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HomeMy WebLinkAboutHULL ORCHARDS - PDP230002 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT CTL|Thompson, Inc. Denver, Fort Collins, Colorado Springs, Glenwood Springs, Pueblo, Summit County – Colorado Cheyenne, Wyoming and Bozeman, Montana Hull & Hyline Development Taft Hill & Hyline Drive Fort Collins, Colorado Prepared for: The True Life Companies 1800 Wazee Street, Suite 300 Denver, Colorado 80524 Attention: Mark Foster Project No. FC10462-115 July 27, 2022 PRELIMINARY GEOTECHNICAL INVESTIGATION Table of Contents Scope ................................................................................................................................... 1 Summary Of Conclusions ................................................................................................... 1 Site Description ................................................................................................................... 2 Proposed Development ....................................................................................................... 2 Site Geology ........................................................................................................................ 2 Slocum Alluvium .............................................................................................................. 3 Post-Piney Creek Alluvium .............................................................................................. 3 Geologic Hazards ................................................................................................................ 3 Collapse-Prone Soils ....................................................................................................... 4 Expansive Soils and Bedrock .......................................................................................... 4 Groundwater .................................................................................................................... 5 Surface Drainage ............................................................................................................. 5 Frost Heave ..................................................................................................................... 5 Seismicity ......................................................................................................................... 6 Radioactivity ..................................................................................................................... 6 Field and Laboratory Investigations .................................................................................... 7 Subsurface Conditions ........................................................................................................ 7 Development Recommendations ........................................................................................ 8 Site Grading ..................................................................................................................... 8 Permanent Cut and Fill Slopes ........................................................................................ 8 Utility Construction ........................................................................................................... 9 Preliminary Pavement Recommendations ........................................................................ 10 Subgrade Preparation ................................................................................................... 10 Preliminary Pavement Thickness Design ...................................................................... 10 Preliminary Recommendations for Structures .................................................................. 11 Foundations ................................................................................................................... 12 Slabs-on-Grade and Basement Floor Constru ction ...................................................... 12 Below-Grade Construction ............................................................................................ 12 Surface Drainage ........................................................................................................... 13 General Design Considerations .................................................................................... 13 Water-Soluble Sulfates ..................................................................................................... 14 Recommended Future Investigations ............................................................................... 14 Limitations ......................................................................................................................... 14 FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 – SUMMARY LOGS OF EXPLORATORY BORINGS APPENDIX A – LABORATORY TEST RESULTS APPENDIX B – GUIDELINE SITE GRADING SPECIFICATIONS THE TRUE LIFE COMPANIES 1 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Scope This report presents the results of our Geologic and Preliminary Geotechnical Investigation. The purpose of our investigation was to identify geologic hazards that may exist at the site and to evaluate the subsurface conditions to assist in planning and budgeting for the proposed development. The report includes descriptions of site geology, our analysis of the impact of geologic conditions on site development, a description of subsoil and groundwater conditions found in our exploratory borings, and discussions of site de velopment as influenced by geotechnical considerations. The scope was described in our Service Agreement (CTL |T Proposal No. FC-22- 0117) dated March 14, 2022. This report was prepared based upon our understanding of the develop ment plans. The recommendations are considered preliminary and can be used as guidelines for further planning of development and design of grading. We should review development and grading plans to determine if additional