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Home My WebLink AboutMOUNTAIN'S EDGE - Filed SEPD-SURFACE EXPLORATION/PAVEMENT DESIGN REPORT - 2019-03-20Soilogic, Inc. 3522 Draft Horse Court  Loveland, CO 80538  (970) 535-6144 March 8, 2019 GLH Construction, LLC 780 East Garden Drive Windsor, Colorado 80550 Attn: Mr. Justin T. Marshall Re: Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic Project # 18-2066P Mr. Marshall: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration and pavement section design you requested for the proposed improvements to Overland Trail as part of the off-site roadway improvements associated with the Mountain’s Edge Subdivision in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. Final pavement section design recommendations for Overland Trail are also included. The purpose of our exploration was to describe the subsurface conditions encountered in the completed site borings and develop the test data necessary to provide recommendations concerning construction of the widening area roadway embankments and final pavement section design options for the widening area. The conclusions and recommendations outlined in this report are based on the results of the completed field and laboratory testing and our experience with subsurface conditions in this area. We understand this project involves the widening of Overland Trail as part of the off-site roadway improvements associated with the Mountain’s Edge Subdivision in Fort Collins, Colorado. At this time, we understand Overland Trail will be widened to the east to allow for turn lane construction facilitating access into the development. We understand an interim 2-lane arterial roadway configuration will be constructed with the ultimate buildout consisting of a 4-lane arterial. Overland Trail currently serves as a two-lane asphaltic concrete surfaced roadway with gravel shoulders. Maximum fills on the order APPROVED 03/19/2019 Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 2 of 3 feet are anticipated to develop widening area embankment. At the time of drilling, a majority of the widening area embankment construction had been completed. FIELD EXPLORATION To develop subsurface information for the proposed improvements, a total of three (3) soil borings were drilled at approximate 500 foot intervals along the length of the proposed widening to a depth of approximately 10 feet below the existing embankment surface. The boring locations were established in the field by Soilogic personnel based on approved offsite roadway improvement plan and using a mechanical surveyor’s wheel. A diagram indicating the approximate boring locations is included with this report. The test holes were advanced using 4-inch diameter continuous-flight auger, powered by a truck-mounted CME-45 drill rig. Samples of the subsurface materials were obtained at regular intervals using California and split-barrel sampling procedures in general accordance with ASTM specification D-1586. As part of the D-1586 sampling procedure, the standard sampling barrels are driven into the substrata using a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the samplers a distance of 12 inches is recorded and helpful in estimating the consistency or relative density or hardness of the soils and/or bedrock encountered. In the California barrel sampling procedure, lesser disturbed samples are obtained in removable brass liners. Samples of the subsurface materials obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing. LABORATORY TESTING The samples collected were tested in the laboratory to measure natural moisture content and visually and/or manually classified in accordance with the Unified Soil Classification System (USCS). The USCS group symbols are indicated on the attached boring logs. An outline of the USCS classification system is included with this report. As part of the laboratory testing, a calibrated hand penetrometer (CHP) was used to estimate the unconfined compressive strength of essentially-cohesive specimens. The CHP also provides a more reliable estimate of soil consistency than tactual observation Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 3 alone. Dry density, Atterberg limits, -200 wash and swell/consolidation tests were completed on selected samples to help establish specific soil characteristics. Atterberg limits tests are used to determine soil plasticity. The percent passing the #200 size sieve (-200 wash) test is used to determine the percentage of fine-grained materials (clay and silt) in a sample. Swell/consolidation tests are performed to evaluate soil volume change