Elizabeth Perry of AECOM

The Occurrence of Methane 

in Shallow Groundwater 

from Extensive Pre-Drill 

Sampling 

A. Elizabeth Perry, PG - AECOM Bert Smith - Chesapeake 

Rikka Bothun - AECOM 

Mark Hollingsworth - Chesapeake

Presentation Outline 

• Purpose 

– Pre-drill sampling associated with 

Utica/Marcellus unconventional shale 

gas development provides data not 

previously available on a regional scale 

• Overview of sampling program 

• Results 

– Occurrence/distribution of methane 

– Geographic distribution 

– Relationships with geology 

– Relationships with other parameters 

Evaluation of Baseline (Pre-Drill) Data 

Page 2

Baseline (Pre-Drill) Sampling Program 

Samples collected on behalf of Chesapeake 

Energy 

• Four independent national consulting firms 

• Independent commercial laboratories 

Water supplies within 1,000 to 4,000 ft radius of 

planned gas well 

• Property owner surveys 

• Identification of water supply sources 

• Permission for sampling 

Water supplies sampled 6-9 months prior to pad 

construction 

• Groundwater samples from actively used water wells 

• Analysis for methane plus metals, inorganics, BTEX, etc. 

• QA/QC program by independent consultants 

Results provided to well owners and agencies 

• Over 14,000 samples in PA, OH, WV, 2009-2012 

• Results provided to well owners and state agencies as 

required 


Page 3

Summary of Methane in Groundwater 

• 14,209 water wells 

sampled in PA, OH, 

WV 

• Methane detected 

in 3,542 wells 

(24.9%) 

• Methane greater 

than PA Action 

Level of 7 mg/L in 

494 wells (3.5%) 

Number of Samples 

350 

300 

250 

200 

150 

100 

50 

0 

0.036 

0.054 

0.08 

0.12 

0.18 

0.27 

0.41 

0.61 

0.92 

1.4 

2.1 

3.1 

4.7 

7 

PA Action Level 

7 mg/L 

10.5 

15.8 

Detected Methane Concentration (mg/L) 

23.7 

35.5 

53.3 

Evaluation of Baseline (Pre-Drill) Data



Evaluation of Baseline (Pre-Drill) Data Page 7







Relationship with Geologic Units 

1000 

100 

Northeastern PA | OH WV SW PA 

Detected Results Only 

PA Action Level (7 mg/L) 

max 

Concentration (mg/L) 

10 

1 

0.1 

p90 

p75 

p50 

p25 

PA 

Action Level 

(7.0) 

p10 

0.01 

min 

0.001 

n=1,576 1,083 81 427 188 123 64 

Lock Haven Catskill NE PA 

Other 

Allegheny- 

Pottsville 

Conemaugh 

& Glenshaw 

Dunkard 

& Green 

OH WV SWPA 

Other 


Methane Occurrence Inversely Related to Sulfate 

100 

10 


1 

0.1 

Median SO4 conc for 

samples in range 

Median CH4 detected 

conc for samples in 

range 

0.01 

n=1,198 1,509 1,217 1,318 1,337 1,161 1,267 1,167 1,278 1,276 1,426 

55 

Sulfate concentration range (mg/L) 


Methane Occurrence Inversely Related to Sulfate 

100 

80% 

70% 


10 

1 

0.1 

CH4 FOD for samples in 

range 

Median SO4 conc for 

samples in range 

Median CH4 detected conc 

for samples in range 

60% 

50% 

40% 

30% 

20% 

10% 

Frequency of Methane Detections (%) 

0.01 

n=1,198 1,509 1,217 1,318 1,337 1,161 1,267 1,167 1,278 1,276 1,426 

55 

Sulfate concentration range (mg/L) 

0% 


Samples with Methane Non-detected, NE PA 

• Predominantly Ca- 

HCO 3 -type water 

• Catskill and Lock Haven 

Formations have greater 

proportions of Na, Cl 

• Samples with 100% Na 

may represent treated 

water (water softeners) 


