§ 153.1652 STORM WATER MANAGEMENT PLAN.

   (A)   Number of copies. The applicant shall provide two blue- or black-line copies of the plat together with two construction drawings.

   (B)   Format.

      (1)   Plats shall be drawn in India ink on Mylar on sheets 18 inches wide and 24 inches long, with a margin of two and one-half inches on the left side of the sheet, and appropriate margins on the other three sides. Plats shall be drawn at a scale of 100 feet equals one inch unless a smaller scale is approved by the Code Enforcement Officer. Plats that include one-half acre or less in area shall be drawn at a scale of 50 feet equals one inch.

      (2)   Where more than one sheet is necessary to accommodate the entire area to be subdivided, an index sheet showing the entire subdivision at an appropriate scale shall be attached to the plat.

   (C)   Contents.

      (1)   To standardize the review process and minimize the time for approval by the city during review of the plat and construction drawings for a subdivision, a complete submittal regarding the analysis of existing drainage conditions and the design of modifications or new drainage facilities is necessary. The owner of the property to be developed is required by the City Manager to provide, at the owner’s expense and as a condition of construction plan approval, a storm water management report for the total development area to be ultimately constructed. The storm water management report shall contain all of the necessary support data, methodologies used in calculations, and conclusions.

      (2)   A checklist (see subsection (E) below) will be used by the city reviewer as a guide during the evaluation of all storm water management reports submitted to the city. The purpose of the checklist is to expedite the review process for both the professional engineer and the city, and to aid the professional engineer in the preparation of reports for the city’s review. The storm water management report shall be submitted to the City Manager prior to approval of any construction plans.

   (D)   Report. The storm water management plan shall include two copies of a written report, which include the following information, as applicable:

      (1)   A vicinity map of the site and affected reach of the out-fall channel;

      (2)   A detailed map of the area and the outfall channel with all pertinent physiographic information;

      (3)   A watershed map showing the existing and proposed drainage area boundary along with all subarea delineations and all areas of existing and proposed development;

      (4)   United States Geological Survey (USGS) quadrangle map showing overall drainage areas, run-off coefficients, time of concentration, intensity and quantities;

      (5)   Subdivision master drainage plan with overall interior drainage area of subdivision showing drainage area, time of concentration run-off coefficients, intensities, quantities for the street and alley flows and channel and underground system design;

      (6)   Subdivision plat showing interior drainage areas, time of concentration, run-off coefficients, intensities, quantities for street and alley flows and channel and underground system design;

      (7)   Discharge calculations specifying methodology and key assumptions used, including a table of discharges at key locations;

      (8)   Hydraulic calculations specifying methodology used, assumptions and values of the design parameters;

      (9)   Profiles of the affected channels, including water surface elevations for the specified design frequencies; all existing and proposed bridge, culvert and pipeline crossings; the location of all tributary and drainage confluences; and the location of all hydraulic structures;

      (10)   Detention basin design calculations, including those used for design of the control structure;

      (11)   Right-of-way and easement requirements and a map showing locations of all rights-of-way and easements;

      (12)   A soils report that addresses erosion and slope stability of new or altered channels and detention facilities;

      (13)   Digital files of all existing and proposed condition United States Army Corps of Engineers Hydrologic Engineering Center (HEC) models HEC-1 and HEC-2 used in analysis;

      (14)   Information for preparation of an HEC-2 model as provided in this subsection (D);

      (15)   The following drainage calculations:

         (a)   Open channel design;

         (b)   Underground systems;

         (c)   Box culverts;

         (d)   Pipe culverts;

         (e)   Hydraulic jump;

         (f)   Super elevation in channel bends;

         (g)   Retard spacing;

         (h)   Backwater curves with cross sections;

         (i)   Drawdown curves with cross sections;

         (j)   Energy dissipators;

         (k)   Hydraulic grade lines of pipes;

         (l)   Inlets on grades;

         (m)   Inlets in sump;

         (n)   Drop-curb openings;

         (o)   Sidewalk culverts;

         (p)   Regulatory floodway conveyance calculations with cross sections;

         (q)   Weir structures;

         (r)   Orifice formulas;

         (s)   Grade to drain channels;

         (t)   Upstream pickup and flared section;

         (u)   Downstream backwater control and flare to match downstream condition;

         (v)   Required free board;

         (w)   Improper “N” value;

         (x)   Improper velocity used;

         (y)   Improper easement width;

         (z)   Access road on each sodded channel;

         (aa)   Improper run-off coefficient used;

         (bb)   Improper time of concentration used;

         (cc)   Improper quantities used;

         (dd)   Steel calculations for box culvert; and

         (ee)   Street quantities for five-year (30-foot street) and 25-year (greater than 44-foot street) frequency showing that street capacities are correct based on Division 11 of this chapter.

