Unless otherwise noted, the following design standards and requirements apply to construction plans submitted for review by the City of Roseville for all types of developments or drain-related construction activities.
The following general stormwater management requirements apply to all new developments and redevelopments in the City of Roseville.
A. The design process shall begin by identifying sensitive areas located on the site and laying out the site to protect the sensitive areas.
B. Best management practices. Best management practices (BMPs) that reduce the amount of stormwater runoff and improve water quality are required and shall be designed on a site-specific basis. Rate and volume reduction BMPs shall be used to protect open channel storm drains. All BMPs shall be included on the plans and will be subject to review and approval by the City of Roseville, the Macomb County Public Works Office (MCPWO) and the Michigan Department of Environment, Great Lakes and Energy (EGLE formerly MDEQ), or the authorized state regulatory agency, as necessary for permits.
(1) During construction, all sites that disturb one or more acres of land, or are located within 500 feet of waters of the state, BMP usage shall be monitored and recorded in the weekly soil erosion sedimentation control (SESC) reports. In such cases, weekly SESC reports shall also be required during construction.
(2) Land uses with potential for significant pollutant loading ("hot spots"), including but not limited to gas stations, commercial vehicle maintenance and repair, auto recyclers, recycling centers, and scrap yards, will require BMPs which address regulation of the specific hazard as determined by the MCPWO or the City Engineer. In such cases, weekly SESC reports shall also be required.
(3) The developer/owner shall include a long-term operation and maintenance schedule for all permanent BMPs. A maintenance agreement between the developer/owner and the City is necessary for permanent BMPs which shall include but not be limited to: inspection of structural or vegetative BMPs, performance of maintenance and corrective actions when BMPs are neglected by the owner, and deed restrictions. All such maintenance agreements shall be binding on the property and shall remain in effect in the event the property ownership is transferred or sold.
C. On-site management of stormwater is required first and foremost, unless site constraints consistent with the flow chart preclude this approach.
D. Stormwater shall be managed using four standards: channel protection, flood control, water quality, and pretreatment to protect both water resources and real property.
E. Channel protection control system shall be provided on all new developments connecting to an open drain to protect the drain's channel and banks from erosion due to the increased flow. Direct discharges to the Macomb County Public Works Office drains are generally governed by MCPWO design standards. Open drains within the City of Roseville jurisdiction shall be protected by incorporating a restricted flow of the channel protection volume. It is required that the postdevelopment project site runoff volume and peak flow rate must be maintained at or below predevelopment levels for all storms up to the two-year, twenty-four-hour event. "Predevelopment level" means the runoff flow volume and rate for the last land use prior to the planned new development or redevelopment. Compliance with this requirement is determined by calculating the existing ("predevelopment") and postdevelopment runoff volume and rate for the two-year and smaller storm events. The method is described in the Department of Environmental Quality (DEQ) publication, Computing Flood Discharges for Small Ungaged Watersheds, dated July 2003 (updated January 22, 2010).
(1) If it is demonstrated using the Alternative Approach Flowchart (Exhibit A) that the development cannot meet the required channel protection performance standard, the development may propose incorporation of green infrastructure [i.e., rain gardens, green (vegetated) roofs, permeable pavement, impervious cover removal, use of trees, etc.] This includes instances where site conditions (e.g., space limitations or tight soils that prevent infiltration, or soil or groundwater contamination, "hot spots") challenge or prohibit feasibility of maintaining the project site's predevelopment runoff levels for all storms up to the two-year, twenty-four-hour event. Green infrastructure shall be allowed under all circumstances consistent with the flowchart. Review of these proposals will be consistent with the SEMCOG Low Impact Development Manual for Michigan, 2008 or current standards.
F. Flood control shall be provided for all sites through retention or detention. On-site detention or retention of stormwater is required of all new developments or redevelopments to maintain the peak outflow to a rate similar to the predevelopment runoff rate. On-site flood control may be reduced or waived for direct discharges to large lakes and rivers if the developer demonstrates no negative impacts, or if provided in a regional facility with adequate upstream infrastructure.
G. Overland flow routes and the extent of high water levels for the 100-year storm shall be identified for all sites.
H. Water quality treatment shall be provided for all sites. A minimum treatment volume equal to one inch of runoff from the project site is required. A minimum volume of 900 cubic feet per acre is required for directly connected disturbed pervious areas (i.e., lawns). BMPs shall be designed to reduce postdevelopment solids loadings by 80% or to not exceed solids loadings of 80 milligrams per liter. Developments that disturb less than one acre, and are not part of a larger common plan of development or sale, may be exempted from the City's water quality treatment standards as approved by the City Engineer.
