[HISTORY: Adopted by the City Commission of the City of Royal Oak 8-12-1991 by Ord. No. 91-8; amended in its entirety 11-15-2004 by Ord. No. 2004-20. Subsequent amendments noted where applicable.]
This chapter shall be known and cited as the "Stormwater Detention Ordinance of the City of Royal Oak" and will be referred to herein as "this chapter."
This chapter is intended to specifically apply to stormwater detention which is a prevailing need and which the absence of detention could endanger the property, health, safety and general welfare of the residents and property owners of the City.
As used in this chapter, the following terms shall have the meanings indicated:
- Any addition to an existing building.
- Written approval by the City Engineer of the City of Royal Oak, Michigan, or by his duly authorized agents, assistants, or representatives, limited to the specific duties assigned or entrusted to them.
- All designated or specified areas or devices where stormwater is detained to meet the requirements of this chapter.
- The City of Royal Oak, Michigan. When used in this chapter in connection with any filing, submittal, delivery or payment to, or review, approval or other action, refers to the City Engineer.
- CITY'S RIGHT-OF-WAY OR RIGHT-OF-WAY
- Any and all public rights-of-way, streets, highways, roads, sidewalks, alleys, thoroughfares, public easements and public places located within the City, including within any curbs, shoulders, landscaped areas and/or other areas incidental and/or appurtenant.
- Any new building, or paved driveway, parking lot or sidewalk, not including public roadways.
- ENGINEER or CITY ENGINEER
- City Engineer of the City of Royal Oak, Michigan, or his duly authorized agents, assistants or representatives, limited to the specific duties assigned or entrusted to them.
- PUBLIC EASEMENT
- Any area of land which has been granted or dedicated to the City or to public use, including, but not limited to, road or right-of-way, utility, water main, sewer line, access, drainage, recreation, conservation and other public areas, whether in easements or in fee.
- Any existing building converted to other use or structurally altered, and which requires a City building permit and/or site plan for City Plan Commission review and approval as described in § 770-12, Site plan review, or any similar ordinance. Also, any paved parking lot, private street, drive or sidewalk removal and replacement. Renovation shall also include the pulverizing and/or crushing of existing pavement for use as a new pavement base material.
- SITE IMPROVEMENTS
- Additions, developments and renovations proposed for a specific property as defined.
- STORM DETENTION SYSTEM
- All features that comprise the requirements of this chapter, including but not limited to storm detention basins and their required components and finishes, restrictors, pumps and freeboard structures; and all collection and outlet piping, drainage structures and conveyance features, including curbing, swales, ditches; and all fences, gates and signage.
Any development, renovation or addition to an existing development within the City, excluding property in the Central Business District Zones and properties used for one- and two-family residential purposes, must detain the stormwater runoff from the improvement on-site.
Developments, renovations or additions less than 0.14 acre or 6,100 square feet in area will not require stormwater detention at the time of the improvement. For such case, a recordable lien to the City must be executed by the property owner. The recordable lien shall state that when the next future improvement occurs on the property which will make the accumulated area of the recorded lien(s) and the future improvement greater than 0.14 acre or 6,100 square feet, the property owner will make the stormwater detention improvements as specified in this chapter on the accumulated area.
Renovations and additions that do not involve parking lot, private street, drive or sidewalk removal and replacement will not require stormwater runoff detention at the time of the improvement, unless adequate undeveloped land is available for detention on the property. If stormwater detention is not included as part of the renovation, a recordable lien to the City must be executed by the property owner. The recordable lien shall state that when the next future improvement occurs on the property, the property owner will make the stormwater detention improvements as specified in this chapter on the accumulated area.
Lien(s) shall be prepared by the property owner using the standard form available from the City Engineering Department.
The Oakland County Method of Detention Basin Design, as made available by the Oakland County Drain Commissioner's office, shall be utilized in determining the volume of detention required. Basins with orifice or pumped outlets will be required to hold the volume for a ten-year storm while basins with no outlets will be required to hold two one-hundred-years storms. Discharge on an orifice or pumped outlet must be throttled to a restricted rate of 0.2 cfs per acre, or throttled to a restricted flow of 0.3 cfs if the total property area requiring detention is 1.5 acres or less.
For City approval of stormwater detention, the applicant shall furnish the City Engineering Department three sets of detention plans, 24 inches by 36 inches, with detention calculations shown on the plans.
