US Bridges

HWY 241 over Isthmus Slough

FairPosted for load

Coos County, Oregon · 00.2 MI SW Eastside Scl · Structure no. 01132F241 00051

Built
1931
94 years old, rebuilt 1960
Condition
Fair
inspected August 2023
Type
Movable - Bascule
Steel
Length
1,691 ft
1 main span
Daily traffic
10,903
2022 count
Owner
State
State Highway Agency

About this bridge

HWY 241 over Isthmus Slough is a steel movable - bascule carrying HWY 241 over Isthmus Slough in Coos County, Oregon. It was built in 1931 and reconstructed in 1960, so it is 94 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. Its operating status is: posted for other load-capacity restriction.

It carries about 10,903 vehicles a day, roughly 6% of them trucks, projected to reach 17,500 by 2042. The structure is 1,691 ft (515.4 m) long and 36 ft wide. If it were closed, the detour would be 8.7 mi (14 km).

Location

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CarriesHWY 241
CrossesIsthmus Slough
Location00.2 MI SW Eastside Scl
RouteState Highway 241
CountyCoos County
StateOregon
Coordinates43.35651, -124.194
Functional classUrban Minor Arterial

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusPosted for other load-capacity restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry3: Basically intolerable, requiring high priority of corrective action
Waterway adequacy9: Superior to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating24.7 US tons
Inventory rating19 US tons

Structure

Structure typeMovable - Bascule
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+32 approach)
Design loadH 15
Structure length1,691 ft (515.4 m)
Longest span140 ft (42.7 m)
Deck width36 ft (11 m)
Roadway width27 ft (8.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,903 (2022)
Projected traffic17,500 by 2042
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed8.7 mi (14 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$9.5 million
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was HWY 241 over Isthmus Slough built?

It was built in 1931, making it 94 years old in 2025. It was reconstructed in 1960.

What condition is HWY 241 over Isthmus Slough 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 August 2023.

How much traffic does HWY 241 over Isthmus Slough carry?

About 10,903 vehicles per day (2022 count), of which roughly 6% are trucks.

How long is HWY 241 over Isthmus Slough?

The structure is 1,691 ft (515.4 m) long with a longest span of 140 ft (42.7 m) and a deck 36 ft wide.

Who owns HWY 241 over Isthmus Slough?

It is owned by the State Highway Agency.