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HomeMy WebLinkAboutAWEIDA - PDP - PDP180008 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO SOILOGIC # 18-1038 February 26, 2018 Soilogic, Inc. 3522 Draft Horse Court  Loveland, CO 80538  (970) 535-6144 P.O. Box 1121  Hayden, CO 81639  (970) 276-2087 February 26, 2018 Aweida Properties, Inc. 500 Discovery Parkway, Suite 300 Superior, Colorado 80027 Attn: Mr. Neil Aweida Re: Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road Fort Collins, Colorado Soilogic Project # 18-1038 Dear Mr. Aweida: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed mixed-use building to be constructed at 4101 South Taft Hill Road in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. The subsurface materials encountered in the completed site borings can be summarized as follows. Brown/beige sandy lean clay with gravel which was identified as possible existing fill material was encountered at the surface at the locations of borings B-1 and B-3. The lean clay apparent fill varied from medium stiff to very stiff in terms of consistency, exhibited low to borderline low/moderate swell potential at current moisture and density conditions and extended to a depth of about 3 feet below ground surface, where it was underlain by reddish-brown/beige/rust clayey sand with varying amounts of gravel. Apparently natural reddish-brown/beige/rust clayey sand with varying amounts of gravel was also encountered at the surface at the locations of borings B-2 and B-4. The clayey sand varied from loose to medium dense in terms of relative density, exhibited no to low swell potential at in-situ moisture and density conditions and extended to the maximum depths explored in each of the borings at depths between 10 and 15 feet below present site grades. Groundwater was not encountered in the completed site borings to the depths explored (approximately 10 to 15 feet below ground surface) when checked immediately after drilling. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 2 Based on the subsurface conditions encountered, results of laboratory testing and type of construction proposed, it is our opinion the proposed mixed-use building could be designed and constructed using conventional spread footing foundations bearing on natural, undisturbed clayey sand and/or properly placed and compacted overexcavation/backfill (where required). Care will be needed at the time of construction to ensure all footing foundations bear on like materials with suitable strength and low volume change potential. Possible existing undocumented fill soils were identified in borings B-1 and B-3. If/where undocumented fill is identified underlying footing foundations at the time of excavation, extending footing foundations to bear on natural, undisturbed clayey sand with no to low swell potential at slightly greater depth, or extending overexcavation/backfill procedures to low swelling clayey sand to redevelop foundation bearing would be required. Overexcavation/backfill procedures extended to natural, undisturbed clayey sand with no to low swell potential should also be completed below the building floor slab if/where undocumented fill is identified. Similar methods should be used in order to develop LVC- potential pavement and exterior flatwork subgrades if/where undocumented fill soils are identified underlying these improvements. The overexcavation/backfill procedures would help develop LVC-potential foundation, floor slab/flatwork and pavement support across the building footprint and pavement areas and reduce the potential for total and differential movement of those supported elements subsequent to construction. Based on the results of completed laboratory testing, the existing fill and natural site clayey sand soils appear suitable for use as low volume change (LVC) fill and overexcavation/ backfill (if/where required) to develop the site. Other opinions and recommendations concerning design criteria and construction details for the proposed site improvements are included with this report. Pavement section design options are also included. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 3 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. Wolf von Carlowitz, P.E. Project Engineer Principal Engineer GEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO SOILOGIC # 18-1038 February 26, 2018 INTRODUCTION This report contains the results of the completed geotechnical subsurface exploration for the proposed mixed-use building to be constructed at 4101 South Taft Hill Road in Fort Collins, Colorado. 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 proposed building foundations and support of floor slabs, exterior flatwork and site pavements. 