6 Rio Grande Valley Wastewater Plants Are Failing. Here Is What They Are Dumping Into Your Water.

EPA data reveals E. coli at 6x the legal limit in McAllen, cyanide in Brownsville, ammonia surging 68% in Edinburg, and discharge water toxic enough to kill lab organisms in Alamo. All of it flows to the same place: Laguna Madre.

I did not set out to find this.

I started with one facility. The City of Edinburg Wastewater Treatment Plant. I pulled the discharge monitoring data from the EPA ECHO database, which is public, free, and available to anyone with an internet connection. What I found led me to a second facility. Then a third. Then a fourth.

By the time I stopped, I had pulled compliance records, discharge monitoring reports, effluent exceedance data, and quarterly noncompliance histories for six facilities across Hidalgo and Cameron counties. Every single one was in violation of its federal discharge permit. Some had been in violation for years.

None of this data is hidden. It has been sitting in the EPA database the entire time. Nobody was putting it together.

Until now.

McAllen: E. coli at 6 Times the Legal Limit

Let me start with what I found most recently because it hits closest to home for the most people.

The City of McAllen South Wastewater Treatment Plant, permit TX0047449, has been discharging E. coli at levels that should alarm anyone who lives, works, fishes, or sends their kids to school in the RGV.

E. coli is fecal bacteria. It is the standard indicator regulators use to determine whether human sewage has been properly disinfected before it leaves a treatment plant. The permit limit for daily maximum E. coli at this facility is 399 CFU/100mL.

Here is what the plant actually discharged:

July 2025: 1,235 CFU/100mL. 3.1 times the limit.

September 2025: 2,420 CFU/100mL. 6.1 times the limit.

October 2025: 1,027 CFU/100mL. 2.6 times the limit.

December 2025: 790 CFU/100mL. 2.0 times the limit.

Four E. coli exceedances in six months. More than one in three required monitoring reports showed a violation. At 2,420 CFU/100mL, the discharge contained bacteria levels consistent with raw or minimally treated sewage.

And here is the part that makes it worse: this is the second time. The same seasonal failure happened in Q3 and Q4 of 2023. The problem was formally marked "Resolved" in early 2025. Six months later, it came back. Same months. Same pattern. Worse numbers.

Every other parameter at this plant is clean. Ammonia, BOD, suspended solids, dissolved oxygen, pH, chlorine, all whole effluent toxicity tests. All compliant. McAllen South can treat wastewater. It just cannot keep fecal bacteria out of the discharge during the hottest months of the year. And nobody has fixed the problem that keeps causing it.

Edinburg: 40.7 Million Pounds and Climbing

The City of Edinburg Wastewater Treatment Plant is a designated Significant Non-Complier by the EPA. That means exactly what it sounds like: the violations are significant, and the facility is not in compliance.

I pulled the full discharge data for 2024 and 2025. The year over year numbers are staggering.

Ammonia: 482,013 pounds in 2024. 810,165 pounds in 2025. That is a 68.1% increase in a single year.

Total Suspended Solids: 709,560 pounds to 1,078,108 pounds. Up 51.9%.

BOD (Carbonaceous): 205,598 pounds to 600,973 pounds. Up 192.3%. Nearly tripled.

The Edinburg WWTP alone went from 1.4 million pounds of total discharge in 2024 to 2.5 million in 2025. A 78.2% increase.

Across all four major Edinburg dischargers (including Calpine Hidalgo Energy Center, Doolittle RO Facility, and Magic Valley Generation), the total was 40,748,956 pounds in 2025. Over 40 million pounds of pollutants discharged into local waterways in one year. Up 8.4% from 2024.

All of it flows through the West Main Drain and the Edinburg North Main Canal system into the Arroyo Colorado watershed and ultimately toward Laguna Madre.

Despite the Significant Non-Complier designation, no formal enforcement action has been taken.

Alamo: The Water Killed the Test Organisms

The City of Alamo WWTP might be the most alarming finding in this entire investigation. Not because of a single headline number, but because of what the biological testing revealed.

Ammonia at this facility is at Significant/Category I Noncompliance, the worst designation the EPA assigns. It is currently active. Not resolved. Not pending. Active right now.

Seven of the ten monitored pollutant parameters at the primary outfall are in violation: ammonia, E. coli, BOD, dissolved oxygen, total suspended solids, pH, and chlorine residual. The plant is failing across virtually every metric of treatment effectiveness.

But the real story is the Whole Effluent Toxicity tests. WET tests take the actual discharge water and put living organisms in it. Water fleas. Fathead minnows. Then they watch what happens.

10 out of 12 toxicity test parameters failed.

Both species. Lethal tests failed. Sub-lethal tests failed. Reproduction tests failed. The water coming out of the City of Alamo WWTP is toxic enough to kill organisms in a controlled laboratory setting.

That is not a marginal exceedance of a chemical limit. That is a biological confirmation that the effluent is actively harmful to aquatic life.

Harlingen: Five Consecutive Quarters and Counting

The City of Harlingen Waterworks System WWTP has been in continuous violation for five straight quarters, from Q1 2025 through Q1 2026, with no recovery.

The severity escalated in Q2 2025 from "Other Violation" to "Reportable Noncompliance," a higher severity tier that triggers mandatory reporting to EPA. It has remained at Reportable Noncompliance for three consecutive quarters.

The violations span three pollutant categories: E. coli (fecal bacteria), total suspended solids, and pH.

