New Orleans mandates permeable pavement to control stormwater runoff
David Wagman | September 12, 2019
Permeable paving allows stormwater to drain into the soil rather than flow into drainage systems. Source: Wikipedia
New surface parking areas in New Orleans will need to be built using water-permeable materials as a result of a new ordinance passed by council members in early September.
The ordinance is intended to reduce stormwater runoff into Lake Ponchartrain and mitigate soil subsidence in the city. During heavy rainstorms the city's drainage system can become overwhelmed and result in local flooding. Porous surfaces will allow rain water to soak into the ground where it falls.
Under the new ordinance, concrete bases and mortar are prohibited from new parking areas. Permitted materials include pervious concrete, porous asphalt, aggregate if stabilized with a grid system that prevents compaction and washout and permeable pavement such as open-jointed blocks, pavers or bricks.
Once in place, the paving is subject to water infiltration testing based on ASTM International C1701 or C1781 standards. Pavement must maintain a minimum infiltration rate of 200 in per hour, the ordinance said.
The ordinance also requires new paving installations to have a minimum aggregate subbase of 24 in, measured from the base of the permeable pavement system.
More broadly, the City of New Orleans was awarded $141 million through the U.S. Department of Housing and Urban Development for its proposed resilience district in Gentilly with projects to reduce flood risk, slow land subsidence and encourage neighborhood revitalization.
A tech brief from the U.S. Department of Transportation said that porous asphalt pavements have been successfully used for more than 35 years in a variety of climates around the country. They provide a pavement surface that is also part of the stormwater management system, reducing stormwater runoff and pollutants and replenishing groundwater. The brief said that a number of porous asphalt parking lots have lasted more than 20 years with little maintenance other than cleaning.
Does this help when the land is below sea level?
In reply to #1
Below sea level would aid in water returning to the streets on storm surges and Tsunamis. Would this be a form of perverse odd Moses?
This is going to be a disaster.
Either; Someone is in someone's back pocket, and / or they have absolutely no knowledge of the soils under New Orleans, to have gotten this pushed through.
a) The city is below sea level. 50% is -6.5 ft. below sea level, at the highest it's only 20 ft. The Mississippi River is 10 to 15 ft ABOVE Sea level, there are Levees All the way along the river to keep the water out of New Orleans The rest of the surrounding area is swamp land. Where is the water going to go? Water does not flow up-hill!
b) The city is built on the Mississippi Delta and at the base of an alluvial fan. An alluvial fan is a geographic area composed of loose soil and sediment at the mouth of a river. It is classified as alluvial sandy loam—containing a mix of sand, silt, and clay. Permeability is a problem due to the low percentage of large pores in the soil, plus it Stays Wet Year Round. How is it going to absorb water run off through a porous pavement? It Wont!
This may have worked in the upper states not near water. but it will not work in New Orleans.
It took 3 weeks and 14 billion dollars to pump out New Orleans including rebuilding the levees, after Katrina in 2005.
In reply to #3
I'd say both.
In reply to #3
The best that they can hope for is that all these "dry wells" that probably won't be very dry, is that they act like a sponge to absorb a rain storm, so that tempers the flows to the pumps that have to run all the time to keep the bilges of New Orleans from over-flowing. New Orleans is akin to a boat with a leaky hull. At some point, we're just going to have to scuttle her.