NC0026051_Authorization to Construct_19991210

State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Kerr T. Stevens, Director
December 10, 1999
Mr. Chuck Hill
County of Durham
120 East Parrish Street, Law Building, Suite 100
Durham, North Carolina 27701
Dear Mr. Hill:
NCDENR
Subject: Authorization to Construct
ATC No. 026051ACE
NPDES Permit No. NCO026051
Triangle WWTP
Durham County
The Division of Water Quality's NPDES Unit has reviewed Durham County's request for an
Authorization to Construct at the Triangle WWTP. The Division finds the proposed improvements and
design to be satisfactory and hereby grants authorization for the following:
• construction and installation of a post -aeration system and all related structures,
piping, monitoring systems and controls, and other appurtenances as specified in the
design documents.
Completion of these improvements does not affect the approved treatment capacity of the facility, which
remains at 6.0 MGD.
This Authorization to Construct is issued in accordance with Part Ell, Paragraph A of NPDES Permit No.
NCO026051 issued March 4, 1996, and shall be subject to revocation unless the wastewater treatment
facilities are constructed in accordance with the conditions and limitations specified in Permit No.
NCO026051.
Additional Conditions
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 Permittee shall notify the Raleigh Regional Office, telephone number [phone], 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 of 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 the modified facility, the Permittee shall
provide the Division with a certification from a professional engineer certifying that the permitted facility
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer Internet: http://h2o.enr.state.nc.us/

County of Durham - Triangle W WTP
NPDES Permit No. NC0026051
ATC No. 026051ACE
Page 2
has been installed in accordance with the NPDES Permit, this Authorization to Construct, and the
approved plans and specifications. Mail the Certification to the NPDES Unit, 1617 Mail Service Center,
Raleigh, North Carolina 27699-1617
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 8G, .0200. 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 comply with all other conditions of Title 15A, Chapter 8G, .0200.
The Operational Agreement between the Permittee and the Environmental Management Commission is
incorporated herein by reference and is a condition of this Permit. Noncompliance with the terms of the
Operational Agreement shall subject the Permittee to all sanctions provided by G. S. 143-215.6 for
violation of or failure to act in accordance with the terms and conditions of this Permit.
Failure to abide by the requirements contained in this Authorization to Construct may subject the
Permittee to an enforcement action by the Division of Water Quality 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.
The Permittee shall maintain a copy of the approved plans and specifications on file for the life of the
facility. One (1) copy of the approved plans and specifications is enclosed for your records.
If you have any questions about this Authorization to Construct, please contact Mike Templeton, at (919)
733-5083, extension 541.
Sincerely,
Kerr T. Stevens
Director
Enclosures: Project Plans and Specifications
Engineer's Certification Form
cc: Mr. Ron Ketteman, ORC, Triangle WWTP
Mr. David Duty, Pete Duty & Associates (w/ certification form)
Raleigh Regional Office, Water Quality
Technical Assistance and Certification Unit
Central Files
NPDES Unit Files

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NCDENR Division of Water Quality
Water Quality Section
Raleigh Regional Office
Interoffice Memo
To: Mike Templeton, NPDES Unit
From: Tim Baldwm�t�%2��rg%ylG*�
Environmental ngmee- O
Through: Ken Schuster, P.E.
Water Quality Sup sor - RRO
Randy Jones n /
Environmental Engineer - RRO � Quit✓
Re: Durham Triangle WWTP ATC Staff Report
Permit No. NCO026051
ATC No. 026051ACE
Durham County
Date: November 5, 1999
The Raleigh Regional Office received a request for an ATC permit for Durham Triangle WWTP
on June 22, 1999. The Raleigh Regional Office submitted a staff report to the NPDES Unit on
August 5, 1999, stating that the submittal was incomplete and that we could not provide a
recommendation until further information was received. Additional information was received by
this office on October 19, 1999.
This memo is serving as a Staff Report Modification/Addendum for the revised ATC request.
The Staff Report for the original project, which was dated August 5, 1999, is included with this
memo. All of the information from the August 5, 1999, Staff Report is still current, except for
those specifically numbered comments provided in this memo.
Part IV Evaluation and Recommendations
The Raleigh Regional Office has reviewed the current submittal package
requesting an ATC for reconstruction of the Effluent Reaeration System for the
Durham Triangle WWTP. Our staff has reviewed our files of the above
referenced site, as well as the plans and specifications submitted, in order to make
the following comments and recommendations for the request.

