§ 27-137. Final stormwater management plan requirements.

This section sets forth the requirements that shall apply to final stormwater management plans for proposed covered development projects as required by this article.

(a)

General.

(1)

The stormwater management plan shall display and present the information required by this section through the use of maps, illustrations, reports, and calculations.

(2)

The stormwater management plan shall specify the type, location, and size of stormwater management system to be provided, using final calculations and detailed construction drawings.

(3)

If the development will be completed in phases, the stormwater management plan shall be prepared and submitted for the total project and for all phases. Further, upon completion of each phase, the stormwater management plan for the project shall be fully functional for the phases already completed and its functionality shall not be reliant in any way upon the completion of future phases. Final approval of one or more phases shall not ensure approval of subsequent phases.

(b)

Plan preparation. The stormwater management plan shall be prepared, signed, and sealed by a professional civil engineer registered in the State of Michigan.

(c)

Scale for mapping. The stormwater management plan shall be drawn to a scale not less than 1" = 50', or as otherwise required by the civil engineer.

(d)

Required elements and information. A stormwater management permit shall not be approved unless the applicant has provided a final stormwater management plan that contains all of the submittals required by this subsection (d). (The city engineer may require the same or similar requirements for a preliminary stormwater management plan submitted by an applicant during earlier stages of the stormwater management permit review process, but using preliminary calculations and without requiring detailed construction drawings, as determined appropriate by the city engineer.) A final stormwater management plan shall include all of the following elements and information:

(1)

Location and size. The location of the development by means of a small location map, drawn to a scale no less than 1" = 2000', and the size of the development in acres.

(2)

Zoning. The zoning classification of the development site and all abutting parcels.

(3)

On-site and off-site features. The location and description of all on-site features and all adjacent off-site features within fifty (50) feet (unless another distance is specified by the city engineer based on the circumstances at the site), and all other off-site features that may be impacted in determining the overall requirements for the development.

This shall include:

a.

Property lines of the development and of adjoining developments.

b.

Existing site topography with contours at two-foot intervals or less based on the NAVD88 datum.

c.

On-site public and private streets and street right-of-way lines; and adjoining public and private streets and street right-of-way lines.

d.

Railroads.

e.

High-tension power lines or underground transmission lines.

f.

Cemeteries.

g.

Parks.

h.

Natural and artificial watercourses, wetlands and wetland boundaries, environmental feature boundaries, floodplains, lakes, bays, existing stormwater storage facilities, conveyance swales (natural or artificial) with identification of permanent water elevations.

i.

Location of woodlands.

j.

Designated natural areas.

k.

Any proposed environmental mitigation features.

l.

Existing and proposed public and private drains, storm sewers, sanitary sewers, and water mains, and any related easements.

m.

A map, at the U.S.G.S. scale, showing the drainage boundary of the proposed development and its relationship with existing drainage patterns.

n.

Boundaries of any off-site drainage area contributing flow to the development.

o.

All watercourses passing through the development, along with the following:

1.

Area of upstream watershed and current zoning.

2.

Final calculations of runoff from the upstream area for both the one hundred-year and two-year 24-hour design storms, for fully developed conditions according to the current land use plan for the area.

p.

Soil borings at the sites of proposed retention/detention and infiltration facilities, and as needed in areas where high groundwater tables or bedrock near the surface exist, and at any other locations as required by the city engineer.

q.

Proposed development site improvements including lot divisions and building footprints.

r.

Drinking water wells, public wellheads, wellhead protection areas (WHPAs), underground storage tanks, and brownfields.

s.

Any areas of unique geological formations (e.g., karst areas).

t.

Any other on-site or off-site features as determined necessary by the city engineer.

(4)

Stormwater BMP construction plans. The stormwater management plan shall include final stormwater BMP construction plans. The BMP construction plans shall be drawn to a scale not less than 1" = 50', and on sheets no larger than 24" × 36". The scales used shall be standard engineering scales and shall be consistent throughout the plans. When plans have been completed with computer aided design technology, locations should be geo-referenced and a copy of the electronic file shall also be provided. The construction plans and related documents shall, at a minimum, include:

a.

Location and specifications of all proposed stormwater management practices, methods, and facilities (plan and profile).

b.

Proposed storm drains, including rim elevations, invert elevations, pipe sizes, and pipe materials.

c.

Calculations of runoff from upstream areas for both the one hundred-year and two-year, 24-hour design storms for fully developed conditions according to the current land use plan for the area.

d.

Identification of stormwater quality and quantity treatment facilities and method of stormwater conveyance.

e.

Calculation of runoff volume captured by BMPs for treatment facilities.

f.

Proposed open channel facilities including slope, cross-section detail, bottom elevations, and surface material.

g.

Final sizing calculations for stormwater quality and quantity treatment facilities and stormwater conveyance facilities.

h.

Storage provided by one-foot elevation increments.

i.

Tributary area map for the stormwater management system and all components thereof indicating total size and average runoff coefficient for each sub-area.

j.

Analysis of existing soil conditions and groundwater elevation (including submission of soil boring logs) as required for proposed retention and infiltration facilities.

k.

Plans and details of proposed soil erosion and sedimentation control measures, both during construction (as required by Part 91 of the Public Acts of 1994) and permanent measures.

l.

Details of all stormwater BMPs, including but not limited to:

1.

Outlet structures.

2.

Overflow structures and spillways.

3.

Riprap.

4.

Manufactured treatment systems.

5.

Underground detention cross-section and product details.

6.

Cross section of infiltration and/or bio-retention facilities.

m.

Location of proposed stormwater management facility easements (consistent with subsection (d)(6) of this section.)

n.

