(A) Purpose. This section is designed to ensure, when development is proposed in those areas in the city, which have distinctive and special environmental characteristics which are of significant value to the public and which make these properties susceptible to damage through improper development. It is the purpose of these regulations to encourage and guide development that will preserve existing hillsides and their character through:
(1) Innovative approaches to the development of housing units and other projects in hillside areas, encouraging the use of community unit planning concepts;
(2) Prevention of damage or destruction of trees, shrubbery and other ground cover, where possible, to prevent loss of their stabilizing influence in areas where soils are, or likely to become, unstable and prone to landslides;
(3) Prevention of land from becoming unstable or prone to landslides through improper development;
(4) Prevention of the loss or damage to mature trees and other vegetation, significant scenic views and other similar natural features which are necessary to preserve the aesthetic and visual integrity of the hillsides; and
(5) Prevention of soil erosion and stream siltation caused by improper development.
(B) General requirements. Areas of land on which development is physically restricted due to excessive hillside slopes shall be limited according to the following requirements, notwithstanding any other section of this of any other ordinance adopted by the city.
(1) Those properties or areas of land which lie totally or partially within land areas identified in the comprehensive plan for the city, as “physically restrictive development areas”;
(2) Any other areas which have slopes equal to 20% or greater;
(3) Certain soil and bedrock conditions which exhibit characteristics of moderate environmental concern of construction activity such as, but not limited to, exposures of the Kope geological formation;
(4) Hillsides which support a substantial natural wooded cover; or
(5) Land area that has known experience of landslides.
(C) Development standards.
(1) It shall be unlawful to locate, extend, convert or structurally alter any structure or otherwise develop any land, including, but not limited, the excavation, removal or placement of any soil within those areas defined in division (B) above, unless such development meets the applicable standards set forth in this section.
(2) The registered professional engineer or landscape architect, in developing the design of any proposed development, shall do so with consideration of the following standards and guidelines. These standards and guidelines shall be considered as minimum standards, and the professional engineer or landscape architect may enact greater standards in order to comply with the intent of this section. When restrictions of land development occur within these standards appear to conflict with other associated standards, the most strict standard shall apply.
(a) Identification of landslide-prone areas. All on-site areas which are vulnerable to landslide damage shall be identified. The risk to off-site property shall then be minimized by locating development away from areas which are vulnerable to sliding.
(b) Clearance activities standards.
1. In all areas, trees and natural vegetation shall be retained, where feasible, in order to minimize erosion, sedimentation and the disruption of views to and from hillsides.
2. The natural redevelopment condition of the crest of the slope shall be maintained by tree planting and other landscape measures.
3. The natural slope line of the hill as seen in profile shall be retained, except in areas of approved excavation. Vegetation lines which convey this slope line shall be maintained, restored and supplemented.
4. Earth disturbing activities shall be limited to only those areas involved in the construction activities. Any grading performed shall be in keeping with generally accepted engineering and soil conservation practices to avoid erosion and land sliding and to minimize the effect on the environment. The smallest practical areas of land should be exposed at any one time during development and length of exposure should be kept to the shortest practice amount of time.
5. Trees around the perimeter of the construction shall be protected to prevent root, trunk and branch injury or dismemberment.
6. No tree larger than eight inches in diameter, measured 24 inches above the ground, may be destroyed or removed unless specifically approved during the permit process.
7. All areas of land exposed during construction shall be temporarily revegetated and restored as soon as possible to blend with the surrounding terrain. All excavations shall have stable side slopes and be constructed so that revegetation can occur readily.
(c) Development restrictions on drainage areas. No more than 50% of any area of a proposed development may be developed when such area conveys storm water runoff from surrounding land, either as a natural flow or as a result of existing land alterations, to a watercourse.
(d) Building construction standards.
1. Any building shall be designed and located so as to relate to the natural slope and contours of the land and to minimize grading, excavation and placement of fill.
2. No building constructed between the toe and crest of a slope within the areas defined in division (B) above, should be higher than two stories or 35 feet, whichever is less, as measured from the highest point where the building meets the natural slope.
3. Any building located within the areas defined in division (B) above shall be required to have geotechnically and structurally engineered foundations, as evidenced by certifications on the building plans by a registered professional engineer and a registered professional geotechnical engineer.
4. Buildings placed on columns or stilts for structural reasons shall have space below the buildings screened from view by earth mounding or vegetation. Supports for decks shall be screened by vegetation.
(e) Parking area standards. Parking areas, whenever possible, shall be located within structures to limit the amount of paved land.
(f) Pavement limitations. Paved areas intended for vehicular use shall be designed to follow the natural contours of the land and provide the least disruption to the hillside environment.
(g) Retaining wall standards.
1. Retaining walls shall be no higher than six feet high above the ground at the base of the wall. Walls may be built in a series of smaller walls to minimize the visual impact of a higher wall; provided that, the series of walls can be built without excessive removal of vegetation during construction.
2. All retaining walls shall be properly engineered, backfilled and maintained.
3. Retaining walls shall be faced with stone, textured block, textured concrete or other textured material that will blend with the hillside. Medium earth tone colors shall be encouraged. Highly reflective surface materials are prohibited.
