16.18E.060 Critical area report – Additional requirements for geologically hazardous areas.
A. Preparation by a Qualified Professional. A critical areas report for a geologically hazardous area shall be prepared by an engineer or geologist, licensed in the state of Washington, with experience analyzing geologic, hydrologic, and ground water flow systems, and who has experience preparing reports for the relevant type of hazard.
B. Areas Addressed in Critical Area Report. The following areas shall be addressed in a critical area report for geologically hazardous areas:
1. The project area of the proposed activity; and
2. All geologically hazardous areas within two hundred feet of the project area or that have potential to be affected by the proposal.
C. Geological Hazards Assessment. A critical area report for a geologically hazardous area shall contain an assessment of geological hazards including the following site- and proposal-related information at a minimum:
1. Site and Construction Plans. The report shall include a copy of the site plans for the proposal showing:
a. The type and extent of geologic hazard areas, any other critical areas, and buffers on, adjacent to, within two hundred feet of, or that are likely to impact the proposal;
b. Proposed development, including the location of existing and proposed structures, fill, storage of materials, and drainage facilities, with dimensions indicating distances to the floodplain, if available;
c. The topography, in two-foot contours, of the project area and all hazard areas addressed in the report; and
d. Clearing limits;
2. Assessment of Geological Characteristics. The report shall include an assessment of the geologic characteristics of the soils, sediments, and/or rock of the project area and potentially affected adjacent properties, and a review of the site history regarding landslides, erosion, and prior grading. Soils analysis shall be accomplished in accordance with accepted classification systems in use in the region. The assessment shall include, but not be limited to:
a. A description of the surface and subsurface geology, hydrology, soils, and vegetation found in the project area and in all hazard areas addressed in the report;
b. A detailed overview of the field investigations, published data, and references; data and conclusions from past assessments of the site; and site specific measurements, tests, investigations, or studies that support the identification of geologically hazardous areas; and
c. A description of the vulnerability of the site to seismic and other geologic events;
3. Analysis of Proposal. The report shall contain a hazards analysis including a detailed description of the project, its relationship to the geologic hazard(s), and its potential impact upon the hazard area, the subject property, and affected adjacent properties; and
4. Minimum Buffer and Building Setback. The report shall make a recommendation for the minimum no-disturbance buffer and minimum building setback from any geologic hazard based upon the geotechnical analysis.
D. Incorporation of Previous Study. Where a valid critical areas report has been prepared within the last five years for a specific site, and where the proposed land use activity and surrounding site conditions are unchanged, said report may be incorporated into the required critical area report. The applicant shall submit a hazards assessment detailing any changed environmental conditions associated with the site.
E. Mitigation of Long-Term Impacts. When hazard mitigation is required, the mitigation plan shall specifically address how the activity maintains or reduces the pre-existing level of risk to the site and adjacent properties on a long-term basis (equal to or exceeding the projected lifespan of the activity or occupation). Proposed mitigation techniques shall be considered to provide long-term hazard reduction only if they do not require regular maintenance or other actions to maintain their function. Mitigation may also be required to avoid any increase in risk above the pre-existing conditions following abandonment of the activity. (Ord. 1104-15 § 1 (Att. A)).