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HomeMy WebLinkAboutIMPALA REDEVELOPMENT - FDP230001 - 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 306 and 400 IMPALA CIRCLE Fort Collins, Colorado Prepared for: HOUSING CATALYST 1715 West Mountain Avenue Fort Collins, Colorado 80521 Attention: Nichole Rex Senior Project Manager Project No. FC10389-115 June 3, 2022 PRELIMINARY GEOTECHNICAL INVESTIGATION Table of Contents i Scope .................................................................................................................................. 1 Summary Of Conclusions ................................................................................................... 1 Site Description and Proposed Development .................................................................... 2 Site Geology........................................................................................................................ 2 Geologic Hazards ............................................................................................................... 2 Existing Fill ...................................................................................................................... 3 Expansive Soils and Bedrock ......................................................................................... 3 Flooding ........................................................................................................................... 4 Seismicity ........................................................................................................................ 4 Radioactivity .................................................................................................................... 4 Field And Laboratory Investigations ................................................................................... 5 Subsurface Conditions ........................................................................................................ 5 Existing Fill ...................................................................................................................... 6 Development Recommendations ....................................................................................... 6 Site Grading .................................................................................................................... 6 Permanent Cut and Fill Slopes ....................................................................................... 7 Utility Construction .......................................................................................................... 7 Preliminary Pavement Recommendations ......................................................................... 9 Subgrade Preparation ..................................................................................................... 9 Preliminary Pavement Thickness Design ....................................................................... 9 Preliminary Recommendations for Structures .................................................................... 9 Foundations ................................................................................................................... 10 Slabs-on-Grade and Basement Floor Construction ..................................................... 10 Below-Grade Construction ............................................................................................ 10 Surface Drainage .......................................................................................................... 11 General Design Considerations .................................................................................... 11 Water Soluble Sulfates ..................................................................................................... 12 Recommended Future Investigations ............................................................................... 12 Limitations ......................................................................................................................... 13 FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 – SUMMARY LOGS OF EXPLORATORY BORINGS APPENDIX A – LABORATORY TEST RESULTS APPENDIX B – GUIDELINE SITE GRADING SPECIFICATIONS HOUSING CATALYST 1 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Scope This report presents the results of our 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, bedrock and groundwater conditions found in our exploratory borings, and discussions of site development as influenced by geotechnical considerations. The scope was described in our Service Agreement (CTL |T Proposal No. FC-22-0062) dated March 29, 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 final 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. Existing fill, expansive soils and bedrock and regional issues of seismicity, radioactivity are the primary geologic concerns pertaining to the development of the site . No geologic or geotechnical conditions were identified which would preclude development of th is site. 2. In general, the soils and bedrock encountered in our borings consisted of sandy clay or clayey sand overlying weathered to competent claystone bedrock to the depths explored of 25 feet. The upper approximately 5 feet of borings TH-2 through TH-4 was comprised of man-placed