18.05.100 Topographic change (cut and fill) limits.
Cuts or excavations shall conform to the provisions of this section, unless the director approves alternative recommendations as contained in a peer-reviewed soils engineering report or engineering geology report. A cut that is less than four feet in height shall not be required to meet the requirements of this section.
A. The slope of cut surfaces shall be no steeper than one unit vertical to three units horizontal or a 33 percent slope.
The director, in consultation with the community development director, may approve an alternative maximum gradient that exceeds a one unit vertical to three units horizontal only when:
1. The applicant has provided a peer-reviewed soils engineering report stating that the site has been investigated and a qualified expert determines that a cut at a steeper slope will not create a geologically hazardous condition and will not create a hazard to public or private property; and
2. The directors determine the increased gradient either:
a. Reduces potential adverse impacts to a critical area or buffer as defined by Chapter 14.04 BMC;
b. Retains existing significant trees or other existing vegetation; or
c. Permits the installation of transportation improvements.
B. Slopes shall be stabilized after the cut or excavation operations cease. Further, during grading activities, erosion control consistent with the Bothell Standards is required. The soils engineering report or the engineering geology report, or both, shall verify that the slopes shall not be subject to ongoing erosion that would adversely impact public safety or public or private property. Erosion hazard areas and landslide hazard areas, as defined in BMC 14.04.800, shall be described, shown in the soils engineering report and protected or mitigated pursuant to BMC 14.04.800 through 14.04.880 or as recommended in the peer-reviewed soils engineering report.
C. Cuts or excavations within streams, wetlands, lakes, marine waters, fish and wildlife habitat conservation areas, erosion hazard areas, landslide hazard areas or the buffers of or setbacks from any of these areas shall not occur unless a critical area study is prepared and mitigation is provided consistent with the applicable requirements of Chapters 14.04 and 13.13 BMC.
D. Cut and fill slopes shall be designed in accordance with the following criteria:
1. Terraces at least six feet in width shall be established at not more than 25-foot vertical intervals on all cut or fill slopes to control surface drainage and debris, except that where only one terrace is required, it shall be at mid-height of the slope. Suitable access shall be provided to terraces to permit proper cleaning and maintenance of drainage facilities, if any;
2. Surface water swales or ditches on terraces shall comply with the Bothell Standards for minimum and maximum gradient;
3. Cut or fill slopes shall be provided with subsurface drainage consistent with the Bothell Standards to ensure slope stability and proper conveyance of groundwater;
4. All drainage facilities shall be designed to carry waters in a safe manner and shall comply with the Bothell Standards and all appropriate BMPs and construction procedures that prevent or minimize erosion pursuant to said Standards.
E. Interceptor drains shall be installed as required by the city engineer and shall be consistent with the Bothell Standards.
F. Retaining structures, including, but not limited to, rockeries, modular block walls, rock walls, or any other structures which retain soil, retain earth surcharge, protect an exposed soil face, or serve as a gravity retaining wall, rockeries, and cast-in-place walls, shall be consistent with Chapter 12.14 BMC.
G. Vegetation shall be installed on all cut and fill slopes in accordance with the landscape requirements of Chapter 12.18 BMC. (Ord. 2269 § 1, 2018).