The URL can be used to link to this page

Home My WebLink AboutPLATTE RIVER POWER AUTHORITY CAMPUS - PDP - PDP170040 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGeotechnical Engineering Report PRPA New Headquarters Campus 2000 East Horsetooth Road Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Prepared for: Platte River Power Authority Fort Collins, Colorado Prepared by: Terracon Consultants, Inc. Fort Collins, Colorado TABLE OF CONTENTS Page EXECUTIVE SUMMARY ............................................................................................................1 1.0 INTRODUCTION .............................................................................................................1 2.0 PROJECT INFORMATION .............................................................................................1 2.1 Project Description ...............................................................................................2 2.2 Site Location and Description...............................................................................3 3.0 SUBSURFACE CONDITIONS ........................................................................................3 3.1 Typical Subsurface Profile ...................................................................................3 3.2 Laboratory Testing ...............................................................................................3 3.3 Corrosion Protection (Water-Soluble Sulfates) .....................................................4 3.4 Groundwater ........................................................................................................4 3.5 Percolation Testing ..............................................................................................5 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................6 4.1 Geotechnical Considerations ...............................................................................6 4.2 Earthwork.............................................................................................................6 4.2.1 Site Preparation ........................................................................................6 4.2.2 Demolition ................................................................................................6 4.2.3 Excavation ................................................................................................7 4.2.4 Subgrade Preparation ...............................................................................8 4.2.5 Fill Materials and Placement ......................................................................9 4.2.6 Compaction Requirements ......................................................................10 4.2.7 Utility Trench Backfill ...............................................................................10 4.2.8 Grading and Drainage .............................................................................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 ...........13 4.3.3 Helical Piles - Design Recommendations ...............................................14 4.3.4 Spread Footings - Design Recommendations .........................................15 4.3.5 Spread Footings - Construction Considerations ......................................16 4.4 Seismic Considerations......................................................................................17 4.5 Floor Systems ....................................................................................................17 4.5.1 Floor System - Design Recommendations ..............................................17 4.5.2 Floor System - Construction Considerations ...........................................18 4.6 Lateral Earth Pressure .......................................................................................19 4.7 Pavements .........................................................................................................20 5.0 GENERAL COMMENTS ...............................................................................................21 TABLE OF CONTENTS (continued) Appendix A – FIELD EXPLORATION Exhibit A-1 Site Location Map Exhibits A-2 & A-3 Exploration Plan Exhibits A-4 & A-5 Field Exploration Description Exhibits A-6 to A-17 Boring Logs Appendix B – LABORATORY TESTING Exhibit B-1 Laboratory Testing Description Exhibits B-2 & B-3 Atterberg Limits Test Results Exhibits B-4 to B-8 Grain-size Distribution Test Results Exhibits B-9 to B-16 Swell-consolidation Test Results Exhibits B-17 & B-18 Unconfined Compression Test Results Exhibit B-19 R-value Test Results Exhibits B-20 & B-21 Water Soluble Sulfates Test Results Exhibits B-22 & B-23 Summary of Laboratory 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 Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable i EXECUTIVE SUMMARY A geotechnical exploration has been performed for the proposed PRPA New Headquarters Campus to be constructed at 2000 East Horsetooth Road in Fort Collins, Colorado. As part of a previous preliminary geotechnical study of a portion of the site, four (4) borings, presented as Exhibits A-6 through A-9 and designated as Boring No. 1 through Boring No. 4 were performed to depths of approximately 25 to 35 feet below existing site grades. Eight (8) supplemental borings, presented as Exhibits A-10 through A-17 and designated as Boring No. B05 through Boring No. B12, were performed to depths of approximately 25 to 35 feet below existing site grades. This report specifically addresses the recommendations for the proposed structures and pavements. 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: n Subsurface conditions encountered in our exploratory borings generally consisted of about 14 to 29 feet of lean clay with varying amounts of sand over about 7 to 21 feet of interbedded claystone bedrock. The upper approximately 2 to 7½ feet of bedrock was highly weathered and comparatively soft. Boring logs are presented in the Exploration Results section of this report. n Groundwater was encountered in most of our test borings at depths of about 12 to 24 feet below existing site grades at the time of drilling or when checked several days after drilling. Groundwater levels can fluctuate in response to site development and to varying seasonal and weather conditions, irrigation on or adjacent to the site and fluctuations in nearby water features. n Expansive clay soils and claystone bedrock were encountered in our borings completed at this site. These materials will present a risk of heave and related damage to shallow foundations, slabs-on-grade, concrete flatwork and pavements constructed on this site. To reduce soil related movement and to enhance performance, we recommend ground modification (over-excavation, moisture conditioning and recompaction) of the soils and/or bedrock below foundations and floor slabs. Ground modification depths and recommendations are discussed in the report. n The proposed single-story metal buildings may be supported on shallow, spread footing foundations bearing on the native soil or on newly placed engineered fill. Without ground modification, we recommend a maximum allowable soil bearing pressure of 1,500 psf. In order to increase the maximum allowable soil bearing pressure to 2,000 psf, we recommend over-excavating the soils below footings to a depth of at least 2 feet and replacing with moisture conditioned, properly compacted engineered fill. On site soils may be reused as over-excavation backfill below foundations. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable ii n Low strength and compressible soils are present on this site. For the proposed headquarters, warehouse, and pool car garage structures, we do not believe the subsoils at and within the zone of influence of shallow foundations have adequate strength to support anticipated loads with less than an inch of settlement. The proposed structures may be supported on a drilled pier or a helical pile foundation system bottomed in bedrock. We believe drilled piers and/or helical piles would provide a reliable foundation system to mitigate post-construction movement. Drilled piers will likely require temporary casing and a concrete pump truck with tremie extension to properly construct piers. Heavy-duty drilling equipment may be required to penetrate the medium hard to hard bedrock. Geotechnical recommendations and design criteria for drilled pier and helical pile foundations are presented in this report. As an alternative to drilled pier and helical pile foundations, consideration could be given to other types of competent deep foundation systems. One approach would include rammed aggregate-pier foundation elements or stone columns to support shallow foundations. Aggregate-pier foundation elements are usually part of the foundation contractor’s design- build system. Therefore, the subsurface exploration information contained in this report should be provided to the foundation contractors for detailed analysis and design and cost information. Another approach would include helical pile foundation elements. Geotechnical recommendations and design criteria for helical pile foundations are presented in this report. n We recommend a slab-on-grade floor system for the proposed buildings of the headquarters campus provided the soils are over-excavated to a depth of at least 2 feet below the proposed floor slabs and replaced with moisture conditioned, properly compacted engineered fill. On- site soils are generally suitable for lower portions of the over-excavation backfill. The upper 12 inches of over-excavation backfill should consist of Colorado Department of Transportation (CDOT) Class 1 structure backfill. n On-site soils free of vegetation, organic matter and other unsuitable materials or low volume change import materials approved by Terracon may be used as fill/backfill material on the site provided they are placed and compacted as described in this report. On-site bedrock materials or cuttings from pier excavations may be used as fill provided the material is broken down and processed into a “soil-like” consistency, and recompacted. Import materials (if needed) should be evaluated and approved by the geotechnical engineer prior to delivery to the site. n Surface drainage should be designed, constructed and maintained to provide rapid removal of surface water runoff away from the proposed buildings. Water should not be allowed to Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable iii pond adjacent to foundations or exterior slabs and conservative irrigation practices should be followed to avoid wetting the subsoils. The amount of movement of foundations, floor slabs, pavements, etc. will be related to the wetting of underlying supporting soils. Therefore, it is imperative the recommendations discussed in the 4.2.8 Grading and Drainage section of this report be followed to reduce potential movement. n ASCE 7-10 Table 20.3-1 seismic site classification for this site is D. n Recommended Pavement thicknesses for this project include 3½ inches of asphalt over 6 inches of aggregate base course in light-duty parking areas, 5 inches of asphalt over 6 inches of aggregate base course in medium-duty parking areas and 7½ inches of asphalt over 8 inches of aggregate base course in heavy-duty drive lanes and loading areas. Additional pavement section alternatives and discussion are presented in the report. n Close monitoring of the construction operations and implementing drainage recommendations discussed herein will be critical in achieving the intended foundation, slab and pavement performance. 