ENGI 7718 – Environmental Geotechniques

ENGI 9621 – Soil Remediation Engineering

Spring 2011

Faculty of Engineering & Applied Science

Lecture 4: Contaminated Site

Characterization

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Site characterization a systematic investigation

aimed at obtaining appropriate and adequate data in

order to define the type and extent of contamination as

well as to assess the fate and transport of contaminants

under various scenarios

(1) Information required for site characterization

4.1 Introduction

Geologic data

Hydro-geologic data

Contamination data

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(2) Questions to be answered by site characterization

Nature and extent of contamination

where is it?

What is future migration and control

where is it going?

What are receptors and their risk

what harm will it do?

What are technical options for remediation

how do we fix it?

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(3) General methodology for site characterization

Source: Sharma and Reddy, Geoenvironental Engineering, 2004

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4.2 Preliminary and exploratory site assessment

to collect and review available or published site-specific

or regional data involves two tasks: literature review and

site visit

(a) Literature review

(1) Phase I: Preliminary site assessment

site use and history

site permits

water well logs and records

aerial photos

other sources

site personnel interviews

geological maps and reports

topographic maps

soil survey maps

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Action I Get a topo map understand geographic

setting, topography, nearby water bodies

Action II Get background geologic data through

Effective actions:

consulting ground-water atlas of Canada

getting reports on geology, hydrology,

meteorology

checking for reports from province and national

geological surveys

Action III Investigate regional geology and hydrogeology

help to understand site geology and hydrology

understand effects on contaminant movement6

Where were chemicals handled or disposed?

What site structures or activities are potential

sources?

What chemicals are and were handled?Prevention of costly mistakes such as multi-aquifer

wells

(b) Site visit observe/record all potential important

surface site features + collect surface water and near-

surface soils

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to confirm findings in the preliminary assessment

to obtain preliminary site-specific data to facilitate

design of a detailed site investigation program

(2) Phase II: Exploratory site investigation

sampling and testing procedures

sampling locations and frequency

QA/QC plan

health and safety (H&S) plan

schedule

cost assessment

a written work plan for phase III

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H&S plan

Source: US EPA, Emergency response program, 20029

More information about H&S plan , visit http://www.worksafebc.com/publications

/health_and_safety/by_topic/assets/pdf/howtoimplement_ohs.pdf

Health and Safety Levels

Source: Rast, Environmental Remediation Estimating Methods, 1997

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4.3.1 Methods of obtaining soil and rock data

4.3 Detailed site investigation

Phase III : detailed site investigation a

comprehensive field and laboratory test program,

along with S&H and QA/QC plans

Direct methods

Geophysical methods

Drive methods

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Source: Sharma and Reddy, Geoenvironental Engineering, 2004

bucket augers; spiral or ram’s horn auger

Direct methods – near surface soil sampling

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Direct methods – soil sampling by solid-stem

auger drilling

Source: Sharma and Reddy, Geoenvironental Engineering, 2004

Power-driven solid-stem augers: (a) solid-

flight auger; (b) relationship of surface

cuttings and subsurface

Drilling stop at the desired depth

augers remove from the borehole

a sampler is attached to the end

of the drill put the entire string

back to the borehole a sample is

taken from the bottom flight by

Only for sampling from soil, not

applicable to saturated zones

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Direct methods – soil sampling by hollow-stem

auger drilling

Source: Sharma and Reddy, Geoenvironental Engineering, 2004

Typical components of a hollow-stem auger:

a hollow pipe with a continuous ramp of

upward-spiraling flight welded around them

Drilling a center rod (with a pilot

bit and plug) is lowered inside the

auger till the sampling position is

reached the center rod/bit/plug

are removed soil sampler is

applied

Applicable to soil/uppermost level

of groundwater sampling

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solid-stem (left) and hollow-stem (right)

augur flights

a hollow-stem augur in actionSource: DeJong & Boulanger, 201015

Source: Sharma and Reddy, Geoenvironental Engineering, 2004

Direct methods – popular samplers

A split-spoon sampler

Thin-walled tube samplers

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Drilling boreholes drilling fluid is

