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NH175 over Mill Brook

Grafton County, New Hampshire · rated Fair in the 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

NH175 over Mill Brook in Grafton County, New Hampshire, is rated in fair condition in the 2025 National Bridge Inventory (as of August 20, 2026).
Its lowest-rated component is the deck, rated 6 (satisfactory condition) on the 0-9 scale.
It was built in 1935 and reconstructed in 1979, making it 90 years old at the 2025 inventory.
It carries about 1,610 vehicles a day (traffic count year 2023).
Its listed owner is the state highway agency.
It is one of 242 of the 547 inventoried bridges in Grafton County rated fair (44.2%); 43 (7.9%) are rated poor.
A fair rating means the lowest-rated major component scores 5 or 6 on FHWA's 0-9 scale: some deterioration or minor section loss, but the structure is sound. It is the middle class, not a warning.

Component ratings

Source: FHWA National Bridge Inventory, 2025 data as reported by the New Hampshire department of transportation.

Bridge	Built	Vehicles/day	Condition
I-89 NB over Plaza Connector Road	2012	28,690	Fair
I-89 Nh 10 over Brook Atv Trail	1959	25,062	Fair
I-89 Nh 10 NB over Truck Road Mascoma River	1966	23,084	Fair
I-89 NB over US 4 Nh 10	1966	22,727	Good
I-89 NB over Connecticut River Necrr	1966	22,288	Poor
I-89 Nh 10 SB over US 4	1966	21,937	Good