NC0085812_NOV-2020-LV-0025 Response_20200225

Department of Public Works
Water/Wastewater Division
4600 Goldmine Road
Monroe, NC 28110
T. 704-289-1434
F. 704-289-7395
www.unioncountync.gov
February 25, 2020
W. Corey Basinger,
Regional Supervisor
NCDEQ
610 East Center Avenue, Suite 301
Mooresville, NC 28115
Dear Mr. Corey Basinger,
_ r =, € # P_
wo � x
This letter is in response to NOD-2020-LV-0025, outlining the exceedance in monthly flow that
was experienced at our Grassy Branch WRF in December 2019. This exceedance was a result
of continuous, high rain events in the system (almost 5" in three days).
In our meeting on 05/02/2019, we detailed our efforts in reducing the I&I that is entering the
Grassy Branch collection system. Since that meeting our Collections team has continued
working to improve the system. Such efforts include:
• Smoke testing
• Camera work and jetting
• Visual inspections during rain events
• Manhole rehab
• Installation of inflow collector dishes
As stated in our last response letter, we are also wrapping up a comprehensive flow monitoring
study by Frazier Engineering. This study will give us more than 12 months of data, including
both dry and wet season flow characteristics. Once we evaluate this data, we will then start
micro -monitoring to pinpoint areas in the system that could profit from future repair/rehab efforts.
Since that last response, we have submitted a task order to keep the six flow monitors in place
for an additional six months to further evaluate the system.
In addition to the I&I reduction, we are in the process of finalizing our application package for a
Special Order by Consent as addressed in our 5/16/19 letter. We contracted with Hazen &
Sawyer Engineering to develop a stream model which has since been approved by NCDEQ.
Using this information, the engineers then designed upgrades to the facility which will alleviate
the issues causing these exceedences. These upgrades would include:
• Anew .070MGD treatment train that would bring total plant capacity to .120MGD
Cloth -disc filters
• New UV system sized for both trains
• Significant changes to the influent pump station

® New, larger blowers
We intend to continue our efforts finding and reducing the I&I in the Grassy Branch basin even
as we address the treatment/capacity issues at the Grassy Branch WRF. If you have any
questions or concerns please contact me at 704-296-4215.
Sincerely,
U& An rew Neff, P�EL4
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