http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
Mixing Zones
Fact Sheet
What is a mixing zone?
Even with the best treatment technology, wastewater discharges from sewage treatment
and industrial facilities (i.e. mining, seafood processing, oil exploration or production,
etc.) sometimes have low levels of pollutants. Most wastewater discharges permitted in
Alaska are to surface waters such as the ocean, lakes, streams, or rivers. The area where
treated wastewater is authorized by DEC to mix with a water body is called a mixing
zone.
How do they work?
All wastewater discharges into surface water require a permit that may contain
authorization for a mixing zone. Mixing zone authorizations take into consideration
habitat and aquatic life, water flow, water quantity, natural currents, and the quantity and
quality of the wastewater that’s being discharged. If the circumstances surrounding a
proposed mixing zone do not meet the State’s standards, a mixing zone cannot be
authorized. Requiring an authorization for mixing zones ensures that they are carefully
designed using waterbody-specific information, water quality is monitored, and that
water quality standards are met outside the mixing zone boundary so as not to create
long-term impacts to people or the environment.
Who uses mixing zones?
Most mixing zones are authorized for sewage treatment plants run by local governments,
as well as seafood processors, fish hatcheries, oil and gas facilities, mining operations and
other industrial facilities.
Why are mixing zones used?
Mixing zones are an important tool regulators use to control water pollution. They allow
Alaska to have very high standards for water quality. Without the authority to issue
mixing zones, the State would have to use other methods to adjust for current limitations
in treatment technologies, which could result in lowering the overall standards. Without
mixing zones, sewage treatment plants would have to treat raw sewage to a level that
could serve as a source of drinking water before being discharged into a water body.
Although this goal may be technically achievable by NASA standards, it is not yet an
economically feasible option for most communities or industries. There are no sewage
treatment plants or seafood processors in Alaska that discharge wastewater to a surface
water body (and the vast majority do) that could operate without a mixing zone.
G:Comm:Subject/Mixing Zones
10/14/2005
9:53 AM
What does the law say about mixing zones?
States have authority to allow mixing zones under the Clean Water Act; the
Environmental Protection Agency has published mixing zone guidance; and all other
states use them in addition to Alaska. Mixing zones have been included in the Alaska
water quality standards regulations since 1973.
By State statute, the department must designate specific uses of water and establish
standards for quality and purity to protect those uses. The water quality standards, which
include mixing zone provisions, must protect the growth and propagation of aquatic life,
the public health of those who consume the water or the aquatic organisms, and other
water uses such as industrial, agricultural and recreational use. State statute also directs
the Departments of Natural Resources and Fish and Game to protect salmon and resident
fish habitat quality and establishes requirements for construction in, or use of waters (for
example, as a mixing zone) that are important to fish.
G:Comm:Subject/Mixing Zones
10/14/2005
9:53 AM
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
Examples of Mixing Zones in Alaska Today
Nearly every wastewater discharge to Alaska’s surface waters has a permit that includes
provisions for a mixing zone. The most common are for municipal wastewater treatment
systems. Under current regulations mixing zones may be authorized in streams and rivers that
that contain salmon, but may not be authorized in spawning areas for salmon and specified
resident fish in these waters. Mixing zones are also commonly authorized in marine waters.
Below are some examples of mixing zones authorized in Alaska today.
General Permit for Shore-based Seafood Processing Facilities
The large majority of seafood processing facilities operate under a general permit. The mixing
zone is for residues, dissolved gas, oil and grease, pH, color, turbidity, fecal coliform, total
residual chlorine and temperature. The mixing zone is defined as a cylindrical volume with a
horizontal radius of 100 feet from the diffuser and the full depth of the waterbody.
Mendenhall Wastewater Treatment Plant – Juneau
A mixing zone for municipal wastewater is allowed in the Mendenhall River for fecal coliform
bacteria, dissolved oxygen, pH, metals, nutrients, and whole effluent toxicity (WET). The
mixing zone for this discharge is defined as the area within a rectangle centered over the diffuser
with a width of 30 meters and extending both upstream and downstream from the diffuser a
distance of 150 meters, and to the full depth of the river. The mixing zone size is based on a 10year, 7-day low river flow. The mixing zone provides a dilution of 10:1.
Soldotna Wastewater Treatment Facility – Soldotna
A mixing zone for municipal wastewater is allowed in the Kenai River for fecal coliform
bacteria, dissolved oxygen, temperature, total chlorine residual, pH, metals, nutrients, and whole
effluent toxicity (WET). The mixing zone for this discharge is defined as the area extending
downstream from the diffuser a distance of 47 meters and having a width of 5 meters. The
mixing zone provides a dilution of 30:1.
