The dictionary defines erosion as the removal of soil by the action of wind, water, and gravity. Aldo Leopold said that “the destruction of soil is the most fundamental kind of economic loss that the human race can suffer.” (Erosion and Prosperity 1921, cited in The Essential Aldo Leopold). But, really, most of us hardly notice let alone care.
Soil erosion happens every day, all around us, and we are the culprits. We pick up native soil from the neighborhood natural area on the thick treads on our lightweight hiking shoes. When we get home we scrape it off on the nearest pavement—and down the storm drain it goes.
The local contractor’s front-end loader working on a church remodeling project tracks soil into a busy highway above a lake–from where passing motorists and bicyclists hardly notice the soil washing into the storm sewer grate.
The neighbor’s backyard deck project means a bit more soil destruction, as soil is carried on heavy equipment into the neighborhood street–the next rain carries the soil into the storm sewer in the middle of the night.
Each of these typical scenarios cause what is called “soil erosion” But perhaps “erosion” is too weak a term to get our attention. The word erosion describes a gradual and inevitable activity; something that just sort of unavoidably happens. The wind and rain are to blame. Wrong. I think Leopold had it right, we should call it soil destruction and soil loss. Soil loss and destruction can be prevented. Because soil loss and destruction only happen through our neglect, as a result we are engaged in an extreme form of passive-aggressive behavior against the land, and a slow motion environmental destruction.
Why Is Soil Erosion a Concern?
There are several ways a person can answer this question, depending upon his or her point of view.
To the restoration ecologist soil is the basis of all life; it is habitat. Soil loss and destruction diminishes the ecological, social, and cultural basis of human civilization.
The ecologist (as should every other human be) is concerned about the loss of soil nutrients and fertility because they are transported down stream where they fill our springs, streams, and lakes. Anything in between also suffers. The wetlands surrounding our beloved Lake Wingra and our treasured Arboretum, for example, are suffocating under the load of former upland soil that was flushed down the storm drain by neighborhoods, backyards and municipal and commercial construction projects all over the Lake Wingra Watershed.
Filling in of wetlands is not without consequences. Added and misplaced soil smothers small invertebrates and micro organisms that are the foundation of the food chain. Fishes, frogs, and toads plus the birds that feed on them suffer from the destruction of soil in the uplands.
To the US EPA erosion is a thing to be prevented. The EPA regulates soil erosion under authority of The Clean Water Act. The goal of The Clean Water Act is to restore and maintain the chemical, physical and biological integrity of the Nation’s waters, (CWA section 101, 33 U.S.C. 1251). Despite substantial improvements in the nation’s water quality since the inception of the Clean Water Act, many of the nation’s surface waters continue to be impaired. http://www.gpo.gov/fdsys/pkg/FR-2009-12-01/pdf/E9-28446.pdf
A City of Madison Streets Department engineer would define the problem this way: “Uncontrolled erosion, sedimentation and runoff during construction is a pollution source that negatively impacts storm water quality, clogs City sewers, and is hazardous for pedestrians, cyclists and motorists.” https://www.cityofmadison.com/developmentcenter/landdevelopment/erosioncontrol.cfm
Why Are Construction Projects a Soil Loss Problem?
To the urban ecologist, conservationist, and municipal, state and federal regulator, storm water from construction sites is a concern. Storm water, because runoff is the primary vehicle by which eroded soil (sediment) is transported to water bodies, and thus regulation of storm water is a major focus of EPA regulations. Construction activity, because it typically strips the vegetative cover off of soil, leaving it exposed to wind, rain, and the treads of trucks, trailers, and earth movers.
According to the EPA, “The sediment, turbidity, and other pollutants entrained in storm water discharges associated with construction activity contribute to aquatic ecosystem degradation, increased drinking water treatment costs, and impairment of the recreational use and aesthetic value of impacted waters. Sediment can also accumulate in rivers, lakes, and reservoirs, leading to the need for dredging or other mitigation in order to prevent reduced water storage or navigation capacity.”
Why The Emphasis on Small Construction Projects?
