LTN Appendix VIII Jan 2006

Appendix VIII

Use Support Methodology
and
Use Support Ratings

Appendices

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Introduction to Use Support

All surface waters of the state are assigned a classification appropriate to the best-intended uses
of that water. Waters are assessed to determine how well they are meeting the classified or best-
intended uses. The assessment results in a use support rating for the use categories that apply to
that water.

Use Support Categories

Beginning in 2000 with the Little Tennessee River Basinwide Water Quality Plan, DWQ assesses
ecosystem health and human health risk through the use of five use support categories: aquatic
life, recreation, fish consumption, water supply, and shellfish harvesting. These categories are
tied to the uses associated with the primary classifications applied to NC rivers and streams.
Waters are Supporting if data and information used to assign a use support rating meet the
criteria for that use category. If these criteria are not met, then the waters are Impaired. Waters
with inconclusive data and information are Not Rated. Waters where no data or information are
available to make an assessment are No Data. The table below specifies which use support
categories apply to which primary classifications.

A single water may have more than one use support rating corresponding to one or more of the
use support categories, as shown in the following table. For many waters, a use support category
will not be applicable (N/A) to the classification of that water (e.g., shellfish harvesting is only
applied to Class SA waters). A full description of the classifications is available in the DWQ
document titled: Classifications and Water Quality Standards Applicable to Surface Waters of
North Carolina (15A NCAC 2b .0100 and .0200). Information can also be found within each
basin plan and at http://h2o.enr.state.nc.us/csu/.

Use Support Categories

Primary
Classification
Ecosystem
Approach
Human Health
Approach
Aquatic
Life
Fish
Consumption Recreation Water
Supply
Shellfish
Harvesting
C X X X N/A N/A
SC X X X N/A N/A
B X X X N/A N/A
SB X X X N/A N/A
SA X X X N/A X
WS I – WS IV X X X X N/A

Assessment Period

Data and information are used to assess water quality and assign use support ratings using a five-
year data window that ends on August 31 of the year of basinwide biological sampling. For
example, if biological data are collected in a basin in 2004, then the five-year data window for
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use support assessments would be September 1, 1999 to August 31, 2004. There are
occasionally some exceptions to this data window, especially when follow up monitoring is
needed to make decisions on samples collected in the last year of the assessment period.

Data and information for assessing water quality and assigning use support ratings for lakes uses
a data window of October 1 to September 30. Any data collected by DWQ during the five-year
data window that ends on September 30 of the year of biological sampling will be used to
develop a Weight-of-Evidence approach to lakes assessment. Refer to page 16 of this appendix
for more information.

Assessment Units

DWQ identifies waters by index numbers and assessment unit numbers (AU). The AU is used to
track defined stream segments or waterbodies in the water quality assessment database, for the
303(d) Impaired waters list, and in the various tables in basin plans and other water quality
documents. The AU is a subset of the DWQ index number (classification identification number).
A letter attached to the end of the AU indicates that the AU is smaller than the DWQ index
segment. No letter indicates that the AU and the DWQ index segment are the same.

Interpretation of Data and Information

It is important to understand the associated limitations and degree of uncertainty when
interpreting use support ratings. Although these use support methods are based on data analysis
and other information, some best professional judgment is applied during these assessments.
Use support ratings are intended to provide an assessment of water quality using a five-year data
window, to describe how well surface waters support their classified uses, and to document the
potential stressors contributing to water quality degradation and the sources of these
contributions.

Use support methods continue to improve over time, and the information and technology used to
make use support determinations also continue to become more accurate and comprehensive.
These improvements sometimes make it difficult to make generalizations comparing water
quality between basin plans. However, technology and methods improvements result in more
scientifically sound use support assessments.

Assessment Methodology

Introduction

Many types of data and information are used to determine use support ratings and to identify
stressors and sources of water quality degradation. All existing data pertaining to a stream
segment for each applicable use support category are entered into a use support database.
Assessments and data entries may include use support ratings for each of the five use support
categories, basis of assessment, stressors and potential sources, biological, chemical/physical
(ambient monitoring), and lakes assessment data, fish consumption advisories from the NC
Department of Health and Human Services, swimming advisories and shellfish sanitation
growing area classifications from the NC Division of Environmental Health, and available land
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cover and land use information. The following describes the data and methodologies used to
conduct use support assessments. These methods will continue to be refined as additional
information and technology become available.

Basis of Assessment

Assessments are made on an overall basis of either monitored (M) or evaluated (E), depending
on the level of information available. A monitored rating is based on the most recent five-year
data window and site-specific data and is therefore treated with more confidence than an
evaluated rating. Evaluated ratings are used when there are no site-specific data.

Rating
Basis
Use Support
Category
Assessment
Applicability*
S/M AL Biological community data or ambient water quality parameters do not exceed criteria in
AU during assessment period. Biological and ambient data are independently applied.
S/M REC Ambient fecal coliform bacteria levels do not exceed criteria in AU or AU with DEH
sites is posted with advisories for 61 days or less during assessment period.
S/M SH AU is a DEH Approved shellfish growing area.

