(Amended by Ord. No. 171,939, Eff. 4/15/98.)
91.7011.1. Height. (Amended by Ord. No. 185,587, Eff. 7/16/18.) No fill slope shall exceed a vertical height of 100 feet (30.48 m) unless horizontal benches with a minimum width of 20 feet (6.096 m), as shown in Figure D of this division are installed at each 100 feet (30.48 m) of vertical height.
91.7011.2. Slope. (Amended by Ord. No. 171,939, Eff. 4/15/98.) No fill shall be made which creates an exposed surface steeper than one unit vertical in two units horizontal (50% slope). The fill slopes abutting and above public property shall be so placed that no portion of the fill lies above a plane through a public property line extending upward at a slope of one unit vertical in two units horizontal (50% slope).
EXCEPTION: The Department or the Board in case an appeal is made to it under LAMC Section 91.105 may permit a fill to be made which creates an exposed surface steeper in slope than 1 unit vertical in 2 units horizontal (50% slope), provided: (Amended by Ord. No. 185,587, Eff. 7/16/18.)
1. The use of the steeper slope is determined to be necessary due to special design limitations on the site,
2. The gradient does not exceed one unit vertical in one and one-half units horizontal (66.7% slope) and
3. The applicant shows through investigation, subsurface exploration, analysis and report by both a soils engineer and an engineering geologist, to the Department’s satisfaction, that the fill to be used and the underlying bedrock or soil supporting the fill have strength characteristics sufficient to produce a stable slope with a minimum factor of safety not less than 1.5 for static loads. The soils engineer shall verify by necessary testing and observation and shall certify attainment of the required strength characteristics in the fill materials as specified in the approved report.
91.7011.3. Compaction. (Amended by Ord. No. 180,619, Eff. 5/12/09.) All manufactured fills shall be placed on natural undisturbed material or approved compacted fill. Fills shall be compacted throughout their full extent to a minimum relative compaction of 90 percent of maximum dry density within 40 feet (1219 mm) below finish grade and 93 percent of maximum dry density deeper than 40 feet (1219 mm) below finish grade, unless a lower relative compaction (not less than 90 percent of maximum dry density) is justified by the soils engineer. The relative compaction shall be determined by ASTM soil compaction test D1557. Every manufactured fill shall be tested for relative compaction by a soil testing agency approved by the Department. A compaction report including a Certificate of Compliance setting forth densities so determined shall be submitted to the Department for review before approval of any fill is given. For slopes to be constructed with an exposed slope surface steeper than two horizontal to one vertical, compaction at the exposed surface of the slope shall be obtained either by overfilling and cutting back the slope surface until the compacted inner core is exposed, or by compacting the outer horizontal ten feet of the slope at least 92 percent of relative compaction.
Prior to permitting building on deep fills of 40 feet or more, the Department may require the determination of the settlement characteristics of the fills to establish that any movements have substantially ceased. In those cases, a system of benchmarks shall be installed at critical points on the fill and accurate measurement of both horizontal and vertical movements shall be taken for a period of time sufficient to define the settlement behavior. In no case shall the period of time be less than one year, with at least four consecutive checks made at intervals of three months.
1. The Department may approve uncompacted fill in self-contained areas where the fills are not to be used to support buildings or structures and no hazard will be created.
2. Fill material placed in areas within cemeteries used or to be used for internment sites shall be compacted to a minimum of 80 percent, unless the fill is placed on a slope steeper than three horizontal to one vertical, or placed on slopes adjacent to public properties or private properties in separate ownership, or is to be used to support buildings or structures, in which cases it shall be compacted to a minimum of 90 percent.
3. Compaction report is not required for gravel backfill behind retaining walls provided the following conditions are met:
A. The retaining wall does not exceed ten feet in height.
B. The maximum distance between the retaining wall and the backcut shall not exceed 36 inches. (Amended by Ord. No. 186,488, Eff. 12/27/19.)
C. The gravel backfill shall be mechanically compacted and covered with concrete pavement or be capped with a 24-inch thick soil blanket mechanically compacted to the Department's satisfaction.
D. The gravel backfill does not provide vertical or lateral support for any structures or adverse bedding planes.
Where cohesionless soil having less than 15 percent finer than 0.005 millimeters is used for fill, it shall be compacted to a minimum of 95 percent relative compaction based on maximum dry density.
At cut-fill transition zones, there shall be a minimum of 3 feet (914 mm) of compacted fill at the cut pad area. The depth of fill shall be measured from the bottom of the deepest footings and extend horizontally throughout the cut pad area under the building and extend a minimum of 3 feet (914 mm) beyond exterior footings.
91.7011.4. Fill Slopes. Fill slopes shall be prepared for planting in one of the following three ways:
1. The slope surface of fills may be prepared for planting by casting topsoil over the slope surface. The topsoil layer shall not exceed three inches (76 mm) in depth.
2. The slope surface may be scarified to a depth not to exceed three inches (76 mm).
3. Loose material not to exceed three inches (76 mm) in depth may be left on the slope.
91.7011.5. Toe of Fill Slope. The toe of fill slope shall be made not nearer to a site boundary line adjoining other private properties than one half the height of the fill slope with a minimum of two feet (610 mm) and a maximum of 20 feet (6096 mm).
In the event retaining walls are constructed to retain fill, the height of the fill shall be measured from the elevation of the fill behind the wall and the setback distance may be measured from the face of the wall to the boundary line.
Setback dimensions shall be horizontal distances measured perpendicular to the site boundary. Setback dimensions shall be as shown in Figure E of this division. (Amended by Ord. No. 185,587, Eff. 7/16/18.)
91.7011.6. Old Fills. (Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.) All manufactured fills, whether compacted or not, which were placed prior to April 25, 1963, shall be investigated by the soils engineer to determine their suitability for the proposed use before any approval to build is issued.
91.7011.7. Combined Cut and Fill Slopes. Where a combined cut and fill slope exceeds 25 feet (7620 mm) in height, the required drainage bench shall be placed at the top of the cut slope. The effect of surcharge of the fill upon the cut bedrock shall be considered by the soils engineer and engineering geologist, and specific recommendations shall be made relative to the setback between the cut and fill.
91.7011.8. Fill Areas. Areas on which fill is to be placed shall be investigated by the soils engineer, or by the soils engineer and geologist to determine if they are adequate to support the fill without undue detrimental consolidation. Slopes exceeding one unit vertical in five units horizontal (20% slope) shall be benched prior to placing fill.
EXCEPTION: The Department may waive this investigation where it determines by inspection that the underlying material is adequate to support the proposed fill.