10.10A.040 Development standards and controls

Compliance with the development standards and controls of this chapter shall be required in connection with all structures and construction on sensitive lands; provided, however, that the development standards and controls contained in this chapter shall not circumvent or diminish the zoning controls of underlying zoning designations. Instead, the development standards and controls in this chapter are intended to, and shall, enhance the city’s regulatory control regarding building and development surrounding and within sensitive lands. A. Slopes. The applicant will submit a predevelopment map with contour lines not to exceed 2’ intervals and indicating all slopes that are 30% or greater. Slope areas in excess of 30% may not be developed, and no more than 30% of a development’s slope areas in excess of 30% may be included in the area calculation to determine residential density. The planning commission may modify this requirement to include no more than 50% of the slope in excess of 30% toward density calculations upon finding that: 1. No significant or moderate harm will result; 2. The proposed modification will result in a more functional and improved plan; 3. The developer agrees to comply with any conditions or requirements imposed by the planning commission to mitigate any adverse effects which may result from the proposed modification; and 4. If reasonably requested by the city in compliance with applicable legal standards for, inter alia, development exactions, the developer agrees to dedicate as open space any portion of the project that is not developable under this title. B. Single Family Lots. For developments containing single family lots, the minimum lot size and yard requirements of the underlying zone shall apply, with the following exceptions: 1. Every lot shall have at least 5,000 square feet of buildable area, consisting of the area of the lot where the slope is 30% or less, which is completely contiguous and which has a minimum dimension of 50 feet either length or width. 2. Lots shall be designed to allow dwelling units to be located within 250 feet from a public street. All main and accessory buildings shall be built entirely within the buildable area. C. Density Limitations. 1. The density limitations of the underlying zoning district shall control residential density. 2. The planning commission shall not adjust other zoning controls related to bulk and massing, including increased maximum structure height. D. Maximum Impervious Surface. The total maximum allowable coverage by impervious material within a project or portion of a project within a sensitive lands district shall not exceed 30% of the total project area. Areas of roofs and private driveways will be estimated and included in the total impervious surface area. E. Grading, drainage, and erosion control. The area of the watershed shall be used to determine the amount of storm water runoff generated before and after construction. 1. A grading and drainage report shall be prepared in which the developer shall describe the methods intended to be employed to control the erosion increase while in construction. 2. The developer is responsible for interim stabilization of all disturbed areas during periods of construction to prevent erosion offsite effects, and for final stabilization once construction is completed. 3. The SCS, Curve Number Method, or Rational Method, or other storm water computation method as approved by the city engineer, shall be used in computing runoff. 4. Lots shall be arranged so as to ensure adequate setbacks from drainage channels. The 100-year storm event shall be that basis for determining the minimum floor elevation. No structure shall be allowed in the 100 year floodplain as determined by the City Engineer. 5. Existing natural drainage channels shall remain as historically located except that roads and utilities may be installed across such channels as approved by the city engineer. Where these channel modifications are planned, the developer shall obtain applicable state Division of Water Rights and U.S. Army Corps of Engineers permits. The developer shall provide evidence of such permits to the city. 6. Facilities for the collection of storm water runoff shall be constructed on the development sites and according to the following requirements: (a) Such facilities shall be the first improvements or facilities constructed on the development site. (b) Such facilities shall be designed so as to detain safely and adequately the maximum expected storm water runoff for a 100-year storm event while allowing an offsite discharge not to exceed one tenth (0.1) cubic foot per second per acre. (c) Such facilities shall be so designed so as to divert surface water away from cut faces or sloping surfaces of a fill. (d) The existing drainage system, including natural drainage channels, shall be utilized to the greatest extent practicable, as directed by the city engineer. (e) Where drainage channels are required, wide shallow swales lined with appropriate vegetation, rock, or other approved material shall be used instead of cutting narrow, deep drainage ditches. Flow retarding devices, such as detention ponds, check dams, and recharge berms, shall be used where practical to minimize increases in runoff volume and peak flow rate due to development. 7. Construction on a development site shall be of a nature that will minimize the disturbance of vegetative cover. 8. Erosion control measures on a development site shall minimize increased suspended solids loading in runoff from such areas. A drainage system design to control storm water erosion during and after construction shall be contained in a detailed grading and drainage report submitted by the developer. 9. No grading or stripping shall be permitted except as part of a development plan approved in advance by the DRC pursuant to this chapter. F. Cut and Fill Slopes. Cut and fill slopes shall comply with the following unless otherwise recommended in an approved soils and geology report: 1. Cut and fill slopes shall not exceed 12 feet. 2. Cut and fill slopes shall not exceed a slope ratio of 2:1 except as follows: (a) No slopes shall be cut steeper than the bedding plane, fracture, fault or joint in any formation where the cut slope will lie on the dip of the strike line of the fracture, bedding plane, fault or joint. (b) No slopes shall be cut in an existing landslide, mud flow or other form of naturally unstable slope. (c) If the material of a slope is of such composition and character as to be unstable under the anticipated maximum moisture conditions, the slope angle shall be reduced to a stable value or increased through retention using a method approved by the city engineer and certified as to its stability by a professional soils engineer. 