US Bridges

State Route 84 over West Union Creek

Fair

San Mateo County, California · 04-SM-084-19.89-WDS · Structure no. 35 0044

Built
1903
122 years old
Condition
Fair
inspected May 2024
Type
Arch - Deck
Concrete
Length
23 ft
1 main span
Daily traffic
6,600
2005 count
Owner
State
State Highway Agency

About this bridge

State Route 84 over West Union Creek is a concrete arch - deck carrying State Route 84 over West Union Creek in San Mateo County, California. It was built in 1903, so it is 122 years old, older than the California average of 54.8 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 6,600 vehicles a day, roughly 2% of them trucks, projected to reach 26,076 by 2046. The structure is 23 ft (7 m) long and 22 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesState Route 84
CrossesWest Union Creek
Location04-SM-084-19.89-WDS
RouteState Highway 84
CountySan Mateo County
StateCalifornia
Coordinates37.42525, -122.26719
Functional classUrban Minor 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.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating30 US tons
Inventory rating17.9 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 width22 ft (6.7 m)
Roadway width20 ft (6.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,600 (2005)
Projected traffic26,076 by 2046
Trucks2%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was State Route 84 over West Union Creek built?

It was built in 1903, making it 122 years old in 2025.

What condition is State Route 84 over West Union Creek 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 May 2024.

How much traffic does State Route 84 over West Union Creek carry?

About 6,600 vehicles per day (2005 count), of which roughly 2% are trucks.

How long is State Route 84 over West Union Creek?

The structure is 23 ft (7 m) long with a longest span of 20 ft (6.1 m) and a deck 22 ft wide.

Who owns State Route 84 over West Union Creek?

It is owned by the State Highway Agency.