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Pocock Racing Shells September 15, 2016 JN 16391 Page 3 outside of the work area. Soil and mud should not be tracked off the site, and silty runoff should be prevented from leaving the property. The dense to very dense, glacially -compressed soils beneath the site are essentially impervious. This makes on -site infiltration of storm water infeasible. 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 C (Very Dense Soil Class). The dense soils are not susceptible to seismic liquefaction under the Maximum Considered Earthquake (MCE), which has a theoretical probability of 2 percent in 50 years (once in 2,475 years). CONVENTIONAL FOUNDATIONS We recommend that new 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. An allowable bearing pressure of 3,500 pounds per square foot (psf) is appropriate for footings supported on competent native soil. This can also be assumed for existing perimeter foundations that surround the existing concrete slab in the western portion of the planned addition. A one-third increase in this design bearing pressure may be used when considering short-term wind or seismic 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 inch, with differential settlements on the order of one-half inch in a distance of 25 feet along a continuous footing with a uniform load. Lateral- .loads _due. to wind -or seismic -forces may .be_..r_esisted.by__friction_between the -foundation -and. the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the foundation. For the fatter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level, well -compacted fill. We recommend using the following ultimate values for the foundation's resistance to lateral loading: Coefficient of Friction 0.45 Passive Earth Pressure 300 pcf Where: (1) pcf is pounds per cubic foot, and (il) passive earth pressure Is computed using the equivalent fluid density. GEOTECH CONSULTANTS, INC.