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Report OFFICE COPY �`^���- 1,14l050Sw 41th hie - _ g CITY OF TIGARD BUILDING DIVISION Geotechnical Investigation Twality Middle School Track and Field Upgrades Tigard, Oregon January 26, 2021 Prepared for Tigard-Tualatin School District 6960 SW Sandburg Street Tigard, OR 97223 Prepared by G RA 9750 SW Nimbus Avenue Beaverton, OR 97008-7172 (503) 641-3478 www.gri.com 1 GRO TABLE OF CONTENTS 1 INTRODUCTION 1 2 PROJECT DESCRIPTION 1 3 SITE DESCRIPTION 1 3.1 General 1 3.2 Geology 1 4 SUBSURFACE CONDITIONS 2 4.1 General 2 4.2 Soils 2 4.3 California Bearing Ratio 3 4.4 Infiltration Testing 3 4.5 Groundwater 4 5 CONCLUSIONS AND RECOMMENDATIONS 4 5.1 General 4 5.2 Earthwork 4 5.3 On-Site Disposal of Stormwater 7 5.4 Track Surface Condition 7 6 DESIGN REVIEW AND CONSTRUCTION SERVICES 7 7 LIMITATIONS 8 8 REFERENCES 9 APPENDICES Appendix A: Field Explorations and Laboratory Testing FIGURES Figure 1: Vicinity Map Figure 2: Site Plan Figure 3: Observed Pavement Distress GRI PN#5970-M-Twality Middle School Track and Field Upgrades January 26,2021 1 INTRODUCTION As requested, GRI provided geotechnical consultation for the track and field upgrades project on the Twality Middle School campus in Tigard, Oregon. The Vicinity Map, Figure 1, shows the general location of the site. As you know, GRI completed a geotechnical investigation for the Twality Middle School replacement project. Our previous work on campus is summarized in the following report: "Geotechnical Investigation and Site-Specific Seismic Hazard Evaluation, Twality Middle School, Tigard, Oregon," dated June 28, 2017, prepared for the Tigard- Tualatin School District. The purpose of this investigation was to evaluate subsurface conditions within the footprint of the track and field and develop geotechnical recommendations for use in the design and construction of the proposed improvements. The investigation included a review of existing geotechnical information for the site and surrounding area, subsurface explorations, limited laboratory testing, and limited engineering analyses. This report describes the work accomplished and provides conclusions and recommendations for use in the design and construction of the proposed project. 2 PROJECT DESCRIPTION We understand the existing field at Twality Middle School will be replaced with synthetic turf,and the existing track will be resurfaced with a rubberized material.The track and field are located immediately east of the main middle school building. The Site Plan, Figure 2, shows the location of the track and field to be upgraded with respect to the school building.We anticipate the new field will be established at or near existing site grades, and cuts and fills to establish grades across the field will be minimal. We understand on-site disposal of stormwater is being considered for this project. 3 SITE DESCRIPTION 3.1 General The Twality Middle School campus is developed with school buildings, driveways and parking lots, and athletic facilities. The campus is bordered by residential structures in all directions, with James Templeton Elementary School campus to the south and SW 97th Avenue to the west. Review of satellite imagery and our observations at the site indicate the ground surface of the track and field is generally flat and slopes downward at about 3H:1V (Horizontal to Vertical) on the south and east. 3.2 Geology Published geologic mapping indicates the site is mantled with Missoula flood deposits, locally referred to in the project area as the Willamette Silt Formation (Madin, 1990). In general, Willamette Silt is composed of beds and lenses of silt and sand. Stratification GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 1 January 26, 2021 within this formation commonly consists of 4- to 6-inch-thick beds, although in some areas,the silt and sand are massive and the bedding is indistinct or nonexistent. Based on explorations completed in the project vicinity,the Willamette Silt is underlain by Columbia River Basalt at depths of about 27.5 feet to 75 feet. 4 SUBSURFACE CONDITIONS 4.1 General Subsurface materials and conditions were investigated on December 10, 2020,with seven hand-augered borings, designated HA-1 through HA-7, and seven corresponding Kessler dynamic cone penetrometer(DCP) probes,designated DCP-1 through DCP-7.The borings were advanced to depths of about 2.5 feet to 5.5 feet, and the Kessler DCP probes were advanced to a depth of about 3 feet below existing site grades.The approximate locations of the explorations completed for this project are shown on the Site Plan, Figure 2. Logs of the borings are provided on Figures 1A through 4A. Details of the subsurface explorations and laboratory-testing program completed for this project are provided in Appendix A. The terms and symbols used to describe the materials encountered in the borings are defined in Table 1A and on the attached legend. 