US Bridges

Andersen Drive over Mahon Creek

Fair

Marin County, California · W of Andersen & Lindaro · Structure no. 27C0171

Built
1997
28 years old
Condition
Fair
inspected July 2023
Type
Slab
Concrete Continuous
Length
91 ft
2 main spans
Daily traffic
3,500
2021 count
Owner
City
City or Municipal Highway Agency

About this bridge

Andersen Drive over Mahon Creek is a concrete continuous slab carrying Andersen Drive over Mahon Creek in Marin County, California. It was built in 1997, so it is 28 years old, younger 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 3,500 vehicles a day, roughly 2% of them trucks, projected to reach 4,000 by 2040. The structure is 91 ft (27.6 m) long and 60 ft wide.

Location

Open in Google Maps
CarriesAndersen Drive
CrossesMahon Creek
LocationW of Andersen & Lindaro
RouteCity Street 0
CountyMarin County
StateCalifornia
Coordinates37.96849, -122.52635
Functional classUrban Local

Condition and inspection

Fair

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

ComponentRatingMeaning
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating59.6 US tons
Inventory rating35.7 US tons

Structure

Structure typeSlab
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length91 ft (27.6 m)
Longest span44 ft (13.3 m)
Deck width60 ft (18.3 m)
Roadway width42 ft (12.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,500 (2021)
Projected traffic4,000 by 2040
Trucks2%
Lanes on structure3
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed—
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was Andersen Drive over Mahon Creek built?

It was built in 1997, making it 28 years old in 2025.

What condition is Andersen Drive over Mahon 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 July 2023.

How much traffic does Andersen Drive over Mahon Creek carry?

About 3,500 vehicles per day (2021 count), of which roughly 2% are trucks.

How long is Andersen Drive over Mahon Creek?

The structure is 91 ft (27.6 m) long with a longest span of 44 ft (13.3 m) and a deck 60 ft wide.

Who owns Andersen Drive over Mahon Creek?

It is owned by the City or Municipal Highway Agency.