3611 FEDERAL AVE 2018-01-02 MF Import

Geologic hwestijeation and Geotechnical F_n¢ineerin¢ Rerort .Jones Residence 3611 Federalave. Everett. Washington 98-08-10 slightly easier with the backhoe and was in general damp to the touch. The weathered silt was overlain at the surface by one (1) to approximately three (3) feet of sandy to silty Topsoil in all of the test pits except TP-02 in the northeast corner of the property. In this location, the surficial soil consisted of a gray, silty fill that extended to an approximately depth of six (6) feet below existing grades. The underlying in -place soil indicated a fairly steep drop in the natural soil (to the northeast) in this corner of the property. This ravine or drop off had been filled in with the silty fill. Correlation between the mapped geology of the area as shown on the Geologic Map and that found and interpreted from the test pits was not good. Based on the soil found in the test pits, we conclude that the silt found throughout the site is part of the Transitional Beds (Oth) that have been mapped and shown to the north of the project site. The very dense sands of the Advance Outwash (Ora) have been eroded away from the area leaving exposed the underlying silts of the Transitional Beds (C)lb), The stability of steep slopes through Transitional Beds (Qth) in the Puget Sound Lowland is highly variable. In areas where the Transitional Beds (O1h) are associated with ground water, stability tends to be poor. Landslides and mass movements of soil are common. Where ground water is not associated with this soil unit, steep slopes through Transitional Beds (Orb) ate stable and reflect the underlying engineering characteristics of the soil. 3.4 Ground Water and Surficial Drainage There was no ground water encountered or observed within the test pits excavated during the site investigation. The massive silts of the Transitional Beds (O1b) are generally not very permeable and unless they are interbedded with thin lenses of sand. will not transmit useable quantities of ground water through them. Interbedded sands were not observed within the silts underlying this site. Slight mottling within Oie surticial weathered zones does indicate minor percolation of small amounts of water down through the upper couple of feet of silt around the site. 6 GES, Inc.