streamlined water-effect ratio procedure for discharges of copper · 2018. 10. 24. · values for a...

United StatesEnvironmental ProtectionAgency

Office of Water4304

EPA-822-R-01-005March 2001

StreamlinedWater-Effect Ratio Procedurefor Discharges of Copper

StreamlinedWater-Effect Ratio Procedure

for Discharges of Copper

March 2001

U.S. Environmental Protection AgencyOffice of Water

Office of Science and TechnologyWashington, D.C.

Notices

This document provides guidance to states and tribes authorized to establish andimplement water quality standards under the Clean Water Act (CWA), to protectaquatic life from acute and chronic effects of copper. Under the CWA, states andtribes are to establish water quality criteria to protect designated uses. The CWAand EPA regulations at 40 CFR Part 131 contain legally binding requirements. Thestatutory provisions and EPA regulations described in this document containlegally binding requirements. This document does not substitute for the CWA orEPA’s regulations; nor is it a regulation itself. Thus, it does not impose legallybinding requirements on EPA, states, tribes, or the regulated community, and maynot apply to a particular situation based upon the circumstances. State and tribaldecision makers retain the discretion to adopt approaches on a case-by-case basisthat differ from this guidance when appropriate. Therefore, interested parties arefree to raise questions and objections about the substance of this guidance and theappropriateness of the application of this guidance to a particular situation. EPAwill, and States should, consider whether or not the recommendations orinterpretations in the guidance are appropriate in that situation. While thisguidance constitutes EPA’s scientific recommendations on procedures forobtaining site-specific values for aquatic life criteria for copper, EPA may changethis guidance in the future.

This document has been approved for publication by the Office of Science andTechnology, Office of Water, U.S. Environmental Protection Agency. Mention oftrade names or commercial products does not constitute endorsement orrecommendation for use.

Acknowledgment

This document was prepared by Charles Delos, Health and Ecological CriteriaDivision, Office of Science and Technology. Appendix A was adapted andmodified from the 1994 document Interim Guidance on the Determination andUse of Water-Effect Ratios for Metals, which had been prepared by CharlesStephan and others. Appendix B is based primarily on a literature review by GaryChapman of the Great Lakes Environmental Center.

Peer review of this document was performed by Paul Jiapizian of the MarylandDepartment of Environment, William Dimond of the Michigan Department ofEnvironmental Quality, and Cindy Roberts of U.S. EPA. This is documented inResponse to Peer Review Comments on Streamlined Water-Effect Ratio forDischarges of Copper, available in portable document format (pdf) from thecontact below.

Please submit questions to: Charles Delos, U.S. EPA, Mail Code 4304,Washington, DC 20460 (e-mail: [email protected]).

Contents

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Synopsis of the Streamlined Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Discussion of Technical Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Appendix A. Sampling and Testing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Appendix B. Species Mean Acute Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Appendix C. Assessment of Streamlined Procedure . . . . . . . . . . . . . . . . . . . . 23

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Introduction

This guidance presents a StreamlinedProcedure for determining site-specificvalues for a Water-Effect Ratio (WER), acriteria adjustment factor accounting for theeffect of site-specific water characteristics onpollutant bioavailability and toxicity toaquatic life. This guidance is intended tocomplement the 1994 Interim Guidance onDetermination and Use of Water-EffectRatios for Metals (EPA-823-B-94-001).

Whereas the 1994 Interim Procedure appliesto essentially all situations for most metals,the Streamlined Procedure is recommendedonly for situations where copperconcentrations are elevated primarily bycontinuous point source effluents. Becausethis is a relatively common regulatorysituation, a great deal of experience isavailable to guide the development of a moreefficient procedure.

The Streamlined Procedure does notsupersede the 1994 Interim Procedure, evenfor the limited situations to which it applies. Rather, it provides an alternative approach. In these situations the entity conducting thestudy may choose between using the InterimProcedure or using the StreamlinedProcedure.

Synopsis of the Streamlined Procedure

The Streamlined Procedure involves thesampling of two events, spaced at least onemonth apart. Flow during each event shouldbe stable, and water quality unaffected byrecent rainfall runoff events. Samples ofeffluent and upstream water are to be taken. These are mixed at the design low-flowdilution, to create a simulated downstreamsample, to be used as the site-water sample

in toxicity tests spiked with variousconcentrations of soluble copper salts.

In manner similar to the Interim Procedure,the side-by-side, laboratory-water and site-water toxicity tests are run to obtain the 48-hour acute EC50 with either Ceriodaphniadubia or Daphnia magna. The result may beexpressed as either dissolved or totalrecoverable copper. After adjusting for anyhardness differences, the WER for thesample is the lesser of (a) the site-waterEC50 divided by the laboratory-water EC50,or (b) the site-water EC50 divided by thedocumented Species Mean Acute Value (themean EC50 from a large number ofpublished toxicity tests with laboratorywater). The geometric mean of the two (ormore) sampling event WERs is the siteWER.

The design of the Streamlined Procedure isintended as a more efficient approach forgenerating the information needed to make apollution control decision. The intent is toprovide a method that is both easier for theperforming organization to carry out, andeasier for the regulatory agency to review. The Streamlined Procedure omits laboratoryor field measurements that experience withthe Interim Procedure has shown to be oflittle practical value. The design is alsointended to be inherently less subject torandom sampling variability, therebyallowing a reduction in the number ofsamples while maintaining reliability.

Table 1 compares the provisions of theStreamlined Procedure with those of the1994 Interim Procedure.

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Table 1. Comparison of Streamlined Procedure and 1994 Interim Procedure

Characteristic 1994 Interim Procedure Streamlined Procedure

Applicability Universal Copper from continuousdischarges

Minimum number ofsampling events

3 2with recommended restrictions

Minimum number of WERmeasurements

4 2

Minimum number of WERmeasurements consideredin obtaining final site WER

3 2

Preparation of constructeddownstream water

Mix effluent and upstreamsamples at the dilution ratiooccurring at the time ofsampling

Mix effluent and upstreamsamples at the design low-flowdilution ratio

Calculation of sampleWER

Site water LC ÷ Lab water LC Site water LC ÷ The greater of (a) Lab water LC, or (b) SMAV

Calculation of final siteWER

Complicated scheme withsix “if...then...else” clauses and12 possible paths

Geometric mean of the twomeasurements

Discussion of Technical Approach

The key facets of the procedure arepresented below, with an explanation of theirpurpose. The detailed protocol forcollecting samples, obtaining measurements,and conducting tests is presented inAppendix A. An analysis, through MonteCarlo simulation, of the protectiveness of theapproach is presented in Appendix C.

1. Purpose of procedure. The procedure isfor deriving a dissolved and/or totalrecoverable WER for copper from

continuous point source effluents. Theresults may be used to obtain:a. A dissolved WER used to obtain the

site-specific value of a dissolvedcopper criterion.

b. A total recoverable WER used toobtain either (i) the site-specific valuefor a total recoverable criterion, or(ii) a total recoverable effluent limitfrom a dissolved criterion, mergingthe functions of a dissolved WER anda dissolved-to-total permit translatorfactor.

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Commentary: If obtained from dissolvedcopper EC50s, the site WER multipliedby the national or state’s hardness-normalized dissolved criterion becomesthe site value of the dissolved coppercriterion. Likewise, if obtained fromtotal recoverable measurements, theWER is used to obtain the site value ofthe total recoverable criterion. A totalrecoverable WER may be applied to adissolved criterion by first converting thedissolved criterion to a total recoverablecriterion, then multiplying by the WER. In this case it eliminates the permit-specific dissolved-total translator factorby replacing the original dissolvedcriterion with a site-specific totalrecoverable criterion.

2. Recommended applicability of theStreamlined Procedure. The procedureis designed to apply to regulatorysituations where most of the copper isfrom continuous point source effluents. The procedure is not designed forregulatory situations where the copperoriginates primarily from wet weather ornonpoint sources.

Commentary: The StreamlinedProcedure is intended to apply tosituations where the copper from theregulated discharge is expected to attainits maximum concentrations under low-flow or low-dilution conditions. Continuous point source discharges fitthis pattern. The most common suchsituation involves municipal effluents,which past experience and currentknowledge have generally shown to yieldlow risks for copper toxicity, due to thesequestering of copper by organicmatter. Nevertheless, the procedure isjust as suitable for non-municipal pointsource effluents.

The Streamlined Procedure should not beapplied to situations where elevatedcopper concentrations are the result ofwet weather runoff. In this case thecritical copper concentrations may notoccur under low-flow conditions, suchthat the Streamlined Procedure’s focuson simulating low-flow conditions wouldnot be appropriate.

3. Collection of samples. Sampling forWER measurements involves:a. Two sampling events, at least one

month apart, and as recommendedbelow,

b. Samples of upstream and effluentduring each event.

Commentary: The Interim Procedurecalls for sampling three events. TheStreamlined Procedure, by more focusedsampling, can achieve equivalentreliability using samples of two events, asindicated by the Monte Carlo modelingpresented in Appendix C.

4. Plant performance during samplingevents should be as follows:a. Average or better operating

conditions,b. CBOD (carbonaceous biochemical

oxygen demand) and suspendedsolids concentrations within permitlimits.

Commentary: Because the WER issensitive to the concentration of organicmatter being discharged, the plant shouldbe operating normally, as measured byCBOD and suspended solids discharges.

