1. DEPARTMENT OF ENVIRONMENTAL PROTECTION
      2. DOCUMENT ID: 391-2000-013
      3. AUTHORITY:
      4. POLICY:
      5. PURPOSE:
      6. APPLICABILITY:
      7. DISCLAIMER:
      8. REVISED: FEBRUARY, 1987 REVISED: NOVEMBER 4, 1997
      9. IMPLEMENTATION OF SECTION 93.7 AMMONIA CRITERIA
      10. IMPLEMENTATION GUIDANCE - AMMONIA
      11. I. SUMMARY OF NH3-N IMPLEMENTATION GUIDANCE
      12. II. INTRODUCTION
      13. III. REGULATORY BASIS
      14. IV. IMPLEMENTATION OF SECTION 93.7
      15. TABLE 1
      16. Design Flow Calculation
      17. Occurrence Interval Preliminary Value
      18. TABLE 2
      19. Sensitivity Analysis Ranges For Stream Flow
      20. Recommended
      21. Multiplier
      22. Standard Deviation
      23. TABLE 3
      24. Recommended Upstream Design pH and Temperature Default Values
      25. TABLE 4
      26. SOURCES OF DESIGN CRITERIA
      27. Exposure Period Basis for Effluent Limitations
      28. TABLE 5
      29. Summary of Procedures
      30. TABLE 7
      31. Treatment Technology Ranges
      32. C-BOD5 Range NH3-N Range
      33. Stream Effluent
      34. TABLE 8
      35. Design C
      36. Stream Design Flow Instream Criteria (NH3-N)
      37. TABLE 9
      38. APPENDICES
      39. APPENDIX A
      40. Revisions to the Simplified Method
      41. APPENDIX B
      42. Revisions to NPDES Permit Writing Manual
      43. APPENDIX C
      44. Excerpts from the EPA Guidance
      45. APPENDIX D
      46. REFERENCES
      47. APPENDIX E
      48. Rationale Paper Ammonia Criteria
      49. WATER QUALITY STANDARDS RATIONALE PAPER
      50. STATEWIDE AMMONIA CRITERIA
      51. Prepared by
      52. Dennis F. Lee and Carol A. Sudick
      53. Division of Water Quality Assessment and Standards
      54. BACKGROUND
      55. APPENDIX F
      56. Rationale Paper for the Simplified Procedures
      57. REVISED NOVEMBER 1986
      58. APPENDIX F
      59. DEVELOPMENT OF THE SIMPLIFIED METHOD
      60. OF IMPLEMENTING SECTION 93.7
      61. Stream Name Min.
      62. Daily
      63. Q7-10 Q-Min
      64. Q7-10
      65. Computed Q-Min
      66. Pct.
      67. Error
      68. Sqrd. Var
      69. Stream Name Min.
      70. Daily
      71. Q7-10 Q-Min
      72. Q7-10
      73. Computed Q-Min
      74. Pct.
      75. Error
      76. Sqrd. Var
      77. APPENDIX G
      78. Database of Streamflows
      79. APPENDIX H
      80. Computer Program Listing
      81. APPENDIX I
      82. Criteria Tables
      83. Chapter 93.7 - Maximum In-Stream Ammonia
      84. Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
      85. Chapter 93.7 - Maximum In-Stream Ammonia
      86. Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
      87. 30-Day Average Total Ammonia-Nitrogen Concentration
      88. 30-Day Average Total Ammonia-Nitrogen Concentration
      89. Seven-Day Average Total Ammonia-Nitrogen Concentration
      90. Seven-Day Average Total Ammonia-Nitrogen Concentration
      91. APPENDIX J
      92. Alkalinity
      93. Simplified Wasteload Allocation Procedure for Ammonia Toxicity
      94. Monitoring and Data Support Division
      95. U. S. EPA, Headquarters
      96. Contract No. 68-02-3172
      97. Project Officer
      98. Jonathan R. Pawlow
      99. Prepared By:
      100. GXY and Associates, Inc. 5411-E Backlick Road Springfield, Virginia 22151
  1. TOTAL CARBONATE CARBON (mg/l)
  2. pH CONTROLS
  3. pH CONTROLS
  4. TOTAL CARBONATE CARBON (mg/l)

391-2000-013
/November 4, 1997/Page 1
DEPARTMENT OF ENVIRONMENTAL PROTECTION
DOCUMENT ID: 391-2000-013
TITLE:
Implementation Guidance of Section 93.7 Ammonia Criteria
EFFECTIVE DATE
: November 4, 1997
AUTHORITY:
Pennsylvania Code, Title 25, Environmental Protection, Chapter 93, Water Quality
Standards, Section 93.7.
POLICY:
This guidance is designed to implement DEP's water quality criteria regulation contained in Section
93.7. BWC's Water Quality Analysis Model (WQAM Model version 6.3) is the focal point for
implementing the regulation.
PURPOSE:
This document is intended as a support document for implementing the 1984-85 revisions to
Pennsylvania's water quality standards and criteria for ammonia.
APPLICABILITY:
This guidance applies to all NPDES dischargers in the Commonwealth of Pennsylvania.
DISCLAIMER:
The policies and procedures outlined in this guidance are intended to supplement existing
requirements. Nothing in the policies or procedures shall affect regulatory requirements.
The policies and procedures herein are not an adjudication or a regulation. There is no intent on the
part of DEP to give the rules in these policies that weight or deference. This document establishes the
framework within which DEP will exercise its administrative discretion in the future. DEP reserves
the discretion to deviate from this policy statement if circumstances warrant.
PAGE LENGTH:
80 Pages
LOCATION:
Volume 29, Tab 15

391-2000-013
/November 4, 1997/Page 2
IMPLEMENTATION GUIDANCE
FOR
CHAPTER 93.7
AMMONIA CRITERIA
REVISED: FEBRUARY, 1987
REVISED: NOVEMBER 4, 1997
WATER QUALITY STANDARDS AND IMPLEMENTATION SECTION
DIVISION OF WATER QUALITY ASSESSMENT AND STANDARDS
BUREAU OF WATERSHED CONSERVATION

391-2000-013
/November 4, 1997/Page 3
IMPLEMENTATION OF SECTION 93.7 AMMONIA CRITERIA
Page No:
I. SUMMARY OF NH
3
-N IMPLEMENTATION GUIDANCE
5
II. INTRODUCTION
7
A. Background to Regulatory Change
7
B. Discussion of Guidance Document
8
III. REGULATORY BASIS
9
A. Section 93.7
10
B. Discussion of Regulation
11
IV. IMPLEMENTATION OF SECTION 93.7
12
A. Design Conditions
13
1. Design Flows
13
2. Temperature
15
a. Stream Temperature
15
b. Discharge Temperature
15
3. pH
15
4. Criteria
17
B. Requirements for Field Data
17
C. Determination of Effluent Limitations
18
1. Determination of Water Quality Based Effluent Limitations
18
2. Permit Effluent Limitations
24
3. Seasonal Limitations
24
4. Potential Impact on Water Supplies
25
5. Wasteload Allocations
26
D. Incorporation of Effluent Limits into NPDES Permits
28
E. Example Calculations
29
V. STREAM MODELS
31
VI. APPENDICES
32
A. Revisions to Simplified Method (*)
33
B. Revisions to NPDES Permit Writing Manual (*)
34
C. Excerpts from EPA Guidance(*)
35

391-2000-013
/November 4, 1997/Page 4
D. References
36
E. Rationale Paper - Ammonia Criteria
37
F. Rationale Paper - Simplified Method
47
G. Data Base of Streamflows
61
H. Computer Program Listing (*)
65
I. Criteria Tables
66
J. Alkalinity
73
(*) Appendices are not revised and are not included with this revision.

391-2000-013
/November 4, 1997/Page 5
IMPLEMENTATION GUIDANCE - AMMONIA
I. SUMMARY OF NH3-N IMPLEMENTATION GUIDANCE
This guidance is designed to implement DEP's water quality criteria regulation contained in Section
93.7. BWC's Water Quality Analysis model (WQM Model Version 6.3) is the focal point for
implementing the regulation. The WQM 6.3 is designed to determine effluent limitations for
Carbonaceous Biological Oxygen Demand (C-BOD
5
) and Ammonia Nitrogen (NH
3
-N) for single and
multiple point source discharge scenarios. When used in multiple discharge scenario, the model
determines whether a wasteload allocation situation exists either for C-BOD
5
or NH
3
-N, and if it does,
calculates reductions for each discharge(s). Detailed documentation of the two wasteload strategies,
the WLA model WQM 6.3 and some sample examples are contained in the BWC's wasteload
allocation policy and procedures document.
On January 6, 1987, BWC approved the use of WQM model 6.3 in
UNIFORM TREATMENT
MODE ONLY
. Beginning immediately, all regions will start using the WQM 6.3 for all permit
reviews and/or renewals and discontinue use of both the DOSAG and NH
3
CALC models. Note that
use of "Equal Marginal Percentage Reduction" (EMPR) method of wasteload allocation for writing
NPDES permits is not yet approved. The regions are encouraged, however, to run the model in EMPR
mode for comparison purposes and report the results to Central Office for future revisions/refinements
to the WQM 6.3 model.
The WQM 6.3 model results, if interpreted and translated correctly into NPDES effluent limitations,
will require a minimum of effort on the part of the user to comply with the ammonia regulation and this
implementation guidance. For NH
3
-N evaluations, WQM 6.3 determines toxicity and DO based
limitations for 30-day and 1-day duration. The user will have to establish the most critical (summer
and/or winter period) design condition and perform appropriate evaluations. For purposes of this
guidance, summer (July - October) and winter (November - January) periods will be used for ammonia
evaluations.
Upon user data input, the model will use appropriate equations, perform computations and display
WQBEL’s for toxicity and DO considerations. The user simply has to select appropriate values from
the "Effluent Limitations Display" screen.
Step by Step Procedures for Ammonia Evaluations
1. Get WQM 6.3 up and running by inserting program Disk and turning on Power to the computer.
SELECT UNIFORM TREATMENT MODE FOR USE
.
2. Complete user data inputs (Option 1 on main Menu and Options 1 through 5 on Data Management
submenu). For relevant key input data items, refer to next section summary of design conditions.
3. Run NH
3
-N Allocation Model (Option 2)

391-2000-013
/November 4, 1997/Page 6
4. Run DO Allocation Model (Option 3)
5. Display "Effluent Limitations" Screen (Option 6)
6. Select more stringent of 30-day average toxicity or DO based on NH
3
-N effluent limitation for the
discharge under evaluation.
Summary of Design Conditions
The implementation of ammonia regulation requires four key design conditions data input items for
running the WQM 6.3 model. Detailed discussion on each of them is contained later in the guidance.
A brief summary of these items is presented below:
1. Stream Flows: (Reference to Pages 13-14)
The Q
30-10
and Q
1-10
are two design stream flows required for ammonia evaluations. All flows (Q
7-10
,
Q
30-10
, and Q
1-10
) should be determined using B-12 and other data/methods wherever available. The
model requires input of Q
30-10
/Q
7-10
and Q
1-10
/Q
7-10
flow multiplier ratios. If no data are available, the
model built in default multipliers of 1.36 for Q
30-10
and 0.64 for Q
1-10
may be used. For regulated
streams downstream flow release data if available should be used.
2. Stream Temperatures: (Reference Pages 15)
For ammonia evaluations, 90th percentile temperature data will be used. If no data is available, a
default of 20 degrees (C) for summer and 5 and 15 degrees (C) for winter (November and January
months) may be used.
3. Stream pH: (Reference Pages 15-17)
The model computes complete mix median pH values for ammonia calculations from user input of
stream and discharge median pH values. For existing discharges, available pH data on discharge and
stream (upstream/downstream) should be used. For proposed discharges, the design pH should be
representative of proposed unit treatment process. If no data is available, the model default of 7 for
stream pH and 7.5 for discharge pH may be used.
4. Design NH
3
-N Criteria: (Reference Pages 17-18)
The WQM 6.3 model is designed to calculate and use appropriate ammonia criteria for the user
specified stream flow, temperature and pH conditions.

391-2000-013
/November 4, 1997/Page 7
Specifying NH
3
-N Effluent Limitations in NPDES permits
The effluent limitation display option of WQM 6.3 will provide a 30-day C-BOD
5
value(s) and both
30-day and 1-day ammonia nitrogen limitations. The user will select the more stringent of the toxicity
or DO based ammonia effluent limitations for NPDES permits. If both of the values are greater than
15 mg/l, a minimum treatment technology for ammonia (as defined by BWC), no NH
3
-N effluent
limitation will be placed in the permit.
Weekly ammonia effluent limitations, where required by EPA in NPDES permits, will be calculated
using a technology based multiplier of 1.5 applied to the 30-day average ammonia limitation.
Additional discussion of specifying ammonia effluent limitations is contained in BWC's C-
BOD
5
/BOD
5
discussion paper released on December 29, 1986.
II. INTRODUCTION
This document is intended as a support document for implementing the 1984-85 revisions to
Pennsylvania's water quality standards and criteria for ammonia. This implementation material is the
third piece in the criteria revision process. The first item was the Rationale Paper (February 17, 1984)
which presented the technical justification for the proposed criteria. The second item was the final
rulemaking material published in the Pennsylvania Bulletin (February 16, 1985) which contained the
specific changes to Section 93.7.
Background to the Regulatory Change
Pennsylvania's previous ammonia criteria were developed in 1968 for inclusion in Chapter 93. As
stated in Chapter 93, these criteria were:
Am1 - not more than 0.5 mg/1 as ammonia nitrogen
Am2 - not more than 1.5 mg/1 as ammonia nitrogen
The 0.5 mg/l criterion was recommended by the Pennsylvania Fish and Boat Commission for trout-
stocking fisheries (TSF) and cold water fisheries (CWF). Their experiences at the state's trout
hatcheries indicated that any greater concentration adversely affects trout.
The 1.5 mg/l criterion for warm water fisheries (WWF) was adopted based on work by M. M. Ellis
(1937), who stated that this concentration was not harmful to most varieties of fish.
These ammonia criteria were not applied to all surface waters. Instead, they have been applied
selectively to about one-half the streams in Pennsylvania, as indicated in Chapter 93.
For those streams which did not have an ammonia criterion, effluent limitations were established on a
case-by-case basis under provisions of Section 93.6. Effluent limitations were calculated to meet both
total and un-ionized ammonia criteria. The less stringent effluent limit was then applied. In these

391-2000-013
/November 4, 1997/Page 8
cases, trout stocking water bodies were treated as warm water fisheries. However, TSF streams were
treated as cold water fisheries in developing ammonia criteria under Chapter 93.7. As a result, two
different ammonia criteria were applied to streams of the same classification, which is clearly
contradictory.
In the 1978 Water Quality Standards review, statewide un-ionized ammonia nitrogen criteria were
considered. The criteria were based on EPA's Quality Criteria for Water (1976, Red Book)
recommendation of 0.02 mg/l un-ionized ammonia nitrogen for CWF and 0.05 mg/l for WWF.
Bioassay information supported this concept; however, the Air and Water Quality Technical Advisory
Committee (AWQTAC) recommended postponing implementation of such a standard pending
additional considerations of potential stream and economic impacts.
Data amassed since that time further support the concept that un-ionized ammonia is the determining
factor in ammonia toxicity to fish, although the initially proposed level of 0.02 mg/l NH
3
N has been
questioned in light of current information.
The results of toxicity testing of ammonia to various species of aquatic organisms is detailed in EPA's
draft report Ambient Water Quality Criteria for Ammonia (1983). This data shows no clear-cut
distinction between salmonids and other species of fish in their responses to ammonia concentrations.
Furthermore, other information indicated that warm water fish ultimately react similarly to trout to
ammonia exposures. For these reasons, it is appropriate to consider one set of criteria for all species
and to eliminate the distinction between cold water and warm water fishes toxicities.
Therefore, the 1984 revision to Section 93.7 implemented an instream criteria that varied with
temperature and pH, and which presented different criteria for acute and chronic exposures. (A
detailed discussion of this new criteria can be found in the Rationale Paper attached as Appendix E.)
Discussion of Guidance Document
Section IV, Implementation, presents the technical procedure to be followed when developing water
quality-based effluent limits for ammonia. The primary factor is ammonia toxicity, but the impact of
ammonia on dissolved oxygen is also addressed, as are the cost trade-offs between BOD and NH
3
removal.
The guidance represents an extension of the DEP/EPA Simplified Method.
Section IV.C presents the general procedure for estimating effluent limits using applicable default
values. Section IV.A discusses the selection of design conditions.
Section IV.C presents the procedures for calculating seasonal effluent limits, and addresses situations
where two or more dischargers interact, i.e., wasteload allocations.

