In the summer of 2012, John Struzziery, principal engineer at Kleinfelder/ SEA, was faced with a challenge: a failing 12-in. VCP sanitary sewer located on Terminal Road in Cambridge, Mass. The section had recently been CCTV-inspected using the Pipeline Assessment Certification Program (PACP) and numerous condition grade 5 defects were found. The pipe segment was literally collapsing as pieces ofpipe were dropping into the invert.
Making the project even more complicatedwas the fact that the full 140-ft run waslocated within a gated power transfer station.The station posed extensive coordination issuesrequiring all work hours and oversightto be coordinated through the utility company.Excavation of this segment posed ahigh risk of power outage and even personalinjury if a utility damage was to occur.
The utility company was very concernedwith excavation, as was the project’sgeneral contractor. Based on all of thefacts, it was determined that a trenchlessinstallation was the best alternative. Preliminaryplanning proved that installationof a thermally fused pipe through a typicalcontinuous installation was not practical,as an insertion pit would not be able to beexcavated inside of the utility easement.Segmental pipe installation would be theprocess of choice; however it would addcomplexity to the planning and executionphases. The Ted Berry Co. Inc. accepted thechallenge to provide a non-conventionalsolution by using pipe bursting technologies.The project team included the principalowners Jim and Matt Timberlake, seniorproject manager Shawn Ready and pipebursting foreman Eric Gemelli.
The decision was made to install a10.75-in. O.D. DR 17 IPS HDPE ThreadLiner in 24-in. laying lengths to facilitatea manhole pipe insertion process. TheHDPE pipe was manufactured by ISCOIndustries and supplied locally by EverettJ. Prescott, who was instrumental in thedesign of the pipe for acceptable tensileloads. The Ted Berry Co. estimated thatit was going to require, at a minimum,a 40-ton pulling machine to ensure thepartially collapsed host pipe could beexpanded open with a pipe burstingexpander head. The project moved forward,but with a challenge that requiredthe pulling forces would be sufficientlylow to prevent the new segmental pipefrom exceeding its allowable tensile loadcapacity. Additionally, there was a parallel36-in. RCP storm drain and expandingthe host pipe beyond its original outsidediameter posed much greater risk.
The Ted Berry project team was able tomake basic modifications to one of its specialized40-ton static pipe bursting systemsto allow it to overcome project challengesincluding being able to provide ample pullforces to the expander head without passingunwanted pull load (pipe drag) to thenew segmental pipe as it was pulled intoplace. These challenges were overcomethrough the use of a “Tensile Control Device”run through the individual segmentsas they were advanced forward, while pullingwith the 40-ton hydraulic unit. This allowedthe operator to advance the pipesegments 24 in. under load, attach the nextsection of pipe and then re-apply the pullingload to the burst head. No pre-cleaningwas performed due to the condition of theVCP pipe and the potential for additionalcollapse caused by high pressure cleaning.
Installation Steps Included:
• 100 percent Flow Isolation fromupstream access point, continuousthroughout actual installations.
• Manhole preparations/invert removals.
• Pre-CCTV inspection.
• String existing host pipe for install of136 ft of 5/8-in. Pulling Chain.
• Set up 40-ton pulling frame inSMH1010, pulling frame shored againstexisting manhole wall surface area wasmaximized to reduce wall pressure asmuch as possible.
• Installed 8-in. by 10-in. reducer, 11.5-in.expander/expander spud and associatedtooling on leading pipe segment,bolted to a half segment of ThreadLiner to be the “starter piece.”
• Pre-Strung new pipe segments aboveground with tensile control chain.
• Strung existing pipe with 40T / 5/8-in.chain.
• Attach 40-ton pulling chain to leadingsegment of Thread Liner Pipe with toolingassembly.
• Pull first segment of new pipe into hostpipe.
• Slide second segment of Thread Liner pipedown tensile control chain, assemble, andactuate resistance plate, advance newpipe segment into host VCP pipe approximately22 in. This process/step was repeatedapproximately 68 times until leadingsegment of pipe/associated toolingreach Hydraulic Pull Frame at SMH1010.
• CCTV inspection of newly installed 136ft of 10.75-in. Thread Liner HDPE pipe.
Once the pipe was installed and thepipe joints were fully “homed,” a PACPpost-rehabilitation CCTV inspection wasperformed, which indicated that the newpipe had no signs of leakage or deflection.The project was completed in December2012 on time and within budget.
Although installation of threaded segmentalpipe for a static pipe burst isnot common and there are significantconsiderations from both a design anda construction standpoint, in the case ofthis project it allowed the end goal to beaccomplished with no excavation and amanaged risk approach.
This article was provided by the InternationalPipe Bursting Association (IPBA),a division of NASSCO.