AMERICA’S BIGGEST WELL
This article, written by the American Ground Water Trust was originally published in
THE AMERICAN WELL OWNER, 2001, Number 1]
Kansas City, Kansas has the honor of having the largest capacity alluvial well in the world. However, this well isn’t like the standard vertically drilled wells found in backyards and communities that many of us are familiar with. The Kansas City well is a collector well 135 feet below the surface with horizontal drilled laterals extending radially outwards into alluvial sediments (loose sands and gravels) laid down long ago by the Missouri River. This large well is capable of producing up to 40 million gallons of water a day. If you consider that a typical home well produces about 400 gallons a day then the Kansas City well has a capacity equivalent to 100,000 home wells!
What kind of well is this exactly? A horizontal collector well pumps water from an aquifer that is recharged from a nearby surface body of water like a lake or river. Depending on local geology, this type of well can deliver a large amount of water that otherwise would have been very costly to provide. The multiple horizontal wells (laterals) extend outward radially from a large central shaft (like spokes on a bicycle wheel without an outer rim and tire). The central shaft contains piping to bring the water collected in the laterals to the surface for treatment and then distribution to the city.
Kansas City chose this system because it was the most cost-effective alternative for expanding its water supply. Water quality concerns associated with groundwater or surface water in the area would have cost the city more money to treat effectively. Ground water in the Kansas City area has high levels of dissolved minerals such as iron, manganese and "hardness." Vertical wells tapping this source would have required extensive treatment to remove minerals before delivery to the city. Direct pumping from the Missouri River would have required treatment to control turbidity from mud and suspended solids. Also, expensive filtering would have been necessary to protect consumers from potential unhealthy impacts from surface waterborne organisms such as Cryptosporidium parvum and Giardia lamblia.
The horizontal well system located adjacent to the Missouri River provides a dependable water source for the city’s residents by drawing about 90 percent of the water through induced recharge (flow) from the river. The remaining 10 percent is from groundwater in the aquifer itself. Water from the horizontal well system does not have to be treated as rigorously before delivery because the sand and gravel layers between the well and the river naturally filter out suspended solids and organisms in the surface water and the river water is naturally low in dissolved minerals.
The horizontal well system combines the healthy aspects of ground water with the high yields and low-mineral chemistry of surface water to protect human health, reduce treatment costs and maintain high yield. Currently the well is not operating at peak capacity allowing room for future water demands; a desirable quality for Kansas City’s growing population.
[© American Ground Water Trust. This article may be reprinted for non-commercial educational purposes provided it is used in its entirety and that reference is made to its source as an article in THE AMERICAN WELL OWNER, 2001, Number 1]