A. The area on which fill is to be placed shall be cleared of all vegetation, such as trees, logs, stumps, and roots of trees, brush, heavy growth of grass and weeds, and any other objectionable material, such as debris, concrete foundations, metal, or nonearthen materials which cannot be properly consolidated or will not support the load of the embankment or structures. The cleared area shall extend to a width of two feet outside the area to be filled. All trees, existing stumps and large roots shall be removed, except that within the area where fills will be three feet or more in height, trees may be cut flush with the existing ground and grubbing of the remaining stumps will not be required except at locations where sub-drainage, trenches, drain pipes, foundations or other structures are to be constructed or where unsuitable material is to be removed before construction of the embankment.
B. The existing ground shall be prepared to receive fill construction by:
1. The installation of subdrains to intercept and dispose of waters from springs, aquifers, or other underground sources of water; and storm drains to intercept and dispose of surface waters where required on approved plans.
2. Compacting the ground area upon which any embankment is to be constructed to a minimum relative compaction of ninety percent throughout the top six inches.
C. Embankment fills shall not be constructed upon natural ground slopes which are steeper than five horizontal to one vertical unless such embankments are keyed into the natural ground; and the native material together with the fill material shall be recompacted to a relative compaction of ninety percent. The width of the steps for keying new embankments to existing slopes shall be the width of the compaction equipment plus five feet but not less than ten feet. The construction operation shall be such that a slip plane is not created between the original material and the newly compacted material.
D. Fill slopes shall be no steeper than necessary, but shall in no case be steeper than two feet horizontal to one foot vertical.
E. No fill slope shall be higher than thirty feet unless approved by the public services director.
F. Except as noted below for rock fill, material for embankments and backfill for excavations, slides, walls and other structures shall be spread in layers not exceeding eight inches in loose thickness before compaction, and each layer shall not be compacted to a relative compaction of not less than ninety percent.
G. The side slopes of all embankments shall be compacted by means of tampers or rollers to a minimum of eighty-five percent relative compaction.
H. When fill material includes rock, individual rocks shall not be greater than three feet in greatest dimension, and no rock larger than six inches in greatest dimension will be permitted closer than eighteen inches below finished grade of the embankment. No large rocks will be permitted to nest, and all voids shall be filled with earth or other fine material and properly compacted.
I. At the time of compaction, the moisture content of the embankment material shall be such that the relative compaction specified may be obtained with the compacting equipment being used. Water shall be added in the required amount to obtain the optimum moisture content for achieving maximum density. Compaction of embankment material which contains excessive moisture shall be delayed until material has been allowed to dry to such an extent that the relative compaction specified may be produced with the compacting equipment being used.
J. Sufficient field tests to determine the relative compaction of the ground and embankment material shall be taken and shall be reported to the city.
K. The top and bottom of fill slopes shall not be closer than three feet to the site boundary.
L. Slopes less than thirty percent shall require six inches of topsoil on all unpaved areas. Topsoil shall satisfy the requirements specified in Section 15.36.260 D of this chapter. (Ord. 535 §2(part), 1990; Ord. 486 (part), 1986).