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603284-001 <br />4.0 CONCLUSIONS <br />Based on the results of our study, it is our opinion that the project is feasible from a <br />geotechnical standpoint. The geologic/seismic hazards impacting the site can be <br />mitigated with proper design and construction. The following factors should be <br />considered: <br />• The site is mantled by undocumented artificial fill, which is underlain by Quaternary <br />age fluvial and floodplain deposits consisting predominately of silts, clays and sands. <br />• Subsurface materials at the site include unconsolidated sands, which are subject to <br />collapse in shallow trench-like exposures. The surficial stability of excavations will <br />be dependent upon the composition and cohesive characteristics of the material <br />exposed in the cut. <br />• Evidence for active faulting was not encountered during our field exploration. Our <br />review of the geologic literature (Appendix A) indicates there are no known active <br />faults on or in the immediate vicinity of the site. Accordingly, the potential for surface <br />rupture at the site is considered low. <br />• The main seismic hazard that may impact the site is ground shaking. The nearest <br />known active Type A fault, located 28 miles (45 kilometers) from the site, is the <br />Sierra Madre fault, which is capable of producing a 7.0 Mw event along the mountain <br />front. The nearest active-zoned Type B fault, located 8.6 miles (13.9 kilometers) <br />from the site, is the NIFZ, capable of producing a 6.9 Mw earthquake. <br />• Liquefaction-induced settlement is expected to take place in relatively thin layers at <br />depths generally greater 20 feet bgs. As such, surface manifestation of liquefaction <br />is deemed unlikely. Seismically-induced settlement at is expected to be between 1 <br />to 2 inches. Seismically-induced differential settlement is expected to be about <br />16 inch over a horizontal distance of 100 feet. <br />• Perched and regional groundwater were encountered during the exploration at <br />depths between 25 and 40 feet bgs. Groundwater is not expected to impact <br />construction. <br />• Based on the results of our site exploration and laboratory testing, near surface <br />expansive soils are not likely to be encountered at the site. <br />-17- <br />Leighton