(A) Submittal procedure. For village approval of storm sewer systems, the applicant shall furnish the Village Clerk with four sets of the storm sewer plans along with any required fees and deposits. Concurrently, a detailed estimate of cost must be submitted. The Clerk will then stamp three sets as authorized to be reviewed, and the applicant will submit these copies to the Village Engineer for review, comments and/or approval. Detailed storm sewer design computations and the drainage area map showing the various areas contributing to the points of inlet shall be provided. The Village Engineer shall check the plans for conformity to the standards set forth herein, after which he or she will return one of the sets with appropriate comments. The applicant, after making any changes requested on the set of plans returned to him or her, shall submit three sets of revised plans to the Village Engineer for final approval. The Village Engineer shall review these revised plans for conformity to the comments mentioned heretofore, and if they have been properly made, will return one approved copy to the applicant. The applicant shall obtain approval of the Oakland County Road Commission, the County Drain Commission, MDOT or any other agency where applicable.
(B) Design standards.
(1) The following notes shall appear on the plans:
(a) All workmanship and materials shall be accordance with the current Bingham Farms standards and specifications as adopted by resolution of the Village Council;
(b) It shall be the contractor’s responsibility to verify the existence and location of all underground utilities;
(c) All sewer trenches under or within four inches of existing or proposed pavement or road shoulder to be backfilled with thoroughly compacted sand to grade (95% maximum unit weight);
(d) All storm sewers shall be installed on a Class “B” bedding;
(e) Joints for all storm sewers shall be plain joints with:
1. Modified grooved tongues with rubber gaskets;
2. Rubber gasket joints; or
3. Bituminous joints (Dewitt #10). Sewers 27 inches in diameter and larger shall have inside mortar pointing.
(2) Storm drainage systems shall be designed for a minimum of a ten-year storm. The rational method for arriving at storm sewer runoff shall be used. An “n” value of 0.013 shall be used, except for uncoated and unpaved corrugated metal pipe where 0.025 shall be used. The design engineer shall provide design assumptions and calculations. The initial T is generally 20 minutes for residential areas and 15 minutes for high runoff areas. The Project Engineer shall use judgment in arriving at proper imperviousness factors.
(3) Sufficient capacity shall be provided in the storm sewer system to take fully developed upstream drainage into the system. When a storm sewer is designed to provide capacity for upstream areas, the hydraulic gradient shall remain in the pipe. If a storm sewer is designed to take on-site drainage only, the hydraulic gradient must be no higher than one foot below ground. When the hydraulic gradient is above the top of the sewer pipe, the design elevation of the hydraulic gradient shall be indicated on the profile at each manhole. If the height of the hydraulic gradient exceeds two feet above the top of the pipe, rubber joints shall be used.
(4) Manholes shall be located at:
(a) Changes in alignment in the main sewer;
(b) Points where the size of the sewer changes;
(c) Points where the slope of the sewer changes;
(d) The junction of sewer lines;
(e) Street intersections or other points where catch basins or inlets are to be connected.
(5) (a) Manhole spacing for storm sewers shall be as follows:
Diameter of sewer
|
Maximum manhole spacing
|
12 inches to 15 inches | 350 |
18 inches to 30 inches | 400 |
36 inches to 48 inches | 500 |
54 inches and 60 inches | 550 |
66 inches and 72 inches | 650 |
6 feet, 6 inches and larger | 1,000 |
(b) The minimum size of a public storm sewer is 12-inch diameter. Catch basin leads may tap directly into sewers 48 inches and larger.
(6) The following information shall be indicated on the storm sewer profile:
(a) Length of run between manholes;
(b) Type and class of pipe between manholes;
(c) Size and slope of sewer between manholes;
(d) Class of bedding;
(e) Top elevation of all manholes;
(f) Top of curb line/pavement/ground surface;
(g) Plus or minus top of curb elevations at 100 feet stations;
(h) Existing and proposed ground elevations above the route of the sewer;
(i) A logical numbering system for manholes shall be as included;
(j) Invert elevations of all sewers at manholes.
(7) (a) The following table of minimum slopes for storm sewers shall be adhered to in order to provide a design velocity greater than 2½ feet per second:
Size
|
Minimum slope
|
Size
|
Minimum slope
|
12 inches | .32% |
15 inches | .24% |
18 inches | .20% |
21 inches | .14% |
24 inches | .12% |
27 inches | .10% |
30 inches | .10% |
36 inches | .08% |
42 inches | .06% |
48 inches | .05% |
54 inches | .04% |
60 inches | .04% |
(b) The maximum desired velocity of storm sewers is 12 feet per second. Greater velocities may be allowed for unusual conditions.
(8) Where possible, provide a minimum of three feet of cover from the top of curb (or road centerline) to the top of any storm sewer. All catch basin leads within a street shall be a C-76 IV minimum, including the leads to the manhole. Under drain pipe shall be a six feet minimum and shall be fabric wrapped.
(9) A prefabricated bar screen shall be used on all storm sewer openings 12 inches in diameter and larger. The bar screens shall be constructed according to an approved separate enlarged detail in the drawings and shall be designed to be sturdy, permanent, easily maintained, nonclogging and shall have clear openings of no more than six inches.
