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Geotechnical Engineering Report- Revised lierracon <br /> Proposed CFT Retail •Everett,Washington <br /> February 1, 2018 ■Terracon Project No. 81185002 <br /> where it should be capped with compacted cohesive or low-permeable fill to reduce infiltration of <br /> surface water into the drain system. <br /> Slope to drain <br /> away from building <br /> Layer of <br /> cohesive fill -- <br /> Foundation wall <br /> Backfill(see report <br /> Free-draining graded ' 1 requirements) <br /> granular filter material or t;. <br /> II _ <br /> non-graded free-draining <br /> material encapsulated in <br /> an appropriate <br /> filter <br /> bra <br /> a i Native,undisturbed <br /> fabric(see report) ,`-�� , ; I ' I soil or engineered fill <br /> i t :l <br /> i' <br /> ' 4 1'.. Perforated drain pipe(Rigid PVC <br /> unless stated otherwise in report) <br /> As an alternative to free-draining granular fill, a pre-fabricated drainage structure may be used. <br /> A pre-fabricated drainage structure is a plastic drainage core or mesh which is covered with filter <br /> fabric to prevent soil intrusion, and is fastened to the wall prior to placing backfill. <br /> If controlling hydrostatic pressure behind the wall as described above is not possible, then <br /> combined hydrostatic and lateral earth pressures should be calculated. For granular backfill, an <br /> equivalent fluid weighing 85 and 90 pcf should be used for active and at-rest conditions, <br /> respectively. These pressures do not include the influence of surcharge, equipment or pavement <br /> loading, which should be added. Heavy equipment should not operate within a distance closer <br /> than the exposed height of retaining walls to prevent lateral pressures more than those provided. <br /> 4.7 Pavements <br /> Explorations in the areas of proposed paved parking lots and drive lanes encountered existing fill <br /> soil to depths of up to approximately 7 feet below existing site grades. Provided the owner is willing <br /> to accept the risk of unpredictable settlement response of leaving some of the existing fill under <br /> pavement sections, we recommend limiting risk mitigation measures to removal of a minimum of <br /> 24 inches of existing fill followed by scarification and recompaction of the fill in proposed pavement <br /> areas. If construction is scheduled for wet winter months, however, reworking of the moisture <br /> susceptible existing fill soil will likely not be feasible and at least 2 feet of new structural fill may be <br /> needed to provide adequate pavement support. <br /> Responsive ■ Resourceful ■ Reliable 16 <br />