Columbus' relentless northward sprawl inevitably adds more homes, roads and sewers near the Olentangy River and its tributaries.

The Mid-Ohio Regional Planning Commission is lobbying communities along the river to join an effort to allow building on selected areas within the 372-square-mile Olentangy watershed while protecting other areas.

The carrot: the potential for those communities to obtain more state money for projects.

Incentives could include reduced rates on loans to build water and sewer lines and treatment facilities or extra points on grant applications for water-related projects, said Gail Hesse, an administrator with the Ohio Water Resources Council. The planning commission is applying for a $100,000 state grant to pay for a two-year study to identify areas to be developed.

The Olentangy has been designated a state scenic river in the 22-mile section between Delaware and Worthington. But the river still is polluted by sewer overflows, failing septic systems and runoff from farm fields and buildings. An Ohio Environmental Protection Agency study of 74 sites in the watershed found that 46 percent were meeting water-quality goals, but 31 percent were only partly meeting them and 23 percent weren't meeting them at all.

"It's not simply protecting priority conservation areas," said Jerry Tinianow, director of MORPC's Center for Energy and Environment. "It's designating priority development areas, making them more livable, clustering housing and jobs and transportation nodes."

Now, the commission must persuade 75 percent of the communities in the watershed (by number, population and land area) to form a planning partnership.

The Columbus City Council adopted a resolution last week supporting the effort. Other communities on board include Grandview Heights, Powell and Worthington, Tinianow said.

MORPC also hopes to use the grant to leverage $400,000 in federal money for a regional transportation plan that would include much of the watersheds of the Scioto River, Big Darby Creek and Big Walnut Creek.

The water resources council and the Ohio Lake Erie Commission are to announce the grant winners in December. Four similar partnerships have been formed in northern Ohio.

Malcolm Porter, a lobbyist with the Building Industry Association of Central Ohio, said he wasn't familiar with the Olentangy plan.

"Developers are supportive of planning and predictability," he said. "We'll see how it goes."

The group Friends of the Lower Olentangy Watershed is willing to support MORPC's effort because it is aimed in part at preserving the environment near the river, said Heather Dean, the group's watershed coordinator. "I think there's been a lot more attention (being paid) to the Olentangy. I think we can always do more."

mferenchik@dispatch.com