NC0085553_NOV/NOI-2022-LV-0329_20220602

The Village of Bald Head Island
June 2, 2022
Tom Tharrington, Asst. Regional Supervisor
Water Quality Regional Operations Section
Wilmington Regional Office
Division of Water Resources, NCDEQ
Subject:NOV Letter Response — Tracking Number NOV-2021-LV-0329
Permit No. NC0085553
Village of Bald Head Island WTP
Brunswick County
Mr. Tharrington:
The Village of Bald Head Island has received your Notice of Violation (NOV) letter, tracking
number NOV-2021-LV-0329, regarding reported exceedances of the Daily and Monthly effluent
limits associated with the Village's reverse osmosis (RO) water treatment plant (WTP)
processing. The effluent discharge at sample location 001 Effluent for March 9, 2022, daily
maximum exceeded and March 31,2022, monthly average exceeded under current NPDES
permit number NC085553. Per your letter, the Village is providing additional information to
continue the good faith efforts under way by the Village to resolve this compliance problem.
Based on previous correspondence and meetings between the Division of Water Resources
(DWR) and Village staff, I believe that you are already aware that we have been working with a
consulting team, Tony Boahn of McKim and Creed and Trevor Clements, Tetra Tech
Incorporated. The team has been in correspondence with David A. Hill, Environmental
Specialist II, of your Division's Industrial Permitting Unit and his office since the Fall of 2020 to
plan and conduct a mixing zone analysis for the WTP discharge. In February 2021 the team
submitted a Mixing Zone Analysis Report which provides a scientific basis for estimating acute
and chronic dilution ratios that would resolve the issue of periodic non-compliance with the
existing total Arsenic limit in the Village's current NPDES Permit (NC0085553). This submittal
included a request for consideration of modifying the instream waste concentrations for
toxicant limits and whole effluent toxicity requirements in the WTP's reverse osmosis
concentrate discharge.
The effort followed a Modeling Plan discussed and approved by DEQ during a virtual meeting on
November 19,2021. During that meeting, the Tetra Tech modeling team agreed to refine their
approach and documented the results as requested by David Hill. In addition, background
metals monitoring information was collected during the Spring of 2021 for DWR to conduct a
Reasonable Potential Analysis (RPA) that would support new effluent limits and monitoring
requirement decisions for specific parameters including Total Arsenic, Total Copper, and Total
Zinc.
P.O. Box 3009 BALD HEAD ISLAND, NC 28461 [phone] FAX [phone]
E-MAIL: [e-mail] WEBSITE http✓/www.villagebhi.org

David Hill indicated in a July 30 email that the DEQ Permitting Unit concurs with Tetra Tech's
recommendations for mixing zone dilution factors of 10:1 for human health and chronic criteria
and 6.5:1 for acute criteria which when applied will bring the WTP effluent discharge into
compliance.
The Village of Bald Head Island has invested monies and is working to resolve this related
reporting exceedance of Total Arsenic. The mixing zone analysis and the results indicate our
efforts to resolve the problem and the Village requests not to be fined or found in violation since
the current limits are not based on the most current and scientifically defensible information.
The current arsenic (and other toxicant) chronic limits should be multiplied by a factor of 10, and
the acute limits by a factor of 6.5, based on these decisions by the DEQ Permitting Unit and both
the Village's and DEQ's determinations of appropriate limits. Also at this time, the Village of
Bald Head Island requests your assistance in modifying the permit effluent limits, to the correct
values, if that is what is needed to stop the NOV's. This should not just be for arsenic, but for all
toxic limits and our chronic WET test should also be adjusted to a 10 percent instream waste
concentration (IWC) using ceriodaphnia or an appropriate test species.
The Village looks forward to resolving this matter. Thank you.
Sincerely,
JP Mc -Ca
JP McCann
Public Services Director
Village of Bald Head Island
P.O. Box 3009 BALD HEAD ISLAND, NC 28461 [phone] FAX [phone]
E-MAIL: [e-mail] WEBSITE http://www.villagebhi.org