Best Management Practices
Guidance,
Dredged or Fill Activities
U.S. ENVlKONMExNTAL PROTECTION AGENCY
Water Planning Division
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We have attempted to draft the guidance in a format and style that
makes the information presented easy to read and understand. Please
transmit any comments regarding suggested revisions or additions
to Robert E. Thronson by September 14,1978. His address and phone
number is:
Robert E-. Thronson
«U.S. Environmental Protection Agency
Water Planning Division (HH-554)
Washington, D.C. 20460
Phone (202) 755-4913
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
DATE:
JUL13197B
SUBJECT: Transmittal of Final Draft of "Best Management Practices
Guidance, Dredged or Fill Activities. "n
FROM: Merna Hurd, DirectoKK?
Water Planning Div/sndfl
TO: State 208 Agencies
State Resources Agencies
Federal Agencies
National Environmental and
Other Concerned Groups
Conservation Organizations
The enclosed document is submitted to you for final review. It has
been prepared principally to provide the State agencies that will
be involved in programs to control the discharge of dredged or fill
materials, under authorities of Section 208 and 404 of P.L. 92-517,
with guidance regarding Best Management Practices. It was designed also
to provide other State agencies, Federal organizations, and concerned
public groups with readily-available information on how detrimental
environmental impacts resulting from projects involving the discharge
of dredged or fill materials can be prevented or minimized.
The initial draft was reviewed by many State agencies, Federal agencies
environmental groups, EPA Headquarters and Regional organizations, and
other concerned individuals and groups. Comments received were evaluated
and used to develop this final draft submitted to you.
This guidance defines the problems; discusses, what adequate programs
could involve; and provides information on suggested practical
engineering structures, procedures, and schedules for preventing or
minimizing problems that could result from the discharge. Best
Management Practices presented have been subdivided into categories
and described in the following chapters:
1 - Minimizing The Impairment of Water Flow or Circulation
2 - Preventing or Controlling The Runoff of Excess Sediment
Loads or Turbidity Increases
3 - Ensuring Containment of Potential Pollutants Within A Mass
of Dredged or Fill Materials
4 - Enhancement - - The Replacement, Relocation, or Reconstruction
of Existing Environments
5 - Protecting Existing Habitat and Providing For Fish and Wildlife
Propagation.
EPA FORM 1320-6 (REV. 3-76)
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BEST MANAGEMENT PRACTICES GUIDANCE,
DREDGED OR FILL ACTIVITIES
U.S. ENVIRONMENTAL PROTECTION AGENCY
Water Planning Division
Nonpoint Source Branch
Washington, D.C. 20460
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ACKNOULEDGEMENT-S
Sincere appreciation is expressed.to all Federal, State,and
local agencies and personnel that so freely contributed documents,
photographs, and other information for the preparation of this document
under an accelerated time schedule.
Federal agencies include the:
1. Department of Agriculture, Forest Service and Soil
Conservation Service
2. Department of the Army, Corps of Engineers
3. Department of the Interior, Fish and Wildlife Service and
Bureau of Reclamation
4. Department of Transportation, Federal Highway Administration
5. Environmental Protection Agency, Regional Offices
Other agencies, particularly State Departments of Highways or
Transportation, Conservation, Forestry, and Fish and Game, made an out-
standing effort to provide information, analyses, or other input to this
guidance. They include:
California Virginia
Colorado Washington
Louisiana Wisconsin
Wyoming Port of San Diego, Unified Port District
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PREFACE
Section 404 of the Clean Water Act of 1977 (P. L. 95-217) authorizes
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the States to assume the responsibility for controlling the discharge of
dredged or fill materials into navigable waters under their jurisdiction
through individual and general permit programs. Section 208(b)(4) authorizes
States to establish regulatory programs to control the discharge of such
materials through the implementation of "Best Management Practices". The
208(b)(4) programs must complement and be coordinated with the States permit
programs developed under Section 404. Evaluations of proposals for the
discharge of dredged materials must comply with guidelines prepared by the
Administrator of EPA pursuant to Section 404(b)(4)(l) and Section 307 and
403 of the Federal Water Pollution Control Act.
Before a decision can be made regarding the discharge of dredged or
fill materials into waters within a State's jurisdiction, all feasible
alternatives should be considered. They will include an evaluation of such
factors as the necessity for the discharge; sensitivity of the area to
environmental inpacts, both long and short term; effectiveness of available
Best Management Practices to prevent, or minimize the impacts; and possible ~':
alternative ;site areas or a scheduling of operations. Applicable Federal
and individual State's wetlands policy and laws, and other relevant
legislation should be recognized and complied .with.
This guidance document was developed to provide State 208 and 404
agencies, other State agencies, Federal organizations, and other concerned .
groups with the most readily available information on how detrimental
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environmental impacts resulting*from the discharge of dredged or fill
materials can be prevented or minimized through the use of Best Management
Practices-(BMP's).
The. oollution control measures described here and included under*.
the term "Best Management Practices" will be developed, in accordance with
site-specific conditions, by dischargers and, subject to approval by a
responsible State management agency, applied under a 208 regulatory program.
They also may be specified, along with appropriate design criteria, as a
requirement for obtaining a State 404 permit. Decisions regarding whether
or not to implement dredged or fill Best Management Practices through a
208 regulatory program or a State 404 permit program will be made on the
basis of the environmental sensitivity of the area in which the activities
are to be conducted and its relationship .with the^potential for these
activities to cause water pollution. If the potential to pollute the area
is great, BMP's should be implemented under the 404 permit-program to
ensure that all possible data, opinions, and evaluations are obtained
concerning the project through the review and public participation processes.
There will be more assurance through this program that possible detrimental
impacts resulting from the activities will be detected and identified and
that criteria.for the design and effective application of a BMP system will
be optimized. If conditions existing at a site for dishcarging dredged or
fill materials are so sensitive that available BMP's will not prevent
significant environmental degradation, an alternate, less sensitive site
should be used or the discharge prohibited.
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ACKNOWLEDGEMENTS ii
PREFACE 111
INTRODUCTION . 0-1
Analysis of The Problem . 0-2
Adequate Program Planning, and Development 0-5
Best Management Practices^, Summary 0-8
CHAPTER 1 - MINIMIZING THE IMPAIRMENT OF WATER FLOW OR CIRCULATION
Properly Locating, Orienting, and Shaping Masses of Dredged or Fill
Materials 1-1
Providing Flow Through Dredged or Fill Materials 1-2
Preventing Detrimental Elevation Changes In Channels 1-5
CHAPTER 2 - PREVENTING OR CONTROLLING THE RUNOFF OF EXCESS SEDIMENT LOADS
OR TURBIDITY INCREASES 2-1
During Discharge or Placement of Materials 2-1
Protecting Masses of Emplaced Dredged or Fill Materials
From Erosion 2-14
CHAPTER 3 - ENSURING CONTAINMENT OF POTENTIAL POLLUTANTS WITHIN MASS OF
DREDGED OR FILL MATERIALS 3-1
CHAPTER 4 - ENHANCEMENT—THE REPLACEMENT, RELOCATION, OR RECONSTRUCTION OF
EXISTING ENVIRONMENT 4-1
Wetlands 4-1
Streams 4-2
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CHAPTER 5 - PROTECTING EXISTING HABITAT AND PROVIDING FOR FISH AND
WILDLIFE PROPOGATION 5-1
Creating Passageways For Aquatjc or Water-Dependent Wildlife Through
Around, Or Over Structures . .' 5-2
Providing Protective Devices For Wildlife Contacting or Crossing
Structures 5-9
Habitat Improvement Measures 5-19
REFERENCES 6-1
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GUIDANCE FOR BEST MANAGEMENT PRACTICES TO CONTROL THE DISCHARGE
OF DREDGED QR FILL MATERIALS
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INTRODUCTION
The discharge of dredged or fill materials involves man's deliberate
introduction of what can be considered principally naturally-occuring
sedimentary, rock, or earthen materials into the waters and adjacent wetlands
of the United States. Dredged materials generally are discharged for disposal
purposes while fill materials are placed to provide for engineering structures
of one kind or another.
Although fill generally consists of natural geologic materials,
it can be made up of masses of concrete, wood, or any other substances
used to displace the water and change bottom surface elevations. Fill
materials are placed into wetlands or water bodies to provide adequate
foundations, at required elevations, for municipal, industrial, commercial,
recreational, or residential developments or structures. They can form
bridge approaches, highway and railroad causeways, dams, dikes, levees,
road fills across stream channels, and artificial islands or reefs; function.
to protect property from erosion by stream or wave action through the use
of groins, rip rap blankets, revetments, breakwaters, and structural walls
of one type or another; and fullfill other useful purposes. Materials
dredged from a water body can become fill materials if they are used for
providing adequate sites for structures. They could include small linear
backfills in excavations for subaqueous utility lines or communication
cables and fills of large area extent in low lands to provide surface
elevations high enough for land development purposes.
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Analysis of the Problem
Streams, wetlands, lakes, and other water bodies can accept,
accommodate, or adapt to certain stress conditions caused by the discharge
or placement of dredge or fill materials. Exceeding these conditions will
cause readjustments to take place in natural processes which can initiate
water pollution or other undesirable effects. Stresses imposed by the discharge
of dredged and fill materials into an aquatic environment can be induced by
or result from:
1. Changes in the natural flow or circulation of surface and/or
subsurface waters.
2. The addition of pollutants into the water in excess quantities
to cause changes in the chemical or physical characteristics of
the waters.
3. Alternations of the elevation of the substrate, or bottom of the
water body.
The stresses are interrelated and can be superimposed upon one another
to severely damage, or even destroy wetlands or water bodies. Masses, or ;•_.;_
accumulations, of discharged dredged or fill materials often cause detrimental
changes in the flow or circulation of waters. They change substrate, or
bottom elevations, and obstruct or restrict the flow of surface waters or
ground waters by reducing the cross-sectional areas through which they flow.
Local or areawide changes in water levels, normal flunctuations, velocities,
directions of movements, and other characteristics occur. They can initiate •
adverse effects in the production, movement, and occurrence of aquatic
life and water-dependent wildlife; cause changes in the chemical and physical
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quality and other characteristics of the water; and function to increase
normal erosion and sediment transport and deposition rates. The particles
of various sizes that comprise-the principal, mass of dredged and fill
materials (sediments) can become pollutants if moving water erodes them
from their area of placement and transports them into adjacent areas. They
can reduce the light-transmitting capacity of the water body to create
undesirable environmental effects, blanket its bottom to smother or reduce
aquatic life, and impair its quality for beneficial uses.
Dredged materials often contain additional pollution-causing materials
such as nutrients, metallic compounds, pesticides, oils, and greases, or
other materials. Many of them are adsorbed to the fine-grained dredged
material such as silts and clays. Others form coatings on materials of any
size. Fill materials may contain pollutants similar to those in the dredged
materials if they are obtained from a polluted source. Even if they are
obtained from a source that has not been affected by pollutants, fill materials
may contain naturally-occuring substances that change status and become
pollutants when transported to and placed into a different environment,
particularly an aquatic one. These substances may include such mineral
compounds as iron sulfide (pyrite), calcium sulfate, sodium chloride, and ""
other materials which, through chemical or physical processes, can become
soluble and be transported into adjacent area.
Some pollutants, such as nutrients, can cause accelerated eutrophication
(enrichment) of waters with accompanying detrimental changes in aquatic life.
