vvEPA
United States
Environmental Protection
Agency
Office of Water
Planning and Standards
Washington, D.C. 20460
September 1979
EPA 440/3-79-028
Water
Best Management
Practices Guidance,
Discharge of
Dredged or Fill Materials
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J. ;**";. f"
Placement of Fill Materials
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I UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
* WASHINGTON. DC 20460
27JUU979
SUBJECT: Transmittal of Document Entitled "Best Management Practices
Guidance, Discharge of Dredged or FJJ4—Materials"
c_^ s\ r
FROM : Swep T. Davis, Deputy Assistant AdrrnTKstrator'' / )
Office of Water Planning and ^Iffia^i^scll^hSSff-)-!, ___—-^
TO : All Regional Water Division Directors *
ATTN: All Regional 208 Coordinators
All Regional 404 Coordinators
All Regional NPS Coordinators
All State and Areawide Water Quality Management Agencies
Other Concerned Groups
TECHNICAL GUIDANCE MEMORANDUM - TECH - 50
Purpose
This "Best Management Practices Guidance" document has been prepared
to provide State and areawide water quality management agencies,
other State and Federal agencies, and the concerned public with
information on readily-available processes, procedures, methods,
and techniques that can be used to minimize or prevent environmental
impacts that could result from the discharge of dredged or fill
materials. It has been written in a manner that makes it easy
to follow so that the reader does not have to be an expert in the
discipline to be able to understand what the problems are and some
of the solutions that are presently available.
Guidance
The document is the latest provided in accordance with policies and
procedures of 40 CFR, Part 131 which states that "EPA will prepare
guidelines concerning the development of water quality management
plans to assist States and areawide planning agencies in carrying
out the provisions of these regulations." Management regulations
being drafted for Statewide dredged and fill discharge programs
under 40 CFR 35.1570 state that "Any BMP's developed by a
Statewide dredged and fill program, certified as appropriate for
inclusion in a State 404 permit, and accepted by the Regional
Administrator for those purposes must be included in a State 404
permit, when they are not less stringent than other requirements
in the 404 permit."
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EPA 440/3-79-028
BEST MANAGEMENT PRACTICES GUIDANCE,
DISCHARGE OF DREDGED OR FILL MATERIALS
Robert E. Thronson
Environmental Engineer, Implementation Branch
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER PLANNING AND STANDARDS
WATER PLANNING DIVISION
WASHINGTON, D.C. 20460
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ACKNOWLEDGEMENTS
Sincere appreciation 1s 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 and reviewed it.
Federal organizations include the:
1. Department of Agriculture, Forest Service and Soil
Conservation Service
2. Department of Commerce, National Marine Fisheries Service
3. Department of the Army, Corps of Engineers
4. Department of Energy
5. Department of the Interior, Fish and Wildlife Service,
Bureau of Reclamation, and National Park Service
6. Department of Transportation, Federal Highway Administration
7. Environmental Protection Agency, Regional Offices
8. National Science Foundation
State agencies, particularly Departments of Highways or Transportation,
Conservation, Forestry, Water Resources, and Fish and Game made outstanding
efforts to provide information, analyses, or other input to this guidance.
They include:
California Oklahoma
Colorado Virginia
Florida Washington
Louisiana West Virginia
Minnesota Wisconsin
North Carolina Wyoming
Other contributors or reviewers include:
The Susquehanna River Basin
The Port of San Diego, Unified Port District
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PREFACE
Before any decision can be made regarding the discharge of dredged or
fill materials into waters of the United States, all probable impacts and
feasible alternative sites must be considered. This will include an evalu-
ation of such factors as the necessity for discharges; sensitivity of the
area to environmental impacts, both long and short term; possible alter-
native sites or a scheduling of operations; and effectiveness of available
site-specific Best Management Practices to prevent, or minimize, the Impacts.
Discharges of dredged of fill materials must comply with guidelines prepared
by the Administrator of EPA pursuant to Section 404(b)(l).
Section 404 Of the Federal Water Pollution Control Act, as Amended
(33 U.S.C. 466 et seq.) establishes a permit program for the regulation of
discharges of dredged or fill materials into the waters of the United States.
The Section 404 permit program is currently administered by'the U.S. Army
Corps of Engineers. Sections 404(g) and (h) provide that, upon approval by
the Administrator of EPA, a State may administer its own individual and
general permit program to control discharges of dredged or fill material.
Approved state Section 404 programs regulate the discharge of dredged or
fill in all waters and adjacent wetlands of the State except for those
which are "...presently used or susceptible to use in their natural con-
dition or by reasonable improvement as a means to transport interstate or
foreign commerce..." The Corps of Engineers, in all cases, administers
the Section 404 program in such commercially navigable waters.
The Act further authorizes states with approved statewide regulatory
programs under Section 208(b)(4) to regulate certain discharges of dredged
or fill materials through those programs in lieu of the Section 404 permit
program. Actions regulated by a statewide 208(b)(4) program must be those
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IV
which EPA has designated as appropriate for this alternative method of
regulation, and for which specific Best Management Practices criteria
have been developed by the State and approved by EPA.
The guidance presented in this document on dredged and fill activities
was developed to provide the State 208 and 404 agencies, other State
agencies, Federal organizations,and other concerned groups with the most
readily available general information on how adverse environmental impacts
resulting from certain discharges of dredged or fill materials can be pre-
vented, or minimized, through the use of Best Management Practices (BMP's).
The BMP-'s in this guidance are intended to support legal requirements in
Section 404 and 208(b)(4) programs, but do not constitute requirements
unless they are made part of a permit or regulatory program.
A multi-disciplinary approach is critical for adequate evaluation of the
discharge and determination of appropriate BMP's. competent geologists,
biologists or wildlife specialists, engineers, hydrologists, soil scientists,
and other personnel from 208 and 404 management agencies as well as
involved Federal and State fish and game, water resource, and conservation
agencies should be consulted. Their opinions and views should be obtained
and evaluated and the long-term as well as short-term results of the activities
and projects considered.
