US Bridges

Six Prong Road over Alder Creek

Fair

Klickitat County, Washington · 1.8 N JCT SR 14 · Structure no. 079952000000000

Built
1986
39 years old
Condition
Fair
inspected July 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
100 ft
1 main span
Daily traffic
141
2021 count
Owner
County
County Highway Agency

About this bridge

Six Prong Road over Alder Creek is a prestressed concrete stringer/multi-beam or girder carrying Six Prong Road over Alder Creek in Klickitat County, Washington. It was built in 1986, so it is 39 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 141 vehicles a day, roughly 30% of them trucks, projected to reach 176 by 2043. The structure is 100 ft (30.5 m) long and 27 ft wide. If it were closed, the detour would be 19.3 mi (31 km).

Location

Open in Google Maps
CarriesSix Prong Road
CrossesAlder Creek
Location1.8 N JCT SR 14
RouteCounty Highway 45400
CountyKlickitat County
StateWashington
Coordinates45.857, -119.92222
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.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
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 evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating55 US tons
Inventory rating34.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length100 ft (30.5 m)
Longest span97 ft (29.6 m)
Deck width27 ft (8.2 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic141 (2021)
Projected traffic176 by 2043
Trucks30%
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 statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.3 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Six Prong Road over Alder Creek built?

It was built in 1986, making it 39 years old in 2025.

What condition is Six Prong Road over Alder Creek 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 2023.

How much traffic does Six Prong Road over Alder Creek carry?

About 141 vehicles per day (2021 count), of which roughly 30% are trucks.

How long is Six Prong Road over Alder Creek?

The structure is 100 ft (30.5 m) long with a longest span of 97 ft (29.6 m) and a deck 27 ft wide.

Who owns Six Prong Road over Alder Creek?

It is owned by the County Highway Agency.