G:\COMM\Subject\Mixing Zones\Factsheet on Examples of Mixing Zones in Alaska.doc
DEPARTMENT OF ENVIRONMENTAL CONSERVATION
FRANK H. MURKOWSKI, GOVERNOR
410 Willoughby Avenue, Suite 303
Juneau, Alaska 99801-1795
PHONE: (907) 465-5066
FAX: (907) 465-5070
http://www.dec.state.ak.us/
OFFICE OF THE COMMISSIONER
October 17, 2005
Dear Alaskan:
Last year you commented on proposed changes to the mixing zone provision of the
Alaska water quality standards regulation (18 AAC 70). During the public review,
we received many comments concerning the potential effects of the proposed
changes on Alaska’s fish resources. In response to those comments, the
Department of Environmental Conservation (DEC) has drafted a new proposal.
Given the significant interest in these regulations, it is important to share the new
proposal with the public for further review. The enclosed water quality mixing
zone regulations will be available for public review and comment for sixty days.
The Legislature sets public policy by enacting statutes and it is the responsibility
of the Executive Branch of government to faithfully execute those laws by
developing and implementing regulations. These new proposed mixing zone
regulations better reflect the Department of Environmental Conservation’s duty to
adopt and enforce water quality standards that protect all uses of Alaska’s waters,
including the growth and propagation of fish.
In addition to DEC’s authority to enforce water quality standards for all state
waters (AS 46.03), Alaska’s legislature established additional protections for rivers,
lakes, and streams that are important to spawning, rearing, or migration of
anadromous fish (AS 16.20 and AS 41.14). Specifically, State laws currently direct
the Department of Natural Resources (DNR), and the Department of Fish and
Game (DFG) under AS 41.14 and AS 16.20 respectively, to approve proposed
construction in, or use of, anadromous waters if approval of the activity will ensure
the proper protection of spawning, rearing and migration. While anadromous
waters must be protected, there is no absolute prohibition in state statute on the
use of, or construction in, rivers, lakes, and streams important to spawning,
rearing, or migration of anadromous fish.
Following this legislative direction, the proposed regulations generally prohibit
mixing zones in fish spawning areas while allowing a narrow range of exceptions.
Specifically, DEC may authorize a mixing zone in a spawning area if a permit
applicant can demonstrate that the timing of the discharge or the types of
pollutants will not affect present and future spawning, incubation and rearing, or
G:\COMM\Subject\Mixing Zones\Dear Alaskan Final.doc
Alaskan
2
October 17, 2005
submits a mitigation plan which demonstrates that discharge effects will be
mitigated subject to approval by DNR or DFG. These two state agencies have the
statutory authority and regulatory expertise to mitigate adverse impacts on fish
and fish habitat.
The regulated community and the public have a right to regulations that are
clearly written and consistent with legislative policy. DEC has drafted this
proposed mixing zone regulation with these principles in mind. Thank you for
your interest. I welcome your review and comment.
Sincerely,
Kurt Fredriksson
Commissioner
G:\COMM\Subject\Mixing Zones\Dear Alaskan Final.doc
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
S
tate F
ish P
rotection P
olicy
Alaska’s legislature has enacted a protective legal framework for all waters important to
fish with additional protections for rivers, lakes and streams that are catalogued as
important for the spawning, rearing, or migration of anadromous fish (relevant statutory
excerpts below).
State law directs the Department of Environmental Conservation (DEC) to establish and
enforce water quality standards that protect the use of all waters for the growth and
propagation of fish. Authorization is also required from DEC and the Department of
Natural Resources (DNR) prior to the construction or use of the waters important to
spawning, rearing, or migration of anadromous fish. Comparable authority is reserved to
the Department of Fish and Game (DFG) in legislatively designated special areas.
All S
tate W aters
AS 46.03.070 - Pollution standards
After public hearing, the department (DEC) may adopt standards…and determine what
qualities and properties of water indicate a polluted condition actually or potentially
deleterious, harmful, detrimental, or injurious to …aquatic life or their growth and
propagation…
AS 46.03.100 - Waste management and disposal authorization
A person may not …dispose of or conduct an operation that results in the disposal of …
liquid waste material or heated process or cooling water into the waters…of the state
without prior authorization from the department (DEC).
