Sydney Road Reclaimed Water Main, Plant City, Florida. Prepared for: Jones Edmunds & Associates, Inc.

Transcription

1 . Geotechnical Report Sydney Road Reclaimed Water Main, Plant City, Florida Prepared for: Jones Edmunds & Associates, Inc. Prepared by: MADRID ENGINEERING GROUP, INC Hwy 60 E. Bartow, FL Project No December 2009

2 CERTIFICATIONS Engineering Certification I hereby certify that I am a registered professional engineer in the State of Florida practicing with Madrid Engineering Group, Inc. under license number EB issued by the Florida Department of Business and Professional Regulation and the Board of Professional Engineers. I certify that I, or others under my direct supervision, have prepared the geotechnical engineering evaluations, findings, opinions and conclusions represented in this report. Sydney Road Reclaimed Water Main Geotechnical Investigation MEG # 6811 SIGNATURE: NAME: Mathew Chinault, P.E. LICENSE #: DATE:

3 TABLE OF CONTENTS 1.0 INTRODUCTION Site Location and Description Soil Survey Map Review GEOTECHNICAL INVESTIGATION Hand Auger Borings Standard Penetration Test Borings Laboratory Testing SUBSURFACE CONDITIONS Description of Soils Water Table Information CONCLUSIONS SITE PREPARATION AND EARTHWORK Clearing and Stripping Excavation and Shoring Dewatering Settlement Monitoring Program Pipe Bedding and Backfilling Unsuitable Materials TRENCHLESS CROSSINGS SHALLOW SPREAD FOUNDATIONS BASIS FOR RECOMMENDATIONS FIGURES Figure 1 Figure 2 Figure 3 Site Location Map Soil Survey Maps Boring location Maps APPENDICES Appendix A Boring Logs Appendix B Laboratory Test Data

4 1.0 INTRODUCTION This report presents the results of a geotechnical investigation performed to provide soils information to the design engineers in support of the Sydney Road Reclaimed Water Project. This project consists of new reclaimed water main that will roughly follow Sydney Road / Woodrow Wilson Street North and the surrounding areas in Plant City. The design engineer for this project, Jones Edmunds & Associates, Inc. (Jones Edmunds), is designing the project for the owner (The City of Plant City). 1.1 Site Location and Description The includes the installation of a reclaimed water main along portions of Sydney Road, Old Sydney Road, Airport Road, Woodrow Wilson Street, and other surrounding local roads as Shown in Figure 1. We understand that the new pipeline will typically be constructed to invert depths of 5 to 10 feet below existing grade. Greater depths may be required at some roadway and utility crossings due to conflicts with utilities and the requirements of special construction methods. Trenchless crossings are proposed at areas listed in section 4.2 of this report and invert depths generally range from 5 to 13 feet bgs in these areas. 1.2 Soil Survey Map Review Soils data from the Soil Survey of Hillsborough County, Florida (USDA-SCS) were reviewed as part of the investigation. Portions of the map have been provided for each sub-project in Figure 2. Mapped soil groups in the vicinity of the project according to the Hillsborough County Soil Survey include: 5 Basinger, Holopaw, and Samsula soils, depressional. The soils in this map unit are nearly level and very poorly drained. They are in swamps and depressions on the flatwoods. Generally, Basinger soil is along the exterior of swamps or in shallow depressions. Holopaw and Samsula soils are in the interior areas of the swamps or in deeper depressions. Undrained areas are frequently ponded for very long periods. The slope is 0 to 2 percent. Typically, the surface layer of Basinger soil is black fine sand about 7 inches thick. The subsurface layer, to a depth of about 28 inches, is gray fine sand. The subsoil, to a depth of about 42 inches, is brown and grayish brown fine sand. The substratum to a depth of about 80 inches is light brownish gray fine sand. Similar soils included in mapping, in some areas, have a surface layer of mucky fine sand, and it is more than 7 inches thick. Typically, the surface layer of Holopaw soil is black mucky fine sand about 6 inches thick. The upper part of the subsurface layer, to a depth of about 12 inches, is dark gray fine sand. The middle part, to a depth of about 42 inches, is light gray fine sand. The lower part, to a depth of about 52 inches, is grayish brown fine sand. The upper part of the subsoil, to a depth of about 64 inches, is grayish brown fine sand. The lower part to a depth of about 80 inches is gray, mottled sandy loam. Similar soils included in mapping, in some areas, have a black surface layer more than

