Frequent Questions

EPA maintains two data management systems containing water quality information for the nation's ambient waters: the Legacy Data Center (LDC) and STORET. What is the difference between the Legacy Data Center and STORET databases?

The LDC is a static, archived database, and STORET is an operational system actively being populated with water quality data.  The LDC contains historical water quality data dating back to the early part of the twentieth century and collected through 1998.  STORET contains data collected beginning in 1999, along with older data that have been properly documented and migrated from the LDC.  Each sampling result in the LDC and in STORET is accompanied by information on where and when the sample was taken, the medium sampled, and the name of the organization that sponsored the monitoring.  In addition, STORET includes why the data were gathered, the sampling and analytical methods, the laboratory used to analyze the samples, the quality control checks, and the personnel responsible for the data.  More information regarding the LDC and STORET is available at
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