Earlier in 2023 and 2024, the plant would stumble and recover. A bad quarter followed by clean quarters. Starting in 2025, it stopped recovering. Something structural changed, and whatever it is has not been fixed.

Fishing Harbor WWTP: Cyanide at a Place Called Fishing Harbor

The Fishing Harbor WWTP in Brownsville, permit TX0100242, might have the single most disturbing data point in this entire investigation.

In June 2024, enterococci (fecal bacteria) hit 2,419.6 CFU/100mL against a permit limit of 104. That is 23.3 times the legal limit. The daily average that same month was 1,101.97 against a limit of 35. 31.5 times the limit. Those are levels consistent with raw sewage going out the outfall. At a fishing harbor. Where people handle catch with their hands.

But the enterococci is not even the most concerning pollutant at this facility. Cyanide is.

This facility recorded 13 cyanide violations across the monitoring period. In September 2023, total cyanide hit 0.082 mg/L against a permit limit of 0.018 mg/L. That is 4.6 times the legal limit. Cyanide is acutely toxic to aquatic life.

The question nobody is answering: where is the cyanide coming from in a municipal wastewater system? Cyanide at these levels in WWTP influent typically points to an uncontrolled industrial source discharging into the sewer system. Someone upstream is putting cyanide into the wastewater and it is coming out the other end into the water at a fishing harbor.

This facility has been in violation for 10 of the last 13 quarters. It reached Significant/Category I Noncompliance twice.

SpaceX Starbase: 56 Violations at Boca Chica

SpaceX's Starbase Launch Pad Site 1 in Boca Chica, permit TX0146251, has racked up 56 violations since its enforcement order began in March 2025.

The Chemical Oxygen Demand numbers are extreme. The permit limit is 200 mg/L.

October 2025: 765 mg/L. 3.8 times the limit.

December 2025: 270 mg/L. 1.35 times the limit.

January 2026: 1,370 mg/L. 6.85 times the limit. 585% over.

COD at these levels means the discharge is so loaded with chemical and organic waste that it consumes the dissolved oxygen in whatever water body it enters. At nearly 7 times the legal limit, it can create localized dead zones where nothing survives.

The monitoring panel includes mercury, thallium, copper, and zinc. The February 2026 mercury reading logged at 4.26 mg/L. The EPA human health water quality criterion for mercury is 0.012 mg/L.

The facility submitted monitoring reports up to 152 days late. For the first four months of the enforcement order, the treatment system was reported as "Not Constructed." The outfall did not physically exist while the enforcement order was running.

This is Boca Chica. Right on the edge of Laguna Madre. Right next to the Lower Rio Grande Valley National Wildlife Refuge.

Where It All Goes

Here is the part that ties all of this together.

Every one of these facilities discharges into the same interconnected system. The RGV does not have natural rivers flowing to the coast. It has a network of man-made canals, irrigation channels, and drainage ditches built over the past century. These same channels now carry the discharge from every wastewater treatment plant, every industrial outfall, and every stormwater system in the region.

The canals feed the Arroyo Colorado, the primary drainage corridor for the central Valley. The Arroyo Colorado runs approximately 90 miles from Mission to the coast. It is already designated as an impaired waterway under the Clean Water Act for bacteria and depressed dissolved oxygen. It has a documented history of fish kills.

And the Arroyo Colorado floods. Every year. When it floods, contaminated water enters homes, schools, and businesses across the RGV.

The Arroyo Colorado empties into Laguna Madre, one of only five hypersaline lagoons in the world. Laguna Madre supports seagrass beds among the most extensive in the Western Hemisphere. It is nursery habitat for shrimp, redfish, and spotted seatrout. Nesting grounds for piping plovers. Part of the Central Flyway for migratory birds. Bordered by the Lower Rio Grande Valley National Wildlife Refuge.

Every pound of ammonia from Edinburg and Alamo. Every colony of E. coli from McAllen and Harlingen. Every milligram of cyanide from Fishing Harbor. Every spike of COD and mercury from Starbase. It all flows downstream through the same system to the same place.

Laguna Madre.

Who Lives Here

EPA demographic data for the communities surrounding these discharge points tells a consistent story. Populations exceeding 90% people of color. Poverty rates approaching 50%. These are environmental justice communities by any federal definition.

These communities do not have funded environmental advocacy organizations. They do not have investigative newsrooms covering water quality. They do not have the monitoring infrastructure that Houston, Dallas, and San Antonio rely on to detect and respond to contamination.

What they have are wastewater treatment plants that are failing, discharging E. coli, ammonia, cyanide, and toxic effluent into the waterways that flood their homes. And they have been told their health problems are the result of personal choices.

Personal choices do not explain ammonia up 68% in a year. Personal choices do not explain cyanide at a fishing harbor. Personal choices do not explain discharge water that kills lab organisms.

Infrastructure failure explains it. Lack of enforcement explains it. And the fact that nobody was connecting the data and making it public explains how it went on this long.

The Data Is Public

Every number in this report came from the U.S. EPA ECHO database at echo.epa.gov. Discharge Monitoring Reports. Quarterly Noncompliance Reports. Effluent Limit Exceedance Reports. Water Pollutant Loading Tool data. All publicly available. No FOIA requests required. No special access needed.

The information has always been there. What was missing was anyone putting it together.

Six facilities. Three counties. One watershed. One destination.

The ammonia does not stop at the city limits. The E. coli does not stop at the canal bank. The cyanide does not stop at the property line.

It all flows downstream.

Joshua Moroles is an investigative journalist and documentary filmmaker