391-2000-013
/November 4, 1997/Page 9
III. REGULATORY BASIS
The Environmental Quality Board, under the authority contained in Sections 5 and 402 of the Act of
June 22, 1937 (P.L. 1987), as amended, 35 P.S. §§691.5 and 691.402, known as the Clean Streams
Law; and Section 1920-A of the Act of April 9, 1929 (P.L. 177), as amended, 71 P.S. §510-20, known
as the Administrative Code of 1929, approved proposed changes to Pennsylvania's water quality
standards contained in 25 Pa. Code.
Pennsylvania's water quality standards, embodied in 25 Pa. Code Chapter 93 and portions of 25 Pa.
Code Chapter 95, are designed to implement the requirements of the Clean Streams Law and Section
303 of the Federal Clean Water Act. The water quality standards consist of designated uses of the
surface waters of the Commonwealth, along with specific numerical and narrative criteria necessary to
achieve and maintain those uses. Thus, water quality standards are instream water quality goals which
are implemented by imposing specific regulatory requirements (such as treatment requirements and
effluent limitations) on individual sources of pollution.
Section 303(c)(1) of the Clean Water Act requires states to periodically, but at least once every three
years, review, and revise as necessary, its water quality standards. In addition, Section 24 of the
Municipal Wastewater Treatment Construction Grant Amendments of 1981 (P.L. 97-117, 95 Stat.
1632, December 29. 1981) prohibits the issuance of a construction grant after December 29, 1984
unless the state has completed its review of water quality standards influencing that construction grant
decision.

391-2000-013
/November 4, 1997/Page 10
A. Section 93.7
TITLE 25. RULES AND REGULATIONS
PART 1. DEPARTMENT OF ENVIRONMENTAL PROTECTION
SUBPART C. PROTECTION OF NATURAL RESOURCES
ARTICLE II. WATER RESOURCES
CHAPTER 93. WATER QUALITY STANDARDS
Ammonia Nitrogen Am
The maximum total ammonia-nitrogen concentration at all times shall be less than or equal to the
numerical value given by:
un-ionized ammonia-nitrogen (NH
3
-N) x (log
-1
[pKt - pH] +1), where:
un-ionized ammonia-nitrogen = 0.12 x f(T)/f(pH)
f
??
pH
?
pH
?
??
1 10
1..
03 732?
f
?
T
?
T
o
C
??1, 10
??
?
?
fT
?
?
T
C
pH
pK pH
o
t
?
?
?
?
?
?
1 10
1 10
10
9.73
,
and
pKt
?
?
T
??
?
0 090
2730
273 2
.
.
, the dissociation constant for ammonia in water.
The average total ammonia-nitrogen concentration over 30 consecutive days shall be less than or equal
to the numerical value given by:
un-ionized ammonia-nitrogen = (NH
3
-N) ? (log
-1
[pKt-pH]+1), where:
un-ionized ammonia-nitrogen = 0.025 x f(T)/f(pH)
f
?
pH
?
??1,
pH
7. 7
f
?
pH
?
?
?
pH
pH
?
?
10
?
0.74 7.7
,
7.7
f
?
T
?
T
o
C
??1,
10
??
?
?
fT
?
?
T
C
pH
pKt pH
o
?
?
?
?
?
?
1 10
1 10
10
9.73
,
The pH and temperature used to derive the appropriate ammonia criteria shall be determined by one of
the following methods:

391-2000-013
/November 4, 1997/Page 11
1) Instream measurements, representative of median pH and temperature - July through September.
2) Estimates of median pH and temperature - July through September - based upon available data or
values determined by the Department.
For purposes of calculating effluent limitations based on this value the accepted design stream flow
shall be the actual or estimated lowest 30 consecutive day average flow that occurs once in 10years.
B. Discussion of Section 93.7
The statewide ammonia criteria are based on EPA's ammonia toxicity models, which express allowable
ammonia concentrations for specific pH and temperature conditions. The criteria, which are to be
expressed as total ammonia-nitrogen concentrations, will be determined for site-specific pH and
temperature values.
Studies indicate un-ionized ammonia as the primary concern in aquatic toxicity, but total ammonia is
also toxic to some degree and can also impact on dissolved oxygen. Dissociation of ammonia in water
is highly dependent on pH and temperature. Additionally, un-ionized ammonia itself becomes more
toxic at low pH/temperature conditions. The EPA model for allowable ammonia concentration
includes all of these considerations.
Distinctions between cold water and warm water fish species in their responses to ammonia are not
considered significant. Pennsylvania, however, retains its classifications of cold water and warm water
fisheries since stream temperature remains an important factor in other criteria. This distinction sets
the default temperature values to 20 and 25 degrees (see Table 3).
Because past analytical procedures measured total ammonia nitrogen content, and because
extrapolation to un-ionized ammonia is a strictly mathematical computation which has been accounted
for in the EPA models, there is no reason to change the expression of the statewide ammonia criteria
from its historical form, that is, total ammonia nitrogen (NH
3
-N).
The most critical considerations in determining statewide ammonia criteria are pH and temperature. It
has been demonstrated that instream pH values can be subject to wide daily variation based on algal-
driven CO
2
changes, while the median pH for a stream on a long term basis is relatively constant.
Temperature variations, while subject to wide daily variation, are more predictable on a seasonal basis.
Because allowable total ammonia concentrations are lower at higher temperatures, the temperature to
be used should be representative of the median value during the summer period (July through
September).
The preferred method for determining the appropriate pH and temperature should be based on instream
measurements or estimates using available data. In the absence of actual field data, default values for
pH and temperature can be used, depending on the type of stream, i.e., limestone, free stone, warm
water, trout stocking, cold water. These are included in Table 3.

391-2000-013
/November 4, 1997/Page 12
The regulation requires that pH and temperature be estimated (via instream measurements or default
data) for each discharger and stream before the allowable effluent concentration can be set. This could
significantly increase the cost and effort of setting appropriate effluent limits if site specific data are
required in every case. In general, however, there will be available data in most cases to provide
reasonable estimates for these values.
Interpretation of "maximum concentration": As detailed in Section IV.C and Appendix F, the design
period for the maximum concentration has been interpreted to be a 24 hour period. Any use of the
terms "maximum" or "instantaneous" in this document should be interpreted as "daily maximum".
Thus, this concentration is actually the maximum daily concentration. This interpretation is based on
the data supplied by EPA.
Use of Default Data: Many default data values are used throughout this document. They involve best
engineering and professional judgments on the part of the evaluator. The default data are generalized
values and may not be applicable to a specific stream or discharge situation.
The permit writer should attempt to obtain as much actual data on a case as possible. There is no
substitute for actual field data. The defaults should be used with caution and only as a last resort. A
sensitivity analysis should be performed whenever default data is used in developing water quality
based permit limits.
IV. IMPLEMENTATION OF SECTION 93.7
This section presents procedures for applying the ammonia criteria to NPDES permit writing with
subsections on design conditions, seasonal limits and multiple discharge wasteload allocations.
As with other aspects of permit writing, two levels of data may be applicable. The first is generally
referred to as the "Simplified Method" (Ref. (1)). This refers to agreed-upon assumptions which may
be used for preliminary modeling.
The second level of data precision applies in cases where the assumptions in the Simplified Method are
not applicable. In such cases, field data must be obtained before revised permits may be issued.
NPDES Guidance for writing permits for municipal discharges requires three values for ammonia
concentrations: average monthly, average weekly, and "instantaneous maximum". (Ref. (2): NPDES
Permit Manual, Table 5-2, Item 3). The EPA National Criteria for ammonia, however, presents criteria
for only two of these items: Daily- maximum and 30-day average which is sufficient for privately
owned discharges. A procedure for determining a seven-day average concentration is presented below.
Instream criteria serve as goals. They are based on design pH and temperature conditions, and
complete mix of the stream flow and the discharge flow. Design pH is assumed to be constant for all
conditions. Design temperature may vary depending on the season of the year. Discharge flow is
assumed to be continuous and constant for any 24 hour period. (See "Interim Policy, Real Time
Management Control of Precipitation Induced Point Source Discharges," February, 1983.) Design

391-2000-013
/November 4, 1997/Page 13
streamflow, however, is different for each design condition and may also vary by season of the year. In
general, the design stream flows may be estimated as multiples of Q
7-10
for the design period July-
September.
A. Design Conditions
Before the calculations for a permit can be performed, the key design parameters must be determined.
Next, appropriate values must be determined for each critical variable in the calculations. Since
ammonia toxicity is critical just below the outfall, only mass balance, i.e., dilution, variables are of
concern for setting single discharge effluent limits.
Instream reaction rates become important in multi-discharge water quality limited segments. The
selection and use of reaction rates will not be discussed in this document. The reader is referred to the
joint DEP/EPA document titled "Implementation Guidance for Determining Water Quality Based Point
Source Effluent Limitations".
To calculate effluent limitations for ammonia using simplified procedures, four design variables are
critical:
1. flows
2. temperature
3. pH
4. instream criteria
Information on a fifth variable, alkalinity, may be necessary if simplified procedures do not apply.
Appropriate values for each variable for both stream and effluent flows must be determined. Each is
discussed below.
1. Design Stream Flows
Two design stream flows are important: instantaneous (assumed to equal minimum daily flow) and
monthly. For preliminary modeling purposes, these flows may be derived from Q
7-10
. The specific
multipliers for estimating minimum daily flow and Q
30-10
are based on analysis of free-flowing streams
data presented in Appendix G and discussed in Appendix F and do not apply to regulated streams with
controlled releases.
A regulated stream should not, theoretically, be subject to the same variations in flow exhibited by
free-flowing streams. Q
30-10
, Q
7-10
, and Q
1-10
should generally be the same value, usually the
established minimum release flow.

391-2000-013
/November 4, 1997/Page 14
In most cases, this can be verified from "post-control" stream flow data. Available data should be
reviewed to assure that a minimum guaranteed release is maintained. The minimum controlled release
flow should be used for conducting NH
3
-N evaluations for all design conditions.
In the absence of actual stream flow data, the first step is to estimate the Q
7-10
flow. This value is then
multiplied by 0.64 and 1.36 to determine the acute (1 day) and chronic (30 day) exposure stream flows.
TABLE 1
Design Flow Calculation
Occurrence Interval
Preliminary Value
Daily
0.64 X Q
7-10
*
Monthly
1.36 X Q
7-10
*The issue of estimating Q
7-10
is not addressed in this paper.
These multipliers cannot be used to adjust effluent limits directly, since the instream criteria also
changes with the exposure period.
Regulatory Note: The regulation references the use of Q
30-10
, whereas this procedure uses 1.36 x Q
7-10
.
This is not seen as a conflict, since, in the absence of site-specific data, this is actually another method
of deriving Q
30-10
.
Sensitivity Analysis: Based on the engineer's judgment of the significance of data precision relative to
the preliminary permit limitation and the possible resulting cost, several levels of data refinement could
be persued.
The first level would be a sensitivity analysis on the design stream flow. This would be done by
varying the default multipliers (0.64 and 1.36) within a range of plus-and-minus two standard
deviations.
TABLE 2
Sensitivity Analysis Ranges For Stream Flow
Recommended
Multiplier
Standard Deviation
Daily (Q
1-10
)
0.64
0.12
Monthly (Q
30-10
)
1.36
0.25
This sensitivity analysis could be pursued further by varying the initial value for Q
7-10
. In the above
table, this value is held constant. A further discussion, along with an example, is included in Appendix
F.

391-2000-013
/November 4, 1997/Page 15
2. Temperature
When selecting an instream ammonia nitrogen goal from the table of criteria values, both pH and
temperature values are required. Two levels of precision are applicable to selecting a design
temperature.
a. Stream Temperature
The first level of precision assumes that the design stream temperature to be either 20
o
or 25
o
depending upon the stream. Suggested design temperatures are included in Table 3.
The second level of data precision makes use of historical data where available (via STORET, for
example) or transferable from another stream. Derivation of a design temperature using long term data
is discussed in the Simplified Method (Item 8.a.). Briefly, the design temperature is selected as the
median, i.e., 50th percentile, temperature for the July through September period.
b. Discharge Temperature
In the absence of specific discharge data (as in the case of a new discharge) the design discharge
temperature should be set at 20
o
C. Where discharge data is available, the design temperature is the 90
th
percentile temperature for the July through September period.
3. pH
The allowable instream concentration of ammonia is very sensitive to pH changes, as Table 6
illustrates.
The Regulations require only that stream pH remain in the 6-9 range. The same applies to effluent pH.
Ideally, an effluent should not alter the pH of a stream. Thus, in the past, it has been the generally-
accepted policy to assume that the effluent will not alter the pH of the stream after complete mix, and
therefore the pH upstream of the discharge was used to select the appropriate values from ammonia
toxicity tables. Because of the extreme sensitivity of instream criteria to pH, this assumption can no
longer be used.
For the purposes of calculating ammonia effluent limitations, the complete mix pH shall be used to
determine the appropriate instream criteria. For existing discharges, the discharge and the upstream
and downstream pH should be measured. The point of measurement of downstream pH should be
carefully selected to assure that complete mix has occurred, and to assure that it is not being unduly
influenced by possible non-point sources of pollution. Where it can be determined, the complete mix
pH should be used to determine appropriate effluent limits.
For proposed discharges, the design effluent pH should be representative of the proposed unit process
train. The adjustment of effluent pH for the sole purpose of obtaining a more liberal effluent limit shall
not be permitted.

391-2000-013
/November 4, 1997/Page 16
When actual field data are not available, upstream default values can be used for preliminary modeling.
Table 3 below lists recommended upstream default values.
The instream pH values will fluctuate on a diurnal basis as CO
2
is absorbed and released. In the
presence of algae, CO
2
concentrations will fall during the light period as a result of respiration. This
will tend to raise the pH. During this same period, the stream temperature will also rise. Both factors
will lower the maximum instream criteria. The resulting exposure period, however, is less than one
day, and therefore is not considered to be a critical toxicity problem.
The suggestion of effluent pH adjustment in lieu of treatment was raised in an EPA guidance
document, "Simplified Wasteload Allocation Procedure for Ammonia Toxicity," Draft, July 30, 1982,
pg. 10.
In situations where the DO analysis does not indicate a need for advanced treatment levels, but the
ammonia toxicity analysis predicts toxicity problems, consideration should be given to using pH
adjustments (i.e., pH reductions) of the effluent during critical conditions to control ammonia toxicity
in lieu of requiring nitrification. This consideration should include a determination of whether the
temporary lowering of pH and increase in total dissolved solids (TDS) concentration would have any
significant instream ecological or other effects.
This issue was reviewed by aquatic biologists in both DEP and EPA Region III. All agreed that an
instream pH change of 0.5 units or more would result in “...significant instream ecological effects" and
would, therefore, not be accepted.
TABLE 3
Recommended Upstream Design pH and Temperature Default Values
Cold Water Fisheries
Warm Water/Trout Stocking Fisheries
Limestone
Free Stone
Limestone
Free Stone
pH
Temp
pH
Temp
pH
Temp
pH
Temp
8
20
6.5
20
8
25
7
25
The accurate calculation of the complete mix (downstream) pH should include the alkalinity of the
stream and the discharge flows. Preliminary modeling, however, can use a mass balance of the
hydrogen ion equivalent of the pH (calculated as 10
-pH
) if alkalinity data is not available.
Example:
Stream:
pH
s
= 7, Q
s
= 3 MGD
Waste:
pH
w
= 6, Q
w
= 1 MGD
pHsw
=-log[(Q
s
? 10
-
-
pHs
+ Q
w
? 10
-pHw
)/Q
sw
]
=-log[(3
? 10
-7
+ 1 ? 10
-6
)/4]
=6.49
If alkalinity data is available, it should be used to calculate the design pH. See Appendix J for
guidance on how to incorporate alkalinity data into pH calculations.

