20042019 Ver 3_Staff Comments_20110125

I RR-
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Dee Freeman
Governor Director Secretary
January 25, 2011
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
Mr. Brad Shaver, Acting Field Chief
U.S. Army Corps of Engineers
Wilmington Regulatory Field Office
69 Darlington Avenue
Wilmington, North Carolina 28403
Subject Property: Anderson Creek Development
Dear Mr. Shaver:
DWQ Project # 04-2019, Ver. 3
Harnett County
On behalf of the NC DWQ 401/Wetlands Permitting Unit, we again respectfully request that you
consider the following comments within your review of the 404 Individual Permit request for the
above referenced property:
I . Applicant's Stated Purpose within the Public Notice states, "The purpose of the project is to
construct a unique public recreational amenity within Anderson Creek to increase
marketability. " yet, the Project Description located within 18. Nature ofActivity (Project
Description) as part of the application, states the project is the development of Anderson Creek
South (an expansion of the existing 773-acres Anderson Creek North residential Development)
and requires the development of a road network, sewer outfalls, and an amenity to ensure the
success of the development. It is unclear why the stated purpose does not include the residential
development, road network and utility installation, since it would seem there would be no need
for the recreational amenity were it not for the residential development to support it. Please
clarify this inconsistency. Additionally, although the applicant's narrative attempts to convey the
need for the "sailing" lake, the reader is left believing that the true need for the project in the area
is the projected demand for reasonably priced housing due to the Base Relocation And
Consolidation (BRAC). Our position regarding this understanding is further supported by
enclosure of the letter from retired Brigadier General Paul R. Dordal to Ken Jolly of the USACE
which states in the first paragraph, "this tremendous growth (at Fort Bragg) is straining our
infrastructure and housing requirements, and we are encouraging developments, such as
Anderson Creek South that meet the needs of military related growth while not encroaching on
the installation." The second paragraph continues to discuss the need for housing in the area and
ends with a comment regarding the applicant's avoidance and minimization of impacts to onsite
wetlands for the project. It is not until the third paragraph in a four paragraph letter that the
proposed "sailing lake" is mentioned. Therefore it is the opinion of this Office that the "sailing
lake" should be regarded as an amenity to the residential and commercial development and not
vice versa.
2. This project cannot be properly reviewed due to the lack of information contained in the Public
Notice and the incredibly small scale of the submitted maps. Therefore, concerns regarding
Wetlands, Buffers, Stormwater, Compliance and Permitting Unit (WeBSCaPe)
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
Phone: [phone] FAX: [phone]
Internet: hUp://pogal.ncdenr.org/web/wq/ws
An Equal Opportunity lAffirmative Action Employer
USACE
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January 14, 2011
impacts to resources and water quality cannot be properly evaluated at this time. These
deficiencies include:
a. Lack of a map and tables describing the residential and commercial development, both
proposed and existing within the project boundaries (specific map and data requests are
cited later in this commenting letter).
b. Lack of a map and tables describing roads and infrastructure, both proposed and existing
within the project boundaries (specific map and data requests are cited later in this
commenting letter). This should include road designs and traffic studies/justifications.
3. The compensatory mitigation plan included is not satisfactory. What was submitted is not even
conceptual, but only speculative.
4. On page 2 of 6 of the Public Notice under 23. Avoidance, Minimization, and Compensation, the
applicant states that the "we are of the opinion that any regulatory position that all ponds are
detrimental to water quality and aquatic resources is based on subjective science that represents
worst case scenarios... and believe that current technology can be employed to mitigate all
practically foreseeable potential adverse impacts" (and yet the applicant offers no information to
support their position). This Office very strongly disagrees with this statement. This Office
recommends the applicant carefully read adjoining state Tennessee's study of the impact of small
impoundments on stream (link:
http://www.state.tn.us/environment/wpc/publications/pdf/isp report pdf ), and please carefully
read DWQ's attached Selected Bibliography - Stream Impoundment Perspectives - 2008, and
please consider the NC Dam Safety statewide dam assessment at this link:
http://sections.asce.orWn carolina/ReportCard/dams pdf Additionally, a preimpoundment study
conducted by Hayden M. Ratledge of the North Carolina Wildlife Resources Commission titled
Preimpoundment Study of the French Broad River Watershed;1962: Anticipated Effects of the
Presence of Ponds on Trout Streams in Transylvania and Henderson Counties North
Carolina, concluded the following: a.) "It can be anticipated that the proposed flood control
impoundments will increase the temperature below those impoundments approximately 13°F.
This will make the water of the tributaries below the dams, and also of the main river, unsuitable
for trout. " b.) "The construction of the proposed impoundments appears to be in contravention
of the stated U.S. Forest Service Policy. " and c.) "The construction of the proposed
impoundments appears to be in contravention of the N. C. State Stream Sanitation classifications
so far as thermal pollution is concerned. " While this Office acknowledges this study was
conducted in the mountains of the State, and the proposed "sailing lake" project is located within
the Sandhills region of the state, the effect of impoundments on streams within either region of
the State is comparable. Should you have any questions or need any clarification we will be
happy to assist you in any way we can. Finally, please note that because the DWQ has a very
strong opinion on this issue and it is very important to us, we were awarded a US EPA grant this
year to conduct a similar study to the one Tennessee performed.
