20-Attachment B - GeotchRpt.pdf

Time Honored Experience. Progressive Ingenuity.

P.O. Box 921 Riverview, Florida 33568 – Main Office/Facsimilie 813.642.3965

September 15, 2021

Watermark Engineering Group, Inc.

3686 Sun City Center Blvd.

Sun City Center, Florida 33573

Attention: Mark Flint, P.E.

Subject: Report of Geotechnical Engineering Services Kirby Street Pump Station 5200 E. Kirby Street Tampa, Hillsborough County, Florida Hillsborough County CIP No. 46144001

Anticus Project No: 01.3883.18

Dear Mr. Flint:

Anticus Engineering, LLC (Anticus) has completed a geotechnical exploration for the above referenced project, and we are submitting a supplemental comment with regard to slope stability at the request of the client.

Based on engineering best practice, global slope stability analysis is typically not required on a well compacted sandy slope that is flatter than 2 horizontal to 1 vertical (2:1) (reference FDOT Soils and

Foundations Handbook, 2021, page 105). In our opinion, depending upon the specific soil type/density with depth, there may be some localized erosion, such as in SM (Silty SAND) embankment/slope [soil classification in accordance with the Unified Soil Classification System].

Our conclusions have been prepared using generally accepted standards of geotechnical engineering and engineering geology practice in the State of Florida.

Anticus appreciates the opportunity to be of service to you. We look forward to helping you through project completion. Please contact us if you have any questions.

Respectfully submitted, Anticus Engineering, LLC P.O. Box 921 Riverview, Florida 33568

J. Wesley Parker, P.E Date: 9/15/2021 Jeanne Berg, P.E. Date: 9/15/2021 Florida License No. 78637 FL License No. 50699 Project Manager Chief Engineer

Copies Submitted: One (1) Electronic (PDF) Copy – Mark Flint, Watermark Engineering

REPORT OF GEOTECHNICAL ENGINEERING SERVICES

KIRBY STREET PUMP STATION

TAMPA, HILLSBOROUGH COUNTY, FLORIDA

HILLSBOROUGH COUNTY CIP NO. 46144001

ANTICUS PROJECT NO.: 01.3883.18

Prepared for:

WATERMARK ENGINEERING GROUP, INC.

3686 SUN CITY CENTER BOULEVARD

SUN CITY CENTER, FLORIDA 33573

Prepared by:

P.O. Box 921 Riverview, Florida 33568

Florida Certificate of Authorization No. 30846

Time Honored Experience. Progressive Ingenuity.

P.O. Box 921 Riverview, Florida 33568 – Main Office/Facsimilie 813 642 3965

Revised January 21, 2021

Watermark Engineering Group, Inc.

3686 Sun City Center Blvd.

Sun City Center, Florida 33573

Attention: Herby Jean, Environmental Engineering Designer

Subject: Report of Geotechnical Engineering Services Kirby Street Pump Station 5200 E. Kirby Street Tampa, Hillsborough County, Florida Hillsborough County CIP No. 46144001

Anticus Project No: 01.3883.18

Dear Mr. Jean:

Anticus Engineering, LLC (Anticus) has completed a geotechnical exploration for the above referenced project, and we are submitting our findings in this report. We conducted this project in general accordance with our Letter of Commitment No. 01.3883.18, dated December 12, 2018 and August 14, 2020. Original field services were performed and addressed in our Report of Geotechnical Engineering Services, dated May 20, 2019. Due to design changes, the client has requested an additional SPT boring (B-2) in the southwest portion of the site for the proposed revised pump station location.

This report explains our understanding of the project, provides a description of the site and subsurface conditions encountered, and presents our recommendations regarding the site preparation and foundation recommendations.

Anticus appreciates the opportunity to be of service to you. We look forward to helping you through project completion. Please contact us if you have any questions.

