MAYFIELD
OperatingHydro power plant
- Capacity
- 162 MW
- Primary fuel
- Hydro
- County
- Lewis County
- Operator
- CITY OF TACOMA - (WA)
- Status
- Operating
- Commissioned
- 1963
- EIA plant ID
- 3917
- Coordinates
- 46.5035, -122.5927
MAYFIELD, a 162 MW Hydro power plant in Lewis County, Washington. Operated by CITY OF TACOMA - (WA), commissioned 1963.
Weather peril exposure
MAYFIELD is a 162 MW hydro power plant in Lewis County, WA, operated by CITY OF TACOMA - (WA), commissioned in 1963. Lewis County carries low modeled catastrophe exposure in the FEMA National Risk Index, scoring 1.3 of 5 at the 8th national percentile. Earthquake is the leading peril, rated Relatively Moderate by FEMA at the 97th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a hydro plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Lewis County hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Earthquake | Relatively Moderate | 97th | 4.9 of 5 | 0.02 |
| Riverine flooding | Relatively Moderate | 95th | 4.8 of 5 | 0.29 |
| Heat wave | Relatively Low | 60th | 3.4 of 5 | 3.2 |
| Wildfire | Relatively Low | 47th | 2.9 of 5 | <0.01 |
| Winter weather | Relatively Low | 27th | 2.1 of 5 | 29.3 |
| Strong wind | Relatively Low | 23rd | 1.9 of 5 | 0.02 |
| Ice storm | Relatively Low | 22nd | 1.9 of 5 | 0.51 |
| Tornado | Very Low | 8th | 1.3 of 5 | 0.14 |
| Hail | Very Low | 6th | 1.2 of 5 | 0.03 |
| Lightning | Relatively Low | 4th | 1.2 of 5 | 6.6 |
Perils not assessed in Lewis County
These perils carry no usable National Risk Index figure for this county, so they are excluded from the scoring rather than scored zero. A zero would claim the peril was assessed and found benign.
| Peril | Why it is not scored |
|---|---|
| Hurricane | FEMA rating is "Not Applicable" for this county |
| Coastal flooding | FEMA rating is "Not Applicable" for this county |
Model hail, wind and flood exposure for Lewis County in the weather risk calculator
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.