The Marin County Sheriff’s Office is using a grant from the U.S. Department of Homeland Security to help purchase a new $534,357 patrol boat.

The sheriff’s office received a $401,002 Port Security Initiative grant from Homeland Security in February. A 25 percent local match, required by the grant, came from the sheriff’s rural county trust. The purchase, approved by supervisors March 13, uses no money from the county’s general fund.

“When we get money from the federal government or the state government for frontline law enforcement, it goes into that trust,” said Marin County Sheriff Robert Doyle.

The new boat will be purchased from SAFE Boats International, based in Bremerton, Washington, a supplier to military, federal, state and local law enforcement, fire and rescue agencies throughout North America.

The new boat will replace “Marin Rescue I,” an aging 33-foot vessel built by Almar Boats in Tacoma, Washington.

Doyle said Rescue I has been in use for 18 years and requires costly repairs and maintenance and time out of the water to keep it in serviceable condition.

In addition to Rescue I, the sheriff’s office has “Rescue II,” a smaller rubber-hulled vessel that is used when rescues are necessary on Tomales Bay.

The new boat will be a 33-foot full cabin vessel.

“They are custom-made patrol boats from the keel out,” said Steve Ingle, a sales director at SAFE Boats. Ingle said it will take six to seven months to build the vessel.

In his report to county supervisors, Doyle said the new boat will have a patented hull design able to sustain a hull breach.

He said the craft’s full buoyancy flotation collars will provide displacement on tight turns and enable the boat to maneuver more accurately and provide quicker response times during emergencies.

Doyle said he isn’t sure what he will do with the old patrol vessel.

“We will probably sell it,” he said. “It does have value.”

The money to purchase that vessel came from money left over when the county removed dilapidated dry docks in Richardson Bay, Doyle said.

A 2010 report based on government records showed that in the nine years since Sept. 11, 2001, the county of Marin had been awarded some $5.6 million in Homeland Security funds and the Golden Gate Bridge district another $5 million.

Items purchased with the money included air purifying respirators, chemical resistant gloves, radios, a decontamination tent, cameras, computers, training exercises, a hazardous materials response vehicle, a SWAT vehicle, radiological monitors, a satellite phone network, dive team equipment and uniforms.

Doyle couldn’t provide an immediate estimate of how much in Homeland Security funds the sheriff’s office has received since then.