Appendix_6_-_Geotechnical_Report_Tierra.pdf

TIERRA

7351 Temple Terrace Highway Tampa, Florida 33637

Phone (813) 989-1354 Fax (813) 989-1355

April 7, 2022

Geosyntec Consultants, Inc.

19321 U.S. Highway 19 North, Building C, Suite 200 Clearwater, Florida 33764

Attn: Mr. Mark Ellard, P.E.

RE: Geotechnical Engineering Services Report

Starkey M10 Retrofit

Pinellas County, Florida

Tierra Project No.: 6511-21-102-001

Mr. Ellard:

Tierra, Inc. has completed the geotechnical engineering study for the above referenced project.

The results of the study are provided herein.

Should there be any questions regarding this report, please do not hesitate to contact our office at

(813) 989-1354. Tierra would be pleased to continue providing Geotechnical services throughout the implementation of the project. We look forward to working with you and your organization on this and future projects.

Respectfully Submitted, TIERRA, INC.

Trevor J. Bianco, E.I. Daniel R. Ruel, P.E.

Geotechnical Engineering Intern Geotechnical Engineer Florida License No. 82404

Kevin H. Scott, P.E.

Senior Geotechnical Engineer Florida License No. 65514

This item has been digitally signed and sealed by Daniel R. Ruel, 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 the electronic any copies.

The official record of this report is the electronic file signed and sealed under Rule 61G15- 23.004, FAC.

TABLE OF CONTENTS

PROJECT DESCRIPTION

Project Information

Scope of Geotechnical Services

REVIEW OF PUBLISHED DATA

General Site Information

Pinellas County Soil Survey

SUBSURFACE CONDITIONS

General

Groundwater Information

EVALUATION AND RECOMMENDATIONS

Drainage Design

Structural Fill

Drainage and Groundwater Concerns

Excavations

REPORT LIMITATIONS

APPENDIX

Boring Location Plan Soil Profiles

Geotechnical Engineering Services Report

Pinellas County, Florida

Tierra Project No.: 6511-21-102-001

PROJECT DESCRIPTION

Project Information

Based on information provided, we understand the project consists of designing an approximate 1 to 1½ acre Stormwater Management Facility (SMF) in the northern portion of Pinellas County parcel 12-30-15-70542-200-1000. This report provides geotechnical data within the proposed SMF footprint to assist in the drainage design.

Scope of Geotechnical Services

The objective of our study was to obtain information concerning subsurface conditions within the proposed SMF area. The geotechnical investigation addressed the following:

Stormwater Management Facility

Identify soil types encountered by test borings

Identify depth to confining layer, if encountered, within the depth of the test borings

Determine soil suitability for reuse

Estimate the Seasonal High Groundwater levels

We provided the following services in order to achieve the preceding objectives:

1. Reviewed published soils and topographic information. This published information was obtained from the appropriate Florida Quadrangle Map published by the USGS, and the Soil Survey of Pinellas County, published by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS).

2. Executed a program of subsurface exploration consisting of borings, subsurface sampling and field testing.

Drainage Detention Area

Performed mulching/clearing of pathways to access the field work locations.

Performed four (4) SPT borings to a depth of 25 feet below grade.

Performed five (5) hand auger borings to estimate the SHGWT. The auger borings were performed to depths on the order of 6 to 7 feet below grade.

3. Visually classified the samples in the laboratory using the Unified Soil Classification System (USCS) classification system. Identified soil conditions at each boring location.

4. Prepared an engineering report in accordance with this proposal, which summarizes the course of study pursued, the field data generated, subsurface conditions encountered and the results of our findings.

Pinellas County, Florida

The scope of our services did not include an environmental assessment for determining the presence or absence of wetlands or hazardous or toxic materials in the soil, geologic hazards, bedrock, groundwater, or air, on or below or around this site. Also, the scope of our services did not include determination of potential sinkhole activity. Any statements in this report or on the boring logs regarding odors, colors, unusual or suspicious items or conditions are strictly for the information of our client.

REVIEW OF PUBLISHED DATA

General Site Information

At the time of this report, the site was heavily vegetated. A canal/ditch was located south of the subject parcel and a “wet” pond was located to the east. Based on the “Clearwater, Florida” United States Geological Survey (USGS) Quadrangle Map, the natural ground elevation at the proposed pond site ranges from approximately +10 to +20 feet, National Geodetic Vertical Datum of 1929

(NGVD 29).

