7-20-20 Steep and Potentially Unstable Slopes

(b) Forty-five (45) Percent or Greater Gradient

Development is prohibited on slopes with a slope gradient equal to or exceeding forty-five (45) percent, except:

1. Where:
   • (a) The lot is in a legally platted subdivision, recorded prior to 1972, and
   • (b) There is no alternative building site that avoids areas of slope exceeding forty-five (45) percent, and
   • (c) An engineer or geologist licensed in the State of Colorado demonstrates that the site can be engineered so that there is no hazard posed by the location of development on such slopes, and
   • (d) The proposed development complies with all standards in subsection (c)(1) below applicable to slopes of thirty (30) percent or greater; and
2. As provided in subsections (c)(3) or (c)(4) below.

(c) Thirty (30) Percent or Greater Gradient

Development is prohibited on slopes with a slope gradient of thirty (30) percent or more, except as follows:

(1) No Alternative Building Site

• If there is no alternative building site available on the parcel with slopes of less than thirty (30) percent, development (but not roads or driveways) may be approved by the Community Development Department through the Site Plan process subject to the following development standards:
  • (a) An engineer or geologist licensed in the State of Colorado shall be required to demonstrate that the site can be engineered so that there is no hazard posed by the location of development on such slopes.
  • (b) To the extent possible, the development shall be designed so as to: avoid adding water to the site that would cause decreased stability; avoid removing the toe of the slope without adequate mechanical support; avoid increasing the weight load on top of the slope; re-contour disturbed slopes so that they can be re-vegetated; avoid steepening of existing slopes.
  • (c) Any development approved pursuant to this section shall be conditioned upon compliance with the engineer or geologist’s recommended mitigation measures.
  • (d) Following Site Plan review, and prior to the application for a Building Permit, a precise engineer or geologist approved mitigation plan shall be submitted by the applicant that shows the area of disturbed slope, any re-grading required and the exact size and location of all mitigation devices. The mitigation measures must be determined by the Community Development Department to be the least visually and ecologically obtrusive alternatives.

(2) Parcels with Some Areas of Less than Thirty (30) Percent Slopes

• (a) If a parcel contains areas with less than thirty (30) percent slopes that are accessible by a road or driveway that meets the requirements of this Land Use Code, but such areas (after exclusion of Constrained Areas) are not large enough to develop the floor area permitted by underlying zoning, then areas containing slopes of less than thirty (30) percent must be utilized to develop as much of the floor area as can feasibly be accommodated. Areas containing slopes of thirty (30) percent or greater (but not exceeding forty-five (45) percent) may then be used for development of the remainder of the permitted floor area. The resulting area specified for development should define a contiguous area with slopes of less than thirty (30) percent to the maximum extent practicable.
• (b) Development on slopes equal to or exceeding thirty (30) percent (but less than or equal to forty-five (45) percent) shall be subject to the development standards in Sec. 7-20-20(c)(1)(a) through (d)., and shall minimize disruption of natural terrain as viewed from any of those roads identified in Sec. 7-20-120(b).

(3) Minor Slope Anomaly

• Through the Site Plan process, exceptions for minor changes in slope-development may be permitted on lands that have a slope equal to or in excess of thirty (30) percent when the slope is due to the presence of a minor natural or minor man-made change in the gradient of a continuous slope, provided that an engineer or geologist licensed in the State of Colorado demonstrates that the slope's ground surface is not prone to instability or failure and that the proposed development will not cause greater instability or increase the potential for slope failure.

(4) Existing Roads and Driveways

• Through the Site Plan process, an exception for minor road and driveway improvements may be permitted to existing roads and driveways that traverse previously disturbed slopes equal to or in excess of thirty (30) percent, provided that the applicant demonstrates that all of the following conditions are met:

• (a) The road or driveway was legally created, as demonstrated by (i) a valid copy of the permit for the road or driveway, or (ii) evidence that the road or driveway was constructed prior to the County’s road or driveway permit system in 1993, or (iii) that a permit was not required to construct the road or driveway.
  • (b) The proposed use of the road is an existing legal use (i.e., if residential development is proposed, it shall be demonstrated that the road already services an existing, legal residential structure). The current use of the road or driveway shall not change between residential, commercial, lodging or industrial use. No road improvements shall be permitted pursuant to this provision to allow the development of any structure where there is no pre-existing, legal structure (e.g., a mining road or jeep road that provides access to a vacant parcel shall not be improved pursuant to this provision to create access to a new residence).
  • (c) The improvements shall be limited to existing roads and driveways that traverse previously disturbed slopes equal to or in excess of thirty (30) percent and comply, or can comply without impacting slopes equal to or in excess of thirty (30) percent, with the minimum requirements in the Pitkin County Road Management and Maintenance Plan for width, grade and curvature. New road and driveway improvements that traverse undisturbed slopes equal to or in excess of thirty (30) percent are prohibited.
  • (d) The improvements shall be minor in scope and shall be the minimum required to ensure the safety of both the general public and safety agency personnel. Improvements that may be permitted pursuant to this provision may include, but not be limited to, pullouts, turnarounds or grading, if the road or driveway otherwise complies with the standards of the Pitkin County Road Management and Maintenance Plan. Improvements that would create further impacts on slopes equal to or in excess of thirty (30) percent in order to bring an existing road or driveway into compliance with the minimum standards of the Pitkin County Road Management and Maintenance Plan are prohibited.
  • (e) An engineer or geologist licensed in the State of Colorado demonstrates that the slope’s ground surface is not prone to instability or failure, and that the proposed improvements will not cause greater instability or increase the potential for slope failure.

