NC0025526_Authorization to Construct_19950403

NPDES DOCUHENT SCANNIN` COVER SHEET
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NC0025526
Walnut Cove WWTP
NPDES Permit:
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct
(MC)
Permit Modification
Complete File - Historical
Renewal Application
Speculative Limits
Instream Assessment (67b)
Environmental Assessment (EA)
Permit
History
Document Date:
April 3, 1995
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State of North Carolina
Department of Environment,
Health and Natural Resources
Division of Environmental Management
James B. Hunt, Jr., Governor
Jonathan B. Howes, Secretary
A. Preston Howard, Jr., P.E., Director
April 3, 1995
Mr. J. David Epley
Town of Walnut Cove
PO Box 127
Walnut Cove, NC 27052
A;*A.1
C)EHNR
Subject: Permit No. NC0025526
Authorization to Construct
Town of Walnut Cove
Wastewater Treatment Facility
Stokes County
Dear Mr. Epley:
A letter of request for an Authorization to Construct was received November 1, 1994 by the
Division and final plans and specifications for the subject project have been reviewed and found to be
satisfactory. Authorization is hereby granted for expansion to 0.500 MGD with the construction of 1540
linear feet of 42 foot wide duckweed constructed wetland with a maximum depth of two feet and
windbreak berms, a separate duckweed collection basin with a floating boom and a maximum depth of
three feet, flow splitter, dual 1140 linear feet cattail constructed wetlands with a width of 63 feet and a
maximum depth of one foot, chlorine contact chamber, two chlorine gas disinfection feeds with separate
injectors, two sulfur dioxide dechlorinators with separate injectors, effluent Parshall flume with flow
monitor and all related piping and appurtenances with discharge of treated wastewater into Town Fork
Creek. In addition, construct piping to allow series or parallel flow through the two existing lagoons with
discharge piping to the head of the duckweed constructed wetland and decommission of the existing
chlorine disinfection system and effluent discharge line.
The permittee shall receive approval from the State Engineering Review Group and finish
construction of the influent pump station upgrade to include permanent backup power supply and pumps
with a two and a half times peak flow pumping capacity before the constructed wetland is put into
operation.
The bottom for the duckweed and cattail wetlands at the Walnut Cove WWTP shall be compacted
or a waterproof liner installed to meet the requirements of 15A NCAC 2H .0219 (f) for a hydralic
conductivity of no greater than 1 x 10-6 cm per second.
This Authorization to Construct is issued in accordance with Part III, Paragraph C of NPDES
Permit No. NC0025526 issued April 23, 1993, and shall be subject to revocation unless the wastewater
treatment facilities are constructed in accordance with the conditions and limitations specified in Permit No.
NC0025526.
The sludge generated from these treatment facilities must be disposed of in accordance with G.S.
143-215.1 and in a manner approved by the North Carolina Division of Environmental Management.
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/ 10% post -consumer paper

Permit No. NC0025526
Authorization to Construct
Town of Walnut Cove
April 3, 1995
Page 2
In the event that the facilities fail to perform satisfactorily, including the creation of nuisance
conditions, the Permittee shall take immediate corrective action, including those as may be required by this
Division, such as the construction of additional or replacement wastewater treatment or disposal facilities.
The Winston-Salem Regional Office, telephone number 910 771-9600, shall be notified at least
forty-eight (48) hours in advance of operation of the installed facilities so that an in -place inspection can be
made. Such notification to the regional supervisor shall be made during the normal office hours from 8:00
a.m. until 5:00 p.m. on Monday through Friday, excluding State Holidays.
Upon completion of construction and prior to operation of this permitted facility, a certification
must be received from a professional engineer certifying that the permitted facility has been installed in
accordance with the NPDES Permit, this Authorization to Construct and the approved plans and
specifications. Mail the Certification to the Permits and Engineering Unit, P.O. Box 29535, Raleigh, NC
27626-0535.
Upon classification of the facility by the Certification Commission, the Permittee shall employ a
certified wastewater treatment plant operator to be in responsible charge (ORC) of the wastewater treatment
facilities. The operator must hold a certificate of the type and grade at least equivalent to or greater than the
classification assigned to the wastewater treatment facilities by the Certification Commission. The
Permittee must also employ a certified back-up operator of the appropriate type and grade to comply with
the conditions of Title 15A, Chapter 8A, .0202. The ORC of the facility must visit each Class I facility at
least weekly and each Class II, III, and IV facility at least daily, excluding weekends and holidays, and
must properly manage and document daily operation and maintenance of the facility and must comply with
all other conditions of Title 15A, Chapter 8A, .0202.
A copy of the approved plans and specifications shall be maintained on file by the Permittee for the
life of the facility.
Failure to abide by the requirements contained in this Authorization to Construct may subject the
Permittee to an enforcement action by the Division of Environmental Management in accordance with
North Carolina General Statute 143-215.6A to 143-215.6C.
The issuance of this Authorization to Construct does not preclude the Permittee from complying
with any and all statutes, rules, regulations, or ordinances which may be imposed by other government
agencies (local, state, and federal) which have jurisdiction.
One (1) set of approved plans and specifications is being forwarded to you. If you have any
questions or need additional information, please contact Mr. Charles Alvarez, telephone number 919/733-
5083.
Sincerely,
�/
/
" A. Preston Howard, Jr., P.E.
cc: Stokes County Health Department
Winston-Salem Regional Office, Water Quality
Training and Certification Unit
ATC Files
Highland Engineering

