HomeMy WebLinkAboutAPA3320DEPARTMENT OF ENVIRONMENTAL CONSERVATION
Ja . aminond
. Governor
Ernst Mueller
Commissiorer of
Environmental Conservation
TO
224
.A4
A35
1980
TRANSPORTATION
and WATER QUALITY
~ l ater Quality Management Planning Program
Non-Point Source Study Series
Section 208, PL 92-500, 95-217 MAY 1980
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MANUAL OF RECOMMENDED PRACTICES
FOR
TRANSPORTATION CORRIDOR DEVELOPMENT
ROADS, RAILROADS, PIPELINES, SUBDIVISIONS
ARLIS Alfl~kft Reso~rces Lib~ary & Information Services
Library Building, Suite 111
321 i Providence Drive
flnchorage,AJ( 99508-4614
Prepared by the Alaska Department of Environmental Conservation Water Quality
Planning Program pursuant to Section 208 PL 92-500 as amended. This project
was assisted by a grant from U.S. Environmental Protection Agency.
Prepared in part by
R&M Consultants, Inc.
Apri 1 1980
TABLE OF CONTENTS
Introduction
1. Earthwork
2.
l.A.1 Clearing, Grubbing and Slash Disposal (Guidelines)
1. B .1 Surface Preparation
l.C .1 Borrow and Disposal Practices
Drainage
2.A.1 Culverts
2.A.2 Low Water Crossings
2.A.3 Grading, Cross Drains
2.B.1 Grass Channels
Appendix 2.B.1 Calculation of Channel Size.
2.B.2 Ditch Checks, Checkdams --Temporary Measures
2.B.3 Mechanical Channel Liners
Appendix 2.B.3 Calculation of Required Stone Size to Prevent
Channel Erosion and Estimation of Scour for Waterways
2.C.1 Outlet Protection [for roadside drainage]
2.0.1 Inlet Protection
3. Sediment Retention
3.A.1 Sediment Basins --Permanent & Temporary
Appendix 3.A.1 Settling Pond Sizing
3.B.1 Buffer Strips, Barriers, Fences
3.C.1 Traps and Filters for Storm Drain Inlets
3.0.1 Silt Curtain
4. Slope Stabilization
4.A.1 General --Non-Permafrost Areas
4.B.1 Revegetation --Biotechnical ~1ethods
4.C.1 Temporary Downdrains
4.C.2 Permanent Oowndrains
4.0.1 Diversions and Benches
4_n_? IPVP 1 SnrP;HiPrc:
5. Revegetation and Mulching
5.A.l Grasses, Herbaceous and Woody Plants
5.A.2 Stabilizing Critical Areas with Sod
5.B.l Organic Mulches
5.B.2 Nettings, Mattings, and Mulch Blankets
5.B.3 Chemical Stabilizers and Soil Binders
Introduction to Group 6, Stream Stabilization
6. Streambank Stabilization
7.
6.A.l Vegetative
6.A.2. Mechanical Methods Revetment
6.A.3 Bio-technical Methods
6.A.4 Mechanical Methods Deflector Jetties
Thermal Erosion Control
7.A.l Treatment of Disturbed Surfaces, Prevention of Disturbance
7.B.l Cut Slope Stabilization
8. Icing Control
8.A.l Specialized Drainage Structures
8.B.l Culvert Thawing
8.C.l Channel Maintenance
9. Final Restoration
9.A.l "Putting to Bed"
10. Miscellaneous
lO.A.l Tracking Control
lO.B.l Wind and Dust Control
INTRODUCTION
This is a manual of recommendations for controlling erosion and sedimentation in
development of transportation facilities, roads, railroads, pipelines, and
subdivisions. Recommendations apply to design, construction an~ maintenance.
Construction activities are classified by the headings, GROUP and PRACTICE.
Each PRACTICE is described under a series of subsequent headings. Many of the
PRACTICES {construction_ activities) serve s_ome primar.}' pul"p_ose other than_
erosion and sediment control; but discussions under the subheadings (PURPOSE,
SITE CHARACTERISTICS, DESCRIPTION) refer only to those applications which in
some way control erosion and sediment.
The selection of alternative design features, such as bridges or culverts for
stream crossings, is not directly addressed here. Those decisions should be
made on the basis of sound engineering judgement applied to specific sites and
situations. This manual does, however, provide information and suggestions on
how to protect water quality in the design, installation and maintenance of such
structures. Trade-offs will occur between such things as initial cost,
maintenance required, project life, and right of way required. Frequently
several other professional disciplines should also be included in decision
making.
Guidelines presented here are not intended to serve as design standards. A
number of design publications already are available; these are reviewed and
referenced on the appropriate procedure sheets.
No attempt is made to represent all possible solutions. Many of these
procedures are intended only as examples. Innovative engineering solutions are
encouraged. The PRACTICES will be modified or supplemented periodically; the
format is expandable.
Recommendations refer mainly to roads, because land-based transportation systems
in Alaska are primarily roads. These, therefore, provide the most information.
However, the same basic design and construction methods are used whether an
embankment is intended to support a roadway, rails, or a pipeline workpad.
For several PRACTICES it is indicated that to use a specified erosion control
measure will result in some additional cost. However, expenses necessary for
meeting water qua 1 ity standards should be cons ide red as a norma 1 cost of doing
business.
It will suffice to mention administrative requirements (permits, etc.) once, in
this introduction, to avoid repeating the list each time a procedure touches on
an agency • s res pons ibi 1 ity. The state and federa 1 programs most frequently
affecting highways and other transportation corridors are:
Fed era 1
U.S. Army Corps of Engineers
Section 404 permits (P.L. 92-500, Clean Water Act). Required for placing
dredge spoils or fill in navigable waters and wetlands. Section 10 permits
(Rivers and Harbors Act). Required for obstruction, alteration or
improvement in navigable water.
U.S. Coast Guard
Section 9 permit (Rivers and Harbors Act). For construction, modification,
or removal of bridge or causeway in navigable water.
State
Department of Environmental Conservation
Section 401 Certification (P.L. 92-500). U.S. Army Corps of Engineers
permits require certification from the state that they comply with other
provisions of the Clean Water Act (SECS. 301, 302, 306, 307).
Water Quality Standards (AS 46.03). Apply to all activities which result in
point or non-point source discharges into state waters.
-Depar-tment of Fish and Game _ _ _
Anadromous Fish Protection Permits (AS 16.05.870). Requires ADF&G approval
before conducting activities which impact anadromous fish streams.
Department of Natural Resources
Water use permits (AS 46.15). Require permit before constructing water
impoundment or diversion.
Division of Policy Development and Planning
Coastal Management (AS 44.19.891-894, AS 46.35). Requires determination of
project consistency with district and state coastal programs.
State Clearinghouse (Circular A-95). Federally funded projects require
review of numerous agencies through the state clearinghouse.
For a more complete list, please contact the ADEC permit coordination center in
either Anchorage or Juneau for the Directory of Permits.
Nothing in this manual limits responsibility for compliance with any law or
regulations.
-·
NUMBER l.A.l
Earthwork
Clearing, Grubbling and Slash Disposal {Guidelines)
To prevent erosion of areas disturbed by clearing and excavation.
SrT£ CHD..eAC.T'EI2..lSTICS
The following set of guidelines apply to all areas where vegetation and timber are
removed, topsoil stripped and soils excavated for construction. Permafrost areas
may require special techniques to avoid thermal degradation.
ADVANT~6E:5
1. Minimizes erosion and sedimentation
from disturbed areas.
DESCR t PTlOtJ
Guidelines for clearing, grubbling and early construction phase.
1. Minimizing Disturbed Area
Clearing should immediately precede excavation activities to minimize exposed,
unprotected surfaces.
Erodible cutslopes, fills and other exposed soils should not be left over winter
unprotected by vegetation, or coarse, adhesive or blanketing materials.
Equipment should not be operated outside of the designated area within the R-0-W.
In permafrost terrain, unless snow roaded even a single pass by a wheeled vehicle
can damage the organic layer, resulting in thermal erosion.
Preserve the organic mat above cuts. Handclearing should be done on ice rich
permafrost {for summer construction) and at the top of cut banks. Any
disturbance which may lead to erosion should be promptly reported and treated
{See section 7 for further discussion of permafrost).
In muskegs, slash can be used as a mat for overlay materials.
2. Conservation of Topsoil
Organic soils stripped from the R-0-W should be stockpiled whenever possible for
later use, or immediately respread over surfaces to be revegetated. Proper
staging can prevent double handling.
I
DE5CJ(lPTION C.CNTlNUED NUMBER l.A.1
3. Slash Disposal
Slash should not be mixed into fill.
-Salvage all merchantable timber.
-Slash can be used for ditch checks, sediment filters, or can be chipped for
mulch.
4. Stream Crossings
Equipment operation instreams should be kept to an absolute minimum for crossing
anadromous streams with equipment.
Buffer strips at the approach to streams should be maintained until actual
construction is to proceed.
Avoid felling trees or allowing other debris to enter streams. In some case this
may be unavoidable. Remove such debris within 48 hours. Avoid damaging natural
streambanks.
MAl NTE.ND.NC.E
If these activities are carried out properly, very little maintenance should be
needed, particularly if excavation and final construction follow closely behind.
~EFERENC.E
1) Tourbier, J. Water Resources Protection Measures in Land Development, Water
Resources Center, Univ. of Delaware, April 1974. 2) Environmental Protection
Agency Guidelines for Erosion and Sediment Control Planning and Implementation
August 1972. 3) Environmental Protection Agency. Logging Roads and
Protection of Water Quality, EPA 910/9-75-007 March 1975.
NUMBER 1. B .1
lu~CUP Earthwork
1 PeAcTtc..E Surface Preparation
PURPOSE
To promote revegetation efforts and reduce erosion from disturbed areas as well
as from driving surfaces.
61TE C.HAf<:hCTERISTIC.S
Applicable to any areas to be revegetated, particularly sloping terrain. May be
used to reduce wind and water erosion of exposed areas and stabilize driving
surfaces.
ADVANTA6E.S
1. Promotes seed germination.
2. Helps increase soil moisture
retention and reduces movement
DISADV/lNTA6ES
of seed and fertilizer.
3. Increased runoff infiltration.
4. Stable driving surfaces.
None -should be a part of recommended practices.
DESC.I< l PTI ON
Surface preparation includes a variety of techniques to stabilize exposed areas,
promote revegetation and reduce erosion from construction areas. Some techniques
apply to the surface treatment and others to its configuration.
Scarification Many types of equipment can be used to "roughen" a surface prior
to revegetat1on. The roughened surface helps infiltration and moisture retention,
which promotes germination. "Cat-tracking" consists of running tracked vehicles up
and down or along slopes creating mini-benches. This can usually be done on
slopes up to 2:1. Discs, harrows, sheepsfoot rollers are also used to roughen
surfaces.
Serrated Cuts Slopes in certain materials can be cut or serrated into
mini-benches along the contours. This also improves infiltration.
Topsoilin9 Although not always economical, topsoil stripped during clearing
should be stockpiled and later respread over areas to be revegetated. This
provides a more effective seed bed, particularly in dry soils areas.
Roadbed Construction
Aggregate Cover A surface dressing of clean aggregate provides a good driving
surface, even in wet weather and minimizes surface erosion. It can be used as
a base for final surfacing (such as asphalt) or simply for heavily travelled
access roads or pipeline R-O-W's to reduce soil tracking.
DE5C.~tPTIDN CDNTtNUED NUMBER 1. B .1
Surface Configuration The geometry of the roadbed is critical to providing .
surface drainage and in minimizing surface saturation and runoff of eroded soils.
Comsaction The final lift of each day's work should be compacted and shaped
to rain.
Crowning or Sloping The surface should be crowned or cross-sloped to direct
runoff to ditches, berms or other stabilized areas.
Aggregate Cover, Temporar~ Seed and Mulch If the surface is to remain unused
fOr extended periods, sue as for final completion the following season, a
treatment of temporary revegetation (see 5.A.) or aggregate cover will
minimize erosion.
E.XAHPLE
Highway fill slope shown was •cat-walked'
prior to revegetation. Grass was
beginning to germinate in cleat tracks.
Other slopes in the area which had not
been scarified showed rilling and gullying
erosion.
Location: Glenn Highway, Eklutna, Alaska
Source: R&M Consultants, Inc., Anchorage,
Alaska
REFERENCE
.,
' , ....
1) Environmental Protection Agency. Guidelines for Erosion and Sediment Control
Planning and Implem~ntation, August 1972. 2) Fairfax County, Virginia. Erosion.
and Sediment Control Handbook. Dec. 1974. 3) Environmental Protection Agency •.
Log~ing Roads and Protection of Water Quality. EPA 910/9-75-007. March 1975.
.•
NUMBER l.C.1
[ur<ouP Earthwork I
PI<.AC.TJLE. Borrow and Disposal Practices
To prevent erosion from mining and disposal sites during and after construction.
6tTE CttAI<~C..l"E.KlSTlC.S
Recommendations are applicable to all disposal sites, and all upland and
floodplain borrow sites.
b.DVANTAGES
1. Protection of water resources from
mining and disposal activities.
DISADVANTA.6E.S
1. None -cost of erosion control should
be considered part of normal expense.
DESC.J<.l PTION
BORROW AREAS
1. Mining Plan
Each site will impose special requirements to prevent or m1n1m1ze sedimentation
from mining activities. Before and during mining a detailed mining plan should
be on site. The plan should include:
site sketch to scale;
mining procedures;
stockpiling and overburden handling procedures;
erosion and sedimentation control procedures;
overburden depth;
material properties quantity and depth;
buffer areas;
excavation dimensions;
plan modifications;
time frames;
traffic routes; and
final restoration measures.
Time frames should be determined well in advance so that the contractor will
have proper equipment on hand.
Mining Plans should be changed as field conditions change.
I DE.SC.~I PrtDN CONTINUED NUMBER 1. C .1
2. Sediment Control During Operation of Upland Borrow Sources
Mining should take place wherever possible in upland areas rather than in
floodplains.
Pits should be located out of the path of heavy seepage. Avoid locations
where pit backwalls adjoin steep slopes (recommend less than 40%) except
where pit adjoins solid rock slopes.
Floodplain Sites
Mining should not go deeper than a foot or more above the water table to
prevent hydraulic changes and siltation.
Gravel washing should be avoided. If there isn•t an alternative, effluents
should be passed through settling basins with low energy exits. If possible,
direct effluents away from streams to vegetated areas, provided that energy
can be dissipated to prevent erosion.
Remove borrow materials from floodplain sites as soon as possible. When
removal is not feasible., stockpiling materials in rows in the direction of
flow lessens the potential for erosion.
Avoid vegetated portions of the floodplain, especially inside meanders.
Locations inside meanders have high potential for short cutting stream flow,
and may have high potential for fish entrapment.
Avoid work in active channels, especially spawning and overwintering areas.
Where floodplain sites are used, scalping and crowning unvegetated bars have the
following advantages.
No vegetation would be disturbed;
Mining does not enter the water table;
By crowning, fish are not trapped by receding flood waters.
However, maintaining bank integrity is important to prevent change in stream
configuration (prevent braiding). Scalping and crowning should not be done where
banks are unstable and could be damaged at high flows if bars are removed.
All Borrow Sites
Runoff upslope/upstream of any borrow sources should be diverted with dikes or
ditches. Runoff from the pit should pass through sediment basins or revegetated
buffer strips before entering a watercourse.
Keep equipment operation within approved working limits.
3. Preventing Channel Charges
.;
Floodplain Sites
Retrain undercut and vegetated banks.
Avoid borrow in streams where banks are unstable.
Avoid disturbing edge of active channel -subsequent floods could establish
braiding.
DESLR.\ PTION C.ONTINUED NUMBER 1. C .1
For pits in the floodplain, locate where buffer zone is stable. A flow path
through the pit should be a greater distance than existing channels.
High Water Channels
Maintain channel shape in material site similar to shape of the channel as it
enters and leaves the site.
Retain bed slope in site not greater than naturally occurring slopes.
4. Phased Development
Phased development borrow sources can minimize disturbed area. As use of one
segment is completed, it may be stabilized while the next is developed. By mining
in an upslope or upstream direction the portions first developed may be used as
settling basins for higher portions.
5. Fish Entrapment
This is often a potential hazard when borrow sources are in floodplains. Sites
should not be left so that fish can be trapped when floodwaters recede. If
settling basins are used the final outlet should be perched.
Maintain fish passage in active channels. Avoid constriction of flows which
would increase velocity.
6. Restoration
Up 1 and sites
Stockpiling, and respreading overburden following operation greatly
assists in borrow pit restoration.
Floodplains
Remove overburden immediately to a location above high water for
disposal, stockpiling or rehabilitation of other sites.
If settling basins were required fine solids should be removed beyond the
floodplain or the basin should be rehabilitated such that fine solids will not
be introduced into the stream.
All borrow sources
All sites should be stabilized by returning to stable angles
and revegetating. (See Section 5 on revegetation)
DISPOSAL AREAS
Disposal of organic soils, ice-rich soils, slash and other materials requires
careful planning. Spoil areas should be graded to stable conditions and should
provide for impoundment of waterborne sediment. Some waste materials can be
used to restore old haul roads being "put to bed." Disposal areas should mulched
and seeded as in Section 5. · · · ··
Both borrow and disposal area plans should incorporate appropriate tracking and
dust control procedures as discussed in Section 10.
EXAMPLE
A portion of this borrow site where
mining was completed has been final
graded and revegetated.
Location: Trans-Alaska Pipeline
Source: R&M Consultants, Inc.
Anchorage, Alaska
REFE.RENC.E
NUMBER 1. C .1
1) Burger, C., Swenson, L. Environmental Surveillance of Grave1 Removal on the
Trans-Alaska Pipeline System with Recommendation for Future Gravel Mining. Joint
State/Federal Fish and Wildlife Advisory Team. Special Rpt. No. 13. 1977.
2) Highway Research Board. Erosion Control on Highway Construction. 1973.
3) Soil Conservation Service. Field Manual for Conservation Practices. 1969.
4) Woodward-Clyde Consultants. Gravel Removal Studies in Arctic and Sub-Arctic
Floodplains in Alaska. Draft Technical Report. U.S. Fish and Wildlife Service.
November, 1979.
NUMBER 2.A.l
jui<DUP Drainage -Structures
I PUC.TIC:..E Culverts
PuRPoSE
To provide non-erosive passage of stream flow on temporary and permanent roads.
51TE CH-ARACTE.I<.ISTICS
Used on any roadway section where continuous access is required and where
flow volume, gradient and/or length of span do not mandate bridging.
ADVANT66E.S
1. Permanent or temporary
i nsta 11 ati on.
2. Allows continuous access.
DISilDVANTA6ES
1. Requires regular maintenance.
2. If maintenance is discontinued
usually requires removal to
prevent eventual plugging and
washout.
DESC..RI PTl oN
3. Can be designed to allow
fish passage.
4. Relatively inexpensive
and quick.
3. Requires accurate staking
for proper installation.
