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Home My WebLink AboutSNOW RIDGE APARTMENTS - FDP240003 - SUBMITTAL DOCUMENTS - ROUND 1 - Geotechnical (Soils) Report (2) Soilogic, Inc. 3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144 September 14, 2023 MMD Built 1425 Pikes Peak Avenue Fort Collins, Colorado 80524 Attn: Matt Deault Re: Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence Tract 2 & Part of Tract 3, Maxfield 1509 S. Shields Street Fort Collins, Colorado Soilogic Project # 23-1207 Mr. Deault: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed remodel and additions to the existing residential structure located at 1509 S. Shields Street, in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. We understand the existing residence to receive the remodel and additions consists of a split-level (1½-story) wood-frame structure constructed over a basement and contains two residential units. We understand the proposed remodel improvements will include the reconfiguration of interior partition walls within the existing residence and demolition of the existing attached garage. We understand the additions to the residence will consist of two-story wood frame structures constructed over crawl spaces in order to create six (6) additional residential units. Foundation loads for new improvements are expected to be relatively light, with continuous wall loads less than 3.5 kips per lineal foot and individual column loads (if any) less than 75 kips. Small grade changes (if any) are anticipated to develop finish site grades in the areas of the proposed improvements. 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 new foundations as well as an assessment of the result of increased foundation loads on the existing structure foundations and support of Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 2 floor slabs (if any) and site pavements. Pavement section design options for private site drive and parking areas 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. SITE DESCRIPTION The proposed remodel and addition improvements will be constructed to the existing residence situated on Tract 2 & Part of Tract 3 in the Maxfield residential neighborhood, located at 1509 S. Shields Street in Fort Collins, Colorado. We anticipate the existing residence is supported by some type of spread footing foundation system. At the time of our site exploration, the area surrounding the residence contained several mature, medium to large-diameter deciduous and coniferous trees, and various landscape and flatwork improvements. The ground surface was observed to be relatively level, with the maximum difference in ground surface elevation across the existing residence and proposed addition footprints estimated to be on the order of about two (2) to three (3) feet or less. EXPLORATION AND TESTING PROCEDURES To develop subsurface information in the areas of the proposed additions and site pavements, five (5) soil borings were extended to depths between approximately 5 and 30 feet below present site grade within/near the proposed addition and new pavement areas. The boring locations were established in the field by Soilogic personnel based on staking done by the client to indicate the locations of select building corners and proposed pavement improvement areas. 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 by the client 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 Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 3 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. The samples collected were tested in the laboratory to measure natural moisture content and were visually 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/bedrock consistency than tactual observation alone. Dry density, Atterberg limits, -200 wash and swell/consolidation tests were completed on selected samples to help establish specific soil/bedrock characteristics. Atterberg limits tests are used to determine soil/bedrock plasticity. The percent passing the #200 size sieve (-200 wash) test is used to determine the percentage of fine-grained materials (clay and silt) in a sample. Swell/consolidation tests are performed to evaluate soil/bedrock volume change potential with variation in moisture content. The results of the completed laboratory tests are outlined on the attached boring logs and swell/consolidation test summaries. Water-soluble sulfate (WSS) content tests are currently being completed on two (2) selected samples to help evaluate corrosive soil characteristics with respect to buried concrete and results will be provided as they become available. SUBSURFACE CONDITIONS The materials encountered in the completed site borings can be summarized as follows. Approximately 2 to 6 inches of turf/sod vegetation and topsoil, concrete flatwork or asphalt pavement were encountered at the surface at the boring locations, underlain by dark brown/ red-brown/beige silty, sandy lean clay which varied to silty, clayey sand. The lean clay/ silty, clayey sand varied from medium stiff to hard in terms of consistency, or from loose to medium dense in terms of relative density, exhibited low swell potential at current Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 4 moisture and density conditions, and extended to the bottom of each boring at depths between approximately 5 and 30 feet below present site grade. 