2721 WETMORE AVE MARQUEE APARTMENTS 2023-06-28

Subsurface Exploration, Geologic Hazard,and 2721 Wetmore Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations considered damp-proofing. If a more elaborate waterproofing system is desired, we recommend a waterproofing expert be consulted for design parameters that best fit the project. 12.0 DRAINAGE CONSIDERATIONS The natural sediments underlying the site contain substantial quantities of silt, and construction traffic across these materials when they are wet or damp will result in disturbance of the otherwise firm stratum. Therefore, prior to site work and construction, the contractor should be prepared to provide drainage and subgrade protection as the excavation progresses. This can be accomplished by the contractor through the use of a temporary drainage system to keep the base of the excavation "dry." In order to control water that may accumulate below the floor slab, we recommend construction of a subslab drainage system. This system should consist of at least two rigid, perforated, 6-inch-diameter, polyvinyl chloride (PVC) pipes surrounded by washed pea gravel that span the full length of the underslab area, oriented parallel to the long axis of the building. The pipes should be located approximately midway between the central axis and the building perimeter. A minimum thickness of 12 inches of washed gravel should be provided below the slab that is continuous with the underslab drains. The subgrade below the slab should be graded at a minimum 1 percent slope toward the drainpipes. The collected flow should then drain to one or more sump tanks from where it can be pumped to a suitable point of discharge. We recommend that the system include an auxiliary pump and backup power supply. When permanent exterior walls are constructed, a drainage system should be incorporated to collect water seeping through or behind the temporary shoring wall. Prior to constructing the permanent exterior walls, a proprietary drainage mat, such as Mira-Drain, should be placed in 4-foot-wide strips spaced no greater than 8 feet center-to-center from near the top of the shoring wall to its base. The bottom of the drainage mats should communicate with a permanent perimeter drainage system. This system could consist of either an exterior or interior perimeter foundation drain. The perimeter drain can be incorporated with the subslab drainage system, if required. ., 13.0 TEMPORARY EXCAVATION SHORING SYSTEM A deep excavation is currently being planned for this project, extending up to approximately 25 feet below existing site grades on the west side of the site. Temporary excavation shoring • will be required to support all four sides of the excavation and surrounding streets, existing structures, and utilities. Surcharge loading associated with the adjacent buildings to the north tb, May 28,2019 ASSOCIATED EARTH SCIENCES,INC. FSM/Id-190168E001-2-Projects`20190168\KE\WP Page 12 18185B Page 7 of 180