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City of Stockton and County of San Joaquin Page 27
<br /> NPDES Permit CAS0083470
<br /> Response to Comments
<br /> time. For example, over the last five years, San Joaquin River net flow was less than 3000 cfs
<br /> approximately 77% of the time,with net flows continuously less than 3000 cfs for 242 days from 16
<br /> May 1997 to 13 January 1998. Staff notes that this data was collected primarily during wet years so
<br /> receiving water conditions may be worse during dry years. Id. This problem is exacerbated in the
<br /> small urban waterways that source within the City. In these waterways, stone water runoff
<br /> comprises virtually all of the upstream flow. Subsequent incoming tides can restrict outflow thereby
<br /> increasing the residence time of pollutants.
<br /> Storm water runoff is arguably the most significant and intractable source of pollution to local
<br /> waterways. The September 2000 study by the San Francisco Estuary Institute titled Contaminate
<br /> Loads, From Storm water to Coastal Waters in the San Francisco Bay Region, Comparison to
<br /> Other Pathways and Recommended Approach for Future Evaluation reveals that storm water runoff
<br /> is a dominate source of pollutant loading to waterways. The study compared the relative mass
<br /> loading of pollutants from storm water runoff, effluent discharges, atmospheric deposition and
<br /> dredged material disposal. It concluded that storm water mass loading of cadmium, copper, zinc,
<br /> nickel and chromium, as a percentage of total loading,was 95%, 89%, 87%, 76% and 70%,
<br /> respectively. Yet, storm water programs are grievously under-funded and understaffed as compared
<br /> to efforts to control discharges of wastewater.
<br /> Storm water runoff from the City of Stockton and contiguous urban areas of San Joaquin Country
<br /> discharge to urban waterways (Bear Creek, Mosher Slough, Five-Mile Slough, the Calaveras River,
<br /> Smith Canal,Mormon Slough, Stockton Deep-Water Channel, Walker Slough/French Camp
<br /> Slough, the San Joaquin River, the Calaveras River and the Sacramento-San Joaquin Delta Estuary
<br /> (Delta).
<br /> Examination of bioassay TIE results and water quality data collected from 1992 through 1998
<br /> reveals that the geometric mean concentration these storm water discharges are acutely toxic to
<br /> aquatic life because of metals (copper, lead, zinc),pesticides, (diazinon, chlorpyrifos and possibly
<br /> diuron), surfactants and unknown toxicity. Analytical results from ambient water samples reveal
<br /> that receiving waters are frequently toxic to aquatic life. DeltaKeeper ambient monitoring has
<br /> established that, following rainfall, all of the Stockton urban waterways experience prolonged
<br /> dissolved oxygen sags (Dissolved Oxygen Depletion in Stockton Sloughs, G. Fred Lee &Assoc.,
<br /> 2000; frequent toxicity from pesticides (Review of the City of Stockton Urban Storm water Runoff
<br /> Aquatic Life Toxicity Studies Conducted by the CVRWQCB, DeltaKeeper and the University of
<br /> California, Davis, Aquatic Toxicology Laboratory between 1994 and 2001, G. Fred Lee &Assoc.,
<br /> November 2001) and excessive levels of bacteria that threaten those who come in contact with the
<br /> water(Pathogen Monitoring of Stockton Area Waterways 2000-2001, see proposed 303(d) update).
<br /> The Regional Board has been provided these studies and we incorporate them by reference in the
<br /> record of this proceeding.
<br /> Contaminates potentially found in storm water runoff can bioaccumulate in fish tissue and pose a
<br /> threat to the health of those who consume them. Examination of fish caught in local waterways
<br /> reveals that concentrations of mercury, PCBs and DDT exceed levels protective of public health(J
<br /> Davis et a1.,.September 2000, Contaminate Concentrations in Fish from the Sacramento-San
<br /> Joaquin Delta and Lower San Joaquin River 1998, San Francisco Estuary Institute). Indeed,
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