Chapter 10 Stressors

Chapter 10
Water Quality Stressors

10.1 Stressor Identification

10.1.1 Introduction and Overview

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 category 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 to
identify stressors. It is important to identify stressors and potential sources of stressors so that
water quality programs can target limited resources to address these issues.

Most stressors to the biological community are a complex grouping of many different stressors.
Individually, they may not degrade water quality or aquatic habitat, but together they can
severely degrade both water quality and aquatic habitat. 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.

10.1.2 Stressor Sources

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. 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 French Broad River basin during this assessment period
include urban or impervious surface areas, construction sites, road building, agriculture, and
forestry. Point source discharges are also considered a water quality stressor source.

10.2 Habitat Degradation

Instream habitat degradation is identified in the use support summary (Appendix X) where there
is a notable reduction in habitat diversity or a negative change in habitat. This term includes
sedimentation, bank erosion, channelization, lack of riparian vegetation, loss of pools or riffles,
loss of woody habitat, and streambed scour. 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
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harvest and agricultural activities) or a large percentage of impervious surfaces. 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.
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
Determining the cause and quantifying amounts of
habitat degradation is very difficult in most cases.
To assess instream habitat degradation in most
streams would require extensive technical and
monetary resources and perhaps 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.

10.2.1 Sedimentation

Introduction
Soil erosion, transport and redeposition are among the most essential natural processes occurring
in watersheds. However, land-disturbing activities such as the construction of roads and
buildings, crop production, livestock grazing and timber harvesting can accelerate erosion rates
by causing more soil than usual to be detached and moved by water. If best management
practices (BMPs) are not used effectively, accelerated erosion can strip the land of its topsoil,
decreasing soil productivity and causing sedimentation in streams and rivers (NCDEHNR-DLR,
1998). Sedimentation is the process by which eroded soil is deposited into waters. Sediment
that accumulates on the bottom of streams and rivers smothers aquatic insects that fish feed upon
and buries fish habitat that is vital to reproduction. Sediment filling rivers and streams decreases
their storage volume and increases the frequency of floods (NCDEHNR-DLR, 1998).

Suspended sediment can decrease primary productivity (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 impairment,
reduced tolerance to diseases and toxicants, and increased physiological stress (Roell, June
1999). Suspended sediment also increases the cost of treating municipal drinking water.

One of the most commonly noted types of habitat degradation in the French Broad River basin
was a result of sediment entering streams from adjacent land uses. During 2002 basinwide
monitoring, DWQ aquatic biologists reported streambank erosion and sedimentation throughout
the French Broad River basin. Lower bioclassification ratings were assigned because of
sedimentation; bottom substrate was embedded by silt and/or pools were partially filled with
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sediment. Unstable and/or undercut (eroding) streambanks were also noted in explanation of
lower ratings (NCDENR-DWQ, June 2003b).

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.

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 French Broad River basin is
available in Chapter 12 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 February 1999, the
NC Sedimentation Control Commission adopted significant changes for strengthening the
Erosion and Sedimentation Control Program (NCDEHNR-DLR, July-September 1999) as
follows:

ƒ Allows state and local erosion and sediment control programs to require a pre-
construction conference when one is deemed necessary.
ƒ Reduces the number of days allowed for establishment of ground cover from 30
working days to 15 working days and from 120 calendar days to 90 calendar
days. (Stabilization must now be complete in 15 working days or 90 calendar
days, whichever period is shorter.)
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.
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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 (NCDEHNR-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.
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.
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
The two most popular sediment control devices are silt fences and sediment basins. In 2001,
DWQ staff conducted a review of peer-reviewed research publications and consulted with
experts at NC State University (NCSU) to investigate the effectiveness of current sediment and
erosion control practices. In addition, engineering calculations have been conducted to obtain
theoretical effectiveness of sediment basins and silt fences. Research conducted in North
Carolina showed that construction sites in North Carolina produce 10 to 188 tons per acre per
year of sediment. Such wide variation might be attributed to the significant spatial and temporal
differences in rainfall intensity and duration, soil characteristics, slope, and the type of soil cover.
DLR currently uses the assumption that (on average) construction sites produce 84 tons/acre-
year. For comparison, erosion in undisturbed natural systems is only 0.1-0.2 tons/acre-year.

