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Basing the Driveway. Why its Important to Get it Right.

Posted March 16, 2021 @ 8:51am | by Tori

Basing the Driveway. Why it’s important to get it right.

If you happen to notice Spring’s heave and pothole haven around town you begin to understand the importance of a good foundation. Not only is a good foundation vital to a home’s structural soundness, it’s also vital to a pavement’s longevity.

Preparing a good foundation for a driveway involves a few things. 

First, understanding what native subsoils exist. Yep, back into the soil type discussion. Certain types of soil can be more problematic than others. Soil type can be broken down into silt, sand and clay, and most likely your property is a blend of two or all three. Below is a fun visual to understand the 3 main catagories and mixtures within. 

 

Now how do soil particles play out with your driveway’s structural soundness?

Spring is one of the times that you’ll see a great deal of movement on the pavement surface. As the frozen ground is unfreezing, the moisture has to go somewhere. If the soils are not well-draining for the water molecule to move down (or the frost is still in the ground), then there will be movement of that moisture going up. Aye, there’s the heave.

 

In clay soils, this can be extremely noticeable particularly when the ground is thawing, still freezing or doing the thaw and refreeze action.

Sandy soils present less complications as this soil type drains quicker. 

So if you had to choose the perfect soil type of your property, sandier soils would be the way to go. That is as long as the surface grades are working right for drainage on the property, but that’s an entirely different issue.

 

However, an important item to note are layers. Generally your property doesn’t have the same soil type 20’ down. So what might appear to be sandy for the first 12” may change below that and of course what’s below can play a role in things too.

So how does this discussion of soil types relate to installing a driveway?

Well, the pavement surface needs to be supported properly. And what does this mean exactly? Yeah, think of it as two things; 1. The shock absorber to all the movement that’s happening below ground with freeze/thaw conditions and 2. The structural stabilizer of what’s on top. 

 

The base layer is composed of aggregate. In a driveway this generally means a ¾” minus aggregate meaning that it’s a rock of a ¾” diameter and smaller. By incorporating fines (the smaller) allows for compaction. Another important factor is for the aggregate ideally to be fractured or angular to allow for maximal density. 

 

There are certain circumstances where it may be reasonable to install a layered aggregate base in really unstable soils. This might be a 1-3” aggregate below a ¾” for instance. 

     

How deep should the base layer be?

Yeah. This isn’t set in stone. The standard in the Twin Cities Metropolitan area for driveway construction is  4-6”. Is that enough in clay? No. Enough in sand? Yes. But again, no property has the one soil type 20’ down so how exactly do you know how deep is deep enough?

 

Without involving a civil engineer to analyze and design - ‘cause that can add to the cost of things - one of the best ways is for a driveway contractor to proof roll. Why? Because it’s specific to your site and is the best approach to know enough is enough...and without doing too much (‘cause that can get costly too). Over-engineering, or over-compensating on designing, is a thing too and more trucking, labor and materials in and out means more expense.

 

How is proof rolling done?

A loaded truck drives on the surface to see how much displacement (aka “rutting”) occurs. If significant, that area is dug out and a new base aggregate layer, potentially geotextiles as well, installed to reinforce that “soft spot.” It could be limited to one location, several or the entire length of your driveway.

If you really want to geek out on proof rolling, Purdue has a great research publication. find it Here  

 

Images by Indiana DOT and Purdue University Here

 

 
Filed Under: Paving | Permalink
 

Greening the Driveway.

Posted March 5, 2021 @ 6:08am | by Tori

Greening the Driveway

 

As we have started to come to terms with the changing environment, many of us have become aware of the choices that we make. 

 

For the past 20 years, Earth Wizards has designed, installed and maintained various environmentally friendly driveways so we’ll share our take with you.

 

Just as a refresh, there are two terms that you’ll often hear. Permeable and impermeable. 

 

Permeable, or pervious, allows water to move through, whereas impermeable, or impervious, does not. 

