Chapter 13

Chapter 13
Water Quality Stressors

13.1 Stressor and Sources Identification

13.1.1 Introduction - Stressors

Water quality stressors are identified when impacts have been noted to biological (fish and
benthic) communities or water quality standards have been violated. Stressors apply to one or
more use support categories and may be identified for Impaired, as well as Supporting but
impacted/noted waters. In many cases, identifying stressors is challenging because direct
measurements of the stressor may be difficult or prohibitively expensive. DWQ staff use field
observations from sample sites, special studies and data from ambient monitoring stations as well
as information from other agencies and the public to identify potential water quality stressors. It
is important to identify stressors and potential sources of stressors so that the limited resources of
water quality programs can be targeted to address the water quality problems. Specific aquatic
life stressors are defined in Section 13.2 and 13.3.

Most stressors to the biological community are composed of a complex grouping of many
different stressors that individually may not degrade water quality or aquatic habitat, but together
can severely degrade aquatic life. Sources of stressors are most often associated with land use in
a watershed, as well as the quality and quantity of any treated wastewater that may be entering a
stream. During naturally severe conditions such as droughts or floods, any individual stressor or
group of stressors may have more severe impacts to aquatic life than during normal climatic
conditions. The most common source of stressors is from altered watershed hydrology.

Stressors to recreation use include pathogenic indicators such as fecal coliform bacteria, escheria
coli (E. coli) and enterococci. In the fish consumption category, mercury is typically the noted
stressor. However, other substance may also result in the issuance of a fish consumption
advisory or advice by the NC Division of Health and Human Services (NCDHHS) such as dioxin
and selenium.

13.1.2 Introduction - Stressor Sources

As discussed above, sources of stressors most often come from a watershed where the hydrology
is altered enough to allow the stressor to be easily delivered to a stream during a rain event along
with unnaturally large amounts of water. DWQ identifies the source of a stressor as specifically
as possible depending on the amount of information available in a watershed. Most often the
source is based on the predominant land use in a watershed. Stressors sources identified in the
Roanoke River basin during this assessment period include urban or impervious surface areas,
residential and commercial development, road building, agriculture, and forestry/timber
harvesting. Point source discharges are also considered a water quality stressor source.

Chapter 13 – Water Quality Stressors 125
13.1.3 Overview of Stressors Identified in the Roanoke River Basin

The stressors noted below are summarized from all waters and for all use support categories.
Figure 18 identifies stressors noted for Impaired waters in the Roanoke River basin during the
most recent assessment period. The stressors noted in these figures may not be the sole reason
for an Impaired use support rating. Stressors that are listed due to standards violations may
require TMDL development for waters where these stressors are identified (dissolved oxygen,
turbidity, and fecal coliform bacteria). All waters in the basin are Impaired on an evaluated basis
in the fish consumption category where mercury is the stressor of concern (not depicted in the
graphs; 2,204 freshwater stream miles, 37,543 freshwater acres, and 1,467 saltwater acres).
Figures 19 and 20 identify stressors noted for Impacted waters in the Roanoke River basin during
the most recent assessment period (1999 to 2004). The stressors noted in these figures did not
necessarily result in an Impaired use support rating. However, these could lead to future
Impairment if corrective action is not taken. For specific discussions of stressors to Impaired or
Impacted waters refer to the subbasin chapters 1 through 10. Stressor definitions and impacts are
discussed in the remainder of this chapter.
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Figure 18 - Noted Stressors to Impaired Freshwater Streams Miles and Saltwater Acres in the
Roanoke River Basin.

126 Chapter 13 – Water Quality Stressors

Low DO
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Figure 19 - Noted Stressors to Impacted Freshwater Streams/Rivers in the Roanoke River Basin

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Figure 20 - Noted Stressors to Impacted Freshwater Acres in the Roanoke River Basin
Chapter 13 – Water Quality Stressors 127
13.1.4 Overview of Stressors Sources Identified in the Roanoke River Basin

The sources noted below are summarized for all waters and for all use support categories. Figure
21 and 22 identify sources of stressors noted for waters in the Roanoke River Basin during the
most recent assessment period. Refer to the subbasin chapters (Chapters 1 – 10) for a complete
listing and discussion of sources by stream.

WWTP NPDES
Agriculture
Land Clearing
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Figure 21 - Sources of Stressors Identified in the Roanoke River Basin (Freshwater Stream
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Wastewater treatment plants (WWTPs) were noted as a potential source to many of the
freshwater stream miles (155) and saltwater acres (1,476) in the Roanoke River basin. WWTPs
are just one of many sources that can contribute excess nutrients that may increase the potential
for algal blooms and cause exceedances of the chlorophyll a standard. This can include all
discharges upstream of the area of Impairment or noted impacts. Most of these impacts were
localized and based on permit violations. Better treatment technology and permit compliance
has greatly decreased the number of stream miles locally impacted by WWTPs.

