4937 SEA BREEZE WAY 2017-01-13 - Laserfiche WebLink

� � Geotechnical Engineering Evaluation NCA File No. 916915 Pepe Retaining Wall April 27, 2015 Everett, Washington Page 7 All grading operations, drainage improvements, and wall repair or replace�nent planned as part of this development'should be planned and completed in a matter that enllances the stability of the steep slope, not reduces it. Any excavation spoils should not be stockpiled on or near any slopes on the southern side of the residence or below the wall. Also, runoff generated within the site should be collected and routed into an appropriate permanent discharge system away from the slope. Puture vegetation manageinent on thc slope should be the subject of a specific eval�iation and a plan approved by the City of Everett. "Thc slope should be monitored on an on-going basis, especially during the wet season, for any signs of instability, and con�ective actions promptly taken should any signs of instability be observed. Lawn clipping and any other ho�isehold trash or debris should never be allowed to reach the slope to the sough of the residence or below the wall. The fill and trash that e�ist on the slope below the wall is considered unstable and will likely fail during rain events. This would lead to serious undermining of the retaining wall. We recommend that all that fill be hauled off site and the slope restored. The soils encountered on this site are considered highly moisture-sensitive, and will disturb when wet. We recom��end that constr�iction take place during dry weather, if possible. If construction is to take place during wet weather, the soils may disturb and additional expenses and delays may be expected d��e to the wet conditions. Additional expenses could include the need for placing a blanket o1� rock spalls to protect exposed subgrades and construction traffic areas. We do not recommend re-�ising any of the on- site soils for backfiilling the wall or any other arcas. Any till used on this site should be granular, pit run material. NGA should be retained to cvaluate any soils to be used as structural fill material during construction. Under no circtimstances should water be allowed to flow over or concentrate on the site slopes or over the wall, both during construction, and after construction has been completed. The slopes should be protected froir� erosion. We recommend that all disturbed areas be replanted with vegetation to re- establish vegetation cover as soon as possible. Specific recommendations for erosion control are presented in the Erosion Control and Slope Protection Measures subsection of this report. Erosion Control and Slope Measures The erosion hazard for the on-site soils is listed as moderate, but the actual hazard will be dependent on how the site is graded and how water is allowed to concentrate. Best Management Practices (E3MPs) NELSON GEOTECHNICAL ASSOCIATES, INC.