United States

Department of
Agriculture
Natural
Resources
Conservation
Service

Chapter 7

Part 651
Agricultural Waste Management
Field Handbook

Geologic and Groundwater

Considerations

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Issued August 2010

The U.S. Department of Agriculture (USDA) prohibits discrimination in all

its programs and activities on the basis of race, color, national origin, age,
disability, and where applicable, sex, marital status, familial status, parental
status, religion, sexual orientation, genetic information, political beliefs,
reprisal, or because all or a part of an individuals income is derived from
any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should
contact USDAs TARGET Center at (202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights,
1400 Independence Avenue, SW., Washington, DC 202509410, or call (800)
795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
b

(210VIAWMFH, Amend. 38, August 2010)

Acknowledgments

Chapter 7 was originally issued in 1992 and reprinted with minor revisions
in 1999 under the direction of by James N. Krider (retired), national
environmental engineer; Soil Conservation Service (SCS), now Natural
Resources Conservation Service (NRCS). James D. Rickman (retired), environmental engineer, NRCS, Fort Worth, Texas, provided day-to-day coordination in the development of the handbook. The author for chapter 7 was
John S. Moore (retired), national hydrogeologist, NRCS, Washington, DC.
This version was prepared under the direction of Noller Herbert, director,
Conservation Engineering Division (CED), Washington, DC. Revisions to
the chapter were provided by Marie Marshall Garsjo, geologist, National
Design, Construction and Soil Mechanics Center (NDCSMC), Fort Worth,
Texas; Nga Watts, environmental engineer, NRCS, Florida; Karl Visser,
hydraulic engineer, NDCSMC, Fort Worth, Texas; Bill Reck, environmental
engineer, East National Technical Support Center, Greensboro, North Carolina; and Jerry Bernard, national geologist, CED, Washington, DC. It was
finalized under the guidance of Darren Hickman, national environmental
engineer, CED, Washington, DC. The editing, graphic production, and publication formatting were provided by Lynn Owens, editor; Wendy Pierce,
illustrator; and Suzi Self, editorial assistant, NRCS, Fort Worth, Texas.

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

7ii

Geologic and Groundwater

Considerations

(210VIAWMFH, Amend. 38, August 2010)

Part 651
Agricultural Waste Management
Field Handbook

Chapter 7

Contents

Geologic and Groundwater

Considerations

651.0700

Introduction

71

651.0701

Overview of geologic material and groundwater

72
(a) Geologic material............................................................................................. 72
(b) Groundwater..................................................................................................... 72

651.0702 Engineering geology considerations in planning

79
(a) Corrosivity......................................................................................................... 79
(b) Location of water table.................................................................................... 79
(c) Depth to rock.................................................................................................... 79
(d) Stability for embankment and excavated cut slopes................................. 711
(e) Excavatability................................................................................................. 711
(f) Seismic stability.............................................................................................. 712
(g) Dispersion....................................................................................................... 712
(h) Permeability.................................................................................................... 712
(i) Puncturability................................................................................................. 713
(j) Settlement potential....................................................................................... 713
(k) Shrink/swell.................................................................................................... 714
(l) Topography..................................................................................................... 714
(m) Availability and suitability of borrow material........................................... 714
(n) Presence of abandoned wells and other relics of past use....................... 715
651.0703

Factors affecting groundwater quality considered in planning

715
(a) Attenuation potential of soil......................................................................... 715
(b) Groundwater flow direction.......................................................................... 716
(c) Permeability of aquifer material................................................................... 716
(d) Hydraulic conductivity.................................................................................. 716
(f) Hydraulic gradient.......................................................................................... 718
(g) Hydrogeologic setting.................................................................................... 718
(h) Land topography............................................................................................. 718
(i) Proximity to designated use aquifers, recharge areas, and well head..... 718
protection areas......................................................................................................
(j) Type of aquifer................................................................................................ 718
(k) Vadose zone material..................................................................................... 718

651.0704

Site investigations for planning and design

719
(a) Preliminary investigation.............................................................................. 719
(b) Detailed investigation.................................................................................... 719

651.0705

References

(210VIAWMFH, Amend. 38, August 2010)

722

7iii

Chapter 7

7iv

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Appendix 7A

Determining Groundwater Flow Direction and Hydraulic

Gradient

7A1

Appendix 7B

Identifying Soils for Engineering Purposes

7B1

Tables

Table 71

Porosity and specific yield for various geologic materials 78

Table 72

Engineering geology consideration for selected waste

management components

710

Table 73

Excavation characteristics

711

Table 7B1

Criteria for describing angularity of coarse-grained

particles

7B2

Table 7B2

Criteria for describing particle shape

7B2

Table 7B3

Criteria for describing moisture condition

7B2

Table 7B4

Criteria for describing the reaction with HCL

7B2

Table 7B5

Criteria for describing cementation

7B2

Table 7B6

Criteria for describing structure

7B2

Table 7B7

Criteria for describing consistency

7B3

Table 7B8

Criteria for describing dry strength

7B3

Table 7B9

Criteria for describing dilatancy

7B3

Table 7B10 Criteria for describing toughness

7B3

Table 7B11 Criteria for describing plasticity

7B3

Table 7B12 Field identificationcoarse-grained soils

7B6

Table 7B13 Field identificationfine-grained soils

7B8

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Figures

Figure 71

Agricultural sources of potential groundwater contamina- 71

tion

Figure 72

Karst areas in the United States

73

Figure 73

Zones of underground water

74

Figure 74

Aquifers

75

Figure 75

Unconfined aquifer

76

Figure 76

Confined (artesian) aquifer

76

Figure 77

Cross section through stream valley showing groundwater 77

flow lines and flowing (artesian) well from unconfirmed
aquifer

Figure 78

Perched aquifer

Figure 79

Porosityhow groundwater occurs in geologic materials 78

Figure 710

Karst topography

714

Figure 711

Permeability of various geologic materials

717

Figure 7A1 Determining direction of groundwater flow and hydraulic 7A2

gradient

Figure 7B1 Flow chart for identifying coarse-grained soils

(less than 50% fines)

7B5

Figure 7B2 Flow chart for identifying fine-grained soils

(50% or more fines)

7B9

(210VIAWMFH, Amend. 38, August 2010)

77

7v

Chapter 7

7vi

Geologic and Groundwater

Considerations

(210VIAWMFH, Amend. 38, August 2010)

Part 651
Agricultural Waste Management
Field Handbook

Chapter 7

Geologic and Groundwater

Considerations
nate groundwater (fig. 71). Many agricultural waste
management components can be installed on properly
selected sites without any special treatment other
than good construction procedures. The key is to be
able to recognize and avoid potentially problematic
site conditions early in the planning process. An appropriately conducted onsite investigation is essential
to identify and evaluate geologic conditions, engineering constraints, and behavior of earth materials. The
requirements for preliminary (planning) and detailed
(design) investigations are explained in this chapter.
This chapter provides guidance in a wide variety of
engineering geologic issues and water quality considerations that may be found in investigation and planning of an AWMS.

651.0700 Introduction
Chapter 7 covers geologic and groundwater considerations that may affect the planning, design, and construction of an agricultural waste management system
(AWMS). Two main issues are addressed:
engineering suitability of the soil and foundation
characteristics of the site
potential for an AWMS component to contaminate groundwater
Storing, treating, or utilizing agricultural wastes at or
below the ground surface has the potential to contami-

Figure 71

Agricultural sources of potential groundwater contamination

Leaking holding
tank and pipeline

Precipitation

Leaking
fuel tank

ff

Runo

Equipment
rinse water
Septic tank
ne
zo
drain field
ot
o
R
se
do
Va one
z

Lagoon
Fertilizers,
pesticides

Water
supply
well

Infiltration

Water table

Saturated
zone

Land application
of agricultural
waste

Rapid groundwater
flow through
fractures

Unsaturated
zone

Feedlot

er

uif

Aq
Well
screen

(210VIAWMFH, Amend. 38, August 2010)

71

Chapter 7

Geologic and Groundwater

Considerations

651.0701 Overview of geologic

material and groundwater
(a) Geologic material
The term geologic material, or earth material, covers
all natural and processed soil and rock materials. Geologic material ranges on a broad continuum from loose
granular soil or soft cohesive soil through extremely
hard, unjointed rock.

(1) Material properties

Material properties of soil or rock are either measured in the laboratory using representative samples
or assessed in the field on in-place material. Common examples of material properties include mineral
composition, grain size, consistency, color, hardness
(strength), weathering condition, porosity, permeability, and unit weight. Some properties may be inferred
by index tests of samples; for example, permeability
may be roughly inferred in soils from their gradation
and plasticity values.
(2) Mass properties
Mass properties of geologic materials are large scale
features that can only be observed, measured, and
documented in the field. They typically cannot be
sampled. These properties include regional features
such as geologic structure or karst topography. Geologic structure refers to the orientation and deformation characteristics such as faults and joints. Karst
topography is formed primarily in limestone terrain
and characterized by joints that have been widened
by dissolution. Mass properties also include discontinuities that are distinct breaks or abrupt changes in
the mass. The two broad types of discontinuities are
stratigraphic and structural, depending on mode of formation (see Title 210, Technical Release (TR)78), The
Characterization of Rock for Hydraulic Erodibility).
The presence of discontinuities complicates the design
of an AWMS.
Stratigraphic discontinuities originate when the
geologic material is formed under distinct changes
in deposition or erosion. They are characterized by
abrupt lateral or vertical changes in composition or
other material property such as texture or hardness.
These features apply to all stratified soil and rocks and
can occur in many shapes described with common
72

Part 651
Agricultural Waste Management
Field Handbook

geologic terms such as blanket, tongue, shoestring, or

lens. Abrupt changes in composition or material property can result in contrasting engineering behavior of the
adjacent geologic materials. A common example of a
stratigraphic discontinuity is the soil/bedrock interface.
Structural discontinuities are extremely common in
almost any geologic material. They include fractures
of all types that develop some time after a soil or rock
mass has formed. Almost all types of bedrock are
fractured near the Earths surface. Forces acting on the
mass that cause deformation include physical geologic
stresses within the Earths crust; biological, such as
animal burrows or tree roots; or artificial, such as blasting. Fractures in rock materials may be systematically
oriented, such as joint sets, fault zones, and bedding
plane partings, or may be randomly oriented. In soil
materials, fractures may include soil joints, desiccation
cracks, and remnant structure from the parent bedrock
in residual soils.
Many rural domestic wells, particularly in upland areas, derive water from fractures and joints in bedrock.
These wells are at risk of contamination from waste impoundment facilities if fractured bedrock occurs within
the excavation limits, within feedlots or holding areas,
and in waste utilization areas. Fractures in bedrock may
convey contaminants directly from the site to the well
and significantly affect water quality in a local aquifer.
Although karst topography (fig. 72) is well known as
a problem because of its wide, interconnected fractures and open conduits, almost any near-surface rock
type will have fractures that can be problematic unless
treated in design.

