NC0023884_201 Plan_19810824

ilk North Carolina Department of Natural
mr. Resources &Community Development
James B. Hunt, Jr., Governor Joseph W. Grimsley, Secretary
DIVISION OF ENVIRONMENTAL MANAGEMENT
August 24, 1981
Mr. Emmett Smith
Peirson and Whitman, Inc.
5510 Munford Road
Raleigh, NC 27612
Dear Mr. Smith:
Subject: Salisbury Grant's Creek WWTP
Greater Salisbury 201 Plan
In response to your telephone request of August 12, 1981, we have
attached a corrected tabulation of the effluent limits requested. The
limits reflect current policies and methodologies in the State Continuing
Planning Process and are part of the Yadkin River Basin Plan. Please
contact Ms. Jennifer Buzun of my staff if you have any questions concerning
the limits.
Attachment
cc:
Dick Peace
Jennifer Buzun
Louis Eckley
Allen Wahab
Donald L. Weinhold, Jr.
Sincerely,
,f2l4rdt/
Forrest R. Westall, Head
Monitoring & Technical Services Branch
1
•i
T
SEP I 1981
PEIRSOU & 114
P. O. Box 27687 Raleigh, North Carolina 27611
An Equal Opportunity Affirmative Action Employer

DISCUSSION OF EFFLUENT LIMITATIONS
Effluent limitations for BOD5, NH3-N, and dissolved oxygen are established in
the State Water Quality Management Planning Process to attain water quality stream
standards for dissolved oxygen. The limits for BOD and NH3-N are. usually specified
as maximum monthly mean values. ,Maximum weekly values, normally 1.5 times the monthly
values, are also specified -in the affected discharge permits.
There are two basic levels of analysis ("B" and "C") used to establish the
effluent limits. In each case the analysis can conclude an infinite number of
combinations of effluent BOD5, NH3-N, and D.O. that will attain water quality
standards. Obviously it would be impossible to list all combinations and since
specific values must be in the NPDES permits; the Division staff selects a likely
r.ombination.for specif.ication'of the waste load allocation. Because of the numerous
combinations which can be -conceived, it is possible that some combination other than
the one selected by the Division of Environmental Management (DEM) will prove to be
the optimum.. For this reason, DEM encourages the consideration of alternative
combinations in the 201 Planning Process which may be advantageous due to the
particular waste or waste treatment being considered. Since the waste load
allocations and often the NPDES permits precede the development of 201 plans, it
will be necessary to update plans and modify permits in a continuing process.
The "13" and "C" levels of ana.lysis.differ primarily by• the amount of data
,available. The 'C" analysis is based on intensive water quality survey data while
the "13" analysis is an empirical analysis based largely on the slope and other
physical characteristics of the receiving stream. Additional explanation of. the
"B" and "C" analyses is contained in Appendix E of the Basin flans. Loth analyses
use the basic Streeter -Phelps theory. In a."B" level analysis effluent ultimate
BOD (BODu) is set equal to BOD5 + 4 x NH3-N. The combination of BOD5 and NH3-N may
be modified as long as BODu is not changed. In_ most level "C" analyses Carbonaceous
BODu (CBOD) is equal to 1..5 x BOD5 and Nitrogenous BODu (NBOD) is equal to 4.5 x NH3-N.
Although tradeoffs between BOD5 and NH3-N are acceptable in the level "C" allocations,
the equation of BODu = 1.5 x BOD5 + 4.5 x NH3-N cannot be used in all cases. When a
large difference between Carbonaceous BOD and Nitrogenous BOD stream removal rates
exist, the trade-offs will be less in accordance with the equation. In any case,
modifications to the waste load allocations have to be approved by DEM before 201
plans or NPDES permits are completed. Proposed allocation modifications should be
coordinated through the Local Programs or Technical Services Sections.
As a result of regulation changes, the effluent limits on suspended solids may
be increased from the normal 30 mg/1 to 90 mg/1 for lagoon waste treatment systems.
Since'the attached table does not address the type of treatment system to be employed,
this consideration should be utilized in the design of the waste treatment system.
Even though higher suspended solids are allowable for lagoon systems, the systems
must be designed to allow attainment of the BOD, N113-N, and D.O. effluent limits.