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 6 | Page 5.0 DESIGN RECOMMENDATIONS 5.1 General Our geotechnical evaluation is based upon the previously presented project information as well as the field data obtained during this geotechnical exploration. If final structure or foundation loads are significantly different from those described or if the subsurface conditions during construction are different from those revealed by our boring, we should be notified immediately so that we might review our recommendations presented in this report. Our recommended site preparation is presented in Section 6.0, General Site Preparation. 5.2 Auger Cast Piles The proposed stage and playground roof structure should be constructed on 14-inch auger cast piles. We recommend the piles be installed to a depth of 35 feet below the existing ground surface. An allowable axial compression capacity of 35 kips and an allowable axial tension capacity of 20 kips can be used for design. Installing auger cast piles requires equipment consisting of a mobile base carrier fitted with a hollow-stem flight auger. The auger is drilled into the ground to the desired depth and then grout is pumped through the auger as it is extracted. A continuous flow of fluid should be observed at the ground surface during grouting. Reinforcement is placed after the pile is grouted. We recommend a load test be performed on a non-production pile to evaluate the performance of the pile installation equipment and to confirm the design allowable pile capacity. The test should be performed on a non-production pile test loaded to a minimum of two times the allowable compressive design capacity or to failure. Installation of production piles may proceed upon successful completion of the load test. Installation should be monitored by a geotechnical engineer or engineering technician working under the direction of a geotechnical engineer. 5.3 Settlement Settlement of pile supported structural elements should be small and tolerable for a typical foundation configuration. Based on the subsurface soil conditions encountered in the soil borings performed for this report and our past experience with similar soil conditions, we do not anticipate significant downdrag loads acting on the piles. 5.3 Floor Slab Design It is expected that the floor slab of the stage will be supported on compacted existing soils or structural fill. If site preparation is performed in accordance with the recommendations presented in this report, the modulus of vertical subgrade reaction (k) for the slab bearing soils is expected to be on the order of 150 pounds per square inch per inch of vertical deflection (pci). Our evaluation was based on satisfactory performance of our