HomeMy WebLinkAboutFile Documents.1050 Matchless Dr.0113-2020-BRES (21) GEOTECHNICAL ENGINEERING REPORT
GARAGES
RACQUET CLUB CONDOMINIUMS
1040 & 1050 MATCHLESS DRIVE
ASPEN, COLORADO
November 5, 2019
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Prepared By: Prepared For:
Engineering Racquet Club Condominium Assoc.
286 Red cliff
CI Ge 1040 & 1050 Matchless Drive
&Consulting,Inc. Glenwcwd SPnnga,CG A1601
P:(970)230-9208 Aspen, CO 81611
Project No. 19-038G-G1
RECEIVED
05/01/2020
ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
TABLE OF CONTENTS
1.0 PROJECT INFORMATION 1
1.1 Purpose and Scope 1
1.2 Proposed Construction 1
1.3 Site Conditions 1
2.0 SITE INVESTIGATION 2
2.1 Subsurface Investigation 2
2.2 Subsurface Conditions 2
2.2.1 Groundwater 3
3.0 SITE GRADING 3
4.0 FOUNDATION RECOMMENDATIONS 4
4.1 Foundations placed on Natural Soils 4
5.0 FOUNDATION AND RETAINING WALLS 5
6.0 FLOOR SLABS 5
7.0 CONCRETE 6
8.0 SURFACE DRAINAGE 6
9.0 LIMITATIONS 6
LIST OF FIGURES
Figure 1 —Approximate Test Hole Locations
Figure 2 —Test Hole Logs and Legend
Summary of Laboratory Test Results
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
1.0 PROJECT INFORMATION
1.1 Purpose and Scope
This report presents the results of our geotechnical investigation and recommendations for
design and construction of two garage structures at 1040 & 1050 Matchless Drive in Aspen,
Colorado. The investigation was performed to provide foundation and construction
recommendations for the proposed garages.
The site investigation consisted of geologic reconnaissance and exploratory test hole drilling to
investigate subsurface conditions. Test hole drilling was observed by a representative of RJ
Engineering. Samples obtained during the field exploration were examined by the project
personnel and representative samples were subjected to laboratory testing to determine the
engineering characteristics of materials encountered. This report summarizes our field
investigation, the results of our analyses, and our conclusions and recommendations based on
the proposed construction, site reconnaissance, subsurface investigation, and results of the
laboratory testing.
1.2 Proposed Construction
We anticipate the structures will not have below grade areas and excavation depths will likely be
on the order of 5 feet below grade. Plans indicate the back walls of the structure will act as
retaining walls where an existing timber crib wall is located.
1.3 Site Conditions
The site consists of an asphalt paved parking lot. A timber crib retaining wall is located along
the north side of the parking lot. The timber crib wall is about 4-5 feet in height. The
condominium buildings are located on the south side of the parking lot. Grades are relatively
flat where the garages are planned. The site is landscaped around the parking lot and
condominium buildings.
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
2.0 SITE INVESTIGATION
2.1 Subsurface Investigation
Two test holes were drilled on October 17, 2019. The test holes were drilled as close to the
center of the proposed structures as possible. We were unable to drill near the center of the
east garage because a vehicle was parked in that area. The approximate test hole locations
are presented on Figure 1.
The test holes were advanced with a Diedrich D90 track mounted rig using 4-inch continuous
flight auger where modified California or a standard split spoon sampler was used to record
blow counts and obtain samples. Test hole logs are presented on Figure 2.
To perform the modified California penetration resistance tests, a 2.0-inch inside diameter
sampler was seated at the bottom of the test hole, then driven up to 12 inches with blows of a
standard hammer weighing 140 pounds and falling a distance of 30 inches utilizing an "auto"
hammer (ASTM D1586). The number of blows (Blow Count) required to drive the sampler 12
inches or a fraction thereof, constitutes the N-value. The N-value, when properly evaluated, is
an index of the consistency or relative density of the material tested. Split spoon samples are
obtained in the same manner, but with a 1.5-inch inside diameter sampler. The test hole logs
and legend are presented on Figure 2.
