US Bridges

NM-170 over LA Plata River

Fair

San Juan County, New Mexico · 2.7 MI N of JCT NM-574 · Structure no. 000000000005499

Built
1955
70 years old
Condition
Fair
inspected September 2024
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
199 ft
5 main spans
Daily traffic
3,467
2023 count
Owner
State
State Highway Agency

About this bridge

NM-170 over LA Plata River is a steel continuous stringer/multi-beam or girder carrying NM-170 over LA Plata River in San Juan County, New Mexico. It was built in 1955, so it is 70 years old, older than the New Mexico average of 51.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 3,467 vehicles a day, roughly 11% of them trucks, projected to reach 4,715 by 2043. The structure is 199 ft (60.7 m) long and 28 ft wide. If it were closed, the detour would be 65.2 mi (105 km).

Location

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CarriesNM-170
CrossesLA Plata River
Location2.7 MI N of JCT NM-574
RouteState Highway 170
CountySan Juan County
StateNew Mexico
Coordinates36.96765, -108.19124
Functional classRural Major Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating50 US tons
Inventory rating26.8 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans5
Design loadH 15
Structure length199 ft (60.7 m)
Longest span42 ft (12.8 m)
Deck width28 ft (8.5 m)
Roadway width24 ft (7.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,467 (2023)
Projected traffic4,715 by 2043
Trucks11%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed65.2 mi (105 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$760,000 (2020 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was NM-170 over LA Plata River built?

It was built in 1955, making it 70 years old in 2025.

What condition is NM-170 over LA Plata River in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in September 2024.

How much traffic does NM-170 over LA Plata River carry?

About 3,467 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is NM-170 over LA Plata River?

The structure is 199 ft (60.7 m) long with a longest span of 42 ft (12.8 m) and a deck 28 ft wide.

Who owns NM-170 over LA Plata River?

It is owned by the State Highway Agency.