Agriculture was noted as a potential source of water quality stressors when field observations
and watershed studies noted agriculture as the predominant land cover. In the Roanoke River
basin, the majority of agricultural land is cultivated crop. Impacts to streams from agricultural
activities can include excessive nutrient loading, pesticide and herbicide contamination, bacterial
contamination, and sedimentation. Agriculture was noted as a source of stressors in 23 stream
miles. Agriculture impacts and programs are discussed in more detail in Chapter 16.
128 Chapter 13 – Water Quality Stressors

Unknown WWTP NPDES
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Figure 22 - Sources of Stressors Identified in the Roanoke River Basin (Fresh and Saltwater
Acres)

Land clearing activities for residential and commercial development, for road/highway
construction as well as for timber harvest/clear cutting were noted as potential sources of water
quality stressors to 44 stream miles. Streams where land clearing is a noted source are likely to
be more heavily impacted in the future by increased development and impervious surfaces.
Impervious surface accounted for an additional 37 stream miles with noted impacts in the
Roanoke River basin. Refer to Chapter 12 for more information related to population growth
and land cover changes and its potential impacts on water quality.

In the Roanoke River basin there are 11 major impoundments. These are used as water supply
reservoirs as well as for flood control and hydropower production. Impacts to water quality can
also be magnified by the presence of a reservoir. Dams significantly slow the flow of water and
create conditions not present in riverine systems. These conditions increase nutrient availability
and give algae more time to grow. In theory, a reservoir may suffer the symptoms of excessive
nutrient and sediment inputs, while a river receiving the same level of pollutants may not. The
way in which these reservoirs/lakes are managed influence the quality of the water in the basin.
For example, the amount of water released into the lower Roanoke River influences the
extensive floodplain. As water is released from the floodplain back into the Roanoke River
mainstem it carries low dissolved oxygen water as well as a high BOD material. This can result
in dissolved oxygen sags, which impacts the water quality and aquatic health (i.e., fish kills) in
the river.

Stressor sources could not be identified for 225 stream miles in the Roanoke River basin. These
stream segments may be in areas where sources could not be identified during field observations,
but the streams had noted impacts (e.g., habitat degradation). DWQ and the local agencies will
work to identify potential sources for these stream segments during the next basinwide cycle.

Chapter 13 – Water Quality Stressors 129
13.2 Aquatic Life Stressors - Habitat Degradation

13.2.1 Introduction and Overview

Instream habitat degradation is identified as a notable reduction in habitat diversity or a negative
change in habitat. This term may include sedimentation, lack of organic (woody and leaf)
habitats and channelization. These stressors to aquatic insect and fish communities can be
caused by many different land use activities and less often by discharges of treated wastewater.
In the Roanoke River basin, 60 stream miles are
Impaired where at least one form of habitat
degradation has been identified as the stressor.
There is an additional 163 stream miles where
habitat degradation is a noted impact to water
quality. Many of the stressors discussed below
are either directly caused by or are a symptom of
altered watershed hydrology. The altered
hydrology increases both sources of stressors and
delivery of stressors to receiving waters. Refer to
the subbasin chapters (Chapters 1-10) for more
information on the types of habitat degradation
noted at sample locations and in watershed
studies.

Good instream habitat is necessary for aquatic life
to survive and reproduce. Streams that typically
show signs of habitat degradation are in
watersheds that have a large amount of land-
disturbing activities (construction, mining, timber
harvest and agricultural activities) or a large
percentage of impervious surface area. A watershed in which most of the riparian vegetation has
been removed from streams or channelization has occurred also exhibits instream habitat
degradation. Streams that receive a discharge quantity that is much greater than the natural flow
in the stream often have degraded habitat as well. All of these activities result in altered
watershed hydrology.
Some Best Management Practices

Agriculture
• No till or conservation tillage practices
• Strip cropping and contour farming
• Leaving natural buffer areas around
small streams and rivers

Construction
• Using phased grading/seeding plans
• Limiting time of exposure
• Planting temporary ground cover
• Using sediment basins and traps

Forestry
• Controlling runoff from logging roads
• Replanting vegetation on disturbed areas
• Leaving natural buffer areas around
small streams and rivers
• Avoid stream crossings during forest
operations

Quantifying amounts of habitat degradation is difficult in most cases. To assess instream habitat
degradation in most streams would require extensive technical and monetary resources and even
more resources to restore the stream. Although DWQ and other agencies are starting to address
this issue, local efforts are needed to prevent further instream habitat degradation and to restore
streams that have been Impaired by activities that cause habitat degradation. As point sources
become less of a source of water quality impairment, nonpoint sources that pollute water and
cause habitat degradation need to be addressed to further improve water quality in North
Carolina’s streams and rivers.

