By Jim Bloch
Safely treating human waste is an expensive proposition.
Port Huron City Council members got a close-up look at how expensive at their regular meeting May 13.
After a lengthy explanation of needed work at the city’s sewer plant by City Manager James Freed, the council approved $4,661,500 in upgrades.
J. F. Cavanaugh Co. Inc., Farmington Hills, won the $1,525,500 contract to replace equipment related to primary clarification at the plant. Cavanaugh was the lowest of three bidders. Midwest Power Systems, Inc., of Milford, submitted the second lowest bid at $1,705,293. Weiss Construction Company, of Novi, was high at $2,018,233. The city budgeted $900,000 for the work.
Weiss was the lower of two bidders to replace the splitter box at the plant and make related improvements. Weiss quoted $3,136,000 for the work. Sorensen Gross Company, LLC, of Flint, was high at $4,215,920.
“This is something that has to be done,” said Freed, as heard on the recording of the meeting posted on YouTube.
“It’s horrible,” said council member Anita Ashford, referring to the corrosion on the splitter box and its piping.
The vote was 6-0 on each contract. Mayor Pauline Repp was absent.
Shared payment
The city sewer plant serves 55,000 customers and treats nine million gallons of wastewater a day, serving city residents and businesses as well as the three surrounding townships. The improvements will be paid for by each governmental entity based on their share of the plant’s output.
The city claims 67.41 percent of the plant’s capacity. Port Huron Township uses 13.35 percent of the plant; Kimball Township, 5.41 percent; Fort Gratiot Township/St. Clair County, 13.83 percent.
For the primary clarification work, the cost breakdown is: Port Huron Township, $203,654; Kimball Township, $82,530; Fort Gratiot Township/St. Clair County, $210,977; and for the city of Port Huron, $1,028,340.
For the splitter box, the cost breakdown is: The city of Port Huron, $2,113,978; Port Huron Township, $418,656; Fort Gratiot Township/St. Clair County, $433,709; and Kimball Township, $169,659.
Primary clarification
Interested in the minutiae of the two upgrades?
“The treatment of wastewater consists of three main processes: primary treatment, secondary treatment and solids handling,” said Freed in his memo to the council about the work. “The facility was built in 1951 and expanded in the mid-70’s to provide secondary treatment capability. The primary treatment process consists of influent from the sewer collection system passing through bar screens at the head of the plant, (which is) pumped to a grit channel and then to the primary clarifier tanks. The bar screens stop debris and solids larger than ½-inch and the raw sewage pumps pump the flow to the grit channels where the wastewater is slowed to allow metals, sand and inorganics to settle out, leaving organic matter in suspension.
“From the grit channel, wastewater flows to the eight primary clarifier tanks. The primary clarifier tanks are rectangular and arranged in four pairs with four sets of independent mechanisms. The primary clarifier tanks allow for suspended solids to further settle, forming primary sludge at the bottom of the tanks. This sludge is scraped out and pumped to thickener tanks. The lighter floating wastes are skimmed off, dewatered and deposited in a dumpster. The equipment and mechanisms that remove the sludge and floatables, including sludge collectors, conveyor cross-collectors, floor tracks, return tracks, supports, shafts, drives, slide gates and bearings have had increased and ongoing maintenance issues and are in need of being replaced.
“In September 2023, City Council adopted a resolution for an agreement with AECOM to evaluate the primary clarifier equipment and complete construction documents for equipment replacement and recommended improvements. The design included replacing the mechanisms in all eight tanks, replacing existing lighting fixtures, repairing spalling concrete, installing emergency backup lights and exit signs, and replacing two existing lighting panels and associated transformers with one new panel and transformer.”
The splitter box
“After the primary and secondary processes, liquid wastewater is disinfected and released back to the river,” said Freed in a second memo. “The remaining solid waste, or sludge, is treated in the solids handling process. This involves thickening the sludge, raising the pH to kill pathogenic bacteria, and storing it to be land applied as biosolids on farm fields.
“The solids handling process includes three thickener tanks, a decant tank (220,000 gallons each), a splitter box, various pumps and pipes to convey primary and secondary sludge, dilution water, and chemicals to and from the various processes and into the solids storage tanks.
“The splitter ‘box’ is a 15-foot-tall double cylinder steel drum with an exterior diameter of 5-feet. It is located at the south side of the thickener building and spans two floors. It was installed in the mid-70’s as part of the expansion project. The drum receives near constant flow of primary and secondary sludge, supernatant from the thickeners, and dilution water. These flows are pumped into the interior 30-inch diameter center column, where they combine, rise up the column and spill over into the space between the interior and exterior drums. It is then pumped from this space proportionately amongst the thickener and decant tanks.
“The thickener building is a corrosive environment and the metal of the splitter box and connected piping is notably deteriorated. The condition of the interior of the drum is unknown. There are various appurtenances within the building and connected galleries (underground tunnels) that have deteriorated as well, including, piping, brackets, pipe supports and hangers, the scum tank, check valves, concrete, wall paint, labels, and electrical equipment and boxes.
“In September 2022, City Council adopted a resolution for an agreement with Fishbeck, Inc. to evaluate the splitter box and complete construction documents for equipment replacement and recommended improvements. The components of the splitter box, including the drums, incoming and outgoing pipe work, and associated mechanical and electrical equipment (pumps, valves, and controls) have all been evaluated and identified for either removal, remove and replace, or repair. The splitter box is identified to be removed and replaced as its age and condition doesn’t warrant repairing it. It is a critical component of the solids handling process and must remain in operation for wastewater processing. To accommodate this, there will be bypass pumping during a majority of the project. Another complication is the space constraints and congestion of the work areas. Due to these conditions, the project scope included repairs and improvements that will be more accessible during this project, such as wall and floor repair and coating, electrical improvements, and pipe restraint replacement and painting in the connecting galleries.”
Jim Bloch is a freelance writer based in St. Clair, Michigan. Contact him at bloch.jim@gmail.com.
