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Texas Environmental Almanac, Chapter 2, Water Quality, Page 8



The federal Safe Drinking Water Act, enacted in 1974 and amended in 1986, was designed to ensure safe drinking water by establishing drinking water standards for treated water and by creating special protection for underground sources of drinking water.


The law classifies public water systems into two major categories. Those serving permanent populations like cities and towns are called "community systems." Those serving facilities like hotels, restaurants, youth camps, highway rest stops and travel trailer campgrounds are called "non-community systems." These non-community systems are further divided into those serving a transient population, such as users of restuarants and campgrounds, and those serving a non-transient population like hotels and schools. Of the approximately 7,200 public water systems in Texas, about 4,600 are community systems and 2,600 are non-community systems.(100)

Under the federal Safe Drinking Water Act, the level of regulation depends on the type of system. Transient non-community systems are required only to monitor and treat for nitrate and nitrites and fecal coliform. Both community systems and non-transient non-community systems must monitor and treat water to standards set by the federal government and enforced by the states. Communities with less than 15 connections or 25 people are not considered to be "public water systems" and are therefore not regulated at all.


The federal Safe Drinking Water Act contains a number of safeguards to protect groundwater used for drinking water. First, the Act's Sole Source Aquifer provision gives special protection to aquifers designated as the sole source of drinking water in the area. Any construction or development project that could impact that sole source aquifer cannot receive federal assistance. In Texas, the Edwards Aquifer, which supplies San Antonio with drinking water, has been designated as a sole source aquifer for all or part of Uvalde, Medina, Bexar, Comal and Hays Counties. Interestingly, the Edwards Aquifer is the only major supply of water in Texas that requires no advanced treatment. The water is merely pumped out of the aquifer, chlorinated and drunk by over one million San Antonio residents.

The Act's second major safeguard for groundwater is its Wellhead Protection Program. This provision seeks to protect from man-made contamination the wells used for municipal water supplies as well as the land surrounding those wells (known as well supply areas). To participate in the Wellhead Protection Program a city must conduct a field inventory to identify all potential sources of contaminants for the public water supply, and must adopt an ordinance that requires generators of contaminants to use best management practices to reduce the risk of contamination. It may also require limits on certain agricultural or industrial activities to prevent contamination from occurring. Since the program's inception in Texas, 171 local governments have delineated 856 wellhead protection areas encompassing 1,550 public water supply wells. Fifteen Texas cities have adopted wellhead protection ordinances to plug abandoned wells and limit the potential for contamination.(101)


In Texas, EPA has delegated authority for regulating drinking water to the state government. Currently, the state requires water systems to test for 126 chemicals, of which 72 have Maximum Contaminant Levels or MCLs. These include 21 volatile organic compounds, 33 synthetic organics, 15 inorganics and 3 radionuclides. In addition, the state requires public water suppliers to test for bacteria, lead and copper, and for 16 secondary contaminants such as iron, manganese and chloride which do not affect human health but lead to odor or taste problems.(102)


While the list of potential drinking water contaminants is large and continues to grow, two sources pose the most acute threat to human health: nitrates and bacteria. Nitrates in concentrations above the national standard can threaten the health of infants. They can react with the blood's hemoglobin, interfering with its ability to carry oxygen and resulting in the sometimes fatal blue baby syndrome. Bacteria in contaminated water can cause diseases such as typhoid, cholera, infectious hepatitis and dysentery.(103) These disease-causing bacteria are signaled by high levels of coliform bacteria, itself a relatively benign bacteria. Fecal coliform bacteria are commonly found in human and animal waste and may indicate sewage contamination and the presence of disease-causing organisms.