pumped down hollow rotary drill rods

the fluid circulates back to surface

by moving up the annular space

between drill rods and borehole wall

stabilization of the borehole wall

installation of the

piezometer/monitoring wall

If the circulation medium is air instead

of water air rotary drilling

Source: Sharma and Reddy, Geoenvironental Engineering, 2004

Direct methods – Installing piezometers and

monitoring wells by wet rotary drilling

Direct mud rotary circulation system

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This image shows a rotary

wash boring set-up. The

drilling "mud," a mixture of

water and bentonite, is

circulated through the tank in

the left-foreground of the

photo. The mud is pumped

down the drill stem to the

hole bottom, where it picks

up soil cuttings and carries

them to the surface and into

the tank. The mud also serves

to support the borehole walls. Source: DeJong & Boulanger, 2010

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Direct methods – we should also know…

Logging

Field testing

Surveying

Borehole abandonment

Laboratory testing

Geophysical methods

Borehole geophysical methods a probe into the

borehole using a cable transmit signals to surface

instruments generate logs or charts

Surface geophysical methods no requirement of

boreholes conduct electric/seismic/electromagnetic

surveys as well as the use of ground penetrating radar19

Geophysical methods – Electrical resistivity

Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration, 198520

Geophysical methods – Seismic reflection

Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration, 198521

Geophysical methods – Electromagnetic Induction

Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration, 198522

Geophysical methods – Ground penetrating radar

Source: van Ea, Geophysical Techniques for Sensing Buried Wastes and Waste Migration, 198523

Drive methods e.g. cone penetrometer technology

CPT a method of providing real-

time data for use in characterizing the

subsurface, as opposed to older methods

of analyzing subsurface conditions in the

laboratory

It consists of a steel cone that is

hydraulically pushed into the ground at

up to 40,000 pounds of pressure

Sensors on the tip of the cone collect

data

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4.3.2 Methods of obtaining hydrogeologic data

Direct methods

Drive methods

Piezometers and monitoring wells

Water-level measurement

In-situ hydraulic conductivity test

Packer test

Slug test

Pumping test

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Installing Piezometers with

a Manual Slide Hammer Structure of a piezometer

Piezometers

Source: Shanahan, Waste Containment and Remediation Technology, 2004 26

Monitoring wells -- Structure

Source: Shanahan, Waste Containment and Remediation

Technology, 2004 27

Monitoring wells -- Development

Source: Shanahan, Waste Containment and Remediation Technology, 2004 28

Source: Shanahan, Waste Containment and Remediation Technology, 2004 29

Well development by surge block

Source: Shanahan, Waste Containment and Remediation Technology, 2004 30

Source: Shanahan, Waste Containment and Remediation Technology, 200431

A developed well with a cover

Source: Shanahan, Waste Containment and Remediation Technology, 200432

Water-level measurement

Source: Shanahan, Waste Containment and Remediation Technology, 200433

(a) Applying a bailer a portion of the water is removed from the bore

hole after which measurement can commence The rise rate of the

groundwater is determined by using a measuring tape with a float and a

stopwatch

(b) The determination of the saturated water permeability using the Guelph

permeameter.

In-situ hydraulic conductivity test

(a) (b)Source: Eijkelkamp, Agrisearch Equipment, 2010 (http://www.eijkelkamp.com/)

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Sources: Groundwater data collection, USGS Illinois Water Science Center Searchable Publications Database, 2010,

http://il.water.usgs.gov/pubs/ofr01-50_chapter4_8.pdf (Left)

Cutting Edge Drilling , 2010, http://cuttingedgecoredrilling.com/_wsn/page4.html (Right)

(a) The schematic of a packer test apparatus (b) Field packer test

Packer test

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Source: Butler, et al., Analysis of slug tests in formations of high hydraulic conductivity, Ground

Water, v. 41, no. 5, 620-630, 2003

Slug test

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Pumping test

Single well pumping test

Source: Sharma and Reddy, Geoenvironental Engineering, 2004 37

4.3.3 Methods of obtaining contaminant data

Contaminant in soil analyze the samples

from soil sampler

Contaminant in water analyze the samples

from piezometers and/or monitoring wells

Contaminant in soil vapor analyze the

samples from soil gas sampler

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Soil gas sampler

Source: Environmental Support Technologies, Inc., 2002 39

Potential character of soil gas contamination

Source: Cohen and Mercer, DNAPL site evaluation, 1993 40