 

As the built landscape has moved to a predominantly impervious nature, that means less water reaches our aquifers underground. Not only does that affect our highly-valued drinking water supply, but the damage of runoff has become detrimental to property, livelihoods, habitat, soil erosion and a host of other ills.

 

What type of driveway is right for me to lessen my impact?

 

It might seem like a simple answer but of course it never is. Let’s cover a few options and then we’ll delve into what really might make the most sense for you.

 

  • Permeable/Pervious

This can be done as pavers (both concrete and clay), concrete and/or asphalt. It’s important that the underlayment (gravel) is designed with a uniform-sized angular aggregate. 

 

Think of a tubful of angled marbles. The water collects in between the marbles until the drain can move the water through. 

 

  • Less surface

Concrete runners work great for a single car garage. Less pavement means less runoff. What to do with the non-pavement areas? Can be grass or a low ground cover that is suitable.

 

A driveway with a permeable paver pad. Concrete runners allow cars and SUV's alike to maneuver properly.

 

  • Rerouting

Often we consider rerouting runoff onto the property, ideally a raingarden or bioswale. 

 

A raingarden should be designed to handle the amount of runoff it receives and pond (6-18”) for no more than 72 hours. A bioswale is a graded vegetated channel that doesn’t pond with any significance (less than a few inches)

 

  • Underground Storage

This type of system allows for stormwater to be collected underground. Think of a bathtub underground. Similar to raingardens being designed to function properly, underground storage units also need to be designed appropriately to collect runoff and then allow it to infiltrate into the underlying subsoils.

 

By randomly putting a barrel with some rock (the old “french drain”) approach, the size of the system is limited and it’s important to know at what point it will fail and how water will move on/off your property when that happens.


 

What other considerations should be factored into my decision?

 

Subsoil type. Generally sandy soils are ideal for permeable, raingardens and underground systems. This isn’t to say that it can’t be done in less than appealing soils such as a more clayey type but it gets trickier in terms of designing appropriately.

 

One of the most often overlooked considerations is the carbon footprint. The amount of material coming off-site and being moved in. If there’s significant excavation, as with these options there’s more than a conventional approach, that means more equipment, more trucking and more disposal. 

 

Additionally looking at the location source of the new materials. The ideal aggregate to use in permeable pavements is an angular granite base rock as the rock is more igneous base than sedimentary so it will hold up better to the introduction of large amounts of water. For the Mpls/St.Paul metropolitan area this means St. Cloud. 

 

What else to consider? 

  • Budget. Permeable pavements and underground storage will be more expensive than rerouting into a raingarden or bioswale. 

 

  • Maintenance. Permeable pavements will require attention to areas that get clogged. Often overhanging trees or surrounding exposed soils will contribute to this issue. At some point, it may be necessary to remove the pavers, underlying choker course and replace that top layer of aggregate and pavers. So there’s some decent labor involve either that you hire out or do yourself.

 

With a raingarden or bioswale, the maintenance is similar to any garden area. If you choose to be a messy gardener because it’s better for pollinators less so than the Kew Gardens attendant. 

 

  • Available space/mixed use. What amount of green space might I have to install a raingarden or bioswale? Can my driveway also be used as an outdoor patio rather than two separate hardscape areas?

 

  • Pollinators. It’s the talk of late and for good reason! A native planted garden will do so much more for pollinating habitat than permeable pavements. 

 

Then there’s your aesthetic. Your preference with how you want your property to look and feel. 

 

The last important thing to mention is combining approaches. An entire driveway need not be permeable. Maybe it’s a portion of the driveway to be made permeable, some portion downsized and a spot for water runoff to flow into a native planting. 

 

So many choices and this is where it becomes fun! 

 

Start with how you want your property to function, flow and feel. All these things can be incorporated into that ideal green driveway. 

 

And then it’s become more than a driveway but a reflection of your style, your ethics and your home to be proud of.

