David GingrichRiekman – Environmental Stewardship and Urban Infrastructure

November 23, 2016September 28, 2017

Index of Ecological Importance

T O P I C O V E R V I E W

This week I decided to read a selection of the book “Sustainable Infrastructure : The Guide to Green Engineering and Design” by S. Bry Sarte. This reading investigated applications of sustainable infrastructure and explored several case studies in order to demonstrate these applications. I found the case study of development on Isla Pedro Gonzalez (known locally as Pearl Island) in the Gulf of Panama to be particularly interesting. As the book discusses, islands make great examples for sustainability case studies as it is easy to see and appreciate that resources are limited, and to define the system boundaries. One can clearly observe the effort required to transport resources to and from the island, and see the trash piling up on the island’s beaches and in surrounding waters.

Pearl Island is unique in that a master plan for development on the island was developed by a team of local residents and stakeholders, engineers, ecologists, architects, and community planners prior to significant human habitation, development, and use. This allowed the island to be developed sustainably from the ground up with all environmental factors considered, without having to modify an existing poorly developed site. Many interesting and useful design strategies were employed in throughout the development of the master plan and are discussed at length in the book. However, I found the idea of an “Index of Ecological Importance” particularly intriguing.

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Figure 1: Looking out towards Isla Pedro Gonzalez (Pearl Island) in the Gulf of Panama

The index of ecological importance is a design approach developed as a starting point for understanding the relative value of the green infrastructure system on a project site. The intent of the index is to provide an overview of these conditions and opportunities, identify areas which are most critical (no development allowed) and critical (employ environmentally responsive design techniques), and to establish a framework for biological connectivity between these areas and the surrounding area. Once developed, the index is then used to inform all other development plans, and as a general guide through the master planning process – focusing development with greater impact away from critical habitats, and ecologically sensitive areas. In order to ensure they achieved the most accurate model possible, as the project team for Pearl Island’s understanding of the island’s ecosystems improved, the index was continually updated and re-evaluated. Looking forward to future projects, I think this list could be expanded to include areas which provide ecosystem services in order to minimize their loss through to human development and preserve critical ecosystem functions.

In order to develop an index of ecological importance, a decision matrix is created which assigns relative value to specific known physical and ecological conditions on the island (or any subject area). Ecological data such as slope analysis (to asses the impact of deforestation on slope stability and resulting dirty surface runoff into surrounding bodies of water), a vegetation survey, existing development, waterways, and mapping of critical bird and wildlife habitats can be included as the analysed data sets. This sets of data are then weighted by relative importance and layered to for a single map of ecological importance for the subject area. This transformation of the environmental data and relative comparison of ecological importance into a physical space can be used to inform decisions regarding the impact and placement of buildings, infrastructure, and other development. An example of this map or index of ecological importance for Pearl Island can be seen below. capture

Figure 2: Index of Ecological Importance on Pearl Island. Darker areas are most critical.

S U G G E S T E D A S S I G N M E N T

In order for students to learn about the concept Indices of Ecological Importance an assignment such as the following could be completed.

Part One: Reading

Students would be asked to complete a reading on Indices of Ecological Importance. Pages 300-302 of S. Bry Sarte’s Sustainable Infrastructure : The Guide to Green Engineering and Design would be appropriate.

Part Two: Questions

Students would be asked to complete the following questions:

In your own words, summarize the concept of Indices of Ecological Importance in a few sentences.
What are some of the benefits of this approach?
For which types of projects would this approach be most appropriate?
Are there projects where this approach would not be appropriate? Explain.
Name at least two ways in which this design approach could be improved.

Part Three: Create an Index of Ecological Importance

Students would be given a sample area and development project for which to create an Index of Ecological Importance. A map of the area would be provided. Students would be expected to come up with a list of at least ecological conditions or data sets, and then create a decision matrix to weigh the relative values of these criteria. Finally, students would be asked to create a rough map of the ecological importance of the site based on their decision matrix and the map provided.

R E F E R E N C E S

Sarte, S. B., Mr. (2010). Sustainable Infrastructure: The Guide to Green Engineering and Design. Hoboken, NJ: John Wiley & Sons.

November 2, 2016September 28, 2017

Constructed Wetlands II

This weeks learning, titled “Design for Water conservation and Waste-Water management” explored how the ecosystem approach to urban infrastructure design required engineers to consider the whole water cycle. That allows us as engineers to build infrastructure that restores the natural balance of water in ecosystems. While much of the reading was highly applicable and interesting, I was particularly intrigued by the idea of constructed wetlands and decided to investigate this topic further.

4130876_orig Above – A beautiful constructed wetland in action at the Lincoln Park Zoo in the USA. Source:http://www.acornponds.com/bog-filtration.html

What is a Constructed Wetland?

Constructed wetlands are engineered systems that use natural functions of vegetation, soil, and organisms to treat different water streams. Depending on the type of wastewater that has to be treated the system has to be adjusted accordingly which means that pre- or post-treatments might be necessary.

Constructed wetlands can be designed to emulate the features of natural wetlands, such as acting as biological-filters or removing sediments and pollutants such as heavy metals from the water. Constructed wetlands sometimes serve as a habitat for native and migratory wildlife, although that is usually not their main purpose.

There are three main types of Constructed Wetland:

Subsurface flow constructed wetland – this wetland can be either with vertical flow (the effluent moves vertically, from the planted layer down through the substrate and out) or with horizontal flow (the effluent moves horizontally, parallel to the surface)
Surface flow constructed wetland
Floating treatment wetland

Cost of Constructed Wetlands

Constructed wetlands are self-sustaining, and thus their lifetime costs are significantly lower than those of conventional treatment systems. Often their capital costs are also lower compared to conventional treatment systems. They do take up significant space, and are therefore not preferred where real estate costs are high. Overall, constructed wetlands are generally significantly cheaper than conventional treatment systems.

