3313 OAKES AVE 2020-07-14 - Laserfiche WebLink

GeoTest Services, Inc. December 9,2016 3313 Oakes Avenue,Everett,WA Job No. 16-0659 The invert of the footing drain pipe should be placed slightly below the elevation of the bottom of the footing or 12 inches below the adjacent floor slab grade, whichever is deeper, so that water will not seep through walls or floor slabs. The footing drain should discharge to an approved drain system and include cleanouts to allow periodic maintenance and inspection. Although groundwater seepage was not encountered in the explorations, it is expected that groundwater may be found perched atop the impervious till soils during the wetter winter months. We understand that the proposed duplex building will contain a basement. Because this excavation will extend into low permeability soils, we recommend that the client and design team carefully evaluate the completed grading plan, cut depths, and properly anticipate the potential for perched groundwater to impact the development. Robust subsurface drainage measures, such as enhanced waterproofing, waterstops, perimeter, wall, footing, and sub-slab drainage may need to be incorporated into the project plans to mitigate ground and surface water impacts. We recommend that GeoTest be allowed to review plans and specifications for this project during development and prior to the start of construction. The purpose of the review would be to confirm that our recommendations are being properly implemented and incorporated into the design of the project. We are also available to assist with the development of site specific drainage plans once more formal construction plans are available. Positive surface gradients should be provided adjacent to the proposed building to direct surface water away from the building/foundation and toward suitable drainage facilities. Roof drainage should not be introduced into the perimeter footing drains, but should be separately discharged directly to the stormwater collection system or other appropriate outlet. Surface water should not be allowed to pond and soak into the ground surface near buildings or paved areas during or after construction. Construction excavations should be sloped to drain to sumps where water from seepage, rainfall, and runoff can be collected and pumped to a suitable discharge facility. We recommend that appropriate waterproofing be applied to the exterior of all buried concrete elements. Alternatively, an admixture waterproofing compound can also be added to the concrete mix prior to placement to enhance the ability of the concrete to resist water transmission. We are available to help provide additional site drainage and/or waterproofing recommendations or a more specific foundation and excavation drainage plan upon request. As the site excavations for the planned structure will be within low permeability glacial deposits, excavations will act as "bathtubs" or basins that can potentially retain water. Accordingly, we recommend that the base of all excavations be sloped slightly towards the daylight portions of the excavations, such that passive drainage can occur by gravity and low spots within the building footprint do not fill up with water. Temporary and Permanent Slopes Actual construction slope configurations and maintenance of safe working conditions, including temporary excavation stability, should be the responsibility of the contractor, who is able to monitor the construction activities and has direct control over the means and methods of construction. All applicable local, state, and federal safety codes should be followed. All open cuts should be monitored during and after excavation for any Page 12 of 17