Manatee County offers insight into dam operations

Since 18 billion gallons of water were released from the dam into the Manatee River during Hurricane Debby, residents have questioned if that's why their homes flooded and if a 57-year-old dam is even safe.

From press conferences immediately following the storm to commission meetings held weeks later, Manatee County staff members have consistently stated that relentless rain caused the flooding of homes and that the dam operated as it should have.

Instead of simply saying it again, the county invited members of the media to hear from key staff members while getting an up-close look at the dam for themselves Sept. 4. 

On hand to present "Dam 101" was Deputy County Administrator Evan Pilachowski, Deputy Director of Potable Water Katie Gilmore, Director of Natural Resources Charlie Hunsicker and Utilities Director Patrick Shea.

The message was the same — 17 inches of rain did the damage.

Hunsicker repeated it and used a map of the watersheds to drive home the point that heavy rainfall, not the release of water from the dam into the Manatee River, caused homes in Lakewood Ranch to flood. 

He pointed to the map and urged people to “look at the elevations.” 

“It’s a matter of math and geography,” he said. “Water always flows downhill.” 

Hunsicker has lived in the River Club for 14 years. As a resident and county employee, he’s adamant that the problems in his neighborhood and Summerfield could not have been caused by the water release because watersheds and geological basins don’t intermix. The water flows out to the sea. 

He said the Braden River overflowed its banks. It backed up because it was struggling to push so much water through a small channel. 

As far as the dam, Shea said it’s in good working order. 

“In 2013 and 2014, some significant deficiencies were determined on the dam, and that report created some confusion, I think, in the aftermath of Debby. That work was commissioned and completed by September 2014. We’re in the stages of some of the additional work that was identified in that project in 2014, but they’re noncritical things that you should look at over time.” 

Finding balance

Information Outreach Manager Bill Logan said the plan is to also invite the public to see the dam, but there are logistics to work out. Because the dam is considered “critical infrastructure,” it’s under the authority of Homeland Security.

The reservoir serves over 320,000 Manatee County residents and wholesale customers like Tropicana. 

Dam 101 was held to offer the public a better understanding of how the dam works and is operated. A major component of decision making comes down to protecting the county’s water supply. 

Lake Manatee was lowered to 36 feet in the days leading up to Hurricane Debby; why wasn’t it lowered to 34 feet instead? 

“It would make an almost immeasurable difference,” Pilachowski said. “If we did, it’s simply a gamble that would not benefit downstream residents, but it could put us in jeopardy of not having water supply.”

That scenario happened once already in the early 1980s. Hunsicker remembered it. Staff dropped the lake level to between 34 and 35 feet, but the weather reports were wrong. The county barely got an inch of rain. 

“We were left with a reservoir with probably 70% of the capacity,” Hunsicker said. “We were not in trouble, but we were very worried about the viability of that water supply being able to carry us through to the next year’s rainy season.”

There’s almost a full backup of groundwater available under emergency circumstances, but severe water restrictions would be put in place if that needed to be tapped.

“If we had a repeated event with our current population and current water demands, it would be even more difficult for us to get through the dry season,” Pilachowski said. “(The extensive water restrictions) would make an even bigger impact on the community, so it really is a balancing act, trying to make sure that we are providing drinking water and fire protection for our residents.”

Photo by Lesley Dwyer

Gilmore said it’s not only the quantity of supply that is of concern when the lake levels are lowered. 

“Everyone knows about the taste and odor issues we have," she said. "When the lake is low and it’s more shallow, there’s sunlight penetration and the algae grow a lot easier. So you’re balancing a lot of factors. For the quantity and quality, you cannot go too low in the dry season.”

Typically, the dry season begins in October and lasts through May. According to the Southwest Florida Water Management District, about 60% of the area’s average rainfall is received between June and September. The average monthly rainfall drops from about 7.8 inches during the rainy season to about 3 inches during the dry season. 

Looking ahead

Pilachowski said Manatee's staff members can’t stop the rain, but there are actions they can take to better communicate with residents and to control flooding during future rain events.

The county has a messaging system in place now called Everbridge. Residents have to sign up to receive alerts. Staff is looking at enhanced uses of the Everbridge system to get messages out more effectively, such as storing emergency messages so they’re ready to go at a moment’s notice.

A series of watershed management plans, being conducted by a third party, are in process. The plans look at flood control measures and identify improvements that can protect the facilities within each watershed. 

Pilachowski said some plans have been implemented, and some are still in the planning phase, but focus has been placed on the Braden River, Mill Creek, Gamble Creek and Pearce Drain/Gap Creek.

But not everything can or will be fixed to avoid flooding again. 

When the current stormwater systems were installed, a decision was made based on projections and investments at that time.

Hunsicker used an analogy involving traffic on Manatee Avenue. To keep traffic flowing at all times, it would have to be six or eight lanes wide. That’s too large of an investment for the avenue’s day-to-day traffic.

Highways are designed to the highest standards of stormwater management because that's major infrastructure, but Hunsicker said some of the residential systems in Manatee County were only built to handle 20-year storms, which is roughly 6 inches of rain. 

Debby dropped almost three times that amount.

“This is not a Manatee County issue, this is nationwide,” Pilachowski said. “There’s always going to be an event that goes beyond what the design anticipated.”