10901 27TH AVE SE Geotech Report 2025-07-29

1 Subsurface Exploration, Geologic Hazards, and Proposed James Monroe Elementary School Replacement Revised Geotechnical Engineering Report Everett, Washington Design Recommendations present at the time the work is completed. Decisions on appropriate preparation procedures should be made in the field at the time of construction when site, soil, and weather conditions are known. A typical scenario might include replacement of the upper 2 feet of existing fill with new structural fill. During wet site or weather conditions, select fill may be needed for this application. It should be noted that leaving existing fill in place below planned paving carries some risks of future settlement. Such risks are offset by a substantial saving in initial construction costs. We are available to answer questions regarding cost savings and risks associated with leaving the existing fill in place below planned paving. ' 9.1 Construction Site Drainage and Surface Water Control ' The site should be graded to prevent water from ponding in construction areas and/or flowing into excavations. Exposed grades should be crowned, sloped, and smooth-drum rolled at the end of each day to facilitate drainage. Accumulated water must be removed from subgrades ' and work areas immediately prior to performing further work in the area. Equipment access may be limited, and the amount of soil rendered unfit for use as structural fill may be greatly increased if drainage efforts are not accomplished in a timely sequence. If an effective drainage system is not utilized, project delays and increased costs could be incurred due to the greater quantities of wet and unsuitable fill, or poor access and unstable conditions. ' We anticipate that perched ground water could be encountered in excavations completed during construction. We do not anticipate the need for extensive dewatering in advance of excavations. The contractor should be prepared to intercept any ground water seepage entering ' the excavations and route it to a suitable discharge location. Depending on grading plans, the use of cutoff drains might be warranted where grades will slope toward pavement edges or buildings. If cutoff drains are planned, they should be installed early in the site work phase to ' enhance drainage for the remainder of the project. Drainage recommendations are included in Section 11.1 of this report. ' Final exterior grades should promote free and positive drainage away from the buildings at all times. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. We recommend that a gradient of at least 3 percent for a minimum distance of 10 feet from the building perimeters be provided, except in paved locations. In paved locations, a minimum gradient of 1 percent should be provided, unless provisions are included for collection and disposal of surface water adjacent to the structures. ' 9.2 Subgrade Protection If building construction will proceed during the winter, we recommend the use of a working surface of sand and gravel, crushed rock, or quarry spalls to protect exposed soils, particularly in areas supporting concentrated equipment traffic. In winter construction staging areas and areas that will be subjected to repeated heavy loads, such as those that occur during construction of masonry walls, a minimum thickness of 12 inches of quarry spalls or 18 inches tOctober 5, 2009 ASSOCIATED EARTH SCIENCES, INC. BWG/[d-KE090312,13-Projects 1200903121KEIWP Page 12