United States
Environmental Protection
Agency
Office Of Water
(4305)
EPA 823-R-95-003
March 1995
SEPA
Allocated Impact Zones For
Areas Of Non-Compliance
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ALLOCATED IMPACT ZONES FOR
AREAS OF NON-COMPLIANCE
William A. Brungs *
Water Management Division
Region I
U.S. Environmental Protection Agency
October, 1986
REPRINTED MARCH 1995
* Author is currently on an IPA to
Save the Bay, Inc.
434 Smith Street
Providence, RI 02908
401/272-3540
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TABLE OF CONTENTS
Page
Executive Summary ^
Introduct ion ±
Allocated Impact Zone Procedure 3
Determine Need for Allocation 4
Water body Boundaries 5
Discharge Data 5
Ecosystem Data 5
Environmental Mapping 8
Relative Environmental Value 11
Level of Protection 12
Allocation Opt ions 13
Quality Within Allocated Impact Zones 16
Example Allocations. . 18
Example One - Lentic System with 7 Zones
and 6 Discharges. 18
Acknowledgements , 27
References , 28
Appendix A (Historical Perspective) A-l
Appendix 3 (Relative Environmental Value) 3-1
Appendix C (Level of Protection) C-l
Appendix D (Example Two - Lotic System with 4 Zones
and 10 Discharges ) D- 1
Appendix E (Example Three - Single Discharge
with 4 Zones) E-l
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EXECUTIVE SUMMARY
The present means of regulating water quality standards and estab-
lishing permit limitations for point source discharges are limited
by the absence of any rationale placing mixing zone limits on the
area where adverse environmental impacts may occur. Mixing zones
have been defined by plume location, need for dilution volume, or a
uniform linear distance for all discharges or classes of discharges.
Mixing zone boundaries derived by this engineering approach ignore
the multiple or additive discharge conditions that characterize
receiving waters and have had little to do with the goal of protec-
ting our environment.
Current state water quality standards programs provide mixing zone
guidance incorporating a fraction of the cross-sectional or surface
area of streams and lakes or a uniform linear distance limitation.
This guidance fails to consider multiple source impacts, sensitivity
of aquatic resources, and socioeconomic factors.
To address the limitations of current practice, an impact allocation
procedure is presented and discussed in this report. This procedure
addresses many of the socioeconomic and ecological factors that need
to be considered in waste management:
0 All present and projected future discharges are to be
considered together.
0 Ecological and toxicological data are needed to whatever
level of detail they exist or can be determined.
0 Waterbody uses are prioritized and assigned numerical r-ei.3-
tive values based upon socioeconomic considerations. si~ :.-:r
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considerations are necessary to select an appropriate level of
protection. These decisions are part of the risk management
process, and are separate from the risk assessment parts con-
ducted by scientists and engineers.
0 Each discharger is assigned a fraction of the available envi-
ronmental value of a waterbody based upon an allocation model
and expressed by area.
0 If the assigned area is too limiting, alternatives such as
discharge relocation or redesign, toxicity reduction, termi-
nation of limiting process, etc., are to be considered.
Purchase of unneeded allocation from another discharger is
appropriate.
The data requirements and socioeconomic decisions required to satisfy
all levels of this allocated impact zone procedure are extensive and,
in most present instances, not practically achievable. However,
several of the initial steps are not unreasonable and the use of the
entire procedure utilizing effluent volume and toxicity may be con-
sidered to be the eventual goal. A goal that could be achievable
during the third round of effluent permit review and revision around
1991. During this period of time many more effluent toxicity -iata
will be available as a result of the second round of permits and i~e
socioeconomic decisions could be made.
This procedure is intended for the use of both state and USEPA w^-.-r
quality standards coordinators and permit writers who should w-r-;
concert with each other.
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INTRODUCTION
This report describes a procedure to determine the environmentally
acceptable size of mixing zones, called allocated impact zones (AIZ)
herein, around point source discharges into freshwater and saltwater
ecosystems. This term has been used previously in USEPA (1984, 1985,
1985), Neely (1982) and Bergman e_t a_l (1986) in their workshop sum-
mary. The more commonly used term, mixing zones, will not be used
because of historical confusion about which of two definitions apply.
Engineering oriented professionals consider a mixing zone as that
area or volume of dilution water necessary to reduce contaminant
concentrations to some acceptable level or to a totally mixed condi-
tion (Villemonte e_t al . , 1973 and Lillesand e_t al. , 1975). Plume
shape, size and depth are additional similar engineering concepts of
mixing zones (Neely, 1982). Another historical definition for a
mixing zone is the area contiguous to a discharge where receiving
water quality is not required to meet water quality criteria nor
other requirements applicable to the receiving water (USEPA, 1976).
This concept is supported by environmental scientists and water
quality managers. The two definitions are rarely compatible as
demonstrated by the conflicts of applicability when the two groups
(e.g., plant engineers and state and EPA permit writers) address the
issue.
The concept of allocated impact zones has been chosen for several
reasons:
0 It avoids the historical confusion concerning definition of
mixing zones.
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0 The concept defines that the AIZ boundary'as tne point where
water quality characteristics permit long-term exposure with-
out interfering with any activity of aquatic organisms or
causing ill effects to any life history stage (Fetterolt,
1973).
0 The word "allocated" was chosen since this approach demands
consideration of all point sources within a defined waterbody
rather than on a discharge by discharge basis as is done when
mixing zone is the common concept. As with wasteload allo-
cation, acceptable areas of non-compliance with water quality
standards should be considered holistically to avoid excessive
potential damage.,
0 The word "impact"1 is realistic, as well as descriptive, since
there is the potential for adverse impact on aquatic life when
water quality standards are allowed to be exceeded, as is the
case in the AIZ.
•
Mixing zone concepts focused on farfield requirements. The
recent incorporation of effluent toxicity testing in discharge
permits is emphasizing also the concern about nearfield im-
pacts. The new term, AIZ, incorporates both.
A detailed discussion of the historical development of mixing zone
guidance is presented in Appendix A. This guidance has resulted in
defining mixing zone boundaries that are based on cross-sectional
area or volume and uniform linear limits.
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ALLOCATED IMPACT ZONE PROCEDURE
In the absence of any holistic approach to the allocation of poten-
tial impact areas, many ecosystems have been degraded or are in the
process of degradation, due to case-by-case decisions for point
source discharges from industrial and municipal outfalls and dredging
or construction activities. The allocated impact zone procedure
organizes and manages discharges by including all point source
discharges in the dec is lonmaking process!
There are several opportunities that regularly occur when the AIZ
procedure could be initiated:
0 Anticipated revisions in water quality standards.
0 Impending permit review/revision period.
0 New ecosystem uses are being considered.
0 Expansion of industrial or municipal discharge is anticipated.
t° New pollution control organization is being developed.
Figure I is the chronological sequence of the steps in the allocated
impact zone procedure and will form the outline for the balance of
this report.
Determine Need for Allocation
In addition to the above mentioned opportunities to initiate this
plan, there are other reasons for organizing impact allocation in
an holistic manner. In each state there are examples of excessive
damage to aquatic ecosystems as a result of present management.
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Determine Need for Allocation
l
Establish Waterbody Boundaries
i
Analyze Current and Future Discharge Data
Analyze Ecosystem Data
I
Develop Environmental Mapping
Assign Relative Values
V
Determine Level of Protection
Select Allocation Procedure
V
Allocate AIZ
Specify Quality Within AIZ
Figure 1 Chronology of Allocated Impact Zone (AIZ) Designation
Act iv it ies .
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procedures. Since a case-by-case approach led to these problems, a
similar approach for rehabilitation will not be successful or, if so,
not cost effective. Current federal and state budget limitations
necessitate using the most cost-effective procedures in environmental
management. Instead of attempting to eliminate the impact of one
stress at a time, the whole of a particular waterbody must be consid-
ered so that only the necessary prioritized problems are scheduled fo:
improvement.
Waterbody Boundaries
Care must be taken in establishing the boundaries for the rivers,
lakes, and estuaries of concern. Since this approach is an attempt
to assess cumulative impacts, the boundaries should not be so limited
that the present case-by-case approach is maintained. If too large,
the area would not be manageable.
Common sense can frequently be of use in this part of the exercise.