investigation is merited, or if we need to revise our recommendations. Additional investigations will be required to design building foundations and pavements. A summary of our findings and recommendations is presented below. More detailed discussions of the data, analysis, and recommendations are presented in the report. Summary Of Conclusions 1. The site contains geologic hazards that should be mitigated during planning and development. No geologic or geotechnical conditions were identified which would preclude development of this site. Collapse-prone soils, expansive soils, regional issues of seismicity, and radioactivity are the primary geologic concerns pertaining to the development of the site. 2. The subsurface conditions encountered in our borings were variable acro ss the site. In general, the soils encountered in our borings generally consisted of sandy clay over slightly clayey to clayey sands with occasional sandy clay interlayers. No bedrock was encountered during this investigation. Groundwater was encountered at depths ranging from 14 to 24 feet below the existing ground surface. Depending on the planned depths, groundwater levels may affect utility installation at this site. Groundwater is not anticipated to otherwise affect the proposed development. 3. We measured low to very high swell potential in several samples of the upper sandy clay. Soils at 9 feet or greater appeared to be non-swelling in all borings except TH- 6. We anticipate footing or pad-type foundations extended to basement level will be appropriate for most structures. If basements are not cons tructed or if additional expansive soils are found at depth in future investigations, over-excavation to mitigate expansive soils should be anticipated. THE TRUE LIFE COMPANIES 2 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 4. Pavement subgrade mitigation for swell is likely over a portion of the site. Based on our boring and laboratory information, we anticipate roughly half of the si te will require subgrade mitigation. Mitigation may consist of moisture and/or chemical treatment of the subgrade soils. Up to 24 inches of chemical treatment (fly ash or lime) should be expected within these areas. Anticipated pavement thickness recommendations are provided in this report. Site Description The site is comprised of three adjacent lots, addressed at the time of this writing as 1901 Hull Street, 1925 Hull Street, and 1839 Hyline Drive. The lots are located east of Taft Hill Road and south of Drake Road in Fort Collins, Colorado. The site is gene rally in a plains area and is primarily vegetated with grasses and weeds. At the time of our exploration the site was in use as low-density rural-residential, occupied by several residences and outbuildings, with the majority of area at each lot being used for pasture. The building site on the 12+ acre parcel slopes gradually to the southeast. Proposed Development We understand the site is planned for residential development. We assume the residences will be 1 to 2-story, wood frame structures with basements or over crawl spaces. Access roads and other improvements will be constructed. Site Geology The geology of the site was investigated through review of mapping by R. B. Colton (Geologic Map of the Boulder-Fort Collins-Greeley Area, 1978). Geology was further evaluated through review of conditions found in explorator y borings, and our experience in the area. According to the referenced mapping, the site is located within an area of Slocum Alluvium, with nearby margins to Post-Piney Creek Alluvium deposited by Spring Creek. THE TRUE LIFE COMPANIES 3 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Slocum Alluvium Slocum Alluvium includes gravels, cobbles, and boulders in a matrix with sand, silt and clay typical of alluvial materials. This unit is well-stratified and has a well-defined soil profile of about 3 feet of clay generally underlain by cleaner and coarser materials with occasional cementation. Post-Piney Creek Alluvium Post-Piney Creek Alluvium is a younger sandy and gravelly alluvium . This unit has a poorly- defined soil profile, with thicknesses of 5 to 15 feet. The materials encountered in our bo rings were in general agreeance with the re ferenced mapping and related units. We judge the materials to be generally consistent with the Slocum Alluvium unit, with the characteristic soil profiles observed in four of the borings, and the remaining borings appear to be the same unit with the upper soil profile removed or replaced due to geomorphological activity related to the younger Post-Piney Creek Alluvium. Clays were encountered to slightly greater depths than indicated by the mapping alone. Weak cementation was observed across most samples underlying the clay or exposed where clay was believed to be removed. No cobbles or boulders were encountered in our borings but may well be encountered in excavations at the site. Oversize materials are not suitable for fill. Geologic Hazards Our investigation identified several geologic hazards that must be considered during the planning and development phases o f this project. None of the geologic hazards identified will preclude development of the property. Development plans are preliminary. Planning should consider the geologic hazards discussed below. The hazards require mitigation which could include av oidance, non-conflicting use or engineered design and construction during site development. Geologic hazards at the site that need to be addressed include collapse-prone soils, expansive soils, surface drainage, frost heave, and regional issues of seismicity and radioactivity. The following sections discuss each of these geologic hazards and associated development concerns. Mitigation concepts are discussed below and in the DEVELOPMENT RECOMMENDATIONS section of the rep ort. THE TRUE LIFE COMPANIES 4 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Collapse-Prone Soils Soils encountered in the borings