I. Pretreatment is required for infiltration, filtration and detention BMPs for ease of maintenance and to protect BMP integrity and preserve longevity.
J. Stormwater discharges from activities with a high risk for an accidental spill of pollutants (stormwater hot spots) shall provide spill containment.
K. The design maximum release rate, volume or concentration of stormwater discharged from a site shall not exceed the capacity of existing infrastructure or cause impairment to the off-site receiving area. Evaluation of the existing outlet must be performed and an adequate outlet must be provided.
L. The use of many decentralized low-impact development (LID) BMPs is not mandated but is encouraged on private sites.
M. Unless otherwise noted, hydraulic and hydrologic calculations (including rainfall volumes and distributions) shall be based on current EGLE standards (i.e., NOAA Atlas 14) and procedures in place at the time of application.
N. Construction plans for a phased development shall show the existing and/or proposed drainage systems for all prior phases of the development, unless the drainage system for the current phase is entirely independent of the prior phases. Furthermore, drainage plans for a phase of a development must not be dependent upon work planned to be performed in a future phase.
O. Plans shall include a grading plan showing existing and proposed topographic contour lines and proposed finish floor and basement floor elevations.
P. All existing natural or man-made watercourses shall be shown on the plans. The proposed changes to the site must not interfere with common law natural flow rights. Existing watercourses must be preserved or relocated, or the flow otherwise accommodated by the proposed plans. Provisions for the maintenance of the watercourse must be included in the deed restriction or an equivalent legally binding agreement. EGLE and/or the Army Corps of Engineers may also require permits for changes made to such watercourses.
Q. No construction activities shall be allowed without approval of the City of Roseville Building Official in a 100-year floodplain as determined by the City of Roseville.
R. The cover sheet of the plans shall include a "permit status table" indicating the status of all permits being obtained.
S. If an established drain is involved, construction plans shall include a note indicating that "All work performed in the right-of-way of an established drain shall require a permit from the Drain Commissioner."
T. The engineer's seal shall be affixed to all sheets of the construction plans.
U. Unless the storm sewers are to be owned and maintained by a single private entity (i.e., municipal or commercial development, manufactured housing community, etc.), all storm sewers shall be located within an easement. The minimum easement width for a storm sewer shall be 12 feet centered on the sewer center line. City Engineer may require a larger easement as necessary for access and to facilitate maintenance and future repairs. The dedication of the easement shall be required prior to acceptance of the continuous maintenance and service by the City.
V. Privately maintained storm infrastructure, including but not limited to pipes, stormwater detention facility, water treatment units, bioswales, etc., will require a maintenance agreement.
W. All existing and proposed on-site drainage easements shall be clearly shown.
X. No public right-of-way runoff shall be routed through private storm sewer unless approved by City Engineer. All storm sewer intended to be public (i.e., road drainage), shall be within a public right-of-way except as may be necessary to outlet said public storm sewer to another public sewer.
A "retention basin" is a facility with no engineered outlet (other than an emergency-type outlet) designed to hold runoff for a considerable length of time. The water in a retention basin is not discharged to a natural watercourse, although it may be consumed by plants, evaporate, or infiltrate into the ground. A retention basin should not be confused with a "detention basin," a facility designed to detain runoff for a short period of time and then release it to a watercourse.
A. On-site retention (or detention; see §
256-59, Detention storage facilities) is required of all new developments or redevelopments to prevent an increase in peak flows downstream in the drainage district.
(1) Retention basins are an acceptable stormwater management practice on sites where the soil has an infiltration rate of at least 0.52 inch per hour and a clay content of less than 30% (per recommendations in Guidebook of Best Management Practices for Michigan Watersheds). The required storage volume of a retention basin is that of the runoff from a 100-year design storm as determined using the SCS Method. On sites with soils having a lower infiltration rate and/or higher clay content, the City Engineer may allow retention basins with storage volume for the runoff from two consecutive 100-year design storms.
(2) Retention basins shall accommodate runoff from off-site areas that drain onto/across the developing site. An exception to this rule would be if off-site runoff were to be routed around the site to a receiving watercourse, if done in a manner such that runoff from the developing site would not contribute to this off-site flow. If the off-site flow were to be concentrated from overland flow to a point discharge into a receiving watercourse without valid rights-of-way, written agreement from the affected property owners would have to be obtained per common law natural flow rights and the Michigan Drain Code.
