ADDENDUM_1_-_Geotechnical_Engineering_Report.pdf

Report of Geotechnical Engineering Investigation

DRAINAGE IMPROVEMENTS AT 134 FLORIDANA ROAD

DeBary, Florida GEC Project No. 4311G

December 4, 2018

Pegasus Engineering, LLC 301 West State Road 434, Suite 309 Winter Springs, Florida 32708

Attention: Mr. David Hamstra, P.E.

Subject: Report of Geotechnical Engineering Investigation

DRAINAGE IMPROVEMENTS AT 134 FLORIDANA ROAD

DeBary, Florida GEC Project No. 4311G

Dear Mr. Hamstra:

Geotechnical and Environmental Consultants, Inc. (GEC) is pleased to submit this Report of Geotechnical Engineering Investigation for the above-referenced project. This study was performed in general accordance with our Proposal No. 9590G dated October 17, 2018. The purpose of this investigation was to explore shallow soil and groundwater conditions at the project site and to use the information obtained to develop geotechnical engineering recommendations to aid in the design and construction of the new stormwater pipes. This report describes our exploration procedures, exhibits the data obtained and presents our conclusions and recommendations regarding the geotechnical aspects of the project.

GEC appreciates the opportunity to be of service to you on this project and we trust that the information contained in this report is sufficient for your current needs. Should you have any questions concerning the contents of this report, or if we may be of further assistance, please contact us.

GEC Project No. 4311G ii Report of Geotechnical Engineering Investigation Drainage Improvements at 134 Floridana Road

Very truly yours, GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS, INC.

919 Lake Baldwin Lane Orlando, Florida 32814 Certificate of Authorization No. 5882

Ryan J. Petersen Daniel C. Stanfill, P.E.

Engineering Intern Senior Vice President

Florida License No. 42763

This Report has been digitally signed and sealed by Daniel C. Stanfill, 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 any electronic copies.

RJP/DCS/dbj

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GEC Project No. 4311G iii Report of Geotechnical Engineering Investigation

TABLE OF CONTENTS

1.0 SITE AND PROJECT DESCRIPTION

2.0 NRCS SOIL SURVEY REVIEW

3.0 SUBSURFACE EXPLORATION

3.1 SPT Borings

3.2 Machine Auger Borings

3.3 Groundwater Measurement

3.4 Manual Muck Probes

4.0 LABORATORY TESTING

5.0 SUBSURFACE DATA

5.1 Soil Boring Results

5.2 Groundwater Levels

6.0 CONCLUSIONS AND RECOMMENDATIONS

6.1 Pipe Bedding, Backfill and Compaction

6.2 Lateral Earth Pressure

6.3 Foundation Support and Estimated Settlements of Structures

6.4 Earth Pressure on Shoring and Bracing

6.5 Temporary Dewatering

6.6 Utility Excavations

6.4 Temporary Excavations

6.6 Noise and Vibration Monitoring

7.0 USE OF THIS REPORT

APPENDIX

Figure 1: USGS Quadrangle and NRCS Soil Survey Maps Figure 2: Boring Location Plan Figure 3: Soil Boring Results

GEC Project No. 4311G 1 Report of Geotechnical Engineering Investigation

1.0 SITE AND PROJECT DESCRIPTION

The project site is located on the south side of Angeles Lake in DeBary, Florida. More specifically, the project site is located by the residential property at 134 Floridana Road. We understand that during rain events, ponded water conditions occur in the yard at 134 Floridana Road.

We understand proposed drainage improvements include the addition of approximately 325 linear feet of new stormwater pipe, two curb inlets at 134 Floridana Road and one ditch bottom inlet at 137 Floridana Road and one mitered end section outfall pipe into Angeles Lake.

The approximate project area is depicted on an excerpt from the United States Geological Survey (USGS) Quadrangle Map shown on Figure 1 in the Appendix. According to the USGS Orange City, Florida Quadrangle Map, the existing ground surface elevation at the project site ranges from approximately +25 to +30 feet NGVD. Based on the survey information, the ground surface elevations descend west to east along the proposed pipeline.

2.0 NRCS SOIL SURVEY REVIEW

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

Table 1 NRCS Soil Survey Classifications

Unit No.

