City of Chattanooga


The City of Chattanooga has enacted a Stormwater Management Ordinance in order to reduce and minimize pollutants from entering streams from the MS4 drainage system. The City of Chattanooga 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 City of Chattanooga 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 City of Chattanooga and businesses can qualify for relief by implementing Best Management Practices on their property. The City of Chattanooga, 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. 

Stormwater Fee

(b) Nonresidential Properties.  The annual water quality fee per ERU as of the adoption of this ordinance shall be set at $115.20 per ERU

Sec. 31-356 Adjustment to Water Quality Fee

  1. Increase adjustments (debit) can be made to non-residential service charges by property owners adding additional impervious area such as rooftops, parking lots, driveways and walkways. Decrease (credit) adjustments can be made to non-residential service charges by property owners performing activities that reduce the impact of storm water runoff to the water quality system.
  2. Upon application by any user adequately supported by documentation, the user shall be entitled to an adjustment of their water quality fee as provided in this section. The water quality credits (applied in 5% increments) are offered to non-residential property owners billed three (3) or more Equivalent Residential Units (ERU) that perform an activity or activities (Stormwater Best Management Practice; BMP) that reduce the burden on the City storm water system and provide water quality benefit. The Water Quality Manager shall promulgate a Water Quality Fee Credits Outline to provide guidance on combining multiple credits and showing examples of credit and credit calculation methods.
  3. A Credit Fee cap is placed at sixty-five percent (65%) for all BMPs, unless a Low Impact Development practice, LEED Certified Development, or Retrofit/Mitigation Plan is approved and installed, whereby the credit cap will be raised to eighty-five percent (85%).
  4. Proper Maintenance of BMPs is required in order to annually receive the credits provided in this section. Maintenance shall be performed according to the BMP manual adopted by the City. The owner must document that the BMPs have been properly maintained and serviced as required annually. BMPs are subject to inspection and verification of proper maintenance by the Water Quality manager or his designee. Failure to provide this documentation will result in the denial of these credits.

1) Retrofit/Mitigation Plan (25% 1st year, maximum of 85% 2nd and 3rd year). A water quality fee credit of 25% for the 1st year will be offered to those sites submitting a proposal that results in the installation of structural measures (BMPs) that reduce the City’s stormwater burden.

(i) After completion and inspection of proposed stormwater BMP, a maximum of 85% credit will be offered for year 2 and 3. After the 3rd year the allotted credit will follow the appropriate BMP category found in the Credits Outline promulgated by the Water Quality Manager upon submission of as-built drawings following completion of the work.

             (ii) Maximum credit offered for years 2 and 3:

  • 85% for LID practices (see City BMP Manual for examples) or Detention Retention Facilities controlling the 24-hr storm event for the 1, 2, 5, 10, 25, 50 and 100 year storm flow design to a pre-construction runoff rate.
  • 80% for Detention/Retention Facilities controlling the 24-hr storm event for the 1, 2, 5, 10, 25 and 50 year storm flow design to a pre-construction runoff rate.
  • 75% for Detention/Retention Facilities controlling the 24-hr storm event for the 1, 2, 5, 10 and 25 year storm flow design to a pre-construction runoff rate.
  • 50% for Water Quality Devices

(iii) As-Built Drawings must be submitted upon completion of the improvements to obtain credit in years 2 & 3.

(iv) Fee credits will be offered only for those impervious areas impacted by the proposed improvements.

(v) Proposed improvements must be approved by the City Water Quality Manager to qualify for the first year of credits.

(vi) Improvements shall be constructed as approved. Those sites not constructing the approved BMPs within 12 months of the design approval will forfeit those credits and will be liable for repayment of any credits received.

2) Tree Planting (20% max). A maximum of 20% credit will be offered for planting of new trees and/or maintenance of existing trees. Maximum credit will be given upon implementation of a tree planting plan that will provide mature tree canopy over 25% of the impervious area. Credit will be prorated (in 5% increments) for plans that do not achieve 25% coverage.

(i) New trees must be planted in accordance with a tree planting plan (per City Tree Planting Guide) and follow the City of Chattanooga Landscape Ordinance.

(ii) Tree planting plans must be submitted to and approved by the City Water Quality Manager.

