7423 LOWER RIDGE RD 2024-10-25 - Laserfiche WebLink

• • COBALT Cobalt Geosciences,LLC GEOSCIENCES P.O.Box 192 North Bend,WA 98045 February 1,2024 D ECEEllOV RR Foundation Specialist Attn:Alesha,Ty-Lynn,Jordan,or Amanda MAR 14 2024 RE: Limited Geotechnical Evaluation Foundation Mitigation CITY OF EVERETT 7423 Lower Ridge Road Permit Services Everett,Washington In accordance with your authorization,Cobalt Geosciences,LLC has prepared this letter to discuss the results of our limited geotechnical evaluation at the above-referenced location. Site and Project Description The site is located at 7423 Lower Ridge Road in Everett, Washington. The site consists of one irregularly shaped parcel(No.00392000002002)with a total area of about 0.62 acres. The western portion of the site is developed with a residence with a daylight basement, detached garage,and driveway.The remainder of the property is vegetated with grasses,shrubs,bushes,and sparse trees. The east-central portion of the site is slightly sloping downward to the east. The approximate magnitude of the slope is about 20 percent with a total relief of about 25 feet. The site is bordered to the north,south,and east by residential properties,and to the west by Lower Ridge Road. We understand that the residence has settled up to 3.375 inches over time,likely beginning after construction and potentially continuing today. The settlement is in several locations within the structure. The project includes installation of at least it helical anchors extending to refusal in relatively dense native soils below affected foundation elements. Anchors will be attached with steel brackets, C channel,and angle iron if necessary. Lifting will be performed as feasible. Additional composite pads with adjustable brackets will be placed in crawlspace areas to support beams. Area Geology The site lies within the Puget Lowland. The lowland is part of a regional north-south trending trough that extends from southwestern British Columbia to near Eugene, Oregon. North of Olympia,Washington, this lowland is glacially carved, with a depositional and erosional history including at least four separate glacial advances/retreats. The Puget Lowland is bounded to the west by the Olympic Mountains and to the east by the Cascade Range. The lowland is filled with glacial and non-glacial sediments consisting of interbedded gravel,sand,silt,till,and peat lenses. The Geologic map of the Everett 7.5-minute quadrangle, indicates that the site is underlain by Vashon Glacial Till. These deposits consist of mixtures of silt,sand,gravel,and clay in a non-sorted matrix or diamict. These deposits become denser with depth below a weathered zone. www.cobaltgeo.com (206)331-1097 SIT