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• April 29,2015 <br /> HWA Project No.2014-162-21 <br /> There are several alternatives for replacement or remediation of the existing rockery walls. <br /> However, we recommend that the existing lower rockery be removed and replaced with newly <br /> constructed rockery that is designed to resist anticipated seismic forces. The newly constructed <br /> rockery should be constructed as shown in the typical rockery detail, Figure 4. Replacing the <br /> existing rockeries with newly constructed and better quality rockeries will be the most <br /> economical, as well as fastest and thus least disruptive approach. Rockery demolition and <br /> reconstruction should be done in segments, such that the entire cut is not exposed at once. The <br /> new rockeries should be built in general accordance with Associated Rockery Contractors (ARC) <br /> guidelines, if not already defined in City code. Specific recommendations associated with <br /> replacement of the existing rockeries are provided in the sections below. <br /> Rock Material <br /> Rock quality is an important factor in rockery wall performance. Numerous rockery wall <br /> failures occur because of degradation of poor quality rocks under freeze-thaw and weathering <br /> conditions. Rock should be obtained from an established source that has demonstrated it <br /> produces suitable rock and has been approved by the Engineer. The rock shall be visibly <br /> assessed upon delivery to verify it is free from fractures, clay seams and evidence of weathering. <br /> The rock should be tested for quality as specified in the table contained in WSDOT Standard <br /> Specification Section 9-13.1(1) (WSDOT, 2014). The size categories for rock should be as <br /> prescribed in Table 2: <br /> Table 2. <br /> Minimum Rock Size Categories for Facing Height <br /> Wall Height Embedment Base Block Top Block Batter <br /> (feet) Depth Size Size <br /> 4-9 24 inches* 5-man 3-man Match Existing <br /> Max 1 H : 3V <br /> *Embedment of bottom rock should be measured from the top of the existing cast in place concrete wall to the base <br /> of the subgrade excavation. <br /> Quarry Spalls <br /> Drainage filter material composed of 2 inch to 4 inch quarry spalls shall be placed between the <br /> face of the native soil and the rear of the rock facing. The thickness of the drainage filter layer <br /> should be at least 6 inches. <br /> 2014-162 Letter Report 6 HWA GEOSCIENCES INC. <br />