(A) No fill shall be made which creates any exposed surface steeper in slope than two horizontal to one vertical. The Engineer may require a fill to be constructed with an exposed surface flatter in slope if such flatter slope is determined to be necessary for stability and safety.
(B) Unless otherwise approved by the Engineer, no fill shall be made with materials other than clean soil or earth.
(C) No fill slope shall be constructed over 30 feet in height unless the Engineer has been furnished satisfactory evidence by a qualified geologist or soils engineer that such slope will be stable. Terraces not less than five feet in width shall be constructed in all fill slopes at the rate of one terrace for each 20 feet of height (or portion thereof) above 20 feet.
(D) All fills intended to support buildings or structures, or where otherwise required by the Engineer to be compacted for stability of material, shall be compacted, inspected and tested in accordance with the following provisions:
(1) All timber, logs, trees, brush, objectionable amounts of vegetable matter and other rubbish shall be removed from the site, so as to leave the area free from all debris. All soft, spongy or other unsuitable matter shall be removed to a depth required to produce a stable subgrade.
(2) The subgrade surface shall be scarified to a depth of at least six inches, if necessary to free the surface from ruts, hummocks or other uneven features which would tend to prevent uniform compaction by the equipment to be used.
(3) Where fills are made of slopes greater than one vertical to five horizontal, steps or benches shall be cut in the original ground before filling operations begin. The design of such steps or benches shall be subject to review and approval by the Engineer.
(4) The prepared surface shall be compacted in the same manner and to the same degree as required for the fill material.
(5) The fill material shall be placed in layers having a maximum compacted thickness of six inches. Compaction shall be by sheepsfoot roller or other approved method.
(6) The moisture content of the fill material shall be controlled at the time of spreading and compaction to obtain the required maximum density.
(7) The fill material, after compaction, shall have a minimum density of 90%, as determined by the Modified AASHO Soil Compaction Test, or other approved testing method.
(8) A written report of the compaction as specified in
§ 15.28.120 shall be submitted to the Engineer for review and approval.
(E) The Engineer may request additional test information, or may modify or delete any of the above provisions, if the site conditions or materials so warrant. However, in no case shall the Engineer approve a slope steeper than that called for in this chapter without the Planning Commission first finding that the steeper slope would lead to an improvement in the overall quality of the development. A steeper slope may be permitted only if two reports prepared by registered soils engineers concur that minimum factors of safety exist for both surficial and gross stability. The cost of both reports shall be borne by the developer.
(`83 Code, § 15.28.180) (Ord. 85-11 § 1 (part), 1985)