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Home My WebLink AboutENCLAVE AT REDWOOD - PDP210004 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT2180 South Ivanhoe Street, Suite 5 Denver, Colorado 80222 www.agwco.com (303) 759-8100 Project Number 201023 February 25, 2020 Geotechnical Site Development Study Old Town North Fort Collins, Colorado D R Horton 9555 South Kingston Court Suite 200 Englewood, Colorado 80112-5943 TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY .................................................................................................. 1 2.0 PURPOSE ..................................................................................................................... 1 3.0 PROPOSED CONSTRUCTION .......................................................................................... 2 4.0 SITE CONDITIONS ........................................................................................................ 2 5.0 FIELD EXPLORATION .................................................................................................... 2 6.0 LABORATORY TESTING ................................................................................................. 2 7.0 SUBSURFACE CONDITIONS ........................................................................................... 3 7.1 Natural Soil ......................................................................................................... 3 7.2 Bedrock .............................................................................................................. 3 7.3 Ground Water ...................................................................................................... 3 8.0 GEOTECHNICAL CONCERNS .......................................................................................... 4 8.1 Ground Water ...................................................................................................... 4 9.0 SITE DEVELOPMENT ..................................................................................................... 4 9.1 Overlot Grading ................................................................................................... 4 9.2 Slopes and Retaining Walls ................................................................................... 5 9.3 Construction Excavation ....................................................................................... 5 9.4 Utility Construction ............................................................................................... 6 9.5 Subsurface Drainage ............................................................................................ 6 9.6 Surface Drainage ................................................................................................. 7 10.0 SITE CONCRETE AND CORROSIVITY .............................................................................. 7 11.0 PRELIMINARY FOUNDATION DESIGN CONCEPTS ............................................................ 8 11.1 Footings........................................................................................................... 8 11.2 Post-Tensioned Slab Foundation ........................................................................ 8 11.3 Raft Foundations .............................................................................................. 9 11.4 Lateral Earth Pressures ..................................................................................... 9 11.5 Interior Floors (Basement Products) ................................................................... 9 11.6 First Floor Construction (Crawl Space Products) ................................................... 9 11.7 Interior Floors (Slab-On-Grade Products) ............................................................ 9 11.8 Drain Systems .................................................................................................. 9 11.9 Backfill and Surface Drainage ............................................................................ 9 12.0 PRELIMINARY STREET PAVEMENT DESIGN ................................................................... 10 13.0 FINAL DESIGN CONSULTATION AND CONSTRUCTION OBSERVATION ............................ 11 14.0 GEOTECHNICAL RISK .................................................................................................. 11 15.0 LIMITATIONS ............................................................................................................. 12 ii TABLE OF CONTENTS (continued) ATTACHMENTS SITE PLAN AND VICINITY MAP ..................................................................................... FIGURE 1 TEST BORING LOGS ............................................................................... FIGURES 2 THROUGH 5 ESTIMATED DEPTH TO GROUNDWATER ....................................................................... FIGURE 6 ESTIMATED ELEVATION OF GROUNDWATER ................................................................. FIGURE 7 GENERALIZED BENCHING DETAIL ................................................................................ FIGURE 8 LABORATORY TEST RESULTS ................................................................................... APPENDIX A SPECIFICATIONS FOR PLACEMENT OF FILL ............................................................... APPENDIX B Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 1 1.0 EXECUTIVE SUMMARY A. G. Wassenaar, Inc. (AGW) completed the geotechnical site development study for the proposed residential development at the subject site. The data collected during our field exploration and laboratory work and our analysis, opinions, and conclusions are presented. The purpose of our study is to provide design recommendations for planning and site development and preliminary design concepts for foundation systems, interior floor support, and streets. The subsurface materials encountered in our test borings consist of topsoil, clay, sand, and gravel overlying sedimentary bedrock. Claystone bedrock was encountered at depths ranging from 18 to 21½ feet below the ground surface. Ground water was measured at depths ranging from 3½ to 12 feet during this study. Site development considerations should include provisions for the presence of shallow ground water. Site development should be planned to avoid or manage the ground water. Based upon the results of this preliminary study, we anticipate that of the structures will be founded on footings or footing pads. Stabilization of the bearing soils may be necessary in areas of shallow ground water. Preliminary foundation design concepts are presented. Floors and flatwork being considered for construction on-grade will require a specific risk analysis by the Client because of the potential for movement of the soils and bedrock encountered. Where footings are constructed, slabs-on-grade may be possible depending on the expansion potential of the supporting materials and the Client's analysis of risk. Slabs supported by soil will be subject to movement. Options for floor support are discussed. Foundation subsurface drainage systems will be necessary for all below grade areas. Extensive drain systems will be required when foundations are within 4 feet of ground water. Depending on site grading, it may not be possible to construct basements in some areas. Water soluble sulfate test results indicate that site and foundation concrete may be designed for negligible sulfate exposure. Preliminary pavement and other geotechnical-related recommendations are presented in the following report. We encourage the Client to read this report in its entirety and not to solely rely on the cursory information contained in this summary. 2.0 PURPOSE This report presents the results of a geotechnical site development study for the proposed residential development to be located northeast of Suniga Road and Redwood Street in Fort Collins, Colorado. The study was conducted by AGW to assist in determining geotechnical design criteria for planning, site evaluation, and development considerations. Preliminary geotechnical design concepts are also presented for foundations, interior floor support, foundation drainage, and street construction. Factual data gathered during the field and laboratory work are summarized on Figures 1 through 5 and in Appendix A. Our opinions and recommendations presented in this report are based on the Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 2 data generated during our field exploration, laboratory testing, our understanding of the proposed project, and our experience with similar projects and geotechnical conditions. This study was performed in general conformance with our Proposal Number 201023, dated January 15, 2020. This report is not intended to provide design criteria for individual foundations or street construction. Additional geotechnical studies will be required to provide final design criteria and construction recommendations. 3.0 PROPOSED CONSTRUCTION We understand the proposed development will include 40 duplex lots, 24 alley-loaded single-family lots, 51 front-loaded single-family lots, and the associated utility and roadway infrastructure. It is our understanding slab-on-grade, crawl space, and basement products are being considered. Preliminary overlot grading plans were not available at the time of this study. The contents of this report must be reviewed by AGW when grading plans are available. 4.0 SITE CONDITIONS The site is vacant with vegetation consisting of grasses and weeds with bushes and trees along the perimeter of the site. The Lake Canal is located along the southeast property boundary. No water was observed in the canal at the time of our field work. The site is bounded by existing residences to the north and west, Redwood Street to the west, and vacant land to the south and east. The ground surface is relatively level. No bedrock outcrops were observed on the site. 5.0 FIELD EXPLORATION Subsurface conditions for the proposed development were explored by drilling 16 test borings at the approximate locations indicated on Figure 1. The test borings were advanced using a 4-inch diameter, continuous flight auger powered by a truck-mounted drill rig. At frequent intervals, samples of the subsurface materials were obtained using a Modified California sampler which was driven into the soil by dropping a 140-pound hammer through a free fall of 30 inches. The Modified California sampler is a 2.5-inch outside diameter by 2-inch inside diameter device. The number of blows required for the sampler to penetrate 12 inches and/or the number of inches that the sampler is driven by 50 blows gives an indication of the consistency or relative density of the soils and bedrock materials encountered. Results of the penetration tests and locations of sampling are presented on the "Test Boring Logs", Figures 2 through 5. Ground water measurements were made at the time of drilling and subsequent to drilling. 