HomeMy WebLinkAboutReport - DigitalGeotechnical Services – 3-Level Custom Home 4805 Watersong Way, Fort Pierce, FL
15 January 2021 21-117
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Phoenix Custom Homes
1760 Jog Road, Suite 120
West Palm Beach, FL 33411
Subject: Report of Geotechnical Services – 3-Level Custom Home
4805 Watersong Way, Fort Pierce, Florida
Allterra Engineering & Testing respectfully submits this report of geotechnical services for the subject
project. Allterra’s services have been performed to meet certain requirements of chapter 18 of the
2020 Florida Building Code, its subsequent revisions, and local amendments. This report is Allterra’s
instrument-of-service provided for sole reliance and use by Phoenix Custom Homes. Third parties
may read this report for information purposes.
Project and Scope
Reference Documents. Digital copies of the following documents were provided for Allterra’s
reference in performing its services:
• Preliminary drawings 1, 2, 3, 5, and 6 dated 11-16-20 by M.A. Corson & Associates
• Boundary & Topo Survey dated 10-2-2019 by Culpepper & Terpening (their file number 19-
239 Lot 3)
Project Information. The project is a 3-level custom home proposed for construction upon the subject
property. The property is bounded on the west by Watersong Way, on the east by the Atlantic Ocean,
and on the north and south by other residential properties. Allterra understands the project is
seaward of the Coastal Construction Control Line. For this reason, it is to be designed for supported
upon a foundation of grade beams and piles.
Scope and Constraints. Allterra was tasked with performing soil-test borings to characterize
subsurface conditions and providing recommendations for foundation design (pile length, diameter,
and capacity). Specific information on design storm parameters has not been provided at this
time. These parameters are provided by the project coastal engineer and typically include
information such as breaking wave-crest elevations, eroded-grad elevation, wave impact force and
elevation of force resultant, debris impact force and elevation of force resultant, etc. For purposes
of this report, Allterra assumed: head-of-pile at 9 feet above existing surface grade and fixed against
rotation, and eroded grade at 6 feet below existing surface grade. If these assumptions are
erroneous, the conclusions and recommendations of this report may warrant change.
Field Work
Allterra mobilized personnel and equipment to the project site on 13 January 2021 to perform two
soil-test borings. These were advanced from surface grade at opposing corners of the project
footprint as field marked by the Client. Penetration testing was performed in the soil-test borings by
driving a 2-inch diameter steel sampler with blows of a 140-pound hammer free-falling 30 inches.
Copies of the boring logs are attached to this report for the reader’s reference.
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982
Geotechnical Services – 3-Level Custom Home 4805 Watersong Way, Fort Pierce, FL
15 January 2021 21-117
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Findings
Subsurface Profile. Allterra’s borings encountered variable subsurface conditions at each boring
location. The conceptual subsurface profile can be described as:
• Topsoil sampled as dark-gray, fine sand with occasional roots from surface grade to
approximately 6 inches below grade, underlain by
• Stratum 1 - firm, brown and gray, fine sand to approximately 3 to 4 feet below grade,
underlain by
• Stratum 2 – firm to very-firm, gray, fine sand with trace of shell to approximately 7 to 7½
feet below grade, underlain by
• Stratum 3 – soft to firm, dark-brown peat and dark-gray muck to approximately 8 to 9 feet
below grade, underlain by
• Stratum 4a – firm to loose, gray, fine sand to silty sand-and-shell to approximately 13 to
14 feet below grade, underlain by
• Stratum 4b – very-firm to dense, gray, sand-and-shell with occasional lenses of loose sand
and organic silt to approximately 27 to 32 feet below grade, underlain by
• Stratum 4c – very-firm, gray, sand-and-rock-and-shell to 37 feet below surface grade,
underlain by
• Refusal (presumed sandstone, limestone, or cemented coquina)
Exceptions to the conceptual profile include:
• Stratum 4a was sampled as dense, brown, sand-and-rock in B-2.
• Refusal was encountered 27 feet below grade in B-1.
Groundwater. Groundwater depth is estimated approximately 4 feet below surface grade. Actual
depth to groundwater may vary at other times due to changes in hydrologic conditions.
