Debunked: Siesta Key water discharge did not cause red tide

Red tide is upon us once again and, over the past week, you may have heard a rumor about why the algae are back with a vengeance and leaving thousands of dead fish along damn near every local beach.

The rumor links Sarasota County’s decision to discharge millions of gallons of partially treated wastewater into a canal during Hurricane Hermine and the emergence of red tide over the past 10 days.

But what you’ve heard is just wrong.

[tl;dr county dumped wastewater in canal during hurricane and didn’t tell neighbors, they find out weeks later as red tide shows up, rumors say discharge caused red tide, science says hell no, county to notify neighbors next time]

What happened?

During the height of Hurricane Hermine’s record rainfall, Sarasota County discharged 3.3 million gallons of partially treated wastewater from its overflowing Siesta Key treatment plant into the Grand Canal.

In a matter of hours the storm dumped 6 to 9 inches of rain across the county, which overwhelmed the water treatment system designed to handle up to 70 million gallons a day.

Around 8 p.m. the Wednesday night of the storm (Aug. 31), the decades-old plant on Siesta Key was at capacity. Utilities personnel decided about an hour later the plant would have to dump partially treated water into the canal that runs through the Siesta neighborhoods to Roberts Bay to take pressure off the system.

Without the discharge — a last resort — the system’s treatment process would have been compromised, with the potential for raw sewage spills or backups into people’s homes, causing dangerous health conditions, county Public Utilities Manager David Cash said this week. That could have put the entire plant offline for days as the storm continued, he added.

“I don’t want to minimize it, but it’s a relatively small amount of water in comparison to what actually goes through the facility,” Cash said. “Unfortunately for this facility being where it is, it susceptible to those heavy downpours and us having to implement that procedure.”

But the 3.3 million gallons discharged was only about 18 percent of the more than 18 million gallons of total volume that went through the treatment plant during the storm, Cash said Wednesday. The remaining 15 million gallons were fully treated.

Did they tell anyone?

Yes and no.

The county reported it to the Department of Health and the Florida Department of Environmental Protection, per the rules that allow these types of discharges in emergencies. No-swimming signs were posted in the canal, too.

But county officials did not tell We, The Media nor did they directly notify the Siesta residents who live along the canal and watched it rise into their backyards.

Over the weeks since, residents have slowly heard bits and pieces of what happened and they are, needless to say, pissed.

So what’s the rumor?

That the red tide affecting Siesta Key over the past week is a result of that discharge.

Because it took homeowners along Grand Canal weeks to hear bits and pieces of this story, they’re learning about it while looking at thousands of dead fish on Siesta beaches and red tide expanding along the coast. It’s only natural for someone to ask if they’re related.

Without a concerted public information campaign against it, that rumor has swirled and grown in email chains and Facebook posts that picked up steam and made its way onto the evening news and the Herald-Tribune’s news meetings.

It’s convenient and fits the oversimplified (yet in so many other instances correct — we see you, Mosaic) “big, bad government kills environment” trope.

But it’s simply not true here, and it shouldn’t take a phytoplankton ecologist to tell you that. Though, of course, he will.

What does science think?

No, the discharge did not cause this bloom of red tide algae, said Vincent Lovko, a staff scientist in Mote Marine Laboratory’s phytoplankton ecology program.

First, the discharge happened weeks before red tide began effecting Siesta Key late last week. Second, red tide concentrations have been recorded since July and higher concentrations first hit Longboat Key about 10 days ago before expanding to Siesta.

“Our current understanding is these blooms initiate offshore, 30 or 40 miles, off bottom,” Lovko said. “What influences begin that bloom, we don’t fully understand. Obviously there has to be some nutrient source, but you’re far enough out that it’s not nutrients from the land.”

Nutrients from runoff or this discharge can contribute to the blooms once they get to shore. But the discharge is indistinguishable from the immense total runoff that has poured into local waterways and the gulf from Hermine and the rain since, Lovko said.

Just think about the numbers: 3.3 million gallons is 18 percent of the total volume handled just by the Siesta treatment plant during the storm. That makes it a small fraction of the overall runoff volume the storm dumped into local waterways across the entire county.

Conclusion

The real issue here is that the county admits it should have directly notified homeowners in the area of the discharge, and it plans to create a new type of notification to make sure this kind of confusion doesn’t happen again, Cash and Siesta Key Association leaders said.

All agree a discharge is better than actual shit backing up into your house, but it certainly could be handled better next time. Lesson learned and science prevails.