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Home My WebLink AboutLARIMER COUNTY CORRECTIONS ALTERNATIVE SENTENCING - SPA210002 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT Subsurface Exploration Program Larimer County Alternate Sentencing Department Additions Fort Collins, Colorado Prepared For: Larimer County Facilities Department 2004 West Oak Street 4th Floor Fort Collins, Colorado 80521 Attention: David Bragg Job Number: 20-0047 December 3, 2020 Approximate Project Site TABLE OF CONTENTS Page Purpose and Scope of Study ..................................................................................... 1 Planned Construction ................................................................................................ 2 Site Conditions .......................................................................................................... 3 Geologic Setting .......................................................................................................... 3 Subsurface Exploration ............................................................................................... 4 Laboratory Testing .................................................................................................... 5 Subsurface Conditions .............................................................................................. 5 Seismic Classification ................................................................................................ 6 Geotechnical Considerations for Design ....................................................................... 7 Drilled Pier Foundation System .................................................................................. 10 Slab-on-Grade Floors Alternative ............................................................................... 16 Lateral Earth Pressures .............................................................................................. 19 Water-Soluble Sulfates ................................................................................................ 20 Soil Corrosivity ............................................................................................................ 22 Project Earthwork ........................................................................................................ 24 Excavation Considerations .......................................................................................... 27 Utility Pipe Installation ................................................................................................. 28 Surface Drainage ........................................................................................................ 31 Subsurface Drainage ................................................................................................... 34 Pavement Sections ..................................................................................................... 36 Pedestrian Flatwork..................................................................................................... 42 Closure ....................................................................................................................... 46 Locations of Test Holes ................................................................................... Figure 1 Logs of Test Holes ................................................................................ Figures 2 to 3 Legend and Notes ........................................................................................... Figure 4 Drilled Pier Axial and Lateral Capacity Reductions ...................................... Figure 5 to 6 Summary of Laboratory Test Results .............................................................. Table 1 Summary of Soil Corrosion Test Results ............................................................. Table 2 Detailed Drill Logs ........................................................................................ Appendix A Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 1 PURPOSE AND SCOPE OF STUDY This report presents the results of the geotechnical evaluation performed by GROUND Engineering Consultants, Inc. (GROUND) for the Larimer County Facilities Department in support of design of the proposed additions to the Larimer County Alternative Sentencing Department at the Midpoint Campus in Fort Collins, Colorado. Our study was conducted in general accordance with GROUND’s Proposal No. 2009-1777 dated September 21st, 2020. A field exploration program was conducted to obtain information on the subsurface conditions. Material samples obtained during the subsurface exploration were tested in the laboratory to provide data on the engineering characteristics of the on-site soils. The results of the field exploration and laboratory testing are presented herein. Additional information was obtained from a previous CTL Thompson report of a geotechnical evaluation of the property that was utilized in design for the original Larimer County: Alternative Sentencing Department, Geotechnical Investigation, The Midpoint Campus Master Plan Update, Fort Collins, Colorado, Project No. FC05290-125, prepared for Larimer County Facilities Department, dated September 10, 2010, and GROUND Engineering, Consultants materials testing documentation from the construction of the Larimer County: Alternative Sentencing Department in 2011. This report has been prepared to summarize the data obtained and to present our findings and conclusions based on the proposed development/improvements and the subsurface conditions encountered. Design parameters and a discussion of engineering considerations related to the proposed improvements are included herein. This report should be understood and utilized in its entirety; specific sections of the text, drawings, graphs, tables, and other information contained within this report are intended to be understood in the context of the entire report. This includes the Closure section of the report which outlines important limitations on the information contained herein. This report was prepared for design purposes of the Larimer County Facilities Department based on our understanding of the proposed project at the time of preparation of this report. The data, conclusions, opinions, and geotechnical parameters provided herein should not be construed to be sufficient for other purposes, including the use by contractors, or any other parties for any reason not specifically related to the Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 2 design of the project. Furthermore, the information provided in this report was based on the exploration and testing methods described below. Deviations between what was reported herein and the actual surface and/or subsurface conditions may exist, and in some cases those deviations may be significant. PROPOSED CONSTRUCTION Provided information indicates that proposed construction will consist of an addition to the west side of the existing Alternative Sentencing Department building located at 2307 Midpoint Drive in Fort Collins, Colorado. Similar to the existing facility, the addition is planned as a two-story building approximately 27,000 square feet in footprint area with no below grade level. Additionally, preliminary information indicates that additional drive lanes and parking are planned near the proposed additions. We also anticipate relocation/installation of supporting underground utilities. If the proposed development differs significantly from that described above, GROUND should be notified to re-evaluate the conclusions and parameters contained herein. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 3 SITE CONDITIONS At the time of our subsurface exploration program, the site supported the existing Larimer County Alternative Sentencing Department facility. The site is bordered by the Larimer County Jail to the east, the Larimer County Community Corrections building to the west and north, and a gravel surface walking trail to the south. Slopes at the Alternative Sentencing Department additions are generally flat. Man-made fill was observed locally in several of the test holes during the subsurface exploration program and is likely present elsewhere on the site. The exact extents, limits, and composition of the man- made fill were not determined as part of the scope addressed by this study and should be expected to exist at varying locations and depth throughout the site associated with previous construction/development. Based on our cursory exterior observations, the existing structure appears to be performing well. GEOLOGIC SETTING Published maps depict the site as underlain Post-Piney Creek Alluvium (Qpp) (e.g., Colton, 19781; see map below). These surficial materials consist of alluviual clays, sands and gravels. The maps depict the surficial materials as underlain by the Upper Member, Pierre Shale, (Kpu). The Pierre Shale Upper member consists largley of gray silty shales, that can be moderately to highly expansive. 1 Colton, R.B., 1978, Geologic map of the Boulder-Fort Collins-Greeley area, Front Range Urban Corridor, Colorado: U.S. Geological Survey, Miscellaneous Investigations Series Map I-855-G Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 4 SUBSURFACE EXPLORATION Subsurface exploration for the project was conducted on October 7th, 2020. A total of eleven (11) test holes were drilled using a buggy-mounted drill rig advancing continuous flight auger. The eight foundation test holes were advanced to depths of about 25 to 35 feet below existing grades at locations within the proposed footprint of the addition. The three pavement test holes were advanced to depths ranging from 3 to 9 feet below existing grades. Test holes were advanced to their planned termination depths to evaluate the subsurface conditions as well as to retrieve samples for laboratory testing and analysis. A representative of GROUND directed the subsurface exploration, logged the test holes in the field, and prepared the samples for transport to our laborat ory. The test holes were backfilled following drilling operations due to safety. Samples of the subsurface materials were retrieved with a 2-inch I.D. ‘California’ liner sampler and a 1.375-inch I.D. standard split spoon sampler. The samplers were driven into the substrata with blows from a 140-pound hammer falling 30 inches, a procedure similar to the Standard Penetration Test described by ASTM Method D1586. Penetration resistance values, when properly evaluated, indicate the relative density or consistency of soils. Depth and elevations at which the samples were obtained and associated penetration resistance values are shown on the test hole logs. Project Site Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 5 The approximate locations of the test holes are shown on Figure 1. A summary of the test holes is presented on Figures 2 and 3. Explanatory notes and a legend are provided on Figure 4. Individual drill logs can be found in Appendix A. Note: Elevations of the test holes were obtained with a transit level based on a manhole benchmark provided by JE Dunn (General contractor for the 2020 Larimer County Jail Expansion.) LABORATORY TESTING Samples retrieved from our test holes were examined and visually classified in the laboratory by the project engineer. Laboratory testing of soil and bedrock samples included standard property tests, such as natural moisture contents, dry unit weights, grain size analyses, Atterberg limits, swell/consolidation testing, and unconfined compressive strength. Water soluble sulfate and corrosivity testing was performed on select samples as well. Laboratory tests were performed in general accordance with applicable ASTM protocols. Results of the laboratory testing program are summarized in Tables 1 and 2. SUBSURFACE CONDITIONS In general, the foundation test holes penetrated a thin layer of surficial materials consisting of topsoil2, concrete and/or roadbase approximately 4 to 12 inches thick. The overburden materials encountered below the surficial materials consisted of man-made fill materials consisting of sandy clay, native sandy clay, and sand and gravel with local cobbles. Bedrock encountered below the overburden materials consisted of claystone. Specific material distribution/thicknesses can be found in Figures 2 and 3, and Appendix A. It also should be noted that coarse gravel, cobbles and boulders are not well represented in samples obtained from small diameter test holes. At this site, therefore, it should be anticipated that gravel and cobbles, and possibly boulders, may be present in the fill and native soils, as well as comparably sized fragments of construction debris, even where not included in the general descriptions of the site soil types below. 2 ‘Topsoil’ as used herein is defined geotechnically. The materials so described may or may not be suitable for landscaping or as a growth medium for such plantings as may be proposed for the project. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 6 Fill materials consisted of sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. Clay materials were locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. Sand with Gravel materials were low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Clayshale was medium to highly plastic, fine grained, slightly moist to moist, hard to very hard, and brown to gray-brown to dark gray in color. Groundwater was encountered in the test holes at depths ranging from 11 to 13 feet at the time of drilling. The test holes advanced for this study were backfilled immediately following drilling due to safety concerns. Groundwater levels can be expected to fluctuate, however, in response to annual and longer-term cycles of precipitation, irrigation, surface drainage, land use, and the development of transient, perched water conditions. Swell-Consolidation Testing yielded results ranging from 0.6 consolidation to 5.8 percent swell under surcharge loads approximately equal to the anticipated overburden pressure (Table 1). SEISMIC CLASSIFICATION According to the 2018 International Building Code® (Section 1613 Earthquake Loads), “Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthq uake motions in accordance with Chapters 11, 12, 13, 17 and 18 of ASCE 7, as applicable. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 (2018 IBC) or ASCE 7.” Exceptions to this are further noted in Section 1613. Based on extrapolation of available data to depth and our experience in the project area, we consider the site likely to meet the criteria for a Seismic Site Classification of C Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 7 according to the 2018 IBC classification (Section 1613.2.2). If, however, a quantitative assessment of the site seismic properties is desired, then sampling or shear wave velocity testing to a depth of 100 feet or more should be performed. Utilizing the OSHPD Seismic Design Maps Tool (https://www.seismicmaps.org ), assuming a Site Class C the project area is indicated to possess an SDS value of 0.161g and an SD1 value of 0.055g for the site latitude and longitude. If however, local codes require quantitative assessment of the site then assuming a Site Class D the tool provides an SDS value of 0.199g and an SD1 value of 0.088g for the site latitude and longitude. GEOTECHNICAL CONSIDERATIONS FOR DESIGN The conclusions and parameters provided in this report were based on the data presented herein, our experience in the general project area with similar structures, and our engineering judgment with regard to the applicability of the data and methods of forecasting future performance. A variety of engineering parameters were considered as indicators of potential future soil movements. Our parameters and conclusions were based on our judgment of “likely movement potentials,” (i.e., the amount of movement likely to be realized if site drainage is generally effective, estimated to a reasonable degree of engineering certainty) as well as our assumptions about the owner’s willingness to accept geotechnical risk. “Maximum possible” movement estimates necessarily will be larger than those presented herein. They also have a significantly lower likelihood of being realized, in our opinion, and generally require more expensive measures to address. We encourage the Larimer County Facilities Department upon receipt of this report, to discuss these risks and the geotechnical alternatives with us. Depth of Wetting at the Site The “depth of wetting” (the depth to which foundation soils will gain moisture and experience volume change over the design-life of a structure) estimated for a given site strongly affects the anticipated performance of structures at that site. Based on the data obtained at this site and our experience with similar geotechnical settings, a ‘depth of wetting’ of 15 feet was used to develop geotechnical parameters for foundation system design. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 8 ‘Depths of wetting’ of 30, 40, or 70 feet or more have been considered (e.g., Chao and others, 2006)3 and have been encountered locally in the field. Depths of wetting of such magnitudes, however, generally are in unusual geologic conditions, such as the Dipping Bedrock Overlay District to the west, or identified forensically in unusual circumstances such as a pipe leak that has remained un-repaired for an extended period. In our experience, such deep ‘depths of wetting’ are considered only rarely in engineering consulting practice in more typical geologic settings in the Colorado Front Range area. Based on the observed depth of groundwater at the project site, GROUND considers wetting to a depth of 15 feet to be appropriate for the proposed project. However, if Larimer County Facilities Department prefers that a more conservative (or less conservative) depth be used to develop geotechnical parameters for design, GROUND should be contacted to revise the criteria provided herein. Existing Construction It is our understanding based on documents provided by the client, that the existing Alternative Sentencing Department(ASD) facility is founded on a drilled pier foundation with a slab-on-grade floor system. Per the above noted CTL soils report for the original ASD facility, the floor system is placed on 4 feet of controlled fill materials consisting of either CDOT Class 1 structural fill materials or site generated materials. Our review of GROUND Engineering Consultants’, construction materials testing documentation indicated that the CDOT Class 1 Structural fill materials were utilized below the slab-on-grade construction. General Geotechnical Risk The overburden clay materials underlying the site exhibited moderate potentials for post-construction heave that can cause damaging, post- construction, structural movements. This condition, if not mitigated, will affect nearly all improvements at the site. Mitigating the expansive materials and/or their effects, controlling the surface waters and shallow subsurface moisture changes are the principal geotechnical design considerations for the site. Specific geotechnical parameters in these regards are provided in subsequent sections of this report. Additional discussion and information 3 Chao, K-C, D.D. Overton, and J.D. Miller, 2006, The Effects of Site Conditions on the Predicted Time Rate of Heave, Unsaturated Soils 2006, American Society of Civil Engineers, Special Publication No. 147, pp. 2086 – 2097. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 9 regarding these parameters and the geotechnical risks that they address are provided below. Likely Post-Construction Movements Utilizing the above assumptions and data obtained for this study, our estimates indicate vertical, post-construction movements on the order of 3 to 4 inches where structure elements for the ASD addition are supported directly on the existing earth materials. Lateral movements will result, as well. As noted above, significant structure distress could result from foundation movements of these magnitudes. Building Foundation and Floor Types Deep Foundations In GROUND’s opinion a deep foundation consisting of drilled piers advanced into the bedrock at the project site will provide the least risk of post- construction movements. Additionally, the foundation system of the existing facility consists of drilled piers so in order to achieve similar performance to the adjacent facility the addition also should be founded on drilled piers. Supporting the proposed facility on a drilled pier foundation system will provide likely post-construction foundation movements of about ½ inch, with similar differential movements over spans of about 40 feet. Geotechnical parameters for drilled piers are provided below. Utilizing a structural floor system, also supported on drilled piers, will provide the least risk for post construction movement. However, it is our understanding that the slab-on- grade floor system is performing acceptably in the existing ASD facility. GROUND can be contacted to provide structural floor parameters upon request. Slab-on-Grade Floor As a higher risk alternative, the addition may be provided with a concrete, slab-on-grade floor provided that it is placed on a remedial fill section constructed in accordance with the criteria below and elsewhere in this report. In order to reduce estimates of likely, post-construction movements to about 1 inch, the remedial fill section should extend to a depth of at least 4 feet below the bottom of the slab + sub- slab gravel system, i.e., at least 5 feet below existing grades. If grades at the addition are raised (and/or the sub-slab gravel is omitted) then the remedial fill section should be thickened correspondingly.) We anticipate that excavations to these depths to construct Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 10 the remedial fill section will remove all of the existing fill soils. Geotechnical parameters for design of the slab-on-grade floor are provided in the Slab-on-Grade Floor section of this report. Differential movements, if the remedial fill section is constructed properly, likely will be on the order of ½ inch over spans of 40 feet. The remedial fill section should consist of properly moisture-conditioned and compacted fill derived from on-site soils or approved, imported soils. In general, we anticipate that the majority of the existing site soils, including the fill soils, will be suitable geotechnically to be reused as compacted fill. However, because not all of the fill materials were not sampled and tested, some of these materials may not be suitable for reuse. Where the local bedrock shales are excavated, that material should not be used in the remedial fill section. More detailed parameters for fill placement and compaction, etc., are provided in the Project Earthwork section of this report. Additional Considerations Inadequate site drainage and/or ineffective fill processing (moisture treatment and compaction) will result in an increase in the movement estimates provided. Actual movements may be more or less depending on the subsurface materials present and the overall site drainage after construction is completed, and when landscape irrigation commences. DRILLED PIER FOUNDATION SYSTEM Geotechnical Parameters for Design of Drilled Piers: Based on the results of the field exploration, laboratory testing, and experience, the design criteria presented below should be observed for a straight-shaft, drilled pier foundation system. 1) Drilled piers should bear in ‘comparatively unweathered’ bedrock underlying the site. For design purposes, ‘comparatively unweathered’ bedrock may be taken to be at and below approximate elevations of 4883 to 4885 feet for the Addition. For bidding purposes, these elevations may vary. 2) Drilled piers should be at least 18 inches in diameter. The pier length / diameter ratio will be determined by the structural engineer. Useful guidance in this regard may be found in appropriate AASHTO or FHWA Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 11 manuals or other publications. In our experience, drilled pier diameters are rarely modified in the field. However, for various factors as discussed herein, pier lengths commonly must be increased in the field beyond the nominal design lengths. Actual depths to bedrock will vary. Therefore, it may be beneficial to select project pier diameter(s) based on potential pier length increases so that the minimum length / diameter ratio included in the design is not exceeded. 3) Drilled piers should have a minimum length of 30 feet. The actual drilled pier lengths should be determined by the structural engineer based on loading, etc., with further increases in length possibly required by the conditions encountered during installation at each drilled pier location. 4) Drilled piers also should penetrate at least 6 feet into relatively un-weathered bedrock or 3 drilled pier diameters, whichever is greater. Based on the minimum length and bedrock penetration, and taking the top of relatively un-weathered bedrock to be about 26 to 30 feet below existing grade, drilled pier lengths on the order of 36 to 39 feet are anticipated to meet the geotechnical criteria. Actual drilled pier lengths commonly will be greater due to structural considerations, conditions in the drilled pier holes, actual depths to relatively un-weathered bedrock, clean out, etc. 5) Drilled piers bearing in relatively un-weathered bedrock at and below depths of 30 feet may be designed for an allowable end bearing pressure of 30,000 psf. The portion of the drilled pier penetrating relatively un-weathered bedrock at depths greater than 30 feet may be designed for a skin friction value of 2,250 psf. However, skin friction above the competent bedrock and the depth of wetting, i.e., in the upper 15 feet of the pier should be ignored for axial load resistance. 100 percent of the skin friction may be used to resist both compressional loads and uplift. 6) Estimated settlement of properly constructed drilled piers will be low – on the order of ½ inch – to mobilize skin friction. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 12 7) Drilled piers should be designed for a minimum dead load pressure of 6,000 psf based on drilled pier cross-section area to a) avoid lengthening of the pier to achieve adequate uplift resistance and b) reduce tensile stresses in the pier. Where the minimum dead load cannot be applied, it will be necessary to increase the drilled pier length beyond the recommended minimum, even where the minimum bedrock penetration has been achieved or exceeded. This can be accomplished by assuming that skin friction on the extended zone acts to resist uplift. 8) Drilled piers should be reinforced as determined by the structural engineer. At a minimum, each drilled pier should be reinforced for its full length to resist the tensile loading created by the uplift force exerted on the pier by the swelling soils and bedrock, and the deficit between the actual dead load applied to a pier and the indicated minimum dead load. The uplift load on a pier may be estimated using an uplift skin friction of 1,050 psf acting on the surface area above the depth of wetting (the upper 15 feet of the pier). 9) A 6-inch or thicker continuous void should be provided beneath grade beams, drilled pier caps, foundation walls, and floor slabs. The void space should be protected from backfill intrusion. 10) Deep Foundations Resisting Lateral Loads Based on the data obtained for this study and our experience with similar sites and conditions, lateral load analysis using the “L-Pile” or a similar computer program should use the following geotechnical parameters for input. The parameters are based on a simplified soil / bedrock profile. These include, unit wet weights (γ'), angles of internal friction (), cohesion (c), for the earth materials, as well as values for strain at 50 percent of failure stress (50) and horizontal soil modulus (k). Resistance to lateral loads should be neglected in the upper 3 foot of soils, whether fill or native. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 13 GEOTECHNICAL PARAMETERS FOR LATERAL LOAD ANALYSIS USING L-PILE Soil / Bedrock Material Approximate Depth Range Range Parameter Value Overburden Fill and Native Clays (model as Stiff Clay without Free Water) 3 feet – 12 feet γ' 128 pcf (0.072 pci) cu 700 psf (4.86 psi) 50 0.005 Overburden Sands and Gravels (model as Sand with Free Water) 10 feet to 30 feet γ' 62 pcf (0.0358 pci)  32 degrees k 0.130 x 106 pcf (75 pci) Claystone Bedrock (model as Stiff Clay without Free Water) > 30 feet γ' 130 pcf (0.075 pci) cu 4,000 psf (27.8 psi) 50 0.011 11) Penetration of comparatively unweathered bedrock in drilled pier shafts should be roughened artificially to assist the development of peripheral shear between the drilled pier and bedrock. Artificially roughening of drilled pier holes should consist of installing shear rings 3 inches high and 2 inches deep in the portion of each drilled pier penetrating comparatively unweathered bedrock and below a depth of 26 feet. The shear rings should be installed 18 inches on centers. However, the specifications should allow a geotechnical engineer to waive the requirement for shear rings depending on the conditions actually encountered in individual drilled pier holes. 