The types of pollution control measures described here and included
under the term "Best Management Practices" will usually be designed, in
accordance with site-specific conditions, by dischargers and, subject to
approval under criteria established by a responsible State management
agency, applied under a 208 regultory program. They also may be speci-
fied, along with appropriate design criteria, as conditions within issued
State 404 permits.
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Determination of whether to implement dredged or fill Best Managment
Practices through a 208 regulatory program or a State 404 permit program are to
be based primarily upon changes in the use of areas of navigable waters and
the impacts of proposed activities upon water flow, circulation, and the
reach of the water bodies. Where the use has been changed, the flow or
circulation impaired, or the reach of the water body reduced, regulation under
Section 208 is precluded. Under these conditions, BMP's must be implmented
under the 404 permit program (Section 404 (f)(2)). The review requirements of
this permit program will ensure that all possible data, opinions, and evaluations
are obtained prior to the decision of whether, and on what terms, the
project is to be authorized. There will be more assurance through this
program that adverse impacts resulting from the activities will be detected
and identified and that criteria for design and effective application of
a BMP system, or other protective measures, will be optimized. If conditions
existing at either a proposed site, or at a practical alternative site, for
discharging dredged or fill materials are so sensitive that available
BMP's or other mitigating features will not reduce environment degradation
to acceptable levels, the discharge must be prohibited.
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C_ 0 N, J_i N. J_i
ACKNOWLEDGEMENTS ii
PREFACE iii
INTRODUCTION 0-1
Analysis of The Problem 0-2
Adequate Program Planning and Development 0_5
Best Management Practices, Summary 0-7
CHAPTER 1 - MINIMIZING THE IMPAIRMENT OF WATER FLOW OR CIRCULATION 1-1
Properly Locating, Orienting, and Shaping Masses of Dredged or Fill
Materials 1-2
Providing Flow Through Dredged or Fill Materials . . . i_5
Preventing Detrimental Elevation Changes In Channels . . 1-20
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 - PROTECTING EXISTING HABITAT AND PROVIDING FOR FISH AND
WILDLIFE PROPAGATION 4-1
Creating Passageways For Aquatic or Water-Dependent Wildlife Through
Around, Or Over Structures 4-2
Providing Protective Devices For Wildlife Contacting or Crossing
Structures 4-7
Habitat Improvement Measures 4-12
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CHAPTER 5 - ENHANCEMENT—THE REPLACEMENT, RELOCATION, OR RECONSTRUCTION OF
EXISTING ENVIRONMENT 5-1
Wetlands 5-1
Streams 5-2
SELECTED REFERENCES 6-1
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GUIDANCE FOR BEST MANAGEMENT PRACTICES TO CONTROL THE DISCHARGE
OF DREDGED OR FILL MATERIALS
INTRODUCTION
The discharge of dredged or fill materials involves man's
introduction of what can be considered principally naturally-occurring
sedimentary deposits, rocks, or earthen materials into 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 development or structures. They can form bridge approaches,
portions of causeways, dams, dikes, levees, fills for roads 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 full fill 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 larger area! extent in low lands to provide surface
elevations high enough for construction 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. Alterations of the elevation of the substrate, or bottom of
the water body.
4. Changes in key ecological relationships and interdependencies
5. Permanent loss of part of the aquatic environment through conversion
to dry land.
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 fluctuations, velocities,
directions of movements, and other characteristics occur. They can initiate
adverse effects in the production, movement, and occurrence of terrestial
and aquatic wildlife; cause changes in the chemical and physical quality
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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-occurring 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
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organisms and wildlife depending on it. As higher order organisms consume
lower aquatic 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. (See
Figure No. 0-1).
BIOLOGICAL MAGNIFICATION
Figure No. 0-1 - Biological Concentration of Strontium - 90
The Average Concentration Factors for Strontium - 90
In the Perch Lake food web. (Adapted from Ophel, I.L,
"The Fate of Radiostrontium in Freshwater Community
Source" in Radioecology, 1963).
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Adequate Program Planning and Development
Advanced planning, conducted prior to initiating the discharge or
placement of dredged or fill materials into a stream and adjacent wetlands,
is essential for preventing environmental problems. 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 should be selected and implemented to minimize the
environmental problems that could result from the activities. Sites in
which very severe environmental problems could arise should be avoided.Usually,
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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 measures.
An adequate pollution control 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
discharger; adequate review and approval of these plans by a responsible
management agency; adjustment of the plans after the review to maximize
the effectiveness of the Best Management Practices; implementation of
the BMP's; monitoring by the management agency for adherence to the plan;
and, when required, effective and aggressive enforcement of violations
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 the local environment. They should achieve required
environmental protection at the least possible cost. Important factors
to consider in their development include the occurrence and movement
of both ground and surface water; geologic, soils, and topographic
conditions; and the existence, needs, and sensitivities of aquatic and
other wildlife 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 those 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.
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The BMP's defined in site plans, however, must be developed and designed
on a site-specific basis by those most familiar and knowledgeable regarding
the site area.
Guidance should always be flexible enough to allow initiative to
be used for developing new, less expensive, and more effective BMP's. A
flexible BMP program also allows for the application of State and local
expertise towards the understanding of site-specific environmental
characteristics 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.
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 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 implemented. They involve practical engineering designs,
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structures, procedures, and schedules for operations adapted from those that
have been developed and 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 propagation of fish, shellfish and wildlife.
The specific characteristics of the site must be evaluated and considered
critically before finalizing BMP's to be applied or used.
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 many structures and the procedures for
their placement or construction are essential to reverse this trend and
protect the environment rather than damage it.
Environmental problems that could result from the discharge of dredged
or fill materials into streams, estuaries, lakes, or wetlands can be
prevented or minimized 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 practices which can be conducted or applied to ensure that:
(1) stream or current flow changes are not adversely affected, (2) increased
sediment loads or turbidity levels are effectively reduced, and (3) other
pollutants included with dredged or fill materials are restricted from
entering water bodies. BMP's may also involve (4) protecting existing
habitat and providing for fish and wildlife propagation and (5) the
relocation, reconstruction, or enhancement of an area of wetlands or a
stream if a significant portion of the water body will be affected and
no other alternative exists.
