The federal government has again turned down a request for money to help pay for dredging around piers and wharves in Portland Harbor.

Local officials said they learned Friday that the latest request for funding from the U.S. Department of Transportation had been denied.

Dan Haley Jr., chair of the Board of (Portland) Harbor Commissioners, said the cost of dredging the harbor and disposing of the waste will run about $30 million. The state, cities of Portland and South Portland, and wharf owners would all contribute, but most of the money would come from the federal government.

The dredging would be performed around piers and wharves, which tend to fill with silt flowing into the harbor from the Fore River, Haley said. Channels and shipping lanes are maintained and regularly dredged by federal agencies.

Chuck Kamilewicz, Portland’s assistant harbor master, said as much as 25 percent of the space around piers has been lost because of the silt buildup.

He said the amount of silt carried by the river varies depending on rainfall and runoff upstream, so it’s difficult to determine if the problem is getting dramatically worse.

“We’ve probably had a good year because of how dry it’s been,” Kamilewicz said, but if dredging was performed, “obviously, it would make the whole harbor better.”

Haley said the effort to get funding for the dredging has been going on for about 30 years. He said this year’s application was made under a public works grant program from which Maine received about $50 million, mostly for bridge repairs.

He said he’s disappointed that Maine’s dredging plan wasn’t approved, but feels the application was a good one and it will be resubmitted next year. The proposal was backed by the state’s congressional delegation, he said.

Haley said the dredging proposal has received nearly all required approvals from state and federal regulators. The permits are good for four years, he said, so harbor officials will continue to push for the remaining approvals while seeking federal funds.

If it’s clear the federal aid won’t come through before the permits expire, he said, officials might ask for a state bond to cover much of the cost, a move that would require approval of voters.

Charlie Poole, one of the owners of Union Wharf in Portland, said no one likes to have to dredge, but it’s a necessary chore to keep a working harbor in good order.

“As a port, dredging is just part of the maintenance,” he said.

While the shipping channel gets regular attention, “the waterways between the piers is just as important as the federal channel,” Poole said. “I don’t think the need ever goes away. We’re watching it year in and year out and it’s getting shallower and shallower.”

Dredging around his wharf would allow him to lease out space to two or three more boats, probably lobster boats, he said.

The project would use a disposal method called “confined aquatic disposal,” Poole said, which involves clearing a large space underwater to contain the dredge waste, which would likely be covered with clean material from the ocean or bay floor. He said a space near the Coast Guard station in South Portland has been approved as the disposal site.