NC0020290_Other Agency Documents_20210321

Water Resources
ENVIRONMENTAL QUALITY
Ronny Tipton
Public Works Director
March 21, 2017
Town of Burnsville
PO Box 97
Burnsville, NC 28714
Subject: Pretreatment Review of Headworks Analysis
Program: Town of Burnsville; NPDES #: NCO020290
Yancey County
Dear Mr. Tipton:
ROY COOPER
Governor
MICHAEL REGAN
Secretary
S. JAY ZIMMERMAN
Director
The Pretreatment, Emergency Response and Collection Systems (PERCS) Unit of the Division of
Water Resources has reviewed the Headworks Analysis (HWA) submitted by the Town of
Burnsville. This submission was received by the Division on July 29, 2016. Additional information
was requested and was received on January 17 and 18, 2017 and again on March 17, 2017.
The Division concurs with the HWA calculations for all pollutants of concern, with corrections
discussed below. These approved Maximum Allowable Headworks Loadings (MAHL), Maximum
Allowable Industrial Loadings (MAIL), and the basis for these values are found on the last page of
the enclosed HWA spreadsheet, which has the corrections highlighted. The results of the HWA
are also listed in the bottom section of the enclosed Allocation Table.
The following observations were noted during the review of the HWA:
1) POTW and Uncontrollable Average Flows: Were updated using all DMR flow data during the
HWA timeframe of July 2015 through June 2016. The uncontrollable flow was determined by
subtracting the actual SIU flow duringthis timeframe (data from 2015 and 2016 pretreatment
annual reports- PARS) from the POTW average flow.
2) Sludge to Disposal Flow: The sludge to disposal flow in MGD was updated by using the 2015
annual residuals of 115.83 dry tons and the percent solids of 31%.
3) Stream Standards: Do not have to be entered for parameters that have a NPDES limit. The
stream standard was removed for cadmium.
4) Removal Rates:
a) Actual site specific removal rates were used for the following parameters using the STMP
results combined with any additional DMR results. There were no overallocations caused
as a result of these changes.
i) BOD and TSS: The removal rates were re -calculated using the STMP results combined
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State of North Carolina I Environmental Quality I Water Resources
1617 Mail Service Center I Raleigh, North Carolina 27699-1617
919-807-6300

with DMR results. The removal rates were reduced to 95.7% for BOD, 96.7% for TSS.
ii) Ammonia: The site specific removal rate was re -calculated using the STMP results
combined with DMR results. As the majority of the data is above detection, the site
specific removal rate of 73.4% was entered into the HWA.
iii) Cu: When using all DMR data in addition to STMP data, only 38% of the data is below
detect. The site specific removal rate of 65.5% was entered into the HWA.
iv) CN and Zn: The site specific removal rates were used as more than 50% of the data is
above detection.
b) Literature removal rate was used for Ni as 50%ofthe data is below detection. This change
resolves the over allocation as the literature removal rate of 42% shows less nickel being
"removed" into the sludge.
5) Mass Balance Spreadsheet: This spreadsheet was updated using actual SIU data in lieu of
permitted data for uncontrollable concentration determination. Data used from the second
6 months of the 2015 PAR and the first 6 months of the 2016 PAR.
6) Detection Levels: It appears that STMP detection levels are not being met for TSS, NH3 and
effluent Hg sampling. Please ensure all future STMP sampling meets the levels outlined in
the Division approved STMP.
7) Next HWA Due Date: The HWA was based primarily on 2015-2016 data. Unless conditions
at the POTW change significantly and thus warrant an earlier submittal (new NPDES renewal
for example), the POTW must submit an updated HWA on or before May 1, 2021. The next
STMP sampling will occur during calendar year 2020. Please be reminded that all STMP
effluent is required to be included on DMRs. STMP data from July 2015 and June 2016 was
not included on the DMRs. Also, the December 2015 and March 2016 DMRs did not
included data for As, Mo or Se.
Thank you for your continued cooperation with the Pretreatment Program. If you have any
questions or comment please contact Sarah Bass [email: [e-mail]] at 919-807-
6310 or Deborah Gore, Unit Supervisor at 807-6383 or via email [[e-mail]].
Sincerely,
- 41, �- "6G�^
for S. Jay Zimmerman, P.G., Director
Division of Water Resources
smb/Burnsville.hwa.03
Cc: Sarah Bass, PERCS Unit File
Linda Wiggs, Asheville Regional Office (via email)
Central Files