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' October 16,2020 <br /> Project No. T-8221 <br /> 5.7 Drainage <br /> I <br /> Surface <br /> Final exterior grades should promote free and positive drainage away from the building areas. We recommend <br /> providing a positive drainage gradient for a minimum distance of ten feet from the building perimeter. If positive <br /> ' drainage cannot be provided in paved locations provisions for collection and disposal of surface water adjacent to <br /> the structure in trench drains should be made. <br /> ' Subsurface <br /> ' In our opinion,with the area immediately adjacent to the structure paved,and positive surface drainage maintained, <br /> perimeter foundation drains would not be necessary. If the grade is not positively drained away from the structure <br /> or is landscaped,perimeter foundation drains should be installed. <br /> I <br /> 5.8 Utilities <br /> Utility pipes should be bedded and backfilled in accordance with American Public Works Association(APWA),or <br /> City of Everett specifications. As a minimum,trench backfill should be placed and compacted as structural fill, as <br /> ' described in Section 5.2 of this report. Most inorganic native and existing fill soils excavated on the site should be <br /> suitable for use as backfill material during dry weather conditions. However, if utility construction takes place <br /> during the wet winter months, it may be necessary to import suitable wet weather fill for utility trench backfilling. <br /> Depending on final utility grades, the utility contractor should also be prepared for encountering unstable soils <br /> below the pipe invert elevations. If not removed from below the pipe and replaced with crushed rock or additional <br /> bedding material,pipe deflections will occur as a result of the soil yielding and compressing in response to loading <br /> imposed by the trench backfill. <br /> 5.9 Pavements <br /> Pavement subgrades should be prepared as described in Section 5.2 of this report. Regardless of the degree of <br /> ' relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade <br /> should be proofrolled with heavy rubber tired construction equipment such as a loaded 10 yard dump truck to verify <br /> this condition. <br /> The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic <br /> conditions to which it will be subjected. We expect traffic at the facility will consist of cars and light trucks, along <br /> with heavy traffic in the form of tractor-trailer rigs. For design considerations, we have assumed traffic in parking <br /> and in car/light truck access pavement areas can be represented by an 18-kip Equivalent Single Axle Loading <br /> (ESAL) of 50,000 over a 20-year design life. For heavy traffic pavement areas, we have assumed an ESAL of <br /> 300,000 would be representative of the expected loading. These ESALs represent loading approximately equivalent <br /> to 3 and 18,loaded(80,000 pound GVW)tractor-trailer rigs traversing the pavement daily in each area,respectively. <br /> Page No. 9 <br />