Since the passage of the Clean Water Act
(CWA), the quality of our Nation’s waters has improved
dramatically. Despite this progress, however, degraded
waterbodies still exist. According to the 2000 National
Water Quality Inventory (Inventory), a biennial summary of
State surveys of water quality, approximately 40 percent of
surveyed U.S. waterbodies are still impaired by pollution
and do not meet water quality standards. A leading source of
this impairment is polluted runoff. In fact, according to
the Inventory, 13 percent of impaired rivers, 18 percent of
impaired lake acres and 32 percent of impaired estuaries are
affected by urban/suburban stormwater runoff.
Phase I of the U.S. Environmental
Protection Agency’s (EPA) stormwater program was promulgated
in 1990 under the CWA. Phase I relies on National Pollutant
Discharge Elimination System (NPDES) permit coverage to
address stormwater runoff from:
(1) "medium" and "large" municipal
separate storm sewer systems (MS4s) generally serving
populations of 100,000 or greater, (2) construction activity
disturbing 5 acres of land or greater, and (3) ten
categories of industrial activity.
The Stormwater Phase II Final Rule is the
next step in EPA’s effort to preserve, protect, and improve
the Nation’s water resources from polluted stormwater
runoff. The Phase II program expands the Phase I program by
requiring additional operators of MS4s in urbanized areas
and operators of small construction sites, through the use
of NPDES permits, to implement programs and practices to
control polluted stormwater runoff. See Fact Sheets 2.0 and
3.0 for overviews of the Phase II programs for MS4s and
construction activity.
Phase II is intended to further reduce
adverse impacts to water quality and aquatic habitat by
instituting the use of controls on the unregulated sources
of stormwater discharges that have the greatest likelihood
of causing continued environmental degradation. The
environmental problems associated with discharges from MS4s
in urbanized areas and discharges resulting from
construction activity are outlined below.
