A few months back we wrote about our work to strengthen the Total Maximum Daily Load (TMDL) Revision for the Charleston Harbor, Cooper, Ashley, and Wando Rivers developed by DHEC. This work is part of our Permit Watchdog Program. Check out the details of that effort here.
A TMDL is simply a plan to restore the quality of a waterway that does not meet one or more of its water quality standards. Currently, portions of the Charleston Harbor, Cooper, Ashley, and Wando Rivers do not meet their water quality standard for dissolved oxygen (DO). Abnormally low levels of DO are known impair the ability of aquatic life to survive and reproduce. This, in turn, impacts our right to fishable and harvestable waterways.
In late May, DHEC placed two draft permits on public notice: BP Amoco Chemicals and DAK Americas, LLC. Because both discharge to the Cooper River, their draft permits included revised limits for Ultimate Oxygen Demand (UOD) based on the TMDL. UOD represents the amount of organic material in a wastewater discharge that can reduce natural in-stream levels of DO.
After researching the draft permits, TMDL, and available data, we grew concerned about the proposed UOD limits in BP and DAK Americas’ draft permits. The Clean Water Act prohibits “backsliding” or weakening permit limits except in certain limited circumstances. However, both draft permits written by DHEC propose UOD limits roughly 2 times higher than current limits.
The proposed UOD limits are derived from research and water quality modeling work completed to develop a UOD cap for the TMDL. That cap is the upper limit of the amount of UOD that can be discharged without lowering in-stream DO levels below state water quality standards. Accordingly, the proposed limits represent the maximum amount of UOD that can be discharged by BP and DAK Americas without lowering in-stream levels of DO below water quality standards.
We are particularly concerned about the limits proposed by DHEC because both BP and DAK Americas have demonstrated the ability to regularly comply with their current more strict permit limits. For example, Chart 1 shows BP’s compliance history for its monthly average UOD permit limit between July 2009 and December 2012:
DAK Americas has achieved a similar compliance history. Chart 2 shows DAK’s compliance history for its monthly average UOD permit limit between June 2008 and April 2013:
BP and DAK Americas should be commended for their ability to achieve routine compliance with their UOD limits. Accordingly, allowing UOD discharges by BP and DAK Americas up to the maximum is unnecessary.
In our comment letter, we requested DHEC perform an “antibacksliding” analysis and explain why weakening BP and DAK Americas’ permit limits is permissible under the Clean Water Act. We also requested DHEC justify why weaker permit limits are needed considering BP and DAK Americas’ routine compliance with their current more strict permit limits.
We are currently awaiting DHEC’s response. Once received, we’ll throughly consider the justification provided and determine our next steps. This work is part of our Permit Watchdog Program which regularly reviews the NPDES discharge permits in our watershed. The program is designed to provide a system of checks and balances on DHEC and permit holders.
DHEC takes public comments seriously, especially when they come from individuals like you who regularly use the waterway where a discharge is located. If you fish, SUP, kayak, or boat our local waterways, stay tuned to our Twitter and Facebook accounts. We’ll be sure to let you know when the next opportunity to comment arises. If you’re interested, we’re also available to help you through the public commenting process.