Recent task order could have opened door to old proposal to raise seawall

Idea to install 32 ‘lift stations’ floated to council members recently too

Official says inspect check valves alone as first step

MANDEVILLE — A recently killed task order could have brought back to the table a proposal to raise the seawall along Lakeshore Drive, if not for a stand taken by some on the City Council at its July 8th meeting.

Task Order 4A/B (a two-part task order) was pulled from consideration once it became apparent it did not have the votes. It was the wording of the task order that drew scrutiny from Councilman at Large Jason Zuckerman and District III Councilwoman Jill McGuire.

The task order, potentially worth $250,000 in and of itself, would have authorized Principal Engineering Inc. to inspect the seawall system along Lakeshore Drive and then offer proposals to address future “tidal protection alternatives” based on its previous analyses and proposals, which include a 2019 $2 million proposal to raise the seawall by a foot.

McGuire raised concerns at the meeting that it could have negated the need for a promised “Flood Summit” where various experts — such as land planners, hydrologists, coastal engineers, general engineers, horticulturists, and others — might gather to discuss and offer comprehensive solutions to address Old Mandeville’s flooding.

On the surface, the task order appeared to be a mundane but necessary maintenance inspection of the seawall, but a careful reading of its language reveals that it could have opened the door to a controversial $2 million plan to raise the Lake Pontchartrain seawall by a foot, a proposal that was presented to the public on Sept. 8, 2019, by Principal Engineering and then-Mayor Donald Villere.

The task order contained two parts, A and B, but it effectively would have done three different things:

1. Part A called for Principal Engineering to conduct the inspection of the seawall;
2. Part A also called for an inspection of the check-valve system designed and implemented by Principal Engineering several years ago, whose effectiveness is now being questioned; and
3. Part B called for Principal Engineering to propose flood and tidal protection options to the city and help choose a path forward based on its “data and knowledge” from previous analyses and proposals, including the 2019 proposal to raise the seawall by a foot.
   

The stated reason at the 2019 public forum at City Hall for raising the seawall a foot would be to reduce wave energy during flooding — not to prevent flooding — and Villere and other officials at the forum specifically said as much, but added that making this change would have a positive effect on which homes lie in the FEMA Flood Insurance Rates Map’s more affordable “AE” zones versus the less affordable “VE” zones.

FEMA requires the purchase of flood insurance in certain areas defined by Special Flood Hazard Areas (SFHA) zones.

The estimated cost of the project at the time was approximately $2 million, according to documents provided by Principal Engineering.

Zuckerman said that a determination concerning Mandeville’s future “tidal protection alternatives” should be made by a panel of various experts, like what would be assembled at a flood summit, and not a single engineering firm.

“I’d like to see a comprehensive team put together and a comprehensive strategy. I just don’t think it ought to be treated like another roadway project that we’re hiring an engineering firm to go solve that problem,” Zuckerman said.

During the 2019 presentation by Principal Engineering, computer-simulated photographs were on display depicting views of the lake from near the seawall, not the roadway, making it appear that an observer’s view of the lake would not be obstructed if an additional foot were to be added.

However, Mandeville Daily conducted its own line-of-sight experiments, including videos, photographs with props, and computer-simulated photographs in an effort to objectively demonstrate the difference a one-foot extension would make visually from the road surface. (See media at end of story.)

These findings reveal that the view of Lake Pontchartrain would be completely or mostly blocked for someone in a sedan-size vehicle or bicycle on the roadway surface at most points along Lakeshore Drive.

However, the view is far less obstructed as the observer walks up the raised, grassy ground toward the seawall as Principal Engineering’s presentation confirmed. By design, the Lakeshore Drive road surface is the lowest point along the lakefront.

Zuckerman and McGuire both said that Part B of Task Order 4 was unrelated to the scope of work spelled out in Part A, and that in Part A, inspecting the check-valve system should be done first and before anything else is approved or considered, because the results of that inspection would determine what the next step should be.

Zuckerman told Mandeville Daily the first thing that needs to happen is to inspect just the check valves with cameras. “Let’s find out for sure if those are working before we authorize a large-scale inspection or revive plans to raise the seawall.”

Zuckerman said that based on previous conversations with Public Works Director Keith LaGrange Jr., he believes there is uncertainty as to whether the check valves work as intended.

It was Principal Engineering that played a significant role in the design and implementation of the so-called check-valve system that was intended to allow water to flow out to Lake Pontchartrain but not inland.

He said LaGrange told him that he thinks the check valves will never work as Principal Engineering intended and had proposed removing them completely at one point.

McGuire, whose district includes the seawall, raised concerns at the July 8th council meeting about having the same firm that designed the check-valve system be the one to inspect it, considering there is a question as to whether or not it’s working.

Another option, which Zuckerman said was informally presented to council members by LaGrange recently, is the idea to install an array of 32 so-called “drain lift stations” along Lakeshore Drive that would completely replace all existing gravity driven drainage.

A lift station is a water pump of sorts, that could help speed the rate at which water recedes after flooding, but because this system would replace all gravity driven drainage, it would be vulnerable to factors such as mechanical issues, availability of operators, and electricity outages, according to Zuckerman.

Zuckerman says this plan would forever change the “character” of the lakefront, with these lift stations being spaced approximately every 230 feet.

“We really need to assemble this team of experts from various fields that we keep talking about before we do this (lift stations) or any other idea like raising the seawall. We have to quit just talking about it and do it,” he added.

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