WHAT IS CONCRETE WASHOUT?
Construction sites have long been identified as a large contributor to urban runoff pollution if the proper pollution prevention practices are not regularly performed. Materials washed into the storm drain have a direct impact on local waterways and habitat living in that environment.
The most common discharge into our storm drains from concrete construction is the residue and contaminants from washing down equipment such as concrete trucks, pumps, mixers, chutes, hand tools, and wheelbarrows. It also comes from other cementitious type products such as grout, mortar, and stucco.
CONCRETE WASH WATER IS CAUSTIC
Concrete or cementitious (mortar, grout, plaster, stucco, cement, slurry) washout wastewater is caustic and considered to be corrosive with a pH near 12, essentially the same as Liquid Drano®, Ammonia, or other household cleaning detergents. The primary ingredient in ready mixed concrete is Portland Cement, which consists of Portland Cement Clinker, Calcium Sulfate, Calcium and Magnesium Oxide, metals and trace elements of potassium and sodium sulfate compounds, chromium compounds and nickel compounds. Contact with wet (unhardened) concrete, mortar, cement or other cementitious materials can cause skin irritation, SEVERE CHEMICAL BURNS (THIRD-DEGREE), or serious eye damage.
EFFECTS OF HIGH pH ON VEGETATION AND SOIL
The effects of high pH on vegetation may include: inhibited growth, damage to soil and plants, and substantial alteration of the soil and plant chemical composition even after the pollution source is gone. High pH may also increase the toxicity of other substances causing further problems. The safe range for plant life is between 6.5 – 7.0 pH units. The average pH of concrete washout water is near 12 pH units.
HIGH SUSPENDED SOLIDS COUNT
Concrete wash water is basically a slurry of fine Portland Cement particles in water or suspended sediments. When illegally discharged into a fish-bearing waterway, it will clog fish gills; reducing the amount of oxygen they receive which can ultimately lead to death. It can also smother aquatic habitat, impair their feeding ability, and permanently damage the ecosystem we enjoy.
Turbidity, which refers to water clarity, is related to suspended solids. In clear water, the turbidity is 0 NTU. The average turbidity of concrete washout water is 27,000 NTU. The average total of suspended solids in concrete washout water is 79,000 ppm.
WHAT IS pH?
pH is a measure of how acidic or alkaline a substance is. The pH scale goes from 0 to 14, where 7 is neutral. A low pH value means the sample is acidic while a high pH value means that the sample is basic or alkaline. A change is one pH unit means a tenfold change in concentration, similar to the Richter scale and measuring earthquakes.
EFFECTS OF HIGH pH ON AQUATIC LIFE
The effects of high pH on fish may include: DEATH; damage to outer surfaces like gills, eyes, and skin; and an inability to dispose of metabolic wastes. High pH may also increase the toxicity of other substances. For example, the toxicity of ammonia is ten times more severe at a pH of 8 than it is at pH 7. The safe range for aquatic life is between 6.5 – 9.0 pH units. The average pH of concrete washout water is near 12 pH units.
Several inadequate containment measures that are being used on construction sites include a hay bale pit lined with plastic, pits dug into the ground, sludge boxes and plastic bags. These systems all have a common problem, they use plastic and they almost always leak, resulting in the release of caustic wastewater into the ground or down a stormdrain.
This results in an illegal discharge which exposes the companies to civil liability and costly fines.
Concret Washout System is a watertight system that controls, captures and contains all of the caustic wastewater and washout material, eliminating almost any possibility of an illegal discharge and thus protecting clients interests and our environment.
Up to 50 concrete loads per week producing up to 1000 litres of wash water / week
51 - 100 concrete loads per week producing 1000 - 2000 litres of wash water /week
More than 100 concrete loads per week producing more than 2000 litres of wash water per week
IT’S THE LAW
The United States Environmental Protection Agency (US EPA) and numerous other states including California Environmental Protection Agency (CalEPA) have stepped up their efforts to keep SWPPP’s compliant to the NPDES. All of these criteria mandate the utilization of Best Management Practices (BMP’s) on construction sites. Potential discharges into the storm drain systems from concrete work has become a priority of the federal and state EPA, water quality control officials, regional and local inspectors as well as a strategic target of the advocacy and environmental groups. Illegal discharges into our waterways can bring fines of $32,500 per day if the US EPA becomes involved. In 2004, the US EPA conducted approximately 21,000 inspections, 425 criminal investigations and 455 civil investigations relating to pollution activities. The investigatory activities, both civil and criminal, help ensure a level playing field, removing any economic or competitive advantage which may be gained through noncompliance. The EPA identifies, apprehends, and assists prosecutors in successfully convicting those responsible for the most significant and egregious criminal violations of environmental law.
The most publicized of these investigations was Walmart’s $3.1 Million settlement in May 2004 for their failure to adequately implement BMP’s and control runoff. „….no designated concrete wash area, concrete piles were scattered about the site, inadequate concrete wash water controls that allow drainage into the storm drain inlet and failure to install proper concrete washout area…“