ITB-2018-0341_Exhibit_4_Geotech_Engineering_Report.pdf

Report of Geotechnical Engineering Investigation

CASSELTON DRIVE IMPROVEMENTS

Seminole County, Florida GEC Project No. 3735G

GEC Project No. 3735G ii Report of Geotechnical Engineering Investigation

Casselton Drive Improvements

TABLE OF CONTENTS

1.0 SITE AND PROJECT DESCRIPTION

2.0 NRCS SOIL SURVEY

3.0 SUBSURFACE EXPLORATION

3.1 Machine Auger Borings

3.2 Pavement Cores

3.3 Field Permeability Test

3.4 Groundwater Measurement

4.0 LABORATORY TESTING

5.0 DESCRIPTION OF SUBSURFACE CONDITIONS

5.1 Boring Results

5.2 Groundwater Levels

5.3 Pavement Core Results

5.4 Pavement Surface Condition and Cracking

6.0 CONCLUSIONS AND DESIGN RECOMMENDATIONS

6.1 Pavement Rehabilitation Recommendations

6.2 Pipe Bedding, Backfill and Compaction

6.3 Utility Excavations

6.4 Stormwater Swales

6.5 Temporary Dewatering

7.0 USE OF THIS REPORT

APPENDIX

Figure 1: USGS Quadrangle and NRCS Soil Survey Maps Figure 2: Boring and Pavement Core Location Plan Figure 3: Auger Boring Results Pavement Core Photographic Logs

GEC Project No. 3735G 1 Report of Geotechnical Engineering Investigation

1.0 SITE AND PROJECT DESCRIPTION

The project site is located in southwest Seminole County in Casselberry, Florida. This project includes an approximately 2,200-foot long section of Casselton Drive from Semoran Boulevard to Greencastle Boulevard, as well as an approximately 500-foot long section of Greencastle Boulevard from Casselton Drive to Semoran Boulevard. Casselton Drive is an existing 2-lane, undivided curb and gutter typical section, while Greencastle Boulevard is a 2-lane, divided curb and gutter typical section. Land use in this area includes a mix of residential and commercial structures. We understand that project plans include the narrowing of the asphalt roadways, as well as milling and resurfacing of the existing asphalts. Also included in the project plans is the construction of new roadside swales located along the west side of Casselton Drive. In addition, an existing water main and deep drainage pipe will be replaced.

Based on a review of the USGS Orlando East, Florida Quadrangle map, the ground surface elevation at the site is approximately +85 feet NGVD. The project site is shown on an excerpt of the United States Geological Survey (USGS) Orlando East, Florida Quadrangle map on Figure 1 in the Appendix.

2.0 NRCS SOIL SURVEY

The Natural Resources Conservation Service (NRCS) (formerly SCS) Soil Survey of Seminole County, Florida was reviewed for near-surface soil and groundwater information at the project site. The NRCS Soil Survey map of the site vicinity is shown on Figure 1 in the Appendix. The NRCS soils near the project site are summarized in Table 1 below:

Table 1 NRCS Soil Survey Classifications

Unit No.

Soil Name Depth

(inches) Soil Description

Unified Classification

Symbol

Depth to Seasonal High Groundwater

(feet) 34 Urban Land --- --- --- ---

…the project includes the narrowing of the asphalt roadways...construction of new roadside swales…

GEC Project No. 3735G 2 Report of Geotechnical Engineering Investigation

The NRCS Soil survey map depicts Urban Land (Soil Unit No. 34) within the project area. Urban Land refers to areas where most of the ground surface is covered by asphalt, concrete, buildings and other impervious surfaces that modify surface/subsurface drainage and obscure or alter the soils so that their identification is not possible.

Information contained in the NRCS Soil Survey should be considered very general and may be outdated. Therefore, it may not be reflective of actual soil and groundwater conditions, particularly if recent development in the site vicinity has modified soil conditions or surface/subsurface drainage. The information obtained from the soil borings presented in this report should be considered a more current and accurate characterization of actual site conditions.

