(1) MS4 Stormwater design or BMP manuals.
(a) Adoption. The city adopts as its MS4 stormwater design and best management practices (BMP) manuals for stormwater management, construction and permanent, the following publications, which are incorporated by reference in this ordinance as if fully set out herein:
(i) TDEC Erosion Prevention and Sediment Control Handbook; most current edition.
(ii) The Nashville-Davidson County Metro Stormwater Management Manual (BEST MANAGEMENT PRACTICES (BMP) MANUAL - Volume 4) most current edition.
(iii) A collection of MS4 approved BMP's developed or collected by the MS4 that comply with the goals of the MS4 permit and/or the CGP.
(b) The city's BMP manual(s) include a list of acceptable BMP's including the specific design performance criteria and operation and maintenance requirements for each stormwater practice. These include city approved BMP's for permanent stormwater management including green infrastructure BMP's.
(c) The city manual(s) may be updated and expanded from time to time, at the discretion of the governing body of the city, upon the recommendation of the City Manager, based on improvements in engineering, science, monitoring and local maintenance experience, or changes in federal or state law or regulation. Stormwater facilities that are designed, constructed and maintained in accordance with these BMP criteria will be presumed to meet the minimum water quality performance standards.
(2) Land development. This section shall be applicable to all land development, including, but not limited to, site plan applications, subdivision applications, land disturbance applications and grading applications. These standards apply to any new development or redevelopment site that meets one or more of the following criteria:
(a) One (1) acre or more;
(i) New development that involves land development activities of one (1) acre or more;
(ii) Redevelopment that involves other land development activity of one (1) acre or more;
(b) Projects or developments of less than one acre of total land disturbance may be required to obtain authorization under this ordinance if:
(3) the Codes Enforcement Officer has determined that the stormwater discharge from a site is causing, contributing to, or is likely to contribute to a violation of a state water quality standard;
(4) the Codes Enforcement Officer has determined that the stormwater discharge is, or is likely to be a significant contributor of pollutants to waters of the state;
(5) changes in state or federal rules require sites of less than one acre that are not part of a larger common plan of development or sale to obtain a stormwater permit;
(6) Any new development or redevelopment, regardless of size, that is defined by the Codes Enforcement Officer to be a hotspot land use; or
(7) Minimum applicability criteria set forth in item (a) above if such activities are part of a larger common plan of development, even multiple, that is part of a separate and distinct land development activity that may take place at different times on different schedules.
Note: Any discharge of stormwater or other fluid to an improved sinkhole or other injection well, as defined, must be authorized by permit or rule as a Class V underground injection well under the provisions of Tennessee Department of Environment and Conservation (TDEC) Rules, Chapter 1200-4-6.
(8) Submittal of a copy of the NOC, SWPPP and NOT to the local MS4 Permittees who discharge stormwater through an NPDES-permitted municipal separate storm sewer system (MS4) who are not exempted in section 1.4.5 (Permit Coverage through Qualifying Local Program) of the Construction General Permit (CGP) must provide proof of coverage under the Construction General Permit (CGP); submit a copy of the Stormwater Pollution Prevention Plan (SWPPP); and at project completion, a copy of the signed notice of termination (NOT) to the City of Paris. Permitting status of all permittees covered (or previously covered) under this general permit as well as the most current list of all MS4 permits is available at the TDEC's DataViewer web site.
Copies of additional applicable local, state or federal permits (i.e.: ARAP, etc.) must also be provided upon request. If requested, these permits must be provided before the issuance of any land disturbance permit or the equivalent.
(9) Stormwater Pollution Prevention Plan (SWPPP) for Construction Stormwater Management: The applicant must prepare a stormwater pollution prevention plan for all construction activities that complies with subsection (5) below. The purpose of this plan is to identify construction/contractor activities that could cause pollutants in the stormwater, and to describe measures or practices to control these pollutants during project construction.