Others can change the physical or chemical characteristics of the water,
impart undesirable tastes to it and the aquatic life" in it, and initiate
undesirable environmental effects in the life cycle of all aquatic orbanisms
and wildlife depending on it. As higher order organisms consume lower aquatic
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organisms that have ingested minor quantities of pollutants, concentration
of the pollutants may occur in the higher organisms. This is termed bio-
magnification. Its severity is" influenced by the physiology of the organisms
involved and the characteristics of the pollutants.
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Adequate Program Planning And Development
Advanced planning, prior to initiating the discharge or placement
of dredged or fill materials into a stream and adjacent wetlands, is
essential for preventing environmental problems from resulting. Often,
it can prevent, through management decisions, the development of conditions
that could add materially to the potential for environmental degradation.
If problems can be foreseen during the planning stages, alternative sites,
scheduling of operations, methods, or practices may be used to minimize them.
Program planning and development probably will be done most advantageously
on a multi-disciplinary type approach. Personnel with engineering, geologic,
wildlife and biologic, soils, and hydrologic backgrounds should all be involved
in the process to enable all possible aspects of the problems and their
solutions to be considered. If personnel competent in any of these disciplines
are needed and not available in the staff of the management agency, they
may be obtained, on a consulting basis or some other type of arrangement,
from one of the various Federal, State or local agencies that are knowledgeable
in the field.
All necessary pertinent information on the proposed disposal site,
and alternative sites, should be collected and evaluated. Factors to be
considered include the existing environmental conditions, potential for the
discharge to cause pollution, and Best Management Practices for pollution
prevention or reduction. The best combination of sites, types of discharges,
and management practices will function most effectively to minimize the
environmental problems that could result from the activities. Sites in which .
insurmountable environmental problems could arise should be avoided or
discharge schedules changed to reduce the potential for pollution. Often,
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minor changes prior to initiating an activity will serve to prevent pollution
problems or habitat destruction much more effectively than remedial after-the
fact measures.
An adequate Best Management Practices program for preventing environmental
problems that could result from the discharge of dredged or fill materials
can best be achieved through the proper development of plans by the dis-
charger; adequate review and approval of these plans by a responsible manage-
ment agency; adjustment of the plans after the review to maximize the
effectiveness of the Best Management Practices prior to their application;
monitoring by the management agency for adherence to the plan; and, when
required, effective and aggressive enforcement of environmental laws.
Effective Best Management Practices must be based upon a consideration
of all existing conditions at the site that interrelate to maintain the
long-term integrity of environment there. They should achieve needed
environmental protection at the least possible cost. Important factors to
consider in their development include the occurrence and movement of both
ground and surface waters; geologic, soils, and topographic conditions; and
the existence, needs, and sensitivities of aquatic and other life occurring
in the area. Proper scheduling, or timing of activities, often is as important
to a Best Management Practice as an adequate design and application.
Guidance for the development, selection, and application of Best
Management Practices, such as that presented in this document, can be provided
by governmental agencies. On a national scale it must be general in nature
such as that provided in this document. At the State, and possibly local,
level the guidance will be more specific regarding local conditions. The
BMP's defined in site plans, however, must be made on a site-specific basis
by those most familiar and knowledgeable regarding the site area.
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Guidance should always be flexible enough to allow initiative to be
used for developing new, less expensive, and more effective BMP's. . A .
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flexible BMP program also allows for the application of State and local
expertise towards the understanding of site-specific environmental character-
istics and problems. This is essential as official guidelines often are
interpreted to represent minimum standards. These standards, in reality,
then tend to become enforceable criteria for performance. As long as the
guidance does not become too rigid and management agencies do not begin to
feel that it covers all site-specific requirements that are to be encountered,
the approach is good. If, for a management agency, the guidance represents
a "cookbook" to use in lieu of good professional and management experience
and judgement, it will become a poor tool. They must ensure that rote and
complacency do not begin to supersede the use of logic and common sense in
the development and use of Best Management Practices.
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Best Management Practices, Summary
Best Management Practices for preventing environmental impacts from
the discharge of dredged or fill materials into waters of the United States
are, to a large extent, technically feasible and readily available. After
all alternatives to a project have been evaluated, based upon 404(b)(l)
guidelines, and the decision has been made that the discharge, or placement
of dredged or fill material is to be conducted, effective procedures, measures,
and practices for preventing environmental problems can be devised and imple-
mented. They involve practical engineering designs, structures, procedures,
and schedules for operations that have been used for many years to control
surface or subsurface flows of water, prevent the loss of materials from a
site area, and provide for the protection and propogation of fish, shellfish,
and wildlife.
Since many of the environmental concerns we have now were not-of vital
interest during the conduct of past engineering projects, many of the existing
techniques and structures are inadequate for environmental protection
or create, rather than prevent, such problems. In view of this, modification
of the design of structures and procedures for their placement or construction
must be considered to reverse this trend and protect the environment rather
than damage it.
Environmental problems that can result from the discharge of dredged
or fill materials into streams, lakes, or wetlands can be prevented or
minimized only through implementation of effective Best Management Practices.
Descriptions, discussions, and examples of BMP's are presented in the
following five chapters of this guidance document. They include, but are
not limited to operating procedures, scheduling of activities, or management
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practices which can be conducted or applied to ensure that: (1) stream
or current flow changes are minimized, (2) increased sediment loads or.
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turbidity levels effectively reduced, and (3) other pollutants included
with dredged or fill materials are restricted from entering water bodies.
BMP's may also involve (4) the relocation, reconstruction, or enhancement
of an area of wetlands or a stream if no other alternatives exist and
(5) protecting existing habitat and providing for fish and wildlife propagation,
Best Management Practices involving minor discharges of dredged or
fill materials with relatively insignificant impacts on the aquatic environ-
ment are similar to those needed for major discharges with significant impacts.
They are much less elaborate and expensive; however, and generally require
no formal design or rigid application specifications. It must be emphasized
here that the results desired with regard to the protection of the chemical,
biological, and physical integrity of our Nation's waters are the same with
either large or small discharges.
Preventing Impairment of Water Flow or Circulation
Masses of dredged or fill materials placed (or discharged) into streams,
lakes, or wetlands can impair the natural movement or circulation of wa-ter. '.',...-
in them. The degree of impairment will depend upon the volume, permeability,
and location of the material that is discharged where it can reduce the cross-
sectional area through which the water flows. This applies to the sub-surface
flow of water as well as to surface movement.
There are several ways to reduce, or prevent, the impairment of
circulation or flow. They involve one or more of the following basic
techniques regarding discharge, or placement, of dredged or fill materials:
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1. Minimizing the extent of individual fills or the concentration
of numbers of fills.
2. Providing continuous open channels through, or around, masses
of materials parallel to natural flow directions.
3. Using alternate sections of impervious fill with pervious
sections or open structures to permit free flow of water.
4. Designing channel - spanning structures:
a. To pass flood flows with no significant adverse impacts
from flow restriction.
b. To minimize debris blockage which can obstruct flow.
c. In accordance with upstream and downstream hydraulic flow
conditions (do not cause drastic changes in flow regime).
5. Aligning bridges, culverts, and other structures to limit adverse
impacts from flow disruption resulting from abutments or other
fills.
Preventing, or Controlling, The Runoff of Excess Sediment Loads or Turbidity
Increases
Excess sediment loads or turbidity increases can occur in streams as a
result of the placement of dredged or fill materials into water bodies and -•-
wetlands. The erosion and transportation of particulates can take place during
the actual placement of the dredged and fill materials if no preventative
measures such as cofferdams, caissons,filter cloth fences, or other preventative
devices or procedures are used. To prevent in-place, or completed, dredged or
fill deposits from being subjected to the erosive forces of high-velocity
surface flows, effective surface protection measures "such as rip rap blankets
(or layers), concrete walls, and similar measures should be provided. The
erosion and transport of sediments can be minimized, or prevented by one or
more of the following measures or practices:
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1. Placing materials on dry land by scheduling operations during
low flows, using structures to exclude the water, or by
temporarily diverting.the stream from the site;
2. Protecting slopes that will be subject to erosion by surface
flows with erosion-resisting coverings such as vegetation, rip
rap blankets (with or without underlying filters), gabions, retaining
walls, aprons, wing walls, and similar measures.
3. Designing bridge-supporting members such as piers, piles, etc.,
to minimize scour.
4. Providing filter cloth, or some other type of filtering media to
remove sediment being transported from an area of placement.
5. Avoiding placement of dredged or fill material during conditions
that may be extremely critical for sensitive aquatic life and
wildlife such as spawning seasons or migration times.
6. Using placement procedures to prevent, or restrict, the movement
of mobile equipment in the water.
Extreme care should be taken during the planning, design, and placement
of a fill to ensure that structural failure does not occur during the project
life to allow the material to enter a water body or adjacent wetland. Adequa-te
criteria should establish the factors of safety to be used in the design,
analysis^nd placement.
Ensuring Containment of Potential Pollutants Within The Discharged Mass
of Dredged or Fill Materials
At times, dredged or fill materials placed, or discharged, into streams,
lakes, wetlands, or other water bodies may contain natural materials such as
iron sulfide (pyrite), calcium sulfate (gypsum), and various salts. These
materials are not pollutants in their source areas but can become pollutants
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when transported and deposited in another aquatic environment. If polluted
materials can be effectively contained by effective BMP's and prevented from
affecting water quality, their discharge should not be precluded, provided they
are not toxic. Effective containment within the mass of materials is essential
for use. It can be done by:
1. Surrounding the poor quality material during placement with walls
and blankets of relatively impervious materials such as compacted
fill, concrete, or similar materials. Drain blankets for pumpout
of fluid may be desirable.
2. Restricting the use of poor quality materials to areas above
high-water elevations and capping with relatively impervious
blankets of fill to prevent infiltration of rainfall and subsequent
leaching.
3. Blending poor quality materials, such as pyrite, with naturally-
occurring neutralizing materials such as crushed limestone during
placement.
Enhancement or Replacement, Relocation, or Reconstruction of
Existing Environment
If, after evaluating all alternatives, the placement of dredged or.fill! .
materials into wetlands or other water bodies is justified; and available
Best Management Practices will not effectively prevent adverse effects,
enhancement or replacement of the existing environment may be feasible.
This could include such practices as:
1. Creating and maintaining additional wetlands equivalent in
area to those destroyed by the discharged deposits.
2. Providing shallow or deep water areas equivalent to those
destroyed by the placement of materials for the maintenance of
aquatic and water dependent wildlife.
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3. Providing for the relocation of streams which have been designed
and constructed to flew under the same gradient, hydraulic, and
aquatic habitat conditions as before.
A multi-disciplinary approach is critical in determining the feasibility -
of enhancing or replacing, relocating, or reconstructing existing environmental
conditions in a site area and developing appropriate BMP's. Competent hydro
legists, geologists, biologists and wildlife specialists, engineers, soil
scientists, and other personnel from 208 or 404 management agencies, the dis-
chargers, and involved State or Federal fish and game and resource agencies
should be consulted and their opinions considered and evaluated. Long-term
as well as short-term results of the activities and projects must be considered.
Protecting Habitat and Providing For Fish and Wildlife Propagation
The disposal of dredged or fill materials into water bodies or wetlands
can cause detrimental changes to occur in the habitat for fish and wildlife,
particularly in the immediate locality of the discharge. Migration routes or
access to select food sources can be blocked or restricted, propagation
activities interfered with, and key ecological relationships and interdependences
disturbed. > - ... '.'.'•...•
Best Management Practices for mitigating, or preventing, these
environmental problems can involve scheduling of operations to avoid creating
problems during conditions that are critical for aquatic and other wildlife.
