McAllen, City Commission, Brackish Groundwater Desalination Facility, McAllen Public Utility, Carollo Engineers
Arnoldo Mata
McAllen TX - The McAllen City Commission held a workshop Sept. 14 to review ongoing planning and engineering design for the city’s brackish groundwater desalination facility, a project intended to provide McAllen with a water supply independent of the Rio Grande.
Sergio Espinosa, an engineer with Carollo Engineers, presented an update on the project alongside representatives from McAllen Public Utility, hydrogeology firm RWH, and other project partners.
Espinosa said the project began with a study of 170 acres owned by MPU near its existing water plant, where four test wells were initially planned to assess groundwater quality and volume. Following test drilling, hydrogeologists determined the site could support five well locations rather than four, and could produce 10 million gallons per day of raw brackish groundwater rather than the original estimate of 8 million gallons per day. The project is now designed for 90% water recovery, yielding 9 million gallons per day of potable water, using 13 wells across the five sites — five deep wells, five intermediate wells and three shallow wells.
Espinosa said the project requires deep well injection to dispose of concentrated brine waste produced by the reverse osmosis treatment process, noting that without deep injection, the city would need to blend the waste with several million gallons of surface or groundwater daily to meet discharge permit limits.
The project is being funded in part through a low-interest loan from the Texas Water Development Board’s State Water Implementation Fund for Texas program, with annual commitments of $30 million in year one, $49.3 million in year two, $51.3 million in year three, $44.8 million in year four, and $19.7 million in the final year.
Espinosa said the project will be divided into four separate design and construction packages to attract more local contractors and control costs: raw water production wells, estimated at $35.7 million; raw water yard piping and electrical facilities, estimated at $10.1 million; the desalination plant and related facilities, estimated at $121.6 million; and deep injection wells, estimated at $15.2 million, for a total estimated construction cost of $182.7 million. Espinosa cautioned that the figures remain estimates and that attracting more contractor bids could affect final costs.
Under the current project timeline, bidding for the raw water production wells and related yard piping and electrical work is expected to begin as early as May 2027, with completion of the 13 production wells targeted for June 2028 and substantial completion of the desalination plant targeted for December 2030.
A project team member said the city has already applied for a Texas Commission on Environmental Quality discharge permit for surface disposal and is pursuing a Hidalgo County Drainage District permit as a secondary discharge option.
Staff also noted that the city’s water system has recently reached record demand, with the south water plant reaching a peak of 40 million gallons per day in recent weeks, compared to a previous peak of 35 million gallons per day, which staff attributed to unusually hot conditions extending into September.
In response to questions from commissioners, project representatives said the facility’s 13 wells would range from 350 to 400 feet deep for shallow wells and up to 800 to 850 feet deep for deeper wells, while two deep injection wells would extend approximately 5,000 to 6,000 feet deep into a separate aquifer and geologic strata to prevent contamination of the freshwater aquifer. Representatives said the project has been modeled to sustain 30 years of continuous production at 10 million gallons per day, though actual operations are expected to run at a lower, more sustainable rate.
Asked about the facility’s effect on the city’s dependence on the Rio Grande, a project representative said the effort began about 18 months ago after regional reservoir levels fell to 17%, prompting the city to pursue a water source independent of the river. The new facility would provide additional capacity at the city’s north water plant, which currently produces 10 to 11 million gallons per day, compared to a rated capacity of about 54 million gallons per day at the city’s south plant. Combined, the north plant’s capacity would increase to about 20 million gallons per day. Representatives said the plant’s production could be adjusted throughout the year to help meet the city’s overall water demand, which ranges from about 18 to 20 million gallons per day in winter months to as much as 40 million gallons per day during peak summer demand.
A commissioner asked whether the well drilling process would be similar to oil drilling techniques. Project representatives confirmed that wells are cased and cemented using a similar drilling process, but do not involve hydraulic fracturing, and instead use manufactured slotted steel screens to prevent sand production.
Commissioners also asked about the project’s cost trajectory compared to unsuccessful desalination efforts in other Texas cities. Project representatives said dividing the project into four separate bid packages, rather than awarding it to a single general contractor, was intended to reduce markup costs and control overall project expenses. One commissioner voiced support for the approach, saying it could help control costs, while acknowledging the added complexity of managing multiple contractors.
Staff noted the city previously received a $9.6 million grant from the U.S. Bureau of Reclamation and has submitted an application for additional federal funding under a second phase of that program.
Asked whether the project would require an additional water rate increase, MPU representatives said they do not anticipate one at this time, based on current cost estimates, though they noted utilities typically implement modest rate increases every three to five years to address inflation and maintenance costs. Representatives said the total project cost was originally estimated at $185 million when it was first presented to the commission more than a year ago.
MPU representatives said the city’s water rates remain below the Rio Grande Valley average, which includes Weslaco, Harlingen, Donna, Brownsville, Mission and Edinburg, based on typical residential consumption of 10,000 gallons per month.
Project representatives said they would provide the commission with updates after each phase of the project moving forward.