Officials in Topeka, Kan. want septic tanks gone, so they use GIS maps to locate households capable of switching to the municipal sewer system. The project has been ongoing since the city passed an ordinance in 1997 mandating that homes close to the sewer system remove their septic tanks, said Kyle Tjelmeland, GIS system analyst for Topeka.

"It becomes a revenue stream for the city," said Tjelmeland. Citizens pay the city more than $1,000 to hook up to the municipal sewer system.

To locate prospects for conversion to the sewer, Topeka's GIS staff crafted a map with layers showing houses near the sewer system that receive water service but no sewer service.

"If they're paying a water bill, but they're not paying a sewer bill, there's a good chance they're using a septic system. Either that, or they're connected to the sewer system illegally," said Tjelmeland.

Septic Tanks Can Pollute

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Andy Opsahl  | 

Andy Opsahl is a former writer and features editor for Government Technology magazine.