Woodbury well testing to determine impact on groundwater aquifer
A new practice will make Woodbury test water wells poised to serve new development before starting to tap the groundwater aquifer.
The three-month process comes with a $168,000 price tag and will determine whether the city will get an appropriation permit to pump 2,000 gallons of water per minute.
The purpose of the test is to stress the groundwater aquifer under a worst case scenario, pumping more water than ever out of Well 18, which is located in the eastern portion of the city.
The well is located in the headwaters of a trout stream that’s dependent on the groundwater for trout sustainability. The test is to determine the impact on groundwater levels, which in turn may impact the trout stream.
“The concern is that if you were to drop the groundwater levels permanently you could potentially cut off the source of groundwater to the stream,” said Minnesota Department of Natural Resources hydrologist Molly Shodeen. “If you lower it so far that it no longer flows to the stream then you impact the stream.”
A new state law requires municipalities to get preapproval from the DNR before drilling any wells, which is what Woodbury did in June 2013, and later go through the testing process before an appropriation permit is granted.
The DNR could respond by saying the requested amount of water may or may not be as much as ideal.
“And that’s kind of where we’re at with the city of Woodbury,” Shodeen said. “They put their well in, but they want to pump it to a fairly high capacity because there is enough water there that they can draw a lot of water out.
“But if it impacts the stream then we would have to limit how much they can take at any one time.”
Woodbury is requesting to get at least 2,000 gallons a minute out of Well 18 to meet peak demand during warmer summer months and in case of an emergency.
Environmental resource specialist Jim Westerman said there is always potential impact to existing wells when a new well is installed and operated.
“We do not expect that the test will result in a limit of water or substantial impact,” he said. “However, this is exactly why we are performing the test. It is to determine to the best of our ability what the aquifer can produce without negative impact to private water supply wells or natural features.”
While municipalities are required to test new wells, agricultural users pump water without renewing permits on a regular basis.
According to the DNR, large irrigation users are required to pay an annual fee and file the amount of water used.
Woodbury Public Works Director Klayton Eckles sees it a “double standard” that many agricultural and industrial users receive appropriation permits without going through the same testing process.
But Shodeen said it wasn’t until recently that irrigation pumping has increased due to droughts. That, combined with Twin Cities growth and declining lake levels, have shifted the focus to aquifer levels.
“Until recently that wasn’t a big issue in the state,” she said. “But now that we are seeing impacts … you’re having to look at the irrigators, you’re having to look at the municipal supplies up in those areas too to make sure the groundwater that’s available is being used in a sustainable manner.”
The Minnesota DNR is currently studying aquifer impacts in the north and east metro, but the studies aren’t far enough along to determine any conclusions.
The “Groundwater Management Area” which includes Washington County, Ramsey County and parts of Anoka County, all communities using the Prairie du Chien-Jordan aquifer, is the focus.
Shodeen said results of these studies, expected to be released in early 2015, may play a role in how well testing is done in the future.
A big question is whether private wells, though not required to apply for appropriation permits, will have to test, too.
Some of them don’t hit the trigger for a mandatory permit, but some suburban developments with large lots and lots of lawn to water may actually be using more water than expected.
“That is one of the parts of this puzzle that nobody has a handle on because typically private wells don’t trip any permit categories for the DNR,” Shodeen said. “We really don’t have information on how much water is actually used in a domestic well.”
Though individual private wells may not use the minimum 10,000 gallons a day that requires an appropriation permit, a number of wells combined could potentially pump that much water.
“You take enough of those wells and they do start to have an impact as well,” Eckles said.
Woodbury is set to start testing Well 18 this summer. The process will end in September and if an appropriation permit is granted, the city will begin incorporating the well into the rest of the system in spring 2015.