4704 HARBOR LN 2018-01-02 MF Import

Final Summary Letter Anderson Slope Stabilization Everett, Washington NGA File No. 816909 May 14, 2010 Page 3 Detailed plans for the proposed wall, drainage, and slope restoration were prepare by CG Engineering and Weland Resources, Inc. A soldier pile wall approximately 100 feet long with exposed heights varing from 4 to 14 feel was installed at the top of the steep slope. One to two rows of tiebacks were also installed within the wall, and the tiebacks varied in length from 34 to 52 feet. We provided construction monitoring for the installation of the retaining wall, as documented in Field Reports #1 through #20 dated November It, 2009 through December 15, 2009, which were submitted to you. A bench was created in front of the wall to reduce the total height of the slope, and to remove some of the material that was more susceptible to sliding. To control crosiou on this bench, and to stabilized the exposed soil within the landslide area, heavy erosion control matting was placed on the exposed soil and staked with metal stakes. After the matting was placed, native vegetation was planted on the slopes and below the wall by Wetland Resources, Inc., as approved by the City. 'llte overall drainage for the site was improved after the installation of the retaining wall and erosion control measures. It was determined through site investigation, that all of the downspouts, yard drains, and footing drains were directed to a single pipe that previously transported the collected water to the bottom of the slope. 'I'his pipe, however, extended onto the neighboring property (Lot 48) and was ultimately severed by that property owner. As part of the drainage improvements, runoff from the residence was directed into a new catch basin that was installed directly behind the wall. A new lightlined pipe was extended from this catch hasin, down to the bottom of the slope. The new drain line was placed within a 10-foot wide casement on Lot 49 with the permission of the property owner. A "T dispersion pipe was attached to the end of the train line to act as an energy dissipater. I1te pipe was secured to the slope by metal slakes. To improve the overall stability of the slope, the large trees that were cut down on your property and Lot 49 were cut into smaller pieces and taken off site. Care was taken to not cause further disturbance to die slope. Exposed soil was covered with jute netting, and additional vegetation was planted as agreed upon by you, the City, and the I.ot 49 property owner. NELSON GEOTECHN/CAL ASSOCIATES, INC.