The South Padre Island desalination plant cost
A joint venture called RGV Desal, made up of US Desalination and IDE Technologies, wants to build a Gulf of Mexico seawater desalination plant on the north end of South Padre Island. Desalination is the process of removing salt from seawater to make it drinkable. At a June 2026 public forum, developer Doug Allison put a number on what he calls inside the fence line, the plant itself.
The facility, what I am going to call inside the fence line is probably right at 1 billion dollars for a 50 million gallon per day facility.
Doug Allison, of US Desalination. Source 1.
The company has also floated a possible expansion to 120 million gallons a day, more than double its opening size. Filings with the Texas Commission on Environmental Quality were expected within 2 months of that forum, and separate reporting from April 2026 put the total permitting process at about 18 months, with the plant potentially online between 2029 and 2031.
The Laguna Madre Water District figure is the plan the region already follows, source 5. Both RGV Desal figures come from the plan the developer has stated, sources 1 and 2, not yet permitted or built.
Show the numbers
| State recommended, Laguna Madre | 5 |
| RGV Desal, initial phase | 50 |
| RGV Desal, expansion | 120 |
Why the region wants Gulf water now
The water crisis behind this proposal has a specific number attached to it. Under the 1944 United States Mexico water treaty, Mexico must deliver a minimum of 350,000 acre feet of water to the United States every year, averaged over a 5 year cycle, according to the International Boundary and Water Commission. An acre foot is enough water to cover 1 acre of land 1 foot deep. Brownsville, McAllen, 2 water supply corporations and Port of Brownsville industrial users have all expressed interest in buying water from the proposed plant, a sign the shortfall is a shared concern rather than 1 city problem.
A stretch of coast studied 4 times since 2004
Seawater desalination has been studied on this exact stretch of Texas coast before, and never built. The Texas Water Development Board has funded 3 feasibility and pilot studies for Brownsville and South Padre Island seawater desalination since 2004, totaling 2,071,000 dollars, a sum MAOWCE calculated from project records kept by the agency. None of the 3 produced an operating plant.
We are really pleased that we have developed the relationships in the Valley to do this project before it gets to be the 11th hour.
Doug Allison, of US Desalination. Source 1.
A 4th study, lessons learned from the Brownsville seawater pilot study in 2009, states no funding figure in the source and is not included for that reason.
Show the numbers
| Brownsville, feasibility study 2004 | 500,000 |
| Brownsville, pilot plant study 2008 | 1,340,000 |
| South Padre Island, feasibility and pilot study 2010 | 231,000 |
A smaller plant already recommended, and a bay the developer avoided
The current water plan for the region does not treat this idea as unprecedented or uniquely needed at this scale. The 2026 Rio Grande Regional Water Plan, the state mandated plan the region already follows, recommends its own seawater desalination project, a 5 million gallon a day plant at a total cost of 127,001,000 dollars. MAOWCE calculated that the proposed RGV Desal plant would cost about 7.9 times as much for a plant 10 times the size.
Allison says the company chose an offshore Gulf intake over the nearby Laguna Madre bay specifically to avoid harming it.
I can tell you the reason we took it off shore is because we understand there is rightfully a concern about environmental impacts on Laguna Madre.
Doug Allison, of US Desalination. Source 1.
But the same regional water plan describes the bay as naturally hypersaline in parts, saltier than the ocean itself, and states that the biggest recent threat to its wildlife has come from too much fresh water flowing in, not too much salt, the opposite of the risk the offshore choice assumes. Neither document claims this proves the siting choice right or wrong. It shows the tradeoff is more complicated than either explanation alone suggests.
As of September 2026, RGV Desal has not filed for its state permits with the Texas Commission on Environmental Quality, and no seawater desalination study on this stretch of coast has yet become an operating plant.