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Best Management Practices involving singular minor discharges of
dredged or fill materials with relatively insignificant impacts on the
aquatic environment 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 water. 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. A permit for
discharge may be required in accordance with Section 404 if flow or circulation
will be impaired and the BMP£ implemented as a requirment of this program.
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:
1. Minimizing the extent of individual fills or the concentration
or numbers of fills.
2. Providing continous 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.
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4. Designing channel - spanning structures:
a. To pass flood flows with no significant adverse impacts
from flow restriction.
b. To minimize debris or other 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 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 preventive
measures such as cofferdams, caissons, filter cloth fences, or other
preventive 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 a 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:
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.
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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 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. Equipment used should be that
having the least damaging effect on ground conditions.
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.
Adequate criteria should establish the factors of safety to be used in
the design and placement. Adequate and continuing processes will be
necessary to assure that conditions are maintained,
Ensuring Containment of Potential Pollutants Uithin 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 into and deposited in another environment. If polluted
materials can be effectively contained by effective BMP's and prevented
from affecting water quality, their discharge should not be precluded
only because of their quality. 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 them 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.
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, fish spawning
areas destroyed or 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
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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 management of activities as well as the modification or construction
of structures and techniques to offset terrain changes, water level
and flow alterations, and revision in the natural physical or biologic
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 encountering or crossing
structures formed of dredged or fill materials.
3. Creating necessary habitat improvement measures.
Enchancement 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
other available Best Management Practices will not effectively prevent
adverse effects, enhancement or replacement of the existing environment
may be feasible. This must receive consideration if a significant percentage
of the water body becomes dry land due to the discharge and/or placement of
materials.Practices may include:
1. Creating and maintaining additional wetlands equivalent in
productivity 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 life and other wildlife.
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3. Providing for the relocation or replacement of streams that have been
designed*and constructed to function under original gradient, hydraulic,
and aquatic habitat conditions.
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CHAPTER 1
MINIMIZING THE IMPAIRMENT OF WATER FLOW OR CIRCULATION
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. If the use of the water body is changed, flow or circulation impaired,
or the reached reduced, a permit may be required under the Section 4o4 program.
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-sectional 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 im-
pairment of flow or circulation will depend upon the volume and characteristics
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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Properlyj-ocatlng, Orienting, and Shaping Masses of Dredged or
Fill Materials
The material presented in this and the following section of the guidance
is not intended as a justification for, or to condone, the placement of
dredged or fill materials into shallow waters or wetland areas. These
practices have been done in the past and have caused severe environmental
problems. They probably will be done in the future only after full
consideration of site conditions,alternatives available, need for the
project, and applicable Best Management Practices to ensure that
expected adverse environmental impacts will be reduced to acceptable
ranges.
Dredged materials discharged for disposal and large fills placed in
shallow water or wetlands for engineering purposes can have a major effect
on the flow and circulation patterns 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 and circulation. 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 surface and
water body, characteristics of the drainage through or around the filled
area, and the need to minimize the length of containment dikes. These
dikes must be constructed for containment before any discharge of materials
takes place. Fills for engineering purposes may consist entirely of
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1-3
materials derived from underwater sources or of these materials capped by
a 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
proper design and discharge of these deposits, however, could result in
the creation of a wetland habitat to enhance the environment as well as
minimizing impairment of flow and circulation.
If 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
such deposits will have only a minor effect on currents which move along
the shore. Figure 1-1 illustrates how dredged materials can be placed
with rip-rapped containment dikes in indentations of a stream. In properly
located areas, the lineal extent of dikes can be minimized, particularly if
the landward side has sufficient topographic relief to contain the materials.
PROPER LOCATION 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
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1-4
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 be devised to provide for diverting the drainage around the contained
dredged or fill materials or passing it through or beneath them. Diversions
should be designed to prevent subsequent erosion by concentrated flow and
to simulate natural features. Passing surface water through the deposit
will require a spillway over the containment dike that will not allow
erosion or cause failure of the structure and release of the contained materials,
If culverts, or other structures, are to be used to pass flows through or
beneath the deposit, they will have to be considered during the design
stages and placed when constructing the dikes and before discharge begins
behind them.
Dredged materials can be used to create marshy islands and perhaps
shallow wetlands in areas where deeper water existed before. These
deposits, if placed in open waters, must be shaped to provide the least
feasible cross-sectional area to be exposed to the natural flow of water.
Figure No. 1-2 illustrates desirable shaping and orientation for such
placements. They can 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 an obstruction in the water
and deposit it into another area.
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PREVAILING
DIRECTION
OF
WAVES
OR
CURRENTS
1-5
lin^n POOR ORIENTATION
CONTAINMENT
DIKES
. __7^<\ PROPER ORIENTATION
Figure No. 1-2 - Properly-Oriented Deposit of Dredged Materials Should
Have Long Dimension Parallel To Prevailing Movement of
Waves or Currents (After Reference No. 18).
Providing Flow Through Dredged or Fill Materials
Dredged or fill materials 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 areal deposits may include those used for
disposing of quantities of dredged or fill materials through the development
of sites for port facilities, power generating stations, and similar projects.
Extensive lineal deposits include causeways and roads, canals, and similar
structures.Materials placed into these deposits may consist of sediments dredged
from water bodies and earth or rock fill obtained from land sources.
Permits for discharge of these materials may be required under Section
404 if changes in the use of areas of navigable waters are involved, flow
or circulation impaired, or reaches reduced.In these cases, implementation of
BMP's will be conducted in accordance with requirements of the 404 program.
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1-6
Deposits of Large Area! Extent
Large masses of materials can be located, shaped, and oriented to
minimize changes in water flow and circulation patterns. If this is not
adequate, practices can be utilized 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 alter-
nating sections of each should be considered for application, either singly
or in combination.
