Iowa Department of Natural Resources
Environmental Protection Commission
Item 8
Decision
Topic - Adopted and Filed – Update to Wasteload Allocation Procedure document Chapter 61, “Water
Quality Standards” and Chapter 62, “Effluent and Pretreatment Standards: Other Effluent Limitations or
Prohibitions”
The purpose of this rule making is to revise the rule referenced document “Supporting Document for Iowa
Water Quality Management Plans”, which was last updated in 2009. This document establishes the technical
methodologies that the Iowa Department of Natural Resources uses to develop wasteload allocations and
water quality-based effluent limits for point source dischargers. The proposed revision will incorporate the
most up-to-date scientific information and provide more flexibility for facilities seeking to use alternative
permitting options. For example, the revision will update the stream low-flow values based on the most
recent published USGS low-flow study report, provide alternative methodologies for deriving site-specific
permit limits, and streamline sampling requirements for site-specific data collection. These changes will
result in cost savings for some permitted facilities and are also protective of designated uses. The document
will be revised to make it more understandable and better describe the procedures used in wasteload
allocation calculations. The proposed revision also changes the title of the document to more clearly reflect
its contents. The revised document will be titled “Iowa Wasteload Allocation (WLA) Procedure.”
The Department received comments from eight different organizations or individuals in response to the
revised document. A responsiveness summary has been prepared to address these comments. Some of
these comments have led to changes in the revised document which have been detailed in the
responsiveness summary. The final version of the “Iowa Wasteload Allocation (WLA) Procedure” document
and responsiveness summary can be found at: http://www.iowadnr.gov/Environmental-Protection/WaterQuality/Water-Quality-Standards.

Matthew Dvorak, Environmental Specialist
Water Quality Bureau
Environmental Services Division

1

 ENVIRONMENTAL PROTECTION COMMISSION[567]
Adopted and Filed
Pursuant to the authority of Iowa Code sections 455B.105(11)“a,” and 455B.173(3), the Environmental
Protection Commission (Commission) hereby amends Chapter 61, “Water Quality Standards,” and Chapter
62, “Effluent and Pretreatment Standards: Other Effluent Limitations or Prohibitions,” Iowa
Administrative Code.
The purpose of the amendments is to update the name of the document referenced in the rules from
“Supporting Document for Iowa Water Quality Management Plans, Chapter IV, July 1976, as revised on
November 11, 2009” to “Iowa Wasteload Allocation (WLA) Procedure” to more clearly reflect the contents
of the document. A wasteload allocation (WLA) is the portion of a water body’s assimilative capacity that
is allocated to an existing or future point source discharge. This document establishes the technical
methodologies the Department of Natural Resources (Department) uses to develop WLAs and water qualitybased effluent limits for point source dischargers. In addition to updating its name, the document will be
revised to make it more understandable and better describe the procedures used in WLA calculations.
The revision will also provide greater flexibility to facilities seeking alternative permitting options.
The major elements of the Iowa WLA Procedure document revision are as follows:

a.

Update the Stream Low-Flow Values for United States Geological Survey (USGS) gaged sites and

ungaged sites based on the USGS low-flow study report “Methods for Estimating Selected Low-Flow
Frequency Statistics and Harmonic Mean Flows for Streams in Iowa,” by David A. Eash and Kimberlee
K. Barnes, published in 2012 and revised in 2013. This change will incorporate the most up-to-date
stream critical low flows published by USGS to better reflect actual stream low flows;

b.

Incorporate statewide default background chemical concentrations using the most up-to-date

monitoring data available;

c.

Incorporate statewide default effluent chemical concentrations for different types of wastewater

treatment plants using the most up-to-date effluent monitoring data available;

d.

Replace the total residual chlorine default decay value in the mixing zone with site-specific

decay measurements;

2

 e.

Incorporate the current implementation procedures for the chloride and sulfate criteria that were

adopted in 2009;

f.

Revise the E. coli WLA procedures for both continuous and noncontinuous discharges in accordance

with the limitation on end of pipe permit limits established at 62.8(2);

g.

Revise the E. coli decay rate coefficient to be consistent with other Department programs;

h.

Revise the temperature criteria implementation procedure to incorporate all elements of

the temperature criteria in Chapter 61 for different designated uses. The proposed revision to the
temperature criteria implementation procedure provides flexibility for facilities seeking alternative
permitting options;

i.

Modify the WLA procedure for pH so that pH criteria must be met at the boundary of the mixing

zone instead of the boundary of the zone of initial dilution. This modification will result in increased
dilution for pH WLA calculations;

j.

Clarify the current mixing zone procedures and the requirements for mixing zone and diffuser

studies;

k.

Incorporate a Site-Specific Data Collection procedure in order to standardize the site-specific

data collection process. The proposed revision will have fewer sampling requirements and will result in cost
savings for point source discharge facilities seeking site-specific permit limits;

l.

Revise the Water Quality Modeling section to replace previous models with commonly used

and modernized QUALIIK and modified Streeter-Phelps models. The revisions will also update decay rates
and reaeration rates to reflect the latest scientific data;

m.

Add a reference to the antidegradation implementation procedure document; and

n.

Add a new section on Alternative Site-Specific Methodology for Water Quality Based Limits that

provides point source discharge facilities with the flexibility to develop site-specific NPDES permit limits.
Other minor revisions to the document include improvements in the estimation of ammonia nitrogen
decay calculations in discharge pipes and general use segments, clarification of the procedure for
determining discharge flows used in WLAs, and clarification of various sections to make the document
more understandable. The “Iowa Wasteload Allocation (WLA) Procedure” document is available

3

 at www.iowadnr.gov/Environmental-Protection/Water-Quality/Wasteload-Allocations.
The amendments also update references to the Department’s Web site.
Notice of Intended Action was published in the Iowa Administrative Bulletin as ARC 3202C on July 19,
2017. Public hearings were held on September 5, 6, and 7, 2017. Public comments were received and
considered.

