The south prong of the Alafia River is polluted with fluorides, making its water unsuitable for drinking, Hillsborough County environmental chemist Tom Cardinale said yesterday.

“If that’s so, the Picnic dam and reservoir are shot down right now,” John Logan, Hillsborough water resources director, responded. Removing fluoride from water is prohibitively costly, he said.

The state of the river was made known during a staff meeting of county resources and engineering personnel. It was one environmental factor leading the staff to recommend unanimously that a proposal before the county commission to endorse the dam be drastically altered in meaning.

The south prong contains as much as three times the fluoride level the U.S. Public Health Service would permit in the controversial fluoride-additive program, it was disclosed. The fluoride comes from phosphate and phosphate mining.

The staff recommended that the commission withhold any approval for mining phosphate in the Alafia River floodplain until “economic engineering and environmental feasibility is demonstrated” for the dam and reservoir.

Critics of the resolution’s first draft, including Roger Stewart, county environmental protection director, and his chief environmental biologist, Rick Wilkins, contended that the draft implied county commission consent for the project.

Edward Melchen, director for county development, insisted that resolution was not intended to convey “a preconceived conclusion.”

He readily agreed to changes, including eliminating a statement that the U.S. Department of Agriculture “proposed” the dam.

It never has, according to Ken Inglis, Soil Conservation Service agent.

Logan, meanwhile, estimated that two years of study would be necessary of such things as water-quality and the impact of more mining in the Alafia basin, as well as of engineering factors regarding the amount of water the reservoir might hold or leak.