Conductor Barrel Installation Makes Boston’s Logan Airport HDD Project a Success

摘要

The success or failure of a horizontal directional drilling HDD operation is usually determined priorto one stick of drill stem entering the ground. If the soil conditions at the designed entry point are problematic thesuccess of the entire project could be at stake if proper precautions are not implemented. The use of a HDD assistcasing (a.k.a. Conductor Barrel) has taken problematic soil conditions and made them drillable.Boston’s Logan Airport required additional electric capacity as part of their 2010/2011 terminal upgrade. SoutheastDirectional Drilling, Casa Grande, Arizona was hired on by NSATR, Massachusetts-based, investor-owned electricand gas utility, to do the HDD crossing beneath the Chelsea River. The project involved installing three conduitbundles across the Chelsea River. Each bundle consisted of seven 8-inch diameter HDPE conduits. The threeparallel river crossings were spaced 20 feet apart with lengths of 1,600 feet each.Southeast Directional Drilling (SEDD) was given a 3-month schedule to complete their portion of the project. Itwas determined that contaminated soil conditions were present along the bore path. SEDD decided to install a 48-inch diameter steel conductor barrel at each proposed HDD entry point to help isolate the contaminated soils. Thesteel casings were driven a length of 120 feet at the entry angle to the bore using a 24-inch diameter pneumatichammer. The 24-inch pneumatic hammer can generate impact forces in excess of 4 million pounds. The HDDportion of the project was completed within the 3-month schedule.Difficult and challenging HDD projects, in diverse and challenging soils and locations are becoming more and moreprevalent throughout North America. The pneumatic pipe ramming hammers are proving their value on thesechallenging projects be it with HDD assist, HDD extraction or conductor barrel installations.