(a) Any person or persons seeking approval for an earth disturbing activity listed below shall prepare a SMP as described in this chapter.
(1) Activities disturbing greater than or equal to one acre, or less than one acre, if part of a larger common plan of development or sale.
(2) Activities that require the extension of public utilities (roadways, water mains, sanitary sewer mains, storm sewers, etc.).
(3) Activities that will modify an existing and/or approved drainage way, drainage structure, and/or drainage easement.
(4) Activities that will channelize, straighten, and/or modify a watercourse within the identified 100 year floodplain (studied and unstudied).
(b) SMPs are intended to provide information on all soil erosion and runoff control activities and best management practices (BMPs) to be used and incorporated on the site both during and after site development. This information includes, but is not limited to, site grading, storm water management facilities and practices, erosion and runoff control information, maintenance plans, and other measures that focus on managing the effects of earth disturbing activities that occur as a result of site development.
(c) Each SMP shall provide site designs that meet the performance standards presented in this chapter and provide practical treatment for both water quality and quantity of storm water from the site as appropriate.
(d) In general, the SMP needs to address:
(1) Erosion and sediment control. Providing measures to insure that earth disturbing activities at the site during and after development will be managed in a manner that will not result in increased erosion and sedimentation from the site resulting in impacts to water quality and that meet the performance standards.
(2) Runoff control. Providing measures to insure that the quantity of surface water runoff from the development site during and after construction will mimic the pre-development conditions and that meet the performance standards.
(e) If a SMP is required, such plan shall specifically include all the following:
(1) The minimum elements required in the site development plan;
(2) The contents of the storm water pollution prevention plan (SWP3) required by the Ohio EPA's NPDES Construction Activity Permit #OHC000002 and incorporated here by reference. This plan may be submitted as developed for the Ohio EPA, in conjunction with the other requirements of this section.
(3) The contents of the Ohio EPA's SWP3 include, but are not limited to:
A. A description of prior land uses at the site.
B. Existing data describing the soils on the site and, if available, the quality of any discharge from the site.
C. A determination of runoff coefficients for both the pre-construction and post construction site conditions.
D. For all large earth-disturbing activities (involving the disturbance of five or more acres of land or will disturb less than five acres, but part of a larger common plan of development or sale which will disturb five or more acres of land), a description of post construction BMP(s) chosen and designed to detain and treat a water quality volume (WQ
V
) equivalent to the volume of runoff from a 0.75-inch rainfall (See Ohio EPA Construction Activity Permit for methodology).
E. For all small earth-disturbing activities (which 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), a description of measures that will be installed during the development process to control pollutants in storm water discharges that will occur after construction operations have been completed.
F. An implementation schedule which describes the sequence of major construction operations (i.e., grubbing, excavating, grading, utilities and infrastructure installation) and the implementation of erosion, sediment and storm water management practices or facilities to be employed during each operation of the sequence.
G. For subdivided developments where the SWP3 does not call for a centralized sediment control capable of controlling multiple individual lots, a detail drawing of a typical individual lot showing standard individual lot erosion and sediment control practices.
H. A detailed description of the storm water controls to be incorporated and how these meet or exceed the appropriate performance standards presented in this chapter. This shall include the identification of which entity (developer, contractor, owner) is responsible for implementation of each individual control (e.g., contractor A will clear land and install perimeter controls and contractor B will maintain perimeter controls until final stabilization).
I. A detailed maintenance plan that describes procedures (e.g. inspections) needed to ensure the continued performance of control practices. Such plans must ensure that pollutants collected within structural post-construction practices, be disposed of in accordance with local, State, and Federal regulations.
J. A site map that includes:
1. Limits of earth-disturbing activity of the site including associated off- site borrow or spoil areas.
2. Soil types on the site, including locations of unstable or highly erodible soils.
3. Existing and proposed contours. A delineation of drainage watersheds expected during and after major grading activities as well as the size of each drainage watershed, in acres.
