Download Soil Structure - ASCE Philadelphia Section

ASCE - Philadelphia
Soils & Stormwater Management
Matthew C. Hostrander, CPSS, SEO
Soil Scientist
Gilmore & Associates, Inc.
Course Overview
COURSE OUTLINE
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Soil Science Fundamentals –Discuss United States Department of Agriculture (USDA)
soil classification in the field, as well as briefly review the Unified Soil Classification
System (USCS) classification system and its differences from the USDA system. Review
standard deep-hole test pit logging procedures.
Soil Water Characteristics and Behavior – Examine the movement of water, or lack
there of, in relation to specific soil features and properties.
Soils & Stormwater Engineering – So, why stormwater management? In this section
we will discuss the importance of stormwater management and the start to finish
process to developing a successful BMP.
Web Soil Survey Tutorial – Online resources continue to improve - the official soil
survey is available on the USDA National Resource Conservation Service website,
known as the Web Soil Survey (WSS).
Soil Science Fundamentals
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Soil classification and profile descriptions
United States Department of Agriculture (USDA)
versus Unified Soil Classfication System (USCS)
classification systems
Soil forming factors
Rock depth and drainage classification
General deep-hole test pit log methods
Soil Science - USDA
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Soil Profile Horizons
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Soil Color
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Soil Texture
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Soil Structure
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Wet Soil Consistence
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Redoximorphic Features (Mottling)
Soil Profile Horizons
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O – Layers dominated by organic matter (e.g. forest leaf litter layer).
A – Mineral horizon formed at the surface or below an organic horizon. These
horizons are typically topsoil layers.
E – Mineral horizon in which the dominant feature is the eluvial loss of clay, iron,
aluminum, or organic matter. These losses result in a concentration of sand and silt
particles and lighter colors.
B – Horizons that formed below an A, E, or O horizon and are dominated by
obliteration of all or much of the original rock structure and show one or more of the
following: illuvial concentration of silicate clay, iron, aluminum, humus, carbonates,
or silica; evidence of removal of carbonates; residual concentration of sesquioxides;
and brittleness.
C – Mineral horizons that are relatively unaffected by soil-forming processes.
Properties are dominated by the parent material. Unconsolidated with low to
moderate excavation difficulty, but is still considered soil.
R – Hard bedrock that is difficult to excavate.
Soil Color
Soil color should be documented
using the Munsell color charts,
and utilize Hue, Value, and
Chroma. The matrix color of each
horizon should be described.
Changes in color may often
provide important information
about a particular soil horizon.
Soil Texture
Soil texture refers to the weight
proportion of the sand, silt, and
clay particles that are 2 mm and
less. The percentages of these
mineral particles determines the
texture of the soil. Rock
modifiers are added for
percentages of rock fragments
in a given horizon.
Soil Texture
Clay, Clay Loam, Loam,
Sandy Clay, Sandy Clay
Loam, Sandy Loam,
Coarse Sandy Loam, Fine
Sandy Loam, Very Fine
Sandy Loam, Loamy Sand,
Loamy Coarse Sand,
Loamy Fine Sand, Loamy
Very Fine Sand, Sand,
Silty Clay, Silty Clay Loam,
Silt Loam, Silt
Soil Texture
Modifiers for Percent Rock
Fragments
Gravelly, Channery, Flaggy,
Stony, Bouldery
Example:
0-15% - None
15-35% - Gravelly
35-60% - Very Gravelly
>60% - Extremely Gravelly
Soil Structure
Structure is the shape of a unit of
soil as it is naturally bound
together. These units, called
peds, are like pieces of a puzzle
that fit together. Structure is
defined by type, grade, and size.
Structure types are granular,
blocky, platy, and prismatic.
Grades are structureless, weak,
moderate, and strong. Sizes are
fine, medium, and coarse.
Soil Structure
PRISMATIC STRUCTURE IN NJ SOILS
GRANULAR SOILS
Wet Soil Consistence
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Soil consistence is the resistance of the soil structural unit to
deformation at various moisture contents. Consistence may
be a good indicator of liquid penetration. Typically, firm to
very firm soil consistence results in slow permeability.
