The following were among actions taken by the Fairfax County Board of Supervisors at its Monday meeting. For more information, call 691-3187.

RTE. 28 TAX DISTRICT -- The board unanimously voted in principle to pay between $18 million and $22 million in the next five to six years to widen Rte. 28.

Public funds will pay 20 percent of the expected $110 million cost. A special property tax surcharge on land will pay the rest.

The project originally was intended to be completely financed by developers, but until new roads are built, there will not be enough development to cover the costs, according to Supervisor T. Farrell Egge.

Egge said he was disappointed that less money would be available for other projects, but he hoped the special property tax would recoup the public money.

TRUCK RESTRICTIONS -- The board voted unanimously to ask the Commonwealth Transportation Board to prohibit through truck traffic on Annandale Road and Hummer Road between Hillwood Avenue and Little River Road.

For years, residents have protested large trucks, including oil tankers, using their quiet suburban street as a shortcut between Rte. 50 and Rte. 495. The Virginia Department of Transportation rejected earlier requests by some board members to end the truck traffic.

Fairfax County officials do not believe the two roads meet new revised criteria for state truck prohibitions, but Supervisor Thomas Davis (R-Mason) said the truck prohibition ''should succeed on its merits, but if it doesn't, there'll be a fight down in Richmond."

SEQUOIA DEVELOPMENT -- The board approved by a 6 to 1 vote a 93-acre, 130-unit housing development between Ox Road (Rte. 123) and Silverbrook Road north of Lorton prison, over objections from Supervisor Audrey Moore (D-Annandale).

Calling Lorton unsafe, Moore said, " . . . It is not in the interests of the the County of Fairfax to approve subdivision development or greater density (near the prison)."

Moore also said that the roads and soil in the area could not handle more development. But Board of Supervisors Chairman John Herrity said some homes could be built at the site even without the Sequoia development.

He said that even if the board didn't approve the Sequoia development, people would still build there and people would still live near the prison.

Supervisors Joseph Alexander (D-Lee) and Katherine Hanley (D-Providence) were absent for that particular vote.

TAX DISCLOSURE -- The board voted unanimously to adopt a motion by Supervisor Nancy Falck (R-Dranesville) to urge all supervisors and supervisor candidates to disclose their federal and state tax returns. The motion also would require the board to study placing such a requirement in the county's legislative package.

Supervisors now are required only to disclose their state returns after election.