1. Public Utility Easements. Easements of not less than 10 feet in width shall be provided on each side of all rear lot lines and/or side lot lines where necessary for poles, wires, conduits, and storm utilities. Easements of greater width may be required along lines or across lots where necessary for the extension of main sewers and similar utilities.
2. Lot Arrangement and Design. The lot arrangement and design shall be such that they are topographically desirable building sites and avoid unstable landforms or significant slopes prone to erosion and collapse, which includes significant slopes, as defined in Section 85.08. Maintaining vegetative cover and limiting disturbance on significant slopes reduces property losses and water quality issues related to erosion. Lot design shall also preserve critical natural resource areas to the fullest extent possible.
A. Lot Arrangement and Design for Significant Slopes (greater than or equal to 15%).
(1) Determination and classification of significant slopes shall be completed by the applicant, using United States Geological Survey topographic maps featuring the contour lines at two-foot intervals or a survey. Applicants may request such contour maps from the Story County Planning and Development Department.
(2) When development is proposed on natural slopes greater than or equal to 15% or within a buffer measured two (2) feet for every one (1) foot of vertical rise from the toe or summit of a significant slope (see Figure 1) on lots, parcels, or tracts existing prior to the adoption of this ordinance, as well as buildable parcels and lots in subdivisions of two or fewer lots created after the adoption of this ordinance:
a An erosion and sediment control plans as outlined in 88.05(3) shall be required and the development shall be subject to inspections for conformance to erosion and sedimentation prevention best practices.
b A geotechnical analysis is encouraged to be completed and the analysis reviewed by an Iowa licensed engineer for special design considerations and recommendations, including for foundation design, construction sequencing, retaining walls, slope stability, excavation, and shoring for existing structures on the subject property and any neighboring properties.
c Limits of disturbance shall be denoted on site plans, and on-site.
Figure 1 Significant Slope Diagram
(3) For subdivision plats with three or more development lots, conditional use permits, or commercial site plans submitted after the adoption of this ordinance, the following standards shall apply:
a. A development envelope will be shown on the site plan or the preliminary and/or final plat for each lot that contains significant, natural slopes to show the area where a dwelling or other proposed development may be sited. The development envelope shall meet the required setbacks for the applicable zoning district and shall be large enough to accommodate a 1,200-square-foot dwelling with a two-car garage or other proposed use.
b. When the development envelope includes slopes greater than or equal to 15%, or includes an area within a buffer of two (2) feet for every one (1) foot of vertical rise measured from the toe or summit of a significant slope, a geotechnical analysis shall be required, and shall be submitted with the site plan or preliminary plat. The analysis shall be completed/reviewed by an Iowa-licensed engineer to ensure the suitability of a site for development and any special design considerations and recommendations, including for foundation design, construction sequencing, retaining walls, slope stability, excavation, and shoring for existing structures on the subject property and any neighboring properties. These recommendations may be included as conditions of approval. Lots and/or development envelopes determined to be unsuitable for development shall be reconfigured to provide a suitable building site that accommodates the required development envelope.
c. Slopes with a grade greater than 35%, shall be considered protected. The area within a buffer measured two (2) feet for every one (1) foot of vertical rise, not to exceed fifty (50) feet, from the summit and toe of a slope with a grade greater than 35%, shall also be considered protected. These areas shall not be impacted for any reason, including by any impervious surface such as gravel or concrete driveways, with the exception of installing required erosion control practices, or the installation of essential utilities.
d. Major disturbance to the natural terrain to create a site suitable for development is discouraged. Major disturbance includes removal of the natural slope or terracing to create a building pad.
e. An erosion control plan and a plan to re-vegetate the site shall be required, completed by a qualified professional such as an Iowa-licensed engineer, landscape architect, or other professional certified in erosion and sediment control plan development.
f. Limits of disturbance shall be denoted on site plans, and on-site when development is proposed.
B. Reduction in Minimum Lot Sizes. A reduction in minimum lot size may be allowed when 50% or more of agricultural lands are preserved as an outlot, in an easement, or through a deed or other permanent restriction to provide buffering to other adjacent agricultural lands or when critical natural resources are preserved in accordance with 88.05.
(1) The reduction shall be allowed so that the development yield is equivalent to a net density of one unit per acre prior to the preservation of agricultural lands and critical natural resources.
(2) Lot sizes may be reduced to a minimum of 10,000 square feet. All bulk standards for the applicable or requested zoning district shall be met.
(3) For the reduction to apply, the development shall meet Iowa Department of Natural Resources requirements for minimum separation distances for dwellings and wells from open feedlots and confined animal feeding operations. These distances shall be maintained from existing operations. Buffers of no less than 250 feet shall also be maintained from other agricultural uses.
(4) The reduction shall be allowed only when a site evaluation is conducted by a certified engineer or soils professional for septic systems. In the case of a subdivision plat, the evaluation shall accompany the plat. In the case of a major subdivision, the evaluation shall accompany the preliminary plat.
a. All lots shall comply with Story County Environmental Health or Iowa Department of Natural Resources requirements for common or private sewage disposal systems. For lots under a half-acre, a common wastewater treatment system may be necessary and is encouraged.
b. A subdrain system may be required to divert discharged effluent away from critical natural resource areas.
(Ord. 310 – Oct. 23 Supp.)
3. Side Lot Lines. All side lot lines shall be substantially at right angles or radial to street centerlines.
4. Double Frontage Lots. Double frontage lots shall be avoided except where essential from major traffic arteries or to overcome specific disadvantages of topography. Any double frontage lot extending from road to road shall provide the required front setbacks on both roads.
5. Flag Lots. Flag lots shall be avoided wherever possible.
6. Bulk Regulations. The minimum dimensions for lots shall be in accordance with the bulk regulations of the district within which the subdivision is located; provided, however, the minimum depth for a development lot shall be 100 feet and that the depth shall not be in excess of three times the width.
7. Comer Lots. Comer lots shall be of such width as to permit the maintenance of all yard requirements as required by the Ordinance.
8. Lots at Street Intersections. All lots at street intersections shall have a radius of not less than 25 feet at the street comer. A greater radius shall be required for intersections involving one or more major streets. A cut-off or chord may be substituted for the circular arc.
9. Setback Lines. Setback lines shall be shown on all lots intended for residential, commercial or industrial use. Such setback lines shall not be less than the minimum yard requirements of the district within which the property is located.
10. Required Dimensions and Setbacks. The setback of the building for front, rear, and side yards shall in all cases be measured at a right angle from the lot line exclusive of public right-of-way or easement to the nearest point of the adjacent building wall of the building.
11. One Principal Building to a Residential Lot. There shall be no more than one principal building on a residential lot, parcel, or tract, unless otherwise specified in the Ordinance.
(Ord. 317 – Apr. 24 Supp.)