202 ALDER ST Geotech Report 2018-01-02 MF Import

1 , Proposed VieH R�Jge Suhsurface Erplormion. Geolagic Hnzards, lnfiltrarion Potential, Elvmentary Schnol Replacement ond Preliminary Geoferhni�a( Engineenng Report Everett. Washiqe�on Preliminary Design Recommendatioru , lU. PRELIMINARY DESIGN RECOMMENDATIONS I8.0 INTRODUCTION ' The site is underlain by native soils consisting of dense to very dense advance outwash sediments. These materials are suitable for structural support with proper preparation. Some , portions of the site are underlain by a layer of surficiat existing filt that is loose and variable. Existing fill should be remo�•ed and recompacted where it ocwrs below planned buildings, and warrant� remedial preparation where it occurs below paving and similar lightly loaded ' structures. ' 9.0 SITE PREPARATION Erosion and surface water control should be established around the clearing limits to satisfy , local requirements. Existing buildings, fou�dations, floor slabs, paving, buried utilities, vegetation, topsoil, and any other deleterious materials should be removed where they are located below planned construction areas. All dismrbed soils resulting from demolition ' activities should be removed to expose underlying, undisturbed native sediments and replaced with swctural fill, as needed. All excavations below final grade made for demolition activities ' should be backfilled, as needed, with structural fill. Once demolition has been completed, existing fill should be addressed. The observed fill ' depth in nur exploration borings was up to approximately 10 feet below existing grade. [t seems likely that fill observed on-site was associated with existing utilities (EB-1), backfill of existing foundations (EB-6 and EB-7), and an area of visually conspicuous fill between the ' existing parking area and building (EB-3). Of these areas of observed existing fill, only Ute fill around EB-3 appears to be laterally and vertically extensive and at the location of a planned new buiiding. ' We recommend that existing fill be removed from below areas of planned foundations to ' expose underlying, undisturbed native sediments, followed by resroration of the planned foundation grade with structural fill. Removal of existing fill should extend laterally beyond the building footpriot by a distance equal to the depth of overexcavation. For example, if ' existing fill is removed to a depth of 2 feet below a planned footing area, the excavation should also extend laterally 2 feet beyond the building footprint in that area. Where existing fill is removed and replaced with structural fill, conventional shallow foundations may be used for � building support. If euthwork for the project is completed in dry siee and weather eonditions, we anticipate that the excavated existing fill material can be recompacted as structural fill to ' September 22, 20/0 ASSOC1.17ED£ARTH SCIENCES, /NC. B�/�b�KEIOY1135ri:� 7�o/enr�I01CVI1551KEIWP Page ]2 