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Wet soil consistence
terminology: Loose,
Very Friable, Friable,
Firm, Very Firm,
Extremely Firm
Redoximorphic Features
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Soil mottling, which is a type of redoximorphic feature, is a
soil characteristic associated with wetness. Mottling, or
redox features, result from the reduction and oxidation of
iron and manganese compounds in the soil. This splotchy
appearance indicates intermittent saturation and
desaturation.
Redoximorphic features are
described in terms of abundance and
contrast, as well as size.
Abundance: Few, Common, Many
Contrast: Faint, Distinct, Prominent
Redoximorphic Features
USDA versus USCS
Unified Soil Classification System
Soil Forming Factors
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Climate – primarily precipitation and temperature.
Time – the period of time since the parent materials
became exposed to soil formation.
Biota – living organisms, especially native vegetation,
microbes, soil animals, and human beings.
Topography – slope, aspect, and landscape position.
Parent Material – geologic or organic precursors to the
soils.
Soil Forming Factors
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Classification of Parent Materials
 Formed in place from rock – Residual
 Transported
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Colluvial – by gravity
Alluvial, Marine, Lacustrine – by water
Glacial – by ice
Eolian – by wind (wind-blown loess)
 Accumulated plant debris – Organic
Rock Depth
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Rock Depth
 0-20” – Shallow
 20-40” – Moderately
Deep
 >40” – Deep, and
Very Deep
Drainage Classification
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Drainage Classification
 <10” – Poorly Drained
 10-20” – Somewhat Poorly Drained
 20-40” – Moderately Well-drained
 >40” – Well Drained, and
Excessively Well Drained
Deep-Hole Soil Log
ASCE - Philadelphia
Soil Water: Characteristics and Behavior
Matthew C. Hostrander, CPSS, SEO
Soil Scientist
Gilmore & Associates, Inc.
Overview
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Soil water behavior
Soil organic matter
Perched water tables versus regional ground water
tables
Permeability testing methodologies
Soil Water Behavior
Sandy soils will generally drain
more vertically than
horizontally; while soils high in
clay will generally show
drainage more uniformly in the
horizontal and vertical
directions.
Water movement in stratified soils
explained:
Coarse soils over fine-grained
soils and visa versa.
Soil Water Behavior
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Perched water tables can occur in some of the sandier soils around
southeastern PA due to the following:
 Soil textural differences
 Structure
 Consistence
 Compaction
 Fill soil areas
Soil Organic Matter
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Soil Organic Matter
 Can increase infiltration rate
 Can increase water-holding capacity
 Can decrease erosion through aggregate stability
 Can increase nutrient removal through adsorption
 Can increase water retention over time
 Can provide macropores and channels for air and water
 Can increase food sources
Overall, soil organic matter can help to keep irrigation and fertilizer
use down, while providing less water pollution and greater
groundwater recharge.
Soil Organic Matter
Water Tables
Water Tables
Seasonally high
water table due to
poor draining soils
and compaction
Water Tables
Prismatic soil structure is
evident due to vertical
redoximorphic features.
A perched water table
would existing above and
within that horizon
during wet parts of the
year.
Water Tables
Redoximorphic features
in a sandy soil can still
occur. Also, the picture
shows mobility of the
surface sands into the
sub-horizons through
macropores.
Permeability Testing Methods
Double-ring infiltrometer
Permeability Testing Methods
Standard percolation test hole
Permeability Testing Methods
Maryland falling-head cased borehole
Permeability Testing Methods
Basin Flood testing, as
modified from the New
Jersey septic and
stormwater regulations
Permeability Testing Methods
Percolation testing allows
horizontal and vertical water
movement during the test.
Double-ring infiltrometer
testing mimics saturated
vertical gravity flow with
measurements taken from the
inner ring.
Permeability Testing Methods
Darcy’s Law for calculating saturated
hydraulic conductivity (ksat).
Elrick & Reynolds equation for calculating the
reduction factor, which accounts for the exfiltration
occurring through the sides of percolation hole. It
assumes that the percolation rate is affected by the
depth of water in the hole and that the percolating
surface of the hole is in uniform soil.
ASCE - Philadelphia
Soil & Stormwater Engineering
Matthew C. Hostrander, CPSS, SEO
Soil Scientist
Gilmore & Associates, Inc.
Why Stormwater Management?
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Groundwater Recharge
Mechanism
Erosion & Sediment
Control (volume control)
Safeguard Water Quality
Waterway Protection
PA Best Management Practices
Manual
Provides guidance for system
selection, testing, analysis,
construction, and
maintenance.