5. Stream conditions during samplingevents should be as follows:a. Stable flow condition, preferably

during a drier weather season

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(wherever regulatory schedulesallow).

b. Water quality conditions should becompatible with those occurringduring time periods when nonpointsource inputs of organic matter andsuspended solids are relatively low.

Commentary: Sampling of events withelevated runoff is not desirable becauseof the confounding influences ofnonpoint inputs that would not bepresent under low flow conditions. Because the upstream and effluentsamples are to be mixed at a ratioequivalent to the low flow dilution, theupstream water quality should not begreatly dissimilar to the quality expectedduring low flow conditions. Upstreamwater quality is of greater concern ifthere is a substantial fraction of upstreamwater present during the design low-flowevent, and if a total recoverable WER isto be used. Conversely, where littleupstream water is to be used in creatingthe simulated low-flow downstreamsample, or if a dissolved WER is to beapplied, the quality of the sampledupstream water is less important.

6. Merging of effluent and upstreamsamples. The effluent and upstreamsamples are to be combined at thedilution corresponding to the design low-flow condition that the permittingauthority uses in permit limitcalculations.

Commentary: Extensive data from theState of Connecticut (discussed in theSupplement to Appendix C) indicate norelationship between upstream dissolvedcopper WER values and streamflow. Consequently, for continuous dischargesthe critical condition, that conditionwhere the copper concentration can be

expected to be highest relative to theWER, should be expected to occur atlow dilution. The most efficient way(and often the only feasible way) topredict conditions at low flow is to mixthe upstream and effluent samples at thelow-flow dilution ratio.

By contrast, the 1994 Interim Procedurecalled for mixing the samples at thedilution occurring during the samplingevent. The Interim Procedure was,however, a general purpose procedure,not restricted to the situations to whichthe Streamlined Procedure applies. TheInterim Procedure thus also applies tosituations where there is littleunderstanding of what flow conditionscould be critical.

By restricting the use to well understoodsituations, the Streamlined Procedure hasbeen designed to be more efficient and itsresults more predictable than the InterimProcedure. Monte Carlo simulationindicates that the Streamlined Procedure,under the conditions to which it applies,is less subject to chance variation(sampling error) than the InterimProcedure.

7. Chemical analyses.a. Dissolved and/or total copper

concentrationb. Hardness, alkalinity, pH, dissolved

organic carbon, and total suspendedsolids

Commentary: The method may beapplied to either dissolved or totalcopper. If applied to dissolved copper,the permit authority will need to derive atranslator in order to derive a totalrecoverable permit limit. If applied tototal copper, there is no need for atranslator.

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Hardness measurements are needed tonormalize the laboratory water and site-water EC50s to the same hardness. Theremaining measurement parametersprovide ancillary information forunderstanding the chemistry influencingthe observed results and for providing alink with the Biotic Ligand Model, whichis ultimately intended to replace theWER toxicity test procedures for copper.

8. Toxicity testing.a. Tested taxon: Either Ceriodaphnia

dubia or Daphnia magna.b. Test: 48-hr EC50, spiking with

copper sulfate, nitrate, or chloride.c. Side-by-side tests in laboratory

dilution water and site water.

Commentary: These stipulations aremore specific than those of the InterimProcedure. Experience has shown thatthe daphnids, which are quite sensitive tocopper, have been the most useful testorganisms for WER studies. Furthermore, for these two species thereis a substantial amount of data on therange of EC50s observed in laboratorywater.

Other daphnid species, such as Daphniapulex, probably have similar sensitivity,but have not been recommended herebecause they have fewer data availablefor estimating the appropriate value ofthe Species Mean Acute Value. Othertest species, either fresh or saltwater,could be substituted, provided that ampledata were available to determine theappropriate SMAV. There is notechnical reason why the approach couldnot be extended to saltwater copper testsor to other metals in fresh or saltwater. The current document’s focus onfreshwater copper stems from the greaterdemand for a streamlined procedure

among the numerous freshwater copperdischargers.

The 1994 Interim Procedurerecommendation for a test with a secondspecies has been dropped, because theadditional test has not been found tohave value.

The simultaneously measured laboratorywater EC50, as presented in the detailedprotocol (Appendix A), is necessaryunless the state substitutes a rigorousreference toxicant program involvingcopper.

9. Analysis of data.a. For site-water samples, if there is less

than 50 percent mortality at thehighest copper treatmentconcentration, then assume that theEC50 is the highest treatmentconcentration.

b. The sample WER is the lesser of (i)the site-water EC50 divided by thelab-water EC50, or (ii) the site-waterEC50 divided by the Species MeanAcute Value (from Appendix B).

c. Final site WER is the geometric meanof the two (or more) sample WERs.

d. The acute and chronic criteriaconcentrations for the site are thenational criteria concentrations (orcomparably derived state values)multiplied by the final site WER.

Commentary: (a) As in the InterimProcedure, it is not necessary to ascertainthe precise value of the WER, if theactual WER is greater than the range ofvalues of regulatory interest. (b) TheStreamlined Procedure eliminates onesource of concern about the InterimProcedure: the variability and apparentnon-protective bias of the lab waterordinarily used in the side-by-side tests.

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(c) Monte Carlo modeling indicates thatuse of the geometric mean of the twosamples can be expected to yield acriterion as protective as or moreprotective than intended for chemical-specific criteria. (d) In accord with the1994 Interim Guidance and withcommon practice, the WER derived fromacute tests is applied to both acute andchronic criteria. Because theinvolvement of strong binding agentscauses the WER to increase as the effectconcentration decreases, the WERderived from acute tests is expected to beprotective of chronic effects.

Implementation

Implementation policies for the StreamlinedProcedure are the same as for the 1994Interim Procedure. WER-based site-specificcriteria provisions are subject to EPA reviewunder Section 303(c) of the Clean Water Actand its implementing regulations at 40 CFRPart 131. This can be structured in twoways.

1. A state may submit each individualdetermination of a WER-based site-specific criteria value to EPA for reviewand approval.

2. A state may incorporate WERadjustment provisions into its waterquality standards, submitted to EPA forreview and approval. Once theprovisions are in place, the results ofeach site-specific application of theprocedure would be subject to publicparticipation requirements, but would notbe submitted for further Section 303(c)review.

In all cases, it should be noted that the WERderivation is part of the standards settingprocess. In the absence of an appropriatespecification of the site criterion, WERs arenot used for adjusting reasonable potentialcalculations, wasteload allocations, or permitlimits.

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Appendix A

Sampling and Testing Protocol for the Streamlined WER Procedure

The procedure set forth below is for derivinga WER for copper discharged to fresh waterprimarily from continuous point sourceeffluents, using Daphnia as the test taxon.

A. Background Information

1. Obtain information on the mean flowand design dilution flow for the waterbody segment for which the WER isbeing determined. If the proposedeffluent limit was calculated using time-variable modeling without reference to aparticular design low flow, then forpurposes of applying the StreamlinedProcedure, use the design flow that thestate customarily applies to steady-statedilution calculations.

2. Estimate the values of the site-specificcriterion and WER corresponding to keydecision points, for example, theminimum values needed for thedetermination of “no reasonablepotential”, upon which depends the needfor copper permit limits.

3. Consult the state or tribal pollutioncontrol agency in order to assure thatthe study will respond to all concernswith respect to the peculiarities of thespecific site.

B. Acquiring and Acclimating TestOrganisms

1. Obtain, culture, hold, acclimate, feed,and handle the test organisms asrecommended by U.S. EPA (1993)and/or by ASTM (1999, 2000a, 2000b).

2. Acclimation to the site water is desirablebut optional.

C. Collecting and Handling UpstreamWater and Effluent

1. Obtain samples during two (or more)sampling events, spaced at least fourweeks apart. When regulatoryschedules allow, schedule events for aseason when low streamflows are morelikely to occur.

2. For each sampling event, obtain arepresentative sample of upstreamwater, relatively unaffected by recentrunoff events that might elevate the totalsuspended solids and organic matterconcentrations.

3. For each sampling event, obtain arepresentative sample of effluent duringa period when the discharger isoperating normally, relatively unaffectedby short-term perturbations due torainfall inflow or slug loads. Compositesamples are preferred over grab samples.

4. Collect, transport, handle, and storesamples as recommended by U.S. EPA(1993). Obtain a sufficient volume sothat some can be stored for additional

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testing or analyses if unusual results areobtained. Store samples at 0 to 4°C in thedark with no air space in the samplecontainer.

5. During the sampling event, measureeffluent parameters that are normallyrequired to be reported in the DischargeMonitoring Report for the dischargeunder study. These measurementsprovide information on therepresentativeness of the effluentsamples.

6. For the sampling event, obtainstreamflow data at the nearest relevantgaging station, and rainfall data and anyother relevant meteorologicalinformation for the preceding twoweeks.

7. Consider using chain of custodyprocedures for all samples of site waterand effluent.

8. Begin toxicity tests as soon as practical,but always within 96 hours aftercollecting samples, in accord with EPA(1993) recommendations for using sitewater for the dilution water. Becausethese tests are not intended formeasurement of whole effluent toxicity(which might attenuate over time), it isnot essential to begin tests within 36hours after the collection of the samples(as would be recommended by EPA(1993) for measuring the toxicity of aneffluent). This is a change from the1994 Interim Procedurerecommendation.

