A 910/9-75-007
1975
LOGGING ROADS AND
PROTECTION OF WATER QUALITY
U,S. ENVIRONMENTAL PROTECTION AGENCY
REGION X
WATER DJVJSION
1200 SIXTH
SiATTLE, WASHINGTON
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This document is available to the public through the
National Technical Information Service, Springfield, Virginia 22161
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EPA 910/9-75-007
MARCH 1975
LOGGING ROADS AND PROTECTION OF WATER QUALITY
PREPARED BY:
PART I; PART II, pp 273-300
EPA REGION X
WATER DIVISION
1200 Sixth Avenue
Seattle, Washington 98101
PART II, pp 91-272
ARNOLD, ARNOLD AND ASSOCIATES
1216 Pine Street
and
DAMES AND MOORE
Seattle, Washington 98101
for
EPA REGION X
ix-onmtuvrl Protection'
230 Sc.--.. ,; i^ja^bcrn Street
Chicago, Illinois 606QH
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The Environmental Protection Agency, Region X, has reviewed
this report and approved it for publication. Mention of
trade names or commercial products does not constitute
endorsement or recommendation for use.
ENVIRONMENTAL PROTECTION AGENCY
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TABLE OF CONTENTS
Page
List of Tables 7
List of Figures g
INTRODUCTION 11
Purpose 11
Scope 13
PART I: OVERVIEW
FOREST LANDS OF REGION X 19
PHYSIOGRAPHY AND SOILS 19
Terrain 19
General Physiographic and Soil Variations 23
GEOLOGY 35
CLIMATE 38
FOREST STATISTICS 43
Forest Ownership , 43
Logging Road Activity 43
Logging Road Costs 47
EFFECT OF LOGGING ROADS ON WATER QUALITY 51
GENERAL WATER QUALITY PROBLEMS AND PROTECTION CONCEPTS . . 52
Logging Road Sediment 53
water quality problem areas 55
DETERMINING POTENTIAL FOR POLLUTION FROM LOGGING ROADS . . 62
Other Use Classifications 63
standards 63
basin plans 65
WATER QUALITY RISK ANALYSIS 66
SURVEILLANCE AND MONITORING 71
MONITORING NONPOINT SOURCES OF POLLUTION 71
Parameters and Frequency 75
monitoring approaches 76
parameters 78
Use of Water Quality Data 82
REFERENCES 85
PART II: DESIGN CRITERIA
INTRODUCTION 91
SUMMARY AND CONCLUSIONS 96
RECOMMENDATIONS 99
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CONTENTS
Page
ROUTE PLANNING AND RECONNAISSANCE 101
ROUTE PLANNING '. 103
Management-Engineering Dialogue 103
Engineer's Assessment of Management's Decision .... 105
state of the art techniques 106
roads and harvest method relationships Ill
Conclusions 113
ROUTE RECONNAISSANCE '..'.' 113
Factors Affecting Surface Erosion 115
Surface Erosion and Mass Wasting Considerations .... 118
aids 120
aerial photographs 120
topographic maps 122
soil surveys 122
geologic maps 124
other aids 124
field reconnaissance 124
surface erosion 126
mass wasting 133
Civil and Forest Engineering 136
harvest method 136
existing road audit 137
route placement 138
field survey information 142
ECONOMIC EVALUATIONS 145
Cost Analysis 145
Economic Justification 150
DESIGN 153
ROADWAY 154
Horizontal and Vertical Alignment 155
Road Prism 156
excavation 156
embankment 158
balanced construction 160
Road Surfacing 160
Buffer Strips 162
SLOPE STABILIZATION 167
Surface Erosion 167
seeding and planting 167
revegetation objectives 168
seed mixtures 169
planting 171
techniques used in establishing plants 171
when to seed or plant 172
fertilizers 173
mulching
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CONTENTS
Page
mulches and chemical soil stabilizers 175
need for slope protection during vegetation
establishment 177
performance of various mulches and chemical
soil stabilizers 180
mechanical treatment 188
diversions or terraces 189
serrations • 189
roughness and scarification 191
Mass Wasting 192
retaining walls 195
bulkheads 196
reinforced earth 196
rock rubble facing 197
lowering groundwater levels 197
deep rooted vegetation 198
fill placement 199
DRAINAGE DESIGN 200
Ditches and Berms 200
size and placement 201
ditch profiles 205
ditch outlets 207
sloped roadway alternate to roadside ditches .... 207
rock sub-drain alternate to roadside ditches .... 211
Culverts 212
sizing culverts 217
design aspects of culvert installation 220
roadway culverts 220
stream culverts 221
Water Course Crossings 223
sediment features of stream crossing design .... 224
stream crossing methods 227
fords 227
culverts 228
bridges 229
Culvert Outlet Treatments 232
Hydrology 241
logging and roadbuilding 241
subsurface water considerations 243
forest location 244
CONSTRUCTION SPECIFICATIONS 246
Standard Specifications 247
Special Provisions 248
Conclusions 250
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CONTENTS
Page
CONSTRUCTION TECHNIQUES 251
CLEARING AND GRUBBING 252
EARTHWORK 253
DRAINAGE 256
Drainage During Construction 256
Drainage Construction 257
CONSTRUCTION EQUIPMENT 259
MAINTENANCE " 263
DRAINAGE SYSTEM 265
Culverts and Ditches 265
Cut and Embankment Slopes 267
ROAD SURFACE 267
REMEDIAL MEASURES FOR SLIDES 269
Removing Slide Debris 270
Wasting Slide Debris 271
Relocation vs Correction 271
Failure Mechanism Investigation 272
INTERMITTENT AND SHORT TERM USE 273
Intermittent Use 274
roadway 275
stream channel crossings 276
pre-planned crossing 278
existing crossings . . . 279
Short Term Use 281
roadway 281
channel crossings 284
ROAD MAINTENANCE CHEMICALS 285
Dust Palliatives 285
pollution from oil based dust palliatives 287
control of pollution from oil dust palliatives . . . 289
oil spills 290
oontrol practices 291
Other Chemicals 293
salts 293
pulp wastes 297
others 299
REFERENCES 301
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LIST OF TABLES
Table Page
1 Mean Monthly and Annual Variability 40
of Climatic Conditions
2 Construction and Reconstruction Costs 48
of Logging Roads
3 Comparison of Some Stream Classification 64
Systems
4 Guide for Placing Common Soil and Geologic 128
Types into Erosion Classes
5 Unified Soil Classification 129
6 Siuslaw National Forest-Plant Indicators 144
7 Comparison of Annual Road Costs Per Mile, 147
10,000 Vehicles Per Annum (VPA)
8 Comparison of Annual Road Costs Per Mile for 148
20,000 and 40,000 Vehicles Per Annum (VPA)
9 Comparison of Single-lane Versus Double-lane 149
Costs for Three Different Vehicle-Per-Annum
(VPA) Categories
10 Protective - Strip Widths 166
11 Comparison of Cumulative Erosion From Treated 179
Plots On a Steep, Newly Constructed Road Fill
12 Erosion Control and Vegetation Establishment 182
Effectiveness of Various Mulches
13 Maximum Permissible Velocities in Erodible 202
Channels, Based on Uniform Flow in Continuously
Wet, Aged Channels
14 Cross-drain Spacing 209
15 Settling Velocities for Various Particle Sizes 240
10.00 mm to 0.00001 mm
16 Chemicals Used on Logging Roads 286
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LIST OF FIGURES
Figure Page
1 Map of Region X 12
2 Relatively Undissected Slopes 21
3 Highly Dissected Slopes 21
4 Examples of Landslide, Slump Indicators 24
5 Physiographic Provinces 25
6 Soils Developed in Granitic Rocks 28
with Stability Problems
7 Surface Soil Erosion in Batholith 28
Area of Idaho
8 Sedimentation from Logging Road in 31
Cascade Province
9 Continual Road Instability in Pacific 31
Border Province
10 Mass Failure Associated with Logging 33
Roads in Pacific Border Province
11 Mean Annual Precipitation 41
12 Ownership Distribution of Commerical 44
Forest Land, All States, Region X
13 Ownership Distribution of Commercial 45
Forest Land by States Region X
14 Erosion from Long Water Transport 58
15 Culvert Outlets 59
16 First Year Damage to Logging Roads 60
17 Season of Use Damage 60
18 Water Quality Monitoring Approach 79
for Cumulative Impacts
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Figure Pa€e
19 Workload Analysis-Geotechnical Investigations 109
for Timber Sale Roads-Siuslaw National Forest
20 Sediment Movement Down- slope from Shoulders 165
of Logging Roads
21 Soil Losses from a 35 Foot Long Slope
22 Ditch Water Surf ace -Road Subgrade 203
23 Minimum Interceptor Ditch Size 204
24 Berm 204
25 Ditch Placement 206
26 Ditch Outlet Near Stream 206
27 Rock Sub -drain 211
28 Ditch Inlet Structure 213
29 Ditch Inlet Structure with Catch Basin 214
30 Upstream Embankment Face Treatment 222
31 Gabion Ford 228
32 Culvert Outlets 234
33 Culvert Outlet Near Stream 235
34 Pipe Channel Detail 235
35 Rock Dike 236
36 Alternate Pipe Channel Detail 236
37 Gravel Filled Crib Wall 238
38 Energy Dissipating Silo 239
39 Culvert Outlet to Sediment Pond 239
40 Alternate Waste Site 255
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Figure Page
41 Kaniksu Closure 277
42 Modified Culvert Removal
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INTRODUCTION
PURPOSE
The Federal Water Pollution Control Act Amendments of 1972, Public
Law 92-500, set a national goal of water quality which provides for the
protection and prppagation of fish, shellfish, and wildlife and which
provides for recreation in and on the waters. This goal must be achieved
by 1983. The Act mandates that pollution caused by runoff from forest
lands, as well as other nonpoint sources (mining, construction, agri-
culture, etc.), be controlled in addition to the control of point
sources in order to achieve the national goal of water quality.
This report is a state-of-the-art reference on the protection of
water quality in planning, designing, constructing, reconstructing,
using, and maintaining logging roads based on data collected in Region X.
It is intended to be an aid for dealing with nonpoint source pollution
control; and is designed to inform and assist state, federal and local
agencies; industry; and the general public. The report is specifically
intended to assist in the (1) identification of potential hazards to
water quality, and (2) selection of procedures, practices, or methods
suitable for preventing, minimizing, or correcting water pollution
problems. It also is a reference source to other publications, informa-
tion and materials; and it provides some regional data and perspective.
Figure 1 shows the geographical boundaries of Region X.
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UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
Regional Offices
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FIGURE 1 REGION X
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The Environmental Protection Agency has already prepared a report
entitled "Processes, Procedures and Methods to Control Pollution from
Silvicultural Activities", which was published in October, 1973. That
report covers all forest practices and is, therefore, general in nature.
In contrast, this report deals specifically with one important aspect
of forest practices.
"Silvicultural activities" comprises a major portion of those
forest land activities in Region X that can impact water quality.
"Silvicultural activities" is used in a broad context; and covers the
actions and results of all forest harvest, production, management and
protection systems. Some of the categories of activities included are:
logging roads, harvesting methods, silviculture systems, residue manage-
ment, reforestation, and use of chemicals.
Of all the types of silvicultural activities, improperly constructed
and inadequately maintained "logging roads" are conceded to be the
principal man-caused source of sediment. Although different logging
systems have different road access requirements, all involve to some
degree the construction or reconstruction and use of logging roads.
SCOPE
"Logging Road", as used in this document, refers to truck roads
which are built or used mostly for log hauling or logging operations.
These roads are often subsequently used for the protection and manage-
ment of successive timber crops and for other forest access purposes.
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The text deals with a range of logging road design standards—
varying from low-speed narrow, unsurfaced roads to moderately high
speed, rocked or paved roads. Paved, two-lane (or more) roads that
have design characteristics similar to or higher than secondary state
highway standards are beyond the scope of this document.
Although logging haul roads (within the standards range described
above) are the primary focus, most of the principles and techniques
described have a wider application and can be extended to include all
other forest access roads which are similar in standard but are
constructed for different specific purposes—e.g., for mining, grazing,
recreation and fire protection—or for multi-purposes.
It should be recognized that roads are not an independent entity
and must be considered in an overall context. For example, in relation
to the total physical systems operating in a watershed, such factors as
the total area of land surface exposed by roads at a given time, effects
of runoff from roads on channel stability and the degree to which a
transportation system can be effectively maintained may be important.
Another important interrelationship is that of the road to total
planning of a silvicultural activity. For instance, from a water quality
consideration viewpoint, impacts of a total harvesting system must be
examined—including logging methods and logging roads. For example,
a skyline cable system might result in a low total impact, including
fewer roads. However, individual roads might require special design
standards to accomodate the overall low impact system.
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The foregoing discussion is for illustration only. Detailed
examination of total systems' interrelationships is beyond the scope
of this report.
Region X, excluding interior Alaska i/, served as the specific
study area for the compilation of this report. While state-of-the-art
information was compiled primarily from within Region X, relevant data
from outside the Region was also evaluated and used as appropriate.
Information from scientists and practitioners outside the Region
indicates that most of the principles and many of the techniques in
this report will have application to a much wider area that just
Region X. As can be noted throughout the report, an important key
for incorporating water quality management needs into logging road
activities is the intelligent tailoring of available technology to site
specific application. This applies irrespective of geographical
location.
-I Two other reports should be useful for dealing with interior
Alaska conditions:
Lotspeich, F. B. 1971. Environmental Guidelines for Road
Construction in Alaska. Alaska Water Laboratory, U.S.
Environmental Protection Agency, College, Alaska.
Lotspeich, F. B. and Helmers, A. E. 1974. Environmental
Guidelines for Development Roads in the Subarctic.National
Environmental Research Center, U.S. Environmental Protection
Agency, Corvallis, Oregon.
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PART I
Overview And Setting Of Region X
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FOREST LANDS OF REGION X
The information in this section describes some of the physical
features of Region X. It is intended to facilitate Region-wide under-
standing and perspective of potential water quality degradation.
Specific principles and application are discussed in Part II and in
cited references.
Although significant features are discussed separately, most of
them are not independent. They should be viewed together, and in the
context of the relationship of logging roads to the water handling and
resistance to soil movement—either surface erosion or mass movement—
characteristics of a watershed.
It should be noted that soil movement—including mass failure—
occurs naturally. The emphasis in this section, however, is "man-caused"—
i.e., road related—events.
PHYSIOGRAPHY AND SOILS
TERRAIN
"Terrain", as used in this report, refers to external character-
istics (features) of the land such as slope, shape, drainage density,
smoothness (or unevenness), slumps and slides. The Encyclopedia of
Geomorphology (10) describes geology-terrain relationships and descrip-
tive classifications.
This section is intended only to illustrate the importance of terrain
factors in anticipating and estimating potential impacts of logging roads.
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Discussion of specific elements, evaluation criteria and procedures for
dealing with these factors are discussed in more detail in Part II.
Several terrain features have been specified or implied to be
important in planning and constructing stable roadways. Brown (l)
cites aspect, elevation and steepness of slope. Way (2) uses topography,
drainage—including texture (number of streamcourses) and pattern—and
vegetation for terrain analysis. Kojan, et al (3) use slope gradient,
sub-surface structure and evidence of landslides. Other authors have
cited similar factors.
Several terrain features consistently emerge as important indicators
which can aid in estimating the probable impact of logging roads on the
terrain and resultant impact on water quality. These are:
(a) drainage density (degree to which streamcourses
dissect the land);
(b) slope (gradient, length, shape, position on the slope);
(c) geologic factors such as substrata fracture planes
(not always visible externally, but may be observable
in landslides); and
(d) "hummooky" slopes.
Generally, the more drainage that dissects the landscape, the more
acute the necessity to plan for avoiding water quality impacts in
constructing and stabilizing roads. Figure 2 illustrates relatively
undissected ("smooth") slopes, and Figure 3 highly dissected slopes.
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FIGURE 2 RELATIVELY UNDISSECTED SLOPES - ESPECIALLY
IN FOREGROUND
FIGURE 3 HIGHLY DISSECTED SLOPES
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Steepness and length are among the more obvious slope indicators.
Swanston and Dyrness (4), Swanston (44), Burroughs et al (5) and others
describe relationships of slope gradient to potential soil displacement.
Usually, the steeper and more sustained the slope, the greater the risk
and more frequent the occurrence. There is no precise universal rule
that links a given slope steepness to a specific set of problems because
other factors must be considered. For example, where the terrain is
relatively undissected and relatively stable, road-triggered soil move-
ment problems may become acute when sustained slopes are 60 to 65 percent
(or steeper). However, where the terrain is highly dissected and
relatively stable, impacts may become severe on slopes 40 to 45 percent
(or steeper). If soils or geologic substrata are unstable, major impact
problems may occur on slopes of 30 percent or less. Kojan et al (3)
reported that few debris slides occurred on slope gradients less than
50 percent. However, they also reported an increasing incidence of
translational-rotational earth slides (deep slides associated with sub-
strata failure) on slopes steeper than 30 percent in certain rock material
types.
Of all ownerships in Region X, roughly 1/4 of the commercial
forest land (CFL) is on slopes steeper than 45 percent and about 1/5
is on slopes steeper than 55 percent (6). The 45 and 55 percent figures
are arbitrary demarcations of "steepness".
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Kojan et al (3) state "The type and distribution of existing
landslides, both active and dormant, is the single most important
factor determining the performance and impact from roads..." Others
have reported or stated that evidence of past mass soil movement is
an important clue for anticipating the results of man's activities on
unstable areas. Figures 4 and 10 illustrate some examples of mass
soil movement as related to terrain, soils, geology and climate.
GENERAL PHYSIOGRAPHIC AND SOIL VARIATIONS
The major physiographic areas within the Region may be divided into
areas of similar geologic structure and climate. These provinces can be
separated into major subdivisions, (Figure 5), each subdivision having
significantly different characteristics that affect road planning, design,
construction, maintenance and use.
Road construction, timber harvest, and many other land management
activities have an effect on soil and water resources. It is important
to understand the effect and potential consequence relationships. Soils
can be grouped according to similar characteristics and general condi-
tions as topography, elevation, climate, water resources and land use.
Groupings may include broad areas with similar soil characteristics. The
objective of most groupings is to identify areas of land that are rela-
tively uniform in many important relationships.
The general physiographic variations and soils discussion is
intended only for a broad regional perspective of soil and land character-
istics. The optimum level of information for minimizing water quality
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LANDFLOW
ROAD TRIGGERED DEBRIS SLIDE ALONG
A PARALLEL SUBSTRATUM PLANE
FIGURE 4 EXAMPLES OF LANDSLIDE, SLUMP INDICATORS
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VJl
PHYSIOGRAPHIC
PROVINCES {
_ -i |
Province Boundary
Sub-Province Boundary
ASIN AND RANGE
FIGURE 5
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impacts from logging roads is an on-site assessment or site specific
field evaluation of proposed road locations to determine soil and
geological characteristics on a project basis. See Section on Route
Planning and Reconnaissance, Part II.
Various authors have divided the Region differently. The divisions
used in Figure 5 are largely those outlined by Allison (7). Areas
treated as subprovinces by some authors are considered provinces by
others. However, the basic subdivisions are nearly the same. Soils
and geologic information for this section come from several sources:
Baldwin (8), Burroughs (5), Campbell (9); several soils survey reports
for parts of the Region; and discussions and field observations with
forest land managers.
The seven physiographic provinces that lie partly or wholly within
the Region (Figure 5):
Northern Rocky Mountains.
Middle Rocky Mountains.
Columbia Intermontane.
Basin and Range.
Cascade Mountains.
Pacific Border.
Pacific Mountain System (Alaska). I/
ik' Not shown in Figure 5
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Northern Rocky Mountains Province
The province includes parts of northeastern Washington and northern
and central Idaho. It is characterized by high mountain ridges and deep
intermontane valleys eroded from rocks of moderately complex structure.
The irregular mountains of Central Idaho developed from erosion of
massive granite rocks. Much of the province is submature to mature in
the geomorphic cycle.
Logging road construction is particularly damaging in highly erodible
areas of the province, such as the 41,500 km2 (16,000 square miles) Idaho
Batholith. The Batholith of Central Idaho consists of soils developed
in granitic materials. These soils present erosion problems, as shown
in Figure 6. The Batholith is characterized by steep topography and
shallow to moderately deep, coarse-textured soils overlying granitic
bedrock. In parts of the province, the concentration of coarse sand
increases the susceptability to erosion, during road construction.
Surface soil erosion is the major problem in much of the area as shown
in Figure 7, where slopes are less than 60 percent. Where slopes are
greater than 60 percent, mass erosion is an important problem.
Middle Rocky Mountain Province
A part of the Middle Rocky Mountain Province extends into southern
Idaho, where northwesterly trending mountain ridges and valleys have
eroded from folded, thrust-faulted, or tilted rocks. The valleys are
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FIGURE 6 SOILS DEVELOPED IN GRANITIC ROCKS
WITH STABILITY PROBLEMS
FIGURE 7 SURFACE SOIL EROSION IN
BATHOLITH AREA OF IDAHO
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about 1,850 meters (6,000 feet) above sea level, with ridges 600 to
1,200 meters (2,000 to 4,000 feet) higher.
The logging road problems in the province are principally related
to mass gravity soil movements, such as slumps. Mass failures are
a-ssociated with sedimentary deposits of sandstone, shale, siltstone,
limestone, and volcanic ash. Surface soil erosion may also cause
water quality problems in some areas.
Columbia Intermontane Province
This province includes the Columbia Basin, Central Mountains,
Harney High Lava Plains, Malheur-Owyhee Upland, and Snake River Lava
Plain.
A relatively small percentage of the province is managed for wood
fiber production. Logging road activities are limited as compared to
the major timber producing provinces (Cascades and Pacific Border).
Steep slopes (greater than 60$) are few and are associated with
isolated basaltic buttes or canyons. Because of the general climatic
conditions (low precipitation), water quality problems relating to
logging roads are rather localized, with surface soil erosion being the
principal problem.
Basin and Range Province
The northern edge of the Great Basin section of the Basin and Range
Province extends into south central Oregon and into southern Idaho. The
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logging road conditions are generally similar to those discussed for the
Middle Rocky Mountain Province.
The part in Oregon in contrast to Idaho is a youthful high lava
plain. Small cinder cones are numerous in the western portion, where a
sheet of pumice from Mt. Mazama extends over a large area, 26,000 square
kilometers (more than 10,000 square miles). This pumice sheet greatly
modifies vegetation, surface runoff, and land use. With disturbance for
logging road construction and extensive use during the summer or dryer
seasons, the soils become very friable and susceptible to surface erosion.
Because of the relatively gentle topography in much of the area and the
moderate-to-rapid soil permeability, water quality problems due to logging
roads are localized.
Cascade Mountains Province
The Cascades of Oregon and the southern half of Washington are a
broad upwarp composed of a basal portion of tuffs, breccias, lavas,
mudflows, a thick middle section of basalt, and an upper section of
andesites and basalts that form the less dissected High Cascade lava
platform.
Soils in the province are generally weakly developed and have been
influenced by volcanic ash and pyroclastic materials. There is a
potential for severe surface erosion on steep slopes when the organic
layer is removed. The problem is accentuated by the abundance of streams
and surface water and high precipitation in much of the area. Figure 8
illustrates some of the serious water quality impacts associated with
logging roads in this province.
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FIGURE 8 SEDIMENTATION FROM LOGGING ROAD
CASCADE PROVINCE
FIGURE 9 CONTINUAL ROAD INSTABILITY PACIFIC
BORDER PROVINCE
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Pacific Border Province
The province includes the Klamath-Siskiyou Section, Coast Range,
Olympic Mountains, and Willamette-Cowlitz Puget Lowlands (Figure 5).
Compared to the other provinces the Pacific Border province has some
of the most severe and continuous water quality impacts associated with
logging roads. The major problem areas are the coastal areas of
Washington and Oregon and the Olympic Peninsula. These areas are
characterized by high precipitation, as shown in Figure 11. Soils are
developed in a wide range of materials, principally sedimentary deposits.
They have a variety of textures and drainage characteristics. With the
dominance of very high rainfall and steep slopes, many of the soils,
especially those in disturbed conditions (some undisturbed), have a high
degree of continual instability as shown in Figure 9.
Mass soil failures associated with logging roads as shown in Figure 10,
occur in the province. The water quality impacts are particularly acute
in steep headwall areas of drainages. These drainages are the principal
tributaries to many of the major streams and water bodies of the area.
A more detailed discussion of the nature, source and extent of the erosion
problem and recommended procedures for dealing with this problem are
discussed by Burroughs (5), Brown (l), and Dyrness (35).
Pacific Mountain System
This coastal province extends from the southern boundary of Alaska
to the Aleutian Islands (41). However, the following discussion is
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FIGURE 10 MASS FAILURE ASSOCIATED WITH LOGGING ROADS
IN PACIFIC BORDER PROVINCE
Photograph taken from road edge looking downslope
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limited to the southeast portion of this province, from the southern
border to Yakutat Bay (42).
The southeast area is composed of a mainland strip and a wide
belt of rugged islands with summits generally 750 to 1,050 meters
(2,500 to 3,500 feet) in elevation. Most of the mainland strip is
deeply indented by fiords. Its peaks rise to about 3,050 meters
(10,000 feet) along the Canadian Border. Many of the inter-island water-
ways and major fiords and streams occupy long linear depressions, most
prominent of which is Chatham Strait, a deep trench 6 to 24 kilometers
(4 to 15 miles) in width and some 320 kilometers (200 miles) long.
Soils on the broad coastal plain at Yakutat are shallow to deep,
gravelly, sandy to silty loams in association with moss peats of variable
thickness and depth. Small amounts of waterlaid sands, gravels, and silts
occupy broad stream channels and low areas adjoining the fiords. Logging
road limitations are slight on well drained soils, becoming moderate to
severe with increasing wetness.
Soils on the moraines and foot slopes bordering the plain are shallow,
stony and gravelly loams with finer sediments in the vicinity of fiords
and peat deposits in depressions. Limitations for these soils are moderate
to severe for logging roads, depending on slope. Soils of steep hills
and low mountain slopes are very gravelly silt loams over shallow bedrock
in association with similar soils having a firm subsoil and occupying
low moraines. Peat deposits occupy depressions extensively throughout
these soils. Limitations are moderate to severe for use of these soils
for road construction (43).
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GEOLOGY
Geology as it relates to the physical character and areal
distribution of various rock types plays a major role in controlling
or effecting the quality of water in streams and rivers. Geology governs
the character of soils as rock formations are the parent material for
most soils. The erodibility of many sedimentary rock formations is
directly related to the degree or amount of cementation. Fine-grained
unconsolidated formations can "be easily eroded while tightly cemented
sediments may be very resistant to erosion.
The physical properties of the rock formations also play an important
role in the quantity and time distribution of runoff from a watershed.
Rock formations having high porosity and permeability will adsorb water
during wet seasons and discharge it to streams throughout the year. The
Metolius River in Oregon is an outstanding example of a large stream
being maintained at an almost uniform flow throughout the year by the
porous and permeable rocks of the area. Conversely, rocks of low porosity
and permeability do not have the capability of adsorbing and transmitting
large quantities of water. Consequently, streams heading in areas under-
lain with these rocks exhibit a" tremendous fluctuation in flow from season
to season and in some cases may respond rapidly to almost every heavy
rainstorm. The general geologic character of a drainage basin can
generally be interpreted by how a stream draining the area responds to
climatic changes.
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Construction within a drainage basin may not measurably effect the
total loading of sediment being transported by a stream, but it can
change the seasonal distribution of the load. A small amount of sediment
washed or pushed into a stream in the late shimmer or early fall months
may have a marked effect on water quality, while a similar increase in
load during high water periods may be undetectable.
Rock types, as they relate to water quality effects, can be divided
into three principal groups:
1. Volcanic Rock
2. Intrusive and Metamorphic Rocks
3. Sedimentary including Pyroclastic Rocks
Volcanic rocks are very common to many forested areas of the Pacific
Northwest. They include the basaltic and andesitic lava flows that
underlie a large part of the Cascade Mountain Range in Oregon and in the
southern part of Washington. They also underlie the Blue Mountains in
Southeastern Washington and Northeastern Oregon.
Most volcanic rocks are jointed which provides for the adsorption
and storage of water. Permeable lava flows and permeable contact zones
between flows generally provide for the movement of water through the
formation. Volcanic rocks are the source of many of the very large
springs in the Region.
In some of the more humid areas of the Region the older volcanic rocks
have been weathered into red lateritic clays. When disturbed or naturally
eroded, these weathered lavas can create very turbid water. In the dryer
36
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areas of the Eegion or in areas underlain with younger volcanic rocks,
as the High Cascade area in Oregon, the volcanic rocks are relatively
unweathered and are resistant to erosion and generally contribute to
excellent water quality.
Metamorphic and intrusive rocks which include gneiss, granite and
grandiorite are common to the Northern Cascades in Washington, North
Central and Northeastern Washington, much of central Idaho, and the
Wallowa and Siskiyou Mountains in Oregon. These rocks have relatively
few joints or cracks and generally do not adsorb or transmit large quanti-
ties of water. Streams draining unweathered rocks of this group gener-
ally have large seasonal fluctuation and respond rapidly to rainstorms.
Intrusive rocks in the early stage of weathering break down into a sandy
material composed chiefly of individual crystals of feldspar. Continued
weathering produces kaolinitic clay that can be easily eroded when
disturbed.
Sedimentary rocks which are composed of fragments of other rock
types exhibit a very large range in porosity and permeability, ranging
from an almost impermeable glacial till to very permeable open-work
gravel formations that are almost void of sand and silt fractions.
A large part of the Coast Range in Oregon, the Willapa Hills in
Washington and most of southeastern Alaska are underlain by sedimentary
rocks. Because of the widespread occurrence of volcanism in the Region,
a very large part of the sedimentary rocks are composed of volcanic ejecta
consisting of pumice and ash. These pyroclastic materials are composed
37
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chiefly of volcanic glass, weathered to bentonitic clays. These clays
are easily eroded, and can create widespread turbidity problems and also
serious engineering problems from slides in road construction. The Corps
of Engineers in studying the water turbidity problems in the Rogue River
Basin of Oregon in connection with the construction of the Lost Creek
Dam found that the tributary stream basins underlain with pyroclastic
sediments were the chief areas contributing suspended material to that
river system.
Detailed geologic maps should be' a prerequisite to any large develop-
ment that will disturb the landscape. Unfortunately, most geologic maps
do not have the details necessary to identify rock permeabilities, degree
of weathering, erodibility, and such hazards to construction as the
probability of slides or slumping. As all of these factors can play an
important role in subsequent water quality effects arising from road
construction and use, a geologic evaluation of the proposed construction
area should be a part of the design of any project. Equally important
however is the subsequent use of a geologist to evaluate conditions
encountered during construction.
CLIMATE
Climate considerations are essential for logging road planning,
design, construction, maintenance and use. Climate, as with soils,
terrain and other physical considerations, varies widely throughout the
Region. It is apparent from this wide variability, that an understanding
of site specific conditions is essential to minimize impacts from logging
38
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roads. Pollution from sediment, deicers and oils used in road
maintenance are greatly influenced by climate.
The wide diversity of precipitation and temperatures for January,
July, and annually for dominant forested areas is shown by the mean
monthly data in Table 1 for Seattle near the Pacific Coast; Meacham,
Oregon and Potlatch, Idaho inland; and Juneau in Southeastern Alaska.
Figure 11 illustrates the general regional pattern (excluding Alaska)
of mean annual precipitation. More detail maps are essential for
project planning. These maps are available from the U.S. Weather
Bureau.
PACIFIC NORTHWEST
Precipitation (including both rain and snow) generally increases from
south to north, from east to west, and from valleys to mountains. The
general movement of storms is easterly from the Pacific Ocean. Annual
precipitation varies from 180 centimeters (70 inches) on the southern
end of the coastal ranges to more than 380 centimeters (150 inches) on
the north. There is also wide variability within some general areas,
for example, rainfall varies from approximately 410 centimeters
(160 inches) on the northwest tip of the Olympic Peninsula to less than
50 centimeters (20 inches) in the Dungeness area, 130 kilometers (80 miles)
to the east. Inland eastward from the coast, precipitation decreases in
the Puget Sound—Willamette Trough, increases again in the Cascades,
drops very low in the arid central Washington valleys and plateaus, and
rises again in the Northern Rocky Mountain Province.
39
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TABLE 1
MEAN MONTHLY AND ANNUAL VARIABILITY OF CLIMATIC CONDITIONS IN REGION
Period
Precipitation
Temperature
January
July
Annually
January
July
Annually
January
July
Annually
January
July
Annually
cm
13
3
86
10
3
84
3
3
64
10
13
140
inches
Seattle, Washington
5
1
34
Meacham, Oregon
4
1
33
Potlatch, Idaho
3
1
25
Juneau, Alaska
4
5
55
°C
5
19
12
-3
17
7
_2
19
8
-4
13
4
OF
41
66
53
26
63
44
29
66
47
25
55
40
40
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ENVIRONMENTAL PROTECTION AOENCT
tfOION X
1300 SIXTH AVENUE UATTU, WASHINGTON tRHM
WASHINGTON, OICOON, * IDAHO
ITE MEAN ANNUAL
PRECIPITATION
SCALE 1:1,000,000
DATE COMPLETED
JULY, 1974
DRAWN BV ^
CHECKED BY
&7
SCALE OF MILES
FIGURE 11 MEAN ANNUAL PRECIPITATION
-------
Snow is an important form of precipitation over most of the Region.
Mountain snowpacks furnish much of the summer streamflow to the larger
rivers. Snow accumulates from December through March, and melts mainly
from April through July. Stream throughout the Region drops to low
levels in summer and stream temperatures increase.
Temperatures are moderate in coastal areas where, because of marine
influence, there is little frost in winter. In the interior the climate
is continental with cold winters and hot summers; the winters are longer
and summers shorter at higher elevations.
SOUTHEAST ALASKA
The climate is mostly maritime with considerable rain and moderate
temperatures. The south coast averages 200 wet days per year, while
Raines and Skagway in the north average less than 100. Transitional
climate occurs in higher mountains of the mainland.
Regional annual precipitation in the form of snow and rain varies
from about 510 centimeters (200 inches) at Port Waller, 391 centimeters
(154 inches) at Ketchikan, 155 centimeters (61 inches) at Raines and
140 centimeters (55 inches) at Juneau. Mean daily January temperatures
are -3°C (27°F) at Yakutat, 2oc (35°F) at Ketchikan and -4°C (25°F) at
Juneau. Mean daily July temperatures range from 12°C (54°F) at Yakutat,
H°C (58°F) at Ketchikan and 13°C (55°F) at Juneau. The rugged terrain
greatly influences temperatures and the distribution of precipitation,
creating considerable variations in both within relatively short distances
(13).
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FOREST STATISTICS
FOREST OWNERSHIP
There are about 25 million hectares (65 million acres) of commercial
forest land in Region X (14). "Commercial Forest Land" is defined as
forest land producing or capable of producing crops of industrial wood
(in excess of 20 cubic feet per acre per year) and not withdrawn from
timber utilization (14). Ownership distributions for Region X and for
individual states are shown in Figures 12 and 13 (15).
"Coastal Alaska" as used in this report is a geographical area
described by the Pacific Northwest Forest and Range Experiment Station,
U.S. Forest Service (45). It includes southeast Alaska and a narrow
zone along the coast north to Kodiak Island. The remainder of the state
is termed "Interior Alaska."
There are about 43 million hectares (106 million acres) of forested
land in Interior Alaska. By the above definition, these are not classified
as "commercial forest land." However, commercial logging is being conducted
in some of the Interior forests. As noted previously in this report,
other information dealing with Interior Alaska conditions has been
published.
LOGGING ROAD ACTIVITY
As of January 1, 1974, there is estimated to be about 400,000
kilometers (250,000 miles) of logging roads, all ownerships, in Region X
(16). Within each State, the approximate totals, were:
43
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59%
17%
PRIVATE (Industrial)
PRIVATE (Farm & Misc)
COUNTY A MUNICIPAL
STATE
FEDERAL
TOTAL COMMERCIAL FOREST LAND: 26 MILLION HECTARES (65 MILLION ACRES)
FIGURE 12 OWNERSHIP DISTRIBUTION OF COMMERCIAL FOREST LAND,
ALL STATES, REGION X
-------
n
less them 1% H
negligible E
6% 9
93% •
COASTAL
ALASKA
13 MILLION HECTARES
(5.6 MILLION ACRES)
PRIVATE (IND)
PRIVATE (FARM A MBC)
COUNTY A MUNICIPAL
STATE
FEDERAL
IDAHO
6.1 MILLION HECTARES
(15.2 MILLION ACRES)
WASHINGTON
7.4 MILLION HECTARES
(18.4 MILLION ACRES
OREGON
10.4 MILLION HECTARES
(25.7 MILLION ACRES)
FIGURE 13 OWNERSHIP DISTRIBUTION OF COMMERCIAL FOREST LAND
BY STATES REGION X
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Oregon
Washington
Idaho
Alaska (Coastal)
175,000 kilometers (110,000 miles);
155,000 kilometers (95,000 miles);
70,000 kilometers (45,000 miles); and
less than 5,000 kilometers (3,000 miles),
On the average, including all ownerships, about 13,000 kilometers
(8,000 miles) of new logging roads are built each year in the Region, and
roughly 6,100 kilometers (3,800 miles) are rebuilt (16). "Rebuilding"
(reconstruction) means relocating, substantially altering the original
road prism, or reexposing stabilized cut and fill slopes of existing roads.
Although rebuilding a road does not usually add new roads to the system,
this activity is often similar to construction in potential water
quality impacts.
The estimated average total miles of logging roads built every
year in each state of Region X are:
Oregon
Washington
Idaho
Alaska
(Coastal)
Kilometers
5,700
3,400
4,400
1,600
2,600
1,100
300
Under 100 rebuilt
(Miles)
(3,500)
(2,100)
(2,700)
(1,000)
(1,600)
( 700)
( 200)
built
rebuilt
built
rebuilt
built
rebuilt
built
46
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LOGGING ROAD COSTS
Road construction costs vary considerably. Factors which influence
this include:
(a) standard of road;
(b) amount of road surfacing needed and location
of suitable surfacing;
(c) number and size of culverts and bridges;
(d) difficulty in excavating material—amount
of rock, terrain, soil types, etc;
(e) density and size of vegetation to be cleared
and disposed of;
(f) organizational policies;
(g) amount and kinds of specialized structures and
practices—e.g., bin walls, end hauling, etc.;
(h) overhead, engineering, labor and materials costs.
There is a noticeable and consistent difference between construction
costs east and west of the Cascade Mountains in both Oregon and Washington.
In these States, the road cost per mile west of the Cascades may range
from two to ten times more than that east of the Cascades. Reconstruction
has a similar cost pattern; but also varies according to the degree of
reconstruction.
Table 2 summarizes construction and reconstruction for cost range
and for unit costs (16).
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TABLE 2
CONSTRUCTION AND RECONSTRUCTION COSTS
OF LOGGING ROADS IN EPA REGION X
a — cost per kilometer, thousands of dollars
b — cost per mile, thousands of dollars
Coastal
Oregon
a_ b_
Average 11 17
Minimum <1 1
Maximum 199 320
Average 5.5 .5
Minimum <.5 <.5
Maximum 15.5 25
Washington Idaho Alaska
a b_ a b a
Construction Costs
8 13 7 11 43
<1 <1 <1 <1 25
68 110 39 62 75
Reconstruction Costs
3.5 6 3 5 6
<.5 <.5 <.5 <.5 4.5
18 29 15 24 8.5
b_
70
40
120
10
7
14
The estimated total average annual investment, all ownerships, in
construction and reconstruction of logging roads is about $156,000,000
(16). By states, the approximate investment is as follows:
Oregon
Washington
Idaho
Alaska
(Coastal)
$59 million construction
18 million reconstruction
36 million construction
6 million reconstruction
18 million construction
4 million reconstruction
15 million construction
Less than one million reconstruction
48
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These costs and investments include a range of variations in the
types and usage of water quality control measures including the
structures needed for this control. Some measures appear to be used
consistently by most people, others more sporadically, and some only
rarely or by only some organizations.
49
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EFFECT OF LOGGING ROADS
ON WATER QUALITY
Water pollution is defined as man-made or man-induced alteration of
the chemical, physical, biological, and radiological integrity of water
(PL 92-500, Sec. 502(19)). Implicit in the definition are various uses
of water to be protected. Water quality generally relates to a degree
of excellence of conformance to standards established for various uses.
The discussions in this section are based on the assumptions that:
(a) Construction, reconstruction and use of logging roads
will continue in the future.
(b) The use of logging systems requiring low density road
systems will increase in some areas.
(c) Impacts on water quality caused by roads can be reduced
but not completely eliminated.
(d) It is usually cheaper and more effective overall, to
prevent problems from occurring than to correct problems
afterward.
(e) Consistent application of preventive technology that
applies to areas of potential hazards will result in
significant reductions of water quality impacts.
