In order to control post-construction water quality damage and damage to public and private lands, the owner of each development area shall be responsible for developing a Post-Construction Storm Water Management Control Plan.
(a) This plan will be combined with the Storm Water Pollution Prevention Plan and the Riparian Setback and Wetland Setback Plans that are also developed for the site.
(b) The Post-Construction Water Quality Control Plan shall describe how the quantity and quality of storm water will be managed after construction is completed for every discharge from the site and/or into a water resource or small municipal separate storm sewer system (MS4).
(c) This plan will contain a description of controls appropriate for each construction operation covered by these regulations, and the operator will implement such controls in a timely manner.
(d) The BMPs used to satisfy the conditions of these regulations shall meet the standards and specifications in the current edition of the Ohio Rain Water and Land Development manual, ODOT post-construction storm water standards, or other manual that is acceptable to the City Engineer or Ohio EPA.
(e) The plan must make use of the practices that preserve the existing natural condition to the maximum extent practicable (MEP).
(f) To meet the post-construction requirements of this regulation, the Post-Construction Water Quality Control Plan must contain a description of the type, location, and dimensions of every structural and non-structural SCM incorporated into the site design, and the rationale for their selection. The rationale must address the anticipated impacts on the channel and floodplain morphology, hydrology, and water quality.
(g) This plan will identify the person or entity responsible for continued maintenance of all vegetative and/or mechanical BMPs for both the construction and post-construction phases of the development.
(h) Long-term maintenance requirements and schedules of all BMPs for both the construction and post-construction phases of the development will be identified.
(i) This plan will contain long-term maintenance inspection schedules, including the printed name and contact point of the post-construction landowner (e.g., president of the homeowners association, store manager, apartment complex manager, etc.).
(j) This plan will identify the person or entity financially responsible for maintaining the permanent inspection and maintenance of permanent storm water conveyance and storage structures and other conservation practices.
(k) The method of ensuring that finding will be available to conduct the long-term maintenance and inspections of all permanent storm water; soil erosion and sediment control and water quality practices will be identified.
(l) The Post-Construction Water Quality Control Plan will also contain the following information depending on the size of the development sites as well as any additional information required by the City Engineer:
(1) Development sites smaller than five acres: A development site that will disturb one or more, but less than five acres of land and is not a part of a larger common plan of development or sale which will disturb five or more acres of land shall identify:
A. Storm water issues: A statement as to how the decreased storm water quality that will be caused by the planned development project will be handled.
B. Description of measures: A description of the BMPs that will be installed during the construction process to control pollutants in storm water discharges that will occur after construction operations have been completed.
C. Upland areas: Structural measures placed on upland areas to the degree attainable.
D. Map: A map of the entire site showing the overall development.
E. Riparian and/or wetland setback: All riparian and wetland setback areas will be identified on the plans. They will also be marked in the field prior to the start of construction.
F. BMPs: Best Management Practices used in the Post-Construction Water Quality Control Plan may include but are not limited to:
1. Permanent storm water detention ponds that provide extended detention of the water volume.
2. Flow attenuation by use of open vegetated swales and natural depressions.
3. Onsite infiltration of runoff.
4. Sequential systems that combine several practices.
5. Permanent conservation easements, preferably with the easement being held by a third party with no vested interest in ever seeing the property developed.
6. Natural channel design for drainageways.
7. Bioengineering in drainageways.
8. Recreating floodplains.
9. Chemical and biological filters in storm sewer inlets.
10. Sand filters.
11. Allowing roof water from buildings to run across lawn areas to remove pollutants.
12. Onsite sewage disposals system replacement or conversion to sanitary sewers.
13. Low impact development design.
14. Aquatic benches in retention basins and ponds.
G. Technical basis: The plans will contain a rational statement utilized to select the BMPs used to control pollution and to maintain and protect water quality.
