"SF6 tracer tests were performed at the Rock Springs Site 12 (RS 12) oil shale true in situ retorting field site during the October 7-12, 1978 time period. Tracer tests were performed on the sideburn and main patterns, and included both surface (wellhead-to-wellhead) and downhole tracer injection and detection sequences for each pattern. For the sideburn pattern, the three test series were as follows: Test Series I: Surface test series with tracer injection at air injection wellhead 6 and tracer detection at air recovery wellhead 5. Under these conditions the tracer is transported with the total air injected and tracer response represents the entire formation swept by the airflow. Individual tracer tests of the series were performed over a range of water level conditions in the pattern in order to assess water intrusion effects and for comparison with downhole specific fracture tracer tests . Test Series II : Downhole test series with tracer injection confined to the primary air entry horizon (215 ~ l1'depth) of air injection well 6 and tracer detect In directly above the air recovery screen in well 5 . Under these conditions tracer response represents only those flow paths swept by air entering well 6 at the 215'horizon and normal air flow through all horizons was maintained. Test Series III: Downhole test series with tracer injection confined to the secondary air entry horizon (203 ~1'depth) of air injection well 6 and tracer detection directly above the air recovery screen in well 5. Similarly to Test Series II, the tracer response represents only those flow paths swept by air entering well 6 at the 203'horizon and normal air flow through all horizons was maintained. For each of the test series a number of repeatable individual tests were performed , and data on arrival times, response curve shape , tracer recovery, air flow and water level conditions was obtained."