Sewage Flows In to 15 Mile Repair Trench No Injuries;
Cause Under Investigation
During the overnight hours of Monday-Tuesday, Aug. 21-22, the trench being used to repair the 15 Mile Sewer Collapse filled with sewage. Initially, about 9 feet of sewage filled the bottom of the trench and the level later went down to about 6 feet. The sewage is in the process of being pumped out and returned to the sanitary sewer system further downstream.
No one was in the trench at the time of the incident and there were no injuries.
An investigation is underway to determine the cause of the incident. The sewage flowed into the trench from the downstream side of the sewage line. All of the sewage was contained in the repair trench. No sewage entered into the Clinton River or other local waters. The Macomb County Office of Public Works collected and tested 100 samples of water from the dewatering wells and other collection points around the trench and found no E.coli or other contaminants outside the trench.
“Obviously, this is a setback,” said Macomb County Public Works Commissioner Candice Miller. “We are relieved first and foremost that no one was hurt and, equally, that there was no impact to the Clinton River. In fact, the recovery trench was actually designed in such a way that, if there was an incident like this, the trench would contain any sewage, which is exactly what happened here.”
“Our engineers have only just now been able to physically get down into the trench and access the situation. Once we have their full report, we will be able to determine how this incident will impact our schedule. It is our hope and our belief that, while serious, this setback will not prevent us from completing this project to the point where 15 Mile Road will still be re-opened sometime in December of this year,” Miller said.
“The engineers working on this project, along with the construction teams, have done and are continuing to do an amazing job on this project. Even with this new challenge, our team out on the job site has my complete confidence,” Miller said.
Three vehicles being used at the bottom of the 300-foot by 28-foot by 65-foot deep trench were completely submerged. One was a small tractor and another was an excavator. The third vehicle, dubbed the “bat-mobile,” is a specialized piece of equipment that was being used to insert the new pipe into the existing sewer line at the work site. It is uncertain when that vehicle will be able to be returned to working condition. An alternate plan is being developed to continue that work. About 3,000 feet of the total 4,000 feet of pipe that was being put in place at the repair has already been installed. A new timeline estimate for completion of the new pipe installation will be developed over the next several days.
Miller said the project has been running slightly under budget to date.
“We’re hopeful that the fact that we were running under budget so far will still allow us to complete this project within our anticipated budget of $75 million. We will know more by the end of the week,” she said.
It is estimated that some 1.5 million gallons of sewage filled the trench during the incident. The pump out of the trench is expected to completed by mid-day on Aug. 23. A cement slab exists at the bottom of the trench and the sides of the trench are completely ringed by cement pillars, which prevented any sewage from seeping out.
Initially, during the back-up in the downstream line, as much as 9 feet of sewage filled the trench. The sewage water later found its own level and settled at about 6 feet deep. The pump-out of the sewage was expected to be completed by mid-day today, Aug. 23.
All of the sewage being pumped out of the trench is being returned to a sewer line further downstream for eventual treatment at the treatment facility in Detroit.