US Bridges

ST 9 Boylston ST over Water Hemlock Gorge

Fair

Middlesex County, Massachusetts · At Quinobequin RD · Structure no. N120052EHDOTNBI

Built
1932
93 years old
Condition
Fair
inspected September 2024
Type
Arch - Deck
Concrete
Length
23 ft
1 main span
Daily traffic
53,100
2024 count
Owner
State
State Highway Agency

About this bridge

ST 9 Boylston ST over Water Hemlock Gorge is a concrete arch - deck carrying ST 9 Boylston ST over Water Hemlock Gorge in Middlesex County, Massachusetts. It was built in 1932, so it is 93 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 53,100 vehicles a day, roughly 2% of them trucks, projected to reach 136,136 by 2031. The structure is 23 ft (7 m) long and 186 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesST 9 Boylston ST
CrossesWater Hemlock Gorge
LocationAt Quinobequin RD
RouteState Highway 9
CountyMiddlesex County
StateMassachusetts
Coordinates42.31684, -71.22804
Functional classUrban Other Principal Arterial

Condition and inspection

Fair

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

ComponentRatingMeaning
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; action required to protect exposed foundations
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating110.1 US tons
Inventory rating110.1 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckNot applicable
Main spans1
Design loadUnknown
Structure length23 ft (7 m)
Longest span20 ft (6.1 m)
Deck width186 ft (56.6 m)
Roadway width99 ft (30.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic53,100 (2024)
Projected traffic136,136 by 2031
Trucks2%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusListed on the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$4.4 million (2025 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was ST 9 Boylston ST over Water Hemlock Gorge built?

It was built in 1932, making it 93 years old in 2025.

What condition is ST 9 Boylston ST over Water Hemlock Gorge 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 ST 9 Boylston ST over Water Hemlock Gorge carry?

About 53,100 vehicles per day (2024 count), of which roughly 2% are trucks.

How long is ST 9 Boylston ST over Water Hemlock Gorge?

The structure is 23 ft (7 m) long with a longest span of 20 ft (6.1 m) and a deck 186 ft wide.

Who owns ST 9 Boylston ST over Water Hemlock Gorge?

It is owned by the State Highway Agency.