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
flow and circulation problems at later dates.
Figure 1-3 is a sketch of a fill for a small power plant incorporating
open channels through which water can flow and minimize disruption due to this
facility. Bridges can be used for channel crossings but culvert installation
also may be practical.
Figure 1-3 - Fill For Small Power Plant With Open Channels Provided For
Water Movement. Retaining Dikes and Channel Banks Should
Be Protected With Rip-Rap
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1-7
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
often extend across the natural drainage of streams or wetlands. Bridges
or culverts usually are installed where stream channels occur. Ground
water and surface flows may have to move laterally through or over natural
linear features to reach these structures. As a result, more extensive
and drastic differential water surface elevations can occur to initiate
movement of water through the few open structures. Depth changes, erosion
and sediment deposition, and other environmental problems may result.
Wetlands often consist of soft, compressible deposits of fine-grained
silts and clays, loose sands, and organic matter. The weight of a
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
MATERIAL DISPLACED
BY FILL
GROUND WATER
FORCED TO THE SURFACE
BEDROCK
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
materials used are relatively impervious compared to the natural deposits,
the cross-sectional 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 environmental problems on either side of the causeway.
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 characteristics of the material. Sand, sand and gravel, or similar
materials allow movement of water through them and may be used to provide
a pervious fill section. The BMP's should 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.
ROCKHLL
SECTION
DIRECTION OF
-^-
GROUNO 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
\
j j j I CULVERTS
1
I ' !
j NOTE: GROUND WATER
j I CLOSE TO SURFACE
j •
' / / /
PILING
Figure No. 1-6 - Causeway Across Wetland Designed To Minimize Disruption
of Surface and Ground Water Circulation. Fills Composed
of Pervious Rock or 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 passes and, to some extent, obstruct the flow or 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 if it
places no obstruction in it. (See Photo No. l-l). If piers in the channel
are used, they should be located and spaced to minimize the flow obstruction
and disturbance• (See Figure Nos. 1-7 and 1-8). During flood flows in
forested areas, fallen timber may be carried downstream to obstruct flows
when they are trapped across bridge piers. When designing a bridge,
consideration must be made of the probable length of trees or logs expected
during floods. The distance between piers should exceed this length, other-
wise obstruction of flow, flooding, excessive erosion, or bridge failure
may result to cause damage to local aquatic habitat as well as downstream
flood-prone areas. If this is not feasible, arrangements should be made
to quickly remove blockages during flood flows.
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1-10
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1-11
Freeboard allowance (the distance between the design stormwater
surface and the bottom of the bridge deck) should always be designed to
reduce the potential for debris blockage (Compare Figure No's. 1-7 and 1-8).
The superstructure, especially the guardrails, should be constructed to
maximize debris passage.
Culverts should be designed, constructed,and maintained so that they
not only pass high flows without creating environmental problems, but also
the low flows. During low flows, passage for aquatic life may be restricted.
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
JHHHHHHHMH^^
DESIGN STORM WATER SURFACE
NORMAL WATER SURFACE
Figure No. 1-7 - Stream Crossing With No Construction Required In The
Normal Channel .
POORER ENVIRONMENTAL DESIGN
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 well up into the lower
section of the structure to allow fish passage and still retain its
capacity for passing flood flows. After a period of time, gravel or other
sediments will deposit in 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)
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1-14
Figure No. 1-9 - Round Corrugated Culvert Placed Below Streambed To
Provide Fish Passage During Low Flows (Adapted After
Reference No. 10).
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 BMPs 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 improper culvert installation there
are remedial structures, or measures, that can be utilized 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 which
provide 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.
The capacity of culverts to pass flood flows should always be maintained,
This must be considered during the design and placement of culvert structures.
DOWNSTREAM
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.
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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. (Reference No. 28).
Note Gravel In Bottom of Culvert.
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1-17
Multiple culverts can be installed through a fill of greater linear
extent in wetlands to prevent concentration and restriction of flow.
(See Photo No. 1-6). One or two 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.
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.
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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. 28).
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1-19
Photo No. 1-8 - Fish Ladder Allows Fish To Move Around Dam, or Other
Water - Retaining Structure (U.S. Bureau of Reclamation).
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1-20
Preventing Detrimental Elevation Changes In Channels
Some stream-crossing structures such as culverts and bridges may
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 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, or 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. They provide the required
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1-21
VELOCITY TOO GREAT
NO RESTING POOL BELOW CULV*ERT /
FLOW IN THIN STREAM OVER BOTTOM
Figure 1-12 - Culvert Installations Which Restrict Fish Passage (Reference No. 10)
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1-22
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 the drop-off to progressively reduce
abrupt elevation change; and placing rock obstruction in the channel 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 and transport processes
can occur during the placement, or discharge, of dredged .and fill materials
or after the mass of materials is actually in position. Best Management
Practices to prevent or minimize this problem must receive full con-
sideration during the entire process from planning prior to placement,
through the implementation 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 waters from sites 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 measures
should be designed and constructed to extend above projected design flood
elevation and prevent underlying materials 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 in
this chapter, 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 that moving water can erode and transport downstream during
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2-2
discharge or placement. Because of this, all possible efforts should
be exerted to discharge dredged materials into contained areas and to
place fill materials on foundations that are not submerged at the time
of placement.
Dredged Materials
Disposal of dredged materials must be done in areas 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, 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
in the design to ensure that failure does not occur to release the contained
material back into the water.
r
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 .
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2-3
Dredged materials generally consist of a slurry made up of water
and solid sedimentary materials. After being discharged into the disposal
area, the coarser particles settle out; and the water, containing fine-grained
sediment particles (silts and clays), becomes 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 consist 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.
DREDGED MATERIAL
LEVEL SPREADER
OUTLET PIPE **J
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 periods 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
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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 flocculant
be obtained. In addition, a separate partition in the containment area may
be required 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 will be dependent on the amount of solids entering
it and the filtering capacity of the medium through which it moves. Good or
effective filtration will 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 alternative techniques.
