Results of Survey on Water Quality Problems
Caused by Urban and Highway Stormwater Runoff
G. Fred Lee, Ph.D., P.E., D.E.E. and Anne Jones-Lee, Ph.D.
G. Fred Lee & Associates
El Macero, California
The US EPA (1995) in their 1994 Report to Congress on the water quality status of the US waterbodies claims as they have in previous biennial reports to Congress that urban area and highway stormwater runoff is one of the major causes of water quality impairment in the US. It appears that the US EPA's claim is based largely on the way the agencies and the states assessed water quality impacts in the National Water Quality Inventory in which they assumed that any exceedance of a water quality standard by any amount and duration represented a "use impairment." However, those familiar with how the US EPA water quality criteria and state standards based on these criteria are developed know that considerable exceedance of these standards can occur for potentially toxic chemicals, such as heavy metals and organics, without adversely impacting the real aquatic life-related beneficial uses of the waterbody receiving the stormwater runoff (Lee and Jones-Lee, 1995). There is, therefore, considerable controversy as to what real water quality - use impairment problems are caused by highway and urban area street stormwater runoff-associated chemical constituents.
Are the water quality problems that the US EPA has cited largely administrative, related to the use of overly-protective water quality criteria and state standards or are there significant adverse impacts on the numbers, types and characteristics of desirable forms of aquatic life in the nation's waters due to the presence of elevated concentrations of heavy metals and other potentially toxic constituents in urban area and highway stormwater runoff? This issue is of considerable importance to the national as well as state and local stormwater runoff water quality management programs that are currently being formulated across the country since it will determine the need for non-structural and structural best management practices (BMP's).
The US EPA's national urban area and highway stormwater quality management program (US EPA, 1990) requires stormwater managers to control pollution of the receiving waters for the stormwater runoff to the maximum extent practicable (MEP) using BMP's. The key issue that has to be defined in developing technically valid, cost-effective stormwater management programs is what constituents in stormwater runoff cause pollution (impairment of uses) of the receiving waters for the runoff. This issue has to be assessed on a site-specific basis.
It is the authors' experience, having worked in this topic area over the past 30 years, that it is indeed rare that chemical constituents in urban and highway stormwater runoff cause real water quality use impairments in the receiving waters for the runoff. This would be expected based on the chemical nature of many of the constituents in urban and highway stormwater runoff since they are in non-toxic, non-available forms, and runoff events are of a short-term, episodic nature thereby allowing higher concentrations of toxic-available forms to be present in runoff waters without adverse impact on the beneficial uses of the receiving waters.
In an effort to try to gain as wide a variety of stormwater runoff water quality impact experience as possible, a survey has been conducted through several national magazines and journals, professional groups, governmental agencies and others for the purpose of finding documented cases of real water quality use impairments associated with urban and highway stormwater runoff. This survey has included a review of the technical literature on stormwater runoff water quality impact studies. Presented below is a synopsis of the results of this survey. It also presents information developed from the authors' work over the past 30 years devoted to evaluating the water quality impacts of urban area and highway stormwater runoff-associated constituents on the beneficial uses of the receiving waters for this runoff.
It is concluded that:
In most situations where the urban stormwater discharges occur to large waterbodies, diazinon-associated toxicity in the discharge likely has limited impact on the receiving water water quality due to the rapid dilution of the stormwater runoff discharge with the receiving waters. However, for small urban creeks where the stormwater runoff could become the dominant flow for a sufficient period of time to be toxic to aquatic life, the diazinon-caused toxicity could be significantly adverse to the beneficial uses of these types of waterbodies.
Request for Additional Information
The authors are interested in continuing this survey and request that any instances of documented cases of urban area, residential and commercial streets and highway stormwater runoff has, in fact, caused aquatic life toxicity or adverse impacts in receiving waters that are detrimental to the designated beneficial uses of these waters, be brought to their attention. These adverse impacts should be manifested in terms of altered numbers, types and characteristics of desirable forms of aquatic life or excessive bioaccumulation of constituents in tissue that renders the aquatic life hazardous in terms of exceedance of a health advisory for consumption by humans or wildlife. In making this assessment, it is important to distinguish between altered habitat characteristics associated with stormwater conveyance systems and the presence of toxic forms of hazardous or deleterious chemicals which would require their control in stormwater runoff.
The authors thank all of those who participated in this survey. They also thank S. Taylor of Silverado - RBF, Irvine, California and Richard Watson of Richard Watson and Associates, Mission Viejo, California for review of this paper.
Lee G.F., and Jones-Lee, A., "Stormwater Runoff Management: Are Real Water Quality Problems Being Addressed by Current Structural Best Management Practices? Part 1," Public Works, 125:53-57,70-72 (1994). Part Two, 126:54-56 (1995).
US EPA, "National Pollutant Discharge Elimination System Permit Application Regulations for Stormwater Discharges; Final Rule," 40 CFR Parts 122, 123, and 124, Federal Register55(222):47990-48091, November 16 (1990).
US EPA, "National Water Quality Inventory 1994 Report to Congress: Individual State and Territorial Summaries," US Environmental Protection Agency, Office of Water, Washington, D.C., December (1995).
Prepared as a report by G. Fred Lee & Associates, El Macero, CA, June 1996.
Reference as:"Lee, G. F. and Jones-Lee, A., 'Results of Survey on Water Quality Problems Caused by Urban and Highway Stormwater Runoff,' Runoff Reports, 4(5):3 (1996)."
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