US Bridges

US 101 over Hamma Hamma River

Fair

Mason County, Washington · 5.1 S Jefferson CO · Structure no. 0000734A0000000

Built
1924
101 years old
Condition
Fair
inspected June 2024
Type
Arch - Thru
Concrete
Length
153 ft
1 main span
Daily traffic
2,911
2023 count
Owner
State
State Highway Agency

About this bridge

US 101 over Hamma Hamma River is a concrete arch - thru carrying US 101 over Hamma Hamma River in Mason County, Washington. It was built in 1924, so it is 101 years old, older 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 2,911 vehicles a day, roughly 20% of them trucks, projected to reach 3,502 by 2039. The structure is 153 ft (46.6 m) long and 26 ft wide. If it were closed, the detour would be 37.9 mi (61 km).

Location

Open in Google Maps
CarriesUS 101
CrossesHamma Hamma River
Location5.1 S Jefferson CO
RouteU.S. Route 101
CountyMason County
StateWashington
Coordinates47.54889, -123.04389
Functional classRural Principal Arterial - Other

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 protection8 Very GoodNo problems noted.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating23.6 US tons
Inventory rating18.2 US tons

Structure

Structure typeArch - Thru
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadUnknown
Structure length153 ft (46.6 m)
Longest span150 ft (45.7 m)
Deck width26 ft (7.9 m)
Roadway width20 ft (6.1 m)
Vertical clearance over deck16 ft (4.8 m)

Traffic and service

Average daily traffic2,911 (2023)
Projected traffic3,502 by 2039
Trucks20%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed37.9 mi (61 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$2.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 101 over Hamma Hamma River built?

It was built in 1924, making it 101 years old in 2025.

What condition is US 101 over Hamma Hamma 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 June 2024.

How much traffic does US 101 over Hamma Hamma River carry?

About 2,911 vehicles per day (2023 count), of which roughly 20% are trucks.

How long is US 101 over Hamma Hamma River?

The structure is 153 ft (46.6 m) long with a longest span of 150 ft (45.7 m) and a deck 26 ft wide.

Who owns US 101 over Hamma Hamma River?

It is owned by the State Highway Agency.