2701 ROCKEFELLER AVE NIMBUS Geotech Report 2023-12-29

OpportundytZone Development LLC JN 19152 June 6, 2019 Page 5 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 Gods (IBC), the she class within 100 feet of the ground surface is best represented by Site Class Type C (Very Dense Soil and Soft Rock). As noted in the USGS website, the mapped spectral acceleration value for a 0.2 second (Sa) and 1.0 second period (Sr) equals 1.31g and 0.50g, respectively. The IBC and ASCE 7 require that the potential for liquefaction (soil strength loss) during an earthquake be evaluated for the peak ground acceleration of the Maximum Considered Earthquake (NICE), which has a probability of occurring once In 2,475 years (2 percent probability of occurring In a 50-year period). The VICE peak ground acceleration adjusted for site class effects (FEW equals 0.54g. The soils beneath the site are not susceptible to seismic liquefaction under the ground motions of the VICE because of their dense nature and the absence of near -surface groundwater. CONVENTIONAL FOUNDATIONS The proposed structure can be supported on conventional continuous and spread footings bearing on undisturbed, dense to very dense silty sand (glacial till) and sand (glacial outwash); it appears mostly that the footings will reach the lower sand. soil. 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 h 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. Thickened slabs are often used to support Interior walls In multifamily and commercial structures. It is important to remember that thickened slab areas support building loads, just like conventional footings do. For this reason, the subgrade below thickened slabs must be prepared in the same way as for conventional footings. All unsuitable soils have to be removed and any structural fill compacted In accordance with the recommendations of this report. We recommend against the use of thickened slabs for most projects, particularly single-family residential, as it is difficult to ensure that the subgrades have been appropriately prepared. Also, the compacted slab fill has to be protected from disturbance by the earthwork, foundation, and utility contractors. An allowable bearing pressure of 8,000 psi is appropriate for footings on the very dense soils. A one-third increase in these design bearing pressures may be used when considering short-term wind or selsmlc loads. For the above design criteria, It is anticipated that the total post -construction settlement of footings founded on competent native soil will be about one-half Inch, with differential settlements on the order of one-half Inch in a distance of 50 feet along a continuous footing with a uniform load. Lateral bads due to wind or seismic forces may be resisted by friction between the foundation and the bearing soli, or by passive earth pressure acting on the vertical, embedded portions of the GEOTECH CONBULTANTs, INC.