A

responsiveness

summary

has

been

prepared

and

is

available

at: http://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Quality-Standards. The most
notable change made in response to public comments is to retain the single sample maximum criterion for
E. coli in Chapter 61. The Notice of Intended Action proposed to remove this criterion. The Department will
instead consider potential changes to the E. coli criteria during its regular triennial review process and will
solicit further public input at that time.
After analysis and review of this rule making, these amendments are expected to have a positive
impact on jobs. The amendments are projected to result in a total cost savings for cities, industries, and
semipublic entities ranging between $26 million and $58 million. This total savings is expected to be
achieved by approximately 94 facilities across the state. These cost savings will likely lead to further
investment in production and job growth.
These amendments are intended to implement Iowa Code sections 455B.105(11)“a,” and 455B.173(3).
These amendments will become effective on February 21, 2018.
The following amendments are adopted.
ITEM 1.

a.

Amend paragraph 61.2(4)“a” as follows:

Due to extreme variations in wastewater and receiving water characteristics, spatial dimensions of

mixing zones shall be defined on a site-specific basis. These rules are not intended to define each
individual mixing zone, but will set maximum limits which will satisfy most biological, chemical,
physical and radiological considerations in defining a particular mixing zone. Additional details are noted
in the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV, July 1976, as revised
on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018,
for considering unusual site-specific features such as side channels and sand bars which may influence
a mixing zone. Applications for operation permits under 567—subrule 64.3(1) may be required to

4

 provide specific information related to the mixing zone characteristics below their outfall so that mixing
zone boundaries can be determined.
ITEM 2.

b.

Amend paragraph 61.2(4)“b,” introductory paragraph, as follows:

For parameters included in Table 1 only (which does not include ammonia nitrogen), the

dimensions of the mixing zone and the zone of initial dilution will be calculated using a mathematical
model presented in the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV, July
1976, as revised on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on
February 21, 2018, or from instream studies of the mixing characteristics during low flow. In addition,
the most restrictive of the following factors will be met:
ITEM 3.

Amend subparagraph 61.2(4)“d”(4) as follows:

(4) A discharger to interior streams and rivers, the Big Sioux and Des Moines Rivers, and the
Mississippi or Missouri Rivers may provide to the department, for consideration, instream data which
technically supports the allowance of an increased percentage of the stream flow contained in the mixing
zone due to rapid and complete mixing. Any allowed increase in mixing zone flow would still be
governed by the mixing zone length restrictions. The submission of data should follow the guidance
provided in the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV,
July 1976, as revised on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on
February 21, 2018.
ITEM 4.

e.

Amend paragraph 61.2(4)“e,” introductory paragraph, as follows:

For ammonia criteria noted in Table 3, the dimensions of the mixing zone and the zone of initial

dilution will be calculated using a mathematical model presented in the “Supporting Document for
Iowa Water Quality Management Plans,” Chapter IV, July 1976, as revised on November 11,
2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018, or from instream
studies of the mixing characteristics during low flow. In addition, the most restrictive of the following
factors will be met:
ITEM 5.

Amend paragraph 61.2(4)“f” as follows:

5

 f.

For ammonia criteria noted in Table 3, the stream flow used in determining wasteload

allocations to ensure compliance with the chronic criteria of Table 3 will be that value contained at the
boundary of the allowed mixing zone. This stream flow may not exceed the percentages of the design low
stream flow noted in 61.2(4)“e”(1) as measured at the point of discharge.
The pH and temperature values at the boundary of the mixing zone used to select the chronic
ammonia criteria of Table 3 will be from one of the following sources. The source of the pH and
temperature data will follow the sequence listed below, if applicable data exists from the source.

(1) Specific pH and temperature data provided by the applicant gathered at their mixing zone
boundary.

Procedures for obtaining this data are noted in the “Supporting Document for Iowa

WaterQuality Management Plans,” Chapter IV, July 1976, as revised on November 11, 2009 “Iowa
Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018.

(2) Regional background pH and temperature data provided by the applicant gathered along the
receiving stream and representative of the background conditions at the outfall. Procedures for obtaining
this data are noted in the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV, July
1976, as revised on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on
February 21, 2018.

(3) The statewide average median background values presented in Table IV-2 of the
“Supporting Document for Iowa Water Quality Management Plans,” Chapter IV, July 1976, as revised on
November 11, 2009 as determined by the department.
The stream flow in the zone of initial dilution used in determining effluent limits to ensure compliance
with the acute criteria of Table 3 may not exceed 5 percent of the calculated flow associated with the
mixing zone for facilities with a dilution ratio of less than or equal to 2:1, and not exceed 10 percent of the
calculated flow associated with the mixing zone for facilities with a dilution ratio of greater than 2:1. The pH
and temperature values at the boundary of the zone of initial dilution used to select the acute ammonia
criteria of Table 3 will be from one of the following sources and follow the sequence listed below, if
applicable data exists from the source.

1.

Specific effluent pH and temperature data if the dilution ratio is less than or equal to 2:1.

6

 2.

