A. The slope of cut surfaces shall be no steeper than is safe for the intended use and shall be no steeper than two horizontal to one vertical (2:1), unless a design professional can demonstrate to the planning director substantial evidence that steeper slopes are feasible, taking into account safety, stability, erosion control, revegetation and overall water quality impacts. Subsurface drainage shall be provided as necessary for stability. All engineering reports are subject to review by the planning director or designee.
B. Fill slopes shall be no steeper than is safe for the intended use and shall be no steeper than two horizontal to one vertical (2:1), unless a design professional can demonstrate to the planning director substantial evidence that steeper slopes are feasible, taking into account safety, stability, erosion control, revegetation and overall water quality impacts. Fill slopes shall not be constructed on natural slopes of forty percent (40%) (21/2 horizontal to 1 vertical) or steeper, without special treatment or design. In addition, the toe of fill slopes shall not be closer to the top of existing or planned downhill cut slopes than the height of that cut (e.g., if an 8 foot cut is planned, the toe of the uphill fill slope shall not be closer than 8 feet to the top of that cut), unless the design professional has demonstrated that comparable stability can be achieved with lesser setbacks.
C. Prior to placement of fill, the ground surface shall be prepared to receive fill by removing vegetation, topsoil, forest duff and any other unsuitable material. The area to receive fill shall be scarified to provide a bond with the new fill. Fill shall not be placed until the area is prepared by constructing a level or slightly insloped toe bench into competent material at the base of the new fill. The planning director may waive the benching requirement for minor fills which are not intended to support a road, driveway or structure where the project design professional provides adequate evidence the fill is not at risk for slippage or movement. In high risk areas where slopes exceed fifteen percent (15%), or where highly erosive soils, seepage areas or known areas of subsidence exist, the position, width and configuration of the bench shall be determined by a design professional. Fill slopes and the transition zone into natural terrain shall be configured to a generally smooth, planar configuration so that runoff traverses the area as sheet flow and is not concentrated. Fill material shall be composed of mineral soil that is free of organic material. Roadway fills shall be placed in lifts and compacted to a minimum of ninety five percent (95%) of the maximum density as determined by the AASHTO T-99 or ASTM D-698 compaction procedure, or as specified in the design professional's report.
D. Except where roads or driveways cross property lines, the tops and toes of cut and fill slopes shall be set back from property boundaries one-half (1/2) of the height of the slope with a minimum of five feet (5') and a maximum of twenty feet (20'), unless a design professional has demonstrated to the planning director that smaller setbacks provide a sufficient measure of safety and stability for activities which may occur on adjacent property.
E. Terracing shall be required on all cut or fill slopes which exceed fifty feet (50') in height. Spacing, width and drainage requirements of the terrace shall be determined by a design professional. (Ord. 501, 11-18-2008)