If a part of the aquatic environment is physically, chemically, or
ecologically distinct, that part may be considered to be a candidate
for analysis. A river pool between dams is an example as would be
a lake. A side arm of an estuary that has a uniquely low flushing
rate could be another example. The presence of a space-limited
biological population or community could define the limits of an
area. A water quality limited area could also be a separate con-
s ide rat ion.
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Discharge Data
All.point source discharges, including combined sewer overflows,
should be identified for the waterbody of concern. Available
characterization information, such as discharge flow rates, toxic
components, general water quality, toxicity, diurnal and seasonal
variability, etc., should be obtained. Anticipated changes in
operations, such as expansion, process changes, level of treatment,
etc., should be documented. Similar information, if available,
should be obtained for planned future discharges.
Ecosystem Data
No attempt will be made here to list all of the appropriate data
desirable to conduct an allocated impact zone analysis. Rather,
categories will be identified witn examples and highlights that may
not be readily apparent. The analysis should initially be con-
ducted with available data, regardless of source. If data gaps
become apparent, or if additional data are desirable to establish
status and trends, a decision must be made as to whether the time
and cost are justified on the criterion that a better allocation
could be made or that such efforts would not aid substantively in
the allocation process.
0 Identify all public and private water supply intakes.
0 Water quality and sediment and pollutant transport models
available for the waterbody of concern should be evaluated
as to 'their utility in the allocation process. Annual and
seasonal flow data will oe used to determine appropriate
models.
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0 Ambient water quality data, including toxic chemicals, will be
needed. Data for existing water quality limited areas will be
especially critical.
Useful guidance and additional suggestions are available in the Water
Quality Standards Handbook (USEPA, 1984) and the Technical Support
Document for Water Quality-based Toxics Control (USEPA, 1985).
As with the abiotic data needs, the states should use their expertise
to determine their specific or unique needs for biological data. The
following is general guidance as to the most important data needs.
Once the available data have been gathered, synthesized, and evaluated
for completeness, site specific characteristics and the cost effec-
tiveness of additional data production will determine the extent of
additional data needs.
0 Primary producers - Data for autotrophic organisms such as
phytoplankton , periphyton, rnacrophytes , and macroalgae are
needed. Habitat-forming groups are especially important.
0 Macroinvertebrates - The major categories of importance are
crustaceans, shellfish, polychaetes and others that are impor-
tant in aquatic and human food chains or indicators of water
quality. Data on human pathogens in commercial species are
also necessary.
0 Fish - Data from creel censuses, surveys, etc., will be most
useful. All major groups need to be analyzed as to spawning
and nursery areas, residue data when available and migr=it:r/
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pathways. Historical data will assist in the determination of
what indigenous species were important, before recent major
anthropogenic changes.
0 Threatened or endangered species - Such a species is any
aquatic plant or animal that has been determined by the Secre-
tary of Commerce or the Secretary of the Interior to be a
threatened or endangered species pursuant to the Endangered
Species Act of 1973, as amended. The present or past occur-
rence of any such species should be considered.
0 Recreational and Other Uses - These should be identified due
to their role in determining relative values. Examples are
body contact activities, recreational fishing and she!1fishing,
irrigation, and boating.
The ecosystem data should be organized, where possible, into environ-
mental maps. This format will be quite useful in determing the
potential impact of existing point source discharges. These maps
will also be useful if there is a need to locate, relocate, or modify
an existing or proposed discharge.
Environmental Mapping
The following mapping examples each had a different goal and there-
fore is not as broad an application as desired to develop allocated
impact zones. Diener (1975) described seven Texas estuarine ar?*s :-
terms of dimensions; major vegetation types; geology and geol >.; : : 11
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history; drainage basins and stream discharge records; hydrological,
biological and benthic properties; populations a.nd economic develop-
ment; pollution; and navigation projects. Hunt (1975) described a
study to improve the presentation of coastal zone data. Various
methods were discussed for the presentation of data on shellfish
growing areas, salinity, groundwater level, flood tide currents and
current velocities, distribution of zooplankton, sediment type versus
benthic organisms, and a variety of water quality characteristics.
Thurlow and Associates (1975) completed a report on Ecological Sensi-
tivity Mapping of the Lower Great Lakes Watershed as a planning tool
to handle spills of hazardous materials. Their mapping was concerned
with various types of recreational areas and water supply intakes as
well as biological populations, both land-based and aquatic, and
locations of toxic chemicals and oil storage. The International
Joint Commission sponsored a Workshop on Environmental Mapping of the
Great Lakes (1976) in which papers were presented on such subjects as
uses of environmental maps in determining areas of noncompliance,
industrial and power plant siting needs, dredge and fill, navigation,
municipal intakes and discharges.
An atlas for Narragansett Bay, Rhode Island (Olsen et al. , 1980) dis-
plays similar presentations but also includes sections on recreation,
shipping, pollution, dredging, and particle movement.
An atlas of the natural resources of Chesapeake Bay (Lippson, 1973)
graphically presents depths, tides, currents, salinity, sediments,
marshes, and aquatic plants. A variety of invertebrate and fisn
species are represented as to seasonal distribution and spawnir— v^
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nursery areas. The locations for concentrations of ducks, geese, and
swans were also represented.
The USEPA (1980) conducted a remote sensing demonstration project
using the Boston Harbor marine discharge 301(h) application data.
The project report included a variety of maps and overlays to show
the relationship of metal contaminated sediments to outfalls, location
of discharges and monitoring stations, and one excellent map showing
existing and proposed beaches and boating facilities, diving and
fishing areas, parks, camping, historical sites, etc. Another map
showed areas of commercial finfish and shellfish resources, lobster
buoy counts, and areas of closed or restricted shelIfishing.
In the process of developing environmental maps, it is usually not
sufficient to consider only present conditions which include the
results of anthropogenic activities that have already negatively
affected the fisheries populations, physical habitat, and water
quality. Consequently, historical perspectives, when available,
should be considered in order to know what the unaffected condi-
tions were before man's activities.
Environmental maps have many uses other than for the definition of
allocated impact zones. State and federal regulatory agencies can
use them in a variety of ways (Fetterolf, 1977):
0 Identifying concurrent or conflicting water uses.
0 Selecting management objectives.
0 Preparing environmental impact statements leading to
impact minimization.
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0 Designing research and monitoring programs.
0 Understanding status and trends tnrough time.
0 Identifying habitat that must be protected, preserved,
or res tored .
0 Future planning
Displays of environmental maps have great potential in raising the
environmental consciousness of the public. Maps can be a solution
to the problem of explaining environmental concepts and issues to
lay people and scientists alike. In addition, environmental maps
can facilitate the transmission of factual information, communicate
the interrelationships of uses and other factors in the ecosystem,
and link environmental science to the personal interests and con-
cerns of the public.
Relative Environmental Value
A comparative numerical, rating will be established for the numerous
environmental uses of aquatic ecosystems from spawning habits of
endangered species to anoxic hypolimnetic waters to municipal water
supplies and bathing beaches. The past unwillingness to accept this
responsibility is one of the major reasons for the case-by-case
impact assessment that has ignored any approach that considers the
cumulative impact of multiple stresses. The assignment of numerical
relative values is manageable if we consider it as an acceptable part
of environmental management and a prioritization process. Using this
more comfortable approach at the beginning allows the value part to
be considered after the prioricization has occurred.
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Each state agency has the best knowledge of the various environmen-
tal, social, industrial, municipal, and recreational uses of the
waters under their jurisdiction. Detail is provided in the environ-
mental use area (Appendix B) to ensure adequate guidance in the
prioritization and assignment of relative value.
Level ot Protection
The concept of level of protection has been used and misused for
many years. It is controversial, but, like the AIZ concept itself,
is an essential step in the protection of aquatic resources. It is
acknowledged that any estimate of the amount of area assigned to
AIZ must be based on "expert opinion". However, there are varying
degrees of protection desired or required for different waterbodies;
therefore, the acceptable risk differs between waterbody segments.
Consequently, several degrees of protection are recommended: maxi-
mum level of protection for fragile environments; low level of protec>
tion for the less valuable environment or an environment most capable
of withstanding insults; and a moderate level of protection interme-
diate between the two. The percent of environmental value to be
consigned to impact zones could be, for example, 1 percent of tne
total environmental value (see Example 1) for maximum protection to
10 percent for a low level of protection, with values from 1-10
percent being selected for intermediate protection. One could allot
more than 10 percent where economics or other considerations warrant,
or restrict the risk to less than 1 percent for waterbody segments
with unique biological environments. Additional guidance is incited
in Appendix C.