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 in boring B-3 at a depth of about 17 feet below ground surface, but was not encountered in any of the other borings to the depths explored when checked immediately after the completion of drilling. When checked about seven (7) days after drilling, groundwater level remained unchanged in boring B-3, and all other borings remained dry to the depth explored at that time. 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 Careful observation of the exposed foundation bearing materials should be completed at the time of construction by Soilogic personnel or another qualified geotechnical engineer to ensure all new footing foundations will be supported on natural, undisturbed materials with suitable strength. Care should be taken during excavation to avoid disturbing those soils providing support to the existing residence foundations (extending down and away from the bottom/outside edges of the foundations at a 1:1 slope). Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 5 Undocumented fill soils are expected to exist adjacent to the residence foundation walls. Undocumented fill soils would not be considered suitable for support of any site improvements. If/where existing fill is identified underlying new foundations, offsetting new foundation elements to bear outside of the foundation wall backfill zone, extending footing foundations to bear on natural, undisturbed lean clay/silty, clayey sand with low volume change potential at greater depth, or performing overexcavation/backfill procedures to redevelop controlled and compacted fill beneath new footing foundations in these areas could be considered. Demolition and Site Development Within the new building addition, pavement and any proposed fill areas, all existing foundations, floor slabs, pavements/flatwork 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 development are also completely removed at this time. In addition, all trees, tree root systems and dry and desiccated soils associated with the tree root systems should be completely removed from within the proposed building, pavement 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 fill, removal area backfill or exterior flatwork concrete, we recommend the exposed subgrade soils be scarified to a depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the materials standard Proctor maximum dry density. The moisture content of the scarified soils should be adjusted to be within the range of -1 to +3% of standard Proctor optimum moisture content at the time of compaction. Fill and removal area backfill soils required to develop the site should consist of approved, low-volume-change (LVC) soils free from organic matter, debris and other objectionable materials. Based on results of the completed laboratory testing, it is our opinion the natural site lean clay and silty/clayey sand could be used as fill and backfill provided the proper moisture content is developed in those materials at the time of placement and compaction. Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 6 If required, imported soils should consist of approved LVC and relatively impervious soils free from organic matter and debris. Site fill and backfill should contain a minimum of 25% fines in order to reduce the ability of those materials to pond and transmit water. Suitable fill and backfill soils should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as recommended for the scarified soils above. Care should be taken to avoid disturbing all subgrade soils prior to placement of any overlying improvements. Soils which are allowed to dry out or become wet and softened or disturbed by the construction activities should be removed and replaced or reworked in place prior to concrete placement. Foundations Based on the materials encountered in the completed site borings and results of laboratory testing, it is our opinion the proposed lightly-loaded remodel improvements, additions to the existing residence and trash enclosure could be supported by continuous spread footing and/or isolated pad foundations bearing on natural, undisturbed lean clay/silty, clayey sand with low volume change potential and/or properly placed and compacted fill or overexcavation/backfill (if/where required). For design of new footing foundations bearing on natural, undisturbed medium stiff to hard/loose to medium dense to dense lean clay/silty, clayey sand and/or properly placed and compacted fill or overexcavation/backfill, we recommend using a maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, new footing foundations should be sized to maintain a minimum dead-load pressure of 500 psf, or as high as practical on the foundation bearing materials. In evaluation of existing footing foundations subjected to additionally-imposed loads as a result of the proposed remodel improvements or addition (if any), a maximum net allowable soil bearing pressure of 2,000 psf could be used. Exterior footings should bear a minimum of 30 inches below finished adjacent exterior grade to provide frost protection. We recommend formed strip footings have a minimum width of 12 inches and isolated pad foundations have a minimum width of 24 inches in order to facilitate construction and reduce the potential for development of eccentrically loaded footings. Actual footing widths should be designed by a structural engineer. Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 7 For design of new 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. Care should be taken to ensure new foundations will not be supported on any disturbed or previously placed backfill soils associated with construction of the existing residence. If/where encountered, extending footing foundations through existing fill to bear on natural soils at greater depth or overexcavation/backfill procedures would be required in these areas to develop suitable foundation bearing. Structurally spanning the existing residence foundation wall backfill zone could also be considered. Soilogic estimates settlement of new spread footing foundations designed and constructed as outlined above and resulting from the assumed structural loads would be less than 1 inch. If/where additional loads are imposed on existing footing foundations, some additional settlement of those footings will occur subsequent to construction of the addition. Assuming typical residential construction footing widths, we estimate additional settlement of the existing footing foundations of ½ inch or less will occur subsequent to construction as a result of the additionally-imposed loads. Some differential settlement should be anticipated between the existing and any newly-constructed footings. An allowance for some differential movement should be included in the design. Similarly, some differential settlement should be expected between existing footing foundations not subjected to additionally-imposed loads and those that are subjected to additionally- imposed loads. Based on the subsurface conditions encountered and uniform loading anticipated, we expect differential settlement across the existing structure would be limited to ½ inch or less. Even limited differential settlement can result in some cosmetic distress to existing residence finishes and some repair efforts may be required subsequent to improvement construction and loading. The existing basement foundation walls may be subjected to additional lateral earth pressure loads imposed by the addition footing foundations. Soilogic recommends the existing foundation system and basement walls be evaluated by a qualified structural Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 8 engineer prior to design and construction of the additions to ensure the walls will be able to withstand additional surcharge loads. If it is determined the residence is not supported by conventional spread footing foundations after additional investigation, alternative foundation systems may be required. Crawl Space Construction As a precaution, we recommend a perimeter drain system be constructed around all below- grade areas to help reduce the potential for water infiltration into the crawl space areas of the additions and/or the development of hydrostatic pressures behind the foundation walls. The perimeter drain system(s) 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(s). The invert of the drain pipe, at its high point, should be placed at approximate foundation bearing level, run around the interior or exterior of 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. Care should be taken at the time of perimeter drain installation to avoid disturbing those soils providing support to the existing residence and new addition 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 the 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(s). The owner/client should consider consulting with a mold prevention specialist for additional precautions that 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 below-grade walls should consist of relatively impervious soils free from organic matter, debris and other objectionable materials. The site lean clay and silty/clayey sand could be used as backfill in this area provided the proper moisture content is developed in those materials at the time of placement and compaction. We recommend the site lean clay, silty/clayey sand or similar backfill soils be placed in loose lifts not to Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 9 exceed 9 inches thick, adjusted in moisture content and compacted as previously outlined in the “Demolition and Site Development” section of this report. Excessive lateral stresses can be imposed on foundation walls when using heavier mechanical compaction equipment. We recommend compaction of unbalanced foundation wall backfill soils be completed using light mechanical or hand compaction equipment. Lateral Earth Pressures For design of below-grade walls where preventative measures have been taken to reduce the potential for development of hydrostatic loads on the walls, we recommend using an at-rest equivalent fluid pressure value of 65 pounds per cubic foot. A modified active equivalent fluid pressure of 55 pounds per cubic foot could be used for partially restrained conditioned where some rotation of the below-grade walls must occur to develop the active earth pressure state. That rotation can result in cracking of the below-grade 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. Variables that affect lateral earth pressures include but are not limited to the shrink/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 soil backfill, excessive compaction of the wall backfill or surcharge loads placed adjacent to the below-grade walls can add to the lateral earth pressures causing the equivalent fluid pressure values used in design to be exceeded. Floor Slabs The addition and any other at-grade floor slabs (if any) could be supported directly on reconditioned lean clay/silty, clayey sand with low swell potential and/or properly moisture conditioned and compacted fill or overexcavation/backfill soils (if/where required) developed as outlined in the “Demolition and Site Development” section of this report. Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 10 Care should be taken to maintain the proper moisture content and avoid disturbing all floor slab subgrade soils prior to concrete placement. The exposed floor slab subgrade soils should not be left exposed for extended periods of time. In the event that the subgrade soils are allowed to dry out or if rain, snowmelt or water from any source is allowed to infiltrate those materials, reworking of the subgrade soils or removal/replacement procedures may be required. Floor slabs should be designed and constructed as floating slabs, separated from foundation walls, columns and plumbing and mechanical penetrations by the use of block-outs or appropriate isolation material. Additionally, we recommend all 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 residence. A minimum one and one-half (1½) inch void space is recommended beneath all floating walls. Special attention to door and stair framing, garage floor tracks, 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 structure. Depending on the type of floor covering and floor covering adhesive used in finished slab- on-grade areas, a vapor barrier may be required immediately beneath the floor slabs in order to maintain flooring product manufacturer warranties. A vapor barrier would help reduce the transmission of moisture through the floor slab. However, the unilateral moisture release caused by placing concrete on an impermeable surface can increase slab curl. The amount of slab curl can be reduced by careful selection of an appropriate concrete mix, however, slab curl cannot be eliminated. We recommend the owner, architect and flooring contractor consider the performance of the slab, in conjunction with the proposed flooring products to help determine if a vapor barrier will be required and where best to position the vapor barrier in relation to the floor slab. Additional guidance and recommendations concerning slab-on-grade design can be found in American Concrete Institute (ACI) section 302. Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 11 Site Pavements Pavement subgrades could be developed as outlined in the “Demolition and Site Development” section of this report. Site pavements could be supported directly on the reconditioned subgrade soils and suitable fill and removal area backfill soils placed and compacted as outlined in that section. The pavement subgrades are expected to consist of lean clay/silty, clayey sand. The reconditioned lean clay/silty, clayey sand would be subject to low remolded shear strength. A resistance value (R-value) of 5 was estimated for the subgrade soils and used in 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 occasional 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 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. 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. Isolated areas of subgrade instability can be mended on a case-by-case basis. If more widespread subgrade instability is observed at the time of proofrolling, we recommend consideration be given to stabilization of the pavement subgrades with Class C fly ash or Portland concrete cement (pending results of WSS testing). With the increase in support strength developed by the chemical 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 I. Chemical stabilization can also eliminate some of the uncertainty associated with attempting to pave late in the season and during periods of inclement weather. Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 12 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 a full-depth asphalt section be constructed for this project. Alternative pavement sections could be considered and we would be happy to discuss any alternatives at your request. 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 - Portland Cement Concrete Pavement PCCP 5” 6” Asphaltic concrete should consist of a bituminous plant mix composed of a mixture of aggregate, filler, binders and additives if required meeting the design requirements of the City of Fort Collins. Aggregate used in the asphaltic concrete should meet specific gradation requirements such as Colorado Department of Transportation (CDOT) grading 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 chemical stabilization procedures will be completed, we recommend the addition of 12% Class ‘C’ fly ash (or 4% Portland cement pending WSS test results) based on component dry unit weights. A 12-inch-thick stabilized zone should be constructed by thoroughly blending the fly ash or Portland cement 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 Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 13 standard Proctor maximum dry density within two (2) hours of fly ash and 30 minutes of cement 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. Thicker concrete pavement sections may be warranted depending on the actual type and quantity of heavy truck traffic anticipated to utilize areas of the site. The concrete used for site pavements should be air entrained and have a minimum 28-day compressive strength of 4,000 or 4,500 psi (pending results of WSS testing). 