As a start, derive “simple” TMDL using data generated to refine the problem definition as described above and to complete the source analysis described below. Such “simple” TMDLs would be derived for watersheds deemed representative of impaired urban creeks and would guide development of potential prevention and control options.
TMDL product: TMDLs for representative urban creeks
The primary source of diazinon in urban creeks is storm water runoff from urban areas. Sampling of runoff from urbanized areas in Alameda County indicated that residential areas were a significant source of diazinon, but runoff from commercial areas also may have been a source. It is not known what portion of the diazinon found in local creeks is attributable to use in accordance with label directions versus improper disposal or over-application, but a preliminary study of runoff from residential properties suggests that the concentrations found in creeks may be attributable to proper use.