HomeMy WebLinkAbout20040946.tiff lierracon
July 20, 2001 1242 Bramwood PI
Longmont,Colorado 60501
(303)776-3921 Fax:(303)776-4041
Dagney Designs
7001 West 117th Avenue, Unit 4
Broomfield, Colorado 80020
Attn: Kate Brooks
Re: Test Pit Observation/Foundation Recommendations
Proposed Modular Unit at the School for Youth
745 Colorado Highway 119
Longmont, Colorado
Terracon Project No. 22015172
Terracon has completed a test pit observation for a proposed modular unit to be placed at the
School for Youth, located at 745 Colorado Highway 119, in Longmont, Colorado. The purpose
of the observation was to provide foundation recommendations for the proposed modular unit.
The study was implemented by observing a nine (9) foot deep test pit and retrieving relatively
undisturbed samples for laboratory testing and analysis. The test pit was observed on July 17,
2001. Relatively undisturbed samples were retrieved from the test pit at selected depths for
laboratory testing and analysis. The test pit record for the site, along with results of laboratory
testing of selected samples, are attached. Geotechnical recommendations for the design of
foundations are outlined below.
Proposed Construction: We understand that the proposed development at the site will include
the construction of pre-manufactured modular unit. The modular unit will consist of a single-story
wood framed structure with a crawl space. A typical foundation system currently being used for
support of the proposed structures consists of a series of spread footings or shallow piers, which
transmit structural loads to the foundation soils. Dry stack and/or CMU blocks with shims are
placed on top of each pier foundation to support the structure's framing. Considering the size and
type of construction being used, only light foundation loads are expected.
Subsurface Conditions: In general, the subsurface soils encountered in the test pit consisted of
a thin layer of roadbase type fill for the parking lot surface, overlying sandy lean clays. No
bedrock was encountered in the test pit to the maximum depth explored of nine (9) feet. In
addition, groundwater was not encountered in the test pit to the depth explored at the time of our
field investigation. Please refer to the Logs of Test Pit for more comprehensive strata
descriptions.
Laboratory Test Results: Field penetration tests results indicate that the clay soils are generally
medium stiff in consistency. Swell-consolidation tests indicate that the site clays typically have low
swell potential when wetted. However, one sample at a depth of about 6 feet showed a low
Arizona■Arkansas■Colorado■Georgia■Idaho■Illinois■Iowa■Kansas■Kentucky■Minnesota■Missouri
Montana■Nebraska■Nevada■New Mexico IN Oklahoma■Tennessee 1 Texas■Utah■Wisconsin■Wyoming
Quality Engineering Since 1965
2004-0946
Dagney Designs
Terracon
Modular Unit,School for Youth,745 CO Hwy 119
Longmont,Colorado
Terracon Project No.22015172
potential for collapse. Based on the swell data from this study and our experience in the area, we
judge the site soils at and within the zone of influence of shallow foundations to have low swell
potential and low collapse potential overall.
Foundation Recommendations: Based on the subsurface conditions encountered in the test pit,
and the engineering characteristics of the soils likely to influence foundation performance, we
believe that the use of spread footings or shallow piers is an appropriate foundation system for
support of the proposed structure. Spread footings or shallow piers should bear on undisturbed
natural soil or on properly compacted structural fill and may be designed for an allowable soil
bearing pressure of not to exceed 1,000 pounds per square foot (psf). The design bearing
pressure applies to dead loads plus design live load conditions. Exterior footings and footings in
unheated areas must be protected from frost action. The normal depth of frost protection in this
area is assumed to be around 30 inches.
Based on the swell-consolidation test data from this study, we estimate total foundation movement
to be on the order of 3/a to 1'h inches depending primarily upon the depth of wetting below
foundations. Differential movement should be on the order of th to 3A of the estimated total
movement. Additional foundation movement is possible should deeper than normal wetting of the
foundation soils occur. Therefore, proper surface drainage should be provided and maintained for
the life of the structure. Considering the type of construction being used, we feel that the
estimated foundation movement should not result in significant damage to the structure.
However, if greater movement/heave does occur, we believe that the structural defects (if any)
could be repaired relatively easily by adjusting the height of the blocking system below the
structure.
Foundations should be reinforced as necessary to reduce the potential for distress caused by
differential foundation movement. Foundation excavations should be observed by the
geotechnical engineer to confirm that satisfactory bearing materials are present and that
subsurface conditions are consistent with those found in our test borings. If the soil conditions
encountered differ from those presented in this report, supplemental recommendations will be
required.
Surface Drainage: Positive drainage should be provided during construction and maintained
throughout the life of the proposed residence. Surface drainage can be critical to the performance
of foundations and concrete flatwork. Infiltration of water into utility or foundation excavations
must be prevented during construction. Planters and other surface features that could retain
water in areas adjacent to the building or pavements should be sealed or eliminated. In areas
where sidewalks or paving do not immediately adjoin the structure, we recommend that protective
slopes be provided with a minimum grade of approximately 10 percent for at least 5 feet from
2
Dagney Designs
Modular Unit,School for Youth,745 CO Hwy 119 Terracon
Longmont,Colorado
Terracon Project No.22015172
perimeter walls. Backfill against exterior walls should be moistened at or near optimum and
should be well compacted.
Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when the
ground surface beneath such features is not protected by exterior slabs or paving. Sprinkler
systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent
to the foundation system should be minimized or eliminated.
Corrosion Protection (Concrete): We measured soluble sulfate concentrations for
representative samples of the subsoils that will likely be in contact with structural concrete. The
sulfate concentrations measured in the samples varied from negligible to 35 parts per million.
Results of soluble sulfate testing indicate that Type I Portland cement is suitable for all concrete
on and below grade. However, due to the minimal cost differential, use of Type II Portland
cement is recommended for additional sulfate resistance of construction concrete. Foundation
concrete should be designed in accordance with the provisions of the ACI Design Manual, Section
318, Chapter 4.
General Comments: The analysis and recommendations presented in this report are based
upon the data obtained from the borings performed at the indicated locations and from other
information discussed in this report. This report does not reflect variations that may occur
between borings or across the site. The nature and extent of such variations may not become
evident until construction. If variations appear, it will be necessary to reevaluate the
recommendations of this report.
The scope of services for this project does not include either specifically or by implication any
environmental assessment of the site or identification of contaminated or hazardous materials
or conditions. If the owner is concerned about the potential for such contamination, other
studies should be undertaken.
This report has been prepared for the exclusive use of our client for specific application to the
project discussed and has been prepared in accordance with generally accepted geotechnical
engineering practices. No warranties, either express or implied, are intended or made. In the
event that changes in the nature, design, or location of the project as outlined in this report, are
planned, the conclusions and recommendations contained in this report shall not be considered
valid unless Terracon reviews the changes, and either verifies or modifies the conclusions of
this report in writing.
3
Dagney Designs
Modular Unit,School for Youth,745 CO Hwy 119 Terracon
Longmont,Colorado
Terracon Project No.22015172
We appreciate the opportunity to be of service to you on this phase of your project. If you have
any questions concerning this letter/report, or if we may be of further service to you, please do
not hesitate to contact us.
Sincerely,
TERRACON "'"""""°"rplatita) EE W �
i
akt
Darrel J. DiCarlo s
Staff Engineer `rG j .
::1 i14tt:,Y1
Attachments: Log of Test Pit
Swell-Consolidation Curves
Copies to: Addressee (3)
4
•
•
LOG OF TEST PIT NO. TP
CLIENT Page 1 of 1
Dagney Designs
SITE 745 Colorado Highway 119 PROJECT
Longmont, Colorado Schools for Youth
SAMPLES TESTS
DESCRIPTION > a w°' 0 COIL
z
a = y w > ¢` ¢w z z¢ oio
O w O
0 Approx. Surface Elev.: Grade a z ¢ a s g° o a c`31,7) [1'0,9
iD' • 0.5 FILL MATERIAL, Gravel Roadbase type fill
\in parking lot.
SANDY LEAN CLAY, brown, beige, rust, _
medium stiff, slightly moist to moist, porous,
slightly calcareous.
%..
CL HS 12/1.7€ 9 90 -1.0/500
/��
•
5-
CL HS \1/1.7E 10 88 -2.1/500
9 CL HS 14/1.7€
Bottom of Test Pit
a
0
0
CC
Q
W
r The stratification lines represent the approximate boundary lines
,�-- . between soil and rock types: in-situ,the transition may be gradual.
ai WATER LEVEL OBSERVATIONS, ft BORING STARTED 7-17-01
WL g Dry 7/17/01 s 1��rr�con BORING COMPLETED 7-17-01
w RIG FOREMAN DJD
m\L , _ PROVED EJP JOB# 22015172
8
r
6 -
4
J
J
W
3
2
a �♦
z N
0
p -2
0
2
Z
Q
T U
-4
-6
-8
0.1 1 10
100
APPLIED PRESSURE,ksf
P.
Specimen Identification Classification I Yd, pcf I WC,%
•I TP 3.0ft I Sandy Lean Clay(CL) 90 9
z
0
0
Notes:
w
I
0
,r n_
N
SWELUCONSOLIDATION TEST
lierracon Project: Schools for Youth
y Site: 745 Colorado Highway 119 Longmont, Colorado
$ ^� Job #: 22015172
Date: 7-20-01
•
6
4 _
-J
J
W
CO
N
2
Z
O
o -2
J
0
CO
Z
0
-4 \
•
-6
-8
0.1 1 10
100
APPLIED PRESSURE,ksf
Specimen Identification Classification Yd, pcf WC,%I
o •I TP 6.0ft Sandy Lean Clay(CL) 88 10
i
0
v
Notes:
w
a
0
O
NN
SWELUCONSOLIDATION TEST
Project: Schools for Youth
lierracon
Site: 745 Colorado Highway 119 Longmont, Colorado
0 Job#: 22015172
Date: 7-20-01
Hello