B. One foot of freeboard shall be provided above the design high water elevation.
C. Retention volume must be provided above the elevation of the groundwater table. Soil boring data used to determine the groundwater table elevation shall be submitted with the plans.
D. All retention basins must have a spillway for emergency overflow at the high water level.
(1) The spillway must provide adequate capacity to overflow the peak 100-year basin inflow with no more than two feet of head (i.e., water level must not exceed the two feet of freeboard).
(2) The plans must identify where the overflow would be directed to flow or stored in the event of an overflow.
E. The side slopes shall not be steeper than six feet horizontal to one foot vertical unless fenced in accordance with City requirements. Slope protection shall be provided as necessary. Basin side slope elevation contours shall be shown on the plans.
F. A twelve-foot-wide access easement shall be provided to and around all retention basins.
G. An agreement for acceptance and maintenance of the retention basin system, if executed by the proprietor, shall be submitted to the City of Roseville prior to final approval. The agreement both as form and content shall be subject to the approval of the City.
H. If at any time during the construction period the retention basin is to function as a sediment basin, the proprietor shall be responsible for sediment removal prior to completion of construction. (See Macomb County Public Works Office for requirements regarding soil erosion and sedimentation control during construction.)
Oil must be removed from stormwater as appropriate prior to discharge to a receiving watercourse. The City Engineer will consider means of oil removal on a case-by-case basis.
When standalone BMPs such as permanent first flush basins and prefabricated sediment collection units are proposed or required for a specific site, the following design standards shall apply:
A. A settling pond (first flush pond) is a means to detain the first flush volume so that a minimum of 80% of the TSS settle to the bottom of the pond.
B. A settling pond may be standalone or adjacent to a detention pond as a settling forebay.
C. The bankfull volume is calculated as the rainfall from a 1.5-year storm while the first flush volume is calculated as the first one inch of runoff from the on-site impervious tributary area, or
Vff (cf) = A x C x 3630 cf/ac-impervious |
D. The outlet of a first flush basin or sediment collection unit shall be designed to release the first flush volume over 24 to 36 hours.
E. The outlet of a first flush basin or sediment collection unit shall not be submerged by the receiving watercourse at a ten-year design level.
F. The first flush basin or sediment collection unit shall contain a bypass structure and/or berm to allow the ten-year peak flow to bypass without hydraulic interference.
Monitoring of discharges.
A. Applicability.
(1) This section applies to all facilities that have stormwater discharges, facilities associated with industrial activity, and those having construction activity.
B. Access to facilities.
(1) The City of Roseville shall be permitted to enter and inspect facilities subject to regulation under this article as often as may be necessary to determine compliance with this article. If a discharger has security measures in force which require proper identification and clearance before entry into its premises, the discharger shall make the necessary arrangements to allow access to representatives of the City.
(2) Facility operators shall allow the City ready access to all parts of the premises for the purposes of inspection, sampling, examination and copying of records that must be kept under the conditions of an NPDES permit to discharge stormwater, and the performance of any additional duties as defined by state and federal law.
(3) The City shall have the right to set up on any permitted facility such devices as are necessary and/or required by the MS4 permit to conduct monitoring and/or sampling of the facility's stormwater discharge.
(4) The City has the right to require the discharger to install monitoring equipment as necessary. The facility's sampling and monitoring equipment shall be maintained at all times in a safe and proper operating condition by the discharger at its own expense. All devices used to measure stormwater flow and quality shall be calibrated to ensure their accuracy.
(5) Any temporary or permanent obstruction to safe and easy access to the facility to be inspected and/or sampled shall be promptly removed by the operator at the written or oral request of the City and shall not be replaced. The costs of clearing such access shall be borne by the operator.
(6) Unreasonable delays in allowing the City access to a permitted facility is a violation of a stormwater discharge permit and of this article. A person who is the operator of a facility with a NPDES permit to discharge stormwater associated with industrial activity commits an offense if the person denies the authorized enforcement agency reasonable access to the permitted facility for the purpose of conducting any activity authorized or required by this article.
(7) If the City has been refused access to any part of the premises from which stormwater is discharged, and he/she is able to demonstrate probable cause to believe that there may be a violation of this article, or that there is a need to inspect and/or sample as part of a routine inspection and sampling program designed to verify compliance with this article or any order issued hereunder, or to protect the overall public health, safety, and welfare of the community, then the City may seek issuance of a search warrant from any court of competent jurisdiction.