2.2 Subsurface Conditions
Subsurface conditions encountered in test holes TH-1 and TH-2 consisted of 5 feet of silty sand
fill underlain by natural silty sand and gravel to the maximum explored depths of 12 and 8 feet,
respectively, where practical drill rig refusal was encountered. The fill consisted of a silty sand
with gravel and occasional cobbles and was loose to medium dense. The natural silty sand
contained gravel with abundant cobbles and boulders and was dense to very dense.
Two fill samples had 22 and 29 percent fines (material passing the No. 200 sieve). Atterberg
limit testing indicated the fill was non-liquid and non-plastic. One natural sand sample had 16
percent fines. Atterberg limit testing indicated the natural sand had a liquid limit of 36 and a
plasticity index of 11. The fill samples classified as a silty sand (SM), and the natural sand
sample classified as a silty sand (SM) according to the Unified Soil Classification System
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BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
(USCS). Results of the laboratory testing are summarized in the Summary of Laboratory Test
Results.
2.2.1 Groundwater
Groundwater was not encountered during drilling, and the test holes were backfilled for safety
reasons. We do not anticipate groundwater will be encountered to planned excavation depths.
Variations in groundwater conditions may occur seasonally. The magnitude of the variation will
be largely dependent upon the amount of spring snowmelt, duration and intensity of
precipitation, site grading changes, and the surface and subsurface drainage characteristics of
the surrounding area.
3.0 SITE GRADING
Fills are likely planned at this site to achieve finished grades. Grading plans were not available
at the time of this investigation. Based on drilling and our observations, we believe that material
can be excavated by conventional construction equipment. Large boulders may be
encountered during excavation. The boulders may be of such size that on site splitting may be
required before conventional equipment could remove the material.
We recommend fill slopes be constructed at 2H:1V or flatter. Fill slopes should be protected
from erosion. Surface drainage should be directed around slopes. Surface water ponding
behind or flowing over the face of fill slopes may cause significant erosion and instability.
The on-site soils can be used in site grading fills provided the material is substantially free of
organic material, debris and particles are no larger than 6 inches. Areas to receive fill should be
stripped of vegetation, organic soils and debris. Topsoil is not recommended for fill material.
Imported granular soils should contain less than 30 percent fines (passing No. 200 sieve) and a
maximum particle size of 6 inches. Fill should be placed in thin, loose lifts of 8 inches thick or
less. We recommend fill materials be moisture conditioned to within 2 percent of optimum
moisture content and compacted to at least 95 percent of maximum standard Proctor dry
density (ASTM D 698). Placement and compaction of fill should be observed and tested by a
geotechnical engineer.
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
4.0 FOUNDATION RECOMMENDATIONS
We believe that the natural sands with gravels, cobbles and boulders encountered at the site
are comparatively favorable for the proposed construction. Existing fill soils are not suitable for
support of foundations. Foundations should be placed on natural sand and gravel soils and not
on existing fill soils. We recommend foundations be placed at least 5 feet below existing grade
or at the natural sand soils, whichever is deeper. As an alternative, existing fill soils could be
removed and replaced with properly placed fill in accordance with section 3.0 of this report.
Foundation recommendations for structures supported by the natural soils are presented below.
4.1 Foundations placed on Natural Soils
Foundations should be constructed on undisturbed natural soils at a depth of at least 5 feet
below existing grade. Existing fill or loose, disturbed soils encountered at foundation level
should be removed and the foundation should be extended to natural soils and/or replaced with
properly compacted fill. We recommend fill be placed in accordance with the specifications
presented in section 3.0.
1. Footings should be placed on undisturbed natural sand and gravel soils or properly
placed fill. Foundations can be designed for a maximum allowable soil pressure of
3,000 psf. Based on experience, we anticipate settlement of footings designed and
constructed as recommended will be about 1-inch or less.
