In 2001, The University of Alabama in collaboration with the Center for Watershed Protection started the development of a database that summarized the stormwater characterization efforts conducted by NPDES Phase I communities throughout the U.S. The National Stormwater Quality Database (NSQD) includes information about sampling locations by state, land use, percentage of imperviousness, and EPA geographical region. The database also includes even mean concentrations (EMC) of conventional pollutants, nutrients, metals, and microbiological constituents.
NSQD 4.0 has been used by stormwater managers, regulators, researchers, and stormwater professionals to develop stormwater plans, identify typical concentrations expected in stormwater, calibrate stormwater models, and provide supporting information to set up monitoring programs. The data available in the database can be used to identify trends and differences between different sampling methods, including the use of automatic samplers. The current version of the database includes more than 9,000 stormwater events at approximately 600 sampling locations. It includes information obtained from previous stormwater characterization efforts including the National Urban Runoff Program (NURP), and the International BMP database. New features of NSQD 4.0 include an analysis of the effects that censored data (non-detects) causes in the probability distribution of stormwater constituents, including the mean and standard deviation.