9. If the site water might contain predatorsof the daphnid test organisms, removethem by filtering through a 37-60 µmsieve or screen.

D. Laboratory Dilution Water

1. Use laboratory water that accords withU.S. EPA (1993) or ASTM (1999,2000a). Use ground water, surfacewater, reconstituted water, dilutedmineral water, or dechlorinated tapwater that has been demonstrated to beacceptable to aquatic organisms. If asurface water contains predators,remove them by filtering through a 37-60 µm sieve or screen. Do not usewater prepared by such treatments asdeionization or reverse osmosis unlesssalts, or mineral water are added asrecommended by U.S. EPA (1993) orASTM (1999, 2000a).

2. Do not use laboratory water with DOC,TOC, or TSS >5 mg/L.

3. Use laboratory water with hardnessbetween 40 and 220 mg/L. Within theseranges use laboratory water withhardness relatively close to that of thesite water.

4. The alkalinity and pH of the laboratorydilution water is to be appropriate for itshardness. Values for alkalinity and pHthat are appropriate for some values ofhardness are given by U.S. EPA (1993)and ASTM (1999, 2000a); othercorresponding values should bedetermined by interpolation. Ifnecessary, adjust alkalinity using sodiumbicarbonate, and pH using aeration,sodium hydroxide, and/or sulfuric acid.

E. Conducting Tests

1. Conduct the tests such that there are nodifferences between the side-by-sidetests other than the composition of the

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dilution water, the concentrations of metaltested, and possibly the water in which thetest organisms are acclimated just prior tothe beginning of the tests.

2. A single laboratory water test may becompared with tests of multiple sitewater samples conducted side by side.

3. Follow the recommendations of U.S.EPA (1993) and/or ASTM (1999,2000a, 2000b) regarding setting upfacilities for conducting toxicity testsand selecting and cleaning the testchambers.

4. Prepare a stock solution of copperchloride 2-hydrate (CuCl2@2H2O),copper nitrate 2.5-hydrate(Cu(NO3)[email protected]), or copper sulfate 5-hydrate (CuSO4@5H2O).

a. Use reagent-grade material.b. Only as necessary to get the

metal into solution, acidify thestock solution using metal-freenitric acid.

c. Use the same stock solution forall tests conducted at one time.

5. In the unusual situation where theeffluent is dominated by highly stablemetallo-organic compounds, such ascopper phthalocyanine dyes, then anexception to using the above listedcopper salts may be considered. That is,it may be acceptable to include themetallo-organic compounds in the stocksolution. In such case, prepare the stocksolution such that the stable metallo-organic compounds constitute the samepercentage of total copper in the stocksolution as in the site water to be WERtested. This exception to the usualprocedure requires case-by-case reviewof its appropriateness, afterdocumenting the usual presence of the

compounds in the effluent, the stabilityof the compounds, and the importanceof distinguishing the compounds fromother forms of copper.

6. Run the 48-hour test with Ceriodaphniadubia or Daphnia magna to obtain anEC50 (U.S. EPA 1993; ASTM 1999,2000a, 2000b), using a sufficient volumeto accommodate the needed chemicalmeasurements. With appropriatemodification of the protocol, other testspecies may be substituted on a case-by-case basis, only if (a) the daphnidSMAV is either significantly below thesite criterion obtained by theRecalculation Procedure, or daphnia isnot viable at the site water salinity; and(b) there is sufficient data to establish anSMAV with high reliability.

7. Static tests may be used if dissolvedoxygen remains sufficient, and if either(a) measured dissolved copperconcentrations do not decrease morethan 50 percent by the end of a testintending to use the dissolved coppermeasurements as the basis for the WER,or (b) total recoverable concentrationsare to be used as the basis for the WER.

8. Renew the test solutions after 24 hoursif either (a) dissolved oxygen woulddecrease too much, or (b) dissolvedcopper would decrease more than 50%by the end of a test intended for adissolved WER, or (c) the analyst favorsrenewal for any other reason. a. If solutions in one test in a pair of

side-by-side tests are renewed,renew solutions in the other test aswell.

b. To renew site water solutions,prepare new test solutions from theremaining site water sample(s)stored at 0 to 4°C in the dark.

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9. Follow recommendations ontemperature, loading, feeding, dissolvedoxygen, aeration, disturbance, andcontrols given by U.S. EPA (1993)and/or ASTM (1999, 2000a, 2000b).

10. Use range-finding tests, of 8 to 48-hourduration where necessary and wherethey will not unduly delay the beginningof the test.

11. Use a dilution factor of 0.6 or greaterfor nominal concentrations, balancingfor the particular situation the needs forcovering the range of possible results,reducing the uncertainty in thecalculated EC50, and curbing the cost ofthe test. The value of the WER neededfor a “no reasonable potential”determination or other decisionbenchmarks should be kept in mind inselecting the dilution series. Withregard to the risk that the dilution serieswill not span the possible range of theEC50, note that in site water (a) a “lessthan value” for the EC50 would beunusable for obtaining a WER>1, and(b) a “greater than” value” for the EC50would be interpreted as “equal to” incalculating the WER. In contrast, in labwater (c) a “greater than value” for theEC50 would be unusable for obtaining aWER>1, (d) a “less than value” for theEC50 would be interpreted as “equalto”; however, (e) the SMAV fromAppendix B would be used in place ofany lab water EC50 less that SMAV.

12. Use an unspiked dilution water controlfor each test.

13. Use at least 20 organisms for eachtreatment concentration (includingunspiked controls). It is desirable to usetwo or more test chambers per

treatment. Assign test organismsrandomly, or at least impartially to theside-by-side tests, and to all treatmentchambers (U.S. EPA 1993; ASTM1999, 2000a). When assigningimpartially, do not place more than 20%of any chamber’s total number oforganisms at one time. In addition, thetest chambers should be assigned tolocation in a random arrangement or in arandomized block design.

14. Use appropriate glassware for makingserial dilutions, such as graduatedcylinders, volumetric flasks, andvolumetric pipettes.

15. For the test using site water, mixeffluent and upstream waters to accordwith the design dilution, correspondingto the upstream design flow and effluentflow normally used for steady statemodeling calculations. Generally useany one of the following procedures toprepare the test solutions for the testchambers and the "chemistry controls",if any (see section F.1):a. Thoroughly mix the sample of the

effluent and place the same knownvolume of the effluent in each testchamber; add the necessary amountof metal, which will be different foreach treatment; mix thoroughly; letstand for 2 to 24 hours (ifovernight, keep at 0 to 4°C); addthe necessary amount of upstreamwater to each test chamber; mixthoroughly; let stand for 1 to 3hours.

b. Add the necessary amount of metalto a large sample of the effluent andalso maintain an unspiked sample ofthe effluent; perform serial dilutionusing a graduated cylinder and thewell-mixed spiked and unspikedsamples of the effluent; let stand for

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2 to 24 hours (if overnight, keepat 0 to 4°C); add the necessaryamount of upstream water toeach test chamber; mixthoroughly; let stand for 1 to 3hours.

c. Prepare a large volume of simulateddownstream water by mixingeffluent and upstream water in thedesired ratio; place the same knownvolume of the simulateddownstream water in each testchamber; add the necessary amountof metal, which will be different foreach treatment; mix thoroughly andlet stand for 1 to 4 hours.

d. Prepare a large volume of simulateddownstream water by mixingeffluent and upstream water in thedesired ratio; divide it into twoportions; prepare a large volume ofthe highest test concentration ofmetal using one portion of thesimulated downstream water;perform serial dilution using agraduated cylinder and the well-mixed spiked and unspiked samplesof the simulated downstream water;let stand for 1 to 4 hours.

Procedures "a" and "b" allow the metalto equilibrate with the effluent beforethe solution is diluted with upstreamwater.

16. For the test using the laboratory dilutionwater, either of the followingprocedures may be used to prepare thetest solutions for the test chambers andthe "chemistry controls" (see sectionF.1):a. Place the same known volume of

the laboratory dilution water in eachtest chamber; add the necessaryamount of metal, which will bedifferent for each treatment; mix

thoroughly; let stand for 1 to 4hours.

b. Prepare a large volume of thehighest test concentration in thelaboratory dilution water; performserial dilution using a graduatedcylinder and the well-mixed spikedand unspiked samples of thelaboratory dilution water; let standfor 1 to 4 hours.

17. Add the test organisms, acclimated persection B.1, to the test chambers for theside-by-side tests at the same time.

18. Observe the test organisms and recordthe effects and symptoms as specified byU.S. EPA (1993) and/or ASTM (1999,2000a).

F. Chemical and Other Measurements

1. To reduce the possibility ofcontamination of test solutions before orduring tests, do not place thermometersand probes for measuring pH anddissolved oxygen into test chambers. Rather, perform such measurements on"chemistry controls" that contain testorganisms or on aliquots that areremoved from the test chambers. Theother measurements may be performedon the actual test solutions at thebeginning and/or end of the test or therenewal.

2. Measure hardness, pH, alkalinity, TSS,and DOC for the tested site water andthe laboratory dilution water.

3. Measure dissolved oxygen, pH, andtemperature during the test at the timesspecified by U.S. EPA (1993) and/orASTM (1999, 2000a, 2000b), using thesame schedule for both of the side-by-

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side tests. If chemistry controlsare used, obtain measurements onboth the chemistry controls andactual test solutions at the end ofthe test.