Soil Name Depth

(inches) Soil Description

Unified Classification

Symbol

Depth to Seasonal High Groundwater

(feet)

Hydrologic group

Apopka fine sand, 0 to 5 percent slopes

0 – 6 6 – 62

62 – 80

Fine sand Fine sand Sandy loam, sandy clay loam

SP, SP-SM

SP, SP-SM

SC, SC-SM

--- A

Basinger fine sand, frequently ponded, 0 to 1 percent slopes

0 – 5 5 – 14

14 – 36 36 - 80

Fine sand Fine sand Fine sand Fine sand, sand

SP-SM, SM

SP-SM, SM

SP-SM, SM

SP-SM, SM

+2.0 – 0.0 A/D

99 Water --- --- --- --- ---

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

GEC Project No. 4311G 2 Report of Geotechnical Engineering Investigation surface/subsurface drainage. The information obtained from the soil borings presented in this report should be considered a current 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 and groundwater conditions at the project site, which included the following:

Two Standard Penetration Test (SPT) borings to a depth of 15 feet below the existing ground surface for stormwater structures along Floridana Road.

One auger boring to depth of 10 feet below existing ground near the proposed outfall structure.

Manual muck probes in the lake around the proposed outfall structure.

The boring locations were surveyed by Southeastern Surveying and Mapping Corp. for horizontal and vertical control using datum NAVD88. The approximate boring locations are depicted on Figure 2 in the Appendix.

3.1 SPT Borings

Standard Penetration Test (SPT) borings were drilled in general accordance with ASTM Procedure D-1586. The boreholes were advanced by the rotary wash method with bentonite-based mud used as the circulating fluid to help remove cuttings and to help stabilize the borehole. Casing was used as necessary to further stabilize the borehole and prevent loose surficial sands from raveling into the lower more stable portions of the borehole. GEC’s field crew obtained SPT samples continuously in the borings to a depth of 10 feet and at 5-foot depth intervals thereafter. A GEC engineering technician supervised the drilling operation, and collected, examined and visually classified each sample. Our technician collected representative samples for further visual examination and classification in our laboratory.

3.2 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. The samples were placed in sealed jars and transported to GEC’s laboratory for further examination and limited laboratory testing as needed.

GEC Project No. 4311G 3 Report of Geotechnical Engineering Investigation

3.3 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.

3.4 Manual Muck Probes

Manual muck probes were performed by pushing a slender metal rod into the surficial soil and evaluating the relative resistance of the soil to manual penetration. Highly organic soils, such as muck and/or peat, are characteristically very soft and will easily yield to the manual probe.

Manual probes, however, cannot detect peat or muck layers which are present beneath layers of sand or dense soils which cannot be penetrated by the probe. The probes can also penetrate to some extent in very loose sands which may be present beneath peat or muck layers. No soil samples are obtained for visual examination or laboratory testing when using this exploratory technique. The soil type being penetrated is inferred solely by evaluating the relative resistance of the soil to penetration. These limitations can lead to some under-estimation or over-estimation of peat or muck layer thicknesses. The probe data presented in this report should be evaluated with these limitations in mind.

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 in the following table:

Table 2 Summary of Laboratory Testing Program

Type of Test Number of Tests Percent Fines (AASHTO T 88) 4 Atterberg Limits (AASHTO T 89/90) 1 Natural Moisture Content (AASHTO T 265) 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 Soil Boring Results sheet (Figure 3) in the Appendix.

GEC Project No. 4311G 4 Report of Geotechnical Engineering Investigation

5.0 SUBSURFACE DATA

Detailed records of subsurface conditions encountered at our boring locations are shown on Figure 3 in the Appendix. The soils encountered in the Auger Borings were classified in accordance with Unified Soil Classification System (USCS) (SP, SM, CH), and ASTM soils description (eg sand with silt). We based our soil classifications and descriptions on visual examination and the limited laboratory soil classification testing performed.

The borings 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.

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 results of the borings will vary from the actual quantities measured during construction.

5.1 Soil Boring Results

In general, the borings performed across the project site encountered the following generalized subsurface profile:

Depth (ft)

Soil Description Average

N-Value (bpf) Typical Range of N-Values (bpf)

0 – 6 Light brown to brown fine sand (SP) 6 3 – 8 6 – 13 Light brown silty fine sand (SM) 16 5 – 25

13 – 15 Light brown fine sand (SP) 20 15 - 26

Notable exceptions to this profile include an N-Value of 27 in Boring SPT-2 at a depth of 2 feet and a layer of clayey fine sand (SC) in Boring SPT-2 from depths of 7.5 to 8.1 feet. For detailed soil boring results, please refer to Figure 3 in the Appendix.

The manual muck probes did not encounter any surficial muck or loose sediment. For detailed muck probe results, please refer to Figure 2 in the Appendix.