Conclusions
Pile Capacity. Considering the conceptual subsurface profile and assumption of eroded grade,
Allterra estimated the following capacities for 14-inch and 16-inch-diameter auger-cast piles installed
to approximately 30 feet below surface grade (approximately 24 feet below eroded grade).
Pile Diameter CAXIAL CVERTICAL CHORIZONTAL Uplift Resistance
14 inches 190 Kips 62 Kips 5 Kips 110 Kips
16 inches 220 Kips 72 Kips 8 Kips 126 Kips
Notes: CAXIAL = ultimate compressive load capacity.
CVERTICAL = allowable compressive load capacity.
CHORIZONTAL = allowable horizontal at-fixed-head shear-load capacity (½-inch displacement at
eroded grade)).
Uplift Resistance = (weight of pile + skin friction)/1.5.
Kips = 1000 pounds.
Pile Evaluation. The pile modeling was based on a conceptual subsurface profile and certain
assumptions about the design storm event. The client shall engage a Florida-licensed professional
engineer experienced in coastal engineering to review the information and assumptions presented
in this report against his expert evaluation. Without the coastal engineer’s agreement, additional
evaluation may be required.
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982
Geotechnical Services – 3-Level Custom Home 4805 Watersong Way, Fort Pierce, FL
15 January 2021 21-117
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Recommendations – Building-Pad Preparation
The building pad is defined as the footprint of construction plus 5 feet in all accessible directions.
Allterra recommends:
1. Strip topsoil and vegetation (including roots) from building pad and properly waste.
2. Thoroughly wet the exposed surface and allow it to drain to optimum moisture.
3. Mechanically compact exposed surface to at-least 95 percent of maximum-dry-density as
determined by the Modified-Proctor compaction test (ASTM D-1557 / AASHTO T-180).
4. Engage Allterra to perform probe-rod and field-density tests to verify compaction standards are
achieved.
5. Place fill, where needed, to achieve construction-ready grades in thin lifts and compact (at or
near optimum moisture) to at-least 95 percent of maximum-dry-density as determined by the
Modified-Proctor compaction test (ASTM D-1557 / AASHTO T-180). Lift thickness will depend
upon methods and equipment employed to achieve the target densities.
6. Engage Allterra to perform probe-rod and field-density tests on each 2-foot rise in fill height to
verify compaction standards are achieved.
7. Once the building pad is prepared, the contractor shall maintain its condition to prevent erosion
or other degradation through the placement of subsequent work.
Recommendation – Auger-Cast Piles
Pile Materials. Piles shall be formed with minimum 4000 PSI grout placed under pressure as the
auger is progressively withdrawn from the borehole. Piles shall be reinforced with five full-depth
number-5 steel bars and number-3 ties spaced not more than 16 inches on-center. The structural
engineer shall determine the number and distribution of piles considering structural loads and
geometry. Piles shall be drilled 8 feet into rock or refusal (less than 1 foot/minute advance).
Pile Layout. The number and distribution of piles shall be determined by the structural engineer
considering project loads and geometry. Piles shall be spaced at-least 3 diameters center-to-center
to avoid group effect on stress distribution in the bearing stratum.
Pile-Installation Monitoring. Engage Allterra to monitor installation of piles. For auger-cast piles,
monitoring shall include:
1. Check pile layout for conformance to design foundation plan.
2. Observe field trial and calculate gout-pump factor.
3. Observe drilling of pile to verify target depths are achieved.
4. Observe grouting of pile bore to verify acceptable grout return.
5. Sample grout for compressive-strength testing.
6. Observe installation of reinforcing steel to verify full-depth penetration.
7. Test grout specimens to verify design compressive strength is achieved.
8. Calculate grout factors and summarize installation data for each pile.
9. Prepare report of work acceptance signed and sealed by Professional Engineer.
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982
Geotechnical Services – 3-Level Custom Home 4805 Watersong Way, Fort Pierce, FL
15 January 2021 21-117
4
Qualification
Allterra has based its conclusions and recommendations upon certain client-provided information
and interpretation of data obtained at discrete points within the limits of exploration. It is possible
that conditions may vary between boring locations or beyond the limits of the boring array. Project
designs may also change. If additional information about the project or site is discovered that does
not appear to conform to the conditions presented in this report, Allterra reserves the right to review
the new information and modify its conclusions and/or recommendations where warranted.