(f) Current water quality standards probably do not adequately
reflect realistic upper limits for nonpoint sources of
water pollution in some areas.
51
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GENERAL WATER QUALITY PROBLEMS AND PROTECTION CONCEPTS
Forest lands are the best source of high quality water on a yield
per hectare "basis. In comparison to runoff from other major land uses
as agriculture, grazing, etc., runoff from forests is high in yield and
generally of good quality. It is well documented that the quality of
this water may be affected by the number and location of forest roads
in watersheds and the manner in which they are constructed and main-
tained (1, 5, 17, 18, 19, 20).
Potential water quality impacts caused by logging roads are best
dealt with by prevention or by minimizing their effects, rather than
attempting to control them after the fact (21). For example, controlling
sedimentation from a mass soil movement and channel scour area often is
virtually impossible after the occurrence (short of a massive correction
and/or backstop system).
Practices designed to prevent short-term and long term problems may
sometimes cost more initially; however, evaluation of available alterna-
tives and options now in use should result in workable solutions.
Hartsog and Gonsior (22), in a report analyzing the performance of
a road project in Idaho, indicate that, "a gap remains between the possible
and achieved results in many road projects." In some instances where all
apparent practical measures were taken to achieve a quality result,
problems still occurred. Similar gaps between possible and achieved
results were observed during the EPA field review of logging roads in
Region X.
52
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The above information suggests that:
(a) A strong preventative approach is not necessarily free of
failure, and supplemental backstop corrective measures
usually are also necessary to minimize sedimentation, and
(b) Although much progress is being made in recognizing the
potential water quality impacts of roads, additional
improvements are still necessary to minimize many of the
common recurring road problems.
LOGGING ROAD SEDIMENT
Sediment has consistently been identified as the most significant
pollutant resulting from timber harvesting (l, 19, 20, 23, 24, 25).
Sediments are produced from forest lands by surface erosion, mass soil
movement, and channel erosion. Logging road activities may influence
all of these and especially accelerate the surface erosion and mass soil
movement.
There is considerable evidence that logging roads are the primary
source of accelerated erosion and sedimentation caused by silviculture
activities. Packer (23) concluded that, "of man's activities that disturb
vegetation and soil in mountainous terrain, few cause more damage to the
quality of water than the construction of roads." Many others have sub-
stantiated Packer's conclusion.
In central Idaho, Megahan and Kidd (17) reported that nearly 84
percent of all sediment resulting from surface erosion on logging roads
53
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was produced during the first year after construction. Sediment
production decreased substantially after the first year to less than
10 percent the second year, and less than 3 percent annually for the
remaining four years of the study. The Frewing Committee Report on
Management of Forest Resources in the Bull Run Watershed near Portland,
Oregon (40), indicates that on the basis of regional statistics,
70 percent of the sedimentation in streams resulted from road construc-
tion rather than any particular type of logging practice.
In a study by Fredriksen (38) in the Oregon Cascades, 1.65 miles
(2.66 kilometers) of road were constructed in a steep 250 acre
(101 hectare) watershed. Immediately after construction, storms caused
the stream to carry 250 times (1,850 mg/l) more sediment than the
undisturbed watershed nearby. Within two months, the sediment content
diminished to only slightly above preconstruction levels. This research
and other similar research (17, 26, 27) and field observations as shown
in Figures 7 and 9, all demonstrate the essential need for a concurrent
erosion control plan with road construction.
The most common and significant water quality impact from forest
roads in much of the Region results from mass soil movements as discussed
in the section on major physiographic and soil variations. In most cases,
mass soil movements are caused by undercutting unstable slopes, improperly
constructing embankments, wasting of excavated materials on steep unstable
slopes, and drainage system failures (5, 28). Evaluation of the mass
failure potential of a road corridor is essential to minimize water quality
impacts.
54
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The compacted surfaces of logging roads often carry road surface
runoff, with sediment during storms (l). Roads increase surface
erosion by baring soil and concentrating runoff. The amount of surface
erosion associated with roads is proportionate to the road density. It
is well documented that as the miles of road increase in a watershed,
the potential for water quality degradation also increases. Rosgen (29)
used road density as a factor in evaluating and predicting response of
a watershed to logging and road building activities.
To minimize water quality impacts from roads, prevention and control
measures must be considered in every part of road planning, design,
construction, maintenance, and use. The erosion control plan (plan of
implementation for minimizing erosion such as seeding, mulching,
terracing, use of structural measures, etc.) must be part of the planning
process with erosion control measures being applied concurrently with
construction, whenever practical.
Water Quality Problem Areas
It is obvious from field reviews of road activities in much of the
Region that road construction is being extended further into rugged
topography. Many of the easily accessible commercial forest sites have
been harvested. Therefore, as the difficulty of construction (because of
topography, geology, soils, climate, etc.,) increases, the potential of
water quality impacts near sources of good quality water in mountainous
watersheds also increases. As suggested by Tarrant (30), the key to
55
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producing multiple benefits from the forest, including good quality
water, is the amount of care that the forest watershed manager can and
will exert in all his activities.
Several recurring water quality problem areas were observed during
field reviews of logging roads in the Region. The most frequently
recurring problems or problem situations are summarized below. Most of
the items listed are interrelated. For example, an adequate reconnaissance
survey should identify and assess potential location, stability and
drainage problems. The items are separated only for discussion purposes
to identify the most frequently observed water quality related aspects
of logging road planning, design, construction, maintenance and use
problems. This listing is not intended to be comprehensive or to
include all of the problems related to roads. Also, items are not
listed on the basis of priority.
Reconnaissance Survey, Looat-Lon, Unstable Slopes and Drainage. The
lack of an adequate reconnaissance survey causes many water quality-
related road problems. Many potential water quality impacts can be
identified, minimized, or eliminated as a result of an adequate
reconnaissance survey. Site specific information on such factors as
geology, soils and climate should be obtained during the survey, as
discussed in Part II. Proper road location initially will avoid or
minimize water quality impacts. In general, as the proximity of roads
to streams and water bodies increases, the potential of degrading water
quality also increases.
56
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In steep or unstable topography, road construction often causes
greater soil disturbances, especially mass movement, than any other
forest activity. In many instances, stability is an inherent problem
because of the limitations of the site. Water volume and velocity
controls detachment and transport of soil particles. Water running
long distances (over 427 meters, 1,400 feet) observed in some areas
along roadsides, in ditches, or down the roadbed is one of the most
common occurrences that degrade water quality in the Region. Erosion
from long transport distance is shown in Figure 14. Lack of energy
dissipators at culvert outlets to prevent water from being discharged
directly on fill slope is also a common cause of erosion and subsequent
sedimentation; culvert outlets with and without dissipators are illus-
trated in Figure 15. Adequate subsurface drainage is essential to
reduce mass movement events. Water adds a buoyancy to the soil mass
reducing shearing resistance resulting in mass failures. Avoiding
concentrations of water in road cuts and fills will help minimize mass
failure problems.
Erosi-on First Hear After Construction^ Season of Use. Because
freshly-exposed material is highly susceptible to erosion, it is
estimated that approximately one-half to two-thirds of the erosion from
a road occurs during the first year after construction, except for mass
failure related discharges. An example of first year damage is shown in
Figure 16. Heavy road use during periods of precipitation and soil
saturation may result in immediate water quality degradation, as shown
57
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FIGURE 14 EROSION FROM LONG WATER TRANSPORT.
58
-------
WATER QUALITY IMPACT FROM LACK OF ENERGY DISSIPATOR.
MINIMAL WATER QUALITY IMPACT WITH
USE OF CULVERT DISSIPATOR.
FIGURE 15 CULVERT OUTLETS
59
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09
asn do NOSVUS LI
'Savon ONIOOOT oi
XSHU 91
-------
in Figure 17. Use of logging roads by hunters and recreation visitors
produce similar-type impacts. The degradation is usually short-term or
until rainfall or snowmelt decreases. However, the combined impacts of
such activities on watersheds may result in significant deterioration
of both water quality and the roadbed.
Road Density. The miles of road constructed is related to the
timber harvesting method. Detailed aspects of the relationship between
logging systems and roads is beyond the scope of this report. However,
it is generally recognized that harvesting methods that reduce the kilo-
meters (miles) of road result in less water quality impacts (18, 26).
Sources of Surfacing Materials. Locating adequate sources of
surfacing materials for roadbeds is a problem in many parts of the
Region. The highly weathered nature or absence of accessible rock
materials creates the problem. The disturbance due to excavation and
removal may cause water pollution problems. Streambeds and water bodies,
such as beaches in areas as southeast Alaska, are often used as sources
of surfacing materials. However, removing the accumulated alluvial
gravels from these areas may produce serious sedimentation and water
quality impacts where removal is done below the existing water level.
Channel Crossing. Roads are often required to cross streams in
order to take advantage of the landform or to minimize construction and
related difficulties. This is one of the primary causes of water quality
problems associated with roads. Immediate and long term water quality
impacts often occur in these areas, from disturbance within the stream
61
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and from blockages of culverts and failures. The number of road channel
crossings in a watershed is an important factor in evaluating water
quality response to disturbance (29).
DETERMINING POTENTIAL FOR POLLUTION FROM LOGGING ROADS
An appreciation and understanding of the intent and objectives of
some of the commonly used stream classification systems is essential
for water quality protection in areas with logging road activities.
Consideration of water quality and stream classifications should be
part of all phases of logging road planning, design, construction and
use.
It has been recognized for sometime that the type of water uses to
be protected are important in determining necessary quality criterion.
The classification of water bodies on the basis of desired use is often
a convenient and useful mechanism for decision making by land managers
and regulators. As noted earlier in this report, the FWPCA Amendments
of 1972, identify uses of water to be protected.
States in Region X have various types of stream and lake classifi-
cations relating to kind of water use, most refer to this use or zoning
as a stream classification system. The systems are related to such uses
as domestic supply, fishery, recreation, industrial, agriculture, and
aesthetics. Inherent in any use classification related to natural
resources are potential conflicts requiring the establishment of prior-
ities. The use priorities are included as part of the water quality
standards of the States.
62
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Some of the stream classification systems used in the Region are
presented in Table 3. The number of classes varies from two to five.
The system of the Department of Fish and Game in Alaska is based on
streams being specified as important for anadromous fisheries. The
system however, is not all inclusive and lack of classification does
not indicate unimportance. Specification of a stream is usually related
to a significant project or action that has a potential for impacting
anadromous fishery values. The major elements of systems used by other
states in the Region are included in Table 3.
The differentiating criteria used in most of the systems have many
common parameters. For example, value for domestic use, importance for
angling or other recreation, and use by significant numbers of fish for
spawning, rearing or migration are used in most systems. The continuity
of water flow as intermittent or perennial is also included in some
systems.
OTHER USE CLASSIFICATIONS
Standards
The water quality standards of the States in the Region are also
related to water use classifications. The designated use for which waters
of the various States are to be protected include, but are not necessarily
limited to, domestic and industrial supplies, irrigation and stock water-
ing, fish and wildlife, recreation and aesthetic qualities. The States
have general and special standards for specifically designated waters.
63
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COMPARISON OF S
States Alaska
Legislative Basis. Alaska Statutes
16.10.010.
Number of Classes. None.
TABLE 3
OME STREAM CLASSIFICATION SYS
Idaho Oregon
Administrative Decision of State Forest Practices
Dept. of Fish & Game.
Differentiating
Criteria.
Requirements.
Activities
Controlled.
The Dept. of
Fish & Game
may classify
waters as
important for
spawning or
migration of
anadromous
fish.
Written approval
for activities
in specified
streams of ana-
dromous fishery
value.
Instream acti-
vities in speci-
fied anadromous
streams as
obstruction,
diversion, and
pollution of
spawning beds.
I thru V.
Aesthetics.
Availability
(road access).
Use (fishing pressure).
Fish productivity.
Size.
None.
None.
Act.
I and II.
Value for domestic use.
Important for angling,
or other recreation.
Use by significant
numbers of fish for
spawning, rearing or
migration routes.
Notification of opera-
tion.
Requires reforestation,
cleanup and protection
(more stringent depend-
on class).
Timber harvesting includ-
ing reforestation, fell-
ing, bucking, yarding,
decking, and hauling
road construction.
Treatment of slash &
site preparation.
Application of Chemicals
Pre-commercial thinning.
TEMS USED IN R
Washington
State Forest Practices
Act.2
I thru V.
Value for domestic use.
Important for angling
or other recreation.
Use by significant
numbers of fish for
spawning, rearing or
migration.
Water flow continuity.
Plan of operation,
reforestation, cleanup
and protection (more
stringent depending on
class).
E G I 0 N X
Forest Service, Region 6
Administrative Decision
of Regional Forester.
I thru IV.
Direct source for domestic
use, including recreation
sites used by large numbers
of fish for spawning, rear-
ing or migration as a major
influence on water quality.
Water flow continuity.
Streams must be classified
as streams!de management
units, cleanup and pro-
tection (more stringent
depending on class).
Timber falling, yarding.
Application of chemicals.
Disposal of slash.
Road construction and
maintenance.->
Harvesting.
Reforestation.
Man-caused woody debris into
streams.
Roads.
Livestock grazing.
I/ Rules and regulations for Stream Channel Protection Act (Title 42, Chapter 38, Idaho Code)
specifies minimum standards for stream channel alterations.
i/ Act will govern all forest practices after Jan. 1, 1975. Information in table from interim
guidelines for 1974 prepared by Ad Hoc Committee sponsored by State Department of Natural
Resources. Formal rules and regulations will "be adopted Jan. 1, 1975.
I/ State hydraulics project approval law (for channel alteration) and Shoreline Management
Act controls some activities on forest land.
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The designations include lakes, streams, segments of streams, or river
basins. Various classes related to the uses as M, A, B, C through G
inclusive are also used to identify specific bodies of water.
The criteria in the water quality standards are related to the
classes. A detailed discussion of water quality standards is beyond
the scope of this report. The concepts and principles related to use
classifications are introduced only for completeness. References 31,
32, 33;. 34, provide detailed information on State water quality standards,
Basin Plans
Basin plans are developed to document pollution problems for some
of the States in the Region, Most of the States have a continuing
planning process (Sec. 303(e) FWPCA). The process provides the method
for the States to coordinate their water quality management planning,
programming, and management. The basin plans identify and document the
nature, source and extent of water quality impacts and procedures for
minimizing the impacts. Stream segments in the basin are classified as
part of the plan development. The classification of segments is based
upon measured instream water quality when available. Basin stream
segments are classified as water quality limited or effluent limited.
These stream classifications are used to identify water quality problem
areas and assist in setting priorities for pollution abatement.
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The definitions of classified basin stream segments are as follows:
Water Quality Limitation. Any segment where it is known that
water quality does not meet applicable water quality standards and/or
is not expected to meet applicable water quality standards even after
the application of the effluent limitations required for point sources
of pollution (FWPCA—Sections 30l(b)(l)(A) and 30l(b )(l)(B)).
Effluent Limitation. Any segment where it is known that water
quality is meeting and will continue to meet applicable water quality
standards after the application of the effluent limitations required
for point sources of pollution.
WATER QUALITY RISK ANALYSIS
A rational assessment of the potential water quality impacts of
roads is an important ingredient of an effective water quality control
program. The following discussion is intended to highlight the con-
ceptual framework of risk analysis. More detailed information and
evaluation techniques are covered in Part II of this report.
A number of different risk analysis procedures are being used to
assist in estimating the potential consequences of road construction
activities (and other silvicultural activities). The following examples
illustrate some of the analytical approaches.
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A risk analysis procedure to evaluate the potential for waste
discharge caused by logging roads is proposed by Jones and Stokes (21).
A number of risk factors and evaluation criteria are identified, and
the relationship of various practices to potential water quality
degradation is explained. A somewhat arbitrary correlation was developed
between the factors and those road practices suitable for such an
analysis. However, on the basis of much of the available research and
field observations, the basic risk factors are accurate and do apply
to road activities in Region X.
Rosgen (29), in northern Idaho, uses a watershed response rating
system which considers six criteria for evaluation: surface erosion
hazard, mass wasting hazard, recovery potential of the land, stream
channel stability, stream recovery potential, and road impact index
(road density times the number of stream crossings). This system is
designed to help analyze the hydrologic response of a watershed to
climatic events and man's activity on the land. As part of this system,
recommended prescriptions are developed as needed for minimizing
potential impacts of roads (and other activities) on water quality
( and other resources).
A geologic hazards approach was used for the Portland, Oregon
Bull Run watershed (ll). As discussed earlier, Kojan et al (3)
developed a system of risk analysis based on geologic hazard and mass
erosion susceptibility.
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The following concepts are included in most of the risk analysis
systems:
(a) identification of potential problems (i.e., water
quality impacts);
(b) identification of significant factors;
(c ) evaluation criteria;
(d) estimating the probability of problem
(water quality impact) occurrence;
(e) estimating the potential magnitude of
impact occurrence;
( f) suggested criteria or solutions for
preventing or minimizing impacts.
However, it must be recognized that such analyses are not "cure alls".
Rather they should be viewed as aids to recognizing and assessing potential
water quality impact hazards in advance in order to address them before
the fact. Any such analyses still require judgment and the "risk ratings"
derived are dependent upon the quality of the investigative work and the
predictive capabilities. The art of predicting the location and magnitude
of road-triggered events is neither precise nor refined. For example,
problems are not always evident; the capability for predicting mass-wasting
on a site specific basis is not well-developed except in the most obvious
situations; and predicting the magnitude of problem occurrence with a
high degree of accuracy is not now practicable.
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An evaluation of some of the risk systems being used suggest the
following conclusions:
(a) Risk analysis is an important feature of a strong
water quality management program.
(b) Although such systems cannot be viewed as highly
accurate predictive devices, they are a rational
basis for improving the probability of anticipating
major water quality impacts (and thus an aid for
preventing or minimizing the impacts).
(c) Multi-professional (i.e., geology, soils, hydrology,
engineering, forestry) skills are needed to develop
high quality analyses and prescriptions—especially
in high risk situations or areas.
(d) Some form of detailed site evaluation is necessary.
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SURVEILLANCE AND MONITORING
MONITORING NONPOINT SOURCES OF POLLUTION
This chapter will present an overview of some important aspects
of water quality monitoring relative to nonpoint sources of pollution.
The emphasis is on logging road activities; however, many of the concepts
presented apply to other silvicultural activities and other nonpoint
sources of pollution. The discussion is not intended to develop a how
to do it approach, or solve the many contemporary problems associated
with various aspects of water quality monitoring. It is intended to
emphasize some of the fundamentals and complexities involved in
monitoring related to logging road activities.
Comprehensive water quality monitoring is a difficult, expensive
and time consuming process. It involves many interrelated variables
such as time of sampling, frequency, flow characteristics, climate and
such physical considerations as soils, geology and topography. Nonpoint
sources of pollution are not confined to discernible, confined and
discrete conveyances. As a result, nonpoint source pollution presents
uniquely difficult monitoring problems, because of the wide variability
of many physical factors.
Measurement of a highly variable, diverse system such as found in
any natural system requires a great deal of effort. Careful considera-
tion must be given to determining if the end results are worth the costs
involved. In many instances, the cost to obtain high quality data are
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considered prohibitive and therefore something much less than optimum
is considered acceptable. The less than optimum level of sampling is
generally utilized in everything other than a research study, with the
end result being the data is almost useless in determining the cause-
effect relationships necessary to evaluate management activities.
The FWPCA Amendments of 1972 is the first national legislation to
recognize pollution problems of a nonpoint source nature. It is
recognized that the kind of pollution control for nonpoint source areas
as silvicultural activities, cannot be the same as those for conventional
collection and treatment of polluted effluents immediately prior to
discharge into water bodies. The treatment and control methods generally
relate to the forest management system. They may include a combination
of practices and methods for minimizing pollutant discharges.
The concepts for the control of pollution from point sources, or
discernible, confined and discrete conveyances, are clearly identified
in the Act. The control regulations include, but are not limited to
(a) effluent limitation for point sources; (b) application of best
practical control technology; (c) compliance schedules to meet effluent
limitations; and (d) compliance monitoring.
There are some similarities between point sources and nonpoint
sources pollution problems. The basic goal for both is to reduce water
pollution. The effects they cause are similar—they degrade the chemical,
physical, and biological integrity of water. The major differences
between point sources and nonpoint sources are their mode of entry into
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the aquatic environment, timing of pollution input, the levels of the
dispersion of material downstream, and most of all, the extreme
variation caused by a number of factors both natural and man caused.
These differences limit the application of conventional pollution
control methodology of treatment prior to discharge.
Many of the transport pathways for pollutants from nonpoint
sources are not fully understood. However, it is feasible to apply
the principles of best preventative techniques which are somewhat
similar in concept to best practicable technology for control of point
sources of pollution. Best preventative techniques are those procedures,
methods, techniques and structural measures which are currently avail-
able for preventing or minimizing water quality impacts. Much of the
information presented in Part II includes best preventative techniques
for logging road activities.
Some of the common needs for water quality monitoring are to:
(a) evaluate the presence of pollution; (b) define causes or sources of
pollution; (c) evaluate data for development of preventative measures;
and (d) determine the natural background quality of water in the water-
shed, and to be able to distinguish between natural and man-caused
sediment inputs in a system of extreme variability.
Road construction and maintenance have short-term impacts during
and immediately following construction and generally decreasing long-term
impacts during the life of the roads. However, in some instances road
cuts are progressively less stable as roots rot and exposure causes
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weathering. The major pollutant is eroded mineral sediments. Signifi-
cant, localized pollution problems can be caused by organic matter from
the forest floor and in the soil originating from plant and animal
sources; tree debris (another source of organic matter) in the form of
leaves, twigs, and slash; pesticides used in the maintenance program;
and nutrient elements (principally nitrogen and phosphorus) from soils
and plant and animal matter or from fertilizers. Thermal pollution can
also occur by removing shade cover and exposing streamflow to solar
heat. Of all these pollutants, sediment is the most serious cause of
water quality degradation (19).
In many instances, it is difficult to determine what pollution
results from logging roads, what is caused by other man related
activities, and what is the natural background level. The most
convenient and conventional approach is to monitor or quantify water
quality in an area without logging road construction, as was discussed
earlier related to work by Fredriksen (38). The approach obviously has
limitations after initial reading of an area is started. The subsequent
water quality impacts from road construction are difficult to separate.
Consequently, the most effective approach for documenting water quality
related to roads and other silvicultural activities is to monitor as
small a watershed as practical for cumulative impacts. Larger water-
sheds should be used to document long term trends.
The principal needs to increase effectiveness in nonpoint source
monitoring are: (a) a better definition by forest land managers and
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regulators of what and where monitoring should occur; (b) a better
understanding and definition of the probability of sedimentation in
undisturbed areas within a defined time frame; and (c) a better
definition of pollution levels and impacts. Some important aspects
of nonpoint source monitoring that must be recognized in developing
a monitoring system are:
a. Sediment is the most significant pollutant from
nonpoint sources on forest land in the Region.
b. Stream systems have naturally-caused sediment for
any defined time frame.
c. Land management objectives should be related to
a defined time frame in order to identify water
pollution impacts.
The above indicates that general prescription approaches for
monitoring nonpoint sources are of limited value. Monitoring activities
should be related to a predefined purpose.
PARAMETERS AND FREQUENCY
Monitoring should normally be limited to those parameters most
likely to be significantly affected by logging roads and relat-ed silvi-
cultural activities. The most significant ones are sediment and
turbidity. Temperature, dissolved oxygen, nutrients, and chemicals such
as deicers, oils and pesticides may require monitoring in special
situations. Stream flow should also be measured to assist in interpreting
water quality data.
75
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The sampling frequency must be carefully established so that all
the ranges of water quality experienced from logging road and related
activities are observed. Monitoring schemes must be built on knowledge
of how and when the pollutant is likely to be produced. For example,
it is known that sediment enters streams primarily during storm events
or during the rising stage of streams. It is also documented that
chemicals as deicers and oils used in dust-coating roads have the
greatest potential for entering streams during and immediately after
rainfall and runoff. For water temperature monitoring, the sampling
should be geared to diurnal variations including mid-summer, midday
periods during clear hot weather (19).
Monitoring Approaches
Two types of monitoring approaches may be used to document water
quality in a forested watershed—long-term or trend monitoring and short
term monitoring.
Long Term Monitoring. This type of monitoring is designed to
establish representative water quality for runoff and document long-term
fluctuations. The monitoring stations should be on major drainages
within a watershed to represent the combined effect of all activities
within a drainage. The information will give an overview of the quality
of water within the yield area.
Many long term monitoring stations already exist in the Region and
are operated by the EPA, U.S. Geological Survey, U.S. Forest Service,
76
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State Agencies, Universities and various timber industries. In special
interest areas as municipal watersheds where logging roads are constructed
over a period of time, it may be desirable to establish long-term
stations to document water quality impacts. The information may be used
in developing preventative and corrective measures.
Short Term Monitoring. This type is designed to monitoring project
activities before implementation (to establish existing quality), during
implementation (to establish the effect of the activity on quality as a
control) and after implementation (to establish time frames for return
to pre-disturbance conditions or recovery as a measure to quantify
degradation).
Short-term monitoring stations should be located near activities
to be monitored. The paired-station approach, one station upstream and
one station downstream, is the most convenient and conventional. It is
appropriate for monitoring many road activities. The shortest possible
time should occur between the two sample intervals.
The potential limitations of the paired-station approach are (a)
In situ changes in pollutant concentration due to past natural—or—man
caused activities; (b) locating downstream stations to insure adequate
mixing, yet avoiding unrelated sedimentation or other pollutants from
instream areas; (c) the approach does not indicate the frequency of
changes, or their meaning at water use points; (d) in order to achieve
any degree of statistical significance in the sampling procedure a
77
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number of samples will be required. In addition, it way not be possible
to utilize this technique in certain instances. Many small watersheds
where monitoring is desirable occupy a position in the upper reaches of
a drainage system. It may not be possible to establish a station
upstream and downstream of an activity in such a situation where a stream
originates within the activity area.
It is essential to understand the limitations and applications of
any monitoring approach prior to its use. Recognizing its limitations,
the paired station approach is still appropriate for monitoring logging
road activities in many instances, because the major impact during the
first year after construction generally occurs within a short time.
The approach is shown graphically in Figure 18.
The technique of paired watershed analysis may also be used in
monitoring logging road activities as used by Fredriksen (38). This
method is not without limitations, however it does have advantages in
certain instances. The largest disadvantage is one of long calibration
time. The principal advantage of the approach is that the control water-
shed may more accurately represent natural levels of water quality.
Parameters
The water quality parameters most likely to be influenced by road
activities include sediment, turbidity, and temperature. In some instances,
specific conductance, dissolved oxygen and stream discharge may be
affected. The key parameters are discussed below:
78
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SAMPLING POINT
POTENTIAL WATER USE
FISHING
SPAWNING
AREA
SPUR ROAD
'/
' .^ SMALL
WATERSHED
." BOUNDARY
MAIN HAUL
._£ ROAD
ROAD
CONSTRUCTION
IN PROGRESS
POTENTIAL
WATER USES
MUNICIPAL
SUPPLY
FISH REARING
FIGURE 18 WATER QUALITY MONITORING APPROACH FOR CUMULATIVE IMPACTS
79
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Sediment. As previously discussed, sediment is the major
pollutant related to logging road activities. Detail quantification of
sedimentation sources, rates, etc., present difficult problems because
of wide variability of flow, soil, and geologic characteristics of an
area. Many of the problems involved in monitoring and interpreting
sediment transport and deposition data are well documented in literature
(1, 12, 19, 24, 36, 46, 47).
To evaluate the relative contribution of sediment sources and
transport processes that affect streams in the forest, problems in
monitoring sedimentation characteristics should be recognized. They
involve determining where in the watershed the characteristic should be
measured or identified, and how well the sample represents time and
spatial variations (37). In evaluating the contribution of sediment
sources from roads and other forest activities, environmental character-
istics such as the hydrology of the soil, the landform which the soil
occupies, the erosional processes, and the high sensitivity of each
process to change must be considered in surveillance and monitoring
activities. Erosion is but one of the three basic processes of sedi-
mentation, the other two are sediment transport and deposition. Each
of these basic processes may in turn serve as a source of sediment or
be involved in the transport process, depending on the particular
measurement of sediment delivery being considered.
Much of the available information on sedimentation from forest
land activities including roads has come from subjective evaluations or
80
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observations of muddy streams during and following road construction and
use. In some instances, research has provided quantitative data on
sediment production from forest roads built prior to other types of man
caused disturbances in an area (17, 26, 38, 39). Most of the quantitative
information that's available on impacts of forest roads on water quality
have been obtained from experimental watersheds. Some of these water-
sheds have had complete timber harvest operations (24, 38). Others
have been located in soils and geologic materials that are of relatively
minor importance making the transportability of some of the information
questionable. More baseline information on various common road acti-
vities and other forest land management practices is needed to better
understand and quantify water quality impacts associated with logging
road activities.
Turbidity. It is a measure of an optical property of water
normally expressed in Jackson Turbidity Units (JTU). Turbidity may be
related to the suspended sediment content of the water although the
correlation may be quite variable from stream to stream and even for
the same stream at different locations and times of the year. Turbidity
gives only a crude index to sediment content, unless a specific correla-
tion for a stream is developed.
Temperature. The purpose of water temperature monitoring is to
determine whether shade removal or ponding increases water temperature.
If shade is not removed as a result of stream crossings or other
81
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construction in the immediate vicinity of streams or any ponding effects
introduced, the monitoring of water temperature loses its primary
importance.
In some instances, it may be well to consider measurements of
monitoring outside the standard water quality parameters discussed above.
As discussed, these parameters are so highly variable it may be advis-
able to evaluate both source area and end results for a measurement of
the impact of the logging road activity. Analyzing source areas is
particularly important where mass failures are involved. In addition,
measurement of changes to the aquatic system or biological monitoring
should also be considered. Such things as measuring channel erosion and
degradation, and changes in particle size distribution of deposits may
be helpful in determining effects of logging road activities on the
aquatic system and other water uses.
USE OF WATER QUALITY DATA
Good water quality data can provide a means of assessing the effec-
tiveness of various erosion control measures and engineering design
features. The information should encourage designers and contractors to
make a more conscientious effort to prevent water quality degradation.
Water quality information may also be helpful in controlling construction
and related road activities.
There are several sources of water quality data that can be used
by planners or engineers to assess the potential water quality impacts
82
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of roads and other silvicultural activities. The Environmental Protection
Agency, U.S. Forest Service, U.S. Geological survey, State water pollu-
tion control agencies, and universities in the Begion all have water
quality data related to various aspects of forest land management.
Most of the groups have inventories of data collected. The EPA's
STORET System also contains data of most of the other agencies and
groups. The system is a comprehensive source of water quality data
and may be useful for planners and engineers, especially during the
planning and design phases of logging roads. Data can be retrieved
at Region EPA Offices (19).
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REFERENCES
Text
No.
1. Brown, George W. Forestry and Water Quality. School of Forestry,
Oregon State University, Corvallis. 1973.
2. Way, Donald S. Terrain Analysis. A Guide to Site Selection Using
Aerial Photographic Interpretations. Community Development Series.
1973.
3. Kojan, E., J. R. Wagner and R. M. Wisehart. Environmental Impact
Report, Fox Unit Study Area, Six Rivers National Forest, Del Norte
County, California, Unpublished.1973.
4. Swanston, D. N. and C. T. Dyrness. "Stability of steep land."
Journal of Forestry. 1973. 71:264-269.
5. Burroughs, E. R., G. R. Chalfant and M. A. Townsend. Guide to Re
duce Road Failures in Western Oregon. Bureau of Land Management,
Portland, Oregon.1973.
6. U. S. Environmental Protection Agency. Region X. "Slope Calcula-
tions." Data from U. S. Forest Service, Regions 1, 4 & 6 and PNW
and Intermountain Research Stations. Unpublished. 1974.
7. Allison, Ira S. "Landforms of the Northwestern States." Atlas of
the Pacific Northwest. Edited by R. M. Highsmith, Jr. Oregon
State University, Corvallis, 1968. pp. 27-30.
8. Baldwin, E. M. Geology of Oregon; Distributed by University of
Oregon Cooperative Bookstore, Eugene. 1964.
9. Campbell, C. D. "Washington geology and resources." State College
Wash. Res. Stud. 1953. 21: 114-153.
10. Fairbridge, Rhodes W. Encyclopedia of Geomorphology. Earth Science
Series, Volume III. 1961T
11. State of Oregon. Department of Geology and Mineral Industries.
"Geologic Hazards of The Bull Run Watershed Multnomah and Clackamas
Counties, Oregon." Bulletin 82. 1974.
12. Pollution Control Council, Pacific Northwest Area. Watershed Con-
trol for Water Quality Management Reproduced by U. S, Public Health
Service. 1961.
13. NOAA—National Weather Service. Climate of Alaska. Anchorage,
Alaska. Undated.
85
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REFERENCES (Cont'd)
Text
No.
14. U. S. Forest Service. The Outlook for Timber in the United States.
Forest Resource Report No. 20. U. S. Government Printing Office,
Washington, D. C. 1973.
15. U. S. Environmental Protection Agency, Region X Silviculture Project
Staff. "Forest Land Statistics for Region X." Unpublished. 1974.
16. U. S. Environmental Protection Agency, Region X Silviculture Project
Staff. "Summary of logging road information from various sources."
Unpublished. 1974.
17. Megahan, W. F. and W. J. Kidd. "Effects of logging roads on sedi-
ment production rates in the Idaho Batholith." USDA Forest Service,
Research Paper INT.-123.
18. Rice, R. M., J. S. Rothacher and W. F. Megahan. "Erosion consequen-
ces of timber harvesting: An appraisal." Proceedings of a Sympos-
ium on Watersheds in Transition, Ft. Collins, Colorado, June 19-22,
1972. pp. 321-329.
19. U. S. Environmental Protection Agency. "Processes, Procedures and
Methods to Control Pollution Resulting from Silvicultural Activities."
Office of Water Programs, Washington, D. C. 1973.
20. Haupt, H. F. and W. J. Kidd, Jr. Good logging practices reduce
sedimentation in central Idaho. J. Forest. 1965. 63: 664-670.
21. California State Water Resources Control Board. "A Method for
Regulating Timber Harvest and Road Construction Activity for Water
Quality Protection In Northern California." Prepared by Jones and
Stokes Associates, Inc. Publication No. 50. 1973.
22. Hartsog, W. S. and M. J. Gonsior. "Analysis of Construction and
Initial Performance of The China Glenn Road, Warren District,
Payette National Forest." USDA Forest Service, General Technical
Report INT-5. 1973.
23. Packer, Paul E. "Forest treatment effects on water quality." Conf.
Proc. on Forest Hydrology, 1%7, pp. 687-699.
24. Brown, George W. and James T. Krygier. "Clearcut logging and sedi-
ment production in the Oregon Coast Range." Water Resources Re-
search, -1971, 7(5): 1189-1199.
86
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REFERENCES (Cont'd)
Text
No.
25. Krygier, J. T. and J. D. Hall, Editors. Proceedings of a Symposium
"Forest Land Use and Stream Environment." Oregon State University,
Corvallis. 1971.
26. Anderson, H. W. and J. R. Wallis. "Some interpretations of sediment
sources and causes, Pacific Coast Basin in Oregon and California."
Proceedings of the Federal Interagency Sedimentation Conference, 1%3>
Misc. Pub. 970. 1965. pp. 22-30, USDA, Washington, D.C.
27. Rice, R. M. and J. R. Wallis. How a logging operation can affect
strearaflow. Forest Ind. 1962. 89(11), pp. 38-40.
28. Larse, Robert W. "Prevention and control of erosion and stream
sedimentation from forest roads." Proceedings of a symposium
"Forest Land Use and Stream Environment." Oregon State University,
Corvallis, 1971. pp. 76-83.
29. Rosgen, Dave R. "Watershed response rating system." Forest Hy-
drology Hydrologic Effects of Vegetation Manipulation, Part II.
USDA Forest Service, Missoula, Montana. 1974.
30. Tarrant, Robert F. "Man caused fluctuations in quality of water
from forested watersheds." Proceedings of the Joint FAO/U.S.S.R.
International Symposium on "Forest Influences and Watershed Manage-
ment, " Moscow, U.S.S.R., 1970.
31. State of Alaska. Title 18. Environmental Conservation Chapter 70.
"Water Quality Standards." 1973.
32. State of Idaho. Department of Environmental and Community Services.
"Water Quality Standards and Wastewater Treatment Requirements."
1973.
33. State of Oregon. Department of Environmental Quality. "Standards
of Quality for Public Waters of Oregon and Disposal Therein of Sew-
age and Industrial Waste." 1973.
34. State of Washington. Department of Ecology. "Water Quality Stan-
dards." 1973.
35. Dyrness, C. T. "Mass soil movement in the H. J. Andrews Experimental
Forest." USDA Forest Service, Research Paper PNW-42. 1967.
36. U. S. Environmental Protection Agency. National Environmental Re-
search Center. "Report on Nonpoint Source Monitoring." Unpublished
Draft. 1974.
87
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REFERENCES (Cont'd)
Text
No.
37. Anderson, H. W. "Relative contributions of sediment from source
areas and transport processes." Proceedings of a symposium, "Forest
Land Uses and Stream Environment." Oregon State University, Corvallis,
1971. pp. 55-63.
38. Fredriksen, R. L. "Erosion and sedimentation following road construc-
tion and timber harvest on unstable soil in three small Western Oregon
Watersheds." USDA Forest Service, Research Paper PNW-104. 1970.
39. Packer, Paul E. and Harold F. Haupt. "The influence of roads on
water quality characteristics" in Proceedings of "Society of Ameri-
can Foresters," Detroit, Michigan, 1965.
40. Frewing Committee Report. "Management of forest resources in the
Bull Run Watershed near Portland, Oregon." 1973.
41. Joint Federal State Land Use Planning Commission for Alaska. Re-
sources of Alaska A Regional Summary, 1974, p. 8.
42. Ibid, p. 586.
43. Ibid, p. 588.
44. Swanston, D. N., "Principal Mass Movement Processes Influenced
by Logging, Road Building and Fire." Proceedings of a symposium
"Forest Land Uses and Stream Environment." Oregon State University,
Corvallis, 1971, pp. 34-36.
45. Hutchison, K. 0., Alaska's Forest Resource, USDA Forest Service,
Institute of Northern Forestry, Resource Bulletin PNW-19, 1968.
46. Guy, Harold P., Techniques of Water Resources Investigations of
the United States Geological Survey. "Field Methods of Measure-
ment of Fluvial Sediment." U. S. Government Printing Office,
Washington, D. C., 1970.
47. Guy, Harold P. and Vernon W. Norman, Techniques of Water Resources
Investigations of the United States Geological Survey. "Fluvial
Sediment Concepts." U. S. Government Printing Office, Washington,
D. C., 1970.
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PARTH
Engineering Design And Technical Criteria
For The Control Of Sediment
From Logging Roads
and
The Control Of Pollution
From Road Maintenance Chemicals
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INTRODUCTION
Engineering criteria for the planning, design, construction and
maintenance of logging haul roads directed toward sediment minimization
is a part of the total engineering criteria need for these roads. The
appropriate spectrum of this criteria is related to the major role log-
ging roads play in forest land management.
Sediment control design criteria may be the same as, or parallel to,
other design criteria that will result in an efficient, economic logging
road system for sound forest land management. Examples of "overlap" or
parallel criteria are:
1. Relating road location and design to the total forest resource,
including short and long term harvest patterns, reforestation,
fire prevention, fish and wildlife propogation and water quality
standards.
2. Relating road location and design to current timber harvesting
methods.
3. Preparing road plans and specifications to the level of detail
appropriate and necessary to convey to the road builder, be he
timber purchaser or independent contractor, the scope of the
project and enable him to prepare a comprehensive construction
plan of procedure, time schedule, and cost estimate.
4. Design investigations and companion design decisions directed
toward minimizing the opportunity for "changed conditions"
during construction with their consequent costs in dollars and
time.
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5. Analysis of certain road elements relative to first cost versus
annual maintenance cost such as culverts and embankments versus
bridges; ditch lining versus ditches in natural soils; paved
or lined culverts versus unlined culverts; sediment trapping
devices (catch basins, sumps) versus culvert cleaning costs;
retaining walls versus placing and maintaining large embankments
and embankment slopes; roadway ballast or surfacing versus
maintenance of dirt surfaces; and balanced earthwork quantities
versus waste and borrow.
Specifically including design criteria to minimize sediment can
broaden the design criteria spectrum under some conditions. In these cir-
cumstances additional first cost may not result in companion annual main-
tenance cost reductions as suggested in the previous paragraph. Examples
of these circumstances are:
1. Spur roads built for one harvest in one season of a small area
and/or to one use landings.
2. Short-term sedimentation control measures during road construc-
tion and immediately thereafter until long-term measures are
installed or established.
3. Improvements outside of what has been regarded as the road
right-of-way, or corridor, such as specially constructed filter
strips, "downhill" culvert extensions, settling basins and pro-
visions for debris collection.
