(a)

Purpose. To establish impervious surface standards to protect water quality, fish and wildlife habitat and to protect against pollution of navigable waters. The county impervious surface standards shall apply to the construction, reconstruction, expansion, replacement or relocation of any impervious surface on a riparian lot or parcel and any non-riparian lot or parcel that is located entirely within 300 feet of the ordinary highwater mark of any navigable waterway.

(b)

Calculation of percentage of impervious surface. Percentage of impervious surface shall be calculated by dividing the surface area of the existing and proposed impervious surfaces on the portion of a lot or parcel that is within 300 feet of the ordinary highwater mark by the total surface area of that lot or parcel, and multiplied by 100. Impervious surfaces described in subsection (e) of this section shall be excluded from the calculation of impervious surface on the lot or parcel.

(1)

If an outlot lies between the ordinary highwater mark and the developable lot or parcel and both are in common ownership, the lot or parcel and the outlot shall be considered one lot or parcel for the purposes of calculating the percentage of impervious surface.

(2)

For properties under alternative forms of ownership such as condominiums, cooperatives and associations, the limits to expansion on structures and caps on impervious surfaces shall be attributable to the total number of units within the development. For example, if owners within a three-unit condominium development have 1,500 square feet of expansion opportunity available to the units under the impervious surface limitations and they want to expand their structures, then the expansion opportunity for principal or accessory structures shall be split equally amongst the three units so that no more than 500 feet of expansion to impervious surfaces is afforded to each unit.

(c)

General impervious surface standard. Except as authorized in subsections (d) and (e) of this section, up to 15 percent impervious surfaces are allowed on the portion of a lot or parcel that is within 300 feet of the ordinary highwater mark.

(d)

Maximum impervious surface. A property may exceed the impervious surface standard under subsection (c) of this section, provided the following standards are met:

(1)

A property owner may have more than 15 percent impervious surface but not more than 30 percent impervious surface on the portion of a lot or parcel that is within 300 feet of the ordinary highwater mark.

(2)

For properties that exceed the standard under subsection (c) of this section, but do not exceed the maximum standard under subsection (d)(1) of this section, a permit can be issued for development with a mitigation plan that meets the standards found in section 38-749.

(e)

Treated impervious surfaces. Impervious surfaces that can be documented to show they meet either of the standards in subsection (d) of this section shall be excluded from the impervious surface calculations under subsection (b) of this section.

(1)

The impervious surface is treated by devices such as stormwater ponds, constructed wetlands, infiltration basins, rain gardens, bio-swales or other engineered systems.

(2)

The runoff from the impervious surface discharges to an internally drained pervious area that retains the runoff on or off the parcel and allows infiltration into the soil.

(3)

To qualify for the statutory exemption, property owners shall submit a complete permit application that is reviewed and approved by the county. The application includes the following:

a.

Calculations showing how much runoff is coming from the impervious surface area.

b.

Documentation that the runoff from the impervious surface is being treated by a proposed treatment system, treatment device or internally drained area.

c.

An implementation schedule and enforceable obligation on the property owner to establish and maintain the treatment system, treatment devices or internally drained area. The enforceable obligations shall be evidenced by an instrument recorded in the office of the register of deeds prior to the issuance of the permit.

(f)

Existing impervious surfaces. For existing impervious surfaces that were lawfully placed when constructed but that do not comply with the impervious surface standard in subsection (c) of this section, or the maximum impervious surface standard in subsection (d) of this section, the property owner may do any of the following:

(1)

Maintain and repair the existing impervious surfaces;

(2)

Replace existing impervious surfaces with similar surfaces within the existing building envelope;

(3)

Relocate or modify an existing impervious surface with similar or different impervious surface, provided that the relocation or modification does not result in an increase in the percentage of impervious surface that existed on the effective date of the county shoreland ordinance, and the impervious surface meets the applicable setback requirements in section 38-743(1) and (2).

(Code 2000, § 38-598; Res. No. 72-16, 9-20-2016)