Well project underway to stem salt water intrusion

A $3.2 million project located along North Street and 31st Avenue in Baton Rouge could provide another 30 to 50 years of life to drinking water wells located near Lula Avenue.

This “scavenger well” project, being drilled by the Baton Rouge Water Co., is designed to keep salty water from encroaching on the wells.

The salty water is coming across the Baton Rouge fault, located roughly along I-10 from the Mississippi River bridge and then along I-12, and is getting closer to wells that serve Baton Rouge residents.

“Good fences make good neighbors and this is going to be our fence,” said Patrick Kerr, chief executive officer of the Baton Rouge Water Company. “Our goal is to protect Lula (wells).”

Although the Southern Hills Aquifer that provides this water has many layers of water-bearing sand, it’s the layer at 1,500-foot that is of most concern. As more water is pumped out of the ground north of the fault, water south of the fault moves northward. As the water moves north it is made more salty as it moves by salt domes across the fault.

“This is a new old problem,” said Eugene Owen, chairman of the Baton Rouge Water Company.

He said the earliest document he could find about the saltwater intrusion issue came out in January 1964 from the state Department of Public Works.

“This problem has been acknowledged and realized for a long time,” Owen said.

Owen explained that although the water company had talked about the possibility of doing a scavenger well project for a number of years, a determination had to be made on whether the salty water and fresh water were mixed or if the heavier salty water was in a layer at the bottom of the sand layer.

If the salty water and the fresh water were mixed, the scavenger well would be useless. However, if the heavier salty water was in a wedge at the bottom of the sand layer, then one well could be drilled down to tap that layer and another well would be drilled shorter to draw from the freshwater layer.

“We had to prove it was stratified,” Owen said.

Several studies done in 2010 and a test well drilled in 2011 helped prove that the salty water was indeed stratified, and the water company moved forward with plans for the scavenger well.

The “scavenger well” project is made up of two wells. One well will go deeper into the ground into the leading toe of this saltwater wedge and another well will be drilled about 20 to 30 feet away to a shallower depth to access the freshwater layer on top.

It took some time to find property to use for the scavenger well drilling, but the company closed on a parcel of land along North Street and between 31st and 32nd avenues in May, Kerr said. By mid-June, a drilling team from Layne was on site and the drilling on the first well, which will bring up salty water, began.

“If we can stem that (saltwater intrusion) and accomplish what we set out to do. It can really make a dent,” said Bruce Duhe, district manager for Layne. “It’s important for all of Baton Rouge.”

This first well needs to be finished before drilling on the second well begins. Once both wells are complete, the two wells need to be “tuned” to make sure that water from both layers, salty and fresh, flow directly into the pipes they’re supposed to.

When the well has been “tuned,” the fresh water drawn from the well will go into the public supply system while the salty water will be pumped through a pipeline to the Mississippi River.

The salinity of this water is too high for drinking standards, but it’s not seawater, Kerr said.

“We’re not going to be discharging salt water to the Mississippi River,” he said, instead describing the water as brackish. In fact, studies the company did about initial plans to put the water into Capitol Lake showed the level of salinity wouldn’t have had an effect there either.

For comparisons, the average ocean salinity is about 35,000 parts per million and this discharge from the scavenger well will be at about 1,200 parts per million, Kerr said.

“It would taste salty if we taste it,” Kerr said.

The water company got approval to discharge the water into Capitol Lake, but company officials were concerned about possibly disturbing pollution located in lake sediment, so authorization was obtained to discharge the salty water into the Mississippi River instead, he said.

Owen said the two wells combined will pump about 700 gallons a minute, or about a million gallons a day. However, those rates could changed based on what they find during the test operation of the wells, likely to occur in the spring.

Of that water, about 250 to 350 gallons a minute would be the brackish water which will be piped to the Mississippi River at an outlet along River Road just south of the state Capitol. The rest would go into the public supply.

“If this works, there’s nothing that says we can’t move south” and install additional scavenger wells, Kerr said.

In the meantime, the Baton Rouge Water Co. has property along the Mississippi River if future demand calls on water to come from the Mississippi River.

Editor’s note: The story was changed on Ju ly 1, 201 3, to correct the average ocean salinity level.