HomeMy WebLinkAboutMaster Permit.1015 Waters Ave.0204.2019 (56).ARBK H-P KU MAR 5020 County Road 154
Glenwood Springs, CO 81601
Geotechnical Engineering I Engineering Geology Phone:(970)945-7988
Materials Testing I Environmental Fax: (970)945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver(HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
SUBSOIL STUDY
FOR FOUNDATION DESIGN
PROPOSED RESIDENCE
1015 WATERS AVENUE
ASPEN, COLORADO
PROJECT NO. 17-7-737
NOVEMBER 9,2017
PREPARED FOR:
HENDRICKSON CONSTRUCTION
ATTN: CHRIS HENDRICKSON
130 PRIMROSE PATH
ASPEN, COLORADO 81611
chris@hendricksoninc.com
RECEIVED
04/06/2018
ASPEN
BUILDING DEPARTMENT
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1 -
PROPOSED CONSTRUCTION - 1 -
SITE CONDITIONS - 1 -
MINE SUBSIDENCE - 2 -
FIELD EXPLORATION - 2 -
SUBSURFACE CONDITIONS - 3 -
SLOPE STABLIZATION - 3 -
DESIGN RECOMMENDATIONS - 3 -
FOUNDATIONS - 3 -
FOUNDATION AND RETAINING WALLS -4 -
FLOOR SLABS - 6 -
UNDERDRAIN SYSTEM - 6 -
SURFACE DRAINAGE - 7 -
DRYWELL - 7 -
FIGURE 1 - LOCATION OF EXPLORATORY BORING
FIGURE 2 - LOG OF EXPLORATORY BORING
FIGURE 3 - GRADATION TEST RESULTS
TABLE 1- SUMMARY OF LABORATORY TEST RESULTS
TABLE 2-PERCOLATION TEST RESULTS
RECEIVED
04/06/2018
H-P*-KUMAR
ASPEN
Project No. 178;tLL'ING DEPARTMENT
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsoil study for a proposed residence to be located at 1015
Waters Avenue, Aspen, Colorado. The project site is shown on Figure 1. The purpose of the
study was to develop recommendations for the foundation design. The study was conducted in
accordance with our proposal for geotechnical engineering services to Hendrickson Construction
dated September 27, 2017.
An exploratory boring was drilled to obtain information on the subsurface conditions. Samples
of the subsoils obtained during the field exploration were tested in the laboratory to determine
their classification and other engineering characteristics. The results of the field exploration and
laboratory testing were analyzed to develop recommendations for foundation types, depths and
allowable pressures for the proposed building foundation. This report summarizes the data
obtained during this study and presents our conclusions, design recommendations and other
geotechnical engineering considerations based on the proposed construction and the subsurface
conditions encountered.
PROPOSED CONSTRUCTION
The proposed residence will be a two-story wood frame structure over a full basement level. The
basement and attached garage floors will be slab-on-grade. Grading for the structure is assumed
to be relatively minor with cut depths between about 5 to 12 feet. We assume relatively light
foundation loadings, typical of the proposed type of construction.
If building loadings, location or grading plans change significantly from those described above,
we should be notified to re-evaluate the recommendations contained in this report.
SITE CONDITIONS
The site is occupied by an existing two-story residence and detached garage. The existing
structures will be razed prior to new construction. Vegetation at the site consists of lawn and
scattered fir and deciduous trees. The driveway and parking surface areas are crushed rock�ErEIvED
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H-Pk,KUMAR ASPEN
Project No. 1 7BYtIt�NNANG DEPARTMENT
- 2 -
site is relatively flat with a slight slope down to the north in the area of our exploratory boring.
Access to the site was limited by a rock berm and existing garage.
MINE SUBSIDENCE
Portions of the Aspen area are underlain by mine workings. The workings are primarily
underground tunnels between Aspen and Smuggler Mountains southeast and east of the
downtown area. The works consist of numerous tunnels beginning a few hundred feet below the
ground surface becoming shallower to the south. Under certain conditions these workings may
collapse and cause surface subsidence. Glory Hole Park, which is located about two blocks west
of the subject site, is believed to have been caused by the collapse of one or more tunnels. The
subject site appears to be about 600 feet east of these main tunnel works.