This could include spawning, migration, nesting, and other periods where the
effects of discharge activities could be much more critical than during other
times. Other practices may involve the proper placement and management of
activities as well as the modification or construction of structures and
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techniques to offset terrane changes, water level and flow alterations, and
revision in the natural physical or biological integrity of the water bodies
and wetlands due to the discharge. They could include:
1. Creating avenues for movement of aquatic life and wildlife
through structures formed of dredged or fill materials.
2. Providing protective devices for wildlife when contacting or
crossing structures of dredged or fill materials.
3. Creating necessary habitat improvement measures.
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CHAPTER 1
MINIMIZING THE IMPAIRMENT OF WATER FLOW OR CIRCULATION
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Best Management Practices to reduce, or prevent, the adverse impairment
of flow or circulation of waters can involve properly locating, shaping, and
orienting masses of dredged or fill materials to minimize flow disruption;
limiting their unbroken extent or providing continuous open channels through
them; preventing abrupt changes in the elevation of the bottom of stream
channels which restrict free movement of aquatic life; and ensuring that
the transmission capacity of surface or ground water systems is not adversely
affected.
The discharge, or placement, of a mass of dredged or fill materials
into a water body or its adjacent wetlands will alter the elevation of the
bottom surface (substrate) of the water or the surface of the wetland. It
will reduce the cross-section area through which surface or ground water
moves and cause subsequent changes in their flow and circulation patterns.
Local or areawide changes in water levels, normal fluctuations, velocities,
direction of movement, and other characteristics will occur perhaps within the
affected body and both upstream and downstream. The degree of the impairment.
of flow or circulation will depend upon the volume of materials discharged
or emplaced and the reduction in cross-section resulting.
Adverse effects caused by the alteration of flow or circulation patterns
may involve changes in the occurrence, movement, and natural productive
capacity of aquatic life; chemical and physical characteristics of the
water; and energy capacity for moving sediment and other materials through . .
the natural water system .
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Property Locating, Orienting, and Shaping Masses of Dredged or
Fill materials
Dredged materials discharged for disposal and large fills placed in
shallow water or wetlands for land development purposes can have a major
effect on the flow and circulation pattern of water both locally and areawide.
These effects can be reduced to a large extent by locating, orienting, and
shaping the masses of materials so that they minimize the disruption of flow.
The potential for erosion and the subsequent sediment losses will be minimized
also by these practices.
Factors to be considered in designing the most advantageous shape,
orientation, or location include the topography of the surface upon which
the material is to be discharged or placed, direction of prevailing current
or wave movement, irregularity of the contact between land and surface and
the water body, and the need to minimize the length of containment dikes.
These dikes must be constructed to contain the materials before any discharge
of materials takes place. Large fills for land development purposes may
consist entirely of fill materials derived from underwater sources and
capped by a thick layer of stronger more competent fill obtained from land ;
sources.
Areas of indentation in shorelines of water bodies can be considered
for the location of deposits of dredged or fill materials. If they are
sensitive wetlands they should be avoided, if at all possible. The design and
proper discharge of these deposits; however, could result in the creation and
development of a wetland habitat to enhance the environment as well as minimizing
impairment of flow and circulation.
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If the indentations are located in the straighter portions of stream
channels and on the inside of stream bends, properly shaped masses of dredged
or fill materials situated in them will be outside of the main currents and
have a minimal effect on their flow. In lakes or other open water bodies
they also will have only a minor effect on currents along the shore.
Figure 1-1 illustrates how dredged materials can be placed with rip-rapped
containment dikes in such indentations of a stream. In these areas, the
lineal extent of the dikes can be minimized, particularly if the landward
side has sufficient topographic relief to contain the materials.
POORLY LOCATED AND SHAPED
CONTAINMENT
DIKE
Figure No. 1-1 - Deposits of Dredged Materials Contained by Dikes Can
Be Located So They Do Not Project Into .Main Currents
If the areas of indentation are the result of overland erosion rather
than stream meanders, or wave action in open bodies of water, they represent
areas where surface drainage will concentrate. In this case, measures must
provide for diverting the drainage around the contained dredged or fill
materials or passing it through or beneath them. Diversions should be
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designed to prevent subsequent erosion by concentrated flow and to look like
natural features. Passing surface water through the deposit will require a
spillway over the containment dike that will not erode or cause failure of
the structure and release the contained materials. If culverts, or other
structures, are used to pass flows beneath the deposit, they will have to
be considered in the design stages and placed during construction of the
dikes and before discharge begins behind them.
Dredged or fill materials placed in open waters must be shaped to provide
the least feasible cross-sectional area to be exposed to the natural flow of water.
Dredged materials can be used to create islands and perhaps shallow wetlands
in areas where deeper water existed before. Figure No. 1-2 illustrates proper
shape and orientation for such placements. They must be contained by dikes
of some type or another. Rip-rap or some other erosion-protecting devices will
be needed as either current or wave action will tend to remove the obstruction
and deposit it into another area.
PREVAILING
DIRECTION
OF
' WAVES
OR
CURRENTS
1 POOR ORIENTATION
CONTAINMENT
DIKES
-^T~_L- '_T"JTj) PROPER ORIENTATION
Figure 1-2 - Properly-Oriented Deposit of Dredged Materials Should Have
Long Dimension Parallel To Prevailing Movement of Waves or
Currents (After Reference No. 18).
-------
1-5
Providing Flow Through Dredged or Fill Materials
Dredged or fillmaterials should not be discharged or placed -into
•*
water bodies or wetlands over such extensive areas or alignments that
they adversely disrupt the normal flow or circulation of either surface or
ground waters. Extensive areas can include those used for disposing of large
quantities of dredged materials or large fills for airports, subdivisions,
shopping centers, and other facilities. Extensive lineal deposits include
causeways for highways, and other roads, railroads, canals, and similar
structures. Materials placed into these deposits may consist of that dredged
from water bodies and that obtained from land sources.
Deposits of Large Area! Extent
Large masses of materials can be located and oriented to minimize changes
in water flow and circulation patterns. If this is not adequate, practices
should be developed to allow movement of water through these dredged and
fill deposits. Open channels, culverts, systems of channels and culverts,
pervious rockfill surface and subsurface sections, and alternating sections
of each should be considered.
The occurrence, nature, movement, and extent of-both ground and - ... -.. .
surface waters must be considered in the design of Best Management Practices
to minimize detrimental flow and circulation changes. In general, the
direction of ground water flow is similar to that of surface water but
anomalies do occur. They must be considered to prevent the occurrence of
problems at a later date.
Figure 1-3 represents a sketch of a fill for a" small park incorporating
open channels through which water can flow and minimize disruption due to
this facility. Bridges are used for channel crossings but culvert installation
also may be practical.
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1-6
Figure 1-3 - Fill For Small Park With Open Channels Provided For
Water Movement. Retaining Dikes and Channel Banks Should
Be Protected With Rip-Rap
Deposits of Large Linear Extent
Fills that are installed to provide for such linear structures as
causeways for highways or railroads, levees, and similar facilities
generally extend across the natural drainage of streams or wetlands. Bridges
or culverts usually are installed where stream channels occur. Ground water
and surface flow, however, must move laterally through or over natural
linear features to reach them. As a result, more extensive and drastic
differential water surface elevations must occur to initiate these move-
ments through the few open structures. Depth changes, erosion and
sediment deposition, and other environmental problems may result.
-------
1-7
Wetlands often consist of soft, compressible deposits of fine-grained
silts and clays, loose sands, and organic matter. The weight of the
causeway fill can cause these materials to consolidate and/or move laterally
to make way for and .support the fill (See Figure No. 1-4). If the fill
materials used are relatively impervious compared to the natural deposits,
the area through which the ground water moves will become reduced,and the
flow restricted. Ground water levels on the up-gradient side of the fill
will rise and force water to the surface. On the down-gradient side, water
levels will be lowered. These water level changes can cause severe environ-
mental problems on either side of the causeway.
MATERIAL DISPLACED
BY FILL
GROUND WATER
FORCED TO THE SURFACE
—_ ROADWAY I--
-~- FOR I—II—JT—I
I—I CAUSEWAY -—-~-~-^
WATER FLOW
Figure No. 1-4 - Impervious Roadfill Section Placed On Wetland Consisting
Of Soft Organic Sediments With Sand Lenses. The Natural
Material Consolidates and Restricts Ground Water Flow.
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1-8
Best Management Practices for preventing, or minimizing detrimental
changes in both surface and ground water flow and circulation patterns
can include such measures as using pervious fill materials and alternating
sections of pervious and impervious fill and open channel sections. (See
Figure Nos.,1-5 through 1-8). Perviousness, or permeability, is a function of
the material. Sand, sand,and gravel, or similar materials may be used to provide
a pervious fill section. The BMP's must function to prevent restriction of
surface and ground water flow and circulation. Structures must be constructed
to pass low flows without restricting movement of aquatic creatures and other
water-dependent wildlife as well as the high discharges from floods.
ROCKFILL
SECTION
DIRECTION OF
GROUND WATER FLOW
Figure No. 1-5 - Pervious Roadfill Section On Wetland Allows Movement
Of Ground Water Through It and Minimizes Flow Changes.
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1-9
[ NOTE: GROUND WATER
I CLOSE TO SURFACE
/7~7
PILING
Figure No. 1-6 - Causeway Across Wetland Designed To Minimize Disruption
of Surface and Ground Water Circulation. Fill Composed
of Pervious Rock and Impervious Earth Materials.
Fills For Stream Crossings
Any fill, or other structure, placed into a stream channel through which
water moves will restrict the cross-sectional area through which the flow
moves and, to some extent, obstruct the flow and cause changes in circulation
patterns. Best Management Practices include techniques for minimizing the
obstruction of flow and circulation changes. For example, a bridge that spans
the entire stream does not constrict the channel as it places no obstruction
in it. (See Photo No. 1-1). If piers are used, they should be located and
spaced to minimize the flow obstruction and channel disturbance. (See Figure
Nos. 1-7 and 1-8). In forest areas during flood flows, fallen timber may be
carried downstream to obstruct flows when they are trapped across bridge piers.
When designing the bridge, consideration must be made of the probable length
of trees or logs expected during floods. The distance between piers should
exceed this length, otherwise obstruction of flow, flooding, excessive erosion,
or bridge failure may result and cause damage to aquatic habitat as well as
the downstream areas. If this is not feasible, arrangements should be made to
remove blockages during flood flows.
-------
I
o
Photo No. 1-1 - Small Wooden Suspension Bridge Spanning Stream (U.S. Forest Service)
-------
1-11
Culverts should be designed and constructed not only to pass high
flows without creating environmental problems, but also the low flows.
