Programs / Restoring the Harpeth

A little girl is crouched in the Harpeth River

A pollution reduction plan is in the works for the Harpeth River, and you can help!

ADD YOURSELF to the Tennessee Department of Environment & Conservation (TDEC) Harpeth River TMDL email distribution list so you can stay up to date on the process of establishing a pollution reduction study and plan.

CONTACT US here at the Harpeth Conservancy if you are interested in joining a stakeholder group to help develop a successful pollution reduction plan for the Harpeth River and/or if you want to receive email updates.

BECOME A CITIZEN SCIENTIST by downloading the free Water Reporter app and documenting problems you see on the Harpeth River.

LEARN MORE about TMDLs in general, the Harpeth River TMDL specifically, and other stakeholder-led TMDLs across the country on our resources page.


The Harpeth River is polluted. It is on Tennessee's list of impaired waters because the conditions of the river violate state water quality standards. A primary concern is high levels of phosphorus, a nutrient that can cause excessive algae growth (including toxic blue-green algae), deplete dissolved oxygen stores in the water, harm or kill aquatic life, and potentially poison the community water supplies. 

dead fish floating in algae-filled water
Image 1, U.S. Geological Survey, Paul Terrio

Polluting the water with phosphorus can trigger cultural eutrophication, where artificially elevated nutrients cause runaway plant and algae growth. Excessive nutrients act on algae in streams the same way fertilizer acts on your grass lawn, by increasing the growth rate and size. Thick algal blooms can block the sunlight from penetrating the surface of the water, which starves the plants growing on the riverbed. When the excessive algae dies and decomposes, it robs the water of oxygen, creating a "dead zone" that suffocates fish and other aquatic animals.

Worst of all, excessive nutrients can trigger a bloom of cyanobacteria (also known as blue-green algae), which can be toxic and dangerous to aquatic life and humans. The toxins produced by blue-green algae have been linked to gastrointestinal diseases, neurological diseases like Parkinson's and Alzheimer's, liver failure, and even death. CLICK HERE for more information about the dangers of blue-green algae.


The Tennessee Department of Environment & Conservation (TDEC) is the lead agency for an effort to study the Harpeth River watershed, establish pollution limits needed to meet water quality standards, and implement those limits successfully. To that end, TDEC has begun the process of developing a pollution reduction study and plan, called Total Maximum Daily Load (TMDL) to restore the Harpeth River.  

ABCs of TMDLs 

303(d) List: Under Section 303(d) of the Clean Water Act, all states must maintain a list of water bodies that fail to meet water quality standards and update the list every two years. The "303(d) List" identifies a state's impaired waters so the sources of impairment can be described and corrective actions can be taken. Once a river is on the 303(d) List, it can only be delisted if the river was listed accidentally in the first place or it achieves applicable water quality standards. The Harpeth River has been listed as impaired by phosphorus pollution since 2004 (and for nutrients since 1996), leaving little doubt that the listing was not in error and the river is not on track to achieve water quality standards based on current practices.   

TMDL: A TMDL is the maximum amount of a pollutant that a waterbody can receive and still meet state water quality standards, including allocations of specific limits to each of the pollutant's sources – "waste load allocations" for point sources (e.g. sewer treatment plant discharges) and "load allocations" for nonpoint sources (e.g. agricultural runoff). The calculated TMDL must also factor in a margin of safety and consideration of seasonal variation and critical conditions. The term "TMDL" is used to refer both to the limits set for a pollutant in a river body and to the study conducted to determine those limits. 

A sewage treatment plant in Athens TNWLA: Waste load allocations (WLAs) are limits to point sources of pollution, such as wastewater treatment plant discharges. Implementation is relatively straightforward. Point sources that discharge to waters of the United States are regulated by National Pollutant Discharge Elimination System (NPDES) permits, so implementing a WLA tends to be done through NPDES permits. The City of Franklin, for example, has a sewage treatment plant that discharges large amounts of phosphorus into the Harpeth River but (usually) operates within the limits of its NPDES permit. The Harpeth TMDL may result in a WLA that forces Franklin's sewage treatment plant to obtain an updated NPDES permit with a more stringent phosphorus limit.

LA: Load allocations (LAs) are limits to nonpoint sources of pollution, such as agricultural runoff and unregulated stormwater. Unlike point sources, there is no direct regulatory control over nonpoint sources. Implementing LAs relies on voluntary landowner participation in best management practices (BMPs) to limit nonpoint pollutant discharges into the impaired water. Because LAs do not have the regulatory backing of NPDES permits, compliance cannot be presumed and the EPA instructs that a TMDL should provide "reasonable assurances that nonpoint source control measures will achieve the expected [pollutant] load reductions." CLICK HERE to learn more about reasonable assurances in the context of the Chesapeake Bay TMDL.


