Turbidity Issues Agenda

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Turbidity Issues Agenda

• Summary of Proposed Standards
• Wastewater Turbidity
• Stormwater Turbidity
• Turbidity and CWA Permits
• 401 Certifications
• 303(d) Listed Waters
• Remaining Process for Adoption of the Standard

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Turbidity Standards Overview

• States are required to review and revise their
  water quality standards at least every three
  years (33 U.S.C. 1313c1).
• New or revised standards are to be established
  taking into consideration their use and value
  for public water supplies, propagation of fish
  and wildlife, recreational purposes,
  agricultural, industrial, and other purposes, and
  also taking into consideration their use and
  value for navigation. (33 U.S.C. 1313c2A).

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Turbidity Standards Overview

• Oregons turbidity standard was first adopted in
  the 1970s and last revised in 1990.
• The only substantive change occurring at that
  time shifted measurement from Jackson Turbidity
  Units (JTUs) to Nephelometric Turbidity Units
  (NTUs).
• The use of NTUs has allowed more accurate
  measurement at the low end of the turbidity scale
  and set a lower measurable level with respect to
  the allowable increases above background levels.

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Current Turbidity Standard

• The current Oregon water quality standards
  specify (with certain exceptions) for all
  waterbodies and uses that a source cannot cause
  an increase of more than 10 percent in the
  turbidity of the receiving water measured
  upstream of the discharge.

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Proposed Turbidity Standards

• Allowable Increases
• Instantaneous, monthly average, and visual
  contrast criteria based upon background turbidity
  levels.
• Limited Duration Exceedances
• Continue 401 Certification or NPDES permits
• Potential applications for Forest Practices Act
  (FPA) or Senate Bill (SB) 1010 Plans
  (Agricultural Water Quality Management Plans)

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Proposed Turbidity Standards

• Limited Duration Exceedances (continued)
• Revise limited duration criteria to be of
  specified duration and magnitudes to be applied
  as a temporary substitute of the instantaneous
  criteria.
• Allow additional flexibility, similar to current
  limited duration conditions in 401 Certifications
  and Emergency and Channel Restoration Projects.
• Provide an option of more stringent limited
  duration criteria for special waters of concern.

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Proposed Turbidity Standards

• Compliance Determinations
• Develop guidance for flowing and ponding
  systems (OAR 340-041-00364).

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Proposed Turbidity Standards
Maximum Allowable Increase in Turbidity OAR
340-041-0036(2)

• NOTES
• Where a turbidity meter is not available, the
  activity will be subject to the visual criteria
  in subsection (2)(d) of OAR 340-041-0036.
• Visual Criteria. A conspicuous plume must not
  extend further than the compliance point
  distances in subsection (4)(b)(B), except as
  consistent with the numeric or other applicable
  criteria stated in OAR 340-041-0036.

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Proposed Turbidity Standards

• Limited Duration Criteria
• If authorized, instantaneous turbidity criteria
  may be exceeded
• Turbidity may exceed 5 NTUs above background
  during a single period for no more than 8 hours
  on allowable dates.
• On allowable dates, turbidity increases above
  background may exceed 30 NTUs for no more than 2
  hours and may not exceed 50 NTUs.
• Limited duration criteria (OAR 340-041-0036
  3a) are allowed for no more than 6 calendar
  days out of any 30-day period, unless monitoring
  can demonstrate compliance with monthly average
  turbidity criteria.

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Proposed Turbidity Standards

• Limited Duration Criteria
• Activities authorized under this subsection must,
  
• Utilize all reasonable and practicable measures
  to maintain turbidity at lowest achievable level.
• Monitor BMPs to demonstrate conditions allowing
  for exceedances have been met.
• Monitor and document turbidity to demonstrate BMP
  effectiveness and/or compliance.

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Proposed Turbidity Standards

• Limited Duration Criteria Continued
• DEQ may establish more stringent criteria to
  protect beneficial uses,
• such as
• Scenic waterways
• 303(d) listed waterways (turbidity and
  sedimentation)
• Upstream of public drinking water intakes
• Upstream of redds or active spawning areas or
• Any location where special circumstances,
  cumulative impacts, or other conditions require
  additional protection.

