Lesson 04

Breaches & Vulnerability

In Lesson 1 we met the clay shield — the Upper Claiborne Confining Unit that protects Memphis's drinking water from what happens on the surface.

But the shield isn't perfect. In places, it's thin, absent, or fractured. Hydrogeologists call those places breaches.

Shelby County

Here's where Memphis pumps its water

Those navy polygons are MLGW wellfields — the places where Memphis Light, Gas & Water pumps the city's drinking water out of the Memphis Sand Aquifer.

More than 160 production wells, spread across eight wellfields, lifting 200+ million gallons per day.

The Recharge Zone

The recharge zone — where rainwater enters

The teal area is the Memphis Sand Aquifer recharge zone. This is where the clay shield is missing or thin by geological design — so rainwater can percolate down and refill the aquifer.

Most of this recharge zone sits in eastern Shelby, Fayette, Tipton, and Haywood counties. That's the land that has to stay clean if we want Memphis's water to stay clean.

Known Breaches

Now watch what appears.

Every red polygon is a known breach — a place where CAESER and USGS researchers have confirmed the clay layer is thin, absent, or fractured.

Notice how many of these breaches sit directly under or next to wellfields.

Suspected Breaches

And the ones we're not sure about.

The yellow polygons are suspected breaches — places where well data or geological interpretation suggests the clay shield is compromised, but confirmation is still pending.

Every one of these is a research priority. Some will be confirmed; some will turn out to be artifacts. The scientists at CAESER map more every year.

Case Study

Why Collierville worries POA

Look at Collierville, in the southeast corner. A large breach sits on top of the recharge zone — and industrial contamination from sites like Carrier/Smalley-Piper has been documented there since the 1980s.

That's the POA thesis in one map: known contamination + known breach + active pumping = a problem that requires vigilance.

The whole picture

The aquifer's protection is not uniform. Some places, the clay is 200 feet thick and contamination can't get through. Other places, it's patchy or broken — and the drinking water is exposed.

That's why POA watches these breaches, tracks every proposed industrial site near them, and fights development that could put contaminants where the clay can't stop them.