Respectfully submitted, Anticus Engineering, LLC P.O. Box 921 Riverview, Florida 33568 Certificate of Authorization No. 30846

J. Wesley Parker, P.E. Jeanne Berg, P.E. Date 1/21/21 Project Manager Chief Engineer FL License No. 78637 FL License No. 50699

Copies Submitted: One (1) Electronic (PDF)

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 GENERAL DISCUSSION

1.2 REPORT SUMMARY

2.0 PROJECT INFORMATION

2.1 EXISTING SITE

2.2 PROPOSED CONSTRUCTION

3.0 SITE INFORMATION

3.1 SOIL SURVEY INFORMATION

3.2 REGIONAL GEOLOGY

4.0 EXPLORATION AND TESTING METHODS

4.1 FIELD EXPLORATION AND TESTING

5.0 SUBSURFACE CONDITIONS

5.1 GENERAL SOIL PROFILE

5.2 GROUNDWATER

5.3 TYPICAL SEASONAL HIGH WATER TABLE

6.0 CONCLUSIONS

7.0 RECOMMENDATIONS

7.1 STRUCTURAL FILL

7.1.1 Structural Fill Definition

7.1.2 Structural Fill Availability

7.1.3 Structural Fill Placement and Compaction

7.2 SITE DEGRADATION DURING CONSTRUCTION

7.3 RETAINING WALLS (WET WELL)

7.4 EXCAVATIONS

7.5 GROUNDWATER CONTROL

8.0 FOLLOW-UP SERVICES

9.0 LIMITATIONS OF REPORT

APPENDIX

Sheet 1 Field Test Location Plan Sheet 2 Soil Profile Sheet 3 Report of Core Boring Sheet 4 Web Soil Survey/Topographic Map

REPORT OF SUBSURFACE EXPLORATION

KIRBY STREET PUMP STATION

5200 E. KIRBY STREET

TAMPA, HILLSBOROUGH COUNTY, FLORIDA

HILLSBOROUGH COUNTY CIP NO. 46138-005

ANTICUS PROJECT NO. 01.3883.18

1.0 INTRODUCTION

1.1 GENERAL DISCUSSION

Anticus conducted a subsurface exploration for the proposed horizontal well located at 5200 E.

Kirby Street in Tampa, Hillsborough County, Florida. We provided our services in general accordance with our Letter of Commitment No. 01.3883.18, dated December 12, 2018 and

August 14, 2020. The purpose of the exploration was to evaluate subsurface conditions for the proposed construction and to provide geotechnical engineering recommendations regarding site preparation and earthwork procedures at the location of the proposed improvements. The improvements generally consist of upgrading the existing pump station to include a horizontal well adjacent to the existing pond. Original field services were performed and addressed in our

Report of Geotechnical Engineering Services, dated May 20, 2019. Due to design changes, the client has requested an additional SPT boring (B-2) in the southwest portion of the site for the proposed revised pump station location. This report presents a brief discussion of our understanding of the project, the exploration procedures and results, and our conclusions and recommendations regarding the above considerations.

1.2 REPORT SUMMARY

Two (2) Standard Penetration Test (SPT) borings were performed to depths of 25 to 31 feet and twenty (20) hand auger borings were performed to an approximate depth ranging from 3.5 to 8 feet to evaluate the subsurface soils and groundwater conditions with respect to the proposed construction. The following is an overview of the exploration findings and our geotechnical recommendations. This summary should not be used for planning and design without reading the entire report, which contains more detailed information and the assumptions made in developing the recommendations.

1. Groundwater was encountered in SPT boring B-1 at a depth of 10 feet below existing ground surface (May 2019 – end of dry season) and was encountered in SPT boring B-2 at a depth of approximately 4 feet below existing ground surface (January 2021 – middle of dry season). Groundwater was not encountered in hand auger borings HA-1 through

HA-20. Based on the Soil Survey of Hillsborough County, Florida, prepared by the U.S.

Department of Agriculture Natural Resource Conservation Service (NRCS), the historic

Seasonal High Ground Water Table (SHGWT) ranges from approximately 2 to greater than 6 feet. Based on our hand auger borings performed at the site, the estimated

Report of Geotechnical Engineering Services Revised January 21, 2021 Kirby Street Pump Station – Tampa, Florida Anticus Project No. 01.3883.18

SHGWT ranges approximately 3 to 6 feet below existing grade at the hand auger locations.

2. Based on ground elevations from the provided survey, the ground surface elevation is approximately +28 feet North American Vertical Datum of 1988 (NAVD88). Based on a review of contour maps published by the U.S. Geologic Survey (USGS) and Southwest

Florida Water Management District, May 2010 and September 2010 editions, the

Floridan aquifer potentiometric water levels in the vicinity of this site are approximately

El. +20 and +22 feet National Geodetic Vertical Datum of 1929 (NGVD), respectively (or approximately +23.6 and +25.6 NAVD88, respectively). Additionally, the Floridan aquifer is considered unconfined in this area.