4. End haul of excess excavation to selected waste areas.
5. More restrictive limitations on the road construction season
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thereby, in some instances, requiring more seasons to complete
the road with companion delay in the timber harvest (time cost
of money).
6. "Tipping the scales" in an evaluation of a fragile or sensitive
area toward the conclusion that existing road design and con-
struction technology will allow no_ road construction.
7. Restriction or elimination of a timber harvest method due to the
road needs of the method and conversion to another harvest method
that results in a higher long term harvest cost.
Many regional writers believe that forest roads have often signifi-
cantly contributed to sediment reaching streams by road surface erosion
and mass soil movement. George W. Brown states that: "The compacted sur-
faces of logging roads, skid trails, and fire lines often carry surface
run-off during storm events. Road surfaces are a significant source of
sediment in forest because of such run-off" (l). Fredriksen's studies in
Western Oregon watersheds report that "Landslides are the major source of
stream sedimentation" and that "their occurrence is more frequent where
logging roads intersect stream channels" (2). He also suggests that mid-
slope road mileage be minimized and further where these roads are neces-
sary across steep side slopes, "all knowledge available to the engineer
should be used to stabilize roads".
Swanston's investigations on mass soil movements in forests indicate
that road building is the most damaging activity and believes that soil
failures therefrom result primarily from slope loading with embankments,
sidecasting, inadequate provision for slope drainage and cut slopes (3).
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Mass movements have occurred in the Alaska maritime coast, Idaho and
on the western slopes of the Cascades. These movements have often
produced companion sedimentation problems and significant water quality
degradation.
Megahan and Kidd's studies of sediment production rates in the
Idaho Batholith showed increases of sediment production an average of
770 times per unit area of road prism for a six year study period (4).
Although surface erosion following road construction decreased rapidly
with time, major impact occurred from a road fill failure after a single
storm event.
This section deals with engineering techniques that have been used
or can be used to minimize the sedimentation originating from logging
haul roads. The techniques reported or discussed do not have universal
application throughout all forested lands in Washington, Oregon, Idaho
and Alaska. To the contrary, the first and cardinal rule for the solu-
tion of any engineering design problem is to deal with the actual cir-
cumstances at the individual site in question. As Robert W. Larse has
suggested, "the designer must have a knowledge and understanding of design
criteria and principles, but must be free and have sufficient experience
and ability to design for specific conditions, rather than to apply general-
lized design rules to all situations" (5).
In the Summary and Recommendations Section of their report on slope
failures in the Idaho Batholith, M. J. Gonsior and R. B. Gardner suggest
a need for a reorientation or philosophical change in engineering approach
as follows:
"In addition, there appears to be a need for a subtle philosophical
change in the traditional engineering approach to problem solving
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and design. Usually, the integrity of a road, dam, or any other
structure is viewed as the primary goal, and thus natural processes
such as erosion, seepage, and settlement are considered as imposi-
tions on the structure which must be controlled or withstood. In-
stead, the road or structure might better be viewed as an imposi-
tion upon the various natural processes, and location and design
might better be oriented toward assuring the continuity of, or at
least compensation for changes in, these natural processes. By
so reorienting design philosophy not only should the integrity of
roads and structures be better guaranteed, but the chances for caus-
ing undesirable changes in the functioning of natural systems should
be considerably reduced. Of course, by changing the question from
"What are the natural processes which will endanger the road's in-
tegrity"? to "How will the road influence natural processes"? the
designer is forced to consider a broader spectrum of environmental
factors. Thus, multidisciplinary cooperation and teamwork become
not only desirable, but absolutely essential to the completion of
the planners' and designers' work" (6).
The discussion that follows is in the order that a logging road de-
velops namely: (l) planning and reconnaissance, (2) design, (3) construc-
tion and (4) maintenance. These divisions do not imply that an appro-
priate engineering organization for every forest land owner will be simi-
larly structured. Each owner's engineering staff will be structured in
accordance with his individual circumstances in terms of size, terrain,
policy, ownership, product and goals. Small landowners may find it
economic to retain consultants or to seek help from governmental or univer-
sity sources when the need for engineering or other specialists occurs.
A good case can be made for the procedure that assigns to one indi-
vidual or team the responsibility to deliver a completed road. Such a
procedure provides continuity in the planning and reconnaissance, design
and construction phases. Also, an organization whose personnel policies
result in the maintenance of a stable engineering staff possessing many
years of experience on the land that it manages and/or harvests has a
great asset when approaching the problem of minimizing the creation and
transport of sediment.
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Writings on the subject of sediment creation and transport in the
forest are extensive. A large reservoir of unrecorded knowledge is also
possessed by individual experienced forest engineers. There are no doubt
many successful techniques of sedimentation control omitted from the
chapters that follow.
SUMMARY AND CONCLUSIONS
There is an abundance of information available on the subject of
minimizing the creation and transport of sediment accruing from logging
haul roads. Further sources of information are the experiences of indi-
viduals long associated with the design, construction and maintenance of
these roads.
The value of a thorough planning and reconnaissance program for a
proposed road is emphasized by many authorities. No amount of design or
construction expertise can recover from an approach based upon inadequate
reconnaissance information. Field reconnaissance evaluations must in-
clude attention to the potential for mass movements as well as surface
erosion. In steep terrain, it is likely that the engineering investment
to insure a stable road will be much more exhaustive than on gentle terrain.
The general approach to design must be the classic engineering ap-
proach of according individual treatment to the individual circumstances
of the site. Creative design is needed.
Many mass failures are drainage associated. Drainage design often
appears to have lacked attention to one or more of the following features.
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1. Determination of the design flood.
2. Evaluation of the potential for debris blockage.
3. Choice of stream crossing method.
-4. Attention to installation requirements at both the design
and construction levels to insure structural integrity.
Minimizing surface erosion and sediment transport begins with the appro-
priate treatment or design of slope protection, and continues with the
necessary attention to ditch size, lining, culvert intakes, culvert in-
tegrity and culvert outlets.
Under most conditions vegetative or other forms of permanent cover
are essential to prevent excessive surface erosion from cut and fill
slopes. Vegetation establishment should be initiated as soon after soils
disturbance as possible. Various grass and legume seed mixtures are
suitable for establishment of vegetation in Region X depending on climatic
and other environmental conditions. Seeding should be accompanied by
fertilization and re-fertilization as necessary and by watering to main-
tain vegetative vigor. Mulches, chemical soil stabilizers, or mechanical
measures are necessary to prevent high initial rates of soil loss during
vegetation establishment and in some cases to aid in vegetation estab-
lishment.
It is important to sequence the construction in a manner that affords
the least exposure to storm damage during construction. Contractual
relationships between owner and road builder should be such that a quick
response can be made by all parties to changed circumstances during con-
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struction. Failure to respond promptly can greatly enhance the potential
for sediment creation and transport.
New types of construction equipment are needed for the proper and
efficient clearing of steep slopes in a manner that reduces the opportunity
for mixing of clearing slash and organic debris with excavated material.
End haul projects on narrow roads have resulted in increasing unit excava-
tion costs. New equipment that will produce more yardage at less unit
cost is needed.
The key to a successful maintenance program is the motivation and
knowledge of maintenance personnel. Individuals control sediment trans-
port attendant to maintenance operations.
Occasional slides can be expected along logging roads even with the
best location and design practices. In some cases, abandoning the road
may be preferable to removing slide debris and correcting the problem.
Where it is necessary to remove slide debris, it should be placed in
selected spoil areas.
Although inclusion of design criteria for sediment control may in-
crease initial capital outlay, it does not necessarily increase total
annual cost over road life. There may be offsetting savings in annual
maintenance costs. Stable cuts and fills and adequate culverts and
bridges are desired by forest owners and users for many reasons other
than sediment control. Features constructed outside of the roadway
corridor for sediment transport minimization are the most obvious examples
of capital outlay for sediment purposes only.
When construction is accomplished in accordance with adequate plans
and specifications in a workmanlike manner under strict supervision, the
minimization of sediment creation and transport may be coincident.
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RECOMMENDATIONS
The trend toward obtaining a thorough field reconnaissance for
logging roads should be continued and even accelerated.
Several methodologies (e.g. Universal Soil Loss Equation) have
been developed for prediction of soil loss under various conditions.
However, none have been specifically developed or tested for use in a
forest environment. Additional research is required to test the avail-
able equations for use on forest logging roads.
A system of high altitude rain and stream gaging stations, estab-
lished in advance of logging or road building operations, would be
helpful to the determination of mountain stream flows for stream cross-
ing design purposes.
Organizations should assign responsibility and authority to exper-
ienced engineers at the local level for planning and designing the log-
ging roads. Personnel policies should support the retention of exper-
ienced engineers in or near the forests they serve.
Highway engineering tools, criteria and techniques developed for
state, county or municipal roads should not be blindly applied to forest
roads.
An equipment research program directed toward the modification
of current equipment or development of new equipment for excavating
narrow roads in steep terrain is needed. The goal of the research
should be relative economy in the earth excavating and loading operation
for end haul projects as compared to the costs of these operations using
presently available equipment.
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ROUTE PLANNING AND
RECONNAISSANCE
Route Planning and Reconnaissance is regarded by many as the most
important phase of logging haul road development. It is at the planning
and reconnaissance level that first evaluations of soil erodibility, the
potential for mass movement, and the potential for sediment transport
must be made. These evaluations may confirm the proposed road corridor,
cause a change in forest harvest procedure, indicate the need to survey
an alternate corridor or contribute to a no road decision.
The importance of road reconnaissance is detailed in several refer-
ences. Crown Zellerbach Corporation's Environmental Guide, Northwest
Timber Operations, states in Chapter V, "Road Building": "Special
emphasis must be placed on proper road planning, design of cross sections,
and field location to reduce soil erosion problems and consequent stream
siltation and stream blockages" (7). Larse, in a paper entitled "Preven-
tion and Control of Erosion and Stream Sedimentation from Forest Roads",
emphasized planning and reconnaissance when he stated: "Road planning and
route selection is perhaps the most important single element of the road
development job" (5). The U. S. Forest Service Region 6's Recommendation
3.1 from Timber Purchaser Road Construction Audit is: "Preconstruction
geotechnical investigations, transportation planning, and construction
inspection on earthwork and drainage should receive the highest priority
for manpower" (8). The Siuslaw National Forest's Implementation Plan to
the Region 6 Audit agrees that "the greatest potential for land impacts
from road construction lies in areas of steep topography and unstable
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soils" (9). The Boise National Forest's Erosion Control on Logging
Areas states: "To a great extent erosion can be prevented by controlling
the location of roads and skidways in relation to the natural drainage,
slopes, and soil conditions" (10).
In the recommendations contained in Flood Damage In The National
Forest of Region 6, Jack S. Rothacher and Thomas B. Glazebrook believe
that any procedures designed to minimize unusual weather impacts on soil
must be based on increased knowledge of geomorphic history, climate, hydro-
logy, vegetation, soils and landscape features of the land (ll). "The
importance of reconnaissance is indicated by the fact that failure to con-
sider all alternates may result in future excessive costs far beyond any
savings effected by not accomplishing a complete reconnaissance" (12).
(Bureau of Land Management Roads Handbook)
R. D. Forbes in Forestry Handbook provided one estimate of the total
planning and design effort required when he stated: "The importance of
adequate surveys, and careful planning for road construction justifies engi-
neering costs up to 5% of total cost for low standard while 10$ to 15$ is
reasonable for engineering permanent heavy-duty hauling roads in rough
country" (13). Any estimate of engineering costs should recognize the in-
dividual circumstances of the project under consideration.
Neither the competent designer nor the competent road contractor can
economically overcome faults in a road concept that are related to inade-
quate planning and reconnaissance.
The following discussion of route planning and reconnaissance begins
when the forest land manager has determined that a road is required. The
manager has made some preliminary decisions about the purpose of the road
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and companion decisions as to the general corridor that is preferable
from a management viewpoint. He conveys this information to his engi-
neering staff for implementation. Results of the subsequent engineering
planning-reconnaissance phase may alter the initial management decision.
The first part of this chapter covers engineering planning aspects
and the engineer's communication with land management. The second part
discusses the field reconnaissance by geotechnical, forest and civil
engineering personnel. The last part (third) discusses economic evalua-
tions. The chapter is divided in this manner partly for the convenience
of presentation. The planning and reconnaissance activities are often
very interrelated depending upon the type of organization and the nature
of the road project under study.
ROUTE PLANNING
MANAGEMENT-ENGINEERING DIALOGUE
After the engineers' introduction to the Forest Land Manager's road
requirement, a dialogue often develops between the two parties. The com-
munication may encompass road standards, intended use, harvest methods
and road life. The discussion may result in a program of road feasibility
studies or simply a direct road reconnaissance and design.
Initial communications become critical to the road development parti-
cularly when minimum environmental impact roads, including sediment mini-
mization, are required. In their communications, both the engineer and
the land manager must attempt to reach a complete and explicit understand-
ing and avoid communication gaps. An illustrative case is the China Glen
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Road on the Warren Ranger District, Payette National Forest, Idaho.
The road was to serve a salvage timber sale in three fragile water-
shedsnr Management gave special instructions to minimize watershed
damage. Road standards had, to some extent, been established by the
forest management and engineering appeared to have accepted these
standards.
Prior to construction, management reviewed the design documents
and road construction was begun. However, gaps in their initial com-
munication became evident as is reported by W. S. Hartsog and M. J.
Gonsior.
"During field inspection, land managers expressed
concern that the road would have more impact than had
been anticipated. They felt that cuts and fills were
larger than desirable or necessary. Apparently, they
could not fully visualize the final product from the
design sheets, which indicates a need for better com-
munications" (14).
The China Glenn Road experience demonstrates the need for com-
munication when roads in ecologically sensitive areas are envisioned.
In some cases (particularly in steep terrain), small soil and geologic
disturbances may result in measurable ecological differences including
the presence of stream siltation. In these circumstances the responsi-
ble forest engineer continues the dialogue and provides "feed back" to
the forest land manager by evaluating the terrain's in situ condition.
The engineer will evaluate the terrain for elevation, aspect, soil
strength, ground slope, ground water, geologic formation and precipita-
tion.
The need for the engineer to evaluate management's decision is
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accentuated by the fact that a large part of the commercial forest
lands in Region X are located on land that requires a careful assess-
ment of the road's potential performance. This assessment should in-
clude determination as to whether or not existing technology is equal
to the ambient circumstances within a particular road corridor.
ENGINEER'S ASSESSMENT OF MANAGEMENT'S DECISION
The technological tools available to the engineer to accomplish a
pre-field reconnaissance evaluation of a proposed road corridor might
include his own knowledge of the area, performance of existing roads
in similar terrain, topographic maps, geology maps, aerial photographs
and photo interpretation equipment, soil resource maps and hydrology
data. His evaluation should permit him to advise management that a
preliminary assessment of the proposed road corridor has led to one of
the following answers:
1. There is no chance of constructing a stable road; or
2. The road envisioned by management cannot be constructed but
one of lesser design criteria in terms of width, grade and
horizontal curvature might be constructed pending confirma-
tion by field reconnaissance; or
3. A road might be constructed into the general area with com-
panion modification of the harvest procedure; or
4. Management's road might be constructed pending confirmation
by field reconnaissance; or
5. Management's road can be constructed with relative ease pending
confirmation by a brief field reconnaissance; or
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6. Managements' road cannot be constructed with the allocated
dollar amount.
State of the Art Techniques
Within the past few years, some forest land owners have become
keenly aware of the hazards of sediment production. As a result of
this awareness, a number of land management devices which attempt to
evaluate the timber production land base have been developed. Several
of these devices focus on the effect of unstable terrain on forest land
management practices including road construction. These land evalua-
tion tools are of basically two orders, regional to sub-regional (i.e.
Pacific Northwest divided into homogenous land form unit like the North-
west Olympic Peninsula), sub-regional to local (i.e. Northwest Olympic
Peninsula land form units of 10 acres or larger homogenous units). The
following paragraphs illustrate techniques which have been developed
by Region X researchers and practitioners to critique sensitive terrain.
1. The Forest Residue Type Areas Map produced by the U. S.
Forest Service for Region 6 is an example of the larger
scale representation. This information shows geomorphic pro-
vinces, timber species associations and geomorphic sub-provinces,
The smallest mapping unit is approximately 10 miles square (15).
2. The U. S. Forest Service's soil resource inventory for Forest
Service Region 6 and other regions represents the next level
of forest land identification. "Soils have been defined and
mapped at an intensity sufficient for broad management inter-
pretations which can be used to develop resource management
policies" (16). In addition to these uses, forest soils are
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rated as to their potential erosion class, very slight, slight,
moderate, severe and very severe. "The land manager can use
this information to determine which areas will need special ero-
sion protective measures. These will need to be developed on
a site by site basis" (17). These maps serve transportation
planning needs as well. "Conditions and problems can be met or
avoided based on information such as landscape stability, soil
depth, soil drainage and/or bedrock type and competency" (17).
3. The Bureau of Land Management, Oregon State Office, is accom-
plishing intensive inventories of its western Oregon lands.
The objective is to provide the manager with detailed, in
place information about timber production sites for which he
is responsible (18). The intensive inventories deal with the
total land mass by separating the land base into various cate-
gories of potential forest production. One category, designated
as fragile, pertains to adverse soil and geologic conditions.
Fragile sites are defined by slope gradient, ground water, geo-
logic material (bedrock) and soil strength. Appendix 5 to
Bureau of Land Management Manual Supplement No. 5250 - "Inten-
sive Inventories", dated February 7, 1974, deals with procedures
for identifying fragile sites. Guide to Reduce Road Failures in
Western Oregon by Burroughs, Chalfant, and Townsend includes a
general outline of Western Oregon geology, and discusses basic
slope stability, and techniques for constructing stable roads on
specific geologic materials and soils (19).
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4. The Siuslaw National Forest has developed two schemes for eval-
uating terrain readability.
a. "Workload Analysis - Geo-technical Investigation
for Timber Sale Roads" (9).
b. "A Proposed Method of Slope Stability Analysis,"
Jennings and Harper.
The work load analysis uses a factor "P" which expresses a
percent probability that a given section of road location will
require a given level of geotechnical investigation. Figure
19, taken from Appendix E of the Siuslaw National Forest
Implementation Plan illustrates the use of the "P" factor.
The Proposed Method of Slope Stability Analysis attempts
to answer many forest land administrators and planners who have
expressed a need for a quantitative evaluation system to rate
slope stability. This report proposes a slope evaluation sys-
tem based on a soil mechanics safety factor formula named "The
Stability Index (Si)". It is intended to describe the general
slope stability of a soil mapping unit, separating only the
effect of slope. It is not to be used to evaluate on-site sta-
bility for specified projects 'Taut with additional input it could
be used as a starting point for project site analysis" (20).
5. "Highway Cut and Fill Slope Design Guide Based on Engineering
Properties of Soils and Rock" by Larry G. Hendrickson and John
W. Lund is a valuable design guide for specifying cut and embank-
ment slopes (21). This design approach attempts to reduce the
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use of intuitive techniques and to substitute a more rational
approach. The procedure uses soil strength properties together
with flatter slopes as cut heights increase. This work is in-
corporated into the U. S. Forest Service's Transportation
Engineering Handbook for Region 6 as Supplement No. 19, dated
February 1973. The supplement digest explains the Design Guide
as follows:
"Incorporates slope design guide. This is a guide
which provides general values or recommendations
for cut and fill slope ratios. Data needed to use
the guide are soil classifications, general field
conditions in respect to density and moisture, and
height of cut or fill.
The recommendations given must be modified to fit
local conditions and experiences" (22).
6. Douglas N. Swanston and others of the U. S. Forest Service
developed a pilot program for determining landslide potential
in glaciated valleys of southeastern Alaska. This development
was in response to investigations which had shown erosion to
be a predominate problem in southeast Alaska.
Land stratification techniques were- used to classify
potential landslide hazard. Data on land features were
characterized by "accurate location and distribution of all
active and potential landslides and snowslides and the estimated
or probable major variations in a slope stability characteristics
from one location to the next within the investigated area".
From this information a hazard rating system was devised to
stratify land zones (23).
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Their experience with the southeast Alaska's steep slopes
with shallow coarse grained soils lead them to use three clas-
sifications.
a. "A slope above 36° is highly unstable even under
the most favorable of natural conditions.
b. Slopes between 26° and 36° may or may not be stable
depending on local variations in basic soil charac-
teristics, soil moisture content and distribution,
vegetation cover, and slope.
c. Slopes below 26° (49$) were considered stable
although local steep, hazardous areas not picked
up in the initial survey may exist, and opera-
tions on them should be governed by the rules
for more unstable areas."
Swanston emphasizes the many natural unstable slope condi-
tions in southeastern Alaska and observes that man's activities
will aggravate them. He believes that the land manager must
decide whether "to accept the consequences of logging over
steepened slopes or to control the effects of these activities
in order to minimize mass movements" (24). He suggests that
control can be accomplished by direct methods of slope stabili-
zation or by avoiding areas of known or expected instability.
Roads and Harvest Method Relationships
There is a general trend in forest land management toward a closer
coordination of road planning with harvest 'methods. One of the factors
supporting this trend is the realization that past practices have some-
times resulted in haphazard road patterns resulting in more total road
mileage than necessary. Minimizing the road mileage is also a way to
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minimize the need to deal with the sediment creation and transport
problem.
Recognition of the problems attendant to over roading is not new.
In 1956, the Boise National Forest's guidelines for erosion control
reported a tendency for an excess of roads with the increased use of
heavy construction equipment, "especially if the construction chance is
easy." This publication further stated: "Too many roads within an area
completely destroy the protective soil mantle" (10).
Fredriksen studied erosion and sediment resulting from timber har-
vest and road construction in watersheds within the H. J. Andrews Experi-
mental Forest (2). A watershed harvested by clearcutting using Skyline
logging without roads yielded less sediment than a watershed harvest
by patch clearcutting, high lead logging and parallel logging roads.
Although harvest method - road relationships are not exclusively
the forest engineers domain, nor are they exclusively pertinent to the
subject of sediment, serious attention to these relationships is be-
lieved to be an important part of the engineer's initial discussions with
the land manager. The engineers pre-field reconnaissance response to
the land manager about the engineering feasibility of a proposed road may
appropriately include a response to management's assumed logging method
as previously mentioned. Alternately, the engineer may be asked to
assist the land manager determining what harvest method is compatible to
the type and location of road that can be constructed in the proposed
corridor.
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A detailed discussion of the road-harvest method relationship is
beyond the scope of this report. Harvest systems and road location,
density and standards are interrelated. As neither the harvest system
nor the road network are independent of each other, both must be consi-
dered in the evaluation of total system impacts. Knowledge of the har-
vest method and its effect on road location, width and alignment is of
vital importance in defining the scope of the field reconnaissance.
CONCLUSIONS
After the engineer's report to the land manager, a mutually agree-
able definition for the road reconnaissance should be ideally established.
Since a "no road" decision is complicated in marginal terrain, a field
reconnaissance to affirm this decision may be necessary.
A specific understanding of management objectives is a need that
was emphasized in Recommendation 6.1 of the U. S. Forest Service Region 6
Road Audit (8). The Siuslaw National Forest Implementation Plan urges
detailed management inputs including trade-offs considered, allowable
impacts on road geometry that are acceptable to attain an objective and
the inclusion of "realistic confidence levels expected in the designer"(9).
ROUTE RECONNAISSANCE
Route reconnaissance is the examination of the entire area surround-
ing the proposed project with the intent to segregate routes on their
relative merits of economics, service and ecological impacts. The tal-
ents appropriately involved in a reconnaissance for a particular project
will vary with the scope of the proposed road, the relative sensitivity of
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the terrain, the knowledge and experience of personnel and the amount of
data already available about the proposed corridor.
Larse points out that "all too frequently the location of a specific
road is a one-man effort with little consideration or recognition of al-
ternative opportunities, watershed values, land form or soil character-
istics and stability, or other environmental conditions" (5). A recon-
naissance team might consist of a hydrologist, soil scientist or soils
engineer, geologist, landscape architect, forester, forest engineer,
civil engineer, watershed specialist, biologist and others. The discip-
lines listed above might be those assembled for a major undertaking in
highly sensitive terrain about which little applicable data is available.
Members of a reconnaissance team whose duties would include obser-
vations for and the gathering of data to determine potential problems
of sediment creation and transport are the geologist and/or soils engi-
neer, the forest engineer and the civil engineer. The depth of investiga-
tion necessary for these disciplines cannot be generalized in the abstract
without specific knowledge of the actual site conditions for a proposed
road. As pointed out in "State of the Art Techniques" in this Chapter,
the Siuslaw National Forest has a procedure for determining the depth of
geo-technical investigation required for a given road location.
As the introduction to this Chapter emphasized, an adequate field
reconnaissance is of great importance when the goal of sediment minimi-
zation is a part of logging road performance criteria. Historically,
sedimentation problems have been related to the following oversights or
errors.
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1. Inadequate geo-technical information.
2. Lack of engineering input.
3. Application of rigid rules regarding horizontal curvature
and vertical gradients.
4. Over-roading or misplaced roads due to a lack of or a poor
land management and transportation plan.
5. Road locations that support an inappropriate harvest procedure.
The discussion that follows is divided into three parts: (l)
factors affecting surface erosion, (2) erosion and mass wasting consi-
derations, and (3) civil and forest engineering reconnaissance.
FACTORS AFFECTING SURFACE EROSION
Surface erosion includes sheet erosion and channel erosion. Sheet
erosion, including rill erosion, involves the detachment and removal of
soil particles by overland runoff, while channel erosion involves removal
and transport of material by concentrated flow. The concentrated flows
may be contained in large mainstem channels, small tributary drainage
channels, or road ditches (25).
Many factors with often complex interrelationships are involved in
surface erosion. The primary factors involve precipitation characteristics,
soil characteristics, topography, and cover conditions (26, 27, 28, 29,
30).
Precipitation intensity and amount affect both sheet and channel
erosion. The higher the rainfall intensity or snowmelt, the greater the
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detachment and transport of soil particles through sheet erosion and the
greater the rate of runoff which is reflected in increased channel
flows. As runoff discharges increase, velocities likewise increase.
The erodibility of a particular soil depends upon its resistance to
detachment and, once detached to its resistance to transport. The
resistance to detachment is primarily controlled by particle-size and
aggregation, while the resistance to transport is primarily governed by
particle-size. Clays, for example, have very small particle-size and
are easily transported by water, but are not easily detached because of
high aggregation. Coarse sands or gravels are noncohesive, but are not
easily detached or transported because of much larger particle-size.
Silts, including fine sands, have relatively small particle-size, although
not as small as clays, and are generally relatively easily detached and
easily transported, thus making them most vulnerable to erosion. Silts
become less erodible as either the sand and gravel or the clay fractions
increase. Also, for a given increment of silt, increases in the clay-
to-sand ratio decrease the erodibility (31, 32). Adverse effects upon
water quality, however, may be increased with increasing clay content
because of the extremely poor settling characteristics of clay thus
causing turbidity.
The capability of runoff to detach and transport soil material
increases rapidly with increases in runoff velocity which is controlled
by topography, among other factors (33)- Theoretically, doubling
velocity enables water to move particles 6/4 times larger, carry 32 times
more material in suspension, and increase the erosive power 4 times (25).
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Runoff velocity increases as the runoff rate increases, as the flow
concentrates (often because of increased slope length), or as the slope
steepens. Increasing the steepness of a slope from 10 percent to -40
percent, for example, doubles the flow velocity.
Sheet erosion is greatly affected by cover conditions. Raindrops
striking bare soil act like minature bombs to break up soil aggregates
and splatter soil particles as much as 2 feet into the air. Raindrops
also compact exposed soil surfaces resulting in increased rates of
surface runoff. Some conception of the striking force can be envisioned
from the fact that raindrops strike the ground at velocities of about 30
feet per second and 1 inch of water over an acre of area weighs more
than 110 tons. Sheet erosion is reduced by maintenance of a dense
ground cover. Vegetation is the most effective means of providing this
cover. Vegetation acts to absorb and disperse raindrop impact and
stabilizes the soil surface with a dense mat of roots. Mulches and
other forms of ground cover can also be quite effective (34, 35).
Channel erosion is also affected by cover conditions, both in the
channel and in the tributary drainage area. Poor areal cover not only
results in high rates of sheet erosion but also results in high channel
flow. Noncohesive, fine-grained soils such as silts and fine sands
erode readily when channel velocities exceed 2 feet per second. Good
grass cover in the channel may enable more than doubling of these
velocities before serious erosion develops. Riprap cover or other means
of channel protection may protect the channel from scour for velocities
up to 10 feet per second or more (25).
117
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The relationships among the principal factors controlling soil
erosion, notably sheet erosion, have been embodied in several somewhat
similar predictive equations (25, 26, 27). Most of the equations
presently available have been developed for cropland areas. Of
these, the "Universal Soil Loss Equation" for predicting sheet
erosion, as presented by Wischmeier and Smith in USDA-ARS Argriculture
Handbook 282 (26), has gained the most widespread acceptance. The
available predictive methodologies still fall far short of accurate
prediction of soil erosion or resultant downgradient sediment production
in a forested environment. Additional research is needed to test the
available equations for use on forest logging roads, or, if necessary,
for development of new prediction techniques.
SURFACE EROSION AND MASS WASTING CONSIDERATIONS
Roads seriously impact the hydrologic functioning of watersheds.
In many areas of highly decomposed granitic soil, 90 percent of the
increased sediment caused by use of the forests has been attributed to
roads (36). Higher runoff rates, increased surface erosion, and mass
wasting account for these increases. Much of the soil movement can be
avoided by proper road location and design. Adequate field and office
investigative work is necessary to assure that the essential information
needed for selection of the best route and proper road design is available.
During the planning process discussed in a previous section, the
need for the road is established and road termini and intermediate
points are defined resulting in delineation of a general road corridor(s).
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Other controlling design parameters, such as type and volume of anti-
cipated use, type of road, and any special features required, are also
defined. However, prior to any actual design work, reconnaissance
studies must be conducted to locate the best road alignment and gather
information needed for design of the road itself and associated drainage,
erosion, mass wasting, and other control measures. The source of the
reconnaissance information can range from office maps and reports to
detailed investigative programs involving field explorations and labora-
tory analyses.
A broad-based team of technical specialists should evaluate the
available information to develop a road design that best suits the
intended purposes while also minimizing economic and environmental
costs. However, because of the scope of this study, only those factors
affecting road performance with regard to surface erosion and mass
wasting as they affect water quality are included in this report. Some
of the information that should be considered to guard against stream
pollution resulting from surface erosion and mass wasting includes soil
texture and aggregation; subsurface soil strength, depth, and other soil
or rock conditions; slope lengths, steepness and aspect; existing surface
erosion and mass movement behavior along the route; precipitation and
streamflow characteristics; groundwater conditions; surface drainage
network; soil fertility and other conditions affecting vegetation
establishment; and up-gradient and down-gradient slope vegetation
patterns (36).
119
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The importance of the reconnaissance investigation cannot be over-
emphasized. It is during the reconnaissance work that the major decisions
are made. Once the road is located and constructed, mistakes are often
difficult or impossible to correct later on. Failure to do an adequate
job of reconnaissance can easily result in future construction, main-
tenance, transportation, and environmental costs far in excess of any
savings realized from an incomplete or inadequate reconnaissance (12).
Aids
Aids are of primary value during the planning phase. However, use
should be made of all available aids, including topographic maps, geologic
and soils maps and reports, aerial photographs, and others during the
reconnaissance investigations to gain an overall perspective of the
route or routes being considered and to obtain any detailed information
they may provide. During these investigations, aids should only be used
as supplements, however, and not substitutes for field investigations.
As a minimum for simple cases where these aids offer sufficient information
for design purposes, their accuracy should be field checked. Some of
the available aids and potential applications are described in the
following sections.
Aerial photographs. Aerial photographs are particularly valuable
in the planning stage for gaining an overall feel for a general area and
detecting differences between local areas that are important to route
corridor selection. However, they are also of considerable value in
final route selection and design during the reconnaissance investigation.
Aerial photographs of at least one usable scale are available for most
120
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areas, and in some areas more than one scale is available. Many photos
are available in stereoscopic pairs permitting viewing in three dimen-
sional perspective. Land forms, vegetation, or geologic and hydrologic
features are easily identifiable from such photographs.
Small-scale aerial photographs provide a broad perspective of an
area. Whole landscapes can be surveyed, enabling study of drainage
networks, geologic features and land forms, and vegetation patterns.
Mass movements, particularly large failures, are easier to detect.
Rotational movements are often indicated by arc-shape bedrock exposures
accompanied by uneven lands downslope or variations or abrupt changes in
vegetative patterns. Avalanche activity can be similarly identified by
abrupt changes in vegetative patterns perpendicular to the ridge system.
Large features of this nature are often much easier to identify from
such photographs than through use of other aids or on-ground observations.
Large-scale aerial photographs can be used to refine interpretations
made from the small-scale photos as well as enable more detailed inferences
of drainage, geologic, topographic, vegetative, and other factors.
Geologic bedrock types can often be identified and some degree of accuracy
can be developed regarding the fracturing and jointing pattern of a
particular bedrock type. The extent of talus, alluvial, and other
deposits can usually be identified. Slope gradients can be determined
with some degree of accuracy, and stream channel and other drainage
characteristics can be studied. Vegetative patterns and types can be
identified. Other interpretations, such as soil types, can often be
121
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made based upon interaction of geologic and land form characteristics,
vegetation, color, and other factors. Small-scale mass movement or
erosion activity can often be identified.
Topographic Maps. Topographic maps of various scales are available
for most areas. Such maps, particularly the 7J- and 15-minute series,
are quite useful for road location and design purposes (37). Infor-
mation on slope gradients and other topographic features can generally
be obtained with a reasonable degree of accuracy, particularly if over-
story vegetation was not dense at the time of photography for mapping.
Geologic inferences, including landform, slope steepness and irregularity,
arrangement and incision of drainage networks, and other features can be
made from topographic information. Topographic maps provide considerable
information on stream systems such as gradients and channel sizes in
easily obtainable form. Topographic maps are quite useful as base maps
and provide an easily available source of gradient information for trial
road alignments.
Soil Surveys. Numerous types of soils are exposed during road
construction in EPA, Region X. They are formed from many different
parent materials including glacial till, alluvial deposits, and granite.
These soil materials all have various unfavorable physical and chemical
properties that affect road performance, stability against surface
erosion and mass wasting, and revegetation. Soil or geologic character-
istics and related topographic conditions that may affect subsequent
road behavior include steep slopes, aspect, shallowness to rock or other
restrictive layers, unfavorable pH, low fertility, fine soil texture
122
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and low aggregation, low permeability, high groundwater table, high
shrink-swell potential, massive disturbance as a result of previous
slide activity, low strength characteristics, and high compressibility.
Soil surveys furnish considerable information on the extent of
these interacting features. Such surveys are generally compiled as a
single unit for large areas such as counties or national forests. This
provides a wealth of information on a broad scale that is well suited to
route selection, as well as for general guidance in road design. Soil
surveys are made and published by a variety of governmental agencies and
private organizations but mostly by the federal government. The Soil
Conservation Service has published detailed soil surveys for many counties
within EPA, Region X, and the Forest Service has published soil surveys
for many of the national forests (16, 17). New surveys are continually
being developed by these agencies and older surveys are continually
updated. The Weyerhaeuser Company has recently completed and published
an extensive soil survey of their land holdings as well as of contiguous
adjacent lands.
In addition to providing information on many of the individual soil
properties, most surveys also provide considerable interpretative
information on soil suitability for various uses, including limitations
on uses. Such ratings may include suitability for road location and
construction; potential for surface erosion; susceptibility to cut
or fill bank mass movement, sloughing, or raveling; limitations on cut
and fill slope seeding; suitability for various types of vegetation
establishment; and numerous other behavioral characteristics under
various uses.
123
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Geologic Maps. Geologic maps or reports of various degrees of
detail are available for many areas. The maps range in scale from state
or areawide to much smaller areas, such as portions of counties or 7|-
or 15-minute topographic quadrangles. Depending upon the degree of
detail, geologic maps may include information on topography, descrip-
tions and extent of surface outcrop materials, and strike and dip of
formations. Such maps may also include geologic hazards such as faults,
degree of slope, flood-prone areas, high groundwater table areas, landslide
topography, and areas susceptible to various types of surface erosion.
Other Aids. Several other less used but often equally important
aids are of value. These include precipitation intensity-duration maps
(38, 39), vegetation maps, hydrographic studies, or other general or
detailed reports available for the study area or similar areas.
Field Reconnaissance
Field reconnaissance is an essential step in any road location or
design study. In all but the simplest cases where the designer has
access to proven aids and is thoroughly familiar with an area, a field
reconnaissance should be made before final route location or design.
The purpose of the field reconnaisssance is to confirm inferences made
from other information sources and to gather otherwise unavailable or
more detailed information needed for either road location or design.
Only in rare cases will published information be detailed and accurate
enough to be suitable for final design purposes.
-------
During field reconnaissance, the applicable published information
on maps and aerial photographs should be used. These are valuable in
determining the location of control points, and are generally reliable
for use as base maps for field layout work.
The depth of the field reconnaissance is dependent upon the amount
of data already available, the importance of the road, and the magnitude
of the impacts the road is expected to generate. Generally, more than
one field reconnaissance trip will be necessary. These field investi-
gations may be phased and include a preliminary field reconnaissance and
soil survey of the corridor by a team of experienced specialists. The
team should include an experienced soils engineer, engineering geologist,
or similar specialist. The preliminary reconnaissance and soils'.'Survey
should establish the surface erosion and mass wasting potential within
the corridor and areas adjacent to the corridor and potential access of
eroded or wasted materials to streams. This preliminary work should
also include delineating areas of potential hazard and, where possible,
outlining alternate routes to avoid the hazards.
The next phase of work should consist of detailed investigations of
the hazard areas and possible alternate routes. The detailed investi-
gation may include test pits, borings, undisturbed sampling for strength
testing, installation of piezometers to obtain valid water table infor-
mation, and in some cases installation of slope indicators to determine
the degree of mass movement.
125
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Many factors must be considered and properly evaluated during field
reconnaissance surveys if surface erosion and mass movement are to be
minimized. The factors primarily include surface and subsurface soil
and geologic conditions; topography, including slope steepness, length,
and aspect; precipitation; groundwater conditions; and vegetation. How
each of these and other factors affects sediment contribution to streams
due to surface erosion and mass wasting will be discussed in the following
sections.
Surface Evasion. Numerous factors affect the potential for soil
erosion from forest roads and contribution of such sediments to streams.
These factors, which were discussed in a previous section, primarily
include soil texture, aggregation, and other intrinsic properties;
topographic factors such as slope steepness, length and aspect; nearness
of the road to the stream system; precipitation amounts, types and
severity; and up-gradient and down-gradient vegetation. Roadway design,
including slope protection and drainage provisions, can also have a
significant influence.
By far the most important factor influencing surface soil erosion
is soil texture and aggregation, although several other characteristics
are involved (32). Silt-size particles are the most erodible, and the
erosion potential decreases as the percentage of sand or larger and
clay-size particles increases. Clay-size particles, however, have more
adverse effects upon water quality because of their extremely poor
settling characteristics.
126
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Detailed evaluation of the soil texture, aggregation, and other
characteristics affecting erosion would be somewhat difficult in the
field. However, in many cases experienced field personnel could make a
reasonably accurate estimate of the necessary information by visual
inspection and by use of shake, pat, kneading, and other types of simple
field tests. One such field classification guide to estimate inherent
soil erosion potential is shown in Table 4 (40). This guide is based,
in part, on the Unified Soil Classification System. This system is
presented in Table 5 (41) along with field identification procedures and
several simple tests used in classifying soils according to the system.
There are numerous procedures which may be used during a field
reconnaissance to obtain soil samples for textural identification.
Among these are small hand augers. With the use of extensions, these
augers can be used to obtain small samples from depths of 3 to 15 feet.
However, these augers are of limited use in soils containing large
percentages of gravel or in bedrock. Shallow samples for textural
identification can be obtained from hand-dug pits in coarser grained
soils. Also, information on shallow as well as deeper soil strata can
be obtained from natural or man-made exposures within or near the
corridor and these soil conditions correlated with those along the
proposed route.
Other soil factors besides those strictly influencing surface
erosion and mass wasting should also be investigated during the field
reconnaissance. These include moisture regime and fertility. They are
of value in planning the revegetation program.
