Frequent Questions

What are the source water monitoring requirements of the Long Term 2 Enhanced Surface Water Treatment Rule (LT2)?

The LT2 Rule requires public water systems (PWSs) using surface water or ground water under the direct influence of surface water sources to monitor their source water to assess the level of Cryptosporidium, E. coli, and/or turbidity. However, filtered systems are not required to conduct source water monitoring if the system will provide a total of at least 5.5-log of treatment for Cryptosporidium (40 CFR 141.701(d)(1)), and unfiltered systems are not required to conduct source water monitoring if the system will provide a total of at least 3-log Cryptosporidium inactivation (40 CFR 141.701(d)(2)). The requirements for the initial round of monitoring in 40 CFR 141.701(a) differ by PWS size (above or below 10,000 people served) and treatment plant type (filtered or unfiltered PWS). Systems that do not meet the monitoring avoidance criteria in 40 CFR 141.701(d) must monitor as follows:

1) Filtered systems serving at least 10,000 people must sample their source water for Cryptosporidium, E. coli, and turbidity at least monthly for 24 months.

2) Unfiltered systems serving at least 10,000 people must sample their source water for Cryptosporidium at least monthly for 24 months.

3) 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, unless they notify the state that they will monitor for Cryptosporidium. Filtered systems serving fewer than 10,000 people must sample their source water for Cryptosporidium if they exceed the screening level of E. coli based on source type. The state may approve an alternate indicator other than E. coli or an alternate screening level.

4) Unfiltered systems serving fewer than 10,000 people must sample their source water for Cryptosporidium at least twice per month for 12 months or at least monthly for 24 months.

More information on the source water monitoring requirements of the LT2 Rule is available in the document Source Water Monitoring Guidance for Public Water Systems (EPA815-R06-005). The document and additional information on the LT2 Rule are available at http://water.epa.gov/lawsregs/rulesregs/sdwa/lt2/index.cfm.
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