Page 17

Samples with Methane up to 3 mg/L, NE PA 

• Predominantly Ca- 

HCO 3 -type water 

• Increasing Na and Cl 

content 

• Na-HCO 3 and Na-Cl 

water types in Catskill 

and Lock Haven Fms 


Page 18

Samples with Methane ≥ 3 mg/L, NE PA 

• Predominantly Na- 

HCO 3 and Na-Cl type 

waters 

• Sulfate depleted 

(

Methane and Water Type, Northeastern PA 

Number of Samples 

2000 

1800 

1600 

1400 

1200 

1000 

800 

600 

400 

200 

CH4 >20 mg/L 

CH4 7 - 20 mg/L 

CH4 3 - 7 mg/L 

CH4 >0.026-3 mg/L 

CH4 ND (

Methane and Water Type, Northeastern PA 

Percent of Samples 

100% 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

Ca-HCO3 Other Na-HCO3 Na-Cl 

Water Type (primary ions) 

CH4 ND (0.026-3 mg/L 

CH4 3 - 7 mg/L CH4 7 - 20 mg/L 

CH4 >20 mg/L 

CH 4 

3-7 

mg/L 

CH 4 

7-20 

mg/L 

CH 4 

>20 

mg/L 

Ca-HCO 3 21% 15% 9% 

Na-HCO 3 47% 47% 42% 

Na-Cl 30% 37% 44% 

Other 2% 1% 5% 

• For samples with > 3 mg/L 

methane, 81% associated 

with Na-Cl or Na-HCO 3 

water type 

• Methane > 20 mg/L, only 

9% of samples Ca-HCO 3 


Page 21

Methane and Sodium, NE PA 

10000 

1000 

max 

All NE PA Baseline Samples 

Na HAL (20 mg/L) 

Median Na 

Sodium Concentration (mg/L) 

100 

10 

1 

p90 

p75 

p50 

p25 

p10 

min 

HAL 

(20) 

0.1 

n=8,543 2,050 286 266 117 

ND ND to 3 3 to 7 7 to 20 >20 

Methane Concentration Range (mg/L) 


Methane and Chloride, NE PA 

100000 

10000 


Cl SMCL (250 mg/L) 

Median Cl 

max 

Chloride Concentration (mg/L) 

1000 

100 

10 

1 

p90 

p75 

p50 

p25/p10 

min 

SMCL 

(250) 

0.1 

n=8,543 2,050 286 265 117 

ND ND to 3 3 to 7 7 to 20 >20 



Methane and TDS, NE PA 

10000 


TDS SMCL (500 mg/L) 

max 

Median TDS 

TDS Concentration (mg/L) 

1000 

100 

10 

p90 

p75 

p50 

p25 

p10 

min 

SMCL 

(500) 

1 

n=8,543 2050 286 266 117 

ND ND to 3 3 to 7 7 to 20 >20 



Methane and Barium, NE PA 

100 

10 

max 


Ba MCL (2 mg/L) 

Median Ba 

Barium Concentration (mg/L) 

1 

0.1 

0.01 

p90 

p75 

p50 

p25 

p10 

min 

MCL 

(2) 

0.001 

n=8,543 2,050 286 266 117 

ND ND to 3 3 to 7 7 to 20 >20 



Methane and Strontium, NE PA 

100 


Sr RSL (9.3 mg/L) 

Median Sr 

Strontium Concentration (mg/L) 

10 

1 

0.1 

max 

p90 

p75 

p50 

p25 

p10 

min 

RSL 

(9.3) 

0.01 

n=2,637 710 89 62 30 

ND ND to 3 3 to 7 7 to 20 >20 








Influences on Groundwater Quality 

• Aquifer geochemistry 

• Groundwater residence 

time 

• Recharge 

• Depth 


Page 32

Overall Findings and Conclusions 

• Pre-drill sampling associated with unconventional shale-gas 

development provides regional information about natural 

occurrence and distribution of methane in groundwater 

• Presence of methane in groundwater natural and not unusual 

– Detected in 24.9% of Baseline samples 

– Exceeds PA Action Level of 7 mg/L in 3.5% of Baseline samples 

– Present throughout area sampled; differences between geologic units 

• Occurrence of methane appears associated with: 

– Geologic units 

– Depleted sulfate (i.e., redox conditions) 

– Water type (Na-HCO 3 and Na-Cl) 

– Higher concentrations of TDS, Na, Cl, Ba, Sr 

– Topographic position (NE PA) 


Page 33

Thank you! 

Stray Gas Incidence & Response Forum 

Cleveland, Ohio 

24-26 July 2012 

www.gwpc.org 

Elizabeth Perry, AECOM 

Rikka Bothun, AECOM 

Bert Smith, Chesapeake 

Mark Hollingsworth, Chesapeake

Elizabeth Perry of AECOM

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