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 PRPA New Headquarters Campus 2000 East Horsetooth Road Fort Collins, Colorado Terracon Project No. 20175041 October 30, 2017 1.0 INTRODUCTION This report presents the results of our geotechnical engineering services performed for the proposed PRPA New Headquarters Campus to be located at 2000 East Horsetooth Road in Fort Collins, Colorado (Exhibit A-1). The purpose of these services is to provide information and geotechnical engineering recommendations relative to: n subsurface soil and bedrock conditions n foundation design and construction n groundwater conditions n floor slab design and construction n grading and drainage n pavement construction n lateral earth pressures n earthwork n seismic considerations Our geotechnical engineering scope of work for this project included the initial site visit, the advancement of eight test borings to depths ranging from approximately 25 to 35 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 Exploration Plans (Exhibit A-2 & A-3) 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. Previously, Terracon prepared a Preliminary Geotechnical Engineering Report (Project No. 20165049; report dated June 15, 2016) for the northern portion of the expansion project. Data from this previous study has been reused during this design-level study and supplemented with additional borings as described in this report. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 2 2.0 PROJECT INFORMATION 2.1 Project Description Item Description Site layout Refer to the Exploration Plans (Exhibit A-2 & A-3 in Appendix A) Building construction We understand the proposed headquarters building will be a two- story structure with a slab-on-grade floor system at ground level and no basement. The superstructure is anticipated to be either a braced timber structure with wood deck or a hybrid moment resisting steel frame/timber beams and wood deck. The warehouse and utility buildings will be single-story, steel-framed structures with masonry. Several earth retaining walls will be planned throughout the site. New pavements will consist of asphalt, concrete and permeable pavements. Existing building and site elements will be demolished and removed from the site prior to new construction. Finished floor elevation Finished floor elevations are unknown at the time of this report. Maximum loads Interior Columns: 300 kips maximum (provided) Exterior Columns: 200 kips maximum (provided) Walls: 2 to 4 kips per linear maximum (assumed) Slabs: 150 pounds per square foot maximum (assumed) Grading Grading plans were not provided at the time of the proposal; however, we anticipate cuts and fills on the order of the 5 feet or less for this project. Demolition may require deeper cuts and fills to properly prepare the site for new construction. Below-grade areas We understand the proposed headquarters building will contain one elevator shaft pit. No basement levels are planned. Traffic loading Anticipated traffic is as follows: Autos/Light Trucks: 700 vehicles per day Light Delivery and Trash Collection Vehicles: 10 vehicles per week Heavy Delivery Trucks: 4 vehicles per week Tractor-trailer trucks: 2 vehicles per week The pavement design period is 20 years. 2.2 Site Location and Description Item Description Location The new headquarters campus is planned at the existing PRPA facility with some expansion planned to the north. The facility is located at 2000 East Horsetooth Road in Fort Collins, Colorado. The approximate Latitude/Longitude of the center of the site is 40.53892° N/105.04124° W Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 3 Item Description Existing site features The existing facility consists of several single and two-story structures with paved access drives and parking areas. A pond is located in the south-central portion of the site with a solar panel site in the southwestern portion of the property. Irrigated grass, shrubs/bushes, and many mature deciduous trees are located throughout the property in landscaping areas. A railroad line is to the west of the property with residential development beyond. The expansion site to the north of the existing facility is currently a vacant field covered with native grasses and weeds. Surrounding developments North: Various office buildings and parking areas East: Two restaurants and a gas station with a carwash among undeveloped land covered with native grasses and weeds. West: Railroad tracks running north and south followed by a large residential development extending to the west and north. South: Several retail stores and businesses. Existing topography The site is currently relatively flat with variations of only a few feet. 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 Lean to fat clay with varying amounts of sand About 7 to 29 feet below existing site grades. Soft to very stiff Sand with varying amounts of clay About 13 to 24 feet below existing site grades. Loose to medium dense Weathered claystone bedrock Upper up to about 7½ feet of bedrock. Weathered Claystone bedrock To the maximum depth of exploration of about 35 feet. Firm to hard Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 4 3.2 Laboratory Testing Representative soil samples were selected for swell-consolidation testing and exhibited no movement to 0.7 percent compression when wetted. Two samples of clay soils exhibited unconfined compressive strengths of approximately 3,200 and 5,200 pounds per square foot (psf). Samples of site soils and bedrock selected for plasticity testing exhibited moderate plasticity with liquid limits ranging from 32 to 61 and plasticity indices ranging from 11 to 38. Laboratory test results are presented in Appendix B. 3.3 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. 3.4 Groundwater These observations represent groundwater conditions at the time of the observations only, and may not be indicative of other times, or at other locations. Groundwater conditions can change with varying seasonal and weather conditions, and other factors. The possibility of groundwater fluctuations should be considered when developing design and construction plans for the project. 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 some borings. The water levels observed in the boreholes are noted on the attached boring logs, and are summarized below Boring Number Depth to groundwater while drilling, ft. Depth to groundwater 1 day after drilling, ft. Elevation of groundwater 1 day after drilling, ft. B5 15.5 Backfilled after drilling Backfilled after drilling B6 15 13 4942.2 B7 15 15 4942.1 B8 20 14 4938.9 B9 15.5 Backfilled after drilling Backfilled after drilling B10 11.5 Backfilled after drilling Backfilled after drilling B11 24 Backfilled after drilling Backfilled after drilling B12 17 16.5 4935.4 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. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 5 Groundwater level fluctuations occur due to seasonal variations in the water levels present in nearby water features, 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 structures 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. 3.5 Percolation Testing Percolation testing was conducted at one additional location near the east-central portion of the site (Figure 1). The percolation rate test results are summarized in the following table. Percolation Test Results Test Hole Date Performed Depth (inches) Visual Soil Classification1 Percolation Rate (minutes/inch) Perc-1 8/1/17 36 Lean clay with sand (CL) 620 1 Visual soil classification was based upon our observations of subsurface conditions exposed in the percolation borehole as well as laboratory testing completed on sample obtained from nearby borings. The average percolation rate in test hole P-1 was approximately 620 minutes per inch. Very low infiltration rates should be used during design of any storm water infiltration elements. 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 structures, pavements, and other site improvements. 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 Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 6 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. 4.2.1 Site Preparation Prior to placing any fill, strip and remove existing vegetation, concrete and asphalt pavements or flatwork from the proposed construction areas. Stripped organic materials should be wasted from the site or used to re-vegetate landscaped areas 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 the existing PRPA Headquarters Campus 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 existing PRPA Headquarters Campus are not known. If some or all of the existing buildings are supported by drilled piers, the existing piers should be truncated a minimum depth of 3 feet below areas of planned new construction. Consideration could be given to re-using the asphalt and concrete provided the materials are processed and uniformly blended with the on-site soils. Asphalt and/or concrete materials should be processed to a maximum size of 2-inches and blended at a ratio of 30 percent asphalt/concrete to 70 percent of on-site soils. 4.2.3 Excavation It is anticipated that excavations for the proposed structures 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. 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. Any over-excavation that extends below the bottom of foundation elevation should extend laterally beyond all edges of the foundations at least 8 inches per foot of over-excavation depth below the Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 7 foundation base elevation. The over-excavation should be backfilled to the foundation base elevation in accordance with the recommendations presented in this report. 