HomeMy WebLinkAboutFile Documents.630 W Hopkins Ave.0052-2020-BRES (47) I( A Kumar&A te
G nicaland Materials Engineers 5020 County Road 154
and Environmental Scientists Glenwood Springs,CO 81601
phone:(970)945-7988
fax:(970)945-8454
email:kaglenwood@kumarusa.com
An Employee Owned Company www.kumarusa.com
Office Locations: Denver(HQ),Parker,Colorado Springs,Fort Collins,Glenwood Springs,and Summit County,Colorado
April 6, 2020
S2 Architects
Attn: Joseph Spears
215 South Monarch Street, Suite G-102
Aspen, Colorado 81611
joseph@s2architects.com
Project No. 20-7-128
Subject: Subsoil Study for Foundation Design,Proposed Basement Footings and Light
Well Walls, 630 West Hopkins Avenue, Aspen, Colorado
Gentlemen:
As requested, we are providing the results of a subsoil study and recommendations for design of
foundations at the subject site. The study was conducted as additional services to and in
accordance with our proposal for geotechnical engineering services to S2 Architects dated
January 22, 2020. The data obtained and our recommendations based on the proposed
construction and subsurface conditions encountered are presented in this report.
Proposed Construction: The proposed improvements include new footing pads below the slab-
on-grade floor at basement level and new light well retaining walls to the west side of the
existing residence shown on Figure 1. Foundation loadings for this type of construction are
assumed to be relatively light and typical of the proposed type of construction.
If building conditions or foundation loadings are significantly different from those described
above, we should be notified to re-evaluate the recommendations presented in this report.
Subsurface Conditions: The subsurface conditions at the site were evaluated by drilling one
exploratory boring at the approximate location shown on Figure 1. The log of the boring is
presented on Figure 2. The subsoils encountered,below the asphalt pavement, consist of
relatively dense, silty sand, gravel and cobbles with probably boulders. Results of a gradation
analysis performed on a combined sample of the sand and gravel (minus 11/2-inch fraction)
obtained from the boring are presented on Figure 3. No free water was encountered in the boring
at the time of drilling and the soils were moist.
Foundation Recommendations: Considering the subsoil conditions encountered in the REp! VE re)
exploratory boring and the nature of the proposed construction, we recommend spread footirl6/3 0/2 0 2 0
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BUILDING DEPARTMENT
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placed on the undisturbed natural granular soil designed for an allowable soil bearing pressure of
4,000 psf for support of the proposed basement level loadings and exterior window well walls.
The soils have low compressibility potential and post-construction foundation settlement should
be minor. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for
columns. Loose disturbed soils and existing fill encountered at the foundation bearing level
within the excavations should be removed and the footing bearing level extended down to the
undisturbed natural granular soils. We should observe the completed excavations for bearing
conditions prior to placing concrete. Exterior footings should be provided with adequate cover
above their bearing elevations for frost protection. Placement of footings at least 36 inches
below the exterior grade can be used at this site. Continuous foundation walls should be
reinforced top and bottom to span local anomalies such as by assuming an unsupported length of
at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist
a lateral earth pressure based on an equivalent fluid unit weight of at least 45 pcf for the on-site
granular soil as backfill excluding rock larger than 6 inches. A sliding coefficient of 0.50 and
equivalent fluid passive earth pressure of 450 pcf can be used to resist lateral loading on
foundations.
Underdrain System: Although free water was not encountered during our exploration, it has
been our experience in the area that local perched groundwater can develop during times of
heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched
condition. We recommend below-grade construction, such as retaining walls and basement
areas,be protected from wetting and hydrostatic pressure buildup by an underdrain system.
The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above
the invert level with free-draining granular material. The drain should be placed at least 1 foot
below lowest adjacent finish grade and sloped at a minimum 1%to a suitable gravity outlet or
into the natural granular soils below the basement level. Free-draining granular material used in
the underdrain system should contain less than 2%passing the No. 200 sieve, less than 50%
passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should
be at least PA feet deep.
Surface Drainage: The following drainage precautions should be observed during construction
and maintained at all times after the improvements have been completed: RECEIVED
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Kumar&Associates,Inc.® Project No. 20-7-128
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BUILDING DEPARTMENT
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1) Inundation of the foundation excavations and underslab areas should be avoided
during construction.
2) Exterior backfill should be adjusted to near optimum moisture and compacted to
at least 95%of the maximum standard Proctor density in pavement and slab areas
and to at least 90%of the maximum standard Proctor density in landscape areas.
Free-draining wall backfill should be covered with filter fabric and capped with at
least 2 feet of the on-site, finer graded soils to reduce surface water infiltration.
3) The ground surface along the exterior of the building should be sloped to drain
away from the foundation. We recommend a minimum slope of 6 inches in the
first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet
in pavement and walkway areas.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
Limitations: This study has been conducted in accordance with generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty either
express or implied. The conclusions and recommendations submitted in this report are based
upon the data obtained from the exploratory boring drilled at the location indicated on Figure 1
and to the depth shown on Figure 2, the proposed type of construction, and our experience in the
area. Our services do not include determining the presence,prevention or possibility of mold or
other biological contaminants (MOBC)developing in the future. If the client is concerned about
MOBC, then a professional in this special field of practice should be consulted. Our findings
include interpolation and extrapolation of the subsurface conditions identified at the exploratory
boring and variations in the subsurface conditions may not become evident until excavation is
performed. If conditions encountered during construction appear different from those described
in this report, we should be notified at once so re-evaluation of the recommendations may be
made.
