Experts Talk: Using NEPA Assignment to Expedite Transportation Project Delivery with Diane Nulton and Taylor Horne

Experts Talk is an interview series with technical leaders from across our transportation program. 

Enhancing Success Through NEPA Assignment

While important for safeguarding our communities and environmental resources, the National Environmental Policy Act (NEPA) environmental review process can be time-consuming, especially for major infrastructure projects. Expediting the NEPA process has been a focus of numerous efforts for decades, with recent statutory updates requiring completion of environmental assessments (EAs) within one year and environmental impact statements (EISs) within two years.

Senior Environmental Project Manager Diane Nulton and Transportation Environmental and NEPA Lead Taylor Horne have decades of experience navigating the NEPA process. While working for the Alaska Department of Transportation and Public Facilities, Taylor was the statewide environmental program manager and led the negotiation that resulted in Alaska’s successful implementation of NEPA Assignment. Diane has worked with transportation agencies across the U.S., helping guide complex programs through the NEPA process, authoring and teaching NEPA courses, updating agency handbooks and advising on the complex environmental review process. In this interview, they describe the NEPA Assignment initiative that states can use to expedite reviews, the benefits and drawbacks of these programs, and how to best implement them. 

Q. What is NEPA Assignment?

Diane: NEPA Assignment is a tool available to state departments of transportation (DOTs) to expedite the project development process by assuming the majority of environmental approval responsibilities administered by federal DOT agencies. With the downsizing of the federal government in 2025, the secretary of transportation sent a letter to state governors encouraging state DOTs to consider taking on NEPA Assignment to facilitate NEPA reviews and expedite delivery of their major projects.  

To date, nine states have assumed full NEPA Assignment responsibility — California, Texas, Ohio, Florida, Utah, Alaska, Arizona, Nebraska and Maine. HDR has helped seven of these nine states, and we are currently assisting several other states working toward NEPA Assignment, making HDR the national leader in helping states navigate the NEPA Assignment process.  

Taylor: There are two NEPA Assignment options that allow a state transportation agency to assume the federal government's responsibility for completing the environmental process under NEPA. 

• NEPA Assignment (23 U.S.C. 327): This program allows states to take over federal agency environmental review and approval responsibilities for all classes of actions under NEPA, including categorial exclusions (CEs), EAs and EISs. The requirements for review are the same, but the state is responsible for completing that review, rather than a federal agency.
• CE Assignment (23 U.S.C. 326): This program allows states to take over approving CE determinations, finding that specific actions will have no significant effect on the environment, and therefore, neither an EA nor an EIS is required. Approximately 95% of projects are covered by CEs. Under the CE Assignment program, federal agencies are still responsible for overseeing EAs and EISs. With fewer requirements and covering most projects, the CE Assignment program has been used in the past as a stepping stone to full NEPA Assignment.

Q. What are the benefits of taking on NEPA Assignment?

Diane: State DOTs receiving federal funding for a project must complete the NEPA process, which can be long and cumbersome. One major advantage of NEPA Assignment is the elimination of federal agency review and approval. Eliminating federal sequential review, revision and backchecking time saves time, money and ultimately enables a DOT to deliver projects sooner.

The time savings can be significant. In California, for example, the state’s 2024 report on its NEPA Assignment shows draft EA/EIS approvals are completed 12 to 31 months faster compared with approvals before California started the program. 

Taylor: NEPA Assignment puts the state DOT in the driver’s seat. The state DOT directly consults and negotiates with federal agencies acting as a lead agency themselves rather than using the Federal Highway Administration (FHWA) or another funding agency as an intermediary. It gives states a seat at the table during discussions with federal agencies and a direct line of communication.

More control means more flexibility. When overseeing the NEPA Assignment program in Alaska, one of the biggest benefits I observed was the ability to innovate without having to ask FHWA for permission on every adjustment. The environmental requirements did not change, but how Alaska DOT&PF met them — the procedures and forms and processes — could flex and become more efficient.

NEPA Assignment delivers more transportation benefits to the public sooner. Completing major projects faster and cheaper creates more capacity in your pipeline. And that means more federal aid available for other projects. 

Q. Why haven’t more states implemented NEPA Assignment? What are the hesitations or hurdles?

Diane: The hesitations can vary. When pursuing CE or NEPA Assignment, some states may have a great relationship with their federal agency contacts and may not want to put in the time and effort to change a process that seems to be working well already. Depending on the state, some also deal with the EA/EIS process much less often, with a handful of projects every few years, making the benefits of full NEPA Assignment less appealing. That said, the 2025 downsizing of the federal government has resulted in a scarcity of NEPA reviewers and decision makers, making NEPA Assignment more attractive. 

Taylor: The NEPA Assignment application process is a hurdle, as it involves several steps and requires an upfront investment to complete. Relying on the expertise of those who have gone through it before and understand the process helps, but getting to a NEPA Assignment Memorandum of Understanding (MOU) still requires a concerted effort on the part of state leadership.

An often-raised concern for many states is the required limited waiver of sovereign immunity. This action, which typically requires legislative approval, means states can then be sued in federal court for their NEPA actions and decisions. Because this waiver must be passed by legislators who are likely not familiar with the particulars of infrastructure environmental review, it can require some political savvy and patience to explain exactly what is involved in this program and the benefits that make waiving sovereign immunity worthwhile. 