If the dilution ratio is greater than 2:1, the logarithmic average pH of the effluent and the

regional or statewide pH provided in 61.2(4)“f” will be used. In addition, the flow proportioned average
temperature of the effluent and the regional or statewide temperature provided in 61.2(4)“f” will be
used. The procedures for calculating these data are noted in the “Supporting Document for Iowa
Water Quality Management Plans,” Chapter IV, July 1976, as revised on November 11, 2009 “Iowa
Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018.
ITEM 6.

Amend subparagraph 61.2(4)“g”(4) as follows:

(4) A discharger to interior streams and rivers, the Big Sioux and Des Moines Rivers, and the
Mississippi and Missouri Rivers may provide to the department, for consideration, instream data which
technically supports the allowance of an increased percentage of the stream flow contained in the mixing
zone due to rapid and complete mixing. Any allowed increase in mixing zone flow would still be
governed by the mixing zone length restrictions. The submission of data should follow the guidance
provided in the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV,
July 1976, as revised on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on
February 21, 2018.
ITEM 7.

g.

Amend paragraph 61.3(2)“g” as follows:

Cations and anions guideline values to protect livestock watering may be found in

the “Supporting Document for Iowa Water Quality Management Plans,” Chapter IV, July 1976, as revised
on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018.
ITEM 8.

Amend subrule 61.3(5) as follows:

61.3(5) Surface water classification. The department hereby incorporates by reference “Surface
Water Classification,” effective June 17, 2015. This document may be obtained on the department’s
Web

site

at http://www.iowadnr.gov/InsideDNR/RegulatoryWater/WaterQualityStandards/Rules.aspx http://www.i
owadnr.gov.
ITEM 9.

Amend subrule 61.3(6) as follows:

7

 61.3(6) Cold water use designation assessment protocol. The department hereby incorporates
by reference “Cold Water Use Designation Assessment Protocol,” effective December 15, 2004. This
document

may

be

obtained

on

at http://www.iowadnr.com/water/standards/index.html
ITEM 10.

the

department’s

Web

site

http://www.iowadnr.gov.

Amend subrule 61.3(7) as follows:

61.3(7) Warm water stream use assessment and attainability analysis protocol. The department
hereby incorporates by reference “Warm Water Stream Use Assessment and Attainability Analysis
Protocol,” effective March 22, 2006. This document may be obtained on the departments department’s
Web site at http://www.iowadnr.com/water/standards/index.html http://www.iowadnr.gov.
ITEM 11.

Adopt the following new subrule 61.3(9):

61.3(9) Iowa wasteload allocation (WLA) procedure. The department hereby incorporates by
reference “Iowa Wasteload Allocation (WLA) Procedure,” as revised on February 21, 2018. This
document may be obtained on the department’s Web site at http://www.iowadnr.gov.
ITEM 12.

Amend subrule 62.8(2) as follows:

62.8(2) Effluent limitations necessary to meet water quality standards. No effluent, alone or in
combination with the effluent of other sources, shall cause a violation of any applicable water quality
standard. When it is found that a discharge that would comply with applicable effluent standards in
567—62.3(455B), 567—62.4(455B) or 567—62.5(455B) or effluent limitations in 567—62.6(455B) would
cause a violation of water quality standards, the discharge will be required to meet the water qualitybased effluent limits (WQBELs) necessary to achieve the applicable water quality standards as established
in 567—Chapter 61. Any such effluent limit shall be derived from the calculated waste load allocation, as
described in “Supporting Document for Iowa Water Quality Management Plans,” ChapterIV, July 1976, as
revised on November 11, 2009 “Iowa Wasteload Allocation (WLA) Procedure,” as revised on February
21, 2018, or the waste load allocation as required by a total maximum daily load, whichever is more
stringent. The translation of waste load allocations to WQBELs shall use Iowa permit derivation
methods, as described in the “Supporting Document for Iowa Water Quality Management Plans,”

8

 Chapter IV, July 1976, as revised on November 11, 2009, “Iowa Wasteload Allocation (WLA) Procedure,”
as revised on February 21, 2018 except that the daily sample maximum criteria for E. coli set forth in Part
E of the “Supporting Document for Iowa Water Quality Management Plans” 567—Chapter 61 shall not
be used as an end-of-pipe permit limitation

9

 PUBLIC PARTICIPATION RESPONSIVENESS SUMMARY
FOR
RULEMAKING ON CHAPTER 61 & CHAPTER 62
Iowa Wasteload Allocation Procedure Document
&
E. coli Criteria Update

DEPARTMENT OF NATURAL RESOURCES
ENVIRONMENTAL SERVICES DIVISION
November 27, 2017

 TABLE OF CONTENTS
INTRODUCTION ..............................................................................................................................................1
TOPIC: Comments in Support of the Proposed Rule .........................................................................................2
Item 1: Iowa Wasteload Allocation (WLA) Procedure ......................................................................................2
Item 2: E. coli Criteria Update............................................................................................................................2
TOPIC: Comments Recommending Revision of the Proposed Rule .................................................................3
Item 1: Iowa Wasteload Allocation (WLA) Procedure ......................................................................................3
Item 2: E. coli Criteria Update............................................................................................................................8
TOPIC: Comments Opposed to the Proposed Rule ..........................................................................................10
Item 1: Iowa Wasteload Allocation (WLA) Procedure ....................................................................................10
Item 2: E. coli Criteria Update..........................................................................................................................10
TOPIC: Comments Not Directly Pertaining to the Proposed Rule ..................................................................11
APPENDIX ......................................................................................................................................................12
Item 1: Iowa Wasteload Allocation (WLA) Procedure ....................................................................................12
Item 2: E. coli Criteria Update..........................................................................................................................12

