Stormwater Pollution and Treatment Education
Importance of Stormwater Care
Pollution from stormwater runoff is a major concern, especially in urban and sub-urban areas. Rainwater washing across streets and sidewalks can pick up spilled oil, detergents, solvents, de-icing salt, pesticides, fertilizer, and bacteria from pet waste.
- Drainage- Aspen’s stormwater drains do not channel water to a treatment facility. Though a good majority the urban core is carried to the Jennie Adair wetlands, a bio-engineered detention area, before making its way to the Roaring Fork River, the remainder of the city’s runoff flows directly into the Roaring fork river, Hallam lake, and other neighboring waterbodies within the city limits.
- Surface Pollutants & Runoff- Most surface pollutants are collected during the first one-quarter inch of rainfall or "first-flush" in any storm or snowmelt event. This is the period when the majority of pathogens, sediment, waste, and debris are picked up by flow across lawns and roadways. The runoff is then carried untreated into waterways, these materials become "non-point source pollutants" which can increase algae content, reduce aquatic life, and require additional costly treatment to make the water potable for downstream water systems.
Best Management Practices
Best Management Practices (BMPs) are actions done to control water pollution and improve water quality. Throughout Aspen many BMPs are implemented to reduce runoff and keep pollutants out of the Roaring Fork River. Below is a summary of BMPs that are utilized in Aspen. Further information on BMPs can be found in the Urban Runoff Management Plan in the sections listed with each summary.
- Street Sweeping- Street sweeping plays an important role in keeping pollutants out of stormwater. Debris, dirt, sand and silt collect in gutters and along the sides of streets. Sweeping and collecting this material keeps it from entering the river.
- Vaults- The city of Aspen has installed vaults to help improve stormwater quality. Sediment stays suspended in water when water moves. You can visualize this by picturing a jar filled with water and dirt. When you shake the jar the dirt mixes with the water and the water becomes murky. However, if you leave the jar sitting on a table the dirt will eventually settle to the bottom. Stormwater vaults work in the same manner. Water running off the streets is turbulent, mixed, and carries high concentrations of sediment. When the water reaches a vault a couple things happen that remove unwanted pollutants. First, the water passes through a trash rack. A trash rack is a series of bars that stop large debris. The water also slows down greatly. The water is deep and slow moving. This allows sediment to settle to the bottom of the vaults. The water then has to pass under a structure which essentially “skims off” any pollutants floating on the water. This helps keep oil and gas, which floats on top of water, out of the river. At the end of the vault a structure comes up from the bottom of the vault. Only water on top pours over and out of the vault. This keeps the sediment on the bottom from flowing out of the vault. Aspen has vaults located above the Jenny Adair wetlands located on the south side of Puppy Smith Street, as well as underneath the parking area in the Rio Grande Recycle Center. The Jenny Adair vaults treat stormwater that drains from nearly the entire town west of Mill St, while the Rio Grande Recycle Center treats drainage from the east and middle portion of town as well as drainage from Aspen Mountain’s two major gulches, Copper and Spar.
Section 184.108.40.206 of the Urban Runoff Management Plan (PDF) has more information and specific requirements for stormwater vaults in the City of Aspen.
Bioengineered Wetland - Jenny Adair Wetlands
A constructed wetlands basin is a shallow retention pond that has a continuous base flow which promotes the growth of rushes, willows, cattails and reeds. The shallow pond, along with vegetation, slows down runoff and allows time for sedimentation, filtering, and biological uptake. Wetlands greatly improve water quality while at the same time providing natural aesthetic areas, increasing wildlife habitat, and providing erosion control. Constructed wetlands are engineered to mimic natural wetlands which can be viewed as the “kidneys” of the hydrologic cycle due to their filtering and cleansing capabilities.
More information on constructed wetland basins can be found in section 220.127.116.11 of the Urban Runoff Management Plan (PDF).
When managing stormwater the main objective is to reduce runoff and increase infiltration. There are a variety of ways this can be accomplished in residential areas. Below is a list of helpful techniques that can be implemented.
- Direct downspouts to previous areas. A significant amount of water is collected on roofs. By way of gutters and downspouts, this water can be directed to pervious areas, such as lawns or gardens, where it can infiltrate into the ground instead of running off over impervious areas.
