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Home My WebLink AboutALLIED BUILDING PRODUCTS - PDP - PDP180015 - SUBMITTAL DOCUMENTS - ROUND 2 - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL SUBSURFACE EXPLORATION REPORT ALLIED BUILDING PRODUCTS STORAGE BUILDING LOT 2, CENTERPOINT PLAZA 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO SOILOGIC # 18-1265 September 26, 2018 Soilogic, Inc. 3522 Draft Horse Court  Loveland, CO 80538  (970) 535-6144 P.O. Box 1121  Hayden, CO 81639  (970) 276-2087 September 26, 2018 Baseline Engineering 1950 Ford Street Golden, Colorado 80401 Attn: Ms. Deanne Frederickson, RLA Re: Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Project # 18-1265 Ms. Frederickson: Soilogic, Inc. (Soilogic) personnel have completed the geotechnical subsurface exploration you requested for the proposed Allied Building Products storage building to be constructed on Lot 2 of the Centerpoint Plaza industrial/commercial development 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 consisted of a thin mantle of vegetation and topsoil or gravel surfacing underlain by brown/rust, medium stiff to very stiff lean clay at the location of borings B-1 and B-2 and loose to medium dense, brown/rust/grey silty to clayey sand and gravel at the location of borings B-3 and B-4. The near-surface sand and gravel encountered at the location of boring B-4 was identified as possible existing fill material which may have been placed to develop finish site grades and extended to a depth of approximately two (2) feet below ground surface, where it was underlain by lean clay. The lean clay soils encountered in boring B-1 were relatively dry at the time of drilling and exhibited moderate swell potential at current moisture and density conditions. Higher moisture content lean clay soils exhibiting no swell potential were encountered in borings B-2 and B-4. At the location of borings B-1, B-2 and B-4, the lean clay extended to a depth of approximately eight (8) feet below ground surface, where it was underlain by reddish brown silty sand and gravel. The sand and gravel varied from loose to dense in terms of relative density, would be expected to be non-expansive based on the material’s physical properties and engineering Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 2 characteristics and extended to the bottom of all borings at depths ranging from approximately 10 to 15 feet below present site grade. Groundwater was measured in borings B-1 and B-2 at a depth of approximately 12 feet below ground surface when checked immediately after completion of drilling. Groundwater was not encountered in borings B-3 and B-4 terminated at a depth of approximately 10 feet below ground surface at that time. Based on the subsurface conditions encountered, results of laboratory testing and proposed construction, it is our opinion the proposed storage building could be constructed with conventional spread footing foundations bearing on natural, undisturbed lean clay with no to low swell potential and/or properly placed and compacted overexcavation/backfill (if/where required). Although most of the lean clay soils encountered in the test borings drilled for this exploration exhibited no swell potential at current moisture and density conditions, one sample obtained from boring B-1 at a depth of about 4 feet below ground surface exhibited moderate swell potential. Additionally, approximately two (2) feet of apparent undocumented fill was encountered near-surface at the location of boring B-4. Overexcavation/backfill procedures are recommended beneath footing foundations and floor slabs in the northern portion of the building area where expansive lean clay soils were identified. Similar methods should be used in order to develop LVC-potential pavement and exterior flatwork subgrades if/where undocumented fill and/or expansive lean clay soils are identified underlying these improvements. The overexcavation/backfill procedures would help develop LVC- potential foundation, floor slab support across the building footprint, reducing the potential for total and differential movement of those supported elements subsequent to construction. Based on the results of completed laboratory testing, the existing fill and natural site lean clay soils appear suitable for use as low volume change (LVC) fill and overexcavation/backfill (if/where required) to develop the site. Other opinions and recommendations concerning design criteria and construction details for the proposed site improvements are included with this report. Pavement section design options are also included. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 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: Wolf von Carlowitz, P.E. Darrel DiCarlo, P.E. Principal Engineer Senior Project Engineer 36746 44271 GEOTECHNICAL SUBSURFACE EXPLORATION REPORT ALLIED BUILDING PRODUCTS STORAGE BUILDING LOT 2 – CENTERPOINT PLAZA 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO SOILOGIC # 18-1265 September 26, 2018 INTRODUCTION This report contains the results of the completed geotechnical subsurface exploration for the proposed Allied Building Products storage building to be constructed on Lot 2 of the Centerpoint Plaza industrial/commercial development in Fort Collins, Colorado. The purpose of our exploration was to describe the subsurface conditions encountered in the completed site borings and develop the test data necessary to provide recommendations concerning design and construction of the proposed building foundations and support of floor slabs, exterior flatwork and site pavements. The conclusions and recommendations outlined in this report are based on the results of the completed field and laboratory testing and our experience with subsurface conditions in this area. PROPOSED CONSTRUCTION We understand the proposed storage building will be a three-sided pre-engineered steel structure constructed as slab-on-grade, encompassing a plan area of approximately 6,600 square feet. Foundations loads for the building are anticipated to be relatively light, with maximum continuous wall loads on the order of 3 to 4 kips per lineal foot and individual column loads less than 100 kips. Paved drive and parking areas are also anticipated as part of the proposed site improvements. Small grade changes are anticipated to develop finish site grades in building and pavement areas. If proposed construction or assumed loadings differ significantly from those assumed, Soilogic should be notified to reevaluate the recommendations in this report. SITE DESCRIPTION The development parcel includes approximately an approximate 1.9-acre parcel of land identified as Lot 2 of the Centerpoint Plaza industrial/commercial development, located at 2155 Midpoint Drive in Fort Collins, Colorado. At the time of our exploration, the site contained a sparse to moderate growth of grass and weed vegetation and gravel-surfaced Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 2 drive and parking areas. The site was relatively level, with the maximum difference in ground surface elevation across the property estimated to be less than 4 feet. Evidence of prior building construction was not observed in the proposed construction areas by Soilogic personnel at the time of our site exploration. SITE EXPLORATION Field Exploration To develop subsurface information for the proposed site improvements, a total of four (4) soil borings were completed. Two (2) borings were advanced in the area of the proposed storage building to a depth of approximately 15 feet below present site grade. Two (2) additional borings were completed in site pavement areas to a depth of approximately 10 feet below ground surface. The boring locations were established in the field by Soilogic, Inc. (Soilogic) personnel based on a provided site plan, using a mechanical surveyor's wheel and estimating angles from identifiable site references. A diagram indicating the approximate boring locations is included with this report. The boring locations outlined on the attached diagram should be considered accurate only to the degree implied by the methods used to make the field measurements. Graphic logs of each of the auger borings are also included. The test holes were advanced using 4-inch diameter continuous flight auger powered by a truck-mounted CME-45 drill rig. Samples of the subsurface materials were obtained at regular intervals using California barrel sampling procedures in general accordance with ASTM specification D-1586. As part of the D-1586 sampling procedure, the standard sampling barrel is driven into the substrata using a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampler a distance of 12 inches is recorded and helpful in estimating the consistency 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 obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 3 Laboratory Testing The samples collected were tested in the laboratory to measure natural moisture content and were visually and/or manually classified in accordance with the Unified Soil 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. Water Soluble Sulfates (WSS) tests were completed on two (2) selected soil samples to evaluate corrosive soil characteristics with respect to buried concrete. The results of the completed laboratory tests are outlined on the attached boring logs and swell/ consolidation test summaries and/or discussed subsequently in this report. SUBSURFACE CONDITIONS The subsurface materials encountered in the completed site borings consisted of a thin mantle of vegetation and topsoil or gravel surfacing underlain by brown/rust, medium stiff