UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                     GUIDANCE FROM HOTLINE COMPENDIUM

                                                                            WSGH28

SUBJECT:   Monitoring Requirements for Consecutive
             Public Water Systems (Surface Water Treatment Rule)

SOURCE:    Clive Davies

On June 29, 1989, National Primary Drinking Water Regulations (NPDWRs) were promulgated
which established disinfection and filtration requirements for public water systems (54 FR
27846). These regulations are commonly referred to as the Surface Water Treatment Rule or
SWTR. In reference to the SWTR, the following question was raised:

How are consecutive public water systems required to meet the monitoring requirements of the
SWTR?

       Response:

       40 CFR, Section 141.29, deals with consecutive systems.  This section gives primacy
       agents the option to consider suppliers and consecutive systems as single systems for the
       purposes of monitoring under any of the drinking water regulations. Therefore, a primacy
       agent has the authority1 to consider a supplier and a consecutive system as a single
       system, or as separate systems, for purposes of compliance with the monitoring
       requirements of the SWTR and Total Coliform Rule (TCR).

       For compliance with the requirements of the two rules, it will often be appropriate for the
       primacy agent to consider the supplier and consecutive systems as a single system.  The
       requirements, under the SWTR, for source water monitoring, Concentration x Time (CT)
       value determination, maintenance of entry point disinfectant residuals, dual disinfection
       components, watershed control programs, operator qualifications, etc., will likely be the
       responsibility of the supplier. Requirements for distribution system disinfectant residual
       monitoring under the SWTR and for distribution system coliform monitoring under the
       TCR will be the responsibility of both supplier and consecutive systems. If treated as one
       system, the required monitoring plan must address both the supplier's and the consecutive
       system's distribution system. Computation of compliance with the coliform MCL and
       disinfectant residual requirements must also be based on the combined results of the
       sampling from both the supplier and consecutive systems.
       Mo CFR §141.29 requires that primacy agents obtain EPA concurrence on decisions to
reduce monitoring for consecutive systems.

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      UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
              GUIDANCE FROM HOTLINE COMPENDIUM
                                                                    WSGH28
We believe, however, that because of the range of factors involved (e.g., the use of
booster chlorination, the possible existence of emergency surface water sources, the
relative sizes and capabilities of the parent and secondary systems, etc.) the decision of
how to treat a secondary system must be made on a case-by-case basis, and that the
primacy agent is in the best position to make that decision1.

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