5 10 inches thick. Typically, the upper part of the surface tiers of Samsula soil is black muck about 10 inches thick. The lower part, to a depth of about 34 inches, is dark reddish brown muck. The layer below the organic material, to a depth of about 40 inches, is black fine sand. The underlying material to a depth of 80 inches is light brownish gray fine sand. Similar soils included in mapping, in some areas, have organic material that is more than 51 inches thick. In most years, the undrained areas in this map unit are ponded for about 6 months. Permeability is rapid in Basinger and Samsula soils. It is rapid in the surface and subsurface layer of Holopaw soil and moderately slow or moderate in the subsoil. The available water capacity is low in Basinger soil, low or moderate in Holopaw soil, and high in Samsula soil. 7 Candler fine sand, 0 to 5 percent slopes. This soil is nearly level to gently sloping and excessively drained. It is on the uplands. Typically, this soil has a surface layer of dark gray fine sand about 6 inches thick. The upper part of the subsurface layer, to a depth of about 35 inches, is light yellowish brown fine sand. The middle part, to a depth of about 72 inches, is very pale brown fine sand. The lower part to a depth of about 80 inches is a mixture of very pale brown fine sand and strong brown loamy sand lamellae that are about one-sixteenth to one-quarter of an inch thick and 2 to 6 inches long. In some places, similar soils included in the mapped areas do not have lamellae in the lower part of the subsurface layer. Other similar soils, in some areas, have a subsurface layer that consists of 5 to 10 percent silt and clay; and some similar soils also included in mapping, in some of the lower parts of the landscape, are well drained. A seasonal high water table is at a depth of more than 80 inches. Permeability is rapid. The available water capacity is very low. 25 Lake fine sand, 0 to 5 percent slopes. This soil is nearly level to gently sloping and excessively drained. It is on the uplands. Typically, this soil has a surface layer of dark grayish brown fine sand about 4 inches thick. The underlying material extends to a depth of about 80 inches. The upper 24 inches is strong brown fine sand. The next 40 inches is reddish yellow fine sand. The lower 12 inches is strong brown fine sand. Similar soils included in mapping, in some places, are gray or light gray in the lower part of the underlying material. Other similar soils, in some areas, consist of less than 5 percent silt and clay in the underlying material. The included similar soils, in some of the lower parts of the landscape, are well drained. A seasonal high water table is at a depth of more than 80 inches. Permeability is rapid. The available water capacity is very low or low. 2

6 29 Myakka fine sand. This soil is nearly level and poorly drained. It is on broad plains on the flatwoods. The slope is 0 to 2 percent. Typically, this soil has a surface layer of very dark gray fine sand about 5 inches thick. The subsurface layer, to a depth of about 20 inches, is gray fine sand. The upper part of the subsoil, to a depth of about 25 inches, is black fine sand. The middle part, to a depth of 30 inches, is dark reddish brown fine sand. The lower part, to a depth of about 38 inches, is brownish yellow fine sand. The upper part of the substratum, to a depth of about 55 inches, is very pale brown fine sand. The lower part to a depth of about 80 inches is dark grayish brown fine sand. Similar soils included in mapping, in some areas, have a surface layer that is more than 8 inches thick. Other similar soils, in some places, have a subsoil within 20 inches of the surface, and some included similar soils have a subsoil at a depth of more than 30 inches or have a brown or dark brown subsoil, or both. In most years, a seasonal high water table fluctuates from the soil surface to a depth of 10 inches for 1 to 4 months and recedes to a depth of 40 inches during prolonged dry periods. Permeability is rapid in the surface and subsurface layers, moderate or moderately rapid in the subsoil, and rapid in the substratum. The available water capacity is low. 33 Ona fine sand. This soil is nearly level and poorly drained. It is on broad plains on the flatwoods. The slope is 0 to 2 percent. Typically, this soil has a surface layer of very dark gray fine sand about 4 inches thick. The upper part of the subsoil, to a depth of about 8 inches, is black fine sand. The lower part, to a depth of about 22 inches, is very dark brown fine sand. The substratum to a depth of about 80 inches is light gray fine sand. Similar soils included in mapping, in some areas, have a gray or dark gray subsurface layer. Other similar soils, in some places, have a subsoil at a depth of more than 10 inches. In most years, a seasonal high water table fluctuates from the soil surface to a depth of 10 inches for more than 2 months and recedes to a depth of 10 to 40 inches for 6 months or more. Permeability is rapid in the surface layer, moderate or moderately rapid in the surface layer, moderate or moderately rapid in the subsoil, and rapid in the substratum. The available water capacity is low or moderate. 41 Pomello fine sand, 0 to 5 percent slopes. This soil is nearly level to gently sloping and moderately well drained. It is on low ridges on the flatwoods. Typically, this soil has a surface layer of very dark gray fine sand about 3 inches thick. The subsurface layer, to a depth of about 43 inches, is light gray fine sand. The upper part of the subsoil, to a depth of about 46 inches, is dark brown fine sand. The lower part, to a depth of about 55 inches, is brown fine sand. The substratum to a depth of about 80 inches is grayish brown fine sand. Similar soils included in mapping, in some places, have a subsoil within 30 inches of the surface. Other similar soils, in some areas, have 3