How do they Work?

A constructed wetland is an engineered sequence of water bodies designed to filter and treat waterborne pollutants found in sewage, industrial effluent or storm water runoff. Constructed wetlands are used for wastewater treatment or for greywater treatment, and can be incorporated into an ecological sanitation approach. They can be used after a septic tank for primary treatment, in order to separate the solids from the liquid effluent. Some CW designs however do not use upfront primary treatment.

Vegetation in a wetland provides a substrate (roots, stems, and leaves) upon which microorganisms can grow as they break down organic materials. This community of microorganisms is known as the periphyton. The periphyton and natural chemical processes are responsible for approximately 90 percent of pollutant removal and waste breakdown. The plants remove about seven to ten percent of pollutants, and act as a carbon source for the microbes when they decay. Different species of aquatic plants have different rates of heavy metal uptake, a consideration for plant selection in a constructed wetland used for water treatment. Constructed wetlands are of two basic types: subsurface flow and surface flow wetlands.

tilley_et_al_2014_schematic_of_the_vertical_flow_constructed_wetland

Above is an example Horizontal Subsurface Flow Constructed Wetland. Source: https://en.wikipedia.org/wiki/File:Tilley_et_al_2014_Schematic_of_the_Horizontal_Subsurface_Flow_Constructed_Wetland.jpg

tilley_et_al_2014_schematic_of_the_vertical_flow_constructed_wetland-1

Above is an example of a Verticale Subsurface Flow Constructed Wetland. Source: https://en.wikipedia.org/wiki/Constructed_wetland#/media/File:Tilley_et_al_2014_Schematic_of_the_Vertical_Flow_Constructed_Wetland.jpg

How well does this connect to this weeks reading?

The concept of Constructed Wetlands connects very well to our reading. The following are some key connections:

An excellent use of innovative technologies.
Provides a long term water management plan.
Address both wastewater and stormwater concerns.
A great example of the ecosystem approach – not only are constructed wetlands providing an ecosystem service to the human population (waste control), but they also create additional oxygen producing plants and provide a habitat for local birds and wildlife.

References:

Canada Mortgage and Hoursing Corporation – “Constructed Wetlands” https://www.cmhc-schl.gc.ca/en/inpr/su/waho/waho_008.cfm

USA Environmental Protection Agency – “Constructed Wetlands” https://www.epa.gov/wetlands/constructed-wetland

Water Canada – “Constructed Wetlands: How Cold Can You Go?” http://watercanada.net/2009/constructed-wetlands/

School of Environment Sciences, University of Guelph – “Constructed Wetlands” http://www.ces.uoguelph.ca/water/NCR/ConstructedWetlands.pdf

October 19, 2016September 28, 2017

Passive Ventilation

“Design of Healthy Environments” explores many design principles and topics related to human health in indoor environments. I find this topic particularly useful and interesting as all of the topics pertain to buildings – specifically the subjects of structural engineering and building science – which are the focus of my studies. This post explores some details of one of the “Design of Healthy Environment” topics, namely: passive ventilation.

Passive ventilation (sometimes refereed to as passive cooling) is a design approach to the management of internal building temperature that focuses on heat gain control and heat dissipation in a building through passive means in order to improve indoor conditions with minimal energy consumption. This is accomplished either by preventing heat from entering the building’s interior (known as heat gain prevention) or by removing heat from the building by promoting air movement or though diffusion through building surfaces. Methods to control indoor temperature can be broken into two broad categories – preventative techniques and heat dissipation techniques.

Preventative Techniques:

Micro-climate and Site Design: By accounting for the local climate and site location, specific cooling strategies/methods can be employed which are appropriate for the specific site.
Solar Control: By creating a shading system, solar gains can be effectively minimized. Shade can be cast on both transparent and opaque surfaces. Solar gains can also be minimized by using reflective surfaces on the building exterior, or painting the exterior white/light colours.

Heat Dissipation Techniques:

Cross Ventilation: This strategy relies on wind to pass through the building to cool the interior. Cross ventilation requires openings on two sides of the space, called the inlet and outlet. The sizing and placement of the ventilation inlets and outlets will determine the direction and velocity of cross ventilation through the building.
Stack Ventilation: This method relies on the buoyancy of warm air to rise and exit through openings located at ceiling height. Cooler outside air replaces the rising warm air through carefully designed inlets placed near the floor.
Night Flushing: This is a passive or semi-passive cooling strategy that requires increased air movement at night to cool the structural elements of a building. To execute night flushing, the building envelope typically stays closed during the day, causing excess heat gains to be stored in the building’s thermal mass. The building structure acts as a sink through the day and absorbs heat gains from occupants, equipment, solar radiation, and conduction through walls, roofs, and ceilings. At night, when the outside air is cooler and not too humid, the envelope is opened, allowing cooler air to pass through the building so the stored heat can be dissipated by convection.

Below is a diagram while clearly displays several methods of passive ventilation

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References:

http://sustainabilityworkshop.autodesk.com/buildings/natural-ventilation

https://en.wikipedia.org/wiki/Passive_cooling#Ventilation

http://www.windowmaster.com/solutions/natural-ventilation/passive-ventilation

http://www.level.org.nz/passive-design/ventilation/design-of-passive-ventilation/