Also known as stormwater runoff control, erosion prevention and sediment control is not one technology, but rather a suite of methods that can be used to both prevent soils from eroding from a piece of land, and to capture any that do erode. These individual techniques, or erosion best management practices (BMPs) are each applicable to different situations and must be chosen carefully for each project.
Why Practice Erosion Prevention and Sediment Control?
Eroded particles of soil, or sediments, can easily be moved off construction and landscaping sites by flowing water and end up in natural water bodies. These sediments can cause damage to receiving water bodies. Sediment in water bodies can reduce the amount of sunlight reaching aquatic plants, clog or abrade fish gills causing suffocation, smother aquatic feeding sites and spawning areas and interfere with fishes’ ability to navigate. Preventing and controlling erosion is essential to protection of natural streams, rivers and salt water ecosystems.
In Canada, the Fisheries Act prohibits the deposit or release of a deleterious (toxic) substance to fish-bearing waters. In high concentration, sediment is recognized as a deleterious substance. In addition, most municipalities have bylaws making it illegal to allow sediment-laden water to enter municipal storm drains or ditches. Provincial legislation in British Columbia also makes it an offence to pollute a stream. As a result, everyone who undertakes a construction or landscaping project that could cause erosion is advised to consider erosion prevention before they begin their project. For more information about watershed-wise development, see the CRD Developer’s Guide.
Whether simply replacing a driveway, re-landscaping a yard, or constructing a large and complex urban building, planning ahead for erosion prevention and sediment control can save time, money, potential litigation and help protect our environment.
Erosion Prevention & Sediment Control Best Management Practices
While there are many sediment and erosion Best Management Practices (BMPs) available, the key facts to consider before beginning any construction or land clearing activity are that water moves downhill and, any unprotected soils can be moved off the site by any kind of water moving across the land. Typical sources of water on work sites include rainwater, drainage channels that cross the site and pump-out water from excavation holes.
Examples of BMP’s for erosion and sediment control include:
- Compost: One relatively new technique is the use of high organic content soils (compost) in socks, berms and blankets both at construction sites, and as important components of roadside bioswales and rain gardens.
- Bio-Engineering: Another technique being used more often in North America is bio-engineering, where living plant material is used strategically to help restore eroding stream banks, stabilize slopes of all types, and deactivate roads in logging areas.
In addition, a standard historical practice, the use of straw bales on construction sites, has been largely discredited. At best, hay bales don’t work, at their worst, they can make erosion problems worse. Both the US Environmental Protection Agency and Metro Vancouver have excellent information publications detailing alternatives to the straw bale.
The first and most important BMP is an Erosion Control Plan. Some municipalities require these as part of the building permit approval process, often basing the complexity of the plan required on the size of the building project.
An Effective Erosion Control Plan
The following points can help guide the development of an erosion control plan that takes a comprehensive approach to addressing construction site runoff. It is recommended to hire a qualified professional to design a plan for your site.
Minimize Clearing & Grading
Avoid clearing/grading any soils not absolutely required to be cleared. Map and flag all areas to be protected on site, sharing this information with site crews.
Clearing and grading activities near streams should be minimal, and appropriate BMPs installed to prevent any sediment from moving into the stream.
Phase Construction to Limit Soil Exposure
Ideally, construction site soils would not be exposed during the rainiest seasons, but activities can at least be broken into phases. Construction scheduling should allow for installation of erosion BMPs prior to start of construction; soil stabilization after grading and BMP maintenance.
Immediately Stabilize Exposed Soils
Exposed soils should be stabilized as soon as possible, and any stockpiles covered when not being worked.
Protect Steep Slopes & Cuts
Cutting and grading of steep slopes (>15 percent) should be avoided. If a steep slope exists, any water flowing onto it should be redirected with appropriate BMPs. Further techniques will be needed to protect the slope from erosion, stormwater, and slippage.
Install Perimeter Controls to Filter Sediments
Specialized BMPs should be properly installed around the perimeter of the construction site. Catch basins receiving stormwater flows from the construction site must be also protected with adequate BMPs.
Employ Advanced Sediment Settling Controls
BMPs, such as sediment basins, should be created on site to allow for settling out of sediments from any stormwater.
Train Contractors on Erosion Control Plan Implementation
Site crews should be trained in erosion control practices or an environmental consultant hired to oversee all aspects of the BMP installation and maintenance.
Control Construction Waste
A plan should describe the type of waste anticipated for the site (such as discarded building materials, concrete truck washout, chemicals, litter, and sanitary waste) and how that waste will be managed to prevent impacts to water quality.
Inspect & Maintain BMPs
Erosion Control BMPs will not work unless properly & regularly maintained, especially before and after rainfalls. Always assign inspection responsibility to a specific crew member(s).