Fills shall conform to the provisions of this section, unless the department approves the recommendations contained in a soils engineering report required under SCC 30.63B.230. The requirements of this section shall not apply to fills that are less than four feet in height and which are not intended to support structures.
(1) Fill slopes shall not be constructed on natural slopes steeper than one unit vertical to two units horizontal (50 percent slope). The slope of fill surfaces shall be no steeper than is safe for the intended use. The slope shall be protected pursuant to SCC 30.63A.445 and 30.63A.450. Fill slopes steeper than 33 percent shall require a geotechnical engineering report pursuant to chapter 30.62B SCC, as applicable.
(2) Fill material.
(a) Deleterious amounts of organic material shall not be permitted in fills. Except as permitted by the department under subsection (2)(b) of this section, no rock or similar irreducible material with a maximum dimension greater than 12 inches shall be buried or placed in fills.
(b) The department may allow rock greater than 12 inches in diameter to be buried or placed in fills when the soils engineer properly devises a method of placement, inspects the site during the placement of the rock, and approves the fill stability. The following conditions shall also apply:
(ii) Rock greater than 12 inches in diameter shall be located no less than 10 feet or more below the finish grade, measured vertically; and
(iii) Rocks or other similar irreducible material shall be placed so as to assure filling of all voids with well-graded soil.
(3) All fills intended to support structures or private roads shall be compacted to a minimum of 90 percent of maximum density. All fills within public rights-of-way, private tracts and easements shall be compacted in accordance with the EDDS. All fills in the floodplain shall be designed to resist or prevent scour and erosion from floodwaters. Fills in the floodplain shall be regulated pursuant to chapters 30.43C and 30.65 SCC. If fill is allowed in the floodplain, a zero-level rise analysis shall be performed and provided in the land disturbing activity permit application.
(4) Fill shall not be placed in streams, wetlands, lakes, marine waters, fish and wildlife habitat conservation areas, erosion hazard areas, landslide hazard areas or in the buffers of or setbacks from any of these areas unless a critical area study is prepared and mitigation is provided consistent with the applicable requirements of chapters 30.62A and 30.62B SCC. (Ord. 15-103 , 2016; Amended Ord. 13-042 , 2013; Amended Ord. 10-023 , 2010.)