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Home My WebLink AboutHOWES SIX TWO NINE - PDP210008 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED TOWNHOME DEVELOPMENT NORTH ½ OF LOT 2 AND SOUTH ½ OF LOT 3, BLOCK 96, HARRISON’S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO SOILOGIC # 19-1182 April 30, 2019 Soilogic, Inc. 3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144 August 30, 2019 Carlson Land Development 14570 Clay Street Broomfield, Colorado 80023 Attn: Blake Carlson Re: Geotechnical Subsurface Exploration Report Proposed Townhome Development North ½ of Lot 2 and South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic Project # 19-1182 Mr. Carlson: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed 7-plex and 3-plex multi-family townhome residences to be constructed on the north ½ of Lot 2 and the south ½ of Lot 3, Block 96 in the Harrison’s Addition residential neighborhood 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. A thin mantle of vegetation and topsoil was encountered at the surface at the boring locations underlain by light brown/brown/rust lean clay with sand which became silty in some areas. The lean clay varied from medium stiff to very stiff in terms of consistency, exhibited no to low swell potential at in-situ moisture and density conditions (although two samples obtained from our borings at a depth of about 2 feet below ground surface exhibited moderate and high swell potential) and extended to the bottom of borings B-1 and B-2 at a depth of approximately 15 feet below ground surface, or to depths ranging from approximately 9½ to 14 feet below ground surface at the locations of borings B-3 through B-6, where it was underlain by brown/rust clayey sand. The clayey sand varied from loose to medium dense in relative density, exhibited no swell potential at in-situ moisture and density conditions and extended to the bottom of these borings at a depth of approximately 15 feet below present site grade. Groundwater was not encountered in any of the completed site borings to the full depth of exploration when checked immediately after drilling. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 2 Based on the materials encountered in the completed site borings and results of laboratory testing, it is our opinion the proposed lightly-loaded multi-family residential structures could be supported by continuous spread footing and isolated pad foundations bearing on natural, undisturbed site lean clay with no to low swell potential and/or properly placed and compacted fill. The natural site lean clay soils appear suitable for use as low-volume- change (LVC) fill to develop the site. The reconditioned natural site soils and properly placed and compacted fill could also be used for support of at-grade floor slabs, site pavements and exterior flatwork. 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 natural, undisturbed materials with suitable strength and low volume change potential. In order to develop consistent low-volume-change (LVC) foundation bearing across the building footprints, we recommend extending all footing foundations through any expansive near- surface lean clay to bear on natural lean clay soils with no to low swell potential, anticipated to be encountered at depths between 2 and 4 feet below present site grades. Based on results of the completed field and laboratory testing, it is our opinion overexcavation/backfill procedures could be completed beneath at-grade floor slabs and site flatwork/pavements where expansive near-surface lean clay soils are identified in order to reduce the potential for movement of those supported elements subsequent to construction. Recommendations concerning overexcavation/backfill procedures to redevelop low-volume-change (LVC) potential at-grade floor slab and flatwork/pavement support are outlined in this report. Pavement section design options for private site drive lanes and parking areas are also included. Other opinions and recommendations concerning design criteria and construction details for the proposed site improvements are also provided. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 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: Darrel DiCarlo, P.E. Wolf von Carlowitz, P.E. Senior Project Engineer Principal Engineer GEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED TOWNHOME DEVELOPMENT NORTH ½ OF LOT 2 AND SOUTH ½ OF LOT 3, BLOCK 96, HARRISON’S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO SOILOGIC # 19-1182 April 30, 2019 INTRODUCTION This report contains the results of the completed geotechnical subsurface exploration for the proposed multi-family townhome/carriage house residences to be constructed on a property identified as the north ½ of Lot 2 and the south ½ of Lot 3, Block 96 in the Harrison’s Addition residential neighborhood, located on the west side of South Howes Street 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 multi- family residential building foundations and support of floor slabs, exterior flatwork and site pavements. 