King County logo

King County Water Quality Monitoring

King County monitors the ecological health of the Pipers Creek basin in a variety of ways, including collecting and analyzing water and benthic macroinvertebrate samples. Station KSHZ06 is located at the mouth of the creek, which is upstream of the railroad tracks before entering the beach area. Water quality sampling at this site began in 1988 and continues today. Station KTHA02 is located just above the confluence of Venema Creek with Pipers Creek. Station KTHA03 is located at the mouth of Venema Creek. Regular water quality sampling at both KTHA02 and KTHA03 began in 1988, and both were discontinued from 2008 to 2013 due to budget restrictions. Monthly sampling resumed again at KTHA03 in 2013 and KTHA02 in 2014. Bacteria has been sampled at Station KTHA01, located upstream of the Carkeek Park treatment facility, since the 1970s. KTHA01 became part of the routine stream monitoring program in 2016. King County began collecting benthic macroinvertebrate samples from in 2010 (though regular sampling will likely decrease in the future).

From time to time, additional studies are conducted on Pipers Creek. Click here for information about Special Studies.


Water Shed Image

The Pipers Creek watershed is highly urbanized with a total drainage area of roughly 1,835 acres (Kerwin, 2002). The creek and tributaries flow in a northeasterly direction, for combined total length of approximately 5.0 miles, before draining into the Puget Sound estuary at the City of Seattle, Washington's Carkeek Park Beach.

Land use in the Pipers Creek basin is mostly developed. Most of the development is low to medium intensity. The upper portion of the watershed is occupied primarily by single-family residences with some small businesses and multifamily housing (Kerwin, 2002). The upper watershed makes up roughly 80% of the Pipers Creek drainage area. Most of the creek runs within the boundary of Carkeek Park in the lower 20% of the watershed. Steep ravines, covered with second growth forest, characterize the park. There is relatively little forest and wetlands and no agriculture or scrub. See Table 1 below for more details on land use.

Table 1. Total land use in the basin

Developed Forest Scrub
Total 87% 10% 3%

For more information about the City of Seattle's Carkeek Park, please visit theSeattle Parks and Recreation webpage.


Chum salmon, coho salmon, rainbow trout, and coastal cutthroat are known species to inhabit the Pipers Creek (Kerwin, 2002). Historically, Pipers Creek and its tributaries had runs of summer/winter steelhead, coastal cutthroat, coho, and chum. The Carkeek Watershed Community Action Project has released coho (1980 - 83) and chum (1984 - present) each spring.

From 1999 to 2015, volunteers with the Salmon Watcher Program have been making observations at various locations in the watershed. Volunteers in Pipers Creek have consistently seen chum and coho salmon. Less commonly spotted are cutthroat trout.

Water Quality

Water quality samples are analyzed monthly for temperature, dissolved oxygen (DO), pH, conductivity, turbidity, total suspended solids, ortho-phosphorus, total phosphorus, ammonia, nitrate-nitrogen, total nitrogen, and fecal coliform (FC) 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 (see link at top of page to view current water data).

State water quality standards were revised in 2003. Piper Creek is now categorized as "Core Summer Salmonid Habitat" for aquatic life use and "Extraordinary Contact" for recreational use. As part of the updated water quality standards, portions of Pipers Creek have been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 16 °C. The creek is on the Washington State Department of Ecology's (Ecology) 303(d) list for violation of DO (Category 5). The creek also has an EPA-approved Pipers Creek Bacteria total maximum daily load (TMDL) plan in place and implemented for FC bacteria (Category 4a).

Occasional water quality problems occur as a result of the shifting hillsides due to steepness of the slopes in the park. Over time, these shifts have caused leaks in the sewer lines. In April 2000, there was a small leak from a Seattle Public Utilities (SPU) sewer pipe (that eventually hooks up with the King County trunk line) just above the Carkeek Stormwater Facility. A similar incident occurred again in March 2002.