4. For a dissolved WER calculated fromdissolved measurements, measuredissolved copper in the appropriate testsolutions. For a total recoverable WER,measure total recoverable copper. It isdesirable but not essential for bothdissolved and total recoverable copperto be measured. EPA methods (U.S.EPA 1997, 1999) are recommended. Inany case use appropriate QA/QCtechniques to assure attaining the targetlevel of accuracy.a. Rather than measuring the metal

in all test solutions, it is oftenpossible to store samples and thenanalyze only those that are neededto calculate the results of thetoxicity tests. Measure (i) allconcentrations in which some, butnot all, of the test organisms wereadversely affected, (ii) the highestconcentration that did notadversely affect any testorganisms, (iii) the lowestconcentration that adverselyaffected all of the test organisms,and (iv) the controls.

b. For total recoverable copper,measure once for a static test, ortwice for a renewal test (once perday). For measurement of totalrecoverable copper in the testchamber, mix the whole solutionin the chamber before the sampleis taken for analysis. Do notacidify the solution in the testchamber before the sample istaken. Rather, acidify after it isplaced in the sample container.

c. Measure dissolved metal at thebeginning and end of a static test,or at the beginning and end of thefirst day in a renewal test (that is,just before renewal). Formeasurement of dissolved metal ina test chamber, mix the wholesolution in the test chamber beforeremoving a sufficient amount forfiltration. Do not acidify beforefiltration. Filter the sample withinon hour after it is after it is taken,then acidify the filtrate.

5. Perform QA/QC checks.

G. Calculating and Interpreting theResults

1. Evaluate the acceptability of eachtoxicity test individually.a. Reject tests where deviations from

the above presented laboratorypractices are substantial,particularly with respect toacclimation, randomization,temperature control, measurementof metal, and/or disease ordisease-treatment.

b. Reject tests where more than 10percent of the organisms in thecontrols were adversely affected.

2. Calculate the EC50 using methodsdescribed by U.S. EPA (1993) orASTM (1999, 2000a). If two or moretreatments affected between 0 and 100percent in both tests in a side-by-sidepair, use probit analysis to calculateresults of both tests, unless the probitmodel is rejected by the goodness of fittest in one or both of the acute tests. Ifprobit analysis cannot be used, eitherbecause fewer than two percentages arebetween 0 and 100 percent or because

13

the model does not fit the data, usecomputational interpolation; do not usegraphical interpolation. Use the samecomputational method for each of the side-by-side tests.

3. For laboratory water:a. Calculate or assign the EC50 for

the lab water only if the percent ofthe organisms that were adverselyaffected is greater than 50 percentin at least one treatment (althoughit is preferable if at least 63percent of organisms wereaffected). That is, if there isinsufficient toxicity at allconcentrations in the laboratorywater, the side-by-side tests arenot usable for obtaining aWER>1.

b. If no treatment other than thecontrol affected less than 50percent of the test organisms, setthe EC50 equal to the lowest testconcentration (preceded by <sign) . That is, if there isexcessive toxicity at all testedconcentrations (except thecontrol), the laboratory waterEC50 is known only to be lessthan the lowest treatmentconcentration.

c. If the hardness-normalized EC50in laboratory water is less than thedocumented SMAV for thespecies, then use the SMAV inplace of the laboratory waterEC50 in the dominator of theWER. See Appendix B for theSMAVs for Ceriodaphnia dubiaand Daphnia magna.

4. For site water:a. Calculate or assign the EC50 for

the site water only if the percentof the organisms that were

adversely affected is less than 50percent in at least one treatment(although it is preferable if lessthan 37 percent of organisms wereaffected). That is, if there isexcessive toxicity at all testedconcentrations in site water, thesample is not usable for obtaininga WER>1.

b. If no treatment affected more than50 percent of the test organisms,set the EC50 equal to the highesttest concentration (preceded by >sign). That is, if there isinsufficient toxicity at all testedconcentrations, the site waterEC50 is known only to be greaterthan the highest treatmentconcentration.

5. In reporting results, highlight anythingunusual or questionable about the testfindings.a. Report if dissolved metal

decreased by more than 50percent from the beginning to theend of a 48-hour static test.

b. Report if there were inversions inthe data for more than twoconcentrations in the range of 20to 80 percent mortality (or asmodified by Abbott's formula).

6. Normalize the (a) laboratory-waterEC50, (b) the site-water EC50, and (c)the SMAV EC50 to the same hardness,using the formula:

14

Where “Std Hdns” is any particularstandard hardness value to which allvalues will be normalized, and “SampleHdns” is the hardness of the laboratorywater, the site water, or the SMAV. The exponent 0.9422 is the log-logslope for the 1984/1985 and 1995 EPAacute criteria. If different from 0.9422,it is appropriate to use the hardnessslope of the state criterion.

7. Calculate the sample WER from valuesnormalized to the same hardness.a. If the laboratory-water, hardness-

normalized EC50 is greater thanthe hardness-normalized SMAV,the sample WER equals the site-water EC50 divided by thelaboratory-water EC50.

b. If the laboratory-water, hardness-normalized EC50 is less than thehardness-normalized SMAV, thesample WER equals the site-waterEC50 divided by the SMAV. SeeAppendix B for a value of theSMAV. Other comparably well-documented values for the SMAVmay be used.

8. Calculate the site WER as the geometricmean of the two (or more) sampleWERs. Compare the result againstWER values typically expected for thetype of situation under study. Additional chemical or toxicologicaldata may be needed to support unusuallyhigh WERs.

9. Calculate the site acute and chroniccriteria concentrations as the ordinaryhardness-adjusted criteria concentration(that is, the value that would have beenapplicable for a default assumption thatWER=1), multiplied by the final siteWER.

H. Reporting the Results

1. Include the following generalinformation in the report submitted tothe appropriate regulatory agency:a. Identity of the investigators and

the laboratory.b. Name, location, and description of

the discharger; description of theeffluent and the receiving water.

c. Effluent and upstream water flowsused to calculate the dilution ratio.

d. Dilution ratio used in mixingeffluent and upstream water toprepare the site water.

e. Downstream design hardnessexpected to be used for the permitderivation.

f. The values of the site-specificcriterion and WER estimated tocorrespond to a determination ofno reasonable potential or to otherpollution control decisionbenchmarks relevant to thepurpose of the study.

g. Identification of each samplingstation.

h. Procedures used to obtain,transport, and store the samples ofthe upstream water and theeffluent.

i. Any pretreatment, such asfiltration, of the effluent, sitewater, and/or laboratory dilutionwater.

j. Description of the laboratorydilution water, including source,and preparation.

k. Results of all chemical andphysical measurements onupstream water, effluent, actualand/or simulated downstreamwater, and laboratory dilutionwater, including hardness,alkalinity, pH, and concentrations

15

of total recoverable or dissolvedmetal, TSS, and DOC.

l. Description of the experimentaldesign, test chambers, volume ofsolution in the chambers,photoperiod, and numbers oforganisms and chambers pertreatment.

m. Source and grade of the coppersalt, and how the stock solutionwas prepared.

n. Species and source of the testorganisms, age, and holding andacclimation procedures.

o. The average and range of thetemperature, pH, hardness,alkalinity, and the concentration ofdissolved oxygen (mg/L) duringacclimation.

2. Include the following information foreach sample or toxicity test.a. Date and time of sampling site

water and date of toxicity test.b. Effluent flow during the sampling

event.c. Upstream flow during and prior to

the sampling event, eithermeasured directly or estimatedfrom relevant neighboring gages.

d. Prior meteorological conditionsaffecting flow and sampled waterquality.

e. Measurements of hardness,alkalinity, pH, and DOC.

f. The average and range of themeasured concentrations ofdissolved oxygen (in mg/L).

g. The average and range of the testtemperature.

h. A summary table of theconcentrations of copper in eachtreatment, including controls, andthe number of organisms affected,in sufficient detail to allow

independent statistical analysis ofthe data.

i. The EC50 and the method used tocalculate it.

j. Anything unusual about the test,any deviations from theprocedures described above, andany other relevant information.

k. All differences, other than thedilution water and theconcentrations of metal in the testsolutions, between the side-by-side tests using laboratory dilutionwater and site water.

3. Include the following information in asummary table:a. EC50s and hardness for each test

in a site-water, laboratory-watercomparison, not normalized forhardness.

b. EC50s for each site-water,laboratory-water (or SMAV)comparison, after normalizing forhardness.

c. The calculated sample WERs.

4. Present the calculated site WER and sitecriterion.

References for Appendix A

ASTM. 1999. ASTM Standards onBiological Effects and Environmental Fate,2nd Edition. American Society for Testingand Materials, West Conshohocken, PA.

ASTM. 2000a. E729-96 Standard Guidefor Conducting Acute Toxicity Tests on TestMaterials with Fishes, Macroinvertebrates,and Amphibians. American Society forTesting and Materials, West Conshohocken,PA.

16

ASTM. 2000b. E1192-97 Standard Guidefor Conducting Acute Toxicity Tests onAqueous Effluents with Fishes,Macroinvertebrates, and Amphibians. American Society for Testing and Materials,West Conshohocken, PA. U.S. EPA. 1993. Methods for Measuringthe Acute Toxicity of Effluents andReceiving Waters to Freshwater and MarineOrganisms. Fourth Edition. http://www.epa.gov/ost/WET/disk2/. EPA/600/4-90/027F. National ServiceCenter for Environmental Publications,Cincinnati, OH.