Anadromous W
aters
AS. 41.14.870. Protection of fish and game
The deputy commissioner (DNR) shall…specify the various rivers, lakes, and streams or
parts of them that are important for the spawning, rearing, or migration of anadromous
fish.
If a person…desires to…use,… pollute, or change the natural flow…of a specified river,
lake, or stream… the person…shall notify the deputy commissioner of this intention
before the beginning of the…use.
The deputy commissioner shall approve the proposed…use…unless the deputy
commissioner finds the plans and specifications insufficient for the proper protection of
fish...
AS 16.10.010 - Interference with salmon spawning streams and waters
A person may not, without first…obtaining a permit… from the Department of
Environmental Conservation…pollute waters of the state, either fresh or salt, utilized by
salmon in the propagation of the species…
L
egislatively D
esignated p
Secial Areas
AS 16.20.050 - Multiple land use
Where the use…in state game refuges created by AS 16.20.010 - 16.20.080 is under the
control or jurisdiction of the state,…the responsible state department or agency shall
notify the commissioner of fish and game before initiating any use…
AS 16.20.060 - Submission of plans and specifications
The commissioner (DFG) shall…require the person… to submit full plans for the
anticipated use,… and specifications for the proper protection of fish, … and shall require
the person… to obtain the written approval of the commissioner… before construction is
commenced.
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
Alaska S
tatutory F
ish
P
rotection P
olicy
S
tate fish protection policy is established in several statutes that taken together and
summarized, say:
If a person provides plans approved by the state that will protect the growth and propagation of
fish, the state agencies shall allow the person to use, pollute, or change the natural flow of a river,
lake, or stream important for the spawning, rearing, or migration of anadromous fish.
P
ermitted Activities
All activities within or across a specified anadromous waterbody including:
Blasting
Excavation, deposition, or removal of any material
Use of vehicles or equipment in the waterway
Stream realignment, diversion or fluming
Dam and impoundment construction
Recreational suction dredging
Road crossings
Gravel removal
Placer mining
Water withdrawals
Bank stabilization
Bridge or culvert placement
Waste disposal
S
tatute R
eferences
AS 41.14.870 - Anadromous Fish Act
AS 41.14.870 - Protection of fish and game
AS 16.10.010 - Interference with salmon spawning streams and waters
AS 16.20.050 - Multiple land use
AS 16.20.060 - Submission of plans and specifications
AS 46.03.100 - Waste management and disposal authorization
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
epartmen t of E
D
nvironmental Conservation
W
ater Q
uality S
tandards R
evision
s for Mixing Zones
Comparison of the xEisting eRgulations, the 2004 rPoposed eRgulations, and the 2005
P
roposed eRgulations
xEisting R
egulations
Contain an absolute general
prohibition on mixing zones in
areas of anadromous fish spawning
or resident fish spawning for
specific species in streams, rivers,
or other flowing fresh waters.
No provisions for exceptions to the
prohibition on mixing zones in
spawning areas.
2004 P
roposed R
egulations
Removed the current prohibition
on mixing zones in areas of
anadromous fish spawning or
resident fish spawning for specific
species in streams, rivers, or other
flowing fresh waters.
2005 P
roposed eRgulations
Retains the existing general
prohibition on mixing zones in
areas of anadromous fish spawning
or resident fish spawning for
specific species in streams, rivers,
or other flowing fresh waters.
Expands the prohibition on mixing
zones to explicitly include areas in
lakes where anadromous fish
spawning or resident fish spawning
for certain species occurs.
Allowed mixing zones in spawning Allows for exemptions from the
areas where there will be no effect prohibition on mixing zones in
on the capability of an area to
fish spawning habitat in certain
support spawning, incubation or
specific situations if a discharger
rearing of anadromous or certain
complies with all other provisions
resident fish.
of the mixing zone regulations and
makes one of three specific
demonstrations:
x wastewater discharges are
timed to avoid spawning
and will not adversely
affect the capability of the
area to support future
spawning, incubation, and
rearing;
x discharges do not contain
substances that adversely
affect present and future
spawning, incubation, and
rearing; or
x a mitigation plan has been
approved by DNR or F&G.
No requirements for DEC to
consult with DNR or F&G when
making mixing zone decisions.
Not required to consult with DNR
and F&G regarding spawning
areas, although consultation
recommended in guidance.
Protection of fish and shellfish
populations and a limitation on
permanent displacement of
indigenous organisms are applied
only to streams, rivers, or other
flowing fresh waters.
