A seepage investigation was conducted of 4,600 acres of Bear Creek Valley southwest of the Y-12 Plant, Oak Ridge, Tennessee, for the period of January through September 1994. The data were collected to help the Y-12 Environmental Restoration Program develop a better understanding of ground-water and surface-water interactions, recharge and discharge relations, and ground-water flow patterns. The project was divided into three phases: a reconnaissance and mapping of seeps, springs, and stream-measurment sites; a high base flow seepage investigation; and a low base flow seepage investigation. The reconnaissance was conducted from January 6 to March 1, 1994, to identify and map the locations of seeps, springs, and stream-measurement sites. A total of 701 sites were identified. They consisted of 382 stream- measurement sites, 265 seeps, 48 springs, and 6 wetlands. A global positioning system was used to locate 680 sites to within 3- to 5-meter accuracy. The high base flow seepage investigation was conducted from March 14 through March 19, 1994. Measurements were made at 579 of the 701 sites identified in the reconnaissance that still had flowing water. Flow rates ranged from less than 0.005 to 6.89 cubic feet per second for the streams, from less than 0.005 to 0.13 cubic foot per second for the seeps, and from less than 0.005 to 1 cubic foot per second for the springs. pH ranged from 5.0 to 8.4 for the streams, from 5.1 to 8.2 for the seeps, from 5.3 to 8.0 for the springs, and from 6.7 to 6.8 for the wetland sites. Specific conductance ranged from 16 to 1,670 microsiemens per centimeter for the streams, from 17 to 1,710 microsiemens per centimeter for the seeps, from 14 to 1,150 microsiemens per centimeter for the springs, and from 102 to 160 microsiemens per centimeter for the wetland sites. Temperature ranged from 4.5 to 16.0 degrees Celsius for the streams, from 5.0 to 21.0 degrees Celsius for the seeps, from 6.0 to 13.5 degrees Celsius for the springs, and from 13.0 to 19.5 degrees Celsius for the wetland sites. Dissolved oxygen ranged from 4.8 to 11.2 milligrams per liter for the streams, 1.2 to 11.3 milligrams per liter for the seeps, and from 0.6 to 11.0 milligrams per liter for the springs. Dissolved oxygen at a wetland site measured 3.8 milligrams per liter. The low base flow investigation was conducted from September 9 through September 29, 1994. The stream sites, seeps, and springs that had flow during the high base flow seepage investigation were revisited. One-hundred seventy-six of the stream sites visited still had flow. Discharge ranged from less than 0.005 to 0.76 cubic foot per second; pH, from 4.8 to 8.3; specific conductance, from 47 to 2,030 microsiemens per centimeter; temperature, from 13.5 to 22.5 degrees Celsius; and dissolved oxygen, from 3.6 to 8.7 milligrams per liter. Twenty-five of the seeps visited were flowing and had discharge ranging from less than 0.005 to 0.01 cubic foot per second; pH, from 6.0 to 7.7; specific conductance, from 36 to 395 microsiemens per centimeter; temperature, from 16.0 to 21.0 degrees Celsius; and dissolved oxygen, from 2.2 to 9.0 milligrams per liter. Thirty springs visited were flowing and had discharge ranging from less than 0.005 to 0.37 cubic foot per second; pH, from 6.5 to 7.7; specific conductance, from 26 to 1,220 microsiemens per centimeter; temperature, from 14.0 to 20.0 degrees Celsius; and dissolved oxygen, from 1.0 to 9.2 milligrams per liter. All of the wetland sites visited were dry.