-Nicole Eastman, Riverkeeper Assistant/Watershed Protection Specialist
The Mocksville Sewage Spill was identified on Tuesday, August 27th, 2024 by the Cooleemee Water Treatment Plant. Mocksville estimated 950,000 gallons of sewage were lost due to an underground pipe breaking at a pump station near Bear Creek. The Town of Mocksville reported the sewage was discharged underground and percolated to surface waters at Bear Creek. The Town of Mocksville repaired the pipe by the evening of August 27th.
A picture of the dam at the Riverpark at Cooleemee Falls on August 30th, 2024, a few days after the spill.
Yadkin Riverkeeper coordinates water sampling every Wednesday from Memorial Day to Labor Day to assess E. coli levels at river and lake access areas across the River basin. One volunteer collects a sample each week from the Riverpark at Cooleemee Falls, located downstream of the sewage spill on the South Yadkin River. He collected an additional sample from the mouth of Bear Creek where it meets the South Yadkin River and downstream at the boat ramp on Trestle Lane in Cooleemee Junction. Yadkin Riverkeeper uses the EPA’s guidelines to determine if a river site is safe for recreational use. This guideline states that if a 100mL sample of water has more than 235 E. coli colonies (cfu), it is not safe to recreate at that site. After reading the samples, two sites failed to meet this water quality guideline. Bear Creek had 248.1 cfu/100mL and Cooleemee Junction had 235.9cfu/100mL. The Riverpark located further downstream from the location of the sewage spill, met the guideline with an E. coli level of 71.7 cfu/100mL.
Yadkin Riverkeeper collects samples monthly as part of its South Yadkin Watershed Restoration Plan at two locations on the South Yadkin River, the Hannah Ferry Boat Ramp and the Cooleemee Junction Boat Ramp on Trestle Lane. Yadkin Rivekeeper had prior plans to sample at these two locations downstream of the spill on Thursday, August 29, 2024. The samples indicated passing levels for E. coli on this date. Hannah Ferry had a level of 117.8 cfu/100mL and Cooleemee Junction had a level of 110.6 cfu/100mL.
Finally, on Friday, August 30, 2024, Yadkin Riverkeeper collected a sample at the popular swimming hole, Riverpark at Cooleemee Falls to assess the E. coli level. The Riverpark had a level of 30.5 cfu/100mL indicating it was safe for recreational use.
It seems the sewage spill did not substantially increase E. coli levels a few days after the occurrence. Our main concern is the potential for groundwater contamination due to the spill occurring 6 feet underground. If the groundwater was contaminated, Yadkin Riverkeeper is unsure of how long Bear Creek and the South Yadkin Riverkeeper may have been impacted by the spill due to the hydrologic connection between groundwater and surface waters. However, we do not know if the groundwater was contaminated or if the sewage spill seeped through the soil to enter Bear Creek without contaminating groundwater.
When contamination such as a sewage spill enters a stream or river, the bacteria levels increase initially to break down the waste. Over time, bacteria levels return to normal levels when the sewage dissipates and degrades. The waste is also diluted by the river water as it moves downstream.