9001 AIRPORT RD SNO ISLE SKILL CTR EXPANSION 2009 Geotech Report 2018-01-02 MF Import

i I Subsurface Ezploration. Geologic Hazard, and ISho-lsle SA1�ls Center Addition Preliminary Geotechnicd Engi:�atring Repon Everett Washingron PreGminary Design Recpmmendations IDepending on construction staging and desired performance, the crushed base cowse material may be substituted with asphalt treated base (ATB) beneath t6e final asphalt surfacing. The , substitution of ATB should be as follows: 6 inches of crushed rock can be substituted with 4 inches of ATB. ATB should be placed over a properiy compacted, native or structural fill subgrade compacted to minimum 95 percent relative densiry, and a 1'h- to 2-inch thickness of I crushed rock to act as a working surface. If ATB is used for construction access a� staging azeas, some rutting and disturbance of the ATB surface should be expected. The general I convactor should remove affected azeas and replace t6em with properly compacted ATB prior to final surfacing. � 14.0 DRAINAGE CONSIDERATIONS � Traffic across the on-site soils when they aze damp or wet will result in disturbance of tt►e otherwise firm stratum. Therefore, during site work and construction, the concractor should provide surface drainage and subgrade protection, as necessary. 1 Any retaining walls and all perimeter footing walls taller than 3 feet should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, polyvinyl chloride i (PVC) pipe sunounded by washed pea gravel. The level of the perforadons in che pipe should be set at the bottom of the footing, and the drains should be constructed with sufficient gradient to allow gravity dischazge away from the buildings. The perforations should be located on the � lower portion of the pipe. In addition, any retaining or basement walls should be lined with a minimum, 12-inch-Urick, washed gravel blanket, or backfilled completely with free�raining material and lined with a drainage mat, such as Mira-Drain 6000, over the full height of the ' wall (excluding the first 1 foot below the surface). The drainage mat cannot be substituted for the washed gravel blanket drain unless the entire wall backfill is free-draining. Drainage ' material should tie into the footing drains. Roof and surfacc runoff should not dischazge into I the footing drain system, but shouid be handled by a sepazate, rigid, tightline drain. � In planning, exterior grades adjacent to walls should be sloped downwazd away from the structure to achieve surface drainage. Runoff water from impervious surfaces should be � collected by a storm drain system that discharges into the site storm water system. I15.0 LA'I'ERAL WALL PRESSURES All backfill behind walls or azound foundation units should be placod as per our I recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which aze free to yield laterally at least 0.1 percent of their height, may be designed asing an equivalent fluid equal to 35 pounds per cubic foot (pc�. Fully restrained, Ihorizontally backfilled rigid walls, which cannot yield, should be designed for an equivalent Jw�e 11. 2008 ASSOCIATED EAR7H SCIENCES.INC. � iEGqQ-EEQ9p2i3A5-Projn'nINA�l01i31F�'INP �flgC 17