Update of the Rationale for the Derivation of EC & SAR Standards Montana Board of Environmental Review May 13, 2011

Tongue River at State Line Station

Powder River near Moorehead, MT

Administrative and Legal Proceedings DEQ began investigating need for standards in late 1990’s BER petitioned to establish EC & SAR standards in 2002 MT used a narrative standard at the time DEQ completed an exhaustive review and administrative record, including many public meetings, BER adopted numeric standards in 2003 BER left the narrative standard in place for antidegradation significance threshold, but asked the department to consider alternative approaches Administrative and Legal Proceedings DEQ began investigating need for standards in late 1990’s BER petitioned to establish EC & SAR standards in 2002 MT used a narrative standard at the time DEQ completed an exhaustive review and administrative record, including many public meetings, a collaborative group, and hired a technical expert BER adopted numeric standards in 2003 BER left the narrative standard in place for antidegradation significance threshold, but asked the department to consider alternative approaches

BER petitioned in 2005 to establish numeric antidegradation threshold,require reinjection of produced water, and other administrative adjustments Following thorough review and development of another administrative record, BER adopted numeric antidegradation criteria, but did not adopt the requirement for reinjection WY filed suit against the Board in state district court in MT WY producers filed suit in federal district court in WY against EPA for not disapproving the MT standards MT won in state district court in MT; upheld by Montana Supreme Court WY producers won in federal district in WY

Federal judge remanded approval to EPA and found that EPA: failed to consider the entire administrative record from the state rulemaking failed to consider the entire administrative record from the state rulemaking Failed to articulate a thorough analysis for its decision Failed to articulate a thorough analysis for its decision Failed to determine whether the MT standards are based on appropriate technical and scientific data, and Failed to determine whether the MT standards are based on appropriate technical and scientific data, and Failed to provide proper notice and comment Failed to provide proper notice and comment DEQ solicited specific input on EC & SAR standards as an element of the 2010 Triennial Review Compiled about 40 studies & research projects conducted between Compiled about 40 studies & research projects conducted between day public comment period ending June day public comment period ending June comments containing 48 issues received 70 comments containing 48 issues received Comments & responses in Appendix II of Rationale Comments & responses in Appendix II of Rationale

Salinity v. Sodium 1. Salinity Typically measured as TDS or Electrical Conductivity (EC) Typically measured as TDS or Electrical Conductivity (EC) Harmful to plants Harmful to plants 2. Sodicity, typically measured in terms of proportion of Na + relative to Ca ++ & Mg ++ SAR = [Na] / ( [Ca] + [Mg] ) -2 SAR = [Na] / ( [Ca] + [Mg] ) -2 Harmful to soils with clay content Harmful to soils with clay content

EC effects depend on: Crop Crop For example, field beans can tolerate about half the soil water salinity that alfalfa can tolerate For example, field beans can tolerate about half the soil water salinity that alfalfa can tolerate Irrigation practices Irrigation practices Soil water EC tends > irrigation water EC due to evapotranspiration Soil water EC tends > irrigation water EC due to evapotranspiration “leaching fraction”, the percentage of irrigation applied in excess of crop need to carry excess salts beyond root zone “leaching fraction”, the percentage of irrigation applied in excess of crop 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)

Soil Water EC vs Irrigation Water EC with lines for different leaching fractions (Univ. Calif. Water Management pub. 3375)

Setting EC Criterion for Crop Identify: Identify: Most sensitive crop Most sensitive crop Soil water EC threshold, above which crop production starts to decline Soil water EC threshold, above which crop production starts to decline Typically more concentrated than irrigation water Typically more concentrated than irrigation water Leaching fraction necessary to protect soil from excess salt buildup Leaching fraction necessary to protect soil from excess salt buildup Determine relative proportion of irrigation water & precipitation to meet crop needs, if those needs can be fully met (Tongue) Determine relative proportion of irrigation water & precipitation to meet crop needs, if those needs can be fully met (Tongue)

Correction Factor on Tongue Effective Infiltration = (Annual Precip)(Infiltration Factor) Effective Infiltration = (Annual Precip)(Infiltration Factor) Effective Infiltration = (14.44”)0.8 = 11.5” Effective Infiltration = (14.44”)0.8 = 11.5” Agronomic need = (crop need)(leaching fraction) = (30”)1.15 = 34.5” Agronomic need = (crop need)(leaching fraction) = (30”)1.15 = 34.5” Irrigation water = Agron need – effective infiltration = 34.5” – 11.5” = 23” Irrigation water = Agron need – effective infiltration = 34.5” – 11.5” = 23” Correction Factor = (Precip + Irrig)/Irrig = Correction Factor = (Precip + Irrig)/Irrig = ( )/23 = 1.5 ( )/23 = 1.5

