HomeMy WebLinkAboutSubsoils Report Addendum 11.07.23GTL ITHOMPSON
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November 7,2023
Andover Management Group
333 East Main Street, Suite 300
Louisville, KY 40202
Attention: Dan Kunau
Subject:Geotechnical Engineering lnvestigation - Addendum
214 Center Drive
(a.k.a. Parcel 21 85061 00042)
Garfield County, Colorado
CTLIT Project No. GS06693.001-125
CTLlThompson, lnc. (CTLIT) performed a geotechnicalengineering investigation regard-
ing 214 Center Drive (a. k.a. Parcel 218506100042) in Garfield County, Colorado. Subsequent to
our report, we were asked to prepare this addendum. This letter provides geotechnical engi-
neering recommendations and design criteria for earth retaining walls, seismic design, and
belled pier foundations.
Site Earth Retaininq Walls
We understand site earth retaining walls are included in the current plans for the project
Earth retaining walls must be designed to resist lateral eadh pressures. Many factors affect the
values of the design lateral earth pressure. These factors include, but are not limited to, the
type, compaction, slope, and drainage of the backfill, and the rigidity of the wall against rotation
and deflection.
For a very rigid wall where negligible or very little deflection will occur, an "at-rest" lateral
earth pressure should be used in design. For walls that can deflect or rotate 0.5 to 1 percent of
wall height (depending upon the backfill types), design for a lower "active" lateral earth pressure
may be appropriate.
For backfill soils conforming with recommendations in the Foundation Wall Backfill sec-
tion of our report that are not saturated, we recommend design equivalent fluid densities of at
least 45 pcf and 60 pcf for the "active" and "at-rest" conditions, respectively. Passive earth pres-
sure calculated with an equivalent fluid pressure of 300 pcf is appropriate for this site, provided
backfill in front of the retaining wall footings will not be removed during the lifespan of the struc-
tures.
Surface water from precipitation and landscape irrigation is likely to infiltrate backfill
placed adjacent to site earth retaining walls. This water can cause reduced backfill strength and
result in hydrostatic pressures on the retaining walls. Drains should be constructed behind the
bases of the footings for the walls.
CTllThompson. lnc.
Denver, Fort Collins, Colorado Sprinqs, Glenwood Sorings, &b!9, Summit Countv - Colorado
Cheyenne, Wyoming and Bozeman, Montana
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Piers should be reinforced full-length. Reinforcement should extend into the
grade beams and foundation walls. Additional reinforcement may be required
depending on structural analysis.
The belling tool should be used immediately upon completion of drilling the
straight-shaft portion of the pier. The belling tool should be used to its full capaci-
ty. Casing should be available on-site to prevent caving of soils into pier holes.
Piers should be carefully cleaned prior to placing concrete. Concrete should be
on-site and placed in the pier holes immediately after the holes have been drilled,
cleaned and observed. We recommend concrete with a minimum slump in the
range of 5 to 7 inches to reduce possibility of voids in the belled portion of the
pier.
lnstallation of drilled piers should be observed by a representative of CTLIT to
verify subsoils are as anticipated and to observe the contractor's installation
technique.
5.
We are available to discuss the contents of this letter. Please contact us if you have
questions or need additional information.
CTLITHOMPSON, lNC.Reviewed by:
3.
Barbone,
Division Manager
ANDOVER MANAGEMENT GROUP
214 CENTER DRIVE
crLlT PROJECT NO. GS06693.00'l-125
D. Ke r
ncipal Engineer
lloqq@ctlthompson. com
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