A proposed alignment for the controversial dry levee in southwest Manteca that is a critical element to meet the state mandate to provide 200-year flood protection for a swath of the city as well as all of Lathrop and Weston Ranch in Stockton could be selected by the City Council Tuesday for more intense study.

The consulting firm of Drake Haglan & Associates is recommending what is being referred to as “Alternative 2A.”

The consultants contend 2A minimizes farmland impact, stays on property lines as much as possible, accommodates entitled subdivision projects within Manteca’s city limits, makes the best use of existing easements, and has the greatest consensus among stockholders of all of the alternatives. The projected cost of the 2A dry levee alignment alternate is $12.1 million.  Overall the cost of putting in 200-year flood protection throughout southwest Manteca, Lathrop, French Camp, and the Weston Ranch portion of Stockton  is pegged at $200 million plus.

The alternate uses the existing dry levee alignment south of Woodward Avenue until it reaches a point that is midway between the existing McKinley Avenue alignment and Airport Way. It then swings south until it reaches a point to the west of Fig Avenue. It turns east along a path that would be slightly north of Fig Avenue if it was extended due west from Airport Way. Before reaching Airport Way, it jogs further north a bit so that it aligns as much as possible with existing property lines before ending at Oleander Avenue.

A staff report from Community Development Director Frederic Clark stresses, “it is important to note that the council’s potential action on selecting a preferred alignment is not the final selection of an alignment.”

The final selection will occur as part of the environmental review process which will study a no-build alterative and possible variations of the preferred alternative that the council may pick Tuesday when they meet at 7 p.m. at the Civic Center, 1001 W. Center St.

The environmental review process would start in 2017. The environmental work would be done and final engineering begun in 2020. That is the same year right-of-way acquisition would start. The target to secure the land and begin the permitting process is in 2022. Construction under the timetable would start in 2024.

What is at stake?

The dry levee needs to be designed to address a 200-year flood event that has a 1 in 200 chance of happening in any given year and not that it happens only once every 200 years.

Should a 200-year flood occur with multiple levee failures along the Stanislaus and San Joaquin rivers south of the Interstate 5 bridge before the merger with the 120 Bypass, it would create a soggy Armageddon of sorts that would:

uflood 4,200 existing homes with 3 feet or more of water.

uendanger and force the evacuation of 10,698 residents in Lathrop outside of River islands, Weston Ranch in Stockton, and southwest Manteca.

uforce the evacuation of San Joaquin Hospital — the county’s major trauma center — as well as the county jail.

uforce first responders at nine fire stations, the Lathrop Police Department and the county sheriff to abandon their stations and key communication centers in the middle of a major emergency.

uLathrop High and Weston Ranch High would have water flowing through their campuses as would six other Manteca Unified elementary schools.

uforce the closure of portion of Interstate 5 — the major West Coast freeway running from Mexico to Canada — and the 120 Bypass.

uwater would swamp the wastewater treatment plant serving 75,000 existing Manteca residents and more than 13,000 of Lathrop’s nearly 20,000 residents.

udisrupt Union Pacific Railroad train movements as well as damage tracks that Altamont Corridor Express relies on.

u182 commercial and industrial properties from Costco to the Lathrop Target and Tesla Motors to Simplot would be flooded.

And that’s just for starters. Modeling shows a number of other existing homes would likely suffer water damage in fringe areas that could receive upwards of three feet of flood water.

Manteca, Lathrop, and Stockton aren’t the only communities impacted by the Senate Bill 5 mandate. There are 85 cities in 33 Central Valley counties that have to comply.

Critics argue dredging

would reduce need

for dry levee work

Critics have pointed to other flood protection solutions such as dredging between the confluence of the Stanislaus and San Joaquin rivers and Mossdale Crossing. Years ago the river during that stretch was deep enough to move barrages of grain. Silt build-up has now made such river movements impossible. Federal and state bureaucracies have made it clear that is not an option. 

At the same time the 200-year flood protection model is not being allowed to take into account work in nearby areas including the widening of the critical Paradise Cut that serves as a pressure valve relief for high water on the San Joaquin River. River Islands has gained approval to widen the cut and restore the environment but has yet to been given the final permits to begin work.

Critics also noted the state required a model that has as many as nine levee breaks south of Manteca with no other level breaks occurring elsewhere to take pressure off local levees. Such a scenario is considered virtually impossible to happen but those bureaucrats implementing Senate Bill 5 in Sacramento had said flood protection must be based on such a scenario.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com