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HomeMy WebLinkAboutKECHTER FARM MIXED-USE TOWNHOMES - FDP210021 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTPRELIMINARY GEOTECHNICAL SUBSURFACE EXPLORATION REPORT KECHTER FARM TOWNHOMES LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 FORT COLLINS, COLORADO SOILOGIC # 21-1014 February 18, 2021 Soilogic, Inc. 3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144 February 18, 2021 Kechter Townhomes, LLC 417 Jefferson Street Fort Collins, Colorado 80524 Attn: Mr. Kyle Meyer Re: Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes Lot 1, Block 15, Kechter Farm PLD Filing 1 Fort Collins, Colorado Soilogic Project # 21-1014 Mr. Meyer: Soilogic, Inc. (Soilogic) personnel have completed the preliminary geotechnical subsurface exploration you requested for the proposed multi-family residential development to be constructed on Lot 1 of Block 15 in the Kechter Farm PLD Filing 1 residential subdivision in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. In summary, approximately 3 to 6 inches of vegetation and topsoil was encountered at the surface at boring locations underlain by reddish-brown to light brown/beige lean clay with varying amounts of sand. The lean clay varied from soft to very stiff in terms of consistency, exhibited high swell potential near-surface and no to low swell potential with depth at in-situ moisture and density conditions and extended to depths of about 12½ to 13½ feet below ground surface, where it was underlain by gray/rust/olive siltstone/claystone bedrock. The bedrock varied from weathered to firm in terms of relative hardness and extended to the bottom of both borings at a depth of approximately 15 feet below ground surface. Based on our experience with similar bedrock encountered in the vicinity of the subject site, we anticipate the unweathered portion of the bedrock may possess moderate or higher swell potential at in-situ moisture and density conditions. Groundwater was measured at depths of approximately 15 and 13 feet below present site grade in borings B-1 and B-2, respectively, when checked immediately after the completion of drilling. When checked about 24 hours after completion of drilling, Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 2 groundwater was measured at depths of approximately 13 and 10 feet below grade in borings B-1 and B-2, respectively. Care will be needed across the development in order to maintain adequate separation distances between footing foundations and the observed levels of groundwater. Typically, we recommend foundation bearing elevations be established a minimum of three (3) feet above the observed groundwater level. Based on the subsurface conditions encountered in the completed site borings, results of field and laboratory testing and type of construction proposed, we expect the proposed lightly-loaded residential structures could be constructed with conventional footing foundations and floor slabs bearing on natural site lean clay with no to low volume change potential and/or a suitable zone of properly moisture conditioned and compacted overexcavation/backfill (where required). Overexcavation/backfill procedures are also recommended to develop low volume-change (LVC) floor slab, exterior flatwork and pavement support if/where expansive soils are identified underlying these improvements. Expansive lean clay soils were identified at the location of boring B-1 extending to depths between approximately 3 and 4 feet below present site grade. Lean clay soils with higher in-situ moisture content and resultant low swell potential were identified underlying the expansive soils in that area. Full-depth basement construction and/or extending footing foundations through any expansive near-surface lean clay to bear on higher moisture content soils with low swell potential at greater depth could also be considered, however, overexcavation/backfill procedures would still be required beneath at-grade floor slabs in areas where expansive near-surface soils are identified. In addition to the presence of near-surface lean clay soils exhibiting high swell potential, comparatively soft, high moisture content clay soils exhibiting moderate compressibility were encountered with depth in boring B-2 such that care will be needed to ensure footing foundations are supported on soils with suitable strength. Overexcavation/ backfill procedures or other approved stabilization measures, or alternative deep foundation systems could be considered in areas of soft/compressible clay to reduce the potential for excessive post-construction settlement of the proposed structures. If raising the site through fill placement will be undertaken, areas of the site expected to receive fill depths greater than about 4 to 5 feet should be developed as early as possible during the development Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 3 process and