HomeMy WebLinkAbout20191537.tiffColorado
Geoscience & Design, Inc.
P.O. Box 68 Franitown, Colorado 80ii6 • Phone: 303.688.215o • Fax: 303.688.1295 * CoGeonesign.Com
Danny Oenes
15104 St. Paul Street
Thornton, CO 80602
SUBSURFACE INVESTIGATION
OF
587 WELD COUNTY ROAD 7
WELD COUNTY, COLORADO
REPORT NO. neo 7
March 10, 2017
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GEOTECHNICAL
STRUCTURAL
�. ENGINEERS
Colorado
Geoscience & Design, Inc ,
P.O. Box 68 Frankton, Colorado 80116 • Phone: 303.688.2150 • Fax: 3O34688.1295 • CoGeoDesign.Com
Danny Oenes
15104 St. Paul Street
Thornton, CO 80602
SUBSURFACE INVESTIGATION
OF
587 WELD COUNTY ROAD 7
WELD COUNTY, COLORADO
REPORT NO.1 -067
March 10, 2017
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STRUCTURAL
OWL ENGINEERS
TABLE OF CONTENTS
General
Site Conditions
Field and Laboratory Investigation
Foundation Recommendations
Criteria for Concrete Slab on Grade Construction
Placement of Foundation Fill
Subsurface Drainage
Surface Drainage
Foundation Excavation
General Information
Location Map
Log of Test Holes
Swell / Consolidation Charts
Summary of Laboratory Testing
I
Details of Foundation Drain System
Foundation Grading Detail
Appendix
+I
1
I
2
3
5
5
6
7
7
Figure 1
Figure
Figure
Table I
Detail I
Detail 2
Information about the Report
Subsurface Investigation
Danny Oenes
Colorado Geoscience and Design, Inc. Report No. 17-067
GENERAL
This report presents the results of data obtained during the subsurface investigation at
587 WELD COUNTY ROAD 7, WELD COUNTY, COLORADO.. This investigation was
made to determine the type of foundation required, allowable bearing capacity, and
groundwater conditions encountered at the time of the field investigation.
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SITE CONDITIONS
•
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At the present time the site is vacant. It is our understanding a steel building at grade is
planned for this site. The proposed structure will consist of steel framed construction
with a steel reinforced concrete foundation. We anticipate the foundation loads for the
residence to range from 750 to 1,500 pounds per lineal foot of foundation wall.
The general topography of the site slopes approximately 1% to the east. The
vegetation at the site consists of native grass and weeds. The weather was cool and
clear at the time of the investigation.
if the type of construction changes from that specified above, please contact this office
for additional recommendations and/or requirements.
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FIELD AND LABORATORY INVESTIGATION
•
Two (2) exploratory test holes were drilled on February 20, 2017 at the site shown on
the Location Map, Figure 1. The test holes were drilled with a four -inch (4) diameter
auger advanced with a CME-45 soil exploration drill rig,
At specific intervals, the drilling tools were removed from the test holes and soil samples
were obtained with a two-inch (2") diameter spoon sampling tube, The depths at which
soil samples were taken and a description of the soil encountered are shown on the Log
of Test Holes, Figure 2, and the Summary of Laboratory Testing, Table I.
Ali soil samples were carefully observed in the field during the drilling operation. These
samples were classified in the laboratory through visual observation and laboratory
testing to determine the pertinent properties. The natural moisture content and dry
density was obtained from relatively undisturbed drive samples of typical soils. Swell -
consolidation tests were performed on typical soil samples see Figure 3. These tests
indicate the behavior of the soil upon various loadings in a wetted condition.
Groundwater was not encountered at the time of the field investigation. These
observations represent the groundwater conditions at the time of drilling or
measurement and may not be indicative of the conditions at other times. Groundwater
levels can be expected to fluctuate with varying seasonal weather conditions and if the
sites use irrigation for lawns.
