Griz, the problem I'm seeing is that paving/concrete is done over compacted base. There are porous paving materials showing up in the marketplace these days. While I don't have a link for you, a little searching should turn up many hits.

The other thing I'm envisioning is lots of roots being cut or mangled. Tree roots grow out and away from the trunk, not down. So to protect trees in a construction zone means any fencing that is placed to keep machinery and supplies away must be placed out farther than many realize.

Deep layers of woodchips have been used successfully during such projects. The chips act to dissipate the weight of whatever is running on top of them. And if allowed to remain afterward, which I realize is not always possible, these woodchips can serve to mitigate some of the damage that has been done to the soil.

Props to you for having this concern in the first place. I've seen far too many building projects where the contractors had either no clue or no concern over what was happening as a result of their activities.

+oM

Hiring an ISA-certified arborist that could work with you to create a management plan might be a very good investment. You might also find it surprising affordable.

This^. I should have said. What you are facing is a common thing. And ISA in particular has done much to address this set of issues. See what/who you can find. It could be the best money you'll have ever spent.

+oM

I would try to reroute the drive way IF possible.

My last house was about forty years old. when the house was new someone planted two maples on both sides of the drive. The one on the house side was also border by a side walk and the house itself. On the other side the tree was between the drive and the corner of the neighbors house. When planted each tree had a 15" radius to grow in.

They were a big asset to the house from the shade they provided and the landscape asset. However because so much of the root structure was covered by house and concrete, they started to die in the ten years we lived there. It was sad to see them die and see the naked house. (Not that the house was ugly, but they were such great trees.)

Construction is brutal on the soil. The majority of trees roots are in the top 4 feet of the soil or so. You have 5 ton trucks driving over the soil, that cant be too good. As well as few ton slab of concrete definitely wont help. In the places you put the driveway and have the trucks and what not go, the soil will basically sink.

Im not saying that all your trees will die, and that its the last thing you should do or what not lol. Just keep in mind that these trees have been there and used to that soil level and level of compaction.

Also, compaction basically makes it nigh impossible for tree roots to go through the soil.

How far away will the driveway/work be from the trees? If theyre liek 30 feet away you shouldnt have too many problems. Most of the time compaction is bad for newly planted trees, or if your within 2 or 3 feet out from the drip line ( thats based on the "usual" space for roots, I would personally stay as far away from them as possible.

Thanks everyone for your thoughts.
We have had 2 different arborists here. Unfortunately their only suggestion was to not build or perhaps lowering equipment from balloons. The second one was to evaluate moving some trees. They quoted $6000 per tree. I love the trees but I do not have that kind of money.
Due to the location and number of trees it is not possible for the equipment to avoid the drip line of the trees. I will try putting down a thick layer of chips. I am going to try moving a couple of the trees with an air spade. If they are not moved they will have to be cut so a week or so of labor and a couple of thousand dollars for rental equipment, this much I can gamble. These particular trees are too close to the house to use a tree spade so again not many options.
If anyone has any suggestions about the fine points of using an air spade they would be greatly appreciated.
Thanks griz

"We have had 2 different arborists here. Unfortunately their only suggestion was to not build or perhaps lowering equipment from balloons."

Well, maybe there's more to this than we know, but that suggestion sounds like a major cop-out from someone that didn't know what they were doing. There's a "science" to this stuff, and it doesn't involve balloons. I'd almost bet that your "arborists" weren't ISA-certified (in other words, they were probably just dudes that had figured out how to start their homey-light saws and thought that made them experts).

What it sounds like you are doing is saving a collection of tree trunks, not really considering what preserving the trees entails. Building amongst existing trees is rarely successful, sorry. Add to the problem with how expensive it will be to remove those trees as they begin to fail in a few months or a couple of years.

The house has been designed to fit among the trees (makes an odd shaped house)

===>>> any chance at seeing a pic of this design ... and a pic of the site???

i am playing devils advocate here.. it all sounds so cool.. but ....

so if the trees fail.. then what??? .. you are left with a weird shaped house???

how would you replant .. could you get the stump removed.. to plant a new tree???

if the lot is heavily wooded ... i would suggest that the safest way to go.. is to simply sacrifice some to the project.. and replant new when done ...

over the years.. we have had so many posts.. about 5.. or 10 years later.. how the home owner is losing all the mature trees .. down the driveway.. and immediately near the house ...

i really fear for you.. on this plan ... but i wish you ....

good luck

ken

ps: what about harvesting the trees.. and actually using them in the project ..???? .. at least they wouldnt be going to a landfill ... i suspect the project is much beyond change ....

What I've seen happen since the beginning of time is that the owner wants to "save all the big, nice trees, get rid of all the brush". Now that person doesn't know the difference between a buckthorn bush and a young oak tree sapling. So what they invariably do is have all the young, vigorously growing stuff removed and leave behind the big mature trees that have no chance of adjusting to the new grade, the compacted soil, the cut up root system, that will result from the project. Then later, the sound of saws and chippers can be heard as all those trees become unsafe as their top portions die off. But that's well after the developer has cashed his check and gone on to new "wooded subdivisions".

+oM

Mabey its a good time to think of what to do with them when theyre gone? You can use the chips from them to reinvigorate the soil after construction, after some composting..

Is there a possibility of saving some seeds from them, and plant them in pots till you can plant them, maybe start a few cuttings of a few favorites?