BUT…
The BMP Manual provides
broad guidelines and should be
expanded upon through testing
and design. In practice, we
have found that some sections
need to provide more detailed
guidance and information.
START TO FINISH
STORMWATER PROCESS
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Desktop Review
In-situ Field Testing
Reporting / Recommendations
Stormwater Management Design
System Installation
System As-Builts
System Maintenance
DESKTOP REVIEW
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Review Site Soils
• County Soil Survey
• Web Soil Survey
• Soil Map Website
Review Site Geology
• PA Geology Map
• Web Sources
Review Municipal
Regulations
DESKTOP REVIEW
Possible Limitations
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Seasonal High Water Table
/ Perched Water Table
Fine Grained Soils
Shallow Groundwater
Shallow Bedrock
Karst Geology
Wetlands
FIELD TESTING
Soil Profile Descriptions
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Textural Class
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Limiting Zones
1. Seasonal High Water
Table (indicated by…)
2. Bedrock
3. Groundwater
FIELD TESTING
Infiltration Testing Methods
 Double-Ring Infiltrometer
 Standard Percolation Hole
 Basin Flood
 Maryland Borehole
FIELD TESTING
Sealed cased borehole
testing within existing
athletic fields
Confirmation double-ring
infiltrometer testing during
subsurface system installation
REPORTING &
RECOMMENDATIONS
Report Components
 Describe on-site soils and
underlying geology
 Summarize infiltration rates
and locations
 Discuss site limitations, if
applicable
 Recommend appropriate
stormwater management
systems, if required
STORMWATER MANAGEMENT DESIGN
Stormwater Management Systems
 Surface Systems
Basins, Rain Gardens, Vegetated Swales,
Berms, etc.
 Subsurface Systems
Subsurface Infiltration Bed, Dry Wells,
Infiltration Trenches, Constructed Filters
 Other Systems
Permeable Paving with Infiltration Beds
STORMWATER MANAGEMENT DESIGN
Goal
To best match field conditions with a stormwater management design
that responsibly promotes infiltration and mimics natural processes.
SYSTEM INSTALLATION
Installation Challenges
 Compaction of the
subgrade
 Construction practices
 Material selection
 Engineering (size,
location, function)
SYSTEM MAINTENANCE
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Trim plantings
Mow grasses
Rehabilitation & Restoration
(sediment)
Observation port inspections
(subsurface)
Vacuum cleaning (permeable
pavements only)
Structural inspections
Q&A
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Stormwater Testing
Stormwater BMP Design
Regulatory BMP Manuals / Guidance Documents
Consultant’s Role
Stormwater’s Future
ASCE - Philadelphia
Web Soil Survey: The Official Soil Survey
Matthew C. Hostrander, CPSS, SEO
Soil Scientist
Gilmore & Associates, Inc.
Overview
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Web Soil Survey from the USDA – Natural Resource
Conservation Service
Creating AOIs and Soil Reports
Soil Data Explorer
Soil Suitabilities, Properties, and Qualities
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Soil Map from PSU
Web Soil Survey
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Provides alternative to traditional hardcopy publication
Provides means for quicker delivery of information
Provides interactive access to most current data
Web Soil Survey
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Web Soil Survey allows the customer to get just the
information they want or select
 The customer can obtain their geographic area of
interest (AOI) information
 The customer can obtain relevant information to help
answer their land use concerns
(e.g. basements, crops, septic systems, etc.)
Web Soil Suvey provides color imagery or topographic
map backdrops for the AOI selected by the user
Once the AOI is selected, a myriad of Soil Data Mart
tables are available for viewing and use
Web Soil Survey
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Web Soil Survey can provide the user with a
custom soil resource report (pdf format) via the
free shopping cart
The customized report can be prepared by AOI,
soil map, map unit legend, map unit
descriptions, etc.
The user has the ability to customize the report
with multiple soil data properties, capabilities,
uses, and many others
Web Soil Survey Demonstration
NRCS has 76 page WSS Tutorial available for use
Web Soil Survey
WSS will generate a customized
soil report for any project. The
report, if small, can be printed
directly from the website;
however, for larger files, the
report can be compiled
externally and emailed to you
when complete.