Subsurface Investigation
Danny Genes
Colorado Geoscience and Design, Inc. Report No. 17-067
Site soil conditions encountered may appear different from the test borings as
presented in this report. An excavation observation is required and must be
performed by a representative of this office to verify existing soil conditions, tions, and
the proposed design bearing pressure. The excavation observation mu
st be
performed only after the entire building footprint has been excavated to the bottom of
bearing elevation. in addition, it may be necessary to revise our '
fou i�dat�o n
recommendations based upon results of the excavation. The fee for this observation
and/or devised foundation recommendations is not included i n the cost of the so;;
re art. -- —�-
Failure to follow the observation requirements noted herein may the
success of this construction project and shall absolve Colorado Geoscience and
Design Inc, from any and all responsibility for any damages arising from the
failure to obtain proper site observations.
FOUNDATION RECOMMENDATIONS
Based on our evaluation of the subsurface conditionswe recommend the e proposed
steel building be founded on drilled piers and grade beams. A professional engineer
rn+eer
should use the following design criteria to design the foundations.
1. Piers shall be a minimum 12 -inch diameter.
2. Piers shall be a minimum of 22 feet deep with a minimum embedment of 10 feet
into the claystone bedrock.
3. Piers shall be designed for a maximum end bearing capacity of 2 000 pounds p t� p urns
per square foot.
4. Side shear resistance of 2,000 pounds per square foot for the 10 foot
�' portion of
the pier embedded into the claystone bedrock.
5. Piers shall be designed for a minimum dead load of 1 000poundsper
• .. a square
foot to resist uplift. If the minimum dead loadpressure cannot be met, the '
increased
pier
length should be increased to offset a n y dead load deficiency.
6. All piers shall be reinforced their full length with steel rebar. r. The pier reinforcing
nfo rcrng
shall be designed to resist the tension resulting from the maximum ' uplift
pressures. No less than 1% of steel based on the pier end area shall be used.
The pier reinforcing steel shall extend into the foundation wall a sufficient
distance to fully develop the bars in tension.
7. The recommended diameter must be maintained at the top of each
pier hole.
We recommend forming the top portion of the pier with cylindrical cardboard
board
forms to prevent mushrooming
Subsurface Investigation
Danny oenea
Colorado Gecscience and Design, Inc. Report No. 17-067
8. The drilled pier holes shall be cleaned of all loose material and filled immediately
with concrete to prevent sloughing of loose soil or infiltration of water.
9. The foundation walls shall be designed for an active horizontal pressure based
on an equivalent fluid density of 40 pounds per cubic foot plus any applicable
surcharge or hydrostatic loads and shall be designed to distribute the applied
loads between piers.
10•A void form of a minimum of four inches (4") shall be placed under the foundation
grade beam walls between the drilled piers.
114If water is present in the drilled pier hole, the concrete shall be pumped or
tremmied to the bottom of the pier to displace the water.
CRITERIA FOR SLAB -ON -GRADE CONSTRUCTION
Virtually all concrete stabs undergo some type of movement. Concrete slabs placed on
soils comprised of medium dense or dense granular material, or comprised of soft or
stiff clays with swell potential less than 1% under a 1000 lb surcharge is considered
unlikely to sustain intolerable movement by standard engineering practice.
Cracking of slabs -on -grade is difficult to control and should be expected to occur with
time, cracking may be the result of many factors such as concrete shrinkage and daily
and seasonal variability in temperature and humidity and not necessarily the result of
soil movement.
Further, cracks and movement of slabs -on -grade can be transmitted through rigid floor
coverings such as ceramic tile. Performance expectations should be taken into
consideration in the selection of floor slab coverings.
•
If floor coverings or coatings less permeable than the concrete slab are used, or if
moisture is a concern, we recommend a vapor retarder be placed beneath the slab.
Flooring installation should be consistent with the flooring manufacturer's
recommendations for subsoil and slab construction and moisture testing prior to
installation.
