Low Impact Development Stormwater Treatment - Avion Mixed-Use Development
Avion Burbank is a 60-acre master-planned, mixed-use development located in Burbank, CA. The development is immense and includes 17 buildings and 1.25 million square feet of space.
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 all stormwater runoff generated at the site be treated.
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 onsite 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) engineers selected the Filterra Bioretention System. Filterra is an approved alternative to Attachment H of the Los Angeles County. With its high flow media, Filterra provides a high level of treatment in a much smaller footprint than traditional bioretention. The smaller treatment footprint was a significant benefit to the developer, given the value of land at the development. The smaller footprint will also reduce long-term maintenance costs, providing another benefit to the developer.
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 goal, engineers utilized clusters of 44 Offline Filterra systems of various sizes, with the largest being 22"x8". The Filterra systems provide the necessary treatment and enhance the site's aesthetics. They will be planted with native vegetation, providing a visible reminder to the occupants of the developer's site's commitment to sustainability.
The EOR incorporated two CDS hydrodynamic separators into the drainage system to provide pretreatment for the Filterra systems placed in large, parallel clusters. They were able to make the place the systems in parallel by integrating a manifold off the storm drain that distributes flow as evenly as possible throughout multiple Filterra systems, preventing any one system from providing a majority of the treatment and increasing its maintenance interval.
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 Storm Water Consultant reviewed site plans with the specifying engineer and provided preliminary product recommendations. At the same time, the Storm Water 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 Consultant's provided site supervision. The combined sales team's consistent interface with the General Contractor, sub-contractor, and distribution partner, everyone's effort resulted in a tremendous success.
Editor's Note: Scranton Gillette Communications and the SGC Water Group are not liable for the accuracy, efficacy and validity of the claims made in this piece. The views expressed in this content do not reflect the position of the editorial teams of Water & Wastes Digest, Water Quality Products and Storm Water Solutions.
