LEWISTON, Idaho (AP) -- A northern Idaho group is working to protect a deep basin aquifer that has stored water for thousands of years and supplies much of the region with drinking water.

The Lewiston-Clarkston Drinking Water Source Protection Planning Team recently completed a plan intended to inform area residents how to keep contaminants from reaching the aquifer.

"We have this protected, deeper aquifer," said Anna Moody of the Idaho Department of Environmental Quality in Lewiston. "Our intention is to get the word out that we want to protect it into the future because the shallower water is not good to drink."

Wells draw drinking water for customers in the Lewiston Orchards Irrigation District and the Asotin County Public Utilities District.

Most of Lewiston's water comes from the Clearwater River, but the city also has wells to get drinking water.

Officials say water in the Lewiston deep basin aquifer has been there for up to 35,000 years. Moody said keeping the water pure by preventing contaminants from reaching the aquifer is important because the aquifer recharges at a slow rate.

On Saturday, Moody and members of the team marked storm water drains in Lewiston.

"Not all the storm drains are up to snuff," she told The Lewiston Tribune. "Things that leak have potential to impact drinking water and there are areas where storm drains are near city wells."

Other potential sources of pollution include septic systems, old wells, disposed household materials, and spills.

The protection plan the group has put together is voluntary.

"There are no regulatory requirements for this plan," Moody said.

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Information from: Lewiston Tribune, http://www.lmtribune.com

Copyright 2010 The AP.