Durham Triangle W WTP Staff Report Modification/Addendum
Permit No. NC0026051
ATC No. 026051 ACE
November 5, 1999
Page 2
The diffuser system utilizes rubber membranes, which require occasional
maintenance and replacement. However, they are fixed to the bottom of the
common channel of the sand filters, for which we are unaware of any way of
bypassing without bypassing the sand filters completely (which we only assume is
possible). This situation can lead to maintenance difficulties in the future.
Possible solutions would be to use a diffuser which requires less maintenance
such as a stainless steel course -bubble diffuser, placing them in a different
location that can be taken off line occasionally without bypassing a major
treatment unit, or to put the diffusers on flexible hoses and have the ability to pull
the diffuser assemblies out of the basin for maintenance and replacement.
The RRO recommends that the subject project be awarded an ATC once the
above issue, and any additional requirements, are addressed to the satisfaction of
the NPDES Unit. Please provide this office with copies of any further
correspondence on this project.

STAFF REPORT AND RECOMMENDATIONS
FOR AUTHORIZATION TO CONSTRUCT A BLOWER AND DIFFUSER
SYSTEM FOR INCREASING THE DISSOLVED OXYGEN IN THE FINAL
EFFLUENT AT THE DURHAM TRIANGLE WWTP
SOC PRIORITY PROJECT: Yes _ No X
If Yes, SOC No.:
Date: August 5,1999
To: NPDES Unit
Attention: Mike Templeton
County: Durham
Permit No.: NCO026051
ATC Permit No.: 026051ACE
PART I -GENERAL INFORMATION
1. Facility and Address: Triangle WWTP
NC Highway 55 and NCSR 2028
West of RTP
Durham County
2. Report Prepared by: Timothy D. Baldwin
3. Date of most recent NPDES Staff Report (attach copy): November 29, 1995
4. Changes since previous action on NPDES Permit: ATC Permit No. 026051ACD issued for
construction of a barscreen bypass.
5. Discharge Point(s), list for all discharge points:
Latitude: 35° 52' 50" Longitude: 78° 53' 50"
Attach a USGS map extract and indicate treatment facility site and discharge point on map.
U.S.G.S. Quad No.: D23NW U.S.G.S. Quad Name: Southwest Durham, NC
Non -Discharge Staff Report
Page I

6. Treatment plant classification (attach completed rating sheet): IV((;raljG
PROVIDE ADDITIONAL INFORMATION FOR PARTS I, II, AND III ONLY IF IT IS Q
NOT PROVIDED IN ATTACHED STAFF REPORT
7. Date of Investigation:
8. Persons Contacted and Telephone Number:
9. Directions to Site:
10. Site size and expansion area consistent with application? Yes: _ No:
If No, explain:
11. Topography (relationship to flood plain included):
12. Location of nearest dwelling:
13. Receiving stream or affected surface waters:
a. Classification:
b. River Basin and Subbasin No.:
C. Describe receiving stream features and pertinent downstream uses:
PART II - DESCRIPTION OF DISCHARGE AND TREATMENT WORKS
a. Volume of Wastewater to be permitted:
b. What is the current permitted capacity of the Waste Water Treatment facility?
Actual treatment capacity of the current facility (current design capacity)?
d. Date(s) and construction activities allowed by previous Authorization to Construct
issued in the previous two years: ATC Permit No. 026051ACD for a barscreen
bypass issued February 10,1999.
e. Please provide a description of existing or substantially constructed wastewater
treatment facilities:
f. Please provide a description of proposed wastewater treatment facilities: Installation
of a blower and diffuser piping to increase the final effluent dissolved oxygen.
Non -Discharge Staff Report
Page 2