4.2 Soils For the purpose of discussion, the materials disclosed by the explorations have been grouped into the following units based on their physical characteristics and engineering properties: 1. FILL a. Silt b. Gravel 2. Sandy SILT and Silty SAND The following paragraphs provide a description of the materials encountered in the explorations completed by GRI for this project and a discussion of the groundwater conditions at the site. a. FILL a. SILT. Fill consisting of silt soil was encountered at the ground surface in borings HA-5 through HA-7 and extends to depths of about 2 feet to 4 feet. In general,the silt fill is brown, has a variable clay content ranging from a trace to some clay, and contains a variable amount of fine-grained sand ranging from a trace of sand to sandy. The relative consistency of the silt fill is medium stiff to stiff based on observations during hand augering. The natural moisture content of the silt fill ranges from 21%to 24%. GRI PN#5970-M—Twality Middle School Track and Field Upgrades Page 2 January 26,2021 GRI b. GRAVEL. Fill consisting of gravel was encountered beneath the silt fill in borings HA-5 through HA-7 and extends to the maximum depths explored of about 2.5 feet to 4.5 feet. In general, the gravel fill is subrounded to angular and contains some fine- to coarse-grained sand and a trace of silt. The relative density of the gravel fill is medium dense based on observations during hand augering. b. Sandy SILT to Silty SAND Interbedded layers of sandy silt to silty sand were encountered at the ground surface in borings HA-1 through HA-4 and extend to the maximum depth explored of about 5.5 feet. The soils are generally light brown to dark brown, with gray mottling observed below about 5 feet in boring HA-1. In general, the sandy silt contains fine- to medium-grained sand and up to a trace of clay, and the silty sand is fine to medium grained. Based on observations during auguring, the relative consistency of the silt is medium stiff to stiff and the relative density of the silty sand is medium dense. The natural moisture contents of the silt and sand soils range from 12% to 23% and 19% to 20%, respectively. Atterberg-limits test results indicate the sandy silt has a liquid limit of 24% and plasticity index of 3%, see Figure 5A. 4.3 California Bearing Ratio The data from the DCP probes were used to estimate the California bearing ratio (CBR) value of the in-situ subgrade soils. Details regarding the DCP testing methods are provided in Appendix A.The CBR values estimated using the DCP probe blow counts are tabulated below. Probe CBR Value Soil Classification DCP-1 6 Sandy SILT DCP-2 3 Sandy SILT DCP-3 3 Sandy SILT DCP-4 5 Sandy SILT DCP-5 2 Sandy SILT DCP-6 3 Sandy SILT DCP-7 4 Sandy SILT 4.4 Infiltration Testing On December 10, 2020, infiltration testing was conducted in boring HA-4 at a depth of about 4.5 feet below existing site grades. Details regarding the infiltration testing methods are provided in Appendix A. The unfactored,field-measured infiltration rate recorded at a specific depth within a specific soil unit is tabulated below. GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 3 January 26,2021 G ' p\ Depth of Average Infiltration Boring Infiltration Test,ft Rate,in./hour Soil Classification HA-4 4.5 0 Sandy SILT 4.5 Groundwater Groundwater was not encountered in the borings at the time of excavation.Our review of U.S. Geological Survey (USGS) groundwater data suggests the regional groundwater level at the site typically occurs at depth in the highly fractured, hard basalt that underlies the site. However, our experience in the project vicinity indicates perched groundwater can occur in the fine-grained soils that mantle the site, particularly during the wet winter months or following periods of intense or prolonged precipitation. 5 CONCLUSIONS AND RECOMMENDATIONS 5.1 General Subsurface explorations completed for this investigation indicate the southern and eastern portions of the field are mantled with fill soils, which were likely placed from on-site excavations during mass grading for construction of the track and field.The fill soils extend to depths exceeding 4.5 feet and are underlain by silty sand to sandy silt soils that also mantle the northern and western portions of the field. Groundwater was not encountered at the time of exploration; however, we anticipate perched groundwater may approach the ground surface during the wet winter months or following periods of intense or prolonged precipitation. We recommend the new synthetic turf field be installed in accordance with the manufacturer's recommendations. The primary geotechnical considerations associated with construction of the new field include the presence of fine-grained soils at the ground surface that are extremely moisture sensitive; the potential for shallow, perched- groundwater conditions;the presence of silt and gravel fill soils;and the need for subgrade stabilization for support of construction equipment.The primary pavement considerations associated with resurfacing the existing track include repairing cracks and areas damaged by construction traffic. The following sections of this report provide our geotechnical conclusions and recommendations for use in the design and construction of the new track and field. 