Bernie Sanders and four other Democratic senators are asking President Barack Obama to halt construction of the four-state Dakota Access pipeline until a full environmental review can be completed. The proposed Dakota Access Pipeline would transport crude oil from North Dakota through South Dakota and Iowa and into Illinois. At issue is a small stretch of the pipeline that would run across Lake Oahe, which is a sacred site to the Standing Rock Sioux tribe. The tribe is concerned that the construction would desecrate the land and pollute the water.