The following standards for grading and erosion and sedimentation control (subsections A and B of this section) apply to all excavation and grading activity, regardless of whether a permit is required.
A. Grading:
1. 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 the design professional can demonstrate to the Administrator substantial evidence that steeper slopes are feasible, taking into account safety, stability, erosion control, revegetation, maintenance, and overall water quality impacts. Subsurface drainage shall be provided as necessary for stability. All engineering reports are subject to review by the Administrator.
2. 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 the design professional can demonstrate to the Administrator substantial evidence that steeper slopes are feasible, taking into account safety, stability, erosion control, revegetation, maintenance, and overall water quality impacts. Fill slopes shall not be constructed on natural slopes of two to one (2:1) 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.
3. 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. Fill shall not be placed until the area is prepared by constructing a level bench into competent material at the base of the new fill. The Administrator may waive the benching requirement for minor fills which are not intended to support a road, driveway, or structure. 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-180 or ASTM D-1557 compaction procedure, or as specified in the design professional's report.
4. 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 the design professional has demonstrated to the Administrator that smaller setbacks provide a sufficient measure of safety and stability for activities which may occur on adjacent property.
B. Erosion And Sedimentation Control:
1. Erosion and sedimentation control BMPs for all sites must be sufficient to prevent sediment from leaving the site.
2. Stabilized construction entrances and driveways Best Management Practices shall be required for all construction sites to prevent sediment tracking onto roadways. Parking of vehicles shall be restricted to paved or stabilized areas.
3. The erosion and sedimentation control BMPs must be installed or otherwise in effect, and the boundary of the area to be disturbed must be clearly marked, as indicated in the approved plan, prior to any site disturbance.
4. All surfaces where bare soil is exposed during clearing and grading operations, including spoil piles, shall be covered or otherwise protected from erosion.
5. The property owner, construction operator, contractor, and design professional shall be responsible for the design and construction of revised temporary erosion and sedimentation control if application of the approved plan fails. The applicant shall immediately notify the Administrator of alterations to plans.
6. All cut and fill slopes shall be revegetated or otherwise protected from erosion to the greatest extent possible.
C. Stormwater Detention And Conveyance:
1. Stormwater conveyance mechanisms must be sized to convey runoff from a 25-year storm event without causing flooding or other damage to public or private property, the stormwater management system, or other improvements.
2. Culvert size within public rights-of-way shall be determined by the public highway agency with jurisdiction. All other culvert sizing shall be done by an appropriate design professional.
3. Stormwater systems shall provide for sufficient storage volume and detention time to result in no increase in the peak rate of runoff from the site for a 25-year storm.
4. Runoff from impervious and pervious surfaces shall be considered in meeting this requirement.
D. Stormwater Treatment:
1. Treatment of the first one-half inch (1/2") of stormwater runoff from all impervious surfaces shall be required prior to discharge of the stormwater overland or to ground or surface waters. Roof runoff may be directly discharged to an infiltration BMP without treatment.
2. For development of public or private roads, stormwater shall be managed utilizing a combination of stormwater treatment and erosion control.
E. Ground Water And Springs: Springs and other ground water sources that are encountered during grading or excavation activity shall be returned to subsurface flow where possible or conveyed through the site by an appropriate means of conveyance that shall be nonerosive, avoids sediment transport, and dissipates energy, in accordance with the Best Management Practices guidelines. The construction operator must ensure that the ground water will not interfere with the implementation or function of the planned stormwater or erosion control improvements. (Ord. 256, 10-4-2018)