Texas Groundwater Contamination Tracker
Fifty-seven landfills. Three hundred and fifty dry cleaners. Nine hundred and seventy-eight underground petroleum tanks.
These are some of the 2,870 documented sources of active groundwater contamination sites in Texas’ latest monitoring report, one fifth of which fall within Harris County.
The state document, published each year by the Texas Groundwater Protection Committee, is one of the most comprehensive resources in Texas that tracks underground water pollution. The report also listed 2,000 inactive cases from the past three decades in its last report – 425 in Harris County alone – at locations that could still be contaminated, though their state enforcement actions ended.
The Houston Chronicle collected, manually labeled and analyzed nearly a decade’s worth of monitoring reports to create a first-of-its-kind database of contamination events in Texas. Our interactive map locates and contextualizes each spill with information about contaminants’ potential health effects, offering a starting point for Texans concerned about groundwater pollution near their homes or businesses.
Groundwater flows gradually through sediment in distinct layers called aquifers. Its quality can be affected by natural processes such as mineralization, but the state focuses on human-triggered contamination like ground-level spills and underground pipe breaks that cause “detrimental alteration of the natural quality of groundwater.”
This contamination can pose problems for Texas taps: over half of the state’s drinking water is pulled from underground aquifers.
Still, contamination near your home does not necessarily mean your tap water is affected.
Only 14% of Houston Public Works’ total supply comes from wells, though this percentage varies for homes in different parts of the city. Many Houston-area residents also have their own wells or rely on a smaller Municipal Utility District for their water.
“(The city’s) water wells that are designated for drinking water are really deep,” said Erin Jones, spokeswoman for Houston Public Works. “Groundwater contamination would take so long to ever reach that deep.”
Even when a groundwater contamination incident leaves taps untouched, the event may poison plants, run into nearby bayous or rise up into homes as toxic vapor.
Each toxin contaminating groundwater behaves differently.
Plumes of contamination gradually travel, and some substances can move up or down in the subsurface or end up in other bodies of water: “Groundwater discharges into surface water via the sea floor, right at the bottom of the river or bay,” said Dini Adyasari, a hydrogeologist at Texas A&M Galveston.
Groundwater movement is very slow, though, compared to a river or stream. Some groundwater plumes have remained on the state’s active case list since the 1980s.
“They can be there in the subsurface for a long time, especially if the contaminant itself is difficult to biodegrade,” Adyasari said, adding that many industrial chemicals fall into this category.
Chlorinated solvents, a family of chemicals among the most-commonly listed in groundwater contamination cases across the state, are among them. These solvents can be used to degrease surfaces or dry clean clothing, but also feature in multiple plastic production processes.
While some contaminants including chlorinated solvents are heavier than water, diving gradually deeper into the earth, others – like gasoline – are lighter and tend to float above the water table.
The concentration of sites in the Houston area is not surprising to environmental activists such as Jackie Medcalf, founder of Texas Health and Environment Alliance. She has worked with communities living near well-known local groundwater contamination sites such as Union Pacific’s former creosote facility in Fifth Ward, and the chemical contamination from a former dry cleaner on Cypress’ Jones Road.
“When you have a region that manufactures (so many) different chemical compounds, the potential for contamination is great, particularly because we don't have a perfectly impermeable layer that would prevent contamination at the land surface from getting down into water,” Medcalf said.
She thinks residents concerned about water contamination should follow their guts and seek more information.
A suite of overlapping local, state and federal agencies and rules regulate groundwater pollution, depending on their source, impact, severity and location. Still, the primary agency responsible for taking action against parties that are responsible for groundwater contamination is the Texas Commission on Environmental Quality.
Texas law requires the agency to notify people with private wells within 30 days of the moment they find out about groundwater contamination in an area. Public water systems also have to notify their users of contamination that violates the law’s maximum contaminant levels within 30 days in less urgent situations, and within 24 hours for immediate threats.