US Bridges

Umptanum Road over Anderson Slough

Fair

Kittitas County, Washington · 0.1 W. Anderson Rd. · Structure no. 086730000000000

Built
1982
43 years old
Condition
Fair
inspected November 2023
Type
Culvert
Steel
Length
22 ft
2 main spans
Daily traffic
6,083
2022 count
Owner
City
City or Municipal Highway Agency

About this bridge

Umptanum Road over Anderson Slough is a steel culvert carrying Umptanum Road over Anderson Slough in Kittitas County, Washington. It was built in 1982, so it is 43 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 5 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 6,083 vehicles a day, roughly 25% of them trucks, projected to reach 13,091 by 2040. The structure is 22 ft (6.7 m) long and 39 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesUmptanum Road
CrossesAnderson Slough
Location0.1 W. Anderson Rd.
RouteCounty Highway 96937
CountyKittitas County
StateWashington
Coordinates46.98097, -120.55721
Functional classUrban 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
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Culvert5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionNovember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating106.8 US tons
Inventory rating106.8 US tons

Structure

Structure typeCulvert
MaterialSteel
DeckNot applicable
Main spans2
Design loadHS 20
Structure length22 ft (6.7 m)
Longest span9 ft (2.7 m)
Deck width39 ft (11.9 m)
Roadway width39 ft (11.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,083 (2022)
Projected traffic13,091 by 2040
Trucks25%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed6.8 mi (11 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$1.2 million (2022 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Umptanum Road over Anderson Slough built?

It was built in 1982, making it 43 years old in 2025.

What condition is Umptanum Road over Anderson 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 November 2023.

How much traffic does Umptanum Road over Anderson Slough carry?

About 6,083 vehicles per day (2022 count), of which roughly 25% are trucks.

How long is Umptanum Road over Anderson Slough?

The structure is 22 ft (6.7 m) long with a longest span of 9 ft (2.7 m) and a deck 39 ft wide.

Who owns Umptanum Road over Anderson Slough?

It is owned by the City or Municipal Highway Agency.