Pinellas County Soil Survey

Soil data published by the USDA Soil Survey of Pinellas County, Florida was reviewed as part of the subsurface investigation. This information indicates that there is one (1) primary mapping unit within the vicinity of the proposed pond site. The following paragraph and table provide a brief description of the soil unit as presented in the Soil Survey.

Myakka soils and Urban land (Soil Unit 17)– The Myakka component makes up 50 percent of the map unit. Slopes are 0 to 2 percent. This component is on flatwoods on marine terraces on coastal plains. The parent material consists of sandy marine deposits. Depth to a root restrictive layer is greater than 60 inches. The natural drainage class is poorly drained. Water movement in the most restrictive layer is moderately high. Available water to a depth of 60 inches (or restricted depth) is low. Shrink-swell potential is low. This soil is not flooded. It is not ponded. A seasonal zone of water saturation is at 12 inches during June, July, August, September, October, and November. Organic matter content in the surface horizon is about 4 percent.

SUMMARY OF USDA SOIL SURVEY

PINELLAS COUNTY, FLORIDA

USDA Map

Symbol and Soil

Name

Soil Classification pH

Seasonal High Water

Table

Depth

(in)

USCS AASHTO

Permeability

(in/hr)

Depth

(feet) Months

(17) Myakka

Urban land

0-4 SP, SP-SM A-3 6.0 - 20.0 3.5 - 6.5

0.5 - 1.5 June - Nov

4-22 SP, SP-SM A-3 6.0 - 20.0 3.5 - 6.5

22-36 SM, SP-SM A-2-4, A-3 0.6 - 6.0 3.5 - 6.5

36-80 SP, SP-SM A-3 6.0 - 20.0 3.5 - 6.5

Information Not Provided

It should be noted that information contained in the USDA/NRCS Soil Survey may not be reflective of current subsurface conditions, particularly if recent development in the project vicinity has modified existing soils or surface/subsurface drainage.

Pinellas County, Florida

SUBSURFACE CONDITIONS

General

The subsurface conditions at the site were explored using four (4) SPT borings performed to depths of 25 feet below existing grades and five (5) hand auger borings performed to depths ranging from approximately 6 to 7 feet below existing grades. The borings were located in the field by a representative of Tierra using hand-held Global Positioning System (GPS) devices. The approximate boring locations are presented in the Appendix. If a more accurate determination of the boring locations and elevations is required, then Tierra recommends the boring locations be survey located by the project surveyor.

The SPT borings were performed with the use of a drill rig using bentonite mud drilling procedures utilizing an automatic hammer system. The soil sampling was performed in general accordance with American Society for Testing and Materials (ASTM) Test Designation D-1586. SPT resistance N-values were taken continuously to a depth of approximately 10 feet and at intervals of 5 feet to the boring termination depth.

The hand auger borings were performed by manually twisting and advancing a bucket auger into the ground, typically in 6-inch increments. The soil sampling was performed in general accordance with the American Society for Testing and Materials (ASTM) test designation D-1452.

The soil strata encountered in the borings performed at the proposed site are summarized in the following table:

Stratum

Number Soil Description

USCS

Symbol

1 Light Gray to Brown Sand to Sand with Silt SP/SP-SM

2 Green Silty Sand SM

3 Green Clayey Sand SC

The subsurface soil stratification is of a generalized nature to highlight the major subsurface stratification features and material characteristics. The soil profiles included in the Appendix should be reviewed for specific information at individual boring locations. These profiles include soil descriptions, stratifications and penetration resistances when applicable. The stratifications shown on the boring profiles represent the conditions only at the actual boring location. Variations did occur and should be expected between boring locations. The stratifications represent the approximate boundary between subsurface materials and the actual transition may be gradual.

Groundwater Information

The groundwater levels were encountered at depths ranging from approximately 5½ to 6 feet below the existing ground surface. The encountered groundwater levels are depicted adjacent to the soil profiles on the Soil Profiles sheet in the Appendix.

