Is Memphis Drinking Water in Danger?

Proposed projects in Fayette County are being reviewed by the TN Dept. of Transportation (TDOT) and the TN Dept. of Environment and Conservation (TDEC). Public meetings to learn more and participate in the decision are scheduled at Collierville Town Hall, 500 Poplar View Parkway:
Aug. 2 (Mon.), TDOT meeting, 5 pm
Aug. 3 (Tues.), TDEC meeting, 6 pm

Ground Water Protection: Chickasaw Group, Tennessee Sierra Club Position
By Nancy Brannon, Ph.D.
Environmental Sociologist

It has been brought to the attention of the Executive Committee of the Chickasaw Group of Tennessee Sierra Club that some new developments are being considered that are potential threats to the region’s drinking water source. That source is the multi-layered aquifer system known as the Mississippi Embayment Regional Aquifer System. Of particular interest to Memphis, TN, west Tennessee, northern Mississippi, and eastern Arkansas are the Memphis Sands aquifer, primary source of drinking water, and the surficial aquifer(s) that overlie the Memphis Sand. The surficial aquifer(s) are a source of drinking water in some rural areas, a source of irrigation water, and a potential conduit for surface contaminants to the deeper aquifers.

Reasons for Concern:
Research at the Ground Water Institute at the University of Memphis and the U.S. Geological Survey has identified potential threats to the region’s drinking water source, the Memphis Sands aquifer. These threats could affect both the quality and quantity of the water. They are:
(1) Places where the confining/ protective clay layer over the primary drinking water aquifer is not contiguous; where there are “breaches.” To what extent do breaches in the clay layer exacerbate the potential for contamination? One highly documented case is a breach in the clay layer at Shelby Farms east of Memphis, TN where a former landfill is leaking leachate into the Memphis Sands aquifer. This and other breaches in Memphis/ Shelby County area allow for any toxic substances from the land surface or underground (such as underground storage tanks and landfills) to quickly reach the drinking water aquifer.
(2) As development moves into the recharge area, the potential to adversely affect sustainability of the aquifer and water quality exists. In recharge areas, the Memphis Sands aquifer is near or at the surface and is directly affected by land surface activities. Surface activities that adversely affect the aquifer are paving over or otherwise making impermeable the land surface, which impairs recharge and decreases water quantity; and any activities that have/ use toxic substances or water pollutants pose contamination threats and harm water quality.
(3) The influence of surface water on ground-water quantity and quality. In places where there are breaches and in recharge areas, surface water and ground water are/ can be in direct contact. So any pollutants in surface waters can quickly reach the drinking water aquifer source.

Potential Threats:
Two currently proposed land uses which can impair ground water quantity and quality are: (1) an extension of Walnut Grove Rd. at Shelby Farms, a roadway that will be built directly over the breach in the clay layer. This creates another potential source of contaminants to the Memphis Sands aquifer from roadway runoff that includes but is not limited to oil and petroleum products. (2) A 500+ acre intermodal facility on the former Twin Hill Ranch in Fayette County, TN. The site sits directly on an outcrop of the Memphis Sands aquifer. The paving over and making impervious the land surface will inhibit rainfall recharge to the aquifer and will dramatically alter surface water drainage. The truck and train traffic, plus contents of containers, pose potential contamination sources that would directly reach the Memphis Sands aquifer.

Policies for sustainable use of the ground water must include (1) recharge protection areas and (2) breach protection areas.
Aquifer recharge protection areas would be designated areas (or zoning boundaries) where the Memphis Sands aquifer outcrops or is near the surface, and is uncovered by the protective clay layer. These recharge areas for the Memphis Sands aquifer have been delineated by research at the Ground Water Institute and the U.S. Geological Survey. In these areas there must be careful consideration of all land uses, with a full Environmental Impact Statement that evaluates all the potential threats to both quality and quantity of the ground water. No land uses that could pose a threat to quality or quantity of ground water should be allowed in these areas.
The breach protection areas would be modeled after the existing wellhead protection areas: a designated area within whose boundaries no potential sources of contamination could be located.
The Chickasaw Group of the Tennessee Chapter Sierra Club recognizes that the Mississippi Embayment Aquifer system, the region’s source of drinking water, is our most valuable natural resource asset. This plentiful source of high quality water has served the region for over 100 years. For the water source to be sustainable, and the region remain viable, careful conservation of the resource is absolutely necessary. Conservation means balancing withdrawal with recharge, and refraining from locating any potential harmful land uses in areas that will directly affect the quality and quantity of ground water.

For an overview and illustrations on water quality issues in Memphis area, click TN Water Sentinels.