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Jennie Henthorn Henthorn Environmental Services LLC.

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Presentation on theme: "Jennie Henthorn Henthorn Environmental Services LLC."— Presentation transcript:

1 Jennie Henthorn Henthorn Environmental Services LLC

2  Permit limits are in terms of total recoverable aluminum  Water quality criteria are in terms of dissolved aluminum  Applying the dissolved Al criteria as a total Al effluent limits can be overly restrictive  A translator is an attempt to fix the disparity between the dissolved criteria and total recoverable effluent limits

3  “...the fraction of total recoverable metal in the downstream water that is dissolved” The Metals Translators Guidance  Allows for higher permit limits that better reflect potential toxicity (usually, only a fraction of the total Al will be dissolved)

4 Warm water (end of pipe)Trout water (end of pipe) Ave Mon (mg/l)Max Daily (mg/l)Ave Mon (mg/l)Max Daily (mg/l)  The translator is a fraction: F d = C d /C t  The effluent limits are divided by the translator to calculate the new limits

5  Translators require a study with multiple samples  The spreadsheets used to calculate translators are changing (and hopefully will continue to do so…)  Study must be well designed  Decisions on how to proceed can be evasive.

6  Translator must be protective of critical flow  this is not the necessarily the same as 7Q10 flow  The amount of dissolved Al is dependent on parameters such as TSS, pH, hardness  sampling should occur when the combination of parameters makes it so there is the most dissolved Al in stream  this is “critical flow” or “design flow”

7  But… no way to determine what these conditions are without a separate study – and results can be less than clear  DEP has determined that the default “critical” flow is when precipitation induced discharges are not occurring. ◦ Low flow usually has low TSS = higher dissolved Al ◦ Simplifies preparation and review of a study plan

8  Time/season of sampling  Low flow is usually July- October in WV  DEP now requires 20 samples collected no more frequently than once per two weeks.  The time to collect samples can easily stretch to a year or more due to precipitation requirements.

9  EPA guidance suggest sampling should occur at edge or beyond mixing zone  But…in most circumstances for mining permits, no mixing zone is usually available (EOP limits)  Often, the nearest downstream monitoring point used for instream sampling is used.  Watershed approach may be more appropriate

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13  Take a sample or two – make some informed decisions  Prepare a sampling plan and get DEP’s approval  Remember, translators are not just for aluminum! Do you need to consider other parameters? Choose your path carefully, or you may fall flat on your face (or worse)

14  Dissolved Al  Total Al  TSS  Precipitation  Hardness  Others “A complete data set allows for more complete understanding of the environmental fate and transport processes and may result in a more accurate permit limit because of reduced variability and uncertainties.” EPA guidance

15  Recall that, translator is determined by dividing the dissolved Al by the total Al  this gives the translator for each sample ◦ f D =C D /C T This means that you have different translators- how do you decide which one to use for determining permit limits???

16  Determine if translators are lognormally distributed (Shapiro-Wilks)  Determine if translators are TSS-dependent using regression analysis ◦ If translators are lognormally distributed and are NOT TSS-dependent, use the geometric mean for permit limit caculations But what if the translators are not log-normal????

17  Attempt to make translators lognormal by transforming the data (arcsine square root) ◦ If translators are lognormal transformed and NOT TSS-dependent, use the transformed geometric mean for permit limit calculations OR  Use the 95 th percentile of the translators But what if the translators are TSS-dependent?

18  Although sampled at low flow, translators will be used over a wide variety of flows and TSS concentrations  Translators can be developed relating dissolved Al to other parameters, such as pH or hardness   TSS usually has the largest influence and therefore is the focus of EPA guidance

19  Develop regression equation relating TSS and translator  Use “critical TSS” in regression equation to determine appropriate translator ◦ The critical TSS is representative of a TSS that would give the highest dissolved Al in the stream ◦ The EPA guidance gives little information on how to determine critical TSS OR  Use the 95 th percentile of the translators

20  Use DEP’s current spreadsheet to calculate effluent limits!

21  Requires 20 samples exactly  Determines if data is lognormal using Shapiro-Wilks  Determines if data are TSS-Dependent  Requires rain data to determine critical flow

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25  Only accepts data taken during critical flow ◦ If a TSS-dependent equation is being developed, critical flow should not be used ◦ Uses only one method for determining “critical” flow – other methods include TSS concentration, and 25 th percentile of low-flow  Does not have a regression equation for TSS- dependent translators ◦ If translators are TSS-dependent, it defaults to using the 95 th percentile

26  If data are not lognormal, spreadsheet does not determine if data are lognormal transformed The combination of these problems amounts to using the 95 th percentile as a default, when other values may be equally defensible (regression equation, transformed geometric mean).

27  Addition of lognormal transformed calculation  Addition of regression analysis for TSS- dependent data sets  Potentially the addition of using the arithmetic mean when data are normally distributed (and not TSS-dependent) These changes will determine translators that more accurately represent the stream!

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