Date: Tue, 28 May 1996 13:22:16 -0300 From: Mark Corrales Subject: car manure/NPS (vehicle fluid/ runoff) I have recently completed a major report (250 pages) on the environmental impacts of transportation, and have included a small section of that report below. Hope you find it useful. The consulting firm I'm with (Apogee Research) wrote this report for the US EPA's Office of Policy, Planning and Evaluation. The full text, graphics and all, will soon be available on the web. Here is the section on runoff (sorry I'm not including the whole bibliography here): HIGHWAY AND ROAD RUNOFF PRESENTATION OF INDICATORS OUTPUT INDICATORS AND NATIONAL EXAMPLES Average pollutant concentrations of lead and copper in road runoff are more than twice as great as those from residential and commercial areas (U.S. DOT, 1986; U.S. EPA(d), 1983).ù Some studies suggest that eventhough highways often occupy only 5-8% of the urban catchment area, highway drainage can contribute as much as 50% of the total suspended solids, 16% of total HC, and 75% of total metal inputs to a receiving stream (Hamilton et al., 1991).ù Roads occupy about 19% of the surface areas in large cities (Tolley, 1995). ù Pollutant levels in highway runoff (see table) ù oil and grease in road runoff may total hundreds of thousands of tons per year (Apogee estimate - see discussion below). Selected Road and Highway Storm Water Pollutant Concentrations and Comparisons to Typical Runoff from Residential and Commercial Areas Constituent Road/Highway Runoff Mean Concentration(mg/l) Runoff from Residential and Commercial Areas(mg/l) BOD (Biological oxygen demand) 24 12 COD (Chemical oxygen demand) 160 94 TKN (a measure of nitrogen) 3.0 2.3 Total Phosphate 0.9 0.5 Lead 4.3 0.24 Copper 0.19 0.053 Cadmium 0.02 - Nickel 5.0 - Oil and grease 9 - PAHs (Polycyclic aromatic hydrocarbons) 4.6 - Pesticides/Herbicides 0.03 - PCBs (Polychlorinated biphenyls) 0.335 - Source: U.S. DOT, 1986; U.S. EPA, 1982 as cited in Weiss, 1993. Note: lead levels have dropped considerably since these estimates. OUTCOME INDICATORS AND NATIONAL EXAMPLES In 1992, urban runoff contributed to the impairment of 11% of the nationÉs assessed river miles, 24% of assessed lake acres, and 59% of assessed ocean shore miles. It was cited as a major source of impairment for 5-15% of assessed surface water bodies (U.S. EPA, 1994b). The exact contribution of transportation to urban runoff is not known, but it is expected to be large, since road surfaces occupy a significant portion of land in urban areas, 19% according to Tolley, 1995. OTHER INDICATORS AND LOCAL EXAMPLES One study of runoff in CaliforniaÉs Santa Clara Valley found that vehicles were the source of 67% of the zinc, 50% of the copper, and 50% of the cadmium found in runoff (Santa Clara Valley Nonpoint Source Pollution Control Program as cited in Weiss, 1993). Over 50% of the annual pollutant loads in entering a section of the Pawtuxet River adjacent to I-95 in Rhode Island came from highway runoff (Hoffman, 1985). Investigations on a small Norwegian lake ecosystem found that the road had no effects of the highway on oxygen condition, but considerable effects on conductivity and high concentrations of cadmium, zinc, sodium, and chloride. Also the diversity and abundance of the benthic communities near the highway were reduced relative to a control location (Baekken, 1994). ù Of the vehicle-related particulates in highway runoff, 37% comefrom tire wear, 37% from pavement wear, 18.5% from engine and brake wear, and 7.5% from settleable exhaust (PEDCO as cited in Hamilton et al, 1991). Highways have been found to contribute up to 50% of suspended solids, 16% of hydrocarbons, and 75% of metals in some streams (Hamilton and Harrison, 1991). Since indicators are not available on total tonnage emissions from runoff, it may be helpful to examine the implications of the runoff concentration statistics cited above, such as the 9 mg/liter concentration of oil and grease in runoff. Simply for the sake of an example to provide perspective, let us suppose that a meter of rainfall and water in the form of snow is typical per year (not an unreasonable figure, at least for some parts of the country). This means that roughly a meter of water falls on a square meter of pavement, or a volume of 1 cubic meter of water per year. If oil and grease concentration in this water is 9 mg/l as it runs off, the mass of oil and grease in this cubic meter would be 9 grams. This would equal almost a metric ton of oil and grease per year per 100,000 square meters of road surface (a length of road 10 meters wide and 10 km long). Assuming roughly 3 meters width per lane and perhaps about 4 million paved lane-miles, there are approximately 20,000 square kilometers of paved road in the U.S.. The above implies there could be 200,000 metric tons of oil and grease in road runoff annually nationwide, if the above assumptions were valid (actual average