Twin water wells drilled along North Street are working as expected, but it could be two years before the Baton Rouge Water Co. sees if they fulfill the goal of extending the lives of other freshwater wells to the north.

The “scavenger well” system is meant to intercept the salt water that is slowly moving northward toward important public drinking wells near Lula Avenue. This dual system includes one well drilled down to the saltwater layer and a second drilled to the freshwater layer above.

By pumping water in both wells, the goal is to help bring more fresh water to the well areas from the north, east and west that could help push back the salt water for a time, said Eugene Owen, chairman of Baton Rouge Water Co.

After being in operation for three months, the dual wells that make up the scavenger well system pump just more than a million gallons a day with about two-thirds of that being fresh water that goes into the public supply system and the remaining salt water being pumped through a pipeline to the Mississippi River.

Although it could be a few years before the water company will know if the scavenger well system is working to keep salt water at bay, the initial signs are encouraging, Owen said.

When the pumping started on March 6, the freshwater chlorides — which indicate levels of salt in the water — were at 155 parts per million. The level went up a little to the highest reading of 211 ppm, then has steadily fallen to 133 ppm on June 5, Owen said.

“That’s what really is encouraging,” he said.

The long-term hope is that by drawing off the salt water within the 1,500-foot layer of water-bearing sand in the Southern Hills Aquifer, the water company can give the major public supply wells at Lula Avenue an additional 30 years to even 50 years of life.

The water company started by taking daily water samples to measure the salinity at the scavenger well system but has since scaled back to three times a week because the pumping rates will remain steady for the time being.

In the long-term, the water company will measure chlorides at a well located between the scavenger well to the south and the Lula Avenue wells to the north to keep track of whether the saltwater plume has slowed down over time.

The issue of saltwater intrusion into the drinking water sands of the Southern Hills Aquifer that serves as a freshwater supply for many areas, including Baton Rouge, has been known for decades. As pumping levels increased to the north of the Baton Rouge fault, salt water located to the south of the fault continued to be pulled through the fault and farther north toward water wells.

The Capital Area Ground Water Conservation Commission was formed by the state Legislature in the 1970s to address the problem. In the meantime, Baton Rouge Water Co. decided to look into the possibility that a scavenger well could help in the short term.

In 2011, the water company drilled a test well in Mary J. Lands Park (also known as Progress Park) to help determine if the salt water and fresh water in the 1,500-foot sand layer of the aquifer were stratified as was theorized, Owen said. Salt water is heavier than fresh water.

The water company found the water types were indeed stratified, which meant it was possible to try out a scavenger well concept that would involve the dual well system they installed last year for about $3 million. The well at the park will act as a type of sentinel to help determine if salt water will continue to inch toward the Lula Avenue wells or if it will slow down, Owen said. Water tests at this well will happen quarterly.

Follow Amy Wold on Twitter, @awold10.