3. Fill slopes shall not be constructed on natural slopes steeper than 2:1. 4. Roadway cut and fill slopes located outside the dedicated public right-of-way shall be within recorded easements providing for slope protection and preservation. The easements shall be in a form acceptable to the city. G. Earthwork. 1. All surface areas to receive fill shall be stripped of any surface vegetation, topsoil, and organics and cleared of any trash and debris that may be present at the time of construction. 2. After the site has been cleared and stripped, the exposed subgrade soils in those areas to receive fill shall be scarified to a depth of eight inches. 3. All fill material shall be earth materials that are free from organic material, (less than 30% by volume) and other deleterious materials as well as free of metal, concrete, asphalt and other construction debris. Imported fill material should be a non-expansive (less than 2% swell) granular materials and should not contain rocks or lumps over 6-inches in greatest dimension and not more than 15% of the material larger than 2½ inches. 4. Surface areas disturbed by trench excavations shall be contained within the limits of the development or within approved rights-of-way, except as may be necessary in order to comply with Occupational Safety and Health Administration requirements and as approved by the city engineer. Trench boxes shall be used whenever required to ensure compliance with this requirement. 5. The following compaction criteria shall be met for filling operations based on ASTM test designation 698-78: Compaction Effort 95% 97% 95% 97% 90% Description Subgrade Structural fill Trench backfill Trench backfill (top 12-inches beneath pavement or concrete) Basement wall backfill Fill material shall be spread and compacted in uniform horizontal lifts not exceeding eight inches in uncompacted thickness. Before compaction begins, the fill shall be brought to within 2% +/of the optimum moisture content. Each lift should be thoroughly mixed before compaction to ensure a uniform distribution of moisture. 6. All structures shall bear on well compacted fill material or firm, undisturbed natural soil. No organic material, mud, muck, frozen material or ponded water shall be allowed in the footing foundation. 7. A written summary report of the completed compaction, showing location and depth of tests, materials used, moisture-density curves, moisture contents and relative density (if appropriate), prepared by a civil engineer, geotechnical engineer, or soils engineer shall be submitted to the city engineer for review. 8. The city engineer may require additional tests or information if the results of his review indicate that the conditions or materials are such that additional information is necessary. H. Setbacks. The setbacks and other restrictions specified by this subsection are a minimum, and may be increased by the city if necessary for safety and stability, to prevent damage of adjacent properties from deposition or erosion, or to provide access for slope maintenance and drainage. Setbacks dealing with distances from property lines, structures or faults must satisfy the requirements of the following paragraphs. Retaining walls may be used to reduce the required setbacks when approved by the city. 1. Setbacks from property lines shall comply with most restrictive requirements that are applicable under this title and the city’s building code. 2. Setbacks between graded slopes (cut or fill) and structures shall comply with this title, the city’s building code and all other applicable ordinances. 3. No habitable structure, essential facility or critical facility shall be located over a fault. Determinations of the appropriate setback distance from the fault shall be made using data obtained in the geological report by the person or firm who prepared the geological report, but in no case shall this distance be less than fifteen feet. I. Vegetation and Re-vegetation. 1. All areas on development sites cleared of natural vegetation in the course of construction of offsite improvements shall be replanted with drought tolerant vegetation which has good erosion control characteristics. 2. The use of persons or firms having expertise in the practice of re-vegetation (i.e., licensed landscape architects, erosion control specialists or nurserymen) shall approve the planning and installation of vegetative cover. 3. Vegetation shall be removed only when absolutely necessary, e.g., for the construction of buildings, roads and filled areas. 4. No vegetation shall be removed on a continuous hillside, crest (upslope or downslope) or a slope 30% or greater unless otherwise determined by the planning commission upon recommendation of the DRC. 5. Approval from the city engineer for uses such as trails and open space improvements. Any re-vegetation method of a trail, open space or hillside shall be subject to the approval of the city engineer. 6. Topsoil removed during construction shall be conserved whenever practicable for later use on areas requiring vegetation or landscaping (i.e., cut and fill slopes). 7. All disturbed soil surfaces shall be stabilized or covered prior to November 1st. If the planned impervious surfaces (i.e., road, driveways, etc.) cannot be established prior to November 1st, a temporary treatment adequate to prevent erosion shall be installed on those surfaces. 8. The property owner and/or developer shall be fully responsible for any destruction of native or applied vegetation identified as necessary for retention and shall be responsible for such destroyed vegetation. They shall carry the responsibility both for employees and subcontractors from the first day of construction until the final acceptance of improvements. The property owner and developer shall replace all destroyed vegetation with varieties of vegetation approved by the DRC. The property owner shall assume co-responsibility with the developer upon purchase of the property. J. Geology. 1. No habitable structure or critical or essential infrastructure shall be built on or within 15 feet of any identified fault. Actual setbacks shall be determined through the process outlined in Appendix B. 2. No structures or off-site improvements shall be allowed on any active landslide area. 3. Problems associated with development on or near perched ground water and/or shallow ground water must be mitigated in a manner as approved by the planning commission. K. Fire Protection. 1. Footing and foundation permits shall not be issued until work on an approved water system has commenced. A full building permit shall be issued only when the water system is completed and operational to provide fire protection. 