Total Coliform

Background & Timeline

In May 2020, during routine monthly water quality testing, a single distribution bacteriological sample tested positive for Total Coliform. By regulation, any positive result at a testing station requires the City of Paramount to retest that station and all wells that were in service at the time of testing within 24 hours. Two wells were in service at the time of the Total Coliform positive result and the City immediately retested the well closest to the sample station that reported the positive result, given that the other well was located at the opposite end of that sample point and all nearby samples had been negative. All recollect samples (5) should have been collected on May 7, 2020. The second well was tested on May 19, 2020, as part of the City’s routine sampling. However, because the City did not test the other well in the time frame specified by the regulations, the City is required to inform its customers.

The immediate retest of the initial sampling station and the nearest well tested negative for Total Coliform. When tested on May 19, 2020, the second well in use at the time of the positive result was also negative for Total Coliform. All samples tested in relation to this incident have been negative for coliform bacteria. No coliform bacteria have been observed in the City system in the past seven years.

Total Coliforms are considered surrogate, or indicator organisms, and are an efficient way to monitor the distribution system. Total Coliforms are used because they are easy to test and, if found in a distribution system, may be a signal for the utility to review operations and ensure that the treatment processes are properly working. Common environmental factors that can cause a positive Total Coliform sample include: rain and wind storms, landscaping and construction activities and/or contamination occurring in the sample collection process via tools or equipment. In this case, all retests and all additional samples were negative for coliform bacteria, an indication the drinking water system was and continues to be safe.

wdt_ID Water Terms
1 Total Coliforms are a group of bacteria that are ever-present in the environment. They are commonly found in plant material and soil and are easy to identify. Most coliform bacteria do not cause disease.

Historical Total Coliform Testing in Paramount

wdt_ID Year Number of Samples Collected Sample Results Percentage Positive
1 2013 957 1 positive; 956 negative 0.001%
2 2014 936 0 positive; 936 negative 0%
3 2015 936 0 positive; 936 negative 0%
4 2016 936 0 positive; 936 negative 0%
5 2017 936 0 positive; 936 negative 0%
6 2018 936 0 positive; 936 negative 0%
7 2019 936 0 positive; 936 negative 0%
8 2020 939 0 positive; 938 negative 0.001%
9 2021 252 YTD (as of 4/12/21) 0 positive; 252 negative 0%

Paramount Water Sample Locations Map

C-701_Water System Schematic Samples

Documents & Presentations

May 4, 2021 Presentation to City Council

Video Recording

Power Point Presentation

CCR 2020 05-04-21

 

2020 Consumer Confidence Report

2020 CCR Complete -APPROVED BY DDW ON 4-14-21

Frequently Asked Questions

For more information, please contact Paramount Public Works Department – Water Division at 562-220-2020. Please share this website information with others who may not have access to our website.

The Department has reviewed the relevant regulations, guidelines, and procedures with staff and increased training. Following the event, all City staff have had refresher training regarding the sampling requirements. In addition, all Total Coliform sampling since the single positive sample have been negative for Total Coliform.

There is nothing you need to do at this time. Your drinking water is safe and reliable.

When coliform bacteria are found, water systems investigate to find out how this got into the water. They collect additional, or “repeat,” water samples for testing, and often inspect the entire system. Taking repeat samples helps determine whether an actual problem exists in the system. If any of the repeat samples detect coliform bacteria, the initial findings are considered confirmed. In the event of the City incident, all recollect samples were negative, an indication that the one positive result was irregular. As shown in the table above, the City has not had a positive result from 2013 to 2020 and since the May 2020 sampling event.

Total Coliforms are a group of bacteria that are ever-present in the environment. They are commonly found in plant material and soil and are easy to identify. Most coliform bacteria do not cause disease. Because testing for them is simple and inexpensive, they are used as indicator organisms to evaluate the effectiveness of treatment and assess the integrity of the distribution system. Their presence is a signal of possible treatment issues, which is why resampling is required. 

However, like all microbial tests, there is the opportunity to observe what are known as false positive results. A false positive means that something in the actual test did not perform correctly, resulting in the positive presence of Total Coliform when none were actually present. This is a rare event, but nonetheless it does occasionally occur. A positive result can also occur because an environmental factor such as rain or wind contaminated the sample as opposed to there actually being contamination in the water supply. The reason to perform the resampling is to confirm if the contamination is real and ongoing. Negative resample results indicate the water system is in compliance and safe.

It is important to understand why monitoring for Total Coliform is performed and what it means. Total Coliforms are considered surrogate, or indicator organisms, and are an efficient way to monitor the distribution system. Total Coliforms are used as a regular test item because they are easy to test for and, if found in a distribution system, may be a signal for the utility to review operations and ensure that the treatment processes are properly working. In this case, all retests and all additional samples were negative for coliform bacteria, an indication the drinking water system is safe.  

By regulation, the City is required to test all wells every month as well as sites throughout the distribution system. The City continues this routine sampling and reporting to the state. The City performs up to 93 Total Coliform tests each month from the wells and at sample stations throughout the City and have had no positive results in more than 7 years.


Additional Resources

CA State Water Resources Control Board
www.waterboards.ca.gov

Environmental Protection Agency
www.epa.gov