GEOTECHNICAL INVESTIGATION KIPP JOURNEY MODULAR CAMPUS KIPP WAY HOUSTON, TEXAS. Reported to KIPP Texas Public Schools Houston, Texas

Transcription

1 GEOTECHNICAL INVESTIGATION KIPP JOURNEY MODULAR CAMPUS KIPP WAY HOUSTON, TEXAS Reported to KIPP Texas Public Schools Houston, Texas by Aviles Engineering Corporation 5790 Windfern Houston, Texas REPORT NO. G December 2018

2 December 28, Windfern Road Houston, Texas Tel: (713) Fax: (713) Mr. Terry Hawkins KIPP Texas Public Schools KIPP Way Houston, Texas Reference: Geotechnical Investigation KIPP Journey Modular Campus KIPP Way Houston, Texas AEC Report No. G Dear Mr. Hawkins, Aviles Engineering Corporation (AEC) is pleased to present this report of the results of our geotechnical investigation for the above referenced project. The terms and conditions of the project were authorized via Service Contract between KIPP Texas, Inc. and AEC, by Mr. Bradley Welter of KIPP Texas, Inc. The project scope is based upon AEC Proposal No. G R2, dated December 3, AEC appreciates the opportunity to be of service to you. Please call us if you have any questions or comments concerning this report or when we can be of further assistance. Respectfully submitted, Aviles Engineering Corporation (TBPE Firm Registration No. F-42) Wilber L. Wang, P.E. 12/28/2018 Project Engineer Reports Submitted: 1 KIPP Texas Public Schools (electronic) Z:\ENGINEERING\REPORTS\2018\G KIPP JOURNEY MODULAR CAMPUS - KIPP TEXAS PUBLIC SCHOOLS (JACOB)\G DOCX

3 TABLE OF CONTENTS 1.0 INTRODUCTION Project Description Purpose and Scope SUBSURFACE EXPLORATION LABORATORY TESTING SITE CONDITIONS Subsurface Conditions Hazardous Materials Subsurface Variations ENGINEERING ANALYSIS AND RECOMMENDATIONS Modular Buildings Spread Footings Subgrade Preparation Ground Anchors Pavement Rigid Pavement Pavement Subgrade Fill Requirements Lime Stabilized Clay Select Fill General Fill CONSTRUCTION CONSIDERATIONS Site Preparation and Grading Groundwater Control Construction Monitoring GENERAL LIMITATIONS ATTACHMENTS Plate 1 Vicinity Map Plate 2 Boring Location Plan Plates 3 and 4 Boring Logs - AEC Report G171-11, B-1 and B-2 Plates 5 to 9 Boring Logs, B-3 to B-7 Plate 10 Key to Symbols Plate 11 Classification of Soils for Engineering Purposes Plate 12 Terms Used on Boring Logs Plate 13 ASTM & TXDOT Designation for Soil Laboratory Tests

4 GEOTECHNICAL INVESTIGATION KIPP JOURNEY MODULAR CAMPUS KIPP WAY HOUSTON, TEXAS 1.0 INTRODUCTION 1.1 Project Description This report presents the results of a geotechnical investigation performed by Aviles Engineering Corporation (AEC) for the KIPP Texas Public School s proposed Journey Modular Campus, to be located at KIPP Way (to the immediate west of the existing KIPP Houston High School campus), in Houston, Texas. A vicinity map is presented on Plate 1 in the Attachments. Based on a site plan prepared by Gensler, AEC understands that the proposed campus includes 4 modular campus buildings, with Buildings A through C each having an area of 11,300 square feet and Building D having an area of 1,728 square feet, plus driveways and parking areas. 1.2 Purpose and Scope The purpose of this geotechnical investigation is to evaluate the subsurface soil and ground water conditions at the project site and to develop geotechnical engineering recommendations for design and construction of the modular buildings and pavement. The scope of this geotechnical investigation is summarized below: 1. Drilling and sampling five soil borings (Borings B-3 through B-7) ranging from 5 to 10 feet below existing grade; 2. Performing soil laboratory testing on selected soil samples; 3. Engineering analyses and recommendations for foundation types, bearing depth, allowable bearing capacity, ground anchors, and subgrade preparation for the modular buildings; 4. Engineering analyses and recommendations for driveways and parking areas, including concrete pavement thickness design and subgrade preparation; 5. Recommendations for building foundations and pavement construction. 2.0 SUBSURFACE EXPLORATION Subsurface conditions at the site were investigated by drilling a total of five new borings (Borings B-3 through B-7) ranging from 5 to 10 feet below existing grade. The total drilling footage was 40 feet. AEC also performed two soil borings (Borings B-1 and B-2, AEC Report G171-11, dated September 8, 2011) for the concession building located to the south of the modular buildings. These borings have also been incorporated into this 1