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. Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed additions and associated site improvements. We recommend positive drainage be developed away from the residence and additions during construction and maintained throughout the life of the site improvements, with twelve (12) inches of fall in the first 10 feet away from the residence and additions. Shallower slopes could be considered in hardscape areas. In the event that poor or negative drainage develops adjacent to the residence and/or additions over time, the original grade and associated positive drainage outlined above should be immediately restored. Care should be taken in the planning of landscaping to avoid features which could result in the fluctuation of the moisture content of the foundation bearing and/or flatwork subgrade soils. We recommend watering systems be placed a minimum of 5 feet away from the perimeter of the site structure and be designed to discharge away from all site Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 14 improvements. Gutter systems should be considered to help reduce the potential for water ponding adjacent to the building with the gutter downspouts, roof drains or scuppers extended to discharge a minimum of 5 feet away from structural, flatwork and pavement elements. Water which is allowed to pond adjacent to site improvements can result in unsatisfactory performance of those improvements over time. GENERAL COMMENTS This report was prepared based upon the data obtained from the completed site exploration, laboratory testing, engineering analysis and any other information discussed. The completed borings provide an indication of subsurface conditions at the boring locations only. Variations in subsurface conditions can occur in relatively short distances away from the borings. This report does not reflect any variations which may occur across the site or away from the borings. If variations in the subsurface conditions anticipated become evident, the geotechnical engineer should be notified immediately so that further evaluation can be completed and when warranted, alternative recommendations provided. The scope of services for this project does not include either specifically or by implication any biological or environmental assessment of the site or identification or prevention of pollutants or hazardous materials or conditions. Other studies should be completed if concerns over the potential of such contamination or pollution exist. The geotechnical engineer should be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. The geotechnical engineer should also be retained to provide testing and observation services during construction to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with the generally accepted standard of care for the profession. No warranties express or implied, are made. The conclusions and recommendations contained in this report should not be considered valid in the event that any changes in the nature, design or location of the project as outlined in Geotechnical Subsurface Exploration Report Proposed Remodel & Additions to Existing Residence 1509 S. Shields Street, Fort Collins, Colorado Soilogic Project # 23-1207 15 this report are planned, unless those changes are reviewed and the conclusions of this report modified and verified in writing by the geotechnical engineer. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed information or if we can be of further service to you in any way, please do not hesitate to contact us. Very Truly Yours, Soilogic, Inc. Reviewed by: Darrel DiCarlo, P.E. Alec Kaljian, P.E. Senior Project Engineer Project Engineer 09/14/2023 09/14/2023 LOG OF BORING B-1 1/1 CME 45 4" CFA Automatic JJ / NB Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" TOPSOIL & VEGETATION - 1 - 2 - 3 CS 15 12.4 112.7 9000+0.9%2400 --- - 4 - 5 CS 45 5.1 -9000+----- - 6 CL-ML SILTY, SANDY LEAN CLAY - to varies to SILTY, CLAYEY SAND 7 SC-SM red-brown, beige - stiff to hard / medium dense 8 trace to minor GRAVEL - 9 - 10 CS 15 21.7 101.5 8500 1.2%1600 --- - 11 - 12 - 13 - 14 - 15 CS 15 13.8 120.3 3500 ----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 US C S Sa m p l e r Atterberg Limits Surface Elev.-Field Personnel:7 Days After Drilling None Finish Date 8/29/2023 Hammer Type:After Drilling None Sheet Drilling Rig:Water Depth Information Start Date 8/29/2023 Auger Type:During Drilling None REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic JJ / NB Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 3 - 4" CONCRETE DRIVEWAY - 1 - 2 - 3 CS 13 12.5 119.3 9000+--23 8 55.8% - 4 - 5 CS 16 7.3 118.4 9000+0.4%900 --- - 6 CL-ML SILTY, SANDY LEAN CLAY - to varies to SILTY, CLAYEY SAND 7 SC-SM red-brown - stiff to very stiff /8 loose to medium dense - trace to minor GRAVEL 9 - 10 CS 22 10.8 112.0 9000+1.7%2900 --- - 11 - 12 - 13 - 14 - 15 CS 18 11.6 121.1 6000 ----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 7 Days After Drilling None US C S Sa m p l e r Atterberg Limits Start Date 8/29/2023 Auger Type:During Drilling None Finish Date 8/29/2023 Hammer Type:After Drilling None Surface Elev.