Water Quality Standards for Water Quality Standards for Protection of Irrigated Protection of Irrigated

Agriculture in the Powder River Agriculture in the Powder River BasinBasin

Bob Bukantis

MT Dept Environ Quality

OverviewOverview

CBM & Need to protect irrigated agriculture Why Electrical Conductivity (EC) & Sodium

Adsorption Ratio (SAR) standards– Technical issues addressed

Process leading up to adoption of 2003 standards Petitioner’s 2005 request to the Board 2006 modifications Current challenges

The setting: Coal Bed Methane (CBM) The setting: Coal Bed Methane (CBM) development is occurring in Tongue, Powder & development is occurring in Tongue, Powder & Rosebud watersheds in SE MontanaRosebud watersheds in SE Montana

CBM Produced Water in Powder CBM Produced Water in Powder River Basin River Basin

2000 ~ 1 million bbls/dayLikely 3 times that now ~ 62% of produced water in WY is

discharged into drainages

CBM WellCBM Well

CBM development:CBM development:

Large volumes of produced water– ~ 2 bbls/mcf gas

Variable in quality, but typically– High in salts, EC ~ 2,000– Very high SAR ~ 50

What is EC & why is it important?What is EC & why is it important?Measure of salinity – commonly expressed as µS/cm

–Ability of solution to conduct electricity

As EC in soil water increases a threshold is As EC in soil water increases a threshold is reached where further increases in EC cause reached where further increases in EC cause decreases in plant growthdecreases in plant growth

–Different plants have different thresholdsDifferent plants have different thresholds

EC of the Tongue River is about 800 µS/cmEC of the Powder River is about 1,900 µS/cm

EC of CBM water is about 2,000 µS/cm

EC effects depend on:EC effects depend on:

– CropCrop TongueTongue

– Field beansField beans PowderPowder

– Alfalfa Alfalfa

– Irrigation practicesIrrigation practices ““leaching fraction”, the percentage of irrigation applied in leaching fraction”, the percentage of irrigation applied in

excess of agronomic need to carry excess salts beyond excess of agronomic need to carry excess salts beyond root zoneroot zone

Proportion of rainfall to irrigation water (dilutes salt Proportion of rainfall to irrigation water (dilutes salt concentration)concentration)

What is SAR & why is it What is SAR & why is it important?important?

Abundance of Sodium relative to Abundance of Sodium relative to Calcium & MagnesiumCalcium & Magnesium– SAR = Na/(Ca+Mg)SAR = Na/(Ca+Mg)-2-2

High SAR water can cause serious long-term damage to soil structure– Adversely affects water movement into soil

Sodium Adsorption RatioSodium Adsorption Ratio

Tongue River:Tongue River:– At Wyoming border ~ 0.5At Wyoming border ~ 0.5– At confluence with Yellowstone ~ 1.5At confluence with Yellowstone ~ 1.5

Powder River ~ 4Powder River ~ 4CBM produced water ~ 50CBM produced water ~ 50

SAR Effects depend on:SAR Effects depend on:

Soil typeSoil type– Sensitivity of individual soils variable

e.g. related to amount & type of clay

Salinity of waterSalinity of water– EC moderates SAR effectEC moderates SAR effect– However, precipitation decreases EC, but has little However, precipitation decreases EC, but has little

effect on SAR in soil water (rainfall effect)effect on SAR in soil water (rainfall effect)

HighlightsHighlights

1999– DEQ initiates discussions with WPCAC

2000 – WPCAC supports numeric standards development– Redstone MPDES Permit– DEQ initiates public scoping meetings (WQS)

Much public interest

2001– DEQ proposes to develop numeric EC & SAR

Standards

20022002

February: DEQ brings conceptual approach to WPCAC May: draft EC & SAR WQS

– Proposes numeric standards rulemaking to WPCAC WPCAC concurs

– Numeric EC & SAR standards to protect agriculture as most sensitive use

July: initiate rulemaking– 2 alternatives proposed– 3rd alternative proposed by petition– Board directs parties to enter into collaborative meetings

Sept: Board tour & public meetings

March 2003: CBM-related March 2003: CBM-related WQS adoptedWQS adopted

Numeric EC & SAR (ARM 17.30.670)

– Tongue, Powder & Rosebud drainages Tributaries & Tongue Reservoir Expressed as monthly averages and sample maxima

– Irrigation & non-irrigation season Narrative nondeg approach (ARM 17.30.670(6))

Flow-based permitting (ARM 17.30.670(7)) Non-severability of nondeg & flow-based

permitting provisions (ARM 17.30.670(8))

May 2005 Petition Proposed:May 2005 Petition Proposed:

Changes to MT Water Quality Standards:– treatment of EC & SAR as harmful rather than

narrative for nondegradation– Require use of annual 7Q10 for permit calculations – remove non-severability clause

New rules for minimum treatment requirements for CBM produced water

Zero discharge / technology-Zero discharge / technology-based CBM discharge based CBM discharge

regulationregulation

1. Reinjection (shallow aquifers) where feasible

2. When not feasible to reinject, proposed rule would have provision for waiver

– Would have required technology-based MPDES permit

– Allowed for stock water use exception

2005-62005-6

May 2005 BER petitioned June 6: WPCAC provides review & comment July 19: BER initiates rulemaking Fall 2005 BER hearings in Lame Deer, Miles City

& Helena March 2006 BER modified nondeg policy for EC

& SAR EPA approval pending

Water Quality StandardsWater Quality Standards

State Waters

Nondegradation

Policy

Standards(narrative or

numeric)

Beneficial Uses

ImplementationProcedures

Water Quality Standard Water Quality Standard ExampleExample

Beneficial Use: Irrigated Agriculture Numeric standard for SAR in Tongue River

during irrigation season is monthly average of 3 and no sample may exceed 4.5

Nondegradation Policy: “Changes in…..water quality….with respect to EC and SAR….are considered nonsignificant….provided the change will not have a measurable effect….on any….use or cause measurable changes in aquatic life or ecological integrity.” (ARM 17.30.670(6))

NondegradationNondegradation

State Policy to protect high quality water Significance determination

– Carcinogens– Toxics– Harmful– Narrative

If significant change to water quality, then need authorization to degrade– Includes alternatives analysis

0

100

10

Standard

Ambient

High Quality

Nondegradation

Impaired waters

Significance ThresholdsSignificance ThresholdsIn

crea

sing

Cha

nge

Existing water quality: Carcinogen: any changeExisting water quality: Carcinogen: any change

15% of Standard (toxics)15% of Standard (toxics)

10%, if ambient < 40% of Standard (harmful)10%, if ambient < 40% of Standard (harmful)

StandardStandard Narrative standard: measurable Narrative standard: measurable

0

xeffect on use or measurable effect on use or measurable change in aquatic life or change in aquatic life or ecological integrity)ecological integrity)

Harmful Nondegradation ApproachHarmful Nondegradation Approach

40 %

0

Standard

Allow 10%, if > 10requires auth. to degarade

50 %

Requiresauthoriz.

to degrade

Exceeds standard, No authorization to degrade allowed

OngoingOngoing

Litigation– both 2003 standards rulemaking & 2006 modifications

challenged by industry & Wyoming– Federal court (WY)

Judge granted “time out” until august for parties to come to compromise

Negotiations ongoing

– MT court Oral argument scheduled for 2 July