Completion Date: December 2010 NTH Value Added: NTH mobilized to the site within hours to assess the situation and develop options for the emergency repair. NTH worked closely with the Owner, the contractor, utility providers, home owners, and other involved parties to implement a safe and cost effective solution to this potentially dangerous and catastrophic sewer failure.
Middlebelt Road Sinkhole Emergency Bypass Pumping and Repair
In September 2010, a significant sinkhole developed within the driving lanes of Middlebelt Road just south of 13 Mile Road in Farmington Hills, Michigan. The sinkhole was located over a 35-foot deep 36-inch diameter sewer that is part of the Evergreen Farmington Sewage Disposal System, maintained by the Office of the Oakland County Water Resources Commissioner (OCWRC). A CCTV inspection of the sewer line revealed a partial collapse of the pipe at the sinkhole location. The OCWRC, having worked with NTH Consultants, Ltd. (NTH) in previous sewer projects contacted NTH for assistance. Within hours, NTH mobilized to the site, assisted with identifying adjacent utilities, drilled test borings to determine subsurface conditions, and developed a preliminary plan for emergency stabilization of the sinkhole and repair of the sewer. Almost immediately, it became apparent that the sinkhole stabilization and sewer repair would be significantly complicated by the presence of an adjacent 300psi gas transmission main was in danger of rupture and potentially exploding if not stabilized. Further, the ground conditions did not allow for excavation without dewatering to prevent flowing ground and unacceptable movement of the gas main. Also in danger, were a 90 psi gas transmission main immediately above the sinkhole, as well as adjacent water main, and numerous other utilities.
Over the next few days and months, NTH worked hand in hand with the OCWRC personnel (24/7 in the beginning) to provide the engineering services necessary to develop and implement emergency protection measures to the gas main, and repairs to the sewer.
NTH services included:
Assisted with implementation of a 26 cfs bypass pumping program.
Developed a ground stabilization plan (to minimize movement of the high pressure gas main.)
Worked with the OCWRC to develop options for short term repairs.
Developed design drawings and specifications for the sewer repair and related ground support.
Developed a groundwater pumping and dewatering plan.
Performed geotechnical investigation for the purposes of design of repairs.
Designed and installed a geotechnical instrumentation program to monitor ground movements (to protect adjacent utilities and homes.)
Performed environmental testing of groundwater and consulted to protect adjacent residential wells exposed to sewage from the sewer break.
Worked with utility providers (particularly Consumer’s Power) and the OCWRC to determine the best approach for protection of the utilities
Designed a structural support system to protect the 300 psi gas main from movement and potential catastrophic consequences
Developed a grouting and leak sealing plan for the remainder of the sewer in the vicinity of the break, to prevent similar problems along that same reach of sewer
Assisted with review and oversight of a cured-in-place-pipe lining effort and associated pre and post installation CCTV inspections for the remainder of the sewer in the vicinity of the break
Monitored construction repair through the duration of the repair, often 24/7.