5 report, for reference. Boring locations were marked by AEC in the field using a handheld GPS unit. The approximate boring locations (include existing borings) are shown on the attached Boring Location Plan on Plate 2, in the Attachments. Borings B-3 through B-7 were drilled using a buggy-mounted drill rig and were advanced using dry auger method. Undisturbed samples of cohesive soils were obtained from the borings by pushing 3-inch diameter thin-wall, seamless steel Shelby tube samplers in accordance with ASTM D Strength of the cohesive soils was estimated in the field using a hand penetrometer. The undisturbed samples of cohesive soils were extruded mechanically from the core barrels in the field and wrapped in aluminum foil; all samples were sealed in plastic bags to reduce moisture loss and disturbance. The samples were then placed in core boxes and transported to the AEC laboratory for testing and further study. After completion of drilling, the boreholes were backfilled with bentonite chips. Details of the soils encountered in the borings (including Borings B-1 and B-2) are presented on Plates 3 through 9, in the Attachments. 3.0 LABORATORY TESTING Soil laboratory testing for Borings B-3 through B-7 was performed by AEC personnel. Samples from the borings were examined and classified in the laboratory by a technician under supervision of a geotechnical engineer. Laboratory tests were performed on selected soil samples in order to evaluate the engineering properties of the foundation soils in accordance with applicable ASTM Standards. Atterberg limits, moisture contents, percent passing a No. 200 sieve, sieve analysis, and dry unit weight tests were performed on representative samples to establish the index properties and confirm field classification of the subsurface soils. Strength properties of cohesive soils were estimated by means of unconfined compression (UC) tests performed on undisturbed samples. The test results are presented on their representative boring logs. A key to the boring logs, classification of soils for engineering purposes, terms used on boring logs, and reference ASTM Standards for laboratory testing are presented on Plates 10 through 13, in the Attachments. 4.0 SITE CONDITIONS 4.1 Subsurface Conditions Soil strata encountered in our borings are summarized below; Borings B-1 and B-2 are included for reference. 2

6 Boring Depth (feet) Description of Stratum B Fill: hard, Sandy Lean Clay (CL), with calcareous nodules, roots, and ferrous stains 2-8 Hard, Sandy Lean Clay (CL), with calcareous nodules and ferrous stains 8-18 Firm to very stiff, Fat Clay (CH), with calcareous nodules Lean Clay with Sand (CL), with abundant silt and sand partings B Fill: hard, Sandy Lean Clay (CL), with calcareous nodules and brick pieces 2-20 Firm to hard, Lean Clay with Sand (CL), with calcareous nodules and ferrous stains B Fill: very stiff, Sandy Lean Clay (CL), with abundant silt partings 3-10 Stiff to hard, Lean Clay (CL) B Fill: very stiff, Lean Clay with Sand (CL), with fat clay pockets and silty sand pockets 2-10 Stiff to hard, Lean Clay (CL) B Fill: very stiff to hard, Lean Clay with Sand (CL) 3-5 Fill: hard, Lean Clay (CL), with silt and fat clay pockets 5-10 Very stiff to hard, Lean Clay (CL) B Fill: very stiff, Lean Clay with Sand (CL), with calcareous nodules, silty sand partings, and roots 1-5 Hard, Sandy Lean Clay (CL), with silty sand partings and calcareous nodules B Fill: stiff, Lean Clay with Sand (CL), with fat clay pockets and calcareous nodules 2-4 Fill: hard, Sandy Lean Clay (CL), with silty sand partings 4-5 Hard, Sandy Lean Clay (CL), with calcareous nodules Details of the soils encountered during drilling are presented on the boring logs. The cohesive soils (both fill and natural) encountered in the borings have Liquid Limits (LL) ranging from 20 to 57 and Plasticity Indices (PI) ranging from 8 to 35. In general, the cohesive soils encountered in the borings have slight to high expansive potential (see Plate 11 in the Attachments). The cohesive soils encountered are classified as CL and CH type soils and the granular soils encountered as classified as SC type soils in accordance with ASTM D Groundwater: A summary of groundwater levels encountered in the borings is presented on Table 1. Groundwater depths from Borings B-1 and B-2 are also included in Table 1 for reference purposes. 3

7 Boring No. Date Drilled Table 1. Groundwater Depths in Borings Boring Depth (ft) Groundwater Depth in Boring (ft) Boring Cave-in Depth (ft) B-1 8/25/ (Drilling) 14 (Complete) - B-2 8/25/ (Drilling) 17 (Complete) - B-3 12/7/ Dry (Drilling) - B-4 12/7/ Dry (Drilling) - B-5 12/7/ Dry (Drilling) - B-6 12/7/ Dry (Drilling) - B-7 12/7/ Dry (Drilling) - The information in this report summarizes conditions found on the dates the borings were drilled. However, it should be noted that our ground water observations are short term; ground water depths and subsurface soil moisture contents will vary with environmental variations such as frequency and magnitude of rainfall and the time of year when construction is in progress. 4.2 Hazardous Materials Chemical or hydrocarbon odors were not detected in the borings during drilling or during processing of the samples in the laboratory. However, AEC notes that the presence of potential hazardous material within the project area cannot be discounted based upon the very small and limited number of samples taken. 4.3 Subsurface Variations It should be emphasized that: (i) at any given time, ground water depths can vary from location to location, and (ii) at any given location, ground water depths can change with time. Ground water depths will vary with seasonal rainfall and other climatic/environmental events. Subsurface conditions may vary away from and in between borings. Clay soils in the Houston area typically have secondary features such as slickensides and contain sand/silt seams/lenses/layers/pockets. It should be noted that the information in the boring logs (Borings B-3 through B-7) is based on 3-inch diameter soil samples which were generally obtained from the borings continuously at intervals of 1 foot from the ground surface to the boring termination depths of 5 to 10 feet. A detailed description 4