A change in water content in soils is a major contributor to slab movement.
Colorado Geosctence and Design recommends that steps be taken to reduce the
possibility of intolerable concrete slab movement due to changes in water content.
Properly landscaped yards, drainage from the foundation walls, and the installation of
perimeter and/or under slab drainage systems are ways to mitigate changes in the
water content of the indigenous soils (See "Surface Drainage").
A slab performance risk evaluation was conducted in general compliance with industry
guidelines for the local area. The risk assessment of a site for potential movement is
Subsurface Investigation
Danny Oenes
Colorado Geoscience and Design} Inc. Report No. 17-067
not absolute; rather, it represents a judgment based upon the data available and our
experience in the area. Movement of foundations and concrete flat work will occur over
time in low to very high risk areas as the soil moisture content increases. On low and
moderate rated sites, slab movements of up to 3 inches across the slab with cracking of
up to inch in width and/or differential movement are not unusual. The damage
generally increases as the risk assessment increases and as the depth of wetting
increases. It must be understood, however, that assessing risk is an opinion, and the
prediction of heave is not an exact science. Therefore, it may be possible that heave
less than or in excess of what is described herein may be experienced. This risk should
be communicated to the subsequent homebuyer, We recommend the owner or
prospective buyer review 'A Guide to Swelling Soils for Colorado Homebuyers and
Ho eownersil, which is a special publication produced (5P43) by the Colorado
Geological Survey to assist homeowners in reducing damage caused by swelling soils,
Swell Potential Chart
Slab Performance Risk Category
Low
Representative Percent Swell
(1,000 psf Surcharge)
0 to <
Moderate
2to<4
High
<6
Very High
Note: the representative percent swell values presented are not necessarily measured values; rather,
they are a judgment of the swell of the soil and bedrock profile likely to influence slab performance.
The swell potential of the indigenous soils for the residence at this site meet the criteria
for moderate risk to of slab -on -grade movement. Concrete slabs may be used for
exterior surface (sidewalks, patios and aprons) placed on the native soil but may move.
Furthermore, intolerable movement of any slab on grade may occur at the site as a
result of future factors beyond the control of Colorado Geoscience and Design, inc.
If differential slab -on -grade movement is not acceptable to the owner/builder and,
if the owner/builder is unwilling to accept the risk of differential slab -on -grade
movement a structural floor above a crawl space is required.
The owner/builder shall be cautioned that problems with mold may arise when floors are
built over a crawl space or with a structural floor. In order to prevent such problems, it
may be necessary to take specific actions to mitigate the potential for molds, such as
installing actively controlled humidistat systems and devices, providing adequate
ventilation of enclosed spaces below the floor, and/or treatment of the soils with anti -
mold, anti -fungal chemical agents. Colorado Geoscience and Design, Inc. will not be
responsible for any and all claims arising from issues of mold or fungal contamination.
It is the builder's responsibility to adequately address these issues during construction.
If the owner/builder accepts the risk of slab -on -grade movement and chooses a slab -on -
grade floor, the following steps shall be part of the concrete slab design:
Subsurface Investigation
Danny Oenes
Colorado Geosodence and Design, inc. Report No. 17-067
• Any soil disturbed during construction shall be compacted by use of a vibratory
plate in the case of loose granular soils or wheel rolled by heavy ui ment in
the case of soft clay or silt soils prior to placement of the concrete slab.
The soil should bekept moist but not wet during the compaction process as well
as immediately prior to the placement of the concrete slab directly onto the soil.
Steps shall be taken to ensure that subsurface moisture beneath the concrete
slab remains constant during the construction process.
• The concrete slab shall be structurally isolated from all foundations and shall be
isolated from penetrations by suitable expansion material not less than thick.
The floating concrete slab shall be completely isolated from ail utility lines.