TMDL development circle graphic
Virginia DEQ graphic - "BMPs" are best management practices


Typically, TMDLs are done in five steps: ​

First, the river is identified as impaired on the state's 303(d) list.

Second, the state water quality and NPDES permitting agency (here TDEC) initiates a study to determine the sources of impairing pollutant(s) and potential remedies.

Third, the agency publishes a draft TMDL, receives public comment on the draft, and submits a revised draft to the EPA for approval. The TMDL allocates WLAs and LAs (along with a margin of safety and seasonal variation) to restore the impaired river to state water quality standards.

Fourth, an implementation plan helps to organize continued water quality improvement efforts, especially voluntary landowner measures to acheivce LAs and incentives therefor.

Finally, ongoing efforts to monitor and maintain water quality ensure than the TMDL was successful in getting the river delisted and that there is no significant backsliding, or else the process starts again.

Monitoring water quality is critical throughout the process. TDEC uses data collected from monitoring efforts to compose the 303(d) List of impaired waters, and monitoring is necessary to ensure the post-implementation efficacy of a TMDL in restoring the water. Anyone can participate in collecting water quality data; there are several parties contributing monitoring data to the Harpeth River TMDL. 

Water Reporter logoYou can help collect valuable monitoring data on the Harpeth River! CLICK HERE to learn more about becoming a Harpeth Conservancy citizen scientist and using the Water Reporter app to document issues you see on the Harpeth, such as algae blooms and construction silt runoff.  


he EPA has approved over 70,000 TMDLs across the country, and most of them follow a similar development structure – the state water quality agency develops the TMDL and supporting analysis, reaching out for input from third parties as needed and soliciting comment from the public on the draft TMDL only just before submitting it to the EPA for approval.

In 2013, the U.S. Government Accountability Office (GAO) published a report entitled "Clean Water Act: Changes Needed If Key EPA Program Is to Help Fulfill the Nation's Water Quality Goals" (available HERE). The report looked at TMDLs across the country and found that a "representative sample [shows]...pollutant [reductions], but few impaired water bodies have fully attained water quality standards." In other words, most TMDLs reviewed by the GAO had failed their primary goal of restoring water quality to state standards. One reason for this problem was the fact that TMDLs "seldom contained all features key to attaining water quality standards..." Some of the key features the GAO report identified that were missing in many TMDLs were (1) identifying pollution-causing stressors; (2) showing how addressing such stressors would help attain such standards; (3) specifying how and by whom the TMDL would be implemented; and (4) ensuring periodic revisions as needed.

TDEC is ultimately responsible for submitting a draft TMDL for the Harpeth River to the EPA for approval. TDEC should be implementing processes that have the best chances to restore the Harpeth – one of the most heavily recreated rivers in the state – as soon as possible. Citizen interest groups such as the Harpeth Conservancy, point source dischargers such as the Franklin sewage treatment plant, and other parties impacted by the regulation and water quality of the Harpeth River hold stakes in the outcome of the TMDL and must help lead the process. The greater the level of stakeholder engagement, the more likely the final TMDL will reflect local concerns and knowledge and will be implemented effectively and voluntarily.


The Water Environment Federation published the "Third Party TMDL Development Toolkit" in 2007 (available HERE) and stated the following regarding potential benefits of third-party participation in TMDL development: 

Third parties are often very familiar with local watershed issues. They can provide valuable insights to the TMDL process. The involvement and economic support of third parties can leverage state funds, as well as the resources and expertise of other agencies and nongovernmental organizations. Greater funding can improve data quality and analysis supporting the TMDLs. Although the state must sanction TMDL decisions, third-party entities can be directly involved in decisions on TMDL approaches. This may improve the level of stakeholder support for the TMDL, increasing the likelihood of effective implementation of pollutant controls. The involvement of more nongovernmental entities may also increase the degree of public understanding of TMDLs and water quality protection issues through more opportunities for public involvement and education.

In the context of the Harpeth River, there are several additional reasons why a stakeholder-led process is needed.

First, Franklin has noted its main motivation for participating in the TMDL process is to avoid stricter phosphorus limits and TDEC has indicated that it might allow the Franklin sewage treatment plant to increase its phosphorus discharges into the Harpeth River, despite the fact that the river is already impaired by excessive phosphorus. 

