GeoStabilization International
The Bellwood Quarry site.
A stunning backdrop surrounds crews in Georgia, as they work to convert a 100-year-old quarry into a water storage facility. The $280 million project calls for the construction of a 5-mi. (8 km), 10-ft. (3 m) diameter tunnel system linking the Chattahoochee River to Atlanta's Bellwood Quarry — a move that will increase the city's water supply reserves to more than 30 days and ensure its water sustainability for the next 100 years.
“Right now, the city of Atlanta has only a three-day supply of raw water on hand,” said Jo Ann Macrina, Department of Watershed Management commissioner. “Catastrophes like what happened with the Elk River in 2014 have a real impact on the people who depend on clean, safe drinking water every day. Should a similar event happen to the Chattahoochee River and impact the city of Atlanta, modest estimates suggest it would cost the local business community $100 million each day. With the world's busiest passenger airport, numerous Fortune 500 companies and 1.2 million users each and every day, we're not willing to take the risk.”
The city of Atlanta's raw water system infrastructure forms the foundation and starting point for delivering clean drinking water, along with fire protection service for more than 1 million users of the system. More than a century ago, when Atlanta faced major public health issues with water quality and water availability, the investment in raw water conveyance and storage was the first step in securing a sound future for the area. Since then, the investment has been key to the success of Atlanta's economy and the health of its citizens. Now, there's a critical need for reliable delivery of clean and safe drinking water to the city and neighboring jurisdictions.
Located just a few miles west of downtown Atlanta, Bellwood Quarry is a granite quarry surrounded by acres of wooded land. In early April, 2016, the Department of Watershed Management began blasting operations at the site, in preparation for the Water Supply Program.
“One of the main transmission pipes that brings water into the city of Atlanta was installed in the 1890s,” Macrina said. “We're racing the clock to replace pipes that have been in use long after their lifespans. Certainly, we've outlasted the expectancy here. Because we'll be primarily working with granite, a tunnel makes great sense. We'll reinforce it with a concrete lining.”
As part of a $1.2 billion capital improvement program, the project is being funded through water and sewer rates, as well as a one-cent municipal options sales tax reauthorized by voters in March. The project will increase storage capacity from roughly 525 million gallons of water to 2.4 billion gallons. Once the work is complete, Atlanta will lead the country in municipal water reserves. Washington, D.C., for example, only has a 36-hour backup supply of water.
Phase I construction is scheduled for completion in December 2017 and includes a new pump station, the conversion of the water storage facility, and a 10-ft. diameter underground tunnel from the water storage facility to the Hemphill Water Treatment Plant.
Macrina described the Water Supply Program as representing a triple bottom line for Atlanta through employment opportunities, environmental protection and economic development.
“Mayor Kasim Reed recognized the need for reliable delivery of drinking water and redundant water storage in the event of a crisis. Through Mayor Reed's vision, this program will address Atlanta's goal of achieving a sustainable water infrastructure for future generations and flexibility in system operations,” said Macrina.
“There's a saying that 'where water goes, the economy grows.' Aside from being able to offer stable infrastructure to a thriving business economy, national averages show that for every job created in the water sector, an additional 3.68 jobs are added to the national economy. Additionally, for every $1 spent on infrastructure improvements, the United States generates $6 in returns.
“When complete, the tunnel boring machine will be impossible to assemble in one place and then transport. It will be shipped from Ohio to Atlanta on 70 tractor trailers, and assembled at the bottom of the quarry by the tunnel boring machine experts. It will take a lot of time and a lot of space. We expect for it to arrive in the end of June and will be ready to begin its journey in September.”
Recently, workers have been spotted climbing the side of Bellwood Quarry chipping away at rock. The crew from GeoStabilization International, based in Grand Junction, Colo., works under superintendent Byron Brown.
“Boulders crashing down 100-foot cliffs are really cool,” said Macrina, who explained that work at the quarry involved almost two dozen rock remediation technicians (RRTs).
“Their goal for this project was to remove loose rock that could damage equipment or injure workers on the tunneling project. They used scale bars and airbags with compressors to remove any rocks that could fall as a result of the vibrations or weather. They worked 10 hours a day, six days a week. More work may take place as we get closer to the tunneling.”
GeoStabilization International, a geohazard mitigation firm operating in the United States and Canada, specializes in emergency landslide repairs, rockfall mitigation and grouting using design/build and design/build/warranty contracting. On the quarry project, it serves as sub-contractor for Atkinson Construction, which is performing the tunneling and shafts.
Trevor Ames, engineer, mining geotechnical services director, said, “GeoStabilization International was one of the first contractors on site, and is tasked with improving the quarry's geologic stability to allow work crews' safe access to the lower part of the quarry via the long perimeter passageway.
“To be most effective at rockfall protection requires years of extensive training to ensure the safest and most reliable outcome for the project. To execute a project of this size takes over 20 men working in relatively close proximity to each other.”
GeoStabilization's limited access RRTs focused on areas with potential rockfall hazards along the narrow ramp access to remove unstable rock structures using scale bars, air bags and other methods deemed appropriate. The ramp plays an important role in the project, as it provides the only access to the quarry lower elevations where inlet tunnels will be constructed from.
Scaling is completed by testing the face with a miner's bar for areas that have potentially loose material. By tapping the rock face with the bar and listening, RRTs can differentiate loose material or detached rock, which has a drummy, hollow sound, versus intact rock which pings when hit.
“Once the face is tested with a bar for rocks that aren't attached, the areas are pried out and removed,” said Ames. “Larger rock blocks can be dislodged with airbags, incorporating bolder busters or other methods. This process moves identified potential rockfall hazards. Of course, some areas can be visually identified as being dilated and/or detached, which are also removed.”