GEC Project No. 4311G 5 Report of Geotechnical Engineering Investigation

5.2 Groundwater Levels

Our technician identified the groundwater surface in the boreholes at depths ranging from 3.4 to

5.9 feet (or elevations ranging from approximately +24.1 to +24.6 feet NAVD88). Groundwater elevations measured at all boreholes are presented in Figure 3 in the Appendix.

Water depths at the muck probes ranged from 0.2 to 1.5 feet deep. For detailed water depths at the muck probe locations, please refer to Figure 2 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 current site conditions. We define a “normal rainfall” year as a year in which rainfall quantity and distribution were at or near historical averages.

Seasonal high groundwater levels are estimated to range from elevations of +26.4 to +26.6 feet NAVD88. However, it is noted that groundwater levels at our boring locations are directly dependent on the water levels of Angeles Lake, and may differ from our estimates during extreme storm or drought conditions. The encountered and estimated seasonal high groundwater levels are depicted adjacent to the boring profiles on Figure 3 in the Appendix.

6.0 CONCLUSIONS AND RECOMMENDATIONS

The conclusions and recommendations contained in this report are based in part on the data obtained from a limited number of soil samples and groundwater measurements obtained from widely-spaced borings. If variations from the subsurface 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. We also recommend that GEC be allowed to review the construction plans prior to bidding so that we can verify that our recommendations were properly interpreted.

Seasonal high groundwater levels were estimated to range from elevations of +26.4 to +26.6 feet NAVD88.

We… recommend that GEC be allowed to review the construction plans prior to bidding…

GEC Project No. 4311G 6 Report of Geotechnical Engineering Investigation

6.1 Pipe Bedding, Backfill and Compaction

In general, the soils encountered at the boring locations, with the exception of the clayey sand soils (SC) encountered at depths of 7.5 to 8.5 feet at the boring SPT-2, are generally suitable for use as pipe bedding soil and backfill soil. All fill soils should be selected in accordance with Index 505 of the FDOT Design Standards.

The majority of the near-surface soils encountered in our borings classified as fine sand with silt (SP, SP-SM) should be treated as Select (S) material. Any plastic materials (SC, CH) should be removed beneath pipe alignments as discussed below. In addition, organic soils (PT) are not suitable for use as pipe bedding soil or backfill soil and should be removed if encountered during pipe installation as discussed below.

Ideally, pipe bedding and backfill soils should consist of non-plastic sands with less than about 12% fines content and should not contain any significant amount of organic substances (less than 3% by weight) or other deleterious materials. 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 bedding soil as described above.

Any plastic soils (SC, CH) encountered at the pipe invert depth should be overexcavated to a minimum depth of 6 inches below the pipe invert and backfilled with suitable compacted bedding material.

Compact pipe bedding soil and trench backfill soil 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.

Excavate and shape bedding soils to accommodate pipe “bells,” valves, and fittings 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 lineal feet, with at least one test at an elevation of 1 foot above the top of

Any plastic materials (SC, CH) should be removed beneath pipe alignments as discussed below.

…organic soils (PT) are not suitable for use as pipe bedding soil or backfill soil...

GEC Project No. 4311G 7 Report of Geotechnical Engineering Investigation 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.

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 sidewalks, the backfill should be compacted to 98% of the soil’s Modified Proctor maximum dry density for a depth of 2 feet below ground surface.

6.2 Lateral Earth Pressure

This section is for use in design of any buried structures along the drainage pipe and outfall pipe alignments. These recommendations are applicable for excavations that will penetrate the surficial sandy soils classified as SP, SP-SM, and SM on the boring logs included with this report.

Lateral earth pressures for design of below grade and/or earth retaining structures can be calculated using a hydrostatic pressure distribution from an equivalent fluid having varying densities for various conditions. These values assume sandy soil (SP, SP-SM, SM) with an angle of internal friction of about 30 degrees and a moist unit weight of 110 pcf and a saturated unit weight of 115 pcf. The table below summarizes the recommended equivalent fluid densities for active, passive and at-rest conditions and drained or undrained conditions. The actual lateral earth pressure will be a function of both the soil unit weight (submerged or moist) and the depth below ground surface.

Table 3 Lateral Earth Pressure

Lateral Earth Pressure Condition

Equivalent Fluid Density Undrained (pcf)

Equivalent Fluid Density Drained (pcf)

Active 80 37 Passive 158* 330 At-rest 89 55

*Note - This value is a recommended conservative Equivalent Fluid Density that does not include the unit weight of water.

GEC Project No. 4311G 8 Report of Geotechnical Engineering Investigation

Undrained conditions assume that full water pressure can develop behind the structure, in addition to the retained earth pressure. Drained conditions assume hydrostatic (water) pressure cannot develop due to positive drainage behind the structure, and includes only the moist soil earth pressure. The designer should use the appropriate condition and factor of safety based on the specific design and groundwater conditions.