127
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TABLE 4. GUIDE FOR PLACING COMMON SOIL AND GEOLOGIC TYPES INTO EROSION CLASSES (40)
00
Erosion
Class I
Erosion
Index 10
SM-
-o
0)
•H
<3 ML
•l~l
•0
3
w
(D
i
-p 03
0) p)
H 0
i — 1 C_3
•H
O i — 1
W -H
O
T3 CO
cd €
9 CO
II III IV
20 30 40
SM Silt (Un- Silt (Con-
consoli- solidated )
dated )(B) (B)
ML OL OL
MH MH
V
50
Silty
clay
loam( A )
Silty
clay(A)
Clay,
VI
60
Clay
loam
(A)
Silty
loam
(A,B)
varying
cohesiveness &
CL
Sandy
clay(B)
SC, GM
OH, CH
(A)
Sandy
clay
(B)
CH, GM
VII VIII IX
70 80 90
Loamy Coarse Fine
sand sand gravel
(c) (c) (c)
Sandy SW
loam SP
(B)
with type,
compaction
Sand
(B)
GC
X
100
Rock
(c)
Cobble
(c)
Gravel
(c)
GW, GP
NOTE: (A) indicates nonporous materials; (B) indicates moderately porous materials; (C) indicates highly
porous materials.
— SM, ML, etc. refer to the Unified Soil Classification System.
-------
TABLE 5 UNIFIED SOIL CLASSIFICATION
(Including Identification and. Description_)_
Major Divisions
1
Coarse-grained Soils
More than half of material is larger than No. 200
sieve size.
mallest particle visible to the naked eye.
Fine-grained Soils
More than half of material is smaller than No . 200
sieve size.
The No. 200 sieve size is about the s
2
Sands Gravels
More than half of coarse More than half of coarse
fraction is samller than fraction is larger than
No. 4 sieve size. No. 1+ sieve size.
(For visual classification, the 1/4 in. size may he used as
equivalent to the No. 4 sieve size)
Sands with Gravels with
Fines Clean Sands Fines Clean Gravels
(Appreciable (Little or (Appreciable (Little or
amount no fines ) amount no fines )
of fines) of fines)
>> -P O
3 |g
T) £i
d tj +>
& -3 »
ra o< en
S 33
3
co o
>i -p ir\
H ^ fi
o -H a)
H X
-a +=
C T3
aj -H FH
-P -H 03
iH i-^l
•H FH
W hO
Group
Symbols Typical Names
3 4
GW i Well-graded gravels, gravel-sand mix-
tures, little or no fines.
GP
GM
GC
SW
SP
SM
sc
ML
CL
OL
MH
CH
OH
Highly Organic Soils Pt
Poorly-graded gravels, gravel-sand mix-
tures, little or no fines.
Silty gravels, gravel-sand-silt mixtures.
Clayey gravels, gravel-sand-clay mix-
tures.
Well-graded sands, gravelly sands, little
or no fines .
Poorly-graded sands, gravelly sands,
little or no fines.
Silty sands, sand-silt mixtures.
Clayey sands, sand-clay mixtures
Inorganic silts and very fine sands, rock
flour, silty or clayey fine sands or
clayey silts with slight plasticity.
Inorganic clays of low to modiura plas-
ticity, gravelly clays, sandy clays,
silty clays, lean clays.
Organic silts and organic silty clays of
low plasticity.
Inorganic silts, micaceous or diatoma-
ceous fine sandy or silty soils, elastic
silts.
Inorganic clays of high plasticity, fat
clays .
Organic clays of medium to high plas-
ticity, organic silts .
Peat and other highly organic soils.
Field Identification Procedures
(Excluding particles larger than 3 inches
and basing fractions on estimated weights)
5
Wide range in grain sizes and substantial
amounts of all intermediate particle sizes.
Predominantly one size or a range of sizes
with some intermediate sizes missing.
Nonplastic fines or fines with low plasticity.
(for identification procedures see ML below)
Plastic fines (for identification procedures
see CL below) .
Wide range in grain sizes and substantial
amounts of all intermediate partical sizes.
Predominantly one size or a range of sizes
with some intermediate sizes missing.
Nonplastic fines or fines with low plasticity.
(for identification procedures see ML below).
Plastic fines (for identification procedures
see CL below).
Identification Procedures
on Fraction Smaller than No. 40 Sieve Size
Dry Strength Dilatancy Toughness
( Crushing ( Reaction ( Consistency
characteristics) to shaking) near PL)
None to slight Quick to slow None
Medium to high None to ver^ Medium
slow
Slight to Slow Slight
medium
Slight to Slow to none Slight to
medium medium
High to very None High
high
Medium to high N°ne to ve™ S1j-?ht to
sl ow mprhnm
Readily identified by color, odor, spongy feel
and frequently by fibrous texture.
(l) Boundary classifications: Soils possessing characteristics of two groups are designated by coml
ib mat ions of group symbols.
Source: Reference 41.
129
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Topographical considerations are very important in road location.
Among these are slope steepness, slope length, slope aspect, and near-
ness to stream channels.
Roads should be located in stable areas well away from streams in
order to minimize stream sedimentation. Routes through steep narrow
canyons; slide areas; through steep, naturally dissected terrain;
through marshes or wet meadows; through ponds; or along natural drainage
channels should be avoided. Where it is impractical to avoid any of
these conditions, corrective stabilization measures should be incorporated
into the road design. It is particularly important that road locations
be fitted to the topography so that minimum alterations of natural
conditions are necessary (4-2).
Valley bottoms have the advantages of low gradient, good alignment,
and little earth movement. Disadvantages are flood hazard, number of
bridge crossings, and proximity to stream channels. Because of the near
proximity to streams, erosion or mass failures are much more likely to
result in stream sedimentation than from roads along more distant
alignments. Wide valley bottoms are good routes if stream crossings are
few and roads are located away from stream channels. Roads in or
adjacent to stream channels should be avoided. Roads should be located
far enough away to prevent transport of sediment into stream channels
(43).
Roads in valley bottoms should be positioned on the transition
between the toe slope and terrace to protect the road slopes from flood
erosion and allow road drainage structures to function better and discharge
130
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less turbid water into live streams. However, road location in these
areas should be avoided if it involves undercutting old slides or land-
flows. Any stream crossings required should be selected with particular
care to minimize channel disturbance, minimize approach cuts and fills,
and produce as little disturbance as possible of natural stream flow.
Valley bottoms should not be roaded where the only choice is encroach-
ment on the stream (44).
Hillside routes have the advantage of being located away from
streams which eliminates flood and stream damage, and intervening
undisturbed vegetation acts as a barrier to sediment transport. Dis-
advantages are higher grades, more excavation, longer slopes, poor
alignment from following grade contours, and cut banks that expose soil
to erosion (43). When locating roads along side hill routes, benches
and the flatter transitional slopes should be used if they are stable.
Steep, unstable, dissected slopes, particularly in areas of deep plastic
soils or weathered or decomposed rock formations, should be avoided
because of potential mass stability problems (44).
Ridge routes have the advantages of good drainage, less excavation,
and fair grades (43). Other advantages include practically nonexistent
up-gradient slopes and large expanses of undisturbed vegetation or
logging slash to act as buffer strips for protection against stream
sedimentation. Disadvantages are poor alignment in some areas because
of excessive dissection of the ridges, and secondary roads that may have
adverse hauling grades and greater total road mileage (43). Ridgetop
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roads should be located to avoid headwalls at the source of tributary
drainages. These are often extremely unstable slopes, and any erosion
or slope failure will flow directly into live streams (44).
Another locational characteristic, aspect, also has some influence
on soil stability. However, aspect influences the functional character-
istics of forest roads more than it does their geometric design and
stability. North-facing slopes retain snow and ice for longer periods
than south-facing slopes (40). However, Renner's (45) study on the
Boise River watershed showed that erosion differed sharply according to
exposure. Soils on south exposures eroded most severely.
Packer and Christensen's (46) study also showed that erosion
rates are higher on south-facing slopes. This was attributed to the
loosening of the soil by frost heaving. Also, south and west slopes
in many areas are considerably less densely vegetated than north and
east slopes. Runoff and sediment trapping characteristics are greatly
influenced by. this. Aspect also helps determine the degree of success
or failure in reestablishment of vegetative cover after disruption by
road construction.
During the field reconnaissance, vegetation along the proposed
route should be surveyed. Vegetation along this route is an indicator
of other factors, such as soil fertility and moisture regime, but most
important is its effect on retarding runoff both upslope and downslope
of the road prism. Upslope vegetation and ground litter can have a
significant effect on the amount of water reaching the road prism. Long
unimpeded, up-gradient slopes with poor infiltration characteristics
can contribute large quantities of overland flow causing erosion of
the road prism.
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Probably more important than upslope vegetation is the vegetative
and ground cover downslope of the road prism. Downslope vegetative
cover can retard overland runoff and discharges from cross drains and
other road drainage structures causing suspended sediments to be settled
out before reaching stream systems. Several investigators, including
Trimble and Sartz and Packer, have studied the buffering and filtering
performance of vegetation strips. Packer's investigative work was
particularly comprehensive as to the individual parameters affecting
buffer strip performance. Packer found that obstructions such as rocks,
stumps, and herbaceous vegetation and trees, and numerous locational and
design factors such as amount of aggregates in the soil, amount of
disturbed slope, cross drain spacing, and distance to the first obstruc-
tion, all influenced buffer strip performance. More detailed information
on factors affecting buffer strip performance is contained in a following
section. All of these factors should be considered during field recon-
naissance, especially during the road location work, to ensure that
adequate buffering is provided between roads and stream systems.
Mass Wasting. The most common and perhaps the most significant
erosion from forest roads is mass movement. This is caused by under-
cutting unstable slopes, improper embankment construction, wasting on
steep slopes, and drainage system failures (44). Some of the factors
affecting mass wasting which should be determined during the recon-
naissance are cross slope angles; soil texture, depth, and in situ
strength; groundwater conditions; and identification of old, existing,
and potential future unstable areas. These should be investigated, not
only within the corridor, but up and downslope of the corridor.
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There are several topographic and vegetation indicators that can
indicate existing mass wasting. Among these are U-shaped depressions,
downslope depressions, stream bank overhang, mucky surfaces, tension
cracks, curved tree butts, and "jaekstrawed" or "crazy" trees. Some of
the indicators of potentially unstable areas are slopes greater than 70
percent, horseshoe-shaped drainage headwalls, fracture patterns, seeps
and springs, and piping (24). These can be identified by experienced
personnel.
Other important conditions which should be determined to evaluate
mass wasting potential of an area are in situ soil strengths, amount of
overburden to bedrock, and natural bedding planes within bedrock. An
approximation of in situ soil strengths can be made by visual inspection
of hand-dug pits and existing soil exposures, both within the corridor
and within areas outside the corridor which are similar in nature. The
thickness of overburden is often difficult to determine; however, an
experienced engineering geologist or similar specialist familiar with
the area and its geologic history can often provide good approximations
after a field reconnaissance. A geophysical survey may be applicable in
some areas to evaluate overburden thickness but they are often expensive
(47, 48). It must be realized that a geophysical survey cannot be used
to evaluate the type or strength of the soils within the overburden.
In addition to these other factors, the location of the water table
(which in most cases will be perched) along the alignment should be
investigated during the reconnaissance phase of investigation. The
134
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water table may be located by mapping springs and seeps in the corridor;
identifying certain types of vegetation which exist only where water is
readily available; locating areas which exhibit some thickness of soft,
spongy, highly organic materials; or from a geophysical survey. In
unconsolidated materials the water table may be located by relatively
shallow explorations such as hand-dug pits, hand-auger holes, or by
probing.
After compilation and interpretation of the data obtained during
the reconnaissance, areas that present potential hazards should be
further investigated by more sophisticated means. The major problems
involved in performing a detailed investigation of potential problem
areas is that these areas normally have only limited accessibility and,
in many cases, may require that equipment needed for such an investi-
gation be either packed in or flown in by helicopter. Detailed in-
vestigation of these areas should be accomplished by a specialist in
soil mechanics or rock mechanics. Such an investigation should be
specifically tailored to the field conditions at each site.
The conditions encountered during construction may vary somewhat
from those encountered in the geologic reconnaissance due to the com-
plicated nature of deposition and formation of soils and bedrock.
Provisions should be made to alter the design during construction
according to the actual conditions encountered.
In addition to in situ factors as discussed above, the design of
the road can have a very significant effect on mass stability. Roads
that impose themselves on the landscape because of poor location or
135
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overdesign (e.g. excessive width, large cuts and fills to avoid occasional
steep gradients, large radii curves, etc.) rather than conform to the
landscape are the primary cause of excessive mass stability problems on
many roads. In order to avoid designing mass stability problems into
roads, road alignments should follow the existing topography to the extent
possible and be designed to meet the minimum standards (e.g. minimum
width, minimum length and height of cut and fill slopes, etc.) consistent
with their intended use.
CIVIL AND FOREST ENGINEERING
The task of the civil and forest engineers on field reconnaissance
is to establish a road location that best satisfies the intended road use
within the constraints of the terrain. The engineers are assisted and
advised by geotechnical specialists (see the previous section) and by
field surveyors. Hopefully, experienced engineers enter the field recon-
naissance phase with some rational guidelines from their superiors about
road use and harvest method and with latitude to interpret these guidelines
in the light of actual field conditions.
Harvest Method
Planning aspects of the road-harvest method relationship are dis-
cussed in the planning part of this Chapter. Adoption of modern logging
methods such as cable, balloon and helicopter appears to be increasing
partially due to environmental constraints that have the effect of reduc-
ing the miles of spur and secondary roads. In addition to less roads,
the advantage from the sediment aspect is that landings for some of these
136
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logging methods are preferably located near ridge tops or on high benches
as uphill yarding distances are much greater than downhill yarding dis-
tances . Roads that connect these landings are therefore high on the
hillside away from the live stream. Downhill yarding can concentrate
ground cover disturbance at the road or landing and may create the poten-
tial for sediment movement to roadside ditches.
Although high lead systems are used in Alaska, downhill (e.g. Grabinski)
yarding is often employed. Many ridge or hill tops are above the timber
line or are above the zone of merchantable timber. Further, it is often
desirable to leave timber on the upper sections of a hillside to inhibit
avalanches. Roads tend to be appropriately located near valley bottoms.
The high mobility of new equipment suggests that logging operations
may be accomplished in more inclement weather than was previously con-
sidered appropriate. However, equipment size may place constraints on
allowable horizontal road curvature and equipment weight may require
closer scrutiny of the stability of proposed landings or the road itself
if it utilizes a road turnout as a landing.
Existing Road Audit
An audit of existing nearby roads in similar terrain and their main-
tenance and construction records may be of value to reconnaissance engi-
neers. This audit will be useful from an overall design standpoint as
well as for potential sediment control problems. Specific features
deserving attention are:
1. Surface condition of cut and fill slopes (Slope raveling).
2. Ditch adequacy in terms of size, shape, and effectiveness of
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any lining.
3. Culvert entrances and exits.
4. Performance of sediment control devices such as trash racks,
settling basins, and downslope debris barriers.
5. Culvert spacing.
6. Geology and soils as may be revealed by exposed cut banks.
7. Road surface condition, i.e. crown, ballast performance,
presence of surface rills.
8. Alignment relative to shape of terrain.
Maintenance records of the audited road, if available, or similar
roads may be valuable as a cross check of personal observations. The
records may provide a chronological order of events and data on the
amount and kind of work accomplished for each maintenance problem. These
records may indicate that certain culverts were undersized, improperly
constructed or should have had different entrance or exit treatments.
They might also indicate the extent and location of sloughing and road-
side slumping and the frequency at which roads were reshaped. These
recordings will aid engineers in identifying potential problem conditions
during the field reconnaissance.
Construction inspection reports are not always available as a part
of maintenance records. These reports may record particular problems
during construction and indicate if they were due to the road design
or specific construction techniques.
Route Placement
In the process of establishing a route, the engineer may ask himself
the following questions as a guide for ensuring a thorough study of the
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circumstances:
1. What are the potential risks and attendant damages?
2. What precautions are necessary to mitigate the risks?
3. What deviations in the road standard are acceptable in order
to better accommodate corridor conditions?
4. What are the costs in time and money in the event of failure
or of success?
5. What are the environmental results of failure?
6. What are the alternates in terms of road location, road
alignment and alternate solutions to specific features?
Natural features of the corridor that should receive particular atten-
tion when there is the potential for a sediment problem include:
1. Proximity of live streams.
2. Capability of downslope areas to act as filters or buffers.
3. Terrain slope.
4. Shape of terrain in terms of degree of natural dissection.
5. Type of vegetative cover.
6. Evidence of natural soil erosion.
7. Presence of ground water.
8. Signs or indicators of natural slope stability or instability.
9. Circumstances at possible stream crossing points.
The civil and/or forest engineer will be assisted in the evaluation of
some of the above features by the geotechnical specialist. However, the
engineer, as the generalist, should make his own evaluation of the cir-
cumstances based on his knowledge of the area and his concept of the
potential effect of a road. Road effect includes not only the effect
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after road completion but during construction including the practicali-
ties of construction season, construction practices and construction
equipment.
An important aspect in road location is the desirability of fitting
the road to the terrain. This is stressed both in writing and orally by
experienced forest engineers. Although it may be appropriate to enter
a reconnaissance with idealized criteria about minimum horizontal curva-
ture, maximum and minimum vertical gradients, and balancing of earthwork
quantities, these criteria must yield to the shape of the terrain. For
example, where short lengths of steep vertical gradients will avoid or
reduce midslope roads in the type of terrain described by Frederiksen
(2), they should be utilized. Where a "field adjusted" horizontal curve
will avoid or reduce excavation into a potentially unstable hillside,
it should be considered over adherence to the mathematical niceties of
a constant radius curve.
All other factors being equal, a minimum vertical gradient of 2 to
3 percent is desirable to provide good drainage. Flatter grades are
difficult to drain, may contribute to ponding and consequent road sur-
face deterioration under heavy truck traffic. This in turn can cause
sediment. Rolled grades provide convenient places to collect and remove
drainage. Grades exceeding 10 percent may require special attention to
the potential for ditch and roadway surface erosion.
Where roads are close to live streams, an evaluation of the ability
of the vegetation, the terrain and the terrain slope between the road
and stream to act as a natural barrier to the transport of sediment
should be made. Brown believes there are limits to the value of the
HO
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buffer strip in dissected terrain because buffer strip function assumes
that sheet flow similar to eastern agricultural soils is the major soil
erosion mechanism. He points out that the highly dissected, rough sur-
faced topography in most forest watersheds precludes sheet flow. Water
flows to rills or channels which converge to larger channels. "Since
channel flow predominates, eroded materials are carried through a buffer
strip"(l). The effectiveness of the buffer strip may vary with the tex-
ture of the soils.
All other factors being equal, crossing a stream at right angles
to its axis affords the minimum construction in and around the channel.
The designer will rely heavily on the reconnaissance observations in
determining the appropriate stream crossing method. The importance of
stream crossings is discussed by many writers including Frederiksen's
studies in Western Oregon watersheds (2), and Jack S. Rothacher and
Thomas B. Glazebrook's evaluation of Region 6 flood damage during the
1964-1965 floods (11).
Features of the proposed stream crossing requiring reconnaissance
evaluation include:
1. Non-manufactured debris in the channel at and above the proposed
crossing.
2. Stability of natural banks.
3. Evidence of old abandoned channels or presence of natural over
flow channels.
4. Natural constrictions to high water.
5. "High water mark" signs.
6. Suitability of circumstances for ford, culvert or bridge.
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7. Classification of visible soils strata.
8. Opportunity for flood water bypass channel over proposed
approach roadway.
9. If culvert, round, pipe arch or plate arch?
Advantages and disadvantages of type of topography are discussed in the
field reconnaissance portion of the Route Reconnaissance section.
Ground water can be converted to surface flow in mountainous areas
where a slope is cut to form a level roadbed. Shallow coarse textured
soils overlaying relatively impermeable bedrock is a circumstance where
this phenomenon can occur. Megahan observes that conditions are ideal
for its occurrence in the Idaho Batholith (49). The potential for this
occurrence should be evaluated during reconnaissance so that the designer
may recognize ground water effects in his design of drainage features
and his evaluations of cut and fill stability.
Field Survey Information
In addition to the normal route traverse and cross sectioning done by
route surveyors, there are field data to record relating specifically to
the sediment control portion of the road design. The following is a
listing of such information:
1. Survey crews should be made aware of key vegetative slope
stability and ground condition indicators (see Table 6 for
a plant indicator key developed for use in the Siuslaw
National Forest). These indicators (plant colonies and tree
dispositions) should be plotted with the traverse.
2. Survey crews should be alerted to take additional cross sec-
tions at suspect problem sites or abutting sensitive areas
H2
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(i.e. locations adjacent to old slide areas and streams) as
may be designated by the engineers and geotechnical special-
ists.
3. Additional information regarding cross sections at streams
should be emphasized by the engineer. This is particularly
important in order to design the appropriate culvert entrance
and exit and for determination of channel capacity. At a
stream crossing which will require a large culvert or bridge,
the engineer must visit the site with the land surveyor and
prescribe the topographic data required.
4. The engineer, from his field reconnaisance, may direct the
route surveyor to take notes on natural residue and debris
that could prove to be maintenance problems.
5. The surveyor should be directed to provide location data on
unique features that influence the road in the road corridor
and not just "on line" data. The following items are examples.
a. Rock outcroppings and their condition.
b. Hummocky surfaces.
c. Terracetts.
d. Over steepened slopes.
e. Ground cracks or fissures.
f. Islands of over or under vigorous trees.
g. Natural stream scouring (continuous or intermittent streams).
h. Natural drainage courses.
i. Natural slumps and slides.
Survey notes are one of the designer's basic aids. Recorded observations
by survey crews and accompanying sketches, if appropriate, are of great
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TABLE 6
SIUSLAW NATIONAL FOREST - PLANT INDICATORS
11-9-72
Very Dry
Douglas fir x
W. hemlock '
W. red cedar
Red alder
Goats beard lichen x
Madrone c
Ocean spray x
Poison oak c
Oregon grape c
Salal R
Red huckleberry R
Rhododendron R
Vine maple
Sword fern
Oxalis
Salmonberry
Wild lily-of-the-valley
Indian lettuce
Deerfern
Bleeding heart
Devils club
Stink currant
Horse tail
Skunk cabbage
Lady fern
Maiden hair fern
Bracken fern s
Thimble berry
Trailing blackberry
Grasses s
Dry
s
x
c
R
c
x
c
c
R
R
s
s
s
Ti t** -! *-i 4-
Moist
s
X
s
R
R
X
X
X
R
R
R
R
s
s
s
s
lMrt +
wet
s
x
X
s
R
R
' X
c
X
c
c
c
R
s
s
s
s
Very We"
s
R
x
s
c
c
c
R
c
c
c
c
c
c
c
X
X
s
s
) Leaning, bowed, or pistol butt trees indicate
) recent slide activity.
) Young trees may indicate recent slide activity,
) Serai also on deeply disturbed dry area.
Indicates Site Class V
Site Class IV with yellow-green lichen.
Usually Site Class III.
) With Salal may indicate igneous rock.
) Site Class I or II when together.
)
) Dominance increased by disturbance.
) Expect intense brush competition and
) slide hazard.
)
)
)
) Only red cedar or red alder adapted to the
) extremely wet conditions (slide hazard) - also
) drainage problems.
Mature height indicates site quality, moisture
forms dense serai stands with salmonberry
) preferred elk food.
x = CLIMAX DOMINANT s = SERAL DOMINANT
Source: Siuslaw National Forest Engineer
c = COMMON
R = RARE
-------
value. A portable dictating machine is of value for recording observa-
tions.
The USFS Region 6 audit points out that "inaccurate compaction factors
and unanticipated soil changes can lead to overwidth roads and earthwork
waste" ($). From the sediment aspect, it is desirable to handle the mini-
mum earth possible. "Overwidth" roads may not fit the terrain as initially
conceived thereby introducing extra load on steep terrain or a stability
problem for a sliver fill. Appropriate field survey data is mandatory to
the goals of obtaining accurate earthwork quantities, minimum changes
during construction, handling only the earth quantities necessary and
fitting the road to the terrain.
ECONOMIC EVALUATIONS
The introduction to this report suggested that when sediment con-
trol design criteria was the same or parallel to other road design
criteria, a road design specifically including sediment control features
may cost no more. No forest land manager or logger relishes the costs
of a road failure to his operation in terms of repair cost and lost
time during a harvest season. R. B. Gardner observed that: "The invest-
ment that may be required to achieve satisfactory stability will generally
be repaid by the road's longer useful life, reduced maintenance cost,
serviceability and contributions to improved water quality and quantity"(36).
COST ANALYSIS
The trend toward fitting the,road to the terrain with companion
change or revision of road standards to support this goal often results
U5
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in less quantities of earthwork per station or mile than accrued with
wider roads and/or roads with higher traveling speed alignments. Off-
setting the potential cost reduction from less quantities of material
may be the earth handling method. A narrow road constructed full bench
with a requirement that the waste be endhauled may cost more than a
wider road constructed without full benching and with no specific waste
disposal requirement. This latter procedure was often used.
Wherein road elements are designed to satisfy the goal of road
stability such as stable cuts and fills and adequate stream crossings,
the cost of sediment minimization related to these elements is likely
to be included in the cost necessary to obtain a stable design. Other
road features can be analyzed by comparing construction cost versus
maintenance cost such as ditch cleaning where tributary slopes are bare
versus ditch cleaning where tributary slopes are planted. Elements
specifically included for sediment control such as settling basins and
downstream check dams outside of the roadway corridor are examples of
capital costs that are likely to be unrelated to road stability or main-
tenance savings.
The Western Wood Products Associations' Forest Roads Subcommittee
has studied the minimum land impact road concept. Appendix A to the
minutes of one of the committee's meetings listed the following as part
of criteria for minimum land impact roads.
1. "It should be understood that a minimum land impact road will
not necessarily be a low-cost road, especially in steep-sloped
terrain with highly erodible soils. However, provisions for
minimum roadway and clearing width in difficult terrain situa-
tions will mean less cost for initial road construction and
subsequent maintenance, site restoration, and revegetation fo"
soil erosion control."
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2. "The total cost of construction, operation, and maintenance of
a road should be carefully assessed at various design standards
to find the optimum output for the three principal cost centers.
The various levels of road design standards should be compared
to the degree of impact each design standard places on the re-
sources and immediate environment. A possible output mix of
costs and impacts could be developed for comparison between
alternatives" (50).
Gardner offers some guidance on road standards, economics and environ-
ment in terms of amortized construction cost over road life, maintenance
and operating cost, the cost centers suggested by WWPA. Tables 7 and
B demonstrate the value of an investment in roadway ballast as the annual
cost of gravel roads is less than stabilized and primitive roads. On the
basis that ballasted roads have less potential for sediment production
than primitive roads, the ballast investment pays in terms of sediment
minimization as well as minimum annual cost.
TABLE 7
COMPARISON OF ANNUAL ROAD COSTS PER MlLEj
10,000 VEHICLES PER ANNUM (VPA)
•
*
Cost ; Road standard
distribution :2-lane :2-lane: 2-lane: 1-lane :1-lanei1-lane
;paved ; chip-seal : gravel ; gravel ;spot stabilization; primitive
------------Dollar per mile --------------
Initial
construction 50,000 -40,000 30,000 20,000 15,000 10,000
------- Annual dollars
— Depreciation
Maintenance
Vehicle use
4,360
200
2,200
3,490
400
2,300
2,610
600
2,700
per mile (20-year period)
1,740
800
3,000
1,310
1,100
4,400
870
500
8,500
2/
Total annual 6,760 6,190 5,910 -5,540 6,810 9,870
__
_,20 years at 6% using capital recovery.
— Lowest annual cost.
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TABLE 8
COMPARISON OF ANNUAL ROAD COSTS PER MILE FOR
20,000 AND 40,000 VEHICLES PER ANNUM (VPA)
Cos't ;
distribution : 2-lane :2-lane
Road standard
2-lane : 1-lane :
: paved
1-lanei1-lane
chip-seal: gravel : gravel :spot stabilization: primitive
Dollars per mile
Initial
construction
50,000 40,000
30,000 20,000
15,000
10,000
-"- Depreciation
Maintenance
Vehicle use
Total annual
Depreciation
Maintenance
Vehicle use
Total annual -'•
4,360
400
4,400
9,160
4,360
800
8,800
13,960
3,490
800
4,600
i/8,890
3,490
1,600
9,200
14,290
2,610 1,740
1,200 1,600
5,400 6,000
9,210
- ( Z.O
2,610
2,400
10,800
15,810
9,340
non VPA ^
1,740
3,200
12,000
16,940
1,310
2,200
8,800
12,310
1,310
4,400
17,600
23,310
870
1,000
17,000
18,870
870
2,000
34,000
36,870
—.20 years' depreciation at 6% using capital recovery.
— Lowest annual cost.
On the basis that the minimum road has less environmental impact,
Gardner suggests that the user cost for the environment is represented
in Table 9 by the difference in annual cost between two lane paved and
one lane gravel roads (51). Ignoring environmental considerations, the
lower annual cost road is a two lane paved one when traffic is 20,000
vehicles per year or more. With environmental factors requiring a one
lane gravel road, the annual cost is greater for more than 20,000 vehicles
per year.
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TABLE 9
COMPARISON OF SINGLE-LANEi VERSUS DOUBLE-LANE COSTS FOR
THREE DIFFERENT VEHICLE-J>ER-ANfflJM (VPA) CATEGORIES
*
VPA :
:
10,000
20,000
40,000
Total annual
1-lane
gravel
5,5-40
9,340
16,940
cost per mile :
• •
: 2 -lane :
: paved :
6,760
9,160
13,960
Difference
-1,220
+ 180
+2,880
Source: Gardner, R. B., "Forest Road Standards As Related to Economics and
the Environment," USDA Forest Service Research
Note INT-45, August 1971, 4 pages
The cost figures shown in the table are not applicable to all of
Region X. Gardner's work was published in 1971. However, he does suggest
a cost analysis approach that includes environmental considerations.
For readers interested in vehicle operating costs on logging roads,
R. J. Tangeman has proposed a model for estimating these costs relative
to characteristics of forest roads (52).
The Environmental Protection Agency's publication Comparative
Costs of Erosion and Sediment Control, Construction Activities includes
a procedure for determining the annual economic cost of conserving soil.
The procedure recognizes amortized cost of the capital investment and
annual maintenance costs. The report cautions that "each particular
location offers a unique soil loss potential, erosion control costs and
corresponding sediment removal penalties" (53).
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ECONOMIC JUSTIFICATION
An economic justification for additional capital investment in road
elements to achieve greater road stability under adverse conditions is
the risk of potential cost of a road failure. To illustrate this, cul-
verts and bridges should be designed to survive an anticipated storm
event. This means that hydrology studies and site surveys at bridge and
culvert crossings are necessary. Hydrology studies and detailed site
surveys cost money and the results of these studies may produce large
capital expenditures. Even so, this type of investigation is essential
if washed out bridges and culverts are to be prevented.
The 196/4-65 winter season floods in Oregon have been classified as
50 year floods in higher elevations. "The transportation system suffered
by far the greatest monetary loss. Damage to roads, bridges and trails
in Oregon alone was estimated at $12,500,000 - 4 percent of the total
investment of $355 million" (ll). This estimate does not include down
time cost or other inconveniences which accompanied these losses. The
flood damage estimates to USFS Region 6 roads and bridges for the 1973-74
season is in excess of the 1964-65 damage estimate.
Sediment control can also act as preventative maintenance. Seeding
slopes for erosion control can prevent slope raveling. Slope raveling
can diminish the roadway prism and cause high ditch and culvert main-
tenance costs.
Economic justification should be related to the role the intended
road is to play in the overall land management goal. The broader the
goal, the more varied are the inputs to the economic analysis. Legal
150
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requirements such as water quality criteria are "givens" to the engineer
as a part of the land management goal. Within these "givens", the engi-
neer must exercise his traditional role of preparing cost effective,
economic designs.
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DESIGN
"Road design is the process of transplanting planning objectives,
field location survey data, materials investigations and other
information into specific plans, drawings and specifications to
guide construction" (5).
The designer's task is to translate this data into a design which recog-
nizes and provides for sediment control.
When initiating a design, a designer must grasp an understanding of
the field work, reconnaissance and planning that has preceded him. He
must also understand management objectives and policy. This information
may be provided in a number of ways depending upon the organization's
structure. In some organizations, the designer has been a part of the
reconnaissance, and will be the construction supervisor. In others he
may have only limited personal contact with reconnaissance people.
Regardless of the organizational size and procedures or the designer's
disposition, there are several general features which the designer should
know in order to intelligently proceed. The following list is not all
inclusive.
1. The designer must be aware of the road's intended use, such as,
whether it will be principally a truck haul road, log landing
or yarding platform, or will have other demands. Prior know-
ledge of this kind may affect such choices as water bars or
pavement, fords or bridges, and grades and curvature.
2. A review of the reconnaissance and field information should
indicate to the designer the conditions within the reconnais-
sance corridor. If this review arouses doubt or lack of under-
standing, he must communicate with those who accomplished the
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field work. Preferably, the designer should at least visit
the site of specific key features within the project such as
stream crossings and steep hillsides.
3. The designer should have authority to obtain additional field
information and to alter design standards in order that a stable
road will be attained.
4. The designer should know to what extent he will be able to
follow the job through, and what control he or others will
exercise on workmanship. Quality construction is imperative
to the control of sediment.
The designer must familiarize himself with erosion control and road-
way stabilizing techniques. He must also be committed to sediment con-
trol and to the exercise of a degree of creative thinking.
This chapter is divided into four parts. The first part discusses
matters of the roadway design itself, the second part is devoted to fea-
tures of slope stabilization including a discussion of seeding and plant-
ing, mulches and mechanical treatments. Since many of the recorded mass
failures on forest roads appear to be drainage related, the third part is
devoted entirely to drainage design including ditches, culverts and stream
crossings. The last (fourth) part discusses features of the construction
specifications, prepared as part of the design task, that support the
goal of minimizing sediment.
ROADWAY
>
Many features or concepts for the roadway design may have been
developed or established as a part of the reconnaissance. However, the
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process of converting field reports, field survey notes and planning
goals to drawings with attendant horizontal and vertical control will
help resolve key details and controls that will appropriately refine
and execute the reconnaissance and planning information. This part dis-
cusses sediment features of the following roadway design elements: align-
ment, roadway prism, roadway surfacing, buffer and filter strips.
HORIZONTAL AND VERTICAL ALIGNMENT
Horizontal and vertical alignment are design features that can be
used to develop a road sensitive to sediment control. In developing
such a road, these features must be manipulated by the designer to
adjust the road alignment as the constraints of the terrain demand.
The discussion on reconnaissance in the previous chapter emphasized the
importance of fitting the road to the terrain.
The designer must also recognize the limits that may be placed on
him by the reconnaissance data and location. With the aid of field sur-
veys, geotechnical, civil and forest engineering information, he can
adjust the horizontal and vertical alignment to the terrain with compan-
ion attention to road use requirements.
The potential for generating roadway sediment can be mitigated by
utilizing a horizontal alignment that reduces roadway cuts and fills,
and avoids or minimizes intrusion upon unstable ground. If necessary,
the designer must have flexibility to adjust curve radii from that
established by arbitrary road standards. The designer's practical
experience and judgement are a part of his approach. The sediment con-
trol aspect has to be weighed with other features.
155
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Vertical alignment, like horizontal alignment, can be used to help
control sediment. In unstable steep terrain, adjusting the vertical
alignment to reduce cuts and fills and to position the road on stable
benches is an intelligent approach. In level areas sediment control is
aided by providing appropriate drainage to the roadway and roadway ditch.
A minimum grade of 2 percent will prevent ponding and reduce subgrade
saturation.
Roads from log landings provide another opportunity to practice
sediment control and preventive maintenance. A 5 percent adverse grade
from landing to road for approximately one hundred feet will reduce the
potential for mud and debris movement to the haul road.
Use of steep pitches to reach stable terrain must be accompanied by
appropriate treatment of the road surface; otherwise, the road surface
can be subject to serious rill erosion. This matter is discussed further
under Road Surfacing.
ROAD PRISM
The roadway prism is defined as the geometric shape generated by a
through fill, through cut, partial bench or full bench. The third part
of this chapter discusses the roadway ditch portion of the prism, the
next part discusses slope stabilization and the road surface paragraph
of this part, roadway surfacing. The following discussion is limited
to excavation, embankment and balanced construction.
Excavation
Back slopes can contribute up to 30 percent of the total road
sedimentation and up to 85 percent of the first year road sedimenta-
156
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tion (43,4). Sediment can be reduced by slope stabilization tech-
niques as considered in the next part and/or by designing the back
slope for the given soil characteristics. The Route Planning and
Reconnaissance chapter discusses geotechnical and engineering recon-
naissance techniques to develop field data for the design of stable
back slopes. There are two approaches to back slope design, one is
experience, and the other is rational or technical procedure.
Use of "rules of thumb" or "standard" backslope steepness guides
without knowledge of specific soils conditions is dangerous. However,
if an able forest engineer with long experience in a particular area
has been successful in establishing stable backslopes for road cuts,
his approach, advice and experience should be utilized.
The route planning discussion in the previous chapter noted that
the U.S. Forest Service has adopted a method of specifying cut and
embankment slopes developed by Hendrickson and Lund (21). This concise,
rational method does not require extensive laboratory equipment to ob-
tain soil type, grain size, and distribution for the unified soil classi-
fication. It also considers blow count, ground water, site conditions
and slope height. This design method is presented in both graphical
and tabular form for convenient use along with illustrative examples.
Also, and perhaps equally important, are the application and limitation
discussions that accompany the design guide (22).
Rodney W. Prellwitz has developed a slope design procedure for low
standard roads in USDA Forest Service Northern Region (Montana, Northern
Idaho and Eastern Washington). Prellwitz's procedures are most applicable
to Northern Region conditions of (l) steep natural slopes and cut slopes,
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(2) seepage - often parallel to surface slope, (3) "non-cohesive" soils,
(4) shallow and erratic soil depth, and (5) seasonal ground water fluc-
tuations (5-4).
Vertical cuts in banks less than six feet are being tried in
various parts of Region X including Idaho and Alaska. The rationale
behind the vertical cut concept is that these cuts will reduce excava-
tion quantities and the area of exposed new backslope. However, it is
difficult to predict the reliability of this practice from a sediment
control standpoint or how universally this practice can be applied.
Embankment
Numerous researchers suggest that fill slopes are significant ini-
tial producers of road sediment. They also point out that fill slope
erosion can be drastically reduced by erosion control techniques.
Mass failure of the fill is the other source of sediment. Mass
failures can be the result of poor fill material, improper fill compac-
tion, incorrectly designed fill slope, improper foundation preparation,
weak foundation support, improper culvert design and installation with-
in the fill, or a combination of one or more of these conditions. The
design of a fill is a structural problem with the companion necessity
to recognize the site circumstances. The procedure developed by Hendrick-
son and Lund, mentioned in the discussion on excavation, can also be
applied to embankment design.
Examination of the underlying strata where a fill is proposed must
be accomplished during the reconnaissance. If the strata is too weak
for the proposed load, the road must be relocated, the fill height re-
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duced or an alternate structural solution such as a trestle considered.
A common fault has been lack of proper ground preparation by
clearing and stripping vegetation and organic material. A further
problem has been the presence of too much organic matter in fill mater-
ial. The next chapter discusses fill placement techniques.
Benching of fills into sloping terrain has been utilized success-
fully. On narrow roads in steep terrain, the bench may be equal to the
road width. This suggests that there is a point where terrain slope
and road width combine to require a full bench section rather than a
fill from a practical as well as a stability viewpoint.
A stable fill slope is dependent upon the quality of the fill
material and the required area of supporting ground that must be util-
ized to support the superimposed load. The chapter on Construction
Techniques discusses fill compaction.
Provision for the passage of uphill overland water through a fill
can often be made by placing a granular blanket on the ground as the
first fill layer. Otherwise, the fill may act as a dam to the water
with dangerous damage potential. This blanket also aids in equipment
operation when the ground is soft.
The foregoing are a few observations on fill stability. The stabi-
lity question is broader in scope than the matter of sediment minimiza-
tion only. Waste sites are also fills and must be designed accordingly.
Culvert design is discussed in the third part of this chapter.
159
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Balanced Construction
No simple statement can be made as to whether or not the concept of
balancing the quantities of excavation and fill materials has merit from
the viewpoint of sediment minimization. If the excavation can be con-
fined to the amount of earth needed for fill and other factors are equal,
this is advantageous.
On steep terrain full bench excavation to obtain stability often
results in the production of excess material. "Sliver" fills on steep
terrain have proven difficult to stabilize. In order to reduce excava-
tion, an alternate to the "sliver" fill might be a driven sheet of soldier
pile and lagging wall. The economic tradeoffs would be excess excavation
costs plus haul of excess material and waste site development versus the
wall cost.
ROAD SURFACING
There is a broad range of surfaces and surface treatments used on
logging roads. Selection of surfacing or surface treatment may depend
upon material availability, road use, road location and construction
practices. In southeastern Alaska, nearly all roads are constructed
with "shot rock" ballast and overlaid with gravel or crushed rock. In
some areas of Oregon, Washington and Idaho, the absence of quality sur-
facing rock may result in soil surface roads of bituminous surfacing.
