The Boston Police Department's operational plan for the convention calls for police to work 12-hour shifts, equipped with riot gear, and provides new details about the city's security efforts during the first political convention since the terror attacks of Sept. 11, 2001.

City and police officials say they are trying to devise an airtight security plan that will still allow the city and the neighborhood around the FleetCenter to remain open during the four-day event. The federal government is paying $25 million to cover security costs.

"The city will see unprecedented security for this event," said Police Commissioner Kathleen O'Toole. "It should reassure the public that an inordinate amount of planning has gone into this event. The draft is very comprehensive and has been under development for 17 months. Plans will continue to evolve as we get closer to the event."

The 30-page draft plan outlines the roles of the Boston police and 20 other federal and state law enforcement agencies in providing security during the convention. It does not give specific deployment numbers or assignments.

Officials declined to provide further details about training, but the plan details dozens of training exercises that some or all of the officers have participated in or will take part in by mid-July. All personnel will be trained in suspicious package detection, bomb threats, hazardous material response, and evacuation procedures, the plan says.

Additionally, according to the document, the so-called "hard" security zone around the convention arena -- where only credentialed delegates, journalists, convention employees, and police can enter -- has been enlarged from previous plans. The zone, which originally encircled the FleetCenter and the Thomas P. O'Neill federal building, now stretches several blocks to North Washington Street to the east and New Chardon Street to the south, and includes the area where buses and trucks bringing delegates and cargo to the area will park.

Delegates, reporters, and employees will have to pass through metal detectors and X-ray machines at a tightly guarded checkpoint in order to enter, according to the plan. All participants, even police, will have to show credentials. All bags and packages will be hand searched.

Once inside the secure area, police will not be able to leave. They will eat and take their breaks inside the zone and will arrive and depart by bus, according to the plan.

A soft security zone -- where cars will be excluded but uncredentialed pedestrians will be allowed -- encompasses a several-block area bounded by Causeway, New Chardon, Canal and Merrimac streets, according to the plan. Cars will be excluded beginning July 23.

Owners of area businesses had hoped for a large pedestrian area. They said an increase in foot traffic might offset the disruption in business caused by the convention.

The plan also calls for extra vigilance for delegates. "Disruption by demonstrators to delegate transportation to the convention and DNC-related events is a major concern. The department will maintain 24-hour security at each hotel," according to the plan.

More than 20 agencies will play a role in providing security for the delegates, politicians, and the public during the convention that will take place July 26 to 29.

The US Secret Service is the lead agency, but Boston police are responsible for providing backup security inside and outside of the FleetCenter, hotels where delegates and the Democratic National Convention Committee will be housed, and at the special delegate parties and other events around the city, according to the document.

Boston police and the Secret Service will be aided by the Massachusetts State Police, the Massachusetts National Guard, and the Massachusetts Department of Correction. Correction officers will be called in if there are mass arrests.

Boston police officers will not be allowed a day off or vacation during the convention week.

In addition to regular patrol officers, the department will assign special units, such as the drug control unit and youth violence strike force, to convention duty.

Each day, the officers on duty will assemble at UMass-Boston for roll call and credential checks. They will then be bused to their assignments, the report said.

All officers will be required to wear bulletproof vests and have riot gear with them, including a helmet with a face shield, a 36-inch baton, and a gas mask. They will be authorized to use pepper spray to "engage law violators."

"The department's response to problems must be proactive, immediate, and interdictive but not disproportional to the problem," says the report. "The operational plan's main objectives are to maintain order, protect lives, protect individual rights, protect vital facilities, arrest law violators, and protect property. To achieve these objectives, the department must have a balanced, proportional response that prevents incidents from developing to an unacceptable level."

State officials have already said they will close Interstate 93 while the convention is in session and the North Station MBTA station will be closed. Several businesses in the area, including Massachusetts General Hospital and several court buildings, are cutting back operations during the week the delegates are in town.

- Rick Klein of the Globe staff contributed to this report