(iii) Trees that do not survive must be replanted as required.

3) Water Quality Education (up to 35% for calendar year 2009, up to 30% for calendar year 2010, up to 25% thereafter). A maximum of 25% credit will be offered to Public and Private Schools, K through 12, which integrate a curriculum in each grade level, approved by the City, for the purpose of providing water quality and watershed management education programs. A similar credit may be offered to non-traditional watershed based institutions (i.e. museums, arboretums, and community gardens) that provide appropriate water quality and watershed management education programs.

4) Water Quality Devices (up to 30%)

(i) Skimmers: A maximum of 15% credit will be offered for floatable skimmers that are used to control oil, floatable materials, and sediments from entering the City storm water system.

(ii) Proprietary Devices: A maximum of 30% credit will be offered for water quality propriety devices that have verifiable independent testing to reduce the average annual total suspended solid (TSS) loadings by 80 percent or effectively remove other pollutants of concern as determined by the Water Quality Manager.

              (iii) Other Water Quality Devices could receive up to 30% credit.

5) Detention/Retention Facilities (up to 40%). Detention/Retention Facilities designed to control the 24-hour storm event in the categories set forth below shall receive the corresponding credit.

          (i) 2, 5, 10 year storm flow design: 10% credit

          (ii) 1, 2, 5, 10 year storm flow design: 15% credit

          (iii) 2, 5, 10, 25 year storm flow design: 20% credit

          (iv) 1, 2, 5, 10, 25 year storm flow design: 25% credit

          (v) 2, 5, 10, 25, 50 year storm flow design: 25% credit

          (vi) 1, 2, 5, 10, 25, 50 year storm flow design: 30% credit

          (vii) 2, 5, 10, 25, 50, 100 year storm flow design: 35% credit

          (viii) 1, 2, 5, 10, 25, 50, 100 year storm flow design: 40% credit

As-built drawings must be submitted with the credit application. One-time additional credit (up to 10%, not to exceed cap) will be given for submitting as-built drawings.

6) Low Impact Development (LID) (up to 75%). A maximum of 75% credit will be offered for the installation and proper maintenance of green storm water controls such as green roofs, cisterns/rain barrels, bio-retention areas (rain gardens), bio-swales, wetlands, porous pavement, grass strips, or other proven LIDs approved by the Water Quality Manager.

(i) Cisterns/rain barrels must be capable of capturing the runoff from at least one (1) inch rainfall over the entire impervious area. Captured runoff shall be connected to an irrigation system or similar re-use system.

(ii) Bio-retention areas, when used in conjunction with other LID or green storm water controls, shall be eligible for:

  • Up to 65% credit when controlling the 1, 2, 5, 10 and 25 year storm flow event
  • Up to 70% credit when controlling the 1, 2, 5, 10, 25 and 50 year storm flow event
  • Up to 75% credit when controlling the 1, 2, 5, 10, 25, 50 and 100 year storm flow event

(iii) Filter strips and swales designed in compliance with the BMP Manual adopted by the City shall be eligible for up to 15% credit.

As-built drawings must be submitted with the credit application. One-time additional credit (up to 10%, not to exceed cap) will be given for submitting as-built drawings.

7) LEED Certified Development (up to 60%). A maximum of 60% credit will be offered for a property that has received LEED certification and has obtained 5 credits for "Sustainable Sites" which includes Credits 6.1 (Storm Water Design Quantity Control) and 6.2 (Storm Water Design Quality Control).

8) Stream Buffers or Conservation Easements (up to 40%). A credit will be offered for constructing and/or maintaining a natural buffer on either side of the stream or jurisdiction wetland:

(i) Stream buffer credit (up to 25%) for buffers up to three (3) times the average stream width (measured from top of the bank) with a maximum of 100 feet.

(ii) Conservation easement credit (up to 15%) adjacent to streams or jurisdictional wetlands.

(iii) All credits and buffers designs are subject to the review and approval by the City Water Quality Manager.

9) Property Line Buffers (up to 10%). A maximum of 10% credit for property line buffers required by zoning and maintained per an approved landscape plan.

10) NPDES Permitted Facilities (up to 20%). A maximum of 20% credit will be offered to properties that have an NPDES stormwater permit in good standing for at least 12 months prior to the application date.