130 Chapter 13 – Water Quality Stressors

13.2.2 Sedimentation

Sedimentation is a natural process that is important to the maintenance of diverse aquatic
habitats. Overloading of sediment in the form of sand, silt and clay particles fills pools and
covers or embeds riffles that are vital aquatic insect and fish habitats. A diversity of these
habitats is important for maintenance of biological integrity. Suspended sediment can decrease
primary productivity (i.e., photosynthesis) by shading sunlight from aquatic plants, affecting the
overall productivity of a stream system. Suspended sediment also has several effects on various
fish species including avoidance and redistribution, reduced feeding efficiency, and therefore,
reduced growth by some species, respiratory problems, reduced tolerance to diseases and
toxicants, and increased physiological stress (Roell, 1999). Sediment filling rivers, streams and
reservoirs also decreases their storage volume and increases the frequency of floods (NCDENR-
DLR, 1998). Suspended sediment also increases the cost of treating municipal drinking water.
Sediment overloading to many streams has reduced biological diversity to the point of the stream
being Impaired for aquatic life.

Sediment is the earthen material that is dislodged and transported from its original location by
the erosive forces of wind, water or ice. The redeposition of the sediment is sedimentation. The
grading and tilling of surfaces for construction of roads and buildings, crop production, livestock
grazing and timber harvesting contribute to accelerated erosion rates by loosening the soils
thereby allowing more soil than usual to become detached and transported by wind or water.

Streambank erosion, caused by very high stormwater flows after rain events, is another source of
sediment overloading. Watersheds with large amounts of impervious surfaces transport water to
streams very rapidly and at higher volumes than occurs in watersheds with little impervious
surfaces. In many urban areas, stormwater is delivered directly by storm sewers. This high
volume and velocity of water after rain events undercuts streambanks causing bank failure and
large amounts of sediment to be deposited directly into the stream. Many urban streams are
adversely impacted by sediment overloading from the watershed as well as from the
streambanks.

Sedimentation can be controlled during most land-disturbing activities by using appropriate
BMPs. Substantial amounts of erosion can be prevented by planning to minimize the amount
and time that land is exposed during land-disturbing activities and by minimizing impervious
surface area and direct stormwater outlets to streams. Refer to chapter 14 for more information
on programs designed to reduce sedimentation.

Land Clearing Activities
Erosion and sedimentation can be controlled during most land-disturbing activities by using
appropriate BMPs. In fact, substantial amounts of erosion can be prevented by planning to
minimize the (1) amount and (2) time the land is exposed. DWQ’s role in sediment control is to
work cooperatively with those agencies that administer sediment control programs in order to
maximize the effectiveness of the programs and to protect water quality. Where programs are
not effective, as evidenced by a violation of instream water quality standards, and where DWQ
can identify a source, then appropriate enforcement action can be taken. Generally, this entails
requiring the landowner or responsible party to install acceptable BMPs.

Chapter 13 – Water Quality Stressors 131
As a result of new stormwater rules enacted by EPA in 1999, construction or land development
activities that disturb one acre or more are required to obtain a NPDES stormwater permit. An
erosion and sediment control plan must also be developed and approved for these sites under the
state’s Sedimentation Pollution Control Act (SPCA) administered by the NC Division of Land
Resources. Site disturbances of less than one acre are required to use BMPs, but an approved
plan is not required.

Forestry operations in North Carolina are subject to regulation under the Sedimentation Pollution
Control Act of 1973 (G.S. Chapter 113A, Article 4 referred to as "SPCA"). However, forestry
operations may be exempted from the permit requirements in the SPCA, if the operations meet
compliance standards outlined in the Forest Practices Guidelines Related to Water Quality (15A
NCAC 1I .0101-.0209, referred to as "FPGs") and General Statutes regarding stream obstruction
(G.S. 77-13 and G.S. 77-14). More information on forestry in the Roanoke River basin is
available in Chapter 17 and on the Water Quality Section of the Division of Forest Resources
(DFR) website at http://www.dfr.state.nc.us.

For agricultural activities that are not subject to the SPCA, sediment controls are carried out on a
voluntary basis through programs administered by several different agencies (see Appendix VIII
for further information).

Stronger Rules for Sediment Control
The Division of Land Resources (DLR) has the primary responsibility for assuring that erosion is
minimized and sedimentation is reduced during construction activities. In November 2005, the
NC Sedimentation Control Commission adopted significant changes for strengthening the
Erosion and Sedimentation Control Program (NCDENR-DLR, November 2005) as follows:

ƒ allows state and local erosion and sediment control programs to require a pre-
construction conference when one is deemed necessary;
ƒ surfaces must be non-erosive and stable within 15 working days or 90 calendar days after
completion of the activity;
ƒ graded slopes must be vegetated or otherwise stabilized within 21 calendar days of
completion of a phase of grading;
ƒ provides that no person may initiate a land-disturbing activity until notifying the agency
that issued the plan approval of the date the activity will begin; and
ƒ allows assessment penalties for significant violations upon initial issuance of a Notice of
Violation (NOV).

