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King County Water Quality Monitoring

King County monitors the ecological health of the creeks on Vashon-Mary Island. Monthly water quality sampling on Vashon Island began in November 2006 at the seven stations listed below. Currently sampling continues at Judd and Gorsuch creeks.

Shinglemill Creek - Station VA12A is located just downstream of the SW Cedarhurst Rd crossing. Shinglemill Creek flows from Fisher Pond on the north side of Bank Road to where it empties into Fern Cove on the northwest corner of Vashon. Sampled from 2006-2012.

Christensen Creek - Station VA23A is located upstream of the mouth on private property just south of Lisabuela Park. Christensen Pond forms the headwaters of Christensen Creek, which flows into Colvos Passage. Sampled from 2006-2007.

Tahlequah Creek - Station VA37A is located just upstream of the SW Pohl Rd crossing near the Talequah Ferry Terminal. Sampled from 2006 - 2007.

Fisher Creek - Station VA41A is located just upstream of the Vashon HWY SW crossing between Shawnee RD and 115th Ave SW. Fisher Creek drains into the western shore of Quartermaster Harbor. Sampled from 2006 - 2012.

Judd Creek - Station VA42A is located upstream of the mouth at the SW 225th St crossing on private property. Judd Creek empties into the northwest end of Quartermaster Harbor. Sampled from 2006 - 2008 then resumed in 2013.

Mileta Creek - Station VA45A is located near the mouth, downstream of Dockton Rd SW just north of the intersection with 75th Ave SW. Mileta Creek empties into the northeast end Quartermaster Harbor. Sampled from 2006 -2012.

Gorsuch Creek - Station VA65A is located just upstream of the mouth on private property at the end of SW Gorsuch Rd on the northeast end of Vashon Island. Sampled from 2006 - 2008 then resumed in 2013.

Please see the links at the bottom of the page for additional information regarding resources and special studies taking place on Vashon-Maury Island.


Water Shed Image

Vashon-Maury Island encompass approximately 37 square miles of which 29.7 square miles are on Vashon Island and 7.0 square miles on Maury Island. The two islands are linked by an arrow isthmus and are not, therefore, truly independent islands. Vashon-Maury Island is bordered on the west by Colvos Passage from the Kitsap Peninsula, on the south by Dalco Passage from Tacoma, on the East by Puget Sound and King County, and on the north by Puget Sound. Vashon Island is about 13 miles long (north to south) and 4 miles across (east to west) in the widest areas. Maury Island is about 5 miles long (northeast to southwest) and about 1 mile across (northwest to southeast).

The topography of Vashon-Maury Island varies from sea level to elevations in excess of 460 feet based on U.S. Geological Survey topographic maps. New LiDAR (Light Detecting And Ranging) data has improved the accuracy of the surface topography data. The maximum elevation on the Island is just over 500 feet at Maury Island Marine Park. The shoreline extent of Vashon-Maury Island is just over 58 miles most of which lies beneath steep, slide-prone slopes. The Island has numerous (>70) stream basins and two of these are larger with subbasins, Judd Creek and Shinglemill Creek. All of these stream basins drain into Puget Sound.

All of Vashon-Maury Island is designated as rural and as such is outside the urban growth boundary. Low-density residential development covers much of the Island with zoning of one home per five and ten acres. Higher density residential areas are concentrated in the Vashon Town Center, Vashon Heights, Burton, Dockton, and along parts of the shoreline. Multifamily, commercial and industrial uses are presently concentrated in the unincorporated town of Vashon and adjacent areas where sewer and other urban services are available. The predominant land covers for Vashon-Maury Island are forested areas. The percentage of forested land is ~73 percent when compiled into three broad categories of forest, non-forest and developed land. The other two categories, non-forest and developed land, have percentages of 16 percent and 11 percent respectively (King County 2005).


With funding from the Vashon/Maury Island Audubon Society, the Trout and Salmon Foundation, the General Service Foundation, and King County Department of Natural Resources, Washington Trout performed a comprehensive water-typing survey on Vashon Island in 2000 and 2001 to ensure that the trout and salmon streams receive the maximum legal protections available in the face of growing development (Washington Trout, 2001 ). During the survey Washington Trout found direct evidence of coho salmon in at least two streams, Shinglemill Creek and Baldwin Creek, and substantial use by sea-run cutthroat trout throughout the island's streams. Washington Department of Fish and Wildlife records indicate that coho and chum salmon (O. keta) have historically used several other island streams. Volunteers with the Salmon Watcher Program have reported seeing coho and chum salmon, and cutthroat trout in both Fisher and Judd creeks.