Control joints shall be provided in the concrete slab. These control joints must be
saw cut or tooled to a minimum of one third of the thickness of the slab. No
portion of the concrete slab will have an area greater than neither 100 square
feet nor a maximum dimension of 12'-0" in any direction without a control joint,
• All non-bearing partition walls shall be constructed with a minimum of 3 inches of
float to allow for slab -on -grade movement.
•
•
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PLACEMENT OF FOUNDATION FILL
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Expansive soil is not suitable for backfill material ad Acent to the foundation
backfill or for retaining walls. Any soil disturbed or imported material adjacent to the
foundation walls shall be re -compacted to a minimum of 85% of Standard Proctor
Density, ATM D-698. Compaction of each lift adjacent to walls should be
�
accomplished with hand -operated tampers or other lightweight compactors. Over
compaction may cause excessive lateral earth pressure, which could result in wall
movement. No water flooding techniques should be used in the compaction of backfill.
The installation of an exterior foundation perimeter drainage system is required for any
habitable space below grade level. See Perimeter Drain Detail 1, for a suggested
method of installing this system. The perimeter drain shall discharge at a daylight
location a minimum of 15 -feet away from the home. The daylight end shall have a
screened end section to prevent rodents from entering the drain. Alternatively, the
perimeter drain may discharge into a sump pit with a sump pump. If a sump it is used,
p
homeowners should perform routine observations of the sump pumsystem to make
sure it remains in good working order. Failure to install and failure of a sump um pump
system can cause serious foundation problems. Water accumulation around
foundation elements is the major cause of foundation stress, therefore proper
installation of the perimeter d ra i n is very important.
Subsurface Investigation
Danny Oenes
Colorado Geoscience and Design, Inc. Report No. 17-067
SURFACE DRAINAGE
The backfill soil around the foundations should be moistened and well -compacted in 12 -
inch maximum lifts with hand operated mechanical compaction equipment to prevent
future settling. Controlled puddling of the backfill soils is not allowed.
Site grading is critical, A simple means of reducing moisture change to prevent water
infiltration into the soil is to slope the ground away from the foundations For proper
drainage, a slope of 10% (1 in 10') away from the foundations in all directions is
required. This slope must be maintained for a minimum distance of I O' -O"
The property owner should inspect the area around the foundation regularly particularly
after rainstorms to determine if proper drainage away from the structure has been
maintained. The owners are advised to immediately fill in any settled area near the
foundations to eliminate containment of water.
Roof drainage should include gutters, downspouts, extensions, and splash blocks.
Down spouts must discharge onto concrete splash blocks or into metal gutter
extensions at least 6 foot away from the foundation walls and beyond any backfill zones
directing water away from the foundation.
The owners should be cautioned regarding the installation of a lawn adjacent to the
foundation walls. Lawn irrigation must be more than five feet (5') from the foundation
walls to prevent wetting of the subsurface soils. Lawn and/or plants should not be
planted within five feet (5') of the foundation walls, We recommend providing decorative
gravel or bark around the foundations, as shown in Foundation Grading Detail 2. This
method will prevent ponding of water and provide for proper drainage from the
foundations. Non -woven geo textile fabric can be placed under the mulch to reduce
weed growth and still allow some evaporation of soil moisture,
sprinkler heads and emitters should not be located or spray within 5 feet of the
foundation or patio slabs and beyond backfill zones. Plantings near the foundations
should not trap surface runoff. Furthermore, sidewalks or low-water consumption
groundcover are recommended to further reduce the risk of water infiltration near the
foundation walls. All pressurized irrigation lines and valve boxes should be located at
least 10 feet from the foundation or patio slabs.
Buried rain gutter discharge pipes are not recommended because of often undetected
seepage problems caused by clogging, crushing and adverse grading of the pipes,
similarly, infiltration basins are not recommended adjacent to or upgrade of adjacent
structures. If detention is required by statute, infiltration basins should be located down
gradient and at least 30 feet from foundations.
