Bridge conditions in Merrimack County, New Hampshire
326 inventoried bridges · 27 rated poor · 2025 National Bridge Inventory
United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled
The federal inventory lists 326 bridges in Merrimack County: 146 rated good, 153 fair, and 27 poor.
- 27 of the 326 bridges in Merrimack County, New Hampshire, are rated in poor condition (8.3%) in the 2025 National Bridge Inventory, as of .
- 146 bridges (44.8%) are rated good and 153 (46.9%) fair.
- The median Merrimack County bridge was built in 1966.
- The busiest poor-rated bridge is I-89 over South Street (built 1959), carrying about 46,612 vehicles a day.
Good 44.8% · Fair 46.9% · Poor 8.3% of 326 bridges
Bridges rated poor
Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-89 over South Street | 1959 | 46,612 | Poor |
| US202 over Nhrr Constitution Av. | 1958 | 45,555 | Poor |
| I-393 US 4 US202 over Fort Eddy Rd | 1980 | 40,527 | Poor |
| Nh 9(LOUDON Road) over Merrimack River | 1966 | 23,721 | Poor |
| I-393 US 4 US202 over I-93 | 1958 | 22,391 | Poor |
| I-89 SB over Turkey Pond | 1959 | 20,703 | Poor |
| I-89 NB over Turkey Pond | 1959 | 20,387 | Poor |
| NH104 over Smith River | 1940 | 2,913 | Poor |
| Nh 11 over Nhrr(abd) | 1929 | 2,674 | Poor |
| Nh 11 over Sucker Brook | 1929 | 2,674 | Poor |
| Nh 11 over Sucker Brook | 1929 | 2,674 | Poor |
| US 4 over Blackwater River | 1933 | 2,652 | Poor |
| US202 Nh 9 over Ash Brook | 1970 | 2,610 | Poor |
| US 4 over Smith River | 1929 | 2,087 | Poor |
| NH127 over Warner River | 1937 | 1,581 | Poor |
| NH127 over Blackwater River | 1941 | 1,472 | Poor |
| NH103 over I-89 SB Warner River | 1966 | 1,372 | Poor |
| Delta Drive over I-93 US 4 | 1958 | 612 | Poor |
| Clothespin Br Road over Blackwater River | 1954 | 457 | Poor |
| Wales Bridge Road over Soucook River | 1934 | 372 | Poor |
| Bridge Road over Blackwater River | 1882 | 96 | Poor |
| Last Street over Sucker Brook | 1936 | 96 | Poor |
| Johnson Hill Road over West Branch Brook | 1950 | 96 | Poor |
| Zaccaria Road over Smith River | 1950 | 96 | Poor |
| Walker Brook Road over Frazier Brook | 1950 | 75 | Poor |
| Jack Wells Road over Frazier Brook | 1950 | 73 | Poor |
| Shop Road over Needle Shop Brook | 1930 | 64 | Poor |
Busiest bridges in the county
| Bridge | Built | Vehicles/day | Condition |
|---|---|---|---|
| I-93 Fee Tpk Ramp over Hackett Hill Road | 1978 | 86,013 | Fair |
| I-93 Fee Tpk over Cross Road | 1956 | 82,029 | Fair |
| I-93 Fee Tpk over Ramp A-b | 1957 | 79,640 | Fair |
| I-93 Fee Tpk over Dow Road | 1957 | 78,501 | Fair |
| I-93 Fee Tpk over Robinson Road | 1957 | 78,501 | Fair |
| I-93 Fee Tpk over US 3 Manchester Street | 2000 | 75,054 | Good |
| I-93 Fee Tpk over Nh 9 Loudon Road | 1966 | 72,557 | Fair |
| I-89 over South Street | 1959 | 46,612 | Poor |
| US202 over Nhrr Constitution Av. | 1958 | 45,555 | Poor |
| US202 over CSX | 1949 | 45,555 | Fair |
Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.
All of New Hampshire: New Hampshire bridge conditions by county · every download on the data page.
Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.