The Trump administration is moving forward with plans for a southern border wall with the release of a request for proposals, opening up bidding for the project. The U.S. Customs and Border Protection agency released two separate RFPs, one for a concrete wall and another for other types of barriers.

The concrete wall RFP states the design will be reinforced concrete and be physically imposing in height, approximately 30 feet tall. The government is flexible on that number, but will not consider designs below 18 feet. In both RFPs, a key design feature highlighted is making the wall impervious to climbing or tunneling above 6 feet. The RFPs also request the U.S. side of the wall be aesthetically pleasing, blending in with the landscape around it. The prototypes should cost between $100K and $300K.

The wall will span 1,200 miles from San Diego to Brownsville. About 650 miles of wall already exists on the border.

A February pre-solicitation notice had more than 700 firms showing interest. Payment could be tricky. The president's budget blueprint only includes $3B for infrastructure security measures at the border. Recent reports estimate the wall's cost at $21B. Further complicating matters, some organizations have already begun blacklisting companies seeking to bid on the wall.