ORLANDO SANFORD INTERNATIONAL AIRPORT OUTPARCEL 1 SANFORD, FLORIDA

Transcription

1 PRELIMINARY GEOTECHNICAL STUDY ORLANDO SANFORD INTERNATIONAL AIRPORT OUTPARCEL 1 SANFORD, FLORIDA November 9, 2015 Prepared For: Ms. Diane H. Crews, A.A.E. Sanford Airport Authority 1200 Red Cleveland Boulevard Sanford, Florida Prepared By: Bechtol Engineering and Testing, Inc. 605 West New York Avenue DeLand, Florida 32720

2 November 9, 2015 TO: RE: Ms. Diane H. Crews, A.A.E. Sanford Airport Authority 1200 Red Cleveland Boulevard Sanford, Florida Preliminary Geotechnical Study Orlando Sanford International Airport - Outparcel 1 Sanford, Florida Dear Ms. Crews: As requested, Bechtol Engineering and Testing, Inc. (BET) has completed a Preliminary Geotechnical Study relative to potential development of a parcel of land on Red Cleveland Boulevard in Sanford, Florida. The purpose of BET s study was to gain general insight as to the project site s shallow soils and groundwater characteristics, and based on these characteristics, to evaluate the general suitability of the site for development of a multi-story hotel or other commercial development. The following report summarizes BET s findings and preliminary evaluations. BET appreciates the opportunity to be of service, and trusts this report is sufficient for your immediate needs. However, if you should have any questions, or if BET may be of further service, please do not hesitate to call. Respectfully, Bechtol Engineering & Testing, Inc. Certificate of Authorization No Thomas Bechtol, P.E. President / Principal Engineer Florida Registration No TB/tb

3 TABLE OF CONTENTS 1.0 INTRODUCTION 1.1 Purpose Of Study Intended Use/Limitations SITE AND VICINITY CHARACTERISTICS 2.1 Site Location Regional Geology Site Physical Characteristics GEOTECHNICAL FIELD STUDY 3.1 Auger Borings ENCOUNTERED SUBSURFACE CONDITIONS 4.1 General Soil Conditions Groundwater Conditions Soil Permeability PRELIMINARY GEOTECHNICAL EVALUATIONS 5.1 Soils Suitability and Stability Site Grading Foundations Pavement Sections Stormwater Retention LIST OF APPENDICES APPENDIX A - BORING LOCATION PLAN, SOIL PROFILES, SOIL LEGEND i

4 1.0 INTRODUCTION 1.1 Purpose Of Study Bechtol Engineering and Testing, Inc. (BET) has completed a Preliminary Geotechnical Study relative to potential development of a parcel of land on Red Cleveland Boulevard in Sanford, Florida. The purpose of BET s study was to gain general insight as to the project site s shallow soils and groundwater characteristics, and based on these characteristics, to evaluate the general suitability of the site for development of a multi-story hotel or other commercial improvements. The following report summarizes BET s findings and preliminary evaluations. 1.2 Intended Use/Limitations This report is prepared solely for the use of BET s client and their various design professionals as an aid in preliminarily evaluating the potential suitability of the project site for development. Evaluations presented herein are based on very limited subsurface data derived from soil borings, and without the knowledge of any conceptual or final developmental scheme. Subsurface conditions not disclosed by the borings performed may occur, and could influence the suitability of the site for future development. Varying developmental schemes may alter the applicability of BET s preliminary evaluations. -1-