2. Each development site proposal and building permit application shall be reviewed by the fire department to assure compliance with the city’s fire code. Non-compliant developments shall not be approved. 3. Spark arresters shall be installed in every fireplace, whether constructed indoor or outdoor. The diameter of screen openings in such arresters shall not exceed ¼ inch. 4. Development adjacent to public lands shall provide access for fire protection vehicles and equipment. 5. A development in a sensitive lands district shall not permit the use of wood shake shingles or wood exterior siding, regardless of whether or not such materials have been treated with fire retardant. L. Streets and Ways. Streets, roadways, and private access ways shall follow as nearly as possible the natural terrain. The following additional standards shall apply: 1. At least two ingress and egress routes shall be provided for each subdivision or PUD project. 2. Points of access shall be provided to all developed and undeveloped areas for emergency and fire-fighting equipment. Driveways located upon each lot extending from a public or private street shall have sufficient width and design to admit and accommodate fire-fighting equipment and must comply with all applicable city standards. 3. Cul-de-sacs shall not exceed 600 feet in length and shall have a fire-department-approved turnaround with a back of curb line radius of at least 55 feet. Stub-streets that are longer than the width or length of any adjacent single lot or 200 feet, whichever is less, shall have a temporary turnaround at the end thereof. 4. Centerline curvatures shall not be less than a 100 foot radius on any curved street pattern. 5. Variations of the street design standards developed to solve special hillside visual and functional problems may be presented to the planning commission for consideration and approval. Examples of such variations may be the use of split roadways to avoid deep cuts, oneway streets, modifications of surface drainage treatments, sidewalk design. 6. Development sites which are located near canyon trails will provide public access to those trails. Public parking areas may be required by the planning commission at trail heads. 7. Developments adjacent to public lands shall provide for access by fire protection equipment. 8. The maximum amount of impervious surface for streets and roadways shall be 20% of the entire development site. 9. All streets or rights-of-way for vehicular traffic shall be subject to the following limitations: (a) The maximum grade of such streets or rights-of-way shall be 12% except as hereafter provided. (b) The provisions of this subsection shall not apply to streets or rights-of-way already constructed or which have heretofore been granted preliminary approval by the planning commission. (c) Roads shall be designed to meet the city’s road base, asphalt and compaction standards. M. Trails upon hillsides. 1. The subdivider or other developer shall dedicate and improve to city standards trails necessary to provide public access to public lands and other trails shown on city or county master plans or required by the planning commission. Trails shall be located so that the route is feasible for both construction and long-term maintenance; side slopes shall not exceed 70% and rock cliffs and other insurmountable physical obstructions shall be avoided. The specific location of the trail right-of-way shall be verified on the ground before approving the subdivision. 2. A trail may be constructed to access upper/lower portions of residential property subject to the following conditions: (a) No un-engineered cut or fill of the hillside shall be in excess of four feet. All cuts or fills shall be properly retained. (b) The trail shall follow a meandering course, and not use a direct line pathway to the desired location. Where possible, the trail should follow the natural contours of the hillside. (c) The grade of trails shall not exceed 12%. Trails, and retainage of adjacent slopes, shall be designed as directed by the city engineer. (d) New trails shall be planned to harmonize with nature, including minimizing the destruction of existing stands of vegetation. (e) New trails shall include the installation of bridges across natural drainages with permanent or temporary flow that cannot be crossed without entering the drainage. (f) The trail shall be appropriately landscaped with native materials. (g) Prior to construction and/or hillside cuts, the trail plan shall be submitted to the director and city engineer for review and approval. N. Architectural Design. Architectural controls are primarily regulated by underlying zoning districts; however, the architectural requirements of this chapter include the following as determined by the Planning Commission: 1. The design of buildings and structures proposed for construction shall be visually compatible with the natural beauty of the foothills and canyon areas and other surrounding sensitive lands. 2. The materials used for buildings, structures and fences shall blend harmoniously with the natural setting. 3. The planning commission may review the design and comment on the specified exterior materials and colors for all structures. 4. Exposed foundation walls shall not exceed four feet above finished grade at any point. 5. The design and construction of structures within the urban interface area shall be consistent with the 2006 Utah Wildland-Urban Interface Code, as amended. O. On-Site Development. The property owner and developer shall be fully responsible for making all improvements in accordance with the development site approval, e.g., drainage, erosion and vegetation requirements. P. Bond. In addition to the requirements of this code requiring the posting of a completion bond for a development, the developer or owner shall be required to guarantee (via a cash bond, cash escrow or bank letter of credit, all in such form as city may require) the completion of revegetation projects, the stabilization of grading sites, cuts and fills, construction of storm water runoff facilities, and the construction of recreation space as required in this code. Such bond shall be in an amount equal to 125% of the city’s estimate of the cost of construction of such work, and shall continue for 18 months after the completion date of all such project, improvements or facilities. Q. FEMA. All habitable living space for new construction shall be at least one (1) foot above the 100 year flood plain elevation. Any additions to existing structures that includes any additional square feet shall meet this requirement.