Thanks again for your continuing thoughts.
The lot in question is an acre in the city with an old house with much "deferred maintenance ". The old lady died in her late eighties and many of the trees were planted when she was a girl. The only thing holding up the house is the termite tubes.
The project has not even left the CAD program. We are seeking out as much information as possible from as many sources as possible.
Both arborists were professional and certified. The balloon analogy was an exaggeration but his view was extreme. I respect his opinions because he was obviously a true tree lover and I can relate to that, but he lacked practcality. He did suggest bringing material onto the property with a large crane to avoid driving over the roots. Every house in this area has driveways running within inches of large trees. Most of the would be arbutus but there are some redwoods as well. His contention was that such a driveway would kill the trees although local practice would tend to suggest otherwise.
On our property we have several large arbutus by the street. Back from there are the old ornamental shrubs, many of which are so old they have been pruned into trees. There is a pittosporum well over thirty feet. Crepe myrtle, strawberry tree and others of the same vintage. There are New Zealand tea roses that have a trunk more than six inches in diameter.
While I certainly concede that it is easier to cut down and then replant the beauty of this place is the mature trees and realistically I doubt we will be here more than ten years at the most. No where near enough time for planted trees to mature to anything approaching the beauty of what is here.
The plan for the house at the moment is a kind of right angle z. At one time the design featured cut outs to accommodate the existing trees. That has since been modified as it seems most people are afraid to have trees close to there house. Personally i feel i can always build or repair a house. I can't build a tree.
Much of the house will be on the same foot print as the old one but due to local design requirements the garage must be attached to the house which forces a very long hallway/ sunroom leading back to the garage area. It will probably end up as a kind of greenhouse.
I did briefly consider designing it with an atrium around the biggest of the crepe myrtles but in addition to circumscribibg the roots I don't think it would get enough light.
And just one more complicating factor 6 of these beautiful old trees are within 4 feet of the existing house. At the time this was built it seems that pouring the foundation on the ground was acceptable. That being said it seems to be surprisingly crack free even though the roots must criss cross the whole thing. Apparently to move them will require carefully tearing down the house and then trying to move them. I am not sure this is possible let alone practical.
My current plan will be to sink metal posts roughly at the drip line of the most at risk trees, then fence them in.
So a question after all this rambling. For the most part any roadway / driveway to be used by the crews will be constrained and I will cover it with a thick layer of chips (as suggested here) in areas where it is practical should I encourage vehicles to take different paths?

I would make reasonable efforts to save whatever trees possible, because it sounds like you have a unique if not historic property. However, if you need to remove a tree or two during your construction project, it is not the end of the world.

I don't know where you live, but here in the fairly wet northeast US, I think it is better that dwellings and structures are not oppressed by too much vegetation, including trees and their limbs overhanging or touching the structure. Houses need airflow and sunlight to encourage proper ventilation and drying. This greatly lengthens the lifespan of the roof, siding, paint job, etc. not to mention it is safer for the structure.

The first time I had tree work done in this yard, the tree service removed a huge limb from a Silver maple, which was practically a 3rd trunk, that was overhanging the corner of the house and the utility wires. To do so, they had to drive the bucket truck over a sidewalk and septic system right in front of the house. They put down huge sheets of plywood to protect the pipes and sidewalk. I assume this was to dissipate the weight, similarly to how the woods chips might do. Perhaps that might help.

I am inland in northern California. It is dry for 8 months of the year and then intermittent storms during the winter although it has been raining pretty much for the last month.

In this neck of the woods the more trees you have shading your house the happier you are. The local utility will even give you shade trees. Mature trees make the difference between enjoying your yard and simply running from your air conditioned car to your air conditioned house four months of the year.

Your suggestion with the plywood is good for the smaller trucks. It is the cement delivery that worries me most but it might be possible to pump it in.

Thanks for the thoughts.

I hate giving much advise without seeing what you are working with, but, in general, I'd try to design the driveway so that it was as far away from as many of the trees (that you want to keep) as possible. Weaving around some trees might be helpful, but it can also be disadvantageous by damaging a larger portion of the rootzone. Figuring out the happy-medium is part of a proper design process.

The "average" (almost meaningless, but useful for the concept) tree rootzone is about three times the diameter of the tree's crown. Keep that in mind when you are evaluating the situation. Damaging some of the roots is not necessarily going to do significant damage to the tree. I've seen multiple examples of trees, where a decent portion of the rootzone was completely removed (especially where trails/roads were cut into a hillside), that did just fine and are continuing to do fine years after major roots were just chopped off flush with the terraced hillside.

If roots (especially larger ones) are cut, I would recommend trying to make the cuts as clean (not ripped or ragged) as possible. I would also leave these cuts exposed, at least for a while, rather than burying the fresh cuts.

I would definitely advise against making multiple paths (in hopes of lessening the damage at any one location). If you review studies of soil compaction in situations like this, you'll notice that the degree of compaction is much greater initially (to non-compacted soil) than in subsequent passes. So, by making multiple paths, you're makings lots of areas bad as opposed to making the one bad area just a little worse. Another aspect of this is that you probably wouldn't be there to monitor traffic all the time anyway, and the builder people probably would tend to always take the shortest path when you weren't there. By limiting their access to one path, you have at least some control over the spread of damage. Many workers are also aware of the concept of not infringing on restricted areas (from previous jobs).

Thanks Brandon,
Good advice all around.
Griz.