Chapter 2: A Two Pronged Solution

The Stormwater Solutions Team identified two major approaches to reducing impacts of stormwater runoff:

1. Improving the way stormwater is managed by promoting green infrastructure and other best management practices
2. Reducing the sources of pollutants commonly found in stormwater
   

Excellent work toward these ends is already taking place in many of Oregon’s cities and towns. The Stormwater Solutions Team seeks to promote and expand upon these efforts, to create a shift so that sustainable stormwater management and pollution prevention become standard practice throughout Oregon.

Sustainable Stormwater Management

 

A rain garden at Villebois, a 500-acre community currently under construction in Wilsonville

Conventional stormwater systems with pipes, detention ponds and drywells manage stormwater as a waste product and were designed to convey water as quickly as possible away from developed areas; protecting water quality and stream health was not a priority when they were designed. The unintended consequences of conventional stormwater systems include increased runoff, higher flood potential, system overflows, and the transport of pollutants to streams, rivers, wetlands, and groundwater. Modern approaches to stormwater management slow the water down near its source, filter out pollutants, and allow the cleansed water to infiltrate into the soil and recharge groundwater supplies, maintaining the natural hydrologic regime of a watershed. The terms “green infrastructure” and “Low Impact Development” (LID) describe stormwater systems and site development practices designed to maintain or restore the natural, pre-developed ability of a site to absorb and filter stormwater.

Low Impact Development

Shallow, grassy swales like this one can be found in new neighborhoods in the City of Boardman, in eastern Oregon. They capture water from the street and the residence on a right of way that is designed to be indistinguishable from the front lawn. The sidewalks are angled to drain toward the swale, away from the street.

According to the Low Impact Development Center: “LID is an innovative stormwater management approach with a basic principle that is modeled after nature: manage rainfall at the source using uniformly distributed decentralized micro-scale controls. LID's goal is to mimic a site's predevelopment hydrology by using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source. Techniques are based on the premise that stormwater management should not be seen as stormwater disposal. Instead of conveying and managing / treating stormwater in large, costly end-of-pipe facilities located at the bottom of drainage areas, LID addresses stormwater through small, cost-effective landscape features located at the lot level. LID is a versatile approach that can be applied equally well to new development, urban retrofits, and redevelopment / revitalization projects. The LID approach includes five basic tools:

1. encourage conservation measures (i.e., preserving natural areas)
2. promote impact minimization techniques such as impervious surface reduction
3. provide for strategic runoff timing by slowing flow using the landscape
4. use an array of integrated management practices to reduce and cleanse runoff
5. advocate pollution prevention measures to reduce the introduction of pollutants to the environment ”

Green Infrastructure

 

Salem’s Pringle Creek Community is one of Oregon’s most low-impact residential developments. 30% of the site is public open space, 80% of trees were saved, and the neighborhood has the largest pervious asphalt street system in the United States.

Green infrastructure is the term the U.S. Environmental Protection Agency (EPA) uses to describe a similar concept. According to the EPA, “Green infrastructure techniques utilize natural systems, or engineered systems that mimic natural landscapes, to capture, cleanse and reduce stormwater runoff using plants, soils and microbes. On the regional scale, green infrastructure consists of the interconnected network of open spaces and natural areas (such as forested areas, floodplains and wetlands) that improve water quality while providing recreational opportunities and wildlife habitat. On the local scale, green infrastructure consists of site-specific management practices (such as rain gardens, pervious pavements, and green roofs) that are designed to maintain natural hydrologic functions by absorbing and infiltrating precipitation where it falls. ” In March 2007, EPA Assistant Administrator Ben Grumbles issued a statement of support for states using green infrastructure to manage stormwater and protect water quality (see appendix).

As you can see from the above definitions, the terms “Low Impact Development” and “green infrastructure” are used to describe essentially the same concept. In this report we also use the term “sustainable stormwater management” to encompass LID, green infrastructure, and other best management practices that reduce urban runoff pollution. Sustainable stormwater management practices are beginning to be used throughout Oregon and the Pacific Northwest. Following are a few illustrative examples.