- Minimize impervious areas. This can be done by reducing the size of paved areas, patios, walkways, and parking areas. If a paved area needs to be repaired, consider using permeable pavers, or gravel instead of concrete or asphalt.
- Use a broom instead of a hose. When cleaning your driveway or other paved areas, consider using a broom and collecting the debris instead of washing the area with a hose. When driveways are washed with a hose, all the debris and pollutants get washed directly into the stormwater system, which deposits the pollutant filled water into the river.
- Take your car to the car wash or wash it over a grassy area. Detergents used for car washing can be very harmful to river ecosystems. Car wash facilities have the proper infrastructure to handle contaminated water. The water is treated before it is released back into the ecosystem. Taking your car to a car wash is the best option, but if you do wash your car at home, wash it over a grassy area and not in the driveway or over pavement. By washing your car on the grass it keeps detergents out of the stormwater system. Soapy water is allowed to infiltrate into the grass. This is a much better option than depositing the water into the river. It is also helpful to reduce the amount of soap you use and wash with mild detergents that are labeled as “biodegradable” or “phosphate free.”
- Keep your vehicle well maintained. Any leaks or debris that comes from your car will get washed by the next rainstorm down to the river. By keeping a well maintained car, you can help keep these pollutants out of the water.
- Clean up after your pet. If pet waste is improperly disposed of it can be picked up by stormwater and carried to a storm drain and nearby water body. Feces carry bacteria, viruses, and parasites that are unhealthy both for wildlife and humans. Feces that are carried to the river can make recreational users of the river very sick. Always properly dispose of pet waste in your own yard as well as throughout town. The city of Aspen has pet waste stations that provide bags and waste receptacles, making it easy to clean up after your pet.
Whenever anything is built, construction disturbs the soil in which the site sits. This dug up and disturbed soil is no longer held in place and can easily be washed into the stormwater system by a runoff event. High concentrations of sediment can greatly damage river ecosystems, thus sediment from construction sites must be controlled and kept out of stormwater drains. Drain covers, silt fences, sediment barriers, hay bales, and soil covers must be used to keep sediment from construction on-site and out of the river.
- Drain Covers- Drain covers cover stormwater drains that are near construction sites. These covers prevent larger sediment from entering the drain, while still allowing water to pass. This is a temporary solution as the covers quickly fill with sediment and can clog if left too long.
- Silt Fences- Silt fences are placed along the perimeter of a construction site or anywhere runoff could carry sediment away from the construction site. Silt fences don’t filter runoff but rather cause runoff to pool behind the fence. Sediment then settles in these small pools of water and is kept on-site. It is important the silt fences are properly installed and maintained to be truly effective.
- Soil Covers- It is important to cover any piles of soil during construction. Loose uncovered soil is easily carried away by rain.
Low Impact Development (LID) aims to mimic the natural, pre-development hydrologic pattern. The goal is to manage stormwater as close to its source as possible. In the past the driving force behind stormwater management was exclusively to move water away from buildings and streets as quickly as possible without any regard to water quality. This meant using pipes and gutters to direct water to detention ponds, retention basins and rivers.This technique has caused significant damage to water quality and the environment.
Water Quality Improvement With LID
Without any contact with soil or plants, stormwater has no chance to deposit any of the contaminants that it carries. These contaminants are brought to the river and carried to the next town downstream. To improve water quality people began implementing Low Impact Development. LID is a relatively new approach that began in Maryland in 1990. To treat stormwater near its source a variety of methods are used, but the main objective is to create small scale projects throughout the town to treat stormwater instead of costly large scale projects that do not have the capability to treat stormwater as efficiently.
LID aims to increase the time water is in contact with soil and plants before it reaches the river. Plants and soil essentially work as a filter and remove pollutants. LID also allows water to infiltrate into the ground which recharges the water table.
Examples of LID Projects
- Bioretention Areas
- Green Roofs
- Green Streets
- Green Swales
- Permeable Pavers
- Rain Gardens
Low Impact Development can be seen throughout Aspen. Find examples and pictures of these practices in Aspen.
Grass Swales & Grass Buffers
Grass swales are densely vegetated drainage ways. These swales slow down and filter stormwater. Grass swales can be seen throughout town in residential areas. Grass Buffers are similar to Grass Swales, but buffers are designed to treat sheet flow instead of concentrated or channelized flow. As water flows over grass buffers the water slows down which allows sediment to settle.
