Piers are installed, the pier installation equipment and crews have moved off site, and excavation began on the “15 Mile Sewer Repair Recovery Shaft” began on June 1. The “pre-cut” has been completed, eliminating the eastbound lane of 15 Mile, and leaving only one lane of pavement on the north side of the damaged interceptor site.
While it has been more than five months since the 15 Mile Interceptor Sinkhole was discovered on Christmas Eve morning in December 2016, much has been accomplished in the herculean effort to mitigate and reach the damaged interceptor pipeline so that full repairs can be made, the site restored, and life can return to normal for everyone impacted by this unexpected incident on that fateful December morning.
Full bypass pumping is handling the all-weather flow at this time, emergency bypass pumps that were causing the most difficulty for motorists and businesses have been removed and relocated to less intrusive locations, the 260 piers that help to form the protective barrier around the approximately 40 ft. x 300 ft. excavation for the repair recovery shaft are in place, the drilling rigs and personnel are off to another job, and work continues to bring a final resolution to this huge project that impacts the lives of almost 500,000 Macomb residents.
The initial cut (about 10 ft.) of the shaft is complete, and the first set of “wales” (horizontal steel beams for perimeter shaft support) is being installed in preparation for further excavation.
Each of the piers has approximately 24 cubic yards of concrete in them, bringing the total for the pier project to more than 6,400 cubic yards of concrete, and one-half of them also have a 70 ft. long I-beam installed inside. These serve as the “foundation” for recovery site, and steel “wales” are being installed around the shaft site perimeter that will enable the digging to continue to the required depth while providing a safe work environment for the personnel who will be working in the shaft.
Purchase and installation of virtually indestructible 9.2 ft. diameter Hobas pipe has been approved by the Macomb Interceptor Drainage District (MIDD) Board members to reline the 300 ft. of the excavated area, as well as 3,700 ft. of the 11 ft. diameter pipeline between the damaged section and Control Structure #3 (CS3) to help ensure the long-term repair of the vital interceptor. CS3 is located approximately one-quarter mile west of Garfield Road on the south side of 15 Mile, and that’s the location where eight of the nine bypass pumps work 24/7 to draw the sewage out of the interceptor 60 ft. below ground, and send it through the bypass piping where it is once-again pumped back into the pipeline west of Hayes at the corner of Fontana Street where the flow continues to the pump station and treatment plant.
The repair site has been “pre-cut” to approximately 12 ft. in depth, with the sides sloped to help secure the area and allow personnel and equipment to operate more safely, and with the installation of the “retaining wall” piers, workers have removed about ten additional feet of soil on their way to excavating the entire shaft to a depth of 60 ft. to enable replacement as repair as needed.
With bulkheads (dams/gates) installed, cleaning is underway in the sections of pipe that aren’t collapsed. This will enable even further, more thorough inspection, and the damaged areas can be cleaned and treated with “chemical grouting,” which serves to repair damaged areas in the drain walls, and additional grouting with a mortar-like material that will seal cracks and joints is also being performed.
Installation of the 260 piers that “outline” the recovery shaft area is completed, “wales” are being installed, and work continues to reach the damaged pipes that are 60 ft. below the surface so the repair work can be completed.
Dewatering efforts have been successful in lowering the groundwater table to help take the pressure off the damaged pipeline, and to make it more feasible for crews to perform the needed excavation and repair work. There are 27 – 30 of these wells in operation, and their work will continue until the new piping and associated repairs are complete and back-fill operations are under way.
Engineers are working to help keep the project moving forward while at the same time working through delays that weren’t known at the onset of the recovery efforts. The recovery shaft has been extended an additional 20 ft. from first estimates, adding to the time and work required, and they’re now working with the current contractor and the contractor who will be installing the Hobas pipe with the goal of having the work done concurrently.
Plans are also being made to demobilize smaller diameter bypass piping and equipment that is no longer needed, to help facilitate the final remediation of the entire work area. Everyone associated with the recovery project wants to help residents, businesses and motorists return to their normal routines and lifestyles while at the same time working to provide complete and effective repairs of this very important interceptor.