4945 OCEAN AVE 2018-01-02 MF Import

GEOTECHNICAL ENGINEERING STUDY Mr. Rick Remsing E-10558 May 5, 2003 Page 8 Slab -on -Grade Floors Slab -on -grade floors may be supported on competent native soil subgrade or on structural fill. Disturbed subgrade soil must either be recompacted or replaced with structural fill. Concrete slabs resting on soil ultimately cause the moisture content of the underlying soils to rise. This results from continued capillary rise and the ending of normal evapotranspiration. As concrete is permeable, moisture will eventually penetrate the slab resulting in a condition commonly known as a "wet slab" and poor adhesion of floor coverings. Therefore if slab moisture is a concern, the slab should be provided with a minimum of four inches of free -draining sand or gravel. In areas where slab moisture is undesirable, a vapor barrier such as a 6-mil plastic membrane may be placed beneath the slab. Two inches of damp sand may be placed over the membrane for protection during construction and to aid in curing of the concrete. Seismic Design Considerations The Puget Lowland is classified as a Seismic Zone 3 in the 1997 Uniform Building Code (UBC). Earthquakes occur in the Puget Lowland with regularity, however, the majority of these events are of such low magnitude they are not detected without instruments. Large earthquakes do occur, as indicated by the 1949, 7.1 magnitude earthquake in the Olympia area, the 1965, 6.5 magnitude earthquake in the Midway area, and the 6.8 magnitude earthquake of February 28, 2001, in the Olympia area. There are three potential geologic hazards associated with a strong motion seismic event at this site: ground rupture, liquefaction, and ground motion response. Ground Rupture The strongest earthquakes in the Puget Lowland are widespread, subcrustal events, ranging in depth from thirty (30) to fifty-five (55) miles. Surface faulting from these deep events has not been documented to date. Therefore, it is ECI's opinion, that the risk of ground rupture during a strong motion seismic event is negligible. Earth Consultants, Inc.