12) Groups of closely spaced drilled piers placed to support concentrated loads will require an appropriate reduction of the estimated capacities. Reduction of axial capacity generally can be avoided by spacing drilled piers at least 3 diameters center to center. At this spacing or greater, no reduction in axial capacities or horizontal soil modulus values is required. Drilled pier groups spaced less than 3 diameters center to center should corrected with the axial capacity reductions provided in Figure #5 Linear arrays of drilled piers, however, must be spaced at least 8 diameters center to center to avoid reductions in lateral capacity when loaded in line with Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 14 the array (parallel to the line connecting the drilled pier centers). Linear arrays of drilled piers spaced more closely than 8 diameters center to center should have their lateral capacities corrected per Figure #6. Drilled Pier Construction The following should be considered during the construction of drilled pier foundations. 13) The depth of comparatively unweathered bedrock should be determined in the field at each drilled pier location and may differ from other information provided herein. 14) Lenses or beds of relatively soft bedrock, including coal or lignite seams, (not suitable for foundation support) may be encountered in the bedrock materials. Such circumstances may result in lengthening the drilled piers. 15) The bedrock beneath the site was hard to very hard and resistant, particularly with depth. The pier-drilling contractor should mobilize equipment of sufficient size and operating capability to achieve the design lengths and bedrock penetration. If refusal is encountered in these materials, a geotechnical engineer should be retained to evaluate the conditions to establish whether true refusal has been met with adequate drilling equipment. 16) Groundwater was encountered at depths ranging from 11 to 13 feet below existing grades at the time of drilling. Therefore, we anticipate that soils and bedrock will yield significant volumes of water when penetrated by the pier excavations, casing will likely be required to reduce water infiltration. Seating of the casing in the upper layers of the bedrock may not create positive cutoff of water infiltration. In the event that casing is seated into the bedrock, the minimum bedrock penetration should be taken from the bottom of the casing. 17) In no case should concrete be placed in more than 3-inches of water, unless placed through an approved tremie method. The proposed concrete placement method should be discussed during the pre-construction meeting by the Project Team. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 15 18) Where groundwater and unconsolidated soils and/or caving bedrock materials are encountered, the installation procedure of drilled piers can be a concern. Commonly in these conditions, the drilling contractor utilizes casing and slurry during excavation of the drilled pier holes, which may adversely affect the axial and/or lateral capacities of the completed drilled piers. During casing withdrawal, the concrete should have sufficient slump and must be maintained with sufficient head above groundwater levels to displace the water or slurry fully to prevent the creation of voids in the drilled pier. Because of these considerations, the drilling contractor should submit a written procedure addressing the use of casing, slurry, and concrete placement prior to commencement of drilled pier installation. 19) Drilled pier holes should be properly cleaned prior to placement of concrete. 20) Concrete utilized in the drilled piers should be a fluid mix with sufficient slump so that it will fill the void between reinforcing steel and the drilled pier hole wall, and inhibit soil, water, and slurry from contaminating the concrete. The concrete should be designed with a minimum slump of no less than 5 inches. 21) Concrete should be placed by an approved method to minimize mix segregation. 22) Concrete should be placed in a drilled pier on the same day that it is drilled. Failure to place concrete the day of drilling may result in a requirement for lengthening the drilled pier. The presence of groundwater or caving soils may require that concrete be placed immediately after the pier hole drilling is completed. 23) The contractor should take care to prevent enlargement of the excavation at the tops of drilled piers, which could result in “mushrooming” of the drilled pier top. 24) Sonic integrity testing (sonic echo or cross-hole sonic) can be performed at the discretion of the structural engineer to assess the effectiveness of the drilled pier construction methods and to check any suspect piers. Additional information on sonic integrity testing can be provided upon request. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 16 SLAB-ON-GRADE FLOORS ALTERNATIVE The geotechnical parameters below may be used for design of slab-on-grade floors for the proposed buildings. ACI Sections 301/302/360 provide guidance regarding concrete slab-on-grade design and construction. Geotechnical Parameters for Design of Slab-on-Grade Floors 1) A slab-on-grade floor system should bear on a section of properly compacted fill soils as discussed in the Geotechnical Considerations for Design section of this report. The selected fill section beneath a given building should extend at full thickness across the building footprint and at least 5 feet laterally beyond the foundation margins with the exception of the portion of the additions that abuts the existing structure. Considerations for fill placement and compaction are provided in the Project Earthwork section of this report. The fill section beneath the building structure should be laterally consistent and of uniform depth to reduce differential, post-construction foundation movements. A differential fill section will tend to increase differential movements. The contractor should provide survey data of the excavation beneath each building indicating the depth and lateral extents of the remedial excavation. 2) Floor slabs should be adequately reinforced. Floor slab design, including slab thickness, concrete strength, jointing, and slab reinforcement should be developed by a structural engineer. 3) An allowable vertical modulus of subgrade reaction (Kv) of 80 pci may be used for design of a concrete, slab-on-grade floor bearing on compacted fill. This value is for a 1-foot x 1-foot plate; they should be adjusted for slab dimension. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 17 4) Floor slabs should be separated from all bearing walls and columns with slip joints, which allow unrestrained vertical movement. Slip joints should be observed periodically, particularly during the first several years after construction. Slab movement can cause previously free-slipping joints to bind. Measures should be taken to assure that slab isolation is maintained in order to reduce the likelihood of damage to walls and other interior improvements. 5) A concrete slab-on-grade should be provided with properly designed control joints. ACI, AASHTO, and other industry groups provide guidelines for proper design and construction concrete slabs-on-grade and associated jointing. The design and construction of such joints should account for cracking as a result of shrinkage, curling, tension, loading, and curing, as well as proposed slab use. Joint layout based on the slab design may require more frequent, additional, or deeper joints, and should reflect the configuration and proposed use of the slab. Particular attention in slab joint layout should be paid to areas where slabs consist of interior corners or curves (e.g., at column blockouts or reentrant corners) or where slabs have high length to width ratios, significant slopes, thickness transitions, high traffic loads, or other unique features. Improper placement or construction will increase the potential for slab cracking. 6) Interior partitions resting on a floor slab should be provided with slip joints so that if the slabs move, the movement cannot be transmitted to the upper structure. This detail is also important for wallboards and doorframes. Slip joints should allow 1 ½ inches or more of vertical, differential movement. Accommodation for differential movement also should be made where partitions meet bearing walls. 7) Post-construction heave may not displace s slab-on-grade floor and utility lines in the soils beneath them to the same extent. Design of floor penetrations, connections, and fixtures should accommodate up to 2 inches of differential movement. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 18 8) Moisture can be introduced into a slab subgrade during construction and additional moisture will be released from the slab concrete as it cures. A properly compacted layer of free-draining gravel, 4 or more inches in thickness, should be placed beneath the slabs. This layer will help distribute floor slab loadings, ease construction, reduce capillary moisture rise, and aid in drainage. The free-draining gravel should classify as an ASTM C33 Class 57/67 concrete aggregate or similar material. The capillary break and the drainage space provided by the gravel layer also may reduce the potential for excessive water vapor fluxes from the slab after construction as mix water is released from the concrete. We understand, however, that professional experience and opinion differ with regard to inclusion of a free-draining gravel layer beneath slab-on-grade floors. If these issues are understood by the owner and appropriate measures are implemented to address potential concerns including slab curling and moisture fluxes, then the gravel layer may be deleted. 9) A vapor barrier beneath a building floor slab can be beneficial with regard to reducing exterior moisture moving into the building, through the slab, but can retard downward drainage of construction moisture. Uneven moisture release can result in slab curling. Elevated vapor fluxes can be detrimental to the adhesion and performance of many floor coverings and may exceed various flooring manufacturers’ usage criteria. Per the 2006 ACI Location Guideline, a vapor barrier is required under concrete floors when that floor is to receive moisture-sensitive floor covering and/or adhesives, or the room above that floor has humidity control. Therefore, in light of the several, potentially conflicting effects of the use vapor- barriers, the owner and the architect and/or contractor should weigh the performance of the slab and appropriate flooring products in light of the intended building use, etc., during the floor system design process and the selection of flooring materials. Use of a plastic vapor-barrier membrane may be appropriate for some building areas and not for others. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 19 In the event a vapor barrier is utilized, it should consist of a minimum 15 mil thickness, extruded polyolefin plastic (no recycled content or woven materials), maintain a permeance less than 0.01 perms per ASTM E-96 or ASTM F-1249, and comply with ASTM E-1745 (Class “A”). Vapor barriers should be installed in accordance with ASTM E-1643. Polyethylene (“poly”) sheeting (even if 15 mils in thickness which polyethylene sheeting commonly is not) does not meet the ASTM E-1745 criteria and should not be used as vapor barrier material. It can be easily torn and/or punctured, does not possess necessary tensile strength, gets brittle, tends to decompose over time, and has a relatively high permeance. Construction Considerations for Slab-on-Grade Floors 10) Loose, soft, or otherwise unsuitable materials exposed on the prepared surface on which the floor slab will be cast should be excavated and replaced with properly compacted fill. 11) The fill section beneath a slab should be of uniform thickness. 12) Concrete floor slabs should be constructed and cured in accordance with applicable industry standards and slab design specifications. 13) All plumbing lines should be carefully tested before operation. Where plumbing lines enter through the floor, a positive bond break should be provided. LATERAL EARTH PRESSURES Structures which are laterally supported and can be expected to undergo only a limited amount of deflection should be designed for “at-rest” lateral earth pressures. The cantilevered retaining structures will be designed to deflect sufficiently to mobilize the full active earth pressure condition, and may be designed for “active” lateral earth pressures. “Passive” earth pressures may be applied in front of the structural embedment to resist driving forces. The at-rest, active, and passive earth pressures in terms of equivalent fluid unit weight for the on-site backfill is summarized on the table below. Base friction may be combined with passive earth pressure if the foundation is in a drained condition. The values for the Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 20 on-site material in the upper 10 feet provided in the table below were approximated utilizing a unit weight of 128 pcf and a phi angle of 26 degrees, and are un-factored. Appropriate factors of safety should be included in design calculations. Lateral Earth Pressures (Equivalent Fluid Unit Weights) Material Type Water Condition At-Rest (pcf) Active (pcf) Passive (pcf) Friction Coefficient On-Site Backfill Drained 72 50 285 (max. 2,850 psf) 0.33 The lateral earth pressures indicated above are for a horizontal upper backfill slope. The additional loading of an upward sloping backfill as well as loads from traffic, stockpiled materials, etc., should be included in the wall/shoring design. Project Retaining Walls We are not aware of any significant retaining structures proposed as part of the facility improvements. Therefore, the above parameters should be considered preliminary with regard to design of walls, etc. In the event that retaining walls are added once project design begins, a geotechnical engineer should be retained to develop parameters for retaining wall parameter design. Global stability analysis may be needed, as well. The Larimer County Facilities Department should realize that additional subsurface exploration may be necessary. WATER-SOLUBLE SULFATES The concentrations of water-soluble sulfates measured in selected samples retrieved from the test holes ranged up to approximately 0.21 percent by weight (See Table 2). Such concentrations of soluble sulfates represent a severe environment for sulfate attack on concrete exposed to these materials. Degrees of attack are based on the scale of 'negligible,' 'moderate,' 'severe' and 'very severe' as described in the “Design and Control of Concrete Mixtures,” published by the Portland Cement Association (PCA). The Colorado Department of Transportation (CDOT) utilizes a corresponding scale with 4 classes of severity of sulfate exposure (Class 0 to Class 3) as described in the published table below. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 21 REQUIREMENTS TO PROTECT AGAINST DAMAGE TO CONCRETE BY SULFATE ATTACK FROM EXTERNAL SOURCES OF SULFATE Severity of Sulfate Exposure Water-Soluble Sulfate (SO4) In Dry Soil (%) Sulfate (SO4) In Water (ppm) Water Cementitious Ratio (maximum) Cementitious Material Requirements Class 0 0.00 to 0.10 0 to 150 0.45 Class 0 Class 1 0.11 to 0.20 151 to 1500 0.45 Class 1 Class 2 0.21 to 2.00 1501 to 10,000 0.45 Class 2 Class 3 2.01 or greater 10,001 or greater 0.40 Class 3 Based on our test results and PCA and CDOT guidelines, GROUND recommends use of sulfate-resistant cement in all concrete exposed to site soil and bedrock, conforming to one of the following Class 2 requirements: (1) ASTM C 150 Type V with a minimum of a 20 percent substitution of Class F fly ash by weight (2) ASTM C 150 Type II or III with a minimum of a 20 percent substitution of Class F fly ash by weight. The Type II or III cement shall have no more than 0.040 percent expansion at 14 days when tested according ASTM C 452 (3) ASTM C 1157 Type HS; Class C fly ash shall not be substituted for cement. (4) ASTM C 1157 Type MS plus Class F fly ash where the blend has less than 0.05 percent expansion at 6 months or 0.10 percent expansion at 12 months when tested according to ASTM C 1012. (5) A blend of Portland cement meeting ASTM C 150 Type II or III with a minimum of 20 percent Class F fly ash by weight, where the blend has less than 0.05 percent expansion at 6 months or 0.10 percent expansion at 12 months when tested according to ASTM C 1012. (6) ASTM C 595 Type IP(HS); Class C fly ash shall not be substituted for cement. When fly ash is used to enhance sulfate resistance, it shall be used in a proportion greater than or equal to the proportion tested in accordance to ASTM Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 22 C 1012, shall be the same source, and it shall have a calcium oxide content no more than 2.0 percent greater than the fly ash tested according to ASTM C 1012. All concrete exposed to site soil and bedrock should have a minimum compressive strength of 4,500 psi. The contractor should be aware that certain concrete mix components affecting sulfate resistance including, but not limited to, the cement, entrained air, and fly ash, can affect workability, set time, and other characteristics during placement, finishing and curing. The contractor should develop mix(es) for use in project concrete which are suitable with regard to these construction factors, as well as sulfate resistance. A reduced, but still significant, sulfate resistance may be acceptable to the owner, in exchange for desired construction characteristics. SOIL CORROSIVITY Data were obtained to support an initial assessment of the potential for corrosion of ferrous metals in contact with earth materials at the site, based on the conditions at the time of GROUND’s evaluation. The test results are summarized in Table 2. Reduction-Oxidation testing in a selected sample indicated a negative potential of approximately -88 millivolts. Such low potentials typically create a more corrosive environment. Sulfide Reactivity testing indicated a ‘Positive’ result in the local soils. The presence of sulfides in the soils suggests a more corrosive environment. Soil Resistivity In order to assess the “worst case” for mitigation planning, a sample of material retrieved from the test holes was tested for resistivity in the laboratory, after being saturated with water, rather than in the field. Resistivity also varies inversely with temperature. Therefore, the laboratory measurements were made at a controlled temperature. Measurement of electrical resistivity indicated a value of approximately 3,128 ohm-centimeters in selected sample of site soils. pH Where pH is less than 4.0, soil serves as an electrolyte; the pH range of about 6.5 to 7.5 indicates soil conditions that are optimum for sulfate reduction. In the pH range Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 23 above 8.5, soils are generally high in dissolved salts, yielding a low soil resistivity.4 Testing of a selected samples of site soils indicated a pH value of about 8.6. Corrosivity Assessment The American Water Works Association (AWWA) has developed a point system scale used to predict corrosivity. The scale is intended for protection of ductile iron pipe but also is valuable for project steel selection. When the scale equals 10 points or higher, protective measures for ductile iron pipe are indicated. The AWWA scale is presented below. The soil characteristics refer to the conditions at and above pipe installation depth. Table A.1 Soil-Test Evaluation Soil Characteristic / Value Points Redox Potential < 0 (negative values) ....................................................................................... 5 0 to +50 mV ................................................................................................…. 4 +50 to +100 mV ............................................................................................… 3½ > +100 mV ............................................................................................... 0 Sulfide Reactivity Positive ........................................................................................................…. 3½ Trace .............................................................................................................… 2 Negative .......................................................................................................…. 0 Soil Resistivity <1,500 ohm -cm ..........................................................................................… 10 1,500 to 1,800 ohm-cm ................................................................……......…. 8 1,800 to 2,100 ohm-cm .............................................................................…. 5 2,100 to 2,500 ohm-cm ...............................................................................… 2 2,500 to 3,000 ohm-cm .................................................................................. 1 >3,000 ohm-cm ................................................................................… 0 pH 0 to 2.0 ............................................................................................................ 5 2.0 to 4.0 ......................................................................................................... 3 4.0 to 6.5 ......................................................................................................... 0 6.5 to 7.5 ......................................................................................................... 0 * 7.5 to 8.5 ......................................................................................................... 0 >8.5 .......................................................................................................... 3 Moisture Poor drainage, continuously wet ..................................................................…. 2 Fair drainage, generally moist ....................................................................… 1 Good drainage, generally dry ........................................................................ 0 4 American Water Works Association ANSI/AWWA C105/A21.5-05 Standard. * If sulfides are present and low or negative redox-potential results (< 50 mV) are obtained, add three (3) points for this range. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 24 We anticipate that drainage at the site after construction will be effective. However, based on the values obtained for this study, the overburden soils appear to comprise a corrosive environment for ferrous metals (11.5 points). If additional information is needed regarding soil corrosivity, then the American Water Works Association or a corrosion engineer should be contacted. It should be noted, however, that changes to the site conditions during construction, such as the import of other soils, or the intended or unintended introduction of off-site water, might alter corrosion potentials significantly. PROJECT EARTHWORK The following information is for private improvements; public roadways or utilities should be constructed in accordance with applicable municipal / agency standards. General Considerations Site grading should be performed as early as possible in the construction sequence to allow settlement of fills and surcharged ground to be realized to the greatest extent prior to subsequent construction. Prior to earthwork construction, concrete/asphalt, vegetation and other deleterious materials should be removed and disposed of off-site or stockpiled for reuse evaluation. Relic underground utilities should be abandoned in accordance with applicable regulations, removed as necessary, and properly capped. Topsoil present on-site should not be incorporated into ordinary fills. Instead, topsoil should be stockpiled during initial grading operations for placement in areas to be landscaped or for other approved uses. As mentioned, the topsoil encountered was not tested for quality and may not be suitable for all landscaping purposes. Existing Fill Soils Man-made fill was encountered during the exploration. Actual contents and composition of any man-made fill materials are not known; therefore, some of the excavated man-made fill materials may not be suitable for replacement as backfill. The geotechnical engineer should be retained during site excavations to observe the excavated fill materials and provide guidance for its suitability for reuse. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 25 Use of Existing Native Soils Overburden soils that are free of trash, organic material, construction debris, and other deleterious materials are suitable, in general, for placement as compacted fill. Organic materials should not be incorporated into project fills. Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) larger than 3 inches in maximum dimension will require special handling and/or placement to be incorporated into project fills. In general, such materials should be placed as deeply as possible in the project fills. Existing asphalt or road base materials, if processed sufficiently, could potentially be used as grading materials. A geotechnical engineer should be consulted regarding appropriate parameters for usage of such materials on a case-by-case basis when such materials have been identified during earthwork. Standard parameters that likely will be generally applicable can be found in Section 203 of the current CDOT Standard Specifications for Road and Bridge Construction. Imported Fill Materials If it is necessary to import material to the site, the imported soils should be free of organic material, and other deleterious materials. Imported material should consist of soils exhibiting 50 percent or less passing the No. 200 Sieve and should have a plasticity index of 15 or less. Representative samples of the materials proposed for import should be tested and approved by the geotechnical engineer prior to transport to the site. Fill Platform Preparation Prior to filling, the top 12 inches of in-place materials on which fill soils will be placed should be scarified, moisture conditioned and pro perly compacted in accordance with the parameters below to provide a uniform base for fill placement. If over-excavation is to be performed, then these parameters for subgrade preparation are for the subgrade below the bottom of the specified over-excavation depth. If surfaces to receive fill expose loose, wet, soft, or otherwise deleterious material, additional material should be excavated, or other measures taken to establish a firm platform for filling. The surfaces to receive fill must be effectively stable prior to placement of fill. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 26 Fill Placement Fill materials should be thoroughly mixed to achieve a uniform moisture content, placed in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted. Soils that classify as GP, GW , GM, GC, SP, SW, SM, or SC in accordance with the USCS classification system (granular materials) should be compacted to a least 95 percent of the maximum modified Proctor dry density at moisture contents within 2 percent of optimum moisture content as determined by ASTM D1557. Site soils that classify as ML or CL should be compacted to at least 95 percent of the maximum standard Proctor density at moisture contents within 2 percent of the optimum moisture content as determined by ASTM D698. No fill materials should be placed, worked, rolled while they are frozen, thawing, or during poor/inclement weather conditions. Excavated shale and soils that classify as MH or CH should not be used for fill except in landscape area. Care should be taken with regard to achieving and maintaining proper moisture contents during placement and compaction. Materials that are not properly moisture conditioned may exhibit significant pumping, rutting, and deflection at moisture contents near optimum and above. The contractor should be prepared to handle soils of this type, including the use of chemical stabilization, if necessary. Compaction areas should be kept separate, and no lift should be covered by another until relative compaction and moisture content within the ranges are obtained. Settlements Settlements will occur in filled ground, typically on the order of 1 to 2 percent of the fill depth. If fill placement is performed properly and is tightly controlled, in GROUND’s experience the majority (on the order of 60 to 80 percent) of that settlement will typically take place during earthwork construction, provided the contractor achieves the compaction levels provided herein. The remaining potential settlements likely will take several months or longer to be realized, and may be exacerbated if these fills are subjected to changes in moisture content. Cut and Filled Slopes Permanent site slopes supported by on-site soils up to 5 feet in height may be constructed no steeper than 3 (H) to 1 (V). In the event slopes greater Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 27 than 10 feet in height are planned, a slope stability analysis should be performed. Minor raveling or surficial sloughing should be anticipated on slopes cut at this angle until vegetation is well re-established. Surface drainage should be designed to direct water away from slope faces. Use of Squeegee Relatively uniformly graded fine gravel or coarse sand, i.e., “squeegee,” or similar materials commonly are proposed for backfilling foundation excavations, utility trenches (excluding approved pipe bedding), and other areas where employing compaction equipment is difficult. In general, GROUND does not suggest this procedure for the following reasons: Although commonly considered “self-compacting,” uniformly graded granular materials require densification after placement, typically by vibration. The equipment to densify these materials is not available on many job-sites. Even when properly densified, uniformly graded granular materials are permeable and allow water to reach and collect in the lower portions of the excavations backfilled with those materials. This leads to wetting of the underlying soils and resultant potential loss of bearing support as well as increased local heave or settlement. Wherever possible, excavations should be backfilled with approved, on-site soils placed as properly compacted fill. Where this is not feasible, use of “Controlled Low Strength Material” (CLSM), i.e., a lean, sand-cement slurry (“flowable fill”) or a similar material for backfilling should be considered. Where “squeegee” or similar materials are proposed for use by the contractor, the design team should be notified by means of a Request for Information (RFI), so that the proposed use can be considered on a case-by-case basis. Where “squeegee” meets the project requirements for pipe bedding material, however, it is acceptable for that use. EXCAVATION CONSIDERATIONS Excavation Difficulty Test holes for the subsurface exploration were advanced to the depths indicated on the test hole logs by means of conventional, truck-mounted, geotechnical drill equipment. We anticipate no significant excavation difficulties with heavy duty excavation equipment in good working condition. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 28 Temporary un-shored excavation slopes for other areas up to 10 feet in height should be cut no steeper than 2 (H) to 1 (V) in the site soils in the absence of seepage. Some surficial sloughing may occur on slope faces cut at this angle. As stated, local conditions encountered during construction, such as loose, dry sand, or soft or wet materials, or seepage will require flatter slopes. Stockpiling of materials should not be permitted closer to the tops of temporary slopes than 5 feet or a distance equal to the depth of the excavation, whichever is greater. Should site constraints prohibit the use of the provided slope angles, temporary shoring should be used. The shoring should be designed to resist the lateral earth pressure exerted by structure, traffic, equipment, and stockpiles. GROUND can provide shoring design upon request. Groundwater was observed as shallow as 11 feet below existing grades in the test holes at the time of exploration. Therefore, with the exception of drilled piers or excavations on the order of 9 feet or greater below existing grades, groundwater is not anticipated to be a significant factor in excavations. If seepage or groundwater is encountered in project excavations, the geotechnical engineer should evaluate the conditions and provide additional parameters and considerations, as appropriate. Good surface drainage should be provided around temporary excavation slopes to direct surface runoff away from the slope faces. A properly designed swale should be provided at the top of the excavations. In no case should water be allowed to pond at the site. Slopes should be protected against erosion. Erosion along the slopes will result in sloughing and could lead to a slope failure. Any excavations in which personnel will be working must comply with all OSHA Standards and Regulations (CFR 29 Part 1926). The contractor’s “responsible person” should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. GROUND has provided the information above solely as a service to the client, and is not assuming responsibility for construction site safety or the contractor’s activities. UTILITY PIPE INSTALLATION Pipe Support The bearing capacity of the site soils appeared adequate, in general, for support of the proposed utility lines. The pipe + contents are less dense than the soils Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 29 which will be displaced for installation. Therefore, GROUND anticipates no significant pipe settlements in these materials where properly bedded. Excavation bottoms may expose soft, loose, or otherwise deleterious materials, including debris. Firm materials may be disturbed by the excavation process. All such unsuitable materials should be excavated and replaced with properly compacted fill. Areas allowed to pond water will require excavation and replacement with properly compacted fill. The contractor should take particular care to ensure adequate support near pipe joints which are less tolerant of extensional strains. Trench Backfilling Settlement of compacted soil trench backfill materials will occur, even where all the backfill is placed and compacted correctly. Typical settlements are on the order of 1 to 2 percent of fill thickness. However, the need to compact to the lowest portion of the backfill must be balanced against the need to protect the pipe from damage from the compaction process. Some thickness of backfill may need to be placed at compaction levels lower than specified (or smaller compaction equipment used together with thinner lifts) to avoid damaging the pipe. Protecting the pipe in this manner can result in somewhat greater surface settlements. Therefore, although other alternatives may be available, the following options are presented for consideration: Controlled Low Strength Material: Because of these limitations, the most conservative option consists of backfilling the entire depth of the trench (both bedding and common backfill zones) with “controlled low strength material” (CLSM), i.e., a lean, sand-cement slurry, “flowable fill,” or similar material along all trench alignment reaches with low tolerances for surface settlements. If used, the CLSM used as pipe bedding and trench backfill should exhibit a 28-day unconfined compressive strength between 50 to 200 psi so that re-excavation is not unusually difficult. Placement of the CLSM in several lifts or other measures likely will be necessary to avoid ‘floating’ the pipe. Measures also should be taken to maintain pipe alignment during CLSM placement. Compacted Soil Backfilling For most projects, site-generated materials are utilized for backfilling. Where compacted soil backfilling is employed, using the site soils or similar materials as backfill, the risk of backfill settlements entailed in the selection of this higher Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 30 risk alternative must be anticipated and accepted by the Larimer County Facilities Department. We anticipate that the on-site soils excavated from trenches will be suitable, in general, for use as common trench backfill within the above-described limitations. Backfill soils should be free of vegetation, organic debris and other deleterious materials. Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) coarser than 3 inches in maximum dimension should not be incorporated into trench backfills. Soils placed for compaction as trench backfill should be conditioned to a relatively uniform moisture content, placed and compacted in accordance with the Project Earthwork section of this report. Pipe Bedding Pipe bedding materials, placement and compaction should meet the specifications of the pipe manufacturer and applicable municipal standards. Bedding should be brought up uniformly on both sides of the pipe to reduce differential loadings. As discussed above, the use of CLSM or similar material in lieu of granular bedding and compacted soil backfill should be considered where the tolerance for surface settlement is low. (Placement of CLSM as bedding to at least 12 inches above the pipe can protect the pipe and assist construction of a well-compacted conventional backfill, although possibly at an increased cost relative to the use of conventional bedding.) If a granular bedding material is specified, with regard to potential migration of fines into the pipe bedding, design and installation follow ASTM D2321. If the granular bedding does not meet filter criteria for the enclosing soils, then non-woven filter fabric (e.g., Mirafi® 140N, or the equivalent) should be placed around the bedding to reduce migration of fines into the bedding which can result in severe, local surface settlements. Where this protection is not provided, settlements can develop/continue several months or years after completion of the project. In addition, clay or concrete cut-off walls should be installed to interrupt the granular bedding section to reduce the rates and volumes of water transmitted along the sewer alignment which can contribute to migration of fines. If granular bedding is specified, the contractor should anticipate that significant volumes of on-site soils may not be suitable for that use. Materials proposed for use as pipe bedding should be tested for suitability prior to use. Imported materials should be tested and approved prior to transport to the site. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 31 SURFACE DRAINAGE The site soils are relatively stable with regard to moisture content – volume relationships at their existing moisture contents. Other than the anticipated, post-placement settlement of fills, post-construction soil movement will result primarily from the introduction of water into the soil underlying the proposed structure, hardscaping, and pavements. Based on the site surface and subsurface conditions encountered in this study, we do not anticipate a rise in the local water table sufficient to approach foundation or floor elevations. Therefore, wetting of the site soils likely will result from infiltrating surface waters (precipitation, irrigation, etc.), and water flowing along constructed pathways such as bedding in utility pipe trenches. The following drainage measures should be incorporated as part of project design and during construction. The facility should be observed periodically to evaluate the surface drainage and identify areas where drainage is ineffective. Routine maintenance of site drainage should be undertaken throughout the design life of the project. If these measures are not implemented and maintained effectively, the movement estimates provided in this report could be exceeded. 1) Wetting or drying of the foundation excavations and underslab areas should be avoided during and after construction as well as throughout the improvements’ design life. Permitting increases/variations in moisture to the adjacent or supporting soils may result in a decrease in bearing capacity and an increase in volume change of the underlying soils, and increased total and/or differential movements. 2) Positive surface drainage measures should be provided and maintained to reduce water infiltration into foundation soils. A minimum slope of 12 inches in the first 10 feet in the areas not covered with pavement or concrete slabs should be established. For areas covered with asphalt pavement or concrete slabs, slopes should comply with ADA requirements where required. Increasing slopes to a minimum of 3 percent in the first 10 feet in the areas covered with pavement or concrete slabs will reduce, but not eliminate, the potential for moisture infiltration and subsequent Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 32 volume change of the underling soils. In no case should water be allowed to pond near or adjacent to foundation elements, hardscaping, etc. 3) Drainage should be established and maintained to direct water away from sidewalks and other hardscaping as well as utility trench alignments. Where the ground surface does not convey water away readily, additional post-construction movements and distress should be anticipated. 4) In GROUND’s experience, it is common during construction that in areas of partially completed paving or hardscaping, bare soil behind curbs and gutters, and utility trenches, water is allowed to pond after rain or snow-melt events. Wetting of the subgrade can result in loss of subgrade support and increased settlements / increased heave. By the time final grading has been completed, significant volumes of water can already have entered the subgrade, leading to subsequent distress and failures. The contractor should maintain effective site drainage throughout construction so that water is directed into appropriate drainage structures. 5) Roof downspouts and drains should discharge well beyond the perimeter of the structure foundations (minimum 10 feet) and backfill zones and be provided with positive conveyance off-site for collected waters. 6) Based on our experience with similar facilities, the project may include landscaping/watering near site improvements. Irrigation water – both that applied to landscaped areas and over-spray – is a significant cause of distress to improvements. To reduce the potential for such distress, vegetation requiring watering should be located 10 or more feet from building perimeters, flatwork, or other improvements. Irrigation sprinkler heads should be deployed so that applied water is not introduced near or into foundation/subgrade soils. Landscape irrigation should be limited to the minimum quantities necessary to sustain healthy plant growth. 7) Use of drip irrigation systems can be beneficial for reducing over-spray beyond planters. Drip irrigation can also be beneficial for reducing the amounts of water introduced to foundation/subgrade soils, but only if the total volumes of applied water are controlled with regard to limiting that introduction. Controlling rates of Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 33 moisture increase beneath the foundations, floors, and other improvements should take higher priority than minimizing landscape plant losses. Where plantings are desired within 10 feet of a building, it is GROUND’s opinion that the plants be placed in water-tight planters, constructed either in-ground or above-grade, to reduce moisture infiltration in the surrounding subgrade soils. Planters should be provided with positive drainage and landscape underdrains. As an alternative involving a limited increase in risk, the use of water-tight planters may be replaced by local shallow underdrains beneath the planter beds. Colorado Geological Survey – Special Publication 43 provides additional guidelines for landscaping and reducing the amount of water that infiltrates into the ground. GROUND understands many municipalities require landscaping within 10 feet of building perimeters. Provided that positive, effective surface drainage is initially implemented and maintained throughout the life of the facility and the Owner understands and accepts the risks associated with this requirement, vegetation that requires little to no watering may be located within 10 feet of the building perimeter. 8) Inspections must be made by facility representatives to make sure that the landscape irrigation is functioning properly throughout operation and that excess moisture is not applied. 9) Plastic membranes should not be used to cover the ground surface adjacent to the building as soil moisture tends to increase beneath these membranes. Perforated “weed barrier” membranes that allow ready evaporation from the underlying soils may be used. Cobbles or other materials that tend to act as baffles and restrict surface flow should not be used to cover the ground surface near the foundations. 