 RESPONSIVENESS SUMMARY
INTRODUCTION
This is a summary of and response to the comments received in response to amendments proposed for 567
IAC Chapter 61
erein
by reference as well as 567 IAC C
nt
The proposed amendments were published as a Notice of Intended Action
(NOIA) in the Iowa Administrative Bulletin on July 19, 2017 as ARC 3202C.
The following amendments were proposed:
Item 1: Iowa Wasteload Allocation Procedure
Chapter IV, July 1976, as revised on November 11,
is
allocated to an existing or future point source discharge. This document establishes the technical
methodologies that the Department of Natural Resources (Department) uses to develop WLAs and water
quality-based effluent limits for point source dischargers. The revision will make the document more
understandable and better describe the procedures used in WLA calculations. The update will also
provide greater flexibility to facilities seeking alternative permitting options.
Item 2: E. coli Criteria Update
Revise the bacteria water quality criteria table at 567 IAC Chapter
The revision will
eliminate the single sample maximum values of 235 organisms per 100 milliliters of water for
Recreational Use Classes A1 and A3 and 2,880 organisms per 100 milliliters of water for Recreational
Use Class A2. Also, to eliminate the reference to the sample maximum E. coli standard in 567 IAC
Chapter 62.8(2) due to the fact that the E. coli sample maximum criterion is recommended to be removed
in the proposed rule in 567 IAC
Public hearings were held on September 5th, 6th, and 7th, 2017 at the towns of Washington, Urbandale, and
Harlan in Iowa. Written comments were accepted through September 8th, 2017. A total of eight persons or
organizations provided oral or written comments on the proposed Item 1: Iowa Wasteload Procedure during
the public comment period; more than 700 persons or organizations provided oral or written comments on
the proposed Item 2: E. coli Criteria Update during the public comment period. The responsiveness summary
addresses all of the comments received. The commenters names are listed in the Appendix.

1

 TOPIC: Comments in Support of the Proposed Rule
Item 1: Iowa Wasteload Allocation (WLA) Procedure
Comments:
We commend the IDNR on updating the language, procedures, and making clarifications to the
WLAP document; the language is easier to read, and the concepts and procedures provided within
the document are much clearer.
The proposed manual more clearly defines the permit limit derivation procedures than the current
process. As part of the advisory committee, we provided technical review and input in the
development of this most important document that is used as the basis for establishing wastewater
discharge permit limits.
The proposed rule would create more flexibility for industrial NPDES permit holders and potentially
save companies money, while still providing adequate and desired environmental protections for
urces. We also support encouraging site-specific sampling, incorporating better
science, and more accurate assumptions as part of the Wasteload Allocation Procedure (WLAP).
articipation.
IDNR has done its part to carefully evaluate the basis for the proposed changes as well as the
potential impact to NPDES permit holders and the environment.
The proposed rule makes our flows and background data accurate compared to what is on the books
now which I am in favor of. I think a WLA should be based on this science. I am in favor of these
proposed changes.
.
We appreciate that the DNR has incorporated updated USGS low flow study results in the proposed
. The use of the USGS low-flow study provides more accurate data
for the purpose of calculating critical low flows for the purpose of setting protective effluent limits.
IDNR Response: Iowa DNR appreciates the support for the proposed rule.
Item 2: E. coli Criteria Update
Comment: We agree with the revision to the E. coli bacteria standards with the deletion of the single sample
maximum values standard. The single sample maximum is not an appropriate parameter for water quality
assessment.
IDNR Response: Iowa DNR has determined that it will no longer be seeking this revision at this time. For
further explanation, please see pages 10-11, below.

2

 TOPIC: Comments Recommending Revision of the Proposed Rule
Item 1: Iowa Wasteload Allocation (WLA) Procedure
Comment: Using monthly or seasonal variable low flow limits instead of the annual low flow (7Q10) to
calculate permit limits decreases the margin of safety and reduces assurance that there will be no adverse
impacts to the water body. We recommend some constraints to the use of monthly or seasonal variable low
flow limits such as real-time monitoring of flow to confirm that the actual flow in the receiving stream is at
or above the assumed monthly or seasonal low flow used to establish the effluent limit.
IDNR Response: The WLA Procedure document states that monthly or seasonal low flows will be explored
on a case-by-case basis and the evaluation considers whether there is a nearby USGS gage that has an
adequate flow record that can be used to reasonably estimate the monthly low flows at the discharge location.
Thus, the proposed rule includes limitations to the use of monthly or seasonal low flows. It is important to
hat allow seasonable
stream low flows to develop effluent limits. The EPA letter dated on September 20, 1996 states that,
Permits should be evaluated on a case-by-case basis for the appropriateness of seasonal limits.
Where dilution is the primary factor affecting development of an appropriate wasteload allocation,
permitting authorities might consider the use of seasonal limits based on seasonal receiving water
flow.
The monthly critical low flows are calculated using USGS standard methodology and take drought
conditions into account. Since the monthly critical low flows are calculated based on the same frequency of
occurrence (once in 10 years) as annual low flows, the margin of safety is preserved.
Comment: We appreciate that DNR is addressing multiple discharges into the same reach, but we still have
concerns with the way that DNR has addressed assimilative capacity. DNR should assess the full assimilative
capacity of the river for common pollutants of concern before starting to allocate capacity to single or
multiple dischargers and specifically reserve a portion of the assimilative capacity as a margin of safety.
IDNR Response: The WLA Procedure will be revised as follows:
ed on the impact to water
quality resulting from the combined discharges, the assimilative capacity for the river reach, and the
The WLA Procedure calculates water quality based limits under critical low flow conditions. Thus, the
margin of safety is implicit.
Comment: We have concerns that the proposed WLA procedure does not specifically address diurnal algal
effects for permits that discharge to streams with significant algae present. DNR should require assessments
to determine if algae are present in significant amounts in the receiving stream. This assessment would
typically require a field visit in the growing season and incorporate visual observations and collect DO
readings associated with varying times of day and sunlight conditions. If it is determined that algae is
impacting the DO dynamics of the receiving stream, then permit limits should be determined based on the
most critical time period to ensure adequate DO levels necessary for protection of aquatic life.
IDNR Response: Iowa DNR ambient monitoring program assesses stream conditions and the information is
summarized in the 303(d)/305(b) report. If the waterbody is impaired, a Total Maximum Daily Load is
performed on a watershed basis, which incorporates both point and nonpoint sources. The WLA procedure
focuses on point sources. The QUALIIK model in the proposed Iowa WLAP can incorporate diurnal algal
effects on a site-specific basis.
3

