Loading...
HomeMy WebLinkAboutBANK ONE PUD - PRELIMINARY & FINAL - 54-87W - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTSUBSURFACE EXPLORATION REPORT PROPOSED BANK ONE DEVELOPMENT HARMONY ROAD AND BOARDWALK DRIVE FORT COLLINS, COLORADO EEC PROJECT 1942040 EARTH ENGINEERIN( CONSULTANTS, INC. � a June 2, 1994 Bank One P.O. Box 29 Loveland, Colorado 80539 Attn: Mr. Don Churchwell RE: Subsurface Exploration Report Proposed Bank One Development Harmony Road and Boardwalk Drive Fort Collins, Colorado EEC Project No. 1942040 Mr. Churchwell: EARTH ENGINEERING CONSULTANTS, INC. Enclosed, herewith, are the results of the subsurface exploration you requested for the referenced project. In summary, the subsurface soils encountered at this site consisted of low plasticity lean clay with varying amounts of silt and sand interbedded with occasional zones of granular and essentially granular materials. Based on the results of our field borings and laboratory testing, it is our opinion these soils can be used for direct support of footing foundations for the proposed lightly loaded buildings. These soils could also be used for direct support for floor slab and pavements. Geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements are presented in the text of the attached report. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed report, or if we can be of further service to you in any other way, please do not hesitate to contact us. Very truly yours, s, Inc. Lester L. Litton, P.E. Principal Engineer cc: Eldon Ward, Cityscape Urban Design 'SS L i Z nrs a - Curtiss T,"" Oin, P.E. Principal Engineer 2600 Canton Ct, Suite A Fort Collins, CO 80525 (303) 224-1522 FAX 224-4564 SUBSURFACE EXPLORATION REPORT PROPOSED BANK ONE DEVELOPMENT HARMONY ROAD AND BOARDWALK DRIVE FORT COLLINS, COLORADO EEC PROJECT 1942040 I INTRODUCTION The subsurface exploration for the proposed Bank One Development to be located southwest of the intersection of Harmony Road and Boardwalk Drive in Fort Collins, Colorado, has been completed. Three (3) soil borings extending to depths of approximately 15 feet below present site grades were advanced to develop information on subsurface conditions in the proposed development area. Individual boring logs and a diagram indicating the approximate boring locations are included with this report. We understand the proposed Bank One Development will include the construction of single - story, slab on grade (non basement) bank building and the future construction of a one or two story office building which may or may not contain a basement. Foundation loads for the site structures are expected to be light with continuous wall loads less than 3 kips per lineal foot and individual column loads less than 50 kips. Floor loads will be light, less than 100 psf. Paved drive and parking areas will be constructed in conjunction with the new buildings. We expect grade changes less than 2 feet will be required to develop general site grades for this project. The purpose of this report is to describe the subsurface conditions encountered in the borings, analyze and evaluate the test data and provide geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavement for the proposed development. IEXPLORATION AND TESTING PROCEDURES The boring locations were selected and established in the field by Earth Engineering Consultants, Inc. (EEC) personnel. The field locations were determined by pacing and estimating angles from the references indicated on the attached boring location diagram. The locations of the borings should be considered accurate only to the degree implied by the methods used to make the field measurements. Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 2 The borings were performed using a track -mounted, rotary type drill rig equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 4-inch nominal diameter continuous flight augers and samples of the subsurface materials encountered in the borings were obtained using thin -walled tube and split -barrel sampling procedures in general accordance with ASTM Specifications D-1587 and D-1586, respectively. In the thin -walled tube sampling procedure, a seamless steel tube with a sharpened cutting edge is pushed into the soil with a hydraulic pressure to obtain a relatively undisturbed sample of cohesive or moderately cohesive soil. In the split barrel sampling procedure, a standard 2-inch O.D. split -barrel sampling spoon is driven into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the split -barrel sampler is recorded and is used to estimate the in -situ relative density of cohesionless soils and, to a lesser degree of accuracy, the consistency of cohesive soils and hardness or weathered bedrock. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. Moisture content tests were completed on each of the recovered samples. In addition, unconfined compressive strength tests were completed on appropriate samples and the unconfined compressive strength estimated on other samples using a calibrated hand penetrometer. Atterberg limits, washed sieve analysis and swell/consolidation tests were also completed on selected samples. Results of the outlined tests are shown on the attached boring logs. As a part of the testing program, all samples were examined in the laboratory by an engineer and classified in accordance with the attached General Notes and the Unified Soil Classification System, based on the soil's texture and plasticity. The estimated group symbol for the Unified Soil Classification System is shown on the boring logs and a brief description of that classification system is included with this report. SITE AND SUBSURFACE CONDITIONS The proposed Bank One Development will be located southwest of the intersection of Harmony Road and Boardwalk Drive in south Fort Collins. The project site is currently open field with Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 3 ground cover of sparse vegetation. Evidence of prior building construction was not observed at the site by EEC field personnel. An EEC field geologist was on -site during drilling to direct the drilling activities and evaluate the materials recovered. Classification of subsurface materials in the field was based on visual and tactual observation of disturbed samples and auger cuttings. The boring logs included with this report may contain modifications to the field logs based the results of laboratory testing and engineering evaluation. Based on results of the field and laboratory testing, subsurface conditions can be generalized as follows. Approximately four to six inches of vegetation and/or topsoil was encountered at the surface at the boring locations. The topsoil/vegetation was underlain by stiff to very stiff lean clay with varying amounts of sand and gravel. Occasional sand zones were encountered in borings B-1 and B-2, interbedded with the cohesive soils. The sand zones were medium dense to dense and were generally colored red -brown. Except for the isolated sand zones, the cohesive soils extended to the bottom of the borings at depths of approximately 15 to 20 feet. The stratification boundaries shown on the boring logs represent the approximate locations of changes in soil types; in -situ, the transition of materials may be gradual and indistinct. WATER LEVEL OBSERVATIONS Observations were made while drilling and after completion of the borings to detect the presence and level of free water in the open boreholes. Free water was encountered at a depth of approximately 14 feet in boring B-3 while water was not observed at the other drilling locations. Longer term observations including the installation of piezometers and/or monitoring wells would be required to more accurately evaluate groundwater conditions. Zones of perched and/or trapped water may be encountered in more the permeable zones interbedded with the cohesive soils. The location and amount of perched water and the level of Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 4 the hydrostatic groundwater table can vary over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. ANALYSIS AND RECOMMENDATIONS FOUNDATIONS Based on the materials observed at the test boring locations, it is our opinion the proposed buildings can be supported on conventional footing foundations. We recommend those foundations extend through all existing vegetation and/or topsoil and bear in the natural, stiff to very stiff cohesive soils or medium dense to dense granular materials. For design of footing foundations bearing on the natural, sandy lean clay or fine to medium sand, we recommend using a net allowable total load soil bearing pressure not to exceed 2,500 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load implies full dead and live loads. Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches below adjacent exterior grade to provide frost protection. We recommend formed continuous footings have a minimum width of 16 inches and isolated column foundations have a minimum width of 30 inches. Trenched foundations (grade beam foundations) could be used in near surface lean clay. If used, we recommend those trenched foundations have a minimum width of 12-inches. Care should be taken during construction to avoid disturbing the bearing soils. Materials which are loosened or disturbed by construction activities or materials which are dry and desiccated or wet and softened should not be used for foundation bearing. The foundation should be extended through unacceptable materials to bear in the natural undisturbed soils. When excavating for basement areas, it should be noted that zones of granular materials will likely be encountered interbedded with the cohesive materials. Perched groundwater may be 0 Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 5 encountered in those more permeable areas. In addition, the granular soils will require flatter excavation slopes to maintain stable excavations. We estimate slopes no steeper than 2 horizontal to 1 vertical would be stable for a short term construction activities. We estimate the long term settlement of footing foundations designed and constructed as outlined above would be small, less than 3/4 inch. BELOW GRADE AREAS If basement areas are constructed as a part of the office building, we recommend a perimeter drain system be designed and constructed around the below grade areas. The perimeter drain would eliminate the buildup of hydrostatic forces on below grade walls and would reduce the potential for seepage of water entering below grade areas. In general, the perimeter drain system should consist of perforated metal or plastic pipe placed at approximate foundation bearing level around the exterior perimeter of the below grade areas. The perimeter drain system should be surrounded by a minimum of 6-inches of appropriately sized granular filter material. We recommend the filter material or drain line be wrapped in a filter fabric to reduce the potential for an influx of fines into the system. The perimeter drain should allow for the free flow of water to a sump area where it can be removed without reverse flow into the system. Backfill placed adjacent to the basement walls should consist of approved, low volume change material free from organic matter and debris. Normally, soils with a liquid limit of 40 or less and have plasticity index of 18 or less could be considered low volume change material. The near surface silty granular soils and low plasticity cohesive soils could be used as backfill. Those fill materials should be placed in loose lift not to exceed 9-inches thick, adjust moisture content and compacted to at least 90% of the materials maximum dry density as determined in accordance with ASTM Specification D-698, the standard Proctor procedure. The moisture content of cohesive soils should be adjusted to be within the range of plus or minus 2% of standard Proctor optimum moisture and the moisture content of granular soil should be adjusted to a workable -moisture. Backfill used to support sidewalks, steps, pavements or other similar a Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 a Page 6 uses adjacent to the building should be compacted to at least 95 % of standard Proctor maximum dry density. Compaction of backfill adjacent to the basement walls should be accomplished using light weight mechanical or hand equipment. Care should be taken to avoid the use of heavy equipment immediately adjacent to the building as excessive lateral stresses could be transmitted to the below grade walls. For design of below grade walls for which appropriate steps have been taken to eliminate hydrostatic loads, we recommend using an equivalent fluid pressure of 60 pcf. That stress distribution is based on an at -rest condition which includes the assumptions of no wall rotation. Surcharge loading or point loads placed adjacent to below grade wall could add to the lateral stress on those walls. We will be pleased to provide additional evaluation of those conditions as warranted. 