I/M AL Biological community data or ambient water quality parameters exceed criteria in AU
during assessment period. Biological and ambient data are independently applied.
I/M REC Ambient fecal coliform bacteria levels exceeds criteria in AU or AU with DEH sites is
posted with advisories for more than 61 days during assessment period.
I/M FC Fish tissue data collected in AU during assessment period and basin is under mercury
advice or site-specific advisory.
I/M SH AU is a DEH Conditionally-Approved, Prohibited or Restricted shellfish growing area.

NR/M AL Biological community is Not Rated or inconclusive, or ambient water quality parameters
are inconclusive or there are less than 10 samples in AU during assessment period.
Biological and ambient data are independently applied.
NR/M REC Ambient fecal bacteria parameter exceeds annual screening criteria, but does not exceed
assessment criteria of five samples in 30 days in AU during assessment period.
NR/M FC AU does not have site-specific advisory and is not under a mercury advice or drains to
areas within a mercury advice; fish tissue data available.

S/E AL AU is a tributary to a S/M AU and land use is similar between AUs.
S/E WS AU is classified as WS, and DEH report notes no significant closures at time of
assessment.

I/E FC AU is in basin under a mercury advice or drains to areas within a mercury advice and has
no fish tissue data.

NR/E AL AU is tributary to I/M AU, or AU is in watershed with intensive and changing land use,
or other information suggests negative water quality impacts to AU. Discharger in AU
has noncompliance permit violations or has failed three or more WET tests during the
last two years of the assessment period.
NR/E REC Discharger has noncompliance permit violations of fecal bacteria parameter during last
two years of assessment period.
NR/E FC AU does not have site-specific advisory and is not under a mercury advice or drains to
areas within a mercury advice, or has no fish tissue data.

ND AL, REC,
SH
No data available in AU during assessment period.

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Note: S/M = Supporting/Monitored I/M = Impaired/Monitored NR/M = Not Rated/Monitored
S/E = Supporting/Evaluated I/E = Impaired/Evaluated NR/E = Not Rated/Evaluated
ND = No Data
AL = Aquatic Life REC = Recreation FC = Fish Consumption
SH = Shellfish Harvesting WS = Water Supply
AU = Assessment Unit WET = Whole Effluent Toxicity
DEH = Division of Environmental Health
* = for lakes assessments, see page 16

Supporting ratings are extrapolated up tributaries from monitored streams when there are no
problematic dischargers with permit violations or changes in land use/cover. Supporting ratings
may also be applied to unmonitored tributaries where there is little land disturbance (e.g.,
national forests and wildlife refuges, wilderness areas or state natural areas). Problem stressors
or sources are not generally applied to unmonitored tributaries. Impaired ratings are not
extrapolated to unmonitored tributaries.

Stressors

Biological and ambient samplings are useful tools to assess water quality. However, biological
sampling does not typically identify the causes of impairment, and ambient sampling does not
always link water quality standards to a biological response. Linking the causes of impairment
and the biological response are a complex process (USEPA, 2000) that begins with an evaluation
of physical, chemical or biological entities that can induce an adverse biological response. These
entities are referred to as stressors. A stressor may have a measurable impact to aquatic health.
Not all streams will have a primary stressor or cause of impairment. A single stressor may not
be sufficient to cause impairment, but the accumulation of several stressors may result in
impairment. In either case, impairment is likely to continue if the stressor or the various
cumulative stressors are not addressed. Use support assessments evaluate the available
information related to potential stressors impacting water quality.

A stressor identification process may be initiated after a stream appears on the 303(d) list in
order to address streams that are Impaired based on biological data. Intensive studies are
required to summarize and evaluate potential stressors to determine if there is evidence that a
particular stressor plays a substantial role in causing the biological impacts. Intensive studies
consider lines of evidence that include benthic macroinvertebrate and fish community data,
habitat and riparian area assessment, chemistry and toxicity data, and information on watershed
history, current watershed activities and land uses, and pollutant sources. These studies result in
decisions regarding the probable stressors contributing to or causing impairment. The intensity
of a stressor study may be limited due to a lack of resources. In these cases, it may still be
appropriate to include stressors in use support assessments, but to also note where additional
information is needed in order to evaluate other stressors.

Where an ambient parameter is identified as a potential concern, the parameter is noted in the
DWQ database and use support summary table. Where habitat degradation is identified as a
stressor, DWQ and others attempt to identify the type of habitat degradation (e.g., sedimentation,
loss of woody habitat, loss of pools or riffles, channelization, lack of riparian vegetation,
streambed scour and bank erosion). Habitat evaluation methods are being developed to better
identify specific types of habitat degradation.
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Aquatic Life Category

The aquatic life category is an ecosystem approach to assessing the biological integrity of all
surface waters of the state. The biological community data and ambient water quality data are
used in making assessments in this category. These represent the most important monitoring
data for making water quality assessments in the aquatic life category. Evaluation information
such as compliance and whole effluent toxicity information from NPDES dischargers, land
cover, and other more anecdotal information are also used to identify potential problems and to
refine assessments based on the monitoring data. The following is a description of each
monitoring data type and the criteria used in assigning use support ratings. Criteria used to
evaluate the other information and assign use support ratings are also described. Refer to page
14 for lakes and reservoir assessment methods as applied in the aquatic life category.