4. All retaining walls shall be covered with a minimum of 50% coverage by vegetation by:
a. Planting at the base of the wall;
b. Planting within the wall;
c. Plants hanging from the top of the wall; and
d. Any combination of divisions (C)(2)(g)1. through (C)(2)(g)4. above.
(h)
Screening requirements. Visual prominence of a development shall be minimized by using tree clusters or depressions for view screens. Where total screening is impractical or undesirable, partial screening should be employed to at least lessen the full visual impact of the development by breaking up the horizontal lines of long structures and/or reducing the apparent height of buildings or walls. See § 3.18 of this ordinance for screening standards. (i) Lighting standards. Unobtrusive forms of lighting shall be employed for exterior areas (e.g., light where the light source itself is screened from direct view or low garden type lighting). See § 5.0(O)(2) of this ordinance for lighting standards.
(j) Excavation and fill standards.
1. The toes and crests of excavations and their slopes shall be set back from property boundaries and structures as far as necessary for the safety of adjacent properties and adequacy of foundation support and to prevent damage as a result of water runoff.
2. Fill shall not be placed over stumps or other organic or unstable material, unless in compliance with recommendations from a geotechnical engineer. All fill should be compacted to provide stability of material and to prevent undesirable settlement or landsliding, and proper benching shall be provided, as required, in accordance with the recommendations of a geotechnical engineer.
3. In any development with slopes greater than 30%, a registered professional engineer shall design the structure, in cooperation with the project geotechnical engineer, so that there shall be adequate support against downhill creep acting upon each caisson or pier penetrating soil that is prone to creep.
4. No soil from excavations of any kind shall be placed on slopes, except as permitted by these regulations.
5. Grading under tree drip lines, including trenching for utilities, shall be avoided. Drainage around existing trees shall remain undisturbed to ensure preservation of trees.
6. All permitted excavation and fill operations shall be reviewed by a qualified soils technician under the direction of a registered professional geotechnical engineer; such review and inspection reports shall be the responsibility of the developer and shall be submitted to the Zoning Inspector in a timely manner.
(D) Administration and review procedures.
(1) Prior to any development of any lot or land which lies totally or partially within the areas defined in division (B) above, the following information shall be submitted in the form of a site plan as regulated by §
3.21 of this ordinance and shall accompany each request and shall be considered as part of the required application for a zoning certificate for development within the city in quadruplicate:
(a) Identification of slopes 18% and greater;
(b) Identify exposures of the Kope geological information;
(c) Hillsides which support a substantial natural wooded cover;
(d) Identification of land area that has known experience of landslides;
(e) A report shall be prepared by a professional geotechnical or soils engineer showing the following:
1. Results of surface and subsurface exploration, conditions of the land, the major soils types on the site and extent and patterns of the soils and procedures for performing the operations;
2. An evaluation of the effect on off-site slopes adjacent to the proposed development;
3. Recommendations for foundation type, depth and locations;
4. Specifications for the borrow material or fill material, the method to be used for filling and the requirements of its proposed construction;
5. Proposed preparation of existing ground surface to receive fill;
6. Proposed terraces and ditches where necessary to control surface drainage and debris; and
7. Proposed subsurface drainage if necessary for stability.
(f) Identify areas of excavation and fill, and estimated number of cubic yards displaced;
(g) Identify existing drainage on the site, the proposed method and storage and disposal of water generated by development of the tract and calculated surface water fun-off from the site before and after construction, measured in cubic feet per second; and
(h) Provide a timing schedule and sequence indicating the anticipated starting and completion dates of the development sequence; stripping or clearing; rough grading; construction; final grading; and vegetative establishment and maintenance. The schedule shall also indicate the time o exposure of each area prior to the completion of effective erosion and sediment control measures.
(2) The Planning Commission, and/or its duly authorized representative, may waive or modify the requirements of this regulation for plans, specifications, field supervision and summary reports only if the application for a zoning certificate contains a written statement by a registered professional engineer or geotechnical engineer which states, to the satisfaction of the Planning Commission and/or its duly authorized representative, that the proposed development, if his or her recommended procedures are followed, will not:
(a) Obstruct, damage or adversely affect existing sewerage or drainage, public or private;
(b) Cause a stagnant pond of water to form;
(c) Create slope stability problems on the subject and/or adjacent properties;
(d) Cause detrimental erosion or sedimentation; or
(e) That the proposed excavation or fill is in an isolated, self-contained area and that there is no apparent danger or environmental damage to adjacent public or private property.
(3) The site plan, cut and fill permit and other information required in division (B)(2) above shall be reviewed by the City Engineer who will recommend to the Planning Commission, or its duly authorized representative, what effect the proposed development will have on hillside slippage and soil erosion.
(4) After consideration of the recommendations of the Planning Commission, and/or its duly authorized representative, may grant a permit for use of the site in accordance with the submitted plans.
If, after review of the plans required by this section of the ordinance, the Planning Commission, or its duly authorized representative, determines that said proposed plans will not minimize hillside slippage, the Planning Commission shall deny a permit for the development of said land and the site shall be limited to those open type uses, excluding structures, as permitted or conditionally permitted in the Conservation Zone (CO).