Here’s a good quote and fully factual!
The original 2006 act provided for "at least two layers of reinforced fencing" to be built. However, the U.S. Department of Homeland Security (DHS) successfully argued to Congress "that different border terrains required different types of fencing, that a one-size-fits-all approach across the entire border didn't make sense."[6] An amendment introduced by Senator Kay Bailey Hutchison, Republican of Texas, was passed, amending the law to read: "nothing in this paragraph shall require the Secretary of Homeland Security to install fencing, physical barriers, roads, lighting, cameras, and sensors in a particular location along an international border of the United States, if the Secretary determines that the use or placement of such resources is not the most appropriate means to achieve and maintain operational control over the international border at such location."