Sidewalks are a neighborhood's status symbol, but do they help the environment?

A new state Department of Transportation study suggests that sidewalks may help a bit with climate change. But there can be other approaches than our big, traditional sidewalks. 

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There have been problems with a project to add drainage in a Ballard neighborhood that already had sidewalks.

A new state Department of Transportation study suggests that sidewalks may help a bit with climate change. But there can be other approaches than our big, traditional sidewalks. 

In Seattle whether a neighborhood has “arrived” is often measured in poured concrete. Sidewalks have long been the indicator of whether a neighborhood has the attention of City Hall planners and politicians. Lack of sidewalks can also provide a rallying point for disaffection. A new study of the relationship between sidewalks and climate change released by the Washington State Department of Transportation may provide some new backing for the concrete crusade being led by some neighborhoods. But the city needs to be careful to consider other factors like the impacts on water quality.

Here’s the key paragraph from the study:

The results provide early evidence in the potential effectiveness of sidewalks to reduce CO2 and VMT [vehicle miles traveled], in addition to a mixed land use pattern, shorter transit travel and wait times, lower transit fares and higher parking costs. Sidewalk completeness was found to be marginally significant (at the 10 percent level) in reducing CO2, and insignificant in explaining VMT.

In this sense the term “marginally” might read as “small.” But in a research context “marginally significant” also means sidewalks can make a difference along with other factors to significantly reduce CO2 emissions.

One thing to consider, however, is that sidewalks need drainage. We have lots of water in Seattle, and when it rains surface water runoff ends up in creeks, streams, rivers, lakes and in the Puget Sound where it can bring with it lots of bad stuff. Lisa Stiffler at the Sightline Institute has done lots of work on this topic and her writing on the topic there and from her days at the Seattle Post-Intelligencer is encyclopedic on the topic. (Crosscut will publish an InvestigateWest report by Stiffler on Friday, April 22; it will cover some of the stormwater and runoff issues raised here.)

According to the Seattle Department of Transportation, the city has more than 2,000 miles of sidewalk. After it rains, water hits all that pavement and it starts rolling around, picking up the petroleum drippings from cars, pesticides from lawn care products, and a legion of other things that end up harming fish and other creatures trying to survive in urban creeks and streams. Ultimately, all that water winds up in the Puget Sound, where the Partnership for Puget Sound says at least two species of salmon are threatened with extinction because of stormwater runoff.

But many neighborhoods don’t have sidewalks at all. And the city is paying attention, supporting a serious effort to get sidewalks to areas where they are needed most. Perhaps one of the most notorious areas for having few or no sidewalks is in Greenwood neighborhood of Seattle. North of 85th Street there are many stretches of residential streets that have no concrete walkways. A few years back the city completed an innovative project that addressed the dearth of sidewalks in Greenwood and the problems sidewalks create for our lakes, streams, and sound.

The Cascade project created swales instead of simply installing traditional sidewalks, which treat the water naturally preventing it from hitting the local watershed untreated. A city brochure explains the benefits this way:

In the 110th St. Cascade design, water quality is improved when polluted sediments settle out in catch basins. Plants, soils, and natural river rock in the swale further filter out sediments organically as runoff passes through the system. Bacteria in healthy soils can also help break down carbon based pollutants like motor oil.

The project seems to be working, creating not only walking paths but also verdant growth of local plants.

What makes a lot of sense about the Cascade effort is that it meets the neighborhoods needs for walkability that reduces auto-dependence that, in turn, can have a salutary effect on CO2 emissions according to the WSDOT study. But Cascade does this without the usual sidewalk-curb-drainage combo that, while assuaging neighborhood worries about where they fit in the vast scheme of City Hall budget priorities, can end up putting a lot of pollutants into our water.

Now this effort won’t work everywhere. In Ballard, a similar effort isn’t yielding very attractive results.

But the effort is important. The new WSDOT study shows sidewalks are important for reducing climate changing carbon emissions. The Cascade project shows that we can have both walkable neighborhoods and clean water, the Ballard project notwithstanding. And the Ballard project might yield good results, even though right now it may not rival the Greenwood project in how it looks.

Finally, neighborhoods should be careful what they ask for. Encroachment into the area where sidewalks could be laid is a serious problem in Greenwood. Lots of people have made the best of what presumably is a bad thing by extending their yards into the right of way where sidewalks could go. Do these neighbors really want sidewalks? Or is the lack of sidewalks a really good talking point that they might want to keep along with the extra square feet of front yard at pedestrian expense?

In the end walkability doesn’t have to mean concrete walkways. Neighborhoods should demand investment in walkability, whether that’s sidewalks or something even better. 


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