Human and Ecological Risk Assessment - Earthjustice

Appendix CSite DataEPACMTP Climate Centers Assigned to CCW DisposalSites. (continued)Climate CenterStateNumber ofCCW Sites78 Jacksonville FL 179 Watkinsville GA 480 Norfolk VA 281 Shreveport LA 485 Knoxville TN 487 Lexington KY 389 Nashville TN 490 Little Rock AR 191 Tallahassee FL 493 Charleston SC 495 Atlanta GA 996 Lake Charles LA 2C.6 Surface Water DataThe surface water model used in the CCW risk assessment requires information onsurface waterbody type (river or lake), flow conditions, dimensions, and water quality. Inaddition, the groundwater model requires the distance between the waterbody and the WMUbeing modeled. Surface waterbody data were collected on a site-based, regional, or national basisdepending on the variable and data availability. Collection methods are described below by datasource. Attachment C-4 provides a summary of waterbody assignments, waterbody types, andflow conditions.C.6.1 Waterbody Type, Stream Flow Conditions, and DimensionsWaterbody type and flow parameters were obtained by matching the CCW plants tostream segments in the Reach File Version 1.0 (RF1) database (U.S. EPA, 1990). Stream flowestimates for all RF1 flowing reaches were estimated in the early 1980s. Statistics developed foreach flowing reach were mean annual flow, low flow (approximately 7Q10), 5 and mean monthlyflow. RF1 also contains velocities corresponding to mean annual and low flow, estimated from acompendium of time-of-travel studies. For streams and rivers, the CCW risk assessment used thelow flow statistic and the corresponding flow velocity, along with a waterbody type alsoincluded in the RF1 database. All RF1 data are indexed by USGS cataloging unit and streamsegment (CUSEG).To assign the CCW plants to the nearest downgradient reach (i.e., the nearest waterbodyin the direction of groundwater flow), a GIS was used to identify the closest RF1 stream segmentto each CCW plant location. Because of several uncertainties in the nearest reach approach (i.e.,5 The 7Q10 is the minimum 7-day average flow expected to occur within a 10-year return period (i.e., at least oncein 10 years).April 2010–Draft EPA document. C-14