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Allocation Options
Once the judgements have been made regarding environmental value and
level of protection, the administrative process of allocating impact
zones beg ins.
First, one must decide how much of the acceptable loss in environ-
mental value can be assigned to present discharges and how much can
be allocated to future applicants. There are several considerations
that should be given attention when making this decision. Available
projections on future m.un ic ipal- industrial growth can be evaluated to
estimate the potential need for future zones. Planned plant closures
due to obsolescence, etc., should be considered. Also, some classes
of industry are utilizing production or waste treatment technology
based on more efficient use of water (e.g., closed-cycle cooling,
water reclamation and re-use. If non-point source pollution is a
significant factor, as it frequently is, it may be desirable to
allocate a portion of potential impact to that source.
As was stated briefly in the Executive Summary, this AIZ procedure
using all aspects presented and the allocation option based on toxi-
city mass is unlikely at present to be achievable for more than a few
waterbodies. Each step taken in the procedure results in a more
ecologically sound allocation, even if the allocation option chosen
is one of the more simple of the following suggestions.
Since many of the second round permits being developed contain
requirements for effluent toxicity testing, such data will beco-ie
much more common and the inevitable syntheses of these data will
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provide useful generalizations that will satisfy the toxicity data
requirements of this procedure. Until that time an estimate of
high, medium, or low toxicity could be based on a comparison of
effluent chemical concentrations with water quality criteria.
Increased public awareness and the need to establish priorities
will result in an atmosphere conducive to making the necessary
judgements on relative value and level of protection. In the
interim, the AIZ procedure can evolve in practice to the final goal
of complete utilization in anticipation of the third round of per-
mit review/revision around 1991.
Next, one must select a method for allocating the size of individual
impact zones. Several options are available:
1, All AIZ are allocated equal amounts of environmental value.
Advantages -- simple, direct and easy to calculate.
Disadvantages — large volume discharges would require a
much greater level of treatment than would small volume
discharges. May allow small number of dischargers to dis-
charge relatively large quantities of toxic or persistent
pollutants.
2. Each discharger within in a general class of discharges
(paper mills, metal finishing plants, municipal waste treat-
ment plants, power plants) is allocated the same amount of
environmental value, but different classes of dischargers
are given different amounts of environmental value.
Advantages -- simple and direct, could better allow for general
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differences in volume of discharge, could take into account
general persistence of toxicity of different classes of
di scharges.
Disadvantages -- there is a rather large variation in dis-
charge volumes and toxicity in any given class.
3. Impact zone allocation directly proportional to the volume
of the discharge (e.g., tor each unit volume of the flow,
the zone would be allocated a unit of environmental value).
Advantages -- simple calculation, superficially fair to
al1 dischargers.
Disadvantages — encourages dilution pumping to obtain a
larger zone and does not consider toxicity or persistence.
4. Impact zone allocation proportional to some monotonic
• increasing function of the discharge volume, that has a
finite upper bound.
Advantages -- in contrast to Option 3, would discourage
dilution pumping and would not unduly favor large volume
d ischarges.
Disadvantages -- assumes that all discharges have the
same toxicity when available data have demonstrated a
range of at least 1 to 2 orders of magnitude.
5. Impact zone apportionment based on toxicity mass that con-
siders toxicity and volume of waste.
This approach has as a basis the actual cause for con-
cern — hazard to the environment. Its chief d isadv a^.r i ;•-
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lies in the need for effluent toxicity data before deci-
sions can be made. However, regulatory discharge permits
are incorporating toxicity testing requirements that
will provide some data with which to consider this more
realistic approach to allocation. The Technical Support
Document for Water Quality-based Toxics Control (USEPA,
1985) contains procedures for effluent toxicity modeling
using the product of toxicity units and stream or effluent
flow. DiToro, et al. (In press) used an approach similar
to toxicity mass in their study of the Naugatuck River in
Connecticut. Their interest was to develop a mathematical
modeling approach for effluent and ambient toxicity to
Ceriodaphnia sp., a freshwater cladoceran. Toxicity load was the
product of toxic unit concentration and stream flow.
Quality Within Allocated Impact Zones
In addition to developing an allocated impact zone that will define
the regulatory boundary where water quality standards are to apply,
it is also necessary to state the conditions that are not to be
exceeded within an AIZ.
The Water Quality Standards Handbook {USEPA, 1984) has stated tnat
any zone should be free of point and nonpoint source related:
Materials in concentrations that will cause acute toxicity
(lethality) to aquatic life;
Materials in concentrations that settle to form obj ect ionan 1-?
depos it s;
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0 Floating debris, oil, scum and other matter in concentra-
tions that form nuisances;
0 Substances in concentrations that produce objectionable
color, odor, taste, or turbidity and;
Substances in concentrations which produce undesirable
aquatic life or result in a dominance of nuisance species.
In addition to these general guidelines for AIZ quality, the Techni<
cal Support Document for Water Quality-based Toxics Control (USEPA,
1985) nas provided design criteria to prevent lethality in the allo-
cated impact zone:
The criteria maximum concentration (CMC) for whole effluent
toxicity must be met within 10% of the distance from the
edge of the outfall structure to the edge of the regulatory
AIZ in any direction;
The CMC must be met within a distance of 50 times the dis-
charge length scale in any direction. The discharge length
scale is defined as the square-root of the crosssectional area
of any discharge outlet;.and
The CMC must be met within a distance of 5 times the local
water depth in any horizontal direction from any discharge
outle t.
The outfall design must ensure that the most restrictive of the aoove
three conditions are met (USEPA, 1985).
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EXAMPLE ALLOCATIONS
The following example of a lentic ecosystem and the additional two
examples in Appendices D and E are completely hypothetical and
decisions as to relative value and level of protection are not
meant to be recommendations or average values. Each site must be
considered independently. The numerical values in these examples
may be quite different from those that would be developed using
actual conditions.
All calculations were carried out to four significant numbers
before rounding to two significant numbers.
The allocation procedure used in these examples is the one
involving effluent toxicity ana volume of discharge. The inherent
purpose of waste treatment based on permits and water quality
standards is to protect the aquatic ecosystem from unacceptable
toxic effects. Since it is impractical to expect all undiluted
effluents to be chronically non-toxic, allocation of potential
impact should be based when possible on the toxicity and volume
(toxicity mass) of the effluent. In the absence of sufficient lata
and decisions on relative value and level of protection, the other
allocation procedures discussed earlier may be used, in the intern
as long as all discharges in a waterbody are considered together.
Example 1
This example will be of a simplified lentic system such as a I ^ •-. > ,
reservoir or small estuary that is divided into m environments.
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zones with known areas (A]_, A2....Am) and assigned relative values
(RV1,.RV2, ...RVm). There are presently n discharges with toxicity
masses of Ql, Q2,...Qn, From this information, allocated impact zones
will be determined.
Several technical and socioeconomic decisions should be made before
proceeding. The level of protection (p) and the fraction of the
total AIZ for the waterbody to be assigned to present dischargers
(r) must be chosen. Additionally, environmental maps demonstrating
areas of use need to be developed at whatever level of detail is
necessary to accomplish the allocation process.
Any site-specific unique characteristics or uses, such as municipal
or irrigation water supply, endangered species, etc., should be
considered. In this first example, there are two municipal intakes
and hypothetical local requirements preclude any discharges within
0.5 miles.
The areas of each environmental zone can be in any consistent unit
since the normalization to fraction of total area will eliminate
units of area. The area designated as living space for aquatic
species will be assumed to be the total area available for AIZ
consideration (this will exclude, in this example, the area arounc
the water supply intakes) minus the sum of all other areas. The
total available area for example 1 is 4,800 acres.
Given these factors the allocation procedure follows:
1. The total environmental value (TEV) for this waterbo<: v . ^
the sum of the environmental values (ARV) for each u-;-
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zone (Table 1). Each ARV is the product of the normalized
area and its relative value.
TEV = AiRV]. + A2RV2 4- + AmRVm
TEV = 4.8
2. In this example, the ecosystem is characterized by a low
flushing rate, significant recreational use, and a low
biotic diversity with limited potential recoverability.