H. Post-Construction Water Quality Control Plans for redevelopment projects must accomplish one of the following options:
1. Reduce existing site impervious areas by at least 25 percent, a one-for-one credit towards the 25 percent net reduction of impervious area can be obtained through the use green roofs.
2. Infiltrate at least 25 percent of the WQv.
3. Capture, treat and release 50 percent of the WQv.
(2) Development Sites Five Acres or Larger: A development site that disturbs five or more acres of land or will disturb less than five acres, but is a part of a larger common plan of development or sale, which will disturb five or more acres of land shall identify:
A. Storm water detention: The post-construction BMP(s) chosen must be able to detain storm water runoff for protection of the stream channels, stream erosion control, and improved water quality.
B. Structural BMPs: Structural (designed) post-construction storm water treatment practices shall be incorporated into the permanent drainage system for the site.
C. Properly sized BMPs: The BMP(s) chosen must be sized to treat the water quality volume (WQv) and ensure compliance with Ohio's Water Quality Standards in OAC Chapter 3745-1. The WQv shall be equivalent to the volume of runoff from a 0.75-inch rainfall and shall be determined according to one of the two following methods:
1. Through a site hydrologic study approved by the local municipal permitting authority that uses continuous hydrologic simulation and local long-term hourly precipitation records or
2. Using the following equation:
a. WQv = C * P * A / 12 where: WQv = water quality volume in acre-feet C = runoff coefficient appropriate for storms less than 1 inch (see Table 1) P = 0.75 inch precipitation depth A = area draining into the BMP in acres
Runoff coefficients required by the Ohio Environmental Protection Agency (Ohio EPA) for use in determining the WQv can be determined using the list in Table 1 or using the following equation to calculate the runoff coefficient:
C=0.858i3 – 0.78i2 + 0.774i + 0.04, where:
i = fraction of the drainage area that is impervious
Table 1 Runoff Coefficients Based on the Type of Land Use | |
Land Use | Runoff Coefficient |
Industrial & Commercial | 0.8 |
High Density Residential (>8 dwellings/acre) | 0.5 |
Medium Density Residential (4 to 8 dwellings/acre | 0.4 |
Low Density Residential (<4 dwellings/acre) | 0.3 |
Open Space and Recreational Areas | 0.2 |
Where the land use will be mixed, the runoff coefficient should be calculated using a weighted average. For example, if 60% of the contributing drainage area to the storm water treatment structure is Low Density Residential, 30% is High Density Residential, and 10% is Open Space, the runoff coefficient is calculated as follows (0.6)(0.3) + (0.3)(0.5) + (0.1)(0.2) = 0.35. | |
D. Each individual SCM must be sized to treat the WQv associated with its entire contributing drainage area. Exceptions to this may be granted by the City Engineer and/or the OEPA on a case-by-case basis.
E. An additional volume equal to 20 percent of the WQv shall be incorporated into the BMP for sediment storage and/or reduced infiltration capacity. The BMPs will be designed according to the methodology included in the Ohio Rainwater and Land Development manual, ODOT post-construction storm water standards, or other manual that is acceptable to Ohio EPA.
F. BMPs shall be designed such that the drain time is long enough to provide treatment, but short enough to provide storage available for successive rainfall events as described in Table 2 below.
G. Sites within watersheds of coldwater habitat streams shall include SCMs to infiltrate the water quality volume or reduce the temperature of discharged runoff. SCMs that reduce the temperature of discharged runoff include bioretention, permeable pavement, underground detention, and incorporation of shading and infiltration in parking lot design.