6.0 LABORATORY TESTING The samples obtained during drilling were returned to the laboratory where they were visually classified by a geotechnical engineer. Laboratory testing was then assigned to specific samples to evaluate their engineering properties. The laboratory tests included swell-consolidation tests to evaluate the effect of wetting and loading on the selected samples. Gradation analysis and Atterberg limits tests were conducted to evaluate grain size distribution and plasticity. In addition, Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 3 representative samples were tested for water soluble sulfates, pH, resistivity, and chlorides. The test results are summarized on Figures 2 through 5 and presented in Appendix A. 7.0 SUBSURFACE CONDITIONS The subsurface materials encountered in our test borings consist of topsoil, clay, sand, and gravel overlying sedimentary bedrock. Claystone bedrock was encountered at depths ranging from 18 to 21½ feet in 14 of the 16 test borings. Ground water was encountered in 11 of the 16 test borings at the time of drilling and/or when checked subsequent to drilling. A more complete description of the subsurface conditions is shown on Figures 2 through 5. 7.1 Natural Soil Topsoil was found in all 16 test borings. The topsoil encountered consisted of clayey sand up to ½- foot thick. It was organic, moist, and dark brown. Clay was encountered in nine of the 16 test borings. The clay was medium stiff to stiff, silty, slightly sandy to very sandy, with trace gravel and sand lenses, moist to very moist, and brown. The clay is considered to possess low expansion and consolidation potential. Sand was encountered in six of the 16 test borings. The sand was medium dense, silty, clayey, with scattered gravel and clay lenses, moist to very moist, and brown to light brown. The sand is considered to possess low expansion and settlement potential. Sand and gravel was encountered in all 16 test borings. The sand and gravel was medium dense to very dense, slightly silty to silty, clean to clayey, moist to wet, and brown to light brown to gray. The sand and gravel is considered to possess low expansion and settlement potential. 7.2 Bedrock Claystone bedrock was encountered in 14 of the 16 test borings at depths ranging from 18 to 21½ feet. The claystone was very hard, silty, with trace sand to very sandy, with sandstone and shale lenses, moist to very moist, and gray to dark gray. The claystone bedrock is considered to possess high expansion potential. 7.3 Ground Water Ground water was measured at depths ranging from 7 to 12 feet in 15 of the 16 test borings at the time of drilling. Ground water was measured at depths ranging from 7½ to 12 feet in 11 of the 16 test borings when checked two to 11 days after drilling. Five of the 16 test borings wet caved at depths ranging from 3½ to 7½ feet when checked 2 to 11 days after drilling. Ground water levels fluctuate with changing seasons and irrigation patterns and are expected to rise after construction is complete and landscape irrigation commences. Estimated depth and elevation of the ground water are shown on Figures 6 and 7. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 4 8.0 GEOTECHNICAL CONCERNS 8.1 Ground Water Ground water was encountered less than 10 feet beneath the existing ground surface across about 90% of the site. Ground water less than 15 feet below the site grading elevation will likely affect utility construction and some site grading operations. Ground water less than 10 feet below the site grading elevation will likely affect foundation excavations. In addition, ground water less than 5 feet below the existing or final ground surface will pose stabilization problems during site grading, foundation construction, and may cause problems during pavement construction. We recommend that foundations be constructed at least 4 feet above ground water level to reduce the potential for future water problems. Site development should be planned to avoid or manage the ground water. Avoidance may entail raising the site grades to provide sufficient distance between the bottom of foundations and the ground water, allowing only at-grade construction (no basements) or other methods. Removing the ground water may entail the construction of drain systems and/or barriers that draw the ground water down sufficiently to allow below grade construction. A geohydrologist familiar with long term dewatering of projects of this nature should be consulted. 9.0 SITE DEVELOPMENT 9.1 Overlot Grading We understand the fill materials to be used at the site will be from on-site cut areas. In general, suitable inorganic on-site or off-site soils may be used for structural fill. Topsoil, soil containing significant vegetation, organic debris or other deleterious material should be excavated and removed from the structural areas. Off-site material considered for new fill should be evaluated by AGW prior to importing to the site. Construction of the fill embankments throughout the site should consist of proper foundation preparation, constructing embankment benching where necessary, disposition of strippings, proper fill placement and compaction, and designing slopes in accordance with the recommendations provided in this report and the applicable governing regulations. The following are general site grading recommendations: 1.It is recommended that we be retained on an essentially full-time basis to observe and test the fill placement. We should also be retained to provide observations and/or testing of the other items discussed below. The purpose of this observation and testing is to provide the Client with a greater degree of confidence that the work is being performed within the recommendations of this geotechnical study and the project specifications. 