(See Append ix C) .
Also, the current socioeconomic trend is toward increased
water-oriented tourism and second home development. Conse-
quently, a high level of protection (p) is warranted and
would permit that only 2% (0.02) of the TEV could be all-
ocated as potential impact zones. The TEV to be allocated
to present and future discharges will be:
p(TEV) = (0.02) (4.8 ) = 0 .096
3. As a result of the abovementioned socioeconomic trends,
industrial development (requiring discharges to the water-
body) will be scrupulously evaluated and limited. The
master plan for development of this watershed will reserve
25% (0.25) of the TEV for future discharges and that amount
available for present discharges (r = 0.75) will be:
pr(TEV) = (0.02) (0.75) (4.8 ) = 0.072
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Table 1 - Calculation of Total Environmental Value (TEV) for Example 1
Area
Normalized
Relative
Environmental -Value
1.
2.
3.
4.
5.
6.
7.
Zone3
Migration
Spawning
Fishing
Nursery
Swirnning
Marina
Living Space^
(Acres)
460
120
1,200
450
100
40
2,430
Area (A)
0.096
0.025
0.250
0 . 094
0.021
0.0083
0.51
Value (RV)
3
10
5
7
12
9
4
(ARV) of Each Zone
0.29
0.25
1.3
0.66
0.23
0.075
2.0
TEV = 4.8C
a.
b.
Two domestic water supply intakes exist in this waterbody. Current require-
ments, for this example, do not permit an AIZ within 0.5 miles of these in-
takes. These areas have been subtracted from the total area of the waterbody,
Unless there is a valid reason not to do so (e.g., anoxic zone), living space
will be assumed to be the total area available for allocation minus the sum
of all other areas. In this example the total available area is 4,800 acres.
c. Amount of TEV to be allocated = pr(TEV) = (0.02)(0.75)(4.8) = 0.072.
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4. Therefore, the environmental value available for allocation
to present dischargers is 0.072 (Table 1). As stated
earlier, of the allocation procedures available for consid-
eration, the preferred procedure involves the volume and
toxicity of the effluents. The amount of environmental
value to be allocated to a discharger (EVAk) with an
effluent toxicity mass Qk is:
f (Qk )
EVAk = pr(TEV)
where the subscript k denotes a specific discharge, and
toxicity mass (Qk, unitless) is the product of the nor-
malized discharge flow rate (fraction of total flow rate
of all discharges) from each discharge and toxicity ex-
pressed as toxic units chronic (TUC). The latter is
defined in the Technical Support Document for Water Quality
based Toxics Control (USEPA, 1985) as the reciprocal of
the effluent dilution tnat causes no unacceptable effect
on tne test organisms by the end of the chronic exposure
period. (Detailed discussion and examples of the determina
tion of the TUC values are in this Technical Support
Document). In the calculation of EVAk ,
n
Qk
f(Qk) = -- and
Qk + Q
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-23-
The results of calculations to determine the amount of total
environmental value allocated to each present discharger
(SVAk) are shown in Table 2.
5. Once the EVAk values have been calculated, an individual
AIZ can be established with regard to areal size. The area
within a given environmental zone allocated to an
impact zone is given by:
AIZjk = EVA
where the subscript j denotes the specific environmental zone
where the discharge exists and the subscript k denotes that
specific discharge. The results of calculations to determine
the area assigned to each discharger and the percentage of the
total area in a zone assigned to AIZ are shown in Table 3.
Since the initial allocation is for a specified amount of environ-
mental value, the more valuable or smaller the zone in which the AIZ
is located, the smaller this AIZ would be. Also, the more is reserved
for future discharges, the smaller is the size of each present AIZ.
Since this allocation approach is two-dimensional, the AIZ limitation
is to surface area of the waterbody. A discharger, who determines
that the assigned AIZ is too limiting and the discharge cannot be
relocated to a different zone, may choose to relocate the discharge
from the shallow, ecologically important shore area to a deeper, less
important area within the same environmental zone. That would increase
the dilution volume but not change the assigned surface area. Tie
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-24-
Table 2 - Calculation of Amount of Total Environmental Value
Allocated to Each Discharger (EVA^)
Discharge
Number
1
2
3
4
5
6
Discharge
Flow Rate
(m3/day)a
2,400,000
180,000
710,000
50,000
10,000,000
250,000
Normalized
Flow Rate
0.18
0.013
0.052
0.0037
0.74
0.018
Toxicity Units
Chronic (TOjb
V— t
4.4
15
2.4
21
1.9
7.0
Toxicity
Mass
(Ok)c
0.78
0.20
0.13
0.077
1.4
0.13
f(Q)
0.63
0.31
0.22
0.15
0.76
0.23
£
EVAk
0.020
0.010
0.0068
0.0046
0.024
0.0073
IH
= 0.072
^
a.
b.
c.
d.
Any consistent unit will suffice since only the relative flow rates are
important as the result of normalization.
For the definition and use of toxicity unit chronic see the Technical
Support Document (USEPA, 1985).
Toxicity mass (Q^) is the product of the normalized flow rate and TUC
(both are without units).
The sum of the individual EVAk values should equal or approximate
pr(TEV), which is 0.072 in this example.
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-25-
discharger also may benefit from more rapid mixing by the use of high
velocity diffusers. If the assigned AIZ is still limiting, the dis-
charger may have to move the facility or implement toxicity reduction
procedures within the plant.
For future discharges, this process of allocating impact zones
will provide significant useful guidance in site selection and
choice of discharge configurations to ensure minimum adverse impact
and the ability to achieve the limitations of the AIZ.
The allocation procedure, like any similar set of calculations, may
at times result in what would appear to be unreasonable results.
These results need to be considered and evaluated in light of
available experience and common sense.
Once the AIZ decision has been finalized, the assigned area must
be configured (shape) by the discharger with knowledge as to sea-
sonal plume shape and variability and adjacent biological popula-
tions and communities. The shape should be such (square, rectangular,
etc.) that in-stream monitoring programs have no difficulty in
establishing appropriate stations for sampling at the margins of
the AIZ.
Examples of a lotic system with 4 zones and 10 discharges and a
single discharge with 4 zones are included in Appendix D and Appendix
E, respectively.
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-26-
Table 3 -
Discharge
Number
1
2
3
4
5
6
EVAR
0.02
0.010
0.0068
0.0046
0.024
0.0073
Zone
Fishing ( 3)
Nursery ( 4)
Migration(l)
Swimning (5)
Living Space(7)
Living Space(7)
Area in
Zone
(Acres)
1,200
450
460
100
2,430
2,430
ARV..
1.3
0.66
0.29
0.23
2.0
2.0
AIZa
( acres )
19
6.6
11
2.0
28
8.7
Percent of
Total Zone
1.6
1.5
2.4
2.0
1.2b
0.36b
a.
is the product of EVA^ and Aj/ARVj .
b. Since two discharges exist in this zone, the total area allocated is
36.7 acres or 1.54 percent of the 2,430 acres.
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-27-
ACKNOWLEDGEMENTS
Several of the basic concepts of this allocated impact zone proce-
dure are not original with the author. They should be attributed
to Dr. Donald I. Mount, Environmental Research Laboratory, Duluth,
Minnesota, who in 1971, prepared the first (six pages long) of a
series of mixing zone recommendations that culminated in testimony
on mixing zones in Lake Michigan in 1974. While at the same labora-
tory during that time and later, the author had the opportunity to
pursue this subject in more depth and detail with the assistance
of Dr. Mount and Dr. Todd Thorslund for the initial modelling
effort. Mr. Carlos Fetterolf, of the Great Lakes Fishery Commis-
sion, published several papers on this subject and, with him, the
author initiated the International Joint Commission workshop on
environmental mapping (see references). His continuing support
and enthusiasm were critical to the development of this concept.
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-28-
REFEKENCES
Bergman, H.L., R.A. Kimerle, and A.W. Maki, 1986. Editors.
Environmental Hazard Assessment of Effluents. Proceedings of a
Pellston Environmental workshop. Cody, Wyoming, August 22-27,
1982. Pergamon Press. 366 p.
Diener, R.A. 1975. Cooperative Gulf of Mexico Estuarine Inventory
and Study - Texas: Area Description. NOAA Technical Report, NMFS
CIRC-393. 129 p.
