11632 EVERGREEN WAY BASE FILE 2018-01-01 MF Import

Propo°ed Retail Development J-1443 112'�Street and Hwy.99 Feb�uary 26,2004 ( Evcrett,Washington Page 19 an allowablc passive earth pressure of 250 and 300 pcf in structural fill and medium dense to dense native soils, respcctive�y. We recommend usi*�g an allowable base &iction coefficient of 0.35. To reduce the lalerz: carth pressure and prevent buildup of water pressure against the walls, the backfill adjacent to the walls should consist of free-draining granulaz material and should extend a lateral distance behind the walls a minimum distance of 18 inches. The free- draining backfill should be continuous to either a footing drain or a weephole drain system. Wc recommend that all w;,:l backtill conform to Section 9-03.12(2), Gravel Backfill for Walls, as presented in the 2002 WSDOT Standard Specifications. Compacdon of the backfill is recommended to achieve a density of 90 pereent of ASTM D-1557 and light hand operatcd equipment is recommended so that excessive ctress is not applied to the walls. The above equivalent fluid pressures are based on the assunuption of a uniform horizontal backfill and no buildup of hydrosiatic pressure behind the wall. Surcharge pressures due to sloping ground, adjacent footings, vehicles, construction cquipment, etc., must be added to lhese values. For loading docks, sw�hazge loading on the floor slab abovc ihe dock will result in a horizontal, uniformly distributed surcharge on the wall equal to 40 percent of the distributed verticalloading. Pavcment Desi�n Parameters ( The native subgrade soils are anticipated to consist of sand and silty, gravelly sand soils. A California Bearing Ratio (CBR) test was completed on a representauve near-surface sample of silty sand and a CBR value of 18 percent was obtaincd. All fill used to raise low areas must have pavement support chazacteristics at least equivalcnt to the existing soils and must be placed under engincering controlled conditions. It is our opinion that the non-organic native soils encountered at the site would mcet the minimum recommended CBR criteria. Asvhalt Concrete Pavement It must be recognized that pavement desi�t is a compromise between tugh initial cost and little maintenancc on one side azid low initial cost coupled with the need for periodic repairs on the other. As a result, thc owner will need to take part in the development of an appropriate pavcment section. Critical features which govern the durability of the surface include the level of compaction of the subgrade, the slability of the subgrade, the presence or absence of moisture, }'ree water and organics, the fines content of the subgade soils, the traffic volume, and the ' frequcncy of use by heavy vehicles. Our recommendations are based upon a 20-yeaz design life for standard duty and heavy-duty pavements. The pavement design recommendations assumc that the subgrade and any structural fill will be prepared in accordance with the recommendations presented in this report. All till,as well as the upper 12 inches bcncath the subbase section should be compacted to a minimum of 95 percent relative compaction, using AASHTO T-180 (ASTM:D 1557). SpecificaUons for manufacturing and placement of pavements and crushed top couise should conform to specifications presented in Divisions 5 and 4, respectively, of the 2004 Washington State J-1443,0?2G04 Iq i