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Turbidity Standards
Implementation

• To date, with few exceptions, DEQ has only
  referenced turbidity criteria in NPDES
  stormwater-only permits.
• Upon EPA approval, DEQ will apply the revised
  criteria to all permitted sources with a
  reasonable potential to exceed the criteria.
• The revised rule describing mixing zones and
  limited duration criteria, to be consistent in
  implementation, may be used in 401
  Certifications, NPDES permits, FPA, SB1010,
  developing TMDLS, and identification of 303(d)
  listed waterways.

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Wastewater TurbidityIndividual NPDES Permits
(Except MS4s)
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Wastewater Turbidity Permitting
Applicable Criteria

• Wastewater sources under NPDES permits must
  meet turbidity criteria in OAR 340-041-0036(2),
  outside a permitted mixing zone.

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Wastewater Turbidity Permitting
Reasonable Potential Analysis

• For all sources that have a reasonable potential
  to cause or contribute to an exceedances of the
  turbidity criteria, effluent limits must be
  calculated to meet applicable turbidity criteria
  at the edge of the permitted mixing zone.
• NOTE Effluent limits are calculated as an
  increase above background turbidity using stream
  background turbidity and dilution data.

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Wastewater Turbidity Permitting

• Background turbidity is defined as the turbidity
  that would occur in the receiving water body
  without anthropogenic (human-caused) impacts.
• For long-term continuous discharges, background
  turbidity is that associated with base flow
  conditions unaffected by human activities,
  rainfall induced runoff, or storm events.
• Multiple seasonal background levels may be
  established in a permit

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Wastewater Turbidity Permitting

• Background data may be established using
  representative monitoring data or a default
  value.
• Background turbidity is measured as
• the turbidity upstream of a turbidity-causing
  source or
• If multiple sources are contributing to
  overlapping plumes of turbidity, upstream of the
  cumulative plume from the sources

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Wastewater Turbidity Permitting
Required Data to Determine Background Turbidity

• Select data from an existing DEQ, USGS, or other
  established monitoring site upstream of the
  discharge area.
• Background data should be
• Representative of the central tendency of ambient
  turbidity immediately upstream or outside of the
  point of discharge and unaffected by pulses of
  high turbidity,
• Expressed in NTUs, and
• Regularly spaced to represent each season, with
  multiple years of data and at least 10 data
  points per season of calculation.

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Wastewater Turbidity Permitting
Methods for Calculating the Background Data

• 25th PERCENTILE
• Background as turbidity at the low-end 25th
  percentile (EPA approach minimally impacted
  conditions) on either an annual or seasonal
  basis.
• BASE FLOW
• Parse out the base-flow (30-day period with
  lowest flow average) turbidity data on an annual
  or seasonal basis. Calculate background as the
  median turbidity of the prescribed data set.
• Select flow data for annual period(s) or
  season(s).
• DEFAULT VALUE
• If sufficient monitoring data is not available,
  use 3 NTUs as the background turbidity level for
  calculating effluent limits.

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Wastewater Turbidity Permitting
Calculating the Effluent Limit

• The water quality based effluent limit for
  monthly average and maximum (or daily limits
  MDL) both use same background turbidity. The
  average monthly limit (AMT) will typically use
  the WLA AML.
• FORMULA
• Calculate WLA AML as Te Dmz?T Tb
• Te effluent turbidity
• Dmz dilution factor or the sum of the flow of
  the effluent and the
• flow of the river within the mixing
  zone divided by the flow
• of the effluent.
• ?T 3 (monthly average cycle)
• Tb background turbidity
• Calculate the MDL using the same process
  by substituting the
• maximum allowable turbidity increase as
  ?T.

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Wastewater Turbidity Permitting

• Dilution Factor Data
• Use data from mixing zone study
• Calculate the dilution at the edge of the mixing
  zone using stream base-flow on annual or seasonal
  basis and average dry weather design effluent
  flow levels.
• Dilution should not exceed the critical design
  flow, 30B, 30Q10, or 7Q10 flows using EPA
  biologically based flows default values of 120
  days excursion and 5 excursions per cluster.
• If dilution data is not available, direct measure
  of dilution should be used, or distances outlined
  in the rule for turbid mixing.