Another alternative to consider is the use of spray irrigating
techniques to dispose of the water containing fine-grained materials and
prevent its runoff. If this is done properly, the water portion of the mixture
will infiltrate soils and leave the sediments on the surface where they
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
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2-5
DRAIN PIPE
3(a) PERVIOUS DIKE WITH MULTI-LAYERED IMPERVIOUS COVER
(Adapted From Reference No. )
OVERFLOW FROM CONTAINMENT
STOP LOGS
WATER LEVEL
EFFLUENT
DISCHARGE
TROUGH
3(b) DOWNFLOWSANDFILLWEIR (Reference No. )
FILTER MEDIUM
GRADED GRAVEL
COARSE STONE
FOUNDATION SOIL
Figure No. 2-3 - Techniques For Filtering Fine-grained Sediments From
Effluent (After Reference No. 17).
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2-6
done only when essential and no other alternative exists. Equipment used
should be designed to minimize ground disturbance. Filtering out sediment
being transported in the water from the construction site may be accomplished,
if practical, through the use of filter-fabric made of polypropylene mono-
filament sheeting or similar materials produced by manufacturers for this
purpose. If possible, structures such as bridges should be designed so
that the need for support piers 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 above the
water sufaces when the potential for erosion by surface water is minimal.
A technique of temporarily diverting a stream for placement of a
culvert and a road fill is shown in Figure No. 2-4 and a 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 channel should be
lined with impervious material such as plastic sheeting or some other
protection provided to prevent bank or bed erosion and the excavated
material protected from erosion.) The 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 may 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).
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DIVERSION CHANNEL EXCAVATED
STREAM DIVERTED, CULVERT PLACED IN EXCAVATION
EMBANKMENT-FILL PLACED OVER CULVERT
COMPLETED ROADFILL 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 .
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Cofferdams are temporary structures used to exclude water from or
permit dewatering of an area for the construction of fills on foundation
surfaces that are not 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.
They can be made of earth embankments, steel or timber sheet piling, and
other watertight materials.
Caissons are similar to cofferdams. While cofferdams usually 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 that
seeps in. Proper disposal of the pumped water is essential. It may be e
sprayed on land or held temporarily in detention ponds until sediments have
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 placed, and other activities conducted without being
subjected to water flows which can cause sediment runoff and pollution
problems.
DOWNSTREAM
PERMANENT
COFFERDAM
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 sheet pile 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
EXCAVATED
MATERIALS
0 CIRCULAR SHEET PILE COFFERDAM INSTALLED,
FOUNDATION BEING EXCAVATED.
@ 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
Pier and Prevent Runoff of Sediments During Construction
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2-13
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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 be provided by 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 adequate vegetative cover. Temporary
protection can be obtained with layers of organic or chemical mulches,
by burlap netting, or plastic sheeting.
In order to prevent erosion of fill materials and changes in water flow,
fill placed into subaqueous trenches should not be allowed to extend above
the adjacent underwater ground surface. 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 rigid structures function to retain as well as 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 ac 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 reinforced
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)
Photo No. 2-5 - Bridge in Forest Area with Abutments Supported and
Protected From Erosion By Concrete Retaining Walls
(U.S. Forest Service).
RAILROAD
STREET
ANNUAL HIGH WATER ELEVATION
GROUND
3REINFORCED EARTH
~ EMBANKMENT
LIMITS OF EXCAVATION
Figure No. 2-7 - Reinforced Earth Embankment, Protected From Erosion
By Concrete Panel Face, Was Completed Behind Cofferdam
Which Excluded 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 reinforced concrete
with the joints between them sealed with plastic fillers. Open cracks or
holes which develop must be sealed promptly or the action of surface
water and waves may displace or break up the slabs. Openings to relieve
hydrostatic pressures behind the panels may be needed to prevent failure.
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 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 (See Photo No. 2-8). The rock can be
placed in a layer upon an exposed slope by machine or by hand.
x -N,
te *1 ' -«•> k
i3^^1^^^ T^T^V v " * -
&£a&-•*'•#. ;>,- .^., -^:r*"^^^^$
Photo No. 2-8 - Carefully-Placed Rip-Rap "Armor" To Protect Roadfill From
Stream Erosion. Material To The Right Has Been Sealed
With Grout (A Thin Mortar).
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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; velocity of water
flow or severity of wave action expected; methods of placement; and the size,
shape, and specific gravity of the rock used. Size of the material will
be related to the velocity and direction of flow. Some sources suggest
that 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" (Reference No. 9). A reduced .thickness
can be achieved if compaction techniques are used on the rock 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 of 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-rao blocks.
DESIGN HIGH WATER
PLACE LARGER ROCKS
AT BASE AND ON FACE
FILTER
BLANKET
BELOW LOWER
LIMIT OF SCOUR
APPROXIMATELY 2X
THICKNESS OF BLANKET
Figure No. 2-8 - Rip-Rap Blanket Protecting Slope From Erosion By
Current and Wave Action. Note Filter Blanket. (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 will remain in place upon much steeper slopes (See
right-hand side of Photo No. 2-8). Wire mesh also can be used to stabilize
rip-rap when small-sized 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 stabilizer (Figure No. 2-9). Vegetation
often establishes itself in rip-rap blankets above high water where sediment
particles have filled in voids between the rocks to form soil.
A. WIRE MESH ON RIP RAP
HIGH WATER
REINFORCING ROD
STAPLES
^ CONCRETE-FILLED PIPE
BELOW SCOUR LINE
B. DOUBLE LAYER OF WIRE MESH
WIRE FASTENERS
POSITION AFTER SCOUR
HAS OCCURRED
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 have been used to protect the surface of exposed fill materials
above normal water levels (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 anchoring the brush mats may be
made of "live" woody plant material 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
THAN1'/z = 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 Long-Term
Protection. (After Reference No. 12)
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3-1
CHAPTER 3
ENSURING CONTAINMENT OF POTENTIAL POLLUTANTS
WITHIN MASS OF DISCHARGED DREDGED OR FILL MATERIALS
Naturally-occurring materials interspaced 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 minerals 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, nearby
water bodies will be subject to pollution. If any of these materials are
suspected, geologic studies should be initiated to identify their location,
concentration, and extent so that sources of alternate materials can be
located.
