HomeMy WebLinkAboutGeotechnical ReportExhibit "E" RECEIVED
Nova 1 9
5T, Fm@'s C4uhty, 9ermitting
Allterra Engineering
Geotechnical Report
3066 PROSPECT AVHNIIE - SMITE 9 • WE57 PALM HEACH, FLORIDA 33404 • (5611 881-1939
19 November2018
Gary Hribar
c/o Kelly & Kelly Architects
119 SW 60 Street
Stuart, FL 34094
9hr a gsborn-snq_com
Subject: Report of Geotochnical Services — 3-Level Water -Front Custom Home
112 Island Dunes Cove, Jensen Beach, 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 2017 Florida Building Code and local amendments. This report Is Allterra's Instrument-or•-
eervice provided for the sole reliance and use by Gary Hribar. Third parties may read this report
for information purposes only.
Project and Scope
Reference Documents. Digital copies of drawings 1 and 3 through 9 dated 12-Oct-18 by Kelly &
Kelly Architects (their commission number 18150) were provided .for Allterlh's reference in
performing Its services.
Prolect Information. The project is a 3-level custom Home and Its associated swimming pool
proposed for construction upon the subject property. The property Is bounded on the west by the
Indian River lagoon and on the north, east and south by other residential properties. Access to the
property is from Island Dunes Cove on the southeast quadrant of the site. The overall dimensions
of the custom -home footprfnt are approximately 40 by 56 feet. Overall dimension of the swimming
pool are approximate 12 by 44 feet. _A retalning sea-wall Isunder design for location between the
swimming -pool area and the Indian River lagoon.
Scope and Constraints. Allterra was tasked with performing sall-test borings to characterize
subsurface condldons and providing recommendations foundation design. Specific Information on
design will and column loads has not been' provided at this time. For purposes of this report,
Allterra assumed maximum design wall load of 4000 PLF and maximum design column load of 18
tons. If actual loads are greater, the conclusions and recommendations of this report may warrant
change. Specific Information on design constraints for the seawall has not been provided. Any
comments on seawall in this report shall be considered provisional and subject to change.
Field Work
Allterre mobilized personnel and equipment to the project site on 14 November 201 B. The site was
relatively clear and accessible :to the truck -mounted drill rig. Allterra drilled five 20-foot soil-fest
borings as represented on the Bodng Location Plan of this report. Penetration lasts were
performed in the.soll-test borings by driving a nominal 2-inch diameter steel sampler with blows of
a 140-pound hammer free -falling 30 inches, These test results are useful to evaluating certain soil
Geotochnlcal Ekplora8on-3-Level Custom -Home 1 112IslandDunesCove, Jansen Bench, FL
19 November 2018 18 - 443
properties such as relative density and shear strength. Copies of the boring logs are attached for
the reader's reference.
BORXNG LOCATION PLAN
Flndings
Subsurface Profile. Allterra encountered generally comparable subsurface conditions at each
boring location. The conceptual subsurface profile can be described as:
o Topsoll sampled as dark -gray, fine sand with occasional roots from surface grade to 6 inches
below ground surface, underlain by
• Stratum la - loose, dark -gray to brown, fine sand with trace of shell to approximately 4 feet
below grade, underlain by .
• Stratum lb — firm to occasionally very -firm, Ilght-brown to tan, fine sand with shell to
approximately 10 to 13 feet below grade, underlain by
• Stratum 2a — very firm to occasionally dense, gray to tan, fine sand with trace of shell to
approximately 15 to 18 feet below grade, underlain by
• Stratum 2b - very -loose to loose, gray, silty, fine sand with trace of shell to approximately
17 feet below grade, underlain by
Stratum 2c -- firm, gray to dark -gray, fine sand and shellto 20 feet below grade.
Stratum 2b was not encountered in borings B-1 and B 2.
Groundwater. Groundwater was encountered approximately 5% feet below surface grade at the
time of borings. The depth to groundwater may vary at other times due to changes in hydrological
conditions, Including tidal changes.
Geolachnloal4plorallon — 3devel Custom -Home 2 112Island Danes Cove, Jensen Beach, FL
19 November 2018 18 - 443
Conclusions
Foundations. The presence of loose sand in the near subsurface (Stratum I of this site) Is
problematic for shallow foundations such as conventional or monolithlc-slab footings. These
problematic soils are subject to excess settlement under applied structural load and possible
bearing-oapeolty failure. This condition can be corrected by excavating Stratum 1a to
approximately 2 feet below existing surface grade, compacting the exposed surface, acid restoring
the building pad to constructlon-readygrade well -compacted clean granular soil. A well -prepared
building pad can develop a net allowable bearing pressure of 2500'PSF for 20- to 40-Inch-wide
footings bearing 18 Inches below grade on well -compacted soli.