4 FLOOR SLAB AND PAVEMENT SUBGRADES All existing vegetation and/or topsoil should be removed from beneath the floor slab and pavement areas. After stripping and completing all cuts and prior to placement of any fill, floor slabs or pavements, we recommend the exposed soils be scarified to minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95 % of the material's maximum dry density as determined in accordance with the standard Proctor procedure. The moisture content of the scarified soils should be adjusted to be within the range of plus or minus 2% of standard Proctor optimum moisture. Scarification and compaction of the subgrade soils in basement areas would not be required. Fill soils required to develop the floor slabs or pavement subgrades should consist of approved, low -volume change material, free from organic matter and debris. The near surface cohesive site soils could be used as fill in these areas. Those fill soils should be placed in loose lifts not 4 Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 7 to exceed 9 inches thick, adjusted moisture content as recommended for the scarified soils and compacted to at least 95 % of standard Proctor maximum dry density. After preparation of the subgrades, care should be taken to avoid disturbing the prepared materials. Materials which are disturbed by the construction activities or materials that become dry and desiccated or wet and softened should be reworked in -place or removed and replaced prior to placement of the floor slabs or pavements. Positive drainage should be developed away from the proposed buildings and across and away from the pavements. Water allowed to pond on or adjacent to the buildings and pavements could result in wetting in the subgrades and unacceptable performance. PAVEMENTS Based on previous work we have completed in this area, we estimate a Hveem R-value of 7 would be appropriate for design of the pavements. We anticipate traffic on the drive and parking areas for the buildings would consist predominately of automobiles and light trucks. The volume of traffic expected is relatively light. Based on the anticipated site usage and subgrade materials, we recommend pavements for the drive and parking areas consist of at least 6-inches of aggregate base overlain by 3-inches of asphalt surfacing. A thinner pavement section consisting of 4-inches of aggregate base and 21h- inches of asphalt surfacing could be considered for the parking areas. The recommended pavement sections are minimums and, as such, periodic maintenance should be expected. Asphalt for use in the pavement section should consist of either Class SC-1 or SC-2 as defined by the City of Fort Collins Standard Specifications. The aggregate base should consist of either Class 5 or Class 6 base as defined Colorado Department of Transportation (CDOT) Standard Specifications. The aggregate based should be placed and compacted as recommended for fill soils beneath the pavements. Earth Engineering Consultants, Inc. Bank One Development June 2, 1994 Page 8 Consideration could be given to stabilization of the pavement subgrades using Class C fly ash. The subgrade stabilization would result in a higher quality pavement and reduce the required long term maintenance. In addition, the stabilized subgrade would result in a reduced pavement section. In general the stabilized subgrade would result in elimination of the aggregate base although the thickness of the asphalt surfacing would remain the same. We would be pleased to provide additional information concerning stabilization of the subgrades if desired. GENERAL COMMENTS The analysis and recommendations presented in this report are based upon the data obtained from the soil borings performed at the indicated locations and from any other information discussed in this report. This report does not reflect any variations which may occur between borings or across the site. The nature and extent of such variations may not become evident until construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. It is recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. It is further recommended that the geotechnical engineer be retained for testing and observations during earthwork and foundation construction phases to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of Bank One for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranty, express or implied, is made. In the event that any changes in the nature, design or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing by the geotechiiical engineer. HARMONY ROAD w PROPOSED SITE AREA a B-2 J 3 O BANK ONE B m OFFICE / RETAIL BLDG, B-3 BUILDERS SOUARE ENTRANCE / EXIT DRIVE'.,,;Y Boring Location Diagram BANK ONE DEVELOPMENT Fort Collins, Colorado