potential with variation in moisture content. Swell/consolidation tests completed on samples obtained at a depth of approximately 2 feet below ground surface were inundated with water at a 150 psf confining pressure, while samples obtained at a depth of approximately four (4) feet below ground surface were inundated with water at a 500 psf confining pressure. As part of the completed laboratory testing, one (1) Resistance value (R-value) test was completed on a representative subgrade sample for use in evaluation of the existing subgrade. The results of the completed laboratory test are outlined on the attached boring logs and swell/consolidation and R-value test summaries. SUBSURFACE CONDITIONS Dark brown, brown, beige clayey sand to sandy lean clay with gravel was encountered at the surface at the boring locations. A portion of the near-surface clayey sand/lean clay appeared to be fill soils placed to developed finish subgrade elevation. The clayey sand/lean clay varied from loose to dense in terms of relative density or from medium stiff to hard in terms of consistency, exhibited no to low swell potential at current moisture and density conditions and extended to the bottom of all borings at a depth of approximately 10 feet below ground surface. The stratigraphy indicated on the included boring logs represents the approximate location of changes in soil types. Actual changes may be more gradual than those indicated. Groundwater was not encountered in the completed site borings at the time of drilling. Groundwater levels will vary seasonally and over time based on weather conditions, site development, irrigation practices and other hydrologic conditions. Perched and/or trapped groundwater conditions may also be encountered at times throughout the year. Perched water is commonly encountered in soils overlying less permeable soil layers and/or bedrock. Trapped water is typically encountered within more permeable zones of Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 4 layered soil and bedrock systems. The location and amount of perched and/or trapped water can also vary over time. ANALYSIS AND RECOMMENDATIONS Roadway Embankment Construction The clayey sand/lean clay with gravel subgrade soils encountered in the completed site borings exhibited no to low swell potential (with the average swell less than 2.0%) at in- situ moisture and density conditions and in our opinion, could be used for direct support of any additional embankment fill and pavement materials. Prior to the placement of any additional embankment fill or aggregate base course materials, we recommend the exposed subgrade soils be scarified to a depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the materials standard Proctor maximum dry density. The moisture content of the reconditioned subgrade soils should be adjusted to be within the range of ±2% of standard Proctor optimum moisture content at the time of compaction. Slopes steeper than 4(H) to 1(V) that are expected to receive fill should be continuously benched during fill placement to reduce the potential for development of a shear plane between the existing soils and proposed fill. Fill soils required to develop the roadway embankment should consist of approved low volume change (LVC) soils free from organic matter, debris and other objectionable materials. The clayey sand/lean clay overburden soils located on the Mountain’s Edge Subdivision site could be used as fill to develop the widening area embankment. Additional embankment fill (if any) should have a minimum R-value of 15. We recommend suitable fill materials be placed in loose lifts not to exceed 9 inches thick, adjusted to within the range of ±2% of standard Proctor optimum moisture content and compacted to at least 95% of standard Proctor maximum dry density. The reconditioned subgrade soils and properly placed and compacted fill soils developed as outlined above could be used for direct support of new pavements. Proofrolling of the finished subgrade soils should be completed prior to paving to help identify any areas of soft/unstable soils. Those areas identified as unstable would need to be mended prior to Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 5 paving. Isolated areas of instability can be mended on a case by case basis. If more extensive areas of subgrade instability are encountered, and depending on the time of year when construction occurs and other hydrologic conditions, stabilization of the subgrade soils may become necessary to develop a suitable paving platform. Based on the materials encountered in the completed site borings and