During low flows, passage .for aquatic life may be restricted if'this was
not considered during the design stages. Species of fish occurring in the
stream involved must receive consideration. If possible, the existing stream
bed should be completely spanned by a half-round culvert. (See Photo No. 1-2)
BETTER ENVIRONMENTAL DESIGN
HHHHHk
DESIGN STORM WATER SURFACE
MAXIMUM NORMAL WATER SURFACE
.*.A.<_A_^-r<.<.«..-OV^^^
Figure No. 1-7 - Stream Crossing With No Construction Required In
The Normal Channel
POORER ENVIRONMENTAL DESIGN
HHHHHHHHHH^
SCOUR
PROTECTION
SCOUR PROTECTION
Figure No. 1-8 - Stream Crossing With Pier In Central Section Of Normal
Channel
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1-12
Photo No. 1-2 - View Through Large Half-round Culvert. Note Natural-
appearing Stream Channel For Fish. (Reference No. 28)
If a round culvert is used, it should be installed sufficiently
below the stream channel to have the water level up into the larger
section of the structure. After a period of time, gravel and other
sediments will fill its bottom and create a naturally-appearing channel
(See Figure No. 1-9). An example of a culvert installed at too shallow
a depth to allow passage of fish during low flows is shown in Photo No. 1-3,
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1-13
Photo No, 1-3 - Large Culvert Installed With Little Consideration
For Adequate Depth of Flow For Fish Passage (U.S. Forest Service)"
-------
1-14
Figure No. 1-9 - Round Corrugated Culvert Placed Below Streambed To
Provide Fish Passage During Low Flows (Adapted After
Reference No JO)
Culverts should also be installed with their inverts (bottoms) on the
same gradient as the streambed. Steeper gradients may create velocities too
great for aquatic life, and gradients that are too low will create ponding
upstream and probably have a limited capacity to pass the designed flows
(See Figure No. 1-10)
Figure No. 1-10 - Round Corrugated Culvert Placed At A Gradient Steeper
Than Stream Gradient^ High Velocities Result (Adapted
After Reference no.10).
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1-15
Many BMP's can be used to enhance the flow characteristics through
culverts to provide better conditions for fish passage. For many of
the detrimental flow problems created by culvert installation there are
remedial structures, or measures, that can be used to minimize them.
Several are illustrated in the following illustrations (Figure No. 1-11
and Photo Nos. 1-4 and 1-5). Best Management Practices for culverts
designed for passage of fish and aquatic life should include a consideration
of routine maintenance to keep them clear of debris and sediment. In the
absence of maintenance, the fish passage design feature can be negated.
DOWNSTREAM
T/f//
ROCK STRUCTURE
Figure No. 1-11 - Rock Barrier Structure At Discharge End of Culvert
Providing Adequate Depth of Water For Fish Travel.
Resting Pools Help Fish Conserve Energy
-------
1-16
Photo No. 1-4 - Gabion Structure Being Installed To Provide Adequate
Depth of Flow Through Culvert. For Detail See Figure
No. 1-11 (U.S. Forest Service)
Photo No. 1-5 - Reinforced Concrete Box Culvert With Baffles To Provide
Adequate Flow For Fish Migration. Note Gravel In Bottom
of Culvert (Reference No. 28)
-------
1-17
Multiple culverts should be installed through a fill of linear
extent in wetlands to prevent concentration and restriction of flow.
(See Photo No. 1-6). One or twb large culverts through the center of
the fill could transmit as much water as the many smaller ones but would
require much more lateral flow changes and concentrations of discharge. One
or more of the smaller multiple culverts can be placed at lower elevations
than the others to provide adequate flow for passage of fish and other
aquatic life during low flows.
•^fes*
Photo No. 1-6 - Multiple Culverts Provide More Uniform Passage of Streamflow
and Prevent Concentration of Flow (Reference No. 28).
Another type of structure which minimizes stream flow restriction is
shown in Photo No. 1-7. It consists of a concrete low-water bridge which
permits free flow of water under it during low water. High flows will
overtop the structure.
-------
1-18
Photo No. 1-7 - Example of Low Water Bridge That Does Not Restrict Low
Flows and Allows Free Passage of Aquatic Life (Reference
No. ^
-------
1-19
Photo No. 1-8 - Fish Ladder Allows Fish To Move Around Dam, or Other
Water - Retaining Structure (U.S. Bureau of Reclamation)
-------
1-20
Preventing Detrimental Elevation Changes In Channels
Some stream-crossing structures such as culverts and bridges create
abrupt stream-channel and water surface elevation changes that can have
detrimental effects on the movement of aquatic life and possibly cause
other environmental problems such as erosion and sediment losses.
Figure No. 1-12, obtained from the U.S. Forest Service, illustrates
four different problems that anadromous fish can encounter as a result of
culverts being installed above streambed elevations. All of these problems
can be resolved by lowering the culvert to reduce the elevation change,
decreasing the culvert gradient, increasing the depth of water in the
culvert bottom, and providing for resting pools at either end. To provide
adequate design at a minimal cost, information must be obtained regarding
the jumping ability of the fish involved and their speed and endurance.
Structural aids to provide increased water depths and other advantages are
shown in Figure No. 1-11 on Page 1-15.
-------
1-21
VELOCITY TOO GREAT
NO RESTING POOL BELOW CULVERT
\
m,f, fa
JUMP TOO HIGH K l • sVl
:LOW IN THIN STREAM OVER BOTTOM
•,'v -._*—
;$$®&3\ - ^~&-~
''£?•&&$$• ! - *ULL—K^r
Figure 1-12 - Culvert Installations Which Restrict Fish Passage (Reference No.28)
-------
1-22
They provide the required resting areas and depth of water for passage.
Some types of bridges, particularly those with concrete aprons, or other
foundation slabs can act .as barriers to the movement of aquatic life. If
water flowing over the apron is extremely shallow or flowing at high
velocity, fish cannot move through it (See Photo No. 1-9).
Photo No. 1-9 - Bridge Foundation Slab Showing Thin, High-Velocity Flow
of Water and the Extent of Jump Required for Passage
(Reference No. ,28).
Best Management Practices to prevent such problems can involve sloping
the apron to concentrate water flow into one end and make it deeper;
providing a narrow and deep low-flow channel through apron; constructing
several small pools downstream from drop-off to progressively reduce
abrupt elevation change; and placing rock obstructions to minimize
velocities of flow.
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2-1
CHAPTER 2
PREVENTING', OR" CONTROLLING THE RUNOFF OF EXCESS SEDIMENT
LOADS OR TURBIDITY INCREASES
Loss of sedimentary materials by erosion processes can occur during
the placement, or discharge, of dredged and fill materials and after the
mass of materials is actually in position. Best Management Practices to
prevent or minimize this problem must receive full consideration during
the entire process from planning prior to placement, through the imple-
mentation or installation period, and until the materials are stabilized
and protected adequately or removed. If possible, discharge of materials
should take place in areas of containment or on dry land. This can be done
by scheduling the discharge during low flows, temporarily diverting, or
by-passing the stream, or excluding surface waters through the use of some
type of retaining structures such as cofferdams, caissons, and embankments.
Following placement, the mass of dredged or fill materials must be protected
from erosion by rainfall; sheet runoff; and concentrated streamflow, wave
action, and water currents. Surface protection should be designed and
constructed to extend above projected design flood elevation and to prevent
underlying material from being eroded and transported into downstream areas.
Examples of Best Management Practices to prevent or restrict the
runoff of excess sediment loads and increased turbidity are presented
here, along with discussions regarding some factors to consider in their
application.
During Discharge or Placement of Materials
Most dredged and fill materials consist of relatively fine-grained
sediments; and moving water will erode and transport them downstream during
-------
2-2
discharge or placement. Because of this, all possible efforts should
be exerted to discharge dredged material into a contained area and to
place fill materials on foundations that are not submerged.
Dredged Materials
Disposal of dredged materials must be done in an area of containment
so that runoff of the materials is prevented. Containment generally can be
achieved through the use of dikes, or embankments, made from materials obtained
in the vicinity. If disposal is in a lowland area, a dike may be required to
surround the area completely. In an upland, however, a dike may be needed
only across the lower boundary of the area to provide storage (See Figure 2-1).
The stability of the dikes must always be considered to ensure that failure
.does not occur and release the contained material back into the water.
RIVER
DREDGED
MATERIALS
BORROW AREA
FOR DIKE
CROSS SECTION (Not to Scale)
Figure No. 2-1 - Containment For Dredged Material In Upland Area
Adjacent To River
-------
2-3
Dredged materials generally consist of a slurry made up of water
and solid sedimentary materials. After discharging them into the disposal
area, the coarser particles settle out; and the water, containing fine-grained
sediment particles (silts and clays) becomes an effluent when it leaves the
containment site. Control of this effluent poses a major solid-liquid
separation problem if the containment has a limited storage capacity, much
of the material is fine-grained, and periodic removal of the effluent is
necessary.
If the dredged materials are principally of sand, or coarser materials,
the detention time in the containment may be sufficient to remove most of
the sediments. In this case, an outlet pipe with the intake high in the
water column will provide for removal of the relatively clear effluent (See
Figure No. 2-2). An energy dissipator or level spreader should be provided
below the discharge to prevent erosion and provide additional settling and
filtering capacity.
EFRAJEJVIT^rTT/ DIKE \ LEVEL SPREADER
DREDGED MATRIAL
OUTLET PIPE
Figure No. 2-2 - Outlet Pipe For Draining Clear Effluent From Containment
Fine-grained sedimentary materials such as silts and clays stay in
suspension for longer perios of time than coarser materials and need
additional efforts to make them settle out. Certain chemicals added to
dredged materials as they enter a containment area can cause these materials -
to flocculate (aggregate into small lumps) and settle out. Lime has been used
-------
2-4
as well as organic polymers. Effective use of flocculants requires that a
knowledge of the fine-grained sediment particle's reaction to each floccument
*
be obtained. In addition, a separate partition of the containment area may
be necessary to provide an area for the flocculated material to settle out.
If fine-grained materials are still present in the effluent to leave the
containment, filtration through pervious sand or sand and gravel sections
in the dike, sandfilled weirs, filter cloth screens, and similar structures
should be considered (Figure No. 2-3). The quality of effluent discharging
from a given filter system is dependent on the amount of solids entering it
and the filtering capacity of the medium through which it moves. Good or
effective filtration is considered to achieve removal efficiencies of 90%
or more in the intermediate or low ranges of effluent suspended solids
(between 1 and 10 grams/liter). Proper engineering judgement is essential
to obtain the optimal use of all alternaive techniques.
Another alternative to consider would be to use spray irrigating
techniques to dispose of the fine-grained material and prevent its runoff
into water. If done properly, the water will infiltrate soils and leave the
sediments on the surface where it can be stabilized by vegetative growth.
Fill Materials
To prevent the runoff of sediments and their accompanying pollutants,
the preparation of foundations for and the placement of fill materials
should take place on land that is not submerged, if at all possible. If
the fill materials consists only of large, consolidated rock fragments that
are not subject to water movement, placement into a water body may result
in no sediment runoff problems.
Disturbance of the ground and movement of mobile land equipment in
water bodies where excess sediment losses and runoff can occur should be
-------
2-5
3(a) PERVIOUS DIKE WITH MULTI-LAYERED IMPERVIOUS COVER
OVERFLOW FROM CONTAINMENT
STOP LOGS ••
WATER LEVEL
EFFLUENT
!DISCHARGE
TROUGH
3(b) DOWNFLOWSANDFILL WEIR
FILTER MEDIUM
GRADED GRAVEL
COARSE STONE
FOUNDATION SOIL
Figure No. 2-3 - Techniques For Filtering Fine-grained Sediments From Effluent
(After Reference No. 17).
-------
2-6
done only when essential and no other alternative exists. Filtering out
sediment being transported in*the water from the construction site may be
practical through the use of filter-fabric sheeting made of polyprohylene
monofilament materials or similar substances similar to produced bu manu-
facturers for this purpose. If possible, structures such as bridges should
span the stream so that the need for piers for support located in the channel
section can be avoided. (See Photo No. 2-1).