Franklin email re participating in TMDL development to get weaker phosphorus regulations
An email exchange between Franklin and TDEC revealed Franklin's motive for participating in the TMDL process

The draft permit ultimately reflected TDEC's concession to Franklin that a TMDL could increase phosphorus limits, despite the fact that the Harpeth River was already impaired by excessive phosphorus. The permit states:

“This [phosphorus limit] constitutes an interim limitation until a new TMDL is finalized and approved by EPA, at which time the limitation will be revised to be consistent with the assumptions and requirements of the new wasteload allocation. This may result in either a decreased or increased limitation. If the latter, the new limitation would not constitute backsliding because it would be based on new information and would comply with the Antidegradation Statement because it would be part of an overall effort to reduce pollutant loading in the receiving waters.”

-- NPDES Permit No. TN0028827, pgs 4-5 (available HERE)

Second, there has been little progress on developing a TMDL for the Harpeth River thus far. After four years there is still no internal decision-making or leadership structure for the stakeholders, no scientific advisory panel, and no substantive technical work plan. 

A work plan is critical to a transparent and well-organized TMDL development process. Mike Corn, President of environmental engineering and consulting firm AquAeTer, submitted a report to TDEC that listed recommendations for running a TMDL study for the Harpeth River, including:

"A Work Plan should be developed for conducting the 2018 studies. It is impossible to conduct a waste assimilative capacity study and then conduct the subsequent modeling if a definitive plan is not developed and in place before the project begins. This is a fundamental part of any scientific study."

-- Recommendations for the 2018 Waste Assimilative Capacity Study of the Harpeth River for Establishing Defensible Wasteload Allocations (WLAs) (available HERE)

Finally, TDEC has expressed concern over a lack of resources available within the agency to dedicate to a Harpeth River TMDL, and has shown interest in substantively engaging stakeholders in the development process. Stakeholders can help defray the burdens associated with monitoring the Harpeth River and processing the water quality data. 


TDEC started discussing the development of a TMDL for the Harpeth River in 2014, and the first stakeholder meeting was held on May 16, 2016. Since then, TDEC has set up a Harpeth River Watershed TMDL Development webpage that includes a brief overview of the process, the minutes from previous meetings, and additional resources.

As of November 2018, TDEC states under "Current Happenings" that the agency is "compiling sampling data and continuing to evaluate all of the data that has been collected."

At this early stage in the process, it is critical for stakeholders to be clear about their roles and have internal decision-making mechanisms. The data collection phase of TMDL development is also the ideal time to create and use a scientific advisory panel that can compose a work plan laying out benchmarks and target deadlines, make empirically sound decisions on data collection and hydrologic modelling, and serve as a constant, independent, scientifically qualified companion to the TMDL development process.


In order to ensure the integrity and success of a Harpeth River TMDL, we need the following:

leadership council that formalizes and coordinates the roles of stakeholders in developing the Harpeth River TMDL;

An independent scientific advisory panel involved in "real time" in the process; and

A comprehensive work plan that outlines what parties are responsible for each aspect of the TMDL and when critical milestones are expected to be reached.

TDEC has already published a draft work plan on their website, but it needs more detail. A technical work plan produced by a scientific advisory panel would provide helpful context and expectations for the TMDL development process moving forward. TDEC has also taken laudable steps toward engaging stakeholders in developing the Harpeth River TMDL. A leadership council composed of qualified representatives for the parties most interested in the health and regulation of the Harpeth River would be invaluable to the stakeholders for dispute resolution, decision-making, and task delegation. 

The Harpeth River TMDL is an excellent opportunity to restore water quality in our beloved river. We must ensure the process engages stakeholders, is grounded in science, and is structured for success to the greatest extent possible.


ADD YOURSELF to TDEC's Harpeth River TMDL email distribution list so you can stay up to date on the TMDL development process.

CONTACT US here at the Harpeth Conservancy if you are interested in joining a stakeholder group to help develop a successful pollution reduction plan for the Harpeth River and/or if you want to receive email updates.

BECOME A CITIZEN SCIENTIST by downloading the free Water Reporter app and documenting problems you see on the Harpeth River.

A stakeholder-led TMDL that puts science and citizens first will restore the water quality and health of the Harpeth River. 

We will add to this webpage as the TMDL process moves forward, and send email updates to those who join our mailing list. 

CLICK HERE to explore resources on TMDLs in general, the Harpeth River TMDL specifically, and other stakeholder-led TMDLs across the country.