4. May plug and wash out due
to icing. (See procedures
8A and 88, Icing control).
DESIGN CRITERIA AND OUTLINE SPECIFICATIONS:
Different sets of procedures are needed for fish streams and non-fish streams.
They are separated accordingly below. "Fish streams" include streams which
support resident migratory, or anadromous fishes during some part of the year.*
All Streams
1. The natural stream path should be normal (90°) to the road, insofar as
possible. Culverted flows should not involve stream realignment.
*Intermittent streams (those that flow only part of the year), common to interior
Alaska, often provide significant habitat for resident fishes. For example,
grayling sometimes spawn and hatch in streams that are dry by midsummer
(Hickman, G.L. Asst. Area Director, USFWS. Letter to E.I. Lipson. August, 1978}.
DESC.RlPTICN c.DNTINUED NUMBER 2.A.1
2. Depth of headwater at design flow should be no greater than 1~ times the
culvert diameter. Design should not allow culvert headwaters to exist on
fish where high flow could coincide with fish migrations.
3. In permafrost areas where ice rich soils could occur, culverts should be
designed with particular care to avoid ponding.
4. Install cross drains to intercept flows in ditches on upstream side so
that outlet is downstream of main bridge or culvert.
Non-Fish Stream (Includes roadside drainage)
1. Culvert should match the gradient of the natural channel.
2. If grade is steep or culvert outlet is above streambed, energy dissipation
may be required (see procedure 2.C.).
Fish Stream
A goal of maintaining culvert flow velocity under 1.5 fps for "fish streams"*
at least half the time is recommended, and was used in preparing some of the
specific guidelines given below. Higher velocities reduce or eliminate the
use of upstream locations as rearing areas for juvenile salmonids and as
spawning and rearing areas for grayling.
1. Embankment slope in the vicinity of the upper end of culverts should be
armored as necessary to prevent erosion.
2. Minimum culvert size for a fish stream should be 24 inches (larger depending
on flow rate). Arch-or open-bottomed culverts with comparable cross section
and natural-bottom conditions are also acceptable.
3. Culverts in fish streams should be buried to one-fifth of their diameter
below the natural stream grade, or the invert of the culvert should be buried
six inches below the stream bottom.
4. Culvert slopes should match stream gradient unless:
a) outfall armoring is designed, constructed and maintained to prevent
outlet erosion and resultant perching of outfall;
b) armor allows minimum water depth and velocity for fish passage.
In general, if the stream gradient is too steep to match with culvert
slope, then a bridge is preferred.
The recommended culvert slopes to approximate the 1.5 fps goal for fish
streams are as follows:
Diameter (in)
24
36
48
60
Slope (%)
1.0
0.6
0.4
0.2
(From: U.S.F.S. Alaska Region Fish/Culvert Roadway Drainage Guide. 1977),
(Hickman, G.L. Asst. Area Director, USFWS. Letter to E.I. Lipson. Aug, 1978)
..
OE.SC~\ PilON CONTI NUf:D NUMBER 2.A.1
Experimental structures such as baffled culverts may pass fish (including
fry) at much steeper gradients. However, baffles are debris collectors.
They should seldom be used as they require maintenance attention to prevent
blockage·not available in most areas.
5. All drainage structures should be of sufficient size to prevent scouring. All
drainage structures and related facilities should be armoured with sufficient
rip rap to preclude erosion.
6. The embankments above the culvert ends should not wash sediment into the
stream.
7. Culverts should be properly bedded to prevent undermining and eroding seepage
flows.
8. The jumping ability of juvenile salmonids is assumed to be zero, so there
must be no dropoff at the culvert outlet.
9. Reach of the stream should be chosen that has a low gradient.
10. Consider bridging as an alternative if proper culvert design results in too
high a cost.
MAINTENANCE
1. Culverts require periodic inspection and may require cleaning, especially
after storms.
2. Culverts may require thawing.
REFEf<..ENC.'E.
1) State of Alaska, Department of Highways. Hydraulics Manual. 2) U .• S.
Department of Agriculture, Forest Service. Roadway Drainage Guide for Installing
Culverts to Accommodate Fish. Alaska Region Report No. 42. Juneau. September,
1979. 3) American Iron and Steel Institute. Handbook of Steel Drainage and
Highway Construction Material.
NUMBER 2.A.2
I6RDUP Drainage --Structures
Low Water Crossings
Put<. PoSE
To provide passage of stream flow on roads having low traffic volumes.
5\TE CHARACTER\ST,CS
Can be used on forest roads or pipeline work pads where traffic volume is low and
continuous access is not required.
~ DVANTA6ES
1. Inexpensive to install.
'DISt:..OVANTA6ES
1. Not usable during high stream flows.
2. May be washed out.
3. Not suitable for heavy construction
traffic.
4. Not suitable for deeply incised
streams. Such streams may require
excessive disturbance during
construction.
DESC..I2-\ Pr10N
2. Less susceptable than culverts
to damage from debris or icing.
5. Not suitable for some fish streams.
For any fish stream, necessary
maintenance would be greater.
Access should be restricted or
denied during periods of migration
or spawning, which would usually
coincide with construction.
6. May be subject to icing.
The intent of the low water crossing is to match the natural geometry as closely
as possible; therefore, it is only applicable in situations where stream banks
are low and approach grades are flat. Configuration of the crossing varies with
stream geometry and streambed material.
Side slopes of crossing should match natural geometry as closely as possible and
still provide trafficability.
Size of rock armor required is determined by maximum anticipated flow velocity.
(See Appendix 2.B.3)
PLAt-J
I
. .
OE.SC.RI Pf\ON CONT\NUE.D NUMBER 2.A.2
Application of low water crossings has frequently resulted in more maintenance
costs than initial installation costs for temporary bridges. Fish blockage,
sedimentations, traffic lane failure and icing were continuous problems along
taps. (Logan, R. Chief, ADF&G Habitat P~otection. Memo to B. Walker. Apr. 18,
1980).
EXAMPLE
A low water crossing for a small ,
drainage along the Trans-Alaska
Pipeline workpad.
Source: R&M Consultants.
MlliNTENANC.E
...... "'
.... · ..
-·
' . ~·
Will require periodic, perhaps frequent, regrading. More frequent regrading will
be necessary for fish streams.
REFE.RENC.E
1) Environmental Protection Agency. Logging Roads and Protection of Water
Quality. EPA 910/9-75-007. Seattle, March, 1975. 2) Highway Research Board.
Erosion Control on Highway Construction. 1973. 3) Alaska Dept. of Highways.
Hydraulics Manual. 1972.
..
NUMBER 2.A.3
6RDUP Drainage -Non-Paved Road Surfaces
IPR~TIL.E Grading, Cross Drains
Pui<.PDS£
To prevent erosion of unpaved road surfaces.
SITE' CH-AR~TERlSTlC.S
Being in constant use, construction service and access roads are an important
source of pollution. All are susceptable. Steep slopes and highly erodible soils
are especially vulnerable. All unpaved road surfaces must be provided with
adequate drainage.
/..\DV8NTA6ES
1. Reduces on-site erosion.
2. Can avoid immobilizing machinery and
generally improve site efficiency 3.
4.
DlSA DVANTA6ES
and working conditions during
adverse weather.
Minimize regrading.
Economical to build.
1. Measures must be inexpensive both to interfere with eventual surfacing.
install and to remove if they would 2. Outlets must be stable.
DEsc.glPTION
1. Grading
Temporary and other unpaved roadways should be carefully graded for cross
drainage. Otherwise runoff will build up and gullying will occur. A cross fall
of~~~ per foot is recommended. Roadside drainage is also required.
Use dips and rolls in the grade, where practical, to break up surface flows on or
parallel to the road.
2. Cross Drains
For cross drainage dips or installations such as open culverts the following
spacings are recommended.
For other soils distance between cross drainage dips or installations such as
open culverts, should be less than 100 feet for slopes over 5 percent. In silt
soils intervals should be: 10 percent slope, 55 feet, 8 percent, 65 feet;
6 percent, 70 feet; 4 percent 80 feet; 2 percent, 95 feet. (Adopted from Ref. 2).
Install crossdrains (usually round culverts) to intercept flows in ditches on
the upstream side so that outlet is downstream of a main bridge or culvert.
Examples shown below are box or pole open culverts, dip gravel trench drain, and
for less highly traveled roads simple gravel berms.
E)(.AMPLE NUMBER 2.A.3
Fkl>wt P&_~g ~ c~~-n::.l\l~E.l\..l
~------------. -----·-----··-----r--------'---'-----=-----,.--..,
MA\ NTEf'JAN(.E
Berms and tracks which prevent desired cross drainage should be graded out.
Drainage structures should be inspected periodically. On haul roads used in
winter, snow berms should be removed before breakup to permit lateral drainage.
Rf.FEIZENGE.
1) Haussman, R. F. 1960. Permanent Logging Roads for Better Woodlot Management.
USDA Forest Service, Division of State and Private Forestry, Eastern Region, Upper
Darby, Pa. 2) Packer, P. E., Christianson, G. F. (pre 1964) Guides for
Controlling Sediment from Secondary Logging Roads. USDA Forest Service,
Intermountain Forest and Research Experiment Station, Ogden, Utah and Northern
Region Missoula, Montana 42 p. 3) EPA. Control of Erosion and Sediment
Deposition from Construction of Highways and Land Development. 1971 4) EPA.
Guidelines for Erosion and Sediment Control Planning and Implementation. 1972.
NUMBER 2.B.l
Drainage Control -Runoff
Grass Channels
PURPOSE
To economically provide drainage with grass lined channels.
SITE C\-tb.RAC.TE R\STlCS
Runoff from roadside ditches and other graded areas can be handled by grass
channels for velocities up to 8 fps. Maximum allowable velocity depends on soil
and species of cover. Usually restricted to channel gradients less than 10%.
~DV6NTA6ES
1. Grass 1 ined channels are less
expensive than those lined with
concrete or stabilized by a 'bio-
technical' measure (see section
2.B.3).
2. Grass will delay runoff and
DISADVANTA6ES
consequently reduce its erosive
capacity.
3. Grass channels are visually more
~cceptable than those lined with
concrete or rip rap.
4. A vegetated channel reduces surface
runoff through infiltration.
1. Very careful design and good to exceed design capacity.
maintenance are necessary to 3. Channels should not be constructed
prevent gully erosion. for maximum flow velocity. In
2. New areas of impermeable surfacing practice vegetation may not be well
upstream/upslope of grassed channels maintained. Actual vegetation would
may increase runoff volume and velocity then provide inadequate protection
against erosion at design velocity.
DE.SLR.l PT\ON
Channel flow velocities on well established soil of good quality generally should
not exceed 5-6 fps except for special situations. Respreading topsoil may be
essential.
Most waterways are constructed to accommodate the peak flow from a storm of at
least 10 years frequency before overbank flow occurs.
The flow retarding factor of different vegetation should be considered in the
design.
Construction
Avoid excessive compaction during construction, as it will result in an inferior
sward. Between the time of seeding and the time of actual establishment, the
waterway will be unprotected and subject to damage. Provision should be made to
divert flows during construction.
I
DESL"IPTlDN CONTINUED NUMBER 2.8.1
Channel sections may be V-shaped, trapezoidal or parabolic. Parabolic cross
sections have proven most satisfactory. Trapezoidal sections tend to revert to
a parabol-ic-shape. Due to flow velocity distribution, v-shaped channels should
not be used if the channel side slopes would exceed 6:1.
To maintain a good turf the channel should not be continuously wet. A tile drain
can help. Recommended placement is offset from the center of the channel by at
least ~ channel width.
Cover Species
Kentucky bluegrass
Smooth brome
Tall fescue
Grass mixture
Red fiscue
Sodding
Permissible Velocity
Erosion Easily
Resistant Eroded
Slope Soils Soils
(%) (fps) (fps)
0-5 7 5
5-10 6 4
over 10 5 3
0-10 5 4
0-5 3.5 2.5
The Rural Development
Council 1 s Revegetative
Guide gives other
species which can be
used for channe 1
vegetation.
Sodding can be expensive, but may be required for immediate stabilizing.
Overlapping involves the placement of sod strips parallel to the water flow and
is used in relatively flat ditches that carry large volumes. Shingling can be
used on short grades that are steeper than 10%. Grass strips are laid
______
1
__ Re rge nd i c u 1 a r to fl o_w_._S_tak_i_og_o_v_e_r_lappe_d_po_r_t_i_mls_w_i_lJ_incr_ease_the ____________ _
effectiveness in both cases.
~ODD IN~
MAlNTEN6.NCE
Maintenance can increase capacity of grassed waterways. A yearly dressing of
fertilizer may be helpful if applied so that it will not be carried away by runoff.
Regular mowing encourages a tight sward.
REFERENCE NUMBER 2.8.1
1) Soil Conservation Service. Field Manual for Conservation Practices. 1969.
2) Minnesota Department of Highways, Conservation Division~ Erosion prevention
and Turf Establishment Manual. 1970. 3) Alaska Department of Highways.
Hydraulics Manual. 1972. 4) Alaska Rural Development Council. A Revegetative
Guide for Alaska. 1977.
·'
APPENDIX 2. B .1.
Calculation of Channel Size
The discharge capacity of a channel {Q in cfs) is determined from V, the
velocity in the channel {in fps) and a, the end area of the channel
(sq. ft.) by the formula ·
Q= Va. £QUA-noN 1
V varies according to the •coefficient of roughness•, n, of the channel
which is normally 0.04 for grass-lined channels, the hydraulic radius,
r, (end area, a, divided by wetted perimeter, p) and the slope or
gradient of channel, s. This relationship is expressed by the formula
e-quA noN .2.
Substituting V in Equation 1
The selection of channel size using the above equations is a
trial-and-error process of selecting for a channel, checking whether its
velocity is within the safety limits for the type of grass lining
(Table 7) and whether the cross section is sufficient for the discharge
of runoff from the area drained.
Exa_!!IP 1 e A 1
Select a channel alignment and cross section to drain an area with a
peak discharge, Q, of 160 cfs. An ideal alignment for the channel has a
slope, s, of 0.03 and it is decided that the side slopes should be a
maximum of 4:1 to allow high speed maintenance by mowing. Soil
conditions are very good and it is anticipated that the quality of turf
will allow a maximum velocity, V, of 6 fps.
Step i)
Step ii)
~ tl.:t' .X:
y
~t.' 7( 8''----;>~G,~
Select ideal channel section (for ease of calculation,
this is trapezoidal).
Calculate area of section.
a. = .:<; fi :z
Step iii) Calculate nrgraulic radius.
r =a.+ p f = y +.2x = ~ + ..2. 1} (p.;?.+ t.5;J. == :2o. r~
:. r=~t..;...:J.o.t"-1-== /.03
Step iv) Calculate discharge capacity of channel.
0 :::: {.If~~ X /. o:L. X ./7 3d-X :1/ = /3 J '$ c/s
0. 0'1'
This is not sufficient to carry the peak discharge of 160 cfs.
Step v) Select a larger cross section.
Note that both a deeper or a wider channel will increase capacity but
a deeper channel will result in a higher velocity of flow.
~------,-.,2'1'--
~ t~'t
f-"~ (;;}_-
a == t:27 ft. ::z..
r = 2..1 ~ :; .. 4. 3fc, = r. !I
Q == ~~~ X /. 07.2 X 0. f13;)_ X :L 7 = f'i 0 cf5
This is sufficient with a safety margin to take 160 cfs discharge.
Step vi) Check that the velocity of flow wi 11 not be too
great for the grass lining.
V= ~ f((uA-noAl 1
V == ~~; -= (p. 'i f:ps
But this is too great (the maximum velocity decided on was 6 fps). One
velocity decided on was 6 fps) One could argue that peak discharge is
160 cfs.
Maximum design velocity = 160 = 5.9 fps --n
and is O.K
However, if not considered safe, then:
Step vii) If velocity is too great, make the channel wider
but shallower.
~----------------~'---------~~'==============~k='=/====
~~~~,~(~----------~~~'--------
.21.-. Q y = ._3;1.. :;J..'f = 0. 0 7
/.1~fo {) = -o:o;( '1. 0. 'Iff x O.t73d-X. ;;1.8 = /(pJ/J. f cfs
Channel is sufficient to take discharge of 160 cfs.
Step viii) Check that ~locity of flow in channel (step vii)
is not too great.
,;_ Q v -a..
V = !Jf -= 5. 7 f-:p..s W# IC-H 15 D. k.
The same technique may be applied to a parabolic or •v• shaped section;
this just makes the calculation slightly more complex.
Note: One could have done this example a different way. For instances,
if space were very tight one could start by finding the minimum cross
section for a velocity of 6 fps to take a discharge of 160 cfs, thus:
Say, then, that only 24' is available; we know fran Steps v and vi above
that a 24' channel width will give too great a velocity. Therefore, the
gradient nust be decreased. N:>te that if the gradient is the same but
the side slopes are increased, it effectively increases (a) but also Q,
and therefore is not advisable.
Note: About 10% should be added to width and 0.5' to depth for
freeboard in pennanent channels.
Design a channel with a macimum velocity, V, of 3 fps and a slope, s, of
0. 05 with a peak discharge Q of 30 cfs. On Table 3 enter the chart on
line reading 30 cfs, follow to right in column reading 5% ( 0. 05) slope.
For a velocity of 3 fps, top width is 45' and depth of 0. 4' (add 4' to
width and 0. 5' to depth for freeboard in permanent channels) .
N:>te: The dimensions given in this example are for a parabolic section
for a Manning's coefficient of 0.04. If the maximum allowable velocity
had been 4 fps, the width could be reduced to 23' and depth increased to
0.5'; and if 5 fps, a 13' width and 0. 7' depth would have been
pennissible.
Using Method A for the above example,
Reference
~---.;!.J'---~
t.5/ '{:1 ~==
~.;~.'--....,-. 19 1 ~~.2~
r:::: a+ p = to.5 -7-a~. I = o.t./5
I. '-{1Jtp ,.,.-c:1.. Oi.f7:2 Q == o.o'f -x: o.S-57 x o. X..3(p x: ro . .::J = o. Dtf
5i.;L. -( ,, ) V = --Lf..'7J7(p Too 111GH /0..5 -
Q-= 3o c_{.s I v~ fo~s-= :;_q f:ps (O.K.)
URS Company. Stormwater Management, Procedures and Methods. Snohomish
County, King County, City of Everett. EPA Grant Id. No. P-000091.
September 1977.
NUMBER 2.8.2
Drainage Control -Runoff
P~ACTIC.E. Ditch Checks, Checkdanis --remporary Measures
PU.RP05£
To slow velocities within a ditch to reduce erosion or trap eroded sediments.
SITE CH-bi<ACTE~ISTICS
Used in any small ditch or channel (not used as fish habitat) where soils may be
eroded by expected flows. Required more often for poorly drained soils where more
runoff occurs.
On steeply sloping channels, checks may be used as gradient breaks to reduce slope.