5 2.0 SITE AND VICINITY CHARACTERISTICS 2.1 Site Location The project site is situated on the southeastern corner of Red Cleveland Boulevard and Marquette Avenue, about 0.5 miles north of East Lake Mary Boulevard, in Sanford, Seminole County, Florida. The property is located in Section 8, Township 20 South, Range 31 East, and is centered near Latitude 28 45' 47", Longitude 81 14' 18". 2.2 Regional Geology The project site lies in north-central Seminole County in a region characterized by moderate sand ridges and flatwoods, interspersed with marshlands, drainageways and some closed depressions and lakes. Elevations throughout the region generally range from +5' to +50' NGVD. Groundwater levels throughout most of the region are within 10 feet of ground surface, and in some depressed areas, groundwater levels are near or above ground surface. Sediments of Pleistocene and Recent Age, consisting mostly of sand and some clay blanket the region. Underlying deposits are of Miocene or Pliocene Age, consisting mostly of clay with some shell, and some limestone and phosphate at depth. In the immediate site vicinity these deposits extend to an estimated elevation of about -70' NGVD, and are underlaid by Ocala Group and/or Avon Park Limestone formations associated with the Floridian Aquifer. Potentiometric surface level of water in the Floridian Aquifer in the immediate site vicinity is estimated to be on the order of +20' NGVD. The project site does not lie in an area of significant Karst Topography. The general geology and groundwater conditions suggest that potential for sinkhole development in the immediate site vicinity is probably relatively low. 2.3 Site Physical Characteristics The project site consists of a nearly rectangular shaped parcel of land, containing approximately 11 acres. The site is bounded to the west by Red Cleveland Boulevard, to the north by Marquette Avenue, and to the south and east by vacant wooded land. At the time of BET s field study on May 20, 2015, except for a small potion of the site near the northwest property corner, the northern-most +/-5 acres site was moderately to heavily wooded, with vegetation consisting mostly of pines and oaks with understory of palmetto, grasses and scrub. The southern-most +/-6 acres consisted of wetland with vegetation consisting of various hardwood and palm trees with understory of and scrub. In reference to Seminole County Interactive Mapping, existing site elevations appear to mostly be in the range of 33' to 42' NGVD

6 3.0 GEOTECHNICAL FIELD STUDY 3.1 Soil Borings In order to gain general insight as to the site s shallow soil and groundwater characteristics, a series of soil borings were conducted at random locations throughout the northern-most +/- 5 acres (upland area) of site. A total of four (4) auger borings were advanced to depths ranging from 7 to 15 feet below existing ground surface. The auger borings were supplemented with one (1) Standard Penetration Test (SPT) boring (ASTM D1586), to a depth of 50 feet, in order to gain insight as to the physical and strength characteristics of deeper-seated subsurface soils. Approximate locations of the borings are shown on the Boring Location Plan presented on Sheet A1 in Appendix A. Encountered subsurface conditions are presented in the form of Soil Profiles along with Soil and Symbol Legend also on Sheet A1 in Appendix A. -3-

7 4.0 ENCOUNTERED SURFACE / SUBSURFACE CONDITIONS 4.1 General Soil Conditions In general, the borings encountered a few inches to as much as 1.5 feet of surficial topsoil comprised of very loose slightly silty, slightly organic fine sand (Stratum 1). Underlying soils consisted of fine sands and slightly silty sands (Strata 2, 3 and 4), existing in a very loose to loose condition to depth of about 5 feet, then becoming dense to very dense to depth of about 22 feet, then becoming medium dense to depth of about 42.5 feet. Underlying soils consisted of very loose silty sand (Stratum 5) to depth of about 45 feet, underlaid by loose to medium dense slightly clayey sand with shell (Stratum 6) to the SPT boring termination depth of 50 feet. For a more in-depth soil stratification, please refer to the Soil Profiles presented on Sheet A1 in Appendix A. 4.2 Groundwater Conditions Groundwater levels, as measured at the soil boring locations, were encountered at depths ranging from 5.0 to 6.0 feet below existing ground surface. BET notes that groundwater levels are subject to variation due to seasonal climate changes and man-induced influences. Average seasonal high groundwater levels are estimated to be within 24 to 36 inches of existing ground surface in the upland area of the site, and at or above ground surface in the wetland area to the south. 4.3 Soil Permeability Generally, the site s subsurface soils are considered to be poorly drained to moderately well drained. BET envisions that subsurface soil permeability rate is probably moderately rapid in the upper few feet of sandy surface soil, and relatively low in the underlying subsoil. -4-