results of laboratory testing, it is our opinion fly ash stabilization of the pavement subgrades could be completed to develop a suitable paving platform. With the increase in support strength developed by the chemical stabilization procedures, it is our opinion the zone of stabilized subgrade could be included in the pavement section design, reducing the required thickness of overlying aggregate base course and/or asphaltic concrete. A pavement section design option incorporating partial structural credit for the fly ash stabilized subgrade soils is outlined below in Table I. If full structural credit for the fly ash stabilized subgrade soils is preferred, a fly ash mix design will need to be completed and the strength of the subgrade soils verified at the time of stabilization. Fly ash stabilization can eliminate some of the uncertainty associated with attempting to pave during periods of inclement weather. If fly ash stabilization will be completed, we recommend the addition of 13% class ‘C’ fly ash based on component dry unit weights. A 12-inch thick stabilized zone should be constructed by thoroughly blending the fly ash with the in-place subgrade soils. Some “fluffing” of the finish subgrade level should be expected with the stabilization procedures. The blended materials should be adjusted to within ±2% of standard Proctor optimum moisture content and compacted to at least 95% of the material’s standard Proctor maximum dry density within two (2) hours of fly ash addition. Care should be taken to avoid disturbing the developed subgrade soils prior to paving. In addition, efforts to maintain the proper moisture content in the subgrade soils should be made. If subgrade soils are disturbed by the construction activities or allowed to dry out or become elevated in moisture content, those materials should be reworked in place or removed and replaced prior to surfacing. Pavement Design For design of new pavements, a Traffic Impact Study (TIS) completed for the subject property and associated roadways by Eugene G. Coppola, P.E. dated May 31, 2016 was Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 6 reviewed. Short term total traffic was determined using the traffic count information provided in the TIS. The greatest total traffic volume anticipated to utilize Overland Trail is located north of the Drake Road intersection and these values were used in design. Total Peak Hour Traffic volumes were estimated at 10% of Total Annual Average Daily Traffic. Long term total traffic was calculated utilizing a 3% annual growth rate. Design ESAL’s were determined using the midpoint of short-term and long- term total traffic, a lane factor of 0.45 for a 4-lane arterial and an estimated 3% heavy truck traffic (1.5% single-unit trucks and 1.5% combination-unit trucks). Traffic conversion calculations are included with this report. An R-value of 15 was determined on a representative subgrade sample obtained from the completed site borings and was used in the pavement section design. A pavement section design for the proposed construction was completed in accordance with the Larimer County Urban Area Street Standards (LCUASS) and is outlined below in Table I. Alternative pavement sections could be considered and we would be happy to discuss any design alternatives at your request. TABLE I – NEW PAVEMENT SECTION DESIGN Roadway Classification Calculated ESAL’s R-value/CDOT (Mr) Reliability (%) Serviceability Loss Design Str. Number Overland Trail 4-Lane Arterial 1,163,552 R-15, 4165 90% 2.0 (4.23) Option A – Composite Asphaltic Concrete (Grading S) Aggregate Base (Class 5 or 6) (Structural Number) 7½” (0.44/inch 9” (0.11/inch) (4.29) Option B – Composite with Fly Ash Asphaltic Concrete (Grading S) Aggregate Base (Class 5 or 6) Fly Ash Treated Subgrade (Structural Number) 6½” (0.44/inch 8” (0.11/inch) 1” (10 @ .05/inch) (4.24) Asphaltic concrete should consist of a bituminous plant mix composed of a mixture of aggregate, filler, binders and additives (if required), meeting City of Fort Collins (LCUASS) design criteria. Based on the roadway classification, we expect grading S Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 7 materials will be required for the roadway improvements utilizing 100 design gyrations. We understand PG(64-22) asphaltic cement will be required for lower lifts in the hot-mix asphalt section with PG(64-28) required for the surface lift. Hot mix asphalt designed using “Superpave” criteria should be compacted to within 92 to 96% of the materials Maximum Theoretical Density. Aggregate base should be consistent with CDOT requirements for Class 5 