Centralia Coal Mine Dam No 6b is an earth dam located in Lewis County, Washington, built in 1970. It carries a Low hazard potential classification.
Dam profile
NID height · 13 ft13 ft tall. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Centralia Coal Mine Dam No 6b
The primary purpose of Centralia Coal Mine Dam No 6b is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is owned by Transalta Centralia Mining LLC (public utility). It impounds the Tr-hanaford Creek.
The dam stands 13 feet tall, creates a reservoir covering 15 acres, has a maximum storage capacity of 74 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1970, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. An emergency action plan is in place for this dam. The most recent inspection on record was 07/03/2001. That was over 25 years ago.
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Location
| State | Washington |
| County | Lewis |
| River/Stream | Tr-hanaford Creek |
| Coordinates | 46.74861, -122.84474 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 13 ft |
| Year Completed | 1970 (56 years old) |
Storage & Hydraulics
| NID Storage | 74 acre-ft |
| Max Storage | 74 acre-ft |
| Normal Storage | 62 acre-ft |
| Surface Area | 15 acres |
| Drainage Area | 0 sq mi |
| Max Discharge | 69 cfs |
Ownership & Safety
| Purpose | Tailings |
| Owner | Transalta Centralia Mining LLC |
| Owner Type | Public Utility |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 07/03/2001 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00290 |
| Federal ID | WA00290 |
| More Info | State Dam Safety Program |