US Nitrogen Site

US Nitrogen produces liquid ammonium nitrate at its Pottertown Road facility in Midway. The site houses complex machinery used to produce a product that goes to parent company Austin Powder production facilities within a 400-mile radius.

Between January and October 2020, there were 129 instances at a company operating on the US Nitrogen property in Midway where a cooling tower process exceeded permitted levels.

The Linde, Inc., cooling tower emitted excess electrical conductance used as part of a carbon dioxide liquefaction process, according to the Tennessee Department of Environment and Conservation’s Division of Air Pollution Control.

Linde, Inc., logs showed the process exceeded the permitted maximum amount allowed under a permit. The violation was communicated in a Sept. 28 letter to a Linde official from Amanda Davis, manager of TDEC’s Division of Air Pollution Control in the Johnson City office.

Most Linde Inc. operating systems were found in compliance during a July 30 inspection that included a review of records and logs from 2020, when the COVID-19 pandemic prohibited regular TDEC visits to the site.

The company applied for and was granted an increase in average daily conductivity limits on Oct. 14, 2020, with no subsequent violations, Davis wrote in the letter to Terry Tyler, CO2 operations manager of Linde, which produces industrial gasses and liquid carbon dioxide on the Pottertown Road site.

No violations were found at US Nitrogen by TDEC’s Division of Water Resources in a separate letter on Sept. 28 summarizing two inspections in September 2020 and April 2021, a TDEC environmental protection specialist wrote to plant manager Dylan Charles.

Some record-keeping and flow measurement procedure issues were noted in the letter.

TDEC’s inspection findings regarding US Nitrogen are all “clerical and administrative in nature,” Charles said Wednesday in an email response to questions.


A July records review at Linde for logs kept between Jan. 30 and Oct. 14, 2020, noted that an established average daily cooling tower evaporative condenser water level rate of 803.5 microsiemens, a measure of electric conductance, was regularly exceeded.

Company cooling tower logs for a carbon dioxide liquefaction facility were reviewed and indicated there were 129 dates in 2020 when the daily average conductivity exceeded 803.5 microsiemens.

Linde successfully applied to have the limit increased to 7,100 microsiemens in its TDEC permit. Limits within the new daily average limit were not exceeded again, according to logs reviewed by TDEC after the new standard became effective on Oct. 14, 2020, the TDEC letter to Linde states.

“Therefore, no further corrective action is required,” the TDEC letter states.

TDEC noted the action did violate Tennessee Air Pollution Control Regulations.

Compliance with the Tennessee Air Quality Act helps maintain “an equitable balance between the benefits of clean air and the economic cost of achieving clean air in our state,” according to the letter.

Linde was given 20 days to respond with any additional information about the TDEC finding.


TDEC also performed a compliance evaluation inspection at US Nitrogen. Areas evaluated in the inspection included compliance with the National Pollutant Discharge Elimination System, known as NPDES, along with stormwater runoff.

US Nitrogen produces liquid ammonium nitrate, a component known as ANSOL that’s used in blasting agents. The company also makes ammonia and nitric acid in order to create ANSOL.

Water for production processes is piped in from the Nolichucky River, treated and then discharged back into the waterway.

A NPDES permit authorizes discharge of process and non-process wastewater and cooling water into the Nolichucky River.

An NPDES permit to continue the process was renewed on Feb. 1.

“Based on site observations and discussion during the inspection, existing permit coverage appears to address site operations adequately and accurately,” the TDEC letter said.

Only “a limited production area walk-through” was performed during the inspections due to social distancing concerns relating to the COVID-19 pandemic.

Some record-keeping practices needing corrective action were identified, as were deficiencies with flow measurement procedures. Discrepancies were found with US Nitrogen’s two effluent flow meters, which are rotated in and out of service, but “no records were provided to clearly document which meter was in service at any given time.”

Records examined by TDEC “revealed apparent instances of effluent flow not included in monthly Discharge Monitoring Reports” submitted to TDEC. A plant official told TDEC gaps resulted “because of recirculation of pond contents during periods of no discharge.”

No deficiencies were noted in a TDEC bio-assessment of river samples collected on Sept. 13. An additional bio-assessment must be performed between July 2023 and the NPDES permit expiration date on Jan. 31, 2025.

Accumulated stormwater in secondary containment areas within the facility production area are checked for water acidity, free chlorine residual, nitrate, ammonia and oil sheen before drainage to a retention pond near a stormwater outfall pipe. Drainage logs between 2018-2020 were reviewed. The inspection recommends “development and implementation of stormwater management controls appropriate to the facility” as part of a Best Management Practices plan.

No deficiencies were found in US Nitrogen’s stormwater pollution prevention plan.

TDEC requested that US Nitrogen develop and submit “a detailed corrective action plan” and implementation schedule by Nov. 1 addressing issues cited in the letter.


Charles said Wednesday regarding the TDEC Division of Water Resources letter, “I assure you there were no permit violations noted in (it).”

“The findings reported by TDEC are clerical and administrative in nature. None of the findings pose any threat to the environment or human health,” he said. “My staff and I are in the processes of developing the response and action plan for submittal to TDEC.”

Charles said that all TDEC findings “will be addressed in a timely manner.”

Charles said that US Nitrogen production “has continued to be strong through 2020 into 2021. We were able to maintain full employment through the unprecedented events of 2020 and continue to do so in the wake of the challenges a post-pandemic world poses.”

US Nitrogen has not started any new processes recently at the Midway facility and “production continues to be as it has been for many years,” Charles said.

US Nitrogen installed a siren system in 2018 to alert residents and industries within a 2-mile radius in the event of an emergency at the facility at 471 Pottertown Road. The complex is situated within a 500-acre plot of land and wetlands area that serves as a buffer zone to the plant’s operation.


Despite assurances from US Nitrogen management, some members of the public remain concerned about potential environmental damage to nearby waterways and from air emissions coming from the plant.

Park Overall, an environmental activist who lives near the Nolichucky River in Greene County, is critical of facility operations and the scope of TDEC oversight.

“Why does TDEC continue to enable this nitric acid plant? Why do they continue to give them waivers and extensions and allow them to experiment on the people of Mosheim, Mohawk, Midway?” Overall asked this week.

“Has TDEC forgotten they work for the people, not the industry? And why is the (federal Environmental Protection Agency) so absent when these serious violations continue unabated since 2013?”

Overall said US Nitrogen operators “keep adding ponds” on the plant site “neatly tucked away under an EPA two-year stormwater permit for now.”

Overall believes multiple environmental violations occurred at US Nitrogen in the last eight years, and that regulatory agency inspections are lax in identifying them.

“Covid is not a viable response at this point. TDEC missed the bio-assessment date,” she wrote in a Sept. 15 email to a TDEC official.