There is no doubt that durable surface roads result in less potential
for surface erosion. However, surfacing a road does not necessarily elim-
inate sediment problems. In many parts of the region the logging season
carries into wet weather periods and, in lower elevations, logging may
160
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continue year around with only occasional winter shut-downs. Log haul-
ing operations during this period place additional demands on roads. It
is the designer's task to anticipate this use if appropriate and to de-
sign a base and surface for the particular subgrade and wheel loads.
(The design must be coupled with good construction practice).
The road surfacing does more than provide smooth travel and a load
distributing media. It also provides a "roof" for the subgrade by being
a dense roadway surface, crowned sufficiently to rapidly disperse water.
Non-bituminous log haul roads should be crowned 4 percent minimum
to insure the movement of surface water. This reduces potential sub-
grade saturation.
In addition to designing a road base and surfacing to support
truck traffic and road crown selection, the following are other design
considerations that may directly or indirectly affect the potential
for roadway erosion and sediment.
1. Pit-run gravel surfacing must have an aggregate gradation
which will compact to a dense water dispersing surface.
2. Crushed rock surfaces rely on their angular faces and grada-
tion of the aggregate to knit the surface into a dense, near-
impervious layer.
3. Asphaltic concrete or other pavements decrease the time for
rain water to concentrate in ditches and other drainage
structures.
4. Granular-surfaced roads can become sediment producers if a
soft crushed rock is used or if the gradation does not permit
a dense, locked, shear resistant surface.
161
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5. Water bars—spaced,transverse surface depressions are often
used as cross drains on steep longitudinal grades. However,
they require continual maintenance if they are placed on too
flat a grade. A minimum longitudinal roadway grade of 5 per-
cent is suggested for use of water bars.
6. If steep grades in excess of 10 percent are used, asphaltic
concrete or bituminous surfacing may be required in lieu of
water bars to maintain a stable road surface.
7. Asphaltic concrete or bituminous surface can be used as
approach aprons to bridges. They reduce material tracking
which wears bridge decks, and washes sediment into streams.
8. Gravel surfaces may have an economic trade-off when the
annual traffic operating costs and maintenance costs off-
set those of soil stabilized or primitive roads (51).
9. Choice of gravel surfacing on outslope roads, versus stabi-
lized or soil surface is related to the potential for rill
erosion. See the discussion in the drainage section.
BUFFER STRIPS
The concept of minimizing or retarding downslope sediment movement
with vegetation and/or obstructions has been studied and used for a num-
ber of years. The procedure is often coupled with the outslope road
with surface cross drains. Drainage features of the outslope road in-
cluding criteria for cross drain spacing are discussed in the third part
of this chapter. Reservations regarding the ability of vegetation and
terrain to act as a barrier to sediment movement as expressed by one
writer are mentioned in the discussion on route reconnaissance.
162
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Most of the data developed is based on studies in Idaho, Eastern
Washington and Montana where the outslope road is quite common. Harold
F. Haupt studied sediment movement in the Boise National Forest in 1959.
He developed an equation relating sediment flow distance to a slope
obstruction index, cross ditch interval, embankment slope length and
cross ditch interval times road gradient. The Slope Obstruction Index
was approximately equal to the average spacing in feet of major obstruc-
tions along the direction of slope.
"With proper substitution of the variables, this equation pre-
determines the distance or width of protective strip needed to
dissipate sediment movement that may occur from a road to be
built" (55).
Haupt pointed out that the method was a tool for designers and was not
a substitute for experience and good judgement.
Packer believes that the interaction between the spacing of down-
slope obstructions and the kind of obstruction, and the spacing between
obstructions are the two most important factors in evaluating sediment
movement. Figure 20, "Obstruction Spacing", is reprinted from Packer's
1967 Study (56). Packer also discovered that, as the age of the road
increased, the distance sediment moved downslope also increased. This
was because the capacity of obstructions to stop sediment decreased the
longer they were installed.
Packer also developed criteria for protective strip widths based
on obstruction spacing, kinds of obstructions, age of road and cross
spacing. Table 10 is reproduced from Packer's report. The table is
also contained in the booklet Guides for Controlling Sediment from
Secondary Logging Roads by Packer and George F. Christensen (4-6). This
163
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field manual is pocket size and contains a complete treatment of the
subjects of cross drain spacing, and protective strip widths. It also
tells how to apply the information in a manner that will control erosion
and sediment. The booklet is geared for use in USDA Forest Service
Northern Region.
164
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H
03
5 80
«60
O
S 40
•
H
fe
S 8<>
^^
Q
H
QQ
X
X/^r/
/e» ^U^
V^'V*
*y/' ^«0c&
8468
OBSTRUCTION SPACING
FIGURE 20
Distances of sediment movement down-slope froa the
shoulders of logging roads built on soil derived from
basalt, having 30-foot cross-drain spacing, 100-percent
fill slope oover density, and zero initial obstruction
distance under varying obstruction spacings and kinds
of obstructions.
165
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TABLE 10
Protective-strip widths required below the shoulders(l) of 5-year old(2)
logging roads built on soil derived from basalt,(3) having 30-foot cross-
drain spacing,(4} zero initial obstruction distance,(5) and 100 percent
fill slope cover density( 6).
Protective-strip widths
Obstruction Depressions Logs Rocks Trees and Slash and Herbaceous
spacing or mounds stumps brush vegetation
1
2
3
4
5
6
7
8
9
10
11
12
35
37
39
40
41
37
40
43
46
48
50
52
53
54
38
43
47
52
56
59
62
65
67
40
46
52
58
63
68
73
77
81
85
88
41
49
57
64
71
77
84
89
95
100
104
43
52
61
70
78
86
94
101
108
115
121
127
(l) For protective-strip widths from centerlines of proposed roads, in-
crease above widths by one-half the proposed road width.
(2) If storage capacity of obstructions is to be renewed when roads are
3 years old, reduce protective-strip widths 24 feet.
(3) If soil is derived from andesite, increase protective-strip widths
1 foot; if from glacial silt, increase 3 feet; if from hard sediments,
increase 8 feet; if from granite, increase 9 feet; and if from loess, in-
crease 24 feet.
(4) For each 10-foot increase in cross-drain spacing beyond 30 feet, in-
crease protective-strip widths 1 foot.
(5) For each 5-foot increase in initial obstruction distance beyond zero
(or the road shoulder), increase protective-strip widths 4 feet.
(6) For each 10-percent decrease in fill slope cover below a density of
100 percent, increase protective-strip widths 1 foot.
Source: Packer, Paul E., "Criteria for Designing and Locating Logging
Roads to Control Sediment", Reprint from Forest Science^
Volume 13, Number 1, March, 1967.
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SLOPE STABILIZATION
Stream sedimentation can result from surface erosion or mass
wasting. Some of the measures which may be utilized to reduce surface
erosion and mass failures are discussed in the following sections.
SURFACE EROSION
The construction of forest roads is the major cause of stream
sedimentation in the forest harvest system. Large quantities of
sediment are produced from roads as a result of surface erosion and
mass wasting.
Revegetation of areas disturbed by logging road construction
is the most effective means of reducing sediment production. Mulches,
chemical soil stabilizers, and mechanical treatment measures are
often required initially to help establish vegetation and to reduce
erosion during this critical period. The various types of slope
stabilization procedures and their effectiveness in reducing sedimentation
are discussed in the following sections.
Seeding and Planting
IntToduoti-on. Numerous studies indicate that forest cover is
among the most effective vegetation in maintaining and protecting
soil from erosion (43). This cover reduces the effects of raindrop
impact; decreases runoff velocity and erosive power; increases granulation,
soil porosity, and biological processes associated with vegetative
growth; and dries soil by evapotranspiration.
Logging road construction removes natural vegetation and exposes
soils which commonly have properties unfavorable for plant growth (57).
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Revegetation by seeding and transplanting can be a successful method
of stabilizing backslopes and fills, of "putting roads to bed" that
are no longer being used, and of filtering sediment-laden water flowing
into water courses (58).
The decisions as to which plant species and methods to use in
EPA, Region X, for roadside stabilization are currently made by a
variety of agencies and individuals, usually the Soil Conservation
Service, individual county extension agents, landscape architects,
and the Forest Service. These decisions depend upon the management
objectives, financial problems, and the unique soil and climatic
features of each site. Although there are published standard specifications
for erosion control using revegetation techniques, the actual methods
used by the Forest Service vary from forest to forest and even among
districts of a given forest (59).
Revegetation Objectives. The main objective of seeding roadsides
is stabilization of soils against surface erosion. Recolonization
by native shrubs and herbs is generally encouraged (60). Native
plants generally require less expense and maintenance as well as
being visually harmonious with the forest landscape although many
exotic species are also well suited for this purpose. In addition
to physically enhancing the soil, seeded grasses and legumes— improve
the organic-mineral balance of road-cut soils. They also act as
"nurse plants" to young native species by providing shade thereby
reducing evaporation from the soil.
I legume : any of a large group of plants of the pea family. Because
of their ability to store and fix nitrates, legumes are often plowed
under to fertilize the soil.
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Grass seeding is usually considered as an erosion prevention
treatment applied at a sacrifice to tree regeneration, although tree
regeneration is not always sacrificed. In southeast Alaska, grass
seeding of exposed mineral soils helps establish spruce and hemlock
seedlings by reducing the disruptive influence of frost heave and
by retarding alder invasion (6l).
Shrubs are sometimes planted on wet silty and clayey soils where
the slope is not steep. Native willows (Salix spp.) and alders (Alnus
spp.) are used in EPA, Region X, because they absorb large amounts
of water from the soil and, in effect, dry it out. They are also
more deeply rooted than grasses or legumes.
Seed Mixtures. The proper seed mixture for a particular site
is dependent upon many factors. Among these are (l) slope stability,
angle, aspect, and exposure; (2) general climatic conditions, including
conditions at the time of planting; (3) competitive ability of species
to be planted in relation to native weed species or desired ultimate
vegetation establishment; (<4) susceptibility to foraging by livestock
and big game species; (5) visual and aesthetic considerations; and
(6) physical and chemical characteristics of the soil. Soil conditions
are particularly important because much of the material is often
C-horizon soils at best and not well suited for growing vegetation.
Because of wide variations between sites and the adaptability
of individual grass and forb species, no specific grass mixtures
are recommended in this report. Unless related to individual site
conditions, specific mixture recommendations are of little value.
Appropriate specialists should be consulted in each case to tailor
169
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the seed mixture to site conditions. These specialists include soil
scientists, agronomists, ecologists, range conservationists, and
wildlife biologists within the Forest Service and Soil Conservation
Service; universities; extension agents; landscape architects; and
consulting "biologists.
Rarely are grasses seeded without legumes, and the choice of
legumes is an important decision (62). The inclusion of a vigorous
fast-spreading legume in the seeding mixture in some cases results
in a denser and longer lasting stand of herbaceous vegetation, presumably
because of the nitrogen incorporated into the soil (59). Seeding
a legume requires that one also applies an inoculant of the associated
root bacteria. The inoculant is usually "glued" to the legume seeds
before the seed mixture is made (63).
Several legumes including big trefoil, white Dutch clover and
New Zealand white clover, birdsfoot trefoil, and alfalfa have been
found suited for use in the Northwest (59).
However, one problem of including most legumes in a seeding
mixture is their high palatability to deer, elk, and livestock.
Alfalfa is particularly palatable. Grazing animals will trample
out mechanical structures, pack the soil, and create a more erosive
condition than existed prior to seeding (10). Legumes should not
be included in seed mixtures on sites readily accessible to big game
animals, cattle or sheep. The Forest Service Experiment Stations
are continuing to search for vigorous, unpalatable legumes to use
in seeding mixtures (59, 62, 64).
170
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Plant-Ing. Planting in logging road stabilization is for utility,
not aesthetics. Where soils are plastic (e.g., silty and clayey),
growth of native willows or alders should be encouraged because they
inhibit slumping by depleting soil moisture rapidly, and their roots
bind soil to a deeper level than do those of grasses and legumes.
Red alder (Alnus rubra) is the species used in Washington and Oregon,
and Sitka alder (Alnus sitchensis) is used in southeast Alaska.
There are many species of willow common to EPA, Region X, and nearly
all root readily from cuttings, as do the alders.
Recent research in Idaho indicates that many native forbs have
outstanding qualities for roadway planting. The most promising species
is Louisiana Sagebrush (Artemisia ludoviciana).
Plantings are much more expensive than seeding operations because
of the increased cost of plant materials and labor. Hand planting
of grasses and legumes in small, hard to reach sites which require
revegetation is done in some parts of Oregon and Washington (60).
This procedure is not yet used in Idaho or Alaska (6-4, 65), primarily
because of the expense.
Techniques Used -In Establishing Plants. Seeding, as mentioned
previously, is much less expensive and, therefore, much more widely
used than other planting methods. Commonly used methods of seed
application are hydroseeding, hand-operated cyclone seeders, and
truck-mounted broadcast seeders. Hydroseeding is the application
of a seed and water slurry to the soil, in some cases followed by
an application of fertilizer and mulch (63). If seed and mulch are
applied simultaneously, much of the seed may stick to the mulch and
171
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never contact the ground. A variety of mulches—wood cellulose fiber,
ground hay, ground newspaper—have been applied by this method.
Hydroseeding is used in all parts of EPA, Region X, by highway
departments. In Oregon and Washington, the Forest Service hydroseeds
(60). The use of cyclone seeders and seed blowers is quite common
for areas which cannot be hydroseeded because of the expense involved.
The Forest Service in Alaska usually uses a cyclone seeder (64).
In Idaho, seeding is typically accomplished by using a cyclone seeder.
If the seedbed is packed, it may be necessary to drill the seed (10).
Drill seeding is superior where it is possible, but it is limited
to only the flatter slopes.
Hand planting is generally restricted to critical areas with
high priority because of the high cost. Hand planting of grass or legume
plants in Washington and Oregon is done in difficult to reach places
(60).
Proper seedbed preparation is very important. The soil surface,
if not freshly prepared, should be roughened along the contours in
order to reduce the chance of rilling and to provide small depressions
which retain the seed.
When to Seed ov Plant. From the standpoint of minimizing sediment
production, roadside revegetation should be started as soon as roads
are constructed if conditions are favorable. The highest volume
rate of soil movement off road cut and fill slopes is in the one to two
months immediately following road construction (66, 67). If this
period does not coincide with the season which favors the species
being planted, mulches or other temporary stabilization measures
should be used in the interim period.
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Generally, seeding during the spring or fall is best. Summer
seeding should generally be avoided because of limited moisture avail-
ability. In western Washington and Oregon, seeding before the fall
rains is recommended. One source reported success with seeding in
September, another in April (66, 67). In Idaho, seeding should be done
in late summer or early fall in order to take advantage of the fall rains
(10). In Alaska, seed should be applied in April or early May, but
summer application before August 1 is acceptable where spring application
is not possible (68). For quick temporary cover in Alaska after the
recommended planting season, annual ryegrass can be seeded immediately,
followed by seeding perennial grasses the next spring or summer (69).
The advantage to seeding and planting prior to fall rains is that
the newly introduced plants are not subjected to undue moisture stress
as in summer. This is especially true in dry areas such as eastern
Washington and Oregon and southern Idaho.
Ferti-l-izers. In all cases, application of fertilizer enhances
revegetation. Fertilizer should be applied at the time of seeding and
again the following spring. Subsequent fertilizations at one or two-year
intervals may be required in some instances, particularly where soils are
composed largely of B- and C-horizon materials which are normally very
low in nutrients. The fertilizer type and quantity, as with seeding
mixtures, should be tailored to the individual conditions encountered at
each site. Usually, a nitrogen-phosphorus-potassium fertilizer is suffi-
cient; although if the soil pH is less than 5, an application of lime may
be required (69). In general, ammonium phosphate (15#N, 20%P and 0$IC),
ammonium sulfate (21$N, 0%P, 0%K and 24$S) is excellent. Soil sampling
173
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and testing will reveal any serious nutrient deficiencies, and ferti-
lizer types and application rates can be tailored to satisfy these
deficiencies.
Because native shrub and grass establishment is the primary goal
of roadside grass plantings on Forest Service roads in Washington
and Oregon, only one to two fertilizer treatments are applied. Continued
fertilizer treatments result in such a vigorous growth of the seeded
species that the natives cannot establish on the seeded area (60).
Mulching. Mulching is essential if a good seedbed cannot be
prepared, if soil is highly erodible, or if slopes are steep (70). If
seed cannot be applied immediately after construction, the application
of a mulch alone will greatly reduce soil movement down the slope.
Mulches not only decrease soil loss by buffering rain effects and
slowing runoff, but they also retain soil moisture and provide shade
for better seed germination and seedling establishment. Mulches are
discussed in more detail in a subsequent section.
Summary. In spite of the variety of revegetation methods used
in EPA, Region X, and the uniqueness of each roadside stabilization
project, some generalizations about the usefulness of plants for
erosion control can be made. The combination of vegetation and structural
methods recommended depend on the objectives of the action. The seed
mixtures used in Region X should be tailored to the conditions existing
at each site. Although quite expensive, planting of willow and alder
is an effective way of drying out wet, heavy soils. Hydroseeding and
cyclone seeding are the most common methods of seed mixture application
used. Hand planting is expensive but necessary in hard to reach
spots. Application of slope stabilization measures should be
174
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commenced immediately after construction. The best season to seed
is generally fall or spring. Applying fertilizer and a mulch consistently
improves seed germination and growth and minimizes erosion which
can take place before the seedlings are established.
Mulches and Chemical Soil Stabilizers
Introduction. Measures intended for overall surface soil stabiliza-
tion of broad areas, exclusive of vegetation, can generally be classified
as mulches or chemical soil stabilizers, although some variations
of each exist. A mulch can be described as any organic or inorganic
material applied to the soil surface to protect the seed, maintain
more uniform soil temperatures, reduce evaporation, enrich the soil,
or reduce erosion by absorbing raindrop impact and intercepting surface
runoff (58, 71). Chemical soil stabilizers can be described as any
organic or inorganic material applied in an aqueous solution that
will penetrate the soil surface and reduce erosion by physically
binding the soil particles together. Some chemical stabilizers also
reduce evaporation, enrich the soil, and protect the seed (58, 71).
In addition to their functions in protecting against water erosion,
these measures also protect denuded soil, seeds, and young plants
from wind erosion.
Mulches and chemical stabilizers are generally temporary measures
which can be expected to lose their effectiveness within one to two
years or less. Their primary purpose is generally to provide suitable
short-term protection, including erosion reduction, during establishment
of permanent vegetative cover, usually over winter months or through
175
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hot summer months until conditions are more favorable for vegetative
stabilization (58). However, some mulches can be used to provide
permanent slope protection in areas where adequate vegetative cover
cannot be established.
Some of the more commonly available mulches are hay or straw,
woodchips, and small stones or gravel. For some types of mulch,
particularly hay or straw, it is necessary to provide some means
of holding the material in place. Methods of attachment include
mechanical means (e.g., notch-bladed disks, crawler tractor with
deep treads, sheepsfoot rollers, and others), asphalt or chemical
binders, or various commercially available netting products (58).
In order for mechanical attachment to be effective, the surface of
the slope must be free of significant quantities of rock material.
Besides their use for mulch stabilization, many of the chemical
stabilizers and netting products are designed to themselves protect
slopes under appropriate circumstances. Also, several commercially
available products incorporate netting and mulch in a single cover.
These products (e.g., Excelsior Blanket, Conwed Turf Establishment
Blanket, etc. ) are more specifically applicable on steep slopes, in
small drainage swales, or in other areas where erosive stresses are
particularly high (58). Long wire staples are generally used to fasten
these and other netting-type products to the slope.
Numerous studies have been conducted to evaluate the need for
mulches and chemical stabilizers to establish vegetation and control
erosion. Most of these studies have as their primary purpose evaluated
the relative effectiveness of different types of mulches and chemical
176
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soil stabilizers in performing these functions. In the following
sections, the need for slope protection to aid vegetation establishment
and control erosion and the relative effectiveness of various types
of mulches, mulch rates, and chemical stabilizers will be discussed.
Need for Slope Protection During Vegetation Establishment.
Mulches serve two primary purposes during vegetation establishment:
(l) preventing erosion while vegetation is becoming established,
and (2) providing a suitable microclimate for vegetation establishment.
Both functions are important. If severe erosion occurs, most of
the seed is generally washed off the slope, resulting in poor vegetation
establishment even if the microclimate is suitable. After vegetation
is established, the need for mulch or other protection rapidly declines.
Numerous investigators have concluded that a good mulch or similar
cover is essential to protect against erosion for the first few months
following construction. Dyrness (66) found that test plots seeded
in early fall in Willamette National Forest in Oregon did not begin
vegetation growth until the following April and were not fully protected
by vegetation until June. Of the various means of slope protection
studied by Dyrness, the only plots that showed consistently high
losses by surface erosion during vegetation establishment were the
unmulched plots. It was also noted that dry season losses by ravelling
were almost as great as rain-caused soil loss. Dyrness concluded
that mulching backslopes may be essential for reducing soil loss
to a minimum during the first few critical months following construction.
He also concluded that contrary to appearances, a luxuriant growth
of grass and legumes during the first growing season was not conclusive
evidence that soil loss was negligible during the preceding winter
months.
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Research conducted by Bethlahmy and Kidd (72) in Boise National
Forest, Idaho on 80 percent fill slopes yielded much the same results.
The results of their research are provided in Table 11. Test plots
without treatment or with mechanical or chemical treatment combined
with seeding and fertilization lost soil at rates of 70,000 to 100,000
pounds per acre during the first 80 days after treatment. Other
plots protected with mulch and mechanical treatment or mulch and
netting in addition to seeding and fertilization had soil losses
of less than 7,400 pounds per acre during this same period.
In his study of the effectiveness of numerous mulches and mulch
rates, Meyer (73) found that soil losses from simulated rainfall
on an unmulched plot was over 20 times that of well protected test
plots. Other investigators, including Plass (71) and Barnett, et
al (74), have observed similar results.
Research results, however, differ considerably over the value
of mulch protection to establishment of vegetative cover. Apparently,
this depends on the severity of environmental conditions. In Oregon,
Dyrness (66) found that seeded but unmulched plots produced good
vegetative cover and that mulch without seeding also produced good
vegetative cover. Only the control plots without seeding or mulching
produced poor vegetative cover. Similarly, Plass (71) tested the
effects of numerous mulches and chemical soil stabilizers on vegetative
establishment in the eastern United States and observed that some
mulches and chemical soil stabilizers improve the growth and vigor
of grasses, while some appear to have the opposite effect.
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TABLE 11
COMPARISON OF CUMULATIVE EROSION FROM TREATED PLOTS ON A STEEP, NEWLY
CONSTRUCTED ROAD FILL (IN 1,000 LBS. PER ACRE) (72)
Cumulative : Cumulative : :
Elapsed : Precipita- : : Group A
Time : tion : Control: (Seed,
(days) : (inches) : Plot : Fertilizer
: Group B
: (Seed,
: Fertilizer,
): Mulch)
: Group C
: (Seed, Ferti-
: lizer, Mulch,
: Netting)
Plot Number
1
17
80
157
200
255
322
1.
4.
12.
15.
17.
20.
41
71
46
25
02
40
31.
70.
72.
79.
82.
84.
9
0
2
1
3
2
2
38.7
99.2
100.2
101.0
102.8
104.7
: 4
38.0
85.7
86.9
87.6
88.8
89.4
: 3
0.1
7.4
11.1
11.4
11.5
11.9
: 8
32.6
34.6
35.1
35.7
35.8
36.0
: 5 :
0
0.9
1.1
1.1
1.1
1.1
6
0
0
0
0
0
0
: 7
0
0.3
0.4
0.4
0.4
0.4
Description of Treatment Measures:
Plot Number
1
2
3
4
5
6
7
Type of Treatment
Control - no treatment at all.
Contour furrows, seed, fertilizer, holes.
Contour furrows, straw mulch, seed,
fertilizer, holes.
Polymer emulsion, seed, fertilizer.
Straw mulch, paper netting, seed, fertilizer.
Straw mulch, jute netting, seed, fertilizer.
Seed, fertilizer, straw mulch, chicken
wire netting.
Seed, fertilizer, straw mulch with asphalt
emulsion.
Mechanical treatment - Contour furrows placed 6 feet apart and
holes punched 2 inches deep at 6-inch intervals.
Mulch and chemical soil stabilizer application rates - Straw mulch
at 2 tons per acre. Polymer emulsion at concentration of
1 gallon Soil Set to 9 gallons of water. Asphalt emulsion at
rate of 300 gallons per acre.
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In their tests, Meyer et al (73) concluded that good mulch protection
was necessary to establish vegetation. Stands having more than 75
percent of the seedlings necessary for complete cover were established
on test plots mulched with 240 and 135 tons per acre stone, 12 tons
per acre woodchips, 70 tons per acre gravel, and straw-mulched slopes.
Unmulched plots, cement-stabilized plots, and 15 tons per acre stone-
mulched plots had very little vegetation establishment.
Other researchers have reached similar conclusions. Heath (75)
reported that 50 to 90 percent of the seed planted on a slope is
saved from washing away when a mulch is used. Diseker and Richardson
(76) have stated that using mulch over seedings often made the difference
between success and failure and that mulch was necessary on steep
slopes. The question of need for mulch protection for vegetation
establishment is probably best summed up by Blaser (77) who concluded
that mulches aid in turf establishment, particularly under environmental
and moisture stress.
Performance of Various Mulches and Chemiaal Soil Stabilizers.
The effectiveness of mulches and other soil stabilization measures
is a function of surface cover and overall lateral stability of the
protection network, including its ability to bind or penetrate into
the slope (73). Erosive and other environmental stresses determine
the effectiveness of a particular treatment measure under a particular
set of circumstances. A mulch rate or combination of mulch and other
stabilization measures may perform satisfactorily under one set of
circumstances and be completely ineffective under others. The performance
of several types of mulch products in controlling erosion and establishing
vegetation under various conditions are compared in Tables 11 and
12 and Figure 21.
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FIGURE 21
SOIL LOSSES FROM A 35-FOOT LONG SLOPE (73)
39.6 No Mulcha
2 T/A Portland Cement
2 T/A woodchipsa
15 T/A stonea
70 T/A gravel
2.3 T/A straw
60 T/A stone
4 T/A woodchips
7 T/A woodchipsa
135 T/A stonea
240 & 375 T/A stonea
12 & 25 T/A woodchipsa
0 10 20 30 40
Soil Loss (T/A-tons per acre)
aBased on one replication only. Values for other treatments based on
average of two replications.
Soil Type: 6-inches silt loam topsoil underlain by compacted calcareous
till (AASHO A-4) (Unified ML).
Slopes: Uniform 20 percent
Rainfall Rate:
Simulated rainfall at rate of 2 1/2 inches per hour - 1 hour
the first day followed by two 30-minute applications the second day.
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TABLE 12
EROSION CONTROL AND VEGETATION ESTABLISHMENT
EFFECTIVENESS OF VARIOUS MULCHES (78)1/
Straw & Wood
Jute Excelsior Straw Asphalt Asphalt Fiber Sod
Erosion Control
Sheet Erosion -
1:1 slope 9.0 10.0 8.0 10.0 6.0 3.0 10.0
Sheet Erosion -
2:1 slope 9.0 10.0 9.0 10.0 7.0 6.0 10.0
Sheet Erosion -
3:1+ slope 10.0 10.0 10.0 10.0 9.0 10.0 10.0
Rill Erosion -
1:1 slope 6.0 10.0 8.0 10.0 6.0 3.0 10.0
Rill Erosion -
2:1 slope 8.0 10.0 9.0 10.0 7.0 5.0
Rill Erosion -
3:1+ slope 10.0 10.0 10.0 10.0 9.0 10.0 10.0
Slump Erosion -
1:1 slope 10.0 8.0 6.0 7.0 3.0 3.0 8.0
Slump Erosion -
2:1 slope 10.0 9.0 7.0 8.0 5.0 4.0 9.0
Slump Erosion -
3:1 slope Slumps usually do not occur.
Vegetation Establishment
1.5:1 glacial
till cut
slope 7.5 9.0 7.5 8.5 7.5 6.0
2:1 glacial
till cut
slope 8.9 9.5 8.0 9.3 8.7 6.2
2:1 sandy loam
fill slope 9.0 10.0 9.0 10.0 7.5 8.5 10.0
2.5:1 silt loam
cut slope 5.0 10.0 - 7.8 6.0
I/Effectiveness rating: 10.0 = most effective,1.0 = not effective.
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TABLE 12 (cont.)
Location: Highways in eastern and western Washington.
Slopes: 1.5:1 to 3:1+ cut and fill slopes.
Soils: Silty, sandy and gravelly loams; and glacial till consisting of
sand, gravel and compacted silts and clays. All are subsoil
materials without topsoil addition.
Slope Lengths: Apparently maximum of 165 feet.
Application Rates:
Cereal straw - 2 tons/acre
Straw plus asphalt - 2 tons/acre straw plus asphalt at rate of
200 gal/ton of straw (one test at rate of 100 gal/ton of straw)
Asphalt alone - .20 gal/sq. yd. (968 gal/ac)
Wood cellulose fiber - 1,200 Ibs/ac.
Sod - bentgrass strips 18 inches by 6 feet pegged down every
third row.
Straw (or hay) is one of the oldest and probably by far the most
commonly used form of mulch material. Straw mulch has proven to be
quite effective if slope gradient, slope length, and rainfall intensity
are not excessive. In his studies, Dyrness (66) found straw mulch
applied at a rate of 2 tons per acre to be relatively effective in
reducing erosion. Bethlahmy and Kidd (72) found straw mulch to be
quite effective when supplemented by mechanical treatment measures
or netting (Table 11). Goss et al (78) have noted that straw mulch
alone is moderately effective in a number of erosion-prevention
applications but that its effectiveness is improved when used in
combination with an asphalt tack (Table 12). Straw plus asphalt
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emulsion was found to be one of the most effective mulches in controlling
erosion and establishing vegetation. Meyer et al (73) indicated
that straw mulch is moderately effective in preventing erosion but
that its performance is considerably exceeded by suitably heavy applications
of other mulches (Figure 21).
Several researchers, including Meyer et al (73), have observed
a breakdown of straw mulches due to rill formation. Besides problems
with rill formation, straw mulches must also be protected from strong
winds (58, 78). Chemical stabilizers, mechanical measures such as
contour furrowing, and application of netting over the mulch can
be used to improve attachment of mulch to the slope, thus guarding
against both rill formation and wind erosion.
Chemical stabilizers, used as the sole means of slope protection,
generally cannot be relied upon to be as effective as several other
measures (Tables 11 and 12). However, use of chemical stabilizers
in combination with mulches, or as a minimum with wood fibers added,
generally increases their effectiveness significantly in controlling
erosion and encouraging vegetation establishment (71, 78).
Chemical soil stabilizers, by virtue of their chemical composition,
can affect vegetation establishment. Plass (71) reported that some
treatments improve growth and vigor of vegetation, while others have
an adverse effect. Adverse effects of some products on vegetation
establishment have also been noted by the Washington State Highway
Department (79).
A wide variety of chemical stabilizers, probably totalling 40
or more, with differing performance levels under differing environmental
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conditions are available. Of the numerous products available some
may exceed the performance capability of commonly used mulches such
as straw. The chemical soil stabilization field is rapidly developing
with new products being introduced frequently. With continuing develop-
ments, this field appears to offer good potential for the future.
Commercially available combination mulch-netting products are
available. Some of these products have proven relatively effective,
even under severe conditions. Except for sod protection, Goss et al
(Table 12) found one such product (Excelsior) to be the most consistently
effective product tested for both erosion control and vegetation
establishment. Plass (71) has also found some of these products
to be quite effective. However, the material and installation costs
may be too high to warrant their use for forest road application, except
in the most severely stressed areas. Similar products, such as jute
netting, are also effective in preventing erosion. Use of jute netting
is particularly attractive where high tensile strengths are needed
to protect against shallow surface slump erosion during the initial
postconstruction period before natural consolidation processes can act
to increase the soil strength (Table 12). Good attachment of netting-
type materials to the slope is of prime importance to prevent rill
erosion underneath. Jute, for instance, has sufficient strength
to bridge even large rills and allow erosion to continue unchecked (78).
Meyer et al (Figure 21) have found gravel and crushed stone
mulches to be quite effective, even under relatively severe conditions.
Various application rates of stone and gravel mulches were found
to be considerably more effective than 2 tons per acre of straw mulch.
Resistance to rill formation is a prime advantage of stone and gravel
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mulches. They tend to impede rill formation by sloughing into them,
rather than bridging them as do straw mulches or being washed down
the slope as do woodchip mulches when subjected to severe erosive
stresses. Meyer et al found a rate of application of 135 tons per
acre of stone mulch, which averages less than 1-inch depth, to be
effective under all conditions tested (73).
Stone mulches also appear to have other advantages. Meyer et
al found that grass stands on inert stone and gravel plots were much
more vigorous than those on the woodchip and particularly the straw
plots where grasses showed symptoms of a nitrogen deficiency. Also,
unlike straw and other mulches, stone mulches are not subject to
rapid decomposition. Their resistance to decay makes them uniquely
valuable for permanent applications where vegetation cannot be established.
Woodchip mulches appear to have promise for forest applications.
Along with stone mulches, Meyer et al (Figure 21) found woodchip
mulches to be a good mulch material if applied at adequate rates.
Woodchip mulch at the rate of 4 tons per acre was found to be more
effective on 35-foot long slopes than 2 tons per acre straw mulch.
Woodchip application at a rate of 25 tons per acre (1J inches depth)
offered good protection under relatively severe conditions of 20
percent slopes as long as 160 feet (73). Crabtree (80) found 5 tons
per acre of woodchip mulch to be quite effective on 3 to 1 slopes
in Iowa. Woodchip mulches are relatively long lasting compared to
other mulches such as straw or hay, require no tacking to hold them
in place, and the raw materials for their manufacture are readily
available in forested areas.
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An adequate rate of woodchip application and uniform distribution
of the mulch material is particularly important. Meyer et al (73)
noted that the consequences of breakdown are more serious for woodchip
mulches than for stone, gravel, and straw mulches. When a woodchip
mulch broke down, woodchips were grossly displaced and large, deep
rills developed. Anchoring the woodchips with asphalt or other materials
might improve their performance at some application rates (81).
As mentioned previously, vegetation on woodchip mulched slopes
generally exhibits a nitrogen deficiency. Application of about 20
pounds of additional nitrogen per air dry ton of mulch is required
when wood products are used.
Wood fibers have proven beneficial in preventing erosion when
used alone or in combination with chemical soil stabilizers. The
Washington State Highway Department has found that wood cellulose
fiber, particularly when used in combination with chemical binding
agents to enable them to better resist wind erosion, is an economical
and successful alternative in western Washington where straw is not
readily available (79). A University of California study (63) of
hydroseeding on clay-loam soils reported soil losses of 0, 1,000,
and 9,000 pounds per acre from plots with wood cellulose fibers applied
at rates of 3,000, 2,000, and 1,000 pounds per acre, respectively,
compared with losses of 81,000 pounds per acre where no fiber was
applied. On the fiber-treated areas, there were 300, 262, and 86
grass seedlings per square foot compared with none on areas without
fiber treatment. Plass (71) reported that plots treated with soil
stabilizers lacking wood fibers generally did not have as tall or
dense vegetative cover as when stabilizers with wood fibers and other
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mulch products were used. Plass noted that there is a growing trend
toward incorporating wood fibers into soil stabilizers to increase
their effectiveness.
Others have reported less favorably on the use of wood fiber
for slope protection. Goss et al found that wood fiber does not
have sufficient damming ability nor tensile strength to prevent erosion
on long slopes, particularly if steeper than 3 to 1 (78). Crabtree
(80) found when wood fiber was applied at rates of 1,000 to 1,400
pounds per acre on 3 to 1 slopes in Iowa, it was only poorly to moderately
effective in checking erosion.
Mechanical Treatment
Introduction. Mechanical measures can inhibit erosion on slopes.
Several such measures are currently being successfully used. They
consist of diversions and terraces, either atop or on slope faces;
serrations or other variations in gradient; and roughening or scarification
of the slope. Although most of these measures can be used individually
for slope protection, their primary purpose is to supplement mulches
and other forms of slope stabilization.
Mechanical slope stabilization measures generally function by
reducing the volume and velocity of surface runoff through a reduction
of effective slope length and -an increase in infiltration. These
measures can also prevent concentration of flow in erodible areas
and provide an improved microclimate for vegetation establishment.
Although numerous references suggest the usage of or describe
many of these mechanical measures in a general way, very little specific
information is provided on their application, design, and effectiveness.
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Specific design criteria must generally "be developed on an individual
basis. Descriptions of the various mechanical measures in common
usage are provided in the remainder of this section.
Diversions or Terraces. Diversions and terraces are channels
with a supporting ridge on the lower side constructed across or atop
cut or fill slopes. Terraces are generally level and have closed
ends to retain the runoff, while diversions are designed to carry
water at nonerosive velocities to planned disposal areas. Their
purpose is to intercept surface or shallow subsurface runoff and
store it or divert it to an outlet where it can be safely disposed
of. They can reduce slope length into nonerosive segments or divert
water away from critical areas.
Terraces and diversions are not applicable for some soils on
steep slopes. During periods of high moisture inflow terraces can
become saturated, leading to slump failures. Use of terraces on
slopes exceeding approximately 40 percent is not recommended in the
Idaho Batholith.
Diversion outlets should be located where water will empty into
natural drainage channels or into relatively low-gradient upland
areas between drainage channels. Care must be exercised to avoid
excessive flow concentration or erosive velocities when conveying
or discharging water. Buffer strips of vegetation between points
of discharge and stream courses are extremely desirable to allow
sediment to deposit.
Serrations. Serrations are steps or benches in steep slopes.
The areas between the steps are generally constructed vertical, although
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they can be sloped. If properly located and designed, serrations
reduce slope length and divide the volume of runoff into workable
slugs that can be more easily handled. They are usually constructed
level to retain precipitation in place, but they can be graded with
a longitudinal gradient and an outside edge higher than the inside
to function as diversions.
In addition to their function of retarding runoff, benches provided
by serrations also improve the microclimate for vegetation establishment
on steep slopes. The flat areas better enable vegetation to gain a
foothold.
Serrated slopes are a relatively new method of erosion control
and are only applicable under certain conditions. These conditions
include cut slopes of soft rock or similar material that will stand
vertically or near-vertically for a few years in cut heights of approxi-
mately a couple of feet. Several states, including the highway
departments of Washington (82) and Idaho, are currently using this
method successfully in selected areas.
Serrations generally consist of steps of 2 to 4 feet cut vertically
and horizontally along the normal, intended slope gradient. After
construction, the slope is seeded, fertilized, and mulched as with
normal slopes. The horizontal areas provide an improved environment
for vegetation establishment, free of sliding forces normally experienced
on steep slopes. The steps gradually slough and practically disappear
within a few years following construction, generally after vegetation
has become well established. If the slope material is soft, the
slope should be allowed to slough before seeding until about one-third
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of the steps are filled. Otherwise, grass may be destroyed by the
excessive rate of initial slough. This method is not applicable
to soil types where the rate of slough is so high that vegetative
cover is buried and destroyed.
Roughness and Scarification. Smoothly graded cut-and-fill slopes
are attractive to the eye, but they do not benefit erosion control
and establishment of vegetative cover. Roughness and scarification
serve to increase infiltration and impede runoff (58). If the surface
is to be seeded, the roughness or scarification marks retain seed
even after severe runoff. These measures also help mulch adhere
better to the slope.
Slopes may be roughened by a wide variety of construction methods.
Soils can be scarified with a bladed implement having a ripper
attachment which loosens surface soils in place without turning them
over. Deep-cleated dozers traveling up and down the slope can be
used to obtain a satisfactory texture on slopes that are too steep
for normal equipment operation. The Washington Highway Department
(79) has found that a sheepsfoot roller works well for roughening
slopes.
The texture of the roughened slope should trend perpendicular
to the flow direction (58). Up and down or angular cross slope roughness
texture causes flow concentration, which is harmful. Also, care
must be exercised to prevent excessive loosening of the upper soils
such that the propensity for rill and slump erosion are increased.
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MASS WASTING
Mass wasting is the primary cause of stream sedimentation in
many areas of EPA, Region X. Mass wasting problems are most common
in the coastal regions where rainfall is greatest, but they are by
no means limited to these areas (2, 6, 24).
Mass wasting occurs when gravitational and other forces, such
as seepage or seismic, which act on a soil or rock mass are greater
than the strength which can be mobilized within the mass. The resulting
instability usually involves a net downward migration of the mass
until a condition of temporary or permanent equilibrium is attained.
The two primary forms of mass failure are (l) deep, rotational
types of soil movement, including slumps and earthflows, and (2)
shallow debris movements, including rockslides, debris avalanches,
and debris flows. The latter type of movement is more common in
mountainous forested areas. Debris movements are likely to develop
suddenly in bedded sediments or on shallow, relatively coarse-textured,
cohesionless soils on steep hillsides. They are characterized by
rapid downslope movement of fractured rock, soil, and/or organic
material along a slip surface roughly parallel to the topographic
surface. Large rotational slumps, earthflows, or soil creep are
most likely to occur in deep, saturated, fine-textured soils on more
moderate slopes (19). These will normally extend over a lesser area.