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. PROPOSED CONSTRUCTION We understand the proposed mixed-use (commercial/residential) building will be a two- story, steel frame structure constructed as slab-on-grade, encompassing a plan area of approximately 2,667 square feet. Foundations loads for the building are anticipated to be relatively light, with maximum continuous wall loads on the order of 3 to 4 kips per lineal foot and individual column loads less than 150 kips. Paved drive and parking areas are also anticipated as part of the proposed site improvements. Small grade changes are anticipated to develop finish site grades in building and pavement areas. If proposed construction or assumed loadings differ significantly from those assumed, Soilogic should be notified to reevaluate the recommendations in this report. SITE DESCRIPTION The development parcel includes an approximate 0.46-acre parcel of land located at 4101 South Taft Hill Road in Fort Collins, Colorado. At the time of our exploration, the site was sparsely vegetated with grasses and weeds and was relatively level, with the maximum difference in ground surface elevation across the site estimated to be on the order of two to Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 2 three (2-3) feet. We understand a previously existing residence and associated outbuildings were razed and removed from this property prior to our site exploration. SITE EXPLORATION Field Exploration To develop subsurface information for the proposed site improvements, a total of four (4) soil borings were completed. Two (2) borings were advanced in the areas of the proposed mixed-use building to a depth of approximately 15 feet below present site grade. Two (2) additional borings were completed in the site pavement areas to a depth of approximately 10 feet below ground surface. The boring locations were established in the field by Soilogic personnel based on a provided site plan, using a mechanical surveyor's wheel and estimating angles from identifiable site references. The boring locations should be considered accurate only to the degree implied by the methods used to make the field measurements. A diagram indicating the approximate boring locations is included with this report. Graphic logs of each 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. As part of the D-1586 sampling procedure, the standard sampling barrel is driven 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, relative density or hardness of the soils/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 were visually and/or manually classified in accordance with the Unified Soil Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 3 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. Classification of bedrock was completed through visual and tactual observation of disturbed samples. Other bedrock types could be revealed through petrographic analysis. 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/bedrock 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/bedrock characteristics. Atterberg limits tests are used to determine soil/bedrock 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/bedrock volume change potential with variation in moisture content. As part of the completed laboratory testing water soluble sulfate (WSS) tests were completed on two (2) selected soil samples to evaluate corrosive soil characteristics with respect to buried concrete. The results of the completed laboratory tests are outlined on the attached boring logs and swell/ consolidation test summaries and/or discussed subsequently in this report. SUBSURFACE CONDITIONS The subsurface materials encountered in the completed site borings can be summarized as follows. Brown/beige sandy lean clay with gravel which was identified as possible existing fill material was encountered at the surface at the locations of borings B-1 and B-3. The lean clay apparent fill varied from medium stiff to very stiff in terms of consistency, exhibited low to borderline low/moderate swell potential at current moisture and density conditions and extended to a depth of about 3 feet below ground surface, where it was underlain by reddish-brown/beige/rust clayey sand with varying amounts of gravel. Apparently natural reddish-brown/beige/rust clayey sand with varying amounts of gravel was also encountered at the surface at the locations of borings B-2 and B-4. The clayey sand varied from loose to medium dense in terms of relative density, exhibited no to low swell potential at in-situ moisture and density conditions and extended to the maximum depths explored in each of the borings at depths between 10 and 15 feet below present site grades. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 4 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 to the depths explored (approximately 10 to 15 feet below ground surface) when checked immediately after drilling. Groundwater levels will vary due to seasonal variations in precipitation, 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 and/or trapped water can also vary over time. ANALYSIS AND RECOMMENDATIONS General Possible existing undocumented fill was encountered at the locations of borings B-1 and B-3 extending to a depth approaching 3 feet below present site grade. As a precaution, and in order to develop consistent foundation bearing, we recommend all shallow stemwall footing foundations be extended through any existing fill (if/where present) to bear on natural, undisturbed moist clayey sand with no to low swell potential. Overexcavation/ backfill procedures extended to natural, undisturbed clayey sand with no to low swell potential could also be considered to redevelop foundation bearing in these areas. Careful observation of the exposed foundation bearing materials should be completed at the time of construction to ensure all footing foundations will be supported on like materials with suitable strength and low volume change potential. If/where existing fill soils are identified underlying the building floor slab at the time of excavation, overexcavation/backfill procedures extended to low swelling clayey sand in these areas are recommended to redevelop low volume-change (LVC) floor slab support for this improvement. Similar overexcavation/backfill procedures below exterior flatwork and site pavements are also recommended prior to concrete/asphalt placement/surfacing if/where undocumented fill is identified in these areas. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 5 Demolition and Site Development Any remaining foundations, flatwork/landscaping features, underground utilities and other site improvements should be completely removed from within the building, exterior flatwork and pavement areas. In addition, we recommend all existing vegetation and topsoil, including all tree root systems (if any) and dry and desiccated soils associated with the tree root systems be completely removed. Undocumented fill soils identified within the proposed building, site pavement and exterior flatwork areas should also be completely removed to natural, undisturbed clayey sand with no to low swell potential at this time. After stripping and completing all cuts and removal procedures and prior to placement of any new fill, removal area backfill, exterior flatwork or site pavements, we recommend the exposed subgrades be scarified to a depth of 9 inches, adjusted to within ±2% of optimum moisture content and uniformly re-compacted to at least 95% of the maximum standard Proctor density (ASTM D698). Fill and overexcavation/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 opinion the existing fill (if any) and site clayey sand could be used as fill and/or overexcavation/backfill to develop the site provided the proper moisture content is developed in the materials at the time of placement and compaction. If it is necessary to import additional material to the site for use as fill, those materials should consist of approved relatively impervious LVC materials. We recommend suitable fill materials be uniformly placed and compacted in loose lifts not to exceed 9 inches thick, moisture conditioned and compacted as recommended for the scarified subgrade soils above. Care should be taken to avoid disturbing the reconditioned subgrade soils and placed fill materials prior to placement of any overlying improvements. Soils which are allowed to dry or 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 and/or paving. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 6 Foundations Based on the materials encountered in the completed site borings and results of field and laboratory testing, it is our opinion the proposed mixed-use building could be supported by continuous spread footing and isolated pad foundations bearing on natural, undisturbed, clayey sand with no to low swell potential and/or properly placed and compacted overexcavation/backfill (if/where required) developed as outlined above. For design of foundations bearing on natural, undisturbed, loose to medium dense clayey sand and/or properly placed and compacted overexcavation/backfill (if completed), we recommend using a maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, we recommend the footing foundations be sized to maintain a minimum dead- load pressure of 500 psf (or as high as practical) on the bearing soils. Exterior footings shall 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. 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 existing fill and site clayey sand could be used as backfill in this area provided the proper moisture content is developed in those materials at the time of placement and compaction. We recommend the existing fill and site clayey sand or similar backfill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture and compacted as previously outlined in the “Demolition and Site Development” section of this report. For design of footing foundations and foundation walls to resist lateral movement, a passive equivalent fluid pressure value of 275 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 0.45 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. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 7 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 movement estimated above. If water from any source is allowed to infiltrate the foundation bearing soils, additional movement of the foundations could occur. Seismic Design Based on the results of this investigation and Soilogic review of the International Building Code (IBC - 2003), a soil profile type D could be used for the site strata. Based on our review of United States Geologic Survey (USGS) mapped information, design spectral response acceleration values of SDS = .231 (23.1%) and SD1 = .094 (9.4%) could be used. Floor Slab, Exterior Flatwork and Pavement Subgrade In slab-on-grade, exterior flatwork and pavement areas, those slabs/pavements could be supported directly on reconditioned natural site soils and/or properly placed and compacted fill or overexcavation/backfill (if/where required) developed as outlined in the “Demolition and Site Development” section of this report. A modulus of subgrade reaction (k) value of 150 pci could be used for design of at-grade floor slabs supported on reconditioned natural site clayey sand and/or properly placed and compacted fill. Disturbed subgrades or subgrade soils that have been allowed to dry out or become wet and softened should be removed and replaced or reconditioned in place prior to floor slab construction. 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 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 sections of the structure. A minimum one and one-half (1½) inch void space is recommended beneath all floating walls. Special attention to door and stair framing, drywall installation 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. Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 8 Depending on the type of floor covering and floor covering adhesive used in finished slab- on-ground areas, a vapor barrier may be required immediately beneath the floor slab to maintain flooring product manufacturer warranties. A vapor barrier would help reduce the transmission of moisture through the floor slabs. 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. 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. Subgrade soils expected to receive floor slabs, exterior flatwork and pavements should be evaluated closely immediately prior to concrete placement. If areas of disturbed, wet and softened, or dry subgrade soils are encountered at that time, reworking of those materials or removal/replacement procedures may be required. Some movement of site pavements and exterior flatwork should be expected as the moisture content of the subgrade soils increases subsequent to construction. Based on results of the completed field and laboratory testing, we expect the amount of movement of pavements and exterior flatwork supported on reconditioned natural site soils and/or properly placed and compacted fill and/or overexcavation/backfill would be limited. Care should be taken to ensure that when site pavements and exterior flatwork move, positive drainage will be maintained away from the structure. Pavements The site clayey sand would be subject to low remolded shear strength. A resistance value (R-value) of 7 was estimated for the site clayey sand and used in the pavement section design. Traffic loading on site pavements is expected to consist of low volumes automobiles and light trucks as well as areas of higher light-vehicle traffic volumes and heavier trash, delivery and emergency vehicle traffic. Equivalent 18-kip single axle loads (ESAL’s) were estimated for the quantity of site traffic anticipated. Two (2) general design classifications are outlined below in Table I. Standard duty pavements could be considered Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 9 in automobile drive and parking areas. Heavy duty pavements should be considered for access drives and other areas of the site expected to receive higher traffic volumes or heavier trash, delivery and emergency truck traffic. Proofrolling of the pavement subgrades should be completed to help identify unstable areas. Areas which pump or deform excessively should be mended prior to asphalt, PCC or aggregate base course placement. Isolated areas of subgrade instability can be mended on a case-by-case basis. If more extensive areas of subgrade instability are observed and depending on the in-place moisture content of the subgrade soils immediately prior to paving, the time of year when construction occurs and other hydrologic conditions, overall stabilization of the subgrade soils may become necessary to develop a suitable paving platform. If required, we recommend consideration be given to stabilization of the pavement subgrades with Class C fly ash. With the increase in support strength developed by the fly ash stabilization procedures, it is our opinion some credit for the stabilized zone could be included in the pavement section design, reducing the required