DiToro, D.M., J.A. Hallden,and J.L. Plafkin. In press. Modeling
Ceriodaphnia Toxicity in Receiving Waters. In: Toxic Substances and
Aquatic Ecosystem Health. John Wiley and Sons, New York, New York.
Fetterolf, C.M., Jr., 1977. Environmental Value Mapping: An
Indispensable Tool or Trap? Presented at the National Symposium
on Classification, Inventory, and Analysis of Fish and Wildlife
Habitat. Phoenix, Arizona. January 24-27, 1977.
Hunt, J.P. 1975. A Study to Improve the Presentation of Coastal
Zone Data for Planners and Managers. New York Ocean Science Labo-
ratory, Montauk, New York. 14 p. plus Appendix.
International Joint Commission. 1976. Workshop on Environmental
Mapping of the Great Lakes. Proceedings of a Symposium. Inter-
national Joint Commission. Windsor, Ontario. 224 p.
Lillesand, T.M., F.L. Scarpace, and J.L. Clapp. 1975. Water
Quality in Mixing Zones,, Photoy rarnmetr ic Engineering and Remote
Sensing. pp. 285-298.
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-29-
Lippson, A. J. (Ed.) 1973. the Chesapeake Bay in Maryland. An
Atlas of Natural Resources. The John Hopkins University Press,
Baltimore, Maryland. 5b p.
Neely, W.B. 1982. The Definition and Uses of Mixing Zones. Envi-
ronmental Science and Technology 16(9): 518A-521A.
Olsen, S., D.D. Robadue, Jr., and V. Lee. 1980. An Interpretative
Atlas of Narragansett Bay. Coastal Resources Center. University of
Rhode Island. Marine Bulletin 40. 82 p.
Thurlow and Associates. 1975. Ecological Sensitivity Mapping for
the Lower Great Lakes Watershed. Ottawa, Ontario 290 p.
U.S. Environmental Protection Agency. 1976. Quality Criteria for
Water. Washington, D.C. 256 p.
U.S. Environmental Protection Agency. 1980. Remote Sensing Demon-
stration Project Using the Boston Marine Discharge 301(h) Applica-
tion Data. EMSL Project AMD 8049. Environmental Monitoring Systems
Laboratory. Las Vegas, Nevada. 18 p.
U.S. Environmental Protection Agency. 1984. Water Quality Stan-
dards Handbook. Office of Water Regulations and Standards (WH-585),
Washington, D.C.
U.S. Environmental Protection Agency. 1985. Technical Support
Document for Water Quality-based Toxics Control. Office of Water
Regulations and Standards (WH-535), Washington, D.C.
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-30-
Villemonte, J.R., J.A. Hoopes , D.S. Wu, and T.M. Lillesand. 1973.
Remote Sensing in the Mixing Zone. Institute for Environmental
Studies, Remote Sensing Program Report No. 22. University of
Wisconsin, Madison, Wisconsin. 32 p.
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A-l
APPENDIX A
HISTORICAL PERSPECTIVE
Most early recommendations focused on zones of passage to ensure
no adverse effects of mixing zones on migration or passive drifting
of aquatic species. The U.S. Department of the Interior (1968)
recommended a zone of passage of 75 percent of the cross-sectional
area and/or volume of flow of the stream or estuary. In these
passageways, concentrations of waste materials should meet the
water quality standards for the receiving water. This report also
suggested that if several discharges are close together they
should be on tne same side so the passageway is continuous. Their
recommendation that "mixing should be accomplished as quickly as
possible through devices which insure that the waste is mixed with
the allocated dilution water in the smallest possible area" is
still a generally appropriate guide.
The National Academy of Sciences/National Academy of Engineering
(1973) discussed mixing zones in a regulatory sense at great length
and that discussion is therefore compatible with allocated impact
zones. Since all life stages, such as spawning and larval develop-
ment, are necessary functions of aquatic organisms and are not
protected in AIZ, they concluded that it is essential to insure
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A-2
that adequate portions of every waterbody are free of these zones.
"The Decision as to what portion and areas must be retained at
receiving water quality values is both a social and scientific
decision." Information used to arrive at this decision should
include current and projected types and location of intakes and
discharges and percentage of shoreline necessary to provide ade-
quate spawning, nursery and feeding areas. other data needs were
also discussed. The following quotation from this publication
is presented in its entirety because it might be considered the
genesis of this procedure for allocating impact zones.
"To avoid potential biological damage or interference with
other uses of the receiving system it is recommended that
mixing zone characteristics be defined on a case-by-case
basis after determination that the assimilative capacity of
the receiving system can safely accommodate the discharge
taking into consideration the physical, chemical and bio-
logical characteristics of the discharge and the receiving
system, the life history and behavior or organisms in the
receiving system, and desired uses of the waters."
The earliest attempt by the USEPA to regulate areas of non-compli-
ance was technical guidance for thermal discharges. This technical
guidance (USEPA, 1974) was in response to section 316(a) of the
Federal Water Pollution Control Act, as amended (33 U.S.C. 1251,
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A-3
1326(a), and 40 C.F.R. Part 122) to develop effluent limitations
for thermal discharges. (A more recent draft of this document in
1977 deleted the following guidance and was never officially pub-
lished.) In addition to stating that a mixing zone is an area
contiguous to a discharge where receiving water quality does not
meet the otherwise applicable water quality standards, this
guidance provides the following salient points:
0 The effluent or plume may be identified at distances or in
places outside the mixing zone.
0 The mixing zone is a place to mix and not a place to treat
ef fluents.
0 The permissible size of the mixing zone is dependent on the
acceptable amount of damage.
The size and shape of the mixing zone should be specified so
that both the discharger and the regulatory agency knows
its bounds.
A mixing zone should be determined taking into consideration
unique physical and biological features of the receiving
water.
0 Any mixing zone must be limited to a temporal and spatial
(area, volume, location, and configuration) distribution
which will assure the protection and propagation of a bal-
anced, indigenous community of shellfish, fish and wildlire
in and on the receiving waterbody.
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A-4
0 The acceptable size for a mixing zone depends also on the
number of mixing zones on a body of water. The greater the
number, the smaller each must be. In this connection, future
growth of industry and population must be considered.
Numerous ecological considerations were presented in these effluent
guidelines for thermal discharges that must be considered before
defining a mixing zone.
The extensive details presented for effluent guidelines for thermal
effluents by the USEPA have not been repeated in subsequent guid-
ance. However, the Water Quality Standards Handbook (USEPA, 1984)
provided some very general recommendations and incorporated three
significant progressive statements:
0 A limited mixing zone, .serving as a zone of initial dilution
in the immediate area of a point or nonpoint source of pol-
lution, may be allowed. Whether to establish a mixing zone
policy is a matter of state discretion. Such a policy,
however, must be consistent with the Act and is subject to
approval of the Regiona^ Administrator.
0 The methodology used by the states should be sufficiently
precise to support regulatory programs, issuance of permits
and determination of best management practices for nonpoint
sources.
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A-5
0 In the broadest sense, the zone surrounding, or downstream
from a discharge location is an "allocated impact zone"
where numeric water quality criteria can be exceeded as long
as acutely toxic conditions are prevented.
In an earlier publication summarizing the mixing zone policies
incorporated into state water quality standards (USEPA, 1980), it
is clear that numerous states had some generally appropriate eco-
logical considerations. However, the majority had quantita-
tive limitations related to cross-sectional areas or volumes that
only respond to needs for drifting and migration of aquatic species,
Single linear limits (e.g., 300 meters) were incorporated into many
States' standards and were based on ease in development and sim-
plicity in enforcement. Fetterolf (1973) eloquently summarized
his feelings about this approach by stating that this procedure
"is a pretense, a crutch for administrative laziness, and suggests
either ignorance of or disregarc for intelligent, scientifically-
based evaluations of a mutually desirable platform for enforcement
programs".
