A handful of workers manually hoisted the spillway gates on Lake Marion, “feathering” the Santee Dam to stay ahead of the swamping floodwaters. They were among any numbers of timely heroes and cautionary lessons that are emerging from the freak onslaught of October rain, a deluge heavier than training could have prepared for.
At the worst of the historic flooding last year, 38 million gallons per minute were spilling through the dam. That’s enough to fill nearly 60 Olympic-sized swimming pools — every minute.
The Santee Cooper utility workers mitigated flooding and erosion downstream with the feathering technique: opening or closing specific gates to specific heights in sequence along the half-mile long spillway. They adjusted not in reaction to the rising of water, but anticipation of it.
They were directed by engineers who watched radar to calculate rainfall in real time to make flow estimates. They needed the estimates because the protocol is governed by upstream flow gauges, but more of the flooding was from heavy rain falling in and around the lake, downstream of the gauges.
The historic flood left a devastating toll. Floodwaters swept a heavy duty-military truck clean off the road in Berkeley County. Hundreds of people had to be evacuated from Charleston County subdivisions nowhere near a major river.
Dozens on dozens of others rode it out traveling back and forth by boat. Dogs in the Frances Willis SPCA in Summerville had to be rescued from their swamped cages.
And that doesn’t begin to tell it. All the numbers are not in because the toll is still being counted. But the flood:
Caused an estimated $6 million in damages to houses and other structures in Charleston County alone, and more than $3 million in Dorchester County, according to officials in each county. Berkeley County did not immediately provide an estimate.
Led to more than 100 water rescues in Dorchester County; 67 in Berkeley County along French Quarter Creek alone.
Closed nearly 90 bridges or sections of road across the three counties. In one instance, the military truck that swept off Highway S.C. 402 near Huger stranded for an hour two firefighters who had been deployed to rescue others.
The biggest takeaway for emergency officials was the difficulty in getting the word out to the public as well as communicating in the field. All three counties are exploring options to better handle it. As one example, Berkeley County officials are looking at establishing a clearinghouse.
Without the touch of the Santee Cooper utility crew, the flooding along the Santee River at the northern edge of Berkeley County and below could have been much worse, said county Emergency Preparedness Director Tom Smith.
The gates don’t open electronically. Workers had to get out on the spillway and haul them up. They call it “throttling the gates.” The monster flow they released had enough power to create updraft winds of several miles per hour.
“Not quite Niagara Falls, but it’s an impressive amount of water,” said Mark Carter, chief dam engineer.
The seat-of-the-pants computations by the engineers, though, kept it in check.
“Our engineers did some tremendous calculations,” said Stony Martin, Santee Cooper system operations planning supervisor. The estimates and the actual water that piled into the dam matched up pretty accurately, he said.
“It allowed us to get ahead of (the flood), which is what you want to do,” said Tom Abrams, planning and power supply vice president.
The peak average discharge rate, 84,844 cubic feet per second, was the third-highest in the history of the dam. The highest, 138,000 cubic feet per second, occurred in September 1945. The “normal” maintenance flow is 500 cubic feet per second.
“It’s something everybody should get to see,” said John Steed, crew supervisor. “When you get to that point of the spill, when you look to the west at all the water, you realize what you are actually doing and the consequences if you don’t.”
Fortunately for county residents, the lake level had been lowered just before the rain, to prep for Hurricane Joaquin.
If the lake had been full when the deluge started, “we would have had to spill it,” Abrams said.
Among other flood takeaways:
When flooded roads were barricaded in Berkeley County, a few people just moved the barricades and drove through. Moncks Corner Fire and Rescue crews had to make rescues from three cars submerged in ditches the first night alone, said Fire Chief David Miller.
Rescue crews were forced to patrol homes in the rising waters of the Edisto River in Dorchester County to make sure people who had refused to evacuate still were safe.
People were slow to evacuate in a lot of instances because they didn’t want to leave or be separated from their pets.
The Berkeley County SPCA took in four times the animals it was capable of handling, including dozens of horses, and had to farm out rescues to other animal care agencies, county Emergency Preparedness Director Tom Smith said. After the Willis shelter flooding, people turned out for emergency adoptions to give shelter to dozens of animals.
Along with the impromptu animal adopters at the Willis shelter were a host of groups and individuals who came out to help.
The S.C. State Guard supported local law enforcement and emergency responders with search and rescue, professional services and manual labor in the three-county area. Spokesman Bryan Hilferty did not have figures for the counties, but said more than 800 members put in more than 20,000 hours statewide.
“All volunteer. No cost to the state. Unlike the National Guard, we don’t get paid,” he said.
Dozens of churches and community groups in Berkeley County, Summerville and elsewhere came out on their own to provide assistance to people caught short, many going door to door. Among other contributions, Joint Base Charleston provided cranes and other equipment.
Private companies donated mobile homes to eligible people among more than 30 in Berkeley County that lost homes.
Reach Bo Petersen at 843-937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.