391-2000-013
/November 4, 1997/Page 17
Because of the variability and uncertainty associated with pH data, the complete mix pH used to
determine effluent limitations (See Section C below) should be rounded to the nearest one-tenth of a
pH unit.
Discharges to waters polluted by abandoned mine drainage are regulated by Section 95.5. Under
certain conditions it allows "secondary" treatment or minimum technology (BPT) limits. Since there is
no "secondary" or minimum technology definition for ammonia, it eliminates the need for establishing
an effluent limit except where (1) the water quality of the receiving water is expected to improve
significantly (for purposes of this guidance - that the quality is expected to improve primarily due to an
on-going or proposed reclamation project; or other identifiable causes within the next 5 years), and (2)
the discharge would cause pollution in downstream waters. The most recent water quality and/or
biological information available should be consulted to assure that receiving waters commonly known
to be polluted have not improved significantly and to establish the downstream pollution boundary.
4. Criteria
The instream criteria are based on technical guidance material developed by the U.S. Environmental
Protection Agency. This document contains equations for calculating the criteria (in mg/l un-ionized
ammonia) for 1-day and 30-day exposure periods. Chapter 93.7 also expresses the criteria through
equations except that they have been adjusted to yield concentrations of ammonia-nitrogen.
The basis for calculating effluent limits for two exposure periods (daily and monthly) are shown in
Table 4, below:
TABLE 4
SOURCES OF DESIGN CRITERIA
Exposure Period
Basis for Effluent Limitations
Daily
Table 6 "One Day Average"
Monthly
Table 6 "30-day Average"
B. Requirements for Field Data
The procedure presented in Section C may be employed with little or no field data. In many cases,
however, this procedure may not be adequate and actual data will be required.
The use of generalized multipliers to estimate Q
1-10
and Q
30-10
from Q
7-10
, should be limited to cases
where site specific date is not available.
For construction grant cases (Federal Register, Vol. 49, No. 99, pg. 21462), the simplified procedure
may be used provided that:
(a) The cost of the change is less than $3,000,000 (consult with the regional permits/grants chief)

391-2000-013
/November 4, 1997/Page 18
and
(b) Nitrification unit processes will not be required.
The design streamflow, Q
7-10
, cannot generally be measured directly. Generally, a nearby gauged
stream is used to derive a yield for the stream in question. As an alternative, an estimated value for Q
7-
10
can be calculated using the method found in Water Resources Bulletin B-15. If Bulletin B-15 is
used, the estimated value can be refined by adjusting the calculated value by the same percentage error
found in Bulletin B-15 for a nearby, gauged stream. Also, actual streamflow measurements can be
indicative of the expected Q
7-10
. If, for example, a drought period flow measurement was not near the
calculated Q
7-10
, then the calculated Q7
-10
would have to be reconsidered.
In general, the default values listed in Table 3 are believed to be conservative, i.e. - their use is likely to
result in somewhat more stringent effluent limitations than would be the case if actual field data is
used. It is therefore in the discharger's best interest to collect and provide actual field data to DEP.
The discharger should be made aware of this. Where a discharger elects to collect and provide field
data, a written protocol should be developed and agreed to. The protocol should provide for adequate
quality assurance.
(Internal Note: As soon as practicable, Central Office will develop a suggested protocol for field data
collection by dischargers and/or their consultants, and distribute it to the Regional Offices. Until this
can be accomplished, regions should use best professional judgment to develop such protocols.)
C. Determination of Effluent Limitations
1. Determination of Water Quality Based Effluent Limitations
To facilitate the implementation of the criteria, the following simplified procedure is to be used, where
appropriate (see general limitations, above):
TABLE 5
Summary of Procedures
Permit Value
Ch. 93 Instream Criteria
Design Stream Flow*
Instantaneous (1-day)
"maximum"
0.64 x Q
7-10
Monthly (30-day)
"30-day"
1.36 x Q
7-10
*Does not include flow augmentations, i.e., upstream discharges

391-2000-013
/November 4, 1997/Page 19
Daily Maximum Water Quality Based Effluent Limits
The Water Quality Based Effluent Limit will be calculated using a mass balance equation and a design
stream flow 0.64 times the Q
7-10
. The 0.64 factor value is in the range of the ratio of (lowest 24-hour
flow)/(Q
7-10
) values taken from Bulletin No. 12. The use of 24-hour low flows rather than lowest flow
ever recorded is justified by examination of Appendix F, Figure II which shows that the maximum
value (based on a multiple of the 30-day value) for Rainbow Trout falls at 18 hours, approximately.
Thus EPA's acute criteria do not correspond exactly to the shortest time period possible.
The instream criteria will be based on the "maximum" equation provided in Section 93.7 and on the
concentrations listed in Table 6.

391-2000-013
/November 4, 1997/Page 20
TABLE 6
Chapter 93.7 - Maximum In-Stream Ammonia
Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6.0
18.35 17.02 15.79 14.66 13.62 12.65 11.77 10.94 10.19 9.43 8.83 8.23 7.68 7.15
6.68
6.24
6.1
18.28 16.95 15.73 14.60 13.56 12.60 11.72 10.90 10.14 9.44 8.60 8.20 7.65 7.13
6.66
6.22
6.2
18.15 16.83 15.62 14.50 13.47 12.52 11.64 10.82 10.07 9.38 8.74 8.14 7.59 7.09
6.61
6.17
6.3
17.96 16.66 15.46 14.35 13.33 12.39 11.52 10.71
9.97
9.28 8.65 8.06 7.52 7.01
6.55
6.11
6.4
17.70 16.42 15.23 14.14 13.14 12.21 11.35 10.56
9.83
9.15 8.53 7.95 7.41 6.91
6.45
6.03
6.5
17.36 16.10 14.94 13.87 12.88 11.97 11.13 10.35
9.64
8.97 8.36 7.79 7.27 6.78
6.33
5.91
6.6
16.92 15.69 14.56 13.51 12.55 11.67 10.85 10.09
9.39
8.75 8.15 7.60 7.08 6.61
6.17
5.76
6.7
16.37 15.18 14.08 13.08 12.15 11.29 10.50
9.77
9.09
8.48 7.89 7.35 6.86 6.40
5.73
5.58
6.8
15.70 14.56 13.51 12.55 11.65 10.83 10.07
9.37
8.72
8.12 7.57 7.06 6.58 6.14
5.73
5.35
6.9
14.91 13.83 12.84 11.92 11.07 10.29
9.57
8.90
8.29
7.72 7.19 6.71 6.26 5.84
5.45
5.09
7.0
14.01 13.00 12.06 11.20 10.41
9.67
9.00
8.37
7.79
7.26 6.76 6.37 5.88 5.49
5.13
4.79
7.1
13.01 12.07 11.20 10.40
9.66
8.98
8.36
7.78
7.24
6.74 6.28 5.86 5.47 5.10
4.77
4.45
7.2
11.92 11.06 10.27
9.54
8.86
8.24
7.66
7.13
6.64
6.13 5.76 5.38 5.02 4.68
4.37
4.09
7.3
10.78 10.00
9.29
8.62
8.01
7.45
6.93
6.45
6.01
5.60 5.22 4.87 4.54 4.24
3.96
3.70
7.4
9.62
8.92
8.28
7.69
7.15
6.65
6.19
5.76
5.36
5.00 4.66 4.35 4.06 3.79
3.54
3.31
7.5
8.46
7.85
7.29
6.77
6.29
5.85
5.45
5.07
4.73
4.40 4.11 3.83 3.58 3.34
3.13
2.92
7.6
7.35
6.82
6.33
5.88
5.47
5.09
4.74
4.41
4.11
3.81 3.58 3.34 3.12 2.91
2.73
2.55
7.7
6.30
5.85
5.44
5.05
4.70
4.37
4.07
3.79
3.54
3.30 3.08 2.87 2.69 2.51
2.35
2.20
7.8
5.35
4.97
4.62
4.29
3.99
3.72
3.46
3.23
3.01
2.81 2.12 2.45 2.29 2.14
2.01
1.88
7.9
4.50
4.18
3.89
3.61
3.36
3.13
2.92
2.72
2.54
2.37 2.22 2.07 1.94 1.81
1.70
1.59

391-2000-013
/November 4, 1997/Page 21
TABLE 6 (Continued)
Chapter 93.7 - Maximum In-Stream Ammonia
Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
8.0
3.75
3.49
3.24
3.02
2.81
2.62
2.44
2.28
2.13
1.99
1.86
1.74
1.63
1.53
1.43
1.34
8.1
3.11
2.89
2.69
2.51
2.34
2.18
2.03
1.90
1.77
1.66
1.55
1.45
1.36
1.28
1.20
1.13
8.2
2.57
2.39
2.22
2.07
1.93
1.80
1.68
1.57
1.47
1..36
1.29
1.21
1.14
1.07
1.00
.94
8.3
2.11
1.96
1.83
1.71
1.59
1.49
1.39
1.30
1.22
1.14
1.07
1.01
.95
.89
.84
.79
8.4
1.73
1.61
1.51
1.41
1.31
1.23
1.15
1.08
1.01
.98
.89
.84
.79
.74
.70
.66
8.5
1.42
1.32
1.24
1.16
1.08
1.01
.95
.89
.84
.79
.74
.70
.66
.62
.59
.56
8.6
1.16
1.09
1.02
.95
.89
.84
.79
.74
.70
.66
.62
.59
.55
.52
.50
.47
8.7
.96
.90
.84
.79
.74
.70
.66
.62
.56
.55
.52
.49
.47
.44
.42
.40
8.8
.79
.74
.70
.66
.62
.58
.55
.52
.49
.43
.44
.42
.40
.38
.36
.35
8.9
.66
.62
.58
.55
.52
.49
.46
.44
.42
.40
.38
.36
.34
.33
.31
.30
9.0
.55
.52
.49
.46
.44
.41
.39
.37
.36
.34
.32
.31
.30
.29
.27
.26

391-2000-013
/November 4, 1997/Page 22
TABLE 6
30-Day Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6.0
5.04
4.68
4.34
4.03
3.74
3.48
3.23
3.01
2.80
2.61
2.43
2.26
2.11
1.97
1.84
1.71
6.1
4.75
4.40
4.09
3.79
3.52
3.27
3.04
2.83
2.64
2.45
2.29
2.13
1.99
1.85
1.73
1.62
6.2
4.47
4.15
3.85
3.57
3.32
3.09
2.87
2.67
2.48
2.31
2.15
2.01
1.87
1.75
1.63
1.52
6.3
1.21
3.91
3.63
3.37
3.13
2.91
2.70
2.51
2.34
2.16
2.03
1.89
1.76
1.65
1.54
1.43
6.4
3.97
3.68
3.2
3.17
2.95
2.74
2.55
2.37
2.20
2.05
1.91
1.78
1.66
1.55
1.45
1.35
6.5
3.74
3.47
3.22
2.99
2.78
2.58
2.40
2.23
2.08
1.93
1.30
1.68
1.57
1.46
1.36
1.27
6.6
3.52
3.27
3.03
2.82
2.62
2.43
2.26
2.10
1.96
1.82
1.70
1.58
1.48
1.36
1.29
1.20
6.7
3.32
3.08
2.86
2.65
2.46
2.29
2.13
1.98
1.84
1.72
1.60
1.49
1.39
1.30
1.21
1.13
6.8
3.13
2.9
2.69
2.50
2.32
2.16
2.01
1.87
1.74
1.62
1.51
1.41
1.31
1.22
1.14
1.07
6.9
2.95
2.73
2.54
2.36
2.19
2.03
1.89
1.76
1.64
1.53
1.42
1.33
1.24
1.15
1.08
1.01
7.0
2.78
2.58
2.39
2.22
2.06
1.92
1.78
1.36
1.54
1.44
1.34
1.25
1.17
1.09
1.02
.95
7.1
2.62
2.43
2.25
2.09
1.94
1.81
1.68
1.56
1.46
1.36
1.26
1.18
1.10
1.03
.96
.90
7.2
2.47
2.29
2.13
1.97
1.83
1.70
1.59
1.48
1.67
1.28
1.19
1.11
1.04
.97
.91
.85
7.3
2.33
2.16
2.00
1.86
1.73
1.61
1.50
1.39
1.30
1.21
1.13
1.05
.98
.92
.86
.80
7.4
2.20
2.04
1.89
1.76
1.63
1.52
1.41
1.31
1.22
1.14
1.06
.99
.93
.87
.81
.76
7.5
2.07
1.92
1.78
1.66
1.54
1.43
1.33
1.24
1.16
1.08
1.01
.94
.88
.82
.77
.72
7.6
1.96
1.81
1.69
1.57
1.46
1.35
1.26
1.17
1.09
1.02
.95
.89
.83
.78
.73
.68
7.7
1.85
1.71
1.59
1.48
1.38
1.28
1.19
1.11
1.04
.97
.90
.84
.79
.74
.69
.64
7.8
1.47
1.37
1.27
1.18
1.10
1.02
.95
.89
.83
.77
.72
.67
.63
.59
.55
.52
7.9
1.17
1.09
1.01
.94
.88
.82
.76
.71
.66
.62
.58
.54
.51
.47
.44
.42

391-2000-013
/November 4, 1997/Page 23
TABLE 6 (Continued)
30-Day Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
8.0
.94
.87
.81
.75
.70
.65
.61
.57
.53
.50
.46
.43
.41
.38
.36
.34
8.1
.75
.70
.65
.60
.56
.53
.49
.46
.43
.40
.37
.35
.33
.31
.29
.27
8.2
.60
.56
.52
.49
.45
.42
.39
.37
.34
.32
.30
.28
.27
.25
.23
.22
8.3
.48
.45
.42
.39
.36
.34
.32
.30
.28
.26
.25
.23
.22
.20
.19
.18
8.4
.39
.36
.34
.32
.29
.28
.26
.24
.23
.21
.20
.19
.18
.17
.16
.15
8.5
.31
.29
.27
.26
.24
.22
.21
.20
.19
.17
.16
.15
.15
.14
.13
.12
8.6
.25
.24
.22
.01
.20
.18
.17
.16
.15
.14
.14
.13
.12
.11
.11
.10
8.7
.21
.19
.18
.17
.16
.15
.14
.13
.13
.12
.11
.11
.10
.10
.09
.09
8.8
.17
.16
.15
.14
.13
.12
.12
.11
.11
.10
.09
.09
.09
.08
.08
.07
8.9
.14
.13
.12
.12
.11
.10
.10
.09
.09
.08
.08
.08
.07
.07
.07
.06
9.0
.12
.11
.10
.10
.09
.09
.08
.08
.08
.07
.07
.07
.06
.06
.06
.06

391-2000-013
/November 4, 1997/Page 24
Monthly Water Quality Based Effluent Limits
The Water Quality Based Effluent Limit will be calculated using a mass balance equation and a design
stream flow of 1.36 times the Q
7-10
, unless 30-day gauge station data is available or transferable from a
nearby station. Based on an average of 66 streams taken from Bulletin No. 12, this calculated flow is
equivalent to Q
30-10
(See Appendix G).
The instream criteria will be based on the "30 day average" equation provided in Section 93.7 and
listed in Table 6.
2. Permit Effluent Limitations
The effluent limitations to be incorporated into an NPDES permit as a 30-day average value should be
based on the more stringent of the two WQBEL's. To determine which WQBEL is the more stringent,
the daily maximum WQBEL should be converted to an equivalent 30-day average value by multiplying
the daily maximum WQBEL by the estimated coefficient of variation. (For a discussion of how to
determine the coefficient of variation, see Chapter 6 III (pages 51-59) of EPA's Technical Support
Document for Water Quality Based Toxics Control, September 1985). In the absence of site (i.e.;
treatment plant) specific information, the coefficient of variation may be assumed to be equal to 0.5.
Instantaneous and (where applicable) 7-day average permit values should be determined using the
procedures outlined in the NPDES permits manual. The weekly values are calculated as 1.5 times the
monthly values; the instantaneous or daily maximum values as 2.5 times monthly values for industrial
and 2.0 times for POTW and non-municipal sewage discharges.
3. Seasonal Effluent Limits
In general, winter effluent limits will continue to be set as a multiple of summer limits except where
winter time modeling/evaluation indicates more stringent effluent limitations are required. First, the
summer limits will be set based on water quality considerations. Next, the winter effluent limit will be
set at three-times the summer limits for each exposure period, i.e., daily, weekly and monthly.
Winter Interactions: DO problems are generally a summer phenomenon. The winter period (November
through April) not only have an increased design flow, but also have reduced reaction rates due to the
lower temperatures. Both November and January months are considered critical for winter period
evaluations. For example, during November, stream flows are still relatively lower with moderate
temperatures up to 15
o
C. This may cause an adverse toxicity impact on stream if not evaluated.
Computer simulation runs show that at a stream temperature of 5
o
C, significant NH
3
-N loads pass
downstream, unmet. This may create a wintertime ammonia toxicity multiple discharge wasteload
allocation (WLA) problem. Downstream dischargers may see increased upstream loads during the
winter months. This may have a significant impact on the downstream discharger's winter time
toxicity-related effluent limit.
In setting winter time ammonia-nitrogen effluent limitations for multiple discharge situations,