 Comment: We continue to believe that it is better to use more representative travel time assumptions, such as
using the median or mean flow of a stream to calculate bacteria die-off. We request that the IDNR provide a
section in the WLAP that describes the process the IDNR will use in determining travel times and die-off
Iowa DNR Response: It is important to note that as part of this rule making, the bacteria decay rate is
reduced by more than 5-fold from 5.28/day to 1.0/day. The use of the 7Q10 flow to estimate bacteria decay
Quality Criteria for Bacteria March 2004, which states:
"Continuous loadings, that is, sources that discharge at about the same level
regardless of the rainfall, often most greatly impact water quality under low-flow,
dry-weather conditions, when dilution is minimal. For these sources, EPA
recommends that the allowable loading be calculated for the geometric mean as the
product of the geometric mean water quality criterion and the 30Q5 flow statistic
(i.e., the lowest 30-day flow occurring once every five years), and for the individual
sample as the product of the upper percentile value water quality criterion and 1Q10
flow statistic (i.e., the lowest one-day flow occurring once every 10 years) or the low
flow specified in the state or tribal water quality standards, if one is so specified."
The draft Wasteload Allocation Procedure document includes a Section (9.2) on E. coli
Decay Rate and a Section on Flow Velocity Calculations (Section 16.3.6). The
information provided in these two sections is adequate to estimate the E. coli decay.
Comment: Page 10, Section 5.4 Mixing Zone and Zone of Initial Dilution as related to Ammonia Nitrogen:
This section of the document discusses basing the dilution ratio for ammonia nitrogen WLA calculations on
7Q10, whereas the EPA bases ammonia nitrogen calculations on 30Q10. Did the IDNR intend to use 7Q10
for an ammonia MZ and ZID? (See the 1999 Update Ambient Water Quality Criteria for Ammonia for
further clarification.)
Iowa DNR Response: 567 IAC Chapter 60.2(455B) defines the dilution ratio as follows:
r discharger, the ratio of the seven-day, ten-year low
stream flow to the effluent design flow, e.g., a dilution ratio of 2:1 has two parts stream flow to one part
effluent flow.
Thus, the 7Q10 flow is required in Iowa rule to be used for the dilution ratio calculation.
Comment: The temperature limits calculated in the WLAP are not protective under conditions of variable
background temperatures and variable heat discharge rates. For Monthly Average Limit calculations, in
months where average temperatures were below the Maximum Background Temperature, facilities could
comply with permit limits while still warming the mixing zone more than 3°C. In addition, Maximum
Background Temperatures exceed, or are close to, temperature "cap" values in all months in Zones II and III
on the Missouri River and in May-September on the Missouri River; the adding of a 3°C mixing zone to
these background values would allow a violation of the Maximum Allowed River Temperature criterion in
Iowa's WQS.
Iowa DNR Response: Iowa DNR addressed this comment in earlier communications with the EPA. Currently
there are
In the past, Iowa
only partially implemented the temperature criteria due to its complexity. The implementation procedure
included in the WLAP implements all elements of the temperature criteria. To develop the temperature
4

 implementation procedure, Iowa DNR staff conducted detailed research on EPA guidance documents and
other states implementation procedures. In addition, Iowa DNR staff worked with stakeholders for over a
year to develop the new temperature procedure to ensure that the procedure is protective of the beneficial
uses and is reasonable to implement.
Please note that the 3°C rise is not an instantaneous criterion that is a never to be exceeded value. The 3°C
harges, which is the reason it is