Include technical provisions such
as a description of human health
risk assessment prohibiting “a risk”
to human health, without defining
risk; and includes specific flow
calculations.
Mixing zone provisions are poorly
organized, spread throughout six
separate sections of the
regulations, and include
redundancies.
Protection of fish populations and
a limitation on permanent
displacement of indigenous
organisms were applied only to
flowing fresh waters, similar to
current regulations.
Simplified some technical
provisions or moved them to a
draft guidance document, including
provisions dealing with risk
assessment, flow calculations, and
mixing zone models.
Reorganized the mixing zone
regulations to improve clarity and
reduce redundancy.
\\jn-svrfile\groups\COMM\Subject\Mixing Zones\MZ regs current 2004 2005 comparison table.doc
Requires DEC to consult with
F&G and DNR when an exemption
for discharge in a spawning area is
considered. When a discharger
requests authorization of a mixing
zone in a spawning area and is
required to submit a mitigation
plan, that plan must be approved
by DNR or F&G.
Expands to all waters the
protections for fish and shellfish
populations and the limitation on
permanent displacement of
indigenous organisms.
Reinserts/introduces some specific
technical provisions in the
regulation, such as flow
calculations and references
existing human health risk level.
Reorganized the mixing zone
regulations to improve clarity and
reduce redundancy. Organization
remains the same as the 2004
proposal.
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
In determining whether to authorized a mixing zone, D
E
C must consider:
x
the characteristics of the receiving water
x
the characteristics of the effluent
x
the effects, including cumulative effects of multiple discharges, along with Nonpoint sources of pollution on
the uses of the water
x
any measures that would mitigate potential adverse effects to aquatic resources
x
any other relevant factors
In order to authorize a mixing zone, D
E
C must find that the:
x
effluent will be treated to remove, reduce and disperse the pollutants using the most effective methods
technologically and economically feasible
x
existing uses of the waterbody outside the mixing zone will be maintained and protected
x
overall biological integrity of the waterbody will not be impaired
x
mixing zone is as small as practicable
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
T
o obtain a mixing zone approval, the mixing zone can not :
x
result in a toxic effect in the water column, sediments, or biota outside the boundaries of the mixing zone
x
create a public health hazard that would preclude or limit existing uses of the waterbody for water supply or
contact recreation
x
preclude or limit established processing activities, commercial, sport, personal-use, or subsistence fish and shellfish
harvesting;
x
result in a reduction in fish or shellfish population levels
x
result in permanent or irreparable displacement of indigenous organisms
x
adversely affect threatened or endangered species under the Endangered Species Act
x
form a barrier to migratory species or fish passage
x
contain pollutants that bioaccumulate, bioconcentrate, or persist above natural levels in sediments, water, or biota
x
present an unacceptable risk to human health from carcinogenic, mutagenic, teratogenic, or other effects
x
settle to form objectionable deposits
x
produce floating debris, oil, scum and other material in concentrations that form nuisances
x
result in undesirable or nuisance aquatic life
x
produce objectionable color, taste, or odor in aquatic resources harvested for human consumption
x
cause lethality to passing organisms
x
exceed acute aquatic life criteria beyond a smaller initial mixing zone near the outfall
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
18 AAC 70.240 is repealed and readopted to read:
18 AAC 70.240. Mixing zones. (a) Upon application, the department may
authorize in a discharge permit or certification, a mixing zone or multiple mixing zones
in which the water quality criteria and any limit set by or under this chapter may be
exceeded. The applicant shall provide to the department all available evidence reasonably
necessary to demonstrate that a mixing zone will satisfy this section and shall provide
information in a form and using methods approved by the department. The department
may approve, approve with conditions, or deny a mixing zone application.
(b) In determining whether to authorize a mixing zone under this section, the
department will consider
(1) the characteristics of the receiving water, including biological,
chemical, and physical characteristics such as volume, flow rate, flushing and mixing
characteristics;
(2) the characteristics of the effluent, including volume, flow rate,
dispersion, and quality after treatment;
(3) the effects, if any, including cumulative effects of multiple discharges
and diffuse, nonpoint source inputs, that the discharge will have on the uses of the
receiving water;
(4) any additional measures that would mitigate potential adverse effects to
the aquatic resources present; and
(5) any other factors the department finds must be considered to determine
whether a mixing zone will comply with this section.
