2825 COLBY AVE COLBY CENTER Geotech Report 2018-01-02 MF Import

i - I GEOTECHNICAL ENGINEERING STUDY Mr. Arthur Skotdai I c/o Dykeman Architects E-6225 July 27, 1993 Page 10 I — It is our understanding that the foundation of the First Interstate Bank building extends ten (10) feet below existing grade adjacent to the north property line of the project. Thus, a vertical excavation can be made along the north propeny line, provided that this - foundation wall will not be destabilized by removal of the existing soils. We recommend that the project structural engineer review this situation before any excavation takes piace. Based on the conditions observed in our boring, the site soils are classified Type "A" by OSHA, and as such, temporary cuts greater than four feei in height should be sloped at ' an inclination no steeper than 3/4H:1V. In accordance with WAC 296-155-66109 (Washington State Administrative Code) excavations may be cut steeper than OSHA guidelines. However, the geotechnical e�giner_r of record must review the performance of these cuts on a daily basis, whenever significant soil types or canditions change, ' weather conditions change, or excavation procedures change. If it is so designed to cut steeper slopes, we are available to prov�de recommendations for steeper cut slopes. If unstable areas are identified, slopes should be cut back to more stabie configurations. If loose or saturated native or fill soils are encountered, the excavation should be cut at 1.5H:1 V starting on the slope face where the IQose conditions are encountered. Similar recommendations would be appropriate for utility trench excavations, except that the lower four feet of the trench excavation may be vertical. Excavation operations are inherently unpredictable regarding activity around the excavation and trench walis which all contribute to surcharge loading above these cuts, Combined with the variability of soil conditions and the necessity to periodically have workmen within the trenches, ECI does not recommend the use of fully vertical cuts for safety concerns. � If slopes of this inciination, or flatter, cannot be constructed, temporary shoring may be necessary. This shoring will help protect against slope or excavation collapse, and will I provide protection to workmen in the excavation. As previously mentioned, if temporary I shoring is required, we will be available to provide shoring design criteria, if requested. We also recommend that alf cut slopes be examined by Earth Consultants, Inc. during ( excavation to verify that condit6ons are as anticipated. All permanent cut and fill siopes should be inclined no steeper than 2H:1 V or flatter. i Permanently-exposed slopes should be seeded with an appropriate species of vegetation I to reduce erosion and improve stability of the surficial layer of soil. i I Earth Cc •sultants, Inc. I �