Changes in site grading by landscapers or property owners can have damaging effects
on foundations and concrete garage slabs -on -grade. It is the property owner's
Subsurface Investigation
Danny Oenes
Colorado Gecscrencce and Design, Inc. Report No. 17-067
responsibility to control water and maintain the site to prevent infiltration near
foundations. Additionally, it is the property owner's responsibility to maintain
downspouts and buried sprinkler system conduits.
Precautions should be taken in deep excavations for safety of workers and to protect
nearby structures. The sides of the temporary excavations should be sloped or
benched at a "AId to 1V maximum rates Spoils for the excavation should not be placed
within 2 feet of the excavation sidewalls d ewa l is and the excavation should not be subject to
excess vibration wetting or drying. The owner contractor should be familiar with the
OSHA Safety and Health Standards for the Construction Industry, 29 CFR, Part 1926,
or the appropriate foundation chapters of the International Building Code prior to
construction 4
GENERAL INFORMATION
Based on this subsurface investigation, the proposed foundations appear to be
technically feasible to be constructed at the proposed site. The structures should be
designed for construction in the direct vicinity of the boring location. If the proposed
locations change, additional borings will be required to assess the soil conditions at the
new location.
Permitting work will be required to obtain any local and state approval, and design work
will need to be performed by a qualified professional engineer to bring this project into
final design, and subsequent construction.
A qualified contractor experienced with similar projects should carry out the construction
of this project. The construction process should be carefully observed and documented
to ensure the construction is performed in accordance with the design drawings and
technical specifications.
In any soil investigation it is necessary to assume that the subsurface soil conditions do
not vary greatly from the conditions encountered in our field and laboratory testing. Our
experience has been that at times soil conditions do change and variations do occur
and may become apparent at the time of excavation for the foundation system.
The work contained herein was performed by, or under the direct supervision of a
licensed Professional Engineer in the State of Colorado. Professional judgments and
evaluations are presented based on information gathered during the drilling operations,
conversations with the owner and/or contractor, and on experience with similar projects.
The performance of the project is not guaranteed in any manner, only that the
engineering work and judgments rendered meet the standard of care of the engineering
profession. The engineering services performed are within the limits set by the Client,
with the usual thoroughness and competence of the engineering profession. No other
Subsurface Investigation
Danny Oenes
Colorado Geoscience and Design, Inc. Report No. 17-067
representation, expressed or implied, is included or intended.
The parties specifically agree that Colorado Geoscience and Design,Inc. has not been
retained nor will they render an opinion concerning any environmental issues,
hazardous waste or any other known or unknown conditions that may be resent on this
site, since this is not in the scope of this report.
PROPERTY UNE
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LEGEND
SOIL PROFILE 'US _ 1' PIT
FOUNDATION SOIL TES C BORINGS
0 PERCOLATION TEST HOLM
SOIL PROFILE HOLE
UNSUITABLE SOIL PROFILE HOLE
8
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III
CPS LOCATOR
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1 -I
40 1'Y 0 0599'
10459.968' 59.968' W
5.C47
PIT' 1
40°00.601' N
1045'59.968' W
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4600.580' N
10459.986'
5275
Colorado
Geoscience & Design1In c.
P.Q, SOX I, FRAIEYwi 4, co.slit
PHONE•4303T 50
SITE MAP
ALL LOCATIONS SHOWN ARE BASED ON SPECIFIC INFORMATION
FURNISHED BY OTHERS OR ESTIMATES MADE INTHE FIELD BY
COLORADO CEOSCIEN£E PERSONNEL. THE LOCATIONS, DISTANCES,
DIRECTIONS, ETC. ARE NOT THE RESULTOP A PROPERFYSURVEY BUT
ARE APPROXIMATIONS AND ARE NOT WARRANTED ID BE EXACT. IT IS
THE OWNER/BUILDER'S RESPONSIBILITY TO DEFINE PROPERLY
BOUNDARIES AND ENSURE ALL ON•SITE IMPROVEMENTS ARE LOCATED
WITHIN THE PLATTED STYE AND OUT OF INAPPROPRIATE EASEMENTS.
