3105 PINE ST 2018-01-01 MF Import

• Voth Brothers Construction, Inc. E-1201-1 October 20, 1980 Page 9 � Estimates of site seismic response are based on overburden ,� depth and the shear wave velocities of the materials in the soil mantle. The procedure used in UBC allows neglecting the soil " mantle below a depth of 500 feet. At the site, most of the soil above that depth is the Esperance sand. Shear wave velocities j4 in this material have been measured in a borehole 100 feet deep at Fort Lawton, where the soil profile is similar to that at the Everett site. At 0.001 percent shear straiti, the measured shear " wave velocities increased from about 1900 fps at the ground sur- face to 2000 fps at depth 100 feet. Shear wave velocities are known to increase with confining pressure. Based on published -, data, we have extrapolated the Fort Lawton shear wave velocities to obtain estimated values on the order of 2`�0 to 3000 fps at depth 500 feet. In addition, at the value of shear strain recom- mended by UBC, 0.0001 percent, shear wave velocities will be � higher than measured at Fort Lawton. We conclude that the aver- age shear wave velocities at the site in the depth interval above 500 feet are probably in the range of 2000 to 2500 fps. ' Using these values of shear wave velocity and the strain correc- tion factor recommended in UBCS No. 23-1, we estimate a charac- teristic site period of 1.2 to 1.5 seconds. We recommend using . a value of 1.35 seconds for design. ' Additional Services It is recommended that Earth Consultants, Inc. be provided ,� the opportunity for a general review of the final design and specifications in order that earthwork and foundation recommenda- i • tions may be properly interpreted and implemented in the design and construction. , The analyses and recommendations submitted in this report are based upon tha data obtained from the test pits and borings. '-� The nature and extent of variations between test pits and bor- ings may not become evident until construction. If variations the.� appear evident, Earth Consultants, Inc. should be allowed ._ to reevaluate the recommendations of this report prior to pro- ceeding with the construction. It is also recommended that Earth Consultants, Inc. be � retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifi- cations or recommendations and to allow design changes in the '� event subsurface conditions differ from those anticipated prior to the start of construction. � ,` Farth Consultanu, Inc. ... � —,