at this site include dry silty sand soils. Some of these soils had a porous, friable structure and relatively low density. These soils have the potential for consolidation or collapse upon wetting. Based on the results of our investigation, we believe risk due to settlement of collapsible soils at this site is low. More problematic areas may be evidenced in excavations or further investigation at the site. Some increase in subsurface moisture must be assumed due to the effects of site development. Engineered design of foundations, slabs-on-grade, pavements, and surface drainage can mitigate the effects of collapse -prone soils. Methods for mitigation of collapse-prone soils are discussed in following sections of the report. Expansive Soils and Bedrock Colorado is a challenging location to practice geot echnical engineering. The climate is relatively dry, and the near-surface soils are typically dry and relati vely stiff. These soils and related sedimentary bedrock formations ten d to react to changes in moisture conditions. Some of the soils and bedrock swell as they increase in moisture and are called expansive soils. Other soils can settle significantly upon w etting and are referred to as collapsing soils. Most of the land available for development east of the Front Range is underlain by expansive clay or claystone bedrock near the surface. The soils that exhibit collapse are more likely west of the continental divide; however, both types of soils occur all over the state. Covering the ground with houses, streets, driveways, patios, etc., coupled with lawn irrigation and changing drainage patterns, leads to an increase in subsurface moisture conditions . As a result of this moisture fluctuation, some soil movement due to heave or settlement is inevitable. There is risk that improvements will experience damage. It is critical that precautions are taken to increase the chances that the foundations and slabs-on-grade will perform satisfactorily. Engineered planning, design and construction of grading, pavements, foundations, slabs-on-grade, and drainage can m itigate, but not eliminate the effects of expansive and compressible soils. The soils at this site include very high swelling, near-surface clays. Approximately 60 percent of the site is judged to be high swell risk at existing grades. As severe as the swell appears, the problem materials are relatively shallow . Mitigation can likely be achieved by extending THE TRUE LIFE COMPANIES 5 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 foundations through expansive clays or over-excavating expansive clays where basements are not constructed. Problems associated with the existence of expansive materials are typically mitigated through currently utilized foundation and floor slab techniques. Design level soils and foundation investigations conducted should address procedures for mitigating problems associated with expansive soils. Groundwater Groundwater was encountered at depths of 14 to 24 feet during drilling and 15 to 18 feet when the holes were checked several days after drilling. Boring TH-1 was backfilled immediately following drilling to protect livestock penned in this area. Remaining borings were backfilled following secondary groundwater measureme nts. We do not expect current groundwater levels will affect site development outside of sewers, depending on depths of installation . Groundwater may rise due to site development. The depth to groundwater should be evaluated during Geotechnical Investigations at the site. In general, grading should be designed to rai se the elevations in areas of shallow groundwater. Construction of underdra in systems with the sanitary sewer trenches is a commonly employed method to mitigate the accumulation of shallow groundwater after construction. A minimum separation of 5 feet is desirable between the groundwater elevations and the lowest elevation of any below-grade structure. Surface Drainage The Civil Engineer should evaluate and quantify the potential flow in each drainage during peak precipitation events, and design surface drainage and storm collection systems to accommodate the water. Active drainageways should be avoided for development. Structures should not be located within a lateral distance from the cr est equivalent to twice the depth of the drainageway where slopes are steeper than about 2:1. Storm drainage should be collected in detention basins and released at historic rates or less. Frost Heave Our borings indicate shallow ground water is present and the majority of overburden soils at the site consist of materials that are susceptible to frost heave. Based on our experience and local THE TRUE LIFE COMPANIES 6 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 construction practice in the area, the minimum depth of cover for frost protection is 30 inches. We recommend foundations have a minimum cover of 30 inches. If the foundations are constructed with the appropriate frost protection, we do not believe frost heave will affect the proposed structures. Slabs-on-grade may experience some movement due to frost heave. If the buildings are insulated or heated, the potential for slab movement due to frost heave is minimal. If the buildings are not insulated or heated, slabs-on-grade should be constructed with frost protection. Seismicity This area, like most of central Colorado, is subject to a l ow degree of seismic risk. No indications of recent movements of any of the faults in the Larimer County area have been reported in the available geologic literature. As in most areas of recognized low seismicity, the record of the past earthquake activity in Colorado is somewhat incomplete. Based on the subsurface conditions encounte red in our borings and our understanding of the geology, the site classifies as a Seismic Site Class D (2018 International Building Code). Only minor damage to relatively new, properly designed and built buildings would be expected. Wind