Settlement. Subject to successful Implementation of this report's recommendations, Allterra
estimates settlement of approximately% inch for 24-Inch-wide continuous footings loaded to 4000
PLF and 48-Inch-wide square footings loaded to 18 tons. Because the Boll Is elastic In nature, the
dead -load portion of settlement -should be realized promptly upon completion of construction.
Lateral Earth Pressure, The stability of retaining walls Is subject to. the applied lateral earth
pressure of backflll. Allterra estimates lateral earth pressures summarized In the following table for
design of the retalning seawall,
per foot of depth,
Recommendations - Custom Home
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 from building pad and properly waste.
¢ofoya_}gxjsttnyB W[fac6Vfdi3 Stockpile cut loll for later use as fill.
3. Compact the exposed grade with multiple passes of a heavy (12- to 20-ton), vibratory roller to
at-leas196 percent of the soil's maximum -dry -density, as determined by the Modlfled-Proctor
compaction test (ASTM D4657 / AASHTO T-180).
4, ,Engage Allterra to perform probe -rod and Held -density tests to verily compaction standards are
achieved.
5. To restore bullding-pad to construction -ready grade, place and compact fill In a controlled
manner. Cohesionless lolls typlcally used for fill In this geographic area can be placed in 12-
Geofechnfcal Exploraflon — 3-Level Custom -Home 3 112101and Dunes Cove, Jensen Beach, FL
f0 November2018 18 - 443
Inch lifts and compacted to at least 95 percent of the Modified -Proctor mexlmum-dry-denslty
by multiple passes of a heavy smooth -drum vibratory roller. If lighter equipment Is used, limit
thickness of fill lifts to 8 Inches (loose measure).
6. Engage Allterra to perform probe -rod and field-denslty tests for each 2-foot rise !n f l height to
verify compaction standards are schleved.
7. Once the building pad has been prepared, the contractor must maintain Its condition
throughout the construction process.
Foundation 6earinp Surfaces, Allterra recommends:
1. Excavate to footing bearing level with care to avoid over -excavating.
2. Mechanically compact exposed bearing grade, near optimum moisture, to at least 95 percent
of the maximum•dry-density.
S. Engage Alfterra to perform probe -rod and fleld-density tests to verify compaction standards are
schleved,
4.. Foaling bearing surfaces shall be kept firm, level,,and free of standing water, debris, and
detritus through the placement of concrete,
ftecommendatlons — Swimming -Pool Area
Excavation. it Is the responslbjllty of the contractor to avoid undermining the foundations of
adjacent structures when performing the awlmming-pool excavation, If undermining Is a threat,
foundations solls maybe retained with sheet piles orstabilized with permeation grouting orfoolings
may be temporarily underpinned with helical piers. If the excavation is within five feet of any
adjacent structure, field density tests shall be performed when filled to restore original grade.
Backflll soll should be compacted to at least 96-percent of maximum -dry density. Engage Allterra
to perform probe -rod and flold-denslty testing to verify compaction standards are achieved.
De -Watering. If excavation for awlmming-pool construction Is deeper than the groundwater
surface, the contractor shall Implement groundwater drawdown and control procedures for the
duration of construction. This may be achieved by Installing a well -point system, or Installing a
sump pump below target excavation depth (about 3 feet deeper in a protected hora or cut). it is
.the responslblllty of the contractor to control de -watering operations to avoid damage to adjacent
structures or properties
Annulus Fill. Allterra recommends that clean sand be used as fill between the pool shell and
excavation surface. The clean sand should be placed In thin lifts (not more than 12 Inches loose
measure) and compacted. Allterra recommends that contact between mechanical compaction
equipment and the pool phall be avoided.
Patio or Deck Subgmde. In the patio or deck areas surrounding the pool, Allterre recommends:
• Compact the subgrade to at least 95 percent of maximum -dry -density as determined by the
Modified -Proctor compaction test (ASTM D-15571 AASHTO T-180).
• -If rill Is required to achieve construotion-ready grade, It should be. ultlformlyplaced In lifts (not
more than 8 Inches loose measure) and compacted to at least 96 percent of maximum-dry-
denstty. The finish grade of.the fill should extend 6 feet beyond the edge of the deck surfacing
(typically concrete or sand -set paving blocks) to reduce the possibility of damage to the
surfacing bysoll erosion or eccentric loading.
