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I-405 (I-5 to SR-55)


The I-405 South Improvement Project from I-5 to SR-55 is a proposed freeway improvement project currently in the Project Approval and Environmental Document (PA/ED) phase, commonly referred to as the environmental study phase. The Orange County Transportation Authority (OCTA) and the California Department of Transportation (Caltrans) are studying how to address congestion and enhance freeway operations between the I-5 and SR-55 freeways, by adding one or two general-purpose (regular) lanes in each direction, converting buffer-separated HOV (carpool) lanes to continuous access, extending merge lanes, and making various operational improvements to I-405 in the City of Irvine.

OCTA is funding and managing the environmental study phase, and Caltrans is the Lead Agency under the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA) and is responsible for oversight and approval of the alternative to move forward for design and construction.

The I-405 freeway through Irvine plays a central role in progressing Orange County’s mobility, economy and quality of life. This section of I-405 is already at capacity and in need of operational improvements. Studies forecast that average daily traffic will grow from 255,000 to 291,000 by 2050. So, improving operations is necessary to keep this segment of I-405 and Orange County moving.

The proposed project is developed to address existing and projected congestion, and improve freeway operations. Some specific benefits include: better travel times, reduced congestion, and improved weaving and ramp operations. For more information, consult Chapter 1 and Chapter 2.1.6 of the draft environmental document.

In 2006, nearly 70% of voters approved OC Go, formally Measure M, a county-wide half-cent sales tax to fund Orange County’s Transportation Investment Plan. In doing so, voters supported improving I-405. In the OC Go Next-10 Plan, adopted by the OTCA Board of Directors in late 2016, the I-405 Improvement Project (from I-5 to SR-55) is identified as one of the M freeway projects to be approved through the environmental study phase. The project is part of OC Go, and is committed to be delivered and constructed beyond the Next-10 plan timeframe with a combination of OC Go and external funding sources. For more information on OC Go, consult The environmental study phase of the project is also funded in part by OC Go and the federal Surface Transportation Block Grant Program.

Three alternatives were evaluated in the draft environmental document, including one No Build Alternative and two Build Alternatives. Alternative 1 represents the No Build Alternative which includes no improvements from the proposed project but assumes completion of other planned improvements in the study area that are currently underway by Caltrans. Two Build Alternatives add lanes from north of Irvine Center Drive to south of Jamboree Road. Alternatives 2 adds a single general-purpose (regular) lane and an auxiliary (merge) lane in each direction. Alternative 3 includes the general-purpose (regular) lanes described in Alternative 2 and an additional general-purpose (regular) lane in each direction. Build Alternatives 2 and 3 also propose ramp capacity improvements, changing the existing HOV (carpool) lane buffer to continuous access, as well as numerous operational improvements.

The environmental study is mandated by the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA), which were enacted to protect the quality of human, physical, and biological environments. In accordance with these laws, agencies must follow a protocol of analysis and public disclosure in their decision making process for any proposed project which may potentially impact the environment. In this process, OCTA and Caltrans analyze effects the project may cause on physical, biological and human environments. If it is determined that the proposed project may have potentially significant effects, measures to avoid, minimize, and/or mitigate such impacts must be considered and implemented. For more information on CEQA, go to, and for more info on NEPA, go to

Numerous environmental areas are studied, including but not limited to: noise, air quality, traffic, water quality, animal/plant communities, visual/aesthetics, land use, cultural and paleontological resources, community impacts and cumulative impacts. All environmental technical studies are prepared in accordance with legal regulations and policies.

Yes. Consistent with Measure M, Alternatives 2 and 3 would mostly be constructed within the existing public right-of-way. No full acquisitions, residential displacements, or nonresidential displacements are proposed. However, one partial acquisition and some temporary construction easements would be required to construct the proposed improvements, including soundwalls. The area subject to partial acquisition is generally the back slope of a parking lot serving commercial property. For more information on right-of-way, refer to Chapter of the draft environmental document and/or speak with a Right-of-Way Specialist at the public hearing.

A Noise Study Report (NSR) and Noise Abatement Decision Report (NADR) were completed as part of the environmental study. Noise abatement in the form of soundwalls are proposed when the future noise level with the project exceeds or approaches the noise abatement criteria (NAC) and are both feasible and reasonable. The final decision on noise abatement will be made upon completion of the project design. Feasibility generally relates to a soundwall’s expected capacity to reduce noise, while reasonability generally relates to the soundwall’s cost. As part of Alternatives 2 and 3, six soundwalls are proposed for further consideration along the project to reduce noise impacts. Existing soundwalls that will not be relocated or replaced will remain in place.

Members of the public can view noise study results in the NSR. Similarly, members of the public can view reasonable allowances, estimated costs and noise barrier recommendations in the NADR. By consulting these documents and data, members of the public will confirm why a studied soundwall was determined to be not feasible and/or not reasonable.