ALL DISTANCES ARE TO BE VERIFIED PRIOR 10 EXCAVATION.
DANNY OENES
SI1E LOCATION
587 WELD COUNTY ROAD 7
WELD COUNTY,
COLORADO
SCALE
1II =1001
JOB NO.
17-067
FIG. 1
SWELL aCONSOLIDATION TESTS
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APPLIED PRESSURE (PSF)
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Test Hole No, °1 Depth 8' Soil Descriptor; Weathered claystone, moist, gray brown
28,000
JOB NO.17•067 FIGURE 3
SWELL CONSOLIDATION TESTS
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26,000
JOB NO. 17-067
FIGURE 3
SWELL - CONSOLIDATION TESTS
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28,000
JOB NOa 17-067
FIGURE 3
SWELL CONSOLIDATION TESTS
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APPLIED PRESSURE (PSF)
Test Hole No. Depth 19' cif De cri tion: Claystone r oist, qra rout brown
28,000
JOB NO. 17-067
FIGURE 3
Address: 587 Weld County Road 7
Weld County, Colorado
Job Number:
17-067
Hole
No.
Depth
(feet)
Moisture
Content %
Gradation
1
'140 #
Hammer
Blo
Relative
Swell/
Consolidation:
Dry
Density
pa
Soil Description
Gravel
Sand
Passing
#200 sieve
0
41
Clay, slightly sandy to very sandy, stiff very Stiff, moist,
brown
1
1
1
8
18
5
95
14/12
r1.0
100
[Weathered
claystone,
moist, gray brown
1
14
1
B
0
1
�:
38/12
1,
101
Claystone, moist, gray rust brown
1
24
13
0
L 4
96
/ 50/11
1.4103
Claystone, moist, gray rust brown
2
4
16
0
17
83
14/12 .
1
0,1
109
Clay, slightly
brown
sandy to very sandy, stiff to very stiff, moist,
2
91
0
6
94
40/12
0.3
105
Claystone, moist, gray rust brown
2
19
12
0 1
s
1
9
5011 1
4.0
1CIaystone, moist, gray rust brown
1 06
COLORADO GEOSCIENCE AND DESIGN, INC.
TABLE I
CONia
&RARE Ste'.
INTERIOR
EXPANSION JONI
V-1/2' CLEAN RA 'EL
FOL t E 4 PLE E EXTENDED `em
—
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FLOOD. 6LA5
tialaIkkaiow
ISO FELT
i/ MIN, e►ENEATk NEW
CONCRETE S' _Ar' ON
G.FRADE.
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SLOPED
6 PER 5 FT. MN.
EXTERIOR'
\ 7 AAD MATERIAL
`12 tt MINd
4 ' D Lt PERFORATED PIPE.
SLOPE BRAIN PIPE tea' iz)R
;0O1- TA SUMPPITO TFALLI
PIER FOUNDATION
N,
��- FELT
FQUNPA I ION
C)R INI
00 NOT DIKE Uffirl
SOD OR EDGING
BRACE WALLS; TOP & BOTTOM
PRIOR TO B ACK FI LLI N
CONCRETE GRADE BE -AM
FLOOR SLAB
1
p
EXPANSION JOIP\
VOID BETWEEN PI
WELL SLOPED - 12" PER
10 FT. MIN, DO NOT DIKE WITH
CSOD OR EDGING
TOP 12" OF WELL -COMPACTED
BACKFILL
MODERATELY COMPACTED
p
BACKFILL
F
fee
DAMP PROOFING
POLYETHYLENE GLUED TO WALL
AND EXTENDED ALONG THE
BOTTOM OF THE EXCAVATION.
15# BUILDING FELT
4" MIN
4" MIN.
3/4" TO 1 1/2" CLEAN GRAVEL
4" DIAMETER PERFORATED PIPE.