They are helpful while establishing vegetative channel liners. (See 2.8.1.)
h.DVANT~6£S
1. Reduces flow velocities.
2. Traps eroded sediments and prevents
DtSADV ~NTb6E5
1. May require clean out to maintain
effectiveness. If they silt up,
percolation through permeable
structures will be reduced and flow
may go over banks.
DE<Sl..Kl PTION
gullying of the channel.
3. Economical. Can be built with scrap
or native materials.
2. These are usually temporary
measures. Long term protection
will require more substantial
measures and design.
3. May need to be removed.
DESIGN CRITERIA AND OUTLINE SPECIFICATIONS:
These procedures are suited for use during construction as ditching proceeds or
to protect natural channels. They can help control gully erosion until permanent
liners such as vegetation or stone can be established. (See 2.8.1, 2.8.3)
Straw Bale Checks
1. Channels over g• wide. Bales are staked down with two 2~· wooden or metal
stakes, and tied, preferably with nylon or wire. Place rip rap downstream for
a minimum of 4', and at the edges to bring its height level with the crest of
channel.
DESLI<..lPTtON C..ONTtNUED NUMBER 2.B.2
2. On channels less than 9'. The small YtEW'~
checks shown may be used without ~~ "-f1P-1N~M
rip rap. They should be spaced ·pf.Ev,
about 50' apart. ~.~~;~~
', ~: ttOLE.
Both these checks must be removed : '~4'
before final channel stabilization. 1 · ~~
: r:¥
I
I
I EP
I
I R..A~ ~T~W ~U: Cfiect.s
Po( 5'"VoU-~~~
Wire Fence Check with Straw Bales
A 3' cyclone fence is nailed on the upstream side of 4" x 4" wooden stakes across
the channel. Straw bales are placed on the upstream side as shown. These are
wired together and to the fence.
Rip rap is placed as in the Straw Bale Checks section. In some cases the straw
bales may be covered in crushed stone.
This installation must be removed prior to final channel stabilization.
This is prefered over the first method shown above when protection is required
for longer than 6 months, as straw bales may be quickly and easily replaced
without disturbing rip rap.
~4'~
Wire Fence Check with Brushwood Bundles
1.1.51=-1<tP R~P t>N
.PowA>.S-n:(EJ! 11'1 5I DE.
When straw is not available but where there are large quantities of brushwood on
site, brushwood bundles approximately 28" in diameter can be made up with #9 wire
laid in stagged formation upstream of the fence and wired together and to the
fence. Rip rap is placed as in the Straw Bale Checks.
This installation must be removed prior to final channel stabilization.
Wooden Stakes
4" minimum diameter wooden poles or stakes are driven in across the swale. Rip
rap protection is used downstream. Permeability of structure may be reduced by
nailing polyethylene sheeting on upstream side.
DE"SCIClPTIQ(\J CDN'TlNUED NUMBER 2.B.2
Brush Between 2 Rows of Stakes
4" minimum diameter stakes are driven at 2'6." centers in 2 rows 2'6" apart.
Brush is packed between, and wired down securely by criss-crossing #9 wire
between stakes.
6R,U5H-6ETu.>EENZ. f(.OW5 ~r~e7
.f4"01Jr5TAr/OoN2.' CB\l~
~~'-~u
, lJ tl ~ '
USE £ ti'-t:A-f Aflti:;,N
Dumped Rock
Ai'on1 r.tRS, 1q77
A semi-permeable check may be constructed of dumped rock. (9" diameter is .
sufficient for velocities of up to 8 fps which is the maximum for grass channels.)
The installation may become permanent.
Sandbags
100 pound sandbags may also be used as a temporary check in a swales. An apron
should extend at least 4' downstream. This type is useful in areas where rock is
unavailable.
The ditch checks may require periodic clean-out or replacement, particularly to
remain effective in filtering out sediments from flows.
1) North Carolina State Highway Commission. Temporary Erosion and Pollution
Measures. 1972. 2) Environmental Protection Agency. Guidelines for Erosion and
Sediment Control Planning and Implementation. 1972. 3) Pennsylvania Department
of Environmental Resources. Soil Erosion and Sedimentation Control Manual.
September, 1972. 4) URS Company. Stormwater Management, Procedures and Methods.
Snohomid County, King County, City of Everett. EPA Grant ID. No. P-000091.
September 1977.
NUMBER 2.8.3
jGROLLP Dra1nage Control -Runoff
I PRAC.TI(..£ Mechanical Channel Liners
PURPOSE
To carry surface runoff in stable waterways where flow velocities exceed those
acceptable for vegetated channels (2.8.1).
51TE C.H-AR~LTERlSTICS
To carry runoff in stable waterways where flow velocities are excessive for
channels with vegetation alone, or to protect channels before vegetation
becomes established.
ADVANT66£S
1. Stone liners are effective for
higher flow velocities.
2. Some mechanical measures can aid in
establishment of vegetation on sites
DISADVANTb6ES
1.
2.
3.
Initial cost may be higher.
Checkdams and drop structures are
prone to damage during high 4.
velocity flows. Netting should be
used only with low velocities.
Energy dissipaters in drop spillways
DESLRI PTIDN
that would otherwise be unsuitable.
The use of vegetation in combination
will slow flow velocity and
increase infiltration.
collect silt and debris and require
cleaning.
Plastic nettings should not be used
where they could wash into fish
streams, as they can act as gill
nets.
Mechanical liner~ provide several levels of protection based on channel
configuration, runoff quantities and velocities and soil conditions. Consult
Alaska Division of Highways Hydraulics Manual and SCS Field Manual for detailed
design considerations.
Netting and Seeding
A variety of materials, such as jute and plastic nettings are available. They are
often used with vegetation but do offer some protection of their own.
In larger channels, where several widths of netting are required, they should
overlap 2". Overlaps should be stapled 4-10' apart. Ends of rolls should
also be overlapped. The top ends should be buried in trenches 4" deep, and
stapled 10" apart. (Hairpin-shaped wire staples recommended.)
After completion, water ways should be rolled to insure contact with soil.
Nettings are effective for medium velocities up to 6 fps. (See procedure
on nettings.)
DESL.R..I PT I ON L..ON T\ N U ED
NUMBER 2.8.3
Erosion Checks
Erosion cheeRs are usually constructed -of fiberglass Which are insta-lled across
drainage swales and function as a spreader, avoiding the formation of gullies and
aiding in the establishment of vegetation. Preferably they are installed at
changes in gradient and downstream from confluence of tributaries. Construction:
1) excavate trench of 1' depth; 2) install vertical membrane and secure with
staples, backfill, compact, and trim flush with surface; 3) center netting or
mat on top of vertical strip to form cap to extend ~· above design flow elevation
and staple on 6" centers~ ·
Stone Center Drains
Are used in drainage channels that experience prolonged flow and wetness,
preventing the growth of adequate turf. Gravel bedding and packed stone
provide for drainage in the center of the grassed swale. Acceptable flow
velocities and gradients are determined by standard rip rap specifications.
(See Appendix to this procedure.) .
Latticework Concrete Blocks
Can be used to stabilize the banks of waterways that experience high velocity
flows. Gaps in the concrete blocks are backfilled with soil, compacted, and
seeded with grass. Other materials used as channel liners include paving,
sacked sand, and concrete filled mattresses.
Drop Structures and Checkdams
Counteract gully erosion in waterways by reducing that gradient of the channel.
These should be used rather than impermeable concrete or asphalt linings, when
physical conditons are too severe for the satisfactory establishment of vegetative
cover. Selection of materials will depend on strength requirements, cost,
permanence and aesthetic aspects (temporary checkdams were considered in procedure
2.8.2.). Structures can be divided into rigid or slightly flexible and into
straight drop spillways and chute-type spillways. Material can consist of timber,
rock, gabions, concrete, and brush or sod. To prevent undercutting at the toe,
all structures should extend several feet or more below the existing ground
surface. The selected design capacity should be for a storm of greater frequency
than the one used for the drainage channel because of the damage that could be
done to the structure if it were to overtop. (A method for calculating channel
sizes and capacities is given in Appendix 2.8.1).
~--
611ll!5ft . :#14-Wif<.(
{/JERSPecn~ f ~noN)
ltl' MIN
~~~3=:::;::::---__.,( 3' MIW ,, (HJ ,.;~~
:j;MPEP'.'
~~~~'~:-~~~~~{;.:.:.~
o1216ttiPcL 7
..:JtRefiM .J!iCI>
E.X6MPL£
Outlet channel of this drainage
structure in highly erodible fill
has been treated with straw mulch,
jute netting and seeded.
Location: Trans-Alaska Pipeline
Source: R&M Consultants, Inc.
MAt NTE.NANL.E.
NUMBER 2.8.3
Methods require some maintenance due to scour, although with proper design and
construction, many structures have long life effectiveness.
REFE.f?.ENCE
1) USDA, Soil Conservation Service. Engineering Field Manual for Conservation
Practices. 1969. 2) Soil Conservation District, Montgomery County, Pennsylvania.
Erosion and Sediment Control Handbook. 3) USDA. Controlling Erosion on
Construction Sites. Soil Conservation Service Agriculture Information Bulletin
#347. 1970. 4) Environmental Protection Agency. Guidelines for Erosion and
Sediment Control and Planning and Implementation. 1972. 5) Brandt, G. H. and
others. An Economic Analysis of Erosion and Sediment Control Methods for
Watersheds Undergoing Urbanization. USDI. OWRR. 1972. 6) Alaska Department
of Highways. Hydraulics Manual. 1972. 7) Tourbier, J. Water Resources
Protection Measures in Land Development. University of Delaware. April 1974.
8) URS Company. Stormwater Management, Procedures and Methods. Snohomish County,
King County, City of Everett. EPA Grant Id. No. P-000091. September 1977.
APPENDIX 2.8.3
Calculation of Required Stone Size to Prevent Channel Erosion
and Estimation of Scour for Waterways
Calculation of Stone Size for Waterway with Stone Center Drain
Use the nomography below (Figure 1) to determine the size of stone for waterways
with s-tone -center-dra-ins (used where there is -a problem-with prolonged flow and
wetness).
Example: Design grass waterway in the normal way, determining the top width and
the depth of flow (See Appendix 2.8.1). For a design depth of 1.0' and a
longitudinal slope (gradient) of 5.5% (0.05), 25% of the rock should be in sizes
slightly larger than 7 .9" and the remainder should be well-graded material of
less than 7.9", including sufficient sands and gravels to fill the voids between
larger r9cks. ___ ----=:::.._,r==T=~~--.----.~-,--_.:.._,_~=r-:~
1'1*711£ '!71
' 7S f>I..Df'€."5• 3 r
OC.IbiV DE.PTU.'J:J 11 1S'l'. tF f"t<r R«L 01= DW<AJ
11/FC.Ef IN IIV4B IN 'Yo
~.D r:o.tt 2JJ.Q t z.
: 2.5 J~.D J7~
to.o
------.s.D O,i = 7-'llti. 4D
~
t.>
1
1.0
O.f
o.-f
os
1
Estimation of Depth of Scour at Channel Construction
Note: This technique gives only a very rough indication of depth of scour and
should be used only with extreme caution. In practice, scour depth depends on
soil erodibility and other variables.
a) Depth of Scour at Long Channel Constrictions.
1
Step i) Determine reduction in channel width at point of construction.
Determine ratio of w1;w 2•
Step i i) On Figure 2 read equivalent value of D1;D 2 for width of channel
ratio.
New York Dept. of Trans., Div. of Design and Constrcution. "Bank and Channel
Lining Procedures." 1971.
Step iii) Knowing design depth of flow D1 , estimatedepth of scour D2.
b) Depth of Scour at Short Channel Constrictions
\
Step i) Determine the extent of the construction w0•
___ Step __ _; t) _Dete.rmtne de_stgn _ dep_th of flow __ up_stregll1 __ o'f __ c.onstric_t i_on __ [)_1.
Determine ratio w0;D 1• ·
Step iii) On Figure 3 read equivalent value of D0;D 1 •
Step iv) Knowing D1 , estimate depth of scour D0•
~e..fere,-n c. e.. :
URS Company. Stormwater Management, Procedures and Methods.
King County, City of Everett. EPA Grant Id. No. P-000091.
Snohomish County,
September 1977.
NUMBER 2.C.l
16ROUP Drainage -Structures
Outlet Protection [for roadside drainage]
PuRPoSE
To slow flow velocity at drainage structure outlets.
The velocity of flow is nearly always speeded during passage through a culvert, and
always when passing down a chute. A scour hole or pluge pool will develop, unless
protection is provided. Headward erosion of the fill may also result.
ADVANT66ES
1. Reduce or eliminate erosion of
stream and fill material.
DlSADVANTA6€S
Requires special design and suitable
2. Some structures can permit sediment
collection through stilling process.
unsightly. 1.
2.
rock or other armor. 4. In permafrost soils, structures which
impound water should not be used. Some types of structures may be
DE.SGQ.I PTI D N
Several examples are shown for outlet protection for roadside drainage. Choice
depends on 1) soil and topography of the site; 2) anticipated flows; 3) height of
fi 11 or outlet.
Structures which impound water should not be used in permafrost soils.
The increase in water velocity through a culvert will tend to form a plunge pool
where it flows into an unlined channel.
1. Plunge Pools
A plunge pool will dissipate a large amount of excess energy, but could
undermine the toe of the embankment if not adequately armored. Not to be
used in permafrost soils.
When plunge pool is acceptable may choose from three measures:
DE.5C.Rl Prto CONilNU~ NUMBER 2.C.1
a. Cantillver the end section of the culvert and support with wood (temporary),
or concrete (permanent). Not aesthetically desirable.
o. A cut-off wall extending below anticipated depth of scour will prevent
undermining •
c. Use armor layer in pool. Depending on natural soil conditions one or
more filter layers may be required below armor.
2. Protective Aprons
Dumped rock, hand-placed rip rap or rock-filled gabion baskets or mats may be
used.
Width of apron should be at least one culvert width each side of culvert.
Height should be to or above design high water.
Dumped stone is most effective due to roughness. A plunge pool will often
form beyond a concrete apron lacking baffles.
3. Stilling Basins
For flows that are excessive for
available stone size. The function
is similar to a plunge pool. See
reference 4 for design details.
Outlets are shaped to conform to
the receiving channel.
HAl f\JTENAN(.E
1. ~utlets should be inspected periodically for damage, such as undercutting.
2. Pools and basins require periodic clean out of sediment and debris.
1) U.S. Dept of Transportation. Highways in the River Environment, Hydraulic and
Environmental Design Considerations. May 1975. 2) Tourbier, J. Water Resources
Protection Measures in Land Development. Water Resources Center, University of
Delaware. 1974. 3) Environmental Protection Agency. Logging Roads and
Protection of Water Quaity. EPA 910/9-75-007. March, 1975. 4) State of Alaska,
Department of Highways. Hydraulics Manual. 1972. 5) URS Company. Stormwater
Management, Procedures and Methods. Snohmish County, King County, City of
Everett. EPA Grant Id. No. P-000091. September 1977.
NUMBER 2.D.l
Drainage -Structures
Inlet Protection
PUI<.PDSE
To prevent accumulation of debris at culvert inlets.
Structures can be used at culvert installations where debris presents a problem, to
avoid plugging. Therefore avoid resulting flooding and potential erosion of
roadway section.
~DVANTb.C:t~S
1. Avoids need to clean out culvert
barrels.
DISADV6.NTA6ES
1. Requires regular maintenance.
DE.se,e I Pll 0 N
2. Provides full culvert capacity
during high flows.
2. High initial cost.
Debris -Control structures can have many shapes and can be constructed of a
variety of materials. Some typical examples are:
1. Debris Deflectors
Structures placed at the culvert inlet to deflect the major portion of the
debris away from the culvert entrance. Normally "V"-shaped with apex
upstream.
2. Debris Racks
Structures placed across the stream channel to collect debris before it
reaches the culvert entrance. Usually vertical and at right angles to
the stream flow.
3. Debris Risers
Closed-type structure placed directly over the culvert inlet in log-cabin
fashion to prevent inflow of coarse bed load and light floating debris.
4. Debris Fins
Walls built in the stream channel upstream of the culvert, and aligned with
the direction of flow. Their purpose is to align debris, such as logs, with
the culvert axis so that debris will pass through the culvert barrel.
Sometimes used on bridge piers to deflect drift.
NUMBER 2.D.1
DE.SC.RlPTIDI\J. LDNTl NUEO
6. Debris Dams and Basins
Structures olaced across well-defined channels to form basins which impede
the stream flow and provide storage space for deposition of detritus and debris
(see also Procedure 3.A).
EX.AKPLES
-
RAt'-])EJ3Rt5
1?/JC+(
~---
'' ...
MA\NTENANC..E
CoAJcRETE J:CBi?tS RAJS
Requires regular clean-out to maintain effectiveness. Ease of access should be
considered during design.
1) U.S. Department of Transporation, Federal Highway Administration, "Hydraulic
Engineering Circular No.9, Highways, Debris-Control Structures." 2) Alaska
Department of Highways, Hydraulics Manual, 1972.
NUMBER 3.A.1
joe.OLLP Sediment Retention
Sediment Basins --Permanent and Temporary
PUQ.POS£
To retain runoff waters and remove sediments generated from construction areas,
preventing deposition into drainage ways and property below the site.
While erosion control reduces sediment in runoff from construction sites,
developers should also use impoundments to precipitate sediments before runoff
leaves the site. Particularly important on steep and highly erodible sites,
and on poorly drained sites where the erosive potential of rainfall and melting
snow will be greater.
ADVANTA6E5
1. Downstream riparian properties will
not be damaged by sediment deposits
originating from that development.
2. Prevents sediment deposits
downstream which would reduce
DlS~DV ~NTA6ES
1. May require additional R-0-W or
flow easements.
2. Periodic clean-out and disposal is
required.
DE.Sc..." \ PT\ON
the capacity of the stream channel.
3. Can be incorporated into the
permanent erosion control plan.
4. Can be designed for large flows.
3. Can be aesthetically unsatisfactory
or a safety hazard if'not designed
or maintained properly.
Large permanent-type basins will require full design consideration and would
normally be included in construction plans. Small basins and traps for temporary
retention should be included in construttion plans also, but can be field located
as needed by the project engineer when temporary sediment retention is required.
The SCS Field Manual (Ref. 3) provides detailed design information for permanent
sediment basins. Generally, the basin consists of a dam, a pit or a combination
of the two.
·7
·I
DESC.e\PTtoN CONnNUEO NU~1BER 3.A.1
Pond Size 'PLAN -The effectiveness of a sediment pond
depends upon the settling velocity of
sediment particles. Settling velocity
can be calculated from the volume,
5PILLWAY
~
size, and density of the particle and
the density of the fluid. This velocity
is then compared with the geometry and-
retention time of the planned pond.
The effectiveness of a pond will increase
as its surface area increases.
Assuming that construction costs increase
as the volume of the pond is increased,
a relatively shallow pond with a large
surface area appears to be the most
economical design (1). Appendix 3.A.1
shows that the economics of sediment ponds
depends primarily on particle size. For
particle sizes of less than 10 microns,
the size of the sediment basins required
suddenly becomes very large.
