From the DEP website “Total Maximum Daily Loads (TMDLs) – The sum of the individual waste load allocations and load allocations; a margin of safety is included with the two types of allocations so that any additional loading, regardless of source, would not produce a violation of water quality standards.”
To sum this up in layman’s terms, the TMDL tells you how much of a particular pollutant a stream can handle before being impaired by legal standards. Legal standards for individual pollutants change through out the years, but are based on some sort of scientific reason. Most reasons are either based on ecology (the study of animal & plant interactions with their environment) or environmental biology (the study of human interactions with their environment), the latter being more important especially if the water is being used as a drinking water source. Please visit the PA DEP Bureau of Water Standards and Facility Regulation Water Quality Standards Website to see specific legal standards and an integrated list of streams showing status of impairment.
To see if your stream has a TMDL study, please visit the DEP Bureau of Watershed Management TMDL Website.
Think your stream, or a section of the stream, has improved enough to be removed from the Impaired Streams List? Help us report it.