2.All topsoil and vegetation should be stripped and removed prior to fill placement. The vegetation, organic soils, or topsoil should be wasted from the site, placed in non- structural areas (e.g., parks, landscaping, tracts, etc.) and/or stockpiled for future use in revegetating the surface of exposed slopes. In no case should these materials be used in the structural areas or where the stability of slopes will be affected. If placed in lots, topsoil must be placed outside of the structure setbacks and should not be Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 5 placed where the fill depths exceed 5 feet. If placed in depth across the back of lots, movements of fences and dry utilities should be expected. 3.Where soft, rutting soils are found beneath planned fill areas, removal, in-place drying, or stabilization may be necessary. Stabilization prior to fill placement may be accomplished by placing crushed rock or equivalent material, which should be evaluated by AGW prior to use. The material should be spread across the area and worked into the underlying soft or loose soils with fully loaded rubber-tired equipment. This procedure should continue until scraper-type equipment can be supported on the rock fill with no significant deflection or rutting. In some instances, a geogrid or geotextile stabilization fabric may be economical for use in conjunction with rock stabilization. 4.Where the existing slopes are steeper than a 5:1 (horizontal:vertical), benching will be required for structural integrity of any fills (see Figure 8). 5.The stripped foundation areas should be observed by AGW prior to fill placement. Any soft soils found in these areas must be removed or stabilized as necessary prior to fill placement. 6.After the fill areas have been cleared, the exposed soils should be scarified to a minimum depth of 6 inches, brought to the proper moisture content, and then compacted according to Appendix B. 7.The compaction and moisture content of the soils will be dependent upon material types and the depth and location of placement. The specifications outlined in Appendix B are based upon providing a fill with sufficient shear strength to support structures and sufficient moisture to reduce the potential of swell of the expansive soil used in the fill. 8.Particular attention should be paid to compaction of the exterior faces of slopes. 9.Placement and compaction of fill should continue to final overlot grade. We recommend that the lots not be left low or "dished-out" and that placement of fill not stop at foundation elevation. 10.Other specifications outlined in Appendix B should be followed. 9.2 Slopes and Retaining Walls Slope stability and retaining wall analyses were not conducted as part of this study. In areas where existing slopes exceed 5:1 (horizontal:vertical), benching prior to fill placement will be required (see Figure 8). Construction of conventional fill slopes should be limited to 3 to 1 or flatter. Cut slopes steeper than 2 to 1 should be evaluated for stability. Specific analysis will also be necessary if retaining walls are to be constructed. 9.3 Construction Excavation In our opinion, the majority of the site grading, utility, and foundation excavations may be constructed using conventional earth-moving equipment for the Front Range area. Excavations deeper than 3 feet should be properly sloped or braced to prevent collapse of potentially caving soils. For planning purposes, fills, sand, and any soil influenced by ground water can be considered as a "Type C", the clay can be considered as "Type B", and the underlying bedrock can be considered as a "Type A" according to OSHA regulations. A final determination of the soil type must be made by Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 6 the Contractor's "Competent Person" (as defined by OSHA Regulation). Local, city, county, state, and federal (OSHA) regulations should be followed. The presence of ground water will be a significant constraint on construction excavation. It will be necessary to dewater all excavations constructed below the ground water level. Dewatering may include pumping from the work area or construction of well points. The excavation and utility contractor(s) must be made aware of the ground water conditions so that contract bidding will include the appropriate provisions. 