7 a subsoil at a depth of more than 50 inches, and similar soils, in some of the lower parts of the landscape, are somewhat poorly drained. In most years, a seasonal high water table is at a depth of 24 to 40 inches for 1 to 4 months and recedes to a depth of 40 to 60 inches during dry periods. Permeability is very rapid in the surface and subsurface layers, moderately rapid in the subsoil, and rapid in the substratum. The available water capacity is very low. 46 St. Johns fine sand. This soil is nearly level and poorly drained. It is on low-lying plains on the flatwoods. The slope is 0 to 2 percent. Typically, the upper part of the surface layer is black fine sand about 6 inches thick. The lower part, to a depth of about 12 inches, is very dark grayish brown fine sand. The subsurface layer, to a depth of about 29 inches, is light brownish gray fine sand. The upper part of the subsoil, to a depth of about 36 inches, is black fine sand. The middle part, to a depth of about 46 inches, is dark reddish brown fine sand. The lower part, to a depth of about 50 inches, is dark yellowish brown fine sand. The substratum to a depth of about 80 inches is light brownish gray fine sand. Similar soils included in mapping, in some areas, have a surface layer that is less than 10 inches thick. Other similar soils, in some places, do not have a subsurface layer; and in some places these included soils have a subsoil that is brown or dark brown. In most years, a seasonal high water table fluctuates from the soil surface to a depth of 15 inches for 2 to 6 months and recedes to a depth of 15 to 30 inches during prolonged dry periods. Permeability is rapid in the surface and subsurface layers, moderately slow or moderate in the subsoil, and rapid in the substratum. The available water capacity is moderate. 47 Seffner fine sand. This soil is nearly level and somewhat poorly drained. It is on the rims of depressions and on broad, low ridges on the flatwoods. The slope is 0 to 2 percent. Typically, this soil has a surface layer that is about 13 inches thick. The upper 9 inches is very dark gray fine sand, and the lower 4 inches is very dark gray, mottled fine sand. A transitional layer, to a depth of about 21 inches, is dark gray, mottled fine sand. The upper part of the underlying material, to a depth of about 35 inches, is very pale brown, mottled fine sand. The middle part, to a depth of about 63 inches, is light gray, mottled fine sand. The lower part to a depth of 80 inches is white, mottled fine sand. Similar soils included in mapping, in some areas, have a surface layer that is less than 10 inches thick. Other similar soils, in some places, have a surface layer that is more than 24 inches thick; and in some of the higher parts of the landscape, the included similar soils are moderately well drained. In most years, a seasonal high water table is at a depth of 20 to 40 inches for 2 to 6 months and recedes to a depth of less than 60 inches during prolonged dry periods. Permeability is rapid. The available water capacity is low or moderate. 4