3. We encountered very loose silty sands ranging from approximately 20 to 30 feet below existing ground surface. It is our understanding that a bottom elevation for the wet well has not been set. Due to the very loose conditions, hydraulic loading near the base of the well may cause subsidence from the water movement after installation. If the bottom elevation of the wet well is between 20 and 30 feet below existing grade, we recommend that a minimum of 18 inches of compacted FDOT No. 57 or 67 stone (or engineer approved equivalent) be utilized beneath the bottom of the wet well compacted in accordance with subsequent sections in this report.

4. The preferred soil used for structural fill (material for pump station construction) should be fine sand free of organics and debris and containing less than 15 percent fines

(materials conforming to SP and SP-SM in the Unified Soil Classification System

[USCS], and materials conforming to A-3 and A-2-4 (with less than 15 percent fines) in the AASHTO Classification System). SP/SP-SM/A-3/A-2-4 sand is generally present in the upper 8 to 10 feet at the site and may be considered as a source of structural fill when excavated and approved by the Engineer for use. Silty SAND (SM/A-2-4) and

Clayey SAND (SC/A-2-4/A-2-6) were encountered in the SPT and hand auger borings ranging from depths of existing ground surface to 8 feet and if excavated, may be used in accordance with SSRBC Section 125 for pipe backfill.

2.0 PROJECT INFORMATION

2.1 EXISTING SITE

The subject site proposed for improvements is at 5200 E. Kirby Street in Tampa, Hillsborough

County, Florida. The site is generally flat and level and of similar elevations to adjacent sites. An approximate 300 foot by 300 foot pond is located centrally at the property and the elevation difference between toe of slope to top of bank ranges from approximately 4 to 9 feet. An approximate 100 sf pump station is located to the northeast of the existing pond.

2.2 PROPOSED CONSTRUCTION

It is our understanding that the improvements will consist of a proposed wet well to the southwest of the existing pond.

3.0 SITE INFORMATION

3.1 SOIL SURVEY INFORMATION

According to the Soil Survey of Hillsborough County, Florida, prepared by the U.S. Department of Agriculture Natural Resource Conservation Service (NRCS, formerly the Soil Conservation

Service), the subject property is underlain by three (3) primary mapping units – Candler-Urban land complex, 0 to 5 percent slopes (Unit 9); Tavares-Millhopper complex, 0 to 5 percent slopes

(Unit 53); and Zolfo fine sand, 0 to 2 percent slopes (Unit 61). The general soil descriptions as described in the Soil Survey are presented in the following table.

SUMMARY OF USDA SOIL SURVEY

HILLSBOROUGH COUNTY, FLORIDA

USDA Map Symbol and Soil Name

Depth (in)

Soil Classification

Permeability (in/hr) pH

Seasonal High Water Table

Risk of Corrosion

USCS AASHTO

Depth (feet)

Months Uncoated

Steel Concrete

(9) Candler-

Urban Land

0-6 SP, SP-SM A-3 6.0 - 20.0 4.5-6.0

>6.0 Jan-Dec Low High

6-76 SP, SP-SM A-3 6.0 - 20.0 4.5-6.0

76-80 SP-SM A-2-4, A-3 6.0 - 20.0 4.5-6.0

0.0 - 0.0

(53) Tavares- Milhopper

0-7 SP, SP-SM A-3 20.0 - 50.0 3.5-6.0

3.5-6.0 June-Dec Low High

7-80 SP, SP-SM A-3 20.0 - 50.0 3.5-6.0

0-4 SM, SP-SM A-2-4, A-3 6.0 - 20.0 4.5-6.5

3.5-6.0 Jan-Feb, Aug-Dec

Low Moderate 4-57 SM, SP-SM A-2-4, A-3 6.0 - 20.0 4.5-6.5

57-80

SC, SC-

SM, SM

A-2-4, A-4 0.1 - 2.0 4.5-6.0

(61) Zolfo

0-3 SP-SM A-2-4, A-3 6.0 - 20.0 4.5-7.3

2.0-3.5 June-Nov Low Moderate 3-60 SM, SP-SM A-2-4, A-3 6.0 - 20.0 4.5-7.3

60-80 SM, SP-SM A-2-4, A-3 0.6 - 2.0 3.5-6.5

It should be noted that information contained in the USDA Soil Survey may not be reflective of current subsurface conditions, particularly if recent development in the project vicinity (which includes man-made ditches, earthwork and water features) has modified existing soils or surface/subsurface drainage.