If construction activity or placement of fill must take place in the
stream or other water area, foundation surfaces that are not submerged (in
the dry) can be obtained by temporarily diverting the stream or by using
some type of cofferdam, caisson, or other structure to exclude the water.
Scheduling the activity during periods of low flow or low water levels
also will enable placement of fill to take place in the dry when the potential
for erosion by surface water is minimal.
The technique of temporarily diverting a stream for placement of a
culvert and a road fill is shown in Figure No. 2-4 and the completed facility
in Photo No. 2-2. A small section of new channel is excavated, or a flume
constructed, adjacent to the existing channel. (The new channel should be
lined with impervious material such as plast-ic sheettng, if necessary).- Thfe*
stream is diverted, the culvert installed, and the road embankment placed.
Then the stream is diverted back into the original channel. The diversion
channel is backfilled, and the road fill is completed. Temporary diversion
of streamflow should be done for placement of fills ranging from minor
embankments for logging roads to major ones for the construction of earth
dams (See Photo No. 2-3).
Cofferdams are temporary structures to permit dewatering an area for
the construction of fills and structures on foundation surfaces that are not
-------
ro
i
Photo No..2-1 - Bridge Spanning Stream. No Stream Disturbance Required For Pier
Construction In Channel (I.S. Forest Service)
-------
NATURAL STREAM
DIVERSION CHANNEL EXCAVATED
STREAM DIVERTED, CULVERT PLACED IN EXCAVATION
FILL PLACED OVER CULVERT
COMPLETED ROAD FILL WITH STRUCTURAL PLATE ARCH CULVERTS
STREAM BACK IN ORIGINAL CHANNEL
Figure No. 2-4 - Procedure For Installing Culvert When Excavation In
Channel Section of Stream Will Cause Sediment Movement
and Turbidity Increases
-------
ro
i
vo
Photo No. 2-2 - Example of Completed Culvert That Does Not Restrict Streamflow or
Movement of Aquatic Life (U.S. Forest Service)
-------
2-10
submerged. The type of cofferdam used depends upon the depth of water at
the site, characteristics of the foundation materials, geometry of the
structure proposed, and expected water-level fluctuations. Cofferdams are
made of earth embankments, steel or timber sheet piling, and other watertight
materials.
Caissons are similar to cofferdams. While cofferdams are removed
following completion of the construction or fill placement, caissons generally
form an integral part of the structure. Caisson means "box" in French.
These structures can be rectangular, cylindrical, or in other configurations.
They are driven, jacked, or allowed to sink under their own weight into
position to exclude the water.
As none of these structures are totally impervious, particularly at
contacts with natural materials, they may require pumping out water the
seeps in. Proper disposal of the pumped water is essential. It may be
sprayed on land or temporarily held in a detention pond until sediments
have settled out.
Photo No. 2-3 Flume For Temporary Diversion of Water Through an Earthfill
Dam Site. (Reference No. 19),
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2-11
Cofferdams used to dewater foundations of earthfill or rockfill
dams often become portions of'the principal structure (Figure No. 2-5).
They function as barriers in the river'channel immediately upstream from
the dam foundation while a diversion tunnel or other structure transmits
the water flow back to the channel downstream from the site. The site can
be excavated, fill can be placed, and other activities can be conducted
without being subjected to water flows which can cause sediment runoff
and a pollution problem.
DOWNSTREAM
s
, WATER LEVEL „ ' '
^gss&r k \^
\
PERMANENT
COFFERDAM
-» " ' ' V x
MAIN / 1 DAM ^
/ 1
' 1
/ 1 *"*
/CLAYj Vv
'COREl X>.
^
Figure No. 2-5 - Sketch Showing Cofferdam, Which Diverted Water To
A Tunnel, To Be Incorporated in Main'Structure
Cofferdams are used to exclude water from foundations for any
type of structure. Figure No. 2-6 illustrates how a cofferdam is used to
permit excavation, construction, and backfilling for a large bridge pier.
Photo No. 2-4 shows a smaller, easily-constructed earthfill cofferdam used
to exclude the water during construction of smaller .bridge piers.
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2-12
ENVIRONMENTAL
MATERIALS
(I) CIRCULAR SHEET PILE COFFERDAM INSTALLED,
FOUNDATION BEING EXCAVATED.
(2.) FOUNDATION PILES DRIVEN. THEN CONCRETE SEAL
PLACED UNDERWATER THROUGH TREMIE TUBES.
3J COFFERDAM DEWATERED AND BRIDGE PIER BUILT.
(£) FOUNDATION BACKFILLED WITH SAND AND RIPRAP
TO UNDERWATER SURFACE. COFFERDAM THEN
FLOODED AND SHEET PILING REMOVED.
Figure No. 2-6 - Use of Cofferdam To Permit Installation of Bridge
Pl'er and Prevent Runoff of Sediments Dueing Construction
-------
V
v^vSr^^ s
Photo No; 2-4 -
Small, Easily-Constructed Earthfill Cofferdam Used to Exclude Water
During Construction of Bridge Piers. (Wyoming Highway Department)
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2-14
Protecting Masses of Emplaced Dredged or Fill Materials From Erosion
Surface protection must be provided to any mass of emplaced dredged
*
or fill materials if it contains particles small enough to be eroded or
transported by the action of rainfall, runoff water, or wave action.
Protection from streamflow or wave action can consist of rigid structures
such as concrete, stone, or wood retaining walls or panels and relatively
flexible, as well as permeable, blankets of rip-rap or armor stone,
systems of rock-filled wire mesh baskets (gabions), tree or brush mats,
and other materials. Long term protection from rainfall, above the ordinary
high water mark, can be provided by sufficient vegetative cover. Temporary
protection can be obtained with layers of organic or chemical mulches or
by burlap netting, or plastic sheeting.
If subaqueous trenching has been done, fill placed into the trench
should not extend above the adjacent underwater surface to prevent erosion
and changes in water flow. Often, erosion protection such as rip rap also
may be needed. (See rip-rap protection on sketch no. 4 of Figure No. 2-6).
Rigid Fill-Protecting Structures
These structures function to retain and protect the fill material -.-• -•-
behind them and to reduce the extent of an individual fill needed for
a particular purpose. Photo No. 2-5 shows reinforced concrete retaining
walls for a bridge in the forest area. The angular wing walls channel
water under bridge as well as provide erosion protection for the fill behind
them.
Figure No. 2-7 shows a sketch of another type of retaining and
protecting structure, consisting of layers of compacted earth reinforded
with horizontal strips of metal. The earth layers are compacted on the
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2-15
strips and friction (without slippage), between the earth and the strips
provides strength for the entire unit. Tensile forces are absorbed by
the reinforcing strips and earth movement is therefore controlled by this
stiffer material. The concrete panels function to protect the earth from
erosion by water and allow free drainage of water from the fill (photo No. 2-6)
> ^*T£S =••^< -* - ^3v • * " * *
l^s^^jt'----x
Photo No. 2-5 - Bridge in Forest Area with Abutments Supported and
Protected From Erosion By Concrete Retaining Walls
(U.S. Forest Service)
RAILROAD
_2 Q_
STREET
ANNUAL HIGH WATER ELEVATION
GROUND
-REINFORCED EARTH
I EMBANKMENT
LIMITS OF EXCAVATION
Figure No. 2-7 - Reinforced Earth Embankment Protected. From Erosion
By Concrete Panel Face Construction Completed Behind
Dike Cofferdam to Exclude Creek (After Reference No. 24),
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2-16
Photo No. 2-6 - Concrete panel Facing For The Reinforced Earth
Embankment Showns in Figure No. 2-7 (Reference No. 24).
Concrete facing that does not function as a retaining structure can also
be used to provide surface protection for masses of fill materials (See
Photo No. 2-7). It generally is formed of slabs of reimforced concrete
with the joints between them sealed with plastic fillers. Open cracks or
holes which develop must be sealed promptly or the action of water and
waves may displace or break up the slabs.
Photo No. 2-7 - Precast Concrete Panels Protect Slope From Erosion
(Reference No. 4).
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2-17
Flexible Fill-Protecting Structures
Rip-rap should consist of hard, dense, durable angular rocks. They
protect the underlying material from the erosive energy of moving water
and increase the surface roughness of the bank to reduce the velocity of
moving water and cause deposition. The rock can be placed in a layer
upon an exposed slope by machine or by hand. Segregation of materials
should be prevented during placement (See Photo No. 2-8).
^•^•*^aa*»*^v*<«ii^^y-^-">'^?TJa-Sg-^^T..^^vaTrt*aBgs^-i*--f*^r vfsv-r-rr0";^*'**'
Photo No. 2-8 - Carefully Placed Rip-Rap "Armor" To Protect Roadfill From
Stream Erosion. Material To The Right Has Been Sealed
With Grout.
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2-18
The thickness of the rip-rap blankets (layers) needed depends upon
the steepness of the slope upon which they are to be placed; stream velocities
or severity of wave action expected; methods of placement; and- the size,
shape, and specific gravity of the rock used. Some sources say the thickness
of the blanket should be about 1.5 times the diameter of the smallest
"immovable" rock if the rip-rap is hand placed, and 1.9 times that diameter
if it is "dumped". A reduced thickness can be achieved if compaction
techniques are used such as "plating" with a large flat weight. This
densifies the rip-rap blanket and smoothes its surface. Provisions should
be made to ensure that the toe area is secure from scour action by currents
to prevent lateral sliding of the entire blanket (See Figure No. 2-8).
An underlying filter blanket of sand and gravel or fine-mesh filter fabric
should be provided beneath the rip-rap to prevent upward movement of the
protected materials through voids between the larger rip-rap blocks.
DESIGN HIGH WATER
BELOW LOWER
LIMIT OF SCOUR
PLACE LARGER ROCKS
AT BASE AND ON FACE
FILTER
BLANKET
OR FILTER
FABRIC
APPROXIMATELY 2X
THICKNESS OF BLANKET
Figure No. 2-8 - Rip-Rap Blanket Protecting Slope From Erosion By
Current and Wave Action. Note Filter Blanket and
Toe Construction. (After Reference No. 9).
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2-19
If blocks of rock large enough to remain in place during high velocity
flows or heavy wave action are not available, smaller rocks can be bonded
together after placement by grouting ('cementing). These grouted blankets,.
with the rocks, cemented to one another, do not have to be as thick as
loose rip-rap and they will remain in place upon much steep slopes (See
right-hand side of Photo No. 2-8, Page 2-18). Wire mesh also can be laid
over rip-rap when small stone is used. The mesh should be pinned in place
using staples made of reinforcing rods and its lower edge held down with
a weighted pipe or similar stabilizers (Figure No. 2-9). Vegetation often
establishes itself in rip-rap blankets above high water as sediment particles
fill in voids between the rocks to form soil.
A. WIRE MESH ON RIP RAP
REINFORCING ROD
STAPLES
•CONCRETE-FILLED PIPE
BELOW SCOUR LINE
B. DOUBLE LAYER OF WIRE MESH
STREAMBED
POSITION AFTER SCOUR
HAS OCCURRED
WIRE FASTENERS
Figure No. 2-9 - Wire Mesh Stabilizing Small Rock Blanket (Reference No. 9).
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2-20
Rip-rap also can be placed into pre-constructed wire mesh baskets called
"gabions". The mesh should be small enough so that most of the rock
cannot pass through it. Strength required of the wire mesh depends upon
the desired life of the blanket and the type of support the system of
baskets is to provide. Gabions can be arranged, or stacked to form steep,
or near vertical walls protecting a fill (See Photo No. 2-9).