8 60 Winder fine sand, frequently flooded. This soil is nearly level and poorly drained. It is on the flood plains. This soil is flooded for very long periods following prolonged intense rain. Many areas are isolated by stream channels and steep escarpments. The slope is 0 to 2 percent. Typically, this soil has a surface layer of black fine sand about 5 inches thick. The subsurface layer, to a depth of about 14 inches, is grayish brown fine sand. The upper part of the subsoil, to a depth of about 18 inches, is gray sandy clay loam and white fine sand. The lower part of the subsoil, to a depth of about 34 inches, is grayish brown, mottled sandy clay loam. The substratum, to a depth of about 80 inches, is light brownish gray fine sand. Similar soils included in mapping, in some areas, have a subsoil at a depth of more than 20 inches. Other similar soils, in some areas, have a surface layer that is more than 8 inches thick or is stratified, or both. In some places are similar soils that have a thin, discontinuous stratum of fragmented limestone in the upper part of the subsoil. In most years, a seasonal high water table fluctuates from the soils surface to a depth of about 10 inches for 2 to 6 months. Permeability is rapid in the surface and subsurface layers, slow or very slow in the subsoil, and rapid in the substratum. The available water capacity is moderate. 61 Zolfo fine sand. This soil is nearly level and somewhat poorly drained. It is on broad, low ridges on the flatwoods. The slope is 0 to 2 percent. Typically, this soil has a surface layer of very dark gray fine sand about 3 inches thick. The upper part of the subsurface layer, to a depth of about 15 inches, is grayish brown, mottled fine sand. The middle part, to a depth of about 51 inches, is light gray, mottled fine sand. The lower part, to a depth of about 60 inches, is grayish brown fine sand. The subsoil to a depth of about 80 inches is dark brown fine sand. Similar soils included in mapping, in some places, have a subsoil that extends to a depth of more than 80 inches. Other similar soils, in some of the higher parts of the landscape, are moderately well drained. In most years, a seasonal high water table is at a depth of 24 to 40 inches for more than 2 to 6 months and recedes to a depth of 60 inches during prolonged dry periods. Permeability is rapid in the surface and subsurface layers and moderate in the subsoil. The available water capacity is low. It is noted that some soil units such as 5 and 60 have a greater chance of encountering unsuitable soils containing either high organic or clay content. It is expected that soils will vary with mapped units and actual soils encountered in the field should be evaluated for suitability during construction. 5

9 2.0 GEOTECHNICAL INVESTIGATION 2.1 Hand Auger Borings Sixty-four hand auger borings, labeled HA-1, HA-2, etc., were completed during site visits between May 4 and December 18, 2009, at the locations shown on Figure 3. The borings were advanced to depths ranging from 4 to 8 feet below ground surface (bgs) using a bucket auger, and were completed in general accordance with ASTM D Hand auger boring profiles are included in Appendix A. Some hand augers were given alphabetical designations because they were added during the drilling portion of the investigation in an effort to better delineate unsuitable soils in some areas. 2.2 Standard Penetration Test Borings Twelve standard penetration test (SPT) soil borings were completed during site visits on May 7, May 12, and May 15, The borings were completed to a depth of 20 feet bgs along portions of the proposed alignment of the reclaimed water main at locations designated by Jones Edmunds where trenchless crossings are expected at the locations shown in Figure 3. The borings were completed in accordance with ASTM Standard D-1586 using the mud-rotary drilling method. Soil samples were collected from each borehole using a 1.4-inch I.D. split-spoon sampler driven with a 140-pound slide hammer falling a distance of 30 inches. An engineering technician familiar with soil classification and field evaluations logged the borings in the field and placed samples in sealed containers and returned them to MEG s laboratory for further classification. Upon completion, the boreholes were filled with cement grout and / or bentonite hole plug. Boring profiles are included in Appendix A. 2.3 Laboratory Testing Laboratory tests for natural water content (ASTM D2216) and organic content (ASTM D 2974) were performed on selected samples from the borings to verify the visual and tactile soil classifications. Laboratory test reports are included in Appendix B. The laboratory tests indicate variable organic contents in sediments at depths from 2 feet to 10 feet bgs in the samples tested. Percent organic for samples tested ranged from 0.6 to 7.3 percent. 6

10 3.0 SUBSURFACE CONDITIONS 3.1 Description of Soils The soil strata encountered across this site generally consists of the following strata: Sand Stratum (USCS = SP) The surficial strata in all of the borings were generally loose to medium dense sand. This stratum made up the bulk of the soils encountered in this project. This stratum consists of slightly organic topsoil (3 to 10 inches at the surface) and fine grained sand. The non-organic portion of this unit will be suitable for use as pipe bedding, structural backfill, and common backfill. This unit has a unified soil classification (USCS) of SP (poorly graded sand). Slightly Clayey Sand and Slightly Silty Sand Strata (USCS = SP-SC, SP-SM) Sporadic slightly clayey sand and slightly silty sand units were observed at varying depths in the borings. These lenses ranged from loose to dense with cementation in some cases and fines content less than 12%. These units will be slightly more difficult to use as backfill and will require a greater effort to excavate and compact. These units are not suitable for pipe bedding but are suitable for structural backfill and common backfill. These units have a USCS designation of SP-SC (slightly clayey sand) and SP-SM (slightly silty sand). Clayey Sand Stratum (USCS = SC) Clayey sand was encountered in some of the borings and was generally medium dense to dense. These units were generally found at depths greater than 12 to 17 feet bgs in some of the deep SPT borings and shallower in very few of the hand auger borings. This stratum consists of fine grained sand with less than 50% clay. These units will be significantly more difficult to use as backfill and will require a much greater effort to excavate and compact. This unit does not meet the requirement for pipe bedding or structural fill in its natural state. However, if mixed with clean sands so that the fines content is reduced to below 12%, these soils may be used as structural backfill. These soils may already have less than 35% fines; if not, they may be mixed with clean sand so that the fines content is below 35% so they may be used as common fill. These units have a USCS designation of SC (clayey sand). Clay Stratum (USCS = CL) Clay was encountered in a limited number of the borings and was generally soft to firm. These units were generally found at depths greater than 17 feet bgs in some of 7