g. Possible toxic impacts to surface waters:
h. Pretreatment Program (POTWs only):
in development: _ approved:
should be required: _ not needed:
2. Residuals handling and utilization/disposal scheme:
a. If residuals are being land applied, please specify DWQ permit no.:
Residual Contractor:
Telephone No.:
b. Residuals stabilization: PSRP: _ PFRP:
Other:
C. Landfill:
d. Other disposal/utilization scheme (Specify):
3. SIC Code(s):
4. Wastewater Code(s) of actual wastewater, not particular facilities i.e.., non -contact cooling
water discharge from a metal plating company would be 14, not 56. Include more than one
code if applicable:
5. Main Treatment Unit Code:
PART III - OTHER PERTINENT INFORMATION
1. Is this facility being constructed with Construction Grant Funds or are
any public monies involved. (municipals only)? No
2. Special monitoring or limitations (including toxicity) requests:
3. Important SOC, JOC or Compliance Schedule dates: (Please indicate)
Pate
Submission of Plans and Specifications
Begin Construction
Complete Construction
Non -Discharge Staff Report
Page 3

4. Alternative Analysis Evaluation: Has the facility evaluated all of the non -discharge options
available? Please provide regional perspective for each option evaluated.
Spray Irrigation:
Connection to Regional Sewer System:
Subsurface:
Other disposal options:
Other Special Items:
PART IV - EVALUATION AND RECOMMENDATIONS
The Raleigh Regional Office has reviewed the current submittal package requesting
Authorization to Construct (ATC) a blower and diffuser system to increase the dissolved
oxygen level in the final effluent at the Durham County Triangle WWTP facility. Our staff
has reviewed our files of the above referenced site, as well as the plans and specifications
submitted, in order to make the following comments and recommendations for the request.
The information which this office received as a submittal for our comments on the proposed
addition of a blower and diffuser system for increasing the dissolved oxygen in the final
effluent is incomplete. There was no information showing where this was going to be installed
in the plant. We were therefore not able to provide any opinion on how well it relates to the
other processes of the plant, whether it will interfere with any other devices such as the final
sampler or effluent flow measuring device, or whether it will be possible to take whatever tank
or structure the diffusers are proposed to be installed in off line to clean or replace the
diffusers without disrupting the flow of wastewater through the facility. Without any detailed,
specific information, this office is unable to provide an opinion on the proposed construction
project.
Non -Discharge Staff Report
Page 4

Based on the above, the RRO recommends that the subject project NOT be awarded an ATC
as requested, until the necessary information is submitted for review. The RRO requests that
we be copied on any future correspondence pertaining to the ATC request, as well as the
chance to provide a revised staff report once we are able to review any additional information.
Signature of/ep6rt preparer
VI �MTv z
vc� Water Quality Regional Supervisor Da
Permit No. NC0026051
ATC No. 026051 ACE
File: h:\atc-sr\ac26051e.sr
Non -Discharge Staff Report
Page 5

To: Permits and Engineering Unit
Water Quality Section
Attention: Dave Goodrich
(formerly assigned to Dana Bolden)
Date November 29, 1995
NPDES RENEWAL STAFF REPORT AND RECOMMENDATION
County Durham
Permit No. NC0026051
PART I - GENERAL INFORMATION
1. Facility and Address:Durham Co. Triangle Plant
County of Durham
Durham County Courthouse
300 West Main Street - Seventh Floor
Durham, N.C. 27701
2. Date of Investigation:November 14, 1995
3. Report Prepared by: Babette McKemie, P.E.
4. Persons Contacted and Telephone Number: 919/560-7999
5. Directions to Site:I 40 to Hwy 55 exit, cross 54 site is 2
miles on the right at SR 2028
6. Discharge Point(s), List for all discharge points:
Latitude: 35052'51" Longitude:78°53'S0"
Attach a USGS map extract and indicate treatment facility
site and discharge point on map.
U.S.G.S. Quad No. D23NW U.S.G.S. Quad Name Southwest
Durham
7. Site size and expansion area consistent with application ?
X_ Yes No If No, explain:
8. Topography (relationship to flood plain included): flat,
influent pump station and effluent discharge prone to floods
9. Location of nearest dwelling:none within 400 feet
10. Receiving stream or affected surface waters:Northeast Creek
a. Classification:WS IV NSW
b. River Basin and Subbasin No.:03-06:05
C. Describe receiving stream features and pertinent
downstream uses:Lake Jordan