Geotachnical Exploration — 3-Love! Custom -Home 4 112 island Dunos Cove, Jensen Beach, FL
1g Ivovember201ti M - 443
Engage AlRorra to perform, probe -rod and Held -density tests to verify compaction standards are
achieved, Frequency of testing shall be approximately one per each 500 square feet of deck
area or a minimum or four density tests.
Recommendations — Drive -Way Pavement
Subarade 'and Base Course. To prepare in -situ soils for pavement sub -grade, Allterm
recommends they be compacted to at least 98 percent of the Modgted-Proctor maximum -dry -
density (ASTM D4557 / AASHTO T-1$0), Stabilizers (aggregate or•sludge, for examples) maybe
blended with sub -grade soils to Improve the design LBR to 40 or better. For base course, Aliterra
recommends clean well -graded aggregate or shell -rock (minimum LBR 100) compacted to at least
98 percent of the Modlfled-Proctor maximum-dry-denslly. Base•course thickness will be
determined by the civil designer considering material qualities and project traffic loads. Base
course shall be at least 18 Inches above the wel-season ground -water _table. Engage Aliterra to
perform probe -rod and field -density testing to verify compaction standards ar 0achleved.
Sand -Set Paver Surface Course. When applying send -set pavers for vehicular -traffic surface
course, Allterra recommends.-
a Use Interlock -shape blocks, or rectangular blocks set In a herringbone pattern. Avoid placing
rectangular block in a stretcher -bond pattern over relatively large areas.
o Limit bedding -sand thickness to 1. Inch. Bedding sand Is a construction necessity but It Is
structurally the weakest layer In the pavement section.
m Provide lateral support In the form of perimeter curbs and full -depth jointing sand. Block
pavers are subject to horizontal creep if not properly restrained.
Qualification
Aliterra has based its conclusions and recommendations upon certain cllent-provided information
and Interpretation of data obtalned.at discrete points within the limits of exploration. It Is possible
that conditions may very 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, Aliterra reserves the right to
review the new Information and modify Its conclusions and/or recommendations where appropriate,
Closing
Thank you for engaging Allterre to as your geotechnical consultant. Please call the undersigned If
you have questions about [his report or need other services.
Attachments
Geolechnkal Exploration— 3-Level Custom -Homo 5 112 island Dunes Cove, Jensen Basch, FL
19 November 2018 18 - 443
3'80e PR06PECT AVENUE . SUITE 9 .
PROJECT
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au,•,..v
DEPTH
DESCRIPTION OP MATERIAL
eu�np1a
'ryo
emw.-
P.rroot
ona
2
0 Dark Grey Fine Sand, trace of roots (topsoil)
8'44' Light Brown Fine Sand, slight trace of shell
4'-12' Light Brown Fine Sand, some'¢hell
12'-93.6' Tan Fine band, trace of shell
13.6'-18' Grey Fine sand (blue lint), trace of shell
16'$U' Dark Grey Flne Sand (blue tint), some shell
1-1
1
3
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cuENT GeryWharolo Kelly & KellyAlnhilects JDD NO. 18.443
DR6LER DOW WATER TAaLE 6.6' DATE 11/14/18
TE3r DATA In neneral aco9rdence with ASTM D-16AR -
PROJECT Las Torlygas at Hulabbison island -LOT 114 -112 ISLAND'DUNES COVE - Be Lucie County, F1
LOCATION NadheastComer ofBulldlpgArea(Approximate) BORING NO. 2
DEPTH
0050HIPTION OP-MAT6nIAL
DIM,
Par°°I
nm
1
0° 6" Dad( Grey Fine sand, [race of roots (topsoll)
6".4' Brown Fine Send, slight trace of Bhell
4'-10' Light Brown Fine Sand, some shell
10'-12' Tan Fine Sand
12'-18' Grey Fine Sand (blue tint), trace of shell
1 V-20' Dadc Grey Fine Send (blue tint),'end shell
1
2
14
8
1.2
-2
3
4
2 6
4
6
7-8
5
8
4.6
6-7
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7
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9
8. 0
10 -
12-13
1p
11
0.1
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- 6-18
12
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22-24
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2040-1
1
9
31-27
16
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20
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26
21
22
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22
23
24
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2
28
27
2
28
28
29
2B
30
31
00
32
3
3a
9
34
38
30
37
36
77
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30
39
041
40
41
2
72
43
43
4
