The final public outreach for a dry levee that has the potential to alter the character of rural areas south of Manteca in order to protect existing and future city development from a 200-year flood takes place on Thursday.
The San Joaquin Area Flood Control Agency is staging the meeting at 6:30 p.m. on Thursday, Dec. 16, at the Manteca Transit Center, 220 Moffat Boulevard.
The project consultant will present their findings regarding the final alignment during the meeting. Community input is being sought on the proposed alignment.
Climate modeling by the Department of Water Resources assumes that within 45 years water flow may triple in the San Joaquin River.
If that is the case it underscores the urgency for plans and designs for state-mandated protection against a 200-year flood — a reference to a 1 in 200 chance of an event of such a magnitude in a given year and not the frequency — to protect more than 50,000 existing residents. The 200-year flood protection upgrades are pegged at $180 million.
The modeling means flooding frequency could increase significantly in rural South Manteca in the 5,000-acre River Junction Reclamation District. The area at the confluence of the Stanislaus and San Joaquin rivers has flooded 11 times in the 94 years since 11 miles of levees were built in 1927 during the farm area. A 12th major flood was barely averted two years ago when an alert farmer noticed a boil growing and was able to rally other volunteers to work to stop a breach before state re-enforcement arrived.
An extension sought under Senate Bill 5 that put the mandate in place for the 200-year flood protection allowed for one justified 5-year extension to 2030.
If work is not started on actual levee improvements by then, no new construction will be allowed in the identified 200-year floodplain. That runs the gamut from new commercial, residential, and industrial to improvements that increase square footage such as home additions as well as new outbuildings such as barns.
The SJAFCA project would protect southwest Manteca, Lathrop on the east side of the San Joaquin River and a portion of Stockton, French Camp, and the rural area between Weston Ranch and Lathrop.
River Islands at Lathrop — with 300-foot wide super levees — isn’t expected to have issues if water flows in the San Joaquin River triple by 2065.
What would impacts
of 200-year flood be
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, engineers have indicated it would:
*flood 4,200 existing homes with 3 feet or more of water.
*endanger and force the overall evacuation of 50,000 residents in Lathrop outside of River Islands, Weston Ranch in Stockton, southwest Manteca, and rural areas
*force the evacuation of San Joaquin Hospital — the county’s major trauma center — as well as the county jail.
*force first responders at five 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.
*Lathrop High and Weston Ranch High would have water flowing through their campuses as would six other Manteca Unified elementary schools.
*force the closure of portion of Interstate 5 — the major West Coast freeway running from Mexico to Canada — and the 120 Bypass.
*water would swamp the wastewater treatment plant serving 88,000 existing Manteca residents and more than 13,000 of Lathrop’s nearly 26,000 residents.
*disrupt Union Pacific Railroad train movements as well as damage tracks that Altamont Corridor Express relies on.
*182 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 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.
To contact Dennis Wyatt, email dwyatt@mantecabulletin.com