Our boring was relatively shallow and for foundation design only, however, no indications of
subsurface voids were found at the subject site. We believe the risk of subsidence due to the
collapse of underground mine works throughout the service life of the proposed development to
be low. If further evaluation of the mine works subsidence potential is desired, we should be
contacted.
FIELD EXPLORATION
The field exploration for the project was conducted on October 5, 2017. One exploratory boring
was drilled at the location shown on Figure 1 to evaluate the subsurface conditions. The boring
was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted CME-
45B drill rig. The boring was logged by a representative of H-P/Kumar.
Samples of the subsoils were taken with 1%inch and 2 inch I.D. spoon samplers. The samplers
were driven into the subsoils at various depths with blows from a 140 pound hammer falling 30
inches. This test is similar to the standard penetration test described by ASTM Method D-1586.
The penetration resistance values are an indication of the relative density or consistency of the
subsoils. Depths at which the samples were taken and the penetration resistance values are
shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory
for review by the project engineer and testing. RECEIVED
04/06/2018
H-PEKUMAR ASPEN
Project No. 17B-01TANG DEPARTMENT
- 3 -
SUBSURFACE CONDITIONS
A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The
subsoils consist of about 5 feet of medium dense, sand and gravel fill overlying relatively dense,
slightly silty sand and gravel with cobbles and small boulders down to the bottom of the boring
at 11 feet. Drilling in the dense granular soils with auger equipment was difficult due to the
cobbles and boulders and drilling refusal was encountered in the deposit.
Laboratory testing performed on samples obtained from the boring included natural moisture
content, density and gradation analyses. Results of a gradation analyses performed on small
diameter drive samples (minus 11/z inch fraction) of the coarse granular subsoils are shown on
Figure 3. The laboratory testing is summarized in Table 1.
No free water was encountered in the boring at the time of drilling and the subsoils were slightly
moist.
SLOPE STABLIZATION
The City of Aspen requires an engineered excavation slope stabilization plan if proposed
foundations are within 15 feet of neighboring structures or public travel ways. The plan is not
required if excavations are less than 5 feet below the existing grade or further than 15 feet from
travel ways and less than 15 feet deep. Slope bracing could be required depending on the
residence location, size and excavation depth. Slope bracing through use of a variety of systems
such as grouting, micro piles and soil nails should be feasible at the site. A shoring contractor
should provide design drawings to support the proposed excavation slopes where needed. Other
City requirements may also be applicable.
DESIGN RECOMMENDATIONS
FOUNDATIONS
Considering the subsurface conditions encountered in the exploratory boring and the nature of
the proposed construction, we recommend the residence be founded with spread footings bearing
on the natural granular soils. RECEIVED
04/06/2018
H-P-KUMAR ASPEN
Project No. 17B:t} jG DEPARTMENT
-4 -
The design and construction criteria presented below should be observed for a spread footing
foundation system.
1) Footings placed on the undisturbed natural granular soils should be designed for
an allowable bearing pressure of 4,000 psf. Based on experience, we expect
settlement of footings designed and constructed as discussed in this section will
be about 1 inch or less.
2) The footings should have a minimum width of 16 inches for continuous walls and
2 feet for isolated pads.
3) Exterior footings and footings beneath unheated areas should be provided with
adequate soil cover above their bearing elevation for frost protection. Placement
of foundations at least 42 inches below exterior grade is typically used in this
area.
4) 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
lateral earth pressures as discussed in the "Foundation and Retaining Walls"
section of this report.
5) All existing fill, debris, topsoil and any loose or disturbed soils should be
removed and the footing bearing level extended down to the relatively dense
natural granular soils. The exposed soils in footing area should then be moistened
and compacted. If water seepage is encountered, the footing areas should be
dewatered before concrete placement.
6) A representative of the geotechnical engineer should observe all footing
excavations prior to concrete placement to evaluate bearing conditions.
FOUNDATION AND RETAINING WALLS
Foundation walls and retaining structures which are laterally supported and can be expected to
undergo only a slight amount of deflection should be designed for a lateral earth pressure
computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting
of the on-site granular soils. Cantilevered retaining structures which are separate from the RECEIVED
04/06/2018
H-P�KUMAR ASPEN
Project No. 1714311ANG DEPARTMENT
- 5 -
residence and can be expected to deflect sufficiently to mobilize the full active earth pressure
condition should be designed for a lateral earth pressure computed on the basis of an equivalent
fluid unit weight of at least 40 pcf for backfill consisting of the on-site granular soils.
