Human and Ecological Risk Assessment - Earthjustice

Section 3.0Analysissediment and porewater in the sediment layer. These distributions were derived from publishedempirical data as described in U.S. EPA (1999b).Table 3-9. Sediment/Water Partition Coefficients: Empirical Distributions aChemicalAluminumDistributionType Minimum Mean Maximum SDnot usedAntimony log normal 0.6 3.6 4.8 1.8Arsenic log normal 1.6 2.4 4.3 0.7Barium log normal 0.9 2.5 3.2 0.8Boron log normal 0.5 0.8 1.4 0.5Cadmium log normal 0.5 3.3 7.3 1.8Cobalt log normal 2.2 3.9 5.3 0.8Lead log normal 2.0 4.6 7.0 1.9Molybdenum log normal 1.3 2.2 3.2 0.9Selenium IV log normal 1.0 3.6 4.0 1.2Selenium VI log normal 1.4 0.6 3.0 1.2Thallium log normal 0.5 1.3 3.5 1.1Total Nitrate Nitrogen constant 0 0 0 0Source: U.S. EPA (1999b).SD = standard deviation.a All values are log values.Following calculation of the constituent loading and loss rates, the surface water modelestimates steady-state, equilibrium waterbody contaminant concentrations in each compartmentusing equations presented in Attachment E-1 to Appendix E. For evaluating risks to humanhealth from fish consumption, the model calculates waterbody concentrations using groundwaterloadings that are explicitly averaged over the exposure period for the each human receptor (i.e.,adult and child fishers). These average waterbody concentrations are then used to calculate fishconcentrations as described in Section 3.7.2. Ecological risks were based on waterbodyconcentrations calculated using the peak annual groundwater loading value from EPACMTP.The equilibrium–partitioning model, as implemented, is conservative because there are no lossmechanisms (e.g., burial) for any of the constituents.3.7.2 Aquatic Food Web ModelAn aquatic food web model was used to estimate the concentration of CCW constituentsthat accumulate in fish. This risk assessment assumed that fish are a food source for arecreational fisher. Trophic level three (TL3) and four (TL4) fish 12 were considered in thisanalysis because most of the fish that humans eat are T4 fish (e.g., salmon, trout, walleye, bass)and medium to large T3 fish (e.g., carp, smelt, perch, catfish, sucker, bullhead, sauger). Theaquatic food web model has been peer reviewed as part of the 3MRA model development effort(see http://www.epa.gov/osw/hazard/wastetypes/wasteid/hwirwste/peer03/aquatic/aqtfoods.pdf).12TL3 fish are those that consume invertebrates and plankton; TL4 fish are those that consume other fish.April 2010–Draft EPA document. 3-38