 
 

Asphalt Seams/Joints

Posted September 3, 2020 @ 2:44pm | by Stacy

Asphalt Seams/Joints

Asphalt seams, or joints, occur as a result of the paving process. The standard size paver that lays the asphalt generally ranges from 8’ – 14’. Most driveways are a double car (16’ -24’) or a 3 car garage (~ 36’).

 

Laying the asphalt occurs in passes, where there are mats that are laid up against one another. This can be a weakness in the product if it’s not “sewn” up properly. Think of it as pieces of fabric that need to be joined (sewn) to stay together. If the seam isn’t joined well it can unravel or separate in the case of asphalt. You will see this happening on roadways.

 

One important process is the temperature of the two mats. When the asphalt leaves the plant it is between 300 and 350 degrees Fahrenheit. Depending upon how far away the plant is from the jobsite, the ambient air temperature, and how the project is staged with pulling passes the asphalt temperature will be affected. 

 

Other factors that allow a good seam construction are the paver and roller operators. Ensuring that the side of the paver is overlapping/abutting the adjacent mat properly and the seam is compacted at just the right time also are major contributors. 

 

When the seam is noticeable you see a strip or shadow where the mats join. This doesn’t mean that the adherance is insufficient but it can be an aesthetic issue for some homeowners. Using a propane torch, skilled looters to loot (or rake) the larger rock and smaller fines as well as talented roller operators will lessen the look. Unfortunately weather, especially cool fall days, will make it rather difficult. 

 

If your driveway shows too much of that seam for your preference or any other minor surface variation, a simple emulsion sealcoat will unify your surface. Make sure to use an asphalt-based sealer only. Not a coal tar sealer. Not only is an asphalt-base a smarter enviromental choice but your asphalt will appreciate it too. As the asphalt wants to expand and contract with changes in temperature, the sealant needs to move with it. A coal tar sealer is a rigid product and on a flexible material such as asphalt that means hairline cracks.

 

Enjoy your asphalt driveway!

 

 

 

 

 

 

 

 

 
Filed Under: Paving | Permalink
 

April Featured Project

Posted April 19, 2020 @ 12:45pm | by Victorian

April Featured Project

Erickson Residence

Project: Driveway Replacement with Channel Drain and Raingarden

 

Todd and Christina felt it was time to redo their driveway and it was important for them to consider ways to do it in a more earth-friendly manner. An asphalt driveway replaced the broken concrete and made things easier for them in the winter to remove snow.

Later a channel drain was installed to reroute water to the side of the driveway keeping the stormwater runoff on their property. Now every rain event, water coming off a portion of the house and the upper portion of the driveway, enters into the channel drain that diverts the runoff into a beautiful tiered raingarden. Not only are they capturing over a 1” rainfall event each time but they’re supporting native plants, pollinators and contributing to replenishing the aquifer!

Let’s elaborate on asphalt a bit more. Conventional asphalt, although seemingly not ecologically-sensitive has some redeeming aspects that do make it sensible when it comes to the environment, and you:

  • most highly recycled product in the world (based on weight)

  • low carbon footprint compared to a permeable driveway

  • easy to repair and overlay unlike concrete

  • in winter climates, it can be much easier to shovel or snow blow.

  • most economical compared to other surface types (spend your money on other things)

 
Filed Under: Featured Project | Permalink
 

Earth Wizards Response to COVID-19

Posted April 16, 2020 @ 5:05pm | by Victorian

You may know Earth Wizards as your eco friendly paving and landscape company.

And it’s true! We do care about the health of our ecosystems. We also care about the health of you and your family. That’s why we are taking this pandemic seriously, and taking all necessary precautions to ensure your safety.

 

It starts with our estimates.

Upon arriving at the site our sales representative will give you a call, and you can talk us through the project without ever having to leave your home. Our sales reps would love to shake your hand and meet face to face, but we will have to settle for a friendly wave through the window. 

