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HomeMy WebLinkAboutPOWERHOUSE 2 - PDP220006 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT400 North Link Lane | Fort Collins, Colorado 80524 Telephone: 970-206-9455 Fax: 970-206-9441 GEOTECHNICAL INVESTIGATION PROPOSED POWERHOUSE 2 NE CORNER EAST VINE DRIVE AND COLLEGE AVENUE FORT COLLINS, COLORADO POWERHOUSE 2 DEVELOPMENT COMPANY, LLC 320 East Vine Drive, Suite 101 Fort Collins, Colorado 80524 Attention: Bryan Wilson Project No. FC10223-125 March 14, 2022 TABLE OF CONTENTS SCOPE 1 SUMMARY OF CONCLUSIONS 1 SITE CONDITIONS AND PROPOSED CONSTRUCTION 2 INVESTIGATION 4 SUBSURFACE CONDITIONS 4 Groundwater 5 GEOLOGIC HAZARDS 5 Shallow Groundwater 5 Expansive Soils 6 Seismicity 6 SITE DEVELOPMENT 6 Excavations 7 Dewatering 7 Fill Placement 8 SUBSURFACE IMPROVEMENT 10 Chemical Grouting 10 Compaction Grouting 10 Vibropiers and Grouted Aggregate Piers 11 FOUNDATIONS 11 Spread Footings 12 Reinforced Concrete Mat 13 Drilled Piers Bottomed in Bedrock 14 Franki Piles 15 Augercast Piles 15 Helical Piers 15 Driven H-Piles 16 Laterally Loaded Piers 17 Closely Spaced Pier Reduction Factors 17 RETAINING WALLS 18 SETTLEMENT 19 LATERAL EARTH PRESSURES 19 BELOW GRADE AREAS 20 FLOOR SYSTEMS 21 Exterior Flatwork 22 PAVEMENTS 23 Pavement Selection 24 Subgrade and Pavement Materials and Construction 24 Pavement Maintenance 24 WATER-SOLUBLE SULFATES 25 SURFACE DRAINAGE 25 CONSTRUCTION OBSERVATIONS 26 GEOTECHNICAL RISK 26 LIMITATIONS 26 FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 – SUMMARY LOGS OF EXPLORATORY BORINGS APPENDIX A – RESULTS OF LABORATORY TESTING APPENDIX B – SAMPLE SITE GRADING SPECIFICATIONS APPENDIX C – PAVEMENT CONSTRUCTION RECOMMENDATIONS APPENDIX D – PAVEMENT MAINTENANCE PROGRAM POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 1 SCOPE This report presents the results of our Geotechnical Investigation for the proposed Powerhouse 2 facility in Fort Collins, Colorado. The purpose of the investigation was to evaluate the subsurface conditions and provide foundation recommendations and geotechnical design criteria for the project. The scope was described in our Service Agreement (Proposal No. FC-21-0545) dated October 15, 2021. The report was prepared from data developed during field exploration, laboratory testing, engineering analysis, and experience with similar conditions. The report includes a description of subsurface conditions found in our exploratory borings and discussions of site development as influenced by geotechnical considerations. Our opinions and recommendations regarding design criteria and construction details for site development, foundations, floor systems, slabs-on-grade, lateral earth loads, pavements and drainage are provided. The report was prepared for the exclusive use of Powerhouse 2 Development Company, LLC in design and construction of the proposed improvements. If the proposed construction differs from descriptions herein, we should be requested to review our recommendations. Our conclusions are summarized in the following paragraphs. SUMMARY OF CONCLUSIONS 1. Subsurface conditions encountered in our borings generally consisted of 4 to 7 feet of clayey sand or sandy clay fill over clean to clayey sand and gravel, underlain by sandstone bedrock to the depths explored. Three of the borings were overlain by 4 to 6 inches of asphaltic concrete. All of the soils encountered are considered non-swelling to low swelling. 2. Groundwater was encountered in six borings during drilling at depths of 8 to 11 feet. When measured several days later, groundwater was at depths of 5 to 10 feet in four borings. Existing groundwater levels may affect proposed construction. We recommend a minimum 3-foot separation between foundation elements and groundwater. Groundwater will likely be encountered during construction of below grade areas and deeper utilities unless final grade is raised. Dewatering should be anticipated. 3. Existing fill was encountered in four borings to depths of 4 to 6 feet. The fill was likely placed during previous site grading activities. It is of unknown age and origin and should not support foundations or floor slabs. We recommend removal and recompaction of the existing fill beneath the building. The fill is likely acceptable below pavements provided it can pass proof roll. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 2 4. We understand that multiple foundation options are being considered, with a focus on reducing the use of cement. Drilled piers socketed into the sandstone bedrock, helical piers, driven H-piles, and aggregate piers are acceptable for the proposed structure and discussed in this report. Casing and pumped concrete methods for drilled piers will likely be required because borings will be advanced through groundwater and caving granular soils. The displaced water may need to be filtered, treated, or disposed of. We believe it is also possible to use a shallow foundation system such as footings and/or reinforced concrete slabs (mat) with tolerable movements. The founding soils can be improved by vibropier (stone column) or compaction grouting techniques to reduce potential settlement. A specialty contractor should evaluate the feasibility and maximum allowable soil pressures for these ground improvement methods. Design and construction criteria for these options are presented in the report. 5. Site grading is expected to be raised with imported fill. If deep foundations are used, the building floors should be structurally supported. We believe slab-on- grade floors, placed on approved fill are also appropriate for this site. Some movement of slab-on-grade floors should be anticipated. We expect movements will be minor, on the order of 1-inch or less if compacted properly. If movement is unacceptable, structural floors should be used. 6. Surface drainage should be designed, constructed and maintained to provide rapid removal of surface runoff away from the proposed structure. Conservative irrigation practices should be followed to avoid excessive wetting. 7. Samples of the subgrade soils generally classified as AASHTO A-6 soils. We anticipate that the parking lot will have semi -frequent heavy truck traffic for deliveries and waste removal. For heavy traffic areas and parking, we recommend 6 inches of asphaltic concrete over 6 inches of aggregate base course. Some areas of the site will be predominantly for pedestrian traffic but may also take vehicular traffic. We understand brick or concrete pavers may be used in these areas. Where pavers will receive vehicular traffic , we recommend that they be placed over 5 inches of rigid pavement. SITE CONDITIONS AND PROPOSED CONSTRUCTION The site is located at the northeast corner of the intersection of East Vine Drive and College Avenue, north of East Vine Drive, between College Avenue and Jerome Street in Fort Collins, Colorado (Figure 1). The property is currently occupied by a vehicle repair shop, and a semi-truck service yard. Some areas are paved in asphalt and the rest of the property is gravel paved. The Lake Canal (aka Josh Ames Ditch) irrigation ditch is directly north of the site. It was dry during our investigation. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 3 Figure A: Google Earth Aerial of Site Only preliminary plans were available at the time of this report, structural details and construction plans were not provided. We understand that an approximately 153,260 square foot, 5-story building is to be constructed at this site. Based on cut/fill plans provided by the client we understand that fill will be imported to raise the grade of the area around the building by 2 to 7 feet (Figure B). The only below grade construction planned is an elevator pit. The property will have paved parking and access drives connecting to East Vi ne Drive and College Avenue. An approximately 3-foot-deep detention pond is planned in the southeast corner of the property. Figure B: Cut/Fill Map by Connell Resources POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 4 INVESTIGATION The field investigation included drilling seven exploratory borings at the locations presented on Figure 1. The borings were drilled to depths of approximately 10 to 3 0 feet using 4-inch diameter, continuous-flight augers, and a truck-mounted drill. Drilling was observed by our field representative who logged the soils and bedrock. Summary logs of the borings, including results of field penetration resistance tests, are presented on Figure 2. Soil and bedrock samples obtained during drilling were returned to our laboratory and visually examined by our geotechnical engineer. Laboratory testing was assigned and included moisture content, dry density, swell -consolidation, particle-size analysis, Atterberg limits and water-soluble sulfate tests. Swell-consolidation test samples were wetted at a confining pressure which approximated the pressure exerted by the overburden soils (overburden pressures). Results of the laboratory tests are presented in Appendix A and summarized in Table A-I. SUBSURFACE CONDITIONS Subsurface conditions encountered in our borings generally consisted of 4 to 7 feet of clayey sand or sandy clay fill over clean to clayey sand and gravel. Three of the borings were overlain by 4 to 6 inches of asphaltic concrete . Samples of the soils from the upper 5 feet exhibited low plasticity and nil to low-swell potential. The clean to clayey sands and gravel were loose to very dense according to standard penetration testing. Very hard sandstone bedrock was encountered in four borings at 16 to 19½ feet to the depths explored. Further descriptions of the subsurface conditions are presented on our boring logs and in our laboratory test results. Existing fill, comprised of clayey, gravelly sand, was encountered in the upper 4 to 6 feet in four borings during this investigation. Fill is likely present in other places and at greater depths not explored by our borings. The fill presents risk of settl ement. We recommend removing, moisture treating and re-compacting any existing fill below structures. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 5 Groundwater Groundwater was encountered in six borings during drilling at depths of 8 to 11 feet. When measured several days later, groundwater was at depths of 5 to 10 feet in four borings. Groundwater will fluctuate seasonally and will be affected by water levels in nearby irrigation ditches, if present. Groundwater may develop on or near the bedrock surface or other low permeable soil or bedrock when a source of water not presently contributing becomes available. We recommend a minimum 3 -foot separation between foundation elements and groundwater. Existing groundwater levels may affect proposed construction unless final grade is raised. GEOLOGIC HAZARDS Our investigation addressed potential geologic hazards, including shallow groundwater, expansive soils, and seismicity that should be considered during planning and construction. None of these hazards considered will preclude proposed construction. The following sections discuss each of these geologic hazards and associated development concerns. Shallow Groundwater Shallow groundwater was encountered at depths of 5 to 10 feet in four borings. Groundwater will likely be encountered during construction of below grade areas such as the elevator pit and deeper utilities. Groundwater levels fluctuate seasonally and may rise during the wet season from March to September. Dewatering should be anticipated and is discussed in SITE DEVELOPMENT. We understand that fill may be imported to raise the grade up to 7 feet above current elevation in the area of the planned structure. If that is the case, groundwater may be less of a concern unless excavations will exceed approximately 12 feet. Other options to control groundwater could be lining or piping the nearby irrigation ditches. Groundwater control recommendations are outside of the scope of this investigation but should be considered prior to construction. Additional investigation would be required. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 6 Expansive Soils Expansive soils are present at the site. The presence of expansive soils constitutes a geologic hazard. There is a risk that ground heave will damage slabs -on-grade and foundations. We believe that risk to be low at this si te and mitigation is not required for the proposed construction. The risks associated with swelling soils can be mitigated, but not eliminated, by careful design, construction, and maintenance procedures. We believe the recommendations in this report will help control risk of foundations and/or slab damage; they will not eliminate that risk. Seismicity This area, like most of central Colorado, is subject to a low degree of seismic risk. As in most areas of recognized low seismicity, the record of the past earthquake activity in Colorado is incomplete. According to the 2021 International Building Code and the subsurface conditions encountered in our borings, this site probably classifies as a Site Class D. Only minor damage to relatively new, properly designed and built buildings would be expected. Wind loads, not seismic considerations, typically govern dynamic structural design for the structures planned in this area. SITE DEVELOPMENT Site development will be primarily impacted by shallow groundwater and undocumented fill. The fill presents risk of settlement and is not recommended for structural support unless it is removed and recompacted. Groundwater and/or saturated conditions will likely be encountered in below grade excavations that approach or exceed 4 feet below existing grades. Groundwater and caving soils will likely affect utility and deep foundation installation. Ground improvement could be employed to achieve greater bearing capacity and to reduce settlement. There are many different options for ground improvement. We believe the most feasible options include chemical grouting, vibropiers, and rigid inclusions. These as well as other site development considerations are described in detail in the following sections. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 7 Excavations We believe the materials found in our borings can be excavated using conventional heavy-duty excavation equipment. Excavations should be sloped or shored to meet local, State, and Federal safety regulations. Based on our investigation and OSHA standards, we believe the granular soils classify as Type C soils. Type C soils require a maximum slope inclination of 1.5:1 in dry conditions. Excavation slopes specified by OSHA are dependent upon types of soil and groundwater conditions encountered. The contractor’s “competent person” should identify the soils and/or rock encountered in the excavation and refer to OSHA standards to determine appropriate slopes. Stockpiles of soils, rock, equipment, or other items should not be placed within a horizontal distance equal to one -half the excavation depth, from the edge of excavation. Excavations deeper than 20 feet should be braced or a professional engineer should design the slopes. Dewatering Groundwater was encountered in six borings at depths of approximately 5 to 10 feet. The elevator pit is anticipated to be near, or below, current groundwater depths, at existing grade. Our experience in this area suggests that gro undwater depths can vary with season, precipitation, and depending on the time of construction, could be higher than measured in our borings. If grade is raised according to the cut and fill plans provided, groundwater may not be a concern. If not, excavation near groundwater depths should consider temporary dewatering prior to and/or during construction. Buoyant forces may need to be considered in the design if a structure is planned below groundwater. The predominantly granular material at this site is expected to have a fairly rapid hydraulic conductivity. Dewatering can likely be maintained using trench drains and pumps. The sumps should be several feet below the bottom of excavations to pump water d own through the soil rather than up through the bottom of the excavation. Pumping water up through the base of the excavation will likely result in destabilization of the base of the excavation. If destabilization of the soil becomes a problem, a system of well points should be considered. Discharge volumes and the outfall will need to be considered. Additionally, dewatering efforts need to be monitored to avoid conditions where exit velocities could destabilize the soil surface. Also, adjacent areas s hould be sloped to avoid runoff into the excavation. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 8 The contractor should anticipate extensive dewatering and possibly caving soils in excavations below the water table. The design of a well point system will require further exploratory drilling to deeper depth and permeability tests, both of which were not in the scope of this study. Planning construction to avoid seasonal high groundwater, which is typically March to September, should be considered to reduce the need for dewatering. Fill Placement Existing fill was encountered in four borings to depths of up to 6 feet. Deeper fill areas may be encountered during site development. The fill is of unknown origin and age , and presents risk of settlement to improvements constructed on it. It also has a relatively low bearing capacity. We recommend the fill be removed, moisture treated and recompacted in the building area or load bearing structures. Clean portions of the fill can be reworked and reused as new, moisture conditioned, compacted fill. Unsuitable material, if present, may need to be removed, handled and disposed properly. The fill removal area should extend beyond the building footprint at least one footing width. If the excavations to remove existing fill are deeper than about 10 feet in the planned building area, additional measures should be considered to reduce the potential settlement of backfill. We should be advised if any of the excavations are deeper than 10 feet below the proposed floor. The excavation can be filled with on-site soils, moisture-conditioned and compacted as described above. This procedure should remove the existing fill and provide more uniform support for improvements. We understand that imported fill is planned. Import material should be tested and approved as acceptable fill by CTL Thompson. In general, import fill should meet or exceed the engineering qualities of the onsite soils. Imported fill should have a maximum particle size of 3 inches, less than 50 percent passing a No. 200 sieve, a liquid limit less than 30 and a plasticity index of less than 15. CDOT Class 5 or 6 materials or clean recycled concrete may also be considered. The existing onsite soils are suitable for re-use as fill material provided debris or deleterious organic materials are removed. Areas to receive fill should be scarified, moisture-conditioned and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D698, AASHTO T99). If soft or loose soils are encountered, stabilization can likely be achieved by crowding 1½ to 3-inch nominal size crushed rock into the subsoils until POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 9 the base of the excavation does not deform by more than about 1 -inch when compactive effort is applied. Sand soils used as fill should be moistened to within 2 percent of optimum moisture content. Clay soils should be moistened between optimum and 3 percent above optimum moisture content. The fill should be moisture-conditioned, placed in thin, loose lifts (8 inches or less) and compacted as described above. We should observe placement and compaction of fill during construction. Fill placement and compaction should not be conducted when the fill material is frozen. Backfill behind retaining walls is discussed in the RETAINING WALL section of this report. Our experience indicates that fill and backfill can settle even if properly compacted to criteria specified above. Factors that influence the amount of settlement are depth of fill, soil type, degree of compaction and time. The length of time for the compression to occur can be a few weeks to several years. The degree of compression of the recommend fill , under its own weight, will likely be about 1 percent of the fill depth. Any improvements placed over backfill should be designed to accommodate movement. Increased compaction criteria can be employed to reduce the potential compression risk. The existing fill can also affect pavements and exterior flatwork. We believe the fill has been in place long enough that it will most likely perform adequately as pavement subgrade as long as it passes proof roll. However, the lowest risk alternative for exterior pavement and flatwork would also be complete removal and recompaction. The cost could be significant. If the owner can accept a risk of some movement and distress in these areas, then partial depth removal is an alternative. We suggest removal of the existing fill to a depth of 1 to 2 feet below existing grade, proof rolling the exposed subgrade, and additional removal or stabilization of areas where soft, yielding or organic soils or debris is encountered. After this, fill placement can proceed to construction grades. Water and sewer lines are often constructed beneath slabs and pavements. Compaction of utility trench backfill can have a significant effect on the life and serviceability of floor slabs, exterior flatwork and pavements. We recommend utility trench backfill be placed in thin loose lifts and moisture conditioned and compacted according to the specifica tions presented previously. The placement and compaction of utility trench backfill should be observed and tested by a representative of our firm during construction. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 10 Site grading in areas of landscaping where no future improvements are planned can be placed at a dry density of at least 90 percent of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99). Example site grading specifications are presented in Appendix B. SUBSURFACE IMPROVEMENT The bearing support characteristics at this site could be improved to increase bearing capacity or reduce potential settlements. A variety of options could be considered and are discussed below. Chemical Grouting Chemical grouting involves injecting a cement slurry to permeate granular soils to increase strength and reduce permeability. It permeates the soils, binding them together which can stop water movement in granular soil and/or rock while improving bearing capacity. The grouting is typically injected in a grid pattern to depths that would be determined by the contractor. Compaction Grouting Compaction grouting techniques can be employed to densify the fill and/or granular soils in place and enhance performance of shallow foundations and floors. Compaction grouting involves pumping a low-mobility, aggregate grout to displace and densify the surrounding soils. This approach is best suited for soils that are soft to medium stiff or very loose to medium dense, such as the majority of the upper soils at this site. Injection points should be located within improvement areas and spaced at 8 feet on -center. The extent of the grouting will depend on the grout volume and pressure. Based on our investigation, we anticipate grouting to depths of about 15 to 20 feet, will be required. To provide a guide specification, the grout should have a maximum slump of 1 -inch and should be injected at a volume between 4 to 6 cubic feet per foot. Inject ion pressures should not exceed 250 psi. We typically prefer a bottom-up grouting procedure. Adjustments may be needed in the field as grouting progresses, depending on actual conditions encountered. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 11 The top of the compaction grout bulbs will be at vario us elevations relative to foundations and finished floor grades in the building. Generally, they are terminated about 1.5 to 3 feet below the footing, slab elevations. We recommend installation of a minimum 12- inch-thick layer of ¾-inch crushed rock below the foundations and floor slabs. A geogrid should be installed below the base of the gravel layer, along the tops of the compaction grout bulbs, to help the floor span and bridge the improved ground. The below -slab gravel layer can also serve as the vapor mitigation system in some cases. Vibropiers and Grouted Aggregate Piers Vibropiers, also known as aggregate piers or stone columns, may also be considered, where a grid of large-diameter holes is drilled, or vibrated, and gravel aggregate is rammed or vibrated into each hole, densifying surrounding soils and creating stiff columns of gravel to reduce differential and total settlement by increasing the overall stiffness of the treated mass. We believe these piers can be grouted to help transmit loads to deeper, denser materials below the building foundation. The vibratory energy densifies the aggregate and any surrounding soil. The dense aggregate interlocks to form a stiff pier that engages the surrounding soil to provide reinforcement and increased shear resistance. If this technique is selected, we recommend installation of a layer of ¾-inch crushed rock and geogrid below the floor slab, along the tops of the stone columns, to help span the improved ground. Vibropiers are believed to be difficult to install at this site because holes could cave in before aggregate can be placed. FOUNDATIONS We understand that different foundation options are being examined. Considering the anticipated loads and height of the proposed construction, deep foundations are judged to be the safest foundation system for the structure. However, drilled piers , augercast piles and franki piles will be challenging to install because of possible cobble, caving material and shallow groundwater. Other deep foundation options such as large diameter helical piers and driven H-pile can also be considered. The use of shallow footings or reinforced mat foundations can be considered. if the available bearing capacity of the site soils are insufficient, existing ground is improved by methods discussed in the previous section. Most of the ground improvement options will generally be hampered by the water, caving, and POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 12 cobbles in a similar manner to some of the deep foundations. We recommend considering simple re-compaction (over-excavation and replacement) of the near surface sandy fill which should improve bearing capacities and reduce potential settlement of shallow foundations provided higher compaction criteria is employed. Design criteria for footings, mats and deep foundations developed from analysis of field and laboratory data and our experience are presented below. Spread Footings 1. Footings should be constructed on properly compacted fill or ground improvement described in the SITE DEVELOPMENT section of this report. Ground improvement methods previously discussed will increase net allowable bearing capacity to a degree that would be determined by the method selected. This will be determined by the specialty contractor selected for the desired ground improvement method. All existing, uncontrolled fill should be removed from under footings and within one footing width around footings and replaced with properly compacted fill as discussed in the Fill Placement section. Where soil is loosened during excavation, it should be removed and replaced with compacted fill. 2. Footings placed on properly compacted fill can be designed for a net allowable soil pressure of 3,000 psf. The soil pressure can be increased 33 percent for transient loads such as wind or seismic loads. We recommend a minimum 3- foot separation between foundation elements and groundwater. 3. We anticipate footings designed using the soil pressure recommended above could experience 1-inch of movement. Differential movement of ½- inch should be considered in the design. 4. Footings should have a minimum width of at least 18 inches. Foundations for isolated columns should have minimum dimensions of 24 inches by 24 inches. Larger sizes may be required depending on loads and the structural system used. 5. The soils beneath footing pads can be assigned an ultimate coefficient of friction of 0.3 to resist lateral loads. The ability of grade beam or footing backfill to resist lateral loads can be calculated using a passive equivalent fluid pressure of 250 pcf for the upper clayey, sand and 300 pcf for granular materials. This assumes the backfill is densely compacted and will not be removed. Deflection of grade beams is necessary to mobilize passive earth pressure; we recommend a factor of safety of 2 for this condition. Backfill should be placed and compacted to the criteria in the Fill Placement section of this report. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 13 6. Exterior footings should be protected from frost action. We believe 30 inche s of frost cover is appropriate for this site. 7. Foundation walls and grade beams should be well reinforced , both top and bottom. We recommend reinforcement sufficient to simply span 10 feet. The reinforcement should be designed by a structural engineer. 8. We should observe completed footing excavations to confirm whether the subsurface conditions are similar to those found in our borings. Reinforced Concrete Mat 1. Reinforced concrete mat foundations should be constructed on properly compacted fill or ground improvement as described in the SITE DEVELOPMENT section of this report. The reinforced concrete mat foundation should be designed for a net allowable soil pressure of 3,000 psf if constructed on properly compacted fill. The soil pressure can be increased 33 percent for transient loads such as wind or seismic loads. If other ground improvement methods are used, bearing capacity will be determined by the installing contractor. 2. Reinforced slabs are typically designed using a modulus of subgrade reaction. We recommend use of a modulus of 100 pounds per square inch per inch of deflection (pci). 3. The soils beneath mat foundations can be assigned an ultimate coefficient of friction of 0.5 to resist lateral loads. The ability of foundation backfill to resist lateral loads can be calculated using a passive equivalent fluid pressure of 300 pcf. This assumes the backfill is densely compacted and will not be removed. Backfill should be placed and compacted to the criteria in the Fill Placement section of the report. A moist unit weight of 120 pcf can be assumed for natural soils and compacted fill. These values are considered ultimate values and appropriate factors of safety should be used. Typically, a factor of safety of 1.5 is used for sliding and 1.6 for lateral earth pressure. 4. The edges of the mats should be thickened or turned down for structural strength. 5. Materials beneath the mat foundation should be protected from frost action. We believe 30 inches of frost cover is appropriate for this site. 6. We should be retained to observe the completed excavations for mats to confirm that the subsurface conditions are similar to those found in our borings. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 14 Drilled Piers Bottomed in Bedrock 1. Piers should be designed for a maximum allowable end pressure of 50,000 psf and an allowable skin friction of 5,000 psf for the portion of pier in bedrock. Skin friction should be neglected for the upper 3 feet of pier below grade beams. Pier end pressure can be increased 30 percent for short duration live loads such as wind loads. 2. Piers should penetrate at least 5 feet into the comparatively fresh sandstone bedrock. Based on our boring data, piers could have a total length of 20 to 25 feet. Longer piers may be necessary to achieve proper bedrock penetration. 3. Uplift due to swelling soils is expected to be negligible. 