Photo No. 2-9 - Completed Gabion Wall Illustrating How Steep
Protective Structures Can Be Made (Reference No. 3),
Brush mats, planted with shrubs and protected at the toe with rock rip-rap,'
also can be used to protect the surface of exposed fill materials (Figure
No. 2-10). The mat itself has a short life; its principal purpose is to
provide protective covering for both the slope and the shrubs and trees
planted beneath. Slopes should be planted before matting is installed.
preferably in the spring or other appropriate season. Stakes used for
anching the brush mats may be made of "live" wood which can take root,
grow, and protect the slope when the mat breaks up.
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2-21
CREST TO BE VEGETATED
ORDINARY HIGH WATER
FILL MATERIAL
NORMAL WATER LEVEL
SLOPE NOT STEEPER
THAN V/zTO 1
PROFILE
PLAN VIEW:
DETAIL OF STAKES
AND WIRE ANCHORING
Figure No. 2-10 - Brush Mat Protecting Slope From Erosion.
Brush Planted Beneath Mat Provides Protection
After It Decays. (After Reference No.12).
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3-1
CHAPTER 3
ENSURING CONTAINMENT OF POTENTIAL POLLUTANTS
WITHIN DISCHARGED MASS OF DREDGED OR FILL MATERIALS
Naturally-occurring materials interspersed through masses of dredged
or fill materials can become pollutants when discharged or placed into a
new environment. Their use should be avoided if at all possible. They
may include such materials as gypsum (calcium sulfate), pyrite (iron
sulfide), salt (sodium chloride), or other substances. Contact of these
materials with air and water can cause changes in their chemical composition
and/or put them into solution. Unless Best Management Practices similar
to those presented in this chapter are implemented to restrict their contact
with air and water and prevent the runoff of dissolved materials, nearly
water bodies will be subject to pollution. If any of these materials are
subjected, geologic studies should be initiated tp identify their location,
concentration, and exten so that sources of alternate materials can be located.
In arid areas, the only available fill materials consist of clay shales
of marine origin which may contain quantities of gypsum, salt, or similar
soluble materials, in veins or disseminated throughout beds. These soluble-
materials result from the evaporation of seawater following deposition.
Many dry lake deposits in enclosed basins in arid areas contain high salt
contents as do the sediments adjacent to the lakes. Any area where extensive
evaporation of water has taken place should be suspect. If fill for bridges,
culverts, or other facilities to be placed into water bodies are obtained
from such geologic units, they must be considered potential sources of pollution,
Pyrite and other iron sulfide minerals, occur in many different types
of rocks which may be used for fill materials. Soft easily-excavated
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3-2
sedimentary rock, readily usable for fill, or hard consolidated material
that requires blasting to obtain such materials as rip-rap may contain
quantities of iron sulfides. -Sulfides are readily oxidized when exposed
to air, moisture, and bacteria (thiobacilles) and can create high concentratons
of mineral acids. As the acid solutions flow over adjacent fill materials,
they dissolve heavy metals such as iron, manganese, copper, aluminum, and
zinc to add to the pollution problem.
Formations containing any of these types of substances may underly
beds of rivers that are being dredged and source (borrow) areas where
fill materials are to be obtained. If they can be identified, isolated,
removed and properly disposed of separately from the dredge or fill
material, they will not pose a threat to the environment. If they are
interspersed through the main body of materials they probably cannot
be separated and will cause the entire body to be a pollutant threat.
This situation probably is more characteristic of fill than dredged materials
as most river beds are formed on fresh water alluvial deposits that are
relatively "clean" chemically.
Best Management Practices to prevent pyrite, gypsum, or salt-bearing
dredged or fill materials from causing possible water pollution when discharged
or placed into water bodies or in wetlands include techniques for containing
and isolating these materials from contact with air and water. It may involve
installing them within relatively impervious layers (blankets) or barriers
of compacted earth materials. (See Figure No. 3-1).
On steep fill slopes, where stability may be a problem or quantities
of impervious soils are limited, gabions (wire mesh baskets) full of
compacted soils may be considered. In these cases, the imperviosu blankets
are thinner but also function to resist failure due to the tensile strength
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3-3
GROUND-WATER LEVEL
COMPACTED IMPERVIOUS FILL
Figure No. 3-1 -.Impervious Fill Surrounding Roadfill Containing
Pyrite Restricts Contact With Water and Air
of the baskets. Ensuring the placement of impervious materials between
gabions will be controled with this type of barrier. If fill material
being contained beneath the gabion blanket, is extremely coarse-grained,
a filter consisting of sand and gravel or filter doth may be necessary
to prevent downward movement and loss of the fine-grained impervious blanket
materials into the fill below. (See Figure No. 3-2).
The basic premise for using impervious blankets and seals, is to
provide water and air barriers to isolate the materials containing potential-
pollutants and prevent chemical actions from occurring. When pyrite or
other sulfide minerals are involved, excluding the air and water also
acts to prevent breakdown of individual particles in the fill and the
exposure of fresh pyrite crystals to the elements. The impervious materials
also provide exterior surfaces that are relatively easily vegetated and
require little future maintenance.
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3-4
An additional, and supportive, BMP available involves the chemical
neutralization of potential pollutants. Agricultural lime can be blended
with pyrite-bearing fill or placed in a layer on outer surfaces under the
impervious soil. The addition of the lime will minimize the production
of acid, partially neutralize acid being produced, and prevent toxicity
to vegetation when impervious blankets are thin (See Figure No. 3-2).
.SHOULDER SEAL
.SURFACE TREATED
WITH LIME
GABIONS FILLED
WITH IMPERVIOUS SOIL
PYRITE-BEARING
•'. FILL.y.;::'•"!
GROUND SURFACE
Figure No. 3-2 - Earth-filled Gabions Providing An Impervious Blanket
On Roadfill Containing Pyrite (After Reference No. 29)
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3-5
Blankets function as barriers which only restrict, not stop, the
movement of water into or out of the materials they are designed to
isolate. If different water levels are maintained on either side of
these barriers for a long enough period of time, water will move through
them, but only at a slow rate. As a result, the estimated time when
differential water levels are to be maintained on either side of impervious
blankets or barriers, as well as their degree of impermeability and
thickness, must be determined to provide adequate protection. If only
rainfall and sheet runoff of short duration are to be excluded, relatively
thin blankets of only moderately water tight materials may be adequate.
In cases where large differences in water levels occur for long periods
of time on either side of a blanket or barrier, it must be a thick,
highly-compacted impervious layer. If water finally moves out of the
fill after being degraded |»y the poor-quality contained material, it will
move so slowly that it probably will be diluted by the faster-moving water
outside and not pose a threat to its quality.
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4-1
CHAPTER 4
ENHANCEMENT OR THE REPLACEMENT. RELOCATION,
OR RECONSTRUCTION OF EXISTING ENVIRONMENT " "
In certain extreme situations, the discharge of dredged or fill materials
into water or wetlands may be necessary although the potential for severe
damages to or destruction of the existing local environment may be recognized.
When this situation occurs, the only alternative that remains is to consider,
as a Best Management Practice, the enhancement or replacement of existing,
or similar type of environment on an acre for acre basis. In other words,
to artificially create an equal area of new aquatic environment for that
damaged or destroyed. Limited information is available regarding these
practices and their long-term effectiveness, particularly in wetlands.
Creating environmental conditions in a new area that will be similar
to the natural environmental conditions that occurred in another is extremely
difficult since they result from numerous interrelated surface and sub-
surface hydrologic, geologic, topographic, climatic, plant and animal, and
other factors. Changes in one or more of the factors sets up a chain
reaction which results in changes ensuing in other factors. The end result.;
of the changes may be unpredictable unless sufficient data is available
concerning the entire system.
Wetlands
In wetlands, water is the dominating factor in determining the nature
of soil development and the types of plant and animal communities occurring
in them. Wetland soils periodically are saturated due to fluctuations in
surface or ground water bodies. As a result, knowledge of water flow
into and through the wetlands is essential for evaluating the practicality
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4-2
of enhancing or replacing an area of wetlands. The regimen and depth of
water flow and the physical and chemical character of the soils in the new
wetlands should duplicate as -closely as possible, those in the area
damaged by the discharge or placement of dredged or fill materials.
Vegetation and animal life characteristic of the adjacent wetlands may
quickly migrate into the new area and establish itself. If they do not,
re-establishment by transplanting probably will be essential to enable
the new wetland to quickly establish itself and support communities of
aquatic life and other water-dependent wildlife.
The long-term stability of a newly-created wetland should receive
prime consideration. All of the factors brought into play to create it
must operate conjunctively to maintain its existence and productivity.
The net energy inflow into the wetland from surface and ground waters
transporting nutrients, sediments, and other materials necessary for
maintenance of life should be made approximately equal to the outflow if
at all possible. In wetlands where the energy inflow comes from both
salt water sources in coastal areas and fresh water in upland areas, the
system is extremely difficult to assess and to duplicate. The interplay
between saline water and fresh water and their effects upon the aquatic '
communities and the wetland development must be evaluated.
Streams
No stream channel relocation can be made without changing the length
(and thus the gradient) and roughness of the channel. This in turn
changes the velocity of flow and the energy available for channel erosion
(degradation) and sediment transport. These changes may be controlled,
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4-3
through the use of Best Management Practices, to provide significant
beneficial impact upon the aquatic environment, particularly with regard
to the fish, vegetative, and invertebrate communities.
Large sediment loads often develop to become the most destructive
elements. Flowing water in all streams has energy. This energy is used
to modify the channel by eroding, transporting, and depositing sediments
until an equilibrium has been reached between energy and resistance. During
equilibrium, stream channel changes are occurring constantly but the net
flows of water and debris into and out of the system are equal. Total
energy is influenced by the velocity of flow which in turn is a function
of the stream gradient, volume of flow, and the characteristics of the
channel cross section and bed. It has been estimated that more than 95%
of this energy is converted to heat by turbulence and bed and bank friction
and so lost. The remaining is all that's available for eroding and trans-
porting sediments.
If a reach of a stream is to be relocated, it must be designed so that
the net inflow of water and sediment in the new section is the same as that
in the older section or instability will result and detrimental channel
changes will occur progressively both upstream and downstream. If the
channel has been shortened, velocities will be increased and excessive
erosion and transport of sediments will occur. Reduction in stream velocities
can be achieved through the use of check dams to reduce gradients, by
placing obstructions such as boulders in the stream to increase the roughness
of the channel, or by creating meanders. Roughness also is increased by
vegetation, logs, sandbars or any other irregularities in the channel
section. When a channel is lengthened, the gradient of a stream is
decreased and deposition of sediment loads and local filling-in, or clogging,
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4-4
of the bed may result. Practices for minimizing the detrimental effects
in this situation may involve re-designing the channel section so it is
narrower and deeper and the water reaches higher velocities to transport
the sediment load through it.
All measures (BMP's) should ensure that the relocated stream is
stable under the new conditions as an unstable stream will generally
deteriorate the quality of the environment. It is imperative that any
changes be followed by compensating Best Management Practices to minimize
adverse effects of these changes. They must be designed to maintain, as
closely as possible, the original channel's gradient, shape and width,
alignment and aquatic productivity as these factors are all interrelated
and changing one has an effect on others. Channel slopes can be changed
through installation of check dams made to look like natural features such
as fallen logs. (See Photo No. 4-1); width changes, particularly for the
benefit of maintaining adequate depth of flow for aquatic life, can be
minimized by providing dual-type channels (See Figure No. 4-1). The smaller,
deeper channel on the left provides adequate depths for aquatic life during
low flows. All of these practices are used to stabilize the stream regime
and provide for the development and propagation of fish and wildlife nature""
to the area.
