(a) Height. Cut slopes shall not exceed a vertical height of twenty-five (25’) feet unless approved by the Planning Commission or City Council. If a cut slope is permitted above such height, a horizontal bench with a minimum width of twenty-five (25’) feet may be required to be installed at each one hundred (100’) feet of vertical height, and intervening terraces may also be required as set forth in subsection (e) of this section. Slope height shall be measured by taking the difference in the elevation of the top of slope and the toe of slope. The top of slope height shall be measured at the center of the radius where slope rounding to blend with natural terrain is employed.
(b) Slope. Excavations shall not be made with a cut face steeper in slope than two (2) horizontal to one vertical.
Exceptions.
(1) The City Engineer may authorize a cut slope which is steeper in slope than two (2) horizontal to one vertical, and has a slope height of less than six (6') feet, if:
(i) The applicant can demonstrate that because of special circumstances applicable to the property, including size, shape, topography, location, or surroundings, the strict application of this section would deprive such property of the ability to be reasonably developed; and
(ii) The applicant produces sufficient data from a soils engineer, an engineering geologist, and a landscape architect to demonstrate that the material of which the slope is composed and that the material underlying the slope is capable of permanent stability on a steeper slope, and that the required slope planting can be adequately maintained.
(2) The Planning Commission or City Council may authorize a cut slope which is steeper in slope than two (2) horizontal to one vertical and which exceeds six (6’) feet in height if:
(i) The applicant can demonstrate that because of special circumstances applicable to the property, including size, shape, topography, location, or surroundings, the strict application of this section would deprive such property of the ability to be reasonably developed; and
(ii) The applicant produces sufficient data from a soils engineer, an engineering geologist, and a landscape architect to demonstrate that the material of which the slope is composed and that the material underlying the slope is capable of permanent stability on a steeper slope, and that the required slope planting can be adequately maintained.
(c) Unstable material. If the material of the slope is of such composition and character as to be
unstable, considering all types of anticipated loading and moisture conditions, the engineering geologist and soils engineer shall, by testing and analysis, provide specific criteria for the stabilization of such material by the reduction of the slope angle, by buttressing, or by a combination of these or other means.
(d) Cut slope limits. Tops of cut slopes shall not be made nearer than one (1’) foot plus one-fifth (1/5) the height of the cut to the project boundary but need not exceed a horizontal distance of ten (10’) feet. Cut slopes shall not be divided horizontally by property lines, and cut slopes occurring on a side or rear lot line shall be made a part of the downhill lot. If the City Engineer determines that such requirement is unnecessary because of special conditions, he may make adjustments as a condition of the grading permit.
(e) Intervening terraces. Terraces shall be paved (concrete or gunite) terraces on cut slopes, shall have a minimum width of six (6’) feet, shall be extensively landscaped in accordance with an approved landscaping plan, and shall be spaced at intervals of thirty (30’) feet measured vertically. Where only one terrace is utilized, it shall be placed at approximate mid-height. For slopes flatter than two (2) to one, or where soil conditions warrant, additional intervening terraces may be required.
(f) Temporary excavations and shoring. Excavations shall not remove the lateral support from a public way or from an existing structure. For the purposes of this section, the lateral support shall be considered to have been removed when any of the following conditions exist:
(1) The excavation exposes any adverse geological formations which would affect the lateral support of a public way or of an adjacent structure.
(2) The excavation extends below a plane extending downward at an angle of forty-five (45) degrees from the edge of the public way.
Exception: Normal footing excavations not exceeding two (2’) feet in depth shall not be construed as removing lateral support.
(3) The excavation extends below a plane extending downward at an angle of forty-five (45) degrees from the bottom of a footing of an existing structure.
(g) Excavations adjacent to an existing structure or public way. Excavations adjacent to an existing structure or public way may be steeper than one horizontal to one vertical where either:
(1) A foundation investigation by a soils engineer recommending that the slope may be steeper than one to one has been approved by the City Engineer; or
(2) Temporary shoring is designed to support the excavation and plans are approved and a permit is issued by the City Engineer.
(i) The temporary shoring shall be designated for an earth pressure equivalent to that erected by a fluid weighing not less than thirty (30) pounds per cubic foot, plus all surcharge loads, or as recommended by a soils engineer and approved by the City Engineer.
(ii) The soil bearing values shall be those recommended by a soils engineer and approved by the City Engineer.
(iii) The design of the required temporary shoring and necessary underpinning shall include a sequence of construction and installation.
(iv) The allowable stresses used in the design of the temporary shoring may be increased thirty-three and one-third (33-1/3%) percent for structural and reinforcing steel and twenty-five (25%) percent for wood. No increase shall be permitted for concrete.
No action of the Council, Planning Commission, or City Engineer shall be construed to waive the requirements of the General Safety Orders of the Department of Industrial Relations of the State.
(§ 2, Ord. 156-NS, eff. August 27, 1970, as amended by § I, Ord. 534-NS, eff. June 19, 1975, and § 1, Ord. 1098-NS, eff. April 11, 1991)