Storage Capacity
I
I
I
\ ,.---\. _, --------
SECTION
Basins are commonly maintained at a minimum depth of s•-a•. This allows
sufficient space above the flood storage zone for settling to occur in a
low velocity boundary zone between the surface (where flow is close to the
average overflow rate) and the static bottom layer.
Spillway
Sloped culverts are less expensive than perforated risers. An emergency spillway
should be incorporated.
Embankment
Fill is built in compacted lifts. Normally top width equals height. Embankment
should be stabilized against erosion.
Temporary Basins
These range from very simple ditch checks, as in 2.B.2., to structures similar to
the permanent basins. Shown below are two simple but effective techniques which
could be used at outlets of drainage structures, ditches or other areas.
~11 LLI ~G BA~I t-...1
BARRIER
--
MAl NTE.NANCE. NUMBER 3.A.1
Periodic inspection and cleanout will be necessary. Sediment basins must not be
left where they could eventually wash out and become a long term sediment source.
REFER.ENC.E
1) Thronson, R.E. Comparative Costs of Erosion and Sediment Control,
Construction Activities. Washington, D.C. EPA -430/9-73-016. July, 1973.
2) Tourbier, J. Water Resources Protection Measures in Land Development.
llniv. of Delaware. 1974. 3) Soil Conservation Service. Engineering Field
Manual for Conservation Practices. 1975. 4) U.S. Dept. of Transportation.
Suggestions for Temporary Erosion and Siltration Control Measures. Feb, 1973.
5) Mallony, C. W. the Beneficial Use of Stormwater. Office of Hesearch and
Monitoring. 1973.
APPENDIX 3.A.l
Settling Pond Sizing
To determine the theoretical size of pond to be used:
1) Obtain representative particle size distribution for the suspended solids
in the inflow water.
2) Determine the size of particle that must be removed to meet the state
water quality standards.
3) The settling velocity associated with the selected particle size can be
obtained by using Stokes Law:
L(; ::: ~ ( s-1) Do2
Where:
~ :::: 5e#t,·YIJ veloc.+y) erxfo-ec..
0 = () CC-elif'a.:ftlm_ of gra.vdy I tf~ 0 cmjsec..:l.
~ = kf·-ne-ma+t"c.. Vtswsl-ty of f'lwi:l, I!"))'J~ ft~e.
S = Spec.·'h·c. 8rcu/t'f"y of' ~r.f,cfe.
7J "" Jxa. "me:fe r> c...:nt.
4) Next, the anticipated flow rate to the pond should be determined and then
the area can be calculated by:
Where:
A== ~
II ~ rt?ju.irw ix:!st"n st":ce.-/n rn~ (o,. ftot)
f) = Flow ra.+e..llv"o(f'-+A.e poYJd 1 -m3jse.e. (or-Pt 3/sec)
Vs :::: Crt'-f-tC.oJ se:lflt"r'lq_ t/eJoc..t"fy, 1'Yljsec. (or .ft-(sec)
( 1 ""'(.5ee. o-= .3 . .:t r .f!.f ;.su )
5) Apply correction factor to account for non-ideal settling:
It should be noted that the settling velocity, Vs, is inversely proportional
to the kinematic viscosity, u. That is, as the viscosity increases, the
velocity decreases. For a given pressure, the viscosity of liquids decreases
with an increase in temperature. The decrease per degree is much greater at
low than at high temperatures. This is illustrated in the following list of
kinematic viscosities of water at various temperatures:
Temperature (F 0
)
32
39.2
50
60
70
80
100
Viscosity (cm 2/sec)
0.017939
0. 015672
0.013099
0. 011306
0.009838
0.008640
0.006865
ln practica I app I ication the settling velocity is reduced due to turbulence
resulting from wave action, or due to interaction between suspsended
particles. This lower settling velocity, or rate, significantly affects the
particle size that will settle in a pond of a given area.
(Huber 3, in testimony prepared for the adjudicatory hearing on NPDES permits
for placer miners, computed the hindered settling velocities at a variety of
concentrations of suspended solids. At the high suspended solids
concentrations found in mining operations hindered velocity was predicted to
be 0.73 to 0.85 of the free velocity.)
The following table was given in reference (4). Water temperature and
particle specific gravities assumed in the computations were not given. The
table shows that for particle sizes less than 10 microns required basin size
suddenly becomes very large.
Diameter Settling Rate
Material (micron) em/sec
1. Coarse Sand 1000 10.0
2. Coarse Sand 200 2.1
3. Fine Sand 100 0.8
4. Fine Sand 60 0.38
5. Fine Sand 40 0.21
6. Silt 10 0.015
7. Coarse Clay 1 o. 00015
8. Fine Clay 0.1 0.0000015
1) Environmental Protection Agency. Erosion and Sediment Control, Surface
Mining in Eastern U.S. EPA-625/3-76-006, October 1976. 2) King, H.W.;
Brater E. J. Handbook of Hydraulics. New York: McGraw-Hill Book Co. 1954.
3) Huber, M. E. Testimony in the Matter of NPDES Placer Mining Adjudicatory
Hearing Docket No. X WP7630C. August 1977. Appended to testimony of A. L.
Renshaw, Jr. Available from EPA, Seattle. 4) URS Co. Stormwater Management
Procedures and Methods. Snohomish County, King County, City of Everett. EPA
Grant Id. #P-000091. September 1977.
NUMBER 3.8.1
Sediment Retention
PI<~LTlc.E Buffer Strips, Barriers and Fences
PUI2VOS£
To retard runoff, increase infiltration and contain sediments eroded from
construction areas.
Almost any stand of vegetation or other materials will retain some amount of
sediments. These techniques are used at inlets and outlets of drainage structures,
in ditches and any other area where sediments are being eroded. See also 5.A.
l\DV6.NTA6ES
1. Can be incorporated into the
permanent erosion control plan
DI5ADVANT~6ES
1. Some maintenance required to remove
sediments accumulated.
DE~IZ.IPnoN
2. Most techniques are very
economical. No cost with
undisturbed strips.
Areas commonly subject to erosion include cut slopes, embankments, drainage
outlets, and ditches. If buffer strips of undisturbed vegetation are left, these
can filter out much of the runoff sediments which are generated. Stands of
timber, brush or grass between streams and roadways should be kept intact.
Barriers at the toes of slopes are also recommended. Straw bales or brush can be
placed to trap or filter sediment from runoff waters.
DE5C..R\ PTto C..ONTI NUE..D
NUMBER 3.8.1
The following illustrate some simple techniques . .
..5£alfi~Alr F£AJ~
(I'EiiP~f.JbiC.tJdlil. 7tJ .~L.ow)
Vegetative Buffer Strip
It costs virtually nothing to leave a buffer zone between construction areas and
small drainages or other water bodies. Studies have shown these buffer strips
to be effective in filtering sediment and increasing infiltration. This idea not
only pertains to roadways adjacent to streams but to all construction areas.
MAlNTENANC.£
If long-term use is desired, accumulated seoiments should be removed, taking care
to avoid damage to vegetation.
REFE.RENLE.
1) Environmental Protection Agency. Guidelines for Erosion and Sediment Control
Planning and Implementation. Aug. 1972. 2) Environmental Protection Agency.
Logging Roads and Protection of Water Qualtiy. EPA 910/9-75-007. March 1975.
NUMBER 3.C.l
Sediment Retention -Temporary Measures
Pe.Ac.. T\C.E. Traps and Filters for Storm Drain Inlets
To prevent eroded sediments from entering natural or constructed drainageways,
storm sewers or drainage structures.
~\TE Cl-tbeALTER.\STlC.S
Normally applied as a temporary measure until exposed construction surfaces are
stabilized. Used to remove sediment from small flows.
For Urbanizing Areas Where permanent roads or roadbeds are used during
construction and inlets have already been installed, sediment laden water should
not enter an incomplete storm sewer system. Dry wells, seepage pits etc. should
also be protected.
~DV~NTA6ES
1. Usually economical to build and
maintain.
2. Prevents clogging of storm sewers
or drainage structures.
0\5~DVANTA6ES
1. Will not usually remove all
sediments.
2. Usually requires removal after
DESCIZ.tPTION
3. Can be built as needed.
4. Easily cleaned with available
equipment.
construction.
3. Subject to vandalism or damage
during clean-out.
A number of methods, vegetative and mechanical can be employed, largely depending
on available materials. Economy of these procedures allows liberal use at all
suitable locations. Choice should consider: 1) size of structure, 2) anticipated
flows and sediment quantities, 3) clean-out requirements, 4) cost, 5) availability
of materials.
1. Protection of Storm Sewer Inlets
Whenever permanent roads are used during construction and storm systems or other
drainage structure are installed, measures should be taken to prevent sediment
laden waters from entering inlets.
otsc.e\PTION c.oNT\NUED
Straw-bale Barrier
Used before paving, stake to ground and
wfre together. Bale can be used off
paved surfaces to slow overland flow.
Sod filter Strip
2. Protection of Drainage Inlets
To prevent sediment-laden waters from
entering culverts, ditches and other drainage
transport structures. Other examples
applicable to drainage inlets are shown in
2.B.2. See procedure 2.0 for examples of
debris control.
M6t NTEN~f\jC.~
NUMBER 3.C.1
Sand and Gravel Filter
Used before or after paving.
Accumulated sediments must be removed periodically to maintain sediment trap
effectiveness.
~eFE I{ENC.E.
1) County of Fairfax, Va. Erosion and Sediment Control Handbook. Dec. 1974.
2} Environmental Protection Agency. Guidelines for Erosion and Sediment Control
Planning and Implementation. 1972. 3) U.S. Dept. of Transportation. Erosion
and Sediment Control in Highway Construction Projects. Feb, 1973. 4) URS Co.
Stormwater Management, Procedures and Methods. Snohomish County, King County,
City of Everett. EPA Grant ID. No. P-000091. September 1977.
. •
NUMBER 3.0.1
Sediment Retention
I PRAC:TlC.t Silt Curtain
PuR.PDSE
To prevent sedimentation of water bodies adjacent to construction activity.
Where construction abuts or encroaches on a lake. Not effective for stream where
turbulent flow will prevent settling. Also ineffective for deep lakes, or where
there is wind induced mixing.
~DVANTA6ES
1. Retains sediments which were not
held within the work area.
Dl5ADVANTA6£5
1. Temporary only.
2. Requires regular maintenance.
OE.SC.Rl PT&ON
2. Construction is relatively easy
and inexpensive--a cost effective
method of maintaining water
quality.
3. May require permit.
Occassionally, the route selection process cannot avoid the necessity of
construction activity encroaching on a body of water. One of the more common
examples is the widening of a roadway section immediately adjacent to a lake or
stream. The intent of the curtain is to prevent muddied water caused by the
construction activity from spreading over the entire body of water.
The curtain is generally fastened at both ends and fitted with anchors and
flotation devices in such a manner that it remains as much as possible in a
vertical position. The curtain can be constructed of heavy plastic, canvas, or
any other suitable material, but should be of sufficient strength and density
to withstand wave action and infiltration of fine-grained material.
Some space must be allowed below the curtain to allow escape of runoff entering
the enclosed area. The curtain is effective for silt size particles and larger.
Turbulence in the enclosed area will keep particles in suspension •
If the curtain is placed in a body of navigable water, warning devices shoul~ be
placed with the flotation devices, with sufficient visibility to prevent any ·
problem for boaters.
EXAMPLE
The two photos show the installation of a
filter fabric silt curtain used during
1973 construction work on the Parks Highway.
Location: Wasilla Lake
Wasilla, Alaska
Source: J. Henry
A&G Construction
Anchorage, Alaska
MAl NTE.N~NGE
NUMBER 3.0.1
Subject to damage by floating objects. Should have regular surveillance.
NUMBER 4.A.l
luROUP Slope Stabilization
PRACTILE General --Non-Permafrost Areas
To prevent erosion and sloughing of cut and fill slopes by one or more vegetative
or mechanical means .
.SlTE CH-~RACfERISTIC.S
Methods below require knowledge of soils, ground water hydrology and hydrology of
receiving waters.
If soils are saturated and have a tendency to liquify or slump it is desirable
to convey water quickly away with minimal infiltration. This could include,
paving slopes or ditches, and constructing diversion ditches for maximum
non-erodible velocities.
If soils are not saturated and slumping is not anticipated practices should be
chosen to maximize infiltration to reduce downstream flood flow and erosive power
and to delay peak flow (peak would then be smaller).
f1DYANTA6E5 I See Be low
'DISADV A.NTA6ES I See Below
OCSC:R.l Pfl D N
A number of techniques, both vegetative and mechanical, are available to provide
temporary cover or permanent stabilization of cut and fill slopes, or other sloping
areas. The following illustrated examples demonstrate a few choices.
Cut Slopes
Serrated Cuts -lower velocity of runoff
and collect sediment. Minor sloughing
possible if saturated. Generally for
fragmented rock or shale materials.
Pavement or Rip-Rap -immediate protection
for high risk slopes. Expensive and may
be difficult to install and maintain.
DESC.eiPTION CONTINUED
Diversion Ditch -good for cut slopes in
erodible soils. Diverts runoff through
stable channels and outlet~. Requires
sufficient slope to prevent ponding and
saturation. See 4.C. for further discussion.
Cut or Fill Slopes
Benches or Fill Berms -slows runoff and
helps seeding and maintenance programs.
Additional R-0-W may be needed for
increased slope lengths.
Slope Drains -prevents gullying erosion
of slope by carrying runoff through slope
drain. Energy dissipation needed at
outlet. Procedures 4.B. provide further
details.
Diversion Berms -diverts runoff away
from face of slope. Berm material must
be stable. Either temporary or permanent
protection. Procedures 4.C. provide greater
detail for this technique.
Sodding -immediate cover for critical
slopes. Is usually expensive but will
give permanent protection.
Seeding and Mulch -either temporary cover
or permanent stabilization. Must be
watered and fertilized until grass is
established. Mulch needed on steeper
slopes. Revegetation procedures 5.A.
and 5.8. give further recommendations.
Woody Vegetation -in combination with
grass ground cover where root mass is
necessary to stabilize slope.
Temporary Cover -other materials such as
netting, plastic sheeting and others
can be used to cover slopes left exposed
until final procedures are performed.
Plastic sheeting may be difficult to keep
in place.
NUMBER 4.A.l
E NUMBER 4.A.1
Large benched cut slope. Benches are 10 feet wide, placed at every 20 foot
increment in s 1 ope height. When ori gina l_ly _ex~_av<!_t_~d.__Q~I]l9 frQSJ with yj_s_i_b J.e
ice was encountered.
Location: Simpson Hill
Mile 113
Richardson Highway
Source: R&M Consultants, Inc.
Anchorage, Alaska
M~t NTENANL£
All slopes should be maintained periodically. Materials eroded from the slope
. should be removed to prevent eventual sedimentation of water courses or clogging
of culverts.
REFERENLE
1) Highway Research Board. Erosion Control on Highway Construction. 1973.
2 ) Tourbier, J. Water Resources Protection Measures in Land Development. Water
Resources Center, Univ. of Delaware. April 1974.
NUMBER 4.8.1
6g_DUP Slope Stabilization
PR~CTtLE Revegetation ~-~iotechnical Methods
PuRPosE
To prevent erosion and sloughing of cut and fill slopes through a combination of
vegetative and technical means.
?tTE C~At(AC.IE{(ISTICS
Revegetation can take the following forms:
Seeding to prevent sheet or rill erosion (Section 5);
Using woody plants (usually willow or alder) to provide additional root mass.
This is necessary for steeper, less stable slopes (Section 5);
Biotechnical methods are also used for steep, unstable slopes, especially where
regeneration may be difficult, and where there is g~eater risk of damage to water
related resources, or of economic loss such as in urbanizing areas. Biotechnical
methods combine vegetation with mechanical methods.
ADVANTA6ES
1. Vegetation reduces sheet erosion on
slopes and impedes sediment at the
toe of the slope.
2. Shrubs and trees shelter slopes
against the impact of rainstorms,
and the humus formed by decaying
leaves further helps to impede
runoff.
DISADVAl\.lTA6ES
3. Where soils are unstable and
liable to slip due to wet
conditions, use of soil moisture
by vegetation can reduce the
problem.
4. Mechanical measures help to
stabilize soil long enough to
allow vegetation to become
established.
1. There is a general reluctance to 2. Knowledge of soil, hydrology
work with live material where its
planting cannot be highly mechanized.
DE.SL(2.l PTI ON I (See also Section 5, Revegetation.)
and other physical data is
required to design measures
that will adequately solve the
problem and stand up to the test
of time.
1. Sod walls or retaining banks are
used to stabilize terraces. Sod is
piled by tilting it slightly toward
the slope and should be backfilled
with soil and compacted as they are
built up. Sod walls can be as steep
as 1:2 but should not be higher
than 5 1
•
2. Timber frame stabilization is
effective on gradients up to 1:1 and
involves the following steps in
construction: 1) Lay soil retarding
frames of 2 x 4" vertical members and
1 x 4" horizontal members on slopes.
Frames op slopes over 15 1 in length
need to be anchored to slope to
prevent buckling. 2) Attach 14 gauge
galvanized tie wires for anchoring
wire mesh. 3) Fill frames with moist
topsoil and compact the soil.
4) Spread straw 6" deep over slope.
5) Cover straw with 14 gauge 4" mesh
galvanized reinforced wire. ·
6) Secure wire mesh at least 6 1 back
of top slope. 7) Plant ground cover
plants through straw into topsoil.
3. Woven willow whips may be used to
form live barriers for immediate erosion
control. Construction: 1) 3 1 poles are
spaced at 5• distances and driven into
the slope to a depth of 2•. 2) 2 1 willow
sticks are inserted between poles at
1 1 distances. 3) Live willow branches of
5 1 length are sunk to a depth of 1"
and interwoven with poles and sticks.
4) Spaces between the woven •fences• are
filled with topsoil. Fences are generally ~~rAiii'fiN6--51ie11:S:riCi®~
arranged parallel to the slope or in a
grid pattern diagonal to the direction of
the slope.
NUMBER 4.B.1
4. Berm Planting 1) Excavate ditches at 3-5 1 distance along the slope and shape
berm on the downslope side. Construct ditches with 5% longitudinal slope.
2) Plant rooted cuttings on 3 1 centers and mulch. Suitable trees are willow,
alder, birch, pine and selected shrubs. In extremely dry situations, rooted
cuttings can be planted in bio-degradable plastic bags that are watered at the
t1me of planting.
5. Brush Layers 1) Prepare 3 1 "niches" as shown. 2) Lay unrooted s• live
branches of willow or poplar at close spacing. 3) Starting at foot of slope,
backfill lower ditch with excavated material from ditch above it. Operation
should be carried out during dormant season.
REFE~ENLE NUMBER 4.B.l
1) URS Company. Stormwater Management, Procedures and Methods. Snohomish County,
King County, City of Everett. EPA Grant Id. No. P-000091. September 1977.