4. Existing and planned locations of buildings, roads, parking facilities and utilities.
5. The location of all erosion and sediment control practices, including areas likely to require temporary stabilization during site development.
6. Sediment and storm water management basins noting their sediment settling volume and contributing drainage area.
7. Permanent storm water management practices to be used to control pollutants in storm water after construction operations have been completed.
8. Areas designated for the storage or disposal of solid, sanitary, and toxic wastes, including dumpster areas, cement truck washout areas, and vehicle fueling and maintenance.
9. The location of designated construction entrances where vehicles will access the site.
10. The location of any in-stream activities, including stream crossings.
(4) Copies of pertinent notices of intent (NOI), permits, public notices and letters of authorization must be included with SMP submissions. These may include, but are not limited to, Ohio EPA NPDES permits authorizing storm water discharges associated with construction activity, Ohio EPA Phase II Storm Water Permits, Section 401 and 404 Clean Water Act Permits, Ohio EPA Isolated Wetland Permit, and Ohio Dam Safety Law Permits.
(5) Supplemental requirements as provided below.
(f) Storm water discharge to critical areas with sensitive resources (i.e. wetlands, steep slopes, scenic river designation, recharge areas, etc.) may be subject to additional criteria, or may need to utilize or restrict certain storm water practices.
(g) Supplemental Post Construction Requirements.
(1) Determination of post development runoff.
A. Each SMP shall include an evaluation of pre-development conditions together with during, and post-development impacts that quantifies the volume and rate of runoff from the site by subdrainage areas. This evaluation shall be prepared according to methods prescribed in the latest edition of Rainwater and Land Development or other appropriate sources. The evaluation shall:
1. Show delineation and sequence of subdrainage units which comprise the area proposed for development.
2. Indicate the hydraulic length of slope per individual subdrainage unit and the length of the natural or manmade watercourse which accommodates the surface runoff from each subdrainage unit.
3. Indicate within the legend the average percent slope, erosion factor (K) and runoff curve number (CN) per individual subdrainage unit for a 24-hour storm of a one-year frequency.
4. Include a hydrograph for a 24-hour storm of the critical frequency to be controlled as determined below in this chapter and all calculations made pertinent to evaluating the effects of the proposed development on the pre-development runoff conditions of the site.
B. Calculations for the design of storm water management facilities shall demonstrate the following for each subdrainage unit:
1. The peak rate of runoff from the critical storm and all more frequent storms occurring on the site does not exceed the peak rate of runoff from a one year frequency, 24 hour storm occurring on the same site under pre-development conditions.
2. Storms of less frequent occurrence than the critical storm, up to the 100 year storm shall have its peak runoff rates no greater than the peak runoff rates from equivalent storms under pre-development conditions. Consideration of the 1, 2, 5, 10, 25, 50, and 100 year storms in design and construction will be considered meeting this standard.
3. Calculation of a critical storm for each subdrainage unit of the site shall be determined as follows:
a. Calculate by appropriate hydrologic methods, such as the NRCS Technical Release 55, the total volume of runoff from a one-year frequency, 24-hour storm occurring on the development area before, during, and after development.
b. From the volumes determined in a. above, determine the percentage increase in volume of runoff due to the proposed development, and using this percentage, select the 24-hour critical storm from this table:
If the percentage of increase in volume of runoff is (see chart below):
% Equal To or Greater Than | % Less Than | The Critical Storm for Peak Rate Control |
% Equal To or Greater Than | % Less Than | The Critical Storm for Peak Rate Control |
- | 10 | 1 year |
10 | 20 | 2 years |
20 | 50 | 5 years |
50 | 100 | 10 years |
100 | 250 | 25 years |
250 | 500 | 50 years |
500 | - | 100 years |
4. The City's authorized agent shall approve or reject any calculation method based on its technical validity for the given situation.
