As aggregate producers supply the 55 pounds of aggregates that every Texan consumes daily, the industry remains keenly focused on conserving and protecting the state’s natural resources, including water. Aggregate materials are the building blocks of our infrastructure and are used in nearly all residential, commercial and industrial construction, such as roads, bridges, schools, homes and hospitals.As the industry works to meet the state’s ever-increasing demand for these materials, some misconceptions have developed about the industry’s use of water. Here are the facts.
Aggregate water management programs ensure the responsible use of water and comply with many legal requirements. Water is used for two primary purposes – for aggregate washing and/or separation and for dust suppression to control emissions. Most of the water used by an aggregate operation is recirculated, with the actual amount of water consumed remaining relatively small.
Aggregate washing – Washing of aggregates is an essential processing step to remove fine inert mineral particles, such as silt and clay that are naturally contained in the limestone, sand and gravel deposits. The washing process allows the aggregate to obtain sufficient adhesion for use in producing concrete and asphalt. This also helps to separate the different product gradations of stone, sand and gravel. Aggregate wash facilities are typically designed for water recycling with the use of a closed-loop water recycle system. As a result, only about 2 to 8 percent of water used during the aggregate washing process is consumed. Furthermore, no additives are introduced into the fresh or recycled water used for washing that would cause pollution of water supplies or the underlying aquifer.
Dust suppression – Suppressing and controlling dust is required by the facility’s air quality permit issued by the Texas Commission on Environmental Quality (TCEQ). To minimize dust emissions, water is sprayed at strategic locations on process equipment, such as conveyor transfer points, stockpiles, internal haul roads and trucks exiting the site. Aggregate producers have developed and implemented best practices for water conservation that are designed to use only the amount of water that is needed to control dust emissions (i.e., particulate matter).
Source control BMPs are the most effective means of preventing water pollution and protecting water quality and are designed to prevent or minimize pollutants at a potential source. Baseline BMPs are designed to reduce the possibility of storm water contact with pollution-causing activities and focus on good housekeeping, preventive maintenance, spill prevention and response, employee training, monitoring, inspections and recordkeeping.
Quarry operators institute many best practices to help preserve water, including: