Water Quality Standards for Protection of Irrigated Agriculture in the Powder River Basin Bob Bukantis MT Dept Environ Quality

Overview 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) development is occurring in Tongue, Powder & Rosebud watersheds in SE Montana

CBM Produced Water in Powder River Basin 2000 ~ 1 million bbls/day Likely 3 times that now ~ 62% of produced water in WY is discharged into drainages

CBM Well

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? Measure of salinity – commonly expressed as µS/cm – Ability of solution to conduct electricity As EC in soil water increases a threshold is reached where further increases in EC cause decreases in plant growth As EC in soil water increases a threshold is reached where further increases in EC cause decreases in plant growth – Different plants have different thresholds EC of the Tongue River is about 800 µS/cm EC of the Powder River is about 1,900 µS/cm EC of CBM water is about 2,000 µS/cm

EC effects depend on: – Crop Tongue Tongue –Field beans Powder Powder –Alfalfa – Irrigation practices “leaching fraction”, the percentage of irrigation applied in excess of agronomic need to carry excess salts beyond root zone “leaching fraction”, the percentage of irrigation applied in excess of agronomic need to carry excess salts beyond root zone Proportion of rainfall to irrigation water (dilutes salt concentration) Proportion of rainfall to irrigation water (dilutes salt concentration)

What is SAR & why is it important? Abundance of Sodium relative to Calcium & Magnesium Abundance of Sodium relative to Calcium & Magnesium – SAR = Na/(Ca+Mg) -2 High SAR water can cause serious long-term damage to soil structure – Adversely affects water movement into soil

Sodium Adsorption Ratio Tongue River: Tongue River: – At Wyoming border ~ 0.5 – At confluence with Yellowstone ~ 1.5 Powder River ~ 4 Powder River ~ 4 CBM produced water ~ 50 CBM produced water ~ 50

SAR Effects depend on: Soil type Soil type – Sensitivity of individual soils variable e.g. related to amount & type of clay Salinity of water Salinity of water – EC moderates SAR effect – However, precipitation decreases EC, but has little effect on SAR in soil water (rainfall effect)

Highlights 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

2002 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 – 3 rd alternative proposed by petition – Board directs parties to enter into collaborative meetings Sept: Board tour & public meetings

March 2003: CBM-related WQS adopted Numeric EC & SAR (ARM ) – Tongue, Powder & Rosebud drainages Tributaries & Tongue Reservoir Expressed as monthly averages and sample maxima – Irrigation & non-irrigation season Narrative nondeg approach (ARM (6)) Flow-based permitting (ARM (7)) Non-severability of nondeg & flow-based permitting provisions (ARM (8))

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- based CBM discharge regulation 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

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 Standards State Waters Non degradation Policy Standards (narrative or numeric) Beneficial Uses Implementation Procedures

Water Quality Standard Example 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 (6))

Nondegradation 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

Standard Ambient High Quality Nondegradation Impaired waters

Significance Thresholds Increasing Change Existing water quality: Carcinogen: any change 15% of Standard (toxics) 10%, if ambient < 40% of Standard (harmful) Standard Narrative standard: measurable 0 x effect on use or measurable change in aquatic life or ecological integrity)

Harmful Nondegradation Approach 40 % 0 Standard Allow 10%, if > 10 requires auth. to degarade 50 % Requires authoriz. to degrade Exceeds standard, No authorization to degrade allowed

Ongoing 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