9.4 Utility Construction In our experience, utility excavations may be constructed using conventional earth-moving equipment for the Front Range area. All excavations should be sloped or shored in the interest of safety, following local and federal (OSHA) regulations. For planning purposes, OSHA soil type designations are discussed under "Construction Excavations". Final determination of the soil types must be made by the contractor's "Competent Person" (as defined by OSHA) at the time of construction. The presence of ground water will be a constraint upon utility construction. It will be necessary to dewater all trenches constructed below the ground water level. A possible method for dewatering would be to begin construction of the deeper (sewer) utilities at their outfall and to work upstream. Other methods include pumping from the trench in the work area or construction of well points along the trenches. The utility contractor must be made aware of the ground water conditions. Trench backfill within all structural areas should, as a minimum, be compacted using the same methods and to the same specifications as required for overlot grading. This is especially important where utility lines and laterals are constructed beneath foundation, alley, and driveway areas. Trenches in streets should be compacted to the City of Fort Collins specifications. Observation and testing of fill placement must be performed during trench backfilling. The choice of compaction equipment can have a significant effect on the performance of trench fills. It is our experience that utility trench backfills compacted with a compaction wheel attached to an excavator experience more settlement (both in area and magnitude) than those compacted with self- propelled equipment. While the contractor has control of the means and methods of construction, the Client should be aware of this issue. 9.5 Subsurface Drainage The ground water encountered is anticipated to cause significant problems across the site during development. As discussed under "Geotechnical Concerns", ground water should be avoided wherever possible. Additionally, clay soils were encountered in the test borings drilled for this study. These types of material have a relatively low permeability and can develop a perched water condition. Perched water conditions generally occur after development and construction have taken place, when landscape irrigation and surface drainage conditions are changed. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 7 We believe that the presence and control of ground water will be a long-term concern for the development. We recommend that a geohydrologist be consulted to determine ground water flow and potential methods of dewatering. These methods may include the installation of an interceptor drain along the northern and eastern property lines and/or the installation of an area drain system. An overall area drain (underdrain) should be considered for the site. In addition, the overall area drain could also provide for a discharge and collection point for individual foundation drains. If an area drain discharge is not available, the individual foundation drains will discharge collected water to the ground surface near each residence. Surface discharge can result in water recycling to the foundation drain and ponding of water where surface grading is not sufficient for water flow. Foundation drain discharge can also result in algae growth where water continually crosses sidewalks which become ice hazards on walkways and gutters in the winter months. Typically, overall area drains can be designed and constructed with installation of the sanitary sewer system. However, the City of Fort Collins should be consulted to determine where an overall system is allowed. The civil engineering company contracted to design the infrastructure should be able to provide this design. We are available to assist in drain design. For the system to work, the area drain must be graded to a positive discharge point. If a permanent outfall for an area drain cannot be determined, the area drain should not be constructed. If it is decided not to install an overall area drain, an alternative would be to establish points of positive gravity discharge for the gravel bedding beneath the sewer. We also recommend any basement or below grade area be provided with a perimeter subsurface drainage system sloped to drain to a positive gravity discharge such as a sump or connected directly to the overall area drain system. 9.6 Surface Drainage We recommend that provisions be made to divert surface runoff away from development areas. This may reduce potential problems associated with excess water in structure bearing soils. The site should be designed such that a 10% slope can be established near the structures after foundation construction. Slopes of at least 2% should be planned in landscaped areas once the water is away from the foundations. 10.0 SITE CONCRETE AND CORROSIVITY Laboratory tests conducted on selected soil samples yielded water soluble sulfates ranging from less than 100 parts per million (ppm) to 200 ppm. Based upon these results and our experience in the area, the site soils and bedrock are assigned to possess negligible (S0 or RS0) sulfate exposure per ACI 318 or ACI 332. We recommend the "ACI Manual of Concrete Practice", of the most recent edition be used for proper concrete mix design properties as they relate to these conditions. The pH test results were 7.9, resistivity test results at in-situ moisture ranged from 1,753 to 4,296 ohm∙cm, and chloride test results ranged from 0.0010% to 0.0020%. These results are summarized on Figures 2 through 5 and in Appendix A. The results of this testing should be used as an aid in Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 8 choosing the construction materials in contact with these soils which will be resistant to the various corrosive forces. Manufacturer's representatives should be contacted regarding the specific corrosivity resistance for their particular product. In addition, local specifications should be consulted when selecting pipe materials. 