Closing
Thank you for engaging Allterra as your geotechnical consultant. Please call the undersigned if you
have questions about this report or need other services.
Yours truly,
Allterra Engineering & Testing
Certificate of Authorization 9139
Wendell Rodgers, PE
Principal Engineer
FL Lic. No. 55960
Attachments
This item has been digitally signed and
sealed by Wendell K. Rodgers, P.E. on the
date adjacent to the seal.
Printed copies of this document are not
considered signed and sealed and the
signature must be verified on electronic
copies.
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982
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PROJECT Watersong PUD - PLAT NO. 1 - LOT #3 - 4805 WATERSONG WAY - Caruso Residence - St. Lucie County, Fl
LOCATION Northwest Corner of Building Area (Approximate)
PROPOSED THREE-LEVEL CUSTOM RESIDENCE
BORING NO. 1
0"-6" Dark Grey Fine Sand, trace of roots (topsoil)
6"-3' Brown Fine Sand
3'-7' Grey Fine Sand, trace of shell (fragmented)
7'-8' Peat
8'-10' Grey Fine Sand
12'-14' Grey Silty Sand, some shell (fragmented)
14'-15' Grey Fine Sand, and shell (fragmented)
18'-20' Grey Fine Sand, and shell (fragmented)
23'-25' Brown and Grey Fine Sand, trace of organics and silt
27'- Refusal (rock)
CLIENT Phoenix Custom Homes JOB NO. 21-117
DRILLER TM/TRM WATER TABLE N/A 1/13/21
TEST DATA In general accordance with ASTM D-1586
DEPTH DESCRIPTION OF MATERIAL Sampl e
Blows
Per Foot
No
.
D E P T H
DATE
These Soil Boring Tests are Representative of and Apply to the Exact Location and Depth of the Boring.
AUTHORIZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM
OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL.
A L L T E R R A
E N G I N E E R I N G & T E S T I N G
ENGIN 3 8 6 6 P R O S P E C T A V E N U E • S U I T E 9 • W E S T P A L M B E A C H , F L O R I D A 3 3 4 0 4 • ( 5 6 1 ) 8 8 1 -1 9 3 9
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982
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PROJECT Watersong PUD - PLAT NO. 1 - LOT #3 - 4805 WATERSONG WAY - Caruso Residence - St. Lucie County, Fl
LOCATION Southeast Corner of Building Area (Approximate)
PROPOSED THREE-LEVEL CUSTOM RESIDENCE
BORING NO. 2
0"-6" Dark Grey Fine Sand, trace of roots (topsoil)
6"-4' Brown and Grey Fine Sand, trace of marl
4'-7.5' Grey Fine Sand
7.5'-9.5' Muck and Peat
9.5'-13' Brown Fine Sand, some rock
13'-15' Grey Fine Sand, and shell (fragmented)
18'-20' Grey Fine Sand, and shell
23'-25' Grey Sand and shell
28'-30' Grey Fine Sand, and shell
33'-35' Grey Fine Sand, some shell and rock
37'- Refusal (rock)
CLIENT Phoenix Custom Homes JOB NO. 21-117
DRILLER TM/TRM WATER TABLE N/A 1/13/21
TEST DATA In general accordance with ASTM D-1586
DEPTH DESCRIPTION OF MATERIAL Sampl e
Blows
Per Foot
No
.
D E P T H
DATE
These Soil Boring Tests are Representative of and Apply to the Exact Location and Depth of the Boring.
AUTHORIZATION FOR PUBLICATION OF STATEMENTS, CONCLUSIONS OR EXTRACTS FROM
OR REGARDING OUR REPORTS IS RESERVED PENDING OUR WRITTEN APPROVAL.
A L L T E R R A
E N G I N E E R I N G & T E S T I N G
ENGIN 3 8 6 6 P R O S P E C T A V E N U E • S U I T E 9 • W E S T P A L M B E A C H , F L O R I D A 3 3 4 0 4 • ( 5 6 1 ) 8 8 1 -1 9 3 9
DocuSign Envelope ID: 53AA2B20-08EE-4AEC-8D0C-CA708F693982