From Regional Transportation Commission:

Monday, the RTC and Granite Construction conducted a drone flyover to assess the condition of the stockpiles of soil containing mercury in proximity to the Steamboat Creek flood waters. 

The SouthEast Connector Project is located within a floodplain and is designed to handle flood water during and after construction. The project does not exacerbate the impact of a flood event during or after construction. 

During the day on Sunday, January 8, Steamboat Creek overtopped its banks and water flowed onto the construction site. This is to be expected and is encouraged as a way to allow the Creek to access its natural floodplain. Once the Creek water entered the construction site, the water did come into contact with stockpiles of soil containing mercury, however those stockpiles were surrounded with berms of soil without mercury. A total of 12 stockpiles of soil containing mercury are located between South Meadows Parkway and Mira Loma Drive. At this time it appears 11 of the 12 stockpiles are undamaged. One stockpile appears to have had a partial failure of the clean soil berm. However, we are unable to ascertain the degree of contact, if any, of the actual stockpile of soil containing mercury which may have experienced erosion. Once the floodwater recedes, the project team will be able to more closely inspect and assess the situation.

Additionally, they collected water quality samples today. Water quality samples are done weekly and prior to and following storm events. Water quality results will be available in approximately one week and will be submitted to the Nevada Department of Environmental Protection. These water samples are tested for mercury concentrations and other naturally occurring contaminants. RTC has consulted with the US Army Corps of Engineers and the Environmental Protection Agency and is in compliance with the requirements of the permits issued for the projects. The 401 and 404 permits are  designed to protect the public health. 

They do not anticipate the test results showing a higher concentration of mercury than what is in Steamboat Creek naturally and upstream of the project. We do not expect there to be a risk to the public health and the environment.

For background information, 125,000 cubic yards of soil containing mercury has already been permanently sequestered underneath the roadway embankment already constructed. Prior to construction, this soil would have been exposed to the floodwaters. There is less mercury exposed now than prior to construction.

From Regional Transportation Commission