Communities within the Delta region use the estuary to dispose of sewage and stormwater. While these discharges are subject to state and federal regulation, most local entities that release sewage and stormwater into the Delta are in violation of those laws and permit requirements.
In many cases, these communities are not just breaking the law, but actually poisoning the water for native fish and wildlife. Toxicity in urban stormwater runoff includes harmful substances from streets, lawns and gardens, such as automotive oil, zinc from brake residue, and pesticides. In fact, urban areas contribute more pesticide runoff than agriculture in many parts of the state, including the Delta. According to the California Department of Pesticide Regulation, in the Sacramento Valley between 1995 and 2006, urban application of pesticides was 21 percent greater than for agriculture.
To get a picture of how urban water discharges can affect Delta wildlife, UC Berkeley Professor Donald Weston studied the effects of pyrethroids, a common household pesticide contained in urban stormwater and wastewater discharges and known to harm aquatic species, and a native crustacean to the Delta, Hyalella azteca. In his sampling, Weston found that virtually all urban stormwater runoff contained pyrethroids, typically at about 4 times the concentration that would paralyze Hyalella. Meanwhile, the study found that typical wastewater treatment plant effluent in the Delta contains pyrethroids at about 0.5-1.5 times the concentrations that cause Hyalella paralysis.
Although it is impossible to keep all pollutants out of the Delta waters, local water dischargers often fail their legal responsibility to meet permit requirements and stop preventable pollution. According to Central Valley Regional Water Quality Control Board records, municipalities across the Delta have continuously violated stormwater and wastewater discharge permit requirements. Keeping in mind that those records do not necessarily reflect all violations, even those limited records show repeated violations across the board. For example, from 2007 to 2012, records show that at least eleven municipalities have over 100 violations, among them the City of Stockton (196 violations), San Joaquin County (175 violations) and even the tiny Town of Discovery Bay (140 violations). While violations range in magnitude from exceeding maximum allowable effluent discharges for harmful nitrates or bacteria, to smaller reporting and monitoring violations, all show a callous disregard by local municipalities for the Delta ecosystem and the species it supports.
Indeed, in 2011, the City of Stockton Regional Wastewater Control Facility, incurred over $60,000 in fines for violations including the discharge of thousands of pounds of excess ammonia, which is known to be extremely toxic to fish and wildlife.
The Sacramento region is a large polluter and each day discharges millions of gallons of partially treated sewage into the Delta. Contained in this wastewater are significant concentrations of ammonia. On a monthly basis, Sacramento adds high levels of ammonia to the Delta – far more than any other source. These discharges are believed to have a significant impact on Delta Smelt and other threatened and endangered species.
In addition to discharges from sewage treatment plants in violation of permit requirements, many municipalities are also in violation of their separate municipal stormwater sewage system (MS4) permits. Pollutants from MS4s in the Delta in excess of allowable levels include aluminum, copper, iron, zinc, E. coli, fecal coliform, and dissolved oxygen, all of which can have severe detrimental effects on the Delta ecosystem.
Above is a list of the largest discharge permit violators in the Bay-Delta watershed from 2007-2012. Proper maintenance and compliance with state laws can stop much of the pollution caused by these violations. But stronger actions must be taken against repeat violators who callously continue to poison the Delta ecosystem.