The Metropolitan Government of Nashville and Davidson County has enacted a Stormwater Management Ordinance in order to reduce the adverse impacts of stormwater runoff from development sites in Davidson County to the greatest extent possible, by establishing minimum requirements and procedures to control the quantity and quality of stormwater runoff associated with land development. The Metropolitan Government of Nashville and Davidson County is the permitting authority for all land disturbing activities and requires the land owner to maintain all on-site stormwater control facilities and all open space areas (e.g. parks or “green” areas) required by the approved stormwater control plan. The Metropolitan Government of Nashville and Davidson County will only provide construction permits to projects that establish a plan to manage stormwater runoff occurring during the construction process. Stormwater fees will be collected by The Metropolitan Government of Nashville and Davidson County. The Metropolitan Government of Nashville and Davidson County, under the NPDES program, also has the authority to inspect properties for noncompliance and can issue a notice of violation (NOV) for any deficiency or infraction onsite.
The Director of MWS, the Director of Codes Administration, or any of their duly authorized representatives may enter upon the premises of any land within Metropolitan Nashville and Davidson County for the purposes of inspecting the site before, during, and after construction to determine compliance with these regulations.
The Director of MWS or any of his or her duly authorized representatives may enter upon the premises of any land and enter facilities within Metropolitan Nashville and Davidson County for the purposes of inspecting potential impacts to stormwater quality or any activities that may violate the NPDES MS4 permit.
Care must be taken to ensure that any required detention facilities do not become nuisances or health hazards. Stormwater quality management practices generally require more maintenance than stormwater quantity management practices. Detention facilities should be designed to require minimal maintenance, and maintenance responsibility must be clearly stated on the plans. Detention facilities may be designed to serve multiple purposes whereby runoff may be detained under wet-weather conditions, but also serve as common or recreational areas during dry-weather conditions. Where multi-purpose facilities are provided, or where flat grades or poorly draining soils are encountered, provisions for adequate low flow stormwater management system may be required. Where the retention/ detention facility is planned to be used as a lake, pond or stormwater quality management practice with a permanent pool, water budget calculations shall be performed and submitted to demonstrate that an adequate pool is expected during dry summer months. More detailed specifications on detention structures can be found in Volume 4 Section 6.
All stormwater quantity and/or quality control BMPs must be located within public utility and drainage easements and must be maintained by the landowner or the homeowner’s association.
A Maintenance Document must be submitted with the Grading Permit application and must include the following:
1. Either an Inspection and Maintenance (I&M) Agreement, which includes an easement requirement, or a Declaration of Restrictions and Covenants, whichever is appropriate as determined by Stormwater staff, signed by the current owner. Copies of the two alternative forms may be found in Appendix C.
2. A long-term maintenance plan prepared by the design engineer. The maintenance plan must include a description of the stormwater system and its components, inspection priorities and inspection schedule for each component, and BMP schematics for each BMP.
3. A system location map to enable MWS to locate BMPs, which include water quality buffers, as needed.
The Maintenance Document must be recorded prior to final Grading Permit approval. If the final configuration of the stormwater system components or BMP differs from the original configuration proposed with the Grading Permit application, the Maintenance Document must be revised, finalized, and rerecorded. Failure to follow the Maintenance Document could result in enforcement action. Nothing in these regulations alters, amends, or negates requirements under existing detention pond agreements between the Metropolitan Government and property owners.
The long-term maintenance plan within the Maintenance Document contains the inspection priorities and schedule for the stormwater system components and BMPs. The BMP owner is responsible for inspecting the stormwater system, including BMPs, according to the schedule and annually submitting completed inspection reports to MWS to document that inspections have been completed and necessary maintenance has been performed. MWS must be notified through the annual inspection process of any BMP ownership changes. Failure to file annual inspection reports and perform required BMP maintenance could result in enforcement action.
A comprehensive inspection of BMPs must be performed every 5 years by a qualified professional as specified by MWS or a professional engineer or a landscape architect. The inspection report shall be submitted to MWS and shall include the following:
• Facility Type,
• Inspection date,
• Latitude and longitude and nearest street address,
• BMP owner information (e.g., name, address, phone number, email)
• A description of BMP condition including: vegetation and soils; inlet and outlet channels and structures; embankments, slopes, and safety benches; spillways, weirs, and other control structures; and any sediment and debris accumulation,
• Photographic documentation of BMPs, and
• Specific maintenance items or violations that need to be corrected by the BMP owner along with deadlines and re-inspection dates.