loads, not seism ic considerations, typically govern dynamic structural design in this area. If it is determined that seismic site class is critical to the design, CTL|Thompson can provid e a proposal for services to determine the site class based on a geophysical study. Radioactivity It is normal in the Front Range of Colorado and nearby eastern plains to measure radon gas in poorly ventilated spaces in contact with soil or bedrock. Rad on 222 gas is considered a health hazard and is one of several radioactive products i n the chain of the natural decay of uranium into stable lead. Radioactive nuclides are common in the soils and sedimentary rocks underlying the subject site. Because the se sources exist on most sites, there is potential for radon gas accumulation in poorly ventilated spaces. The amount of soil gas that can accumulate is a function of many factors, including the radio -nuclide activity of the soil and bedrock, construction methods and materials, pathways for soil gas and existence of poorly-ventilated accumulation areas. It is difficult to predict the concentration of radon gas in finished construction. THE TRUE LIFE COMPANIES 7 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 During our investigation, we did not detect any radiation levels above normal background levels for the area. No potential bedrock source of radon was encountered during this investigation. We recommend testing to evaluate radon levels after construction is completed. If required, typical mitigation methods for residential construction may consist of sealing soil gas entry areas and periodic ventilation of below-grade spaces and perimeter drain systems. It is relatively economical to provide for ventilation of perimeter drain systems or underslab gravel layers at the time of construction, compared to retrofitting a structure after construction. Radon rarely accumulates to significant levels in above-grade, heated and ventilated spaces. Field and Laboratory Investigations Subsurface conditions were investigated by drilling six exploratory borings at the approximate locations shown on Figure 1. The borings were drilled using a truck-mounted drill rig with 4-inch diameter continuous-flight auger. Our field representative observed drilling, logged the soils found in the borings, and obtained samples. Summary logs of the soils found in the borings and field penetration resistance values are presented on Figure 2. Samples of soil were obtained during drilling by driving a modified California-type sampler (2.5 inch O.D.) into the subsoils using a 140-pound hammer falling 30 inches. Samples recovered from the test holes were return ed to our laboratory and visually classified by the geotechnical engineer. Laboratory testing included determination of moisture content and dry density, swell - consolidation characteristics, Atterberg limits, particle-size analysis, and water soluble sulfate content. Laboratory test results are presented in Appendix A. Subsurface Conditions Subsurface conditions encountered in the borings were variable and included 3 feet of sand and gravel or 3 to 17 feet of sandy clay, underlain by clayey sand with interlayers of clean to clayey sands and gravels or sandy clay. No bedrock was encountered during this investigation. Groundwater was encountered at depths ranging from 14 to 24 feet below the existing ground surface. Groundwater levels may complicate sewer installation, depending on the depths required. Groundwater levels will not likely otherwise affect planned development at this site. A more detailed description of the subsurface conditions is presented in our boring logs and laboratory testing. THE TRUE LIFE COMPANIES 8 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Development Recommendations Site Grading At the time of this investigation, site grading p lans were not available for review in conjunction with this subsurface exploration program. It is important that deep fills (if planned) be constructed as far in advance of surface construction as possible. It is our experience that fill compacted in accordance with the compaction recommendations in this report may settle about 1 percent of its height under its own weight. Most of this settlement usually occurs during and soon after construction. Some additional settlement is possible after development and la ndscape irrigation increases soil moisture. We recommend delaying the construction of buildings underlain by deep fills as long as possible to allow for this set tlement to occur. Delaying construction of structures up to one year where located on deep fill s is recommended. The existing on-site soils are suitable for re-use as fill material provided debris or deleterious organic materials are removed. Prior to fill placement, all trash and debris should be removed from fill areas and properly disposed. Import fill should generally have similar or better engineering properties as the onsite materials and should be approved by CTL|T. The ground surface in areas to be filled should be stripped of vegetation, topsoil, and other deleterious materials, scarified to a depth of at least 8 inches, moisture conditioned and com pacted as recommended below. The depth of any topsoil is not anticipated to be more than 2 to 4 inches in most areas. Site grading fill should be placed in thin, loose lifts, moisture conditioned and compacted. In areas of deep fill, we recommend higher compaction criteria to help reduce settlement of the fill. Compaction and moisture requirements are presented in Appendix B. The placement and compaction of fill should be observed, and density tested during construction. Guideline site grading specifications are presented in Appendix B. Permanent Cut and Fill Slopes We recommend permanent cut and fill slopes be designed with a maximum inclination of 3:1 (horizontal to vertical). Structures should be setback from the top or bottom of cut and fill slopes. If site constraints (property