Slumps and earthflows are relatively fast moving, but may be preceded
or followed by soil creep which can occur over a very long period.
Many factors are responsible for mass failures along logging
roads. In some cases, a specific factor can be isolated, but usually
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a failure is caused by several interrelated factors. By far the
greatest proportion of these influences along logging roads are directly
or indirectly related to human activity. Specific factors include
undercutting of unstable or marginally stable slopes, oversteepening
of cut and fill slopes, sidecasting of excavated materials on steep
slopes, improper embankment construction (particularly compaction),
and drainage system failures (3> 5, 19).
Often the basic causes of mass failures are "overroading" and
"overdesign." Overroading or misplacement of roads results from
a poor land management or transportation plan. Overdesign of roads
results from rigid application of design criteria regarding curvature,
width, gradient, and cut and fill slope steepness; or design of roads
to higher standards than required for their primary intended uses.
By lowering design standards when possible and allowing flexibility
in application of alignment, width, grade, and other design criteria,
many mass wasting problems can be avoided (6, 19). This is particularly
true where it is possible to reduce cut and fill slope heights or
roadway widths.
The maximum control of mass wastage is achieved by concentrating
on preventive measures prior to and during construction rather than
attempting to control problems after the fact. The control of sedimentation
resulting from mass movement near a stream is virtually impossible
once the mass movement has occurred. Minimization of mass wastage
can take place only by thorough planning and reconnaissance investigation?
as discussed in previous sections.
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Unfortunately, of all causes of stream sedimentation, mass movement
is the most difficult to predict in advance. No precise universal
rules can be developed relating the main causative factors of slope
steepness, soil strength, and groundwater conditions. Many predictive
methodologies have been developed for local areas but they are based
on empirical, or at best semiempirical, factors and usually require
modification before they can be applied to areas other than for which
they were developed (20, 23). Additional research is needed to improve
methods for mass wastage prediction.
Mass wasting problems rarely can be completely avoided. Even
with the best of planning and reconnaissance investigations to avoid
unstable conditions, a few problems are likely to develop in all
but the most stable areas. In other cases, it may be necessary to
locate roads in unstable areas because of a lack of feasible alternatives.
This can result in serious mass wasting problems unless corrective
measures are included in road design.
Many of the potential means of slope stabilization, both structural
and nonstructural, and their possible applications are discussed
in the remainder of this section. The selection of the proper corrective
action to be used in any given situation depends upon the nature
of the problem, the foundation conditions at the site, and economic
considerations. No attempt is made to provide specific design recommendations
or procedures since the actual design of corrective measures is heavily
dependent upon the conditions at each location.
The adequate design of structural retention systems involves
a high level of professional skill. All designs should include
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engineering analysis by personnel experienced in soil and rock mechanics.
In most cases, design should be preceded by detailed geotechnical
investigations to assess the conditions at each site.
Retaining Walls
Retaining walls are used to bring about an abrupt change in
grade or to enable the utilization of a steeper overall slope than
would otherwise be possible in a particular soil or rock mass. Several
types of retaining walls are available. Among the basic types are
gravity walls, crib walls, and cantilever walls.
Gravity walls or buttresses are usually constructed of plain
masonry, rock rubble, stone, or concrete. The weight of the structure
acts to counterbalance and resist earth pressures. This type of
wall is usually the simplest and easiest to construct but generally
can be used only for relatively low walls (less than 8 to 10 feet
in height) with moderate soil pressures (83).
A crib wall is essentially a gravity-type structure made of
timber, precast concrete or metal which forms an open structure of
some dimension. When this open structure is filled with soil, it
becomes relatively large and massive. This type of wall is usually
suitable for small- to moderate-height walls (less than 20 feet in
height) subjected to only moderate earth pressures (83). Crib walls
are usually flexible enough to be used where settlement is a particular
problem.
There are three basic kinds of cantilever walls. The first
kind is a plain cantilever wall that can be used for heights up to
approximately 25 feet. These walls usually consist of a reinforced
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concrete stem founded on a reinforced concrete base slab. The other
two kinds are modifications of a cantilever where counterforts or
buttresses are added to the wall. The counterforts or buttresses
add strength to the stem portion of the wall and a degree of rigidity
to the entire wall. These additions may be used for walls higher
than 25 feet with most soil conditions (83).
All retention walls are expensive to design and construct.
Of the various forms discussed, crib walls are probably cheapest
for forest applications. The great expense of retaining walls reemphasizes
the need to study all possible alternatives to the location of roads
in areas of potential mass wastage.
Bulkheads
In cases where soil conditions permit, use of sheet pile bulkheads
may be advisable. The sheet piles may either be cantilevered or
restrained near the top with anchors. In either case, relatively
deep penetration into the soil mass is required to ensure stability
of the bulkhead. This method of retention is often expensive. However,
installation of a cantilever bulkhead is relatively simple and can
be done without form work. These walls are usually less than 20
feet in height and include the installation of drainage measures
behind the wall (8/4).
Reinforced Earth
Construction of reinforced earth structures consists of placing
metal strips perpendicular to the front of either a thin shell concrete
or steel wall. Soil is then compacted over the strips for a shallow
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depth, another set of strips is then placed, and the process repeated
until the full height of the wall is attained. This process is restricted
to granular backfills and to walls usually less than 15 feet in height.
Rock Rubble Facing
Slope embankments may be lined with rock rubble to protect against
shallow surface slumping. Rock rubble protects the slope face from
the effects of weathering and provides a ready outlet for groundwater
seepage. Surface erosion is also prevented. However, it should
be realized that rock rubble, unless applied in large enough quantities
to act as a gravity-type retaining wall, offers no significant protection
against deep-seated or avalanche-type slide failures.
Lowering Groundwater Levels
Groundwater conditions contribute heavily to slope instability.
As the water table rises, buoyant forces on the individual soil
particles reduce their interlocking strengths and thus the frictional
resistance to sliding. The improvement of surface drainage is one
of the cheapest and most effective techniques of lowering groundwater
levels and one that is often overlooked. Sag ponds and depressions
can be connected to the nearest stream channel with ditches excavated
by bulldozers or other means. Improved surface drainage removes
water quickly, lowers the groundwater level, and helps stabilize
slumps (19).
Another technique is to lower the groundwater level by means
of perforated pipes installed in drill holes augered into the slope
at a slight upward angle. Such drains are usually installed in road
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cut "banks to stabilize areas above an existing road, or below roads
to stabilize fills. Installation of perforated pipe is relatively
expensive and there is a risk that slight shifts in the slump mass
may render the pipe ineffective. In addition, periodic cleaning
of these pipes is necessary to prevent blockage by algae, soil, or
iron deposits (19, 85).
A third technique of lowering groundwater levels is installation
of an interceptor drain to collect groundwater moving laterally downslope
and under the road. A backhoe can be used to install interceptor
drains in the ditch along the upslope side of the road (19). The
drain can consist entirely of graded granular materials with gradations
sufficient to carry the intercepted flow efficiently without becoming
plugged with fine native soils; or, preferably, a perforated pipe
bedded in granular material.
Deep Rooted Vegetation
The effect of tree root strength on slope stability is not fully
understood. However, results of research studies indicate that living
tree roots help maintain slope stability. Reports by the Forest
Service from southeast Alaska indicate that the number of landslides
from cut-over areas increases within 3 to 5 years after logging.
This increase is attributed to a reduction in soil shear strength
caused by the decay of tree roots following logging. The presence
of living tree roots to anchor shallow soils to the underlying subsoil
appears to be particularly important in small drainages where winter
storms can cause the groundwater level to rise sharply (24). Similar
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observations have been noted in other areas (6, 20). A contributing
factor to gain of soil strength with deep rooted vegetation establishment
may be lowering of groundwater levels as a result of water uptake.
Fill Placement
Many measures can be utilized to increase the stability of fill
embankments. One of these is proper keying of the embankment to
the slope through removal of all vegetation and organic material
from the existing surface and scarification of the underlying native
soils. On steeper side slopes the excavation of a slot or keyway
just ahead of the fill will help to prevent the formation of a failure
surface at the interface of the embankment and the slope. The stability
of an embankment can be greatly enhanced by compaction of the fill
to engineering standards, with special attention given to maintaining
proper lift thickness, moisture content, and quality of the fill
materials (e.g. exclusion of organic debris, etc.). Studies of mass
failures in the Idaho Batholith revealed that liquefaction of fill
embankments attributed to minimal compactive effort was the triggering
factor in some embankment failures (6).
Fills should not be placed on steep slopes that are themselves
marginally stable. Both avalanche-type failures on the hillside below
the slope and deep-seated failures either on the upslope or downslope
sections of the road can occur. Avalanche-type failures or deep-seated
failures of the lower road section are particularly likely if excavated
material is sidecast. End-hauling of excavated material to stable
areas is necessary to reduce overloading of unstable slopes to an
absolute minimum (19).
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DRAINAGE DESIGN
"A major contributor to both accelerated surface soil erosion and
mass soil failures was lack of adequate drainage provided at man-
made improvements. Drainage includes practices that prevent con-
centration of water and those that foster dispersal of water into
stabilized land areas or into stabilized stream channels. Failure
or impairment of road drainage facilities was involved in almost
all road-connected storm damage" (ll).
To minimize sediment production and transportation from forest roads,
the planning, design and construction of drainage facilities must be
executed for the particular conditions encountered and not on a basis
of generalized criteria.
The Maintenance chapter of this section discusses drainage mainte-
nance but designers and owners should recognize that the designs and
suggestions contained under this heading will not function adequately
without inspection, maintenance and possible change of individual drain-
age features. The first such inspections should be made, hopefully by
the design engineer, during or immediately after the first storm.
DITCHES AND BERMS
The two primary functions of ditches and berms are to intercept
runoff before it reaches erodible areas, and to carry sediment, during
high flows, to properly designed settling basins when circumstances
warrant the use of these basins. Important places to install ditches
or berms are at the top of cut and fill slopes and adjacent to the road-
way. Midslope berms with ditches may be especially helpful in con-
trolling sediment before erosion control cover is established.
The ditch size (area) can be determined by considering the slope
of the ditch, area intercepted, estimated intensity and volume of run-
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off, and the amount of sediment that may be deposited in the ditch
during low flow conditions. The shape of the ditch may "be trapezoidal
or triangular, whichever is appropriate to the particular location.
Size and Placement
For ditch design, a good reference is "Design Charts for Open
Channel Flow," Hydraulic Design Series No. 3, by the Bureau of Public
Roads, (Federal Highway Administration) 1961 or later revision (86).
In addition to the ditch size required for full flow capacity, an allow-
ance should be made for anticipated sediment deposit. Minimum full
capacity flow velocities should be 2.5 to 3.0 feet per second to permit
sediment transport. Refer to Table 13 for scour velocities in ditches
of various materials.
The depth of potential sediment deposit in ditches is directly
related to the erodibility of the soils over which water flows to the
ditch and the ditch slope. The ditch depth allowance for sediment
deposit should recognize the soil erodibility, the kind of erosion con-
trol cover planned for tributary slopes and the anticipated maintenance
program. Some ditches, due to their slope and/or soil type, may not
require a depth allowance for sediment build-up. The designer should
refer to the information obtained during the planning-reconnaissance
phase of the project for data relating to the erodibility of the soils
that will be encountered within the road corridor.
All ditches constructed in erodible soils are themselves subject to
erosion from runoff and may require stabilization by such means as rip-
rap, rock rubble lining, jute matting, seeding and/or other acceptable
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TABKB 13—
Maximum permissible velocities in erodible channels, based on uniform
flow in continuously wet, aged channels
Maximum permissible
velocities for—
Material
Sandy loam (noncolloidal)
Silt loam (noncolloidal)
Fine gravel
Stiff clay (very colloidal)
Graded, loam to cobbles (noncolloidal) .
Graded, silt to cobbles (colloidal). . .
Alluvial silts (noncolloidal)
Alluvial silts (colloidal)
Coarse gravel (noncolloidal) .
Shales and hard pans
Clear
water
F.p.s.
1.5
1.7
2.0
2.5
2.5
2.5
3.7
3.7
4.0
2.0
3.7
4.0
5.0
6.0
Water
carrying
fine
silts
F.p.s.
2.5
2.5
3.0
3.5
3.5
5.0
5.0
5.0
5.5
3.5
5.0
6.0
5.5
6.0
Water
carrying
sand and
gravel
F.p.s.
1.5
2 0
2.0
2.2
2.0
3.7
3.0
5.0
5.0
2.0
3.0
6.5
6.5
5.0
— As recommended by Special Committee on Irrigation Research, American
Society of Civil Engineers, 1926, for channels with straight alinement.
For sinuous channels multiply allowable velocity by 0.95 for slightly
sinous, by 0.9 for moderately sinuous channels, and by 0.8 for highly
sinous channels (45, p. 1257)
Source: Design of Roadside Drainage Channels, U. S. Department of
Commerce, Bureau of Public Roads V/ashington: 1965, page 54.
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erosion control device. Plastic sheeting can be used as a temporary
erosion control device during the construction period.
Riprap or rubble lined ditches will tend to act as a flow retard-
ent which will allow movement of water and retain the sediment at low
flow periods. The depth allowance for ditches lined with riprap or
rock rubble can coincide with the depth allowance for sediment deposit.
The full flow water surface for roadway ditches should be at least
one foot below the roadway subgrade. This position will prevent ditch
water from entering the ballast material, removing the fines and de-
stroying the ballast's effectiveness in supporting the roadway surface.
Figure 22 show's the water surface level relative to the road subgrade.
, If used
DITCH WATER SURFACE-ROAD SUBGRADE
FIGURE 22
The suggested minimum size of interceptor ditches is shown in
Figure 23.
Berms (Figure 24) can be constructed of native material provided
that the material contains enough fines to make the berm impervious
and the material can be shaped and compacted to about 90$ of maximum
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TRAPEZOIDAL
TRIANGULAR
MINIMUM INTERCEPTOR DITCH SIZE
FIGURE 23
BERM
FIGURE 24
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density.— An extruded asphalt or portland cement concrete curb can
also be used to intercept water at the roadway shoulder edge. The curb
occupies less room than does a berm.
Figure 25 portrays the general location for ditches and berms in
relation to a finished roadway section. Additional locations for temp-
orary ditches and other drainage facilities may be necessary during the
construction phase. Refer to the Construction chapter.
Ditches at the top of slopes may be needed when:
1. The natural ground above slope "daylight" point continues up
sharply.
2. Ground cover above "daylight" point has low moisture absorbing
ability.
3. Exposed soils on cut slope are highly erodible, the exposed
area is large, rain intensities are high and erosion control
measures need time for establishment.
4. Quantity of runoff will flood or tend to flood the roadway
ditch below the cut slope.
Ditch Profiles
Roadway ditch profiles will generally follow the roadway grade. The
minimum grade should be 1 percent. If flatter grades are necessary,
ditches may need to be larger or alternately, the ditch can be separate-
ly profiled to obtain the necessary minimum gradient.
— Maximum density is a term used in earthwork specifications to mean the
oven-dry weight per cubic foot of soil at optimum moisture content. The
American Association of State Highway Officials (AASHO), the American
Society of Testing Materials (ASTM) and other organizations have estab-
lished field testing procedures to determine if compacted earthwork
meets a specified percentage of maximum density.
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di+ch or
curb
DITCH PLACEMENT
FIGURE 25
Bas/h
DITCH OUTLET NEAR
STREAM
206
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Other ditch profiles should "be consistent with the ditch section
used and quantity of flow. As previously suggested, the full flow
velocity in all ditches should be at least 2.5 to 3.0 feet per second
to permit sediment transport.
Ditch Outlets
Ditches will outlet or discharge into natural streams, other drain-
age channels, culverts or settling basins. Ditches that outlet into
natural drainage channels or streams may require a catch basin with cul-
vert outlet or other sediment trapping device, 100-150 feet upstream from
the intersection with the drainage channel or stream as shown in Figure
26. If the roadway cut slopes, fill slopes and ditches are stabilized,
there should be minimal risk of sediment entering the stream or natural
channel from the last 100-150 feet of the ditch shown in Figure 26.
Ditches also outlet into culverts. If the soils are erodible in
and around the ditch, the circumstances may require a catch basin struc-
ture prior to culvert entry. See the following discussion on culverts
and catch basins.
Sloped Roadway Alternate to Roadside Ditches
Construction of out and in sloped roadways with surface cross
drains has been a popular way to build forest roads. Although this
type of construction has a place in forest road work, misuse of the
concept can result in a sediment problem.
From the "Proceedings of A Symposium Forest Land Uses and Stream
Environment" at Oregon State University, Larse recommends: "Design out-
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slope or alternating inslope and outslope roadbed sections without a
drainage ditch when overland surface flows are slight and road gradients
can be 'rolled' sufficiently to self-drain without surface channeling"(5).
Packer studied the control of rill or gully erosion on outslope
road surfaces in the Northern Rocky Mountains (56). Each study site
had to meet the following criteria:
1. "Drainage structures immediately above and immediately below
the road segment must have diverted all surface runoff and
eroded soil originating above them onto the fill slope below
the road without allowing any discharge to continue down the
road surface."
2. "The road segment must not have been affected by waterflow
from side drainages."
3. "The road segment must not have had an inside ditch along the
toe of the road cut."
4. "Sediment discharged from the lower or downgrade drainage
structure, or eroded from the fill below it, must have been
stopped on the slope before reaching a stream channel, a
downslope road, or a major topographic barrier, such as a
bench."
5. "The entire study site, including the slope above the road cut
and the slope below the fill, must have been located on soil
derived from similar parent material."
6. "The site must have been on an area where the timber sale was
not more than 5 years old."
The report included a table for cross drain spacing required to prevent
rill or gully erosion deeper than one inch on secondary logging roads in
certain types of soils on various road grades. The Guides for Control-
ling Sediment from Secondary Logging Roads by Packer and Christensen
also contains the table. The table is included herein as Table 14.
Care must be exercised in the use of the table to ascertain that it is
applied under circumstances that are closely comparable to the conditions
under which Packer's studies were made. Packer and Christensen recommend
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TABLE
Cross-drain spacings required to prevent rill or gully erosion deeper than
1 inch on secondary logging roads built in the upper topographic position
(1) of north-facing slopes (2) having a gradient of 80 percent. (3)
Road
Cross-drain spacing
grade Hard Glacial
(percent) sediment Basalt Granite silt
Andesite Loess
2
4
6
8
10
12
14
167
152
144
137
128
119
108
154
139
131
124
115
106
95
137
122
114
107
98
89
78
135
120
112
105
96
87
76
105
90
82
75
66
57
46
95
80
72
65
57
48
37
(l) On middle topographic position, reduce spacings 18 feet; on lower
topographic position, reduce spacings 36 feet.
(2) On south aspects, reduce spacings 15 feet.
(3) For each 10-percent decrease in slope steepness below 80 percent,
reduce spacings 5 feet.
Source: Packer, Paul E., "Criteria for Designing and Locating Logging
Roads to Control Sediment," reprinted from Forest Science,
Volume 13, Number 1, March, 1967.
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that where combination of soil and topographic features require cross
drain spacings of less than thirty feet, "no logging roads should be
built unless they will be surfaced with gravel or crushed rock" (4-6).
In their China Glenn road report, Hartsog and Gonsior offer the
following conclusion as to the success of the outslope road section as
used at this particular location:
"The authors suspect that outsloping is more an idealistic concept
than a realistic solution to the water control problem. In theory,
water generally will be uniformly distributed in minimal concentra-
tion over the road shoulder. However, unless the road can be
graded to close tolerances and left undistorted, concentration is
virtually unavoidable. Depressions left by wheels allow water to
concentrate and run along the road. Even if the road has no grade,
water will tend to concentrate and spill over depressions. If
soils are loose and erodible, slight concentrations tend to erode
depressions and channels that lead to greater concentrations and
accelerated erosion. Although it can be argued that such problems
rarely occur, the major part of all stream sedimentation is caused
by relatively infrequent circumstances. Most of any stream's an-
nual sediment load is contributed and transmitted (under natural or
disturbed conditions) during a few hours or days. It is tentatively
recommended that outsloping be specified only where surfaces are
relatively nonerodible (e.g., at full-bench sections)" (14).
The following conditions are favorable for the use of no ditch out-
slope roads with surface cross drains.
1. Short backslopes.
2. Terrain slope less than 20 percent.
3. Seasonal road use.
4. Spur (light traffic) roads.
5. Favorable geographic area.
6. Non continuous longitudinal grades steeper than 3 percent.
7. Conditions permitting immediate planting and growing of
vegetation on cut and fill slopes.
The following conditions are unfavorable for the use of no ditch
outslope roads.
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1. Long backslopes.
2. Continuous steep longitudinal grades.
3. Terrain steeper than 20 percent.
Rock Sub-drain Alternate to Roadside Ditches
Another alternate is the use of the rock sub-drain. The rock sub-
drain is located between the toe of the cut slope and the edge of the
roadway, as shown on Figure 27. An advantage for its use as compared to
an open ditch is that the total grading width of the road will be less.
ROCK SUB-DRAIN
FIGURE 27
Rock sub-drains may be used when longitudinal grades are steeper than 2
percent. Critical to the longevity of the sub-drain is the establishment
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and maintenance of vegetation on the slopes above the drain. Any limita-
tions on construction procedures for installing the rock sub-drain in
order to maintain backslope stability and prevent contamination of the
sub-drain should be included on the plans or in the accompanying speci-
fications.
Rock sub-drains can outlet similarly to the open ditch, through a
Ditch Inlet Structure, as discussed in the next part, and a cross culvert
or to a natural channel.
CULVERTS
"A culvert is an enclosed channel serving as a continuation of and
a substitute for an open ditch or an open stream where that ditch or
stream meets an artificial barrier such as a roadway, embankment or
levee" (87). Forest road culverts are used primarily to drain the road-
way surface (outletting roadside ditches) and to allow streams or natural
channels to pass through a roadway embankment.
"Culvert failure, another common cause of road damage, was most
often related to plugging with debris. In most cases, the hydraulic
capacity of the culvert was sufficient to carry the volume of water as
long as it remained unplugged" (11).
The fact that culvert intakes do become blocked with debris, sedi-
ment, rocks, etc., requires that serious consideration be accorded the
use of a culvert intake protecting device. A Ditch Grating Inlet Struc-
ture, with or without a Catch Basin (Figures 28 and 29), is such a
device. The degree or amount of culvert intake protection needed will
vary with individual site circumstances from a simple riprap treatment
of ditch bottom and sides at the intake point to the more elaborate
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8-4.
V)
' /
//
//*- Cu/vert-
/
Oitch
PLAN
SECTION A-A
DITCH INLET STRUCTURE
FIGURE 28
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DITCH INLET STRUCTURE
WITH CATCH BASIN
FIGURE 29
treatments that can include trash, racks, catch basins and/or the grat-
ing inlet structure. Intake protection should also be evaluated in
the light of the anticipated ditch and culvert maintenance program and
the companion treatment that may be accorded the culvert outlet. In a
series of several culverts outletting a ditch, varying degrees of treat-
ment to intakes might be considered so that at least one or more of the
culverts would function under very adverse circumstances.
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The minimum cover depth for a culvert should be determined on the
basis of manufacturer's recommendations, appropriate vertical position
of culvert relative to ditch bottom and ditch full flow line (I'd minimum
below subgrade), nature of backfill and kind of backfill equipment,
anticipated haul truck and other logging equipment loads, and construc-
tion equipment loads. An inactive culvert (crushed) can cause roadway
wash-out, erosion and sediment.
"The frequency, location and installation method of ditch drainage
culverts is much more important than capacity or size. However, minimum
sizes of 15 inch or 18 inch diameter is the accepted practice, depending
on the rainfall intensity (runnoff and area intercepted) and the
influence of ditch debris" (11).
Ditch outlet culverts should be designed so that the half full
velocities are 2.5 to 3.0 feet per second in order to transport sediment
through the culvert. If the ditch becomes over silted and the catch
basin or other intake device fails to function, the sediment should pass
through the roadway culvert to an outlet or other necessary downstream
sediment collectors. Cleaning culverts is a difficult, expensive,
neglected, ignored and often imperfect procedure. Provision for necessary
sediment collection before or at the culvert intake and/or at or after the
culvert outlet is recommended. Culvert outlet treatments are discussed
later in this chapter.
Common culvert materials are corrugated galvanized steel and cor-
rugated aluminum. When culverts are on steep slopes where design flow
velocities are 10 feet per second and greater, paved inverts are desir-
able to reduce barrel wear resulting from sediment scour. The type of
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coupling band necessary for an installation and whether or not the use
of gaskets is appropriate should be related to the anticipated differential
settlement that might occur along the length of the culvert. Culvert
separation under a roadway has great potential for causing roadway fail-
ure and subsequent sediment transport.
Culverts used to transport streams under roadway embankments can
be round, structural pipe arch or structural plate arch. The latter two
are preferred. The structural pipe arch enables the wide flat bottom to
be buried in the stream bed. The structural plate arch has no bottom,
so the stream can remain virtually untouched if care is exercised during
its installation. (A further discussion of stream crossings follows this
section.)
Ideally, outfall ends of culverts under roadways should terminate
beyond the toe of the fill. When the fill is shallow, this condition
may be satisfied by simply extending the pipe as a cantilever beyond
the fill slope a sufficient distance to clear the toe of the fill. On
deep embankments, where the outlet point is a considerable distance above
natural ground, a culvert extension anchored to the fill slope may be
required. Half round culvert extensions are also employed for this
purpose. Whether the half round will be satisfactory depends on its
anchorage, the quantity and velocity of discharge, and the length
and steepness of the embankment. Where discharge and flow velocities
are high, splash from half round sections can spill onto the slope,
possibly cause slope erosion and sometimes failure of the anchors.
Canvas or "elephant trunk" culvert extensions have also been
employed. They have been subject to vandalism and to freezing shut
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in cold weather. Placing riprap on the fill slope below the culvert
outlet will aid in preventing slope wash.
The problem of protecting the fill slope at the culvert outlet
point can be minimized by placing the culvert entirely on or within
natural ground. Determining whether to adopt this alternate is a
matter of evaluating the circumstances at the culvert location in
question.
Sizing Culverts
The complete hydraulic design procedure for all culverts requires:
1. Determination of the design flow - See discussion below and the
paragraphs on stream crossings and hydrology.
2. Selection of the culvert size.
3. Determination of the outlet velocity.
"The many hydraulic design procedures available for
determining the required size of a culvert vary from empiri-
cal formulas to a comprehensive mathematical analysis. Most
empirical formulas, while easy to use, do not lend themselves
to proper evaluation of all the factors that affect the flow
of water through a culvert. The mathematical solution, while
giving precise results, is time consuming. A systematic and
simple design procedure for the proper selection of a culvert
size is provided by Hydraulic Engineering Circular No. 5,
Hydraulic Charts for the Selection of Highway Culverts and
No. 10, Capacity Charts for the Hydraulic Design of Highway
Culverts, developed by the Bureau of Public Roads." (Federal
Highway Administration.) (88,89)
This method is based on the results of both laboratory experiment and
prototype tests. The method is believed to provide a more rational
approach than older procedures for determining culvert capacity.
"The procedure for selecting a culvert is to determine the head
water depth from the charts for both assumed inlet and outlet controls.
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The solution which yields the higher head water depth indicates the
governing control" (89). However, the minimum velocity must be 2.5 to
3.0 feet per second at half capacity for transporting sediment through
the culvert. The procedure stated above includes a determination of the
outlet velocity. Knowledge of this velocity is pertinent to the evalua-
tion of the potential for erosion at the outlet point of the culvert.
The sizing procedure, outlined above, may be augmented by the follow-
ing considerations:
1. Arbitrarily reduce roadway culvert spacing below the spacing
required by mathematical calculation, to recognize the potential
for debris and sediment blocking of culvert intakes and/or the
circumstances at the outlet end. Large volume high velocity
discharge may be difficult to control regardless of the sophis-
tication of the treatment.
2. Arbitrarily increase roadway culvert sizes and/or reduce culvert
spacing in recognition of the level of accuracy of data used in
determining the design flow.
3. In a run of three or four cross roadway culverts, make one a
size or two larger than calculations require as an "insurance"
mechanism in case one or more culverts become plugged.
4. Be realistic in forecasting or assuming the level of ditch
and culvert maintenance.
5. Size culverts at the low point of sag vertical curves for twice
the calculated flow or alternately size all culverts upstream
from the low point for 20 percent more than the calculated flow.
Provide an inlet structure for the culvert at the vertical curve
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low point. Make liberal use of trash racks or inlet structures
for the culverts along the adjacent negative grades.
6. Evaluate the potential for subsurface flow interception by the
road excavation and the possibility that this flow will substan-
tially increase peak flow to a culvert.
7. Since live stream culverts are preferably installed parallel to
stream gradient with invert buried in the stream bed, recognize
this circumstance in flow capacity evaluation.
8. Evaluate stream culvert calculated size relative to potential
stream bed constriction. Pipe arch or plate arch culverts have
advantages as previously described.
9. Evaluate the potential for manufactured debris upstream from
stream culverts in terms of the land management program for the
drainage area. If the area is to be logged, provisions must be
made to keep manufactured debris out of the stream or the culvert
must be sized accordingly. The former is the better procedure,
the latter is guess work.
10. For a stream crossing ascertain the performance record of any
existing culverts on the stream above and below the point under
consideration.
11. From the reconnaissance information, recognize the potential for
natural stream bed erosion during storms.
12. Recognize any effects land management's activities may have on
water yield to ditches and their associated culverts.
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Design Aspects of Culvert Installation
Culvert design usually includes features of the installation that
are important to the performance of the culvert in accordance with design
expectations. These features, when appropriately specified by the
designer and accomplished by the installer, are germane to the sediment
creation potential occasioned by culvert failure.
Roadway Culverts. It is usual to specify that the trench width
shall be limited (pipe diameter plus a distance) and that the trench
walls be vertical for a height at least equal to the pipe diameter and
preferably more. These limitations are used because wider trenches tend
to increase load on the pipe and require more excavation and backfill.
Reasonable care in installation is assumed for all design criteria or
design tables developed for determining necessary pipe gage. Handling
the minimum amount of soil when installing a culvert is also advantageous
with respect to the potential for sediment creation. Culverts may be
crowned when installed to provide for the deflection anticipated by em-
bankment consolidation.
Culvert trenches are often over excavated and backfilled with select
material (pea gravel is popular) in order to obtain proper pipe bedding
in lieu of shaping the trench bottom for the pipe barrel, or because of
unsuitable foundation material. The select backfill is usually placed
at least to the spring line (mid height) of the pipe. If a situation
existed where water was being forced along the outside of a culvert,
the presence of pea gravel backfill would tend to allow this passage as
opposed to the circumstances of pressure build up and possible culvert
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blow out. Thus the use of pea gravel backfill for reasons of structural
integrity of the culvert could also have the accompanying advantage of
minimizing sediment potential. The Ditch Grating Inlet Structure
(Figures 28 and 29) will act to reduce the opportunity for water to pass
along the outside of the culvert.
Stream Culverts. The advantages of using structural plate or pipe
arch culverts as a means of minimizing stream bed disturbance have been
previously mentioned. As with roadway culverts, all of the installation
procedures important to the structural integrity of the installed culvert
(foundation, backfill quality and method) may have bearing on the poten-
tial for creating sediment.
Upstream fill slopes will usually require erosion protection by the
use of concrete headwalls, rock riprap or gabions. (See Figure 30) A
conservative estimate of the height and width of the fill slope adjacent
to the culvert requiring this protection is suggested.
In some circumstances, an additional safety factor can be included
by provision for an overflow channel across the roadway adjacent to the
culvert. The roadway profile might be adjusted to form an adjacent low
spot or sag with companion fill slope armoring within the planned over-
flow channel. Although some sediment creation and transport may occur,
the amount will be much less than that created by a culvert "blow out".
Clearing of the approach channel of natural debris for some dis-
tance upstream from the culvert is strongly recommended. The amount of
clearing necessary depends on the individual circumstances at the site,
100 feet upstream is offered as a guideline. Clearing of the approach
channel should be at least an annual accomplishment.
221
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wate
Cu/vert
UPSTREAM EMBANKMENT FACE TREATMENT
FIGURE 30
222
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WATER COURSE CROSSINGS
One of the important forest road design problems is the live stream
crossing. Sudden earth slides and minor roadway surface disintegration
are capable of disabling a road but the potential for road loss and sedi-
ment creation and transport from a washout due to a plugged culvert or
extraordinary high water at a stream crossing is probably greater. It is
therefore extremely important to exercise the utmost care in the planning,
design and construction of water course crossings. Robert W. Larse
observed that: "Surveys of road damage and erosion resulting from high
stream flows indicates floatable debris to be a major contributing factor,
and causing severe road embankment, stream bank erosion or channel
changes" (5).
Design criteria for minimizing the sediment potential from stream
crossings is interrelated with other design factors whose application is
necessary to satisfy the functional requirements of the site. If these
criteria are not satisfied, the crossing will not provide satisfactory
service to the land manager. Therefore the following discussion of
criteria is necessarily broader than the topic of sediment minimization.
The discusion is not, however, a complete treatment of the design
spectrum for stream crossings.
Genera I
Each stream crossing must receive individual study to determine the
best crossing method. Sufficient site data must be available so that
the responsible designer can accomplish this individual study. This data
will be a part of the findings of the reconnaissance phase supplemented
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by appropriate topographic, foundation, fisheries considerations and
other information that will define the ambient site circumstances in
adequate detail for design purposes. A site visit by the project de-
signer is strongly recommended.
The responsible design professional must know the use and purpose
of the road of which the stream crossing is a part. The intended road
use may relate to the designer's options in selecting a crossing method.
His task is to meld the use requirements to the site requirements in a
manner that will produce a satisfactory result.
Sediment Features of Stream Crossing Design
The following aspects of stream crossing design have particular
relevance to the potential for sediment creation.
1. Hydraulic capacity of opening.
2. Allowances for debris.
3. Bank protection (stream or roadway slopes) adjacent to or
within the crossing area.
4. Effect of channel changes or relocation.
5. Amount of excavation of foundation work needed within wetted
perimeter of stream.
6. Type of streambed material.
7. Timing of construction relative to high water.
Based on the quality of information available to him, and his com-
petence, the designer can recognize and treat the first six items listed
above in his design solution. The seventh item involves those who pro-
gram the actual construction as well as the type of design. Appropriate
224
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communication on this subject is mandatory.
Sufficient topographic field data for the designer to determine the
hydraulic characteristics of the stream channel is basic to an analysis
of hydraulic capacity. This data is needed for several hundred feet up-
stream and downstream from the crossing point in order to determine the
water surface level relative to stream banks for various design flows.
Even with an adequate channel section at the crossing, an inadequate
section upstream could cause channel banks to overflow, resulting in
erosion of approach embankments. This situation may indicate a need to
consider embankment protection riprap, overflow culverts in approach
embankments, overflow approach spans for bridges, or provision for flood
waters to overtop approach embankments.
Determination of design flows for mountain streams and rivers is
more difficult due to the lack of stream gaging stations and rainfall
intensity records in high altitude areas. Further, some researchers
believe that there are no appropriate models available for the predic-
tion of mountain stream flows.
A nationwide series of water-supply papers entitled "Magnitude and
Frequency of Floods in the United States" has been prepared by the United
States Geological Survey. Calculations of design flows by the USGS method
or other approach should be cross checked by the following:
1. Known flood history of the area.
2. Performance of crossings of similar streams.
3. All available gaging records of this and comparable streams.
4. Field data indicating high water marks, natural overflow
channels, old stream beds, etc.
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Any proposed changes to natural channels or the inclusion of flood
way obstructions should be evaluated to determine the changes that might
occur in the hydraulic behavior of the stream. Channel relocations,
when constructed in the dry, are not necessarily detrimental to the
stream. Easing or elimination of sharp bends may remove a constriction
to hydraulic capacity. (Stream bed scour may also increase.) The rule
is to make a total evaluation of the proposed design including water
quality and fisheries considerations. The U.S. Bureau of Public Roads
(Federal Highway Administration) Hydraulics of Bridge Waterways is a
good reference for the analysis of stream obstructions (i.e. bridge
piers) for streams or rivers (90).
Table 13 gives scour velocities for certain kinds of ditch soils.
Values shown in this table provide an indication as to the maximum
velocities that can be tolerated in channels without using riprap
treatments of rock or gabions. The U.S. Bureau of Public Roads Design
Chart for Open Channel Flow includes data for grassed channels. Design
charts include a procedure for determining maximum permissible velocities
without channel scour (91).
Important to the satisfactory performance of riprap lined channels
is the sizing of the riprap and the companion channel side slope. The
Bureau of Public Roads Design of Roadside Drainage Channels 1965 includes
procedures for evaluating the adequacy of channel linings relative to
channel slope and flow velocity. This publication recommends that "if
the mean velocity at the design flow exceeds the permissible velocity
for the particular soil type, the channel should be protected from
erosion" (92). Design procedures using various linings are discussed.
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Riprap bank protections should extend a minimum of two feet "below
the stream bed. This is to prevent erosion of the bank material and sub-
sequent displacement of the riprap.
Stream Crossing Methods
There are three stream crossing methods employed on forest roads,
fords, culverts and bridges. Factors influencing the selection of the
appropriate crossing method include stream size, debris potential, ver-
tical position or road relative to stream, foundation conditions, con-
struction cost and maintenance cost, and contemplated road use and life.
Fords. Fords are an attractive alternate for secondary or spur
road crossings of small drainages particularly if road use is limited to
the dry season when no flowing water is in the channel. Ford installa-
tion requires minimal disturbance to the stream channel. Problems
attendant to bridge or culvert installation such as size of opening,
provision for debris passage and channel or embankment riprap are
largely avoided.
Gabions for ford crossings have been successfully used in the Modoc
National Forest. Allen J. Leydecker in an article entitled "Use of
Gabions for Low Water Crossings on Primitive or Secondary Forest Roads"
(93) describes the design use. A typical installation cost $3,000 in
1971 and was accomplished on a force account basis. The installation
consists of gabions placed at the roadway grade backfilled by stream
gravel to form the road surface. "In about a year's time, fines trans-
ported by the stream cement the gravel backfill and construction scars
heal, leaving a satisfactory stream crossing ..." Figure 31 is a
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reproduction from Leydecker's paper portraying a section through the
ford. The ford was not damaged during the following winter when peak
flows were estimated by Leydecker to have been approximately 400 cfs.
ti^nsn^n
Source:
GABION FORD
FIGURE 31
Leydecker, Allen D., "Use of Gabions for Low Water Crossings on
Primitive or Secondary Forest Roads"
Culverts. Culverts have been regarded by many designers as the
economic solution for small stream highway crossings during the past
twenty-five years. They have largely displaced the previously used
short span bridge for reasons of economy and the goal of maintaining an
uninterrupted roadway and shoulder width. The performance of culverts
on forest roads suggests that the determination of use should not be
as quickly assumed as has been the case for county roads, city street?
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and state highways. The site circumstances that may be different from
those of a typical public highway installation are steepness of terrain,
potential for debris, ability of steep terrain to retain fills adjacent
to the culvert and difficulty in compacting fills with equipment usually
used in forest road construction. Reliability of the calculation for
required culvert capacity is another factor.
The foregoing discussion is particularly directed toward the round
culvert. No specific guidelines or "rules of thumb" are available to
assist the designer in making a choice between bridge or culvert. Atten-
tion to the individual circumstances of the site by a competent pro-
fessional is the only known rule.
Other features of culvert design are discussed under that subject
heading.
Bridges. Forest road bridges have been designed using a variety
of structural materials for substructure and superstructure. The selec-
tion of a bridge type for a particular site is dependent upon the func-
tional requirements of the site, economics of construction at that site,
live load requirements, foundation conditions, policies or opinions of
the owner, maintenance evaluations and preferences of the project designer.
The type of design selected can have a bearing on the potential for sedi-
ment creation.
The bridge design can go awry if insufficient attention is accorded
the site circumstances. A quick conclusion that the site permits the
use of an accomplished design from a "similar" site should be avoided.
Location of bridge foundations relative to the normal stream channel
and forecasted flood channel can be an important element. While it is
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not suggested that all bridges must span flood channels, an evaluation
of the effect on the channel with an obstruction therein is necessary.
Channel obstructions can cause channel scour and contribute to debris
blockage.
Although there are different views on the minimum desirable hori-
zontal and vertical stream clearances in streams not subject to naviga-
tion, some arbitrary rules based on judgment and experience in the area
should be established. Vertical clearances should not be less than 5
feet above the 50 year flood level plus .02 of the horizontal distance
between piers. Horizontal clearance, between piers or supports in
forested lands or crossings below forested lands, should not be less
than 85 percent of the anticipated tree height in the forested lands or
the lateral width of the 50 year flood.
