1130 RAINIER AVE Geotech Report 2025-07-28

> Everett Housing Authority JN 12080 May 16, 2012 Page 4 • 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 soil profile within 100 feet of the ground surface is best represented by Site Class Type D (Stiff Site Class). As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (Ss) and 1.0 second period (Si) equals 1.15g and 0.40g, respectively. The IBC states that a site-specific seismic study need not be performed provided that the peak ground acceleration be equal to Sip8/2.5, where Sips is determined in ASCE 7. It is noted that Sips is equal to 2/3SMs. SMS equals Fa times Ss,where Fa is determined in Table 11.4-1. For our site, Fa = 1.04. Thus, the calculated peak ground acceleration that we utilized for the seismic-related parameters of this report equals 0.32g. The site soils are not susceptible to seismic liquefaction because of their dense nature and/or the absence of near-surface groundwater. CONVENTIONAL FOUNDATIONS As noted earlier, where overexcavation depths are not significant, the proposed structures can be supported on conventional continuous and spread footings bearing on undisturbed, medium-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 adjacent finish ground surface for protection against frost and erosion. The local building codes should be reviewed to determine if different footing widths or embedment depths are required. Footing subgrades must be cleaned of loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints, this may require removing the disturbed soil by hand. GEOTECH CONSULTANTS,INC.