Little Falls Continues Implementation of Wellhead Protection Plan
From the Spring 2014 Minnesota Department of Health Public Water Supply Unit, Waterline, Minnesota Department of Health
Little Falls, a central Minnesota city of 8,400, is midway through the implementation phase of its 10-year wellhead protection plan, developed with the help of the Minnesota Department of Health (MDH) and set to expire in 2017. The city had fallen behind with implementation efforts but has made great progress thanks to a grant, a significant find, and dedicated employees.
As part of implementing its wellhead protection plan, Little Falls has to seal unused and abandoned wells. “Unused, unsealed wells can provide an open channel between the surface and an aquifer—or between a shallow aquifer and a deeper aquifer,” said MDH hydrologist Geoff Nash. “An unused well can act as a drain, allowing surface water runoff, contaminated water, or improperly disposed waste to reach an uncontaminated aquifer.”
Recently a city employee came across a 1947 map showing the locations of these wells. Nash called it “the holy grail,” as it allowed the department’s Source Water Protection (SWP) Unit to assign unique well numbers. “It was an exact map of what they needed,” said Nash. “It just couldn’t have been any better.”
Little Falls then applied for and received an $8,300 implementation grant from MDH with money available from the fund established by the 2008 Clean Water, Land, and Legacy amendment to the state constitution.
Some of the 12 abandoned wells were accessible via manholes, others were under buildings, and some under streets. Before tearing up pavement and concrete, the city wanted additional evidence of the locations of these wells.
With a portion of the grant money, Little Falls hired 3Dgeophysics, Inc., of Chaska, Minnesota, to use a proton magnetometer with GPS. The magnetometer identified anomalies, produced by metal, in the earth’s magnetic field, a means of finding and confirming the location of the wells. The additional GPS capability allowed for a map to be made to provide a permanent record of the locations, necessary as the city is phasing in the well sealing over the next few years.
Of the four wells targeted for sealing in 2013, 3Dgeophysics found three. As for the other, it’s likely it was removed sometime in the past, possibly during a utility installation. Little Falls has applied for a well-sealing permit to MDH, which will evaluate the situation and determine the status of that well.
Former wells 7, 10, and 12 were found. Well 7 was just outside of City Hall (which occupies a building that served as the water treatment plant from the time it was built in the 1930s until 1973). The well casing was only a few inches beneath the ground. Though filled with debris and gravel, the locating of the well was an “easy job,” according to Nash. Well 10 was under the basement of City Hall and also posed few challenges.
Well 12 was a tougher find. Curtis Wunderlich of the MDH Well Management Section, using a magnetometer at a location indicated by the 1947 well map and by a faint anomaly from 3Dgeophysics, found a Class V injection well. “The unexpected reuse of what was originally a brick well structure as a Class V well puzzled us at first,” said Nash.
Wunderlich suspected that the sediment, including a chunk of concrete, at the base of the Class V well was covering a well casing. Nash added, “We suspected that the chunk of concrete was part of a past well-sealing effort. Troweling or dumping concrete into the upper few feet of a well was a method of ‘abandoning’ wells before regulations.”
To avoid entering a confined space, Wunderlich lowered a magnetometer on a rope into the Class V well structure and found a magnetic signature for well 12 beneath it. “Curtis is like a bloodhound when it comes to locating wells,” said Dwayne Heinen, the assistant water supervisor for Little Falls. “He just doesn’t give up.”
The next day a city worker (complying with requirements for confined-space entry) moved the concrete to reveal a six-inch diameter pipe, from 1926, that was well 12. At that point, city crews put a sleeve over the casing to make for easier access for the drillers. Wells 7 and 12 were later cleaned of obstructions and sealed in accordance with the Minnesota Well Code by Northland Drilling of Randall, Minnesota.
Gail Haglund, Mark Wettlaufer, and Trudi Witkowski of the MDH SWP Unit praised the efforts of Heinen, who came on board in June 2011 just in time to be given the implementation duties. In addition to the well sealing, Heinen has been busy with educational activities, including nitrate clinics, and working with local units of government on the plan. “He didn’t just want to meet the minimum requirements,” said Witkowski. “He did more than was needed.”
Little Falls will be applying for additional grants to continue its program of sealing the rest of the wells. Nash notes that the city’s efforts are protecting the aquifers beneath it and ultimately its drinking water and public health.
Heinen said the experience has reinforced the importance of protection efforts and the sealing of wells. “There can be a 100-foot pipe going right down into the aquifer. The possibility of contamination is high. It’s not just about one well. It’s about the entire area.”
On working with Little Falls, Nash said, “They went from nearly being out of compliance to being enthusiastically on board. It was a lot of fun to watch.”Note: The MDH Well Management Section also has grants available for sealing public wells. For current information, go to Well Management Well Sealing.