8 5.0 PRELIMINARY GEOTECHNICAL EVALUATIONS 5.1 Soils Suitability and Stability Surficial topsoil materials (Stratum 1) may contain appreciable quantities of roots and organic matter, and should therefore be considered unsuitable for use as building and pavement section subgrade or as structural fill. Surface topsoils should be stripped from all structural areas during standard clearing and grubbing operations. Soils underlying the surficial topsoil deposits are primarily granular in nature and should generally be suitable for use as foundation and pavement section subgrade and as structural fill, pending adequate degrees of compaction. BET cautions that materials excavated from below groundwater level may retain excess water and therefore be difficult to compact, unless allowed to sufficiently drain prior to placement. The subgrade soils should provide for stable embankments with slopes as steep as 2 horizontal to 1 vertical (2:1). 5.2 Site Grading Encountered and estimated seasonal high groundwater levels suggest that some areas of the site may need to be raised 1 to 2 feet, or more, to allow for construction of structures and pavement sections. Fill materials used to raise the site to desired finish grades should consist of clean, granular soils with less than 20% passing No. 200 U.S. Standard Sieve. Generally, it appears that soils, other than surface topsoil deposits, excavated from stormwater retention ponds or other areas of the site, should be suitable for use as structural fill in building and pavement areas. BET cautions that materials excavated from below groundwater level may retain excess water and therefore be difficult to compact, unless allowed to sufficiently drain prior to placement. 5.3 Foundations Based on the results of this preliminary study, BET envisions that suitable support of 3 to 4 story hotels or similar commercial structures should be attainable with conventional shallow foundations, proportioned for allowable soil bearing pressures in the range of 2,500 to 3,500 PSF. However, actual foundation recommendations would be dependant on several earthwork considerations including adequate clearing of vegetation, stripping of surface organics and any other deleterious materials encountered, and compaction of native and fill soils. It appears that depth of stripping necessary to remove surface organics would be on the order of 6 inches throughout the majority of the probable development area. However, stripping to depths as much as 18 inches, or more, may be required in some areas, primarily those areas bordering the wetland area in the southern portion of the site. The required depth and degree -5-

9 of native soils compaction would be dependent on design grading and structural loading characteristics. BET envisions that the required depth of native soils compaction may be in the range of about 2 to 3 feet, while the required degree of compaction may be in the range of 95% to 98% of the materials Modified Proctor (ASTM D-1557) maximum dry density. Fill soils should be placed in loose lifts of about 8 to 16 inches and compacted to a similar degree. The suitability of conventional shallow foundations would also be dependent on the potential degrees of foundation settlement which might be expected. Considering the relatively firm nature of the shallow subsurface soils, and provided that adequate degrees of foundation subgrade soils compaction are achieved, BET envisions that foundation settlement can be kept well within tolerable limits. 5.4 Pavement Sections BET envisions that suitable pavement sections should be attainable with either asphaltic concrete surface course over limerock or crushed concrete base and stabilized subgrade (LBR 40), or Portland Cement concrete over stabilized subgrade (LBR 30). Required pavement section layer thicknesses would be dependent on anticipated vehicle frequencies and wheel loadings. For asphalt pavement sections, BET envisions minimum asphalt thickness of 1.5 inches, minimum base thickness of 6 inches, and minimum stabilized subgrade thickness of 6 inches. Minimum concrete thickness is envisioned to be 6 inches over minimum stabilized subgrade thickness of 8 inches. The suitability of asphalt pavement sections constructed with limerock base course would be dependent on design finish pavement grades. If limerock base is desirable, it is recommended that finish pavement grades be set a minimum of 24 inches above seasonal high groundwater level. If lower finish grades are anticipated, the use of soil-cement base or crushed concrete base in lieu of limerock should be considered. 5.5 Stormwater Retention Considering the potential for seasonal high groundwater levels near existing ground surface, and the anticipated low permeability of subsurface soils, BET envisions that the most effective means of stormwater management would likely be through the use of wet retention / detention ponds. Depending upon finish grades and the characteristics of fill soils used, small isolated dry retention ponds may work in some areas of the site. -6-

10 APPENDIX A BORING LOCATION PLAN SOIL PROFILES SOILS LEGEND

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