 

When we get to work on your project.

We will ensure that any part of your home our crews come into contact with is thoroughly disinfected, this includes water spigots, garage door openers, and electrical outlets. Many homeowners are interested in and enjoy observing the construction process. We love that. But for your safety and ours, we ask that you maintain a safe distance while doing so. 

 

A family owned and operated business.

Earth Wizards also cares about the well being of its employees and contractors. We want to do everything we can to ensure they get through this with as little financial disruption as possible, while also ensuring their safety. 

 

Lucky for us, our business lends itself to social distancing.

For starters, we work outdoors! This means our crews can safely work together while still maintaining a social distance. We also maintain a large enough fleet of trucks, that there is no need to share rides to or from any jobsite. Our employees and crew understand that it’s up to us to keep each other safe.That means not exposing themselves to others if they have any symptoms. 

 

Earth Wizards was deemed an essential business by the state of Minnesota. 

We are committed to continue providing excellent service to you and a safe and stable working environment for our employees.

 

 
Filed Under: News | Permalink
 

The Garage Apron/Driveway Joint. What the heck happens there?

Posted April 16, 2020 @ 4:22pm | by Victorian

The Garage Apron/Driveway Joint. What the heck happens there?

One of the most common repairs is the joint between the garage and the driveway.  If you’ve experienced this, repaired it, to only have it happen again you’re probably not a happy camper. 

 

Frustrating? A waste of money? 

 

Absolutely. We’d rather you spend money on other pleasures in life than fixing a pavement collapse situation at your garage over and over again.

 

We’d like to elaborate why this happens and what can be done to permanently fix the issue.

 

First, garage construction. To be clear, this is not our expertise. :)

During construction of the garage foundation work, there are concrete blocks placed around the entire perimeter. 

 

Certainly there are many particulars beyond our scope of expertise, we’ll only expound on what we experience. 

 

Each concrete block contains two large holes. Generally the corner blocks of a structure are filled with concrete but the center ones are left open. 

 

This is where issues can happen years later. 

 

Initially soils and base aggregate for the driveway are moved around and fill these holes (to some extent) but those materials are neither compacted or filled in a way that ensures any permanent stability. So then...

 

The power of water.

As time passes and the joint between the garage floor and the driveway are exposed to water from rainfall events, the power of the water will move soil with it. 

 

If there’s a place for it to go. It will go. 

 

Once any of the top layers of soil move through those open holes of the concrete block the surface of the driveway will start to collapse. If you have a concrete driveway, you won’t notice as much of a collapse? Why? 

 

Concrete is a rigid pavement and will create a “bridge” over an unsupported area. 

 

We actually have seen some major wash-out under garage floors, up to 6’ deep because of concrete’s amazing bridging abilities.

 

Why asphalt why?

One of the many pros of asphalt is that it’s considered a flexible surface. And deemed self-healing meaning

that as it expands and contracts with swings of temperature the oils in the asphalt will become rejuvenated and self repair where concrete’s rigidity is not as forgiving.

 

Here’s where the con doesn’t work in our favor. 

 

When the pavement surface of asphalt is unsupported, it begins to collapse, especially in areas where it’s exposed to loads (your car driving over). The adjacent pavement will join in and collapse as well.

 

The fix.

For these circumstances, it’s imperative to expose the concrete block, fill with sand or other self-compacting materials, and then cap with concrete.

 

Then the driveway joint can be reconstructed with compacting base aggregate and new asphalt. 

 

There! You’re good to go not having to revisit that issue any longer. Now you have the time and energy to focus on all those other household projects!

 

 
Filed Under: News Letter | Permalink
 
 
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I have already recommended you! Our consultant, Shelly, was extremely knowledgeable. She explained (the process) in technical detail. She is the reason I chose Earth Wizards over the other 5 bidders. Installation crew was terrific and exceeded my expectations.

- Don P.
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