or 6 aggregate base, placed in loose lifts not to exceed 9 inches thick and compacted to at least 95% of the materials standard Proctor maximum dry density. Drainage Positive drainage is imperative for long-term performance of the improved roadway. Water which is allowed to pond on asphalt pavements can degrade these pavement materials over time. In addition, water which is allowed to pond adjacent to the roadway pavements can result in a loss of subgrade support and premature failure of the overlying pavement section. LIMITATIONS This report was prepared based upon the data obtained from the completed site exploration, laboratory testing, engineering analysis and any other information discussed. The completed borings provide an indication of subsurface conditions at the boring locations only. Variations in subsurface conditions can occur in relatively short distances away from the borings. This report does not reflect any variations which may occur across the site or away from the borings. If variations in the subsurface conditions anticipated become evident, the geotechnical engineer should be notified immediately so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any biological or environmental assessment of the site or identification or prevention of pollutants or hazardous materials or conditions. Other studies should be completed if concerns over the potential of such contamination or pollution exist. Geotechnical Subsurface Exploration and Pavement Design Report Overland Trail Widening at Mountain’s Edge Fort Collins, Colorado Soilogic # 18-2066P 8 The geotechnical engineer should 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. The geotechnical engineer should also be retained to provide testing and observation services during construction to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with the generally accepted standard of care for the profession. No warranties express or implied, are made. The conclusions and recommendations contained in this report should not be considered valid in the event that any changes in the nature, design or location of the project as outlined in this report are planned, unless those changes are reviewed and the conclusions of this report modified and verified in writing by the geotechnical engineer. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed information or if we can be of further service to you in any way, please do not hesitate to contact us. Very Truly Yours, Soilogic, Inc. Reviewed by: Zach Gordon, E.I. Wolf von Carlowitz, P.E. Project Engineer Principal Engineer LOG OF BORING B-1 1/1 CME 45 4" CFA Automatic JL / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - 1 - 2 - 3 CS 22 12.7 123.1 9000+ 0.1% @ 150 - - - - - SC-CL CLAYEY SAND to SANDY LEAN CLAY 4 w/G with GRAVEL - dark brown, brown, beige 5 CS 17 5.7 - 1000 - - - - - loose to medium dense / - medium stiff to very stiff 6 - 7 - 8 - 9 - 10 CS 10 6.5 87.4 - - - - - - BOTTOM OF BORING @ 10.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 USCS Sampler LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic JL / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - 1 - 2 - 3 CS 21 13.7 107.3 9000+ 1.2% @ 150 - 31 25 42.1% - SC-CL CLAYEY SAND to SANDY LEAN CLAY 4 w/G with GRAVEL - dark brown, brown, beige 5 CS 48 3.8 105.9 9000+ 0.3% 600 - - - medium dense to dense / - very stiff to hard 6 - 7 - 8 - 9 - 10 CS 37 4.0 137.0 9000+ - - - - - BOTTOM OF BORING @ 10.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 24 Hours After Drilling - USCS LOG OF BORING B-3 1/1 CME 45 4" CFA Automatic JL / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - 1 - 2 - 3 CS 20 13.0 112.5 9000+ 2.5% @ 150 - - - - - SC-CL CLAYEY SAND to SANDY LEAN CLAY 4 w/G with GRAVEL - dark brown, brown, beige 5 CS 9 23.3 98.4 8000 - - - - - loose to medium dense / - medium stiff to very stiff 6 - 7 - 8 - 9 - 10 CS 10 10.3 113.4 9000+ - - - - - BOTTOM OF BORING @ 10.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 24 Hours After Drilling - USCS Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 123.1 150 Final Moisture 12.9% % Swell @ 150 psf 0.1% Swell Pressure (psf) - Sample ID: B-1 @ 2 (Swell Only) Initial Moisture 12.7% Sample Description: Dark Brown/Brown/Beige Clayey Sand to Sandy Lean Clay w/ Gravel (SC-CL) SWELL/CONSOLIDATION TEST SUMMARY OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit 31 Plasticity Index 25 % Passing #200 42.1% Dry Density (pcf) 107.3 150 Sample Description: Dark Brown/Brown/Beige Clayey Sand to Sandy Lean Clay w/ Gravel (SC-CL) Final Moisture 18.8% % Swell @ 150 psf 1.2% Swell Pressure (psf) - Sample ID: B-2 @ 