8 of the soil secondary features may not have been obtained due to the small sample size and sampling interval between the samples. Therefore, while some of AEC s logs show the soil secondary features, it should not be assumed that the features are absent where not indicated on the logs. 5.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS Based on a site plan prepared by Gensler, AEC understands that the proposed campus includes 4 modular campus buildings, with Buildings A through C each having an area of 11,300 square feet and Building D having an area of 1,728 square feet, plus driveways and parking areas. 5.1 Modular Buildings Soil Conditions: Based on Borings B-3 through B-7, the soils at the Modular buildings generally consist of approximately 2 to 5 feet of very stiff to hard lean clay (CL) fill material at the ground surface, underlain by stiff to hard lean clay (CL) to the boring termination depth of 10 feet. Based on our borings, the clay soils encountered in our borings have slight to high expansive potential (see Plate 11 in the Attachments). Foundations: AEC understands that the floors of modular buildings are typically lifted above existing grade (on concrete block or steel piers ) to form a crawlspace beneath them. The modular buildings are then supported either on pads bearing on the ground surface or on shallow concrete footings (with a strip footing around the modular building perimeter), typically founded from 12 to 36 inches deep. Furthermore, ground anchors are installed around the perimeter of the building (and connected to steel straps) to provide lateral and uplift resistance to wind loads. AEC should be notified if a slab-on-grade type foundation will be used instead for the modular buildings, so that the recommendations presented in this report can be revised, if necessary Spread Footings Based on the soil conditions encountered in Borings B-3 through B-5, there is approximately 2 feet of sandy clay (CL) fill within the modular building footprint areas. To mitigate the impact of surface fill vertical settlement and differential settlement on the modular buildings, AEC recommends that the modular buildings be supported on shallow spread footings (or strip footings, which for the purposes of this report can be used interchangeably with spread footings), founded at least 30 inches below existing/original grade. However, AEC notes that the modular building foundations will still be subject to some degree of movement due to the natural clay soils that 5

9 are present beneath the fill layer. These natural clay soils have a slight to high expansive potential [i.e. Potential Vertical Rise (PVR)], and will be subject to varying degrees of shrink and swell movement as the moisture content of the soil fluctuates throughout the seasons. Periodic maintenance, such as re-leveling of the modular buildings (i.e. jacking and shims) may be required, although this can be mitigated by increasing the depth of the footings beyond 30 inches (up to a depth of approximately 60 inches). In general, increasing the minimum bearing depth of the footings will result in less PVR impact. AEC recommends that the final depth of the footings should be determined by the Owner and the modular building foundation designer, comparing initial construction cost versus potential maintenance cost over the life of the structures. Potential Vertical Rise: PVR is an estimate of the potential of an expansive soil to swell from its current state. For the top 10 feet of the existing soils encountered in Borings B-3 through B-5, the total PVR is estimated to range from 0.8 to 1.0 inches based on in-situ moisture conditions; the estimated PVR considers a minimum footing depth of 30 inches. PVR was computed using Texas Department of Transportation (TxDOT) test method Tex-124-E. Additional movements can occur in areas if water is allowed to pond during or after construction on soils with high plasticity, or if highly plastic soils are allowed to dry out prior to fill or concrete placement. High plasticity clay may also experience shrinkage during periods of dry weather as moisture evaporation occurs at the ground surface and the groundwater table drops. The actual PVR of the site will be highly dependent upon the actual PI and moisture regime of the clayey soils at the time of construction. Therefore, uniformity and preservation of the moisture contents of the near surface clays during construction and during the life of the structure is critical to reducing potential shrink-swell movement of the footings. Table 2. Estimated PVR vs. Spread Footing Depth (Based on Borings B-3 through B-5) Spread Footing Depth Beneath Existing/Original Grade (in) PVR (in)