to very stiff lean clay at the location of borings B-1 and B-2 and loose to medium dense, brown/rust/grey silty to clayey sand and gravel at the location of borings B-3 and B-4. The near-surface sand and gravel encountered at the location of boring B-4 was identified as possible existing fill material which may have been placed to develop finish site grades and extended to a depth of approximately two (2) feet below ground surface, where it was underlain by lean clay. The lean clay soils encountered in boring B-1 were relatively dry at the time of drilling and exhibited moderate swell potential at current moisture and density conditions. Higher moisture content lean clay soils exhibiting no swell potential were encountered in borings B-2 and B-4. At the location of borings B-1, Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 4 B-2 and B-4, the lean clay extended to a depth of approximately eight (8) feet below ground surface, where it was underlain by reddish brown silty sand and gravel. The sand and gravel varied from loose to dense in terms of relative density, would be expected to be non-expansive based on the material’s physical properties and engineering characteristics and extended to the bottom of all borings at depths ranging from approximately 10 to 15 feet below present site grade. The stratigraphy indicated on the included boring logs represents the approximate location of changes in soil types. Actual changes may be more gradual than those indicated. Groundwater was measured in borings B-1 and B-2 at a depth of approximately 12 feet below ground surface when checked immediately after completion of drilling. Groundwater was not encountered in borings B-3 and B-4 terminated at a depth of approximately 10 feet below ground surface at that time. Groundwater levels will vary due to seasonal variations in precipitation, site development, irrigation practices and other hydrologic conditions. Perched and/or trapped groundwater conditions may also be encountered at times throughout the year. Perched water is commonly encountered in soils overlying less permeable soil layers and/or bedrock. Trapped water is typically encountered within more permeable zones of layered soil and bedrock systems. The location and amount of perched and/or trapped water can also vary over time. ANALYSIS AND RECOMMENDATIONS General Lean clay soils exhibiting moderate swell potential were encountered relatively near- surface at the location of boring B-1 completed at the approximate northwest corner of the proposed building. Total and differential heaving of site improvements placed directly on or immediately above the expansive lean clay soils would be expected as the moisture content of those materials increases subsequent to construction. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 5 Based on the subsurface conditions encountered in the completed site borings, results of laboratory testing and type of construction proposed, it is our opinion overexcavation/ backfill procedures could be completed beneath the building foundation and floor slab in this area to reduce the potential for movement of those supported elements subsequent to construction. Similar overexcavation/backfill procedures could be completed beneath pavements and exterior flatwork if planned for this area. Recommendations concerning overexcavation/backfill procedures to redevelop low volume change (LVC) foundation and floor slab support for the northern portion of the building are outlined below. Drilled pier foundations could also be considered for support of the structure and in order to reduce the potential for total and differential movement of the storage building subsequent to construction in the expansive soils environment. Drilled piers would anchor the building into bedrock underlying the site, significantly reducing the potential for movement of the structure. Deeper subsurface exploration would be required to develop soil design parameters for use in drilled pier design. If drilled pier foundations are to be used, structural flooring systems or overexcavation/backfill procedures to develop LVC floor slab subgrades would be required. Recommendations concerning the design and construction of drilled pier foundations and structural flooring systems can be provided at your request. Building, Exterior Flatwork and Pavement Subgrade Development To develop low-volume-change (LVC) potential foundation bearing and floor slab support (if expansive lean clay soils are observed within close proximity to finish floor slab subgrade levels), and reduce the potential for total and differential movement of the northern portion of the building and building floor slab subsequent to construction, we recommend a zone of reconditioned soil be developed beneath those supported elements. The reconditioned mat