PARROTTS FERRY RD

over NEW MELONES RESERVOIR

4 MILES SOUTH OF ROUTE 4, Tuolumne County, California

Condition

Poor

Year Built

1978

Daily Traffic

2,500

Length

129 ft

About This Bridge

PARROTTS FERRY RD carries traffic over NEW MELONES RESERVOIR in Tuolumne County, California. Built in 1978, this structure is 48 years old, placing it among the older bridges still in active service. The bridge features prestressed concrete continuous construction with a segmental box girder design, a combination chosen by engineers to meet the specific requirements of this crossing.

Approximately 2,500 vehicles cross this bridge daily, indicating lower traffic volumes common for local roads and rural routes. While traffic is lighter, these bridges still serve essential community transportation needs. Commercial trucks account for 3% of all crossings. This proportion of commercial traffic is typical for this roadway classification and is factored into the bridge's design load ratings.

The bridge is currently rated in poor condition based on federal inspection criteria established by the Federal Highway Administration. It is classified as structurally deficient, meaning one or more components have received a rating of 4 or below on the 0-9 scale. This designation indicates significant deterioration that warrants attention, though the bridge remains safe for travel within its posted limits. Structurally deficient does not mean unsafe—rather, it signals that repairs or replacement should be prioritized in transportation planning. With a total length of 129 feet, this structure falls within the typical range requiring standard inspection procedures conducted by certified bridge inspectors.

The construction materials used in this bridge were selected based on engineering requirements, cost considerations, and local conditions at the time of construction.

Federal law requires that all highway bridges be inspected at least every 24 months by qualified inspectors following the National Bridge Inspection Standards (NBIS). Some bridges with known issues or unusual characteristics may be inspected more frequently. Inspection data is reported to the National Bridge Inventory, a database maintained by the Federal Highway Administration that tracks the condition of all public highway bridges in the United States. This bridge data is sourced from that federal database and reflects the most recent available inspection results.

Condition Ratings

Structurally Deficient

This bridge has one or more component ratings of 4 or below, indicating significant deterioration that requires attention. The bridge remains safe for travel but may have load restrictions.

7

Deck Condition

Good

4

Superstructure

Poor

5

Substructure

Fair

9

Channel & Protection

Excellent

4

Lowest Rating

Determines condition category

NBI condition ratings range from 0 (failed) to 9 (excellent). Ratings of 4 or below are considered poor. The overall condition category is determined by the lowest individual component rating.

The superstructure rating of 4 shows advanced deterioration in beams or girders.

For a structure built in 1978, the current condition reflects the cumulative effects of age, traffic, and environmental exposure. If this bridge were closed, traffic would face a detour of approximately 19 miles, underscoring the importance of maintaining this crossing.

Bridge Details

Prestressed Concrete Continuous is the primary structural material, which influences maintenance requirements and expected lifespan. The segmental box girder design was selected based on span requirements, load capacity needs, and site conditions at the time of construction. Maintenance responsibility falls to County Highway Agency.

Construction

Year Built1978
MaterialPrestressed Concrete Continuous
Design TypeSegmental Box Girder
OwnerCounty Highway Agency

Dimensions

Total Length129 ft (39.4 m)
Max Span64 ft (19.5 m)
Deck Width4 ft
Deck Area4,846 sq ft

Span dimensions affect structural design choices and load distribution. The deck area of 4,846 sq ft determines surface maintenance scope.

Classification

Route TypeCounty Road
Route Number0
Lanes On Bridge2
Lanes Under Bridge

Status

Toll BridgeNo
Historical SignificanceNot eligible
Scour Critical8
Detour Length19 mi (30 km)

Traffic Data

Traffic volume data helps engineers assess bridge wear patterns and plan maintenance schedules. Average Daily Traffic (ADT) counts are updated periodically and represent typical weekday usage.

2,500

Avg Daily Traffic (2016)

Vehicles per day crossing this bridge

3%

Truck Traffic

Commercial vehicle percentage

3,571

Projected Future ADT

Estimated future demand

This bridge carries approximately 2,500 vehicles per day, translating to roughly 912,500 crossings annually. Lower traffic volumes generally result in less structural wear over time.

Commercial trucks comprise 3% of traffic. Heavy vehicles cause disproportionate wear—a single fully loaded truck can have the impact of thousands of passenger cars on bridge deck surfaces.

Traffic projections estimate future volumes of 3,571 vehicles daily, a 43% increase from current levels. These projections inform capacity planning and potential upgrade requirements.

Load Ratings

Load ratings determine what weight this bridge can safely support. These values are critical for routing heavy vehicles and issuing overweight permits.

Operating Rating

5.4 tons

Maximum allowable load for special permits

Inventory Rating

3.2 tons

Load level for normal traffic

The operating rating of 5.4 tons represents the absolute maximum load this bridge can carry under controlled conditions with special permits. The inventory rating of 3.2 tons is the safe load limit for everyday traffic without restrictions. These relatively low ratings may result in posted weight limits or route restrictions for heavy vehicles.

5-Year Condition Trend

Stable

Condition has remained relatively stable since 2020

Status Changes

  • Exited poor condition in 2023
  • No longer structurally deficient as of 2023
  • Entered poor condition in 2024
  • Became structurally deficient in 2024

Data: 2020-2024 FHWA National Bridge Inventory

Location

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38.643333, -121.041111

Identification

Structure Number32C0076
NBI IDCA-32C0076
State FIPS06
County FIPS109

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Data Source: Federal Highway Administration (FHWA) National Bridge Inventory 2024

Bridge inspection data is typically updated every 24 months. Conditions may have changed since the last inspection.

“Structurally deficient” does not mean a bridge is unsafe or likely to collapse. It indicates that one or more key structural elements are in poor or worse condition. Bridges are inspected regularly and may have load restrictions in place.

This data is for informational purposes only and should not be used for route clearance or vehicle weight decisions.

PARROTTS FERRY RD over NEW MELONES RESERVOIR | California