The remains of Virginia Lt. Gov. Alexander Spotswood's 18th century mansion, saved once from a planned residential development, have been donated to Mary Washington College in Fredericksburg.

The 65-acre colonial plantation site is listed on the National Register of Historic Places. Spotswood was lieutenant governor of the Virginia colony from 1710 to 1722.

Ivor Noel Hume, former resident archaeologist with the Colonial Williamsburg Foundation, called it "the most important 18th century archaeological site in Virginia."

The site was donated by Historic Gordonsville Inc., which rescued it from becoming part of a development in 1984. The group secured loans from the National Trust for Historic Preservation and support from the General Assembly and bought the property in 1985.

The Center for Historic Preservation at Mary Washington College will administer the site and use it as an educational resource and for archaeological research.

"The excavations will reveal how what was then 'the West' was settled and how Governor Spotswood and other planters tamed Virginia's frontier," said Carter Hudgins, director of the center.

"Had it not been for the inspired and determined efforts of Historic Gordonsville, this nationally important site and the dozens of related archaeological sites which surround it might have been forever lost," Hudgins said.

The mansion was built in the 1720s on a bend of the Rapidan River west of Culpeper. William Byrd II of Charles City County visited the plantation in the 1730s and was so impressed he called it an "Enchanted Castle."

The site also contains the camp and dwelling sites of prehistoric Indians, the site of Spotsylvania's first courthouse, late 18th and early 19th century domestic sites and Civil War earthworks.

Excavations so far have uncovered the foundations of the mansion and the colonnades and outbuildings that once formed a formal court. Resident archaeologist Douglas Sandford and his crew also have found the remnants of formal terraced gardens and other landscape features.

Two sisters have been charged in Delaware and Florida with bilking thousands of time-share participants out of hundreds of thousands of dollars by promising to resell their interests in vacation condominiums and campgrounds.

Connie Sue Burks, 51, and Mary Frances Baker, 43, will be arraigned in U.S. District Court in Wilmington, Del., next week. They have waived extradition and returned to Fort Lauderdale, Fla., to face 109 state charges of fraud and grand theft in what police there describe as one of the biggest time-share scams ever.

As many as 2,000 consumers may have lost $1 million, Florida authorities say. Burks and Baker moved to Delaware after Florida enacted tougher time-share laws.

They had operated Time Exchanges of Delaware Inc. since last fall. According to the 10-count indictment, Time Exchanges of Delaware solicited customers who own time shares and campground memberships to list their interests for resale at a fee of $380. The fee was refundable at the time of the sale or after 18 months if the time share or campground membership was not sold.

Typically the fee was charged to the customers' credit cards, sometimes more than once, the charges said. The operators allegedly pocketed the money. No properties were resold and few refunds were made.

Burks and Baker had operated with Dieter Siegelin and his wife, Doris, who were arrested in Texas and pleaded guilty to 43 counts of fraud and theft.

Burks said last year that the company tried to help people, particularly the elderly, the sick or those who had fallen on hard times, to find a resale market for the vacation property shares they could no longer use.

"They were real pros ... very convincing," said Fort Lauderdale Det. Kevin Allen. "We still have victims trickling in." The sisters could face up to 15 years in prison if convicted on the Florida charges, said Broward County prosecutor Virginia Tanner-Otts.

In Delaware, where the charges involve federal wire and mail fraud, the maximum prison sentence is up to 45 years upon conviction, according to Assistant U.S. Attorney Richard G. Andrews.

Mary Frances Baker faces another five years in prison if convicted of obstruction of justice for allegedly altering and withholding business records subpoenaed by the grand jury.

A group affiliated with James Rouse's Development Enterprise Co., which made its mark on the East Coast with a signature line of festival marketplaces, helped open a Japanese version of the retail complex this week in Osaka.

The Rouse group served as consultant developers for the $145 million Tempozan Marketplace on Osaka's waterfront, providing advice to the project's owners.

The Osaka marketplace is a 160,000-square-foot complex of shops and restaurants, similar in concept to other Rouse projects in Baltimore, Boston, Norfolk and Richmond.

Tempozan Marketplace, which opened to the public yesterday, is among the first such projects involving an American development company working with the public sector in Japan. Rouse officials helped choose an architect and contractor, review designs for the three-story complex and develop a leasing strategy.

The Japanese project has some of the same elements of Baltimore's Harborplace, designed by Rouse, which marked its 10th anniversary this month.

The American Bankers Association's economic advisory committee predicts that the number of housing starts will improve slightly, from 1.3 million this year to 1.4 million in 1991.

Interest rates charged on 30-year fixed-rate mortgages, now averaging 10.04 percent, will fall to 9.91 percent by the end of the year and then rise to 10.05 percent by the end of 1991, the committee predicted.

IN THE BUSINESS ... Single-family home sales in Howard County totaled 266 in June, up from 251 in June 1989. So far this year, 1,464 houses have been sold in the county, up 12 percent from 1,296 in the first half of 1989. The average price this year was $185,856 ... Bozzuto & Associates opened St. Johns Wood, a $19 million, 250-unit rental apartment community in Reston ... Town & Country Properties Inc. plans to hold a free seminar for first-time home buyers on Wednesday at 7 p.m. at 8313 Arlington Blvd. in Fairfax. Call 356-1323 to register ... Pobiak Properties of Bethesda opened a new office in Annapolis ... Equity Venture Group Inc., a real estate investment consulting firm, opened an office in Arlington ... James A. Peterson formed a real estate consulting firm in Fairfax serving the Baltimore and Washington metropolitan areas called Peterson Real Estate Consulting Services ... Harvey Construction Company Inc. of Bethesda completed construction of Van Dorn Station, a $4 million, 75,000 square-foot retail and warehouse complex in Alexandria ... Donohoe Construction Co. completed construction of Park Vista, a 300-unit apartment complex in Arlington ... Mitchell & Best Co. of Rockville opened a custom homes division, Mitchell, Best and Visnic.

PERSONNEL FILE ... The Home Builders Association of Maryland named Francis X. Borgerding president for the 1990 term ... Norman E. Samuel was named senior vice president and chief financial officer of Realty World Corp. of Fairfax ... Lightworks Construction Inc. of Bethesda named Gary A. Bank vice president of the firm's commercial division ... The JBG Cos. promoted Herbert A. Behre III senior vice president of property management ... Lehrer McGovern Bovis Inc. of Fairfax appointed Rodney H. Cornell vice president. -- Compiled from staff reports and news services