boundaries and streets) do not permit construction with recommended slopes, we should be contacted to evaluate the subsurface soils and steep er slopes. THE TRUE LIFE COMPANIES 9 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Utility Construction We believe excavations for utility installa tion in the overburden soils can be performed with conventional heavy-duty trenchers or large backhoes. Some underlying soils were partially cemented and may cause difficulty for excavation operations. The excavation contractor should anticipate that rock excavation techniques may be required. If groundwater is encountered during construction, dewatering may be accomplished by sloping excavations to occasio nal sumps where water can be removed by pumping. Utility trenches should be sloped or shored to meet local, State , and federal safety regulations. Based on our investigation, we believe the sandy clay classifies as Type A soil, the clayey sands as Type B and sands and gravels classify as Type C soil based on OSHA standards. Excavation slopes specified by OSHA are dependent upon soil types and groundwater conditions encountered. Seepage and ground water conditions in trenches may downgrade the soil type. Contractors should identify the soils encountered in the excavation and refer to OSHA standards to determine appropriate slopes. Excavations deeper than 20 feet should be designed by a professional engineer. The width of the top of an excavation may be limited in some areas. Bracing or “trench box” construction may be necessary. Bracing systems include sheet piling, braced sheeting, and others. Lateral loads on bracing depend on the depth of ex cavation, slope of excavation above the bracing, surface loads, hydrostatic pressures, and allowable movement. For trench boxes and bracing allowed to move enough to mobilize the strength of the s oils, with associated cracking of the ground surface, the “active” earth pressure conditions are appropriate for desi gn. If movement is not tolerable, the “at rest” earth pressures are appropriate. We suggest an equivalent fluid density of 30 pcf for the “active” earth pressure condition and 45 pcf for the “at r est” earth pressure condition, assuming level backfill. T hese pressures do not include allowances for surcharge loading or for hydrostatic conditions. We are available to assist further with brac ing design if desired. Water and sewer lines are usually c onstructed beneath paved roads. Compaction of trench backfill can have significant effect on the life and serviceability of pavements. We believe trench backfill should be placed in thin, loose l ifts, and moisture conditioned to between optimum and 3 percent above optimum content for clay soils and within 2 per cent of optimum moisture content for THE TRUE LIFE COMPANIES 10 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 sand. Trench backfill should be compacted to at least 95 percent of maximum dry density (ASTM D 698). The placement and compaction of fill and backfill should be observed and tested by our firm during construction. If deep excavations are necessary for planned utilities, the compaction requirements provided in Appendix B should be considered. Preliminary Pavement Recommendations Subgrade Preparation Based on the borings, the near surface soil s on this site will consist of highly expansive sandy clays or relatively clean sands and gravels. The clay soils will range from moderately to highly plastic and will provide relatively poor subgrade support below the pavements. Lime, cement or fly ash stabilization of these soils will improve their subgrade support characteristics, in addition to enhancing the workability of the clays and reducing water infiltrat ion into the underlying subgrade and the potential movements under the pavements. We anticipate up to 2 feet of treatment will be required where expansive clay subgrade is exposed. Sands and gravels are anticipated to provide fair to good subgrade support. Preliminary Pavement Thickness Design Preliminary guidelines for pavement systems on this site are provided. Final pavement sections should be determined based on a design level geotechnical investigation and anticipated frequency of load applications on the pavement during the desired design life. Flexible hot mix asphalt (HMA) over aggregate base course (ABC) or rigid Portland cement concrete (PCC) pavements can be used at this site for automobile and light truck traffic use. Rigid pavements are recommended in any areas subject to heavy truck traffic. We anticipate asphalt pavement sections for local residential streets will be on the order of 4 to 5 inches thick over 6 inches of aggregate base course (ABC). Collectors and other higher volume pavement will likely require thicke r pavement sections, estimated on the order 6 to 7 inches over 7 to 9 inches of ABC. We defer to the 2016 Larimer County Urban Street Standards for minimum pavement requirements. Minimum pavement section thicknesses are provided in Table 1. THE TRUE LIFE COMPANIES 11 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Table 1: Minimum Pavement Thickness Roadway Designation Hot Mix Asphalt (HMA) + Aggregate Base Course (ABC) Full Depth Asphalt Portland Cement Concrete (PCC) Local 4.0” HMA + 6.0” ABC 6.0” 6” Residential Cul-de-sac 5.4” HMA + 6.0” ABC 6.5” 6” Collector Minor 5.5” HMA + 7.0” ABC Not Allowed 6” Collector Major 6.5” HMA + 9.0” ABC Not Allowed 6” Portland cement concrete (PCC) pavement is recommended in areas subject to any heavy truck traffic such as garbage pickup and/or dumpster trucks and any heavy delivery trucks. We anticipate the use of 6 inches of PCC for general area pavements which are not subject to truck traffic. A minimum 6 inch thick section is anticipated in main drives and any areas subject to some moderately heavy truck traffic. Any areas subject to frequent heavy trucks should be designed based on frequency and wheel loads. PCC pavements in this area are typically