US Bridges

Black Mountain RD over Mason Dam Spillway

Fair

Baker County, Oregon · Mason Dam · Structure no. 15MAS001

Built
1968
57 years old
Condition
Fair
inspected April 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
22 ft
1 main span
Daily traffic
50
2023 count
Owner
Federal
Bureau of Reclamation

About this bridge

Black Mountain RD over Mason Dam Spillway is a steel stringer/multi-beam or girder carrying Black Mountain RD over Mason Dam Spillway in Baker County, Oregon. It was built in 1968, so it is 57 years old, older than the Oregon average of 49.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 50 vehicles a day, projected to reach 50 by 2043. The structure is 22 ft (6.8 m) long and 27 ft wide. If it were closed, the detour would be 85.1 mi (137 km).

Location

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CarriesBlack Mountain RD
CrossesMason Dam Spillway
LocationMason Dam
RouteFederal Lands Road 0
CountyBaker County
StateOregon
Coordinates44.67289, -118.00013
Functional classRural Local

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionApril 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment5: Somewhat better than minimum adequacy to tolerate being left in place as is
Operating rating52.9 US tons
Inventory rating31.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadH 20
Structure length22 ft (6.8 m)
Longest span20 ft (6.1 m)
Deck width27 ft (8.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic50 (2023)
Projected traffic50 by 2043
Trucks—
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed85.1 mi (137 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerBureau of Reclamation
Maintained byOther Local Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Black Mountain RD over Mason Dam Spillway built?

It was built in 1968, making it 57 years old in 2025.

What condition is Black Mountain RD over Mason Dam Spillway in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in April 2023.

How much traffic does Black Mountain RD over Mason Dam Spillway carry?

About 50 vehicles per day (2023 count).

How long is Black Mountain RD over Mason Dam Spillway?

The structure is 22 ft (6.8 m) long with a longest span of 20 ft (6.1 m) and a deck 27 ft wide.

Who owns Black Mountain RD over Mason Dam Spillway?

It is owned by the Bureau of Reclamation and maintained by the Other Local Agency.