Stage 2 Disinfection By-Products Countdown to Compliance

Are you ready for Stage 2? Hopefully so, because if not, it’s already here! If you’re not sure what the Stage 2 Disinfection By-Products rule is or what it affects, read below for a comprehensive explanation of the changes. 

  • The Stage 2 Disinfection By-products (DBP) Rule changes how drinking water systems monitor and comply with trihalomethanes (THM) and haloacetic acids (HAA). 
    • Compliance will be by location—no more averaging results from different sites to get one compliance number. Now each individual location will be used to determine compliance.
    • Compliance monitoring must be done 90 days apart based on the warmest month.
    • Most important—consecutive systems will now monitor on their own instead of being included in their providing system’s monitoring. 

Once again, the Stage 2 Compliance Schedule

  • Schedules include a producing system and all those systems that purchase water from it.  The largest system in that group sets the schedule. 



Compliance Date

Additional Information


Greater than 100,000

April 1, 2012



50,000 to 99,999

October 1, 2012



10,000 to 49,999

October 1, 2013



Less than 10,000

October 1, 2013



Less than 10,000

October 1, 2014

If triggered into Crypto monitoring under LT2

What are the implications of not complying with Stage 2?

  • Drinking water quality is considered out of compliance with EPA and state regulations.
  • Violations are issued.
  • Public notification is required to be delivered to all customers.
  • Continued noncompliance will result in a Kentucky Division of Water (DOW) referral of the drinking water system to the Division of Enforcement.  
  • Enforcement actions include initial and stipulated monetary penalties and the development of a corrective action plan.
  • Corrective action plans could result in system improvements that require funding decisions. 

What should a drinking water system be doing to prepare for Stage 2?

  • Management
    • Locate and review your Initial Distribution System Evaluation (IDSE)Report. In it, you chose your Stage 2 monitoring sites and set your schedule. Look at the results of the IDSE sampling. Were those results out of compliance?
    • Make sure your system submitted an updated Specific Site Information form for the new THM and HAA locations. If the new sites aren’t in the compliance database, a violation will be issued.
    • Make sure your lab has the new sample sites, new schedule and new Stage 2 Report Form.
    • Don’t forget about the Operational Evaluation Level review that must be done every quarter. It is a process of “predicting” the next quarter’s results so that operational changes can be made to avoid a violation.
    • Include water system operators when evaluating engineering projects that could affect DBP compliance. They understand how changes in design, flow and storage affect compliance.
    • Be supportive of the operators’ efforts to evaluate different approaches to staying in compliance, such as changing coagulant dosages, adjusting pumpage to improve tank turnover and water age.
    • Treatment Plant
      • Monitor the plant tap as a “special” sample. It may be an extra sample, but it helps determine where the DBPs are being formed.
      • Set DBP goals below the regulatory limits and give your system a “safety factor.”
      • Optimize disinfection and coagulation. This may mean increased cost for coagulant, but it could offset the cost of a public notification for both total organic carbon (TOC) and DBPs.
      • Distribution
        • Decrease water age in storage tanks. Old water plus chlorine equals higher DBPs.  Moving the water through the storage tanks keeps the water age low.
        • Carefully evaluate booster chlorination. This is often a “quick fix” for areas of low chlorine residual, but should be balanced against future DBP noncompliance.
        • Also, carefully evaluate how to adequately serve customers without creating operational and compliance problems, such as long dead-end lines with little to no usage.
        • Optimize disinfectant residuals (working with the treatment plant). In today’s world of water treatment, more is not always better. When chlorine is low in the distribution system, look for other ways to boost the residual other than raising the chlorine leaving the plant. 
        • Develop and implement a flushing program and stick to it. A regular flushing program can help maintain chlorine residuals, decrease water age and improve overall water quality. BUT, don’t flush just to meet compliance. Track flushing volumes as part of a water-loss program.
        • Evaluate corrosion control. The pH levels can cause DBPs to change. High pHs associated with lime-based corrosion control could cause higher THMs. Carefully balance lead and copper compliance with pH levels and DBPs. It’s a balancing act.
        • Consecutive Systems
          • First and foremost–develop a good working relationship with your providing system(s).
          • See the information on Distribution above. 

What assistance is available for complying with Stage 2?

  • The DOW has staff in the drinking water program that provides one-on-one assistance with complying with the drinking water regulations. This also includes the DOW’s regional offices.
  • Other technical assistance organizations also provide help.
    • Kentucky Rural Water Association (KRWA)
    • Rural Community Assistance Program (RCAP)
    • Engineering firms may have staff that can provide assistance. 

Don’t hesitate to call. 

Ky. DOW       502-564-3410  DW Compliance and Technical Assistance Branch               

KRWA            270-843-2291 

RCAP             502-875-5863              

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