US Bridges

Thorne Bay Road over Gravelly Creek

Poor

Prince of Wales-Hyder Census Area, Alaska · Mile Point 14.1 · Structure no. 1464

Built
1989
36 years old
Condition
Poor
inspected July 2023
Type
Tee Beam
Prestressed Concrete
Length
97 ft
1 main span
Daily traffic
190
2020 count
Owner
State
State Highway Agency

About this bridge

Thorne Bay Road over Gravelly Creek is a prestressed concrete tee beam carrying Thorne Bay Road over Gravelly Creek in Prince of Wales-Hyder Census Area, Alaska. It was built in 1989, so it is 36 years old, older than the Alaska average of 35.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 190 vehicles a day, roughly 26% of them trucks, projected to reach 230 by 2039. The structure is 97 ft (29.6 m) long and 30 ft wide. If it were closed, the detour would be 123.7 mi (199 km).

Location

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CarriesThorne Bay Road
CrossesGravelly Creek
LocationMile Point 14.1
RouteState Highway 929
CountyPrince of Wales-Hyder Census Area
StateAlaska
Coordinates55.70944, -132.60278
Functional classRural Major Collector

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 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 adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating105.2 US tons
Inventory rating63.1 US tons

Structure

Structure typeTee Beam
MaterialPrestressed Concrete
DeckConcrete, precast panels
Main spans1
Design loadHS 20
Structure length97 ft (29.6 m)
Longest span94 ft (28.7 m)
Deck width30 ft (9.1 m)
Roadway width29 ft (8.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic190 (2020)
Projected traffic230 by 2039
Trucks26%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed123.7 mi (199 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway 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 Thorne Bay Road over Gravelly Creek built?

It was built in 1989, making it 36 years old in 2025.

What condition is Thorne Bay Road over Gravelly Creek in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in July 2023.

How much traffic does Thorne Bay Road over Gravelly Creek carry?

About 190 vehicles per day (2020 count), of which roughly 26% are trucks.

How long is Thorne Bay Road over Gravelly Creek?

The structure is 97 ft (29.6 m) long with a longest span of 94 ft (28.7 m) and a deck 30 ft wide.

Who owns Thorne Bay Road over Gravelly Creek?

It is owned by the State Highway Agency.