§ 124-4-2. Water Quality Design Criteria Requirements.

A.

In order to protect the quality of state waters and to control the discharge of stormwater pollutants from regulated activities, the following minimum design criteria and standards for stormwater management shall be applied to the site.

1.

New development. The total phosphorus load of new development projects shall not exceed 0.41 pounds per acre per year, as calculated pursuant to § 124-4-3.

2.

Development on prior developed lands.

a.

For land-disturbing activities disturbing greater than or equal to one acre that result in no net increase in impervious cover from the predevelopment condition, the total phosphorus load shall be reduced at least 20% below the predevelopment total phosphorus load.

b.

For regulated land-disturbing activities disturbing less than one acre that result in no net increase in impervious cover from the predevelopment condition, the total phosphorus load shall be reduced at least 10% below the predevelopment total phosphorus load.

c.

For land-disturbing activities that result in a net increase in impervious cover over the predevelopment condition, the design criteria for new development shall be applied to the increased impervious area. Depending on the area of disturbance, the criteria of subdivisions a or b above, shall be applied to the remainder of the site.

d.

In lieu of subdivision c, the total phosphorus load of a linear development project occurring on prior developed lands shall be reduced 20% below the predevelopment total phosphorus load.

e.

The total phosphorus load shall not be required to be reduced to below the applicable standard for new development unless a more stringent standard has been established by the County.

B.

The Board has established a Water Supply Protection Overlay District (WSPOD) in the Occoquan Watershed to prevent water quality degradation of the Occoquan Reservoir due to pollutant loadings within the watershed. WSPOD boundaries have been established on the Official Zoning Map. Use limitations are established which require that there shall be water quality control measures designed to reduce the projected phosphorus runoff by at least one-half for any subdivision which is subject to the provisions of Chapter 101 of the Code or any use requiring the approval of a site plan in accordance with the provisions of Article 17 of Chapter 112 of the Code, unless a modification or waiver is approved by the Director. In no instance shall the requirement for water quality control measures be modified or waived except where existing site characteristics make the provision impractical or unreasonable on-site and an alternative provision is not or cannot be accommodated off-site, and where it can be established that the modification or waiver will not affect the achievement of the water quality goals for the public water supply watershed as set forth in the adopted comprehensive plan.

C.

Compliance with subsections A and B above shall be determined in accordance with § 124-4-3.

D.

Requirements of all applicable TMDL action plans developed by the County in accordance with the County's MS4 permit shall be met. (08-14-124.)