Old Lyme — The town has received a $1.6 million grant from the state Department of Transportation to dredge the Black Hall and Four Mile rivers.

The dredging project will deepen the rivers so boats can safely navigate the waterways at all tides, according to project descriptions.

The town is expected to finish the project by next spring.

In announcing the grant at Monday's Board of Selectmen meeting, First Selectwoman Bonnie Reemsnyder congratulated the Harbor Management Commission and the town.

She said it would have been difficult for the community to fund the project without this grant.

The dredging project costs more than the closure of the town landfill, an endeavor for which the town had saved funds for more than 10 years to be able to afford.

"This is really, really a big deal, and it's very exciting," Reemsnyder said.

The project will remove an estimated 13,176 cubic yards of sediment from the Black Hall River southwest of Route 156, and 9,787 cubic yards from the Four Mile River, according to permits from the state Department of Energy and Environmental Protection.

"In both locations, the navigation channels are extremely shallow and silted in," said Harbor Management Commission Chairman Steve Ross in a phone interview on Tuesday.

Ross said the dredging will have commercial, recreational and environmental benefits.

The rivers are home to marinas and state boat launches used by both local residents and visitors from all over the state, he said. The waterways are busy each summer with people launching small power boats, kayaks and canoes.

Ross said the dredging, most importantly, also will ensure that the upstream wetlands continue to benefit from the "flushing effects" of the tide.

Without dredging, the waterflow in the rivers will lessen over time. If the waterways are blocked too much, the tidal wetlands, crucial to the environment and aquatic wildlife, will stagnate and die, he explained.

The Harbor Management Commission previously had worked on a three-part feasibility study on dredging the rivers after receiving $200,000 from the state DOT. Coastline Consulting of Branford conducted the study.

Patriot Marine of Winthrop, Mass., is slated to conduct the dredging work, Ross said.

The Board of Finance and townspeople will need to approve spending the $1,614,074 grant before the project can move forward.

DEEP permits stipulate that the contractor should dredge the rivers between Oct. 1 and March 31.

For the Black Hall River, DEEP's Marine Fisheries Division reserves the right to limit dredging to the outgoing tide if it determines "that conditions are developing, or have developed, that may cause the mortality of striped bass in the river," according to the permit.

k.drelich@theday.com

Twitter: @KimberlyDrelich