These regulations apply to all hillside areas in the city. A hillside area as referred to herein is defined as one with an average slope of more than 15%. The subdivider shall submit sufficient detailed information as to geologic conditions, soil types, and underground water level in order that a determination can be made by the City Engineer as to the safety of development of the particular location.
(A) Determination of average slope. The average slope for any hillside development shall be determined by the Planning Commission from the preliminary subdivision submittal. Determination will be on area-by- area basis with each lot sized according to the average topographic change falling within each area.
(B) Minimum requirements for single-family homes. The minimum lot requirements shall be used to determine the minimum lot area for a single-family home. The average percent of slope is determined by the appropriate planning agency. The lot area in thousands of square feet shall then be determined by charting the average natural ground slope and the minimum lot area. Rounding shall be made to the nearest five-foot frontage interval. Deviations from these requirements may be allowed subject to determination by the Planning Commission where exceptional circumstances warrant.
Average Percent of Natural Ground Slope
EXAMPLE:
The minimum lot size for a single-family house on a lot with an average slope of 28% is 26,000 square feet.
The minimum lot width is 130 feet.
The resulting lot depth is 200 feet 26,500 = 200
(C) Grading plan and controls. The overall development plan shall show contour lines at two-foot intervals. Elevations are to be based on the sea level datum (U.S.G.S.), with conversions shown to local datum. The lot layout and the approximate dimensions shall be shown for each lot and each building site. Where pads are utilized or proposed for building sites, engineering data shall show the existing topography and the proposed finished grades, location and size of each building site, and finished grade of streets prior to consideration of the final record plat.
(D) Cuts and fills. No land shall be graded, cut, or filled so as to create a slope exceeding a vertical rise of one-foot for each three feet of horizontal distance between abutting lots, unless a wall of sufficient height and thickness is provided to retain the graded bank. Major cuts, excavation, grading, and filling, where the same materially changes the site and its relationship with the surrounding areas or materially affects such areas, shall not be permitted if such excavation, grading, and filling will result in a slope exceeding a vertical rise of one-foot for each three feet of horizontal distance between abutting lots or between adjoining tracts of land, except where adequate provision is made to prevent slides and erosion by cribbing and retaining walls.
(E) Compaction of fill. All fill shall be compacted to a density of 90% or greater in accordance with ASTM D-6-98. Inspection of fill shall be conducted by the City Engineer.
(F) Retaining walls. Retaining walls may be required whenever topographic conditions warrant. Retaining walls shall be designed in accordance with currently accepted design practices and approved by the City Engineer.
(G) Minimum design requirements. Minimum front yard, rear yard, side yard, and setback requirements shall be in accordance with specifications as set forth by the zoning regulations of the applicable political subdivision. Minimum right-of-way and pavement widths shall conform to the street design standards as stated in this subchapter.
(H) Street alignment. The following regulations shall govern street alignment:
(1) Vertical profile grades shall be connected by vertical curves;
(2) Waiver of visibility requirements may be given subject to the approval of the Planning Commission and the City Engineer; and,
(3) Waiver of vertical curve requirements may be given subject to the approval of the Planning Commission and the City Engineer.
(I) Driveways. The maximum grade on driveways shall not exceed 10% to the street.
(J) Sidewalks. Concrete sidewalks having a minimum width of five feet and having a minimum thickness of five inches shall be installed along the uphill side.
(K) Conservation easement required. Those areas within a hillside development exceeding a 15% slope and not containing a building footprint shall designate those non-building areas to be a non-disturbance area. A conservation easement requiring no permanent structures be constructed in this area and no removal of existing vegetation shall be recorded with the final record plat to preserve these areas in perpetuity as non-disturbance zones.
(Ord. 09-3306, passed 10-15-09)