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 an existing single-family residence and associated flatwork and landscaping improvements will be remodeled and repurposed, in addition to construction of the new townhome/multi-family residences. We understand the existing residence is a two-story wood frame structure constructed over a full basement and understand it is supported by spread footing foundations. The proposed new residences will be three- story wood-frame structures constructed as slab-on-grade and may contain crawl space areas. Foundation loads for the structures are expected to be relatively light, with continuous wall loads less than 3.5 kips per lineal foot and individual column loads less than 75 kips. Small grade changes are anticipated to develop finish site grades in the new residence areas. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 2 SITE DESCRIPTION The proposed residences will be constructed adjacent to the existing residence located at 629 South Howes Street in Fort Collins, Colorado. At the time of our site exploration, the ground surface outside of the residence contained a sparse to moderate growth of grass vegetation and was relatively level, with the maximum difference in ground surface across the proposed construction area estimated to be three to four (3-4) feet. Several medium to large diameter deciduous trees were noted along the northwest property boundary and south-central area of the lot. SITE EXPLORATION Field Exploration To develop subsurface information in the area of the proposed structure, six (6) soil borings were extended to a depth of approximately 15 feet below present site grades at the approximate corners of the new residences. The boring locations were established in the field by Soilogic personnel based on a provided site plan 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 Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 3 obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing. Laboratory Testing The samples collected were tested in the laboratory to measure natural moisture content and visually and/or manually classified in accordance with the Unified Soil Classification System (USCS). The USCS group symbols are indicated on the attached boring logs. An outline of the USCS classification system is included with this report. As part of the laboratory testing, a calibrated hand penetrometer (CHP) was used to estimate the unconfined compressive strength of essentially-cohesive specimens. The CHP also provides a more reliable estimate of soil consistency than tactual observation 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 subsurface materials encountered in the completed site borings can be summarized as follows. A thin mantle of vegetation and topsoil was encountered at the surface at the boring locations underlain by light brown/brown/rust lean clay with sand which became silty in some areas. The lean clay varied from medium stiff to very stiff in terms of consistency, exhibited no to low swell potential (although two samples taken from 2 feet below ground surface did exhibit moderate and high swell potential) at in-situ moisture and density conditions and extended to the bottom of borings B-1 and B-2 at a depth of approximately 15 feet below ground surface, and to depths ranging from approximately 9½ to 14 feet below ground surface in borings B-3 through B-6 where it was underlain by brown/rust clayey sand. The clayey sand varied from loose to medium dense in relative density, exhibited no swell potential at in-situ moisture and density conditions and Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 4 extended to the bottom of the remaining borings at a depth of approximately 15 feet below present site grades. 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 any of the completed site borings to the full depth of exploration 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 General 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 natural, undisturbed materials with suitable strength and low volume change potential. In order to develop consistent low-volume-change (LVC) foundation bearing across the building footprints, we recommend extending any other shallow, upper-level foundations through any expansive near-surface lean clay to bear on natural lean clay soils with no to low swell potential, anticipated to be encountered at depths between 3 and 4 feet below present site grades. Based on results of the completed field and laboratory testing, it is our opinion overexcavation/backfill procedures could be completed beneath at-grade floor slabs to reduce the potential for movement of those supported elements subsequent to construction. Recommendations concerning overexcavation/backfill procedures to redevelop low-volume-change (LVC) potential at-grade floor slab support are outlined below. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 5 Site Development Within the new residences, exterior flatwork and any proposed fill areas, all existing foundations, floor slabs and other site improvements should be completely removed. Care will be needed to ensure all in-place fill/backfill materials associated with the existing site improvements and potentially-expansive lean clay soils are also completely removed from within residence footprints at this time. In addition, all tree root systems and dry and desiccated soils associated with the tree root systems should be completely removed from within the area of the proposed residence and beneath exterior flatwork and any proposed fill areas. 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 new fill, 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 ±2% of standard Proctor optimum moisture content at the time of compaction. Slopes steeper than 4:1 (H:V) expected to receive fill 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. 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 opinion the 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 soils free from organic matter and debris. 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. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 6 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 residences could be supported by continuous spread footing and isolated pad foundations bearing on natural, undisturbed lean clay with no to low swell potential. Extending any other shallow, upper- level footing foundations to bear on natural, undisturbed lean clay with no to low swell potential (anticipated to be encountered at depths between 3 and 4 feet below present site grades) should be anticipated to develop consistent LVC foundation bearing conditions. For design of footing foundations bearing on natural, undisturbed, medium stiff to very stiff lean clay, we recommend using a maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, we recommend the footing foundations be designed to maintain a minimum dead-load pressure of 500 psf (or as high as practical) on the bearing 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. 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. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 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 settlement estimated above. If water from any source is allowed to infiltrate the bearing soils, additional movement of the foundations could occur. Floor Slabs At-grade floor slabs could be supported directly on natural, undisturbed lean clay with no to low swell potential and/or on fill or overexcavation/backfill soils placed and compacted as outlined in the “Site Development” section of this report (if/where required). Care should be taken to maintain the proper moisture content in all floor slab subgrade soils prior to concrete placement. The exposed crawl space area subgrade soils and developed at-grade floor slab fill and/or overexcavation/backfill 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 residence and garage 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 structures. 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 slabs, allowing for some differential floor slab-to-foundation movement to occur without transmitting stresses to the overlying structures. 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 Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 8 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. Crawl Space Construction As a precaution, we recommend a perimeter drain system be constructed around any crawl space areas to help reduce the potential for water infiltration into the crawl space areas of the residences and/or the development of hydrostatic pressures behind the foundation walls. The perimeter drain system 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 system. The invert of the drain pipe, at its high point, should be placed at approximate foundation bearing level, run around the interior or exterior perimeters of the crawl space areas with a minimum slope of ⅛-inch per foot to facilitate efficient water removal and should discharge to a sump pump and pit system or systems. Care should be taken at the time of perimeter drain installation to avoid disturbing those soils providing support to the residence footing foundations (extending down at a 1:1 slope from the bottom edges of the footings). As an additional precaution, we recommend a vapor barrier be installed in crawl space areas in order to help maintain in-situ soil moisture conditions and reduce the potential for migration of soil moisture into the crawl space areas. Subgrades in the crawl space areas should be sloped to drain to the perimeter drain system. The owner/client should consider consulting with a mold prevention specialist for additional precautions that Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 9 could be implemented to reduce the potential for development of moist air conditions in the crawl space areas of the structure. 