Briefly, because there are so many of them and because they are largely unregulated or go un-noticed. In 1998, there were 1709 residential building permits issued in Dane County, Wisconsin. The number of housing starts has since sunk due to the bursting of the housing bubble and the financial crisis of 2008 but you can be sure that the number is not zero.
For several other reasons small construction projects make a significant contribution to soil loss and destruction.
- Paved roads, curbs, and gutters are good at carrying soil away from small construction sites (see photo above).
- More vehicles are taken on and off of small sites per unit area than for lager sites. Mud and debris is tracked onto streets with every trip. What is not swept up at the end of the day is washed down the storm drain into the nearest water body.
- Soil compaction from heavy equipment decreases the soil’s ability to absorb water; thus rainfall runs off more readily, and in greater amounts.
- Small construction sites are likely to pile up soil into steep, high-slope piles when topsoil is stripped, or basements excavated. These high piles are prone to soil loss from rain and wind and from on-site construction vehicle traffic.
- The majority of construction projects in urban areas like Madison, WI fall below the current regulation threshold of 4000 square feet and thus do not need a soil erosion plan. Thus they do not need to apply for an erosion permit, nor file an erosion plan.
- Even if the construction site does have an erosion plan and permit, city regulators and enforcers are so thinly stretched that the inspector may not catch any violations.
It is a fact that soil loss and destruction from small (fewer than 5 acres) urban, and rural construction projects (new houses, church remodel, patios, decks, and driveways; and large new buildings in the city center) are a major source of total sediment and solids in storm water runoff. This is backed up by data from a study conducted in Dane County, Wisconsin in 1998 by the United States Geological Survey (USGS).
According to the USGS study and report:
“Small construction sites are potential sources of large amounts of sediment erosion. Sediment loads from the two monitored construction sites were 10 times larger than typical loads from rural and urban land uses in Wisconsin.”
“Total and suspended solids concentration data indicate the active construction phase produced concentrations that were orders of magnitude higher than pre- and post- construction periods.” (2000. USGS Fact Sheet FS-100-00) http://wi.water.usgs.gov/pubs/fs-109-00/index.html#Figure1)
Although soil erosion on construction sites has been recognized for many years as a significant contributor to sediment and other solids in storm water runoff, construction sites under 5 acres in size (the majority of construction sites are less than 5 acres) have not (until recently) been required by federal regulations to install erosion control measures. Meanwhile, in the City of Madison, construction sites that disturb fewer than 4,000 square feet of protective ground cover, or that excavate or fill fewer than 400 cubic yards of material are not required to obtain a soil erosion permit. If the site does not have an erosion permit, violations can’t be tracked and inspectors have no incentive to investigate.
In 2009 a revised final rule by the US EPA (40 CFR Part 450) will help correct this situation by requiring erosion control on all construction sites to meet certain “non-numeric effluent limitations”. Construction sites over 10 acres will in addition be required to monitor discharges from the site and comply with numeric effluent limitations. The numeric effluent limitations will be phased in over 4 years (taking full effect on December 1, 2013) to give regulators and the regulated community time to comply with the new regulations. See the Federal Register publication for further details on the new EPA regulations: http://www.gpo.gov/fdsys/pkg/FR-2009-12-01/pdf/E9-28446.pdf. The EPA estimates that when fully implemented, pollutant reductions will total about four billion pounds per year and result in a dollar value of about $369 million per year.
Until the 2009 EPA rule goes into effect on December 1 of 2013, the local action plan is: continual vigilance, early detection, and rapid response by citizens and City of Madison regulators and inspectors.
If you see an instance of soil erosion in your neighborhood, report it to the City of Madison Report a Problem web site: https://www.cityofmadison.com/reportaproblem/
Don’t assume that the contractor will take precautions or improve its performance.
Don’t assume that the City of Madison inspectors will have time find the problem on their own—they are just too busy.
If you see something, say something.
Take responsibility and report the problem.
Curt Meine and Richard L. Knight, eds., The Essential Aldo Leopold: Quotations and Commentaries (Madison: University of Wisconsin Press, 1999). Cited as EAL.