ARTICLE 070.100
Development in Areas of Geologic Hazards
070.100.010 Purposes of Article
070.100.020 General Provision
070.100.030 Geologic Hazards District Regulations
070.100.040 Variance
070.100.041 Appeal of Administrative Decision
070.100.050 Public Improvements in Areas of Geologic Hazard
070.100.010 Purposes of Article.
The purpose of this Article is to promote the public health, safety and general welfare and to minimize public and private losses due to geologic conditions in specific areas by provisions designed to:
(1) Protect human life, safety and property;
(2) Minimize damage to public facilities and utilities;
(3) Minimize the need for relief and clean-up operations due to geologic events with their accompanying public and private costs;
(4) Minimize the need for expensive mitigation measures to protect public and private property; and
(5) Alert property owners and potential buyers of geologic hazards existing in certain areas so that they may protect their own property and avoid endangering the property of others.
070.100.020 General Provisions.
(a) Areas of geologic hazards. As used in this Article, the term geologic hazard shall include the following hazards, as defined in Colorado Geological Survey Open File Report 78-10 ("C.G.S. 78-10"):
Corrosive soils are potentially corrosive to concrete and steel.
Debris flow hazard means severe and moderate debris flow hazard. Severe debris flow hazard poses possible serious damage to structures and risk to life, and mitigation is necessary. Moderate debris flow hazard poses possible minor damage to structures and risk to life. Mitigation is recommended and major cleanup is probable.
Hydrocompaction hazard means severe and moderate hydrocompaction hazard. Severe hydrocompaction hazard poses a high probability of major and/or rapid settlement accompanied by local piping and slope instability due to soil structure disruption. Moderate hydrocompaction hazard poses a low probability of rapid major settlement but a high probability of significant long-term settlement.
Landslide hazard is shown in areas of identified landslide features. Slides are mostly older features but have potential for reactivation.
Rockfall hazard criteria includes an identifiable source area for rocks and the presence of fallen rocks with intermediate diameters of two (2) feet or more.
Slope instability denotes areas of past and current mass wasting processes.
(b) Establishment of Geological Hazards Districts. There are hereby created within the City the following Geologic Hazards Districts:
(1) Hazard Avoidance District. This District includes undeveloped parcels with the potential or presence of severe debris flow, hydrocompactive soils and/or rockfall according to C.G.S. 78-10. The District also includes developed parcels with the potential or presence of the aforesaid severe geologic hazards according to C.G.S. 78-10 where additional development will significantly increase the risk of damage from the hazard or significantly increase the cost to the community of mitigating the hazard.
(2) Hazard Mitigation District. This District includes parcels with the aforesaid severe geologic hazards where significant development already exists and where additional development will not significantly increase the risk of damage from the hazard nor significantly increase the cost to the community of mitigating the hazard. It also includes areas with the potential or presence of moderate debris flow, hydrocompactive soils and/or rockfall hazards according to C.G.S. 78-10. (R & Re 35-88 §1)
(c) Incorporation of Geologic Hazards District Map. The locations and boundaries of the Geologic Hazards Districts established by this Article shall be those established by the official report entitled "Geologic Hazards of the Glenwood Springs Metropolitan Area" as released by the C.G.S. 78-10. The map shall be interpreted by the City Engineer as follows:
(1) Hazard Avoidance Districts.
a. Undeveloped parcels lying entirely or partly in any area identified as a severe hazard zone on the Map of Debris Flow Fan Deposits and Hazards and/or the General Geologic Hazards Map.
b. Developed parcels identified as lying entirely or partly in any area identified as a severe hazard zone on the aforesaid maps where the City Engineer has determined that additional development will increase the risk of damage from the hazards and/or significantly increase the cost to the community of mitigating the hazards.
(2) Hazard Mitigation Districts.
a. Parcels lying entirely or partly in any area identified as a moderate hazard zone on the Map of Debris Flow Fan Deposits and Hazards and/or the General Geologic Hazards Map.
b. Developed parcels identified as lying entirely or partly in any area identified as a severe hazard zone on the aforementioned maps where the City Engineer has determined that additional development will not increase the risk of damage from the hazard and/or will not significantly increase the cost to the community of mitigating the hazard. (R & Re 35-88 §2)
(d) (R 35-88 §3)
(e) Adoption of official geologic hazards maps. The geologic hazards maps which accompany C.G.S. 78-10, prepared by Lincoln-Devore Testing Laboratory for the Colorado Geological Survey, are hereby adopted as the official maps of hazard areas. These maps shall serve as official reference in case of dispute regarding the location of hazards, and the City Engineer's interpretation of these maps shall be final.
