What Can I Do to Limit My Impact on Stormwater Runoff?

Avoiding and Minimizing Harmful Chemicals

A lush lawn, beautiful flowers, and bountiful crops are every gardener’s goal. Regrettably, some achieve these by applying pesticides and fertilizers that often wind up washing right into our streams and creeks. Excess nutrients from these chemicals can cause drinking water contamination, undesirable algal blooms, and fish kills; contamination from pesticides can result in waters that are not fishable or drinkable.

Here are a few tips to help minimize the effect of chemicals on our water resources:

  • Read labels carefully. If you must apply, pay attention to the label. Look for the words slow-release, time-release fertilizer with water-insoluble or slowly available soluble nitrogen. Avoid using combination fertilizer/herbicide/pesticide products, which have excess chemicals that can pollute our water. 
  • Pay attention to where and when you work. Avoid using fertilizers or pesticides near wellheads or within 75 feet of waterways. Check the weather forecast, and don’t apply fertilizers or pesticides when there is rain predicted and the likelihood of runoff is high.
  • Fertilize sparingly; use organic/low impact practices. Apply fertilizers and pesticides as directed. The Cooperative Extension Service has recommendations for application rates if you decide to use inorganic products. Using less is good for the water supply and will save you money, too! If you use a lawn care company, ask them about environmentally friendly options and certifications.
  • Cover or store items that may contain pollutants. Avoid leaving any items outside that could release pollutants into the stormwater system or nearby waterways. This includes machinery and equipment, paints and stains, cleaning solutions, etc.
  • Practice low-impact yard care. Mow high and leave grass clippings on the lawnwhich supports health and quality and reduces the need for fertilizer. Hand-pick weeds whenever possible. If you must use herbicides or pesticides, spot treat rather than dousing the entire lawn.
  • Replace part or all of your lawn with native vegetation. Native plants increase water infiltration due to their deeper roots and provide habitat for native pollinators and other animals. Replacing part (or even all!) of your grass lawn with native shrubs, herbaceous plants and flowers can be one of the most beautiful ways to manage stormwater on your property.

Leaf Litter and Landscaping Debris

Leaf litter from stream buffers is natural in streams and is an important source of nutrients and energy to stream food webs. However, too much of a good thing can be bad. Because Carrboro’s streams and creeks drain into Jordan and University Lakes, we are regulated to limit the nutrients draining from our watershed into these water supplies. Excess urban leaf litter from yards that is directly deposited on streets can enter the stormwater system, significantly raising the nutrient load (by up to 80%[1]). This decreases water quality and can be detrimental to aquatic life. Leaves can also clog or block drains and pipes, leading to flooding, excess standing water, damage to system components, safety issues and threats to properties. Please do not place your leaves in ditches and swales or directly on the street!

The Town provides roadside leaf collection not only as a service to residents and source of mulch but also to limit the nutrients that reach creeks and Jordan Lake. Composted leaves are made available for free to the public. For more information on our compost program you can visit the Solid Waste Department’s Yard Waste page[2].

Property owners can also compost at home and adopt green landscaping techniques to further reduce the risk of overloading our storm drains and creeks with leaf litter. Residents interested in alternative lawn, vegetation and landscaping options for environmental benefits should reach out to the Town’s Environmental Sustainability Coordinator or Stormwater staff for more information. See Appendix 1 for contact details.

Pet Waste

Pet waste is a problem for the health of our waterways; it can contain bacteria, viruses, and parasitic worms that harm aquatic life and transmit diseases to humans. In Carrboro, stormwater does not pass through a sanitary sewer treatment facility. Anything on or in the ground may eventually end up in nearby streams, rivers and lakes where people recreate. When high levels of bacteria are found in a body of water, swimming, fishing and shellfish harvesting must be restricted. Pet waste also contains nutrients that cause weeds and algae to grow more rapidly than normal, changing the balance of the ecosystem.

