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King County Water Quality Monitoring
Since 1995, King County has been conducting monthly baseline water quality monitoring in Lewis Creek at one site, near the mouth. Station A617 is located at a bridge near the intersection of 187th Ave SE and 185th Pl. SE. (Click here for information about Special Studies of Lewis Creek.)
Lewis Creek Watershed
 Lewis Creek is placed in Ecology’s Noncore Salmon/Trout Aquatic Use Category which sets criterion for the protection of spawning, core rearing, and migration of salmon and trout, and other associated aquatic life.
The mainstem of Lewis Creek is a relatively short, 1.5 miles, with numerous branched tributaries (Kerwin 2001). The mainstem originates in a low gradient area above the Eastgate region of Bellevue on the northeast side of Cougar Mountain. The creek then flows through a steep, wooded ravine before entering another low gradient reach downstream of Interstate 90 and where it drains into the southern end of Lake Sammamish.
The basin encompasses 1,209 acres. The dominant land use in the Lewis Creek basin is single family residential and rural residential (Kerwin 2001). In 2000, it was determined that approximately 28 percent of the basin was impervious surfaces.
Fisheries
Numerous fisheries studies have been done on Lewis Creek (The Watershed Company 1988, 1989; URS Corp., 1987; King County, 1995; Ostergaard, 1998; King County 2000c). A culvert located at river mile 0.75 at Interstate 90 is a barrier to fish migration. Below this barrier, in the lower reaches of the creek, kokanee, sockeye, coho and cutthroat trout were observed during a recent habitat and barrier assessment done by the Washington Department of Fish and Wildlife (WDFW, 2000). King County staff and volunteer salmon watchers have also observed adult coho, sockeye, kokanee, and chinook in the last seven years (King County 2000c, 2001b, 2001c, June 2002). A fish habitat and population assessment conducted in 1992 by the Watershed Company noted the presence of cutthroat trout, steelhead trout, kokanee, and coho (Kerwin 2001).
Water Quality
Studies conducted as part of the Lakemont Development process found exceedences of State water quality criteria for lead, zinc, and fecal coliform bacteria (Herrera 1995). More recently, Lewis Creek was rated a stream of “moderate concern” using the Water Quality Index rating system developed by Washington State Department of Ecology.
Hydrology
King County maintains a streamflow gauge: Lewis Creek at West Lake Sammamish Parkway SE (63a) and a precipitation gauge: Lewis Creek Rain Gauge (63u) on Lewis Creek.
Lakemont Boulevard
Public concern over the 1998 construction of Lakemont Boulevard in the sensitive Lewis Creek corridor led to major environmental controls. Bellevue and King County staff worked together to control stormwater road runoff. Several reports have been written in relation to this project including:
Small Streams Toxicity/Pesticide Study
As part of King County’s Small Streams Toxicity/Pesticide Study, pesticide concentrations and toxicity were measured in Lewis Creek in 1999 and 2000. The County collected samples for analysis of pesticides, other organics, metals, suspended solids, and toxicity (Ceriodaphnia dubia, and Selenastrum capricornutum). For more information, visit the pesticide study Web site.
Habitat Assessment
Washington Department of Fish and Wildlife conducted a fish barrier evaluation and habitat assessment on Lewis Creek in 2000.
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