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HomeMy WebLinkAboutPLANETSCALE LIVING - FDP220004 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT Soilogic, Inc. 3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144 March 17, 2020 Wayne D. Anderson, AIA, LLC 7825 West Ontario Place Littleton, Colorado 80128 Re: Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street Fort Collins, Colorado Soilogic Project # 20-1045 Mr. Anderson: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed additions to the existing building located at 906 East Stuart Street in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. We understand the project involves construction of an addition on the north side of the existing building and the possible construction of an addition on the east side of the existing building. The additions will be one to two-story wood-frame structures constructed as slab-on-grade. Foundation loads for the additions are expected to be relatively light, with continuous wall loads less than 3 kips per lineal foot and individual column loads (if any) less than 50 kips. Small grade changes are anticipated to develop finish site grades in the areas of the proposed additions. 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 design and construction of the addition foundations and support of floor slabs and exterior flatwork. The conclusions and recommendations outlined in this report are based on results of the completed field and laboratory testing and our experience with subsurface conditions in this area. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 2 SITE DESCRIPTION The proposed/possible additions will be constructed on the north and east sides of the existing building located at 906 East Stuart Street in Fort Collins, Colorado. We understand the existing building is a single to two-story structure constructed as slab-on- grade and is supported by some type of conventional spread footing foundation system. We anticipate new footing foundations for the additions will bear at approximately the same elevation the as existing foundations. At the time of our site exploration, the proposed construction areas contained several small to medium-sized diameter deciduous trees, wood chips, a thin mantle of vegetation and topsoil, exterior flatwork and other landscaping improvements and were relatively level. The maximum difference in ground surface elevation across the addition footprints was estimated to be less than two (2) feet. EXPLORATION AND TESTING PROCEDURES To develop subsurface information in the area of the proposed additions, two (2) soil borings were extended to a depth of approximately 15 feet below present site grade as near to the approximate addition footprints as site access would allow. The boring locations were established in the field by Soilogic personnel based on discussion with the client, the accessibility of the site and by pacing and estimating angles and distances from identifiable site references. A diagram indicating the approximate boring locations is included with this report. The boring locations indicated on this diagram should be considered accurate only to the degree implied by the methods used to make the field measurements. Graphic logs of the auger borings are also included. 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 barrel sampling procedures in general accordance with ASTM specification D-1586. Penetration resistance measurements were obtained by driving the standard sampling barrel into the substrata using a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampler a distance of 12 inches is recorded and helpful in estimating the consistency or relative density of the soils encountered. In the California barrel sampling procedure, lesser disturbed samples are obtained in removable brass liners. Samples of the subsurface materials Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 3 obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing. The samples collected were tested in the laboratory to measure natural moisture content and were 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 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. The results of the completed laboratory tests are outlined on the attached boring logs and swell/consolidation test summaries. SUBSURFACE CONDITIONS The materials encountered in the completed site borings can be summarized as follows. A thin layer of landscaping wood chips was encountered at the surface at the location of boring B-2 and a thin mantle of vegetation and topsoil at the location of boring B-1. The wood chip and vegetation layers were underlain by brown/reddish-brown lean clay with varying amounts of sand and trace to minor amounts of gravel. The lean clay varied from medium stiff to very stiff in terms of consistency, exhibited low swell potential at current moisture and density conditions and extended to the bottom of both borings at a depth of approximately 15 feet below present site grade. 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. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 4 Groundwater was not encountered in either of the completed site borings to the depth explored (about 15 feet below ground surface) when checked immediately after 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 layered soil and bedrock systems. The location and amount of perched/trapped water can also vary over time. ANALYSIS AND RECOMMENDATIONS Demolition and Site Development Within the proposed addition and new exterior flatwork areas, all existing foundations, floor slabs and any other site improvements should be completely removed. Care will be needed to ensure all in-place fill/backfill materials associated with the existing building are also completely removed at this time. In addition, all trees, tree root systems and dry and desiccated soils associated with the tree root systems should be completely removed from within the areas of the proposed additions and beneath exterior flatwork. The depth and extent of required removal can best be established at the time of excavation through openhole observation. If/where required, the excavated/removed materials should be replaced as controlled and compacted fill as outlined below. After stripping and completing all cuts and removal procedures and prior to placement of any fill, removal area backfill or exterior flatwork concrete, 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 scarified soils should be adjusted to be within the range of -1% to +3% of standard Proctor optimum moisture content