2) Alaska Rural Development Council. A Revegetative Guide for Alaska. Alaska
Cooperative Extension Service. March 1977.
NUMBER 4.C.l
Slope Stabilization -Structures
I P~AC.TIGE Temporary Downdrains
PuRPDS£
A temporary structure to safely convey a concentration of runoff from one
elevation to another without erosion of the slope.
StTE C.HARACTERISTIGS
All sites are vulnerable to erosion during construction but particularly steep
slopes and highly erodible soils. Fill slopes are very susceptible. Temporary
downdrains can be used as a gradient break to reduce velocities; they can be
extended as construction of the slope progresses.
Also can serve as an inlet to channels or a transition from grassed to open
waterways.
ADVANTA6E5
1. Eliminates saturation of slopes
and R-0-W.
2. An efficient temporary drainage
system minimizes the delays caused
by severe storms during the
construction period.
DISP\DVANTA6E5
1. Removing temporary structures can
cause additional disturbance and
will entail some costs.
DE~R\P\lON
3. An efficient temporary drainage
system minimizes the amount of
regrading, etc. needed to repair
erosio,n during the construction
period.
4. Can be built and extended as
construction proceeds.
2. Diversion while reducing soil
saturation in some areas may
increase seepage in others,
causing local soil instability.
Temporary downdrains can be effective during construction to protect the slopes
until permanent stabilization, such as revegetation and mulching, is possible.
These structures usually require a diversion and collection system to direct
runoff to the inlet (See 4.C.)
Energy ,dissipaters are required at the outlet (See 2.C.).
Secttonal Downdrain
1/2 or 1/3 round culvert sections are normally used. These can easily be
extended as slope length is increased during construction. The sections
must be securely fastened and anchored to prevent leaking and erosion under
the pipe.
DE'Sl:.R..l PTlON CONTINUED
~PNP;J!D ME'f11r.o.. -
etD SEC.170N
p£f<SF'l:c:TIVE 'll'EW
oF ft.£1't&e ~
l>fA.IN ROWit.U~ fU.U..
Paved Chute
NUMBER 4.C.l
Asphalt is commonly used. These are best used on cut slopes rather than fills.
Asphalt apron should extend at least 3 1 beyond the toe of the slope. Inlet
should be constructed to prevent runoff piping under the structure --a very
common problem.
Flexible Downdrain
Consists of a flexible conduit of heavy fabric or other material. Must be well
anchored to prevent movement. Flexibility allows use on benched or terraced
slopes and is easily removed. Fabric conduit usually not recommended for use
through the winter as freezing could damage the fabric and result in leaking.
Calculate sizes from SCS Engineering Field Manual for Conservation Practices.
EXAMPLE
ecation: Glenn Highway, near Mirror Lake.
his half-round downdrain was set in the
ill slope. Runoff is collected by curbs
nd diverted to the structure. Note
rock energy dissipitator at the outlet.
ource: R&M Consultants, Inc.
Anchorage, Alaska
H~\NTENANLE NUMBER 4.C.l.
Each structure should be inspected periodically and damage quickly repaired.
Inlets should be checked for piping which could undermine the slope. Care should
also be taken to prevent damage by equipment, such as during snow removal
operations. If the structures are removed, the area must be restabilized to
prevent erosion.
1) Tourbier, J. Water Resources Protection Measures in Land Development. Water
Resources Center, University of Delaware. 1974. 2) Alaska Dept. of Highways.
Hydraulics Manual. 1972. 3) Soil Conservaton Service. Field Manual for
Conservation Practices. 1971. 4) URS Company. Stormwater Management,
Procedures and Methods. Snohomish County, King County, City of Everett. EPA
Grant I d. No. P-000091. September 1977.
NUMBER 4.C.2
6ROUP Grade Stabilization Structures
I f'RACTILE Per-manent Downdrains
PugPDS£
A permanent structure to carry runoff water from one elevation to another without
erosion of the slope or channel.
51TE CH-Af(ALTERlSTICS
Can be applied to cut or fill slopes or to provide a gradient break in a channel
to reduce velocities. Usually applied when flows are continuous or runoff
quantities dictate a permanent level of protection.
ADVANTA6£S
1. Prevents erosion or saturation of
slopes.
DISADYANTA6ES
1. Will require full design
consideration.
DESLl2.l PTl ON
,2. Provides permanent protection
of channels and slopes.
2. More expensive than temporary
structures.
These types of structures can have many applications besides simply transporting
runoff down cut and fill slopes. They are used as inlets or transition structures
for transporting water from a channel at a higher elevation to a lower one. They
can a~so be used to make non-erosive gradient breaks to reduce channel velocities.
For slope stabilization purposes, corrugated pipe, bituminous concrete or cement
are often used for these structures. A collection system (4.0.1.) is needed to
direct runoff flow~ Refer to the Alaska Hydraulics Manual or the SCS Field Manual
for actual design criteria and specifications.
Generally, the design is similar to
that for channels. Cross-section
can be trapezoidal, parabolic or
U-shaped. An energy dissipater is
usually needed at the outlets.
These structures should be included
in the permanent erosion control
design for the site.
-TYPt<!.lfL
Cwt:.Kc.-r.€ CHute
Of? FUAI'Yic
EX.AMPLE
One type of concrete flume with
continuous energy dissipaters in
the channel.
Source: EPA, Guidelines for Erosion
and Sediment Control Planning and
Implementation, 1972.
MAINTENANCE
NUMBER 4.C.2
If properly built, these structures are virtually maintenance-free. Inlets and
outlets should be checked periodically for undermining and erosion. Debris which
could clog the structure should be removed.
1) Alaska Dept. of Highways. Hydraulics Manual. 1972. 2) Soil Conservation
Service. Field Manual for Conservation Practices. 1971. 3) County of Fairfax,
Va. Erosion and Sediment Control Handbook. 1974. 4) Environmental Protection
Agency. Guidelines for Erosion and Sediment Control Planning and Implementation
1972.
NUMBER 4.D.1
j6f<OUP Slope Stabilization
·Diversions and Benches
PuRPDSE
To divert runoff waters and sediments away from critical areas and convey it to
stable outlets.
... .. -·--
SITE CHAKAC.TERtSTtC-S
Can be used on any site to keep runoff away from exposed construction areas or as
a part of a permanent stabilization plan. It can break up concentrations on long,
gentle slopes or keep runoff flows away from steeper, erodible areas. Recently
constructed fill slopes are especially susceptable to damage.
ADVANTA6ES
1. Increased infiltration of runoff.
2. Diversion of storm runoff may
minimize construction delays.
3. Protects erodible, steep sloping
sites.
DISADVANTA6ES
1. Increased infiltration of slopes
or other areas may temporarily
prevent access.
2. Channels may require additional
protection such as regular
maintenance of channel vegetation
or use of rock lining.
DESL~l PTLON
1. Types
Diversions are generally of three types.
Diversion Levees -are compacted earth
ridges normally placed along the top of
steep slopes or cut sections. Usually
a diversion ditch is associated. Runoff
can be conveyed to downdrains (4.C.) or
stable outlet.
4. Can provide permanent protection.
5. Can delay runoff by increasing
overland flow distance. This
will reduce downstream storm
peaks.
3. Channel may act as a sediment
basin and require cleanout,
especially while drainage area
is undergoing construction.
Diversion channel -consists of a channel with a supporting berm on the lower
side constructed across sloping areas. Runoff is conveyed laterally at slow
velocity to protected area or outlet channel.
DESC..l2..1 PTION C..ONIINUE[)
NUMBER 4.0.1
Benches -are flat areas constructed along the contours of the slope. If wide
enough, access for equipment can be provided. Benehes can be built with a natural
or reverse fall, often with a small swale at the lowest point.
5fdll£ci< om:.ff
Pett"SPECTJVE ~
..
DIVERSION C.HANNEL
2. Design
The design storm frequency should provide protection compatible with the hazard
if the diversion should overtop. There should be an emergency path where runoff
which overtops the facility will not cause too much damage. Where overflow may
cause very limited erosion damage a ten year frequency would be appropriate with
a freeboard of 0.3'. If overflow would be a hazard to water related resources
or structures, frequencies of as much as 50 years may be needed, with a freeboard
of 0.5'.
References 1 and 2 provide design details for runoff estimation and channel design.
Design velocities may be determined from the tables below.
Average Length Retardance
of Veg., Inches Good Stand Fair Stand
11-24 B c
6-10 c D
2-6 D D
Rermissible Velocitl -Ft.LSec.
Bare Channel Vegetation
Soi 1 Texture Channel Retardance Poor Fair Good
Sand, silt, B 3.0 4.0
Sandy loam and 1.5 c 1.5 2.5 3.5
Silty loam D 2.0 3.0
B 4.0 5.0
Silty clay loam 2.0 c 2.5 3.5 4.5
Sandy clay loam D 3.0 4.0
B 4.0 5.0
Clay 2. 5. c 3.0 4.5 5.5
D 4.0 5.0
Tables from References 3 and 4.
DE5C..RlPTION C.ONTt NUED
NUMBER 4.0.1
Location and spacing of diversions will depend on slope, soils and estimated
runoff. Channel gradients are normally 0.5-1.0% but can be higher in resistant
soils. For channel protection see 2.B.1-2.B.3. Outlets for diversions can be
vegetated channels, natural water courses, level spreaders, etc. If flows are
carrying sediment eroded from the site, sediment retention techniques , as shown
in section three are necessary.
EXAMPLE
A diversion ditch along the top of the cut
slope directs flow to sectional downdrain
(lower left).
Location: Glenn Highway
Eklutna, Alaska ---------------------------------------~
Source: R&M Consultants,
Anchorage, Alaska
MAINIENAI\1L£
Sediment may need to be removed from channels.
Vegetation in channels may require maintenance to remain effective in controlling
eros ion.
KEFERENLE
1) ~laska ~ept. of Highways. Hydraulics Manual. 1972. 2) Soil Conservation
Serv1ce. F1eld Manual for Conservaton Practices. 1971. 3) URS Com an
S!ormwater Management, Procedures and Methods. Snohomish County , Kin~ C~~nty Clt~ of Everet!. EPA G~ant Id. No. P-000091. September 1977. 4) Northeast' Reg1ona~ Tech~lcal Serv1ce Center, SCS. Guidelines for the Cont rol of Erosion
and Sed1ment 1n Urban Areas of the Northeast. 1970.
•
NUMBER 4.0.2
61ZOUP Slope Stabilization
Level Spreaders
PuRPOSE
To convert concentrated flow to sheet flow at non-erodible velocities over stable
areas. Time of concentration of runoff is increased and storm peaks are reduced.
5tTE CH-AI<.ALTEI< lSTIC.S
Infiltration is increased, so level spreaders should be used where they will
outlet to undisturbed stable soils. Spreaders should not be built on fills.
ADVANTA6ES
1. Reduced erosion can m1n1m1ze
regrading of completed areas.
0\SADVANTA6ES
1. May not be applicable on poorly
drained or ice-rich permafrost
soils.
0E5Lfl..t PTI ON
Runoff spreaders convert concentrated
flow to sheet flow where it can be
dispersed at non-erosive velocities
into undisturbed, vegetated areas.
Much of the flow will infiltrate in
undisturbed areas. The spreader
should outlet to undisturbed soils
which are well drained and are not
highly erodible. Care must be taken
to insure the outlet lip is level.
Inflow value (Q) in cfs must be
estimated to determine the length
of the spreader.
Design Q (CFS)
up to 10
10 to 20
20 to 30
30 to 40
40 to 50
Length (L)
15
20
26
36
44
2. Increased overland flow time
and increased infiltration can
reduce storm peaks.
2. Spreader lip must be stable and
level or flow will concentrate,
with high potential for gully
erosion.
2. TO I 0~ FLAit'l=R
6 FOCIT MINIMUM
?e.c.TION
See Section 4.0.1. for permissible channel velocities for grass lined channels.
MAINTENANL£
Periodic inspection and maintenance is vital.
storms. Trapped sediments should be removed.
erosion may result.
NUMBER 4.0.2
Spreaders should be inspected after
If the lip is not kept level gully
1) USDA, SCS College Park, MD. Detail of Level Spreader. L.S.I., Md. SCS
Design Standard. 2) __ Thr-onson,_ R.E. Comparattye Costs o_f_ErosiQn _and_S~gjment
Control, Construction Activities. Env. Prot. Agency. EPA-430/9-73-016.
Sept. 1973. 3) County of Fairfax, Va. Erosion and Sediment Control Handbook.
Dec. 1974.
NUMBER S.A.l
I6R.OUP Revegetation and Mulching
Pf<.AGTILE Grasses, Herbaceous and Woody Plants
To provide vegetation to control runoff and prevent erosion and sedimentation.
~ ITE CH AR:Ac... TE R.tSTICS
Applicable to all sites such as cleared or graded areas, slopes and others which
require either temporary or long-term protection against erosion.
ADVANTA6ES
1. Increases infiltration and can
help trap sediment movement.
2. May provide both surface cover and
root mass for slope stabilization.
DlSADVANTA6E'S
3. Economical form of protection.
4. Once established mostly maintenance
free; allows native species of
vegetation to return.
1. Some limitation imposed by soil, 2. Commerical sources limited.
topographic and climatic conditions.
DE?c.i2.l PrtoN
The Revegetative Guide for Alaska published by the Rural Development Council
provides an excellent guide to selecting grass species, fertilizers, application
methods and physiographic limitations. It is also recommended that, where
possible, the local Soil Conservation Service be contacted for information to
assist any revegetation effort.
GRASSES AND HERBACEOUS PLANTS
1. Site Preparation
Respreading loamy materials will assist revegetation, and in many cases is
essential for vegetative recovery. For upland borrow pits stockpiling and
respreading topsoil should be standard procedures.
Soils must be porous for root penetration, and friable enough for good seedbed
preparation. On construction sites a scarified surface is usually best to help
retain seed.
2. Timing
Seeding should normally be done between May 15th and August 15th, as close after
disturbance as feasible. Temporary covers such as'annual rye can be seeded later.
Disturbed soils should not be left unstabilized over winter.
DESGRlPTlON C..ONTl NUED NUMBER 5.A.l
3. Application Methods
A number of techniques are used, each with limitations.
DRILLING: The Revegetative Guide for Alaska recommends drilling as the best
method for nearly level to gently sloping land, where equipment access is not
limited.
HYDROSEEDING is preferred for steeper slopes where access is a problem. Seed,
and sometimes fertilizer and mulch are applied as a slurry. It is best to apply
seed and fertilizer first, to ensure seed contact with the soil, followed by
mulch. The guide recommends mixing ratios a~d application rates.
BROADCAST seeding, such as aerial appreciation offers rapid application for large
areas. The guide recommends application rate twice that required for drilling.
SPRIGGING (planting a root shoot or sprout) and SODDING, although expensive may
be necessary for critical areas requiring quick ground cover. (See procedures
2.B.l. and 5.A.2.)
4. Fertilization
On many construction sites, fertilization is critical to successful establishment
and survival of plantings. Reference 1 provides application rates for various
conditions. Fertilizer is often required during initial seeding as well as
successive applications to promote growth. Where it is desirable to allow native
species to take over areas planted with exotics, the reapplication of fertilizers
is gradually reduced during the succeeding seasons until the native species are
. es tab 1 is hed.
5. Mulching
Revegetation on sloping terrain, especially with minerals soils will usually
require some form of mulching. (See Procedure 5.B.)
WOODY PLANTS
There is advantage to establishing woody plants, most commonly willow or alder,
in addition to grass and herbacious ground covers for:
slopes where additional root mass would help stabilize soils;
stabilizing streambanks by additional root mass and by slowing stream
velocity along banks. (See Section 6)
Plants may be started from seed, seedlings, and for some deciduous species, stem
cuttings.
Species must be adapted to soil pH. The Revegetative Guide gives pH tolerances.
Timing. Seeding should take advantage of high soil water content, so late fall or
early spring seeding is desirable. Transplanting can be early spring or fall.
Cuttings can be planted in spring.
DE~C.I<.I PTlDN CONTINUED
NUMBER 5.A.l
Timing for collection of seeds and cuttings is extremely important, and varies
with species. (See references 1, 2 for recommended times.) Seeds and cuttings
(8-10") should be stored below-freezing as soon as possible after collection.
Seedlings should be kept dormant at 35-40°F and should be kept from excessive
drying.
For seeding, the discussion under grasses and herbaceous plants applies. For
planting seedlings and cuttings there must be close contact with the soil.
Cuttings are usually just pushed into the ground.
EX.AMPL£
Hydroseeding operation along
Yukon to Prudhoe Bay Haul
Road
Source: R&M Consultants, Inc.
HAtNTENANC.E.
Seedlings must be kept moist until reaching a height of 1-2 inches. Watering may
be required in some areas or during periods of drought. Watering and fertilizing
woody plants may be critical during the first year.
1) U.S. Forest Service. Seeds of Wood~ Plants in the United States. USDA.
Agricultural Handbook No. 450, 1974. 2) Alaska Rural Development Council. A
Revegetative Guide for Alaska. Alaska Cooperative Extension Service. March 1977.
3) Erosion and Sediment Control Handbook. Country of Fairfax Virginia.
December 1974. 4) Tourbier, J. Water Resources Protection Measures in Land
Development. Univ. of Delaware. April 1974.
NUMBER 5.A.2
6ROUP Revegetation -After Final Grading
PlU\L. TlC.E Stabilizing Critical Areas with Sod
Pul<..POSE
To establish a protective layer of vegetation as fast as possible to prevent soil
erosion by wind or water.
-.. ----.. ---
61TE C.HAIZAC.TER.lSTICS
Sodding gives the fastest possible protection by vegetation and, thus is used
where immediate protection is essential. It is an expensive operation and should
be applied to critical areas only. These include steep slopes, highly erodible
soils and disturbed areas in the floodplain, drainage channels and other critical
areas.
ADVANTA6ES
1.
2.
Sod gives immediate vegetative
cover which is effective in checking
erosion and aesthetically pleasing.
Good sod has a high density of growth
and this gives superior protection to
a recently seeded sward.
DI"SADVAt\lTAbES
1.
2.
3.
Sod is expensive.
Sod is heavy and handling costs are
high.
Good quality sod may be difficult to
obtain.
DE5C£ I PTl ON
3. Sod can be placed at any time
that soil moisture is adequate
and the ground is not frozen.
4. Grass species in available sod may
not be suitable for site conditions.
5. If mowing is required do not use on _
slopes steeper than 3:1 (use minimum
maintenance ground covers.)
Sod Specifications (Taken from Reference 1)
Local SCS office.
I. Sod should be unifonn thickness (approximately 1 ").
2. Sod should have a dense root mat to give adequate mechanical strength.
4. Sod should be moist and fresh when delivered to the site.
Site Preparation
1. Where possible, grade to allow use of conventional equipment for cultivation,
spreading lime, fertilizing and seeding.
2. Apply lime and fertilizer according to soil tests (or according to
recommendations in reference 2).
3. Disc harrow to a depth of 2-3" until a unifonn, fine, firm bed is attained.
Where possible, final cultivation should be along the contour.