reinforced due to the underlying active clays. Properly designed control joints and other joints systems are required to control cracking and allow pavement movement. Preliminary Recommendations for Structures The property is currently planned for residential construction. Our field and laboratory data indicate the soil conditions vary across the site. The following discussions are preliminary and are not intended for design or construction. After grading is completed, a detailed soils and foundation investigation should be performed. (Due to the preliminary nature of this project, subdivision organization or site grading plans have not been prepared, and therefore not available for review in conju nction with this subsurface exploration program. Therefore, recommendations provided here are gen eral and for planning purposes only.) THE TRUE LIFE COMPANIES 12 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Foundations Our geologic and preliminary geotechnical investigation for this site indicates structures may be founded on a shallow foundation where expansive clays are not encountered or where foundations can be extended through expansive clays. Where expansive clays are antic ipated at foundation level, over-excavation can likely be used to create conditions suitable for footing foundations. A design level geotechnical investigation may identify potential hazards for specified areas not indicated by our borings which may suggest the need for a deeper foundation system. Slabs-on-Grade and Basement Floor Construction The use of slab-on-grade floors for unfinished basements should be limited to areas where soils within the depth likely to influence floor performance are consolidating to low swelling granular soils or clay. We believe most of the lots will be rated with low risk of poor basement slab performance. Structurally supported floor systems should be planned in all non-basement finished living areas and in basements where slab risk is judged high or very high. Our firm also generally recommends structurally supported basement floors for moderate (2 to less than 4 percent), high (4 to less than 6 percent) and very high (greater than 6 percent) risk sites where walkout and garden level basements are planned. Slab performance risk should be more t horoughly defined during the design level soils and foundation investigation. Below-Grade Construction With long-term development and associated landscaping, a “perched” water table may develop on relatively impermeable soil layers. To reduce the risk of hydrostatic pressure developing on foundation walls, foundation drains will be necessary around all below -grade areas. We suggest foundation drains be tied to the sewer underdrain system. They may also discharge to sumps where water can be removed by pumping. In our opinion, underdrain systems offer more comprehensive control of groundwater and will better mitigate impacts of groundwater and swelling soils on foundations, slabs, and pavements. Foundation walls and grade beams should be designed to withstand lateral ea rth pressures. The design pressure should be established during design-level soils investigations. THE TRUE LIFE COMPANIES 13 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 Surface Drainage The performance of foundations will be influenced by surface drainage. The ground surface around proposed residences sho uld be shaped to provide runoff of surface water away from the structure and off of pavements. We generally recommend slopes of at least 12 inches in the first 10 feet where practical in the landscaping areas surrounding residences. There are practical limitations on achieving these slopes. Irrigation should be minimized to control wetting. Roof downspouts should discharge beyond the limits of backfill. Water should not be allowed to pond on or adjacent to pavements. Proper control of surface runoff is also important to limit the erosion of surface soils. Sheet flow should not be directed over unprotected slopes. Water should not be allowed to pond at the crest of slopes. Permanent slopes should be re-vegetated to reduce erosion. Water can follow poorly compacted fill behind curb and gutter and in utility trenches. This water can soften fill and undermine the performance of the roadways, flatwork , and foundations. We recommend compactive effort be used in placement of all fill. General Design Considerations Exterior sidewalks and pavements supported above the on-site clays are subject to post construction movement. Flat grades should be avoided t o prevent possible ponding, particularly next to the building due to soil movement. Positive grades away from the buildings should be used for sidewalks and flatwork around the perimeter of the buildings in order to reduce the possibility of lifting of this flatwork, resulting in ponding next to the structures. Where movement of the flatwork is objectionable, procedures recommended for on-grade floor slabs should be considered. Joints next to buildings should be thoroughly sealed to prevent the infiltrat ion of surface water. Where concrete pavement is used, joints should also be sealed to reduce the infiltration of water. Since some post construction movement of pavement and flatwork may occur, joints around the buildings should be periodically observed and resealed where necessary. Roof drains should be discharged well away from the structures, preferably by closed pipe systems. Where roof drains are allowed to discharge on concrete flatwork or pavement areas next to the structures, care should be tak en to ensure the area is as water-tight as practical to eliminate the infiltration of this water next to the buildings. THE TRUE LIFE COMPANIES 14 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 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 measured in both samples were 0.01 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 any type of cement can be used for concrete that comes into cont