TBM components arrive in Atlanta for quarry tunnel project
7 July 2016USA—The main beam of a Robbins TBM arrived in Atlanta on June 29 for assembly at the Bellwood Quarry, where a USD 270M project will build a 5-mile- (8km-) long tunnel connecting the Chattahoochee River and flooding the former rock quarry.
The 12.5ft (3.8m) diameter TBM will arrive over the next month in shipments from Ohio and will be assembled at the bottom of the quarry.
A concrete liner will be installed for the 10ft (3m) diameter tunnel, which will create a 30-day raw water storage vessel whereas there is currently only a three-day supply.
The project will include new pump stations to draw water through the tunnel, which would be approximately 10ft (3m) in diameter and 200ft (61m) below ground, connecting to the Hemphill Water Treatment Plant and the quarry.
Work also includes replacing aging water transmission lines that are still in service. Cast iron mains of diameters 30", 36", and 48" were installed in 1893, 1908, and 1924 respectively. "Although these were renewed with a cement liner in the 1950s, they have far exceeded their design life. A fourth line, 72" steel main, was built in 1975 and metallurgical weaknesses restrict its operation to warm weather months," according to the City of Atlanta's Department of Watershed Management.
The council authorized a construction manager at Risk contract with PC Construction/H.J. Russell & Company on June 1, 2015. Atkinson Construction secured the USD 81M contract for the Atlanta Water Supply Program Phase 1 Extension in February. Work includes construction of four shafts; approximately 1,000lft of adit connections joining the shafts; the main 400ft deep tunnel; and another five additional small-diameter well shafts at the Hemphill site.