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 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 site lean clay and/or similar backfill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as previously outlined in 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. Lateral Earth Pressures For design of below-grade walls where preventative measures have been taken to reduce the potential for development of hydrostatic pressures on the walls, we recommend using an active equivalent fluid pressure value of 45 pounds per cubic foot. Some rotation of the foundation wall must occur to develop the active earth pressure state. That rotation can result in cracking of the foundation walls typically in between corners and other restrained points. The amount of deflection of the top of the wall can be estimated at 0.5% times the height of the wall. An equivalent fluid pressure value of 65 pounds per cubic foot could be used for restrained wall conditions. Variables that affect lateral earth pressures include, but are not limited to; the swell potential of the backfill soils, backfill compaction and geometry, wetting of the backfill soils, surcharge loads and point loads developed in the backfill materials. The recommended equivalent fluid pressure values do not include a factor of safety or an allowance for hydrostatic loads. Use of expansive or high plasticity soil backfill, excessive compaction of wall backfill or surcharge loads placed adjacent to the Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 10 foundation walls can add to the lateral earth pressures, causing the equivalent fluid pressure values used in design to be exceeded. Exterior Flatwork & Pavement Subgrade Preparation Natural lean clay with moderate and/or high swell potential may support sidewalks, driveways and other at-grade features on portions of this site. The performance of sidewalks, driveways and other at-grade features on expansive soils is erratic and these features will likely move and crack when the underlying soils increase in moisture content. Performance of these features may be unreasonable in some instances and may require frequent maintenance or replacement. If movement of these features must be reduced, undocumented fill and swell/heave mitigation should be completed. Mitigation would involve removal of at least 2 feet of the expansive lean clay subgrade (if/where identified) and replacing these materials with approved LVC fill or re-compacting the on-site lean clay with strict moisture and density control to reduce movement potential. In order to effectively reduce the potential for excessive post-construction movement, the site lean clay would need to be properly processed and re-compacted as previously outlined in the “Site Development” section of this report. At a minimum, all existing topsoil and vegetation should be removed from exterior flatwork/pavement areas. After stripping and completing all cuts and overexcavation (if undertaken), and prior to placement of any new fill, overexcavation/backfill or flatwork concrete, we recommend the exposed subgrade soils be scarified to a depth of 9 inches, adjusted in moisture content and compacted as previously outlined. Fill and overexcavation/backfill soils required to develop exterior flatwork subgrades should consist of approved LVC soils, 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 or overexcavation/backfill beneath exterior flatwork, 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 previously recommended. Exterior flatwork could be supported directly on Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 11 the reconditioned site soils or suitable fill or overexcavation/backfill soils placed and compacted as outlined above. Care should be taken to avoid disturbing exterior flatwork/pavement subgrades prior to placement of the overlying improvements. Subgrade soils expected to receive exterior flatwork concrete should be evaluated closely immediately prior to concrete placement. 