All foundation and retaining structures should be designed for appropriate hydrostatic and
surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The
pressures recommended above assume drained conditions behind the walls and a horizontal
backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will
increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain
should be provided to prevent hydrostatic pressure buildup behind walls.
Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum
standard Proctor density at a moisture content near optimum. Backfill placed in pavement and
walkway areas should be compacted to at least 95% of the maximum standard Proctor density.
Care should be taken not to overcompact the backfill or use large equipment near the wall, since
this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall
backfill should be expected, even if the material is placed correctly, and could result in distress to
facilities constructed on the backfill. Deep foundation wall backfill could be compacted to a
higher density of 98% of the standard Proctor density to help reduce long term settlement.
The lateral resistance of foundation or retaining wall footings will be a combination of the
sliding resistance of the footing on the foundation materials and passive earth pressure against
the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated
based on a coefficient of friction of 0.50. Passive pressure of compacted backfill against the
sides of the footings can be calculated using an equivalent fluid unit weight of 425 pcf. The
coefficient of friction and passive pressure values recommended above assume ultimate soil
strength. Suitable factors of safety should be included in the design to limit the strain which will
occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against
the sides of the footings to resist lateral loads should be compacted to at least 95% of the
maximum standard Proctor density at a moisture content near optimum.
RECEIVED
04/06/2018
H-Pk ASPEN
Project No. 17WJ ANG DEPARTMENT
- 6 -
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade
construction. To reduce the effects of some differential movement, floor slabs should be
separated from all bearing walls and columns with expansion joints which allow unrestrained
vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage
cracking. The requirements for joint spacing and slab reinforcement should be established by the
designer based on experience and the intended slab use. A minimum 4 inch layer of free-
draining gravel should be placed beneath basement level slabs to facilitate drainage. This
material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve
and less than 2% passing the No. 200 sieve.
All fill materials for support of floor slabs should be compacted to at least 95% of maximum
standard Proctor density at a moisture content near optimum. Required fill can consist of the on-
site granular soils devoid of vegetation, topsoil and oversized rock.
UNDERDRAIN SYSTEM
Although free water was not encountered during our exploration, it has been our experience in
mountainous areas that local perched groundwater can develop during times of heavy
precipitation or seasonal runoff. Frozen ground during spring runoff can also create a perched
condition. We recommend below-grade construction, such as retaining walls, crawlspace 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 each level of
excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to
a suitable gravity outlet. 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
RECEIVED
04/06/2018
H-PmKUMAR
ASPEN
Project No. 17}RUNG DEPARTMENT
- 7 -
maximum size of 2 inches. The drain gravel backfill should be at least 2 feet deep.
SURFACE DRAINAGE
The following drainage precautions should be observed during construction and maintained at all
times after the residence has been completed:
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.
3) The ground surface surrounding the exterior of the building should be sloped to
drain away from the foundation in all directions. 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 paved areas. Free-draining wall backfill should be
capped with about 2 feet of the on-site soils to reduce surface water infiltration.
4) Roof downspouts and drains should discharge well beyond the limits of all
backfill.
DRYWELL
Drywells and bio-swales are often used in the Aspen area for site runoff detention and disposal.
The natural granular soils encountered are typically free draining and should be suitable for
surface water treatment and disposal. The results of percolation testing performed in Boring 1,
presented in Table 2, indicate an infiltration rate of about 1 minute per inch. The bedrock is
generally known to be relatively deep in this area and groundwater level was not encountered to
the boring depth of 11 feet. The drywell should have solid casing down to at least basement level
and perforation below that level.
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 im 1 E IvE D
04/06/2018
H-P-KUMAR ASPEN
Project No. 17B1f1WiNG DEPARTMENT
- 8 -
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, 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 so
that 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 recommendations
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.
Respectfully Submitted,
H—Pt KUMAR
be„.7.41:6144.....:.
Daniel E. Hardin, P.E.