On page 5 of 6 of the Public Notice under 23. Avoidance, Minimization, and Compensation, the
applicant states that the "amenity must be constructed to comply with local zoning
requirements.", and on page 1 of 4 of your application narrative, under 20. Reason(s) for
Discharge, the applicant states that "Development of size and scope of Anderson Creek legally
and practically require amenities to make them marketable." Please provide documentation of
this requirement and a contact name of an individual member of the local zoning board who
would be available to discuss this requirement, and cite a source stating that Anderson Creek is
legally required to have amenities.
USACE
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January 14, 2011
6. This Office was unable to locate an alternatives analysis for other properties that were considered
for this project and would like the applicant to address this concern.
7. To DWQ's knowledge, a geotechnical study has not been performed within the area identified for
the proposed "sailing lake." This Office has concerns regarding whether a lake is truly feasible in
this area, and strongly encourages such a study be undertaken.
8. It is our understanding that several years ago DWQ had concerns that this lake was being
proposed in an area that included an impressive stand of Atlantic white cedar. It is unclear if the
current proposed "sailing lake" is located in the area that includes the aforementioned stand of
Atlantic white cedar?
9. On page 3 of 6 of the application under 18. Nature ofActivity (Project Description), the
applicant states, "Proposed amenities include a tennis center, small recreational parks, and a 40-
acre public access lake to accommodate the establishment of a sailing school and beach areas."
and on page 5 of 6 of the Public Notice under 23. Avoidance, Minimization, and Compensation,
the applicant states "smaller more dispersed ponds are not conducive to providing organized
swimming under the supervision ofli eguards. " The proposed lake is located in Class C waters
which are, "waters protected for uses such as secondary recreation, fishing, wildlife, fish
consumption, aquatic life including propagation, survival and maintenance of biological
integrity, and agriculture. Secondary recreation includes wa ing, boating, and other uses
involving human body contact with water where such activities take place in an infrequent,
unorganized, or incidental manner. " Will the applicant be seeking a re-classification of the
surface water to "B"? Class "B" waters are, "waters protected for all Class C uses in addition to
primary recreation. Primary recreational activities include swimming skin diving water skiing
and similar uses involving human body contact with water where such activities take place in
an organized manner or on a frequent basis."
10. It is not clear to this Office why there is a need for a 40-acre "sailing lake" at the proposed
location when Harris Lake and Jordan Lake, which are much larger than the proposed lake, and
allow for sailing, are both located approximately one-hour from the project site. This position is
further supported by our calculation that approximately five million gallons of water per month
will be lost from this proposed lake through evaporation. This would be a significant concern in
light of recent statewide droughts.
11. Are the proposed lakes to be located in streams that contain migrating or spawning fish? Please
provide documentation of any studies or data collected that indicate that no fish species spawn in
the stream segments proposed for impact.
12. We would like to hear from the applicant on how they propose to maintain water quality
standards upstream from the impoundment, within the entire impoundment, and downstream of
the impoundment. The explanation provided is insufficient.
13. Staff with the North Carolina Division of Water Resources have the following comments:
Our major interest is the release from the dam forming the "amenity" lake and the resulting
downstream flow regime. To evaluate this release the applicant will need to provide the drainage
area, mean annual flow and 7Q10 flow for the dam site. The latter two flow statistics should be
obtained from the USGS.
USACE
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January 14, 2011
The application should also provide a description of how downstream flows will be provided -
both how a constant minimum flow will be maintained and how the dam structure will provide an
outflow equal to the inflow to the lake (assuming that is how it will operate).
The application should also indicate whether the lake will be used for irrigation or any other
activity requiring withdrawal. If not, then the applicant should indicate through covenants or
some other mechanism how this will be assured for the life of the project. If the lake will be used
for withdrawals, then this will need to be incorporated in how the downstream release is made,
and may require gauging of inflow so the release can match inflow prior to any loss of water via
irrigation or other withdrawal
14. This Office will need to see the applicant's complete and comprehensive lake design and dam
details.
15. Will the lake shoreline be a natural shoreline or an "armored" shoreline (having installed
bulkheads/seawalls)?
16. This Office identified fourteen (14) ponds currently on the subject property. Are all of these too
small for a "sailing school"? Could any be expanded or combined to accommodate the applicants
"sailing lake"?
17. On page 3 of 6 of the Public Notice under 23. Avoidance, Minimization, and Compensation, this
Office believes there is an intent to dismiss several State regulations as "inappropriate" or "not
applicable" based upon the assumption of natural condition. First, an impoundment is not a
"natural condition". With that said, impoundments once completed, would be held to water
quality standards in accordance with NC 15A NCAC .0213 and federal Clean Water Act
provisions. One comment relating to applicability of a water quality standard notes that "the
violation of the numerical water quality standard (temperature, pH, etc) would need to
compromise the use before a violation is incurred: in other words, the violation would occur only
after the water could no longer be able to support aquatic life (i.e. dead fish are floating on the
lake), wildlife, or be used for recreation (i.e. can't sail a boat due to algae)." This statement is
incorrect. An exceedence of a water quality standard that precludes "aquatic life propagation and
maintenance of biological integrity" on a short or long term basis is indeed a violation of water
quality standards. The regulations do not allow for fish to die before determining that a water
body is not supporting its designated use, and in fact would defeat the purpose of water quality
standards protecting wildlife and biology before mortality or extreme stress occurs.