5.2 Earthwork 5.2.1 General The fine-grained soils that mantle the field are moisture sensitive, and perched groundwater may approach the ground surface during the wet winter months. Therefore, it is our opinion earthwork can be completed most economically during the dry summer months typically extending from June to mid-October. It has been our experience that the GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 4 January 26,2021 G REI moisture content of the upper few feet of silty soils will tend to decrease during extended warm, dry weather. However, the moisture content of the soil tends to remain well above the optimum moisture content for compaction. As a result, the contractor should use construction equipment and procedures that protect the subgrade from disturbance and softening. To reduce the potential for disturbance of the moisture-sensitive fine-grained soils, site grading can be completed using track-mounted hydraulic excavators. Excavations should be finished using a smooth-edged bucket to produce a firm, undisturbed surface. It may also be necessary to construct granular haul roads and work pads concurrently with excavation to minimize subgrade disturbance. If the subgrade is disturbed during construction, soft, disturbed soils may need to be overexcavated to firm soil and backfilled with structural fill depending on the stabilization alternative selected. 5.2.2 Site Preparation The ground surface in the fields should be stripped of existing vegetation,surface organics, and loose surface soils.We anticipate stripping up to a depth of about 4 inches to 8 inches will likely be required in the field; however, deeper stripping may be required in localized areas. All organic material should be removed from within the limits of the fields. Organic strippings should be disposed of off site or stockpiled on site for use in landscaped areas. Following stripping, the exposed subgrade should be evaluated by a qualified member of GRI's geotechnical engineering staff or an engineering geologist. 5.2.3 Subgrade Stabilization Although the field will be subjected to negligible loading after completion, subgrade stabilization will be required to construct the new field. Based on our experience with similar projects and subgrade conditions, we recommend the following three alternatives for construction of the new fields: 1) Aerate and dry the subgrade to within 3% of optimum moisture content to allow for re-compaction. Aeration and drying can best be accomplished by tilling the subgrade to a depth of 12 inches to 14 inches below the planned subgrade elevation. Drying rates are dependent on weather factors such as wind, temperature, and relative humidity; however, we anticipate a minimum of two weeks to three weeks of dry weather will be required to achieve the moisture content required for compaction. Following drying, the subgrade should be compacted using a segmented-pad or sheepsfoot roller to at least 95% of the maximum dry density as determined by ASTM International (ASTM) D698. The compacted subgrade should be capped with a minimum-6-inch-thick section of relatively clean crushed rock underlain by a woven geotextile fabric to support lighter construction equipment and limited traffic by dump trucks. GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 5 January 26, 2021 GRV 2) Construct a granular work pad to protect the underlying silt subgrade and provide a firm working surface.A 12- or 18-inch-thick granular work pad combined with a triaxial geogrid or woven geotextile fabric, respectively, should be sufficient to reduce the risk of disturbance by lighter construction equipment and limited traffic by dump trucks. The subgrade should be excavated using a track-mounted hydraulic excavator equipped with a smooth-edged bucket to produce a firm, undisturbed surface. If the subgrade is disturbed during construction, soft, disturbed soils should be overexcavated to firm soil and backfilled with crushed rock. The geogrid or geotextile fabric should be placed at the base of the excavation and crushed rock should be used to construct the work pad. The crushed rock should be end-dumped,spread using a track-mounted bulldozer,and compacted to at least 95% of the maximum dry density as determined by ASTM D698. 