EPA Contract Number 68-W6-0053 RTI Project Number 92U-6720-001 Supplemental Background Document; NonGroundwater Pathway Risk Assessment; Petroleum Process Waste Listing Determination Prepared for U.S. Environmental Protection Agency Office of Solid Waste, OSW (Note: Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009) Research Triangle Park, NC 27711 Prepared by Research Triangle Institute P.O. Box 12194 Research Triangle Park, North Carolina 27709 March 20, 1997 CONTENTS 1.0 Background. . . . . . . . . . . . . . . . . . . . . . 1 2.0 Waste Stream and Waste Management Unit Characterization. . . . . . . . . . . . . . . . . . . 3 2.1 Waste Stream Characteristics . . . . . . . . . . 3 2.2 Characterization of Onsite Land Treatment Units. 3 3.0 Soil Erosion to Adjacent Waterbody and Intervening Receptor Site . . . . . . . . . . . . . . . . . . . . 5 3.1 Methodology in Proposed Listing Decision (Independent Settings) . . . . . . . . . . . . . 5 3.2 Revised Methodology for Integrated Setting. . . 5 3.2.1 Soil Load from LTU to Receptor Site. . 6 3.2.2 Total Constituent Load to Waterbody. . 11 3.2.3 Summary. . . . . . . . . . . . . . . . 15 4.0 Biodegradation of PAHs in Soil. . . . . . . . . . . . 16 5.0 Exposure Factors for Nongroundwater Pathways. . . . . 17 6.0 Shower Model and Exposure Factors for Inhalation and Dermal Risk from Residential Use of Groundwater . . . 18 6.1 Description of Shower Model. . . . . . . . . . . 19 6.2 Exposure Factors . . . . . . . . . . . . . . . . 22 6.3 Dermal Exposure to Tap Water . . . . . . . . . . 24 7.0 Codisposal Scenarios. . . . . . . . . . . . . . . . . 24 7.1 Codisposal in Onsite Land Treatment Units. . . . 25 7.2 Codisposal in Offsite Land Treatment Units . . . 25 8.0 Crude Oil Tank Sludge . . . . . . . . . . . . . . . . 29 9.0 Clarified Slurry Oil. . . . . . . . . . . . . . . . . 54 10.0 Unleaded Gasoline Tank Sludge . . . . . . . . . . . . 79 11.0 Sulfur Complex Sludge . . . . . . . . . . . . . . . . 104 12.0 Hydrofluoric Acid Alkylation Sludge . . . . . . . . . 129 13.0 Sulfuric Acid Alkylation Sludge . . . . . . . . . . . 154 14.0 Off-specification Products and Fines. . . . . . . . . 179 15.0 Codisposal of Petroleum Refining Waste Streams. . . . 204 16.0 References. . . . . . . . . . . . . . . . . . . . . . 268 LIST OF FIGURES 3.1 Diagram of Integrated Soil Erosion Setting. . . . . . 7 LIST OF TABLES 2.1 Recalculated Quantity Distributions of Wastes Managed in Land Treatment Units with Hazardous Wastes Removed. . . . . . . . . . . . . . . . . . . . 4 2.2 Revised Distribution of Areas for Onsite Land Treatment Units . . . . . . . . . . . . . . . . . . . 4 3.1 Guide to Modified Equations for Overland Transport. . 8 4.1 Biodegradation Rates Used for Receptor Site Soil Loss Equations. . . . . . . . . . . . . . . . . . . . 16 5.1 Exposure Factors Used in Risk Assessment. . . . . . . 18 5.2 Meteorologic Parameters Used in Risk Analysis . . . . 18 6.1 Exposure Factors Used to Determine Risk from Inhalation Exposure to Contaminated Tap Water . . . . 23 6.2 Physical and Chemical Properties of Benzene Used in Shower Inhalation Exposure Model. . . . . . . . . . . 23 7.1 Nonhazardous Onsite Land Treatment Units and Codisposal Waste Streams. . . . . . . . . . . . . . . 26 7.2 Nonhazardous Offsite Land Treatment Units and Codisposal Waste Streams. . . . . . . . . . . . . . . 27 8.1 Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher . . . . 29 8.2 Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer . . . . 30 8.3 Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Home Gardener. . . . . . . 31 8.4 Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Adult Resident . . . . . . 32 8.5 Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher. . 33 8.6 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher. . 34 8.7 Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Close Receptor Subsistence Farmer. . . . . . 35 8.8 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Close Receptor Subsistence Farmer. . . . . . 36 8.9 Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Close Receptor Home Gardener . . . . . . . . 37 8.10 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Close Receptor Home Gardener . . . . . . . . 38 8.11 Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident. . . . 39 8.12 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident. . . . . . . . . . . . . . . . . . . . . . . 40 8.13 Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher. . . . 41 8.14 Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer. . . . 42 8.15 Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Home Gardner. . . . . . . 43 8.16 Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Adult Resident. . . . . . 44 8.17 Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Subsistence Fisher. . . . 45 8.18 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Subsistence Fisher. . . . 46 8.19 Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Close Receptor Subsistence Farmer. . . . . . . . 47 8.20 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Close Receptor Subsistence Farmer. . . . . . . . 48 8.21 Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Close Receptor Home Gardener . . . . . . . . . . 49 8.22 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Close Receptor Home Gardener . . . . . . . . . . 50 8.23 Media Concentrations for Crude Oil Tank sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Adult Resident. . . . . . 51 8.24 Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Adult Resident. . . . . . 52 9.1 Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher. . . . . . . . . . . . . . . . . . . . . . . . 54 9.2 Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer. . . . . . . . . . . . . . . . . . . . . . . . 55 9.3 Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Home Gardener . 56 9.4 Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Adult Resident. 57 9.5 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher. . 58 9.6 Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . . . . . . . . . . . . 59 9.7 Media Concentrations for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer. . 60 9.8 Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer. . 61 9.9 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener . . . . 62 9.10 Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener . . . . 63 9.11 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident. . . . 64 9.12 Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident. . . . 65 9.13 Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher. . . . . . . . . . . . . . . . . . . . . . . . 66 9.14 Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer. . . . . . . . . . . . . . . . . . . . . . . . 67 9.15 Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Home Gardener. 68 9.16 Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Adult Resident 69 9.17 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . . . . . . 70 9.18 Individual Risk by Pathway for Clarified Slurry Oil Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . . . . . . 71 9.19 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . . . . . . 72 9.20 Individual Risk by Pathway for Clarified Slurry Oil Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . . . . . . 73 9.21 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardner . . . . . . . . . . . . . . . . . . . . . . . 74 9.22 Individual Risk by Pathway for Clarified Slurry Oil Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener. . . . . . . . . . . . . . . . . . . . . . . 75 9.23 Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident. . . . . . . . . . . . . . . . . . . . 76 9.24 Individual Risk by Pathway for Clarified Slurry Oil Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident. . . . . . . . . . . . . . . . . . . . 77 10.1 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 79 10.2 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 80 10.3 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Home Gardener. 81 10.4 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Adult Resident 82 10.5 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 83 10.6 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 84 10.7 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 85 10.8 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 86 10.9 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. 87 10.10 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . . . . . . . . 88 10.11 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . . . . 89 10.12 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adust Resident . . . . . . . . . . . . . . . . . . . . . . 90 10.13 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 91 10.14 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 92 10.15 Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Home Gardener 93 10.16 In Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Adult Resident. . . . . . . . . . . . . . . . . 94 10.17 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . 95 10.18 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . 96 10.19 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . 97 10.20 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . 98 10.21 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . 99 10.22 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . 100 10.23 Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Adult Resident . . 101 10.24 Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit, Small Area/Long Exposure Duration Adult Resident . . 102 11.1 Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher . . 104 11.2 Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer . . 105 11.3 Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Home Gardener. . . . . 106 11.4 Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Adult Resident . . . . 107 11.5 Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 108 11.6 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 109 11.7 Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 110 11.8 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 111 11.9 Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 112 11.10 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 113 11.11 Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 114 11.12 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 115 11.13 Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher . . . 116 11.14 Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer . . . 117 11.15 Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Home Gardener. . . . . . 118 11.16 Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Adult Resident . . . . . 119 11.17 Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 120 11.18 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 121 11.19 Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 122 11.20 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 123 11.21 Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 124 11.22 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 125 11.23 Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 126 11.24 Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 127 12.1 Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher. . . . 129 12.2 Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer. . . . 130 12.3 Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Home Gardener . . . . . . 131 12.4 Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Adult Resident. . . . . . 132 12.5 Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 133 12.6 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . 134 12.7 Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 135 12.8 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . 136 12.9 Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 137 12.10 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. . . . 138 12.11 Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 139 12.12 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident . . . 140 12.13 Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher . . . 141 12.14 Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer . . . 142 12.15 Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Home Gardener. . . . . . 143 12.16 Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Adult Resident . . . . . 144 12.17 Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . 145 12.18 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . 146 12.19 Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . 147 12.20 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . 148 12.21 Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener. . . . . . . . . . . . . . . . . . . . 149 12.22 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener. . . . . . . . . . . . . . . . . . . . 150 12.23 Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . 151 12.24 Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . 127 13.1 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . 154 13.2 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . 155 13.3 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Home Gardener. 156 13.4 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Adult Resident 157 13.5 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 158 13.6 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . 159 13.7 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 160 13.8 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . 161 13.9 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener. 162 13.10 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . . . . . . . . 163 13.11 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Adult Resident 164 13.12 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . . . . 165 13.13 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 166 13.14 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 167 13.15 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Home Gardener 168 13.16 Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Adult Resident . . . . . . . . . . . . . . . . . . . . . . 169 13.17 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 170 13.18 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . 171 13.19 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 172 13.20 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . 173 13.21 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener. 174 13.22 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . . . . . . . . 175 13.23 Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Adult Resident 176 13.24 Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit, Close Receptor/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . . . . 177 14.1 Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . 179 14.2 Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . 180 14.3 Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Home Gardener . . . . . . . . . . . . . . . . . . . . . . 181 14.4 Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Adult Resident . . . . . . . . . . . . . . . . . . . . . . 182 14.5 Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 183 14.6 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . 184 14.7 Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 185 14.8 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . 186 14.9 Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener. 187 14.10 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . 188 14.11 Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident 189 14.12 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit, Large Quantity/Long Exposure Duration Adult Resident. . . . . . . . . . . . . . . 190 14.13 Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Subsistence Fisher . . . . . . . . . . . . . . . . . 191 14.14 Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Subsistence Farmer . . . . . . . . . . . . . . . . . 192 14.15 Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Home Gardener . . . . . . . . . . . . . . . . . . . . . . 193 14.16 Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Adult Resident . . . . . . . . . . . . . . . . . . . . . . 194 14.17 Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher. . . . . . . . . . . . . 195 14.18 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/ Long Exposure Duration Subsistence Fisher. . . . . . 196 14.19 Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer. . . . . . . . . . . . . 197 14.20 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/ Long Exposure Duration Subsistence Farmer. . . . . . 198 14.21 Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener . . . . . . . . . . . . . . . 199 14.22 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/ Long Exposure Duration Home Gardener . . . . . . . . 200 14.23 Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident. . . . . . . . . . . . . . . 201 14.24 Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/ Long Exposure Duration Adult Resident. . . . . . . . 