thickness of overlying asphaltic concrete and aggregate base course. Fly ash stabilization can also eliminate some of the uncertainty associated with attempting to pave during periods of inclement weather. Pavement section design options incorporating some structural credit for the fly ash-stabilized subgrade soils are outlined below in Table I. TABLE I – PAVEMENT SECTION DESIGN Standard Duty Heavy Duty Option A – Composite Asphaltic Concrete (Grading S or SX) Aggregate Base (Class 5 or 6) 4” 6” 5” 8” Option B – Composite on Stabilized Subgrade Asphaltic Concrete (Grading S or SX) Aggregate Base (Class 5 or 6) Fly Ash Stabilized Subgrade 3” 4” 12” 4” 6” 12” Option C - Portland Cement Concrete Pavement PCCP 5” 6” Asphaltic concrete should consist of a bituminous plant mix composed of a mixture of aggregate, filler, binders and additives (if required) meeting the design requirements of the City of Fort Collins. Aggregate used in the asphaltic concrete should meet specific gradation requirements such as Colorado Department of Transportation (CDOT) grading Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 10 S (¾-inch minus) or SX (½-inch minus) specifications. 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 Class 6 aggregate base, placed in loose lifts not to exceed 9 inches thick, adjusted to within ±2% of standard Proctor optimum moisture content and compacted to at least 95% of the materials standard Proctor maximum dry density. If fly ash stabilization procedures will be completed, we recommend the addition of 12% 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 in moisture content to within the range of ±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. For areas subjected to truck turning movements and/or concentrated and repetitive loading such as dumpster or truck parking and loading areas, we recommend consideration be given to the use of Portland cement concrete pavement with a minimum thickness of 6 inches. The concrete used for site pavements should be entrained with 4% to 8% air and have a minimum 28-day compressive strength of 4,000 psi. Woven wire mesh or fiber entrained concrete should be considered to help in the control of shrinkage cracking. The proposed pavement section designs do not include an allowance for excessive loading conditions imposed by heavy construction vehicles or equipment. Heavily loaded concrete or other building material trucks and construction equipment can cause some localized distress to site pavements. The recommended pavement sections are minimums and periodic maintenance efforts should be expected. A preventative maintenance program can help increase the service life of site pavements. Corrosive Soil Characteristics We measured the soluble sulfate concentration for two (2) representative samples of the subsoils which will likely be in contact with structural concrete. The sulfate concentrations Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 11 measured in the samples varied from 0 to 0.015 percent by weight. ACI rates the measured concentrations as being defined as a “negligible risk” category for concrete sulfate attack; therefore Type I cement should be suitable for concrete members on and below grade. As an added precaution, Type I/II Portland cement could be considered for additional sulfate resistance of construction concrete. Foundation concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed building and associated site improvements. We recommend positive drainage be developed away from the structure 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. Shallower slopes could be considered in hardscape areas. In the event that poor or negative drainage develops adjacent to the building 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 flatwork and pavement subgrade soils. We recommend watering systems be placed a minimum of 5 feet away from the perimeters of the site structures 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 structure, 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. 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 Geotechnical Subsurface Exploration Report Proposed Mixed-Use Building 4101 South Taft Hill Road, Fort Collins, Colorado Soilogic Project # 18-1038 12 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. 