act with the subsoils. In our experienc e, 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 material 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 be air entrained. Future investigations may indicate higher levels of water-soluble sulfates which could change the exposure class at the site. Recommended Future Investigations Based on the results of this investigation and the proposed development, we recommend the following investigations be performed: 1. Review of final site grading plans by our firm; 2. Construction testing and observation for site development; 3. Subgrade investigation and pavement design after site grading is complete; 4. Design-level soils and foundation investigations after grading; 5. Construction testing and observation for residential building construction and paving. Limitations Our exploratory borings were located to obtain preliminary subsoil data indicative of conditions on this site. Although our borings were spaced to obtain a reasonably accurate picture of subsurface conditions, variations in the subsoils not indicated in our borings are a lways possible. We believe this investigation was conducted in a manner consistent with that level of skill and care ordinarily used by members of the profession currently practicing under similar conditio ns in the locality of this project. No warranty, express or implied, is made. THE TRUE LIFE COMPANIES 15 HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 This report was prepared from data developed during our field exploration, laboratory testing, engineering analysis, and experience with similar conditions. The recommendations contained in this report were based upon our unde rstanding of the planned construction . If plans change or differ from the assumptions presented herein, we should be contacted to review our recommendations. If we can be of further service in discussing the contents of this report or in the analysis of the building and pavement from the geotechnical point of view, please call. Very truly yours, CTL|THOMPSON, INC. Taylor H. Ray, PE Spencer Schram, PE Geotechnical Project Manager Geotechnical Project Manager TH-3 TH-4 TH-5 TH-6 TH-1 Hyline Drive Hull Street Fisch Drive Kinnison DriveTaft Hill RoadTH-2 S. TAFT HILL RD.W. DRAKE RD. W. HORSETOOTH RD.S. SHIELDS ST.SITE LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING PROPERTY BOUNDARY TH-1 THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL I T PROJECT NO. FC10462-115 FIGURE 1 Locations of Exploratory Borings VICINITY MAP (FORT COLLINS, COLORADO) NOT TO SCALE 250'125' APPROXIMATE SCALE: 1" = 250' 0' 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 25/12 13/12 15/12 16/12 13/12 10/12 WC=6.6-200=51 WC=9.3DD=90-200=54 WC=6.6-200=51 WC=9.3DD=90-200=54 TH-1 26/12 23/12 20/12 11/12 22/12 WC=4.7-200=38WC=4.7-200=38 TH-2 39/12 33/12 21/12 15/12 8/12 4/12 pF=4.82 WC=9.9DD=122SW=8.8SS=0.010 WC=3.5DD=110SW=-2.2 pF=4.82 WC=9.9DD=122SW=8.8SS=0.010 WC=3.5DD=110SW=-2.2 TH-3 44/12 15/12 22/12 8/12 10/12 5/12 WC=2.4-200=16 WC=6.3DD=120-200=33 WC=2.4-200=16 WC=6.3DD=120-200=33 TH-4 29/12 19/12 20/12 12/12 20/12 WC=12.0DD=116SW=12.1 WC=12.0DD=116SW=12.1 TH-5 18/12 38/12 12/12 8/12 28/12 WC=7.0DD=91SW=1.4SS=0.010 WC=16.7DD=114SW=3.2 WC=7.0DD=91SW=1.4SS=0.010 WC=16.7DD=114SW=3.2 TH-6 THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING. GRAVEL, SANDY, SLIGHTLY CLAYEY, SLIGHTLY MOIST, MEDIUM DENSE, BROWN, GREY (GP) DRIVE SAMPLE. THE SYMBOL 25/12 INDICATES 25 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. CLAY, SANDY, MOIST, STIFF, BROWN (CL) 1. NOTES: 3. LEGEND: SAND, CLAYEY, SILTY, SLIGHTLY MOIST TO VERY MOIST, LOOSE TO DENSE, WHITE, RED (SC) SAND, GRAVELLY, SLIGHTLY MOIST TO WET, MEDIUM DENSE, RED (SP)DEPTH - FEETWATER LEVEL MEASURED AT TIME OF DRILLING. Summary Logs of Exploratory Borings THE BORINGS WERE DRILLED ON JUNE 30TH AND JULY 7TH, 2022 USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. FIGURE 2 WC DD SW -200 SS - - - - - INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES SOLUBLE SULFATE CONTENT (%). 2.DEPTH - FEETTHE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL | T PROJECT NO. FC10462.000-115 APPENDIX A LABORATORY TEST RESULTS TABLE A-I: SUMMARY OF LABORATORY TEST RESULTS Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=122 PCF From TH - 3 AT 4 FEET MOISTURE CONTENT=9.9 % THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL | T PROJECT NO. FC10462-115 APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-1 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of SAND, CLAYEY (SC) DRY UNIT WEIGHT=110 PCF From TH - 3 AT 9 FEET MOISTURE CONTENT=3.5 % THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL | T PROJECT NO. FC10462-115 APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-2 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=116 PCF From TH - 5 AT 2 FEET MOISTURE CONTENT=12.0 % THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL | T PROJECT NO. FC10462-115 APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-3 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=91 PCF From TH - 6 AT 2 FEET MOISTURE CONTENT=7.0 % Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=114 PCF From TH - 6 AT 9 FEET MOISTURE CONTENT=16.7 % THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL | T PROJECT NO. FC10462-115 APPLIED PRESSURE - KSF APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation FIGURE A-4COMPRESSION % EXPANSION-4 -3 -2 -1 0 1 2 3 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING -3 -2 -1 0 1 2 3 4 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 0.1 1.0 10 100 WATER-PASSING APPLIED SOLUBLENO. 