501 RIVERSIDE RD REGIONAL DISPOSAL COMPANY EVT TRANSFER FACILITY PHASE 1 SITE IMP Geotech Report 2025-07-28

RDC EVERETTTRANSFER FACILITY Everett,Washington areas as described on the boring logs. Deeper zones of organic soils should be expected in areas I of dense vegetation or where tree bulbs are located outside of previously paved areas. Subgrade Preparation After stripping and removal of existing asphalt and prior to placing geogrid reinforcement and pavement base course materials,the exposed subgrade areas should be evaluated by proof rolling I and probing to locate any soft or pumping soils. Proof rolling can be completed using a piece of heavy tire-mounted equipment such as a loaded dump truck. During wet weather, the exposed subgrade areas should be probed to determine the extent of soft soils if proof rolling cannot be accomplished. If soft or pumping soils are observed, they should be removed and replaced with structural fill. All unsuitable soils should be removed from below pavement areas. Once approved, the subgrade areas should be recompacted to a firm and unyielding condition, if pp g possible. The achievable degree of compaction will depend on when construction is performed. If the work is performed during dry weather conditions, we recommend that all subgrade areas be recompacted to at least 95 MDD in accordance with the American Society for Testing and Materials(ASTM) D 1557 test procedure (modified Proctor). If the work is performed during wet weather conditions, it may not be possible to recompact the subgrade to 95 percent of the MDD. In this case, we recommend that the subgrade be compacted to the extent possible without causing undue weaving or pumping of the subgrade soils and/or protected with ATB. Subgrade disturbance or deterioration could occur if the subgrade is wet and cannot be dried. If the subgrade deteriorates during compaction, it may become necessary to modify the compaction criteria or methods. I Structural Fill All fill, whether on-site or imported supporting pavement areas or in utility trenches should meet the criteria for structural fill presented below. The suitability of soil for use as structural fill depends on its gradation and moisture content. I MATERIALS Materials used to construct the pavement areas or to backfill utility trenches are classified as — structural fill for the purpose of this report. Structural fill material quality varies depending upon its 111 use as described below: ■ Structural fill placed to raise grades and to backfill utility trenches should consist of gravel I borrow as described in Section 9-03.14(1) of the 2012 WSDOT Standard Specifications, with the additional restriction that the fines content be limited to no more than 5 percent. • Structural fill placed as crushed surfacing base course below pavements should conform to Section 9-03.9 (3) of the 2012 WSDOT Standard Specifications. REUSE OF EXISTING ASPHALT,BASE AND CONCRETE RUBBLE t Existing asphalt pavement and PCCP rubble may be reused as structural fill if properly crushed during demolition. Recycled PCCP rubble and base course materials may be reused as structural fill throughout the project. Recycled asphalt may be used under new pavement and hardscape areas, in utility trenches, and below floor slabs. For use as general structural fill across the site, I GEOENGINEERS_.0 June 18,2013 Page 7 File No.4322-002-00 1