will provide a zone of material immediately beneath the building foundation and floor slab in the northern portion of the structure which will have low potential for volume change subsequent to construction. At this time, overexcavation/ backfill procedures do not appear to be warranted for the south portion of the building where lean clay soils with elevated moisture content and no swell potential were identified. The LVC mat and surcharge loads placed on the underlying soils by the reconditioned mat would reduce the potential for total and differential movement of the Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 6 supported improvements subsequent to construction. The reconditioned zone would also assist in distributing movement in the event that some swelling of the materials underlying the reconditioned zone occurs. The overexcavation zone should extend to a depth of four (4) feet below foundation bearing and finish floor slab subgrade elevation or to moist lean clay with low swell potential, whichever results in the lesser overexcavation depth. Complete removal of the expansive lean clay anticipated to extend up to a depth of approximately eight (8) feet below present site grade in the northern portion of the building could also be considered to further reduce the amount of anticipated post-construction heave of the building foundation and floor slab. The overexcavation area should extend a minimum of 8 inches laterally past all four edges of column pad foundations for every 12 inches of overexcavation depth (32 inches). Since movement of site pavements and exterior flatwork is generally considered to be less consequential than structural and floor slab movement, it is our opinion the overexcavation zone beneath site pavements and exterior flatwork could be reduced to a minimum of 24 inches below finish subgrade levels (if/where expansive lean clay soils are identified underlying these improvements at the time of site development), with the understanding that some movement of exterior flatwork and site pavements will occur subsequent to construction. The 24-inch LVC zone beneath flatwork and site pavements could be developed through any combination of overexcavation/backfill procedures, subgrade reconditioning and new fill placement. Soils used as fill and overexcavation/backfill should consist of approved materials free from organic matter, debris and other objectionable materials. Based on results of the completed laboratory testing, it is our opinion existing fill (if any) free from organic matter and deleterious materials and natural site lean clay could be used as overexcavation/backfill provided care is taken to develop the proper moisture content in those materials at the time of placement and compaction. Essentially-granular structural fill materials should not be used as overexcavation/backfill due to the ability of those materials to pond and transmit water. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 7 All existing topsoil and vegetation should be removed from the proposed building, exterior flatwork, pavement and any proposed fill areas. All existing undocumented fill should also be completely removed from these areas at this time. After stripping and completing all cuts and overexcavation procedures and prior to placement of any new fill or overexcavation/backfill, we recommend the exposed subgrades 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 overexcavation/backfill materials consisting of existing fill, site lean clay and/or similar soils should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as outlined for the scarified soils above. At the high end of the above recommended moisture content range, some pumping of the lean to fat clay overexcavation/backfill soils may be observed and would be expected. Care should be taken to maintain the proper moisture content in the bearing/subgrade soils prior to foundation and floor slab concrete placement and/or paving. The prepared structural mat should not be left exposed for extended periods of time. In the event that the reconditioned soils are allowed to dry out or if rain, snowmelt or water from any source is allowed to infiltrate the bearing/subgrade soils, reworking of those materials or removal/replacement procedures may be required. Inherent risks exist when building in areas of expansive soils. The overexcavation/ backfill procedures outlined above will reduce but not eliminate the potential for movement of the building foundation, floor slab, exterior flatwork and site pavements subsequent to construction. The in-place materials below the moisture conditioned zone can increase in moisture content causing movement of the overlying improvements. Some movement of the lightly-loaded building floor slab, exterior flatwork and site pavements should be expected. If some structural and floor slab movement and associated distress cannot be tolerated, drilled pier foundations and structural floor systems should be employed. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 8 Foundations For design of spread footing foundations bearing on natural undisturbed medium stiff to very stiff lean clay with no to low swell potential and/or a suitable zone of overexcavation/backfill soils placed and compacted as outlined above, we recommend using a maximum net allowable soil bearing pressure of 1,500 psf. As a precaution, we recommend continuous spread footing and isolated pad foundations be designed to maintain a minimum dead-load pressure of 500 psf (or as high as practical) on the supporting soils. Exterior footings should bear a minimum of 30 inches below finished adjacent exterior grade to provide frost protection. We recommend formed strip footings have a minimum width of 12 inches and isolated pad foundations have a minimum width of 24 inches in order to facilitate construction and reduce the potential for development of eccentrically loaded footings. Actual footing widths should be designed by a structural engineer. For design of spread 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/subgrade soils to resist sliding. The recommended passive equivalent fluid pressure value and coefficient of friction do not include a factor of safety. We estimate settlement of footing foundations supported on a suitable mat of properly- placed and compacted overexcavation/backfill and resulting from the assumed structural loads would be less than 1 inch. Differential settlement could approach the amount of total settlement estimated above. If water from any source is allowed to infiltrate the foundation bearing soils, additional movement of those supported elements could occur. Seismicity Based on the results of our exploration and our review of the International Building Code (2003), a soil profile type D could be used for the site strata. Based on our review of Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 9 United States Geologic Survey (USGS) mapped information, design spectral response acceleration values of SDS = .218 (21.8%) and S D1 = .092 (9.2%) could be used. Floor Slabs The building floor slab could be supported directly on reconditioned lean clay with no to low swell potential and/or properly placed and compacted fill or overexcavation/backfill (if/where required) developed as outlined above. A modulus of subgrade reaction (k) value of 150 pci could be used for design of floor slabs supported on reconditioned site lean clay or similar soils. Disturbed subgrades or subgrade materials that have been allowed to dry out or become wet and softened should be removed and replaced or reconditioned in place prior to concrete placement. The structure floor slab will be located in an unheated area and subject to movement associated with freezing soils. Placement of a low frost susceptible material immediately beneath the building floor slab could be considered to reduce the amount of frost heave. If completed, care should be taken to crown lean clay subgrade soils and develop positive free drainage of structural fill soils placed beneath the building floor slab. The floor slab should be designed and constructed as a floating slab, separated from foundation walls, columns and plumbing and mechanical penetrations by the use of block outs or appropriate isolation material. In addition, we recommend all partition walls supported above isolated slabs-on-grade be constructed as floating walls to help reduce the potential for differential slab-to-foundation movement causing distress in upper sections of the structure. A minimum one and one-half (1½) inch void space is recommended beneath all floating walls. Special attention to door and stair framing, drywall installation and trim carpentry should be taken to isolate those elements from the floor slab, allowing for some differential floor slab-to-foundation movement to occur without transmitting stresses to the overlying structure. Depending on the type of floor covering and floor covering adhesive used, a vapor barrier may be required immediately beneath the floor slab in order to maintain flooring product manufacturer warranties. A vapor barrier would help reduce the transmission of moisture through the floor slabs. However, the unilateral moisture release caused by placing Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 10 concrete on an impermeable surface can increase slab curl. The amount of slab curl can be reduced by careful selection of an appropriate concrete mix. Slab curl cannot be eliminated. We recommend the owner, architect and flooring contractor consider the performance of the slab in conjunction with the proposed flooring products to help determine if a