WQCS00033_NOI_NOV2019DV0449_Response_20191223

CITY OF MOUNT AIRY
PUBLIC WORKS DEPARTMENT
NC Department of
Quality
1 Post Office Box 70
Airy, North Carolina 27030
nviro Received
M6nt
Phone: [phone]
DEC 2 7 2019
Fax: [phone]
Winston-Salem
.,
Regional Office
-Ari.
December 23, 2019
Mr. Lon T. Snider
-- egional.Supervisos—
Water Quality Regional Operations Section
Division of Water Resources, NCDEQ
450 West Hanes Mill Road, Suite 300
Winston-Salem, NC 27105
RE: NOV-2019-DV-0449
Incident No. 201901598
City of Mount Airy — Collection System Permit No. WQCS00033
Dear Mr. Snider:
This correspondence is in response to your letter of December 11, 2019 concerning the referenced
incident. The City of Mount Airy is committed to maintaining our sanitary sewer system in an exemplary
manner. We aggressively address every identifiable problem with the system as soon as practicable. We
rigorously follow the rules established by your agency and always report every sewer overflow as
required. Our response to the incident is as follows.
Description: On September 26, 2019 a 10-inch sewer line became stopped up, causing sewage to flow out
of the nearest upstream manhole and into a nearby small stream.
Cause of Non -Compliance: Material accumulated in the line, creating the backup. Staff originally
thought that grease, rags, and debris were the primary culprits, but after additional investigation we found
an undetermined substance in the line. This material apparently started as a type of "paste" that solidified
over time. (Please see attached picture.) This material was very dense and difficult to break through to
open up the line.
Remedial Actions: Upon discovery, City forces responded immediately to the incident. The crews
attempted to jet out the line repeatedly, workingovernight vernight and into the next day until finally able to open
the line. They tried various heads and worked continuously until the problem was resolved. Then the area
of the spill was treated with lime and the stream was inspected for environmental damage, with none
found and no recreational area closures were necessary.

Other Actions: City staff evaluated the sewage contributors to this point and could find no probable
source of the material. Therefore we came to the conclusion that it likely was a one-time dumping into the
system from an unknown person. However, we also bought a guide to keep the rotating jet head in the
center of the pipe to better address the situation should it occur again.
The City of Mount Airy has an excellent iecord maintaining the sewer system. The previous sanitary
sewer overflow was January 12, 2018, or over 20 months before this one occurred.
I hope this information is sufficient for your needs. We have enjoyed our partnership with NCDEQ and
look forward to the future as we work together to protect North Carolina's water resources.
Sincerely,
- -46-
Jeffrey M. Boyles, PE
Public Works Director