Urban Area Water Testing Results
What are the results from last year's testing?
The table shows which compounds were detected in your drinking water. The following are a few terms which need to be defined to understand the table.
- 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 that is allowed in the drinking water. MCLs are set as close to the MCLGs as possible using the best available treatment technology.
- Maximum Residual Disinfectant Level (MRDL): the highest level of a disinfectant allowed in drinking water. The addition of a disinfectant is necessary for control of microbial contaminants.
- Maximum Residual Disinfectant Level Goal (MRDLG): the level of a drinking water disinfectant below which there is no known or expected health risk.
- ppb: parts per billion, or micrograms per liter (ug/l). One part substance per billion parts of solution.
- ppm: parts per million, or milligrams per liter (mg/l). One part substance per million parts of solution.
- pCi/l: picocuries per liter. This is a measure of radioactivity.
- Nephelometric Turbidity Unit (NTU): a measure of the clarity of water. Turbidity in excess of 5 NTU is just noticeable to the average person.
- Action Level (AL): the concentration of a contaminant, which, if exceeded, triggers treatment or other actions by the water provider. This term is typically limited to discussions of lead and copper concentrations.
- n/a: not applicable.
- < : less than.
Click on the chart above to enlarge.
- 1Unit of measure for total and fecal coliform bacteria is the presence or absence of bacteria in a 100 ml sample.
- 2Of the 960 samples collected in 2017, two (2) samples indicated the presence of total coliform bacteria. Neither of these two (2) samples indicated the presence of fecal coliform bacteria.
- 3Fecal coliform MCL: A routine sample and a repeat sample are total coliform positive, and at least one is also fecal coliform positive.
- 4No sample indicated a positive result for fecal coliform bacteria.
- 5The MCL for turbidity is for no single measurement to exceed 1 NTU, and for 95% of all measurements to be below 0.3 NTU.
- 6Sampled at all three treatment plants in 2017.
- 7EPA considers 50 pCi/l to be the level of concern for beta particles.
- 8Sampled in July, 2016 from select, high-risk residences.
- 9The value reported is the 90th percentile of all data (30 samples) collected.
- 10The value reported is the highest quarterly, system-wide average.
- 11TTHM and HAA results are averaged over four quarters at each sampling location to determine compliance with the MCL.
What do all these numbers mean?
Of great importance, this information shows that your drinking water met and exceeded all regulatory requirements during 2017. We are fortunate to have reliable sources for your drinking water needs and well-operated treatment facilities. Additional information is provided on the left that will give you more detail on each potentially harmful contaminant or compound detected in your drinking water.
Cryptosporidium is a microbial pathogen found in surface waters throughout the U.S. Ingestion of Cryptosporidium may cause cryptosporidiosis, an abdominal infection characterized by nausea, diarrhea, and abdominal cramps. Most healthy individuals can overcome the disease within a few weeks, but immuno-compromised people are at risk of developing a potentially life-threatening illness.
In 2017, one raw water sample from the North Fork Rivanna River showed 0.09 organisms per liter. Cryptosporidium was absent from all other raw water samples from each of the three treatment plants.
Although filtration removes the pathogen, the most commonly used filtration methods cannot guarantee 100% removal. The RWSA makes every effort to optimize the filtration process at all of the WTPs to ensure the greatest degree of Cryptosporidium removal. Based on the results of this study, our water supplies have been placed in the lowest risk category for exposure to Cryptosporidium. A second round of sampling will be completed in 2017.