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 We recommend that the top 10 inches of the exposed ground surface is 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, foundation or pavement is placed. If pockets of soft, loose, or otherwise unsuitable materials are encountered at the bottom of the foundation excavations and it is inconvenient to lower the foundations, the proposed foundation elevations may be reestablished by over-excavating the unsuitable soils and backfilling with compacted engineered fill or lean concrete. 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. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 8 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. Use of lime, fly ash, cement or geotextiles could also be considered as a stabilization technique. Laboratory evaluation is recommended to determine the effect of chemical stabilization on subgrade soils prior to construction. 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 upper 12 inches of over-excavation backfill below floor slabs should consist of CDOT class 1 structure backfill. The soil removed from this site that is free of organic or objectionable materials, 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 the onsite soil may require reworking to adjust the moisture content to meet the compaction criteria. CDOT Class 1 structure backfill should meet the following material property requirements: Gradation Percent finer by weight (ASTM C136) 2” 100 No. 4 Sieve 30-100 No. 50 Sieve 10-60 No. 200 Sieve 5-20 Soil Properties Values Liquid Limit 35 (max.) Plastic Limit 6 (max.) 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 15-50 Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 9 Soil Properties Values Liquid Limit 35 (max.) Plastic Limit 6 (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. 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 9 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 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 structures 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. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 10 Utility trenches are a common source of water infiltration and migration. All utility trenches that penetrate beneath the buildings should be effectively sealed to restrict water intrusion and flow through the trenches that could migrate below the buildings. 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 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 buildings 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. Water permitted to pond near or adjacent to the perimeter of the structures (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 5 feet beyond the perimeter of the proposed buildings, 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 buildings. Backfill against foundations 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 buildings 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 structures, care should be taken that joints are properly sealed and maintained to prevent the infiltration of surface water. Planters located adjacent to structures 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 be used sparingly near the building. Roof drains should discharge on to pavements or be extended away from the structures 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 PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 11 4.3 Foundations Terracon considered several foundation and ground modification alternatives for support of the proposed structures at the PRPA New Headquarters project including: n Drilled piers n Helical piles n Rammed aggregate-piers n Spread footings (single-story buildings) Low strength and compressible soils are present on this site. Therefore, it is our opinion that shallow foundations bearing on the site soils are not feasible for support of the proposed headquarters, warehouse, and pool car garage structures. The proposed structures can be supported by deep foundations bottomed in bedrock, in accordance with our design recommendations below. The proposed single-story metal buildings may be supported on shallow, spread footing foundations bearing on the native soil or on newly placed engineered fill. Without ground modification, we recommend a maximum allowable soil bearing pressure of 1,500 psf. In order to increase the maximum allowable soil bearing pressure to 2,000 psf, we recommend over- excavating the soils below footings to a depth of at least 2 feet and replacing with moisture conditioned, properly compacted engineered fill. On site soils may be reused as over-excavation backfill below foundations. Terracon recommends constructing the proposed headquarters, warehouse, and pool car garage structures on either drilled piers or helical piles bottomed in bedrock. As an alternative to drilled pier or helical foundations for the proposed headquarters, warehouse, and pool car garage, consideration could be given to ground modification/improvement techniques to improve strength and compressibility characteristics of the foundation soils and to allow for support of the structure on shallow foundations. One approach would include rammed aggregate-pier foundation elements or stone columns to support shallow foundations. Stone columns and rammed aggregate piers consist of a series of drilled holes filled with highly compacted, well graded aggregate to form very stiff, high-density aggregate piers. The stone column and rammed aggregate piers are generally extended below the low strength soil layer to a layer of higher bearing capacity soils or bedrock. Installation of these elements results in significant strengthening and stiffening of the foundation bearing layer to support footings within typical settlement tolerances. Shallow foundations are then constructed over the piers/columns in a conventional manner. Aggregate-pier foundation elements are usually part of the contractor’s design-build system. Therefore, the subsurface exploration information contained in this report should be provided to the foundation contractors for detailed analysis and design and cost information. Design recommendations for foundations for the proposed structures and related structural elements are presented in the following sections. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 12 4.3.1 Drilled Piers Bottomed in Bedrock - Design Recommendations Description Value Minimum pier length 25 feet Minimum pier diameter 18 inches Minimum bedrock embedment (competent bedrock) 1 6 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. Actual structural loads and pier diameters may dictate embedment deeper than the recommended minimum penetration. The upper approximately 2 to 7½ feet of claystone bedrock encountered in our borings was highly weathered. Thicker layers of weathered bedrock may be present below other areas of the site. Penetration or embedment into competent, unweather bedrock should be considered below the weathered zone of bedrock to be determined during pier drilling. 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 type Stiff clay w/o free water Sand (Reese) Stiff clay w/o free water Effective unit weight (pcf) above groundwater 120 120 130 Effective unit weight (pcf) below groundwater 60 60 70 Average undrained shear strength (psf) 2,000 N/A 9,000 Average angle of internal friction, F (degrees) N/A 34 N/A Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 13 Parameters Clay Sand and Gravel Claystone Bedrock Coefficient of subgrade reaction, k (pci)* 500 - static 200 - cyclic 90 (Submerged) 2,000- static 800 – cyclic Strain, e50 (%) 0.007 N/A 0.004 1. For purposes of LPILE analysis, assume a groundwater depth below existing ground surface corresponding to nearby borings 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 layers (if encountered). In addition, 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. 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. 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. 4.3.3 Helical Pile Foundations We believe helical piles bottomed in bedrock are appropriate for support of the proposed headquarters, warehouse, and pool car garage structures. Design recommendations for helical pile foundations and related structural elements are presented in the following paragraphs. Description Value Bearing material Claystone bedrock Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 14 Description Value Anticipated pile length About 22 to 30 feet from existing slab subgrade levels (top of grade beams) Net allowable end-bearing pressure 25,000 psf Individual pile settlement About ½ inch Void thickness (between piles and below pile caps) 4 inches We do not recommend using vertically installed helical piles to resist lateral loads without approved lateral load test data, as these types of foundations are typically designed to resist axial loads. Only the horizontal component of the allowable axial load should be considered to resist the lateral loading and only in the direction of the batter. Terracon should be retained to observe helical pile installation to verify that proper bearing materials have been encountered during installation. In accordance with local building code requirements, a load test should be performed by the helical pile installer to validate achieving the allowable design load. Load tests should be performed using helical piles consistent in size and materials with those piles planned for use during construction. Similarly, the same installation techniques and equipment planned for use during installation of production piles should be used when installing piles for load testing. If a helical pile foundation system is selected by the project team, we recommend the helical pile designer follow the recommendations presented in Chapter 18 of the most current International Building Code (IBC). We recommend the helical bearing plates for each helical pile bear in the claystone bedrock encountered below the site. We do not recommend helical bearing plates bottomed in native clay soils. The helical pile designer should select the size and number of helical bearing plates for each helical pile based on planned loads and bearing materials described in our exploratory boring logs. Torque measurements during installation of helical piles should be used to verify the axial capacity of the helical piles. Terracon should be provided with the torque to capacity relationships for each type of pile used on the project for our review and comment prior to mobilization to the site. We recommend the helical pile installation contractor provide confirmation that the installation equipment has been calibrated within one year of installation at this project. The helical foundations should be installed by a qualified specialty contractor per the manufacturer’s recommendations. 