Currently, sediment basins are designed to have 1,800 cubic feet of storage space for each acre of
disturbed land and a surface area based on the flow from all areas draining to the sediment basin.
Based on the reference review and consultation, DWQ has concluded that these basins have
numerous deficiencies, including:

ƒ Insufficient volume.
ƒ Inadequate cleaning frequency. (In many cases, effectiveness of the basins is
significantly reduced because they are not maintained.)
ƒ Short-circuiting. (In many cases, inlet and outlet in basins are constructed in very
close proximity, which results in a shorter than predicted retention time.)
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ƒ Water to be drained from the surface where concentration of the sediment is the
lowest.
ƒ Basins need to be designed with consideration of total drainage area. Water from
undisturbed areas should be diverted around the basins. (In many cases, basins
are treating runoff from the entire drainage area, which is significantly larger than
that of cleared land.)

New research indicates that use of new technologies such as installation of baffles in the
sediment basins, application of flocculents, and use of skimmers can significantly increase
efficiency of sedimentation basins. Research funded by the Sedimentation Control Commission
(SCC) and the NC Department of Transportation (NCDOT) at NCSU demonstrated that turbidity
levels can 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 mulches that are adequately tacked. It has been conclusively
proven that use of ground cover (temporary or permanent) dramatically reduces erosion rates.

10.2.2 Loss of Riparian Vegetation

During 2002 basinwide sampling, DWQ biologists reported degradation of aquatic communities
at numerous sites throughout the French Broad 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 (NCDENR-DWQ, June 2003b).

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
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.

Livestock grazing with unlimited access to the stream channel and banks can cause severe
streambank erosion resulting in degraded water quality. Although they often make up a small
percentage of grazing areas by surface area, riparian zones (vegetated stream corridors) are
particularly attractive to cattle that prefer the cooler environment and lush vegetation found
beside rivers and streams. This concentration of livestock can result in increased sedimentation
of streams due to "hoof shear", trampling of bank vegetation, and entrenchment by the
destabilized stream. Despite livestock’s preference for frequent water access, farm veterinarians
have reported that cows are healthier when stream access is limited (EPA, 1999).

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 (NCDENR-DWQ, February
2004). To obtain a free copy of DWQ’s Buffers for Clean Water brochure, call [phone],
ext. 558.
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10.2.3 Loss of Instream Organic Microhabitats

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 French Broad 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.

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.

10.2.4 Channelization

Channelization refers to the physical alteration of naturally occurring streams and riverbeds.
Typical modifications are described in the text box. 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).

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 become locked in an
endless cycle of erosion and entrenchment. Once the benefits of channelization are 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
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French Broad River basin and continues to occur in some watersheds, especially in small
headwater streams.

10.2.5 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
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.

(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 French Broad 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.
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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
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.

10.3 Fecal Coliform Bacteria

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 do not actually pose a
danger to people or animals; however, where fecal coliform are present, other disease-causing
bacteria may also be present. Water that is polluted by human or animal waste can harbor other
pathogens that may threaten human health.

Fecal coliform bacteria, and other potential pathogens associated with waste from warm-blooded
animals, are not necessarily harmful to fish and aquatic insects; however, they can potentially
impact human health. High levels of fecal coliform bacteria can indicate high levels of sewage
or animal wastes that could make water unsafe for human contact (e.g., swimming). 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. High levels of fecal
coliform bacteria may indicate contamination that increases the risk of contact with other
harmful pathogens in surface waters. In the French Broad River basin, data from DWQ’s
ambient monitoring stations in subbasins 04-03-02 and 04-03-05 (Chapters 1 and 5) show high
levels of fecal coliform bacteria in portions of the French Broad River mainstem and Richland
Creek. Both are Impaired in the recreation use support category.

Throughout the state, there are many waters that have high levels of fecal coliform bacteria
associated mostly with stormwater runoff in urban areas. Under favorable conditions, fecal
coliform bacteria can survive in bottom sediments for an extended period of time (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.

Water quality standards for fecal coliform bacteria are intended to ensure safe use of waters for
recreation and shellfish harvesting (refer to Administrative Code Section 15A NCAC 2B .0200).
The North Carolina fecal coliform standard for freshwater is 200 colonies/100ml based on the
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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.
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
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 pathogenic bacteria. Although fecal
coliform standards have been used to indicate the
microbiological quality of surface waters for
swimming and shellfish harvesting 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.

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 10 – Water Quality Stressors 111