Water Quality

p>Water quality samples are analyzed monthly for temperature, dissolved oxygen, pH, conductivity, turbidity, total suspended solids, ortho-phosphorus, total phosphorus, ammonia, nitrate-nitrogen, total nitrogen, and fecal coliform bacteria. Results are compared to State water quality standards. Water quality standards are designed to protect public health and aquatic life. Comparing monitoring results to water quality standards allows an understanding of how safe the creek is for recreational contact as well as for aquatic life.

State water quality standards were revised in 2003. Vashon-Maury Island creeks are now categorized as "Core Summer Salmonid Habitat" for aquatic life use and "Extraordinary Primary Contact Recreation" for recreational use because these streams are tributaries to extraordinary quality marine waters (WAC 173-201A-610 through 173-201A-612 ). Fisher, Judd, Shinglemill, and Tahlequah creeks all are listed on on the Washington Department of Ecology’s (Ecology) 303(d) list, Category 5, for violations of stream temperature standards. See Table 1 for a summary statistics for the routine water quality data collected at this site to date.

Water Quality Index

A Water Quality Index (WQI) rating system was developed by the State Department of Ecology that evaluates several water quality parameters and gives and overall rating of “high,” “moderate,” or “low” concern. To view WQI scores for the stations located on Vashon Island, visit the Water Quality Index page. You can also access site specific WQI reports from the Streams List or the Water Quality Index links on the left.

Table 1. Routine monitoring summary statistics for this station from 2006 to 2018
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)14411.
Temperature (°C)1449.20.416.29.43.2
Turbidity (NTU)1436.230.97153.002.8414.54
Conductivity (mSIEMS/cm)144131.959.1180.0134.028.8
Total Suspended Solids (mg/L)14415.431.10488.004.6050.94
Ortho-Phosphorus (mg/L)1440.02390.00710.05450.02110.0099
Total Phosphorus (mg/L)1430.05050.02230.33000.04340.0400
Ammonia (mg/L)1440.01180.00310.02870.01110.0048
Nitrate (mg/L)1440.93100.47901.96000.90600.2164
Total Nitrogen (mg/L)1431.25420.79003.29001.16000.3454
Fecal Coliform(CFU/100ML)1443551110000701070


King County maintains numerous gauges on Vashon-Maury Island:

Stream Continuous Sites: Judd Creek (28A); Shingle Mill Creek (43A); Tahlequah Creek (65A); Fisher Creek (65B); Green Valley Creek (65C) and McCormick Creek (17A).

Stream Stage/Crest sites: Robinwood Creek (VA20); Christensen Creek (VA23); Bates Creek (VA30); Tsugwalla Creek (VA43); Raab's Creek(VA44); Mileta Creek (VA45); Ellis Creek(VA62); Ellisport Creek (VA63); Beall Creek (VA64); Gorsuch Creek (VA65); Dilworth Creek (VA66); Glen Acre Creek (VA67).

Precipitation sites: West Judd Ck (28Y); Maury Island (36U); East Maury Island (36V); North Vashon (43U); South Vashon (65U).

Benthic Invertebrates

The County also monitors stream health by collecting samples of benthic invertebrates from selected streams as part of King County's Benthic Invertebrate Program. Benthic invertebrates are an important link in the food chain for fish in the creek and are an excellent indicator of stream health. Selected creeks were sampled in 2001. Benthic invertebrate samples have been collected at several sites on the island.

Special Studies

Vashon-Maury Island Water Resources Evaluation

The Vashon-Maury Island Water Resources Evaluation (WRE) is a project designed to describe and assess the water resources of the island. This project will provide a better understanding of how different activities can adversely affect the island's water quality and quantity and lead to an updated, more accurate water supply budget for the island.

Vashon-Maury Island is part of the Central Puget Sound Watershed. For more information about this watershed please visit the Vashon-Maury Island watershed home page