The EPA is requiring some systems to monitor for E.coli as part of the Enhanced Treatment for Cryptosporidium rule (LT2).
The rule itself is a thrilling volume of legalese that can be found at the following link (scroll down to R309-215-15):
In case your eyes glazed over when attempting to read this fascinating text, here is a short version of what you need to know:
How do I know if my system is impacted by the LT2 Rule?
This is what the rule says:
“Applicability. The requirements of this subpart apply to all surface water systems, which are public water systems supplied by a surface water source and public water systems supplied by a ground water source under the direct influence of surface water.”
“Filtered systems serving fewer than 10,000 people must sample their source water for E. coli at least once every two weeks for 12 months.”
So you need to sample for LT2 if your source is surface water or influenced by surface water and if you are a filtered system.
Easiest way to monitor your requirements is to go to waterlink.utah.gov. Click on Water Monitoring and scroll down to your sources. Below is an example of what you will see if you are lucky enough to have an LT2 requirement.
Unlike your routine monthly monitoring from your distribution system, you can’t simply use the present/absent test because the action you may be required to take after the study will depend on the amount of E.coli found. You can actually have some amount of E.coli and still be okay as long as it doesn’t exceed the following criteria from the rule:
“For systems using lake/reservoir sources, the annual mean E. coli concentration is greater than 10 E. coli/ 100 mL.”
“For systems using flowing stream sources, the annual mean E. coli concentration is greater than 50 E. coli/ 100 mL.”
For this reason you need to be sure you ask for the enumerated version of the Total Coliform and E.coli test. Most of our chains of custody are pre-filled with this test. Just look for the word “enumerated.” It costs a few bucks more than the present/absent test because, rather than incubating your sample in the sampling container, we need to pour it off into a special tray that separates the water into individual packets.
Another fun (annoying) fact is that you have to stick pretty tightly to the dates you submitted in your sampling schedule, as per the quote below from the rule:
“Systems must collect samples within two days before or two days after the dates indicated in their sampling schedule”
Also note that two samples are normally required, and they are generally expected to be taken at different times during the month. Again, you’ll have to look at your site sampling plan.
If any of this still doesn’t completely make sense, don’t hesitate to give us a call and ask for one of our project managers.