3530 COLBY AVE COCOON HOUSE Geotech Report 2022-10-25

Cocoon House JN 16422 November 3, 2016 Page 4 is necessary to periodically maintain or modify temporary erosion control measures to address specific site and weather conditions. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied areas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a build up of excessive water vapor within the planned structure. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. We recommend including this report, in its entirety, in the project contract documents. This report should also be provided to any future property owners so they will be aware of our findings and recommendations. SEISMIC CONSIDERATIONS In accordance with the International Building Code (IBC), the site class within 100 feet of the ground surface is best represented by Site Class Type D (Stiff Site Soils). As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (Se) and 1.0 second period (Si) equals 1.34g and 0.51g, respectively. The site soils are not susceptible to seismic liquefaction because of their dense nature. This statement regarding liquefaction includes the knowledge of the peak ground acceleration that is anticipated under a 1-in-2,500-year seismic event, which is significantly higher than the above- calculated ground acceleration. CONVENTIONAL FOUNDATIONS The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, competent, medium-dense to dense, native soil, or on structural fill placed above this competent native soil. See the section entitled General Earthwork and Structural Fill for recommendations regarding the placement and compaction of structural fill beneath structures. Adequate compaction of structural fill should be verified with frequent density testing during fill placement. Prior to placing structural fill beneath foundations, the excavation should be observed by the geotechnical engineer to document that adequate bearing soils have been exposed. We recommend that continuous and individual spread footings have minimum widths of 16 and 24 inches, respectively. Exterior footings should also be bottomed at least 18 inches below the lowest GEOTECH CONSULTANTS, INC.