U.S. EPA. 1997. Trace Metals Guidance(diskette). EPA 821/C-97-002. http://www.epa.gov/OST/pc/analytic.html. EPA Office of Water Resource Center,Washington, DC.

U.S. EPA. 1999. Methods and Guidancefor the Analysis of Water, Revision 2 (onCD-ROM). EPA 821/C-99-004. http://www.epa.gov/OST/pc/analytic.html. EPA Office of Water Resource Center,Washington, DC.

17

Appendix B

Species Mean Acute Valuesfor Ceriodaphnia dubia and Daphnia magna

Species Mean Acute Values, SMAVs, for Ceriodaphnia dubia and Daphniamagna were obtained by tabulating available toxicity data, normalizing forhardness differences using the 1985 and 1995 EPA hardness slope for copper, andcalculating the geometric mean of all EC50 results for each species.

Normalized to a hardness of 50 and 100 mg/L as CaCO3 , the results are asfollows:

Species SMAV EC50, µg/L

At Hardness = 50 mg/L At hardness = 100 mg/L

Total Cu Dissolved Cu Total Cu Dissolved Cu

Ceriodaphnia dubia 12.49 11.51 24.00 22.11

Daphnia magna 10.47 10.05 20.12 19.31

The SMAV at any other hardness is obtained as follows:

The exponent, 0.9422 is the EPA’s copper criterion hardness slope. It is slightlyhigher than found in those Table B-1 studies that investigated the effect ofhardness: Belanger et al. 1989, Belanger and Cherry 1990, Chapman et al.manuscript, and Borgmann and Charlton 1984. Other well documented slopesmay also be suitable for normalizing the data.

18

Table B-1: EC50s for 59 reported results with Ceriodaphnia dubia and 55 reportedresults with Daphnia magna.

Species Methoda

Hrdns(mg/L asCaCO3)

EC50Total(µg/L)

EC50Diss.(µg/L)

EC50 Total,Adjusted toHrdns=100

(µg/L)b

EC50 Diss.,Adjusted toHrdns=100

(µg/L)bReference

Ceriodaphniadubia (<24 h)

S, M 45 25.017.030.024.028.032.023.020.019.0

53.0536.0763.6650.9359.4267.9048.8142.4440.32

Belanger et al.1989


S, M 94.1 26.021.027.037.034.066.063.071.0

27.5322.2428.5939.1836.0069.8966.7275.19

Belanger et al.1989


S, M 179 67.038.078.081.0

38.7121.9645.0746.80

Belanger et al.1989


S, M 97.6 142831

14.32 28.65 31.72

Belanger andCherry 1990


S, M 113.6 527691

46.11 67.40 80.70



S, M 182.0 568493

31.85 47.78 52.90



S, M 90 13.4 14.80 Oris et al. 1991

Ceriodaphniadubia

S, M 87.580.880.86030

11.2513.1725.2511.254.5

12.7616.1030.8718.2013.99

Neserke 1994

Ceriodaphniadubia

S, U 188204428410494440

36.619.136.411.712.312.0

20.19 9.76 9.25 3.10 2.73 2.97

Bright 1995


S, M 80 6.98 8.61 Diamond et al.1997b

Species Methoda

Hrdns(mg/L asCaCO3)

EC50Total(µg/L)

EC50Diss.(µg/L)


(µg/L)b


(µg/L)bReference

19

Ceriodaphniadubia

S, M 99707472148148142144148200193198194

10.114.656.726.5923.324.9918.9173.518.4831.7758.8231.5339.38

10.6513.346.534.5517.7415.3414.749

8.2420.9932.3921.1418.25

10.2020.508.928.9816.1017.2713.5952.1312.7716.5331.6616.5721.09

10.7518.678.676.2012.2610.6010.5634.755.7010.9217.4311.119.77

Tetra Tech1998

Ceriodaphniadubia

S, M 789090

13.18.8810.3

16.569.8111.37

Dimond 2000

Daphnia magna(<24 h)

S, U 45.3 9.8 20.67 Biesinger &Christensen1972

Daphnia magna(1 d)

S, U 99 8550

85.81 50.48

Adema &Degroot-vanZijl 1972

Daphnia magna S, U 45 10 21.22 Cairns et al.1978

Daphnia magna S, M 100 31.8 31.80 Borgmann &Ralph 1983


S, U 45 54 114.59 Mount &Norberg 1984


S, U 240 41 17.97 Elnabarawy etal. 1986

Daphnia magna(<4 h)

S, M 54 7 12.51 Nebeker et al.1986

Daphnia magna (1 d) (2 d) (3 d) (4 d) (5 d) (6 d)

S, M 80 106

147

1018

12.34 7.40

17.28 8.64

12.34 22.21

Nebeker et al.1986

Daphnia magna S, U 240 93 40.76 Khangarot andRay 1989

Daphnia magna S, U 10 21.5 188.21 Hickey andVickers 1992

Species Methoda

Hrdns(mg/L asCaCO3)

EC50Total(µg/L)

EC50Diss.(µg/L)


(µg/L)b


(µg/L)bReference

20

Daphnia magna S, U 33.8 11.5 31.96 Koivisto et al.1992

Daphnia magna S, U 50 7 13.45 Oikari et al.1992

Daphnia magna S, M 52105106207

26303869

48.15 28.65 35.97 34.76

Chapman et al.Manuscript

Daphnia magna S, M 170 41.210.520.617.370.731.3

24.99 6.37

12.50 10.49 42.88 18.99

Baird et al.1991


S, M 100 7.118.718.9

7.10 18.70 18.90

Meador 1991


S, M 170 31383558375139505231304663

18.80 23.05 21.23 35.18 22.44 30.93 23.66 30.33 31.54 18.80 18.20 27.90 38.21

Lazorchak andWaller 1993


S, M 7276807284844444367688

4.86.246.176.6210.210.84.67.83

10.416.9

6.54 8.08 7.61 9.02

12.02 12.73 9.97

16.91 7.86

13.47 19.06

Dimond 2000

a Methods: S = Static, M = Measured, U = Unmeasuredb Adjusted EC50 at hardness 100 mg/L is obtained from the test measured dissolved or total EC50 as follows:

Where only the test total EC50 is known, the test dissolved EC50 is estimated from EC50D = EC50T @ 0.96. Where only the test dissolved EC50 is known, the test total EC50 is estimated from EC50T = EC50D/0.96.

21

References for Appendix B

Adema, D.M.M. and A.M. Degroot-van Zijl.1972. The influence of copper on the waterflea Daphnia magna. TNO Nieuws 27:474.

Baird, D.J., I. Barber, M. Bradley,A.M.V.M. Soares and P. Calow. 1991. Acomparative study of genotype sensitivity toacute toxic stress using clones of Daphniamagna straus. Ecotoxicol. Environ. Saf.21(3):257-265.

Belanger, S.E., J.L. Farris and D.S. Cherry.1989. Effects of diet, water hardness, andpopulation source on acute and chroniccopper toxicity to Ceriodaphnia dubia.Arch. Environ. Contam. Toxicol. 18(4):601-11.

Belanger, S.E. and D.S. Cherry. 1990.Interacting effects of pH acclimation, pH,and heavy metals of acute and chronictoxicity to Ceriodaphnia dubia(Cladoceran). J. Crustacean Biol. 10(2):225-235.

Biesinger, K.E. and G.M. Christensen. 1972.Effects of various metals on survival,growth, reproduction, and metabolism ofDaphnia magna. Jour. Fish Res. Board Can.29:1691.

Borgmann, U. and K.M. Ralph. 1983.Complexation and toxicity of copper and thefree metal bioassay technique. Water Res.17:1697.

Bright, G.R. 1995. Variability of the “watereffect ratio” for copper toxicity - a casestudy. Proc. Toxic. Subst. Water Environ.

5/23-5/30. Water Environment Federation,Alexandria, VA.

Cairns, J., Jr. et al. 1978. Effects oftemperature on aquatic organism sensitivityto selected chemicals. Bulletin 106. VirginiaWater Resources Research Center,Blacksburg, VA.

Chapman, G.A. et al. Manuscript. Effects ofwater hardness on the toxicity of metals toDaphnia magna. U.S. EPA, Corvallis, OR.

Diamond, J.M., D.E. Koplish, J. McMahon,III and R. Rost. 1997b. Evaluation of thewater-effect ratio procedure for metals in ariverine system. Environ. Toxicol. Chem.16(3):509-520.

Dimond, W.F. 2000. Letter to CharlesDelos: peer review of Streamlined Water-Effect Ratio Procedure. July 21, 2000. State of Michigan, Department ofEnvironmental Quality. Lansing, MI.

Elnabarawy, M.T., A.N. Welter and R.R.Robideau. 1986. Relative sensitivity of threedaphnid species to selected organic andinorganic chemicals. Environ. Toxicol.Chem. 5(4):393-8.

Hickey, C.W. and M.L. Vickers. 1992.Comparison of the sensitivity to heavymetals and pentachlorophenol of the mayfliesDeleatidium spp. and the cladoceranDaphnia magna. N.Z.J. Mar. FreshwaterRes. 26(1):87-93.

