NC0021211_Speculative Limits_20200127

ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Director
Tonya Mann
Utilities Director
City of Graham
PO Box 357
Graham, North Carolina 27523
Dear Ms. Mann:
NORTH CAROLINA
Environmental Quality
January 27, 2020
Subject: Speculative Effluent Limits
Graham WWTP
Permit No. NCO021211
Alamance County
Cape Fear River Basin
This letter provides speculative effluent limits for 5 MGD and 6.2 MGD at the Graham WWTP. The
Division received the speculative limits request in a letter dated June 6, 2019 from Mary Sadler, P.E., of
Hazen and Sawyer. On October 20, 2019, Mary Sadler requested seasonal (winter) limits for the facility.
This letter provides seasonal limits and corrects the nutrient limits that had been mistakenly transposed in
the October 1, 2019 speculative limits letter. Please recognize that speculative limits may change based on
future water quality initiatives, and it is highly recommended that the applicant verify the speculative limits
with the Division's NPDES Unit prior to any engineering design work.
Receiving Stream. The Haw River is located within the Cape Fear River Basin. The Haw River has a
stream classification of WS-V, NSW, and waters with this classification have a best usage for the
protection of downstream drinking water supplies. The NSW supplementary classification designates
the waterbody as a nutrient sensitive water subject to 15A NCAC 02B .0270 for wastewater discharges
to the B. Everett Jordan Reservoir. The Haw River has a summer 7Q10 flow of 34 cfs, a winter 7Q10
flow of 85 cfs, a 30Q2 flow of 114 cfs, and an annual average flow of 553 cfs.
Based upon a review of information available from the North Carolina Natural Heritage Program
Online Map Viewer, there are not any Federally Listed threatened or endangered aquatic species
identified within a 5 mile radius of the proposed discharge location. If there are any identified
threatened/endangered species, it is recommended that the applicant discuss the proposed project with
the US Fish and Wildlife Service to determine whether the proposed discharge location might impact
such species.
Speculative Effluent Limits. Based on Division review of receiving stream conditions and water quality
modeling results, speculative limits for the proposed expansion to 5 MGD and 6.2 MGD are presented
in Tables 1 and 2, respectively. A complete evaluation of these limits and monitoring requirements for
metals and other toxicants, as well as potential instream monitoring requirements, will be addressed
upon receipt of a formal NPDES permit application. Some features of the speculative limit
development include the following:
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BOD/NH3 Limits. These speculative limits are based on freezing current permitted BOD
ultimate loading (i.e., facility will not be allowed to discharge oxygen -consuming waste above
what is currently permitted). The resultant limits at expanded flows are considered
technologically -feasible.
Nutrient Limits. Annual mass limits for total nitrogen (TN) and total phosphorus (TP) are
allocated by rule 15A NCAC 02B .0270. These annual limits will be carried over unless
additional TN or TP allocation credits are acquired. The permittee will be required to
demonstrate that their design will be capable of achieving these limits upon application for
expansion.
TABLE 1. Speculative Limits for City of Graham WWTP (Proposed Expansion to 5 MGD)
Effluent Characteristic
Effluent Limitations
Monthly
Average
Weekly
Average
Daily Maximum
Flow
5.0 MGD
BOD5 (April -October)
8.4 mg/L
12.6 mg/L
BOD5 (November -March)
16.8 mg/L
25.2 mg/L
NH3 as N (April -October)
2.8 mg/L
8.4 mg/L
NH3 as N (November -March)
5.6 mg/L
16.8 mg/L
Dissolved Oxygen (minimum)
5.0 mg/L
TSS
30 mg/L
45 mg/L
TRC
28 ug/L
Fecal coliform (geometric
mean)
200/100 ml
400/100 ml
Total Nitrogen
56,315
lbs/year (annual load)
Total Phosphorus
7,079 lbs/year (annual load)
Chronic Toxicity Pass/Fail
(Quarterly test)
19%
Note: At 5 MGD, nutrient load limits are approximately TP = 0.46 mg/L, and TN = 3.7 mg/L.
TABLE 2. Speculative Limits for City of Graham WWTP (Proposed Expansion to 6.2 MGD)
Effluent Characteristic
Effluent Limitations
Monthly
Average
Weekly
Average
Daily Maximum
Flow
6.2 MGD
BOD5 (April -October)
6.7 mg/L
10.0 mg/L
BOD5 (November -March)
13.4 mg/L
20.1 mg/L
NH3 as N (April -October)
2.2 mg/L
6.6 mg/L
NH3 as N (November -March)
4.4 mg/L
13.2 mg/L
Dissolved Oxygen (minimum)
5.0 mg/L
TSS
30 mg/L
45 mg/L
TRC
28 ug/L
Fecal coliform (geometric
mean)
200/100 ml
400/100 ml
Total Nitrogen
56,315
lbs/year (annual load
Total Phosphorus
7,079 lbs/year (annual load)
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Chronic Toxicity Pass/Fail
220//o
(Quarterly test
Note: At 6.2 MGD, nutrient load limits are approximately TP = 0.37 mg/L and TN = 3.0 mg/L.
Engineering Alternatives Analysis (EAA). Please note that the Division cannot guarantee that an
NPDES permit for a new or expanding discharge will be issued with these speculative limits. Final
decisions can only be made after the Division receives and evaluates a formal permit application for
the new/expanded discharge. In accordance with North Carolina Administrative Code 15A NCAC
2H.0105( c), the most environmentally sound alternative should be selected from all reasonably cost
effective options. Therefore, as a component of all NPDES permit applications for new or expanding
flow, a detailed engineering alternatives analysis (EAA) must be prepared. The EAA must justify
requested flows and provide an analysis of potential wastewater treatment alternatives. A copy of the
Division guidance for preparing EAA documents is attached.
State Environmental Policy Act (SEPA) EA/EIS Requirements. A SEPA EA/EIS document may be
required for projects that: 1) involve $10 Million or more of state funds; or 2) will significantly and
permanently impact 10 or more acres of public lands. Please check with the DWR SEPA coordinator
(David Wainwright, 919-707-9045) as to whether your project requires SEPA review. For projects that
are subject to SEPA, the EAA requirements discussed above will need to be folded into the SEPA
document. Additionally, if subject to SEPA, the NPDES Unit will not accept an NPDES permit
application for a new/expanding discharge until the Division has approved the SEPA document and
sent a Finding of No Significant Impact (FONSI) to the State Clearinghouse for review and comment.
Should you have any questions about these speculative limits or NPDES permitting requirements,
please feel free to contact David Hill at [phone] or Julie Grzyb at [phone].
Respectfully,
Grzyb
pervisor, NPDES Complex Permitting Unit
Hardcopy:
Central Files
NPDES Permit File
Electronic Copy:
DWR/Water Quality Regional Operations/Winston-Salem Regional Office
DWR/Basinwide Planning, Ian McMillan
DWR/NPDES Server>Specs
Hazen and Sawyer, Mary Sadler [e-mail]
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