A professional engineer, licensed in the State of Michigan, shall affix his or her seal on the plans.
The plans shall not be drawn to a scale smaller than one inch equals 30 feet. The City Engineer shall review the plans and calculations for conformity to the standards set forth in this chapter, and certify that they are consistent with the overall utility plans of the City, after which he will return a letter of review with appropriate comments. The applicant, after making any changes requested, shall resubmit three sets of the revised plans to the Engineering Department for approval. The applicant may be required to obtain approval of the City of Royal Oak Building Department, Oakland County Drain Commissioner, the Road Commission for Oakland County or the Michigan Department of Transportation when the outlet discharges to facilities under their jurisdiction.
The detention plans shall clearly indicate the perimeter of all acreage contributing to the detention basin. The perimeter of the water surface for the volume of detention provided shall also be indicated on the plans including the water surface elevation.
The plans shall include the calculation of an overall coefficient of runoff for the acreage contributing to the detention basin. The range of this coefficient shall vary from 0.15 for completely grassed areas to 0.90 for completely paved areas.
The detention calculations for each site shall include the number of total acres calculated to the nearest hundredth contributing to the detention basin. The total cumulative volume of required detention shall be calculated using all areas of proposed site improvements and shall include previous site improvement areas covered by this chapter.
The detention calculations shall include the sizing of the restricting orifice or structure cover. The calculations for the restricting orifice size or restricted structures cover openings shall be made using a coefficient for a sharp-edged orifice entrance. Details for the restrictor are to be clearly indicated on submitted plans. The smallest pipe orifice size allowed is 2.5 inches in diameter. The orifice size shall be rounded down to the nearest one-half inch from the actual calculated size.
Calculations for the volume of detention provided shall be included on submitted plans. The volume calculations shall be made using standard geometric formulas to determine the volume between appropriate contour elevations. For irregular-shaped basins, the geometric formula for the volume of a frustum of a cone or pyramid shall be used to estimate the volume between appropriate contour elevations.
Plan approval constitutes conformance with this chapter in regards to calculations and method used to control runoff and achieve the required detention. Plan approval does not infer sanction or approval of construction governed by any other permit or subsequent approvals.
After approval of plans, any change to the storm detention system shall be submitted to the City Engineer for approval prior to its construction.
All basin design shall incorporate components that allow for visual inspection and maintenance by mechanical means of all areas designated for stormwater storage or restricted outflow.
Acceptable means of detention can be achieved through standing water in parking areas, landscaped ponds, or buried vaults, chambers, pipes or other approved buried device. Either one or any combination of these designs may be utilized to achieve the required detention.
All components of storm detention systems shall be constructed entirely on the private property of the proposed development, except for discharge piping and connections to public sewers. No portion of a basin shall be installed within a publicly owned utility easement. Connections to public sewers shall be at locations as approved by the City Engineer.
Basins with orifice or pumped outlets must be constructed to drain entirely unless designed to retain a permanent water level that conforms to a Plan Commission approved landscape plan.
Basins with no outlets must be constructed in soils that have a saturated hydraulic conductivity of at least 0.004 feet per minute.
A minimum of 12 inches of freeboard must be provided above the retained water surface of all detention basins and below the finished floor of all adjacent buildings. A minimum of six inches of freeboard must be provided above the maximum water surface created by the required positive nonerodable overflow to both adjacent buildings and adjacent properties.
A positive nonerodable overflow capable of handling the capacity of a one-hundred-year storm must be provided and clearly identified on the plans, which shall not discharge onto abutting private property.
Drainage from a development, renovation and addition shall not be diverted onto abutting private property. Drainage from a development, renovation and addition requiring detention shall be directed to the detention basin. Discharge from the basin and overflow shall not be diverted onto abutting private property.
The City requires a building permit for all piping and drainage structures for compliance with other codes and ordinances including the current Michigan Plumbing Code requirements for approved materials and drainage pipe cleanouts. Section P-708 of the code requires that manholes be provided as cleanouts at each major change of direction for underground piping over 10 inches in diameter.
All storm detention systems shall be maintained in proper working order, free of debris, trash or anything else that may adversely affect the operability of the system, the required volume and outlet capacity. The storm detention systems shall be kept free of vermin and any creatures that may cause the system to become inoperable or harm the public. Maintenance of the storm detention system also requires treatment to prevent and control insects and microbes.
