Response Letter 879 MillerCheck Response Letter #2 REV0www.geostructuralengineering.com
7172 Regional St #440~Dublin, CA 94568
Email: andre.hawks@geostructuralengineering.com~Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles &Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
GeoStructural Engineering Inc
April 20, 2021 P. 1 of 3
FROM: Andre Hawks, PE
Principal & Founder
TO: Arnold Hom, PE
Plan Check Engineer, City of Cupertino
RE: 877/879 Miller Ave Cupertino CA Response Letter #2
Plan Check #BLD-2021-0216 & BLD2021-0314
Dear Mr. Hom:
Please find my response to the plan check comments below:
1.Initial Review: Sheet S0, General Notes 5: Specify the maximum load (in pounds/kips) allowed for each
push pier. Specify the test loading criteria for each push pier and duration used for test loading.
2ND REVIEW: Response letter from the Engineer of Record dated March 16, 2021 stated that,
“The minimum depth and pressure are specified on the plans. Once the pressure is exceeded or
met, it is held or a minimum of 10 minutes and observed for creep.”
Maximum loads in pounds/ kips were not stated on the Foundation Plan on sheet S1. Note 1 of
sheet S1 specifies 18-inch or 36-inch grip piers, but no loading was provided. Sheet S0
Installation Note 5 gives calculations on how to do the loading, but the actual loading is not
stated.
Please specify the maximum loading (in pounds/ kips) and specify the duration of the loading. In the
response letter, please specify which sheet has this information and where this info is found.
RESPONSE: See note added to Sheet S1. Maximum load not to exceed 21.7 kips per pier
bracket location. Design load is 11.7 kips per pier bracket location as calculated on page 3 of the
calculations. Please see note 7 on Sheet S0 with testing information.
3. Initial Review: Provide manufacturer’s listing/ cut-sheets for the Push Pier system and the Brackets.
Provide listing approval from a nationally recognized testing agency for the products (such as an ICC/
ESR Report). Listing must allow this usage for this seismic design category. Further comments may
follow due to lack of information.
2ND REVIEW: Received the UES Evaluation Report 391. Additional comments 11 thru 13 are generated
due to information provided in UES Evaluation Report 391.
Arnold Hom
05/03/21
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
RESPONSE: Attached is UES ER531 for Push Piers. Comments 11 – 13 addressed below.
6. Initial Review: Sheet S2: Specify the method of backfilling soil from the exposed cut. Specify soil
parameters for backfill (e.g. specify the type of soil allowed for backfill, compaction percentage, thickness of
each lift of backfill for each compaction). Brackets are not shown to anchor into the existing foundation
and are connected via skin friction; specify mechanical connection of brackets into the existing
foundation. Per sections 1604.8.1 and 1613.1 of the 2019 CBC and ASCE 7-16 section 12.1.
2ND REVIEW: Sheet S2: Per original comment, specify the compaction percentage for the backfill of
soil.
RESPONSE: 90% compaction at pier locations has been added to the notes on Sheet S2.
10. Initial Review: Sheet S0, General Notes: Pending the outcome of comment 3, if a soils report is
required, specify the soils report date, soils report number, and soils engineer company. Specify design
shall be per soils report. If a soils report is required, provide a soils review letter of the proposed
foundation system.
2ND REVIEW: Per UES Evaluation Report 391 sections 2.1 and 2.7, please provide a geotechnical
investigation from a licensed soils engineer per section 1803 of the 2019 CBC. Soils report to address soil
resistivity in ohms, pH value, sulfate content if greater than 1,000 ppm, or if there is a high organic
content in the soils.
RESPONSE: As agreed to, no soils report is required, or the need to address the soil values. We
are aware of the soils in the south bay and are comfortable using the Grip Tite Pier bracket and
pier tube products at this site.
11. 2ND REVIEW: Per UES Evaluation Report 391 section 2.2, spacing between helical plates shall be at
least a distance of 3D clear from edges of helical plate to helical plate, or 4D measured center to center of
helical plates, where D is the diameter of the plate. On sheet S1, unable to determine spacing since Note 1
specifies 18-inch or 36-inch piers. Specify the exact diameter of the pier system is to be used. Specify
on the Foundation Plan if the distances are measured center to center, or edge to edge. Piers 16 and
17 seem too close. Piers 12 and 13 seem too close.
RESPONSE: The pier locations are based on the center line of each 3” Diameter pier tube.
There are no helices on the push piers, so the minimum spacing of 4D= 12” for the piers is met
even at these corner piers of concern.
12. 2ND REVIEW: Per UES Evaluation Report 391 section 2.5, the piles are required to be laterally
braced for stability per IBC section 1810.2.2. Section 1810.2.2 of the 2019 CBC.
On sheet S2, on the sectional elevation detail, show how the piers meet the stability requirements of
section 1810.2.2. Dimension the width of the existing foundation, specify the location of the centerline of
GeoStructural Engineering Inc
Email: andre.hawks@geostructuralengineering.com Cell: 707-322-3507
Tunnels/Shafts ~ Underpinning ~ Micropiles ~ Soil Nails/Tiebacks ~ Helical Piles & Tiebacks ~ Auger Cast Piles
Soils Reports ~ Structural Engineering ~ Temporary & Permanent Shoring ~ Special Inspections ~ Retaining Walls
the pier, and dimension the distance of the centerline of the pier to the foundation to show that it meets
Exception 2 of section 1810.2.2 of the 2019 CBC.
RESPONSE: The reference in the IBC section references Concentric Piers. This project is
engineered using an Eccentric Pier Bracket System. The 2 ea. ½” x 5” long titan bolts that
fasten pier bracket to foundation are the lateral connection. See calculation below:
ASD Base Shear = 8.7 kips
Loading Per Side = 8.7 / 2 = 4.4 kips
Allowable Shear Load for 1/2 Anchor Bolt = Pi x R^2 x 0.5 x Fy = 3.5 kips
3.5 kips x 2 titan bolts per pier x 2 push piers (least amount of piers on any wall) = 14 kips > 4.4
kips Therefore OK
13. 2ND REVIEW: Per UES Evaluation Report 391 doesn’t have the parts indicated as shown on sheets
S2 and S3. System is using a helical pile system, but piles are designated as FP3SPH, FP3TRO, FPSTRI,
FP3T, FP4C, and FP3FCH. None of these components are listed in UES Evaluation Report 391. Please
revise drawings to match listing report.
RESPONSE: My apologies, please see attacehd ER531. The Cut sheets on S2 and S3 reference
the part number referenced in ER531.
If questions arise please contact me via email at andre.hawks@geostructuralengineering.com
Best Regards,
EXP: 3-31-22