Water Quality Improvement Projects
Stillaguamish Basin

North Fork Stillaguamish River, Washington State.  Photograph courtesy of Steve Hirshey.

© Steve Hirshey.

Introduction

The Stillaguamish River watershed is located in western Washington State. Located in northern Snohomish and southeastern Skagit Counties, the Stillaguamish is the fifth largest watershed draining to Puget Sound. Its headwaters originate in the Cascade Mountains and flow westerly to Puget Sound. A small portion of the basin travels to Skagit Bay through the Old Stillaguamish Channel. The watershed covers 683 square miles and provides numerous recreational opportunities including fishing, swimming, and boating.

The Stillaguamish watershed is home to nearly all salmon and trout species found in the Puget Sound area, with 870 miles of anadromous salmon habitat. The watershed is also heavily used for recreation and agriculture. Fishing, recreational boating, swimming, and tubing are popular activities. Ranchers and farmers depend on clean water from the watershed to raise livestock and grow safe and healthy food.

Water quality issues

In many respects water quality is good in the Stillaguamish watershed. However, there are several areas that need improvement: bacteria levels and water temperatures are too high at times, and dissolved oxygen levels are too low in some areas. Bacteria levels in the North and South Forks look good, but are too high in many tributary streams. Water temperatures throughout the watershed are much too high during the summer—the removal of trees and other modifications to the land have made the watershed a much less hospitable place for cold-water fish to live. Low oxygen levels occur in some key pool areas in the mainstem river during parts of the summer where fish tend to congregate. Mercury and pH levels exceed state standards at certain times. Mercury levels are related to natural sources, not industrial byproducts. Ecology expects pH levels to improve as part of efforts to increase dissolved oxygen levels and reduce water temperatures.

Why this matters

Fecal coliform is a type of “bacteria” common in human and animal waste. It indicates that sewage or manure is entering a water body. As the level of fecal coliform increases the risk of people getting sick from playing or working in the water increases. Bacteria can get into our waters from untreated or partially treated discharges from wastewater treatment plants, from improperly functioning septic systems, and from livestock, pets and wildlife. Excessive bacteria levels in freshwaters increases the risk that shellfish in Port Susan and South Skagit Bay will be unsafe for human consumption.

People can help keep bacteria out of the water. Properly collect, bag, and trash dog poop. Check your on-site sewage system to make sure it is maintained and working properly. Ensure livestock and manure are kept away from the water.

Excessive mercury levels can affect both humans and aquatic life. Mercury levels only exceeded chronic aquatic life criteria during two high-flow events and were related to the level of suspended solids in the water. Mercury levels would need to remain at these high levels for an extended period to cause harm to fish. Fisheries enhancement work being done in the Stillaguamish watershed includes efforts to control sediment discharges, which should reduce mercury levels.

Oxygen dissolved in healthy water is vital for fish and aquatic life to “breathe” to survive. It is more difficult to transfer oxygen from water to blood than it is to transfer oxygen from air to blood. Therefore, it is critical that an adequate amount of oxygen is maintained in the water for this transfer to take place efficiently and sustain aquatic life. Oxygen is also necessary to help decompose organic matter in the water and bottom sediments as well as for other biological and chemical processes.

pH is a measure of how acidic or alkaline the water is. The pH is measured on a scale of 0-14. A pH of 7 is neutral. The lower the number the more acidic the conditions; the higher the number, the more alkaline the conditions. Optimal pH levels to support fish and wildlife should range from 6.5 to 9.0.

pH can affect the solubility of nutrients and metal compounds. By affecting the solubility of nutrients, it can change the amount of nutrients available for plant growth. If too many nutrients are available, aquatic plants can grow out of control. When these plants decompose, they can deplete the water of oxygen. The solubility of many metal compounds also changes greatly with pH. Generally, a reduction in pH (more acidic) increases the solubility of heavy metals. When more metals are dissolved in the water, aquatic animals may absorb them faster. Therefore, a lower pH (more acidic) may make these metals more toxic to aquatic life.

Water temperature influences what types of organisms can live in a water body. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Many fish need cold, clean water to survive.

One way to cool water temperature is to shade the water body by adding or retaining streamside vegetation.

Status of the projects

Temperature

Ecology finalized the Stillaguamish River Watershed Temperature TMDL in July 2006. Our study documented high water temperatures throughout the watershed and pointed out the warmest areas of the watershed. We completed the implementation plan for this TMDL in June 2007.

Currently, the salmon recovery resources of the Stillaguamish Tribe, Snohomish County, Sound Salmon Solutions, Snohomish Conservation District, and the city of Arlington are working to reduce water temperatures in the basin. You can learn more by reading the implementation plan at the link in the Technical Information section.

Fecal coliform, dissolved oxygen, pH, and mercury

We finalized the Stillaguamish River Watershed Fecal Coliform, Dissolved Oxygen, pH, Mercury, and Arsenic TMDL in April 2005. Our study documented high bacteria concentrations and low dissolved oxygen levels in the watershed. The implementation plan for this TMDL was completed in June 2007. Currently, the salmon recovery resources of the Stillaguamish Tribe, Snohomish County, Sound Salmon Solutions, Snohomish Conservation District, and the city of Arlington are working to improve water quality as part of salmon recovery and stormwater management activities. You can learn more by reading the implementation plan at the link in the Technical Information section. The Stillaguamish River Clean Water District is the lead organization overseeing and helping to coordinate activities to reduce bacterial pollution and protect shellfish resources in Port Susan and portions of South Skagit Bay.

