1029 52ND ST SW Geotech Report 2022-10-31

the storage aggregate and native subgrade for subgrade soil with fines content greater than 7 percent passing the U.S. Standard No. 200 sieve. The non-woven separation geotextile should conform with Table 3 of WSS 9-33.2(3)-Geotextile for Separation or Soil Stabilization. • 8.6.3 M„Fill Placement and..Compaction Placement and compaction of fill material for permeable pavement should consist of end dumping and spreading the fill material over the prepared subgrade and non-woven separation geotextile. Over-compaction of the storage aggregate and exposure to construction traffic should be avoided. A choker aggregate beneath permeable pavement can be used to facilitate grading of the pavement areas. For infiltration trenches, placement and compaction of fill material should consist of backfilling the infiltration trenches with storage aggregate onto the prepared subgrade and non-woven separation geotextile and tamping it to a firm condition. 8.6.4 Permeable Pavement Materials All permeable pavement materials and construction methods should comply with the most recent APWA GSPs presented in Section 4-4.3 (5) - Permeable Pavement of the City of Everett's °Design•and Construction Standards and Specifications-for Development (City of Everett, 201 8b). 9.0 MATERIALS Fill material and geotextiles will be required for site grading, backfilling over-excavations, pavement support, installation of utilities, and drainage. Recommended materials are discussed below. • 9.1 ON-SITE SOIL The on-site material has a high fines content, is sensitive to changes in moisture content, and will deteriorate under construction traffic and/or when exposed to wet weather. Although the on-site material does not meet the gradation requirements for imported structural fill, as defined below, we anticipate that some of the on-site material identified as silty sandy with gravel can be used for fill but will be limited to use during the dry season and it will require moisture conditioning prior to use. Deleterious material..(such.aswood, organics, and man-made material) should be removed from • native soil prior to use as fill. The use of on-site soil as fill should be subject to review'and approval by GeoDesign. It will be prudent to provide a 12-inch-thick cap of imported structural fill over areas where on-site soil is exposed or used as fill. The use of on-site materials as fill should be subject to review by a qualified geotechnical 'engineer.''During-the wet'season,-exposed subgrade areas will deteriorate under construction traffic. It will be prudent to provide a 12-inch-thick cap of imported structural fill over areas where on-site soil is exposed or used as fill. G EO DESIGN= 12 NWHome-1-01:101618