A paved open channel must be provided along the bottom of all detention basins designed to drain entirely. The open channel shall begin at the outlet for the basin and shall run the entire length of the basin with the channel extending to all pipes discharging into the basin. The channel shall be sized to equal the capacity of the outlet for the basin when flowing full with no pressure head. The channel shall provide a minimum velocity of two feet per second when the basin outlet is flowing full with no pressure head.
The entire basin must be either sodded, paved, or have some other City approved method of stabilization. The maintenance of all stabilization and fencing in and around the detention basin shall be the responsibility of the property owner.
All grass and noxious weeds growing in or around the basin shall be maintained in accordance with Chapter 757, Weeds, as amended, or other similarly adopted property maintenance code. No hydrophilic plants such as rushes, reeds, water iris, willow or cattails shall be allowed to grow or thrive within an open basin, or any tree, shrub or plant not specifically shown and approved on the required plans.
Minimum grade on the bottom of the detention basin shall be 1.2% when sodded. For paved open channels in basins, the minimum grade shall be 0.5%.
All pipes entering a detention basin shall have either a headwall or end section at the end of the pipe. Bar screens must be installed on all open ends of pipe 12 inches or larger in diameter. Restricting orifices shall be located in an accessible structure outside of the basin limits.
All open pond detention basins must be fenced if the side slopes exceed one vertical to six horizontal, or if the basin is designed to hold water to a depth of more than 18 inches when filled to capacity. This requirement may be waived by the City Plan Commission when the design is an integral part of the landscaping and the location and depth does not present a potential hazard.
A three-foot minimum shoulder shall be provided between the fence and the side slopes for the basin. The side slopes shall not exceed one vertical to three horizontal.
Fences shall be a minimum of four feet high chain link or other fencing material of comparable durability and safety as approved by the City Plan Commission with a locked access gate, 10 feet wide with double opening. A key for a City Engineer approved lock shall be supplied to the City Public Service Department.
Depending upon location in relation to adjoining properties or rights-of-way, the City Plan Commission may require a landscape screen in front of the fencing.
All gates constructed directly in front of a paved roadway are to have an end of roadway marker (ER-1) and a "road ends" sign (W-14-2-a) securely fastened to the gate in accordance with the "Michigan Manual of Uniform Traffic Safety Control Devices." The sign material shall be high intensity reflectorized Scotchlite on 0.080 aluminum.
In cases where the drain outlet for the detention basin is not deep enough to completely dewater the basin by gravity, pumps must be installed. The pumps shall be installed in duplicate with each pump capable of handling the flow. Controls shall be set in the receiving water to regulate the flow.
The controls may be electrodes placed inside a galvanized pipe stilling well at a location adequately protected from the backwater curve during discharge.
A bubbler system in a stilling well protected as in Subsection A above. The operating controls and pumps shall be set in a fully designed pump house with adequate dimensions for working area. The pump house and west well must be located inside the fenced area.
Pump controls shall be designed in a manner that accounts for the water level in the receiving sewer.
Complete specifications for the pumps and controls and performance curves for the pumps called for must be submitted to the City Engineer for approval, including two operation manuals provided from the manufacturer.
The City requires a building permit for all piping, electrical work and concrete structures for compliance with other codes and ordinances.
A manhole with inside diameter of six feet is required between the lift station and the outlet. The twin discharge lines shall be ductile iron. They shall enter the manhole and a storm sewer shall be installed from the manhole to the outlet. The manhole cover shall be East Jordan Iron Works (EJIW) No. 8247A hinged type or equivalent.
The pump house and gate to the detention basin shall be locked at all times. A key for a City Engineer approved lock to the pump house shall be supplied to the City Department of Public Service and Recreation.
Easement for discharge piping. The property owner of any development, renovation or addition that contains a detention basin, excluding surface basins within vehicular parking areas, shall grant the City an easement for the detention basin discharge piping and all discharge piping appurtenances. The easement shall be a minimum 12 feet wide, unless otherwise determined by the City Engineer. The grant of easement shall provide the City the rights to access, inspect, and to rectify any City ordinance violation within the easement if the property owner fails to commence work on compliance within 21 days from the date of written notification by the City of a violation unless emergency circumstances dictate immediate compliance. All costs incurred by the City in rectifying an ordinance violation shall be assessed to the property owner.
