REPORT OF SUBSURFACE EXPLORATION AND GEOTECHNICAL ENGINEERING SERVICES

Transcription

1 REPORT OF SUBSURFACE EXPLORATION AND GEOTECHNICAL ENGINEERING SERVICES NORTH SHORE SCHOOL DISTRICT 11 HIGHLAND PARK, ILLINOIS ECS PROJECT NO. 1:8 FOR NORTH SHORE SCHOOL DISTRICT 11 SEPTEMBER, 1

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3 REPORT PROJECT Subsurface Exploration and Geotechnical Engineering Services Highland Park, Illinois CLIENT Mr. John Fuhrer 19 Green Bay Road Highland Park, Illinois 00 SUBMITTED BY ECS Midwest, LLC 1 Barclay Boulevard Buffalo Grove, Illinois 0089 Illinois Professional Design Firm No. -00 PROJECT #1:8 DATE September, 1

4 TABLE OF CONTENTS EXECUTIVE SUMMARY PROJECT OVERVIEW 1 Introduction 1 Existing Site Conditions 1 Proposed Construction 1 Purposes of Exploration and Scope of Services EXPLORATION PROCEDURES Subsurface Exploration Procedures Laboratory Testing Program EXPLORATION RESULTS Soil Conditions Groundwater Observations ANALYSIS AND RECOMMENDATIONS 8 Overview 8 Subgrade Preparation and Earthwork Operations 8 Fill Placement Foundation Recommendations 11 Floor Slab Design 1 Underslab Sub-Drainage 1 Exterior Pavement Design 1 Pavement Maintenance 1 Adjacent Construction and Monitoring 1 PROJECT CONSTRUCTION RECOMMENDATIONS 1 General Construction Considerations 1 Construction Dewatering 1 Closing APPENDIX 19 Page

5 EXECUTIVE SUMMARY The subsurface conditions encountered during our exploration and ECS Midwest, LLC s conclusions and recommendations are summarized below. This summary should not be considered apart from the entire text of the report with all the qualifications and considerations mentioned herein. Details of our conclusions and recommendations are discussed in the following sections and in the Appendix. Based on our understanding of the proposed project, we anticipate the proposed construction will consist of a new middle school with the associated parking lot, drive lanes, and sports fields. The middle school structure will consist of three aboveground stories supported by a steel structure and may or may not include a partial basement. The new middle school and associated development will be constructed at either the Olson Park site or the Sherwood/Red Oak site. ECS estimates column and wall loads will range from about 0 to 00 kips and about klf, respectively. Based on 9 soil borings performed at the Olson Park project site, and soil borings and hand augers performed at the Sherwood/Red Oak site, the subsurface soils can be summarized as outlined below. At the Olson Park site the surficial soils were observed to consist of about to 1 inches of topsoil, 9 inches of gravel FILL or inches of gravel FILL underlain by 8 inches of topsoil. At boring locations A-1 through A-8 the existing surficial soils were underlain by strata of natural Silty CLAY and Clayey SILT to boring termination at 1 to feet below grade. Surficial materials at the Sherwood/Red Oak site were observed to consist of about to 8 inches of topsoil or to have no discernable surficial materials. Beneath the surfical topsoil, boring locations B-1, B-, B- and B- and hand augers HA-1 and HA- were comprised entirely of natural Silty CLAY to boring/hand auger termination at depths of to feet below existing site grades. Boring location B- exhibited a thin layer of Silty Clay FILL to about 1¾ feet below grade underlain by natural Silty CLAY to boring termination at about feet below grade. The Silty Clay Fill at boring B- was observed to exhibit an unconfined compression strength value of ½ tsf (very stiff consistency) and moisture content of about 0 percent. The natural Silty CLAY and Clayey SILT soils at both the Olson Park and Sherwood/Red Oak sites exhibited unconfined compressive strength values ranging from 1¼ to greater than ½ tsf (stiff to hard consistencies, but typically very stiff to hard) and moisture contents in the range of about 1 to percent (typically about 1 to 19 percent). Due to the uniformity of and high unconfined compressive strength values of onsite soils at the Olson Park and Sherwood/Red Oak sites, we anticipate the subgrade preparation efforts required during construction will not be very extensive. Once the subgrade has been exposed, the subgrade can be proofrolled using a loaded dump truck having an axle weight of at least tons. The intent of the proofroll is to aid in identifying localized soft, particularly moist, unstable or unsuitable material which requires removal. Shallow Silty Clay FILL similar to the material encountered at soil boring location B- and higher moisture contents exhibited by near-surface soils in the boring logs may result in some areas requiring removal. If soft or yielding soils are observed during the proofroll of the subgrade, the soft soils should be undercut up to a maximum of feet and replace with properly manipulated onsite soils (see the Fill Placement section for guidelines) or compacted engineered fill to the design subgrade. We recommend the proposed middle school structure be supported on a shallow foundation system bearing in the competent natural Silty CLAY soils or on compacted engineered fill overlying competent natural soils can be designed for a maximum net allowable soil bearing pressure of,00 psf. This recommendation applies to both the Olson Park and Sherwood/Red Oak sites. Competent natural Silty CLAY soils for a shallow foundation system can be identified on the boring logs and in the field as those soils having an unconfined compressive strength of at least ¾ tsf. More detailed recommendations with regard to foundations, subgrade preparation and earthwork operations, fill placement, slab and pavement design, underslab drainage and construction dewatering are included herein and must be fully reviewed and understood so that the intent of the recommendations are properly utilized during design and construction of the proposed development. We recommend that ECS be retained to review the project drawings and specifications prior to the start of construction to verify that the recommendations detailed herein are followed. We recommend that ECS be retained during construction of the proposed development to monitor all earthwork/subgrade preparation to verify that the exposed subgrade materials and the soil bearing pressures will be suitable for the proposed structure. Report Prepared By: Rachel E. Miller Project Manager Report Reviewed By: Brett Gitskin, P.E. Senior Principal Engineer

