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HomeMy WebLinkAboutUPTOWN PLAZA - FDP - FDP140010 - SUBMITTAL DOCUMENTS - ROUND 1 - RECOMMENDATION/REPORTGeotechnical Engineering Report Uptown Plaza 1501 West Elizabeth Street Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Prepared for: D.K. Investments, Inc. Windsor, Colorado Prepared by: Terracon Consultants, Inc. Fort Collins, Colorado TABLE OF CONTENTS Page EXECUTIVE SUMMARY ............................................................................................................ i 1.0 INTRODUCTION .............................................................................................................1 2.0 PROJECT INFORMATION .............................................................................................2 2.1 Project Description ...............................................................................................2 2.2 Site Location and Description...............................................................................2 3.0 SUBSURFACE CONDITIONS ........................................................................................3 3.1 Typical Subsurface Profile ...................................................................................3 3.2 Laboratory Testing ...............................................................................................3 3.3 Groundwater ........................................................................................................3 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................4 4.1 Geotechnical Considerations ...............................................................................4 4.1.1 Existing, Undocumented Fill .....................................................................4 4.1.2 Shallow Groundwater ...............................................................................5 4.1.3 Expansive Soils ........................................................................................5 4.2 Earthwork.............................................................................................................5 4.2.1 Site Preparation ........................................................................................6 4.2.2 Demolition ................................................................................................6 4.2.3 Excavation ................................................................................................6 4.2.4 Subgrade Preparation ...............................................................................7 4.2.5 Fill Materials and Placement ......................................................................7 4.2.6 Compaction Requirements ........................................................................9 4.2.7 Utility Trench Backfill .................................................................................9 4.2.8 Grading and Drainage .............................................................................10 4.2.9 Exterior Slab Design and Construction .....................................................11 4.2.10 Corrosion Protection ................................................................................11 4.3 Foundations .......................................................................................................11 4.3.1 Drilled Piers Bottomed in Bedrock - Design Recommendations ..............12 4.3.2 Drilled Piers Bottomed in Bedrock - Construction Considerations ...........12 4.3.3 Spread Footings - Design Recommendations .........................................13 4.3.4 Spread Footings - Construction Considerations ......................................15 4.4 Seismic Considerations......................................................................................15 4.5 Floor Systems ....................................................................................................15 4.5.1 Floor System - Design Recommendations ..............................................16 4.5.2 Floor Systems - Construction Considerations .........................................17 4.6 Hydraulic Conductivity Testing ...........................................................................17 4.6.1 Hydraulic Conductivity – Field Investigation ............................................17 4.6.2 Hydraulic Conductivity - Discussion ........................................................18 4.7 Pavements .........................................................................................................18 4.7.1 Pavements – Conventional Subgrade Preparation .................................18 4.7.2 Pavements – Permeable Pavement Subgrade Preparation .......................19 4.7.2 Pavements – Design Recommendations ................................................19 4.7.3 Pavements – Maintenance .....................................................................21 5.0 GENERAL COMMENTS ...............................................................................................22 TABLE OF CONTENTS (continued) Appendix A – FIELD EXPLORATION Exhibit A-1 Site Location Map Exhibit A-2 Boring Location Plan Exhibit A-3 Field Exploration Description Exhibits A-4 to A-9 Boring Logs Exhibits A-10 to A-11 Hydraulic Conductivity Boring Logs Appendix B – LABORATORY TESTING Exhibit B-1 Laboratory Testing Description Exhibit B-2 Atterberg Limits Test Results Exhibit B-3 Grain-size Distribution Test Results Exhibits B-4 to B-6 Swell-consolidation Test Results Exhibits B-7 and B-8 Field Hydraulic Conductivity Test Results Appendix C – SUPPORTING DOCUMENTS Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification System Exhibit C-3 Description of Rock Properties Exhibit C-4 Laboratory Test Significance and Purpose Exhibits C-5 and C-6 Report Terminology Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable i EXECUTIVE SUMMARY A geotechnical investigation has been performed for the proposed Uptown Plaza project to be constructed at 1501 West Elizabeth Street in Fort Collins, Colorado. Six (6) borings, presented as Exhibits A-4 through A-9, and designated as Boring No. 1 through Boring No. 6, were performed to depths of approximately 10½ to 34.3 feet below existing site grades. Two (2) field hydraulic conductivity borings, presented as Exhibits A-10 and A-11, and designated as Boring DP-1 and DP-2, were performed to depths of approximately 3 feet below existing site grades. This report specifically addresses the recommendations for the proposed 2-story building and associated pavements. Detailed recommendations for the design of permeable pavements and associated reservoir are outside our scope of work. Borings performed in these areas are for informational purposes and will be utilized by others. Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. However, the following geotechnical considerations were identified and will need to be considered: Existing, undocumented fill was encountered in the borings performed on this site to depths ranging from about 3 to 4 feet below existing site grades. Deeper fills may be present on the site where buried tanks were removed during demolition of the gas station previously occupying the site. We do not recommend supporting shallow spread footing foundations or floor slabs on the existing fill materials. We recommend removing the existing fill, moisture conditioning, and recompacting prior to building construction. However, if compaction test results recorded during fill placement are available, Terracon should be provided with the test results for review. If we determine the compaction test results are sufficient to indicate the fill was placed properly, removal and recompaction of the existing fill is not necessary. The proposed building may be supported on a drilled pier foundation system bottomed in bedrock. Spread footing foundations may also be considered for support of the proposed building provided the existing fill below footings is removed and recompacted prior to foundation construction. We measured groundwater at depths ranging from about 2.5 to 6.1 feet below existing site grades. Shallow groundwater conditions will likely affect removal and recompaction of existing fill, deep utility installation, construction of shallow spread footing foundations, and infiltration rates below permeable pavements. If spread footing foundations are selected, we recommend a separation of at least 3 feet between the bottom of footings and measured groundwater levels. Subgrade stabilization will be necessary for site improvements constructed within 3 feet of groundwater. A slab-on-grade floor system is recommended for the proposed building provided the existing fill below slab is removed and recompacted prior to floor slab construction. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable ii The 2009 International Building Code, Table 1613.5.2 IBC seismic site classification for this site is D. Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support. We therefore recommend that Terracon be retained to monitor this portion of the work. This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations. Responsive Resourceful Reliable 1 GEOTECHNICAL ENGINEERING REPORT Uptown Plaza 1501 West Elizabeth Street Fort Collins, Colorado Terracon Project No. 20135023 July 24, 2013 1.0 INTRODUCTION This report presents the results of our geotechnical engineering services performed for the proposed Uptown Plaza project to be located at 1501 West Elizabeth Street in Fort Collins, Colorado. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: subsurface soil and bedrock conditions foundation design and construction groundwater conditions floor slab design and construction grading and drainage pavement construction seismic considerations earthwork Our geotechnical engineering scope of work for this project included the initial site visit, the advancement of six (6) test borings to depths ranging from approximately 10½ to 34.3 feet below existing site grades; two (2) hydraulic conductivity test borings to depths of 3 feet below existing site grades; laboratory testing for soil engineering properties; and engineering analyses to provide foundation, floor system and pavement design and construction recommendations. Logs of the borings along with a Boring Location Plan (Exhibit A-2) are included in Appendix A. The results of the laboratory testing performed on soil and bedrock samples obtained from the site during the field exploration are included in Appendix B. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 2 2.0 PROJECT INFORMATION 2.1 Project Description Item Description Site layout Refer to the Boring Location Plan (Exhibit A-2 in Appendix A) Structures We understand a post and beam, two-story building with approximately 16,000 square feet of commercial space on the first level and 18 multifamily units on the second level is planned for this site. The approximate finished floor elevation of the building was provided to us by Hillhouse Architects, Inc. to be 5040 feet. We also understand paved parking areas are planned for this site utilizing conventional pavements as well as permeable asphalt or permeable paving blocks. Maximum loads Building: Gravity Column Load – 300 kips (max.) Wall Load – 4 to 5 klf (assumed) Grading in building area We assume cuts and fills on the order of 3 feet or less will be required in building areas with the deeper cuts to allow installation of utilities. Cuts and fills in parking areas and drive lanes are assumed to be less than 2 feet. Below-grade areas No below-grade areas are planned for this site. 2.2 Site Location and Description Item Description Location The project site is located at 1501 West Elizabeth Street in Fort Collins, Colorado. Existing site features Currently a concrete access drive is located near the south side of the site with a detention pond bordering the site on the south. We understand a gas station and a car wash building, located to the south of the gas station, previously occupied the site and were demolished and removed prior to our study. Surrounding developments The site is bordered to the north by West Elizabeth Street with multifamily housing beyond. The east and west are bordered by restaurants with residential housing beyond and to the south. Current ground cover The ground surface is covered with concrete pavements, landscaped grasses, other vegetation, and trees, and exposed subgrade from the demolition of the previous gas station and car wash. Existing topography The site is relatively flat. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 3 3.0 SUBSURFACE CONDITIONS 3.1 Typical Subsurface Profile Specific conditions encountered at each boring location are indicated on the individual boring logs included in Appendix A. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual. Based on the results of the borings, subsurface conditions on the project site can be generalized as follows: Material Description Approximate Depth to Bottom of Stratum (feet) Consistency/Density/Hardness Fill materials consisting of lean clay, sand, and gravel About 3 to 4 feet below existing site grades. -- Gravel lense About 6 – inches thick at depths of 6 to 13½ feet below existing grades. -- Sandy lean clay About 14 to 16 feet below existing site grades. Medium stiff to very stiff Weathered claystone bedrock About 15 to 18 feet below existing site grades. Weathered Claystone bedrock To the maximum depth of exploration of about 34.3 feet. Hard to very hard 3.2 Laboratory Testing Representative soil samples were selected for swell-consolidation testing and exhibited no movement to 0.18 percent swell when wetted. The claystone bedrock is also considered to have low expansive potential or non-expansive. Samples of site soils and bedrock selected for plasticity testing exhibited medium plasticity with liquid limits ranging from 31 to 43 and plasticity indices ranging from 18 to 25. Laboratory test results are presented in Appendix B. 3.3 Groundwater The boreholes were observed while drilling and after completion for the presence and level of groundwater. In addition, delayed water levels were also obtained in the borings. The water levels observed in the boreholes are noted on the attached boring logs, and are summarized below: Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 4 Boring Number Depth to groundwater while drilling, ft. Depth to groundwater 1 day after drilling, ft. Elevation of groundwater 8 days after drilling, ft. 1 6 2.5 5,035.8 2 6 6.1 5,032.6 3 13.5 4.9 5,034.9 4 6 3.2 5,035.7 5 Not encountered 3.8 5,034.5 6 Not encountered 3.5 5,035.9 DP-1 Not encountered -- -- DP-2 2.7 -- -- These observations represent groundwater conditions at the time of the field exploration, and may not be indicative of other times or at other locations. Groundwater levels can be expected to fluctuate with varying seasonal and weather conditions, and other factors. Groundwater level fluctuations occur due to seasonal variations in amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Fluctuations in groundwater levels can best be determined by implementation of a groundwater monitoring plan. Such a plan would include installation of groundwater piezometers, and periodic measurement of groundwater levels over a sufficient period of time. 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 4.1 Geotechnical Considerations Based on subsurface conditions encountered in the borings, the site appears suitable for the proposed construction from a geotechnical point of view provided certain precautions and design and construction recommendations described in this report are followed. We have identified geotechnical conditions that could impact design and construction of the proposed structure, pavements, and other site improvements. 4.1.1 Existing, Undocumented Fill As previously noted, existing undocumented fill was encountered to depths up to about 4 feet in the borings drilled at the site. Deeper fills may be present on the site where buried tanks were removed during demolition of the gas station previously occupying the site. We do not recommend supporting shallow spread footing foundations or floor slabs on the existing fill Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 5 materials. We recommend removing the existing fill, moisture conditioning, and recompacting prior to building construction. We do not possess any information regarding whether the fill was placed under the observation of a geotechnical engineer. However, if compaction test results recorded during fill placement are available, Terracon should be provided with the test results for review. If we determine the compaction test results are sufficient to indicate the fill was placed properly, removal and recompaction of the existing fill is not necessary. Support of footings, floor slabs, and pavements on or above existing fill soils is discussed in this report. However, even with the recommended construction testing services, there is an inherent risk for the owner that compressible fill or unsuitable material within or buried by the fill will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill, but can be reduced by performing additional testing and evaluation. 4.1.2 Shallow Groundwater As previously stated, groundwater was measured at depths ranging from about 2½ to 6.1 feet below existing site grades. We understand below-grade areas are not planned for this site. However, Terracon recommends maintaining a separation of at least 3 feet between the bottom of foundations and measured groundwater levels. 4.1.3 Expansive Soils Laboratory testing indicates the on-site soils exhibited low expansive potential at the samples in- situ moisture content. However, it is our opinion these materials will exhibit a higher expansive potential if the soils and bedrock undergo a significant loss of moisture. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and cracking in the structures, pavements, and flatwork should be anticipated. The severity of cracking and other damage such as uneven floor slabs will probably increase if any modification of the site results in excessive wetting or drying of the on-site soil and bedrock. Eliminating the risk of movement and distress is generally not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. It is imperative the recommendations described in section 4.2.8 Grading and Drainage of this report be followed to reduce movement. 4.2 Earthwork The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project. All earthwork on the project should be observed and evaluated by Terracon on a full-time basis. The evaluation of earthwork should include observation of over-excavation operations, testing of engineered fills, subgrade preparation, subgrade stabilization, and other geotechnical conditions exposed during the construction of the project. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 6 4.2.1 Site Preparation Prior to placing any fill, strip and remove existing vegetation, the existing fill, pavements, and any other deleterious materials from the proposed construction areas. Our borings suggest the existing fill extends to depths of approximately 3 to 4 feet below existing site grades. However, deeper fills may exist particularly in areas where buried tanks were removed during the demolition of the gas station previously occupying the site. Stripped organic materials should be wasted from the site or used to re-vegetate landscaped areas or exposed slopes (if any) after completion of grading operations. Prior to the placement of fills, the site should be graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed structures. 