(b) Groundwater
Many U.S. Department of Agriculture (USDA) Natural
Resources Conservation Service (NRCS) programs
deal with the development, control, and protection of
groundwater resources. The planners of agricultural
waste management practices should be familiar with
the principles of groundwater. NRCS references that
include information on groundwater are Title 210,
National Engineering Handbook (NEH), Section 16,
Drainage of Agricultural Lands, Part 631, Chapter 30,
Groundwater Hydrology and Geology, Chapter 31,
Groundwater Investigations; Chapter 32, Well Design
and Spring Development, and Chapter 33, Groundwater
Recharge, and Part 650, Engineering Field Handbook
(EFH), Chapter 12, Springs and Wells and Chapter 14,
Water Management (Drainage).

(210VIAWMFH, Amend. 38, August 2010)

Legend

Generalized map of areas of karst and

analogous terrains in the conterminous United States

Karst areas in the United States

(210VIAWMFH, Amend. 38, August 2010)

100

200 300

400

500 Miles

Terrain analogous to karst resulting from

deep-seated piping (erosion by water)

Terrain or lava analogous to karst or

karst buried beneath deep soil cover

Geologic and Groundwater

Considerations

Karst terrain

Figure 72

Chapter 7
Part 651
Agricultural Waste Management
Field Handbook

73

Chapter 7

Geologic and Groundwater

Considerations

(1) Zones of underground water

All water beneath the surface of the Earth is called
underground water, or subsurface water. Underground
water occurs in two primary zones: an upper zone of
aeration called the vadose or unsaturated zone and a
lower zone of saturation called the phreatic or saturated zone. The vadose zone contains both air and
water in the voids, and the saturated zone is where all
interconnected voids are filled with water (fig. 73).
The term groundwater applies to the saturated zone.
Groundwater is the only underground water available
for wells and springs.

Figure 73

Part 651
Agricultural Waste Management
Field Handbook

The vadose zone has three components with differing

moisture regimes: the soil-water zone, intermediate
zone, and basal capillary zone (fig. 73). The soil-water
zone extends from the ground surface to slightly below the depth of root penetration. Water in this zone is
available for transpiration and direct evaporation, and
the zone is unsaturated except during rainfall or irrigation events. Depending on the depth of the vadose
zone, there may be an intermediate zone where water
moves either downward under gravity or is held in
place by surface tension. There are areas in the country where the intermediate zone is hundreds of feet
thick.

Zones of underground water (AIPG 1984; Heath 1983; and Todd 1980)
Soil moisture
Ground surface
Soil particles
Air spaces

Unsaturated zone
(Vadose zone)

Intermediate zone

Groundwater

Capillary zone

Soil particles
Water table

Saturated zone
(Phreatic zone)

Underground (subsurface) water

Soil-water zone

Sand and gravel

Soil
Rock
(weathered)

Groundwater

Bedding plane
parting
Zone of
Rock
(fractured) fracture
concentration

Joints

Fault

Creviced rock

74

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Directly above the water table there can be a saturated zone called the capillary zone or fringe. Water
in the capillary fringe overlies the water table, where
the fluid pressure in the pores is exactly atmospheric
pressure; therefore, the pore pressure above the
water table is less than atmospheric. Surface tension
and capillary action cause water in this zone to rise.
It can rise between a few inches to more than a few
feet above the water table, depending on the soil type.
Capillary rise increases as the pore spaces decrease
and the plasticity of the soil increases.

(2) Aquifers
An aquifer is a saturated, permeable geologic unit
capable of storing and conveying usable amounts
of groundwater to wells or springs. When designing
any agricultural waste management component, it is
important to know:
what type(s) of aquifers are present and at what
depth
the use classification of the aquifer, if any
Figure 74

Part 651
Agricultural Waste Management
Field Handbook

Aquifers occur in many types of soil or rock materials.

Productive aquifers include coarse-grained alluvial deposits; glacial outwash; coarse-grained, highly porous
or weakly cemented sandstones and conglomerates;
and limestones that dissolve into karst conditions.
An aquifer need not be highly productive to be an
important resource. For example, there are millions
of private domestic wells throughout the country that
yield 10 gallons per minute or less. In upland areas,
often the only source of water available to wells occurs in fractured bedrock within about 300 feet of the
surface. Below this depth, it is likely that the weight of
the overlying rock materials will hold fractures closed
and limit the volume of water they can convey.
An aquifer may be unconfined, confined, or perched
(fig. 74). An unconfined aquifer, also known as a
water table aquifer, occurs in relatively homogeneous,
permeable materials that extend to a deeper, less
permeable zone (fig. 75). It occurs near the ground
surface and is affected only by atmospheric pressure
and the weight of the water; it is generally recharged

Aquifers (AIPG 1984)

Recharge area for a

confined artesian aquifer

Artesian well

Water pressure level

(potentiometric surface)
of artesian aquifer
Water table
well

Flowing
artesian well

Water table

Unconfined aquifer

Stream

Upper confining bed

Artesian aquifer

Lower confining
bed

(210VIAWMFH, Amend. 38, August 2010)

75

Chapter 7

Geologic and Groundwater

Considerations

locally. The water table is the undulating surface that

marks the top of an unconfined aquifer; it usually
follows the general topography although with lesser
relief. The water table, or static water level, is the elevation at which water stabilizes in a well under atmospheric pressure, although a well-developed capillary
fringe will extend the saturated zone above the water
table. Changing atmospheric pressures during heavy
storms can cause relatively large changes in the water
levels in shallow, unconfined aquifers.
A confined aquifer occurs at depth and is bounded
above and below by geologic materials with lower

Figure 75

permeabilities (fig. 76) known as an aquiclude. An

aquiclude is a saturated geologic unit that is incapable
of transmitting water, whereas an aquitard can transmit small volumes of water, but very slowly. The static
water level in a confined aquifer, known as the potentiometric surface, will rise above the elevation at the top
of the confining unit in a tightly cased, well penetrating
the aquifer materials. It is controlled by the potentiometric pressure at the recharge area, which must
be higher in elevation than that of the well. Recharge
areas can be a long distance away. Slowly leaking
aquitards overlying a confined aquifer can also create
potentiometric pressures.

Unconfined aquifer (AIPG 1984)

Rain recharge

Pumping
well

Ground surface

Water table
Cone of drawdown
Unconfined aquifer

Figure 76

Confined (artesian) aquifer (AIPG 1984)

Pumping
well

Ground surface
Original pressure level

Impermeable clay confining bed

Cone of pressure decline
Confined aquifer

76

Part 651
Agricultural Waste Management
Field Handbook

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Confined aquifers are also known as artesian aquifers.

Any well in which the static water level rises above the
elevation at the top of the confining unit is called an
artesian well (fig. 77). An artesian well that flows at
the surface is called a flowing artesian well; not all artesian wells flow. To flow, the elevation of the surface
of the well must lie below that of the potentiometric
surface.
A perched aquifer (fig. 78) is a local zone of unconfined groundwater occurring at some level above
the regional water table, with unsaturated conditions existing above and below it. They form where
downward-percolating groundwater is blocked by a
zone of lesser permeability and accumulates above it.
This lower confining unit is called a perching bed, and
they commonly occur where clay lenses are present,
particularly in glacial outwash and till. These perched
aquifers are generally of limited lateral extent and may
not provide a long-lasting source of water. Perched
aquifers can also cause problems in construction
dewatering and need to be identified during the site
investigation.

(1974), has the authority to designate aquifers as sole

source aquifers. A sole source aquifer is an aquifer
that provides the primary, or sole, source of drinking
water to an area. No Federal funds can be committed
to any project that the EPA finds would contaminate
a sole source aquifer and cause a significant health
hazard.
An individual State may designate groundwater use
classifications, in addition to their designated surface
water use classifications. These designated use classifications protect aquifers for future use. There are
States that regulate against groundwater overdraft,
where pumping exceeds aquifer recharge.

(3) Porosity
Most materials within a few hundred feet of the Earths
surface contain solids and voids. Downward percolating water collects in voids and becomes available for
wells and springs. Porosity is defined as the ratio of
the volume of voids to the total volume of a soil or
rock mass, expressed as a percentage.

The U.S. Environmental Protection Agency (EPA),

under the provisions of the Safe Drinking Water Act

Figure 77

Cross section through stream valley showing

groundwater flow lines and flowing (artesian)
well from unconfined aquifer (Fetter 1980)

Part 651
Agricultural Waste Management
Field Handbook

Porosity (% ) =

Figure 78

Volume of voids in a given mass ( L3 )

Volume of given soil mass ( L3 )

Perched aquifer

Water table
Flowing well

Perched water table

Stream
Perching bed
Flow line

Regional water table

Sand
and
gravel

Unconfined aquifer
Impermeable boundary

(210VIAWMFH, Amend. 38, August 2010)

77

Chapter 7

Geologic and Groundwater

Considerations

The two main types of porosity are primary and secondary (fig. 79).
Primary porosity refers to openings that developed
at the time the material was formed or deposited. An
example of primary porosity is the voids between particles in a sand and gravel deposit. Primary porosity of
soil depends on the range in grain size (sorting) and
the shape of the grains and is independent of particle
size. Thus, a bathtub full of bowling balls has the same
porosity as the same tub full of BBs. This assumes the
arrangement (packing) is the same for balls and BBs.
However, the tub full of a mixture of bowling balls and
BBs will have a lower porosity than either the BBs or
the bowling balls because BBs will occupy space between the bowling balls. Secondary porosity refers to
openings formed after initial formation or deposition
of a material. Processes that create secondary porosity
include physical weathering (freezing-thawing, wetting
and drying, heating and cooling), chemical or biological action, and other stresses that produce fractures
and joints. Secondary porosity is extremely common
in most geologic materials near the Earths surface.
This type of porosity enables contaminants to move
with little attenuation (reduction) or filtration.

