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.