200DRYMOISTURE PRESSURESWELL*SULFATESSIEVESUCTIONDENSITYCONTENTDEPTH BORING (FEET)(%)(PCF)(%)(PSF)(PF)(%)(%)DESCRIPTION CLAY, SANDY (CL)516.62TH-1 CLAY, SANDY (CL)54909.34TH-1 SAND, CLAYEY (SC)384.74TH-2 CLAY, SANDY (CL)4.822TH-3 CLAY, SANDY (CL)0.015008.81229.94TH-3 SAND, CLAYEY (SC)1,100-2.21103.59TH-3 GRAVEL, CLAYEY, SANDY (GP)162.42TH-4 SAND, CLAYEY (SC)331206.34TH-4 CLAY, SANDY (CL)20012.111612.02TH-5 CLAY, SANDY (CL)0.012001.4917.02TH-6 TH-6 9 16.7 114 3.2 1,100 CLAY, SANDY (CL) SWELL TEST RESULTS* TABLE A-I SUMMARY OF LABORATORY TESTING Page 1 of 1 * NEGATIVE VALUE INDICATES COMPRESSION. THE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTL|T PROJECT NO. FC10462-115 APPENDIX B GUIDELINE SITE GRADING SPECIFICATIONS HE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTLT PROJECT NO. FC10462-115 Appendix B-1 GUIDELINE 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 preliminary street and overlot elevations. These specifications shall also apply to compaction of excess cut materials that may be placed outside of the development boundaries. 2. GENERAL The Soils Engineer shall be the Owner's representative. The Soils 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 vegetation and debris 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 material 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 until the surface is free from ruts, hummocks or other uneven features, which would prevent uniform compaction. 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 (0 to 3 percent above optimum moisture content for clays and within 2 percent of optimum moisture content for sands) and compacted to not less than 95 percent of maximum dry density as determined in accordance with ASTM D698. 6. FILL MATERIALS Fill soils shall be free from organics, debris, or other deleterious substances, and shall not contain rocks or lumps having a diameter greater than six (6) inches. Fill materials shall be obtained from cut areas shown on the plans or staked in the field by the Engineer. HE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTLT PROJECT NO. FC10462-115 Appendix B-2 On-site materials classifying as CL, CH, SC, SM, SW, SP, GP, GC, and GM are acceptable. Concrete, asphalt, organic matter and other deleterious materials or debris shall not be used as fill. 7. MOISTURE CONTENT AND DENSITY Fill material shall be moisture conditioned and compacted to the criteria in the table, below. Maximum density and optimum moisture content shall be determined from the appropriate Proctor compaction tests. Sufficient laboratory compaction tests shall be made to determine the optimum moisture content for the various soils encountered in borrow areas. FILL COMPACTION AND MOISTURE REQUIREMENTS Soil Type Depth from Overlot Grade (feet) Moisture Requirement (% from optimum) Density Requirement Clay 0 to 20 feet +1 to +4 95% of ASTM D 698 Sand -2 to +2 95% of ASTM D 698 Clay Greater than 20 feet -2 to +1 98% of ASTM D 698 Sand -2 to +1 95% of ASTM D 1557 The Contractor may be required to add moisture to the excavation materials in the borrow area if, in the opinion of the Soils 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 disc the fill soils to provide uniform moisture content through the soils. The application of water to embankment materials shall be made with any type of watering equipment approved by the Soils 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. HE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTLT PROJECT NO. FC10462-115 Appendix B-3 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 density. Fill shall be compacted to the criteria above. At the option of the Soils Engineer, soils classifying as SW, GP, GC, or GM may be compacted to 95 percent of maximum density as determined in accordance with ASTM D 1557 or 70 percent relative density for cohesionless sand soils. Fill materials shall be placed such that the thickness of loose materials does not exceed 12 inches and the compacted lift thickness does not exceed 6 inches. 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 for soils classifying as CL, CH, or SC. Granular fill shall be compacted using vibratory equipment or other equipment approved by the Soils 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 density is obtained. 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 not appreciable amount of loose soils 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. PLACEMENT OF FILL ON NATURAL SLOPES Where natural slopes are steeper than 20 percent in grade and the placement of fill is required, benches shall be cut at the rate of one bench for each 5 feet in height (minimum of two benches). Benches shall be at least 10 feet in width. Larger bench widths may be required by the Engineer. Fill shall be placed on completed benches as outlined within this specification. 11. DENSITY TESTS Field density tests shall be made by the Soils Engineer at locations and depths of his choosing. Where sheepsfoot rollers are used, the soil may 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 density or moisture content of any layer of fill or portion thereof is not within specification, the particular layer or portion shall be reworked until the required density or moisture content has been achieved. HE TRUE LIFE COMPANIES HULL & HYLINE DEVELOPMENT CTLT PROJECT NO. FC10462-115 Appendix B-4 12. 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 Soils Engineer indicates that the moisture content and density of previously placed materials are as specified. 13. NOTICE REGARDING START OF GRADING The Contractor shall submit notification to the Soils Engineer and Owner advising them of the start of grading operations at 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 grading operations have been stopped for any reason other than adverse weather conditions. 14. REPORTING OF FIELD DENSITY TESTS Density tests made by the Soils Engineer, as specified under "Density Tests" above, shall be submitted progressively to the Owner. Dry density, moisture content, and percentage compaction shall be reported for each test taken. 15. DECLARATION REGARDING COMPLETED FILL The Soils Engineer shall provide a written declaration stating that the site was filled with acceptable materials, and was placed in general accordance with the specifications.