391-2000-013
/November 4, 1997/Page 25
compliance with instantaneous and monthly in-stream criteria using technology based winter effluent
limitations should be verified for November and January months. For purposes of verification, a
stream temperature of 5
o
C should be used. Q
1-10
and Q
30-10
design stream flows should be estimated
on the basis of either a winter Q
7-10
(usually occurring in November or January), or by setting winter
Q
7-10
as two-times the summer Q
7-10
. If it is determined that a winter violation will occur, winter
effluent limitations should be adjusted accordingly. It should be noted that discharges that do not
display any interaction during summer design conditions, may because of slower reaction rates, display
an interaction during winter conditions. Winter evaluations may therefore require the incorporation
and consideration of additional downstream discharges that are not included in the summer design
conditions evaluation.
4. Potential Impact on Water Supplies
The presence of excessive ammonia at a water supply intake can increase the chlorine demands and
cause taste and odor problems in the water supply. In some cases, this revision to Chapter 93.7 will
result in an increase in instream ammonia concentrations. This will be the case on water quality
limited cold water fisheries with a background pH of less than 7.0.
For example, a stream which previously had an AM1 classification and a design pH of 6.5 would have
had an instream criteria of 0.5 mg/l ammonia nitrogen. If, in this case, the design temperature is 20
o
,
the revised instream criteria would be 2.58, or 416 percent increase At the same pH, an AM
2
stream
would see only a 20 percent increase.
During the winter, when reaction rates are low and the effluent limits have been relaxed, downstream
water suppliers could encounter ammonia levels higher than usual.
If a water supply is operated for the maintenance of a free available chlorine residual, the formation of
bi- and tri-chloramines may occur, thus causing taste and odor problems. (This will not, however, lead
to public health problems.)
Short-term ammonia-based taste and odor problems are an ongoing problem for water suppliers, often
being caused by weather related non-point source loads such as spring snow-melt or fertilizer runoff.
At this time, it is not anticipated that this ammonia criteria will result in any significant increase in
chlorine requirements for potable water supplies, or in any significant increase in taste and odor
problems. However any complaints received by DEP from downstream water supplies should be
thoroughly investigated in cooperation with the Bureau of Water Supply Management. If it is
determined that relaxation of effluent limitations is leading to increased chlorine demands, or taste and
odor problems, appropriate adjustments to permitted discharge effluent limitations should be made.

391-2000-013
/November 4, 1997/Page 26
5. Wasteload Allocations
The Water Quality Standards and Implementation Section has completed a revised wasteload allocation
(WLA) policy and procedure and WQM 6.3 computer model. The model utilizes uniform treatment
strategy (continuation of existing practice), and an equal marginal percent reduction strategy. Use of
the WQM 6.3 in uniform treatment mode has been approved by the Bureau Director in a January 6,
1987 memo.
A wasteload allocation (WLA) situation occurs when an upstream discharge load is not sufficiently
assimilated before reaching the next downstream discharge point, and the resulting combined load
results in a criteria violation. In the absence of any equity procedure, this would reduce the effluent
limit of the downstream discharger.
Due to the reduced reaction rates during the winter months, increasing fractions of C-BOD
5
and NH
3
-N
will be passed downstream. Note, however, that aquatic life is also less sensitive to ammonia toxicity
impacts at lower temperatures. This mitigates some of the potential WLA situations.
Summer or winter, however, WLA problems will arise. The general procedure for allocating
assimilative capacity between discharges is:
1. Set starting point effluent limitation for each discharger at the more stringent of:
a. Technology based limits, i.e. BPT/BAT (See Table 7),
b. Water Quality based limits, assuming each discharge is to be the only discharge to the receiving
stream.
2. Check for downstream ammonia toxicity violations with all discharges set according to #1, above.
3. If toxicity violations are present, reduce NH
3
-N concentrations for all discharges from the levels
determined in #1, by equal increments until the toxicity violation no longer occurs.
4. Check for DO violations,
5. If DO violations are present, allocate oxygen-consuming loads beginning with C-BOD
5
.
The key word above is "allocate". First, it refers to the method of equity. Second, it refers to the
distribution of the load between carbonaceous and nitrogenous components.
The first process is a "mechanical" procedure which will be performed by the WLA computer program.
The second process may require the use of judgment to suit site specific conditions (i.e., raw waste
loads, available unit processes, etc.)

391-2000-013
/November 4, 1997/Page 27
The WLA model uses the following procedure to set the oxygen consuming portion of the effluent
identified in Step 5, above.
6. Reduce C-BOD
5
toward lower i.e., unit process-based, limit.
7. If DO violation persists at C-BOD
5
= lower limit:
a. Reduce ammonia one increment,
b. Raise C-BOD
5
back to the starting point,
c. Return to Step 6.
The assumption used in the WLA model is that above a certain minimum C-BOD
5
value it is less
expensive to remove carbonaceous BOD than to remove ammonia. The computer model uses a
balanced technology approach to restrict C-BOD
5
and NH
3
-N effluent limits to the three ranges listed
below:
TABLE 7
Treatment Technology Ranges
C-BOD5 Range
NH3-N Range
25 - 20
25 - 10
19 - 10
9 - 4
9 - 1
3 - 0.5
Although these ranges will not be universally applicable, their use will prevent the program from
calculating unreasonable combinations.
This process incorporates two factors. The first is the relative economics of removal. The removal of
ammonia, beyond that needed for toxicity, is avoided until further C-BOD
5
removal become
prohibitively expensive.
The second factor is that, while each mg/l of NH
3
-N ultimately consumes 4.57 mg/l of oxygen, (C-
BOD
5
ultimately consumes only 1.5 mg/l), it consumes it at a slower rate, and thus does not impact the
point of DO-minimum as directly as these stoichiometrically based values would indicate.
See Section VI of this document for a further discussion of water quality modeling.

391-2000-013
/November 4, 1997/Page 28
D. Incorporation of Effluent Limits Into NPDES Permits
General Note on Level of Precision:
Because of the variability in the data used to determine effluent limitations, the following rules (see
NPDES Manual, Chapter 5.C.2) should be used in specifying effluent limitations in permits:
1) Effluent limitation > 10 mg/l - Round down to the nearest whole number.
2) Effluent limitation < 10 mg/l - Round down to the nearest 0.5.
3) Effluent limitation < 1 mg/l - Round down to the nearest one-tenth.
This implementation guidance includes one change to the procedures for issuing NPDES permits as
described in the "Technical Guidance for the Development and Specification of Effluent Limitations
and Other Conditions in NPDES Permits", revised August 1983.
According to this NPDES manual, ammonia is classified as a "Non-Conventional" pollutant, requiring
Best Available Technology Economically Achievable (BAT).
Chapter 3 of the NPDES manual lists ammonia as being either conservative or non-conservative. For
ammonia toxicity modeling, however, this distinction is not important since the critical point for setting
effluent limits is at the point of complete mix, before either dilution or decay.
Chapter 3 of the NPDES Permit Writing Manual is currently under review. Chapter 3.D.7 (page 27)
will be revised approximately as follows:
7. Ammonia
Appropriate water quality criteria for all streams in Pennsylvania will be determined according to
Chapter 93.7. Water quality modeling will use stream flows which correspond to the exposure periods
of 30-day, 7-day and 1-day, appropriate site-specific upstream and effluent pH and temperature data,
and instream criteria based on the complete-mix pH and temperature data. Seven day (weekly) NH
3
-N
limits will be calculated by applying a multiplier of 1.5 to 30 day effluent limits. Winter effluent limits
will be three times the summer limits, except where winter evaluation indicates that a violation of
water quality standards would result.
This page will be formally revised and distributed separately.
E. Example Calculations

391-2000-013
/November 4, 1997/Page 29
The following examples will use the design and background data listed below:
Stream
Effluent
Q
7-10
Flow (Q
0
) = 1.547 cfs (1 MGD)
Flow (Q1) = 1 MGD
pH = 7
pH = 7
NH
3
-N = 1 mg/l
Temperature = 20
o
C
Temperature = 20
o
C
First, the design stream flow and criteria values must be set for each of the three exposure periods.
This is shown in Table 8 below:
TABLE 8
Design C
Stream Design Flow
Instream Criteria (NH
3
-N)
Daily
1 ? 0.64 MGD
9.67 mg/l
Weekly
1 MGD
NA
Monthly
1
? 1.36 MGD
1.92 mg/l
Next, the general mass balance equation:
Q
WS
C
WS
= Q
S
C
S
+ Q
W
C
W
(Eq. 1)
Where: Q
S
C
S
= upstream conditions
Q
W
C
W
= effluent conditions
Q
WS
C
WS
= downstream (complete mix) conditions
is applied to calculate C
W
, the effluent concentration, when C
WS
is set at the criteria and Q
S
is set at the
design stream flow.
For the one-day water quality based effluent limit this calculation is as follows:
?
?
?
?
CW
Q
QC
QC
Q
SW
WS
S
S
W
?
??
(Eq. 2)
Set:
Q
s
= 0.64?Q
7-10
= 0.64MGD(0.99 cfs)
Q
7-10
= 1
cf
C
S
= 1
mg/
l
Q
W
= 1 M
GD
C
WS
= 9.67
mg/l as total NH
3
-
N

391-2000-013
/November 4, 1997/Page 30
Then:
C
W
=
?
?
064 1 1
?
9 67
?
064 1
?
1
?
1
15 22
.
.
.
.
/
? ? ? ? ? ?
?
mg l
The equivalent 30-day average value for this one-day WQBEL is
15.22
? C.V = 15.22 ? 0.5 = 7.61 mg/l.
For the 30-day water quality based effluent limit, this calculation is as follows:
?
?
?
?
C
Q
QC
QC
w
Q
sw
ws
s
s
w
?
??
Set:
Q
S
= 1.36 ?
Q
7-10
Q
7-10
= 1.00
cfs
C
S
= 1
mg/l
Q
W
= 1
MGD
C
WS
= 1.92
mg/l as total NH
3
-
N
Then:
C
W
= (C 1.36 ? 1 + 1) ? 1.92 - (1.36 ? 1) ? 1)/1.0 = 3.17
mg/l
The 30-day average value for this WQBEL is 3.17 mg/l.
This 30-day WQBEL is more stringent than the equivalent 30-day average value for the one-day
WQBEL
The resulting toxicity-based NPDES permit effluent limitations are shown in Table 9 below.
TABLE 9
Example NPDES Permit Effluent Limits
(**)
Period
Instantaneous
Weekly
Monthly
*
Summer
7.5 mg/l
4.5
3.0*
Winter
22.5
13.5
9.0
*Note: The weekly values are calculated as 1.5 times the monthly values; the instantaneous or Daily
Maximum values as 2.5 times the monthly value for Industrial discharges and 2.0 times the monthly
value for POTW's and non-municipal sewage discharges.
** Rounded as per Section IV(D).

391-2000-013
/November 4, 1997/Page 31
V
.
STREAM MODELS
BWC has completed a Water Quality Analysis model (WQM Model Version 6.3) that is designed to
determine effluent limitations for Carbonaceous Biological Oxygen Demand (C-BOD
5
) and Ammonia
Nitrogen (NH
3
-N) for single and multiple point source discharge scenarios. When used in multiple
discharge scenario, the model determines whether a wasteload allocation situation exists, and if it does,
calculates the necessary reduction required for each discharge. The model is capable of applying a
balanced technology option and utilizes two general strategies in making evaluations. They are (1)
Uniform Treatment
, and (2)
Equal Marginal Percent Reduction
. The uniform treatment strategy is
BWC's existing WQM strategy and requires assignment of equal treatment requirements to all
discharges within a given watershed. The equal marginal percent removal is a proposed WQM strategy
which calculates equal percent wasteload reductions from a baseline treatment determined necessary if
it was the only discharge on the stream. Detailed documentation of the two wasteload strategies, the
WLA model WQM 6.3 and some sample examples are contained in the BWC's wasteload allocation
policy and procedures document.
On January 6, 1987, BWC approved use of WQM model 6.3 in
UNIFORM TREATMENT MODE
ONLY
. The use of WQM 6.3 for reviewing existing and for writing new NPDES permits would
eliminate use of both the DOSAG and NH
3
CALC models.
As far as NH
3
-N evaluations are concerned, WQM 6.3 determines toxicity and DO based limitations
for 30-day and 1-day durations. The user is required to establish most critical (summer and/or winter
period) design condition and perform appropriate evaluations. The user performs ammonia toxicity
evaluations by first running NH
3
-N option of the WQM 6.3. The DO Allocation option (with balanced
technology) is run next to determine need for additional ammonia reductions for DO. The final
effluent display option of WQM 6.3 will provide a 30-day C-BOD
5
value and both 30-day and 1- day
ammonia nitrogen limitations. The user is required to select the more stringent of toxicity or DO based
ammonia effluent limitations for NPDES permits. If both values are greater than 15 mg/l (minimum)
technology ammonia limit (as defined by BWC), no NH
3
-N limits are placed in the permit. Weekly
ammonia effluent limitations, where required in NPDES permit, should be calculated using a
technology based multiplier provided earlier in this guidance.
Additional discussion of specifying ammonia effluent limitations is contained in BWC's C-
BOD
5
/BOD
5
discussion paper released on December 29, 1986.

391-2000-013
/November 4, 1997/Page 32
APPENDICES
A. Revisions to Simplified Method
B. Revisions to NPDES Permit Writing Manual
C. Excerpts from EPA Guidance
D. References
E. Rationale Paper - Ammonia Criteria
F. Rationale Paper - Simplified Method
G. Database of Stream flows
H. Computer Program Listing
I. Criteria Tables
J. Alkalinity

391-2000-013
/November 4, 1997/Page 33
APPENDIX A
Revisions to the Simplified Method
(Not Revised)

391-2000-013
/November 4, 1997/Page 34
APPENDIX B
Revisions to NPDES Permit Writing Manual
(No Revisions)

391-2000-013
/November 4, 1997/Page 35
APPENDIX C
Excerpts from the EPA Guidance
(No Revisions)

391-2000-013
/November 4, 1997/Page 36
APPENDIX D
REFERENCES
(1) PA DEP and U.S. EPA, Simplified Method for Determining Point Source Effluent Limitations for
Discharges to Free-Flowing Streams, December 14, 1981.
(2) PA DEP, BWC, Technical Guidance for the Development and Specification of Effluent Limitations
and Other Conditions in NPDES Permits, August 1983, (REV 8/84).
(3) U.S. EPA, Simplified Wasteload Allocation Procedure for Ammonia Toxicity
, July 30, 1982.

