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Avion Mixed-Use Development

Burbank, California

Stormwater Treatment


Overton Moore Properties


Thienes Engineering


GJ Gentry 

Western Water Works (Distributor)


Summer/Fall 2020

Technical Description:

  • (2) CDS ® Hydrodynamic Separators
  • (44) Filterra ® Bioretention Systems

Avion Burbank is a 60-acre master-planned, mixed-use development located in Burbank, CA. With a theme of "Connect. Create. Innovate," the development seeks to set a new vision for today's workforce by creating a space that combines creative office, industrial, retail, and lodging in a sustainable campus environment. 

The development is immense and includes 17 buildings and 1.25 million square feet of space. The project developer, Overton Moore Properties (OMP), has a commitment to sustainability in all new projects, with Avion Burbank achieving LEED Silver Core and Silver Design status from the U.S. Green Building Council. 

According to the City's MS4 Permit requirements, a Low Impact Development (LID) Plan was submitted by OMP to the City of Burbank Community Development Director. The LID Plan was required because the project would alter 50 percent or more of the impervious surfaces of a previously existing development that was not subject to post-construction stormwater quality control requirements. Therefore, the project was classified as a "Planning Priority Project" and was required to comply with regulations that call for treatment of all stormwater runoff generated at the site.

The LID Plan was designed to control pollutant loads and runoff volumes to the maximum extent feasible by minimizing impervious surface areas and controlling runoff from impervious surfaces through infiltration, evapotranspiration, bioretention and/or rainfall harvest and use. Since infiltration of stormwater runoff was determined to be infeasible due to groundwater contamination, the LID plan included the use of bioretention, as required by Attachment H of the Los Angeles County MS4 permit.

Given the tremendous amount of runoff needed to be treated, the Engineer of Record (EOR) selected the Filterra Bioretention system. Filterra is an approved alternative to Attachment H of the Los Angeles County MS4 Permit. With its high flow media, Filterra provides a high level of treatment in a much smaller footprint than traditional bioretention. Given the value of land at the development the smaller treatment footprint was a significant benefit to the developer. The smaller footprint will also reduce long-term maintenance costs. 

Engineering for the treatment of stormwater from over 1 million square feet of impervious surfaces was a challenge. Stormwater Design Engineers at Contech needed to treat at least 93% of the average annual runoff volume to provide treatment on par with a properly sized conventional biofilter.  To accomplish this, engineers utilized clusters of parallel Offline Filterra systems of various sizes (44 units in total) with the largest being 22"x8". The Filterra systems provide the necessary treatment and enhance the site's aesthetics. Planted with native vegetation, they provide a visible reminder to the occupants of the developer's commitment to sustainability. 

The EOR incorporated two CDS hydrodynamic separators into the drainage system to provide pretreatment for the Filterra systems. After being pretreated by the CDS systems, a pipe manifold from the storm drain distributes flow as evenly as possible throughout multiple Filterra systems allowing each system in the cluster to operate in parallel. This helps prevent any one system from providing a majority of the treatment and maximizes the maintenance interval.

Contech worked closely with the contractor, GJ Gentry, and the distributor, Western Water Works Supply Company, to coordinate the production and delivery of the Filterra systems to meet the aggressive production schedule. 

As clusters of systems were manufactured, they were shipped and installed at ten units per construction day.  Since most of the units were too heavy to ship with the media installed inside the vaults, Contech worked with GJ Gentry to provide the Filterra media the day after delivering the vaults. A Contech Field Representative was on site to guide GJ Gentry during the delivery and installation of the vaults and media. Contech activated the Filterra systems, which included installing the vegetation and mulch, once the site had been stabilized.

"This job was successful with much of the credit going to Contech for staying on schedule and providing terrific customer service to the whole team; Millie and Severson General Contractors, Western Water Works Supply Co., and GJ Gentry General Engineering,"  said Bryan Copping, VP, GJ Gentry.

To date, this is Contech's largest single-phased Filterra project in history. The aggressive schedule the Contech team needed to meet displayed the knowledge and efficiency of everyone involved and proved the team's dedication to meeting customer's needs. During the design phase, the Stormwater Consultant reviewed site plans with the EOR and provided preliminary product recommendations. At the same time, the Stormwater Design Engineer developed site-specific drawings. When it was time for construction, the Project Coordinator managed all the manufacturing and delivery details with the contractor, while the Field Consultants provided site supervision. The team's consistent interface with the general contractor, sub-contractor, and distribution partner, resulted in tremendous success.

"What a project to have teamed up with Contech for. We are very proud of the work the whole team accomplished. From G. J. Gentry's expertise installing all these Filterra units, Pre-Con Products with quality manufacturing, Contech's professionalism and capabilities, to Western Water Works Supply Co.'s support all along the way.  Great job by all," said Ruben Pena, Sales Director and Jim McDowell, Vice President of Special Products at Western Water Works Supply Company.

Technical Description:

  • (2) CDS ® Hydrodynamic Separators
  • (44) Filterra ® Bioretention Systems

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