US Nitrogen Violated Permit Conditions

By Walter F. Roche Jr.

US Nitrogen violated the terms of one of its state permit for six days in a row due to an overflow in one of its retention ponds, the company has reported.
In a letter sent Monday to the Tennessee Department of Environment and Conservation, US Nitrogen Plant Manager Dylan Charles said the overflows started on Feb. 20 and continued for the next six days, ending on the date of the letter. He said the company was not yet sure of how to prevent a recurrence.
Charles told TDEC the overflows were first discovered at 1:30 a.m. on Feb. 20 and lasted until 2:15 p.m. on Monday.
He said the overflows in the North Retention Pond were triggered by "days of excessive rain."
He wrote that the company recorded the levels of ammonia and nitrates in the retention pond on the days of the overflows. The ammonia levels recorded ranged from 5.2 parts per million to 8.5 parts per million.
The levels of nitrates in the spillover water ranged from 8.4 parts per million to a high of 11 parts per million. The pH level (a measure of acidity) of the spillover water ranged from 7.46 to 7.87.
"The routine operation of the the retention pond is to keep the level low, approximately 15 to 20 percent, to reduce the the occurrence of a non-complying discharge," Charles wrote in the letter to Brian Carter of TDEC.
He added that the company monitors the weather and the retention pond levels several times per day "to ensure the pond has sufficient freeboard for rain events."
He said that normally the company pumps liquid from the retention pond to the raw water pond "for re-use or to the effluent ponds for discharge to Outfall 001."
He added that during the recent overflows "the water was being pumped continuously to reduce the amount of un-permitted flow."
But, he wrote, the company's permit limits the amount of retention pond water that can be transported to the effluent ponds.
"Furthermore, the amount of stormwater that was entering the retention pond was in excess of the amount of water that could be transported to the effluent or raw water ponds due to pipe and pump limitation," Charles wrote.
He said the company was "evaluating options to re-direct the stormwater runoff from outside the production area away from the retention pond."