The Water Institute of the Gulf is in the early stages of a study that will devise 50-year sustainable solutions for preventing saltwater intrusion into the Southern Hills Aquifer, a critical Baton Rouge-area water source. Over the years, saltwater has become a growing threat to the freshwater supply as usage has increased by consumers and industry.
Funded by the Capital Area Ground Water Conservation Commission, the $237,000 first phase is expected to take a year as a Water Institute team collects existing data about the aquifer to extrapolate a suite of possible solutions. The three-phased study could eventually result in a temporary fee hike of $10 per million gallons of usage, amounting to mere pennies for the average household.
Alyssa Dausman, vice president for science at the Water Institute, says most coastal cities need long-term strategies for managing groundwater resources to ensure a long-term, sustainable supply. She has experience with modeling groundwater systems and most recently worked on a similar effort in south Florida. “Even though people don’t think of Baton Rouge as a coastal city, when you get your resources from aquifers in the ground saltwater intrusion is a fairly common problem.”
The Water Institute plans to take a “structured decision making” approach by working closely with commission members to identify possible alternatives. Fortunately, the commission has already invested “in a lot of science and modeling through both the U.S. Geological Survey (which has numerous monitoring wells in the Baton Rouge area) and LSU,” Dausman says.
“We’re going to pull all of that science and information together and provide them with alternatives for long-term strategic planning. That could include looking at various conservation strategies, additional scavenger wells or possible alternative sources of water.”
Dausman says while Southern Hills Aquifer currently produces “pristine” drinking water, it is under constant threat from saltwater south of an underground fault line along Interstate 10. The freshwater aquifer is comprised of a series of pockets at elevations ranging from 800 to 2,800 feet deep that are separated by layers of clay. “As you remove freshwater from the aquifer system, that space has to be filled by something, so it gets filled by saltwater,” she adds. To date, scavenger wells have been successful in preventing saltwater intrusion, but that approach might not be sustainable as water consumption increases in the coming years.
Industrial usage on the decline
As of 2016, the aquifer’s four biggest users—Entergy, ExxonMobil, Georgia Pacific and Baton Rouge Water Company—were averaging 132 million gallons of water a day. That comprises about 85% of the total usage. Plants south of the fault line don’t have the option of tapping into Southern Hills, so they get much of their water from the shallower Mississippi River Aquifer. “In those locations, anything below 600 feet is all saltwater,” Dausman says.
Megan Manchester, spokesman for ExxonMobil (a CAGWCC member), says the company’s Baton Rouge plants have invested more than $5 million to reduce water usage, yielding a reduction of about 4.5 million gallons per day over the past decade, primarily in the 2,000-foot depth.
In a prepared statement, Manchester says ExxonMobil uses river water instead of groundwater when possible, primarily for cooling purposes and steam production. Currently, about half of the water used by the company comes from the Mississippi River. “Our clarified river water unit was built in 1971, and over the years the unit has been upgraded to treat more river water,” she adds. “This unit has allowed ExxonMobil to convert six cooling towers from groundwater to river water over the last seven years, resulting in a downward groundwater usage trend.”
Barry Hugghins, CAGWCC chairman, says the commission is managing the pump rates of all regulated users—those who pump 50,000 gallons a day or more—in an attempt to prevent depletion. Somewhat counterintuitively, he says industrial usage has actually slowed saltwater intrusion in some cases, since water is pulled from the 2,000-foot depth instead of the public water supply. CAGWCC is charged with managing saltwater intrusion and is comprised of representatives from a variety of public and private entities.
“The computer models we’ve generated through USGS show that if you cut off industry from the water supply the plume of saltwater would turn to the east and run into public supply wells. It actually gets there quicker.” He hopes that the science produced by the Water Institute study will enable the commission to achieve much-needed consensus on the problem.
Matt Reonas, education and marketing representative with the State Office of Conservation, says recent studies have shown very little impact on overall water usage, despite reductions imposed by industry. The CAGWCC has projected short- and long-term usage by the major users since 2012. “The numbers that we’re seeing reported by USGS and CAGWCC are basically status quo,” Reonas says.
The bulk of the challenges are in Baton Rouge, due to the concentration of users and the city’s proximity to the saltwater-freshwater fault line. “Baton Rouge Water Company and the various industries are all clustered within a fairly close proximity, so it creates a big local draw in this area,” says Reonas. “It just so happens to be right next door to the fault where there’s a big load of saltwater just waiting to come north.”
For these reasons, Reonas says the time is now for the Water Institute study. “All these questions need to be answered in an open, transparent way. It’s a tough conversation because you have so many vested interests. This study is the best opportunity, to date, to find a solution.”
Tackling the problem
Utilizing an “integrated science” approach, the Water Campus will tackle the problem in a transdisciplinary fashion. Dausman, along with coastal geologist Ryan Clark, social geographer Scott Hemmerling and others, will work collaboratively throughout the process. “I’m also bringing in two consultants who are experts in structured decision making and decision analysis,” Dausman says. “We’ll look at it from several different angles because we can sit in a room together and brainstorm.”
During Phase One, the Water Institute will compile all the science that’s available and look for gaps in the data. “We will identify the alternatives. Phase Two (which could include some field work) will be involve evaluating the alternatives, then narrowing those down to one or two. Phase Three will require the long-term strategic plan for moving forward.” The entire process could take several years.
The ultimate goal is to develop a sustainable water resource for the greater Baton Rouge area, so that the larger community can grow and prosper over the long term. “And not just for drinking water, but for industry … for everybody,” Dausman says, adding “science needs to be transformed into a usable way” so long-term strategic planning can be done.
“We’ll also look at the economic tradeoffs, because we need to think about the future population of Baton Rouge and the economics of the next 20 to 50 years,” she adds. “After all, it’s not a static problem.”