500 LAUREL DR 2016-01-01 MF Import

Geotechni:al Engineering Study �0-2267 Three Story Addition - 500 Laurel Street, Everett January 31, 200 i DISCUSSION AND RECOMMENDATIONS General Page 11 ` Based on the results of our limited study it is our professional opinion that it is geotechnically feasible to develop this site generally as desired and tu build the proposed three story residential addition essentially as planned. The addition may be supported on conventional spread footings. After satisfactorily redensifying the exposed subgrade, the foundations should bear an the firm and unyieltl�ng or redensified native silty sand soil or, as an altemative, on a rninimum of two ieet of compacted structural fill placeo ov�r the firrn native silt subgrade. Where a fill is used, it should extend for a similar horizontal distance beyond the foundatian perimeters equal to, or greater than, the thickness beneath thefooting. This helps to avoid the risk of a lateral shear failure occurring beneath the footings. The carefully and thorouyhly redensified in-place native soils, or a cc,ntrolled compacted structural fill material, sl�ould also be capable of supporti�g conventional concrete floor slabs and floor loads without undergoing any significant deformation. Frum our examin�tion of the site conditions, and the apparent competency of the majority of the in-place site soils, it is our opinion that the site should be subject to little or no settlement under the proposed building loads, providing the soils are treated as descriCed later in this report. We estimate that the potential building load related settlement should be well within the building's tolerable limits. Sased on the relatively dense and granular nature of the sfte soils, and the lack of a shallow water level that could surge and saturate the soil, it is our opinion that the properiy developed and maintained site i., unlikely to be susceptible to any significant degree of liquefaction, or to liquefaction related settlement, under even re�atively severe earthquake conditions. The majority of the shallow surficial in-situ silty sand and sandy silt soil are also considered suitable for reuse as a compacted structural fill elsewhere en the property, if desired. We recommend, however, that they (or any other imported fill source material) be kept within about two points of their optimum Modified Proctor moisture content to help avoid pumping under compaction or construction ZL I � � I 1 I !� I 1 I 1 � I I I �