4.2.2 Demolition Demolition of existing site features should include complete removal of all foundation systems, below-grade structural elements, pavements, and exterior flat work within the proposed construction area. This should include removal of any utilities to be abandoned along with any loose utility trench backfill or loose backfill found adjacent to existing foundations. All materials derived from the demolition of existing structures and pavements should be removed from the site. The types of foundation systems supporting the previous buildings are not known. If some or all of the previous buildings are supported by drilled piers, the existing piers should be truncated a minimum depth of 3 feet below areas of planned new construction. Demolition should include the complete removal of existing fill and thoroughly cleaning all construction debris from the fill. During the field investigation evidence of abandoned utilities, previous pavements, and building elements were observed to be mixed in with the fill. Cleaning of the existing fill should be closely monitored to assure complete removal of all demolition debris. Consideration could be given to re-using the concrete provided the materials are processed and uniformly blended with the on-site soils. Concrete materials should be processed to a maximum size of 2-inches and blended at a ratio of 30 percent concrete to 70 percent of on-site soils. 4.2.3 Excavation It is anticipated that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. Excavations into the on-site soils will encounter weak and/or saturated soil conditions with possible caving conditions as excavations approach the groundwater level. The soils to be excavated can vary significantly across the site as their classifications are based solely on the materials encountered in widely-spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 7 Although evidence of underground facilities not removed during demolition of the gas station and car wash previously occupying the site, such as septic tanks, vaults, and basements were not observed during the site reconnaissance, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed and the excavation thoroughly cleaned prior to backfill placement and/or construction. Depending upon depth of excavation and seasonal conditions, surface water infiltration and/or groundwater will likely be encountered in excavations on the site. It is anticipated that pumping from sumps may be utilized to control water within excavations. Well points may be required for significant groundwater flow, or where excavations penetrate groundwater to a significant depth. The subgrade soil conditions should be evaluated during the excavation process and the stability of the soils determined at that time by the contractors’ Competent Person. Slope inclinations flatter than the OSHA maximum values may have to be used. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottom. All excavations should be sloped or shored in the interest of safety following local, and federal regulations, including current OSHA excavation and trench safety standards. As a safety measure, it is recommended that all vehicles and soil piles be kept a minimum lateral distance from the crest of the slope equal to the slope height. The exposed slope face should be protected against the elements. 4.2.4 Subgrade Preparation After the existing fill and any other deleterious materials have been removed from the construction areas, the top 8 inches of the exposed ground surface should be scarified, moisture conditioned, and recompacted to at least 95 percent of the maximum dry unit weight as determined by ASTM D698 before any new fill, foundations, or pavements are placed. After the bottom of the excavation has been compacted, engineered fill can be placed to bring the building pad and pavement subgrade to the desired grade. Engineered fill should be placed in accordance with the recommendations presented in subsequent sections of this report. The stability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unstable conditions develop, workability may be improved by scarifying and drying. Alternatively, over-excavation of wet zones and replacement with granular materials may be used, or crushed gravel and/or rock can be tracked or “crowded” into the unstable surface soil until a stable working surface is attained. Lightweight excavation equipment may also be used to reduce subgrade pumping. 4.2.5 Fill Materials and Placement The on-site soils or approved granular and low plasticity cohesive imported materials may be used as fill material. The soil removed from this site that is free of organic or objectionable materials, Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 8 as defined by a field technician who is qualified in soil material identification and compaction procedures, can be re-used as fill for the building pad and pavement subgrade. It should be noted that on-site soils will require reworking to adjust the moisture content to meet the compaction criteria. Imported soils (if required) should meet the following material property requirements: Gradation Percent finer by weight (ASTM C136) 4” 100 3” 70-100 No. 4 Sieve 50-100 No. 200 Sieve 10-50 Soil Properties Value Liquid Limit 30 (max.) Plastic Limit 15 (max.) Maximum Expansive Potential (%) Non-expansive1 1. Measured on a sample compacted to approximately 95 percent of the maximum dry unit weight as determined by ASTM D698 at optimum moisture content. The sample is confined under a 100 psf surcharge and submerged. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 9 4.2.6 Compaction Requirements Engineered fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. Item Description Fill lift thickness 8 inches or less in loose thickness when heavy, self- propelled compaction equipment is used 4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used Minimum compaction requirements 95 percent of the maximum dry unit weight as determined by ASTM D698 Moisture content cohesive soil (clay) -1 to +3 % of the optimum moisture content Moisture content cohesionless soil (sand) -3 to +3 % of the optimum moisture content 1. We recommend engineered fill be tested for moisture content and compaction during placement. Should the results of the in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved. 2. Specifically, moisture levels should be maintained low enough to allow for satisfactory compaction to be achieved without the fill material pumping when proofrolled. 3. Moisture conditioned clay materials should not be allowed to dry out. A loss of moisture within these materials could result in an increase in the material’s expansive potential. Subsequent wetting of these materials could result in undesirable movement. 4.2.7 Utility Trench Backfill All trench excavations should be made with sufficient working space to permit construction including backfill placement and compaction. All underground piping within or near the proposed structure should be designed with flexible couplings, so minor deviations in alignment do not result in breakage or distress. Utility knockouts in foundation walls should be oversized to accommodate differential movements. It is imperative that utility trenches be properly backfilled with relatively clean materials. If utility trenches are backfilled with relatively clean granular material, they should be capped with at least 18 inches of cohesive fill in non-pavement areas to reduce the infiltration and conveyance of surface water through the trench backfill. Utility trenches are a common source of water infiltration and migration. All utility trenches that penetrate beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches that could migrate below the building. We recommend constructing an effective clay “trench plug” that extends at least 5 feet out from the face of the building exteriors. The plug material should consist of clay compacted at a water content at or above the soil’s Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 10 optimum water content. The clay fill should be placed to completely surround the utility line and be compacted in accordance with recommendations in this report. It is strongly recommended that a representative of Terracon provide full-time observation and compaction testing of trench backfill within building and pavement areas. 4.2.8 Grading and Drainage All grades must be adjusted to provide effective drainage away from the proposed building and pavements during construction and maintained throughout the life of the proposed project. Infiltration of water into foundation excavations must be prevented during construction. Landscape irrigation adjacent to foundations should be minimized or eliminated. Water permitted to pond near or adjacent to the perimeter of the building (either during or post- construction) can result in significantly higher soil movements than those discussed in this report. As a result, any estimations of potential movement described in this report cannot be relied upon if positive drainage is not obtained and maintained, and water is allowed to infiltrate the fill and/or subgrade. Exposed ground (if any) should be sloped at a minimum of 10 percent grade for at least 10 feet beyond the perimeter of the proposed building, where possible. The use of swales, chases and/or area drains may be required to facilitate drainage in unpaved areas around the perimeter of the building. Backfill against footings and exterior walls should be properly compacted and free of all construction debris to reduce the possibility of moisture infiltration. After construction of the proposed building and prior to project completion, we recommend verification of final grading be performed to document positive drainage, as described above, has been achieved. Flatwork and pavements will be subject to post-construction movement. Maximum grades practical should be used for paving and flatwork to prevent areas where water can pond. In addition, allowances in final grades should take into consideration post-construction movement of flatwork, particularly if such movement would be critical. Where paving or flatwork abuts the building, care should be taken that joints are properly sealed and maintained to prevent the infiltration of surface water. Planters located adjacent to building should preferably be self-contained. Sprinkler mains and spray heads should be located a minimum of 5 feet away from the building lines. Low-volume, drip style landscaped irrigation should not be used near the building. Roof drains should discharge on to pavements or be extended away from the building a minimum of 10 feet through the use of splash blocks or downspout extensions. A preferred alternative is to have the roof drains discharge by solid pipe to storm sewers or to a detention pond or other appropriate outfall. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 11 4.2.9 Exterior Slab Design and Construction Exterior slabs on-grade, exterior architectural features, and utilities founded on, or in backfill or the site soils will likely experience some movement due to the volume change of the material. Potential movement could be reduced by: Minimizing moisture increases in the backfill; Controlling moisture-density during placement of the backfill; Using designs which allow vertical movement between the exterior features and adjoining structural elements; and Placing control joints on relatively close centers. 4.2.10 Corrosion Protection Results of water-soluble sulfate testing indicate that ASTM Type I or II portland cement should be specified for all project concrete on and below grade. Foundation concrete should be designed for low sulfate exposure in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. 4.3 Foundations The proposed building can be supported by a drilled pier foundation system bottomed in bedrock. A shallow, spread footing foundation system is considered a feasible alternative provided the existing fill is removed and recompacted below footings. We understand post and beam construction is planned for this building with anticipated column loads of up to 300 kips. To reduce the size of column pads for the proposed building, ground modifications will be necessary to increase the bearing capacity of the foundation subgrade. Shallow groundwater conditions encountered below this site will likely impact spread footing foundations. Foundation excavations approaching the level of groundwater will likely encounter soft to very loose and nearly saturated to wet soil conditions. Stabilization of foundation subgrade soils will be required prior to spread footing foundation construction. Design recommendations for foundations for the proposed structures and related structural elements are presented in the following sections. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 12 4.3.1 Drilled Piers Bottomed in Bedrock - Design Recommendations Description Value Minimum pier length 20 feet Minimum pier diameter 18 inches Minimum bedrock embedment 1 10 feet Maximum allowable end-bearing pressure 35,000 psf Allowable skin friction (for portion of pier embedded into bedrock) 2,500 psf Void thickness (beneath grade beams) 4 inches 1. Drilled piers should be embedded into hard or very hard bedrock materials. Site grading details were not fully understood at the time we prepared this report. If significant fills are planned in the proposed building areas, longer drilled pier lengths may be required. Piers should be considered to work in group action if the horizontal spacing is less than three pier diameters. A minimum practical horizontal clear spacing between piers of at least three diameters should be maintained, and adjacent piers should bear at the same elevation. The capacity of individual piers must be reduced when considering the effects of group action. Capacity reduction is a function of pier spacing and the number of piers within a group. If group action analyses are necessary, capacity reduction factors can be provided for the analyses. To satisfy forces in the horizontal direction using LPILE, piers may be designed for the following lateral load criteria: Parameters Clay Sand and Gravel Claystone Bedrock LPILE soil type1 Stiff clay without free water Sand (submerged) Stiff clay without free water Unit weight (pcf) 125 125 130 Average undrained shear strength (psf) 500 N/A 9,000 Average angle of internal friction, (degrees) N/A 35 N/A Coefficient of subgrade reaction, k (pci)* 100 - static 30 - cyclic 60 2,000- static 800 – cyclic Strain, 50 (%) 0.010 N/A 0.004 1. For purposes of LPILE analysis, assume a groundwater depth of about 5 feet below existing ground surface (approximately Elev. 5033 feet). 2. The upper 3 feet of soils should be neglected during lateral load analysis. 4.3.2 Drilled Piers Bottomed in Bedrock - Construction Considerations Drilling to design depth should be possible with conventional single-flight power augers on the majority of the site; however, specialized drilling equipment may be required for very hard bedrock Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 13 layers. In addition, possible caving soils and groundwater indicate that temporary steel casing may be required to properly drill the piers prior to concrete placement. Groundwater should be removed from each pier hole prior to concrete placement. Pier concrete should be placed immediately after completion of drilling and cleaning. If pier concrete cannot be placed in dry conditions, a tremie should be used for concrete placement. The use of a bottom-dump hopper, or an elephant's trunk discharging near the bottom of the hole where concrete segregation will be minimized, is recommended. Due to potential sloughing and raveling, foundation concrete quantities may exceed calculated geometric volumes. Casing should be withdrawn in a slow continuous manner maintaining a sufficient head of concrete to prevent infiltration of water or caving soils or the creation of voids in pier concrete. Pier concrete should have a relatively high fluidity when placed in cased pier holes or through a tremie. Pier concrete with slump in the range of 5 to 7 inches is recommended. We recommend the sides of each pier should be mechanically roughened in the claystone bearing strata. This should be accomplished by a roughening tooth placed on the auger. Shaft bearing surfaces must be cleaned prior to concrete placement. A representative of Terracon should observe the bearing surface and shaft configuration. Free-fall concrete placement in piers will only be acceptable if provisions are taken to avoid striking the concrete on the sides of the hole or reinforcing steel. The use of a bottom-dump hopper, or an elephant's trunk discharging near the bottom of the hole where concrete segregation will be minimized, is recommended. 4.3.3 Spread Footings - Design Recommendations As previously stated, anticipated column loads of up to 300 kips are planned for this project. If spread footings are selected as the foundation system, column pads will be comparatively large when constructed on the native soils or recompacted on-site soils. To reduce column pad sizes, the bearing capacity of the foundation subgrade will need to be increased. To achieve a higher bearing capacity of the foundation subgrade, we recommend placing a single layer of geogrid below 12 inches of imported granular fill beneath footings. Geogrid should consist of Hanes Geo. Components TerraGrid® RX1100 or engineer approved equivalent and should extend at least 8 inches outside the edges of the proposed footing or column pad foundations. Imported granular fill should consist of CDOT Class 6 aggregate base course or recycled concrete base course. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 14 Description Value Maximum net allowable bearing pressure 1 Native on-site soils or Reworked existing fill: 2,500 psf Geogrid and 12 inches of ABC: 3,500 psf Lateral earth pressure coefficients 2 Active, Ka = 0.49 Passive, Kp = 2.04 At-rest, Ko = 0.66 Sliding coefficient 2 µ = 0.50 Moist soil unit weight = 125 pcf Minimum embedment depth below finished grade 3 30 inches Estimated total movement 4 About 1 inch Estimated differential movement 4 About ½ to ¾ of total movement Compaction requirements Scarify subgrade to a depth of at least 8 inches, moisture condition, and compact to at least 95 percent of the maximum dry unit weight as determined by ASTM D698. 1. The recommended maximum net allowable bearing pressure assumes any unsuitable fill or soft soils, if encountered, will be over-excavated and replaced with properly compacted engineered fill. The design bearing pressure applies to a dead load plus design live load condition. The design bearing pressure may be increased by one-third when considering total loads that include wind or seismic conditions. 2. The lateral earth pressure coefficients and sliding coefficients are ultimate values and do not include a factor of safety. The foundation designer should include the appropriate factors of safety. 3. For frost protection and to reduce the effects of seasonal moisture variations in the subgrade soils. The minimum embedment depth is for perimeter footings beneath unheated areas and is relative to lowest adjacent finished grade, typically exterior grade. 4. The estimated movements presented above are based on the assumption that the maximum footing size is 4 feet for column footings and 1.5 feet for continuous footings. Footings should be proportioned to reduce differential foundation movement. As discussed, total movement resulting from the assumed structural loads is estimated to be on the order of about 1 inch. Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, proper drainage should be provided in the final design and during construction and throughout the life of the structure. Failure to maintain the proper drainage as recommended in the 4.2.8 Grading and Drainage section of this report will nullify the movement estimates provided above. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 15 4.3.4 Spread Footings - Construction Considerations Spread footing construction should only be considered if the estimated foundation movement can be tolerated. Subgrade soils beneath footings should be moisture conditioned and compacted as described in the 4.2 Earthwork section of this report. The moisture content and compaction of subgrade soils should be maintained until foundation construction. Footings and foundation walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. Unstable subgrade conditions are anticipated as excavations approach the groundwater surface. Unstable surfaces will need to be stabilized prior to backfilling excavations and/or constructing the building foundation, floor slab and/or project pavements. The use of angular rock, recycled concrete and/or gravel pushed or “crowded” into the yielding subgrade is considered suitable means of stabilizing the subgrade. The use of geogrid materials in conjunction with aggregate base course as previously discussed could also be considered and could be more cost effective. Unstable subgrade conditions should be observed by Terracon to assess the subgrade and provide suitable alternatives for stabilization. Stabilized areas should be proof-rolled or probed prior to continuing construction to assess the stability of the subgrade. Foundation excavations should be observed by Terracon. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required. 4.4 Seismic Considerations Code Used Site Classification 2009 International Building Code (IBC) 1 D 2 1. In general accordance with the 2009 International Building Code, Table 1613.5.2. 2. The 2009 International Building Code (IBC) requires a site soil profile determination extending a depth of 100 feet for seismic site classification. The current scope requested does not include the required 100 foot soil profile determination. The borings completed for this project extended to a maximum depth of about 34.3 feet and this seismic site class definition considers that similar soil and bedrock conditions exist below the maximum depth of the subsurface exploration. Additional exploration to deeper depths could be performed to confirm the conditions below the current depth of exploration. Alternatively, a geophysical exploration could be utilized in order to attempt to justify a more favorable seismic site class. 4.5 Floor Systems A slab-on-grade may be utilized for the interior floor system for the proposed building provided the existing fill is removed and recompacted prior to floor slab construction. If very little Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 16 movement can be tolerated, a structurally-supported floor system, supported independent of the subgrade materials, is recommended. Subgrade soils beneath interior and exterior slabs should be scarified to a depth of at least 8 inches, moisture conditioned and compacted. The moisture content and compaction of subgrade soils should be maintained until slab construction. 4.5.1 Floor System - Design Recommendations Even when bearing on properly prepared soils, movement of the slab-on-grade floor system is possible should the subgrade soils undergo an increase in moisture content. We estimate movement of about 1 inch is possible. If the owner cannot accept the risk of slab movement, a structural floor should be used. If conventional slab-on-grade is utilized, the subgrade soils should be over-excavated and prepared as outlined in the 4.2 Earthwork section of this report. For structural design of concrete slabs-on-grade subjected to point loadings, a modulus of subgrade reaction of 100 pounds per cubic inch (pci) may be used for floors supported on re- compacted existing soils at the site. A modulus of 200 pci may be used for floors supported on at least 1 foot of non-expansive, imported granular fill. Additional floor slab design and construction recommendations are as follows: Positive separations and/or isolation joints should be provided between slabs and all foundations, columns, or utility lines to allow independent movement. Control joints should be saw-cut in slabs in accordance with ACI Design Manual, Section 302.1R-37 8.3.12 (tooled control joints are not recommended) to control the location and extent of cracking. Interior utility trench backfill placed beneath slabs should be compacted in accordance with the recommendations presented in the 4.2 Earthwork section of this report. Floor slabs should not be constructed on frozen subgrade. A minimum 2-inch void space should be constructed above or below non-bearing partition walls placed on the floor slab. Special framing details should be provided at doorjambs and frames within partition walls to avoid potential distortion. Partition walls should be isolated from suspended ceilings. The use of a vapor retarder should be considered beneath concrete slabs that will be covered with wood, tile, carpet or other moisture sensitive or impervious floor coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 17 should refer to ACI 302 for procedures and cautions regarding the use and placement of a vapor retarder. Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1R are recommended. 4.5.2 Floor Systems - Construction Considerations Movements of slabs-on-grade using the recommendations discussed in previous sections of this report will likely be reduced and tend to be more uniform. The estimates discussed above assume that the other recommendations in this report are followed. Additional movement could occur should the subsurface soils become wetted to significant depths, which could result in potential excessive movement causing uneven floor slabs and severe cracking. This could be due to over watering of landscaping, poor drainage, improperly functioning drain systems, and/or broken utility lines. Therefore, it is imperative that the recommendations presented in this report be followed. 4.6 Hydraulic Conductivity Testing Two (2) hydraulic conductivity borings, presented as Exhibits A-10 and A-11, and designated as Boring DP-1 and DP-2, were performed to depths of approximately 3 feet below existing site grades. Logs of the borings along with a Boring Location Plan (Exhibit A-2) are included in Appendix A. 4.6.1 Hydraulic Conductivity – Field Investigation We understand a carwash building previously occupying the site was demolished and removed prior to our field investigation. During our field investigation, two (2) field hydraulic conductivity test borings were completed to a depth of approximately 3 feet below existing site grades. The field hydraulic conductivity test borings were completed in areas of the site planned for permeable pavements. One of the field hydraulic conductivity test borings (DP-1) was completed in the area where the car wash building previously occupied the site. The second field hydraulic conductivity test boring (DP-2) was completed in the area of the site where we believe an existing detention area is present. Field hydraulic conductivity test boring DP-1 was drilled with a CME-45 truck mounted drill rig with 4-inch outer diameter solid-stem augers. Field hydraulic conductivity test boring DP-2 was completed with a 3¾-inch hand auger. During the drilling operations, lithologic logs of the borings were recorded by the field engineer. Slotted PVC pipe was placed in each of the field hydraulic conductivity test holes full-depth and the annulus surrounding the slotted PVC pipe was filled with clean filter sand. The borings were then saturated with water and left to stabilize overnight. The soils encountered in DP-1 were visually classified in the field and consisted of existing fill materials comprised of lean clay with sand and gravel. The existing fill was slightly moist to Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 18 moist. The soils encountered in DP-2 were also visually classified in the field and consisted of native sandy lean clay. The soils encountered in DP-2 were very moist to wet. Groundwater was not encountered in field hydraulic conductivity test boring DP-1. Groundwater was encountered in field hydraulic conductivity test boring DP-2 at a depth of approximately 2.7 feet below existing site grade while drilling. During delayed groundwater measurements taken in other borings completed on the site, groundwater was measured in Boring No. 5 (located near hydraulic conductivity test boring DP-2) at a depth of approximately 3.8 feet below the existing ground surface. The groundwater levels measured in our borings at the time of our field study were used when calculating the field hydraulic conductivity at this site. 4.6.2 Hydraulic Conductivity - Discussion The field hydraulic conductivity testing performed as part of our study was developed by the U.S. Bureau of Reclamation and was referred to as the well permeameter method. The field hydraulic conductivity tests were performed by adding water to the test holes to maintain a constant water level (constant head test). The calculated hydraulic conductivity value for field hydraulic conductivity test holes DP-1 and DP-2 were 3 feet per day (ft/day) and 108 ft/day, respectively. The calculated value for DP-1 is within the expected ranges for the soil types encountered in our borings and is considered to be a representative value. The calculated value for DP-2 is much higher than the expected ranges for the soil types (upper clays) encountered in our borings. However, a layer of clean to silty gravel with sand was encountered in some of the other borings completed at this site at a depth of approximately 6 feet below existing site grades. It is likely the gravel layer extends below most of the site and would be expected near the bottom of DP-2. We believe the comparatively higher field hydraulic conductivity value measured in DP-2 is due to the higher flow rates that occur as water flows into the gravel layer below the site. The test results and schematics of the field hydraulic conductivity test hole details, Exhibit B-7 and B-8, are included in Appendix B. The field hydraulic conductivity test results and soils encountered in our borings completed at the site indicate infiltration of storm water retained in a reservoir below permeable pavements into the soils underlying this site will be favorable for the design of permeable pavements. However, shallow groundwater conditions may limit the allowable depth of the retention area below permeable pavements. The slotted PVC pipe was left in place for future groundwater readings. 