Pinellas County, Florida

Groundwater conditions will vary with environmental variations and seasonal conditions, such as the frequency and magnitude of rainfall patterns, as well as man-made influences (i.e. existing swales, drainage ditches/ canals, ponds, underdrains and areas of covered soils, such as paved parking lots). It should be noted that groundwater levels tend to fluctuate during periods of prolonged drought and extended rainfall and may be affected by man-made influences. In addition, a seasonal effect will also occur in which higher groundwater levels are normally recorded in rainy seasons.

Seasonal High Groundwater Table

The Seasonal High Groundwater Table (SHGWT) was estimated at depths ranging from approximately ¾ foot to 2½ feet below grade. The SHGWT estimates are presented on the Soil

Profiles sheets in the Appendix.

EVALUATION AND RECOMMENDATIONS

Drainage Design

Based on the results of the subsurface exploration, the provided site plan and topographic information, and our engineering judgment, Tierra recommends the following elevations be used for the storm water pond design.

Boring

Name

Boring/Test

Locations(1)

(FL West NAD 83) Date

Recorded

Ground

Elevation(3)

(ft, NAVD 88)

Depth of

Groundwater

(feet)

Elevation of

Groundwater

(feet, NAVD88)

Estimated

SHGWT

Depth

(feet)

Estimated

SHGWT

Elevation(2)

(feet, NAVD88)

Depth of

Confining

Layer

(feet)

Elevation of

Confining

Layer

(feet, NAVD88)

Easting Northing

PBA-1 410659 1292995 1/19/2022 16.0 5.5 10.5 2.5 13.5 ≥7.0 ≤9.0

PBS-1 410672 1293038 2/1/2022 16.5 6.0 10.5 N/D ≥25 ≤-8.5

PBA-2 410734 1293042 1/19/2022 16.0 5.5 10.5 2.0 14.0 ≥6.5 ≤9.5

PBS-2 410822 1293036 2/1/2022 16.2 6.0 10.2 N/D 15.0 1.2

PBA-3 410833 1293000 1/19/2022 16.5 5.7 10.8 1.0 15.5 ≥6.0 ≤10.5

PBS-3 410689 1292923 2/1/2022 16.3 6.0 10.3 N/D 15.0 1.3

PBA-4 410744 1292943 1/19/2022 16.1 5.5 10.6 0.8 15.4 ≥6.0 ≤10.1

PBS-4 410833 1292970 2/1/2022 16.4 6.0 10.4 N/D ≥25.0 ≤-8.6

PBA-5 410750 1293012 1/19/2022 15.8 5.3 10.5 2.5 13.3 ≥7.0 ≤8.8

(1) The boring/test locations were determined in the field using hand-held, non-survey grade Garmin Global Positioning System (GPS) equipment with a manufacturer's reported accuracy of ± 10 feet. The boring/test locations should be considered approximate.

(2) Seasonal High Groundwater Table (SHGWT) estimated based on soil stratigraphy, measured groundwater levels from the borings, the Pinellas County, Florida USDA soil survey information and past experience with similar soil conditions. Estimated SHGWT is the historical normal wet season ground water level.

(3) Ground elevation estimated based site survey information.

Tierra understands the pond bottom is set at elevation +1 feet, NAVD. Based on the four SPT borings performed, the underlying limestone (bedrock) is more than 25 feet below grade (approximate elevation -9 feet, NAVD). With this minimum 10 foot separation, the pond excavation will not encounter the underlying bedrock. Additionally, the amount of clayey soils to be removed is less than 1 foot and is not anticipated to impact to the natural conditions. Based on the minimum separation required by SWFWMD (2 feet between the pond bottom and the top of limestone), it does not appear the design creates adverse conditions that would allow for lesser quality water to pass, either way, between two water systems.

Pinellas County, Florida

Structural Fill

If necessary, all materials to be used for structural fill or backfill should be evaluated and tested by Tierra prior to placement to determine if the materials are suitable for the intended use. Suitable fill materials should consist of fine to medium sand with less than 12% passing the No. 200 sieve, free of debris, material remnants, rubble, organics, clay, debris and other unsuitable material and evaluated against project engineering requirements.

In general, the soils of Stratum 1 (SP/SP-SM) may be moved and used for grading purposes, site leveling, general engineering fill, structural fill and backfill in other areas, provided the fill is free of organic materials, clay, debris or any other material deemed unsuitable for construction and evaluated against engineering fill requirements.

