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Arlington Transit Operations and Maintenance Facility

Arlington, Virginia

Stormwater Treatment


Arlington County


Timmons Group


Turner Construction/WB Hopke Company           


December 2022

Technical Description:

(2) Stormwater Management StormFilter Vaults 

Construction on the new Arlington Transit (ART) Operations and Maintenance Facility began in June 2022 and is expected to be completed in late 2024. The facility will perform regular preventive bus maintenance, repairs and other unscheduled maintenance work. It also will include administration and operations functions and parking for buses and staff. This project is essential for ART's long-term sustainability and will address the current and future needs for parking, operations, and maintenance of Arlington's growing bus fleet.

All new and redevelopment projects in Virginia must adhere to the Virginia Stormwater Management Plan (VSMP) Total Phosphorous Reduction requirement. To do this, engineers specified a Stormwater Management StormFilter with PhosphoSorb media; an approved treatment device on the Department of Environmental Quality (VADEQ) BMP Clearinghouse VADEQ BMP Clearinghouse website with a 65% Total Phosphorous Removal Efficiency Rating.  

Contech and Timmons explored cost and footprint-effective solutions utilizing various Contech VADEQ-approved filtration products before deciding upon the two low-drop StormFilter vaults in parallel; an 8'x18' Peak Diversion StormFilter with 35 low-drop cartridges and an 8'x16' Peak Diversion StormFilter with 33 low-drop cartridges.

The Peak Diversion StormFilter provides treatment and high flow bypass in one precast vault, eliminating the need for an external bypass or junction structures. Low-drop cartridges provide treatment with only 1.8 feet of headloss; and are used on sites limited by hydraulic constraints. The cartridges in both vaults were filled with PhosphoSorb®, a media made from a Perlite base that removes total phosphorus (TP) by adsorbing dissolved-P and filtering particulate-P simultaneously.

The site was very tight, as it needed to provide detention and treatment in a small footprint. The low-drop StormFilters downstream of the detention system allowed the engineer to meet the design challenges and regulatory requirements.
Contech provided engineering support throughout the design, including site-specific drawings with rim elevation, pipe orientation, inverts, shop drawings, field installation support, and a review letter. Contech also held a preconstruction meeting with the contractor. 

The two StormFilters vaults were delivered and installed in one day. There was a short delay due to the excavation being too low. The contractor resolved the issue, and the installation went smoothly. 

“I am very pleased with the outcome of the project and the solutions from Contech to provide water quality for the project," said Osvaldo Ramos, PE, Project Manager at the Timmons Group. "Contech was able to assist during the design stages to provide two separate facilities due to space and cost. The installation was quick with no issues during construction."

Technical Description:

(2) Stormwater Management StormFilter Vaults 


800-338-1122 |
Project #: 692544


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