3620 36TH PL NE 2018-01-02 MF Import

L • Stockpiles should be kept away from settlement sensitive structures (e.g., the pads), if the stockpile areas are not preloaded. Otherwise the stockpiles may induce settlement under the structures. We recommend a 20-foot minimum setback from the toe of a stockpile to any settlement sensitive structure. • Asphalt concrete (AC) pavement sections recommended for the project are governed by front-end loader traffic (assumed CAT 980) and include 5 inches AC over 15 inches of crushed surfacing base course, over 28 inches of sand/gravel subbase over a geotextile separator. If asphalt treated base (ATB) is used then the recommended section includes 4 inches AC over 8 inches ATB over 28 inches of sand/gravel subbase over a geotextile separator. Less robust pavement sections can be considered 1 in areas not subject to front end loader traffic. Note that over -excavation may be required to establish the pavement section thickness while maintaining design grades. Geo-grid reinforcement could be used to reduce the thickness of the subbase and base layers. These geotechnical issues and other considerations are discussed further and recommendations pertaining to the geotechnical aspects of the project are presented in the following sections. 4.2 EARTHWORK 4.2.1 Erosion and Sedimentation Control Potential sources or causes of erosion and sedimentation depend upon construction methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather. The project impact on erosion -prone areas can be reduced by implementing an erosion and sedimentation control plan. The plan should be designed in accordance with applicable city and/or county standards. The plan should incorporate basic planning principles including: • Scheduling grading and construction to minimize soil exposure, • Retaining existing vegetation whenever feasible, • Revegetating or mulching denuded areas, • Directing runoff away from denuded areas, • Minimizing the length and steepness of slopes with exposed soils, • Decreasing runoff velocities, • Preparing drainage ways and outlets to handle concentrated or increased runoff, • Confining sediment to the project site, and • Inspecting and maintaining control measures frequently. Temporary erosion protection should be used and maintained in areas with exposed or disturbed soils to help minimize erosion and reduce transport of sediment to adjacent areas and receiving waters. Permanent erosion protection should be provided by re-establishing vegetation by hydroseeding or landscape planting. Until the permanent erosion protection is established and the site is stabilized, site monitoring should be performed by qualified personnel to evaluate the effectiveness of the erosion control measures and ly G e o E n g i n e e r s 9 File No. 10625-001-021123003