10 Allowable Bearing Capacity and Footing Depth: Spread footings founded at a depth of at least 30 inches (and up to a maximum depth of 60 inches if desired to mitigate PVR) below existing/original grade should be designed for an allowable bearing capacity of 2,700 pounds per square foot (psf) for sustained loads and an allowable bearing capacity of 4,050 psf for total loads; whichever allowable bearing capacity is critical should be used for design. The allowable bearing capacities provided include a factor of safety (FS) of 3 for sustained loads and a FS of 2 for total loads. Footing Spacing: AEC recommends that the minimum edge-to-edge clear spacing between spread footings should not be less than one times the width of the larger footing to reduce stress overlap from adjacent footings and potential construction problems. Footing Settlements: Based on the soil conditions encountered and the anticipated structural loads, we estimate that spread footings, designed and constructed as recommended in the report, will experience total settlements on the order of 1 inch Subgrade Preparation Subgrade preparation should extend a minimum of 2 feet beyond the modular building perimeters. Existing pavement and base (if any) should first be demolished. A minimum of 6 inches of surface soils, debris, roots, and other deleterious materials shall be removed and wasted. The excavation depth should be increased when inspection indicates the presence of organics or otherwise deleterious materials to greater depths. The exposed subgrade should then be proof-rolled in accordance with Item 216 of the 2014 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges to identify and remove any weak, compressible, or other unsuitable materials; such materials should be replaced with clean onsite clay soils. After proof rolling, the exposed subgrade should be graded to provide positive drainage away from the modular building footprints; compacted general fill (see Section of this report) can be used to achieve design grades, as needed. Foundations should then be excavated and installed to the required depth below original grade (i.e. without considering any fill placement) Ground Anchors Tie downs (steel straps) are typically connected to ground anchors in order to provide resistance to wind and uplift loads. The type of anchor will depend on the ground condition around the perimeter of the modular 7

11 building. In the Houston area, anchors are typically installed either into concrete (either into a pavement slab or into concrete footings), or into the soil (usually screw-in auger-type). Soil anchors are typically 30 to 60 inches long. Anchor Length and Spacing: Based on available information, AEC understands that anchor length and spacing is primarily a function of Wind Zone, identified in the Basic Wind Zone Map within the Manufactured Home Construction and Safety Standards at 24 CFR 3280 (i.e. HUD Code). AEC recommends that anchor length and spacing be in accordance with the Manufactured Housing Research Alliance (MHRA) Maximum Anchor Spacing Selector chart, unless specified otherwise by the Modular Building foundation designer. 5.2 Pavement Traffic volume and vehicle loads were not available at the time this report was prepared. However, AEC anticipate that the driveways of the site will handle primarily school buses, garbage trucks, and passenger vehicles. Fire lanes will also support emergency vehicles. A site grading plan was not available at the time this report was prepared, but AEC assumes that the pavement will be constructed at or near existing grade. AEC should be notified if the final grade in the paved areas will be more than 6 inches above existing grade, so that our recommendations can be revised if necessary. The pavement design recommendations developed herein are in accordance with the AASHTO Guide for Design of Pavement Structures, 1993 edition Rigid Pavement Rigid pavement design is based on the anticipated design number of 18-kip Equivalent Single Axle Loads (ESALs) the pavement is subjected to during its design life. The parameters that were used in computing the rigid pavement section are as follows: Overall Standard Deviation (S 0 ) 0.35 Initial Serviceability (P 0 ) 4.5 Terminal Serviceability (P t ) 2.5 Reliability Level (R) 75% Overall Drainage Coefficient (C d ) 1.0 Load Transfer Coefficient (J) 3.2 Loss of Support Category (LS) 1.0 Roadbed Soil Resilient Modulus (M R ) 4,500 psi 8

12 Elastic Modulus (E sb ) of Stabilized Soils Concrete Compressive Strength Composite Effective Modulus of Subgrade Reaction (k) Mean Concrete Modulus of Rupture (S c) Concrete Elastic Modulus (E c ) 30,000 psi 3,000 psi (at 28 days) 91 pci 570 psi (at 28 days) 3.37 x 10 6 psi For the pavement design, AEC assumes that the concrete pavement will have a 28 day compressive strength of 3,000 psi and a 28 day flexural strength of 570 psi. AEC should be notified if a different 28 day compressive strength will be used for pavement construction, so that our recommendations can be updated as necessary. Recommended rigid pavement sections are provided on Table 3 below. Pavement Layer Table 3. Recommended Rigid Pavement Sections Parking Thickness (in) Driveways (without buses) Bus Lanes, Fire Lanes, Dumpster Pad Portland Cement Concrete Lime-Stabilized Subgrade Note: Stabilized subgrade recommendations are presented in Section of this report. Given the above design parameters, the parking area, driveway (without buses), and bus lane/fire lane/dumpster pad sections should sustain 175,283, 458,769, and 1,057,425 repetitions of 18-kip ESALs, respectively. The design engineer should verify whether the proposed pavement sections will provide enough ESALs for the anticipated amount of site traffic. AEC should be notified if different standards or constants are required for pavement design at the site, so that our recommendations can be updated accordingly. Concrete Pavement: Portland Cement Concrete (PCC) pavement should be constructed in general accordance with Section of the 2018 City of Houston Standard Construction Specifications (COHSCS). In accordance with AEC s concrete pavement design, AEC recommends that the concrete mix design is based on a concrete compressive strength of 3,000 psi at 28 days also meets a minimum concrete flexural strength of 500 psi at 7 days and 570 psi at 28 days. Reinforcing Steel: Reinforcing steel is required to control pavement cracks, deflections across pavement joints and resist warping stresses in rigid pavements. The cross-sectional area of steel (A s ) required per foot of slab width can be calculated as follows (for both longitudinal and transverse steel). A s = FLW/(2f s )... Equation (1) 9

13 where: A s = Required cross-sectional area of reinforcing steel per foot width of pavement, in 2 F = Coefficient of resistance between slab and subgrade, F = 1.8 for stabilized soil L = Distance between free transverse joints or between free longitudinal edges, ft. W = Weight of pavement slab per foot of width, lbs/ft f s = Allowable working stress in steel, 0.75 x (yield strength), psi i.e. f s = 45,000 psi for Grade 60 steel Pavement Subgrade Subgrade Preparation: Subgrade preparation should extend a minimum of 2 feet beyond the paved area perimeters. Existing pavement, base, or structures should first be demolished. After demolition, we recommend that a minimum of 6 inches of surface soils, existing vegetation, trees, roots, and other deleterious materials be removed and wasted. The excavation depth should be increased when inspection indicates the presence of organics and deleterious materials to greater depths. The exposed soils should be proof-rolled in accordance with Item 216 of the 2014 TxDOT Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges to identify and remove any weak, compressible, or other unsuitable materials; such materials should be replaced with compacted general fill. General fill recommendations are presented in Section of this report. Scarify the top 6 inches of the exposed subgrade and stabilize with at least 5 percent hydrated lime (by dry soil weight). Lime stabilization shall be performed in accordance with Section of the 2018 COHSCS. The percentage of lime required for stabilization is a preliminary estimate for planning purposes only; laboratory testing should be performed to determine optimum contents for stabilization prior to construction. The stabilized soils should be compacted to 95 percent of their ASTM D 698 (Standard Proctor) dry density at a moisture content ranging from optimum to 3 percent above optimum. 5.3 Fill Requirements As noted in Section of this report, AEC anticipates that the modular buildings will have crawlspaces, and will be supported on concrete spread footings founded between 30 to 60 inches below original grade. As a result, any fill placement required for surface grading around/beneath the modular buildings can be performed using general fill. General fill requirements are presented in Section of this report. Structural fill (if any) that may be required at the site, such as backfill for foundations, retaining walls, or other important structures, should be either lime stabilized clay or select fill, as presented in Sections and of this report, respectively. 10

14 5.3.1 Lime Stabilized Clay Soils Stabilized with Hydrated Lime: AEC prefers that lime-stabilized clay be used as structural fill. Either: (i) imported lime-stabilized clay soils (stabilized offsite before delivery to the project site); or (ii) clay soils excavated onsite and treated with hydrated lime can be used. Clay soils excavated onsite should first be stabilized with a minimum of 5 percent hydrated lime (by dry soil weight). The amount of hydrated lime provided in this report is for estimation purposes only. The actual amount of lime required for stabilization should be determined by lime-series curve or ph method in a laboratory prior to construction. Lime stabilization should be done in general accordance with Section of the 2018 COHSCS. AEC prefers using stabilized soil as structural fill since compacted stabilized soil generally has high strength, low compressibility, and relatively low permeability. Lifts and Compaction: Lime-stabilized clay fill should be placed in loose lifts not exceeding 8 inches in thickness. Backfill within 3 feet of walls or columns should be placed in loose lifts no more than 4-inches thick and compacted using hand tampers, or small self-propelled compactors. Lime-stabilized clay should be compacted to a minimum of 95 percent of the ASTM D 698 (Standard Proctor) maximum dry unit weight at a moisture content ranging between optimum and 3 percent above optimum Select Fill Select Fill: It is AEC s experience that select fill material imported from sand and clay pits in the Greater Houston area is generally non-homogenous (i.e. composed of a mixture of sands, silts, and clays, instead of a homogenous sandy clay material) and of poor quality, and either contains too much sand or has large clay clods with high expansive potential. Use of this non-homogenous soil can result in poor long term performance of structures and pavements placed on top of the fill. Select fill (whether imported from offsite or is already onsite) should consist of uniform, non-active inorganic lean clays with a PI between 10 and 20 percent, and more than 50 percent passing a No. 200 sieve. Material intended for use as select fill shall not have clay clods with PI greater than 20, clay clods greater than 2 inches in diameter, or contain sands/silts with PI less than 10. Sand and clay mixtures/blends are unacceptable for use as select fill. Sand/silt with clay clods is unacceptable for use as select fill. Mixing sand into clay or mixing clay into sand/silt is also unacceptable for use as select fill. Prior to construction, the Contractor should determine if he or she can obtain qualified select fill meeting the above select fill criteria. The testing lab 11

15 shall reject any material intended for use as select fill that does not meet the PI, sieve, and clay clod requirements above, without exceptions. Lifts and Compaction: All material intended for use as select fill should be tested prior to use to confirm that it meets select fill criteria. The fill should be placed in loose lifts not exceeding 8 inches in thickness. Backfill within 3 feet of walls or columns should be placed in loose lifts no more than 4-inches thick and compacted using hand tampers, or small self-propelled compactors. Select fill should be compacted to a minimum of 95 percent of the ASTM D 698 (Standard Proctor) maximum dry unit weight at a moisture content ranging between optimum and 3 percent above optimum. Testing: If select fill will be used, at least one Atterberg Limits and one percent passing a No. 200 sieve test shall be performed for each 10,000 square feet (sf) of placed fill, per lift (with a minimum of one set of tests per lift), to determine whether it meets select fill requirements. Prior to placement of pavement or concrete, the moisture contents of the top 2 lifts of compacted select fill shall be re-tested (if there is an extended period of time between fill placement and concrete placement) to determine if the in-place moisture content of the lifts have been maintained at the required moisture requirements General Fill General fill can be used beneath modular building crawl spaces or for fill areas that will not support proposed (or future) structures or pavements (i.e. for mass site grading). AEC recommends that general fill consist of a clean, cohesive soil (USCS Classification CL or CH ). Granular soils (i.e. sands, silts, and gravel; not more than 50 percent retained on No. 200 sieve) should not be used as general fill. General fill should be placed in loose lifts not exceeding 8 inches in thickness. The fill should be compacted to 95 percent of the ASTM D 698 (Standard Proctor) maximum dry unit weight at a moisture content ranging between optimum and 3 percent above optimum. 12