4. Irrigate before laying sod.
DE:LIZ.IPTION C.ONrll\lUED NUMBER 5.A.2
SOD Placement
1. Lay sod strips along contour, never up and down slope. (See exception,
Section 2.8.1.). Start at the bottom of the slope and work up. Stagger
joints and make sure joints are snug.
2. Roll or tamp thoroughly after placement.
3. On steep slopes secure sod with wood pegs, wire staples or split shingles
(8-10" X 3/4").
4. Use jute or plastic netting to secure sod in place at the crown of very steep
slopes, in drainage swales and at other areas where water could undercut sod.
5. Irrigate sod thoroughly until moisture penetrates the soil layer beneath.
Maintain optimum moisture for at least two weeks.
Future Developments Outside Alaska rapid progress is being made in growing very
high quality sod in shallow pans on a thin bed of polystyrene granules. This
product is very light and can be handled in wide rolls, unlike traditional sod.
When unrolled onto bare ground which should have received a light dressing of
fertilizer and thorough irrigation, the sod will become established very rapidly.
This technique, when generally available, will combine the advantages of
traditional sod with the advantages of lightweight erosion control blankets.
1) URS. Co. Stormwater Management, Procedures and Methods. Snohomish County,
King County, City of Everett. EPA Grant Id. No. P-000091. September 1977.
2) Alaska Rural Development Council. A Revegetative Guide for Alaska. Alaska
Cooperative Extension Service. March 1977. 3) U.S. Soil Conservation Service.
Interim Standard and Specification for Critical Area Stabilization with Sod.
Somerset, New Jersey.
NUMBER 5.8.1
6R.DUP Revegetation -Mulches
PRACTicE Organic Mulches
PUR..PDSE
Application of plant residues or other suitable organic material can reduce
erosion by reducing impact of rainfall and checking runoff; also will stimulate
plant growth by retaining moisture.
6lTE U+/\12ACTE 1(.1-:, TICS
Especially steep slopes and highly erodible soils, and where large areas of soil
are exposed at one time. May be used on any area subject to erosion, particularly
where revegetation would otherwise by difficult. May require netting or chemical
binders.
ADVANTA6E,S
1. Improved germination and growth.
2. Helps retain moisture in soil.
DI~ADVANTA6ES
1. If the area is to be seeded, it must
usually be done simultaneously with
mulching.
2. Straw mulch, one of cheapest and most
DESCRIPTION
3. Helps dissipate rainfall impact
and stop soil erosion.
effective may be a fire hazard,
is subject to wind and is
unavailable in some areas.
Organic mulches include straw or hay, wood fiber, wood chips and other plant
materials which can be used as protective, soil cover. Level areas and other
sites with favorable growth conditions dont generally require mulching. On
slopes, erodible soils, very gravelly sites and other critical areas mulching
assists revegetation by retaining seeds, moisture and soil and improving survival
and growth.
On slopes of 3:1 or less machinery can be used to apply and anchor mulches.
Steeper slopes will require hand application or hydroseeding.
Application rates given below are taken from recommendations for Snohomish and
King County in Washington State and may require local adjustment. One of the
technical agencies should be contacted for local recommendations on appropriate
mulch type and application rate.
DESLI2l PTIDN CONTtNU£0
· NUMBER 5.8.1
1. Straw Mulch
Is usually applied by hand or mulch blowing equipement. It requires anchoring
against wind blow.
-May be punched into soil by discs, etc., or covered with nettings or chemical
agents.
-Effective for more than three months.
-Application: 75-100 lbs. (2-3 bales) 100ft2 or 15-25 tons (90-100 balls)/acre.
2. Wood Fiber Mulch
A number of commerical products are available, mostly applied by hydroseeding.
Mulch is often mixed with seed slurry.
-Does not require anchoring.
-Application 25-30 lbs/100 ft2 or 1,000-1,500 lbs/acre.
3. Wood Chips
This mulch has been used as a temporary mulch over areas not seeded or over newly
seeded areas. Slash and brush from initial clearing can later be processed and
spread.
-Limited to fairly level areas as may be subject to movement by runoff.
-Resistant to wind blow. ·
-Applicaton: 500-900 lbs/100 ft2 or 10-20 tons/acre with 10 lbs nitrogen/ton
recommended.
4. Wood Excelsior
Decomposes slowly and is subject to some windblow.
-Application: 90 lbs/100 ft2 or 2 tons/acre.
5. Other Mulches
Often a good mulch can be had by stockpiling, respreading and incorporating into
soils the organic material removed in clearing. Any number of other materials
such as compost, peatmoss, topsoil, etc. can be used in certain construction
areas.
NA I NTENANLE
Mulched areas should be inspected periodically and damaged areas repaired.
1) Alaska Rural Development Council, A Revegetative Guide for Alaska, Univ. of
Alaska. ~1arch 1977. 2) Environmental Protection Agency. Guidelines for Eros ion
and Sediment Control Planning and Implementation. August 1972. 3) Tourbier, J.
Water Resources Protection Measures in Land Development. Univ. of Delaware.
April 1974.
NUMBER 5.B.2
6KC>UP Revegetation and Mulching
Nettings, Mattings and Mulch Blankets
To prevent soil erosion during establishment of vegetation.
6\TE GttAeALTE f.tSTlC.S
These mulches are used mostly on steep slopes, in swales and other critical areas
to be revegetated. They do not offer much soil moisture retention, as do organic
mulches, so their use is limited to favorable areas or in conjunction with other
mulches such as in 5.B.1.
ADVANTA6E.S
1. Easily installed, by unskilled labor.
2. Resistant to wind and water erosion
DISAOVANTA6£S
1. Will not retain soil moisture, which 3.
may limit use.
2. Synthetic nettings should not be used
where net could be washed into fish
stream.
DESL-et PTtON
but must be well anchored.
If used in swales where there
is high velocity runoff before
vegetation is established, netting
will cause scouring.
Before installing these mulches, the areas should be stabilized with other
procedures such as diversions, perimeter dikes and drainage structures. The
surface should be prepared as in 1.B., and 5.A.2. The area can then be covered
with any number of commercially available nettings or mattings. Manufacturer's
specifications should be followed and it may be desirable to consult with the SCS
or other agencies.
1. Nettings
Either natural {such as jute) or synthetic nettings are available. They can be
used to tack other mulches such as straw, if mulching effect is desired, or used
alone if only erosion prevention is needed. Nettings must be anchored. They
are also used as channel liners for vegetated channels {See 2.B.2.). Nettings
are usually effective on even steep slopes and most soils types.
2. Mattings
Materials such as Excelsior Blanket are a machine produced mat or curled wood
excelsior covered with either a Kraft paper or plastic mesh. The blanket must
be stapled, particularly if used in channels or swales. These blankets offer
somewhat more of a mulching effect than netting alone. Mattings are fairly
resistant to concentrated flows.
DESG2.\ PTlON CoNTINUED NUMBER 5.B.2
3. Mulch Blankets
Consist of wood cellulose fiber bonded with a water soluble binder, forming a
homogeneous mat. A plastic net is bonded to the top surface for anchoring.
These provide a greater mulching effect than nettings alone although they may not
be as resistant to concentrated flows.
Installation of Matting
Unreel the matting downhill. This is best achieved by placing a hollow shaft
(e.g. a metal pipe) through the center of the roll through which is passed a rope.
The roll can be unwound slowly down the slope. Most mesh is reeled on a cardboard
core and a rope may simply be passed through this. The material should not be
stretched nor allowed to lie loosely, but should take up the contours of the
ground. The manufacturer's recommendations for overlapping adjacent strips
should be followed.
Anchoring Matting
Uphill ends should be buried in a 6" deep slot and stapled across on 12" centers.
At joints, the downhill end should be overlapped (shingle fashion).
On very severe slopes check slots should be used (Figure 2). These are 6" deep
slots into which a tight fold of matting is inserted. The slot is filled and
tamped and staples inserted across on 12" centers) just down slope of the check
slot.
Stapling
Matting should be stapled according to the manufacturer's instructions, generally
as above, and on 12" centers down each edge of the mat and down its center line.
After installation, mesh mattings should be rolled with a smooth roller to bring
into close contact with the soil and to consolidate the seedbed.
MAl NTENANGE
Mulched and netted areas should be inspected periodically, especially following
storms. Damaged areas should be repaired.
REFER.ENLE
1) Environmental Protection Agency. Guidelines for Erosion Control Planning and
Implementation. August 1972. 2) Tourbier, J. Water Resources Protection Measure
in Land Development. Univ. of Delaware. April 1974.
NUMBER 5.B.3
Revegetation -Mulching
Pll.AC.TIL£ Chemical Stabilizers and Soil Binders
To bind soils to prevent erosion during revegetation. Some chemicals act as
mulches also.·
.StTE GHAI2.AC.TE f<JSnLS
Are applicable to any site, particularly steep sloping or highly erodible soils.
ADVANIA6ES
1. Many are applied by hydroseeders
allowing labor savings, and access
to areas inaccessable to other
machinery.
DlSADVANTA6E5
1. Not as effective for fine-grained
soils as for sand soils.
2. Requires special equipment for
application.
2. Binds soil surface against erosion.
3. Acts as a mulch under certain
conditions.
3. Rarely superior to straw.
4. Equipment may be difficult to
schedule for small job increments.
Chemical stabilizers include petroleum products, asphalt emulsions, latex
emulsions, plastics and many others. Each material has certain limitations,
particularly in terms of ambient temperature during application and soil types.
Use in Alaska has been rather limited and has had varying success. Technical
agencies, such as the Soil Conservation Service, and the manufacturers should be
consulted. The surfaces must usually be cultivated prior to application. The
following provides general considerations for the use of these materials.
1. Chemical Stabilizers
These materials do not usually penetrate the soil, but rather form a thin crust.
Examples are asphalt emulsion and cutback asphalt. They are applied over the
seeded area and as they cure, the seedlings can penetrate the cover. The seed
bed should be well prepared prior to application of the chemicals.
2. Soi 1 Binders
Are useful where fiber, straw, or other forms of mulches are unavailable. These
are most commonly emulsions of resin or latex and check erosion during the
establishment of vegetation by stabilizing the seedbed. They also help to retain
soil moisture and yet are soluble enough to allow rainwater to reach the soil.
Penetration of soil binders is usually about~·. They are most conveniently
applied together with seed and fertilizer with a hydroseeder. Soil conditions at
the time snould be moist. Soil binders alone, therefore, should only be used in
favorable seasons. Binders remain effective on sandy soils longer than on finer
textured so i 1 s.
DE5U-l PTI ON CONTINuED
NUMBER 5.8.3
In less favorable seasons; so-il binders -can be hydroseeded with short fiber
mulches. More than twice as much stabilizing agent is required. Moisture
retention and insulating properties of the mulch are greater when in combination
with wood fibers.
These materials would normally not be used in areas subject to concentrated flows,
such as in swales or channels.
MAtNT£NA_t4C.E
Damaged areas should be repaired until permanent vegetative cover is achieved.
1) Tourbier, J. Water Resources Protection Measures in Land Development. Univ.
of Delaware. April 1977. 2) Alaska Rural Development Council. A Revegetative
Guide for Alaska. Pub. No. 2. Univ. of Alaska Cooperative Extension Service.
March 1977. 3) URS Co. Stormwater Management, Procedures and Methods.
Snohomish County, King County, City of Everett. EPA Grant Id. No. P-000091.
September 1977.
J.NTt:.DDULTlON
TO 61eoup (o, ~)T\2..6~M STABlLlZ.ArtoN
This introduction described potential grass stream responses to man made changes.
It is presented to provide a background against which the procedures in Section 6
can be reviewed.
The following is from Mackin (1937) (Reprinted in Ref. 1). The engineer who
alters natural equilibrium relations by diversions or damming or channel
improvement measures will often find that he has the bull by the tail and is
unable to let go--as he continues to correct or suppress undesirable phases
of the chain reaction of the stream to the initial •stress• he will necessarily
place increasing emphasis on study of the genetic aspects of the equilibrium in
order that he may work with rivers, rather than merely on them. 11
Natural streams are dynamic systems, though often not viewed as such.
DESLe..l P&L Ol'J
1. Variables in a Stream System
A range of effects from induced changes must be carefully considered in
attempting engineering solutions, to prevent merely transferring a problem to
upstream, downstream, or next year.
In natural alluvial streams the following general relations exist:
channel width, depth and meander wavelength are directly proportional
to discharge;
Width and wavelength are directly proportional to sediment load;
Width to depth ratio is directly related to sediment load;
Gradient is proportional to sediment load and grainsize and inversely
proportional to discharge;
Sinuosity is proportional to valley slope and inversely proportional
to sediment load.
Natural alluvial rivers are broadly classified as straight, meandering or braided.
Meandering rivers change channel shape by erosion at the outside of bends, and
deposition in straight reaches and point bars at the inside of bends.
Braided streams have wide channels, poorly defined and unstable banks, high
velocity and relatively steep gradient, and rapidly shifting subchannels.
Changes in the independent variables (sediment load, grain size, discharge and
valley slope) can be expected to cause major channel changes which will stabilize
only after considerable length of time.
DESGeiPTtotJ C.ONTlNU6D
GROUP 6
2. Qualitative Stream Responses
Activity Potential Stream Response (from Richardson,
May 1975)
1.
2.
3.
4.
Impoundment
Constriction
(e.g. installation
of culvert or bridge
with abutments between
banks) ~
Channel·~
_Straightening
Channel Straightening
and Lining
Upstream: aggradation of bed (deposition); change in
river geometry; increase in flood stage which must be
accommodated by upstream structures; raise base l~y:e_l
for tributaries.
Downstream: channel degradation (increased erosion
of bed and/or banks) to compensate for reduction of
sediment load at impoundment; local scour at bridges
or culverts; possible change in river form; reduced
flood stage; reduced base level for tributaries
causing increased velocity, reduced channel stability,
headcutting, and local scour at instream structures;
tributaries increase sediment transport to main channel.
Increased velocity at the structure; local scour;
backwater and aggradation at flood stage.
Increased gradient and velocity; increased sediment
transport; channel degradation; banks unstable; river
may braid; lowered base level of tributaries straight
Downstream: deposition below straightened channel;
loss of channel capacity; increase in flood stage.
If the lower end of the constructed channel outlets
to the stream base level such as a lake or reservior
the lower portion will first be subject to the above.
Then, as a delta forms or increases at the mouth
and progresses upstream, the channel will
significantly aggrade, and flood levels increase.
Increased velocity and gradient; unless lining is
very rough, velocity increase will be greater than in
unlined channel; if only banks are lined scour will
occur at the base of the linings.
Downstream: If energy is not dissipated at
downstream end of channel there will be scour at
outlet and more severe attack at first bend
downstream.
5. Longitudinal Encroachment
a. Meandering Same as 3. above and: Highway fill subject to scour
. Channel as channel tends to shift to old alignment;
.
~. -~~headcutting may proceed up from downstream end;
~ -____ .-adequate lateral drainage must be allowed. ~ ;I"_ L-'-......,
b. Incised Channel is narrowed, velocity increased; fill subject
Channel to erosion, bed degradation induced; lateral drainage
may be hindered. Upstream: backwater generated,
producing increased flood stage and deposition.
Downstream: large sediment load may cause aggradation;
local scour at end of constructed channel.
DESL.et Prl D N CONTINUED
GROUP 6
c. Floodplain
6. Crossing
Downstream
of Alluvial
Fan
There may be fill erosion during flood; if encroachment is
significant, may increase flood stage upstream.
Streams through fans are very susceptable to channel
shifting. Serious aggradation may occur at bridges;
culverts may be blocked; stream crossing structure may
be bypassed entirely.
Similar problems may occur at rapidly shifting meandering
streams.
The USDOT publication, Highways in the River Environment ••• (1) provides
information for predicting qualitative changes in more detail. It gives methods
to estimate quantitative effects of instream structures on stream hydrology and
on stream crossings.
e.EFERENLE
1) Richardson, E.V. Highways in the River Environment, Hydraulic and
Environmental Design Considerations, Training and Design Manual. U.S. Dept. of
Transportation, FHWA, May 1975.
NUMBER 6.A.l
6f2.DUP Streambank Stabilization
!PRACTICE Vegetative
PuRPOSE
For protection of small streams and their banks to prevent or control erosion and
sedimentation.
~ITE Ct-\A~GTE((ISTIC.S
Should be restricted to areas which have been disturbed by construction activities
or where structures are threatened by degrading banks. Applies to swales, creeks,
streams and rivers as well as man-made ditches, canals and impoundments including
ponds and storage basins.
ADVANTA6E5
1. Retains instream and streambank
habitats.
2. The reduction of velocity lowers
local erosive power.
DlSADVANTA6E5
1. Native plants not carried by
nurseries may have to be collected
by hand.
2. Effects of lowering velocities
on adjacent area must be considered.
3. For severe conditions will not
DESC.f.tPTlON
The lower riparian zone
3. Plants regenerate and adapt to
changing natural situations,
offering economic advantage over
some mechanical methods.
5. Visually agreeable.
provide resistance to erosion as
strong as some mechanical means.
4. Possibly affected by ice or heavy
debris.
5. Methods described here will cause
temporary disturbance during
planting.
This zone has natural growth of willow, alder and cottonwood. These stabilize
stream bank soil with their roots. In periods of high water, their upper
branches slow the current and thereby reduce erosive force. Woody plants are
planted either as 1) individual cuttings or 2) bound together in various forms.
This zone receives primary emphasis in vegetative streambanks protection.
a) Fascines are bundles usually of w.illow, 3 to 12" in diameter, containing
brushwood, sticks, coarse gravel etc. in center tightly wound.
DE"SL~I PTtON Tll\lUEP
NUMBER 6.A.1
b) A packed fascine work can be employed on cut banks. Alternate 1' layers of
branches with rolls of shoots packed with dirt.
-c) Willow mattresses of 4-6' cuttings either braided or wired together, staked
down and covered lightly with dirt.
H A-I NTE NANCE
If willows or alders are cut before they reach 2" in diameter, growth of small
shoots from the base will be encouraged. Cuttings can be used to stabilize
sediment deposits. This also applies to Procedure 6.A.2.
1) URS Co. Stormwater Management, Procedures and Methods. Snohomish County,
King County, City of Everett. Environmental Protection Agency Grant Id. No.
P-000091. September 1977.
NUMBER 6.A.2
6R.DUP Streambank Stabilization
Mechanical Methods -Revetment
fUR.POSE
To control streambank erosion in critical areas which cannot be protected by
grass (maximum velocity 8 fps) or other vegetation.
61TE CH-AI(AC..T£i.J~ncs
Mechanical methods are usually reserved for protection of roads, utilities,
buildings and other structures located on stream banks. Flexible revetments such
as rip rap and mattress-type linings are applicable for protecting banks where
heavy scouring at the toe is anticipated. Sites with highly erodible soils will
be the most vulnerable. Mattresses can be used where rock is in short supply.
ADVANTA6E.S
I. Protection of valuable sites from
erosion.
2. Most practices listed here maintain
channel capacity.
