Today’s LectureGroundwater sampling

AnnouncementsLecture

today: groundwater sampling Thursday: HAZWOP – quiz (Bruce)

Lab Lab 1: Phase I ESA

rewriting Lab 2: Surface water sampling

grading in progress Lab 3: Soil sampling

report due Wed Oct 21

AnnouncementsLab

Saturday, Oct 17 Lab 4 Subsurface

sampling andmonitoring well installationDrilling Engineers, Inc., Fort Collins, 9 am-noon

arrange rides for self-transport

7:30 am departure Google spreadsheet sent

by email only @colorado.edu

accounts

Wednesday, Oct 28 Lab 5 Groundwater

sampling / Slug test East campus

Groundwater SamplingPurpose

collect samples representative of groundwater

determine concentration of contaminants in groundwater

Groundwater SamplingRemoving water from the well

bailers lowered and raised by hand or reel sample poured into bottle PVC, HDPE, Teflon, stainless steel

Groundwater SamplingRemoving water from the well

bailers lowered and raised by hand or reel sample poured into bottle PVC, HDPE, Teflon, stainless steel inexpensive readily portable dedicated / disposable / decontaminated

Groundwater SamplingRemoving water from the well

bailers lowered and raised by hand or reel sample poured into bottle PVC, HDPE, Teflon, stainless steel inexpensive readily portable dedicated / disposable / decontaminated slow atmospheric exposure small-diameter wells

Groundwater SamplingRemoving water from the well peristaltic pumps

install tubing in pump head provide power source

battery, generator, AC choose pumping rate

Groundwater SamplingRemoving water from the well peristaltic pumps

install tubing in pump head provide power source choose pumping rate less expensive portable disposable

material incontact withsample

Groundwater SamplingRemoving water from the well peristaltic pumps

install tubing in pump head provide power source choose pumping rate less expensive portable disposable material in contact

with sample atmospheric exposure

suction pulls VOCs out of water suction pulls CO2 out of water

limited to suction depth

Groundwater SamplingRemoving water from the well

positive-displacement pumps turbine, gear-driven, bladder

Groundwater SamplingRemoving water from the well

positive-displacement pumps turbine, gear-driven, bladder mainly inert materials

stainless steel; Teflon

depths to hundreds of feet flow control

low-flow purging and sampling steady flow versus surging flow

dedicated

Groundwater SamplingRemoving water from the well

positive-displacement pumps turbine, gear-driven, bladder mainly inert materials

stainless steel; Teflon

depths to hundreds of feet flow control

low-flow purging and sampling steady flow versus surging flow

dedicated / well-to-well decontamination between wells

expensive less portable sediment clogging

Groundwater SamplingPurging

removing water standing in well not representative of groundwater gas exchange in well casing

gain of oxygen affects redox potential gain or loss of carbon dioxide affects

pH loss of volatile organic compounds

leaching of contaminants from well casing

sorption of contaminants to well casing

(mixing with surface water in poorly-constructed well)

obtain representative sample generates wastewater for

disposal

Groundwater SamplingPurging

specified volume 3-5 well volumes calculated as water depth well cross-sectional

area

Groundwater SamplingPurging

specified volume 3-5 well volumes calculated as water depth well cross-sectional

area stabilization of field parameters

T; conductivity; pH; EH; dissolved oxygen; turbidity

minutes to hoursT

pH

[O2] turbidity

EH

conductivity

Groundwater Sampling

Groundwater SamplingPumping rate for purging and sampling

high pumping rate (> a few L min-1) less time in the field disturbance of aquifer sediments

higher total contaminant concentrations “fix” by filtering samples?

drawdown in well

Groundwater SamplingPumping rate for purging and sampling

high pumping rate (> a few L min-1) less time in the field disturbance of aquifer sediments

higher total contaminant concentrations “fix” by filtering samples?

drawdown in well low pumping rate (< few hundred mL min-

1) more time in the field undisturbed

more representative ofmobile contaminants

no need for filtration less drawdown in well less wastewater

well casing volumes

Groundwater Sampling

Groundwater Sampling

Groundwater Sampling

Groundwater SamplingPassive sampling

diffusion bags contaminants sorbed to material

within membrane contaminants extracted from material

in lab relies on groundwater flow through

well deployed weeks to months

bottles / sleeves lids closed by trigger

followingequilibration period

Groundwater SamplingSample handling

filtration total and dissolved

preservatives e.g., acid for trace elements

bottles plastic for metals glass for organic compounds air-tight seals for VOCs

storage coolers, ice

shipping chain of custody

lazygroundwatersampling

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