Tmdl schedule and workplans status july 1999

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Exotic Species

Deleterious Examples Include:

Asian clam (Potamacorbula amurensis) – established

Chinese mitten crab (Eriocheir sinensis) - established

European green (or shore) crab (Carcinus maenas) – established

Atlantic cordgrass (Spartina alterniflora) – established

Shipworm (Teredo navalis) – established

Zebra Mussel (Dreissena polymorpha) – threatened to be established

Asian Freshwater Adhesive Mussel (Limnoperna fortunei) – threatened to be established

>30 species of exotic fish established


“A New Pollutant and Source to be Addressed using Clean Water Act Authority”

There is a wide spectrum of significant economic, health, and ecological risks posed by introduction of exotic species in the estuary. In the last ten years, a large number of exotic species have become established and dominant in the San Francisco Estuary and the Sacramento-San Joaquin Delta, with a range of adverse impacts on the local ecology and economy. Ballast water from modern cargo ships is probably the most significant pathway for introduction of exotic species to the estuary. When ships empty ballast water to take on cargo, maintaining proper buoyancy and trim, tens of millions of living organisms from other seas, estuaries and rivers may be discharged from a single ship. Hull fouling organisms transported on the exterior of large ships, commercial fishing vessels, and recreational craft that travel large distances may also be a significant source of exotic species introductions.
The introduction of exotic species into the estuary is currently accelerating, with experts estimating that a new exotic species has been established every 14 weeks since 19616. Considering the recent catastrophic experience of the Black Sea, where fisheries and the ecosystem have been devastated by ballast-borne comb jellies from the Atlantic Ocean (Mnemiopsis leidyi), these introductions represent a significant threat to many beneficial uses of the estuary7. Experts recognize that an exotic species, after it has been established, is extremely difficult to eliminate8. This characteristic of bioinvasions distinguishes them from other forms of pollutant discharge, such as untreated sewage or toxic pollutants, which can be assimilated by natural processes in varying degrees. Once discharged into the environment, deleterious exotic species such as the Atlantic comb jelly exhibit exponential growth rates, which is in sharp contrast to the decay rates in water exhibited by pollutants such as oxygen demand and various toxics. Instead of causing temporary impacts that gradually subside, exotic species cause permanent impacts that can amplify over time.
Given these observed characteristics, ballast water and hull fouling discharges cause pollution as defined under the Porter-Cologne Water Quality Control Act (California Water Code or CWC) at Section 13050(l), because they can cause “an alteration of the quality of the waters of the state by waste to a degree which unreasonably affects either beneficial uses or facilities which serve the beneficial uses.” These discharges also meet the definition of point source under the Clean Water Act (CWA) at Section 502(14), because they are “discernible, confined and discrete conveyances, including…vessels and floating craft, from which pollutants are or may be discharged.” Under the current federal regulations, however, these discharges do not require a National Pollutant Discharge Elimination System (NPDES) permit (40 CFR 122.3(a)).
The 303(d) listing of the San Francisco Estuary and the Delta for exotic species and the forthcoming total maximum daily load (TMDL) are intended to address prevention of introductions of viable exotic organisms in discharges from vessels. Species that have already become established in this region are not the focus of control efforts by the Regional Board.

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