18. This Office requests that the applicant please locate the project boundaries on the most recent
bound and published Harnett County soil survey and the USGS 1:24,000 topographic map for the
project.
19. This Office requests that the applicant please re-submit your site plans on full plan sheets at a
scale of no smaller than 1"=50' with topographic contours shown.
20. This Office requests that the applicant please provide cross section details showing the provisions
for aquatic life passage.
21. This Office requests that the applicant please provide building envelopes for all lots with
wetlands and/or streams on the site plans.
22. This Office requests that the applicant please indicate all existing and proposed lot layouts as
overlays on the site plan. Additionally, please indicate which lots are sold.
USACE
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January 14, 2011
23. This Office requests that the applicant please locate any planned sewer lines on the site plan.
Additionally, please comment on whether there are any septic fields within the Anderson Creek
development.
24. This Office requests that the applicant please indicate all proposed stream or wetland driveway
crossings on your plan sheet (including future proposed).
25. This Office requests that the applicant please indicate all stream impacts including all fill slopes,
dissipaters, and bank stabilization on the site plan.
26. This Office requests that the applicant please indicate all wetland impacts including fill slopes on
the site plan.
27. This Office requests that the applicant please locate all isolated or non-isolated wetlands, streams,
and other waters of the State as overlays on the site plan.
28. This Office requests that the applicant please provide a qualitative indirect and cumulative impact
analysis for the project. Please see DWQ's policy for guidance on our website at:
http://portal.ncdenr.oraJweb/wq/swp/ws/40 I/policies
29. This Office requests that the applicant please assess the need for a storm water management plan
(SMP) on the site. Please comply with the requirements set forth below. In addition, the
applicants shall follow the procedures explained in Protocol for Stormwater Management Plan
(SMP) Approval and Implementation that is in place on the date of the submittal of the SMP.
A. Project Density: Projects with SMPs that require 401 Oversight/ Express Unit approval
shall be classified as either Low or High Density according to the criteria described below.
1. Low Density: A development shall be considered Low Density if ALL of the
following criteria are shown to have been met.
a. The overall site plan, excluding ponds, lakes, rivers (as specified in
North Carolina's Schedule of Classifications) and saltwater wetlands
(SWL), must contain less than 24% impervious surface area considering
both current and future development.
b. All stormwater from the entire site must be transported primarily via
vegetated conveyances designed in accordance with the most recent
version of the NC DWQ Stormwater BMP Manual.
c. The project must not include a stormwater collection system (such as
piped conveyances) as defined in NCAC 2B .0202.
d. If a portion of project has a density greater than 24%, the project shall be
considered low density as long as the higher density portion of the
project complies with Items 1-3 above and the higher density area is
located in upland areas and away from surface waters and drainageways
to the maximum extent practicable.
USACE
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January 14, 2011
II. High Density: Projects that do not meet the Low Density criteria described
above are considered to be High Density, requiring the installation of appropriate
BMPs as described below.
a. All stormwater runoff from the site must be treated by BMPs that are
designed, at a minimum, to remove 85 percent of Total Suspended Solids
(TSS).
b. In addition to controlling 85 percent of TSS, projects requiring located in
watersheds that drain directly to waters containing these supplemental
classifications shall meet the following requirements:
Water Quality Stormwater BMP
Supplemental Classification Requirement
§303(d) Project-specific conditions may be added
by the Division to target the cause of the
water quality impairment.
NSW A minimum of 30 percent total phosphorus
and 30 percent total nitrogen removal.
Trout (Tr) A minimum of 30 percent total phosphorus
and 30 percent total nitrogen removal;
BMPs should also be designed to minimize
thermal pollution.
c. All BMPs must be designed in accordance with the most recent version
of the NC Division of Water Quality Stormwater Best Management
Practices Manual. Use of stormwater BMPs other than those listed in
the Manual may be approved on a case-by-case basis if the applicant can
demonstrate that these BMPs provide equivalent or higher pollutant
removal.
B. Vegetated Buffer: In areas that are not subject to a state Riparian Area Protection Rule, a
30-foot wide vegetated buffer must be maintained adjacent to streams, rivers and tidal waters
as specified below.
a. The width of the buffer shall be measured horizontally from:
i. The normal pool elevation of impounded structures,
ii. The streambank of streams and rivers,
iii. The mean high waterline of tidal waters, perpendicular to shoreline.
b. The vegetated buffer may be cleared or graded, but must be planted with
and maintained in grass or other appropriate plant cover.
c. The DWQ may, on a case-by-case basis, grant a minor variance from the
vegetated buffer requirements pursuant to the procedures set forth in 15A
NCAC 02B.0233(9)(h).
d. Vegetated buffers and filters required by state rules or local governments
may be met concurrently with this requirement and may contain coastal,
isolated or 404 jurisdictional wetlands.