(4) Specific yield

Specific yield is the ratio of the volume of water that
an unconfined aquifer (soil or rock) releases by gravity drainage to the volume of the soil or rock mass. A

Figure 79

Part 651
Agricultural Waste Management
Field Handbook

material that has high porosity, such as clay, does not

necessarily yield a high volume of water if the material also has low permeability (see section 651.0702
(h), Permeability of aquifer material). Such a material
has low specific yield. See table 71 for comparison of
porosity and specific yield of some geologic materials.
Specific yield (% ) =

Table 71

Volume of water drained ( L3 )

Volume of given geologic material ( L3 )

Porosity and specific yield for various geologic materials (from Sterrett 2007)

Geologic material

Porosity
(%)

Specific yield
(%)

Soil:
Gravel (mix)
Sand (mix)
Silt
Clay
Sand, silt, clay mixes
Sand and gravel mixes

2540
2540
3550
4555
2555
1035

1530
1030
510
110
515
1025

Rock:
Fractured or porous basalt
Fractured crystalline rock
Solid (unfractured) rock
Karst topography
Sandstone
Limestone, dolomite
Shale

550
010
01
550
530
120
010

550
010
0
550
515
0.55
0.55

Porosityhow groundwater occurs in geologic materials

Rings of capillary water
(not groundwater)
surround contacts of
rock particles

Air

Air

Approximate
level of the water table

All openings below the

water table are full of
groundwater

78

Gravel

Creviced rock

Primary porosity

Secondary porosity

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

651.0702 Engineering geology

considerations in planning
This section provides guidance in determining what
engineering geology considerations may need to be investigated for various waste management components
(table 72). The significance of each consideration is
briefly described with some guidance given on how to
recognize it in the field. Most issues serve as signals or
red flags that, if found, justify requesting assistance of
a geologist or other technical specialist.

(a) Corrosivity
Soil is corrosive to many materials used in AWMS
components. Soil survey data available through Soil
Data Mart (SDM) (for GIS users) and Web Soil Survey
(WSS) give corrosion potentials for steel and concrete
for soil map units. Note that data for map units normally apply only to the top 60 inches of soil.

(b) Location of water table

The elevation and shape of the water table may vary
throughout the year. High water tables and perched
water tables in borrow areas can create access problems for heavy machinery. Rising water tables can
also crack, split, and lift concrete slabs and rupture
impoundment liners. The occurrence of a high water
table may restrict the depth of excavation and require
installation of relief or interceptor drainage systems to
protect the practice from excessive uplift pressures. A
preliminary field investigation will identify estimates
of the depth to high water table using soil survey data
available through SDM (for GIS users) and WSS. Sitespecific groundwater depths may vary from values
given in these sources. Stabilized water levels observed in soil borings or test pits provide the most accurate determination in the field. Seasonal variations
in the water table also may be inferred from the logs
of borings or pits. Recording soil color and redoximorphic features is particularly important. Redoximorphic
features indicate seasonal changes in soil moisture.
Perennially saturated soil is typically gray. Perennially
aerated soil is typically various shades of red, brown,
or yellow.

Part 651
Agricultural Waste Management
Field Handbook

(c) Depth to rock

The selection of components that make up an AWMS
may be restricted by shallow depth to bedrock because of physical limitations or State and local regulations.
The occurrence of hard, dense, massive, or crystalline
rock at a shallow depth may require blasting or heavy
excavators to achieve the designed grade. If the rock
surface is irregular, differential settlement can be a
hazard for steel tanks and monolithic structures, such
as reinforced concrete tanks. Vegetative practices,
such as filter strips, may be difficult to establish on
shallow soil or exposed bedrock. Waste applied in
areas of shallow or outcropping bedrock may contaminate groundwater because fractures and joints in the
rock provide avenues for contaminants.
For waste impoundments, shallow bedrock generally
is a serious condition requiring special design considerations. Bedrock of all types is nearly always jointed
or fractured when considered as a unit greater than 0.5
to 10 acres in area. Fractures in any type of rock can
convey contaminants from an unlined waste storage
pond or treatment lagoon to an underlying aquifer.
Fractures have relatively little surface area for attenuation of contaminants. In fact, many fractures are wide
enough to allow rapid flow. Pathogens may survive the
passage from the site to the well and thereby cause a
health problem. Consider any rock type within 2 feet
of the design grade to be a potential problem. The
types of defensive design measures required to address shallow rock conditions depend on site conditions and economic factors. Design options include linings, waste storage tanks, or relocating to a site with
favorable foundation conditions.
Sinkholes or caves in karst topography or underground mines may disqualify a site for a waste storage pond or treatment lagoon. Sinkholes can also be
caused by dissolving salt domes in coastal areas. The
physical hazard of ground collapse and the potential
for groundwater contamination through the large
voids are severe limitations.

(210VIAWMFH, Amend. 38, August 2010)

79

Chapter 7

Part 651
Agricultural Waste Management
Field Handbook

Engineering geology consideration for selected waste management components

Agricultural Waste Management Component

En
gin
ee
Co
rin
rro
gg
siv
eo
ity
Lo
lo
ca
gy
tio
co
no
ns
De
id
fw
pth
er
a
at
t
to
er
io
Sta
ro
tab
ns
ck
bili
le
ty f
(
u
or
pli
Ex
em
ft
ca
pr
ba
va
es
n
k
t
su
m
ab
Se
e
res
nt
ilit
ism
an
)
y
de
ic
xc
sta
Di
a
v
b
sp
atio
ilit
ers
nc
y
ion
ut
Pe
ba
rm
nk
s
ea
b
i
Pu
lity
nc
tur
ab
Se
ilit
ttl
y
em
en
Sh
t
po
rin
ten
k/s
tia
we
To
l
ll
po
gra
ph
Av
y
ail
ab
ilit
ya
nd
su
ita
bil
ity
of
bo
rro
w
ma
ter
ial

Table 72

Geologic and Groundwater

Considerations

1. Waste empoundments
A. Earthfill embankment
B. Excavated cutbank
C. Clay liners

2. Waste storage structure (tanks and stacking

facilities)

X
X
X

X
X

X
X

X
X

5. Constructed wetland

X
X

X
X

X
X
X

3. Vegetative filter strips

4. Waste utilization area (land application)

X
X

6. Composting facility

X
X

7. Waste transfer - (e.g., concrete lined waterways,

buried piplines)

8. Heavy use area protection

9. Waste separation facility/components

710

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

(d) Stability for embankment and

excavated cut slopes
Embankments and excavated cut slopes must remain
stable throughout their design life. Control of groundwater prevents stability problems related to excessive
pore pressure. Subsurface interceptor drains, relief
drains, or open ditches may be needed to control excessive water pressure around structures. The foundation must be free-draining. This will prevent increased
loads caused by the static or dynamic weight of a
component from causing downslope sliding or slumping, especially for a clay foundation with low shear
strength.
Embankments and excavated cutbanks may be vulnerable to failure when wastewater is emptied or pumped
Table 73

Part 651
Agricultural Waste Management
Field Handbook

out of a waste impoundment. Rapid drawdown of

wastewater may leave the soil in the bank above the
liquid level saturated, which may then lead to bank
caving. Designers must consider this in determining
the stable side slope of embankments and cut banks
and in designing the liner thickness. Consideration
should be given in operation and maintenance plans to
addressing the maximum rate that wastewater should
be withdrawn from waste impoundments to minimize
this problem.

(e) Excavatability
Excavation characteristics of the geologic materials
at the site determine the type and size of equipment
needed and the class of excavation, either common or
rock, for pay purposes (table 73). Commonly avail-

Excavation characteristics

Classification elements

Class I

Class II

Class III

Very hard ripping to

blasting

Hard ripping

Easy ripping

Rock material requires

drilling and explosives
or impact procedures for
excavation may classify 1/
as rock excavation (NRCS
Construction Spec. 21).
Must fulfill all conditions
below:

Rock material requires ripping techniques for excavation may classify 1/ as rock
excavation (NRCS Construction Spec, 21). Must fulfill all
conditions below:

Rock material can be excavated as common material

by earthmoving or ripping
equipment may classify 1/ as
common excavation (NRCS
Construction Spec. 21). Must
fulfill all conditions below:

Headcut erodibility index,

kh (210NEH, Part 628, Chapter
52)

kh 100

10 < kh < 100

kh 10

Seismic velocity, approximate

(ASTM D 5777 and Caterpillar
Handbook of Ripping, 1997)

2,450 m/s
( 8,000 ft/s)

2,1502,450 m/s
(7,0008,000 ft/s)

2,150 m/s ( 7,000 ft/s)

Minimum equipment
size(flywheel power) required
for to excavate rock. All machines assumed to be for heavyduty, track-type blasting, for
backhoes or tractors equipped
with a single tine, rear-mounted
ripper.

260 kW (350 hp),

for kh < 1,000
375 kW (500 hp),
for kh 10,000
Blasting for kh > 10,000

185 kW (250 hp)

110 kW (150 hp)

1/ The classification implies no actual contract payment method to be used nor supersedes NRCS contract documents. The classification is for
engineering design purposes only.
(210VIAWMFH, Amend. 38, August 2010)

711

Chapter 7

Geologic and Groundwater

Considerations

able equipment may not be suitable in some situations.

Blasting or specialized high horsepower ripping equipment may be required. Cemented pans, dense glacial
till, boulders, an irregular bedrock surface, or a high
water table can all increase the difficulty and cost of
excavation.

(f) Seismic stability

Projects located in seismic zones 3 and 4, as defined
in 210TR60, Earth Dams and Reservoirs, require
special geologic investigations. These include investigations to determine the liquefaction potential of
noncohesive strata, including very thin beds and the
presence of any faults that have been active in the
Holocene Epoch, which began 11,500 years ago.
These considerations are used in the design of embankment slopes, cut slopes, zoned fill, or internal
drainage. A foundation consisting of loose, saturated,
fine-grained, relatively clean sand is most susceptible to liquefaction during seismic events. Most well
compacted embankments consisting of fine-grained
plastic soils are inherently resistant to seismic shock.
Determine the seismic zone of a site using the map in
210TR60 Earth Dams and Reservoirs. Other geologic
hazards may be identified in Section I of the Field Office Technical Guide (FOTG) and local geologic reports and maps and other local technical references.

Part 651
Agricultural Waste Management
Field Handbook

They often occur in layers or lenses within a

soil profile rather than as a mappable unit with
consistent mineral, structural, and hydraulic
characteristics. Color is not a reliable indicator
of dispersive characteristics.
They have high erodibility. Clay and colloidal
fractions go readily into suspension and remain
there. In small ponds and puddles, the colloidal
clay particles stay suspended for long periods of
time, and the water will remain turbid. The water
may rarely clear up, if ever.
Surface exposures, including streambanks and
cut slopes, have the appearance of melted sugar.
Gullying and rilling are extensive, forming a
badland topography of jagged ridges and deep,
rapidly-forming channels and tunnels. Lush
vegetation does not prevent erosion on earthfill
embankments.
They have high shrink-swell potential and are
thus subject to severe cracking when dried.
Jugging can occur when rainfall and runoff
concentrate in a crack. The crack is eroded from
the bottom up, eroding a larger volume of the
underlying soil than at the surface opening. The
result is a jug-shaped feature; erosion to a depth
of 4 to 8 feet is common.

