Miami-Dade ditches plan to shrink wellfields

Miami-Dade County abandoned a plan to shrink the boundaries protecting two of the county’s wellfields after a University of Miami hydrologist complained mistakes were made in calculating potential contamination.

In a resolution passed Wednesday, county commissioners agreed to other minor measures regulating land around the wellfields. But a controversial change to the protection boundary fought by environmentalists was scrapped after UM hydrologist David Chin said it miscalculated how contamination could move through nearby rock pits.

The county relied on a study by the U.S. Geological Survey to predict the speed with which contamination from a spill could make its way through porous limestone to reach the wells that provide drinking water for about 2.5 million residents.

But the wells are now nearly surrounded by rock-mining pits filled with water, which could carry contamination much more quickly, Chin said. The USGS “did not fully grasp when groundwater moves into a lake,” he said.

County officials are now conducting additional studies to determine any boundary changes.

This story was originally published January 21, 2015 at 6:24 PM with the headline "Miami-Dade ditches plan to shrink wellfields."