What are the specific requirements of the IDSE?
The first requirement is to figure out which of the four ways to comply is appropriate for a water system. TCEQ will send Texas PWSs a letter saying which method we believe is appropriate, and give you a chance to confirm or correct our data. If you serve more than 500 people, and have had sample results over 40 µ/L for TTHM or 30 µ/L for HAA5, you will either have to do IDSE sampling or a system-specific study. If you have to do the IDSE sampling, you will need to complete the IDSE plan that TCEQ sends you. If you want to do the system-specific study, you should review the DBP2 rule language with your engineer and submit a plan to TCEQ. The DBP2 rule has very specific requirements for system-specific studies, including specifications for the required hydraulic modeling, and requirements for sampling.
