Technical Support Document: Recommended Estimates For Missing Water .

Office of WaterEPA 820-R-15-106March 2016Draft Technical Support Document:Recommended Estimates for MissingWater Quality Parameters forApplication in EPA’s Biotic Ligand Model

Disclaimer PageThis technical support document (herein referred to as the “Missing Parameters TSD”) summarizesdata analysis approaches EPA used to develop recommendations for default values for water qualityparameters used in the copper BLM when data are lacking. When published in final form, thisdocument will provide information to states, tribes, and the regulated community interested in usingthe Biotic Ligand Model to protect aquatic life from toxic effects of copper. Under the CWA, states andtribes are to establish water quality criteria to protect designated uses. State and tribal decisionmakers retain the discretion to adopt approaches on a case-by-case basis when appropriate. Thisdocument does not substitute for the CWA or EPA’s regulations; nor is it a regulation itself. Thus, itcannot impose legally binding requirements on EPA, states, tribes, or the regulated community, andmight not apply to a particular situation based upon the specific circumstances. EPA may change thisdocument 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 of trade names or commercial products does not constitute endorsement or recommendationfor use. This document can be downloaded ards/criteria/aqlife/copper/2007 index.cfmCover photo: Credit USEPAi

AcknowledgementsLuis A. Cruz(Document Coordinator and Contributor)United States Environmental Protection AgencyHealth and Ecological Criteria DivisionWashington, D.C. 20460ReviewersElizabeth Southerland, Elizabeth Behl, Kathryn GallagherUnited States Environmental Protection AgencyOffice of Science and TechnologyWashington, D.C. 20460ii

Acronyms or POTWsRMSEDefinitionAcute to Chronic RatioAverage Standard ErrorBiotic Ligand ModelBiochemical Oxygen DemandCriterion Continuous ConcentrationCriterion Maximum ConcentrationClean Water ActDegrees of FreedomDissolved Organic CarbonAreas in which ecosystems and the type, quality, and quantity of environmentalresources are generally similar. In this document is represented by EPA Level IIIEcoregionsEnvironmental Monitoring and Assessment ProgramUnited States Environmental Protection AgencyFixed Site CriteriaGeochemical Ions; ion parameters for the Biotic Ligand Model (Ca, Mg, Cl, Na, K, SO4,alkalinity)Geographic Information SystemGreat Lakes Environmental CenterHydrologic Unit Code (a two to eight digit code that identifies each hydrologic unit)Interquartile rangeInstantaneous Water Quality CriteriaLower Confidence LimitLegacy Data Center (EPA historical STORET database, recently renamed)Linear RegressionMilligrams per literNational Hydrography DatasetNational Hydrography Dataset PlusNational Organic Carbon Database (combined organic carbon data from twodatabases: USGS WATSTORE and EPA STORET)National Research CouncilNational River and Stream AssessmentNational Waters Information SystemPermit Compliance SystemRelative Percent DifferencesPrincipal Components AnalysisNegative logarithm of the hydrogen ion concentration (in moles per liter); scale rangefrom 0 to 14Particulate Organic CarbonPublicly Owned Treatment WorksRoot Mean Square Erroriii

al Sum of SquaresScatter Plot MatricesStrahler Stream OrderEPA STOrage and RETrieval Data Warehouse (recently renamed Legacy Data Center,LDC)Total Dissolved SolidsTechnical support documentTotal Suspended SolidsTotal Organic CarbonUpper Confidence LimitUnited StatesUnited States Geological SurveyUSGS National WATer Data STOrage and REtrieval System (predecessor of NWIS)Wadeable Stream AssessmentWater Quality CriteriaMicrosiemens per centimeterMicrograms per literiv

