Construction activities can lead to the contamination of nearby waterways if the appropriate actions are not taken.
In this blog we discuss how properly managing Erosion and Sedimentation Control and Concrete Washout Water can prevent your construction site from polluting waterways.
Erosion and Sedimentation Control
Each year, thousands of acres of land are disturbed and at risk of erosion and sedimentation during construction and development. This results in an estimated 80 million tons of sediment that gets washed from construction sites into U.S. lakes, rivers, and waterways each year, which causes many ecological and financial burdens, including:
- clogs sewer storm drains
- increases the potential for flooding
- increases the costs of power production and drinking water treatment
- harms aquatic life and other species that rely on the water sources
What are the best management practices for sediment control?
Surface roughening – scoring the soil surface. This practice can trap sediment and help create vegetative cover.
Temporary grasses and permanent vegetative cover – to prevent
Mulch – Any place you have loose soil, such as around plants or in gardens, should be mulched. Mulch slows down water, catches any eroding soil, and prevents the force of falling rain from disrupting the soil. Both organic and inorganic materials can be used, common options include bark mulch or even lawn clippings can be used.
Erosion blankets – mats made of organic or inorganic materials held by synthetic or biodegradable netting help prevent erosion from exposed soils in channels or slopes.
Silt fence – a temporary sediment barrier made of woven synthetic filtration fabric supported by steel or wood posts. Install below-disturbed areas where erosion is expected to occur.
Inlet protection – to prevent sediment from entering storm drains.
Sediment basins/traps – temporary reservoirs that retain sediment and debris within a controlled stormwater release structure.
Diversion dike – a channel made across or at the bottom of a slope to intercept surface water runoff.
Slope drain – made of tubing or some non-erosive material – it extends from the top to the bottom of a slope with a dissipater at the outlet end, preventing runoff from eroding a steep slope by containing the runoff as it goes down the slope.
Construction entrance – stone construction entrance lined with filter fabric to reduce the amount of mud being transported off-site. If the conditions are muddy enough that sediment isn’t being removed from exiting vehicles by the stone, then the tires must be washed at a wash rack.
Watering truck – irrigating with a watering truck controls dust from exposed soil. You can take this a step further and use nonpotable or reclaimed water resulting from other site activities.
Rain Barrels & Rain Gardens – Use rain barrels at the ends of your gutters to capture stormwater –Rain, snow melt, or any other water from precipitation. Precipitation from the roof concentrates in gutters moving it faster and causing erosion. A rain barrel collects this water and allows you to distribute it slower and over a larger area. Rain gardens much like rain barrels collect stormwater and allow it to infiltrate slowly, instead of flowing quickly over soil causing erosion. Plant trees or shrubs – Trees and shrubs are especially important near waterways. The roots from these plants help hold onto soil and prevent it from eroding. Trees and shrubs also work to slow down the flow of water over soil, and help it infiltrate into groundwater.
When concrete is poured, there are measures to handle the wastewater created when cleaning concrete skips, trucks, and pump lines.
Concrete washout water is highly alkaline due to the presence of calcium hydroxide. It typically has a pH value of between 11 and 13.6. At this level of alkalinity, even small quantities represent a serious risk to the environment. It’s illegal to discharge untreated water into the sewers or allow it to drain away on site.
The maximum pH for water diverted into sewers is pH10 while it must be lowered to pH9 before it can be released into watercourses. Contractors must request permission from local authorities to release wash water into the drains.
The conventional method for treating concrete wastewater is to chemically lower the pH using acid or carbon dioxide. This can be expensive, when large volumes of water need to be treated and water can be over-dosed and become acidic. This can be equally damaging to the environment.
Have you found other ways to reduce water contamination on your Jobsite? Let us know!
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