This report has been prepared for the exclusive use by our client for design purposes. We are not
responsible for technical interpretations by others of our information. As the project evolves, we
should provide continued consultation and field services during construction to review and
monitor the implementation of our recommendations, and to verify that the recommendati
RECEIVED
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Kumar&Associates,Inc.® Project No. 20-7-128
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BUILDING DEPARTMENT
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have been appropriately interpreted. Significant design changes may require additional analysis
or modifications to the recommendations presented herein. We recommend on-site observation
of excavations and foundation bearing strata and testing of structural fill by a representative of
the geotechnical engineer.
If you have any questions or if we may be of further assistance,please let us know.
Respectfully Submitted,
Kumar & Associates, Inc.
RE
Steven L. P vl P15222 %
Rev. by: D + '
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Attachments: Figure 1 —Location of Exploratory Boring
Figure 2 —Log of Exploratory Boring
Figure 3 —Gradation Test Results
RECEIVED
06/30/2020
Kumar&Associates,Inc.® Project No. 20-7-128
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BUILDING DEPARTMENT
BORING 1
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APPROXIMATE 5CRETTIVED
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20-7-128 Kumar & Associates LOCATION OF EXPLORATORY BORING O6;43O/2 020
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BUILDING DEPARTMENT
BORING 1
EL. 7934' LEGEND
0 (3) 4,7 (3) ASPHALT PAVEMENT; THICKNESS IN INCHES SHOWN IN
PARENTHESES TO LEFT OF THE LOG.
00 20/12 SAND, GRAVEL AND COBBLES (GM); SILTY, PROBABLE
ISO
BOULDERS, MEDIUM DENSE TO DENSE, MOIST, BROWN.
5 v
028/12 DRIVE SAMPLE, 1 3/8-INCH I.D. SPLIT SPOON STANDARD
— PENETRATION TEST.
0 WC= .4
— WC 5. 20/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 20 BLOWS OF
cL
A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED
wo— -200=21 TO DRIVE THE SAMPLER 12 INCHES.
— 10 22/6, 50/2 t PRACTICAL AUGER REFUSAL.
NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON FEBRUARY 10, 2020
15 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY TAPING FROM FEATURES SHOWN ON THE SITE
PLAN PROVIDED.
3. THE ELEVATION OF THE EXPLORATORY BORING WAS OBTAINED
BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN
PROVIDED.
4. THE EXPLORATORY BORING LOCATION AND ELEVATION SHOULD BE
CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE
METHOD USED.
5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY
BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN
MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL.
6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE
TIME OF DRILLING.
7. LABORATORY TEST RESULTS:
WC = WATER CONTENT (%) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 6913);
-200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140);
Ea
osRECEIVED
1 20-7-128 Kumar& Associates LOG OF EXPLORATORY BORING Fi 2
O1
ti 2020
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BUILDING DEPARTMENT
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
24 MR5 7 MRS
100 45 MIN 15 MIN 60 IN 1941N 4M04 11IN 1200 #100 #50 140#30 #16 in #4 --
4 . 4" 1 1 2" 3' §E' fro
1 --- -_ _lam--.
— _ - I - 1--
90 __ _ -- �
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80 20
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70 I 30
-__� - _ -_ _--♦-- - _ --.-I-. _. __ 7J77
c� 60 ---. - - - --_ ..- -. —1._._ _ _I_- - _ --_ _ I
`I - ..- __ - - - ----- - .i. - _. I - _ _ _ _ _--__-
50 - - - - -- -'- - -_
- - - - 1 -- - _ -- ~� 50
b
40 I I - ----- - — I_ 60 '
— ——
20
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I I: - - — - _—
10 F I 1 90
1 f
o ---71 1-. 1.1 I I _ 1 I 1 1 I 1 1 II ---I II-I- 11 I I I 1 1--1 I IllF - I I I- 1 I I-III I
100
.001 .002 .005 .009 .019 .037 .075 .150 .300 I .600 1.18 12.36 4.75 9.5 19 38.1 76.2 127 200
.425 2.0 152
DIAMETER OF PARTICLES IN MILLIMETERS
I
SAND GRAVEL
CLAY TO SILT COBBLES
FINE MEDIUM COARSE FINE COARSE
GRAVEL 36 % SAND 43 % SILT AND CLAY 21 %
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Silty Sand and Gravel FROM: Boring 1 0 5' & 10' (Combined)
IF
These test results apply only to the
° samples which were tested. The
Ed testing report shall not be reproduced,
except In full, without the written
oS approval of Kumar & Associates, Inc.
I N Sieve cco analysis testing is performed in D
accordance with ASTM D6913, ASTM D7
«o ASTM C136 and/or ASTM D1140. 3
r i y 0.
i� 6 R�`J:3 1!'.1
�e 20-7-128 Kumar& Associates GRADATION TEST RESULTS Fig. 3
0670/2020
ASPEN
BUILDING DEPARTMENT