Menan-Lorenzo and Thornton Interchanges

U.S. 20 Menan-Lorenzo Interchange and

U.S. 20 Thornton Interchange

Menan-Lorenzo Interchange Map
Thornton Interchange Map

Project Facts

Menan-Lorenzo
Key Number: 8132
Project Number: NH-6470(125)

Thornton
Key Number: 8454
Project Number: NH-6470(125)

Current Status

A public hearing on the Menan-Lorenzo and Thornton Interchange projects held June 23, 2005, in Rexburg was attended by more than 200 people. Comments were accepted until July 7, after which ITD and its consultant, CH2M Hill, reviewed and addressed each of the comments before presenting the hearing report, environmental documents and other information to the Idaho Transportation Board at its meeting Nov. 17, 2005.

Locations for the Menan-Lorenzo and Thornton interchanges were announced.

ML-A for the Menan-Lorenzo Interchange north of Rigby and south of the Snake River. ML-A is the farther north of the two alternatives presented to the public and will connect to 700 North (Menan-Lorenzo Highway) and the LaBelle Road.
T-G for the Thornton Interchange. T-G is located north of the community of Thornton and would connect to 3300 West and 4700 South.

All remaining at-grade crossings between Rigby and Rexburg will be closed when the interchanges are built. Two potential locations and a no-build option were considered for each interchange.

Funding for the Menan-Lorenzo Interchange is earmarked for FY2010. Final design and purchase of right of way are under way.

The Thornton Interchange project is listed in the State Transportation Improvement Program in preliminary development with no date for construction. ITD will begin the final design for the Thornton Interchange and purchase the needed right of way.

Project Facts

The proposed project involved adding two interchanges to U.S. 20 between Rigby and Rexburg, one in the Thornton area north of the Snake River in Madison County and one south of Lorenzo in Jefferson County. A railroad track parallels the highway with several at-grade crossings within the area. The highway crosses the Snake River, several canals and sloughs. U.S. 20 is classified as a Principal Arterial within the National Highway System (NHS). The existing roadway is four lanes with a variable-width depressed median.

Project Background

U.S. 20 is a critical link within the NHS, which contains Interstate and Primary routes regarded as vital to the nation's highway transportation network. U.S. 20 serves interstate, regional, and local needs; it is the major crossing of the Snake River in this area and is the key link between Idaho Falls and the upper Snake River Valley, an area that serves as a primary gateway to Yellowstone National Park and provides access to major resorts and scenic byways in Idaho, Montana and Wyoming.

Purpose

The U.S. 20 Corridor Plan adopted by the Idaho Transportation Department Board on June 23, 2000, concluded that U.S. 20 should be a full–access control facility in 6.8 miles between Rigby and Thornton to increase safety and improve operational effectiveness by eliminating all at-grade intersections.

The project would also restore local access to U.S. 20 where necessary by means of grade-separated interchanges. The local service area is bisected by the Snake River. It was necessary to address needs both north of the Snake River in Madison County and generally in the vicinity of Thornton, and south of the Snake River in Jefferson County. Interchange locations were sought to connect to the local system.

Need

Average Daily Traffic (ADT) in 2000 on U.S. 20 in the project area was 12,740 vehicles per day, making turning movements from connector roads onto U.S. 20 problematic at the at-grade intersections. The average annual traffic growth rate in the project area varied from 2% to 11%. Growth in traffic volumes was expected to continue to deteriorate existing intersection conditions. Anticipated increases on US-20 and intersecting county roads would raise the accident rate for at-grade crossings above the average, based on observed conditions at higher ADT locations.

Accident statistics from 1996 to 2000 indicated that 11 serious injury accidents, one of which was a fatality, occurred in the project area during these five years. Of the 11, five appear to be related to intersection movements. Due to the projected traffic growth and the corresponding accidents, the District proposed two interchanges.

Contacts

Bruce King, Public Information Specialist, District 6
(208) 745-5611
bruce.king@itd.idaho.gov

Compliance with Title VI of the Civil Rights Act

The Idaho Transportation Department (ITD) is committed to compliance with Title VI of the Civil Rights Act of 1964 and all related regulations and directives. ITD assures that no person shall on the grounds of race, color, national origin, gender, age, or disability be excluded from participation in, be denied the benefits of, or be otherwise subjected to discrimination under any ITD service, program, or activity. The department also assures that every effort will be made to prevent discrimination through the impacts of its programs, policies, and activities on minority and low-income populations. In addition, the department will take reasonable steps to provide meaningful access to services for persons with Limited English Proficiency.