In considering a longer span bridge, there are economic tradeoffs,
higher superstructure cost versus possible reduction in foundation cost
as compared to a short span. Subaqueous foundations are expensive and
involve a degree of risk attendant to the operations of cofferdam con-
struction, seal placement and cofferdam dewatering. In addition to the
water quality degradation that can occur with a lost cofferdam, the time
and money loss will be significant. Subaqueous foundations often limit
the season of construction relative to water level and relative to fish
spawning activities. Thus, construction timing has to be rigidly con-
trolled.
Type of foundation support also deserves consideration from a sedi-
ment perspective. If deep excavations are necessary to reach suitable
strata for direct bearing footings, pile supports may result in less
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disturbance of the ground in and around the stream thereby reducing the
amount of excavation, shoring and backfilling. A careful review of the
economic tradeoffs is appropriate rather than an immediate conclusion
that direct bearing footings are correct because the support strata is
present at some depth.
The remoteness of many forest road bridge sites suggests the maximum
use of precast or prefabricated superstructure units for economic reasons.
The use may be limited by the capability to transport the units over
narrow, high curvature roads to the site, or the horizontal geometry of
the bridge itself. Precast or prefabricated superstructure units avoid
a requirement to falsework the stream as is required for a cast-in-place
concrete bridge. A cast-in-place structure may place limits on the
construction season since the falsework may block the stream and is
very vulnerable to debris damage. Any delays of construction (changed
foundation conditions) that result in falsework being placed later in
the season than initially anticipated can be hazardous. Some streams
are subject to flash floods even in the "dry" season.
The U.S. Forest Service is constructing nine steel girder bridges
on Forest Development Roads in the South Tongass National Forest, Prince
of Wales Island, Alaska. Short construction season and the remote sites
(no local source of concrete aggregates) influenced the designer's de-
cision to maximize use of prefabricated steel elements for both super-
structure and substructure units.
The abutments for three of the bridges are U-shaped made entirely
of steel sheet piling. The structures clear span the normal water level,
end supports interfere slightly with estimated high water. Although
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minimizing sediment potential may not have been a stated design goal,
the abutment design is one that clearly accomplishes this. Placing the
sheet pile abutments requires minimum handling of natural soils as com-
pared to an abutment designed in reinforced concrete.
A conservative vertical clearance for debris at high water was also
provided. A lateral bracing system was provided in the plane of the
lower girder flanges because of vulnerability to drift and debris during
high water (94-).
CULVERT OUTLET TREATMENTS
The last opportunity to control or inhibit the movement of sediment
in the roadway drainage system is at or near the culvert outlet point.
The action of the water at the outlet point can also create sediment if
the flow velocity is of a magnitude that will scour the natural soils
at the outlet.
Due to the many variables involved, all possible solutions to this
problem are not included in the following discussion. A few practical
solutions that can be adapted as the designer may determine are outlined.
If appropriate upstream measures have been taken for sediment con-
trol, the degree of treatment at the culvert outlet may be minimal.
Appropriate upstream measures may include:
1. Adequately designed and constructed ditches with appropriate
linings.
2. A Ditch Inlet Structure with Catch Basin that functions properly
to trap sediment. Sediment that is not deposited in the ditch
and bypasses the catch basin is considered as flowing through
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the roadway culvert to its outlet. Whether or not storm waters
are likely to contain significant sediment at the culvert out-
let depends upon the eroditdlity of soils over which these
waters have passed and the volume and velocity of flow.
Figures 32 and 33 show two roadway culvert outlet conditions. The
culverts shown in Figure 32 outlet at least 150 feet from a live stream.
For this condition a short length of lined culvert apron at the outlet
point to act as an energy dissipator and a scour inhibitor has merit.
The lining can be rock rubble, ten feet minimum in length with a width
equal to twice the culvert diameter as shown in Figure 34.
If the remaining distance to the live stream is relatively flat and
contains vegetation, channel flow velocity will tend to decrease. Remain-
ing sediment will tend to deposit in the vegetation. However, if the
remaining distance to the stream is steep and bare, additional energy
dissipation may be necessary in order to permit sediment deposit. The
rock apron can be continued further beyond the culvert outlet and a rock
dike with height equal to the culvert diameter and width equal to twice
the culvert diameter installed in the outlet channel as shown in Figure
35. In addition, a further measure might be the placing of slash from
the roadway clearing to act as a sediment barrier.
Figure 33 shows a roadway culvert outlet in close proximity to a
live stream. In this case, placing the outlet end of the culvert in a
rock lined channel whose minimum depth is at least twice the culvert
diameter as shown in Figure 36 may be appropriate. If the culvert exit
velocity is 10 feet per second or greater, a rock dike as shown in
Figure 35 to act as an energy dissipator may be necessary in order to
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At least '50
SHALLOW FILL-SHALLOW CULVERT
HIGH FILL-SHALLOW CULVERT
CULVERT OUTLETS
FIGURE 32
-------
j t
//heat
CULVERT OUTLET NEAR STREAM
FIGURE 33
PIPE CHANNEL DETAIL
FIGURE 34
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PLAN
ROCK DIKE
FIGURE 35
ALTERNATE PIPE CHANNEL DETAIL
FIGURE 36
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insure sediment deposit before storm waters intersect the stream.
If suitable rock is not available for a channel lining, an alter-
nate might be the use of clearing slash to construct gravel filled crib
wall channel linings as shown in Figure 37. Gabions and sacked riprap
can also be used but they are costly. The use of slash has the secondary
advantage of providing a disposal method for some of the clearing debris.
An outlet treatment for a large culvert with high storm water flows
is shown in Figure 3$, an Energy Dissipating Silo.
Even with the upstream sediment control features of catch basins
and rock lined ditches, there may be a period when excessive sediment
can be transported. This will happen during construction and for a
time thereafter until new vegetation and soils stabilization measures
become effective. Figure 39 shows a roadway culvert (or combination of
culvert discharges, e.g. collector ditch at toe of slope) discharging
into a sediment pond (basin).
The velocity of flow through the sediment pond should be approxi-
mately one foot per second and preferably less in order for settling to
take place. Settling velocities of sand and silt in still water are
shown in Table 15. The tabulation in this table suggests that the sedi-
ment pond should be large enough to retain the maximum flow input for
at least one hour if the pond is designed for a two foot water depth in
order to settle silt sized sediment.
The designer will have to determine the actual pond size, dependent
upon topography, soils, porosity, water quality requirements, etc. After
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PLAN
AH to** &"
0
SECTION A A
GRAVEL FILLED CRIB WALL
FIGURE 37
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rook
ENERGY DISSIPATING SILO
FIGURE 38
* -/
&oaam/ay
Note: Sediment pond not necessarily located
immediately adjacent to the roadway prism.
CULVERT OUTLET TO SEDIMENT POND
FIGURE 39
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TABLE 15
SETTLING VELOCITIES FOR VARIOUS PARTICLE SIZES
(10.00 mm to 0.00001 mm)
Diameter
of
Particle
Order
of
Size
Settling
Velocity
Time required
to settle
one foot
mm.
mm./sec.
10.0
1.0
0.8
0.6
0.5
0.4
0.3
0.2
0.15
0.10
0.08
0.06
0.05
0.04
0.03
0.02
0.015
0.010
0.008
0.006
0.005
0.004
0.003
0.002
0.0015
0.001
0.0001
0.00001
Gravel 1,000
100
83
63
Coarse Sand 53
42
32
21
15
8
6
3.8
Fine Sand 2.9
2.1
1.3
0.62
0.35
0.154
0.098
0.065
Silt 0.0385
0.0247
0.0138
0.0062
0.0035
Bacteria 0.00154
Clay Particles 0.0000154
Colloidal Particles 0.000000154
0.3 seconds
3.0 seconds
38.0 seconds
33.0 minutes
55.0 hours
230.0 days
63.0 years
i/The Water Encyclopedia by David Keith Todd, 1970 (Page 86)
Water Information Center, Port Washington, N.Y.
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a period of use, the fines will tend to seal the pond. After the road
project is completed and upstream erosion control measures become effec-
tive, the performance of the pond may be less important. It should be
recognized that the circumstance of terrain and road corridor may be
such as to preclude the use of a sediment pond in many situations.
HYDROLOGY
Preceding parts of this discussion on drainage design have pointed
out the importance of the determination of the design flow to the success-
ful performance of a drainage system. The designer is interested in deter-
mining whether logging and road building in the forest, and forest location
will have a significant effect on the flow volumes he should provide for,
with respect to road drainage and stream crossings.
Logging and Roadbuilding
Rothacher reports that an increase in annual stream flow in the
Pacific Northwest may be expected after clearcutting. He also points to
an increase in early Fall seasonal flows after clearcutting because the
soil moisture content is higher in a clearcut area as compared to the
soil moisture content under old-growth forest. Thus less of the Fall
precipitation is needed to recharge storage within the soil. Rothacher
does not believe that clearcutting significantly changes peak flood flows
in areas west of the Cascades. Flood flows normally occur after the soil
is saturated, "wet mantle" condition, and are directly related to the
amount of precipitation. Rothacher points to some contrary evidence on
small drainages containing roads as well as having been clearcut (95).
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R. Dennis Harr and others believe that it is unlikely that there
will be culvert and bridge damage in Oregon Coast drainages as a result
of clearcutting, provided designs are made on a 25 year storm frequency
basis. They believe that the effect on roads in small drainages can be
more serious as roads are permanent and will exist during large storms:
"Success or failure of a certain size culvert or bridge might
depend heavily on the amount of roads that eventually will be
built in the watershed whose outlet stream is to be contained
within a culvert or bridge" (96).
Bethlahmy is convinced that clearcutting a small drainage will
result in greater peak/flows in that drainage. He believes that culvert
capacities and bridge clearances in these drainages should be designed
to accommodate conditions after logging (97,98).
Rothacher and Glazebrook believe that the Pacific Northwest storms
of December 1964 and January 1965 were very unusual. They predict that
storms similar to these can be expected in the Cascade and Coast Ranges
at least once in 50 to 100 years. They also observe that localized
storms of these intensities can occur more often: therefore, "our plans
and actions must give them adequate consideration" (11). The authors
state that flood probabilities and forecasting have been evolved mainly
for the requirements of downstream communities and that "much of the
information currently in use has not been verified for mountainous areas."
These articles suggest that a conservative approach to the calcula-
tion of the design flow for a stream crossing be employed especially if
precipitation data for the immediate area is not available. Other con-
siderations involved in determining the appropriate opening size for bridge
or culvert are discussed in the previous parts on Culverts and Stream
Crossings.
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Subsurface Water Considerations
Another consideration is the potential for roadway cuts to intercept
ground water flows thereby converting this flow to overland flow into
ditches of a roadway drainage system. Attention was invited to this
phenomena in the route reconnaissance discussion with respect to field
reconnaissance. Megahan's studies in the Pine Creek drainage, a tribu-
tary of the Middle Fork of the Payette River, Idaho, showed that the
quantity of water whose source was intercepted ground water flow was
many times greater than the quantity whose source was overland flow.
"Interception of subsurface flow is one of the more insidious
effects of road construction because its occurrence often is not
readily apparent. Subsurface flows occur only during large rains
and/or snowmelt when large volumes of water are supplied to the
soil. Such flows begin, reach a peak, and recede within a short
period. Many times, the climatic event that generates subsurface
flows also limits access, making it impossible to see flows as
they occur. This is particularly true during snowmelt and rain-
on-snow events in the mountains. As soon as subsurface flow
ceases, most exposed roadcuts dry out completely and little evi-
dence of flow remains. Another factor leading to the lack of
recognition of subsurface flow is the fact that flow emergence
is not limited to drainage bottoms, but may occur on straight or
even convex side slopes as well" (49).
Megahan believes that total volume of watershed runoff increases
when subsurface flow is converted to surface flows. Whether peak flow
rates are increased depends on the simultaneous occurrence of the
normal peak flows from the watershed with the flow from intercepted
subsurface water. Certainly the local effect on ditches and culverts
at or near subsurface discharge or outlet point could be significant.
Other effects are related to questions of stability of cut banks,
potential road surface erosion and stability of fills. Megahan believes
that much of the road erosion reported in the Idaho Batholith "is very
2-43
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likely a direct result of subsurface flow interception."
Forest Location
There is little question that total precipitation amounts increase
with elevation, except in areas of pronounced rain shadow effects. How-
ever, considerable controversy appears to exist as to the effects of
elevation on rainfall intensity. Dorroh's (99) evaluation of rainfall
data from the southwestern United States indicated that, although both
total precipitation and thunderstorm frequency tend to increase with
elevation, the heaviest individual rains occur in the valleys. Croft
and Marston (100), however, stated that higher rainfall intensities
could be expected on the windward slopes of the Wasatch Mountains in
Utah than in the adjacent valleys. In the very different climate of
coastal British Columbia, precipitation at higher elevations is apparent-
ly characterized not so much by higher intensities as by longer duration
at a given rate (101).
Schermerhorn (102) studied the effects of various parameters, most
notably elevation, upon annual rainfall amounts in western Oregon and
Washington, where extremes of 20 inches to 150 inches of average annual
precipitation occur. His work revealed very little relation between
station elevation and annual rainfall, but that most of the variation in
average annual precipitation for the 280 stations studied could be
accounted for by relatively simple indexes linked to broad scale topo-
graphic and latitude factors. Three main index parameters were defined:
index elevation, barrier elevation, and index latitude. Use of a graphi-
cal relationship involving these three main parameters to calculate
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annual precipitation for the 280 stations yielded an unadjusted standard
error of estimate of 7.2 inches for an average precipitation of 63 inches.
Schermerhorn did not make any attempt to use his method to develop eleva-
tion-rainfall intensity relationships, a key parameter for determining
peak design flows.
Cooper (103) reported on an extensive study of elevation-precipita-
tion relationships within a 93 square mile area in southwestern Idaho
where continuous rainfall recorders had been installed at an average
density of one per square mile and operated for four years. The area
had an elevation range of 3,500 feet and climatic variations resulting
mostly from elevation and topographic features rather than from regional
air mass differences. The rainfall data indicated that average annual
precipitations increased about 4 inches for each 1,000 feet increase in
elevation and ranged from 8 inches in the lower part of the valley to
28 inches at the higher elevation. Numerous methods of data analyses
that attempt to establish other rainfall-elevation relationships indicate
no relationship between elevation and peak rainfall intensity and eleva-
tion and several other intensity-related parameters. The only relation-
ship that could be established was that the logarithm of the proportion
of rainfall exceeding a given intensity plotted as a straight line
against intensity. There was no difference in this relationship when
the data were separated by elevation classes. Cooper noted that this
relationship is rather universal and holds true for many other parts of
the world as well.
Cooper concluded that the apparent lack of relationship between
rainfall intensity and elevation suggests that data from accessible
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valley stations can be used to estimate the relative occurrence of
high intensity rains throughout an area of appreciable range in eleva-
tion. At least under the conditions encountered in southwestern Idaho,
about the same proportion of the seasonal rainfall exceeds a given in-
tensity at high elevations as at low ones. Because there tends to be
more total rain at high elevations, there is likewise more intense rain
at mountain stations than in the valleys, but the relative proportions
remain nearly constant.
Others believe that much is unknown about rainfall intensities at
the higher altitudes and question the applicability of the currently
available models. As was previously stated in the discussion on stream
crossings, the engineer must cross check his calculated design flows
obtained from the USGS or other method.
CONSTRUCTION SPECIFICATIONS
An essential part of the design for any road project are the com-
panion specifications. Preparation of these specifications must not be
separate or removed from the supervision of the forest or civil engineer
who is preparing the road design.
A serious mistake is made in those cases where separate personnel
are authorized to prepare the specifications for design plans prepared
by others. This inadequacy is frequently represented by notation on the
plans such as "see specifications for detailed requirements", "see speci-
fications for procedures", "see specifications for further requirements".
Such notations frequently mean the designer has not made up his mind as
to what the requirements or procedures should be. Definable accomplish-
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ment cannot be attained without positive and non-contradictable plans
and specifications. The foregoing is a very brief analysis of the
relation between plans and specifications and is placed herein to em-
phasize the need of the utmost correlation between the two companion
documents.
STANDARD SPECIFICATIONS
Many design organizations have prepared volumes or multicopies of
specifications particularly oriented to their endeavor. The volumes
have such titles as Standard Specifications for Road and Bridge Construc-
tion and set forth general, legal, and specific engineering requirements
under which the proposed construction is undertaken as a mutual agree-
ment between the owner and the contractor. These standards are revised
from time to time and vary between regions because of different regional
circumstances. The U.S. Department of Agriculture has prepared such a
volume entitled "Forest Service Standard Specifications for Construction
of Roads and Bridges."
A further group of specifications published at regional, national
and international levels is devoted primarily to materials and methods
of testing materials. Prominent and valuable organizations in this
group are The American Society of Testing Materials, The American Stan-
dards Association, and The American Association of State Highway Officials.
Frequently specifications from one or more of this group are included
by reference, or quotation in the specifications published or adopted
by the owner or agency.
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SPECIAL PROVISIONS
To define and describe the individual items of work, local circum-
stances, special construction items (those not included in the Standard
Specifications), times of accomplishment, legal requirements, and pay-
ment conditions, a further document is written for each project entitled
Special Provisions. This is part of the contract documents. The Stan-
dard Specifications and the Special Provisions combine to form the
Construction Specifications. Items specifically related to sediment
control will usually be a part of the Special Provisions.
The Special Provisions should include a separate paragraph stipula-
ting that the successful bidder shall prepare and submit within 30 days
a detailed schedule of on site construction starts, material purchases
and phase accomplishments. The schedule can be of assistance in evalua-
ting whether the contractor recognizes construction elements and se-
quences relating to sediment control as envisioned by the designers.
It can also point out potential problem circumstances during construction
due to the forecasted timing of certain operations relative to seasons.
A common practice in special provision writing has been to lump
together certain "nuisance" items, including requirements for water qua-
lity control within the work site. Elaborate descriptions are often
written about the Contractor's obligations, all of which are to be en-
forced at the sole discretion of the Engineer and for which compensation
is to be considered as "incidental to the other items of work involved
in the project". Such procedures are of little practical help to a
Resident Engineer. While owner's representative and Contractor feud
over whether the particular issue is or Is not one of the "incidental"
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items, the problem may magnify and its potential for damage to completed
work and resources may increase.
The Special Provisions should provide compensation for the Contractor
for all labor, materials, tools and equipment he is to furnish including
items involved in temporary or permanent sediment control features. They
should advise the Contractor as to the manner in which he will be asked
to perform various tasks, whether the demand will be intermittent, and
whether "extra" or "standby" crews or materials are involved. The impor-
tance of dealing with changed circumstances swiftly is discussed else-
where in this report. The Special Provisions should support this goal
by providing means for swift, equitable adjustments in contract compensa-
tion.
A possible technique is to establish compensation for certain emer-
gency work on a force account basis with an estimated amount included
in the contract documents. This approach has merit provided the estimated
amount is a realistic assessment of the circumstances that may be encoun-
tered.
In the Timber Purchaser Road Construction report by USFS, Region 6,
it was found that scheduling techniques are not being used by timber sale
road builders and the Forest Service.
"Historically timber sale road construction activities have been
triggered by the timber market demand. This factor is a basic
problem in the scheduling difficulty and affects the timing of
construction starts and construction progress. There is a general
lack of documented, or even oral disclosure of construction sched-
ules. Some inspectors wasted valuable time by constantly visiting
project sites just to find out when construction was starting" (8).
Obviously, the potential for sediment creation during construction
is related to the season in which certain construction elements are being
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accomplished. Contract scheduling should provide for construction acti-
vities to be accomplished in their appropriate season. If the project
is to extend over more than one season, the procedures and require-
ments for shutdown at the close of each season should be specified.
The basis for determining when conditions warrant seasonal shutdown
should also be included in the special provisions.
Larse summarizes the construction activity thus:
"Although there are many commonly practiced techniques to mini-
mize erosion during the construction process, the most meaningful
is related more to how well the work is planned, scheduled and
controlled by the road builder and those responsible for deter-
mining that the work satisfies design requirements and land
management resource objectives" (5).
CONCLUSIONS
The foregoing discussion was written in terms of the owner-contractor
relationship. The intent of the comments is believed applicable in in-
tent to the circumstances of road construction by a timber purchaser or
road construction by a land owner's own forces.
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CONSTRUCTION TECHNIQUES
As earlier stated, Route Planning and Reconnaissance are regarded
"by many as the most important phase of logging haul road development.
In design, the planning and reconnaissance data are translated by design
into plans and specifications to meet all of the road objectives and to
guide the construction phase. Larse observed as follows:
"Construction of the designed facility is a challenge to the
road builder to complete the work with a minimum of disturbance
and without damage to or contamination of the adjacent landscape,
water quality, and other resource values. Some of the most severe
soil erosion can be traced to poor construction practices and job
management, insufficient attention to drainage during construc-
tion and operations during adverse weather conditions" (5).
The Engineer in charge (Resident Engineer) or the inspector is the
last link in the long chain of a total effort to produce a logging haul
road in a manner that will minimize sediment. Field changes are to be
expected. The Resident Engineer acting alone, or with the design engi-
neer, must decide the corrective measures to be taken. Other than field
changes the inspector must require adherence to the plans and specifica-
tions .
Manpower may be a limiting factor to supply sufficient inspectors
for the work load in a given region. However as the work load peaks,
qualified individuals having other duties could be assigned to inspection
activities.
The Resident Engineer and the inspectors must be relentless in
their effort to fully implement the plans and specifications as envisioned
and designed. The construction specifications should provide a means
of payment for many of the processes that the contractor may need to
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accomplish and which are of benefit in arresting sedimentation including
those attendant to changed conditions. These items arise from condi-
tions unforseen by the design engineer such as seasonal variations and
foundation and soils inconsistencies. The discussion that follows in-
cludes construction features that require individual analysis and the
application of the appropriate construction technique in order to mini-
mize erosion or sediment transport.
CLEARING AND GRUBBING
The Forest Service Standard Specifications for Construction of
Roads and Bridges and the amendments clearly define clearing and grubbing
activities and methods. Each Region supplements these specifications
with methods peculiar to its area.
Clearing and grubbing then is the first activity in constructing a
forest road that disturbs the forest floor and surrounding soils. Flash
storms under these conditions can produce instant erosion and sediment
problems. This work is a necessary part of the road work. A precaution
that should be taken to prevent a part of the potential sediment flow
is to not disturb more ground than is absolutely necessary until a satis-
factory drainage system is provided. The brush collected from the clear-
ing and grubbing operation can be placed at the toe of embankments or
below culverts to act as a filter and retardant to sediment flow.
Attempts to begin excavation prior to the completion of clearing
have resulted in mixing slash and organic material with earth. The mixed
material acts as a contributor to the sedimentation problem rather than as
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a filter. It also may have too high an organic content to be used as
fill material thus requiring wasting.
Merchantable timber from the clearing operation might be tempor-
arily stacked at the toe of a fill until the fill is stabilized. Small
logs may have use as walls for channel linings as suggested in drainage
design and as shown on Figure 37.
Clearing and grubbing should be scheduled to proceed just in
advance of earthwork. Sections which are not going to be graded in the
current season should not be cleared and grubbed.
EARTHWORK
During excavation and embankment activities the total roadway prism
is vulnerable and is subject to erosion and sediment flow from rain
storms of relatively slight intensity. Larse states:
"When soil moisture conditions are excessive, earthwork
operations should be promptly suspended and measures taken
to weatherproof the partially completed work . . . clearing
debris underlying, supporting or mixed with embankment
material is a common cause of road failure and mass soil
movement. The necessary slope bonding, shear resistance,
and embankment density for maximum stability cannot be
achieved unless organic debris is disposed of before em-
bankment construction is started" (5).
Road builders on Washington's Olympic Peninsula have found that a
shovel can be worked in much wetter weather than bulldozer. The shovel
does not tend to disturb the subgrade in marginal weather to the degree
that a bulldozer does. Shovels on mats are a common soft ground technique
on the Olympic Peninsula and across muskeg in southeastern Alaska.
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Embankment compaction should be accomplished by one or more of the
following types of equipment.
1. Tamping rollers.
2. Smooth wheelpower rollers.
3. Pneumatic-tired rollers.
4. Grid roller.
5. Vibratory rollers.
6. Vibratory compactor.
7. Bulldozer.
In the past, the bulldozer has frequently been the sole compactor
used on forest roads. It has proven to be very ineffective when the
dozer blade is so wide that it prevents the tracks from covering the
entire roadbed width. The dozer may be used provided it can compact from
out to out of the total roadway. A more satisfactory compaction job will
be obtained by having the dozer do its primary job of moving earth and
using equipment specifically designed for compaction to accomplish the
compaction.
Embankments should be placed and compacted to the required density
to avoid instability, control drainage flow and deter massive movement.
Embankment placement in layers with attendant compaction is necessary.
Sidecasting, as a construction method has limited value. The literature
on forest road failures contains many references to failures due to
improperly constructed embankments.
Waste sites should be as carefully prepared as embankment portions
of the roadway. Waste material could be used as a portion of the road-
way embankment (as shown in Figure 40) instead of being end hauled an
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excessive distance. The width and number of benches will be determined
by the height of the fill and the quantity and quality of waste material
involved.
Borrow pits should be closed by dikes or dams to prevent sedimen-
tary flows into adjacent streams or have a sediment pond at the outlet
end. The dikes or dams should be removed when the borrow pit water
ceases to carry sediment. Borrowing from running streams should be pro-
hibited.
B&ichftil
ALTERNATE WASTE SITE
FIGURE 40
Ballast may be placed only on shaped and drained subgrades in a
manner that will not deform, rut or rupture the subgrade.
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DRAINAGE
No other item is as important to the permanence and usefulness of
the forest road and the control of stream sedimentation as the drainage
system.
"In many places, careless and improper construction of a high
mountain logging road can nullify all the effort expended in
well considered design and location . . . Poor construction
and inadequate drainage have triggered land slumps in water-
shed after watershed and have resulted in the most serious
form of accelerated erosion that occurs during timber harvest-
ing .... Therefore during all phases of road construction,
protect water quality by using every possible and applicable
soil and water conservation measure" (4-2).
DRAINAGE DURING CONSTRUCTION
The drainage design discussion indicated that temporary ditches and
other drainage facilities may be necessary during the construction phase.
To achieve the goals of permanence of slopes and road beds and to mini-
mize sedimentation, the following suggestions have been of consequential
advantage.
"Protect all fill areas with surface drainage diversion Systems.
Place culverts so as to cause the minimum possible channel dis-
turbance and keep fill materials away from culvert inlets and
outlets . . . Allow road machines to work in stream beds only for
laying culverts or constructing bridge foundations. Divert stream
flow from the construction site whenever possible in order to
prevent or minimize turbidity. Clear drainage ways of all woody
debris generated during road construction. Windrow the clearing
debris. . . . outside the roadway prism (to use as a drainage
filtering system)" (42).
The previous paragraph mentioned several antidotes to control con-
struction drainage. Also the use of visqueen or plastic sheets, tem-
porary flumes, installation of a second culvert (preferably by jacking),
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culvert extensions and settling basins are other techniques. Roadway
surface dips should be installed as soon as possible so that they
can be utilized to control storm water while construction continues.
The most important technique, however, is that of observing, watching
and promptly correcting an installation that does not accomplish its
intended function.
During the initial construction period, the Resident Engineer must
have all design data, rainfall and stream flow records at hand. If any
drainage installation does not supply the desired results as to capacity,
turbidity, or indicates instability in the early stages of construction,
he must have the knowledge and authority to direct the changes that will
give the desired results of stability, capacity and turbidity standards.
Applying for a re-design study, awaiting authorization from higher
echelons and/or additional funds, will serve only to magnify the adversity.
DRAINAGE CONSTRUCTION
A prevalent concept of drainage construction must be abandoned and
a new one evolved. The prevalent concept that the contractor is permitted
to install various drainage features when he chooses based on available
equipment, subcontractors, accomplishment of like items at one time,
such as placing riprap or headwalls, must be pushed aside for the concept
of doing in order the things that are needed to stabilize slopes and re-
duce to a minimum the transportation of sediment. Without a doubt applica-
tion of this new concept will cost more in initial expenditures for the
drainage system than would accrue under the now prevalent procedure. An
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economical comparison between the two would not be realistic unless
values can be assigned to the potential cost of reconstruction of
water damaged road features and the cost of excessive sediment trans-
port.
The grading of a roadbed should not be extended beyond the con-
struction of the companion and attendant drainage features. Few slides
should occur on hillsides properly graded and drained, or on slopes
guarded against erosion. It is recognized that sudden rains can fall
during the construction season. If the ditches require rock linings,
matting or other protective measures, the actual ditch grading and
shaping should not be too far advanced ahead of the protective treat-
ment. Always grade, shape and finish ditches from the downstream end
to the upstream end.
Culverts should be installed as the road work progresses. The
culvert and its related drainage features, as required, should be in-
stalled in the following order:
1. Place debris and slash to be used as a filter system.
2. Construct sediment ponds.
3. Install energy dissipating devices.
4. Place rock rubble rock or matte channel lining.
5. Lay the culvert from the downstream end to the upstream end.
6. Construct ditch inlet structure with or without catch basin.
It is important to note from the above that all drainage work
should start at the downstream end and progress to the upstream end.
This installation procedure will enable surface and intercepted sub-
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surface waters to flow in a finished channel downstream and away from
the work area. The system must be kept operative at all times. If
it is necessary to install a culvert in a live stream, diverting the
water by parallel channel or pumping around the work area may be
appropriate.
The reader is reminded of the discussion in drainage design
relative to culvert installation, that the designer assumes reason-
able care in culvert installation. Critical features are bedding, back-
filling and pipe joints. Hartsog and Gonsior's China Glenn analysis
indicates a lack of skill, supervision and appropriate equipment con-
tributing to difficulties with culvert installations (14).
All drainage construction activities should be closely super-
vised to insure that the various work items are meshing together at the
scheduled time. Correct those items lagging behind schedule immediate-
ly.
CONSTRUCTION EQUIPMENT
The U. S. Forest Service Region 6 Road Audit states:
"The use of improper and oversized equipment by timber pur-
chasers was identified as a problem area . . . Special equip-
ment is needed to properly accomplish some construction tasks
and to fully protect forest values during the construction
operation . . . almost all road construction was accomplished
with a large crawler (D-8 or D-9) with dozer. In many cases
this was the only equipment . . . Much of the road construction
equipment was developed for wide highway and freeway construc-
tion . . . Evidence was found that timber sale road inspectors
adjusted their enforcement of specifications to meet the capa-
bilities of the contractors available equipment" (8).
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Recommendations from this report include: (l) Constraints on
the maximum size of equipment that can be used for a particular road
project. (2) Directing and supporting inspectors to enforce specifi-
cations relating to equipment size etc. . . (3) Revise cost estimating
guides to include costs of doing work with various sizes or kinds of
equipment. (4) Make equipment manufacturers who are continually de-
veloping new machinery aware of management objectives, such as minimum
environmental impact roads, minimizing soil erosion, sediment and
aesthetic impacts.
The use of the shovel to accomplish roadway excavation on the
Olympic Peninsula and in southeastern Alaska is discussed earlier in
this chapter. The shovel is also commonly used in other areas with
steep terrain for the circumstance of excavating full bench sections on
narrow roads with waste end hauled. This method results in a much
higher unit earthwork cost than was previously experienced with a partial
bench and/or sidecast operation with bulldozer excavation. It also re-
sults in less road miles being constructed in the short season available
in many high altitude areas. Equipment specifically adapted or designed
for more economic full bench excavation work on narrow roads with end
haul is needed.
Hartsog and Gonsior believe that specialized equipment is needed for
clearing on steep slopes. On China Glenn, tractors often worked them-
selves into places low on the slope where they had to be winched upslope
by another machine. They believe tractors with a low center of gravity
equipped with a brush blade are the best of the present equipment. The
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purpose of specialized equipment would be to eliminate or reduce the
pioneer road required for present equipment because of the potential
contamination attendant to a procedure of excavating before clearing
is completed (14).
The necessity for appropriate equipment to install drainage facili-
ties has been previously mentioned.
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MAINTENANCE
Concerning maintenance, Robert W. Larse has stated:
"Planned regular maintenance is necessary to preserve the
road in its (as built) condition, but unfortunately is too
often neglected or improperly performed resulting in deter-
ioration from the erosive forces of the climatic elements
as well as use ... It is neither practical or economical
to build and use a road that requires no maintenance . . .
The additional expense of constructing a road, with proper
attention to its stability and proper drainage can generally
be amortized within a few years by an offsetting lesser cost
of upkeep where soil erosion and sedimentation are of concern
. . . ." (5).
Some observers believe that problems have occurred due to policies
that result in too many miles of road being left open. The decision as
to whether a particular road should be left open is not the sole
prerogative of maintenance personnel but is related to transportation
and land management plans. Blocking primary purpose logging roads off
when this purpose is complete can help eliminate road surface damage
with attendant sedimentation caused by other uses during wet seasons.
If a road is not to be used again for several years or is to be
permanently closed, blocking a road to prevent further use of the road
may not be an effective sediment control technique in itself. If the
drainage integrity and stability of the roadway cannot also be maintained,
additional measures are needed for minimizing sediment. These practices
are described in the Intermittent and Short Term Use section of this
chapter.
To facilitate and expedite maintenance operations and procedures,
a complete set of "as built" plans with a record of all maintenance
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operations and observations should be maintained and be readily available
to the maintenance engineer. This record system will help to equip and
supply new personnel with all the previous experience and observations
of their predecessors.
The "as built" records should contain the following information:
1. Complete job index.
2. Complete history of the project from start to finish
of construction.
3. Photographic records.
4. Exact location of culverts and other drainage features.
5. Unstable conditions in relation to cut and fill slopes
and roadway surface.
6. Wet areas that may have caused over excavation and replace-
ment with selected backfill.
7. All major field changes that were made in the original plans.
The greatest asset available for any maintenance program is the
experience history and knowledge gained by those who have in fact
accomplished the maintenance operation. Usually this knowledge is not
recorded, but every effort should be made by management to keep com-
petent experienced knowledgeable maintenance personnel at their tasks
and/or available for consultation and advice.
The maintenance discussion that follows is divided into five
parts: (l) drainage system, (2) road surface, (3) remedial measures
for slides, (/+) intermittent and short term use, and (5) maintenance
chemicals.
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DRAINAGE SYSTEM
Drainage maintenance is not a spectacular task. The greatest and
best accomplishments occur in wet ditches, plugged culverts, or slides
that impair roadways. For forest roads, particularly in mountainous
areas, maintenance cannot be programmed on the yearly calendar but must
be accomplished when the individual site or circumstances dictate.
Little can be accomplished in snow or in frozen ground with the
possible exception of jacking in culverts or solid rock excavation.
Snow melts do not usually cause the maximum flows or carry fragmented
rock, boulders or fallen timber. The time to accomplish the major
drainage maintenance is usually concurrent with the major forest
operations of cutting, hauling, planting or thinning.
In spite of this peaking of labor demand, the maintenance
program should never be postponed. Rules or procedures for drainage
maintenance can be set up only as guidelines because there is a wide
variance between localities, construction accomplishments, workable
seasons and climatic factors. The following are offered as guidelines
only, as each area must modify or amend their procedures to suit their
circumstances.
CULVERTS AND DITCHES
Ditches, culverts and catch basins must be kept free of debris and
obstructions. On new construction, catch basins may require frequent
cleaning, perhaps after each major storm. Grass in ditches should not
be removed during cleaning operations. Shoulder and bank undercutting
must be avoided. Damaged culverts should be repaired or replaced.
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Culverts and inlet structures should "be cleaned by flushing down-
stream only if adequate filtering to protect watercourses is available.
Debris from cleaning operations should be hauled to a stable waste site
far removed from any watercourse.
"Regular inspections during or after storms will ensure
good drainage because problems are detected before they
become serious. Inspections for detection of weaknesses
in drainage systems are especially important on new roads.
As a general rule, roads should be examined annually in
the Spring after the first rains or at the start of snow
melt" (43).
In Western Washington and Oregon, a fall inspection prior to winter
storms is good practice.
Ditches and culverts are particularly vulnerable to debris block-
age when a logging operation is occurring on or adjacent to the road.
Blockage with limbs, needles and wood chunks can occur rapidly. Main-
tenance personnel should be alert to the ongoing logging operations
and aware of their potential significance to the maintenance program.
Live streams with culverts should be completely free of trans-
portable debris, for at least 100 feet upstream. If the initial con-
struction did not call for debris deflectors or trash racks and sub-
sequent experience shows they are required, install them as part of
the maintenance program. The downstream end should also remain free
flowing. Debris should be removed from streams or channels by grapples
or tongs rather than by equipment in the stream bed.
Ditch and culvert surveillance may be necessary on closed roads
particularly in seasons immediately after logging operations. The
potential for debris blockage, although perhaps less with the road closure,
can still exist.
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CUT AND EMBANKMENT SLOPES
Cut and embankment slopes are so individualistic that only the
most elementary precautions are set forth below. Each slope must
receive separate study.
Erosion clefts in cuts may be filled with rock or coarse gravel
to create a trickling water movement through the rock fill material.
Turf should be replaced in bare earth areas.
Erosion clefts in embankments should be filled and turfed and
the water from the roadway directed to a culvert or flume. In the
event of indicated large movement, the slope may be dewatered by hori-
zontal drains, wells, or well points until the area becomes stable.
Only pervious materials, preferably rock, should be placed as embank-
ment on water giving slopes.
Berms at the top of embankments intended to prohibit water from
flowing onto the slope should be monitored for breaks or ruptures and
repaired as required.
ROAD SURFACE
Road surfaces must be kept well crowned or sloped so they will
drain. Surface blading should preferably be accomplished when the
moisture content of the material results in neither dust nor mud from
the blading operation. Particular attention should be accorded the
road crown or slope just in advance of the wet season.
Roads subject to traffic during the wet season will require con-
tinual monitoring for surface condition including ability to drain,
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presence of rutting and loss of ballast. Provisions should be made
for ballast replacement where necessary as a condition to continuing
operations on the road. Roads sufficiently ballasted for dry weather
operations may not be satisfactory for all seasons.
Surface cross drains should be cleaned as required after the
logging season to restore their functional ability. If the cross
drains do not exist in a road intended for seasonal closure, they
should be cut in advance of the rain and/or snow season.
The snow removal operation can damage the road surface by remov-
ing ballast and/or destroying the roadway crown. Factors that contri-
bute to the potential for damage are improper snow removal equipment,
improper equipment operation and initiating snow removal at the improper
time. Snow removal procedures should allow for proper drainage.
Road condition has to be monitored relative to the freeze thaw
cycle. The potential for surface disruption is greater when frozen
subgrade or surfacing begins to thaw.
The foregoing expresses important provisions or guidelines for
road maintenance. The most important guideline consists of management
educating the maintenance personnel about the importance of minimizing
sediment transport to ditches. No one can control the amount or time
of rainfall or the amount and rate of snowmelt. Therefore the only
control of sediment transport attendant to maintenance operations is
by individuals.
There will be circumstances both planned and unplanned when sedi-
ment from roadway surfaces is transported to side ditches. When this
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Slides cause many problems in conjunction with maintenance and
increased erosion potential along the road alignment. Several of
these problems are discussed in the following paragraphs.
REMOVING SLIDE DEBRIS
Slide debris deposited on roadways may cause significant increased
sediment loads in established roadway drainage systems. In some
cases it may cause erosion channels to develop outside of established
drainages. The removal of material on the road may be accomplished
by heavy construction equipment. Sidecasting of the material should
not be allowed.
Slide debris which is located downslope from the logging road
poses a different and more difficult problem. Most importantly, the
removal operations may trigger further movements. Another problem
involved in removing the material is the possibility of damaging
surface vegetation and erosion control devices on the downslope side
of the road. Therefore, an evaluation of the potential for erosion
from the slide debris versus the potential for erosion caused by
the removal of the slide debris, including that from potential future
slides triggered by debris removal, should be made and carefully
examined before any removal is carried out.
In many cases removal will probably be infeasible. It may be
desirable to leave the material in place and shape and reseed it
or take other measures to reduce the potential for surface erosion.
Specific rules or guidelines for debris removal should not be formulated.
Each case should be evaluated on an individual basis and action taken
in response to the conditions encountered at each site.
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WASTING SLIDE DEBRIS
Once the slide debris is removed the problem arises as to what
should be done with the material. Slide debris is often composed
of a mixture of soil, rock, and organic debris, and is usually very
wet. Material in this condition normally cannot be placed and compacted
as fill within a roadway embankment. However, the material may be
placed in end-haul disposal areas. Proper placement and compaction
of this material must be achieved in order to limit erosion. Again,
it should be emphasized that slide debris material should not be
sidecast from the roadway or placed in a noncompacted fill that is
susceptible to erosion.
RELOCATION VS CORRECTION
Proper evaluation of the erosion potential and the economics
of road relocation versus slide correction is essential, and many
factors should be considered before a decision is made. Among these
are: what caused the slide, how extensive is it, and will it reoccur?