More recently, EPA's Office of Water Enforcement and Permits pub-
lished a Technical Support Document for Water Quality-based Toxics
Control (USEPA, 1985). This document contains much detailed infor-
mation on toxicity assessment of whole effluents and states that
the proper design of a wasteload allocation study for a particular
waterbody requires estimation of the distance from the outfall to
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A-6
the point where the effluent mixes completely with the receiving
water. While this approach is similar to the historical engineer-
ing-oriented plume concept, guidance is given on the use of high
velocity diffusers and deep water discharge techniques to reduce
the area or volume of allocated impact. Numerous mixing and waste-
load allocation models for rivers, lakes, and estuaries are included
in this document. The important factor here is that allocated
impact zone designation is not only necessary for the enforcement
of water quality standards but also in the wasteload allocation
procedures that are becoming much more routine for state regulatory
agencies during permit renewal/revision cycles.
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A-7
REFERENCES
Fetterolf, C.M., Jr. 1973. Mixing Zone Concepts. In: Biological
Assessment of Water Quality, ASTM STP 528, American Society for
Testing and Materials, pp. 31-45.
National Academy of Sciences, National Academy of Engineering. 1973,
Water Quality Criteria 1972. EPA-R3-73-033, March 1973. 594 p.
U.S. Department of the Interior. Federal Water Pollution Control
Administration. 1968. Water Quality Criteria: Report of the
National Technical Advisory Committee to the Secretary of the
Interior. Washington, D.C. 234 p.
U.S. Environmental Protection Agency. 1974. Draft 316(a) Technical
Guidance -- Thermal Discharges. Office of Water and Hazardous
Materials. Washington, D.C.
U.S. Environmental Protection Agency. 1980. Mixing Zones - Water
Quality Standards Criteria Digest. A compilation "of State/Federal
Criteria. Office of Water Regulations and Standards (WH-585),
Washington, D.C. 55 p.
U.S. Environmental Protection Agency. 1984. Water Quality Stan-
dards Handbook. Office of Water Regulations and Standards (WH-585),
Washington, D.C.
U.S. Environmental Protection Agency. 1985. Technical Support
Document for Water Quality-based Toxics Control. Office of Water
Regulations and Standards (WH-585), Washington, D.C.
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APPENDIX 3
RELATIVE ENVIRONMENTAL VALUE
Not all aquatic ecosystems will have the same critical functions or
uses and the following listing is not intended to be complete but
more of a guide to site specific analysis.
o
Migratory pathways of indigenous species are rather fixed
and predictable and could be adversely impacted by noxious
quantities of toxic substances in allocated impact zones.
Spawning grounds are extremely important especially for
those bottom-spawning species dependent on very specific
substrate requirements.
Nursery areas for the development of larval and juvenile
forms are critical not only to the protection of these
forms but also the protection of the food production upon
which they are dependent.
Primary production in marshes and areas with rooted aquatics
are important sources of food and shelter for aquatic organ-
isms .
Living space or shelter for benthic forms is critical for
many species due to rather specific substrate needs and
reduced mobility, especially for some shellfish species.
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B-2
Consideration of endangered species is high on any relative
environmental value scale.
Once the socio-economic, ecological, and other uses have been
prioritized, significant consideration must be given to the numeri-
cal relative importance of these uses. The following discussion
is again primarily ecologically oriented since other uses are
better understood at the local level.
Shallow water in lakes, estuaries, reservoirs, and some rivers
generally has a higher environmental value and is more productive.
Food production is greater in the shallow water zone because light
penetration is sufficiently deep to support growth of penphyton,
attached algae, and rooted vegetation; nutrients from runoff are
commonly more plentiful; terrestrial food organisms are more abun-
dant; there is a greater variety of substrates (sand, sediment,
and rubble as contrasted to mostly fine sediment in deeper water)
that provide diverse habitats for many kinds of food organisms;
and oxygen concentrations are more favorable because wave action
and diffusion processes transport oxygen to the bottom.
The density and variety of organisms is greater in shallow water,
because many species spawn in shallow areas and their progeny
utilize these areas as nursery grounds. In addition, prior to
spawning migrations into tributary streams, numerous species
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B-3
concentrate in shallow waters until conditions are optimal for
spawning runs; cover provides more protection from larger predators;
the more diverse substrates support a greater variety of species
in larger numbers than in the more uniform habitat of deep waters;
and, in rivers and streams, many fish species migrate through the
shallow shore zones. Protected bays and coves on large lakes,
reservoirs, and estuaries are often the most biologically important,
probably for the above reasons, but also because wind and wave
action are less severe.
Recreational uses, such as water contact sports and sport fishing,
are concentrated in the shore zone. This zone is also important
to the aesthetic appeal of waterbodies. The foregoing discussion
identifies certain biotic zones that are more important than others
and are related to water depth. Thus, depth can be used as one
convenient tool to delineate the various zones in some areas.
As discussed above, various biotic zones exist within a waterbody
segment. These biotic zones are not equally important; thus, they
have different environmental values. Common sense indicates that
AIZ should be located in larger or less valuable areas. A value
for the various biotic zones must be established in order to allo-
cate these zones, with zones of high importance assigned high
value .
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B-4
This value determination cannot be strictly objective and must
utilize professional, expert opinion of biologists and ecologists
familiar with the local situation. Highly valued trout waters,
areas inhabited by endangered species and many very productive
estuaries may be assumed to be invaluable and excluded from consid-
eration as potential allocated impact zones. Value can be based
on the species diversity of the zones and the value made propor-
tional to the ratio of species diversity in various zones. Current-
swept mid-channels of large rivers or deep waters in large lakes
that are devoid of dissolved oxygen, may be given low value.
Occasions will arise when there is not an adequate data base upon
which to establish environmental value. In such cases, one may
assume the value to be the same for all biotic zones (i.e., the
value of a unit area is inversely proportional to the total area in
each zone).
AS is shown later, the environmental value is important because it
defines upper limits on the amount of each biotic zone that may be
allocated. The assignment offers dischargers a chance to select
better sites and allows regulatory agencies to encourage potential
dischargers into the areas least likely to be damaged. The concept
of assigning environmental value is also important, because the
total area within a waterbody segment allocated to all impact
zones can be more easily and accurately allocated than can areas
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B-5
for individual zones. This is because the erroY, if any, is dis-
tributed proportionally and the decision considers the potential
combined effects of all discharges. This must be done by competent
staff but only needs to be decided once.
Some states are progressing toward such decisions. The California
State Water Resources Control Board (1976) has designated areas of
special biological significance for the control of wastes discharged
to ocean waters. These areas will be afforded special protection
for marine life to the extent that waste discharges are prohibited
within the areas. These areas were designated as requiring protec-
tion of species or biological communities to the extent that alter-
ation of natural water quality is undesirable.
The assignment of relative values to the prioritized use list may
be simplified by not including point source discharges as a "use",
since these are the concerns to which will be assigned an allocated
impact zone. No numerical range of relative values are specifically
recommended since some areas (endangered species spawning) or uses
(municipal water supply intake) may be given a value (e.g., infinity;
that precludes their inclusion in an AIZ. However, the mathematical
process of allocation may require numerical values and, therefore,
the minimum value (e.g., naturally hypoxic area) should not be given
a relative value of zero, but, for example, a value of one. For
practical reasons a range of values from one to 100 might be rea-
sonable. Physical areas that have more than a single use (e.g.,
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B-6
shellfish, water supply intake and fish migration) would have a
greater value than that for any one of those single uses.
Some recent and forthcoming publications may be useful in assigning
relative values. Section 301(c) of the Comprehensive Environmental
Response, Compensation and Liability Act of 1980 (CERCLA) has led
to the development of a proposed rule by the Department of the Interior
for determining compensation to the public for injury to natural
resources. Technical Information Documents are being prepared that
will include methods for using the U.S. Fish and Wildlife Services
Habitat Evaluation Procedures. These documents are being designed
to estimate the effect of oil and hazardous substances on wildlife
habitats but can be useful in understanding the relative value of
components of aquatic ecosystems. The National Oceanic and At-
mospheric Administration has published a report (Meade and Lee-
worthy, 1986) that describes the amount of money spent by the
public on recreation in coastal counties. A series of technical
support manuals were prepared to assist the states in establishing
water quality standards in wateroody surveys and assessments for
use attainability and analyses in rivers and streams (USEPA, 1983),
estuaries (USEPA, 1984a) and lakes (USEPA, 1984b).
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1-7
REFERENCES
California State Water Resources Control Board. 1976. Areas of
Special Biological Significance. Office of Public Affairs,
Sacramento, California. 56 p.