3) Treat the subgrade with at least 8% cement, based on the dry unit weight of the treated soil, to hydrate excessive moisture and improve the strength properties of the fine-grained subgrade. Treatment should be accomplished by spreading a measured quantity of cement onto the surface and tilling 12 inches to 14 inches into the subgrade using specialized equipment. The treated soils should be subsequently compacted with segmented-pad rollers to at least 92% of the maximum dry density as determined by ASTM D698 and finished with graders and smooth,steel-drum vibratory rollers.Cement-treated soils are typically cured three days to five days to maximize their strength gain prior to being trafficked by equipment or placement of granular base course. The cement-treated subgrade should be capped with a minimum-6-inch-thick section of relatively clean crushed rock to support lighter construction equipment and limited traffic by dump trucks. Haul roads and other high-density traffic areas will require a minimum of 18 inches to 24 inches of fragmental rock, up to 6-inch nominal size, to reduce the risk of subgrade deterioration. Prior to placing the turf components, the fields should be proof rolled with a fully loaded, 10-cubic-yard dump truck.Any soft areas detected by the proof roll should be overexcavated to firm ground and backfilled with relatively clean, compacted crushed rock. It is not unusual for localized areas to require retreatment or replacement with crushed rock. In addition, the presence of fill soils may result in difficult tilling and soil cement operations. Project plans, specifications, and bid items should address the risk and uncertainties associated with these concerns. GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 6 January 26, 2021 G 5.3 On-Site Disposal of Stormwater The unfactored,field-measured infiltration rate for the soils that mantle the site is 0 inches per hour; therefore, it is our opinion the near-surface soils do not meet the requirements for on-site stormwater disposal. 5.4 Track Surface Condition GRI conducted a visual survey of the Twality Middle School track to identify pavement distresses and evaluate repair options.The results of the visual survey are shown on Figure 3. We observed isolated transverse cracking in the asphalt pavement, which has propagated through the rubberized surfacing on the track.We also observed several small areas where the rubber surfacing is missing, exposing the underlying asphalt, and areas of increased deterioration of the rubber surfacing. This is particularly evident on the southwestern end of the track,which had previously been used as a construction entrance. We recommend repairing transverse cracks using crack routing and filling techniques such that the seal is within Vs inch of the pavement surface.The contractor shall verify that crack seal used for repairs is compatible with the new rubberized surfacing being installed on the track. It should be noted that transverse cracking is generally a result of temperature cycling, and cracks in the asphalt may continue to propagate with continued temperature cycling despite being repaired with crack sealant. In areas where the existing rubberized topcoat is missing, we recommend patching the areas, as recommended by the manufacturer,to create a level surface prior to installation of the new surfacing. We anticipate the new rubberized surfacing will be installed using similar means and methods as the original surfacing,and that the existing pavement structure can adequately support lightly loaded application equipment, such as small sprayer machines, for the surfacing installation. GRI should be contacted to modify or reaffirm these recommendations if large construction equipment,such as dump trucks or asphalt pavers, are planned for application of the new track surfacing. 6 DESIGN REVIEW AND CONSTRUCTION SERVICES We welcome the opportunity to review and discuss construction plans and specifications for this project as they are being developed. GRI should be retained to review all geotechnical-related portions of the plans and specifications to evaluate whether they are in conformance with the recommendations provided in our report. In addition,to observe compliance with the intent of our recommendations, the design concepts, and the plans and specifications, it is our opinion all construction operations dealing with earthwork and subgrade stabilization should be observed by a GRI representative. Our construction- phase services will allow for timely design changes if site conditions are encountered differ GRI PN#5970-M—Twality Middle School Track and Field Upgrades Page 7 January 26,2021 GRp from those described in our report. If we do not have the opportunity to confirm our interpretations, assumptions, and analyses during construction,we cannot be responsible for the application of our recommendations to subsurface conditions different from those described in this report. 