BOARD01439 - Laserfiche WebLink

Home Browse Search

, 5 . areas of designated critical habitat has been included as a component of this project, to be completed by the Bureau of Indian Affairs and Bureau of Reclamation. With the completion of these two projects, as components of NIIP, the potential range of the endangered fish species will be expanded by about 22 miles to the Four Corners Generating Station weir, representing a 15% expansion in range. As an element of the proposed action, the Bureau of Indian Affairs has constructed and will operate three ponds to rear razorback sucker to sizes that will support successful stocking of this species in the San Juan River. The question of long term risk caused by the potential of project return flows to increase levels of selenium in the San Juan River and on-project ponds and the effects of such exposure on the endangered fish is a matter of debate among scientific experts. In order to address these concerns, the Bureau of Indian Affairs has included a monitoring program as an integral element of the proposed project. This program will be followed to track selenium levels and provide data to assess risk as additional research is completed concerning chronic toxicity, particularly in razorback sucker. It will be composed of three parts: 1) on-farm monitoring, 2) San Juan River monitoring, and 3) razorback sucker grow-out pond monitoring. . 1. Irrigation return flow from the project is the main source of selenium discharged to the San Juan River. This irrigation return flow leaves the project either through deep percolation and discharge from springs along bedrock contact lines or as artificial drain outflow. Artificial drainage was first installed in the winter of 1998-1999 in two fields, with a total of three drain outfalls. The drainage system completion study is now underway to identify and prioritize drain construction to intercept groundwater before it saturates the soils within the rootzone of the fields. The on-farm selenium sampling program will have three elements: 1 )groundwater wells, 21 subsurface drain outfalls, and 3) main natural drain outflow. There are 51 groundwater observation wells on Blocks 1-7 of the project. Much of Blocks 6 and 7 do not have water tables above the bedrock since irrigation is relatively recent. As water levels rise, observation wells will be added. Also as Blocks 8-11 develop and water tables rise, wells will be added to these blocks. It is anticipated that there will be as many as 100 observation wells at project completion. Water samples will be taken from these wells and selenium levels determined on a semi-annual basis. Sampling will occur in the spring, before irrigation begins, and in the fall, at the end of the irrigation season (typically March and October). . Upon installation of subsurface drains, each drain outfall to a main collector or natural drainage way will be monitored twice annually until selenium levels fall