11 the deep SPT borings. This stratum consists of cohesive clay with less than 50% sand. This unit will require a greater effort to excavate and is not recommended for use as pipe bedding, structural backfill, or common backfill. These units have a USCS designation of CL (clay). Organic Soil Stratum (USCS = OL, and SP-SM or SM with organics notation) Silty soils with varying organic contents were observed in some of the borings. This unit can be expected to decay and consolidate excessively over time. This unit is unacceptable for use as pipe bedding, structural backfill, or common backfill. This unit has a USCS designation of OL (organic silt) or in some cases slightly silty sand (SP- SM) or silty sand (SM) with an organic content notation on the boring logs. In general, any soil type with an organic content in excess of 2 percent is not suitable for use as pipe bedding and greater than 5 percent is not suitable for use as common fill or structural fill. 3.2 Water Table Information The surficial water table elevations recorded, at the time of the investigation, ranged from greater than 15 feet bgs to as shallow as 5 feet bgs. Specific water table information is provided on the specific boring logs in Appendix A. 4.0 CONCLUSIONS The following conclusions and recommendations are based on our understanding of the proposed project, the data obtained from the soil borings, experience with similar conditions, and generally accepted principles and practices of geotechnical engineering. Borings were performed at generally 500-ft intervals and soil conditions between actual borings will also vary. Much of the proposed alignment falls along generally suitable soil conditions. Some organics were encountered at noted places along the alignment. Preliminary pipeline design calls for a reclaimed water main to be installed at approximately 5 to 10 feet below existing grade. Assuming this invert depth, and based on the results of the boring program, the bases of trench excavations will typically expose loose to medium dense sand to slightly silty and slightly clayey sand. Due to the presence of shallow ground water in some portions of the alignment, shallow dewatering systems may be required to control ground water flow into trench excavations up to 10 feet deep. 8

12 Proposed crossings beneath roads, utilities, and railroads will require deeper excavations possibly up to 15 feet below the existing grade to support pipe installation utilizing trenchless methods such as either jack-and-bore (pipejacking) or directional drilling techniques. Minor appurtenant structures if required along the proposed pipeline alignment may generally be supported on shallow spread foundations. 4.1 SITE PREPARATION AND EARTHWORK Clearing and Stripping All construction areas should be cleared of any trees or scrub vegetation, pavements, and the topsoil stripped as necessary to remove roots and other deleterious material. Topsoil typically consists of fine sands with some silt and silty sands. Topsoil should be discarded or may be stockpiled for future reuse in landscape areas if desired Excavation and Shoring In general, the anticipated depth of trench excavations typically ranges from 5 to 10 feet below existing grade. Localized excavations up to 15 feet below existing grade may be required at proposed crossings of drainage ditches, existing buried utilities, railroads, and roadways. The bases of trench excavations will expose soil conditions that are likely to vary along the route. Based on the results of our boring program, materials at the base of trench excavations along most of the route are likely to range from relatively clean sands to slightly clayey sands. If encountered, all soft clays, silts and organic soils encountered at the bases of the trench excavations should be excavated to at least two feet below the design trench depth and replaced with pipe bedding material, placed and compacted as described later in this report. All excavations and shoring should conform to the Occupational and Safety Health Act (OSHA) requirements for Type C soils as described in Federal Register 29 CFR Part 1926 subpart P. Design of a shoring system is the responsibility of the selected contractor. A number of variable factors, such as nature and strength of excavated soils, depth of excavation and groundwater, proximity of adjacent structures, and economics of construction method, etc., will affect the choice of support method. 9