3.0 SUBSURFACE EXPLORATION

In addition to consulting the sources of information previously discussed for regional and site-specific soils data, GEC conducted a subsurface exploration to evaluate soil, groundwater and pavement conditions. GEC explored subsurface conditions at the subject site by performing 4 auger borings (AB-1 to AB-4) to depths of 15 feet below the ground surface. GEC explored the existing pavement conditions by performing 2 pavement cores along the existing asphalt roadway at locations requested by Geosyntec. GEC also performed 2 field permeability tests at auger borings locations AB-2 and AB-3.

The borings and pavement cores were not surveyed in the field but were established in the field using project plans and a handheld, sub-meter accuracy, Global Positioning Satellite (GPS) unit (Trimble Geo7X) and should be considered approximate. Although these boring and core locations are, therefore, given only approximately, the methods used to locate them are, in GEC’s opinion, sufficient to meet the intent of this study. The boring and core locations are indicated on the Boring and Pavement Core Location Plan sheet, Figure 2 in the Appendix.

3.1 Machine Auger Borings

Machine auger borings were performed in general accordance with ASTM Procedure D-4700.

Machine auger borings were performed by hydraulically turning continuous flight, solid-stem, auger into the ground in 5-foot increments until the desired boring termination depth was achieved. The auger flights were retrieved in 5-foot increments, without further rotation of the auger, and the retrieved soil was examined by our technician prior to collection of representative samples. A field auger boring log was prepared that detailed the soils penetrated, records the groundwater depth at the time of drilling, if encountered, and includes other details of the boring, GEC explored subsurface conditions…by performing 4 auger borings…2 pavement cores…

GEC Project No. 3735G 3 Report of Geotechnical Engineering Investigation methods used, and selected other boring and/or site conditions at the time of drilling. The samples were placed in sealed jars and transported to GEC’s laboratory for further examination and limited laboratory testing as needed.

3.2 Pavement Cores

Pavement cores were conducted using a 6-inch diameter core barrel and were cored through the pavement to the bottom of the base material. After the pavement cores were completed, the hole was backfilled with soil cuttings and patched with cold patch asphalt to the pavement surface.

3.3 Field Permeability Test

Constant head permeability tests were performed in the field at this site. The field permeability tests were performed by driving a 3-inch diameter casing into the ground to the desired test depth and washing the soil out of the casing with water. The casing was backfilled with quartz gravel to 32 inches above the bottom of the casing and was then raised a distance of 24 inches. When a constant head permeability test was conducted, water was added to the casing to achieve a stable water level. Once the water level stabilized, the flow required to maintain the stable water level over time was measured.

These relationships were used to calculate the permeability of the soil. Field permeability tests and calculations were performed in general conformance with NAVFAC DM-7.1-108.

3.4 Groundwater Measurement

A GEC engineering technician measured the depth to groundwater in the boreholes at the time of drilling and again after approximately 24 hours. Once the 24-hour groundwater measurement was recorded, the boreholes were then backfilled with soil cuttings to prevailing ground surface.

4.0 LABORATORY TESTING

Selected soil samples retrieved from the borings were tested in general accordance with Florida Standard Testing Methods (FM). Florida Standard Testing Methods are adaptations of recognized standard methods, e.g., ASTM and AASHTO, which have been modified to accommodate Florida’s geological conditions. The GEC laboratory is reviewed annually by the Construction Materials Engineering Council, Inc. (CMEC) to verify compliance with FM. Our laboratory testing program is summarized on the following table:

GEC Project No. 3735G 4 Report of Geotechnical Engineering Investigation

Table 2 Summary of Laboratory Testing Program

Type of Test Number of Tests

Percent Fines (FM 1-T088) 5 Natural Moisture Content (FM 1-T265) 1 Atterberg Limits (FM 1-T89/90) 1

The individual results of our laboratory tests are shown adjacent to the soil profiles at the approximate depths from which the tested samples were obtained on the Auger Boring Results sheet (Figure 3) in the Appendix.

5.0 DESCRIPTION OF SUBSURFACE CONDITIONS

Detailed records of subsurface conditions encountered in our auger borings are shown on Figure 3 in the Appendix. The soils encountered in the auger borings were classified in accordance with the American Association of State Highway and Transportation Officials (AASHTO) Soil Classification System (A-3, A-2-4, etc.) and ASTM soil descriptions (e.g., sand with silt). We based our soil classifications and descriptions on visual examination and the limited laboratory soil classification testing performed.

