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A. Fills which are intended for building sites shall be constructed in conformance with the requirements of the latest edition of the I.B.C., as adopted by Pierce County, and an assignment of allowable soil-bearing pressures will be under the jurisdiction of the Pierce County Building Official in accordance with the I.B.C.

B. Slopes shall be no steeper than is safe for the intended use and shall not be steeper than one and one half horizontal to one vertical, or as recommended by a soils Engineer. Fill sites must be approved by the Engineer as suitable locations for the proposed fill.

C. The ground surface for fills over five feet in height shall be prepared by removing vegetation, noncomplying fill, topsoil, and other unsuitable materials; scarifying to provide a bond with the new fill; and, where existing slopes are steeper than five horizontal to one vertical, by benching into competent material as determined by the Engineer. The bench under the toe of a fill on a slope steeper than 5 horizontal to 1 vertical shall be at least 10 feet wide or as recommended by a soils Engineer.

D. Except as permitted by the County, no material other than earth material shall be buried or placed in fills. Placement of other than earth material is regulated by State statutes or Federal laws, and additional permits may be required.

E. Fills shall be constructed using earth materials, compaction methods, and construction techniques so that stable fills are created.

F. The toe or catch point of fill slopes shall be set back from the site boundary line in accordance with the following table unless a retaining wall is designed by the Engineer and constructed for the project:

Fill Depth

Setback Distance

Under 5 Feet

2 Feet

5 – 40 Feet

Height of Fill/2

Over 40 Feet

20 Feet

G. Slopes constructed with fill shall be created in a manner such that a factor of safety of at least 1.5 is achieved for static conditions and at least 1.2 for seismic dynamic conditions. Analysis of dynamic (seismic) conditions shall be based on a minimum horizontal acceleration as established by the most current version of the Building Code as adopted by Title 17C PCC.

H. The proposed fill slopes shall not create the need for landslide hazard buffers or setbacks on neighboring properties unless approved through a notarized written agreement with the property owner.

I. Interior fill slopes for surface mining projects which are part of an active mining operation are exempt from the 1.5:1 maximum fill slope angle requirement as long as access into the mine is controlled via fencing or other security measures to discourage entrance to unauthorized persons. Interior slopes are those slopes that do not impact the theoretical slope face that is created by applying a 1:5 horizontal to 1 vertical angle and the required setbacks to the property line.

(Ord. 2008-59s § 2 (part), 2008; Ord. 2004-56s § 1 (part), 2004; Ord. 99-24S § 2 (part), 1999)