2 Initial Moisture 13.7% SWELL/CONSOLIDATION TEST SUMMARY OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 105.9 500 Sample Description: Dark Brown/Brown/Beige Clayey Sand to Sandy Lean Clay w/ Gravel (SC-CL) Final Moisture 19.5% % Swell @ 500 psf 0.3% Swell Pressure (psf) 600 Sample ID: B-2 @ 4 Initial Moisture 3.8% SWELL/CONSOLIDATION TEST SUMMARY OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 112.5 150 Sample Description: Dark Brown/Brown/Beige Clayey Sand to Sandy Lean Clay w/ Gravel (SC-CL) Final Moisture 16.0% % Swell @ 150 psf 2.5% Swell Pressure (psf) - Sample ID: B-3 @ 2 Initial Moisture 13.0% SWELL/CONSOLIDATION TEST SUMMARY OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Short Term Total Daily Traffic Ti = 11000 AADT Long Range Total Daily Traffic Tf = Ti(1+i)n Growth Rate (i) = 3% n = 20 yrs Long Range Total Daily Traffic Tf = 19867 AADT Lane Factor (4-Lane Arterial) Lf = 0.45 Short Range Total Daily Traffic for Design Lane (4-Lane Arterial) Ti = Ti*Lf 4950 AADT Long Range Total Daily Traffic for Design Lane (4-Lane Arterial) Tf = Tf*Lf 8940 AADT Midpoint Tm = (T1+T)/2 = Tm = 6945 AADT Passenger Vehicles (97% of Total) Tm = 6737 AADT Single Unit Trucks (1.5% of Total) Tm = 104 AADT Combination Unit Trucks (1.5% of Total) Tm = 104 AADT Daily ESAL's = Tm x Equivalency Factor = 3623 * .003 = 20.210 Passenger Vehicles Daily ESAL's = Tm x Equivalency Factor = 56 * .249 = 25.940 Single Unit Trucks Daily ESAL's = Tm x Equivalency Factor = 56 * 1.087 = 113.24 Combination Unit Trucks Total = 159 (Daily ESAL's) 20 Year Design Period ESAL's = (Daily ESAL's * 365 * 20) = 1,163,552 ESAL's Traffic Conversion Calculations Overland Trail at Mountains Edge City of Fort Collins, Colorado Soilogic # 18-2066P Design Inputs Asphalt Concrete CBR, Calculated Mr 3.0 Mr = 5161 psi K = 110 pci Sugrade Support Used Mr = 4195 psi K = 250 pci Reliability (%) = 90 90 Standard Deviation So = 0.45 0.35 Initial Serviceability = Po = 4.5 4.5 Terminal Serviceability = Pt = 2.5 2.5 Design Serviceability Loss, = DPSI = 2.0 2.0 Asphalt Layer Coefficients a1 = 0.44 AC Surface and Binder a2 = AC Base a2 = 0.11 Aggregate Base a3 = 0.05 Subbase Concrete Compressive Strength 4000 psi Modulus of Elasticity of Concrete = 3,605 ksi Modulus of Rupture of Concrete: = 580 psi Load Transfer ("J" Factor) 3.8 See Table 1 Drainage Coefficient 1.0 See Table 2 Pavement Thickness Designs Traffic Category - Flexible Pavement Tucker Asphalt Section Traffic (18 kip ESAL) = 1,163,552 Calculated ESALs = 11,868 Flexible Pavement Section Drainage, m Di AC Surface + Binder 7.5 in Asphalt Base in Aggregate Base 1.0 9.0 in Subbase 1.0 in Structural Number 4.29 OK 4.7886E-05 Required 4.23 Rigid Pavement Section Traffic Category - Rigid Pavement Typical Minor Road Concrete Section Traffic (18 kip ESAL) = 160,000 Calculated ESALs = 295,382 Concrete Thickness, DPCC 5.08 Equation results require 5.2041 Click button to solve for slab Thickness equality 5.1183 -3.7265 Pavement Design (AASHTO 1993 Method) Solve for DPCC Solve for SN required Design Inputs Asphalt Concrete CBR, Calculated Mr 3.0 Mr = 5161 psi K = 110 pci Sugrade Support Used Mr = 4195 psi K = 250 pci Reliability (%) = 90 90 Standard Deviation So = 0.45 0.35 Initial Serviceability = Po = 4.5 4.5 Terminal Serviceability = Pt = 2.5 2.5 Design Serviceability Loss, = DPSI = 2.0 2.0 Asphalt Layer Coefficients a1 = 0.44 AC Surface and Binder a2 = AC Base a2 = 0.11 Aggregate Base a3 = 0.05 Subbase Concrete Compressive Strength 4000 psi Modulus of Elasticity of Concrete = 3,605 ksi Modulus of Rupture of Concrete: = 580 psi Load Transfer ("J" Factor) 3.8 See Table 1 Drainage Coefficient 1.0 See Table 2 Pavement Thickness Designs Traffic Category - Flexible Pavement Tucker Asphalt Section Traffic (18 kip ESAL) = 1,163,552 Calculated ESALs = 11,868 Flexible Pavement Section Drainage, m Di AC Surface + Binder 6.5 in Asphalt Base in Aggregate Base 1.0 8.0 in Subbase 1.0 10.0 in Structural Number 4.24 OK -4.916E-06 Required 4.23 Rigid Pavement Section Traffic Category - Rigid Pavement Typical Minor Road Concrete Section Traffic (18 kip ESAL) = 160,000 Calculated ESALs = 295,382 Concrete Thickness, DPCC 5.08 Equation results require 5.2041 Click button to solve for slab Thickness equality 5.1183 -3.7265 Pavement Design (AASHTO 1993 Method) Solve for DPCC Solve for SN required UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Clean Gravels Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF Less than 5% finesC Cu < 4 and/or 1 > Cc > 3E GP Poorly graded gravelF Fines classify as ML or MH GM Silty gravelF,G, H Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Gravels with Fines More than 12% finesC Fines classify as CL or CH GC Clayey gravelF,G,H Clean Sands Cu ! 