16 6.0 CONSTRUCTION CONSIDERATIONS 6.1 Site Preparation and Grading To mitigate site problems that may develop following prolonged periods of rainfall, it is essential to have adequate drainage to maintain a relatively dry and firm surface prior to starting any work at the site. Adequate drainage should be maintained throughout the construction period. Methods for controlling surface runoff and ponding include proper site grading, berm construction around exposed areas, and installation of sump pits with pumps. In addition to the recommended subgrade preparation, measures should be taken to reduce the potential for moisture changes in the subsurface soils under the proposed structure, which will in turn mitigate the potential for shrink and swell movements to occur. Measures recommended for consideration include: - Maintain uniform compaction and moisture content for fill/subgrade soils during construction; - Do not allow water to pond or allow the soils to dry out prior to constructing floor slabs; - Locate landscaping away from floor slabs; trees should be located no closer than their mature canopy radius to the structure and pavements; even so, the tree roots influence zone can extend beyond their mature canopy radius; - Design roof drains to discharge into paved areas or into a subsurface drainage system; - Design final grading to provide site drainage away from the structure. 6.2 Groundwater Control The need for groundwater control will depend on the depth of excavation relative to the groundwater depth at the time of construction. In the event that there is heavy rain prior to or during construction, the groundwater table may be higher than indicated in this report; higher seepage is also likely and may require a more extensive groundwater control program. In addition, groundwater may be pressurized in certain areas of the alignment, requiring further evaluation and consideration of the excess hydrostatic pressures. Groundwater control should be in general accordance with Section of the 2018 City of Houston Standard General Requirement (COHSGR). The Contractor should be responsible for selecting, designing, constructing, maintaining, and monitoring a groundwater control system and adapt his operations to ensure the stability of the excavations. Groundwater information presented in Section 4.1 and elsewhere in this report, along with consideration for potential environmental and site variation between the time of our field exploration and construction, should be 13

17 incorporated in evaluating groundwater depths. The following recommendations are intended to guide the Contractor during design and construction of the dewatering system. In cohesive soils seepage rates are lower than in granular soils and groundwater is usually collected in sumps and channeled by gravity flow to storm sewers. If cohesive soils contain significant secondary features, seepage rates will be higher. This may require larger sumps and drainage channels, or if significant granular layers are interbedded within the cohesive soils, methods used for granular soils may be required. Where it is present, pressurized groundwater will also yield higher seepage rates. Groundwater for excavations within saturated sands can be controlled by the installation of wellpoints. The practical maximum dewatering depth for well points is about 15 feet. When groundwater control is required below 15 feet, possible ground water control measures include: (i) deep wells with turbine or submersible pumps; (ii) multi-staged well points; or (iii) water-tight sheet pile cut-off walls. Generally, the groundwater depth should be lowered at least 3 feet below the excavation bottom to be able to work on a firm surface when water-bearing granular soils are encountered. Extended and/or excessive dewatering can result in settlement of existing structures in the vicinity; the Contractor should take the necessary precautions to minimize the effect on existing structures in the vicinity of the dewatering operation. We recommend that the Contractor verify the groundwater depths and seepage rates prior to and during construction and retain the services of a dewatering expert (if necessary) to assist him in identifying, implementing, and monitoring the most suitable and cost-effective method of controlling groundwater. For open cut construction in cohesive soils, the possibility of bottom heave must be considered due to the removal of the weight of excavated soil. In lean and fat clays, heave normally does not occur unless the ratio of Critical Height to Depth of Cut approaches one. In silty clays, heave does not typically occur unless an artificially large head of water is created through the use of impervious sheeting in bracing the cut. 6.3 Construction Monitoring Site preparation (including clearing and proof-rolling), earthwork operations, foundation construction, and subgrade preparation should be monitored by qualified geotechnical professionals to check for compliance with project documents and changed conditions, if encountered. 14

