Structure 23101520003900 · Belknap County, NH

I-93 SB over Old Nh 3b

Carries I-93 SB over Old Nh 3b, Tilton-sanborton Tl.

Overall conditionFair

Set by its lowest-rated component: Substructure at 6 of 9.

How ratings work
Deck7/9 · Good
Superstructure7/9 · Good
Substructuresets the rating6/9 · Satisfactory
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT135 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 7/9Substructure 6/9 · sets the rating

135 ft end to end, longest span 53 ft. 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 multi-beam bridge.

Built1962rebuilt 1986
Length134.8 ft41.1 m
Daily traffic14,214counted 2023
Last inspectedJuly 2024every 24 months

Location

StateNew Hampshire
CountyBelknap
LocationTilton-sanborton Tl
CarriesI-93 SB
CrossesOld Nh 3b
Coordinates43.47930, -71.59011

Physical Characteristics

MaterialSteel
DesignStringer/Multi-beam
Total Length134.8 ft (41.1 m)
Max Span52.8 ft (16.1 m)
Deck Width44.0 ft (13.4 m)
Deck Area550.7 sq m
Main Spans3
Year Built1962 (reconstructed 1986)

Traffic

Avg Daily Traffic14,214 (2023)
Truck Traffic9%
Lanes On Bridge2
Lanes Under Bridge2

Inspection & Ownership

Last InspectionJuly 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is not eligible for the National Register
Scour CriticalNot applicable
Structure Number023101520003900

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.

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