Khangarot, B.S. and P.K. Ray. 1989.Investigation of correlation betweenphysicochemical properties of metals andtheir toxicity to the water flea Daphnia

22

magna Straus. Ecotoxicol. Environ. Saf.18(2):109-20.

Koivisto, S., M. Ketola and M. Walls. 1992.Comparison of five cladoceran species inshort- and long-term copper exposure.Hydrobiol. 248(2):125-36.

Lazorchak, J.M. and W.T. Waller. 1993. Therelationship of total copper 48-H LC50s toDaphnia magna dry weight. Environ.Toxicol. Chem. 12(5):903-11.

Meador, J.P. 1991. The interaction of pH,dissolved organic carbon, and total copper inthe determination of ionic copper andtoxicity. Aquat. Toxicol. 19(1):13-31.

Mount, D.I. and T.J. Norberg. 1984. Aseven-day life-cycle cladoceran toxicity test.Environ. Toxicol. Chem. 3:425.

Nebeker, A.V., M.A. Cairns, S.T. Onjukkaand R.H. Titus. 1986. Effect of age onsensitivity of Daphnia magna to cadmium,copper and cyanazine. Environ. Toxicol.Chem. 5(6):527-30.

Neserke, G. 1994. Written testimony toColorado Department of Health WaterQuality Control Commission on behalf of theCoors Brewing Company.

Oikari, A., J. Kukkonen and V. Virtanen.1992. Acute toxicity of chemicals toDaphnia magna in humic waters. Sci. TotalEnviron. 117-188:367-77.

Oris, J.T., R.W. Winner and M.V. Moore.1991. A four-day survival and reproductiontoxicity test for Ceriodaphnia dubia.Environ. Toxicol. Chem. 10(2):217-24.

Tetra Tech. 1998. Determination of CopperLC50s for Calculation of Water EffectRatios and Effluent Limits for POTWs inSoutheastern Pennsylvania. Tetra Tech,Owings Mills, MD.

23

Appendix C

Assessment of the Streamlined Water-Effect Ratio Procedure

Abstract

The protectiveness of the StreamlinedProcedure for obtaining a copper water-effect ratio (WER) for streams affected bypoint source discharges has been assessedusing Monte Carlo probabilistic modeling.

The Streamlined Procedure uses two WERsamples to set the site WER. Theprobabilistic modeling considered that thetwo WER samples were collected from asituation where the flow, toxicantconcentration, and WER vary over time.

This analysis evaluated the suitability ofcalculating each site’s WER as the geometricmean of the two WER measurements for thesite, when the effluent and upstream samplesare mixed at the design low-flow dilution. Comparison was made against the predictedunbiased value for the WER: that is, thevalue that the WER would have if the site-specific criterion were to have the same levelof protection as intended for the nationalcriterion.

Overall the results of this work indicated thatthe Streamlined Procedure tends to yield asite WER slightly more restrictive than theunbiased site WER. In 50 percent of theMonte Carlo trials, the calculated WER wasless than 0.84 times the unbiased site WER. Within the range of conditions investigated,the design downstream dilution had nosignificant effect on the level of protectionprovided.

In addition, in the Supplement to thisAppendix, an estimate was made of theeffect, relative to the 1994 InterimProcedure, of having the StreamlinedProcedure restrict the lab water EC50 to avalue not less than the EPA SMAV. Sixteenlab water EC50s from three WER studieswere evaluated. By including the differencein the way the two procedures set the labwater EC50, the Streamlined Procedure andthe Interim Procedure could be appropriatelycompared through the Monte Carlosimulation. Results indicated that the twoprocedures yielded similar results.

Introduction

The purpose of this assessment is todetermine, through modeling, whether theStreamlined Procedure provides the degreeof protection intended for aquatic lifecriteria. The Supplement to this Appendixalso deals with the following issues: (a) thepurpose of streamlining the copper WERprocedure, (b) the reason for preparingsamples by mixing at design dilution, (c) theneed for the simultaneous laboratory watertest, (d) the potential for reducing thenumber of samples, and (e) a comparisonwith the 1994 Interim Procedure.

Assessment Strategy

The water-effect ratio (WER) reflects theeffect that local site water constituents haveon increasing or reducing the pollutantbioavailability and toxicity. The

24

concentrations of the site water constituentsthat control the WER can be expected tovary over time, as do all water qualityparameters. A site's WER would thus alsovary over time. Consequently, the number ofsamples in any reasonably feasible samplingscheme cannot fully characterize the site.

The question investigated here is whether itis appropriate to calculate the site WER asthe geometric mean of the two samples,mixed at the low-flow dilution. This issuecan be addressed by asking: How does thelevel of protection provided by such a WERderivation compare with the level ofprotection intended for aquatic life criteria?

If one continually knew what the actualWER was during each increment of time,then one could continually reset the sitecriterion such that it would always correctlyreflect the actual conditions. Thus, if onemade continual WER measurements andcontinual adjustments to the site criterion,then there would be no "final WER" and noissue about its method of calculation. Assuming that the WER measurements werecorrect, the continual adjustments of the sitecriterion would yield a level of protectionexactly equal to what was intended for thecriterion.

It is of course infeasible to continuallymeasure the WER over time. However,since we know something about thestatistical properties of water qualityparameters, it is feasible to set up amathematical modeling experiment to mimiccontinual measurements, using realistic-looking hypothetical distributions of WERvalues and other site parameters. In this wayit is possible to examine the behavior ofvarious sampling and calculation alternatives. That is, given an assumed distribution oftime-variable WERs, one can compare (a)the level of protection provided by any

alternative for obtaining the final WER (andsite criterion), to (b) the neutral or unbiasedlevel of protection provided by continuallyresetting the site criterion using the WERspecific to each event.

The basic strategy for performing thisanalysis (modified from Delos 1998, which inturn evolved from Delos 1994) is to set upone or more scenarios of hypothetical siteapplications by specifying the statisticalproperties of the facility WERs, flows, andtoxicant concentrations. Reflecting the timevariability of a site, a very large number ofsuch WERs, with accompanying flow andtoxicant concentration values, can then berandomly generated. One may then comparethe behavior of (a) the StreamlinedProcedure for deriving a site WER, with (b)the unbiased technique of continuallyresetting the WER and site criterion.

For a situation where the WER is varyingover time, and the site criterion is continuallybeing re-set in accordance with the WER,the time variations in the toxicantconcentration will yield some frequency ofcriteria violations. Assuming that thisfrequency of criteria violations is acceptable,one can find, by trial and error, a single,fixed (time-invariant) value for the WER,and likewise a single, fixed site criterion, thatyields exactly the same frequency ofviolations as the time-variable WER andtime-variable site criterion. This single, fixedvalue for the WER, yielding the sameviolation frequency as the time-variableWER, may be termed the unbiased finalWER.

This fixed unbiased WER represents the“correct” value for site’s final WER. However, its value could only be ascertainedif one had a long record of measured WERsand toxicant concentrations for the site,something that can be obtained for a model

25

simulation site but not a real-world site. In areal-world site only a small sampling isobtained for the values that the WER maytake over time. The purpose of the MonteCarlo modeling is to compare the final WERvalues derived from small samples of the ofthe site’s distribution of WERs to the correctvalue represented by the unbiased finalWER.

The Monte Carlo analysis considers that asite has time-variable values for streamflow,toxicant concentration, and WER. It alsoconsiders that the sites to which theStreamlined Procedure applies differsomewhat in their design flow dilution ratio.

Modeling Procedure

It is not necessary to read this section inorder to understand and use the modelingresults presented later. Readers notinterested in the procedural details may skipto Results, the next section.

The Monte Carlo model is set up as follows. For any particular discharge situation, thefollowing sources of variability are taken intoaccount:

• Time variable dilution ratio of upstreamflow to effluent flow

• Upstream time-variable toxicantconcentration

• Upstream time-variable WER• Effluent time-variable toxicant

concentration• Effluent time-variable WER

That is, the modeling work assumes that thedilution flow, toxicant concentration, andWER vary over time. In addition to timevariability within a site, the analysisrecognizes that between various sites,

discharges differ somewhat in their design-flow dilution.

The steps for setting up and evaluating a sitescenario are set forth below. Thecomputations were set up as a Quattro Prospreadsheet.

1. Consider an effluent discharged to astream. The effluent and upstreamwaters are each characterized by threeparameters: WER, toxicantconcentration, and flow. Thedownstream toxicant concentration andWER are calculated by dilution. Such acalculation for the WER assumes thatthe WER is controlled by and directlyrelated to the underlying concentrationsof water quality parameters (such asdissolved organic carbon) that areappropriately calculated by the dilutionformula.

2. Assume that effluent and upstreamWERs, toxicant concentrations, andflows are log normally distributed, eachwith particular values for its log meanand log standard deviation. Timevariable effluent and upstream flowswere made to fit one of three categories:(a) design IWC of 91%, (b) design IWCof 50%, and (c) design IWC of 33%. Flow parameters were selected such thatdownstream flows less than the designlow flow occurred 3% of the time. Because the copper discharged bysewage treatment facilities (by far themost common copper discharge) isphysico-chemically associated with thedischarged organic matter, effluenttoxicant concentration and effluentWER were modeled to be 40-50%correlated with each other. Such degreeof correlation is directly supported byState of Connecticut data (Dunbar1997c), by wastewater treatment

26

process modeling, and indirectly byPennsylvania municipal dischargerdata (Hall and Associates 1998).