4.7 Pavements 4.7.1 Pavements – Conventional Subgrade Preparation On most project sites, the site grading is accomplished relatively early in the construction phase. Fills are typically placed and compacted in a uniform manner. However as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or rainfall/snow melt. As a result, the pavement subgrade may not be suitable for pavement construction and corrective action will be required. The subgrade should be carefully Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 19 evaluated at the time of pavement construction for signs of disturbance or instability. We recommend the pavement subgrade be thoroughly proofrolled with a loaded tandem-axle dump truck prior to final grading and paving. All pavement areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to paving. 4.7.2 Pavements – Permeable Pavement Subgrade Preparation Unlike conventional pavements, permeable pavement subgrades are not compacted. When preparing the subgrade for permeable pavements, care should be taken to excavate the required reservoir storage volume without disturbing the underlying soils. Groundwater was encountered at depths of about 3.5 and 3.7 feet below existing site grades in the portion of the site planned for permeable pavements. Shallow groundwater conditions will limit the thickness of the rock reservoir layer used to store the storm water runoff. Shallow groundwater will also reduce infiltration rates as the water stored within the rock reservoir layer infiltrates into the groundwater. 4.7.2 Pavements – Design Recommendations Design of pavements for the project have been based on the procedures outlined in the 1993 Guideline for Design of Pavement Structures prepared by the American Association of State Highway and Transportation Officials (AASHTO) and the Larimer County Urban Area Street Standards (LCUASS). A sample of the fill materials selected for swell-consolidation testing exhibited no movement when wetted under an applied pressure of 200 psf which is less than the maximum 2 percent criteria established for determining if swell-mitigation procedures in the pavement sections are required per LCUASS standards. Therefore, we do not believe swell-mitigation of the subgrade materials prior to pavement operations is necessary. Traffic patterns and anticipated loading conditions were not available at the time that this report was prepared. However, we anticipate that the new parking areas (i.e., light-duty) will be primarily used by personal vehicles (cars and pick-up trucks). Delivery trucks and refuse disposal vehicles will be expected in the drive lanes and loading areas (i.e., medium-duty). A maximum of 10 trucks per week were considered developing our recommendations. If heavier traffic loading is expected, Terracon should be provided with the information and allowed to review these pavement sections. Rigid pavement design is based on an evaluation of the Modulus of Subgrade Reaction of the soils (k-value), the Modulus of Rupture of the concrete, and other factors previously described. A Modulus of Subgrade Reaction of 200 pci, and a Modulus of Rupture of 600 psi, were used for pavement concrete. The rigid pavement thickness was determined on the basis of the AASHTO design equation. Recommended minimum pavement sections are provided in the table below. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 20 Conventional Pavements Traffic Area Alternative Recommended Pavement Thickness (inches) Asphaltic Concrete (AC) Aggregate Base Course (ABC) Portland Cement Concrete (PCC) Total Automobile Parking (light duty) A 3 4 - 7 B - - 5 5 Drive Lanes and Loading Areas (heavy duty) A 4 6 - 10 B - 4 5 9 Permeable Pavements Traffic Area Alternative Recommended Pavement Thickness (inches) Porous Asphalt Permeable Concrete Permeable Interlocking Concrete Pavement (PICP) Aggregate Base Course Total Automobile Parking A 3 - - 6 9 B - 6 - 3 9 C - - Typically 3 3 6 Terracon recommends the design and construction of permeable pavements should be completed by a specialty contractor who has demonstrated experience with placing, compacting, finishing, edging, jointing, curing, and protecting permeable pavements. There are several choices for base course depending upon which type of permeable pavement is chosen. Terracon recommends constructing perimeter curbing around permeable pavements and between conventional and permeable pavements to reduce infiltration of water below moisture sensitive subgrades. Where rigid pavements are used, portland cement concrete should be produced from an approved mix design with the following minimum properties: Properties Value Compressive strength 4,000 psi (mimum) Cement type Type I or II cement Entrained air content (%) 5 to 8 Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 21 Concrete should be deposited by truck mixers or agitators and placed a maximum of 90 minutes from the time the water is added to the mix. Longitudinal and transverse joints should be provided as needed in concrete pavements for expansion/contraction and isolation per ACI 325. The location and extent of joints should be based upon the final pavement geometry. Joints should be sealed to prevent entry of foreign material and doweled where necessary for load transfer. Although not required for structural support, a minimum 4-inch thick aggregate base course layer is recommended for the PCC pavements in heavy-duty areas to help reduce the potential for slab curl, shrinkage cracking, and subgrade “pumping” through joints. Proper joint spacing will also be required for PCC pavements to prevent excessive slab curling and shrinkage cracking. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. For areas subject to concentrated and repetitive loading conditions such as dumpster pads, truck delivery docks and ingress/egress aprons, we recommend using a portland cement concrete pavement with a thickness of at least 6 inches underlain by at least 4 inches of granular base. Prior to placement of the granular base the areas should be thoroughly proofrolled. For dumpster pads, the concrete pavement area should be large enough to support the container and tipping axle of the refuse truck. Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements: Site grades should slope a minimum of 2 percent away from the pavements; The subgrade and the pavement surface have a minimum 2 percent slope to promote proper surface drainage; Consider appropriate edge drainage and pavement under drain systems; Install pavement drainage surrounding areas anticipated for frequent wetting; Install joint sealant and seal cracks immediately; Seal all landscaped areas in, or adjacent to pavements to reduce moisture migration to subgrade soils; and Placing compacted, low permeability backfill against the exterior side of curb and gutter. 4.7.3 Pavements – Maintenance Preventative maintenance should be planned and provided for an ongoing pavement management program in order to enhance future pavement performance. Preventive maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventative maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable 22 Permeable pavements require periodic inspection and cleaning. Consideration should be given to installing signage to restrict heavily loaded vehicles (i.e. trash trucks, delivery trucks, etc.) from driving on permeable pavement areas. Also, maintenance of permeable pavements should be completed by properly trained workers. 