(5) Short Driveway Encroachments

• Through the Building Permit process, an exception for short driveway encroachments may be permitted as follows:
  • (a) This exception may only be utilized where there is no alternative alignment on slopes less than thirty (30) percent and the proposed driveway is free of all of the following hazards: high hazard avalanche zone (red zone) and moderate hazard avalanche zone (blue zone), landslide areas, or rockfall areas. (See Sec. 7-20-50).
  • (b) For a maximum of one-hundred (100) linear feet per lot or parcel, the driveway may encroach on slopes between thirty (30) percent and a maximum of forty-five (45) percent gradient. The maximum of one hundred (100) linear feet of permitted encroachment shall be measured along the centerline of the driveway.
  • (c) All development permitted pursuant to this section shall be subject to the development standards of Sec. 7-20-20(c)(1)(a) through (d).

(6) Micro Hydroelectric Systems

• Construction and maintenance of micro hydroelectric system improvements on steep slopes may be approved by the BOCC through the Special Review and Site Plan process subject to the following development standards:
  • (a) An engineer or geologist licensed in the State of Colorado shall be required to demonstrate that the site can be engineered so that there is no hazard posed by the location of the system components on such slopes.
  • (b) To the extent possible, the system components shall be designed so as to: avoid adding water to the site in a manner that would cause decreased stability; avoid removing the toe of the slope; re-contour disturbed slopes so that they can be revegetated; avoid steepening of existing slopes.
  • (c) Any development approved pursuant to this section shall be conditioned upon compliance with the engineer or geologist’s recommended mitigation measures.
  • (d) Following site plan review and prior to the application for a building permit, a precise engineer or geologist approved mitigation plan shall be submitted by the applicant that shows the area of disturbed slope, any re-grading required and the exact size and location of all mitigation devices. The mitigation measures must be determined to be the least visually and ecologically obtrusive alternatives, and can include but are not limited to hand-burial or non-burial of transmission pipelines; prohibition of the use of excavation equipment for foundation improvements; and the positioning of facilities so that vegetation removal is kept to a minimum.

(7) Habitable Retaining Structures

• Through the Site Plan process, an exception for "habitable retaining structures" and similar types of construction may be permitted at the toe, or along the base of slopes equal to or in excess of thirty (30) percent, including slopes in excess of forty-five (45) percent. This section shall not modify other prohibitions on development including but not limited to those in Section 7-20-50 Geologic Hazards. This section is available only when all of the following conditions are met:
  • (a) The property on which the habitable retaining structures are proposed to be built has previously been developed with a structure(s) that meets County Codes for human habitation and that was built pursuant to valid County land use approvals and building permits (as applicable).
  • (b) An engineer or a geologist licensed in the State of Colorado has provided a report demonstrating to the satisfaction of the BOCC that the site can be engineered so there is no hazard posed by the location of the proposed habitable retaining structures on such slopes.
  • (c) The proposed structures shall be designed to function principally as retaining structures, but may also be permitted for human habitation. A habitable retaining structure that also meets the Code definition of a residential dwelling unit, or is a structure that would typically be accessory to a residential dwelling (such as a garage), or any structure that includes plumbing facilities shall not be allowed pursuant to this sub-section.
  • (d) The proposed development at the toe or base of the slope shall be designed to avoid adding water to the site that would cause decreased stability or would increase the weight load on the top of the slope.
  • (e) Slopes that are disturbed by the proposed development shall be re-contoured so they can be re-vegetated, and a plan for such re-vegetation shall be provided which restores the exposed slopes to a stable, natural condition.
  • (f) The proposed habitable retaining structures shall comply with the standards for retaining walls found in Section 7-20-20 (e) (6) of this Code as applicable, but shall not be subject to the limits on changing natural grade, the limits on graded, excavated or filled man-made slopes, and the guidelines for retaining walls found in Section 7-20-20 (e) (2), (3), and (5) of this Code.

(8) Pitkin County Solid Waste Center Operations

• The BOCC may authorize the following types of activities to occur at the Pitkin County Solid Waste Center through the PUB Zone District Master Plan process:
  • (a) Earth moving and similar types of land-disturbing activities necessary to operate the Solid Waste Center on man-made slopes that are in excess of thirty percent (30%) shall be exempt from the provisions of this Sec. 7-20-20 of the Land Use Code if they occur within the “Limit of Earth Moving Activity” line depicted on the adopted Solid Waste Center Master Plan.
  • (b) Earth moving and similar types of land-disturbing activities necessary to operate the Solid Waste Center may also be authorized to occur on natural slopes that are in excess of thirty percent (30%) within the “Limit of Earth Moving Activity” line depicted on the adopted Solid Waste Center Master Plan provided the applicant demonstrates that all of the following conditions are met:
    1. The applicant shall demonstrate that there are no alternative locations available within the Limit of Earth Moving Activity line where the proposed earth moving or similar land-disturbing activities could occur that would avoid disturbing slopes that are in excess of thirty percent (30%).
    2. A plan shall be presented that was prepared by an engineer or a geologist licensed in the State of Colorado that demonstrates that there will be no hazard posed by the proposed earth moving or similar land-disturbing activities on slopes in excess of thirty percent (30%).
       • (a) The plan shall show the area of disturbed slope, any re-grading that will occur, and the size and location of any planned mitigation measures, including how disturbed slopes will be re-vegetated.
       • (b) The plan shall receive the approval of the State of Colorado (if such approval is necessary).
       • (c) The plan shall demonstrate that the slopes resulting from the earth moving or similar land disturbing activities will be stable.
    3. This exemption shall not be used to authorize development of a structure on a slope in excess of thirty percent (30%) and may only be used to authorize earth moving and similar types of land-disturbing activities on such slopes.