A larger sewage leak occurred from September 29 - October 4, 2001 when an estimated 2.0 million gallons of wastewater discharged to Puget Sound from the North Beach Forcemain. This break in the line occurred in Carkeek Park where an abandoned SPU line had recently been capped. The County discharged through the North Beach emergency outfall during the repair work rather than have the discharge continue along the shoreline in the park. Because the pipeline was very near the railline, it is believed that vibrations from train activity caused a large rock positioned under the pipe to eventually cause the break. Exceedance of FC bacteria limits continues to be problematic in the creek as noted above.

See Table 2 below for routine monitoring summary statistics of water quality data collected to date. If stormwater data is available for this site, it will be shown as Table 3. Historical data reviews can be found in the annual reports produced by METRO/King County DNRP.

To view charts of current water quality data, please visit the Data Download webpage.

Water Quality Index

A Water Quality Index (WQI) rating system was developed by Ecology that evaluates several water quality parameters and gives a single rating of “high,” “moderate,” or “low” water quality concern. To see how these ratings compare with other stream sites, please visit the Water Quality Index webpage.

Table 1. Routine monitoring summary statistics for this station from 1987 to 2024
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)26310.87.012.610.80.7
Temperature (°C)38410.72.015.611.02.6
Turbidity (NTU)3624.580.2098.702.0110.00
Conductivity (mSIEMS/cm)231252.4123.0348.2263.033.6
Total Suspended Solids (mg/L)3639.860.50276.003.6026.66
Ortho-Phosphorus (mg/L)3670.05530.01060.16400.05540.0144
Total Phosphorus (mg/L)3680.08000.01800.52700.07320.0366
Ammonia (mg/L)3680.02610.00290.31300.01300.0438
Nitrate (mg/L)3671.51840.55302.88001.51000.2917
Total Nitrogen (mg/L)3161.74631.05003.50001.70500.2873
Fecal Coliform(CFU/100ML)3537676370001303012


King County is not currently operating any stream, rain, or temperature gages in Pipers Creek. However, Seattle Public Utilities is operating a stream gage at Carkeek Park (SPU_STA508).

Stream Sediment

Benthic Invertebrates

Benthic macroinvertebrates are small animals visible to the naked eye (macro) that lack a backbone (invertebrate) and live in or around the streambed (benthic). This group includes aquatic insects (such as mayflies and dragonflies), crustaceans, clams, snails, and worms. Benthic macroinvertebrates are of interest to scientists and water resource managers because they are an excellent indicator of the biological health of stream ecosystems and are a critical component of the food web in aquatic communities. Scientists quantify the composition and diversity of benthic macroinvertebrate populations in a stream to compare the biologic integrity of different streams. King County has utilized benthic macroinvertebrate sampling to assess biological health of numerous creeks across the county (see map).

For more information about benthic macroinvertebrates and King County’s Benthic Macroinvertebrate Program, please visit the King County Stream Bug Monitoring webpage. To see the benthic macroinvertebrate data for Pipers Creek, please visit the Puget Sound Stream Benthos webpage.

Special Studies

Pyrethroid Survey of King County Stream Sediments 2014 Final Report

Pyrethroids are a group of synthetic insecticides commonly used in residential areas. Residential and commercial use has resulted in an increased detection in urban runoff, which can be harmful to aquatic life. In October 2014, a pyrethroid survey was conducted in sediments collected from six King County streams. These streams include: Juanita, Forbes, Thornton, Pipers, Springbrook, and Mill Creeks. Results found that bifenthrin was the only pyrethroid detected in the sediment samples; and most detected concentrations were below the reporting detection limit. Percent finds and TOC content, which varied substantially by creek, may be influencing bifenthrin detections. These results suggest that sediments may contain toxic levels of pyrethroids even if they are not detectable above detection limits in this study.

City of Seattle State of the Waters 2007

The City of Seattle has undergone extensive development in the last 150 years. Using decades worth of existing research, the City of Seattle assessed the conditions of Seattle's waterbodies (watercourses, small lakes, large lakes, estuaries, and marine systems). Of interest was stream hydrology, water quality, physical habitat, and biological communities because these characteristics indicate how well watersheds can perform environmental services. The five major watercourses focused on in the report were: Fauntleroy Creek, Longfellow Creek, Pipers Creek, Taylor Creek, and Thornton Creek.