1001 N BROADWAY 2020 EVCC 2025-10-03

pressure resistance should be calculated from the bottom of adjacent floor slabs or below a depth of 1 foot where the adjacent area is unprotected, as appropriate. The allowable frictional resistance and passive resistance values presented above include a factor of safety of about 1.5. - If soils adjacent to footings are disturbed during construction, the disturbed soils must be recompacted, otherwise the lateral passive resistance value must be reduced. 4.2.4.Construction Considerations We suggest that the excavations for the footings be completed with an excavator equipped with a smooth-edge bucket to minimize subgrade disturbance. Immediately prior to placing concrete, all debris and loose soils that accumulated in the footing excavations during forming and steel placement must be removed. Debris or loose soils not removed from the footing excavations will result in increased settlement. If wet weather construction is planned, we recommend that all footing subgrades be protected using a lean concrete mud mat. The mud mat should be placed the same day that the footing subgrade is excavated and approved for foundation support. 4.3. Footing Drains We recommend perimeter footing drains be.installed around the proposed building. The perimeter drains should be installed at the base of the exterior footings, as shown in Figure 3, Wall Drainage and Backfill. The perimeter drains should be provided with cleanouts and should consist of at least 4-inch-diameter perforated pipe placed on a 4-inch bed of, and surrounded,by,„6 inches of drainage material enclosed in a nonwoven geotextile filter fabric such as Mirafi 140N (or approved equivalent)to prevent fine soil from migrating into the drain material. The footing drainpipe should be installed at least 18 inches below the top of the adjacent floor slab. The drainage material should consist of "Gravel Backfill for Drains" per Section 9-03.12(4) of the 2018 Washington State Department of Transportation (WSDOT) Standard Specifications. We recommend the drainpipe consist of either heavy-wall solid pipe (SDR-35 PVC, or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12, or equal). We recommend against using flexible tubing for footing drainpipes. The perimeter drains should be sloped to drain by gravity, if practicable, to a suitable discharge point, preferably a storm drain. We recommend the cleanouts be covered and placed in flush mounted utility boxes. Water collected in roof downspout lines must not be routed to the footing drain lines. 4.4. Slab-on-Grade Floors 4.4.1.Subgrade Preparation We recommend that concrete slabs-on-grade be constructed on a gravel layer to provide uniform support and drainage, and to act as a capillary break. We expect that slab-on-grade floors can be supported on: (1) medium dense to very dense native glacial soils encountered in our borings, or (2) on properly compacted structural fill extending down to these materials, or (3) on suitable on-site soils. Prior to placing the gravel layer, the subgrade should be proof-rolled as described in the "Earthwork" section of this report. The exposed subgrade should be evaluated during construction and compacted to a firm and unyielding condition, although unsuitable soils should be removed and replaced with structural fill where needed. GWENGINEER� July22,2019 Page 7 File ND.8836-01;-QO -. _.... ........ .