fill. Groundwater was encountered at depths of 18 to 23 feet below the existing ground surface. Groundwater levels will not likely affect planned development at this site. 3. Swell consolidation testing of multiple samples from our borings indicated non- swelling to low swelling soils and bedrock. We anticipate footing or pad-type foundations be appropriate for most structures. Slab-on-grade basement floors are likely acceptable. HOUSING CATALYST 2 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Site Description and Proposed Development The site is located north of West Mulberry Street and east of South Impala Drive in Fort Collins, Colorado. There are occupied homes currently on the site that will be demolished for the future construction. Poudre High School is to the north and residential areas are to the east, west and south. The southwest portion of the site is in a floodplain. The proposed development includes the new construction of ten townhomes, several multi- family apartment buildings, and a community center. The buildings are expected to be two to three- story structures with and without basements, with attached and detached garages. Site Geology The geology of the site was investigated through review of mapping by Roger B. Colton (Geologic Map of the Boulder-Fort Collins-Greeley Area, 1979). Geology was further evaluated through review of conditions found in exploratory borings, and our experience in the area. According to the referenced mapping, th e site is located over alluvium or river deposited soils generally consisting of well graded gravel and cobble overlain by sands and clays. The materials encountered in our borings were in general agreeance with the re ferenced mapping. Geologic Hazards Our investigation identified several geologic hazards that must be considered during the planning and development phases of this project. None of the geologic hazards identified will preclude development of the property. Development plans are preliminary. Planning should consider the ge ologic hazards discussed below. The hazards require mitigation which could include avoidance, non-conflicting use or engineered design and construction during site development. Geologic hazards at the site that need to be addressed include existing fill, expansive soils and bedrock 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 report. HOUSING CATALYST 3 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Existing Fill Three of the borings were overlain by up to 5 feet of, what we determined to be, man-placed fill. The fill was comprised of sandy clay and clayey sand. The fill could exist to greater depths and extents than encountered in our borings. The existing fill is of unknown ag e and origin, and presents risk of heave or settlement. We typically recommend the complete removal of undocumented fill below improvements. Expansive Soils and Bedrock Colorado is a challenging location to practice geotechnical engineering. The climate is relatively dry, and the near-surface soils are typically dry and relatively stiff. These soils and related sedimentary bedrock formations tend 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 mitigate, but not eliminate the effects of expansive and compressible soils. The soils and bedrock at this site include sandy clay and weathered to competent claystone bedrock. Samples tested exhibited predominantly non-swelling to low swelling behavior. We believe the risk of differential movement due to swelling soil to be low for this site. HOUSING CATALYST 4 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Flooding The southeast portion of this site lies within a floodplain fringe zone. Geologic hazards maps indicate the site area may be prone to sheet flow flooding. The civil engineer should address surficial drainage for the site. Seismicity This area, like most of central Colorado, is subject to a low 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 o f the past earthquake activity in Colorado is somewhat incomplete. Based on the subsurface conditions encountered in our borings and ou r 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 seismic considerations, typica lly govern dynamic structural design in this area. If it is determined that seismic site class is critical to the design, CTL|Thompson can provide 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. Radon 222 gas is considered a health hazard and is one of several radioactive products in the chain of the natura l 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. Th e 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. We recommend testing to evaluate radon lev els after construction is completed. If required, typical mitigation methods for residential construction may consist of sealing soil gas entry areas HOUSING CATALYST 5 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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. Rad on rarely accumulates to significant levels in above-grade, heated and ventilated spaces. Field And Laboratory Investigations Subsurface conditions were further investigated by drilling four exploratory borings and a temporary piezometer 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 and bedrock were obtained during drilling by driving a modified California- type sampler (2.5-inch O.D.) into the subsoils and bedrock using a 140-pound hammer falling 30 inches. Samples recovered from the test holes we re returned to our laboratory and visually classified by the geotechnical engineer. Laboratory testing included determination of moisture content and dry density, swell-consolidation characteristics, particle-size analysis and water soluble sulfate content. Laboratory test results are presented in Appendix A. Subsurface Conditions In general, the soils and bedrock encountered in our borings consisted of 14 to 25 feet sandy clay or clayey sand. The upper approximately 5 feet of borings TH-2 through TH-4 was comprised of man-placed fill that generally consisted of sandy clay and clayey sand . The fines content (percent passing the No. 200 sieve) of three samples of the overburden ranged from 17 to 37 percent. Weathered to competent claystone bedrock was below the overburden in two of the borings from 14 to 22 feet to the depths explored. Swell-consolidation testing indicated nil to 1 percent swell potential in the overburden soils and 0.8 to 1 percent swell potential in the bedrock. One sample of the bedrock at 25 feet exhibited unconfined compressive strength of 20,900 pounds per square foot. HOUSING CATALYST 6 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Groundwater was encountered at depths of 18 to 23 feet below the existing ground surface. Groundwater levels are not expected to affect planned development at this site. Groundwater levels fluctuate seasonally. A more detailed description of the subsurface conditions is presented in our boring logs and laboratory testing. Existing Fill Existing fill was encountered in three borings to depths of up to 5 feet. Deeper fill areas may be encountered during site development. The fill i s of unknown origin and age. The fill presents a risk of settlement or heave to improvements supported by the fill. We recommend the fil l be removed and recompacted in planned buildi ng areas. The existing fill can also affect pavements and exterior fl atwork. The lowest risk alternative for exterior pavement and flatwork would also be complete removal and recompaction. The cost could be significant. If some movement and distress in these areas is acceptable, 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 addit ional removal or stabilization of areas where soft, yielding, or organic soils or debris is encountered. After this, f ill placement can proceed to construction grades. Development Recommendations Site Grading At the time of this investigation, site grading plans were not available for review in conjunction with this subsurface exploration program. Based on the existing topography, we anticipate minor additional cuts and fill may be needed. We believe grading can be accomplished using conventional construction techniques and heavy -duty equipment. It is important that deep fills (if planned) be constructed as far in a dvance of surface construction as possible. It is our experience that fill compacted in accorda nce 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 duri ng and soon after construction. Some additional settlement is HOUSING CATALYST 7 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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 settlement 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. Claystone bedrock should be avoided as fill material as it is typically difficult to breakdown sufficiently . Prior to fill placement, all trash and debris shoul d 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 compa cted as recommended below. The depth of any topsoil is not anticipated to be more than 6 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. The placement and compaction of fill should be observed, and density tested during construction. Guideline site grading specifications including compaction recommendations 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). Where fills will be placed on slopes exceeding 20 percent (5:1) the slope should be benched. 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. Utility Construction We believe excavations for utility installation in the overb urden soils can be performed with conventional heavy-duty trenchers or large bac khoes. Groundwater is not anticipated in HOUSING CATALYST 8 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 excavations unless they exceed approximately 16 feet. If groundwater is encountered during construction, dewatering may be accomplished by sloping excavations to occasional 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 with interlayers of clayey sand classifies as Type C soil and the bedrock classifies as Type A 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 excav ation and refer to OSHA standards to determine appropriate slopes. Excavations deeper t han 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 al lowable movement. For trench boxes and bracing allowed to move enough to mobilize the strength of the soils, with associated cracking of the ground surface, the “active” earth pressure conditions are appropriate for design. 