Additionally, during its 1999 session, the NC General Assembly passed House Bill 1098 to
strengthen the Sediment Pollution Control Act of 1973 (SPCA). The bill made the following
changes to the Act (NCDENR-DLR, July-September 1999):

ƒ increases the maximum civil penalty for violating the SPCA from $500 to $5000 per day;
ƒ provides that a person may be assessed a civil penalty from the date a violation is
detected if the deadline stated in the Notice of Violation is not met;
ƒ provides that approval of an erosion control plan is conditioned on compliance with
federal and state water quality laws, regulations and rules;
132 Chapter 13 – Water Quality Stressors

ƒ provides that any erosion control plan that involves using ditches for the purpose of
dewatering or lowering the water table must be forwarded to the Director of DWQ;
ƒ amends the General Statutes governing licensing of general contractors to provide that
the State Licensing Board for General Contractors shall test applicants’ knowledge of
requirements of the SPCA and rules adopted pursuant to the Act; and
ƒ removes a cap on the percentage of administrative costs that may be recovered through
plan review fees.

For information on North Carolina’s Erosion and Sedimentation Control Program or to report
erosion and sedimentation problems, visit the new website at http://www.dlr.enr.state.nc.us/ or
you may call the NC Division of Land Resources, Land Quality Section at [phone].

Recent Review of Sediment Control Research
Two of the most commonly used sediment control devices are silt fences and sediment basins.
In 2005, DLR revised the requirements for these and other BMP’s to make them more efficient
at trapping and containing sediment on site. These revisions are based upon research done by
NC State University, NC Department of Transportation, and other professional engineers.

Currently, sediment basins are designed to have a minimum volume of 1,800 cubic feet per acre
of drainage area and a surface area of 325 square feet per cfs of Q10 peak flow. Sediment basins
are designed to temporarily pool runoff water to allow sediment to settle before the water is
discharged. Unfortunately, they are usually not very efficient due to high turbulence, which
takes the runoff quickly to the outlet with little interaction with most of the basin. Per the 2005
revisions, three baffles are now required for a basin of this size. Baffles improve the rate of
sediment retention by distributing the flow and reducing turbulence, allowing the baffles to
capture soil particles 50 percent smaller than those captured without the use of baffles. Baffles
also lower the chances of short-circuiting. To further improve sediment retention, the use of a
skimmer attached at the bottom of a riser pipe is suggested. Skimmers are a dewatering
mechanism that pulls water from the top of the water column. After the runoff has passed
through the baffles, the sediment has had time to drop to the bottom of the water column.
Therefore, the overflow water at the top will have the least amount of sediment particles.

Sediment fences are also used very frequently and are inefficient at capturing sediment before it
leaves the site. This BMP is overused and, in most cases, is installed improperly. For these
reasons DLR has revised the requirements to make it more efficient. For better support, the use
of steel posts in the place of wooden posts is now required. The fence should be anchored by
placing 12 inches of washed stone on the toe of the fence that should be facing uphill. Another
method to anchor the fence is to slice the fabric into the ground. This method uses specially
designed equipment to insert the fabric into a cut sliced in the ground with a disc. By slicing the
fabric into the ground, excavating a trench can be avoided. Sediment fences require that
installation is done properly and regular maintenance is scheduled.

Other new technologies such as applications of flocculants, rolled erosion control products,
hardware cloth and gravel inlet protection, rock pipe inlet protection, and rock doughnut inlet
protection are specified in the North Carolina Erosion and Sediment Control Planning and
Design Manual, which can be found at http://dlr.enr.state.nc.us/pages/manualsandvideos.html.
These technologies can significantly increase efficiency of trapping sediment on land disturbing
Chapter 13 – Water Quality Stressors 133
sites. Research funded by the Sedimentation Control Commission (SCC) and the NC
Department of Transportation (NCDOT) at NCSU demonstrated that turbidity levels could
approach the current turbidity standard of 50 NTU (for waters not classified Tr) in runoff if these
devices are used. However, the most important factor in reducing sedimentation is timely cover
of cleared land with mulch matting or netting that are adequately tacked. It has been
conclusively proven that use of ground cover (temporary or permanent) dramatically reduces
erosion rates.

13.2.3 Loss of Riparian Vegetation and Organic Aquatic Microhabitats

During the 2004 basinwide sampling, DWQ biologists reported degradation of aquatic
communities at numerous sites throughout the Roanoke River basin in association with narrow
or nonexistent zones of native riparian vegetation. Riparian vegetation loss was common in rural
and residential areas as well as in urban areas. The loss of riparian vegetation and subsequent
reduction of organic aquatic habitats is caused by removal of riparian areas most commonly by
land clearing for development, field agriculture, and pastureland as well as forestry and by
grazing animals. Instream organic habitat removal has also been caused by de-snagging
activities.

