Ranei Nomura

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Mixing Zone IMD UpdateDecember 1, 2005ACWA
Extreme Permit Makeover

• Ranei Nomura
• DEQ Water Quality Division
• Surface Water Management
• [phone]
• nomura.ranei_at_deq.state.or.us

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Overview

• Mixing zones actual vs. regulatory
• Background on regulatory mixing zones
• DEQs upcoming mixing zone internal management
  directive
• Bills in the 2005 Oregon Legislature
• Next steps

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BEFORE
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AFTER
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What is a mixing zone?

• The area in a receiving waterbody where a
  discharge undergoes initial dilution and mixing.

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What is a regulatory mixing zone?
For NPDES permits, a regulatory mixing zone is an
area defined in permit where

• A discharge undergoes initial dilution and mixing
  in the receiving stream,
• Water quality criteria are suspended or lessened
  provided several conditions are met, and
• Despite the lowering of water quality criteria,
  the integrity and uses of the waterbody as a
  whole is protected.

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Regulatory Mixing Zone
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Regulatory Mixing Zone Components
Receiving waterbody
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Effects within a mixing zone (EPA Handbook)

• Concentrations above the chronic criteria are
  likely to prevent sensitive specifies from
  taking-up long-term residence in the mixing zone.
  Benthic and territorial organisms likely to be
  of greatest concern.
• For organisms continuously residing within a
  mixing zone, survival, growth, and reproduction
  likely to be negatively affected.

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Effects outside mixing zone (EPA Handbook)

• If the total area affected by elevated
  concentrations within all mixing zones combined
  is small compared with the total area of a
  waterbody (such as a river segment), then mixing
  zones are likely to have little effect on the
  integrity of the water body as a whole, provided
  that they do not impinge on unique or critical
  habitats.

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EPA rule and guidance for mixing zones

• The federal Environmental Protection Agency (EPA)
  allows states to adopt their own mixing zone
  regulations as part of the states water quality
  standards (40 CFR 131.13) state regulations are
  subject to EPA approval.
• EPA Guidance
• Water Quality Standards Handbook, August 1994 (or
  Handbook)
• Technical Support Document for Water
  Quality-based Toxics Control, March 1991 (or TSD)

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EPA guidance
Allowable mixing zone characteristics should be
established to ensure that

• Mixing zones do not impair the integrity of the
  water body as a whole,
• There is no lethality to organisms passing
  through the mixing zone and
• There are no significant health risks,
  considering likely pathways of exposure.

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IMD Part 1 Allocating regulatory mixing zones

• Allocation Process New vs. Renewal
• Rule Requirements and Guidelines
• Additional Considerations (e.g., anti-degradation
  policy, anti-backsliding, WET, general permits,
  etc.)
• Assessing Regulatory Mixing Zones in the Field
• Evaluation Report and Permit Language

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IMD Part 1Renewal FAQs

• There is no information in the previous
  evaluation report(s) on how the RMZ was
  developed. Can the existing RMZ be rolled over?
• Will better documenting the existing RMZ, adding
  ZID language to the permit that was previously
  omitted, or making other similar changes during
  the renewal process require an in-depth
  antidegradation review?
• Can an RMZ be re-oriented (described differently
  in the renewal permit as larger or smaller or in
  a different location due to new or better
  information) or an outfall be re-located?
• Would increasing the size of an RMZ or ZID be
  considered backsliding and therefore prohibited
  by anti-backsliding regulations?

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IMD Part 1 OAR requirements

• Free of materials in concentrations that will
  cause acute toxicity to aquatic life. (A zone of
  immediate dilution where acute toxicity criteria
  may be allowed if it can be demonstrated that
  immediate dilution of the effluent within the
  mixing zone reduces toxicity below lethal
  concentrations.)
• Free of materials the will settle to form
  objectionable deposits.
• Free of floating debris, oil, scum, or other
  materials that cause nuisance conditions.
• As small as feasible.

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IMD Part 1 More OAR

• Free of substances in concentrations that produce
  deleterious amounts of fungal or bacterial
  growths.
• Avoid overlap with other mixing zones to the
  extent possible.
• Be less than the total stream width as necessary
  to allow passage of fish and other aquatic
  organisms.
• Minimize adverse effects on the indigenous
  biological community especially when species are
  present that warrant special protection.
• Not threaten public health.

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IMD Part 1 OAR for outside mixing zone

• Be free of materials in concentrations that will
  cause chronic toxicity.
• Meet all other water quality standards under
  normal annual low flow conditions.

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Bottom Attachment
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Bank Attachment
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Fish Passage Issue
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IMD Part 1 Evaluation report and permit language

• Document in evaluation report
• Regulatory mixing zone description
• OAR 340-041-0053(2)(c) The limits of the mixing
  zone must be described in the wastewater
  discharge permit.
• Catalogue of existing permit language in
  spreadsheet to be posted on intranet Permit
  Writers corner.

