US Bridges

Moon Road over Black River

Fair

Thurston County, Washington · 1. N JCT SR12 · Structure no. 083520000000000

Built
1976
49 years old
Condition
Fair
inspected March 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
203 ft
3 main spans
Daily traffic
1,003
2021 count
Owner
County
County Highway Agency

About this bridge

Moon Road over Black River is a prestressed concrete stringer/multi-beam or girder carrying Moon Road over Black River in Thurston County, Washington. It was built in 1976, so it is 49 years old, younger than the Washington average of 49.8 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 1,003 vehicles a day, roughly 15% of them trucks, projected to reach 1,551 by 2041. The structure is 203 ft (61.9 m) long and 35 ft wide. If it were closed, the detour would be 19.3 mi (31 km).

Location

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CarriesMoon Road
CrossesBlack River
Location1. N JCT SR12
RouteCounty Highway 13430
CountyThurston County
StateWashington
Coordinates46.83882, -123.13928
Functional classRural Major Collector

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating61 US tons
Inventory rating36 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length203 ft (61.9 m)
Longest span74 ft (22.6 m)
Deck width35 ft (10.8 m)
Roadway width28 ft (8.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,003 (2021)
Projected traffic1,551 by 2041
Trucks15%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed19.3 mi (31 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedDeck rehabilitation with only incidental widening
Estimated improvement cost$2.9 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Moon Road over Black River built?

It was built in 1976, making it 49 years old in 2025.

What condition is Moon Road over Black River 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 March 2023.

How much traffic does Moon Road over Black River carry?

About 1,003 vehicles per day (2021 count), of which roughly 15% are trucks.

How long is Moon Road over Black River?

The structure is 203 ft (61.9 m) long with a longest span of 74 ft (22.6 m) and a deck 35 ft wide.

Who owns Moon Road over Black River?

It is owned by the County Highway Agency.