Total
Maximum Daily Loads (TMDLs)
The Total Maximum Daily Load (TMDL) is a number
that represents the assimilative capacity of a
receiving water to absorb a pollutant. The TMDL
is the sum of the individual wasteload allocations
for point sources, load allocations for nonpoint
sources plus an allotment for natural background
loading, and a margin of safety. TMDLs can be
expressed in terms of mass per time (the traditional
approach) or in other ways such as toxicity or
a percentage reduction or other appropriate measure
relating to a state water quality objective. A
TMDL is implemented by reallocating the total
allowable pollution among the different pollutant
sources (through the permitting process or other
regulatory means) to ensure that the water quality
objectives are achieved
.
