Structure 15302130005400 · Grafton County, NH

Us302 Nh 10 Nh 18 over Ammonoosuc River

Carries Us302 Nh 10 Nh 18 over Ammonoosuc River, 3.9 Mi Lisbon Tl.

Overall conditionGood

Set by its lowest-rated component: Deck and Superstructure and Substructure at 7 of 9.

How ratings work
Decksets the rating7/9 · Good
Superstructuresets the rating7/9 · Good
Substructuresets the rating7/9 · Good
Channelnot part of overall7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
SEMI-TRUCK · 72 FT155 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 7/9Superstructure 7/9Substructure 7/9

155 ft end to end, longest span 72 ft: about 2 semi-trucks nose to tail. 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.

Built1950rebuilt 1987
Length154.9 ft47.2 m
Daily traffic7,962counted 2023
Last inspectedJune 2024every 24 months

Location

StateNew Hampshire
CountyGrafton
Location3.9 Mi Lisbon Tl
CarriesUs302 Nh 10 Nh 18
CrossesAmmonoosuc River
Coordinates44.30538, -71.77003

Physical Characteristics

MaterialSteel
DesignStringer/Multi-beam
Total Length154.9 ft (47.2 m)
Max Span71.9 ft (21.9 m)
Deck Width55.4 ft (16.9 m)
Deck Area797.7 sq m
Main Spans2
Year Built1950 (reconstructed 1987)

Traffic

Avg Daily Traffic7,962 (2023)
Truck Traffic4%
Lanes On Bridge2

Inspection & Ownership

Last InspectionJune 2024
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is possibly eligible (requires evaluation)
Scour Critical3 — Scour critical
Structure Number015302130005400

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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