(c) The department will approve a mixing zone, as proposed or with conditions,
only if it finds that available evidence reasonably demonstrates that
(1) an effluent or substance will be treated to remove, reduce, and disperse
pollutants, using methods found by the department to be the most effective and
technologically and economically feasible, consistent with the highest statutory and
regulatory treatment requirements including
1
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(A) any federal technology-based effluent limitation identified in 40
C.F.R. 125.3 and 40 C.F.R. 122.29, as amended through July 1, 2005 and adopted
by reference;
(B) minimum treatment standards in 18 AAC 72.050; and
(C) any treatment requirement imposed under another state law that
is more stringent than a requirement of this chapter;
(2) existing uses of the waterbody outside the mixing zone will be
maintained and protected;
(3) the overall biological integrity of the waterbody will not be impaired;
and
(4) the mixing zone will not
(A) result in a toxic effect in the water column, sediments, or biota
outside the boundaries of the mixing zone;
(B) create a public health hazard that would preclude or limit
existing uses of the waterbody for water supply or contact recreation;
(C) preclude or limit established processing activities or established
commercial, sport, personal-use, or subsistence fish and shellfish harvesting;
(D) result in a reduction in fish or shellfish population levels;
(E) result in permanent or irreparable displacement of indigenous
organisms;
(F) adversely affect threatened or endangered species under the
Endangered Species Act (16 U.S.C. 1531-1544); or
(G) form a barrier to migratory species or fish passage.
(d) The department will approve a mixing zone, as proposed or with conditions,
only if the department finds that available evidence reasonably demonstrates that within
the mixing zone the pollutants discharged will not
2
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(1) bioaccumulate, bioconcentrate, or persist above natural levels in
sediments, water, or biota to significantly adverse levels, based on consideration of
bioaccumulation and bioconcentration factors, toxicity, and exposure;
(2) present an unacceptable risk to human health from carcinogenic,
mutagenic, teratogenic, or other effects using risk assessment methods approved by the
department and consistent with 18 AAC 70.025;
(3) settle to form objectionable deposits, except as authorized under
18 AAC 70.210;
(4) produce floating debris, oil, scum and other material in concentrations
that form nuisances;
(5) result in undesirable or nuisance aquatic life;
(6) produce objectionable color, taste, or odor in aquatic resources
harvested for human consumption;
(7) cause lethality to passing organisms; or
(8) exceed acute aquatic life criteria at and beyond the boundaries of a
smaller initial mixing zone surrounding the outfall, the size of which shall be determined
using methods approved by the department.
(e) In lakes, streams, rivers, or other flowing fresh waters, except as authorized in
(f) of this subsection, a mixing zone will not be located in a spawning area of
(1) anadromous fish; or
(2) Arctic Grayling, northern pike, rainbow trout, lake trout, brook trout,
cutthroat trout, whitefish, sheefish, Arctic char (Dolly Varden), burbot, and landlocked
coho, king, and sockeye salmon.
3
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(f) Notwithstanding subsection (e), the Department may authorize a mixing zone
in a spawning area of a lake, stream, river or other flowing fresh water if, after
consultation with the Department of Natural Resources, Office of Habitat Management
and Permitting, or the Department of Fish and Game if within a legislatively designated
special area under AS 16.20, the department finds that the applicant has
(1) demonstrated that spawning fish, fish eggs, or alevins are not physically
present within the mixing zone when the discharge will occur and the discharge will not
adversely affect the capability of the area to support future spawning, incubation, and
rearing activities;
(2) demonstrated the discharge does not contain pollutants that will
adversely affect the capability of the area to support present and future spawning,
incubation, and rearing;
(3) submitted a mitigation plan approved by the Department of Fish and
Game under 5 AAC 95.900 if within a legislatively designated special area under AS
16.20; or
(4) submitted a mitigation plan approved by the Department of Natural
Resources, Office of Habitat Management and Permitting, and incorporated as part of the
Department of Environmental Conservation permit, that includes one or more of the
following mitigation actions:
(A) avoid the impact altogether by not taking a certain action or
parts of an action;
(B) minimize the impact by limiting the degree or magnitude of the
action and its implementation;
(C) rectify the impact by repairing, rehabilitating, or restoring the
impacted environment;
(D) reduce or eliminate the impact over time by preservation and
maintenance operations during the life of the proposed use or activity;
(E) compensate for the impact by replacing or providing substitute
resources or environments.
