WQ0007208_Application (FTSE)_20210607

Attn: Ms. Christyn L. Fertenbaugh, PE
Environmental Engineer
RE: Village of Cofield — Sanitary Sewer Rehabilitation Project
Hertford County
Dear Ms. Fertenbaugh,
MUNICIPAL ENGINEERING
SERVICES COMPANY, P.A.
&gineering &ellence.•/nnovakbe Appr lies/Sustainable Solutions
NEE
June 7, 2021
North Carolina Department of Environmental Quality
Division of Water Resources
Municipal Permitting Unit
512 N. Salisbury Street, Rm 925S
Raleigh, NC 27604 JUN 0 9 202i
NCDEQDWWNPDES
RECEIVED
This letter is in response to your email dated July 29, 2020, requesting additional information for
the variance request for the equalization tank as part of the Village's Sanitary Sewer
Rehabilitation Project. We have addressed all of your comments with the responses listed below
in bold:
1. Please provide a complete set of revised, final plans, specifications, calculations, and
supplementary documentation per the comments below via email in PDF format for our
records.
The plans and specifications have been revised based on your comments and included
in pdf format for your review and approval, along with this cover letter.
2. In accordance with 15A NCAC 02T.0105 and GS 143-215.1, any extensions to the sewer
system must be covered under a permit: Please provide a permit application with fee for the
permitting of this EQ tank and associated sewer line/appurtenances. We recommend using
the SSEA application form found on our website here, as this project is not Fast Track
eligible. This should be submitted in hard copy format to my attention at the address listed in
my signature block
The requested SSEA application and fee are included in this revised submittal package.
a. Please confirm which pump station this EQ tank will be located at, as well as the
permit number for that pump station — it appears that PS No. 1 is the station at which
it is proposed to be installed. We recommend modifying the existing pump station
permit to add this EQ tank.
MESCO.COM
License No. C-0281
GARNER PH: [phone]
BOONE PH: [phone]
68 SHIPWASH DR., GARNER, NC 27529 GARNER Fx: [phone]
820 STATE FARM RD., BOONE, NC 28607 BOONE Fx: [phone]

Town of Cofield
San. Sewer Modifications
Page No. 2
The EQ tank will be located at Pump Station 1. Its permit number is
WQ0007208, according to the Washington Regional Office. The Town has
unable to locate their copy of the permit.
3. Please provide clarification as to the usage of this EQ tank as bypasses of the existing
collection system during normal operations are prohibited in accordance with 15A NCAC
02T.0305(d). As an alternative design, EQ tanks in the collection system should generally
only be utilized to mitigate wet weather flows for the purposes of reducing SSOs or other
environmental issues.
Please note that the proposed tank is not a by-pass of the collection system. The
purpose of constructing the 40,000-gallon equalization/surge tank is because the
Village's existing sewer contract with Winton has an excessive surcharge on volumes
greater than 40,000 gpd daily instead of averaging the flow over the month. This
proposed improvement will save the Village money by shaving the peak off of flow
days greater than 40,000 gallons, caused by I/I from wet weather events. Suppose the
wet weather flow exceeds the capability of the tank. In that case, the system will
automatically revert back to its current operating state, and the Town will absorb the
surcharge from the Town of Winton.
a. Please also provide specific information as to how the proposed design meets the
criteria as outlined in 15A NCAC 02T.0105(n).
1. The proposed design better uses the Village's limited financial resources by
reducing the likelihood of a surcharge fee for exceeding the daily volume
threshold providing equal or better treatment of the waste.
2. The proposed design provides additional storage capacity in the sanitary
sewer collection system, reducing the chance of an overflow event.
3. The proposed design is entirely within the Town's property, which is located
far enough away from homes and businesses, so there will be no increase in
nuisance conditions from noise, odor, and or vermin.
4. In accordance with 15A NCAC 02T.0305(b)(2) and 15A NCAC 02T.0105(n), please provide
calculations in support of the following information. All calculations must be signed/sealed
by a Professional Engineer licensed to practice in North Carolina:
a. Demonstrating the rate of filling/draining the tank under normal and wet
weather conditions, including the expected length of storage of the wastewater
as well as if the existing pump station can convey the added flow from draining
the tank
The pump station will continue to operate as it does now unless the total
flow for the day (8:00 AM) reaches 40,000-GPD. Once the limit is reached,
the PLC control will divert flow to the EQ tank for the remainder of the