In arid areas, sometimes the only available fill materials consist
of clay shales of marine origin which may contain quantities of gypsum,
salt, or similar soluble minerals in veins or disseminated throughout.
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 fills 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 areas and in
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3-2
different types of rock which can be used for fill materials. Soft
easily-excavated sedimentary rock that is readily usable for fill or hard
consolidated materials that require blasting such as rip-rap may contain
quantities of iron sulfides. Sulfides are readily oxidized when exposed to
air, moisture, and bacteria (Thiobacillus) and can create high concentrations
of mineral acids. As the acid solutions flow over, or through, 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 also underly
alluvial beds of rivers that are being dredged or source (borrow) areas
where fill materials are to be obtained. If the poor quality materials
can be identified, isolated, removed, and properly disposed of separately
from the principal mass of dredged or fill material to be used, they will
not pose a threat to the environment. If they are interspersed through
the main body of materials, however, they probably cannot be separated and
will cause the entire body to be pollution threat. This situation probably
is more characteristic of fill than of dredged materials since most river beds
are formed on deep freshwater alluvial deposits that do not contain such "natural1
pollutants.
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, Best Management Practices should be in use to
contain these materials and prevent their contact with air and water. The
specific BMPs to be considered could involve placing the poor quality materials
within relatively impervious layers (blankets) or barriers of compacted and
relatively impervious materials. (See Figure No. 3-1).
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3-3
On steep fill slopes, where stability may be a problem, or quantities
of impervious soils for blankets are limited, gabions (wire mesh baskets)
of compacted soils may be considered. In these cases, the impervious
blankets are thinner, but can also function to resist failure due to the
GROUND-WATER LEVEL
COMPACTED IMPERVIOUS FILL
Figure No. 3-1 - Impervious Fill Surrounding Roadfill Containing
Pyrite Restricts Contact With Water and Air.
tensile strength of the baskets. Ensuring the placement of impervious
materials effectively into voids between gabions will be critical 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 cloth 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 . On some projects, agricultural
lime has been 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 that is 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
GROUND SURFACE
Figure No. 3-2 - Earth-filled Gabions Providing An Impervious EHanket
On Roadfill Containing Pyrite (After Reference No. 29)
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3-5
Impervious 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 differential 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, due to their low permeability. Consequently,
the estimated time intervals that differential water levels are to be
maintained on either side of impervious blankets or barriers, as well as
their degree of permeability 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 can occur for long periods of time on either side of a blanket
or barrier, it must be a thick, highly-compacted impervious unit. If
water finally moves out of the contained fill after being degraded by
the soluble materials in it, it will be at such a slow rate 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
PROTECTING HABITAT CONDITIONS AND PROVIDING
FOR FISH AND WILDLIFE PROPAGATION
Water-retaining structures such as dams and reservoirs, regardless
of their size, often function as complete barriers to the movement of
aquatic life and water-dependent wildlife. Linear fills across wetlands
or water bodies such as railroad or highway embankments, causeways, or
even canals and aqueducts can restrict movement of fish or other creatures
unless adequate facilities have been provided for passage through or
under these structures. Deer, quail, foxes, rabbits, and other wildlife
can cross over or travel along these linear facilities, but only with
extreme danger to their lives. Permits for the discharge or placement
of materials to form such structures may be required under Section
404 if changes in the use of nagivable waters are involved, flow or
circulation impaired, or reaches reduced. In such cases application
of appropriate BMP's may be a condition for obtaining a permit. Best
Management Practices to prevent or minimize such environmental impacts
should include providing effective passageways for aquatic animals
and other wildlife through, over, or possibly around such structures,
preventing wildlife and other creatures 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 have not been proven fully effective. There is no intent in
this document to imply that these are the only practices available or
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4-2
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 progation is presented
in the References on Pages 6-1 through 6-4.
Creating Passageways For Aquatic or Water-Dependent
Wildlife Through, Around, Under, or Over Structures
Discharge of water from reservoirs is accomplished through outlet
pipes or penstocks of some sort which extend 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 these structures it does so at high
velocities and the passage of aquatic life through them is difficult or
impossible.
Linear fills extending across wetlands 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
or eliminated 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. 4-1). 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. If the effects
of a dam or reservoir on the habitat of anadromous fish will be severe,
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4-3
l
Photo No. 4-1 - Salmon Migrating Upstream Use Fishladder Facility To
Bypass Dam (U.S. Bureau Of Reclamation).
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4-4
manmade spawning beds may be designed into the project. Additional
facilities then are required to direct and 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 fishes
such as salmon. In these cases fish ladders, or other by-pass structures can
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
returning mature fish to migrate upstream around the dam. Additional
and more detailed 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 Wildlife Habitat and Population
Improvement Measures For Western Dam and Reservoir Projects" (Reference
No. 22).
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4-5
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 wetlands 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 or other hazards.
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. 4-2 illustrates an earth-floored passageway thorouah an
embankment with fences to channel animals through the structures. In general,
facilities for animal passage extend under road or railroad embankments.
and over water facilities such as canals and aqueducts. (See Photo
No. 4-3).
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4-6
Photo No. 4-2! -
Underpass hor Animals Beneath A Highway. Fences At Toe
Of Slopes Prevent Their Movement Up Embankment To Roadway,
(U.S. Federal Highway Administration).
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4-7
Photo No. 4-3 - 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 emplaced
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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4-8
Water Facilities
Fish and other aquatic life can be prevented 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 protective system for fish
is shown in Photo No. 4-4. The fish 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 functions to divert them into holding
tanks where they are collected, transported away from the area of influence
of the pumps, and then released back into the water out of the danger zone.