The boring logs indicate subsurface conditions only at the specific boring locations at the time of our field exploration. Subsurface conditions, including groundwater levels, at other locations of the subject site may differ from conditions we encountered at the boring locations. Moreover, conditions at the boring locations can change over time. Groundwater levels fluctuate seasonally, and soil conditions can be altered by earthmoving operations.

The depths and thicknesses of the subsurface strata indicated on the boring logs were interpolated between samples obtained at different depths in the borings. The actual transition between soil layers may be different than indicated. These stratification lines were used for our analytical purposes. Earthwork quantity estimates based on the boring results will vary from the actual quantities measured during construction.

5.1 Boring Results

The auger borings (AB-1 to AB-4) typically encountered silty fine sand (A-2-4) with intermittent layers of fine sand with silt (A-3) to the boring termination depths of 15 feet below the existing ground surface. Borings AB-1 and AB-2 encountered traces of organic material from 0 to 2 and 5.5 to 8 feet below the existing ground surface, respectively.

GEC Project No. 3735G 5 Report of Geotechnical Engineering Investigation

Please refer to Figure 3 in the Appendix for the specific subsurface profiles at each of the boring locations.

5.2 Groundwater Levels

Our technician measured the groundwater level in the auger borings 24 hours after the date drilled. Encountered groundwater levels ranged from 3.4 to 5.3 feet below existing grade.

Encountered groundwater depths measured in the boreholes are presented on Figure 3 in the Appendix.

Groundwater levels can vary seasonally and with changes in subsurface conditions between boring locations. Alterations in surface and/or subsurface drainage brought about by site development can also affect groundwater levels. Therefore, groundwater depths measured at different times or at different locations on the site can be expected to vary from those measured by GEC during this investigation.

For purposes of this report, estimated seasonal high groundwater levels are defined as groundwater levels that are anticipated at the end of the wet season during a “normal rainfall” year under pre-development site conditions. We define a “normal rainfall” year as a year in which rainfall quantity and distribution were at or near historical averages.

We estimate that seasonal high groundwater depth will range from approximately 1.5 to 3.0 feet below existing ground surface. Our estimated seasonal high groundwater levels are presented on the Auger Boring Results sheet (Figure 3) in the Appendix.

5.3 Pavement Core Results

GEC obtained pavement cores at 2 locations (C-1 and C-2) along the existing asphalt roadway, as depicted in Figure 2 in the Appendix. Asphalt pavement cores were performed to obtain pavement thickness and base course thickness as well as base course type. The measured pavement and base course thicknesses are summarized in the following table:

We estimate seasonal high groundwater levels will range from approximately 1.5 to 3.0 feet below the existing ground surface.

GEC Project No. 3735G 6 Report of Geotechnical Engineering Investigation

Table 3 Summary of Pavement Component Thicknesses

Core No.

Asphalt

Thickness (in)

Base Thickness (in)

Base Type Rut Depth

(in) Cross Slope

C-1 2.75 7.0 Limerock 0.0 1.5 C-2 3.0 10.0 Limerock 0.0 0.9

For cross-slope measurements, two measurements were taken with a six-foot straight edge and the average was recorded. Photographs of the cores are included in the Appendix.

5.4 Pavement Surface Condition and Cracking

As of March 31, 2015, the pavement appears to generally be in fair condition. Cracking was generally light with Class IB (less than or equal to 0.125 inches) single cracking observed at the pavement core locations. Core C-1 was obtained over obvious surface cracks and was cracked the full depth of the asphalt surface. Very minor single surface cracks were observed in the general area of pavement core C-2. The crack details and pavement conditions for each pavement core are summarized in the following table.

Table 4 Summary of Crack Details and Pavement Conditions

Core No.

*Crack Depth

(in) Crack Type Class Extent Pavement Condition

C-1 FD Single IB Moderate Fair C-2 --- Single IB Light Fair

*Full Depth

Based on field observations, lateral cracking was observed in the pavements and into the roadside curbing near core location C-1. Based on our boring AB-1, performed in the general area of the observed cracking, the seasonal high groundwater table is approximately 2 feet below the existing ground surface and in turn is less than 2 feet below the limerock base. This could be weakening the limerock base course and causing some of the cracking, especially if there is existing irrigation within the grassed median and landscaped areas on the outside edges of pavement causing the water table to mound. Based on our field observations and limited field data, there are no obvious signs that base failure is the main cause of the pavement distress. If deemed necessary, to further

…the pavement appears to generally be in fair condition.

