The Connecticut Department of Transportation (CTDOT) is evaluating two options for replacing the so-called "Mixmaster" interchange of highway bridges in Waterbury following a $223.7 million rehabilitation of the crossroads of Interstate 84 and Connecticut Highway 8.
The first option for the "New Mix" program, or the Modern Crossover Interchange, would involve reconstructing Conn. 8 ramps and bridges to the east of the Naugatuck River.
The second alternative is known as the Naugatuck River Shift and would move the river toward the east to provide space for unstacking the series of Conn. 8 ramps and bridges.
On Aug. 26, 2025, CTDOT officials unveiled the two options after reviewing and analyzing potential designs for the permanent replacement of the interchanges that carry I-84 and Conn. 8 over both downtown Waterbury streets and the river. The chosen alternatives are projected to cost $3 billion to $5 billion in 2022 dollars.
Built in 1968, the intricate network of stacked, overlapping bridges and elevated ramps was dubbed the Mixmaster after a trademarked kitchen mixer made by Sunbeam Products.
At that time, the interchange was considered innovative because the stacked bridges allowed the crossroads of the two highways over the Naugatuck River to be constructed in a smaller footprint. It originally had a life span of 50 years.
"The Mixmaster was once a modern engineering marvel, but today it no longer meets the needs of travelers and the greater Waterbury community," CTDOT Commissioner Garrett Eucalitto said in a statement. "We're excited to move this plan forward, which was based on what we heard directly from residents and businesses. This transformative initiative will change how people safely and conveniently travel through and around Waterbury."
The Mixmaster was originally designed to accommodate approximately 100,000 motor vehicle trips a day, but that number has now nearly doubled to 190,000 daily trips. In another 20 years, the state agency expects the number to approach 225,000.
As a result, the wear and tear from all that use across the interchange required multiple major rehabilitation projects over the years.
In November of 2024, CTDOT completed its multi-million-dollar effort to structurally rehabilitate the interchange and extend its life span for another 25 years while plans for a permanent replacement are made. Work on the renovations first began in 2018.
The project included replacing decks on 21 spans along southbound Conn. 8, 36 spans in the northbound lanes and building a temporary bypass and a U-turn. Major structural repairs consisted of strengthening the girders, columns and beams to address fatigue and corrosion.
The plans for I-84 eastbound and westbound included deck patching, paving and joint installation, steel repairs and strengthening, painting and substructure repairs and the installation of sign support structures.
Interstate 84 in Connecticut serves as a critical east-west transportation link between Massachusetts and I-90 to the east, and New York State and beyond to the west. Conn. 8 extends from Bridgeport and the I-95 corridor on the south coast, north to the Massachusetts state line. In Waterbury, the highway parallels the Naugatuck River.
CTDOT Outlines Details of Mixmaster Replacement
The two replacement options announced by CTDOT aim to improve safety and mobility on I-84 and Conn. 8 as well as upgrade the multimodal connections within the surrounding roadway network. In both alternatives, known as the Modern Crossover and the Naugatuck River Shift, the I-84 and Conn. 8 structures would be unstacked and reconstructed with an expected life span of more than 75 years.
"Progress takes patience, and while this work will take decades to fully complete, we are committed to improving lives through transportation by implementing — and completing — certain projects within the next five years," Eucalitto said.
His agency's announcement noted that the two design options originated through the New Mix Planning and Environmental Linkages Study (PEL). Over the last several years, strategies for improving transportation for all users were identified in alignment with Waterbury's economic and developmental goals. The PEL study also involved public outreach and participation.
In addition to the pair of replacement options, CTDOT reported that the analysis also identified breakout projects, including some that have been constructed and several that are in various stages of conceptual development and design.
These breakouts are independent projects designed to improve safety and mobility for the surrounding transportation network, while the state and federal environmental continue to review and design the interchange, CT Insider reported.
State transportation officials ruled out an in-place reconstruction due to the construction difficulties involved, in addition to another rehabilitation of the Mixmaster in 2045 because it would not substantially improve the interchange's functionality, nor would it extend its lifespan relative to the cost of a full replacement. They also concluded that continued rehabilitation would not be able to address the interchange's operational and safety standards.
Another alternative that CTDOT dismissed, according to CT Insider, was constructing a tunnel within the project's footprint because the projected construction and maintenance costs would be considered unreasonable and impractical due to the channel length needed to construct a functioning interchange. The topography also presented limitations because of the required depth for such a tunnel.
Two Engineering Designs Emerge as Best Alternatives
CTDOT noted that the Modern Crossover alternative plan would result in a configuration that satisfactorily addresses the needs of the interchange. Not only would it reduce the potential for crashes but provide substantial benefits for the surrounding community while minimizing effects on environmental and community resources.
In addition, this option would allow for riverfront access along both riverbanks of the Naugatuck River.
The plan would replace the Mixmaster with a full system interchange, using elevated structures that would cross over or under one another. Under this option, I-84 near the core of the interchange would be located just south of the existing alignment, while Conn. 8 would be relocated east of both the existing alignment and the river, just south of I-84. The state highway also would remain on the west side of the Naugatuck River north of I-84.
Likewise, the Naugatuck River Shift alternative also would meet the interchange's requirements, CTDOT concluded.
The option anticipates the river's path could be shifted east to a more favorable position for the Conn. 8 roadway. Moreover, this design choice would allow for ample opportunities for riverfront access along the eastern bank of the Naugatuck and would benefit transportation, safety and environmental and community resources.
Like the Modern Crossover plan, the Naugatuck River Shift option also would replace the Mixmaster with a full system interchange that would be built in an unstacked configuration.
Under this particular scenario, though, I-84 would be located just south of the existing alignment near the interchange core and Conn. 8 would be reconstructed on the west bank of the Naugatuck River. To accommodate the unstacked Conn. 8 configuration, the river would require partial relocation. The width, river flow and capacity of the shifted portion would be maintained in the final condition.