2. Continuous footings should have a minimum width of 16 inches and isolated pads
should have a minimum dimension of 2 feet.
3. The soils below foundations should be protected from freezing. We recommend the
bottom of foundations be constructed at least 3.5 feet below finished exterior grade or as
required by local municipal code.
4. Continuous foundation walls shall be reinforced to span anomalies by assuming an
unsupported distance of 10 feet. Foundation walls acting as retaining structures should
be designed to resist lateral earth pressures as discussed in section 5.0 below.
5. All foundation excavations should be observed by a representative of a geotechnical
engineer prior to placement of concrete.
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
5.0 FOUNDATION AND RETAINING WALLS
Retaining and below grade walls should be designed to resist lateral earth pressure. Cast-in-
place foundation and retaining walls can be backfilled with on-site granular soils meeting
recommendations in section 3.0. For a horizontal backslope with properly placed and
compacted fill, the unfactored earth pressure can be estimated using an equivalent fluid
pressure of 45 pcf for the active condition and 60 pcf for an at-rest condition. Site retaining
walls which are separate from the structure and can be expected to deflect to mobilize the full
active earth pressure condition could be designed using an equivalent fluid pressure of 45 pcf.
These values assume that the backfill materials are not saturated. Wall designs should
consider the influence of surcharge loading such as traffic, construction equipment and/or
sloping backfill.
The lateral resistance of foundations for retaining walls are a combination of sliding resistance
of the footing on foundation materials and passive earth pressure at the toe of the wall. Sliding
resistance could be calculated based on a coefficient of friction of 0.45. Passive pressure for
natural soils or compacted fill can be determined using an equivalent fluid pressure of 400 pcf.
Retaining walls and structures should be constructed with a drainage system to drain away any
excess water immediately behind the wall. The drainage system may consist of free-draining
gravel, pipes, drain board and/or weep holes are commonly used for wall drainage.
6.0 FLOOR SLABS
The existing fill and natural on-site soils are suitable to support lightly loaded slab-on-grade
construction. To reduce distress associated with minor differential movement, floor slabs should
be separated from all bearing walls and columns with expansion joints which provide
unrestricted vertical movement. A minimum 4-inch layer of free draining gravel should be
placed beneath lower level slabs. The free draining gravel should have less than 2 percent
passing the No. 200 sieve, less than 50 percent passing the No. 4 sieve and have a maximum
size of 2 inches. All fill placed below floor slabs should be moisture conditioned and compacted
in accordance with the recommendations in section 3.0.
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
7.0 CONCRETE
Typically, for materials encountered at this site, the concentration of water-soluble sulfate is
negligible/low (Class 0 exposure) degree of sulfate attack for concrete exposed to these
materials. The degree of attack is based on a range of 0.00 to less than 0.10 percent water-
soluble sulfates as presented in the American Concrete Institute Guide to Durable Concrete.
Due to the negligible/low degree, no special requirements for concrete are necessary for this
site.
8.0 SURFACE DRAINAGE
Surface drainage is crucial to the performance of foundations and flatwork. We recommend the
ground surface surrounding the building be sloped to drain away from the structure. We
recommend a slope of at least 6 inches in the first 10 feet for landscape and unpaved areas and
a minimum slope of 2 percent for paved areas. Irrigation should not be discharged within 5 feet
of foundation walls. Backfill around foundations should be moisture conditioned and compacted
as recommended in the section 3.0. Roof downspouts and drains should discharge beyond the
wall backfill area.
9.0 LIMITATIONS
This study was conducted in accordance with generally accepted geotechnical engineering
practices in this area for use by the client for design purposes. The conclusions and
recommendations submitted in this report are based upon the data obtained from exploratory
test holes, field reconnaissance and anticipated construction. The nature and extent of
subsurface variations across the site may not become evident until excavation is performed. If
during construction, conditions appear to be different from those described herein; this office
should be advised at once so reevaluation of the recommendations may be made. We
recommend on-site observation of excavations by a representative of the geotechnical
engineer.
