Colorado Mining Association Standard Framework Meeting ALUMINUM AND IRON
CMA Position - Al � Current standard based on EPA document well over 20 yrs old � New science and analyses are available: hardness based standards
State and Federal Criteria - Al � National Recommended Water Quality Criteria � Non-Priority Pollutant: � Acute (pH 6.5 – 9.0) – 750 µg/L (total recoverable) � Chronic – 87 µg/L (total recoverable) � Water-Effect Ratio may be appropriate. � Colorado Regulation 5 CCR 1002-31 � Table III Metal Parameters: � Acute – 750 µg/L (total recoverable) � Chronic – 87 µg/L (total recoverable) � Where pH ≥ 7, hardness ≥ 50 ppm in receiving water after mixing, Al will be regulated based on acute criterion.
CGS Open-File Report 00-16 Naturally Degraded Surface Waters in CO • Total recoverable Al consistently above Chronic Guideline • Several high total recoverable Al have low Dissolved Al Acute Guideline Chronic Guideline
State and Federal Criteria - Al � Arid West Water Quality Research Project � Evaluation of EPA Recalculation Procedure: � Included review of five EPA water quality criteria including Aluminum � Al criteria updates includes hardness- based relationship, similar to other metals � Provides stronger standard for measurement of potential aluminum toxicity
Updated Aluminum Acute and Chronic Values � AWWQRP (2006) with further review in June 2009 � New acute and chronic data reported � Development of hardness-based equations � More relevant to Al toxicity than current, single- value, std Mean Hardness (mg/L as CaCO 3 ) Aluminum Equations 25 50 75 100 150 200 250 Total Aluminum ( μ g/L) Updated Criteria Acute= e (1.3695 [ln 512 1,324 2,307 3,42 5,961 8,839 11,999 (hardness)]+1.8308) 1 Chronic= e (1.3695 [ln 1,37 205 530 924 2,388 3,541 4,807 (hardness)]+0.9161) 0
CMA Position - Fe � Chronic Aquatic Life Iron Standard 1.0 mg/L total recoverable iron. � Level difficult at times to meet during normal flows. � Level much more difficult during times of measurable suspended sediment. � Total recoverable does not accurately reflect amount available to aquatic life, so dissolved should be used.
State and Federal Criteria - Fe � National Recommended Water Quality Criteria � Non-Priority Pollutant: � Acute – None � Chronic – 1,000 µg/L (total recoverable) � Colorado Regulation 5 CCR 1002-31 � Table III Metal Parameters: � Acute – None � Chronic – 1,000 µg/L (total recoverable)
CGS Open-File Report 00-16 Naturally Degraded Surface Waters in CO • Total recoverable Fe consistently above Chronic Guideline Chronic Guideline
Iron –Water Quality Standard Other States � Illinois - General Use Water Quality Standard – Dissolved Fe = 1.0 mg/L � Wyoming – Aquatic Life Chronic Value - Dissolved Fe = 1.0 mg/L � Consideration to be given to dissolved rather than total recoverable
Iron – Other Issues � Current criterion based primarily on field observation – lack of guidance for deriving values based primarily on field observations � Studies for acute/chronic toxicity insufficient to derive iron criterion � A single criterion based on standard EPA Guideline derivation will not adequately describe bioavailability, toxicity and ecological effects of iron on aquatic organisms due to solubility characteristics of ferrous (soluble) and ferric (generally insoluble) iron.
Colorado Mining Association Water Quality Issues Standards Framework Work Group Presentation August 19, 2009
Low Flow: Issues � Definition of drought conditions � Incorporation of drought conditions into low flow / critical flow calculations � Flow monitoring and estimation techniques � Critical flow application during high receiving water flows (i.e., wet weather conditions)
Low Flow: Recommendations � Consider removal of drought years, or use of other protocols and data collection to assist in low flow / critical flow determination when a period of record is less than 10 years � Recommend using 30E2 (chronic) and 1E2 (acute) rather than 30E3 and 1E3 for setting water quality based effluent limits � Allow permittee to request use of monthly low flow values for all permit constituents � Allow alternate dilution flow allowances for non-continuous discharges that occur in response to storm events (“real- time” permitting)
Reasonable Potential: Issues � Statistical projection of the maximum projected effluent concentration � Accommodation of statistical outliers � Handling small effluent databases
Reasonable Potential: Recommendations � Allow 95 th percentile Multiplying Factor in combination with minimum cap of 1.0 � Expand guidance for to allow permitting options based on statistical outlier � Allow permittee to request use of effluent database of less than 10 samples for unique conditions (detectability)
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