10) Maintenance as described herein may include complete removal and replacement of site improvements in order to maintain effective surface drainage. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 34 SUBSURFACE DRAINAGE As a component of project civil design, properly functioning, subsurface drain systems (underdrains) can be beneficial for collecting and discharging saturated subsurface waters. Underdrains will not collect water infiltrating under unsaturated (vadose) conditions, or moving via capillarity, however. In addition, if not properly constructed and maintained, underdrains can transfer water into foundation soils, rather than remove it. This will tend to induce heave or settlement of the subsurface soils, and may result in distress. Underdrains can, however, provide an added level of protection against relatively severe post-construction movements by draining saturated conditions near individual structures should they arise, and limiting the volume of wetted soil. It is unknown currently if the current ASD facility has an underdrain system. In GROUND’s opinion the proposed addition does not specifically need to be protected with a perimeter underdrain system in the absence of below grade / basement levels assuming that effective surface drainage measures are implemented. However, if the current facility has an existing underdrain system then that system should be extended to also protect the proposed addition. If below-grade or partially below-grade level(s) are incorporated into project design, then an underdrain system should be included to protect those portions of the building. Damp-proofing should be applied to the exteriors of below-grade elements. The provision of Tencate MiraFi® G- Series backing (or comparable wall drain provisions) on the exteriors of (some) below- grade elements may be appropriate, depending on the intended use. If a (partially) below-grade level is limited in extent, the underdrain system, etc., may be local to that area. General Geotechnical Parameters for Underdrain Design: Where an underdrain system is included in project drainage design, it should be designed in accordance with the parameters below. The actual underdrain layout, outlets, and locations should be developed by a civil engineer. An underdrain system should be tested by the contractor after installation and after placement and compaction of the overlying backfill to verify that the system functions properly. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 35 1) An underdrain system for a building should consist of perforated, rigid, PVC collection pipe at least 4 inches in diameter, non-perforated, rigid, PVC discharge pipe at least 4 inches in diameter, free-draining gravel, and filter fabric, as well as a waterproof membrane. 2) The free-draining gravel should contain less than 5 percent passing the No. 200 Sieve and more than 50 percent retained on the No. 4 Sieve, and have a maximum particle size of 2 inches. Each collection pipe should be surrounded on the sides and top (only) with 6 or more inches of free-draining gravel. 3) The gravel surrounding the collection pipe(s) should be wrapped with filter fabric (MiraFi 140N® or the equivalent) to reduce the migration of fines into the drain system. 4) The waterproof membrane should underlie the gravel and pipe, and be attached to the foundation, grade beam, or stem wall. 5) The underdrain system should be designed to discharge at least 10 gallons per minute of collected water. 6) The high point(s) for the collection pipe flow lines should be below the lowest foundation bearing elevation. Multiple high points can be beneficial to reducing the depths to which the system would be installed. Pipe gradients also should be designed to accommodate at least 1 inch of differential movement after installation along a 50-foot run. 7) Underdrain ‘clean-outs’ should be provided at intervals of no more than 100 feet to facilitate maintenance of the underdrains. Clean-outs also should be provided at collection and discharge pipe elbows of 60 degrees or more. 8) The underdrain discharge pipes should be connected to one or more sumps from which water can be removed by pumping, or to outlet(s) for g ravity discharge. We suggest that collected waters be discharged directly into the storm sewer system, if possible. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 36 PAVEMENT SECTIONS A pavement section is a layered system designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and traffic loadings. Standard practice in pavement design describes a typical flexible pavement section as a “20-year” design pavement. However, a pavement should not be anticipated to remain in satisfactory condition without routine maintenance and rehabilitation procedures performed throughout the life of the pavement. Pavement sections for the private pavements at the subject facility were developed in general accordance with the guidelines and procedures of the American Association of State Highway and Transportation Officials (AASHTO) and local pavement construction practice. Subgrade Materials Our data indicate that the shallow soils at the site classification ranges from A-4 to A-6 soils in accordance with the AASHTO classification system. Such soils generally provide poor subgrade support. A resilient modulus value of 3,025 psi was estimated to be representative of the soils at the project site and was used in the development of the pavement sections. It is important to note that significant decreases in soil support have been observed as the moisture content increases above the optimum. Pavements that are not properly drained may experience a loss of the soil support and subsequent reduction in pavement life. Anticipated Traffic Project-specific traffic loads had not been provided to GROUND at the time of preparation of this report. Therefore, assumed traffic loadings were used to develop the pavement section alternatives based on our experience with similar facilities. An ESAL value of 36,500 (corresponding to an EDLA value of 5 for a 20-year design life) was assumed for parking stalls for light vehicles (automobiles and similar). An ESAL value of 73,000 (corresponding to an EDLA value of EDLA of 10 for a 20-year design life) was assumed for the drive lanes of light vehicles. An ESAL value of 219,000 (corresponding to an EDLA value of 30 for a 20-year design life) was assumed for the Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 37 heavy duty traffic such as bus lanes, trash collection routes, fire truck routes, and other pavement areas subject to heavy vehicle traffic. If design traffic loadings differ significantly from these assumed values, GROUND should be notified to re-evaluate the pavement sections below. Pavement Sections The soil resilient modulus and the ESAL values were used to determine the required structural number for the project pavements which then was then used to develop the pavement sections based on the DARWin™ computer program that solves the 1993 AASHTO pavement equations. A reliability level of 80 percent and a terminal serviceability of 2.0 were utilized for design of the pavement sections. A structural coefficient of 0.44 was used for hot bituminous asphalt and 0.1 1 was used for aggregate base course. The minimum pavement sections for a 20-year design are tabulated below. Minimum Pavement Sections Location Full Depth Asphalt Composite Section Rigid Section (inches Asphalt) (inches Asphalt / inches Aggregate Base) (inches Concrete / inches Aggregate Base) Light Vehicle Parking Stalls 5 ½ 4 ½ / 8 6 / 6 Light Vehicle Drive Lanes / Niswender Drive 7 ½ 5 / 10 6 / 6 Fire Truck Routes and Bus Loop Routes 8 ½ 6 / 10 7 / 6 Pavement areas subjected to high turning stresses or frequent starting or stopping of heavy vehicles such as busses, trucks, trash collection areas, should be provided with rigid pavements consisting of 7 or more inches of portland cement concrete underlain by 6 inches of properly compacted CDOT Class 5 or 6 Aggregate Base Course. In our experience, asphalt pavements will not perform as well as rigid pavement in areas of high turning stresses, prolonged static loading, or frequent starting and stopping of heavy vehicles, and additional maintenance costs should be anticipated if the asphalt sections are utilized in these areas. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 38 Pavement Materials Asphalt pavement should consist of a bituminous plant mix composed of a mixture of aggregate and bituminous material. Asphalt mixture(s) should meet the requirements of a job-mix formula established by a qualified engineer as well as applicable municipal design requirements. Based on our experience with similar projects, aggregate gradation S (nominal ¾-inch) and binder type PG58-28 / PG64-22 should be used for the lower lift(s), and gradation SX (nominal ½-inch) and binder type PG58-28 / PG64-22 for the top lift. Other binder types may be appropriate based on the Larimer County Facilities Department’s performance expectations, experience, and project budget. For the lower (S) lift(s), lift thicknesses generally should be between 2¼ and 3½ inches. The top (SX) lift generally should be between 2 and 3 inches in thickness. Aggregate base material should meet the criteria of CDOT Class 5 or 6 Aggregate Base Course. Base course should be placed in and compacted in accordance with the standards in the Project Earthwork section of this report. Pavement concrete should consist of a plant mix composed of a mixture of aggregate, portland cement and appropriate admixtures meeting the requirements of a job-mix formula established by a qualified engineer as well as applicable municipal design requirements design requirements. Concrete should have a minimum modulus of rupture of third point loading of 650 psi. Normally, concrete with a 28-day compressive strength of 4,500 psi should develop this modulus of rupture value. The concrete should be air-entrained with approximately 6 percent air and should have a minimum cement content of 6 sacks per cubic yard. Maximum allowable slump should be 4 inches. These concrete mix design criteria should be coordinated with other project requirements including any criteria for sulfate resistance presented in the Water-Soluble Sulfates section of this report. To reduce surficial spalling resulting from freeze-thaw cycling, we suggest that pavement concrete meet the requirements of CDOT Class P concrete. In addition, the use of de-icing salts on concrete pavements during the first winter after construction will increase the likelihood of the development of scaling. Placement of flatwork concrete during cold weather so that it is exposed to freeze-thaw cycling before it is fully cured also increases its vulnerability to scaling. Concrete placing during cold weather conditions should be blanketed or tented to allow full curing. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 39 Depending on the weather conditions, this may result in 3 to 4 weeks of curing, and possibly more. Concrete pavements should contain sawed or formed joints. CDOT and various industry groups provide guidelines for proper design and concrete construction and associated jointing. In areas of repeated turning stresses, such as truck loading and unloading areas, the concrete pavement joints should be fully tied and doweled. Example layouts for joints, as well as ties and dowels, which may be applicable, can be found in CDOT’s M standards, found at the CDOT website: http://www.dot.state.co.us/DesignSupport/. PCA, ACI, and ACPA publications also provide useful guidance in these regards. Joint spacings less than the 15-foot maximum indicated in in CDOT’s M standards, e.g., 10 feet or 12 feet, may be beneficial to reduce concrete cracking. Subgrade Preparation Subgrade preparation to a depth of 12 inches is typical in the front range area however, due to the swell potential measured in the overburden clay materials the contractor should prepare the subgrade to a depth of at least 24 inches. However, greater depths of preparation may be required to establish stability depending on the conditions exposed during construction. Subgrade preparation should extend the full width of the pavement from back-of-curb to back-of-curb. The subgrade for any sidewalks and other project hardscaping also should be prepared in the same manner. Geotechnical criteria for fill placement and compaction are provided in the Project Earthwork section of this report. The contractor should be prepared to either dry the subgrade materials or moisten them, as needed, prior to compaction. A geotechnical engineer should be retained to evaluate subgrade conditions and provide recommendations to address any areas that are unstable. Additional mitigation such as chemical stabilization with cement or fly ash, rock stabilization, and/or utilization of geogrid type stabilization may be necessary. If chemical stabilization is utilized, a pavement thickness credit on the order of one inch of asphalt or 4 inches of aggregate base course can typically be applied to the pavement thicknesses. Proof Rolling Immediately prior to paving, the subgrade should be proof rolled with a heavily loaded, pneumatic tired vehicle. Areas that show excessive deflection during proof rolling should be excavated and replaced and/or stabilized. Areas allowed to pond Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 40 prior to paving will require significant re-working prior to proof-rolling. Establishment of a firm paving platform (as indicated by proof rolling) is an additional requirement beyond proper fill placement and compaction. It is possible for soils to be compacted within the limits indicated in the Project Earthwork section of this report and fail proof rolling, particularly in the upper range of moisture content. Additional Observations The collection and diversion of surface drainage away from paved areas is extremely important to the satisfactory performance of the pavements. The subsurface and surface drainage systems should be carefully designed to ensure removal of the water from paved areas and subgrade soils. Allowing surface waters to pond on pavements will cause premature pavement deterioration. Where topography, site constraints, or other factors limit or preclude adequate surface drainage, pavements should be provided with edge drains to reduce loss of subgrade support. The long -term performance of the pavement also can be improved greatly by proper backfilling and compaction behind curbs, gutters, and sidewalks so that ponding is not permitted and water infiltration is reduced. Landscape irrigation in planters adjacent to pavements and in “island” planters within paved areas should be carefully controlled or differential heave and/or rutting of the nearby pavements will result. Drip irrigation systems are suggested for such planters to reduce over-spray and water infiltration beyond the planters. Enclosing the soil in the planters with plastic liners and providing them with positive drainage also will reduce differential moisture increases in the surrounding subgrade soils. In our experience, infiltration from planters adjacent to pavements is a principal source of moisture increase beneath those pavements. This wetting of the subgrade soils from infiltrating irrigation commonly leads to loss of subgrade support for the pavement with resultant accelerating distress, loss of pavement life and increased maintenance costs. This is particularly the case in the later stages of project construction after landscaping has been emplaced but heavy construction traffic has not ended. Heavy vehicle traffic over wetted subgrade commonly results in rutting and pushing of flexible pavements, and cracking of rigid pavements. In relatively flat areas where design drainage gradients necessarily are small, subgrade settlement can obstruct proper drainage and yield increased infiltration, exaggerated distress, etc. (These considerations apply to project flatwork, as well.) Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 41 Also, GROUND’s experience indicates that longitudinal cracking is common in asphalt- pavements generally parallel to the interface between the asphalt and concrete structures such as curbs, gutters, or drain pans. Distress of this type is likely to occur even where the subgrade has been prepared properly and the asphalt has been compacted properly. The anticipated traffic loading does not include excess loading conditions imposed by heavy construction vehicles. Consequently, heavily loaded concrete, lumber, and building material trucks can have a detrimental effect on the pavement. Most pavements will not remain in satisfactory condition and achieve their “design lives” without regular maintenance and rehabilitation procedures performed throughout the life of the pavement. Maintenance and rehabilitation measures preserve, rather than improve, the structural capacity of the pavement structure. Therefore, an effective program of regular maintenance should be developed and implemented to seal cracks, repair distressed areas, and perform thin overlays throughout the lives of the pavements. The greatest benefit of pavement overlaying will be achieved by overlaying sound pavements that exhibit little or no distress. Crack sealing should be performed at least annually and a fog seal/chip seal program should be performed on the pavements every 3 to 4 years. After approximately 8 to 10 years after construction, patching, additional crack sealing, and asphalt overlay may be required. Prior to overlays, it is important that all cracks be sealed with a flexible, rubberized crack sealant in order to reduce the potential for propagation of the crack through the overlay. If actual traffic loadings exceed the values used for development of the pavement sections, however, pavement maintenance measures will be needed on an accelerated schedule. Temporary Fire Access Routes Commonly, construction sites are required by local fire departments to provide temporary access for emergency response. It has been GROUND’s experience these access drives are to provide support for trucks weighing up to 90,000 pounds and are typically desired to be gravel/aggregate-surfaced. Based on our experience, a temporary section consisting of at least 12 inches of material meeting the requirements of CDOT Class 5 or Class 6 Aggregate Base Course. In areas where soft soils have been observed a layer of stabilization Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 42 geotextile/geofabric, such as Mirafi® RS380i or the equivalent, could be utilized under the 12 inches of base. The owner should understand that this section is for temporary access during construction only and is not a replacement or an equal alternate to the pavement section(s) that was indicated previously. The aggregate base course placed for this purpose should be compacted to at least 95 percent of the maximum modified Proctor dry density. It should be noted that the aggregate base course sections indicated above are not intended to support fire truck outriggers without cribbing or similar measures. The aggregate comprising such a wearing course will be displaced and rutted under the loads imposed by heavy vehicles. Therefore, regular maintenance including re-grading and application of additional aggregate should be implemented to ensure proper drainage, repair distressed/damaged areas, and re-establish grades. Additionally, the ability of a temporary aggregate-surfaced route to accommodate loads as indicated above is directly related to the quality of the subgrade materials on which the aggregate is placed, not only on the aggregate section. If water infiltrates these areas, additional rutting and other distress, including a reduction in capacity, will result, requiring additional maintenance. PEDESTRIAN FLATWORK We anticipate that portions of the site will be provided with concrete flatwork. Like other site improvements, flatwork will experience post-construction movements as soil moisture contents increase after construction and distress likely will result. The following measures will help to reduce damages to these improvements, but will not prevent all movements. Critical flatwork, which may include flatwork at entrances and exits, should be constructed as a slab-on-grade floor in a similar manner to project f loors. Such areas should be identified by the owner. 1) The subgrade under exterior flatwork or other (non-building) site improvements should be scarified to a depth of 24 or more inches. The scarified soil should be replaced as properly moisture-conditioned and compacted fill as outlined in the Project Earthwork section of this report. This depth of rework will not mitigate the swell potential at the project site, but will tend to make movements due to swelling subgrade materials more uniform. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 43 Greater depths of subgrade preparation will tend to reduce the extent and frequency of maintenance for these surficial improvements. 2) Prior to placement of flatwork, a proof roll should be performed to identify areas that exhibit instability and deflection. The deleterious soils in these areas should be removed and replaced with properly compacted fill. The contractor should take care to achieve and maintain compaction behind curbs to reduce differential sidewalk settlements. Passing a proof roll is an additional req uirement to placing and compacting the subgrade fill soils within the specified ranges of moisture content and relative compaction in the Project Earthwork section of this report. Subgrade stabilization may be cost-effective in this regard. 3) Flatwork should be provided with control joints extending to an effective depth and spaced no more than 10 feet apart, both ways. Narrow flatwork, such as sidewalks, likely will require more closely spaced joints. 4) In no case should exterior flatwork extend to under any portion of the building where there is less than 2 inches of vertical clearance between the flatwork and any element of the building. Exterior flatwork in contact with brick, rock facades, or any other element of the building can cause damage to the structure if the flatwork experiences movements. Construction and Drainage Between Buildings and Pavements Proper design, drainage, construction and maintenance of the areas between individual buildings and parking/driveway areas are critical to the satisfactory performance of the project. Sidewalks, entranceway slabs and roofs, fountains, raised planters and other highly visible improvements commonly are installed within these zones, and distress in or near these improvements is common. Commonly, proper soil preparation in these areas receives little attention during overlot construction because they fall between the building and pavement areas which typically are built with heavy equipment. Subsequent landscaping and hardscape installation often is performed by multiple sub-contractors with light or hand equipment, and necessary over-excavation and soil processing is not performed. Consequently, subgrade soil conditions commonly deviate significantly from specified ranges. Therefore, the contractor should take particular care with regard to proper subgrade preparation in the immediate building exteriors. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 44 Concrete Scaling Climatic conditions in the project area including relatively low humidity, large temperature changes and repeated freeze – thaw cycles, make it likely that project sidewalks and other exterior concrete will experience surficial scaling or spalling. The likelihood of concrete scaling can be increased by poor workmanship during construction, such as ‘over-finishing’ the surfaces. In addition, the use of de-icing salts on exterior concrete flatwork, particularly during the first winter after construction, will increase the likelihood of scaling. Even use of de-icing salts on nearby roadways, from where vehicle traffic can transfer them to newly placed concrete, can be sufficient to induce scaling. Typical quality control / quality assurance tests that are performed during construction for concrete strength, air content, etc., do not provide information with regard to the properties and conditions that give rise to scaling. We understand that some municipalities require removal and replacement of concrete that exhibits scaling, even if the material was within specification and placed correctly. The contractor should be aware of the local requirements and be prepared to take measures to reduce the potential for scaling and/or replace concrete that scales. In GROUND’s experience, the measures below can be beneficial for reducing the likelihood of concrete scaling. Which measures, if any, used should be based on cost and the owner’s tolerance for risk and maintenance. It must be understood, however, that because of the other factors involved, including weather conditions and workmanship, surface damage to concrete can develop, even where all of these measures were followed. Also, the mix design criteria should be coordinated with other project requirements including criteria for sulfate resistance presented in the Water- Soluble Sulfates section of this report. 1) Maintaining a maximum water/cement ratio of 0.45 by weight for exterior concrete mixes. 2) Include Type F fly ash in exterior concrete mixes as 20 percent of the cementitious material. 3) Specify a minimum, 28-day, compressive strength of 4,500 psi for all exterior concrete. 4) Including ‘fibermesh’ in the concrete mix also may be beneficial for reducing surficial scaling. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 45 5) Cure the concrete effectively at uniform temperature and humidity. This commonly will require fogging, blanketing and/or tenting, depending on the weather conditions. As long as 3 to 4 weeks of curing may be required, and possibly more. 6) Avoid placement of concrete during cold weather so that it is not exposed to freeze-thaw cycling before it is fully cured. 7) Avoid the use of de-icing salts on given reaches of flatwork through the first winter after construction. We understand that sometimes it is not practical to implement some of these measures for reducing scaling due to safety considerations, project scheduling, etc. In such cases, where these measures are not implemented, additional costs for flatwork maintenance or reconstruction should be incorporated into project budgets. Frost and Ice Considerations Nearly all soils other than relatively coarse, clean, granular materials are susceptible to loss of density if allowed to become saturated and exposed to freezing temperatures and repeated freeze – thaw cycling. The formation of ice in the underlying soils can result in heaving of pavements, flatwork, and other hardscaping (“ice jacking”) in sustained cold weather up to 2 inches or more. This heaving can develop relatively rapidly. A portion of this movement typically is recovered when the soils thaw, but due to loss of soil density, some degree of displacement will remain. This can result even where the subgrade soils were prepared properly. Where hardscape movements are a design concern, e.g., at doorways, replacement of the subgrade soils with 3 or more feet of clean, coarse sand or gravel should be considered or supporting the element on foundations similar to the building and spanning over a void. Detailed guidance in this regard can be provided upon request. It should be noted that where such open graded granular soils are placed, water can infiltrate and accumulate in the subsurface relatively easily, which can lead to increased settlement or heave from factors unrelated to ice formation. Therefore, where a section of open graded granular soils are placed, a local underdrain system should be provided to discharge collected water. GROUND will be available to discuss these concerns upon request. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 46 CLOSURE Geotechnical Review The author of this report or a GROUND principal should be retained to review project plans and specifications to evaluate whether they comply with the intent of the measures discussed in this report. The review should be requested in writing. The geotechnical conclusions and parameters presented in this report are contingent upon observation and testing of project earthworks by representatives of GROUND. If another geotechnical consultant is selected to provide materials testing, then that consultant must assume all responsibility for the geotechnical aspects of the project by concurring in writing with the parameters in this report, or by providing alternative parameters. Materials Testing Larimer County Facilities Department should consider retaining a geotechnical engineer to perform materials testing during construction. The performance of such testing or lack thereof, however, in no way alleviates the burden of the contractor or subcontractor from constructing in a manner that conforms to applicable project documents and industry standards. The contractor or pertinent subcontractor is ultimately responsible for managing the quality of his work; furthermore, testing by the geotechnical engineer does not preclude the contractor from obtaining or providing whatever services that he deems necessary to complete the project in accordance with applicable documents. Limitations This report has been prepared for the Larimer County Facilities Department as it pertains to design and construction of the proposed addition to the Larimer County Alternative Sentencing Department as described herein. It may not contain sufficient information for other parties or other purposes. In addition, GROUND has assumed that project construction will commence by spring/summer 2021. Any changes in project plans or schedule should be brought to the attention of a geotechnical engineer, in order that the geotechnical conclusions in this report may be re-evaluated and, as necessary, modified. The geotechnical conclusions in this report relied upon subsurface exploration at a limited number of exploration points, as shown in Figure 1, as well as the means and methods described herein. Subsurface conditions were interpolated between and Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 47 extrapolated beyond these locations. It is not possible to guarantee the subsurface conditions are as indicated in this report. Actual conditions exposed during construction may differ from those encountered during site exploration. If during construction, surface, soil, bedrock, or groundwater conditions appear to be at variance with those described herein, a geotechnical engineer should be retained at once, so that re-evaluation of the conclusions for this site may be made in a timely manner. In addition, a contractor who obtains information from this report for development of his scope of work or cost estimates may find the geotechnical information in this report to be inadequate for his purposes or find the geotechnical conditions described herein to be at variance with his experience in the greater project area. The contractor is responsible for obtaining the additional geotechnical information that is necessary to develop his workscope and cost estimates with sufficient precision. This includes current depths to groundwater, etc. ALL DEVELOPMENT CONTAINS INHERENT RISKS. It is important that ALL aspects of this report, as well as the estimated performance (and limitations with any such estimations) of proposed improvements are understood by the Larimer County Facilities Department. Utilizing these criteria and measures herein for planning, design, and/or construction constitutes understanding and acceptance of the conclusions with regard to risk and other information provided herein, associated improvement performance, as well as the limitations inherent within such estimates. If any information referred to herein is not well understood, then the Larimer County Facilities Department, or members of the design team, should contact the author or a GROUND principal immediately. We will be available to meet to discuss the risks and remedial approaches presented in this report, as well as other potential approaches, upon request. GROUND makes no warranties, either expressed or implied, as to the professional data, opinions or conclusions contained herein. This document, together with the concepts and conclusions presented herein, as an instrument of service, is intended only for the specific purpose and client for which it was prepared. Re-use of, or improper reliance on this document without written authorization and adaption by GROUND Engineering Consultants, Inc., shall be without liability to GROUND Engineering Consultants, Inc. Subsurface Exploration Program Larimer County: Alternate Sentencing Department Fort Collins, Colorado Job No. 20-0047 GROUND Engineering Consultants, Inc. Page 48 GROUND appreciates the opportunity to complete this portion of the project and welcomes the opportunity to provide Larimer County Facilities Department with a proposal for construction observation and materials testing. Sincerely, GROUND Engineering Consultants, Inc. Kelsey Van Bemmel, P.E. Reviewed by Brian H. Reck, P.G., C.E.G., P. E. 1LOCATION OF TEST HOLESJOB NO.:20-0047FIGURE:1ENGINEERINGIndicates test hole number and approximate location.NOT TO SCALESITE PLAN PROVIDED BY CLIENTP-312345678P-1P-2 1LOCATION OF TEST HOLESJOB NO.:20-0047FIGURE:1ENGINEERINGIndicates test hole number and approximate location.NOT TO SCALEGOOGLE EARTH AERIAL IMAGE (11/8/2019)P-312345678P-1P-2 4,875 4,880 4,885 4,890 4,895 4,900 4,905 4,910 4,915 4,875 4,880 4,885 4,890 4,895 4,900 4,905 4,910 4,915 - 11/12 - 5/12 - 15-20-15 - 50/12 - 50/4 - 12/12 - 7/12 - 5-6-6 - 8/12 - 14/12 - 20-22-25 - 16/12 - 23-26-24 - 18-20-18 - 23/12 - 17-23-28 - 6-7-6 - 11/12 - 20-20-13 - 9-22-35 - 50/4 - 10/12 - 30/12 - 10-14-16 - 13/12 - 9/12 - 4-4-7 - 50/3 - 50/2 - 50/3 LOGS OF THE TEST HOLES Elevation (ft)CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 PROJECT LOCATION:Fort Collins, CO 1 ELEV. 4912.8 2 ELEV. 4913.4 3 ELEV. 4913 4 ELEV. 4911.9 5 ELEV. 4911.9 6 ELEV. 4911.2 7 ELEV. 4910.8 8 ELEV. 4911.1 4,875 4,880 4,885 4,890 4,895 4,900 4,905 4,910 4,915 4,875 4,880 4,885 4,890 4,895 4,900 4,905 4,910 4,915 - 17/12 - 6-7-8 - 27/12 - 18/12 - 10/12 LOGS OF THE TEST HOLES Elevation (ft)CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 PROJECT LOCATION:Fort Collins, CO P-1 ELEV. 4913 P-2 ELEV. 4913 P-3 ELEV. 4913 1. Test holes were drilled on 10/7/2020 with 6" hollow stem auger. 2. Locations of the test holes were determined approximately by pacing from features shown on the site plan provided. 3. Elevations of test holes were surveyed by a subcontractor and the logs of test holes are hung to elevation. 4. The test hole locations and elevations should be considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the test hole logs represent the approximate boundaries between material types and the transitions may be gradual. 6. Groundwater level readings shown on the logs were made at the time and under the conditions indicated. Fluctuations in the water level may occur with time. 7. The material descriptions on these logs are for general classification purposes only. See full text of this report for descriptions of the site materials & related information. 8. All test holes were immediately backfilled upon completion of drilling, unless otherwise specified in this report. JOB NO:20-0047 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition Modified California Liner Sampler 23 / 12 Drive sample blow count indicates 23 blows of a 140 pound hammer falling 30 inches were required to drive the sampler 12 inches. Standard Penetration Test Sampler 20-25-30 Drive sample blow count, indicates 20, 25, and 30 blows of a 140 pound hammer falling 30 inches were required to drive the sampler 18 inches in three 6 inch increments. Water Level at Time of Drilling, or as Shown NOTE: See Detailed Logs for Material descriptions. LEGEND AND NOTES No Value Non-Plastic SAMPLER SYMBOLS Water Level at End of Drilling, or as Shown Water Level After 24 Hours, or as Shown NV NP ABBREVIATIONS MATERIAL SYMBOLSMATERIAL SYMBOLS NOTES CONCRETE TOPSOIL ROAD BASE FILL CLAY SAND AND GRAVEL CLAYSHALE JOB NO.:20-0047 FIGURE:5 Axial Capacity Reductions as Functions of Closely Spaced Pier / Pile Elements. The graph above provides estimated reductions in total axial capacity for closely spaced piers. Pier / Pile reductions should be interpolated from the graph above. ENGINEERING AXIAL CAPACITY REDUCTION FACTORS FOR CLOSELY SPACED PIERS / PILES JOB NO.:20-0047 FIGURE:6 Lateral Capacity Reduction (p multipliers) as Functions of Closely Spaced Pier / Pile Elements The "1st" or "lead" pier / pile is the element that leads movement in the direction that the lateral load will cause the piers to deflect, as shown. For lateral loads oriented perpendicular to the row of piers / piles, use the 1st pier / pile p-multiplier. Pier / pile reductions should be interpolated from the graph above. Figure to be reproduced in color for clarity. ENGINEERING LATERAL CAPACITY REDUCTION FACTORS FOR CLOSELY SPACED PIERS / PILES Natural Natural Test Moisture Dry Volume Surcharge Hole Content Density Change Pressure No.(feet)(%)(pcf)(%)(%)(%) (%)(psf)(psi)(ksf) 1 4 19.4 110.2 17 83 35 13 -0.2 500 --(CL)s A-6 (10)CLAY with sand 1 29 16.5 SD 6 48 46 27 11 ----SC A-6 (2)Clayshale Bedrock 1 34 12.6 118.6 3 97 43 17 --95.9 13.81 CL A-7-6 (19)Clayshale Bedrock 2 3 19.5 108.9 20 80 36 15 ----(CL)s A-6 (11)CLAY with sand 2 13 8.5 SD 39 54 7 NV NP ----(SP-SM)g A-1-a (0)poorlgy graded silty SAND with gravel 3 2 20.1 104.8 19 81 35 16 ----(CL)s A-6 (12)Fill: CLAY with sand 3 7 20.0 107.1 25 75 42 21 -0.2 1000 --(CL)s A-7-6 (15)CLAY with sand 4 4 17.3 108.6 18 82 39 19 3.3 500 --(CL)s A-6 (15)CLAY with sand 4 14 8.4 SD 44 49 7 NV NP ----(SP-SM)g A-1-a (0)poorlgy graded silty SAND with gravel 5 3 7.7 120.7 42 58 26 8 5.8 500 --s(CL)A-4 (2)sandy CLAY 6 30 12.0 118.6 4 96 43 18 -0.6 3000 --CL A-7-6 (20)Clayshale Bedrock 7 2 18.6 107.9 16 84 39 16 ----(CL)s A-6 (14)CLAY with sand 8 9 17.9 113.1 25 75 33 13 ----(CL)s A-6 (8)CLAY with sand P-2 2 8.8 SD 1 28 71 40 17 S/D ---(CL)s A-6 (11)CLAY with sand SD = Sample disturbed, NV = No value, NP = Non-plastic Job No 20-0047 Depth Larimer County Alternative Sentencing Department Additions TABLE 1: SUMMARY OF LABORATORY TEST RESULTS Gradation USCS Equivalent Classification Sample Location Sample Description AASHTO Equivalent Classification (Group Index) Swell/ConsolidationAtterberg Limits Unconfined Compressive StrengthGravelSandFinesLiquid Limit Plasticity Index Water Test Soluble Hole Sulfates No.(feet)(%)(mv)(ohm-cm) 1 29 0.07 ----SC A-6 (2)Clayshale Bedrock 3 2 0.21 8.6 -88 Positive 3,128 (CL)s A-6 (12)Fill: CLAY with sand Job No 20-0047 Larimer County Alternative Sentencing Department Additions Redox Potential AASHTO Equivalent Classification (Group Index) USCS Equivalent Classification ResistivitySulfide ReactivityDepth Sample Location pH Sample Description TABLE 2: SUMMARY OF SOIL CORROSION TEST RESULTS Appendix A Detailed Logs of the Test Holes (CL)s SC CL13.81 11/12 5/12 15-20- 15 50/12 50/4 13 11 17 35 27 43 19.4 16.5 12.6 110.2 SD 118.6 83 46 97 -0.2 (500) TOPSOIL CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 13 feet at time of drilling. CLAYSHALE:Medium to highly plastic, fine grained, slightly moist to moist, hard to very hard, and brown to gray-brown to dark gray in color. Bottom of borehole at Approx. 34.33 feet.Graphic LogElevation(ft)4913 4908 4903 4898 4893 4888 4883 Depth(ft)0 5 10 15 20 25 30 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 1 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s (SP-SM)g 12/12 7/12 5-6-6 15 NP 36 NV 19.5 8.5 108.9 SD 80 7 TOPSOIL CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 12.5 feet at time of drilling. Bottom of borehole at Approx. 25 feet.Graphic LogElevation(ft)4913 4908 4903 4898 4893 4888 Depth(ft)0 5 10 15 20 25 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 2 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s (CL)s 8/12 14/12 20-22- 25 16 21 35 42 20.1 20.0 104.8 107.1 81 75 -0.2 (1000) TOPSOIL FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. Groundwater encountered at 12 feet at time of drilling. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Bottom of borehole at Approx. 25 feet.Graphic LogElevation(ft)4913 4908 4903 4898 4893 4888 Depth(ft)0 5 10 15 20 25 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 3 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s (SP-SM)g 16/12 23-26- 24 18-20- 18 19 NP 39 NV 17.3 8.4 108.6 SD 82 7 3.3 (500) TOPSOIL FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 11.5 feet at time of drilling. Bottom of borehole at Approx. 25 feet.Graphic LogElevation(ft)4912 4907 4902 4897 4892 4887 Depth(ft)0 5 10 15 20 25 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 4 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 s(CL)23/12 17-23- 28 6-7-6 8267.7 120.7 58 5.8 (500) TOPSOIL FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 12.5 feet at time of drilling. Bottom of borehole at Approx. 25 feet.Graphic LogElevation(ft)4912 4907 4902 4897 4892 4887 Depth(ft)0 5 10 15 20 25 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 5 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 CL 11/12 20-20- 13 9-22- 35 50/4 184312.0 118.6 96 -0.6 (3000) FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 11 feet at time of drilling. CLAYSHALE:Medium to highly plastic, fine grained, slightly moist to moist, hard to very hard, and brown to gray-brown to dark gray in color. Bottom of borehole at Approx. 30.33 feet.Graphic LogElevation(ft)4911 4906 4901 4896 4891 4886 4881 Depth(ft)0 5 10 15 20 25 30 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 6 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s10/12 30/12 10-14- 16 163918.6 107.9 84 CONCRETE: Approximately 4.75 inches of Concrete. FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 11.5 feet at time of drilling. CLAYSHALE:Medium to highly plastic, fine grained, slightly moist to moist, hard to very hard, and brown to gray-brown to dark gray in color. Bottom of borehole at Approx. 30 feet.Graphic LogElevation(ft)4911 4906 4901 4896 4891 4886 4881 Depth(ft)0 5 10 15 20 25 30 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 7 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s 13/12 9/12 4-4-7 50/3 50/2 50/3 133317.9 113.1 75 CONCRETE: Approximately 7 inches of Concrete. FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. SAND withGRAVEL:low to non-plastic, fine to coarse grained with gravels and local cobbles, slightly moist to very moist, medium dense to very dense, and were brown to gray-brown in color. Groundwater encountered at 12.5 feet at time of drilling. CLAYSHALE:Medium to highly plastic, fine grained, slightly moist to moist, hard to very hard, and brown to gray-brown to dark gray in color. Bottom of borehole at Approx. 35.25 feet.Graphic LogElevation(ft)4911 4906 4901 4896 4891 4886 4881 4876 Depth(ft)0 5 10 15 20 25 30 35 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE 8 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 17/12 6-7-8 TOPSOIL FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. Bottom of borehole at Approx. 5.5 feet.Graphic LogElevation(ft)4913 4908 Depth(ft)0 5 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE P-1 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 (CL)s27/12 17408.8 SD 71 ROAD BASE: Approximately 6 inches of road base. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. Bottom of borehole at Approx. 3 feet.Graphic LogElevation(ft)4913 Depth(ft)0 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE P-2 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047 18/12 10/12 FILL:Sandy clay were, low to moderately plastic, fine to coarse grained, moist, and brown in color. CLAY:Locally sandy, fine to coarse grained with local gravel, low to moderately plastic, dry to very moist, medium stiff to stiff, and were brown to light brown in color with local caliche deposits. Bottom of borehole at Approx. 9 feet.Graphic LogElevation(ft)4913 4908 Depth(ft)0 5 Sample TypeUSCSEquivalentClassificationUnconfinedCompressiveStrength(ksf)Blow CountAtterberg Limits PlasticityIndexLiquid LimitNatural MoistureContent (%)Natural DryDensity (pcf)Percent PassingNo. 200 SieveSwell/Consolidation(%) at SurchargePressure (psf)Material Descriptions and Drilling Notes PAGE 1 OF 1 TEST HOLE P-3 PROJECT LOCATION:Fort Collins, CO CLIENT:Larimer County Facilites Management PROJECT NAME:Larimer County ASD Addition JOB NO:20-0047