3620 36TH PL NE 2018-01-02 MF Import

stress ratio required to cause liquefaction to the cone tip and sleve resistance values. Estimated ground settlement resulting from earthquake -induced liquefaction was analyzed using an empirical procedure that relates settlement to average SPT N-values, which we correlated from the CPT tip values. The results of our liquefaction analyses are discussed in detail in Section 4.7 of this report, Earthquake Engineering. 4.0 CONCLUSIONS AND RECOMMENDATIONS E % KeY4 Z 1 4.-TM Based on the results of our subsurface exploration program, it is our opinion that the proposed Cedar Grove Composting development or. Smith island may be constructed satisfactorily as planned with respect to geotechnical issues. Key geotechnical issues for the project include: • The near -surface, native, on -site soils contain a high percentage of fines and are highly sensitive to small changes in moistute content. These soils are susceptible to disturbance from construction traffic. The native soils are wet and will be difficult, if not impossible, to cumpact to the recommended compaction criteria. The native soils should not be considered for reuse as structural fill. • Existing fill and wood chips/debris overlie most of the central and northern portion of the site. The thickness varies significantly. The fill consists of sand, sand and gravel, and/or quarry spalls. The wood chips may be up to about 5 feet thick in areas and underlie or are mixed in with the fill soils in most areas where the wood chips were encountered. The thickest fill and wood chip areas exist frcm the north edge of the central part of compost system Nos. 1 and 2, extend south to the central area of compost system No. 3, and range from about 2 to 5 feet thick with some fill layers within the wood chips. • The wood chips and organic debris should be removed from all structural areas. • Imported fill consisting of common borrow will be suitable, during periods of dry weather. If construction is performed during wet weather, gravel borrow with less than 5 percent fines should be used. • Settlement will result from the placement of fill and the loads associated with the compost system buildings and structures. We recommend that areas where buildings/structures will be supported at grade be preloaded to pre -induce the majority of the anticipated settlement. Preloads should be used for settlement sensitive structures such as the compost system pads, tipping building, office/scale area, and the grinder area. • The proposed structuresiequipment can be supported on shallow foundations provided the areas are preloaded. We recommend an allowable soil bearing pressure of 2,500 pounds per square foot (psf) for foundations bearing on a minimum 2-foot thickness of adequately compacted structural fill overlying a geotextile separator. • The compost system slabs should be constructed on a uniform mat of compacted granular structural fill extending at least 2 feet below the bottom of the lowest point of the concrete pad and at least 2 feet below the wall foundations. All wood chips/debris should be stripped from the structural pad areas and a geotextile separator (such as TC Mirafi 600X) should be placed over the prepared subgrade prior to placing the structural fill pad. G eo E n 8 inee rs 13 8 File No. 10625-001-021123003