13 All vertical shoring or prefabricated trench lining systems should be continuous and maintained in place to assure adequate temporary stability during backfilling of the pipe trench as recommended subsequently. Excavated soils should not be stockpiled within 15 feet of the shored excavations, unless specific provisions for surcharge loading have been included in the design of the shoring system. The final decision on appropriate excavation methods and design of shoring systems is the responsibility of the contractor Dewatering Based upon groundwater levels encountered during our field exploration and depending upon the depth of excavation and time of year when construction is scheduled, it appears that groundwater will be a factor along the alignments of much of the project. The variability in soil conditions encountered likely will result in varied performance of dewatering systems. We recommend that, where necessary, a dewatering system be designed and installed to draw the groundwater table down to a minimum depth of three feet below the final excavated grade. For excavations up to 15 feet depth, depending on the local soil profile present, a shallow well-point system may be adequate for trenches and small excavations up to approximately 50 feet in plan dimension. Excavations in excess of 15 feet depth may require a multi-stage well-point system, deep wells or a single stage well-point installed from a reduced grade elevation to accomplish the recommended drawdown. The contractor should employ a registered professional engineer to design all shoring and dewatering systems Settlement Monitoring Program Some minor surface settlement may result from excavation and dewatering operations due to general soil deformation and the compression of loose or soft soils. These settlements and the risk of possible damage to adjacent structures could be minimized by using fully sheeted excavations and controlled recharge of groundwater outside the proposed excavation. Where necessary, a baseline survey and regular monitoring of roadway pavements, any settlement sensitive structures or utilities within 50 feet of any excavation or dewatering operations should be completed prior to construction Pipe Bedding and Backfilling Clean fine sands (SP) containing less than two percent passing the U.S. standard No. 200 sieve and less than four percent organic matter (as determined by 10

14 ASTM D-2974) may be used as select sand pipe bedding material. Suitable pipe bedding should be free of stones, gravel, organics, vegetation and other deleterious material, placed in uniform loose lifts not exceeding six inches thick and compacted to at least 98 percent of its maximum dry density as determined by AASHTO T-180 (Modified Proctor). Pipe bedding material should be placed within one foot above and below the pipe. Particular care needs to be exercised during pipe bedding placement and compaction around pipe elbows and curves. Loose bedding materials may subsequently compact in-service, if subjected to dynamic or vibrational loading due to surge pressures, resulting in excessive pipe deflections and possibly failure. Structural backfill material in trenches above or below the pipe bedding should consist of clean or slightly silty fine sand (SP or SP-SM) with less than 12 percent passing the U.S. Standard No. 200 sieve. Common backfill above or below the pipe bedding should consist of clean, silty or clayey sands with less than 35 percent passing the U.S. Standard No. 200 sieve. All backfill should have less than 5 percent organic matter and organic material should be well dispersed in the backfill. Common fill may be used in the trench outside of existing or proposed roadways, pavements or embankments. Structural fill should be used beneath roads, embankments or other structures. Structural and common fill placed above the pipe bedding should be graded and placed in loose lifts not exceeding 12-inches thick and compacted to at least 95 and 90 percent, respectively, of its maximum dry density as determined by AASHTO T-180. Prior to construction, a minimum of three bulk soil samples each, representative of anticipated bedding and backfill soils, should be obtained for gradation and compaction testing. Excavated spoil material intended for reuse as backfill will likely require moisture conditioning to permit adequate compaction. Shell or limerock base material under pavements should be compacted to 98 percent of the maximum dry density as per AASHTO T Unsuitable Materials Materials identified in this section are deemed to be unsuitable for use in one or more of the three identified backfill classifications and will likely require mixing with clean sand in order to be used for backfill on this project. Simply being identified in this section does not necessarily mean that the soils in question must be totally removed from the project and replaced with other soils. The soils identified herein likely must be properly characterized and used in appropriate backfill classification areas. These soils likely will require mixing with clean sands to meet specific backfill requirements, or if none of the above is possible, removed from the site. Small layers or lenses of soil, especially those involving topsoil at the surface of borings, were not listed in this section 11

