18.08.190 Hillsides, ravine sidewalls and bluffs.
A. Disturbance Limitations. If a hillside, ravine sidewall or bluff is located on or adjacent to a development site, all activities on the site shall be in compliance with the following requirements:
1. Ravine Sidewalls and Bluffs.
a. Buffers. An undisturbed buffer of natural vegetation equal to the height of the ravine sidewall or bluff shall be established and maintained from the top, toe and sides of all ravine sidewalls and bluffs. All buffers shall be measured on a horizontal plane.
b. Buffer Delineation. The edge of a buffer shall be clearly staked, flagged and fenced prior to any site clearing or construction. Markers shall be clearly visible and weather-resistant. Site clearing shall not commence until such time that the project proponent or authorized agent for the project proponent has submitted written notice to the city that the buffer requirements of this section have been met. Field marking of the buffer shall remain in place until all phases of construction have been complete and an occupancy permit has been issued by the city.
c. Buffer Reduction. A buffer may be reduced upon verification by a qualified professional and supporting environmental information to the satisfaction of the city that the proposed construction method will:
i. Not adversely impact the stability of ravine sidewalls;
ii. Not increase erosion and mass movement potential of ravine sidewalls;
iii. Use construction techniques which minimize disruption of existing topography and vegetation;
iv. Includes measures to overcome any geological, soils and hydrologic constraints of the site. The buffer may be reduced to no less than the minimum rear yard setback established in the respective zoning district, pursuant to GHMC Title 17.
d. Building Setback Lines. A building setback line of 10 feet is required from the edge of any buffer of a ravine sidewall or bluff.
2. Hillsides of 15 Percent Slope and Greater – Studies Required. Developments on hillsides shall comply with the following requirements:
a. Site Analysis Reports Required. The following chart sets forth the level of site analysis report required to be developed based upon the range of the slope of the site and adjacent properties:
|
Slope of Site and/or Adjacent Properties |
Length of Slope (Feet) |
Parameters of Report (See Key) |
Report Prepared By |
|---|---|---|---|
|
0% to 15% |
No limit |
Report not required |
|
|
15% to 25% |
> 50 |
1, 2, 3 |
Building contractor or other technical consultant |
|
25% to 40% |
> 35 |
1, 2, 3, 4 |
Registered civil engineer |
|
40% + |
> 20 |
1, 2, 3, 4 |
Registered engineer or geotechnical engineer |
Report Key Contents:
1Recommended maximum site ground disturbance.
2Estimate of storm drainage (gpm) for preconstruction, during construction and postconstruction.
3Recommended methods to minimize erosion and storm water runoff from site during construction and postconstruction.
4Seismic stability of site, preconstruction, during construction and postconstruction.
b. Development Location. Structures and improvements shall be located to preserve the most sensitive portion of the site, its natural land forms and vegetation.
c. Landscaping. The disturbed areas of a development site not used for buildings and other developments shall be landscaped according to the landscape standards of the zoning code (Chapter 17.78 GHMC).
d. Project construction shall be required to implement all recommended requirements of the report referenced in subsection (A)(2)(a) of this section, and any additional requirements as determined by city staff. In addition, should adjacent properties be adversely impacted by the implementation or construction, additional mitigation measures necessary to minimize or eliminate these impacts shall be implemented by the applicant. (Ord. 1036 § 32, 2006).