The third geological formation is the Quaternary, which is divided into two series, the Pleistocene and Recent. This glacial drift is made up of a mixture of silt, clay, sand, gravel, and boulders.
In Lyon County the depth varies from 10 to 550-plus feet. This was formed from glacial intrusions from the north and it forms the substrata systems and topography.
It is marked by the creation of the Buffalo Ridge. Marshall is located at the end of this ridge so streams flowed from the glacier and were deposited in stream beds or aquifers. But these aquifers are difficult to find because they meander and are narrow and therefore costly to find.
During the Pleistocene period, or ice age, which lasted until about 10,000 years ago, Lyon County experienced four major glacial advances. Each advance resulted in large accumulations of glacial drift which forms the surface geology and current topography of the Marshall area. These glacial deposits are composed of large thicknesses of clayey glacial till and more limited areas of glacial outwash.
The outwash deposits are composed of sand and gravel that was deposited by melt water flowing away from the melting glaciers. The outwash deposits can occur at the surface or at any depth within the glacial deposits. These deposits are targeted today for Marshall's municipal wells because they can yield a larger volume of water and tend to have lower concentrations of undesirable compounds such as chloride and sodium compared to the Cretaceous Aquifer. However, water from the glacial drift is harder than water from the deeper sandstone.
The fourth water bearing formation is the Recent. Recent geologic formations tend to be confined to stream valleys and are the result of stream bed erosion and deposition. The non-potable well used to fill bulk tanks behind MMU is a well tapped into this aquifer. These wells are not desired for municipal use because they dry up during periods of drought and need to be treated as surface water under current regulation. It should be noted also, that all aquifers in Minnesota belong to the state - not to towns or cities, so thus are regulated by the state.
Two wells were drilled on the current MMU office site between 1894 at a cost of $24,350 with a daily volume of 324,000 gallons per day. Then in 1920 two more wells were dug. The depth of these wells were 150 feet, 460 feet and two at 600 feet. Some of these were flowing artesian wells when first drilled. Because the wells weren't desirable in terms of providing enough water, the system was cross connected to a well at Marshall Mills (now Turkey Valley), a well at the Chicago NW Railroad, and two wells at the "school house" site (4th Street and Lyon).
In addition, as an emergency back-up, there was a steam pump and suction pipe into the Redwood River for fire protection.
On Jan. 15, 1920, the emergency back-up was used to fight a fire in the business district and a "boil your water" was put into effect.
To disinfect the system, calcium hypochlorite was added to the ground reservoir and pumped into the system Jan. 18-20, 1920, and then the entire system was then flushed. After the fire, the State Board of Health (predecessor to MN Department of Health) did not approve the cross connections or emergency river source and encouraged MMU to find a more plentiful source. A second issue with water from these wells was its hardness and corrosiveness.
Although the water was softer than MMU currently pumped, it created problems with MMU's steam turbines and boilers (MMU was generating its own power and providing steam heat to customers at this time).
In the 1920s, MMU incorporated zeolite softening and marketed Marshall as the "Soft Water City."
In 1928, Marshall relied on three shallow, hand-dug wells (approximately 15 feet deep) next to the river and one drilled well for water. One of the dug wells was connected to 3,000 feet of 12'-foot perforated clay tile. This collector pipe was buried 10 to 12 feet deep along the river and ended near the current swimming pool parking lot in Legion Field. Although the dug wells were approved by the State Board of Health, the collector pipe was not. The sanitary aspect was considered unsatisfactory due to several pit-style privies (outhouses) located in close proximity to this line. The shallow dug wells next to the river were also susceptible to contamination from flooding and drying up during droughts.
In 1926, one of the dug wells was contaminated with salt. The backwash tile line from the zeolite softening process passed within 35 feet of dug well No. 1 and leached into the well. In 1930, the Board of Health recommended Marshall find a new source of water.
(Continued next week.)