3.2 REGIONAL GEOLOGY

Florida is located within the Coastal Plain Physiographic Province. The Coastal Plain is a wedge-shaped deposit of sediment that ranges in thickness from near zero at the contact with the Piedmont Physiographic Province (the Fall Line) along its northwest edge, to thousands of feet at the coast (seaward). Coastal Plain soils are marine deposits that contain various materials including interbedded soft and hard limestones, gravels, sands, silts, and clays, as well as organics.

Published information from the Florida Geological Survey Open File Map Series No. 146 and

No. 80, show this property is associated with the Hawthorne Group, Arcadia Formation, Tampa

Member (That). The lithology of the Tampa Member is very similar to that of the subsurface limestone part of the Arcadia Formation except that the Tampa Member contains noticeably less phosphate (Scott, 1988). The limestone in the Tampa is white to yellowish gray, fossiliferous and variably sandy and clayey mudstone, wackestone and packstone with minor to no phosphate grains. Sand and clay beds are like those in the undifferentiated Arcadia Formation.

Mollusks and corals are common in the Tampa Member as molds and casts, silicified pseudomorphs and original shell material. The Tampa Member and the lower part of the

Arcadia Formation form the upper part of the Floridan aquifer system (FAS) in parts of southern

Florida (Miller, 1986; Scott, 1991).

4.0 EXPLORATION AND TESTING METHODS

The SPT borings were drilled with a track-mounted drilling rig – at the locations shown on the attached Field Test Location Plan, Sheet 1. The SPT borings were performed and split-barrel soil samples obtained at intervals of 2 feet to a depth of 10 feet and intervals of 5 feet thereafter.

Conventional rotary drilling procedures were utilized along with a bentonite drilling fluid to stabilize the borehole.

The following is a brief description of this field test procedure. The exploratory borings were performed in accordance with ASTM D 1586, entitled "Standard Method for Penetration Test and Split-Barrel Sampling of Soils.” After drilling to the required depth and cleaning the bore hole, the sampler (2" O.D.) was driven 18 or 24 inches into the undisturbed soil by a 140-pound drop-hammer falling 30 inches. The number of blows required to drive the sampler the second and third 6-inch increments is known as the Standard Penetration Resistance (N). The various soils encountered in the borings were visually classified in the field and representative soil samples obtained for further examination by a geotechnical engineer. The soils encountered in the borings were classified utilizing the USCS and AASHTO methods. At the completion of the drilling operations, the borehole was abandoned in accordance with Southwest Florida Water

Management District guidelines.

Twenty (20) hand auger borings were performed by manually twisting a post-hole auger into the soil. The auger consists of two curved blades and a bucket which retains the soil as the auger is advanced. At approximately 6 inch intervals the auger is removed and the soil retained in the bucket is classified and placed in sealed containers for further evaluation by a geotechnical engineer. The soils encountered in the borings were classified utilizing the Unified Soil

Classification System (USCS).

The various soils encountered in the borings were visually classified in the field and representative soil samples obtained for further examination by a geotechnical engineer. The soils encountered in the borings were classified utilizing the USCS and AASHTO methods. At the completion of the drilling operations, the boreholes were abandoned in accordance with

Southwest Florida Water Management District guidelines.

The observed procedures used for field sampling and testing were performed in general accordance with ASTM procedures and established engineering practice.

4.1 FIELD EXPLORATION AND TESTING

Two (2) SPT borings (B-1 and B-2) were advanced to approximate depths of 25 to 31 feet below the existing ground surface at the locations shown on the Field Test Location Plan, Sheet 1. The drillers advanced the borings using wet rotary methods and collected soil samples using a split-barrel sampler driven by a cathead and rope with safety hammer according to ASTM D1586.

Twenty (20) hand auger borings were performed to approximate depths of 3.5 to 8 feet below existing ground surface. Hand auger boring HA-3 was terminated due to encountering refusal on cemented sands. The borings were performed to evaluate the shallow soil conditions revealed in the survey and to determine the estimated SHGWT.