More information on grass swales and grass buffers can be found in sections 18.104.22.168 and 22.214.171.124, respectively, in the Urban Runoff Management Plan (PDF).
Impervious areas cause large amounts of runoff. This means the stormwater system has to deal with a much larger quantity of water. The higher runoff also carries more pollutants through the stormwater system and to the river. Pervious pavers allow water to infiltrate through the surface, while still providing a stable and flat paved area.
Near the John Denver Sanctuary by the Theatre Aspen tent, pervious pavers have been installed. The pavers look great while improving the quantity and quality of stormwater in Aspen.
More information on pervious pavers can be found in section 126.96.36.199 of the Urban Runoff Management Plan (PDF).
In areas that are only occasionally used for parking, grass pavers are a great alternative to pavement. Grass pavers stabilize and reinforce grassy areas. This allows bikes, cars, and trucks to pass over the area without damaging the grass. Grass pavers are constructed with either concrete or plastic and are designed with void spaces that allow grass to grow.
More information on reinforced grass pavement can be found in section 188.8.131.52 of the Urban Runoff Management Plan (PDF).
Above Ground Conveyance
Through the center of the Hyman Avenue Mall water is conveyed above ground. This stream collects stormwater and allows contact with the soil and plants along the bank instead of conveying the water underground through a pipe. On N 7th street, between Hallam Street and Main Street, water is directed from the street gutter to pervious areas.
Types of Pollutants
Harmful Waste Bacteria- Pet, wildlife and human waste all carry harmful bacteria. When collected by runoff, the waste is easily transported to nearby waterways. This bacteria contaminates water and can cause diseases and dangerous infections in both people and animals.
Properly Dispose Pet Waste- Please pick up after your pet and dispose of waste properly in the toilet or trash. Aspen has biodegradable pet waste bags strategically placed around the City's open space and trails. Failure to pick up after your pet is a ticket-able offense in Aspen. If you have a septic system, follow proper maintenance procedures to prevent overflow or seepage. If you suspect a sanitary sewer is malfunctioning, contact your local authority immediately.
Water Runoff Caries Chemicals & Metals- Runoff picks up chemicals, metals, and other toxic substances on our streets, roofs, and lawns. These substances combine with our fertilizers, corrosive dusts from vehicles, as well as household chemicals and cleaning agents to form harmful compounds that infect our water bodies.
Correct Storage & Maintenance- Do your part by storing chemicals away from rainwater in a covered location that is raised off the ground and always dispose of chemicals properly. Never dump soap or other washing substances down a storm drain. Maintain vehicles so they don’t leak and wash your car over grass or gravel so water can infiltrate instead of running off into a storm drain.
Hard Surfaces Increase Runoff- Unfortunately, the word development is associated with concrete and other hard or impervious surfaces. Sidewalks, driveways, parking lots, all change the natural path rainwater takes upon contact with the surface. Instead of soaking into the ground or infiltrating, rainwater is “run off” the impervious concrete surfaces. As more and more natural space is converted into developed area, the runoff increases. This increased runoff creates a greater volume of stormwater pollution to our local water bodies.
Improved Development Techniques- Development is a natural part of progression and though it is inevitable, progressive ideas have made development’s impact on stormwater and runoff greatly reduced. Consider using permeable surfaces or rain gardens instead of concrete and roof gutters.
Harmful Overuse of Fertilizers- Though fertilizers help plants grow, when used in excessive amounts, fertilizers can harm water quality and aquatic ecosystems. Fertilizers are high in phosphorus and nitrogen. When it rains, these nutrients are carried by stormwater and their conveyance system into water bodies like the Roaring Fork River. Nutrient overload causes algae to bloom, decreasing the amount of oxygen in the water and suffocating aquatic wildlife causing fish to die.
Practice Thinking Ahead & Thinking Green- Think of the people downstream and the health of our waters when applying fertilizer. Practicing environmental stewardship starts at home. Everyone loves a beautiful lawn however there are plenty of environmentally safe products one can choose to replace common fertilizers. Think Green!
