Waukesha - Both of the city's deep wells equipped with filters to remove radium from water are out of service after the failure earlier this month of the pump for well No. 3, Water Utility General Manager Dan Duchniak said Tuesday.
Loss of the filtered water likely will cause the city to temporarily exceed federal radium limits imposed by a court-ordered consent decree, though customers don't face an immediate health risk, Duchniak said. The limits are established to protect consumers who drink radium-contaminated water over a lifetime.
Filtered deep well No. 10 shut down in February after its pump failed. That closing came several days after a pump failure in unfiltered deep well No. 8. Those two pump failures forced the city to reopen three other radium-tainted deep wells to meet customer demand.
Saturated sandstone
All of the deep wells draw water from saturated sandstone.
No. 3's radium-removal filters became clogged with fine sand in the water in April. After the filters were repaired and the well restarted, its pump failed on May 8, Duchniak said.
The unexpected surge of sand in the water was "more than our filters could handle" and is one more indicator that the city cannot rely on its deep wells as part of a long-term supply, according to Duchniak. It was the first time that radium filters on either well became clogged with sand.
Apart from radium contamination, the deep wells also are providing water with increasingly high amounts of salt.
'Less reliable'
"Our deep wells are becoming less and less reliable because of the overuse of the sandstone aquifer," he said. Water levels in the sandstone have dropped from 500 to 600 feet in the last century and continue to drop up to nine feet per year.
Waukesha is seeking approval from Wisconsin and the other seven Great Lakes states to switch to a Lake Michigan water source. The city would abandon all deep wells in sandstone if the request is approved. Waukesha must be in full compliance with federal radium safe-water standards by June 2018.
Mayor weighs in
Mayor Jeff Scrima does not think recent problems are reason enough to abandon the deep wells.
"There are hundreds of cities across the country with deep wells," Scrima said. "These things happen and we're well equipped to take care of that."
The city's well No. 8 returned to service on May 2 and its tainted water is blended with water from two shallow wells so that it complies with radium limits. One other shallow well also is in use.
Even so, the water utility continues to use two of the previously closed wells with radium contamination on a daily basis, and pumps from the third when needed to meet demand, Duchniak said.