7 LIMITATIONS This report has been prepared to aid in the design of this project. The scope is limited to the specific project and location described herein, and our description of the project represents our understanding of the significant aspects of the project relevant to the proposed new fields. In the event any changes in the design and location of the planned improvements as outlined in this report are planned, we should be given the opportunity to review the changes and modify or reaffirm the conclusions and recommendations of this report in writing. The conclusions and recommendations submitted in this report are based on the data obtained from the borings made at the locations indicated on the Site Plan, Figure 2, and other sources of information discussed in this report. In the performance of subsurface investigations, specific information is obtained at specific locations at specific times. However, it is acknowledged that variations in soil conditions may exist between exploration locations. This report does not reflect any variations that may occur between these explorations. The nature and extent of variation may not become evident until construction. If, during construction, subsurface conditions differ from those encountered in the explorations,we should be advised at once so that we can observe and review these conditions and reconsider our recommendations where necessary. Please contact the undersigned if you have any questions or require additional information. Submitted for GRI, 451/4 tY)PROPecs, GINEF 41b r iso ✓A� 18. 10,6 %� v fI/1( �'�; EY Spp�O Expires 06-2022 Wesley Spang, PhD, PE, GE Nicholas M. Hatch, PE Marissa P. Rauthause, PE Principal Senior Engineer Project Engineer This document has been submitted electronically. GRI PN#5970-M—Twality Middle School Track and Field Upgrades Page 8 January 26,2021 GRD 8 REFERENCES Madin, I. P., 1990, Earthquake-hazard geology maps of the Portland metropolitan area: Oregon Department of Geology and Mineral Studies, Open-File Report 90-02. GRI PN#5970-M-Twality Middle School Track and Field Upgrades Page 9 January 26,2021 14.\ __ i _ J _ _ _ 1__ RICHT OFF WA ;y, I I • IMPROVEMENTS Q-Q INTERSECTION APPROVED UNDER 12+82.35(ROAD A)= /1 /I $ ' I SEPARATE AlE PERMIT 56+85.71 (ROAD e) - -SW INEZ ST L I N 133035 48 '� E 321634.77 1 ID t.j 11'41190'g1 Q . II\c;== ,l I J "►' 58+85.71 r ,(TIA; '7, © �`�,`\..\ +_ ` ry U U �2 j, 1 PLANS, I 1 REFER TO FOR LAYOUT LANDSCAPE o `` ■j L52 00 , 204+,7282 F• \ o ��+•�•u.n....q�••. j OF PATHWAY 1 l E I jf - ••• ;4��; " •4••. NO CIVIL SCOPE .a /71114P,• a••••4** IN THIS PACKAGE _ I $., OD ROAD E 91{00 L70 91+83 1 i_•`•4' • /4 jjarit 4, 8•• 'C • a P09 ••• ,� �- 1 • -N 132904.93 '' / ••r 'e e E 32140395 z1' 44'1* / \ Ni- i ®1 •o �L 8/ME)�, •1 Q-Q INTERSECTION \ \ i� CfBD L1NE5 A AND 11 < 91+85.00(ROAD E)� �; ' 3.23 ( - / 5514283(ROAD B) �•i HA-23•26 r ` - d •'N 132903.06 �- HA-3 I E 721589.94 ���• tion .s. sh, 40, hi, ,,,,,Nklikiip-vq• , M Id 0.7 /46 - ''. "----.. *****. 144 -t..., 1 Poe !di 4,'•• 4 -,, ;: 1 ` N 132725.23 Q, / / 447, 'u, HA-4 E 32142227 ••o el - •••.�, �� �� DYNAMIC CONE PENETRATION TEST AND HAND-AUGERED w :•'���� D' "+" •••••4� �� BORING COMPLETED BYGRI +•• •4,4•40Arii •�• (DECEMBER 12,2020) Q ��••��hf®� o I El . HAND-AUGERED BORING AND DYNAMIC CONE PENETRATION / HA-5 TEST H INFILTRATION COMPLETEDBY GRI Cr' r , ® �"y, ..�••��mi ••.. .�! /� � (DECEMBER 12,2020) • .�ryi4 _; �'• SITE PLAN FROM FILE BY KPFF,2020 Ilro Os 14' //"----„,,,, .. I 1 pe4. y ; / Witt - `v`'- „ASI-02 WO , ' / •4,:4 ' 49.7z If ::i / a HA-6 Ni : ,``,, ri�• • , : r I 0 80 120 FT ri / ii ll' 61 a /POB / 1 TIGARD TUALATIN SCHOOL DISTRICT O ' 19IV {) N 132483 38 ° �11` •• G R TWALITY MIDDLE SCHOOL TRACK AND FIELD • V OD is� /'`"�1 •® //,Q •.." •-.•\ 1•••••ii •••Q C� •©'.d i■Iml■■ 2 t+:. ■■■■■■■TTT7 TIT- !■■•■ ■ 0. - WALLB _ AMil __.--- _ - _ SITE PLAN JAN.2021 JOB NO. 5970-M FIG. 2 r , ^fib., ''f -r 3 '•' f _ ><{ •'E,..,..'#r w b m"' 4 .�y .A k b :..3 5 u .'"v" f • s .y,_. r;n�<• ' f 4 - i y — ab �' ' • s �.. r , Y• i A, raj R /,y► '� • , P"1:4 5. i� • ! 9 . ,_,..,„, . ,„ ,. ... , 1 - - , ,., ,,,.., .3. ...II. �"�", (� a($ #; ,' w < _ art.` r •.,„ ,, y��}`r Y � ;' x , � j ��•yr,, ,, il ' II !!' !_ '. '' .. - ., y ' ( } s qi • .'b i 4 M3 4 .r . . ,%00;,.; - :. . . 1 , `" T. 1 f , It # , ? fie }(} --t 4 ill / LAWNW„. !— • ' *41P4444.' „:'.. ' I/' ; • (t. • i}F is - 1 - k • y7'3C t t `"' ctro 5 r h a e 11 -.Alr y yy Ir 3 • (�l 11 ■ • a^ ..t `s •w" ram` .rr , 'v t fr F 4 SITE PLAN FROM GOGGLE EARTH-ACCESSED 12/14/2020 A 1016k OBSERVED TRANSVERSE CRACKING 0 1200 2400 FT OBSERVED SURFACING DETERIORATION 1 I ( TIGAUT MI LATINDDLESCHOOL SCHOOL DISTRICS TWALITY MI TRACK AND FIELD OBSERVED PAVEMENT DISTRESSES JAN.2021 JOB NO.5970-M FIG.3 11 APPENDIX A Field Explorations and Laboratory Testing GRI PN#5970-M-Twality Middle School Track and Field Upgrades January 26,2021 G ©0 APPENDIX A FIELD EXPLORATIONS AND LABORATORY TESTING A.1 FIELD EXPLORATIONS A.1.1 General Subsurface materials and conditions were investigated on December 10, 2020,with seven hand-augered borings, designated HA-1 through HA-7, and seven corresponding Kessler dynamic cone penetrometer (DCP) probes, designated DCP-1 through DCP-7. The approximate locations of the explorations completed for this investigation are shown on the Site Plan, Figure 2. Logs of the borings are provided on Figures 1A through 4A. The field-exploration work was coordinated and documented by an experienced member of GRI's geotechnical engineering staff,who maintained a log of the materials and conditions disclosed during the course of work. A.1.2 Hand-Augered Borings Seven hand-augered borings, designated B-1 through B-7, were completed to depths of about 2.5 feet to 5.5 feet below the ground surface. The borings were completed using a 4-inch-diameter hand auger provided and operated by GRI. Disturbed soil samples were obtained from the hand-augered boreholes at about 2.5-foot intervals of depth. Samples obtained from the hand-augered borings were examined in the field, and select portions were saved in plastic jars for further examination and physical testing in our laboratory. Logs of the hand-augered borings are provided on Figures 1A through 4A. Each log presents a summary of the various types of materials encountered in the hand-augered boring and notes the depths at which the materials and/or characteristics of the materials change.To the right of the descriptive summary,the numbers and types of samples taken are indicated. Farther to the right, the natural moisture content values are shown graphically along with Atterberg limits and fines contents,where applicable.The terms and symbols used to describe the materials encountered in the hand-augered borings are defined in Table 1A and the attached legend. A.1.3 Dynamic Cone Penetrometer (DCP) Probes Seven DCP probes,designated DCP-1 through DCP-7,were completed to a depth of about 3 feet below the ground surface. The DCP probes were completed using a Kessler DCP manufactured by KSE Testing Equipment. The DCP tests were completed in accordance with ASTM International (ASTM) D6951 by driving a 0.625-inch-diameter steel rod with a cone tip into the soil using a 10.1- or 17.6-pound sliding hammer dropped a fixed height of 22.6 inches. The number of blows required to drive the probe approximately 5 centimeters (2 inches) was recorded to depths ranging from 898 millimeters to 1,000 GRI PN #5970-M—Twality Middle School Track and Field Upgrades Page A-1 January 26,2021 GRO millimeters (2.9 feet to 3.3 feet). The DCP blow counts were used to estimate a California bearing ratio value for the in-situ subgrade. A.1.4 Infiltration Testing One falling-head infiltration test was completed in the field in general conformance with the City of Portland's 2016 Stormwater Management Manual using the encased falling- head method outlined in Section 2.3.6 of the manual.The falling-head infiltration test was conducted in exploration HA-4 at a depth of about 4.5 feet below existing site grades.The borehole was drilled to the selected depths using a hand-operated, 4-inch-outside- diameter auger.A PVC pipe was seated firmly into the base of the hand-augered borehole and filled with water to a height of approximately 1 foot above the drilled depth. After soaking, infiltration testing was conducted by reestablishing the water level in the PVC pipe to the target height and recording the drop in water level over one hour or until the water completely drained, whichever occurred first. Where necessary, the infiltration test was repeated until consecutive tests showed little or no change in the infiltration rate. The average unfactored, field-measured infiltration rate for the soils that mantle the field is 0 inches/hour. After the infiltration testing was completed, disturbed samples of the material were collected and examined in the field, and selected portions were saved in airtight jars for further examination and physical testing in the laboratory. A.2 LABORATORY TESTING A.2.1 General The samples obtained from the borings were examined in our laboratory, where the physical characteristics of the samples were noted and the field classifications modified where necessary.At the time of classification,the natural moisture content of each sample was determined. Additional testing included Atterberg limits and grain-size analyses. A summary of the laboratory-test results is provided in Table 2A. The following sections describe the testing program in more detail. A.2.2 Natural Moisture Content Natural moisture content determinations were made in conformance with ASTM D2216. The results are summarized on Figures 1A through 4A and in Table 2A. A.2.3 Atterberg Limits Atterberg limits testing was performed on one sample of sandy silt obtained from the field In general conformance with ASTM D4318. The test results are summarized on Figure 2A, the Plasticity Chart on Figure 5A, and in Table 2A. GRI PN#5970-M—Twality Middle School Track and Field Upgrades Page A-2 January 26,2021 GRQ A.2.4 Grain-Size Analysis A.2.4.1 Washed-Sieve Method To assist in classification of the soils, samples of known dry weight were washed over a No. 200 sieve. The material retained on the sieve was oven-dried and weighed. The percentage of material passing the No. 200 sieve was then calculated. The results are summarized on Figures 1A through 4A and in Table 2A. GRI PN#5970-M—Twality Middle School Track and Field Upgrades Page A-3 January 26,2021 GRD Table 'IA GUIDELINES FOR CLASSIFICATION OF SOIL Description of Relative Density for Granular Soil Standard Penetration Resistance, Relative Density (N-values)blows/ft Very Loose 0-4 Loose 4- 10 Medium Dense 10 - 30 Dense 30- 50 Very Dense over 50 Description of Consistency for Fine-Grained (Cohesive) Soils Standard Penetration Torvane or Resistance(N-values), Undrained Shear Consistency blows/ft Strength,tsf Very Soft 0 -2 less than 0.125 Soft 2-4 0.125 -0.25 Medium Stiff 4-8 0.25 - 0.50 Stiff 8- 15 0.50- 1.0 Very Stiff 15 -30 1.0- 2.0 Hard over 30 over 2.0 Grain-Size Classification Modifier for Subclassification Boulders: Primary Constituent Primary Constituent >12 in. SAND or GRAVEL SILT or CLAY Cobbles: Adjective Percentage of Other Material(By Weight) 3-12 in. trace: 5 - 15 (sand, gravel) 5 - 15 (sand, gravel) Gravel: 1/4 - 3/4 in.(fine) some: 15-30(sand,gravel) 15-30(sand,gravel) 3/4 -3 in. (coarse) sandy, gravelly: 30 - 50(sand,gravel) 30- 50(sand,gravel) Sand: No.200- No.40 sieve(fine) trace: <5(silt,clay} Relationship of clay No.40- No. 10 sieve(medium) some: 5- 12(silt, clay) and slit determined by No. 10- No.4 sieve (coarse) silty,clayey: 12- 50(silt,clay) plasticity index test Silt/Clay: Pass No.200 sieve GRI PN#5970-M—Twality Middle School Track and Field Upgrades January 26, 2021 k Table 2A SUMMARY OF LABORATORY RESULTS Sample Information Atterberg Limits Moisture Dry Unit Liquid Plasticity Fines Location Sample Depth,ft Elevation,ft Content, % Weight, pcf Limit, % Index,% Content,% Soil Type HA-1 S-1 1.0 -- 21 -- -- -- Sandy SILT S-2 2.5 -- 20 -- -- -- 37 Silty SAND S-3 5.0 -- 19 -- -- -- Silty SAND HA-2 S-1 1.0 -- 23 -- -- -- 54 Sandy SILT 5-2 2.5 -- 20 -- -- -- -- Sandy SILT S-3 5.0 -- 12 -- -- -- -- Sandy SILT HA-3 S-1 1.0 -- 25 -- -- -- -- Sandy SILT 5-2 2.5 -- 21 -- -- -- Sandy SILT S-3 5.0 -- 19 -- -- -- -- Sandy SILT HA-4 S-1 1.0 -- 23 -- -- -- -- Sandy SILT S-2 2.5 -- 20 -- 24 3 52 Sandy SILT S-3 5.0 -- 17 -- -- -- 54 Sandy SILT HA-5 S-1 1.0 -- 24 -- -- -- -- FILL HA-6 S-1 1.0 -- 24 -- -- -- -- FILL HA-7 S-1 1.0 -- 22 -- -- -- 53 FILL S-2 2.5 -- 21 -- -- -- -- FILL GR ' I Page 1 of 1 4 BORING AND TEST PIT LOG LEGEND SOIL SYMBOLS SAMPLER SYMBOLS Symbol Typical Description Symbol Sampler Description .,;.1 LANDSCAPE MATERIALS 2.0 in.O.D.split-spoon sampler and Standard Penetration Test with recovery(ASTM D1586) FILL I Shelby tube sampler with recovery (ASTM D1587) ,� GRAVEL;clean to some silt,clay,and sand I 3.0 in.O.D.split-spoon sampler with recovery (ASTM D3550) o�t o . ° Sandy GRAVEL;clean to some silt and clay H Grab Sample �►� Silty GRAVEL;up to some clay and sand Eil Rock core sample interval ,ft Clayey GRAVEL;up to some silt and sand ' Sonic core sample interval SAND;clean to some silt,clay,and gravel Push probe sample interval E is s{k. Gravelly SAND;clean to some silt and clay INSTALLATION SYMBOLS iftSilty SAND;up to some clay and gravel Symbol Symbol Description Clayey SAND;up to some silt and gravel El Flush mount monument set in concrete ® SILT;up to some clay,sand,and gravel LI Concrete,well casing shown where applicable MI Gravelly SILT;up to some clay and sand eie Bentonite seal,well casing applicable if a licable Sandy SILT;up to some clay and gravel r Filter pack, machine-slotted well casing shown I where applicable IPA Clayey SILT;up to some sand and gravel Grout, vibrating-wire transducer cable shown where applicable ® CLAY;up to some silt,sand,and gravel • Vibrating-wire pressure transducer Gravelly CLAY;up to some silt and sand I 1-in.-diameter solid PVC Sandy CLAY;up to some silt and gravel I 1-in.-diameter hand-slotted PVC IIISilty CLAY;up to some sand and gravel Grout,inclinometer casing shown where applicable WY PEAT FIELD MEASUREMENTS BEDROCK SYMBOLS Symbol Typical Description Symbol Typical Description Z. Groundwater level during drilling and date measured +++ BASALT i Groundwater level after drilling and date o measured MUDSTONE Rock/sonic core or push probe recovery(%) w __I SILTSTONE Rock quality designation(RQD,%) ✓ 1 o SANDSTONE 2 co ° SURFACE MATERIAL SYMBOLS w Symbol Typical Description 8 0 'E. . Asphalt concrete PAVEMENT V2 . Portland cement concrete PAVEMENT 0 z z n Crushed rock BASE COURSE 0 03 co CLASSIFICATION OF MATERIAL wa • MOISTURE CONTENT,% 1— —1 1— Si ❑ FINES CONTENT,% w v LL w w LIQUID LIMIT,% F a r a s �_PLASTIC LIMIT,°k COMMENTS AND w qw w a < ADDITIONAL TESTS 0 (0 0 01 0, 0 50 100 HA-1 Surface Elevation:Not Available 0 50 100 Sandy SILT,brown,medium stiff,fine-to medium-grained sand,3-to 6-in.