391-2000-013
/November 4, 1997/Page 37
APPENDIX E
Rationale Paper
Ammonia Criteria

391-2000-013
/November 4, 1997/Page 38
WATER QUALITY STANDARDS RATIONALE PAPER
STATEWIDE AMMONIA CRITERIA
Prepared by
Dennis F. Lee and Carol A. Sudick
Division of Water Quality Assessment and Standards
BACKGROUND
Current Regulation
- Ammonia criteria for specific streams are included in Chapter 93. These criteria
are as follows:
Am1 - Not more than 0.5 mg/l as ammonia nitrogen
Am2 - Not more than 1.5 mg/l as ammonia nitrogen
The Issue
- Ammonia criteria are not specified for all surface waters because Pennsylvania did not
begin to incorporate ammonia criteria into Chapter 93 until 1973, midway into initial development of
the water quality standards. Therefore, ammonia criteria are specified for only about one-half the
streams of Pennsylvania.
For those streams which do not have an ammonia criterion, effluent limitations are established on a
case-by-case basis under provisions of Section 93.6. Effluent limitations are calculated to meet both
total and un-ionized ammonia criteria, based on consideration of oxygen demand and toxicity
respectively. The less
stringent effluent limit is then applied. In these cases, trout stocking water
bodies are treated as warm water fisheries. However, in assigning ammonia criteria to TSF streams in
Chapter 93, these streams were considered to be equivalent to cold water fisheries. As a result, two
different ammonia criteria are applied to streams of the same classification, which is clearly
contradictory.
EPA has requested that the Department consider consistent statewide ammonia criteria during the
current review of the water quality standards. EPA has collected extensive new information and is
proposing ammonia criteria.
Ammonia Toxicity - Ammonia present in natural waters is generally attributable to the deamination of
organic nitrogen-containing compounds and hydrolysis of urea. However, the amounts associated with
these natural occurrences seldom reach toxic levels. Toxic concentrations of ammonia are more likely
to be anthropogenically introduced from such sources as sewage treatment plant discharges, industrial
discharges, and agricultural runoff.
Ammonia (NH
3
) is a water soluable gas that reacts with water to form ammonium hydroxide, which is
dissociated into its respective ions to a degree determined by temperature and pH. The equilibrium
equation that expresses the relationship of these constituents is:

391-2000-013
/November 4, 1997/Page 39
NH
3
+ H
2
0
NH
3
.nH
2
0
NH
4
+ -
OH - H
2
0
As indicated, un-ionized ammonia exists as a hydrate, but it is usually referred to simply as NH
3
.
Present analytical methods allow only for the determination of total ammonia nitrogen, i.e., the
summation of NH
3
, NH
4
OH, and NH
4
+ nitrogen from aqueous solution. Un-ionized ammonia cannot
be directly measured and is therefore calculated based on total ammonia concentration, pH, and
temperature. Because of their respective effects on the equilibrium of NH
3
/NH
4
+
, each unit rise in pH
increases the concentration of un-ionized ammonia by one order of magnitude and each 10
o
C rise in
temperature yields a two-fold increase in NH
3
.
Toxicity of ammonia at levels that occur in natural or polluted waters is generally not apparent in
humans. The effect on aquatic species is much more adverse, and fish have been shown to be more
sensitive than macroinvertebrates.
ISSUES CONSIDERATION AND ANALYSIS
HISTORICAL PERSPECTIVE:
The 0.5 mg/l criterion for total ammonia was recommended by the Pennsylvania Fish and Boat
Commission for trout-stocking fisheries (TSF) and cold water fisheries (CWF) (3-24-77 memorandum
from R. M. Boardman to C. T. Beechwood). Their experiences at the state's trout hatcheries indicated
that any greater concentration adversely affected trout.
The 1.5 mg/l criterion for warm water fisheries (WWF) was adopted based on work by M. M. Ellis
(1937), who stated that this concentration was not harmful to most varieties of fish.
In 1978 during the Water Quality Standards review, the Department proposed a statewide un-ionized
ammonia nitrogen criterion to provide a more consistent approach to controlling ammonia. The
criterion was based on EPA's Quality Criteria for Water (1976, Red Book) recommendation of 0.02
mg/l un-ionized ammonia nitrogen. Bioassay information supported this concept; however, the Air and
Water Quality Technical Advisory Committee (AWQTAC) recommended postponing such a standard
pending additional consideration of potential stream and economic impacts.
Recent Scientific/Technical Information - Data amassed since 1978 further support the concept that un-
ionized ammonia is the major determining factor in ammonia toxicity to fish, although the level of 0.02
mg/l NH
3
-N initially proposed by EPA has been questioned in light of more recent scientific
information.
The results of toxicity testing of ammonia to various species of aquatic organisms is detailed in EPA's
draft report
Ambient Water Quality Criteria for Ammonia
(1983). This data shows no clear-cut
distinction between salmonids and other species of fish in their responses to ammonia concentrations.
Furthermore, Ball (1967) demonstrated that warm water fish ultimately react similarly to trout to
ammonia exposures. For these reasons, it is appropriate to consider one set of criteria for all species

391-2000-013
/November 4, 1997/Page 40
and to eliminate the distinction between cold- and warm-water fishes toxicities.
Table 1 shows the variability with pH and temperature of the total ammonia nitrogen concentration
which yields 0.02 mg/l un-ionized ammonia nitrogen. Because un-ionized ammonia has been
demonstrated to be the principal toxic form of ammonia, this table clearly shows the inaccuracy of
relying solely on the total ammonia nitrogen levels (0.5 and 1.5 mg/l) established in Chapter 93. For
example, at pH 7.0 and 20° C, a total ammonia nitrogen concentration of 4.2 mg/l is still protective of
the fisheries resource for 0.02 mg/l un-ionized ammonia nitrogen. At pH 8.5 and 20° C, only 0.15 mg/l
total ammonia nitrogen provides the same level of protection.
TABLE 1
Total Ammonia Nitrogen Concentration that Yields
0.2 mg/l Un-ionized Ammonia Nitrogen (mg/l)
pH
6.5
7.0
7.5
8.0
8.5
9.0
Maximum
42.0
13.0
4.2
1.3
0.44
0.15
Stream
10°
28.0
9.0
2.8
0.90
0.30
0.11
Temperature
15°
19.0
6.0
1.9
0.62
0.21
0.076
°C
20°
13.0
4.2
1.3
0.43
0.15
0.058
25°
9.0
2.9
0.90
0.31
0.11
0.045
30°
6.5
2.1
0.67
0.22
0.081
0.037
Other water quality factors affect the toxicity of ammonia, although definitive relationships cannot
generally be established based on present knowledge. Besides pH and temperature, CO
2
levels,
salinity, DO, and the presence of certain chemicals have all been studied relative to their effect on acute
ammonia toxicity to aquatic species.
Reduced dissolved oxygen levels appear to increase ammonia toxicity. Also, in large quantities,
ammonia can stress oxygen supply because it consumes DO in its oxidation to nitrate. Increased
salinity (increased TDS) has been shown to decrease ammonia toxicity, although the mechanism for
this is unclear. Limited studies of the effects of other pollutants (inorganics and phenols) combined
with ammonia generally point out additive effects, but the possibility for synergism cannot be ruled
out. Low temperature has been implicated as increasing the susceptibility of fish to the effects of
ammonia, but further consideration to this relationship is needed.
The allowable un-ionized ammonia concentration increases with temperature and pH because the
toxicity decreases as temperature and pH increase. Further, since the dissociation of ammonia
decreases as temperature and pH increase, the fraction of un-ionized ammonia present will increase
with temperature and pH, making the allowable total ammonia decrease with rising temperature and
pH. Thus there are two opposing tendencies affecting the allowable total ammonia as temperature and
pH change. A more detailed discussion of this phenomenon is presented in EPA's 1983 draft report on
ammonia.

391-2000-013
/November 4, 1997/Page 41
Based on current interpretation of the available data, EPA has proposed models to calculate un-ionized
ammonia concentration that are protective of fresh water aquatic life at various pH and temperature
conditions. These un-ionized values are mathematically convertible to total ammonia nitrogen,
consistent with current DEP criteria. Tables 2 and 3 represent maximum and 30-day average values
derived from these models. Note that, for constant pH, there is not change in the allowable un-ionized
ammonia nitrogen concentration above 10° C and 7.75 pH for the 30-day average values. Decreases in
allowable total ammonia nitrogen concentrations above these limits are related only to the increasing
proportions of un-ionized ammonia present.
CONCLUSIONS
1. The un-ionized fraction of total ammonia is by far the most toxic portion and is of greatest concern
for protection of aquatic life.
2. A single un-ionized ammonia concentration is inappropriate as an upper toxic limit because NH
3
toxicity is dependent on several factors and is highly variable.
3. Temperature and pH have the greatest and most well-defined impact on NH
3
toxicity.
4. Ammonia criteria established for the protection of aquatic life should be based on the un-ionized
portion as a function of temperature and pH.
RECOMMENDATIONS
1. Criteria
The data presented in Tables 2 and 3 summarizes the results of the most comprehensive current
assessment of ammonia toxicity to aquatic life as conducted by EPA. It is based on an extensive
literature review of numerous laboratory and field studies covering a wide range of species and
environmental conditions. Although some generalizing was necessary to reduce laboratory and field
results into a single set of criteria protective of most common aquatic species, the data in these tables
and the formulas upon which they are based are adequate to achieve protection of the designated water
uses and their associated aquatic species identified by Chapter 93. Therefore, it is recommended that
these be adopted by the Department as statewide ammonia criteria.
2. Expression of Criteria
Current analytical procedures (EPA Method 350 and Standard Methods, 15
th
Ed., 417) measure only
total ammonia nitrogen from which direct mathematical calculation of the un-ionized portion can be
accomplished for the corresponding temperature and pH. Therefore, in order to simplify analytical
procedures, it is recommended that the ammonia criteria be expressed as total ammonia nitrogen
values.

391-2000-013
/November 4, 1997/Page 42
3. Temperature/pH Considerations
In order to determine the specific ammonia criteria applicable to a given stream, it is necessary to
identify the appropriate pH and temperature for use in selecting the correct criteria value from Tables 2
and 3. Further, depending on how these parameters are chosen, the appropriate streamflow must be
selected for use in determining corresponding effluent limits.
There are four feasible options for selecting these temperature and pH values:
1. Annual (1 value each for temperature and pH).
2. Semi-annual (2 values).
3. Quarterly (4 values).
4. Monthly (12 values).
For Options 2 and 3 it would also be necessary to select the appropriate monthly periods into which the
year would be divided, based on the variability patterns displayed by historical data.
Since pH is less influenced by seasonal factors (e.g. temperature, streamflow) than by nonseasonal
factors (runoff characteristics, man-made activities), one might not expect the variability of pH to
exhibit seasonal patterns. This conclusion was verified by cursory review of historical data from
typical Water Quality Network stream monitoring stations. These data showed that the historical pH
variation for a given month was greater than the variation from month to month for a given year. Thus
there is little benefit in requiring monthly or even seasonal pH values, since the wide weekly and daily
fluctuations which do occur tend to exceed monthly or seasonal fluctuations and center around a
constant average value throughout the year. Therefore, it is recommended that the design pH be the
median pH measured during low flow conditions for a given stream, either from historical data or from
observation during a survey of the stream.
Since un-ionized ammonia concentration increases with temperature, the critical temperature will occur
in the summer. Because temperature patterns are seasonally consistent, it is recommended that the
temperature to be used be the median of all representative historical values during July through
September, when the critical stream flow generally occurs. As a default value, if no historical
temperature information is available, it is recommended that 20° C be used for cold water streams and
25° C for warm water streams.

391-2000-013
/November 4, 1997/Page 43
4. Maximum Ammonia Nitrogen Concentration
The maximum allowable un-ionized ammonia nitrogen concentration equals 0.12
? f(T)/f(pH), where
f
??
pH
?
pH
?
??
1 10
1..
03 7 32?
f
?
T
?
T
o
C
??1,
10
f
??
T
T
C
pH
pK pH
o
?
?
?
?
?
?
11
10
10
9.73
,
and
pK
T
??
?
0 090
2730
273 2
.
.
,
the dissociation constant for ammonia in water
Table 2 presents these concentrations for a representative range of temperature and pH values.

391-2000-013
/November 4, 1997/Page 44
TABLE 2
Maximum Allowed Concentrations for Ammonia Nitrogen
pH
0°C
5°C
10°C
15°C
20°C
25°C
30°C
Un-ionized Ammonia Nitrogen (mg/liter NH
3
-N)
6.00
0.002
0.003
0.005
0.005
0.005
0.005
0.005
6.25
0.004
0.006
0.009
0.009
0.009
0.009
0.009
6.50
0.007
0.011
0.016
0.016
0.016
0.016
0.016
6.75
0.015
0.017
0.025
0.025
0.025
0.025
0.025
7.00
0.017
0.026
0.039
0.039
0.039
0.039
0.039
7.25
0.025
0.038
0.057
0.057
0.057
0.057
0.057
7.50
0.033
0.050
0.075
0.075
0.075
0.075
0.075
7.75
0.040
0.061
0.090
0.090
0.090
0.090
0.090
8.00
0.046
0.069
0.103
0.103
0.103
0.103
0.103
8.25
0.050
0.075
0.111
0.111
0.111
0.111
0.111
8.50
0.053
0.079
0.116
0.116
0.116
0.116
0.116
8.75
0.056
0.082
0.119
0.119
0.119
0.119
0.119
9.00
0.058
0.085
0.121
0.121
0.121
0.121
0.121
Total NH
3
-N = Un-ionized NH
3
-N x [log
-1
(pK-pH) + 1]
Total Ammonia Nitrogen (mg/liter NH
3
-N)
6.00
26.86
26.86
26.86
18.16
12.56
8.69
6.16
6.25
27.19
27.19
27.19
18.38
12.72
8.80
6.23
6.50
26.20
26.20
26.20
17.90
12.30
8.63
6.09
6.75
24.20
24.20
24.20
16.50
11.40
7.97
5.64
7.00
21.10
21.10
21.10
14.50
9.95
6.97
4.93
7.25
17.10
17.10
17.10
11.70
8.09
5.66
4.01
7.50
12.70
12.70
12.70
8.71
6.03
4.23
3.01
7.75
8.71
8.71
8.71
5.99
4.16
2.93
2.10
8.00
5.62
5.62
5.62
3.87
2.70
1.92
1.38
8.25
3.47
3.47
3.47
2.40
1.69
1.21
0.89
8.50
2.09
2.09
2.09
1.46
1.04
0.76
0.58
8.75
1.26
1.26
1.26
0.90
0.66
0.49
0.39
9.00
0.77
0.77
0.77
0.57
0.43
0.34
0.27

391-2000-013
/November 4, 1997/Page 45
5. Average Ammonia Nitrogen Concentration
The average allowable un-ionized ammonia nitrogen concentration equals 0.025
? f(T)/f(pH), where
f
?
pH
?
? 1,
pH
? 7.7
f
??
pH
?
pH
?
?
10
0.74 7.7?
,
pH < 7.7
fT
? ?
? 1T? 10°C
fT
??
pH
?
pK Ph
?
?
?
?
1 10
1 10
9.73
,
T < 10°C
Table 3 present these concentrations for a representative range of temperature and pH values.