Meade, N.F. and V.R. Leeworthy 1986. Public Expenditures on Outdoor
Recreation in the Coastal Areas of the USA. National Oceanic and
Atmospheric Administration, Washington, D.C. 18 p.
U.S. Environmental- Protect ion Agency. 1983. Technical Support
Manual: Waterbody Surveys and Assessments for Conducting Use
Attainability Analyses. Office of Water Regulations and Standards
(WH-535), Washington, D.C.
U.S. Environmental Protection Agency. 1984a. Technical Support
Manual: Waterbody Surveys and Assessments for Conducting Use
Attainability Analyses. Volume II: Estuarine Sy.stems. Office of
Water Regulations and Standards (WH-585) Washington, D.C.
U.S. Environmental Protection Agency. 1984b. Technical Support
Manual: Waterbody Surveys and Assessments for Conducting Use At-
tainability Analyses. Volume III. Lake Systems. Office of Water
Regulations and Standards (WH-585), Washington, D.C.
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C-l
APPENDIX C
LEVEL OF PROTECTION
The National Academy of Sciences, National Academy of Engineering
(1973) briefly discussed levels of protection of fish against del-
eterious effects of reduced dissolved oxygen concentrations. The
levels of protection were nearly maximum, high, moderate, and low
and were based on productivity and quality of the fisheries. An
extremely important point made in this discussion and one that is
critical to the allocated impact zone concept is that the selection
of a level of protection is primarily a socioeconomic decision,
not a biological decision. The biological and ecological consider-
ations and potential impacts must be evaluated and made known to
those selecting a level of protection of an ecosystem.
The Guidelines for Deriving National Water Quality Criteria for the
Protection of Aquatic Organisms and Their Uses (Stephan et. al. , 1985
states that because aquatic ecosystems can tolerate some stress and
occasional adverse effects, protection of all species at all times
and places is not deemed necessary. If acceptable toxicity data
are available for a large number of appropriate taxa from an appro-
priate variety of taxonomic and functional groups, a reasonable
level of protection will probably be provided if all except a small
fraction of the taxa are protected, unless a commercially or recre-
ationally important species is very sensitive. A small fraction
of 0.05 (1/20) was chosen.
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02
The use of levels of protection in dissolved oxygen criteria con-
tinues in the most recent guidance from the USEPA (Chapman, 1985).
He listed four levels of risk (=levels of protection):
0 No production impairment - representing nearly maximal
protection of fisher/ resources.
Slight production impairment - representing a high level of
protection of important fishery resources, risking only
slight impairment of production in most cases.
0 Moderate production impairment - protecting the persistence
of existing fish populations but causing considerable loss
of production.
0 Severe production impairment - for low level of protection
of fisheries of some value but whose protection in compari-
son with other water uses cannot be a major objective of
pollution control.
Chapman then developed numerical criteria for each of these levels
(as well as an acute mortality limit) for early and other life
stages for salmonid and non-salmonid waters.
These biological criteria options were developed before the socio-
economic considerations were applied that subsequently would deter-
mine which level of protection (risk) would apply for a particular
waterbody.
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C-3
What percent of total environmental value then, could be used for
allocated impact zones? Conditions necessary for all life history
processes may not be provided in these zones. when an excessively
large percent of a waterbody segment is made up of impact zones,
the population of some species will decline and an unpredictable
chain of events may ensue. Furthermore, estimates of an acceptable
percent of an aquatic environment that can be allocated to impact
zones must be conservative, since predictive capabilities are uncer-
tain.
Determination of the amount of a segment's environmental value to be
allocated is based on a variety of criteria, including type of
waterbody, water velocity, depth, the number and type of habitats,
migration patterns, and the nature of the local food chain. Level
of productivity, water temperature, ability of tributary waters to
provide recruitment, value to humans (aesthetic, commercial and
sport fishing, recreational), endangered species, and other criteria
must all be considered.
The ability of an aquatic ecosystem to assimilate wastes is an
important consideration in selecting a level of protection since if
overloading should occur, the system is disrupted and the ability
of the ecosystem to transform those wastes is reduced. If this
were to occur, the capability of that ecosystem to recover from
this assault will vary. Cairns and Dickson (1977) discussed four
characteristics of the ecosystems that relate to the recovery
process:
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04
0 Vulnerability to irreversible damage is more likely with
rivers and estuaries.
0 The elasticity of an ecosystem to recover is determined by
the availability of recruitment pools of organisms from
tributary waters, transportability of various life stages,
condition of the habitat after stress (e.g., pH change
vs. residual toxicants), and degree of disequilibrium of
the chemical-physical environmental quality.
0 Inertia, or ability to resist displacement of structure
and function, is determined by the degree to which the
indigenous organisms are accustomed to highly variable
environmental conditions and the degree of high struc-
tural and functional redundancy. Flow and flushing charac-
teristics are also important.
0 Resiliency of an ecosystem describes its ability to with-
stand a, series of slight impacts without lasting effect.
An aquatic ecosystem with limited nutrients and diversity, low
flushing flow, and few sources for recruitment of aquatic organisms
would have a very low rate of recovery from excessive inputs of
persistent chemicals ana would probably require a maximum level of
protection to ensure that the allocated impact zones do not
collectively have a potential serious effect on the ecosystem.
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C-5
Determination of the level of protection for a waterbody comprises
one of the most difficult decisions in the AIZ process. The pro-
cess demands high priority and the attention of natural, physical
and social scientists, planners, economists, industrialists, lawyers,
administrators, and the lay public. Scientists can define the
choices, but society at large will have a strong hand in making the
final decision (Ferrerolf, iy?3).
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C-6
REFERENCES
Cairns, J., Jr., and K.L. Dickson. 1977. Recovery of Streams from
Spills of Hazardous Materials. In: Recovery and Restoration of
Damaged Ecosystems. University Press of Virginia, Chariottesvi1le.
pp. 24-42.
Chapman, G.A. 1985. Ambient Water Quality Criteria for Dissolved
Oxygen (Freshwater Aquatic Life). U.S. Environmental Protection
Agency.
Fetterolf, C.M., Jr. 1973. Mixing Zone Concepts. In: Biological
Assessment of Water Quality, ASTM STP 528, American Society for
Testing and Materials, pp. 31-45.
National Academy of Sciences, National Academy of Engineering. 1973
Water Quality Criteria 1972. EPA-R3-73-033, March 1973. 594 p.
Stephan, C.E., D.I. Mount, D.J. Hansen, J.H. Gentile, G.A. Chapman,
and W.A. Brungs. 1985. Guidelines for Deriving National Water
Quality Criteria for the Protection of Aquatic Organisms and Their
Uses. U.S. Environmental Protection Agency. 98 p.
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D-l
APPENDIX D
Example 2
This example will be of an industrialized lotic system, such as an
impounded river channel, with limited environmental use due to
developmental impacts and dredging. As before, this waterbody is
divided into m environmental zones with known areas (Aj_, A2...A )
and assigned relative environmental values (RV1, RV2....RV ).
There are presently n discharges with toxicity masses of Q:,
Q2....Qn.
Since the principal environmental uses of this waterbody are im-
pacted by industrial and channelization operations, there are
limited benthic or benthic-dependent aquatic populations. The
example's level of protection (p=0.15) would allocate 15 percent
of the total environmental value (TEV) as potential impact zones.
Due to industrial saturation, no allocation will be held for future
discharges (r=l. 0) .
The assumptions, analyses, and calculations for Example 2 are the
same as for Example 1. The results of these calculations are shown
in Tables 4, 5, and 6. The total available area of the waterbody
is 1,300 acres. This example will be used to present some poten-
tial problem/solution scenarios that can develop during the use
of this allocation procedure:
Discharge *6 is a relatively low volume, high toxicity
example that received an AIZ of 8.4 acres in the most
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D-2
Table 4 - Calculation of Total Environmental Value (TEV) for Example 2
Zone
1. Migration
2. Fishing
3. Overwater
Shipping
4. Living Spacea
Area
(Acres)
150
300
230
620
Normalized
Area (A)
0.12
0.23
0.18
0.48
Relative
Value (RV)
10
6
1
4
Environmental
(ARV) of Each
1.2
1.4
0.18
1.9
TEV = 4.6b
Value
Zone
a. Total area (1,300 acres) minus the first three uses defines the living space
(620 acres).
b. Amount of TEV to be allocated = pr(TEV) = (0.15)(1.0)(4.6) = 0.69.