-thick heavily-rooted zone at ground : surface —trace clay below 1 ft s-1 . I • Silty SAND,trace clay,light brown to brown,medium 2 5 S-2 H • ❑ — ': dense,fine to medium grained . 5—: —light brown to brown mottled gray below 5 ft l S-3 ® i (12/10/2020) Groundwater not encountered 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger Date Started: 12/10/20 I GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbols HA-2 Surface Elevation:Not Available 0 50 100 Sandy SILT,brown to dark brown,medium stiff to stiff,fine- to medium-grained sand,3-to 6-in.-thick heavily-rooted : zone at ground surface . —trace day below 1 ft s-1 ® ♦ CI I S2 ® • 1- — r O r g — —light brown below 4 ft a a a II 0 S-3 O (12/10/2020) ss > — w oGroundwater not encountered z a — a. N a. 0 0.5 1.0 `? •U' TORVANE SHEAR STRENGTH,TSF 0 $ Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger 0 Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbols GRI BORINGS JAN.2021 JOB NO.5970-M FIG.1A • o CLASSIFICATION OF MATERIAL Lu • MOISTURE CONTENT,% 1- of z IDFINES CONTENT,% W W LIQUID LIMIT,% a a ~{PLASTIC LIMIT,% COMMENTS AND w w ¢ < ADDITIONAL TESTS o ( m u) 0 5o 10a HA-3 Surface Elevation:Not Available 0 50 100 Sandy SILT,brown,medium stiff to stiff,fine-to i 1 medium-grained sand,3-in.-thick heavily-rooted zone at : ground surface , , , , , , —trace clay below 1 ft s-i N 1 • I 5 2 N • I I — •• —light brown below 4 ft 5 S-3 N • • 5.5 (12/10/2020) — Groundwater not encountered 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbols HA-4 Surface Elevation:Not Available 0 50 too Sandy SILT,brown,medium stiff,fine-to medium-grained sand,3-to 6-in.-thick heavily-rooted zone at ground - : surface —trace clay,dark brawn below 1 ft s-1 H I I. 1 1 . I . - S-2 N N 7 1- 0 f 5 •— t a I w I Q I 0• 5—.. S-3 ® 4 ❑ o (12/10/2020) 5.5 > _ w o Groundwater not encountered z a — 0. N I '1 a 0 0.5 1.0 o • TORVANE SHEAR STRENGTH,TSF 0 = Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger 0 Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbols G RI] BORINGS JAN.2021 JOB NO.5970-M FIG.2A i 1 o • MOISTURE CONTENT,% CLASSIFICATION OF MATERIAL a 1— Si 0 FINES CONTENT, ' w v " w w LIQUID LIMIT,% d 1- a a ~�PLASTIC LIMIT,% COMMENTS AND is qa w a a ADDITIONAL TESTS o C Cr) 0 50 100 HA-5 Surface Elevation:Not Available 0 50 100 $ SILT,trace to some clay and fine-grained sand,brown, `•1ti:? medium stiff,3-to Gin.thick heavily-rooted zone at ground ni:Pit: surface(Fill) S-1 ® • r• • GRAVEL,some fine-to coarse-grained sand,trace silt, -2 0 S-2 °iS \medium dense,angular to subangular(Fill) ,-2.5 _ (12/10/2020) . Auger refusal at 2.5 ft Groundwater not encountered 5- 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbols HA-6 Surface Elevation:Not Available 0 50 100 SILT,some fine-grained sand,brown,medium stiff,3-to Gin.-thick heavily-rooted zone at ground surface(Fill) • —sandy,trace to some day below 1 ft s1 kl • • GRAVEL,some fine-to coarse-grained sand,trace silt, 2,0 S2 medium dense,subangular to subrounded(Fill) S-3 o • -0 S w (12/10/2020) 3.5 m _ Auger refusal at 3.5 ft Groundwater not encountered L 0 0.5 1.0 o • TORVANE SHEAR STRENGTH,TSF $ Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger 0 Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbds GIRT BORINGS JAN.2021 JOB NO.5970-M FIG.3A o CLASSIFICATION OF MATERIAL d • MOISTURE CONTENT,% o 0 FINES CONTENT,% 0 " w LU LIQUID LIMIT,°k a = a a ~�PLASTIC LIMIT,% COMMENTS AND w 4a w ¢ ¢ ADDITIONAL TESTS o co N 50 100 HA-7 Surface Elevation:Not Available 0 50 100 ;Xi:: SILT,some fine-grained sand to sandy,brown,medium stiff,3-to 6-in.-thick heavily-rooted zone at ground surface (Fill) —trace clay,dark brown,stiff,scattered roots below 1 ft s-i ® • ❑ —interbedded with lenses of SAND below 2.5 ft 5-2 ?,. -4.0 GRAVEL,some fine-tocoars rained sand,trace silt e-9sa \medium dense,subangular to subrounded(Fill) r 4.5 5_ (12/10/2020) Auger refusal at 4.5 ft Groundwater not encountered 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: J.Uding Excavated by: GRI Equipment: Hand Auger Date Started: 12/10/20 GPS Coordinates: Not Available I Note: See Legend for Explanation of Symbds q W a w F F 0 w w 0 z a N 0 0 0 0 J 1 I G R BORINGS JAN.2021 JOB NO.5970-M FIG.4A GROUP UNIFIED SOIL CLASSIFICATION GROUP UNIFIED SOIL CLASSIFICATION SYMBOL FINE-GRAINED SOIL GROUPS SYMBOL FINE-GRAINED SOIL GROUPS ORGANIC SILTS AND ORGANIC SILTY ORGANIC CLAYS OF MEDIUM TO HIGH OL CLAYS OF LOW PLASTICITY OH PLASTICITY,ORGANIC SILTS INORGANIC CLAYEY SILTS TO VERY FINE ML SANDS OF SLIGHT PLASTICITY MH INORGANIC SILTS AND CLAYEY SILT INORGANIC CLAYS OF LOW TO MEDIUM CL PLASTICITY CH INORGANIC CLAYS OF HIGH PLASTICITY 60 50 CH 40 X w 30 CL cn 20 MH or OH 10 CL-ML • ML or OL 0 I 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT,% Location Sample Depth,ft Classification LL PL PI MC,% • HA-4 S-2 2.5 Sandy SILT,trace clay,dark brown 24 21 3 20 ❑ m a LU w C Lt w a w /\/�T Rig >- 1 r V V H PLASTICITY CHART o La w U W JAN.2021 JOB NO.5970-M FIG.5A