Water Quality Improvement Project
Fenwick Lake Area:
Total Phosphorus


Lake Fenwick is a small lake in King County, Washington.; It is located west of the city of Kent. The main recreational activities on the lake are fishing and boating. Fenwick Lake is considered an important recreational resource for the city of Kent.

Water quality issues

Nutrient inputs into the lake encourage eutrophication of the lake. Eutrophication is the process of excessive plant growth in lakes or ponds, due to an enriched supply of nutrients. Stormwater runoff contributes excess external phosphorus to Lake Fenwick.

Fenwick Lake, Washington State.  Photo courtesy of Kimberly Mallady, via Flickr.

© Kimberly Mallady.

Why this matters

Excessive nutrient inputs to lakes provide aquatic plant and algae dominance, making lakes unsuitable for recreation or viewing enjoyment. Phosphorus is one of the nutrients. When it is discharged into a waterbody, like a lake, it fuels the growth of algae.

Excessive algae growth reduces water clarity, increases oxygen demand in the bottom sediments severely impacting coldwater aquatic habitat, and can, depending on the dominant algae present, pose a human health risk.

Status of the project

In 1991, a comprehensive lake and watershed management plan was proposed for Fenwick Lake under EPA's Clean Lakes Program. The proposal included a two-phased implementation approach to resolve the phosphorus issues in the lake. Implementation plans included monitoring to evaluate the effectiveness of the assigned load allocations for phosphorus, as well as other parameters. The second phase was scheduled to begin in December 1998. Based on these plans, EPA approved a total maximum daily load (TMDL) for Fenwick Lake in January 1993.

Despite implementation actions, in 2002 Ecology monitoring determined that goals set by the TMDL were not being achieved. The lake is currently on the 2008 water quality assessment as a category 5 (water cleanup plan required by the Clean Water Act).

Technical information

Fenwick Lake Total Phosphorus Total Maximum Daily Load (Ecology publication)

Effectiveness Monitoring for Total Phosphorus Total Maximum Daily Loads in Fenwick and Sawyer Lakes (Ecology publication)

Related information

WRIA 9: Duwamish-Green Watershed Information (Water web site)


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Last updated May 2015
  Map for water resource inventory area (WRIA) 9, Washington State.


WRIA(s): #9 (Duwamish-Green)
County: King

Water-body Name:
Fenwick Lake

Total Phosphorus

# of TMDLs: 1


Contact Info:
Tricia Shoblom
Phone: 425-649-7288
Email: Tricia.Shoblom@ecy.wa.gov

Northwest Region
Department of Ecology
3190 160th Ave. SE
Bellevue, WA 98008-5452