4. There should be a 6-inch (or thicker) continuous void beneath all grade beams and foundation walls, between piers, to concentrate the dead load of the structure onto the piers. 5. Foundation walls and grade beams should be well reinforced. A qualified structural engineer should design the reinforcement. Lateral earth pressures and the effects of large openings within below grade walls should be considered. 6. Pier borings should be drilled to a plumb tolerance of 1.5 percent relative to the pier length. 7. Groundwater was encountered during this investigation and will affect pier installation. Casing may be required because of groundwater, and also because of granular caving soils. Piers should be carefully cleaned prior to placement of concrete. We recommend a “drill-and-pour” procedure for pier installation. Concrete should be on site and placed in the pier holes immediately after the holes are drilled, cleaned, and observed by our representative to avoid collecting water and possible contamination of open pier holes. We anticipate tremie equipment and/or pumping may be necessary for proper cleaning, dewatering, and concrete placement. Concrete should not be placed by free fall if there is more than about 3 inches of wate r at the bottom of the hole. 8. Concrete placed by the free fall method should have a slump between 5 inches and 7 inches. Concrete placed by pump, tremie or when temporarily cased should have a slump between 6 inches and 8 inches. 9. Formation of “mushrooms” or enlargements at the top of piers should be avoided during pier drilling and subsequent construction operations. 10. We should observe installation of drilled piers to confirm the subsurface conditions are those we anticipated from our borings. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 15 Franki Piles Franki piles are constructed by driving a casing to the desired depth, then driving or pressurizing a dry concrete mix into the area directly below the casing. Additional concrete and reinforcement are then placed as the casing is removed. This technique creates significant additional end bearing capacity as the grouting densifies a larger area directly under the tip. While this option could be used at this site, it will require specialty equipment and contractors to install and will require contractor involvement in the design as the method is proprietary. Additionally, because the support resistance of the pile tip depends greatly on the site soil type, density, ground water and more, the complex interaction of the parts with the freshly cast concrete can vary, requiring a more comprehensive load testing program to verify capacity. Augercast Piles Augercast piles were considered for this site as a means to provide foundation support. Our experience with the gravelly sand layer above the bedrock has shown it often contains cobbles which will significantly hamper the construction of augercast foundations. It is our opinion that other foundation systems will have greater success of installation at this site. Helical Piers 1. Contractor shall use the number and size of helical blades required to achieve the required depth and capacity. However, the ratio of design bearing capacity specified by the structural engineer and the total area of helical blades used by the contractor shall not exceed 15,000 pounds per square foot (psf). 2. The bottom helix should be installed to bedrock. Piers will likely have a total length of at least 16 to 20 feet. Helical piles should be placed as close to vertical as possible. 3. The diameter and blade strength of the helical piles should be appropriate to accommodate the penetration counts of approximately 30/12 as shown on the boring logs. 4. At a minimum, helical piles should be spaced apart a distance equal to three times the average helix diameter to avoid group efficiency effects. 5. Installation of helical piles should be observed by a representative of our firm to confirm the depth and installation torque of the helical piles are adequate. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 16 Driven H-Piles 1. Piles should be designed for an ultimate end bearing capacity (q p) of 15,000 psf and an ultimate skin friction capacity (qs) of 1,500 psf required for the LRFD method for the portion in the overburden soils. These values correspond to a maximum allowable end pressure of 5,000 psf and an allowable skin friction of 500 psf for the portion of the pier in the overburden soils using the ASD method. Piles should be designed for an ultimate end bearing capacity (q p) of 150,000 psf and an ultimate skin friction capacity (qs) of 15,000 psf required for the LRFD method for the portion in bedrock. These values correspond to a maximum allowable end pressure of 50,000 psf and an allowable skin friction of 5,000 psf for the portion of the pier in bedrock using the ASD method. Skin friction of the portion of a pier contained within a casing should be neglected. The ultimate capacities using LRFD method assumes a weighted load factor of 1.35 and a resistance factor (Φ) of 0.45 for end bearing and side shear values. 2. The piles will need to be designed to resist lateral loading. The Laterally Loaded Piers section gives soil data input for LPILE software. 3. We estimate the pile tip elevations will be near the bedrock surface. Based on our borings, bedrock was encountered at approximately 16 to 1 9 feet below current grade. We should be notified if practical refusal occurs shallower than the estimated depth. We define “practical” refusal at this site as an average penetration of 0.25 inch per blow for the final 1-foot of pile penetration with a hammer delivering at least 20,000-foot pounds of energy per blow. The manufacturer's rated energy output of the hammer should be between 1,000 and 2,000 foot-pounds per square inch of steel section. The hammer for pile driving should be operated at manufacturers recommended stroke and speed when "practical refusal" is measured. 4. The maximum allowable pile capacity should not exceed the rated working stress for the chosen steel H-pile section. 5. The efficiency of the hammer and impact should be monitored during driving. The contractor should select a driving hammer and cushion combination which is capable of installing the selected piles without over -stressing the pile. The contractor should submit the pile driving plan and the pile hammer/cushion combination to the engineer for evaluation of the driving stress in advance of the pile installation. 6. Piles should be driven plumb to within plan tolerance or battered as detailed by the structural engineer. 7. Groups of piles required to support concentrated loads will require an appropriate reduction of the estimated bearing capacity based on the effective envelope area of the pile group. This reduction can be avoided by spacing piles a distance of at least 3 widths center-to-center. The Closely Spaced Pile Reduction Factors section contains detailed discussion of this issue. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 17 8. We are available to assist with or advise on settlement calculations for service limit states in LRFD once a preliminary layout and anticipated loading of the foundation are defined. 9. CTL Thompson should observe pile driving and keep the records of driving penetration resistance, pile length, and other factors that affect the performance of a pile foundation. This will permit us to confirm the piles are driving as anticipated from our boring information. Laterally Loaded Piers Several methods are available to analyze laterally loaded piers and piles. With a pier length to diameter ratio of 7 or greater, we believe the method of analysis developed by Matlock and Reese is most appropriate. The method is an iterative procedure using applied loading and soil profile to develop deflection and moment versus depth curves. The computer programs LPILE and COM624 were developed to perform this procedure. Suggested criteria for LPILE analysis are presented in the following table. TABLE 1 SOIL INPUT DATA FOR LPILE or COM624 Clay Soils or Clay Fill Granular Soils Bedrock Soil Type Stiff Clay w/o Free Water Sand and Gravel (below water/above water) Weak Rock Effective Unit Weight (pci) 0.06 0.07 0.07 Cohesive Strength, c (psi) 13 - 100 Friction Angle Degrees - 35 - Soil Strain, ε50 (in/in) 0.007 - 0.003 RQD (%) - - 80 p-y Modulus ks (pci) 500 60/90 2,000 The ε50 represents the strain corresponding to 50 percent of the maximum principle stress difference. Closely Spaced Pier Reduction Factors For axial loading, a minimum spacing of three diameters is recommended. At one diameter (piers touching) the skin friction reduction factor for both piers would be 0.5. End bearing values would not be reduced provided the bases of the piers are at similar elevations. Linear interpolation can be used between one and three diameters. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 18 Piers in-line with the direction of the lateral load should have a minimum spacing of six diameters (center-to-center) based upon the larger pier. If a closer spacing is required, the modulus of subgrade reaction for initial and trailing piers should be reduced. At a spacing of three diameters, the effective modulus of subgrade reaction of the first pier can be estimated by multiplying the given modulus by 0.6. For trailing piers in a line at three diameters spacing, the factor is 0.4. Linear interpolation can be used for spacing between three and six diameters. Reductions to the modulus of subgrade reaction can be accomplished in LPILE by inputting the appropriate modification factors for the p -y curves. Reducing the modulus of subgrade reaction in trailing piers will result in greater comp uted deflections on these piers. In practice, the grade beam can force deflections of piers to be equal. Load -deflection graphs can be generated for each pier in the group using the appropriate p -multiplier values. The sum of the piers’ lateral load resistance at selected deflections can be used to develop a total lateral load versus deflection relationship for the system of piers. For lateral loads perpendicular to the line of piers a minimum spacing of three diameters can be used with no capacity reduction. At one diameter (piers touching) the piers can be analyzed as a single unit. Linear interpolation can be used for intermediate conditions. RETAINING WALLS Site retaining walls can be constructed on footing foundations placed on properly compacted fill. For mechanically stabilized earth (MSE) wall design, we recommend using a friction angle of 25 degrees and no cohesion for the retained soil. We recommend an imported granular soil be used as backfill within the reinforced zone behind the walls. Table 2 provides a typical gradation specification for wall backfill. CDOT Class 6 aggregate base course is also acceptable. The top 2 feet of exterior backfill behind walls should be clayey soils to reduce water infiltration. Backfill behind retaining walls should be placed in thin, loose lifts; moisture conditioned and compacted. Settlement on the order of 1 to 2 percent of the backfill depth may occur; improvements constructed over backfill should be designed to perform considering anticipated settlements. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 19 Table 2: Typical Gradation Specification for Wall Backfill Soil Sieve Size Percent Passing 2-inch 100 No. 4 30-100 No. 50 10-60 No. 200 5-10 Some walls may be subjected to lateral loading. Lateral loads are dependent on the height and type of wall, backfill configuration, and backfill type. For purposes of design, we have assumed backfill will consist of on-site sands and gravels. For walls that are free to rotate, we recommend walls be designed to resist an “active” earth pressure using an equivalent fluid density of 30 pcf without hydrostatic pressure. These values are for dry conditions. We recommend appropriate hydrostatic pre ssure be included in the design. Drains should be installed to help control hydrostatic pressures. The drain should lead to a positive gravity outlet, or the wall could be provided with weep holes. A “passive” resistance calculated using 300 pcf equivalent fluid density can be used for walls subject to lateral loads. The recommended “passive” pressure assumes fill placed in front of walls will be densely compacted and will not be removed. The friction coefficient for concrete sliding on the site soil can be taken to be 0.45. SETTLEMENT We understand that anticipated column loads for the 5-story structure will be 400 kips. Based on these load conditions, the subsurface conditions encountered and our experience, we expect the proposed structure could experience up to 1-inch of vertical movement. Differential movement of ½-inch over a 50-foot horizontal distance should be considered in the design. The majority of movement will occur during construction. Construction of structures on the existing fill will likely experience additional settlement. LATERAL EARTH PRESSURES Below grade walls should be designed to withstand lateral earth pressures. Table 3 provides anticipated equivalent fluid density values for native soils or backfill soils composed of onsite materials. These are considered ultimate values and appropriate factors of safety POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 20 should be applied in design. For native material and dense ly compacted backfill made from on-site materials, a friction coefficient of 0.4 and a moist unit weight of 1 10 pounds per cubic foot (pcf) can be assumed. For medium dense compacted granular fill, a friction coefficient of 0.5 and a moist unit weight of 120 pounds per cubic foot (pcf) can be assumed. Table 3: Lateral Earth Pressure Design Parameters Loading Condition Equivalent Fluid Density (𝜸) Clayey Sand Equivalent Fluid Density (𝜸) Sand/Gravel Active (𝜸A) psf 50 30 At-Rest (𝜸o) psf 65 45 Passive (𝜸p) psf 200 575 The appropriate load distribution to apply for design depends not only on the soil type, but also on the wall type and restraint. For walls that are restrained from rotation, the walls should be designed to resist the “at rest” earth pressure. Walls which are free to rotate to develop the shear strength of the retained soils should be designed to resist the “active” earth pressure. Resistance to lateral loads can be provided by friction between concrete and soil and/or by “passive” earth pressure. Passive earth pressure should be ignored for the top 1- foot of soil against the structure since it can be removed easily with time. The proper application of these loading conditions is the responsibility of the wall designer. Wall backfill should be placed according to the Backfill Placement section of this report. BELOW GRADE AREAS No below grade areas are planned for the buildings with the exception of an elevator pit. For this condition, perimeter drains are not usually necessary. Lateral earth pressure on the pit walls can be calculated using an equivalent fluid density of 45 pcf. This value is for horizontal backfill conditions and does not include pressure due to surcharge or hydrostatic pressure. We should be contacted to provide foundation drain recommendations if plans change to include below grade areas. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 21 FLOOR SYSTEMS In our opinion, it is reasonable to use slab -on-grade floors for the proposed construction if placed on improved ground. Any fill placed for the floor subgrade should be built with densely compacted, engineered fill or an elected ground improvement method as discussed in the SITE DEVELOPMENT section of this report. The existing fill is not an acceptable subgrade for a slab-on-grade floor and should be completely removed from the subgrade under a floor. It is impossible to construct slab-on-grade floors with no risk of movement. We believe movements due to swell are not likely and settlement on improved ground should be less than 1-inch. If movement cannot be tolerated, structural floors should be used. Structural floors will be used with pier foundations and can be considered for specific areas that are particularly sensitive to movement or where equipment on the floor is sensitive to movement. Where structurally supported floors are selected, we recommend a minimum void between the ground surface and the underside of the floor system of 6 inches. The minimum void should be constructed below beams and utilities that penetrate the floor . The floor may be cast over void form. Void form should be chosen to break down quickly after the slab is placed. We recommend against the use of wax or plastic -coated void boxes. Slabs may be subject to heavy point loads. The structural engineer should design floor slab reinforcement. For design of slabs-on-grade, we recommend a modulus of subgrade reaction of 100 pci for anticipated soils. If the owner elects to use slab-on-grade construction and accepts the risk of movement and associated damage, we recommend the following precautions for slab -on-grade construction at this site. These precaution s can help reduce, but not eliminate, damage or distress due to slab movement. 1. Slabs should be separated from exterior walls and interior bearing members with a slip joint that allows free vertical movement of the slabs. This can reduce cracking if some movement of the slab occurs. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 22 2. Slabs should be placed directly on exposed soils or properly moisture conditioned, compacted fill. The 2021 International Building Code (IBC) requires a vapor retarder be placed between the base course or subgrade soils and the concrete slab-on-grade floor. The merits of installation of a vapor retarder below floor slabs depend on the sensitivity of floor cove rings and building use to moisture. A properly installed vapor retarder (minimum 6-mil; 10-mil recommended) is more beneficial below concrete slab-on-grade floors where floor coverings, painted floor surfaces or products stored on the floor will be sensitive to moisture. The vapor retarder is most effective when concrete is placed directly on top of it, rather than placing a sand or gravel leveling course between the vapor retarder and the floor slab. The placement of concrete on the vapor retarder may increase the risk of shrinkage cracking and curling. Use of concrete with reduced shrinkage characteristics including minimized water content, maximized coarse aggregate content, and reasonably low slump will reduce the risk of shrinkage cracking and curling. Considerations and recommendations for the installation of vapor retarders below concrete slabs are outlined in Section 3.2.3 of the 2006 report of American Concrete Institute (ACI) Committee 302, “Guide for Concrete Floor and Slab Construction (ACI 302.R1-04)”. 3. Underslab plumbing should be eliminated where feasible. Where such plumbing is unavoidable it should be thoroughly pressure tested for leaks prior to slab construction and be provided with flexible couplings. Pressurized water supply lines should be brought above the floors as quickly as possible. 4. Plumbing and utilities that pass through the slabs should be isolated from the slabs and constructed with flexible couplings. Where water and gas lines are connected to furnaces or heaters, the lines should be constructed with sufficient flexibility to allow for movement. 5. HVAC equipment supported on the slab should be provided with a collapsible connection between the furnace and the ductwork, with allowance for at least 1-inch of vertical movement. 6. The American Concrete Institute (ACI) recommends frequent control joints be provided in slabs to reduce problems associated with shrinkage cracking and curling. To reduce curling, the concrete mix should have a high aggregate content and a low slump. If desired, a shrinkage compensating admixture could be added to the concrete to reduce the risk of shrinkage cracking. We can perform a mix design or assist the design team in selecting a pre -existing mix. Exterior Flatwork We recommend exterior flatwork and sidewalks be isolated from foundations to reduce the risk of transferring heave, settlement, or freeze-thaw movement to the structure. One alternative would be to construct the inner edges of the flatwork on haunches or steel angles POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 23 bolted to the foundation walls and detailing the connections such that movement will cause less distress to the building, rather than tying the slabs directly into the building foundation. Construction on haunches or steel angles and reinforcing the sidewalks and other exterior flatwork will reduce the potential for differential settlement and better allow them to span across wall backfill. Frequent control joints should be provided to reduce problems associated with shrinkage. Panels that are approximately square perform better than rectangular areas. PAVEMENTS The project will include various paved surfaces. This report addresses paved parking and access drives in anticipation of vehicular traffic. Semi-frequent, heavy truck traffic is expected. The performance of pavements is dependent upon the characteristics of the subgrade soil, traffic loading and frequency, climatic conditions, drainage and pavement materials. We drilled three exploratory borings and conducted laboratory tests to characterize the subgrade soils, which consisted of clayey, gravelly fill and clayey sand. The subgrade soils classified as A-6 soils in accordance with AASHTO procedures. The subgrade soil will likely provide fair to poor support for new pavement. The existing fill is considered acceptable as long as it passes proof rolling. If imported fill is needed, we have assumed it will be soils with similar or better characteristics. Flexible hot mix asphalt (HMA) over aggregate base course (ABC) is appropriate for pavement areas. We understand that pavers are desired in some areas currently designated for pedestrian and light vehicle traffic. Where pavers will be subject to heavy vehicle traffic, we recommend using rigid pavement below the pavers , as conventional pavers tend to transmit heavy wheel loads to the subgrade and cause bearing failure . Rigid Portland cement concrete (PCC) pavement should be used for trash enclosure areas and where the pavement will be subjected to frequent turning of heavy vehicles. Our designs are based on the AASHTO design method and our experience. Using the criteria discu ssed above we recommend the minimum pavement sections provided in Table 4. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 24 TABLE 4 RECOMMENDED PAVEMENT SECTIONS Classification Hot Mix Asphalt (HMA) + Aggregate Base Course (ABC) Portland Cement Concrete (PCC) Commercial Grade Paver + Aggregate Base Course (ABC) Pedestrian/Light Vehicle Area 5" HMA + 6" ABC 5" PCC Paver + 5" PCC Parking Area 5" HMA + 6" ABC 5" PCC - Access Drives / Heavy Traffic Areas 6" HMA + 6" ABC 6" PCC - Trash Enclosures - 6" PCC - Pavement Selection Composite HMA/ABC pavement over a stable subgrade is expected to perform well at this site based on the recommendations provided. HMA provides a stiff, stable pavement to withstand heavy loading and will provide a good fatigue resistant pavement. However , HMA does not perform well when subjected to point loads in areas where heavy trucks turn and maneuver at slow speeds. PCC pavement is expected to perform well in this area; PCC pavement has better performance in freeze-thaw conditions and should require less long- term maintenance than HMA pavement. The PCC pavement for trash enclosures should extend out to areas where trash trucks park to lift and empty dumpsters. Subgrade and Pavement Materials and Construction The design of a pavement system is as much a function of the quality of the paving materials and construction as the support characteristics of the subgrade. The construction materials are assumed to possess sufficient quality as reflected by the strength factors used in our design calculations. Moisture treatment criteria and additional criteria for materials and construction requirements are presented in Appendix C of this report. Pavement Maintenance Routine maintenance, such as sealing and repair of cracks, is necessary to achieve the long-term life of a pavement system. We recommend a preventive maintenance program POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 25 be developed and followed for all pavement systems to assure the design life can be realized. Choosing to defer maintenance usually results in accelerated deterioration leading to higher future maintenance costs, and/or repair. A recommended maintenance program is outlined in Appendix D. Excavation of completed pavement for utility construction or repair can destroy the integrity of the pavement and result in a severe decrease in serviceability. To restore the pavement top original serviceability, careful backfill compaction before repaving is necessary. WATER-SOLUBLE SULFATES Concrete that comes into contact with soils can be subject to sulfate attack. We measured water-soluble sulfate concentrations in two samples from this site. Concentrations were from below measurable limits to 0.06 percent. Sulfate concentrations less than 0.1 percent indicate Class 0 exposure to sulfate attack for concrete that comes into contact with the subsoils, according to the American Concrete Institute (ACI). For this level of sulfate concentration, ACI indicates there are no special requirements for sulfate resistance. Superficial damage may occur to the exposed surfaces of highly permeable concrete, even though sulfate levels are relatively low. To control this risk and to resist freeze -thaw deterioration, the water-to-cementitious materials ratio should not exceed 0.50 for concrete in contact with soils that are likely to stay moist due to surface drainage or high -water tables. Concrete should have a total air content of 6 percent ± 1.5 percent. We advocate all foundation walls and grade beams in contact with the soil (including the i nside and outside faces of garage and crawl space grade beams) be damp-proofed. SURFACE DRAINAGE Performance of foundations, flatwork and pavements are influenced by changes in subgrade moisture conditions. Carefully planned and maintained surface grading can reduce the risk of wetting of the foundation soils and pavement subgrade. We recommend a minimum slope of 5 percent in the first ten feet outside foundations in landscaped areas. Backfill around foundations should be moisture treated and compacted as described in Fill Placement. Roof drains should be directed away from buildings. Downspout extensions and POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 26 splash blocks should be provided at discharge points, or roof drains should be connected to solid pipe discharge systems. We do not recommend directing roof drains under buildings. CONSTRUCTION OBSERVATIONS We recommend that CTL Thompson, Inc. provide construction observation services to allow us the opportunity to verify whether soil conditions are consistent with those found during this investigation. Other observations are recommended to review general conformance with design plans. If others perform these observations, they must accept responsibility to judge whether the recommendations in this report remain appropriate. GEOTECHNICAL RISK The concept of risk is an important aspect with any geotechnical evaluation primarily because the methods used to develop geotechnical recommendations do not comprise an exact science. We never have complete knowledge of subsurface conditions. Our analysis must be tempered with engineering judgment and experience. Therefore, the recommendations presented in any geotechnical evaluation should not be considered risk - free. Our recommendations represent our judgment of those measures that are necessary to increase the chances that the structures will perform satisfactorily. It is critical that all recommendations in this report are followed during construction. Owners must assume responsibility for maintaining the structures and use appropriate practices regarding drainage and landscaping. Improvements performed by owners after construction, such as construction of additions, retaining walls, landscaping , and exterior flatwork, should be completed in accordance with recommendations in this report. LIMITATIONS This report has been prepared for the exclusive use of Powerhouse 2 Development Company, LLC for the purpose of providing geotechnical design and construction criteria for the proposed project. The information, conclusions, and recommendations presented herein are based upon consideration of many factors including, but not limited to, the type of construction proposed, the geologic setting, and the subsurface conditions encountered. The conclusions and recommendations contained in the report are not valid for use by others. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 27 Standards of practice evolve in the area of geotechnical engineering. The recommendations provided are appropriate for about three years. If the proposed construction is not constructed within about three years, we should be contacted to determine if we should update this report. Seven borings were drilled during this investigation to obtain a reasonably accurate picture of the subsurface conditions. Variations in the subsurface conditions not indicated by our borings are possible. A representative of our firm should observe foundatio n excavations to confirm the exposed materials are as anticipated from our borings. We should also test compaction of fill if over-excavation is used. We believe this investigation was conducted with that level of skill and care ordinarily used by geotechnical engineers practicing under similar conditions. No warranty, express or implied, is made. If we can be of further service in discussing the contents of this report or in the analysis of the influence of subsurface conditions on design of the structures, please call. CTLTHOMPSON, INC. Trace Krausse, EI R.B. “Chip” Leadbetter, III, PE Project Geotechnical Engineer Senior Geotechnical Engineer TH-1 TH-7 TH-6TH-5TH-4 TH-3 TH-2 E VINE DRHWY 287HWY 287REDWOOD STCONIFER ST E. VINE DR. SITE LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING TH-1 POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTL I T PROJECT NO. FC10223-125 FIGURE 1 Locations of Exploratory Borings VICINITY MAP (FORT COLLINS, CO) NOT TO SCALE 120'60' APPROXIMATE SCALE: 1" = 120' 0' 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 24/12 50/11 47/12 TH-1 7/12 21/12 WC=16.9LL=30 PI=12-200=49 WC=10.1-200=23SS=0.060 TH-2 8/12 50/2 50/2 WC=14.4-200=36 TH-3 6/12 32/12 14/12 50/3 50/3 50/3 WC=8.0-200=5 WC=9.3-200=6 TH-4 9/12 WC=21.2LL=34 PI=13-200=65 TH-5 39/12 50/2 50/1 TH-6 10/12 9/12 24/12 WC=22.2DD=98SW=0.5SS=<0.01 WC=15.6-200=65 TH-7 DEPTH - FEETDRIVE SAMPLE. THE SYMBOL 24/12 INDICATES 24 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. ASPHALTIC CONCRETE (AC) 1. NOTES: THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING. FILL, SAND, GRAVELLY, CLAYEY, MOIST, MEDIUM DENSE, DARK BROWN, TAN 3. LEGEND: SAND, CLAYEY, MOIST, LOOSE TO MEDIUM DENSE, BROWN (SC) SAND AND GRAVEL, CLEAN TO CLAYEY, MOIST TO WET, MEDIUM DENSE TO VERY DENSE, BROWN, DARK GRAY, TAN (SP, SP-SC, GC) SANDSTONE, CLAYEY, MOIST, VERY HARD, GRAY DEPTH - FEETWATER LEVEL MEASURED AT TIME OF DRILLING. Summary Logs of Exploratory Borings THE BORINGS WERE DRILLED ON JANUARY 12, 2022, USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. FIGURE 2 WC DD SW -200 LL PI SS - - - - - - - INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES SOLUBLE SULFATE CONTENT (%). 