allowed to remain in place for several weeks in order to allow for consolidation of the underlying soils prior to construction of any overlying improvements. If/where moderately to highly expansive siltstone/claystone bedrock is identified at the time of site-specific subsurface explorations, maintaining a six (6) foot offset between siltstone/claystone bedrock and footing foundations and slabs-on-grade or use of drilled pier foundations and structurally-supported floors may be warranted. Based on the results of completed laboratory testing, the site lean clay appears suitable for use as fill and overexcavation/backfill to develop the site. Depending on the in-place moisture content of the pavement subgrade soils at the time of construction, stabilization of the lean clay subgrade soils may become necessary prior to surfacing in order to develop a suitable paving platform. If public street improvements will be constructed as part of this project, a final pavement exploration will be required for these roadways after the sanitary sewer and water utilizes have been installed and the streets graded to approximate finish subgrade elevation in accordance with Larimer County Urban Area Street Standards (LCUASS). Preliminary pavement section design estimates are included with this report. Other preliminary opinions and recommendations concerning design criteria and construction details for the proposed site improvements are also included. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 4 02/18/2021 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, P.E. Darrel DiCarlo, P.E. Project Engineer Senior Project Engineer 02/18/2021 PRELIMINARY GEOTECHNICAL SUBSURFACE EXPLORATION REPORT KECHTER FARM TOWNHOMES LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 FORT COLLINS, COLORADO SOILOGIC # 21-1014 February 18, 2021 INTRODUCTION This report contains the results of the preliminary geotechnical subsurface exploration completed for the proposed Kechter Farm Townhomes residential development to be constructed on Lot 1 of Block 15 of Kechter Farm PLD Filing 1 in Fort Collins, Colorado. The purpose of our exploration was to describe the subsurface conditions encountered in the completed site borings and develop preliminary recommendations concerning design and construction of the multi-family residence foundations and support of floor slabs, exterior flatwork and site pavements. Recommendations concerning the installation of site utilities are also included. 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. PROPOSED CONSTRUCTION We understand the property will be developed as multi-family residential. We anticipate the residences will be lightly-loaded two or three-story wood-frame structures constructed over full basement or crawl space areas. Foundations loads for the structures are expected to be light, with continuous wall loads on the order of 3.5 kips per lineal foot and individual column loads less than 75 kips. Infrastructure improvements for the development will include utility installation and private site drive and parking area pavement construction. Some minor public street construction may also be completed. We expect the site pavements will be utilized by low volumes of automobiles and light trucks with occasional trash, delivery and emergency truck traffic. Small grade changes are anticipated to develop finish site grades. SITE DESCRIPTION The development parcel includes approximately 2.82 acres which is identified as Lot 1 of Block 15 in the Kechter Farm PLD Filing 1 residential development in Fort Collins, Colorado. At the time of our site exploration, the site was moderately vegetated in grass Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 2 vegetation, contained scattered small-diameter deciduous and coniferous trees and consisted of gently rolling terrain. The maximum difference in ground surface elevation across the site was estimated to be less than approximately 10 feet. Evidence of prior building construction was not observed on the development parcel by Soilogic Inc. (Soilogic) personnel at the time of our site exploration. SITE EXPLORATION Field Exploration To develop preliminary subsurface information across the development parcel, two (2) soil borings were extended to a depth of approximately 15 feet below present site grade. The boring locations were established in the field by Soilogic personnel based on a provided site plan and by pacing and estimating angles from identifiable site references. A diagram indicating the approximate boring locations is included with this report. The boring locations outlined on the attached diagram should be considered accurate only to the degree implied by the methods used to make the field measurements. 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. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 3 Laboratory Testing The samples collected were tested in the laboratory to measure natural moisture content and visually 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. 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 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. Results of the completed laboratory tests are outlined on the attached boring logs and swell/consolidation test summaries. SUBSURFACE CONDITIONS The subsurface materials encountered in the completed site borings can be summarized as follows. Approximately 3 to 6 inches of vegetation and topsoil was encountered at the surface at boring locations underlain by reddish-brown to light brown/beige lean clay with varying amounts of sand. The lean clay varied from soft to very stiff in terms of consistency, exhibited high swell potential near-surface and no to low swell potential with depth at in-situ moisture and density conditions and extended to depths of about 12½ to 13½ feet below ground surface, where it was underlain by gray/rust/olive siltstone/claystone bedrock. The bedrock varied from weathered to firm in terms of relative hardness and extended to the bottom of both borings at a depth of approximately 15 feet below ground surface. Based on our experience with similar bedrock encountered in the vicinity of the subject site, we anticipate the unweathered portion of the bedrock may possess moderate or higher swell potential at in-situ moisture and density conditions. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 4 The stratigraphy indicated on the included boring logs represents the approximate location of changes in soil and/or bedrock types. Actual changes may be more gradual than those indicated. Groundwater was measured at depths of approximately 15 and 13 feet below present site grade in borings B-1 and B-2, respectively, when checked immediately after the completion of drilling. When checked about 24 hours after completion of drilling, groundwater was measured at depths of approximately 13 and 10 feet below grade in borings B-1 and B-2, respectively. Groundwater level information is indicated in the upper right-hand corner of the attached boring logs. 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 General Groundwater was measured in both borings at depths between approximately 10 and 13 feet below present site grade, which could impact full-depth basement construction depending on finish site grades. Care will be needed across the development in order to maintain adequate separation distances between footing foundations and the observed levels of groundwater. Typically, we recommend foundation bearing elevations be established a minimum of three (3) feet above the observed groundwater level. Relatively dry near-surface lean clay soils exhibiting high swell potential and extending to depths on the order of approximately 3 to 4 feet were encountered at the location of boring B-1. Where highly expansive near-surface lean clay soils are identified at the time of overlot grading and/or foundation excavation, these materials should be completely Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 5 removed to low swelling soil level beneath the building footprints. Since movement of site and roadway pavements and exterior flatwork is generally less consequential than structural and floor slab movement, it is our opinion the depth of overexcavation in these areas could be reduced to a depth of two (2) feet below finish pavement and exterior flatwork subgrade level. Comparatively soft, high moisture content lean clay soils which exhibit moderate compressibility were also encountered in boring B-2 at a depth of about four (4) feet below grade. The clay soils would be expected to be easily disturbed by grading and construction activities. Care should be taken to avoid disturbing the site soils prior to placement of any fill or overlying improvements. Soils which are disturbed by the construction activities or allowed to dry out or become wet and softened should be removed and replaced or reworked in place prior to construction of any overlying improvements. Some overexcavation/backfill or other approved stabilization procedures may be required to develop suitable strength foundation bearing if more extensive zones of soft lean clay are identified at intended foundation bearing elevation at the time of construction. The comparatively soft, high moisture content clay soils encountered in the completed site borings would be subject to consolidation under additionally imposed fill loads. Areas of the site expected to receive fill depths greater than 4 to 5 feet should be developed as early as possible in the construction process. We recommend the fill materials in these areas be placed and allowed to remain in place for several weeks prior to the installation of site utilities and construction of any overlying improvements in order to allow for consolidation of underlying soils. At this time, we understand the proposed site structures will be constructed over