202 15.1 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Subsistence Fisher. . . . 205 15.2 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Subsistence Farmer. . . . 206 15.3 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Home Gardener . . . . . . 208 15.4 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Adult Resident. . . . . . 210 15.5 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 212 15.6 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . 214 15.7 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . . . . . . . . 216 15.8 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer . 218 15.9 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener. . . . . . . . . . . 220 15.10 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener. . . . . . . . . . . 222 15.11 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident 224 15.12 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident 226 15.13 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Subsistence Fisher . . . 228 15.14 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Subsistence Farmer . . . 231 15.15 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Home Gardener. . . . . . 234 15.16 Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Adult Resident . . . . . 237 15.17 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 240 15.18 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher . . . . . . . . . . . . . . . . . . . . . . . 242 15.19 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 244 15.20 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer . . . . . . . . . . . . . . . . . . . . . . . 246 15.21 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener . 248 15.22 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener . 250 15.23 Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident 252 15.24 Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in an Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident . . . . . . . . . . . . . . . . . . . 254 15.25 Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Subsistence Fisher. . . . . . . . . . 256 15.26 Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Subsistence Farmer. . . . . . . . . . 259 15.27 Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Home Gardener . . . . . . . . . . . . 262 15.28 Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Adult Resident. . . . . . . . . . . . 265 SUPPLEMENTAL BACKGROUND DOCUMENT FOR THE NONGROUNDWATER RISK ASSESSMENT FOR THE PETROLEUM WASTE LISTING INTERIM NOTICE OF DATA AVAILABILITY 1.0 BACKGROUND On November 20, 1995, the U.S. Environmental Protection Agency (EPA) proposed to amend the hazardous waste management regulations under the Resource Conservation and Recovery Act (RCRA) by listing as hazardous wastes three residuals from petroleum refining processes for which certain disposal practices may present an unacceptable risk to human health or the environment (60 FR 57747). The Agency proposed not to list as hazardous 11 process residuals. EPA received a number of comments on the risk analysis performed in support of the proposed rule. This document describes new or expanded analyses performed in response to a number of specific comments received regarding the nongroundwater risk assessment. Following is a brief summary of the comments addressed by this analysis. Waste stream volumes and land treatment unit (LTU) sizes. Comments on the proposed rule pointed out that the majority of active LTUs receiving the petroleum residuals are, in fact, Subtitle C units, and that such units must meet strict runon/runoff control permit requirements. Therefore, the commenters claimed that EPA's assumption on no runon/runoff controls for these units is incorrect. To respond to this comment, EPA examined the status of all land treatment units modeled and limited the unit characteristics used in risk modeling to those units that are not permitted hazardous waste units. EPA also modified the volume data somewhat to remove from modeling consideration all waste volumes that were classified as hazardous waste and could not be sent to a nonhazardous land treatment unit. Several commenters questioned the transport of soil from the land treatment area to the receptors as not being physically possible as described by EPA. Therefore, the commenters believed there to be no direct or indirect exposure to these subpopulations from soils. To respond to these comments, EPA revised its overland transport equations. Two commenters noted that EPA did not consider biodegradation of polynuclear aromatic hydrocarbons (PAHs) in soils at the receptor site. Commenters asserted that biodegradation can significantly affect long-term estimates of soil concentrations and therefore the failure to consider this loss mechanism may result in substantial overstatements of risks resulting from soil exposures. To respond to these comments, EPA included biodegradation in all soils. Commenters noted that EPA incorrectly calculated risks to home gardeners from consumption of root vegetables. The procedures used to compute the exposure from ingestion of soil and aboveground and belowground produce grown in these soils is also flawed. To respond to these comments, EPA reviewed all ingestion rate input parameters and corrected the values used in the analysis where necessary. Commenters noted that EPA failed to consider risks from dermal and inhalation exposure to groundwater contaminants such as benzene from household use of tapwater for activities such as bathing and showering. To respond to this comment, EPA reviewed numerous shower inhalation models and included a model for estimating risk through this pathway. Commenters noted that multiple petroleum wastes are often disposed of in the same treatment or disposal unit; therefore, risk estimates should consider this codisposal scenario in estimating risk of exposure to petroleum waste streams. To respond to this comment, EPA has evaluated specific codisposal scenarios to determine risk from disposal of multiple wastes in a single land treatment unit. Changes to the nongroundwater risk assessment for petroleum refining waste streams in response to comments summarized above are discussed in the following sections: Section 2.0 waste stream and waste management unit characteristics Section 3.0 soil erosion and the use of the Universal Soil Loss Equation (USLE) for estimating soil concentrations in adjacent receptor sites Section 4.0 biodegradation of PAH in soil Section 5.0 changes to exposure factors used in the analysis. The following sections present new analyses that have been added to the risk assessment in response to public comments: Section 6.0 noningestion exposures to contaminated groundwater through bathing and showering Section 7.0 risk assessment methodology for codisposal of petroleum waste streams in nonhazardous land treatment units. In addition, the management in nonhazardous land treatment units of off-specification products and fines is evaluated for the first time. Application of this waste stream to land treatment units was not evaluated for the proposed rule because this management practice was not considered prevalent. However, as a result of public comments, EPA evaluated codisposal of petroleum refining wastes in nonhazardous land treatment units. Because this waste stream is now included in a codisposal scenario, it has been evaluated as a single waste stream, although management in land treatment units is not a common practice (i.e., according to EPA, a maximum quantity of 34 metric tons (t) of off-specification products and fines was managed in at least three onsite units and 21 t of this waste was managed in a single offsite land treatment unit in 1992). The results of the revised risk analyses are presented in the following sections: Section 8.0 crude oil tank sludge Section 9.0 clarified slurry oil sludge Section 10.0 unleaded gasoline tank sludge Section 11.0 sulfur complex sludge Section 12.0 hydrofluoric acid alkylation sludge Section 13.0 sulfuric acid alkylation sludge Section 14.0 off specification products and fines Section 15.0 codisposal of petroleum wastes. Appendix A presents the revised equations used for estimating soil erosion in the revised integrated setting (A-1 through A-4) and the equations added to the analysis for estimating risk through inhalation exposure to household use of groundwater (A-5). Appendix B presents the compound-specific input parameters for PAH compounds required for the risk analysis, including soil biodegradation rates applicable to nonamended soils at receptor locations. 2.0 WASTE STREAM AND WASTE MANAGEMENT UNIT CHARACTERIZATION Waste stream and waste management unit characteristics are the basis for all potential release scenarios. The changes in these data as a result of EPA's reevaluation are presented in this section. 2.1 Waste Stream Characteristics Waste stream quantity distributions have been recalculated to remove waste quantities that were already classified and managed as hazardous. All remaining waste stream characteristics (e.g., constituent concentration, percent organic carbon) remained identical to those presented in the background document for risk assessment supporting the proposed rule. Table 2.1 presents the recalculation of waste quantity distributions sent to land treatment units with hazardous wastes removed. 2.2 Characterization of Onsite Land Treatment Units Onsite land treatment unit area distributions have been recalculated to remove land treatment units already permitted as hazardous (SAIC, 1997). All remaining waste management unit characteristics remain identical to those presented in the background document for risk assessment supporting the proposed rule. Table 2.2 presents the recalculation of land treatment unit areas with those permitted as hazardous waste facilities removed. No facilities reported disposing of sulfuric acid alkylation sludge in onsite nonhazardous land treatment units in the 3007 Questionnaire data; however, any facility that reported the presence of an operational sulfuric acid alkylation unit and the presence of an onsite nonhazardous land treatment unit that could be used for disposal of this waste were considered appropriate for disposal of this waste. Table 2.1 Recalculated Quantity Distributions of Wastes Managed in Land Treatment Units with Hazardous Wastes Removed Table 2.2 Revised Distribution of Areas for Onsite Land Treatment Units 3.0 SOIL EROSION TO ADJACENT WATERBODY AND INTERVENING RECEPTOR SITE Commenters questioned several aspects of the nongroundwater risk assessment utilizing the overland transport pathways (soil erosion) stating that the transport of soil from the land treatment area to the receptors is not physically possible as described by EPA. Therefore, the commenters believed that no direct or indirect exposure to subpopulations from soils was possible. Based on these comments, the overland transport pathways have been reviewed in detail and the following changes have been made in the application of the USLE for this purpose. 3.1 Methodology in Proposed Listing Decision (Independent Settings) The USLE is an empirical erosion model originally designed to estimate long-term average soil erosion losses to a nearby waterbody from an agricultural field having uniform slope, soil type, vegetative cover, and erosion-control practices. In the risk assessment conducted in support of the proposed listing decision, the USLE was used to estimate the mass of soil lost per year per unit area from a land treatment unit and deposited directly onto the adjacent receptor site. A fixed sediment delivery ratio was used to estimate the percentage of eroded soil that ultimately reached the receptor site. The quantity of soil eroded from the LTU and deposited directly on each receptor site (agricultural field, residential lot, home garden) was estimated independently of soil eroded from the LTU and deposited into the nearest surface waterbody. 3.2 Revised Methodology for Integrated Setting In response to comments, the method of estimating risk from the overland transport pathways was modified by EPA's Office of Solid Waste, OSW (Note: Office of Solid Waste, OSW, was renamed Office of Resource Conservation and Recovery, ORCR, on January 18, 2009) and the Office of Research and Development (ORD). The USLE was modified to estimate soil erosion and overland transport of sediment from LTUs across intervening areas to nearby waterbodies by evaluating this process in an integrated setting (Beaulieu et al., 1996). In the proposed rule, overland transport of sediment from LTUs to receptor locations was estimated independently from transport from the LTU to the waterbody. Because the USLE equation estimates only soil erosion to waterbodies, the receptor location is considered to be located between the LTU and the waterbody. The area including the LTU, the receptor site, and the intervening area is considered for the purposes of this analysis to be an independent drainage subbasin. The soil erosion load from the subbasin to the waterbody is estimated using a distance-based sediment delivery ratio and the sediment not reaching the waterbody is considered to be deposited evenly over the area of the subbasin. Thus, using mass balance equations, contributions to the constituent concentrations of the waterbody and of the receptor soil may be estimated. The equations implementing the concept of the integrated setting are based on the following assumptions: The area of the management unit (LTU) and the area between the management unit and the nearest waterbody, including the receptor site, make up a discrete drainage subbasin. These areas are shown in Figure 3.1. The sediment delivery ratio (SDSB) and the soil loss rate per unit area are assumed to be constant for all areas within the subbasin. The amount of soil deposited onto the receptor site through soil erosion is estimated by assuming that the fraction of soil that does not reach the waterbody remains in the subbasin. The entire subbasin drainage system is assumed to be at steady-state. Consequently, steady-state soil concentrations for the different subareas (e.g., receptor site, surrounding area) can be calculated using a mass balance approach. The soils within the watershed are assumed (on the average) to have the same soil properties (e.g., bulk density, soil moisture content), a reasonable assumption for areas with similar irrigation rates with infrequent tilling. The soil/constituent movement within the entire watershed is evaluated separately from the soil/constituent movement that occurs in the drainage subbasin. Only air deposition of constituents contributes to the constituent concentrations in soil outside the subbasin. The contribution of each area within the watershed to the constituent concentration in the waterbody is estimated independently and summed to estimate the total waterbody concentration. No contributions to constituent concentrations are assumed to occur from sources other than the LTU within the subbasin. Table 3.1 lists the modified equations for overland transport used to implement the integrated setting approach to soil erosion and indicates if these equations have been changed or added since the proposed rule. The equations are presented in detail in Appendix A. All soil parameters and environmental factors required to evaluate soil erosion using the revised USLE equations remain identical to those used for the proposed rule. The values for these factors are presented in Appendix A with the equations in which they are used. 3.2.1 Soil Load from LTU to Receptor Site The mass of eroded soil (soil load) from the LTU to the receptor site (SLO,F) is a major input required to calculate the receptor site soil constituent concentration (CF). The receptor site (residential plot, home garden, or agricultural field) soil concentrations are used to estimate risk through the soil ingestion pathway for all scenarios and through the food chain pathways (e.g., aboveground and belowground produce) for the home gardener and subsistence farmer scenarios. By assuming that the probability of soil redeposition is equivalent for all areas within the subbasin (i.e., the LTU, intervening area, and the receptor site), the amount of contaminated soil that erodes onto any area can be calculated by using a simple ratio of the area of concern to the total area for soil deposition: where DS0,F = soil delivery rate from source (LTU) to receptor (kg/yr) Xc,s = unit soil loss rate from LTU (kg/m2-yr) AS = area of the LTU (m2) SDSB = sediment delivery ratio of the subbasin to the nearest waterbody (unitless) SF0,F = deposition area scaling factor (m2/m2) = ratio of the receiving field area to the entire area available for deposition = AF/(AS + AB/Surr + AF) AF = area of the receptor site (m2) AB/Surr = area of the buffer and surrounding areas within the subbasin (m2). 