Reviewed by:
Steven L. Pawlak, P.E. !
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04/06/2018
H-Pk-KUMAR ASPEN
Project No. 1718MUNG DEPARTMENT
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17-7-737 H-Pti RKIJMAR LOCATION OF EXPLORATORY BORING /106 /2018
ASPEN
BUILDING DEPARTMENT
BORING 1 LEGEND
— O FILL: SAND AND GRAVEL, SLIGHTLY SILTY, WITH COBBLES, MEDIUM
DENSE, SLIGHTLY MOIST, MIXED BROWN.
16/12
WC=4.2 X. GRAVEL (GM-GP); SANDY WITH COBBLES, SLIGHTLY SILTY DENSE,
_ DD=116 SLIGHTLY MOIST, MIXED BROWN, CALCAREOUS.
1 -200=8
1-
5 40/12 _ DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE.
w—
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;,v WC=1.0 DRIVE SAMPLE, 1 3/8-INCH I.D. SPLIT SPOON STANDARD PENETRATION
— +4=48 TEST.
a
a_ -200=8
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16/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 16 BLOWS OF
10 A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED
50/3 TO DRIVE THE SAMPLER 12 INCHES.
PRACTICAL AUGER REFUSAL.
15 NOTES
1. THE EXPLORATORY BORING WAS DRILLED ON OCTOBER 5, 2017 WITH A
4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER.
2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED
APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN
PROVIDED.
3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND
THE LOG OF THE EXPLORATORY BORING IS PLOTTED TO DEPTH.
4. THE EXPLORATORY BORING LOCATION 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);
DD = DRY DENSITY (pcf) (ASTM D 2216);
+4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D 422);
-200 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140).
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II 17-7-737 H-PtiKUMAR LOG OF EXPLORATORY BORING Fig. 2
04/06/2018
ASPEN
BUILDING DEPARTMENT
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S.STANDARD SERIES CLEAR SQUARE OPENINGS
24 NRS 7 FIRS
100 45 MIN 15 MIN 60MIN 19MIN 4MIN 1MIN 0200 #100 450 fl I 40 30 #16 #1?48 44 3 8" 3 4" 1 1 2" 3" 5"6" 8"0
1
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80 20
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0 1 I— 1 I I 1 I I I I I I III I 11 I I I II I I U 11111 1 I _I I 1 I I II 100
.001 .002 .005 .009 .019 .037 .075 .150 .300 I .600 1.16 2.36 4.75 9.5 19 38.1 76.2 127 200
I DIAMETER OF PARTICLES IN MILLIMETERS 152
I
SAND GRAVEL
CLAY TO SILT COBBLES
FINE I MEDIUM COARSE FINE COARSE
GRAVEL 48 % SAND 44 % SILT AND CLAY 8 %
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF: Slightly Silty Sand and Gravel FROM: Boring 1 0 5' & 10' (Combined)
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These test results apply only to the
samples which were tested. The
E testing report shall not be reproduced,
except In full, without the written
approval of Kumar & Associates, tit
of Sieve anales s testing Is D422, ��
accordancelowith ASTMAssociates,
A
and/or ASTM D1140.
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I6 17-7-737 H-PtiKUMAR GRADATION TEST RESULTS 04/06/2018
ASPEN
BUILDING DEPARTMENT
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BUILDING DEPARTMENT
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TABLE 2
PERCOLATION TEST RESULTS
PROJECT NO. 17-7-737
HOLE NO. HOLE LENGTH OF WATER WATER DROP IN AVERAGE
DEPTH INTERVAL DEPTH AT DEPTH AT WATER PERCOLATION
(INCHES) (MIN) START OF END OF LEVEL RATE
INTERVAL INTERVAL (INCHES) (MIN./INCH)
(INCHES) (INCHES)
B-1 124 5 24 151/2 81/2 0.6
5 151/2 9'/2 6 0.8
2 91/2 8 11/2 1.3
2 8 6'/2 1'/2 1.3
2 6'/2 5 11/2 1.3
2 5 4 1 1.0
2 4 3 1 1.0
L
Note: The Percolation test was conducted in the completed 4-inch diameter borehole
on October 5, 2017.
RECEIVED
04/06/2018
ASPEN
BUILDING DEPARTMENT