Jetties studied to keep silt out of channel

Friday, Nov. 6, 2009

The channel leading into St. Jerome Creek in Ridge was dredged only a few years ago, but is already shoaling back in. While sand and sediment is creeping in, the U.S. Army Corps of Engineers is studying the best way to keep it out of the channel and presented some options Tuesday to the St. Mary's County commissioners.

Sediment is being washed south along the shoreline of the Chesapeake Bay into the creek's channel, said Bill Grosskopf, a consultant with Offshore and Coastal Technologies. At the same time, sediment is being washed into the channel from the south, "which is why you have so much sand in the system," he said.

The channel was dredged in 1991 and another $1 million was spent in 2006 when it was dredged again to a depth of at least 17 feet. Some of the depths are now back to five feet already, Grosskopf said.

Before dredging in 2006, depths were as shallow as three feet at low tide.

"It's a complex area," said Ed Fulford, consultant with Andrews, Miller Senior Associates. "To have an inlet like this where the sediment comes from two directions, it's a real problem," he said. About 6,400 cubic yards of sediment is washed around the mouth every year.

At the rate it's going, it would need to be dredged every five years, he said.

The $500,000 study includes four alternatives. They all include two jetties to protect the channel, but in different configurations. One alternate cuts a straight channel through the spit of sand on the north side of the creek's mouth.

Shoaling will continue on the north and south sides of the jetties, but the straight channel option prevents the most sedimentation, Grosskopf said.

The jetty projects are estimated to cost between $3.2 million and $4 million.

St. Jerome Creek includes more than 1,100 acres of tidal waters. It is home port to about 90 charter fishing and crabbing vessels, and to two commercial marinas.

Whichever alternative the Army Corps of Engineers comes up with, the channel will have to be dredged again before the jetties are constructed.

"A permanent solution is what's warranted down there," said Commissioner Thomas A. Mattingly Sr. (D).

St. Mary's County government has a spoil site leased nearby which was used for material dredged up in 2006. It is two-thirds full and the lease runs until November 2012.

jbabcock@somdnews.com