Sustainability - Infrastructure and Design Options

June 09, 2007

Written by KAI Interns Carl Sundstrom and James Wong

Although roads are a large and important part of our urban infrastructure, their contribution towards environmental pollution is often overlooked. The areas of maintenance and street design are receiving much focus as new mitigation techniques and strategies are developed.

Green Streets

Roads are usually built as impervious surfaces, that is a surface that doesn’t allow water through, but rather forces water to run off to the sides of the road. For this reason, roads directly deposit pollutants into our water bodies through combined sewer overflows. Therefore, “green” streetscape design is vital in building for a healthy and safe community. One strategy is to employ “Green Streets” techniques as a means of enhancing the functions that streets perform to include cleansing runoff destined for fish habitat, reducing excess heat caused by extensive black surfaces and improving air quality. A valuable side-effect of this green infrastructure is that it creates inviting and walkable streets.

Green Streets consist of several key features:

Mitigating Habitat Fragmentation. This includes optimizing routes during the environmental planning process such that the barrier effect of roads is reduced, particularly in sensitive areas such as stream crossings.

Reduction of Impervious Surface. This reduction can come from integrating planting and landscaping into the streetscape as well as using porous surfaces or a center strip that provides both a usable driving surface and rain water absorption.

Improve Water Quality. Planting and biofiltration is used in Green Street design to treat runoff. Methods such as incorporating swales with native species to absorb water and tree canopy for temperature mitigation and air quality improvement should be used to reduce the amount of water piped directly to streams and rivers and helps recharge the water table. This also provides visual improvements to the community and provide for pedestrian friendliness.

Maintenance

An infrastructure facility’s lifetime is most impacted during design and construction, but the longest time segment for infrastructure is operation and maintenance. Because maintenance is a constantly ongoing process, it is important that maintenance practices are in line with environmental goals.

Deicing roads is a common maintenance problem that municipalities in much of this country deal with. Because of the vast square mileage of pavement that needs to be cared for in snow storms, whatever method is chosen for deicing will have far reaching effects. Salting is most common despite the fact that it kills surrounding vegetation and in turn allows the water to flow further from the pavement making the problem more extensive. Sand is a better alternative because it doesn’t dry out plants and in mild quantities does not severely impact soil composition. It must be cleaned up, however, which can be a costly process.

Unlike deicing which is a necessary maintenance procedure where we can aim to minimize its environmental impact, other types of maintenance have environmental conservation as a main goal and better performing facilities as a byproduct. After each rain, sediment and debris is left behind in enclosed drainage pipes. If maintenance crews are not conscious of this, they will often use high pressure water to clean out the debris forcing it into the waterway, but the alternative is using vacuums to retrieve the larger material before flushing the pipes. This leads to less water contamination and less chance of flooding during heavy rains.

Gravel cleaning along the side of a road is another type of maintenance that benefits both the roadway and environment. Gravel acts as a filter for water runoff. Much of the roadway particles that flow off the surface are caught in gravel before it has a chance to reach vegetation and ecology further away from the road. When it becomes full, water and particles run past it and empty in those regions it was formerly protecting; that is why it needs to be cleaned regularly and the remainder of what was cleaned be disposed of properly. Clean gravel facilitates better drainage and maintains the grading away from the road for safety.

It is critical that maintenance divisions have goals that are in line with that of the environmental agencies in order to create effective strategies. Because of the long lifetime of infrastructure, maintenance procedures have the ability to support or negate environmental efforts made in the design and construction of a facility. By incorporating effective maintenance strategies and Green design concepts, the goal of sustainability will be fulfilled as facilities last longer and leave less environmental impacts on surrounding areas.

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