Climate Change and Stormwater: The Perfect Storm

stormwater-runoffStormwater runoff is a concern year-round, but even more so in the spring when snow is melting and rain is abundant, particularly in humid continental climates. Stormwater starts as precipitation such as snow, sleet, and rain, which lands on natural ground cover such as forests, grass, or gardens. In a natural environment, stormwater soaks into the ground and is filtered by layers of dirt and rock, then finds its way to our groundwater and drinking water supply. Due to urbanization, stormwater in developed areas does not land on natural ground cover but instead washes off roads, driveways, parking lots, rooftops, and other impervious surfaces, becoming stormwater runoff. Stormwater runoff picks up road salt, chemicals, oil, bacteria, sewage, sediment, and garbage, then washes these pollutants into ditches and storm drains, contaminating our streams, rivers, ponds, and lakes. To make matters worse, climate change exacerbates stormwater runoff and contributes greatly to the impairment of surface water supplies.

How Climate Change Exacerbates Stormwater Runoff

flash-flood-stormwater
Climate change will likely bring more intense storms to all areas of the country.

A study by scientists from the National Center for Atmospheric Research in Boulder, Colorado published in December 2016 indicates that climate change will likely bring more intense, frequent, damaging storms to all areas of the country, particularly to the Northeast and the Gulf Coast. In fact, studies show that storms in these areas could become up to five times as frequent and bring 70% more rain if greenhouse gas emissions are not reduced. Storms of this magnitude will likely cause flash floods, landslides, and an overabundance of stormwater runoff – far more than current municipal stormwater systems are designed to handle.

California has recently been experiencing severe drought combined with intense storms.

The study also indicated that regions such as the Pacific Northwest and central United States will likely become drier, but with more intense, extreme rainfall. We have already seen this in northern California, where the Oroville Dam suffered serious damage after drenching rains in February. Prior to these rains, the state had been plagued by severe drought. Rising temperatures increase atmospheric humidity, causing extreme precipitation and an increased risk of flash flooding. And while it may seem counterintuitive, drought only intensifies the problem. Drought leads to less vegetation and more firmly packed soil, both of which inhibit infiltration. When heavy rains follow drought, soil tends to erode, washing remaining plants away as well. Regular, gentle rain is the key to restoring soil, and without it, soil degradation will only intensify.

Managing Increased Stormwater Runoff

Unfortunately, the above-mentioned factors will likely lead to an increase in stormwater runoff and its accompanying problems. Municipal stormwater systems, already faced with increased nutrient regulations, will likely become overwhelmed, resulting in backups, localized flooding, and increased runoff of contaminants such as bacteria and nutrients into waterways.  Also, combined stormwater and wastewater systems overwhelmed by extreme precipitation will release more combined sewer overflows (CSOs) into our rivers, lakes, and streams, degrading water quality and affecting aquatic life. At the same time, drought exacerbates the problem by lowering water levels, leading to more concentrated levels of pollutants in our waterways. These combined factors cause water quality deterioration and create major problems for water treatment plants. Already facing dwindling budgets, municipalities will have difficulty meeting water quality standards if stormwater runoff continues to increase unabated.

Fortunately, successfully managing stormwater runoff is a realistic goal with proper planning and incorporation of best management practices (BMPs). Systems that proactively develop strategies to address stormwater runoff will find themselves far better prepared to manage both increased stormwater and more stringent regulations. Stormwater management strategies include the following:

  1. Rain gardens are a beautiful and sustainable way to manage stormwater.

    Increase the use of Low Impact Development. Low Impact Development (LID), also known as green infrastructure, is a stormwater management approach that maintains natural hydrology during site development. LID minimizes impervious surfaces and utilizes existing natural site features along with conservational controls to manage stormwater. Examples of LID design include bioretention basins, grassed swales, and rain gardens.

  2. Minimize impervious surfaces. Impervious surfaces such as roads, parking lots, and rooftops prevent infiltration. Install pervious pavements on driveways and walkways, stormwater bumpouts on streets, and tree boxes on sidewalks. Also, disconnect impervious surfaces by installing grass or gravel buffer zones. Lastly, plant green roofs and roof gardens to greatly reduce stormwater runoff while enhancing the environment.
  3. Protect and create wetlands. Wetlands are of great value due to their ability to retain water and recharge groundwater. Constructed wetlands provide the same benefit as natural wetlands and help to mitigate water pollution.
  4. White clover is native to New England, drought resistant, and soft under the feet.

    Landscape with native flora. Native trees and plants provide habitat for and attract birds, butterflies, and other beneficial local wildlife, and are acclimated to local rainfall amounts and climate. Unlike turf grass, native plants require very little maintenance because they are naturally resistant to local pests and disease. Because they do not need fertilizers, pesticides, or supplemental watering, they are easy and inexpensive to maintain and are environmentally friendly.

  5. Plant trees. Trees help to manage stormwater by reducing erosion and runoff along streams and waterways. They also help to cool urban areas and improve the air quality.
  6. Separate combined sewer overflows. By separating the collection of sewage and stormwater, overflow of sewer systems and treatment plants during rainy periods prevents the mixing of the surface runoff, which is lightly polluted, with municipal wastewater, which is highly polluted.


