HomeMy WebLinkAboutSoil Bearing for Foundation - PLN General - 4/6/1995 s 's
April 6, 1995
Mason County Department of Community Development
L - Attention: Hugo Flores
✓Mason County Building Department
Attention: Larry Waters
426 W. Cedar
P. O. Box 578
Shelton WA 98584
SUBJECT: Proposed residence for Dave/Carol Watts
Parcel#32205 20 00260
In accordance with correspondence received from Mr. Hugo Flores, Land Use Planner, written
on March 31, 1995 and earlier letter correspondence from Mr. Jason Manassee and Mr. Larry
Waters relative to the proposed residence on this site, the following report is enclosed.
The undersigned, a registered professional engineer in the state of Washington, has inspected the
site on four different occasions and has conducted soil borings for establishing soil
characteristics and allowable soil bearing for purposes of foundation design.
Site visit#1: The immediate site for the proposed residence was too heavily covered
with trees,bushes and debris to adequately assess applicable slopes or direct soil
conditions. However, inspection of the uplands access route from the county road
indicated an acceptable access gradient into the site. All visible cuts into existing banks
along the adjacent portion of the county road displayed gravelly sand cut surfaces with
high degrees of angle of repose. There was no evidence of any underlying clay seams or
perceptible slide history above the site. The coniferous trees were tall and straight with
no indication of trunk realignment due to previous slide history.
Site visit#2: The access area had been more thoroughly cleaned out leading to the
proposed building site which had likewise had a measure of clearing undertaken to more
adequately assess the preferred residence siting alternatives. A soils inspection pit had
been dug within 20 feet of the proposed residence area to a depth of approximately 6 1/2
feet and 15 feet long. Two additional inspection holes were dug in the proposed
Robert N. Boehm
P. O. Box 428
Crrapeview WA 98546
(360)275-8020
Mason County Department of Community Development
& Mason County Building Department
RE: Dave/Carol Watts
residence siting area to determine any soil characteristics differing from those in the large
inspection test pit.
The logs of the pit and inspection holes were tabulated as follows:
Hole Depth Vertical Layering Comments
Designation
Soils Inspection 616" 2-3" leaf mold&humus Assessed on a allowable soil
Test Pit 2' sandy gravel bearing basis, design value
3' gravelly sand would be 2000 pounds per
1' gravelly sand square foot.
compacted with fine clay
particle
Tree and shrubbery roots
were encountered to
depth of approximately
3-3 1/2 feet.
Excellent vertical
percolation properties
Hole No. 2 5'6' 2-3" leaf mold&humus Same as above
2 1/2' sandy gravel
3' gravelly sand, lightly
compacted
slight clay particle at
bottom
Tree and shrubbery roots
were encountered to
depth of approximately
3-3 1/2 feet.
Excellent vertical
percolation properties
Mason County Department of Community Development
& Mason County Building Department
RE: Dave/Carol Watts
Hole Depth Vertical Layering Comments
Designation::::,
Hole No. 3 5 2-3" leaf mold&humus Same as above
1 1/2' sandy gravel
3 1/2' gravelly sand
Tree and shrubbery roots
were encountered to
depth of approximately
3-3 1/2 feet.
Excellent percolation
properties
The results of the inspection holes coordinated with the surveyor's topographical
elevations at the site led to a foundation structure that straddles the existing knoll. This
site permitted minimal excavation requirements, minimal tree removals and limited any
extremes of slope on which walls or footing pads would be placed.
Site Visit#3: Site inspection and residence location verification with Hood Canal
Cooperative representatives.
Site Visit#4: Physical layout of outside walls on site with architect and proposed
contractor. Lines defined by surveyor tape connected to pipes or stakes defining
pertinent control points.
General Structural Design Criteria
Footing and Column Pads: designed to a bearing allowable of 1250 pounds per square foot
which is conservative. (U.B.C. Table 29-B allows 2000 pounds per square foot.)
Concrete Foundation Walls: upland walls designed as modified cantilever retaining walls with
drainage at their bases to limit any hydrostatic load buildup.
The timber framing has been designed to utilize the floors as horizontal diaphragms and walls as
vertical diaphragms with all diaphragm loads intended to be sheared through above mentioned
modified retaining walls.
Mason County Department of Community Development
& Mason County Building Department
RE: Dave/Carol Watts
Conclusion:
In view of the visual evidence at the site and the surrounding area,this does not display any
characteristics of a geological hazard site. I would be more concerned about run-off erosion
damage than anything relating to soil conditions. Fortunately, this property lies within the Hood
Canal Cooperative, whose membership firmly believes in the retention of all natural vegetative
growth, which limits any possibility of severe run-off erosion occurring. Likewise, the extreme
distances between approved construction sites makes for little possibility that man-induced run-
off by virtue of construction would occur.
p
b e watts