More than a decade ago, the city of Atlanta faced a significant water crisis stemming from a severe, extended drought from 2007 through 2009. It left the city on the verge of a potentially crippling crisis: just a three-day reserve of emergency raw water.

Today, the city has a 30- to 90-day supply of emergency water available, depending on what water-use restrictions are imposed. And it no longer fears the looming specter of an estimated $250 million-a-day loss in business activity for every day it’s without water, as one study had predicted.

The difference-maker is an ambitious and innovative $360 million project that transformed a more than 100-year-old granite quarry into a raw-water storage reservoir, filled by the Chattahoochee River via a 5-mile-long tunnel carved out of bedrock hundreds of feet underground.

“It’s the biggest single project we’ve ever undertaken and we think it might be the only project of its kind in America,” says Ade Abon, senior watershed director of the city’s Department of Watershed Management, which manages Atlanta’s water and sewer systems. “It was a very complex feat of engineering with many logistical challenges.

“We’ve had a lot of people from other municipalities and even those from foreign countries visit us because they’re interested in doing this kind of project.”

The project’s main component is the 53-acre quarry, which the city bought in 2006 for $26 million. Located about four miles northwest of downtown Atlanta, the quarry now holds 2.4 billion gallons of raw water the utility can tap into during droughts or other emergencies, such as river water contamination. 

An interesting aside: Scenes from television shows such as The Walking Dead and Stranger Things, as well as several movies, were filmed at the quarry.

Other primary components include the 10-foot-diameter tunnel, about 70% of which is lined with concrete for structural strength; 11 vertical shafts that are hundreds of feet deep; two new pump stations, one located adjacent to the quarry and another at the DWM’s Hemphill Water Treatment Plant; and six adits that connect various parts of the system.

In addition, 280 acres of land next to the quarry were transformed into Westside Park, now the city’s largest greenspace.

PERSISTENT SUPPLY ISSUES

Atlanta is no stranger to water problems, due to geological conditions that make groundwater largely inaccessible. As such, the city relies almost entirely on surface water. About 70% of its drinking water comes from Lake Lanier, a 38,000-acre, constructed lake; the remainder comes from nearby Allatoona Lake and two small city-owned reservoirs.

Lake Lanier was created in the mid-1950s when the U.S. Army Corps of Engineers built the Buford Dam on the Chattahoochee River. The USACE owns and manages the lake, from which the river drains.

Under the terms of a regional water use agreement, the city is allowed to take up to 180 million gallons of water a day from the river.

But while Atlanta’s growth has mushroomed, its water supply has remained constant. As a result, demand for water has increased exponentially over the last several decades, leaving the city vulnerable to water shortages.

The severe drought from 2007 through 2009 dramatically underscored that vulnerability, Abon says.

“Lake Lanier dried up enough that we could see the bottom of parts of the lake,” he says. “If Lake Lanier dries up, we have no water.

“It got to the point where we were praying for rain.”

In addition, the city could be crippled by any kind of pollution spill in the Chattahoochee River, Abon notes. As a case in point, he cites the Elk River in West Virginia. In 2014, a faulty storage tank leaked 10,000 gallons of an industrial coal-processing liquid into the river, disrupting water supply for thousands of downstream residents.

The drought, coupled with the need to replace four aging transmission lines, spurred DWM officials to develop the water supply program. Two of the lines take water from the river to the Hemphill treatment facility, located about 4 miles from the river, and the other two transport water to the city’s second plant, the older Chattahoochee Water Treatment Plant, located near the river.

Some of the pipes date back to the late 1890s and early 1900s and have reached the end of their usable life cycles, Abon says.

A BORING PROJECT

Construction of the tunnel, which connects the river, the quarry and two water treatment facilities, was a formidable project in and of itself. Boring began in March 2016 at a point inside the roughly 350-foot-deep quarry.

From the quarry, the tunnel travels northeast and passes below a 345 million-gallon reservoir at the Hemphill treatment plant. From there it slowly curves in a northwesterly direction and eventually passes under the Chattahoochee treatment plant. It then terminates a short distance from there at a shaft that will connect to a not-yet-built pumping station that, in turn, will connect to an existing intake in the riverbed.

The project also features 11 vertical shafts that range in depth from 250 to 450 feet, with finished diameters ranging from 20 to 35 feet. The shafts, most of them equipped with submersible pumps, allow the utility to control the flow of water and raise it to the required elevations along the tunnel route.

“By the time water flows into the quarry via gravity, it will only rise to a certain level because the quarry filled to its highest point is much higher than the river level,” Abon says. “So there’s not enough head to fill the quarry to its peak level.”

To solve that problem, the tunnel is plugged right before it meets the quarry, which forces the water to rise up one shaft (a riser shaft) and travel via an adit into another shaft (a drop shaft) that connects to the quarry, he says. 

The system also was designed to allow water from the quarry to be sent from the quarry and back through the tunnel to the treatment plants without having to build two separate tunnels, which saved millions of dollars, Abon says.

INTRICATE SYSTEM

Two of the shafts — a 250-foot-deep primary shaft and a 340-foot-deep low-level shaft — are located inside the new quarry pump station. Pumps inside the shafts push water from the quarry back into the tunnel.

The drop shaft and riser shaft, both 320 feet deep and located across the quarry from the pumping station, allow the utility to convey water through the tunnel in both directions based on its needs. They’re connected to each other and to the pump station shafts by adits.

Five 420-foot-deep shafts are located inside a new pumping station by the Hemphill treatment plant; four of them are equipped with pumps that bring water from the tunnel up to the treatment plant.

Another shaft equipped with a pump moves water from the tunnel up to a transmission line, where it flows by gravity to the Chattahoochee plant. The last shaft is by the river and eventually will be connected to the aforementioned yet-to-be-built pumping station, which will replace a nearby aging pumping station.

Furthermore, to recirculate the quarry reservoir water and keep it fresh, operators at the quarry pumping station can pull water from different levels through small adits and push it upward.

“We don’t want that water sitting there forever,” Abon says.

PROVING VALUE

It took several weeks to fill the quarry after the tunnels and shafts were completed in late 2020.

“We filled it very slowly so we could test the controls at the same time,” Abon explains.

Now the only piece of the water supply puzzle left to complete is the new pump station by the river, he says.

Since its completion, the system has not been pressed into emergency use. But it already proved its usefulness in 2020 when a break occurred in one of the old transmission lines and prevented water from getting to the Hemphill plant, potentially leaving around 65% of city residents without water. But water from the quarry reservoir helped avert such a crisis.

“We shut down that line and pumped water from the quarry to the Hemphill plant,” Abon says.

After the new pump station is completed, three of the old transmission lines will be abandoned, and the fourth one, which is more structurally sound, will be lined and remain in use.

“We hope to get a few more decades of use out of it,” Abon says.

A GREAT ACHEIVEMENT 

Looking back, Abon feels immensely relieved as well as proud of how his department helped add both capacity and resilience to the city’s water system, leaving it much better equipped to handle climate change and other threats.

The system is expected to provide the city with a reliable source of drinking water for the next 100 years.

“This was a major, major accomplishment for us,” he says. “I lived through that drought and remember the panic and the frustration everyone felt, from residents and city council members to business owners and the people in our department.

“For the first time in decades, Atlantans aren’t worried about their water supply.”