4.3.4 Spread Footings - Design Recommendations Description Values Bearing material Properly prepared on-site soil Properly placed engineered fill Maximum allowable bearing pressure 1 1,500 psf 2,000 psf Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 15 Description Values Lateral earth pressure coefficients 2 Active, Ka = 0.36 Passive, Kp = 2.77 At-rest, Ko = 0.53 Active, Ka = 0.28 Passive, Kp = 3.54 At-rest, Ko = 0.44 Sliding coefficient 2 µ = 0.42 Moist soil unit weight = 120 pcf = 135 pcf Minimum embedment depth below finished grade 3 30 inches Estimated total movement About 1 inch Estimated differential movement About ½ to ¾ of total movement 1. The recommended maximum 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. 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. 4.3.5 Spread Footings - Construction Considerations To reduce the potential of “pumping” and softening of the foundation soils at the foundation bearing level and the requirement for corrective work, we suggest the foundation excavation for the single-story metal buildings be completed remotely with a track-hoe operating outside of the excavation limits. 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. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 16 Footings and foundation walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. 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 gravel 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 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 Table 20.3-1 of ASCE 7-10 1 D 2 1. Table 20.3-1 of ASCE 7-10 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 30 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. However, we believe a higher seismic site class for this site is unlikely. 4.5 Floor Systems A slab-on-grade may be utilized for the interior floor system for the proposed structures provided the native soils are over-excavated to a depth of at least 2 feet, moisture conditioned, and compacted. On-site soils are generally suitable for lower portions of the over-excavation backfill. The upper 12 inches of over-excavation backfill should consist of Colorado Department of Transportation (CDOT) Class 1 structure backfill. Subgrade soils at the base of the over-excavation below proposed floor slabs should be scarified to a depth of at least 10 inches, moisture conditioned and compacted. The moisture content and compaction of subgrade soils should be maintained until slab construction. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 17 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 presented 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 200 pounds per cubic inch (pci) may be used for floors supported the recommended over-excavation backfill. Additional floor slab design and construction recommendations are as follows: n Positive separations and/or isolation joints should be provided between slabs and all foundations, columns, or utility lines to allow independent movement. n 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. n 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. n Floor slabs should not be constructed on frozen subgrade. n 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 should refer to ACI 302 for procedures and cautions regarding the use and placement of a vapor retarder. n 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. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 18 For warehouse slabs that will support traffic loading (if any), we recommend the slab be designed using the Portland Cement Association method or similar mechanistic stress-based design for concrete slabs. For slabs that will carry significant traffic, we also recommend doweled joints be considered for the slab connections. To control the width of cracking (should it occur) continuous slab reinforcement should be considered in exposed concrete slabs. 4.6 Lateral Earth Pressures Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls. EARTH PRESSURE COEFFICIENTS Earth Pressure Conditions Coefficient for Backfill Type Equivalent Fluid Density (pcf) Surcharge Pressure, p1 (psf) Earth Pressure, p2 (psf) Active (Ka) Imported Fill - 0.28 Lean Clay - 0.36 38 43 (0.28)S (0.36)S (38)H (43)H Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 19 Earth Pressure Conditions Coefficient for Backfill Type Equivalent Fluid Density (pcf) Surcharge Pressure, p1 (psf) Earth Pressure, p2 (psf) At-Rest (Ko) Imported Fill - 0.44 Lean Clay - 0.53 59 64 (0.44)S (0.53)S (59)H (64)H Passive (Kp) Imported Fill - 3.54 Lean Clay – 2.77 478 332 --- --- --- --- Applicable conditions to the above include: n For active earth pressure, wall must rotate about base, with top lateral movements of about 0.002 H to 0.004 H, where H is wall height; n For passive earth pressure to develop, wall must move horizontally to mobilize resistance; n Uniform surcharge, where S is surcharge pressure; n In-situ clay soil backfill weight a maximum of 120 pcf and import is 135 pcf n Horizontal backfill, compacted between 95 and 98 percent of maximum dry unit weight as determined by ASTM D698; n Loading from heavy compaction equipment not included; n No hydrostatic pressures acting on wall; n No dynamic loading; n No safety factor included in soil parameters; and n Ignore passive pressure in frost zone. To control hydrostatic pressure behind the wall, we recommend that a drain be installed at the foundation wall with a collection pipe leading to a reliable discharge. If this is not possible, then combined hydrostatic and lateral earth pressures should be calculated for lean clay backfill using an equivalent fluid weighing 90 and 100 pcf for active and at-rest conditions, respectively. For granular backfill, an equivalent fluid weighing 85 and 90 pcf should be used for active and at-rest, respectively. These pressures do not include the influence of surcharge, equipment or floor loading, which should be added. Heavy equipment should not operate within a distance closer than the exposed height of retaining walls to prevent lateral pressures more than those provided. 4.6.1 Wall Drainage Free-draining granular backfill should be used behind retaining walls to help relieve hydrostatic pressure and provide drainage. We recommend a free-draining gravel material with less than 5 percent fines (material passing the No. 200 sieve) be used for a zone within at least 1-foot behind the walls. The drainage material should be tested and approved by our office prior to delivery to Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 20 We recommend weep holes and/or installation of a drain pipe at the base of the free-draining backfill zone. If a drain is installed, it should consist of a minimum 4-inch perforated rigid PVC pipe encased in free-draining gravel. The drain pipe should slope at least ½ percent to a positive gravity outlet at either or both ends of the wall, or be connected to outfall more than 5 feet in front of the wall. Where the backfill zone is not covered with pavement or flatwork, we recommend the entire backfill zone be capped with at least 18 inches of clay fill to reduce infiltration and conveyance of surface water through the wall backfill. 4.7 Pavements 4.7.1 Pavements – 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 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 – 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 on-site soil selected for swell-consolidation testing compressed about 0.3 percent when wetted under an applied pressure of 150 psf. The upper clay soils encountered in our borings were generally comparatively moist and visual observations confirmed low swelling to slightly compressive characteristics. Therefore, we do not believe swell-mitigation of the subgrade materials prior to pavement operations is required. Traffic patterns and anticipated loading conditions were estimated by others to assist with development of our pavement thickness recommended actions. 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 and heavy-duty). For our pavement thicknesses design recommendations, we assumed a 18-kip equivalent single-axle load (ESAL) of 73,000 for automobile parking areas, an ESAL of 365,000 for medium truck traffic areas, and an ESAL of 1,095,000 for heavy truck traffic areas. These assumed traffic design values should be verified Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 21 by the civil engineer or owner prior to final design and construction. If the actual traffic values vary from the assumed values, the pavement thickness recommendations may not be applicable. When the actual traffic design information is available Terracon should be contacted so that the design recommendations can be reviewed and revised if necessary. For flexible pavement design, a terminal serviceability index of 2.0 was utilized along with an inherent reliability of 85 percent and a design life of 20 years. Using the measured R-value of 9, appropriate ESAL, environmental criteria and other factors, the structural numbers (SN) of the pavement sections were determined on the basis of the 1993 AASHTO design equation. In addition to the flexible pavement design analyses, a rigid pavement design analysis was completed based upon AASHTO design procedures. 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 outlined. The design k-value of 100 for the subgrade soil was determined by correlation to the laboratory test results. A modulus of rupture of 600 psi (working stress 450 psi) was used for pavement concrete. The rigid pavement thickness for each traffic category was determined on the basis of the AASHTO design equation. Recommended minimum pavement sections are provided in the table below. Traffic Area Alternative Recommended Pavement Thicknesses (Inches) Asphaltic Concrete Surface Aggregate Base Course Portland Cement Concrete Total Automobile parking areas (light-duty) A 3½ 6 -- 9½ B - - 6 6 Occasional truck traffic areas (medium- duty) A 4 6 - 10 B - - 7 7 Truck traffic areas (heavy- duty) A 5 8 - 13 B - - 8 8 Aggregate base course (if used on the site) should consist of a blend of sand and gravel which meets strict specifications for quality and gradation. Use of materials meeting Colorado Department of Transportation (CDOT) Class 5 or 6 specifications is recommended for aggregate base course. Aggregate base course should be placed in lifts not exceeding 6 inches and compacted to a minimum of 95 percent of the maximum dry unit weight as determined by ASTM D698. Asphaltic concrete should be composed of a mixture of aggregate, filler and additives (if required) and approved bituminous material. The asphalt concrete should conform to approved mix Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 22 designs stating the Superpave properties, optimum asphalt content, job mix formula and recommended mixing and placing temperatures. Aggregate used in asphalt concrete should meet particular gradations. Material meeting CDOT Grading S or SX specifications or equivalent is recommended for asphalt concrete. Mix designs should be submitted prior to construction to verify their adequacy. Asphalt material should be placed in maximum 3-inch lifts and compacted within a range of 92 to 96 percent of the theoretical maximum (Rice) density (ASTM D2041). Where rigid pavements are used, the concrete should be obtained from an approved mix design with the following minimum properties: Properties Value Compressive strength 4,000 psi Cement type Type I or II portland cement Entrained air content (%) 5 to 8 Concrete aggregate ASTM C33 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. 