Yes. Both Alternatives 2 and 3 call for modifying the carpool lanes from “buffer-separated carpool lanes” to “continuous access carpool lanes” throughout the project limits. Continuous access carpool lanes are striped with broken white lines to allow “carpoolers” to enter and/or exit the carpool lanes at any time along the route. By contrast, the existing “buffer-separated” lanes only allow carpoolers to enter and exit at specific locations. In Orange County, continuous access carpool lanes are operational on freeways such as SR-22, SR-55, SR-57 and SR-91.

Yes. In Alternatives 2 and 3, two bridge structures including the San Diego Creek Channel Reach 1 and San Diego Creek Channel Reach 2 would be widened to the north. In addition, a new bridge is proposed on the northbound side of I-405 for new braided ramps between SR-133 and Sand Canyon Avenue.

Alternatives 2 and 3 would not result in any direct permanent impacts to recreation areas. During construction, however, Alternatives 2 and 3 would result in temporary impacts to the San Diego Creek Trails (north and south) and the Freeway Trail. On these trails, full closure would likely be necessary for a period of time to accommodate bridge widening and soundwall construction. Detour paths will be provided during closure. For more information, refer to Appendix A of the draft environmental document.

Caltrans is currently managing and implementing a series of planned improvements that are intended to further enhance safety and improve traffic operations along I-405 within the study area of the proposed project. These improvements are expected to be completed by the time the proposed project may begin construction, should a Build Alternative be approved. The I-405 South Improvement Project assumes completion of these improvements in all alternative designs.

Alternatives 2 and 3 would likely decrease the amount of vegetation along the freeway and change the visual character and quality of the corridor, but would not be adversely impacted. Construction of the Build Alternatives would replace landscaping and replant trees to minimize visual impacts. The replanted trees would be skyline trees, more than 40 feet tall at mature height, which would help provide a similar character to the corridor over time. For more information, refer to Chapter 2.1.7 of the draft environmental document.

As with other freeway improvement projects, the proposed project alternatives were developed through a preliminary planning document, the Project Study Report-Project Development Support (PSR-PDS). Approved by Caltrans on December 10, 2013, this document describes transportation issues within the project corridor, identifies the scope of viable alternatives, and provides an estimate of the project development support resources required. Those alternatives were carried forward to the current environmental study phase, and were further studied and refined based on technical studies.

Caltrans is legally responsible for operating the I-405. As a result, the Director of Caltrans District 12 has the authority to approve a preferred alternative. The project development team (PDT), which is comprised of professional and technical staff from OCTA, Caltrans, the City of Irvine, and other agencies of jurisdiction, will recommend a Preferred Alternative.

Throughout the environmental study phase, OCTA and Caltrans will implement a public communications and community outreach program. The environmental study phase includes a public review and comment period, from Nov. 14, 2017 through Dec. 15, 2017. Members of the public have the opportunity to ask questions, view study results, and comment on the draft environmental document during a public hearing on Tuesday, Dec. 5, 2017. You can also receive project information and updates by visiting the project webpage and subscribing to the project email list.

The document is available for public review at or at the following locations from November 14 to December 15, 2017:

  • Caltrans District 12; 1750 East 4th Street, Suite 100, Santa Ana, CA 92705
  • Heritage Park Branch Library; 14361 Yale Avenue, Irvine, CA 92604
  • Mesa Verde Branch Library; 2969 Mesa Verde Drive E, Costa Mesa, CA 92626
  • El Toro Branch Library; 24672 Raymond Way, Lake Forest, CA 92630

You may submit comments in writing. There are three ways to comment:

  • Submit at the public hearing (open house format) on December 5, 2017
  • Email
  • Mail to Scott Shelley, Caltrans District 12, Division of Environmental Analysis, 1750 E 4th Street, Suite 100, Santa Ana, CA 92705

Public comments received during the public review period of the draft environmental document will be reviewed and considered by Caltrans in the selection of the preferred alternative. Comments will be recorded and responded to within the final environmental document, and responses will not be sent directly to commenters. Responses will be available for the public to view in the final environmental document, anticipated to be approved mid-2018.

The project’s environmental study phase was initiated in January 2015 and is anticipated to conclude in mid-2018. Throughout the environmental study process, preliminary design and technical studies for the environmental document were conducted. The draft environmental document has been published for public review and comments beginning on November 14, 2017 through December 15, 2017. A public hearing (open house format) will be held on December 5, 2017, during the 30-day public review period. At the conclusion of the comment period, the PDT will gather the input received and address comments as part of the final environmental document. Release of the final environmental document is expected by mid-2018. We anticipate the opening year of construction to be around 2030 and that is assumed in the studies. However, there is currently no funding identified for final design or construction. Should funding sources be identified, the earliest construction could begin is 2025.

Based on current information, the earliest construction could occur is 2025. However, funding sources for the subsequent development phases, beyond the environmental study phase, have not yet been identified.

The estimated cost of construction is between $240 and $260 million, depending on the build alternative approved.

The December 5, 2017 public hearing (open house) will be held along the project corridor in Irvine, at University Community Park, 1 Beech Tree Lane, Irvine.