LYMAN, S.C. (WSPA) The South Carolina Department of Health and Environmental Control has determined the cause of death for dozens of fish in the Middle Tyger River last month.

DHEC said the fish kill was caused by an overflow of sodium hypochlorite (bleach) tank at the Startex-Jackson-Wellford-Duncan Water District Facility on September 17th.

A representative told 7NEWS satisfactory clean-up was completed by September 22nd. Immediate action was taken to prevent future overflows.

In a statement, released Wednesday SJWD said:

“The cause of the overflow was mechanical and human error. A hypochlorite pump did not shut off after filling the day tank. Unfortunately, there was a seal failure within the containment area that allowed the hypochlorite to flow into the basement of the building. Once the attending operator discovered the overflow the solution had flowed to the river.

After meeting with DHEC, SJWD proceeded with standard clean-up and investigation protocol. SJWD used spill containment socks, sodium bisulfite, and water to rid the parking lot of any residual.  The containment seal is being repaired and additional containment alarms are being added.”

No other fish kills have since been reported.