USACE
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January 14, 2011
C. Stormwater Flowing to Wetlands: Stormwater conveyances that discharge to wetlands
must discharge at a non-erosive velocity prior to entering the wetland during the peak flow
from the ten-year storm.
D. Phased Projects: The DWQ will allow SMPs to be phased on a case-by-case basis, with a
final SMP required for the current phase and a conceptual SMP for the future phase(s). If the
current phase meets the Low Density criteria, but future phase(s) do not meet the Low
Density criteria, then the entire project shall be considered to be High Density.
Thank you for your attention. If you have any questions, please contact Ian McMillan in our Central Office
in Raleigh at [phone].
Sincerely
Ian McMillan, Acting Supervisor
Acting Supervisor - Wetlands, Buffers, Stormwater,
Compliance and Permitting Unit (WeBSCaPe)
IJM
Enclosure: Selected Bibliography - Stream Impoundment Perspectives - 2008
cc: Crystal Amschler, U.S. Army Corps of Engineers - Wilmington Regulatory Field Office
Chad Turlington, DWQ Fayetteville Regional Office
File Copy
Chris Huysman, WNR, P.O. Box 1492, Sparta, NC 28675
Jim Mead, DWR
Connie Brower, DWQ
Jennifer Derby, Wetlands, Coastal, and Oceans Branch, Water Protection Division, U.S.
Environmental Protection Agency, 61 Forsyth Street, SW, 15th Floor, Atlanta, GA 30303
Becky Fox, 1307 Firefly Road, Whittier, NC 28789
D.J. Gerken, SELL, 29 N. Market St., Suite 604, Asheville, NC 28801
Filename: 042019 Ver3AndersonCreekDevelopment(Hamett)IP_Commenting_Letter_USACE
Selected Bibliography - Stream Impoundment Perspectives
Compiled by North Carolina Division of Water Quality Staff
June 2008
Introduction:
Although Egyptians first constructed dams for the purpose of river regulation thousands of years
ago (Smith, 1971), Man has only recently begun to understand and appreciate the dramatic and
widespread effects of dams on river systems. The recent volume of work on impoundments,
primarily published by environmental scientists in the United States and abroad in the last 50
years, suggests that the benefits associated with some impoundments (e.g. water supply,
hydroelectric power, flood control, etc.) are accompanied by a great number of costs to nature, and
ultimately, society. While far from comprehensive, the following summary document provides a
good foundation on the many consequences of river impoundment. It is important to note that the
literature uses the term "impoundment" to describe everything from large, water supply reservoirs
to farm ponds created by small, earthen dams. It is also important to recognize that the
summarized environmental, social, and economic effects will vary in magnitude depending on the
impoundment's size and location. That said, the literature supports the following conclusions
regarding the effects of river impoundment:
Conclusions:
1. Impoundments negatively impact the physical, chemical, and biological characteristics of
water (i.e. water quality)
2. Impoundments negatively impact ecological systems and native faunal/floral communities
3. Impoundments/dams create numerous maintenance and safety issues
4. Impoundments cause numerous hydrological, biological, and geomorphological impacts
downstream due to changes in the flow regime and water quality
Supporting Information:
1. Impoundments negatively impact the physical, chemical, and biological characteristics of
water (i.e. water quality)
a. Water temperature and dissolved oxygen
When an impoundment is created, temperature and oxygen stratification may occur
as water depth increases and flow velocity decreases. This process involves the in-
flow of cooler, denser stream water to the bottom layer (hypolimnion) which pushes
the water above it into the impoundment's top layer (epilimnion). Here, according
to Maxted, McCready, and Scarsbrook (2005), the water warms and decreases in
density as it is subject to "incoming solar radiation, unhindered by any of the
topographic or vegetation shading characteristic of a stream channel". As the
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suspended particles and substances in the epilimnion absorb solar radiation, the
temperature in this shallow surface layer typically rises above the high daily
maximum temperature of the inflowing stream. Maxted, McCready, and
Scarsbrook observed temperature stratification in each of the six small ponds
(ranging from 69-390 acres) they studied. Temperature (24° C) and dissolved
oxygen (4 mg/L) were exceeded 46% and 86%, respectively, during a 40-day
summer period. Maxted, McCready, and Scarsbrook also observed that
thermoclines (i.e. zones of rapid temperature change) occurred above .5 meters in
the small ponds.
According to Higgs (2002), the hypolimnion and epilimnion seldom mix well
enough to promote gas transfer from the highly-oxygenated surface water to the
poorly-oxygenated bottom layer. As a result, the bottom water layer in an
impoundment may become hypoxic and fail to support aquatic life. Depending on
how water is released from the impoundment, these oxygen and temperature
stratifications can lead to numerous problems downstream as well. In an attempt to
preserve habitat for cold-water species such as trout, some dams release water from
the cooler hypolimnion layer. However, while the temperature may be desirable for
cold-water species, the lack of dissolved oxygen may still render the downstream
habitat unsuitable. If the highly-oxygenated but warmer surface water is released
downstream, cold-water fish may have adequate oxygen, but a "thermal block" is
established which still prevents populations from reaching upstream spawning
habitats (Higgs, 2002).
