Structure 690 · Matanuska-Susitna County, AK

Denali Highway over Seattle Creek

Carries Denali Highway over Seattle Creek, Mile Point 111.4.

Overall conditionGood

Set by its lowest-rated component: Substructure at 8 of 9.

How ratings work
Deck9/9 · Excellent
Superstructure9/9 · Excellent
Substructuresets the rating8/9 · Very Good
Channelnot part of overall9/9 · Excellent
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT124 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 9/9Superstructure 9/9Substructure 8/9 · sets the rating

124 ft end to end. Lengths and the semi-truck on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a tee-beam bridge.

Built201610 years old
Length124.0 ft37.8 m
Daily traffic90counted 2020
Last inspectedJuly 2023every 24 months

Location

StateAlaska
CountyMatanuska-Susitna
LocationMile Point 111.4
CarriesDenali Highway
CrossesSeattle Creek
Coordinates63.32510, -148.25010

Physical Characteristics

MaterialPrestressed Concrete
DesignTee Beam
Total Length124.0 ft (37.8 m)
Max Span121.1 ft (36.9 m)
Deck Width33.1 ft (10.1 m)
Deck Area381.8 sq m
Main Spans1
Year Built2016

Traffic

Avg Daily Traffic90 (2020)
Truck Traffic21%
Lanes On Bridge2

Inspection & Ownership

Last InspectionJuly 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour Critical8 — Stable, low risk
Structure Number0690

How Bridge Ratings Work

Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."

0Failed
1Imminent failure
2Critical
3Serious
4Poor
5Fair
6Satisfactory
7Good
8Very good
9Excellent
Good · lowest component 7–9
Fair · lowest component 5–6
Poor · lowest component 0–4

A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.