1915 W MUKILTEO BLVD 2018-01-02 MF Import

Plan Review Letter 1915 W Mukilteo Boulevard Everett, Washington December 1, 2006 NGA File No. 743206 Page 2 recommended that stormwater runoff he directed into a permanent storm drain system, and that stormwater runoff from impervious surfaces not be allowed to flow uncontrolled over the site slopes. In addition, we recommended that if possible, construction should take place during the drier months in order to lessen the impact to the slopes and reduce the potential for additional expenses. PLAN REVIEW AND CONCLUSIONS We have reviewed geotechnical aspects of the provided plans and found the plans to be in general compliance with our geotechnical report. The wall has been designed for a maximum height of 13 feet, rather than our recommended minimum height of 10 feet. Also, the wall is shown to be vertical rather than at the recommended 15-degree inclination. In our opinion, these deviations from our recommendations are not detrimental. All other aspects of wall design are in compliance with our report. On Page S-3.1 in Detail I — Shoring Wall, we recommend that it cut-off drain should be shown on the plans upslope of the repaired area as per Figure 10 of our geotechnical report. We also recommend that a note be added indicating that Best Management Practices (BMPs) should be used to prevent dirty water from flowing over the site slopes or down towards Possession Sound. On Page S4.1 in Detail I — Section, we recommend that the plans indicate a finished Sround surface down slope of the wall toe that consists of 4-foot wide, level benches backfilled with 4- to 8- inch rock spalls. MINIMUM RISK STATEMENT Provided recommendations stated in the soil report and this letter, including collecting and diverting all storm runoff into a permar._nt system are followed during construction, the areas disturbed by construction should be stabilized. Therefore, the risk of damage to the proposed development or to adjacent properties from soil instability should be minimal, and the proposed grading and development should not increase the potential for soil movement. CLOSURE We recommend that NGA be retained to provide monitoring and consultation services during construction to confirrn that the conditions encountered are consistent with those indicated by the explorations, to provide NELSON GEOTECHNICAL ASSOCIATES, INC.