The Cobb County Water System (CCWS) selected Jordan, Jones & Goulding for the design of the South Cobb tunnel and influent lift station in Cobb County. Valued at some USD143 million, the project's design elements include some 9,150 m of 7.32 m-diameter tunnel, a 378.5 million-litres-per-day wet well/dry pit influent lift station at the South Cobb water reclamation facility and approximately 1,220 m of 1.8 m gravity sewer. It is anticipated that construction will begin in 2007 with construction funding to be provided through the Georgia Environmental Facilities Agency. The tunnel will pass through the same geologic formations (rock) as the south drive of the Chattahoochee tunnel. Visit www.jjg.com 47/05.The Cobb County Water System (CCWS) has given Parsons and its subcontractor Jacobs Associates the contract to supervise work on the USD200 million South Cobb tunnel. Parsons and Jacobs Associates will oversee construction activities, make independent cost estimates to validate those made by the engineering team, advise CCWS on contracting issues, enact a quality control plan, and assist with community outreach. Visit www.parsons.com and www.jacobssf.comThe South Cobb tunnel is a 9,150 m-long, 8.2 m-diameter tunnel with a concrete lining, construction and drop shafts, inlet structures and smaller connector tunnels. The project also includes a lift station to convey wastewater flows from the tunnel to the South Cobb water reclamation facility. When operational in 2013, the tunnel will replace existing wastewater infrastructure and provide conveyance capacity for build-out of the basin. Visit http://water.cobbcountyga.gov or www.cobbwater.org.The tunnel was designed by Jordan Jones & Goulding. A prequalification for construction will be advertised within the next six weeks. Bids will be taken in summer of 2007. The contract is to be awarded in October 2007. Tunnelling may begin around the end of 2008. A hard rock TBM will be used to bore the tunnel. Visit www.jjg.comThe project is located in the Piedmont region of the southeastern United States. In general, the geology of the Piedmont in the greater Atlanta area consists of medium-grade metamorphic rocks that have been intruded by granitic rocks in some places. A key characteristic of the Piedmont region is the thick mantle of residual soil and partially weathered rock that overlies fresh bedrock. This mantle commonly ranges from three to over 30 metres thick. The soil zone typically forms the upper 60 to 80% of this weathered mantle. The transition zone forms the remainder. The soil zone consists of residual soil plus any overlying alluvium, fill, or colluvium that might be present locally. The transition zone consists of highly fractured rock that is structurally degraded by chemical weathering that penetrates deeply into the rock matrix. The bedrock zone lies beneath this mantle and consists of both fractured and solid bedrock. 07/07.Contractors are invited to prequalify, deadline 12th April, 2007 for the South Cobb tunnel project. This project entails the construction of a large diameter, deep rock tunnel and a lift station to convey wastewater flows from the tunnel to the South Cobb water reclamation facility. The construction cost of the project has been estimated at USD200 million. The tunnel will be approximately 8,845 m in length with a 8.2 m excavated diameter and will be located in rock with depths ranging from 45.7 to 122 metres. Most of the tunnel will be excavated using a TBM with smaller drill and blast tunnels to connect five diversion/drop shaft structures to the tunnel. Approximately 75% of the tunnel is expected to be lined with cast-in-place concrete lining. The lift station will be approximately 58 m deep and will contain six vertical non-clog centrifugal pumps in a conventional wet well/dry pit configuration. The project also includes a separate electrical building. Contact Judy B. Jones, Cobb County Water System, Engineering & Records Division, 660 South Cobb Drive, Marietta, Georgia 30060. Tel. +1 770 4196339. E-mail jbjones@cobbcounty.orgThe owner anticipates advertising this project for bid in June 2007 and accepting bids in July 2007. Only contractors who have been prequalified through this process will be allowed to bid on this project. Click us/95. Visit http://purchasing.cobbcountyga.gov/documents/S3017_000.pdf 12/07.Cobb County on 11th March awarded a USD305 million contract to J.F. Shea and Traylor to build the 8.8 km 8.2 m OD South Cobb tunnel that will drain about 40% of Cobb. The tunnel will average 76 m in depth as it runs south through bedrock from near the boundary with Douglas County and then east to a treatment plant on the Chattahoochee River near I-20. Four smaller tunnels totalling 1.6 km and 1.8 to 3 m in diameter, are included. The contract contains about USD10 million in potential options that could be trimmed if necessary. The deep tunnel will cost USD38 million more than last spring's estimate and about USD105 million over projections from October 2006. Construction materials costs have gone up more than one would expect over the past year. Visit www.jfshea.com and www.traylor.comA supplemental agreement to Jordan, Jones & Goulding's original contract, the company that designed the tunnel project, was approved in the amount not to exceed USD7.5 million for providing construction engineering services (responding to RFIs, reviewing submittals, geological mapping, etc). Visit www.jjg.comThe tunnel will allow the county to avoid replacing 26 kilometres of aging sewer lines and two pumping stations. It will be the second tunnel for Cobb, which in 2004 opened a 15.3 km tunnel in East Cobb. Work is expected to begin this summer and be completed in 2014. Click us/95 for more details. 12/08.
