Irmo's Harbison Exit Gets Rebuilt Starting in 2027. SCDOT Kept the Layout Familiar.

Coming off westbound I-26 at Harbison Boulevard today, you take a tight loop ramp down to the light at Woodcross Drive. From there you can turn left, go straight, or take the free-flowing right turn toward the stores. Across the road, eastbound drivers stack up in a left-turn lane about 300 feet long. That short lane fills fast on a Saturday afternoon.

That interchange was supposed to be torn out completely. The original Carolina Crossroads plan called for a tight urban diamond at Exit 103. In April 2026, the Federal Highway Administration approved an environmental reevaluation that replaced the diamond with a partial cloverleaf "similar to the existing interchange configuration." So the interchange Irmo gets after construction will have roughly the same layout it has now, with more lanes added in the places where traffic backs up.

For anyone who lives off Harbison, Broad River Road, or Lake Murray Boulevard, that's the main local story in the "Malfunction Junction" project. The rebuild is headed west toward Irmo, and the version arriving here is smaller and more familiar than the one first drawn up. The cost Irmo will notice most directly is trees at Broad River Road.

Where the work is now, and when it reaches Irmo

Most of what's been built so far is closer to downtown. SCDOT's phases page lists Phases 1, 2, and 3B as complete, Phase 3C as under construction, and Phases 3A and 4/5 as expected to start construction in 2027. The Irmo work is in Phase 4/5.

Over the whole program, The State reports full completion by 2034, and SCDOT's own wording is the "mid 2030s." For Irmo, that means roughly seven years of work after the 2027 start, moving between different interchanges you probably use.

The active work today is on I-20 at the Saluda River. SCDOT's September 2026 newsletter says crews are partway through demolishing the westbound I-20 bridge over the river and have started drilled-shaft foundations for the new one. Cranes and barges are already on site. All existing lanes are open but a little narrower. A temporary eastbound exit ramp serves Bush River Road at Exit 63 while the permanent ramp is rebuilt. Drivers should expect periodic nighttime lane closures "over the next two years." In the next stage, traffic moves onto the new outside lanes so crews can build the median sections of the bridges.

If your weekday route goes from Irmo through I-20 toward Lexington or West Columbia, you're already driving through this phase. Starting in 2027, the I-26 corridor itself becomes a work zone.

What changes at Harbison, lane by lane

According to the April 2026 reevaluation, Exit 103 was revised "to minimize right of way impacts." The new ramps sit slightly east of where they end today. Here are the changes it describes:

1. Westbound loop off-ramp. The ramp is realigned and widened to two lanes as it leaves westbound I-26. Where it meets Harbison, it keeps essentially the same setup as today, with separate left, through, and free-flow right lanes.
2. Today's right-turn lane becomes a full lane. The channelized right turn turns into a third westbound lane that continues across the interchange.
3. Westbound on-ramp. There will be a single-lane westbound on-ramp leaving the intersection.
4. Westbound Harbison at Woodcross Drive. Today's left, single through, and right lanes become a left lane, two through lanes, and a right lane.
5. Eastbound left-turn lane. The eastbound approach stays essentially the same, but the left-turn storage and taper grow from about 300 feet to about 725 feet.

The eastbound turn-lane change is the easiest to picture. A lane about 725 feet long holds well over twice as many waiting cars as today's 300 feet, so fewer of them should spill back into the through lanes.

The smaller footprint also changed which businesses stay. The reevaluation puts it this way:

"Due to the minimized footprint of the interchange, three (3) previously documented business relocations (Applebee's, Hooters, Best Buy) would be avoided."

So under the current design, those three Harbison businesses remain where they are. The same document says the level of service for traffic movements at the interchange "remains the same or improves" compared with the original diamond concept.

SCDOT doesn't present any of this as final. Its April 2026 project handout describes Phase 4/5 as being in early-stage design. The Phase 4/5 page also lists no contractor and no completion date. The lane counts above are the approved concept as of spring 2026, and they could change before construction.

Broad River Road: where Irmo picks up the bill

Exit 101 at Broad River Road is the westernmost piece of the whole project. Because it falls inside town limits, state law required SCDOT to get a municipal agreement. Irmo Town Council approved one on April 21, 2026, covering ramp, frontage-road, and utility-line relocations. Work is planned to start in 2027. The 2026 environmental update also lists ramp improvements at Exit 101 and a relocated driveway for one parcel affected by them.

The part Irmo will see first is the trees. According to documents presented to council, trees in the greenspace around the on- and off-ramps and a line of trees along the interstate near Columbiana Drive are likely to be removed during construction. Under SCDOT's standard encroachment permit, the town is responsible for replacing removed landscaping. Project director Brad Reynolds told council the same thing. The State's full report on the Broad River interchange agreement has the background, and the shorter takeaways piece lists the main points.

There's one reassuring detail in the same discussion. Reynolds said SCDOT confirmed there are no town utilities in the affected area, so Irmo's local utility customers shouldn't feel the work at their taps.

From a construction standpoint, replanting along an interchange takes time. New trees along a ramp take years to reach the size of the ones being cleared. Even once the ramps are finished, the Exit 101 area will likely look more open for a while.

The exits with no published plan yet

The State lists Lake Murray Boulevard, Harbison Boulevard, Piney Grove Road, and St. Andrews Road as part of the project. Being on that list doesn't mean each one gets a new interchange. The current public material breaks down like this:

• Lake Murray Boulevard, Exit 102. It's listed among affected interchanges, but the current Phase 4/5 scope doesn't spell out a ramp redesign or a ramp removal.
• Piney Grove Road, Exit 104. The Phase 4/5 widening begins just east of Piney Grove. The posted scope doesn't describe a separate ramp reconstruction there.
• St. Andrews Road, Exit 106. This exit is in Phase 3E, with construction expected to start in 2030. The concept follows the same pattern as Harbison. A planned single-point urban interchange was revised to a partial cloverleaf "similar to the existing interchange," with tie-ins to new I-26 collector-distributor roads.

St. Andrews shows the same trend. At both of the larger interchanges nearest Irmo, SCDOT moved away from the more compact designs and back toward layouts close to what drivers already use. According to the reevaluation, the St. Andrews change improves operations on St. Andrews Road and supports the design of the new I-20/I-26 interchange.

Keeping up with it between now and 2027

The best primary source is SCDOT's Carolina Crossroads phases page, which posts percent-complete figures and start years for each phase. The September 2026 construction newsletter covers the current I-20 staging. It also lists the project hotline at 1-800-601-8715 and the email [email protected]. If you want the Harbison and St. Andrews design details in SCDOT's own words, the April 2026 environmental reevaluation has them, including the comparison graphics.

The newsletter also notes that utility relocation for Phase 3A has started, with construction expected in early 2027. Frontage roads and utility crews will probably show up along the corridor before any new lanes do.

If you own a home near the Broad River or Harbison interchanges and wonder how years of ramp work and tree clearing might affect your street, I'm glad to talk it through. That includes what nearby construction tends to mean when it's time to sell. You can reach me through Bill Prebeck. Let's Connect.

This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.