2. POWERHOUSE 2 DEVELOMPMENT COMPANY, LLC POWERHOUSE 2 CTL | T PROJECT NO. FC10223-125 APPENDIX A RESULTS OF LABORATORY TESTING Sample of FILL, CLAY, SANDY (CL) DRY UNIT WEIGHT=98 PCF From TH - 7 AT 2 FEET MOISTURE CONTENT=22.2 % POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTL | T PROJECT NO. FC10223-125 APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-1 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of SAND, CLAYEY (SC)GRAVEL 0 %SAND 64 % From TH - 3 AT 4 FEET SILT & CLAY 36 %LIQUID LIMIT % PLASTICITY INDEX % Sample of SAND, GRAVELLY, SLIGHTLY CLAYEY (SP-SC)GRAVEL 36 %SAND 59 % From TH - 4 AT 14 FEET SILT & CLAY 5 %LIQUID LIMIT % PLASTICITY INDEX % POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTL | T PROJECT NO. FC10223-125 FIGURE A-2 Gradation Test Results 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR.7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSING0 10 20 30 50 60 70 80 90 100 PERCENT RETAINED40 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR.7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSINGPERCENT RETAINED0 10 20 30 40 50 60 70 80 90 100 Sample of SAND, SLIGHTLY CLAYEY (SP-SC)GRAVEL 11 %SAND 83 % From TH - 4 AT 19 FEET SILT & CLAY 6 %LIQUID LIMIT % PLASTICITY INDEX % Sample of FILL, CLAY, SANDY (CL)GRAVEL 0 %SAND 35 % From TH - 7 AT 4 FEET SILT & CLAY 65 %LIQUID LIMIT % PLASTICITY INDEX % POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTL | T PROJECT NO. FC10223-125 FIGURE A-3 Gradation Test Results 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR.7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSING0 10 20 30 50 60 70 80 90 100 PERCENT RETAINED40 0.002 15 MIN. .005 60 MIN. .009 19 MIN. .019 4 MIN. .037 1 MIN. .074 *200 .149 *100 .297 *50 0.42 *40 .590 *30 1.19 *16 2.0 *10 2.38 *8 4.76 *4 9.52 3/8" 19.1 3/4" 36.1 1½" 76.2 3" 127 5" 152 6" 200 8" .001 45 MIN. 0 10 20 30 40 50 60 70 80 90 100 CLAY (PLASTIC) TO SILT (NON-PLASTIC)SANDS FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES DIAMETER OF PARTICLE IN MILLIMETERS 25 HR.7 HR. HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS PERCENT PASSINGPERCENT RETAINED0 10 20 30 40 50 60 70 80 90 100 PASSING WATER- MOISTURE DRY LIQUID PLASTICITY APPLIED NO. 200 SOLUBLE DEPTH CONTENT DENSITY LIMIT INDEX SWELL*PRESSURE SIEVE SULFATES BORING (FEET)(%)(PCF)(%)(PSF)(%)(%)DESCRIPTION TH-2 2 16.9 30 12 49 SAND, CLAYEY (SC) TH-2 4 10.1 23 0.06 SAND, CLAYEY (SC) TH-3 4 14.4 36 SAND, CLAYEY (SC) TH-4 14 8.0 5 SAND, SLIGHTLY CLAYEY (SP-SC) TH-4 19 9.3 6 SAND, SLIGHTLY CLAYEY (SP-SC) TH-5 2 21.2 34 13 65 FILL, CLAY, SANDY (CL) TH-7 2 22.2 98 0.5 200 <0.01 FILL, CLAY, SANDY (CL) TH-7 4 15.6 65 FILL, CLAY, SANDY (CL) SWELL TEST RESULTS* TABLE A-I SUMMARY OF LABORATORY TESTING ATTERBERG LIMITS Page 1 of 1 POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTL|T PROJECT NO. FC10223-125 APPENDIX B SAMPLE SITE GRADING SPECIFICATIONS POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 B-1 SAMPLE SITE GRADING SPECIFICATIONS 1. DESCRIPTION This item shall consist of the excavation, transportation, placement and compaction of materials from locations indicated on the plans, or staked by the Engineer, as necessary to achieve building site elevations. 2. GENERAL The Geotechnical Engineer shall be the Owner's representative. The Geotechnical Engineer shall approve fill materials, method of placement, moisture contents and percent compaction, and shall give written approval of the completed fill. 3. CLEARING JOB SITE The Contractor shall remove all trees, br ush and rubbish before excavation or fill placement is begun. The Contractor shall dispose of the cleared material to provide the Owner with a clean, neat appearing job site. Cleared material shall not be placed in areas to receive fill or where the mate rial will support structures of any kind. 4. SCARIFYING AREA TO BE FILLED All topsoil and vegetable matter shall be removed from the ground surface upon which fill is to be placed. The surface shall then be plowed or scarified to a depth of 8 inches until the surface is free from ruts, hummocks or other uneven features, which would prevent uniform compaction by the equipment to be used. 5. COMPACTING AREA TO BE FILLED After the foundation for the fill has been cleared and scarified, it shall be disked or bladed until it is free from large clods, brought to the proper moisture content and compacted to not less than 95 percent of maximum dry density as determined in accordance with ASTM D 698 or AASHTO T 99. 6. FILL MATERIALS On-site materials classifying as CL, SC, SM, SW, SP, GP, GC, and GM are acceptable. Fill soils shall be free from organic matter, debris, or other deleterious substances, and shall not contain rocks or lumps having a diameter greater than three (3) inches. Fill materials shall be obtained from the existing fill and other approved sources. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 B-2 7. MOISTURE CONTENT Fill materials shall be moisture treated. Clay soils placed below the building envelope should be moisture-treated to between optimum and 3 percent above optimum moisture content as determined from Standard Proctor compaction tests. Clay soil placed exterior to the building should be moisture treated between optimum and 3 percent above optimum moisture content. Sand soils can be moistened to within 2 percent of optimum moisture content. Sufficient laboratory compaction tests shall be performed to determ ine the optimum moisture content for the various soils encountered in borrow areas. The Contractor may be required to add moisture to the excavation materials in the borrow area if, in the opinion of the Geotechnical Engineer, it is not possible to obtain uniform moisture content by adding water on the fill surface. The Contractor may be required to rake or disk the fill soils to provide uniform moisture content through the soils. The application of water to embankment materials shall be made with any ty pe of watering equipment approved by the Geotechnical Engineer, which will give the desired results. Water jets from the spreader shall not be directed at the embankment with such force that fill materials are washed out. Should too much water be added to any part of the fill, such that the material is too wet to permit the desired compaction from being obtained, rolling and all work on that section of the fill shall be delayed until the material has been allowed to dry to the required moisture content. The Contractor will be permitted to rework wet material in an approved manner to hasten its drying. 8. COMPACTION OF FILL AREAS Selected fill material shall be placed and mixed in evenly spread layers. After each fill layer has been placed, it shall be uniformly compacted to not less than the specified percentage of maximum dry density. Fill materials shall be placed such that the thickness of loose material does not exceed 8 inches and the compacted lift thickness does not exceed 6 inches. Fill placed under foundations, exterior flatwork and pavements should be compacted to a minimum of 95 percent of maximum standard Proctor dry density (ASTM D698). Compaction, as specified above, shall be obtained by the use of sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other equipment approved by the Engineer. Compaction shall be accomplished while the fill material is at the specified moisture content. Compaction of each layer shall be continuous over the entire area. Compaction equipment shall make sufficient trips to ensure that the required dry density is obtained. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 B-3 9. COMPACTION OF SLOPES Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction operations shall be continued until slopes are stable, but not too dense for planting, and there is no appreciable amount of loose soil on the slopes. Compaction of slopes may be done progressively in increments of three to five feet (3' to 5') in height or after the fill is brought to its total height. Permanent fill slopes shall not exceed 3:1 (horizontal to vertical). 10. DENSITY TESTS Field density tests shall be made by the Geotechnical Engineer at locations and depths of his choosing. Where sheepsfoot rollers are used, the soil ma y be disturbed to a depth of several inches. Density tests shall be taken in compacted material below the disturbed surface. When density tests indicate that the dry density or moisture content of any layer of fill or portion thereof is below that required, the particular layer or portion shall be reworked until the required dry density or moisture content has been achieved. 11. SEASONAL LIMITS No fill material shall be placed, spread or rolled while it is frozen, thawing, or during unfavorable weather conditions. When work is interrupted by heavy precipitation, fill operations shall not be resumed until the Geotechnical Engineer indicates that the moisture content and dry density of previously placed materials are as specified. 12. NOTICE REGARDING START OF GRADING The contractor shall submit notification to the Geotechnical Engineer and Owner advising them of the start of grading operations a t least three (3) days in advance of the starting date. Notification shall also be submitted at least 3 days in advance of any resumption dates when grad ing operations have been stopped for any reason other than adverse weather conditions. 13. REPORTING OF FIELD DENSITY TESTS Density tests performed by the Geotechnical Engineer, as specified under "Density Tests" above, shall be submitted progressively to the Owner. Dry density, moisture content and percent compaction shall be reported for each test ta ken. APPENDIX C PAVEMENT CONSTRUCTION RECOMMENDATIONS POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 C-1 SUBGRADE PREPARATION Moisture Treated Subgrade (MTS) 1. The subgrade should be stripped of organic matter, scarified, moisture treated and compacted to the specifications stated below in Item 2. The compacted subgrade should extend at least 3 feet beyond the edge of the pavement where no edge support, such as curb and gutter, are to be constructed. 2. Sandy and gravelly soils (A-1-a, A-1-b, A-3, A-2-4, A-2-5, A-2-6, A- 2-7) should be moisture conditioned near optimum moisture content and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99). Clayey soils (A-6, A-7-5, A-7-6) should be moisture conditioned between optimum and 3 percent above optimum moisture content and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99). 3. Utility trenches and all subsequently placed fill should be properly compacted and tested prior to paving. As a minimum, fill should be compacted to 95 percent of standard Proctor maximum dry density. 4. Final grading of the subgrade should be carefully controlled so the design cross-slope is maintained and low spots in the subgrade that could trap water are eliminated. 