Removing trees, shrubs and other vegetation to plant grass or place rock (also known as riprap)
along the bank of a river or stream degrades water quality. Removing riparian vegetation
eliminates habitat for aquatic macroinvertebrates that are food for trout and other fish. Rocks or
concrete lining a bank absorb the sun’s heat and warm the water. Some fish require cooler water
temperatures as well as the higher levels of dissolved oxygen cooler water provides. Trees,
shrubs and other native vegetation cool the water by shading it. Straightening a stream, clearing
streambank vegetation, and lining the banks with grass or rock severely impact the habitat that
aquatic insects and fish need to survive.

Establishing, conserving and managing streamside vegetation (riparian buffer) is one of the most
economical and efficient BMPs. Forested buffers in particular provide a variety of benefits
including filtering runoff and taking up nutrients, moderating water temperature, preventing
erosion and loss of land, providing flood control and helping to moderate streamflow, and
providing food and habitat for both aquatic and terrestrial wildlife. To obtain a free copy of
DWQ’s Buffers for Clean Water brochure, call [phone], ext. 558.

Organic microhabitat (leafpacks, sticks and large wood) and edge habitat (root banks and
undercut banks) play very important roles in a stream ecosystem. Organic matter in the form of
leaves, sticks and other materials serve as the base of the food web for small streams.
Additionally, these microhabitats serve as special niches for different species of benthic
macroinvertebrates, providing food and/or habitat. For example, many stoneflies are found
almost exclusively in leafpacks and on small sticks. Some beetle species prefer edge habitat,
such as undercut banks. If these microhabitat types are not present, there is no place for these
specialized macroinvertebrates to live and feed. The absence of these microhabitats in some
streams in the Roanoke River basin is directly related to the absence of riparian vegetation.
Organic microhabitats are critical to headwater streams, the health of which is linked to the
health of the entire downstream watershed.

134 Chapter 13 – Water Quality Stressors

13.2.4 Channelization

Channelization refers to the physical alteration of
naturally occurring stream and riverbeds.
Channelization is caused by mechanical straightening
of channels or by hydraulic overloading during rain
events. Often streams in urban areas become
channelized as part of the development process in
essence using the stream channels as stormwater
conveyances. Although increased flooding, bank
erosion and channel instability often occur in
downstream areas after channelization has occurred,
flood control, reduced erosion, increased usable land
area, greater navigability and more efficient drainage
are frequently cited as the objectives of
channelization projects (McGarvey, 1996).

Typical Channel Modifications

• Removal of any obstructions,
natural or artificial, that inhibit a
stream’s capacity to convey
water (clearing and snagging).
• Widening, deepening or
straightening of the channel to
maximize conveyance of water.
• Lining the bed or banks with
rock or other resistant materials.

Channelization reduces the sinuosity of streams greatly increasing the velocity of water flowing
down these streams. Direct or immediate biological effects of channelization include injury and
mortality of benthic macroinvertebrates, fish, shellfish/mussels and other wildlife populations, as
well as habitat loss. Indirect biological effects include changes in benthic macroinvertebrate,
fish and wildlife community structures, favoring species that are more tolerant of or better
adapted to the altered habitat (McGarvey, 1996).

Restoration or recovery of channelized streams may occur through processes, both naturally and
artificially induced. In general, streams that have not been excessively stressed by the
channelization process can be expected to return to their original forms. However, streams that
have been extensively altered may establish a new, artificial equilibrium (especially when the
channelized streambed has been hardened). In such cases, the stream may enter a vicious cycle
of erosion and continuous entrenchment. Once the benefits of a channelization project become
outweighed by the costs, both in money and environmental integrity, channel restoration efforts
are likely to be taken (McGarvey, 1996).

Channelization of streams within the continental United States is extensive and promises to
become even more so as urban development continues. Overall estimates of lost or altered
riparian habitats within US streams are as high as 70 percent. Unfortunately, the dynamic nature
of stream ecosystems makes it difficult (if not impossible) to quantitatively predict the effects of
channelization (McGarvey, 1996). Channelization has occurred historically in parts of the
Roanoke River basin and continues to occur in some watersheds, especially in small headwater
streams.

13.2.5 Recommendations for Reducing Habitat Degradation

In March 2002, the Environmental Management Commission (EMC) sent a letter to the
Sedimentation Control Commission (SCC) outlining seven recommendations for improving
erosion and sedimentation control, based on a comprehensive performance review of the
Chapter 13 – Water Quality Stressors 135
turbidity standard conducted in 2001 by DWQ staff. Specifically, the recommendations are that
the EMC and SCC:

1. evaluate, in consultation with the Attorney General’s Office, whether statutory
authority is adequate to mandate temporary ground cover over a percentage of the
uncovered area at a construction site within a specific time after the initial disturbance
of the area. If it is found that statutory authority does not exist, then the EMC and
SCC should prepare resolutions for the General Assembly supporting new legislation
to this effect;

2. prepare resolutions supporting new legislation to increase the maximum penalty
allowed in the Sedimentation Pollution Control Act from $5,000 to $25,000 for the
initial response to a noncompliant site;