at the time of compaction. Fill and removal area backfill soils required to develop the site should consist of approved, low-volume-change (LVC) soils free from organic matter, debris and other objectionable materials. Based on results of the completed laboratory testing, it is our Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 5 opinion the natural site lean clay could be used as fill and backfill provided the proper moisture content is developed in those materials at the time of placement and compaction. If required, imported soils should consist of approved LVC and relatively impervious soils free from organic matter and debris. Site fill and backfill should contain a minimum of 25% fines in order to reduce the ability of those materials to pond and transmit water. Suitable fill and backfill soils should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as recommended for the scarified soils above. Care should be taken to avoid disturbing all subgrade soils prior to placement of any overlying improvements. Soils which are allowed to dry out or become wet and softened or disturbed by the construction activities should be removed and replaced or reworked in place prior to concrete placement. Foundations Based on the materials encountered in the completed site borings and results of laboratory testing, it is our opinion the proposed lightly-loaded building additions could be supported by continuous spread footing and isolated pad foundations bearing on natural, undisturbed lean clay with low volume change potential and/or properly placed and compacted overexcavation/backfill (if/where required). For design of new footing foundations bearing on natural, undisturbed medium stiff to very stiff lean clay and/or properly placed and compacted overexcavation/backfill, we recommend using a maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, we recommend continuous spread footing and isolated pad foundations be designed to maintain a minimum dead-load pressure of 500 psf (or as high as practical) on the supporting soils. Exterior footings should bear a minimum of 30 inches below finished adjacent exterior grade to provide frost protection. We recommend formed strip footings have a minimum width of 12 inches and isolated pad foundations have a minimum width of 24 inches in order to facilitate construction and reduce the potential for development of eccentrically loaded footings. Actual footing widths should be designed by a structural engineer. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 6 For design of footing foundations and foundation walls to resist lateral movement, a passive equivalent fluid pressure value of 250 pcf could be used. The top 30 inches of subgrade could be considered a surcharge load but should not be used in the passive resistance calculations. A coefficient of friction of 0.35 could be used between foundation and floor slab concrete and the bearing soils to resist sliding. The recommended passive equivalent fluid pressure value and coefficient of friction do not include a factor of safety. Backfill placed adjacent to foundation walls should consist of LVC potential and relatively impervious soils free from organic matter, debris and other objectionable materials. The natural site lean clay soils could be used as backfill in this area, provided the proper moisture content in those materials at the time of placement and compaction. We recommend the natural site lean clay or similar backfill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture and compacted as recommended for the scarified soils in the “Demolition and Site Development” section of this report. Excessive lateral stresses can be imposed on foundation walls when using heavier mechanical compaction equipment. We recommend compaction of unbalanced foundation wall backfill soils be completed using light mechanical or hand compaction equipment. We estimate settlement of footing foundations designed and constructed as outlined above and resulting from the assumed structural loads would be less than 1 inch. Differential settlement could approach the amount of total settlement estimated above. If water from any source is allowed to infiltrate the foundation bearing soils, additional movement of the foundations could occur. Some differential settlement should be anticipated between the existing structure and proposed additions. An allowance for some differential movement should be included in design. Floor Slabs & Exterior Flatwork The addition floor slabs and exterior flatwork could be supported directly on reconditioned lean clay with low swell potential and/or properly moisture conditioned Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 7 and compacted fill or overexcavation/backfill soils (if/where required) developed as outlined in the “Demolition and Site Development” section of this report. Care should be taken to maintain the proper moisture content and avoid disturbing all floor slab/flatwork subgrade soils prior to concrete placement. The exposed floor slab/ flatwork subgrade soils should not be left exposed for extended periods of time. In the event that the subgrade soils are allowed to dry out or if rain, snowmelt or water from any source is allowed to infiltrate those materials, reworking of the subgrade soils or removal/ replacement procedures may be required. Floor slabs should be designed and constructed as floating slabs, separated from foundation walls, columns and plumbing and mechanical penetrations by the use of block outs or appropriate isolation material. Additionally, we recommend all addition partition walls supported above slabs-on-grade be constructed as floating walls to help reduce the potential for differential slab-to-foundation movement causing distress in upper section of the building and/or additions. A minimum 1½-inch void space is recommended beneath all floating walls. Special attention to door framing, drywall installation, stair systems and trim carpentry should be taken to isolate those elements from the floor slab, allowing for some differential floor slab-to-foundation movement to occur without transmitting stresses to the overlying structure. Depending on the type of floor covering and floor covering adhesive used in finished slab-on-grade areas, a vapor barrier may be required immediately beneath the floor slabs in order to maintain flooring product manufacturer warranties. A vapor barrier would help reduce the transmission of moisture through the floor slab. However, the unilateral moisture release caused by placing concrete on an impermeable surface can increase slab curl. The amount of slab curl can be reduced by careful selection of an appropriate concrete mix, however, slab curl cannot be eliminated. We recommend the owner, architect and flooring contractor consider the performance of the slab, in conjunction with the proposed flooring products to help determine if a vapor barrier will be required and where best to position the vapor barrier in relation to the floor slab. Additional guidance and recommendations concerning slab-on-grade design can be found in American Concrete Institute (ACI) section 302. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 8 Exterior flatwork will experience some movement subsequent to construction as the subgrade soils increase in moisture content. Based on results of the completed field and laboratory testing, we expect the amount of movement of exterior flatwork supported on reconditioned natural site soils and/or properly placed and compacted fill and/or removal area backfill would be limited. If undocumented fill is encountered in exterior flatwork areas, overexcavation/backfill procedures could be considered to reduce the potential for total and differential movement in these areas. Care should be taken to ensure exterior flatwork is designed to provide positive drainage away from the building and addition and that positive drainage is maintained throughout the life of the proposed improvements. Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed addition and associated site improvements. We recommend positive drainage be developed away from the additions during construction and maintained throughout the life of the site improvements, with twelve (12) inches of fall in the first 10 feet away from the building and building additions. Shallower slopes could be considered in hardscape areas. In the event that poor or negative drainage develops adjacent to the building and/ or building additions over time, the original grade and associated positive drainage outlined above should be immediately restored. Care should be taken in the planning of landscaping to avoid features which could result in the fluctuation of the moisture content of the foundation bearing and/or flatwork subgrade soils. We recommend watering systems be placed a minimum of 5 feet away from the perimeter of the site structure and structure additions and be designed to discharge away from all site improvements. Gutter systems should be considered to help reduce the potential for water ponding adjacent to the building and building additions with the gutter downspouts, roof drains or scuppers extended to discharge a minimum of 5 feet away from structural, flatwork and pavement elements. Water which is allowed to pond adjacent to site improvements can result in unsatisfactory performance of those improvements over time. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 9 GENERAL COMMENTS 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 can be completed and when warranted, alternative recommendations 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. 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. Geotechnical Subsurface Exploration Report Proposed Renovation/Additions to Existing Building 906 East Stuart Street, Fort Collins, Colorado Soilogic Project # 20-1045 10 3/17/2020 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: Alec Kaljian, E.I. Darrel DiCarlo, P.E. Project Engineer Senior Project 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 (%) 4-6" VEGETATION & TOPSOIL - 1 - 2 - 3 CS 8 17.8 102.4 9000+0.4%---- - 4 - 5 CS 8 18.5 103.7 7000 --36 22 72.2% - 6 - CL LEAN CLAY with varying 7 amounts of SAND - brown, reddish-brown 8 medium stiff to very stiff - trace to minor GRAVEL 9 - 10 CS 10 9.3 101.0 9000+0.4%800 --- - 11 - 12 - 13 - 14 - 15 CS 20 12.2 117.1 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 Sheet Drilling Rig:Water Depth Information Start Date 2/27/2020 Auger Type:During Drilling None Finish Date 2/27/2020 Hammer Type:After Drilling None USCSSamplerAtterberg Limits --Field Personnel:-- 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 (%) 2-4" MULCH - 1 - 2 - 3 CS 8 17.7 101.3 9000+0.3%---- - 4 - 5 CS 11 12.6 103.3 9000+1.2%1800 --- - 6 - CL LEAN CLAY with varying 7 amounts of SAND - brown, reddish-brown 8 medium stiff to stiff - trace to minor GRAVEL 9 - 10 CS 10 11.8 105.6 8500 ----- - 11 - 12 - 13 - 14 - 15 CS 11 16.9 110.0 6500 ----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 --USCSSamplerAtterberg Limits --Field Personnel: Start Date 2/27/2020 Auger Type:During Drilling None Finish Date 2/27/2020 Hammer Type:After Drilling None Sheet Drilling Rig:Water Depth Information PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)102.4 500 Final Moisture 19.0% % Swell @ 500 psf 0.4% Swell Pressure (psf)- Sample ID: B-1 @ 2 Sample Description: Brown Lean Clay with Sand (CL) (Swell Only) Initial Moisture 17.8% SWELL/CONSOLIDATION TEST SUMMARY PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 -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)101.0 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 Initial Moisture 9.3% Sample ID: B-1 @ 9 Sample Description: Brown Sandy Lean Clay (CL) with trace Gravel 500 Final Moisture 21.6% % Swell @ 500 psf 0.4% Swell Pressure (psf)800 -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)101.3 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 Initial Moisture 17.7% Sample ID: B-2 @ 2 Sample Description: Brown Lean Clay with Sand (CL) (Swell Only) 500 Final Moisture 19.6% % Swell @ 500 psf 0.3% Swell Pressure (psf)- -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)103.3 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED RENOVATION/ADDITIONS TO EXISTING BUILDING 906 EAST STUART STREET, FORT COLLINS, COLORADO Project # 20-1045 March 2020 Initial Moisture 12.6% Sample ID: B-2 @ 4 Sample Description: Brown Sandy Lean Clay (CL) with trace Gravel 500 Final Moisture 22.1% % Swell @ 500 psf 1.2% Swell Pressure (psf)1,800 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF Clean Gravels 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 Cu ! 6 and 1 " Cc " 3E SW Well graded sandI Clean Sands 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 PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M Silts and Clays 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 Liquid limit - oven dried Organic clayK,L,M,P Organic 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 = 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. 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+