6 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois Introduction PROJECT OVERVIEW This report presents the results of our subsurface exploration and geotechnical engineering analysis performed for the proposed middle school to be constructed at either 1 Ridge Road (the Olson Park site) or directly northwest of 0 Red Oak Lane (the Sherwood/Red Oak site) in Highland Park, Illinois. A General Location Map, included in the Appendix of this report, shows the approximate location of the project site. This exploration was conducted in general conformance with our Proposal No. 18-GPR (revised July, 1) and authorized by you. In preparing this report, we have utilized information from our current subsurface exploration as well as information from nearby sites. Existing Site Conditions The potential Olson Park project site is located at 1 Ridge Road in Highland Park, Illinois. The site is bound to the north, south and east by residential buildings and to the west by Ridge Road. The property is currently occupied by Olson Park which consists of a grassed field with a gravel covered drive and parking area within the western portion of the site. This scope of geotechnical services includes the western half of the grassy site. Our review of Google Earth indicates existing site grades at the site are in the range of approximately EL. + to EL. + feet (+/-) and gently slopes downward from west to east. The second possible middle school site, the Sherwood/Red Oak site, is located directly northwest of 0 Red Oak Lane in Highland Park, Illinois. The site is bound to the north by Sherwood Elementary School and Stratford Road, to the south by Red Oak Elementary School and a residential development, to the east by Red Oak Lane and to the west by residences. The property is currently occupied by a wooded area which covers the majority of the site and grassy areas in the northern portion of the site. A small asphalt concrete parking area and playground area, both belonging to Red Oak Elementary School, are located in the southeast corner of the site. The Sherwood Elementary School playground is located in the north-central portion of the site. Our review of Google Earth indicates existing site grades at the site range from approximately EL. +8 to EL. + feet (+/-). Please note ground elevations from Google Earth can vary and may not represent the actual elevations at the project sites. Ground elevations at the boring locations interpreted from Google Earth should not be used in design. If the actual elevations are substantially different from those assumed, please contact ECS so that we may reevaluate our recommendations, as appropriate. Proposed Construction Based on the RFP and our conversation with the architect, we understand the proposed construction at the project site will consist of a new middle school with the associated parking lots, drive lanes, and sports fields. The middle school structure will consist of three aboveground stories supported by a steel structure and may or may not include a partial basement.

7 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois The new middle school and associated development will be constructed at either the Olson Park site or the Sherwood/Red Oak site. If the Olson Park site is developed, the middle school building will be constructed in the northern portion of the property, with approximately 0 parking spaces to the south. If the Sherwood/Red Oak site is developed, the middle school structure will be larger and will occupy the (currently wooded) area directly northeast of Red Oak Elementary School and south of Sherwood Elementary school. Proposed structural loading was not known at the time this report was written. ECS estimates column and wall loads will range from about 0 to 00 kips and about klf, respectively. ECS anticipates that the finished floor elevation of the new structures will match existing site grades. We anticipate only minor grading would be required at the Sherwood/Red Oak site. At the Olson Park site, soil borings were placed at locations exhibiting about a -foot differential in elevation; therefore, we can anticipate some filling/cutting onsite if the Olson Park property is developed. If our understanding of the proposed construction is inaccurate, please inform ECS as soon as possible so that we can review our recommendations herein and potentially revise our recommendations according to the updated construction plans. Purposes of Exploration and Scope of Services The purposes of this exploration were to explore the soil and groundwater conditions at the project site and to develop engineering recommendations to guide in the design and construction of the project. We accomplished these purposes by performing the following scope of services: 1. Reviewing the geotechnical reports prepared for nearby sites by ECS;. Drilling nine (9) SPT (standard penetration test) soil borings at the Olson Park project site using an auger drill rig;. Drilling five () SPT (standard penetration test) soil borings at the Sherwood/Red Oak project site using an auger drill rig;. Drilling two () hand auger soil borings within the wooded area at the Sherwood/Red Oak site;. Performing laboratory tests on selected representative samples from the borings to evaluate pertinent engineering properties;. Analyzing the field and laboratory data to develop appropriate engineering recommendations; and,. Preparing this geotechnical report of our findings and recommendations. The conclusions and recommendations contained in this report are based on fourteen (1) SPT (standard penetration test) soil borings and two () hand auger borings. Nine (9) SPT soil borings, designated as A-1 through A-9, were drilled to depths of about 1 to feet below the

8 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois existing grades in the area of the proposed middle school and parking areas at the Olson Park location. Five () SPT soil borings, designated as B-1 through B-, were drilled to a depth of about feet below site grades in the vicinity of the proposed middle school at the Sherwood/Red Oak site, as the wooded area precluded access to more appropriate locations for the standard SPT borings. Two () hand auger borings were augered to a depth of feet below grade within the proposed middle school footprint at the Sherwood/Red Oak site. The purpose of the hand auger borings was to explore the near-surface soils in an area of the proposed building that is currently wooded and therefore unreachable by drill rig. The subsurface exploration included split-spoon soil sampling, standard penetration tests (SPT) and groundwater level observations in the boreholes. The results of the completed soil borings, along with Boring Location Diagrams are included in the Appendix of this report. The borings were located in the field by an ECS representative and the locations are shown on the Boring Location Diagrams. Based on our review of existing on-line resources (i.e., Google Earth ), existing site grades at the project sites are anticipated to be in the range of approximately EL. + to EL. + feet for the Olson Park site and approximately EL. +8 to EL. + feet at the Sherwood/Red Oak site (+/-). Ground elevations derived from Google Earth can vary and should not be used in the project design. Existing site grades should be surveyed prior to project design.

9 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois Subsurface Exploration Procedures EXPLORATION PROCEDURES The borings were located in the field by an ECS representative based on the proposed layouts of the proposed construction. An ECS subcontracted driller contacted the State of Illinois Utility One-Call Center, JULIE, to clear and mark underground utilities in the vicinity of the project sites prior to drilling operations. In addition to the JULIE utility clearance, ECS engaged a private utility locator to identify private utilities on the proposed school properties in the vicinity of the proposed borings locations. The soil borings were performed by a truck-mounted drill rig with a rotary-type auger drill, which utilized continuous flight augers to advance the boreholes. Representative soil samples were obtained by means of conventional split-barrel sampling procedures. Samples were typically obtained at ½-foot intervals in the upper feet and at -foot intervals thereafter. In this procedure, a -inch O.D., split-barrel sampler is driven into the soil a distance of inches by a -pound hammer falling 0 inches. The number of blows required to drive the sampler through a 1-inch interval, after initial setting of inches, is termed the Standard Penetration Test (SPT) or N-value and is indicated for each sample on the boring logs. The SPT value can be used as a qualitative indication of the in-place relative density of cohesionless soils. In a less reliable way, it also indicates the consistency of cohesive soils. This indication is qualitative, since many factors can significantly affect the standard penetration resistance value and prevent a direct correlation between drill crews, drill rigs, drilling procedures, and hammer-rodsampler assemblies. The drill rig utilized an automatic trip hammer to drive the sampler. Consideration of the effect of the automatic hammer s efficiency was included in the interpretation of subsurface information for the analyses prepared for this report. A field log of the soils encountered in the borings was maintained by the drill crew. After recovery, each geotechnical soil sample was removed from the sampler and visually classified. Representative portions of each soil sample were then sealed in jars. The soil samples were then brought to our laboratory in Buffalo Grove, Illinois for further visual evaluation and laboratory testing. After completion of the drilling operations, the boreholes were backfilled with auger cuttings to the existing ground surface. At the two hand auger locations at the Sherwood/Red Oak site, the boreholes were advanced through the soil utilizing a -inch diameter hand auger. Hand augering operations were supplemented with split-barrel sampling to obtain blow counts. In split-barrel sampling, a -inch split-barrel sampler is driven into the soil a distance of to inches by a 0-pound hammer falling about to inches. The number of blows were recorded and converted based on hammer energy to a conventional SPT N-value. Upon completion, the boreholes were backfilled with the excavated spoils.

10 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois Laboratory Testing Program Representative soil samples were selected and tested in our laboratory to check field classifications and to determine pertinent engineering properties. The laboratory testing program included visual classification of the soil samples, unconfined compressive strength testing utilizing a calibrated hand penetrometer on cohesive soil samples and moisture content testing. Each soil sample was classified on the basis of texture and plasticity in accordance with the Unified Soil Classification System. The group symbols for each soil type are indicated in parentheses following the soil descriptions on the boring log. A brief explanation of the Unified System is included with this report. The various soil types were grouped into the major zones noted on the boring log. The stratification lines designating the interfaces between earth materials on the boring log are approximate; in situ, the transitions may be gradual. Unconfined compressive strength (Qp) tests were performed on cohesive soil samples with the use of a calibrated hand penetrometer. In the hand penetrometer test, the unconfined compressive strength (Qp) of a soil sample is estimated, to a maximum of ½ tons per square foot (tsf), by measuring the resistance of a soil sample to penetration of a small, calibrated spring-loaded cylinder. The soil samples will be retained in our laboratory for a period of 0 days, after which, they will be discarded unless other instructions are received as to their disposal.

11 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois Soil Conditions EXPLORATION RESULTS Nine (9) SPT soil borings, designated as A-1 through A-9, were drilled to depths of about 1 to feet below the existing grades in the area of the proposed middle school and parking areas at the Olson Park location. Five () SPT soil borings, designated as B-1 through B-, were drilled to a depth of about feet below site grades in the areas of the proposed middle school at the Sherwood/Red Oak site. Two () hand auger borings, designated as HA-1 and HA-, were augered to a depth of feet below grade within the proposed middle school footprint at the Sherwood/Red Oak site. The subsurface conditions encountered at the borings performed at the site can be summarized as follows. The specific soil types observed at the boring locations are noted on the boring logs enclosed in the Appendix. SPT Soil Borings At the Olson Park site the surficial soils were observed to consist of about to 1 inches of topsoil, 9 inches of gravel FILL at boring A-, or inches of gravel FILL underlain by 8 inches of buried topsoil at boring A-. At boring locations A-1 through A-8 the existing surficial soils were underlain by strata of natural Silty CLAY and Clayey SILT to boring termination at 1 to feet below grade. Soil boring A-9 was observed to consist of natural Silty CLAY with the exception of a stratum of Clayey SAND with Gravel from about ½ to 8 feet below existing site grades. Surficial materials at the Sherwood/Red Oak site were observed to consist of about to 8 inches of topsoil or to have no discernable surficial topsoil materials. Beneath the surficial topsoil, boring locations B-1, B-, B- and B- and hand augers HA-1 and HA- were comprised entirely of natural Silty CLAY to boring/hand auger termination at a depth of feet below existing site grades. Boring location B- exhibited a thin layer of Silty Clay FILL to about 1¾ feet below grade underlain by natural Silty CLAY to boring termination at about feet below grade. The Silty Clay Fill at boring B- was observed to exhibit an unconfined compression strength value of ½ tsf (very stiff consistency) and moisture content of about 0 percent. The natural Silty CLAY and Clayey SILT soils at both the Olson Park and Sherwood/Red Oak sites exhibited unconfined compressive strength values ranging from 1¼ to greater than ½ tsf (stiff to hard consistencies, but typically very stiff to hard) and moisture contents in the range of about 1 to percent (typically about 1 to 19 percent). General It should be noted that bid quantity estimation by averaging depths and strata changes from boring logs is not recommended. Too many variations exist for such averaging to be valid, particularly in the surficial material (i.e., bituminous pavement and gravel subbase) thicknesses, soil types and condition, depth, and groundwater conditions. A different scope of professional services would be required to obtain subsurface information needed for land purchase considerations and earthwork bid preparation. This scope could include additional borings and possibly test pits. Even with this additional information, contingencies should always be carried in construction budgets or land purchase agreements to cover variations in subsurface

12 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois conditions. Soil borings cannot present the same full-scale view that is obtained during complete site grading, excavation or other aspects of earthwork construction. Groundwater Observations Observations for groundwater were made during sampling and upon completion of the drilling operations at the boring locations. In auger drilling operations, water is not introduced into the boreholes, and the groundwater position can often be obtained by observing water flowing into or out of the boreholes. Furthermore, visual observation of the soil samples retrieved during the auger drilling exploration can often be used in evaluating the groundwater conditions. Groundwater was observed at borings A-1, A- and A-9 at depths ranging from about 8 to 1 feet during drilling operations, and at boring A-1 groundwater was observed after drilling operations at a depth of about ½ feet. Groundwater was not observed at any of the Sherwood/Red Oak soil boring locations. Glacial till soils in the Midwest frequently oxidize from gray to brown above the level at which the soil remains saturated. The long-term groundwater level is often interpreted to be near this zone of color change. Based on the results of this exploration, the static long-term groundwater level at the project site is estimated to be located at a depths ranging from approximately 8 to 1 feet below the existing surface grades at the two possible sites. It should be noted that the groundwater level can vary based on precipitation, evaporation, surface run-off and other factors not immediately apparent at the time of this exploration. Surface water runoff will be a factor during general construction, and steps should be taken during construction to control surface water runoff and to remove water that may accumulate in the proposed excavations as well as floor slab and pavement areas.

13 ECS Project No. 1:8-8- September, 1 Highland Park, Illinois Overview ANALYSIS AND RECOMMENDATIONS The conclusions and recommendations presented in this report should be incorporated in the design and construction of the project to reduce possible soil and/or foundation related problems. The following sections present specific recommendations with regard to the geotechnical design and construction aspects of the proposed middle school in Highland Park, Illinois. These include recommendations with regard to subgrade preparation and earthwork, fill placement, foundations, floor slab design and pavement design. Discussion of the factors affecting the building foundations for the proposed construction, as well as additional recommendations regarding geotechnical design and construction at the project site are included below. We recommend that ECS review the final design and specifications to check that the earthwork and foundation recommendations presented in this report have been properly interpreted and implemented in the design and specifications. Subgrade Preparation and Earthwork Operations Due to the uniformity of and high unconfined compressive strength values of onsite soils encountered at the boring locations within both the Olson Park and Sherwood/Red Oak sites, we anticipate that conventional subgrade preparation efforts, as discussed in the following paragraphs, should be appropriate during construction. The relatively stiff and consistent soils observed during this geotechnical exploration may be due to the sites proximity to the Red Oak moraine, which typically is associated with relatively high strength soils. The initial site preparation should consist of the complete removal of existing topsoil, gravel FILL material, vegetation, trees, and other deleterious material. The stripped topsoil can be stockpiled for later use in landscaping and non-structural areas. Once the surficial materials have been removed, the limits of the building footprints, parking lots and drive lanes should be excavated to the design subgrade elevation. ECS does not recommend the slab and pavement subgrades remain exposed to the elements or construction traffic for a prolonged period of time as the subgrade may be disturbed and/or softened. If the slab and/or pavement section is not planned to be constructed within a few days after exposing the final design subgrade, consideration should be given to leaving the subgrade approximately 1 foot above the final design subgrade to help prevent softening of the design subgrade soils (if feasible). We anticipate the soils at the slab and pavement subgrades will typically consist of natural Silty CLAY at the majority of the project site (at Olson Park or Sherwood/Red Oak) after completion of the initial subgrade preparation. Based upon site grades at the Olson Park site some cut and fill will likely be required to reach final subgrade elevation. Once the subgrade has been exposed, the subgrade can be proofrolled using a loaded dump truck having an axle weight of at least tons. The intent of the proofroll is to aid in identifying localized soft, particularly moist, unstable or unsuitable material which requires removal. Shallow Silty Clay FILL similar to the material encountered at soil boring location B- and higher moisture contents exhibited by near-surface soils in the boring logs may result in some areas requiring removal. If soft or yielding soils are observed during the proofroll of the subgrade, the

14 ECS Project No. 1:8-9- September, 1 Highland Park, Illinois soft soils should be undercut up to a maximum of feet and replaced with properly manipulated onsite soils (see the Fill Placement section for guidelines) or compacted engineered fill to the design subgrade. This proofrolling procedure will only identify near surface soils that are unsuitable for slab and pavement support and any potential deeper pockets of unsuitable fill soils could lead to premature deterioration/cracking of the slab and pavements. Steps should be taken by the contractor to control surface water runoff and to remove water from precipitation that may accumulate in the subgrade areas, especially during the wet season. When wet and subjected to construction traffic, softening and disturbance of the exposed subgrade may occur. Construction traffic should be limited when the subgrade is wet. During final preparation of the subgrade, a smooth drum roller is often used to provide a flat surface and provide for better drainage to reduce the negative impact of rain events. We also recommend crowning or sloping the subgrade to provide positive drainage off the subgrades. Care should be exercised during subgrade preparation (i.e. compaction operations) to reduce pumping of the subgrade soils and observations should be made during earthwork operations to determine whether the weight of the construction equipment is negatively impacting the on site soils. Minimizing disturbance to the exposed subgrade is important for proper construction of the pavements and slabs-on-grade. Exposure to the environment may weaken the subgrade soils if the excavations remain open for too long a period. If the subgrade soils are softened by surface water intrusion or exposure, the softened soils must be removed from the subgrade excavation bottom immediately prior to placement of pavement, concrete and/or engineered fill. The silt content of the soils appeared to increase with depth. The more silty soils at the site will be even more susceptible to disturbance when wet. Therefore it is extremely important the foundation excavations do not remain open for long. We recommend the foundation excavations be filled with concrete the day they are excavated, or if not feasible, the subgrade protected with a crushed stone or lean concrete working mat, if the excavations will be left open overnight. The need for and most appropriate type of stabilization required will be dependent upon soil, groundwater and weather conditions, as well as, the construction schedule and methods of construction that will be used. In general, scarifying, drying and recompacting moderately unstable soil areas is expected to be the most economical means of improving the poor and high moisture content soils prior to final preparation of building pad and pavement subgrades. The best period for air drying soils typically occurs in dry times of the year (i.e., summer), and the warm weather experienced in the summer months usually is more conducive to dry site conditions. Alternatives for subgrade stabilization could also include undercutting and replacing unsuitable soils as recommended herein. Excavations should comply with the requirements of OSHA 9CFR, Part 19, Subpart P, "Excavations" and its appendices, as well as other applicable codes. This document states that the contractor is solely responsible for the design and construction of stable, temporary excavations. The excavations should not only be in accordance with current OSHA excavation and trench safety standards but also with applicable local, state, and federal regulations. The contractor should shore, slope or bench the excavation sides when appropriate. Due to the depths of excavations, there is the potential to undermine the existing foundation and slabs. The contractor should use care as to not undermine the existing foundations and slabs and incorporate underpinning or other support methods as appropriate.

15 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois If problems are encountered during the earthwork operations, or if site conditions deviate from those encountered during our subsurface exploration, ECS should be notified immediately. We recommend that the project geotechnical engineer or his representative should be on site to monitor stripping and site preparation operations and observe that unsuitable soils have been satisfactorily removed and observe the proofrolling of the subgrades. Subgrade preparations should be performed a minimum of lateral feet beyond the limits of the building footprint and lateral feet beyond the footprint of the pavement areas. Fill Placement All fills should consist of an approved material, free of organic matter and debris, particles greater than -inches and have a Liquid Limit and Plasticity Index less than 0 and 1, respectively. Unacceptable fill materials include topsoil and organic materials (OH, OL), high plasticity silts and clays (CH, MH), and low-plasticity silts (ML). Under no circumstances should high plasticity soils be used as fill material in proposed structural areas or close to site slopes. The existing Silty Clay FILL soils observed at boring B- could be re-used as engineered fill provided they are screened of any organic material. The existing natural Silty CLAY also appears to be suitable for reuse as engineered fill. Similarly the on-site Clayey SILT may also be used, however the Clayey SILT material may be difficult to work with especially when wet and is also frost susceptible. Therefore if Clayey SILT is used as engineered fill, it should not be used within ½ feet of the final grade on exterior applications such as pavements. The on-site soils may require moisture content adjustments, such as the application of discing or other drying techniques or spraying of water to the soils prior to their use as compacted fill (termed manipulation). The planning of earthwork operations should recognize and account for increased costs associated with manipulation of the on-site materials considered for reuse as compacted fill. Fill materials should be placed in lifts not exceeding 8-inches in loose thickness and moisture conditioned to within ± percentage points of the optimum moisture content. Soil bridging lifts should not be used, since excessive settlement of overlying structures will likely occur. Controlled fill soils should be compacted to a minimum of 9% of the maximum dry density obtained in accordance with ASTM D1, modified Proctor method. The zone of the engineered fill placed below the foundations should extend 1 foot beyond the outside edges of the footings and from that point, outward laterally 1 foot for every feet of fill thickness below the footing. The expanded footprint of the proposed structure pad, parking lot and fill areas should be well defined, including the limits of the fill zones at the time of fill placement. Grade control should be maintained throughout the fill placement operations. All fill operations should be observed on a full-time basis by a qualified soil technician to determine that the specified compaction requirements are being met. A minimum of one compaction test per,00 square foot area or 0 linear feet of wall should be tested in each lift placed. The elevation and location of the tests should be clearly identified at the time of fill placement. Compaction equipment suitable to the soil type used as fill should be used to compact the fill material. Theoretically, any equipment type can be used as long as the required density is

16 ECS Project No. 1:8-11- September, 1 Highland Park, Illinois achieved; however, the standard of practice typically dictates that a vibratory roller be utilized for compaction of granular soils and a sheepsfoot roller be utilized for compaction of cohesive soils. In addition, a steel drum roller is typically most efficient for compacting and sealing the surface soils. All areas receiving fill should be graded to facilitate positive drainage from building pad areas of free water associated with precipitation and surface runoff. It should be noted that prior to the commencement of fill operations and/or utilization of off-site borrow materials, the Geotechnical Engineer of Record should be provided with representative samples to determine the material s suitability for use in a controlled compacted fill and to develop moisture-density relationships. To expedite the earthwork operations, if off-site borrow materials are required, it is recommended they consist of suitable fill materials in accordance with the recommendations previously outlined in this section. If frost susceptible soils are imported to the project site, the frost susceptible soils should not be placed within ½ of final site grades in unheated areas. Fill materials should not be placed on frozen soils or frost-heaved soils and/or soils that have been recently subjected to precipitation. All frozen soils should be removed prior to continuation of fill operations. Borrow fill materials, if required, should not contain frozen materials at the time of placement. All frost-heaved soils should be removed prior to placement of controlled, compacted fill, granular subbase materials, and foundation or slab concrete. Foundation Recommendations We recommend the proposed middle school structure be supported on a shallow foundation system bearing in the competent natural Silty CLAY soils or on compacted engineered fill overlying competent natural soils can be designed for a maximum net allowable soil bearing pressure of,00 psf. This recommendation applies to both the Olson Park and Sherwood/Red Oak sites. The net allowable soil bearing pressure refers to that pressure which may be transmitted to the foundation bearing soils in excess of the final minimum surrounding overburden pressure. Competent natural Silty CLAY soils for a shallow foundation system can be identified on the boring logs and in the field as those soils having an unconfined compressive strength of at least ¾ tsf. Please note significant cutting and filling may be required at the Olson Park site due to the observed differential in elevations. Foundations should not bear on any disturbed natural soils created by the cutting/filling operations. Only foundations bearing on undisturbed, competent natural soils or properly compacted, engineered fill overlying undisturbed, competent natural soils can be designed for a maximum net allowable soil bearing pressure of,00 psf. General We recommend the foundation excavations be filled with concrete the day they are excavated, or if not feasible, the subgrade protected with a crushed stone or lean concrete working mat, if the excavations will be left open overnight. It should be noted that existing Silty Clay FILL was present at boring B- on the Red Oak Elementary School site, surficial gravel FILL was present at borings A- and A- on the Olson