Drainage and Groundwater Concerns

We recommend that the Contractor determine the actual groundwater levels at the time of the construction to determine groundwater impact on the construction procedure. Care should be given to open excavations and site grading to minimize ponding of surface water and direct surface water flow away from the excavation.

Excavations

The contractor is solely responsible for designing and constructing stable, temporary excavations and should shore, slope, or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom in accordance with OSHA 29 CFR, Part 1926, Subpart P as well as the “Trench Safety Act” in Chapter 90-96 of the Florida Statutes. The contractors “responsible persons”, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. In no case should slope height, slope inclination, or excavation depth, including utility trench excavation depth, exceed those specified in all local, state, and federal safety regulations.

We are providing this information solely as a service to Geosyntec Consultants and their clients.

Tierra does not assume responsibility for construction site safety or the contractor’s or other party’s compliance with local, state, and federal safety or other regulations.

Pinellas County, Florida

REPORT LIMITATIONS

The analyses, conclusions and recommendations contained in this report are opinions based on the site conditions and project layout described herein and further assume that the conditions observed in the exploratory borings are representative of the subsurface conditions throughout the site, i.e., the subsurface conditions elsewhere on the site are the same as those disclosed by the borings. If, during construction, subsurface conditions different from those encountered in the exploratory borings are observed or appear to be present beneath excavations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary.

This report was prepared for the exclusive use of Geosyntec Consultants and their clients for evaluating the design of the project as it relates to the geotechnical aspects discussed herein. It should be made available to prospective contractors for information on factual data only and not as a warranty of subsurface conditions included in this report. Unanticipated soil conditions may require that additional expense be made to attain a properly constructed project. Therefore, some contingency fund is recommended to accommodate such potential extra costs.

APPENDIX

Boring Location Plan

Soil Profiles

PBA-2

PBA-3

PBA-4

PBA-1

PBA-5

PBS-1

PBS-3

PBS-2

PBS-4

TB

SW

FEB 2022

DRR

NOTED 6511-21-102-001

PINELLAS COUNTY, FLORIDA

STARKEY M10 RETROFIT

GEOTECHNICAL ENGINEERING SERVICES

SHEET 1

ENGINEER OF RECORD:

PROJECT NUMBER:

DATE:

SCALE:

APPROVED BY:

CHECKED BY:

DRAWN BY:

LEGEND

PLAN SCALE

0 50'

BORING LOCATION PLAN

APPROXIMATE LOCATION OF AUGER BORING

APPROXIMATE LOCATION OF SPT BORING

TIERRA

7351 Temple Terrace Highway Tampa, Florida 33637 Phone: 813-989-1354 Fax: 813-989-1355

DANIEL R. RUEL, P.E.

FLORIDA LICENSE NO.:

82404

AutoCAD SHX Text

AutoCAD SHX Text

AutoCAD SHX Text

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TALL PINES DRIVE

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ASPHALT PAVEMENT WIDTH VARIES

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OCC #8721

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OCC #8721

AutoCAD SHX Text

O.R. 16486, PAGE 1587

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6'CLF

AutoCAD SHX Text

DEAD

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O.R. 19906, PAGE 974

AutoCAD SHX Text

O.R. 19906, PAGE 974

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TB

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HW

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HW

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TB

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TB

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TB

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TB

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TS

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TS

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TS

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TB

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HW

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TB

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TS

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TS

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6'CLF

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GATE

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6'CLF

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EPA

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EPA

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BC

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DWC

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EPA

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BC

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EPA

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BC

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TB

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TS

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HW

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TB

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TS

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EPA

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BC

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6'CLF

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6'CLF

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6'CLF

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6'CLF

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PRIVATE DRIVE

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ASPHALT PAVEMENT

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PP

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OH

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OH

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OH

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WATER EL = 10.70' ON 2/13/20

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30"RCP

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30"RCP

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ES-17

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ES-18

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ES-19

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ES-20

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ES-21

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ESS-1

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ESS-2

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ES-23

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10" PVC

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ES-24

ENGINEER OF RECORD:

PROJECT NUMBER:SCALE:

APPROVED BY:

DATE:

DRAWN BY:

CHECKED BY:

SOIL PROFILES

TIERRA

7351 Temple Terrace Highway Tampa, Florida 33637 Phone: 813-989-1354 Fax: 813-989-1355

LEGEND

SP

N

OF PENETRATION (UNLESS OTHERWISE NOTED)