You limit pet waste’s impact on stormwater and our streams when you:

  • Pick up after your pet. Whether at home or out and about, pet waste needs to be scooped. Long handled “pooper scoopers” make it easy to pick up after your dog without bending over. Bring plastic bags with you when you walk your dog. A map of public pet waste stations is available at [map under development]. Wherever you scoop, tie the bags securely and toss in the trash.
  • Double-bag kitty litter. Cat waste is an issue, too, so double-bag the litter, tie the bags closed and place in the garbage.
  • Avoid flushing pet waste down the toilet. Septic systems and wastewater treatment plants are not designed to treat dog or cat waste.
  • Compost pet waste with great care. The disease-causing organisms in pet waste are not killed by backyard composting.
  • Watch what you feed your pet. The type of food affects the quantity of pet waste you must deal with. Consult your vet if you have any questions.

Figure 12. Carrboro’s Pet Waste Initiative

For more information on pet waste and its effect on stormwater please see visit the Stormwater Division’s Pet Waste webpage[3] or contact us as shown in Appendix 1.

Pools and Spas

Discharging wastewater from swimming pools and spas into the stormwater system or surface waters is against the law because it can be hazardous to the environment and public health (Figure 13). Common pollutants associated with pool and spa draining include chlorine, bromine, copper, salt, hydrogen peroxide, and acids. 

Figure 13 Improper Discharge of Pool Wastewater

Pool and Spa Maintenance

Plastering, grouting, guniting, acid washing and other activities generate wastewater that cannot be discharged into the storm drain system. Do not wash out equipment and tools used for maintenance work in an area that discharges to the storm drain system. Collect and store the wastewater and contact an environmental waste company regarding treatment and disposal. Contact OWASA[4] regarding their rules for disposal into the sanitary sewer system. 

Filtering Backwash

Discharge filter backwash onto a landscaped area, not into the storm drain system, and put filter material and collected debris in the trash. Rinse filters over your lawn or landscaped area. This allows for clean, dechlorinated water to re-enter our local water systems without damaging our drinking water supply or impacting the ecosystem surrounding Carrboro.

Pool and Spa Draining

Clean, dechlorinated water may be drained to your yard or landscaped area if and only if:

  • It does not cause flooding or other nuisance conditions on adjacent properties (notify your neighbors first!)
  • You drain at slow rate, allowing the water to percolate into the ground, to prevent soil erosion and discharge into the storm drain system or creek.

This may be difficult to do because most properties are designed to drain off site. If discharge into a storm drain or water conveyance is needed, contact the Carrboro Stormwater Division[5] for guidance in advance of work.

Vehicle Maintenance

Routine vehicle maintenance is a leading contributor to stormwater pollution. Runoff from rain carries pollutants like detergents, soaps, oil, antifreeze, gas, transmission fluid and other products into local waterways. These pollutants are harmful to people and the natural aquatic ecosystem. You can reduce the impact of vehicle maintenance and protect local waterways with these practices:

  • Perform vehicle maintenance in an area where chemicals and fluids won’t be washed into a storm drain.
  • Check all vehicles, including motorcycles, watercraft and outdoor recreational vehicles for fluid leaks. Use drip pans to capture leaks until they can be addressed.
  • Immediately clean up any chemical leaks and spills with an absorbent material such as cat litter. Do not hose down.
  • Cover dirty or leaky vehicles to keep rain from falling on them and creating runoff.
  • Change vehicle fluids carefully, using a funnel and drip pan to contain spills. Drain fluids from vehicles and parts before storing.
  • Wash vehicles at a car wash where used water is recycled and does not generate runoff.
  • If you wash vehicles at home, park them on the lawn so rinse water is absorbed into the grass. Use a trigger- or twist-style hose nozzle to prevent unnecessary water use. Choose waterless car cleaning products or phosphate-free, biodegradable soap.
  • Dispose of household hazardous waste and electronics properly. Please visit the Carrboro Hazardous Waste[6] or Orange County Hazardous Waste[7] websites for more information.

Reducing Runoff

In addition to pollutants in runoff, the excess volume and flowrate of urban stormwater is also a problem. The shared goal for the Town and residents is to improve the quality of runoff and reduce the quantity and velocity of the water running off property – to lower and slow the flow. Luckily, there are many ways homeowners can contribute:

Replace impervious surfaces. Take a look at the hard surfaces around your home that don’t absorb water, like your roof, driveway, patio, or deck. Since the rain can’t soak into the soil as it would in a natural system, the result is more runoff. You can alleviate runoff by replacing these surfaces with permeable materials, directing roof flows to pervious surfaces, and disconnecting downspouts from the stormwater conveyance system (i.e. allow water from your downspouts to flow across a vegetated area, like your lawn).