t that
will raise the temperature of the water (at the expected minimum daily flow for that month) more
than 5°F. In lakes, the temperature of the epilimnion in those areas where important organisms are
most likely to be adversely affected should not be raised more than 3°F above that which existed
before the addition of heat of artificial origin. The increase should be based on the monthly average
Several other EPA guidance documents such as the Quality Criteria for Water 1986
also indicates that the 3°C rise is a weekly or chronic criterion. Due to the chronic nature of the 3°C rise
criterion, it is implemented as an average limit in wasteload allocation calculations.
Due to the fact that the maximum temperature criteria are derived based on the upper incipient temperature it
is implemented as daily maximum temperature. The daily maximum limit is calculated using 10-year critical
low flows and the 90th percentile background temperature. Thus, the daily maximum limit ensures that the
maximum temperature criteria are met. If the monthly temperature limits based on the 3°C rise criterion are
higher than the daily maximum limits, the daily maximum limits will govern.
Comment: The WLAP allows pH criteria to be met at the boundary of the mixing zone instead of the ZID.
While pH in and of itself is generally not thought to be acutely toxic, it can be an aggravating factor for other
pollutants making them more toxic. If pH can be outside of the criteria range up to the edge of the chronic
MZ, the extreme pH must be used to calculate other pH-dependent acute criteria in the ZID.
Iowa DNR Response: The technology based pH limit of 6 to 9 applies to the vast majority of point source
discharges at the end of pipe and it ensures that the pH values in the zone of initial dilution will be close to
the pH criteria of 6.5 to 9. Also, pH is not a pollutant and the criteria value of 6.5 to 9 does not constitute an
acute criterion. In addition, the WLAP allows the use of site-specific pH values to calculate effluent limits to
ensure that the designated uses are protected.
Comment: page 36, Section 12.1, General Use Segments (567 IAC Chapter
translator procedure uses one half of a 96 hour or 48 hour LC50 to represent a no-effect level. However, this
value would not represent an acute no-effect level. We strongly recommend that an aquatic life ambient
distribution of accepted acute toxicity values for at least one species from a minimum of eight different
families to be representative of the aquatic community. Using the results of a single species acute toxicity
test does not provide broader protection to the aquatic community.
Fathead minnow for General Use Segments. Fathead minnows are
in many cases unlikely to be sensitive relative to other species that potentially could be present in these
waters.

5

 Application of the approach described in the WLAP, using a single test species with data taken from a
database (e.g., ECOTOX), does not appear to account for site-specific conditions (e.g., hardness, DOC, etc.),
which could be taken into account (where applicable to a chemical) through the use of an aquatic life
criterion.
The discussion above outlines the lack of scientific defensibility of using one half of a 96-hour or 48-hour
LC50 to represent a no-effect level. Where specific numerical criteria for a chemical or biological parameter
(such as toxicity) are absent, compliance with WQS must be based on the general narrative criteria and on
protection of the designated uses.
We strongly recommends the IDNR adopt the EPA's recommended criteria for whole effluent toxicity as
follows: to protect aquatic life against chronic effects, the ambient toxicity should not exceed 1.0 chronic
toxic unit (TUc) to the most sensitive of at least three different test species. For protection against acute
effects, the ambient toxicity should not exceed 0.3 acute toxic units (TUa) to the most sensitive of at least
three different test species.
Iowa DNR Response After further consideration, the language related to the use of fathead minnow as the
default most sensitive representative resident species for General Use segments is being eliminated in the
revised WLAP (Section 12.1). As a result, the implementation of narrative criteria for General Use segments
will revert to the existing language in the current Basin Support Document, which was previously approved
by EPA on June 16, 2004. The Iowa DNR is no longer proposing to revise the approved current Iowa rule.
Please
Whole Effluent Toxicity (WET) testing is a separate topic which would require a water quality standard
change and will be addressed at a later date.
Comment: Page 37, Equation 12.1-1, last sentence:
-of-pipe for
General Use waters since General Use segments are ephemeral streams with zero design low flows
unless site-spec
This statement is not consistent with the definition of General use segments in 567 IAC Chapter 61.3(1)a.
Iowa DNR Response: Iowa DNR believes that the above statement is consistent with the General Use
Segments definition in 567 IAC Chapter 61.3(1)a due to the fact that General Use Segments are ephemeral
waters usually with critical low flows of zero. However, to make the sentence more clear, the sentence is
revised as follows:
a translator value is applied at the end-of-pipe for
General Use waters unless site-specific data prove otherwise. This approach is based on the
definition of General Use segments in 567 IAC Chapter 61.3(1) a .
Comment: Page 40, Section 13.0 Mixing Zone Procedure: Please provide an explanation/justification as to
why the reference to the General Water Quality (narrative) Criteria has been deleted at 61.2(4)
Iowa DNR Response: The paragraph is meant to refer to the purpose of the mixing zone as stated in 567 IAC
Chapter 61.2(4), not to copy the entire section into the document.
Comment: Pages 51-52, Section 14.0 Flow Variable Limitation Procedure: When Flow Variable Limits are
granted, permits must require reporting of both flow variable discharge (Ex. Pounds/day/cfs) and the actual
mass discharged (Ex. Pounds/day). Knowing the mass discharged is essential for water quality planning,
TMDLs, and full public disclosure of discharges such as ECHO or TRI databases.
6

 Iowa DNR Response: Several conditions were added to the current flow variable procedure in the Basin
Support Document in order to strengthen it. Section 14.0 Flow Variable Limitation Procedure states that,
e factors in
Equation 14.0Thus, the discharge concentration, discharge flow and stream flow are reported along with the flow variable
discharge (in lbs/day/cfs). With this information the actual mass discharged can be calculated.
Comment: Page 73, Section 17.1 Maximum Daily Limits and Average Monthly Limits: Under the statistical

Iowa DNR Response

.