      (16)   Subdivision plat showing:

         (a)   All interior drainage easements;

         (b)   Outfall drainage easements;

         (c)   USGS contour map and all other necessary drainage information;

         (d)   Outfall drainage easements to the centerline of existing natural low;

         (e)   Finished fill contours; and

         (f)   Interceptor drainage easements.

      (17)   Typical details for the following elements:

         (a)   Box culvert with headwalls or wingwalls;

         (b)   Pipe culverts with headwalls or wingwalls;

         (c)   Culvert headwalls shown with proper safety measures;

         (d)   Drop-curb openings;

         (e)   Inlets on grade;

         (f)   Inlets on sump;

         (g)   Drop structures;

         (h)   Retards;

         (i)   Sidewalks over drains;

         (j)   Guard-post installations;

         (k)   Guard rail on structures;

         (l)   Header curb;

         (m)   Energy dissipators;

         (n)   Junction boxes;

         (o)   Concrete-lined channels with free board;

         (p)   Earth-sodded channels with free board;

         (q)   Other concrete structures;

         (r)   Grade to drain sections;

         (s)   Transition sections;

         (t)   Fencing for vertical wall channels greater than two feet deep; and

         (u)   Side slope.

      (18)   Street plans and profiles;

      (19)   Drainage plan and profile, including the following:

         (a)   Proposed flowline slopes with grades and elevations shown every 50 feet in profile;

         (b)   Proposed top-of-channel profile;

         (c)   Existing ground right and left profile at property line;

         (d)   Finished fill profiles;

         (e)   Locations and size of culverts;

         (f)   Drop structures;

         (g)   Retards;

         (h)   Grade to drain profiles;

         (i)   Flowline elevations at every 50-foot station and at each structure and change in grade;

         (j)   Junction boxes;

         (k)   Channel plan views;

         (l)   Channel sections;

         (m)   Pipes with hydraulic grade lines on profile;

         (n)   Cross sections of existing natural channels or lows, which are not to be improved but are left in natural state and dedicated to high water calculated;

         (o)   Angles, bearings and distances for structures and channels;

         (p)   Lot grading-layout drains; and

         (q)   Culvert structural details.

      (20)   Unit and storm hydrographs for major streams (over 2,000 acres);

      (21)   Drainage easements to the centerline of natural low area;

      (22)   Cost estimate; and

      (23)   Professional engineer’s seal.

   (E)   HEC-2 Submittal Checklist. The applicant shall include the following information in the preparation of HEC-2 studies and reports and to expedite the city’s review procedure. Any information required for a floodplain development approval supersedes the requirements of this section in the regulatory floodplain.

      (1)   Certification of a professional engineer certified to practice in the state, including the name of the submitter and professional engineer registration number;

      (2)   Electronic media with all input files;

      (3)   Copy of condensed printouts;

      (4)   Project description and history;

      (5)   Location;

      (6)   Scope and objective of analysis;

      (7)   Previous and related studies that may affect the analysis;

      (8)   Methodology;

      (9)   Sources of discharges;

      (10)   Bridge routines;

      (11)   Base or effective models (mention source);

      (12)   Revised base model;

      (13)   Proposed model;

      (14)   Summary, conclusions, and recommendations;

      (15)   Water surface elevation impacts;

      (16)   Information in tabular format, including:

         (a)   Water surface comparison table at each cross section;

         (b)   Floodway table;

         (c)   Cross-section numbering table (if stationing changes);

         (d)   Vicinity map;

         (e)   Plan view of project reach;

         (f)   Water surface profiles for design storm;

         (g)   Channel cross sections showing limits of drainage easements and property lines;

         (h)   Bridge cross sections;

         (i)   Plan view of bridge; and

         (j)   Photographs (if available).

      (17)   Survey and/or certified “as-built” information for all revisions to base model; and

      (18)   Sample calculations.

(Ord. 3020, passed 9-10-2013, § B-12)