HomeMy WebLinkAboutB15-0106_Helical Pier signed_1434456960.pdf I,..I Hepworth-Paw Zak Geotechnical, Inc.
�h 5020 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970-945-7988
HEPWORTH-PAWLAK GEOTECHNICAL
FIN: 970-945-845 }
email: hpgeo,3hpgeotech.enu
June 12, 2015
Michael Barney
5074 Main Gore Drive, Unit A
Vail, Colorado 81657
tandmbamev a,comcast.net
Job No. 115 168A
Subject: Observation of Excavation and Helical Pier Installation, Proposed
Additions to Unit A Residence, Lot 5, Filing 1, Vail Meadows, 5074
Main Gore Drive, Vail, Colorado
Dear Mr. Barney:
As requested by Wayne Haskins, a representative of Hepworth-Pawlak Geotechnical,
Inc. observed the excavations at the subject site on June 4 and 8, 2015 to evaluate the
soils exposed for foundation support. We subsequently observed helical pier
installation designed to support the western portion of the garage addition on June 11,
2015. The findings of our observations and recommendations are presented in this
report. The services were supplemental to our proposal for geotechnical engineering
services to you, dated April 2, 2015.
The proposed construction is similar to that discussed in our previous report. The
additions will be attached to the north (bedrooms), to the west (garage) and to the
south (new entryway) sides of the existing building. The additions have been
designed to be supported on spread footings using an allowable soil bearing pressure
of 2,500 psf based on recommendations provided in our previous report.
At the time of our June 4 site visit, the foundation excavation for the new entryway
and bedrooms was underway. The excavations had been cut at several levels from
about 3 to 51/2 feet below the adjacent ground surface. There were minor cuts in the
proposed floor slab areas. The excavation subgrades were about 1 foot below the
existing residence spread footing bearing elevation. The soils exposed in the bottom
of the excavations consisted of medium dense, silty sandy gravel with cobbles.
Groundwater was being encountered in the excavations typically flowing out from
under the existing building footings. At this time we recommended the excavations
be dewatered by shallow trenches leading to sumps (placed outside of footing areas)
where the water could be collected and pumped.
Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989
Michael Barney
June 12, 2015
Page 2
On June 8, we observed the west side (garage area) addition excavation to have been
cut at several levels from about 3 to 4% feet below the adjacent ground surface The
soils exposed in the bottom of the excavation consisted primarily of medium dense,
silty sandy gravel with cobbles. Along the west wall line adjacent the creek there was
about 4 to 5 feet of old fill and topsoil overlying the natural coarse granular soils. No
free water was encountered in this excavation. At this time we recommended the fill
and topsoil be removed to bear the footings entirely on the natural coarse granular
soils or a relatively deep foundation system such as helical piers be used to penetrate
the fill and topsoil and support the foundation wall.
On June 11, we observed the installation of 4 helical piers at the site for the garage
addition on the west side of the residence. The piers were located on the west wall
line and numbered from Pier #1 (at the northwest corner) south to Pier #4 (at the
southwest corner). The piers were designed for allowable (working) capacities of 10
to 15 kips. Our observation of the helical pier installation is provided on the attached
Report of Helical Pier Observation. The piers were installed in into the granular
natural soils at depths from about 7 to 11 feet (11 to 16 feet depth) where refusal to
torque or penetration was encountered. The excavation subgrade soils to the east of
the west wall line where the piers were installed consisted of the natural coarse
granular soils.
The piers should have adequate capacity to support the 10 to 15 kip design working
loads. The natural coarse granular soil conditions exposed in the excavations are
consistent with those previously encountered on the site and suitable for support of
spread footings designed for the recommended allowable bearing pressure of 2,500
psf. There could be some differential settlement for the addition areas with respect to
the existing structure, and between the spread footings and helical pier supported
foundation areas which should be considered in the design. Prior to the footing
construction all loose disturbed soils should be removed in the footing areas to expose
the undisturbed natural granular soils and the subgrade compacted as feasible. The
water seepage into the excavations should continue to be collected and diverted away
from the footing areas and any softened soils and mud removed before concrete
placement. A shallow depth (6 to 12 inches) of screened rock can be placed in the
bottoms of the excavations to aid in the dewatering. Other recommendations
presented in our previous report which are applicable should also be observed.
The recommendations submitted in this letter are based on our observation of the soils
exposed within the foundation excavation and the previous limited subsurface
exploration at the site. Variations in the subsurface conditions below the excavation
could increase the risk of foundation movement. We should be advised of any
Job No. 115 168A
CSC Ugtech
Michael Barney
June 12, 2015
Page 3
variations encountered in the excavation conditions for possible changes to
recommendations contained in this letter.
If you have any questions or need further assistance, please call our office.
Sincerely,
HEPWORTH — PA G 9611101WICAL, INC.
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attachment 6-11-15 Report of Helical Pier Observation
cc: Piper Architects — Duane Piper (dpiperAvail.net)
Wayne Haskins Construction — Wayne Haskins
(wavne wavnehaskinsconstruction.corn)
KRM Consultants — Tim Hennum (tdhRkrmconsultants.com)
Job No. 115 168A
Gertech
I-I P 5020 County Road 154
Glenwood Springs, CO
81501
Phone: 970-945-7988
Fax: 970-945-8454
HEPWORTH-PAWLAK GEOTECHNICAL hpgeo(RhPueotech.com
Report of Helical Pier Observation
Client: Michael Barney Job No.: 115 168A Date: June 11, 2015
5074 Main Gore Drive, Unit A Sheet No.: 1 of 1
Vail, Colorado 81657
Project: Observation of Excavation and Helical Pier Installation, Proposed Additions to Unit A Residence, Lot 5,
Filing 1, Vail Meadows, 5074 Main Gore Drive, Vail, Colorado
General Contractor: Wayne Haskins Construction Helical Pier Contractor: Great Divide
Pier Manufacturer: Heli-Pile Rig Type: 5K Hand Held
Helix Total Design Pier Design Pier Ultimate Measured
Pier Pier Shaft Diameter Depth Load Load Load Refusal Number of
it Location Type p Capacity Capacity Criteria Torque Shear Pins
(m') MO (IdPs) (APs) (APs) (ft-lbs)
1 Northwest 11/2" sq 8" single 11' 10 10 20 P N/A 4
Corner
2 2"a from 11/2" sq 8" single 15' 15 15 30 P N/A 6
North
3 3r° from 11/2" sq. 8" single 14'h' 15 15 30 P
North N/A 6
4 Southwest 11/2„ sq 8" single 16' 10 10 20 T N/A 4
corner
Preliminary Observations and / or Testing Results Verbally Reported To:
Notes: P = Refusal to penetration of pier. T = Refusal by torque limit.
All helices lh-inch in thickness.
Torque measurements are based on shear pins provided by Great Divide Construction.
Design Loads were provided by KAM Consultants
Pier Design Load Capacity is based on the measured torque and a safety factor of 2.0.
H-P Geotech was requested to observe pier installation. H-P Geotech did not provide pier or helix sizing.
Four shear pins = 20 kips (5 kips per pin)
Copies:
Piper Architects—Duane Piper(doiperAvail.net)
Wayne Haskins Construction— Wayne Haskins (wavne a,wavnehaskinsconstruction.com)
KRM Consultants— Tim Hennum (tdh@knnconsultants.com)
Joe Benedict David A. Young, P.E.
Field Observer Reviewed By
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