HomeMy WebLinkAboutObservation Excavation Report 08.08.2018Geotechnical Engineering 1 Engineering Geology
Materials Testing 1 Environmental
5020 County Road 154
Glenwood Springs, CO 81601
Phone: (970) 945-7988
Fax: (970) 945-8454
Email: hpkglenwood@kumarusa.com
Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado
August 8, 2018
Ted Vaughan
259 County Road 320
Rulison, Colorado
vaughanconstco@aol.com
Project No. 18-7-412
Subject: Observation of Building Excavation, Proposed Shop and Vehicle Storage
Building, 259 County Road 320, Rulison, Garfield County, Colorado
Dear Ted:
As requested, a representative of H-P/Kumar observed the excavation at the subject site on June
26 and July 10, 2018 to evaluate the soils exposed for foundation support. The findings of our
observations and recommendations for the foundation design are presented in this report. The
services were performed in accordance with our agreement for professional engineering services
to you, dated June 15, 2018.
Proposed Construction: The proposed shop will be a steel frame/metal skin building supported
on pad footings. Ground floor will be slab on grade. Cut depths are expected to range between
about 1 to 4 feet. Foundation loadings for this type of construction are assumed to be relatively
light to moderate and typical of the proposed type of construction.
At the time of our initial visit to the site, the foundation excavation was underway with many
boulders being encountered. The exposed soils consisted of gravel, cobbles and boulders in a
clayey silty sand matrix. Samples of the matrix soils were taken from approximate footing grade
on the north side of the building area. Results of swell -consolidation testing performed on the
samples, shown on Figures 1 and 2, indicate the matrix soils have low compressibility under
light loading with a low to moderate collapse potential (settlement under constant load) when
wetted. The samples were moderately compressible under increased loading after wetting. No
free water was encountered in the excavation and the soils were slightly moist to moist.
Upon our second visit to the site, the excavation was complete and had been cut in one level
about 2 feet below the adjacent ground surface. Screened 3/4 -inch rock had been placed and
compacted as backfill to re-establish footing grade in areas that were over -excavated by boulder
removal.
Considering the conditions exposed in the excavation and the nature of the proposed
construction, spread footings placed on the undisturbed natural soil designed for an allowable
Ted Vaughan
August 8, 2018
Page 2
soil bearing pressure of 2,000 psf can be used for support of the proposed building. The exposed
matrix soils tend to compress when wetted and there could be some post -construction settlement
of the foundation if the bearing soils become wet. Footings should be a minimum width of 16
inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas
should be compacted or removed and the bearing level extended down to the undisturbed natural
soils. Exterior footings should be provided with adequate soil cover above their bearing
elevations for frost protection. 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 (if any) should also be designed to resist a lateral
earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site soil as
backfill. Structural fill placed within floor slab areas can consist of the on-site soils compacted
to at least 95% of standard Proctor density at a moisture content near optimum. Backfill placed
around the structure should be compacted and the surface graded to prevent ponding within at
least 10 feet of the building.
The recommendations submitted in this letter are based on our observation of the soils exposed
within the foundation excavation and do not include subsurface exploration to evaluate the
subsurface conditions within the loaded depth of foundation influence. This study is based on
the assumption that soils beneath the footings have equal or better support than those exposed.
The risk of foundation movement may be greater than indicated in this report because of possible
variations in the subsurface conditions. In order to reveal the nature and extent of variations in
the subsurface conditions below the excavation, drilling would be required. It is possible the
data obtained by subsurface exploration could change the recommendations contained in this
letter. 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.
If you have any questions or need further assistance, please call our office.
Sincerely,
H -P= KUMAR
00
• to 24443 z }
Daniel E. Hardin, €° �:, 00// ;4
5�lRr�t.
Rev. by: SLP � �
DEH/kac
attachments Figures 1 and 2 — Swell -Consolidation Test Results
H -P —KUMAR
Project No. 18-7-412
CONSOLIDATION - SWELL
0
SAMPLE OF: Clayey Sand Matrix
FROM: Pit 1 0 3'
WC = 11.7 %, DD = 97 pcf
Mee, tell •..orfs eppry 047 to the
e onviot tinea. The Ieet:rp •.:aen
• T.l not be feprodeice0. erelpt m
Ite. without the •t 1104 0pptnrei 01
IWmer 1108 beeenle•, Inc. Swell
[a.wieetlen teehnq pe•roPmce in
e scoaloduce nth A5fV 0-4546.
18-7-412
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1.0 APPLIED PRESSURE — KSF 10 100
H-PVKUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 1
CONSOLIDATION - SWELL
2
0
—6
— 10
— 12
— 14
SAMPLE OF; Clayey Sand Matrix
FROM; Pit 1 @ 3'
WC = 10.4 %, DD = 94 pcf
Seel• leel refuel epsiy Holy 10 041
lolmptw• tested. 1n• telling r•eerl
.Ne% not tie reproduced, •rppl in
NO, without the written dpyo•d of
%yrdd• dnd Atleedk1 . Mc. Steed
Ca+Wi1.1;ov lqulvq ymlennsd rn
noel o, a with ASRI D -45e6.
18-7-412
ADDITIONAL COMPRESSION
UNDER CONSTANT PRESSURE
DUE TO WETTING
1.0 APPLIED PRESSURE - KSF 10 100
H-P=�KUMAR
SWELL -CONSOLIDATION TEST RESULTS
Fig. 2