4
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(g) The department will approve a mixing zone, as proposed or with conditions,
only if it finds that the mixing zone is as small as practicable and will comply with the
following size restrictions, unless the department finds that evidence is sufficient to
reasonably demonstrate that these size restrictions can be safely increased:
(1) for estuarine and marine waters, measured at mean lower low water,
(A) the cumulative linear length of all mixing zones intersected on
any given cross section of an estuary, inlet, cove, channel, or other marine water
may not exceed 10 percent of the total length of that cross section; and
(B) the total horizontal area allocated to all mixing zones at any
depth may not exceed 10 percent of the surface area;
(2) for lakes, the total horizontal area allocated to all mixing zones at any
depth may not exceed 10 percent of the lake’s surface area;
(3) for streams, rivers, or other flowing fresh waters, the length of a mixing
zone may not extend beyond the computed point of complete mixing, as determined
using a standard river flow mixing model or other methods accepted by the department;
(4) for streams, rivers, or other flowing fresh waters, the length of a mixing
zone may not extend downstream beyond the location where the department determines
that a public health hazard reasonably could be expected to occur.
(h) For streams, rivers, or other flowing fresh waters, in calculating the maximum
pollutant discharge limitation, the volume of flow available for dilution must be
determined using
(1) the actual flow data collected concurrent with the discharge; or
(2) for conventional and nontoxic substances, the 10-year, 7-day low flow
(7Q10) as the criteria design flow; for the protection of aquatic life, the 7Q10 as the
chronic criteria design flow and the 10-year, 1-day (1Q10) as the acute criteria design
flow; and for the protection of human health, the 5-year, 30-day (30Q5) as the
noncarcinogenic criteria design flow and the harmonic mean flow as the carcinogenic
criteria design flow; these low flows must be calculated using methods approved by the
department.
5
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(i) If the department finds that available evidence reasonably demonstrates that a
mixing zone authorized by the department has had or is having a significant unforeseen
adverse environmental effect, the department will terminate, modify, or deny renewal of
the permit or certification authorizing the mixing zone. (Eff. 11/1/97, Register 143; am
___/___/____, Register ___)
Authority: AS 46.03.010
AS 46.03.020
AS 46.03.050
AS 46.03.070
AS 46.03.080
AS 46.03.100
AS 46.03.110
AS 46.03.710
AS 46.03.720
18 AAC 70.245 is repealed:
18 AAC 70.245. Mixing zones: appropriateness and size determination.
Repealed. (Eff. 11/1/97, Register 143; repealed ___/___/____, Register ___)
18 AAC 70.250 is repealed:
18 AAC 70.250. Mixing zones: general conditions. Repealed. (Eff. 11/1/97,
Register 143; repealed ___/___/____, Register ___)
18 AAC 70.255 is repealed:
18 AAC 70.255. Mixing zones: in-zone quality and size specifications.
Repealed. (Eff. 11/1/97, Register 143; repealed ___/___/____, Register ___)
18 AAC 70.260 is repealed:
18 AAC 70.260. Mixing zones: application requirements. Repealed. (Eff.
11/1/97, Register 143; repealed ___/___/____, Register ___)
18 AAC 70.270 is repealed:
18 AAC 70.270. Mixing zones: termination, modification, or denial of
renewal. Repealed. (Eff. 11/1/97, Register 143; repealed ___/___/____, Register ___)
18 AAC 70.990 (30) is repealed:
6
Register ___, _________ 2006 ENVIRONMENTAL CONSERVATION
(30) repealed __/__/____.
18 AAC 70.990 is amended by adding a new paragraph to read:
(72) “shellfish” means any species of crustacean, mollusk, or other
invertebrate, in any stage of its life cycle.
7
http://www.state.ak.us/dec/water/wqsar/trireview/trireview.htm
2003-2005 Triennial Review
Section Manager, Nancy Sonafrank
(907) 451-2726
Burden of Proof
in the 2005 Proposed Mixing Zone Regulation
Available Evidence
The proposed mixing zone regulations include numerous conditions that must be met before DEC can
authorize a mixing zone. DEC’s decision to authorize a mixing zone is based on available evidence provided
by the applicant and other credible sources. “Available evidence” is defined in current regulation as:
“All relevant and applicable data and information the applicant has or can obtain, and all relevant and
applicable data and information available to the department from other sources; "available evidence" does not
include data and information that the collection or preparation of which, in the department's determination, is
not practicable.”
Applicant Rights and Responsibilities
The applicant for a mixing zone authorization is responsible for providing evidence (using studies they
currently have or could perform) that demonstrate that a mixing zone is appropriate for a particular water body.
