A draft environmental impact study of Charlotte-Mecklenburg Utilities' proposed Long Creek sewage treatment plant is now online.
The $250 million plant would serve the county's relatively lightly-developed west side as well as the Gaston County towns of Belmont and Mount Holly.
Sewage from the Long Creek basin is now pumped 20 miles to the McAlpine Creek treatment plant in southern Mecklenburg. Lightly populated now (43,000 people), the basin is among the county's fastest-growing areas.
The environmental study done by Black & Veatch is now before the N.C. Division of Water Quality for review. The public will get a chance to comment on it before state and federal permits are issued.
The study concludes the Long Creek plant is the best of the alternatives considered. It would take less energy than pumping sewage across the county, for example, and allow for preservation of open space around the plant.
But a plant that dumps 25 million gallons a day of treated sewage into the Catawba won't be environmentally benign -- and upper Lake Wylie could feel some effects in dry-weather years, the report says.
Treatment plants discharge nutrients that can stimulate algae growth and rob oxygen from the water. Part of South Carolina's portion of Lake Wylie is already listed as impaired by phosphorus and chorophyll-a, an indicator of algae growth.
State regulators have already signaled they will set strict discharge limits on the new plant. The Black & Veatch study says concentrations of nitrogen, phosphorus and chlorophyll-a would meet N.C. and S.C. water quality standards in most years. The new plant would release slightly more nutrients than Belmont's plant does now, it says, despite being five times larger.
In drought years, though, there would be less water in the Catawba to dilute the treated sewage. In those years, phosphorus could exceed state standards in upper Lake Wylie.