Petts (1984) cites two field observations of seasonal dissolved-oxygen sags related
to temperature stratification in upstream impoundments. The first, by Ingols
(1959), occurred along the Holston River, below Cherokee Dam in east Tennessee.
Ingols compared the dissolved-oxygen deficit in this location to be equivalent to
that caused by the effluent from a town of 3,500,000 people. Petts' second example
was from a study conducted by Walker et al. (1979) on the Murray River, below the
Hume Dam in Australia. In this case, a dissolved oxygen sag attributed to lake
stratification was observed for 100 km below the dam.
b. Metal thresholds
Metals can accumulate in impoundment sediments due to upstream pollution
discharges, or from natural sources such as local soils. Problems associated with
metals can be exacerbated by the aforementioned temperature and dissolved oxygen
stratifications. For example, in Lake Toxaway in the Savannah River Basin of
western North Carolina, researchers concluded that odor problems were emanating
from manganese and iron concentrations that "increased significantly in response to
increased hypoxic conditions near the bottom of the lake as summer progressed"
(NC DENR, 2005). Metal concentrations exceeding state water quality standards
have also been documented in impoundments in the Catawba, Yadkin, and Neuse
river basins of North Carolina.
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c. Sedimentation
Sedimentation occurs when geologic or organic material falls out of suspension
and accumulates in a given area. This phenomenon is common in impoundments
for the following reasons: 1) inflowing streams/rivers slow down upon entering
impoundments, and suspended soil particles settle out of the water column, 2)
compared to natural streams and lakes, the water level in impoundments is
regulated to be virtually constant. According to Nakashima, Yamada, and Tada
(2007), nearly constant water levels may cause physical destabilization of
impoundment shorelines, and 3) land-disturbing activities such as construction
around the impoundment itself may lead to direct sedimentation. The sediment
load of a stream is produced by sheet erosion of the surrounding landscape or by
erosion of the stream bank itself (Baxter, 1977). Sedimentation is exacerbated
when erosion increases upstream during storm events or as a result of
construction, agriculture, or other land-disturbing activities. If flow rates decrease
rapidly upon entering the impoundment, sediment may accumulate near this entry
point, in the impoundment's upstream section. More often, however,
sedimentation is a bigger concern further downstream in the impoundment, next to
the dam. Sedimentation is a potential problem for water quality and aquatic life
(e.g. sediment may carry potentially toxic materials, such as phosphorous,
nitrogen, arsenic, chromium and copper), and it reduces the impoundment's water
depth and water storage capacity.
d. Turbidity
Sediment or silt that remains suspended in the water column also causes physical
and chemical changes in impoundments. In addition to detracting from a pond or
lake's aesthetic value, high turbidity limits penetration of visible light, affects the
heating and cooling rates of water, affects conditions on the bottom, and leads to the
retention of organic matter (Ellis, 1936). By limiting the penetration of visible
light, or by scattering light, turbidity can decrease the photosynthetic activity of
plants and reduce the amount of dissolved oxygen. Additionally, suspended
particles absorb heat from solar radiation causing the water to warm. Since oxygen
cannot dissolve as easily in warm water, turbidity can further lower dissolved
oxygen concentrations. High turbidity also leads directly to bottom effects as the
silt or sediment begins to drop from suspension. Fish eggs and insect larvae are
often blanketed and suffocated by silt, and gill structures can become clogged.
e. Nutrient pollution
The release of sewage effluent from point sources, such as wastewater treatment
facilities, and storm water runoff from non-point sources, such as lawns and
agricultural fields, to streams and tributaries, may cause nutrient pollution
problems. As these waters flow into receiving water impoundments, the water may
become eutrophic as elevated levels of phosphorus (P) and nitrogen (N) cause
biological productivity to increase dramatically. This can lead to excessive algal
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growth and decay, dissolved oxygen depletion, increased pH variation, and food-
chain alterations.
f. Algal blooms and Dissolved oxygen
Nutrients are often the limiting factor for algae and other aquatic plant growth. If
excess nutrients are present, such as the case in many impoundments, algae will
grow until some other factor becomes limiting (HALMS, 2007). Algae have other
significant growth advantages in impoundments as well, such as light intensity and
elevated temperatures. Due to the lack of topological or vegetation shading and the
aforementioned temperature stratification, algal photosynthesis can occur rapidly in
impoundments. Although algal photosynthesis actually increases dissolved oxygen
concentrations in the epilimnion, the algal bloom cycle can have far-reaching and
potentially disastrous consequences in the hypolimnion of the impoundment, and
downstream. Other aquatic plants may die during the bloom, and the algae itself
will eventually crash as available nutrients are consumed. This dead organic matter
eventually settles to the bottom and becomes a chief food source for heterotrophic
bacteria. Heterotrophic bacteria will increase in number based on the available food
source and, according to Petts (1984), "oxygen will be consumed in the
hypolimnion, often to exhaustion". This cycle often results in massive fish and
insect kills due to anoxic conditions, and the impoundment temporarily becomes a
dead area (HALMS, 2007). Aside from these immediate ecological effects, algal
blooms can also cause taste and odor problems in water supply impoundments, and
release toxic metals from lake sediments as organic-matter decay becomes
anaerobic (Fang et al., 2005).