5.0 GENERAL COMMENTS Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, foundation construction and other earth-related construction phases of the project. The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as described in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. APPENDIX A FIELD EXPLORATION SITE LOCATION MAP A-1 20135023 6/20/2013 EDB BCJ EDB EDB 1” = 8,000’ Project Manager: Drawn by: Checked by: Approved by: Project No. Scale: File Name: Date: Exhibit Project Site Uptown Plaza 1501 West Elizabeth Street 1901Colorado Sharp Point Drive, Suite C Fort Collins, Colorado 80525 Fort Collins, PH. (970) 484-0359 FAX. (970) 484-0454 0’ 4,000’ 8,000’ APPROXIMATE SCALE DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES 1901 Sharp Point Drive, Suite C Fort Collins, Colorado 80521 PH. (970) 484-0359 FAX. (970) 484-0454 A-2 BORING LOCATION PLAN EXHIBIT Uptown Plaza 1501 West Elizabeth Street Fort Collins, Colorado Project Manager: Drawn By: Check By: Approved By: EDB BCJ EDB EDB Project No. Scale: File Name: Date: 20135023 1”=40’ 6/20/2013 0’ 20’ 40’ APPROXIMATE SCALE LEGEND Approximate Boring Location 1 1 2 3 4 5 6 Approximate Location of Temporary Benchmark (Top Man Hole Lid–Elevation 5,041.2’) DP-1 DP-2 DP-1 Approximate Field Hydraulic Conductivity Location Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable Exhibit A-3 Field Exploration Description The locations of borings and field hydraulic conductivity tests were based upon the proposed development shown on the provided site plan. The borings were located in the field by measuring from existing site features. The ground surface elevation was surveyed at each boring and field hydraulic conductivity test location referencing the temporary benchmark shown on Exhibit A-2 using an engineer’s level. The borings were drilled with a CME-45 truck-mounted rotary drill rig with solid-stem augers. During the drilling operations, lithologic logs of the borings were recorded by the field engineer. Disturbed samples were obtained at selected intervals utilizing a 2-inch outside diameter split- spoon sampler and a 3-inch outside diameter ring-barrel sampler. Disturbed bulk samples were obtained from auger cuttings. Penetration resistance values were recorded in a manner similar to the standard penetration test (SPT). This test consists of driving the sampler into the ground with a 140-pound hammer free-falling through a distance of 30 inches. The number of blows required to advance the ring-barrel sampler 12 inches (18 inches for standard split-spoon samplers, final 12 inches are recorded) or the interval indicated, is recorded as a standard penetration resistance value (N-value). The blow count values are indicated on the boring logs at the respective sample depths. Ring-barrel sample blow counts are not considered N-values. A CME automatic SPT hammer was used to advance the samplers in the borings performed on this site. A greater efficiency is typically achieved with the automatic hammer compared to the conventional safety hammer operated with a cathead and rope. Published correlations between the SPT values and soil properties are based on the lower efficiency cathead and rope method. This higher efficiency affects the standard penetration resistance blow count value by increasing the penetration per hammer blow over what would be obtained using the cathead and rope method. The effect of the automatic hammer's efficiency has been considered in the interpretation and analysis of the subsurface information for this report. The standard penetration test provides a reasonable indication of the in-place density of sandy type materials, but only provides an indication of the relative stiffness of cohesive materials since the blow count in these soils may be affected by the moisture content of the soil. In addition, considerable care should be exercised in interpreting the N-values in gravelly soils, particularly where the size of the gravel particle exceeds the inside diameter of the sampler. Groundwater measurements were obtained in the borings at the time of site exploration and approximately one day after drilling. After subsequent groundwater measurements were obtained, the borings were backfilled with auger cuttings and sand (if needed). The slotted PVC pipe was left in place in the hydraulic conductivity test borings for future groundwater readings. Some settlement of the backfill and/or patch may occur and should be repaired as soon as possible. APPENDIX B LABORATORY TESTING Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado July 24, 2013 Terracon Project No. 20135023 Responsive Resourceful Reliable Exhibit B-1 Laboratory Testing Description The soil and bedrock samples retrieved during the field exploration were returned to the laboratory for observation by the project geotechnical engineer. At that time, the field descriptions were reviewed and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials. Laboratory tests were conducted on selected soil and bedrock samples. The results of these tests are presented on the boring logs and in this appendix. The test results were used for the geotechnical engineering analyses, and the development of foundation and earthwork recommendations. The laboratory tests were performed in general accordance with applicable locally accepted standards. Soil samples were classified in general accordance with the Unified Soil Classification System described in Appendix C. Rock samples were visually classified in general accordance with the description of rock properties presented in Appendix C. Water content Plasticity index Grain-size distribution Consolidation/swell Dry density Water-soluble sulfate content Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado June 27, 2013 Terracon Project No. 20135023 gallons 8:00:00 AM 0 0.00 8:30:00 AM 0.45 0.05 9:00:00 AM 0.48 0.11 9:30:00 AM 0.42 0.16 10:00:00 AM 0.58 0.23 10:30:00 AM 0.59 0.30 11:00:00 AM 0.33 0.34 11:30:00 AM 0.49 0.40 12:00:00 PM 0.38 0.45 12:30:00 PM 0.4 0.49 1:00:00 PM 0.47 0.55 1:30:00 PM 0.44 0.60 2:00:00 PM 0.41 0.65 2:30:00 PM 0.42 0.70 3:00:00 PM 0.43 0.76 3:30:00 PM 0.42 0.81 4:00:00 PM 0.45 0.86 kavg = 3 ft/day 1.0E-03 cm/sec h= 2.56 feet h = hydraulic head in test hole (ft) d= 4.25 inches d = diameter of test hole (ft) r= 0.18 feet r = radius of test hole (ft) Tu= 3.36 feet Tu = depth of unsaturated strata (ft) Q= 0.02 ft 3 /min Q = T 23.59 20 20.5 T = 70 o F T = viscocity of water at temperature T 20 = viscocity of water at 68 o F k= 0.002 feet/min T= temperature of water used ( o F) 2.95 feet/day k = hydraulic conductivity feet/min 5.86 2.85 3.34 3.72 Field Hydraulic Conductivity Test Results Uptown Plaza, Fort Collins, Colorado Terracon Project No. 20135023 Northern Location for Proposed Permeable Pavements (DP-1) Time Water Added (lbs) Cumulative Water 6.29 saturated flow rate of water to maintain a constant head in test hole (ft 3 /min) Geotechnical Engineering Report Uptown Plaza Fort Collins, Colorado June 27, 2013 Terracon Project No. 20135023 gallons 8:00:00 AM 0 0.00 8:30:00 AM 0.77 0.09 9:00:00 AM 1.09 0.22 9:30:00 AM 0.92 0.33 10:00:00 AM 1.37 0.50 10:30:00 AM 1.08 0.63 11:00:00 AM 1.05 0.75 11:30:00 AM 1.39 0.92 12:00:00 PM 1.11 1.05 12:30:00 PM 1.06 1.18 1:00:00 PM 1.19 1.32 1:30:00 PM 1.21 1.47 2:00:00 PM 1.22 1.62 2:30:00 PM 1.26 1.77 3:00:00 PM 1.3 1.92 3:30:00 PM 1.26 2.07 4:00:00 PM 1.35 2.24 kavg = 108 ft/day 3.8E-02 cm/sec h= 2.31 feet h = hydraulic head in test hole (ft) d= 3.75 inches d = diameter of test hole (ft) r= 0.16 feet r = radius of test hole (ft) Tu= 2.01 feet Tu = depth of unsaturated strata (ft) Q= 0.04 ft 3 /min Q = T 23.59 20 20.5 T = 70 o F T = viscocity of water at temperature T 20 = viscocity of water at 68 o F k= 0.08 feet/min T= temperature of water used ( o F) 108 feet/day k = hydraulic conductivity feet/min saturated flow rate of water to maintain a constant head in test hole (ft 3 /min) Field Hydraulic Conductivity Test Results Uptown Plaza, Fort Collins, Colorado Terracon Project No. 20135023 Parameters for DP - 2 Time Water Added (lbs) Cumulative Water 18.63 17.28 16.02 14.72 Southern Location for Proposed Permeable Pavements (DP-2) APPENDIX C SUPPORTING DOCUMENTS UNIFIED SOIL CLASSIFICATION SYSTEM Exhibit C-2 Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification Group Symbol Group Name B Coarse Grained Soils: More than 50% retained on No. 200 sieve Gravels: More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels: Less than 5% fines C Cu 4 and 1 Cc 3 E GW Well-graded gravel F Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F Gravels with Fines: More than 12% fines C Fines classify as ML or MH GM Silty gravel F,G,H Fines classify as CL or CH GC Clayey gravel F,G,H Sands: 50% or more of coarse fraction passes No. 4 sieve Clean Sands: Less than 5% fines D Cu 6 and 1 Cc 3 E SW Well-graded sand I Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I Sands with Fines: More than 12% fines D Fines classify as ML or MH SM Silty sand G,H,I Fines classify as CL or CH SC Clayey sand G,H,I Fine-Grained Soils: 50% or more passes the No. 200 sieve Silts and Clays: Liquid limit less than 50 Inorganic: PI 7 and plots on or above “A” line J CL Lean clay K,L,M PI 4 or plots below “A” line J ML Silt K,L,M Organic: Liquid limit - oven dried 0.75 OL Organic clay K,L,M,N Liquid limit - not dried Organic silt K,L,M,O Silts and Clays: Liquid limit 50 or more Inorganic: PI plots on or above “A” line CH Fat clay K,L,M PI plots below “A” line MH Elastic Silt K,L,M Organic: Liquid limit - oven dried 0.75 OH Organic clay K,L,M,P Liquid limit - not dried Organic silt K,L,M,Q Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-inch (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. DESCRIPTION OF ROCK PROPERTIES Exhibit C-3 WEATHERING Fresh Rock fresh, crystals bright, few joints may show slight staining. Rock rings under hammer if crystalline. Very slight Rock generally fresh, joints stained, some joints may show thin clay coatings, crystals in broken face show bright. Rock rings under hammer if crystalline. Slight Rock generally fresh, joints stained, and discoloration extends into rock up to 1 in. Joints may contain clay. In granitoid rocks some occasional feldspar crystals are dull and discolored. Crystalline rocks ring under hammer. Moderate Significant portions of rock show discoloration and weathering effects. In granitoid rocks, most feldspars are dull and discolored; some show clayey. Rock has dull sound under hammer and shows significant loss of strength as compared with fresh rock. Moderately severe All rock except quartz discolored or stained. In granitoid rocks, all feldspars dull and discolored and majority show kaolinization. Rock shows severe loss of strength and can be excavated with geologist’s pick. Severe All rock except quartz discolored or stained. Rock “fabric” clear and evident, but reduced in strength to strong soil. In granitoid rocks, all feldspars kaolinized to some extent. Some fragments of strong rock usually left. Very severe All rock except quartz discolored or stained. Rock “fabric” discernible, but mass effectively reduced to “soil” with only fragments of strong rock remaining. Complete Rock reduced to ”soil”. Rock “fabric” not discernible or discernible only in small, scattered locations. Quartz