3535 RIVERFRONT BLVD Geotech Report 2023-02-22

September 24, 2018 HWA Project No. 2015-061-21 Pin Pile Option Pin piles can be installed using a vibratory impact hammer operating on the boom of an excavator. The pin piles are driven into the ground until they are deep enough to develop the required design load capacity. We recommend that 6-inch diameter, galvanized, Schedule 80 (extra strong), steel pipes be used for this project. The pin piles must penetrate all the existing fill and organic soils and be embedded into the underlying very dense sands. We anticipate that the pin piles will develop sufficient load-carrying g capacity with about 20 to 30 feet of penetration into the very dense alluvial sands (approximate total pile length of 60 to 70 feet). It is our understanding that the picnic shelter is currently to be constructed as part of future phases of park development but the associated foundations are to be installed ' within the limits of concrete flat work that is to be installed as part of the Phase 1 development. To avoid damage to the proposed concrete flat work, we recommend that the pin pile foundations and associated pile caps of the picnic shelter be installed as part of the Phase 1 project. To avoid damage to the at grade supported flat work surrounding the pile-supported shelter foundations, we recommend that expansion joints be placed within the concrete flatwork around the perimeter of the underlying pile cap. This will allow for easy reconstruction of the concrete around the shelter foundations as the surrounding flat work settles over time due to long-term settlement of the underlying ' organic soils. Each pin pile should be driven to"refusal," which is defined as a minimum penetration during a specified time of driving (e.g., less than 1 inch of penetration during 60 seconds of driving). The driving criteria are determined based on the impact hammer used, pile size, site soil conditions, and load testing. The driving criteria is generally set by the pile driving contractor with pile load testing to confirm the desired capacity is achieved. Based on our experience and available design guidelines, 6-inch diameter pin piles driven sufficiently into the dense alluvial soils, will be capable of developing allowable axial compressive loads of 15 tons each, with an acceptable factor of safety. We recommend P P load testing be performed on a minimum of 3% of the piles up to 5 piles maximum (1 Iminimum), to verify axial capacity and to establish an acceptable driving criteria. The test piles should be tested in accordance with the Quick Load Test Method described in test method ASTM D 1143-81, under the direction of a qualified geotechnical engineer. All pin piles should be driven under the observation of the geotechnical engineer. If the refusal penetration resistance is not achieved with 30 feet of embedment into the very dense alluvial soils (70 feet below ground surface) the pile driving should be stopped to allow the pore water pressures to dissipate around the pile. Redriving of the stopped pil es should occur a minimum of 24 hours after initial pile driving to determine if sufficient set up has occurred to provide the desired capacity. If sufficient setup does not occur, the pile will need to be driven deeper. Final Geotechnical Report-3-Acre Park.docx 17 HWA GeoSciences Inc.