Comment: Page 75, Section 19.0 Alternative Site-Specific Methodology for Water Quality Based Limits:
This section states:
"This Section provides several alternative site-specific options to derive water quality based
limits, which are recommended by U.S. EPA. Other alternative site-specific criteria will be
reviewed and approved as long as they are scientifically defensible."
Individual site-specific criteria are WQS and must be submitted to the EPA for review and approval, unless
the SSC were developed using a performance-based approach that was previously approved by the EPA.
Iowa DNR Response: This comment is addressed in the response to another EPA comment below.
Comment: Page 75, Section 19.0 Alternative Site-Specific Methodology for Water Quality Based Limits:
The WLAP states:
"Although these principals have been best demonstrated for metals (e.g., U.S. EPA, 1992; U. S.
EPA, 1996), they hold true for all chemicals."
Please provide specific evidence to support the statement that all chemicals behave similarly to metals in
matters of species sensitivity.
Iowa DNR Response: The sentence will be removed from the document.
Comment: Page 76, Section 19.0 Alternative Site-Specific Methodology for Water Quality Based Limits:
The WLAP states:
"State rulemaking is required before site-specific water quality criteria are used in a permit
unless the method used to derive the site-specific criteria has been adopted in the state rule."
As noted above in a previous comment, individual site-specific criteria are WQS and must be submitted to
the EPA for review and approval, unless the SSC were developed using a performance-based approach
that was previously approved by the EPA.
Iowa DNR Response: The sentence will be revised as follows:

7

 -specific water quality criteria are subject to the review and approval of the U.S.
Environmental Protection Agency unless the criteria or methodology to derive the site-specific
criteria have been approved by the U.S. EPA.
Comment: Page 77, Section 19.2.1 Recalculation Procedure: The WLAP states:
"The approach may also require a biological assessment of the receiving stream to determine
what criteria database organisms are not "resident to the site" and may not be expected to
"occur at the site" as defined in the Recalculation Procedure."
This evaluation must also take into account that some of the "resident species" may have been extirpated
from the site due to toxic discharges; this needs to be reflected in the WLAP.
Iowa DNR Response: Section 19 states that,
he appropriate EPA guidance document must be used to determine the specific steps to be
The recalculation procedure in the EPA Water Quality Standard Handbook takes into account the condition
described in this comment.
Item 2: E. coli Criteria Update
Comment: If the IDNR removes the Single Sample Maximum (SSM) criteria from the water quality
standard, the IDNR should adopt criteria protective of primary contact recreation use consistent with the
for a geometric mean (GM) and a statistical threshold value (STV). Using the geometric mean alone would
not reflect spikes in water quality.
Iowa DNR Response: Iowa DNR has made the decision to terminate the proposed rule to remove the Single
Sample Maximum (SSM) criterion from 567 IAC Chapter 61.3(3) at this time. The comments received in
regard to the elimination of the SSM criterion raised the issue of whether a replacement criterion can be
identified which evaluates the risk of bacterial exposure over a shorter period than the seasonal geometric
mean. Iowa DNR continues to believe, as indicated by the original scientific analysis used to develop the
SSM, that the SSM is only appropriate for use in determining the need for beach advisories. The DNR is
willing to assess identified alternatives as part of the water quality standards review process. As a result, the
Single Sample Maximum (SSM) criterion will remain in the water quality standards. Iowa DNR will
evaluate the EPA 2012 recreational criteria and address this topic during a future triennial review.
Comment: We are concerned that IDNR has been issuing NPDES permit for continuously discharging
publicly-owned treatment works (POTWs) that do not include both monthly average and weekly average
permit limits consistent with 40 CFR 122.45(d). Specifically, the IDNR is issuing continuously discharging
POTW permits with E. coli limits that contain only monthly average limits and do not have weekly average
limits.
Iowa DNR Response: 40 CFR 122.45(d) requires a short term limit where practicable. Bacteria criteria are
based upon exposure over a recreational season and establish a geometric mean for protection over the full
season. (1) The short term limit is not necessary since the limits based on the geometric mean criteria require
point source facilities to disinfect; (2) the short term limit would be very high due to the use of a site-specific
variability (coefficient of variation) based on Tetra Tech method (the short term limit would be derived
based on the same distribution as the geometric mean criterion and the seasonal duration). Thus, it does not
567 IAC Chapter 62.8(2) does not allow the
use of sample maximum criteria in NPDES permits.
8

 Comment: 40 CFR 131.20(a) requires that the State shall provide an explanation if a State does not adopt
new or revised criteria for parameters for which EPA has published new or updated 304(a) criteria. The EPA
requests that the IDNR provide that explanation for not adopting the EPA 2012 recreational criteria in the
response to comments prior to formal submittal of new and revised WQS to the EPA
Iowa DNR Response: 40 CFR 131.20(a) applies only during the triennial review process. That said, the EPA
is in the process of a 5-year review of the 2012 recreational criteria. Iowa will evaluate the 2012 criteria
during future triennial review after EPA finishes the 5-year review consistent with the commitment described
in the response to table the proposed change to the single sample maximum

