Laserfiche WebLink
<br /> <br />49 <br /> <br />Chapter 17A.06 <br />GEOLOGICALLY HAZARDOUS AREAS <br /> <br />Sections: <br />17A.06.010 Purpose and Intent <br />17A.06.020 Designation, Classification, and Mapping <br />17A.06.030 General Protection Standards <br />17A.06.040 Landslide Hazard Area Standards <br />17A.06.050 Erosion Hazard Area Standards <br />17A.06.060 Alluvial Fan Hazard Standards <br />17A.06.070 Seismic Hazard Standards <br />17A.06.080 Volcanic Hazard Areas <br />17A.06.090 Mine Hazard Areas <br />17A.06.100 Reporting <br /> <br /> <br />17A.06.010 Purpose and Intent <br />The purpose of this Chapter is to protect human life and safety, prevent damage to <br />structures and property, and minimize impacts to water quality and fish and wildlife caused <br />by geologic hazards. <br /> <br />17A.06.020 Designation, Classification, and Mapping <br />1. Designation. Lands classified as landslide, erosion (including channel migration zones), <br />alluvial fan, seismic, and mine hazard areas, are hereby designated as geologically <br />hazardous areas. <br />2. Classification. <br />a. Potential Landslide Hazard Areas. Landslide hazard areas shall include areas <br />potentially subject to landslides based on a combination of geologic, topographic, <br />and hydrologic factors. They include any areas susceptible because of any <br />combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or <br />other factors. Potential landslide hazard areas include but are not limited to the <br />following areas: <br />i. Areas of historic failures; <br />ii. Areas designated as quaternary slumps, earth-flows, mudflows, or landslides <br />on maps published by the U.S. Geological Survey or Washington State <br />Department of Natural Resources; <br />iii. Areas with all three (3) of the following characteristics: <br />1. Slopes steeper than fifteen percent (15%); <br />2. Hillsides intersecting geologic contacts with a relatively permeable <br />sediment overlying a relatively impermeable sediment or bedrock; <br />and <br />3. Springs or groundwater seepage; <br />iv. Areas that have shown movement and/or are underlain or covered by mass <br />wastage debris; <br />v. Slopes that are parallel or sub-parallel to planes of weakness (which may <br />include but not be limited to bedding planes, soft clay layers, joint systems, <br />and fault planes) in subsurface materials; <br />vi. Slopes having gradients steeper than eighty percent (80%) subject to rock <br />fall during seismic shaking; <br />vii. Areas that show evidence of, or are at risk from snow avalanches; and <br />viii. Any area with a slope of forty percent (40%) or steeper and with a vertical <br />relief of ten (10) or more feet except areas composed of competent bedrock.