5. Once final subgrade elevation has been compacted and tested to compliance and shaped to the required cross-section, the area should be proof-rolled using a minimum axle load of 18 kips per axle. The proof-roll should be performed while moisture contents of the subgrade are still within the recommended limits. Drying of the subgrade prior to proof-roll or paving should be avoided. 6. Areas that are observed by the Engineer that have soft spots in the subgrade, or where deflection is not uniform of soft or wet subgrade shall be ripped, scarified, dried or wetted as necessary and recompacted to the requirements for the density and moisture. As an alternative, those areas may be sub-excavated and replaced with properly compacted structural backfill. Where extensively soft, yielding subgrade is encountered; we recommend a representative of our office observe the excavation. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 C-2 PAVEMENT MATERIALS AND CONSTRUCTION Aggregate Base Course (ABC) 1. A Class 5 or 6 Colorado Department of Transportation (CDOT) specified ABC should be used. A reclaimed concrete pavement (RCP) alternative which meets the Class 5 or 6 designation and design R-value/strength coefficient is also acceptable. Blending of recycled products with ABC may be considered. 2. Bases should have a minimum Hveem stabilometer value of 72, or greater. ABC, RAP, RCP, or blended materials must be moisture stable. The change in R-value from 300-psi to 100-psi exudation pressure should be 12 points or less. 3. ABC or RCP bases should be placed in thin lifts not to exceed 6 inches and moisture treated to near optimum moisture content. Bases should be moisture treated to near optimum moisture content, and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698, AASHTO T 99). 4. Placement and compaction of ABC or RCP should be observed and tested by a representative of our firm. Placement should not commence until the underlying subgrade is properly prepared and tested. Hot Mix Asphalt (HMA) 1. HMA should be composed of a mixture of aggregate, filler, hydrated lime, and asphalt cement. Some mixes may require polymer modified asphalt cement, or make use of up to 20 percent reclaimed asphalt pavement (RAP). A job mix design is recommended and periodic checks on the job site should be made to verify compliance with specifications. 2. HMA should be relatively impermeable to moisture and should be designed with crushed aggregates that have a minimum of 80 percent of the aggregate retained on the No. 4 sieve with two mechanically fractured faces. 3. Gradations that approach the maximum density line (within 5 percent between the No. 4 and 50 sieves) should be avoided. A gradation with a nominal maximum size of 1 or 2 inches developed on the fine side of the maximum density line should be used. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 C-3 4. Total void content, voids in the mineral aggregate (VMA) and voids filled should be considered in the selection of the optimum asphalt cement content. The optimum asphalt content should be selected at a total air void content of approximately 4 percent. The mixture should have a minimum VMA of 14 percent and between 65 percent and 80 percent of voids filled. 5. Asphalt cement should meet the requirements of the Superpave Performance Graded (PG) Binders. The min imum performing asphalt cement should conform to the requirements of the governing agency. 6. Hydrated lime should be added at the rate of 1 percent by dry weight of the aggregate and should be included in the amount passing the No. 200 sieve. Hydrated lime for aggregate pretreatment should conform to the requirements of ASTM C 207, Type N. 7. Paving should be performed on properly prepared, unfrozen surfaces that are free of water, snow and ice. Paving should only be performed when both air and surface temperatures equal, or exceed, the temperatures specified in Table 401-3 of the 2006 Colorado Department of Transportation Standard Specifications for Road and Bridge Construction. 8. HMA should not be placed at a temperature lower than 245 oF for mixes containing PG 64-22 asphalt, and 290oF for mixes containing polymer-modified asphalt. The breakdown compaction should be completed before the HMA temperature drops 20 oF. 9. Wearing surface course shall be Grading S or SX for residential roadway classifications and Grading S for collector, arterial, industrial, and commercial roadway classifications. 10. The minimum/maximum lift thicknesses for Grade SX shall be 1½ inches/2½ inches. The minimum/maximum lift thicknesses for Grade S shall be 2 inches/3½ inches. The minimum/maximum lift thicknesses for Grade SG shall be 3 inches/5 inches. 11. Joints should be staggered. No joints should be placed within wheel paths. 12. HMA should be compacted to between 92 and 96 percent of Maximum Theoretical Density. The surface shall be s ealed with a finish roller prior to the mix cooling to 185oF. 13. Placement and compaction of HMA should be observed and tested by a representative of our firm. Placement should not commence POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 C-4 until approval of the proof rolling as discussed in the Subgrade Preparation section of this report. Subbase, base course or init ial pavement course shall be placed within 48 hours of approval of the proof rolling. If the Contractor fails to place the subbase, base course or initial pavement course within 48 hours or the condition of the subgrade changes due to weather or other con ditions, proof rolling and correction shall be performed again. Portland Cement Concrete (PCC) 1. Portland cement concrete should consist of Class P of the 2011 CDOT - Standard Specifications for Road and Bridge Construction specifications for normal placement or Class E for fast-track projects. PCC should have a minimum compressive strength of 4,200 psi at 28 days and a minimum modulus of rupture (flexural strength) of 6 50 psi. Job mix designs are recommended and periodic checks on the job site should be made to verify compliance with specifications. 2. Portland cement should be Type II “low alkali” and should conform to ASTM C 150. 3. Portland cement concrete should not be placed when the subgrade or air temperature is below 40°F. 4. Concrete should not be placed during warm weather if the mixed concrete has a temperature of 90°F, or higher. 5. Mixed concrete temperature placed during cold weather should have a temperature between 50°F and 90°F. 6. Free water should not be finished into the concrete surface. Atomizing nozzle pressure sprayers for applying finishing compounds are recommended whenever the concrete surface becomes difficult to finish. 7. Curing of the Portland cement concrete should be accomplished by the use of a curing compound. The curing compound should be applied in accordance with manufacturer recommendations. 8. Curing procedures should be implemented, as necessary, to protect the pavement against moisture loss, rapid temperature change, freezing, and mechanical injury. 9. Construction joints, including longitudinal joints and transverse joints, should be formed during construction or sawed after the concrete has begun to set, but prior to uncontrolled cracking. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 C-5 10. All joints should be properly sealed using a ro d back-up and approved epoxy sealant. 11. Traffic should not be allowed on the pavement until it has properly cured and achieved at least 80 percent of the design strength, with saw joints already cut. 12. Placement of Portland cement concrete should be observed and tested by a representative of our firm. Placement should not commence until the subgrade is properly prepared and tested. APPENDIX D PAVEMENT MAINTENANCE PROGRAM POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 D-1 MAINTENANCE RECOMMENDATIONS FOR FLEXIBLE PAVEMENTS A primary cause for deterioration of pavements is oxidative aging resulting in brittle pavements. Tire loads from traffic are necessary to "work" or knead the asphalt concrete to keep it flexible and rejuvenated. Preventive maintenance treatments will typically preserve the original or existing pavement by providing a protective seal or rejuvenating the asphalt binder to extend pavement life. 1. Annual Preventive Maintenance a. Visual pavement evaluations should be performed each spring or fall. b. Reports documenting the progress of distress should be kept current to provide information on effective times to apply preventive maintenance treatments. c. Crack sealing should be performed annually as new cracks appear. 2. 3 to 5 Year Preventive Maintenance a. The owner should budget for a preventive treatment at approximate intervals of 3 to 5 years to reduce oxidative embrittlement problems. b. Typical preventive maintenance treatments include chip seals, fog seals, slurry seals and crack sealing. 3. 5 to 10 Year Corrective Maintenance a. Corrective maintenance may be necessary, as dictated by the pavement condition, to correct rutting, cracking and structurally failed areas. b. Corrective maintenance may include full depth patching, milling and overlays. c. In order for the pavement to provide a 20-year service life, at least one major corrective overlay should be expected. POWERHOUSE 2 DEVELOPMENT COMPANY, LLC POWERHOUSE 2 CTLT PROJECT NO. FC10223-125 D-2 MAINTENANCE RECOMMENDATIONS FOR RIGID PAVEMENTS High traffic volumes create pavement rutting and smooth polished surfaces. Preventive maintenance treatments will typically preserve the original or existing pavement by providing a protective seal and improving skid resistance through a new wearing course. 1. Annual Preventive Maintenance a. Visual pavement evaluations should be performed each spring or fall. b. Reports documenting the progress of distress should be kept current to provide information of effective times to apply preventive maintenance. c. Crack sealing should be performed annually as new cracks appear. 2. 4 to 8 Year Preventive Maintenance a. The owner should budget for a preventive treatment at approximate intervals of 4 to 8 years to reduce joint deterioration. b. Typical preventive maintenance for rigid pavements includes patching, crack sealing and joint cleaning and sealing. c. Where joint sealants are missing or distressed, resealing is mandatory. 3. 15 to 20 Year Corrective Maintenance a. Corrective maintenance for rigid pavements includes patching and slab replacement to correct subgrade failures, edge damage, and material failure. b. Asphalt concrete overlays may be required at 15 to 20 year intervals to improve the structural capacity o f the pavement.