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 concrete placement. Exterior flatwork/site pavements will experience some movement subsequent to construction as the subgrade soils increase in moisture content. Theoretically, total free field heave of exterior flatwork of 2 inches could be realized over time if deep wetting of the site occurs and no swell/heave mitigation is performed. The overexcavation/backfill procedures outlined above would reduce the amount of anticipated post-construction movement of those improvements and tend to make movements more uniform. Care should be taken to ensure that when exterior flatwork moves, positive drainage will be maintained away from the residences. Site Pavements Pavement subgrades could be developed as outlined in the “Exterior Flatwork & Pavement Subgrade Preparation” section of this report. Site pavements could be supported directly on the reconditioned subgrade soils and suitable fill and overexcavation/backfill soils placed and compacted as outlined in that section. The pavement subgrades are expected to consist of reconditioned lean clay, which would be subject to low remolded shear strength. A resistance value (R-value) of 5 was estimated for the subgrade soils and used in the pavement section design. Traffic loading on the site pavements is expected to consist of areas of low volumes of automobiles and light trucks, as well as areas of higher light-vehicle traffic volumes and heavier trash and delivery trucks. Equivalent 18-kip single axle loads (ESAL’s) were estimated for the quantity of site traffic anticipated. Two (2) general pavement design classifications are outlined below in Table I. Standard duty pavements could be Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 12 considered 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 heavy truck traffic. Alternative pavement sections could be considered and we would be happy to discuss any alternatives at your request. Proofrolling of the pavement subgrades should be completed to help identify unstable areas. 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, 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. Pavement section design options incorporating some structural credit for the stabilized subgrade soils are outlined below in Table 1. Fly ash stabilization can also eliminate some of the uncertainty associated with attempting to pave during periods of inclement weather. It has been our experience that full-depth asphaltic concrete pavement sections typically do not perform as well as structurally equivalent composite pavement sections in areas of lean clay subgrade soils and we do not recommend full-depth asphalt sections be constructed for this project. TABLE 1 – 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 – Full Depth on Stabilized Subgrade Asphaltic Concrete (Grading S or SX) Fly Ash Stabilized Subgrade 4½” 12” 6” 12” Option D - Portland Cement Concrete Pavement PCCP 5” 6” Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 13 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 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 and compacted to at least 95% of the materials standard Proctor maximum dry density within ±2% of standard Proctor optimum moisture content. 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 air entrained 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. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 14 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 as part of this and the preliminary subsurface explorations completed at this site. The sulfate concentrations measured in the samples fell within the range of 0 to 0.03 percent by weight in soil. 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 residences and associated site improvements. We recommend positive drainage be developed away from the structures 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 buildings. Shallower slopes could be considered in hardscape areas. In the event that poor or negative drainage develops adjacent to the structures occurs 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 structures, 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 on or adjacent to site improvements can result in unsatisfactory performance of those improvements over time. Geotechnical Subsurface Exploration Report Proposed Townhome Development – North ½ of Lot 2 & South ½ of Lot 3, Block 96, Harrison’s Addition 629 South Howes Street, Fort Collins, Colorado Soilogic # 19-1185 15 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 ZG / 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 22 9.7 112.2 9000+3.3%2700 --- - 4 - 5 CS 9 9.4 91.6 9000+None <500 --- - 6 CL LEAN CLAY with SAND - light brown, brown, rust 7 medium stiff to very stiff - silty in places 8 - 9 - 10 CS 12 16.9 106.6 9000+----- - 11 - 12 - 13 increasing GRAVEL with depth - 14 - 15 CS 15 15.0 116.0 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Sheet Drilling Rig:Water Depth Information Start Date 8/8/2019 Auger Type:During Drilling None Finish Date 8/8/2019 Hammer Type:After Drilling None USCSSamplerAtterberg Limits Surface Elev.-Field Personnel:24 Hours After Drilling - LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic ZG / 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 - 4 - 5 CS 8 8.8 47.1 9000+0.4%900 --- - 6 CL LEAN CLAY with SAND - light brown, brown, rust 7 medium stiff to stiff - silty in places 8 - 9 - 10 CS 12 14.0 112.8 9000+0.1%---- - 11 - 12 - 13 - 14 - 15 CS 13 14.8 115.0 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Finish Date 8/8/2019 Hammer Type:After Drilling None Start Date 8/8/2019 Auger Type:During Drilling None 24 Hours After Drilling -USCSSamplerAtterberg Limits Surface Elev.