Because of growing trend, city wants to make ordinance more detailed; it will be voted on later this month.

Johnston is the latest in a list of Des Moines area cities to consider regulations related to construction and use of wind turbines.

City officials feel the current ordinance that addresses wind turbines does not include a strong enough review process as more environmentally conscious homeowners consider obtaining permits for turbine installation.

Although no Johnston residents have yet sought a permit, the market nationally for small residential wind turbines grew by 78 percent in 2008 alone.

Last month, the Clive City Council postponed a vote on a wind turbine ordinance that would prohibit the devices on all but a handful of residential properties there. The West Des Moines City Council approved an ordinance in October that allows turbines on properties one acre or larger, and Altoona allows them as well.

Johnston City Council members discussed potential ordinance changes for their constituents during a work session on Monday after the matter was initially discussed by the city's planning and zoning commission on June 29. A final draft of a revised wind turbine ordinance will be crafted for a vote by the council in the coming weeks.

Councilman Gerd Clabaugh is wary of allowing an increased presence of turbines in a community that is growing both residentially and commercially.

"I really don't think this is a good idea," he said. "There are already large wind farms across Iowa for this express purpose."

According to Johnston city staff, the smaller wind turbine versions average 80 feet tall with a blade diameter of 23 feet. They can usually generate a maximum of 10 kilowatts of energy, depending on wind availability. The cost for an even smaller version can start at $15,000.

Among the requirements being considered for wind turbines in Johnston is that they only be allowed on lots measuring 40,000 square feet or more and do not exceed a designated decibel rating when measured at distance of 300 feet from the nearest residence.

"Those (lots) are really scattered throughout town," said community development director Dave Wilwerding. Wind turbines "wouldn't be allowed in a typical residential zoning district."