In Conclusion

Climate change and stormwater runoff together create the perfect storm for water quality degradation. We are already seeing the effects of climate change on our nation’s infrastructure, and unless we address these complications now, we will likely find ourselves increasingly burdened by boil water orders and expensive water treatment projects. Fortunately, by proactively making some simple and largely inexpensive environmental improvements, we can protect our nation’s water bodies for future generations.

Road Salt: Taming the Beast

snowman2

Winter is fully upon us, and with it comes frigid temperatures, blustery winds, and, of course, snow. While snow brings fun to northern climates, such as ski trips, snowmen, and peppermint lattes, it also brings a toxic and dangerous contaminant: road salt. Road salt is the primary agent used for roadway de-icing, as it is both effective and inexpensive. However, it wreaks havoc on many aspects of our ecosystem, and it is imperative that we thoughtfully examine how we can protect our natural resources while still maintaining safe roadways.

What Is It?

Let’s start by looking at what road salt really is. Road salt is composed primarily of sodium (Na) and chloride (Cl); however, up to 5% of its composition is made up of ferrocyanide, an anti-caking agent that has been on the EPA’s list of toxic pollutants under the Clean Water Act since 2003, and other impurities such as calcium, potassium, iron, magnesium, aluminum, lead, phosphorus, manganese, copper, zinc, nickel, chromium, and cadmium. All of these components end up in our environment through runoff, melting, and vehicle splash, and have a profound impact on many aspects of our environment.

Water Quality

Winter_Pond_(4251468916)NaCl contamination causes water to have a higher density, and this denser water settles at the bottom of lakes and ponds, preventing oxygen from the top of the water from reaching the bottom. The bottom layer of the water is then unable to support aquatic life due to its oxygen void. Road salt contamination also adversely affects the food supply, health, and reproductive capabilities of aquatic life, disrupting aquatic ecosystems.

In addition, water contaminated with chloride is not easily treated, as only costly processes such as reverse osmosis, ion exchange, and distillation remove it. Sodium in drinking water is monitored due to health concerns in individuals restricted to low-sodium diets, and, because well contamination is often due to road salt runoff, treatment of contaminated private water supplies falls squarely on the shoulders of the Department of Transportation — an expensive responsibility. Due to the alarming increase in road salt usage over the past several years, contaminated water supplies are increasing dramatically.

Animal Life

birds in snowIngested road salt can adversely affect the health of your pets. According to the ASPCA\’s website, road salt ingestion, through drinking contaminated puddles, licking paws, or by eating it directly, can cause a myriad of health issues for your pet, from vomiting and diarrhea to seizure and death. In addition, road salt damages the pads of your pets’ feet, making them crack and bleed.

The wildlife population most negatively affected by road salt is birds. Birds eat the salt crystals directly, thinking they are seeds, and they only need to ingest a tiny amount of salt to cause toxosis and death. Also, through its destruction of vegetation, road salt causes depletion of food sources, habitats, and nesting sites for all wildlife. Aquatic populations are also susceptible to road salt contamination, particularly to the anti-caking agent ferrocyanide, which is lethal to fish species.

Plant Life

Road salt damages both aquatic and terrestrial plants by inhibiting nutrient absorption, germination, and flowering, and by causing root damage and dehydration. In fact, NaCl is a registered herbicide due to its toxicity to plants. Plants along roadways act as a protective barrier between pollutants and waters, and destruction of this natural buffer increases water pollution. Road salt also disrupts aquatic ecosystems by eliminating habitats and food supplies and by increasing the prevalence of nuisance algal populations.

Soil

Road salt negatively changes soil chemistry by reducing soil’s pH, decreasing permeability and absorption rates, damaging fertility, and killing beneficial bacteria. Affected soil also erodes at a quicker rate.

Infrastructure

rusty bridge 2Salt corrodes. We notice it mainly on our cars, but it also affects infrastructure such as bridges, support rods, and parking garages. Corrosion poses danger to the public due to compromised structural integrity of bridges and other supported roadways, and it also costs billions of dollars per year in corrosion control and repair costs.

What We Can Do

The best plan of action is to reduce the amount of salt we are using on our nation\’s roadways. And this task is certainly feasible. For example, through the Central Massachusetts Regional Stormwater Coalition (CMRSWC), Tata & Howard developed a process providing a roadway treatment calibration approach that maintains safe conditions while reducing chloride loading to surface waters:

  1. salting truckReview and evaluate the types of materials used for roadway treatment on local roadways
  2. Calculate the total loading rate of chloride (in pounds of chloride per lane-mile) presently applied
  3. Compare the calculated loading rates to the range of rates documented in literature
  4. If a community’s current chloride loading rates are statistically higher than documented values, determine if that community may benefit from efforts to alter their current practices
  5. Recommend a phased approach to achieve the potential reduced loading rate
  6. Perform calibration procedures on equipment to deliver reduced chloride loading rates

By performing these steps, CMRSWC communities have significantly lowered their road salt load, resulting in decreased municipality spending and increased environmental protection, all while maintaining safe roadways.

Conclusion

Road salt is certainly necessary, as it remains the best and most cost-effective defense against slippery, dangerous roadways. However, more care and training need to go into salt application. With combined efforts from municipalities, contractors, and engineers, we can drastically reduce the negative impact of road salt on our environment…and still make it to work on time.

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