a. General Requirements. The Commission shall not recommend for approval any subdivision plat which does not make adequate provision for storm or flood water runoff channels or basins as per the Book of Standards..
b. Nature of Storm Water Facilities.
1. 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 Town's construction standards and specifications.
2. Accessibility to Public Storm Sewers. Where public storm sewer/s is/are accessible, the applicant shall install storm sewer facilities, or if no other outlets are within a reasonable distance, adequate provision shall be made for the disposal of storm water, subject to the specifications of the Town Engineer. However, in subdivisions containing lots of less than fifteen thousand (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 facilities shall be conducted by the Town Engineer.
3. 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 Town Engineer shall approve the necessary size of the facility as determined by Design Engineer, based on the provisions of the required construction standards and specifications assuming conditions of maximum potential watershed development permitted by the Zoning Ordinance.
4. Effect on Downstream Drainage Area. The Design Engineer shall determine the effect of each proposed subdivision with approval of Town Engineer on the existing drainage facilities outside the area of the subdivision. Town drainage studies together with such other studies as may be available and appropriate, shall serve as a guide to needed improvements. The subdivision, when completely developed, shall not discharge water at a faster rate than it did in its natural state. All excess runoff to the extent of the amount of water anticipated in a one hundred (100) year flood event, shall be withheld in a retention or detention basin and discharged at a rate not greater than that of the three (3) year flood event. 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 primary approval of the subdivision until provisions (such as a storage facility) has 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.
5. Areas of Poor Drainage. Areas which are not in the Flood Plain but contain soils which are subject to flooding may be approved for subdivisions by the Commission, provided that the subdivider fills the affected area of said subdivision to an elevation sufficient to place building sites and streets two (2) feet above ponding levels.
6. Floodway Areas. If a subdivision of land is proposed within the flood plain floodways shall be preserved and not diminished in capacity by filling or obstruction, except as approved by the Natural Resources Commission in writing. No residential building site may be located within the floodway, in accordance with Section 10-18 of the Town Code.
7. Floodway Fringe Areas. Where a subdivision is proposed within an area of the flood plain designated as a floodway fringe, the Commission may approve such subdivision, provided that 1) all streets are elevated sufficiently to be above the regulatory flood elevation: 2) all lots for residential usage have a flood protection grade two (2) feet above the regulatory flood elevation; 3) where provided, water and sanitary sewer facilities are constructed to eliminate contamination of or by flood water; [and] 4) approval to fill the area from the Department of Natural Resources has been obtained in writing. Land below the regulatory flood elevation shall not be used for computing the area requirement for any lot, in accordance with Section 10-18 of the Town Code.
8. Flood Plain Areas. Where a subdivision is proposed within an area of the flood plain 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 (2) feet above the regulatory flood elevation; where provided, public water and sanitary sewer facilities are constructed to eliminate contamination of or by flood water; and filling to achieve the above will not raise the level of the regulatory flood elevation more than one- tenth (1/10) of one (1) foot for that reach of the stream. All filling in the flood plain must be approved in writing by the Department of Natural Resources. Lands below the regulatory flood elevation shall not be used for computing the area requirement for any lot, in accordance with Section 10-18 of the Town Code.
9. Recording of Plats in the Flood Plain 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, in accordance with Section 10-18 of the Town Code.
c. Dedication of Drainage Easements.
1. General Requirements. Where a subdivision is traversed by a drainage course, drainage way, channel, or stream, a storm water easement conforming substantially to the lines of such watercourse, and of such width and construction or both as will be adequate for the purpose of both drainage and maintenance of the right-of-way shall be dedicated to the Town of Dyer or appropriate entity thereof. 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.
2. Drainage Easements.
a. 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 fifteen (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.
b. The applicant shall dedicate, either in fee or by drainage or conservation easement land on both sides of existing watercourses of a width to be determined by the Commission and, in the case of legal drains, the County Drainage Board.
c. 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.
d. 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 the average density procedures nor for computing the area requirement for individual lot. (Ord. No. 94-9, § V, N, 8-9-94; Am. Ord. No. 2000-41, 12-19-00)