3. jointly support a review of the existing Erosion and Sediment Control Planning and
Design Manual by DLR. This review should include, but not be limited to, a redesign
of the minimum specifications for sedimentation basins;

4. evaluate, in consultation with the Attorney General’s Office, whether the statutory
authority is adequate for effective use of the "Stop Work Order" tool and, if found not
to be adequate, to prepare resolutions for the General Assembly supporting new
legislation that will enable staff to more effectively use the "Stop Work Order" tool;

5. support increased research into and experimentation with the use of polyacrylamides
(PAMs) and other innovative soil stabilization and turbidity reduction techniques;

6. jointly support and encourage the awarding of significant monetary penalties for all
activities found to be in violation of their Stormwater Construction General Permit,
their Erosion and Sediment Control Plan, or the turbidity standard; and

7. hold those individuals who cause serious degradation of the environment through
excessive turbidity and sedimentation ultimately responsible for restoration of the
area.

DWQ will continue to work cooperatively with DLR and local programs that administer
sediment control in order to maximize the effectiveness of the programs and to take appropriate
enforcement action when necessary to protect or restore water quality. However, more voluntary
implementation of BMPs is needed for activities that are not subject to these rules in order to
substantially reduce the amount of widespread sedimentation present in the Roanoke River basin.
Additionally, more public education is needed basinwide to educate landowners about the value
of riparian vegetation along small tributaries and the impacts of sedimentation to aquatic life.

Funding is available through numerous federal and state programs for landowners to restore
and/or protect riparian buffer zones along fields or pastures, develop alternative watering sources
for livestock, and fence animals out of streams (refer to Chapters 11 and 16). EPA’s Catalog of
Federal Funding Sources for Watershed Protection (Document 841-B-99-003) outlines some of
these and other programs aimed at protecting water quality. A copy may be obtained by calling
136 Chapter 13 – Water Quality Stressors

the National Center for Environmental Publications and Information at [phone] or by
visiting the website at http://www.epa.gov/OWOW/watershed/wacademy/fund.html. Local
contacts for various state and local agencies are listed in Appendix VIII.

13.3 Aquatic Life Stressors – Water Quality Standard Violations

13.3.1 Introduction and Overview

In addition to the habitat stressors discussed in the previous section, the stressors discussed
below are identified by water quality standards. These are usually direct measures of water
quality parameters from ambient water quality monitoring stations. The water quality standards
are designed to protect aquatic life. As with habitat degradation, altered watershed hydrology
greatly increases the sources of these stressors as well as delivery of the stressors to the receiving
waters. The following are water quality standards that were identified for waters with noted
impacts. Refer to the subbasin chapters (Chapter 1 – 10) for more information on the affected
waters.

13.3.2 Low Dissolved Oxygen

Maintaining an adequate amount of dissolved oxygen (DO) is critical to the survival of aquatic
life and to the general health of surface waters. A number of factors influence DO
concentrations including water temperature, depth and turbulence. Additionally, in the Roanoke
River basin, a large floodplain drainage system and flow management from upstream
impoundments also influences DO. Oxygen-consuming wastes such as decomposing organic
matter and some chemicals can reduce DO levels in surface water through biological activity and
chemical reactions. NPDES permits for wastewater discharges set limits on certain parameters
in order to control the effects that oxygen depletion can have in receiving waters.

Waters are Impaired for aquatic life when greater than 10 percent of samples collected exceed
the state DO standard and at least 10 samples were collected. The DO water quality standard for
Class C waters is not less than a daily average of 5 mg/l with a minimum instantaneous value of
not less than 4 mg/l. Swamp waters (supplemental Class Sw) may have lower values if caused
by natural conditions. In the Roanoke River basin during this assessment period, there were 39
stream miles that are Impaired where low DO is a stressor. There were also over 30 freshwater
stream miles where low DO is a stressor for waters with noted impacts, although many of these
streams are in swampy areas where low DO levels are likely from natural sources.

13.3.3 Turbidity

The major sources of elevated turbidity are from agriculture and land clearing activities as well
as from urban stormwater. These sources also add other pollutants beside suspended
particulates. Waters are Impaired for aquatic life when greater than 10 percent of samples
collected exceed the state turbidity standard and at least 10 samples were collected. The
turbidity water quality standard for Class C waters are not to exceed 50 Nephelometric Turbidity
Units (NTU). However, trout waters (Tr) are not to exceed 10 NTUs. In the Roanoke River
basin during this assessment period, there were 55 stream miles Impaired where turbidity is a
Chapter 13 – Water Quality Stressors 137
stressor; of these 11.6 were trout stream miles. There were also 4 freshwater stream miles and
362 freshwater acres that are impacted where turbidity is a stressor.

