Subdivisions and city limits have been spreading into the still-bucolic realms of eastern Durham County. Now, some of those who live there already are trying to put on the brakes.

"We don't want to be in the city," said Kenny Case of Olive Branch Road. "That's why we moved out here."

Residents in the south and west have mounted such campaigns, with varying success, in recent years. But organizing to slow -- or halt -- development is brand new in the east, where population is projected to grow 17 percent by 2012.

"There are a couple of issues around here," said Tina Motley-Pearson, who lives on Olive Branch Road. "And I think there have been some discoveries from other developments ... about what happens when land gets developed."

Erosion, for instance; and the pollution it causes that flows into already-impaired creeks that feed Falls Lake: "The drinking supply for 400,000 Wake County citizens," said Dean Naujoks of the Neuse River Foundation.

"Durham has to be a good neighbor," said Motley-Pearson.

Eastern Durham's current point of contention is the Egypt Property: a 563-unit subdivision proposed for a 208.4-acre tract on Olive Branch Road -- about two miles north of the Brier Creek shopping center. A rezoning request for Egypt came before the Durham Planning Commission Tuesday night. Motley-Pearson and Naujoks were on hand to speak against it.

"We have good reason, backed by scientific data, to believe that this will just lead to more impairment," Motley-Pearson said.

Ron Horvath, president of the design and engineering firm that is working on Egypt, said the project is "to develop a community that is sensitive to the environment ... and protects the natural features of the site."

One natural feature is the Triassic Basin, a geological formation that underlies most of Durham County.

"The Triassic Basin soil type is a very poor soil when it comes to removing vegetative cover and increasing impervious surfaces," said Brian Murphy, who lives on Olive Branch Road and teaches environmental science at Millbrook High School in Raleigh.

Triassic Basin soils are known as fine silt, said Chris Roberts of Durham County's erosion control division. Such soil erodes easily.

Problems have arisen even when eastern-Durham developers have been "actually trying to do everything right," Motley-Pearson said. Sediment itself is problematic for stream health, but soil particles also carry chemical pollutants into the streams and the lake.

Lick Creek, one of the area's major streams, is the subject of a state-financed watershed-restoration project in which Durham County is taking part. Driving forces behind restoration include the creek's status as an "impaired water body" and the suburban development in the area prescribed in Durham's Comprehensive Plan and Unified Development Ordinance.

"We have a real problem here," planning commissioner Wendy Jacobs said at Tuesday's hearing. "It just seems crazy that on the one hand we're spending money to repair these impaired waters and then at the same time we're doing development that impairs waters. I think we need to get this straight here."

The planning commission put off making a recommendation on Egypt's rezoning until July. In the meantime, residents are circulating a petition calling on Durham to halt "all East Durham development until more intelligently designed plans can be drawn up."

"We have to educate ourselves," Motley-Pearson said. "If you see a disaster coming, try to stop it."