GEManualSec9SteepSlopesPage

GRADING AND EXCAVATION MANUAL 2010 Edition

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SECTION 9: STEEP SLOPES

One of the most attractive features of Summit County is its mountainous environment, but it is this environment that can present some of the most dangerous and challenging conditions for recreation and development. For that reason there are very specific requirements and conditions placed on the development of steep lots. The goal of all conditions and regulations is to ensure that development in steep areas does not cause unstable conditions during construction or in the long-term. When special conditions on a property are identified, special follow-up requirements or conditions may be implemented or imposed, such as periodic inspections by a geotechnical engineer, site evaluations by specialized engineers, and final site condition assessment letters from the geotechnical or design engineer.

In accordance with §7102 of the Code, disturbance of slopes greater than 3.33:1 (30%) are allowed only with specific approval of the County Engineer. If a lot contains slopes in excess of 3.33:1, and 15% or more of those slopes are proposed to be disturbed, then a geotechnical report for slope stability will be required. Roadway embankment slopes shall be included in the slope analysis of a property, and disturbance of roadway embankments may be grounds for the requirement of a slope stability report, depending on the extent and severity of the proposed impacts. In circumstances where slopes of 3.33:1 or greater exist but there is little to no likelihood of slope instability being induced by development, the County Engineer may waive the requirement for a geotechnical report. If the County Engineer chooses not to waive this requirement then permit review will be ceased until the report is provided. The geotechnical report for slope stability shall include recommendations and information necessary to protect the area from construction induced instability, including limiting erosion potential, stabilizing fill placement, identifying lateral earth pressures (active, passive, and equivalent fluid pressure) for use in the design of foundations, controlling runoff, and methods of anchoring structures proposed on the property. The slope stability report shall reflect all proposed improvements. Any changes to the proposed plans may necessitate follow-up reviews and amendments to the report by the geotechnical engineer. The submittal of any proposal involving development of a lot with steep slopes shall include a slope analysis plan sheet, graphically depicting the location of steep slopes and those slopes proposed to be disturbed.

Where any development is proposed, finished grades shall be shown clearly on the plans as prescribed in this Manual and the Code. Where finished grades exceed 3:1 slope netting or some other means of temporary stabilization will be required, along with additional temporary erosion and sediment control measures as deemed necessary and appropriate. On slopes in excess of 30% finished grades shall be furrowed perpendicular to the slope in order to slow runoff down the slope and limit seeds being washed down the slope. In all cases the maximum slope of un-retained finished grades will be 2:1. Retaining walls will be constructed in accordance with engineering practices and the design provided. Retaining walls over 4-feet tall shall be engineered, and shall be certified by an engineer prior to final approval. Inspections must be performed as required by the engineer. In the event that a wall exceeds 4-feet tall but was not engineered a certification letter or as-built must still be provided. If the engineer has not observed the wall construction as needed then the wall must be dismantled and reconstructed with observations as required. Per §3505.17.D of the Code, retaining walls over 8-feet tall will not be permitted unless topographic constraints drive such design. Walls over 8-feet tall may be approved at the discretion of the County Engineer. Final inspection of projects with retaining walls over 4-feet tall will not be performed until the certificate of approval from the engineer has been provided.

Any questions regarding the existence of, or regulations and standards pertaining to steep slopes shall be directed to the Engineering Department. See the contact information in the appendices to this Manual for assistance in contacting the Engineering Department.

GRADING AND EXCAVATION MANUAL 2010 Edition

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