Richard Aguirre, GSI's rockfall operations manager, said using scale bars and airbags with compressors is key.
“It's important because, if any rocks come loose throughout the day and people and equipment are in the path of the fall, equipment damage, bodily injury or death can occur. Our job is to ensure that this doesn't happen.”
Ames said, “Quarry highwall instability, sometimes referred to as ground failures, historically is a consistent contributor of quarry injuries and fatalities within surface mines when they are active. The first line of defense to manage potential rockfall dangers is to create effective methods to reduce hazards presented by ground failures, including rockfalls. When we look at contributing factors toward hazards related to ground instabilities, we find most hazards can be managed with effective engineering controls.”
Changing geologic conditions contribute to rock instabilities, as do geologic structure and highwall geometry. Vibrations from blasting activity can adversely affect ground stability over time. Compounding ground stability issues are precipitation, groundwater and weathering and erosion that can accelerate ground instabilities along quarry highwalls.
“Slope stability issues become more prevalent as mines get deeper. Engineering controls are an effective means to guard against rockfalls, unstable ground, and challenging geologic conditions. Once geological issues or geohazards are identified, developing controls can be evaluated and implemented. Ground reinforcement methods, adequate containment areas, scaling methods and advances in rockfall barriers/attenuators are effective engineered solutions to reduce the risk of hazards to workers and equipment within mines,” Ames said.
According to Colby Barrett, GeoStabilization president, “Every individual on the site has completed the Occupational Safety and Health Administration 10 or 30-hour course. Every individual using rope access is certified in two-rope access methods by the Society of Professional Rope Access Technicians and in single-rope access methods by the Professional Climbing Instructors' Association. Additionally, at least one member of each crew is further certified in partner rescue rope access by those same organizations.”
The city has full-time safety experts on site monitoring all the work taking place, including scaling, blasting and drilling to make sure teams are adhering to the highest safety standards. The blasting operations are required prior to construction to create 400-ft. (121.9 m) shafts. Blasting is scheduled to take place six days a week and will continue for approximately four months.
Once the blasting phase is finally complete, construction of the tunnel will begin linking the Chattahoochee River and the Hemphill and Chattahoochee water treatment plants. The new 5-mi. conveyance will connect to the quarry site that's being transformed into the new water storage facility.
PC/Russell is serving as construction manager at-risk, and has been working with the Department of Watershed Management to develop and design construction plans for the Water Supply Program. Department of Watershed Management construction manager Dennis Phillips said planning for the massive project began in 2014. The CMAR contract was awarded in 2015, and the site became active in January 2016.
“Right now, we are blasting four 400-foot shafts that will connect to the future pump station,” said Phillips, who explained each blast takes out 4 to 12 ft. (1.2 to 3.6 m), with an average of 40 blasts to make each shaft. “With controlled blasting, each shaft site is secured. Blast mats help control debris and sound during the dynamite explosions, minimizing the impact both in terms of sound and vibrations. At this point, we have had no complaints from any residents in the area.”
Phillips said, “We've begun preparation work at the Hemphill site. We'll be using blind bores to drill the shafts for the pumping station at that location. We will start drilling in May.
“We'll drain the quarry and prepare the quarry floor to receive the tunnel boring machine. The floor will need to be leveled so the construction of the 400-foot machine can be constructed easily.”
All the rock from the 5-mi. tunnel will be removed from the site during the 24/7 operation. In addition to the tunnel boring machine, cranes with clam shells, drill rigs for drilling and blasting and standard loaders will be required to complete the project, along with bulldozers and blind bores. Key materials used during construction will include concrete for the tunnel lining, rebar, stone aggregates, CMU units and fiberglass, steel and ductile-lined piping.
The entire job will take three to four acres of actual work area. Phillips said preparing the quarry floor to receive the tunnel boring machine is one of the biggest overall concerns.
As for the impact of changing weather, said Phillips, “It's always a factor. The good part about this one is that you're working in rock, and rain doesn't hurt rock.”
According to Atlanta Rail Corridor Archive, for most of its existence, Bellwood Quarry has been a source of granite for paving roads and sidewalks, and for use in some buildings. Fulton County also used the quarry as a camp for prison labor at one time. After the prison labor system in the South was removed, the quarry began to operate under the hands of private corporations. In recent years, it has served as a popular filming location for various television and movie projects.
Macrina said there's been a significant amount of interest in the project, with the community being kept up-to-date on developments.
“We launched a public engagement campaign to help us name the tunnel boring machine. Ultimately, the personality we develop for it will be the vehicle to carry our message about the importance of clean, safe drinking water.”
The quarry will eventually be the site of Atlanta's largest park, when the timing is right.
“Because we are only using our excess draw from the Chattahoochee River to fill the quarry, it will be a slow process,” said Macrina. “While the tunnel will be done at the end of 2017, the quarry won't be full until the end of 2018. The city of Atlanta Department of Parks and Recreation is currently working with the Atlanta BeltLine Inc. for the planning process on the park.”
The property surrounding the reservoir totals approximately 300 acres. Some will go to Watershed Management's operations, and the remaining land will be transformed into a park connected to the BeltLine. It will reportedly feature hiking and biking trails, baseball fields, open meadows and an amphitheater.
The park is expected to be built in phases over the next 15 years and will cost nearly $38 million to develop.
Ames said, “Mines or quarries are usually scrutinized when they're active as being disruptive to its neighbors with truck traffic, blasting operations or even dust in these now developed urban areas. This is a great example of how this critical resource for urban development will become a part of Atlanta's water shortage and, ultimately, the Bellwood Quarry will tie into the planned Westside Reservoir Park, allowing all visitors to enjoy the natural beauty of the area and benefit from its historical background.”
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