330 HEATHER RD 2020-06-17 - Laserfiche WebLink

Brian and Connie Hallgarfh JN 18517 November 15, 2018 =.ge 3 GJ the natural potential for erosion on the steep slope. We recommend that the existing grass and vegetation in the minimum 30-foot setback remain undisturbed. Typically, it is prudent to install a silt fence along this setback line, as a visual reminder to the contractors, and to provide additional erosion protection. Any small amounts of soil stockpiled onsite should be covered with plastic in wet weather. As with any project, care will have to be taken to prevent tracking of soil or mud off the site by trucks or workers. Areas of bare soil outside of the working area should be covered with plastic, straw, mulch, gravel, or similar during wet weather. 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 Soil Profile Type C(very dense soil). The glacially-compressed soil that will support the foundations for the addition will not liquefy under the ground motions of the Code-required Maximum Considered Earthquake (MCE), which has a 2 percent probability of occurrence in a 50-year time period (once in 2,475 years). CONVENTIONAL FOUNDATIONS We recommend that continuous and individual spread footings have minimum widths of 12 and 18 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 2,000 pounds per square foot (psf) is appropriate for footings supported on competent native soil. A one-third increase in this design bearing pressure can 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 less than one-half-inch, with differential settlements on the order of one-quarter-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 resisted 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 latter condition, the foundation must be either poured directly against relatively level, undisturbed soil or be surrounded by level, well-compacted fill. GEOTECH CONSULTANTS,INC.