UNITED STATES ENVIRONMENTAL PROTECTION AGENCY GUIDANCE FROM HOTLINE COMPENDIUM WSGH30 Date Issued: August 1990 Revised: February 1999 Revised by: Ed Thomas SUBJECT: VOC Monitoring Requirements and the Blending of Separate Water Supply Sources as a Form of Treatment SOURCE: Susan MacMullin Section 141.24(g)(l) of the VOC rule (52 FR 25712) specifies that systems with ground water supplies must sample at points of entry to the distribution system that are representative of each well. Furthermore, the preamble states that such ground water systems are required to sample at those distributions system entry points that are located after any treatment (52 FR 25705). Is the blending of water from two separate ground water sources considered to be treatment? If blending is not considered treatment, the operator will need to sample at two locations prior to where blending occurs. If blending is regarded as treatment, the operator will be required to sample at a single location subsequent to where blending occurs. Response: The blending of two separate supply of sources is considered treatment in the context of a system's ability to meet an MCL. A State may require a system to sample at each well head prior to blending, however, the Federal regulations require systems to sample at the point of entry to the distribution system. The sample may be taken at any point between the treatment process (or blending) and the point of entry to the distribution system. It is not, however, appropriate to blend sources of water in the distribution system. ------- |