may be present as dikes or stringers. HARDNESS (for engineering description of rock – not to be confused with Moh’s scale for minerals) Very hard Cannot be scratched with knife or sharp pick. Breaking of hand specimens requires several hard blows of geologist’s pick. Hard Can be scratched with knife or pick only with difficulty. Hard blow of hammer required to detach hand specimen. Moderately hard Can be scratched with knife or pick. Gouges or grooves to ¼ in. deep can be excavated by hard blow of point of a geologist’s pick. Hand specimens can be detached by moderate blow. Medium Can be grooved or gouged 1/16 in. deep by firm pressure on knife or pick point. Can be excavated in small chips to pieces about 1-in. maximum size by hard blows of the point of a geologist’s pick. Soft Can be gouged or grooved readily with knife or pick point. Can be excavated in chips to pieces several inches in size by moderate blows of a pick point. Small thin pieces can be broken by finger pressure. Very soft Can be carved with knife. Can be excavated readily with point of pick. Pieces 1-in. or more in thickness can be broken with finger pressure. Can be scratched readily by fingernail. Joint, Bedding, and Foliation Spacing in Rock a Spacing Joints Bedding/Foliation Less than 2 in. Very close Very thin 2 in. – 1 ft. Close Thin 1 ft. – 3 ft. Moderately close Medium 3 ft. – 10 ft. Wide Thick More than 10 ft. Very wide Very thick a. Spacing refers to the distance normal to the planes, of the described feature, which are parallel to each other or nearly so. Rock Quality Designator (RQD) a Joint Openness Descriptors RQD, as a percentage Diagnostic description Openness Descriptor Exceeding 90 Excellent No Visible Separation Tight 90 – 75 Good Less than 1/32 in. Slightly Open 75 – 50 Fair 1/32 to 1/8 in. Moderately Open 50 – 25 Poor 1/8 to 3/8 in. Open Less than 25 Very poor 3/8 in. to 0.1 ft. Moderately Wide a. RQD (given as a percentage) = length of core in pieces Greater than 0.1 ft. Wide 4 in. and longer/length of run. References: American Society of Civil Engineers. Manuals and Reports on Engineering Practice - No. 56. Subsurface Investigation for Design and Construction of Foundations of Buildings. New York: American Society of Civil Engineers, 1976. U.S. Department of the Interior, Bureau of Reclamation, Engineering Geology Field Manual. Exhibit C-4 LABORATORY TEST SIGNIFICANCE AND PURPOSE Test Significance Purpose California Bearing Ratio Used to evaluate the potential strength of subgrade soil, subbase, and base course material, including recycled materials for use in road and airfield pavements. Pavement Thickness Design Consolidation Used to develop an estimate of both the rate and amount of both differential and total settlement of a structure. Foundation Design Direct Shear Used to determine the consolidated drained shear strength of soil or rock. Bearing Capacity, Foundation Design, and Slope Stability Dry Density Used to determine the in-place density of natural, inorganic, fine-grained soils. Index Property Soil Behavior Expansion Used to measure the expansive potential of fine-grained soil and to provide a basis for swell potential classification. Foundation and Slab Design Gradation Used for the quantitative determination of the distribution of particle sizes in soil. Soil Classification Liquid & Plastic Limit, Plasticity Index Used as an integral part of engineering classification systems to characterize the fine-grained fraction of soils, and to specify the fine-grained fraction of construction materials. Soil Classification Permeability Used to determine the capacity of soil or rock to conduct a liquid or gas. Groundwater Flow Analysis pH Used to determine the degree of acidity or alkalinity of a soil. Corrosion Potential Resistivity Used to indicate the relative ability of a soil medium to carry electrical currents. Corrosion Potential R-Value Used to evaluate the potential strength of subgrade soil, subbase, and base course material, including recycled materials for use in road and airfield pavements. Pavement Thickness Design Soluble Sulfate Used to determine the quantitative amount of soluble sulfates within a soil mass. Corrosion Potential Exhibit C-5 REPORT TERMINOLOGY (Based on ASTM D653) Allowable Soil Bearing Capacity The recommended maximum contact stress developed at the interface of the foundation element and the supporting material. Alluvium Soil, the constituents of which have been transported in suspension by flowing water and subsequently deposited by sedimentation. Aggregate Base Course A layer of specified material placed on a subgrade or subbase usually beneath slabs or pavements. Backfill A specified material placed and compacted in a confined area. Bedrock A natural aggregate of mineral grains connected by strong and permanent cohesive forces. Usually requires drilling, wedging, blasting or other methods of extraordinary force for excavation. Bench A horizontal surface in a sloped deposit. Caisson (Drilled Pier or Shaft) A concrete foundation element cast in a circular excavation which may have an enlarged base. Sometimes referred to as a cast-in-place pier or drilled shaft. Coefficient of Friction A constant proportionality factor relating normal stress and the corresponding shear stress at which sliding starts between the two surfaces. Colluvium Soil, the constituents of which have been deposited chiefly by gravity such as at the foot of a slope or cliff. Compaction The densification of a soil by means of mechanical manipulation Concrete Slab-on- Grade A concrete surface layer cast directly upon a base, subbase or subgrade, and typically used as a floor system. Differential Movement Unequal settlement or heave between, or within foundation elements of structure. Earth Pressure The pressure exerted by soil on any boundary such as a foundation wall. ESAL Equivalent Single Axle Load, a criteria used to convert traffic to a uniform standard, (18,000 pound axle loads). Engineered Fill Specified material placed and compacted to specified density and/or moisture conditions under observations of a representative of a geotechnical engineer. Equivalent Fluid A hypothetical fluid having a unit weight such that it will produce a pressure against a lateral support presumed to be equivalent to that produced by the actual soil. This simplified approach is valid only when deformation conditions are such that the pressure increases linearly with depth and the wall friction is neglected. Existing Fill (or Man-Made Fill) Materials deposited throughout the action of man prior to exploration of the site. Existing Grade The ground surface at the time of field exploration. Exhibit C-6 REPORT TERMINOLOGY (Based on ASTM D653) Expansive Potential The potential of a soil to expand (increase in volume) due to absorption of moisture. Finished Grade The final grade created as a part of the project. Footing A portion of the foundation of a structure that transmits loads directly to the soil. Foundation The lower part of a structure that transmits the loads to the soil or bedrock. Frost Depth The depth at which the ground becomes frozen during the winter season. Grade Beam A foundation element or wall, typically constructed of reinforced concrete, used to span between other foundation elements such as drilled piers. Groundwater Subsurface water found in the zone of saturation of soils or within fractures in bedrock. Heave Upward movement. Lithologic The characteristics which describe the composition and texture of soil and rock by observation. Native Grade The naturally occurring ground surface. Native Soil Naturally occurring on-site soil, sometimes referred to as natural soil. Optimum Moisture Content The water content at which a soil can be compacted to a maximum dry unit weight by a given compactive effort. Perched Water Groundwater, usually of limited area maintained above a normal water elevation by the presence of an intervening relatively impervious continuous stratum. Scarify To mechanically loosen soil or break down existing soil structure. Settlement Downward movement. Skin Friction (Side Shear) The frictional resistance developed between soil and an element of the structure such as a drilled pier. Soil (Earth) Sediments or other unconsolidated accumulations of solid particles produced by the physical and chemical disintegration of rocks, and which may or may not contain organic matter. Strain The change in length per unit of length in a given direction. Stress The force per unit area acting within a soil mass. Strip To remove from present location. Subbase A layer of specified material in a pavement system between the subgrade and base course. Subgrade The soil prepared and compacted to support a structure, slab or pavement system. Unconfined Compression To obtain the approximate compressive strength of soils that possess sufficient cohesion to permit testing in the unconfined state. Bearing Capacity Analysis for Foundations Water Content Used to determine the quantitative amount of water in a soil mass. Index Property Soil Behavior C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 10 60 2 30 D x D (D ) F If soil contains 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. H If fines are organic, add “with organic fines” to group name. I If soil contains 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI 4 and plots on or above “A” line. O PI 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. 0.77 0 13.46 (lbs) 11.03 9.84 8.78 7.67 6.28 5.23 4.15 2.78 1.86 12.24 k = (( ) ( ) ) h SLOTTED PVC PIPE FILTER SAND GROUND SURFACE d Tu WATER TABLE Exhibit B-8 (lbs) 0 0.45 0.93 1.35 1.93 2.52 6.71 7.16 Parameters for DP - 1 4.12 4.59 5.03 5.44 k = ( ( ) ) h SLOTTED PVC PIPE FILTER SAND GROUND SURFACE d Tu WATER TABLE OR IMPERVIOUS LAYER Exhibit B-7 Concrete aggregate ASTM C33 and CDOT Section 703