SLOPE DRAIN PIPE 1/8" PER FOOT TO
DAYLIGHT, OR TO A SUMP Pit IF TO
DAYLIGHT, COVER END WITH SCREEN.
BACKFILL AROUND THE FOUNDATION SHOULD BE MOISTENED AND
COMPACTED AND THE FINAL GRADE SHOULD BE WELL SLOPED TO
PRECLUDE PONDING OF RAINFALL, IRRIGATION WATER, AND SNOW
MELT ADJACENT TO FOUNDATION WALLS.
CAUTION:
DO NOT DIKE OR IMPEDE THE FLOW OF WATER AWAY FROM FOUNDATION
WALLS WITH SOD, EDGING OR DECORATIVE GRAVEL AND POLYETHYLENE.
DOWNSPOUTS AND SILL COCKS SHOULD DISCHARGE INTO SPACE
BLOCKS OR LONG EXTENSIt}NS.
DRAIN SYSTEM BELOW GRADE
AND BACKFILL DETAILS
(FOR PIER FOUNDATION)
DETAIL 1
FO
I
f
NDSAH Jo
i
viCr-
_
00 Dist
oockz, oas-0047‘6120y10 0 co oorr
at\ 1271 IQ
GRADING DETAIL
4T -0t" MINIMUM
• _
---„DECORATIVE GRAVEL
DR BARK AREA.
SOIL TO BE
SLOPED AWAY FROM
FOUNDATION.
-FOUNDATION WALl
Ix \fie
NOTE:
1. PROVIDE A MINIMUM SLOPE OF 6"
a ,a1 THE
FIRST 1 C --� FROM HOUSE(10%).. DOWNSPOUTS AND EXTENSIONS SHOULD
I I
L.� D
EXTENDED 5' 0" EYON D THE FOUNDATION.
GRADL
DE1AIL
APPENDIX
4
Important Information About the Report
The data collected by Colorado Geoscience Design, Inc. during this
investigation was used to provide geotechnical information and recommendations
regarding subsurface conditions on the site investigated, the effect of those ,
. a conditions rti o r�s o r�r
the proposed construction, and the foundation type for the named client,
stratification lines indicated on the boring log are approximate, and subsurface conditions
encountered may differ from those presented herein. This uncertaint.y cannot be
eliminated because of the many variabilities associated withgeology.i - For example,
material and engineering characteristics of soil and bedrock may change more � log � gradually
or inore quickly than indicated in this report, and the actual .engineering r o ertie
s of
non -sampled soil or rock may differ from interpretations made based on boring logs.
Quantitative conclusions regarding the performance of structures
geotechnical
trii es prior to
construction are not possible because of the complexity of subsurface conditions, Rather, judgments and experience are used to estimate likely �1 geotechnical
g l�o.ical
performance mance and provide the necessary recommendations for design and
ld construction,
Put another way, we cannot be sure about what is not visible, so theand
collected data
our training and experience are used to develop and recommendations. predictions There
are no guarantees or warranties implied or expressed.
The owner and/or client must understand that uncertainties are associated with
geotechnical engineering, and they, the owner and/or client, must determine
. the level of
risk they are willing to accept for the proposed construction. The risks
.� can be reduced,
but not eliminated, through more detailed investigation, which costs3
takes g � more money and more time, and through any appropriate construction which might
ght be recommended
nded
as a result of that more detailed investigation. To reduce the level of uncertain
ty, this
report was prepared only for the referenced client and for the proposed construction
indicated in the report. Unless authorized by Colorado Geoscience{.Design, Inc.Zrzcin
writing, the owner will assume additional geotechnical risk if this report is used w
�forany
construction that differs from that indicated in the report. Our firm should be consulted
onstllted
well before changes in the proposed construction occur, such as the nature, size,
configuration, orientation, or location of any improvements. rovements. .dditionall
, the knowledge
and experience of local geotechnicaI practices is continual) expanding � p' g and it must be
understood the presented recommendations were made according the
g to standard of
practice at the time of report issuance, f f the construction cti on occurs one or more years after •
issuance of the report, the owner and/or client should contact our firm to determine if
additional investigation or revised recommendations would be advisable.
