Background

SR 99 serves as an interregional route connecting rural communities with larger metropolitan areas. Traffic on SR 99 is a mixture of vehicles traveling to residential sites, commercial & agriculture establishments, and recreational facilities.

Project Overview

The project will study, design, and construct an alternative intersection control measures such as a roundabout or traffic signal.

Purpose & Need

The purpose of this project is to reduce the number and severity of intersection related collisions at SR 99 and Rio Bonito Road.

Over a five-year period (April 1, 2019 to March 31, 2024), a total of 15 collisions occurred at this intersection, including eight injuries. All collisions were broadside that were caused by a failure to yield. An intersection improvement project is needed to address the collisions identified. 

Funding

This project was approved at the June 2026 California Transportation Commission (CTC) meeting to begin project development and is funded by the State Highway Operation and Protection Program (SHOPP). The CTC is responsible for programming and allocating funds for the construction of highway, passenger rail, transit and active transportation improvements throughout California. 

Total Project Cost Estimate: $12,350,000

Local Agency Outreach

Caltrans is working with the Butte County Association of Governments (BCAG), Butte County Public Works, and City of Biggs. 

Your Voice Matters!

Do you travel through SR 99 & Rio Bonito Road or live near the intersection? Caltrans wants to hear from you! Take the short survey today and help us improve the intersection. 

Just click the "Survey" tab at the top of this page. 

Map

Map of State Route 99 & Rio Bonito Road Intersection

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Project Initiation

October 2, 2025: Caltrans met with local agencies to review proposed project

October 23, 2025: Caltrans presented an overview of the project at BCAG Board of Directors meeting 

May 1, 2026: Caltrans finalized the Project Initiation Report (PIR) 

June 26, 2026: Safety project voted and approved at CTC meeting to begin project development

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Project Approval and Environmental Document

July 2026: PA&ED phase officially started

Fall 2027: Target schedule to finalize PA&ED phase

During this phase, Caltrans:

  • performs technical analysis
  • completes required environmental studies
  • identifies potential impacts and avoidance, minimization, and/or mitigation
  • prepares and approves both the DED and the Final Environmental Document
  • finalizes the project design concept

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Draft Environmental Document (DED) & Public Review

DED target schedule

Summer 2027: DED released for review

Summer 2027: 30-day public comment period

Summer 2027: Public Open House (location TBD) 

Purpose of this stage is to gather formal public comment on the environmental analysis and alternatives.

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planned

Final Project Design

Fall 2027 - Fall 2028: target schedule to finalize design plans

Fall 2028 - Spring 2029: target schedule advertise and award contract to contractor

During this phase, Caltrans will complete project design, prepare engineering plans, and construction specifications. Any necessary right-of-way coordination or utility adjustments will occur in parallel with final project design. 

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planned

Construction

Spring 2029 - Fall 2029: target construction schedule

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