Structure 8700890009900 · Grafton County, NH

Nh 18 over Lafayette Brook

Carries Nh 18 over Lafayette Brook, 2.7 Mi From Sugar Hill Tl.

Overall conditionGood

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

How ratings work
Deck8/9 · Very Good
Superstructure8/9 · Very Good
Substructuresets the rating7/9 · Good
Channelnot part of overall8/9 · Very Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
CAR · 15 FT56 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 8/9Superstructure 8/9Substructure 7/9 · sets the rating

56 ft end to end. Lengths and the car 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 box-beam bridge.

Built1932rebuilt 2019
Length56.1 ft17.1 m
Daily traffic593counted 2023
Last inspectedApril 2023every 24 months

Location

StateNew Hampshire
CountyGrafton
Location2.7 Mi From Sugar Hill Tl
CarriesNh 18
CrossesLafayette Brook
Coordinates44.20536, -71.72301

Physical Characteristics

MaterialPrestressed Concrete
DesignBox Beam - Single/Spread
Total Length56.1 ft (17.1 m)
Max Span51.8 ft (15.8 m)
Deck Width29.2 ft (8.9 m)
Deck Area152.2 sq m
Main Spans1
Year Built1932 (reconstructed 2019)

Traffic

Avg Daily Traffic593 (2023)
Truck Traffic10%
Lanes On Bridge2

Inspection & Ownership

Last InspectionApril 2023
Inspection FrequencyEvery 24 months
OwnerState Highway Agency
Historical SignificanceBridge is eligible for the National Register
Scour Critical8 — Stable, low risk
Structure Number008700890009900

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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