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46
46
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6
47
40
47
40
48
60 -
60
owmT QSN Hrtbar clo M&&Kelly Architects Jon NO. J11443
DRILLER DB/RC WATER TABLE 8.0 DATE 11%14/18
TEST DATA In general accordance with ASTM D-1588
3060 PROSPECT AVENUE ° SUITE 0
PROJECT Las ionugesatHutchinsonIsland -LOT 114-112ISLAND DUNES COVE -St Lucia County, FI
LOCATION Southeast Cornor o(Bultding•Area (Approximate) BORING NO. 3
-' " PRnonA r1T RFR-RTnPV AI IQVAAA ece n
OEPTN
oeeealPTION of MATOWAL
- ryo
P°fPoot
aerpl
_1
2
0"-6" Daric Grey Fine Sand, trace of roots (topsoil)
6'L1' .Dark Grey Fine Sand
1'-4.6' Brown Fine Send, slight trace of shell
4.6'-10' Light Brown Fine Sand, some shell
1
10'-1616, Tan Fine Sand, trace of shell
16,6'-17' Grey Silty Sand (blue lint). trace of shell
1T-20' Grey Fine Sand, some shell
Ll
M
1-2
1
2
3
2-3
a
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2-4
4.8
6
6
4.6
6
7
6.7
7
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8-9
1 -14
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11
12
8. 8
8-9
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1
11
42
43
43
44
a
e
6
48
6
47
47
48
an 1
49
49
6D
60
CLIENT Gary Hribar do Kell & Kelly Architects JOB NO. . 18.443
DRILLER DB/RO WATeR TABLE 6.6' _DATE 11/14/16
TEST DATA InDonural eacordenoe with ASTM D-1688
3086 PROSPECT AVENUE • SUITE 0 . WEaT PALM BEAOH, FLORIDA 33404 . 16011 Aa4.1n3n
PROJECT
DOM
bE60RIPT1OrI OF MATERIAL
9 via
bo
81*'
P!ff
perm
2
Dark Grby Fine Sand, trace of roots (topso l)
6"' Dark Brown Fine Sand, slight trace of shell
4,6'--12' Light Brown Fine Sand, some shell
12'-14:6' Tah Firie Sand, trace of shell
14.6'-16.6' Light Grey Fine Sand, some rock and shell
16.6'-19' Grey Fine Sand (blue tint), trace of shell
19'-20' Dark Grey Fine Sand (blue Unt), some shell
a
a•G
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4
U-G
3
6
a-s
7-9
4
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0
7
48
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8
8.13
0
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1
1
12
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22
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23
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3
26
4
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26
27
28
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29
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31
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33
33
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6
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8
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42
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49
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60
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49
60
CURNT Gary Hilbarc/o KellV3.KellyArchBeale JOB NO. 18-443
PRILIER DIURC 'WATER TAELE SAP _ RME 11/14/18
TEST DATA In.Reneral accordance Willi ASTM WERe
(561). 00 f•1830
PROJECT Los Todunes at Hutchinson Island- LOT44 -112 ISLAND DUNES COVE -.81. Lucle County F1
LOCATION CenlerofPool Area (Aporwdmete) BORING NO. o
ROPOSED THREE-STORY CUSTOM RES
DEPTH
DEOMPTIeN OF.NATER14L
or
'�
EIONo
PorFool
ern,
2
Dark Grey Fine Send, trace of roots (topaoll) -
8"•2' Park Brown Fine Send, alight trace of shell
Brown Fine Send, trace of shell
N-0' Light Brown Fine sand, some shell
9'-13' Ten Fine Sand, trace of shell
131-16, Grey Fine Sand, trace of shell
115,48' Grey Silly Sand (blue lint), trace of shell
18'-20' Dark Grey Fine Sand (blue tint), and shell
1 2
1
2-4
2
3
3.4
3
4041
4.6
4
C•8
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6
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A-H
6
0.8
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12.14
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7-a
1
2
11-12
if 12
13
1846
13
73 2
14
6
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2-1
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1.2
7
10
19
10
5
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20
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20
21
2
2
22
23
23
24"
24
26
26
28
2
27
28
28
20
6
30
0
31
31
2
32
3
34
3
34
38
39
0
37
97
30
38
39
a IL
40
0
41
42
43
3
44
44
6
40
46
46
47
47
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B
60
so
WATER TABLE
TEST DATA
TIT
Jon No. '18;443
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