US Bridges

Milltown RD over Big Ditch

Fair

Skagit County, Washington · 0.02 E JCT SR 530 · Structure no. 084157000000000

Built
1957
68 years old
Condition
Fair
inspected July 2024
Type
Tee Beam
Concrete
Length
50 ft
2 main spans
Daily traffic
413
2021 count
Owner
County
County Highway Agency

About this bridge

Milltown RD over Big Ditch is a concrete tee beam carrying Milltown RD over Big Ditch in Skagit County, Washington. It was built in 1957, so it is 68 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 413 vehicles a day, roughly 8% of them trucks, projected to reach 746 by 2041. The structure is 50 ft (15.2 m) long and 26 ft wide. If it were closed, the detour would be 6.2 mi (10 km).

Location

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CarriesMilltown RD
CrossesBig Ditch
Location0.02 E JCT SR 530
RouteCounty Highway 80260
CountySkagit County
StateWashington
Coordinates48.3085, -122.34747
Functional classRural Minor 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
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure8 Very GoodNo problems noted.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating60 US tons
Inventory rating36 US tons

Structure

Structure typeTee Beam
MaterialConcrete
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length50 ft (15.2 m)
Longest span24 ft (7.2 m)
Deck width26 ft (8 m)
Roadway width24 ft (7.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic413 (2021)
Projected traffic746 by 2041
Trucks8%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed6.2 mi (10 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 proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$2.2 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Milltown RD over Big Ditch built?

It was built in 1957, making it 68 years old in 2025.

What condition is Milltown RD over Big Ditch 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 July 2024.

How much traffic does Milltown RD over Big Ditch carry?

About 413 vehicles per day (2021 count), of which roughly 8% are trucks.

How long is Milltown RD over Big Ditch?

The structure is 50 ft (15.2 m) long with a longest span of 24 ft (7.2 m) and a deck 26 ft wide.

Who owns Milltown RD over Big Ditch?

It is owned by the County Highway Agency.