From Streets to Streams Urban runoff is a relatively recent concern, but it is not an insignificant issue. Although we have less urban area than rural area in Wisconsin, urban areas have more impervious surfaces. That means more water runs off instead of soaking in, and more enters lakes and streams unfiltered by soil or vegetation. Some of the pollutants found in urban runoff are sim- ilar to pollutants found in rural runoff. These are the “conventional” pollutants — sediment, nutrients, oxygen- demanding materials, and bacteria. Urban areas on a per- acre basis deliver as much or more of these conventional pollutants as rural areas. During the last twenty years, urban areas have Sediment Keeping invested billions of dollars in new wastewater Like rural runoff, urban run- It Clean treatment facilities to control water off is loaded with sediment. Keeping pollutants out of stormwater What we do pollution. Despite this effort, many Cities may have less soil runoff is less expensive than installing erosion than rural areas, but on our land of our local lakes and streams are still stormwater treatment facilities. Here urban areas produce their are some ways that you can help is reflected plagued with pollution and cannot own distinctive mix of sedi- prevent stormwater pollution: in our water be used for fishing and swimming. ment — flakes of metal from rusting vehicles, particles Individuals Why? The answer lies in the ways we I from vehicle exhaust, bits of Recycle oil use our land and in the aftermath of a storm. tires and brake linings, I Direct downspouts to lawns chunks of pavement, and I Sweep paved areas to keep waste When rain falls or snow melts, the runoff washes soot from residential chim- out of stormsewers neys as well as industrial I pollutants off our streets, parking lots, construction Keep your car tuned, repair leaks smokestacks. sites, industrial storage yards, and lawns. Urban I As Figure 1 on the follow- Limit fertilizer and pesticide use, leave grass clippings on lawn runoff carries a mixture of pollutants from our cars ing page shows, the leading I and trucks, outdoor storage piles, muddy construc- Clean up pet waste I tion sites and pesticide spills. Efficient systems of Dispose of toxic wastes properly Although we I ditches, gutters and storm sewers carry the polluted Wash your car on your lawn or at have less urban area a car wash runoff to nearby lakes and streams, bypassing than rural area wastewater treatment systems. in Wisconsin, urban Municipalities I areas have more Enforce construction site erosion One way of cleaning up polluted urban runoff is control laws impervious surfaces. I to install stormwater treatment facilities. Another Enact laws requiring stormwater That means more water management in new development less expensive method is to keep runs off instead of I Develop and implement a pollutants out of runoff (see soaking in . comprehensive stormwater sidebar). The potential payoff management plan I Sponsor household hazardous from better land management sources of sediment in exist- waste collections practices is high, promising ing urban areas are industrial healthier waters, quality sites, commercial develop- ment and freeways. But by far the highest loads of sedi- water recreation close to ment come from areas under construction (not shown in home and riverfront devel- Figure 1). The Wisconsin Department of Natural Resources opment possibilities. (DNR) estimates that an average acre under construction delivers 60,000 pounds (30 tons) of sediment per year to Shallow, slow-moving waterways are especially vulnerable downstream waterways, which is much more than any to fish kills caused by oxygen demand from the organic other land use. materials in urban runoff. Indeed, the surge of oxygen Two factors account for the large amount of sediment demand after a storm dumps organic waste into an urban coming from construction sites — high erosion rates and waterway can totally deplete its oxygen supply. Runoff high delivery rates. Construction sites have high erosion from older residential areas (with more pavement, more rates because they are usually pets, and combined storm and sanitary sewers) carries the ANNUAL SEDIMENT LOAD (Lbs./Acre) stripped of vegetation and highest load of oxygen demanding materials. Freeways topsoil for a year or more. Industrial Bacteria Commercial Typical erosion rates for con- The levels of bacteria found in The DNR Shopping Centers struction sites are 35 tons to Multi-Family 45 tons per acre per year as urban runoff almost always estimates that an Small Lot Residential compared to 1 to 10 tons per exceed public health standards average acre under Large lot Residential for recreational swimming and acre per year for cropland. construction delivers Parks Even more importantly, wading. Generally, fecal coli- 0 200 400 600 800 1000 60,000 pounds (30 construction sites have very form bacteria counts for urban Figure 1 tons) of