Table 2: Target Draw Down (Drain) Times for Storm Water Control Measures | |
Storm Water Control Measure | Drain Time of WQv |
Infiltration Basin or Trench1 | 48 hours |
Permeable Pavement – Infiltration1 | 48 hours |
Permeable Pavement – Extended Detention | 24 hours |
Extended Detention Basin (Dry Basins)2 | 48 hours |
Retention Basins (Wet Basins)3 | 24 hours |
Constructed Wetlands (above permanent pool)4 | 24 hours |
Sand & other Media Filtration5, Bioretention6 | 24 hours |
Pocket Wetland | 24 hours |
1 Practices designed to fully infiltrate the WQv shall empty within 48 hours to provide storage for subsequent storm events. 2 The use of a forebay and micropool is required on all dry extended detention basins. Each is to be sized at a minimum 10% of the WQv. 3 Provide both a permanent pool and an extended detention volume above the permanent pool, each sized with at least 0.75*WQV. 4 Extended detention shall be provided for the WQv above the permanent water pool. 5 The surface ponding area shall completely empty within 24 hours so that there is no standing water. Shorter drawdown times are acceptable as long as design criteria in Rainwater and Land Development have been met. 6 This includes grassed linear bioretention, which was previously titled enhanced water quality swale. 7 Pocket wetlands must have a wet pool equal to the WQv, with 25% of the WQv in a pool and 75% in marshes. The EDV EDv above the permanent pool must be equal to the WQv. | |
H. The owner may request approval from the City Engineer to use alternative structural post-construction BMPs if the owner can demonstrate, in a way that is acceptable to Ohio EPA rules and regulations that the alternative BMPs are equivalent in effectiveness to those listed in Table 2 above. The use of alternative or vender supplied post-construction BMPs should be limited to redevelopment projects where justification is provided that the traditional BMPs in Table 2 are technically and economically infeasible.
I. Construction activities shall be exempt from this condition if it can be demonstrated that the WQv is provided within an existing structural post- construction BMP that is part of a larger common plan of development or sale or if structural post-construction BMPs are addressed in a regional or local storm water management plan.
J. Post-Construction Water Quality Control Plans for redevelopment projects must accomplish one of the following options:
1. Reduce existing site impervious areas by at least 25 percent, a one-for-one credit towards the 25 percent net reduction of impervious area can be obtained through the use green roofs.
2. Infiltrate at least 25 percent of the WQv.
3. Capture, treat and release 50 percent of the WQv.
K. Site description:
1. The prior land uses of the site.
2. The name and type of construction activity (e.g., low density residential, shopping mall, highway, etc.)
3. Total area of the site and the area of the site that is expected to be disturbed (i.e., grubbing, clearing, excavating, filling or grading, including off-site borrow, fill or spoil areas and off-site utility installation areas).
4. Amount of the impervious area and percent imperviousness created by the construction activity.
5. Name and/or location of the immediate receiving stream or surface water(s) and the first subsequent named receiving water and the major river watersheds in which it is located.
6. Selection (source and justification) and/or calculations of runoff coefficients for water quality volume determination, peak discharge control (curve number/critical storm method), and rational method.
7. Existing data describing the soils throughout the site, including soil map units including series, complexes, and association, hydrologic soil group, porosity, infiltration characteristics, depth to groundwater, depth to bedrock, and any impermeable layers.
8. If available, the quality of any known pollutant discharge from the site such as that which may result from previous contamination caused by prior land uses.
9. If applicable, identify the point of discharge to a municipal separate storm sewer system and the location where that municipal separate storm sewer system ultimately discharges to a stream, lake, or wetland. The location and name of the immediate receiving stream or surface water(s) and the first subsequent receiving water(s) and the aerial extent and description of wetlands or other special aquatic sites at or near the site which will be disturbed or which will receive discharges from undisturbed areas of the project.
10. TMDLs applicable for the site [refer to TMDL community identifier table at http://www.neohiostormwater.com/]; demonstrate that appropriate (SCMs) have been selected to address these TMDLs.
11. For each SCM, identify the drainage area, percent impervious cover within the drainage area, runoff coefficient for water quality volume, peak discharge, and the time of concentration for each subwatershed per Appendix 1 of Ohio's storm water manual, Rainwater and Land Development. Pervious and impervious areas should be treated as separate subwatersheds unless allowed at the discretion of the community engineer. Identify the SCM surface area, discharge and dewatering time, outlet type and dimensions. Each SCM shall be designated with an individual identification number.
