(a)

All land development projects shall be subject to the provisions of this article, this Code, the city drainage standards, the city standards, and all applicable state and federal regulations.

(b)

When no land use action is required, a final drainage study and a drainage plan must be accepted prior to issuance of a building permit unless explicitly waived based on provisions in the sections set forth in this article.

(Ord. No. 3023, § 1(23.385), 3-3-2008)

(a)

Submittals—Required. Drainage studies and drainage plans are required to demonstrate compliance with this Code, the city drainage standards and city standards. The type of land development application dictates the required submittals as shown in the table in subsection (b) of this section. All submittals shall be signed and sealed by a professional engineer licensed by the state.

(b)

Same—Enumerated. The required submittals are as follows:

(c)

Amendment to PUD requires final drainage study. A minor amendment to a final planned unit development shall require the submittal of an amended final drainage study and drainage plan if the minor amendment creates any change to the hydrologic or drainage characteristics of the land development project.

(d)

Administration. Processing of a properly completed submittal shall be in accordance with chapter 35. Any changes to an accepted drainage study or plan must be reviewed by the city prior to construction of a field change. Minor revisions shall require a written request for the change with any supporting documentation. All preliminary drainage studies, final drainage studies, and drainage plans that are not signed and sealed by a professional engineer licensed by the state will not be reviewed and the entire application will be returned to the applicant.

(e)

Drainage report and plan contents. All reports and plans must be signed, sealed, and dated by a professional engineer with certification that the report and plan is in compliance with good engineering practice and the requirements of this Code.

(1)

Cover letter required. A cover letter shall accompany all submittals and include the following:

a.

Summary statement identifying and characterizing (location, area of project in acres, and proposed land use) the proposed land development project and discussing how the project will adhere to the requirements of this Code.

b.

Brief description of drainage system components, the overall concept of the proposed drainage system, and its interaction with existing drainage facilities.

c.

Policy statement discussing the design criteria and any proposed deviation from methodology, as set forth by this Code.

(2)

Preliminary drainage study. The report submitted as a preliminary drainage study shall be formatted in accordance with the following outline and contain all of the information listed:

a.

Project location map and information. The project location map shall contain the following information:

1.

Map with township, range, section, quarter section.

2.

Name and address of property owner.

3.

Legal description of property.

4.

Streets within and adjacent to the project.

5.

Names of surrounding developments.

b.

Existing drainage map. The existing drainage map shall show the following:

1.

Drainage area map at a scale of one inch equals 20 feet to one inch equals 100 feet identifying all predevelopment drainage basins and subbasins within and that contribute flow through or across the proposed land development project.

2.

Existing land use and predominant cover type (shrubs, trees, grass).

3.

Identify all existing basins and discharge points with unique alphanumeric labels, list area of each basin in acres, and list runoff coefficients or curve numbers appropriate for the existing land use.

4.

Existing contours at two-foot maximum intervals for all basins and subbasins.

5.

Limits of floodplain and floodway located within or adjacent to (within 75 feet of the property) the proposed land development project.

6.

Existing drainage facilities within and adjacent to the proposed land development project to a point 25 feet beyond the property line, or to a greater distance as may be required to reveal influencing features or features which may be influenced by the proposed development.

7.

Location, size and type of easements within and adjacent to the proposed land development project.

c.

Proposed drainage map. The proposed drainage map shall show the following:

1.

Drainage area map at same scale as existing drainage map identifying all proposed (post-development) drainage basins and subbasins and existing basins that will not be altered.

2.

Identify all proposed basins and proposed discharge points with unique alpha-numeric labels, list area of each basin in acres, and list runoff coefficients or curve numbers appropriate for the proposed land use.

3.

Existing and proposed contours at two-foot maximum intervals for all basins and subbasins.

4.

Limits of floodplain and floodway located within or adjacent to (within 75 feet of the property) the proposed land development project.

5.

Existing drainage facilities to remain and proposed drainage facilities within and adjacent to (within 25 feet of the property) the proposed land development project.

6.

Existing and proposed easements within and adjacent to (within 25 feet of the property) the proposed land development project.

d.

Hydrology and hydraulics. The hydrology and hydraulics shall show the following:

1.

A written summary of the existing drainage patterns and off-site drainage patterns and impact on the proposed development.

2.

A summary table of the following:

(i)

Existing (predevelopment) hydrologic characteristics, including, but not limited to, discharge points, basin areas, soil types, runoff coefficients, curve numbers, hydraulic lengths, and time of concentration values; and

(ii)

Assumptions, including a written description of the basis for each assumption used in the calculations.

3.

A summary table of hydrologic analysis results for all of the basins and subbasins based on existing conditions for the minor and major storm events.

4.

A written general description of the proposed stormwater drainage facilities and methods for controlling the post-development drainage including the proposed locations of stormwater drainage facilities required to mitigate any potential adverse impacts.

5.

A summary table comparing existing and proposed peak flow rates at each discharge point for the minor and major storm events.

6.

Design rainfall data used for minor and major storms.

7.

Hydraulic capacity calculations for all existing drainage facilities that currently serve or will serve the proposed land development project.

8.

Volumetric computations for compensatory storage requirements for any alterations of the floodplain.

(3)

Final drainage study. The report submitted as a final drainage study shall include a final drainage plan, shall be formatted in accordance with the following outline, and shall contain all information listed for a preliminary drainage study in addition to the following information:

a.

Drainage facility design. The drainage facility design shall show the following:

1.

Certification statement shall be in conformance with section 35-109.

2.

A summary table of the following:

(i)

Post-development hydrologic characteristics, including but not limited to discharge points, basin areas, soil types, runoff coefficients, curve numbers, hydraulic lengths, and time of concentration values); and

(ii)

Assumptions, including a written description of the basis for each assumption used in the calculations.

