Specifications � JOHN I�c®ONALO ENGINEERING SOILS CIVIL GEOTECHNICAL
Ground - Penetrating RADAR
10116 SE Stanley Avenue
Portland, Oregon 97222 -4351
(503)654 -0180 Fax (503)654 -8755
Tax ID 93 074 6595
October 20, 1999
Dean Smith
Mountain - Pacific Machinery
11705 SW 68th Avenue.
Tigard, Oregon 97223
FOUNDATION SUPPORT FOR BUILDING ADDITION
In making my report of October 13 I was asked about boulders
and in the course of doing that I looked at the building itself,
which I wasn't asked to do. I have since looked inside the
building and it appears that stairs and furnishings have been
adjusted into the settled building so that efforts to raise the
building may make things worse than they are now. Also, what
originally looked like a thin concrete floor slab has appeared,
upon further excavation, to be a concrete overflow when the slab
and walls were poured. In short, I am getting out of my field of
soils engineering on these things.
If it is desired to leave the original building in its
present condition, I think that if the work is done immediately,
before it starts raining, no further settlement would occur. It
would be fine to eliminate the jacking and make whatever
connection between the new and old foundations seems appropriate.
Dowels up from the bottom still have a lot of rock to contend
with. Dowels in from the side sound reasonable to me.
Very truly yours,
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• 10/1 ? /99 13:12 MOUNTAIN PACIFIC MACHINERY 4 6845295
- NO.680 D01
JOHN IticDONALD ENGINEERING
SOILS - CIVIL - GEOTECHNICAL
Ground- Penetrating RADAR
10116 SE Stanley Avenue
Portland, Oregon 97222 -4351
(503)654 -0180 Fax (503)654 -8755
Tax m 93 074 6595
October 13, 1999
Dean Smith
Mountain- Pacific Machinery
11705 SW 68 Avenue
Tigard, Oregon 97223
INSPECTION OF FOUNDATION CONDITIONS AT BUILDING ADDITION
SCOPE
The existing building has a basement or partial basement and
it is desired to make an extension to the basement, but at a
slightly lower level. Excavation has encountered huge boulders
partially under the edge of the existing basement. The purpose
of the inspection was to make recommendations for dealing with
the conditions.
INSPECTION
The boulders already excavated were so closely nestled as to
be almost continuous solid rock. These boulders are Boring Lava
that came from the Mount Sylvania (Mountain Park) area around a
million year ago. Weathering processes or rock breakdown
procesees that occurred since then can be likened to pouring
"corrosive acid" over the ground surface. As the "acid" sinks
deeper into the ground it acts on the cracks and crevices of the
rock to form soil. Rock with widely spaced cracks form boulders
because the "acid" or weathering front only happens once.
The existing building had an original portion with a
basement on a slab, and then a northward addition was made. The
rear wall of the old part of the building has been exposed by the
excavation. Part of the rear wall was founded on buried wood and
organic Boil and part is down close to the boulders. The
basement slab, which is shown in the plane to have a thickened
edge, is just a thin slab. Signs of settlement include roof
distress at the junction between the old part and the northward
addition, a crack open at the top between the old and the newer
basement walla, misalignment of the rear doors, and a further
Received: 10/14/99 13:07; 503 639 7707 -> JOSEPH HUGHES CONSTRUCTION, INC.; Page 2
10/14/99 13:12 MOUNTAIN PACIFIC MACHINERY 4 6845295 NO.680 D02
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Mountain- Pacific Machinery ? October 13, 1999
opening at the top between the wood stud portion and the concrete
portion of the south end rear wall.
DISCtUSSION AND RECOMMENDATIONS
Further attempts at excavating the huge boulders with heavy
machinery are not recommended. The building plane show a
platform with steps over one of the boulders and, if desired,
that boulder could be made part of the platform. A second
maaeive boulder to the north could similarly be made into a
partial platform. However, if the space is valuable, the boulder
will have to be split, or cracked in half, using the "plug and
feather" method, or the "Darda" rock splitter.
To use the "Darda" method, large diameter holes are drilled
into the rock and a hydraulic wedge is inserted that pushes
outward and cracks the rock. The boulders are a crystalline rock
with no layers or weak planes, eo it should split with a smooth
plane.
The plug and feather method consists of 3/4" holes drilled
into the plane of the desired split at about 4" spacing. Wedges
can be made by halving a 3/4" rod lengthwise and grinding the cut
faces to make two halves that fit into the hole. The center
wedge, or feather, is 3/4" square mild steel that is ground to a
sharp wedge in about 4 inches of length. After all the holes
have been fitted with wedge assemblies the protruding feathers
are successively tapped with a hammer to stress and crack the
rock.
The plans show a new foundation wall to be built below the
thickened edge of the floor slab. With no thickened edge present
there will have to be modifications. In addition, with
settlement already.preeent, merely undermining the slab edge will
create more settlement. I recommend jack points at intervals, as
shown on the attached detail. If rocks are closely under the
slab, short pad jacks can be rented or steel wedges driven in to
support the slab.
It may be possible to raise and partially level the existing
slab edge, in which case numerous jacks will be needed. If
merely stabilizing what is there is felt to be beat, one jack can
be used to load up a segment, hold it with adjustable struts, and
move on. It is understood that the existing basement floor slab
has a low portion that collects water. It is possible to have a
Received: 10/14/99 13:08; 503 639 7707 -> JOSEPH HUGHES CONSTRUCTION, INC.; Page 3
10!14/99 13:12 MOUNTAIN PACIFIC MACHINERY - 6845295 NO.680 D03
Mountain - Pacific Machinery 3 October 13, 1999
grouting company drill holes through the slab and inject grout so
as to raise and level the slab somewhat. Finally, if the rear
wall is raised to any extent, grouting under the Blab all along
the rear wall will be necessary to provide continuous support.
SUMMARY
While it is possible with laborious methods to deal with the
partially exposed boulders it is also possible to incorporate
them into the finished work. As for the settled floor slab and
rear wall, as long as an effort is being made to improve the
building, we might as well correct as may problems as we can,
while things are opened up.
Very truly yours,
cc: Froelich Consulting
Engineers, Inc.
� PROF
a4 4 5657 $ `Y
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Received: 10/14/99 13:08; 503 639 7707 -> JOSEPH HUGHES CONSTRUCTION, INC.; Page 4
, 10/14/99 13:12 MOUNTAIN PACIFIC MACHINERY 4 6845295 NO.680 PO4
USEFUL DIGGING TOOLS
Tire Flub Ca Dent Trenching "Bucket
P Shovel
Tool
Use scrap steel plates 12" x 12 ",
3/8" min thickness
top and bottom Bottom of house
foundation wall Ground Surface
f f • '
�-... Alternate Support;
Use 24 -ton jack. 1" Allthread with rod
II I
couplers top and bottom
Cut 2" pipe to
•
fit and drive
in with hamper or
so jack can be am
removed and the
pit filled with
concrete.
Set bottom plate
into wet .
concrete and '
level it Concrete pad 6" min. thickness
If jack is too
gal a short, cut 2"
pipe stub and
Use 8 o #4 rebars 12" long to make use steel plates
Dig to firm ground gridwork. top and bottom
or to minimum 18" _
as an extender
below foundation
wall bottom Kole bottom 18" by 18" minimum DO NOT USE WOOD
BLOCKS
House foundation wall
pETAILS- of JACK PIT
John McDonald Engineering
II
Note: Work must be inspected
by the soil engineer.
SIDE VIEW SHOWING ACCESS DIGGING
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