g. pH
The pH of water can be altered by impoundment, and these changes often affect
how chemicals dissolve in the impoundment and whether they affect resident flora
and fauna. Impoundment eutrophication due to excess nutrients causes increased
biological activity, such as algal photosynthesis, which tends to increase pH.
Elevated pH may contribute to phosphorus release from the sediment and allow for
additional biological productivity (Ceballos and Rasmussen, 2007). When nutrients
are consumed, and dissolved oxygen drops, the water may become more acidic and
contribute to the death of fish and other aquatic organisms. This pH variation is
primarily a lake or impoundment phenomenon and not often observed in rivers or
streams.
2. Impoundments negatively impact ecological functioning and native faunal/floral
communities
Ecological systems and native faunal/floral communities within the impounded stream
reach are negatively impacted due to water quality deterioration, habitat destruction, and
effects on migration. For instance, sedimentation may cover existing rock and gravel
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substrate, including riffles and breaks. This is especially detrimental to gravel-riffle
spawners, such as channel catfish and smallmouth bass, that only deposit eggs where the
water depth, current, temperature, clarity, dissolved oxygen content, and bottom types are
suitable. Also, according to Higgs (2007), dams disrupt river connectivity and create
physical and thermal barriers that prevent migrating fish and other wildlife from moving
up- or downstream in a river system. He emphasizes that this is problematic for sea-run
(anadromous and catadromous) fish as well as for residential fish that migrate up and down
a river system. These physical and thermal barriers affect fish spawning, rearing, and
foraging migrations, and also prevent re-colonization of other species following floods,
droughts, or human disturbances. For instance, during the larval stage, mussels can attach
to fish temporarily and move up- or downstream to re-colonize stream segments.
Neves and Angermeier (1990) found that dams on the upper Tennessee River system
(including parts of NC) have also altered habitat and adversely affected native fishes.
Obligatory riverine fish species typically do not survive in these impoundments, and
neither the reservoirs nor downstream areas receiving tailwaters provide suitable conditions
for native fish reproduction. Neves and Angermeier concluded that the cumulative effects
of dam-related stresses have significantly reduced the biological integrity of the rivers,
including tailwaters areas where faunal diversity has not recovered.
According to Mammoliti (2002), "a substantial body of literature indicates that
construction of dams has a negative impact on native stream fishes. In general, an
impoundment can reduce the quantity and quality of stream habitat, alter reproductive and
feeding behavior or fishes, and increase the number and sizes of predatory fish within a
stream system. These impacts suggest a negative relationship between impoundments and
obligate stream species."
Santucci, Gephard, and Pescitelli (2005) conducted an extensive study on the effects of
low-head dams on a 171-km reach of a warmwater river in Illinois. The river system is
fragmented by 15 dams that create an alternating series of deep-water and free-flowing
river habitats. For each of the three indexes considered (i.e. the index for biotic integrity
(IBI), the macroinvertebrate condition index (MCI), and the qualitative habitat evaluation
index (QHEI)), scores for free-flowing sections were significantly higher than for
impounded sections. In fact, the scores indicated alternating good-quality habitat (free-
flowing sections) and severely-degraded habitats (impoundments). The researchers
concluded, "From this large body of work, we know that dams can have dramatic effects on
rivers and aquatic biota by altering water quality and habitat, disrupting nutrient cycling
and sediment transport, and blocking fish and invertebrate movements". Furthermore,
Santucci, Gephard, and Pescitelli (2005) cited dam removal as the best option to restore a
river's ecological health.
The Tennessee Department of Environment and Conservation (TDEC) sampled 75 streams
below small impoundments and published a report in September 2006 (Amwine, Sparks,
and James, 2006). Benthic macroinvertebrate communities were adversely affected in most
of the streams sampled as only four passed biological criteria guidelines or were
comparable to first order stream references. In fact, 96% of the streams sampled failed to
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meet reference guidelines for the number of distinct Ephemeroptera, Plecoptera, and
Trichoptera (EPT) taxa, and 86% had low EPT density. They also found that 39% of the
dams with year-round (low-flow) discharge provided insufficient flow to supply adequate
habitat for aquatic life during at least one season. Only about half of streams studied
appeared to have relatively stable channel structures, and approximately 80% failed to meet
regional expectations for sediment deposition.