13.3.4 Toxic Impacts

Toxic impacts are noted as a stressor during biological monitoring or when identified from
NPDES compliance reports. Waters are not impaired due to toxic impacts, but toxic impacts can
be noted as a potential stressor on the system, which can ultimately result in impairment. During
the most recent assessment period, toxic impacts were noted on 25.5 stream miles. Of these, 9.2
miles of the Dan River and 4.5 miles of Marlowe Creek are noted as having toxic impacts due to
WWTP whole effluent toxicity (WET) test failures in the last two years of the assessment period
(Chapter 1 and 5). Toxic impacts were also noted as a stressor for 11.8 miles of the Little Island
Creek due to the watershed being encompassed by a defunct Tungsten mine (Chapter 6).

13.3.5 Other Aquatic Life Stressors

Several noted stressors to aquatic life are identified from WWTP NPDES compliance reports.
Waters are not Impaired due to permit violations, however these violation can be noted as a
potential stressor on the system. In the Roanoke River basin during this assessment period, there
were 59, 11, 4, and 1 stream mile impacted where Total Suspended Solids (TSS), ammonia,
chlorine and pH respectively were the noted stressors.

13.4 Recreation Stressor

13.4.1 Fecal Coliform Bacteria

Water quality standards for fecal coliform bacteria are intended to ensure safe use of waters for
recreation (refer to Administrative Code Section 15A NCAC 2B .0200). The North Carolina
fecal coliform standard for freshwater is 200 colonies/100ml based on the geometric mean of at
least five consecutive samples taken during a 30-day period and not to exceed 400
colonies/100ml in more than 20 percent of the samples during the same period. In the Roanoke
River basin, there were 43.3 stream miles where this standard was exceeded. These waters are
Impaired for recreation. An additional 8 stream miles exceeded the fecal coliform bacteria
screening criteria. These waters were not intensively sampled to assess the standard as described
above, but had either a geometric mean above 200 colonies/100ml and/or 20 percent of samples
exceeded 400 colonies/100ml over the five-year assessment period. These waters are discussed
in the subbasin chapters. A total of 230.6 stream miles were monitored for recreation, of these
only 111 stream miles are class B waters.

As stated above, there were 43 stream miles Impaired due to fecal coliform bacteria standard
violations. There were an additional 18 Impaired stream miles that were noted as having fecal
coliform bacteria as a noted stressor and another 26 stream miles for waters with noted impacts.
These come from ambient data as well as from WWTP NPDES compliance reports.

A number of factors beyond the control of any state regulatory agency contribute to elevated
levels of disease-causing bacteria. Therefore, the state does not encourage swimming in surface
waters. To assure that waters are safe for swimming indicates a need to test waters for
138 Chapter 13 – Water Quality Stressors

pathogenic bacteria. Although fecal coliform standards have been used to indicate the
microbiological quality of surface waters for swimming for more than 50 years, the value of this
indicator is often questioned. Evidence collected during the past several decades suggests that
the coliform group may not adequately indicate the presence of pathogenic viruses or parasites in
water.

Fecal coliform bacteria live in the digestive tract of warm-blooded animals (humans as well as
other mammals) and are excreted in their waste. Fecal coliform bacteria generally do not pose a
danger to most people or animals. However, where fecal coliform are present, disease-causing
bacteria may also be present and water that is polluted by
human or animal waste can harbor other pathogens that
may threaten human health.

The presence of disease-causing bacteria tends to affect
humans more than aquatic creatures. High levels of fecal
coliform bacteria can indicate high levels of sewage or
animal wastes that could make water unsafe for human
contact (swimming). Fecal coliform bacteria and other
potential pathogens associated with waste from warm-
blooded animals are not harmful to fish and aquatic
insects. However, high levels of fecal coliform bacteria
may indicate contamination that increases the risk of
contact with harmful pathogens in surface waters.
Pathogens associated with fecal coliform bacteria can
cause diarrhea, dysentery, cholera and typhoid fever in
humans. Some pathogens can also cause infection in open wounds.
Sources of Fecal Coliform
in Surface Waters

• Urban stormwater
• Wild animals and domestic pets
• Improperly designed or managed
animal waste facilities
• Livestock with direct access to
streams
• Improperly treated discharges of
domestic wastewater, including
leaking or failing septic systems
and straight pipes

Under favorable conditions, fecal coliform bacteria can survive in bottom sediments for an
extended period (Howell et al., 1996; Sherer et al., 1992; Schillinger and Gannon, 1985).
Therefore, concentrations of bacteria measured in the water column can reflect both recent inputs
as well as the resuspension of older inputs.

Reducing fecal coliform bacteria in wastewater requires a disinfection process, which typically
involves the use of chlorine and other disinfectants. Although these materials may kill the fecal
coliform bacteria and other pathogenic disease-causing bacteria, they also kill bacteria essential
to the proper balance of the aquatic environment, and thereby, endanger the survival of species
dependent on those bacteria.