Biological Data

Benthic macroinvertebrate (aquatic insects) community and fish community samples are the best
way to assess the biological integrity of most waterbodies. Unfortunately, these community
measures cannot be applied to every stream size and are further limited by geographic region.
These community measures are designed to detect current water quality and water quality
changes that may be occurring in the watershed. However, they are only directly applied to the
assessment unit where the sample was collected.

Where recent data for both benthic macroinvertebrates and fish communities are available, both
are assessed for use support ratings. When the data from multiple biological data types are
gathered, each data type is assessed independently. Biological monitoring is typically assessed
independent of ambient monitoring data and either may be used to assign a use support rating for
an assessment unit.

Benthic Macroinvertebrate Criteria

Criteria have been developed to assign bioclassifications to most benthic macroinvertebrate
samples based on the number of taxa present in the pollution intolerant aquatic insect groups of
Ephemeroptera, Plecoptera and Trichoptera (EPTs); and the Biotic Index (BI), which
summarizes tolerance data for all taxa in each sample. Because these data represent water
quality conditions with a high degree of confidence, use support ratings using these data are
considered monitored.

If a Fair macroinvertebrate bioclassification is obtained under conditions (such as drought or
flood conditions, recent spills, etc.) that may not represent normal conditions or is borderline Fair
(almost Good-Fair), a second sample should be taken within 12-24 months to validate the Fair
bioclassification. Such sites will be Not Rated until the second sample is obtained.

Use support ratings are assigned to assessment units using benthic macroinvertebrate
bioclassifications as follows.

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Waterbody Sample
Type or Criteria
Benthic
Bioclassification
Use Support
Rating
Mountain, piedmont, coastal A3 Excellent Supporting
Mountain, piedmont, coastal A3 Good Supporting
Swamp1 Natural Supporting
Mountain, piedmont, coastal A Good-Fair Supporting
Smaller than criteria but Good-Fair2 Not Impaired Supporting
Swamp1 Moderate Stress Supporting
Mountain, piedmont, coastal A3 Fair Impaired
Swamp1 Severe Stress Impaired
Mountain, piedmont, coastal A3 Poor Impaired
Criteria not appropriate to assign bioclassification Not Rated Not Rated
1 Swamp streams for benthos sampling are defined as streams in the coastal plain that have no visible flow for a part of the year,
but do have flow during the February to early March benthic index period.
2 This designation may be used for flowing waters that are too small to be assigned a bioclassification (less than three square
miles drainage area), but have a Good-Fair or higher bioclassification using the standard qualitative and EPT criteria.
3 Coastal A streams are those located in the coastal plain that have flow year round and are wadeable.

Fish Community Criteria

The North Carolina Index of Biotic Integrity (NCIBI) is a method for assessing a stream’s
biological integrity by examining the structure and health of its fish community. The NCIBI
incorporates information about species richness and composition, indicator species, trophic
function, abundance and condition, and reproductive function. Because these data represent
water quality conditions with a high degree of confidence, use support ratings using these data
are considered monitored. Use support ratings are assigned to assessment units using the NCIBI
bioclassifications as follows:

NCIBI Use Support Rating
Excellent Supporting
Good Supporting
Good-Fair Supporting
Fair Impaired
Poor Impaired

The NCIBI was recently revised (NCDENR, 2001), and the bioclassifications and criteria have
also been recalibrated against regional reference site data (NCDENR, 2000a, 2000b and 2001a).
NCIBI criteria are applicable only to wadeable streams in the following river basins: Broad,
Catawba, Savannah, Yadkin-Pee Dee, Cape Fear, Neuse, Roanoke, Tar-Pamlico, French Broad,
Hiwassee, Little Tennessee, New and Watauga. Additionally, the NCIBI criteria are only
applicable to streams in the piedmont portion of the Cape Fear, Neuse, Roanoke and Tar-Pamlico
River basins. The definition of "piedmont" for these four river basins is based upon a map of
North Carolina watersheds (Fels, 1997). Specifically:
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• In the Cape Fear River basin -- all waters except for those draining the Sandhills in Moore,
Lee and Harnett counties, and the entire basin upstream of Lillington, NC.
• In the Neuse River basin -- the entire basin above Smithfield and Wilson, except for the
south and southwest portions of Johnston County and eastern two-thirds of Wilson County.
• In the Roanoke River basin -- the entire basin in North Carolina upstream of Roanoke
Rapids, NC and a small area between Roanoke Rapids and Halifax, NC.
• In the Tar-Pamlico River basin -- the entire basin above Rocky Mount, except for the lower
southeastern one-half of Halifax County and the extreme eastern portion of Nash County.

NCIBI criteria have not been developed for:

• Streams in the Broad, Catawba, Yadkin-Pee Dee, Savannah, French Broad, Hiwassee, Little
Tennessee, New and Watauga River basins which are characterized as wadeable first to third
order streams with small watersheds, naturally low fish species diversity, coldwater
temperatures, and high gradient plunge-pool flows. Such streams are typically thought of as
"Southern Appalachian Trout Streams".
• Wadeable streams in the Sandhills ecoregion of the Cape Fear, Lumber and Yadkin-Pee Dee
River basins.
• Wadeable streams and swamps in the coastal plain region of the Cape Fear, Chowan,
Lumber, Neuse, Pasquotank, Roanoke, Tar-Pamlico and White Oak River basins.
• All nonwadeable and large streams and rivers throughout the state.

