Centralia Coal Mine Dam No 8a
Centralia Coal Mine Dam No 8a is an earth dam located in Lewis County, Washington, built in 1972. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Centralia Coal Mine Dam No 8a
The primary purpose of Centralia Coal Mine Dam No 8a 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-south Hanaford Creek.
The dam stands 18 feet tall and stretches 530 feet across, creates a reservoir covering 13 acres, has a maximum storage capacity of 102 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1972, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 03/18/2025.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Washington dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Washington |
| County | Lewis |
| River/Stream | Tr-south Hanaford Creek |
| Coordinates | 46.70702, -122.80861 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 18 ft |
| Dam Length | 530 ft |
| Year Completed | 1972 (54 years old) |
Storage & Hydraulics
| NID Storage | 102 acre-ft |
| Max Storage | 102 acre-ft |
| Normal Storage | 58 acre-ft |
| Surface Area | 13 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 2,897 cfs |
Ownership & Safety
| Purpose | Tailings |
| Owner | TransAlta Centralia Mining LLC |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 03/18/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WA00293 |
| Federal ID | WA00293 |
| More Info | State Dam Safety Program |