Aquifer Storage Recovery (ASR)

A Water Supply Strategy for Tampa's Future

Tampa is unique in terms of how it supplies residents with drinking water. While most Florida communities rely extensively on the use of wells to pump water from deep underground reserves called aquifers, the City of Tampa uses surface water as the primary supply. Water from the Hillsborough River Reservoir is treated at the state-certified David L. Tippin Water Treatment Facility (WTF) and distributed to Tampa's customers.

While a traditional well field could be used to meet some of Tampa's future water supply needs, it is not as viable an option as it might have been 20 years ago. Today's regulatory climate and increased knowledge about the potential effects of withdrawals from the aquifer on lakes and wetlands make well fields more difficult and more costly to permit and operate than in the past. In addition, future regulations may require that traditional well fields be rested periodically to avoid long-term stress on the aquifer.

With ever-increasing water demands and seasonal variations in surface supply, it is difficult to provide for all of customers' demands from the river source alone. The City has a variety of innovative projects to improve the availability, quality, and reliability of water supplies. These include:

Tampa Aquifer Storage & Recovery (Tampa ASR)
Water Quality 2000 (WQ2000) - A series of ongoing water treatment improvement and expansion projects at the David L. Tippin WTF to ensure continued exceptional water quality.
Reclaimed Water - A project to provide high quality reclaimed water for lawn watering to reduce drinking water demand.

One significant challenge is that water use and availability vary through the year. During our dry season, demand historically increases as supplies decrease. Aquifer Storage & Recovery (ASR) allows the City to minimize stress on the system by leveling off peaks and valleys in supply and demand.

ASR Overview

What is ASR?

ASR is a proven way to safely store excess water underground when it is available, and to recover that water for use when supplies are short. For example, most of our rain falls in the summer, but customers demand is the highest during the spring, primarily because of lawn watering.

Tampa's ASR program allows the City to treat, store and later recover high quality drinking water for use.

ASR is tested and proven technology. While it is still considered innovative, ASR has already demonstrated its effectiveness at dozens of locations across the United States, including many in Florida. It is also good for the environment. The water pulled out of an ASR well generally is water placed there previously by the ASR system. This is much different from traditional well fields with which many Tampa residents are familiar; traditional well fields do not return water to the aquifer.

ASR is no more expensive than other storage alternatives, such as aboveground tanks or reservoirs. In fact, it is usually much less expensive than most other options because so little land is required and relatively little hardware or construction is necessary. ASR can store vast amounts of water underground at a minimal cost compared to other storage methods. The Tampa ASR program is expected to store up to 1 billion gallons of water underground. If above ground tanks were built to hold that much water three tanks the size of Raymond James Stadium would be needed!

Map of Florida ASRs
Map of ASRs in Florida

How It Works?

tampa water system The Tampa ASR uses a series of wells installed in a suitable recovery area. Ten ASR wells were constructed. The Storage (or recharge) phase of operation stores surplus high quality treated drinking water in the deep underground aquifer when excess surface supply is available. The Tampa ASR system is operated seasonally, storing water during rainy periods.

Testing and Monitoring

Extensive testing at the site has shown no surface water or environmental impacts near the sites. To ensure that the Tampa ASR system does not impact surface waters in the area, a number of monitoring wells and water level gauges are installed and monitored regularly. In the unlikely event that gauge readings indicate water level impacts, a contingency plan will be activated to protect water sources. Some Tampa residents have shallow private wells, but these draw water from a different portion of the aquifer than the deeper zone where the Tampa ASR wells will store and recover water. As a precaution, the monitoring wells near the site will measure underground water levels in shallow zones as well as the deeper storage zones.

Lakes, Wetlands and Other Surface Waters

The Tampa ASR program is designed not to impact lakes and wetlands in Tampa. No impacts are expected for the following reasons:

The water recovered from the aquifer by the Tampa ASR system is the water from the deep aquifer as a result of the system's operation.
The storage zone used by the Tampa ASR system is 300 to 400 feet underground and is separated from the layers near the surface that provide water to lakes and wetlands by "confining layers." These confining layers are usually made of clay. Their presence at the site means that water in one zone is physically separated from water in another zone on the other side of the confining layer, so that what is withdrawn from a deep zone has a negligible effect on water levels in the shallower zone above it.
By letting us store surplus water for later use, ASR allows us to better manage the water supply system to protect lakes, wetlands and estuaries.