As winter weather wanes, drivers are less likely to have to contend with icy roads and the salt applied by road crews to keep the traveling public safe. Applying salt to deice roads is well-known, but what is less obvious is the impact chloride can have on Michigan's surface waters.
As snow melts it can leave behind salt that remains on road surfaces, parking lots and sidewalks. When spring rains arrive, the salt is washed from roads into storm sewer systems, ditches, wetlands or directly to nearby waterways. There, it can be detrimental to plants, aquatic species such as freshwater mussels and have an impact on various aquatic stages of insects, fish and other organisms, from growth and reproduction to the ultimate ability to survive.
Small quantities of salt can have a big impact. Chloride has been shown to be present in lakes and streams around Michigan, at times in high levels. Once in the water, there is no easy way to remove chloride.
That's why the Michigan Department of Environment, Great Lakes, and Energy (EGLE) at the end of February finalized a Chloride and Sulfate Water Quality Values Implementation Plan, which provides path to implementing the recently developed chloride water quality values. These values are long overdue benchmarks for continued protection of aquatic life and surface water quality from chloride impacts. EGLE's Water Resources Division has been monitoring chloride and sulfate levels in surface waters since 2005.
Representatives from a range of sectors having the potential to discharge chloride to surface waters - including drinking water treatment, wastewater treatment, road agencies, food processors, mining operations and drain commissioners - were part of the collaborative process to inform plan development. The plan identifies the process for implementing the chloride water quality values as part of the National Pollutant Discharge Elimination System (NPDES) permitting process. The potential to discharge chloride will be evaluated when the NPDES permit is processed for reissuance. This process may result in a period of monitoring to adequately characterize the discharge of chloride, compliance schedule to meet an effluent limit, submittal of a variance for an effluent limit, or development of a chloride reduction strategy associated with winter salting.
Options for limiting salt discharging chloride to surface waters include source control, optimizing treatment and salt applications, installing treatment, salt storage, proper salt storage and educating employees.
Although the plan is focused on NPDES-permitted point sources, the role of reducing nonpoint sources of salt, especially chloride, is important to improve and protect water quality. EGLE intends to focus on outreach to both nonpoint and point sources of chloride as part of an overall reduction strategy and to ensure protection of Michigan's aquatic life.
By approaching reductions with a reasoned approach, chloride pollution can be prevented. For more information on the plan, contact Christe Alwin, Municipal Separate Storm Sewer System Program Specialist, Water Resources Division, at AlwinC@Michigan.gov.
Photo caption: MDOT salt truck/snowplow