18 7.0 GENERAL AEC should be allowed to review construction documents and specifications prior to release to check that the geotechnical recommendations and design criteria presented herein are properly interpreted. The information contained in this report summarizes conditions found on the date the borings were drilled. The attached boring logs are true representations of the soils encountered at the specific boring locations on the date of drilling. Due to variations encountered in the subsurface conditions across the site, changes in soil conditions from those presented in this report should be anticipated. AEC should be notified immediately when conditions encountered during construction are significantly different from those presented in this report. 8.0 LIMITATIONS The investigation was performed using the standard level of care and diligence normally practiced by recognized geotechnical engineering firms in this area, presently performing similar services under similar circumstances. The report has been prepared exclusively for the project and location described in this report, and is intended to be used in its entirety. If pertinent project details change or otherwise differ from those described herein, AEC should be notified immediately and retained to evaluate the effect of the changes on the recommendations presented in this report, and revise the recommendations if necessary. The scope of services does not include a fault investigation. The recommendations presented in this report should not be used for other structures located at this site or similar structures located at other sites, without additional evaluation and/or investigation. 15

19 ATTACHMENTS Plate 1 Vicinity Map Plate 2 Boring Location Plan Plates 3 and 4 Boring Logs - AEC Report G171-11, B-1 and B-2 Plates 5 to 9 Boring Logs, B-3 to B-7 Plate 10 Key to Symbols Plate 11 Classification of Soils for Engineering Purposes Plate 12 Terms Used on Boring Logs Plate 13 ASTM & TXDOT Designation for Soil Laboratory Tests

20 SITE AVILES ENGINEERING CORPORATION AEC PROJECT NO.: G APPROX. SCALE: N.T.S. VICINITY MAP KIPP JOURNEY MODULAR CAMPUS KIPP WAY HOUSTON, TEXAS DATE: DRAFTED BY: WLW SOURCE DRAWING PROVIDED BY: GOOGLE MAPS PLATE NO.: PLATE 1

21 GRAPHIC SCALE, FT B-6 (5 ) B-5 (10 ) B-4 (10 ) B-3 (10 ) B-7 (5 ) B-1 (20 ) B-2 (20 ) Notes: 1) Boring locations are approximate. 2) Site plan is best fit to aerial. LEGEND: B-# (X ) B-# (X ) BORING LOCATION (DEPTH IN FEET) PREVIOUS BORING LOCATION (DEPTH IN FEET), AEC PROJECT G AVILES ENGINEERING CORPORATION AEC PROJECT NO.: G APPROX. SCALE: 1 = 100 BORING LOCATION PLAN KIPP JOURNEY MODULAR CAMPUS KIPP WAY HOUSTON, TEXAS DATE: DRAFTED BY: WLW SOURCE DRAWING PROVIDED BY: GENSLER PLATE NO.: PLATE 2

22 PROJECT: Modular Building at Kipp Houston School BORING B-1 DATE 8/25/2011 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: hard, dark brown Sandy Lean Clay (CL), with calcareous nodules, roots and ferrous stains Hard, dark brown Sandy Lean Clay (CL), with calcareous nodules and ferrous stains. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF 113 SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX 4 -with sand seams 4'-6' light gray and red, with fat clay seams 6'-8' Firm to very stiff, red and gray Fat Clay (CH), with calcareous nodules -with ferrous nodules 8'-10' with silt partings and sandy clay pockets 13'- 15' Tan Lean Clay w/sand (CL), with abundant silt and sand partings Termination Depth = 20 feet BORING DRILLED TO N/A FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT 18 FEET WHILE DRILLING WATER LEVEL AT 14 FEET AFTER COMPLETE DRILLED BY JH DRAFTED BY LOGGED BY JH PROJECT NO. G PLATE 3

23 PROJECT: Modular Building at Kipp Houston School BORING B-2 DATE 8/25/2011 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: hard, dark brown Sandy Lean Clay (CL), with calcareous nodules and brick pieces. S.P.T. BLOWS / FT. MOISTURE CONTENT, % 12 DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX 4 Firm to hard, dark brown Lean Clay w/sand (CL), with calcareous nodules and ferrous stains -with abundant sand partings 2'-6' -light gray 4'-15' with fat clay pockets 6'-8' with sand seams 8'-10' tan and light gray, with abundant silty sand seam 13'-20' brown and tan, with fat clay pockets 18'-20' Termination Depth = 20 feet BORING DRILLED TO N/A FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT 13 FEET WHILE DRILLING WATER LEVEL AT 17 FEET AFTER COMPLETE DRILLED BY JH DRAFTED BY LOGGED BY JH PROJECT NO. G PLATE 4

24 PROJECT: Kipp Journey Modular Campus BORING B-3 DATE 12/07/2018 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 4 SYMBOL SAMPLE INTERVAL Fill: very stiff, dark brown Sandy Lean Clay (CL), wtih abundant silt partings -with roots 1'-2' Stiff to hard, gray and tan Lean Clay (CL) -with calcareous and ferrous nodules 2'-7' -gray and brown 3'-4' -gray 4'-5' -gray and brown 5'-6' DESCRIPTION. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX reddish tan 6'-7' with clayey/silty sand pockets and ferrous stains 8'-10' 15 Termination Depth = 10 feet BORING DRILLED TO 10 FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT N/A FEET WHILE DRILLING WATER LEVEL AT N/A FEET AFTER COMPLETE DRILLED BY Van & Sons DRAFTED BY WLW LOGGED BY BTC PROJECT NO. G PLATE 5