(h) Permeability
(g) Dispersion
Dispersive clay soils are unusually erodible and have
been responsible for a significant amount of damage
to NRCS channels and structures. Dispersive clay soils
are distinguished from typical clay soils by differing
electrochemical properties. Normal clays are composed primarily of calcium, magnesium, and potassium cations and have two positive charges. Dispersive
clays are characterized by higher sodium contents, and
have only one positive charge. With only one positive
charge, the electrochemical forces are imbalanced.
The imbalance causes the individual particles in a dispersive clay soil to be repulsed rather than attracted
to one another. Because these particles are very small,
they are easily detached and transported by even slow
moving water. Small flows can erode significant volumes of material.
Typical characteristics of dispersive soils:
712

Permeability or hydraulic conductivity refers to rate at

which water flows through a material. The permeability of the underlying material is an important geologic
consideration in the planning process. For example,
permeability of the soil material at the excavation limits of a waste impoundment is an important factor in
determining the need for a liner. Permeability can also
affect the attenuation of contaminants that are land
applied in waste utilization. Soils with lower permeability may allow the time needed for transformation
and plant uptake of nutrients while soils with high permeability may leach contaminants. Permeability can
be measured in the laboratory or estimated based on
the characteristics of the material. Further description
of permeability is given in 210NEH, Part 651, Agricultural Waste Management Field Handbook (AWMFH),
Chapter 10, Appendix D, Design and Construction
Guidelines for Waste Impoundments Lined with Clay
or Amendment-treated Soil.

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

(i) Puncturability

Areas that have been active or abandoned underground mines and areas with high rates of
groundwater withdrawal

Puncturability is the ability of foundation materials

to puncture a flexible membrane liner or steel tank.
Angular rock particles greater than 3 inches in diameter may cause denting or puncturing in contact with a
tank. Angular particles greater than 0.5 inch can puncture plastic and synthetic rubber membranes. Sharp irregularities in the bedrock surface itself also can cause
punctures. Large angular particles can occur naturally
or be created by excavation and construction activity.

Steep abutmentsDifferential settlement of

embankments may occur on abutment slopes
that are steeper than 1 horizontal to 1 vertical.
Compaction must be done by hand to achieve the
density necessary to limit settlement and provide
the necessary bond to retard leakage along the
interface. Settlement cracks may occur in the fill
in the area where the base of a steep abutment
joins the flood plain.

(j) Settlement potential

Uneven rock surfacesA foundation may settle

if it is constructed on soil materials overlying
a highly irregular, shallow bedrock surface or
other uneven, unyielding material. As a rule, consider a foundation problematic if the difference
between the maximum and minimum thickness
of compressible soil above an uneven rock surface divided by the maximum observed thickness
is greater than 25 percent. This thickness ratio is
expressed as:

Monolithic structures are designed to behave as a

structural unit, and they are particularly vulnerable to
settlement. Examples include tanks made out of steel
and poured-in-place reinforced concrete. Differential
settlement occurs when settlement is uneven across
the entire foundation.
The potential for differential settlement can be an
important design consideration in certain earthfill and
concrete waste impoundment structures. Although the
potential for differential settlement may be less significant, some segmentally designed structures may be
susceptible to settlement as well.
Segmentally designed structures are built of structurally independent units such as precast, reinforced
concrete retaining wall units. The designer should be
familiar with the 210NEH, Part 650, EFH, Chapter 4,
Elementary Soil Engineering.
The six common geologic conditions that cause settlement to occur are:
Abrupt, contrasting soil boundariesA foundation is susceptible to differential settlement if
underlain by zones, lenses, or beds of widely
different soil types with boundaries that change
abruptly either laterally or vertically.
Compressible soilSome layers or zones of
materials over 1 foot thick may settle excessively
when loaded by an embankment or concrete
structure. These include soft clays and silts, peat
and organic-rich soil (OL and OH in the Unified
Soil Classification System (USCS)), and loose
sands.

Part 651
Agricultural Waste Management
Field Handbook

min . thickness

100 max . thickness

max . thickness

= thickness ratio (percent)

Collapsible soilThis soil condition is common, particularly in the arid areas of the Western
United States. These soils collapse or consolidate
rapidly in the presence of water. They are characterized by low densities and low water contents
and are generally fine-grained (CL, ML, CL-ML
and MH, with an occasional SM). There are several types of soils which are water-sensitive and
several causes of their unstable structure. They
are:
Fine-grained alluvial deposits with a random
and unstable configuration that have not
been saturated since their depositionMost
were deposited as debris flows from unvegetated watersheds in events with heavy rain.
When they are eventually saturated, they
collapse under their own weight.
Wind-blown silt deposits known as loess
that are very loose and contain appreciable
voidsThey characteristically have clay ma-

(210VIAWMFH, Amend. 38, August 2010)

713

Chapter 7

Geologic and Groundwater

Considerations

terial acting as a binding agent, which rapidly

looses strength when wetted loaded.
Gypsiferous soils in which the gypsum has
been dissolved and then recrystallized
They form a porous mass which collapses
easily.

(k) Shrink/swell
Soil containing montmorillonite clay may undergo
substantial changes in volume when wetted and dried.
Some minerals found as components in rock, such as
gypsum or anhydrite, also may change volume dramatically when wetted and dried. Soil that has a high
shrink/swell hazard is identified in Soil survey data
available through SDM (for GIS users) and WSS. Field
investigations and previous experience in the area may
often be the only ways to foresee this problem.

Part 651
Agricultural Waste Management
Field Handbook

and the formation or presence of numerous sinkholes

and depressions.

(m) Availability and suitability of borrow

material
Borrow must meet gradation, plasticity, and permeability requirements for its intended use and be in
sufficient quantity to build the component. Losses
routinely occur during handling, transport, placement,
and consolidation of fill materials. To compensate, as
much as 150 percent of the design fill requirements
should be identified within an economical hauling distance. Conditions of the borrow area itself may limit
its use as borrow materials. Limitations may include
such things as moisture content, thickness, location,
access, land use, vegetation, and/or cultural resources.

(l) Topography
Recognition of land forms and their associated problems is a valuable asset when planning a component
for an AWMS. For example, flood plain sites generally
have a higher water table compared to that of adjacent
uplands, are subject to surface flooding, and can indicate presence of permeable soils, as the alluvium may
be more permeable.

Figure 710 Karst topography

Topography can indicate the direction of regional

groundwater flow. Uplands may serve as aquifer recharge areas; valley bottoms, marshes, and lowlands
serve as groundwater discharge areas.
Steep slopes restrict use for some structural and vegetative measures. Potential hazards include landslides
and erosion.
Karst topography is formed on limestone, gypsum, or
similar rocks by dissolution and is characterized by
sinkholes, caves, and underground drainage. Common
problems associated with karst terrain include highly
permeable foundations and the associated potential
for groundwater contamination, and sinkholes can
open up with collapsing ground. As such, its recognition is important in determining potential siting problems. Figure 710 illustrates karst topography near
Mitchell, Indiana. Note the lack of stream development
714

Scale 1:24,000
1

(210VIAWMFH, Amend. 38, August 2010)

1
2
Contour interval 10 feet

1 mile

Chapter 7

Geologic and Groundwater

Considerations

(n) Presence of abandoned wells and

other relics of past use
The site and its history should be surveyed for evidence of past use that may require special design
considerations of the site relocation. If there is an
abandoned well on the site, special efforts are required
to determine if the well was sealed according to local requirements. An improperly sealed well can be a
direct pathway for contaminants to pollute an aquifer.
Other remnants of human activity, such as old foundations, trash pits, or filled-in areas, require special
AWMS design or site relocation. See section 651.0704
for guidance in planning investigations.

Part 651
Agricultural Waste Management
Field Handbook

651.0703 Factors affecting

groundwater quality considered
in planning
(a) Attenuation potential of soil
Many biological, physical, and chemical processes
break down, lessen the potency, or otherwise reduce
the volume of contaminants moving through the soils
in the root zone. These processes, collectively called
attenuation, retard the movement of contaminants
into deeper subsurface zones. See 210NEH, Part 651,
AWMFH, Chapter 3, Section 651.0303, Factors affecting the pollution process, for more details. The degree
of attenuation depends on the time a contaminant is in
contact with the material through which it travels. It
also depends on the distance through which it passes
and the total amount of surface area of particles of
the material. Attenuation potential increases as clay
content increases, soil depth increases, and distance
increases between the contaminant source and the
well or spring. Organic materials in the soil also increase the attenuation potential.

(1) Clay content

Increased clay content increases the opportunity for
attenuation of contaminants because of its cation
exchange capacity and its effect of reducing permeability. Clay particles hold a negative charge that gives
them the capacity to interchange cations in solution
and have a very low permeability (see fig. 711). As
such, clay can absorb contaminant ions and thus attenuate the movement of contaminants.
(2) Depth of soil
Deeper soil increases the contact time a contaminant
will have with mineral and organic matter of the soil.
The longer the contact time, the greater the opportunity for attenuation. Very shallow (thin to absent) soil
overlying permeable materials provides little to no
protection against groundwater contamination.
(3) Distance between contaminant source and
groundwater supply
Both the depth and the horizontal distance to a
groundwater supply affect the attenuation of contaminants. The greater the horizontal distance between the
source of the contamination and a well, spring, or the
(210VIAWMFH, Amend. 38, August 2010)

715

Chapter 7

Geologic and Groundwater

Considerations

groundwater supply, the greater the time of travel will

be with increased potential for attenuation of contaminants.

(b) Groundwater flow direction

A desirable site for a waste storage pond or treatment
lagoon is in an area where groundwater is not flowing
away from the site toward a well, spring, or important
underground water supply.
The direction of flow in a water table aquifer generally follows the topography, with lesser relief. In most
cases, the slope of the land indicates the groundwater
flow direction. In humid regions, the shape of the
water table is a subdued reflection of surface topography. Unconfined groundwater moves primarily from
topographically higher recharge areas down gradient
to discharge areas. Lower areas serve as discharge
points where groundwater rises and merges with perennial streams and ponds, drainage ditches, or flows
as springs. Radial flow paths and unusual subsurface
geology can too often invalidate this assumption. Consider the case where secondary porosity governs the
flow. A common example is bedrock in upland areas
where the direction of groundwater flow is strongly
controlled by the trend of prominent joint sets or fractures. Fracture patterns in the rock may not be parallel
to the slope of the ground surface. Thus, assuming that
groundwater flow is parallel to the topography can
be misleading in terrain where flow is controlled by
bedrock fractures.
Appendix 7A demonstrates a method of calculating
groundwater flow direction in a water table aquifer.