(f) Annexation of land within an area of geologic hazard. Upon annexation of any land within an area of geologic hazard, as determined on the official maps of geologic hazards (C.G.S. 78-10), such land shall be added to the appropriate geologic hazards district, and all provisions of this Article shall apply. (A 35-88 §4)
(g) Applicability. The provisions of this Article shall apply to every proposal requiring any one (1) or more of the following:
(1) A development permit;
(2) A grading permit;
(3) A building permit for construction of a new building or structure; or
(4) A building permit for addition, alteration or repair of an existing building or structure, the value of which exceeds fifty percent (50%) of the assessed value or market value, whichever is greater.
(h) Interpretation. The provisions of this Article shall be deemed to be minimum requirements. Nothing herein shall impair the obligations of or interfere with private agreements in excess of the minimum requirements. Where this Article imposes a restriction different from that imposed by other applicable provisions of law, contract or deed, the more restrictive provision shall control.
(i) Disclaimer of liability. This Article is intended to provide some degree of protection to life, safety and property. It is based on scientific and engineering considerations which are continually being developed and proven. Compliance with the provisions herein cannot ensure freedom from risk to life, safety or property. This Article shall not create liability on the part of the City or any officer or employee of the City for any damage that may result from reliance on this Article or any administrative decision lawfully made thereunder.
(R & Re 35-88 §§1, 2; R 35-88 §3; A 35-88 §4)
070.100.030 Geologic Hazards District regulations.
(a) Hazard Avoidance Districts. No improvement, building, structure, excavation, dumping or backfill shall be placed, built, undertaken or approved in a Hazard Avoidance District except for fences, geologic stabilization structures or paths for nonmotorized use unless, before application for a development permit or, if no development permit is required for a grading or building permit, the applicant demonstrates to the City Engineer and the Director by clear and convincing evidence that one (1) of the following conditions is met:
(1) The land to be affected does not lie within an area of severe debris flow, hydrocompaction or rockfall hazard or a drainage basin contributing to any such hazard, as shown on the official geologic hazards map (C.G.S. 78-10), and the proposal is in conformance with the purposes of this Article.
(2) The severe hazard, as specified at C.G.S. 78-10, does not exist on the subject site in the proposal and is in conformance with the purposes of this Article. Such a determination shall require detailed analysis of the area by a qualified geologist and an engineering geology report, which report may be submitted by the City to the Colorado Geologic Survey for review. The area, as used herein, means the site of the proposed development as well as adjacent land and upslope drainage basins as necessary to compare the area analysis with the C.G.S. 78-10 maps. Upon submittal of this report by the applicant, application may be made for a development, grading or building permit, but such a permit shall not be issued until the City Engineer and the Director have determined that the conditions of this Subparagraph are met.
(3) The proposed development meets all of the following conditions:
a. It will include no human habitation;
b. It will not require City water, wastewater, streets or other public service;
c. It will not increase the hazard to other public or private property; and
d. It is consistent with the intent and purposes of this Article.
(4) The subject site lies within an area with rockfall hazard but not debris flow or hydrocompaction hazard and not within a drainage basin contributing to any such hazard as shown on the official geologic hazards map (C.G.S. 78-10). In the case of such a determination by the City Engineer, a mitigation plan shall be required before issuance of a development, grading or building permit. The mitigation plan shall be produced and certified by a qualified engineer and shall demonstrate to the City Engineer and the Director by clear and convincing evidence that rockfall damage will be prevented by a catchment wall or other means. (A 35-88 §5)
(b) Hazard Mitigation Districts.
(1) All new structures and additions or improvements, as set forth in Subsection 070.100.020(g), proposed in a hazard mitigation district shall be subject to the requirements of Paragraphs (b)(2) through (b)(10), inclusive, unless before application for a development permit or, if no development permit is required for grading or building permit, the applicant demonstrates to the City Engineer and the Director by clear and convincing evidence that one (1) of the following conditions is met:
a. The land to be affected does not lie within an area of severe or moderate debris flow, hydrocompaction or rockfall hazard or a damage basin contributing to any such hazard as shown on the official geologic hazards map (C.G.S. 78-10).
b. The severe or moderate hazards as specified in C.G.S. 78-10 do not exist on the subject site and the proposal is in conformance with the purposes of this Article. Such a determination shall require detailed analysis of the area by a qualified geologist in an engineering geology report, which report may be submitted by the City to the Colorado Geological Survey for review. The area, as used herein, means the site of the proposed development, as well as the adjacent land and upslope drainage basin as necessary to compare the area analysis with the C.G.S. 78-10 maps. Upon submittal of this report by the applicant, application may be made for a development, grading or building permit, but such permit shall not be issued until the City Engineer and the Director have determined that the conditions of this Subparagraph are met.
