The Carrollton Water Plant is a vital piece of infrastructure for the east bank of Louisiana’s Orleans Parish, delivering around 135 million gallons of treated water a day to homes in that section of New Orleans. Expanded shale, clay and slate (ESCS) lightweight aggregate is being used to create stable land for a new dedicated electrical substation that will modernize systems that power the water and sewer plant.
Cycle Construction Company, LLC, a family-owned general construction firm located in Kenner, LA, is working on the geotechnical phase of the job. Project Manager Ethan Oddo explains the scope of their assignment.
“Our task on this phase of the project is to provide a blank slate. The site used to be two large holding tanks, which have been abandoned for a few years now,” Oddo says. “They’re about 10 feet deep from the surrounding earth, probably about eight acres in total area. Our earthworks scope is to remove all the structures, walls, slab, etc., and then fill it to grade with compacted materials. So, we’ve got some sand at the bottom, two to three feet of the ESCS lightweight aggregate, and a foot of #610 limestone at the top for a surface.”
Up to 20,000 cubic yards of 3/16″ fine granular lightweight aggregate has been used to bring the building site up to elevation. Because ESCS lightweight aggregates can reduce the density of compacted geotechnical fills by up to one-half, weight and lateral forces won’t affect surrounding basins and water tanks.
“On three sides of this basin, there are active drinking water basins and some tanks filled with drinking water. So lateral force couldn’t be too high. Otherwise, we’d be cracking walls and whatnot. Engineers wanted to have the fill without having too much lateral force on the wall and the lightweight seemed to fit that bill pretty well.”
Cycle’s Civil Superintendent Dennis Grantham says up until now, the only use of lightweight aggregate he’s observed has been for landscape applications. He’s impressed with the manufactured aggregate’s geotechnical performance.
“It has performed better than I expected,” Grantham says. “I thought the compaction of it was going to be almost impossible to achieve, but we actually did get good compaction on it.” Grantham adds, “I expect to see [lightweight aggregate] on future projects. I think it’s something a lot of these contractors are going to start using more of because they realize how good it is.”
He also highlights the handiwork of Three C’s Trucking. “They do an excellent job,” Grantham says. “When we have the material close at hand, we can put in 2000, 3000 yards a day of that really quick. They are excellent at making things happen.”
Oddo says the use of ESCS lightweight aggregate also solves another large problem for him on the Carrollton substation project. “The problem is that we have a lot of water on the site, a lot of issues with water intrusion,” Oddo says. “ And as of right now, the locations we have the lightweight, which is probably about half the site, don’t seem to be having any issues, especially with the geotextiles that we’re pancaking it with below and above.”
The addition of the new on-site substation is part of the city’s Sewerage & Water Board modernization plan to transition away from self-generated steam power and switch to modern-day energy sources. For years, the plant has relied on electricity generated by a series of aging steam-powered turbines that are over 100 years old. The system often breaks down in times of severe weather.
“I’d say it’s pretty crucial to keep the water plant moving,” Oddo says. “We get hit by hurricanes, other random flood events, and it seems like two to three times a year we lose power across the city and therefore the Sewage and Water Board loses power,” Oddo says. “Then you have a low water pressure issue and then everyone’s boiling water. It’s become a problem over the years, and that’s why this was a slam dunk project once it came across the desk.”
A report from Entergy New Orleans, LLC, the electric and gas utility that serves the region, indicates the primary purpose of the project is increased reliability. “The new substation routes power directly from the transmission system which is inherently less susceptible to outages,” Entergy’s report says, “while also providing the increased capacity necessary to serve drainage pumps currently powered by aging and inefficient (Sewerage & Water Board) generation.”
Project Details: Approximately 20,000 CY of lightweight aggregate fill for the foundation for a new electrical substation for the Carrolton Water Plant
Project Location: New Orleans, LA
Project Type: Geotechnical
Supplied By: Erwinville, LA