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Everglades Parkway: the I-75 extension through Alligator Alley

Following the passage of the Federal-Aid Highway Act of 1956, the United States began a national program of highway construction to facilitate more efficient connections between metropolitan areas and provide farmers with better access to local markets. The act authorized the construction of a 41,000-mile system. In 1968, Congress passed another highway bill to expand the interstate system by an additional 1,500 miles. The legislation included an authorization to extend Interstate 75 (I-75) south and east from Fort Myers on the Gulf Coast to an area west of Fort Lauderdale on the Atlantic Coast. The 114-mile extension would become known as the Everglades Parkway.

In 1969, the Florida Department of Transportation (FDOT) began to study alternative routes. Unlike the planning for earlier interstate segments, FDOT was required to comply with the newly-passed National Environmental Policy Act (NEPA). As a result, the I-75 extension included numerous design elements tailored to minimize impacts on the natural environment. Importantly, none of these design elements undermined the original goal of the project: to construct a limited-access, four-lane, divided highway that would connect Gulf and Atlantic Coast population centers, providing increased travel speeds and reduced travel times. 

Large infrastructure projects such as the I-75 extension present states with many technical challenges. Engineers must determine everything from pavement type and interchange design to the sharpness of curves and how to prevent rainwater from forming unsafe pools on the roadway. These challenges share a common thread: They are all related to the design of the roadway. Prior to NEPA, engineers focused narrowly on how to design a facility as opposed to how that facility would affect the surrounding community or natural environment. Part of NEPA’s value is that it requires planners and engineers to widen the aperture of concern. Environmental review necessitates that state and local governments solve the engineering puzzle in a way that minimizes the negative spillover that often accompanies major infrastructure projects. 

Improving flow involved several design modifications. According to FDOT design policy at the time, highways were required to provide at least 100 feet of land between the edge of the roadway and any adjacent body of water. This requirement was intended to reduce the risk of passengers drowning in the event that a driver loses control of a vehicle. In effect, the 100-foot buffer provided a chance for a driver to slow the vehicle and regain control, hopefully avoiding entering the water. In the case of the Everglades Parkway, complying with this requirement would have meant draining additional wetland on either side, further impairing critical habitats and the sheet flow of fresh water. Instead, FDOT chose to waive this policy and add a cable barrier where necessary. The cable barrier would stop wayward vehicles before they reached the water. 

FDOT’s final significant modification dealt with the channels running parallel to the highway on either side as well as the connections spaced at regular intervals that connected the channels on the north and south side of the highway. Experience with the channels along the original State Route 83 showed that the state needed to both modify their depth and regularly remove aquatic vegetation that could reduce sheet flows by as much as 90 percent. FDOT also scheduled construction activity to avoid the heaviest seasonal rains. By adjusting the sequence and timing of work, the state was able to significantly reduce sedimentation—rainwater carrying dirt, rocks, and other loose debris from the construction site into the wetlands.

The environmental review process provided FDOT with the information necessary to make smart and effective changes to the design, construction, and maintenance of the Everglades Parkway, all with an eye toward reducing harmful impacts on the surrounding ecosystem. Far from being a burden, NEPA brought forward the technical expertise of scientists across numerous fields to help the state build a fundamentally better, more sustainable facility that continues to provide benefits to this day.


[1] “Environmental/Section 4(f) Statement Interstate Route 75: State Road 82 near Ft. Myers in Lee County to U.S. Route 27 at Andytown in Broward County” Florida Department of Transportation. August 25, 1972.

[2] Florida Wildlife Federation v. Goldschmidt, 506 F. Supp. 350 (S.D. Fla. 1981). Available at:

[3] August Burghard. Alligator Alley: Florida’s most controversial highway. (Washington: Lanman Company, 1969).

[4] “Final List of Nationally and Exceptionally Significant Features of the Federal Interstate Highway System.” U.S. Department of Transportation, FHWA. Available at:


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