Old Stillaguamish Channel Dissolved Oxygen Study

Ecology initiated the Old Stillaguamish River Channel (OSRC) TMDL study in 2006 to evaluate dissolved oxygen levels in the river and recommend wasteload allocations and load allocations for pollutant sources that are contributing to dissolved oxygen problems. Critical conditions for dissolved oxygen (DO) in the OSRC were believed to occur in the late summer. Ecology collected field data then contracted out the computer modeling for this project to Battelle Pacific Northwest National Laboratory. Unanticipated sources of oxygen demand were encountered making accurate modeling impossible. At this time, this TMDL project is on permanent hold. Ecology is awaiting better marine monitoring models, expected to be available in near future, as well as better information on benthic DO demand in the area. Implementation of the existing Stillaguamish TMDLs is expected to help the existing DO problems in the interim period.

City of Arlington pet waste station, Washington State.  Photograph courtesy of Ralph Svrjcek, WA Department of Ecology.

Technical information

Unless stated otherwise, the following are Ecology publications.

Temperature

Stillaguamish River Watershed Temperature TMDL Study
This is the study to accompany the Implementation Strategy (06-10-057).
https://fortress.wa.gov/ecy/publications/SummaryPages/0403010.html

Stillaguamish River Watershed Temperature Total Maximum Daily Load: Water Quality Improvement Report -- Vol. 2: Implementation Strategy
https://fortress.wa.gov/ecy/publications/SummaryPages/0610057.html

Fecal coliform, dissolved oxygen, pH, and mercury

Data Summary: Fecal Coliform, Dissolved Oxygen, pH, Mercury, and Arsenic Total Maximum Daily Load Study
https://fortress.wa.gov/ecy/publications/SummaryPages/0403037.html

Stillaguamish River Watershed Fecal Coliform, Dissolved Oxygen, pH, Mercury, and Arsenic Total Maximum Daily Load Study
https://fortress.wa.gov/ecy/publications/SummaryPages/0403017.html

Stillaguamish River Watershed Fecal Coliform, Dissolved Oxygen, pH, Arsenic, and Mercury Total Maximum Daily Load (Water Cleanup Plan) - Submittal Report
https://fortress.wa.gov/ecy/publications/SummaryPages/0510044.html

Quality Assurance Project Plan: Old Stillaguamish River Multi-Parameter Total Maximum Daily Load Study
https://fortress.wa.gov/ecy/publications/SummaryPages/0603108.html

Stillaguamish River Fecal Coliform, Dissolved Oxygen, pH, Mercury, and Temperature Total Maximum Daily Load: Water Quality Implementation Plan
https://fortress.wa.gov/ecy/publications/SummaryPages/0710033.html

Related information

Unless stated otherwise, the following are Ecology publications.

Focus on Water Quality Cleanup Plan for Port Susan and Stillaguamish Watershed
https://fortress.wa.gov/ecy/publications/SummaryPages/0410085.html

Focus on Next Steps to Improve Water Quality in the Stillaguamish Watershed and Port Susan
https://fortress.wa.gov/ecy/publications/SummaryPages/0710035.html

Snohomish County NPDES Stormwater Permit Bacteria Pollution Control Plan (Snohomish County website)
www1.co.snohomish.wa.us/Departments/Public_Works/Services/NPDES/npdesbacteria.htm

Snohomish County Water Quality Monitoring Information
https://fortress.wa.gov/ecy/eimreporting/Detail/Detail.aspx?DetailType=Study&SystemStudyId=66789673

Reporting Water Pollution Problems in the city of Arlington:

The city of Arlington Storm Water Department, in accordance with the Department of Ecology Phase II Stormwater permit, has set up a 24-hour hotline (360-403-4600) for reporting discharges and spills such as paint, small fuel or oil spills, illegal dumping, muddy water being discharged into the City's storm system, and other non-emergency situations. The hotline is set up to be responded to during working hours. All emergencies are to go through the 911 system.

Reporting Water Pollution Problems in Snohomish County (Snohomish County website)
http://www1.co.snohomish.wa.us/Departments/Public_Works/Divisions/SWM/WQ/ReportWaterPollution.htm

WRIA 5: Stillaguamish River Watershed Information (Water web site)
www.ecy.wa.gov/water/wria/05.html

Stillaguamish Watershed Salmon Recovery Planning: (Snohomish County website)
www1.co.snohomish.wa.us/Departments/Public_Works/Divisions/SWM/S/Default.htm

Skagit Bay Fecal Coliform Bacteria Loading Assessment
https://fortress.wa.gov/ecy/publications/SummaryPages/1203035.html

 

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Last updated December 2013
  Water resource inventory area (WRIA) 5 map, Washington State.

PROJECT INFO

Location:
WRIA(s): #5 (Stillaguamish)
Counties:
Skagit
Snohomish

Water-body Name:
Stillaguamish River watershed

Parameters:
Dissolved oxygen
Fecal coliform bacteria
Mercury
pH
Temperature

# of TMDLs:
DO, FC, Mercury, pH - 46
Temperature - 10

Status:
DO, FC, Mercury, pH - approved by EPA
Temperature - approved by EPA
Has a multi-parameter implementation plan

Contact Info:
Ralph Svrjcek
Phone: 425-649-7165
Email: Ralph.Svrjcek@ecy.wa.gov

Northwest Region
Department of Ecology
3190 - 160th Ave. SE
Bellevue, WA 98008-5452