Minutiae mustn’t bog down storm-water rules

By JIM DAVIS

Story ran on Sunday, June 3, 2001

Everyone agrees that health and environmental regulations should be grounded in sound science. This is especially true for storm-water regulations, which have a potentially significant impact on quality of life and economic development. But what does it mean to be "grounded in sound science?" Do regulators need to know exactly how much of each type of pollutant will enter streams from construction sites, roads, parking lots and rooftops? Do they need to know exactly how effective each type of best management practice, or BMP, will be in each type of setting? What is a reasonable scientific standard for determining whether regulations should be adopted and what they should require? No matter what type of reasonable standard is adopted, some people will say it is not adequate.

The tobacco industry claimed for decades that the science base was not adequate to prove cigarettes cause cancer. The companies argued that science did not fully understand the underlying complex causal mechanisms for lung cancer. They persuaded Congress to ignore hundreds of studies showing a strong association between smoking and cancer. This age-old debate over the health effects of smoking seems ridiculous now, but the U.S. Food and Drug Administration still does not have regulatory authority over tobacco products. Science must be used to create good regulations, not to immobilize all action.

Recent editorials and columns in the Tribune have argued that many complex interactions among climate, geology, soil, etc. must be taken into account before good regulations can be developed, that the science base is not adequate for limiting development-related impervious surface and that engineered BMPs are adequate to prevent all storm-water damage to streams. This article will examine each of these assertions and make specific recommendations to policy-makers on how they can move forward with confidence.

● Recommendation 1: Policy-makers should use existing scientific information to develop the best possible regulations and not worry about complex details that are not available or fully understood.

Ideally, we should use site-specific information on geology, hydrology, soils, vegetation, rainfall, impervious surface, land use and other factors in every one of our storm-water regulatory decisions. However, this is neither practical nor cost-effective. Good, affordable information is available to identify environmentally sensitive watersheds. Information on other factors related to watershed sensitivity is not available at a reasonable price or scientific methods have not been developed to use the information in a meaningful way at the watershed scale. Excellent information is also available at the site-specific level or local scale - for example, slope, slope length, soil type, soil permeability, etc. This information can be used to identify portions of watersheds that are environmentally sensitive and should be especially protected.

Policy-makers need to identify the best available science at the time and develop regulations that use this information at the appropriate scale and in the most cost-effective way. Prohibitive cost or simple lack of complex information should not be used as an excuse for inaction. In most cases, we will never have complete information for making perfect decisions. Scientists still do not know the exact mechanism by which cigarette smoke causes cancer, but we certainly know that smoking causes cancer and smoking cessation prevents cancer. Detailed scientific information is not available for developing storm-water regulations that would be fully adaptable to every tract of land with complete accuracy. However, a lot of excellent information is available for making practical decisions about the environmental sensitivity of watersheds and smaller critical areas and for selecting strategies to prevent storm-water damage to streams.

● Recommendation 2: Research has clearly demonstrated the effects of impervious surface on stream biological health, and policy-makers should have the confidence to act on this scientific information.

The relationship between impervious surface - roads, parking lots, etc. - and stream damage is well established. As impervious surface increases, storm water overwhelms streams, causing stream bank erosion and sediment deposition. More parking lots, driveways and roads mean more car oil, more pet waste and more spilled chemicals flushed into streams. Additional manicured lawns associated with new homes mean more fertilizer and pesticides contaminating storm water and streams. As impervious surface exceeds 10 percent, significant impact is detected on stream biological health. As impervious surface exceeds 25 percent to 30 percent, streams are degraded to the point that they might never recover, even with expensive restoration efforts.

A review article by Tom Schueler of the Center for Watershed Protection identified 18 research studies on impervious surface throughout the United States. These studies clearly document the relationship between impervious surface and stream health. Preliminary pilot data from my own research in Boone County indicate that the biological health of local streams is significantly related to the percentage of impervious surface in their watersheds. Gans Creek - 2 percent impervious surface - was the healthiest stream in our study, and Flat Branch Creek - 36 percent impervious surface - showed the lowest biological health.

● Recommendation 3: Policy-makers should require engineered BMPs for stream protection, but they should not count on them to solve the whole storm-water problem.

Some people see engineered BMPs as magic bullets that will solve all of our storm-water problems. If we can send a man to the moon, surely we can remove pollutants from storm water. Unfortunately, this is not completely true. Research of storm-water control has not been funded nearly as well as NASA. Research on storm-water control BMPs, however, is being conducted at multiple sites in the United States. The research is showing that engineered BMPs can substantially reduce pollutants in storm water and prevent some of the damage to streams. However, there are many different types of BMPs to be evaluated - detention basins, wetlands, swales, etc. - and their effectiveness is partially dependent on soil type and other local conditions. Science has not identified even one engineered BMP that is 100 percent effective for controlling pollutants.

Developers, engineers and policy-makers need to understand the important difference between storm-water peak flows and total storm-water volume. Properly designed detention basins can reduce storm-water peak flows even below those seen under natural conditions. This helps prevent stream bank erosion and sediment deposition. However, detention basins are not effective at reducing excess storm-water volume generated by impervious surface. Under natural forest and grassland conditions, a substantial portion of storm water is absorbed into the ground and gradually recharges streams over several months. Holding this excess water in a detention basin and releasing most of it over 48 to 72 hours creates extended sub-bank full stream flows that cause saturation and collapse of stream banks and consequent sediment deposition. Engineers cannot just make this excess water disappear. They also cannot hold it for much longer than 72 hours without risk of another storm event that would wash over the already full basin.

Storm-water quality is also a critical issue distinct from storm-water peak flow and volume. Many pollutants are soluble and move along with the water that leaves urbanized surfaces. Some pollutants might settle out in sediments or be absorbed by plants. Depending on the type of pollutant, well-maintained BMPs can remove from 30 percent to 90 percent of the pollutant. Nitrates and phosphates are particularly hard to reduce - 30 percent to 60 percent removal rates. Limited control of these nutrient pollutants results in excess algal growth and reduced oxygen supply for aquatic life. Engineered BMPs must be combined with other storm-water control strategies if we are to protect our streams.

To learn more about the effects of impervious surface on stream biological health, contact the Center for Watershed Protection at http://www.cwp.org. To examine impervious surface and stream health data for Boone County, access http://maps.cares.missouri.edu/analysis/analysis.asp#ESI , a Web page maintained and supported by CARES/ICREST at the University of Missouri and funded by grants from the Raytheon Corporation and the NASA. To obtain more information on storm-water control and what you can do to help keep our streams clean, call the Community Storm Water Project at 874-1637.

Jim Davis is an assistant professor of rural sociology at the University of Missouri-Columbia and a consultant on storm-water runoff issues.