Frequent Questions

Are the combined filter performance and individual filter performance standards based on 4 hour measurements?

Combined filter performance standards are based on measurements taken every 4 hours.  Individual filter performance standards are based on measurements taken every 15 minutes.  These are the same requirements as in the IESWTR and the LT1ESWTR.

For additional guidance on the Long Term 2 Enhanced Surface Water Treatment Rule please visit http://water.epa.gov/lawsregs/rulesregs/sdwa/lt2/index.cfm.

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