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ITEM DATE SUBMITTED BY
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07/20/2006 02:48 2089380453
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T .(Y-ENGINEERING.F.C.
TO: Jerry Timmons
Mr. C's Carpet ter
119 S. Kimball e.
Caldwell, ID 8 6 5
I
DATE: July 19,2005
i RE: Basement Back i 11 tit Kimball(St Arthur Street
i Dear Jcrry:
After reading the report frbrn American GEO Technics, it is my opinion that their method of using the
drain rock over the exi ing slab and separating the drain rock from the general backfill with Geotextile
is an adequate method. lie drain rock and general backfill that was specified is adequate. The use of
Geofoam is an adequat.vy of reducing soil pressure on your existing wall. I disagree with their
method of only core dri prig(21)4"diameter holes in the slab. In my opinion that is not enough area for
all the water to drain. •• at it this way,if it rained or irrigation produced a 'h"of water over the entire
site and we assume that 'A of that water is evaporated or rims off the site. That leaves ''V."of water that
would drain down into e soil,that equals .25 * (45.5*66.4)*144= 108,763 cubic inches of water. The
(21)4"diameter holes -• .1s 21*3.14*4=264 sq. inches. If you could take all that water and place it in
(21)4"diameter tubes, 1 ,tubes would have to be 34 feet tall. It will take several days for that much
water to drain out throu:.h ose holes with the type of soil that was tested below the existing slab. In the
winter. when the weath i. cold,you will not get that much.evaporation and over time will get a build
up of water. That water is sitting against your foundation and causing the seepage through your wall.
This brings up another I em of water pressure on your foundation. Your foundation was probably
not designed for any wa e pressure and depending on how much water pressure builds up, this could
i cause a failure.
The Geofoam blocks w e only installed to prevent soil pressure on your foundation. The use of
bentonite is usually an a.c•unte solution to stop water,but if it was nut.installed exactly as it is spelled
out and the Geofoam h. chunks missing, then the system does not work. If the asphalt sealant was not
installed from the top n f_t Ling to the top of wall, then any water that drains down the face of the wall
between the Geofoam bl• s will find its way into any cracks that are present on the wall,causing
seepage.
If I would have provid' • t e service, I would have made them bust up the slab; they would not need to
haul it off site, to allow ='r much more area for the water to seep out. I then would have probably used a
similar method as Ame an GEO Technics with the use of the drain rock over the busted up slab and
separate the general bac fill with Geotextile. The other thing that I would have done is completely
remove a 4 foot section f the slab along the entire length of your building,then dug down to the
5531 .Glenwood Boise,Idaho :3 14 Phone:208-938-0265 Fax:208-938-0453 Email:darrent @trueng.com
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07/2 @/2006 02:48 2089380453
1KUENUlNLLK1NU t'AUt 0j
TR IT-ENGINEEAINC,P.C.
bottom of the footing and filled this area with drain rock. And finally, lay the Geotextile over the drain
rock and then installed 'he Geofoam.
My final conclusion is that there is not enough area in the(21)4" diameter holes to adequately drain the
water away from your foundation.
If you have any questions or comments regarding this matter,please call me at(208) 938-0265.
Since ,
atf
/r
4111111111111111111°
Darren D. Truchot,P.E.
File# 1226104