Executive SummaryThe United States (U.S.) Environmental Protection Agency (EPA) developed revised freshwater aquaticlife criteria for copper using the Biotic Ligand Model (BLM) in 2007. The 2007 Freshwater Copper BLMpredicts acute copper toxicity based on site-specific water quality parameters, and calculates aquaticlife criteria based on the predicted copper toxicity. The current freshwater copper BLM requires 10input parameters to calculate copper criteria: temperature, pH, dissolved organic carbon (DOC),alkalinity, calcium, magnesium, sodium, potassium, sulfate, and chloride, the last seven of which arealso referred to as geochemical ions (GI). Previously available hardness-based copper criteriaincorporated consideration only of the effects of hardness on bioavailability, while the BLMincorporates consideration of all of the water chemistry parameters that have a major influence onmetal bioavailability. This allows the BLM-based criteria to be customized to the particular water bodyunder consideration. However, given the broad geographical range over which the BLM is likely to beapplied, and the limited availability of data for input parameters in many areas, a practical method toestimate missing water quality parameters was needed to successfully run the BLM. This technicalsupport document (herein referred to as the “Missing Parameters TSD”) summarizes data analysisapproaches EPA used to develop recommendations for default values for water quality parametersused in the Freshwater Copper BLM when data are lacking. These default values could also be used tofill in missing water quality input parameters in the application of other metal BLM models as well,when data are lacking. EPA used three approaches to develop these default value recommendations: Conducted geostatistics and conductivity analyses to predict GI parameters Applied stream order to refine prediction of GI parameters Mined the National Organic Carbon Database (NOCD) to estimate DOCIn brief, EPA found that an approach that used correlation (with conductivity and discharge asexplanatory variables), combined with geostatistical techniques (kriging), and a consideration ofstream order produced the best estimates for BLM GI parameters. Tables 8, 9, and 10 presentestimated inputs for each GI and water hardness in each ecoregion categorized by stream order forlow, medium, and high order streams, respectively. Recommended GI values are based on the 10thpercentile of ecoregional Level III values for the appropriate stream order (size) and are expected toyield appropriately protective criteria values when applied in the BLM model. In Table 20 of Section 4,EPA provides estimates for DOC by ecoregion based on an analysis of a compilation of national organiccarbon databases. The 10th percentile of ecoregional Level III values are recommended for DOC. Therewas insufficient data to refine the DOC estimates by stream order. EPA recommends measurement ofpH and temperature directly to use as an input in the BLM. Temperature is a commonly measuredparameter, and should be easily obtainable for use in the BLM. The following paragraphs summarizethe contents of each section in this report.Section 1 provides an introduction to this study, including background on the BLM. In developing theapproaches outlined in this study, EPA relied upon several previous studies that attempted to estimatevalues for BLM input water quality parameters; these studies are outlined briefly in Section 1 and aredescribed in detail in Appendices A through D. This earlier work demonstrates that protective waterv

quality criteria (WQC) for copper generally corresponded to a low percentile of the distribution ofinstantaneous water quality criteria (IWQC) predicted by the BLM.Section 2 provides a discussion of the approach taken by EPA to estimate BLM GI parameter valuesusing geostatistics, which are a suite of statistical methodologies that use spatial coordinates toformulate models used in estimation and prediction. Section 2 also describes how EPA supplementedthe geostatistical approach with conductivity as an explanatory variable, because conductivity data areabundant and correlate well to the BLM GI parameters.Section 3 provides an analysis and discussion of the EPA approach to estimation of BLM GI parametersincorporating stream order as a variable, with a goal of providing BLM users with tables ofrecommended GI parameter estimates based upon both ecoregion and stream order. For each Level IIIecoregion, we recalculated the 10th percentiles of the distributions of all daily water quality parametersmeasured at all NWIS stations taking into account stream orders or ranges (groups) of stream orderswithin each ecoregion. Values of the BLM GI parameters generally increased with stream order. Basedupon this trend, we grouped the estimates for each parameter by stream order: 1 through 3(headwater streams), 4 through 6 (mid-reaches), and 7 through 9 (rivers).Section 4 discusses the estimation of DOC based on the NOCD and two other databases. The NOCD wascompiled from a number of sources, including EPA’s Storage and Retrieval Data Warehouse (STORET)and the United States Geological Survey’s National Water Data Storage and Retrieval System(WATSTORE) (the predecessor of the National Waters Information System (NWIS)). The two otherdatabases, the Wadeable Stream Assessment (WSA) and the National River and Stream Assessment(NRSA), were used to supplement and update the DOC analysis. Section 4 summarizes the datasources, analysis, and uncertainty associated with ecoregional statistics for the NOCD and outlines howtests for bias in the data influence selection of 10th percentile DOC concentrations from either theNOCD or the WSA or NRSA databases. The importance of field sampling for DOC is highlighted inSection 4 because of limitations of the NOCD and the importance of DOC in criteria calculation.Section 5 provides a summary of the three approaches used to develop EPA’s recommendations. Takentogether, the approaches presented in this TSD describe EPA’s recommendations for default inputparameters in the BLM to derive protective freshwater aquatic life criteria when data are lacking.However, it should be noted that site-specific data are always preferable for developing criteria basedon the BLM and should be used when possible. Users of the BLM are encouraged to sample their waterbody of interest, and to analyze the samples for the constituent (parameter) concentrations as a basisfor determining BLM inputs where possible.vi