CARMEL, N.Y. - Plans are underway to remodel the intersection of Drewville Road and Stoneleigh Avenue—a notoriously dangerous crossroad—and build a traffic circle, sometimes known as a roundabout.

Jeff Gentzler, project engineer for Greenman-Pedersen Inc., the county’s consultants on the undertaking, gave a presentation to the Putnam County Legislature’s Physical Services Committee at its June 22 meeting to reveal the key design features, costs and timeline. The project includes roadway reconfiguration, drainage improvements, enhancements to stormwater treatment and miscellaneous upgrades to signing and guide rails.

The estimated $4.9 million project is a joint venture of the county (Drewville and Stoneleigh are county roads), the state Department of Transportation and the Federal Highway Administration.

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Gentzler said Stoneleigh, on which Putnam Hospital Center is located, was originally identified as a road in need of improvements back in the 2000s.

“An original design from 2009 identified several alternatives to widen the travel lanes of Stoneleigh from the hospital to Route 6,” he said.  “But it was never constructed due to high costs.”

Gentzler noted that the intersection is difficult to engineer. The way it is laid out now provides very poor sight distance for motorists as they approach the intersection. He also noted there is a lack of drainage.

“The intersection was originally constructed without any drainage in mind,” he told the committee. “As it stands now, water flows freely along the edges of the roadway, which is leading to the erosion of the shoulder, as well as the asphalt. Additionally, the runoff is not treated before it enters the adjacent Croton Falls Reservoir.”

Gentzler said planners laid out six design objectives for the project:

• Improve overall traffic conditions to reduce delays

• Provide improved access to Putnam Hospital Center

• Mitigate the skew of the intersection and lack of sight distance for drivers both approaching and waiting at the intersection

• Evaluate and improve the safety of the project corridor

• Construct stormwater treatment system and install a new drainage system

• Install new guardrail and signage where required

Funding for the project will come from the Congestion Mitigation and Air Quality Improvement Program (CMAQ) and the Surface Transportation Program—both funding programs from the Federal Highway Administration.

The final design, permitting, right-of-way and acquisition process are to be completed this fall and in the spring of 2021. Finalized plans are to be ready by the summer of 2021. Construction would begin late winter 2021/early spring 2022 and completed by summer/fall of 2022.

Gentzler said that in the early stages, the county considered several alternative plans, including simply replacing the traffic light with something new and improved. He said that while that would have improved performance and reduced delays at the intersection, it would not have met all the project’s requirements. Another option was to build a new four-way intersection.

“But ultimately the county chose not to pursue that and instead went with another alternative, a single-lane roundabout,” he said.

The roundabout will be a 130-foot circle that can accommodate tractor-trailers.

“It eliminates a traffic light that is subject to power outages and needs maintenance,” Gentzler said of the roundabout. “And it reduces emissions.”

The roundabout plan will also improve the horizontal and vertical curvature of the roadway to increase driver sight distance.

“If it can handle a tractor-trailer, it’s certainly capable of handling a school bus and other types of commercial vehicles,” he added. “It will also reduce entry speeds which will contribute to accident reduction.”

Gentzler said that county officials particularly liked the roundabout plan because it eliminates the traffic signal.

“[Traffic lights] are subject to power outages and given the proximity to the hospital that’s a major concern,” he said. “Roundabouts reduce emissions because they eliminate idling vehicles.”

The roundabout plan will have a closed drainage system and a stormwater treatment system.

“We will put in a series of catch basins and curb the approaches as well as the roundabout’s center which will guide the stormwater into these basins,” Gentzler said. “And we are constructing a new retention pond in the northeast corner. And anywhere you see what is currently asphalt that won’t be part of the future roadway will be removed and turned into green space, so it reduces our impervious areas.”

To improve the sightline heading toward the intersection, Drewville Road will be raised up on both sides of the intersection.

During construction, with some road closures in effect, Gentzler said that project managers will reach out to emergency services ahead of time to coordinate traffic to the hospital.

On an average weekday, Stoneleigh Road carries about 10,700 vehicles; Drewville Road handles 5,700.