(c) Permeability of aquifer material

Permeability is a material property that is determined
by laboratory analysis, but is also commonly determined as a mass property through field testing. The
mass property is more accurately known as the aquifers hydraulic conductivity, which integrates all of the
aquifers characteristics to conduct water.
The time available for attenuation in aquifer materials
decreases as the permeability of the materials increases. Permeability may vary significantly between different types of materials or at different places within
the same material. Permeability is often many times
716

Part 651
Agricultural Waste Management
Field Handbook

greater laterally than vertically. Ignored or undetected,

a thin (0.5 inch or less) clay or shale seam in an otherwise uniform soil or rock aquifer can profoundly
alter the outcome of mathematical analyses and design
assumptions. Figure 711 shows the permeability of
various geologic materials.

(d) Hydraulic conductivity

The hydraulic conductivity of a soil is a measure of
the soils ability to transmit water when submitted to a
hydraulic gradient.
Hydraulic conductivity is one of the hydraulic properties of the soil; the other involves the soils fluid retention characteristics. These properties determine the
behavior of the soil fluid within the soil system under
specified conditions. More specifically, the hydraulic
conductivity determines the ability of the soil fluid to
flow through the soil matrix system under a specified
hydraulic gradient; the soil fluid retention characteristics determine the ability of the soil system to retain
the soil fluid under a specified pressure condition.
The hydraulic conductivity depends on the soil grain
size, structure of the soil matrix, type of soil fluid, and
relative amount of soil fluid (saturation) present in the
soil matrix. The important properties relevant to the
solid matrix of the soil include pore size distribution,
pore shape, tortuosity, specific surface, and porosity.
Hydraulic conductivity is an important soil property when determining the potential for widespread
groundwater contamination by a contaminating
source. Soils with high hydraulic conductivities and
large pore spaces are likely candidates for far reaching
contamination.

(e) Hydraulic head

Hydraulic head is the energy of a water mass produced
mainly by differences in elevation, velocity, and pressure, expressed in units of length or pressure. Groundwater moves in the direction of decreasing hydraulic
head. Hydraulic head in an aquifer is measured using
piezometers. For more information, see 210NEH, Part
631, Chapter 32, Well Design and Spring Development.

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Figure 711 Permeability of various geologic materials (from Freeze and Cherry 1979)
cm3/cm2/s (cm/s)
101
105

10-1

1
104

103

101

10-2
102

101

10-1

10-3

10-2

10-4

ft3/ft2/d (ft/d)
1
ft3/ft2/min (ft/min)
10-3
gal/ft2/d

105
104

104
103

103
102

102
101

10-5
10-1

10-6
10-2

10-4

10-7
10-3

10-5

10-8
10-4

10-6

10-5

10-7

10-8

(gal/ft 2/d)
101

10-1

m3/m 2/d (m/d)

1
10-1

10-2

10-2
10-3

10-3
10-4

10-4
10-5

relative permeability
Very high

High

Moderate

Low

Very low

Range of values
1
2
3
4
5
10
9
8
7
6

Numbers

Representative materials

Soil
types

1.
2.
3.
4.

Rock
types

6. Cavernous and karst limestones and dolomites, permeable basalts

7. Fractured igneous and metamorphic rocks
8. Limestones, dolomites, clean sandstones
9. Interbedded sandstones, siltstones, and shales
10. Most massive rocks, unfractured and unweathered

Clean gravel (GP)

Clean sand, clean sand and gravel mixes (GW, GP, SW, SP, SM)
Fine sand, silty sand and gravel mixes (SP, SM, GM, GWGM, GPGM, SWSM, SPSM)
Silt, clay, and sand-silt-clay mixes, organic silts, organic clays (GM, GC, SM, SC, MH, ML, MLCL, OL, OH, GWGC,
GCGM, SWSC, SPSC, SCSM)
5. Massive clay, no soil joints or other macropores (CL, CH)

(210VIAWMFH, Amend. 38, August 2010)

717

Chapter 7

Geologic and Groundwater

Considerations

(f) Hydraulic gradient

The hydraulic gradient is the change in hydraulic
head per unit distance of flow in a given direction; it
is expressed in units of height (elevation) per length
(distance). Groundwater velocity is a function of the
hydraulic gradient. Most water in an unconfined aquifer moves slowly unless it has been developed during
the well construction process. Well development is a
procedure that alters the physical characteristics of
the aquifer near the borehole so that water will flow
more freely to the well.
Pumping water from a well can steepen local hydraulic
gradients drawdown. This results in acceleration of
flow toward the well, carrying any contaminants with
it. Appendix 7A provides a method to calculate the
hydraulic gradient in water table aquifers.

Part 651
Agricultural Waste Management
Field Handbook

(i) Proximity to designated use aquifers,

recharge areas, and well head
protection areas
State water management and assessment reports and
the following maps should be reviewed to ascertain
the proximity of sensitive groundwater areas:
sole source or other types of aquifers whose uses
have been designated by the State
important recharge areas
wellhead protection areas

(j) Type of aquifer

See section 651.0701, Overview of geologic material
and groundwater, for details on unconfined, confined,
and perched aquifers.

(g) Hydrogeologic setting

Hydrogeology is the study of the occurrence, movement, and quality of underground water. The hydrogeologic setting of an AWMS component includes all
the various geologic factors that influence the quality
and quantity of underground water. Information on
the hydrogeologic setting of a site is in the following
sources:
State water quality management and assessment
reports of surface and groundwater use designations and impairments

(k) Vadose zone material

The types of material in the vadose (unsaturated)
zone affect the flow path and rate of flow of water and
the contaminants percolating through it. Flow rate
is a function of the permeability of the material (fig.
711). Flow rate in the mass is greatly increased by
macropores such as soil joints. The time available for
attenuation in this zone decreases as the permeability
of the materials increases. Permeability rates may be
inferred from the types of materials.

geologic maps showing rock types and structures

regional water table maps and, if available, tables
of static water levels in wells
groundwater vulnerability maps

(h) Land topography

Topographic features that impound contaminated runoff water increase the potential for groundwater contamination by infiltration. Examples include seasonal
wetlands and level terraces. The hazard of contaminating surface water flowing across the ground increases
as the slope and slope length increase.

718

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

651.0704 Site investigations for

planning and design
(a) Preliminary investigation
The purpose of a preliminary site investigation is to
establish feasibility for planning purposes. A preliminary site investigation also helps determine what is
needed in a detailed investigation. A site investigation
should be done only after local regulations and permit
requirements are known. The intensity of a field investigation is based on several factors including:
quality of information that can be collected and
studied beforehand
previous experience with conditions at similar
sites
complexity of the AWMS or site
Clearly defined objectives for investigation are essential in this phase. Table 72 may be useful in defining
objectives. For example, the objectives for investigating a site for a steel storage tank are significantly different from those for an earthen structures. The tanks
involve consideration of differential settlement of the
foundation, while the objectives of the subsurface
investigation of earthen structures involves consideration of excavatability and permeability of foundation
materials.
For many sites the preliminary investigation and experience in the area are adequate to determine the geologic conditions, engineering constraints, and behavior
of the geologic materials. Hand-auger borings and site
examination often provide adequate subsurface information so that a detailed subsurface investigation is
not required. A detailed investigation must be scheduled if reliable information for design cannot be obtained with the tools available during the preliminary
investigation phase.
An initial field evaluation should be performed on
the potential layout(s) of the component, access to
the site, and location of active or abandoned wells,
springs, and other such features.

Part 651
Agricultural Waste Management
Field Handbook

All wells and well records near the site should be examined for proper construction. The condition of the
concrete pad and, if possible, the annular seal or grout
around the well casing also need to be examined. See
the Field Office Technical Guide (FOTG) for the National Conservation Practice Standard (CPS), Code
642, Water Well. Some State water agencies may have
more restrictive minimum requirements.
Valuable background information about a proposed
site is obtained from the following sources:
soil survey reportsProvide soil map units,
aerial photos, information on seasonal flooding
and the water table, and engineering interpretations and classification of soils
topographic mapsUSGS topographic quadrangles or existing survey data from the site provide
information about slopes, location of forested
areas, topographic relief, and distances to identified resource features such as wells, watercourses, houses, roads, and other cultural features
aerial photosProvide information on vegetation, surface runoff patterns, erosion conditions,
proximity to cultural features, and other details.
local geologic maps and reportsProvide information on depth to and types of bedrock, bedrock structure, location of fault zones, characteristics of unconsolidated deposits, depth to water
table, aquifer characteristics, and other geologic
and groundwater information
conservation plans and associated logs

(b) Detailed investigation

The purpose of a detailed geologic investigation is to
determine geologic conditions at a site that will affect
or be affected by design, construction, and operation
of an AWMS component. Determining the intensity
of detailed investigation is the joint responsibility of
the designer and the person who has engineering job
approval authority. Complex geology may require
a geologist. Detailed investigations require application of individual judgment, use of pertinent technical references and state-of-the-art procedures, and
timely consultation with other appropriate technical
disciplines. Geologic characteristics are determined
through digging or boring, logging the types and characteristics of the materials, and securing and testing

(210VIAWMFH, Amend. 38, August 2010)

719

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

representative samples. An onsite investigation should

always be conducted at a proposed waste impoundment location. State and local laws should be followed
in all cases.

pendix 7B provides criteria for identifying soils by the

USCS. Any geologic material, regardless of origin, that
meets the criteria in this standard practice is considered soil for classification purposes.

(1) Investigation tools

Soil probes, hand augers, shovels, backhoes, bulldozers, power augers, and drill rigs all are used to allow
direct observations for logging geologic materials,
collecting samples, and access for field permeability
testing. Soils that have been drilled with an auger are
considered to be disturbed, and soil zones can be
mixed, obscuring thin layers of potential permeability. Test pits expose a detailed view of the subsurface
conditions; however, they cannot be safely excavated
below the water table.

When greater precision is needed, representative samples are analyzed in a soil mechanics laboratory. The
laboratory uses ASTM D 2487, Standard Test Method
for Classification of Soils for Engineering Purposes.
Laboratory determinations of particle characteristics
and Atterberg limits (liquid limit and plasticity index)
are used to classify soils.