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. PROPOSED MIXED-USE BUILDING BORING LOCATION DIAGRAM 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO FEBRUARY 2018 PROJECT # 18-1038 B-1 B-2 B-4 B-3 LOG OF BORING B-1 1/1 CME 45 4" CFA Automatic ZG & ZG Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - POSSIBLE EXISTING FILL MATERIAL; 1 CL SANDY LEAN CLAY with GRAVEL - brown, beige 2 very stiff - 3 CS 34 7.1 116.6 9000+ 2.9% 2400 - - - - 4 - 5 CS 16 11.1 100.4 9000+ None <500 - - - - 6 - 7 - 8 SC CLAYEY SAND with varying - amounts of GRAVEL 9 reddish-brown, beige, rust - loose to medium dense 10 CS 10 8.8 120.9 9000+ - - - - - - 11 - 12 - 13 - 14 - 15 CS 42 3.5 - 9000+ - - - - - BOTTOM OF BORING @ 15.0' - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 USCS Sampler LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic ZG & ZG Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - ± 1-2' POSSIBLE EXISTING 1 FILL MATERIAL - 2 - 3 - 4 - 5 CS 11 9.4 109.4 9000+ 1.3% - - - - - 6 - 7 SC CLAYEY SAND with varying - amounts of GRAVEL 8 reddish-brown, beige, rust - loose to medium dense 9 - 10 CS 19 2.8 114.4 9000+ None <500 - - - - 11 - 12 - 13 - 14 - 15 CS 24 2.7 124.0 9000+ - - - - - BOTTOM OF BORING @ 15.0' - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig: Water Depth Information PROPOSED MIXED-USE BUILDING LOG OF BORING B-3 1/1 CME 45 4" CFA Automatic ZG & ZG Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - POSSIBLE EXISTING FILL MATERIAL; 1 CL SANDY LEAN CLAY with GRAVEL - brown, beige 2 medium stiff - 3 CS 8 13.3 116.0 9000+ 0.4% 2000 - - - - 4 - 5 CS 11 8.8 122.9 9000+ None <500 - - - SC CLAYEY SAND with varying - amounts of GRAVEL 6 reddish-brown, beige, rust - loose 7 - 8 - 9 - 10 CS 11 16.9 111.4 9000+ - - - - - BOTTOM OF BORING 15.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig: Water Depth Information PROPOSED MIXED-USE BUILDING LOG OF BORING B-4 1/1 CME 45 4" CFA Automatic ZG & ZG Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) - ± 1-2' POSSIBLE EXISTING 1 FILL MATERIAL - 2 - 3 CS 23 9.8 99.9 9000+ 0.1% 600 - - - - 4 - SC CLAYEY SAND with varying 5 CS 6 6.2 105.9 9000+ - - 23 11 32.1% amounts of GRAVEL - reddish-brown, beige, rust 6 loose to medium dense - 7 - 8 - 9 - 10 CS 16 1.6 - 9000+ - - - - - BOTTOM OF BORING 15.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig: Water Depth Information PROPOSED MIXED-USE BUILDING Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 116.6 500 Final Moisture 18.7% % Swell @ 500 psf 2.9% Swell Pressure (psf) 2,400 Sample ID: B-1 @ 2 Sample Description: Possible Existing Fill Material; Sandy Lean Clay with Gravel (CL) Initial Moisture 7.1% SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 -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) 100.4 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 11.1% Sample ID: B-1 @ 4 Sample Description: Reddish-Brown/Rust Clayey Sand (SC) (Swell Only) 500 Final Moisture 23.0% % Swell @ 500 psf None Swell Pressure (psf) <500 -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) 109.4 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 9.4% Sample ID: B-2 @ 4 Sample Description: Reddish-Brown/Rust Clayey Sand (SC) 500 Final Moisture 21.7% % Swell @ 500 psf 1.3% 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) 114.4 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 2.8% Sample ID: B-2 @ 9 Sample Description: Reddish-Brown/Rust Clayey Sand (SC) (Swell Only) 500 Final Moisture 14.3% % Swell @ 500 psf None Swell Pressure (psf) <500 -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) 116.0 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 13.3% Sample ID: B-3 @ 2 Sample Description: Possible Existing Fill Material; Sandy Lean Clay with Gravel (CL) 500 Final Moisture 17.4% % Swell @ 500 psf 0.4% Swell Pressure (psf) 2,000 -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) 122.9 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 8.8% Sample ID: B-3 @ 4 Sample Description: Reddish-Brown/Rust Clayey Sand (SC) (Swell Only) 500 Final Moisture 13.4% % Swell @ 500 psf None Swell Pressure (psf) <500 -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) 99.9 SWELL/CONSOLIDATION TEST SUMMARY PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 Initial Moisture 9.8% Sample ID: B-4 @ 2 Sample Description: Reddish-Brown/Beige Clayey Sand (SC) 500 Final Moisture 23.1% % Swell @ 500 psf 0.1% Swell Pressure (psf) 600 -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 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. 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 USCS Sampler Atterberg Limits Start Date 2/8/2018 Auger Type: During Drilling None Finish Date 2/8/2018 Hammer Type: After Drilling None Surface Elev. - Field Personnel: 24 Hours After Drilling - 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 USCS Sampler Atterberg Limits Start Date 2/8/2018 Auger Type: During Drilling None Finish Date 2/8/2018 Hammer Type: After Drilling None Surface Elev. - Field Personnel: 24 Hours After Drilling - 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018 USCS Sampler Atterberg Limits Start Date 2/8/2018 Auger Type: During Drilling None Finish Date 2/8/2018 Hammer Type: After Drilling None Surface Elev. - Field Personnel: 24 Hours After Drilling - Atterberg Limits Surface Elev. - Field Personnel: 24 Hours After Drilling - Finish Date 2/8/2018 Hammer Type: After Drilling None Sheet Drilling Rig: Water Depth Information Start Date 2/8/2018 Auger Type: During Drilling None PROPOSED MIXED-USE BUILDING 4101 SOUTH TAFT HILL ROAD, FORT COLLINS, COLORADO Project # 18-1038 February 2018