7 Del. Admin. Code § 7408-1.0 - Introduction and Background
1.1
Intensive water quality monitoring performed by Delaware Department of Natural
Resources and Environmental Control (DNREC) has shown that the waters of the
Murderkill River and several of its tributaries and ponds are impaired as the
result of low dissolved oxygen and high nutrients. Low concentrations of
dissolved oxygen are harmful to fish, shellfish, and other aquatic life. With
regard to nutrients (nitrogen and phosphorus), although they are essential
elements for both plants and animals, their presence in excessive amounts
causes undesirable conditions. Symptoms of nutrient overenrichment include
frequent phytoplankton blooms, decreased water clarity, dissolved oxygen
deficiency, alteration of composition and diversity of economically important
native species of plants and animals, and possible human health
effects.
1.2 A reduction in the
amount of nutrients and oxygen consuming pollutants reaching the waters of the
Murderkill River and its tributaries and ponds is necessary to reverse these
undesirable impacts. These pollutants and nutrients enter the waters of the
Murderkill River from point sources and nonpoint sources. Point sources are
end-of-pipe discharges from municipal or industrial wastewater treatment
plants. Nonpoint sources include runoff from agricultural and urban areas,
septic tank effluent, and ground water discharges.
1.3 Section 303(d) of the Federal Clean Water
Act (CWA) requires states to develop a list (303(d) List) of waterbodies for
which existing pollution control activities are not sufficient to attain
applicable water quality criteria and to develop Total Maximum Daily Loads
(TMDLs) for pollutants of concern. A TMDL sets a limit on the amount of a
pollutant that can be discharged into a waterbody and still protect water
quality. TMDLs are composed of three components, including Waste Load
Allocations (WLAs) for point source discharges, Load Allocations (LAs) for
nonpoint sources, and a Margin of Safety (MOS) to account for uncertainties and
future growth.
1.4 DNREC listed the
Murderkill River and several of its tributaries and ponds on the Delaware's
1996, 1998, and 2000 303(d) Lists and developed and promulgated a Total Maximum
Daily Load regulation for nitrogen, phosphorous, and 5-day Carbonaceous
Biochemical Oxygen Demand (CBOD5) in 2005.
1.5 Since the promulgation of the 2005 TMDLs,
a multi-year monitoring, research, and modeling study of Murderkill River
Watershed by DNREC and other cooperating agencies and institutions concluded
that new scientifically-based, site-specific dissolved oxygen criteria should
be adopted for the tidal Murderkill River. This amendment of the 2005 TMDLs is
to comply with this proposed site-specific dissolved oxygen criteria for the
tidal Murderkill River.
Notes
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