Improve soils to increase infiltration. Many yards have heavy and compacted soils with little organic matter and very shallow root zones. Soil improvement is one of the best and most applicable watershed-friendly practices that homeowners can pursue. This can be achieved by adding organic materials, such as compost and leaf mulch, to topsoil. You can also replace shallow-rooted turf grass with deeper-rooted native perennial and woody vegetation.  In some cases, compacted soils need to be physically loosened to allow plants to establish and thrive.

Manage roof runoff. Capturing roof runoff during a storm reduces the amount of water running off and the destructive erosion caused by the volume and velocity of flowing water in an urban environment. You can store roof runoff in cisterns or rain barrels and reuse it, or simply allow it to slowly drain into the ground; create swales that direct water to a rain garden, landscaped area, or stream buffer; or install dissipaters or splash pads at the outlet of downspouts. Please note that roof drains should not be directly connected to the roadside public drainage system.

Create a rain-friendly yard. A rain garden is an easy and attractive way to capture runoff, especially when paired with gutters and downspouts. These shallow areas can be planted with herbaceous and woody vegetation that helps infiltrate and filter water into the ground. This helps to replenish the aquifer and slow the flow to local waterways.

Choose native plants. Adapted to the local climate, native plants are more drought- and flood-tolerant than their non-native counterparts and often require less fertilizer and pest control. Many native plants have deeper and more efficient root systems that can better absorb rainwater and control erosion. The NC State Cooperative Extension maintains a list of suppliers of native pollinator plants on their website[8].

Investigate earth-shaping. Regrading or earth-shaping may be necessary for some runoff issues. A system of swales (small dips in the ground) and berms (areas of raised earth) can slow the flow and prevent runoff. Terracing, a system of gradual steps across a slope, helps reduce erosion. Dry stream beds can be created as an alternative to a swale. Major earthworks projects like adding a retaining wall or disturbing a large area may require a permit or engineering plans, so contact the Planning, Zoning and Inspections Department[9] to learn more. See Appendix 1 for contact information.

Maintain a buffer. If your property borders a body of water, use native plants to create a buffer along the waterway that can remain undisturbed. This area supports filtration and lowers the concentration of pollutants and other harmful substances entering the waterway.

Water flowing over yards, driveways, and streets during storms carries everything it comes in contact with – eroded soil, pesticides, fertilizers, oil and grease, leaves, and litter – into storm drains and streams. Even small rainstorms can wash pollutants into waterways. Small changes in yards across town add up to a big impact on both the quantity and quality of our stormwater runoff.

Home Maintenance

Here are some easy, proactive steps property owners can take to address and even ease potential stormwater issues:

  • Do not dump or throw anything into swales or streams. Dumping grass clippings, leaves, trash, yard debris, etc., can accumulate and clog swales, culverts, and channels. This is a violation of Town regulations subject to enforcement action. Keep all swales clear of brush and debris.
  • Property alterations may require permitting. Before you build on, alter, re-grade, or add fill material to your property check with the Zoning Division in the Planning Department. Staff can determine if your project needs a permit and may be able to advise if it may make your or your neighbor’s property more susceptible to flooding.
  • Remove or secure items that can be carried by water flow or the wind. Toys, sports equipment, pots, yard décor, and outdoor furniture often make their way into stormwater conveyances and waterways. This can clog stormwater flow, contribute to pollution and cause damage and drainage issues.
  • Make your property unfriendly to mosquitos. It only takes about or even less than a week for mosquito eggs to hatch from standing water. Reduce mosquitoes and bites by dumping standing water around your yard once a week and placing fine mesh screens over rain barrel openings. Don’t use treatments that may kill mosquito predators as well. For more information on mosquito control visit the Orange County Mosquito Control webpage[10].

[1] Source: “Using leaf collection and street cleaning to reduce nutrients in urban stormwater”, Upper Midwest Water Science Center, 2016

[5] Phone number: 919-918-7426 or stormwater@townofcarrboro.org