Bioretention: rain gardens and bioswales 

Bioretention is the basic process at the heart of green infrastructure, and it can be applied in many different circumstances. Bioretention is an engineered process to manage stormwater runoff using plants, soil and microbes to filter, infiltrate, store, and absorb runoff. Its application can be simple or complex, and it takes the form of swales, rain gardens, stormwater planters, vegetated parking strips, and planted curb extensions. It is extremely versatile because it can be incorporated into landscaped areas with many design possibilities that may provide additional social and environmental benefits such as wildlife habitat, open space, traffic calming, reducing the heat island effect, and increased property values. Both lab and field studies have found that bioretention facilities effectively remove stormwater pollutants, particularly heavy metals; they are moderately effective at removing nitrogen and phosphorous. ^33,34

 

These street planters on SW 12th Avenue on the Portland State University Campus were designed to capture and infiltrate approximately 8,000 square feet of street runoff while still maintaining strong pedestrian circulation and on-street parking in a completely built-out urban environment.

Maintenance of bioretention facilities is similar to that required of any landscaped area. Owners should remove debris, ensure that inlets and outlets are not blocked, and trim and replace plants and remove weeds as necessary. Chemical fertilizers and pesticides should not be used in stormwater facilities. The most critical aspect of maintenance is to inspect the facility on a regular basis to ensure that it is functioning well, and that it has not been filled in or altered.

Green Streets

Since streets often make up more than half of the impervious surface area in a city, using bioretention facilities to treat stormwater from streets can significantly reduce urban runoff. Streets with bioretention facilities are often called “green streets."

There are many different approaches to integrating these facilities into the right of way, depending on the needs of the site. Bioretention can be a very cost-effective approach to managing stormwater from streets and parking lots. For example, when the Oregon Museum of Science and Industry (OMSI) developed its new location, the City of Portland asked them to redesign the site’s parking lot to treat the 522,000 cubic feet of untreated stormwater runoff that was discharging directly to the Willamette River annually. They converted the existing landscaped islands to vegetated swales. OMSI saved about $78,000 in construction costs by using swales instead of installing a traditional stormwater management system such as drywells.³⁵

Pervious pavement

Pervious pavement is a permeable pavement surface, often built with an underlying layer of stone or gravel that temporarily stores surface runoff before it infiltrates into the subsoil. Pervious pavement replaces traditional pavement, allowing stormwater to infiltrate and pollutants to be filtered out. One of the greatest advantages of pervious pavements is that they disperse stormwater instead of concentrating it, similar to a natural system. There are various types of pervious surfaces, including pervious asphalt, pervious concrete, and even grass or permeable pavers.

Pervious asphalt and concrete contain little or no "fines" or sand. By eliminating these smaller particles in the concrete or asphalt mix, voids are created that allow water to pass through. The result looks similar to a rice krispie treat (photo). Permeable pavers are interlocking concrete blocks where the voids are filled with sand or planted with grass to allow water to flow through.

In addition to allowing water to infiltrate, pervious pavements provide water quality treatment. Particles get captured in the pavement or in the top layers of the soil or gravel underneath the pavement as water trickles through. Studies of pervious asphalt, pervious concrete, and concrete pavers show that they remove 50-98% of suspended sediments and associated particulate lead, cadmium, copper and zinc.^36,37,38 In addition, pervious pavements degrade oil pollutants through the biochemical activity of bacteria and fungi that use the pavement and accumulated solids as a substrate. The oils are broken down and disperse safely into the atmosphere as carbon dioxide and water . Studies have shown that 97-99% of applied motor oil is trapped in pervious pavements and biodegraded. ^40,41

Like all best management practices, pervious pavement should be combined with other practices to capitalize on each technology's benefits. For instance, a small facility using pervious pavement may only need several bioretention basins or a grass swale, rather than a large detention basin. This combined approach might prove less land intensive and more cost effective. Pervious pavements are commonly used in low-traffic parking lots, and they can sometimes be used in higher traffic areas. They are currently used as a top layer on some highways, to reduce hydroplaning. Pervious pavement may be inappropriate for areas where heavy accumulation or spills of pollutants may occur.

