(a) Comprehensive Stormwater Management Plan Required: The applicant shall develop a Comprehensive Stormwater Management Plan describing how the quantity and quality of stormwater 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). The Plan will illustrate 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 how these SCMs will address flooding within the site as well as flooding that may be caused by the development upstream and downstream of the site. The rationale will also describe how the SCMs minimize impacts to the physical, chemical, and biological characteristics of on-site and downstream water resources and, if necessary, correct current degradation of water resources that is occurring or take measures to prevent predictable degradation of water resources.
(b) Preparation by Professional Engineer: The Comprehensive Stormwater Management Plan shall be prepared by a registered Professional Engineer and include supporting calculations, plan sheets, and design details. To the extent necessary, as determined by the Village Engineer, a site survey shall be performed by a registered Professional Surveyor to establish boundary lines, measurements, or land surfaces.
(c) Community Procedures: The Village Engineer shall prepare and maintain procedures providing specific criteria and guidance to be followed when designing the stormwater management system for the site. These procedures may be updated from time to time, at the discretion of the Village Engineer based on improvements in engineering, science, monitoring, and local maintenance experience. The Village Engineer shall make the final determination of whether the practices proposed in the Comprehensive Stormwater Management Plan meet the requirements of this regulation. The Village Engineer may also maintain a list of acceptable SCMs that meet the criteria of this regulation to be used in the Village of Gates Mills.
(d) Contents of Comprehensive Stormwater Management Plan: The Comprehensive Stormwater Management Plan shall contain an application, narrative report, construction site plan sheets, a long-term Inspection and Maintenance Plan and Inspection and Maintenance Agreement, and a site description with the following information provided:
(1) Site description:
a. A description of the nature and type of the construction activity (e.g. residential, shopping mall, highway, etc.).
b. Total area of the site and the area of the site that is expected to be disturbed (i.e. grubbing, clearing, excavation, filling or grading, including off-site borrow areas).
c. A description of prior land uses at the site.
d. An estimate of the impervious area and percent imperviousness created by the soil-disturbing activity at the beginning and at the conclusion of the project.
e. 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.
f. 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.
g. 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.
h. The location and name of the immediate water resource(s) and the first subsequent water resource(s).
i. The aerial (plan view) extent and description of water resources at or near the site that will be disturbed or will receive discharges from the project.
j. 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.
k. 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.
l. 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 stormwater 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.
m. Describe the current condition of water resources including the vertical stability of stream channels and indications of channel incision that may be responsible for current or future sources of high sediment loading or loss of channel stability.
(2) Site map showing:
a. Limits of soil-disturbing activity on the site.
b. Soils map units for the entire site, including locations of unstable or highly erodible soils.
c. Existing and proposed one-foot (1') contours. This must include a delineation of drainage watersheds expected before, during, and after major grading activities as well as the size of each drainage watershed in acres.
d. Water resource locations including springs, wetlands, streams, lakes, water wells, and associated setbacks on or within 200 feet of the site, including the boundaries of wetlands or streams and first subsequent named receiving water(s) the applicant intends to fill or relocate for which the applicant is seeking approval from the Army Corps of Engineers and/or Ohio EPA.
e. Existing and planned locations of buildings, roads, parking facilities, and utilities.
f. The location of any in-stream activities including stream crossings.
(3) Contact information: Company name and contact information as well as contact name, addresses, and phone numbers for the following:
a. The Professional Engineer who prepared the Comprehensive Stormwater Management Plan.
b. The site owner.
(4) Phase, if applicable, of the overall development plan.
(5) List of sublot numbers if project is a subdivision.
(6) Ohio EPA NPDES Permit Number and other applicable state and federal permit numbers, if available, or status of various permitting requirements if final approvals have not been received.
(7) Location, including complete site address and sublot number if applicable.
(8) Location of any easements or other restrictions placed on the use of the property.
(9) A site plan sheet showing:
a. The location of each proposed post-construction SCMs.
b. The geographic coordinates of the site AND each proposed practice in North American Datum Ohio State Plane North.
It is preferred that the entire site be shown on one plan sheet to allow a complete view of the site during plan review. If a smaller scale is used to accomplish this, separate sheets providing an enlarged view of areas on individual sheets should also be provided.
(10) Inspection and Maintenance Agreement. The Inspection and Maintenance Agreement required for SCMs under this regulation is a stand-alone document between the Village of Gates Mills and the applicant. A copy of this agreement should be attached to the property deed. The agreement shall contain the following information and provisions:
a. Identification of the landowner(s), organization, or municipality responsible for long-term inspection and maintenance, including repairs, of the SCMs.
b. The landowner(s), organization, or municipality shall maintain SCMs in accordance with this regulation.
c. The Village of Gates Mills 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.
d. The Village of Gates Mills 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.
e. If the Village of Gates Mills 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 Village of Gates Mills.
f. The Village of Gates Mills 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 Village of Gates Mills 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 Village of Gates Mills, or more with written approval from the Village Engineer.
g. The method of funding long-term maintenance and inspections of all SCMs.
h. A release of the Village of Gates Mills from all damages, accidents, casualties, occurrences, or claims that might arise or be asserted against the Village of Gates Mills from the construction, presence, existence, or maintenance of the SCMs.
(11) Inspection and Maintenance Plan. This plan will be developed by the applicant and reviewed by the Village of Gates Mills. Once the Inspection and Maintenance Plan is approved, a recorded copy of the Plan must be submitted to the Village of Gates Mills as part of the final inspection approval as described in 1174.12. The plan will include at a minimum:
a. The location of each SCM and identification of the drainage area served by each SCM.
b. Photographs of each SCM, including all inlets and outlets upon completion of construction.
c. Schedule of inspection.
d. A schedule for regular maintenance for each aspect of the stormwater 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 Stormwater 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 Village of Gates Mills Engineer, to ensure continued performance of SCMs permitted to be located in, or within 50 feet of, water resources.
e. The location and documentation of all access and maintenance easements on the property.
Alteration or termination of these stipulations is prohibited.
(12) Required calculations: The applicant shall submit calculations for projected stormwater runoff flows, volumes, and timing into and through all SCMs for flood control, channel protection, water quality, and the condition of the habitat, stability, and incision of each water resource and its floodplain, as required in Section 1174.09 of this regulation. These submittals shall be completed for both pre- and post-development land use conditions and shall include the underlying assumptions and hydrologic and hydraulic methods and parameters used for these calculations. The applicant shall also include critical storm determination and demonstrate that the runoff from offsite areas have been considered in the calculations.
(13) List of all contractors and subcontractors before construction: Prior to construction or before the pre-construction meeting, provide the list of all contractors and subcontractors and their names, addresses, and phones involved with the implementation of the Comprehensive Stormwater Management Plan including a written document containing signatures of all parties as proof of acknowledgment that they have reviewed and understand the requirements and responsibilities of the Comprehensive Stormwater Management Plan.
(14) Existing and proposed drainage patterns: The location and description of existing and proposed drainage patterns and SCMs, including any related SCMs beyond the development area and the larger common development area.
(15) For each SCM to be employed on the development area, include the following:
a. Location and size, including detail drawings, maintenance requirements during and after construction, and design calculations, all where applicable.
b. Final site conditions including stormwater inlets and permanent nonstructural and structural SCMs. Details of SCMs shall be drawn to scale and shall show volumes and sizes of contributing drainage areas.
c. Any other structural and/or non-structural SCMs necessary to meet the design criteria in this regulation and any supplemental information requested by the Village Engineer.
d. Each SCM shall be designated with an individual identification number.
(Ord. 2016-46. Passed 12-13-16.)