In their haste to get rid of the odor caused by a sewage spill a week ago along Mary’s Creek, Fort Worth Water Department workers inadvertently used a disinfectant they shouldn’t have and killed nearly 3,200 fish in the waterway, the department disclosed Wednesday.
The fish were killed in a half-mile stretch of the creek from Southwest Loop 820 to 4016 Burkett Drive after the workers used Clear Mint disinfectant to alleviate the odor. Many residents had been complaining of eye and throat irritation from the smell, the city said.
The city created its own fish kill upstream from the overflow site, according to a letter it sent to the Texas Commission on Environmental Quality.
City staff takes full responsibility for their actions and this incident.
Bill Lundvall, Fort Worth Water Department superintendent
“City staff takes full responsibility for their actions and this incident,” Water Systems Superintendent Bill Lundvall said.
The fish kill occurred killed June 23 and was reported the same day to the state agency a day after city crews worked to contain a sewer line break along the creek that put 130,000 gallons of raw sewage in the creek.
Environmental agency spokesman Brian McGovern confirmed Wednesday that the agency is investigating the incident and “continues to monitor the situation.”
In all, 3,179 fish, nearly half of them minnows but also including perch, bass and catfish, were killed, the city said. The chemical, which contains rubbing alcohol, eventually evaporated, the city said.
Lundvall said city was trying to be proactive and followed safety procedures and materials it had from its vendor, Carroll Co., which said the product had no toxicological or ecological impacts. So the staff “deviated” from spraying the product along the creek banks and instead “deliberately discharged” 450 gallons into Mary’s Creek, the letter said.
“City staff expected the product to be environmentally safe,” the letter said. “The product is 4.4 percent isopropyl alcohol, which is not only toxic to bacteria, but also to fish.”
The Water Department said it last bought Clear Mint in 2013.
“Our intention was to have the creek bed disinfected at a slow rate and as it filtered down through the creek,” Lundvall said Wednesday.
The city has hired a contractor to replace more than 300 feet of sewer line at Mary’s Creek. That will take several weeks to complete, Water Department spokeswoman Mary Gugliuzza said. In the meantime, the line is being bypassed and crews are still pumping water from the creek until lab results say it’s safe to remove the equipment, she said.
The location of the sewer line break was in Benbrook, which uses the Fort Worth utility. The issue was first reported to the city of Benbrook and then to the state environmental agency. The agency informed Fort Worth on June 22.
Water Department officials say a 40-foot section of pipe collapsed because the creek bed was eroded by heavy rains and flooding this year. The pipe at one time was buried, but at the time of the collapse had nothing holding it up. Workers also discovered a 28-foot section missing downstream, but no sewage was discharged from it.
The Water Department put in sandbags at Winscott Road to contain the spill. The sewage had traveled about 10 miles, but it never threatened the Trinity River. Mary’s Creek enters the Clear Fork of the river.
Downstream from the spill, at Benbrook Boulevard and Mary’s Creek, E. coli counts a day after the incident reached 41,100 bacterial colonies, but that had dropped to 816 on Monday. Where the creek meets the Clear Fork, the counts went from 114 bacterial colonies last week down to 62 on Monday, far below the standard of 394 bacterial colonies that serves as the threshold for human contact.
Another round of testing will be done by Friday.