1907 W MUKILTEO BLVD 2021-11-15 - Laserfiche WebLink

• Pearson Property Slope Stabilization NGA File No 945216 1907 West Mukilteo Boulevard February 19,2016 Everett,Washington Page 7 be cast over the slope. Any future plans for structures near the slope or modifications to the slope should be specifically evaluated by NGA and approved by the City of Everett. Erosion Control and Slope Protection The on-site soils are listed as having a moderate potential for erosion when cleared of vegetation, but the actual erosion potential could be severe depending on how the site is graded and how water is allowed to concentrate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from erosion. Erosion control measures may include diverting surface water away from the stripped areas. Silt fences or straw bales could be erected to prevent muddy water from flowing off the site. Stockpiles should be avoided. Disturbed areas should be planted as soon as practical and the vegetation should be maintained until it is established. The erosion potential for areas not stripped of vegetation should be low to moderate. Disturbed areas outside of the proposed development areas should be replanted with vegetation at the end of construction. The vegetation should be maintained until it is established. Final grading should incorporate permanent erosion control measures and should be designed to route stormwater runoff to appropriate discharge locations away from the structures and sloping ground. Protection of the steep slope should be performed as required by the City of Everett. No material of any kind should be placed on the slope or be allowed to reach the slope, such as excavation spoils, lawn clippings, and other yard waste,trash, or soil stockpiles. Replacement of vegetation should be performed in accordance with City code. Any future proposed development within or near the slope should be the subject of a specific geotechnical evaluation. Under no circumstances should water be allowed to concentrate on the slope either during construction or on a permanent basis after construction has been completed. All irrigation systems on or near the slope should be avoided. Future yard waste, grass clippings, or any other waste material or household trash should never be cast over the slope or piled near the walls. Such activity could lead to future slope instability. Additionally, drainpipes associated with the new retaining walls and existing residence, should all be tightlined to an approved stormwater management system, as described later in this report. Retaining Wall Design and Construction The proposed new retaining wall should consist of minimum 6-inch driven steel "H" piles (W6x25) bridged using pressure-treated timber lagging and anchored back into the slope using grouted tieback NELSON GEOTECHNICAL ASSOCIATES,INC,