Green roofs

A green roof, which may also be called an “ecoroof” or a “living roof”, is a vegetated roof system. An ecoroof consists of a synthetic, waterproof membrane, a drainage layer, and a thin layer of soil or growing medium. Low-maintenance, drought-tolerant plants such as sedums, succulents, and certain grasses make up the vegetation that grows on ecoroofs. They may require irrigation during the establishment period and possibly during drought conditions. An ecoroof can capture and evaporate 10-100% of the precipitation that falls on it, and provides the additional benefits of cooling the building and providing habitat for insects and birds.

Green roofs can be located on flat or pitched roof structures at a slope up to 40% (or 5 in 12 pitch). They can be used on most types of commercial, multifamily, and light industrial structures, as well as single-family homes and garages. Although ecoroofs initially cost more to install than conventional roofs, they are competitive on a life-cycle basis because of reduced maintenance and replacement costs. As the ecoroof market develops, installation costs may decrease. The typical lifespan for an ecoroof is about 40 years, significantly longer than most conventional roofs. This is because the membranes are of good quality and the plants and growth medium protect the membrane from weathering.⁴²

Rainwater harvesting

Rainwater is a valuable resource that can be harvested. Although used throughout the world for many purposes, rainwater harvesting is lesser known in the Pacific Northwest. However, it is gaining traction as an important stormwater management tool and as a water conservation strategy. Rainwater storage systems vary from simple rain barrels to systems capable of storing tens of thousands of gallons. Small rainwater harvesting systems like rain barrels are important awareness-raising tools. However, since a 1,000 square foot roof that receives Portland’s average 36 inches of rain per year will capture about 20,000 gallons of water per year, larger storage is necessary for most applications.

Anyone can harvest up to 5,000 gallons of rainwater and use it for outdoor irrigation without a permit. Large cisterns holding 5,000 gallons or more require assurance that the system will be placed on stable soil and that its weight will not cause structural damage to foundations. A special permit may be required to use rainwater indoors for potable or non-potable purposes. Rainwater harvested for potable uses must be treated to drinking water standards.

Rainwater harvesting reduces stress on surface waters and groundwater by providing an alternative water source for human uses, and it mitigates high urban runoff volumes. It is conceivable that if rainwater were harvested on a massive scale it could alter the natural hydrology of a watershed, but at currently feasible levels of adoption rainwater harvesting is beneficial to water supplies and natural systems.

Tree planting and retaining natural vegetation

Trees capture and hold rainfall in leaves and branches. They slow runoff flow and can decrease stormwater volume by 35% or more for small storms . Mature trees also reduce noise levels, provide shade, filter airborne pollutants, capture carbon dioxide, provide wildlife habitat, and increase property values. Planting trees and protecting existing trees can reduce stormwater runoff. During construction it is critical to reduce soil compaction, which is the leading cause of the death or decline of mature trees in developed areas . While trees are a vital part of a healthy stormwater system, their leaves and needles can clog storm drains. Street sweeping can help reduce the accumulation of leaves.

Site design

A development’s initial design can reduce its impacts on nearby streams. Building narrower streets reduces impervious surface area. Clustering units together can protect open space and natural areas on another part of the site.

Proprietary stormwater devices

In instances when green infrastructure solutions are not feasible, proprietary stormwater devices may be used to reduce the impacts of stormwater runoff. Private manufacturers have developed a wide variety of devices to detain and/or filter pollutants out of stormwater runoff. Some may be installed in existing stormdrains and pipes. They often include filters that must be regularly replaced in order to maintain effectiveness, which increases long-term costs. As with many other stormwater facilities, it can be difficult to ensure that proper maintenance occurs when the devices are used on private property.

Encouraging stormwater retrofits

Retrofits of stormwater systems in already urbanized areas are most often installed when redevelopment is already occurring for some other reason. Otherwise, they can be difficult to fund and incentivize. The city of Portland is exploring the feasibility of establishing a market-based stormwater credit trading system to encourage stormwater retrofits of already developed private properties.

