Completed in 1963, Mayfield Dam is a 250-foot-high, 850-foot-long concrete arch and gravity dam located near Mossyrock. It can generate a maximum of 162 megawatts of electricity, enough to supply about 58,000 homes. The dam created the 2,250-acre Mayfield Lake, which is fed from the Cowlitz and Tilton rivers.
Mayfield Lake Park provides outdoor recreation, including individual and group campsites available April 15 – Oct. 15, a boat launch, a day-use area and a kitchen shelter. We also stock the lake annually with rainbow trout, and the Washington Department of Fish and Wildlife stocks it with tiger muskies for recreational fishing.
Tacoma Power will lower Mayfield Lake to 415 feet of elevation Sept. 15-30, 2019, in order to repair and extend the Mayfield Lake Park boat launch. All boat launches will be inoperable and the shoreline will be closed. Learn more at MyTPU.org/Cowlitz.
Also located on the shoreline of Mayfield Lake is Ike Kinswa State Park, which offers a boat launch, campground and day-use facility. In addition, there are two privately run facilities nearby: Harmony Lakeside RV Park and Lake Mayfield Resort and Marina.
See current details on boat launches and lake levels or call (888) 502-8690 for recorded information.
- Year completed – 1963
- River system – Cowlitz
- Original investment – $44.5 million
- Type of dam – concrete arch/gravity and embankment
- Height – above riverbed, 200 feet; above bedrock, 250 feet
- Length – 850 feet
- Width – top, 5 feet; base, 23 feet
- Volume of concrete in dam – 110,000 cubic yards
- Average flow – 6,120 cubic feet/second
- Drainage area – 1,400 square miles
- Reservoir length – 13 miles
- Miles of shoreline – 33.5 miles
- Reservoir area at maximum elevation – 2,250 acres
- Reservoir elevation – full, 425 feet; lowest allowable, 415 feet
- Average annual generation – 804 million kilowatt-hours
- Equivalent number of NW homes served – 57,500
- Number of generators – Four 40,500 kilowatt generators
- Installed capacity (nameplate rating) – 162,000 kilowatts