(10) Stormwater Pollution Prevention Plan requirements. The erosion prevention and sediment control plan component of the SWPPP shall accurately describe the potential for soil erosion and sedimentation problems resulting from land disturbing activity and shall explain and illustrate the measures that are to be taken to control these problems. The length and complexity of the plan is to be commensurate with the size of the project, severity of the site condition, and potential for off-site damage. If necessary, the plan shall be phased so that changes to the site during construction that alter drainage patterns or characteristics will be addressed by an appropriate phase of the plan. The plan shall be sealed by a registered professional engineer or landscape architect licensed in the state of Tennessee. The plan shall also conform to the requirements found in the MS4 BMP manual, and shall include at least the following:
(a) Project description - Briefly describe the intended project and proposed land disturbing activity including number of units and structures to be constructed and infrastructure required.
(b) A topographic map with contour intervals of five (5) feet or less showing present conditions and proposed contours resulting from land disturbing activity.
(c) All existing drainage ways, including intermittent and wet-weather. Include any designated floodways or flood plains.
(d) A general description of existing land cover. Individual trees and shrubs do not need to be identified.
(e) Stands of existing trees as they are to be preserved upon project completion, specifying their general location on the property. Differentiation shall be made between existing trees to be preserved, trees to be removed and proposed planted trees. Tree protection measures must be identified, and the diameter of the area involved must also be identified on the plan and shown to scale. Information shall be supplied concerning the proposed destruction of exceptional and historic trees in setbacks and buffer strips, where they exist. Complete landscape plans may be submitted separately. The plan must include the sequence of implementation for tree protection measures.
(f) Approximate limits of proposed clearing, grading and filling.
(g) Approximate flows of existing stormwater leaving any portion of the site.
(h) A general description of existing soil types and characteristics and any anticipated soil erosion and sedimentation problems resulting from existing characteristics.
(i) Location, size and layout of proposed stormwater and sedimentation control improvements.
(j) Existing and proposed drainage network.
(k) Proposed drain tile or waterway sizes.
(l) Approximate flows leaving site after construction and incorporating water run-off mitigation measures. The evaluation must include projected effects on property adjoining the site and on existing drainage facilities and systems. The plan must address the adequacy of outfalls from the development: when water is concentrated, what is the capacity of waterways, if any, accepting stormwater off-site; and what measures, including infiltration, sheeting into buffers, etc., are going to be used to prevent the scouring of waterways and drainage areas off-site, etc.
(m) The projected sequence of work represented by the grading, drainage and sedimentation and erosion control plans as related to other major items of construction, beginning with the initiation of excavation and including the construction of any sediment basins or retention/detention facilities or any other structural BMP's.
(n) Specific remediation measures to prevent erosion and sedimentation run-off. Plans shall include detailed drawings of all control measures used; stabilization measures including vegetation and non-vegetation measures, both temporary and permanent, will be detailed. Detailed construction notes and a maintenance schedule shall be included for all control measures in the plan.
(o) Specific details for: the construction of stabilized construction entrance/exits, concrete washouts, and sediment basins for controlling erosion; road access points; eliminating or keeping soil, sediment, and debris on streets and public ways at a level acceptable to the city. Soil, sediment, and debris brought onto streets and public ways must be removed by the end of the work day to the satisfaction of the city. Failure to remove the sediment, soil or debris shall be deemed a violation of this ordinance.
(p) Proposed structures: location and identification of any proposed additional buildings, structures or development on the site.
(q) A description of on-site measures to be taken to recharge surface water into the ground water system through runoff reduction practices.
(r) Specific details for construction waste management. Construction site operators shall control waste such as discarded building materials, concrete truck washout, petroleum products and petroleum related products, chemicals, litter, and sanitary waste at the construction site that may cause adverse impacts to water quality. When the material is erodible, such as soil, the site must be treated as a construction site.
(11) General design performance criteria for permanent stormwater management: the following performance criteria shall be addressed for permanent stormwater management at all development sites:
(a) Site design standards for all new and redevelopment require, in combination or alone, management measures that are designed, built and maintained to infiltrate, evapotranspire, harvest and/or use, at a minimum, the first inch of every rainfall event preceded by 72 hours of no measurable precipitation. This first inch of rainfall must be 100% managed with no discharge to surface waters.
(b) Limitations to the application of runoff reduction requirements include, but are not limited to:
i. Where a potential for introducing pollutants into the groundwater exists, unless pretreatment is provided;
ii. Where pre-existing soil contamination is present in areas subject to contact with infiltrated runoff;
iii. Presence of sinkholes or other karst features.
(c) Pre-development infiltrative capacity of soils at the site must be taken into account in selection of runoff reduction management measures.
(d) Incentive Standards for re-developed sites: a 10% reduction in the volume of rainfall to be managed for any of the following types of development. Such credits are additive such that a maximum reduction of 50% of the standard in the paragraph above is possible for a project that meets all 5 criteria:
i. Redevelopment;
ii. Brownfield redevelopment;
iii. High density (>7 units per acre);
iv. Vertical Density, (Floor to Area Ratio (FAR) of 2 or >18 units per acre); and
v. Mixed use and Transit Oriented Development (within ½ mile of transit).
(e) For projects that cannot meet 100% of the runoff reduction requirement unless subject to the incentive standards, the remainder of the stipulated amount of rainfall must be treated prior to discharge with a technology documented to remove 80% total suspended solids (TSS) unless an alternative provided under this ordinance is approved. The treatment technology must be designed, installed and maintained to continue to meet this performance standard.
(f) For projects that cannot meet 100% of the runoff reduction requirements, the City of Paris may allow runoff reduction measures to be implemented at another location within the same USGS 12-digit hydrologic unit code (HUC) as the original project. Off-site mitigation must be a minimum of 1.5 times the amount of water not managed on site. The off-site mitigation location (or alternative location outside the 12-digit HUC) and runoff reduction measures must be approved by the City of Paris. The City of Paris shall identify priority areas within the watershed in which mitigation projects can be completed. The City of Paris must create an inventory of appropriate mitigation projects, and develop appropriate institutional standards and management systems to value, evaluate and track transactions. Mitigation can be used for retrofit or redevelopment projects, but should be avoided in areas of new development.
(g) To protect stream channels from degradation, specific channel protection criteria shall be provided as prescribed in the MS4 BMP manual.
(h) Stormwater discharges to critical areas with sensitive resources (i.e., cold water fisheries, shellfish beds, swimming beaches, recharge areas, water supply reservoirs) may be subject to additional performance criteria, or may need to utilize or restrict certain stormwater management practices.
(i) Stormwater discharges from hot spots may require the application of specific structural BMP's and pollution prevention practices. In addition, stormwater from a hot spot land use may not be infiltrated.
(j) Prior to or during the site design process, applicants for land disturbance permits shall consult with the Codes Enforcement Officer to determine if they are subject to additional stormwater design requirements.
(k) The calculations for determining peak flows as found in the MS4 BMP manual shall be used for sizing all stormwater facilities.
(12) Minimum volume control requirements. (Note: the volume control requirements are by the MS4 and not the TDEC MS4 Permit) in accordance with 13-501(1)(c )(iii) the MS4 may establish standards to regulate the quantity of stormwater discharged, therefore:
(a) Stormwater designs shall meet the multi-stage storm frequency storage requirements as identified in the MS4 BMP manual.
(b) If hydrologic or topographic conditions warrant greater control than that provided by the minimum control requirements, the Codes Enforcement Officer may impose any and all additional requirements deemed necessary to control the volume, timing, and rate of runoff.
(13) Permanent Stormwater management plan requirements. The stormwater management plan shall include sufficient information to allow the City of Paris to evaluate the environmental characteristics of the project site, the potential impacts of all proposed development of the site, both present and future, on the water resources, and the effectiveness and acceptability of the measures proposed for managing stormwater generated at the project site. To accomplish this goal the stormwater management plan shall include the following:
(a) Topographic base map: Topographic base map of the site which extends a minimum of 100 feet beyond the limits of the proposed development and indicates:
i. Existing surface water drainage including streams, ponds, culverts, ditches, sinkholes, wetlands; and the type, size, elevation, etc., of nearest upstream and downstream drainage structures;
ii. Current land use including all existing structures, locations of utilities, roads, and easements;
iii. All other existing significant natural and artificial features;
iv. Proposed land use with tabulation of the percentage of surface area to be adapted to various uses; drainage patterns; locations of utilities, roads and easements; the limits of clearing and grading.