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. These pressures do not include allow ances for surcharge loading or for hydrostatic conditions. We are available to assist further with bracing 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 lifts, and m oisture conditioned to between optimum and 3 percent above optimum content for clay soils and within 2 percent of optimum moisture content fo r sand. Trench backfill sho uld 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 fo r planned utilities, the compaction requirements provided in Appendix C should be considered. HOUSING CATALYST 9 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 Preliminary Pavement Recommendations Subgrade Preparation Based on the borings, the near surface soils on this site will consist of sandy clay or clayey sand. Some of the soils could be existing fill. These soils will range from low to moderately plastic and will provide relatively poor to fair subgrade support below the pavements. Mitigation for swelling soils is not expected to be necessary. Preliminary Pavement Thickness Design Preliminary guidelines for pavement systems on this site are provided. Final pavement sections should be determined based 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. Based on 2021 Larimer County Urban Street Standards for minimum pavement requirements we anticipate asphalt pavement sections for local residential streets will be on the o rder of 4.5 to 5.5 inches thick. Collectors and other higher volume pavement will likely require thicker pavement sections, estimated on the order 6 to 8 inches. 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 5 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 reinfo rced 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 and bedrock conditions vary somewhat across the site. The following discussions HOUSING CATALYST 10 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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. Foundations Our geologic and preliminary geotechnical investigation for this site indicates structures may be founded on shallow foundations. A design level geotechnical investigation may identify potential hazards for specified areas not indica ted by our borings which may suggest the need for a deeper foundation system. Deep foundations may be required in areas of shallow bedrock, cuts that extend into bedrock, and for structures with heavy column loads . Slabs-on-Grade and Basement Floor Construction The use of slab-on-grade floors for unfinished basements should be limited to areas wher e soils within the depth likely to influence floor performance are consolidating to low swelling granular soils or clay. We believe most of this site will be rated with low risk of poor 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 mode rate (2 percent to less than 4 percent), high (4 percent 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 Groundwater was encountered at 18 to 23 feet during this investigation. With long-term development and associated landscaping, a “perched” water table may develop on the bedrock surface or on relatively impermeable soils and bedrock layers. To reduce the risk of hydrostatic pressure developing on found ation walls, foundation drains will be necessary around all below - HOUSING CATALYST 11 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 grade areas. We suggest foundation drains be tied to the sewer underdrain system if planned. 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 earth pressures. The design pressure should be established during design-level soils investigations. 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 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 HOUSING CATALYST 12 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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. Water Soluble Sulfates Concrete that comes into contact with soils can be subject to sulfate attack. We measured water-soluble sulfate concentrations in one sample from this site. Concentration was measured to be below measurable limits. 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 contact 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. 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 pa vement 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. HOUSING CATALYST 13 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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 always p ossible. 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. 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 understandi ng 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. Trace Krausse, EI R.B. "Chip" Leadbetter, III, P.E. Geotechnical Project Engineer Senior Geotechnical Engineer TH-1 TH-2 TH-3 TH-4 P-1 West Mulberry Street Impala CircleSouth Impala DriveLAPORTE AVE.N. TAFT HILL RD.W. MULBERRY ST. SITE S. OVERLAND TRAILLEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING TH-1 HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL I T PROJECT NO. FC10389-115 FIGURE 1 Locations of Exploratory Borings VICINITY MAP FORT COLLINS, COLORADO NOT TO SCALE 200'100' APPROXIMATE SCALE: 1" = 200' 0' P-1 INDICATES APPROXIMATE LOCATION OF TEMPORARY PIEZOMETER 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 12/12 16/12 13/12 13/12 21/12 WC=17.3DD=109SW=1.0 WC=12.5DD=123SW=0.3 TH-1 44/12 23/12 13/12 19/12 21/12 WC=12.0-200=37 WC=2.7-200=27 WC=5.4DD=128SW=0.2 WC=14.4DD=119SW=0.0 WC=21.7DD=108SW=1.0 TH-2 26/12 45/12 11/12 