HomeMy WebLinkAboutSubsoil Studyßear Uallcg 0ssign, Lfd.
Enginr?fr - tonluhanf¡
P. O. Box #7lo+lS
STEAMBOAT SPRINGS, COLORADO, 8o477 -o47 5
MOBILE: (glolSlg-S+S+
E-MAIL: <bearbvd@mindspring.com>
lune 3,2022
Ms. Maureen O'Brien
PO Box 663
New Castle, Colorado, 81.647
Subject Soil investigation for a proposed residence to be located at 24
Garfield County Road #ILL, in Garfield County, Colorado.
Dear Mr. Reed,
Per your request, we performed a soil investigation and
evaluation on the subject site in April of 2022. The investigation was
performed for the purpose of providing soil design parameters for the
construction of the foundation for a single family residence.
The proposed structure is anticipated to be of two story factory
built, wood framed construction with a full basement and an attached
carport. The foundatíon is proposed to be constructed with reinforced
concrete walls bearing upon reinforced concrete spread footers. The lot
is nearly flat and is covered with grass vegetation with some brush and
varied uncontrolled fill. The site slopes gently downward toward the
north from the County road and is separately from Colorado highway
#133 to the west by a path and a drainage ditch.
A test pit was advanced on the parcel, in the immediate vicinity
of the proposed residence. The pit was advanced using a rubber tire
mounted backhoe. The test pit revealed twelve to fifteen inches of
browrç slightly moist, silty clay topsoil overlying a stratum of very
slightly moist, dark browru hard, fat clay subsoil, approximately 6 feet
thick, which in turn overlay a very dense , yêty slightly moist, medium
brown sandy gravel which extended to the maximum depth explored,
ten feet. No free ground water was observed in the pit.
Our experience with similar soils, taken together with our
observations in the test pit, have led us to form the opinion that the
lower, very dense, sandy gravel will provide stable bearing for the
Page #L of 3
foundation of a structure of the proposed type.
Spread footers for the proposed structure should be designed to
bear on the lower, very dense, sandy gravel, with a maximum net
bearing pressure of 4.5 KSF. No minimum dead load will be necessary.
Any retaining structures should be designed to retain pressure
equivalent to that which would be exerted by a fluid weighing 70 PCF.
Because of the highly pervious nature of the lower gravel, the
footers for the foundation need not be surrounded with a footer drain.
Flowever, in order to provide for the possibility that the water table
might rise at some future time, a sump extending thitty inches below
the slab on grade floor of the proposed basement must be provided,
along with an appropriate sump pumP and a discharge line (protected
from freezing by a vacuum breaker) leading to a point on the lot at
least fifty feet away from the structure. Eighteen inches of ground
cover above the discharge line is sufficient provided that it is protected
by a vacuum breaker and has a uniform dor,rtnward slope with nolow
spots going toward its outfall.
Frost protection for the foundation must be provided by
maintaining a minimum of 48" of earth cover over the footers,
measured in any direction. The finish grade should provide fot a
minimum of.2"/" slope away from the structure in all directions for a
minimum of 10 feet, as well as for positive and continuous drainage
away from the building without any ponding. Native subsoil materials
will provide appropriate backfill. This backfill may be capped with a
maximum six inch thick layer of the native topsoil. The native backfill
material must be placed in lifts a maximum of L0 inches thick, with
each lift moistened and compacted to 93"/" of its Standard Proctor
density. The nature of the native clay subsoil baclfill material will
minimize the possibility of surface water and/or roof runoff from
penetrating to the underlying gravel. If at all possible, we recommend
the installation of rain gutters so as to minimize the chance of roof
runoff penetrating the backfill.
In order to control moisture as well as to minimize heating costs
for the proposed residence the surface of the subsoil beneath the floor
slab in the basement must be covered with a six mil thick sheet of
visquene.
Provision must be provided for positive venting of radon gas
from beneath the basement slab on grade floor should future testing,
completed after construction of the residence, prove such venting to be
necessary. Because of the fact that radon gas is extremely more dense
Page #2of 3
than air, our recommendation is to provide a forced draft fan to
accomplish venting through the roof. This fan should be installed at as
low an elevation as possible above the basement floor. The high
density of radon gas makes it very difficult, if not impossible, for an
induced draft fan installed at a higher elevation in the building to
exhaust radon effectively.
The basement slab on grade floor must be appropriately
reinforced and placed over a 6 mil thick sheet of visquene, which, in
turn must be placed above approximately one foot of compacted
granular fill (we recommend the use of crusher fines), which, in turn
should be placed above the native sandy gravel. ALL of the native clay
subsoil must be stripped from above the gravel beneath the full extent
of the slab floor.
Because the underlying sandy gravel is completely non-
expansive, there will be no need. to provide expansion joints in
partitions situated immediately above thebasement floor slab.
Thank you for the opportunity to have been of professional
service to you in this matter.
¡¡\,\'t\ ì^-
Page #3 of 3