The proposed regulation states “The applicant shall provide to the department all available evidence reasonably
necessary to demonstrate that a mixing zone will satisfy this section…” This clearly places the burden of proof
on the applicant. By requiring “all available evidence,” the regulation also makes clear that the applicant is
required to submit a complete application with all the evidence necessary to fulfill the requirements in the
proposed regulations before a mixing zone can be authorized.
Some of the changes in the proposed regulations were made to reduce uncertainty or the potential for
inconsistent decisions by DEC. If an applicant has submitted credible and sufficient information using
commonly employed science and technology that shows regulatory requirements will be met, then the
applicant can reasonably expect DEC to issue a permit with appropriate conditions.
Department Responsibilities
If a mixing zone application fails to make a required demonstration or violates a prohibition, then the
department cannot approve the proposed mixing zone. The definition of “available evidence” requires the
Department to consider information from the applicant and other sources before making a decision on a mixing
zone authorization. In the proposed regulations, subsections are prefaced by the statement “the department will
approve a mixing zone, as proposed or with conditions, only if the department finds” (emphasis added).
In the case where DEC determines that it is necessary to terminate, modify, or deny the renewal of a permit,
the State assumes some of the burden of proof. It is reasonable for the permitee to expect DEC to have
evidence of adverse effects before taking action on a permit that has already been authorized. However, the
evidence would normally include (but is not limited to) monitoring reports and other information provided by
the permittee.
\\jn-svrfile\groups\COMM\Subject\Mixing Zones\Burden of Proof Factsheet 10-3-05.doc
ALASKA DEPARTMENT OF ENVIRONMENTAL CONSERVATION
DIVISION OF WATER
PROGRAM GUIDANCE
Guidance No. W 05-__
Page 1 of 4
October, 2005
IMPLEMENTATION GUIDANCE:
2005 PROPOSED MIXING ZONE REGULATIONS
DRAFT
Purpose:
This guidance to Department wastewater discharge staff reflects revisions to
regulations for mixing zones in 18 AAC 70.240 adopted on [DATE]
Adverse effects:
When determining whether to authorize a mixing zone, the department will
consider, among other requirements, any proposed measures to mitigate adverse
effects to aquatic resources present (18 AAC 70.240(b)(4). Any mitigation
measures, along with other mixing zone controls, must maintain and protect the
growth and propagation use in the waterbody affected by the mixing zone.
Consideration of the adverse effects of a pollutant will include any available
evidence of sublethal chronic effects and the potential of the pollutant to persist or
bioaccumulate (18 AAC 70.240(d)(1)). For the purposes of this evaluation, the
following guidelines will be used:
Human health:
x
Bioaccumulative pollutants are any chemical that has the potential to cause
adverse effects which, upon entering the surface waters, by itself or as its toxic
transformation product, accumulates in aquatic organisms by a human health
bioaccumulation factor greater than 1000, after considering metabolism and
other physiochemical properties that might enhance or inhibit bioaccumulation.
x
Persistent pollutants are any chemical which is slow to or does not decay,
degrade, transform, volatilize, hydrolyze or photolyze and with a half life
greater than two months in the water column, sediment, and biota.
18 AAC 70.240(d)(2) prohibits mixing zones that would present an unacceptable
risk to human health. To determine health risk, the Department may require an
applicant to perform a site-specific analysis based on exposure pathways, including
exposure duration of affected aquatic organisms in the proposed mixing zone,
patterns of fisheries use, and consumption of water, fish, or shellfish in the area.
The risk assessment method should follow guidelines found in Technical Support
Document for Water Quality-Based Toxics Control. 1991. EPA/505/2-90-001.
Guidance No. W 05-DRAFT
Computer
models:
Initial
mixing/acute
zone:
Page 2 of 4
October, 2005
For carcinogens, an acceptable risk is based on a lifetime incremental cancer risk
level of 1 in 100,000 for exposed individuals under 18 AAC 70.025. For non
carcinogens, an acceptable risk is based on the reference dose (RfD) obtained from
the EPA’s Integrated Risk Information System (IRIS) or other DEC-approved
toxicological data source. The RfD is an estimate of the daily exposure to the
human population that is likely to be without appreciable risk of causing
deleterious effects during a lifetime.
Mixing Zone models are tools used to predict how substances mix upon discharge
to a receiving water. Department staff primarily use two mixing zone models,
CORMIX and PLUMES, however other models, if approved by the department,
may be used to determine mixing zone characteristics. The CORMIX and
PLUMES models are most accurate for near field dilution determinations, but are
also capable of providing estimates of farfield dilution. Both CORMIX and
PLUMES provide graphic representation of the plume size and associated dilutions.