crawl spaces or full basements. Extending garage and other upper-level footing foundations to bear on lean clay with low swell potential at slightly greater depths than typical may be required if/where expansive near-surface lean clay materials are encountered. Completing overexcavation/backfill procedures beneath garage and any at-grade floor slabs would also be required in these areas. Based on the subsurface conditions encountered in the completed site borings, results of field and laboratory testing and type of construction proposed, we expect the proposed Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 6 lightly-loaded structures could be constructed with conventional spread footing foundations and floor slabs bearing on natural site lean clay with no to low volume change potential and/or on a zone of properly placed and compacted overexcavation/ backfill (where required). Individual site explorations should be completed for each of the proposed residences after overlot grading and infrastructure development of the site have been completed to help better define subsurface conditions at the specific residence locations. If expansive bedrock is identified at time of final exploration, maintaining a six (6) foot offset or use of crawl space construction could be considered to allow use of footing foundation and slab-on- grade construction. If City of Fort Collins streets will be constructed as part of this project, a final pavement exploration will be required for these roadways after utilities have been installed and streets graded to approximate finish subgrade elevation in accordance with Larimer County Urban Area Street Standards (LCUASS). Depending on the in-place moisture content of the subgrade soils at the time of construction, stabilization of the pavement subgrade soils may become necessary after grading and/or overexcavation/backfill have been performed and prior to surfacing in order to develop a suitable paving platform. Site Development All existing vegetation and topsoil, including all tree root systems and dry and desiccated soils associated with tree root systems should be removed from the building, exterior flatwork, pavement and any proposed fill areas. Removal of soil identified as expansive in the area of boring B-2 extending to a depth ranging from approximately 3 to 4 feet below ground surface could also be completed at this time. After stripping and completing all cuts and any overexcavation procedures as outlined above and prior to placement of any new fill, overexcavation/backfill, floor slab/flatwork concrete or site pavements, 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 for the site lean clay. Slopes steeper than 4:1 (H:V) expected to receive fill Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 7 should be continuously and horizontally benched level during fill placement in order to reduce the potential for development of a shear plane between the natural site soils and overlying fill. Soils used as general site fill and overexcavation/backfill should consist of approved LVC materials free from organic matter, debris and other objectionable materials. Based on results of the completed laboratory testing, it is our opinion the site lean clay could be used as fill and overexcavation/backfill to develop the site provided the proper moisture content is developed in those materials at the time of placement and compaction. We recommend the site lean clay and/or similar soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as recommended for the scarified materials above. Care should be taken to maintain the proper moisture content in the prepared subgrade soils prior to foundation and floor slab/flatwork concrete placement and/or paving. The prepared structural mat should not be left exposed for extended periods of time. In the event that the reconditioned soils are allowed to dry out or if rain, snowmelt or water from any source is allowed to infiltrate the bearing/subgrade soils, reworking of those materials or removal/replacement procedures may be required. Footing Foundations Based on the materials encountered in the completed site borings and results of laboratory testing, we expect the site structures could be constructed with conventional spread footing foundations bearing on natural, undisturbed site lean clay with no to low swell potential and/or properly-placed and compacted overexcavation/backfill. Extending garage and other upper-level footing foundations to bear on lean clay with low swell potential at slightly greater depths than typical should be expected in some areas. For design of footing foundations bearing on low-swelling lean clay and/or properly placed and compacted overexcavation/backfill, maximum net allowable soil bearing pressures in the range of 1,000 to 2,000 psf with minimum dead load pressures on the order of 500 psf appear suitable. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 8 Individual site explorations should be completed for each of the proposed site structures after overlot grading is complete to help better define subsurface conditions at the specific building locations. Floor Slabs Based on the type of construction proposed and results of the completed field and laboratory testing, we expect lightly-loaded at-grade residence garage floor slabs could be supported on reconditioned natural site soils with no to low swell potential and/or properly placed and compacted fill or overexcavation/backfill (where required). We expect basement floor slabs (if constructed) could bear directly on natural, undisturbed, moist lean clay with no to low swell potential and/or overexcavation/backfill. Care should be taken to avoid disturbing floor slab subgrades prior to concrete placement. Subgrade soils expected to receive floor slab concrete should be evaluated closely prior to surfacing. If areas of disturbed, wet and softened, or dry subgrade soils develop during construction, those materials should be removed and replaced or reworked in place prior to placement of the overlying improvements. Crawl Space and Basement Construction We recommend perimeter drain systems be installed around all below-grade areas (including crawl spaces) to help reduce the potential for development of hydrostatic pressures behind below-grade walls and surface water infiltration into the crawl space and/or basement areas. Perimeter drain systems should consist of a 4-inch diameter, perforated drain pipe surrounded by a minimum of six (6) inches of free-draining gravel. A filter fabric should be considered around the free-draining gravel or perforated pipe to reduce the potential for an influx of fine-grained soils into the systems. The drain pipes should be placed at approximate foundation bearing level at the high point of the systems, run around the interior or exterior perimeters of crawl space areas and exterior perimeters of basement areas with a minimum slope of ⅛-inch per foot to facilitate efficient water removal and be designed to discharge to sump pit and pump systems and or project underdrain system (if available). Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 9 Backfill placed adjacent to the below grade walls should consist of LVC potential and relatively impervious soils which are free from organic matter, debris and other objectionable materials. The site lean clay could be used as backfill in these areas. The site lean clay soils should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as previously outlined in the “Site Development” section of this report. Excessive lateral stress can be imposed on below-grade walls when using heavier mechanical compaction equipment. We recommend compaction of unbalanced basement wall backfill be completed using light mechanical or hand compaction equipment. Utility Installation Bedding around utility pipelines should be placed in accordance with recommendations from the pipeline designer. Backfill soils placed above pipelines should consist of approved materials which are free from organic matter, debris and other objectionable materials. The on-site lean clay could be used as pipeline backfill. Lean clay pipeline backfill should be placed in maximum 9-inch loose lifts, adjusted in moisture content and compacted as previously outlined in the ‘Site Development’ section of this report. Care will be needed to ensure utilities are not placed on or above disturbed or sloughed materials. Utility excavations will likely expose the overburden lean clay. Care will also be needed to develop stable side slopes in pipeline trenches. As such, we expect temporary shoring, bracing, or cutting of shallow slopes may be necessary in deeper excavations. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. As a safety measure, it is recommended that vehicles and soil stockpiles be kept to a minimum lateral distance from the crest of the slope equal to no less than the slope height. Groundwater was encountered as shallow as approximately 10 feet below present site grade in boring B-2, completed in the southeast corner of the project site. Utility excavations extended below groundwater will require dewatering to facilitate proper construction. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 10 Private Drive and Parking Area Pavements We expect overexcavation/backfill procedures will be required to develop LVC potential site pavement subgrades in the area of boring B-1 completed on the northwest side of the project site and other areas where expansive lean clay soils are identified underlying pavements to any appreciable degree. Site pavements could be supported directly on reconditioned natural site soils with no to low swell potential and/or properly placed and compacted overexcavation/backfill soils developed as outlined above (where required). If subgrade instability is observed prior to paving, stabilization of the pavement subgrade soils would be required. Chemical treatment of the pavement subgrade soils could be considered if widespread areas of instability are observed immediately prior to surfacing. After overexcavation/backfill procedures, we expect the pavement subgrades will consist of reconditioned lean clay with low swell potential. Structure pavement design is based, in part, on subgrade support as established by the Hveem R-value test. The site lean clay would be subject to low remolded strength. An R-value of 5 was estimated for the site lean clay and used to develop the preliminary pavement section design estimates outlined below. For preliminary estimates, a composite pavement section consisting of 4 to 5 inches of hot bituminous pavement overlying 6 to 8 inches of aggregate base course and Portland cement concrete section in the range of 5 to 6 inches could be used. Depending on City of Fort Collins roadway classification, thicker pavements sections may be required for city streets (if any). Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed site structures and associated site improvements. We recommend positive drainage be developed away from all site structures and pavement areas to reduce the potential for wetting of the subgrade and bearing materials. Water which is allowed to pond adjacent to site improvements can result in unsatisfactory performance of those improvements over time. Water which is allowed to pond adjacent to site pavements can result in a loss of subgrade support and premature failure of the overlying pavement sections. Preliminary Geotechnical Subsurface Exploration Report Kechter Farm Townhomes (Lot 1, Block 15, Kechter Farm PLD Filing 1) Fort Collins, Colorado Soilogic Project # 21-1014 11 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. 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. 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 (%) 3-6" VEGETATION & TOPSOIL - 1 - 2 - 3 CS 31 12.8 116.2 8000 6.0%8600 --- - 4 - 5 CS 9 26.4 94.8 4000 --39 15 85.6% CL LEAN CLAY with varying - amounts of SAND 6 reddish-brown to light brown, beige - medium stiff to very stiff 7 - 8 - 9 - 10 CS 17 17.7 110.6 9000+2.0%3800 --- - 11 - 12 - 13 SILTSTONE/CLAYSTONE - gray, rust, olive 14 weathered - 15 CS 18 24.1 100.8 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY EXPLORATION FORT COLLINS, COLORADO Project # 21-1014 February 2021 Sheet Drilling Rig:Water Depth Information Start Date 2/2/2021 Auger Type:During Drilling 15' Finish Date 2/2/2021 Hammer Type:After Drilling 15'USCSSamplerAtterberg Limits Surface Elev.-Field Personnel:24 Hours After Drilling 13' 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 (%) 3-6" VEGETATION & TOPSOIL - 1 - 2 - 3 CS 15 15.7 116.9 9000+0.3%1000 --- - 4 - 5 CS 4 13.2 100.7 2000 None <500 --- - CL LEAN CLAY with varying 6 amounts of SAND - reddish-brown to light brown, beige 7 soft to stiff - 8 - 9 - 10 CS 14 18.6 111.9 9000+----- - 11 - 12 - 13 - SILTSTONE/CLAYSTONE 14 gray, rust, olive - firm 15 CS 28 19.1 109.4 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY EXPLORATION FORT COLLINS, COLORADO Project # 21-1014 February 2021 USCSSamplerAtterberg Limits Start Date 2/2/2021 Auger Type:During Drilling 13' Finish Date 2/2/2021 Hammer Type:After Drilling 13' Surface Elev.-Field Personnel:24 Hours After Drilling 10' Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)116.2 LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY KECHTER FARM. FT COLLINS. COLORADO Project # 21-1014 February 2021 SWELL/CONSOLIDATION TEST SUMMARY Sample ID: B-1 @ 2 Initial Moisture 12.8% Sample Description: Reddish-Brown/Beige Lean Clay with Sand (CL) 500 Final Moisture 18.4% % Swell @ 500 psf 6.0% Swell Pressure (psf)8,600 -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)110.6 SWELL/CONSOLIDATION TEST SUMMARY LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY KECHTER FARM. FT COLLINS. COLORADO Project # 21-1014 February 2021 Initial Moisture 17.7% Sample ID: B-1 @ 9 Sample Description: Reddish-Brown Sandy Lean Clay (CL) 500 Final Moisture 19.4% % Swell @ 500 psf 2.0% Swell Pressure (psf)3,800 -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)116.9 SWELL/CONSOLIDATION TEST SUMMARY LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY KECHTER FARM. FT COLLINS. COLORADO Project # 21-1014 February 2021 Initial Moisture 15.7% Sample ID: B-2 @ 2 Sample Description: Brown Lean Clay with Sand (CL) 500 Final Moisture 17.3% % Swell @ 500 psf 0.3% Swell Pressure (psf)1,000 -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)100.7 SWELL/CONSOLIDATION TEST SUMMARY LOT 1, BLOCK 15, KECHTER FARM P.L.D. FILING 1 PRELIMINARY FORT COLLINS, COLORADO Project # 21-1014 February 2021 Initial Moisture 13.2% Sample ID: B-2 @ 4 Sample Description: Brown Lean Clay with Sand (CL) 500 Final Moisture 25.2% % 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) 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+