Stormwater Facilities Maintenance

Typical Inspection & Maintenance Activities for DETENTION or RETENTION PONDS:

• All inlet and outlet structures shall be checked regularly (at least quarterly or after a large rain event) for clogging and destabilization and shall be cleaned and repaired as necessary. Any destabilization area shall be repaired by using Turf Reinforced Matting (TRMs), rip-rap (with geotextiles), etc.

• Check banks and bottom surface of basin (at least quarterly or after a large rain event) for erosion and correct as necessary. The facility should be free of accumulated debris. Any bank erosion shall be repaired immediately by using erosion blankets, Turf Reinforced Matting (TRMs), rip-rap, etc.

• Remove vegetation overgrowth and remove any nuisance vegetation. Pond vegetation needs to be trimmed or harvested as appropriate, grassy areas frequently mowed. Grass should be mowed so that it does not get over 6 inches.

• Remove sediment when accumulation reached 6 inches, or if re-suspension is observed or probable.

• Some sediment may contain contaminants or which the Tennessee Department of Environment and Conservation (TDEC) requires special disposal procedure. If there is any uncertainty about what the sediment contains or it is known to contain contaminants, then TDEC should be consulted and their disposal recommendations followed. The TDEC Division of Water Pollution Control should be contacted at (423) 634.5743. Generally, special attention or sampling should be given to sediment accumulated in facilities serving industrial, manufacturing or heavy commercial sites, fueling centers or automotive maintenance areas, large parking areas, or other areas where pollutants (other than clean soil) are suspected to accumulate and be conveyed by stormwater runoff.

• Some sediment collected may be innocuous (free of pollutants) and can be used as fill material, cover or land spreading. It is important that this material not be placed in any way that will promote or allow re-suspension in storm runoff.

• Any removed vegetation shall be disposed of properly and not allowed to be disposed of at the property stormwater areas.

• Check for possible mosquitoes breeding opportunities (blockage, clogging, poor drainage, trash, etc.) and take proper corrective actions.

Typical Inspection & Maintenance Activities for SWALES and BIO-SWALES (containing bio-filter):

• The facility should be checked (at least quarterly or after a large rain event) for signs of erosion, vegetation loss, and channelization of the flow.

• The grass should be mowed when it reaches a height of 8 inches (20.3 cm) and no shorter than 3 inches (7.6 cm). Allowing the grass to grow taller may cause it to thin and become less effective. The clippings should be bagged and removed.

• Keep all level spreaders even (level) and free of debris.

• Mow grass covered bio-filters regularly to promote growth and pollutant uptake.

• Remove cuttings and dispose of properly (preferably through composting). Do not dispose of in any stormwater structure.

• Remove sediment by hand with a flat-bottomed shovel during dry periods.

• Remove only the amount of sediment necessary to restore hydraulic capacity, leaving as much of the vegetation in place as possible.

• Reseed or plug any damaged turf or vegetation.

• Eventually, sufficient sediment will be trapped that the entire bio-filter will need to be removed and reconstructed.

• Roto-till or cultivate the surface of the sand/soil bed of dry swales if the swale does not draw down within 48 hours.

Typical Inspection & Maintenance Activities for GREEN ROOFS:

• Immediately after construction, green roofs need to be monitored regularly to ensure the vegetation thrives.

• During the first season, green roofs may need to be watered periodically if there is not sufficient precipitation.

• After the first season, extensive green roofs may only need to be inspected quarterly and lightly fertilized approximately once per year.

• The roofs may need occasional weeding and may require some watering during exceptionally dry periods.

• If leaks should occur in the roof, they are relatively easy to detect and fix. Intensive green roofs need to be maintained as any other landscaped area.

LINKS:

Chattanooga Stormwater Fee Ordinance

Chattanooga Stormwater Management Ordinance

Chattanooga BMP Credit Application Form for Permanent Stormwater Control Structures

Water Quality Fee Credit Application Process

Chattanooga Inspection and Maintenance Guidelines for Typical Stormwater BMPs

Inspection and Maintenance Agreement Form

Long Term Inspection and Maintenance Plan

Inspection and Maintenance Form for Stormwater BMPs