Large boulders and cobbles placed into a channel increase its roughness,
reduce the velocity of flow, and, at the same time, provide resting places
or cover for fish and other aquatic life. These rocks, placed on outside
of stream bends where velocities are high, can also act as rip-rap to
prevent bank erosion (See Figure No. 4-2). They should be located with
extreme care so they do not cause the currents to impinge on the bank and
create a more severe erosion problem.
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4-5
Photo No. 4-1 - Check Dam In Stream Decreases .Gradient (U.S. Forest Service)
Figure No. 4-1 - Dual-Purpose Stream Channel Maintaining Adequate
Depth During Low Flows (After Reference No. 27).
Figure No. 4-2 - Rocks Placed In Stream Section To Reduce Velocities
and Prevent Erosion On Outside of Bends (After Reference No. 27).
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4-6
Deflector structures can be used to divert the water into a more
constrictive channel, to create pools, to simulate meander conditions,
and to provide sufficient water depths during low flows. Rubble rock
deflectors, log structures, and similar devices can be devised. Logs
if properly used, can appear to be submerged, partially-buried fallen
trees. They should be submerged permanently to prolong their life.
Photo No. 4-2 illustrates rock rubble deflectors.
-- -•--->»«- —vsap -
?- "-A!-*-"*-i?-"4S-i3?;^?r^j:
Photo No. 4-2 - Meanders Created By Rock Deflector Structures (Reference
No. 27).
If a stream mut be relocated or the channel section altered to make
way for some type of development, the new channel should be designed and
completely constructed, in accordance with projected hydraulic conditions,
prior to diverting water into it. Extreme care should be taken to ensure
that the existing stream does not receive excess sediment runoff from the
disturbed new channel during construction. Measures and structures to
minimize detrimental changes that will occur in the new channel should be
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4-7
in place before it receives the stream's flow and the old channel is plugged.
All structures should have a natural appearance, and vegetation, similar
to that in the old channel are^, should be .provided -for the new one. The
addition of soil may be required. It should be placed so that natural
conditions are duplicated.
After the new stream channel has been in operation for a period
of time, alterations such as acceleration of meanders or changes in depth
may begin to occur. If they appear to be initiating environmental problems,
additional structures, or other Best Management Practices similar to those
initially designed for the channel, can be provided to control them.
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5-1
CHAPTER 5
PROTECTING HABITAT CONDITIONS AND PROVIDING
FOR FISH'ANfrWILDLIFE PROROGATION .
Water-retaining structures such as dams and reservoirs often function
as complete barriers to the movement of aquatic life and water-dependent
wildlife regardless of their size. Linear fills across wetlands or water
bodies such as railroad or highway embankments, causeways, or even canals
and aqueducts can restrict movement of wildlife even though facilities
have been provided to enable water to pass through or under these structures.
Deer, quail, foxes, rabbits, and other creatures can cross over or travel
along these linear facilities, but only with extreme danger to their lives.
Best Management Practices to prevent or minimize such environmental impacts
should include providing passageways for aquatic or wildlife through, over,
or possibly around such structures, preventing wildlife from gaining access
to areas of potential danger, and minimizing adverse habitat changes caused
by the discharge or placement of the dredged or fill materials.
A brief discussion of some of the presently available practices is
presented here. At present, BMP development in this environmental problem -:
area is an art rather than a science and many of the techniques and
practices are not fully proven as effective. There is no intent in this
document to imply that these are the only practices available or that they
will accomplish the desired purposes in all areas and situations. Additional
and more-detailed information on BMP's for protecting habitat conditions
and providing for fish and wildlife propogation is presented in the
References on Pages 6-1 through 6-4.
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5-2
Creating Passageways For Aquatic of Water-Dependent
Wildlife Through, Around, Under, or Over Structures
Discharge or water from reservoirs is accomplished through outlet
pipes or penstocks of some sort which pass through or under the retaining
structures, surface spillways that extend around the end or over structures,
and diversions that channel the water around dams for further transmission.
Generally, when water moves through all these structures it does so at high
velocities and the passage of aquatic life through them is difficult or
impossible.
Linear fills extending across wetland or adjacent water bodies can
restrict the movement of aquatic life and water dependent wildlife into or
within such areas. The restrictions on wildlife movement can be minimized
by providing passageways through embankments in areas where animals are
known to habitually travel.
There are practices available to provide for the passage of migrating
fish through or around water-retaining structures. They involve such facilities
as fish ladders, fish conduits, and similar units. (See Photo No. 5-1).
Once past the structures, fish are free to travel upstream to spawning beds.
For some structures, fish ladders lead to holding ponds where fish are
collected and transported to spawning areas.
-------
5-3
Photo No 5-1 - Salmon Migrating Upstream Use Fishladder Facility To
Bypass Dam (U.S. Bureau Of Reclamation).
-------
5-4
If the effects of a dam or reservoir on the habitat of anadromous fish
are severe, manmade spawning beds may be designed into the project.. Additional
facilities then are required to'channel the fish to these spawning beds.
They can include electric barriers, fish ladders, and bypass channels.
Sometimes a reservoir floods spawning beds for anadromous fish such as
salmon. In these cases, the fish ladders, or other by-passing structures
terminate at fish hatcheries where the migrating fish are collected, killed,
and the roe obtained. The roe is fertilized and then placed in the hatchery
under controlled conditions until the fish are hatched. After having reached
an appropriate stage in their development, the fish are released into the
river downstream of the dam to migrate back to the ocean and complete the age-
old cycle of migration that their parents had initiated.
The generation of power at hydroelectric dams results from the movement
of reservoir water through penstocks and turbines to downstream areas.
Migrating young fish may suffer significant losses when passing through the
turbines unless these facilities have been designed for fish passage. The
survival chances of the downstream migrating fish can be increased by providing
facilities that bypass them into a gatewell before they enter the turbines
and direct them into a channel where they can move safely downstream. Fish
ladders or some similar type of structures should be provided to enable return-
ing mature fish to migrate upstream around the dam. Additional information on
such devices is presented in a document under preparation for the Fish and
Wildlife Service entitled "Interim Guide To The Performance Of Fish and Wild-
life Habitat and Population Improvement Measures For Western Dam and Reservoir
Projects (Reference No. 22).
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5-5
Linear Transportation or Conveyance Facilities
The design of passageways through or under linear embankments should be
based upon the habits and needs of wildlife in order to become fully effective.
Underpasses beneath, or through highway and railroad embankments in wetland
or water bodies probably will be more effective if used in conjunction with
fences to help guide wildlife through the openings. Many animals will be
hesitant to go through such passageways unless guided and restricted by these
fences. Some of them are fully capable of climbing the embankments to cross
or travel along the structures. If they are able to do so, their lives will
be endangered by vehicles.
Passageways for wildlife should be designed to appear as natural as
possible to the animals. Their minimum widths and lengths should be based
upon the size of the animals involved. Floors should be of earth or other
natural materials and skylights or artificial lighting of any kind should be
avoided. Photo No. 5-2 illustrates an earth-floored passageway through an
embankment with fences to channel animals through the structure. In general,
facilities for animal passage extend under road .or railroad embankments. For
water facilities such as canals and aqueducts, they extend over (See Photo
No. 5-3).
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5-6
Photo No. 5-2 - Underpass For Animals Beneath A Highway. Fences At Toe
Of Slopes Prevent Movement Up Embankment To Roadway.
(U.S. Federal Highway Administration).
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5-7
Photo No. 5-3 - Animal Crossing Extending Over Fenced Aqueduct. Wooden
Floor Has Not Been Covered With Earth Yet. (U.S. Bureau
of Reclamation)
Providing Protective Devices For Wildlife Contacting or
Crossing Structures
Aquatic life and water dependent wildlife often place their lives in
jeopardy when attempting to pass through, over, or along masses of • -••
dredged or fill materials. Some may be sucked into pumps and pumping
plants, discharged over spillways, carried through siphons, or trapped in
aqueducts or flumes. Others may surmount road or railroad embankments to
be killed or crippled by moving vehicles. Fish can also be endangered by
spillway flows which cause nitrogen supersaturation of water in spilling
basins immediately downstream from the spillways.
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5-8
Hater Facilities ...
t *
Fish and other aquatic life can be presented from moving into intakes
for water pumps through the use of various types of screens, or barriers.
Large pumping plants that draw tremendous quantities of water may need more
elaborate protective devices. A louvered system is shown in Photo No. 5-4.
Aquatic life being carried toward the pumps by the rapid flow of water are
kept out of them by the louvered screens. A second set of screens and bypass
facilities function to divert fish into holding tanks. Fish are then collected,
transported away from the area of influence of the pumps, and then released
back into the water.
Canals, aqueducts, or dither water bodies, often extend across routes
used by wildlife to gain access to feeding, refuge, reproduction, or other
areas. Animals attempting to cross these facilities, or drink from them,
may have their lives endangered. Steep, smooth slopes on canal, aqueduct,
or reservoir banks can prevent animals from escaping once they descend.
Then, currents in canals and long swimming distances to escape areas in
reservoirs can cause additional dangers to threaten the animals lives. Canals-
may have siphons, or other structures, and reservoirs often have spillways,
outlet works, and penstocks that locally increase current velocities and
create other hazards.
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5-9
TRASH DEFLECTOR
SECONDARY
LOUVERS
HOLDING TANK
SHED
DISCHARGE
SUBMERGED FISH BYPASSES
TO PUMPING PLANT 2.5 MILES (4.0 KM)
Photo No. 5-4 - System With Two Louvers To Prevent Anadromous and Other
Fish From Being Carried Into Major Pumping Plant. They
Are Collected In Holding Tanks and Returned To The River.
(U.S. Bureau of Reclamation).
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5-10
Best Management Practices have been developed and can be used to
prevent wildlife from being trapped in such structures. An effective practice
to prevent some animals from gaining access to and being endangered by a canal
or aqueduct involves fencing. It is generally expensive, however, and will
require crossing facilities such as bridges to be provided for the animals.
These crossings must be located where predominant migration routes or trails
exist. If migration or other movements of animals are restricted by fences
without crossing facilities, they may suffer losses or deterioration in
quality due to inter-breeding, loss of feed sources, or other problems.
Fences must be designed for the particular animal involved. They
should be high enough to prevent animals from jumping over and sturdy
enough to prevent them from being torn down. Animal bridges, or overpasses,
should also be designed for the animals that are to use them. Floors should
be covered with natural materials such as soil, sand, or gravel and the
crossings limited in width to prevent their use by four-wheeled vehicles.
Pipelines rather than open canals should be considered across wetlands
to minimize danger to wildlife, particularly in areas where wildlife tends to;
migrate or travel. If they can be buried, crossing by animals is greatly
faciliated.
Where covered pipes or fencing are not feasible or fully effective to
prevent wildlife from entering a canal or aqueduct, entrapment and escape
structures may be placed into the facility. Many of these structures
are designed also to enable wildlife to enter the canal, descend the slope
to obtain water, and then return up the slope (See Photo No. 5-5).
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5-11
The escape structures shown in the canal in the photograph consists
of a ramp constructed in an indentation in the steep canal bank .with an
angled barrier or other device to divert swimming animals into the ramp.
Other, probably less-effective, structures have been devised and used.