Ambient Water Quality Monitoring Criteria

Chemical/physical water quality data are collected through the DWQ Ambient Monitoring
Program statewide and NPDES discharger coalitions in some basins. All samples collected
(usually monthly) during the five-year assessment period are used to assign a use support rating.
Ambient water quality data are not direct measures of biological integrity, but the
chemical/physical parameters collected can provide an indication of conditions that may be
impacting aquatic life. Because these data represent water quality conditions with a high degree
of confidence, use support ratings assigned using these data are considered monitored. Where
both ambient data and biological data are available, each data type is assessed independently.

The parameters used to assess water quality in the aquatic life category include dissolved
oxygen, pH, chlorophyll a and turbidity. Criteria for assigning use support ratings to assessment
units with ambient water quality data of a minimum of ten samples are as follows:

Ratings Criteria Rating
Numerical standard exceeded in ≤10% of samples Supporting
Numerical standard exceeded in >10% of samples Impaired
Less than 10 samples collected Not Rated
DO and pH standard exceeded in swamp streams Not Rated

Some standards are written with more specific criteria than others and these specific criteria are
used to assess use support. For example, the DO standard for Class C waters is a daily average
of 5 mg/l and an instantaneous value of 4 mg/l. Because DWQ does not collect daily DO levels
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at the ambient stations, the instantaneous value is used for assessment criteria. In areas with
continous monitoring, the daily average of 5 mg/l will also be assessed. In addition, pH has a
standard of not less than 6 and not greater than 9; each level is assessed. To assess the fecal
coliform bacteria standard, five samples must be collected within a 30 day period (see Recreation
Category for more information).

Multiple Monitoring Sites

There are assessment units with more than one type of monitoring data. When the data from
multiple biological data types are gathered, each data type is assessed independently. Biological
monitoring is typically assessed independent of ambient monitoring data and either may be used
to assign a use support rating for an assessment unit. Monitoring data are always used over the
evaluation information; however, evaluation information can be used to lengthen or shorten
monitored assessment units and to assign use support ratings on an evaluated basis to non-
monitored assessment units.

NPDES Wastewater Whole Effluent Toxicity (WET) Information

Whole Effluent Toxicity (WET) tests are required for all major NPDES discharge permit
holders, as well as those minor NPDES dischargers with complex effluent (defined as not being
of 100 percent domestic waste). WET tests are evaluated to determine if the discharge could be
having negative water quality impacts. If a stream with a WET test facility has not been sampled
for instream chronic toxicity, biological community data or has no ambient water quality data,
and that facility has failed three or more WET tests in the last two years of the assessment
period, the assessment unit is Not Rated. Because this information is not a direct measure of
water quality and the confidence is not as high as for monitoring data, this use support rating is
considered evaluated rather than monitored. Problems associated with WET test failures are
addressed through NPDES permits.

NPDES Discharger Daily Monitoring Report (DMR) Information

NPDES effluent data monthly averages of water quality parameters are screened for the last two
years of the assessment period. If facilities exceed the effluent limits by 20 percent for two or
more months during two consecutive quarters, or have chronic exceedances of permit limits for
four or more months during two consecutive quarters, then the assessment unit is Not Rated if no
biological or ambient monitoring data are available. Because discharger effluent data is not a
direct measure of water quality and data confidence is not as high as for stream monitoring data,
the assessment units are considered evaluated rather than monitored. If biological or ambient
data are available, that data will be used to develop a use support rating for appropriate stream
segments.

Fish Consumption Category

The fish consumption category is a human health approach to assess whether humans can safely
consume fish from a waterbody. This category is applied to all waters of the state. The use
support rating is assigned using fish consumption advisories or advice as issued by the NC
Department of Health and Human Services (DHHS). The fish consumption category is different
from other categories in that assessments are based on the existence of a DHHS fish
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consumption advice or advisory at the time of use support assessment. The advice and
advisories are based on DHHS epidemiological studies and on DWQ fish tissue data, so a fish
tissue monitoring site will constitute a monitored assessment unit (AU) and all other AUs will be
evaluated. DWQ fish tissue data are used to inform DHHS of potential fish tissue toxicity.
DHHS is responsible for proclaiming a fish tissue advisory for any waterbody. Fish tissue
monitoring data are not used directly for assigning a use support rating in this category.

If a limited site-specific fish consumption advisory or a no consumption advisory is posted at the
time of assessment, the water is Impaired. If there are no site-specific advisories posted or the
stream is not in a basin where mercury advice is applied, then the assessment unit will be Not
Rated in this category.
The DHHS has developed regional fish consumption advice (all waters south and east of I-85)
for certain fish species shown to have elevated levels of mercury in their tissue. DWQ applies
the DHHS fish consumption advice for mercury on a basinwide scale rather than an AU scale in
recognition that fish move up and downstream regardless of the presence of I-85. All AUs
draining below or intersecting I-85 are Impaired in the fish consumption category. AUs with
monitoring data are considered Impaired/Monitored, and AUs with no monitoring data are
considered Impaired/Evaluated. When a DHHS site-specific advisory is in place for a parameter
other than mercury, the assessment is based on that advisory and the mercury advice will take a
lower ranking in the assessment. Therefore, when a site-specific advisory is in place in a basin
with a mercury advice and the AU has fish tissue monitoring data, the AU will be considered
Impaired/Monitored for the specific parameter, rather than Impaired/Evaluated for mercury.

