Should levees holding back the San Joaquin River fail in a 200-year flood event, Manteca would face a citywide health emergency.

That’s because flood waters would inundate the city’s wastewater treatment plant that is located west of Airport Way in the 200-year floodplain.

It is one of 32 city-owned parcels in the 200-year floodplain subject.

It is one reason when the council meets tonight at 6 p.m. they are expected to authorize City Manager Toni Lungren to cast ballots in favor of a 30-year assessment to pay for the  city’s share of $467 million in  upgrades needed to protect against 200 year flooding.

Manteca Unified has 39 parcels in Lathrop, the Weston Ranch area of Stockton, French Camp, and parts of eastern Manteca that are within the 200-year floodplain.

The annual assessment for the city is $16,641. Without the maximum 4 percent annual inflation for assessments built into the authorization vote the city  will spend $381,000 in fees over the next 30 years.

If approved, work will start on the flood protection upgrades in 2026.

In flood lingo, a 200-year event doesn’t mean a flood that will happen every 200 years.

Instead, it reflects the odds of such an event happening in any given year. That means there is a 1 in 200 chance of an event occurring in any given year requiring the levee work now being pursued.

The choice is simple for 22,000 property owners in parts of Manteca, Lathrop, and Stockton that have received ballots in the mail from the San Joaquin Area Flood Control Agency as the City of Manteca has.

They can:

*vote yes and have annual assessments that, depending upon where their home is located in the 200-year floodplains, could run between $10.52 and $83.44 a year based on an 1,800-square-foot home, to make a $472 million flood protection project possible.

*vote no to effectively spike the project and — if they have a federally guaranteed mortgage — face the likelihood they will be required to obtain FEMA flood insurance at an annual cost averaging around $1,700 annually on top of  existing  home insurance premiums.

The assessments will allow SJAFCA to leverage 67.7 percent of the cost of the $472 million project from federal and state sources.

That leaves a local share of $110.3 million.

Given the cost of the overall project that includes raising levees, developing seepage berms, cutoff walls, erosion protection and the extension of the dryland levee to the south of Manteca, the project cannot move forward without federal and state help.

If the assessments are not approved, it will effectively stop all building — new development to even adding on a room or a garage — in the area in the floodplain unless what is built is elevated out of the flood zone which adds significantly to building costs.

Roughly 40 areas in California including Manteca-Lathrop-Stockton fall within peer reviewed science that designated 200-year flood plains. They must have  — or be in the physical process of constructing — protection to guard against such an event by 2030.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com