9

 TOPIC: Comments Opposed to the Proposed Rule
Item 1: Iowa Wasteload Allocation (WLA) Procedure
Comment: EPA has final approval of state water quality standards and they have been told to stand down. It
bothers me that this is all moving forward now at a time when there will be no effective oversight by region 7
EPA. I noticed changes to the low flow calculations will allow discharges of more ammonia. Greater dilution
of the receiving stream means less stringent limits. Next, changes in the procedures calculating thermal limits
will affect something like 67 of 177 dischargers. It is stated that almost half of the facilities would go from
essentially non-compliance into compliance which means they are discharging at higher temperatures. It is
very concerning to me.
Iowa DNR Response: The proposed wasteload allocation procedure incorporates the latest USGS low flow
study results (developed under the contract by Iowa DNR), which replaces the low flow methodology
developed in the 1970 s. The use of the updated USGS low-flow study provides more accurate data for the
purpose of calculating critical low flows that are in turn used in setting protective effluent limits.
In the past, Iowa only partially implemented the temperature
criteria due to its complexity. The implementation procedure included in the WLAP implements all elements
of the temperature criteria for the first time. To develop the temperature implementation procedure, Iowa
DNR staff conducted detailed research on EPA guidance documents and other states implementation
procedures. In addition, Iowa DNR staff worked with stakeholders for over a year to develop the new
temperature procedure to ensure that the procedure is protective of the beneficial uses and is reasonable to
implement.
Iowa DNR conducted three rounds of stakeholder meetings to seek input on the Wasteload Allocation
Procedure document and the stakeholders include environmental groups and regulated entities. Iowa DNR
also had several meetings with the EPA Region 7 staff to discuss their comments. These proposed rules were
thoroughly vetted over a long period of time. Iowa DNR also convened a technical advisory committee to
comments and is based on the current scientific data. Stakeholders including environmental groups and
regulated entities were supportive of this aspect of the proposed wasteload allocation procedure rule.
Item 2: E. coli Criteria Update
Summary of Comments:
Over 700 comments received oppose the removal of the Single Sample Maximum (SSM) E. coli criteria. The
commenters believe that the proposed rule to remove the SSM criteria
not sufficiently protective of public health. Using the Geometric Mean (GM) alone would not reflect spikes
in water quality because the GM alone is not sensitive to them.
Comment
standards is not sufficiently protective of public health. Using the Geometric Mean (GM) alone would not
reflect spikes in water quality because the GM alone is not sensitive to them. Please explain why DNR
believes the proposed E. coli criteria consisting of a geometric mean component alone is sufficiently
protective of public health, contrary to the 2012 EPA recommendation. Please cite the scientific studies,
sanitary surveys or other data that are the basis for the proposed revised E. coli water quality criteria for A1,
A2 and A3 waters. In the absence of a scientifically valid justification for the proposed criteria, to address
concerns about the SSM being overly stringent the Commission should adopt one of the sets of the 2012
recommended recreational water quality criteria. The Statistical Threshold Value (STV) component of each
set of the 2012 criteria is less stringent th
(A1 and A3), yet still sufficiently protective of public health. Please clarify whether restorative efforts will
10

 continue for the 3 lakes and 3 river segments currently listed as impaired due to violations of the SSM
criteria for which a TMDL restoration plan has already been developed and approved by EPA. Please explain
why DNR believes monitoring and assessing for short-term spikes in E. coli bacteria at certain lakes and
reservoirs with public beaches, and not rivers designated for primary contact recreational uses, is sufficient to
protect public health.
IDNR Response: Iowa DNR has made the decision to terminate the proposed rule to remove the Single
Sample Maximum (SSM) criterion from 567 IAC Chapter 61.3(3) at this time. The comments received in
regard to the elimination of the SSM criterion raised the issue of whether a replacement criterion can be
identified which evaluates the risk of bacterial exposure over a shorter period than the seasonal geometric
mean. Iowa DNR continues to believe, as indicated by the original scientific analysis used to develop the
SSM, that the SSM is only appropriate for use in determining the need for beach advisories. The DNR is
willing to assess identified alternatives as part of the water quality standards review process. As a result, the
Single Sample Maximum (SSM) criterion will remain in the water quality standards. Iowa DNR will
evaluate the EPA 2012 recreational criteria and address this topic during future triennial review.
TOPIC: Comments Not Directly Pertaining to the Proposed Rule
Comment: We believe that instream monitoring should be added as a permit condition for large dischargers
to verify that permit limits based on WLA modeling are protective of water quality standards. DNR should
require instream monitoring as a permit condition for large dischargers to verify that permit limits based on
WLA modeling are protective of water quality standards.
IDNR Response: This issue is related to NPDES permit requirements and it not part of this rule making.
Comment: While not technically a part of the WLA procedure, we would like to suggest an improvement to
part of secondary
treatment standard limits. The Iowa procedure uses BOD for influent monitoring and CBOD for effluent
monitoring. In order to determine compliance with the secondary treatment standard of 85% removal, the
current procedure uses the assumed relationship of CBOD = BOD 5. As noted in the EPA NPDES Permit
Writers Manual, this relationship may not apply outside the range of 30 to 45 mg/l BOD. DNR should
consider a new procedure for determining a site-specific BOD to CBOD relationship for permits where BOD
is outside the range of 30 to 45 mg/l.
IDNR Response: As indicated in the comment, this issue is not part of this rule making
Comment
previously disapproved by the EPA and needs to be removed from subrule 61.3(3) in order to reflect Iowa
WQS rules that are actually in effect for CWA purposes.
Iowa DNR Response: This issue is not part of this rule making and will be addressed in a future triennial
review.

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 APPENDIX
Commenters:
The following is a list of individuals and organizations that commented on the proposed rule during the public
comment period. The commenters are listed in no particular order.
Item 1: Iowa Wasteload Allocation (WLA) Procedure
Government Agencies:
U.S. EPA Region 7
Non-Profit or Trade Organizations:
Iowa Environmental Council (IEC)
Environmental Law and Policy Center (ELPC)
The Iowa Association of Business and Industry (ABI)
The Iowa Water Environment Association (IAWEA)
Businesses:
Keith Hobson Fox Engineering
Lance Aldridge Fox Engineering
Private Citizens:
Steve Vesey
Item 2: E. coli Criteria Update
Government Agencies:
U.S. EPA Region 7
Non-Profit or Trade Organizations:
Iowa Environmental Council (IEC)
Environmental Law and Policy Center (ELPC)
The Iowa Association of Business and Industry (ABI)
The Iowa Water Environment Association (IAWEA)
Businesses:
Keith Hobson Fox Engineering
Lance Aldridge Fox Engineering
Private Citizens:
Over 700 private citizens submitted comments on the proposed E. coli rule. Due to the large number of commenters,
the individual names are not listed and they are available upon request.

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