3.2.2 Total Constituent Load to Waterbody The total load to the waterbody (LT) is the sum of the constituent load via erosion (LE) and the constituent load from pervious runoff (LR). The total load to the waterbody is used to estimate risk to the subsistence and/or recreational fisher from the ingestion of fish. The estimation of LE requires the calculation of a weighted average constituent concentration in watershed soils based on the eroded soil contribution (Sc,erode), and the LR term requires the calculation of a weighted average constituent concentration based on the pervious runoff contribution (Sc,run). The weighted average constituent concentration represents the effective watershed soil concentration based on contributions from the subbasin and the remainder of the watershed. Most important, the weighted average concentration accounts for the differences in constituent concentrations in the different areas within the watershed. The calculation of LTrequires constituent concentrations for each of the following areas within the watershed: the source (LTU), the receptor site, the buffer and surrounding area, and the watershed area outside the drainage subbasin. For the watershed soils outside the subbasin, it is assumed that constituents reach the watershed solely via air deposition (i.e., no erosion component). Calculation of LT requires constituent concentrations for each of the following areas within the watershed: the source (LTU); the offsite field, the buffer, and surrounding area within the subbasin); and the watershed area outside the drainage subbasin. If we consider the erosion load (LE) to the surface waterbody for each of these areas individually,the equation may be written as: where LE = constituent load to watershed due to erosion (g/yr) Xe,SB = unit soil loss in subbasin (kg/m2/yr) ER = enrichment ratio SDSB = sediment delivery ratio for subbasin A0 = area of source (m2) C0 = constituent concentration at the source (mg/kg) Kds = soil water partition coefficient (L/kg) BD = bulk density of soil (g/cm3) = volumetric soil content of soil (cm3/cm3) 0.001 = unit conversion factor ([g/kg]/[mg/kg]). AF = area of receptor field (m2) CF = constituent concentration in receptor site field (mg/kg) AB/Surr = area of buffer and surrounding area (m2) CB/Surr = constituent concentration in buffer and surrounding area (mg/kg) Xe = unit soil loss in watershed outside of subbasin (kg/m2/yr) SDSB = sediment delivery ratio for watershed (unitless) AWS = area of entire watershed (m2) CWS = constituent concentration in watershed soils outside of subbasin (mg/kg). The enrichment ratio (ER) has been added to the revised soil erosion equations. It was not included in the equations used for the proposal rule. This factor represents the reality that erosion favors the lighter soil particles, which have higher surface-area-to-volume ratios and are higher in organic matter content. Therefore, concentrations of organic constituents, which are a function of organic carbon content of sorbing media, would be expected to be higher in eroded soil then in in situ soil. This factor is generally assigned values in the range of 1 to 5. A value of 3 for organic contaminants and a value of 1 for metals would be reasonable first estimates and have been used in this analysis (U.S. EPA, 1994). Alternatively, this equation can be written in terms of an average weighted soil concentration for the watershed that results in the same constituent load as a function of erosion and sediment delivery. The Sc,erode term shown at the end of Equation 3-3 reflects this modification: LT also requires the constituent load from pervious runoff (LR). The LR term is calculated using equation 3-4. where LR = pervious surface runoff load (g/yr) R = average annual surface runoff (cm/yr) Aws = area of entire watershed (m2) AI = impervious watershed area receiving constituent deposition (m2) Sc = weighted average constituent concentration in total watershed soils (watershed and sub-basin) based on surface area (mg/kg) BD = soil bulk density (g/cm3) = volumetric soil content of soil (cm3/cm3) Kds = soil water partition coefficient (L/kg) or (cm3/g) 0.01 = units conversion factor (kg-cm2/mg-m2). Assuming that the ratio of pervious and impervious soils is the same for each of the designated areas, a correction for areas that do not erode (streets, rocks, etc.) can be added to Equation 3-3 by replacing AWS with AWS - AI , where AI equals the total impervious area in the watershed. Setting the LR equal to each other in the previous two equations and solving for Sc,erode yields: Equation 3-5 accounts for differences in the sediment delivery ratios (SD), surface areas (A), and mixing depths (Z) for discrete areas of the watershed (i.e., source, receptor field, buffer/surrounding areas, and the remaining watershed). Similarly, the weighted average for runoff losses (ksr) was derived using the areas for various watershed components (e.g., receptor site field, watershed outside drainage subbasin); however, different sediment delivery ratios were not required because soils in the area were considered to be similar and the slope was considered uniform. It was possible to generate simple area-based weighting factors because the rainfall runoff per unit area was assumed to be constant for the entire watershed area. Constituent Concentrations in Various Watershed Components The constituent concentrations for the receptor site field (CF), the buffer and surrounding area (CB/Surr), and the watershed area outside of the drainage subbasin (CWS) are required to solve Sc,erode. As suggested previously, a mass balance approach was used to calculate the constituent concentrations for all watershed components. For the receptor site field, the mass balance equation is given by: where MF = mass of the field (kg) CF = constituent concentration in the receptor site field (mg/kg) SL0,F = soil load from source to the field (kg/yr) Ds(1),F = air deposition rate from source to the field (mg/kg-yr) SLB,F = soil load from buffer to the field (kg/yr) ksF = constituent loss rate coefficient for the field (per yr). At steady state, this equation can be solved for the constituent concentration in the receptor site field as follows: As with the constituent concentration in the receptor site field, the concentration in the buffer and surrounding area is given by: where MB/Surr = mass of the buffer and surrounding area (kg) CB/Surr = constituent concentration in the buffer and surrounding area (mg/kg) SL0,B/Surr = soil load from source to buffer/surrounding areas (kg/yr) C0 = soil constituent concentration at the source (mg/kg) Ds(1),B/Surr = air deposition rate from source to buffer and surrounding area (mg/kg-yr) ksB/Surr = constituent loss rate coefficient for the buffer/surrounding area (per/yr). At steady state, this equation may be solved for CB/Surr as follows: For the watershed soils outside of the subbasin, we assumed that constituents reached the watershed solely via air deposition (i.e., no erosion component). Using similar mass balance and steady-state assumptions, the constituent concentration in watershed soils outside the subbasin may be calculated using: where CWS = soil constituent concentration in the watershed (mg/kg) Ds(1),WS = air deposition rate from source to the watershed (mg/kg/yr) ksWS = constituent loss rate coefficient for the watershed (per yr). 3.2.3 Summary The equations and default input parameter values used to calculate receptor site soil concentrations and the waterbody concentrations of constituents of concern, including the revised overland transport pathways, are presented in Appendix A. Contaminated particles are transported from the land treatment unit to receptor sites via air deposition as well as runoff/erosion. For a complete discussion of the equations for estimating the contribution to the constituent soil concentration from air deposition, consult the background document for the risk assessment for the proposed rule. For the revised integrated setting analysis, mass balance was applied for each area of interest (e.g., buffer area between source and receptor site, receptor site, or surrounding area). Consequently, the respective air deposition value for each area of interest is included in the evaluation of the mass balance. The air deposition over the entire subbasin area was considered to be uniform and equal to the air deposition modeled for the receptor site. However, in reviewing the spreadsheet equations used to implement the equations presented in the background document it was discovered that a unit conversion from æg/m2 to g/m2 was performed in two locations, creating an underestimation of risk due to air deposition of 6 orders of magnitude. This error has been corrected in the risk analysis presented in this document. The unit conversion correction makes the risk due to air deposition from windblown soil from the LTU the same order of magnitude as the risk attributed to soil erosion in each case; i.e., if the risk due to soil erosion is in the range of 10E-6, the risk due to air deposition is also 10E-6. The revised risk assessment results presented in Sections 8 through 15 of this document are estimated using the integrated setting approach and include the overland transport equations presented in Appendix A and the corrected spreadsheet equations described above and presented in Appendix E of the background document for the proposed rule. 4.0 BIODEGRADATION OF PAHS IN SOIL Biodegradation of polynuclear aromatic hydrocarbons in soil was considered only within the boundaries of the land treatment unit in the risk analysis performed for the proposed rule. Biodegradation was included within the LTU because this soil is frequently amended to ensure the presence of soil organisms adapted for the degradation of petroleum wastes. For the proposal, the Handbook of Environmental Degradation Rates (Howard et al., 1991) was used to identify a range of values for soil degradation rates representing a variety of soil types and climates. EPA selected the lowest soil biodegradation rate reported for use in the risk analysis. Biodegradation outside LTU was not considered for the proposed rule. Commenters questioned EPA's conservative assumption that no biodegradation occurred from the LTU and to the receptor. In response, EPA incorporated biodegradation of PAHs in soils outside the LTU. For this revised risk analysis, the same biodegradation rate has been assumed for all soils, including all soils inside and outside the LTU. Table 4.1 presents the soil half-lives used to calculate the biodegradation rates used in this analysis. The biodegradation rates are also presented in Appendix B with the compound-specific input data. Table 4.1 Biodegradation Rates Used for Receptor Site Soil Loss Equations CAS Number Chemical Name Biodegradation Rate (per yr) 50-32-8 Benzo(a)pyrene 0.478 53-70-3 Dibenz(a,h)anthracene 0.269 56-49-5 3-Methylcholanthrene 0.181 56-55-3 Benz(a)anthracene 0.373 57-97-6 Dimethylbenz(a)anthracene 9.04 193-39-5 Indeno(1,2,3-cd)pyrene 0.347 205-99-2 Benzo(b)fluoranthene 0.415 207-08-9 Benzo(k)fluoranthene 0.118 218-01-9 Chrysene 0.255 Source: Soil half-lives presented in Howard et al., 1991. 5.0 EXPOSURE FACTORS FOR NONGROUNDWATER PATHWAYS All exposure factors used in the risk assessment for the petroleum waste listing decision have been reviewed and are consistent with the EPA guidance presented in the 1990 Exposure Factors Handbook. These values used are documented in the risk equations in which they are used in Appendix A of this document. The values for all exposure factors used in the risk assessment for the proposed rule and the reanalysis are identical except for ingestion of root vegetables. The wrong value for ingestion of root vegetables was used in the analysis for the proposed rule; the correct value was used in the reanalysis. The values presented in column 3 of Table 5.1 were used in the reanalysis. A 1996 update of the 1990 Exposure Factors Handbook has been published in draft form and is currently available to the public (U.S. EPA, 1996a). Copies can be obtained from NTIS. The document numbers are: Volume I - PB97-117683 Volume II - PB97-117691 Volume III - PB97-117709 Set of Volumes I-III - PB97-117675. The document can also be viewed at all EPA libraries and through the Internet. The Internet address is www.epa.gov/ord/whatsnew.htm. This draft document will be revised and issued as final in the Summer 1997. Exposure factors critical to the petroleum risk assessment (e.g., soil ingestion) are unlikely to change between draft and final versions of the handbook. The Agency may use exposure factors from the 1997 final version for the final rule. Based on a preliminary analysis of key exposure factors, the Agency does not believe that use of updated exposure factors will significantly change the outcome of the risk assessment presented in this NODA. The preliminary analysis is provided in Appendix D of this document. The soil ingestion rate for the home gardener remained constant in the revised analysis as indicated in Table 5.1; however, the source of ingested soil has been revised to represent soil from the untilled residential plot instead of representing soil from the tilled home garden as assumed in the proposed rule. The values for the meteorologic parameters used in this analysis are identical to those used in the risk analysis for the proposed rule. These values are used consistently throughout both analyses although typographical errors appeared in some tables in the background document for the proposed rule. The values used for the meteorologic-dependent parameters used in the analysis conducted for the proposed rule and in this revised analysis are presented in Table 5.2. Table 5.1 Exposure Factors Used in Risk Assessment Exposure Factor Central Tendency Central Tendency Adult Exposure Adult (Reanalysis) (Proposed Rule) Soil ingestion 100 mg/da 100 mg/d Aboveground produce 19.7 g/d 19.7g/d (DW) ingestion Root vegetable 1.4 g/d 28 g/db (WW) ingestion Fish, ingestion Subsistence - Subsistence - (fisher scenarios) 60 g/d 60 g/d Recreational - Recreational - 30 g/d 30 g/d Beef, ingestion 57 g/d 57 g/d Milk, ingestion 181 g/d 181 g/d Source: U.S.EPA, 1990. a Standard type face indicates no change from the proposal. b Revised exposure factors are boldfaced. Table 5.2 Meteorologic Parameters Used in Risk Analysis Parameter Central Tendency High End (Houston, TX) (Los Angeles, CA) Annual 119.1 28.7 Precipitation (cm/yr) Annual 22.73 7.31 Evapotranspiration (cm/yr) Annual Runoff 13 1.3 Value (cm/yr) Annual Infiltration 83.7 20.09 Rate (cm/yr) 6.0 SHOWER MODEL AND EXPOSURE FACTORS FOR INHALATION AND DERMAL RISK FROM RESIDENTIAL USE OF GROUNDWATER The multimedia multipathway exposure model used for the proposed petroleum waste listing determination did not include inhalation or dermal exposures to constituents in residential tap water. In response to public comments, shower inhalation exposure models were evaluated for inclusion of these pathways in the groundwater risk analysis for the petroleum waste listing. A detailed discussion of the model review and selection process is provided in Appendix C. 6.1 Description of Shower Model The shower model used in this analysis is based the equations presented in McKone (1987). The shower model estimates the change in the shower air concentration based on the mass of constituent lost by the water (fraction emitted or emission rate) and the air exchange rate between the various model compartments (shower, the rest of the bathroom, and the rest of the house) following the same basic model construct described by Little (1992). The resulting differential equations were solved using finite difference numerical integration. These equations are presented in detail in Appendix A, Equations A-5.1 through A-5.9. The basis for estimating the concentration of constituents in the indoor air is based on the mass transfer of constituent from water to shower air. This equation estimates the overall mass transfer coefficient from tap water to air from showering: where Kol = overall mass transfer coefficient (cm/s) = proportionality constant (cm/s)-1/3 D1 = diffusion coefficient in water (cm2/s) D2 = diffusion coefficient in air (cm2/s) H = Dimensionless Henry's law constant (=41*HLC). The constituent emission rate is estimated from the change in the shower water concentration as the water falls, which is calculated using the overall mass transfer coefficient as follows: where c = liquid phase (droplet) constituent concentration (æg/cm3 or mg/L) t = time (s) A = total surface area for mass transfer (cm2) V = total volume of water within the shower compartment (cm3) ys = gas phase constituent concentration in the shower (æg/cm3 or mg/L) H = dimensionless Henry's law constant. Consequently, in addition to the overall mass transfer coefficient, the emission rate of a contaminant within the shower is dependent on the surface-area-to-volume ratio of