Dust Control – Soil Stabilization – Erosion Control

Posts Tagged ‘best management practices’

An introduction to the EPA’s effluent limitations guidelines and source performance standards.

Check dams at a construction site are configured for use of chemical flocculant treatment.
Jesse Pritts, EPA

Although streams and rivers naturally carry sediment loads, discharges associated with construction activity can elevate these loads to levels above those in undisturbed watersheds. Discharges from land disturbance can increase the proportion of silt, clay, and colloidal particles in receiving streams because these fine-grained particles may not be managed effectively by conventional erosion and sediment controls that rely on simple settling.

In response to these issues, the U.S. Environmental Protection Agency (EPA) promulgated effluent limitations guidelines (ELGs) and new source performance standards for discharges from construction and development (C&D) sites on Dec. 1, 2009. ELGs are technology-based standards for control of wastewater and stormwater discharges from various categories of industry and are not risk-based, so different standards are not set for different receiving waterbodies. ELGs can be numeric standards (i.e., discharge limitations) and/or best management practices (BMPs) and process changes. Many of the C&D ELG requirements are already included in EPA and state construction general permits (CGP) and new requirements will be phased in over the next few years for sites to sample stormwater discharges and comply with a numeric effluent limitation of 280 nephelometric turbidity units (NTU). A sampling requirement will be triggered beginning Aug. 1, 2011, for sites disturbing 20 or more acres at once and beginning Feb. 2, 2014, for sites disturbing 10 acres or more at once.

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Received for publication January 31, 2009. Magnesium chloride (MgCl2)-based dust suppression products are commonly used throughout western United States on nonpaved roads for dust suppression  and road stabilization by federal, state, and county transportation agencies.

The environmental implications of annually applying these products throughout spring and summer months on adjacent stream chemistry are not known. Sixteen streams were monitored biweekly for 1 to 2 yr in two Colorado counties for a suite of water quality variables up and downstream of nonpaved roads treated with MgCl2–based dust suppression products.

Eight of 16 streams had significantly higher downstream than upstream concentrations of chloride or magnesium over the entire monitoring period (p  0.05). Mean downstream chloride concentrations ranged from 0.17 to 36.2 mg/L and magnesium concentrations ranged from 1.06 to 12.8 mg/L. Several other ions and compounds, including those commonly found in dust suppression products such as sodium, calcium, and sulfate, were also significantly higher downstream at some sites.

Downstream electrical conductivity (EC), chloride and magnesium concentrations were positively correlated with road surface area draining water toward the stream and yearly amount of MgCl2 applied (R2 = 0.75, 0.51 and 0.49, respectively), indicating that road managers can limit the amount of product entering roadside streams by assessing drainage characteristics and application rates in best management practices. Although MgCl2–based dust suppressants did move into some roadside streams, the concentrations detected were below those reported to adversely affect fresh water aquatic organisms, but the ultimate fate of these ions in Colorado waterbodies are not known.

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