In order to maintain the functional value of the buffer area, indigenous vegetation may be removed as follows:
a. Dead, diseased, or dying trees that are in danger of falling and causing damage to dwellings or other structures may be removed at the discretion of the landowner.
b. Debris in the buffer area that is caused by storm damage may be removed.
c. Invasive plant species may be removed if they are replaced by native species that are equally effective in retarding runoff, preventing erosion, and filtering nonpoint source pollution from runoff. A buffer restoration plan for removal of invasive species must be approved by MWS. See section 6.9.6 for buffer restoration plan requirements.
d. Woody vegetation growing on a levee or within 15 feet of the levee toe may be removed to protect the integrity of the levee.
e. Vegetation may be maintained in certain areas so as to not conflict with other Metro Code (i.e. Chapter 13 – Traffic and Parking) relating to “sight distances” for ROW, roadway maintenance, driveways, or other paths of travel
Metro has established a post-construction stormwater quality program that applies a consistent standard for pollutant removal, regardless of the type of development. This chapter describes the post-construction stormwater quality program and requirements including:
• The targeted pollutant and pollutant reduction goal;
• Water quality treatment volume requirement for new development;
• Low Impact Development guidance;
• A listing of pre-approved structural Best Management Practices (BMPs);
• Testing requirements for proprietary BMPs; and
• Water quality treatment volume site design credits.
An automated calculator that can be used in developing the post-construction stormwater quality plan can be downloaded from Metro’s Stormwater website.
Stormwater management systems for new development, significant redevelopment, and grading permit sites must be designed to achieve the goal of removing at least 80% of the average annual post-construction total suspended solids (TSS) load. It is presumed that a stormwater management system complies with this performance standard if:
• It is sized to capture and treat the water quality treatment volume, which is defined as the runoff volume resulting from the first 1.1 inches of rainfall from a site; and
• Appropriate structural stormwater controls are selected, designed, constructed, and maintained according to the specific criteria in this Manual.
Please contact MWS Plan Review staff for TSS removal efficiency requirements for sites located in Nashville’s combined sewer area.
Each water quality BMP installed on a site requires maintenance so that it functions properly, ensuring that it helps fulfill the water quality goal for the site. Therefore, a BMP-specific Maintenance Document for each development site is required.
A. Any violation of this chapter shall be punishable by a civil penalty in an amount not to exceed five hundred dollars; provided, however, that any violation of Section 15.64.205 shall be punishable by a civil penalty of not less than fifty dollars nor more than five thousand dollars.
For purposes of assessing civil penalties under this chapter, each day of violation shall constitute a separate violation.
B. In assessing a civil penalty, the following factors may be considered:
C. The department may also assess damages proximately caused by the violator to the municipality which may include any reasonable expenses incurred in investigating and/or enforcing violations of this part, or any other actual damages caused by the violation.
D. In addition to all other remedies provided by law, the metropolitan government shall have the right to injunctive relief for any violation of this chapter
In March 2009, the Metropolitan Council passed a stormwater rate ordinance (BL2009-407) to establish a rate structure for a dedicated user fee to support the stormwater program within Metro Water Services (MWS).
The stormwater user fee provides a stable and adequate source of revenue for the stormwater management program that allocates the costs of stormwater services across every stormwater “user” in the MWS stormwater service area through a stormwater user fee (or service charge). Developed land is charged a fee based on the amount of impervious surface area on the property. The stormwater user fee that a property owner pays is directly proportional to the impervious area found on the property.
A credit is an ongoing downward adjustment in the service charge. The rate ordinance provides for adjustments to the stormwater user fee for properties that reduce demand on the Public System.
The purpose of the credit policy is to provide properties with credit for mitigating stormwater runoff impacts through education, or source controls for water quantity or quality. The available credits are:
Nashville Stormwater Post-Construction Quality Policies and Procedures
Nashville Stormwater BMP Manual
Nashville Stormwater Structural BMP Inspection Checklist
Nashville Stormwater Management Manual Volume 1: Regulations
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