Structure 21000990003400 · Coos County, NH

Murphy Dam Road over Dam Spillway

Carries Murphy Dam Road over Dam Spillway, 0.2 Mi From US RT 3.

Overall conditionPoor

Set by its lowest-rated component: Deck at 4 of 9.

How ratings work
Decksets the rating4/9 · Poor
Superstructure5/9 · Fair
Substructure6/9 · Satisfactory
Channelnot part of overall6/9 · Satisfactory
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
CAR · 15 FT38 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 4/9 · sets the ratingSuperstructure 5/9Substructure 6/9

38 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 girder bridge.

Built193888 years old
Length38.1 ft11.6 m
Daily traffic96counted 2023
Last inspectedNovember 2024every 8 months

Location

StateNew Hampshire
CountyCoos
Location0.2 Mi From US RT 3
CarriesMurphy Dam Road
CrossesDam Spillway
Coordinates45.04901, -71.38264

Physical Characteristics

MaterialSteel
DesignGirder and Floorbeam
Total Length38.1 ft (11.6 m)
Max Span30.8 ft (9.4 m)
Deck Width20.3 ft (6.2 m)
Deck Area71.9 sq m
Main Spans1
Year Built1938

Traffic

Avg Daily Traffic96 (2023)
Truck Traffic4%
Lanes On Bridge2

Inspection & Ownership

Last InspectionNovember 2024
Inspection FrequencyEvery 8 months
OwnerOther State Agencies
Historical SignificanceBridge is possibly eligible (requires evaluation)
Scour Critical8 — Stable, low risk
Structure Number021000990003400

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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