rainfall may be half as high). It is worth noting that this very crude estimate we have developed corresponds to a scenario where the average U.S. vehicle (of which there are roughly 200 million) leaks 1 liter of oil and grease onto roads per year, or less than one tenth of a quart per month (assuming oil has the density of water for simplicity here). This average rate of leakage seems at least plausible. It is also worth noting that if such loadings are occurring, they are larger than estimated improper disposal of used motor oil and larger than reported air or water releases of many pollutants in auto manufacture. The impacts of runoff, of course, depend on many factors other than tons emitted - oil and grease may undergo biodegradation and dilution before they ever reach any body of water or sensitive ecosystem. DESCRIPTION OF IMPACT Highway contaminants are deposited on roadway surfaces, median areas, and rights-of-way from atmospheric fallout, fuel combustion processes, lubrication system losses, tire and brake wear, transportation load losses, deicing agents, and paint from infrastructure. During storm events, rainwater first washes out atmospheric pollutants and, upon surface impact (or snowmelt), picks up roadway deposits and runs off into receiving water bodies. This highway runoff can be highly polluted and have negative impacts on receiving waters such as sedimentation, eutrophication, accumulation of pollutants in sediments and benthic organisms, and destruction of native species. Runoff from roads is greatly affected by whether the road is paved. A graphic below shows that while road mileage has not been growing especially quickly, paved mileage has been growing very rapidly. This has implications for increased runoff impacts, but also has other implications, such as reduced particulate emissions from reentrained dust and perhaps higher speeds of travel and greater emissions per VMT for certain pollutants. Although these tradeoffs are not discussed further here, the trend in paved mileage is notable. The impacts and significance of roadway runoff are highly site-specific. The quantity of runoff generated depends on the frequency, intensity, and duration of precipitation in an area. The water quality characteristics of runoff are affected by local air quality (because of deposition of air pollutants onto roads) and, to some extent, the level of traffic activity. The quantity of pollutants originating from highways and motor vehicles, however, is not well understood runoff is hard to measure and varies by location. Pollutants found in runoff are generally classified under six broad categories: suspended solids or particulates, oxygen consuming constituents (BOD, COD), nutrients, heavy metals, trace organics, and microorganisms. Direct vehicle deposits are a major source of particulates and heavy metals: settleable exhaust, copper from brake pads, tire and asphalt wear deposits, and drips of oil, grease, antifreeze, hydraulic fluids, and cleaning agents. An estimated 46% of vehicles on U.S. roads leak hazardous fluids (AAMA, 1990). Indirectly, vehicles also contribute by carrying solids from parking lots, urban roadways, construction sites, farms, and dirt roads. More than 95% of the solids on roadways originate from sources other than the vehicles themselves (Barrett et al., 1993). Secondary runoff pollutant sources associated with vehicular traffic include gas stations and other auto-related facilities, oil production and transportation operations, petroleum refineries, and improper disposal of used motor oil. Nitrogen and phosphorus-based nutrients generally originate from atmospheric and roadside fertilizer applications. Atmospheric deposition is the main source of PCBs. These pollutants can harm the environment in various ways. Oxygen consumption (from high BOD) harms aquatic life, while nutrients cause eutrophication, where excess aquatic plant growth can block sunlight, also harming aquatic life. Toxic substances can affect human health or various plant or animal species. CAUSAL FACTORS Level of traffic activity: the number of vehicles during a storm event (VPS) is a better determinant of pollutant loading than the average daily traffic (ADT) or antecedent dry period (Barrett et al, 1993). DOT considers impacts negligible on roads with less than 30,000 ADT. Levels over 30,000 ADT are not very common outside urban areas, though some roads surpass 200,000 ADT. ù Rate of deposition of contaminants on road surface per vehicle ù Paved surface area (see graphic on growth in paved surface) [GRAPHIC ON INCREASE IN PAVED AREA GOES HERE] Source: U.S. DOT, FHWA, 1995c ù Precipitation activity: antecedent dry period, storm intensity and duration ù Amount of rainfall/snowmelt ù Drainage characteristics ù Ecology and other aspects of receiving water bodies: type, size, diversity, potential for dispersion ù Toxicity and chemical/physical characteristics of pollutants.