Geophysical methods are indirect techniques that are

used in conjunction with direct methods of investigation such as test pits and soil borings. They require
trained and experienced specialists to operate the
equipment and interpret the results. The data must be
ground truthed at a particular site, and the geology
must be well understood to interpret the additional
information accurately. These methods include electromagnetic induction, resistivity, refraction seismographs, ground penetrating radar, and cone penetrometer testing (see Soil Mechanics Note 11: The Static
Cone Penetrometer: the Equipment and Using the
Data).

(2) Logging geologic materials

During a geologic investigation, all soil and rock materials at the site or in borrow areas are identified and
mapped. From an engineering standpoint, a mappable
soil or rock unit is defined as a zone that is consistent
in its mineral, structural, and hydraulic characteristics
and sufficiently homogeneous for descriptive and mapping purposes. A unit is referred to by formal name
such as Alford silt loam or Steele shale, or is set in
alphanumeric form such as Sand Unit A3.
The NRCS classifies rock material using common rock
type names as given in 210NEH, Part 631, Chapter
12, Rock Material Field Classification System and Part
628, Chapter 52, Field Procedures Guide for the Headcut Erodibility Index; and 210TR78, The Characterization of Rock for Hydraulic Erodibility. Soils are classified for engineering purposes according to the USCS,
ASTM D 2488, Standard Practice for Description and
Identification of Soils, Visual Manual Procedure. Ap720

Use standard NRCS log sheets, such as NRCS533, or

the soil log sheet and checklists in appendix 7B. Logs
also may be recorded in a field notebook. Be methodical when logging soils.
Identify and evaluate all applicable parameters according to criteria given in ASTM D 2488. Thorough logging
requires only a few minutes on each boring or test pit
and saves a trip back to the field to gather additional
or overlooked information. Also, be prepared to preserve a test hole or pit to record the stabilized water
table elevation after 24 hours.
Each log sheet must contain the name of the project,
location, date, investigators name and title, and type
of equipment used (backhoe) including make and
model, and test pit or boring identification number, or
each soil type found in a test pit or drill hole, record
the following information, as appropriate.
station and elevation of test hole or pit
interval (depth range through which soil is consistent in observed parameters)
particle size distribution by weight, for fraction
less than 3 inches
percent cobbles and boulders by volume, for
fraction greater than 3 inches
angularity of coarse material
color of moist material including presence of
redoximorphic feature which occur in the zone
of water table fluctuation
relative moisture content
structure

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

consistency in saturated fine-grained materials or

relative density in coarse-grained materials
plasticity of fines
group name and USCS symbol according to
ASTM D 2488 flow charts
geologic origin and formal name, if known
sample (size, identification number, label, depth
interval, date, location, name of investigator)
other remarks or notes (mineralogy of coarse
material, presence of mica flakes, roots, odor,
pH)
depth (or elevation) of water table after stabilizing; give date measured and number of hours
open
depth to rock, refusal (where the equipment
meets resistance and cannot penetrate any further) or total depth of hole
For more details, see 210NEH, Part 650, EFH, Chapter 4, Elementary Soil Engineering.

(3) Samples
Samples of soil and rock materials collected for soil
mechanics laboratory testing must meet minimum size
requirements given in Geology Note 5, Soil Sample
Requirements for Soil Mechanics Laboratory Testing.
Sample size varies according to testing needs. Samples
must be representative of the soil or rock unit from
which they are taken. A geologist or engineer should
help determine the tests to be conducted and may assist in preparing and handling samples for delivery to
the lab. Test results are used in design to confirm field
identification of materials and to develop interpretations of engineering behavior.
(4) Guide to detailed geologic investigation
For foundations of earthfill structures, use at least
four test borings or pits on the proposed embankment
centerline, or one every 100 feet, whichever is greater.
If correlation of materials between these points is
uncertain, use additional test borings or pits until correlation is reasonable. The depth to which subsurface
information is obtained should be no less than equivalent maximum height of fill, or to hard, unaltered rock
or other significant limiting layer. For other types of
waste storage structures, the depth should be to bedrock, dense sands or gravels, or hard fine-grained soils.

Part 651
Agricultural Waste Management
Field Handbook

Report unusual conditions to the responsible engineer

or State specialist for evaluation. These conditions are
listed in table 72.
For structures with a pool area, use at least five test
holes or pits or one per 10,000 square feet of pool area,
whichever is greater. These holes or pits should be as
evenly distributed as possible across the pool area.
Use additional borings or pits, if needed, for complex
sites where correlation is uncertain. The borings or
pits should be dug no less than 2 feet below proposed
grade in the pool area or to refusal (limiting layer).
Log the parameters listed in this section. Report unusual conditions to the responsible engineer or other
specialist for further evaluation. Pay special attention
to perched or high water tables and highly permeable
materials in the pool area.
Borrow areas for embankment type structures and
clay liners should be located, described, and mapped.
Locate at least 150 percent suitable borrow of the required fill volume. Soil samples for natural water content determinations should be obtained from proposed
borrow and clay liner sources. Samples should be
collected and maintained in moisture proof containers.
The parameters listed in this section should be logged.
Consult soil survey reports and local surficial geologic
maps to help identify potential borrow areas for investigation. Some designs may require bentonite or
chemically treated soil to reduce permeability (see
210NEH, Part 651, AWMFH, Chapter 10, Appendix
10D). A qualified soil mechanics engineer should be
consulted for guidance.
Depth to the water table in borrow areas is an important consideration. Dewatering a borrow area is
usually impractical for small components such as
waste structures. Installing drainage or excavating and
spreading the materials for drying before placement
generally is not cost-effective. It may be necessary to
do so, however, when suitable borrow is limited. Adhere to any State or local requirements for back filling
test pits or plugging borings.

(210VIAWMFH, Amend. 38, August 2010)

721

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

651.0705 References

Sterrett, R. 2007. Groundwater and wells. 3d ed. Johnson Screens, a Weatherford Company. New Brighton, MN.

American Institute of Professional Geologists (AIPG).

1984. Groundwater issues and answers. Arvada, CO.
25 pp.

Todd, D.K. 1980. Groundwater hydrology. 2d ed. John

Wiley & Sons. New York, NY. 535 pp.

ASTM Standard D 2487. 2010. Standard practice for

classification of soils for engineering purposes (Unified Soil Classification System). ASTM International,
West Conshohocken, PA.
ASTM Standard D 2488. 2009. Standard practice for description and identification of soils (Visual-Manual
Procedure). ASTM International, West Conshohocken, PA.
Farm Bureau. 1993. Water quality self-help checklist,
7th ed. American Farm Bur. Fed. Park Ridge, IL. 15
pp.
Fetter, C.W., Jr. 1980. Applied hydrogeology. Merrill
Publ. Co. Columbus, OH. 488 pp.
Freeze, R.A., and J.A. Cherry. 1979. Groundwater.
Prentice-Hall. Englewood Cliffs, NJ. 604 pp.
Heath, R.C. 1983. Basic ground-water hydrology. U.S.
Geol. Surv., Water-Supply Pap. 2220. U.S. Govt.
Print. Off.. Washington, DC. 85 pp.

U.S. Department of Agriculture, Natural Resources

Conservation Service. 2010. National Engineering
Handbook, Part 631, ch. 30, Groundwater hydrology
and geology . Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 2010. National Engineering
Handbook, Part 631, ch. 31, Groundwater investigations. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 2010. National Engineering
Handbook, Part 631, ch. 32, Well design and spring
development. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 2010. National Engineering
Handbook, Part 631, ch. 33, Groundwater recharge.
Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 2005. Earth dams and reservoirs. Technical Release No. 60. Washington, DC.

Humenik, F.J., M.R. Overcash, J.C. Baker, and P.W.

Western. 1980. Lagoons: State of the art. Proceed.
Interntl. Symp. Livestock Wastes. pp. 211216.

U.S. Department of Agriculture, Natural Resources

Conservation Service. 2002. National Engineering
Handbook, Part 631, ch. 12, Rock material field classification system. Washington, DC.

Johnson, A.I. 1967. Specific yieldCompilation of specific yields for various materials. U.S. Geol. Surv.,
Water-Supply Pap. 1662D. U.S. Govt. Print. Off.
Washington, DC. 74 pp.

U.S. Department of Agriculture, Natural Resources

Conservation Service. 2001. National Engineering
Handbook, Part 628, ch. 52, Field procedures guide
for the headcut erodibility index. Washington, DC.

Kirsten, H.A.D. 1987. Case histories of groundmass

characterization for excavatability. In Rock Classification Systems for Engineering Purposes, ASTM,
STP984. L. Kirkaldie (ed.). Philadelphia, PA.

U.S. Department of Agriculture, Natural Resources

Conservation Service. 1999. National Engineering
Manual, Part 531, Geology. Washington, DC.

Mason, S.A., J. Barkach, and J. Dragun. 1992. Effect

of filtration on colloidal transport in soil. Ground
Water, Vol. 30, No. 1. pp. 104106.

U.S. Department of Agriculture, Natural Resources

Conservation Service. 1991. National Engineering
Handbook, Part 633, ch. 13, Dispersion. Washington,
DC.

722

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

U.S. Department of Agriculture, Natural Resources

Conservation Service. 1991. Soil sample size requirements for soil mechanics laboratory testing.
Geology Note 5. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1991. The characterization of
rock for hydraulic erodibility. Technical Release No.
78. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1987. Principles of groundwater for resource management systems. Field Training Manual. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1984. Engineering Field
Handbook, Part 650, ch. 4, Elementary soils engineering. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1984. Engineering Field
Handbook, Part 650, ch. 11, Ponds and reservoirs.
Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1984. The static cone penetrometer: the equipment and using the data. Soil
Mechanics Note No. 11. Washington, DC.
U.S. Department of Agriculture, Natural Resources
Conservation Service. 1983. Engineering Field
Handbook, Part 650, ch. 12, Springs and wells.
Washington, DC.
U.S. Department of the Interior, Bureau of Reclamation. 2005. Ground water manual: A guide for the
investigation, development, and management of
ground-water resources. 3d ed. Washington, DC.

