3206 WAVE DR 2016-01-01 MF Import

GeoTesl Services,Inc. June 3,2005 Baldwin Residence,3206 Wave Drive,Everetl,WA Job No.5233 • The exposed subgrade surface and excavated siope should be observed and evaluated by qualified personnel under the direction of a geotechnical engineer to insure that our design assumptions are met. The minimum 6 inch thick concrete pad or compacted crushed gravel base can then be constructed. • We recommend that the walls be embedded a minimum oi one and one half blocks below the grade in front oi the wall. Fill used to backfill in front of the construcled walls should consist of suitable native soil or importzd granular material thal is compacled in place. • Drainage is essentiai for proper performance of retaining walls. The wall design assumes drained conditions and does not allow for hydrostatic pressure buildup behind the walls, Figure 4, Wall Design Detail. The design therefore requires posilive drainage as detailed on the typical cross sectional drawing. A one-foot thick free draining gravel layer siiould be placed immediately behind the blocks. This drainage layer may consist of pea gravel, drain rock or a clean screened (no fines) crushed rock. The drainage layer should be separated from the native back fill, within the reinforced zone, by using a non-woven filter fabric such as Amoco 240N, or equivalent. • Backfill placed behind the walis should be piaced on a horizontal surface in uniform lifls and be compacted to a dense and non-yielding condition. The fill should be olaced in 8 to 10 inch, loose horizontal lifts and thoroughly compacted. Within the active zone behind the wall, the fill should be compacted to 95% of the maximum dry density as determined by ASTM D-1557 test procedure except within 2 teel immediateiy behind the wall where 90% is recommended. The backfill material should be generally granular, inorganic and free of any debris. We do not recommend using a clay or silt soil wilhin lhe reinforced backfill zone. • The contraclor should ensure that the geogrid installation for INSE type walis is properly oriented in the machine direction to achieve the strengths used in our design. The grid is recommended to be backfilled from the wall back in order to ensure the grid is properly tensioned. Loose grid bubbles or folds should not be allowed within the reinforced soil zone. • Temporary excavations in excess of 4 ft should be shored or sloped in accordance with Safety Standards for Construction Work Part N, WAC 296-155- 657. Temporary unsupported excavations in dense, undisturbed native soils without seepage (Type A soil) may be sloped as steep as '/,H: 1V. All other soil unils and all soils units with seepage are Type C soils and should be at 1YzH: 1V or ilatter. Flatter siopes or temporary shoring may be required in areas where groundwater flow is present and unstable conditions develop. The contractor is responsibie for monitoring and maintaining safe excavation conditions. Please re(erence the Allan Block construction and instailation specifications for other ilems nol specifically addressed above. Page 5 of 7 � � �