Diving into the benefits of true source control
It was big news in the Pacific Northwest storm water world this past December when researchers at Washington State University released research concluding that 6PPD-quinone was killing coho salmon. This chemical is a transformation product of a common tire rubber antioxidant added to prevent damage from ozone. Vehicles are known to release many other chemicals into the environment that ultimately become storm water borne pollutants. These pollutants become more difficult to remove from the environment the more dispersed they become. From the perspective of a storm water program manager, looking upstream all the way to the pollution generating products in a watershed may be the best return on mitigation investments. That leads us directly to “true source control.”
As the 6PPD-quinone identification story illustrates, urban storm water runoff is a chemical cocktail that includes things we don’t even know how to test for or measure. The U.S. EPA’s most recent Toxic Release Inventory report showed between 3 and 4 trillion pounds of toxic chemicals were released into the environment each year over the last decade. Even this large number only includes those regulated pollutants, facilities and industry sectors required to be reported. The pace of development and release of new chemicals outstrips the pace of testing standards designed to measure such releases and our understanding of the environmental and human health impacts of new chemicals moves at a comparatively glacial pace.
To add to the usual suspects like TSS, nutrients, heavy metals and bacteria, in 2021, we have storm water programs committing to spending billions of dollars over this decade to control pollutants like PCBs and DDT, which were banned decades ago but are still causing impairments. We also have a new awareness of pollutants like PFAS, PFOA and microplastics, which have been accumulating for decades but are only recently springing to the front of our collective awareness.
While it may be technically possible to build a treatment train that can remove everything from plastic bags and fast-food packaging to nutrients, bacteria and trace amounts of emerging pollutants, it’s not going to be feasible at a scale that is equal to the problem. Yet, we are legally required to prevent the discharge of these pollutants if they cause or contribute to a water quality violation. It’s no wonder that runoff reduction is a primary mitigation strategy of most storm water programs. This doesn’t remove pollutants from the environment; it only delays their migration somewhat.
True source control eliminates the sources of pollutants through either product substitution or green chemistry. Examples of successful efforts include substituting biodegradable materials for conventional plastics and phasing out persistent pesticides like pyrethroids in favor of organic pest controls. These efforts require multidisciplinary teams. Work by Sustainable Conservation and the California Brake Pad Partnership to pass legislation in 2010 reducing the copper content of brake pads is an excellent case study. After challenging copper TMDLs were adopted, scientists determined that about 60% of the copper load in urban storm water came from brake pad wear. After years of negotiation and cooperation with other states like Washington, a bill was passed, which ultimately reduced the allowable copper content in brake pads to less than 0.5%. The expected result is that copper loads will be reduced to about half of previous quantities by 2024.
Responsibility for protecting receiving waters from storm water-borne pollutants must extend beyond storm water system operators. This means engaging with federal product approval programs, working with local activists and parallel government agencies to support bans of harmful products and promote programs for the unhoused, working with wastewater system operators to eliminate leaks and with water supply professionals to increase the amount of storm water runoff that is harvested for beneficial use. It means working with agricultural interests to reign in nutrient and pesticide loads. As we look to maximize clean water returns on storm water program investments in this time of lean municipal budgets, true source control stands out as a golden opportunity.