-Field Personnel: LOG OF BORING B-3 1/1 CME 45 4" CFA Automatic ZG / 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 13 11.5 120.7 9000+2.0%---- - 4 - 5 CS 7 10.8 92.9 9000+--34 17 78.4% - CL LEAN CLAY with SAND 6 light brown, brown, rust - medium stiff to very stiff 7 silty in places - 8 - 9 - 10 CS 21 15.3 109.7 9000+0.3%800 --- - 11 - 12 - 13 SC CLAYEY SAND - brown, rust 14 loose - 15 CS 13 4.0 116.6 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Finish Date 8/8/2019 Hammer Type:After Drilling None Start Date 8/8/2019 Auger Type:During Drilling None 24 Hours After Drilling -USCSSamplerAtterberg Limits Surface Elev.-Field Personnel: LOG OF BORING B-4 1/1 CME 45 4" CFA Automatic ZG / 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 - 4 CL LEAN CLAY with SAND - light brown, brown, rust 5 CS 7 8.2 97.8 9000+0.5%---- medium stiff to stiff - silty in places 6 - 7 - 8 - 9 - 10 CS 25 5.6 119.5 9000+None <500 --- - 11 - SC CLAYEY SAND 12 brown, rust - loose to medium dense 13 - 14 - 15 CS 13 12.8 113.8 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Finish Date 8/8/2019 Hammer Type:After Drilling None Start Date 8/8/2019 Auger Type:During Drilling None 24 Hours After Drilling -USCSSamplerAtterberg Limits Surface Elev.-Field Personnel: LOG OF BORING B-5 1/1 CME 45 4" CFA Automatic ZG / 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 20 8.1 109.3 9000+6.1%5300 --- - 4 - 5 CS 9 10.5 89.7 9000+0.5%1300 --- - 6 CL LEAN CLAY with SAND - light brown, brown, rust 7 medium stiff to very stiff - silty in places 8 - 9 - 10 CS 20 14.2 111.1 9000+----- - 11 - 12 - 13 - 14 SC CLAYEY SAND - brown, rust, loose 15 CS 7 9.7 117.6 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Finish Date 8/8/2019 Hammer Type:After Drilling None Start Date 8/8/2019 Auger Type:During Drilling None 24 Hours After Drilling -USCSSamplerAtterberg Limits Surface Elev.-Field Personnel: LOG OF BORING B-6 1/1 CME 45 4" CFA Automatic ZG / 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 - 4 - 5 CS 14 8.4 104.3 9000+0.4%900 --- - 6 CL LEAN CLAY with SAND - light brown, brown, rust 7 stiff - silty in places 8 - 9 - 10 CS 12 16.5 108.6 9000+----- - 11 - 12 - 13 - SC CLAYEY SAND 14 brown, rust - medium dense 15 CS 18 3.1 105.9 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 Finish Date 8/8/2019 Hammer Type:After Drilling None Start Date 8/8/2019 Auger Type:During Drilling None 24 Hours After Drilling -USCSSamplerAtterberg Limits Surface Elev.-Field Personnel: Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)112.2 500 Final Moisture 19.5% % Swell @ 500 psf 3.3% Swell Pressure (psf)2,700 Sample ID: B-1 @ 2 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) Initial Moisture 9.7% SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)91.6 500 Final Moisture 27.8% % Swell @ 500 psf None Swell Pressure (psf)<500 Initial Moisture 9.4% Sample ID: B-1 @ 4 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)47.1 500 Final Moisture 28.8% % Swell @ 500 psf 0.4% Swell Pressure (psf)900 Initial Moisture 8.8% Sample ID: B-2 @ 4 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)112.8 500 Final Moisture 17.9% % Swell @ 500 psf 0.1% Swell Pressure (psf)- Initial Moisture 14.0% Sample ID: B-2 @ 9 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)120.7 500 Final Moisture 17.1% % Swell @ 500 psf 2.0% Swell Pressure (psf)- Initial Moisture 11.5% Sample ID: B-3 @ 2 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)109.7 500 Final Moisture 20.3% % Swell @ 500 psf 0.3% Swell Pressure (psf)800 Initial Moisture 15.3% Sample ID: B-3 @ 9 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)97.8 500 Final Moisture 28.2% % Swell @ 500 psf 0.5% Swell Pressure (psf)- Initial Moisture 8.2% Sample ID: B-4 @ 4 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)119.5 500 Final Moisture 14.5% % Swell @ 500 psf None Swell Pressure (psf)<500 Initial Moisture 5.6% Sample ID: B-4 @ 9 Sample Description: Brown/Rust Clayey Sand (SC) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)109.3 500 Final Moisture 19.9% % Swell @ 500 psf 6.1% Swell Pressure (psf)5,300 Initial Moisture 8.1% Sample ID: B-5 @ 2 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)89.7 500 Final Moisture 31.1% % Swell @ 500 psf 0.5% Swell Pressure (psf)1,300 Initial Moisture 10.5% Sample ID: B-5 @ 4 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)104.3 500 Final Moisture 22.4% % Swell @ 500 psf 0.4% Swell Pressure (psf)900 Initial Moisture 8.4% Sample ID: B-6 @ 4 Sample Description: Light Brown/Brown/Rust Lean Clay with Sand (CL) SWELL/CONSOLIDATION TEST SUMMARY PROPOSED TOWNHOMES - N 1/2 OF LOT 2 & S 1/2 OF LOT 3, BLOCK 96, HARRISON'S ADDITION 629 SOUTH HOWES STREET, FORT COLLINS, COLORADO Project # 19-1182 August 2019 -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+