GEC Project No. 3735G 7 Report of Geotechnical Engineering Investigation investigate these pavement conditions and the likelihood of base failure, we would suggest additional borings and cores be performed in this area as well as the installation of temporary piezometers to measure the existing groundwater conditions more accurately.

6.0 CONCLUSIONS AND DESIGN RECOMMENDATIONS

The conclusions and recommendations contained in this report are based in part on the data obtained from a limited number of soil and pavement samples and the groundwater measurements obtained from widely-spaced borings. The sampling methods used indicate subsurface and pavement conditions only at the specific boring and core locations where samples were obtained, only at the time they were obtained, and only to the depths penetrated. Borings and cores cannot be relied upon to accurately reflect the variations that usually exist between boring and core locations and these variations may not become evident until construction.

If variations from the subsurface and pavement conditions described in this report do become evident during construction or if the project characteristics described in this report change, GEC should be retained to reevaluate this report’s conclusions and recommendations in light of such changes.

6.1 Pavement Rehabilitation Recommendations

Based on the results of this investigation, there is no evidence of a deficient pavement section or subsoil causing the observed pavement distress. The asphalt and base thickness appear adequate for the assumed residential traffic loading, and the subsoils appear favorable for good pavement subgrade. The quality of the structural asphalt mixture and the compaction of the limerock base and subgrade could not be ascertained from the normal testing conducted (i.e.; pavement cores and auger borings). A more extensive testing program would be needed to determine if the asphalt mix design and base/subgrade compaction were adequate. The vertical separation between the bottom of base and our estimated seasonal high groundwater table may be inadequate in some areas where shallow groundwater was encountered. Typically, we recommend a minimum vertical separation of 2 feet.

Due to the severe extent and depth of the cracking encountered in the core performed on Greencastle Boulevard, a milling and resurfacing program will not adequately remove the cracks in their entirety and the cracking would likely reflect upward into any new asphalt resurfacing layers soon after repaving. To provide a rehabilitated pavement section with the lowest risk for propagation of existing cracks up into any new resurfaced pavement, we would recommend full reconstruction of the pavement section in this area. The new pavement design should take into account the encountered groundwater conditions.

…we would recommend full reconstruction of the pavement section in this area.

GEC Project No. 3735G 8 Report of Geotechnical Engineering Investigation

If complete reconstruction of the existing pavement section in this area is cost prohibitive at this time, other options would be to perform a milling and resurfacing program with a crack sealant or Asphalt Rubber Membrane Interlayer (ARMI) to prevent propagation of the full depth cracks observed at the Greencastle Boulevard core location. However, ARMI in our experience is very expensive and is rarely chosen as a remediation option. Alternatively, GEC recommends that a milling program be designed to remove as much of the existing cracks as possible, and we recommend that a crack sealant be applied to any remaining visible cracks after milling. We recommend milling as much of the existing asphalt layers as possible while leaving approximately

0.5 inches of asphalt pavement above the existing base material. Resurfacing can then be conducted based on the required pavement design calculations. Resurfacing should use warm-mix asphalt in accordance with the City of Casselberry’s Specification CASB 334, which is based on FDOT design and specifications.

Due to the overall fair condition of the existing pavements and the generally minor cracking observed around the core performed on Casselton Drive, a milling and resurfacing program should adequately remove the cracks in their entirety and prevent the cracking from reflect upward into any new asphalt resurfacing layers after repaving. Therefore, we recommend a milling and resurfacing program be developed for the area near core C-2. Resurfacing should use warm-mix asphalt in accordance with the City of Casselberry’s Specification CASB 334, which is based on FDOT design and specifications.

Based on the thicknesses of the pavement encountered in our pavement cores C-1 and C-2, we would recommend milling the pavements in the areas of the pavement cores to depths of 2 ¼ inches and 2 ½ inches, respectively. If milling is to be performed in other areas along the project alignment we recommend that additional pavement cores be performed to determine the thickness of the existing pavements.

Resurfacing should use warm-mix asphalt in accordance with the City of Casselberry’s Specification CASB 334…

…we recommend a milling and resurfacing program be developed for the area near core C-2.