Final landscaping plans and details.

(5)

Operation and maintenance plans and agreements. The applicant shall provide a stormwater operation and maintenance (O&M) plan and agreement.

a.

The O&M plan and agreement shall be provided by the applicant in such form and substance as required by the city attorney.

b.

The O&M plan and agreement shall contain provisions to ensure that the maximum design performance of stormwater BMPs is maintained on a long-term basis and that the city's standards for stormwater quality and quantity are met.

c.

At a minimum, the O&M plans and agreements shall include all of the following information and contents:

1.

The names and addresses of the property owners, and, the owners of all components of the stormwater system.

2.

The names and addresses of the persons responsible for operation and maintenance.

3.

The names and addresses of the persons responsible for financing operation and maintenance and emergency repairs.

4.

The signatures of the owners and any other persons to be bound by the agreement.

5.

A detailed annual estimated budget for the expected life of the BMPs; and a demonstrated means of financing operation and maintenance and emergency repairs.

6.

A map showing the location of the stormwater systems and facilities, including catch basins, manholes/access lids, main, and stormwater devices.

7.

A schedule for routine, non-routine, emergency, and long-term inspection and maintenance of all structural and vegetative stormwater BMPs, with detailed tasks to be performed, and detailed inspection and maintenance checklists.

8.

Operating instructions for stormwater outlet components.

9.

Vegetation maintenance schedule.

10.

Recordkeeping, tracking, inspection, and notice checklists and requirements.

11.

A statement recognizing the city's right to enter the property for the purpose of inspections.

12.

Provisions regarding the city's right to perform, or cause to be performed, any required operation and maintenance if the responsible persons fail or refuse to do so, and the obligation of property owner to fully reimburse the city for the costs and expenses incurred by the city in connection with such activity.

d.

The O&M plan and agreement shall be binding on all current and subsequent owners of land served by the stormwater BMPs and shall be recorded in the county register of deeds as directed by the city attorney.

e.

Any person responsible for the operation and maintenance of a stormwater management facility shall provide records of all maintenance and repairs to the city engineer upon request.

(6)

Easements for stormwater management system. The applicant shall provide all stormwater management easements as determined necessary by the city engineer to implement the approved final stormwater management plan and to otherwise comply with this article.

a.

Stormwater management easements may be required for any of the following purposes:

1.

To provide access for stormwater management facility inspections and maintenance.

2.

To preserve stormwater runoff conveyance, infiltration, and detention areas and facilities, including flood routes for storm events.

3.

To preserve primary and secondary drainage ways that are needed to serve stormwater management needs of other properties.

4.

To accomplish purposes such as those listed above for all areas used for off-site stormwater control, including undeveloped or undisturbed lands, as applicable.

5.

To serve other purposes and objectives as necessary to achieve the purposes of this article as determined by the city engineer.

b.

All stormwater management easements shall meet the following requirements:

1.

The purpose of each easement shall be specified in writing.

2.

The easements shall be acceptable to the city attorney in form and substance and shall be recorded with the county register of deeds.

(7)

Implementation plan. The applicant shall provide an implementation plan for construction and inspection during and after construction of all stormwater management system components required by the final stormwater management plan, including a schedule of the estimated dates of completing construction of the stormwater management system shown on the plan; identification of the proposed inspection procedures to ensure that the stormwater management system components are constructed and operating in accordance with the final stormwater management plan; and recordkeeping requirements. The implementation plan will include arrangements acceptable to the city engineer for notification by the applicant to the city engineer before the commencement of construction of the stormwater management system (and before construction of critical components of the system) and for final verification of construction by a registered professional engineer.

(8)

Performance guarantee. The applicant shall provide a performance guarantee in a form and amount satisfactory to the city engineer and the city attorney as provided by this section.

a.

The applicant shall submit a performance bond (or other financial guarantee acceptable to the city) for the timely and satisfactory construction of all stormwater management system components in accordance with the final stormwater management plan. The performance bond or other financial guarantee shall be accompanied by a detailed cost estimate provided by the applicant. Upon written certification by a registered professional engineer that all components of the required stormwater management system have been completed in accordance with the final stormwater management plan, including, but not limited to, the provisions contained in subsection (d)(7) of this section (implementation plan) and section 27-151 (as-built certification and final inspection), and subject to final acceptance and approval by the city engineer, the city may release the performance bond or other financial guarantee.

b.

Except as provided in subsection (d)(8)c. of this section, the amount of the financial guarantee shall be in the amount of the cost estimate for the work provided by the applicant, unless the city engineer determines that a greater amount is appropriate, in which case the basis for such determination shall be provided to the applicant in writing. In determining whether a greater amount is appropriate, the city engineer shall consider the size and type of the development, the size and type of the on-site stormwater system, and the nature of the off-site stormwater management system the development will use.

c.

The city engineer may, but shall not be required to, waive or reduce the amount of the financial guarantee for a development that will not increase the impervious surface of the development site by more than two thousand (2,000) square feet.

d.

Nothing in this section or this article shall be construed or interpreted as relieving any person of their obligation to pay all costs associated with on-site private stormwater management systems, as well as those costs arising from the need to make other drainage improvements to reduce a development's impact on a drain consistent with adopted design standards.

(9)

Other information and materials. The stormwater management plan shall include any other information, documents, items, and materials determined necessary by the city engineer to verify that the stormwater management plan complies with the city's design and performance standards for drains and stormwater management systems, and that the plan otherwise complies with the requirements of this article and other applicable laws and regulations.

(Ord. No. 2011.01, § 1, 1-11-11)