the shower water (within the shower) and the concentration driving force between the water and the shower air. The shower emissions can be modeled based on falling droplets as a means of estimating the surface-area-to-volume ratio for mass transfer and the residence time of the water in the shower compartment. Equation 6-2 can then be integrated assuming the compound concentration in the gas phase is constant over the time frame of the droplet fall. The time required for a droplet to fall equals the nozzle height divided by the water droplet velocity. The ratio of the surface area to volume for the droplet is calculated as 6/dp (i.e., by assuming a spherical shape). By assuming the drops fall at terminal velocity, the surface-area-to-volume ratio and the residence time can be determined based solely on droplet size. A droplet size of approximately 1 mm (0.1 cm) was selected. The terminal velocity for the selected droplet size is approximately 400 cm/s. The fraction of constituent emitted from a water droplet at any given time can then be calculated by integrating Equation 6-2 and rearranging as follows: where fem = fraction of constituent emitted from the droplet (dimensionless) cout = droplet constituent concentration at shower floor/drain (mg/L) cin = droplet constituent concentration entering the shower (mg/L) fsat = ys/(H cin) = fraction of gas phase saturation (dimensionless) N = dimensionless overall mass transfer coefficient = Kol (6/dp) (h/vt) dp = droplet diameter = 0.1 (cm) vt = terminal velocity of droplet = 400 (cm/s) h = nozzle height (cm). The gas phase constituent concentration in the shower is then calculated for each time step for the duration of the shower. The air exchange rate between the shower and the bathroom is included in the estimation of the gas phase concentration of the constituents in the shower. where ys,t+1 = gas phase constituent concentration in the shower at the end of time step (mg/L) ys,t = gas phase constituent concentration in the shower at the beginning of time step (mg/L) Qgs = volumetric gas exchange rate between shower and bathroom (L/min) yb,t = gas phase constituent concentration in the bathroom at the beginning of time step (mg/L) (tt=1-tt) = calculation time step Es,t = mass of constituent emitted from shower between time t and time t+1 (mg) Vs = volume of shower stall (L) The shower model also provides direct estimates of the bathroom and whole house exposure. The risk from inhalation exposures in the remainder of the house was several orders of magnitude less than the risk from inhalation exposures in the bathroom and during showering (Coburn, 1996). The gas phase constituent concentration in the bathroom may be estimated by Equation 6-5 for each time step of the exposure duration. where yb,t+1 = gas phase constituent concentration in the bathroom at end of time step (mg/L) yb,t = gas phase constituent concentration in the bathroom at beginning of time step Qgs = volumetric gas exchange rate between bathroom and house yth,t = gas phase constituent concentration in the house at beginning of time step (mg/L) Tt+1 -tt) = calculation time step (min) Ib = bathroom water use (L/min) Cin = constituent concentration in tap water (mg/L) fem,b = fraction of constituent emitted from bathroom water use (unitless) Vb = volume of bathroom (L). The gas phase constiuent concentration in the remainder of the house may be estimated by Equation 6-6 for each time step of the exposure duration. where yh,t+1 = gas phase constituent concentration in the house at end of time step (mg/L) yh,t = gas phase constituent concentration in the house at beginning of time step (mg/L) Qgb = volumetric gas exchange rate between the bathroom and house (L/min) yb,t = gas phase constituent concentration in the bathroom at beginning of time step (mg/L) Qgh = volumetric gas exchange rate between the house and atmosphere (L/min) ya,t = gas phase constituent concentration in the atmosphere (mg/L) (Tt+1 -tt) = calculation time step (min) Ih = house water use - other than bathroom (L/min) Cin = constituent concentration in tap water (mg/L) fem,h = fraction of constituent emitted from household water use - other than bathroom (unitless) Vh = volume of house (L). The average air concentration in the shower and bathroom are obtained by averaging the concentrations obtained for each time step over the duration of the shower and bathroom use. These concentrations and the durations of daily exposure are used to estimate risk from inhalation exposures to residential use of groundwater. 6.2 Exposure Factors Where available, the exposure parameters used in this analysis are central tendency values cited in the Exposure Factors Handbook (U.S. EPA, 1996a). The remaining exposure factors required for this analysis were obtained from McKone (1987). The original articles have been obtained to verify the values used in the analysis. All parameter values are presented in Table 6.1. The physical and chemical parameters for the constituent of concern (benzene) are presented in Table 6.2. These data were used to determine a relative risk factor that may be used to estimate the inhalation risk based upon the risk estimated for the ingestion of contaminated groundwater. The groundwater concentrations are provided in the Supplemental Background Document; Groundwater Pathways Risk Analysis; Petroleum Refining Process Waste Listing Determination (HydroGeoLogic, Inc., 1997). The results of this inhalation risk analysis are presented in that document as well. Showering with contaminated tap water containing 1 mg/L of benzene results in an inhalation risk of 6.06 E-5. The risk value is directly proportional to the concentration of benzene in the water and thus a ratio may be applied to the benzene concentration in groundwater to determine the risk from shower inhalation. The risk values are provided in HydroGeoLogic, Inc., (1997). The equations used in the estimation of risk from the inhalation exposure during showering pathway are presented in Appendix A. These equations are consistent with the approach presented in the Hazardous Waste Identification Rule (HWIR). Table 6.1 Exposure Factors Used to Determine Risk from Inhalation Exposure to Contaminated Tap Water Exposure Factor Parameter Value Reference -------------------------------------------------------------- Shower duration 10.4 min U.S. EPA, 1996a Shower rate 5.5 L/min McKone, 1987 Shower volume 2.30 m3 U.S. EPA, 1996a Water use 15 gal/d per McKone, 1987 person (median) Bathroom volume 13.6 m3 U.S. EPA, 1996a House volume 310 m3 U.S. EPA, 1996a Shower vent rate 100 L/min McKone, 1987 Bathroom vent rate 300 L/min McKone, 1987 House vent. rate 0.45 air changes/h McKone, 1987 (2,325 L/min) Bathroom water use 33 gal/d (125 L/d) McKone, 1987 Fem, bathroom 0.50 McKone, 1987 Time toilet emits 1 h/d McKone, 1987 House water use (tot) 53 gal/d (201 L/d) McKone, 1987 Fem, house water 0.66 McKone, 1987 Time house water emits 16 h/d McKone, 1987 Inhalation rate 13.8 L/min U.S. EPA, 1990 Table 6.2 Physical and Chemical Properties of Benzene Used in Shower Inhalation Exposure Model Property Value Reference -------------------------------------------------------------- Henry's law constant 5.4 E -3 atm-m3/mol U.S. EPA, 1996a Diffusivity in air 8.8 E -2 cm2/s U.S. EPA, 1996a Diffusivity in water 9.8 E -6 cm2/s U.S. EPA, 1996a 6.3 Dermal Exposure to Tap Water Another noningestion route of exposure to groundwater not considered in the groundwater risk assessment for the proposed rule is dermal exposure from bathing and showering. In response to public comments, this pathway has been added to the exposures from ingestion of drinking water and showering for waste streams in which benzene was present in groundwater. The basic equation (U.S. EPA 1992) used in this analysis for benzene (time of exposure ò time to steady-state) is where DAevent = dose absorbed per unit area per event (mg/cm2) Cwater = water concentration (mg/L) Kpw = skin permeability constant in water (cm/h) tevent = duration of event (h) ç = lag time (h) B = bunge constant (unitless) 1/103 = L/ cm3. The risk due to dermal exposures is much less than the risk from inhalation or ingestion exposure to the same concentration of benzene. The equations used in the estimation of risk from the dermal exposure during showering or bathing pathway are presented in Appendix A. 7.0 CODISPOSAL SCENARIOS Commenters noted that many of the waste streams addressed by the proposed listing decision contain many of the same constituents and are frequently disposed of in the same treatment or disposal units. In response to this comment, EPA conducted an analysis of risk associated with codisposal of multiple petroleum waste streams. EPA first identified land treatment units in which petroleum residuals were actually codisposed. The analysis included both the petroleum listing residuals as well as 15 other wastes for which EPA collected data (see SAIC 1997). Four of the units in which codisposal occured are onsite and three are offsite facilities. Site-specific LTU areas and waste quantities were used in the analysis. Only waste streams containing PAHs of concern were considered for the analysis in the nongroundwater risk assessment of codisposal scenarios. In addition, clarified slurry oil (CSO) sludge was not considered in codisposal scenarios because it presents sufficient risk when disposed of independently to be proposed for listing as a hazardous waste and, therefore, would no longer be disposed of in nonhazardous LTUs. 7.1 Codisposal in Onsite Land Treatment Units Table 7.1 presents the four onsite land treatment units in which petroleum wastes are codisposed (SAIC, 1997). Two of these four LTUs (058-2 and 101-12) were not modeled because the codisposed streams did not contain significant levels of PAHs. One unit (170-5) was not modeled because crude oil tank sludge was the only waste stream that was not excluded from consideration based on PAH content or proposed listing status. Only one onsite land treatment unit (171-3) was identified as a site where petroleum wastes (other than CSO) that contain PAHs were actually codisposed. The actual waste combinations and quantities disposed of in this unit were used as inputs to the risk assessment with one exception. EPA did not have the actual quantity of off- specification products and fines that was codisposed in this unit. Therefore, we conservatively used a quantity of 34 t, the maximum amount of off-specification product and fines that was managed in an onsite LTU. Each waste that was codisposed in unit 171-3 was assumed to be placed separately in the LTU and each stream was modeled individually using assumptions for variations in meteorologic data, distance to receptor, concentration of constituents, and duration of exposure and methodology used for single waste stream analysis. The resulting risks for each waste stream codisposed in the land treatment unit were summed to determine total risk for the LTU. For example, the high-end risks for the close receptor, long exposure duration off- specification products and fines was added to the high-end risks for the close receptor, long exposure duration for crude oil tank sludge placed in the same treatment unit. This was true for each pair of high-end variables. The results of the analysis of the onsite codisposal scenario are presented in Section 15. 7.2 Codisposal in Offsite Land Treatment Units Three offsite land treatment units were identified as sites in which PAH-containing petroleum residuals were actually codisposed (SAIC, 1997). Table 7.2 presents the offsite codisposal scenarios identified for evaluation. Two of the three units were modeled. One unit (Facility No. 2) was not evaluated because it contained CSO sludge and another waste stream that did not contain significant concentrations of PAHs. As in the case of the onsite land treatment units, actual waste stream combinations and quantities disposed of in LTUs were identified. As in the case of the onsite codisposal scenarios, each waste stream in the combination was modeled independently. However, instead of evaluating specific sizes of offsite LTUs, the size distribution identified for all offsite treatment units was considered for offsite codisposal because it would be possible for refiners to send wastes to any nearby offsite facility. The 50th percentile offsite LTU area (29.9 acres) was used for both offsite LTU codisposal scenarios. Thus, the unique quantity of each waste identified as being codisposed at Facilities 1 and 3 was assumed to be placed separately in a 29.9 acres LTU and modeled individually using the standard assumptions for variations in meteorologic data, distance to receptor, concentration of constituents, and duration of exposure used for individual waste streams. The resulting risks for each combination of high-end variables for each waste stream codisposed in offsite land treatment units were added to obtain the total risk of the codisposal scenario as described for the onsite codisposal scenarios. The results of the analysis of the onsite codisposal scenario are also presented in Section 15. Table 7.1 Nonhazardous Onsite Land Treatment Units and Codisposal Waste Streams Waste Mgmt Unit Waste Stream Waste Unit Area Quantity (acres) (t) 058-2a 0.6 Desalting sludge 299 HF alkylation sludge 3.7 Unleaded gasoline 2 tank sludge 101-12a 3 Sulfur complex sludge 258 HF alkylation sludge 9 170-5b 15.8 FCC catalyst 512 Unleaded gasoline 11.77 tank sludge Crude oil tank sludge NR CSO sludge 2,520 Off-spec products 1 and fines 171-3c 7.5 Sulfur complex sludge 50 Crude oil tank sludge 65 Off -spec products 34d and fines CSO = Clarified slurry oil. FCC = Fluidized catalytic cracking. NR = Not reported. a Waste streams codisposed in this unit did not contain significant quantities of PAHs. b This LTU was not modeled because neither FCC catalyst nor unleaded tank sludge contain PAHs and CSO sludge was not considered because of proposal to list CSO as hazardous. c LTU used for an onsite codisposal analysis. d Volume disposed of in hazardous unit was used because volume for this unit was not reported. Table 7.2 Nonhazardous Offsite Land Treatment Units and Codisposal Waste Streams Waste Management Waste Stream Waste Quantity (t) Unit Facility No. 1 Crude oil tank sludge 53.9 Off-spec products and fines 21.2 Facility No. 2a CSO sludge 2277.75 Desalting sludge 22.2 Facility No. 3 Crude oil tank sludge 11.12 CSO sludge 111.4a Desalting sludge 29 CSO = Clarified slurry oil. a This unit was not evaluated 8.0 CRUDE OIL TANK SLUDGE Tables 8.1 through 8.4 summarizes the risk results of crude oil tank sludge for onsite land treatment units. The pathway and media tables for the high-end risk for crude oil tank sludge treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 8.5 through 8.12. Results for offsite land treatment units are summarized in Tables 8.13 through 8.16. The pathway and media tables for the high-end risk for crude oil tank sludge treated in an offsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 8.17 through 8.24. Table 8.1. Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 8.2. Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 8.3. Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 8.4. Individual Risk for Crude Oil Tank Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 8.5. Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 8.6. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 8.7. Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Close Receptor Subsistence Farmer Table 8.8. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Close Receptor Subsistence Farmer Table 8.9. Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Close Receptor Home Gardener Table 8.10. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Close Receptor Home Gardener Table 8.11. Media Concentrations for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 8.12. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 8.13. Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 8.14. Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 8.15. Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 8.16. Individual Risk for Crude Oil Tank Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 8.17. Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Subsistence Fisher Table 8.18. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Subsistence Fisher Table 8.19. Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Close Receptor Subsistence Farmer Table 8.20. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Close Receptor Subsistence Farmer Table 8.21. Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Close Receptor Home Gardener Table 8.22. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Close Receptor Home Gardener Table 8.23. Media Concentrations for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Adult Resident Table 8.24. Individual Risk by Pathway for Crude Oil Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Adult Resident 9.0 CLARIFIED SLURRY OIL Tables 9.1 through 9.4 summarizes the risk results of clarified slurry oil sludge for onsite land treatment units. The pathway and media tables for the high-end risk for clarified slurry oil sludge treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 9.5 through 9.12. Results for offsite land treatment units are summarized in Tables 9.13 through 9.16. The pathway and media tables for the high-end risk for clarified slurry oil sludge treated in an offsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 9.17 through 9.24. Table 9.1. Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 9.2. Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 9.3. Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 9.4. Individual Risk for Clarified Slurry Oil Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 9.5. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 9.6. Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 9.7. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 9.8. Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 9.9. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 9.10. Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 9.11. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 9.12. Individual Risk by Pathway for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 9.13. Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 9.14. Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 9.15. Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 9.16. Individual Risk for Clarified Slurry Oil Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 9.17. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 9.18. Individual Risk By Pathway for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 9.19. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 9.20. Individual Risk By Pathway for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 9.21. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 9.22. Individual Risk By Pathway for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 9.23. Media Concentrations for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 9.24. Individual Risk By Pathway for Clarified Slurry Oil Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident 10.0 UNLEADED GASOLINE TANK SLUDGE Tables 10.1 through 10.4 summarizes the risk results of unleaded gasoline tank sludge for onsite land treatment units. The pathway and media tables for the high-end risk for unleaded gasoline tank sludge treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 10.5 through 10.12. Results for offsite land treatment units are summarized in Tables 10.13 through 10.16. The pathway and media tables for the high-end risk for unleaded gasoline tank sludge treated in an offsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 10.17 through 10.24. Table 10.1. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 10.2. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 10.3. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 10.4. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 10.5. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 10.6. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 10.7. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 10.8. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 10.9. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 10.10. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 10.11. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 10.12. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 10.13. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 10.14. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 10.15. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 10.16. Individual Risk for Unleaded Gasoline Tank Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 10.17. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 10.18. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 10.19. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 10.20. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 10.21. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 10.22. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 10.23. Media Concentrations for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Adult Resident Table 10.24. Individual Risk by Pathway for Unleaded Gasoline Tank Sludge Managed in an Offsite Land Treatment Unit Small Area/Long Exposure Duration Adult Resident 11.0 SULFUR COMPLEX SLUDGE Tables 11.1 through 11.4 summarizes the risk results of sulfur complex sludge for onsite land treatment units. The pathway and media tables for the high-end risk for sulfur complex sludge treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 11.5 through 11.12. Results for offsite land treatment units are summarized in Tables 11.13 through 11.16. The pathway and media tables for the high-end risk for sulfur complex sludge treated in an offsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 11.17 through 11.24. Table 11.1. Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 11.2. Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 11.3. Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 11.4. Individual Risk for Sulfur Complex Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 11.5. Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 11.6. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 11.7. Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 11.8. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 11.9. Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 11.10. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 11.11. Media Concentrations for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 11.12. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 11.13. Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 11.14. Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 11.15. Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 11.16. Individual Risk for Sulfur Complex Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 11.17. Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 11.18. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 11.19. Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 11.20. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 11.21. Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 11.22. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 11.23. Media Concentrations for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 11.24. Individual Risk by Pathway for Sulfur Complex Sludge Managed in an Offsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident 12.0 HYDROFLUORIC ACID ALKYLATION SLUDGE Tables 12.1 through 12.4 summarizes the risk results of hydrofluoric acid alkylation sludge for onsite land treatment units. The pathway and media tables for the high-end risk for hydrofluoric acid alkylation sludge treated in an onsite land treatment unit (close receptor/long exposure duration) are presented in Tables 12.5 through 12.12. Results for offsite land treatment units are summarized in Tables 12.13 through 12.16. The pathway and media tables for the high-end risk hydrofluoric acid alkylation sludge treated in an offsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 12.17 through 12.24. Table 12.1. Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 12.2. Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 12.3. Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 12.4. Individual Risk for HF Alkylation Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 12.5. Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 12.6. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 12.7. Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 12.8. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 12.9. Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 12.10. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 12.11. Media Concentrations for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 12.12. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 12.13. Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 12.14. Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 12.15. Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 12.16. Individual Risk for HF Alkylation Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 12.17. Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 12.18. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 12.19. Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 12.20. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 12.21. Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 12.22. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 12.23. Media Concentrations for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 12.24. Individual Risk by Pathway for HF Alkylation Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident 13.0 SULFURIC ACID ALKYLATION SLUDGE Tables 13.1 through 13.4 summarizes the risk results of sulfuric acid alkylation sludge for onsite land treatment units. The pathway and media tables for the high-end risk for sulfuric acid alkylation sludge treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 13.5 through 13.12. Results for offsite land treatment units are summarized in Tables 13.13 through 13.16. The pathway and media tables for the high-end risk for sulfuric acid alkylation sludge treated in an offsite land treatment unit (close receptor/long exposure duration) are presented in Tables 13.17 through 13.24. Table 13.1. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Fisher Table 13.2. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Subsistence Farmer Table 13.3. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Home Gardener Table 13.4. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Onsite Land Treatment Unit Adult Resident Table 13.5. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Fisher Table 13.6. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Fisher Table 13.7. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Farmer Table 13.8. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Farmer Table 13.9. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Home Gardener Table 13.10. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Home Gardener Table 13.11. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Adult Resident Table 13.12. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Onsite Land Treatment Unit Close Receptor/Long Exposure Duration Adult Resident Table 13.13. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Fisher Table 13.14. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Subsistence Farmer Table 13.15. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Home Gardener Table 13.16. Individual Risk for Sulfuric Acid Alkylation Sludge Managed in Offsite Land Treatment Unit Adult Resident Table 13.17. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Fisher Table 13.18. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Fisher Table 13.19. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Farmer Table 13.20. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Subsistence Farmer Table 13.21. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Home Gardener Table 13.22. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Home Gardener Table 13.23. Media Concentrations for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Adult Resident Table 13.24. Individual Risk by Pathway for Sulfuric Acid Alkylation Sludge Managed in an Offsite Land Treatment Unit Close Receptor/Long Exposure Duration Adult Resident 14.0 OFF-SPECIFICATION PRODUCTS AND FINES Tables 14.1 through 14.4 summarizes the risk results of off-specification products and fines for onsite land treatment units. The pathway and media tables for the high-end risk for off-specification products and fines treated in an onsite land treatment unit (close receptor/ long exposure duration) are presented in Tables 14.5 through 14.12. Table 14.1. Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Subsistence Fisher Table 14.2. Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Subsistence Farmer Table 14.3. Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Home Gardener Table 14.4. Individual Risk for Off Specification Products and Fines Managed in Onsite Land Treatment Unit Adult Resident Table 14.5. Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 14.6. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Fisher Table 14.7. Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 14.8. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Subsistence Farmer Table 14.9. Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 14.10. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Home Gardener Table 14.11. Media Concentrations for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 14.12. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Onsite Land Treatment Unit Large Quantity/Long Exposure Duration Adult Resident Table 14.13. Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Subsistence Fisher Table 14.14. Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Subsistence Farmer Table 14.15. Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Home Gardener Table 14.16. Individual Risk for Off Specification Products and Fines Managed in Offsite Land Treatment Unit Adult Resident Table 14.17. Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 14.18. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 14.19. Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 14.20. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 14.21. Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 14.22. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 14.23. Media Concentrations for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 14.24. Individual Risk by Pathway for Off Specification Products and Sludge Managed in an Offsite Land Treatment Unit Maximum Constituent Concentration/Long Exposure Duration Adult Resident 15.0 CODISPOSAL OF PETROLEUM REFINING WASTE STREAMS Risk results for codisposal of the PAH containing waste streams, crude oil tank sludge and off specification products and fines, comanaged in an onsite land treatment unit are summarized in Tables 15.1 through 15.4. The pathway and media tables for the high-end risk codisposal of petroleum waste streams treated in an onsite land treatment unit (close receptor/long exposure duration) are presented in Tables 15.5 through 15.12. Results for codisposal of crude oil tank sludge and off specification products and fines comanaged in an offsite land treatment unit are presented in Tables 15.13 through 15.16. The corresponding media and pathway tables are presented in Tables 15.17 through 15.24. Results for codisposal of crude oil tank sludge and desalting sludge comanaged in an offsite land treatment unit are presented in Tables 15.25 through 15.28. Table 15.1. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Subsistence Fisher Table 15.2. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Subsistence Farmer Table 15.3. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Home Gardener Table 15.4. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit Adult Resident Table 15.5. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Crude Oil Tank Sludge Table 15.6. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Crude Oil Tank Sludge Table 15.7. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer Table 15.8. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Subsistence Farmer Table 15.9. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener Table 15.10. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Close Receptor/Long Exposure Duration Home Gardener Table 15.11. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 15.12. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Onsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 15.13. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Subsistence Fisher Table 15.14. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Subsistence Farmer Table 15.15. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Home Gardener Table 15.16. Individual Risk for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit Adult Resident Table 15.17. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 15.18. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Fisher Table 15.19. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Subsistence Farmer Table 15.20. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration - Subsistence Farmer Table 15.21. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 15.22. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Home Gardener Table 15.23. Media Concentrations for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 15.24. Individual Risk by Pathway for Crude Oil Tank Sludge and Off Specification Products and Fines Co-Managed in Offsite Land Treatment Unit, Maximum Constituent Concentration/Long Exposure Duration Adult Resident Table 15.25. Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Subsistence Fisher Table 15.26. Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Subsistence Farmer Table 15.27. Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Home Gardener Table 15.28. Individual Risk for Crude Oil Tank Sludge and Desalting Sludge Co-Managed in Offsite Land Treatment Unit Adult Resident 16.0 REFERENCES Beaulieu, S., J. Coburn, and E. C. Hubal. 1996. Memorandum to Pat Jennings, Office of Solid Waste, U.S. Environmental Protection Agency. September. Coburn, J. 1996. Memorandum to Rebecca Daiss, Office of Solid Waste, U.S. Environmental Protection Agency. July. Howard, P.H., R.S. Boethling, W.M. Jarvis, W.M. Meylan, and E.M. Michalenko. 1991. Handbook of Environmental Degradation Rates. Chelsea, Michigan: Lewis Publishers. HydroGeoLogic, Inc. 1997. Supplemental Background Document; Groundwater Pathway Risk Analysis; Petroleum Refining Process Waste Listing Determination. Herndon, VA. Little, J.C. 1992. Applying the two-resistance theory to contaminant volatilization in showers. Environ. Sci. Technol. 26(7):1341-1349. McKone, T.E. 1987. Human exposure to volatile organic compounds in household tap water: the indoor inhalation pathway. Environ. Sci. Technol. 21(12):1194-1201. SAIC (Science Applications International Corporation). 1997. Supplemental Background Document, Listing Support Analyses; Petroleum Refining Process Waste Listing Determination. McLean, VA. U.S. Environmental Protection Agency. 1996a. Exposure Factors Handbook (Draft), Office of Research and Development, Washington, DC. April. NTIS PB97-117675. U.S. Environmental Protection Agency. 1996b. Superfund Chemical Data Matrix. EPA/540/R-96/028, PB96-963509. Office of Emergency and Remedial Response, Washington, DC. U.S. Environmental Protection Agency. 1994. Estimating Exposure to Dioxin-Like Compounds Volume III: Site-Specific Assessment Procedures. EPA/600/6-88/005c. Exposure Assessment Group, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC. U.S. Environmental Protection Agency. 1992. Dermal Exposure Assessment: Principles and Applications. Interim Report EPA-600 8-91-011B. Office of Research and Development, Washington, DC. January. U.S. Environmental Protection Agency. 1990. Exposure Factors Handbook. EPA-600/8-89/043. Office of Health and Environmental Assessment, Washington, DC. APPENDIX A EQUATIONS USED IN ANALYSIS Table A-1.1. Constituent Concentration In Residential Plot Due to Erosion Adult Resident Exposure Scenario Description This equation is used to calculate the mass of constituent deposited onto residential plot as a result of erosion from the source. Table A-1.2. Soil Load Delivered to Off-Site Location for Material Originating from Source Area Description This equation is used to calculate the load of eroded soil originating from the source that is deposited onto the off-site location of interest. Table A-1.3. Universal Soil Loss Equation (USLE) for the Source Area Description This equation calculates the soil loss rate from the source, using the Universal Soil Loss Equation; the result is used in the soil erosion load equation. Table A-1.4. Sediment Delivery Ratio Description This equation calculates the sediment delivery ratio for the sub-basin; the result is used in the soil erosion load equation. Table A-1.5. Buffer and Surrounding Areas Description This equation calculates the area of the buffer and surrounding areas for each of the different exposure scenarios. Table A-1.6. Scaling Factor Description This term is used to determine what portion of the total amount of eroded source material available for deposition within the sub-basin will be deposited onto just the off-site location of interest. Table A-1.7. Soil Load Delivered to Off-Site Location for Material Originating from Buffer Area Description This equation is used to calculate the load of eroded soil originating from the buffer area that is deposited onto the off-site location of interest. Table A-1.8. Universal Soil Loss Equation (USLE) for Buffer Area Description This equation is used to calculate the soil loss rate from the buffer area using the Universal Soil Loss Equation; the result is used in the soil erosion load equation. Table A-1.9. Buffer Area Table A-1.10. Scaling Factor Description This term is used to determine what portion of the total amount of eroded buffer material available for deposition within the sub-basin, will be deposited onto just the off-site location of interest. Table A-1.11. Constituent Concentration Due to Erosion in Buffer and Surrounding Areas Description This equation is used to calculate the constituent concentration in the buffer and surrounding areas as a result of erosion from the source. Table A-1.12. Soil Load Delivered to Buffer and Surrounding Area for Material Originating from Source Description This equation is used to calculate the load of eroded soil originating from the source that is deposited onto the buffer and surrounding areas. Table A-1.13. Scaling Factor Description This term is used to determine what portion of the total amount of eroded source material available for deposition within the sub-basin, will be deposited onto just the buffer and surrounding areas. Table A-1.14. Deposition Rate Factor to Buffer and Surrounding Areas Description These equations calculate average air deposition occurring over the exposure duration as a result of wet and dry deposition of particles onto soil, deposition of wet vapors to soil and diffusion of dry vapors to soil. Contaminants are assumed to be incorporated only to a finite depth (the mixing depth, Z). The air deposition rates (per unit area) for the buffer and surrounding areas are assumed to be the same as the air deposition rates (per unit area) to the field. Table A-1.15. Constituent Loss Constant Description This equation calculates the constitutent loss constant, which accounts for the loss of constituent from soil by several mechanisms. Table A-1.16. Constituent Loss Constant Due to Leaching Description This equation calculates the constituent loss constant due to leaching from soil. Table A-1.17. Soil Volumetric Water Content Table A-1.18. Average Annual Recharge Table A-1.19. Constituent Loss Constant Due to Erosion Table A-1.20. Universal Soil Loss Equation (USLE) for Buffer and Surrounding Areas Description This equation is used to calculate the soil loss rate from the buffer and surrounding area using the Universal Soil Loss Equation; the result is used in the soil erosion load equation. Table A-1.21. Constituent Loss Constant Due to Runoff Description This equation calculates the constituent loss constant due to runoff from soil. Table A-1.22. Constituent Loss Constant Due to Volatilization Description This equation calculates the constituent loss constant due to volatilization from soil. Source: IEM. Table A-1.23. Mass of Soil in Mixing Depth of Buffer and Surrounding Areas Description This equation is used to calculate the total mass of soil in the buffer and surrounding areas that will be mixing with the mass of eroded material. Table A-1.24. Deposition Rate Factor to Residential Plot from Source Adult Resident Exposure Scenario Description These equations calculate average air deposition occurring over the exposure duration as a result of wet and dry deposition of particles onto soil, deposition of wet vapors to soil, and diffusion of dry vapors to soil. Contaminants are assumed to be incorporated only to a finite depth (the mixing depth, Z). Table A-1.25. Constituent Loss Constant Adult Resident Exposure Scenario Description This equation calculates the constituent loss constant, which accounts for the loss of constituent from soil by several mechanisms. Table A-1.26. Constituent Loss Constant Due to Leaching Adult Resident Exposure Scenario Description This equation calculates the constituent loss constant to leaching from soil. Table A-1.27. Constituent Loss Constant Due to Erosion Adult Resident Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-1.28. Universal Soil Loss Equation (USLE) for Residential Plot Adult Resident Exposure Scenario Description This equation is used to calculate the soil loss rate from the residential plot using the Universal Soil Loss Equation. Table A-1.29. Area of Buffer Between Field and Waterbody Table A-1.30. Constituent Loss Constant Due to Runoff Adult Resident Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-1.31. Constituent Loss Constant Due to Volatilization Adult Resident Exposure Scenario Description This equation calculates the constituent loss constant due to volatilization from soil. Table A-1.32. Mass of Soil in Mixing Depth of Residential Plot Adult Resident Exposure Scenario Description This equation is used to calculate the total mass of soil in the residential plot that will be mixing with the mass of eroded material. Table A-2.1. Concentration In Home Garden Due to Erosion Home Gardener Exposure Scenario Description This equation is used to calculate the mass of constituent deposited onto either the home garden as a result of erosion from the source. Table A-2.2. Constituent Loss Constant Home Gardener Exposure Scenario Description This equation calculates the constituent loss constant, which accounts for the loss of constituent from soil by several mechanisms. Table A-2.3. Constituent Loss Constant Due to Leaching Home Gardener Exposure Scenario Description This equation calculates the constituent loss constant due to leaching from soil. Table A-2.4. Constituent Loss Constant Due to Erosion Home Gardener Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-2.5. Universal Soil Loss Equation (USLE) for Home Garden Home Gardener Exposure Scenario Description This equation is used to calculate the soil loss rate from the home garden using the Universal Soil Loss Equation. Table A-2.6. Constituent Loss Constant Due to Runoff Home Gardener Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-2.7. Constituent Loss Constant Due to Volatilization Home Gardener Exposure Scenario Description This equation calculates the constituent loss constant due to volatilization from soil. Table A-2.8. Mass of Soil in Mixing Depth of Home Garden Home Gardener Exposure Scenario Description This equation is used to calculate the total mass of soil in the home garden that will be mixing with the mass of eroded material. Table A-2.9. Deposition Rate Factor to Home Garden from Source Home Gardener Exposure Scenario Description These equations calculate average air deposition occurring over the exposure duration as a result of wet and dry deposition of particles onto soil, deposition of wet vapors to soil, and diffusion of dry vapors to soil. Constituents are assumed to be incorporated only to a finite depth (the mixing depth, Z). Table A-2.10. Aboveground Produce Concentration Due to Direct Deposition Home Gardener Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to wet and dry deposition of constituent on the plant surface. Table A-2.11. Aboveground Produce Concentration Due to Air-to-Plant Transfer Home Gardener Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of vapor phase chemicals into the plant leaves. Table A-2.12. Aboveground Produce Concentration Due to Root Uptake Home Gardener Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of chemicals from soil. Table A-2.13. Root Vegetable Concentration Due to Root Uptake Home Gardener Scenario Description This equation calculates the constituent concentration in root vegetables due to uptake from the soil water. Table A-3.1. Constituent Concentration In Agricultural Field Due to Erosion Subsistence Farmer Exposure Scenario Description This equation is used to calculate the mass of constituent deposited onto the agricultural field as a result of erosion from the source. Table A-3.2. Soil Loss Constant Subsistence Farmer Exposure Scenario Description This equation calculates the constituent loss constant, which accounts for the loss of constituent from soil by several mechanisms. Table A-3.3. Loss Constant due to Leaching Subsistence Farmer Exposure Scenario Description This equation calculates the constituent loss constant due to leaching from soil. Table A-3.4. Constituent Loss Constant Due to Erosion Subsistence Farmer Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-3.5. Universal Soil Loss Equation (USLE) for Agricultural Field Subsistence Farmer Exposure Scenario Description This equation is used to calculate the soil loss rate from the agricultural field using the Universal Soil Loss Equation. Table A-3.6. Constituent Loss Constant Due to Runoff Subsistence Farmer Exposure Scenario Description This equation calculates the constituent loss constant due to runoff from soil. Table A-3.7. Constituent Loss Constant Due to Volatilization Subsistence Farmer Exposure Scenario Description This equation calculates the constituent loss constant due to volatilization from soil. Table A-3.8. Mass of Soil in Mixing Depth of Agricultural Field Subsistence Farmer Exposure Scenario Description This equation is used to calculate the total mass of soil in the agricultural field that will be mixing with the mass of eroded material. Table A-3.9. Deposition Rate Factor to Agricultural Field from Source Subsistence Farmer Exposure Scenario Description These equations calculate average air deposition occurring over the exposure duration as a result of wet and dry deposition of particles onto soil, deposition of wet vapors to soil, and diffusion of dry vapors to soil. Constituents are assumed to be incorporated only to a finite depth (the mixing depth, Z). Table A-3.10. Aboveground Produce Concentration Due to Direct Deposition Subsistence Farmer Exposure Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to wet and dry deposition of constituent on the plant surface. Table A-3.11. Aboveground Produce Concentration Due to Air-to-Plant Transfer Subsistence Farmer Exposure Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of vapor phase chemical into the plant leaves. Table A-3.12. Aboveground Produce Concentration Due to Root Uptake Subsistence Farmer Exposure Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of chemicals from soil. Table A-3.13. Root Vegetable Concentration Due to Root Uptake Subsistence Farmer Exposure Scenario Description This equation calculates the constituent concentration in root vegetables due to uptake from the soil water. Table A-3.14. Beef Concentration Due to Plant and Soil Ingestion Subsistence Farmer Scenario Description This equation calculates the concentration of constituent in beef from ingestion of forage and soil. Table A-3.15. Milk Concentration Due to Plant and Soil Ingestion Subsistence Farmer Scenario Description This equation calculates the concentration of constituent in milk from ingestion of forage and soil. Table A-3.16. Forage (Pasture Grass/Hay) Concentration Due to Direct Deposition Subsistence Farmer Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to wet and dry deposition of constituent on the plant surface. Table A-3.17. Forage (Pasture Grass/Hay) Concentration Due to Air-to-Plant Transfer Subsistence Farmer Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of vapor phase chemicals into the plant leaves. Table A-3.18. Forage/Silage/Grain Concentration Due to Root Uptake Subsistence Farmer Scenario Description This equation calculates the constituent concentration in aboveground vegetation due to direct uptake of constituents from soil. Table A-4.1. Watershed Constituent Concentration All Exposure Scenarios Description This equation is used to calculate the mass of constituent deposited onto the watershed area outside of sub-basin as a result of air deposition. Table A-4.2. Deposition Rate Factor to Watershed from Source All Exposure Scenarios Description These equations calculate average air deposition occurring over the exposure duration as a result of wet and dry deposition of particles onto soil, deposition of wet vapors to soil, and diffusion of dry vapors to soil. Constituents are assumed to be incorporated only to a finite depth (the mixing depth, Z). Table A-4.3. Constituent Loss Constant All Exposure Scenarios Description This equation calculates the constituent loss constant, which accounts for the loss of constituent from soil by several mechanisms. Table A-4.4. Constituent Loss Constant due to Leaching All Exposure Scenarios Description This equation calculates the constituent loss constant due to leaching from soil. Table A-4.5. Constituent Loss Constant Due to Erosion All Exposure Scenarios Description This equation calculates the constituent loss constant due to runoff from soil. Table A-4.6. Universal Soil Loss Equation (USLE) for the Watershed All Exposure Scenarios Description This equation is used to calculate the soil loss rate from the watershed using the Universal Soil Loss Equation. Table A-4.7. Sediment Delivery Ratio Subsistence Fisher Scenario Description This equation calculates the sediment delivery ratio