(10) In general, catch basins shall be located as follows:
(a) At the radius return of street intersections. When drainage is required to go around corners, 150 feet maximum distance along the street between a high point and a corner catch basin is allowed;
(b) At all low points in streets;
(c) At intermediate points along the street such that there is a maximum of 500 feet of drainage from a previous intercepting catch basin to this catch basin;
(d) At a location to provide a maximum of 800 feet of drainage from two directions.
(11) Standard rear yard catch basins shall be provided at all low points in easements. The minimum size storm sewer from these catch basins is 12 inches in diameter. The minimum slope for rear yard swales is 0.5%. The intermediate catch basin shall be four feet in diameter with a two-foot sump. Where used, the under drain trench shall be completely filled with gravel to finish grade. Intermediate catch basins are required where rear yard pipe changes direction by more than 30 degrees. All catch basins shall be located within four feet of lot corners. Twelve feet side yard easements to the street shall be included at all catch basins. Beehive type covers are required for yard catch basins. Additional rear yard drainage requirements are listed under § 154.07.
(12) Headwalls and inlet structures shall be placed at all culverts and storm drain inlets and outlets.
(13) Finished easement elevations shall be indicated on the plans.
(14) Improved open drains may be permitted upon special circumstances, with Village Engineer approval.
(a) Oakland County Drain Commission and DNR approvals must also be obtained if they have jurisdiction.
(b) Adequate culverts are required at all roads crossing a drain. Minimum length of culvert is 60 feet or equal to the street right-of-way, whichever is greater. End sections, curtain walls and energy deflectors shall not be considered as part of this minimum length. A curtain wall and/or deflector is required at all culvert ends. Six-inch thick unreinforced concrete rip-rap (or approved equal) is required on all slopes at culvert crossings. This rip-rap must be anchored by a footer a minimum of two feet deep on the ends and edges where washing conditions may occur.
(c) Maximum side slope on a drain is three horizontal to one vertical.
(d) Open drains must have slope protection (riprap) at bends with a radius of 500 feet or less and other points designated by the Village Engineer.
(e) The drain bottom and slopes, to the hydraulic gradient line, must be seeded or sodded. The remainder of the easement may be seeded. The village will not accept the work until all turf is established.
(f) Specific drain cross-section and velocity control measures will be determined by the Village Engineer on an individual basis.
(g) An easement of at least 20 feet wider than the widest point from top of bank to top of bank is to be recorded on the plat and/or dedicated. The easement line must be fenced if side slopes are steeper than one on five. The treatment shall be consistent in the whole development.
(15) Allowable joints:
(a) Modified grooved tongue with rubber gasket;
(b) Tongue and groove with rubber gasket;
(c) Tongue and groove with cold mastic joints (Dewitt #10).
(C) Post Construction Stormwater Requirements. As a requirement of the NPDES Stormwater Discharge Permit and the Villages Municipal Separate Storm Sewer System Permit, the village accepts the following Oakland County Standards for Post-Construction StormWater Runoff:
(1) The Oakland County Water Resources Commissioners Stormwater Engineering Design Standards, as amended from time to time, are hereby adopted by the Village for Bingham Farms in this chapter for the control and treatment of stormwater runoff.
(2) These standards are developed in accordance with the existing “Village of Bingham Farms Engineering Design Standards.”
(3) All permanent and temporary stormwater management BMPs, constructed as part of the requirements of this section, are subject to these standards.
(4) These standards also apply to any activities which may affect the quantity or quality of a private or stormwater conveyance system or any waterway within the village. Any person(s) engaged in activities that may result in excessive quantities or pollutants entering any stormwater conveyance systems or waterways may be subject to the remedies for violation of this section. Examples of such pollutants may include, but are not limited to, debris, concrete washings, de-icing materials, fertilizers, heavy metals, automobile fluids, topsoil, yard wastes, and commercial or light industrial wastes.
(5) Natural swales and channels should be preserved, whenever possible. If channel modification must occur, the physical characteristics of the modified channel will meet the existing channel in length, cross-section, slope, sinuosity, and carrying capacity. Streams and channels will be expected to withstand all events up to the two-year storm without increased erosion.
(6) The construction plan review and approval shall demonstrate compliance with the Oakland County performance standards. The village will pursue enforcement if the site is not constructed in accordance with the approved construction plan.
(7) The village reserves the right to adopt alternative standards as appropriate. The Village Administrator shall have the authority to grant waivers and variances from specific control provisions of the stormwater management standards due to site-specific conditions, but only if the variance(s) are as restrictive as the Oakland County Standards.
(8) The post construction stormwater requirements in this chapter supersede any other post construction stormwater requirements found in other village ordinances.
(9) Long-term operation and maintenance through maintenance agreements of all structural and vegetative best management practices (BMPs) must be implemented to meet the performance standards. The maintenance agreements must allow for BMP inspection, the ability to perform necessary maintenance neglected by the BMP owner or operator, and to track the transfer of operation and maintenance responsibility of the BMP.
(O.C. § 5.703) (Am. Ord. 268, passed 9-19-22)
Cross-reference:
Sewer service, see Ch. 52