These questions will be discussed in more detail in the following
section. Before a decision is made, the amount of surface erosion
and mass wasting potential from construction of a newly relocated
alignment should be determined. A new road may have a higher total
erosion potential than the erosion from the slide debris, particularly
if the general terrain is unstable or if the new alignment is of
considerable length. New roads, particularly initially, often have
a higher erosion potential than the existing ones. Correction of
the slide area may involve constructing retaining structures, installing
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drains, reshaping slopes, and/or replacing fill in the roadway alignment.
Slide correction is often more desirable than constructing new roads.
FAILURE MECHANISM INVESTIGATION
Before corrections can be made within a slide area, the extent
of the slide, the reason for the slide, and the potential for reoccurrence
must be determined.
The first step in defining the failure mechanism should be a
detailed inspection by an experienced soils engineer or engineering
geologist. From this inspection, an approximate failure plan can
be developed and possible causes evaluated. In many cases, this
inspection is all that is required for a proper evaluation of the
failure. In more extensive and complex slide areas, this intial
inspection should be supplemented with a detailed subsurface investigation.
This investigation would include drilling deep holes to obtain undisturbed
samples for strength testing, and installing piezometers within and
above the slide area. In some cases, the installation of inclinometers
may be justified to determine if movement is continuing and to what
extent it may be occurring. The amount and extent of this investigation
is dependent upon the conditions at each individual site. In any
event, this work should be accomplished under the auspices of a specialist
in either soil or rock mechanics.
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INTERMITTENT AND SHORT TERM USE V
Problems arising both from overdesigned roads which do not fit the
terrain and from inadequately designed roads have been described. Field
observations in Region X indicate that sediment control practices are
often neglected or ignored for low standard logging roads. These are
variously described as "work", "branch", "spur" or "temporary" roads.
In most situations they are designed and constructed for relatively low
volume of traffic, and intermittent or short term use. As used in this
discussion, "temporary" means short term use. Design criteria for such
roads usually include minimization of both investment and maintenance
costs. Haul costs are generally of secondary consideration.
The principles for incorporating appropriate sediment control features
into planning, reconnaissance, design and construction have been described
in previous chapters. These principles are applicable to all types of
logging roads. For example, a spur road constructed in the wrong location
can cause as much water quality damage as a poorly located higher standard
road.
Road maintenance procedures and appropriate options discussed
previously in this chapter are applicable to low-standard roads. For
I/ Inclusion of this section in the final report is the result of
~ written comments received following the draft report review;
and subsequent written and verbal communication with selected
practitioners.
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intermittent or short term use roads, additional options and techniques
are available for minimizing sediment production between use periods
or after use is concluded. As noted previously in this report, many
factors must be considered in order to rationally select suitable
options for a specific road.
INTERMITTENT USE
Intermittent use logging roads are those which are planned for a
permanent transportation facility but are not intended for continuous
use. Intervening time between use periods may range from several
months to several years.
In addition to the many elements of consideration described
throughout this report, other factors may influence the selection of
maintenance options for these kinds of roads. These factors include:
type of ballast or surfacing on the roadbed; length of time between use
periods; construction method (sidecast or end haul); whether the road
existed previously or is the result of a planned design and construction
sequence; length of time a previously built road has been in place
(demonstrated stability); type of drainage structures; and cost effec-
tiveness .
Even though an objective may be to minimize maintenance during
non-use intervals, periodic inspection of a road is needed to assure
that the water quality protection measures are performing as expected.
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Roadway
Where the interval between use periods is relatively short, one
approach is to block the entrance to the road to prevent unplanned use
and conduct needed maintenance throughout the non-use period. Tech-
niques for blocking a road include gates and a variety of crude and
sophisticated physical barriers constructed from native materials
(rock, slash, cull logs, etc.).
A more comprehensive approach, in addition to blocking the road,
includes installing a system of water bars and drainage dips (as
described in the Drainage Design section); and stabilizing cuts and
fills (as detailed in the Slope Stabilization section). Scarification
and revegetation of the road surface may also be appropriate—depending
upon the type of road surface, the erosion potential and the non-use
interval. These measures may be sufficient to stabilize the roadway
during non-use periods, but supplemental maintenance may also be needed.
Depending upon the drainage design some roadway renovation may be needed
prior to re-use of the road.
When the interval between use periods is long, additional options
are available. In some cases, the approach described in the previous
paragraph may be sufficient.
Another method is to partially restore the original ground profile
in order to convert some of the surface water flow created by the road
incision back to a subsurface flow and provide more efficient surface
runoff capability.
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The Panhandle National Forest in Idaho has developed a partial
restoration technique, called the "Kaniksu Closure", which involves
moving the outer road berm and part of the fill material and placing
it into the road cut area. Figure 41 illustrates this method. Where
terrain and road conditions permit the use of this technique without
loss of significant amounts of soil over the embankment edge, the work
can readily be accomplished with an angle-blade bulldozer. Dave Rosgen,
hydrologist on the Panhandle National Forest reports that this method
is successful on side slopes up to 60 percent in northern Idaho.
Following the work, the site is revegetated.
The "Kaniksu Closure" was developed initially to deal with an
existing transportation system. Other field practitioners report that
this technique has limitations for use in areas with high precipitation;
on ballasted or surfaced roads; on end haul constructed roads; in some
soil types; and where the interval between use periods is relatively
short. (Re-opening the road may result in more re-exposed roadway
surface than would result with another method. Unless the interval
between use periods is fairly long, this may negate some of the restor-
ation benefits).
Stream Channel Crossings
Stream channel crossings on intermittent use roads deserve special
consideration. Culvert installations with substantial fills are parti-
cularly vulnerable to failure as a result of debris blockage or simply
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Excavated
mat trial
ve
Original
land slope.
Original
road prism
kdjusttd
road prism
(Afitr Rosgen )
Schematic
FIGURE 41 "KANIKSU CLOSURE"
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from being incapable of handling high runoff events. Such problems
occur more often with unattended installations but can also occur—
especially during heavy runoff conditions—even when maintenance is
attempted.
More options are available if the crossing installation is the
result of a planned design-construction sequence than if it is on a
road being re-used.
Pre-planned Crossing. For these installations, the basic alter-
natives are as described previously in this report—culverts; bridges;
or in some circumstances, fords.
Techniques for culvert design, installation and maintenance
discussed elsewhere in this report are applicable. There are some
additional methods used for dealing with intermittent use roads.
Information from field practitioners indicates that, where a culvert
installation is the best option, important design, construction and
maintenance criteria are:
1. Minimize the amount of culvert fill.
2. Use generous culvert end area estimates.
3. Design for a permanent installation.
4. Plan for supplemental maintenance "watch" if there
is doubt about the ability of an installation to
withstand extraordinary runoff events.
5. If a stable installation is not technically or
economically feasible, include subsequent culvert
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removal as part of a planned process if it can be
accomplished with minimal water quality impact.
If not, avoid such sites or select a safer
installation.
Another technique is to use "temporary" log stringer bridges in lieu
of culverts where the culvert installation requires a large fill. Many
of the installation criteria for protecting water quality described in
the Bridges portion of the Design chapter are also applicable to
temporary bridges. Several different kinds of temporary bridge designs
are used in Region X—varying from simple, relatively crude structures
to more elaborate bridges designed for heavy traffic and several
seasons of use. With short lapses between use periods, it may be more
economical to install a longer life "temporary" bridge and leave it in
place. With longer intervals of non-use it may be more advantageous to
use a minimal cost structure and remove it after use. It should be
noted that the practice of placing logs across a stream channel and
placing an earth fill over the logs is neither a good water quality
management practice nor considered to be a "temporary bridge" as used
in this report.
In certain situations (see Stream Crossing Methods subsection),
fords may be a suitable channel crossing installation.
Existing Crossings. If a channel crossing installation has
functioned satisfactorily for years (demonstrated stability) most field
practitioners contacted believe the best solution is to restore the
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installation to its original stability and leave it in place. The
restoration work may involve several elements of the installation other
than the crossing structure itself. This may include removal of stream
channel debris; and roadway reconditioning (e.g., reshaping, cleaning
ditches, reopening drainage, revegetating, etc.) over and on approaches
to the crossing.
However, if it is determined that there is a high risk of culvert
failure following the use period, the water quality management choices
are more difficult. The basic options are continual maintenance or
removal of the installation—entirely or partially. Factors which may
lead to & "high risk" determination include: restoration to original
condition is not feasible; the hydrologic character of the channel and
upstream watershed has materially altered; unstable debris; and instal-
lation stability has not been demonstrated (e.g., high frequency of
failure of similar, nearby installations). Continual, on-site main-
tenance watch before, during and after high runoff events—until the
installation becomes stable—is one way of reducing failure risk.
If continual maintenance is not feasible, most practitioners
contacted believe that the best solution is to remove the installation.
This can be expensive and difficult to achieve without creating water
quality impacts. However, care in timing the removal operation, and
use of proper equipment can aid in reducing impacts.
Where the total removal cannot be accomplished without substantial
impact because of prohibitive costs or technical infeasibility, a
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partial solution is a relief dip in the culvert fill. Rosgen reports
that this technique has been field tested on the Panhandle National
Forest and shows promise. Figure 42 shows this technique in schematic
form. The relief dip does not stabilize the fill. Rather, it reduces
the impact by directing the course of overflow water and reducing the
amount of potential sediment.
SHORT TERM USE
Short term use (temporary) logging roads are those which are not
planned for re-use. The general objectives for such roads should be to
design a facility which can be safely maintained during its life, which
can readily and safely be restored back to as nearly the original ground
conditions as feasible; and to plan to make the time period between
construction and restoration as short as practicable (within the same
season if feasible). Locating temporary roads should be avoided in
areas where these objectives cannot be reasonably accomplished.
Roadway
One alternative is to stabilize the road prism as permanently as
feasible. Methods for accomplishing this include: blocking the road to
further entry; installing a stable system of water bars, drain dips, and
outsloping (where suitable); revegetating the cut and fill slopes and
road surface; and establishing trees if the site was previously forested.
These practices and limitations for using them are discussed elsewhere
281
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Original
excavated material to
roacf approatkef
Original
drainage prof He
VERTICAL
Culvert
Drain and vegetate
(disperse water)
A
V Configuration on exposed
irrn ~~ to disperse surface runoff—
KvA (fmatf. one foot or lest contour trench*)
\ i •
(Atttr
FIGURE 42 MODIFIED CULVERT REMOVAL
282
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in this report. This approach may be most suitable where an existing,
stable roadway has been reopened (but no further use is planned). If
the watershed character has not been materially altered and if the
past performance of these methods has been good for similar sites,
they may also be adaptable for newly constructed temporary roads.
The "Kaniksu Closure" method along with tree establishment as
appropriate will, in general, result in a more complete restoration
of the water handling characteristics of the site. Taking into account
the previously described limitations of this method, it can be used for
existing and newly-constructed roads. The U.S. Forest Service, Region 6,
uses a similar method as one option for obliterating temporary roads
constructed under timber sale contract.
A more comprehensive (and usually considerably more expensive)
technique is to completely restore the original ground profile. As used
by the U.S. Forest Service, Region 6, this method—sometimes termed
"deconstruction"—is to temporarily store excavated material and then
pack it back into the roadway following completion of use. This
technique was developed primarily to deal with critical terrain and
high precipitation problems in portions of the Pacific Border Province.
The more common practice is to sidecast excavated material and, following
use of the road, pull it back up into the road prism with shovel or
dragline. When this practice is used in precipitous terrain, it is
imperative that it be used only where the roadway excavation and
subsequent restoration can be accomplished during the same summer season.
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Sometimes the excavated material is endhauled, stored on a stable waste
site and then placed back in the road prism following use. In this
case, if the restoration cannot be completed during the first season,
additional measures may be needed to prevent erosion of the roadway and
the waste material.
After "deconstruction" is completed, the restored ground is revege-
tated, including tree establishment as appropriate.
It is apparent that even temporary logging roads require thoughtful
planning and design in order to most effectively achieve desired water
quality objectives throughout the life, care, and obliteration of the
facility.
Channel Crossings
Sediment control objectives for channel crossings on temporary
logging roads should include the following:
1. Design crossings which:
(a) can be installed with minimal water quality impact;
(b) remain stable during use; and
(c) can be readily removed without significant impact.
2. After use, stabilize the channel to prevent soil or debris
from moving into the stream during high runoff events.
3. Perform the restoration work in a timely manner.
Generally, temporary bridges are the most suitable for meeting
these objectives. Where bridges are not feasible, culverts may be a
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suitable alternative. In limited circumstances (see Stream Crossing
Methods subsection), properly designed fords may be satisfactory.
However, location and construction of temporary roads should be
avoided in those situations where there are not suitable alternatives
for reasonable accomplishment of the channel crossing objectives.
ROAD MAINTENANCE CHEMICALS
A wide variety of materials is used to maintain logging roads.
Chemicals, as deicers, are used on a limited basis compared to dust
palliatives. Some of the most common asphalt products and other
chemicals used on logging roads are in Table 16. Potential hazards and
use criteria are also included. The criteria for minimizing water
pollution from many of the chemicals used on logging roads have many
common features as shown in Table 16.
DUST PALLIATIVES
Several kinds of materials are used in dust coating logging roads.
The most common materials used are oil based. The principal objective
is to stabilize soil in the road bed. In many parts of the Region, the
soils on roadbeds are very friable when dry, creating excessive dust with
continuous road use. Reducing dust emissions is necessary for safety or
to improve visibility, aesthetics, and to minimize particulate intro-
duction into air and water.
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TABLE 16
CHEMICALS USED ON LOGGING ROADS1
00.
Compound
Herbicides
Asphalt Products
Use
Roadside Vegetation
Control
Dust abatement/paving
Potential Hazard
Poisoning, etc.
Coating of gravel beds.
Hazard From
Spillage, over spray
ingestion
Spillage, over-application.
Use Criteria
Should be:
Approved chemicals
Applied by qualified
applicators
Standard specifications
Emulsified Asphalts
Paving Grade
Cutbacks
Dustoils
Arcadia
Reclaimed wasteoil
PS-300
Paving
Paving, dust abatement
Dust abatement
Introduction of asphalt
into waterway when
mixing in tankers.
As above.
Fire.
As above
Fire as with paving grades.
Introduction of light & middle
distillate volatiles
Aquatic life
May "be toxic to aquatic
organisms
Siphoning Action, runoff
Overheated product
Spillage, over application
Spillage, over application
leaching
and spill reporting.
Require air gap between
pick up & delivery point
Use specified temperature
ranges
Standard specifications & spi
spill reporting
Na Cl
Deicing, dust abatement
Detrimental to atmospheric
& aquatic plant growth &
fishery.
Excess
Na( + )ion: through over applica-
tion & leaching.
This has received only limited
use historically due to most
roads being allowed to snow in.
Cl combines to HC1 form in water. Control by rates of application
Ca Cl,
Dust abatement
Detrimental to fishery
Leaching-Cl combining to HC1
form in water, reducing avail-
able oxygen.
Not used in wet climates
Control by rates of application
Reynolds Road Packer
Soil Stabilizer
Individual project control.
Very limited use currently.
Sulfite Waste pulp
Liquor
Dust abatement
Fisheries
Spillage, over-application
and leaching.
Controlled rates of appli-
cation.
Portland Cement
Soil stabilizer, concrete
I/ Modified from information from Region 6, USFS - 5/10/74
Coating of fish gills
decreasing oxygen
assimilation.
Introduction of cement into
waterway.
Should not use above hatchery
installation & control of
operation in all cases.
-------
Pollution from Oil Based Dust Palliatives
Pollution resulting from oil discharges from logging roads or
spills related to uses of oils may be in the form of floating oils,
emulsified oils, or solution of the water soluble fractions of these
oils (104). Floating oils may interfere with reaeration and photo-
synthesis and prevent respiration of aquatic insects which obtain
their oxygen at the surface. Free and emulsified oils may act on the
epithelial surface of fish gills interfering with respiration, or they
may coat and destroy algae and other plankton. Oil sediments may coat
the bottom of waters destroying benthic organisms and altering spawning
areas.
The water soluble fraction of oils may be very toxic to fish.
Apparently the aromatic hydrocarbons are the major group of acutely
toxic compounds in oil residues (104). Because of the wide range of
results obtained in toxicity tests for oily substances, safe concen-
trations for the many compounds used in dust abatement cannot be
accurately astablished.
The 96 hour LC^g concentrations for various compounds of oil (all
not used in dust coating logging roads) range from 5.6 mg/1 for nephenic
acid to 14,500 mg/1 for No. 2 cutting oil (104). Stickleback fish tests
I/ LC^Q, TL/jQ - In toxicity studies it is the dosage required to kill
~~ 50$ of the test population. It is expressed by the weight of the
chemical per unit of body weight. The designations are used as
reported in the reference cited.
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indicated a toxicity for CSS-1 asphalt emulsion of LC$Q (96 hour) of
9,000 mg/1. CMS-1 and CMS-2 asphalt emulsion had a LC50 of 45 mg/1 (105).
Both CSS-1 and CMS-2 are used for dust coating logging roads. The
toxicity information indicates that a large quantity of these materials
are necessary for lethal effects. There is evidence that oils may
persist and have subtle chronic effects (104).
Laboratory simulation studies on water solubles removed from surfaces
stabilized with emulsified asphalts were conducted by Nielson (106) in the
Region. The studies indicated that a large amount (over 40$) of asphaltic
material could be washed from a road surface during the first few days
after application of an emulsion mix. A much larger amount of leaching
occurred during extreme laboratory conditions than is likely to occur
in the field. After a few days of curing, the amount removable declined
rapidly to approximately two percent of the amount applied. The amount
removed remained nearly constant for the study's 30-day duration.
Two rural roads in New Jersey treated with waste crankcase oil were
examined by Freestone (107) to determine whether or not oil left the road.
Waste crankcase oil is not commonly used for dust coating logging roads;
however, some of the study's conclusions may apply to other oil dust
palliatives. Analyses indicated that roughly one percent of the total
oil estimated to have been applied remained in the top inch of road
surface material. Oil penetration below the top inch of the road was
minimal. Oil could have left the road surface by several means such as
volatilization, runoff, adhesion to vehicles, adhesion to dust particles
288
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with wind transport and penetration into the road surface. Oil remaining
in the road surface may have also been biodegraded.
Most of the studies related to water quality impacts of oils have
been concerned with lethal levels and their effects on the aquatic
environment. Many of the studies are documented in water quality
criteria reports (104, 108). In a recent study by Burger (109), acute
toxicity bio-assays of PS-300 oil on juvenile Coho salmon were conducted
on two weight classes. Comparable TLcQ values of 1,350 and 1,500 mg/1
resulted, indicating no definite difference in toxicity due to size or
age. With the utilization of reduced concentrations, the most obvious
long range effect was that concentrations of 75 mg/1 and 40 mg/1 were
not sub-lethal. Another finding by Burger was that long-term exposure
to reduced oil concentrations affected the feeding behavior of the test
fish, resulting in weight loss and increased susceptibility to disease.
Control of Pollution from Oil Dust Palliatives
As defined in Standard Methods (110), any amount of oil and grease
in public water supplies will cause taste, odor and appearance problems
(110,111,112) and may be detrimental to conventional treatment processes.
It is virtually impossible to express limits in numerical units for
allowable concentrations in waters. Because of the difficulties in
establishing safe levels, the maximum allowable concentrations can only
be determined by bio-assay procedures and by an evaluation of the
chemical composition on a case by case basis. This procedure should be
289
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used when water uses must be protected, and dust palliatives pose a
significant pollution potential.
Criteria for controlling pollution from oil emulsions are avail-
able from a number of sources such as manufacturers, distributors,
agencies and groups using large quantities on a continuous basis,
water pollution control agencies, literature from research and others.
Oil Spills. The greatest potential for serious water quality
impacts associated with the use of oil dust palliatives is the potential
of oil spills. Because of the steep and dissected topography, and the
use of many minimum standard roads, the potentials of oil spills are
increased.
Recent rules and regulations that became effective January 10, 1974,
related to Section 311 (j)(l)(c) of the FWPCA as amended, are designed
to prevent discharges of oil into the waters of the United States and
to contain such discharges if they occur. The regulations endeavor to
prevent such spills by establishing procedures, methods, and equipment
requirements of owners and operators engaged in storing, processing or
consuming oil (Environmental Protection Agency, Oil Pollution Prevention,
Federal Register, Volume 38, No. 237 - December 11, 1973). The regula-
tions apply to facilities that store oil on sites.
Owners or operators of facilities that have discharged or could
reasonably be expected to discharge oil in harmful quantities (those
that violate applicable water quality standards, cause a film or sheen
or discoloration of the surface of the water or adjoining shoreline, or
290
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cause a sludge or emulsion to be deposited beneath the surface of the
water or upon adjoining shorelines) into or upon the waters of the
United States or adjoining shorelines shall prepare a Spill Prevention
Control and Countermeasure Plan (SPCC Plan). The SPCC Plan if properly
prepared and implemented should minimize the water quality impacts of
oil spills associated with dust-coating logging roads.
The rules and regulations indicate that the SPCC Plan shall be
carefully thought-out, prepared in accordance with good engineering
practices, and have the full approval of management at a level with
authority to commit the necessary resources. If the plan calls for
additional facilities, procedures, methods, or equipment not yet fully
operational, these items should be discussed in separate paragraphs and
the details of installation and operational start-up should be explained
separately. The complete SPCC Plan shall follow the sequence outlined
in the Federal Register citation above, and include a discussion of the
facilities' conformance with the appropriate guidelines listed. The
criteria below summarize pollution control techniques being used or
recommended by the various user groups.
Contvol Practices. Acceptable limits and concentrations of oils
in water should be achieved under the following practices and conditions:
a. There is no visible oil on the water surface.
b. Concentrations of emulsified oils do not exceed 1/20 (0.05)
of the 96 hour LCjg value determined using the receiving
water in question and the most important species in the area.
291
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c. Concentrations of hexane extractable substances (exclusive
of elemental sulfur) in air-dried sediments do not exceed
1,000 mg/1 on a dry weight basis.
dk Dust palliative materials are not dumped into an area
where they may flow into streams or bodies of water.
e. Dust palliative materials are not applied during rainy
weather or runoff, or during a threat of rain within a
4.8 hour period after application (this is obviously a
judgment factor). Curing time of the product is the
important factor.
f. The road surface is watered prior to application to
assist in penetration.
g. A small berm or wrinkle is temporarily made on either
road shoulder to prevent the material, in its liquid state
from running off the road during application.
h. Dust oils are applied only when the roadbed has been
properly graded, watered, shaped and compacted, and when
the atmospheric temperature in the shade is above 13°C
(55°F) and steady or rising.
i. Many of the techniques discussed in Part II for minimizing
sedimentation such as buffer strips and drainage design,
will also reduce discharges of oil dust palliatives from
roads if properly used.
j. Properly prepare and implement a Spill Prevention and
Countermeasure plan where necessary.
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OTHER CHEMICALS
Salts
Sodium chloride and calcium chloride are the only salts known to
be used on logging roads in Region X. Salts are used to control snow
and ice (deicing) and dust. The amount of salts used and the degree
to which they are used are not quantified. Information received from
the U.S. Forest Service, Region 6 (Table 16) indicates that these salts
are probably used only to a limited and localized degree in the Region.
Most of the water quality impact information and data on the use
of salts on roads relates to snow and ice control on paved highways
and streets. A state-of-the-art report, Environmental Impact of
Highway Deicing (113) has been published. This 1971 report extracts,
summarizes, and references much of the research and information on the
subject. Information is also available on the use of salts for dust
abatement on unpaved rural roads and on logging roads.
Additives are also commonly used in the salts. These are anti-
caking agents, corrosion inhibitors and rust inhibitors.
Because of the much more limited application of salts on logging
roads, it is assumed that the total magnitude of potential problems
would be far less than on highways and streets. However, for a specific
case, the problem could be similar. Therefore, it is assumed that the
kinds of water quality impact problems created by highway salting can
be extrapolated to logging roads as potentially similar.
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Historically, snow plowing, tire chains and a limited amount of
sanding have been the principal snow control measures on logging
roads. Generally, deicing salts—principally calcium chloride—are used
only on paved roads. As more logging roads become paved there may be
an increased use or interest in using salt for deicing.
Calcium chloride alone but usually a mixture of calcium and
sodium chlorides are used for dust abatement. Wright (114) reported
that a 50:40 mixture of sodium chloride-calcium chloride applied at
9,000 pounds per mile, for a 20 foot application width (4/10 kilogram/
meter^), proved both practical and reasonably effective for dust abate-
ment on a logging road in Canada.
Oil palliatives and sulfite pulp liquor waste are used more
extensively for dust abatement than salts in Region X. However, petro-
leum supply shortages may result in a shift from oil palliatives to
more salts and pulp liquor use.
Several problems associated with use of salt on highways are
pertinent to potential water quality impacts if salts are used on
logging roads.
The potential toxicity of water polluted with road salts is two-fold-
the salts and the additives. Excessive sodium concentrations in drinking
water may be harmful to some people with heart or kidney disease (115).
Schraufnagel (116) refers to studies done on chloride levels harmful
to freshwater fish life—with the lowest lethal level of 400 mg/1 in
one study to the highest, 8,100 to 10,500 mg/1 in another. (Sea water
has a chloride concentration of about 19,000 mg/1).
294
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Evidently, saline concentrations must be at relatively high levels
to seriously affect fish life. However, the salt additives present a
different picture. The highway deicing report (113) concludes:
"The special additives found in most road deicers cause
considerable concern because of their severe latent
toxic properties and other potential side effects.
Significantly, little is known as to their fate and
disposition, and effects on the environment. The com-
plex cyanides used as anti-caking agents and the
ehromate compounds used as corrosion inhibitors have
been found in public water supplies, ground waters....
The phosphate additives....may contribute to nutrient
enrichment in lakes, ponds, and streams...."
In addition to potential toxic effects, deicing salts have resulted
in ground water contamination—including public and domestic water sup-
plies, ponds and streams (113). The Public Health Service Drinking
Water Standards lists the recommended maximum chloride concentration as
250 mg/1, but chromium and cyanide concentrations of .05 mg/1 and .2 mg/1,
respectively, are grounds for rejection of the water supply (117).
Several authors and publications have reported the movement of
deicing salts from road surface (113, 118, 128). Maximum concentrations
of salts may be found at soil surfaces nearest the road. However, salts
are readily leached from the soil surface and into subsurface flow.
Kunkle (119) reports that the highest concentration of chloride in
study streams occurs during summer low-flow—apparently the result of
ground water movement into the streams. (Note: concentrations, i.e.,
mg/1 were higher in the summer; total salt delivery was greater in the
spring but at a lower concentration because of dilution).
295
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For deicing salts, three major application problems were reported
(113); over-application, misdirected application, and improper storage
of stockpiled salts.
Two comprehensive documents, Manual for Deicing Chemicals: Appli-
cation Practices (120) and Manual for Deicing Chemicals; Storage and
Handling (121) are recommended source references to consult for specific
guidance in storing and applying deicing salts.
Two key needs brought out in the above application practices manual
are knowing how much salt is actually being applied (i.e., verifying the
calibration) and making only the essential minimum number of applica-
tions.
The following practices and procedures should assist in minimizing
water quality impacts of salts on logging roads.
1. Limit the use of salt for snow and ice control
on logging roads to minimum essential needs.
2. In lieu of salts for ice and snow control, consider
snow plowing, chains and sanding to the extent feasible.
3. If there is compelling reason to use salt deicers, the
following should be considered:
a. Use only enough salt to provide a safe driving surface.
This includes (l) monitoring the amount of salt actually
applied frequently enough to ensure that equipment cali-
bration is resulting in the prescribed application rate; and
(2) making only the minimum needed number of applications
during each storm.
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b. Salt only on steep grades, at major intersections
and at stop points.
c. Favor sand-salt mixtures in lieu of straight salt
applications.
d. Avoid application near streams or lakes.
e. Avoid spillage off the road surface—i.e., keep the
salt on the road.
f. Locate storage areas where ground water—as well as
surface water—contamination threat is minimal.
g. Protect salt piles from exposure to moisture.
4. For dust abatement purposes, utilize the following practices:
a. Apply only enough salt to provide the desired level of
dust abatement.
b. Ensure that the prescribed application rates are what
is actually being applied.
c. Where appropriate, consider items 3 e. thru g. above.
Pulp Wastes
Sulfite waste liquor (SWL) has apparently been used for road dust
abatement for many years (122). Pearl (123) reports that the largest
use of crude spent sulfite liquor is for roadbinding (including dust
abatement) purposes—with an estimated 125 million pounds used annually,
nationwide. Authors in other countries have also reported on the use of
pulp wastes in road construction (124).
297
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Pulp liquor is a relatively inexpensive and fairly effective dust
abatement material for logging roads. It tends to leach out more
rapidly than oil palliatives and therefore requires more frequent
application to produce a similar degree of dust control. As a result,
use of oil palliatives has increased in the past. As previously noted,
petroleum shortages could alter this trend.
The pollution characteristics of pulping wastes (pertinent to
roads) are their high biochemical oxygen demand (BOD) and their
toxicity (125). The exact constituents responsible for toxicity are
not well known (125 ).
The high BOD agents in the waste liquor tend to oxidize quickly on
the road surface. This suggests a general pollution-minimizing
principle: control the application of waste liquor so that it does not
run off the road surface at the time of application.
Strombom states that application rates for pulp wastes vary
depending upon the porosity of the surface treated—with as little as
1/10 gallon per square yard (4/10 liter per meter^) on denser road sur-
faces to 1/2 gallon per square yard (2-2/10 liter per meter^) on porous
surfaces (126). A Canadian report describes test results of application
rates of about the same magnitude for calcium lignosulfate (pulp liquor)
(127).
Practices and methods to help minimize water quality impacts from
pulp waste liquors are as follows:
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1. Control application—including application rates, use of
equipment, and weather conditions—to prevent free runoff
of the chemical from the road surface, i.e., ensure that
the chemical stays on the road. Some techniques to help
achieve control are:
a. Using temporary retaining terms at the roadway edges;
b. Making trial applications and evaluations to ensure
that the calculated application rate is penetrating
correctly;
c. Not applying the chemical during or immediately
prior to rain;
d. Providing adequate training, performance standards, and
supervision for application personnel and equipment.
2. Avoid applying the chemical where the road is close to a
stream unless there is an adequate filter strip between
the road and the stream.
3. Prevent spillage into or near streams.
4. When cleaning out chemical storage tanks or application
equipment tanks, dispose of the rinse waste fluids on the
road surface or in a place away from potential water
contamination.
Others
There are a number of trade name products developed for use as
road-binders. In many cases, the chemical composition of these products
299
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is not public information, making it difficult to assess potential water
quality impacts. Toxicity tests can be conducted for materials of
unknown composition. However, these tests have limited potential for
evaluating other than short-term effects on the tested organisms.
Knowledge of the constituents of a substance is a key to a comprehensive
evaluation.
Impartial groups are available for making evaluations on a
confidential basis. Data needed for evaluation of a product are:
(a) name and amount of each constituent; (b) associated technical
specification detail; and (c) specific directions, if any, for appli-
cation. Sometimes an evaluation can be made on this basis alone; but
in some cases, further toxicity studies may be necessary.
Specific recommended practices should be tailored for each product.
However, some general recommended practices are listed below.
1. Ascertain the chemical composition of each product.
2. Evaluate each product for its potential hazard.
3. Do not use products with demonstrated or suspected high
toxicity.
4. Incorporate water quality needs into application
specifications.
5. Use those practices described previously in this
section, as applicable.
300
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REFERENCES
Text
No.
1. Brown, George W., "Forestry and Water Quality," School of Forestry,
Oregon State University, OSU Bookstore, 74 pages, 1972.
2. Fredriksen, R. L., "Erosion and Sedimentation Following Road Con-
struction and Timber Harvest on Unstable Soils in Three Small
Western Oregon Watersheds," USDA Forest Service Research Paper
PNW-104, 15 pages, 1970.
3. Swanston, D. N., "Principal Mass Movement Processes Influenced by
Logging, Road Building, and Fire," Proceedings of A Symposium on
Forest Land Uses and Stream Environment, Oregon State University,
August 1971.
4. Megahan, Walter F. and Walter J. Kidd, "Effects of Logging Roads
on Sediment Production Rates in the Idaho Batholith," USDA Forest
Service Research Paper INT-123, 14 pages, May, 1972.
5. Larse, Robert W., "Prevention and Control of Erosion and Stream
Sedimentation from Forest Roads," Proceedings of A Symposium on
Forest Land Uses and Stream Environment, Oregon State University,
August 1971.
6. Gonsior, M. J., and R. B. Gardner, "Investigation of Slope Failures
in the Idaho Batholith," USDA INT-97, 34 pages, June, 1971.
7. Crown Zellerbach Corporation, "Environmental Guide, Northwest Timber
Operations," 32 pages, July, 1971.
8. U. S. Forest Service Region 6, "Timber Purchaser Road Construction
Audit." A Study of Roads Designed and Constructed for the Harvest
of Timber, 31 pages, January, 1973.
9. Siuslaw National Forest, Oregon, "Implementation Plan" to the Region
6 Timber Purchaser Road Construction Audit, 23 pages, June, 1973.
10. Boise National Forest, Idaho, "Erosion Control on Logging Areas,"
36 pages, March, 1956.
11. Rothacher, Jack S. and Thomas B. Glazebrook, "Flood Damage in the
National Forest of Region 6," USDA Pacific Northwest Forest and Range
Experiment Station, Forest Service, Portland, Oregon, 20 pages, 1968.
12. U. S. Bureau of Land Management, "Roads Handbook." 9110-Road, Trails,
and Landing Fields, 200 pages approx.
301
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REFERENCES (Cont'd)
Text
No.
13. Forbes, Reginald D., "Forestry Handbook." Ronald Press Company,
New York, 1100 pages approx., 1961.
14. Hartsog, W. S. and J. J. Gonsior, "Analysis of Construction and
Initial Performance of the China Glenn Road, Warren District, Payette
National Forest." USDA Forest Service INT-5, 22 pages, May, 1973.
15. U. S. Forest Service Region 6, "Forest Residue Type Areas."
Unpublished map of Region 6 showing geomorphic provences, timber
species associations and geomorphic sub-provences, 1973.
16. Snyder, Robert V. and LeRoy C. Meyer. "Gifford Pinchot National
Forest Soil Resource Inventory," Pacific Northwest Region, 135 pages,
July 1971.
17. Snyder, Robert V. and John M. Wade, "Soil Resource Inventory, Snoqual-
mie National Forest." Pacific Northwest Region. 228 pages, August 15,
1972.
18. United States Department of the Interior, Bureau of Land Management
Oregon State Office, "5250 - Intensive Inventories." 15 pages,
Feb. 7, 1974.
19. Burroughs, Edward R. Jr., George R. Chalfant and Martin A. Townsend,
"Guide to Reduce Road Failures in Western Oregon." 110 pages, Aug. 1973.
20. Jennings, John W. "A Proposed Method of Slope Stability Analysis for
Siuslaw National Forest," submitted to Forest Supervisor Siuslaw
National Forest, 37 pages, May, 1974.
21. Hendrickson, Larry G. and John W. Lund, "Highway Cut and Fill Slope
Design Guide Based on Engineering Properties of Soils and Rock,"
paper given at 12th Annual Symposium on Soils Engineering, Boise,
Idaho, 35 pages, 1974.
22. U. S. Forest Service Region 6, Supplement No. 19 to the "Transportation
Engineering Handbook" 24 pages, Feb. 1973.
23. Swanston, Douglas N. "Judging Landslide Potential in Glaciated
Valleys of Southeastern Alaska." An article appearing in The Explorers
Journal, Vol. LI, No. 4. 4 pages, Dec. 1973.
302
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REFERENCES (Cont'd. )
Text
No.
24. Swanston, Douglas N. "Mass Wasting in Coastal Alaska," USDA Forest
Service Research Paper PNW-83. 15 pages, 1969.
25. Chow, Ven Te, Handbook of Applied Hydrology, McGraw-Hill Book
Company, 1964.
26. Wischmeier, W. H., and D. D. Smith. Predicting Rainfall-Erosion
Losses From Cropland East of the Rocky Mountains. Agr. Handbook 282,
U.S. Govt. Print. Office, Washington, D. C., 1965.
27. Musgrave, A. W., "The Quantitative Evaluation of Factors in Water
Erosion - A First Approximation," J. of Soil and Water Conservation,
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312
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BIBLIOGRAPHIC DATA
SHEET
1. Reoort No.
Keoort No.
EPA 910/9-75-007
3. Recipient's Accession No.
4. Title and Subtitle
LOGGING ROADS AND PROTECTION OF WATER QUALITY
5. Report Date
MARCH 1975
6.
7. Author(s)
EPA, REGION X; ARNOLD & ARNOLD AND DAMES & MOORE. SEATTLE, WA
8. Performing Organization Rept.
No- N/A
9. Performing Organization Name and Address
PART I: PART II PP 273-300
U.S. ENVIRONMENTAL PROTECTION AGENCY
1200 SIXTH AVENUE
SEATTLE. WA 98101
10. Project/Task/Work Unit No.
PART II PP 91-272
ARNOLD & ARNOLD
1216 PINE STREET
SEATTLE. WA 98101
11. Contract/Grant No.
12. Sponsoring Organization Name and Address
U.S. ENVIRONMENTAL PROTECTION AGENCY
WATER DIVISION
1200 SIXTH AVENUE
SEATTLE, WA 98101
13. Type of Report & Period
Covered
FINAL
14.
15. supplementary Notes THE ARNOLD AND ARNOLD PORTION OF THE REPORT WAS PREPARED UNDER EPA
CONTRACT #68-01-2277. DAMES & MOORE, SEATTLE, WASHINGTON, WERE SUB-CONSULTANTS
FOR ARNOI H AND ARNOI n
16. Abstracts THIS REpORT Is A STATE-OF-THE ART REFERENCE OF METHODS, PROCEDURES AND
PRACTICES FOR INCLUDING WATER QUALITY CONSIDERATION IN THE PLANNING, DESIGN,
CONSTRUCTION, RECONSTRUCTION, USE AND MAINTENANCE OF LOGGING ROADS. MOST OF THE
METHODOLOGY ALSO IS APPLICABLE TO OTHER FOREST MANAGEMENT ROADS. THE REPORT IS
DIVIDED INTO TWO PARTS. THE FIRST PART PROVIDES GENERAL PERSPECTIVE ON PHYSICAL
FEATURES AND CONDITIONS IN EPA REGION X WHICH ARE RELEVANT TO WATER QUALITY PRO-
TECTION AND LOGGING ROADS. THE SECOND PART OUTLINES SPECIFIC METHODS, PROCEDURES,
CRITERIA AND ALTERNATIVES FOR REDUCING THE DEGRADATION OF WATER QUALITY. TOPIC
COVERAGE IN THIS PART INCLUDES ROAD PLANNING, DESIGN, CONSTRUCTION AND MAINTENANCE
INCLUDING THE USE OF CHEMICALS ON ROADS. SILVICULTURAL ACTIVITIES ARE ONE CATEGORY
OF WATER POLLUTION FROM NONPOINT SOURCES DESCRIBED IN PUBLIC LAW 92-500. OF ALL
SILVICULTURAL ACTIVITIES, LOGGING ROADS HAVE BEEN IDENTIFIED AS THE PRINCIPAL
SOURCE OF MAN-CAUSED SEDIMENT.
17. Key Words and Document Analysis. 17a. Descriptors
LOGGING ROADS
FOREST ROADS
FOREST MANAGEMENT ROADS
WATER MANAGEMENT:ROADS
WATER QUALITY PROTECTION
FOREST ROAD CHEMICALS
LOGGING ROAD CHEMICALS
NONPOINT SOURCE
NONPOINT SOURCE POLLUTION
SILVICULTURAL ACTIVITIES
WOODLAND ROADS
17b. Identifiers/Open-Ended Terms
METHODS, PROCEDURES, PRACTICES FOR REDUCING WATER QUALITY DEGRADATION
FROM LOGGING ROADS AND OTHER FOREST ROADS.
WATER QUALITY CONSIDERATIONS IN LOGGING ROAD PLANNING, DESIGN, CONSTRUCTION
AND MAINTENANCE.
IMPACTS OF LOGGING ROADS AND OTHER FOREST ROADS ON WATER QUALITY
WATER POLLUTION ABATEMENT FROM NONPOINT SOURCES, LOGGING ROADS AND OTHER FOREST ROADS
ROADS AND OTHER FOREST ROADS TO INCLUDE WATER QUALITY MANAGEMENT. "
18. Availability Statement
RELEASE UNLIMITED
19. Security Class (This
Report)
UNCLASSIFIED
~».~.^.-^^^ ~^.u
20. Security Class (This
Page
UNCLASSIFIED
21. No. of Pages
22. Price
FORM NTis-35 (REV. 10-73) ENDORSED BY ANSI AND UNESCO.
THIS FORM MAY BE REPRODUCED
USCOMM-DC 8265-P74
U S. GOVERNMENT PRINTING OFFICE 1975-698-389/136 REGION 10
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