Pollution Prevention

Low Impact Development is a critically important tool in reducing urban runoff. At the same time, we must also reduce the amount of pollutants that enter stormwater in the first place. OEC worked with the Stormwater Solutions Team to conduct an online survey of government staff, stormwater engineers, landscape architects, developers and builders, and environmental advocates to identify barriers and solutions for sustainable stormwater management. Over 150 people participated in the non-scientific survey. See the appendix for detailed survey responses. Survey respondents identified the following four urban stormwater pollution sources as those most in need of additional attention:

1. Oil and fluid leaks from vehicles. Vehicles from time to time leak oil, grease, antifreeze or other fluids on roads and parking lots, and those fluids are picked up by stormwater. These leaks could be very minor in the case of a leaking hose or major if the seals in the motor or transmission are leaking. Evidence of these leaks can often be seen during a rain event as a rainbow on the pavement or a grease spot in a parking space.
2. Erosion from construction. Erosion from construction sites continues to be a problem even though the Oregon Department of Environmental Quality’s (DEQ) Construction General Permit (known as the 1200-C permit) has been in effect for six years. In addition, cities with stormwater permits are implementing construction programs in their communities (see Chapter IV, The Regulatory Context). Education, inspection and enforcement are urgently needed to ensure that contractors install and maintain Best Management Practices (BMPs) to reduce sediment runoff from construction sites.
3. Dumping wastes in storm drains. While intentional or accidental spilling or dumping of wastes directly in stormdrains is infrequent, when it does happen, the impacts can be very harmful, sometimes resulting in fish kills.
4. Urban use of pesticides and fertilizers. Homeowners use up to ten times more pesticides per acre on their lawns than farmers apply to their crops per acre . Excess application of pesticides and fertilizers washes into the stormwater system and degrades water quality. A number of educational programs exist to reduce the use of these chemicals, but they continue to contribute to stormwater pollution.
   

The Stormwater Solutions Team also noted that heavy metals, which enter stormwater from automobiles and roof runoff, are another important stormwater pollutant.

Following are some of the practices that can reduce stormwater pollution. Many local governments have educational programs to help reduce these pollutants, as a component of their municipal stormwater permit programs.

Proper auto maintenance

When oil and other fluids leak from vehicles, they end up on streets and are washed into stormwater runoff. Keeping vehicles well maintained not only reduces air emissions, but it also improves water quality. There are few public education programs to promote better auto maintenance and reduce leaks. Most vehicle owners recognize the warning signs that their vehicle has a leak -- they have to add oil or fluid more frequently than normal, they see fluid spots collecting under their car, or their car smokes. But an education program that involves checking for leaks could help prompt them to do something about it. The barriers to correcting the problem are most likely convenience and cost. A successful public education program might include offering vehicle owners discounts at auto shops for vehicle inspection services and/or repair of leaks.

Even when cars are properly maintained, pollutants from the exhaust and normal wear of parts such as tires and brake pads will continue to contaminate stormwater. Reducing those sources of pollution will require changing the way vehicles are built. In San Francisco, where copper impairs the waters of the San Francisco Bay, a study estimated that more than half the copper in urban runoff to the San Francisco Bay comes from brake pads. An organization called Sustainable Conservation has formed the “Brake Pad Partnership” and is conducting research that is expected to be completed in December 2007. If brake pad wear debris is found to impair water quality, industry manufactures have agreed to voluntarily introduce new products within five years.

Car washes

Washing cars on the street sends soap, dirt, and oil into stormdrains. Car owners are encouraged to either wash their vehicles with biodegradable soap in an unpaved area, not on the street or in a driveway, or better yet, take their car to a commercial car wash. Many car washes recycle their water and all are required to pre-treat it before discharging it into the sewer system. Charity car washes are a pollution source that some jurisdictions are trying to control. Programs involve either having the charities sell coupons for commercial car washes, or offering car wash kits. The kits include a pump and hose to direct the wash water away from the storm drain and into a grassy area, sink, or other drain that directs the water to a sewage treatment plant. Implementing charity car wash kit programs requires consistent follow-up to ensure the kits are being used properly.

Prevent construction erosion

The state’s construction stormwater permit program is designed to prevent erosion and sediment runoff from construction projects. There are a host of management practices that can be used to prevent erosion and control sediment runoff from construction projects to protect water quality. In Section VII of this report, the Stormwater Solutions Team makes some recommendations to improve the effectiveness of the construction permit program.

