Water Quality Improvement Projects (TMDLs) > WRIA 9 > Green River and Newaukum Creek Multi-parameter Project

Water Quality Improvement Project
Green River and Newaukum Creek Area:
Multi-parameter

Introduction

Located in western Washington State, the Green River basin drains about 484 square miles of land area and includes portions of King County and the cities of Auburn, Black Diamond, Covington, Enumclaw, Kent, Maple Valley, Renton, Sea-Tac, and Tukwila. It flows for over 93 miles from the Cascade Mountains to Elliott Bay. Major streams draining to the Green River include Newaukum, Soos, Springbrook, and Mill Creeks.

Newaukum Creek is one of two major subbasins targeted for their own TMDL studies on temperature and dissolved oxygen. Newaukum Creek is a tributary to the Green River. Newaukum Creek runs about 14 miles from its headwaters (3,000 ft above sea level) to the confluence with the Green River near river mile 40.7 (180 ft. above sea level). (See Study Area map)

Land use in the study area varies considerably from a mix of residential, commercial forestry and agricultural land uses around the Middle Green River, to residential, industrial, and commercial land uses near the Lower Green River.

Water quality issues

Portions of the Green River and Newaukum Creek exhibit unhealthy temperature and oxygen conditions that cause them to fail to meet Washington State water quality standards. Fish breathe oxygen in the water (dissolved oxygen). Cooler water holds more oxygen. Warmer water results in less oxygen for fish and other aquatic organisms. When water has too little oxygen or its temperature is too warm, local fish can face thermal stress and harm. These streams serve as important migration corridors and spawning and rearing areas for several salmon species, including Puget Sound Chinook; bull trout; coho; chum; pink; sockeye; kokanee; steelhead/rainbow, and cutthroat trout. These species all need cold waters for optimum health during various stages of their lives.

Status of the projects

To address the water quality issues, in 2006 Ecology initiated water quality improvement (also known as total maximum daily load, or TMDL) projects for temperature and dissolved oxygen in the Green River and Newaukum Creek. Ecology, King County, and others cooperated in a summer field study to collect data for the temperature and dissolved oxygen TMDL studies.

As part of the TMDL study, Ecology identified the pollution problems and specified how much pollution needs to be reduced to achieve clean water. As a follow-up to the TMDL study, Ecology works with the local community to prepare a water quality implementation plan (WQIP) that details the specific actions needed to improve water quality in the basin. The plan describes management roles, activities, and schedules for partners.

Many local partners are involved in this effort, including the Muckleshoot Indian Tribe, King County, U.S. Army Corps of Engineers, State Department of Agriculture, Tacoma Public Utilities, and the cities of Auburn, Black Diamond, Kent, Tukwila, Renton, Covington, Maple Valley, Enumclaw, and others. Volunteer groups, such as Middle Green River Coalition and Midsound Fisheries Enhancement Group, watershed residents, and local businesses also play important roles in improving water quality.

Green River

Ecology developed a water quality improvement report (WQIR, also known as a TMDL) to address water temperature issues in the Green River. The WQIR consists of the results and recommendations of a TMDL study on the Green River and an implementation strategy to determine what needs to be done, and who will carry out the recommendations, to bring the water temperature to meet state water quality standards. The report is a major step toward adopting a water-quality improvement plan for the Green River basin from Tukwila and Renton to just below the Howard Hanson Dam in eastern King County.

The TMDL study focuses on the Middle-Lower Green River which flows about 54 miles from the outlet of the Howard Hanson Dam to the confluence with the Duwamish Waterway at river mile 11 in the city of Tukwila. According to the study, the Green River and its tributaries need tree shade to keep their waters from over-warming during the late summer and early fall. The study predicts that stream temperatures in creeks and parts of the Green River above Auburn can improve over time using current and proposed city and county critical areas ordinances and shoreline master programs, which promote preservation and restoration of streamside vegetation. Assistance from public and private streamside improvement projects will also encourage streamside vegetation and help keep water temperatures cool.

Part of Ecology’s study includes a proposal to implement strategies to protect water from warming in Newaukum Creek, one of Green River sub-basins, which includes the northern part of Enumclaw and surrounding areas.

Newaukum Creek

Ecology developed a WQIR to address water temperature issues in Newaukum Creek Basin. Newaukum Creek Basin includes 27.5 miles of stream length that contributes important cold water fish habitat to the Green River system. Newaukum Creek begins in the Cascade foothills and the mainstem flows about 14 miles from its headwaters into the Green River at river mile 40.7. The Newaukum Creek WQIR consists of the results and recommendations of the TMDL modeling study conducted on Newaukum Creek, and an implementation plan to determine what needs to be done, and who will carry out the recommendations to bring the water temperature to meet state water quality standards.

According to the Newaukum Creek modeling work, Newaukum Creek and its tributaries need additional tree shade to keep their waters from over-warming during the late summer and early fall. The study predicts that stream temperatures in some stream reaches, and especially parts of Newaukum Creek on the Enumclaw Plateau, can improve over time with riparian restoration which provides shade to the stream. Riparian projects may be initiated using current and proposed city and county critical areas ordinances and shoreline master programs, which promote preservation and restoration of streamside vegetation. King County Department of Natural Resources has ongoing riparian restoration projects in Newaukum Basin, and the temperature TMDL should help provide a basis for additional work. Assistance from public and private streamside improvement projects will also encourage streamside vegetation and help keep water temperatures cool.

Green River and Newaukum Creek TMDL Project Timeline

Technical information

Unless otherwise specified, the following documents are Ecology publications.

Green River Temperature Total Maximum Daily Load: Water Quality Improvement Report
https://fortress.wa.gov/ecy/publications/SummaryPages/1110046.html

Newaukum Creek Temperature Total Maximum Daily Load: Water Quality Improvement Report and Implementation Plan
https://fortress.wa.gov/ecy/publications/SummaryPages/1110047.html

Quality Assurance Project Plan for the Temperature and Dissolved Oxygen TMDL in the Green River and Newaukum Creek
https://fortress.wa.gov/ecy/publications/SummaryPages/0603110.html

Green River and Newaukum Creek Temperature and Dissolved Oxygen Total Maximum Daily Load Study: Data Summary Report
https://fortress.wa.gov/ecy/publications/SummaryPages/0703001.html

Related information

Unless otherwise specified, the following documents are Ecology publications.

Focus on temperature and dissolved oxygen in the Green River and Newaukum Creek
https://fortress.wa.gov/ecy/publications/SummaryPages/0610061.html

WRIA 9: Duwamish-Green Watershed Information (Environmental Assessment Program web site)
www.ecy.wa.gov/apps/watersheds/wriapages/09.html

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