The scope of services for this project did not include, specifically or by implication, any
environmental or biological (e.g., mold, fungi, and bacteria) assessment of the site or
identification or prevention of pollutants, hazardous materials or conditions or biological
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ASPEN
BUILDING DEPARTMENT
1040& 1050 Matchless Drive Project No. 19-038G-G1
Aspen,Colorado
conditions. If the owner is concerned about the potential for such contamination, conditions or
pollution, other studies should be undertaken.
The report was prepared in substantial accordance with the generally accepted standards of
practice for geotechnical engineering as exist in the site area at the time of our investigation.
No warranties, express or implied, are intended or made.
Respectfully Submitted,
RJ Engineering & Consulting, Inc.
Richard D. Johnson, P.E.
Principal
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ASPEN
BUILDING DEPARTMENT
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LEGEND: PROJECT NO: PROJECT
19-038G G1 1040& 1050 Matchless Drive,Aspen
TH-1 Indicates approximate test hole location o 10' 20' �� C����
® NJ` Approximate -� I U
re
NOTES: ,r SCALE: 1" =20' a
1. Base plan by Bryan May Architecture. Test est Hole Locations5/01/ 2020
ASPEN
BUILDING DEPARTMENT
TH-1 TH-2
0 �1 0
— � — Sample Types
• Modified California Sampler. The symbol 7/12 indicates that 7
— 07/12 blows from a 140 pound hammer falling 30 inches was used to
_ _ _ drive a 2-inch I.D.sampler 12 inches.
.117/12 19/12
5 �� 5
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—
— Other Symbols
— IP 4 — it Indicates practical drill rig refusal.
10 — 4.I48/12 10 Soil Lithology
- K.LA - FILL,SAND,silty to clayey,gravelly,occasional cobbles and
� — boulders,slightly moist to moist,loose to medium dense,brown,black
Rom
— — .Aim SAND AND GRAVEL,slightly silty to silty,abundant cobbles and
15 15 boulders,slightly moist,dense to very dense,brown,light brown
�;.
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Zi 1") _ - o
0 --
20 20
25 25
30 30
35 35
- - NOTES:
1. The test hole was drilled on October 17,2019 with 4-inch continuous
— — flight auger.
2. Test hole descriptions are subject to explanations contained in this
— report.
40 40
LOGS OF EXPLORATORY BORINGS RECEIVED
Project:
R Engineering 1040 & 1050 Matchless Drive 19-038G-G1
&Consulting, Inc. Aspen, Colorado 0 5/O 1/i2r0?0
ASPEN
BUILDING DEPARTMENT
RJ Engineering & Consulting, Inc.
Summary of Laboratory Test Results
Project No: 19-038G-G1 Project Name: 1040 & 1050 Matchless Drive, Aspen
Sample Location Grain Size Analysis Atterberg Limits Water Swell (+)/
Moisture Dry •Gravel Fines Soluble Consoli-dation
Test Sample Content Density Sand LL PL PI Description
Depth (ft) o >#4 0 (%) (%) (%)
<#200 Sulfate (-)at 1,000 psf
Hole Type (/o) (pcf) (%) (/o) (%) (%) (%)
TH-1 4 CA 13.9 108 29 FILL, sand, silty to clayey
9 CA 7.2 126 16 36 25 11 SAND, gravelly
TH-2 4 CA 7.2 120 22 NL NP NP FILL, sand, silty to clayey
•
•
•
*Laboratory testing by others RECEIVED
CA-Indicates modified California sampler // 2020
NL-Indicates non-liquid LJ-t n N
. •� .
NP-Indicates non-plastic Page 1 of 1 BUI C.::) ARTMENT