On The Efficacy of Monitoring Wells in Karstic

Carbonate Aquifers

Ralph O. Ewers, Ph.D.Ralph O. Ewers, Ph.D.

On The Efficacy of Monitoring Wells in Karstic

Carbonate Aquifersor

How Not to DiagnoseHow Not to Diagnose

Contaminant Problems Contaminant Problems

in Karstin KarstRalph O. Ewers, Ph.D.Ralph O. Ewers, Ph.D.

Monitoring wells may be unreliable in detecting contaminant release.

Simulated Underground Storage Tank Pit Trace

Date- January 26, 2005Date- January 26, 2005

Weather- DryWeather- Dry

Springs- At low base flowSprings- At low base flow

8 pounds of 40% Fluorescein8 pounds of 40% Fluorescein

500 gallons of flush water500 gallons of flush water

Results 1 well detection, Results 1 well detection, weakly positive. weakly positive.

4 Days

Simulated Underground Storage Tank Pit Trace

Date- January 26, 2005Date- January 26, 2005

Weather- DryWeather- Dry

Springs- At low base flowSprings- At low base flow

8 pounds of 40% Fluorescein8 pounds of 40% Fluorescein

500 gallons of flush water500 gallons of flush water

Results 1 well detection, Results 1 well detection, weakly positive. weakly positive.

4 Days

1 Chance in 8

A monitoring well that detects a contaminant is

unlikely to provide appropriate data regarding the quantity of the release or the speed and direction

of the contaminant movement.

Simulated Underground Storage Tank Pit Trace

Date- January 26, 2005Date- January 26, 2005

Weather- DryWeather- Dry

Springs- At low base flowSprings- At low base flow

8 pounds of 40% Fluorescein8 pounds of 40% Fluorescein

16 pounds of 20% Rhodamine-16 pounds of 20% Rhodamine-WTWT

500 gallons of flush water500 gallons of flush water

Results 1 well detection, Results 1 well detection, weakly positive. weakly positive.

4 Days

Garrison, Idstein, and Ewers (2006)

Fluorescein traversed 6.3 Fluorescein traversed 6.3 miles in 4 days.miles in 4 days.

Eosine appeared 2.8 miles Eosine appeared 2.8 miles south 3 days after south 3 days after injection.injection.

Eosine traversed 6.3 miles Eosine traversed 6.3 miles in 5 days, 3 days before it in 5 days, 3 days before it appeared sporadically in a appeared sporadically in a monitoring well 100 feet monitoring well 100 feet distant. distant.

Simulated Underground Storage Tank Pit Trace

Water levels measured in wells often give erroneous indications of groundwater

flow direction.

N=12N=12

N=43N=43

N=30N=30

N=33N=33

NN

Transmissivity between1.1 x 10-5 m2/s and 1.9 x 10-5 m2/s

Ewers, White, Paschl, and Hannish (2005)

N=12N=12

N=43N=43

N=30N=30

N=33N=33

NN

Transmissivity between1.1 x 10-5 m2/s and 1.9 x 10-5 m2/s

Groundwater Velocity at Least 9 m/hr in Conduits

4.2 Miles

Well water levels taken at traditional calendar

intervals give little insight into the fluctuations that

the well presents.

70 80 90 100Ju lian D ate

200

250

300

350

400

450

Co

nd

uctiv

ity (

mic

ro m

ho

s)

80

120

160

200

240

280

Sta

ge

(Fee

t M

SL

)

13 .2

13.6

14

14.4

14.8

15.2

Te

mp

erat

ure

(C

els

ius)

M ills tone Spring

Head fluctuations in wells in response to nearby

pumping do not necessarily indicate flow

connections.

Solvent Pit

Dye Injection WellPumped Well – Intended Remediation Well

Long-Term TCE Release Site – Tool Manufacturing Facility

60 ft.

Solvent Pit

Dye Injection WellPumped Well – Intended Remediation Well

Long-Term TCE Release Site – Tool Manufacturing Facility

Well Pumped For 20 Days

Solvent Pit

Dye Injection WellPumped Well – Intended Remediation Well

Long-Term TCE Release Site – Tool Manufacturing Facility

To Spring 3000 ft Distant

No Dye Detected

Dye Injection WellPumped Well – Intended Remediation Well

Long-Term TCE Release Site – Tool Manufacturing Facility

Increased Flow

Decreased Flow

Dye Injection WellPumped Well – Intended Remediation Well

Long-Term TCE Release Site – Tool Manufacturing Facility

A PRESSURE CONNECTION A PRESSURE CONNECTION IS NOT NECESSARILY IS NOT NECESSARILY A FLOW CONNECTION A FLOW CONNECTION

TRADITIONAL WELL TESTS IN CARBONATE AQUIFERS TYPICALLY DO NOT SENSE

THE MOST IMPORTANT ELEMENTS OF THE

PERMEABILITY STRUCTURE.

(Quinlan, Worthington and Davies, 1992; Teutsch and Sauter, 1992; Worthington, 1992)

Virtually every well in a carbonate aquifer is

influenced by a unique suite of permeability and

recharge elements.

Johnson and Ewers (1994)Recker and Ewers (1990)

Each well responds to storm events differently, with no apparent relation to distance from the conduit.

MONITORING WELLS ARE

UNRELIABLE IN KARST