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Wastewater Turbidity Permitting

• Effluent Turbidity Data
• Instantaneous Turbidity Criteria
• Use single grab sample representative of
  activity-related turbidity for
• each daily or 24-hour period.
• Monthly Average Criteria
• Use a 30-day or monthly average of the
  instantaneous effluent turbidity
• levels using one representative value for each
  day of the period.
• Suspended Sediment Surrogate
• Suspended sediment can be used to demonstrate
  compliance
• with the turbidity standard if there is a
  correlation/statistical relationships between TSS
  and turbidity. To meet the criteria, 90 percent
  of the confidence interval at the TSS criteria
  should be below the limit.

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Wastewater Turbidity Permitting

• Permit Implementation
• DEQ will include turbidity limits in new NPDES
  permits and in existing NPDES permits as they
  come up for renewal.
• DEQ will inform sources early and before permit
  negotiation of the data development and
  evaluations needed to apply the turbidity
  criteria.

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Wastewater Turbidity Permitting

• Permit Implementation (continued)
• Renewal of existing permits without effluent
  limits for turbidity may include a schedule for
  complying with the revised turbidity criteria.
• Existing permits with turbidity criteria, and new
  permits, must comply with the turbidity limits
  immediately upon renewal or issuance of the
  permit.

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Wastewater Turbidity Permitting

• Permit Implementation (continued)
• Compliance for Existing Permits If data is
  available
• During permit cycle, conduct water quality
  analysis to determine existing background,
  effluent turbidity values, and dilution factor
  values for calculating effluent limit.
• Noncompliance when the activity related
  turbidity minus the background turbidity exceeds
  the instantaneous criteria.

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Wastewater Turbidity Permitting

• Permit Implementation (continued)
• Compliance if data is not available
• Use professional judgment to determine whether
  reasonable potential exists and plan data
  collection to evaluate decision.
• For permit renewal, include conditions to gather
  background, effluent turbidity, and dilution data
  to determine limits.
• Include schedule for compliance no more than five
  years from renewal date.

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Wastewater Turbidity Permitting

• Permit Implementation (continued)
• If data is not available (continued)
• If estimating turbidity limits is not feasible or
  schedule can not be met, reopen the permit upon
  completion of data gathering to
• Schedule compliance no later than five years from
  the date permit is reopened,
• Apply for and obtain a variance according to OAR
  340-041-0061(2) before writing the permit,
• Develop site specific turbidity standards, or
• Modify the mixing zone, complete antidegradation
  review, and comply with the effluent limit.

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Wastewater Turbidity Permitting

• Monitoring
• Turbidity should be monitored at least once daily
  using grab samples or continuous monitoring,
  either with a turbidity meter or using visual
  criteria.
• Visual criteria no visible plume extending
  beyond the compliance point.
• If continuous monitoring is employed, any
  elevation of turbidity above the criteria would
  be considered in determining compliance with the
  instantaneous criteria.

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Wastewater Turbidity Permitting

• Based upon ACWA data, secondary treatment plants
  achieve a 3.2 NTU ave (24 hour composite sample).
  Max values ave 6.5 NTU.
• Assuming 3 NTU as background and that turbidity
  is additive, a plant with no dilution could not
  exceed 5 NTU at any time.
• To meet a monthly ave of 6 NTU (3 over
  background), the treatment plant would have to
  operate consistently at or below 3 NTU.

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Stormwater Turbidity
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Stormwater TurbidityMS4 NPDES Permits
INDIVIDUAL

• Applicable Criteria
• MS4s must address stormwater discharges.
• Are required to meet the turbidity criteria in
  OAR 340-041-0036(2).

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Stormwater TurbidityMS4 NPDES Permits
INDIVIDUAL

• Implementation
• Phase I and Phase II MS4 permits that have been
  recently renewed or nearing issuance do not
  include turbidity limits or monitoring.
• Stormwater permits rely on properly functioning
  BMPs to control sediment discharges to waters of
  the state.
• DEQ will include periodic turbidity monitoring
  requirements to
• Help evaluate the effectiveness of BMPs
• Identify potential violations
• Work with cities to modify BMPs to ensure
  turbidity requirements are met.

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Stormwater TurbidityMS4 NPDES Permits
INDIVIDUAL

• Monitoring
• Require periodic monitoring to evaluate BMP
  effectiveness.
• Benchmarks may be established and substituted for
  in-stream monitoring.
• If in-stream monitoring is not required,
  compliance determinations may be used to test
  BMPs or compliance of turbidity criteria.
• Monitoring opportunities may exist in
  coordination with TMDL monitoring.