Basins under the mercury advice are the Cape Fear, Chowan, Lumber, Neuse, Pasquotank,
Roanoke, White Oak and Yadkin-Pee Dee. All waters in these basins are Impaired in the fish
consumption category, even when there is a site-specific advisory. All waters are also
considered Monitored or Evaluated, dependent upon the availability of monitoring data.

Only a small portion of the Catawba River basin is intersected by I-85 (lower Mecklenberg,
Union and Gaston counties). Due to the presence of dams that impede fish travel throughout the
Catawba River basin, only those waters draining to and entering the mainstem Catawba below I-
85 and are not impeded by dams are considered Impaired/Evaluated.
Basins not under the mercury advice are the Broad, French Broad, Hiwassee, Little Tennessee,
New, Savannah and Watauga. All waters in these basins are Not Rated in the fish consumption
category if there is no site-specific advisory; waters are Impaired if there is a site-specific
advisory. All waters are also considered Monitored or Evaluated, dependent upon the
availability of monitoring data.

Recreation Category

This human health related category evaluates waters for the support of primary recreation
activities such as swimming, water-skiing, skin diving, and similar uses usually involving human
body contact with water where such activities take place in an organized manner or on a frequent
basis. Waters of the state designated for these uses are classified as Class B, SB and SA. This
category also evaluates other waters used for secondary recreation activities such as wading,
boating, and other uses not involving human body contact with water, and activities involving
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human body contact with water where such activities take place on an infrequent, unorganized or
incidental basis. Waters of the state designated for these uses are classified as Class C, SC and
WS.

The use support ratings applied to this category are currently based on the North Carolina fecal
coliform bacteria water quality standard where ambient monitoring data are available or on the
duration of local or state health agencies posted swimming advisories. Use support ratings for
the recreation category may be based on other bacteriological indicators and standards in the
future.

DWQ conducts monthly ambient water quality monitoring that includes fecal coliform bacteria
testing. The Division of Environmental Health (DEH) tests coastal recreation waters (beaches)
for bacteria levels to assess the relative safety of these waters for swimming. If an area has
elevated bacteria levels, health officials will advise that people not swim in the area by posting a
swimming advisory and by notifying the local media and county health department.

The North Carolina fecal coliform bacteria standard for freshwater is: 1) not to exceed the
geometric mean of 200 colonies per 100 ml of at least five samples over a 30-day period; and 2)
not to exceed 400 colonies per 100 ml in more than 20 percent of the samples during the same
period. The AU being assessed for the five-year data window is Supporting in the recreation
category if neither number (1) nor (2) of the standard are exceeded. The AU being assessed is
Impaired in the recreation category if either number (1) or (2) is exceeded. Waters without
sufficient fecal coliform bacteria data (five samples within 30 days) are Not Rated, and waters
with no data are noted as having No Data.

Assessing the water quality standard requires significant sampling efforts beyond the monthly
ambient monitoring sampling and must include at least five samples over a 30-day period.
Decades of monitoring have demonstrated that bacteria concentrations may fluctuate widely in
surface waters over a period of time. Thus, multiple samples over a 30-day period are needed to
evaluate waters against the North Carolina water quality standard for recreational use support.
Waters classified as Class SA, SB and B are targeted for this intensive sampling effort due to the
greater potential for human body contact.

Waters with beach monitoring sites will be Impaired if the area is posted with an advisory for
greater than 61 days of the assessment period. Waters with beach monitoring sites with
advisories posted less than 61 days will be Supporting. Other information can be used to Not
Rate unmonitored waters.

DWQ Ambient Monitoring Fecal Coliform Bacteria Screening Criteria

As with other information sources, all available information and data are evaluated for the
recreation category using the assessment period. However, DWQ conducts an annual screening
of DWQ ambient fecal coliform bacteria data to assess the need for additional monitoring or
immediate action by local or state health agencies to protect public health.

Each March, DWQ staff will review bacteria data collections from ambient monitoring stations
statewide for the previous sampling year. Locations with annual geometric means greater than
200 colonies per 100 ml, or when more than 20 percent of the samples are greater than 400
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colonies per 100 ml, are identified for potential follow-up monitoring conducted five times
within 30 days as specified by the state fecal coliform bacteria standard. If bacteria
concentrations exceed either portion of the state standard, the data are sent to DEH and the local
county health director to determine the need for posting swimming advisories. DWQ regional
offices will also be notified.

Due to limited resources and the higher risk to human health, primary recreation waters (Class B,
SB and SA) will be given monitoring priority for an additional five times within 30 days
sampling. Follow-up water quality sampling for Class C waters will be performed as resources
permit. Any waters on the 303(d) list of Impaired waters for fecal coliform will receive a low
priority for additional monitoring because these waters will be further assessed for TMDL
development.

