US Bridges

US 1 Nb/L Mystc L over HWY Chelsea Street

Fair

Suffolk County, Massachusetts · L Mystic Lower · Structure no. B160174WWDOTNBI

Built
1950
75 years old
Condition
Fair
inspected September 2023
Type
Truss - Thru
Steel
Length
439 ft
1 main span
Daily traffic
42,492
2022 count
Owner
State
State Highway Agency

About this bridge

US 1 Nb/L Mystc L over HWY Chelsea Street is a steel truss - thru carrying US 1 Nb/L Mystc L over HWY Chelsea Street in Suffolk County, Massachusetts. It was built in 1950, so it is 75 years old, older than the Massachusetts average of 63.8 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 42,492 vehicles a day, roughly 7% of them trucks, projected to reach 70,595 by 2032. The structure is 439 ft (133.8 m) long and 42 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesUS 1 Nb/L Mystc L
CrossesHWY Chelsea Street
LocationL Mystic Lower
RouteU.S. Route 1
CountySuffolk County
StateMassachusetts
Coordinates42.38018, -71.05172
Functional classUrban Principal Arterial - Other Freeway or Expressway

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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment7: Better than present minimum criteria
Operating rating49.6 US tons
Inventory rating29.8 US tons

Structure

Structure typeTruss - Thru
MaterialSteel
DeckClosed grating
Main spans1
Design loadHS 20
Structure length439 ft (133.8 m)
Longest span439 ft (133.8 m)
Deck width42 ft (12.7 m)
Roadway width36 ft (11 m)
Vertical clearance over deck16 ft (4.9 m)

Traffic and service

Average daily traffic42,492 (2022)
Projected traffic70,595 by 2032
Trucks7%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed5 mi (8 km)
TollToll bridge
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$16.6 million (2025 estimate)
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was US 1 Nb/L Mystc L over HWY Chelsea Street built?

It was built in 1950, making it 75 years old in 2025.

What condition is US 1 Nb/L Mystc L over HWY Chelsea Street 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 2023.

How much traffic does US 1 Nb/L Mystc L over HWY Chelsea Street carry?

About 42,492 vehicles per day (2022 count), of which roughly 7% are trucks.

How long is US 1 Nb/L Mystc L over HWY Chelsea Street?

The structure is 439 ft (133.8 m) long with a longest span of 439 ft (133.8 m) and a deck 42 ft wide.

Who owns US 1 Nb/L Mystc L over HWY Chelsea Street?

It is owned by the State Highway Agency.