Geotech.nical practice in the Denver Region must consider the risk associated with
c�cr ated r� ith
expansive soils and bedrock. Geotechnical practice in the Denver area uses
a relative
scale to evaluate selling Potentials. As stated in the Subsurface Investigation, when '�� helr the
sample is wetted under a surcharge pressure (loading)of 1000 pounds s
1 per square foot
(PSF), the measured amount of swell is classified as low, moderate, high, or very -high.
� ex �
Page 1 of 3
I
Table 1 presents the relative classification criteria `'�
f�l the percentage of expansion relative
to the initial sample height, at the indicated surch
arge pressure.
Swell Potential Chart
SWELL POTENTIAL AT 1,000 LB S.
0to' %%%
IA toIV2%
1 'h fo 3 V.2%
'A to 6%
6 to 8%
Greater than 8%
CLAS SJFICATJQN
Non-expansive/Very ery low
Low
Moderate
High
Very High
Critical
The swel [ potential classifications are based on the percentage
of swell for samples placed on
swell/consolidation machines under a surcharge of 100
� pounds per square foot.
The relative swell classification can be correlated to potential slab damage as
follows:
Low - minor slab cracking, minor differentimo
vement, i��e� ement, and heave
Moderate -lab cracking and differential movement, . � • •
partial framing void and
furnace plenum closure.
High to Very High 4- large slab cracking and differential movement, closed voids,
closed furnace plenum, and possible e i rupture,
pipe 1 eF
These effects are based on monitoring and '•
observation Kati ��� by several firms i���1s in the Denver
metropolitan area and are not limited to the relative
swell classification. More or less
damage can occur in all classifications because of the uncertainty associated with
subsurface conditions and geotechnical engineering.
It i s important to note that measured swell or
soil expansion is not the only geotechnical
criteria for the type of floor and foundation -
recommendations, Additional criteria
considered include:
O Soil and bedrock type and variability
O Stratigraphy
O Groundwater depth and anticipated posts -construction • ,
.� 1 ctr�il moisture conditions.
Surface water drainage and features
0 Post -construction landscaping and irrigation
O Construction details and proposed use
O Local experience
Page 2 of
Postsconstruction landscaping and owner maintenance will greatly affect
structures
etu es on expansive soils and bedrock. Typically, irrigated landscaping increases the
soil moisture content above the pre -constructed water content. pavements, Slabs, avementsa and
structures
significantly reduce evaporation of the soil moisture. Therefore, post.-
construction heave and resulting damage to buildings and other improvements are likely
to occur on sites with expansive soils because of the high probability that subsurface
moisture content will increase as the property and surrounding area is developed. Poor
owner maintenance, such as negative slopes adjacent to foundation walls and irrigated
landscaping adjacent to the foundation, also will significantly increase the risk of damage
from expansive soil and bedrock. The property owner, and anyone he or she plans to sell
the property to, must understand the risks associated with construction in an expansive
soil area and also must assume responsibility for maintenance of the structure. The
owner and prospective purchaser also should review "A Guide to Swelling Soils for
Colorado Homebuyers and Homeowners, " which is a specialpublication(SP
43)
produced by the Colorado Geological Survey to assist homeowners in reducing damage
caused by swelling soils.
Page 3 of 3
Legend
USGS 1-2735 Approx. Mine Depth (ft.)
RANGE
0-50
50-100
100-150
150-200
200-250
250-300
300-350
350-400
>400
Mine Workings
and Subsidence Hazard
in Vicinity of
587 Weld County Road 7, Erie CO
I
0 500 1,000 2,000 3,000
Feet 1 i
4,000 nch = 2,000 feet
Hello