An ASR system directly injects surface water: potable water, reclaimed water or river water, into an aquifer for later recovery and use.
Marco’s system is located nine miles away, off State Route 951, near its intersection with U.S. 41. Since initially coming on-line in 1997, it’s been visited by water system experts from around the world, said Jeff Poteet, general manager of Marco Island’s Utility Department.
Namsik Park, a professor of civil engineering at Dong-A University in Busan, South Korea, recently added his name to the list of visitors with a tour of the facility, led by Poteet, and other utility department managers.
“I specialize in the recharge of coastal aquifers, just like this system here,” said Park, who directs his home country’s government-funded Subsurface Reservoir Research Center. “These systems aren’t in use in South Korea. Artificial recharge is a very new concept in South Korea so I’m here to learn new things.”
He was joined on the tour by Weixing Guo, of Naples, a hydrogeologist for Groundwater Tek Inc., USA, and Kent Feng, lead hydrologic modeler for the South Florida Water Management District, who arranged the visit.
“This is a wonderful facility, said Park, who also visited with water system specialists at Florida Gulf Coast University during his three-day trip. “The Marco Island ASR system is very well known in the profession, so I’m very glad to be here and the people have been very nice in explaining things. Wonderful.”
Marco’s ASR system occupies 205-acres that include two freshwater lakes and the motors, piping, pumps and other equipment needed to move water from the lakes to a line of six storage wells located 780 feet to 785 feet underground and to the city. The wells are bordered on the top and bottom by layers of clay and separated by layers of porous rock.
“All the water is stormwater run-off from Henderson Creek,” said Poteet. “The creek passes by the lakes and then goes to a weir at (U.S.) 41, where that freshwater source is lost to brackish water and goes to the Gulf of Mexico. “So we’re able to capture the freshwater when it’s plentiful, when it’s raining and we have a lot of water, and then during our time of need, during the summer when we haven’t had any rain, we’re able to pull it up out of the ground and supply our community.”
Marco doesn’t have a nearby freshwater supply, instead relying on its reverseosmosis plant and the ASR’s lakes, which also supply the storage wells.
“The surface water site and the groundwater site on the island combined can’t meet our needs without the ASR site,” said Poteet.
Having the ASR and its lakes is a money saver for utility customers because fresh water from that source means less reliance on the wells that feed the reverse-osmosis plant, helping those waters maintain a salinity that makes them economically viable for treatment.
Surface water is less costly to treat than saltwater, added Poteet.
He also pointed out that while the potential for contamination exists for the lakes, but that potential does not exist once water is in the ASR well.
“So we potentially have two years of supply for our citizens in the event a catastrophic failure happened here,” said Poteet. “That’s a huge thing to have. A lot of communities don’t have that.”
So why is Marco’s ASR (and ASRs, in general) of such great interest around the world?
“Because it’s so successful,” said Poteet. “In 2010, we were recognized with the American Academy of Engineers Excellence in Environmental Engineering Competition for Environmental Sustainability. ASRs have really come to the forefront for those communities that have a water need and have a lot of rain and nowhere to store it.”
There are other ASRs in Florida, but they tend to differ from the system used by Marco, said Bruce Weinstein, who was the city’s utility engineer from 2004 to 2014, while the ASR system was being completed.
Weinstein, who’s retired, was present for Park’s visit.
“Almost everyone uses potable water, meaning they fully treat the water and put it in the ground and say the average loss is half of all that water,” he said. “The water they recover, they put right into the potable water distribution system and that water has now cost them twice what the water coming out their plant costs them. It comes out of the plant, goes into the ground and they only get half of it back so it adds to their costs dramatically.”
Marco does minimal treatment to water that goes into the storage wells.
“We rough-filter it and add about one-fifth to one-sixth the amount of chlorine, so it costs very little to put it in the ground and recover it,” said Weinstein. “Even if we lost 25 percent of it, we don’t have a lot of money invested in it, as opposed to a potable-water ASR.”