Green Roof Resource

The WEF Sustainability Conference was held this week in Washington, DC. During the conference, a multitude of available resources were recommended to learn more about green infrastructure and sustainable water management. Below is a brief list of the resources in no particular order that I found interesting. I’ve included links where appropriate. I’m still trying to track down a book that was mentioned during the opening session, Sustainable Watershed Management. Any additional information on it would be helpful.

1. The Santa Clara Valley Water District has taken significant efforts to reduce energy and water consumption through water conservation and recycling programs. Their efforts are summarized in a 2007 report entitled
From Watts to Water.

2. With climate change affecting the frequency and magnitude of storm events, JP Morgan has recently published a guide to evaluating corporate risk with a focus on water. The report, Watching Water, provides tools for assessing impacts on companies due to decreased water quantity and quality.

3. The Civil Engineering Environmental Quality Assessment and Award Scheme (CEEQUAL) is an awards scheme for acknowledging excellent environmental quality on civil projects. CEEQUAL was developed in the UK and is based upon a points system.

4. The Pacific Institute has developed two water to air models. These models provide information on the energy and air quality effects of water management projects in urban and agricultural water districts.

After four years, Green Roof Resource is getting a new look. I am currently updating the site for better readability and organization.

While on the topic of renewing resources, this week I came across the International Stormwater BMP Database. The resource provides data from over 300 BMP (best management practice) studies evaluating performance of these systems. While the database was initiated in 1996, I stumbled across it after reading an article in the May issue of Stormwater. “Can Stormwater BMPs reduce bacteria?” reports that bacteria counts in BMP outlets vary widely, but in general retention ponds and media filters have the potential to reduce bacteria. There is concern that vegetative swales and other similar BMPs may attract wildlife and domestic animals increasing the concentration of fecal coliform in stormwater runoff from these systems. The concentration often exceeds the standard for recreational primary contact in waterways.

It was exciting to see that green roof runoff was included in the evaluation. However, with data being obtained from only one site (Hamilton Ecoroof in Portland, Oregon), analysis of the data was limited.

It would be interesting to evaluated BMPs in combination. For example, if retention ponds are effective at reducing fecal coliform concentration, can bioswales or green roofs reduce the size of a downstream retention pond to enable use of the BMP in areas where land is limited? Or is the apparent reduction simply an artifact of where these systems are typically used? For example, are retention ponds able to reduce fecal coliform concentration in the effluent simply because there is less in the influent? Perhaps in areas where fecal coliform is a greater problem, more conventional methods are appropriate. While fecal coliform concentration is a health concern and is contribute to beach and water closings access after rain events, one must not forget about the volume of storm events. BMPs are effective at reducing total volume of runoff entering waterways, and one should also consider the total load of contaminants exiting these systems in addition to the concentration of contaminants.

It’s time for the annual conference review. I spent most of my time in the research track, so this year’s review is a little limited in scope. First, I was quite impressed with Minneapolis. They have a light rail system from the Mall of America and the airport to downtown. It even goes by a recycling center with a green roof on top. I was impressed with the diversity of restaurants (including one with a green roof for lawn bowling).

Several of the talks focused on stormwater with a greater focus on water quality than in previous years. Lisa Rocha from the Toronto and Region Conservation Authority and Robert Berghage from Penn State both mentioned elevated phosphorus and phosphate concentrations in green roof runoff. Rocha emphasized that while concentrations of nitrates were elevated, the total mass of nitrates were less. A full report of the observations by the TRCA can be obtained here. Berghage included observations on the buffering capacity of green roofs in addition to the observations on nutrients and metals. He also stressed that loads and concentrations from green roof systems should be compared not only to conventional roof systems but also to other landscaped areas. There is concern that by not comparing green roofs to landscaped areas, one could make the otherwise irrational argument of paving up to a waterway as a best management practice for the prevention of nutrient runoff.

Barbara Deutsch from Casey Trees enthusiastically presented on collaborative work with Limno-Tech, Inc. evaluating stormwater management impacts from large-scale green roof scenarios for Washington, DC. It was found that greening efforts could result in operational savings between $1.4 million and $5.1 million ($0.01/gallon) annually due to decreases in water pumping. The full report should be available online by the end of this week from Casey Trees.

Stay tuned for further updates from the conference.

Earlier this month I was in Vienna, Austria to present at a conference on city surfaces. “Towards the City Surface of Tomorrow” focused on emissions from city surfaces and included some discussion on methods to reduce emission flows from surfaces. I attended as green roofs are a city surface technology that can reduce emissions to air and water.

While there were not many talks addressing solutions to diffuse emissions, I did learn more about roof surfaces and how roofs contribute to diffuse pollution. In Europe there are a greater percentage of metal roofs than there are in the United States. As a result, European cities are concerned with metals in stormwater runoff due to rooftop corrosion. While flashings are made of metal, the majority of roofs in the US are bitumen based. Therefore, stormwater runoff in the US can accumulate concentrations of polycyclic aromatic hydrocarbons (PAHs) from roof or road runoff.  Many cities are challenged with managing stormwater, but specific environmental problems such as pollutant loads may be regional.

Water quality trading, while not as established as air quality trading, is included on EPA’s website. One of the presentations at this month’s conference focused on nutrient trading within Virginia’s portion of the Chesapeake Bay’s Watershed. The commonwealth is developing a nutrient trade program to improve the nitrate and phosphate loads within the bay. While the TMDL program is the traditional path for trading, Virginia is implementing this program as a means to avoid the bay falling under a TMDL program.