391-2000-013
/November 4, 1997/Page 46
TABLE 3
30-day Average Allowed Concentrations for Ammonia Nitrogen
pH
0°C
5°C
10°C
15°C
20°C
25°C
30°C
Un-ionized Ammonia Nitrogen (mg/liter NH3-N)
6.00
0.0006
0.0009
0.0014
0.0014
0.0014
0.0014
0.0014
6.25
0.0009
0.0014
0.0021
0.0021
0.0021
0.0021
0.0021
6.50
0.0015
0.0022
0.0033
0.0033
0.0033
0.0033
0.0033
6.75
0.0022
0.0034
0.0050
0.0050
0.0050
0.0050
0.0050
7.00
0.0034
0.0052
0.0077
0.0077
0.0077
0.0077
0.0077
7.25
0.0053
0.0079
0.0118
0.0118
0.0118
0.0118
0.0118
7.50
0.0081
0.0122
0.0181
0.0181
0.0181
0.0181
0.0181
7.75
0.0113
0.0171
0.0255
0.0255
0.0255
0.0255
0.0255
8.00
0.0114
0.0172
0.0255
0.0255
0.0255
0.0255
0.0255
8.25
0.0115
0.0173
0.0255
0.0255
0.0255
0.0255
0.0255
8.50
0.0117
0.0173
0.0255
0.0255
0.0255
0.0255
0.0255
8.75
0.0119
0.0176
0.0255
0.0255
0.0255
0.0255
0.0255
9.00
0.0123
0.0180
0.0255
0.0255
0.0255
0.0255
0.0255
Total NH
3
-N = Un-ionized NH
3
-N x [log
-1
(pK-pH) + 1]
Total Ammonia Nitrogen (mg/liter NH
3
-N)
6.00
7.52
7.52
7.52
5.08
3.52
2.43
1.72
6.25
6.34
6.34
6.34
4.29
2.97
2.05
1.45
6.50
5.61
5.61
5.61
3.82
2.64
1.84
1.30
6.75
4.83
4.83
4.84
3.30
2.27
1.59
1.13
7.00
4.16
4.16
4.17
2.84
1.96
1.37
0.97
7.25
3.58
3.58
3.59
2.45
1.69
1.18
0.84
7.50
3.10
3.10
3.11
2.12
1.46
1.03
0.73
7.75
2.46
2.46
2.47
1.69
1.17
0.82
0.59
8.00
1.40
1.40
1.40
0.96
0.67
0.48
0.35
8.25
0.80
0.80
0.80
0.55
0.39
0.28
0.21
8.50
0.46
0.46
0.46
0.32
0.23
0.16
0.12
8.75
0.27
0.27
0.27
0.19
0.14
0.11
0.08
9.00
0.16
0.16
0.16
0.12
0.09
0.07
0.06

391-2000-013
/November 4, 1997/Page 47
APPENDIX F
Rationale Paper for
the Simplified Procedures
REVISED NOVEMBER 1986

391-2000-013
/November 4, 1997/Page 48
APPENDIX F
DEVELOPMENT OF THE SIMPLIFIED METHOD
OF IMPLEMENTING SECTION 93.7
Water Resources Bulletin No. 12 was used as a data source to develop a computerized database of
stream flow/recurrence interval data. This database is reproduced in Appendix G. This data was
evaluated to develop the multipliers used to convert Q
7-10
to Q
30-10
and Q
1-10
(minimum daily flow).
THE DATABASE
The database represents 70 free-flowing streams listed in Bulletin No. 12. Only 23 stations had data
for minimum daily flow. Stations selected had sufficient data to develop "Magnitude and Frequency of
Annual Low Flow" and "Duration of Daily Flow" tables in B-12. Streams regulated by upstream
reservoirs were rejected, as were stations with short periods of record or other suspected data errors.
For example, Little Yellow Creek (No. 03042200) was rejected because its "98 percent" flow was 18.5
times its Q
7-10
, or its 99 percent flow. The next highest on record was 3 times Q
7-10
.
The flow data used for this analysis represents annual flow values. Since these are low flows, it is
assumed here that these represent summer values.
DATA ANALYSIS
Estimating 30-day Low Flows for Free-Flowing Streams
The multiplier for determining Q
30-10
from Q
7-10
is based on the average of the ratios (of Q
30-10
/Q
7-10
)
for all 70 streams. As shown in Table F-1, the average for all 70 streams is 1.36 with a range of 1.04 to
2.33 and a standard deviation of 0.25.
Use of the multiplier 1.36 to recalculate the Q
30-10
for each stream produced an average error (between
actual and calculated) of three percent (see Figure F-1) with a standard deviation of 15 percent. This is
a slightly non-conservative" error and a wide "spread", e.g., from 26 percent low to 33 percent high at
+
2 standard deviations. An average error on the low side (underestimate of Q
30-10
) could not exceed 26
percent, since this sets Q
30-10
equal to Q
7-10
.
Analysis of the database showed that three streams (Sinnemahoning Creek, South Fork Tenmile Creek
and Turtle Creek) had unusually high ratios of Q
30-10
to Q
7-10
, i.e., 2.2, 2.33 and 2.27, respectively,
which skewed the results, see Figure F-1. Although each has a very low flow per square mile, no
reasons, e.g., regulated flows, could be identified to delete the streams from the database. (Computer
analysis without these three streams produced a multiplier of 1.32, an average error of plus one percent
and a standard deviation of 12 percent.)
A review of the calculated Q
30-10
's for individual streams revealed that the statewide multiple
consistently underestimated the Q
30-10
. If the state were split into two regions, e.g., Map Segments 1-

391-2000-013
/November 4, 1997/Page 49
11 and 12-14, the average errors were reduced to plus one percent. The respective multipliers were
1.29 and 1.46 with standard deviations (in the error in computed Q
30-10
) of 11 and 9 percent.
Another test computed the multiplier as the ratio of the average of all Q
30-10
/sq. mi. to the average of all
Q
7-10
/sq. mi. This produced a 70 stream value of 1.24 and an average error of minus six percent. Use
of this procedure would underestimate Q
30-10
resulting in more stringent chronic ammonia toxicity
limits.
Estimating 1-day Low Flows for Free-Flowing Streams
The development of a similar adjustment factor for estimating design flows for use in setting maximum
concentration limits is less well founded.
First, EPA never clearly defined the exposure period for maximum allowable concentrations. If taken
literally this would require a design flow of the lowest flow ever recorded. Analysis of the data in the
EPA Guidance document, however, indicated (although not conclusively by any means) that the ratio
of 30-day to maximum concentrations correlated to approximately 18 hours. This is based on Figure
F-2, a plot of LC50 data for Rainbow Trout. And, since after Resources Bulletin No. 12 contained
some “minimum daily” flow data, the exposure period of 24 hours was selected for use with EPA’s
maximum allowable concentration criteria.
The Bulletin No. 12 database for minimum daily flows consisted of 23 streams. The ration of these
flows to Q
7-10
was 0.55. Use of this ratio to estimate minimum daily flow produced an average error of
34 percent with a range of minus 34 to plus 354 percent. The standard deviation on the percent errors
was 103.5 percent.
Analysis of the data shown by Figure F-3 reveals a tight cluster of 18 streams (within +
50 percent)
with 5 others having very different flow ratios. These five streams each had low ground water yields,
but could not be deleted from the database on this reason alone. If these five were deleted anyway, the
average ratio became 0.64, with a standard deviation of 0.12. If 0.64 were used to compute the
minimum daily flow, the resulting calculations had an average error of plus four percent with a
standard deviation of 22 percent (see Table F-2). While this experiment produced greatly improved
statistical results, it is less well founded. It does, however, indicate that the typical multiplier to
convert Q
7-10
to minimum daily flow is approximately 0.6, and use of 0.64 is recommended.
Estimating Low Flows for Regulated Streams
A regulated stream, at least theoretically, should have a constant flow year round. Therefore, it should
have the same flow for all (i.e., Q
7-10
,Q
30-10
) design conditions. In most cases, this can be verified from
‘post-control’ stream flow data. Available data should be reviewed to assure that a minimum
guaranteed release is maintained. The minimum controlled release flow should be used for conducting
NH
3
-N evaluations for all design conditions.
Sensitivity Analysis:
Based on the engineer’s judgment of the significance of data precision to the
resulting permit limitations and the possible resulting cost, several levels of data refinement could be

391-2000-013
/November 4, 1997/Page 50
pursued. The first level is to perform a sensitivity analysis on the design stream flow by varying the
streamflow multipliers (0.64 and 1.36) within a range of plus-and-minus two standard deviations.
Based on the data in Tables F-1 and F-2, the applicable range is illustrated in Table F-3 below. The
second level is to collect field data or otherwise collect data (STORET, Water Resources Bulletin, etc.)
to refine the estimates of daily and monthly flow.
TABLE F-3
SENSITIVITY ANALYSIS RANGES FOR STREAM FLOW
Recommended
Multiplier
Standard
Deviation
Minimum
Maximum
Daily
0.64
0.12
0.4
0.88
Weekly
1.00
N/A
N/A
N/A
Monthly
1.36
0.25
1.0
1.86
This sensitivity analysis could be pursued further by varying the initial value for Q
7-10
. In the above
table, this value is held constant.
Example
If the general design stream flow multipliers (Table 1, Section III.A) were used instead of actual flow
data, then a sensitivity Analysis should be performed. This involves the calculation of a high and low
value for the instantaneous and monthly flows since each of these flows were calculated, via default
values, as a multiple of the 7-day flow. This multiple, however, represents an average and other likely
(plus-and-minus two standard deviations) multiples must be examined.
The effluent limit calculated in Section III.E for instantaneous, i.e., daily, flow was 15 mg/l based on a
design stream flow of 0.64 times the Q
7-10
. As shown in Table 2, this value ranges from 0.4 to 0.88.
Using the mass balance equation, the high and low values for the instantaneous limit are:
?
?
?
?
?
?
?
?
High
??
C
w
? ? ?
088 1 1 967 088 ? 1 ? 1
1
.
. _ .
C
w
=17.3 mg/l
?
?
?
?
?
?
?
?
Low
??
Cw
04 ? 1 ? 1 ? 967 ? 04 ? 1 ? 1
1
.
.
.
C
w
=13.14 mg/l

391-2000-013
/November 4, 1997/Page 51
The results of this process are summarized below:
TABLE F-4
RESULTS OF SENSITIVITY ANALYSIS
Daily
Monthly
Original
15 mg/l
3 mg/l
Low Flow
13 mg/l
3 mg/l
High Flow
17 mg/l
3.5 mg/l
Since neither The low nor high values would represent a change in treatment technology (when
compared to the original value shown above) the original values may be used for setting the effluent
limits.
If, however, the high value would have lowered the treatment technology, or the low value would have
raised it, then more accurate sources of stream flow data would have to be found.

391-2000-013
/November 4, 1997/Page 52
TABLE F-1
Flow Duration Analysis
Source: Water Bulletin No. 12
Stream Name
Min.
Daily
Q7-10 Q30-10 Q30-10/
Q7-10
Sqrd.
Var.
Comput
ed Q30-
10
Pct.
Error
Sqrd.
Var.
Q-
Min/
Q7-
10
Computed
Q-Min
Pct.
Error
Lackawanna River
8.00
18.00
26.00
1.44
.0072661
24.47
-0.06
.0073416
0.44
9.85
0.23
Delaware River
412.00
690.00 860.00
1.25
.0127297
937.85
0.09
.0040773
0.60
377.66
-0.08
Bush Kill
NA
7.30
10.00
1.37
1.136E-4
9.92
-0.01
.0011869
NA
4.00
NA
Brodhead Creek
NA
6.80
7.80
1.15
.0450051
9.24
0.18
.0250315
NA
3.72
NA
Lehigh River
NA
12.00
15.00
1.25
.0119253
16.31
0.09
.0036836
NA
6.57
NA
Tunkhannock Creek
NA
3.80
5.20
1.37
8.497E-5
5.16
-0.01
.0011160
NA
2.08
NA
Tohickon Creek
0.10
0.83
1.40
1.69
.1072851
1.13
-0.19
.0487776
0.12
0.45
3.54
Neshaminy Creek
NA
10.00
14.00
1.40
.0016644
13.59
-0.03
.0031148
NA
5.47
NA
Pennypack Creek
NA
7.00
9.00
1.29
.0054006
9.51
0.06
9.295E-4
NA
3.83
NA
Schuylkill River
NA
17.00
20.00
1.18
.0333911
23.11
0.16
.0165516
NA
9.30
NA
Schuylkill River
NA
28.00
34.00
1.21
.0210010
38.06
0.12
.0085885
NA
15.33
NA
Schuylkill River
NA
160.00 200.00
1.25
.0119253
217.47
0.09
.0036836
NA
87.57
NA
Tulpehocken Creek
NA
45.00
50.00
1.11
.0615495
61.16
0.22
.0386567
NA
24.63
NA
Perkiomen Creek
NA
15.00
21.00
1.40
.0016644
20.39
-0.03
.0031148
NA
8.21
NA
Wissahickon Creek
NA
7.30
11.00
1.51
.0217995
9.92
-0.10
.0155384
NA
4.00
NA
Chester Creek
6.50
11.00
14.00
1.27
.0074780
14.95
0.07
.0017037
0.59
6.02
-0.07
Brandywine Creek
42.00
67.00
78.00
1.16
.0380343
91.07
0.17
.0198390
0.63
36.67
-0.13
Susquehanna River
NA
550.00 648.00
1.18
.0327686
747.56
0.15
.0161226
NA
301.0.
NA
Tunkhannock Creek
NA
16.00
24.00
1.50
.0198238
21.75
-0.09
.0145285
NA
8.76
NA
Lackawanna River
NA
40.00
46.00
1.15
.0437659
54.37
0.18
.0241013
NA
21.89
NA
NB Susquehanna R.
NA
770.00 880.00
1.14
.0468055
1046.59
0.19
.0264495
NA
421.44
NA
Manada Creek
0.80
1.50
1.90
1.27
.0085630
2.04
0.07
.0021516
0.53
.082
0.03
Conestoga Creek
7.00
33.00
44.00
1.33
6.692E-4
44.85
0.02
5.281E-5
0.21
18.06
1.58
Muddy Creek
20.00
30.00
33.00
1.10
.0671862
40.78
0.24
.0436682
0.67
16.42
-0.18
Conewango Creek
57.00
69.00
79.00
1.14
.0459139
93.79
0.19
.0257546
0.83
37.77
-0.34
Tionesta Creek
NA
24.00
36.00
1.50
.0198238
32.62
-0.09
.0145285
NA
13.14
NA
Oil Creek
NA
28.00
35.00
1.25
.0119253
38.06
0.09
.0036836
NA
15.33
NA

391-2000-013
/November 4, 1997/Page 53
Stream Name
Min.
Daily
Q7-10 Q30-10 Q30-10/
Q7-10
Sqrd.
Var.
Comput
ed Q30-
10
Pct.
Error
Sqrd.
Var.
Q-
Min/
Q7-
10
Computed
Q-Min
Pct.
Error
Oil Creek
NA
34.00
41.00
1.21
.0235072
46.21
0.13
.0100951
NA
18.61
NA
French Creek
NA
31.00
38.00
1.23
.0177946
42.14
0.11
.0067493
NA
16.97
NA
French Creek
NA
62.00
80.00
1.29
.0047445
84.27
0.05
7.136E-4
NA
33.93
NA
Allegheny River
NA
311.00 364.00
1.17
.0356397
422.71
0.16
.0181245
NA
170.22
NA
WB Clarion River
NA
5.80
6.80
1.17
.0348902
7.88
0.16
.0175962
NA
3.17
NA
Toms Run
NA
0.50
0.60
1.20
.0253456
0.68
0.13
.0112359
NA
0.27
NA
Big Run
NA
0.42
0.54
1.29
.0054006
0.57
0.06
9.295E-4
NA
0.23
NA
Redbank Creek
NA
32.00
43.00
1.34
2.388E-4
43.49
0.01
2.301E-4
NA
17.51
NA
Mahoning Creek
NA
16.00
24.00
1.50
.0198238
21.75
-0.09 .0145285
NA
8.76
NA
Crooked Creek
NA
5.50
8.00
1.45
.0090902
7.48
-0.07 .0085041
NA
3.01
NA
Blacklick Creek
NA
19.00
28.00
1.47
.0131060
25.82
-0.08 .0108896
NA
10.40
NA
Buffalo Creek
NA
3.20
5.00
1.56
.0413297
4.35
-0.13 .0245799
NA
1.75
NA
Dunkard Creek
NA
1.30
1.90
1.46
.0104726
1.77
-0.07 .0093487
NA
0.71
NA
S F 10 Mile Creek
NA
0.30
0.70
2.33
.9489301
0.41
-0.42 .1972728
NA
0.16
NA
Lick Run
NA
0.10
0.17
1.70
.1161426
0.14
-0.20 .0515919
NA
0.05
NA
Redstone Creek
NA
8.50
12.00
1.41
.0027627
11.55
-0.04 .0040833
NA
4.65
NA
Laurel Hill Creek
NA
4.90
7.70
1.57
.0450397
6.66
-0.14 .0261541
NA
2.68
NA
Fishing Creek
NA
37.00
54.00
1.46
.0100514
50.29
-0.07 .0090943
NA
20.25
NA
WB Susquehanna R
16.00
24.00
32.00
1.33
6.692E-4
32.62
0.02
5.281E-5
0.67
13.14
-0.18
Black Moshannon
Creek
7.80
9.70
11.00
1.13
.0507071
13.18
0.20
.0295497
0.80
5.31
-0.32
Sinnemahoning
Creek
1.40
10.00
22.00
2.20
.7069397
13.59
-0.38 .1671584
0.14
5.47
2.91
Kettle Creek
1.20
3.80
6.40
1.68
.1056299
5.16
-0.19 .0482430
0.32
2.08
0.73
Spring Creek
26.00
28.00
28.00
1.08
.0796219
35.34
0.26
.0554355
0.77
14.23
-0.29
Bald Eagle Creek
20.00
115.00 120.00
1.04
.0996821
156.31
0.30
.0761208
.070
62.94
-0.21
Pine Creek
8.00
20.00
28.00
1.40
.0016644
27.18
-0.03 .0031148
0.40
10.95
0.37
Pine Creek
NA
29.00
39.00
1.34
2.067E-4
39.42
0.01
2.554E-4
NA
15.87
NA
WB Susquehanna
River
251.00
450.00 530.00
1.18
.0329151
611.64
0.15
.0162233
0.56
246.30
-0.02
Loyalsock Creek
NA
0.52
27.00
1.35
8.469E-5
27.18
0.01
3.941E-4
NA
10.95
NA
Penns Creek
21.00
35.00
41.00
1.17
.0352592
47.57
0.16
.0178558
0.60
19.16
-0.09