(210VIAWMFH, Amend. 38, August 2010)

723

Chapter 7

724

Geologic and Groundwater

Considerations

(210VIAWMFH, Amend. 38, August 2010)

Part 651
Agricultural Waste Management
Field Handbook

Appendix 7A

Determining Groundwater Flow

Direction and Hydraulic Gradient

If a published water table map is not available for

the area, but several wells and springs are nearby, a
contour map of the water table should be developed.
Plot on a topographic map (at an appropriate scale)
a sufficient number of points of static levels of water
wells, observation wells, and test pits. Include spot
elevations of perennial streams, ponds, and lakes. Using an appropriate contour interval, contour the data
points to produce a useful water table map. Record
dates of observations to allow comparison over time,
from season to season, or in areas of suspected water
table fluctuations.
If information on water table depths is not available
and the aquifer is controlled by primary porosity, such
as alluvium and glacial outwash, sketch several lines
perpendicular to the elevation contours in the area of
interest. The pattern that develops will indicate general groundwater flow directions. Groundwater discharge areas occur where the lines converge, such as
most valleys, perennial streams, and ponds. Recharge
areas, such as hilltops and upland areas converge, occur where the lines diverge.
For planning purposes, the general groundwater flow
direction and hydraulic gradient of the water table
should be calculated using data from three wells
located in any triangular arrangement in the same
unconfined aquifer (Heath 1983). They may be observation wells, test holes, test pits, or water wells. Also,
the elevation of a perennial pond or stream can serve
as an observation point. There is an 8-step procedure
for this planning method, and figure 7A1 gives an
example.

consistent units (meters or feet above mean sea

level or an arbitrary datum plane) throughout this
exercise.
Step 4Measure the distance between the wells
with the highest and lowest water level elevations,
and record on the map.
Step 5Using the map, identify the well with the
intermediate water table elevation (that is, neither
the highest nor the lowest). Interpolate the position between the well with the highest head and
the well with the lowest head where the head is
equal to that in the intermediate well. Mark this
point on the map. Measure the distance between
this point and the well with the lowest water level.
Step 6Draw a straight line between the intermediate well and the point identified in step 5. This
line represents a segment of a water table contour
along which the head is the equal to that in the
intermediate well.
Step 7Draw a line perpendicular from this contour to the lowest head well, and measure the distance. This line is parallel to the groundwater flow
direction. Using the north arrow as a guide, orient
a protractor to measure the compass direction of
the line. Express the orientation of the groundwater flow direction in degrees azimuth (clockwise
east from north).
Step 8Subtract the head of the lowest well from
that of the intermediate well. Divide the difference
by the distance measured in step 7. The result is
the hydraulic gradient.

Step 1Obtain a detailed topographic map of the

site, such as a USGS quadrangle or a field survey
map. Be sure the map has a north arrow.
Step 2Plot the position of the proposed AWMS
component and all springs, wells within at least a
half-mile radius. If the existence of wells is unknown, assume every rural house or farm/ranch
headquarters represents the location of a well.
Black squares on USGS quadrangles symbolize
houses.
Step 3Select three wells not in a line, and measure the static (nonpumping) levels using a commercial water depth meter or a lead weight on
a measuring tape. Record on the map the head
(elevation of the water table) for each well. Use

(210VIAWMFH, Amend. 38, August 2010)

7A1

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Figure 7A1 Determining direction of groundwater flow and hydraulic gradient (from Heath 1983)

x = 77 ft

Well 1
(W.L. 1000 ft) (1000 978) = (1000 940)
x
210

Well 2
(W.L. 978.0 ft)
130 ft

Hydraulic gradient=
(978 940) = 38 = 0.29
130
130

210 ft

90

978 ft contour

Direction of ground
water flow
(N 145 E)

Well 3
(W.L. 940 ft)
0

25

50

100 feet

Scale

7A2

(210VIAWMFH, Amend. 38, August 2010)

(210VIAWMFH, Amend. 38, August 2010)

Group
name

Test hole no.________ Station________ Elevation________ Water table elevation________ after______hours

Notes:

Angularity Color Relative Saturated Density

Interval
(feet) Percent Percent Percent Percent Percent (coarse (when moisture consistency (coarse
fraction) moist) content
of fines fraction)
fines
sand gravel cobbles boulders

Particle size distribution

by volume
by weight

Sheet_____of_____

Unified Geologic Sample

symbol origin
no.

Investigator______________________________ Title_______________________________ Equipment_____________________________

Project__________________________________ Location_____________________________________________ Date_________________

Soil Log Sheet

Appendix 7B
Identifying Soils for Engineering
Purposes

7B1

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

The following tables are derived from ASTM D 2488, Standard Practice for Description and Identification of Soils
(Visual-Manual Procedure). Tables 7B1 through 7B11, except 7B7, copyright ASTM Intl. Reprinted with permission.
Table 7B1

Criteria for describing angularity of coarsegrained particles

Table 7B5

Criteria for describing cementation

Description

Criteria

Description

Criteria

Angular

Particles have sharp edges and relatively

plane sides with unpolished surfaces
Particles are similar to angular descrip tion but have rounded edges
Particles have nearly plane sides but
have well-rounded corners and edges
Particles have smoothly curved sides and
no edges

Weak

Crumbles or breaks with handling or little

finger pressure
Crumbles or breaks with considerable
finger pressure
Will not crumble or break with finger
pressure

Subangular
Subrounded
Rounded

Table 7B2

Criteria for describing particle shape

The particle shape shall be described as follows where

length, width, and thickness refer to the greatest,
intermediate, and least dimensions of a particle, respectively.
Flat
Elongated
Flat and elongated

Particles with width/thickness > 3

Particles with length/width > 3
Particles meet criteria for both flat
and elongated

Table 7B3

Criteria for describing moisture condition

Description

Criteria

Dry
Moist

Absence of moisture, dusty, dry to the touch

Damp but no visible moisture

Wet

Visible free water, usually soil is below

water table

Table 7B4

Criteria for describing the reaction with HCL

Description

Criteria

None
Weak
Strong

No visible reaction
Some reaction, with bubbles forming slowly
Violent reaction, with bubbles forming
immediately

7B2

Moderate
Strong

Table 7B6
Description

Criteria for describing structure

Criteria

Stratified

Alternating layers of varying material or

color with layers at least mm thick; note
thickness
Laminated
Alternating layers of varying material or
color with the layers less than 6 mm
thick; note thickness
Fissured
Breaks along definite planes of fracture
with little resistance to fracturing
Slickensided Fracture planes appear polished or glossy,
sometimes striated
Blocky
Cohesive soil that can be broken down into
small angular lumps which resist further
breakdown
Lensed
Inclusion of small pockets of different
soils, such as small lenses of sand
scattered through a mass of clay; note
thickness
Homogeneous Same color and appearance throughout

(210VIAWMFH, Amend. 38, August 2010)

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Table 7B7

Criteria for describing consistency

Description

Criteria for Fine-grained Saturated Soils

Penetrometer
tons/ft2
or kg/cm2

Std. Penetration
Test (ASTM D 1586)
blows/ft

Very soft
Soft
Firm
Hard
Very hard

Thumb will penetrate soil more than 1 in

Thumb will penetrate soil about 1 in
Thumb will indent soil about 1/4 in
Thumb will not indent soil, but readily indented with thumbnail
Thumbnail will not indent soil

< 0.1
0.100.25
0.251.00
1.002.00
> 2.00

<2
24
415
1530
> 30

Table 7B8

Criteria for describing dry strength

Table 7B10 Criteria for describing toughness

Description

Criteria

Description

Criteria

None

The dry specimen crumbles into powder

with mere pressure of handling
The dry specimen crumbles into powder
with some finger pressure
The dry specimen crumbles into pieces or
crumbles with considerable finger
pressure
The dry specimen cannot be broken with
finger pressure. Specimen will break
into pieces between thumb and a hard
surface
The dry specimen cannot be broken
between the thumb and a hard surface

Low

Only slight pressure is required to roll the

thread near the plastic limit. The thread
and the lump are weak and soft
Medium pressure is required to roll the
thread to near the plastic limit. The
thread and the lump have medium
stiffness
Considerable pressure is required to roll
the thread to near the plastic limit. The
thread and the lump have very high
stiffness

Criteria for describing dilatancy

Table 7B11 Criteria for describing plasticity

Low
Medium

High

Very high

Table 7B9

Medium

High

Description

Criteria

Description

Criteria

None
Slow

No visible change in the specimen

Water appears slowly on the surface of
the specimen during shaking and does
not disappear or disappears slowly upon
squeezing
Water appears quickly on the surface of the
specimen during shaking and disappears
quickly upon squeezing

Nonplastic

A 1/8-in (3-mm) thread cannot be rolled at

any water content
The thread can barely be rolled and the
lump cannot be formed when drier than
the plastic limit
The thread is easy to roll and not much
time is required to reach the plastic
limit. The thread cannot be rerolled
after reaching the plastic limit. The lump
crumbles when drier than the plastic
limit
It takes considerable time rolling and
kneading to reach the plastic limit. The
thread can be rerolled several times
after reaching the plastic limit. The
lump can be formed without crumbling
when drier than the plastic limit

Rapid

Low

Medium

High

(210VIAWMFH, Amend. 38, August 2010)

7B3

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

ChecklistDescription of coarse-grained soils (ASTM D 2488)

1.

Typical Name: Boulders Cobbles Gravel Sand

Add descriptive adjectives for minor constituents.

2. Gradation: Well-graded

Poorly graded (uniformly graded or gap-graded)

3. Size Distribution: Percent gravel, sand, and fines in fraction finer than 3 inches (76 mm) to nearest 5 percent. If desired, the percentages may be stated in terms indicating a range of values, as
follows:

Trace: < 5%

Few: 510%

Little: 1525% Or, with gravel

Some: 3045% Or, gravelly

Mostly: 50100%
4. Percent Cobbles and Boulders: By volume
5. Particle Size Range: Gravelfine, coarse
Sandfine, medium, coarse
6. Angularity of Coarse Material: Angular

Subangular

7. Particle Shape (if appropriate): Flat

Elongated

8. Plasticity of Fines: Nonplastic

Medium

Low

Subrounded

Rounded

Flat and elongated

High

9. Mineralogy: Rocky type for gravel, predominant minerals in sand. Note presence of mica flakes, shaly particles, and organic materials.
10. Color: Use common terms or Munsell notation (in moist or wet condition).
11. Odor (for dark-colored or unusual soils only): None
12. Moisture Content: Dry

Moist

Earthy

Organic

Wet

For intact samples

13. Natural Density: Loose

Dense

14. Structure: Stratified

Lensed

15. Cementation: Weak

Moderate

Nonstratified
Strong

16. Reaction (dilute with HCL): None

Weak

Strong (or pH)

17. Geologic Origin: ExamplesAlluvium, Residuum, Colluvium, Glacial Till, Outwash, Dune Sand, Alluvial
Fan, Talus
18. Unified Soil Classification Symbol: Estimate (see table 7B12, Field identification of coarse-grained soils)
Note: See tables 7B1 through 7B11 for criteria for describing many of these factors.
Copyright ASTM Intl. Reprinted with permission.