vapor barrier will be required and where best to position the vapor barrier in relation to the floor slab. Additional guidance and recommendations concerning slab on grade design can be found in American Concrete Institute (ACI) section 302. Pavement and Exterior Flatwork Subgrades Pavement and exterior flatwork subgrades should be developed as outlined in the “Building, Exterior Flatwork and Pavement Subgrade Development” section of this report. Site pavements could be supported directly on reconditioned natural site soils and/or suitable overexcavation/backfill soils placed and compacted as outlined in that section (if warranted). Care should be taken to avoid disturbing the overexcavation/ backfill soils prior to placement of exterior flatwork and site pavements. In addition, efforts to maintain the proper moisture content in the subgrade soils should be made. If subgrade soils are disturbed or allowed to dry out or become elevated in moisture content, those materials should be reworked in place or removed and replaced prior to paving or concrete placement. Some movement of exterior flatwork and site pavements should be expected as the moisture content of the subgrade soils increases subsequent to construction. Care should be taken to ensure that when exterior flatwork and site pavements move, positive drainage will be maintained away from the structure. Site Pavements Based on the materials encountered in the completed site borings and results of laboratory testing, pavement subgrades are expected to consist of reconditioned lean clay. These soils classify as A-6 soils in accordance with the American Association of State and Highway Transportation Officials (AASHTO) classification system and exhibit low remolded shear strength. A resistance value (R-value) of 5 was estimated for the subgrade soils and used in the pavement section design. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 11 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 categories 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. Thicker pavement sections may be warranted if high volumes of heavy truck traffic are anticipated in areas of the site. we would be happy to complete a pavement section design based on the actual type and quantity of heavy trucks anticipated to utilize these areas. 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. 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 late in the season and 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 constructed upon clay subgrade soils and we do not recommend full-depth asphalt sections be constructed for this project. Pavement section design options are outline below in Table 1. Alternative pavement sections could be considered and we would be happy to discuss any alternatives at your request. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 12 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 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. 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. Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 13 The proposed pavement section designs do not include an allowance for excessive loading conditions imposed by heavy construction vehicles or equipment. Heavily loaded concrete or other building material trucks and construction equipment can cause some localized distress to site pavements. The recommended pavement sections are minimums and periodic maintenance efforts should be expected. A preventative maintenance program can help increase the service life of site pavements. Corrosive Soil Characteristics We measured the soluble sulfate concentration of two (2) representative samples of the subsoils which will likely be in contact with structural concrete. The sulfate concentrations measured in the samples fell within the ‘negligible’ risk category with respect to concrete sulfate attack; therefore Type I cement should be suitable for concrete members on and below grade. As an added precaution, Type I/II Portland cement could be considered for additional sulfate resistance of construction concrete. Foundation concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed building and associated site improvements. We recommend positive drainage be developed away from the structure during construction and maintained throughout the life of the site improvements, with twelve (12) inches of fall in the first 10 feet away from the building. Shallower slopes could be considered in hardscape areas. In the event that poor or negative drainage develops adjacent to the building over time, the original grade and associated positive drainage outlined above should be immediately restored. Care should be taken in the planning of landscaping to avoid features which could result in the fluctuation of the moisture content of the foundation bearing and flatwork