GEC Project No. 3735G 9 Report of Geotechnical Engineering Investigation

6.2 Pipe Bedding, Backfill and Compaction

The majority of the soils encountered in the auger borings are generally suitable for use as pipe bedding material and pipe excavation backfill. Ideally backfill soils should consist of non-plastic sands with less than about 12% fines content.

The fill should not contain any significant amount of organic substances (less than 5% by weight) or other deleterious materials. The borings performed at this site encountered soils at varying depths that had trace organics (estimated to be less than 5% organic content).

The contractor should adhere to the following recommendations for bedding fill placement and compaction.

♦ Remove any soft, loose or organic soils from below the pipe invert elevation, for the full width of the trench, and to the depth required to reach suitable foundation material.

♦ Compact pipe bedding material to a minimum of 95% of the soil’s Modified Proctor maximum dry density to a minimum depth of 6 inches below the bottom of pipe.

♦ Bedding soils that yield or pump during compaction should be undercut and backfilled as described in this report.

♦ Excavate and shape bedding soils to accommodate pipe “bells” to completely support each pipe section and help to eliminate point loading conditions.

♦ Place fill in level lifts no thicker than 12 inches.

♦ Compact each backfill lift to a minimum of 95% of the soil's modified Proctor maximum dry density as determined by AASHTO T-180 for each lift of fill placed.

♦ Compaction tests should be performed for each run of pipe between manholes or at least one test per 300 linear feet, with at least one test at an elevation of 1 foot above the top of pipe. In addition, one test should be run for every foot of backfill from 1 foot above the top of pipe to finished grade elevation.

The majority of the soils encountered in the SPT and auger borings are generally suitable for use as pipe bedding material and pipe excavation backfill.

GEC Project No. 3735G 10 Report of Geotechnical Engineering Investigation

♦ Allow an Engineering Technician, working under the direction of a registered Geotechnical Engineer, to perform in-place density tests to verify that the recommended degree of compaction has been achieved.

♦ Install sheeting and bracing or properly designed trench shields, if required, to support the sides of excavations during utility installation.

♦ All excavations including utility trenches, should comply with the recommendations included in the Utility Excavations section of this report.

♦ Where utility lines will traverse roadways and/or other permanent structures, such as foundations or sidewalks, the backfill should be compacted to 98% of the soil’s Modified Proctor maximum dry density for a depth of 2 feet below the bottom of base elevation for roadways and the top of the bearing layer elevation for structures.

6.3 Utility Excavations

The owner and the contractor should be familiar with local, state and federal safety regulations, including current Occupational Safety and Health Administration (OSHA) excavation and trench safety standards. Construction site safety is the responsibility of the contractor. The contractor should also be responsible for the means, methods, techniques, sequences, and operations of the construction.

A maximum temporary slope inclination of 1.5 horizontal to 1 vertical is recommended by OSHA for the soil types found in the SPT and auger borings for this project unless suitable trench shields or other proper engineering shoring is utilized. The contractor should be familiar with slope height, slope inclination, and excavation depths (including utility trench excavations) as further specified in local, state, or federal safety regulations; e.g., OSHA Health and Safety Standards for Excavations, 29 CFR Part 1926. OSHA regulations are strictly enforced and, if not followed, the owner, contractor, earthwork subcontractor or utility subcontractor could be liable for substantial penalties.

If excavations are required in the vicinity of already completed facilities, the contractor should be required to provide temporary support of completed pavements and structures adjacent to excavations. Prior to performing the work, the contractor should provide a plan to the Engineer of Record for temporary support of completed facilities where adjacent excavations are required.

GEC Project No. 3735G 11 Report of Geotechnical Engineering Investigation

If braced excavations, trench shields, or sheet piling are required to stabilize excavations, all shields, shoring and bracing systems or sheet piling should be designed and reviewed by an experienced professional engineer registered in the state of Florida. Adjacent traffic loads and induced vibrations should be included in the design of these systems.

The soils encountered in the borings performed by GEC at this site are primarily sand with varying amounts of silt. We anticipate that OSHA will classify these materials as Type C. OSHA recommends a maximum temporary slope inclination of 1.5 horizontal to 1 vertical for this soil type. Soils encountered in the construction excavations may vary significantly across the site.