(2) Off-site storm water control facilities. Exceptions to requiring permanent on-site runoff control on the site may be considered by the City authorized agent provided the applicant can prove that:
A. The intent and standards of this chapter for runoff control can be best achieved by the utilization of off-site storm water control facilities.
B. Runoff from the site can be conveyed to off-site storm water facilities in a manner and by means which satisfies or surpasses the standards of this chapter.
C. The applicant has ownership of or the right to use the off-site facility in question.
(3) Maintenance and repair plan. The design and planning of all storm water management facilities shall include detailed maintenance and repair procedures to ensure their continued function. These plans will identify the parts or components of a storm water management facility that need to be maintained and the equipment and skills or training necessary. Provisions for the periodic review and evaluation of the effectiveness of the maintenance program and the need for revisions or additional maintenance procedures shall be included in the plan.
(4) Landscaping plans required. All storm water management practices must have a landscaping plan detailing both the vegetation to be in the practice and how and who will manage and maintain this vegetation. The applicant must present a detailed plan for management of vegetation at the site after construction is finished, including who will be responsible for the maintenance of vegetation at the site and what practices will be employed to ensure that adequate vegetative cover is preserved. This plan must be prepared by a registered landscape architect or the Montgomery County Soil and Water Conservation District.
(5) Maintenance easements. The applicant must ensure access to all storm water treatment practices at the site for the purpose of inspection and repair by securing all the maintenance easements needed on a permanent basis. These easements will be recorded with the plan and will remain in effect even with transfer of title to the property.
(6) Maintenance agreement. The applicant must execute an easement and an inspection and maintenance agreement binding on all subsequent owners of land served by an on- site storm water management measure in accordance with the specifications of this chapter.
(7) Other environmental permits. The applicant shall assure that all other applicable environmental permits have been acquired for the site prior to approval of the final storm water design plan.
(h) Storm Water Management Plan Submission, Review and Action.
(1) The applicant is encouraged to have a pre-submission meeting with the City's authorized agent(s).
(2) Submission of two sets of the SMP and other supporting data required by this regulation to the authorized agent of the City completes the applicant's responsibilities and initiates the review process.
(3) The SMP shall be reviewed by the City authorized agent(s) to:
A. Verify background information furnished by the applicant and evaluate the proposed development in relation to existing site conditions.
B. Assess the SMP in relation to the performance standards and requirements of this chapter.
(4) Upon submission of the SMP the City authorized agent(s) shall complete a review of the SMP within ten business days.
(5) The City authorized agent shall either:
A. Approve the SMP as submitted by the applicant;
B. Conditionally approve the SMP and require the submission of additional and/or revised information by the applicant, in order to fully meet the intent and standards of this chapter; or
C. Disapprove the SMP.
(6) Revisions to conditionally approved SMPs shall be prepared and submitted by the applicant to the City authorized agent(s) for review.
(7) Action by the approval authority and/or the authorized agent(s) approving or disapproving the SMP is a final order for purposes of judicial review.
(i) Construction Inspection.
(1) Notice of construction commencement.
A. The applicant must notify the City authorized agent ten business days in advance before the commencement of construction. Regular inspections of the storm water management system construction shall be conducted by the authorized agent of the City or certified by a professional engineer or their designee who has been approved by the City. All inspections shall be documented and written reports prepared that contain the following information:
1. The date and location of the inspection;
2. Whether construction is in compliance with the approved storm water management plan;
3. Variations from the approved construction specifications; and
4. Any violations that exist.
B. If any violations are found, the property owner shall be notified in writing of the nature of the violation and the required corrective actions. No added work shall proceed until any violations are corrected and all work previously completed has received approval by the City authorized agent.
(2) As built plans. All applicants are required to submit actual “as built” plans for any storm water management practices located on-site after final construction is completed. The plan must show the final design specifications for all storm water management facilities and must be certified by a professional engineer. A final inspection by the City authorized agent is required before the release of any performance securities can occur.
(Ord. 5973. Passed 2-20-07.)