3. Impoundments/dams create numerous maintenance and safety issues
Aside from deleterious effects on water quality and ecological systems, impoundments also
create numerous maintenance and safety issues. Even small, earthen dams installed to
create amenity ponds eventually deteriorate as they are easily damaged by floods, wind,
and ice. If maintenance activities are deferred or neglected, this deterioration can
accelerate and eventually cause dam failure. Therefore, it is important to note that capital
investment does not end when dam construction is complete. As with other critical
infrastructure, such as roads, sewer lines, and bridges, a significant investment is essential
to maintain dam structures and assure public health and safety (American Society of Civil
Engineers (ASCE), 2008).
In the past two years alone, 67 dam incidents, including 29 dam failures, were reported to
the National Performance of Dams program by state and federal regulatory agencies and
private dam owners (ASCE, 2008). According to ASCE, events such as large floods,
earthquakes, and inspections that reveal dam deficiencies and/or safety concerns are
recorded as incidents. However, ASCE estimates that the actual number of dam incidents
and failures is likely to be higher due to non-reporting and understaffed state agencies.
ASCE also reports that the number of high-hazard potential dams (dams whose failure
would cause loss of human life) in the United States has increased from 9,281 in 1998, to at
least 10,213 today. Regrettably, greater than 10% (1046) of all high-hazard potential dams
are located in North Carolina. In their "2006 Infrastructure Report Card", the ASCE gave
the state's dam infrastructure a grade of "D", and estimated that it will cost North Carolina
approximately $400 million to "rehabilitate the most critical deficient structures" (ASCE,
2006).
Regardless of dam size, it is critical to perform regular maintenance activities in order to
reduce threats to downstream life and property. One of the many important dam
maintenance activities is dredging. Many dams silt-in with eroded soil and lose water
depth and storage capacity over time. Mahmood (1987) estimated that worldwide reservoir
storage capacity decreases I% per year due to sedimentation. Evans et al. (1999) arrived at
a similar conclusion in a study prompted by the failure of the IVEX dam on the Chagrin
River in Ohio. They estimated that storage capacity loss due to sedimentation ranged from
.37% to 1.72% per year. Even in carefully managed watersheds where sediment-loading is
minimized due to strict sediment and erosion control measures (e.g. riparian buffers, silt
fencing, stormwater retention ponds, etc.), continual maintenance dredging may be
required (Newman, Perault, and Shahady, 2006).
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Impoundments are also commonly afflicted with invasive aquatic plants like Hydrilla
(Hydrilla verticillata), Creeping Primrose (Ludwigia peploides), and Parrot Feather
(Myriophyllum aquaticum). At the least, these invasive plants are an intractable nuisance
that may out-compete native aquatic flora, and inhibit recreational activities. At the worst,
the presence of these aquatic plants may threaten public water supplies, and create
conditions conducive to anopheles mosquitos, which carry malaria. According to NC
DENR's Lake and Reservoir Assessments, Hydrilla covers approximately 625 acres of
Mountain Island Lake (Catawba River Basin) and is also problematic on Lake Norman (NC
DENR, 2005). In Lake Hickory, Parrot Feather has spread from the original 10 acre
infestation to approximately 84 acres. Duke Energy and NC DENR are now working on a
Parrot Feather management plan as it threatens to clog two drinking water intakes in the
area. To address invasive species and algae problems, impoundment managers have drawn
down water levels, introduced biological controls (e.g. grass carp), and treated water with
chemicals such as copper sulfate, which may create a host of new water quality problems.
Many small impoundments, such as farm ponds and amenity ponds associated with
residential subdivisions, create complex and expensive management issues as well.
However, these impoundments are seldom managed or maintained by experienced resource
managers or civil engineers. In fact, many homeowners associations become dam
"owners" upon completion of subdivision and dam construction activities. As such, they
must assume the daunting maintenance and inspection responsibilities, as well as manage
the aquatic resource. In fact, private companies have been created to capitalize on the
demand for pond management services such as aeration, algae control, water quality
improvement, odor reduction, and nuisance aquatic vegetation control.
4. Impoundments cause numerous geomorphological, hydrological, and biological impacts
downstream due to changes in the flow regime and water quality
The act of impounding streams affects more than just the impounded reach itself. In fact,
some of the most harmful effects may occur well downstream from the impoundment. For
instance, dams often decrease flow rates and prevent flow variations downstream, both of
which can cause geomorphic changes. These changes might include bank instability, loss
of sinuosity, disruption of bank vegetation, destruction of pool and riffle complexes, and
tributary headcutting. As Mammoliti (2002) and Leopold (1997) note in separate studies,
stream channel morphology is formed and maintained by natural flow variations, not by the
steady flows associated with impounded streams.
Higgs (2002) linked flow variation, and the movement of sediment and larger cobbles and
boulders, to the creation of "new and more diverse habitat for aquatic species" downstream.
Such transport cannot occur along impounded stream reaches however, because much of
the sediment carried by the stream is deposited behind the dam. The resulting water
releases from impoundments are characterized as "sediment-starved" or "clear-water
releases". The downstream, sediment-deprived stream reaches "often regain sediments lost
behind the dam by eroding deeper into the river channel and away at the stream banks"
(Higgs, 2007). Evans et al. (1999) describe this bed and bank erosion as a "natural
consequence of the stream adjusting to steepened gradients and low initial sediment load
after exiting the reservoir".
