NC0021644_Speculative Limits_20220601

DocuSign Envelope ID: 1648418E-6312-48AC-82F4-2BC46FE9091C
ROY COOPER
Governor
ELIZABETH S. BISER
Secretary
RICHARD E. ROGERS, JR.
Director
Mr. John P. Craft, Town Manager
Town of La Grange
700 E King St
La Grange, North Carolina 28551-0368
Dear Mr. Craft:
NORTH CAROLINA
Environmental Quality
June 1, 2022
Subject: Speculative Effluent Limits
La Grange WWTP
NPDES Permit No. NC0021644
Lenoir County
Neuse River Basin
This letter provides speculative effluent limits for 0.995 MGD at the La Grange WWTP. The Division received
the speculative limits request in a letter dated May 5, 2022, from Jeffrey S. Thompson, PE., of Black & Veatch
International Company. Please recognize that speculative limits may change based on future water quality
initiatives, and it is recommended that the applicant review the speculative limits with the Division's Municipal
NPDES Unit when the NPDES permit application is submitted.
Receiving Stream. The unnamed tributary (UT) to Mosely Creek is located within the Neuse River Basin. The
UT to Mosely Creek has a stream classification of C;Sw,NSW, and waters with this classification have a best
usage for aquatic life propagation and maintenance of biological integrity, wildlife, secondary recreation and
agriculture. The UT to Mosely Creek has a summer 7Q10 flow of 0.069 cfs, a winter 7Q10 flow of 0.15 cfs, a
30Q2 flow of 0.18 cfs, and an annual average flow of 1.2 cfs.
The UT to Mosely Creek is not currently listed as an impaired waterbody on the 2020 North Carolina 303(d)
Impaired Waters List for biological integrity. The UT to Mosely Creek and Mosely Creek ultimately drains into
Falling Creek, which is also not listed on the 303(d) list.
Speculative Effluent Limits. Based on Division review of receiving stream conditions and specific proposed
discharge location, speculative limits for the proposed expansion to 0.995 MGD is presented in Table 1. 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 complete NPDES permit
application.
Every applicant shall also submit documentation of any additional pollutants for which there are certified methods
with the permit application if their discharge is anticipated. These pollutants may be found in 40 CFR Part 136, if
there are additional pollutants with certified methods to be reported, please submit the Chemical Addendum to
NPDES Application and, if applicable, list the selected certified analytical method used.
NORTH E CAROLINA
Department
m ot Environmental Quality
North Carolina Department of Environmental Quality I Division of Water Resources
512 North Salisbury Street 11617 Mail Service Center I Raleigh, North Carolina 27699-1617
919.707.9000