15 because the general requirements for topsoil removal plus any efforts to excavate and replace them along with the surrounding clean fill will likely be sufficient to dilute the percentages of organics or fines to within the acceptable tolerances without additional effort. Soils deemed unsuitable for use as one or more classifications of backfill as defined in this investigation in their current condition found on this project were identified in the following areas: N. Mobley Street across Highway 92 (Borings SPT-1 and SPT-2). The areas investigated as possible starting and ending points for a trenchless crossing (SPT-1 and SPT-2) encountered slightly clayey sand with organics and slightly silty sand with organics from 2 to 6 feet bgs in both borings. This area was bound to the north by HA-5 and to the west by HA-6 both of which did not encounter unsuitable materials. The soils in this depth range of the proposed excavations in this area do not appear to be suitable for use as pipe bedding on this project due to the presence of excessive fines and possible excessive organics. So long as these soils are properly inspected and or mixed with clean sand, if necessary, these soils may be suitable as use in structural or common fill. Woodrow Wilson Street across Railroad Tracks (Borings SPT-5 and SPT-6) The areas investigated as possible starting and ending points for a trenchless crossing (SPT-5 and SPT-6) encountered slightly silty sand with organics from 8 to 12 feet bgs in boring SPT-5 and organic silt from 4 to 12 feet bgs in boring SPT-6. This area was bound to the north by boring HA-23A and to the south by boring HA-24. The soils in the depth ranges listed for each representative proposed excavation area do not appear to be suitable for use as pipe bedding on this project due to the presence of excessive fines and/or possible excessive organics. So long as these soils are properly inspected and or mixed with clean sand, if necessary, these soils may be suitable as use in structural or common fill. Sydney Road across Railroad Tracks (Borings SPT-11 and SPT-12) The areas investigated as possible starting and ending points for a trenchless crossing (SPT-11 and SPT-12) encountered organic silt from 8 to 12 feet bgs in boring SPT-11 and from 2 to 6 feet bgs in boring SPT-12. Both borings encountered clay from 17 to 20 feet bgs. The organic soils in the depth ranges listed for each representative proposed excavation area do not appear to be suitable for use as pipe bedding on this project due to the presence of excessive fines and/or possible excessive organics. So long as these soils are properly inspected and or mixed with clean sand, if necessary, these soils may be suitable as use in structural or common fill. The clayey soils encountered below 17 12

16 feet bgs in both borings will not be suitable for use as backfill in any of the proposed backfill categories. HA-27 The soils encountered below 3 feet bgs in boring HA-27 encountered slightly silty sand with organics. This appears to be an isolated pocket of organics surrounding this boring as no organics were identified in either of the surrounding borings (HA-27B or HA-27C). The soils in the depth range listed for this area do not appear to be suitable for use as pipe bedding on this project due to the presence of excessive fines and/or possible excessive organics. So long as these soils are properly inspected and or mixed with clean sand, if necessary, these soils may be suitable as use in structural or common fill. HA30A, HA-30B, and HA-30E The soils encountered below 5 feet bgs in borings HA-30A and HA-30B as well as the soils encountered below 3 feet bgs in boring HA-30E consisted of organic silt and sand with buried plant and wood debris. This area is bound by boring HA-30C to the east and boring HA-30F to the west both of which do not indicate organic soils. The soils in the depth ranges listed for this area do not appear to be suitable for use as any of the three backfill categories on this project due to the presence of excessive fines and/or excessive organics. These soils should be removed and replaced to a depth of at least 1 foot below the bottom of the pipe. Other Considerations Classification of soils as suitable for use as backfill should be monitored continuously during construction because the initial spacing of borings along the alignment of the pipeline (approximately 500 feet on center) may not have been sufficient to identify small pockets of organics or fines (less than 500 feet in length) on the project. Due to the spacing of the borings and variability of the soils encountered MEG recommends a multiple of at least 2.0 be applied to estimated volumes of layers of slightly silty sand, slightly clayey sand, slightly organic sand, and clayey sand that will need to be used in appropriate depths or mixed appropriately as detailed above to be considered suitable for backfill applications. 4.2 TRENCHLESS CROSSINGS Trenchless crossings are proposed for six areas as detailed below. Beginning and ending points for trenchless crossings are estimated by SPT boring locations and proposed depths range from approximately 5 to 13 feet bgs for most crossings. Soil conditions appear to be favorable for the use of trenchless methods for road crossings. 13

