During August 2023, transient electromagnetic (TEM) surveys were carried out at select locations in Lake County near Leadville, Colorado upgradient from the Dinero tunnel bulkhead. TEM data were collected using an ABEM WalkTEM2 advanced instrument running acquisition software version 1.3.7.4 and using a single-turn transmitter loop (Tx) and a center-loop receiver (Rx). Tx loop dimensions measured 40 by 40 square meters, and Rx loop dimensions measured 0.5 by 0.5 square meters (effective area of 5 m2). Dual currents of about 1 and 7.5 amperes (A) were injected into the Tx loop, and the Rx coil was centered and concentrically nested inside the Tx loop. Transmitter measurement cycles were stacked (n=10) to create a single sounding, and soundings were repeated (n=1-5) at each site. In locations with multiple soundings, results were stacked, filtered, and averaged for each Tx current (1 and 7.5 Amperes) and set of Rx measurements. This data release includes the raw and processed TEM data and inverted soundings showing resistivity (in ohm-m) with depth.