Need to manage stormwater but don’t have the funds to put in rainwater harvesting systems? Look no further than your landscaping.
Stormwater and soil erosion are becoming a top priority for building owners who want to lower their water disposal fees, comply with local regulations, and earn green building credits for site management. Landscaping measures offer a natural way to reduce pollutants running off your property.
Chris Kloss, green infrastructure coordinator for the EPA Office of Water, and Peter MacDonagh, director of science and design for the Kestrel Design Group, discuss strategies that will beautify and protect the environment.
BUILDINGS: Why should commercial properties be concerned with soil and stormwater management?
Kloss: Stormwater discharges are a significant source of water pollution and degrade the health of thousands of miles of rivers and streams and thousands of acres of lakes across the country. Stormwater pollution sources are often associated with facilities or pipes discharging wastewater, but stormwater can come from any developed land, especially those with large amounts of impervious area such as parking lots and roofs.
MacDonagh: Stormwater disposal is currently buried in a sewer fee that assumes how much water goes into the building is equal to what’s discharged. Because impervious surface rain runoff can create a significant burden on waste sewer pipes, however, stormwater management is starting to be charged as a separate item.
Water quality testing for total maximum daily loads (TMDL) by the EPA can also affect municipal separate storm sewer systems (MS4), which release storm runoff into nearby bodies of water. If a water body is impaired with high levels of pollutants or suspended solids, the MS4 that drains into it must implement measures upstream to bring the water back into compliance. This unfunded mandate forces MS4 cities to add infrastructure upgrades. Unless owners take more responsibility for on-site stormwater management, their stormwater disposal fees will likely increase.
BUILDINGS: What landscaping solutions are available to address these issues?
Kloss: A number of green infrastructure techniques can be integrated into developed properties and landscaped areas to manage rain close to where it falls. Bioretention practices can be installed in areas typically set aside for conventional landscaping, such as parking islands and property buffers. Permeable pavement can be used in parking lots and green roofs are a stormwater-friendly alternative for commercial buildings.
MacDonagh: Instead of putting in a pipe and moving stormwater to another location to be treated, you want to solve the problem by using source control at the surface level.
Rain gardens work well in medians and parking areas. They tend to be comprised of all herbaceous and perennial plants or occasionally trees and shrubs, depending on your region. All need free draining soil that allows water to filter through, around 2 to 4 inches per hour. You also need a good turf grass maintenance program that includes aeration, compost, and scarification.
Soil erosion control is also important. A typical lawn will lose between 1 and 3 tons of soil per acre each year. Make sure slopes around a retention basin are fully vegetated and reduce any other steep slopes, particularly anything over 10%.
You can also create “speed bumps” or a series of small berms on contours. The idea is to slow down, spread out, and soak in rainfall. PageBreak
BUILDINGS: How do you decide which features are compatible with your property?
Kloss: Practices are selected based upon your stormwater management objectives and site-specific factors that influence design criteria. There is a broad range of green infrastructure practices typically employed that are flexible and functional under various climatic conditions.
For instance, many solutions use native vegetation and plants; consequently, a bioretention system in the Northeast can look very different than one in the Southwest, although the overall stormwater performance may be very similar.
Codes and ordinances can also influence the amount of required impervious surface and the type and allowed location of installed stormwater practices.
MacDonagh: For example, many cities have started a rain leader disconnect program – internal roof drains can no longer be connected to the wastewater or stormwater system. The purpose is to manage more water at the site than through conveyance alone, which simply moves the pollution problem.
Because stormwater utility fees are typically levied at a price per square foot of hard surface, start by reducing paved areas. If you’re in a suburban location and land values are low, create as many rain gardens and bioinfiltration swales as possible – they’re the least expensive way to manage stormwater and improve soil quality.
BUILDINGS: What kind of investment costs can building owners anticipate?
Kloss: Greener approaches offer the opportunity to incorporate holistic site designs that can achieve both economic and environmental objectives. Because green infrastructure practices are integrated into site designs, the cost to construct these systems is often an incremental increase over traditional site designs, such as using permeable instead of impervious pavement or installing bioretention rather than conventional landscaping.
Green infrastructure can also provide non-stormwater cost savings as well. Green roofs help to prevent large temperature swings within a building and can reduce energy costs by an estimated 10%.
Rainwater harvesting systems can reduce potable water use and decrease water utility expenditures. The King Street Center in Seattle, for example, uses rainwater for 60% of its toilet flushing needs, reducing potable water demand by more than 1 million gallons each year.
MacDonagh: Capital or first costs vary depending on the solution you use. A detention or dry basin with underdrains and an open medium, such as sand, will cost around 30 cents to treat one gallon. Bioswales and rain gardens are typically $2–3 per gallon and suspended pavement averages $10-15. Green roofs jump to $20 a gallon, but offer energy savings to offset the costs.
Look for grants, rebates, and incentives to help fund your project. We had a client that was paying $4,500 for annual water disposal, but a stormwater utility fee increased the amount to $55,000. We created a series of solutions that included rain gardens, swales, and treatment wetland. The ROI was around seven years, but we negotiated with the city to wave their stormwater fee during the five-year project period, using the annualized fees for financing.
It’s important to understand that green infrastructure measures don’t eliminate runoff, especially from large storms, but they are a quality control for average rainfalls that can significantly improve adjacent water quality and save owners money.
Jennie Morton [email protected] is associate editor for BUILDINGS.