Premier Field Development, Inc. 5/9/2016

-18- lightly loaded parking and driveway areas. For areas where buses or maintenance trucks are expected, and in main entrances and exits, we recommend the section be increased to 3 inches of asphaltic concrete over 6 inches of crushed rock base. Crushed rock base should conform to Section 9-03.9(3) of the 1988 WSDOT/APWA Standard Specifications for I base course. Retaining Walls If retaining walls are incorporated into the design, it is assumed that they will be free to rotate about their bases, and that wall backfill will be free draining. Drainage should be provided by a zone of drain- age material at least 1 foot wide behind the walls, and weep holes at the base of the walls on about 8-foot centers. Drainage material should consist of imported free draining sand and gravel , such as the material described for "Gravel Borrow" in Section 9-03.14 of the Standard Specif- ications. For the recommended construction, walls may be designed based on an equivalent fluid density of 35 pcf. CONSTRUCTION CONSIDERATIONS The primary geotechnical construction consideration for this project is the moisture sensitivity of the on-site soils, combined with their being over optimum moisture content in their natural condition. Soils will need to be dried before being placed as fill . This will require dry, warm weather during construction, and large areas in which to spread the soil for aeration. After soils are dried and properly compacted, they will still be subject to disturbance if subjected to traffic in the presence of water. Dis- turbance can be limited by grading surfaces to drain, sealing surfaces to limit penetration of water, and preventing traffic on wet surfaces.