The SPT and hand auger boring locations were located by measuring distances and estimating right angles from existing landmarks such as fences and the roadway. Therefore, the field test locations shown on the attached Field Test Location Plan should be considered as approximate.

The Soil Profile, Sheet 2 of the attachments, represents our interpretation of the conditions encountered at each boring location. The stratification lines indicated on the Soil Profile represent the approximate boundaries between soil types; however these transitions may be more gradual than indicated.

5.0 SUBSURFACE CONDITIONS

5.1 GENERAL SOIL PROFILE

Detailed descriptions are presented on the attached soil profile. When reviewing the soil profile, the indicated boundaries between soil strata are approximate and the transitions between strata are typically more gradual. Also, variations in subsurface conditions from those encountered may exist between the boring locations.

5.2 GROUNDWATER

Groundwater was encountered in SPT boring B-1 at a depth of 10 feet below existing ground surface (May 2019 – end of dry season) and was encountered in SPT boring B-2 at a depth of approximately 4 feet below existing ground surface (January 2021 – middle of dry season).

Groundwater levels fluctuate with time due to seasonal moisture changes, tidal influences and locally heavy precipitation events. Therefore, future ground water levels may be encountered at depths different from those identified in our borings.

5.3 TYPICAL SEASONAL HIGH WATER TABLE

The SHGWT is typically encountered during late summer following the rainy season. Several factors affect the seasonal high water table including the amount of rainfall; the drainage characteristics of the soils; the land surface elevation; relief points such as lakes, rivers or swamps; and distance to relief points. We evaluated the SHGWT based on soil characteristics such as color, iron staining, mottling, silting and cementitious deposits, depth of root systems encountered and “wash” zones noted. Our SHGWT estimates are noted in the following table.

SHGWT Depth

(feet)

HA-1 HA-5 HA-7 HA-11 HA-15 HA-17 HA-19

5.0 6.0 3.5 3.0 6.0 4.0 4.0

The variability of the SHGWT is generally due to these indicators being historic indicators and are not reflective of the current pond layout; additionally, some of the variability is due to the existing ground surface elevations at the boring locations.

6.0 CONCLUSIONS

We base the following conclusions in part on the preceding project information and the results of the subsurface exploration. The following describes our conclusions concerning geotechnical issues associated with the project:

Groundwater was encountered in SPT boring B-1 at a depth of 10 feet below existing ground surface (May 2019 – end of dry season) and was encountered in SPT boring B-2 at a depth of approximately 4 feet below existing ground surface (January 2021 – middle of dry season).

Groundwater was not encountered in hand auger borings HA-1 through HA-20. Based on our hand auger borings performed at the site, the estimated SHGWT ranges approximately 3 to 6 feet below existing grade at the hand auger locations.

Based on ground elevations from the provided survey, the ground surface elevation is approximately +28 feet North American Vertical Datum of 1988 (NAVD88). Based on a review of contour maps published by the U.S. Geologic Survey (USGS) and Southwest Florida Water

Management District, May 2010 and September 2010 editions, the Floridan aquifer potentiometric water levels in the vicinity of this site are approximately El. +20 and +22 feet

National Geodetic Vertical Datum of 1929 (NGVD), respectively (or approximately +23.6 and

+25.6 NAVD88, respectively). Additionally, the Floridan aquifer is considered unconfined in this area.

We encountered very loose silty sands ranging from approximately 20 to 30 feet below existing ground surface. It is our understanding that a bottom elevation for the wet well has not been set.

Due to the very loose conditions, hydraulic loading near the base of the well may cause subsidence from the water movement after installation. If the bottom elevation of the wet well is between 20 and 30 feet below existing grade, we recommend that a minimum of 18 inches of compacted FDOT No. 57 or 67 stone (or engineer approved equivalent) be utilized beneath the bottom of the wet well compacted in accordance with subsequent sections in this report.

