2000 TOWER ST ARTS AND SCIENCES BLDG 2018-01-02 MF Import

The wet weather season generally begins in October and continues through May in western Washington; however, periods of wet weather may occur during any month of the year. For earthwork activities during wet weather, we recommend that the following steps be taken: • The ground surface in and around the work area should he sloped so that surface water is directed away from the work area. The group: surface should be graded so that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. • Earthwork activities should not take place during periods of moderate to heavy precipitation. • Slopes with exposed soils should be covered with plastic sheeting. • The contractor should take necessary measures to prevent on -site soils and soils to be used as fill from becoming wet or unstable. These measures may include the use of plastic sheeting, sumps with pumps, and grading. The site soils should not be left uncompacted and exposed to moisture. Sealing the surficial soils by rolling with a smooth -drum roller prior to periods of precipitation will help reduce the extent that these soils become wet or unstable. • The contractor should cover all soil stockpiles that will be used as structural fill with plastic sheeting. • Construction traffic should be restricted to specific areas of the site, preferably areas that are surfaced with the existing asphalt or working pad materials not susceptible to wet weather distul bance. • Construction activities should be scheduled so that the length of time that soils are left exposed to moisture is reduced to the extent practical. Routing of equipment on the native till subgrade soils during the wet weather months will be difficult and the subgrade will likely become highly disturbed and rutted. In addition, a significant amount of mud can be produced by routing equipment directly on the glacial soils in wet weather. Therefore, to protect the subgrade soils and to provide an adequate wet weather working surface for the contractor's equipment and labor, we recommend that the contractor protect exposed subgrade soils with sand and gravel, crushed gravel, or ATB. Permanent Cut and Fill Slopes We recommend that permanent cut or fill slopes be constructed at inclinations of 2H:I V or Flatter, and be blended into existing slopes with smooth transitions. To achieve unifo,,,r compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to expose well -compacted fill. To reduce erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of grading. Until the vegetation is established, some sloughing and ravelling of the slopes should be expected. This may necessitate localized repairs and reseeding. Temporary covering, such as clear heavy plastic sheeting, jute fabric, or erosion control blankets (such as American Excelsior Curlex I or North American Green S 150) could be used to protect the slopes during periods of rainfall. 15 G c o li n g i n c e r s 9 Filc No. 5836-002-001040204