Our soil classifications are based on the materials encountered in widely-spaced borings. The contractor should verify that similar conditions exist throughout the proposed excavation area. If different subsurface conditions are encountered at the time of construction, GEC should be contacted immediately to evaluate the conditions encountered.

6.4 Stormwater Swales

We understand that shallow stormwater swales are proposed along the west side of Casselton Drive. The majority of the near-surface soils encountered are generally suitable for construction of the swales and for use as fill material. However, the A-2-4 material may retain excess moisture and will be difficult to dry and compact. The following table summarizes the recommended unconfined aquifer parameters for design of the roadside swales.

Table 5

Stormwater Swale Parameters

Boring No. Northing Easting

Assumed Aquifer Bottom Depth

(ft) Soil Type

(AASHTO)

Estimated Seasonal High Groundwater

Depth (ft)

Measured Horizontal

Permeability Rate

(ft/day)

Estimated

Vertical Infiltration

Rate (ft/day)

Soil Porosity

AB-2 1556665.3589 556891.7762 15 A-3 3.0 2.2 2.2 25

AB-3 1556016.3213 557156.1876 15 A-2-4 2.5 3.8 3.8 25

*Listed permeability rates do not include a factor of safety.

GEC Project No. 3735G 12 Report of Geotechnical Engineering Investigation

Due to the varying subsurface conditions encountered between borings, we recommend using an average permeability rate of 3 ft/day (using the 2.2 ft/day and 3.8 ft/day from the A-3 and A-2-4 soils, respectively). A factor of safety should be used as required for drainage design.

Please refer to the Report of Auger Boring Results sheet (Figure 3) in the Appendix for specific subsurface profiles.

6.5 Temporary Dewatering

Temporary dewatering will likely be required to facilitate stable excavations and placement and compaction of fill during construction. The contractor should be required to provide a dewatering system which maintains groundwater levels at least 2 feet below compaction surfaces, including the bottom of excavations. A system of ditches and sumps may be sufficient in some instances to achieve adequate dewatering, but the contractor should be prepared to install wellpoint dewatering systems as necessary.

If clayey or hardpan soils are present in excavated areas, then dewatering system design will need to consider the relatively impervious characteristic of these soils. Wellpoint screens may need to be placed above and below these soils and/or well points may need to be sanded or placed closer together.

An experienced dewatering contractor should be retained to evaluate specific dewatering system requirements.

7.0 USE OF THIS REPORT

GEC has prepared this report for the exclusive use of our client, Geosyntec Consultants, and for specific application to our client’s project. GEC will not be held responsible for any third party’s interpretation or use of this report’s subsurface data or engineering analysis without our written authorization.

The sole purpose of the borings performed by GEC at this site was to obtain indications of subsurface conditions as part of a geotechnical exploration program. GEC has not evaluated the site for the potential presence of contaminated soil or groundwater, nor have we subjected any soil samples to analysis for contaminants.

…we recommend using an average permeability rate of 3 ft/day…

Temporary dewatering may be required to facilitate stable excavations and placement and compaction of fill during construction.

…dewatering system design will need to consider the relatively impervious characteristic of these soils.

GEC Project No. 3735G 13 Report of Geotechnical Engineering Investigation

GEC has strived to provide the services described in this report in a manner consistent with that level of care and skill ordinarily exercised by members of our profession currently practicing in Central Florida. No other representation is made or implied in this document.

The conclusions or recommendations of this report should be disregarded if the nature, design, or location of the facilities is changed. If such changes are contemplated, GEC should be retained to review the new plans to assess the applicability of this report in light of proposed changes.

APPENDIX

USGS QUADRANGLE AND

NRCS SOIL SURVEY MAPS

BORING AND PAVEMENT CORE

LOCATION PLAN

AUGER BORING RESULTS

PAVEMENT CORE

PHOTOGRAPHIC LOGS

Pavement Core Photographic Log

Client Name:

Geosyntec

Project Name:

Casselton Drive Improvements

Project Location:

Casselberry, Florida

GEC Project No.:

3735G

Photo:

Date:

4/13/15

Core: C-1

2.75” Asphalt

7” Limerock base

Photo:

Date:

4/13/15

Core C-2

3.0” Asphalt

10” Limerock base

7.0 USE OF THIS REPORT