The preferred soil used for structural fill should be fine sand free of organics and debris and containing less than 15 percent fines (materials conforming to SP and SP-SM in the Unified Soil

Classification System [USCS], and materials conforming to A-3 and A-2-4 (with less than 15 percent fines) in the AASHTO Classification System). SP/SP-SM/A-3/A-2-4 sand is generally present intermittently in the upper 8 to 10 feet at the site and may be considered as a source of structural fill when excavated and approved by the Engineer for use. Silty SAND (SM/A-2-4) and

Clayey SAND (SC/A-2-4/A-2-6) were encountered intermittently from existing ground surface to

8 feet and may be used in accordance with SSRBC Section 125 for pipe backfill.

7.0 RECOMMENDATIONS

Site stripping and subgrade preparation should be completed in accordance with current applicable Hillsborough County guidelines and FDOT SSRBC for pipe alignment and ancillary structures.

7.1 STRUCTURAL FILL

7.1.1 Structural Fill Definition

The preferred soil used for structural fill is fine sand free of organics and debris and containing less than 15 percent material by weight that is finer than a number 200 sieve (fines) (materials conforming to SP/SP-SM in the USCS or A-3/A-2-4 with less than 15% fines in AASHTO Soil

Classification System). All fill should be approved by the Engineer before placement.

We recommend following the latest version of the FDOT Standard Specifications for Road and

Bridge Construction (SSRBC) Section 125 for utility trench construction, which allows for additional fill types at different levels within the utility trench.

7.1.2 Structural Fill Availability

SP/SP-SM/A-3/A-2-4 sand is present intermittently to approximate depths of 8 to 10 feet at the site and may be considered as a source of structural fill, where practical. All fill whether imported or excavated on site should be approved by the Geotechnical Engineer.

7.1.3 Structural Fill Placement and Compaction

Structural fill with less than 15 percent fines should be placed in lifts not to exceed one foot thick, or 4 inches if manual equipment is being utilized. The fill material should be compacted to at least 98 percent of its modified Proctor maximum dry density (ASTM D-1557). Please refer to

FDOT SSRBC Section 125 for compaction specifications for pipe and utility trench construction.

7.2 SITE DEGRADATION DURING CONSTRUCTION

It has been our experience that prior to underdrain and structure placement, soil subgrades can be significantly disrupted by construction equipment, utility construction, and inclement weather.

The soils exposed at the subgrade will consist primarily of sands. These materials are particularly susceptible to disturbance. Placement of fill upon these areas must occur promptly, or these areas will need re-compaction and re-testing.

7.3 RETAINING WALLS (WET WELL)

Retaining wall foundations should be designed for a maximum allowable soil bearing pressure of 2,000 psf.

Soils behind the retaining walls are assumed to exert a triangular stress distribution which can be modeled in terms of an "equivalent fluid" for both the active and at-rest cases. If the top of the wall is free to rotate, the active earth pressure condition can be used. If the top of the wall is fixed and not free to rotate, the at-rest earth pressure condition should be used. If a uniform area surcharge is applied behind the wall, a portion of the surcharge is transferred to the wall in the form of a uniform or rectangular lateral stress distribution. The magnitude of the lateral stress transferred to the wall is a function of the soil's strength and the permissible degree of deflection or rotation. It is computed by multiplying the soil's "earth pressure coefficient" by the magnitude of the surcharge.

The following table presents values for earth pressure coefficients and equivalent fluid unit weights for both the at-rest and active conditions previously discussed. These values assume a horizontal backfill behind the walls.

Earth Pressure Condition Earth Pressure Coefficient Recommended Equivalent Fluid

Unit Weight, pcf

Active, Horizontal Backfill 0.33 36

At-Rest, Horizontal Backfill 0.5 55

The recommended equivalent fluid unit weights also assume that constantly functioning drainage systems are installed between walls and soil backfill to prevent the build-up of hydrostatic pressures and lateral stresses in excess of those calculated for drained conditions.

Passive earth pressure of soil adjacent to the footing as well as soil friction of the footing base can be used to resist sliding. The ultimate soil friction force can be computed by multiplying the footing’s applied compressive force by 0.63. The ultimate passive restraint of wall footings embedded adjacent to a horizontal grade can be modeled assuming a fluid with an equivalent unit weight of 330 pcf. We recommend that a safety factor of at least 2 be used when computing restraining forces, as no strength test analysis was performed and a simplified (Rankine) earth pressure distribution was used.

