Big Walnut Augmentation/Rickenbacker Interceptor comprises 5.31 km of 4.45 m-diameter sewer tunnel in soft ground plus open cut reaches, manholes, and flow diversion structures. Lead designer is URS Greiner Woodward Clyde. Currently under design. Expect mid to late 2000 bid. Maintain contact at www.urscorp.com December 1999.  Big Walnut Augmentation/Rickenbacker Interceptor under design by URS Greiner Woodward Clyde as 5.54 km of 4.45 m-diameter soft ground drive with open cut reaches, manholes and flow diversion structures. Expect bid mid to late 2000. Maintain contact at www.urscorp.com January 2000.The bidders for the Big Walnut/Rickenbacker Interceptor in Columbus, Ohio are a JV of Traylor Bros., Jay Dee Contractors and Michels Pipeline Construction (lowest bid with $90.8 million), Affholder ($107.77 million) and a JV between Kenny Construction, J.F. Shea and Kassouf/Mole/Murray Hill ($107.85 million). The Big Walnut/Rickenbacker project is a 5.3 km 4.3 m ID sewer tunnel, a 1,250 m 4.3 m diameter pipe placed via open-cut methods, as well as seven shafts. Bolted and gasketed precast concrete segments will support the tunnel, which requires the use of full EPB or slurry TBM in glacial till and outwash with high groundwater table. The tunnel is the first of two projects designed to reduce stormwater overflow into the Scioto River and Big Walnut Creek, as well as transport flow to the wastewater treatment plant. The second project, the Outfall Augmentation Sewer, is expected to be tendered in 2004. URS Corp. is the lead designer for the City of Columbus with Lachel & Associates providing tunnel specialist services. 44/03.Lovat has delivered on 30th September a new EPB TBM model RME193SE Series 21200 for the Big Walnut Augmentation/Rickenbacher Interceptor (BWARI) tunnel project located on the south side of Columbus, Ohio. The contractor is a JV of Jay Dee, Michels and Traylor. The project is part of a series of improvement projects that will increase flow capacity for sewers conveying sewage from a large part of Columbus to the city's southerly wastewater treatment plant. Part one consists of approximately 7 km of 4.6 m-diameter tunnel. The machine is to bore through a geological profile comprised of two primary types of soil deposits characterised as glacial till and glacio fluvial outwash materials. Additional soil deposits of uniform fine sands and man-made fill may also be encountered.The TBM will be erecting a primary tunnel lining consisting of a bolted and gasketed, precast concrete segments, configured as five pieces plus one key piece. Visit www.lovat.com 42/04.The McNally/Kiewit JV took delivery of their new Lovat TBM RME167SE series 21500, to be used for the Big Walnut Outfall Augmentation Sewer, Part II for the City of Columbus. This is the second Lovat TBM being used for the project. This is an EPB machine, equipped with a Variable Frequency Drive (VFD) for the cutting head. The cutting head drive operates from 2.2 rpm to 4 rpm, with constant horsepower. The major benefit of a VFD cutting head drive is that it is approximately 20% more efficient than that of a traditional hydraulic drive. A two-component grout system (grout and accelerant), injected through each segment's lifting hole, will be used. This allows very fast grout setting times for ring support. The grout system is interlocked with the machine's advance, thereby preventing the TBM from advancing unless the grout is being injected at the correct volume/pressure.The TBM is expected to drive through glacial till composed of clay, silt, sand, cobbles, gravel, boulders as well as glacio-fluvial / outwash and uniform fine sands. Water pressure is expected at 1.5 bar to a maximum of 2 bar. Visit www.lovat.com 30/05.