Posted on July 21, 2016
By Jeff Adelson, The New Orleans Advocate
New Orleans is about to embark on a $115 million, three-year project to upgrade drainage in eight neighborhoods, the largest effort to date to enact new strategies focused on retaining – rather than immediately pumping out – rainwater.
The federally funded projects are spread throughout the city and collectively represent the biggest recent effort to improve New Orleans’ drainage system outside of the massive Southeast Louisiana Urban Flood Control Project being built by the U.S. Army Corps of Engineers.
While the two projects will complement each other, they represent dramatically different philosophies about stopping the street flooding that can plague the city.
Unlike the Corps project, which is focused on upgrading the huge underground culverts and other infrastructure that channels water out, the city’s new projects will rely on using green space and open areas to store water, lessening the amount that pumping stations have to deal with and potentially reducing subsidence within the city.
“This is the next generation of what these things could be,” said Cedric Grant, executive director of the Sewerage & Water Board and Mayor Mitch Landrieu’s chief aide on infrastructure issues.
Eight neighborhoods are included in the effort: Pontilly, Mirabeau Gardens, Lakeview, Hagan-Lafitte, St. Roch, Academy Park, a piece of Algiers and a project referred to as the Broadmoor Drainage Upgrades that also includes Central City, the Garden District and other nearby neighborhoods.
Nearly all of the projects are still in the early design stages, but they must be completed by August 2019 to meet federal guidelines.
The City Council unanimously signed off Thursday on the agreements needed to move forward with the plan.
The project in Pontilly — which comprises Pontchartrain Park and Gentilly Woods — is the furthest along and could be put out for bid in a few months. That project, referred to as a neighborhood stormwater network, includes improvements to the Dwyer Canal as well as turning vacant lots and parks into stormwater retention areas. More green space is expected to be added through streetscaping.
The projects are all built around the basic concepts — outlined in the Greater New Orleans Urban Water Plan and promoted by the S&WB — that are generally characterized as “living with water.”
While the city’s drainage system historically has been designed to funnel rainwater into canals where it can be quickly pumped out of the city, the new strategy focuses on retaining it – at least temporarily – within the city.
Officials say that approach can have multiple benefits. Slowing the rate at which water enters the traditional drainage system, which can pump out between a half-inch and an inch of rainfall per hour, can help reduce flooding from heavy rains. In lighter storms, pumps may not be needed at all — or can be run at a lower rate — which can reduce wear and tear and reduce power usage.
“We had to prove the projects will actually reduce flooding” to get the federal money, said Jeff Hebert, executive director of the New Orleans Redevelopment Authority and the city’s chief resiliency officer. Hebert will soon be stepping into the role of Landrieu’s chief administrative officer.
In addition, the approach is considered to be more ecologically appropriate. Pumping groundwater out of the city’s spongy soil has been linked to high rates of subsidence in New Orleans, as drier ground compacts more. That in turn leads to a multitude of problems, such as cracked streets and foundations.
The Mirabeau Water Garden project, planned for a 25-acre lot between Bayou St. John and the London Avenue Canal, for example, is estimated to be able to hold about 3 million gallons of rainwater, Grant said.
It’s still too early in the design stages to calculate the amount of water that many of the other projects will be able to hold, Grant said.
The projects represent a pivot for the city from using federal hazard mitigation funds to assist individual homeowners with elevating their homes to more generalized efforts aimed at improving drainage for large areas of the city, Hebert said.
That funding, combined with some of the money from a $141 million U.S. Department of Housing and Urban Development grant the city received last year, will pay for the projects.
Contrasted with the traffic snarls that have accompanied the Corps’ various Uptown drainage projects, the city’s plan is expected to have a minimal impact on roadways, Grant said. About half the projects will not involve significant road closures, he said.
With many details of the projects still being worked out, Grant told the City Council there would be an effort to involve neighborhood and community groups and nonprofits in the planning. That effort, he said, would involve soliciting ideas not just on what the city should be building but also on how to ensure the projects are properly kept up over the long term.
“The biggest impact I hope they bring to us is being practical about this,” Grant said. “Sometimes we can do beautiful designs but have difficulty maintaining them.”
Source: The New Orleans Advocate