3. Flexible lines: Rip rap blankets
and mattresses are not as
susceptable to instability or
undercutting as rapid linings.
DlS6DVANTA6ES
I. Loss of aesthetic values.
2. Reach may be damaged or eliminated
as a habitat by eliminating
vegetation or changing hydraulic
characteristics.
3. A large amount of hand labor may
be required.
4. Difficulty in installing in deep
water.
5. Streambank linings often result in
scour of streambeds by increasing
velocity.
6. Some structures such as gabions
4. Mattress: If carefully designed, a
mattress will fall into place after
scouring has taken place, providing
continuous protection.
5. Gabions: Stone of a considerably
smaller size than dumped rock may
be used.
and groins may be expensive to
maintain.
7. Often not a permanent solution.
8. Smooth linings speed flow, which
may aggravate scour downstream.
Acceptable solutions must be
designed to prevent simply
shifting problems to other reaches
of the stream (See Group 6 Intro.).
9. Rigid revetments are subject to
undercutting and collapse.
IO. Usually higher cost associated
with mechanical techniques.
Revetments consist of any number of bank
lining materials such as rip rap, concrete,
grouted stone, gabion blankets, and bagged
concrete.
NUMBER 6.A.2
1. Gabion Mattresses
These are wire mattresses filled with rock, usually by a backhoe or selective
hand packing. To lay in deep water it is necessary to prefill the mattress
on a raft and slide into place. The mattress has similar roughness to hand
placed stone.
If desired, 6" lengths of willow or alder shoots and some silty gravel may be
included during filling. Under favorable conditions this will give a dense
growth over protected banks.
2. Gabions
Gabions are wire baskets filled with stone. They can be used when larger stone
for rip rap is not available, for lining steeper streambanks than mattresses.
Gabions are filled with a backhoe and by selective hand packing. They are
available in plastic covered mesh and have life expectancy of over 25 years.
However, by that time the rock-fill in the gabions will probably have
stabilized itself.
3. Concrete-Filled Nylon Blankets
Blankets are 2 nylon sheets stitched together like a quilt and filled with
Portland cement grout after they are fixed in place. Not recommended on
slopes steeper than 1:1. The upper layer of fabric deteriorates slowly in
sunlight, but this does not greatly reduce its performance. Seams are sewn
in the field with a portable air-operated or electric bag closer. Ready-mix
concrete is injected with a mortar pump filling the toe first.
Blankets are capable of withstanding small movements unlike concrete linings, so
are less susceptible to undercutting, etc. The channel must be dewatered prior
to installation, making them frequently impractical. Fabriform blankets have
similar applications as mattresses (above) but can be used in areas where stone
is unavailable in sufficient quantities. However, they are aesthetically less
acceptable than the gabion mattress, which can become covered with vegetation.
4. Sheet Piling
This must be driven to the point of refusal or to at least ~ its length below the
maximum depth of scour. Piling would generally be used only where a vertical bank
is required, or where deep water is required close to the shore.
5. Rigid Concrete Revetments
These have the following characteristics:
-Dewatering will probably be necessary before placing.
-They are aesthetically unappealing and often have low public acceptance.
-To prevent settling and cracking they should be used only on well
compacted soils.
-The lining should extend to the top of the bank where it is stabilized
with vegetation. Height should be increased on the outside of bends.
-Reinforcement should extend through all construction joints.
-The toe should be extended to the maximum anticipated scour depth and
protected with rip rap.
DESC.e.t PTt ON LOI'JTl N UED NUMBER 6.A.2
6. Grouted Stone Revetments
Grouting is sometimes used when large stones are unavailable to stabilize dumped
stone linings if movement is occurring. This can be effective, but will redute
roughness of lining. Flow velocity will increase. This can result in a plucking
action at any holes or flaws in the grouting, leading to failure. Grouting has
the disadvantage of making the protection layer (dumped stone) rigid.
7. Dumped Stone--Linings and Revetments
Dumped stone forms a flexible lining which will gradually slump into any scour
holes. It has a very rough surface which results in dissipation of the stream's
energy, minimizing scouring problems at the ends of the revetment or lining.
For maximum allowable velocities (dependent on stone, size and channel shapes)
see Appendices 2.B.1. and 2.B.3.
8. Placed Rip Rap or Bagged Concrete
Linings and revetments of hand placed stone or rip rap generally consists of
stones of 100 lbs or more placed in a single layer. They are more subject to
damage than dumped stone. Any shifting of the stone layer will expose bare soil.
Placed stone has a lower coefficient of roughness than dumped rock and therefore,
is more susceptible to scour at the end of lined sections.
Placed stone is aesthetically one of the most acceptable mechanical protection
techniques.
MAl NTENA~C.€..
Dumped Stone
Shifted stones can be rearranged with backhoe. For large scale movement, dump
more stone. Damage to concrete linings MUST BE REPAIRED IMMEDIATELY.
Economic Considerations
1. Access. Rigid linings require good access for construction. Where difficult,
cost may increase considerably; in such cases other alternatives should be
considered.
2. Materials. The cost of hauling rock will be a significant factor in lining
costs. Concrete linings may be required where this is excessive.
3. Labor Costs. Where high and the cost of stone is low, use dumped stone. If
vice versa, use hand placed stone.
e..EFE~ENC£ NUMBER 6.A.2
1) URS Co. Stormwater Management, Procedures and Methods. Snohomish County,
King County, City of Everett. 2) New York Department of Transportation.
Division of Design and Construction. Bank and Channel Lining Procedures. 1971.
3) Bross, J.M. Engineering Evaluation of Erosion Protection for Water Courses
in New Castle County, Delaware. 1970. 4) Maccaferri Gabions of America, Inc.
Technical Literature. Flushing, New York. 5) Construction Techniques, Inc.
Fabriform Literature. Cleveland, Ohio. 6) Leep, A.W. California Soil
Conservation District Streambank Stabilization Program. J. Soil and Water
Conservation. Vol. 20, #1. 7) U.S. Department of Transportation. · Use of Rip
Rap for Bank Protection. Hydraulic Engineering Circular #11. 8) Soil
Conservation Service. Field Manual for Conservation Practices. 1975.
9) Tourbier, J. Water Resources Protection Measures in Land Development. Water
Resources Center, Univ. of Delaware. 1974. 10) Alaska Dept. of Highways.
Hydraulics Manual. 1972.
NUMBER 6.A.3.
61<.DUP Stabilization of stream channels and banks.
Bio-technical methods.
Pui.POSE.
To provide protection of critical sections of streambank through a combination of
vegetative and mechanical means •
...
~IT£ CH-AR.JlC.TE~ISTlCS
Due to large initial disruption, should be used only where area has been
disrupted by construction activity or where structures are threatened. To be used
in streams with swift flow where the flow/soil conditions exceed the stabilizing
effect of purely vegetative channel protection.
ADV~NT66E5
1. Mechanical materials provide for
interim and immediate stabilization
until vegetation takes over.
2. Once established, vegetation can
outlast mechanical structures and
DISADv6Nib.6ES
1. Slightly higher initial cost and
need for profession~l advice.
2. If possible, methods should be
scheduled for time of extreme low
water.
3. The methods described require a
complete knowledge of soils,
hydrology and other physical
data to be lasting solutions,
DE5C..et PTI ON
requires little maintenance while
regenerating itself.
3. Aesthetic benefits and wildlife
propagation.
and to avoid adverse effects on
other streams reaches.
4. Due to cost and initial
disturbance involved these
procedures would usually be
reasonable in urbanizing areas
where streamside structures
require protection.
Streams in urbanizing settings may carry a great increase in runoff. Bio-technical
methods can provide for stabilization without complete visual degradation and
higher effectiveness than purely mechanical techniques.
DESL£..1PrtON CD"-ln uED
Willow jetties can be constructed at the
water level to stabilize a cutbank by
deflecting the current and by encouraging
deposition of sediment. Steps:
1. Dig ditches diagonally to direction
of flow, and place fill to form berm
downstream from ditch.
2. Set 2' willow branches at 45° angle
and 3" spacing facing downstream.
3. Weight down branches with rip rap
extending beyond water level.
In the lower riparian zone efforts
should be concentrated on critical areas
only:
NUMBER 6.A.3
1. Rip rap can be supplemented with willows which will bind soil and screen the
bank. Willow cuttings in joints need to be long enough to extend 1' into
natural soil and should have 2-4 buds above surface. Willow branches and rip
rap should be installed simultaneously.
2. Willow branch matt revetment takes the following steps to install:
a. Grade slope to approximately 2:1 and excavate 3' ditch at toe of slope;
b. Lay live willow brush with butts up the slope, and anchor mat in the ditch
below normal waterline by packing with large stones;
c. Drive 3' willow stakes 2-~· on center to hold down brush; connect stakes
with No. 9 galvanized wire and cover brush slightly with dirt to encourage
sprouting.
M~INTENA~C.E.
Costs vary according to local availability of labor. However, there are
practically no maintenance costs for the vegetation once it is established.
1) USDA, Soil Conservation Service. Engineering Field Manual for Conservation
Practices. 1969. 2) USDA, Soil Conservation Service. Farm Planners Engineering
Handbook for the Upper Mississippi Region, Agricultural Handbook #57. 1953.
3) URS Co. Stormwater Management. Procedures and Methods. Snohmish County,
King County, City of Everett. September 1977.
NUMBER 6,A.4
Streambank Stabilization
Mechanical Methods --Deflector Jetties
Pu~POSE
To deflect streamflow away from an eroding bank, causing a buildup of sediment
which can then be stabilized.
SlTE. C\4-A.R.AC.TEI<lSTlCS
Should not be used on sites where stream cannot compensate for restriction in
channel width, either by bed scouring or by scouring on the inside of the bend.
Generally, used on the outside of bends, especially where soils are highly
erodible or runoff is increased by development upstream.
ADVLlNT~6ES
1. Deflector jetties cause areas of
comparatively still water where
sediment loads are precipitated.
D\S~DvANTb6eS
2. The buildup of sediment against
the bank allows it to be
stabilized by planting.
1. As with all structures in this 3. Jetties are generally not suitable
for glacial streams which carry a
larger quantity of bedload and
which have a tendency for rapid
fluctuations in flow. These
fluctuations dump large
section, potential for causing
changes in the stream course
upstream or downstream must be
fully considered.
2. Deflectors will considerably
restrict the channel capacity.
They should only be used where the
stream•s natural tendency to 4.
compensate by scouring the bed or
the opposite bank will not cause a
problem. Structures which would cause
bed scouring in a fish spawning area
would not be appropriate.
DESc..e..l PT"\0 N
Deflectors and Jetties are used:
quantities of bedload in short
reaches of the stream.
Jetties produce excessive eddying,
and therefore may do more harm
than good in very sinuous channels.
1) To deflect stream flow away from an eroding bank, or
2) Prevent meandering and encourage the stream to increase channel capacity by
scouring its bed, rather than by lateral cutting.
DE'SC.el r:>TIOI\l Lot-JTl t-JUE..D NUMBER 6.A.4
Because of potential acceleration of up or downstream changes, jetties and
deflectors should be designed by a qualified engineer. When curvature of the
bend exceeds 30° (190' radius), it is safer and more economical to use a
revetment.
Frtoro uRs • 1q 7 7
Spacing of Jetties or Deflectors
A rule of thumb should not be applied, but some guidance can be found in the
diagram. A'A is the direction of flow against the eroding bank. Draw a line
parallel from the end of Jetty A to B. AB = BC, which determines the location
of Jetty C. Draw a line from tip of Jetty A to tip of Jetty C and extend it to
intersect the bank. This determines the location of Jetty D. Place smaller
jetty at F (AF = AC). Jetties should not be placed at 90° to the bank but at
one angle to deflect flow with less resistance, causing less turbulence.
Plant willows or insert willow cuttings in the sediment as it builds up behind
the jetty.
HAit'JT£NANGE
Cutting willows regularly every 5-7 years, or before they reach 2" in diameter,
encourages growth of small shoots from the base.
All instream work should be monitored for success of measures used, and for
possible effects on other reaches of the stream.
1) Soil ~onservation Service. Farm Planners Engineering Handbook, Upper
Mississippi Region. Milwaukee, Wisconsin. 1953. 2) URS Co. Stormwater
Management Procedures and Methods. Snohomish County, King County, City of Everett.
EPA Grant Id. No. P-000091. September 1977. ·
NUMBER 7.A.1
I6RouP Thermal Erosion Control
Treatment of Disturbed Surfaces, Prevention of Disturbance
Pur<.PDS6
To prevent damage to permafrost areas by construction activities; to prevent or
minimize thermal degradation of permafrost areas with disturbed organic layers.
In poorly drained permafrost areas, or wherever disturbance of the active layer
could result in melting of underlying frozen soils and cause ponding, gully
erosion and other self-aggravating conditions.
~DV6NT66E.S
1. Prevents or minimizes thermal
related erosion.
DtS~DV~NTA6ES
1. Access to areas may be limited.
Dex..e.1 PTIDN
2. Arrests the problem before it
can seriously aggravate.
2. Can be expensive due to large
amount of hand work required.
1. Whenever possible use overlay construction as opposed to cut and fill.
2. When using overlay avoid stripping the organic layer. Conventional
wheeled or tracked vehicles should not be used for surveying.
3. Consider winter construction to avoid melting and thermal degradation.
4. Avoid induced drainage or standing water over permafrost areas which can
result in rapid thermal degradation. Avoid concentrated discharges from
drainage structures onto undisturbed terrain. Attempt to convert to sheet
flow to prevent headward cutting.
RESTORATION
After the active layer has been disturbed and left untreated, the sequence of
events is : 1) Ponding and minor settlement in the disturbed area; 2) If ground
is sloping, minor gully erosion; 3) Eventually, increasing pending and settlement
or development of ravines. Events are influenced by the topography and soils, as
well as the season the disturbance occurred.
1. Drainage Control -such means as ditch checks and water bars are used to
convey melt and runoff waters safely away from a disturbed area, or control
the.water within the area. This would be necessary where thawing of the act1ve layer can result in the melt water being drained away.
DESLR.tPTtON CONTINUE D NUMBER 7.A.1
2. Rev egetation -the disturbed area should be promptly revegetated to help
retard melting of underlying soils. Seeding and fertilizing should normally
be done by hand or aerial methods to prevent further disturbance.
Transplanting of trees and brushes may be favorable in some areas both for
quick cover and erosion control.
3. Insulation -a number of materials can be used to insulate the permafrost.
This would normally be used in smaller problem areas where rapid thawing
may be occurring. Materials such as straw, excelsior blanket, slash and
styrofoam have been used. Typically this technique would be used where the
active layer had been significantly disturbed or removed. Certain insulators,
such as straw, excelsior or wood chips could also be beneficial to
revegetation.
EXbHPLE
Trail area near the Livengood to Yukon Highway. Area was underlain by massive ice.
Thawing and erosion was arrested with excelsior blanket cover and slash-log ditch
checks.
Source: R&M Consultants, Inc.
Location: Anchorage, Alaska
HALNTE~ANL£
Disturbed areas should be inspected periodically until completely restored and
stabilized. Drainage work and other measures should be performed promptly.
1) BLM. Influence of Man-Caused Disturbance in Permafrost Areas in Ala ska. U.S.
Dept. of Interior. 1973. 2) Lotspeich, F.B. Environmental Guidelines for
Development Roads in the Subarctic. EPA 660/3-74 -0 09 , June 1974.
NUMBER 7.8.1
6RDUP Thermal Eroson Control
Pf<.A.C. Tl LE Cut Slope Stabilization
To prevent erosion as a result of cuts made in permafrost soils.
Cut slopes in frozen soils will exhibit varying degrees of thawing, erosion and
instability depending on the soils, height of cut, and ice content. These
techniques apply to all cut slopes which contain potentially erodible soils, due
to melting, surface runoff or sloughing.
~DV~NTA6ES
1. Prevents or controls erosion from
cut slopes.
2. Controls rapid retreat of slopes.
D I Sll DV ~"-1 Tll6ES
1. Some techniques, such as buttresses
can be expensive.
3. Prevents clogging of ditches and
drainage structures.
The general practice for frozen cuts has been to make a fairly steep slope
(anywhere from 1.5:1 to 1:4) and leave the slope to self-stabilize. This can
result in thawing of ice, release of meltwaters and some degree of sloughing,
but eventually the cut will retreat to a stable condition. If a cut continues
to retreat and appears that it will not self-stabilize, then the slope should be
treated with either a filter buttress or insulation.
Following are several suggestions for application of these techniques:
Vertical Cut
Avoid damaging vegetal mat. Allow to overhang or drape for insulation.
Clear trees by hand far enough back to prevent overhanging on slope. As the bank
retreats due to melting, trees would tear the mat and prevent self-stabilization.
Install ditch checks, sediment filters or others to trap sediment eroded from the
cut.
Observe periodically for any major erosion and sloughing. Apply remedial measures
promptly.
RlPTION LONTINUED
NUMBER 7.8.1
Filter Buttress
If the cut retreats excessively or refuses to stabilize, re-dress slope and place
free-draining gravel filter material to insulate and stabilize the cut. The
filter material can be placed at an angle steeper than natural repose to
eventually settle to a stable repose. Place sediment filters along the toe to
contain si lts from melt flows. The buttress can be dressed with topsoil and
revegetated.
Insulation and Revegetation
Dress s 1 ope to 2:1, overlay with 12"
of free-draining sand or gravel.
Cover with urea foam insulation or
other similar material.
The insulation can be covered with topsoil,
mulched and revegetated.
. ..
"1.
5A"--P ~
Gr?AVEL ~IL-(~12
I tJSU LA110tJ
In some cases, slopes can be simply treated with mulch, such as straw and netting
and revegetated. Selection of the above techniques largely depends on the
severity of the thermal degradation and resultant slope instability.
A vertical cut made in massive ice along the Yukon to Livengood Highway. Photo
at left shows overhanging organic mat as slope retreats. At right, the slope has
self-stabilized with new vegetative growth.
Source: RAM Cnnsult~nt~-Tnr_
N ~I NTE N 8 t-JLE.. NUMBER 7.8.1
All exposed cuts should be inspected periodically until self-stabilized. Sloughed
and eroded materials should be removed from ditches or sediment traps. Remedial
slope treatment should be performed promptly.
REFER..ENLE
1) Pufahl, D.E., Observations on Recent Highway Cuts in Permafrost. Gov•t of
Canada, March 1974. 2) Lotspeich, F.B., Environmental Guidelines for Road
Construction in Alaska. Env. Prot. Agency. EPA-660/3-74-009. June 1974.
NUMBER 8.A.1
Icing Control
Specialized Drainage Structures
Put<. POSE
To provide passage of winter or breakup flow. To avoid icing which encroaches on
road surfaces or which blocks culverts and bridges and could result in damage to
the structure or the embankment.
SrTE c:HAI2Ac.TE~lST1CS
1. Icings can occur naturally or because of road construction. Natural icings
are aggravated by presence of a roadway.