If Yes, SOC No.
PART II - DESCRIPTION OF DISCHARGE AND TREATMENT WORKS
1, a. Volume of Wastewater to be permitted: 6.0 MGD (Ultimate
Design Capacity)
b. What is the current permitted capacity of the Waste
Water Treatment facility? 6.0 MGD
C. Actual treatment capacity of the current facility
(current design capacity)? 6.0 MGD
d. Date(s) and construction activities allowed by previous
Authorization to Construct issued in the previous two years:
none
e. Please provide a description of existing or
substantially constructed wastewater treatment facilities:
bar screen, grit removal at the influent pump station dual
train extended aeration, clarifier, chlorination and
tertiary filters
f. Please provide a description of proposed wastewater
treatment facilities: none
g. Possible toxic impacts to surface waters: Chlorine,
metals, organics
h. Pretreatment Program (POTWs only):
in development approved X
should be required not needed
2. Residuals handling and utilization/disposal scheme:
a. If residuals are being land applied, please specify DEM
permit no. WQ0007989
b. Residuals stabilization: PSRP X
PFRP Other
c. Landfill:
d. Other disposal/utilization scheme (Specify):
3. Treatment plant classification (attach completed rating
sheet):IV - no change
4. SIC Code(s):4952
Wastewater Code(s) of actual wastewater, not particular
facilities i.e.., non -contact cooling water discharge from a
metal plating company would be 14, not 56.
Primary 01_ Secondary 59, 57, 79, 33
Main Treatment Unit Code: 051-3

SOC PRIORI PROJECT: Yes No ,
If Yes, SOC No. _ V"
0
PART III - OTHER PERTINENT INFORMATION
1. Is this facility being constructed with Construction Grant
Funds or are any public monies involved. (municipals only)?
N/A
2. Special monitoring or limitations (including toxicity)
requests: Request Cd and Ag be removed from permit, not detected
in past 12 months. County requests 1 year phasing in of organic
limits. The RRO recommends monitoring to begin with issuance and
limits to become effective 1 year after issuance.
3. Important SOC, JOC or Compliance Schedule dates: (Please
indicate)none
Submission of Plans and Specifications Date
Begin Construction
Complete Construction
4. Alternative Analysis Evaluation: Has the facility evaluated
all of the non -discharge options available. Please provide
regional perspective for each option evaluated.no alternatives
PART IV - EVALUATION AND RECOMMENDATIONS
The RRO has reviewed the package submitted for renewal of
the NPDES permit and the WLA. The WLA indicates that limits for
several organics will be included with this renewal. The County
requests a 1 year phasing in of the limits in order to have time
to find the source and reissue pretreatment permits. The RRO
agrees that this is reasonable, however, monitoring can begin
with permit issuance. Additionally, the County submitted a disc.
with all monitoring for the past 12 months. This disc was unable
to accept the "<" sign. Values for Ag and Cd that were actually
< 5 (detection limit) were reported as 5 on the disc. Therefore,
there was no reportable Ag or Cd in the past 12 months and these
parameters should be removed from the permit.
The RRO recommends that the permit be renewed for a period
Of five (5) years.
46ignature o report preparer
H:\NC26051.SR