Easement for basin. The property owner of any development, renovation or addition that contains a detention basin, excluding surface basins within vehicular parking areas, shall grant the City an easement encompassing the detention basin. The limits of the easement shall be a minimum three feet outside any fencing, or six feet from the tip of the side slope for the detention basin and shall include a minimum twelve-foot width to access the gate for the basin. The grant of easement shall provide the City the rights to access, inspect, and to rectify any City ordinance violation within the easement if the property owner fails to commence work on compliance within 21 days from the date of written notification by the City of a violation unless emergency circumstances dictate immediate compliance. All costs incurred by the City in rectifying an ordinance violation shall be assessed to the property owner.
Easement grants. The property owner shall be responsible for providing the City Engineering Department with all property and easement descriptions. All grants of easement shall be executed by the property owner prior to City issuance of occupancy permits for the development.
Prior to formal written acceptance by the City of the storm detention system, all turf must be established in open basins. In addition, a licensed professional engineer must furnish the City Engineer two sets of sealed as-built detention plans. As-built plans shall verify that the required detention volume has been provided using calculations based on newly constructed elevations within and surrounding the basin(s). Newly constructed elevations within and surrounding the basin shall be shown on the plans in sufficient quantity and interval to verify and correspond to the calculations. The required outlet, pump or restrictor installation, grading that conforms to the approved plans, and freeboard features constructed with overflow provided shall also be indicated on the as-built plans.
All differences and deficiencies shall be noted. Plans to correct deficiencies in detention volume, outlet, pump or restrictor, freeboard and overflow features shall be submitted for City Engineer approval and included with the as-built plans. All deficiencies in detention volume, outlet, pump or restrictor, freeboard and overflow features shall be corrected prior to City issuance of occupancy permits for the development.
A permit will be required from the City for the installation of all parking lot pavements as addressed under this chapter. The permit allows for one post construction site inspection by the City Engineer upon submittal of the required as-built plans to verify compliance with the permit provisions. The City Commission shall establish the permit fee by resolution.
[Amended 8-20-2007 by Ord. No. 2007-13; 6-15-2015 by Ord. No. 2015-13]
The City Engineer is charged with the enforcement of this chapter. The City Engineer shall have the authority to grant variances from the stormwater detention regulations contained in this chapter upon a showing of practical difficulty by a property owner. A property owner requesting a variance shall submit a written request specifically stating which provision a variance is being requested from and describing the practical difficulty involved in strict compliance.
The City Engineer shall have the authority to promulgate rules to allow for pilot projects that may vary from the stormwater detention regulations contained in this chapter as long as any development, renovation or addition to an existing development within the City, excluding property in the Central Business District Zones and properties used for one- and two-family residential purposes, detains stormwater runoff from the improvement on site. The City Commission shall adopt the rules before they become effective.
Any person, permittee, owner, developer or subsequent property owner who violates any provision of this chapter, including failure to submit plans, obtain permits, pay any fees, charges or surcharges imposed, or any condition or limitation of a permit issued pursuant or who knowingly makes false statements, representations or certification in any application, record, report or plan or other document filed or required to be maintained pursuant to this chapter or who tampers with, alters or fails to maintain, or knowingly renders inoperable any detention basin, restrictor, fence or freeboard required under this chapter is guilty of a civil infraction and shall, upon conviction, be punished by the following:
A person violating this chapter for the first time is responsible for a municipal civil infraction and subject to payment of a civil fine of not less than $100 for each day of the violation, plus costs.
A person violating this chapter for the second time is responsible for a municipal civil infraction and subject to payment of a civil fine of not less than $250 for each day of the violation, plus costs.
A person violating this chapter for the third time is responsible for a municipal civil infraction and subject to payment of a civil fine of not less than $500 for each day of the violation, plus costs.
The City Engineer, Royal Oak Building Official and City of Royal Oak Code Enforcement are hereby authorized to seek, through any authorized prosecutorial official, prosecution of charges against any person violating any provision of this chapter.
Ownership of a storm detention system and its subsequent maintenance and liability fall to the legal ownership of the property. In the case of condominiums or other development where shared ownership of the storm detention system is owned by multiple property owners, associations or entities, the association or joint owners of the detention system shall register the legal owner's name(s), contact representative, current address and telephone numbers with the City Clerk office annually before January 30 or 30 days after any change in ownership.