Mississippi Administrative Code › Title 11 - Mississippi Department of Environmental Quality › Part 6 - Wastewater Pollution Control Regulations › Chapter 9 - Mississippi Commission on Environmental Quality, Mississippi 2024 Section 303(d) List of Impaired Water Bodies › Rule 11-6-9.3 - ASSESSMENT METHODOLOGY

Current through June 25, 2024
A.
Consolidated Assessment Listing Methodology (CALM)
All data used to make formal assessments of the quality of
				  the state's waters, regardless of its source, are evaluated in keeping with the
				  requirements and guidelines in the state's Mississippi CALM [Consolidated
				  Assessment Listing Methodology] for 2024, [CALM] (MDEQ, 2024). The 2024 CALM
				  can be found online at:
https://www.mdeq.ms.gov/water/field-services/water-quality-assessment/
Monitoring data and information that may be considered when
				  assessing state waters could include chemical, physical, bacteriological,
				  toxicological, and/or biological (e.g., macroinvertebrate, fish, and algal
				  community measurements) data. In addition to using MDEQ-generated data, MDEQ
				  solicits and considers all readily available data and information within the
				  assessment window collected by other Federal, State, local
				  agencies/organizations, and the public. Data generated by MDEQ, other agencies,
				  and individuals should be of the quality necessary to make credible and
				  realistic assessment decisions on the condition of the state's waters. Whenever
				  possible, data needs to be of the highest quality and developed using sampling
				  and analytical protocols and standard operating procedures recognized by state
				  and EPA quality assurance program plans. This data solicitation effort is
				  facilitated through MDEQ's Basin Management Approach.
B.
Designated Uses
The water quality assessment process begins with the
				  collection and compilation of the available data followed by the analysis of
				  water quality data and information for the purpose of determining the quality
				  of the state's surface water resources. Surface waters in Mississippi are used
				  for a number of purposes including drinking water supply, shellfish harvesting,
				  recreation, fishing, and aquatic life use support (ALUS). Water bodies are
				  designated and assigned various use classifications by MDEQ in the state's
				  Water Quality Standards (11 Miss. Admin. Code Pt. 6, Ch. 2) {WQS}. This
				  designation is made based on the use(s) of the water body as identified by the
				  public and other entities. The use classifications and associated USEPA
				  designated uses for water quality assessment purposes recognized by the State
				  of Mississippi are given in Table 1.
Table 1 Water Body Classification
Water Body Classification
USEPA Associated Designated Use
Public Water Supply
Drinking Water Supply
Recreation
Contact Recreation
Fish and Wildlife
Aquatic Life Use, Fish Consumption, Secondary
								Contact Recreation
Shellfish Harvesting
Shellfish Consumption
C.
				Water Quality Standards
Most of Mississippi's waters are classified as Fish and
				  Wildlife. For each of the water body classifications listed above, there are
				  various water quality criteria that apply to those water body uses. These
				  standards are used in the assessment process. A water body (part or all of a
				  stream, river, lake, estuary or coastline) should support one or more of these
				  uses. Mississippi's WQS specify the appropriate levels for which various water
				  quality parameters or indicators support a water body's designated use(s). Each
				  use assessed for a water body is determined to be either "Attaining" or "Not
				  Attaining" in accordance with the applicable water quality standards and EPA
				  guidelines for assessments pursuant to §305(b). For the 2024 assessments,
				  all monitoring data were collected prior to the approval of the current Water
				  Quality Criteria for Intrastate, Interstate, and Coastal Waters. The applicable
				  criteria was approved in 2021. Mississippi's WQS may be found here:
https://www.mdeq.ms.gov/water/surface-water/watershed-management/water-quality-standards/
D.
Assessment
				Categories
After assessing attainment status of the water body's
				  designated use(s), each water body is assigned to an assessment unit that
				  defines the length of the reach assessed and is placed into one of five
				  assessment categories as per EPA guidance. These categories are summarized in
				  Table 2.
Table 2 Assessment Categories
Assessment Categories
Definitions of Categories
Category 1
All uses associated with the Assessment Unit have a
								use attainment status of "Fully Supporting"
Category 2
All uses associated with the Assessment Unit that
								have been assessed are "Fully Supporting" but there is insufficient data to
								determine if remaining designated uses are met
Category 3
Insufficient data to determine whether any
								designated uses are met
Category 4
More specific categories of 4A, 4B, and 4C are
								required
4A
TMDL has been completed
4B
Other required control measures will result in
								attainment of WQS
4C
Impairment or threat not caused by a
								pollutant
Category 5
Available data indicate that at least one
								designated use is not being supported and a TMDL is needed
5R
Available data indicate that at least one
								designated use is not being supported, but an alternative restoration approach
								is being implement rather than development of a TMDL.
The §303(d) list includes streams that are impaired that
				  do not have completed Total Maximum Daily Loads (TMDLs). Once the TMDL is
				  completed, but prior to the stream being restored, MDEQ modifies the assessment
				  category of the stream. An impaired stream without a TMDL is assessed in
				  category 5. A stream with a TMDL, but still impaired, is assessed in category
				  4A. The §303(d) lists all of the category 5 waters. Completed TMDLs may be
				  found on the TMDL website at:
https://opcgis.deq.state.ms.us/tmdls
For a listing of all assessed waters and their assigned
				  category, please see the §305(b) Water Quality Assessment Report listed
				  below:
https://www.mdeq.ms.gov/water/field-services/water-quality-assessment/
E.
Monitoring Data
Assessments for 2024 are based on current site-specific
				  monitoring data believed to accurately portray existing water quality
				  conditions. A water body is considered monitored if sufficient (in quantity,
				  quality, and frequency) physical, chemical, biological, bacteriological, and/or
				  fish tissue data were collected and assessed on the water body data from
				  January 1, 2018 to December 31, 2023.
Physical and chemical data include such parameters as pH,
				  temperature, dissolved oxygen, toxicants, turbidity, total dissolved solids
				  (TDS), and specific conductance. Biological data include the community
				  structure of aquatic insects, other macroinvertebrates, fish, and/or algae.
				  Bacteriological data include water column surveys for fecal coliform bacteria,
				  E coli, or enterococci bacteria. Fish tissue data include the analyses of fish
				  flesh for the presence of toxic organic chemicals and metals. The length of
				  record of the data, the quality of the data, and the frequency at which the
				  data are collected were considered in making use attainment decisions.
For 2024, MDEQ considered all known and readily available
				  information on the quality of the state's waters in conjunction with the
				  rotating basin approach and MDEQ's §305(b) assessment program. However,
				  only data that allowed for the accurate interpretation of the state's water
				  quality standards or provided compelling evidence were used for §303(d)
				  listing decisions.
Miss. Code
				  Ann. §§
										49-2-1, et seq. and 49-17-1, et
				  seq.