DWQ attempts to determine if there are any swimming areas monitored by state, county or local
health departments or by DEH. Each January, DEH, county or local health departments are
asked to list those waters which were posted with swimming advisories in the previous year.

Shellfish Harvesting Use Support

The shellfish harvesting use support category is a human health approach to assess whether
shellfish can be commercially harvested and is therefore applied only to Class SA waters. The
following data sources are used to assign use support ratings for shellfish waters.

Division of Environmental Health (DEH) Shellfish Sanitation Surveys

DEH is required to classify all shellfish growing areas as to their suitability for shellfish
harvesting. Estuarine waters are delineated according to DEH shellfish management areas (e.g.,
Outer Banks, Area H-5) which include Class SA, SB and SC waters. DEH samples growing
areas regularly and reevaluates the areas by conducting shellfish sanitation shoreline surveys
every three years to determine if their classification is still applicable. DEH classifications may
be changed after the most recent sanitary survey. Classifications are based on DEH bacteria
sampling, locations of pollution sources, and the availability of the shellfish resource. Growing
waters are classified as follows.

DEH
Classification
DEH
Criteria
Approved
(APP)
Fecal Coliform Standard for Systematic Random Sampling:
The median fecal coliform Most Probable Number (MPN) or the geometric mean MPN of
the water shall not exceed 14 per 100 milliliters (ml), and the estimated 90th percentile
shall not exceed an MPN of 43 MPN per 100 ml for a 5-tube decimal dilution test.

Fecal Coliform Standard for Adverse Pollution Conditions Sampling:
The median fecal coliform or geometric mean MPN of the water shall not exceed 14 per
100 ml, and not more than 10 percent of the samples shall exceed 43 MPN per 100 ml for
a 5-tube decimal dilution test.
Conditionally
Approved-Open
(CAO)
Sanitary Survey indicates an area can meet approved area criteria for a reasonable period
of time, and the pollutant event is known and predictable and can be managed by a plan.
These areas tend to be open more frequently than closed.
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Conditionally
Approved-Closed
Sanitary Survey indicates an area can meet approved area criteria for a reasonable period
of time, and the pollutant event is known and predictable and can be managed by a plan.
These areas tend to be closed more frequently than open. (CAC)
Restricted Sanitary Survey indicates limited degree of pollution, and the area is not contaminated to
the extent that consumption of shellfish could be hazardous after controlled depuration or
relaying.
(RES)
Prohibited No Sanitary Survey; point source discharges; marinas; data do not meet criteria for
Approved, Conditionally Approved or Restricted Classification. (PRO)

Assigning Use Support Ratings to Shellfish Harvesting Waters (Class SA)

DWQ use support ratings may be assigned to separate segments within DEH management areas.
In assessing use support, the DEH classifications and management strategies are only applicable
to DWQ Class SA (shellfish harvesting) waters. It is important to note that DEH classifies all
actual and potential growing areas (which includes all saltwater and brackish water areas) for
their suitability for shellfish harvesting. This will result in a difference of acreage between DEH
areas classified as CAC, PRO and RES, and DWQ waters rated as Impaired. For example, if
DEH classifies a 20-acre area CAC, but only 10 acres are Class SA, only those 10 acres of Class
SA waters are rated as Impaired.

The DEH "Closed" polygon coverage includes CAC, RES and PRO classifications, and it is not
currently possible to separate out the PRO from the RES areas. Therefore, these areas are a
combined polygon coverage, and DWQ rates these waters as Impaired.

Sources of fecal coliform bacteria are more difficult to separate out for Class SA areas. DEH
describes the potential sources in the sanitary surveys, but they do not describe specific areas
affected by these sources. Therefore, in the past, DEH identified the same sources for all Class
SA sections of an entire management area (e.g., urban runoff and septic systems). Until a better
way to pinpoint sources is developed, this information will continue to be used. A point source
discharge is only listed as a potential source when NPDES permit limits are exceeded.

DWQ and DEH are developing the database and expertise necessary to assess shellfish
harvesting frequency of closures. In the interim, DWQ has been identifying the frequency of
closures in Class SA waters using an interim methodology (see below) based on existing
databases and GIS shapefiles. There will be changes in reported acreages in future assessments
using the permanent methods and tools that result from this project.

Past Interim Frequency of Closure-Based Assessment Methodology

The interim method was used for the 2001 White Oak, 2002 Neuse and 2003 Lumber River
basin use support assessments. Shellfish harvesting use support ratings for Class SA waters
using the interim methodology are summarized below.

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Percent of Time Closed
within Basin Data Window
DEH
Growing Area Classification
DWQ
Use Support Rating
N/A Approved* Supporting
Supporting Closed ≤10% of data window Portion of CAO closed ≤10% of data window
Closed >10% of the data window Portion of CAO closed >10% of data window Impaired
N/A CAC and PRO/RES** Impaired
* Approved waters are closed only during extreme meteorological events (hurricanes).
** CAC and P/R waters are rarely opened to shellfish harvesting.

For CAO areas, DWQ worked with DEH to determine the number of days and acreages that
CAO Class SA waters were closed to shellfish harvesting during the assessment period. For
each growing area with CAO Class SA waters, DEH and DWQ defined subareas within the CAO
area that were opened and closed at the same time. The number of days these CAO areas were
closed was determined using DEH proclamation summary sheets and the original proclamations.

