City of Spokane

Spokane Municipal Code

***Note: Many local criminal codes can now be located under Chapter 10.60 SMC while others are now cited under the Revised Code of Washington (RCW), which was incorporated into the municipal code in 2022. (See SMC 10.58.010). Code Enforcement, including Noise Control and Animal Regulations are located in Chapters 10.62 through 10.74.

Home
Title 17E
Chapter 17E.040
Section 17E.040.100
 

Title 17E Environmental Standards

Chapter 17E.040 Spokane Geologically Hazardous Areas

Section 17E.040.100 General Performance Standards

The following standards must be met for all development within geologically hazardous areas and associated buffers as classified in this chapter.

  1. The development shall not increase surface water discharge or sedimentation to adjacent properties beyond pre-development conditions unless approved by the department of engineering services.
  1. The development shall not create adverse impacts on surrounding properties. These impacts include but are not limited to increases or decreases in water characteristics, deposition or removal of earth material, or changes that would harm the growth of existing vegetation.
  1. Alterations to the site shall not adversely impact other critical areas occurring on- or off-site.
  1. The proposed development shall not decrease the factor of safety for landslide occurrences below the limits of 1.5 for static conditions and 1.2 for dynamic conditions. Analysis of dynamic conditions shall be based on a minimum horizontal acceleration as established by the current version of the International Building Code.
  1. Structures and improvements shall minimize alterations to the natural contour of the slope and the foundation shall be tiered where possible to conform to existing topography. Terracing of the land shall be kept to a minimum to preserve natural topography where possible. Structures and improvements shall be located to preserve the most critical portion of the site and its natural landforms and vegetation. All development should be designed to minimize impervious lot coverage.
  1. Roads, walkways and parking areas shall be designed parallel to topographic contours with consideration given to maintaining consolidated areas of natural topography and vegetation.
  1. Unless otherwise provided or as part of an approved alteration, removal of vegetation from an erosion or landslide hazard are or related buffer shall be prohibited. Removal of vegetation, including trees, shrubs, grasses and forbs shall be the minimum required for construction. Any replanting that occurs shall consist of trees, shrubs and ground cover that is compatible with the existing surrounding vegetation, meets objectives of erosion prevention and site stabilization and does not require permanent irrigation for long term survival.
  1. Structures and improvements shall be clustered where possible. Driveways and utility corridors shall be minimized through the use of common access drives and corridors where feasible. Access shall be in the least sensitive area of the site.
  1. Point discharges from surface water facilities and roof drains onto or upstream from an erosion or landslide hazard area shall be prohibited except as follows:
    1. Conveyed via continuous storm pipe downslope to a point where there are no erosion hazards areas downstream from the discharge.
    1. Discharged at flow durations matching predeveloped conditions, with adequate energy dissipation, into existing channels that previously conveyed stormwater runoff in the predeveloped state; or
    1. Dispersed discharge upslope of the steep slope onto a low-gradient undisturbed buffer demonstrated to be adequate to infiltrate all surface and stormwater runoff, and where it can be demonstrated that such discharge will not increase the saturation of the slope.
  1. On-site sewage disposal systems, including drain fields, shall be prohibited within erosion and landslide hazards areas and related buffers when sewer is available within two hundred feet or as otherwise provided by chapter 13.03 SMC.

Date Passed: Monday, December 3, 2007

Effective Date: Sunday, January 6, 2008

ORD C34149 Section 8