6 and 1 " Cc " 3E SW Well graded sandI Less than 5% finesD Cu < 6 and/or 1 > Cc > 3E SP Poorly graded sandI Fines classify as ML or MH SM Silty sandG,H,I Sands 50% or more of coarse fraction passes No. 4 sieve Sands with Fines More than 12% finesD Fines classify as CL or CH SC Clayey sandG,H,I Silts and Clays PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M Liquid limit less than 50 Inorganic PI < 4 or plots below “A” lineJ ML SiltK,L,M Liquid limit - oven dried Organic clayK,L,M,N Fine-Grained Soils 50% or more passes the No. 200 sieve Organic Liquid limit - not dried < 0.75 OL Organic siltK,L,M,O Inorganic PI plots on or above “A” line CH Fat clayK,L,M Silts and Clays Liquid limit 50 or more PI plots below “A” line MH Elastic siltK,L,M Organic Liquid limit - oven dried Organic clayK,L,M,P Liquid limit - not dried < 0.75 OH Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels 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. D 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 E Cu = D60/D10 Cc = GENERAL NOTES DRILLING & SAMPLING SYMBOLS: SS: Split Spoon - 1⅜" I.D., 2" O.D., unless otherwise noted HS: Hollow Stem Auger ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA: Power Auger RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA: Hand Auger CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB: Rock Bit BS: Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary The number of blows required to advance a standard 2-inch O.D. split-spoon sampler (SS) the last 12 inches of the total 18-inch penetration with a 140-pound hammer falling 30 inches is considered the “Standard Penetration” or “N-value”. For 2.5” O.D. California Barrel samplers (CB) the penetration value is reported as the number of blows required to advance the sampler 12 inches using a 140-pound hammer falling 30 inches, reported as “blows per inch,” and is not considered equivalent to the “Standard Penetration” or “N-value”. 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 Casing Removal Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater. In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations. DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency. FINE-GRAINED SOILS COARSE-GRAINED SOILS BEDROCK (CB) Blows/Ft. (SS) Blows/Ft. Consistency (CB) Blows/Ft. (SS) Blows/Ft. Relative Density (CB) Blows/Ft. (SS) Blows/Ft. Consistency < 3 0-2 Very Soft 0-5 < 3 Very Loose < 24 < 20 Weathered 3-5 3-4 Soft 6-14 4-9 Loose 24-35 20-29 Firm 6-10 5-8 Medium Stiff 15-46 10-29 Medium Dense 36-60 30-49 Medium Hard 11-18 9-15 Stiff 47-79 30-50 Dense 61-96 50-79 Hard 19-36 16-30 Very Stiff > 79 > 50 Very Dense > 96 > 79 Very Hard > 36 > 30 Hard RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY Descriptive Terms of Other Constituents Percent of Dry Weight Major Component of Sample Particle Size Trace < 15 Boulders Over 12 in. (300mm) With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm) Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand Silt or Clay #4 to #200 sieve (4.75mm to 0.075mm) Passing #200 Sieve (0.075mm) RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION Descriptive Terms of Other Constituents Percent of Dry Weight Term Plasticity Index Trace With Modifiers < 5 5 – 12 > 12 Non-plastic Low Medium High 0 1-10 11-30 30+ F If soil contains ! 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains ! 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains ! 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains ! 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI ! 4 and plots on or above “A” line. O PI < 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. Sampler Atterberg Limits Start Date 3/1/2019 Auger Type: During Drilling None Finish Date 3/1/2019 Hammer Type: After Drilling None Surface Elev. - Field Personnel: Sheet Drilling Rig: Water Depth Information OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 Sampler Atterberg Limits Start Date 3/1/2019 Auger Type: During Drilling None Finish Date 3/1/2019 Hammer Type: After Drilling None Surface Elev. - Field Personnel: Sheet Drilling Rig: Water Depth Information OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019 Atterberg Limits Surface Elev. - Field Personnel: 24 Hours After Drilling - Finish Date 3/1/2019 Hammer Type: After Drilling None Sheet Drilling Rig: Water Depth Information Start Date 3/1/2019 Auger Type: During Drilling None OVERLAND TRAIL WIDENING AT MOUNTAINS EDGE FORT COLLINS, COLORADO Project # 18-2006P March 2019