Canals, aqueducts, or other water-conveyance bodies often extend
across routes used by wildlife to gain access to feeding, refuge, reproduction,
or other areas. Animals attempting to cross these facilties, 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 man-made reservoirs
often have spillways, outlet works, and penstocks that locally increase
current velocities and create other hazards.
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4-9
SUBMERGED RSH BYPASSES
TO PUMPING PLANT 2,5 MILES
Photo No. 4-4 - 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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4-10
Best Management Practices have been developed and can be used to
prsvant wildlife from being trapped in such structures. Fencing is an
effective practice to prevent animals from gaining access to and being endangered
by a canal or aqueduct. It is generally expensive, however, and will require
crossing facilities such as bridges to be provided for the animals. These
crossings must be located at intervals, particularly where predominent migration
routes or trails exist. If migration or other movements of animals are restricted
by fences without crossing facilities, herds may suffer losses or deterioration
in quality due to inbreeding, 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 (See Photo
No. 4-3). 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 in wetlands
to minimize danger to wildlife, particularly in areas where wildlife tend
to migrate or travel. When they are buried, crossing by animals is greatly
facilitated.
Where covered pipes, fencing, and other practices are not feasible
or fully effective in preventing 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 a slope to obtain water, and then return up the slope (See Photo
No. 4-5) •
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4-11
The escape structure 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 have
provided 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. 4-5 - Concrete Escape Ramp With Low Slope (4h:lv)
Built. Into Indentation In Steep-Sided Canal. Note Timber
Boom That Directs Swimming Animals Into Ramp. (Bureau
Of Reclamation).
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4-12
Transportation Facilities
Causeways extending across wetlands for highways, particularly 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 safety. They consist of
structures composed of baler tines and angle irons which allow animals 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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4-13
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 propagation of existing
aquatic life and water oriented wildlife. They may include proper management
of water flow and circulation, and the provision of nesting, spawning,
nursery, resting or feeding areas for aquatic life and water-oriented wildlife.
Proper Hater 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 storage and flow requirements for aquatic life during dry periods
of the year.
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
which function as natural scouring media in the channel farther downstream
Otherwise sediment loads brought into the main streams by tributaries may
build up into 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 excess sediment loads if they have not been periodically
flushed out by high flows.
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4-14
Dams and reservoirs on coastal streams haying anadromous fish populations
must be designed to make available sufficient quantities of water to flush
open sandbar barriers formed by offshore currents across the mouths of
these streams. Unless sufficient high flows can be provided to open.these
bars, anadromous fish will not be able to enter the channel for further
upstream migration and spawning.
Preventing Detrimental Physical or Chemical Water Changes
Water discharging over the spillway of a dam has quantities
of air entrained in it. As it plunges rapidly to depths in a stilling
basin, or plunge pool, hydrostatic pressures increase and force the constituents
of the entrained air into solution in concentrations exceeding normal saturation
values. This is termed "supersaturation". Supersaturation also can occur
in the bodies of fish swimming at depths and cause death. Nitrogen super-
saturation causes most of the problems as it comprises approximately 80% of the
entrained air. The oxygen content (20%) in the fishs1 bodies is mostly le
metabolized and other gases are too minor to affect them.
Anadromous fish populations in rivers of the northwest have suffered
from nitrogen or "gas bubble disease". If they swin at depths greater
than 12 feet in the nitrogen-supersaturated water, the fish are not
affected by the disease, since the external pressure prevents the gas from
forming bubbles in their bodies. As they swin at shallower depths, however,
up fish ladders or near the surface, the nitrogen gas pressure within the
fish's body exceeds the external water pressure and bubbles form. Blisters
and bubbles form under the skin, on the body and fins, on and under the gill
covers, and in the mouth and head.
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4-15
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, BMPs for preventing this problem 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. 4-1). The water can even be caused
to fan out into a thin sheet through the use of a flaring device.
Figure No. 4-1 - Spillway Showing How "Flip" Structure Prevents Flow
From Plunging To Depths.
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4-16
Other Best Management Practices to prevent nitrogen supersaturation
and "bubble disease" can include:
1. Collecting and transporting fish overland through the length
of river where nitrogen supersaturation occurs.
2. Decreasing spillway flows by providing additional reservojr
storage.
3. 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 shallow layers
of the reservoir and discharged through upper water-level outlets, and lower
if obtained from reservoir depths. Water released from outlets deep in a
reservoir also may be oxygen deficient. 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 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 content 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. 4-6). Higher elevation outlets release warmer and more
oxygenated water, while lower ones draw from colder water which contains
less oxygen. The quality of the releases can be regulated to meet the
needs of the aquatic life being protected through a properly designed and
operated outlet system.
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4-17
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5-1
CHAPTER 5
ENHANCEMENT —THE REPLACEMENT. RELOCATION,
OR RECONSTRUCTION OF EXISTING ENVIRONMENT
In certain extreme situations, the discharge of dredged or fill
materials into water bodies 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 the existing or a similar type of
environment to compensate for habitat loss. In other words, arti-
ficially create an equally productive area of new aquatic environment
for^hat damaged or destroyed. As these practices are in the development
stages, limited information is available regarding their long-term
effectiveness, particularly in wetlands.
If a significant percentage of the aquatic area becomes dry land due to
the discharge and the use changed, the flow or circulation of the waters
impaired, or the reach of a water body reduced, a permit may be required in
accordance with the Section 404 program.
Creating environmental conditions in a new area that will be similar
to the natural environmental conditions that occurred in an adjacent area
is extremely difficult since they result from numerous interrelated
surface and sub-surface hydro!ogic, geologic, topographic, climatic,
plant and animal, and other factors. Changes in one or more of the
factors may set up a chain reaction which results in changes ensuing in
others. The end result of the changes may be unpredictable and detrimental
unless sufficient data are available concerning the entire system.
