A. Purpose: The purpose of regulating development on and near steep slopes is to:
1. Promote safety in the design and construction of developments;
2. Minimize flooding, landslides and mudslides;
3. Minimize soil instability, erosion and downstream siltation; and
4. Preserve the scenic character of hillside areas, particularly wooded hillsides.
B. Regulated Slopes Defined:
ALTERED PROTECTED SLOPES: Any slope of forty percent (40%) or steeper created by human activity such as cutting or filling, which activity occurred prior to December 13, 1995, and which slope is not otherwise approved by the city.
CRITICAL SLOPES: A slope of twenty five percent (25%), but less than forty percent (40%).
PERCENT OF SLOPE: The slope of a designated area determined by dividing the horizontal run of the slope into the vertical rise of the same slope and converting the resulting figure into a percentage value.
PROTECTED SLOPES: Any slope of forty percent (40%) or steeper.
STEEP SLOPES: A slope of eighteen percent (18%), but less than twenty five percent (25%).
C. Environmental Review Required: A sensitive areas development plan for property containing regulated slopes must include evidence demonstrating that all regulations of this section will be met. Such plan must include the following information:
1. Delineation of all steep, critical, and protected slopes and any required buffer area.
2. Submission of a grading plan that is in conformance with title 17, chapter 8, "Grading Ordinance", of this code.
3. Delineation of construction area limits and specification of associated restrictions thereof.
D. Buffer Requirements:
1. A buffer will be required around all protected slopes. Two feet (2') of buffer must be provided for each foot of vertical rise of the protected slope, up to a maximum buffer of fifty feet (50'). The buffer area is to be measured from the top, toe and sides of the protected slope. No development activity, including removal of trees and other vegetation, will be allowed within the buffer.
2. The buffer requirements may be reduced under certain circumstances. If a buffer reduction is requested, a level II sensitive areas review is required. A reduction of a protected slope buffer may only be approved if a geologist or professional engineer demonstrates to the satisfaction of the city that the proposed development activity can and will be designed to eliminate hazards and will not undermine the stability of the slope or the buffer area.
E. Design Standards For Regulated Slopes:
1. Construction areas must be delineated on the sensitive areas development plan and must indicate the boundaries of all intended development activities, including grading, excavation, and storage of construction materials. Accordingly, construction areas must be in concert with required grading plans. Except for driveways and utilities installation, no grading or excavation is allowed outside the construction area.
2. Except for commercially or industrially zoned properties, construction areas on lots containing protected slopes must be of a size equal to at least forty percent (40%) of the minimum lot size required by the zone in which it is located. (For example, the construction area for a lot in an RS-5 zone must be at least 3,200 square feet, which is 40 percent of the 8,000 square foot minimum lot size.)
3. Designated construction areas must not extend into protected slopes or protected slope buffers unless expressly permitted according to the provisions of this section.
4. Encroachment of construction areas into steep and critical slopes must be minimized. If disturbance of more than thirty five percent (35%) of critical slopes is proposed a level II sensitive areas review is required.
5. Any area designated as a natural protected slope (40+ percent) must not be graded and must remain in its existing state, except natural vegetation may be supplemented by other plant material.
6. Development activities may be allowed within areas containing "altered protected slopes", as defined in this section. In such cases, a level II sensitive areas review is required. Approval will be based on the following criteria:
a. A geologist or professional engineer must demonstrate to the satisfaction of the city that development activity will not undermine the stability of the slope; and
b. The city further determines that the proposed development activities are consistent with the intent of this article.
7. Cut slopes must be constructed to eliminate sharp angles of intersection with the existing terrain and must be rounded and contoured as necessary to blend with existing topography to the maximum extent possible. The city will not accept the dedication and maintenance of cut and fill slopes, except those within the required street right of way.
8. Street rights of way and public utility corridors must be located so as to minimize cutting and filling.
9. To maintain the stability of ungraded areas, existing vegetation must be retained to the maximum extent possible, and additional plantings to stabilize the slope may be allowed. (Ord. 05-4186, 12-15-2005)