cc: Permits and Engineering
Technical Support Branch
County Health Department
Central Files
WSRO
SOC PRIORITY PROJECT: YES X NO
IF Yes, SOC No.EMC WO 94-22 (PENDING)
To: Permits and Engineering Unit
Water Quality Section
Attention: (Charles Alvarez)
AUTHORIZATION TO CONSTRUCT
NPDES PERMIT REPORT AND RECOMMENDATIONS
Date: November 18. 1994
County: STOKES
Permit No. NC: NC0025526
PART I GENERAL INFORMATION
1. Facility Name and Current Address: Town of Walnut Cove
(facility location) (mailing address)
off NCSR 1918 P.O. Box 127
Walnut Cove, NC Walnut Cove, NC 27052
2. Date of most recent NPDES Staff Report: (attach copy) October 7, 1992
3. Changes since previous action on NPDES Permit: None
4. Verify Discharge Point(s) on plans with current NPDES Permit. List for all discharge
points.
Latitude: 36°17'36" Longitude: 80°07'47"
Attach a ' USGS map extract and indicate treatment facility site and discharge point on
map.
U.S.G.S. Quad No. B-18SW U.S.G.S. Name Walnut Cove

5. Treatment plant classification: (attach completed rating sheet) .7.E.
PART II - DESCRIPTION OF DISCHARGE AND TREATMENT WORKS
(PROVIDE THE FOLLOWING INFORMATION IF IT IS NOT ON THE PREVIOUS NPDES
STAFF REPORT)
1. Existing treatment facility:
a. What is the current permitted capacity of the facility?
192,000 gallons per day (gpd)
b. Date(s) and construction activities allowed by previous Authorizations to
Construct issued in the previous two (2) years:
Previously received an authorization to construct a wastewater treatment plant
consisting of dual sequencing batch reactors, equalization basin and ultraviolet
disinfection, but the Board of Town Commissioners abandoned plans to construct
the system.
c: What is the actual treatment capacity of the current facility (design volume)?
192,000 gpd
d. Please provide a description of existing or substantially constructed wastewater
treatment facilities.
The existing system consists of the following: 15-inch line delivering entire
sewage flow into a wetwell, pumps which convey the flow to a flow divider, an
approximately 3 acre lagoon having two floating aerators, and finally a pump
conveying the effluent to a chlorine contact tank, which chlorinates by tablet
chlorinator. Another lagoon of approximately the same size has been dewatered
and is no longer in use on the site.
2. Please provide a description of proposed wastewater treatment facilities:
The proposed wastewater treatment process is constructed wetlands. Constructed
wetlands are an aquatic farming operation, where the pollutants in the water act
as a fertilizer for growing large quantities of floating duckweed, which can be
used as food for livestock. From the existing flow divider downstream of the
existing pump station, the system is modified and equipment is added for the new
method of treatment.
From the wetwell the influent is pumped to the existing lagoon which functions
as a collection basin, holding tank, and sludge collector. The lagoon has floating

1
aerators for adding oxygen and odor control. Next the effluent flows by gravity
to Lagoon 2. Lagoon 2 also serves as a collection basin, holding tank, sludge
collector, and aeration location. Lagoon 2 will have a longer retention time than
the first lagoon. From Lagoon 2, the effluent flows by gravity to a duckweed
pond. From the duckweed pond, the effluent enters a concrete flow divider with
two weir gates to distribute flow into one of two cattail marshes. From the cattail
marshes, the effluent is disinfected in a chlorine contact tank. The effluent from
the chlorine contact tank is conveyed to a Parshall flume. The flume transmits
signals to the chlorinator and sulfinator for proportional dosing rates of chlorine
and sulfur dioxide: From the flume, the effluent is conveyed to a discharge
structure at Town Fork Creek.
3. Residuals handling and utilization/disposal scheme: According to a technical paper cited
in the Preliminary Engineering Report entitled Sludge Accumulation in Municipal Sewage
Lagoons, buildup of sludge in lagoons is typically about one foot of accumulation every
28 years. The applicant estimates the Walnut Cove lagoons will require dredging in
about 90 years. Sludge buildup around the influent pipe will be dispersed every 5 to 10
years.
a. If residuals are being land applied, please specify DEM permit no.
Residual Contractor: NA
Telephone No.
b. Residuals stabilization: PSRP _ PFRP Other
c. Landfill:
d. Other disposal/utilization scheme (Specify):
4. Important SOC, JOC or Compliance Schedule dates, if applicable: (Please indicate)
A Special Order by Consent (SOC) was drafted and signed by the Town. However, the
Town contacted the Division to advise that due to unforeseen circumstances the Town
could not meet the dates in the SOC. The Town formally requested a new SOC with the
following proposed dates:
Submission of Plans and Specifications
Begin Construction
Complete Construction
Achieve Final Compliance
December 1, 1994
August 15, 1995
December 15, 1995
September 15. 1996

PART III - EVALUATION AND RECOMMENDATIONS
We have a limited knowledge of constructed wetland wastewater treatment. From the
seminar handouts obtained from Division Seminar on constructed wetlands presented by
Tennessee Valley Authority (TVA) Staff in 1990, it appears that the advantages may
outweigh the disadvantages for this type of treatment. The greatest concern is that the
method of treatment allows the NPDES permit limits to be consistently met.
As mentioned in the TVA seminar notes, the ability of constructed wetlands to
consistently meet the ammonia -nitrogen (NH3-N) limits is questionable. According to the
TVA seminar notes, one of the investigated constructed wetlands sites (Benton) had
difficulty meeting regulatory limits for ammonia -nitrogen in the summer months. The
applicant should provide information to demonstrate that consistent
nitrification/denitrification effluent quality will be maintained.
Also, the applicant should determine if the system requires liners to protect the
groundwater. This office recommends that the authorization to construct this project be
issued upon receipt of adequate response to the concerns previously stated.
1/iltiljfliK--
Signature oreport preparer
-.1/19
Water Quality Supervi
y --/ - 95‘
Date