Vermont agency outlines delays, timeline and outreach for Colchester Exit 16 diverging-diamond interchange

Michael LeCroix, a project manager in the Agency of Transportation’s traffic design section, told the House Transportation Committee on May 27 that work on the Colchester Exit 16 corridor — including a reconfigured diverging-diamond interchange (DDI) at Interstate 89’s Exit 16 — is finally moving toward full construction after more than a decade of planning, permitting and litigation.

LeCroix said the project has two construction contracts: a first contract, completed in late 2023, that included utility relocations, ledge removal and retaining walls and cost about $10,600,000; and a second, final construction contract the agency awarded in May to build the roadway, the DDI, signals, sidewalks and stormwater infrastructure. “I have been working on this project for the last 12 years,” LeCroix said.

The DDI is designed to reduce signalized left-turn conflicts and increase capacity. LeCroix cited safety and capacity benefits that DOTs have reported nationwide, saying DDIs can reduce crashes and increase vehicle throughput. He also addressed winter operations: “Short answer is it functions just like any other roadway,” LeCroix said, noting the agency has coordinated with local plow drivers and consulted other states with DDIs.

Why it matters: the project affects Route 2 and Route 7 in Colchester near the Winooski town line and several private businesses, and the interchange reconstruction has required new stormwater infrastructure intended to meet state and federal environmental permits. Delays and increased costs from multi-year permitting and litigation have deferred other work and prolonged construction impacts for local motorists and businesses.

Committee members asked for details about the causes of delay and cost. LeCroix described a sequence of obstacles: protracted Act 250 (Vermont land use) and operational stormwater permitting with appeals by nearby gas-station interests; NEPA litigation in federal court; extended right-of-way negotiations and condemnation proceedings; and a related challenge to the agency’s TS4 transportation stormwater permit. He said some right-of-way compensation negotiations and related litigation remain ongoing even though the agency secured the order of necessity and completed acquisitions in late 2022–2023.

On procurement and schedule, LeCroix said the first construction contract ran from February to November 2023 and cost roughly $10.6 million. He said the contractor that performed contract 1, SD Ireland, submitted the winning bid for contract 2; LeCroix stated the contractor’s base bid was $22,000,000 and that, after adding contingency and construction engineering (CE) costs, the agency expects the second contract to total roughly $25.8 million (LeCroix also made an apparent transcriptionary number error while speaking). He said major work on contract 2 is expected to begin in July or August and that the contract’s completion date is currently listed as June 2026, though he said the agency hopes to finish earlier if possible.

LeCroix described mitigation of construction impacts: the agency will allow daytime work in the busy corridor but requires night work if more than one lane in each direction must close; night work hours are 7 p.m. to 6 a.m. He also described public-outreach efforts the agency hired WSP to run, including explanatory graphics, animations, multilingual materials for nearby Winooski residents and a driving simulator built from design models to let people practice navigating the DDI in a controlled environment.

Several technical and environmental issues framed the multi-year delay. Opponents challenged whether the agency had properly assessed stormwater treatment options, whether the project considered chloride reductions for Sunnyside Brook, and whether phosphorus impacts to Lake Champlain were adequately addressed. Those challenges produced trials, appeals and remands; the agency received its contested permits in November 2020 and moved forward afterward.

What the committee did not decide: the committee received the update and asked questions; there was no formal committee vote or policy change recorded in the meeting. LeCroix encouraged committee members and the public to consult project materials on the agency’s website for schedules and outreach events.

Ending: With right-of-way acquisitions finalized and construction contracting completed, the agency projects major roadway and interchange construction to proceed starting this summer and continuing into 2026, subject to contractor performance, remaining compensation negotiations with affected property interests and routine construction contingencies.