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: n Site grades should slope a minimum of 2 percent away from the pavements; n The subgrade and the pavement surface have a minimum 2 percent slope to promote proper surface drainage; n Consider appropriate edge drainage and pavement under drain systems; n Install pavement drainage surrounding areas anticipated for frequent wetting; n Install joint sealant and seal cracks immediately; n Seal all landscaped areas in, or adjacent to pavements to reduce moisture migration to subgrade soils; and n Placing compacted, low permeability backfill against the exterior side of curb and gutter. Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 23 4.7.3 Pavements – Construction Considerations Openings in pavement, such as landscape islands, are sources for water infiltration into surrounding pavements. Water collects in the islands and migrates into the surrounding subgrade soils thereby degrading support of the pavement. This is especially applicable for islands with raised concrete curbs, irrigated foliage, and low permeability near-surface soils. The civil design for the pavements with these conditions should include features to restrict or to collect and discharge excess water from the islands. Examples of features are edge drains connected to the storm water collection system or other suitable outlet and impermeable barriers preventing lateral migration of water such as a cutoff wall installed to a depth below the pavement structure. 4.7.4 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. 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, and 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 Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable 24 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 PRPA New Headquarters Campus 2000 East Horsetooth Road Fort Collins, CO TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY QUADRANGLES INCLUDE: FORT COLLINS, CO (1984). 1901 Sharp Point Dr Ste C Fort Collins, CO 80525-4429 20175041 Project Manager: Drawn by: Checked by: Approved by: NDH EDB EDB 1”=2,000’ Project No. Scale: File Name: Date: A-1 EDB Exhibit SITE 10/30/2017 approximate location of boring completed 6/7/16 (20165049) approximate location of temporary benchmark for borings completed 6/7/16 (20165049) approximate location of boring approximate location of percolation test EXPLORATION PLAN PRPA New Headquarters Campus 2000 East Horsetooth Road Fort Collins, CO 1901 Sharp Point Dr Ste C Fort Collins, CO 80525-4429 DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES 20175041 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS NDH EDB EDB AS SHOWN 10/30/2017 Scale: A-2 Exhibit Project Manager: Drawn by: Checked by: Approved by: Project No. File Name: Date: EDB East Horsetooth Road South Timberline Road South Timberline Road East Horsetooth Road approximate location of boring completed 6/7/16 (20165049) approximate location of temporary benchmark for borings completed 6/7/16 (20165049) approximate location of boring approximate location of percolation test EXPLORATION PLAN 1901 Sharp Point Dr Ste C Fort Collins, CO 80525-4429 20175041 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS PRPA New Headquarters Campus 2000 East Horsetooth Road Fort Collins, CO DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: Drawn by: Checked by: Approved by: NDH EDB EDB EDB 10/30/2017 Scale: Project No. File Name: Date: AS SHOWN A-3 Exhibit Responsive Resourceful Reliable Exhibit A-4 Field Exploration Description The locations of borings were based upon the proposed development shown on the provided site plan and reasonably accessible areas for a truck-mounted drill rig. The borings were located in the field by measuring from existing site features. The ground surface elevation was determined at each boring location using detailed plans provided by the civil engineer. Previously, Terracon prepared a Preliminary Geotechnical Engineering Report (Project No. 20165049; report dated June 15, 2016) for a PRPA Expansion Project included in the area of four (4) exploratory borings at the approximate locations shown on Exhibits A-2 and A-3. We have included the boring logs and laboratory test results as part of this report to assist with our analyses and development of geotechnical recommendations for the project. Field exploration description for the previously completed borings (Boring Nos. 1 through 4) is presented in the preliminary report. The borings were drilled with a CME-55 truck-mounted rotary drill rig with solid-stem and hollow- 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 and a conventional safety hammer were 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. After Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 Responsive Resourceful Reliable Exhibit A-5 completion of drilling, five of the borings were left open for delayed water level measurements and then backfilled with auger cuttings and patched (if needed). Groundwater measurements were obtained in three of the borings at the time of site exploration and several days after drilling. After subsequent groundwater measurements were obtained, the five borings were backfilled with auger cuttings and patched (if needed). Some settlement of the backfill and/or patch may occur and should be repaired as soon as possible. A percolation rate test was conducted by drilling a 6-inch diameter hole to a depth of about 3 feet, inserting an impermeable membrane around the perimeter of the cylindrical hole, and filling the hole with water. The hole was temporarily capped in order to prevent excessive water level variation from evaporation or contamination from outside sources of water. The height of water was then measured throughout a 6-hour period to produce a percolation rate associated with the on-site clay soils. 79 18 14 17 19 12 13 11 98 57-21-36 92.5 86.5 81.5 65 5-8-8 N=16 2-2-2 N=4 3-6-18 N=24 5-12-18 N=30 6-18-25 N=43 18-28 50/4" 30-47 50/3" 35-43 50/2" 8.0 14.0 19.0 35.1 LEAN CLAY WITH SAND, brown to reddish-brown, medium stiff to very stiff CLAYEY SAND, fine to coarse grained, yellowish-brown to reddish-brown, medium dense WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), gray to yellowish-brown, medium hard, completely weathered SEDIMENTARY BEDROCK - INTERBEDDED SANDSTONE and CLAYSTONE, gray, very hard, laminated bedding, slightly weathered Boring Terminated at 35.1 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic GRAPHIC LOG THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165049.GPJ TERRACON2015.GDT 6/15/16 Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4-inch Solid-Stem Auger Abandonment Method: Borings backfilled with soil cuttings upon completion. 1901 Sharp Point Dr Ste C Fort Collins, CO Notes: Project No.: 20165049 14 84 20 15 13 16 17 15 96 40-17-23 91 81 76 70 -0.2/500 4-4-4 N=8 4-9 3-4-6 N=10 4-8-12 N=20 13-40-45 N=85 16-37-50 N=87 30 50/6" 9.0 19.0 24.0 30.0 LEAN CLAY WITH SAND (CL), brown to reddish-brown, medium stiff to stiff CLAYEY SAND, fine to coarse grained, yellowish-brown to reddish-brown, loose to medium dense WEATHERED BEDROCK: INTERBEDDED CLAYSTONE, gray to yellowish-brown, hard, completely weathered SEDIMENTARY BEDROCK - INTERBEDDED SANDSTONE and CLAYSTONE, gray, very hard, laminated bedding, slightly weathered Boring Terminated at 30 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic GRAPHIC LOG THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165049.GPJ TERRACON2015.GDT 6/15/16 Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4-inch Solid-Stem Auger Abandonment Method: Borings backfilled with soil cuttings upon completion. 1901 Sharp Point Dr Ste C Fort Collins, CO Notes: Project No.: 20165049 Drill Rig: CME-75 Boring Started: 6/7/2016 BORING LOG NO. 2 CLIENT:Authority Platte River Power 80 52 20 13 18 14 16 15 101 37-16-21 32-14-18 89.5 87 81 69.5 -0.2/500 4-7-8 N=15 6-5 2-3-3 N=6 4-7-11 N=18 7-10-11 N=21 14-34-50 N=84 20-43 50/4" 10.5 13.0 19.0 30.4 LEAN CLAY WITH SAND (CL), brown to reddish-brown, stiff CLAYEY SAND, fine to coarse grained, yellowish-brown to reddish-brown, medium dense WEATHERED BEDROCK: INTERBEDDED CLAYSTONE, gray to yellowish-brown, completely weathered SEDIMENTARY BEDROCK - INTERBEDDED SANDSTONE and CLAYSTONE, gray, very hard, laminated bedding, slightly weathered Boring Terminated at 30.3 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic GRAPHIC LOG THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165049.GPJ TERRACON2015.GDT 6/15/16 Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4-inch Solid-Stem Auger Abandonment Method: Borings backfilled with soil cuttings upon completion. 1901 Sharp Point Dr Ste C Fort Collins, CO Notes: Project No.: 20165049 Drill Rig: CME-75 Boring Started: 6/7/2016 BORING LOG NO. 3 CLIENT:Authority Platte River Power 26 12 13 14 16 16 16 17 106 23-15-8 91 81 76 69.5 3-3-3 -0.2/1,000 N=6 2-2-2 N=4 4-4 5-8-13 N=21 8-22-25 N=47 12-20-47 N=67 14-22 50/5" 9.0 19.0 24.0 30.4 LEAN CLAY WITH SAND (CL), brown to reddish-brown, medium stiff CLAYEY SAND (SC), fine to coarse grained, yellowish-brown to reddish-brown, medium dense WEATHERED BEDROCK: INTERBEDDED SANDSTONE, gray to yellowish-brown, hard, completely weathered SEDIMENTARY BEDROCK - INTERBEDDED SANDSTONE and CLAYSTONE, gray, very hard, laminated bedding, slightly weathered Boring Terminated at 30.4 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Automatic GRAPHIC LOG THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20165049.GPJ TERRACON2015.GDT 6/15/16 Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4-inch Solid-Stem Auger Abandonment Method: Borings backfilled with soil cuttings upon completion. 