Scale: None Drawn: SCK im— r E I :1 a I I 0 Ll- 4 7 4 4 ■ BANK ONE FORT COLLINS, COLORADO PROJECT NO: 1942040 DATE: MAY 1994 LOG OF BORING B-1 SHEET 1 OF 1 RIG TYPE: TRACK CME 45 WATER DEPTH ELEV FOREMAN: SCK START DATE 5125194 WHILE DRILLING NONE NIA AUGER TYPE: 4" CFA FINISH DATE 5125/94 AFTER DRILLING NONE N/A SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR NIA NIA SOIL DESCRIPTION TYPE D (FEET) N (BLOWSIFT) QU (PSF) MC (%) DD (PCF) A -LIMITS •200 (%) SWELL LL PI PRESSURE % 500 PSF 6" GRASS & TOPSOIL SANDY CLAY (CL-CM) Dark Brown Moist Es, Medium Stiff _ _ 5 21 *6000 12.3 46 24 66.4 700,psf 1.2% SANDY GRAVEL (GP) Red SS Moist Dense 50 for 10" 1.5 _ 10 SANDY CLAY (CL) Brownish tan Moist Medium Stiff SS 12 "4000 20.6 _ _ _ _ 15 SANDY CLAY (CL) Brownish grayish tan Mottled Moist Medium Stiff SS 13 24.1 20 BOTTOM OF BORING 15' 6". "CHP 25 I a I C BANK ONE FORT COLLINS, COLORADO PROJECT NO: 1942040 DATE: MAY 1994 LOG OF BORING B-2 SHEET 1 OF 1 RIG TYPE: TRACK CME 45 WATER DEPTH ELEV FOREMAN: SCK START DATE 5125194 WHILE DRILLING NONE NIA AUGER TYPE: 4" CFA FINISH DATE 5125I94 AFTER DRILLING NONE NIA SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR NIA NIA SOIL DESCRIPTION TYPE D (FEET) N (BLOWS/FT) au (PSF) Mc I%) Do (PCF) A -LIMITS -200 (%) SWELL LL PI PRESSURE %500 PSF 6" GRASS & TOPSOIL SANDY CLAY (CL) Dark Brown Moist, Medium stiff SS _ _ _ _ 5 7 *7000 13.0 37 16 56.9 <500 NONE SANDY CLAY (CL) Red Moist, Medium stiff SAND AND GRAVEL Red SS Moist, Loose 6 8.9 _ _ _ 10 SANDY CLAY (CL) Brown Moist Soft to Medium Stiff ESS 12 "4000 19.7 _ _ 15 SANDY CLAY (CL) Brownish grayish tan Moist Mottled SS Medium stiff 11 13.1 _ _ 20 BOTTOM OF BORING 15' 6". "CHP 25 tarl:rl Cr1C11i1CCll11U t/Coi— —a I a I I I I a a a 4 4 4 4 4 4 0 Earth Enaineerinn Cnncultantc BANK ONE FORT COLLINS, COLORADO PROJECT NO: 1942040 DATE: MAY 1994 LOG OF BORING B-3 SHEET 1 OF 1 RIG TYPE: TRACK CM 45 E WATER DEPTH E E L V FOREMAN: SCK START DATE 5125/94 WHILE DRILLING 15' NIA AUGER TYPE: 4" CFA FINISH DATE 5125194 AFTER DRILLING 15' NIA SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR 12.80 NIA SOIL DESCRIPTION TYPE D (FEET( N (BLOWS)FT) aU (PSF) Mc (X) Do (PCF) A -LIMITS -200 (%1 SWELL LL PI PRESSURE % 500 PSF 6" GRASS & TOPSOIL SANDY CLAY (CL-CM) Dark Brown Moist SS Medium Stiff _ 5 10 "2500 12.3 SANDY CLAY (CL) Brown SS Moist Soft 8 "2000 16.8 — — _ 10 SANDY CLAY (CL) Orangish brown ET Moist Medium stiff 2140 20.6 97 32 16 77.0 <500 NONE _ _ _ _ 15 SANDY CLAY (CL) Brownish grayish tan Mottled Moist SS Medium stiff 32 14.4 _ 20 BOTTOM OF BORING 15' 6". 'CHP 25 DRILLING AND EXPLORATION DRILLING & SAMPLING SYMBOLS: SS : Split Spoon - 1'1a" I.D., 2" O.D., unless otherwise noted PS : Piston Sample ST : Thin -Walled Tube - 2" O.D., unless otherwise noted WS : Wash Sample R : Ring Barrel Sampler - 2.42" I.D., 3" O.D. unless otherwise noted. PA : Power Auger FT : Fish Tail Bit HA : Hand Auger RB : Rock Bit DB : Diamond Bit = 4", N, B BS : Bulk Sample AS : Auger Sample PM : Pressure Meter HS : Hollow Stem Auger DC : Dutch Cone WB : Wash Bore Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2-inch O.D. split spoon, except where noted. WATER LEVEL MEASUREMENT SYMBOLS: WL :Water Level WS : While Sampling WCI Wet Cave in WD While Drilling DCI : Dry Cave in BCR : Before Casing Removal - AB : After Boring ACR : After Casting Removal Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated levels may reflect the location of groundwater. In tow permeability soils, the accurate determination of groundwater levels is not possible with only short term observations. DESCRIPTIVE SOIL CLASSIFICATION PHYSICAL PROPERTIES OF BEDROCK Soil Classification is based on the Unified Soil Classification DEGREE OF WEATHERING: system and the ASTM Designations D-2487 and D-2488. Coarse Grained Soils have more than 50% of their dry Slight Slight decomposition of parent material on weight retained on a #200 sieve; they are described as: joints. May be color change. boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; Moderate Some decomposition and color change they are described as: clays, if they are plastic, and silts if throughout. they are slightly plastic or non -plastic. Major constituents may be added as modifiers and minor constituents may be High Rock highly decomposed, may be extremely added according to the relative proportions based on grain broken. size. In addition to gradation, coarse grained soils