Prince William Probes Builders

Marine clay, which is especially prevalent in soil closer to the Chesapeake Bay, can be "hard as a brick when dry or mushy as Play-Doh when wet," Lynch said. That means that if there's too much of it in the ground, "if it's next to your concrete wall, it will knock your wall down. It can lift your house up and down."

The marine clay covers eastern Prince William, and another expansive soil called blackjack is more prevalent in the west.

Although neighboring Loudoun and Fairfax counties have had policies on problem soils for several years, Prince William did not have one until January 2005.

The county's rules -- which are unwritten -- say that developers using lime to simply dry suitable soils can do so without county approval. But if they use the lime to chemically change expansive soils -- such as marine clay -- the developers have to include the information in their reports to the county.

In December, the county drafted a more stringent, written policy that requires developers to report any use of lime if there is expansive soil on the site, said Eric Mays, the county's building official. That draft is still being reviewed.

Local developers said the county's lateness in regulating building on the clay has caused the confusion. They pointed out that using lime and marine clay together as a building surface is a common and long-standing method.

Saadeh said the county will continue to struggle with those issues if it does not put several initiatives in place, including a geotechnical review board -- a panel that oversees such policies. Saadeh has been on a board in Fairfax since 1989.

Mays said that the creation of a board is "on the table" but that the Public Works Department is concerned that it would result in "the private sector overseeing the private sector."

Staff writer Alec MacGillis contributed to this report.