HomeMy WebLinkAboutRe: soils testing �Q�Np E N T T�S,,
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337 31ST AVENUE SOUTH • PO BOX 325 • WAITE PARK, MN 56387
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OFFICE: 320-253-4338• FAX: 320-253-4547
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� May 18, 2006
Mr. Jerry Nelson
M A B Homes
2525 Nevada Avenue
Minneapolis, MN 55447
RE: 06-158 Report of Soils Observation & Recommendation
for Foundation Drain Design
Single Family Residence
3619 North Shore Drive, Orono, Minnesota
Dear Mr. Nelson:
As requested by you, Independent Testing Technologies has recently conducted a visual
observation of the house being constructed in Orono, Minnesota. The purpose of our
observation was to assist you in evaluating the potential impact of groundwater on the below
grade foundation and provide recommendations to preclude basement water problems.
DESIGN INFORMATION
The proposed single family residence to be constructed is a two story home with poured
foundation and an attached garage. The house dimensions are 50' x 30'. The lowest floor
slab is at assumed elevation 100. We have assumed a 2,000 pound bearing capacity for this
structure.
SERVICES PERFORMED
Our observation was conducted on May 17, 2006. At that time test pits were excavated in
the area that the house will occupy. These test pits were approximately 3 feet below the
existing grade. These test pits encountered 8 inches of soft, grey lean clay (CL) underlain
with 2 1/2 feet of brown, medium dense, mottled, silty clayey sand (CL-ML). These silty
soils were underlain with a grey, wet poorly graded sand (SP), and poorly graded sand with
silt. Hand auger probes revealed these water bearing sands down to a termination depth of 5
feet below existing grade.
Estimates of soils density were based on the resistance of the hand auger probes. Soil
classifications were determined in accordance with the American Society for Testing and
Materials (ASTM) procedures by examining the hand auger probe cuttings.
An assessment of the site grading and drainage was made. The building site appears to be
poorly drained. The lot appears flat. Grading work will be needed to provide positive
drainage away from the building. Water was encountered at a depth of 2 1/2 feet below
existing grade. We understand there will be a minimum of 3 feet elevation difference
between the lowest floor and groundwater level.
We recommend that the soils below the footings and column pads be excavated one foot
below footing grade and replaced with free drainage course stabilizing aggregate (3/4 inch
to 1 1/2 inches rock)
Based on the results of our visual observation, it appears that the groundwater may have an
impact on below grade walls on the site. However, we recommend that an exterior
perimeter foundation drain be installed. The foundation drain should consist of a 4 inch
diameter perforated flexible "sock-type" p.v.c. pipe surrounded by rock and wrapped in
filter fabric. We recommend that the drain discharge by gravity at a maximum of 5% slope
from the house to daylight. An interior sump pump could also be used to discharge water
from the foundation drain. Roof downspouts should be extended to outfall past the backfill.
In addition, the below grade walls should be damp proofed with bituminous material, 6-mil
poly, or approved damp-proofing material from the top of the footings to the ground level.
A minimum of 4 inches of clean, washed sand should be placed beneath the floor slab to
prevent capillary rise of moisture. The finished exterior wall backfill should be placed so
that any surface water will drain away from the house at a slope of 5%.
SUMMARY
Based upon the result of our observation, it appears that groundwater may have an impact
on below grade walls on this site. However, site grading, damp proofing, and exterior
foundation drains are required to alleviate any potential problems.
It should be noted that standard penetration test borings with power equipment were not
taken to evaluate the soils at depth. However, visible soils and the results of the hand auger
probes indicate that the risk of detrimental settlement due to unsupportive soils at depth is
minimal. In our opinion, it is reasonable that this risk be assumed by the owner.
It should also be noted that fluctuations in the level of the groundwater can occur due to
Report of Observation
L T.T.Project #06-158
May 18,2006
Page 2
variations in rainfall, temperature, spring thaw, and other factors not evident at the time of
our investigation.
Mr. Nelson, it is our pleasure to work with you on this project. Please feel free to contact us
if you have any questions or need additional services.
Sincerely,
��/.i:��G/ (� (/l
Mitchell A. Lycnh, Patrick A. Jo son, P.E.,
Project Manager Geotechnical Division Manager
06158m1(drain)
Report of Observation
l.T.T. Project #06-158
May 18, 2006
Page 3