Town of Cofield
San. Sewer Modifications
Page No. 3
day. (Please refer to the "System Operation" Narrative on sheet C-3 of the
plans.") Should the tank fill at any point, the high water valve will open
and allow the flow back to the pump station wet -well. Should the automatic
controls fail, the tank has an overflow that diverts the flow back to the wet
well.
b. Calculations/modeling depicting the dry and wet weather flows of the collection
system demonstrating the need for this EQ tank as well as supporting how the sizing
of this tank was determined
Dry and wet weather modeling information is not available for this part of the
sanitary sewer collection system. The design and size of the tank is based on the
volume of the existing sanitary treatment contract with Winton. The tank was
sized to handle
i. What type/level of wet weather flows is the tank designed to handle?
The design and size of the tank is based on the volume of the existing sanitary
treatment contract with Winton, of 40,000-gallons. The 40,000-gallon tank is
also approximately 87% of the design's average daily flow rate of 46,800-
GPM.
b. Verifying that the tank can be filled with the existing pumps, in terms of flow and
TDH as well as any other factors that may affect tank filling. If the pumps shall be
replaced or if pumps shall be added, please clam.
The existing pumps will be able to fill the EQ tank. A partially closed valve will
create an artificial increase in the head to create a similar condition as the
existing force main condition. The pumps will operate under the same TDH
conditions for the EQ tank as for the existing force main.
c. Evaluating the flow volumes of the overflow line versus the influent pumps, and how
the overflow line will prevent SSOs at the tank
The existing pumps at the pump station can adequately handle the current flows
in the system. The tank's purpose is to reduce the daily peak flows under 40,000
gallons, so the Village does not incur an expensive surcharge fee on their sewage
treatment contract. The overflow line will drain back into the wet well to
prevent an overflow at the tank.
5. As the new manhole indicated to contain the valve which will direct flow from the existing
system to the EQ tank, is past the intercept point for the EQ line, it appears that there is the
potential for increased water hammer at this valve. Please provide more information about
how this valve will be protected from premature failure, corrosion, and/or damage, per 15A
NCAC 02T.0105(n).

Town of Cofield
San. Sewer Modifications
Page No. 4
I believe the manhole you refer to is to be installed on the line before the flow meter on
the force main goes to the Town of Winton. This valve aims to stop the flow to Winton
and divert it to the tank or vise -versa. The valve will be installed within the manhole
with the motorized control actuator above ground. The force main and valve will be
painted ductile iron, similar to the plug and check valves installed in the valve box aft
of the pumps. The valves will open and close slowly enough and lack sufficient head to
cause water -hammer.
6. Please provide complete profile views for the drainage lines for the tanks, indicating that an
appropriate slope is provided for gravity drainage back to the pump station wet well, per
15A NCAC 02T.0305(b)(1).
All of the new piping shown is considered pressure main, not gravity. The pressure will
either be from the pumps or the head pressure within the tank. These pipes are shown
on Drawing C-2 at 3'-0" minimum bury.
a. Please also provide additional information for the secondary drainage line that is
indicated to be used for solids removal, as it's not clear that this line will not be
affected by clogging due to primarily carrying solids, per 15A NCAC 02T.0105(n).
The purpose of this valve is for occasional maintenance should solids
accumulate in the bottom of the tank.
7. In the provided specifications, the leakage formula provided appears to be based on the
number of joints and is not in accordance with the Minimum Design Criteria. Please revise.
The leakage calculation formula has been revised as requested.
If you have any questions during your review, please do not hesitate to contact me. If you feel it
would be beneficial to meet to discuss your question in person, we will be happy to do so.
Sincerely,
MUNICIPAL ENGINEERING SERVICES CO., PA
Michael L. McAllister
Principal Project Manager
Cc: Ben Clawson, PE