The number of days that APP areas in the growing area were closed due to preemptive closures
because of named storms was not counted. For example, all waters in growing area E-9 were
preemptively closed for Hurricane Fran on September 5, 1996. APP waters were reopened
September 20, 1996. Nelson Bay (CAO) was reopened September 30, 1996. This area was
considered closed for ten days after the APP waters were reopened.

Current Assessment Methodology

Use support assessment is now conducted such that only the DEH classification will be used to
assign a use support rating. By definition, CAO areas are areas that DEH has determined do not,
or likely do not, meet water quality standards and these areas will be rated Impaired, along with
CAC and PRO/RES areas. Only APP areas will be rated Supporting.

Growing areas that have been reclassified by DEH during the assessment period from a lower
classification to APP will be rated Supporting. Areas that are reclassified from APP to any other
classification during the assessment period will be rated Impaired.

Over the next few years, DWQ, DEH, Division of Coastal Management (DCM) and Division of
Marine Fisheries (DMF) will be engaged in developing a database with georeferenced (GIS)
shellfish harvesting areas. The new database and GIS tools will be valuable for the above
agencies to continue to work together to better serve the public. Using the new database with
georeferenced areas and monitoring sites, DEH will be able to report the number of days each
rea was closed excluding closures related to large or named storms. a Water Supply Use Support

This human health related use support category is used to assess all Class WS waters for the
ability of water suppliers to provide potable drinking water. Water quality standards established
for drinking water apply to water delivered to consumers after it has been treated to remove
potential contaminants that may pose risks to human health. Ambient standards established by
states under the Clean Water Act are not intended to ensure that water is drinkable without
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treatment. Modern water treatment technologies are required to purify raw water to meet
drinking water standards as established by the North Carolina Division of Environmental Health.

Water supply use support is assessed by DWQ using information from the seven DEH regional
water treatment plant consultant staff. Each January, the DEH staff consultants are asked to
submit a spreadsheet listing closures and water intake switch-overs for all water treatment plants
in their region. This spreadsheet describes the length and time of the event, contact information,
and the reason for the closure or switch.

The spreadsheets are reviewed by DWQ staff to determine if any closures/switches were due to
water quality concerns. Those closures/switches due to water quantity problems and reservoir
turnovers are not considered for use support. The frequency and duration of closures/switches
due to water quality concerns are considered when assessing use support. Using these criteria,
North Carolina’s surface water supplies are currently rated Supporting on an Evaluated basis.
Specific criteria for rating waters Impaired are to be determined on a case-by-case basis.

Use of Outside Data

DWQ actively solicits outside data and information in the year before biological sampling in a
particular basin. The solicitation allows approximately 90 days for data to be submitted. Data
from sources outside DWQ are screened for data quality and quantity. If data are of sufficient
quality and quantity, they may be incorporated into use support assessments. A minimum of ten
samples for more than a one-year period is needed to be considered for use support assessments.

The way the solicited data are used depends on the degree of quality assurance and quality
control of the collection and analysis of the data as detailed in the 303(d) report and shown in the
table below. Level 1 data can be use with the same confidence as DWQ data to determine use
support ratings. Level 2 or Level 3 data may be used to help identify causes of pollution and
stressors. They may also be used to limit the extrapolation of use support ratings up or down a
stream segment from a DWQ monitoring location. Where outside data indicate a potential
problem, DWQ evaluates the existing DWQ biological and ambient monitoring site locations for
adjustment as appropriate.

Criteria Levels for Use of Outside Data in Use Support Assessments
Criteria Level 1 Level 2 Level 3
Monitoring frequency of at least 10 samples for
more than a one-year period Yes Yes/No No
Monitoring locations appropriately sited and
mapped Yes Yes No
State certified laboratory used for analysis
according to 15A NCAC 2B .0103 Yes Yes/No No
Quality assurance plan available describing
sample collection and handling
Yes, rigorous
scrutiny Yes/No No

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Lakes and Reservoir Use Assessment

Like streams, lakes are classified for a variety of uses. All lakes monitored as part of North
Carolina’s Ambient Lakes Monitoring Program carry the Class C (aquatic life) classification,
and most are classified Class B and SB (recreation) and WS-I through WS-V (water supply).
The surface water quality numeric standard specifically associated with recreation is fecal
coliform. For water supplies, there are 29 numeric standards based on consumption of water and
fish. Narrative standards for Class B and Class WS waters include aesthetics such as no odors
and no untreated wastes. There are other numeric standards that also apply to lakes for the
protection of aquatic life and human health. These standards also apply to all other waters of the
state and are listed under the Class C rules. One of the major problems associated with lakes and
reservoirs is increasing eutrophication related to nutrient inputs. Several water quality
parameters help to describe the level of eutrophication.

