1209 MADRONA AVE 2016-10-05 - Laserfiche WebLink

Geotechnical Engineering Evaluation NGA File No. 870113 Packer Property March 11,2013 Retaining Walls and Steep Slope Evaluation Page 9 Everett,Washington connect with the lowest wall or within a close proximity to that wall. We have provided recommendations for design and installation of a new pipe pile wall with timber lagging and tieback anchors to protect the top of the slope and walls. The anchor system could consist of either grouted tiebacks or mechanically installed anchors. We have also provided recommendations for some improvements on the slope to lessen the potential for future sliding. Detailed recommendations regarding the proposed wall have been included in the Retaining Wall Design and Construction subsection of this report. The recent landslide includes the Packer property and the neighbor's property to the west. We strongly recommend,if possible, that the two property owner's work together on addressing the stability issues on the two properties since these issues can directly affect the proposed improvements if repairs are not performed on the neighboring western property as well. Additional similar slope stability improvements such as erosion control and drainage systems would need to be conducted on the neighbor's property to help prevent future events impacting the new repairs on the Packer's property and to improve overall slope stability within the vicinity of the two properties. All construction operations and drainage improvements should be planned and completed in a manner that enhances the stability of the steep slopes, not reduces it. Excavation spoils should not be stockpiled near the top of the slope, or be left on the slope. Depending on conditions in the field during construction, the excavation spoils may be placed within the gentler ground at the bottom of the slope. This should be evaluated and approved by the geotechnical engineer. Water should not be allowed to concentrate or flow over the steep slope. Future vegetation management on the slope should be the subject of a specific evaluation and a plan approved by the City of Everett. The slope should be monitored on an on-going basis, especially during the wet season, for any signs of instability, and corrective actions promptly taken should any signs of instability be observed. Lawn clipping and any other debris should not be cast over the slope. The soils encountered on this site are considered highly moisture-sensitive and will disturb easily when wet. To lessen the potential impacts of construction on the slope and to reduce cost ovemzns and delays, we recommend that construction take place during the drier summer months if possible. However, the repairs may have to be implemented sooner than that to reduce the potential for additional slides. If construction takes place during the rainy months, additional expenses and delays should be expected. NELSON GEOTECHNICAL ASSOCIATES, INC,