MTD Evaluation Process

The Virginia Department of Environmental Quality (DEQ) has issued guidance that describes a process for approving manufactured treatment devices (MTDs), also referred to as proprietary BMPs. The guidance also describes DEQ’s method to assign a total phosphorus (TP) pollutant removal efficiency for approved proprietary BMPs.

Guidance Memo No. 21-2006 — “Use of Stormwater Proprietary Best Management Practices to Meet Virginia Stormwater Management Program [VSMP] Technical Criteria for Water Quality Compliance” (pdf)

To have a MTD/proprietary BMP evaluated by DEQ:

  1. Complete Attachment 1 – Proprietary BMP Registration Statement* (Word)
  2. Submit the completed registration statement along with supporting documents to DEQ’s Robert Cooper (

The DEQ will review submissions and if approved, assign the applicable percent TP removal efficiency in accordance with DEQ guidance (GM21-2006). After the percent removal has been assigned, this value will be added to the Virginia Stormwater BMP Clearinghouse and can be used to meet the water quality design criteria requirements.

MTDs approved by DEQ are listed by category:

  • Approved Hydrodynamic Devices (Practice 16),
  • Approved Filtering Devices (Practice 17), or
  • Prior-approved Devices: Prior-approved Hydrodynamics and Prior-approved Filters — Proprietary BMPs on the prior-approved lists may only be used to meet the TP water quality requirements of VSMP regulation for stormwater management plans submitted prior to January 1, 2022.

*All information submitted to DEQ will be made publicly accessible to all interested parties. If the MTD/proprietary BMP is approved, the submitted registration statement and other information reviewed by DEQ will be posted on the Virginia Stormwater BMP Clearinghouse website.