NC0087840_Permit Modification_20080812

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Ms. Peggy Bissette
Town of Middlesex
P. 0. Box 69
Middlesex, NC 27557
Dear Ms. Bissette:
Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins, Director
Division of Water Quality
August12, 2008
Subject: NPDES Permit Modification
Permit NCO087840
Nash County
The Division of Water Quality has reviewed the Town's expansion request for the Well #4 WTP. We
will like to point out that until the Town installs a dechlorination unit or takes steps to address the Total
Residual Chlorine (TRC) issues at the plant, the Division cannot grant the flow limit increase at this
time. Per our phone conversation on August 5, 2008, please put in writing all the steps the Town will
take to address the issues raised in our letter dated April 23, 2008.
If you have any questions or comments concerning this letter, you may contact me at the telephone
number [phone]
Sincerely,
9AC
Environmental Engineer
Western NPDES Program
cc: NPDES Unit
Raleigh Regional Office/Surface Water Protection Section
N �OhCarolina
Altura!!y
North Carolina Division of Water Quality t617 Mail Service Center Raleigh, INC 27699-1617 Phone [phone] Customer Service
Internet: www.ncwaterouality.org Location: 512 N. Salisbury St. Raleigh, NC 27604 Fax [phone]
An Equal Opportunity/Affirmative Action Employer— 5016 Rerycled/l DO/6 Post Consumer Paper

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Luther H. Lewis, Jr., Mayor
May 1, 2008
Mr. Agyeman Adu-Poku, Environmental Engineer
Western NPDES Permit Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
Re: Potable Water Supply Well #4
Backwash Water Dechlorination Unit
Flow Increase Engineering Alternative Analysis
Flow Increase Request
Dear Mr. Adu-Poku:
In response to your letter of April 23, 2008, please accept the following:
1. As of this writing the Town of Middlesex intends to utilize a simple tablet dechlorination system
to achieve the residual chlorine limit in our Well #4 NPDES Permit The tablets will be added to the
backwash water on top of the sand filter unit. We intend to begin using this system the very next time we
backwash. The Town has also purchased a new residual chlorine meter that is better suited for the testing
of the water samples we collect at Well #4.
2. The Town's consulting Engineer, Dr. Michael S. Acquesta, PE has submitted to you, under
separate cover, his Engineering Alternative Analysis for the Well #4 backwash water discharge.
3. The Town hereby reiterates its request for the flow rate in our NPDES Permit No. NCO087840 be
increased to 11,000 gallons per month.
4. The Town of Middlesex does hereby request that our new NPDES Permit be modified to require
sampling of the Well #4 backwash discharge only when we backwash the filters. It does not make good
sense to require a sample be collected if the filters have not been backwashed because, in that case, there
would be no discharge water to sample.
Please do not hesitate to contact me if you need additional information.
rely'
Pe sette
Town Administrator