1901 Sharp Point Dr Ste C Fort Collins, CO Notes: Project No.: 20165049 Drill Rig: CME-75 Boring Started: 6/7/2016 BORING LOG NO. 4 CLIENT:Authority Platte River Power 17 18 15 12 24 20 106 42-17-25 4956 4955.5 4937 4934 4930.5 10-15 2-2-2 N=4 4-6-3 N=9 12-10-10 N=20 20-30 50/6" -0.3/150 0.2 0.9 19.0 22.0 25.5 ASPHALT, approximately 2 inches AGGREGATE BASE COURSE, approximately 8 inches SANDY LEAN CLAY, light brown, very stiff to soft WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), brown/gray, medium hard SEDIMENTARY BEDROCK - CLAYSTONE, with sand, brown/gray, hard to very hard at 25.5 Feet GRAPHIC LOG Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Rope and Cathead THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS ELEVATION (Ft.) Surface Elev.: 4956.2 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 SAMPLE TYPE FIELD TEST 20 23 21 27 22 20 21 21 45-17-28 4955 4948 4931 4926 4919.5 3-4-5 N=9 3-4 1-1-2 N=3 5-6-7 N=13 5-10 9-13-18 N=31 12-17-29 N=46 13-22-34 N=56 0.3 7.0 24.0 29.0 35.5 VEGETATIVE LAYER, approximately 4 inches LEAN CLAY WITH SAND, reddish brown, medium stiff to stiff SANDY LEAN CLAY, light brown to tan, soft to stiff WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), light brown with orange, medium hard SEDIMENTARY BEDROCK - CLAYSTONE, with sand, light brown with orange, hard Boring Terminated at 35.5 Feet GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS ELEVATION (Ft.) Surface Elev.: 4955.2 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 15 15 14 24 23 18 110 107 4957 4955.5 4943 4933 4931.5 5-3-3 N=6 3-4-4 N=8 3-6 4-5-7 N=12 4-4-8 N=12 10-18 -0.7/1000 0.2 1.7 14.0 24.0 25.5 ASPHALT, approximately 2 inches AGGREGATE BASE COURSE, approximately 18 inches SANDY LEAN CLAY, trace gravel, reddish brown to light brown, medium stiff to stiff LEAN CLAY WITH SAND, light brown, stiff WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), brown, firm Boring Terminated at 25 Feet GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS ELEVATION (Ft.) Surface Elev.: 4957.1 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 19 25 23 23 21 32 94 100 42-20-22 32-11-21 59-13-46 4952.5 4940 4935 4927.5 4-6 2-4-5 N=9 6-8-22 N=30 8-10-15 N=25 18-30 14-13-16 N=29 +0.0/1000 0.3 13.0 18.0 25.5 VEGETATIVE LAYER, approximately 4 inches LEAN CLAY, light brown, medium stiff to hard LEAN CLAY WITH SAND, light brown with orange and grey, very stiff WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), brown, firm Boring Terminated at 25.5 Feet GRAPHIC LOG Stratification lines are approximate. In-situ, the transition may be gradual. Hammer Type: Rope and Cathead THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS ELEVATION (Ft.) Surface Elev.: 4952.9 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 3210 17 21 19 8 28 23 21 21 96 99 47-18-29 47-21-26 61-23-38 4955.5 4954.5 4944 4932 4927 4920.5 3-5-6 N=11 3-4 2-1-2 N=3 3-9-9 N=18 4-8 10-13-22 N=35 13-17-28 N=45 17-23-32 N=55 -0.6/1000 0.2 1.5 12.0 24.0 29.0 35.5 ASPHALT, approximately 2 inches AGGREGATE BASE COURSE, approximately 16 inches LEAN CLAY WITH SAND, light brown to tan, soft to medium stiff FAT CLAY (CH), light brown, stiff to very stiff WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), light brown with orange and grey, medium hard SEDIMENTARY BEDROCK - CLAYSTONE, with sand, light brown with orange and grey, medium hard to hard Boring Terminated at 35.5 Feet GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT 5150 19 19 21 18 21 15 12 18 107 105 47-21-26 39-18-21 52-22-30 4955 4954 4936 4926 4919.5 3-3-4 N=7 5-8 4-5-8 N=13 2-3-4 N=7 4-13 7-11-12 N=23 30-23-40 N=63 19-23-28 N=51 +0.0/1000 ASPHALT, approximately 2 inches AGGREGATE BASE COURSE, approximately 9 inches LEAN CLAY WITH SAND, light brown to brown, medium stiff to stiff, dark brown to brown at about 4 feet SANDY LEAN CLAY, light brown, stiff to very stiff, with varying amounts of gravel SEDIMENTARY BEDROCK - SANDSTONE and CLAYSTONE, with gravel, light brown to orange, hard Boring Terminated at 35.5 Feet 0.2 1.0 19.0 29.0 35.5 GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG 22 22 15 18 16 18 19 23 100 45-21-24 48-22-26 4952.5 4946 4934 4929 4926 4917.5 3-3-4 N=7 7-10 2-2-3 N=5 2-2-1 N=3 5-3 12-20-22 N=42 21-22-35 N=57 19-22-30 N=52 0.5 7.0 19.0 24.0 27.0 35.5 VEGETATIVE LAYER, approximately 6 inches LEAN CLAY, dark brown/brown, medium stiff SANDY LEAN CLAY, yellow brown to red brown, soft to medium stiff CLAYEY SAND, yellow brown, loose WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), yellow brown, medium hard SEDIMENTARY BEDROCK - CLAYSTONE, with sand, yellow brown, hard, grey brown to yellow brown observed at about 34ft Boring Terminated at 35.5 Feet GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS 19 18 16 20 13 17 15 19 99 45-21-24 4951.5 4938 4933 4928 4926 4916.5 3-3-7 N=10 4-10 2-3-3 N=6 4-5 5-7-8 N=15 14-20-27 N=47 19-40-41 N=81 16-21-37 N=58 -0.1/1000 0.5 14.0 19.0 24.0 26.0 35.5 VEGETATIVE LAYER, dark brown, approximately 6 inches LEAN CLAY WITH SAND, dark brown/brown, medium stiff to stiff CLAYEY SAND, red brown to yellow brown, loose CLAYEY SAND WITH GRAVEL, light brown, medium dense WEATHERED BEDROCK: INTERBEDDED CLAYSTONE (CH), yellow brown, medium hard SEDIMENTARY BEDROCK - CLAYSTONE, with sand, yellow brown, hard, grey and orange layers observed at about 34ft Boring Terminated at 35.5 Feet GRAPHIC LOG StratificationAutomatic lines are approximate. In-situ, the transition may be gradual. Hammer Type: THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 UNCONFINED COMPRESSIVE STRENGTH (psf) WATER CONTENT (%) DRY UNIT WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS APPENDIX B LABORATORY TESTING Geotechnical Engineering Report PRPA New Headquarters Campus Fort Collins, Colorado October 30, 2017 Terracon Project No. 20175041 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, pavement 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. Procedural standards noted in this report are for reference to methodology in general. In some cases, variations to methods are applied as a result of local practice or professional judgment. n Water content n Plasticity index n Grain-size distribution n Consolidation/swell n Compressive strength n Water-soluble sulfate content n Dry density n R-value n Shear strength n pH 0 10 20 30 40 50 60 0 20 40 60 80 100 CL or OL CH or OH ML or OL MH or OH Boring ID Depth PL PI Description FAT CLAY with SAND LEAN CLAY with SAND LEAN CLAY with SAND SANDY LEAN CLAY CLAYEY SAND CH CL CL CL SC Fines P L A S T I C I T Y I N D E X LIQUID LIMIT "U" Line "A" Line 57 40 37 32 23 21 17 16 14 15 36 23 21 18 8 79 84 80 52 0 10 20 30 40 50 60 0 20 40 60 80 100 CL or OL CH or OH ML or OL MH or OH "U" Line "A" Line ATTERBERG LIMITS RESULTS ASTM D4318 P L A S T I C I T Y I N D E X LIQUID LIMIT PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-3 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. ATTERBERG LIMITS 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 2 - 3 2 - 3.5 1 - 2 3 - 4 19 - 20 2 - 3.5 4 - 5 19 - 20 2 - 3.5 4 - 5 29 - 30.5 4 - 5 9 - 10.5 4 - 5 B05 B06 B08 B08 B08 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 100 10 1 0.1 0.01 0.001 1 2 3 3 4 57 40 37 32 23 0.09 0.111 0.314 4.75 4.75 9.5 4.75 19 6 16 20 30 40 50 1.5 6 200 810 0.0 0.0 0.2 0.0 12.3 14 79.1 83.9 80.0 52.3 25.7 %Fines LL PL PI 1 4 3/4 1/2 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 100 10 1 0.1 0.01 0.001 30 40 1.5 50 6 8 200 4 10 14 1 3/4 1/2 60 GRAIN SIZE IN MILLIMETERS PERCENT FINER BY WEIGHT U.HYDROMETERS. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 4 3/8 3 3 100 140 2 GRAIN SIZE DISTRIBUTION ASTM D422 / ASTM C136 6 16 20 PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-5 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 0.0 0.2 0.0 1.4 0.0 4.75 5.6 2.36 5.6 4.75 0.101 45 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 100 10 1 0.1 0.01 0.001 30 40 1.5 50 6 8 200 4 10 14 1 3/4 1/2 60 GRAIN SIZE IN MILLIMETERS PERCENT FINER BY WEIGHT U.HYDROMETERS. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 4 3/8 3 3 100 140 2 GRAIN SIZE DISTRIBUTION ASTM D422 / ASTM C136 6 16 20 PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-6 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 0.0 0.0 0.0 0.0 0.1 4.75 4.75 4.75 4.75 9.5 47 47 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 100 10 1 0.1 0.01 0.001 30 40 1.5 50 6 8 200 4 10 14 1 3/4 1/2 60 GRAIN SIZE IN MILLIMETERS PERCENT FINER BY WEIGHT U.HYDROMETERS. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 4 3/8 3 3 100 140 2 GRAIN SIZE DISTRIBUTION ASTM D422 / ASTM C136 6 16 20 PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-7 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 19.2 0.0 4.7 0.0 12.5 4.75 16 2.36 0.447 0.082 52 45 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample compressed 0.2 percent at an applied load of 500 psf. 1901 Sharp Point Dr Ste C Fort Collins, CO PROJECT: PRPA Expansion Project PROJECT NUMBER: 20165049 SITE: Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO CLIENT: Platte River Power Authority EXHIBIT: B-8 Specimen Identification Classification , pcf 97 20 WC, % 2 4 - 5 ft LEAN CLAY with SAND LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20165049.GPJ TERRACON2012.GDT 6/14/16 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample compressed 0.2 percent at an applied load of 500 psf. 1901 Sharp Point Dr Ste C Fort Collins, CO PROJECT: PRPA Expansion Project PROJECT NUMBER: 20165049 SITE: Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO CLIENT: Platte River Power Authority EXHIBIT: B-9 Specimen Identification Classification , pcf 101 20 WC, % 3 4 - 5 ft LEAN CLAY with SAND(CL) LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20165049.GPJ TERRACON2012.GDT 6/14/16 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample compressed 0.2 percent at an applied load of 500 psf. 1901 Sharp Point Dr Ste C Fort Collins, CO PROJECT: PRPA Expansion Project PROJECT NUMBER: 20165049 SITE: Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO CLIENT: Platte River Power Authority EXHIBIT: B-10 Specimen Identification Classification , pcf 106 14 WC, % 4 9 - 10 ft LEAN CLAY with SAND LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20165049.GPJ TERRACON2012.GDT 6/14/16 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited compression of 0.3 percent upon wetting under an applied pressure of 150 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-11 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 106 17 WC, % B05 2 - 3 ft SANDY LEAN CLAY LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited compression of 0.7 percent upon wetting under an applied pressure of 1,000 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-12 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 110 14 WC, % B07 9 - 10 ft SANDY LEAN CLAY LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited no movement upon wetting under an applied pressure of 1,000 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-13 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 94 19 WC, % B08 3 - 4 ft LEAN CLAY LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited compression of 0.6 percent upon wetting under an applied pressure of 1,000 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-14 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 96 21 WC, % B09 4 - 5 ft LEAN CLAY WITH SAND LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited no movement upon wetting under an applied pressure of 1,000 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-15 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 116 13 WC, % B10 19 - 20 ft SANDY LEAN CLAY LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 AXIAL STRAIN, % PRESSURE, psf SWELL CONSOLIDATION TEST ASTM D4546 NOTES: Sample exhibited compression of 0.1 percent upon wetting under an applied pressure of 1,000 psf. PROJECT: PRPA New Headquarters PROJECT NUMBER: 20175041 Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-16 1901 Sharp Point Dr Ste C Fort Collins, CO Specimen Identification Classification , pcf 99 18 WC, % B12 4 - 5 ft LEAN CLAY WITH SAND LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. 