(2) In areas with moderate or severe debris flow hazard as shown on the official geologic hazards maps (C.G.S. 78-10), before issuance of a development permit or, if no development permit is required, a grading or building permit, the applicant shall demonstrate to the City Engineer and the Director by clear and convincing evidence that any structure or grading change that may divert debris flow or floodwaters from the subject property will not increase hazards to other public or private properties. Such a determination shall require an engineering geology report produced and certified by a qualified engineer. (A 35-88 §6)
(3) Before issuance of a building permit, the applicant shall demonstrate to the City Engineer and the Building Official by clear and convincing evidence that the following requirements are met:
a. Within six hundred (600) feet of gully mouths, as shown on th geologic hazards district map, the following performance specifications shall be met unless the applicant submits a report certified by a qualified geologist and a qualified engineer which provides computations supporting other performance specifications for the specific area in question. Such report shall be subject to the approval of the City Engineer, who may submit the report to the Colorado Geological Survey for review:
1. Within three hundred (300) feet (90 m) of gully mouths, all buildings shall have the uphill wall designed and constructed to resist a horizontal force of 900/lbs/ft2 (43kPa) to a height of six (6) feet above undisturbed or finished ground level, whichever is higher.
2. Between three hundred (300) and six hundred (600) feet (90-180 m) from gully mouths, all buildings shall have the uphill wall designed and constructed to resist a horizontal force of 400/lbs/ft2 (19kPa).
3. The uphill wall shall be considered that wall most likely vulnerable, in terms of direction, to debris flow. In case of dispute, the City Engineer shall determine which walls require reinforcement.
b. In areas with rockfall hazard, as shown on the official geologic hazards maps (C.G.S 78-10), a mitigation plan shall be produced and certified by a qualified engineer and shall demonstrate that rockfall damage will be prevented by a catchment wall or other means.
c. In areas with hydrocompaction hazard, as shown on the official geologic hazards maps (C.G.S. 78-10), a mitigation plan shall be produced and certified by a qualified engineer or geologist and shall demonstrate that all new foundations, roads and underground utilities are designed and will be constructed to prevent significant damage or premature deterioration due to ground subsidence.
d. In areas with landslide hazard, slope instability or corrosive soils, as shown on the official geologic hazards maps (C.G.S. 78-10), the applicant shall demonstrate that all such hazards will be mitigated to accomplish the purposes of this Article. The City Engineer may require an engineering geology report where he/she deems it necessary for determining that any hazards are mitigated.
(4) The design-load requirements of Subparagraph (b)(3)a may be applied to a building located anywhere within a hazard mitigation district where the City Engineer determines, before issuance of a building permit, that the situation warrants such requirement.
(5) Reinforcement of uphill walls is recommended for all structures within hazard mitigation districts, whether or not it is required, except where hydrocompaction is the only hazard present.
(6) Building design which places sleeping quarters on the downhill or less vulnerable side is recommended within hazard mitigation districts except where hydrocompaction is the only hazard present.
(7) All required geology reports shall be submitted in such a form that they can be directly related to C.G.S. 78-10.
(8) A required mitigation plan shall include a description of the geologic hazards, conclusions and recommendations regarding the effect of such hazards on the proposed development, and design criteria and procedures for mitigating such hazards based on sound engineering and geologic practices and information.
(9) For purposes of this Article, a qualified geologist shall be considered a professional geologist as set forth in Section 34-1-201, C.R.S., as amended, and a qualified engineer shall be considered a professional engineer, as set forth in 12-25-101 et seq., C.R.S., as amended.
(10) For any proposal in a Hazard Mitigation or Hazard Avoidance District, the review fee may be increased to cover the actual cost to the City of contracting with a qualified geologist or engineer to review the applicant's proposal, reports and/or plans.
(A 35-88 §§5, 6)
A variance from the strict application of the requirements of this Article may be granted pursuant to the provisions, conditions and procedures as set forth for zoning variances in Section 070.040.050, except that application shall be made directly to the City Council. In addition to the variance criteria set forth in said Section, the following additional conditions must be found:
(1) The hazards as specified at C.G.S. 78-10 will be mitigated so that the development does not increase the hazard to public or private property;
(2) The variance granted does not impair the purposes of this Article; and
(3) The above determinations shall require that the applicant submit a detailed area analysis by a qualified geologist and an engineering geology report, which report may be submitted by the City to the Colorado Geologic Survey for review.
(A 35-88 §7)
070.100.041 Appeal of Administrative Decision.
An appeal of any administrative decision made pursuant to this Article may be made pursuant to the procedures set forth in Section 070.010.050(e), except that the appeal shall be made directly to the City Council. (Ad 35-88 §8; A 23-94 §7)
070.100.050 Public Improvements in Areas of Geologic Hazard.
Public improvements, including but not limited to streets, water, wastewater and electrical services, will not be extended into the Hazard Avoidance District, except where:
(1) An area or a proposed development meets one (1) of the conditions of Subsection 070.100.030(a); or
(2) The public good will be better served by the extension which shall be in compliance with the City goals and policies. Such determination shall be made by the City Council upon a recommendation from the Planning Commission.