NC0020184_Staff Comments_20211213

NC-0021018y
Gastonia/TRU - background on nutrient limits
Yitbarek, Diana <[e-mail]>
Mon 12/13/2021 10:54
To: Templeton, Mike <[e-mail]>
Cc: Montebello, Michael J <[e-mail]>
Bcc: on tuvia <[e-mail]>
Mike - Thanks for the nutrient limits summary. This helped me finish drafting and concluding
decisions with my supervisor. Both permits were issued on 12/1/2021. To document the final
decisions on nutrients, below, I highlighted the reasons why NC DEQ converted the nutrient's limit
concentration to mass limits. To provide context, MikeM and I considered adding limits
concentrations back to be more stringent. The data trends showed concentrations for TN and TP up
to 13 mg/I and 1.3 mg/I for Long Creek and up to 33 mg/I and 3.5 mg/I for Eagle Road; when the
recommended TN and TP by the TMDL were 6.0 mg/I and 1.0 mg/I. But after reading your summary
(noting that the combined discharge meets the concentration limits and per the 1995 Lake Wylie
TMDL mass limits are acceptable, and we do not need to follow the recommended concentration
limits as written, MikeM considered that 1. He did not want to change the direction at this point, and
2. since no effluent limitations were less stringent than the immediate previous permit/At the
expiration of the permit, there were no TP and TN concentration limits in effect; therefore, there
was not antibacksliding.
MikeM recommended opening the discussion in the future when/if Permittees request to remove
nutrients concentration limit and consider maintaining the nutrient concentration limit whenever
possible.
Thank you all for your time with this permit renewal.
From: Templeton, Mike <[e-mail]>
Sent: Wednesday, November 24, 2021 15:58
To: Yitbarek, Diana <diana.yitbarek@ncdenrgov>; on tuvia <[e-mail]>
Subject: Gastonia/TRU - background on nutrient limits
Sorry, I meant for this to be a quick file check; but I had to dig more digging than I expected.
Here is some background info on the Gastonia (and other) permits. Some I found in the files, some in my memory
banks:
The Long Creek permit that preceded the 2017 permit was issued in Feb 2010. It expired Jan 2015 and was
administratively extended. That 2010 permit had 6 & 1 limits for TN &TR
A lot was going on with the Lake Wylie dischargers during this time. After Long Creek's 2010 permit was issued,
Gastonia asked us to make several changes in their nutrient requirements: add allocations for small facilities it
had connected, combine the TN & TP limits at Long Creek and Eagle Road, etc. (The attached emails are a
sampling of those on -going discussions.) Some of the changes they asked for would require a switch to mass
limits.
At the same time, Charlotte was planning a new facility on the Catawba.*** They would treat Belmont's and
Mount Holly's wastes in return for their N&P allocations, and those transfers also required a switch to mass
limits. So we calculated new limits for all facilities affected by the TMDL and have now included them in the
affected permits. (See the attached spreadsheet.) The Jan 2017 Fact Sheet for Long Creek (also attached)
summarizes the new approach.
I also found some performance data for 2015-2020 for Long Creek, for Eagle Road, and for the two discharges
combined. My rough calculations look like this:
Average TN (mg/L) Avg TP (mg/1)

Discharge
Summer
Winter
Annual
Eagle Road WWTP
22-27
20-25
0.46-1.40
Long Creek WWTP
3.0-5.4
5.6-10.3
0.20-0.5
Combined
5.4-6.1
7.1-11.5
0.20-0.5
As we discussed, Eagle Road doesn't have much capacity to remove nutrients, but Long Creek does pretty well.
Since most of the flow comes from the Long Creek plant, the combined discharge should meet its TN & TP limits
pretty easily.
Mike M makes a good point about anti -backsliding, and the numbers indicate that Long Creek can and has readily
met 6 & 1 concentration limits since their 2010 permit. At the same time, our discussions over the past several
years with the Lake Wylie permittees have focused entirely on mass limits, which are also acceptable under the
TMDL. Restoring the concentration limits at this point would be an unexpected change in direction, and we can
expect the City to have some objections, especially since Charlotte's permit has only mass N & P limits.
Let me know if you want to discuss this any further.
I hope you have a great Thanksgiving and enjoy the long weekend!
—MikeT
*** Charlotte's new plant was originally named Long Creek but is now the Joe Stowe Regional WWTP. You might
still come across references to the old name, so don't confuse it with Gastonia's plant.