Attachment B - Report of Geotechnical Exploration Samson Oceanfront Park Revised

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Report of Geotechnical Exploration November 7, 2014 Samson Oceanfront Park AREHNA Project B-14-124 8 | Page 6.0 GENERAL SITE PREPARATION 6.1 General The initial step in site preparation should be the complete removal of all existing vegetation, topsoil, root systems, debris, and other deleterious materials from beneath and to a minimum of five feet beyond the development perimeter. Also, prior to construction, the location of any existing foundations, underground irrigation, septic tanks, drainage, or other utility lines within the construction area should be established. In this regard it should be noted that if underground pipes are not properly removed or plugged, they may serve as conduits for subsurface erosion which subsequently may result in excessive settlements. The structure areas should then be inspected and thoroughly proofrolled as directed by a Geotechnical Engineer. Our recommendations listed in this section should be used as a guideline for the project general specifications prepared by the Design Engineer:  The entire site should be proofrolled with a large vibratory roller with a 4 foot diameter drum and a static weight of at least 8 tons. At least 8 complete coverages (4 in each perpendicular direction) should be performed over the entire stage and playground areas prior to raising site grades. Careful observations should be made during proofrolling to help identify any areas of soft-yielding soils that may require over excavation and replacement. Careful observations should further be made to the adjacent buildings during proofrolling operations.  Following satisfactory completion of proofrolling, additional fill should be placed and compacted as needed to achieve the desired grades. Fill should generally consist of dry fine sand with less than 12 percent passing the No. 200 sieve and be free of rubble, organics, clay, debris and other unsuitable material. Fill should be tested and approved prior to acquisition.  Approved sand fill should be placed in loose lifts not exceeding 12 inches in thickness and should be compacted to a minimum of 95 percent of the Modified Proctor maximum dry density (ASTM D-1557). Foundation bearing soils should be compacted to a minimum of 95 percent of the Modified Proctor maximum dry density (ASTM D-1557). Density tests to confirm compaction should be performed in each fill lift before the next lift is placed.  Prior to beginning compaction, soil moisture contents should be adjusted in order to facilitate proper compaction. A moisture content within 2 percentage points of the optimum indicated by the Modified Proctor Test (ASTM D-1557) is recommended prior to compaction of the natural ground and fill.  Immediately prior to reinforcing steel placement, it is suggested that the bearing surfaces of all floor slab areas be compacted using hand-operated mechanical tampers. In this manner, any localized areas which have been loosened by excavation operations should be adequately re-compacted.