DocuSign Envelope ID: 1648418E-6312-48AC-82F4-2BC46FE9091C
Some features of the speculative limit development include the following:
TABLE 1. Speculative Limits for Town of La Grange WWTP (Proposed Expansion to 0.995 MGD)
EFFLUENT
CHARACTERISTICS
EFFLUENT LIMITS
Monthly
Average
Weekly
Average
Daily
Maximum
Flow
0.995 MGD
BOD5, 20°C - Summer*
5.0 mg/L
7.5 mg/L
BOD5, 20°C - Winter *
10.0 mg/L
15.5 mg/L
NH3 as N - Summer *
1.0 mg/L
3.0 mg/L
NH3 as N - Winter *
1.8 mg/L
5.4 mg/L
Dissolved Oxygen (minimum)
Daily average > 5.0 mg/1
TSS
30 mg/L
45 mg/L
TRC
18 ug/L
Fecal coliform (geometric mean)
200/100 mL
400/100 mL
Total Phosphorus
2 mg/L
Total Nitrogen
8,447 lbs/year (annual cumulative load)**
*Summer: April 1 — October 31 *Winter: November 1— March 31
• NH3 Limits. For a proposed 0.995 MGD facility expansion, the expected instream concentrations would
be summer (1.0 mg/1) and winter (1.8 mg/1). Additional information on how the existing facility or some
modified facility would meet these requirements would be expected as part of the design review. This would
address instream ammonia aquatic life concerns at the increased flow.
• BOD Limits. Note that with the proposed ammonia limits, no changes are considered necessary to the
existing BOD5 concentration requirements (currently 5 mg/1 summer and 10 mg/1 winter) to maintain the
current oxygen demand load to the existing discharge point for the proposed expansion to 0.995 MGD.
• **Nutrient Limits.
1. In order to expand, LaGrange will have to show how they will meet the existing TN Load limit at
the increased flow (as part of the design review for any AtC permit for this project).
2. Alternatively, LaGrange could request raising the proposed speculative limit above by buying
additional nutrient allocation from another discharger or purchasing offset credits from a
mitigation banker (the new TN limit cannot exceed 3.5 mg/L at the increased flow limit). The
technology -based cap would be 10,600 lb/yr, potentially raising the identified loading limit by up
to 2,200 lb/yr.
3.5 mg/L * 0.995 MGD * 365 days/year * 8.34 = 10,601 lb/yr - 8,447 lb/yr = 2,154 lb/yr
The opportunity of finding allocation or credits in time for the expansion may be difficult, and the
cost has been approximately $500 per lb/yr for allocation, and approximately $300-400 per lb/yr
for credits.
3. Another option would be to use a combination of wastewater treatment improvements and some
additional loading purchase. La Grange is a member of the Neuse River Compliance Association
and not subject to the yearly cumulative TN limit in its individual permit. However, for an
expansion your consultant will need to demonstrate how the new wastewater plant design for
0.995 MGD will meet the individual TN limit of 8,447 lb/yr.

DocuSign Envelope ID: 1648418E-6312-48AC-82F4-2BC46FE9091C
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 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 and expanding flow includes a detailed engineering alternatives analysis (EAA) that
must be prepared. The EAA must justify the requested design flow and provide an analysis of potential wastewater
treatment alternatives. A copy of the Division guidance for preparing EAA documents is attached.
In addition to the EAA, please review information available from the North Carolina Natural Heritage Program
Online Map Viewer. Please confirm if there are/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, the applicant may consider reviewing the proposed project with the US Fish and
Wildlife Service to determine whether the proposed expanded discharge might impact such species.
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. If required, a FONSI must be issued prior to
issuance of the NPDES permit for the expansion.
We understand this expansion project is moving forward rapidly; however we would expect that any request for
NPDES permitting action for the expansion be taken within a five year period from the date of this letter, or the
noted speculative limits in Table 1 would be subject to reassessment and review.
Should you have any questions about these speculative limits or NPDES permitting requirements, please feel free
to contact Derek Denard at [phone] / [e-mail] or Doug Dowden at [phone] /
doug.dowden@,ncdenr.gov
Respectfully,
Docu Signed by:
[OlAi) b,t lA,
57287E56E81A40D...
Doug Dowden
Supervisor, NPDES Industrial Permitting Unit
Attachment: EAA Guidance Document
Link to Chemical Addendum Form
Link to NPDES application information
ec: NPDES Files [Laserfiche]
Town of La Grange / John P. Craft, Town Manger [[e-mail]]
Black & Veatch / Jeffrey S. Thompson [[e-mail]]
Tedderfarm Consulting / Steve W. Tedder[[e-mail]]
DWR / Julie Grzyb [[e-mail]]; JeffPoupart [[e-mail]]; Michael J Montebello
[[e-mail]]; Derek Denard [[e-mail]]
WaRO / Robert Tankard [[e-mail]]
NC WRC / Maria Dunn [[e-mail]]
US Fish and Wildlife Service / Sarah McRae [[e-mail]]
DWR/Basinwide Planning, Francis Oggeri [[e-mail]]; Nora Deamer [[e-mail]]