These required improvements pertain to all zoning sections in this chapter except for residential and agricultural zoning.
(B) Storm and surface water drainage.
(1) General requirements. The Commission shall not recommend for approval any subdivision plat, rezoning or site development permit which does not make adequate provision for storm or flood water runoff channels or basins. The storm water drainage system shall be separate and independent of any sanitary sewer system. Storm sewers, where required, shall be designed by methods approved by the Commission, and a copy of the design computations shall be submitted along with the plans. Inlets shall be provided so that surface water is not carried across or around any intersection, nor for a distance of more than 600 feet in the gutter or when the encroachment of storm water into the street disrupts traffic. When calculations indicate that curb capacities are exceeded at a point, no further allowance shall be made for flow beyond that point and catch basins or inlets shall be used to intercept flow at that point. Surface water drainage patterns shall be shown for each and every lot and block. Construction activities that result in the disturbance of one or more acres of land will be required to obtain a rule 5 permit from IDEM.
(2) Nature of storm water facilities.
(a) Location. The applicant may be required by the Commission to carry away by pipe or open ditch any spring or surface water that may exist, either previously to, or as a result of the subdivision. Such drainage facilities shall be located in the street right-of-way where feasible, or in perpetual, unobstructed easements of appropriate width, and shall be constructed in accordance with the county’s construction standards and specifications.
(b) Accessibility to public storm sewers.
1. Where a public storm sewer is accessible, the applicant shall install storm sewer facilities, or if no outlets are within a reasonable distance adequate provision shall be made for the disposal of storm water, subject to the specifications of the Commission. However, in subdivisions containing lots of less than 15,000 square feet in area and in business and industrial districts, underground storm sewer systems shall be constructed throughout the subdivision and be conducted to an approved outfall. Inspection of the facilities shall be conducted upon completion.
2. If a connection to a public storm sewer will be provided eventually, as determined by the Commission, the developer shall make arrangements for future storm water disposal by the public utility system at the time the plat receives final approval. Cost provisions for such connections shall be incorporated by inclusion in the amount of the performance bond or equivalent required for the subdivision plat.
(c) Accommodation of upstream drainage areas. A culvert or other drainage facility shall in each case be large enough to accommodate potential runoff from its entire upstream drainage area, whether inside or outside the subdivision. The Commission shall determine the necessary size of the facility, based on the provisions of the required construction standards and specifications assuming conditions of maximum potential watershed development permitted by this chapter.
(d) Effect on downstream drainage areas. The Commission shall determine the effect of each proposed subdivision on existing drainage facilities outside the area of the subdivision. County drainage studies together with such other studies as may be available and appropriate, shall serve as a guide to needed improvements. All costs that may be needed for any studies required by the Commission shall be provided by the developer. Where it is anticipated that the additional runoff incident to the development of the subdivision will overload an existing downstream drainage facility, the Commission may withhold secondary approval of the subdivision until provisions (such as a storage facility) have been made for the improvement of said potential condition in such sum as the Commission shall determine. No subdivision shall be approved unless adequate drainage from it will be provided to an adequate drainage water course or facility.
(e) Areas of poor drainage. Areas which are not in the floodplain but contain soils which are subject to flooding may be approved for subdivision by the Commission, provided that the subdivider fills the affected areas of said subdivision to an elevation sufficient to place building sites and streets two feet above ponding levels.
(f) Areas of high seasonal water tables. In areas characterized by soils having a high seasonal water table as determined by the County Soil and Water Conservation District, lots shall be limited to slab type construction unless the Commission determines that appropriate engineering techniques will be applied to alleviate the subsurface problem.
(g) Drainage design criteria. The subdivider shall size all storm sewers, culverts, ditches and other drainage structures based on runoff from a ten-year storm event using the appropriate intensity/duration curve for the area and a minimum time of concentration of five minutes. The drainage calculations shall also include the effect of the subdivision on the existing downstream drainage facilities outside the subdivided area. The Area Plan Commission shall also require detention facilities adequate to reduce runoff from proposed development to the extent that the 50-year post development flow is stored and the ten-year pre-development flow may be released.
