Parsons - 2010 Construction Management for AWV.pdf - SCATnow

Bored Tunnel Alternative Design-Build ProjectDesign-Build Construction Management Services SR 99internal structures, systems, and approach structures. Many of these risks mirror the key design and construction technicalelements identified by WSDOT in this RFQ. Our risk assessment and risk response plan evaluated hundreds of risks. Thefollowing sections discuss the risks having the greatest impact on cost and schedule (as related to the key technicalelements identified by WSDOT) and describe the roles of the CM required to mitigate them.1Soft Ground Pressurized Face TBM Tunnels Constructed Below GroundwaterBenefits to WSDOT• SR 99 TBM analysis and tendering provides a greater understanding of the“mega-machine” TBM• Nearly 20 years of experience managing, designing, and constructing softground, pressurized face TBM projects, worldwide• Experts in successfully implementing and monitoring new TBM technologiesParsons has completed over250 tunnel projects worldwide,including successfullyproviding CM services for 11major design-build projectssuch as the Dubai Metro andthe Dulles Rail Extension.The Parsons team has spent several months evaluating TBM design and selection for SR 99. With this knowledge, we provideWSDOT with the best resources to evaluate a first-in-the-world “mega-machine” to be procured to construct this project.Critical review of TBM designs, thrust and torque requirements, and work plans including monitoring of all TBM functions(including soil conditioning) will need to be carried out at all times during the excavation cycle to minimize the risk forTBM induced settlements. In addition, proper sizing of all TBM components are necessary to provide a robust design.Our in-depth analysis provides us with an unmatched understanding of available technologies as directly related to theSR 99 Design-Build project, and allows us to provide WSDOT with a technical review that incorporates our knowledge ofthe project, as well as our lessons learned from U.S. and global tunneling projects. Parsons and Halcrow have worldwideexperience in managing and designing successful soft ground sub-aqueous tunnels, including the Dubai Metro Red andGreen Lines, the Channel Tunnel Rail Link, and San Diego’s South Bay Tunnel Outfall (SBTO). Steve Minassian was the TunnelDesign Manager for the Port of Miami Tunnel, tasked with specifying the largest pressurized face TBM to date in NorthAmerica, and has designed, procured, and managed TBM operations as a contractor’s project manager. Greg Colzani hasserved as a Resident Engineer and Construction Manager on several significant soft ground tunneling projects, includingSBTO and Portland’s Willamette River Combined Sewer Overflow (CSO) Program, where he was involved with the design,procurement, and implementation of the first three slurry mix-shield TBMs in North America. Jon Kaneshiro specified theEPBM machine for the SBTO project (7 bar), and is an industry leader through his comprehensive, worldwide investigationof TBM manufacturers and technologies. He has reviewed tunnel machine specifications for several projects over the last15 years. Shimi Tzobery is a specialist in TBM design and monitoring. Shimi served as Parsons’ TBM specialist tasked withdesign reviews and in-factory inspection and testing of the hybrid TBM for the Lake Mead Intake No. 3 project in Nevada,where the TBM can be exposed to up to 12 bar of hydrostatic pressure.Assessing the RisksKey RisksThe soil properties in downtown Seattle are anticipated to be highlyvariable, with layers of plastic clays with high stickiness potential• TBM designand silts and other zones with non-cohesive soils, including gravel,• Unprecedented tunnel diameter/Proper balance of earth pressureboulders, and high water pressures. Mixed face conditions are• Proper maintenance of the TBM, especially the cutterheadforeseen in most parts of the alignment, so the machine must be able• Proper ring build and filling of annular space• Difficult ground conditions/High water pressuresto adapt rapidly to the ground conditions. Therefore, the design must• Properly operated TBMcover all of the potential issues caused by this variable environment.Soft ground tunneling provides its own set of challenges, butcoupling that with high ground water, an unprecedented tunnel diameter and a congested urban environment creates avery special tunnel challenge. Instabilities in mining can lead to lost ground, unacceptable settlements, sinkholes at the33