A sewer force main break causes wastewater to overflow and spill into the Christina River and Nonesuch Creek.
There was a force main rupture near 419 Old Airport Road in New Castle Wednesday causing the overflow.
The New Castle County Department of Public Works worked through the night Wednesday to stop the spill and repair the break of the 36-inch force main line.
They did close a valve to stop the leak, and the repair was completed around noon on Thursday.
DNREC says the break was caused by a failed weld on a 24-inch air release stack.
DNREC Division of Water and New Castle County wastewater management are assessing the creek and river in the area impacted by the spill.