25 PROJECT: Kipp Journey Modular Campus BORING B-4 DATE 12/07/2018 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 4 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: very stiff, tan and dark brown Lean Clay with Sand (CL), with fat clay pockets and silty sand pockets -with roots 1'-2' Stiff to hard, dark gray Lean Clay (CL) -with sand partings 3'-4' and calcareous nodules 3'-10' -with ferrous nodules 4'-5' -dark gray and tan 5'-10', with fat clay pockets 5'-6' -with silty sand partings 6'-8', with ferrous nodules 6'-7'. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX with ferrous nodules 8'-9' -with silt partings 9'-10' 24 Termination Depth = 10 feet BORING DRILLED TO 10 FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT N/A FEET WHILE DRILLING WATER LEVEL AT N/A FEET AFTER COMPLETE DRILLED BY Van & Sons DRAFTED BY WLW LOGGED BY BTC PROJECT NO. G PLATE 6

26 PROJECT: Kipp Journey Modular Campus BORING B-5 DATE 12/07/2018 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 4 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: very stiff to hard, dark brown Lean Clay with Sand (CL) -with calcareous nodules 0'-2' and roots 0'- 1' -tan and gray 1'-2' -brown and gray, with silty sand pockets 2'- 3' Fill: hard, gray Lean Clay (CL), with silt and fat clay pockets. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX Very stiff to hard, gray and tan Lean Clay (CL) -with silty sand partings 5'-8' -with ferrous nodules 6'-7' with ferrous nodules 8'-10' -wtih silt partings 9'-10' 19 Termination Depth = 10 feet BORING DRILLED TO 10 FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT N/A FEET WHILE DRILLING WATER LEVEL AT N/A FEET AFTER COMPLETE DRILLED BY Van & Sons DRAFTED BY WLW LOGGED BY BTC PROJECT NO. G PLATE 7

27 PROJECT: Kipp Journey Modular Campus BORING B-6 DATE 12/07/2018 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 4 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: very stiff, gray and brown Lean Clay with Sand (CL), with calcareous nodules, silty sand partings, and roots Hard, gray Sandy Lean Clay (CL), with silty sand partings and calcareous nodules -gray and tan 3'-5', with ferrous nodules 3'- 4'. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX Termination Depth = 5 feet BORING DRILLED TO 10 FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT N/A FEET WHILE DRILLING WATER LEVEL AT N/A FEET AFTER COMPLETE DRILLED BY Van & Sons DRAFTED BY WLW LOGGED BY BTC PROJECT NO. G PLATE 8

28 PROJECT: Kipp Journey Modular Campus BORING B-7 DATE 12/07/2018 TYPE 4" Dry Auger LOCATION See Boring Location Plan DEPTH IN FEET 0 4 SYMBOL SAMPLE INTERVAL DESCRIPTION Fill: stiff, gray Lean Clay with Sand (CL), with fat clay pockets and calcareous nodules -with roots 0'-1' -with silty sand partings 1'-2' Fill: hard, dark gray Sandy Lean Clay (CL), with silty sand partings Hard, gray and dark gray Sandy Lean Clay (CL), with calcareous nodules Termination Depth = 5 feet.. S.P.T. BLOWS / FT. MOISTURE CONTENT, % DRY DENSITY, PCF SHEAR STRENGTH, TSF Confined Compression Unconfined Compression Pocket Penetrometer Torvane MESH LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX BORING DRILLED TO 10 FEET WITHOUT DRILLING FLUID WATER ENCOUNTERED AT N/A FEET WHILE DRILLING WATER LEVEL AT N/A FEET AFTER COMPLETE DRILLED BY Van & Sons DRAFTED BY WLW LOGGED BY BTC PROJECT NO. G PLATE 9

29 KEY TO SYMBOLS Symbol Description Strata symbols Fill Misc. Symbols Low plasticity clay Pocket Penetrometer Unconfined Compression Soil Samplers Undisturbed thin wall Shelby tube PLATE 10

30 PLATE 11

31 PLATE 12

32 ASTM & TXDOT DESIGNATION FOR SOIL LABORATORY TESTS SOIL TEST ASTM TEST DESIGNATION TXDOT TEST DESIGNATION Unified Soil Classification System D 2487 Tex-142-E Moisture Content D 2216 Tex-103-E Specific Gravity D 854 Tex-108-E Sieve Analysis D 6913 Hydrometer Analysis D 7928 Tex-110-E (Part 1) Tex-110-E (Part 2) Minus No. 200 Sieve D 1140 Tex-111-E Liquid Limit D 4318 Tex-104-E Plastic Limit D 4318 Tex-105-E Standard Proctor Compaction D 698 Tex-114-E Modified Proctor Compaction D 1557 Tex-113-E California Bearing Ratio D Swell D Consolidation D Unconfined Compression D Unconsolidated-Undrained Triaxial D 2850 Tex-118-E Consolidated-Undrained Triaxial D 4767 Tex-131-E Permeability (constant head) D Pinhole D Crumb D Double Hydrometer D ph of Soil D 4972 Tex-128-E Soil Suction D Soil Sulfate C 1580 Tex-145-E Organics D 2974 Tex-148-E PLATE 13