Low-flow rate and low-flow variability can negatively impact downstream habitats in other
ways as well. The stream may be unable to transfer large particles, such as food sources,
and water levels downstream may be too low to allow habitats to support aquatic life. In
the event that some sediment has accumulated in the downstream reach, perhaps due to
overland flow or sedimentation from an entering tributary, periodic scouring flows are
important to maintaining the type and quality of downstream habitat. According to
Mammoliti (2002), without scouring flow, sediments may "cover coarse substrates and
prevent seepage or subsurface flow that maintains pool refugia during drought periods".
Additionally, dams may reduce the ability of aquatic populations to recover following a
drought if they cause low or no-flow events to increase in frequency and magnitude.
According to Magilligan, Nislow, and Graber (2003), dams can cause other hydrological
and biological changes by reducing out-of-bank flows and prolonging bank full flows.
Over time this can "disconnect riparian zones from riverine influence" because floods
greater than bankfull flow are essentially eliminated. They concluded that the 2-year
interval discharge (bankfull discharge) decreased by approximately 60% as a result of
impoundment. The lack of overbank inundation completely limits the transport of
sediment, nutrients, and water to higher floodplain surfaces that work to sustain riparian
habitat and species, and in-channel structure.
Lake-induced water quality problems, as well as problem-management strategies (e.g.
herbicides used to control invasive aquatic plants), often cause as many problems
downstream as they do within the impoundment. For example, water released from
impoundments often exhibits elevated temperatures compared to up- and downstream
reaches. According to Maxted, McCready, and Scarsbrook (2005), "elevated temperatures
were observed for hundreds of meters downstream owing to the slow rate of cooling (1 °
C/100 m), expanding the extent of adverse effects well beyond the footprint of the pond".
They also concluded that water quality criteria exceedences (i.e. temperature and dissolved
oxygen) significantly decreased invertebrate community richness and diversity for
hundreds of meters downstream. Saila, Poyer, and Aube (2005) reached similar conclusion
after studying 5 impoundments ranging from 8-10 feet in height and 112-358 feet in length.
They found that the small dams increased temperatures 4-5 C° at the source, and the water
did not recover from the warming effects (i.e. recover to 17° C) until 5 miles downstream
of the dam.
Here are some examples of how water quality problems in impoundments affect
downstream segments:
• Heavy metal accumulations in the hypolimnion may be released during anaerobic
organic-matter decay, and cause toxicity in downstream aquatic life
• Nutrient-rich water may create algal colonies that render substrates unusable for
colonization by aquatic fauna
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pH fluctuations may cause regulatory failure and/or an inability to molt among
aquatic insects
Herbicides and pesticides (commonly introduced as a management strategy in
impoundments) may be highly toxic to fish and aquatic invertebrates (e.g. copper
sulfate)
From the works cited above and other materials collected during this literature review, it is
evident that the scientific community is progressing towards a consensus on the subject of
river impoundment. River impoundments negatively impact water quality and ecological
systems, cause undesirable hydrological and geomorphological changes, and create costly
maintenance and safety issues for society. While river impoundment can provide benefits
such as public water supply, hydroelectric power, and flood control, the practice should be
avoided if possible based on the likely environmental, economic, and social consequences.
10
Works Cited
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Report Card. Available online at: htt p://sections.asce.org carolina/ReportCard/dams.pdf
American Society of Civil Engineers (ASCE). 2008. Report Card for America's Infrastructure.
Available online at: http://www.asce.org/reportcard/2005/page.cfm?id=23
Arnwine, D.H., Sparks, K.J., and R.R. James. 2006. Probabilistic Monitoring of Streams Below
Small Impoundments in Tennessee. Tennessee Department of Environment and Conservation
(TDEC), Division of Water Pollution.
Baxter, R.M. 1977. Environmental Effects of Dams and Impoundments. Annual Reviews
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Ceballos, E., and Rasmussen, T. 2007. Internal Loading in Southeastern Piedmont Impoundments.
Warnell School of Forestry and Natural Resources, The University of Georgia.
Ellis, M.M. 1936. Erosion Silt as a Factor in Aquatic Environments. Ecology 17(1): 29-42.
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Evans, J.E., Mackey, S.D., Gottgens, J.F., and W.M. Gill. 1999. Lessons from a Dam Failure. Ohio
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Fang, T., Liu, J.T., Xiao, B.D., Chen, X.G. and X.Q. Xu. 2005. Mobilization potential of heavy
metals: A comparison between river and lake sediments. Water, Air and Soil Pollution 161 (1-
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Higgs, Stephen. 2002. The Ecology of Dam Removal: A Summary of Benefits and Impacts.
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Ingols, R.S. 1959. Effect of impoundment on downstream water quality, Catawba River, S.C.
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Mammoliti, C.S. 2002. The Effects of Small Watershed Impoundments on Native Stream Fishes:
A Focus on the Topeka Shiner and Hornyhead Chub. The Kansas Academy of Science 105(3-4),
2002, 219-231.
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