NC0030210_Speculative Limits_19960424

NIPDES DOCUMENT SCANNING COVER SHEET
NPDES Permit:
NC0030210
Charlotte / Mallard Creek WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Staff Comments
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
Aril 24, 1996
Thies doatamerat Aw printea on reuse paper. - igazore aay
comsat on the reverse side

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 24, 1996
Mr. Barryf
. Gullet, Deputy Director
CharlottecklenburgUtility Department
510Brochire BlvdCharlottC 28216
Subject: Speculative Discharge Limits
NPDES Permit No. NCO030210
CNIUD Mallard Creek WWTP
Mecklenburg County
Dear Mr. Gullet: -N
D LE H N R
The Division of Environmental Management has completed its evaluation of your
request for speculative limits for the expansion of the Charlotte -Mecklenburg Utility
Department's Mallard Creek WWTP. Speculative discharge limits for flows of 9 MGD
and 12 MGD were requested.
Based on available information, the tentative monthly average limits for
coo Velitiol ti-ul paranteters are as follows:
Summer
Wster
BOD5 (mg/1)
5
10
NH3-N (mg/1)
1
2
DO (mg/1)
6
6
TSS (mg/1)
30
30
Fecal Colifonn
(#/100 MI)
200
200
pH (SU)
6-9
6-9
Chlorine u l)
18
18
These limiIs apply to both the 9 MGD and 12 MGD flows.
P.O. Box 29535, 1,,; teigh, North Carolina 21626-0535 Telephone [phone] FAX [phone]
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The evaluation of ammonia and BOD limits considered the interaction between the
proposed expansion in wasteflow and the discharges from both the Town of Mooresville's
Rocky River WWTP and the Cabarrus County WSA's Rocky River Regional WWTP.
The Division's modeling analysis indicates that the specified ammonia limit is necessary to
protect instream dissolved oxygen levels in Mallard Creek and the Rocky River.
Under current DEM procedure, dechlorination and chlorine limits are
recommended for all new or expanding dischargers proposing the use of chlorine for
disinfection. An acceptable level of residual chlorine in the effluent of this plant in order
to protect against chronic toxicity is 18 ug/l. If the facility continues to use UV
disinfection upon expansion, the chlorine limit will apply only when the backup chlorine
disinfection system is in operation.
This speculative analysis does not include limits or monitoring requirements for
metals or other toxicants. If an NDPES permit is requested, a new evaluation of the
constituents present in the discharge would be necessary. The instrealn waste
concentrations (IWC) at which limits for toxic substances will be calculated are 96% for a
9 MGD discharge and 97% for a 12 MGD discharge.
The facility will be required to meet a whole effluent toxicity test limit. At both
the 9 MGD or 12 MGD flows, a chronic (Cerioda.phhnia) test must be performed quarterly
with a pass/fail limit at a test concentration of 90%. As was done when the permit for this
facility was last renewed, a Phase II chronic test may be substituted for this requirement at
your request.
.. Please be advised that response to this request does not guarantee that the Division
will issue an NPDES permit to discharge treated wastewater into these receiving waters.
It should be noted that new and expanding facilities, involving an expenditure of public
funds or use of public (state) lands, will be required to prepare an environmental
assessment (EA) when wasteflows: 1) exceed or equal 0.5 MGD, or 2) exceed one-third
of the 7Q10 flow of the receiving stream. DEM will not accept a permit application for a
project requiring an EA until the document has been approved by the Department of
_ Environment, Health and Natural ResourQ.es and a Finding of No Significant Imnac.t
(FONSI) has been sent to the state Clearinghouse for review and comment.
The EA should contain a clear justification for the proposed facility and an analysis
of potential alternatives which should include a thorough evaluation of non -discharge
alternatives. Nondischarge alternatives or alternatives to expansion, such as spray
irrigation, water conservation, inflow and infiltration reduction or connection to a regional
treatment and disposal system, are considered to be environmentally preferable to a
surface water discharge. In accordance with the North Carolina General Statutes, the
practicable waste treatment and disposal alternative with the least adverse impact oil the
environment is required to be implemented. If the EA demonstrates that the project inay
result in a significant adverse affect on the quality of the environment, an Environmental
Impact Statement would be required. Alan Clark of the Water Quality Planning Branch
can provide further information regarding the requirements of the N.C. Environmental
Policy Act.

DEM is currently developing a water quality plan for the Yadkin -Pee Dee basin.
This effort may include a reassessment of the assimilative capacity of the Rocky River for
oxygen -consuming wastes and nutrients, and may affect the effluent limits of some
perrrittees'. The plan is scheduled for completion in January, 1998.
The above limits are to assist you in your planning and engineering analyses and
are speculative. Final NDPES effluent limitations will be determined after a formal permit
application has been submitted to the Division. If there are any additional' questions
concerning this matter, please feel free to contact Ruth Swanek (ext. 503) o
(ext. 514) of my staff at [phone].
IyoTiald L. �frit,-P.E.
Assistant G rief for Tec nic l Support
Water Oualitv�Se on
cc: David Goodrich, Permits and Engineering
"ex Gleason, Mooresville Regional Office
Central Files