An approximately $70-million, 22-mile long interceptor sanitary sewer project in Genesee County, MI, that will be completed in 2009 has dramatically improved the county's sanitary sewer system. Phase I was completed in 2005. The new interceptor begins in Montrose, MI, and ends in Burton, MI. The interceptor begins as a 72-inch-diameter reinforced concrete pipe, then drops down to a 60-inch reinforced concrete pipe and will end as a 48-inch-diameter reinforced concrete pipe.
“There are multiple purposes for the project. Our county had experienced a series of very bad wastewater effluent backups into homes and spills into our rivers, lakes and streams starting in about 1997 through 2004. As a sidebar to that, we had a county-wide 6-inch rain recently and we did not spill any sewage when every other community around us and, as far as I know, any place in the state that had that kind of rain event dumped a lot of wastewater into the rivers, lakes and streams. So, one of the main goals was to protect the environment and protect the public health. The interceptor has already proven itself, as far as I'm concerned, based on the fact that we've experienced well over a 50-year rain event and did not spill any wastewater into the lakes, rivers or streams. There still has been no reported backups into any of the county residential areas,” Genesee County Drain Commissioner Jeff Wright said.
“The second reason for the project is that it allows for future expansion of the economic base in the county. Until this was built, we were not only experiencing sewer backups in extreme weather conditions, but we had also reached the design capacity of the existing sanitary sewer systems in Genesee County. So, this also increased our future ability to accept new wastewater customers by approximately 90,000 units of capacity. One unit is a single family residential home.
“Finally, when this is fully online, the operations and maintenance cost of the system will be considerably reduced. This project will eliminate 22 pumping stations and convert what used to be a pump and gravity system to a gravity flow system. So, we will have 22 pumping stations taken out of service that we will not have to pay electric bills on, or do pump repair, motor repair, electrical repair, and maintenance on. As an example, the average pump station that we will be taking out of service utilizes approximately $150,000 worth of electricity each year. So, our operations and maintenance costs should be reduced considerably.” Wright added that one pumping station was built in order to eliminate the 22 pumping stations. Spence Brothers was the contractor for the new pump station. Goyette, Post Electric, Eagle Excavating, ACIPCO, and Mersino Dewatering were the subcontractors.
“We call it our Fox Street Pumping Station. It has the capability of handling 60 million gallons per day (mgd). It is a state-of-the-art pumping station and it is 50 feet into the ground. This particular pumping station was $12 million. We went to submersible pumps and we installed one of the state-of-the-art debris removal system. It is a bar screen type automatic rag removal system. We used proven materials that we have full confidence in for the entire project,” Wright said.
The Genesee County drain commissioner's office operates a sanitary sewer collection and treatment system for all of the communities outside of the city of Flint, MI. The townships, small cities and villages may own and operate their own internal systems, but they are connected to these county interceptors. The system also services Shiawassee County, Saginaw County, Lapeer County, Livingston County, and a small portion of Oakland County.
Contractors on the project have included L. D'Agostini & Sons, Zito Construction Co. and D'Alessandro Contracting. Pipe suppliers included Premarc Corporation, Northern Concrete Pipe and Copipe. Subcontractors have included John E. Green Mechanical and J. Ranck Electric. Engineering firms for the project included CTE Engineering Inc.; Wilcox; Wade Trim; and Hubbell, Roth & Clark. The Genesee County Drain Commissioner's Office – Division of Water & Waste Services staff on the project included Matthew T. Raysin, project manager; Mark Horgan and Don Camp, project engineers; and Marty Sweet, Mike Wenzel, Brenda Brockett, Ryan Lynn, and Joe Anklam, inspectors.
The depth of the excavation for the project was a challenge. “Anytime you install a 50-foot-deep wastewater collection system, you will have challenges. The average depth of this system is approximately 45 feet deep, with areas as deep as 50 feet in the ground,” Wright said.
“But, it's worked very well. It is slow going, but the fact that it is 50 feet deep was a challenge that's been overcome. The fact that we needed close to 500 easements from individual property owners was a bit of a challenge; that also was overcome. We actually ended up paying fair market value to the property owners for the easements. Out of the approximately 500 easements, we only had to go to condemnation on one property. The cost for those easements was less than 1 percent of the total cost of the project.”
Wright said that the depth challenge was overcome with large machines. “On this project, not only was the majority of it open trench excavation, which required a tiered system type of excavation, but we had a few miles of deep tunneling. One of the unique pieces of equipment that was brought in by D'Agostini was a product made in Germany that is a closed face tunneling machine. This was for the 48-inch, 54-inch and 60-inch diameter pipe. This machine can shoot through rock and any soil conditions. This closed face tunneling machine grinds the material and at the point of insertion into the machine, mixes it with water and pumps it to the surface as slurry. That slurry is filtered, the spoils are taken away and the water is reused. That's been working very well,” Wright said.
“There was a lot of dewatering on this site, as you can imagine, at 50 feet deep.” Wright pointed out that the funding of the project was unique.
“Usually when you build a project like this, you sell revenue bonds, and then the people that pay for the system, the rate payers, have their rates increased to cover the cost of those revenue bonds. In this instance, back in 2002, my office initiated what we call a County Capital Improvement Fee. It was my feeling that the customers who had already paid for their system should not foot the bill for an expansion of the system for future customers. So, the County Capital Improvement Fee charges $1,000 per unit to any new customer of the system. That fee has generated close to $25 million to date. So, that fee has been paying the bond debt that's been incurred without raising the rates for existing customers,” Wright said.
Coordinating and expediting the construction schedule led to significant cost savings on Contract 1. A crossing under Interstate 75 was completed two years ahead of schedule by coordinating advanced construction procedures with a freeway reconstruction project. This process allowed for placement of the sewer with open cut methods during reconstruction of Interstate 75. Contract 1 was divided between two contractors, L D'Agostini & Sons and Zito Construction, in order to accelerate the project. The system was ready to accept sewer flows at least one year earlier than originally anticipated.
Because the interceptor sanitary sewer project will cross Genesee County when it is completed, fiber optics were installed along the route to provide for an effective communications system that will be used to operate and monitor the pump stations, flow meters and rain gages. Additional fiber conduits were also installed for future use by other public service providers.