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The Regulatory Side

So what exactly does the Chattanooga water quality program do?

We manage stormwater and natural water bodies and are dedicated to preserving and improving their health.

npdes logoFeb20 NPDES

The national pollutant discharge elimination system, or NPDES is a permit issued to states that controls the direct discharge (or point source) of pollutants into waters of the United States. Tennessee has been issued an NPDES permit, and must abide by its regulations. It allows any entities that are dumping pollutants directly into water bodies to do so as long as those pollutants are within certain limits. How much is being dumped, what is being dumped, and where must be reported to the EPA. If dumping occurs either purposefully or accidently of any substance other than stormwater without reporting, it is considered Illicit discharge and is illegal.

At the water quality program of Chattanooga, our goal is to achieve 100% compliance with applicable Federal and State clean water laws and regulations, and to maintain and improve the condition and flow of the storm water infrastructure to address any existing or anticipated problem areas.


 Walnut street bridge


There are two phases of the NPDES program. They are based on population size.

Phase I covers "municipal areas" which are considered medium or large and have a population of 100,000-250,000. It also covers construction areas of 5 acres or larger, and industrial activities.

  • Chattanooga is considered a Phase I city, with a population of 167,674 people.

Phase II covers "urbanized areas" which are considered small and have a population of at least 50,000 people. Phase II also says that those enforcing the NPDES permit must practice minimum control measures. These include:

  1. Public Education and Outreach: Best management practices for municipal separate storm sewer system (MS4) to inform individuals and households about ways to reduce stormwater pollution.
  2. Public Involvement: Best management practices for MS4s to involve the public in the development, implementation, and review of an MS4's stormwater management program.
  3. Construction Site Runoff: Best management practices for MS4s and construction site operators to address stormwater runoff from active construction sites.
  4. Post-Construction Runoff Control: Best management practices for MS4s, developers, and property owners to address stormwater runoff after construction activities have completed.
  5. Illicit Discharge Detection and Elimination (IDDE): Best management practices for identifying and eliminating illicit discharges and spills to storm drain systems.
  6. Pollution Prevention/Good housekeeping for Municipal Operations: Best management practices for MS4s to address stormwater runoff from their own facilities and activities.

Phase I areas like Chattanooga must abide by these same control measures, plus many more, such as: MS4 Mapping, Flood Control, Permanent Stormwater Management in New Development and Redevelopment, Best Management Practices Maintenance, Watershed Inspection, etc. 

Would you like to access the full Tennessee NPDES permit?


The City of Chattanooga's water quality department is also responsible for doing TMDL sampling as required by the NPDES permit. TMDL is Total Maximum Daily Load, and refers to the daily allowed amount of certain pollutants in water bodies. TMDL studies are done on streams that are on the 303(d) list. This is a list of streams that are of limited quality, and require more help in order to not be considered impaired. These streams are not meeting the standards for their uses, and each stream can be categorized by the main use it provides. This could be fish and aquatic life, recreation, irrigation, livestock watering and wildlife, navigation, industrial water supply, and drinking water supply.
During the sampling process, the pH, conductivity, temperature, turbidity (amount of solid particles present) and conductivity are measured at the site. Samples are then taken of the water to measure amounts of E. coli and Total Suspended Solids present. This is done at Moccasin Bend Waste Water Treatment Plant.



Macroinvertebrate Sampling

Macroinvertebrates are organisms without a backbone that can be seen with the naked eye. Every year, the water quality program takes samples of the insect life living in the impaired streams of Chattanooga. By taking samples of the insects and observing what species are present and in what amounts, we can gain a better understanding of the streams' health. There are indicator species that when present can signify either a healthy stream, or more unfavorable living conditions. Certain species thrive in healthy habitats and some are able to tolerate unhealthy ones. Therefore this type of sampling can give us better insight into what it means to live in that body of water.

Field screening

The water quality department implements a method of assessing illicit discharge and improper disposals called field screening. This is required by the NPDES permit. Areas of land whose main use is industrial or heavy commercial usually have more runoff and pollutants as a result, and so these sites are monitored through field screening. There are a total of 578 field screening sites in Chattanooga. Field screening involves going to a site twice in one day, with at least four hours in between sampling in order to get an accurate understanding of the water quality at the site. Temperature, pH, dissolved oxygen and conductivity are all recorded, and testing kits are utilized to detect any chemicals or metals that shouldn't be in the water, such as: copper, chlorine, detergents, phosphates, phenol, ammonia, and hydrogen sulfide.

SCORE- Stream Corridor Evaluation B02 03 Start DS

This is a program that looks at the physical characteristics of streams in order to assess their health. Water Quality team members evaluate things such as stream bank stability, condition of habitat, and sediment build up and then rate or "score" them on a scale in order to better understand the stream's health.


We have discussed the Chattanooga water quality dept.'s role in making sure our natural water bodies are clean, but what does the Water Quality Dept. have to do with Chattanooga's sewer system? While sewer systems are separate from storm drains, torrential rain events can cause water to seep into the sewer, causing it to overflow. This occurrence is called "sanitary sewer overflow", or SSO. When overflow is caused by rain events, it is referred to as a "wet event." Grease, oil and other debris are also hazardous to sewer systems. They can create blockages which can cause the sewer system to overflow. Since these are not caused by rain, they are called "dry events." When illicit discharge from sewers becomes a problem, the city has a solution. A program has been devised that uses an unlikely method- smoke; to identify areas where sewer lines or MS4s have issues. When it is suspected that a sewer system or storm drain has been compromised, smoke is pumped into the pipe in question and monitored to see where it comes out. The program is called S.L.A.P, which stands for sewer lateral assistance program.

If these broken pipes occur on someone's property, they will be notified with a letter and will be informed of a financial assistance program. This assistance is funded by a Community Development Block Grant (CDBG) which is appropriated by the U.S Dept. of Housing and Urban Development (HUD) and is distributed by the City of Chattanooga's Department of Neighborhood Services and Community Development. In order to qualify for assistance, a homeowner must occupy the property for which assistance is being applied for, and the property owner must have no overdue City and County property taxes. The property owner must also fall into the low income range of "Income Limits and Fair Market Rents for Chattanooga" (HUD) non-compliance occurs, written warnings, notices of violation, compliance orders or court citations may be issued.

 Green Infrastructure (GI)

 The water quality program also does maintenance, inspections, and runs incentive programs involving green infrastructure. Green Infrastructure is an approach to water management that protects, restores, or mimics the natural water cycle. Examples of green infrastructure include, but aren't limited to:

  • Detention & retention ponds
  • Green roofs
  • Bioretention / Rain gardens
  • Bioswales

We routinely inspect these to make sure they are in working order, & may enforce maintenance procedures if they are not. We offer incentive programs such as RainSmart & SWEEP that educate residents & help install GI practices, or maintain ones already in place. For businesses & multi-family housing there are programs that have similar goals, such as Green Grants, and the City's Credits/incentives program. We also do maintenance on City owned green infrastructure sites. 


Serve people with integrity and improve the infrastructure and environment through excellence.

Justin Holland, Administrator
1250 Market Street
Chattanooga TN 37402 (map)
(423) 643-6311  


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