3. Using random number generators thatproduce log normal values having theproper mean and standard deviation,generate random values for fiveparameters: effluent and upstreamWERs and toxicant concentrations, andupstream flow. This constitutes oneevent.

4. Using the dilution formula, calculate thedownstream WER and toxicantconcentration for the Step 3 event. Because the streamlined approach mixeseffluent and upstream water at thedesign IWC, irrespective of the actualIWC occurring during the samplingevent, this modeling analysis must keeptrack of two separate downstreamWERs for the event: (a) the downstreamWER calculated to occur for the actualevent IWC, and (b) the downstreamWER that would be measured if effluentand upstream waters were mixed at thedesign IWC.

5. In like manner, generate a large numberof events. For this work, 1000 eventswere used for each of the three dilutioncategories (33%, 50%, and 91% designIWC). Each event is characterized bythe upstream and effluent values forWERs, concentrations, and flows, andby the calculated downstream values forthese parameters.

6. Specify an appropriate relative value forthe national criterion for the toxicant. Then for each of the 1000 eventscalculate a site criterion as the productof the national criterion times the event'sdownstream WER (at the actual eventdilution). For each event determine

whether the toxicant concentrationexceeded the event-specific sitecriterion. Count the number ofexcursions of the event-specific criterionin all 1000 events.

Toxicant concentration and WER meanvalues and relative national criterion valuesin Steps 2 and 6 were selected such thatusing reasonable values for log variances, thesite criterion was violated 1% of the timeoverall.

7. Arbitrarily pick some value for theoverall final WER, to remain a fixedconstant across all events. Calculate afixed value for the site criterion, as theproduct of the national criterion timesthe fixed final WER. For each eventdetermine whether the toxicantconcentration exceeded the fixed valuefor the site criterion. Count the numberof excursions of the event-specificcriterion for all 1000 events. Comparethis excursion frequency with thatobtained in Step 6.

8. Repeat Step 7, adjusting the value bytrial and error, until the fixed final WERyields the same excursion frequency asdid the variable criterion from Step 6. The value so obtained may be called theunbiased final WER. It is the value thefinal WER should have if it were toproduce the level of protection intendedfor the criterion.

The remaining steps consider the possibleoutcomes if (a) sample WERs were obtainedfor two events, in accord with theStreamlined Procedure, and (b) the finalWER is set equal to the geometric mean thetwo sample WERs.

9. For each of 999 pairs of WERmeasurements in each of the three

27

dilution scenarios (33%, 50%, and91% IWC), calculate a site WERequal to the geometric mean of eachpair of measurements. (Form pairsfrom the first and second events,second and third events, and so ondown the list, thereby yielding 999pairs.)

10. For each of the three dilution scenarios,examine the distribution of 999 site WERs obtained by Step 9. Determinethe WERs corresponding to various

percentiles in the distribution (such as 50th,85th, and 95th percentiles). Compare thesewith the unbiased WER obtained from Step8, in order to ascertain how often the siteWER would be under-protective, and howoften it would be over-protective.

Values for key parameters are shown inTable C-1. The log standard deviations arebased on past experience with selected waterquality measurements from well conductedstudies.

Table C-1. Values for key input parameters and selected intermediate outputs.

0.5 Standard deviation of log upstream toxicant concentration

0.5 Standard deviation of log upstream WER

1.0 Standard deviation of log upstream flow

0.5 Standard deviation of log effluent concentration

0.5 Standard deviation of log effluent WER

0.0 Standard deviation of log effluent flow

0.5 Correlation (r2) between log effluent toxicant concentration and log effluent WER

0.43 Correlation (r2) between effluent toxicant concentration and effluent WER

4.0 Ratio, effluent mean WER : upstream mean WER

33% Design IWC for higher dilution facility in scenario

51% Design IWC for medium dilution facility in scenario

91% Design IWC for low dilution facility in scenario

8% Overall geometric mean IWC for higher dilution facilities in group

14% Overall geometric mean IWC for medium dilution facilities in group

63% Overall geometric mean IWC for low dilution facilities in group

3% Frequency of flows below design flow

1% Frequency of site-specific criteria violations

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Results

The results were used to address thequestion: How much protection is providedif the site WER is set equal to the geometricmean of two sample WERs?

The WER established as such a geometricmean will be here termed the procedureWER. Table C-2 shows the ratio of theprocedure WER to the unbiased WER forthe typical or 50th percentile situation andworst case 95th percentile situation amongthe 999 final WERs obtained from the MonteCarlo analysis of each of the three dilutionscenarios.

The level of protection provided by theStreamlined Procedure does not varysignificantly among the dilution scenarios,relative to other uncertainties and randominfluences. Irrespective of design IWC, theTable C-2 Monte Carlo results indicate thatthe substantial majority of cases, astreamlined Procedure WER will be belowthe site’s unbiased WER. The probability ofobtaining a procedure WER greater than thesite’s unbiased WER averaged 29% amongsites.

Data from Dunbar (1997a, 1997b, 1997c)indicate that over time, the measured WERs

at a site are less variable than assumed in thisMonte Carlo analysis. Consequently, theseresults probably represent a conservativeworst case portrayal of the performance ofthe Streamlined Procedure for the type ofscenarios considered.

The possibility that a site could be assigned acriterion concentration somewhat greaterthan ideal is an inherent risk associated withboth national and site-specific criteria. Ifmost dischargers are to be assigned a WERnot too far below what they deserve, the luckof the draw during sample collection willyield some site WERs somewhat higher. However, for the criterion in question, thereis no reason to expect aquatic communitiesto be sensitive to minor errors oruncertainties in criteria setting. Applicationof any criterion will always involve somepotential for inaccuracy, whether adjustedusing the Streamlined Procedure, the 1994Interim Procedure, the Biotic Ligand Model,an empirical hardness relationship, orwhether not adjusted at all for site waterquality.

The performance of the StreamlinedProcedure was also compared with the 1994Interim Procedure. This comparison isdiscussed in the Supplement to Appendix C.

Table C-2. Monte Carlo prediction of relationship between the procedure WER and theunbiased WER.

Design IWC Ratio of Procedure WER : Unbiased WER Probability ofexceeding the

Unbiased WER50th Percentile 95th Percentile

91% Design IWC 0.82 1.49 30%

50% Design IWC 0.81 1.38 25%

33% Design IWC 0.90 1.42 33%

Mean of scenarios .84 1.43 29%

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Conclusion

Analysis of the behavior of the StreamlinedProcedure using Monte Carlo modelingtechniques has indicated that the procedureprovides a level of protection close to thatintended for the criteria.

References for Appendix C

Biological Monitoring, Inc. 1992. Site-Specific Study for Computing MetalStandards for the Lehigh River and City ofAllentown, Pennsylvania. BMI, Blacksburg,VA.

Delos, C. 1994. Probabilistic analysis of thelevel of protection provided by the interimguidance on determining water-effect ratios. Draft. Office of Water, U.S. EPA,Washington, DC.

Delos, C. 1998. Assessment of WER Studyfor Aggregated Southeast PennsylvaniaFacilities. Health and Ecological CriteriaDivision, U.S. EPA, Washington, DC 20460.

Dunbar, L.E. 1997a. Effect of streamflowon the ability of ambient waters to assimilateacute copper toxicity. ConnecticutDepartment of Environmental Protection.

Dunbar, L.E. 1997b. Derivation of a site-specific dissolved copper criteria for selectedfreshwater streams in Connecticut. Connecticut Department of EnvironmentalProtection.

Dunbar, L.E. 1997c. Lotus spreadsheet(data).

Hall & Associates and EnvironmentalEngineering & Management Associates. 1998. Evaluation of copper toxicity andwater effect ratio of treated municipalwastewater. Prepared for PennsylvaniaCopper Group.

MacKnight, E.S. 1997. September 17 letterto James Newbold. U.S. EPA, Region 3.

Neserke, G. 1994. Written testimony ofGeorge Neserke on behalf of the CoorsBrewing Company. Colorado Department ofHealth, Water Quality Control Commission.

U.S. EPA. 1994. Interim guidance ondetermination and use of water-effect ratiosfor metals. EPA-823-B-94-001.

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Supplement to Appendix C

Discussion of Issues Pertaining to the Streamlined Procedure

This supplement discusses several issuesassociated with the Streamlined Procedure.

Why was a streamlined WER proceduredeveloped?

The national recommended criterion forcopper has now taken on the role of ascreening tool. Violation of that criteriondoes not usually trigger immediate pollutioncontrol, but rather triggers WER studies toderive a site-specific value for the criterion.

It is common for sewage treatment facilitiesto exceed the national recommended coppercriterion. However, when evaluated byTIEs, actual toxicity due to copper fromsuch facilities is rare, apparently because ofthe excess of complexing organics.

Screening tools can be judged by theirsensitivity and efficiency. EPA’s approachfor copper appeared to have few problemswith sensitivity, but its efficiency (actualproblems divided by the sum of falsepositives and actual problems) appeared tobe very low, and when applied to sewagetreatment facilities, possibly approachingzero. Because the cost and complication ofthe needless WER studies divert federal,state, and local government resources awayfrom more productive efforts, the criteriaprogram has been subjected to criticism bothfrom within EPA and from outside EPA.