13/12 13/12 WC=18.7DD=105SW=0.9SS=<0.01 WC=19.0DD=108SW=0.0 TH-3 18/12 18/12 17/12 21/12 50/7 WC=4.8-200=17 WC=21.5DD=107SW=0.8 WC=15.9DD=116UC=20,900 TH-4 DEPTH - FEETDRIVE SAMPLE. THE SYMBOL 12/12 INDICATES 12 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. CLAY, SANDY, WITH OCCASIONAL GRAVEL, SLIGHTLY MOIST TO MOIST, STIFF TO VERY STIFF, LIGHT BROWN, BROWN, WHITE, RED-BROWN (CL) 1. NOTES: THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. WATER LEVEL MEASURED ON APRIL 26, 2022. SAND, CLAYEY, MOIST, MEDIUM DENSE TO DENSE, BROWN (SC) 3. LEGEND: WEATHERED CLAYSTONE, FIRM TO MEDIUM HARD, MOIST TO VERY MOIST, BROWN, GRAY, OLIVE CLAYSTONE, HARD, SLIGHTLY MOIST, BROWN, GRAY DEPTH - FEETWATER LEVEL MEASURED AT TIME OF DRILLING. Summary Logs of Exploratory Borings THE BORINGS WERE DRILLED ON APRIL 22, 2022 USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. FIGURE 2 WC DD SW -200 UC SS - - - - - - INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES UNCONFINED COMPRESSIVE STRENGTH (PSF). INDICATES SOLUBLE SULFATE CONTENT (%). 2. HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 FILL, CLAY SANDY AND/OR SAND, CLAYEY, SLIGHTLY MOIST TO MOIST, VERY STIFF AND DENSE APPENDIX A LABORATORY TEST RESULTS TABLE A-I: SUMMARY OF LABORATORY TEST RESULTS Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=109 PCF From TH - 1 AT 4 FEET MOISTURE CONTENT=17.3 % Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=123 PCF From TH - 1 AT 14 FEET MOISTURE CONTENT=12.5 % HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 APPLIED PRESSURE -KSF APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-1COMPRESSION % EXPANSION-4 -3 -2 -1 0 1 2 3 ONER C TSANSNTAION UNDPXE ETTSSU GINTO WRE DUEERP -4 -3 -2 -1 0 1 2 3 TAER C SANS TNONION UNDPXE INGTSSUPETTO WRE DUEER 0.1 1.0 10 100 0.1 1.0 10 100 Sample of SAND, CLAYEY (SC) DRY UNIT WEIGHT=128 PCF From TH - 2 AT 14 FEET MOISTURE CONTENT=5.4 % Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=119 PCF From TH - 2 AT 19 FEET MOISTURE CONTENT=14.4 % HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 APPLIED PRESSURE -KSF APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-2COMPRESSION % EXPANSION-4 -3 -2 -1 0 1 2 3 ONER C TSANSNTAION UNDPXE ETTSSU GINTO WRE DUEERP -4 -3 -2 -1 0 1 2 3 GWETTDMOVNNTIEOUEEMENTO 0.1 1.0 10 100 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=108 PCF From TH - 2 AT 24 FEET MOISTURE CONTENT=21.7 % Sample of FILL, CLAY, SANDY OR SANDY, CLAYEY DRY UNIT WEIGHT=105 PCF From TH - 3 AT 4 FEET MOISTURE CONTENT=18.7 % HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 APPLIED PRESSURE -KSF APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-3COMPRESSION % EXPANSION-4 -3 -2 -1 0 1 2 3 ONER C TSANSNTAION UNDPXE ETTSSU GINTO WRE DUEERP -4 -3 -2 -1 0 1 2 3 TAER C SANS TNONION UNDPXE INGTSSUPETTO WRE DUEER 0.1 1.0 10 100 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=108 PCF From TH - 3 AT 14 FEET MOISTURE CONTENT=19.0 % Sample of CLAYSTONE, WEATHERED DRY UNIT WEIGHT=107 PCF From TH - 4 AT 19 FEET MOISTURE CONTENT=21.5 % HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 APPLIED PRESSURE -KSF APPLIED PRESSURE -KSFCOMPRESSION % EXPANSIONSwell Consolidation Test Results FIGURE A-4COMPRESSION % EXPANSION-4 -3 -2 -1 0 1 2 3 GWDMOVNTIETOUE TEMENTON -4 -3 -2 -1 0 1 2 3 TAER C SANS TNONION UNDPXE INGTSSUPETTO WRE DUEER 0.1 1.0 10 100 0.1 1.0 10 100 Sample of FILL, CLAY, SANDY OR SANDY, CLAYEY GRAVEL 13 %SAND 50 % From TH - 2 AT 4 FEET SILT & CLAY 37 %LIQUID LIMIT % PLASTICITY INDEX % Sample of SAND, CLAYEY (SC)GRAVEL 10 %SAND 63 % From TH - 2 AT 9 FEET SILT & CLAY 27 %LIQUID LIMIT % PLASTICITY INDEX % HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL | T PROJECT NO. FC10389-115 FIGURE A-5 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 UNCONFINED PASSING WATER- MOISTURE DRY APPLIED COMPRESSIVE NO. 200 SOLUBLE DEPTH CONTENT DENSITY SWELL*PRESSURE STRENGTH SIEVE SULFATES BORING (FEET)(%)(PCF)(%)(PSF)(PSF)(%)(%)DESCRIPTION TH-1 4 17.3 109 1.0 500 CLAY, SANDY (CL) TH-1 14 12.5 123 0.3 1,800 CLAY, SANDY (CL) TH-2 4 12.0 37 FILL, CLAY, SANDY OR SANDY, CLAYEY TH-2 9 2.7 27 SAND, CLAYEY (SC) TH-2 14 5.4 128 0.2 1,800 SAND, CLAYEY (SC) TH-2 19 14.4 119 0.0 2,400 CLAY, SANDY (CL) TH-2 24 21.7 108 1.0 3,000 CLAY, SANDY (CL) TH-3 4 18.7 105 0.9 500 <0.01 FILL, CLAY, SANDY OR SANDY, CLAYEY TH-3 14 19.0 108 0.0 1,800 CLAY, SANDY (CL) TH-4 9 4.8 17 SAND, CLAYEY (SC) TH-4 19 21.5 107 0.8 2,400 CLAYSTONE, WEATHERED TH-4 24 15.9 116 20,900 CLAYSTONE, SANDY SWELL TEST RESULTS* TABLE A-I SUMMARY OF LABORATORY TESTING Page 1 of 1 HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 APPENDIX B GUIDELINE SITE GRADING SPECIFICATIONS HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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 t he 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. HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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. HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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 shal l 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). Be nches 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. HOUSING CATALYST 306 AND 400 IMPALA CIRCLE CTL|T PROJECT NO. FC10389-115 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.