L. A vicinity sketch locating:
1. The development area.
2. The larger common plan of development or sale.
3. All pertinent surrounding natural features within 200 feet of the development site including, but not limited to:
a. Water resources such as wetlands, springs, lakes, ponds, rivers and streams (including intermittent streams with a defined bed and bank);
b. Conservation easements; and
c. Other sensitive natural resources and areas receiving runoff from the development.
M. The existing and proposed topography shown in the appropriate contour intervals as determined by the City Engineer (generally one-foot contours are used).
N. The location and description of existing and proposed drainage patterns and facilities, including any allied drainage facilities beyond the development area and the larger common plan of development or sale.
O. Existing and proposed watershed boundary lines, direction of flow and watershed acreage.
P. The person or entity responsible for continued maintenance of all permanent vegetative and/or mechanical post-construction water quality conservation practices (BMPs). Contact information: Company name and contact information as well as contact name, addresses, and phone numbers for the following.
1. The professional engineer who prepared the Comprehensive Storm Water Management Plan.
2. The site owner.
Q. The location of any existing or planned riparian and/or wetland setback areas on the property.
R. Inspection and maintenance agreement. The inspection and maintenance agreement required for SCMs under this regulation as a stand-alone document between the City and the applicant. A copy of this agreement should be attached to the property deed. The agreement shall contain the following information and provisions:
1. Identification of the landowner(s), organization, or municipality responsible for long term inspection and maintenance, including repairs, of the SCMs.
2. The landowner(s), organization, or municipality shall maintain SCMs in accordance with this regulation.
3. The has the authority to enter upon the property to conduct inspections as necessary, with prior notification of the property owner, to verify that the SCMs are being maintained and operated in accordance with this regulation.
4. The City shall maintain public records of the results of site inspections, shall inform the landowner(s), organization, or municipality responsible for maintenance of the inspection results, and shall specifically indicate in writing any corrective actions required to bring the SCMs into proper working condition.
5. If the City notifies the landowner(s), organization, or municipality responsible for maintenance of the maintenance problems that require correction, the specific corrective actions shall be taken within a reasonable time as determined by the City.
6. The City is authorized to enter upon the property and perform the corrective actions identified in the inspection report if the landowner(s), organization, or municipality responsible for maintenance does not make the required corrections in the specified time period. The City shall be reimbursed by the landowner(s), organization, or municipality responsible for maintenance for all expenses incurred within 10 days of receipt of invoice from the City, or more with written approval from the City Engineer.
7. The method of funding long-term maintenance and inspections of all SCMs.
8. A release of the City from all damages, accidents, casualties, occurrences, or claims that might arise or be asserted against the City from the construction, presence, existence, or maintenance of the SCMs.
S. Inspection and Maintenance Plan. This plan will be developed by the applicant and reviewed by the City. Once the Inspection and Maintenance Plan is approved, a recorded copy of the plan must be submitted to the City as part of the final inspection approval. The plan will include at a minimum:
1. The location of each SCM and identification of the drainage area served by each SCM.
2. Photographs of each SCM, including all inlets and outlets upon completion of construction.
3. Schedule of inspection.
4. A schedule for regular maintenance for each aspect of the storm water management system and description of routine and non-routine maintenance tasks to ensure continued performance of the system as is detailed in the approved Comprehensive Storm Water Management Plan. A maintenance inspection checklist written so the average person can understand it shall be incorporated. The maintenance plan will include a detailed drawing of each SCM and outlet structures with the parts of the outlet structure labeled. This schedule may include additional standards, as required by the City Engineer, to ensure continued performance of SCMs permitted to be located in, or within 50 feet of, water resources.
5. The location and documentation of all access and maintenance easements on the property.
T. Alteration or termination of these stipulations is prohibited.
(Ord. 10088- 2017. Passed 6-20-17.)