Structure 23500530006800 · Hillsborough County, NH

Mill Road over Gridley River

Carries Mill Road over Gridley River, 0.5 Mi From Jaffrey Tl.

Overall conditionFair

Set by its lowest-rated component: Substructure at 5 of 9.

How ratings work
Deck6/9 · Satisfactory
Superstructure6/9 · Satisfactory
Substructuresets the rating5/9 · Fair
Channelnot part of overall7/9 · Good
0 failed4 poor6 fair9 excellent

Elevation

Side view, colored by inspection rating
CAR · 15 FT27 FT OVERALL25 FT0ELEVATION · LENGTHS TO SCALE
Deck 6/9Superstructure 6/9Substructure 5/9 · sets the rating

27 ft end to end, longest span 9 ft. 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 slab bridge.

Built192799 years old
Length26.9 ft8.2 m
Daily traffic95counted 2023
Last inspectedJuly 2024every 24 months

Location

StateNew Hampshire
CountyHillsborough
Location0.5 Mi From Jaffrey Tl
CarriesMill Road
CrossesGridley River
Coordinates42.81424, -71.96986

Physical Characteristics

MaterialConcrete
DesignSlab
Total Length26.9 ft (8.2 m)
Max Span8.9 ft (2.7 m)
Deck Width19.0 ft (5.8 m)
Deck Area47.6 sq m
Main Spans2
Year Built1927

Traffic

Avg Daily Traffic95 (2023)
Truck Traffic4%
Lanes On Bridge2

Inspection & Ownership

Last InspectionJuly 2024
Inspection FrequencyEvery 24 months
OwnerCity/Municipal Highway Agency
Historical SignificanceBridge is possibly eligible (requires evaluation)
Scour Critical3 — Scour critical
Structure Number023500530006800

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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