Definitions of Terms
The Texas Natural Resource Conservation Commission (TNRCC) has begun a review of all of the State's drinking water sources including those in the Coastal Bend. This source water assessment will be completed in three years.
The following list explains some of the terms used in the tables presented in this report:
- Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected health risk. MCLGs allow for a margin of safety.
- Maximum Contaminant Level (MCL) - The highest level of a contaminant allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology.
- Treatment Technique (TT) - A required process intended to reduce the level of a contaminant in drinking water.
- Action Level (AL) - The concentration of a contaminant which, if exceeded, triggers treatment of other requirements which a water system must follow.
- Nephelometric Turbidity Unit (NTU) - A measure of turbidity in water.
- Parts Per Million (ppm) - Equivalent to milligrams per liter. One ppm is comparable to one minute in two years.
- Parts Per Billion (ppb) - One ppb is comparable to one minute in 2,000 years.
- Coliforms - In the water industry, coliform bacteria are used as an indicator of microbial contamination because it is easily detected. While not themselves disease producers, they are often found in association with other microbes capable of causing disease. Coliform bacteria are more hardy than many disease-causing organisms; therefore, their absence from water is a good indication that the water is safe for human consumption. Fecal coliform (mostly E-coli) is part of the coliform bacteria group origination in the intestinal tract of warm-blooded animals that pass into the environment as feces. Fecal coliform is often used as an indicator of fecal contamination of a domestic water supply.
- Turbidity - Turbidity has no health effect but can interfere with disinfection and provide a medium for microbial growth. It may indicate the presence of disease-causing organisms which may include bacteria, viruses and parasites that can cause symptoms such as nausea, cramps, diarrhea and associated headaches. Turbidity must be less that 0.5 NTU in 95% of monthly samples.