When using the models for far field determinations, modeling results may not be
reliable when a plume reaches a boundary such as a river bank.
Compliance with 18 AAC 70.240(d)(8) of the Water Quality regulations is
assumed if one of the following methods is used to limit the size of the zone in
which acute aquatic life criteria are exceeded:
1. The initial discharge velocity is 3 m/s or greater; and the mixing zone is no
larger in any direction than 50 times the discharge length scale (i.e. the
square-root of the cross-sectional area of the largest port).
2. Acute aquatic life criteria are met within a distance from the outfall that is
no greater than
x 10% of the distance to the boundary of the mixing zone;
x 50 times the discharge length scale; and
x 5 times the local water depth.
3. A drifting organism reaches the acute mixing zone boundary (i.e. the zone
in which aquatic life criteria are exceeded) in 15 minutes or less.
4. A drifting organism does not receive harmful exposure when evaluated by a
valid toxicological analysis approved by the department.
For additional information on how these methods are implemented see Technical
Support Document for Water Quality-Based Toxics Control. 1991. EPA/505/2-90001.
Flow
calculations for
streams and
rivers:
Low flows should be calculated using methods of
x Ashton and Carlson, Determination of Seasonal, Frequency and Durational
Aspects of Streamflow with Regard to Fish Passage Through Roadway
Drainage Structures (1984);
x Carlson, Seasonal, Frequency and Durational Aspects of Streamflow in
Southeast and Coastal Alaska (1987); or
x Other appropriate regional regression flow model approved by the
G:\COMM\Subject\Mixing Zones\Draft MZ guidance for 2005 proposed regs 100405.doc
10\6\05 Revision
Guidance No. W 05-DRAFT
Page 3 of 4
October, 2005
department.
Actual flow data collected concurrent with the discharge may also be used to
monitor compliance with water quality standards under 18 AAC 240(h)(1). For the
purposes of data collection under this section, “concurrent” will be a set time
period approved by the Department based on the variability of the specific site
conditions. Historic river and effluent flow will initially be used to design a mixing
zone with sufficient dilution capacity during critical low-flow periods as designated
in 18 AAC 240(h)(2). Concurrent flow data may then be used to monitor
compliance with the approved mixing zone boundaries using either of the following
two methods:
1.
Pollutant concentration levels may be calculated for the mixed effluent and
river water at the edge of the mixing zone using concurrent river and effluent
data. The calculated concentration must meet water quality standards. Effluent
flow and/or quality may be varied at the time of discharge depending on the
concurrent river flow volume available for dilution.
The data necessary for this calculation includes the following:
x For conventional pollutants, the volume of effluent discharged daily should
be determined. For toxic pollutants, the maximum 2-3 hour flow during a
daily discharge cycle should be determined.
x The effluent should also be sampled for each pollutant to which concurrent
flow limits apply. Samples should be taken concurrent with the flow data.
x The volume of river water available for dilution purposes should be
measured concurrent with flow data for the discharge.
x Either historic data, if sufficient, or concurrent monitoring of the
background river water concentration of a pollutant may be used for
dilution determinations.
x Other water quality parameters, such as hardness and pH, may also be
necessary to determine compliance with water quality standards.
2.
Pollutant concentration levels may be measured by sampling at the
downstream edge of a mixing zone to demonstrate compliance with water
quality standards. Concurrent in-stream monitoring of flow, pollutants and
other relevant water quality parameters should be collected as necessary. To
minimize the amount of concurrent data to be collected and analyzed,
concurrent limit determinations may be necessary only during low flow
periods, with steady-state conditions applying at less critical, high flow
periods.
Water rights for It is a good business practice for a permittee to ensure that other water users do not
impact their ability to continue to discharge. DEC permitting staff will advise
mixing zones:
mixing zone applicants that they should contact DNR to obtain water rights. Water
rights are not required to obtain a discharge permit, but they are strongly
recommended since sufficient water must be available to comply with the mixing
G:\COMM\Subject\Mixing Zones\Draft MZ guidance for 2005 proposed regs 100405.doc
10\6\05 Revision
Guidance No. W 05-DRAFT
Page 4 of 4
zone permit conditions.
Lynn Kent, Director
Division of Water
Date
G:\COMM\Subject\Mixing Zones\Draft MZ guidance for 2005 proposed regs 100405.doc
10\6\05 Revision
October, 2005