7100 HARDESON RD SITE DEVELOPMENT Geotech Report 2025-03-04

Geotechnical Engineering Report lierracon Merrill Creek Operations Base Expansion • Everett, Washington - December 14, 2020 • Terracon Project No. 81205012 GeoReport Subsurface Drainage for Below-Grade Walls Based upon the depth to groundwater, hydrostatic pressure is not expected. However, installation of wall drainage is much more readily accomplished during initial construction, and a wall drainage system that proves to be inactive is much more cost effective than a retrofit system. A perforated rigid plastic drain line installed behind the base of below-grade walls is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage to a suitable discharge location or a sump pit. A sump discharge line should be included in case the addition of a sump pump ever proves to be necessary. The perforated drain line behind the wall should be surrounded by clean, free-draining granular material having less than 5 percent passing the No. 200 sieve. The free-draining aggregate should be encapsulated in a filter fabric. The granular fill should extend up to the floor slab or pavement subgrade. As an alternative to free-draining granular fill, a pre-fabricated drainage structure may be used. A pre-fabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion, and is fastened to the wall prior to placing backfill. PAVEMENTS Following construction of the building expansion, new concrete pavement will be constructed to match the floor slabs of the maintenance bays, painting bays, and existing pavement beyond the building expansion footprint. Provided that the subgrade preparation steps presented in the Earthwork section are followed, a pavement section that matches the existing pavement's layer thicknesses should perform satisfactorily. Rigid Pavement Section Minimum recommended concrete pavement section thicknesses are presented below: Layer Material Thickness (inches) Surface Portland Cement Concrete 9 Aggregate Crushed Surfacin Base Course 10 Sub�rade _ Properly prepared and proof-rolled subgrade 12 The individual and total material thickness values presented above represent minimum thickness values, not averages. Adequate reinforcement and number of longitudinal and transverse control joints should be placed in the rigid pavement in accordance with ACI requirements. Although it may not be necessary for structural support, the base course layer is recommended to help reduce potential for slab curl, shrinkage cracking, subgrade "pumping"through joints, and provide Responsive • Resourceful • Reliable 17