(b) Proposed structural and non-structural BMP's;
(c) A written description of the site plan and justification of proposed changes in natural conditions may also be required;
(d) Calculations: Hydrologic and hydraulic design calculations for the pre-development and post-development conditions for the design storms specified in the MS4 BMP manual. These calculations must show that the proposed stormwater management measures are capable of controlling runoff from the site in compliance with this chapter and the guidelines of the MS4 BMP manual. Such calculations shall include:
i. A description of the design storm frequency, duration, and intensity where applicable;
ii. Time of concentration;
iii. Soil curve numbers or runoff coefficients including assumed soil moisture conditions;
iv. Peak runoff rates and total runoff volumes for each watershed area;
v. Infiltration rates, where applicable;
vi. Culvert, stormwater sewer, ditch and/or other stormwater conveyance capacities;
vii. Flow velocities;
viii. Data on the increase in rate and volume of runoff for the design storms referenced in the MS4 BMP manual; and
ix. Documentation of sources for all computation methods and field test results.
(e) Soils information: If a stormwater management control measure depends on the hydrologic properties of soils (e.g., infiltration basins), then a soils report shall be submitted. The soils report shall be based on on-site boring logs or soil pit profiles and soil survey reports. The number and location of required soil borings or soil pits shall be determined based on what is needed to determine the suitability and distribution of soil types present at the location of the control measure.
(14) Maintenance and repair plan: The design and planning of all permanent stormwater management facilities shall include detailed maintenance and repair procedures to ensure their continued performance. These plans will identify the parts or components of a stormwater 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.
(15) Buffers and buffer zones: Buffer and buffer zones shall be those buffers and buffer zones as those terms are defined in 13-502(5) and (6), above, and shall met the requirements contained in those provisions.
(a) Construction
i. Construction requires buffer zone widths of a minimum of thirty (30) feet. The thirty (30) foot criterion for the width of the buffer zone can be established on an average width basis. As long as the minimum width of the buffer zone is fifteen (15) feet. The buffer zone shall meet all the other applicable requirements of 13-502 (5) and (6).
ii. Construction on impaired or exceptional waters. The width of the buffer zone shall be a minimum of sixty (60) feet. The sixty (60) feet criterion for the width of the buffer zone can be established on an average basis at a project as long as the minimum width of the buffer is more than thirty (30) feet at any measured location. The buffer zone shall meet all the other applicable requirements of 13-502(5) and (60).
(b) Permanent
iii. More than one (1) square mile drainage area will require buffer zones of a minimum of sixty (60) feet. The sixty (60) foot criterion for the width of the buffer zone can be established on an average width basis, as long as the minimum width of the buffer zone is more than thirty (30) feet at any measured location.
v. Less than one (1) square mile drainage area. Less than one (1) square mile drainage area will require buffer zones of a minimum of thirty (30) feet. The thirty (30) foot criterion for the width of the buffer zone can be established on an average width basis, as long as the minimum width of the buffer zone is more than thirty (30) feet at any measured location. The buffer zone shall meet all the other applicable requirements of 13-502(5) and (6).
(16) Plan Review. Plans submitted by an applicant/developer shall be reviewed by a licensed engineer retained by the City to assure compliance with all development standards required by 13.501 et seq. of the Paris Municipal Code. The City shall charge the applicant/developer a fee in an amount equal to the fee charged the City by its licensed engineer for review of the applicant/developer's plans. Said fee shall be paid by the applicant/developer to the City before any final licenses/permits/certificates of occupancy, or other similar permits are issued.
(Ordinance # 1185, 4/11/2016).