Calculating the EC Criterion - Tongue Target crop: Field Beans Target crop: Field Beans To maintain soil water < 1,000 us/cm To maintain soil water < 1,000 us/cm Irrigation Water needs to be < 667 (from Ayers & Westcott, 1985) Irrigation Water needs to be < 667 (from Ayers & Westcott, 1985) Apply Correction Factor (1.5) Apply Correction Factor (1.5) Criterion = (667)1.5 = 1000 Criterion = (667)1.5 = 1000

Calculating the EC Criterion - Powder Target crop: alfalfa Target crop: alfalfa Soil water must be < 2000 us/cm Soil water must be < 2000 us/cm Irrigation water must by < 2000 us/cm (Ayers & Westcott, 1985) Irrigation water must by < 2000 us/cm (Ayers & Westcott, 1985) Insufficient water available to fully meet agronomic need Insufficient water available to fully meet agronomic need Correction factor cannot be calculated Correction factor cannot be calculated Criterion = 2000 us/cm Criterion = 2000 us/cm

SAR effect depends on: Soil type Soil type Sensitivity of individual soils variable Sensitivity of individual soils variable e.g. related to amount & type of clay e.g. related to amount & type of clay MT standards drawn from published literature & independent of soil type MT standards drawn from published literature & independent of soil type Salinity of water Salinity of water EC moderates SAR effect EC moderates SAR effect However, precipitation decreases EC, but has little effect on SAR in soil water (rainfall effect) However, precipitation decreases EC, but has little effect on SAR in soil water (rainfall effect)

SAR Criterion Threshold of harm depends on salinity in the soil water Threshold of harm depends on salinity in the soil water higher the salinity the higher the SAR can be without adverse dispersive effect on the soil higher the salinity the higher the SAR can be without adverse dispersive effect on the soil however, salinity limited by crop tolerance however, salinity limited by crop tolerance Relationship published (Hanson) Relationship published (Hanson) Rainfall effect must be considered Rainfall effect must be considered

Relationship between EC and SAR

Relationship between EC and SAR (considering precipitation effects)

Tributaries Leaching only occurs once in 8 to 10 years Calculations/approach drawn from: Agricultural Drainage, 1999 deMooy & Franklin, 1977 Ayers & Westcott, 1976 Assumptions made for Initial soil salinity Water holding capacity of soil Standard of 500 us/cm results in soil salinity of 2300 to 2800 us/cm & alfalfa yield decrease of 2 to 5%

Montana Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) Standards Tongue River – Irrigation season – 1000 EC 3 SAR Tongue River – Irrigation season – 1000 EC 3 SAR Nonirrigation season – 1500 EC 4.5 SAR Powder River - Irrigation Season EC 5 SAR - Nonirrigation season – 2500 EC 7.5 SAR - Nonirrigation season – 2500 EC 7.5 SAR Tributaries EC 3 SAR

Recommendations Department finds that the great majority of the literature published since 2003 supports the need for protective numeric standards the need for protective numeric standards the manner in which they were developed the manner in which they were developed the ultimate values that the Board adopted. the ultimate values that the Board adopted. Department has not identified any basis through these recent studies, nor through the public comments received, that argue revisitation of the general approach, the numbers themselves, or the manner in which they are implemented. Department has not identified any basis through these recent studies, nor through the public comments received, that argue revisitation of the general approach, the numbers themselves, or the manner in which they are implemented. Department therefore recommends that the Board not initiate further rulemaking on the EC & SAR standards at this time Department therefore recommends that the Board not initiate further rulemaking on the EC & SAR standards at this time Department intends to submit this Rationale to EPA, and request approval of the numeric standards submitted in 2003 and 2006 Department intends to submit this Rationale to EPA, and request approval of the numeric standards submitted in 2003 and 2006

Nondegradation State Policy to protect high quality water State Policy to protect high quality water Significance determination Significance determination Carcinogens Carcinogens Toxics Toxics Harmful Harmful Narrative Narrative If significant change to water quality, then need authorization to degrade If significant change to water quality, then need authorization to degrade Includes alternatives analysis 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% 50 % Requires authoriz. to degrade Exceeds standard, No authorization to degrade allowed

Montana Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) Standards