1502 WALL ST IMAGINE CHILDRENS MUSEUM Geotech Report 2022-10-25

Imagine Children's Museum Building Addition Revised Geotechnical Engineering Report Everett, Washington Design Recommendations If adjacent foundations or walls fall within the support zone of either new or existing foundations, they will experience surcharge pressures as a result of the adjacent footings. At this time, we are not aware of any situations on this project where such surcharges are expected to occur. If any such situations arise as project plans are developed, we should be allowed to offer situation-specific recommendations. 8.2 Passive Resistance - Foundations Footings cast directly against undisturbed native soils in a trench may be designed for passive resistance against lateral translation represented by an equivalent fluid equal to 350 pounds per cubic foot (pcf). The passive equivalent fluid pressure diagram begins at the top of the footing; however, total lateral resistance should be summed only over the depth of the actual key (truncated triangular diagram). This value applies only to footings/keyways where concrete is placed directly against the trench sidewalls without the use of forms. If footings are placed on grade and then backfilled, the top of the compacted backfill must be horizontal and extend outward from the footing for a minimum lateral distance equal to three times the height of the backfill, before tapering down to grade. With backfill placed as discussed, footings may be designed for passive resistance against lateral translation using an equivalent fluid equal to 250 pcf and the truncated pressure diagram discussed above. Passive resistance values include a factor of safety of 3 in order to reduce the amount of movement necessary to generate passive resistance. The friction coefficient for footings cast directly on undisturbed native lodgement till soils may be taken as 0.35. This is an allowable value and includes a safety factor of at least 2. 9.0 FLOOR SUPPORT Slab-on-grade floors may be used over structural fill or pre-rolled medium dense natural ground. A subgrade modulus of 40 pounds per cubic inch (pci) can be assumed for design. The floors should be cast atop a minimum of 4 inches of washed pea gravel to act as a capillary break. They should also be protected from dampness by an impervious moisture barrier a minimum of 10 mils in thickness. 10.0 DRAINAGE CONSIDERATIONS All footing walls should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, polyvinyl chlroide (PVC) pipe surrounded by washed pea gravel. The level of the perforations in the pipe should be set at the bottom of the footing at all locations, and the drains should be constructed with sufficient gradient to allow gravity discharge away from the buildings. In planning, exterior grades adjacent to walls should be sloped downward away from the structures to achieve surface drainage. March 28,2019;Revised April 16,2019 ASSOCIATED EARTH SCIENCES,INC. _ sGB/Id-190104E001-3-Projects\20190104\KEIWP age //„70�)