Groundwater Pollution

Week 5 – 0407 Investigating the Site and Monitoring

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Some Notes derived from 1.34 Waste Containment and Remediation Technology , As taught in: Spring 2004, by Dr. Peter Shanahan , MIT OpenCourseWare, Creative Commons License, http://ocw.mit.edu/OcwWeb/Civil-and Environmental-Engineering/1 34Spring2004/CourseHome/

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revision of previous week 3

Information to help with the clean up of contamination can be found at http://clu-in.org/ .

For example http://clu in.org/characterization/technologi es/solvr.cfm

helps decide what is the best characterization technique.

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You can click on the different technologies for more information.

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You can also look at each method.

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We then investigate the contaminant.

Where is the contaminant plume?

What is in the plume? How big is the plume? How long has it been there? Where is it going? How fast will it go?

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Q. What is a contaminant

plume?

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The contaminant plume is where the contaminant is dissolved in the ground water.

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Usually - The contaminant plume is where the contaminant is dissolved in the ground water.

Sometimes - It can also mean where the vapor is dissolved in the air.

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Q. Give a meaning for phase.

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Vadose zone Floating Groundwater The phases are when the pollutant is solid (solid phase), liquid (liquid phase), vapor (gaseous phase), or dissolved in the water (aqueous phase).

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In the vadose zone contaminants could be present as: Vapors in the void (

공간

) Free product in the void Dissolved in the soil moisture (

수분

) Adsorbed (

흡착하다

) onto the soil matrix Floating on top of the capillary fringe

Q. Draw a picture of each of the above.

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http://toxics.usgs.gov/photo_gallery/photos/bimidji/bimidji10_lg.jpg

Collecting vapor samples from contaminated areas in the unsaturated zone

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Adsorption (n.)

(

흡착

) is when molecules of gas, liquid, or dissolved solids stick to a surface.

Adsorb (v) Adsorbed (v. and adj) 17

Sorption

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Contaminants could be in the saturated zone as: Dissolved (

녹이다

) in the groundwater Adsorbed onto the aquifer material Sitting on top of the bedrock (for dense nonaqueous phase liquids [DNAPLs])

Q. Draw diagrams of each of these.

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NAPLs coat the Soil Particles

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NAPLs fill the Voids

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The first steps are called remedial

(

개선의

)

investigation 연구

)

(RI) activities

(

행위

) (

Removal of contamination sources Doing some soil borings (

구멍뚫기

) Making groundwater monitoring (

모니터

) wells Soil sample collection and analysis Groundwater sample collection and analysis Aquifer testing

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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?

Waste Containment and Remediation Technology 23

Data needed from site characterization

1. Contaminant sources – research history as well as collect samples 2. Extent of contamination – need to understand transport as well 3. Hydrogeologic setting – use to understand items 1 and 2 4. Restoration potential – how easy is it to clean up?

Waste Containment and Remediation Technology 24

Stages of investigation

Stage 1 – scoping study Is there a problem? How bad is it?

Stage 2 – prepare field study plan Includes sampling and analysis, health and safety, and quality assurance plans Stage 3 – conduct on-site sampling and analysis Stage 4 – interpretation, assessment, modeling (Stages 3 and 4 may be repeated several times) Stage 5 – design remedial action 25 Waste Containment and Remediation Technology

First steps in understanding a site

1. Understand geographic setting, topography, nearby water bodies 2. Get background geologic data Consult ground-water atlas of the area.

Get reports on geology, hydrology, meteorology Check for reports from government geological surveys Waste Containment and Remediation Technology 26

First steps in understanding a site

3. Understand site use and history Where were chemicals handled or disposed?

What site structures or activities are potential sources?

What chemicals are and were handled?

27 Waste Containment and Remediation Technology

The following types of data are collected: Types of contaminants present in soil and groundwater Concentrations of contaminants in the samples Vertical and areal spread of contaminant plumes in soil and groundwater Vertical and areal spread of free-floating product or the DNAPLs Soil characteristics including the types of soil, density, moisture content, etc.

Groundwater elevations Drawdown data collected from aquifer tests

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http://mn.water.usgs.gov/bemidji/results/fact-sheet.pdf

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Engineering calculations remediation.

help site These could include: Mass and volume of soil removed during tank removal Mass and volume of contaminated soil left in the vadose zone Mass of contaminants in the vadose zone Mass and volume of the free-floating product Volume of contaminated groundwater Mass of contaminants in the aquifer Groundwater flow gradient and direction Hydraulic conductivity of the aquifer 30

Understanding the geology and physical contaminants.

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Geophysical Methods Method Electrical resistivity Electromagnetic induction Seismic refraction Seismic reflection Ground penetrating radar (GPR) Magnetometry Gravity survey Object Map conductive or nonconductive contaminants; stratigraphy Map conductive or nonconductive contaminants; metal objects; stratigraphy Stratigraphy (top of bedrock); depth to ground water High resolution mapping of top of bedrock Buried objects (plastic and metal); stratigraphy; depth to ground water Buried metal objects Overburden thickness; landfill boundaries 32 Waste Containment and Remediation Technology

Ground penetrating radar Waste Containment and Remediation Technology 33

Electromagnetic Induction Waste Containment and Remediation Technology 34

Electrical resistivity Waste Containment and Remediation Technology 35

Seismic reflection Waste Containment and Remediation Technology 36

Geophysics suite Waste Containment and Remediation Technology 37

Sampling the gas phase

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Soil gas sampling system Waste Containment and Remediation Technology 39

Output from field GC Waste Containment and Remediation Technology 40

Soil gas survey results Waste Containment and Remediation Technology 41

There are two main methods of getting into the ground.

- Drilling - Direct Push

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Drilling deep test hole

http://nevada.usgs.gov/adrs/images/photos/studyareas/StudyAreasandExperimentalS/study9.html

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Drilling techniques Waste Containment and Remediation Technology 45

Hollow Stem Auger Waste Containment and Remediation Technology 46

Direct-push technology (Geoprobe) Waste Containment and Remediation Technology 47

Direct-push monitoring well Waste Containment and Remediation Technology 48

Direct push - Advantages • Inexpensive to install, replace and abandon • Minimal waste “cuttings” • Fewer well development wastes • Rapid installation and site characterization • Less worker exposure to contaminants • Representative chemistry and field parameter measurements • Improved landowner relations

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Direct push - Disadvantages • Not applicable when cobbles or consolidated materials are present • May not be accepted for long term monitoring in most states • Debate remains regarding aquifer testing capabilities • Well diameter limitations • Pump diameter limitations • Potential for higher turbidity in wells with no filter pack

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Demonstration/Validation of Long-Term Monitoring Using Wells Installed by Direct Push Technologies and Enhanced Low-Flow Groundwater Sampling Methods. DoD 2009 51

Percentage Savings for DP Well Installations Based on Well Diameter and Depth.

Demonstration/Validation of Long-Term Monitoring Using Wells Installed by Direct Push Technologies and Enhanced Low-Flow Groundwater Sampling Methods. DoD 2009 52

http://www.frtr.gov/decisionsupport/index.ht

m http://www.clu in.org/characterization/technologies/solvr.c

fm 53