§ 4. Retention requirements.

In the Grant-Valkaria special area of stormwater concerns, the site drainage plan for building permit applications shall provide for detention storage of one-inch runoff from the lot. Site storage may be accomplished with swales, berms, or ponds. The detention volume may be drawn down with a maximum three-inch diameter pipe or structure. An engineered design is not required. Exhibit 1, shows typical designs that may be used for required detention volumes. Alternate designs may be used provided they are designed, signed and sealed by a professional engineer and deemed acceptable to the county.