Sand with less than 5 percent finer than the Number 200 sieve (SP/A-3 sand) should be used as backfill directly behind the retaining walls. This material should be compacted to at least 95 percent of its standard Proctor maximum dry density. Either light, hand-operated compaction equipment must be used within 4 feet of walls to reduce the risk of over-stressing the walls or the walls must be designed to resist the stressed imposed by large compaction equipment.

The retaining walls should be provided with a drain system or properly designed weep holes to allow for dissipation of water. Sand backfill should be placed, as a minimum, in a wedge drawn upward and away from a line located at least 3 feet outside of the bottom edge of the wall at 45 degree angle or flatter.

7.4 EXCAVATIONS

In general, structural fill should consist of fine sands (SP/SP-SM/A-3/A-2-4), with less than 15% fines, which can 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. All fill should be placed in accordance with the recommendations provided in this report.

In Federal Register, Volume 54, No. 209 (October 1989), the United States Department of

Labor, Occupational Safety and Health Administration (OSHA) amended its “Construction

Standards for Excavations, 29 CFR, Part 1926, Subpart P”. This document was issued to better insure the safety of workmen entering trenches or excavations. It is mandated by this federal regulation that excavations, whether they be utility trenches, basement excavations or foundation excavations, be constructed in accordance with the new OSHA guidelines. It is our understanding that these regulations are being strictly enforced and if they are not closely followed, the owner and the contractor could be liable for substantial penalties.

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. 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 our client. Anticus 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.

7.5 GROUNDWATER CONTROL

The groundwater levels presented in this report are the levels that were measured at the time of our field activities. Fluctuation should be anticipated. We recommend that the Contractor determine the actual groundwater levels at the time of the construction to determine groundwater impact on this construction procedure. Groundwater control may be necessary for the construction of the proposed structure foundations. Groundwater can normally be controlled in shallow excavations or rim ditches with a sump pump, with well-points being utilized for deeper excavations, such as the pond excavations, as necessary. During subgrade soil preparation, any soils below design grade could become disturbed by construction activities. If this becomes the case, the contractor may be directed by the owner’s representative to remove the disturbed or pumping soils to a depth of 12 to 18 inches below design grade and backfill the area with structural fill.

Water should not be allowed to collect in the foundation excavation, on the floor slab areas, or on prepared subgrades of the construction either during or after construction. Undercut or excavated areas should be sloped toward one corner to facilitate removal of any collected rainwater, groundwater, or surface runoff. Positive site drainage should be provided to reduce infiltration of surface water around the perimeter of the building and beneath the floor slabs. The grades should be sloped away from the building and surface drainage should be collected and discharged such that water is not permitted to infiltrate the backfill and floor slab areas of the building.

8.0 FOLLOW-UP SERVICES

Our services do not end with the submission of this geotechnical report. Anticus should be kept involved throughout the design and construction process to maintain continuity and to verify that our recommendations are properly interpreted and implemented. To achieve this, we should review project plans and specifications with the designers to see that our recommendations are fully incorporated. We also should be retained to monitor and test the site preparation and foundation construction.

Anticus’s familiarity with the site and recommendations make us a valuable part of your construction quality assurance team. Anticus recommends that we be retained by the owner to observe earthwork and pipe construction. Our personnel are uniquely qualified to recognize unanticipated ground conditions and can offer responsive remedial recommendations should these unanticipated conditions occur.

9.0 LIMITATIONS OF REPORT

This report has been prepared for the exclusive use of Watermark Engineering Group, Inc.

and Hillsborough County and their designers for specific application to the project previously discussed. Our conclusions and recommendations have been prepared using generally accepted standards of geotechnical engineering and engineering geology practice in the State of Florida. No other warranty is expressed or implied.

Our conclusions and recommendations are based on the design information furnished to us, the data obtained from the previously described exploration and our experience. They do not necessarily reflect variations in the subsurface conditions, which are likely to exist intermediate of our borings and in unexplored areas of the site due to the inherent variability of the subsurface conditions in this geologic region as well as past land use. Should such variations become apparent during construction, it will be necessary to re-evaluate our conclusions and recommendations based upon on-site observation of the conditions.

If changes are made in the overall design or location of grading scheme, then the recommendations presented in this report may no longer be valid. In such cases, our firm should review the proposed changes to evaluate whether our recommendations need to be modified. The results of this review should be provided in writing. We also request the opportunity to review the foundation plan, grading plan and applicable portions of the project specifications when the design is finalized. This review will allow us to check whether these documents are consistent with the intent of our recommendations.

