Project Overview

The City of Gretna, Louisiana, has faced persistent challenges with localized flooding and declining infrastructure in its historic downtown area. In response, city leaders launched an ambitious urban design and stormwater management initiative aimed at transforming the public realm while addressing environmental resilience.

The redevelopment, led by Dana Brown & Associates (DBA), was the first phase of the Gretna Downtown Drainage initiative, encompassing over two acres of public grounds and surrounding streets adjacent to City Hall.

The comprehensive redesign eliminated nearly 40% of existing impervious surfaces, replacing it with porous pavements and urban greening solutions that would allow the landscape itself to manage water more naturally, reliving pressure on outdated stormwater infrastructure during
extreme rainfall events, and disastrous flooding which the city was all too familiar with.

This project also sought to go beyond solving infrastructure issues, seeking to create a safer, greener, and more engaging public space that celebrates Gretna’s historic civic identity.

The design team integrated multiple complementary green infrastructure strategies to address both surface and subsurface hydrological flow.

Rainwater is intercepted at the surface through permeable pavers, which allow runoff to infiltrate the ground rather than flow into the overburdened stormwater system.

Where surface capture was not feasible, bioretention zones were installed to slow, store, and clean water through vegetation and soil filtration.

Beneath the surface, R-Tank underground detention systems were embedded to handle surges in rainfall, temporarily storin water and preventing it from overwhelming downstream drainage infrastructure. These below-grade systems play a crucial role in mitigating flooding during high-intensity storms, an increasingly common event in Southeast Louisiana.

Yet one of the most impactful interventions, both above ground and below, was the integration of Stratavault, Citygreen’s engineered soil vault system.

Stratavault: Engineered for Growth. Built for the Urban Future.

Traditional urban tree planting often compromises root health by forcing trees into small spaces, with limited soil volume and compacted soil conditions. But at Gretna City Hall, the design team avoided this pitfall by incorporating Stratavault, an engineered, modular soil vault system designed to support pavements while delivering optimal growing conditions for trees in challenging urban spaces.

Installed beneath paved surfaces, Stratavault allows for 93-95% of optimal soil volumes to be provided for trees, without the need for compaction to support the pavements.

Compacted soil, like structural soil mixes, compromise the growing conditions trees need, by removing vital oxygen and nutrients from the soil, providing around only 20% of a trees needs.

Instead, Stratavault delivers large volumes of uncompacted, biologically active soil to enable trees to grow to their full, natural potential.

Structural integrity for the pavements is maintained by the interlocking units that provide tremendous vertical

and lateral strength, with every batch load tested to guarantee HS20/W80 load compliance.

This engineered green infrastructure solution served two core purposes on the project:

1. Tree Longevity and Canopy Growth
Trees planted in Stratavault zones have a greater chance of not just surviving but thriving. This results in deeper, healthier root systems and robust canopy expansion, improving shade cover and urban cooling over time, which was an essential consideration for creating a walkable and comfortable civic space.

2. Integrated Stormwater Performance
While Stratavault’s primary benefit is tree health, it also significantly contributes to stormwater management. The soil within each vaulted system can absorb large volumes of stormwater runoff, with a temporarily holding capacity, reducing peak flow rates and promoting filtration at the source. In this way, the soil system acts as a living sponge, working in harmony with the climate challenges created by the surrounding gray infrastructure

The selection of Stratavault aligned seamlessly with Gretna’s vision for a resilient, low-maintenance, high performance civic space. By combining
structural load-bearing capacity with ecological function, Stratavault empowered the project team to extend green infrastructure into every square foot of the site.

The Gretna City Hall project now detains and filters over 14,600 cubic feet of stormwater during major weather events - an impressive feat for a small urban space. But its success is equally measured by how it has transformed the everyday experience for residents and visitors.

Shaded pedestrian walkways lined with thriving trees invite people to linger, gather, and explore. The renewed visibility and accessibility of the historic Jefferson Memorial Arch, a centerpiece inscribed with the names of Jefferson Parish war veterans, deepens the site’s cultural resonance.

In blending environmental function with civic beauty, the project stands as a model for other municipalities seeking climate- adaptive design without compromising on place making.

Engineering the Future in Historic Spaces

DSC 0044 1200x619 DanaBrown 1 e1753416214732 Citygreen

The Gretna downtown redevelopment illustrates what’s possible when engineering innovation, landscape architecture, and sustainable policy converge. With the help of advanced technologies like Citygreen’s Stratavault, this historic town now delivers best-in-class performance in both ecological function and community benefit.

Citygreen is proud to support projects like this, where the right systems, installed the right way, for the right reasons, can change not only the aesthetic urban landscape, but it’s future resilience against extreme climate events and it’s livability for residents.

“Great customer service, quick response times and a very in depth QA system with constant support.”

- Laura Wiesenekker, Project Engineer, Densford Civil -

“Citygreen is a very professional business, and I found everything was great in terms of deliveries, product supply and information. It was all forthcoming and helped us to complete the project.”

- Keith Burns, Architect/Designer, Keith Burns Architect -

“Citygreen offered training and invaluable technical assistance during the works.”

- James Callan, Estimating Manager, Complex Co Pty Ltd -

“Our experience, in working with a Citygreen Design Studio was second to none. We found responses from the design studio to be very timely, and technically thorough. We went backwards and forwards a number of times, looking at different iterations of the design and, nothing was too much trouble to examine and explore different possibilities. I would highly recommend the Citygreen Design Studio to any future client considering using your services.”

- Sandra Smith, Principal Landscape Architect, City Of Monash -

“We are big on compliance on all projects, and the fact that their SmartCertify cloud platform covers all bases, and supports their 20 year warranties, is critical – especially that these pits are being installed under roadways and footpaths.”

- Johny Purkaystha, Civil Program Engineer, Central Coast Council -

"I reviewed all the previous projects that we have installed in the past couple years using your product and I can happily report back that we have 0% mortality in the soil cells, which is incredible!"

- Brendan Wilton, CEO, Trim Landscaping, Bedford, Canada -