Determining the Salinity of

Groundwater for Regulatory

Purposes in Alberta

Banff, Alberta

April 12, 2012

Brent Welsh, P.Eng. District Hydrogeologist

Alberta Environment and Water

Operations, Northern Region

Outline

• Background

• Regulatory Issue

• Methods for Determining Salinity (TDS)

• Case Studies

• Cause of Discrepancies between Methods

• Policy Direction

• Key Information

• Acknowledgements

Background (up to 1996)

• Prior to 1996: Groundwater was licensed regardless of salinity

• 1995: Definition of saline groundwater introduced

– Groundwater that has total dissolved solids (TDS) exceeding 4000 mg/L

• Exemption from licensing requirement for saline groundwater:

– Under Schedule 3 of Water (Ministerial) Regulation

• 1996: Alberta Environment and Water (AEW) stopped issuing and

renewing licences for saline groundwater

– 149 Licences were cancelled (AEW query, 2010) throughout Alberta

Background (2006-Present)

Water Conservation and Allocation Policy for Oilfield

Injection (2006)

Key Objective:

• Non-saline Water Conservation

– Minimizing use of non-saline water

where reasonable and feasible

alternatives exist

Outcome Achieved Since 2006:

• Increased Saline Aquifer Exploration

• Increased Saline Water Use

– Especially at thermal in situ oil sands

projects in Athabasca and Cold Lake

Oil Sands Areas

Deep Saline Aquifer Drilling and

Sampling Programs

Reported cost: > $1 M / well

Oil rig drilling water well Blow-out preventer

Tanking saline water at surface

Regulatory Issue

• Method for determining

TDS not specified by AEW

• Petroleum laboratories

calculate TDS by summing

major ions

• Environmental laboratories

calculate TDS by summing

major ions with gravimetric

factor for HCO3

• Results can be

significantly different for

water from same well

Methods for Determining TDS

• Measured or Gravimetric

– Filtering, evaporating sample to dryness at 180 °C, weighing residue

• Calculation

– TDS = ∑ major cations + ∑ major anions

– Same as above, but sub 0.6 x Alkalinity (mg/L CaCO3) for HCO3 + CO3

• Specific Gravity

– Approximate TDS based on specific gravity

• Conductivity Surrogate or Meter

– TDS = EC x conversion factor

Case Study 1: 1999 Licence not renewed

• 1999: Cardium Formation water source well assessed as saline

based on ∑ of major ions calculation

• 2009: Energy Resources Conservation Board (ERCB) requests re-

testing of well

– Results indicate well is non-saline based on gravimetric method

• Discrepancy in classification due to method

• Discrepancies could be 2000 mg/L TDS high (i.e., well calculated as

6000 mg/L TDS could be 4000 mg/L if measured, thereby requiring

regulation under Water Act)

Calculations from Case Study 1

• 1999 Used Σ Major Ions Method (incl. HCO3):

– TDS = 4759 mg/L

• 2009 Used Σ Major Ions with 0.6 Alkalinity for HCO3 + CO3:

– TDS = Na + K + Ca + Mg + Cl + SO4 + 0.6 x Alk = 3209 mg/L

– TDS = Σ Major Ions = 4656 mg/L

– No significant changes in Water Quality identified from 1999 - 2009

• 2009 Used Gravimetric Method (Dried at 180 oC):

– TDS = 3260 mg/L

Lab ID Na

(mg/L)

K

(mg/L)

Ca

(mg/L)

Mg

(mg/L)

Fe

(mg/L)

Cl

(mg/L)

HCO3 (mg/L)

SO4 (mg/L)

CO3 (mg/L)

T-Alkalinity

(as mg/L CaCO3)

WG38620C

(1999)

1480 3.7 6.1 1.9

Case Study 2: 2009 Referral to AEW

• Lower Grand Rapids Formation

• Operator Inquires with AEW to see

if they need a Licence

• Σ Major Ions:

– TDS = 4987 mg/L

– Ion balance acceptable

– No mud contamination

– 3 Well Volumes were purged prior

to sampling

– No Licence required?

– WRONG

• ∑ Major Ions with 0.4917 HCO3:

– TDS = 3939 mg/L

– Licence required

Case Study 2

• Same well re-sampled during pump test

• 0.6 Alkalinity Method used:

– TDS = 3860 mg/L

– Ion Balance = 0.98

• Conclusion:

– Confirmation of Licensing requirement

• SIDE NOTE:

– Using ∑ Major Ions, you get:

– TDS = 4711.8 mg/L

Why are there Method Discrepancies?

• Main cause of discrepancies is HCO3

• Some methods produce similar results

– Gravimetric method dehydrates HCO3 and off-gases CO2 and H2O

• HCO3- unstable at 100 °C

• 2HCO3- = CO3-2 + H2O(g) + CO2(g)

• i.e., 2 mol of HCO3 yields 1 mol CO3 left on pan

– 0.6 Alkalinity method accounts for HCO3 in equivalent CaCO3

• The calculation by summation varies significantly

– Method accounts for full HCO3 ion concentration

• Variations can be high enough to re-classify groundwater from saline to non-saline

Method for Determining TDS

• Policy:

Groundwater Information Letter 1/2010

Clarification of the Method Used to Calculate Total Dissolved Solids for Regulatory Purposes in Alberta

http://environment.gov.ab.ca/info/library/8547.pdf

• Purpose:

– Standardize the way TDS is measured for Regulatory Purposes

• AEW

» Water Act Licensing

• ERCB

» Base of Groundwater Protection

» Deep well disposal assessments, etc.

• Selected Method for TDS:

– Standard Methods for the Examination of Water and Wastewater

http://environment.gov.ab.ca/info/library/8547.pdf

Key Information for Labs

• Method to be used:

– Standard Methods for the Examination of Water and Wastewater,

1998 (as amended)

• TDS Gravimetric Method is 2540C (180 °C)

• TDS Calculation using 0.6 Alkalinity is 1030E

– This is a correctness check that is part of 2540C

• CAUTION: Total Solids Method is 2540B – not same as 2540C

• Alkalinity Titration Method is 2320B

Key Information for Exploration

Hydrogeologists

• Petroleum Lab Data without Alkalinity can still be useful

– USGS (Hem, 1989) suggests:

• X mg/L HCO3 x 0.4917 = Y mg/L CO3

• Use “Y” instead of “X” for ∑ Major Ions method

• This method produces results similar to Method 2540C

• When is a review of TDS data required?

– Lab results should be checked if:

• ∑ Major Ions or different gravimetric method used for TDS

– i.e., heated to 110 °C instead of 180 °C

• Water with TDScalculated > 6500 mg/L will be saline

Areas to Double Check for Compliance

Purposes

• TDS = 4000 to 6500 mg/L

– i.e., “borderline” saline or brackish

water

• High HCO3 concentrations

• Deep groundwater resources

– Grande Prairie Area

• Cardium Formation

– Athabasca Oil Sands Area

• Grand Rapids Formation

• Clearwater Formation

• Old Water Source Wells (≤ 1996)

Acknowledgments

• AEW Groundwater Policy

– Developed by Petri Nieminen, P.Chem.

– Refined by Bob Chandler, Ph.D.

• AEW Operations

– Northern Region: Glenn Winner, Patrick Murray, Catherine Evans

– Southern Region: Jeff Gutsell, Claude Eckert

• ERCB

– Elena Zimmerman

Questions?

TDS Measurement Method 2540C

Oven at

180 ± 2 °C Desiccators

Scale Filtering

Photos courtesy of Maxxam Analytics, Edmonton