sediment per high delivery rates compared runoff are 20 to 40 times high- ANNUAL PHOSPHORUS LOAD (Lbs./Acre) year to downstream to cropland. During the first er than the health standard for Freeways phase of construction, the swimming. Research shows waterways, which is Industrial these high levels of bacteria are Commercial land is graded and ditches much more than any typical of runoff from small as Shopping Centers or storm sewers are installed other land use. Multi-Family to provide good drainage. well as large cities in Wisconsin. Small Lot Residential This also provides an effi- Sources of bacteria in urban Large lot Residential cient delivery system for runoff include sanitary sewer overflows, pets, and popula- Parks pollutants. Typically, 50% to tions of urban wildlife such as pigeons, geese and deer. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 100% of the soil eroded from Toxic Pollutants a construction site is delivered to a lake or stream, com- One of the special challenges of urban watersheds is toxic pared to only 3% to 10% of the soil from cropland delivered pollution. Toxic pollutants are substances that may cause to lakes or streams. death, disease or birth defects or that may interfere with Nutrients reproduction, child development or disease resistance. According to DNR studies, the toxic pollutants of most Runoff from both urban and rural areas is loaded with concern in urban runoff are metals, pesticides, polychlo- nutrients such as phosphorus and nitrogen. Phosphorus rinated biphenyls (PCBs) and polycyclic aromatic hydro- is the nutrient of greatest concern because it promotes weed carbons (PAHs). and algae growth in lakes and streams. Like sediment, phosphorus concentrations are Metals lower in urban runoff than in What goes Metals are the best understood rural runoff, but annual phos- down the storm toxic pollutants in urban runoff. phorus loads per acre are at least drain ends up in They were extensively moni- comparable to rural areas. our water! tored as part of the National Because phosphorus com- Urban Runoff Program during pounds attach to soil particles, the early 1980s. Recent data areas with high sediment loads from Wisconsin cities confirms also produce high phosphorus that runoff from small as well as loads (see Figure 1). This means large cities is contaminated with that construction sites are signif- metals such as lead and zinc. icant sources of phosphorus as Lead has historically been used well as sediment. Other sources as an “indicator” for other toxic of phosphorus include fertilizer pollutants in urban stormwater spills, leaves and grass left on because it is relatively easy to paved areas, and orthophosphate in vehicle exhaust. monitor and its dangers are well documented. Lead is a problem for both humans and aquatic life. Its human Oxygen Demanding Material health effects include damage to the nervous system and Urban runoff carries organic material such as pet waste, kidneys, high blood pressure and digestive disorders. leaves, grass clippings and litter. As these materials decay, Lead can also be toxic to aquatic life. Wisconsin they use up oxygen needed by fish and other aquatic life. monitoring shows that about 40% of the samples from Figure 2 the primary source of zinc (61%) in industrial areas where Sources of Total Lead and Zinc downspouts discharge onto pavement or directly into storm sewers. Roofs are a less significant source of zinc in Urban Runoff (8%) in residential areas where downspouts discharge INDUSTRIAL AREAS onto lawns. On some roofs, copper flashing contaminates Lead Zinc runoff with copper and lead. In some cities, a significant source of metals is out- Parking Lots Roofs door storage of scrap metal, coal, and salt. According to 62% 61% U.S. Geological Survey monitoring, scrap metal piles are Lawns the primary source of mercury in the area surrounding <1% Parking Lawns 3% Streets the Milwaukee harbor. Other metals found in runoff from 27% Lots Streets 29% outdoor storage include chromium and lead from road Roofs 7% 9% salt piles and arsenic from scrap metal and coal piles. The list of other sources of metals is long, ranging COMMERCIAL AREAS from combustion to deteriorating metal and paint. Air- Lead Zinc borne emissions from burning coal, oil or municipal Streets Streets waste may carry cadmium, copper, lead or mercury. In 57% 51% fact, this is the primary source of mercury for many Side- Side- walks Wisconsin lakes. Other sources of metals include paints walks <1% and plated metals which commonly contain cadmium or 1% Roofs Parking Parking Lots 17% Lots chromium. Bullets, fishing weights, and paint sold before Roofs 4% 38% 32% 1977 may contain lead. Wood used in outdoor construc- tion may contain arsenic, chromium, copper or zinc to prevent rotting. PESTICIDES IN STORMWATER RESIDENTIAL & INSTITUTIONAL AREAS Lead Zinc Pesticides Regulated Insecticides: Aldrin, Chlordane, DDT, Endrin, Heptachlor, Lindane, Toxaphene.