391-2000-013
/November 4, 1997/Page 54
Stream Name
Min.
Daily
Q7-10 Q30-10 Q30-10/
Q7-10
Sqrd.
Var.
Comput
ed Q30-
10
Pct.
Error
Sqrd.
Var.
Q-
Min/
Q7-
10
Computed
Q-Min
Pct.
Error
Frankstown Branch
Juniata River
31.00
44.00
52.00
1.18
.0314653
59.80
0.15
.0152338
0.70
24.08
-0.22
Brush Creek
NA
0.52
0.82
1.58
.0474021
0.71
-0.14 .0271380
NA
0.28
NA
Kishacoquillas
Creek
14.00
18.00
20.00
1.11
.0615495
24.47
0.22
.0386567
0.78
9.85
-0.30
Tuscarora Creek
2.20
8.80
12.00
1.36
1.966E-5
11.96
0.00
8.953E-4
0.25
4.92
1.19
Juniata River
195.00
370.00 440.00
1.19
.0289047
502.91
0.14
.0135249
0.53
202.51
0.04
Yellow Breeches
Creek
64.00
84.00
92.00
1.10
.0696774
144.17
0.24
.0459424
0.76
45.98
-0.28
Green Lick Run
NA
0.08
0.12
1.50
.0198238
0.11
-0.09 .0145285
NA
0.04
NA
Turtle Creek
NA
0.66
1.50
2.27
.8345267
0.90
-0.40 .1837154
NA
0.36
NA
Shenango River
NA
3.50
4.80
1.37
1.495E-4
4.76
-0.01 .0012662
NA
1.92
NA
L. Shenango River
NA
5.20
6.70
1.29
.0050043
7.07
0.05
7.972E-4
NA
2.85
NA
Pymatuning River
NA
1.80
2.90
1.61
.0634577
2.45
0.16
.0334987
NA
0.99
NA
Connoquennessing
Ck
NA
10.00
14.00
1.40
.0016644
13.59
-0.03 .0031148
NA
5.47
NA
Slippery Rock
Creek
NA
30.00
39.00
1.30
.0035050
40.78
0.05
3.561E-4
NA
16.42
NA
Raccoon Creek
NA
7.40
9.50
1.28
.0056880
10.06
0.06
.0010290
NA
4.05
NA
0.10
55.04
412.00
0.08
65.24
770.00
0.12
78.55
880.00
1.04
1.36
2.33
-0.42
0.03
0.30
0.12
0.55
0.83
-0.34
0.34
3.54
Sum Sq. Vr
4.336151
1.589818
N-1
69
69
Standard Deviation
.2506846
.1517921

391-2000-013
/November 4, 1997/Page 55

391-2000-013
/November 4, 1997/Page 56

391-2000-013
/November 4, 1997/Page 57

391-2000-013
/November 4, 1997/Page 58
TABLE F-2
Multiplier to Compute Minimum Daily Flow
Stream Name
Min.
Daily
Q7-10
Q-Min
Q7-10
Computed
Q-Min
Pct.
Error
Sqrd.
Var
Lackawanna River
8.00
18.00
0.44
11.55
0.44
.1636110
Delaware River
412.00
690.00
0.60
442.75
0.07
.0012511
Bush Kill
NA
7.30
NA
4.68
NA
NA
Brodhead Creek
NA
6.80
NA
4.36
NA
NA
Lehigh River
NA
12.00
NA
7.70
NA
NA
Tunkhannock Creek
NA
3.80
NA
2.44
NA
NA
Neshaminy Creek
NA
10.00
NA
6.42
NA
NA
Pennypack Creek
NA
7.00
NA
4.49
NA
NA
Schuylkill Creek
NA
17.00
NA
10.97
NA
NA
Schuylkill River
NA
29.00
NA
17.97
NA
NA
Schuylkill River
NA
160.00
NA
102.67
NA
NA
Tulpehocken River
NA
45.00
NA
28.88
NA
NA
Perkiomen Creek
NA
15.00
NA
9.63
NA
NA
Wissahickon Creek
NA
7.30
NA
4.68
NA
NA
Chester Creek
6.50
11.00
0.59
7.06
0.09
.0021746
Brandywine Creek
42.00
67.00
0.63
42.99
0.02
2.451E-4
Susquehanna River
NA
550.00
NA
352.92
NA
NA
Tunkhannock Creek
NA
16.00
NA
10.27
NA
NA
Lackawanna River
NA
40.00
NA
25.67
NA
NA
NB Susquehanna River
NA
770.00
NA
494.09
NA
NA
Fishing Creek
NA
37.00
NA
23.74
NA
NA
WB Susquehanna River
16.00
24.00
0.67
15.40
-0.04
.0058930
Black Moshannon Creek
7.80
9.70
0.80
6.22
-0.20
.0582246
Spring Creek
20.00
26.00
0.77
16.68
-0.17
.0420663
Bald Eagle Creek
80.00
115.00
0.70
73.79
-0.08
.0136588
Pine Creek
8.00
20.00
0.40
12.83
0.60
.3191197
Pine Creek
NA
29.00
NA
18.61
NA
NA
WB Susquehanna River
251.00
450.00
0.56
288.75
0.15
.0123508
Loyalsock Creek
NA
20.00
NA
12.83
NA
NA
Penns Creek
21.00
35.00
0.60
22.46
0.07
9.102E-4
Frankstown Branch Juniata River
31.00
44.00
0.70
28.23
-0.09
.0165158
Brush Creek
NA
0.52
NA
0.33
NA
NA
Kishacoquillas Creek
14.00
18.00
0.78
11.55
-0.17
.0459106
Juniata River
195.00
370.00
0.53
237.42
0.22
.0317758
Yellow Breeches Creek
64.00
84.00
0.76
53.90
-0.16
.0388405
Manada Creek
0.80
1.50
0.53
0.96
0.20
.0268505
Muddy Creek
20.00
30.00
0.67
19.25
-0.04
.0058930

391-2000-013
/November 4, 1997/Page 59
Stream Name
Min.
Daily
Q7-10
Q-Min
Q7-10
Computed
Q-Min
Pct.
Error
Sqrd.
Var
Conewango Creek
57.00
69.00
0.63
44.28
-0.22
.0689134
Tionesta Creek
NA
24.00
NA
15.40
NA
NA
Oil Creek
NA
28.00
NA
17.97
NA
NA
Oil Creek
NA
34.00
NA
21.82
NA
NA
French Creek
NA
31.00
NA
19.89
NA
NA
French Creek
NA
62.00
NA
39.78
NA
NA
Allegheny River
NA
311.00
NA
199.56
NA
NA
WB Clarion River
NA
5.80
NA
3.72
NA
NA
Toms Run
NA
0.50
NA
0.32
NA
NA
Big Run
NA
0.42
NA
0.27
NA
NA
Redbank Creek
NA
32.00
NA
20.53
NA
NA
Mahoning Creek
NA
16.00
NA
10.27
NA
NA
Crooked Creek
NA
5.50
NA
3.53
NA
NA
Blacklick Creek
NA
19.00
NA
12.19
NA
NA
Buffalo Creek
NA
3.20
NA
2.05
NA
NA
Dunkard Creek
NA
1.30
NA
0.83
NA
NA
S F 10 Mile Creek
NA
0.30
NA
0.19
NA
NA
Lick Run
NA
0.10
NA
0.06
NA
NA
Redstone Creek
NA
8.50
NA
5.45
NA
NA
Laurel Hill Creek
NA
4.90
NA
3.14
NA
NA
Green Lick Run
NA
0.08
NA
0.05
NA
NA
Turtle Creek
NA
0.66
NA
0.42
NA
NA
Shenango River
NA
3.50
NA
2.25
NA
NA
L. Shenango River
NA
5.20
NA
3.34
NA
NA
Pymatuning River
NA
1.80
NA
1.16
NA
NA
Connoquennessing Creek
NA
10.00
NA
6.42
NA
NA
Slippery Rock Creek
NA
30.00
NA
19.25
NA
NA
Raccoon Creek
NA
7.40
NA
4.75
NA
NA
Minimum
0.80
0.08
0.40
-0.22
Average
69.67
69.39
0.64
0.04
Maximum
412.00
770.00
0.83
0.60
Var. SQRD
.8542054
N
18.00
STD DEV
0.12
2241503

391-2000-013
/November 4, 1997/Page 60
APPENDIX G
Database of Streamflows

391-2000-013
/November 4, 1997/Page 61
Flow Duration Analysis
Source: Water Bulletin No. 12
Stream Name
Stream
Code
D.A.
(Sq.
Mi.)
Min.
Daily
Q7-2
Q7-10
Q30-
10
Q-Ave
Q-Mean
(50%)
95%
98%
Lackawaxen River
01431500
290.00
8.00
35.00
18.00
26.00
468.00
200.00
34.00
25.00
Delaware River
01438500
3480.00 412.00 1200.00 690.00 860.00
5757.00
3500.00 1000.00 820.00
Bush Kill
01439500
117.00
NA
18.00
7.30
10.00
230.00
160.00
18.00
11.00
Brodhead Creek
01440400
65.90
NA
12.00
6.80
7.80
121.00
75.00
10.00
8.10
Lehigh River
01447500
91.70
NA
22.00
12.00
15.00
180.00
120.00
22.00
16.00
Tunkhannock Creek
01447680
18.00
NA
6.80
3.80
5.20
39.60
29.00
8.50
.50
Tohickon Creek
01459500
97.40
0.10
2.10
0.83
1.40
137.00
37.00
2.10
1.20
Neshaminy Creek
01465500
210.00
NA
18.00
10.00
14.00
273.00
120.00
19.00
14.00
Pennypack Creek
01467048
49.80
NA
15.00
7.00
9.00
65.00
40.00
15.00
12.00
Schuylkill River
01467500
53.40
NA
24.00
17.00
20.00
99.40
65.00
24.00
20.00
Schuylkill River
01468500
133.00
NA
53.00
28.00
34.00
266.00
180.00
48.00
37.00
Schuylkill River
01471500
880.00
NA
280.00
160.00 200.00
1490.00
940.00
220.00
180.00
Tulpehocken Creek
01471000
211.00
NA
72.00
45.00
50.00
289.00
200.00
62.00
54.00
Perkiomen Creek
01472500
152.00
NA
24.00
15.00
21.00
252.00
110.00
27.00
20.00
Wissahickon Creek
01474000
64.00
NA
18.00
7.30
11.00
79.00
44.00
17.00
14.00
Chester Creek
01477000
61.00
6.50
12.00
11.00
14.00
81.20
55.00
20.00
15.00
Brandywine Creek
01481000
287.00
42.00
120.00
67.00
78.00
381.00
270.00
99.00
80.00
Susquehanna River
01531500
7797.00
NA
948.00
550.00 648.00 10390.00 5200.00
900.00
670.00
Tunkhannock Creek
01534000
383.00
NA
33.00
16.00
24.00
528.00
240.00
49.00
34.00
Lackawanna River
01536000
332.00
NA
89.00
40.00
46.00
493.00
290.00
65.00
52.00
NB Susquehanna River
01543650
9960.00
NA
1300.00 770.00 880.00 13090.00 6700.00 1200.00 960.00
Fishing Creek
01540000
355.00
NA
78.00
37.00
54.00
695.00
400.00
77.00
50.00
WB Susquehanna River
01541000
315.00
16.00
41.00
24.00
32.00
545.00
255.00
40.00
30.00
Black Moshannon Creek
01542000
68.80
7.80
13.00
9.70
11.00
109.00
64.00
13.00
11.00
Sinnemahoning Creek
01543500
685.00
1.40
29.00
10.00
22.00
1087.00
470.00
34.00
23.00
Kettle Creek
01544500
136.00
1.20
10.00
3.80
6.40
218.00
96.00
10.00
7.40
Spring Creek
01546500
87.20
20.00
36.00
26.00
28.00
83.30
61.00
30.00
26.00

391-2000-013
/November 4, 1997/Page 62
Stream Name
Stream
Code
D.A.
(Sq.
Mi.)
Min.
Daily
Q7-2
Q7-10
Q30-
10
Q-Ave
Q-Mean
(50%)
95%
98%
Bald Eagle Creek
01548000
559.00
80.00
145.00
115.00 120.00
783.00
430.00
140.00
130.00
Pine Creek
01548500
604.00
8.00
42.00
20.00
28.00
808.00
360.00
43.00
33.00
Pine Creek
01549700
944.00
NA
57.00
29.00
39.00
1260.00
510.00
55.00
43.00
WB Susquehanna River
01551500
5682.00 251.00
740.00
450.00 530.00
8751.00
4700.00
770.00
590.00
Loyalsock Creek
01552000
443.00
NA
42.00
20.00
27.00
739.00
370.00
41.00
30.00
Penns Creek
01555000
301.00
21.00
51.00
35.00
41.00
412.00
240.00
50.00
41.00
Frankstown Branch
Juniata River
01556000
291.00
31.00
62.00
44.00
52.00
386.00
190.00
58.00
51.00
Brush Creek
01561000
36.80
NA
1.70
0.52
0.82
45.40
21.00
1.80
0.95
Kishacoquillas Creek
01565000
164.00
14.00
27.00
18.00
20.00
203.00
110.00
25.00
21.00
Tuscarora Creek
01566000
214.00
2.20
18.00
8.80
12.00
259.00
110.00
18.00
12.00
Juniata River
01567000
3354.00 195.00
570.00
370.00 440.00
4227.00
2300.00
550.00
440.00
Yellow Breeches Creek
01571500
216.00
64.00
111.00
84.00
92.00
276.00
200.00
100.00
92.00
Manada Creek
01573500
13.50
0.80
2.50
1.50
1.90
23.40
14.00
2.60
2.10
Conestoga Creek
01576500
324.00
7.00
70.00
33.00
44.00
380.00
240.00
59.00
44.00
Muddy Creek
01577500
133.00
20.00
50.00
30.00
33.00
155.00
120.00
39.00
32.00
Conewango Creek
03015000
816.00
57.00
112.00
69.00
79.00
1453.00
880.00
110.00
87.00
Tionesta Creek
03019000
469.00
NA
46.00
24.00
36.00
824.00
390.00
46.00
35.00
Oil Creek
03020500
300.00
NA
41.00
28.00
35.00
516.00
260.00
43.00
36.00
Oil Creek
03021000
315.00
NA
51.00
34.00
41.00
515.00
240.00
50.00
39.00
French Creek
03022500
629.00
NA
50.00
31.00
38.00
1056.00
510.00
51.00
40.00
French Creek
03024000
1028.00
NA
100.00
62.00
80.00
1746.00
920.00
108.00
86.00
Allegheny River
03016000
3660.00
NA
561.00
311.00 364.00
6414.00
3600.00
520.00
430.00
WB Clarion River
03028000
63.00
NA
9.40
5.80
6.80
118.00
64.00
9.50
7.50
Toms Run
03029400
12.60
NA
1.10
0.50
0.60
18.10
7.90
1.10
0.80
Big Run
03031950
7.38
NA
0.58
0.42
0.54
12.00
5.40
0.70
0.60
Redbank Creek
03032500
528.00
NA
49.00
32.00
43.00
843.00
400.00
55.00
43.00
Mahoning Creek
03035000
321.00
NA
27.00
16.00
24.00
561.00
260.00
30.00
22.00
Crooked Creek
03038000
191.00
NA
10.00
5.50
8.00
280.00
120.00
11.00
7.70
Blacklick Creek
03043000
390.00
NA
44.00
19.00
28.00
671.00
340.00
43.00
31.00