17 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois Park site and pockets of soils containing organics were observed at a few locations throughout the project site. If additional fill soils/organic soils are encountered during the foundation excavations, the full depth fill soils shall be removed and replaced with engineered fill/lean concrete to the foundation subgrade elevation. If soft/unsuitable soils or soils with elevated moisture contents are encountered at the proposed bearing elevation, the footings should extend until suitable bearing soils are encountered or the unsuitable soils should be removed beneath the base of the footing and replaced with compacted engineered fill or lean concrete. If engineered fill is utilized, the engineered fill should be compacted to a minimum of 9 percent of the maximum dry density in accordance with ASTM D1 (Modified Proctor Method). The zone of the engineered fill placed below the foundations should extend 1 foot beyond the outside edges of the footings and from that point, outward laterally 1 foot for every feet of fill thickness below the footing. If lean concrete is utilized to replace weaker/low bearing soils or unsuitable soils, no lateral over-excavation will be necessary, but the excavation should be 1 foot wider than the footing ( inches on each side), and the lean concrete should be allowed to sufficiently harden prior to placement of the foundation concrete. If more than feet of engineered fill becomes necessary beneath foundations, the fill must be a well graded granular material. We recommend that the excavation/backfill of foundations be monitored full-time by an ECS Geotechnical Engineer or his representative to verify that the soil bearing pressure is consistent with the subsurface information obtained during the geotechnical exploration. We also recommend that supplemental soil testing such as hand augers and DCP testing be performed during foundation excavations to observe the suitability of the bearing soils. Please note that due to the wooded nature of the Sherwood/Red Oak site, additional borings will be necessary prior to final design. Further it is likely that rootmat from the existing trees could extend several feet below grade. These materials including all the roots and stumps will need to be completely removed beneath all buildings, slabs pavements and in particular foundations. If the Owner proceeds with the Sherwood/Red Oak site, extreme care must be taken during earthwork and foundation activities adjacent to existing structures. Vibratory compaction equipment can in some cases cause interior and exterior building finishes to crack. Mass or localized undercutting adjacent to existing structures may undermine existing foundations and slabs. Excavation below existing foundations and slabs shall consider appropriate preventative measures, such as shoring and underpinning to help prevent loss of subgrade support. In no case shall excavations extend below adjacent foundations and slabs unless underpinning or other forms of engineered support are provided. Due to the depths of excavations, there is the potential to undermine the existing foundation and slabs. The contractor should use care as to not undermine the existing foundations and slabs at the adjacent elementary schools and incorporate underpinning or other support methods as appropriate. To help reduce the potential for foundation bearing failure and excessive settlement due to local shear or "punching" action, we recommend that continuous footings have a minimum width of inches and that isolated column footings have a minimum lateral dimension of 0 inches. In addition, footings should be placed at a depth to provide adequate frost cover protection. For

18 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois this region, we recommend the exterior footings and footings beneath unheated areas be placed at a minimum depth of ½ feet below finished grade. Interior footings in heated areas can be placed at a minimum of feet below grade provided that suitable soils are encountered and that the foundations will not be subjected to freezing weather either during or after construction. Settlement of individual footings, designed in accordance with our recommendations presented in this report, is expected to be small and within tolerable limits for the proposed building. For footings placed on suitable natural soils or properly compacted engineered fill, maximum total settlement is expected to be in the range of about 1 inch or less. Maximum differential settlement between adjacent columns is expected to be about ½ of the total settlement. These settlement values are based on our engineering experience with the soil and the anticipated structural loading, and are to guide the Structural Engineer with his design. Floor Slab Design For the design and construction of the slabs-on-grade for the building, the recommendations provided in the section entitled Subgrade Preparation and Earthwork Operations should be followed. The building floor slab thickness can be determined utilizing an assumed modulus of subgrade reaction of pounds per cubic inch (pci) provided the slabs are supported on suitable bearing natural Silty CLAY soils and/or newly placed engineered fill. We recommend the slab be designed with a minimum thickness of inches. We recommend consideration be given to the floor slab being underlain by a minimum of inches of granular material having a maximum aggregate size of 1½ inches and no more than percent soil passing the No. 0 sieve. This granular layer will facilitate the fine grading of the subgrade and help prevent the rise of water through the floor slab. Prior to placing the granular material, the floor subgrade should be free of standing water, mud, and frozen soil. Before the placement of concrete, a vapor barrier may be placed on top of the granular material to provide additional moisture protection. Welded-wire mesh reinforcement should be placed in the upper half of the floor slab and attention should be given to the surface curing of the slab to minimize uneven drying of the slab and associated cracking and/or slab curling. The use of a blotter or cushion layer above the vapor retarder can also be considered for project specific reasons. Please refer to ACI 0.1R0 Guide for Concrete Floor and Slab Construction and ASTM E 1 Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs for additional guidance on this issue. We recommend that the floor slab be isolated from the foundation footings so differential settlement of the structure will not induce shear stresses on the floor slab. For maximum effectiveness, temperature and shrinkage reinforcements in slabs on ground should be positioned in the upper third of the slab thickness. The Wire Reinforcement Institute recommends the mesh reinforcement be placed inches below the slab surface or upper one-third of slab thickness, whichever is closer to the surface. Adequate construction joints, contraction joints and isolation joints should also be provided in the slab to reduce the impacts of cracking and shrinkage. Please refer to ACI 0.1R0 Guide for Concrete Floor and Slab Construction for additional information regarding concrete slab joint design.

19 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois If problems are encountered during the slab subgrade preparation, or if site conditions deviate from those encountered during our subsurface exploration, ECS should be notified immediately. We recommend that the project geotechnical engineer or his representative should be on site to monitor subgrade preparation and observe that unsuitable soils have been satisfactorily removed and the subgrade soils are suitable to support the slab. Underslab Sub-Drainage Based on the groundwater levels observed during the subsurface exploration, we do not anticipate a significant volume of water will persist at the slab subgrade elevation. It should be noted however that surface runoff and limited groundwater seepage may accumulate at the slab subgrade such as the perched water condition. As such, we recommend that positive drainage be implemented around the perimeter of the proposed structure to reduce the potential for water accumulation under the floor slab and foundation elements, which could potentially weaken the bearing soils. Exterior Pavement Design We recommend that the pavement subgrade be prepared in accordance with the Subgrade Preparation and Earthwork Operations section of this report. Once the subgrade has been properly prepared, we recommend the following minimum pavement sections for the proposed development. The pavement sections were developed based on the anticipated pavement usage/traffic loads and an IBR of for the subgrade soils. Table 1: Pavement Section Recommendations Compacted Material Thicknesses (Inches) Pavement Material Portland Cement Concrete Bituminous Surface Course Bituminous Base Course Crushed Granular Subbase (CA-) Total Pavement Section Thickness Flexible Pavement (Standard) Flexible Pavement (Heavy Duty) Rigid Pavement (Standard) Rigid Pavement (Heavy Duty) ½ 1½ ¼ ¾ 1½ 11 1

20 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois All pavement materials and construction, with the exception of the modified Proctor compaction specification, should be in accordance with Guidelines for AASHTO Pavement Design and IDOT Standard Specifications for Road and Bridge Construction. The pavement sections specified in the table above are general pavement recommendations based on the anticipated usage at the project site and were not developed based on specific traffic patterns/loading and resiliency factors, as those parameters were not provided by the design team. We recommend the project team provide ECS with design traffic loads so that we can verify the recommendations detailed herein are appropriate for the anticipated traffic loads. The table above provides Standard and Heavy Duty flexible and rigid pavement recommendations. The standard pavement section assumes that typical traffic loading will be limited to standard automobiles and does not account for more heavily loaded vehicles (i.e., multiple axle trucks or buses) and should be used for parking lanes or infrequent traffic. The Heavy-Duty pavement section is recommended for pavements to be subjected with frequent traffic such as drive lanes, entrance/exit drives and service lanes including bus lanes. If anticipated traffic will exceed 0 buses per day ECS should be contacted to review and revise our heavy duty pavement sections if required. It should also be noted that the pavement sections specified in the table above were developed for the anticipated in-service traffic conditions only and do not provide an allowance for construction traffic conditions or traffic conditions in excess of typical residential / collector street traffic. Therefore, if pavements will be constructed early during site development to accommodate construction traffic, consideration should be given to the construction of designated haul roads, where thickened pavement sections can be provided to accommodate the construction traffic, as well as the future in-service traffic. ECS can provide additional design assistance with pavement sections for haul roads upon request. An important consideration with the design and construction of pavements is surface and subsurface drainage. Where standing water develops, either on the pavement surface or within the base course layer, softening of the subgrade and other problems related to the deterioration of the pavement can be expected. Furthermore, good drainage should minimize the possibility of the subgrade materials becoming saturated over a long period of time. We recommend the granular base course should be compacted to at least 9 percent of the maximum dry density obtained in accordance with ASTM D1, modified Proctor method. During asphalt pavement construction, the wearing and leveling course should be compacted to a minimum of 9 percent of the theoretical density value. Prior to placing the granular material, the pavement subgrade soil should be properly compacted, observed to be stable during a final proofroll and free of standing water, mud, and frozen soil. Infiltration and subterranean water are the two sources of water that should be considered in the pavement design for the project. Infiltration is surface water that enters the pavement through the joints, pores, cracks in the pavement and through shoulders and adjacent areas pavements as a result of precipitation. Subterranean water is a source of water from a high water table on the site. The static long term groundwater level on the site is estimated to be located at a depth of about 8 to 1 feet below existing site grades. Therefore for the proposed at grade pavements for the project, infiltration is the most important source of water to be considered and based on the proposed use, a likely source of water introduced into the subgrade.

21 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois We recommend pavement subgrades should be crowned, or sloped, a minimum of 1% to promote subsurface water flow across the lean clay subgrades and to prevent ponding. Crowning and sloping the subgrade should help minimize the potential for water to accumulate and the aggregate base course and clay subgrade soils to become saturated. Proper profile grading is essential to avoid the creation of bathtubs beneath the pavements, trapping water. The trapped water or standing water in the bathtubs can result in saturation of the aggregate base course and clayey subgrade soils leading to softening of the subgrade and premature pavement cracking and settlement. Adequate construction joints, contraction joints and isolation joints should be provided in the areas of rigid pavement to reduce the impacts of cracking and shrinkage. Please refer to ACI 0R-9 Guide for Design of Concrete Parking Lots. The Guide recommends an appropriate spacing strategy for the anticipated loads and pavement thickness. It has been our experience that joint spacing closer to the minimum values results in a pavement with less cracking and better long term performance. Pavement Maintenance Regular maintenance and occasional repairs should be implemented to keep pavements in a serviceable condition. In addition, to help minimize water infiltration to the pavement section and within the base course layer resulting in softening of the subgrade and deterioration of the pavement, we recommend the timely sealing of joints and cracks using elastomeric caulk in rigid pavements and hot poured emulsified asphalt sealant in flexible pavements. We recommend exterior pavements should be reviewed for distress/cracks at least twice a year, once in the spring and once in the fall. Sound maintenance programs should help maintain and enhance the performance of pavements and attain the design service life. A preventative maintenance program should be implemented early in the pavement life to be effective. The standard in the industry supported by research indicates that preventative maintenance should begin within to years of the construction of the pavement. Failure to perform preventative maintenance will reduce the service life of the pavement and increase the costs for both corrective maintenance and full pavement rehabilitation. Adjacent Construction and Monitoring If the Owner chooses to proceed with construction at the Sherwood/Red Oak site extreme care must be taken during earthwork and foundation activities adjacent to existing structures. Vibratory compaction equipment can in some cases cause interior and exterior building finishes to crack. Mass or localized undercutting adjacent to existing structures may undermine existing foundations and slabs. Excavation below existing foundations and slabs shall consider appropriate preventative measures, such as shoring and underpinning to help prevent loss of subgrade support. In no case shall excavations extend below adjacent foundations and slabs unless underpinning or other forms of engineered support are provided.

22 ECS Project No. 1:8-1- September, 1 Highland Park, Illinois General Construction Considerations PROJECT CONSTRUCTION RECOMMENDATIONS We recommend that the subgrade preparation, installation of the foundations and construction of the slabs-on-grade and pavements be monitored by an ECS geotechnical engineer or his representative. Methods of verification and identification such as proofrolling, DCP testing, vane shear tests, and hand auger probe holes will be necessary to further evaluate the subgrade soils and identify unsuitable soils. The contractor should be prepared to over-excavate footing and slab-on-grade excavations as necessary. We recommend that excavations of foundations be monitored on a full-time basis by an ECS geotechnical engineer or his representative to verify that the soil bearing pressure and the exposed subgrade materials can support the recommended design bearing pressure and are consistent with the boring log information obtained during this geotechnical exploration. We would be pleased to provide these services. If soft/unsuitable soils or soils with elevated moisture contents are encountered at the proposed bearing elevation, the footings should extend until suitable bearing soils are encountered or the unsuitable soils should be removed beneath the base of the footing and replaced with compacted engineered fill or lean concrete. If engineered fill is utilized, the engineered fill should be compacted to a minimum of 9 percent of the maximum dry density in accordance with ASTM D1 (Modified Proctor Method). The zone of the engineered fill placed below the foundations should extend 1 foot beyond the outside edges of the footings and from that point, outward laterally 1 foot for every feet of fill thickness below the footing. If lean concrete is utilized to replace weaker/low bearing soils or unsuitable soils, no lateral over-excavation will be necessary, but the excavation should be 1 foot wider than the footing ( inches on each side), and the lean concrete should be allowed to sufficiently harden prior to placement of the foundation concrete. If more than feet of engineered fill becomes necessary beneath foundation, the fill must be a well graded granular material. We recommend that the excavation/backfill of foundations be monitored full-time by an ECS Geotechnical Engineer or his representative to verify that the soil bearing pressure is consistent with the subsurface information obtained during the geotechnical exploration. We also recommend that supplemental soil testing such as hand augers and DCP testing be performed during foundation excavations to observe suitability of the bearing soils. Construction Dewatering Based on the groundwater conditions encountered at the project site, we do not anticipate that significant dewatering efforts will be required during construction of shallow foundations, slabon-grade and at grade parking lot/pavement. However, it should be noted that minor groundwater seepage and/or surface runoff may introduce water into the project site, in particular the deeper excavations likely to be required if a partial basement is constructed, and the general contractor should be prepared to remove any accumulated water prior to the placement of fill and concrete. We anticipate that the removal of any accumulated water can be achieved utilizing drainage trenches and a sump and pump system.

23 ECS Project No. 1:8 -- September, 1 Highland Park, Illinois Closing This report has been prepared to aid in the evaluation of this property and to assist the architect and/or engineer in the design of this project. The scope is limited to the specific project and locations described herein and our description of the project represents our understanding of the significant aspects relative to soil and foundation characteristics. In the event that any change in the nature or location of the proposed construction outlined in this report are planned, we should be informed so that the changes can be reviewed and the conclusions of this report modified or approved in writing by the geotechnical engineer. It is recommended that all construction operations dealing with earthwork and foundations be reviewed by an experienced geotechnical engineer to provide information on which to base a decision as to whether the design requirements are fulfilled in the actual construction. If you wish, we would welcome the opportunity to provide field construction services for you during construction. The analysis and recommendations submitted in this report are based upon the data obtained from the soil borings and tests performed at the locations as indicated on the Boring Location Diagram and other information referenced in this report. This report does not reflect variations, which may occur between the borings. In the performance of the subsurface exploration, specific information is obtained at specific locations at specific times. However, it is a well known fact that variations in soil conditions exist on most sites between boring locations and also such situations as groundwater levels vary from time to time. The nature and extent of variations may not become evident until the course of construction. If variations then appear evident, after performing on-site observations during the construction period and noting characteristics and variations, a reevaluation of the recommendations for this report will be necessary. In addition to geotechnical engineering services, ECS Midwest, LLC has the in-house capability to perform multiple additional services as this project moves forward. These services include the following: Environmental Consulting; Geophysical Testing (ReMi and PHSA) Project Drawing and Specification Review; and, Construction Material Testing / Special Inspections We would be pleased to provide these services for you. If you have questions with regard to this information or need further assistance during the design and construction of the project please feel free to contact us.

24 APPENDIX General Location Map Boring Location Diagram Boring Logs Unified Soil Classification System Reference Notes for Boring Logs

25 Approximate Project Site Location Figure 1 GENERAL LOCATION MAP ECS Project No. 1:8 Highland Park, Illinois

26 SCALE: 1 INCH = 0FT 8/11/1 Approximate Boring Location OLSON PARK SITE BORING LOCATION DIAGRAM CHICAGO OFFICE 1 BARCLAY BOULEVARD BUFFALO GROVE IL 0089 ECS PROJECT NO.1:8 NORTH SHORE SCHOOL DISTRICT 11 ST. JOHNS AVENUE HIGHLAND PARK IL 00

27 SCALE: 1 INCH = 0FT 8/11/1 Approximate Boring Location SHERWOOD/RED OAK SITE BORING LOCATION DIAGRAM CHICAGO OFFICE 1 BARCLAY BOULEVARD BUFFALO GROVE IL 0089 ECS PROJECT NO.1:8 NORTH SHORE SCHOOL DISTRICT 11 ST. JOHNS AVENUE HIGHLAND PARK IL 00