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IMD Part 1 Permit language

• Include length AND width
• Describe shape (e.g., band, rectangular, radius,
  triangle, etc.)
• Specify downstream or upstream if applicable
• Note within 50 feet of outfall is a radius
• Include description of ZID if applicable
• The RMZ is that portion of the river contained
  within a band extending out 25 feet from the
  outfall to a point 10 feet upstream to 250 feet
  downstream of the outfall. The ZID is defined as
  that portion of the RMZ within 5 feet of the
  outfall.

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IMD Part 1 Assessing RMZs in the field

• Mixing/dilution studies
• Bioassessments
• When are they needed?
• Close to critical or sensitive habitat,
• In small receiving waters with little available
  dilution,
• In areas where there are multiple mixing zones,
• For allocation of a persistent bioaccumulative
  toxin (PBT), or
• When whole effluent testing results indicate a
  potential problem with the effluent.

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IMD Part 1 Bioassessments
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IMD Part 2 Mixing zone study components

• Environmental mapping
• A map and characterization of the specific
  habitats, critical resource areas, and other
  beneficial uses of the receiving water.
• Outfall and mixing zone characteristics
• A description of the existing or proposed mixing
  zone, including a description of existing or
  proposed outfalls.
• Ambient receiving water conditions
• Discharge characteristics

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IMD Part 2 Mixing zone study components,
continued

• Mixing zone modeling analysis
• Information on the model used, why it was
  selected over other models, and results of the
  modeling exercise. Results of the modeling
  exercise will predict available dilution in the
  receiving water.
• Additional water quality data
• Additional receiving water and discharge quality
  data will likely be needed to determine if the
  applicants discharge will comply with water
  quality standards, especially if it was not
  provided in the permit application or more data
  is needed.

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IMD Part 2 Level of effort (e.g., ambient
receiving water conditions)

• Level I, Simple
• Estimates of average channel velocity based on
  assumptions regarding flow, depth,
  cross-sectional area, slope, and friction factors
  acceptable if actual data not available.
• Level II, Moderate
• Measurements of ambient velocity during critical
  and off-design conditions at a location
  representative of the average water column
  velocity desirable, but estimates acceptable.
  Detailed cross-sectional profile (width and
  depth) data is required if local velocities are
  estimated based on calculations.
• Level III, Complex
• Direct measurements of ambient velocity during
  critical and off-design conditions at multiple
  locations representative of water column velocity
  are necessary. Field data should be collected
  that depicts gradients in velocity dependent of
  stream morphometry (channel width and depth)
  relative to the mixing zone boundaries.

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Decision Flow Chart for Determining Level of
Effort for Mixing Zone Study
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IMD Part 2 Environmental mapping for Levels 1,
2, and 3

• Plan view map delineating the existing or
  proposed mixing zones with length and width
  details.
• Plan view map delineating areas within or near
  the mixing zone that provide unique habitat for
• Shellfish harvesting
• Wildlife dependent on waterbody (waterfowl,
  beaver, eagle, etc.)
• Fish spawning and rearing, including cold water
  refugia and physical structures expected to
  attract fish (e.g., piers, irrigation intakes,
  outfalls, etc.)
• Presence of threatened and endangered species
• Drinking water intakes upstream or downstream
  within ½ mile
• NPDES permittees upstream or downstream within ½
  mile
• Other beneficial uses such as fishing, boating,
  or swimming

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Cold Water Refugia
Structural Habitat
Outfall pipe
Regulatory Mixing Zone
Mixing Zone
Salmon Spawning Bed
Littoral Zone
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IMD Part 2 Additional environmental mapping for
Level 3

• Detailed salmonid TE use (e.g., spawning,
  holding, rearing, migratory pathways, etc.)
• Measure of biologic integrity (i.e., rapid
  bioassessments, benthic surveys, etc.)
• Fish migrations studies (example on next slide)
• Thermal imagery e.g., Forward Looking Infrared
  (FLIR) camera technology
• Maps illustrating channel width and depth and
  receiving water depth in the vicinity of the
  outfall
• Published literature or agency reports in support
  of the environmental mapping

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Fish Migration Study Detailed TE Salmonid Use
in the Lower Willamette River
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Thermal Refugia using FLIR Imaging
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2005 Oregon Legislature Senate Bill 555

• Senate Bill 555
• Sponsored by Senators Courtney and Ringo
• Proposal to direct DEQ to condition discharge
  permits to prohibit discharge of toxic substances
  in amounts or concentrations that may be harmful
  to aquatic life or human health.
• Exception if (permittee must pay DEQ for
  evaluation)
• House Bill 2664
• Sponsored by Representatives Schaufler and Jenson
• Proposal to require person discharging wastes
  into waters of state to mark area with buoys,
  markers or signs if discharge causes waters to
  violate standards for water quality or purity.

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Whats next?

• Prepare final draft (manager and internal team
  reviews)
• Develop implementation plan
• Start of public review for at least 30 days
  likely for end of December 2005
• Finalize in early spring