The following manufactured treatment devices (MTDs) have been approved by the Virginia Department of Environmental Quality and are listed on the Virginia Stormwater BMP Clearinghouse as propriety best management practices (BMPs). In accordance with the Public Facilites Manual (PFM) § 6-0402.3B, manufactured BMPs may be used to meet the water quality control requirements of the Erosion and Stormwater Management Ordinance, Article 4, subject to review and approval by the Director of Land Development Services (Director). Compliance with the total phosphorus (TP) reduction requirements should be demonstrated by manually inserting the Clearinghouse-assigned TP removal efficiency into the drainage area tab in the Virginia Runoff Reduction Method spreadsheet.

To obtain an approval to use an MTD in Fairfax County, please submit the following materials to LDS SAC and copy Alison Avery and Paul Fernandes:

• Application form Land Development Services Waiver/Modification/Exception Application Form. Note, this is a request to modify PFM § 6-0402.3B. Please be sure the product name on the application matches that shown on the Virginia Stormwater BMP Clearinghouse site. Each device must be submitted separately.
• Provide all requested information listed under PFM § 6-0402.3B.
• Include all documents needed to obtain DEQ approval.

Subject to the limitations and conditions listed below, the Director has approved the following MTDs for use in Fairfax County:

Note:

• No plan can utilize DEQ’s "Prior Approved" MTDs to meet water quality design criteria in the County New Technical Guidance Impacting Use of Proprietary Best Management Practices.

Hydrodynamic devices:

1. Aqua-Swirl® Stormwater Treatment System (20% TP removal efficiency)
2. Continuous Deflective Separator® (CDS) Stormwater Treatment Device (20% TP removal efficiency)
3. Downstream Defender® (20% TP removal efficiency)
4. Dual Vortex Separator (DVS) Stormwater Treatment Device (20% removal efficiency)
5. SciClone™ Hydrodynamic Separator (20% TP removal efficiency)

Filtering devices:

1. Aqua-Filter™ Stormwater Filtration System (40% TP removal efficiency)
2. BayFilter™ using Enhanced Media Cartidge (EMC) (64% TP removal efficiency)
3. HydroChain™ Chamber Main Header Row (MHR) by Xerxes (40% TP removal efficiency)
4. Jellyfish® Filter (65% TP removal efficiency)
5. Oldcastle Infrastructure PerkFilter™ (with ZPC Filter Media) (62.4% TP removal efficiency)
6. StormKleener™ Cartridge System (Stormkleener Filter) (40% TP removal efficiency)
7. StormTech® Isolator Row Plus (40% TP removal efficiency)
8. StormTree® Biofiltration Practice (61.6% TP removal efficiency
9. The Stormwater Management StormFilter® with ZPG media (40% TP removal efficiency)

The use of the above devices is subject to the following:

1. Each MTD must comply with PFM § 6-1320, and shall be privately maintained. A private maintenance agreement must be executed prior to plan approval.
2. Pursuant to the PFM § 6-1320.2A, individual manufactured BMPs will have different site constraints and limitations and must be feasible and appropriate for use on a specific site. In accordance with the PFM § 6-0402.5, the Director may preclude the use of any BMP otherwise allowed, or require more stringent conditions upon its use, for a specific land-disturbing activity based on a review of the stormwater management plan and project site conditions provided such limitations are based on site-specific concerns.
3. The manufacturer or manufacturer's representative shall verify, in the form of a letter or certification on the plan, that the size and proposed configuration of the MTD meets the manufacturer's sizing, design, and installation requirements for the product. The plan shall also include the manufacturer's installation requirements and maintenance recommendations, noting the intervals and methods for inspections and routine maintenance.
4. Any MTD that is sized using a flow-based method shall be designed to treat the water quality peak flow rate calculated using the Modified CN method. The design procedure can be found in Appendix A.4.3 of the Virginia Stormwater Management Handbook. In no case shall the treatment capacity be less than the minimum required by Chapter 124.1 of the County Code or an instantaneous flow rate of 0.7 cfs per acre, irrespective of the land cover. Sizing information can be found under 8.4.4.3 of the Virginia Stormwater Management Handbook. Sizing computations must be included on the plan.
5. Any MTD that includes an underground storage chamber shall be subject to the same restrictions as underground detention in accordance with PFM § 6-0303.6.
6. A detailed review of the site-specific application of this product will be conducted as a part of each site plan review where it is specified in order to ensure compliance with Chapter 124.1 of the County Code and the PFM.