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Stormwater TurbidityMS4 NPDES Permits
INDIVIDUAL

• Reporting
• Turbidity monitoring.
• Evaluation of effectiveness of BMPs, including
  recommendations for changes.
• Requirements may also include
• Separate reporting, or
• Allow reporting through a TMDL process.

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Stormwater TurbidityMS4 NPDES Permits
GENERAL1200A, 1200C, 1200CA, 1200CM, 1200COLS,
1200Z

• Applicable Criteria
• Are required to meet the turbidity criteria in
  OAR 340-041-0036(2).

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Stormwater TurbidityMS4 NPDES Permits
GENERAL1200C, 1200CA, 1200CM, 1200COLS, 1200Z

• Implementation
• Existing General permits include the following
  turbidity limits and monitoring requirements
• 1200C, CA, and CM
• Prevent turbid flows of water from leaving site.
  
• Include existing turbidity criteria.
• Daily inspections during runoff and at least
  weekly and within 24 hours of storm event over
  0.5 inches/24 hours.

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Stormwater TurbidityMS4 NPDES Permits
GENERAL1200C, 1200CA, 1200CM, 1200COLS, 1200Z

• Implementation (continued)
• Existing General permits include the following
  turbidity limits and monitoring requirements
• 1200Z and COLS
• Prohibit floating solids.
• No visible discharge.
• Monitoring at least twice/year.
• Monthly reporting of visual observations.

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Stormwater TurbidityMS4 NPDES Permits
GENERAL1200A, 1200C, 1200CA, 1200CM, 1200COLS,
1200Z

• Implementation (continued)
• Existing turbidity limits in the General permits
  are comparable to or more stringent than the new
  criteria.
• DEQ is considering revising the turbidity limits
  in the General permits to reflect revised
  criteria as permits come up for renewal.
• No changes in stormwater management are expected.
• If BMPs are used to achieve compliance,
  benchmarks may be established to evaluate
  effectiveness in meeting criteria.

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Stormwater TurbidityMS4 NPDES Permits
GENERAL1200A, 1200C, 1200CA, 1200CM, 1200COLS,
1200Z

• Monitoring and Reporting
• Maintain monitoring, reporting, and recordkeeping
  as required in permits.

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Turbidity and CWA Permits401 Certifications and
303(d)
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Turbidity and CWA Permits

• 401 Certifications
• Turbidity criteria in OAR 340-041-0036(2) and (3)
  may apply
• to 401 activities (both point and non-point
  sources).
• Applicable Criteria, Implementation, and
  Monitoring
• Apply criteria to discharges.
• Limited duration, as appropriate.
• Additional options for activities requiring
  Section 404 Permits.
• Continue compliance with turbidity criteria.
• Continue monitoring to demonstrate compliance.

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Turbidity and CWA Permits

• 303(d) Listed Waters
• DEQ will continue to require a systematic or
  persistent increase in
• turbidity for listing, incorporating the revised
  criteria
• A systematic or persistent increase of at least 3
  NTUs above
• background turbidity or 10 percent above
  background turbidity over 30
• NTUs at or beyond the appropriate compliance
  point downstream from
• an activity or activities.
• Implementation
• For most discharges, listing would require
  documentation of increases in turbidity above
  levels occurring over at least 10 days out of any
  30 day period and sufficient that a monthly
  average increase would exceed 3 NTUs.
• The revised criteria for listing are equivalent
  to or less stringent than existing criteria, DEQ
  is not anticipating new 303(d) listings to result
  from changes in turbidity criteria.

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Issues

• For wastewater permitting
• Rationale for an instantaneous criteria versus
  a daily maximum.
• Measurement and determination of background
  turbidity levels.
• Monitoring (how, when, and where)
• Use of surrogate monitoring (TSS).
• Compliance strategies?

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Issues

• For stormwater permitting
• Rationale for an instantaneous criteria versus
  a daily maximum.
• Limited duration criteria versus monthly average.
• Measurement and determination of background
  turbidity levels.
• Monitoring (how, when, and where)
• Compliance strategies?

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Next Steps for Adoption of the Standard

• Public Hearings to occur end of July, public
  comment deadline early August.
• EQC briefing in mid-August.
• Adoption of a standard by the EQC in December,
  2005.
• Draft implementation guidance available now.

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Questions?