EarthTech
ATWO lMmatmml(Id. Umoln,
April 30, 2008
Mr. Agyeman Adu-Poku, Environmental. Engineer
Western NPDBS Program
1617 Mail Service Center
Raleigh, NC 27699-1617
lot Corporate Center Drive P 919.854.6200
Suite 475 F 919.854.6259
Raleigh. NC 27607 edAhl6Ch.mm
Subject: Engineering Alternative Analysis
Additional Flow Request - NPDES Permit NCO087840
Town of Middlesex, North Carolina
Dear Mr. Adu-Poku:
s
MAY 5 2008
As the Consulting Engineer for the Town of Middlesex, I have performed an analysis of alternatives
for the discharge of filter backwash water from the Town's Well #4.
One altemative considered was the discharge of the filter backwash water into the Town's sanitary
sewer system. The subject well is situated adjacent to the Town's sanitary sewer system. The sewer
line at the well discharges into a sewer lift station with a pumping capacity of 100 gpm. Because the
filter backwash water rate is well above this rate, the existing pumps in the lift station would not be
able to keep up with the backwash flow. Also, the wetwell volume at the lift station is not adequate to
contain the total backwash flow. This lift station pumps to another lift station, again with 100 gpm
pumps. This second lift station pumps to the sanitary sewer system in the Town's central business
district. Increasing the pumping capacity at the two lift stations is not possible because of the limiting
pressure that the force mains can withstand and because any increase in pumping rate would cause an
overflow of the sewer lines in the central business district. Even if it were possible for the Town to
discharge the filter backwash water into the sanitary sewer system, the wastewater would be
ultimately pumped to the Zebulon WWTP. The Town of Middlesex would have to pay a sewer
charge for that backwash flow. Additionally, the backwash water would consume treatment capacity
that the Town owns in the Zebulon WWTP. This would not be a judicious use of the Town's limited
wastewater treatment capacity. Discussions with the City of Raleigh (who now owns and operates the
Zebulon WWTP) regarding the discharge of the backwash water into the sanitary sewer system
resulted in the Town having to apply for an industrial pretreatment permit from the City. Therefore, it
is my opinion that the discharge of the filter backwash water into the Town's sanitary sewer system is
not a feasible or cost-effective alternative.
Another alternative investigated was the containment of the backwash water in an on -site holding
tank with subsequent usage of that water for reuse purposes amund Town. This was discussed with
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EarthTech Mr. Agyeman Adu-Poke
April 30, 2008
ATyopInZMNdppall0l.ConZOtny Page 2
the Raleigh Regional Office of DWQ. The backwash water would have to be treated to reuse
standards and the holding tank would have to be located at least 100 feet away from the well head.
The Town would have to have a licensed reuse water operator available for this activity. The cost of
treating the water to reuse quality is prohibitive for the Town. Additionally, management of the water
use could potentially be difficult if users/usages of the water are not available when the holding tank.
needs to be emptied. Given these restrictions, it is my opinion that this alternative is not a feasible or
cost-effective alternative for the Town of Middlesex.
There is no available land within the vicinity of the well that would allow the Town to land apply the
backwash water. At a reasonable application rate of 0.3 inches/acre/week, the backwash flow of
11,000 gallons per month would require at least 3 acres of available land, including buffers. Because
the location of the well is in a heavily developed commercial district, there is no nearby land available
for this purpose. The cost of purchasing land and building the facilities to hold and spray the effluent
would not be cost-effective for the Town. Additionally, the Town would need a licensed land
application WWTP operator. This again would not be a cost-effective alternative for the Town.
Based upon my examidnadon of the backwash water rates and other available alternatives for the
discharge/reuse of the water, it is my considered engineering opinion that the best alternative for the
Town of Middlesex is to request a flow increase in its NPDES Peru* for this well #4 filter backwash
water and discharge the water to the ditch along the sick: of Hwy 264 Altcrnatc as it is currcntly doing.
If the Town had requested the higher flow rate when originally applying for its NPDBS Pecnut, that
higher flow rate would likely have been granted at that time. The same alterative analysis was
conducted at that time and the same opinion was rendered then.
Very truly yours,
EARTH TECH OF NORTH CAROLINA, INC.
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EarthTech
A iyca International Ltd. Company
April 30, 2008
Mr. Agyeman Adu-Poku, Environmental Engineer
Western NPDES Program
1617 Mail Service Center
Raleigh, NC 27699-1617
701 Corporate Center Drive P 919,854.6200
Suite 475 F 919.854.6259
Raleigh, NC 27607 earthtech.corn
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DEAR - Vr'AT! OUAihf
Subject: Engineering Alternative Analysis
Additional Flow Request — NPDES Permit NCO087840
Town of Middlesex, North Carolina
Dear Mr. Adu-Poku:
As the Consulting Engineer for the Town of Middlesex, I have performed an analysis of alternatives
for the discharge of filter backwash water from the Town's Well #4.
One alternative considered was the discharge of the filter backwash water into the Town's sanitary
sewer system. The subject well is situated adjacent to the Town's sanitary sewer system. The sewer
line at the well discharges into a sewer lift station with a pumping capacity of 100 gpm. Because the
filter backwash water rate is well above this rate, the existing pumps in the lift station would not be
able to keep up with the backwash flow. Also, the wetwell volume at the lift station is not adequate to
contain the total backwash flow. This lift station pumps to another lift station, again with 100 gpm
pumps. This second lift station pumps to the sanitary sewer system in the Town's central business
district. Increasing the pumping capacity at the two lift stations is not possible because of the limiting
pressure that the force mains can withstand and because any increase in pumping rate would cause an
overflow of the sewer lines in the central business district. Even if it were possible for the Town to
discharge the filter backwash water into the sanitary sewer system, the wastewater would be
ultimately pumped to the Zebulon WWTP. The Town of Middlesex would have to pay a sewer
charge for that backwash flow. Additionally, the backwash water would consume treatment capacity
that the Town owns in the Zebulon WWTP. This would not be a judicious use of the Town's limited
wastewater treatment capacity. Discussions with the City of Raleigh (who now owns and operates the
Zebulon WWTP) regarding the discharge of the backwash water into the sanitary sewer system
resulted in the Town having to apply for an industrial pretreatment permit from the City. Therefore, it
is my opinion that the discharge of the filter backwash water into the Town's sanitary sewer system is
not a feasible or cost-effective alternative.
Another alternative investigated was the containment of the backwash water in an on -site holding
tank with subsequent usage of that water for reuse purposes around Town. This was discussed with

EarthTech Mr. Agyeman Adu-Pok
April 30, 2008
A Tyco International Ltd. Company Page 2
the Raleigh Regional Office of DWQ. The backwash water would have to be treated to reuse
standards and the holding tank would have to be located at least 100 feet away from the well head.
The Town would have to have a licensed reuse water operator available for this activity. The cost of
treating the water to reuse quality is prohibitive for the Town. Additionally, management of the water
use could potentially be difficult if users/usages of the water are not available when the holding tank
needs to be emptied. Given these restrictions, it is my opinion that this alternative is not a feasible or
cost-effective alternative for the Town of Middlesex.
There is no available land within the vicinity of the well that would allow the Town to land apply the
backwash water. At a reasonable application rate of 0.3 inches/acre/week, the backwash flow of
11,000 gallons per month would require at least 3 acres of available land, including buffers. Because
the location of the well is in a heavily developed commercial district, there is no nearby land available
for this purpose. The cost of purchasing land and building the facilities to hold and spray the effluent
would not be cost-effective for the Town. Additionally, the Town would need a licensed land
application W WTP operator. This again would not be a cost-effective alternative for the Town.
Based upon my examination of the backwash water rates and other available alternatives for the
discharge/reuse of the water, it is my considered engineering opinion that the best alternative for the
Town of Middlesex is to request a flow increase in its NPDES Permit for this well #4 filter backwash
water and discharge the water to the ditch along the side of Hwy 264 Alternate as it is currently doing.
If the Town had requested the higher flow rate when originally applying for its NPDES Permit, that
higher flow rate would likely have been granted at that time. The same alternative analysis was
conducted at that time and the same opinion was rendered then.
Very truly yours,
EARTH TECH OF NORTH CAROLINA, INC.
A�_O_
Michael S. Acquesta,
Cc: Town of Middlesex
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