Water development committee digs into aquifer, well data

As Brandon looks at buying a $30,000 part to repair its primary water source, well 6, the water development committee takes a closer look at the aquifers supplying that water.

That discussion began at the committee’s Dec. 19 meeting with experts from the South Dakota Geological Survey, many of whom had studied the Splitrock Creek and Big Sioux aquifers. 

According to Derric Iles, state geologist, South Dakota is unique in that it has a “tremendous and unrivaled history on wells” – about 70 years of research by geologists and hydrogeologists.

While none of the geologists or hydrogeologists could say with certainty that Brandon’s aquifers could sustain its long-term water needs, the scientists did conclude that the city would be safest relying on a combination of water sources.  

The geologists discussed factors and variables such as the aquifers’ ability to replenish, how the speed at which a well is pumped can change test results and water rights to drill.

Iles said the Splitrock Aquifer was an unlikely long-term water supply source for Brandon.

“My gut feeling is considering the amount (of water) you want, I don’t think you’re going to get that out of this,” he said. 

And “the big gorilla in the room,” Iles said, is radium.

Three years ago, well 7 tested at a radium level of around 23. (The Maximum Contaminant Level, or MCL, is 5). “You would dilute it from other sources, but you don’t have enough water from other sources,” Iles said. “You’re going to have to mitigate it.”

The source of that radium can’t be determined, either, he said.

“Maybe it’s the aquifer itself, maybe it’s the content of the sediments, maybe not, maybe it’s just recharge coming from quartzite.”

Jay Gilbertson, a hydrologist with East Dakota Water Development District, spoke about the Splitrock Aquifer. 

“Splitrock Creek provided an additional 5 million gallons per day, according to previous studies, but the quantity and quality of recharge is uncertain,” he said.

Gilbertson noted three wells in southeast Brandon showed a static level of recharge, and four wells northwest of town were declining.

“The Splitrock Creek trend is going down,” he said. 

He pointed out that Brandon has future water rights in the Big Sioux Aquifer.

“Water rights come on a first come, first serve basis,” Gilbertson said. “The best time to do something was obviously 20 years ago or 30 years ago, but the second best time to get started is right now.”

Connecting to Minnehaha Community Water Corp. (MCWC), he said, could give Brandon time to investigate the Big Sioux Aquifer.

“The bulk is fairly shallow, but there may be a few pockets,” Gilbertson said.

Several experts agreed the Big Sioux Aquifer has potential for test drilling, which the city could do inexpensively. Brandon currently has one well in the Big Sioux – well 1, which is not online – and three in the Splitrock Aquifer, well 3 (the city’s backup), well 6 (its primary source) and well 7 (which is not online but plans include it unless the water committee and city council deem otherwise based on the committee’s findings).   

The geologists advised collecting samples at times when the city is pumping wells at its normal rate and performing isolation tests on specific sections of the aquifers.

“It’s time to start looking at your range of options. There doesn’t appear to be a home run,” Gilbertson said. “That ship sailed.”

The water committee will review the information presented at its next meeting, set for 6 p.m. Wednesday, Jan. 3, at city hall.