2. Some small streams develop icings only when exposed in the cleared road R-0-W.
3. The greater the thickness of organic ground cover, the greater the incidence
of icings; very few develop in regions with no ground cover.
4. Most icings occur in hilly to mountainous terrain.
5. Water may pass upward through frozen soil or through ice along cracks, tree
roots or trunks.
6DV6.NTA6ES
1. Reduces or eliminates the need for
periodic thawing. This especially
helpful during breakup when
demands on maintenance personnel
are high.
01SADV6NT66E5
1. Some increase in initial cost.
2. Dual, oversize culverts--require
deeper fill and adequate storage
space for ice accumulation.
DESU<.\PT\ON
1. Dual Culverts-Stacked
2. Dual and oversize culverts, bridges
improve fish passage over standard
culverts.
3. Some techniques can prevent road
surface icing.
3. Subsurface drains--must be
designed so that outlets don't
clog with ice, or outlets must
be periodically opened with steam.
A stacked culvert provides a relief route for meltwater at an ice-dammed culvert,
eliminating the need for spring thawing. Requires a deep fill section and
sufficient storage area for ice accumulated during winter, without plugging the
upper culvert. Offsetting the upper culvert reduces the necessary depth of fill.
In streams which experience wide fluctuations in flows, offset culverts can also
assist in fish passage. (Lotspeich, 1974).
Use of oversize culverts or bridges can delay or prevent total blocking of the
structure.
l
DESGI<.tPIION c.aJTINUED NUMBER 8.A.l
2. Subsurface Drains
Stream flows -used where topography is steep enough to allow diversion of
subsurface flow and exit downslope of structure or roadway. Pipes are placed
upstream of the area of icing, across the stream to intercept sub-bed flow and
allow filtration of low stream flow. Within the stream channel the trench should
be backfilled with coarse material to allow infiltration. Outside of channel
banks, insulation should be placed over subdrain backfill.
The subdrain is for low flows only, and should not be used to replace the
conventional drainage structure at the roadway.
Road Icing from Ground Seepage -Subsurface drains can be used to: 1) reduce
artesian head at the roadside beneath seasonal ice; 2) intercept surface flows.
For a subdrain to function surface flows must be intercepted at the source, since
icing layer is impermeable, and must be buried below maximum freezing depth.
Outlets are downslope from the road embankment.
Subdrain outlets must be designed so they will not freeze or so they can be
periodically thawed.
3. Channel Re-alignment -Straightening and deepening channels can increase flow
velocity and therefore decrease surface icing.
However:
It is usually a temporary solution only. The channel may need to be
reconstructed fairly often. Channel straightening usually causes instability
upstream and/or downstream from the new channel. Chronic maintenance and erosion
problems could thereby be created;
-Channelization and any associated chronic erosion/sedimentation problems are
destructive of aquatic habitat.
.
DESGJ2JPTtON C..ONTINUtD NUMBER 8.A.1
4. Channel Covers
C.R.R.E.L. reports in reference 1 that channel covers are an "unproven technique
of limited applicability." Use should be limited to well defined channels of
limited surface area. Seepage from banks should be negligible. The purpose of
the covers is to accumulate snow and provide insulation. Insulation is frequently
insufficient. Covers may be of any material that will hold snow including brush,
tar paper, scrap sheet metal, plastic sheets, plywood, burlap, spruce trees.
Materials are best suited which provide best insulating effect. Canvas has been
used to cov~r open ends of the structures. If contact is allowed with the ice.
surfac·e the canvas can act as an ice fence, and could aggravate icing conditions.
Any use should follow intensive site study. Channel covers may be useful in
combination with other methods such as heat cables (See 8.8).
Locations of highest heat loss of a culvert are at the culvert ends. A variety
of materials are used to reduce air flow through culverts and to cover exposed
metal at culvert ends. Materials include brush, snow, tar paper. Care must be
taken to prevent formation of an ice fence. (See B.C.)
MAINTENANC..E
Drainage structures should be periodically inspected. Proper design of dual and
oversize culverts, and subdrains should reduce or eliminate the need for culvert
thawing.
REFERENL..E.
1) Carey, K.L. Prevention and Control of Culvert Icing~ U.S. Army C.R.R.E.L.
April 1975. 2) Johnson E.G., Esch, D.C. Investigation and Analysis of the
Paxton Roadway Icing. 1977. In: Proceedings, 2nd Intl. Symp. on Cold Regions
Engineering Fairbanks. Dept. of Civil Engineering Univ. of Alaska, Fairbanks.
Aug. 1976 •
•
NUMBER 8.8.1
Icing Control
Culvert Thawing
1/_URPOSE
To maintain winter flow or provide an opening for passage of spring meltwater.
Suitable for any culverts or small bridges subject to plugging by icing.
1. Technique not limited by expanse of
icing.
2. Thaw cables -can be used either to
keep open throughout winter or to
open before spring.
1. Thaw cables: It may be difficult
to intercept icing feedwater.
2. Thaw cables: Are limited to
locations where electrical power
is available.
DESL~tPTlDN
1. Thaw Cables
3. Thaw cables -for maintaining
opening throughout winter. More
environmentally acceptable than
fire pots and should require less
maintenance.
3. Fire Pots -require continual
maintenance.
4. Fire Pots -have high potential
for spills into streams.
Most efficient use of electrical heat cables is to maintain a small open
passageway through a culvert at low power levels. When roadway surface will
not be threatened with icing, they can also be used to open and keep opened a
plugged culvert in spring.
Culvert ends require more heat than the center portion to maintain opening.
This can be most easily accomplished by doubling back, or tripling the cable
(maintain manufacturer's bending radius) •
A vertical riser (see figure) can help
keep ends open. Operation is most
economical when the cable length is
short, with risers at the culvert
openings. But to collect surface
feedwater the riser must be placed
at the low point in the icing. If
the riser is not well placed, icing
will not be prevented, but there
will be an escape route for spring
meltwater.
DE.SL.f(l PTlOI\1 C.o~Tl NUED NUMBER 8.8.1
Cables are either buried a few inches (3-5") below the culvert and below the
streambed at each end, or suspended inside the culvert.
Power source is usually a nearby service pole with a transformer, but a truck-
mounted genera tor may be used for spring thawing.
Specific engineering criteria must be developed for each site. Ice fences or
other methods in this section may be used in combination with thaw cables.
This is one of the more environmentally acceptable procedures.
2. Steam Thawing
Steam is used to open ice blocked culverts. Usually done in winter when icing
threatens roadway or in spring where winter flow need not be maintained. The
method is suitable for any ice blocked culvert accessible to truck mounted boiler.
Thawing can be done by probe or permanent piping may be installed. The process is
less expensive than thaw cables, but usually must be done more than once.
3. Fire Pots
Unless fuel flow can be automatically and reliably shut off if the flame dies,
fire pots should not be used.
A fire pot consists of a large drum holding a fire of fuel oil (or some mixture
of liquid fuels) or coal placed at culvert entrance to keep it thawed.
Spills during operation or refilling can have harmful effects on overwintering
fish.
Fire pots require continual maintenance to be sure oil is not reaching the
stream --their design requires fuel storage near running water.
These have usually been gravity feed systems. If the flame goes out fuel
continues to flow --into the stream.
The Alaska Railroad uses coal or charcoal fired burners with reported success (1).
M~tNTENANLE:
Culvert thawing is essentially a maintenance activity. All culverts should be
inspected periodically throughout the year.
REFER.E~LE
1) Carey, K.L. Prevention and Control of Culvert Icing U.S. Army C.R.R.E.L.
April, 1975.
•
..
NUMBER 8.C.1
61<.0UP Icing Control ,·
PR£)GT\LE. Channel Maintenance
PURPOSE
To maintain winter flow, or induce icing at some location which will not require
maintenance.
511E CON'Dl\lONS
Suitable for any small-to-medium size channel at culverts or bridge openings.
AD\/ANTA66S
1. Frost dam, air ice covers: no
material removal is required
in spring.
D\"S6DV6NT66ES
1. Frost dam, air ice covers may
become ineffective after warm spell.
2. Frost dam, air ice covers: timing
of construction is critical.
DESLI2..1 PflON
1. Frost Belts
2. Ease of construction.
3. Ice Fence: timing less
critical.
3. Ice Fence requires removal
in spring.
Constructed by excavating a ditch in the ice 10 1
--12 1 wide to the streambed.
The ditch progresses downward as the ice below the ditch thickens. A drainage
ditch may be required to remove accumulated water downstream. Frost belts must
extend well beyond the stream edges. Extension ditches on the banks may be
excavated before freeze up at the selected site, which should be between 600 and
900 feet from the structure. Additional dams should be at least 60 feet apart.
Frost belts are best constructed where stream ice usually freezes solid to the
bed, as in shallows or near rapids.
2. Air-Ice Covers
This method is essentially the same for all situations where it is used. The
intent is to create an insulating layer of air under an ice cover by temporarily
damming the stream early in the season and allowing the water to back up through
the culvert. The dam is placed a short distance downstream from the culvert and
should retain a degree of permeability. After allowing the ice cover to freeze to
a 5 or 6 inch thickness, the dam is removed. With the free flow restored, the
water level drops so that an 8 to 15 inch air gap remains. The intervening layer
of air is generally sufficient to prevent freezing of the flowing water. Extra
snow, peat, branches and other available materials may be placed over the ice
layer for further insulation. Insulation material must be removed in the spring.
DE.SC.IZ..lPTION CONTINUE.D NUMBER 8.C.l
Additional protection is afforded by planting shrubbery along the banks to retain
snow over the stream for additional natural insulation. Where a broad channel is
encountered, support for the ice cover may be provided in the form of short wooden
or concrete posts acting as columns placed before the pond is formed. At a large
icing site, several temporary check dams may be required. Spacing should be
150-200 1
•
3. Ice Fence
Ice Fences are used to store ice accumulation upstream from culverts or bridges.
Icing feedwater sources must be upstream of the fence. If avenues open below the
fence for water to pass upward through the ice, the fence will be ineffective.
Upstream storage space must be adequate for a winter's accumulation.
May be combined with other measures. With thaw cables fences may help move the
lowest point of icing nearer the culvert inlet so a shorter (more economical)
cable can be used to in~ercept surface feedwater.
A wide variety of materials can be used: snow, plastic, canvas, burlap, boards,
brush, galvanized sheet metal, tar paper, wire faced with paper, etc.
Partially-
completed
frost dam.
Operating
frost dam.
Ice Fences
1 ) C a rey, K • L.
Special Rpt. 224.
-P'E,f<MAf RO>'f ---
Prevention and Control of Culvert Icing. U.S. Army C.R.R.E.L.
April 1975.
•
..
NUMBER 9.A.1
6ROUP Final Restoration
P~C.TIL£ "Putting to Bed"
PuR..PDSE
To leave areas used during construction, which are to be no longer used or
maintained, in a stable condition •
SlTE C.J~At<ACTE.I<.\SIICS
For any location where intended use is complete, and for those to remain unused
for extended periods. Includes areas such as unused portions of R-0-W, haul roads,
borrow and disposal sites, campsites, storage yards and others.
~DVANTA6ES
1. Elimination of maintenance costs
for unused facilities.
DtSADVANTA66S
1. Additional cost if facilities or
structures are removed.
DESLR.lPIJON
2. Stabilization against erosion
and sedimentation.
All slopes should receive appropriate treatment for stabilization. Provisions
should be made for access blocks to prevent use of these facilities by unauthorized
persons. It should be stressed that all restoration activities should be complete
and adequate. It can be extremely expensive to return to the site, particularly
in remote areas, to repair that which could have been avoided.
1. Slopes, borrow areas and waste materials should be graded to stable conditions
(normally 2:1 or flatter depending on soils) and provisions made for permanent
drainage.
2. All open culverts should be removed and sufficient cross-road drainages
provided to accommodate runoff at breakup. Culverts in natural drainages
should be removed, as their inlets gather debris and gradually plug, resulting
in washout over the road. For all streams used as fish habitat, fill material
should be removed down to the original stream contour to prevent sediment
problems and blockage from icing.
3. Roadways should be shaped to drain by crowning or outsloping. Water bars,
checks or other measures should be installed.
4. Disturbed bare areas should be seeded with grass, legumes and/or planted with
woody plants and fertilized as necessary (Section 5) with N-P-K mixture, following
recommendations in reference 1, to insure initial quick growth to protect bare
soil.
DE'SC...QJPriON CONTINUED
NUMBER 9.A.1
5. Install access blocks such as berms or ditches to prevent access and damage
to stabilized areas by unauthorized vehicles.
6. Petroleum products, containers, and abandoned equipment should be removed
from landings, service areas, and roadsides before the roads are put to bed.
7. On old haul roads and main skidtrails, special attention should be paid to
cross draining at points just above steep sections and to the erodibility of the
so i 1.
8. Vegetative debris is usable to stabilize sections likely to erode after
abandonment.
One technique suggested in Reference 2 for KA~IK~LJ c. LO.SUR£
logging roads, called a 11 Kaniksu Closure, 11 .;...:..:......:.;_;..;:..__;._;__ __ -=---'-'--=--
may be applicable for improving drainage
of haul and others which will be reopened
at some future date. This technique may
have some limitation in high precipitation .
f d d d f "1 ~)(J.$11~6 areas, on sur ace roa s an or some so1 VE.&E:fAfroN 1
types. It can be effective to keep traffic
off the road. At a future date, the
excavated material can be pulled back
by an angle blade and reshaped for use.
MAINTENANLE
A.t7JUGIE::.D ROAD
PRISM
EX CAVA)£ p MAT ISI<IAL
Restored areas should be inspected periodically until stable and appropriate
action is taken.
I<EFE.I<.ENLE.
1) Alaska Rural Development Council. A Revegetative Guide for Alaska.
University of Alaska Cooperative Extension Service. No. 2, P-238. 1977.
2) Environmental Protection Agency. Logging Roads and Protection of Water
Quality. EPA 910/9-75-007. March 1975. 3) Lotspeich, F. Environmental
Guidelines for Development Roads in the Subarctic. Environmental Protection
Agency. EPA 660/3-74-009. June 1974.
NUMBER 10.A.1
6RouP Miscellaneous
P ((f.lGT I L.E Tracking Control
PuRPDSE
To prevent tracking sediment from construction areas onto public right-of-way by
vehicles or runoff.
SITE CH-ARAL.TERJSTILS
At points of ~ress from construction areas (such as haul roads, borrow and
disposal areas) where mud-laden vehicles may travel onto public roads, parking
lots and private property.
ADVA~TA6ES
1. Prevents sediment problems in storm
drain systems and natural streams.
DISADVANTA6ES
1. Minor inconvenience for
construction equipment.
DESC.RI PTION
2. Reduces safety hazard on public
roads which can become slick from
mud from equipment.
2. Clean gravel may not always be
available.
Construction traffic, such as dump trucks, delivery trucks and others can carry
significant amounts of sediment from construction sites, particularly during wet-
weather periods. The following is adopted from the Anchorage Management Plan
cited in Reference 1 below.
Construction of Stabilized Crushed Aggregate "Wash-Strips" At Entrances to
Construction Sites. The purpose of a stabilized construction entrance is to
reduce or eliminate soil-tracking or flowing of sediment onto paved streets.
This applies to all points of construction ingress and egress in urban areas,
and in suburban areas where 60% of the streets are paved, where storm drains are
directly involved, or in any location where tracked sediment would reach streams.
Stone size -Crushed only, AASHTO M43, Size No. 2 (2 1/2 to 1 1/2")
Thickness
Width
Length
-Minimum 6"
-Minimum full width of driveway
-Minimum 50'
DESC..1ZIPTtON CONT'INUE.D NUMBER lO.A.l
The entrance shall be maintained in a condition which will prevent soil-tracking
onto paved roads. This may require periodic maintenance by adding layers of
crushed stone or washing by water. A sediment trap as outlined under
sedimentation should be provided and periodically repaired and cleaned. All
sediment tracked, spilled, or washed onto paved streets must be removed
immediately. When necessary, wheels must be cleaned to remove sediment prior
to entrance onto paved public roads. When washing is required, it shall be done
on an area stabilized with crushed stone which drains into an approved sediment
trap or sediment basin. All sediment shall be prevented from entering any storm
drain, ditch, or watercourse through the use of sand bags, gravel berms, boards or
other effective methods. (See Section 3.)
f'-tlll NTENANL.E I The above 1s a maintenance activity.
REFEt<.ENC.E
1) Municipality of Anchorage. Soil Erosion and Sediment Control, 208 Areawide
Waste Treatment Management Plan. September, 1977. 2) County of Fairfax, Va.
Erosion and Sediment Control Handbook. Dec. 1974. 3) Tourbier, J. Water
Resources Protection Measures in Land Development. Water Resources Center, Univ.
of Delaware. Apr. 1974.
,
NUMBER 10.8.1
~1iscellaneous
Wind Erosion and Dust Control
Control of surface and wind movement of dust on construction sites and traffic
surfaces.
5\T£ CHAf<AC.IE.I<JSTlC.S
Any areas subject to wind erosion of exposed surfaces or dust generated by
vehicles, where eroded materials can cause on-and off-site damage without
treatment •
. ADVANTA6ES
1. Improves vis ibi 1 i ty, safety and
health on site.
2. Prevents sedimentation of nearby
water courses.
D\SADVANTA65S
1. Certain materials may be toxic to
plants or animals.
DE~UZ..t PTtO N
3. Temporary or permanent control
is provided.
TEMPORARY METHODS -for areas still under construction, the following techniques
can be used:
1. Mulches -material such as straw, wood chips, soil binders and others
described in 5.8. can provide quick cover.
2. Vegetation Cover-quick growing annual grasses (See 5.A.) can be employed
if an area is to be left exposed for a period of time.
3. Scarification-as discussed in 1.8., surface roughening can be used as an
emergency measure before wind erosion starts. The idea is to bring clods to the
surface which will not erode. Plows or harrows can be used.
4. Irrigation -another •emergency• type technique is to simply spray the site
with water. Must be repeated to remain effective.
5. Spray-on Adhesives - a number of chemicals, asphalt emulsions and other
materials have been used. Consult current regulations for each material as many
can be toxic.
6. Barriers -vertical barriers, such as solid board fences, snow fences, burlap
fences and hay bales can control air currents and wind erosion. Generally
effective if placed at·right angles to prevailing winds and spaced at intervals
of approximately 15 times the height of the barrier.
DE~GRt PTI ON C.O"--TI NUE D NUMBER 10.8.1
PERMANENT METHODS
1. Vegetation-permanent seeding or sodding (See 5.A.) and mulching (5.8.)
after construction is completed. Existing trees and shrubs, if left in place,
offer effective protection also.
2~ Topsoiling-this means covering the surface with a less erodible soil.
Other methods may be preferred.
3. Aggregate Cover -th_es_urfa.<:e <:an be covered with crushed stone or gravel.
Can be expensive so is mainly applicable to small areas.
HAlNTEN~NCE
Surfaces should be retreated as necessary.
EEF£~ENLE
1) Fairfax County, Virginia. Erosion Sediment Control Handbook. 1974.
t