The following information and data provided by a state-licensed professional engineer, architect or land surveyor engaged in storm drainage design shall be submitted to the Plan Commission office at the time of application for a building permit for any development, redevelopment or new construction on real estate which meets the criteria of project size and type that is regulated under this chapter.
(A) Topographic and soil maps. A soil map of the proposed development indicating soil’s names and their hydrologic classification must be provided when Natural Resources Conservation Service (NRCS) hydrologic methods are used. In addition, a topographic map of the land to be subdivided and such adjoining land whose topography may affect the layout or drainage of the development must be provided. The contour intervals shall be no greater than two feet. On this map, the following shall be shown:
(1) The location of streams and other floodwater runoff channels, the extent of the floodplains at the established 100-year flood elevation where available (regulatory floodway), and the limits of the floodway, all properly identified;
(2) The normal shoreline of lakes, ponds, swamps and detention basins, their floodplains, and lines of inflow and outflow if any;
(3) The location of regulated drains, farm drains, inlets and outfalls, if any of record;
(4) Storm, sanitary and combined sewers and outfalls, if any of record;
(5) Septic tank systems and outlets, if any of record;
(6) Seeps, springs, flowing and other wells, that are visible or of record; and
(7) Soil names and their hydrologic classification for the proposed development when hydrologic methods requiring soils information are used.
(B) Preliminary drainage plan. A comprehensive plan, in preliminary form (or in combined preliminary and final form), designed to handle safely the stormwater runoff and to detain the increased stormwater runoff must be provided. The plan shall provide or be accompanied by maps or other descriptive materials indicating the feasibility of the drainage plan and showing the following:
(1) The extent and area of each watershed affecting the design of detention facilities as shown on USGS quadrangle maps or other more detailed maps as required by the Plan Commission Office;
(2) The preliminary layout and design of proposed storm sewers, the outfall and outlet locations and approximate elevations, the receiving stream or channel and its 100-year return period water elevation;
(3) The location and design of the proposed street system, especially including depressed pavements used to conveyor temporarily store overflow from the heavier rainstorms, and the outlets for such overflow;
(4) The locations, cross-sections and profiles of existing streams and floodplains to be maintained, and new channels to be constructed;
(5) The materials, elevations, waterway openings and the basis for design of proposed culverts and bridges;
(6) Existing ponds and basins to be maintained, enlarged or otherwise altered and new ponds or basins to be built and the basis of their design;
(7) The estimated depth and amount of storage required in the new ponds or basins;
(8) The estimated location and percentage of impervious surfaces existing and expected to be constructed when the development is completed; and
(9) Any interim plan which is to be incorporated into the development pending completion of the development and the final drainage plan.
(C) Valley cross-section. One or more typical cross-sections must be provided showing all existing and proposed channels or other open drainage facilities carried to a point above the 100-year high water elevation, showing the elevation of the existing land and the proposed changes thereto, together with the high water elevations expected from the 100-year storm under the controlled conditions called for by this chapter and showing the relationship of structures, streets and other facilities.
(D) Site plan. A plan drawn to scale showing dimensions of the site with existing and proposed storm drainage facilities must be provided.
(E) Final drainage plans. Upon review of the preliminary drainage plans by the Plan Director and County Surveyor, final drainage plans shall be submitted to the Plan Commission. The final plans shall provide or be accompanied by calculations, maps and other descriptive material showing the following:
(1) The extent and area of each watershed tributary to the drainage channels in the development;
(2) The street storm sewers and other storm drains to be built, the basis of their design, outfall and outlet locations and elevations, the receiving stream or channel and its high water elevation, and the functioning of the drains during high water conditions;
(3) The parts of the proposed street system where pavements are planned to be depressed sufficiently to conveyor temporarily store overflow from storm sewers and over the curb runoff resulting from the heavier rainstorms and the outlets for such overflow;
(4) Existing streams and floodplains to be maintained, and new channels to be constructed, their locations, cross-sections and profiles;
(5) Proposed culverts and bridges to be built, their materials, elevations, waterway openings and basis of their design;
(6) Existing detention basins and ponds to be maintained, enlarged or otherwise altered, and new basins or ponds to be built and the basis of their design;
(7) The estimated location and percentage of impervious surfaces existing and expected to be constructed when the development is completed;
(8) The slope, type and size of all sewers and other waterways; and
(9) For all detention basins, a plot or tabulation of storage volumes with corresponding water surface elevations and a plot or tabulation of the basin outflow rates for those water surface elevations.
(F) Submittal and consideration of plans.
(1) (a) Preliminary and final drainage plans and/or construction plans shall be submitted to the Plan Commission office at least 21 days prior to their regularly scheduled meeting.
(b) All preliminary plans, final plans and/or construction plans in compliance with the standards of this chapter must be approved by the Plan Commission office.
(c) The Plan Commission office shall stamp such approval on a copy of such plans and deliver the same to the applicant. The Plan Commission office shall approve or disapprove any preliminary plans, final plans and/or construction plans within 60 days of submission unless the applicant consents to a continuance or extension.
(d) All approvals and disapprovals with written reasons shall be incorporated into the Plan Commission minutes.
(2) (a) The County Plan Director and Surveyor are authorized to review engineering summaries of projects and based upon the same, grant exemptions from any and all requirements of this chapter and/or waive any requirements of this chapter.
(b) Any applicant may appeal the decision of the Plan Director or County Surveyor to the Plan Commission which shall also be authorized to grant exemptions from any and all requirements of this chapter and/or waive any requirements of this chapter at its discretion.
(Ord. 2011-03, passed 4-4-2011)