NC0085812_NOV-2020-LV-0405 Response_20200522

Department of Public Works
WaterMtastewater Division
4600 Goldmine Road
Monroe, NC 28110
T. 704-289-1434
F. 704-289-7395 ������#
www.unioncountync.gov
1i-'`
May 22, 2020
W. Corey Basinger,
Regional Supervisor
NCDEQ
610 East Center Avenue, Suite 301
Mooresville, NC 28115
Dear Mr. B roger,
This letter is in response to NOV-2020-LV-0405, outlining the exceedances in weekly/monthly
BOD as well as weekly TSS, experienced at our Grassy Branch WRF in March 2020.
On 3/21 the RAS line on side #2 stopped returning. For the next three days we jetted all lines
only to then determine that it was the airline that was clogged. The only way to gain access to
the clogged section was to empty the basin. Heavy rain was forecasted for 3/25, so we felt we
could not drop the basin at this time (although we did leave clarifier #2 offline to prevent the
extra solids from spilling over the weirs). On 3/25, we experienced a rainfall of 1.4" in the
collection system and the plant. This heavy rain, combined with the use of only one clarifier,
caused the exceedence in BOD and TSS. The BOD was high enough that it also caused a
monthly exceedence. After the rain storm subsided, we dropped the basin level, cut out the
clogged portion of airline, and replaced it.
If you have any further questions, please contact me.
Since ly,
Andrew Neff, PE
Water & Wastewater Division Director
Cc: Hyong Yi, Public Works Administrator
Josh Brooks, Asst. Div. Director, Water & Wastewater
Bart Farmer, WRF Superintendent
Greg Morgan, Utility Services Superintendent