Lead in drinking water is another major concern. Lead usually enters the drinking supply after the water has left the treatment plant. It comes from old lead pipes in homes, from brass fixtures or from lead-based solder in copper pipes.(104) Lead is now banned in the installation or repair of public water systems and household plumbing. Even though most systems in Texas are not built with lead pipes, 70 municipal and industrial water systems throughout the state exceeded lead standards in 1992 and 1993.(105) Fortunately, these systems represented less than 3 percent of all systems tested in the state.(106)


Diagram of Drinking Water Creation

Water is delivered from a groundwater or surface water source to a treatment plant, where it is first aerated to allow volatile gases to escape. Next, small particles are clumped together through the use of coagulating agents and allowed to settle out of the water. Particles that do not settle out through coagulation slowly filter out to the bottom of a maze-like settling tank in a process known as sedimentation. The material at the bottom, called sludge, often creates a disposal problem, since it may contain some toxic elements (see Waste section). Next, water flows through long horizontal tanks with filters made of gravel, sand, or granulated activated carbon and is collected at the bottom of these filters. Filtration removes additional particles and bacteria. Finally, chlorination kills any remaining microbes. All large public water systems are required to monitor for chemicals, which can form when chlorine reacts with solid matter and other constituents in the water. They must also monitor for organics, inorganics, fecal coliform and other constituents.

Source: Raymond Gabler and the Editors of Consumer Reports, Is Your Water Safe to Drink? (Mount Vernon, NY: Consumers Union, 1989), 330-333.

Total Coliforms (Coliform Bacteria, Fecal Coliform Streptococcal and other bacteria) (mg/L): 1 per 100 millilitersNot necessarily disease-producing themselves, but coliforms can be indicators of organisms that cause assorted gastroenteric infections, dysentary, hepatitis, typhoid fever, cholera and others; also interfere with disinfection processHuman and animal fecal matter
Turbidity(mg/L): 1-5tuInterferes with disinfectionErosion, runoff, discharges
Major Inorganic Chemicals
Arsenic(mg/L): 0.05Dermal and nervous system toxicity effectsGeological, pesticide residues, industrial waste and smelter operations
Barium(mg/L): 2.0Circulatory system effects
Cadmium(mg/L): 0.005Kidney EffectsGeological, mining and smelting
Chromium(mg/L): 0.1Liver/kidney effects
Flouride(mg/L): 4.0Skeletal damageGeological; additive to drinking water, toothpaste, foods processed with flouridated water
Lead(mg/L): 0.015Central and peripheral nervous system damage; kidney effects; highly toxic to infants and pregnant womenLeaches from lead pipe and lead-based solder pipe joints
Mercury (mg/L): 0.002Central nervous system disorders; kidney effectsUsed in manufacture of paint, paper, vinyl chloride; used in fungicides; geological
Nitrate (and nitrites)(mg/L): 10.0 Methomoglobinemia ("baby-blue syndrome")Fertilizer, sewage, feedlots, geological (as nitrogen)
Selenium(mg/L): 0.05Gastrointestinal effectsGeological, mining
Organic Chemicals
Benzene0.005CancerFuel (leaking tanks), solvents commonly used in manufacture of industrial chemicals, pharmacueticals, pesticides, paints and plastics.
Carbon tetrachloride0.005Possible cancerCommon in cleaning agents, industrial waste from manufacture of coolants.
2,4-D0.07Liver/kidney effectsHerbicide used to control broad-leaf weeds in agriculture, used on forests, range, pastures, and aquatic anvironments
p-Dichlorobenzene0.075 Possible cancerUsed in insecticides, moth balls, air deodorizers
1,2-Dichloroethane0.005 Possible cancerUsed in manufacture of insecticides, gasoline
1,1-Dichloroethylene0.007Liver/Kidney EffectsUsed in manufacture of plastics, dyes, perfumes, paints, SOCs
Endrin0.002Nervous system/kidney effectsInsecticide used on cotton, small grains, orchards (cancelled)
Lindane0.0002Nervous system/liver effectsInsecticide used on seed and soil treatments, foliage application, wood protection
Methoxychlor0.04Nervous system/ kidney effectsInsecticide used on fruit trees, vegetables
Polychlorinated Biphenyls (PCB)0.0005Developmental effects in fetuses, suspected cancer riskElectrical transformers, lubricants (banned), abandoned hazardous waste sites
2,4,5-TP Silvex0.05Liver/kidney effectsHerbicides, cancelled in 1984
Total Trihalomethanes (TTHM) (Chloroform, Bromoform, Bromodichloromethane, Dibromochloromethane) 0.1Cancer riskPrimarily formed when surface water containing organic matter is treated with chlorine
Toxaphene0.003Cancer riskInsecticide used on cotton, corn, grain
1,1,1-Trichloroethane0.2Nervous system effectsUsed in manufacture of food wrappings, synthetic fibers
Trichloroethylene (TCE)0.005Possible cancerWaste from disposal of dry cleaning materials and manufacture of pesticides, paints, waxes and varnishes, paint stripper, metal degreaser
Vinyl Chloride0.002Cancer riskPolyvinylchloride pipes (PVC) and solvents used to join them, industrial waste from manufacture of plastics and synthetic rubber
Gross alpha particle activity15 pCi/LCancerRadioactive waste, uranium deposits
Gross beta particle activity4 mrem/yrCancerRadioactive waste, uranium deposits
Radium 226 & 2285 pCi/LBone CancerRadioactive waste, geological
Secondary Drinking Water Standards
pH7.0 or Greater.Water should not be too acidic or too basic
Chloride300 mg/LTaste and corrosion of pipes
Color15 color unitsAesthetic
Copper1.0 mg/LTaste and straining of porcelain
Corrosivity Non-corrosiveAesthetic and health related (corrosive water can leach pipe materials, such as lead, into the drinking water)
Flouride2.0 mg/LDental flourosis (a brownish discoloration of the teeth)
Foaming agents0.5 mg/LAesthetic
Iron0.3 mg/LTaste
Manganese0.05 mg/LTaste
Odor3 threshold order numberAesthetic
Sulfate300 mg/LTaste and laxative effects
Total Dissolved Solids1000 mg/LTaste and possible relation between low hardness and cardiovascular disease; also an indicator of corrosivity (related to lead levels in water); can damage plumbing and limit effectiveness of soaps and detergents
Zinc5.0 mg/LTaste