and pavement subgrade soils. We recommend watering systems be placed a minimum of 5 feet away from the perimeter of the site structure and be designed to discharge away from all site improvements. Gutter systems should be considered to help reduce the potential Geotechnical Subsurface Exploration Report Allied Building Products Storage Building (Lot 2 – Centerpoint Plaza) 2155 Midpoint Drive, Fort Collins, Colorado Soilogic Job No. 18-1265 14 for water ponding adjacent to the structure, with the gutter downspouts, roof drains or scuppers extended to discharge a minimum of 5 feet away from structural, flatwork and pavement elements. Water which is allowed to pond adjacent to site improvements can result in unsatisfactory performance of those improvements over time. LIMITATIONS This report was prepared based upon the data obtained from the completed site exploration, laboratory testing, engineering analysis and any other information discussed. The completed borings provide an indication of subsurface conditions at the boring locations only. Variations in subsurface conditions can occur in relatively short distances away from the borings. This report does not reflect any variations which may occur across the site or 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 (%) 0-6" VEGETATION AND TOPSOIL - 1 - CL SANDY LEAN CLAY 2 brown/rust - very stiff 3 With Scattered Gravel - 4 - 5 CS 22 11.2 117.8 9000+ 3.9% 5300 - - - - 6 - 7 - 8 - 9 - SM-GM SILTY SAND with GRAVEL 10 CS 16 2.7 - N/A - - - - 8.7% reddish brown - medium dense to dense 11 - 12 - Gravel and Possible Cobble with Depth 13 - 14 - 15 CS 50 4.8 - N/A - - - - - BOTTOM OF BORING @ 15.0' - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 USCS Sampler LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic ZG/BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N" MC DD qu % Swell @ Pressure # 200 Sieve (ft) (%) (pcf) (psf) 500 psf (psf) LL PI (%) 0-6" GRAVEL SURFACING - 1 - CL SANDY LEAN CLAY 2 brown/rust - medium stiff 3 CS 7 19.3 104.7 4000 None <500 - - - - 4 - 5 CS 8 17.1 103.1 2000 None <500 - - - - 6 - 7 - 8 - 9 SM-GM SILTY SAND with GRAVEL - reddish brown 10 CS 14 16.7 - N/A - - - - - loose to dense - 11 - 12 - Gravel and Possible Cobble with Depth 13 - 14 - 15 CS 50/10 4.6 122.9 N/A - - - - - BOTTOM OF BORING @ 15.0' - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 24 Hours After Drilling - USCS 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 (%) 0-6" VEGETATION AND TOPSOIL - 1 - 2 SM-GM SILTY to CLAYEY SAND with GrAVEL - brown/rust 3 CS 14 2.4 - N/A - - - - 8.7% loose to medium dense - 4 - 5 CS 7 7.5 103.8 N/A - - - - - - 6 - 7 - Increasing Gravel with Depth 8 - 9 - 10 CS 17 5.0 - N/A - - - - - BOTTOM OF BORING @ 10.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 24 Hours After Drilling - USCS 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 (%) 0-6" GRAVEL SURFACING - FILL - SILTY SAND AND GRAVEL 1 brown/grey - 2 - 3 CS 9 19.2 101.6 4000 None <500 - - - CL SANDY LEAN CLAY - brown/rust 4 medium stiff - 5 CS 10 16.0 119.1 5000 - - 37 18 69.7% - 6 - 7 - 8 SM-GM SILTY SAND AND GRAVEL - brown/rust 9 loose - 10 CS 12 6.3 - N/A - - - - - BOTTOM OF BORING @ 10.0' - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 24 Hours After Drilling - USCS Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 117.8 500 Final Moisture 16.3% % Swell @ 500 psf 3.9% Swell Pressure (psf) 5,300 Sample ID: B-1 @ 4 Sample Description: Brown/Rust Sandy Lean Clay (CL) Initial Moisture 11.2% SWELL/CONSOLIDATION TEST SUMMARY ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 104.7 500 Final Moisture 20.8% % Swell @ 500 psf None Swell Pressure (psf) <500 Initial Moisture 19.3% Sample ID: B-2 @ 2 Sample Description: Brown/Rust Sandy Lean Clay (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 103.1 500 Final Moisture 22.2% % Swell @ 500 psf None Swell Pressure (psf) <500 Initial Moisture 17.1% Sample ID: B-2 @ 4 Sample Description: Brown/Rust Sandy Lean Clay (CL) SWELL/CONSOLIDATION TEST SUMMARY ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf) 101.6 500 Final Moisture 16.5% % Swell @ 500 psf None Swell Pressure (psf) <500 Initial Moisture 19.2% Sample ID: B-4 @ 2 Sample Description: Brown/Rust Sandy Lean Clay (CL) (Swell Only) SWELL/CONSOLIDATION TEST SUMMARY ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Clean Gravels Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF Less than 5% finesC Cu < 4 and/or 1 > Cc > 3E GP Poorly graded gravelF Fines classify as ML or MH GM Silty gravelF,G, H Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Gravels with Fines More than 12% finesC Fines classify as CL or CH GC Clayey gravelF,G,H Clean Sands Cu ! 