Recognizing the need for improving theefficiency of the copper WER approach,EPA developed a more streamlinedapproach, simpler to perform, simpler toreview, but fully protective.

What is involved in recommendationsabout the mixing of effluent and upstreamwaters in preparation for the toxicitytests?

The Streamlined Procedure mixes effluentand upstream waters at the design low-flowdilution ratio (the design IWC). The 1994Interim Procedure mixes effluent andupstream waters at the dilution actuallyoccurring during the sampling event.

The thinking behind the 1994 InterimProcedure recommendation, which wasdesigned primarily for application to totalrecoverable metals, was that the suspendedsolids concentration tends to increase withincreasing flow, such that merging the high-flow, high-solids event and the low-dilution,high-organic-matter sample mixture mightyield an unjustifiably optimistic scenario for atotal recoverable WER. However, fordissolved metals, particulate matter is notrelevant, and should have little effect on thedissolved WER. Furthermore, for copper,since total recoverable is generally not muchgreater than dissolved, and since the methodis restricted to copper problems associatedwith continuous point sources, it is onlynecessary to assure that the event sampled isnot substantially influenced by rainfall runoff.

State of Connecticut (Dunbar 1997a) datasupport this: in upstream waters, there is noapparent relationship between the WER andstreamflow. Absent such a relationship inupstream waters, there is no particularreason not to measure the WER using theIWC in which one is most interested: thedesign flow condition.

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The State of Connecticut data comparing theWER with the IWC also suggest that theWER does not increase as rapidly as theIWC. In this case, the IWC of greatestconcern would be the design low-flow IWC. At this time the discharged metal would beexpected to be at its highest level comparedto the WER and the sample-specificcriterion.

The modeling analysis in the main part ofAppendix C nevertheless recognizes andaccounts for the potential difference betweenthe a sampling-event WER measured for theactual event IWC, and the sampling-eventWER measured when the sample is preparedat the low-flow design IWC. Consequently,the assessed protectiveness of theStreamlined Procedure is not an artifact ofany assumption that the low flow conditionis the critical condition with respect tocriteria excursions. The modeling analysisconsidered all criteria excursions no matterwhen they occurred.

Mixing upstream and effluent samples at aspecified dilution substantially reduces theunpredictability of the results, and allows theneeded sampling work to proceed in a timelymanner (an essential feature for an efficientapproach), the only stipulation being thatrainfall runoff impacted events be avoided.

How does the protectiveness of theStreamlined Procedure compare with thatof the 1994 Interim Procedure?

The features of the Streamlined Procedureand Interim Procedures were compared inTable 1 in the main body of this document. There are two key differences that affect therelative protectiveness of the twoprocedures. (1) The Interim Proceduremixes effluent and upstream water at thedilution occurring at the time of sampling;

the Streamlined Procedure mixes effluentand upstream at the low-flow dilution. (2)The Interim Procedure uses the laboratorywater EC50 in the WER denominator; theStreamlined Procedure uses the SMAV if itis greater than the laboratory water EC50. The influence these differences have on theprotectiveness of the procedures appearlargely to balance each other. The twoprocedures are expected to be equallyprotective.

Mixing effluent and upstream water: Because flow at the time of sampling is sucha random parameter, effluent dilution anddownstream organic carbon concentrationare thus random uncontrolled factors in theInterim Procedure. In contrast, flowoccurring at the time of sampling is notrelevant in conducting the test under theStreamlined Procedure. In general, it can beexpected that organic carbon concentrationsin the tested site water will be higher and lessvariable when tested per the StreamlinedProcedure than when tested per the InterimProcedure. This tends to slightly elevate theWER under the Streamlined Procedure.

SMAV versus laboratory water EC50: Experience with the 1994 Interim Procedurehas caused some concern about the values ofthe lab-water EC50 used for the side-by-sidecomparison. There is a perception amongmany WER study reviewers that these lab-water EC50s, while within the range ofreasonable values, are usually less than theSMAV for the test species, thus yielding aslight bias toward increasing the WER. Thecomparatively low calcium-magnesium ratioof the laboratory water commonly used inWER tests may account for their relativelylow EC50s.

Data for 30 separate WER measurementsfrom studies by four different laboratoriesindicated that the laboratory water EC50 for

33

Ceriodaphnia dubia and Daphnia magna,when measured for WER purposes, averagedless than 67% of the SMAVs shown inAppendix B. There was relatively littledifference among the four laboratories in thisregard. This potential for variability and biashas been eliminated from the StreamlinedProcedure by stipulating that thedenominator of the WER is the greater of thelab water EC50 or the SMAV. Thisstipulation tends to slightly depress the WERunder the Streamlined Procedure.

The net result is that the differences betweenthe two procedures appear to essentiallybalance each other. As shown in Table C-3,the Streamlined Procedure yields results thatare comparable to the 1994 InterimProcedure, analyzed by the Monte Carlotechnique in a similar scenario, whileaccounting for the differences between thetwo procedures.

Relative to the Streamlined Procedure, theInterim Procedure may be more variable anduncertain than Table C-3 would suggest,because this analysis accounts only for thetypical bias of the lab-water EC50, and notfor its imprecision or variability. Overall theStreamlined Procedure is expected to yieldsomewhat more stable results than theInterim Procedure.

Could a single WER measurement ever beused to derive a site WER?

The modeling analysis in the main part ofAppendix C easily lends itself to evaluatingthe suitability of using a single WERmeasurement. Table C-4, in format similarto the Table C-2, presents the results. Theresults did not vary significantly with designIWC, so the table shows the combinedresults for all three dilution scenarios (33%-91% IWC).

Table C-3. Comparison of Protectiveness of Streamlined Procedure and 1994 InterimProcedure.

Ratio of Procedure WER : Unbiased WER Probability ofexceeding the


Streamlined Procedure 0.84 1.43 29%

Interim Procedure 0.83 1.51 30%

Table C-4. Monte Carlo predictions comparing the two-sample Streamlined Procedurewith a single-sample approach, both relative to the true unbiased WER.

Ratio of Procedure WER : Unbiased WER Probability ofexceeding the


Two-sample Procedure 0.84 1.43 29%

Single-sample Approach 0.84 1.72 35%

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Using a single sample rather than thegeometric mean of two samples has no effecton the median result. However, the luck ofthe draw has more influence on a singlesample than the mean of two samples. Ofgreatest concern is large difference betweenthe median and the 95th percentile in thesingle-sample approach when compared tothe two sample approach.

Nevertheless, it is recognized that in manymunicipal discharge situations, there is awide margin of safety between value of theWER needed to conclude that there is noreasonable potential for impairment and thevalue of the measured values of the siteWER. In a tiered testing approach thecriterion would be more stringent where lessdata are available. For a single sample,obtained during stable flow events, notinfluenced by rainfall runoff, with treatmentplant operating well, if the measured WER ismore than a factor of two greater than WERneeded to conclude that there is noreasonable potential, the above modelingresults do not suggest any particular need foran additional sample before concluding thedecision making process.

If a single sample is obtained for purposes ofreconfirmation of a previously establishedsite-specific criterion, then a singlereconfirmation sample should be comparedwith the original sample results, withoutreference to the above factor of two. In allcases, occasional reconfirmation testing isdesirable, perhaps on concert with the permitissuance cycle, even though site-specificcriteria do not generally incorporate anylegally recognized expiration date.

Is simultaneous side-by-side laboratorywater and site water testing needed? Canthe laboratory water EC50 be dispensedwith and replaced by the SMAV in

conjunction with reference toxicanttesting?

Over the years this question has remainedwith the WER approach. Insistence onsimultaneous side-by-side testing implies thatthe relative positions of the laboratory waterand site water EC50s are more reliable thanthe absolute values. Nevertheless, theAgency clearly puts a substantial amount oftrust in the absolute values: they are the basisfor the national criterion and the basis fordetermining compliance with WET limits.

The advantage of having the simultaneouslaboratory water test is that it accounts forany variations in the organism culture or testcondition that might affect sensitivity tocopper, even though such variations towardnon-optimal test conditions might often beexpected to depress rather than increase theEC50. The disadvantage of the laboratorywater test is that it is an additional source ofvariation and uncertainty in the WER, andmay be subject to unjustified manipulation. It also adds somewhat to the study cost.

Nevertheless, without some type oflaboratory water EC50 check, there isnothing to discourage use of a daphnidculture that had been bred in water havinghigh concentrations of copper. This might ormight not mimic genetic adaptationprocesses actually occurring at the site. Inany case, it is considered undesirable for thenational criteria program to depend on suchadaptation processes to assure aquatic lifeprotection.

If the simultaneous laboratory water EC50were to be eliminated, a state or tribe wouldneed to substitute in its place a referencetoxicant testing program involving copper. This would be technically necessary to assurethat the organism culture used for testingwas not insensitive to copper toxicity. The

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state or tribe would be responsible forassuring the adequacy of such an approach.

References for the Supplement

Dunbar, L.E. 1997a. Effect of streamflowon the ability of ambient waters to assimilateacute copper toxicity. ConnecticutDepartment of Environmental Protection

streamlined water-effect ratio procedure for discharges of copper · 2018. 10. 24. · values for a...

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