The detection and identification of specific pathogenic bacteria, viruses and parasites such as
Giardia, Cryptosporidium and Shigella are expensive, and results are generally difficult to
reproduce quantitatively. Also, to ensure the water is safe for swimming would require a whole
suite of tests for many organisms, as the presence/absence of one organism would not document
the presence/absence of another. This type of testing program is not possible due to resource
constraints.

Chapter 13 – Water Quality Stressors 139
13.5 Fish Consumption Stressors

The presence and accumulation of mercury in North Carolina’s aquatic environment are similar
to contamination observed throughout the country. Mercury has a complex life in the
environment, moving from the atmosphere to soil, to surface water, and eventually, to biological
organisms. Mercury circulates in the environment as a result of natural and human
(anthropogenic) activities. A dominant pathway for mercury in the environment is through the
atmosphere. Mercury emitted from industrial and municipal stacks into the ambient air can
circulate around the globe. At any point, mercury may then be deposited onto land and water.
Once in the water, mercury can accumulate in fish tissue and humans. Mercury is also
commonly found in wastewater; however, mercury in wastewater is typically not at levels that
could be solely responsible for elevated fish levels

Fish is part of a healthy diet and an excellent source of protein and other essential nutrients.
However, nearly all fish and shellfish contain trace levels of mercury. The risks from mercury in
fish depend on the amount of fish eaten and the levels of mercury in the fish. In March 2003, the
Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) issued a
joint consumer advisory for mercury in fish and shellfish. The advice is for women who might
become pregnant, women who are pregnant, nursing mothers, and young children. Aside from
being issued jointly by two federal agencies, this advisory is important because it emphasizes
positive benefits of eating fish and gives examples of commonly eaten fish that are low in
mercury. In the past, the FDA issued an advisory on consumption of commercially caught fish,
while the EPA issued advice on recreationally caught fish.

By following these three recommendations for selecting and eating fish, women and young
children will receive the benefits of eating fish and shellfish and be confident that they have
reduced their exposure to the harmful effects of mercury. These recommendations are:

• Do not eat shark, swordfish, king mackerel, or tilefish. They contain high levels of
mercury.

• Eat up to 12 ounces (two average meals) a week of a variety of fish and shellfish that are
lower in mercury. Five of the most commonly eaten fish that are low in mercury are shrimp,
canned light tuna, salmon, pollock, and catfish. Another commonly eaten fish, albacore
(“white”) tuna, has more mercury than canned light tuna. So, when choosing your two meals
of fish, you may eat up to 6 ounces (one average meal) of albacore per week.

• Check local advisories about the safety of fish caught by family and friends in your local
lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average
meal) per week of fish you catch from local waters. Don’t consume any other fish during
that week.

For more detailed information, visit EPA’s website at http://www.epa.gov/waterscience/fish/ or visit
the FDA at http://www.cfsan.fda.gov/seafood1.html. The FDA’s food information toll-free phone
number is 1-888-SAFEFOOD.

140 Chapter 13 – Water Quality Stressors

The NC Department of Health and Human Services (NCDHHS) also issues fish consumption
advisories and advice for those fish species and areas at risk for contaminants. NCDHHS
notifies people to either limit consumption or avoid eating certain kinds of fish. While most
freshwater fish in North Carolina contain very low levels of mercury and are safe to eat, several
species have been found to have higher levels. More information regarding use support
assessment methodology related to fish consumption advisories and advice can be found in
Appendix X.

Due to high levels of mercury in seventeen saltwater and five freshwater fish species, the
NCDHHS offers the following health advice (updated March 31, 2006).

Women of childbearing age (15 to 44 years), pregnant women, nursing women, and
children under 15:

• Do not eat the following ocean fish: almaco jack, banded rudderfish, canned
white tuna (albacore tuna), cobia, crevalle jack, greater amberjack, south
Atlantic grouper (gag, scamp, red, and snowy), king mackerel, ladyfish, little
tunny, marlin, orange roughy, shark, Spanish mackerel, swordfish, tilefish, or
tuna (fresh or frozen).
• Do not eat the following freshwater fish: bowfin (blackfish), catfish (caught
wild), chain pickerel (jack fish), or warmouth caught in North Carolina waters
south and east of Interstate 85.
• Do not eat largemouth bass caught in North Carolina waters (statewide).
• Eat up to two meals per week of other fish. A meal is 6 ounces of cooked fish
for adults or 2 ounces of cooked fish for children under 15.

All other people:

ƒ Eat no more than one meal (6 ounces) per week of ocean and/or freshwater fish
listed above. These fish are often high in mercury.
ƒ Eat up to four meals per week of other fish. A meal is 6 ounces of cooked fish
for adults or 2 ounces of cooked fish for children under 15.

For more information and detailed listing of site-specific advisories, visit the NCDHHS website
at http://www.schs.state.nc.us/epi/fish/current.html or call [phone].

Chapter 13 – Water Quality Stressors 141
142 Chapter 13 – Water Quality Stressors