The cost to make sure that when 40,000 of Manteca’s 86,000 residents flush their toilets that it will reach the city’s wastewater treatment plant instead of backing up and overflowing will cost at least $3.6 million more than the $12.3 million originally anticipated.

But if issues that have been uncovered since work started such as an extremely high water table and avoiding critical optic communication lines that engineers were unaware of when the project was put out to bid are more problematic than now anticipated it could require an additional $2.6 million on top of the $3.6 million to complete the work.

The additional $2.6 million set aside that staff is requesting is to make sure that the project can be completed as quickly as possible given the clear public health risk without the need to return to the council for additional funding which would delay completion.

That is why he total additional amount the council s being asked to approve Tuesday when they meet at 7 p.m. is $6.2 million. That will bring the overall project to $17.7 million.

The North Manteca Sewer Trunk Line project became the city’s top public works priority following problems detected after the collapse of the Union Road sewer trunk line that triggered the need for emergency repairs in early 2017.

The current trunk line project from Airport Way at a point north of Yosemite Avenue to Swanson Road’s terminus and then down Swanson Road to connect with the treatment plant was determined to be subject to failure at any time. The trunk line is a half century old. The deterioration is blamed on sewer gases eating into the piping material.

The section is even more critical than the Union Road trunk line because sewage collected along that line and other trunk lines in much of the northern half of Manteca ultimately flows through it before reaching the treatment plant. Just as work started in May, a part of short segment of the pipe did collapse west of Airport Way requiring emergency repairs.

 The project changes that have been identified to date are in various stages of design and price negotiation and require funds in the next few months in order to finish the project and pay the contractor are as follows:

*Install a temporary fire hydrant for emergency service use on Swanson Road.

*Pothole and reroute a 16-inch sanitary sewer force main and replace a crumbling manhole.

* 24-hour monitoring of the sewer by-pass from Airport Way to waste water treatment plant (4 additional months).

* Reroute a 24-inch recycled water line that is in conflict with the micro-tunneling bore pit.

*Upgrade Swanson Road from residential to industrial pavement per new General Plan.

* Shift the micro-tunneling receiving pit on Airport Way to avoid a PG&E gas line.

*Shift the micro-tunneling receiving pit on Yosemite Avenue to avoid a large concrete block.

*Realign the 54-inch sewer line on Swanson Road to avoid communication utility conflicts.

*Modify a sanitary sewer force main manifold on Airport Way

*Construct temporary emergency vehicle access at Swanson Road and Yosemite Avenue intersection per request of Fire and Police.

*Demolish an existing 36-inch sewer line that is located in the new 54-inch alignment.

*Upgrade sewer distribution system on Swanson Road for commercial and residential use.

* Install additional temporary fences and demo additional existing fences along Swanson Road.

* Add more pumps to the bypass system at Airport Way for wet-weather conditions.

*Protect in place an existing AT&T vault discovered during potholing and surveying

Contingency for a large, underground pipeline project in the right-of-way and through easements typically ranges from 20 to 40 percent due to the risks and unknowns associated with replacing underground pipelines such as conflicting utilities, weather, traffic, coordination with other agencies, and operational issues.

 The initial $12.3 million contract awarded to Mozingo Construction in March 2020 was paid from sewer users’ fees paid by city residents and businesses as well as growth fees assessed on growth to pay for additional capacity. Given the city has already levied all of the charges they could for future growth based on the number of additional connections growth will generate, the rest of the funds will come from the sewer maintenance and operation account.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com