Green landscaping

Runoff of fertilizers and pesticides from lawns, parks, and other landscaped areas makes its way into many urban streams and rivers. Practices that reduce water quality impacts of landscaping maintenance include:

• Grasscycling: leave lawn clippings on the grass, where they can break down and fertilize the lawn.
• Use mature compost and other organic, slow-release fertilizers, which reduce nutrient loading to our streams.
• Skip the weed and feed and other products that contain both herbicides and fertilizers. They unnecessarily apply herbicides to the entire lawn when they may only be needed in a few spots.
• Water deeply but infrequently to promote a healthy lawn.
• Aerate lawns to improve infiltration and reduce runoff.
• Reduce lawn space and replace it with low-maintenance, native plants.
• Use an alternative lawn, such as an “eco-lawn”, which is a mixture of grasses, flowers and herbs that provide an easy-to-maintain green space.
  

Many local programs encourage people to reduce their use of chemicals on their lawns. Examples include:

• www.healthylawns.org, a website developed by Oregon DEQ and partners to promote the message “Lawns can look great without chemicals” and demonstrate how to use natural lawn care alternatives.
• Ecological Business Landscaper certification program, www.ecobiz.org, which certifies professional landscaping companies that use environmentally friendly practices.
• Naturescaping programs educate gardeners about landscaping with native plants.
• Salmon-Safe certifies campuses and parks that use salmon-friendly maintenance practices.
  

Only water in storm drains

Many residents still do not realize that most storm drains connect directly to creeks or rivers without any treatment. Household hazardous waste programs, used oil recycling programs, storm drain marking, and basic educational programs help reduce intentional or unintentional spilling of pollutants into storm drains.

Don’t feed the ducks

Birds can be a major source of fecal bacteria in waterways. Communities with high levels of avian bacteria need to take steps to discourage birds from congregating unnaturally near water bodies, such as discouraging people from feeding ducks and geese.

Pick up dog waste

According to a study that used DNA testing to identify sources of bacteria, dog waste accounts for almost 15% of fecal bacteria in some streams.⁴⁵ The current solution is to ask pet owners to use plastic baggies to clean up after their dogs and dispose of the waste in the garbage. But all that waste ends up in the landfill, where it will sit for years in the absence of the oxygen it would need to decompose. Park crews in Eugene haul out at least 18 tons of canine fecal matter a year.⁴⁶ Better alternatives include taking the waste home and flushing it down the toilet (minus the plastic baggie), or developing a composting system or methane-generating system, both of which would require using only bio-degradable bags.

Until one of those alternatives becomes more feasible, many communities are encouraging residents to pick up after their pets and toss the waste in the garbage, which is a better option than leaving it to pollute streams and rivers. Social pressure can have a significant impact on promoting this behavior, especially in public places where people will see if you pick up after your dog or not. Providing baggies and garbage cans in heavily used parks for waste pick-up and disposal makes the task more convenient and reduces excuses. Creative programs such as Clean Water Services’ “Canines for Clean Water” pledge make it fun for dog owners to participate by providing a free bandana with the campaign logo on it, and a pet photo contest. This is a new program, and its effectiveness is not yet known. It helps people understand that pet waste has an impact on water quality, which many pet owners do not realize.

Minimize industrial stormwater runoff

Industrial stormwater permits require facilities to utilize best management practices to control stormwater pollutants from their site to meet water quality benchmarks -- target concentrations for pollutants such as suspended solids, oil, lead or zinc -- that measure whether the management practices are effectively controlling stormwater pollution. The best management practices often involve source controls, such as covering exposed materials. Due to productivity pressures, cost barriers, the high amount of staff training required to effect consistent and successful source control, and the rate at which stormwater pollutants are swept off impervious surfaces, effective stormwater management by industry has been difficult to achieve. Site inspections with advice on when and where to use certain best management practices would be helpful. Allowing industry to incorporate low impact development strategies and on-site water management in certain low risk areas could reduce stormwater runoff and the size and cost of industrial stormwater controls.

NEXT: CHAPTER 3 - REGULATORY CONTEXT