Q. What is the general process of applying for NEPA Assignment and how long does it take?

Diane: The process starts with the state submitting a letter of interest to the U.S. Department of Transportation and waiving their sovereign immunity for the narrow purpose of the NEPA Assignment programs.

A federal team then meets with the state to explain the program and requirements in more detail. From there, when applying for full NEPA Assignment (23 U.S.C. 327), the state is required to complete a meticulous application that shows it is capable of taking on the federal NEPA duties. For both CE Assignment and full NEPA Assignment, the state DOT must demonstrate that it has the appropriate staff, an independent decision-making structure, proper training and knowledge of the process and the right quality assurance/quality control structures in place.

Taylor: After the initial letter of interest, a public comment period is held on the draft application before a final application and decision. Following that decision, the final step is negotiating a detailed MOU that lays out the specific requirements and responsibilities of each party. These negotiations can take quite a while and are often facilitated with the help of an outside consultant and legal expert.

Altogether, the process of applying for and implementing NEPA Assignment can take from six months to up to a year or more. The process of applying for CE Assignment is typically shorter and for that reason it is sometimes used as a first step prior to seeking full NEPA Assignment. 

Q. How can a consultant like HDR assist state DOTs in securing NEPA Assignment? 

Diane: To begin with, by working through the big picture strategy. Organizing and planning the complex application process can be a challenge. To help our clients prepare, we recommend a facilitated workshop to help leaders prepare for the NEPA Assignment application process and map out a plan. This approach has been successful for several of the states we have helped.

To successfully take on the NEPA decision-making role, the federal government needs to be assured that the state DOT has the correct procedures in place and its staff is trained to do the job of environmental reviews meeting federal standards. For states that do not have a lot of environmental staff or that have inexperienced staff, it can be a high bar. State DOTs unsure of how their procedure manuals and staff will stack up can undertake or commission a preliminary readiness assessment/gap analysis of existing manuals, training and staff knowledge, to address deficiencies before an official FHWA analysis. 

Taylor: Once the readiness assessment/gap analysis is completed, actions are undertaken to address deficiencies. It’s likely that environmental procedures manuals will need to be updated, as HDR NEPA specialists did for Alaska, Utah, and Nebraska during their successful applications. New performance measures, QA/QC plans and handbooks will likely need to be created. Training will need to take place on the updated procedures and requirements. Websites and public-facing materials on the state’s environmental process will likely need to be updated. HDR can act as an extension of in-house DOT staff to facilitate updates of materials and delivery of training to help the DOT be prepared to take on federal reviews, approvals and decision-making.  

In addition to, and in parallel with updates to existing guidance materials, policies, procedures, and training is preparation of the NEPA Assignment application itself. Our teams took on this challenge in multiple states, lifting the burden off state DOT staff for creating draft and/or final applications for submittal to federal agencies. We can use those experiences as templates for assisting additional states desiring to take on NEPA Assignment.

Once a state has successfully achieved a signed and executed NEPA Assignment MOU, annual audits for the initial years, and self-assessments are then required. Expanded and continued training may also be needed to get staff up to speed on the latest requirements and new staff receive appropriate training. HDR has assisted several states with these types of activities, including for example, environmental procedure manual updates for Utah, and NEPA/Section 4(f) training every two years for Alaska. 

Inspiration & Advice

Q. How did your career lead to a specialization in NEPA regulations?

Taylor: I studied environmental policy, planning and public affairs in school, and I knew that I wanted a career that involved working with the public on environmental issues. After a few years working in western water rights in Washington, I expanded to doing NEPA work for the Alaska DOT&PF, helping them with their CE assignment program at the time. Successfully growing their program into the full NEPA Assignment program was a rewarding challenge. Now I work with HDR on transportation projects in Alaska and across the country. This work is rewarding because it often deals with big, important infrastructure projects and how they can be accomplished with natural and social impacts in mind.

Diane: With a degree in biology/ecology my first job was with the New Jersey Department of Environmental Protection conducting bioassays at municipal and industrial facilities. After a year or so I transitioned to consulting where I focused on wetland delineations and natural resource assessments, which expanded into work on EISs, many of which were fast-tracked, controversial projects. My next challenge was serving as an extension of PennDOT Central Office environmental staff reviewing documents and developing procedures manuals and training courses for EISs, EAs, CEs, Section 4(f) and other topics. This led to developing NEPA and Section 4(f) courses for the National Highway Institute and teaching courses across the country. Doing the work, reviewing others’ work, developing guidance, teaching others and seeing how many states expedite the environmental process has provided me with a unique perspective and problem-solving skills. I find teaching others and trouble-shooting the controversial and complicated situations most rewarding.

Q. What advice do you have for those entering the environmental review field?

Taylor: Don’t be afraid to try new things, take on tasks that appear daunting at first, and never hesitate to ask for advice. I am repeatedly amazed at the thoughtfulness and generosity of folks who work in this field — they are always willing to help out by offering new perspectives and assistance in tackling big challenges that benefit us all.

Diane: The best way to figure out what you like best in this industry is to try new things. Learn as many aspects of the process as you can. Volunteer to help with traffic counts or shovel dirt for test pits at an archaeological site. Read the regulations and guidance documents relevant to what you are doing. Don’t just follow the last best example; learn why you are doing what you are doing. Think outside the box. Look for innovative ways to do things more efficiently and effectively. When someone says a task is impossible, look for a way to make it possible. Network with others and share your knowledge. 

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