For nutrient enrichment, one of the main causes of impacts to lakes and reservoirs, a more
holistic or weight of evidence approach is necessary since nutrient impacts are not always
reflected by the parameters sampled. For instance, some lakes have taste and odor problems
associated with particular algal species, yet these lakes do not have chlorophyll a concentrations
above 40 µg/l frequently enough to impair them based on the standard. In addition, each
reservoir possesses unique traits (watershed area, volume, depth, retention time, etc.) that
dramatically influence its water quality, but that cannot be evaluated through standards
comparisons. In such waterbodies, aquatic life may be Impaired even though a particular
indicator is below the standard. Where exceedances of surface water quality standards are not
sufficient to evaluate a lake or reservoir, the weight of evidence approach can take into
consideration indicators and parameters not in the standards to allow a more sound and robust
determination of water quality.

The weight of evidence approach uses the following sources of information to determine the
eutrophication (nutrient enrichment) level as a means of assessing lake use support in the aquatic
life category:

• Quantitative water quality parameters - dissolved oxygen, chlorophyll a, pH, etc.
• Algal bloom reports
• Fish kill reports
• Hydrologic and hydraulic characteristics – watershed size, lake volume, retention time,
volume loss, etc.
• Third party reports – citizens, water treatment plant operators, state agencies, etc.
¾ Taste and odor
¾ Sheens
¾ Odd colors
¾ Other aesthetic and safety considerations

In implementing the weight of evidence approach for eutrophication, more consideration is given
to parameters that have water quality standards (see table). Each parameter is assessed for
percent exceedance of the state standard. Parameters with sufficient (ten or more observations),
quality-assured observations are compared to surface water quality standards. When standards
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are exceeded in more than 10 percent of the assessment period, portions or all of the waterbody
are rated Impaired.

However, in many cases, the standards based approach is incapable of characterizing the overall
health of a reservoir. The eutrophication-related parameters and water quality indicators without
numeric standards are reviewed based on interpretation of the narrative standards in 15A NCAC
2B .0211(2) and (3).

A modification to lake use assessment is the evaluation and rating of a lake or reservoir by
assessment units (AUs). Each lake or reservoir may have one or more AU based on the
classification segments (DWQ index numbers). Each sampling date is considered one sample.
Multiple sampling locations within one AU are considered one sample. A minimum of ten
samples is needed to assess use support for any AU. Each AU with documented problems
(sufficient data, ambient data above standards, and supporting public data) will be rated as
Impaired while the other portions are rated as Supporting or Not Rated. The following table lists
the information considered during a lake/reservoir use assessment, as well as the criteria used to
evaluate that information.

References

Fels, J. 1997. North Carolina Watersheds Map. North Carolina State University Cooperative
Extension Service. Raleigh, NC.
North Carolina Department of Environment and Natural Resources (NCDENR). 2000a. Fish
Community Metric Re-Calibration and Biocriteria Development for the Inner Piedmont,
Foothills, and Eastern Mountains (Broad, Catawba, Savannah, and Yadkin River
Basins). September 22, 2000. Biological Assessment Unit. Environmental Sciences
Branch. Water Quality Section. Division of Water Quality. Raleigh, NC.
____. 2000b. Fish Community Metric Re-Calibration and Biocriteria Development for the
Outer Piedmont (Cape Fear, Neuse, Roanoke and Tar River Basins). October 17, 2000.
Ibid.
____. 2001a. Standard Operating Procedure. Biological Monitoring. Stream Fish
Community Assessment and Fish Tissue. Biological Assessment Unit. Environmental
Sciences Branch. Water Quality Section. Division of Water Quality. Raleigh, NC.
____. 2001b. Fish Community Metric Re-Calibration and Biocriteria Development for the
Western and Northern Mountains (French Broad, Hiwassee, Little Tennessee, New and
Watauga River Basins). January 05, 2001. Ibid.
USEPA. 2000. Stressor Identification Guidance Document. EPA/822/B-00/025. Office of
Water. Washington, DC.
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Lake/Reservoir Weight of Evidence Use Assessment for Aquatic Life Category
Assessment Type Criteria
EUTROPHICATION
Water Quality Standards (a minimum of 10 samples is required for use support assessment)
Chl a Above standard in >10% of samples.
DO Below or above standard in >10% of samples.
pH Below or above standard in >10% of samples.
Turbidity Above standard in >10% of samples.
% Total Dissolved Gases Above standard in >10% of samples.
Minor and infrequent excursions of temperature standards due to anthropogenic
activity. No impairment of species evident. Temperature
Metals (excluding copper,
iron and zinc) Above standard in >10% of samples.
Other Data
% Saturation DO >10% of samples above >120%
Algae Blooms during 2 or more sampling events in 1 year with historic blooms.
Fish Kills related to eutrophication.
Chemically/ For algal or macrophyte control - either chemicals or biologically by fish, etc. Biologically Treated
Documented sheens, discoloration, etc. - written complaint and follow-up by a state
agency. Aesthetics Complaints
Trophic Status Index (TSI) Increase of 2 trophic levels from one 5-year period to next.
Historic DWQ Data Conclusions from other reports and previous use support assessments.
AGPT Algal Growth Potential Test ≥5 mg/L
Limiting access to public ramps, docks, swimming areas; reducing access by fish and
other aquatic life to habitat; clogging intakes. Macrophytes
Taste and Odor Public complaints; Potential based on algal spp.
Sediments Clogging intakes - dredging program necessary.

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