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King County Water Quality Monitoring

King County monitors the ecological health of McAleer Creek in a variety of ways, including water quality, sediment, and benthic invertebrates. Station A432 is located at NE 170th and Bothell Way NE, just south of Lake Forest Park. Water quality samples were collected monthly at this station near the mouth of McAleer Creek from 1976 to 2008 when budget cutbacks forced King County to reduce the breadth of its water quality monitoring program. However, regular monitoring at this site resumed in February of 2013. Sediment quality samples have been collected from McAleer Creek as part of the Streams Monitoring Program starting in 1987. King County began collecting benthic macroinvertebrate samples in 2002 to monitor stream health.

From time to time, additional studies have been conducted on McAleer Creek. Click here for information about Special Studies.


Water Shed Image McAleer Creek originates at Lake Ballinger and flows roughly six miles before draining into the northeast corner of Lake Washington just south of Lyon Creek. The drainage basin is approximately 5,700 acres in size and includes portions of the Cities of Mountlake Terrace, Shoreline, and Lake Forest Park, Washington.

Total land use in the basin is almost entirely developed with some forest lands. There is no agriculture in the area; and scrub, wetlands, and other land uses (grassland and open water) amount to less than 3% of total land use. Development is mostly low and medium intensity, as well as some high intensity and open space, and much of the development is for residential use. There is also a golf course, shopping center, and a section of Interstate-5 (I-5) within the basin. The upper subbasins that are within the general vicinity of the I-5 corridor are primarily residential with some commercial areas. The upstream section of McAleer Creek passes through the heavily altered I-5 corridor where it has very limited riparian vegetation (Kerwin, 2002, King County, 2002). The middle sub-basin consists primarily of low-density residential land use with deep ravines and eroded soils. The lower basin flattens and fans into a floodplain across what is now the Lake Forest Park Mall and Bothell Way. Building density increases and consequently encroaches into the creek corridor. See Table 1 below for more details on land use.

Table 1. Total land use in the basin

Developed Forest Scrub Wetlands Other
Total 92% 6% <1% <1% <2%


Salmonid habitat suitability of McAleer Creek was rated good in 1989 based on information collected by Metro staff in 1988 and 1989 (METRO, September 1990). Chinook, sockeye, kokanee, and coho salmon, and steelhead, rainbow, and coastal cutthroat trout have been observed in McAleer Creek (Kerwin, 2002). From 1997 to 2015, volunteers with the Salmon Watcher Program recorded salmon observations in McAleer Creek. Volunteers consistently saw Chinook, coho, and sockeye in the creek. No kokanee salmon or cutthroat trout were seen.

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. McAleer 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, the creek has been assigned an additional “Supplemental Spawning and Incubation Protection” temperature criteria of 13 ºC to be applied from September 15th to May 15th. McAleer Creek is on the Washington State Department of Ecology’s (Ecology) 303(d) list for violation of water temperature, DO, and bioassessment standards (Category 5).

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.

Long-term Trends

A 25-year (1979 – 2004) trend analysis was conducted with baseflow water quality from McAleer Creek. Results indicated that there has not been a significant change in temperature, DO concentration, bacteria, nitrogen (all forms), or total phosphorus over this 25-year period. There was a significant increase in conductivity, which suggests the presence of unidentified dissolved charged substances in the water. McAleer sediments have relatively high metals concentrations – see below. Water in McAleer Creek is becoming more acidic as indicated by the significant decrease in pH. However, the pH remains within acceptable range relative to the state standards. Decreased total suspended solids (TSS) and decreased ortho-phosphorus concentrations indicate some improvements in water quality in the same 25-year period.

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 1976 to 2024
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)30110.78.013.510.61.0
Temperature (°C)46210.51.518.510.83.3
Turbidity (NTU)4615.550.2081.003.657.15
Conductivity (mSIEMS/cm)266205.4108.0270.0208.932.0
Total Suspended Solids (mg/L)46114.640.70422.008.1027.29
Ortho-Phosphorus (mg/L)4600.02920.00300.07200.02700.0131
Total Phosphorus (mg/L)4610.06450.02330.50900.05620.0447
Ammonia (mg/L)4600.02960.00460.25600.01900.0272
Nitrate (mg/L)4591.23600.49302.07001.22000.3237
Total Nitrogen (mg/L)3631.51090.81502.30001.52000.2836
Fecal Coliform(CFU/100ML)42740249992210819

Table 2. Storm water monitoring summary statistics for this station from 1976 to 2024
ParameterNumber of SamplesMeanMinimumMaxmiumMedianStandard Deviation
Dissolved Oxygen (mg/L)3710.
Temperature (°C)5210.14.515.69.92.9
Turbidity (NTU)5431.753.70294.0019.6050.85
Conductivity (mSIEMS/cm)22151.482.7203.0156.036.2
Total Suspended Solids (mg/L)5487.3110.50572.0049.00114.43
Ortho-Phosphorus (mg/L)540.03140.01170.07820.02910.0143
Total Phosphorus (mg/L)540.15270.04030.53700.10950.1140
Ammonia (mg/L)540.04890.01000.17200.04260.0349
Nitrate (mg/L)540.94050.60901.38000.93750.1649
Total Nitrogen (mg/L)511.55651.03003.00001.53000.3639
Fecal Coliform(CFU/100ML)542322501200011002835


King County maintains four streamflow gages on McAleer Creek: McAleer Creek at NE 196th St Dam (35a), McAleer Creek below 15th Ave NE (35b), McAleer at the mouth (35c), and McAleer Bypass (35d).

Stream Sediment

Sediment samples were collected at four stations, approximately a mile apart, along a four mile reach of McAleer Creek in the summer of 2004 (see map). Additional samples were collected at the legacy site (0432) from 2004-2010. The sediment concentrations of bis(2-ethylhexyl)phthalate (a chemical found in some plastics) at the furthest upstream location (UU432) exceeds the Sediment Cleanup Objective (SCO), which suggests the potential for adverse effects in aquatic animals living in the sediments is uncertain. At the most downstream sampling locations (WW432 and 0432) nickel concentrations were also above the SCO. Acid volatile sulfide/simultaneous extracted metals (AVS/SEM) ratios suggest metals at these sites are bioavailable.

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 McAleer Creek, please visit the Puget Sound Stream Benthos webpage.

Special Studies

Blue Heron Extension Project

In 1999, Seattle Tilth undertook a project to restore an undeveloped parcel of land and upgrade the developed section of Blue Heron Park (located near the mouth of McAleer Creek in Lake Forest Park) into an environmentally-friendly demonstration garden. McAleer Creek, a salmon-bearing stream, runs through the park. Community groups removed invasive plant species and planted drought tolerant perennials, native plants, shrubs, and trees. This project will preserve salmon habitat and contribute to clean water flow into Lake Washington. This project is partially funded by a King County Waterworks Grant.

McAleer Creek Project

Transport of suspended sediments has been significant in McAleer Creek. The incising of stream banks and soil erosion was one of the major reasons the 1983 McAleer Creek Project was undertaken. The plan, produced for King County, Mountlake Terrace, and Lake Forest Park, recommended solutions to flooding problems in the drainage basin.