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D-3
Table 5 - Calculation of Amount of Total Environmental Value Allocated to
Each Discharger (EVA^)
Discharge
Number
1
2
3
4
5
6
7
8
9
10
Discharge
Flow Rate
(mVday)
10,000
800,000
2,000
51,000
17,000
15,000
3,000
150,000
45,000
410,000
Normalized
Flow Rate
0.0067
0.53
0.0013
0.034
0.011
0.010
0.0020
0.10
0.030
0.27
Toxic ity Units
Chronic (TUn)
\-r
0.8
3.9
4.1 '
2.3
1.2
10.1
6.2
3.6
1.9
1.2
Toxic ity
Mass
(Qk)
0.0053
2.1
0.0055
0.078
0.014
0.10
0.012
0.36
0.057
0.33
f(Qk)
0.017
0.87
0.018
0.21
0.043
0.25
0.040
0.54
0.16
0.52
1
EVAk
0.0045
0.23
0.0046
0.053
0.011
0.065
0.010
0.14
0.041
0.14
[j= 0.69a
a. The sum of the individual EVAj< values should equal or approximate pr(TEV),
which is 0.69 in this example.
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D-4
Table 6 - Calculation of the Areas for Allocated Impact Zones
Discharge EVA^
Number
1 0.0045
2 0.23
3 0.0046
4 0.053
5 0.011
6 0.065
7 0.010
8 0.14
9 0.041
10 0.14
Area in
Zone
Zone ( acres )
Shipping (3)
Fishing (2)
Shipping (3)
Living Space (4)
Living Space (4)
Migration (1)
Fishing (2)
Shipping (3)
Migration (1)
Living Space (4)
230
300
230
620
620
150
300
230
150
620
ARVj
0.18
1.4
0.18
1.9
1.9
1.2
1.4
0.18
1.2
1.9
AIZ
(acres)
5.8
49
6.0
17
3.6
8.4
2.2
180
5.3
44
Percent of
Total Zone
2.6
16
2.6
2.8a
0.58a
5.6
0.73
80
3.6
7.1a
a.
Several discharges are located, in the .same zones. For example, discharges 4,
5, and 10 are in zone 4 (living space) and the total area assigned to AIZs in
that zone would be 64.6 acres for 10.4 percent of the total area of this zone,
For the three discharges into zone 3 (shipping) the total area assigned to
AIZs would be 191.8 acres for 83.4 percent of the total area of this zone
of very low relative value.
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D-5
valuable zone (migration). Dye and plume studies demon-
strated that the assigned AIZ area, and, therefore,
dilution volume, would result in permit violations of
effluent toxicity limits or water quality standards.
Several options would need to be evaluated and cost com-
pared: plant relocation, toxicity reduction, elimination
of process causing the problem, and relocation or redesign
of the discharge. There may be other options. In this
hypothetical example, the discharge was extended from the
shoreline migration zone (ARV=1.2) to the more valuable
but larger (ARV=1.9) living space zone. That choice in-
creased the total percent area of that zone allocated but
that option was agreeable to the local regulators. In
addition to gaining a larger AIZ (21 acres) in the larger
but more valuable living space zone, the discharge was
moved to deeper water that provided even more dilution in
the two-dimensional AIZ.
'Discharge #8 has the largest assigned AIZ and percent of
total zone (80 percent) and a plant expansion is being
planned that would double the discharge flow and result
in violation of the AIZ limits. Since no allocation for
future discharges was reserved, costs to relocate the
plant or discharge are prohibitive, and discharge redesign
cannot solve the problem, toxicity reduction of the exist-
ing or planned processes will be necessary.
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D-6
0 Most of these discharges will result in violations of ef-
fluent toxicity limits or water quality standards due to
the AIZ's assigned. In such an instance, it would be
likely that the waterbocy was already not meeting societal
goals in that existing environmental damage is unacceptable
This water quality limited waterbody would have to be
seriously considered for a proper, toxicity-based wasteload
allocation with the goal of,at least partial restoration
of environmental uses.
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E-l
APPENDIX E
Example 3
This simple example of a medium to small freshwater riverine eco-
system with one discharge may typify a majority of waterbodies
outside of metropolitan areas. The example can apply to any water-
body with a single point source.
This ecosystem is a warmwater/coolwater environment of unsedimented
rocky riffles and sedimented pools with some small man-made impound-
ments. Sportfishing occurs on shore as limited by access and is
otherwise pursued in canoes and small boats. Campgrounds and
swimming areas occur and in a few areas agricultural runoff has
caused some adverse benthic impacts due to sedimentation. Several
small villages exist on this river, but none has a point source
discharge. One town has a permitted POTW (publically-owned treat-
ment works) which is the only point source on this 15-mile long
waterbody. Its mean width of 200 feet provides an area of* about
355 acres. Environmental mapping needs are limited due to the
small size of the waterbody but will be needed in greater detail
around the existing discharge point. A waterbody of this type
will have less physical and ecosystem diversity than a lentic
system. For example, fishing, migration, spawning and nursery
areas are not distinct but tend to occur together. In this example,
the zones will be swimming, bank to bank shallow waters, pools or
impoundments, and a one-mile long headwater area for put-and-take
trout f i shing .
The level of protection will be high (p=0.01) and land and water
use projections suggest some limited but small industrial deve i .^p.e:",
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E-2
that allows the present discharge to have 35 percent of the total
allocation (r=0.35). The results of the allocation calculations
are shown in Tables 7, 8 and 9. Note that when there is a single
discharge, the calculations to obtain EVAj,, are not necessary since
the sum of EVAk values equals pr(TEV). It is interesting to note
that if this one discharge had been in either zone 1 (swimming, 10
acres) or zone 4 (trout fishing, 24 acres) the assigned AIZ's would
have been 0.88 and 0.53 acres, respectively, as compared to 1.5
acres in zone 3 (pools). This AIZ size reduction (an hypothesis
in an hypothetical example) may not have been achievable by the
discharger or may have been environmentally or socially unaccept-
able due to the location or size since in both the alternative
zones a much higher percentage of that zone would be allocated.
If tnis example typifies many situations in any state and resources
available tor environmental mapping and appropriate ecological
data generation are limited to the point where this allocation pro-
cedure cannot be used in its entirety, a justifiable simplification
may be warranted due to the generally homogenous nature of ecosys-
tem variability in ecosystems comparable to this example. A single
zone with a single environmental value could be used. That value
could be an average of the values expected if detailed knowledge
of the waterbody were attainable as is assumed in this example.
The only data necessary would be the discharge flow rate, effluent
toxicity, and waterbody area. If effluent toxicity data are un-
available, toxicity data for the same process at another site could
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Table 7 - Calculation of Total Environmental Value (TEV) for Example 3
Zone
1. Swimming
2. Shallow waters
3 . Pools
4. Trout fishing
Area
(Acres)
10
85
236
24
Normalized Relative
Area (A) Value (RV)
0.028 12
0,24 9
0.66 7
0.068 20
Environmental
(ARV) of Each
0.34
2.2
4.7
1.4
TEV = 8.5*
Value
Zone
a. Amount of TEV to be allocated = pr(TEV)=(0.01)(0.35)(8.5) = 0.030.
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E-4
Table 8 - Calculation of Amount of Total Environmental Value Allocated
to Discharger (EVA^)
Discharge Toxicity
Discharge Flow Rate Normalized Toxicity Units Mass
Number (m /day) Flow Rate Chronic (TU ) (Q. ) f(Q) EVA
45,000 1.0 3.9 3.9 0.5 0.030a
a. As discussed in the text, the EVA^ calculation is not necessary when there is a
single discharge in a waterbody since the sum of the EV\ values equals pr(TEV),
Table 9 - Calculation of the Area for the Allocated Impact Zone
Area in
Discharge Zone AIZ Percent of
Numoer EVAk Zone (acres) ARVj (acres) Total Zone
0.030 Pools (3) 236 4.7 1.5 Q.64
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E-5
be used with a safety factor to be applied to this extrapolation.
The most important point to remember is that an allocation is
necessary and achievable as a way to direct certain permit limita-
tions and select monitoring stations based on an AIZ with definite
spatial limitations derived from an ecological awareness of the
waterbody and site.
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