Harmful Effects of Litter- Litter is pollution. When thrown on the ground, it can end up in our storm drains, ditches, and streams. Stormwater runoff carries and collects this litter and delivers it directly to our rivers and lakes. Most litter takes hundreds of years to biodegrade and can be harmful to birds and animals as they become entangled or mistake the trash for food.
Recommended Environmental Action- Make a concerted effort to throw all litter in trash cans. Leave no trace when on hiking trails. Keep your litter out of pickup truck beds or places where litter could easily blow away. Do your part when you can, pick up the trash around you as it helps the environment and keeps Aspen beautiful. Lastly, always remember to recycle and reuse whenever possible.
Sediment Pollution Process- Did you know that sediment is the Number 1 National pollutant source? Sediment is commonly picked up in rain and snowmelt runoff as well as during stream erosion when swiftly moving stormwater scours away stream beds and erodes stream banks increasing sediment load within the river. Increased sediment has a devastating effect on our rivers ecosystems. It not only carries harmful pollutants such as phosphorous, it buries aquatic insect life and suffocates fish.
Suspended Solids - Sand- In Aspen, the concentration of suspended solids in stormwater runoff is of special concern. At times the amount of total suspended solids measured in stormwater runoff has been over 55 times the national average. There are three main contributors to the high levels of sediment in Aspen stormwater. The first is due to the steep nature of the area. The slopes that surround Aspen are more likely to erode. Because of the steep terrain, soil is likely to be carried by runoff. Construction that disturbs soil within the city limits is another contributor of sediment in stormwater. Sand that is used to de-ice roads also eventually ends up in the river. In the spring, when roads begin to thaw, all the sand used throughout the winter is collected by stormwater and carried to the river.
Silt fence along a ridge line next to a river Reducing Impact- Certain measures have been taken to reduce the amount of sediment that enters the river system. Aspen's Urban Runoff Management Plan details the measures developers must take to ensure no sediment leaves their site. These actions help prevent sediment from getting to impervious surfaces outside the construction site where they can be easily washed away into storm drains and local water bodies. Installing silt fences, drain covers, hay bales, and covering piles of loose sediment during construction are all techniques used to keep sediment out of stormwater.
Drain cover at curbside Stormwater Vaults- The City of Aspen also has stormwater vaults located above the Jenny Adair Wetlands, and at the Rio Grande Recycle Center. These vaults hold storm water which allows sediment to settle to the bottom. The water is then released to the river with a much lower concentration of sediment.
Sweep Instead of Washing- It takes the effort of everyone within Aspen to clean up after themselves and keep sediment out of stormwater and out of the river system. Instead of washing driveways into the street, take the time to sweep up sediment and dispose of it properly.
Chemicals & Metals Shed From Vehicles- Vehicles are a large source of many pollutants within stormwater. Oil, Antifreeze, and other fluids leaking out of cars onto pavement become major hazards for our water bodies. Even more, copper and other common heavy metal dust are produced during normal automobile use. These fine particulates settled onto paved surfaces and add to the vehicular impact. In Aspen, mud and salt from winter operations are a serious threat to the Rivers and Lakes. These pollutants not only damage the underbelly of your automobile, they combine with other engine discharges and pollutants to form harmful compounds that are even more detrimental to our aquatic ecosystems.
Maintenance Recommendations- Make sure to regularly maintain your automobile, especially in the winter. When washing your vehicle make sure to do so in designated areas where washing water will travel to a sanitary sewer rather than a storm drain or swale. Washing your automobile over grass or gravel is another great way to promote infiltration and prevent runoff.
The City of Aspen participates in the National Flood Insurance Program (NFIP) and encourages all owners with land in the 100 year floodplain to visit floodsmart.gov, the official site of the NFIP, to receive more information on flood insurance.
If you are unsure if your property resides in the 100 year floodplain, the digital images of the Flood Insurance Rate Maps or FIRMs linked below should provide some indication or you can call the Engineering Department for assistance at 970-920-5080. Interactive digitized floodplain maps or DFIRMs will be available in 2012.
Please visit the Pitkin County High Water Runoff Resources website page, for information on preparing for the upcoming runoff and high-water season. You can monitor flows in real-time by checking local USGS gages at Roaring Fork at Stillwater Bridge and Hunter Creek at Rio Grande pedestrian bridge.