17 Either mechanical excavation using rotary drilling equipment and mud stabilization (i.e. directional drilling or microtunneling) or mechanical excavation within a steel or concrete casing pipe installed by pipe jacking (auger boring) should be suitable construction methods. N. Mobley Street across Highway 92 This intersection was investigated with borings SPT-1 and SPT-2. Slightly clayey sand with organics and slightly silty sand with organics was encountered in both borings from approximately 2 to 6 feet bgs. The organic layer appears to be relatively uniform across this intersection at this depth with organic contents ranging from 2 to 5 percent. The water table was encountered at approximately 5 feet bgs at this location. N. Woodrow Wilson Street across W. Reynolds Street This intersection was investigated with borings SPT-3 and SPT-4. Loose to medium dense sand was encountered in the upper 12 feet bgs of both borings at this intersection. The water table was encountered at approximately 12 to 18 feet bgs at this location. A medium dense clayey sand layer was encountered below 12 feet bgs in both borings. Woodrow Wilson Street across Railroad Tracks This intersection was investigated with borings SPT-5 and SPT-6. Organic silt was encountered from 8 to 12 feet bgs in boring SPT-5 and slightly silty sand with organic were encountered from 4 to 12 feet bgs in boring SPT-6. The organic layers have organic contents ranging from 2 to 6 percent. The water table was encountered at approximately 5 to 8 feet bgs at this location. Very dense slightly silty sand was encountered below 12 feet bgs in both borings. Woodrow Wilson Street across Sammonds Road This intersection was investigated with borings SPT-7 and SPT-8. Organic staining was observed in boring SPT-8 however the organic content was very low (Organic Content = 0.6%). The water table was encountered at approximately 9 feet bgs at this location. Very loose sands were encountered at 8 to 10 feet bgs in both borings however dense to very dense sands were encountered near 15 feet bgs also in both borings. 14

18 Airport Road and Old Sydney Road This area was investigated with borings SPT-9 and SPT-10. Loose to medium dense sand was encountered in the upper 10 to 12 feet bgs of the borings at this area. The water table was encountered at approximately 12 feet bgs at this location. Medium dense slightly clayey to clayey sand was encountered near 15 feet bgs in both borings but it is noted that the sands grade very loose to loose near 20 feet bgs. Sydney Road across Railroad Tracks This intersection was investigated with borings SPT-11 and SPT-12. Organic silt was encountered from 8 to 12 feet bgs in boring SPT-11 and from 2 to 6 feet bgs in boring SPT-12. The organic layers have organic contents ranging from 3 to 5 percent. The water table was encountered at approximately 5 to 6 feet bgs at this location. Very dense to dense sands were encountered at varying depths in each boring and soft to firm clay was encountered below 17 feet bgs in both borings. 4.3 SHALLOW SPREAD FOUNDATIONS If minor appurtenant structures are required along the proposed pipeline length, we recommend that these be supported on shallow spread foundations. Shallow foundations up to 15 feet maximum depth may be constructed in densified native sands or compacted granular backfill after complete removal and replacement of all organic or locally soft subsoils. Where footings are to be constructed in natural granular soils, compaction operations should be carried out at the proposed foundation subgrade elevation. Granular subsoils within the upper 12 inches of the foundation subgrade should be compacted to at least 95 percent of the AASHTO T-180 (ASTM D- 1557) maximum dry density. All below grade structures should be designed to resist uplift caused by buoyancy. We recommend a design water table at the ground surface be assumed for all uplift calculations. Uplift forces can be resisted by either adding dead weight to the structure or mobilizing the weight of the surrounding soil by extending the footing width further beyond the structure. 15

19 5.0 BASIS FOR RECOMMENDATIONS The recommendations provided are based in part on project information provided to us and only apply to the specific project and site discussed in this report. If the project information section in this report contains incorrect information, or if additional information is available, Madrid Engineering Group, Inc. can be retained to review the corrected or additional information. We can modify our recommendations, if appropriate based on new information provided. The recommendations and findings herein are based on the exploratory borings drilled at the site and our professional judgment. The soil conditions indicated within this report are accurate with respect to the location and extent that the soil borings were completed. Because soils vary from place to place, and with depth, subsurface conditions different from those encountered in our exploration may exist. Variability is even more likely at this site because of its previous mining and reclamation land use. This investigation was completed in accordance with generally accepted standards of practice. No warranty regarding this investigation is intended, nor should any be inferred. We recommend that this complete report be provided to the various design team members (e.g., structural engineer), and the appropriate contractors. Potential contractors should be informed of this report in the Instructions to Bidders section of the bid documents. 16