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:
ADDITION Any addition to an existing building.
APPROVAL 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.
BASIN All designated or specified areas or devices where stormwater is detained to meet the requirements of this chapter.
CITY 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.
DEVELOPMENT 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.
RENOVATION 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.
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. A professional engineer, licensed in the State of Michigan, shall affix his or her seal on the plans.
B. 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.
C. 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.
D. 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.
E. 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.
F. 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.
G. 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.
H. 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.
I. After approval of plans, any change to the storm detention system shall be submitted to the City Engineer for approval prior to its construction.
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.
A. The controls may be electrodes placed inside a galvanized pipe stilling well at a location adequately protected from the backwater curve during discharge.
B. 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.
C. Pump controls shall be designed in a manner that accounts for the water level in the receiving sewer.
D. 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.
E. The City requires a building permit for all piping, electrical work and concrete structures for compliance with other codes and ordinances.
F. 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.
G. 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.
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]
A. 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.
B. 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.
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.