4920 24TH AVE W Geotech Report 2023-06-22

GeoTest Services, Inc. October 8, 2021 2405 Hillside Lane, Everett,WA Project No. 21-0845 depths of fill were encountered in the explorations performed in the southwest, upslope portion of the subject property. Project Site Image 5.Screenshot from the DNR Geologic Information Portal,in which the entire project site is considered to possess a very low liquefaction susceptibly. GeoTest anticipates that at least 2 to 3 feet of excavation will be required to remove the loose, near-surface fill soils and to reveal competent bearing soils (Transitional Beds) for the proposed house foundations. The proposed depth of excavation will depend on the proposed lower floor elevation, of which preliminary information was not available as of the writing of this report. The depth of required excavation would decrease towards the southern portion of the site. Once bearing soils have been revealed in the proposed house footprint,we recommend that the native subgrade be recompacted to a firm and unyielding condition. The proposed residences can then be constructed with conventional continuous or individual spread foundations bearing directly on firm and unyielding native soils,or on compacted structural fill placed atop these soils. Further recommendations regarding the placement and compaction of structural fill can be found in the Fill and Compaction section of this report. The previously placed fill soils are not suitable for the conventional infiltration of stormwater. The native Transitional Beds encountered in the explorations are glacially consolidated and contain a high percentage of fines. GeoTest anticipates that perched groundwater seepage may be encountered atop the low permeability fill as well as native Transitional Beds depending on the time of year and after an extended period of heavy precipitation. Perched seepage was present in TP-2, and because of the extent of fines observed on site, it appears that the fill and 8