6.3 Foundation Support and Estimated Settlements of Structures

Manholes and other miscellaneous structures can be designed for the following maximum vertical bearing capacities:

1,500 psf on undisturbed natural granular soils.

2,500 psf on compacted natural or backfilled subgrade; this value assumes compaction of 95 percent of the modified Proctor maximum density (ASTM D-1557) for a depth of 2 feet below the structure.

Settlements of the miscellaneous structures are anticipated to be negligible due to the effective net reduction in load when the existing soils are replaced with the structures.

The miscellaneous structures should be designed to resist hydrostatic buoyancy forces (flotation) that would be present when the groundwater is at the estimated seasonal high levels and the structure is completely empty. An appropriate safety factor should also be included in the design of the structure.

6.4 Earth Pressure on Shoring and Bracing

If temporary shoring and bracing is required for any excavations, the system should be designed to resist lateral earth pressure. The design earth pressure will be a function of the flexibility of the shoring and bracing system. For a flexible system restrained laterally by braces placed as the excavation proceeds, the design earth pressure for shoring and bracing can be computed using a uniform earth pressure distribution with depth. If dewatering is required, it is recommended that well points be used to dewater around the excavations. For such dewatered excavations, we recommend using the following uniform pressure distribution over the full braced height as follows:

Uniform Soil Pressure Distribution, p = 0.65 Ka sH p = uniform pressure distribution for design of braced excavation Ka = coefficient of active earth pressure = 0.33 s = unit weight of saturated soils = 115 pcf H = depth of excavation

GEC Project No. 4311G 9 Report of Geotechnical Engineering Investigation

An appropriate factor of safety should be applied for the design of the braced excavations. Lateral pressure distributions determined in accordance with the above do not take hydrostatic pressures or surcharge loads into account. To the extent that such pressures and forces may act on the walls, they should be included in the design.

Construction equipment and excavated fill should be kept a minimum distance of 5 feet from the edge of the braced or shored excavation. Backfill material placed adjacent to (5 feet away from) the braced or shored excavation should have a minimum slope of 2H : 1V.

6.5 Temporary Dewatering

Temporary dewatering may be required along the proposed pipeline alignments (depending on groundwater levels at the time of construction and final design grades) 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 to maintain groundwater levels 2 feet beneath the bottom of excavations.

Additionally, the contractor must provide positive site drainage during the site preparation and fill placement. Surface runoff should not be allowed to accumulate. Temporary rim ditches may be required to facilitate site preparation.

6.6 Utility Excavations

The owner and the contractor should be familiar with local, state and federal safety regulations, including current Occupational Safety and Health Association (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.

The contractor should be aware that slope height, slope inclination, and excavation depths (including utility trench excavations) should not exceed those 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.

Temporary dewatering may be required along the proposed outfall pipe alignment…

GEC Project No. 4311G 10 Report of Geotechnical Engineering Investigation

The soil encountered in the borings performed by GEC at this site is 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.

6.7 Temporary Excavations

The owner and the contractor should be familiar with local, state and federal safety regulations, including current Occupational Safety and Health Association (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.

The contractor should be aware that slope height, slope inclination, and excavation depths (including utility trench excavations) should not exceed those 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.

The soil encountered in the borings performed by GEC at this site is 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.

6.8 Noise and Vibration Monitoring

Existing structures may be affected by vibrations caused by the sheet pile installation and construction of the proposed improvements. To evaluate the existing conditions of the structures, GEC recommends a full preconstruction survey of the adjacent residential structures be performed. This includes documenting and photographing existing cracks and irregularities and obtaining floor elevations at each structure. Prior to the installation of the sheet pile, vibration monitors should be installed. In addition, any cracks observed during the preconstruction survey should be outfitted with crack monitors. The crack monitors should be observed at regular intervals during the entire sheet pile

…GEC recommends a full preconstruction survey of the adjacent residential structures be performed.

GEC Project No. 4311G 11 Report of Geotechnical Engineering Investigation installation. If movement is observed at any of the monitoring devices or vibrations exceed acceptable limits, all operations should stop and the geotechnical engineer should be notified immediately.

7.0 USE OF THIS REPORT

GEC has prepared this report for the exclusive use of our client, Pegasus Engineering, LLC and the City of DeBary, and for specific application to our client’s project. GEC will not be held responsible for interpretation or use of this report for other than its intended purpose.

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.

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 LOCATION PLAN

WITH MUCK PROBE RESULTS

SOIL BORING RESULTS