(h) Floodway areas. If a subdivision of land is proposed within the floodplain, floodways shall be preserved and not diminished in capacity by filling or obstruction, except as approved by the Commission. No residential building site may be located within the floodway.
(i) Floodway fringe areas. Where a subdivision is proposed within an area of the floodplain designated as floodway fringe, the Commission may approve such subdivision provided that: all streets are elevated sufficiently to be above the regulatory flood elevation; all lots for residential usage have a flood protection grade two feet above the regulatory flood elevation; where provided, water and sanitary sewer facilities are constructed to eliminate contamination of or by, flood water; and, approval to fill the area from the Commission. Lands below the regulatory flood elevation shall not be used for computing the area requirement for any lot.
(j) Floodplain areas. Where a subdivision is proposed within an area of the floodplain for which floodway and floodway fringe designations have not been made, the Commission shall not approve such a subdivision unless all streets are raised sufficiently to be above the regulatory flood elevation; all lots for residential usage have a flood protection grade of two feet above the regulatory flood elevation; where provided, public water and sanitary sewer facilities are constructed to eliminate contamination of or by floodwater; and, filling to achieve the above will not raise the level of the regulatory flood elevation more than one-tenth of one foot for that reach of the stream. All filling in the floodplain must be approved in writing by the State Natural Resources Commission. Lands below the regulatory flood elevation shall not be used for computing the area requirement for any lot.
(k) Recording of plats in the floodplain and floodway fringe. All final plats having within their boundaries areas whose elevation is below that of the regulatory flood elevation shall show and label the regulatory flood boundary and elevation, as of the date the final plat is drawn, on the final plat for recording.
(3) Dedication of drainage easements.
(a) General requirements. Where a subdivision is traversed by a drainage course, drainage way, channel or stream, a storm water easement or drainage right-of-way shall be provided, granted or dedicated to the county conforming substantially to the lines of such watercourse, and of such width an construction or both as will be adequate for the purpose of both drainage and maintenance of the right-of-way. Wherever possible, it is desirable that the drainage be maintained by an open channel with landscaped banks and adequate width for maximum potential volume of flow.
(b) Drainage easements.
1. Where topography or other conditions are such as to make impractical the inclusion of drainage facilities within street rights-of-way, perpetual unobstructed easements at least 15 feet in width for such drainage facilities shall be provided across property outside the right-of-way lines and with satisfactory access to the street. Easements shall be indicated on the plat. Drainage easements shall be carried from the street to a natural watercourse or to other drainage facilities.
2. The applicant shall dedicate, either in fee or by drainage or conservation, easement land on both sides of existing watercourse of a width to be determined by the Commission.
3. When a proposed drainage system will carry water across private land outside the subdivision, appropriate drainage rights must be secured and indicated on the plat.
4. Low-lying lands along watercourses subject to flooding or overflowing during storm periods, whether or not included in areas for dedication, shall be preserved and retained in their natural state as drainage ways. Such land or lands subject to periodic flooding shall not be included in the computations for determining the number of lots allowable under average density procedures nor for computing the area requirement for any individual lot.
(C) Sidewalks. All development in said zones shall be required to have a paved sidewalk installed along the street or streets at the discretion of the Commission.
(1) Required improvements.
(a) Sidewalks shall be included within the dedicated, unpaved portions of the right-of-way of all streets within the development.
(b) Concrete curbs shall be installed as required.
(c) Any sidewalk that requires a setback from the road shall have a grassed or landscaped median strip between them.
(d) All sidewalks installed shall have ramps that are handicap accessible.
(e) Concrete shall be four inches by four feet minimum on four inches of stone or asphalt shall be three inches by six feet minimum on six inches of stone.
(2) Pedestrian access. In order to facilitate pedestrian access from the street to schools, parks, playgrounds or other nearby streets, the Commission may require perpetual unobstructed easements. Such easements shall be indicated on the exhibit.
(Ord. passed 9-1-2006) Penalty, see § 154.999