(a) Height. No finished fill slope shall exceed a vertical height of twenty-five (25') feet unless approved by the Planning Commission or City Council. If a fill 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 also may be required as set forth in subsection (e) of this section.
(b) Slope. No fill shall be made which creates any exposed surface steeper in slope than two (2) horizontal to one vertical.
Exceptions:
(1) The City Engineer may authorize a fill slope which is steeper in slope than two (2) horizontal to one vertical and is less than 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.
(2) The Planning Commission or City Council may authorize a fill 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. The City Engineer may require that the fill be constructed with an exposed surface flatter than two (2) horizontal to one vertical if, under the particular conditions, such flatter surface is necessary for stability or safety.
(d) Fill slope limits. Toes of fill slopes shall not be made nearer to a project boundary line than one-half (1/2) of the height of the fill but need not exceed a horizontal distance of twenty (20’) feet. Fill slopes shall not be divided horizontally by property lines, and fill slopes occurring on a side or rear lot line shall be made a part of the downhill lot. If the City Engineer determines 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 terraces, 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 vertical intervals of thirty (30’) feet; provided, however, for slopes less than forty (40’) feet in vertical height, the terraces shall be approximately at mid-height. For slopes flatter than two (2) horizontal to one vertical, or where soil conditions require, additional intervening terraces may be required.
(f) Compaction. All fills shall be placed, compacted, inspected, and tested in accordance with the provisions of this subsection. If the strict enforcement of the provisions of this subsection is determined by the City Engineer to be unnecessary because of the proposed or probable use of the land, he may waive the requirements. The requirements of this subsection shall not be waived when structures are to be supported by the fill, or if the fills are being placed in areas to be designated as hillside, or where they are necessary as a safety measure to aid in preventing the saturation, settling, slipping, or erosion of the fill.
(1) The natural ground surface shall be prepared to receive fill by removing vegetation, noncomplying fill, top soil, and/or porous, compressible soil. Where natural slopes are five (5) horizontal to one vertical or
steeper, and the height of the fill is twenty (20') feet or greater, benching into sound bedrock or other competent material shall be required. Fill slopes which toe on natural slopes shall be provided with adequate drainage.
(2) No deleterious material shall be permitted in fills. Except as otherwise permitted by the City Engineer, no rock or similar irreducible material with a maximum dimension greater than eight (8”) inches shall be buried or placed in fills.
Upon recommendations made by a soils engineer and approved by the City Engineer prior to the grading of any project, rock with dimensions from eight (8”) inches to thirty-six (36”) inches may be placed in compacted fill. Such oversized rocks shall not be in the upper ten (10’) feet of compacted fill or nearer than twenty (20’) feet to the surface of any fill slope. Such rock areas shall be shown on “as built” plans and certified to be compacted by the soils engineer.
(3) The fill shall be spread in a series of layers, each not exceeding eight (8”) inches in thickness, and shall be compacted by an approved method after each layer is spread.
(4) The moisture content of the fill material shall be controlled at the time of spreading and compacting to obtain the required relative compaction and avoid excessive pore pressure as the fill increases in depth.
(5) All fills shall be compacted to a minimum of ninety (90%) percent of the maximum density as determined by A.S.T.M. D 1557-66T, Method A or C, modified to three (3) layers. If the required degree of relative compaction cannot be attained on sloped surfaces, the slope shall be cut back until the compacted inner core is exposed.
The field density shall be measured in accordance with the procedure specified in A.S.T.M. D 1556-58T, or a later revision, using the optional base plate and making a suitable adjustment for volumes of rocks in the test hole or other approved testing methods giving equivalent test results.
(6) A field density test, as set forth in subsection (5) of this subsection, shall be taken for each eighteen (18”) inches of fill, or portion thereof, measured vertically from the lowest point of the area to be filled, or for each one thousand (1,000) cubic yards of fill placed. In addition, in the case of subdivisions, at least one field density test shall be taken on each lot which receives fill.
(7) All fills regulated by the provisions of this chapter shall be tested for relative compaction by the soils engineer. A certificate of compliance with the terms of this section and the grading permit, setting forth densities, relative compaction, the expansive soil report, allowable bearing value, and other soil characteristics, shall be prepared and signed by the soils engineer. Such report shall be submitted to, and be approved by, the City Engineer before any final approval of the fill is given and before any foundation construction begins.
(8) If building is not commenced within one year following the final certification and approval by the City Engineer, a reevaluation as to the adequacy of the intended use and a report shall be filed with the City Engineer for approval. Such report shall contain data on compaction, stabilization, and expansive soils.
(g) Fills toeing out on natural slopes. Fills toeing out on natural slopes which are steeper than two (2) horizontal to one vertical shall not be permitted.
(h) Combined cut and fill slopes. Combined cut and fill slopes shall meet the requirements of subsections (a), (b), (c), and (d) of this section insofar as steepness, height, and benching are concerned except that, where the slope exceeds twenty-five (25’) feet in height, the required drainage bench shall be placed at the top of the cut slope.
Fill placed on or above the top of an existing or proposed cut or natural slope steeper than three (3) horizontal to one vertical shall be set back from the top of the slope a minimum distance of six (6’) feet.
(i) Existing fills. All existing man-made fills on any and all sites shall be properly evaluated, and, if deficiencies exist, recommendations and design criteria for corrective measures shall be included within the soils engineering report.
(j) Progress reports.
(1) Periodic soils reports by a soils engineer certifying the compaction or acceptability of all fills may be required. Such reports shall include, but need not be limited to, the inspection of cleared areas and benches prepared to receive fill and the removal of all soil and unsuitable materials, the bearing capacity of the fill to support structures, the placement and compaction of fill materials, and the inspection of buttress fills, subdrains, and similar devices. The frequency of such reports shall be at the discretion of the City Engineer and shall be a condition of the grading permit.
(2) The City Engineer may require sufficient inspections by an engineering geologist to ensure that all geologic conditions have been adequately considered. Where geologic conditions warrant, the City Engineer may require periodic geologic reports. Such inspections and reports may be required to include, but need not be limited to, the inspection of cut slopes, canyons during clearing, operations for groundwater and earth material conditions, benches or keys prior to the placement of fill, and possible underground water spring locations.
(k) Measure of settlement. On fills of forty (40') feet or more, if recommended by the soils engineer, the City Engineer or the Building Official may require the determination of the settlement characteristics of such fills to establish that any movements have substantially ceased.
In such cases, a system of bench marks shall be installed by a civil engineer or land surveyor at critical points on the fill, and accurate measurements of both horizontal and vertical movements shall be taken and evaluated by the soils engineer for a period of time sufficient to define the settlement behavior. The evaluation period shall in all cases include the period from November 1 through April 15 (the rainy season).
(§ 2, Ord. 156-NS, eff. August 27, 1970, as amended by § I, Ord. 534-NS, eff. June 19, 1975, and § 2, Ord. 1098-NS, eff. April 11, 1991)