7B4

(210VIAWMFH, Amend. 38, August 2010)

(210VIAWMFH, Amend. 38, August 2010)

15% fines

10% fines

5% fines

15% fines

10% fines

5% fines

Poorly graded

SC

fines =CL or CH

SP-SC

fines =CL or CH

SM

SP-SM

fines =ML or MH

fines =ML or MH

SW-SC

fines =CL or CH

<15% gravel
15% gravel
<15% gravel
15% gravel

<15% gravel
15% gravel
<15% gravel
15% gravel
<15% gravel
15% gravel
<15% gravel
15% gravel

SW-SM

fines =ML or MH

SP

Well-graded

<15% gravel
15% gravel
<15% gravel
15% gravel

Poorly graded

fines =CL or CH

<15% sand
15% sand
<15% sand
15% sand

SW

GC

<15% sand
15% sand
<15% sand
15% sand
<15% sand
15% sand
<15% sand
15% sand

<15% sand
15% sand

<15% sand
15% sand

Well-graded

GM

GP-GC

fines =CL or CH
fines =ML or MH

GP-GM

fines =ML or MH

fines =CL or CH

GW-GC

GW-GM

Well-graded

Poorly graded

GP

Poorly graded
fines =ML or MH

GW

Well-graded

GROUP SYMBOL

Silty sand
Silty sand with gravel
Clayey sand
Clayey sand with gravel

Well-graded sand with silt

Well-graded sand with silt and gravel
Well-graded sand with clay
Well-graded sand with clay and gravel
Poorly graded sand with silt
Poorly graded sand with silt and gravel
Poorly graded sand with clay
Poorly graded sand with clay and gravel

Well-graded sand with silt

Well-graded sand with gravel
Poorly graded sand
Poorly graded sand with gravel

Silty gravel
Silt gravel with sand
Clayey gravel
Clayey gravel with sand

Well-graded gravel with silt

Well-graded gravel with silt and sand
Well-graded gravel with clay
Well-graded gravel with clay and sand
Poorly graded gravel with silt
Poorly graded gravel with silt and sand
Poorly graded gravel with clay
Poorly graded gravel with clay and sand

Poorly graded gravel

Poorly graded gravel with sand

Well-graded gravel
Well-graded gravel with sand

GROUP NAME

Flow chart for identifying coarse-grained soils (less than 50% fines) (Source: ASTM D 2488 (g. 2). Copyright ASTM Intl. Reprinted with
permission.)

Geologic and Groundwater

Considerations

Note 1Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 %.
FIG. 2 Flow Chart for Identifying Course-Grained Soils (less than 50% fines)

Sand
% sand
% gravel

Gravel
% gravel >
% sand

Figure 7B1

Chapter 7
Part 651
Agricultural Waste Management
Field Handbook

7B5

Chapter 7

Geologic and Groundwater

Considerations

Table 7B12 Field identificationcoarse-grained soils

Coarse Particle Grade Sizes

Coarse gravel
Fine gravel
Coarse sand
Medium sand
Fine sand

Gravel
and
gravelly
soils2

Coarsegrained
soils1

Sand
and
Sandy
soils2

Grade size
12" +
6" - 12"
3" - 6"

Sieve no
----

3/4" - 3"
1/4" - 3/4"
2.0 - 4.76 mm
0.42 - 2.0 mm
0.074 - 0.42 mm
More than half of coarse fraction
More than half of coarse fraction
(by weight) is smaller than 1/4-inch. (by weight) is larger than 1/4-inch.

Grade name
Boulders
Large cobbles
Small cobbles

Clean gravels
Will not leave
a dirt stain on
a wet palm.

Dirty gravels
Will leave a
dirt stain on
a wet palm.

Clean sands
Will not leave
a dirt stain on
a wet palm.

Dirty sands
Will leave a
dirt stain on
a wet palm.

4 - 3/4"
10 - 4
40 - 10
200 - 40

Comparative size
Basketball or larger
Cantaloupe to basketball
Orange to cantaloupe
Cherry to orange
Pea to cherry
Wheat grain to pea
Sugar to wheat grain
Flour to sugar

Wide range in grain sizes and

substantial amounts of all
intermediate sizes.
Mostly one size or a range of
sizes with some intermediate
sizes missing.
Low to nonplastic fines (for
identifying fines see
Field Identification of Finegrained Soils for ML soils).
Plastic fines (for identifying fines
see Field Identification of
Fine-grained Soils for
CL soils).
Wide range in grain sizes and
substantial amounts of all
intermediate particle sizes.
Mostly one size or a range of
sizes with some intermediate
sizes missing.
Low to nonplastic fines (for
identifying fines see
Field Identification of Finegrained Soils for ML soils).
Plastic fines (for identifying
fines see Field Identification of
Fine-grained Soils for CL soils).

/ To classify as coarse-grained, more than half of the material (by weight) must

2/

consist of individual grains visible to the naked eye. Individual grains finer than
no. 200 sieve cannot be seen with the naked eye nor felt by the fingers.
For visual classification, 1/4-inch size may be used as equivalent to no. 4 sieve.

Copyright ASTM Intl. Reprinted with permission.

7B6

(210VIAWMFH, Amend. 38, August 2010)

Part 651
Agricultural Waste Management
Field Handbook

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

ChecklistDescription of fine-grained soils (ASTM D 2488)

1.

Typical Name: Silt Elastic silt Lean clay Fat clay

Silty clay Organic silt or clay Peat

2. Dry Strength: None

Low

Medium

High

Very high

3. Size Distribution: Percent gravel, sand, and fines in fraction finer than 3 inches (76 mm) to nearest 5 percent. If desired, the percentages may be stated in terms indicating a range of values, as
follows:

Trace: < 5%

Few: 510%

Little: 1525% Or, with sand

Some: 3045% Or, sandy

Mostly: 50100%
4. Percent Cobbles and Boulders: By volume
5. Dilatancy: None

Slow

Rapid

6. Toughness of Plastic Thread: Low

7. Plasticity of Fines: Nonplastic

Low

Medium

High

Medium

High

8. Color: Use common terms or Munsell notation (in moist or wet condition).
9. Odor (for dark-colored or unusual soils only): None
10. Moisture content: Dry

Moist

Earthy

Organic

Wet

For intact samples

11. Consistency: Very soft

Soft

Firm

Hard

12. Structure: Stratified

Laminated (varved)

13. Cementation: Weak

Moderate

Very hard
Fissured

Slickensided

Blocky

Lensed

Homogeneous

Strong

14. Reaction (dilute with HCL): None

Weak

Strong (or pH)

15. Geologic Origin: ExamplesAlluvium, Residuum, Colluvium, Loess, Glacial till, Lacustrine
16. Unified Soil Classification Symbol: Estimate (see table 7B13, Field identification of fine-grained soils)
Note: See tables 7B1 through 7B11 for criteria for describing many of these factors.
Copyright ASTM Intl. Reprinted with permission.

(210VIAWMFH, Amend. 38, August 2010)

7B7

Chapter 7

Geologic and Groundwater

Considerations

Part 651
Agricultural Waste Management
Field Handbook

Table 7B13 Field identificationfine-grained soils

Dry Strength

Dilatancy

Toughness

Plasticity

Symbol

None to low

Slow to rapid

Low or no thread

Nonplastic to low

ML

Medium to high

Slow

Medium

Low to medium

CL

Low to medium

None to slow

Low (spongy)

None to low

OL

Medium

None to slow

Low to medium

Low to medium

MH

Very high

None

High

Medium to high

CH

Medium to high

None

Low to medium (spongy)

Medium to high

OH

Highly organic soils

Primarily organic matter, dark in color, spongy feel, organic odor, and often fibrous texture

PT

NoteTo classify as fine-grained, more than half the material (by weight) must consist of fines (material finer than the no. 200 sieve).
Copyright ASTM Intl. Reprinted with permission.

7B8

(210VIAWMFH, Amend. 38, August 2010)

30% plus No. 200

<30% plus No. 200

30% plus No. 200

<30% plus No. 200

30% plus No. 200

<30% plus No. 200

30% plus No. 200

<30% plus No. 200

GROUP SYMBOL

(210VIAWMFH, Amend. 38, August 2010)

% sand <% of gravel

% sand % of gravel

<15% plus No. 200

15-25% plus No. 200

% sand <% of gravel

% sand % of gravel

<15% plus No. 200

15-25% plus No. 200

% sand <% of gravel

% sand % of gravel

<15% plus No. 200

15-25% plus No. 200

% sand <% of gravel

% sand % of gravel

<15% plus No. 200

15-25% plus No. 200

% sand % gravel
% sand <% gravel
<15% gravel
15% gravel
<15% sand
15% sand

% sand % gravel
% sand <% gravel
<15% gravel
15% gravel
<15% sand
15% sand

% sand % gravel
% sand <% gravel
<15% gravel
15% gravel
<15% sand
15% sand

% sand % gravel
% sand <% gravel
<15% gravel
15% gravel
<15% sand
15% sand

30% plusN o. 200

% sand <% of gravel

% sand % of gravel

<15% plus No. 200

15-25% plus No. 200

% sand % gravel
% sand <% gravel
<15% gravel
15% gravel
<15% sand
15% sand

Note 1Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 %.
FIG. 1 b Flow Chart for Identifying Organic Fine-Grained Soil (50% or more fines)

OL/OH

<30% plus No. 200

GROUP SYMBOL

Organic soil
Organic soil with sand
Organic soil with gravel
Sandy organic soil
Sandy organic soil with gravel
Gravelly organic soil
Gravelly organic soil with sand

GROUP NAME

Elastic silt
Elastic silt with sand
Elastic silt with gravel
Sandy elastic silt
Sandy elastic silt with gravel
Gravelly elastic silt
Gravelly elastic silt with sand

Fat clay
Fat clay with sand
Fat clay with gravel
Sandy fat clay
Sandy fat clay with gravel
Gravelly fat clay
Gravelly fat clay with sand

Silt
Silt with sand
Silt with gravel
Sandy silt
Sandy silt with gravel
Gravelly silt
Gravelly silt with sand

Lean clay
Lean clay with sand
Lean clay with gravel
Sandy lean clay
Sandy lean clay with gravel
Gravelly lean clay
Gravelly lean clay with sand

GROUP NAME

Flow chart for identifying fine-grained soils (50% or more fines) (Source: ASTM D 2488 (gs. 1 a and 1 b). Copyright ASTM Intl. Reprinted
with permission.)

Geologic and Groundwater

Considerations

Note 1Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 %.
FIG. 1 a Flow Chart for Identifying Inorganic Fine-Grained Soil (50% or more fines)

MH

CH

ML

CL

Figure 7B2

Chapter 7
Part 651
Agricultural Waste Management
Field Handbook

7B9