City of Stanwood.

However, for many years, Lake Ketchum suffered from thick growths of blue-green algae. These algae blooms formed unsightly scums on the lake surface that severely impaired use and enjoyment of the lake. The algae blooms, caused by too much phosphorus in the lake, were also frequently toxic, threatening the health of people and pets that used the lake.

Through an ongoing collaboration between Snohomish County and the Lake Ketchum community, the lake water quality has been successfully restored. Specifically, phosphorus levels have dramatically decreased, algae growth has been substantially reduced, and the water is significantly clearer. The Lake is once again healthy allowing people to swim, play, and boat in the lake and are evident for all to see. However, additional action is needed each year to ensure that Lake Ketchum remains healthy.

The Cause of the Water Quality Problems

The Lake Ketchum water quality problems are caused by high levels of phosphorus. Phosphorus is the key nutrient that feeds algae growth. Prior to restoration, phosphorus levels in the lake were 13 times higher than the actions values the state has set causing Lake Ketchum to be listed as impaired by the state under the clean water act. 

An initial study in 1997 recommended actions to restore the lake, but lack of funding prevented clean-up. From 2010-2012, Surface Water Management conducted a new study to find the main pollution sources and identify options for cleaning up the lake. This study found that the main phosphorus sources in Lake Ketchum were:

  • Lake Inlet - 23% The lake inlet drains a former dairy farm. The soils on the dairy farm are overloaded with phosphorus and are the original source of much of the pollution now in the lake.
  • Lake Sediments - 73% Phosphorus has accumulated in the lake bottom sediments for decades. Each year this phosphorus is released back into the lake and fuels the growth of algae.
  • Other - 4% The remaining phosphorus comes from residential sources such as septic systems, pet wastes, and fertilizers, and from rain and groundwater.

Phosphorus Sources

The Algae Control Plan

Using the results of the 2010-2012 study, Surface Water Management and lake residents developed the Lake Ketchum Algae Control Plan. The plan identified five actions to clean up and protect Lake Ketchum:


The most critical item of the restoration plan was an initial large-scale alum treatment followed by smaller annual maintenance alum treatments. Alum treatments are the most successful method used around the world for controlling phosphorus in lakes because: 

  • Alum permanently binds phosphorus in the water and sediments so that it is no longer available to grow algae.
  • Alum is a non-toxic material commonly used in drinking water treatment plants to clarify water.
  • Alum has no lasting negative impacts to the lake or aquatic wildlife.

Initial Large-Scale Alum Treatments

A large-scale alum treatment was performed in May 2014. Contractors applied over 13,400 gallons of liquid aluminum sulfate and 7,400 gallons of sodium aluminate (a pH buffer). The dose was calculated to remove phosphorus from the water column and inactivate the majority of the phosphorus stored in the lake sediments. Unfortunately, the alum treatment had to be stopped prior to completion due to complications that led to a small fish kill.

A second large alum treatment was completed in March 2015. This treatment involved another 13,000 gallons of aluminum sulfate and 8,100 gallons of sodium aluminate. To prevent the same problems faced in 2014, the contractor improved the method of mixing the two chemicals in the water and the treatment was performed earlier in the year prior to the onset of algal blooms. The 2015 treatment was successfully completed with no complications to fish.

Annual Maintenance Alum Treatments 

Small annual maintenance alum treatments occur at Lake Ketchum each spring starting in 2016. The purpose of these treatments is to inactivate the large amount of phosphorus that still flows in from the lake's inlet during the rainy winter months. The treatments also bind phosphorus remaining in the lake sediments. The continuation of small-scale treatments are essential to the long-term success of the project.

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Water Quality Results

Water quality has improved dramatically at Lake Ketchum. Total phosphorus concentrations in the lake have dropped by 95% in the upper waters and by 98% in the bottom waters. This means that the phosphorus being released from the lake sediments, the main source of pollution, was essentially eliminated.

The decrease in phosphorus has corresponded to a significant decrease in algae and potentially toxic algae blooms. Summer levels of algae (as measured by chlorophyll a) have dropped over 85%. There has also been a corresponding six foot increase in average water clarity. There has been only one bloom of potentially toxic algae. It occurred in the in the spring of 2020 and occurred just before the annual alum treatment which was delayed due to COVID. 

Lake Ketchum Phosphorus in Upper Waters Graph

Total phosphorus in the upper waters summer average in micrograms per liter (ug/L). The 2021 summer average was 11 ug/L.

Total phosphorus in the bottom waters summer average in micrograms per liter (ug/L). The 2021 summer average was 18 ug/L.

Lake Ketchum Phosphorus in Bottom Waters Graph
Lake Ketchum Water Clarity Graph

The Lake Ketchum water clarity summer average in meters. The 2021 summer average was 5.3 meters or 17.3 feet. 

Chlorophyll a (measure of algae) summer average in micrograms per liter (ug/L). The 2021 summer average was 2 ug/L.

Lake Ketchum Chlorophyll a Summer Averages Graph

Ongoing Restoration Actions

The remaining elements of the Algae Control Plan are on-going. These include lake monitoring, wetland protection, and reductions in pollution from properties around the lake. To help landowners identify important actions they can take to prevent phosphorus pollution, everyone living in the area that drains Lake Ketchum is invited to participate in the County’s LakeWise program. It is a voluntary program where landowners can be recognized for making small changes on their property to reduce phosphorus coming from their homes and yards. The program focuses on reducing pollution from fertilizers, pet waste, septic systems, and runoff from roofs and driveways. Learn more at

LakeWise Logo
Swimming in Ketchum - July 2015

Project Funding

The 2014 and 2015 alum treatments cost a total of approximately $250,000. The original project planning and initial treatments were funded by:

  • Lake Ketchum area landowners
  • Snohomish County Surface Water Management
  • A grant from the Snohomish County Stillaguamish Clean Water District
  • A grant from the State of Washington's Department of Ecology

Since the initial treatment, funding has come from the Lake Ketchum Area Landowners and Snohomish County Surface Water Management. The 2016-2020 cost of the project, including the annual alum treatments, was fairly stable and ranged between $40,000 - $50,000. Since 2021, the costs have continued to increase due to rising and unpredictable costs of aluminum, higher transportation costs and inflation. (see figures below).

The proposed service charge which includes increased contributions from KSIC and Surface Water Management will support the restoration project for the next five years.

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Lake Ketchum Costs per Type

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Lake Ketchum Funding by Source