Source: League of Women Voters Education Fund, Safety on Tap: A Citizen's Drinking Water Handbook (Washington: League of Women Voters, 1987), 12-13.; and Texas Natural Resource Conservation Commission, State of Texas Water Quality Inventory, 12th Edition (Austin: TNRCC, 1995), 77 - 79.


In Texas, naturally-occurring high levels of fluoride and arsenic, combined with contaminants from human activities, have caused hundreds of public water systems to exceed the state's maximum contaminant levels. Between 1988 and 1993, 179 public water systems exceeded national and state maximum contaminant levels for organic and inorganic substances.

Naturally-occurring contaminants found in public water supply systems in Texas include nitrates in the central Texas area, arsenic along the Gulf Coast and high selenium levels scattered throughout the state. As discussed previously, the nitrates are of special concern from a public health standpoint. In the Panhandle area, high nitrates in the water may be caused by agricultural activity throughout the High Plains. Nitrates also have exceeded state standards in some small drinking water systems in Concho, Ector, Gaines, Glasscock, Howard, Martin, Midland, Terry and Travis counties, most of which rely on groundwater.

Since 1993, the federal government has required public drinking water systems to monitor for pesticides. No pesticides were found in Texas in 1993.(107)


About 1.1 million people rely on private wells for their drinking water.(108) Under the Safe Drinking Water Act, water supply systems for communities with less than 15 connections or 25 people are not regulated, meaning they do not have to meet federal and state monitoring and treatment standards. Those served by private wells must test waters themselves to determine if it is safe to drink, particularly to ascertain high levels of coliform bacteria and nitrates. There are a number of government-run laboratories - mainly local county health departments - around the state that can help citizens test their water.
Texas Environmental Almanac, Chapter 2, Water Quality, Page 8


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