-Field Personnel: Sheet Drilling Rig:Water Depth Information REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 LOG OF BORING B-3 1/1 CME 45 4" CFA Automatic JJ / NB Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 2 - 4" TOPSOIL & VEGETATION - 1 - 2 - 3 - 4 - 5 CS 42 7.0 113.1 9000+2.4%4600 --- - 6 - 7 - 8 - 9 - 10 CS 19 11.9 118.8 9000+0.9%2300 --- - 11 - CL-ML SILTY, SANDY LEAN CLAY 12 to varies to SILTY, CLAYEY SAND - SC-SM red-brown, beige 13 medium stiff to hard /- loose to medium dense 14 - 15 CS 20 18.1 111.7 9000+----- - 16 - 17 - 18 - 19 - 20 CS 9 24.2 101.5 2500 ----- - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - BOTTOM OF BORING @ 30.0'30 CS 15 16.4 114.5 5500 ----- 7 Days After Drilling 17.0' US C S Sa m p l e r Atterberg Limits Start Date 8/29/2023 Auger Type:During Drilling 17.0' Finish Date 8/29/2023 Hammer Type:After Drilling 17.0' Surface Elev.-Field Personnel: Sheet Drilling Rig:Water Depth Information REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 LOG OF BORING B-4 1/1 CME 45 4" CFA Automatic JJ / NB Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" TOPSOIL & VEGETATION - 1 - CL LEAN CLAY with varying 2 amounts of SILT and SAND - dark brown, red-brown 3 CS 23 14.1 112.1 9000+2.4%6200 --- very stiff to hard - trace GRAVEL 4 - 5 CS 50/10 5.3 -9000+----- BOTTOM OF BORING @ 5.0'- 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 7 Days After Drilling None US C S Sa m p l e r Atterberg Limits Start Date 8/29/2023 Auger Type:During Drilling None Finish Date 8/29/2023 Hammer Type:After Drilling None Surface Elev.-Field Personnel: Sheet Drilling Rig:Water Depth Information REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 LOG OF BORING B-5 1/1 CME 45 4" CFA Automatic JJ / NB Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) ±3" ASPHALT PAVEMENT - 1 - 2 - 3 CS 22 14.1 117.6 9000+----- - 4 CL-ML SILTY, SANDY LEAN CLAY - to varies to SILTY, CLAYEY SAND 5 CS 28 7.4 113.0 9000+1.1%2300 --- SC-SM brown, red-brown - very stiff / medium dense 6 - 7 - 8 - 9 - 10 CS 23 12.0 120.3 9000+----- BOTTOM OF BORING @ 10.0'- 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 7 Days After Drilling Backfilled US C S Sa m p l e r Atterberg Limits Start Date 8/29/2023 Auger Type:During Drilling None Finish Date 8/29/2023 Hammer Type:After Drilling None Surface Elev.-Field Personnel: Sheet Drilling Rig:Water Depth Information REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)112.7 500 Final Moisture 15.8% % Swell @ 500 psf 0.9% Swell Pressure (psf)2,400 Sample ID: B-1 @ 2 Initial Moisture 12.4% Sample Description: Brown/Red-Brown Silty Lean Clay with Sand (CL-ML) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)101.5 500 Final Moisture 25.4% % Swell @ 500 psf 1.2% Swell Pressure (psf)1,600 Initial Moisture 21.7% Sample ID: B-1 @ 9 Sample Description: Red-Brown Silty Lean Clay with Sand (CL-ML) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)118.4 500 Final Moisture 15.8% % Swell @ 500 psf 0.4% Swell Pressure (psf)900 Initial Moisture 7.3% Sample ID: B-2 @ 4 Sample Description: Red-Brown Clayey, Silty Sand (SC-SM) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)112.0 500 Final Moisture 16.6% % Swell @ 500 psf 1.7% Swell Pressure (psf)2,900 Initial Moisture 10.8% Sample ID: B-2 @ 9 Sample Description: Brown/Red-Brown Silty Lean Clay with Sand (CL-ML) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)113.1 500 Final Moisture 17.4% % Swell @ 500 psf 2.4% Swell Pressure (psf)4,600 Initial Moisture 7.0% Sample ID: B-3 @ 4 Sample Description: Red-Brown Silty, Sandy Lean Clay (CL-ML) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)118.8 500 Final Moisture 15.0% % Swell @ 500 psf 0.9% Swell Pressure (psf)2,300 Initial Moisture 11.9% Sample ID: B-3 @ 9 Sample Description: Red-Brown Silty, Sandy Lean Clay (CL-ML), trace Gravel SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)112.1 500 Final Moisture 16.8% % Swell @ 500 psf 2.4% Swell Pressure (psf)6,200 Initial Moisture 14.1% Sample ID: B-4 @ 2 Sample Description: Dark Brown Lean Clay with Sand (CL), trace Gravel SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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)113.0 500 Final Moisture 14.8% % Swell @ 500 psf 1.1% Swell Pressure (psf)2,300 Initial Moisture 7.4% Sample ID: B-5 @ 4 Sample Description: Red-Brown Silty, Sandy Lean Clay (CL-ML) SWELL/CONSOLIDATION TEST SUMMARY REMODEL & ADDITIONS TO EXISTING RESIDENCE - TRACT 2 & PART OF TRACT 3, MAXFIELD 1509 S. SHIELDS STREET, FORT COLLINS, COLORADO Project # 23-1207 September 2023 -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: ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA: RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA: CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB: BS: Bulk Sample or Auger Sample WB: Hand Sample Power Auger Hand Auger Rock Bit 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+