Fun fact: a city’s sewage system isn’t like a crockpot — you can’t set it and forget it.

Which is why city leaders unanimously approved an $8 million project to replace the existing 18-inch sewer crossing at Kimball and Oak that’s suspended over the Stanislaus River and connects to the wastewater treatment plant.

“We are very excited to get started on this project as it has been in the planning stages for some time. The main goal for the project is to make sure we can safely and efficiently dispose and use the wastewater produced in the City of Oakdale today and far into the future. This project helps us with that goal,” said Bryan Whitemyer, Oakdale City Manager.

City leaders awarded the bid to T&S Construction Co., Inc. for the Sewer River Crossing Project in the amount of $6,791,500 as well as an additional $931,285 for construction engineering and inspections and $340,000 for contingency for a total project cost of $8,062,785 to be funded from the Sewer Capital Replacement Fund.

According to city documents, the existing sewer crossing was constructed in 1977 and is located above ground, supported by a utility bridge across the river. Two six-inch Modesto Irrigation District (MID) conduits, installed in 2003, also are supported on the bridge and cannot be removed. The conduits provide electrical power for the wastewater treatment plant.

In addition, keeping the existing 18-inch pipeline in place allows for contingency options in the event of emergency need.

Cody Bridgewater, Oakdale Public Works Superintendent, pointed out to council members during his presentation, “Other than some safety measures, we don’t have capacity to grow,” which poses a significant problem for a city trying to plan for the future.

Although the price tag may seem steep, that single 18-inch sewer pipe is responsible for transporting all of the wastewater from the city, which, as a critical asset, could spell catastrophe if it were to fail.

“The bottom line is we can’t say that we don’t need this,” Councilmember Christopher Smith said. “We’re stuck, we need this … it’s going to be inconvenient for a short period of time to do something that we’re going to need for the next 30 to 50 years.”

According to project team leads, Bridgewater and Engineer Jennifer Pratt with Blackwater Consulting Engineers, Inc., two key components finally came into play that enabled the City to finally move forward with this project.

“There were two elements to the time line, one being the funding required to perform the project, and two being the time it takes to receive all of the different permits needed when working near a water body. There were many different groups that needed to review and approve the project such as the Army Corp of Engineers, State Lands Commission, and Department of Fish and Wildlife. Now that funding has been secured and all permits received, the project was bid accordingly,” Bridgewater and Pratt said.

The overall contract period for the project is 450 days. The HDD (Horizontal Directional Drilling) portion of the project is expected to take approximately 45 days to 60 days and the city will be notifying residents in the area 14 days prior to the work starting.

The City has coordinated with the Oakdale Seventh Day Adventist Church (1290 Walnut Street – parcel extending to the intersection of North Oak Avenue and Kimball Street) to address project staging at the southern end of the Project for its duration.

• Improving the reliability and redundancy of the sewer system, a three-barrel inverted siphon located below the river is proposed to replace the existing sewer crossing.

• Re-routing of existing collection system truck sewers to an inverted siphon structure.

• An inverted siphon structure located in the upper portion of an empty lot near the river and intersection of Oak Avenue and Kimball Street which will be the transition point to the multi-barrel inverted siphons crossing under the river.

• Valves and fittings on the downstream portion of the alignment to transition from three siphons to one pipe.

• A connection to existing piping upstream of the existing wastewater treatment plant flow meter.

• The existing pipeline results in surcharging of the collection system and is hydraulically limited during peak flow conditions. The project will increase the pipeline size to address this deficiency. The increased pipeline size will not increase system capacity but will allow for the existing treatment plant to realize its existing design capacity through improved delivery.

Once the project is complete, the area will have landscaping and decorative fencing installed.

According to city documents, horizontal direction drilling (HDD) will be used to install the 3-barrel inverted siphon under the river. HDD is a trenchless construction method whereby a pipeline or pipelines are installed along an arcing drill path; beginning and ending at the ground surface and passing under the obstacle (i.e., the river) in between. HDD generally consists of three stages. The first stage involves directionally drilling a small diameter pilot hole along the design directional path. During the second stage, the pilot hole is reamed to a diameter suitable for installing the pipeline(s). The third stage consists of pulling the pipeline back into the enlarged hole (referred to as pull back).

Drilling fluids are continuously pumped to the drilling tool during all phases of the installation process to transport drilled spoils, reduce friction, and stabilize the hole. Drilling fluids consist of a mixture of water, bentonite, and/or polymers. The generated soil cuttings are mixed with the injected drilling fluids to create a slurry that is removed from the bore using a drilling fluid induced pressure gradient. Spent drilling fluids and spoils are then disposed of in an approved manner, such as a landfill.

An open cut portion of piping would be used from the end of the HDD operation to the connection point with existing piping.

Addressing potential concerns about the new underground piping, Bridgewater and Pratt shared, “The HDPE pipeline that is to be installed under the river is designed and manufactured to withstand the corrosion and loading of the soil and water above it and has a life span of 50 years or more, according to the manufacturer. To ensure the pipeline is watertight, each section of pipe to be installed will be inspected visually for any defects and will be air-tested for leaks before and after installation. The pipe sections are welded together to ensure a proper seal at each joint, therefore eliminating leaks.”

According to the city, there should be no disruption of service during construction.

Any questions or concerns regarding the project should be directed to City Hall, at 209-845-3571.