Leadville Mine Drainage Tunnel Environmental Improvement Act of 2008

Leadville Mine Drainage Tunnel Environmental Improvement Act of 2008 - Amends the Reclamation Projects Authorization and Adjustment Act of 1992 to repeal provisions requiring construction of a water treatment plant to treat effluent discharged from the Leadville Mine Drainage Tunnel, Colorado, and authorizing the Secretary of the Interior to investigate water pollution sources and impacts attributed to development in the Upper Arkansas River basin, develop corrective action plans, and implement corrective action demonstration projects.

Requires the Secretary to operate and maintain the Tunnel in a manner that protects human health and the environment.

Directs the Secretary, in cooperation with the state of Colorado, the Administrator of the Environmental Protection Agency (EPA), and other federal agencies, to: (1) investigate the Tunnel, groundwater and surface water affected by any blockage of the Tunnel, and the upper Arkansas River Watershed (study area); and (2) submit to the state, the Administrator, and Congress annual reports on how any blockages in the Tunnel affect water quality and aquatic life in the study area.

Requires the Secretary, in conjunction with the Administrator, to take actions to: (1) reduce the water level in the mine pool associated with the Tunnel to prevent the risk of a catastrophic rupture and flood; and (2) maintain the water level in the mine pool at a safe level and prevent further mine pool migration.

Directs the Secretary, in conjunction with the Administrator and the state, to implement those portions of the remedy selected by the Administrator, dated September 2003, for the California Gulch Superfund Site that pertain to managing the Tunnel and related mine pool.