Wetlands
In wetlands, water is the dominating factor in determining the nature
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5-2
of soil development and the types of plant and animal communities occurring
there. Wetland soils are saturated periodically due to fluctuations in
surface or ground water elevations. As a result, knowledge of water flow
into and through the wetlands is essential for evaluating the practicality
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 themselves. If they do not,
re-establishment by transplanting pioneer species probably will be
essential to enable the new wetland to quickly establish itself and,
through successional processes, produce and support climax communities
of aquatic life and other 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.
On a long-term basis, 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. 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
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5-3
changes the velocity of flow and the energy available for channel
erosion (degradation) and sediment transport. These changes may be controlled
by designing the new channel, through the use of Best*Management Practices,
to provide significant beneficial impacts to 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 continually modify the channel by eroding, transporting, and depositing
sediments until an equilibrium has been reached between energy and resistance.
During equilibrium, stream channel changes occur constantly but the net
flow 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 lost. Only the remaining energy is available for eroding and
transporting 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 these 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 can be increased by providing
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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5-4
of the bed may result. Practices for minimizing the detrimental effects
in this situation may involve re-designing the channel section so that
the water flow has the capability to transport the sediment load through it.
All measures (BMPs) should ensure, as far as possible, that the '
relocated stream will be as stable, under the new conditions, as the
original one, since an unstable stream will generally have a tendency to
create subsequent environmental problems. 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, since 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. 5-1). 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. 5-1). 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 native
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 (See Figure No.5-2). These large rocks,
placed on the outside of stream bends where velocities are high, can also act as .
rip rap to prevent bank erosion. They should be located so that they do not cause
currents to impinge on the banks and create more severe erosion problems.
severe erosion problem.
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5-5
*'
t' "V '
T~ jl*«
«•»•• /••»«[ - • . _ .-^bfc.. , *** ' ""-% . *«S
' *--». ?«-(ir "-TDfKJK • -«»»;»%, "«•«"•
.'
Photo No. 5-1 - Check Dam In Stream Provided To Decrease Its Gredient
(U.S. Forest Service).
7T77
/gggx&ps;#
Figure No. 5-1 -
Dual-Purpose Stream Channel Designed To Maintain Adequate
Depth During Low Flows (After Reference No. 27)
Figure No. 5-2 -
Rocks Placed In Stream Section To Reduce Velocities
and Prevent Erosion On The Outside of Bends (After
Reference No. 27) .
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5-6
Deflector structures can be used to divert the water into more
constrictive channels, 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 kept submerged permanently in order to prolong
their life. Photo No. 5-2 illustrates rock rubble deflectors.
Photo No. 5-2 - Meanders Created by Rock Deflector Structures
(Reference No. 27).
If a stream must 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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5-7
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 area should be provided for the new
one. The placement of additional soil may be required so that natural
conditions are simulated to the extent needed for site replacement.
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 subsequent
environmental problems, additional structures, or other Best Management
Practices similar to those initially designed for the channel, should be
provided to control them.
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6 - 1
SELECTED REFERENCES
1. Boyer, Peter B. "Gas Supersaturation Problem In The Columbia River".
Paper Presented At The American Society of Civil Engineers,
Irrigation and Drainage Division Specialty Meeting. September
26-28, 1972. Spokange, Washington.
f
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. Kryine and Oudd, "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.
-------
6-2
8. Stubbs, Frank W. Jr. . "Handbook of Heavy Construction". McGraw-
Hill Book Company. 1959.
9. U.S. Department of Agriculture, Forest Service. "Stabilizing
Eroding Streambanks In Sand 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". 1969.
13. U.S. Department of the Army, Corps 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. - - - -. "Guidelines 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 Enviro Control, Inc. January 5, 1978.
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6-4
23. . "Assessment of 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-
ular 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".
Draft Unpublished Report. (Date Unknown)
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. ----. "Highways and Ecology: Impact Assessment And Mitigation"
FHWA-RWE/DEP-78-2, March,1978
31. U.S. Environmental Protection Agency, Region X, "Logging Roads
and Protection for Water Quality". EPA 910/9-75-007. March, 1975.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 440/3-79-028
4. TITLE AND SUBTITLE
"Best Management Practices Guidance, Discharge of
Dredged or Fill Materials"
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
September, 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert E. Thronson
8. PERFORMING ORGANIZATION REPORT NO.
EPA 440/3-79-023
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Water Planning Division, Implementation Branch
Washington, D.C. 20460
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Water Planning Division, Implementation Branch
Washington, D.C. 20460
13. TYPE Of REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16 ABSTRACT . . .
Before any decisions can be made regarding the discharge of dredged or fill
materials into waters of the UNited States, all probable impacts and feasible alterna-
tive sites must be considered. This will include evaluation of such factors as the
necessity for discharges; sensitivity of the area to environmental impacts, both long
and short term; possible alternative sites or a scheduling of operations; and
effectiveness of available site-specific Best Management Practices to prevent or
minimize the impacts. Discharges of dredged of fill materials must comply with
guidelines prepared by the Administrator of EPA pursuant to Section 404 (b) (1) of
Public Law 95-217.
This "Best Management Practices Guidance" document has been prepared to provide State
and areawide water quality management agencies, other State and Federal agencies
and the concerned public with information on readily-available processes, procedures
methods, and techniques that can be used to minimize or prevent environments1
impacts that could result from the discharge of dredged of fill materials It has
been written in a manner that the reader does not have to be an expert in the
discipline to be able to understand what the problems are and some of the solutions
that are presently available.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution Abatement^Aquatic Environment
Pollution Control
Wetlands
Waterways
-Fills
Sedimentation
b.IDENTIFIERS/OPEN ENDED TERMS
Sediment Control
Sediment Discharge
COSATI I'icld/Gioup
Water Pollution
1302.2
Waterways-1302
8. DISTRIBUTION STATEMENJ
To State and areawide WQM agencies, other
State agencies, Federal agencies, and the
concerned public
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
20 SECURITY CLASS (This page/
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
US GOWRNMENT PRINTING OFHCE 1979 -281-147/116
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