SPT N-VALUE IN BLOWS/FOOT FOR 12 INCHES

GREEN SILTY SAND (SM)

GREEN CLAYEY SAND (SC)

LIGHT GRAY TO BROWN SAND TO SAND WITH SILT (SP/SP-SM)

UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM D 2488) GROUP

SYMBOL AS DETERMINED BY VISUAL REVIEW

ESTIMATED SEASONAL HIGH GROUNDWATER TABLE

GROUNDWATER LEVEL ENCOUNTERED DURING

INVESTIGATION

TB

SW

FEB 2022

DRR

NOTED 6511-21-102-001

PINELLAS COUNTY, FLORIDA

STARKEY M10 RETROFIT

GEOTECHNICAL ENGINEERING SERVICES

SHEET 2

DANIEL R. RUEL, P.E.

FLORIDA LICENSE NO.:

82404

WR

WH

FELL UNDER WEIGHT OF ROD

FELL UNDER WEIGHT OF ROD AND HAMMER

BOR # PBA-1

EASTING 410659

NORTHING 1292995

ELEV. 16.0

DATE 1/19/2022

BOR # PBA-2

EASTING 410734

NORTHING 1293042

ELEV. 16.0

DATE 1/19/2022

BOR # PBA-3

EASTING 410833

NORTHING 1293000

ELEV. 16.5

DATE 1/19/2022

BOR # PBA-4

EASTING 410744

NORTHING 1292943

ELEV. 16.1

DATE 1/19/2022

BOR # PBA-5

EASTING 410750

NORTHING 1293012

ELEV. 15.8

DATE 1/19/2022

E L

E V

A T

IO

N

IN

F

E E

T

N A

V D

-5

-10

E L

E V

A T

IO

N

IN

F

E E

T

N A

V D

N

WH

BOR # PBS-1

EASTING 410672

NORTHING 1293038

ELEV. 16.5

DATE 2/1/2022

HAMMER AUTOMATIC

RIG D-25

N

WH

BOR # PBS-2

EASTING 410822

NORTHING 1293036

ELEV. 16.2

DATE 2/1/2022

HAMMER AUTOMATIC

RIG D-25

N

WH

BOR # PBS-3

EASTING 410689

NORTHING 1292923

ELEV. 16.3

DATE 2/1/2022

HAMMER AUTOMATIC

RIG D-25

N

WR

WH

BOR # PBS-4

EASTING 410833

NORTHING 1292970

ELEV. 16.4

DATE 2/1/2022

HAMMER AUTOMATIC

RIG D-25

-5

-10

E L

E V

A T

IO

N

IN

F

E E

T

N A

V D

E L

E V

A T

IO

N

IN

F

E E

T

N A

V D

EASTING

NORTHING

EASTING COORDINATE REFERENCED TO THE FLORIDA STATE

PLANE COORDINATE SYSTEM, FLORIDA WEST ZONE, N.A.D. 83

DETERMINED USING HAND-HELD GARMIN ETREX GPS EQUIPMENT

WITH A REPORTED ACCURACY OF +/- 10 FEET

NORTHING COORDINATE REFERENCED TO THE FLORIDA STATE

PLANE COORDINATE SYSTEM, FLORIDA WEST ZONE, N.A.D. 83

DETERMINED USING HAND-HELD GARMIN ETREX GPS EQUIPMENT

WITH A REPORTED ACCURACY OF +/- 10 FEET

12 TO 24

6 TO 12

24 TO 40

8 TO 24

3 TO 8

GREATER THAN 24

LESS THAN 3

GREATER THAN 40

LESS THAN 1

VERY LOOSE

HARD

VERY STIFF

STIFF

SILTS AND CLAYS

CONSISTENCY

FIRM

SOFT

VERY SOFT

LOOSE

MEDIUM

DENSE

VERY DENSE

3 TO 6

1 TO 3

RELATIVE DENSITY

GRANULAR MATERIALS- SPT

(BLOWS/FT.)

SPT

(BLOWS/FT.)

AUTOMATIC HAMMER

CAVE-IN BORING TERMINATED DUE TO CAVE-IN FROM GROUNDWATER

INTRUSION

CAVE-IN

CAVE-IN CAVE-IN

NAVD 88 NORTH AMERICAN VERTICAL DATUM OF 1988