ATC SUMMARY County of Durham - Triangle WWTP
ATC No. 026051ACE
Northeast Creek, Class WS-IV NSW
Cape Fear River Basin, 030605
Durham County
SCOPE
The County of Durham proposes to install a post -aeration system at its Triangle WWTP. The stated intent of
the system is to ensure that effluent D.O. levels consistently meet the 6.0 mg1L permit limit for the plant.
RECOMMENDATIONS
Approve the ATC request, as revised.
REVIEW SUMMARY
General
Durham County owns and contract -operates the 6.0 MGD Triangle WWTP. The County has reported several
permit violations at the plant over the last two years (including Hurricane Floyd in September of this year).
DMRs show violations of monthly limits: 4 for flow, 3 for BOD5, and 2 for NH3. There are additional
violations for pH and for VOCs, the latter being the focus of a 1997 SOC for the plant.
The County proposes to add post -aeration downstream of its tertiary filters in order to improve compliance
with its D.O. limit. The project will consist of a single blower adjacent to the existing tertiary filters and a
new header and fine bubble diffusers across the length of the filter effluent channel (approx. 43 ft.).
Desien Issues
Key issues with the original design (from NPDES and RRO reviews) were:
I. Access to the header and diffusers is limited but will be needed for routine maintenance. The existing
effluent channel for the filters is fully enclosed, with a reinforced concrete roof and one 2 ft. X 4 ft.
access hatch. The air header will be fixed to the channel floor and is not designed with quick removal in
mind.
Outcome: Any necessary repairs (such as diffuser replacement) will be handled using "confined space" entry
procedures. This should present minimal problems as (1) the membrane diffusers are expected to have
an operating life of 5-7 years (in aeration basin conditions) and (2) the system would continue to
perform reasonably well even if several membranes fail, so that immediate repairs are not critical.
Further, the future of the plant may be limited, because the County is considering replacing the plant
or redirecting flow to Durham's Farrington Road plant.
2. The design calculations for the system use an average flow of 4.0 MGD; the peak monthly flow for last
12 months (excluding Sep99) was 5.4 MGD.
Outcome: The design engineer (Dave Duty) indicated that the design uses 4.0 MGD as a long-term average and
includes other assumptions that keep it conservative. He will review the assumptions and calculations
and submit a copy to verify the air capacity is sufficient.
end -

ATC REVIEW NOTES
INITIAL SUBMITTAL
County of Durham - Triangle WWTP
ATC No. 026051ACE
1. Design package is incomplete: includes generic equipment drawings for new aeration header but no
drawings showing its placement in the existing WWTP. RRO made same comment.
Outcome: These were provided in September, and plant operators and consultants provided additional
information in telephone discussions.
REVISED SUBMITTAL (received 11/17/99)
1. Header is in fixed mount, not readily accessible for routine replacement of diffusers, etc. RRO suggests
SS diffusers for reduced maintenance needs.
Outcome: Any necessary repairs (such as diffuser replacement) will be handled using "confined space" entry
procedures. This should present minimal problems as (1) the membrane diffusers are expected to have
an operating life of 5-7 years and (2) the system would continue to perform reasonably well even if
several membranes fail, so that immediate repairs are not critical. The future of the plant is uncertain,
but the County is considering replacing the plant or redirecting flow to Durham's Farrington Road
plant.
2. The design calculations for the system use an average flow of 4.0 MGD; the peak monthly flow for last
12 months (excluding Sep99) was 5.4 MGD.
Outcome: Received return voice -mail from David Duty on 12/7/99. He indicated that the design uses 4.0 MGD as
a long-term average and includes other assumptions that keep it conservative. He committed to
providing the additional information we needed.
3. Although the effluent channel is enclosed, the system may also strip some of the trace VOCs in the
effluent. It is not clear whether the purpose of post -aeration is more to increase effluent D.O. or to air-
strip VOCs.
4. Single blower only for re -aeration. For 6 MGD plant, backup should be included.
Outcome: Given the probable replacement or closing of the plant in the next 5 years, and the ability to bleed air
from other headers, this should not be a major issue.