3.

A summary table of hydrologic analysis results for all of the basins and subbasins based on proposed (fully developed) conditions for the minor and major storm events.

4.

A summary table of hydraulic capacity calculations for all proposed drainage facilities, including but not limited to streets, storm inlets, storm sewers, drainage channels, swales, culverts, and on-site or regional detention facilities, that will serve the proposed development project (on-site and off-site) or convey pass through runoff from upstream or off-site basins and subbasins.

b.

Conclusions.

1.

A written summary statement indicating compliance with this Code, the city drainage standards and the city standards, as well as any accepted drainage plans, where applicable.

2.

A detailed statement concerning the projected effects of the proposed land development project on property adjoining the site and on existing drainage facilities and systems both on and off-site.

c.

References. List all design criteria and technical information used.

d.

Appendices. The appendices shall contain the following:

1.

Land use assumptions regarding adjacent properties.

2.

Time of concentration flow path characteristics and calculations.

3.

Runoff calculations at specific design points on site and off-site.

4.

Historic and fully developed runoff computations at points of compliance.

5.

Hydrographs at critical design points, if applicable.

6.

Culvert capacity charts.

7.

Storm sewer capacity calculations.

8.

Street capacity calculations.

9.

Storm inlet capacity calculations.

10.

Open channel design calculations.

11.

Grade control and/or channel drop design.

12.

Detention area/volume capacity and outlet capacity calculations (stage-storage-discharge table).

13.

Routing of off-site drainage flow through the development, easements, and/or right-of-way dedications.

14.

Location/alignment of watercourse and the appropriate hydraulic analysis for any alteration of a watercourse.

15.

Hydraulic analysis for compensatory storage requirements for any alterations of the floodplain.

16.

Detention facility outlet details and maintenance plan.

17.

All appropriate FEMA submittal data and application for a LOMR, if applicable.

(4)

Final drainage plan.

a.

A drainage plan must contain a general location map in sufficient detail to identify all surface drainage entering and leaving the development and general drainage patterns. The map should be at a scale of one inch equals 200 feet up to one inch equals 2,000 feet and show the path of all drainage from the upper reach of any off-site basins to the defined major drainageways.

b.

All final drainage plans submitted for final acceptance shall include the certifications as stated in section 35-109.

c.

Maps of the proposed development at a scale of one inch equals 20 feet to one inch equals 100 feet on a full size drawing (22 inches by 34 inches) oriented in plan view with north arrow and scale shall be included with the drainage plan. The plan shall show the following:

1.

Existing and proposed contours at one-foot maximum intervals.

2.

Spot elevations and drainage arrows at all grade breaks within the development and at all locations where proposed surface improvements tie into existing grade around the perimeter of the property. In every instance, the plan shall include topography a minimum of 75 feet beyond the limits of proposed development.

3.

Property lines, easements, and common areas with purposes noted.

4.

Streets, roads, and highways adjacent to the property.

5.

Overall drainage area boundary and drainage sub-area boundaries identified by bold, dashed lines.

6.

Existing drainage facilities and structures, natural or manmade, including roadside ditches, drainageways, gutter flow directions, and culverts. All pertinent information such as material, size, shape, slope and location shall also be included.

7.

Proposed storm sewers and open drainageways, including inlets, manholes, culverts, retaining walls, erosion control measures, and other appurtenances.

8.

Drainage arrows indicating individual lot grading patterns shall be clearly illustrated. Surface drainage from the lesser of three residential lots or three acres is allowed to combine before entering stormwater drainage facilities designed to collect and transport surface drainage.

9.

Proposed discharge points for runoff from the project area and all facilities designed to convey flows to the final outfall point without adverse effects to downstream property.

10.

The on-site 100-year flood elevations and the limits of regulatory floodway, floodplain and/or water surfaces. In every instance, the plan shall include a determination of the 100-year water surface elevation and the area of inundation based on routing off-site drainage flow through the development for a 100-year 24-hour storm.

11.

Location and elevation of all existing and proposed utilities affected by or affecting the drainage design.

12.

Details for the construction of all proposed stormwater drainage facilities at a scale sufficient to demonstrate conformance with city drainage standards and city standards shall be included. Details shall include, but not be limited to, plan and profile view of all drainage facilities, culvert and underground pipe trench details, detention storage and outlet details, street inlet details, low-flow concrete swale and curb cut details and channel and swale standard cross sections.

13.

Water surface profiles for the major storm shall be computed using standard backwater analysis (taking into consideration all losses due to changes in velocity, drops, bridge openings, culverts, and other obstructions) and delineated in the profile view of all channels and drainage facilities.

14.

The existing and proposed surface area (in units of square feet) of impervious materials for nonresidential land development projects shall be calculated and included in tabular form for proper assignment of equivalent residential units (ERUs) for drainage fees.

15.

When construction is phased or when temporary facilities are used, an outline of the sequence of construction activities shall be provided that notes when the various aspects of the drainage study will be implemented.

(5)

Record drawings. Record drawings shall be in compliance with chapter 35 and must be prepared at a scale of one inch equals 20 feet to one inch equals 100 feet on a full size drawing (22 inches by 34 inches) oriented in plan view. The as-built plan shall be clearly titled "as-built" or "record drawing" and contain all information shown on the accepted final drainage plan with any changes noted by striking through the proposed design values and clearly labeling as-built values as such.

(Ord. No. 3023, § 1(23.386), 3-3-2008; Ord. No. 3091, § 4, 1-25-2010; Ord. No. 3246, § 3, 12-16-2013)