NEW ULM - The New Ulm Public Utilities faces serious location and cost challenges in its efforts to find new, secure water wells, according to a report made Tuesday to the Public Utilities Commission,
The report, which was presented by Liesch and Associates senior associate and hydrogeologist Jim de Lambert, explained an investigation the firm conducted to determine issues and potential locations for new wells. The PUC sought the study because it currently has 11 of 13 raw water wells in flood plain areas. These wells are often inaccessible during flooding and are only protected for up to a 100-year flood event. Because the 11 wells account for 90 percent of the water source for the city, the PUC is seeking a site outside the flood plain to guarantee city water supply even in extreme events.
de Lambert said the main problem is the best places for well sites are in the flood plain. Another problem is the construction of protective mounds around the wells are often more expensive than the project itself and come with many regulations from numerous state agencies.
The report detailed New Ulm's geological layers: the top largely contains glacial drift material, which is the loose mix of earth pushed along by massive glaciers during the Ice Age. The loose type of material allows more water to move through it. Next, shale and similar type layers provide usable but limited water flow. Below that, dense layers of various material offer almost no area for water flow. Finally, impenetrable bedrock is at the bottom. New Ulm also has a high amount of clay, which causes water to flow slowly.
The water being sought for wells is largely rainfall slowly draining down through several layers until it reaches a body of water. The water flow can be so deep it passes under rivers without interacting with the river water.
The report concluded that a raw water well will likely need to be built outside of city limits to find a suitable site. New Ulm's current wells are largely located between the Minnesota River and Highway 14's path. The closest identified areas would have to be either the glacial drift region well beyond where Broadway/Highway 14 curves towards Sleep Eye or the shale area a good distance south of New Ulm along Highway 15.
The sites have complications in finding a location because all wells cost roughly the same amount to construct, regardless of the water they yield, and the farther wells are built from existing infrastructure, the more it will cost in piping.
The report also detailed two not-yet-vetted options: first, some of the existing wells have enough water in their vicinity to build more wells. The advantage is the wells can be built far enough back to not require mounds. But, the wells would have limits in how much more they produce and would still be subject to flooding above a 100-year flood.
Second, the PUC could build Ranney collector wells near the river but outside the flood plain, similar to Mankato's well. This approach provides sizable water amounts and allows for good location. But, this option would require the water to go through costly treatment processes.
No immediate action will be taken by the PUC. The data presented in the report will be used to determine the best well site options. In the meantime, the PUC will begin collecting data on the estimated cost of the different approaches and well types.
(Josh Moniz can be e-mailed at email@example.com)