are defined on the basis of their relative in -place density and HARDNESS AND DEGREE OF CEMENTATION: fine grained soils on the basis of their consistency. Limestone and Dolomite: Example: Lean clay with sand, trace gravel, stiff (CL); silty Hard Difficult to scratch with knife. sand, trace gravel, medium dense ISM). Moderately Can be scratched easily with knife, CONSISTENCY OF FINE-GRAINED SOILS Hard Cannot be scratched with fingernail. Unconfined Compressive Soft Can be scratched with fingernail. Strength, Qu, psf Consistency Shale, Siltstone and Claystone: < 500 Very Soft Hard_ Can be scratched easily with knife, cannot 500 - 1,000 Soft be scratched with fingernail. 1,001 - 2,000 Medium 2,001 - 4,000 Stiff Moderately Can be scratched with fingernail. 4,001 - 8,000 Very Stiff Hard 8,001 - 16,000 Very Hard Soft Can be easily dented but not molded with RELATIVE DENSITY OF COARSE -GRAINED SOILS: fingers. N-Blows/ft Relative Density 0-3 Very Loose Sandstone and Conglomerate: 4-9 Loose Well Capable of scratching a knife blade. 10-29 Medium Dense Cemented 30-49 Dense 50-80 Very Dense Cemented Can be scratched with knife. 80 + Extremely Dense Poorly Can be broken apart easily with fingers. Cemented UNIFIED SOIL CLASSIFICATION SYSTEM Soil Classification Crlterla for Assigning Group Symbob and Group Names Using Laboratory Tests' Group a Symbol Group Neme Coarse -Grained Soils more than 50% retained on No. 200 sieve Fine -Grained Soils 50% or more passes the No. 200 sieve Gravels more than 50% of coarse fraction retained on No. 4 sieve Clean Gravels Less than 5% finest . Cu > 4 and 1 < Cc <3E Cu < 4 and/or 1 > Cc > 3E GW GP Well -graded gravel' Poorly graded grave Gravels with FOines c more than 12 % fines Fines classify as ML or MH GM Silty gravel,G,H Fines classify as CL or CH GC Clayey gravel"" Sands 50% or more Clean Sands Less Cu > B and 1 < Cc < 3E S10i Well -graded sand' of coarse fraction than 5% fines6 passes No. 4 sieve Cu < 6 and/or 1 > Cc > 3E Sp Poorly graded sand' Sands with Fines Fines classify as ML or MH SM Silty sand° `1 more than 12% fines° Fines Classify as CL or CH SC Clayey sand"' Silts and Clays inorganic PI > 7 and plots on or above "A line' CL Lean ciayK.L.>+ Liquid limit less than 50 PI < 4 or plots below "A" line' ML SiltK -14 organic Liquid limit - oven dried Organic ciayx-L"" < 0.75 OL Liquid limit - not dried Organic siltI.E.A'0 Silts and Clays inorganic PI plots on or above "A" line CH Fat clayK'L" Liquid limit 50 or more PI lots below "A" line MH Elastic SiItK.Lu Highly organic soils Primaril• ABased on the material passing the 3-in. (75-mm) sieve 61f field sample contained cobbles or boulders, or both, add "with cobbles or boulders, or both" to group name. cGravels with 5 to 12% fines require dual symbols: GW-GM well -graded gravel with silt GW-GC well -graded gravel with clay GP -GM poorly graded gravel with silt GP -GC poorly graded gravel with clay 'Sands with 5 to 12% fines require dual symbols: SW-SM well -graded sand with silt SW -SC well -graded sand with clay SP-SM poorly graded sand with silt SP-SC poorly graded sand with clay rn 10 7 a organic Liquid limit - oven dried < 0.75 OH Liquid limit - not dried organic matter, dark in color, and organic odor 'Cu-Ds. /DLO Cc (D10): DLO Dca Flf soil contains > 15% sand, add "with sand" to group name. cif fines classify as CL-ML, use dual symbol GC -GM, or SC-SM. "If fines are organic, add "with organic fines" to group name. 'if soil contains > 15% gravel, add "with gravel" to group name. 'If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. PT Organic clay"`-' Organic siIt4-L"a.0 Peat 'If soil contains 15 to 29% plus No. 200, ad .with sand" or "with gravel", whichever is predominant. LIP soil contains > 30% plus No. 200 predominantly sand, add "sandy" to group name. 'if soil contains > 30% plus No. 200, predominantly gravel, add "gravelly" to grouF name. "PI > 4 and plots on or above "A" line. oPl < 4 or plots below "A" line. "PI plots on or above "A" line. oPl plots below "A" line. For ctasslficatlon of fine-grained snits / and fine-grained fraction of coarse• grained soils / Ecuauon of "A" • line \� � Horizontal at PI . a to LL . 25.5. then PI . 0.73 ILL .20) , O� +P Equation of -U" • line OR, -- "—' -- —� vertical at LL " 16 to PI " 7. i then PI " 0.9 ILL - 61 i I i G� -- -- .! Gip — -----i -- -- MH OR OH; i CL - ML ML OR OL 1 i 0 0 10 16 20 30 40 5o 60 70 60 90 100 110 LIQUID LIMIT (LL) t