for the watershed. Table A-4.8. Constituent Loss Constant Due to Runoff All Exposure Scenarios Description This equation calculates the constituent loss constant due to runoff from soil. Table A-4.9. Constituent Loss Constant Due to Volatilization All Exposure Scenarios Description This equation calculates the constituent loss constant due to volatilization from soil. Table A-4.10. Total Waterbody Load Subsistence Fisher Scenario Description This equation calculates the total average waterbody load from wet and dry vapor and particle deposition, runoff, and erosion loads. Table A-4.11. Deposition to Waterbody Subsistence Fisher Scenario Description This equation calculates the average load to the waterbody from direct deposition of wet and dry particles and wet vapors onto the surface of the waterbody. Table A-4.12. Diffusion Load to Waterbody Subsistence Fisher Scenario Description This equation calculates the load to the waterbody due to vapor diffusion. Table A-4.13. Overall Transfer Rate Subsistence Fisher Scenario Description This equation calculates the overall transfer rate of constituent from the liquid and gas phases in surface water. Table A-4.14. Liquid Phase Transfer Coefficient Subsistence Fisher Scenario Description This equation calculates the transfer rate of constituent from the liquid phase for a flowing or quiescent system. Table A-4.15. Gas Phase Transfer Coefficient Subsistence Fisher Scenario Description This equation calculates the transfer rate of constituent from the gas phase for a flowing or quiescent system. Table A-4.16. Impervious Runoff Load to Waterbody Subsistence Fisher Scenario Description This equation calculates the average runoff load to the waterbody from impervious surfaces in the watershed from which runoff is conveyed directly to the waterbody. Table A-4.17. Pervious Runoff Load to Waterbody Subsistence Fisher Scenario Description This equation calculates the average runoff load to the waterbody from pervious soil surfaces in the watershed. Table A-4.18. Constituent Concentration in Total Watershed Soils Based on Surface Area All Exposure Scenarios Description This equation is used to calculate the weighted average constituent concentration in the total watershed soils, using the constituent concentration in the watershed soils and the constituent concentration in each of the areas within the sub-basin (e.g., source, residential plot, and buffer and surrounding area). Table A-4.19. Erosion Load to Waterbody Subsistence Fisher Scenario Description This equation calculates the load to the waterbody from soil erosion. Table A-4.20. Weighted Average Soil Concentration Based on Eroded Soil Contributions All Exposure Scenarios Description This equation calculates the average concentration of delivered sediment for the watershed allowing for different unit soil loss factors and sediment delivery ratios for each of the modeled areas. Table A-4.21. Total Waterbody Concentration Subsistence Fisher Scenario Description This equation calculates the total waterbody concentration, including both the water column and the bed sediment. Table A-4.22. Fraction in Water Column and Benthic Sediment Subsistence Fisher Scenario Description These equations calculate the fraction of total waterbody concentration occurring in the water column and the bed sediments. Table A-4.23. Overall Total Waterbody Dissipation Rate Constant Subsistence Fisher Scenario Description This equation calculates the overall dissipation rate of constituent in surface water due to volatilization and benthic burial. Table A-4.24. Water Column Volatilization Loss Rate Constant Subsistence Fisher Scenario Description This equation calculates the water column constituent loss due to volatilization. Table A-4.25. Benthic Burial Rate Constant Subsistence Fisher Scenario Description This equation calculates the water column constituent loss due to burial in benthic sediment. Table A-4.26. Benthic Burial Rate Constant Subsistence Fisher Scenario Description This equation is used to determine the loss of constituent from the benthic sediment layer. Table A-4.27. Deposition Rate to Bottom Sediment Subsistence Fisher Scenario Description This equation is used to determine the loss of constituent from the waterbody as it deposits onto the benthic sediment. Table A-4.28. Total Water Column Concentration Subsistence Fisher Scenario Description This equation calculates the total water column concentration of constituent; this includes both dissolved constituent and constituent sorbed to suspended solids. Table A-4.29. Dissolved Water Concentration Subsistence Fisher Scenario Description This equation calculates the concentration of constituent dissolved in the water column. Table A-4.30. Concentration Sorbed to Bed Sediment Subsistence Fisher Scenario Description This equation calculates the concentration of constituent sorbed to bed sediments. Table A-4.31. Fish Concentration from Dissolved Water Concentration Subsistence Fisher Scenario Description This equation calculates fish concentration from dissolved water concentration using a bioconcentration factor. Table A-4.32. Fish Concentration from Total Water Column Concentration Subsistence Fisher Scenario Description This equation calculates fish concentration from total water column concentration using a bioaccumulation factor. APPENDIX B COMPOUND SPECIFIC INPUT VALUES Benz(a)anthracene Benzo(a)pyrene Benzo(b)fluoranthene Benzo(k)fluoranthene Chrysene Dibenz(a,h)anthracene Dimethylbenz(a)anthracene, 7,12- Indeno(1,2,3-cd)pyrene Methylcholanthrene, 3- 1. Koc is calculated fromKow using a correlation equation from Research Triangle Institute. 1992. Preliminary Soil Action Level for Superfund Sites, Draft Interim Report. Prepared for U.S. EPA Hazardous Site Control Division, Remedial Operations Guidance Branch, Arlington, VA. EPA Contract 68-W1-0021, Work Assignment No. B-03, Work Assignment Manager Loren Henning. December. where Kow = octanol water partition coefficient (unitless) - (see table A1-2) 2. U.S. EPA 1995. Internal Report on Summary of Measured, Calculated and Recommended Log Kow Values. Prepared for Office of Water by Environmental Research Laboratory, Athens, GA. April 10, 1995. 3. Research Triangle Institute. 1992. Preliminary Soil Action Level for Superfund Sites, Draft Interim Report. Prepared for U.S. EPA Hazardous Site Control Division, Remedial Operations Guidance Branch, Arlington, VA. EPA Contract 68-W1-0021, Work Assignment No. B-03, Work Assignment Manager Loren Henning. December. 4. Calculated from Kds and scaled to reflect the different fraction organic carbon in bottom sediment. where: Kdbs = bottom sediment-water partition coefficient (mL/g) Kds = organic carbon partition coefficient (mL/g) - calculated, see below foc,bs = fraction organic carbon in bottom sediment = 0.04 (Addendum) foc,s = fraction organic carbon in soil = 0.01 (Addendum) 5. Calculated from Kds and scaled to reflect the different fraction organic carbon in suspended sediment. where: Kdsw = suspended sediment-water partition coefficient (mL/g) Kds = organic carbon partition coefficient (mL/g) - calculated, see below foc,sw = fraction organic carbon in suspended sediment = 0.075 (Addendum) foc,s = fraction organic carbon in soil = 0.01 (Addendum) 6. U.S. Environmental Protection Agency. 1996. Superfund Chemical Data Matrix. EPA/540/R-96/028, PB96-963509. Office of Emergency and Remedial Response, Washington, DC. 7. U.S. EPA. 1995. Hazardous Waste Treatment, Storage, and Disposal Facilities (TSdegF) - Wasterwater Treatment Air Emission Models, WATER8. Office of Air Quality Planning and Standards, Research Triangle Park, N.C. February. 8. Howard, P.H., R.S. Boethling, W.M. Jarvis, W.M. Meylan, and E.M. Michalenko. 1991. Handbook of Environmental Degradation Rates. Lewis Publishers. Chelsea, Michigan. 9. Calculated from an equation in Briggs, G.G., R.H. Bromilow, and A.A. Evans. 1982. Relationships between Lipophilicty and Root Uptake and Translocation of Non-ionized Chemicals by Barley. Pesticide Science. 13:495-504. where RCF = ratio of concentration in the roots to concentration in soil pore water ([æg/g plant]/[æg/mL pore water]) Kow = octanol water partition coefficient (unitless) - (see table A1-2) where Bamilk = biotransfer factor for milk (day/kg) Kow = octanol water partition coefficient (unitless) - (see table A1-2) 10. Baes, C.F., R.D. Sharp, A.L. Sjoreen, and R.W. Shor. 1984. Review and Analysis of Parameters and Assessing Transport of Environmentally Released Radionuclides Through Agriculture. Oak Ridge National Laboratory, Oak Ridge, Tennessee. 11. Stephan, C.E., et al. 1993. Derivation of Proposed Human Health and Wildlife Bioaccumulation Factors for the Great Lakes Initiative. Office of Research and Development, U.S. Environmental Research Laboratory, PB93-154672. Springfield, VA. 12. Derived from data in Hoffman, F.O., K.M. Thiessen, M.L. Frank, and B.G. Blaylock. 1992. Quantification of the Interception and Initial Retention of Radioactive Contaminants Deposited on Pasture Grass by Simulated Rain. Atmospheric Environment. 26A(18):3313-3321. Hoffman et al. present experimental values of what they term "interception fraction" which corresponds in the methodology used here to the product of Rp and Fw. Fw values were estimated from the Hoffmann et al. values by dividing by an Rp of 0.47 for forage. The values used here apply to organics and correspond to moderate rainfall and apply to anions. 13. U.S. EPA. 1993. Provisional Guidance for Quantitative Risk Assessment of Polycyclic Aromatic Hydrocarbons. Office of Research and Development, Washington, D.C. July. 14. Simonich, S.L. and R.A. Hites. 1994. Vegetation-Atmosphere Partitioning of Polycyclic Aromatic Hydrocarbons. Environmental Science and Technology 28:939-43. 15. U.S. Environmental Protection Agency. 1996. Integrated Risk Information System. Online database. Benzo(a)pyrene. Office of Research and Development (ORD). Cincinnati, OH. 16. U.S. Environmental Protection Agency. 1995. Health Effects Assessment Summary Tables: Annual Update. Office of Emergency and Remedial Response. Washington, D.C. May. APPENDIX C INHALATION EXPOSURE TO TAP WATER THROUGH SHOWERING LITERATURE AND MODEL REVIEW In response to public comments, the following articles containing shower inhalation exposure models have been evaluated for possible inclusion of these pathways in the groundwater risk analysis for the petroleum waste listing: Andelman, Julian B. 1990. Total Exposure to volatile organic compounds in potable water, Chapter 20 in Significance and Treatment of Volatile Organic Compounds in Water Supplies,. N.M. Ram, R.F. Christman, and K.P. Cantor (eds.). Lewis Publishers Chelsea MI. pp. 485-504. McKone, Thomas E. 1987. Human exposure to volatile organic compounds in household tap water: The Indoor Inhalation Pathway. Environmental Science and Technology 21:1194-1201. McKone, Thomas E., and J.P. Knezovich. 1991. The transfer of trichloroethylene (TCE) from a shower to indoor air: Experimental measurements and their implications. Journal of Air and Waste Management Association. 41(3):282-286. Little, John C. 1992a. Applying the two resistance theory to contaminant volatilization in showers. Environmental Science and Technology 26:1341-1349. Little, John C. 1992b. Correspondence. Comment on "Human exposure to volatile organic compounds in household tap water: the indoor inhalation pathway." Environmental Science and Technology 26(4):836-837. McKone, Thomas E., and K.T. Bogen, 1992. Uncertainties in health-risk assessment: an integrated case study based on tetrachloroethylene in California groundwater. Regulatory Toxicology and Pharmacology 15:86-103. Andelman (1990) is the simplest model; it assumes that all volatile constituents (i.e., constituents with a Henry's law constant of 2E-6 atm-m3/mol or greater) are equally volatilized and that below a threshold Henry's law constant of 2E-6 atm-m3/mol no volatilization occurs. In the case of very volatile compounds, this approach may be adequate, but it will tend to over-estimate exposure if semivolatile constituents are included in risk assessment. McKone and Bogen (1992) offered a simple screening model to estimate exposure in the shower based on compound-specific data, Henry's law constant, and air and water diffusivities, but it does not consider the time-dependent variations of the exposure concentrations (uses "steady-state" concentration analysis). Both Little (1992a) and McKone (1987) consider the variation in shower concentration with time based on both the volumes of the different model compartments (house, bathroom, shower) and the air exchange rates between the compartments. The simple exposure models presented by Andelman (1990) and McKone and Bogen (1992) can be used to calculate the shower air exposure concentrations directly. The more detailed shower models presented in Little (1992a) and McKone (1987) require more complicated solution algorithms to calculate the contaminant concentration over time. These concentrations are then averaged over the exposure duration to calculate the average exposure concentrations to be used in the risk analysis. The shower models of Little (1992a) and McKone (1987) use basically the same model construct, except that Little (1992b) suggests a slight modification to the equation proposed by McKone (1987) to estimate the overall mass transfer coefficient. Due to the nature of the variations in the models evaluated, the model evaluation is divided into three parts. First we evaluate and compare the predicted overall mass transfer coefficients by McKone (1987) and Little (1992b). Second we compare the impact of the predicted overall mass transfer coefficient on the estimated emissions when applied with a detailed shower model. Third we compare the predicted exposure concentrations using Andelman (1990), McKone and Bogen (1992), and the detailed shower model based on Little (1992a) and McKone (1987). These comparisons provide support for the selection of a model to be used in the risk analysis. C.1.1 Estimation and Comparison of Overall Mass Transfer Coefficients The basic equation presented in McKone (1987) for estimating the overall mass transfer coefficient from tap water to air is Kol = [2.5/(Dab,l ) + 1/(Dab,g H )]-1 ( 6-1) where, Kol = overall mass transfer coefficient (cm/s) = proportionality constant (cm-s)- . Dab,l = diffusivity of constituent in liquid phase (cm2/s) Dab,g = diffusivity of constituent in gas phase (cm2/s) H = H/RT = 41 H = dimensionless Henry's law constant H = Henry's law constant (atm-m3/mol) R = Ideal gas law constant = 8.205E-5 atm-m3/mol-K T = temperature (K). In a correspondence to the editor, Little (1992b) suggested that another proportionality constant should be included in the equation presented in McKone (1987). The suggested change in the mass transfer equation is as follows: Kol = [2.5/(Dab,l ) + à/(Dab,g H )]-1 ( 6-2) where à = proportionality constant (dimensionless). Based on his compilation and analysis of experimental shower emission data, in which he developed a means to estimate the gas and liquid phase mass transfer coefficients from experimentally observed overall mass transfer coefficients for compounds with differing Henry's law constants, Little (1992a) suggests à ÷ 70 in Equation 6-2 (Little, 1992b). Consequently, the main difference in Equation 6-1 (McKone, 1987) and Equation 6-2 (Little, 1992b) is the suggested value of à. McKone (1987) uses à = 1; Little (1992b) suggests à ÷ 70. The change in the shower water concentration as the water falls, which equals the contaminant emission rate, is calculated using the overall mass transfer coefficient as follows: ëc/ ët = - Kol (A/V)(c - ys/H ) ( 6-3) where c = liquid phase (droplet) constituent concentration (æg/cm3 or mg/L) t = time (s) A = total surface area for mass transfer (cm2) V = total volume of water within the shower compartment (cm3) ys = gas phase constituent concentration in the shower (æg/cm3 or mg/L) H = dimensionless Henry's law constant. Consequently, in addition to the overall mass transfer coefficient, the emission rate of a contaminant within the shower is dependent on the surface-area-to-volume ratio of the shower water (within the shower) and the concentration driving force between the water and the shower air. Instead of estimating the surface area for mass transfer, Little (1992a) lumps the overall mass transfer coefficient and the total surface area for mass transfer (i.e., KolA). McKone (1987) defined transfer efficiencies and used radon emission data to calibrate the model. This treatment eliminates the need to calculate the total surface area for mass transfer, but the approach ideally includes a calibration run for a similar shower nozzle type and flow rate. In effect, the transfer efficiency approach lumps the total surface area into the proportionality constant of Equation 6-1 as follows: KolA = [2.5/(Dab,l ) + 1/(Dab,g H )]-1 (Eqn. 6-6) where = lumped