954 NORTH PARK DR 2023-10-31 - Laserfiche WebLink

GeoTest Services, Inc. September 6, 2019 Proposed Swimming Pool — 954 North Park Drive, Everett, WA Project No. 19-0361 Coastal Zone Atlas According to the Washington State Department of Ecology's Coastal Zone Atlas, the upper portion of the subject property is mapped as "stable," while the lower -elevation portion of the property and adjoining slopes are mapped as "unstable." Based on information from the Coastal Zone Atlas as well as aerial photography, it does not appear that the shoreline has appreciably retreated in the past approximately 42 reviewed years of aerial imagery. It is likely that the artificial embankment supporting the railroad at the toe of the slope provides a buffer that slows possible wave undercutting. The DOE's disclaimer states "...these maps are intended to educate the public about the shoreline and to guide regional land use decisions. The maps SHOULD NOT be used as a substitute for site specific studies carried out by qualified geologists and engineers." Aerial Imagery Review GTS reviewed historic and recent aerial photos of the subject property dating back to 1977. Aerial imagery was obtained from Google Earth/Maps, the United States Geological Survey, the Coastal Zone Atlas, and the Snohomish County Property Information (SCOPI) portal. The earliest aerial photo taken from the Coastal Zone Atlas (1977) shows the property as vacant. Photography from 1990 appears to show the lot under development, while single family residences had already been constructed on adjacent properties. The general ground surface and vegetative cover of the lot was similar from prior to development to the present day; the presence of retaining walls on - site indicate moderate earthwork was conducted, but the general tendency of existing slopes and drainage do not appear to have been significantly altered. For this project, GTS's site reconnaissance also included drone photography of the property and surrounding slopes. Specific attention was given to features that would indicate past slope movements, including scarps, unusual vegetation patterns, or ground areas barren of vegetation that would indicate episodic soil sloughing. For the most part, the slopes were observed to be generally vegetated. However, based on a review of Google Earth/Maps imagery, some bare slope areas were observed on the existing bluff slope to the northwest of the property, and to the northeast of the property on the adjacent eastern ravine face. A review of these areas suggests slope retreat through erosion (skin slides). This is further elaborated in the next section. Limited areas near the toe of the slope featured signs of small-scale movements, where cuts had presumably been made during construction of the railroad. Apparent signs of larger movements were not noted during our drone reconnaissance. Further description of surface conditions and interpretation of associated geologic hazards is provided in the Conclusions and Recommendations section of this report. 6