2017-00020 - new structure - Laserfiche WebLink

Home Browse Search

We recommend that a dewatering contractor be consulted to review the soil boring logs, develop a dewatering plan and evaluate the impact of dewatering on adjacent structures. Backfilling We recommend that backfill placed to attain site grades be compacted to a �nimum of 95 percent of its standard Proctor density(ASTM D 698). Granular fill classifiied as SP should be placed within 65 percent to 105 percent of its optimum moisture content as determined by the standard Proctor. All fill should be placed in thin lifts and be compacted with a large self-propelled vibratory compactor operating in vibratory mode. In areas where fill depths will exceed 10 feet below footings,we recommend that compaction levels be increased to minimum of 98 percent of the materials standard Proctor density. Even with the increased compaction levels a construction delay may be appropriate to allow for post construction settlement of the fill mass. Fill and backfill placed on slopes,if any,must be"benched"into the underlying suitable soil to reduce the potential for slip planes to develop between the fill and underlying soil. We recommend"benching" or excavating into the slope at 5 feet vertical intervaLs to key the fill into the slope. We recommend each bench be a minimum of 10 feet wide. Foundations We recommend the perimeter footings bear a minunum of 42 inches below the exterior grade for frost protection. Interior footings may be placed immediately below the slab provided construction does not occur during below freezing weather conditions. Foundation elements in unheated areas should bear at least 5 feet below exterior grade for frost protection. We anticipate the foundations and floor slabs will bear on compacted engineered fill or native cohesive soils. With the building pads prepared as recommended it is our opinion the footings can be designed for a net allowable bearing pressure up to 2,000 pounds per square foot(ps fl. 4.4 Interior Slabs The anticipated floor subgrade is granular fill following soil corrections. It is our opinion a modulus of subgrade reaction, k, of 250 pounds per square inch of deflection (psi) may be used to design the floor. If floor coverings or coatings less permeable than the concrete slab will be used, we recommend that a vapor retarder or vapor barrier be placed immediately beneath the slab. Some contractors prefer to bury the vapor barrier or vapor retarder beneath a layer of sand to reduce curling and shrinkage, but this practice often traps water between the slab and vapor retarder or barrier. Regazdless of where the vapor retarder or vapor barrier is placed, we recommend consulting the floor covering manufacturer regarding the appropriate type, use and installation of the vapor retarder or vapor barrier to preserve the warranty. We recommend following all state and local building codes in regards to a radon mitigation plan beneath interior slabs. 6