Requirement: No reduction in the after disturbance pollutant discharge is required.
Requirement: The pollutant discharge after disturbance shall not exceed the existing pollutant discharge based on the average land cover condition.
Requirement: The pollutant discharge after disturbance shall not exceed (i) the pollutant discharge based on existing conditions less 10% or (ii) the pollutant discharge based on the average land cover condition, whichever is greater.
Requirement: The pollutant discharge after disturbance shall not exceed the existing pollutant discharge based on the existing percent impervious cover while served by the existing BMP. The existing BMP shall be shown to have been designed and constructed in accordance with proper design standards and specifications, and to be in proper functioning condition.
Table 1* | ||
Water Quality BMP* | Target Phosphorus Removal Efficiency | Percent Impervious Cover |
Vegetated filter strip | 10% | 16-21% |
Grassed Swale | 15% | |
Constructed wetlands | 20% | 22-37% |
Extended detention (2 x WQ Vol) | 35% | |
Retention basin I (3 x WQ Vol) | 40% | |
Bioretention basin | 50% | 38-66% |
Bioretention filter | 50% | |
Extended detention-enhanced | 50% | |
Retention basin II (4 x WQ Vol) | 50% | |
Infiltration (1 x WQ Vol) | 50% | |
Sand filter | 65% | 67-100% |
Infiltration (2 x WQ Vol) | 65% | |
Retention basin III (4 x WQ Vol with aquatic bench) | 65% | |
*Innovative or alternate BMPs not included in this table may be allowed at the discretion of the local program administrator or the department. Innovative or alternate BMPs not included in this table that target appropriate nonpoint source pollution other than phosphorous may be allowed at the discretion of the local program administrator or the department. |
9 Va. Admin. Code § 25-870-96
Statutory Authority: § 62.1-44.15:28 of the Code of Virginia; Chapters 68 and 758 of the 2016 Acts of Assembly.