- August 9, 2017
Paved surfaces, such as sidewalks, driveways, and parking lots are helpful for quick and easy travel and day-to-day use, but these human-made improvements have negative impacts as well, including increased runoff and concentration of pollutants in that runoff, alongside, sometimes substantial, urban heat island effects, and a general decrease in green spaces, which contributes to a growing urban disconnection from nature. If you, however, find that a piece of paved surface is not pertinent to everyday life, the best solution is depaving.
Urban Heat Island is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. Hard surfaces, which can reach 50-90 degrees warmer than the ambient air, are one of many culprits that contribute to heat islands. Cities with a population of 1 million people or more can be an average 1.8 to 5.4 degrees hotter than the surround areaopen_in_new.
Stormwater Runoff is created when rain falls on roads, driveways, parking lots, rooftops, and other paved surfaces that do not allow water to soak into the ground. As the rain water is funneled into our storm drains it picks up pollutants, chemicals, trash…etc. and deposits it into our water resources. In urban areas, paved surfaces can make up 50-90%open_in_new of the environment and some studies have shown that paving more than 10-20 percent of the landscape has an impact on water quality for the city.open_in_new
No sugar-coating here, depaving, or the removal of unnecessary pavement or hard surfaces to create green spaces, is a complex project. Before breaking ground you’ll need to make a plan and take many things into consideration.
First, inspect the area you plan to depave and ask yourself how will this area respond after the pavement is removed?
Things to consider:
- How will stormwater respond/drain?
- Are there structures and buildings relying on this paved area?
- Is there heavy vehicle or foot traffic around the area?
It is highly recommended that first time depavers start out with an area smaller than 500 square feet.
Knowing the history of the site, any soil contaminants, and the infiltration rate is important for planning out your depaving project. Depave is a nonprofit out of Portland, Oregon–suggests researching the history of the site through your local library or assessor office. This can give you input into previous uses of the soils. Paved areas mitigating contaminated soils are not great candidates for depaving, as removing the pavement might expose hidden contamination requiring substantial resources to safely contain. It is suggested to test the soils for lead, cadmium, hydrocarbons, arsenic, and organochlorine pesticides, before you jump into your depaving project. Your local extension office can help you find the best and cheapest resource for soil testing near you.
Make a plan. After removing the paved area, what do you plan on installing in its place? Depaving can revitalize spaces with features that address stormwater management (rain gardens and bioswales, or permeable pavements like gravel or granite pathways). They can create habitat and support biodiversity (pollinator gardens), reduce urban heat (tree planting) and provide green space including food gardens.
Call DigSafe (811) before you dig. It’s a free service that marks utilities within 2 days of calling. This is easier and safer than discovering your gas or water line with your pickaxe.
What are you removing, concrete or asphalt? Concrete is harder and more durable. Check the edges of your paved area to investigate the thickness. If the concrete slab is greater than three inches thick it will require a jackhammer rental to break up and remove the materials. This may sound daunting, but they are relatively simple and cheap to rent and use–not to mention FUN! Under three inches, the job can most likely be done with a pickaxe, sledgehammer, and some muscle. If you happen to come across rebar enforced concrete the best solution will be to consult with a professional.
The concrete debris from your removal efforts can be reused for landscaping materials like walkways, fire pits, hibernacula, and retaining walls, so keep them separated from other debris for recycling.
Asphalt is lighter and easier to remove. A walk-behind diamond blade saw (rental) can be used to cut the section being depaved into small more manageable sections. From there, pry bars (found at all hardware stores) can be used to pry and lift the sections of asphalt to a dumpster or dropbox. Asphalt can also be recycled as gravel for construction jobs, so, like concrete, keep asphalt separated from other debris for recycling.
Materials for Your Depave Job
Eye and ear protection
Water and Food
Wheelbarrow or hand truck
PickAxe and/or Sledgehammer
Jackhammer or Diamond Blade Walk-behind Cutter (Rental)
Underneath most hard surfaces are four to six inches of gravel. In smaller jobs this can be removed using a shovel and wheelbarrow. Larger sites will benefit from use of a bobcat or backhoe to remove this amount of gravel. PRO TIP: The gravel removed can be re-used! Rhiannon Crain, Habitat Network Project Leader, re-used her gravel from her home depaving project as fill in her new rain garden.
You will find compacted soil beneath the gravel layer. Depending on your plans for the project, this compacted soil can be used to install pervious pavers or it will need to be broken-up using a pickaxe or spading fork and then amended for a planting.
Then the best part, planting! After all that hard work, enjoy the fruits of your labor by implementing your planting plan. Select plants that perform desired functions for the purpose of the new green space, like native wildflowers for pollinator gardens. Make sure to plant in the spring or fall to ensure the best survival of your new garden or green space. Keep it watered until it’s established and then watch it grow, attract wildlife, filter run-off, cool your surroundings, and reduce stress.