391-2000-013
/November 4, 1997/Page 63
Stream Name
Stream
Code
D.A.
(Sq.
Mi.)
Min.
Daily
Q7-2
Q7-10
Q30-
10
Q-Ave
Q-Mean
(50%)
95%
98%
Buffalo Creek
03049000
137.00
NA
6.00
3.20
5.00
186.00
77.00
6.40
4.70
Dunkard Creek
03072000
229.00
NA
2.90
1.30
1.90
263.00
81.00
3.00
2.00
S F 10 Mile Creek
03073000
180.00
NA
1.10
0.30
0.70
196.00
58.00
1.20
0.70
Lick Run
03074300
3.80
NA
0.13
0.10
0.17
6.62
2.70
0.20
0.14
Redstone Creek
03074500
73.70
NA
17.00
8.50
12.00
96.60
52.00
16.00
13.00
Laurel Hill Creek
03080000
121.00
NA
12.00
4.90
7.70
264.00
140.00
13.00
8.10
Green Lick Run
03083000
3.07
NA
0.15
0.08
0.12
5.50
2.50
0.15
0.11
Turtle Creek
03084500
55.90
NA
2.60
0.66
1.50
76.80
33.00
2.40
1.30
Shenango River
03100000
152.00
NA
5.70
3.50
4.80
205.00
78.00
6.70
5.00
L. Shenango River
03102500
104.00
NA
8.70
5.20
6.70
139.00
59.00
8.50
6.60
Pymatuning Creek
03103000
169.00
NA
4.30
1.80
2.90
203.00
63.00
4.60
3.00
Connoquennessing
Creek
03106000
356.00
NA
17.00
10.00
14.00
460.00
190.00
19.00
14.00
Slippery Rock Creek
03106500
398.00
NA
45.00
30.00
39.00
555.00
250.00
48.00
34.00
Raccoon Creek
03019000
178.00
NA
12.00
7.40
9.50
183.00
84.00
14.00
10.00
Minimum
3.07
0.10
0.13
0.08
0.12
5.50
2.50
0.15
0.11
Average
722.14
55.04
110.50
65.24
78.55
1057.51
557.19
103.39
81.82
Maximum
9960.00 412.00 1300.00 770.00 880.00 13090.00 6700.00 1200.00 960.00
N =
70

391-2000-013
/November 4, 1997/Page 64
APPENDIX H
Computer Program Listing
(The NH
3
CALC Program has been deleted from this Guidance)

391-2000-013
/November 4, 1997/Page 65
APPENDIX I
Criteria Tables

391-2000-013
/November 4, 1997/Page 66
Chapter 93.7 - Maximum In-Stream Ammonia
Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6.0
18.35 17.02 15.79 14.66 13.62 12.65 11.77 10.94 10.19 9.43
8.83
8.23
7.68
7.15
6.68
6.24
6.1
18.28 16.95 15.73 14.60 13.56 12.60 11.72 10.90 10.14 9.44
8.60
8.20
7.65
7.13
6.66
6.22
6.2
18.15 16.83 15.62 14.50 13.47 12.52 11.64 10.82 10.07 9.38
8.74
8.14
7.59
7.09
6.61
6.17
6.3
17.96 16.66 15.46 14.35 13.33 12.39 11.52 10.71 9.97
9.28
8.65
8.06
7.52
7.01
6.55
6.11
6.4
17.70 16.42 15.23 14.14 13.14 12.21 11.35 10.56 9.83
9.15
8.53
7.95
7.41
6.91
6.45
6.03
6.5
17.36 16.10 14.94 13.87 12.88 11.97 11.13 10.35 9.64
8.97
8.36
7.79
7.27
6.78
6.33
5.91
6.6
16.92 15.69 14.56 13.51 12.55 11.67 10.85 10.09 9.39
8.75
8.15
7.60
7.08
6.61
6.17
5.76
6.7
16.37 15.18 14.08 13.08 12.15 11.29 10.50 9.77
9.09
8.48
7.89
7.35
6.86
6.40
5.73
5.58
6.8
15.70 14.56 13.51 12.55 11.65 10.83 10.07 9.37
8.72
8.12
7.57
7.06
6.58
6.14
5.73
5.35
6.9
14.91 13.83 12.84 11.92 11.07 10.29 9.57
8.90
8.29
7.72
7.19
6.71
6.26
5.84
5.45
5.09
7.1
14.01 13.00 12.06 11.20 10.41 9.67
9.00
8.37
7.79
7.26
6.76
6.37
5.88
5.49
5.13
4.79
7.1
13.01 12.07 11.20 10.40 9.66
8.98
8.36
7.78
7.24
6.74
6.28
5.86
5.47
5.10
4.77
4.45
7.2
11.92 11.06 10.27 9.54
8.86
8.24
7.66
7.13
6.64
6.13
5.76
5.38
5.02
4.68
4.37
4.09
7.3
10.78 10.00 9.29
8.62
8.01
7.45
6.93
6.45
6.01
5.60
5.22
4.87
4.54
4.24
3.96
3.70
7.4
9.62
8.92
8.28
7.69
7.15
6.65
6.19
5.76
5.36
5.00
4.66
4.35
4.06
3.79
3.54
3.31
7.5
8.46
7.85
7.29
6.77
6.29
5.85
5.45
5.07
4.73
4.40
4.11
3.83
3.58
3.34
3.13
2.92
7.6
7.35
6.82
6.33
5.88
5.47
5.09
4.74
4.41
4.11
3.81
3.58
3.34
3.12
2.91
2.73
2.55
7.7
6.30
5.85
5.44
5.05
4.70
4.37
4.07
3.79
3.54
3.30
3.08
2.87
2.69
2.51
2.35
2.20
7.8
5.35
4.97
4.62
4.29
3.99
3.72
3.46
3.23
3.01
2.81
2.12
2.45
2.29
2.14
2.01
1.88
7.9
4.50
4.18
3.89
3.61
3.36
3.13
2.92
2.72
2.54
2.37
2.22
2.07
1.94
1.81
1.70
1.59

391-2000-013
/November 4, 1997/Page 67
Chapter 93.7 - Maximum In-Stream Ammonia
Maximum (One Day) Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
8.0
3.75
3.49
3.24
3.02
2.81
2.62
2.44
2.28
2.13
1.99
1.86
1.74
1.63
1.53
1.43
1.34
8.1
3.11
2.89
2.69
2.51
2.34
2.18
2.03
1.90
1.77
1.66
1.55
1.45
1.36
1.28
1.20
1.13
8.2
2.57
2.39
2.22
2.07
1.93
1.80
1.68
1.57
1.47
1.36
1.29
1.21
1.14
1.07
1.00
.94
8.3
2.11
1.96
1.83
1.71
1.59
1.49
1.39
1.30
1.22
1.14
1.07
.01
.95
.89
.84
.79
8.4
1.73
1.61
1.51
1.41
1.31
1.23
1.15
1.08
1.01
.98
.89
.84
.79
.74
.70
.66
8.5
1.42
1.32
1.24
1.16
1.08
1.01
.95
.89
.84
.79
.74
.70
.66
.62
.59
.56
8.6
1.16
1.09
1.02
.95
.89
.84
.79
.74
.70
.66
.62
.59
.55
.52
.50
.47
8.7
.96
.90
.84
.79
.74
.70
.66
.62
.56
.55
.52
.49
.47
.44
.42
.40
8.8
.79
.74
.70
.66
.62
.58
.55
.52
.49
.43
.44
.42
.40
.38
.36
.35
8.9
.66
.62
.58
.55
.52
.49
.46
.44
.42
.40
.38
.36
.34
.33
.31
.30
9.0
.55
.52
.49
.46
.44
.41
.39
.37
.36
.34
.32
.31
.30
.29
.27
.26

391-2000-013
/November 4, 1997/Page 68
30-Day Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6.0
5.04
4.68
4.34
4.03
3.74
3.48
3.23
3.01
2.80
2.61
2.43
2.26
2.11
1.97
1.84
1.71
6.1
4.75
4.40
4.09
3.79
3.52
3.27
3.04
2.83
2.64
2.45
2.29
2.13
1.99
1.85
1.73
1.62
6.2
4.47
4.15
3.85
3.57
3.32
3.09
2.87
2.67
2.48
2.31
2.15
2.01
1.87
1.75
1.63
1.52
6.3
4.21
3.91
3.63
3.37
3.13
2.91
2.70
2.51
2.34
2.16
2.03
1.89
1.76
1.65
1.54
1.43
6.4
3.97
3.68
3.42
3.17
2.95
2.74
2.55
2.37
2.20
2.05
1.91
1.78
1.66
1.55
1.45
1.35
6.5
3.74
3.47
3.22
2.99
2.78
2.58
2.40
2.23
2.08
1.93
1.30
1.68
1.57
1.46
1.36
1.27
6.6
3.52
3.27
3.03
2.82
2.62
2.43
2.26
2.10
1.96
1.82
1.70
1.58
1.48
1.36
1.29
1.20
6.7
3.32
3.08
2.86
2.65
2.46
2.29
2.13
1.98
1.84
1.72
1.60
1.49
1.39
1.30
1.21
1.13
6.8
3.13
2.9
2.69
2.50
2.32
2.16
2.01
1.87
1.74
1.62
1.51
1.41
1.31
1.22
1.14
1.07
6.9
2.95
2.73
2.54
2.36
2.19
2.03
1.89
1.76
1.64
1.53
1.42
1.33
1.24
1.15
1.08
1.01
7.0
2.78
2.58
2.39
2.22
2.06
1.92
1.78
1.66
1.54
1.44
1.34
1.25
1.17
1.09
1.02
.95
7.1
2.62
2.43
2.25
2.09
1.94
1.81
1.68
1.56
1.46
1.36
1.26
1.18
1.10
1.03
.96
.90
7.2
2.47
2.29
2.13
1.97
1.83
1.70
1.59
1.48
1.37
1.28
1.19
1.11
1.04
.97
.91
.85
7.3
2.33
2.16
2.00
1.86
1.73
1.61
1.50
1.39
1.30
1.21
1.13
1.05
.98
.92
.86
.80
7.4
2.20
2.04
1.89
1.76
1.63
1.52
1.41
1.31
1.22
1.14
1.06
.99
.93
.87
.81
.76
7.5
2.07
1.92
1.78
1.66
1.54
1.43
1.33
1.24
1.16
1.08
1.01
.94
.88
.82
.77
.72
7.6
1.96
1.81
1.69
1.57
1.46
1.35
1.26
1.17
1.09
1.02
.95
.89
.83
.78
.73
.68
7.7
1.85
1.71
1.59
1.48
1.38
1.28
1.19
1.11
1.04
.97
.90
.84
.79
.74
.69
.64
7.8
1.47
1.37
1.27
1.18
1.10
1.02
.95
.89
.83
.77
.72
.67
.63
.59
.55
.52
7.9
1.17
1.09
1.01
.94
.88
.82
.76
.71
.66
.62
.58
.54
.51
.47
.44
.42

391-2000-013
/November 4, 1997/Page 69
30-Day Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
8.0
.94
.87
.81
.75
.70
.65
.61
.57
.53
.50
.46
.43
.41
.38
.36
.34
8.1
.75
.70
.65
.60
.56
.53
.49
.46
.43
.40
.37
.35
.33
.31
.29
.27
8.2
.60
.56
.52
.49
.45
.42
.39
.37
.34
.32
.30
.28
.27
.25
.23
.22
8.3
.48
.45
.42
.39
.36
.34
.32
.30
.28
.26
.25
.23
.22
.20
.19
.18
8.4
.39
.36
.34
.32
.29
.28
.26
.24
.23
.21
.20
.19
.18
.17
.16
.15
8.5
.31
.29
.27
.26
.24
.22
.21
.20
.19
.17
.16
.15
.15
.14
.13
.12
8.6
.25
.24
.22
.21
.20
.18
.17
.16
.15
.14
.14
.13
.12
.11
.11
.10
8.7
.21
.19
.18
.17
.16
.15
.14
.13
.13
.12
.11
.11
.10
.10
.09
.09
8.8
.17
.16
.15
.14
.13
.12
.12
.11
.11
.10
.09
.09
.09
.08
.08
.07
8.9
.14
.13
.12
.12
.11
.10
.10
.09
.09
.08
.08
.08
.07
.07
.07
.06
9.0
.12
.11
.10
.10
.09
.09
.08
.08
.08
.07
.07
.07
.06
.06
.06
.06

391-2000-013
/November 4, 1997/Page 70
Seven-Day Average Total Ammonia-Nitrogen Concentration
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6.0
8.06
7.49
6.94
6.15
5.98
5.57
5.17
4.82
4.48
4.16
3.89
3.62
3.38
3.15
2.94
2.74
6.1
7.60
7.04
6.54
6.06
5.63
5.23
4.86
4.53
4.22
3.92
3.66
3.41
3.18
2.96
2.77
2.59
6.2
7.15
6.64
6.16
5.71
5.31
4.94
4.59
2.27
3.97
3.70
3.44
3.22
2.99
2.80
2.61
2.43
6.3
6.74
6.26
5.81
5.39
5.01
4.66
4.32
4.02
3.74
3.49
3.25
3.02
2.82
2.64
2.46
2.29
6.4
6.35
5.89
5.47
5.07
4.72
4.38
4.08
3.79
3.52
3.28
3.06
2.85
2.66
2.48
2.32
2.16
6.5
5.98
5.55
5.15
4.78
4.45
4.13
3.84
3.57
3.33
3.09
2.89
2.69
2.51
2.34
2.18
2.03
6.6
5.63
5.23
4.85
4.51
4.19
3.89
3.62
3.36
3.14
2.91
2.72
2.53
2.37
2.21
2.06
1.92
6.7
5.31
4.93
4.58
4.24
3.94
3.66
3.41
3.17
2.94
2.75
2.56
2.38
2.22
2.08
1.94
1.81
6.8
5.01
4.64
4.30
4.00
3.71
3.46
3.22
2.99
2.78
2.59
2.42
2.26
2.10
1.95
1.82
1.71
6.9
4.72
4.37
4.06
3.78
3.50
3.25
3.02
2.82
2.62
2.45
2.27
2.13
1.98
1.84
1.73
1.62
7.0
4.45
4.13
3.82
3.55
3.30
3.07
2.85
2.66
2.46
2.30
2.14
2.00
1.87
1.74
1.63
1.52
7.1
4.19
3.89
3.60
3.34
3.10
2.90
2.69
2.50
2.34
2.18
2.02
1.89
1.76
1.65
1.54
1.44
7.2
3.95
3.65
3.41
3.15
2.93
2.72
2.54
2.37
2.19
2.05
1.90
1.78
1.66
1.55
1.46
1.36
7.3
3.73
3.46
3.20
2.98
2.77
2.58
2.40
2.22
2.08
1.94
1.81
1.68
1.57
1.47
1.38
1.28
7.4
3.52
3.26
3.02
2.82
2.61
2.43
2.26
2.10
1.95
1.82
1.70
1.58
1.49
1.39
1.30
1.22
7.5
3.31
3.07
2.65
2.66
2.46
2.29
2.13
1.98
1.86
1.73
1.62
1.50
1.41
1.31
1.23
1.15
7.6
3.14
2.90
2.70
2.51
2.34
2.16
2.02
1.87
1.74
1.63
1.52
1.42
1.33
1.25
1.17
1.09
7.7
2.96
2.74
2.54
2.37
2.21
2.05
1.90
1.78
1.66
1.55
1.44
1.34
1.26
1.18
1.10
1.02
7.8
2.35
2.19
2.03
1.89
1.76
1.63
1.52
1.42
1.33
1.23
1.15
1.07
1.01
.94
.88
.83
7.9
1.87
1.74
1.62
1.50
1.41
1.31
1.22
1.14
1.06
.99
.93
.86
.82
.75
.70
.67