Overview
The Fish Kill - background
On July 31, officials reported that hundreds of fish had been killed and thousands more were gasping along the Elm Fork of the Trinity River (Figure 1), approximately 5 miles southeast of Lewisville, Texas, and dead fish had accumulated behind the Carrollton Dam downstream. Scientists with the Texas Commission on Environmental Quality (TCEQ) were still classifying the dead fish at the time of this report. Among the species affected were smallmouth bass, channel catfish, and white bass, along with several smaller types of fishes including darters and shiners. The cause of the fish kill is unknown and the TCEQ has been tasked with investigating the cause behind it. TCEQ officials reported that the largest concentration of dead fish was reported just north of the Carrollton Dam, where Sand Lake Road crosses the Trinity River. The fisherman that reported the fish kill to TCEQ officials stated the following: “visually the water appeared a bit darker than normal but I didn’t smell anything; the water had a thin, patchy foam on top but I didn’t see any evidence of oil floating on top of the water.” Figure 2: Dead fish found along Trinity river
Officials with the TCEQ also stated that there had been no reports of chemical spills made to the EPA Region 6 Office, TCEQ, National Response Center, local fire department, or the police. Weather information collected for July 31 reported that the temperature ranged from 70°F to 89°F, the average humidity was 73%; no precipitation was reported although it was overcast and other areas reported thunderstorms, and winds were variable from 3 mph to 16 mph. The attached map shows the Trinity River watershed in the north central portion of Carrollton, Texas, which includes the fish kill investigation area and the general location of the known different dischargers. Interstate 35E (Harry Hines Boulevard) runs from the northwest to the southeast across and east of the river. The Missouri – Kansas – Texas Railroad runs parallel to Interstate 35E. Mills Industrial Park is located about ¾ of a mile downstream of where Interstate 35 crosses the river. The Elm Creek West Water Treatment Facility is located approximately ¾ of a mile due south of Mills Industrial Park. The Sandy Sewage Disposal Plant is located on the Denton Creek tributary about ½ of a mile southwest of the Elm Creek Water Treatment Facility. The Elm Creek West Water Treatment Facility water purification process uses chemical treatment, settling, filtration, and disinfection. Water treatment chemicals including lime, ferric sulfate, chloramines (chlorine and ammonia), powdered activated carbon, polymers, ozone, carbon dioxide, and fluoride which are added to water to remove impurities, kill harmful bacteria, eliminate tastes and odors and help prevent tooth decay. The Sandy Sewage Disposal Plant began operations in December of 1959 and serves five member cities: Carrollton, Irving, Grand Prairie, Farmers Branch and a portion of western Dallas. In 1993, the plant was expanded to a capacity of 162 million gallons per day (MGD) with total secondary and tertiary treatment and the ability to treat a 2-hour peak of 335 MGD. Also, dechlorination facilities were added to meet new state and federal guidelines for the removal of chlorine to less than 0.1 mg/l. Task: Five water samples have been collected from various locations along the Trinity River in the vicinity of where the fish kill occurred. Samples were collected as follows: Sample A – collected 500 feet upstream of where the Missouri – Kansas – Texas Railroad crosses the Elm Fork Trinity River. Sample B – collected 1000 feet upstream of the confluence with Timber Creek. Sample C –collected 500 feet downstream of the road to the Mills Industrial Park. Sample D – collected 3,000 feet upstream of the Carrollton Dam. Sample E – collected 950 feet upstream of the Carrollton Dam. Task: Your job is to perform the analyses for the various physical and chemical indicators to identify the cause of the fish kill, record your data on the appended data table, identify the probable cause of the fish kill and write a formal memorandum to the Director of the TCEQ as outlined on the last page of this document (page 11) and attach to this exercise.