They may be temporary or permanent. Layers of soil have been placed, as
temporary escape structures down canal sides, while sandbag layers form
more permanent ones. Concrete steps, or other types of ramps, and
accompanying facilities can be designed into the canal slopes to function
as permanent and effective escape units.
Photo No. 5-5 -
Concrete Escape Ramp With Low Slope (4h:lv)
Built Into Identat'ion In Steep-Sided Canal. Note Timber
Boom That Directs Swimming Animals Into Ramp. (Bureau
Of Reclamation).
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5-12
Transportation Facilities
* •
Causeways extending across'wetlands for highways, particulary large
freeways, often are fenced at their right-of-way boundary. Animals can .
gain access to these structures through one avenue or another and place
their lives in danger from passing vehicles. As they find their escape from
the noisy vehicles on the roadway blocked by the fencing, they become panicked
which places them in even more danger. Facilities have been developed and
installed into the fences at certain localities to permit animals to escape
back into the wetlands and safely. They consist of structures composed of
baler tines and angle irons which allow deer to escape from the roadway, but
prevent re-entrance.
Habitat Improvement Measures
Any structure formed by the discharge of dredged or fill materials into
wetlands or water bodies changes to some extent the regimen of aquatic life
and other water dependent wildlife existing in these areas. Stream-flow
regimes and the chemical or physical characteristics of water can be altered, .
water depths changed, dry land flooded, and perhaps flooded lands dewatered.
As a result of these changes, aquatic life and wildlife in the area will be
affected. They may move to different localities or be replaced by other
types of creatures.
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5-13
The effect and magnitude of these changes may be minimized by habitat
improvement Best Management Practices which remedy the problems or provide
substitute areas to maintain or'provide for the propogation of existing
aquatic life and water oriented wildlife. They may include proper management
of water and streamflow, and water and streamflow, and the provision of
nesting, spawning, nursery, resting or feeding for aquatic life and water-
oriented wildlife.
Proper Water Management
Dams are placed across streams to impound water for further use by
man. Excess quantities of water from flood flows can be stored for later
use. Peak flood flows can be reduced and low flows increased by proper
operation of dam facilities. If too much water from a reservoir is diverted
into other areas, however, or excessive quantities of water released for
use during other periods of time, insufficient water may be available to
maintain flow requirements for aquatic life during dry periods.
During the design, construction, and operation of dams and other water
projects, the flow requirements to support aquatic and.other water-dependent---
wildlife in downstream areas must be considered during the feasibility,design,
construction, and operation stages and sufficient flows made available to meet
these needs. Sufficient water will be needed also for flood releases to
function as natural scouring media in the channel further downstream. Other-
wise sediment loads brought into the main streams by tributaries may deposit
as deltas at their junctions. If they form large enough deposits, they can
obstruct or restrict the main channel flows. Spawning gravels also can be
ruined by these deposits.
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5-14
Dams on coastal streams having anadromous fish populations must
consider making available sufficient quantities of water to flush open_sand-
*
bar barriers formed by offshore currents across the mouths of these streams.
Unless flood flows can open these bars, anadromous fish cannot enter the
stream for further upstream migration and spawning.
Preventing Detrimental Physical or Chemical Mater Changes
Water that discharges over the spillway of a dam and plunges into the
spillway basin or plunge pool immediately downstream can become saturated
with nitrogen and cause fish kills. As the water plunges rapidly to depths,
hydrostatic pressures increase. Entrained air is forced into solution by the
pressure before it can rise to the surface and escape. Since air is
approximately 80% nitrogen, the water becomes supersaturated with it. The
oxygen content in the water is mostly metabolized by the fish and other
gaseous constituents are too minor to effect them. The nitrogen can become
a hazard to fish.
Anadromous fish population in rivers of the northwest have suffered
from nitrogen or "gas bubble disease". If they swim at depths greater. ... :,;.
than 12 feet in the nitrogen-supersaturated water, the fish are not affected
by the disease as the external pressure prevents the gas from forming bubbles
in their bodies. As they swim at shallower depths, up ladder.s,or near the
surface, however, the nitrogen gas pressure within the fish's body exceeds
the water pressure and bubbles form.. They cause blisters and bubbles
under the skin, on the body and fins, on and under the gill covers, and in
the mouth and head.
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5-15
The nitrogen problem is most serious in the Columbia-Snake River
reservoir system of the northwest because the river waters have an over-
abundance of dissolved air in them and most of the spillage occurs during
the principal upstream and downstream migration periods for the fish.
Since spillway discharges must plunge to depths to cause nitrogen
supersaturation, a BMP for preventing this problem should involve designing
or modifying-spillways to cause the flows to be "flipped", as they are
discharged, some distance downstream. Upturned deflectors, cantilevered
extension or "flipbuckets" can be designed for spillway terminal structures
to deflect the water in a downstream direction and prevent the discharge
from plunging deeply (See Figure No. 5-1). They can even be caused to fan
out into a thin sheet through the use of a flaring device. These types of
spillway, terminal structures provide dual benefits to the environment..
•«:*•••.*.••.*.:.•>•.•*.•.•/.••/.•.•.•.•.••;:•:•.*;•::.»••/
._••'. .^••""""T"—"^T*""««—•—ife-"-™•*—•—-i-±*
Figure No. 5-1 - Spillway Showing How "Flip" Structure Prevents Flow
From Plunging To Depths.
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5-16
Other remedial meaures to prevent nitrogen supersaturation and "bubble
disease" can include: .......
s * -
1. Collecting and transporting fish overland through the length
of river where nitrogen supersaturation occurs.
2. Decreasing spillway flows by providing additional reservoir storage.
3. Decreasing spillway flows by passing water through any available
outlet conduit where turbulence will not entrain air.
The physical and chemical character of the water in a stream is
generally changed when it is stored in a reservoir behind a dam. When
released downstream, this water may initiate detrimental effects on aquatic
life and possibly the regimen of the stream. The temperature of released
water may be higher than stream water if obtained from the upper water-level
outlets and lower if obtained from depths. Water released from outlets
deep in a reservoir may also be oxygen deficient. All of these changes can
be detrimental to aquatic life immediately downstream, particularly to
cold-water or anadromous fish such as trout, steelhead, and salmon. Existing
aquatic populations may decrease or even be supplanted by a new type of
species more adapted to the changed conditions.
The physical and chemical changes in released water can be minimized,
particularly with regard to temperatures and oxygen contents by providing
multiple intakes for outlet facilities. These intakes, located at various
depths in the reservoir, regulate releases so that problems are minimized
(See Photo No. 5-6).
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5-17
Higher .elevation outlets release warmer and more oxygenated water
while lower ones draw from colder water which contains less oxygen." The
quality of the release should be based upon the needs of the aquatic life
being protected.
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01
00
Photo No. 5-6 -
Deep-water Intake Installed On Old Concrete Outlet Riser. Water Enters Lower End of
Pipe From Depths And Discharges Colder Water While Water Enters From Top (U.S.D.A.,
Soil Conservation Service).
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6 - 1
REFERENCES
il. Boyer, Peter B. "Gas Supersaturation Problem In Columbia River".
A Paper Presented At The American Society of Civil Engineers,
Irrigation and Drainage Division Specialty Meeting. September
26-28, 1972. Spokane, Washington.
2. California State Resources Agency "Task Force Findings and Re-
commendations On Sediment Problems In The Trinity River Near
Lewiston "Draft Report To The Secretary of Resources. January,
1970.
3. Civil Engineering - ASCE, "Gabions Guard River Banks Against
50,000 cfs Flows", May, 1974.
4. Krynine and Judd, "Principles of Engineering Geology and Geo-
technics." McGraw-Hill Book Company. 1957.
5. Merrit, Frederick S., "Standard Handbook For Civil Engineers."
McGraw-Hill Book Company. 1968.
6. Movie Prepared Cooperatively by the Colorado"Division of Wild- •
life, U.S. Forest Service, and Federal Highway Administration,
"Yellow Bulldozers, Brown Trout, and Blacktop - The Story of
Ten Mile Creek."
7. Portland Cement Association, "Concrete Structures For Flood
Control, Soil and Water Conservation." Date Unknown.
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6-2
8. Stubbs, Frank W. Jr./"Hanbook of Heavy Construction." McGraw-
Hill Book Company. 1959. .
9. U.S. Department of Agriculture, Forest Service. "Stabilizing
Eroding Streambanks In San Drift Areas of The Lake States.
Research Paper NC - 21. 1968.
10. , "Fish Migration and Fish Passage, A Practical Guide to
Solving Fish Passage Problems" September, 1977.
11. , "Correcting Vertical Fish Barriers." Equipment Develop-
ment Center, Missoula, Montana. September, 1977.
12. . Soil Conservation Service. "Engineering Field Manual
For Conservation Practices." -969.
13. U.S. Department of the Army, Crops of Engineers. "Silt Curtains
For Dredging Turbidity Control." A Consultant Report by E.E.
Johanson, Date Unknown.
14. . "Help Yourself, A Discussion of The^Critical Erosion -
Problems Of The Great Lakes and Alternative Methods of Shore
Protection." A brochure prepared by the North Central Division.
Date Unknown.
15. . "Landscape Primer for Confined Dredged Material Disposal."
A brochure prepared by the Environmental Effects Laboratory.
Vicksburg, Mississippi. Date Unknown.
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6-3
16. . "Design and Construction of Retaining Dikes For
Containment of Dredged Material." Tech Report D-77-9.
August, 1977.
17. . "Investigation of Effluent Filtering Systems for
Dredged Material Containment Facilities." Contract Report
D-76-8. Environmental Effects Laboratory, Vicksburg, Mississippi,
August, 1976.
18. --'--. "Guidance For Material Placement In Marsh Creation."
Contract Report D-75-2. Environmental Effects Laboratory,
Vicksburg, Mississippi. April, 1975.
19. U.S. Department of The Interior, Bureau of Reclamation. "Design
of Small Dams". 1974.
20. - - - -. "Final Environmental Statement Tehama-Colusa Canal,
Central Valley Project, California". June 7, 1977.
21. - - - -. "Wild and Domestic Mammal Control In Concrete Lined
Canals "Draft Report By Seaman, E.A., Environmental Specialist •
June, 1978.
22. . Fish and Wildlife Service. "Interim Guide To The Per-
formance of Fish and Wildlife Habitat and Population Improve-
ment Measures For Western Dam and Reservoir Projects" Report
By Enviro1 Control, Inc. January 5, 1978
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6-4
23. .-.. "Assessment pf Effects of Altered Streamflow On Fish
and Wildlife" Report by Jones .and Stokes Associates, Inc."
July 15, 1976.
24. U.S. Department of Transportation, Federal Highway Administration.
"Reinforced Earth Construction." Report No. FHWA-DP-18.
April, 1975.
25. - - - -, "Use of Riprap for Bank Protection". Hydraulic Circ-
cular No. 11. June, 1967.
26. ."Keyed Riprap", by the Oregon Department of Transportation.
Distributed Through Demonstration Project No. 31. Region 15.
Date Unknown.
27. - - —. "Restoration of Fish Habitat In Channelized Streams".
Unpublished Report.
28. , "Fish Passage Through Highway Culverts". By Region 8,
in Cooperation With The Oregon State Fish and Game Commission .
1970.
29. - - - -. "Geologic and Water Quality Study - Tellico-Robbinsville
Highway, Station 804 + 85 ^ to Station 956 + 10 + . Report No. 1.
Region 15. November, 1977.
30. U.S. Environmental Protection Agency, Region X, "Logging Roads
and Protection for Water Quality". EPA 910/9-75-007. March, 1975.
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