SAC-November-2022_StandardsVsAssessment_CJV_PB_CM

NCDP Science Advisory Council
November 18, 2022
Pam Behm & Chris Ventaloro, DWR
Overview of Surface Water Standards &
Assessment
What are Water Quality Standards
State regulations or rules
Protect surface waters of the state from the deleterious effects
of pollution
Establish pollution limits
To "restore and maintain the chemical, physical, and biological
integrity of the Nation's waters“ (CWA. Section 101(a))
Components of a Water Quality Standard
Designated uses
Goals of the waterbody (i.e., protection of aquatic life)
Criteria
Limits on pollutant magnitude, duration & frequency required to
protect the use
Antidegradation
Framework to maintain water quality where standards are
already met (15A NCAC 02B .0201)
Surface Water Standard -Criteria
Magnitude
Numeric value or narrative statement describing conditions
appropriate to protect the use (i.e., concentration value)
Duration
Time period over which magnitude is considered (e.g.,
instantaneous, 96-hour average, etc.)
Frequency
How often the magnitude/duration can not be met without
impacting the use (e.g., not-to-exceed, 1-in-3 years, 10%)
Development of Criteria
Each criteria component based on scientific evidence
indicating appropriate conditions to support use
Toxicology studies
Bioassessments
Field studies/assessment
Chemical properties
Organism stressor-response information
And more…
Development of Criteria -Examples
Toxic substances for aquatic life protection
Magnitude
Aquatic toxicity data adverse effects concentration
Chemical properties environmental persistence
Duration
Lab & field studies chronic and acute exposure times
Frequency
Organism stressor-response data recovery time from
catastrophic events
Development of Criteria -Example
Clarity (SAV protection)
Water quality condition (for aquatic life protection)
Magnitude:
Modeled relationship of light penetration and data on
appropriate light levels for SAV support & recovery
Duration:
Based on data on critical period of growth for SAV
Frequency (preliminary):
Any season with insufficient light can affect support &
recovery
Assessment of Standards
What is water quality assessment?
CWA required water quality standards implementation program
Goal is to identify whether waters are meeting
standards/inconclusive/not meeting standards
Waterbody/parameter combinations are placed in Category 5
(303dlist) of the Integrated Report per the NCDEQ 303(d) Listing &
Delisting Methodology
o Category 5 assessments require development of a restoration plan
(TMDL or Management Strategy)
Integrated Report
•List of ALL assessed waters and assigned categories
•Established by Sections 305(b) and 303(d) of the Clean
Water Act
•Not required to receive public comment
•CWA requires submittal to EPA, but EPA does not
approve/disapprove
305(b) -Integrated Reporting Categories
10
1
2
3
4
5
NC Impaired Waters List
303(d) List
Integrated Report
305(b) Report
EC
MC
DI
Meeting Criteria
Data Inconclusive
Exceeds Criteria
(“impaired”)
303(d) List
•List of impaired waters where a TMDL or alternative management
action is needed
•TMDL –Total Maximum Daily Load –establishes maximum amount
of pollutant in a waterbody and sets limits on sources
•Established by Section 303(d) of the Clean Water Act
•Public review and comment is required, minimum of 30 days
•Due to EPA every even-numbered year on April 1
•EPA has final approval authority
Assessment of Standards
How is an assessment made?
•Water bodies split into assessment units based on like conditions
•Multiple years of quality-controlled data accounts for temporal
variation
•Data includes:
o Chemical, biological, and physical measures
o Fish tissue data
o Swimming advisories, pathogen testing
Assessment of Standards
How is an assessment made?
•Multiple types of assessments used, including:
o Numeric criteria (at least 10 samples; >10% exceedance
w/90% confidence)
o Benthic & fish community rating system
o Recreational criteria (pathogen indicators)
o Shellfish growing areas
o Fish tissue & consumption advisories
•Impacts from natural conditions and other events also
considered
General Example
Chlorophyll-a standard -not greater than 40 ug/l for lakes, reservoirs,
and other waters subject to growths of macroscopic or microscopic
vegetation
General Assessment Procedure
•5 years of data, minimum 10 samples
•Applied station by station
•>10% exceedance with 90% statistical confidence exceeding
criteria = not meeting standards
Assessment of Standards
Clarity assessment development needs?
•Clear understanding of derivation of criteria number
•Clear understanding of uncertainties involved
•A monitoring plan to specify expected:
o Sample locations
o Collection frequency
o Sample numbers
o Sampling procedures (for QA/QC)
o Known/expected challenges