Recently I have been working with a product with excellent cross-application potential in our tree root zone preservation efforts to maintain soil porosity, or prevent soil compaction on construction and development sites.

I am experimenting with this product as a solution in the planning stages where root zones remain undisturbed in future raised-grade scenarios, and where all other efforts avoid construction of roads, or patios inside the protected root zone area have failed.

The intended design purpose of this product is to install temporary, or permanent a road bases on-grade, or to raise soil grades without Keyways, footings or sub-base preparations where soil stabilization and micro-pore compression, or subgrade stress is an issue.

This cellular confinement system is designed to laterally disperse the weight of equipment, or fill-soil loads evenly over the applied surface thereby reducing vertical soil compaction, or "subgrade sensitivity".

The product is sold in 8’ X 20’ ft. sections that are shipped in compressed form. When expanded, the cell walls contain holes in each wall of the cell. Each cell is filled with specified rock to provide a continuous lateral/vertical field of aeration and moisture penetration over the area of application. Interlocking pavers provide the porous road or patio surface to complete the process. Lateral, and vertical aeration tubes can also be incorporated into these applications, as needed in different scenarios.

This is an exciting product, but questions remain, I am interested in your feedback. I will gladly share this information and specifications with those of you that are interested, and with one additional request: that you document your own experiences and results with this product as you employ it, and share it either in this forum, or by email.

Timg@hotcoco.infi.net

Reply to post by Tim Ghirardelli, on April 16, 1999 at 14:17:35:

Tim, Reduction of soil compaction is always on our minds. A recent job specified 12 inches wood chips covered by terra-mats, which are made of recycled tires, and fairly expensive, especially the shipping. If your product is competitive in price, shipping, and labor, there is a markket out there.
So, tell us more. Peter

Reply to post by Peter Torres, on April 16, 1999 at 14:17:35:

Sounds to me like Tim is talking about a permanently installed grade change to meet load bearing engineering standards and Peter is talking about temporary protection. Are we on different pages guys?

Reply to post by Peter Torres, on April 16, 1999 at 14:17:35:

Peter: The product I'm using is Geoweb, manufactured by Soil Stabilazation Products Company, Inc. Their address is P.O.Box 2779, Merced, CA 95344 Phone 800-523-9992. email: staff@sspco.org
I've been working with Sam Randolph who can answer your questions and send you information on various products.

Scott: The application of this product is perminant, and designed to meet road engineering requirements while minimizing impact to existing soil. For temporrary road construction,I have been working with Akwadrain. Any comments on use of this product for this purpose ???.

Tim

Reply to post by Scott Cullen, on April 21, 1999 at 22:54:04:

I am talking about temporary (up to several years) protection for the original grade. If the product discussed can do that at a lower cost, then I would recomend that it be purchased. If it is cheaper to leave it there when the job is done rather than removing it,then let's bury it. I will pursue more info.

Reply to post by Tim Ghirardelli, on April 16, 1999 at 14:17:35:

I did a little searching for the product and have included a reference page and a photo here. I trust Tim will correct me if I've shown the wrong item.

While the product has a clear usefulness in the areas of roadways, banks and structures, I'm not very excited however, about its contributions to raised grades or surface treatments around trees. If fact, there is a letter in Doug's forum today about a tree in significant decline where hidden beneath the soil was a gravel base on top of a solid plastic sheet (the still practiced concept of gravel "mulch" and weed control).

Solutions for engineers are expected to somehow be eternal; i.e., without any change. Solutions for green things should have the concept of change built in. The geoweb may make an engineer happy; a tree will find it very difficult.

The photo shows the rock aggregate that probably is preferred for the fill. The holes in the plastic verticals are meant to form a sort of "tooth" to the sides as a friction for the arches of gravel pieces to push against and transfer their loads to the vertical walls. If the pieces are too small, perhaps like pea-gravel, this concept probably won't work anywhere near as well because the loads can be transmitted vertically by the pieces slipping easily past each other. This vertical slippage should increase as the particles get smaller.

If I hit a sand-packed tube with a hammer and the walls of the tube were strong enough to prevent bursting, I would have just a effective a compaction tool as a solid steel cylinder. Whether I provided the same levels of pressure slowly or quickly as with a hammer, compaction would still occur.

But, if we keep the shown aggregate size to maintain the original mechanical intent, this size is rather inhospitable to roots. The holes in the plastic wall will eventually strangle any roots growing through--as also will happen with the spaces between the gravel. If the thought is that the geoweb will provide diffusion of air to a typical soil surface beneath without compaction, there will be eventual compaction under the gravel faces and the only diffusion will occur at the number of voids available right where the gravel meets the soil. This percentage of interface voids pretty much occurs by chance, so the area of open exchanges can be surprisingly small.

Diffusion does not work well over long distances, inches, in gaseous exchange into the soil itself, and as a biological contribution the offered system may prove extremely ineffective.

There is a comment in the web page about vegetative root growth being encouraged, however, I would think this refers to grasses and the like which would have to grow down past the aggregate and anchor in the soils.

Next, an 8' by 20' item has its own problems in being torn up and pulled out as a unit during some other construction. And, cutting the geoweb into smaller squares may work against providing a coordinated spread of surface loads.

The use of this material might appeal to the engineering side of me in raising the grade around a tree and surfacing it with concrete or asphalt. The green side of me* however, would know that roots would eventually invade this hostile area and find little to support the tree. In that sense, I might delay a decline of the trees, but I probably won't prevent it.

As a steward, my primary goal is to safely extend the life and health of my clients. I am always interested in cross-over methods that can serve multiple needs, but I have often been disappointed when the direction of flow is from engineering concepts to landscape issues. It's a bit too much like resolving a religious dispute over who has the right God. The engineer's God has the biggest budgets and pulls the most weight with vendors and innovators. The acolytes of the green God have squeaky, timid voices too often and the battle is generally uneven and unfair.

Certainly, I'd want a continued dialog from Tim in fine-tuning where possible in support of his thoughts. I've also used the awkadrain style of product extensively--except that I use it backwards--an idea not yet caught on to by the manufacturers.


Bob Wulkowicz


*The green side of me is somewhat mossy and tends to stay to the north face. My wife suggests I can correct that woody quality with more frequent trips to the shower. My response is that she simply doesn't understand what goes into making a real woodsman. She responds that I should then type outdoors to stay consistent--and distant. On my birthday, I got a longer extension cord as a present. Was there a message in that?

bob