"The US Fish and Wildlife Service (FWS) conducted this Streamlined Aquatic Ecological Risk Evaluation under an Interagency Agreement with the Bureau of Land Management (BLM) Royal Gorge Field Office, Canon City, Colorado. As requested, the objective of this evaluation is to assist BLM to determine the amount of metals reduction needed from the Tiger Tunnel in order to meet water quality standards or support downstream fish populations. The BLM requested the information for use in a feasibility study that is examining installation of a sulfate reducing bioreactor (SRB) at the Tiger Tunnel. There are two main tasks being completed in order to complete the stated objective : 1) to quantify metal load contributions from the Tiger Tunnel to Colorado Gulch and Lake Fork; and 2) determine if reduction of metals loading from the Tiger Tunnel would result in water quality improvements to levels that would support fisheries in Colorado Gulch"--from Introduction (page 4).