| DS | Distribution System—the location is in the distribution system of the water system. Examples of this type of sampling point include sampling points for Total Coliform, lead and copper, and perhaps disinfection by-products (see several of the types below for more precise ways to define disinfection by-products sampling points). |
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EP |
Entry Point—location at which water enters the distribution system of a public water system. This is intended to correspond to the regulatory definition of an entry point to the distribution system representative of one or more sources of water. These should not be associated to Distribution System facilities but rather to the facility from which the water is flowing (e.g., a treatment plant, a well (if not treated prior to distribution), a common header). |
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FC |
The first customer after the entry point into the distribution system. While this site is specifically needed for chlorite and chlorine dioxide distribution system samples, it may have other uses. |
| LD | Lowest Disinfectant Residual—the location where the disinfectant residual is the lowest. This type of sampling point comes directly out of the Revisions to the Unregulated Contaminant Monitoring Rule dated September 17, 1999, where the preamble explains, “Some public commentators suggested that sampling for microbiological contaminants not occur at the maximum residence time in the distribution system, but at the point of lowest disinfectant residual, since the monitoring of concern is for effectiveness of treatment and booster disinfection stations that may be in use in long distribution lines. In response, The U.S. Environmental Protection Agency added another sampling point at the ‘‘lowest disinfectant residual’’ in the distribution system.” for trihalomethane (Disinfection By-Products Rule) and/or Total Coliform sampling. |
| MD | Midpoint in the Distribution System—the Unregulated Contaminant Monitoring Rule location at which the chlorine residual would be expected to be typical for the system. This could also be used to designate those sampling points that are considered “representative points in the distribution system” under the Disinfection By-Products Rules. |
| MR | Point of Maximum Retention—the location that represents the maximum residence time of disinfectants within the distribution system under the Disinfection By-Products Rules. This can also be used as the Unregulated Contaminant Monitoring Rule location in the distribution system that is furthest from the entry point to the distribution. |
| PC | Process Control—locations normally associated with treatment plants or storage water system facilities. This sampling point type is used to demonstrate compliance with contact time or other disinfectant or treatment requirements. |
| RW | Raw Water Source—locations normally associated with intake or well water system facilities. Raw water monitoring is triggered by the detection of a contaminant at an entry point to the distribution system. This Sampling Point type can also be used to designate the raw water sampling point for precursor removal. |
| SR | Source Water Point—defined in the Unregulated Contaminant Monitoring Rule as the location at which untreated water is collected at the source. |
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UP |
Unit Process—a sampling point used to evaluate the effectiveness of a unit process. This type might be used, for instance, to determine the contact time under the Surface Water Treatment Rule for a single unit process. |
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WS |
Water System Facility point. |