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

GeoTest Services, Inc. October 8, 2021 2405 Hillside Lane, Everett,WA Project No.21-0845 arm ■ om • Proper drainage controls have a significant effect on erosion. All surface water and any collected drainage water should not be allowed to be concentrated and discharged down the face of an existing steep slope. All collected stormwater should be directed to an appropriate collection system. • All areas disturbed by construction practices should be vegetated or otherwise protected to limit the potential for erosion as soon as practical during and after construction.Areas requiring immediate protection from the effects of erosion should be covered with either plastic, mulch, or erosion control netting/blankets. Areas requiring permanent stabilization should be seeded with an approved grass seed mixture, hydroseeded with an approved seed-mulch-fertilizer mixture or landscaped with a suitable planting design. In addition to the preceding recommendations, typical erosion control measures during construction will be required. These measures can include a rocked construction entrance or downslope silt fencing, depending on EMC regulations. No other mitigations are required to address erosion hazards on the property. Seismic Hazard Areas Seismic Hazard Areas are typically defined as areas that, due to a combination of soil and groundwater conditions,are subject to severe risk of ground shaking,subsidence,or liquefaction of soils during earthquakes. These areas are typically underlain by soft or loose saturated soils (such as Alluvium), have a shallow groundwater table and are typically located on the floors of river valleys. According to the Geologic Information Portal and the PDS Map Portal, the subject property is mapped as having a very low potential for seismic liquefaction and does not exist near active faults or folds. Based on the existing site conditions, proposed construction, and our understanding of the local geology, it is GeoTest's opinion that the potential for seismic liquefaction is very low. Thus, it is GeoTest's opinion that the subject property is not a Seismic Hazard, and no specific seismic hazard mitigations are required for site development. CONCLUSIONS AND RECOMMENDATIONS Based on the evaluation of the data collected during this investigation, it is our opinion that the subsurface conditions at the site are suitable for the proposed development, provided the recommendations contained herein are incorporated into the project design. Subsurface explorations exposed in this study encountered approximately 0.5 to 1 foot of loose topsoil before encountering loose to medium-dense fill soils. Native, medium-stiff to stiff Transitional Bed soils below the near-surface topsoil and/or fill soils at an approximate depth of 0.5 to 3 feet BGS.The native soils became stiff to very stiff with depth. It appears that the thicker 7