proportionality constant (cm5/s) . The shower emissions can be modeled based on falling droplets as a means for estimating the surface-area-to-volume ratio for mass transfer and the residence time of the water in the shower compartment. Equation 6-3 can then be integrated assuming the compound concentration in the gas phase is constant over the time frame of the droplet fall (Little, 1992a, similarly assumes that the gas phase is constant over the residence time of the water in the shower). The time required for a droplet to fall equals the nozzle height divided by the water droplet velocity. The ratio of the surface-area-to-volume for the droplet is calculated as 6/dp (i.e., by assuming a spherical shape). By assuming the drops fall at terminal velocity, the surface-area-to-volume ratio and the residence time can be determined based solely on droplet size. A droplet size of approximately 1 mm (0.1 cm) was selected by calibrating the model for benzene emissions. The terminal velocity for the selected droplet size is approximately 400 cm/s. The fraction of constituent emitted from a water droplet at any given time can then be calculated by integrating Equation 6-3 and rearranging as follows: fem = 1 - cout/cin = (1 - fsat)(1 - e-N) (6-4) where fem = fraction of constituent emitted from the droplet (dimensionless) cout = droplet constituent concentration at shower floor/drain (mg/L) cin = droplet constituent concentration entering the shower (mg/L) fsat = ys/(H cin) = fraction of gas phase saturation (dimensionless) N = dimensionless overall mass transfer coefficient = Kol (6/dp) (h/vt) dp = droplet diameter = 0.1 (cm) vt = terminal velocity of droplet = 400 (cm/sec) h = nozzle height (cm). Equation 6-4 is equivalent to the equation presented in Little (1992a, Equation 5) for liquid phase concentration change, except that Little uses the total surface area for mass transfer (lumped with Kol) and the shower flow rate to dimensionalize the overall mass transfer. Equating the two approaches, the total surface area for mass transfer can be as follows: A = Ql (6/dp) (h/vt) (6-5) where A = total surface area for mass transfer (cm2) Ql = volumetric shower water flow rate(cm3/s). dp = droplet diameter = 0.1 (cm) vt = terminal velocity of droplet = 400 (cm/s) h = nozzle height (cm) The experimentally observed overall mass transfer coefficients (i.e., KolA), as compiled by Little (1992a), are summarized in Table C.1. Most of these experimental overall mass transfer coefficients are based on measurements of the constituent loss from the water, although some are based on measured air concentration data. Overall mass transfer coefficients were also calculated using Equation 6-6 ("McKone (1987) model"), Equation 6-1 combined with Equation 6-5 ("modified McKone, 1987 model"), and Equation 6-2 combined with Equation 6-5 ("Little model"). The value of the proportionality constants was estimated by calibrating the models to predict identical overall mass transfer coefficients for benzene for the model shower (see Section C.3). For the McKone model (1987), = 5.2E+5 (cm5/s) was calculated; for the modified McKone model (1987): = 216 (cm-sec)- ; and for the Little model: = 276 (cm-sec)- and à = 70. Table C.1 also compares the calculated overall mass transfer coefficients with the experimental overall mass transfer coefficients as compiled by Little (1992a). Note that most of the contaminants for which shower data are available are highly volatile. For the two compounds with the lowest volatility (1,2,3-trichloropropane and 1,2-dibromo-3-chloropropane), the Little model shows a sharp contrast to the modified McKone (1987) model, but it significantly underestimates the overall mass transfer coefficient for 1,2-dibromo-3-chloropropane. For the most part, the modified McKone (1987) model provides better estimates of the overall mass transfer coefficients for the different shower studies (i.e., shower conditions) than the McKone (1987) model. Table C.1. Comparison of Overall Mass Transfer Coefficients C.1.2 Comparison of Predicted Shower Emissions for Detailed Shower Model The question arises: How sensitive are the model estimates to the estimated overall mass transfer coefficient? An evaluation of Equation 6-4 reveals that, if the dimensionless overall mass transfer coefficient is large (N>3), the fraction emitted during the droplet fall becomes independent of the overall mass transfer coefficient because the term (1 - e-N) approaches 1. That is, the McKone and Little models may predict different overall mass transfer coefficients, but both models may predict the same amount of contaminant being emitted from the water droplet because the term (1 - e-N) approaches 1 for both models. Therefore, to assess the actual variation of the predicted emissions for the different shower models, we evaluated the total mass of contaminant emitted during a shower event. Although Andelman (1990) is referenced in Risk*Assistant as applying a set fraction emitted from the shower, Andelman (1990) suggests that the set emission fraction (or transfer efficiency) will become limited as the shower air concentration builds up. Therefore, Equation 6-4 is applied with N=1 (transfer efficiency of 63.2 percent) for Henry's law constants greater than or equal to 2.4E-6 atm-m3/mol (H ò 10-4) and N=0 for Henry's law constants greater than 2.4E-6 atm-m3/mol. The evaluation in this section offers a comparison of a simple model for estimating the overall mass transfer coefficient (Andelman, 1990, as just described) with the constituent-specific overall mass transfer equations presented in Section C.1.1 using the same detailed shower model algorithm. The detailed shower model estimates the change in the shower air concentration based on the mass of constituent lost by the water (fraction emitted or emission rate) and the air exchange rate between the various model compartments (shower, the rest of the bathroom, and the rest of the house) following the same basic model construct described by Little (1992a). The resulting differential equations were solved using finite difference numerical integration. The pertinent equations are summarized in Appendix A. The McKone, Little, and Andelman models were compared for constituents exhibiting a wide range of Henry's law constants. Ten compounds were selected for the analysis, representing the 5th, 15th, 25th,..., and 95th percentile of Henry's law constants for the compounds in the exposure model database. The total mass of compounds emitted over a standard shower event, as described in Section C.2 (Table C.5), is presented in Table C.2. [Note: Because the McKone and modified McKone models were calibrated using the same model shower parameters as this simulation, both the McKone and modified McKone models provide identical emission predictions for this model simulation.] In comparing the model predictions presented in Table C.2, the simple Andelman (1990) model, as constrained by the saturation level in the shower using the detailed shower model, provided emission results very similar to the McKone (1987) model. Apparently, both the Andelman and McKone models become "saturation rate" limited at approximately the same Henry's law value for this model simulation. The Little model predicts much lower emissions for compounds in the semivolatile range than the other models, because the Little model predicts that the emissions are mass-transfer-rate-limited for these compounds rather than saturation-rate-limited for this model simulation. It is important to note that the comparison of model emission predictions provided in Table C.2 is somewhat dependent on the shower model parameters selected for the simulation. If shower water parameters that increase the time required to saturate the shower were used (i.e., decreased shower water use rates, increased shower volumes, and increased shower air exchange rates), larger differences would be expected in the emissions predicted by the Andelman and McKone models. If shower water parameters that would decrease the time required to saturate the shower were used (i.e., increased shower water use rates, decreased shower volumes, and decreased shower air exchange rates), the emissions predicted by the Little model would more closely compare to the emissions predicted by the Andelman and McKone models. Unfortunately, emission measurement data on which to base a model recommendation are very limited for compounds in the semivolatile range. The experimental overall mass transfer rate coefficient data presented in Table C.1 does not provide conclusive evidence as to which model best simulates semivolatile compounds (i.e., the Little model provided excellent prediction of Kol for 1,2,3-trichloropropane, but it significantly underestimated the Kol for 1,2- dibromo-3-chloropropane). From the comparison provided in Table C.2, it appears that a very simple mass transfer rate model of Andelman (1990) provides the highest emission estimates; the McKone (1987) model provides similarly conservative emission estimates for the shower model parameters used in this simulation; and the Little model predicts lower shower emissions (or exposure levels) for semivolatile compounds for the model shower parameters used in this simulation. Table C.2. Model Predictions for Total Mass Emitted During Model Showera C.1.3 Comparison of Predicted Average Exposure Concentrations The detailed shower model equations provided in Appendix A were compared to less complicated models that directly estimate the average air exposure concentrations. Again the model comparison was conducted using the 10 compounds selected to represent the range of Henry's law constants for the compounds in the exposure model database. The exposure concentrations predicted by the equations presented in Andelman (1990) and in McKone and Bogen (1992) were compared with the detailed shower model using the McKone (1987) mass transfer correlation as applied using the equations in Appendix A. Table C.3 compares the results of the model predictions of the average shower air exposure concentrations. During the evaluation, it was evident that the simple models - Andelman (1990) and McKone and Bogen (1992) - predicted shower air exposure concentrations greater than saturation (i.e., greater than the equilibrium air concentration based on Henry's law partitioning) for compounds of low volatility. The equilibrium air concentrations based on Henry's law partitioning are also provided in Table C.3 for comparison with the predicted exposure concentrations. The results presented in Table C.3 illustrate the inadequacy of the Andelman (1990) exposure concentration equations for anything but highly volatile compounds. The McKone and Bogen (1992) exposure model provides constituent-dependent exposure variations, but does not account for shower volume (additional dilution air) or the time it takes to reach the maximum concentration. As discussed in Section C.1.2, the detailed shower model using McKone (1987) mass transfer dependency predicts near-saturation exposure concentrations for the mid to low volatility compounds. Thus, it appears that the McKone (1987) model provides a conservative estimate of the shower exposure. The full shower model described in Appendix A also provides direct estimates of the bathroom and whole house exposure. McKone and Bogen (1992) also provide simple equations to estimate bathroom exposure based on shower emissions and whole house exposure based on other water use rates. Table C.4 compares the McKone and Bogen (1992) bathroom air exposure concentration estimates to the bathroom air exposure concentrations estimated by the detailed shower model described in Appendix A for 45 minutes immediately following the shower event. Again, the McKone and Bogen (1992) model provides very high exposure estimates because of its lack of dependence on the bathroom volume (additional dilution air) or the time required to build up the concentration. The risk from inhalation exposures in the remainder of the house was several orders of magnitude less than the risk from inhalation exposures in the bathroom and during showering (Coburn, 1996). Thus, it appears that the whole house compartment of the analysis may be disregarded without significant impacts on the inhalation exposure risk analysis. Table C.3. Model Predictions For Average Shower Air Exposure Concentrationa Table C.4. Model Predictions For Average Bathroom Air Exposure Concentrationa C.2 References Andelman, Julian B. 1990. Total Exposure to volatile organic compounds in potable water, Chapter 20 in Significance and Treatment of Volatile Organic Compounds in Water Supplies,. N.M. Ram, R.F. Christman, and K.P. Cantor (eds.). Lewis Publishers Chelsea MI. pp. 485-504. Bird, R.B., W.E. Stewart and E.N. Lightfoot. 1960. Transport Phenomena. John Wiley & Sons. New York, New York. Coburn, J. 1996. Memorandum to Rebecca Daiss, Office of Solid Waste, Environmental Protection Agency. July. Jo, W.C., P.W. Clifford, and P.J Lioy. 1990. Routes of chloroform exposure and body burden from showering with chlorinated tap water. Risk Analysis. 10(4):575-580. Little, John C. 1992a. Applying the two resistance theory to contaminant volatilization in showers. Environmental Science and Technology 26:1341-1349. Little, John C. 1992b. Correspondence. Comment on "Human exposure to volatile organic compounds in household tap water: the indoor inhalation pathway." Environmental Science and Technology 26(4):836-837. McKone, Thomas E. 1987. Human exposure to volatile organic compounds in household tap water: The Indoor Inhalation Pathway. Environmental Science and Technology 21:1194-1201. McKone, Thomas E., and J.P. Knezovich. 1991. The transfer of trichloroethylene (TCE) from a shower to indoor air: Experimental measurements and their implications. Journal of Air and Waste Management Association. 41(3):282-286. McKone, Thomas E., and K.T. Bogen, 1992. Uncertainties in health-risk assessment: an integrated case study based on tetrachloroethylene in California groundwater. Regulatory Toxicology and Pharmacology 15:86-103. U.S. Environmental Protection Agency. 1990. Exposure Factors Handbook U.S. Environmental Protection Agency. 1996. Exposure Factors Handbook (Draft) APPENDIX D EXPOSURE FACTORS Exposure factors are linearly related to risk results therefore it is possible to predict the effect of using the ingestion rates and exposure durations presented in the 1996 Exposure Factors handbook based upon their relationship to the factors used in the current analysis. Table D.1 presents the ingestion rates and exposure durations used in the current risk assessment, and the corresponding factors presented in the draft exposure factors handbook which are anticipated for incorporation in the final rule, and the ratio of these factors that may be used to estimate the effect on the final risk results. Edchange = (ED1996/ED1990) where EDchange = Relative change in the exposure duration ED1996 = Exposure duration from 1996 draft Exposure Factors Handbook ED1990 = Exposure duration from 1990 Exposure Factors Handbook and IRchange =(IR1996/IR1990) where IRchange = Relative change in the ingestion rate IR1996 = Ingestion rate from 1996 draft Exposure Factors Handbook IR1990 = Ingestion rate from 1990 Exposure Factors Handbook Table D.1 Comparison of Current Exposure Factor Handbook Values and Values from the Draft 1996 Exposure Factors Handbook The combination of the change in the exposure duration for each scenario may be applied to the relative change in the ingestion rate to determine the overall change to the risk estimate by pathway. The overall risk for the scenario is determined by summing the risk by pathway for each combination of high end modeling variables. The relative change for each pathway may be estimated with the following equation: EDchange x IRchange = Total relative pathway change Table D.2 presents the relative change in the risk for each pathway in each scenario presented in the nongroundwater risk assessment performed for Clarified Slurry Oil Sludge managed in an onsite land treatment unit for the petroleum refining listing decision. The high end risk estimates all include the long exposure duration as one of the high end parameters, therefore, for this case the relative change in the long exposure duration is multiplied by the relative change in the central tendency ingestion rate to determine the total relative change in the risk estimate. The 1990 Exposure Factor Handbook does not include high end ingestion rates, thus, this option is not compared in Table D.2, however, the effect of using the high ingestion rate factors and/or central tendency exposure duration factors may be determined using the same method. Table D.2 Relative Change in Risk Assessment Results Expected from Converting to 1996 Exposure Factors for Clarified Slurry Oil Sludge Managed in an Onsite Land Treatment Unit Long Exposure Duration and Central Tendency Ingestion Rates