6 and 1 " Cc " 3E SW Well graded sandI Less than 5% finesD Cu < 6 and/or 1 > Cc > 3E SP Poorly graded sandI Fines classify as ML or MH SM Silty sandG,H,I Sands 50% or more of coarse fraction passes No. 4 sieve Sands with Fines More than 12% finesD Fines classify as CL or CH SC Clayey sandG,H,I Silts and Clays PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M Liquid limit less than 50 Inorganic PI < 4 or plots below “A” lineJ ML SiltK,L,M Liquid limit - oven dried Organic clayK,L,M,N Fine-Grained Soils 50% or more passes the No. 200 sieve Organic Liquid limit - not dried < 0.75 OL Organic siltK,L,M,O Inorganic PI plots on or above “A” line CH Fat clayK,L,M Silts and Clays Liquid limit 50 or more PI plots below “A” line MH Elastic siltK,L,M Organic Liquid limit - oven dried Organic clayK,L,M,P Liquid limit - not dried < 0.75 OH Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well graded gravel with silt, GW-GC well graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well graded sand with silt, SW-SC well graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = GENERAL NOTES DRILLING & SAMPLING SYMBOLS: SS: Split Spoon - 1⅜" I.D., 2" O.D., unless otherwise noted HS: Hollow Stem Auger ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA: Power Auger RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA: Hand Auger CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB: Rock Bit BS: Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary The number of blows required to advance a standard 2-inch O.D. split-spoon sampler (SS) the last 12 inches of the total 18-inch penetration with a 140-pound hammer falling 30 inches is considered the “Standard Penetration” or “N-value”. For 2.5” O.D. California Barrel samplers (CB) the penetration value is reported as the number of blows required to advance the sampler 12 inches using a 140-pound hammer falling 30 inches, reported as “blows per inch,” and is not considered equivalent to the “Standard Penetration” or “N-value”. WATER LEVEL MEASUREMENT SYMBOLS: WL: Water Level WS: While Sampling WCI: Wet Cave in WD: While Drilling DCI: Dry Cave in BCR: Before Casing Removal AB: After Boring ACR: After Casing Removal Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater. In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations. DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency. FINE-GRAINED SOILS COARSE-GRAINED SOILS BEDROCK (CB) Blows/Ft. (SS) Blows/Ft. Consistency (CB) Blows/Ft. (SS) Blows/Ft. Relative Density (CB) Blows/Ft. (SS) Blows/Ft. Consistency < 3 0-2 Very Soft 0-5 < 3 Very Loose < 24 < 20 Weathered 3-5 3-4 Soft 6-14 4-9 Loose 24-35 20-29 Firm 6-10 5-8 Medium Stiff 15-46 10-29 Medium Dense 36-60 30-49 Medium Hard 11-18 9-15 Stiff 47-79 30-50 Dense 61-96 50-79 Hard 19-36 16-30 Very Stiff > 79 > 50 Very Dense > 96 > 79 Very Hard > 36 > 30 Hard RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY Descriptive Terms of Other Constituents Percent of Dry Weight Major Component of Sample Particle Size Trace < 15 Boulders Over 12 in. (300mm) With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm) Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand Silt or Clay #4 to #200 sieve (4.75mm to 0.075mm) Passing #200 Sieve (0.075mm) RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION Descriptive Terms of Other Constituents Percent of Dry Weight Term Plasticity Index Trace With Modifiers < 5 5 – 12 > 12 Non-plastic Low Medium High 0 1-10 11-30 30+ F If soil contains ! 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains ! 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains ! 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains ! 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI ! 4 and plots on or above “A” line. O PI < 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. Sampler Atterberg Limits Start Date 8/30/2018 Auger Type: During Drilling None Finish Date 8/30/2018 Hammer Type: After Drilling None Surface Elev. - Field Personnel: Sheet Drilling Rig: Water Depth Information ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 Sampler Atterberg Limits Start Date 8/30/2018 Auger Type: During Drilling None Finish Date 8/30/2018 Hammer Type: After Drilling None Surface Elev. - Field Personnel: Sheet Drilling Rig: Water Depth Information ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 Sampler Atterberg Limits Start Date 8/30/2018 Auger Type: During Drilling 12' Finish Date 8/30/2018 Hammer Type: After Drilling 12' Surface Elev. - Field Personnel: Sheet Drilling Rig: Water Depth Information ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018 Atterberg Limits Surface Elev. - Field Personnel: 24 Hours After Drilling - Finish Date 8/30/2018 Hammer Type: After Drilling 12' Sheet Drilling Rig: Water Depth Information Start Date 8/30/2018 Auger Type: During Drilling 12' ALLIED BUILDING PRODUCTS STORAGE BUILDING 2155 MIDPOINT DRIVE, FORT COLLINS, COLORADO Project # 18-1265 September 2018