65155045-SWELL/CONSOL 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 0 2 4 6 8 10 12 14 AXIAL STRAIN - % UNCONFINED COMPRESSION TEST ASTM D2166 COMPRESSIVE STRESS - psf PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-17 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. UNCONFINED WITH PHOTOS 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 SAMPLE LOCATION: B09 @ 19 - 20 feet 3214 99 28 Strain Rate: in/min Failure Strain: % Calculated Saturation: % Height: in. Diameter: in. Dry Density: pcf Moisture Content: % 4.66 2.52 SPECIMEN TEST DATA Height / Diameter Ratio: Calculated Void Ratio: Assumed Specific Gravity: SAMPLE TYPE: D&M RING Undrained Shear Strength: (psf) 1607 Unconfined Compressive Strength (psf) 61 23 38 SAMPLE DESCRIPTION: FAT CLAY(CH) SPECIMEN FAILURE PHOTOGRAPH Remarks: 92 Percent < #200 Sieve 6.01 2.39 LL PL PI 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 0 2 4 6 8 10 12 14 AXIAL STRAIN - % UNCONFINED COMPRESSION TEST ASTM D2166 COMPRESSIVE STRESS - psf PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-18 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. UNCONFINED WITH PHOTOS 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/14/17 SAMPLE LOCATION: B10 @ 4 - 5 feet 5154 107 19 Strain Rate: in/min Failure Strain: % Calculated Saturation: % Height: in. Diameter: in. Dry Density: pcf Moisture Content: % 11.78 2.44 SPECIMEN TEST DATA Height / Diameter Ratio: Calculated Void Ratio: Assumed Specific Gravity: SAMPLE TYPE: D&M RING Undrained Shear Strength: (psf) 2577 Unconfined Compressive Strength (psf) 39 18 21 SAMPLE DESCRIPTION: LEAN CLAY with SAND(CL) SPECIMEN FAILURE PHOTOGRAPH Remarks: 81 Percent < #200 Sieve 5.77 2.37 LL PL PI 1901 Sharp Point Drive, Suite C Fort Collins, Colorado 80525 (970) 484-0359 FAX (970) 484-0454 CLIENT: Platte River Power Authority DATE OF TEST: 8/23/2017 PROJECT: PRPA New Headquarters Campus LOCATION: Combined bulk sample from Boring No. 8 at 1 to 2 feet TERRACON NO. 20175041 CLASSIFICATION: CL TEST SPECIMEN NO. 1 2 3 COMPACTION PRESSURE (PSI) 20 60 130 DENSITY (PCF) 113.2 116.4 114.3 MOISTURE CONTENT (%) 27.8 22.1 17.0 EXPANSION PRESSURE (PSI) -0.05 0.00 0.02 HORIZONTAL PRESSURE @ 160 PSI 140 132 125 SAMPLE HEIGHT (INCHES) 2.25 2.13 2.08 EXUDATION PRESSURE (PSI) 274.6 301.4 335.4 CORRECTED R-VALUE 5.6 8.7 11.2 UNCORRECTED R-VALUE 6.2 10.2 13.4 R-VALUE @ 300 PSI EXUDATION PRESSURE = 9 AASHTO T190 PRESSURE OF COMPACTED SOIL RESISTANCE R-VALUE & EXPANSION SAMPLE DATA TEST RESULTS 0 10 20 30 40 50 60 70 80 90 100 0 100 200 300 400 500 600 700 800 R-VALUE EXUDATION PRESSURE - PSI EXHIBIT: B-19 TASK NO: 170822020 Analytical Results Terracon, Inc. - Fort Collins Eric D. Bernhardt Company: Report To: Company: Bill To: 1901 Sharp Point Drive Suite C Fort Collins CO 80525 Eric D. Bernhardt Terracon, Inc. - Accounts Payable 18001 W. 106th St Suite 300 Olathe KS 66061 Platte River 20175041 Date Reported: 8/29/17 Task No.: 170822020 Matrix: Soil - Geotech Date Received: 8/22/17 Client Project: Client PO: CustomerFt Sample ID B5 @ 2-3 Test Method Lab Number: 170822020-01 Result Sulfate - Water Soluble 0.007 % AASHTO T290-91/ ASTM D4327 CustomerFt Sample ID B9 @ 4-5 Test Method Lab Number: 170822020-02 Result Sulfate - Water Soluble 0.010 % AASHTO T290-91/ ASTM D4327 Customer Sample ID B12 @ 2-3.5 Ft. Test Method Lab Number: 170822020-03 Result Sulfate - Water Soluble 0.033 % AASHTO T290-91/ ASTM D4327 240 South Main Street / Brighton, CO 80601-0507 / 303-659-2313 Mailing Address: P.O. Box 507 / Brighton, CO 80601-0507 / Fax: 303-659-2315 DATA APPROVED FOR RELEASE BY Abbreviations/ References: 170822020 AASHTO - American Association of State Highway and Transportation Officials. ASTM - American Society for Testing and Materials. ASA - American Society of Agronomy. DIPRA - Ductile Iron Pipe Research Association Handbook of Ductile Iron Pipe. EXHIBIT: B-20 TASK NO: 160609019 Analytical Results Terracon, Inc. - Fort Collins Eric D. Bernhardt Company: Report To: Company: Bill To: 1901 Sharp Point Drive Suite C Fort Collins CO 80525 Accounts Payable Terracon, Inc. - Lenexa 13910 W. 96th Terrace Lenexa KS 66215 PRPA 20165049 Date Reported: 6/16/16 Task No.: 160609019 Matrix: Soil - Geotech Date Received: 6/9/16 Client Project: Client PO: Customer Sample ID B1 @ 2 Ft Test Method Lab Number: 160609019-01 Result Sulfate - Water Soluble 0.058 % AASHTO T290-91/ ASTM D4327 Customer Sample ID B3 @ 2 Ft Test Method Lab Number: 160609019-02 Result Sulfate - Water Soluble 0.047 % AASHTO T290-91/ ASTM D4327 240 South Main Street / Brighton, CO 80601-0507 / 303-659-2313 Mailing Address: P.O. Box 507 / Brighton, CO 80601-0507 / Fax: 303-659-2315 DATA APPROVED FOR RELEASE BY Abbreviations/ References: 160609019 AASHTO - American Association of State Highway and Transportation Officials. ASTM - American Society for Testing and Materials. ASA - American Society of Agronomy. DIPRA - Ductile Iron Pipe Research Association Handbook of Ductile Iron Pipe. EXHIBIT: B-21 B05 2 - 3 SANDY LEAN CLAY 42 17 25 16.7 106.3 B05 4 - 5.5 17.6 B05 9 - 10.5 15.2 B05 14 - 15.5 11.8 B05 19 - 20 24.0 B05 24 - 25.5 20.3 B06 2 - 3.5 LEAN CLAY with SAND(CL) 45 17 28 82.1 0.0 17.9 19.9 B06 4 - 5 22.7 B06 9 - 10.5 66.8 0.2 33.0 20.7 B06 14 - 15.5 26.7 B06 19 - 20 22.3 B06 24 - 25.5 19.7 B06 29 - 30.5 21.4 B06 34 - 35.5 21.2 B07 2 - 3.5 77.5 0.0 22.5 14.6 B07 4 - 5.5 54.5 1.4 44.1 15.3 B07 9 - 10 SANDY LEAN CLAY 13.6 110.1 B07 14 - 15.5 24.4 B07 19 - 20.5 23.3 B07 24 - 25 18.3 107.5 B08 1 - 2 LEAN CLAY(CL) 42 20 22 89.5 0.0 10.5 B08 3 - 4 LEAN CLAY 32 11 21 19.3 94.4 B08 5 - 6.5 25.5 B08 9 - 10.5 22.9 B08 14 - 15.5 23.3 B08 19 - 20 59 13 46 21.0 99.5 B08 24 - 25.5 32.0 B09 2 - 3.5 LEAN CLAY with SAND(CL) 47 18 29 75.7 0.0 24.3 16.5 B09 4 - 5 LEAN CLAY WITH SAND 47 21 26 79.0 0.0 21.0 20.8 96.2 B09 9 - 10.5 18.8 B09 14 - 15.5 8.0 B09 19 - 20 FAT CLAY(CH) 61 23 38 92.1 0.0 7.9 27.5 99.0 B09 24 - 25.5 22.5 B09 29 - 30.5 21.5 B09 34 - 35.5 21.0 B10 2 - 3.5 LEAN CLAY(CL) 47 21 26 87.0 0.0 13.0 19.4 B10 4 - 5 LEAN CLAY with SAND(CL) 39 18 21 81.3 0.1 18.6 19.4 106.9 B10 9 - 10.5 20.7 B10 14 - 15.5 17.8 B10 19 - 20 SANDY LEAN CLAY 20.8 105.1 B10 24 - 25.5 15.1 B10 29 - 30.5 CLAYEY SAND with GRAVEL(SC) 52 22 30 48.7 19.2 32.1 11.7 Summary of Laboratory Results Depth USCS Classification and Soil Description % <#200 Sieve Dry Density (pcf) Water Content (%) SAMPLE ID Liquid Limit Plastic Limit B10 34 - 35.5 18.2 B11 2 - 3.5 21.7 B11 4 - 5 LEAN CLAY(CL) 45 21 24 86.7 0.0 13.3 21.6 99.8 B11 9 - 10.5 SANDY LEAN CLAY(CL) 48 22 26 58.3 4.7 37.0 14.9 B11 14 - 15.5 18.3 B11 19 - 20 15.5 B11 24 - 25.5 18.5 B11 29 - 30.5 18.5 B11 34 - 35.5 23.0 B12 2 - 3.5 18.8 B12 4 - 5 LEAN CLAY WITH SAND 45 21 24 87.0 0.0 13.0 18.3 99.0 B12 9 - 10.5 16.2 B12 14 - 15 19.6 B12 19 - 20.5 13.2 B12 24 - 25.5 17.4 B12 29 - 30.5 15.3 B12 34 - 35.5 19.2 Summary of Laboratory Results Depth USCS Classification and Soil Description % <#200 Sieve Dry Density (pcf) Water Content (%) SAMPLE ID Liquid Limit Plastic Limit Plasticity Index % Gravel % Sand % Silt % Clay Sheet 2 of 2 Specific Gravity PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-23 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. E2126320 LAB SUMMARY 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 APPENDIX C SUPPORTING DOCUMENTS Exhibit: C-1 Unconfined Compressive Strength Qu, (psf) 500 to 1,000 2,000 to 4,000 > 8,000 less than 500 1,000 to 2,000 4,000 to 8,000 Modified Dames & Moore Ring Sampler Grab Sample Standard Penetration Test Non-plastic Low Medium High DESCRIPTION OF SYMBOLS AND ABBREVIATIONS GENERAL NOTES Over 12 in. (300 mm) 12 in. to 3 in. (300mm to 75mm) 3 in. to #4 sieve (75mm to 4.75 mm) #4 to #200 sieve (4.75mm to 0.075mm Passing #200 sieve (0.075mm) Particle Size < 5 5 - 12 > 12 Percent of Dry Weight Descriptive Term(s) of other constituents RELATIVE PROPORTIONS OF FINES 0 1 - 10 11 - 30 > 30 Plasticity Index Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency. LOCATION AND ELEVATION NOTES Percent of Dry Weight Major Component of Sample Trace With Modifier RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY 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. 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. Trace With Modifier DESCRIPTIVE SOIL CLASSIFICATION Boulders Cobbles Gravel Sand Silt or Clay Descriptive Term(s) of other constituents < 15 15 - 29 > 30 Term PLASTICITY DESCRIPTION Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations. Water Level After a Specified Period of Time Water Level After a Specified Period of Time Water Initially Encountered Standard Penetration Test Resistance (Blows/Ft.) Hand Penetrometer Torvane Dynamic Cone Penetrometer Photo-Ionization Detector Organic Vapor Analyzer Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area. N (HP) (T) (DCP) (PID) (OVA) FIELD TESTS WATER LEVEL STRENGTH TERMS SAMPLING BEDROCK Loose Medium Dense Dense 0 - 3 4 - 9 10 - 29 30 - 50 7 - 18 19 - 58 Very Soft Soft Medium-Stiff Stiff Very Stiff Standard Penetration or N-Value Blows/Ft. 2 - 4 4 - 8 8 - 15 < 3 5 - 9 19 - 42 > 42 30 - 49 50 - 89 20 - 29 Medium Hard Very Dense RELATIVE DENSITY OF COARSE-GRAINED SOILS Descriptive Term (Density) Very Loose > 50 Ring Sampler Blows/Ft. 0 - 6 59 - 98 > 99 Descriptive Term (Consistency) Hard 0 - 1 Ring Sampler Blows/Ft. 3 - 4 10 - 18 Ring Sampler Blows/Ft. < 30 90 - 119 Standard Penetration or N-Value Blows/Ft. Descriptive Term (Consistency) Weathered Firm Very Hard CONSISTENCY OF FINE-GRAINED SOILS (More than 50% retained on No. 200 sieve.) Density determined by Standard Penetration Resistance (50% or more passing the No. 200 sieve.) Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance Standard Penetration or N-Value Blows/Ft. _ 15 - 30 > 30 > 119 < 20 30 - 49 50 - 79 >79 Hard Plasticity Index % Gravel % Sand % Silt % Clay Sheet 1 of 2 Specific Gravity PROJECT NUMBER: 20175041 PROJECT: PRPA New Headquarters Campus SITE: 2000 East Horsetooth Road Fort Collins, CO CLIENT: Platte River Power Authority Fort Collins, Colorado EXHIBIT: B-22 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. E2126320 LAB SUMMARY 20175041 PRPA NEW HEADQUAR.GPJ TERRACON_DATATEMPLATE.GDT 9/19/17 48 45 B10 B11 B11 B12 LL PL PI finefine SILT OR CLAY %Gravel %Sand COBBLES GRAVEL SAND coarse medium %Clay 48.7 86.7 58.3 87.0 %Silt %Fines CLAYEY SAND with GRAVEL (SC) LEAN CLAY (CL) SANDY LEAN CLAY (CL) LEAN CLAY WITH SAND (CL) USCS Classification 12 22 15 WC (%) 29 - 30.5 4 - 5 9 - 10.5 4 - 5 Boring ID Depth Boring ID Depth D60 32.1 13.3 37.0 13.0 29 - 30.5 4 - 5 9 - 10.5 4 - 5 D30 D10 Cc Cu D100 30 24 26 24 22 21 22 21 coarse B10 B11 B11 B12 61 47 39 B09 B09 B09 B10 B10 LL PL PI finefine SILT OR CLAY %Gravel %Sand COBBLES GRAVEL SAND coarse medium %Clay 75.7 79.0 92.1 87.0 81.3 %Silt %Fines LEAN CLAY with SAND (CL) LEAN CLAY WITH SAND (CL) FAT CLAY (CH) LEAN CLAY (CL) LEAN CLAY with SAND (CL) USCS Classification 17 19 WC (%) 2 - 3.5 4 - 5 19 - 20 2 - 3.5 4 - 5 Boring ID Depth Boring ID Depth D60 24.3 21.0 7.9 13.0 18.6 2 - 3.5 4 - 5 19 - 20 2 - 3.5 4 - 5 D30 D10 Cc Cu D100 29 26 38 26 21 18 21 23 21 18 coarse B09 B09 B09 B10 B10 42 B06 B06 B07 B07 B08 LL PL PI finefine SILT OR CLAY %Gravel %Sand COBBLES GRAVEL SAND coarse medium %Clay 82.1 66.8 77.5 54.5 89.5 %Silt %Fines LEAN CLAY with SAND (CL) LEAN CLAY (CL) USCS Classification 20 21 15 15 WC (%) 2 - 3.5 9 - 10.5 2 - 3.5 4 - 5.5 1 - 2 Boring ID Depth Boring ID Depth D60 17.9 33.0 22.5 44.1 10.5 2 - 3.5 9 - 10.5 2 - 3.5 4 - 5.5 1 - 2 D30 D10 Cc Cu D100 28 22 17 20 coarse B06 B06 B07 B07 B08 60 fine 1 2 3 3 4 GRAIN SIZE IN MILLIMETERS PERCENT FINER BY WEIGHT coarse fine U.HYDROMETERS. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 21 17 16 14 15 36 23 21 18 8 D100 Cc Cu SILT OR CLAY 4 D30 D10 %Gravel %Sand 14 - 15.5 2 - 3.5 4 - 5 9 - 10.5 14 - 15.5 3/8 3 100 3 2 140 COBBLES GRAVEL SAND USCS Classification 20.7 15.9 19.8 45.6 62.0 D60 coarse medium Boring ID Depth Boring ID Depth GRAIN SIZE DISTRIBUTION 14 - 15.5 2 - 3.5 4 - 5 9 - 10.5 14 - 15.5 FAT CLAY with SAND (CH) LEAN CLAY with SAND (CL) LEAN CLAY with SAND (CL) SANDY LEAN CLAY (CL) CLAYEY SAND (SC) ASTM D422 / ASTM C136 PROJECT NUMBER: 20165049 PROJECT: PRPA Expansion Project SITE: Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO CLIENT: Platte River Power Authority EXHIBIT: B-4 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GRAIN SIZE: USCS-2 20165049.GPJ 35159097 - ATTERBERG ISSUE.GPJ 6/14/16 B09 B09 B09 B10 B10 B10 B11 B11 B12 LL USCS 82 89 76 79 92 87 81 49 87 58 87 25 28 22 21 46 29 26 38 26 21 30 24 26 24 17 17 20 11 13 18 21 23 21 18 22 21 22 21 42 45 42 32 59 47 47 61 47 39 52 45 48 45 Fines CL CL CL CL CH CL CL SC CL CL CL SANDY LEAN CLAY LEAN CLAY with SAND LEAN CLAY LEAN CLAY LEAN CLAY with SAND LEAN CLAY WITH SAND FAT CLAY LEAN CLAY LEAN CLAY with SAND CLAYEY SAND with GRAVEL LEAN CLAY SANDY LEAN CLAY LEAN CLAY WITH SAND Boring ID Depth PL PI Description CL-ML 26 LL USCS 1 2 3 3 4 ATTERBERG LIMITS RESULTS ASTM D4318 14 - 15.5 2 - 3.5 4 - 5 9 - 10.5 14 - 15.5 PROJECT NUMBER: 20165049 PROJECT: PRPA Expansion Project SITE: Southwest of Danfield Court and Eastbrook Drive Fort Collins, CO CLIENT: Platte River Power Authority EXHIBIT: B-2 1901 Sharp Point Dr Ste C Fort Collins, CO LABORATORY TESTS ARE NOT VALID IF SEPARATED FROM ORIGINAL REPORT. ATTERBERG LIMITS 20165049.GPJ TERRACON2015.GDT 6/14/16 CL-ML ELEVATION (Ft.) Surface Elev.: 4951.9 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 35 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B12 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-17 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 17' at competion of drilling 16.5` on 8/2/17 WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53909° Longitude: -105.04036° See Exhibit A-2 and A-3 4 ELEVATION (Ft.) Surface Elev.: 4953.1 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 35 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B11 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-16 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 24' at competion of drilling WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53832° Longitude: -105.04051° See Exhibit A-2 and A-3 4 LIMITS ELEVATION (Ft.) Surface Elev.: 4955.2 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 35 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Surface capped with asphalt Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B10 CLIENT: Platte River Power Authority Latitude: 40.53889° Longitude: -105.0409° See Exhibit A-2 Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-15 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 12' at competion of drilling WATER LEVEL OBSERVATIONS DEPTH LOCATION and A-3 4 WEIGHT (pcf) LL-PL-PI ATTERBERG LIMITS ELEVATION (Ft.) Surface Elev.: 4955.8 (Ft.) WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 35 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Surface capped with asphalt Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B09 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-14 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 15.5' at competion of drilling WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53871° Longitude: -105.04171° See Exhibit A-2 and A-3 4 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4" Continuous flight auger Abandonment Method: Backfilled with Auger Cuttings Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 08-03-2017 BORING LOG NO. B08 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Blake Boring Completed: 08-03-2017 Exhibit: Menard, Jeff A-13 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 20' at competion of drilling 14` on 8/5/17 WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53945° Longitude: -105.04207° See Exhibit A-2 and A-3 4 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Surface capped with asphalt Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B07 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-12 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 15' at competion of drilling 15` on 8/2/17 WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53872° Longitude: -105.04293° See Exhibit A-2 and A-3 4 5 10 15 20 25 30 35 SAMPLE TYPE FIELD TEST RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 6" Hollow-stem auger Abandonment Method: Backfilled with Auger Cuttings Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 07-31-2017 BORING LOG NO. B06 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Terracon Boring Completed: 07-31-2017 Exhibit: Menard, Jeff A-11 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 15' at competion of drilling 13` on 8/2/17 WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.53953° Longitude: -105.04272° See Exhibit A-2 and A-3 4 RESULTS SWELL- CONSOL /LOAD (%/psf) 2000 East Horsetooth Road Fort Collins, CO SITE: Page 1 of 1 Advancement Method: 4" Continuous flight auger Abandonment Method: Backfilled with Auger Cuttings Surface capped with asphalt Notes: Project No.: 20175041 Drill Rig: CME 55 Boring Started: 08-03-2017 BORING LOG NO. B05 CLIENT: Platte River Power Authority Fort Collins, Colorado Driller: Blake Boring Completed: 08-03-2017 Exhibit: Menard, Jeff A-10 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. PROJECT: PRPA New Headquarters Campus 1901 Sharp Point Dr Ste C Fort Collins, CO 15.5' at competion of drilling WATER LEVEL OBSERVATIONS DEPTH LOCATION Latitude: 40.54085° Longitude: -105.04258° See Exhibit A-2 and A-3 4 Driller: R. Geary Boring Completed: 6/7/2016 Exhibit: A-9 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. Borings referenced to top of manhole rim east of site; assumed elevation = 100.0. PROJECT: PRPA Expansion Project PERCENT FINES WATER CONTENT (%) DRY UNIT WEIGHT (pcf) ATTERBERG LIMITS LL-PL-PI Surface Elev.: 100.1 (Ft.) ELEVATION (Ft.) SAMPLE TYPE WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 SWELL-CONSOL / LOAD (%/psf) FIELD TEST RESULTS DEPTH LOCATION See Exhibit A-2 Latitude: 40.539785° Longitude: -105.042096° 11.8' on 6/8/16 Boring collapsed at 24' and the 34' sample could not be collected 12.6' at completion of drilling 11.8' on 6/8/16 Boring collapsed at 24' and the 34' sample could not be collected WATER LEVEL OBSERVATIONS 12.6' at completion of drilling Driller: R. Geary Boring Completed: 6/7/2016 Exhibit: A-8 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. Borings referenced to top of manhole rim east of site; assumed elevation = 100.0. PROJECT: PRPA Expansion Project PERCENT FINES WATER CONTENT (%) DRY UNIT WEIGHT (pcf) ATTERBERG LIMITS LL-PL-PI Surface Elev.: 99.8 (Ft.) ELEVATION (Ft.) SAMPLE TYPE WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 SWELL-CONSOL / LOAD (%/psf) FIELD TEST RESULTS DEPTH LOCATION See Exhibit A-2 Latitude: 40.53979° Longitude: -105.042562° 12.6' at completion of drilling 11.8' on 6/8/16 WATER LEVEL OBSERVATIONS Driller: R. Geary Boring Completed: 6/7/2016 Exhibit: A-7 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. Borings referenced to top of manhole rim east of site; assumed elevation = 100.0. PROJECT: PRPA Expansion Project PERCENT FINES WATER CONTENT (%) DRY UNIT WEIGHT (pcf) ATTERBERG LIMITS LL-PL-PI Surface Elev.: 100.2 (Ft.) ELEVATION (Ft.) SAMPLE TYPE WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 SWELL-CONSOL / LOAD (%/psf) FIELD TEST RESULTS DEPTH LOCATION See Exhibit A-2 Latitude: 40.540071° Longitude: -105.042091° 12.6' at completion of drilling 12.6' on 6/8/16 WATER LEVEL OBSERVATIONS Drill Rig: CME-75 Boring Started: 6/7/2016 BORING LOG NO. 1 CLIENT:Authority Platte River Power Driller: R. Geary Boring Completed: 6/7/2016 Exhibit: A-6 See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations. Borings referenced to top of manhole rim east of site; assumed elevation = 100.0. PROJECT: PRPA Expansion Project PERCENT FINES WATER CONTENT (%) DRY UNIT WEIGHT (pcf) ATTERBERG LIMITS LL-PL-PI Surface Elev.: 100.3 (Ft.) ELEVATION (Ft.) SAMPLE TYPE WATER LEVEL OBSERVATIONS DEPTH (Ft.) 5 10 15 20 25 30 35 SWELL-CONSOL / LOAD (%/psf) FIELD TEST RESULTS DEPTH LOCATION See Exhibit A-2 Latitude: 40.540075° Longitude: -105.042555° No free water observed WATER LEVEL OBSERVATIONS the site. The gravel zone behind the wall and wall backfill should be placed in thin, loose lifts and compacted. Heavy equipment should not operate within a distance closer than the exposed height of retaining walls to prevent lateral pressures more than those provided. Special precautions (e.g. bracing) should be taken to avoid over-stressing the walls during compaction.