Sampling and testing of the soil, rock, ground water, surface water and air for the presence of environmental contamination was beyond the scope of this exploration. We will be glad to provide these services at your request.

The site is underlain by limestone bedrock that is susceptible to dissolution and the subsequent development of karst features such as voids and sinkholes in the natural soil overburden.

Construction in a sinkhole prone area is therefore accompanied by some risk that internal soil erosion and ground subsidence could affect new structures in the future. It is not possible to investigate or design to completely eliminate the possibility of future sinkhole related problems.

In any event, the Owner must understand and accept this risk.

LL PL PI

HA-1 4 to 4.5 3 4 - - -

HA-5 3.5 to 4 3 5 - - -

HA-7 2.5 to 3 13 23 31 20 11

HA-9 0.5 to 1 12 19 - - -

HA-13 7 to 8 15 28 28 14 14

HA-19 4.5 to 5 3 3 - - -

B-2 2 to 4 16 5 - - -

B-2 6 to 8 17 17 - - -

B-2 8 to 10 16 20 - - -

B-2 18.5 to 20 32 33 52 20 32

Laboratory Results

Hand

Auger

Depth

(ft)

Moisture

-200

Atterberg Limits

Saturated Submerged Active (Ka) Passive (Kp)

0 to 2 14 SP/SP-SM A-3/A-2-4 110.0 47.6 30 0 0.333 3.00

2 to 4 7 SP/SP-SM A-3/A-2-4 105.0 42.6 29 0 0.347 2.88

4 to 6 9 SP/SP-SM A-3/A-2-4 105.0 42.6 29 0 0.347 2.88

6 to 8 8 SP/SP-SM A-3/A-2-4 105.0 42.6 29 0 0.347 2.88

8 to 10 4 SC A-2-4/A-2-6 105.0 42.6 29 400 0.347 2.88

10 to 15 19 SC A-2-4/A-2-6 110.0 47.6 30 1900 0.333 3.00

15 to 20 5 SC A-2-4/A-2-6 105.0 42.6 29 500 0.347 2.88

20 to 25 50/6 SP-SM A-2-4 125.0 62.6 34 0 0.283 3.53

0 to 2 11 SP/SP-SM A-3/A-2-4 110.0 47.6 30 0 0.333 3.00

2 to 5 5 SP/SP-SM A-3/A-2-4 105.0 42.6 29 0 0.347 2.88

5 to 6 9 SC A-2-4/A-2-6 105.0 42.6 29 900 0.347 2.88

6 to 8 19 SM A-2-4 110.0 47.6 30 0 0.333 3.00

8 to 10 22 SC A-2-4/A-2-6 115.0 52.6 32 2200 0.307 3.26

10 to 15 11 SC A-2-4/A-2-6 110.0 47.6 30 1100 0.333 3.00

15 to 20 4 SC A-2-4/A-2-6 105.0 42.6 29 400 0.347 2.88

20 to 30.5 1/18 SM A-2-4 100.0 37.6 26 0 0.391 2.56

30.5 to 31 19** --- --- 135.0 72.6 0 4000 1.00 1.00

SOIL PARAMETERS

Unit Weight (PCF) Earth Pressure Coefficient

(Rankine)Boring ID

Depth

Range

(FT)

SPT "N"

Value

Soil Angle of Friction

(Degrees)

Cohesion

(PSF)

Unified Soil

Classification

AASHTO

Classification

B-2

Environmental

Classification*

Extremely

Aggressive*

Extremely

Aggressive

B-1 tJG11 •

' I

LEGEND

Approximate Site

Location

Note: Yellow number indicates Web Soil Survey Map Unit

ANT ICU S.

ENGINEERING�•►

Post Office Box 921 Riverview. FL 33568

Phone/Fax (813) 642-3965

Certificate of Authorization No. 30846

WEB SOIL SURVEY/TOPOGRAPHIC MAP

(PRODUCED BY THE NATIONAL COOPERATIVE SOIL SURVEY)

Engineer of Record

Jeanne A. Berg, PE License No. 50699

Kirby Street Pump Station 5200 E. Kirby Street

Tampa, FL

Project Sheet

01.3883.18

Date

January 21, 2021 4

Scale

As Shown