11.0 PRELIMINARY FOUNDATION DESIGN CONCEPTS The foundation recommendations for each structure are dependent upon the subsurface profile and engineering properties of the materials encountered at and near the depth of the proposed foundation. These are dependent upon the final configuration of and construction methods used during overlot grading at the site. The information in the following sections presents preliminary foundation concepts which must be finalized for each building site upon completion of the overlot grading operations. AGW should be retained to perform design level soil and foundation studies after completion of site grading. 11.1 Footings Foundations supported by spread footings or footing pads may be possible for where sufficient non- to low expansive clays, sands, or properly placed and compacted fills are encountered beneath the foundation elevation. The footings must be founded below frost depth. The footings will likely be designed for maximum soil bearing pressures ranging from 1,000 to 3,000 pounds per square foot (psf). Minimum dead load pressure on the order of 500 to 1,000 psf may be required. We anticipate all of the structures will be able to utilize this foundation type. 11.2 Post-Tensioned Slab Foundation Where no below grade areas are planned, post-tensioned slab foundation systems may be constructed to support the structures. The foundation should be supported by low expansive clays, sands, and gravels, or properly placed and compacted fills. This type of construction should provide a foundation and floor system which moves together as one unit. The foundations will likely be designed for a soil bearing pressure ranging from 1,000 to 3,000 psf. The range of parameters provided below will likely be used for design of the foundation system. These parameters were developed using practices established by AGW, as well as our evaluation of published information and experience in working with these types of foundations. Center Lift Edge Moisture Variation Distance (em) = 7 to 9 feet Differential Movement (ym) = 1.0 to 3.0 inches Edge Lift Edge Moisture Variation Distance (em) = 4 to 6 feet Differential Movement (ym) = 0.5 to 1.5 inches We suggest that the structural engineer consider the information contained in "Design and Construction of Post-Tensioned Slabs-on-Grade" by the Post-Tensioning Institute (Third Edition) for design of the slab. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 9 11.3 Raft Foundations Where no below grade areas are planned, raft-type slab foundation systems may be constructed to support the structures. Raft foundations are appropriate where non-expansive sands are encountered beneath the proposed foundation elevation. This type of construction should provide a foundation and floor system which moves together as one unit. The foundations will likely be designed for a soil bearing pressure ranging from 1,000 to 3,000 psf. 11.4 Lateral Earth Pressures Foundation walls with fill on only one side will need to be designed for lateral earth pressures. For this site, lateral earth pressures calculated based upon equivalent fluid densities on the order of 40 to 70 pcf should be anticipated. The preliminary estimates are for properly placed and compacted fill at foundation walls. They should not be used for site retaining walls. 11.5 Interior Floors (Basement Products) It is likely that most of the sites will be assessed with low slab risk performance evaluation. Slab-on- grade construction may be appropriate for full, unfinished basement construction on sites with low or moderate evaluations. Structural floors are generally recommended on sites with higher evaluations and for finished basements or any site where floor movement or cracking cannot be tolerated. If slab movement cannot be tolerated, structural floors should be constructed. 11.6 Interior Floors (Slab-On-Grade Products) For post-tensioned or raft products, the interior slabs will be part of the foundation system, and therefore are considered structural. 11.7 First Floor Construction (Crawl Space Products) Some of the structures will be constructed over crawl spaces. Structural floors will be constructed in the living areas of the residences. For the garage areas, it is likely that there will be a low risk of garage slab movement. 11.8 Drain Systems Drain systems will be required around the lowest excavation level for below grade spaces for each structure. Either interior or exterior drains may be used for most of the site. Where ground water is within 4 feet of the foundation, a more extensive drain system will be required. This may include gravel across the entire foundation, drain laterals, or combination interior and exterior drains. The drains must be led to a positive gravity outfall or sump. If an overall subdivision area drain is constructed, individual drains should be connected into this system if allowed by the jurisdiction. Subsurface drainage systems will not be necessary for structures with no below grade areas. 11.9 Backfill and Surface Drainage Foundation backfill should be moistened and compacted to reduce future settlement. The site grading should consider a slope of 10% away from the foundation at the completion of construction. All other drainage swales in landscaped areas should slope at a minimum of 2%. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 10 12.0 PRELIMINARY STREET PAVEMENT DESIGN Pavement design is based on the engineering properties of the subgrade and pavement materials, the assumed design traffic conditions, and the City of Fort Collins pavement regulations. Effective pavement structures are composed of various pavement materials bearing upon properly prepared subgrade soils. The following preliminary pavement recommendations are based upon the subsurface conditions encountered and our experience in the area. It appears the proposed subgrade materials will likely be clay, sand, gravel, or fill constructed from these materials. According to the AASHTO Soil Classification System these materials classify as A-1-a. A-1-b, A-6, and A-7-6 soils. Based upon our laboratory testing and our experience in the area, it is anticipated that the clay subgrade materials encountered on this site can be expected to exhibit enough swell to negatively impact the performance of the pavement and will likely be in excess of those allowed by the City of Fort Collins regulation. Therefore, we recommend that the expansive subgrade materials be modified during site grading operations to reduce the potential future heave of the pavement. The expansive clay should be overexcavated to a depth of at least 2 feet below the subgrade elevation. The overexcavation should be performed during site grading prior to construction of utilities within the right-of-way. Overexcavation should cover the area from 1 foot beyond back of sidewalk (for attached sidewalk areas) or back of curb (for detached sidewalks). The excavated material may be placed as moisture treated fill (see Appendix B) within the right-of-way. All fill placed within 2 feet of the subgrade elevation should be placed as moisture treated fill. Stabilization (fly-ash treated subgrade) may be required if the subgrade cannot pass a proof-roll. Lime or other chemical treatment, mechanical stabilization using geogrids or geotextiles or other methods of subgrade preparation may also be required dependent upon the results of the final pavement design report. Based upon the subgrade soil classifications, we have estimated the relative strengths of the subgrade soils presented above in order to determine the preliminary pavement thicknesses. Based on this information and utilizing the design methodology determined from the pavement design regulations for the City of Fort Collins, the alternatives presented below were calculated. Pavement Thickness Alternatives for Interior Streets Traffic Category HBP (in.) HBP / CTS (in.) HBP / ABC (in.) Local 6.0 to 7.5 4.0 to 5.5 / 12.0 4.5 to 5.5 / 6.0 to 8.0 HBP = Hot Bituminous Pavement CTS = Chemically Treated Subgrade ABC = Aggregate Base Course * Indicates Minimum Pavement Thickness in this Jurisdiction The above preliminary thickness recommendations are based on a design life of 20 years. It should be emphasized that the design alternatives provided above are preliminary for the materials anticipated. The final design thicknesses could be more or less than indicated depending upon the materials sampled during the final pavement design. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 11 Proper surface and subsurface drainage is essential for adequate performance of pavements. It has been our experience that water from landscaped areas can infiltrate pavement subgrade soils and result in softening of the subgrade followed by pavement damage. Therefore, provisions should be made to maintain adequate drainage and/or contain runoff from such areas. Edge drains may be necessary if ground water is encountered within 5 feet of the final grade. In addition, water and irrigation lines should be thoroughly pressure tested for leaks prior to placement of pavement materials. It must be reiterated that the information contained in this section is preliminary in nature. More detailed information will be required by the City of Fort Collins prior to issuance of a paving permit. Therefore, when overlot grading is complete at the site, a final pavement evaluation must be performed. 13.0 FINAL DESIGN CONSULTATION AND CONSTRUCTION OBSERVATION This report has been prepared for the exclusive use of D R Horton for the purpose of providing geotechnical criteria for the proposed project. The data gathered and the conclusions and recommendations presented herein are based upon the consideration of many factors including, but not limited to, the type of structures proposed, the configuration of the structures, the proposed usage of the site, the configuration of surrounding structures, the geologic setting, the materials encountered, and our understanding of the level of risk acceptable to the Client. Therefore, the conclusions and recommendations contained in this report should not be considered valid for use by others unless accompanied by written authorization from AGW. AGW should be contacted if the Client desires an explanation of the contents of this report. AGW should be retained to provide future geotechnical services for the site including, but not limited to, design level geotechnical studies, consultation during design, observation and testing during construction, and other geotechnically related services. Failure to contract with AGW for these services or selection of a firm other than AGW to provide these services will eliminate liability for AGW. We are available to discuss this with you. 14.0 GEOTECHNICAL RISK The concept of risk is an important aspect of any geotechnical evaluation. The primary reason for this is that the analytical methods used to develop geotechnical recommendations do not comprise an exact science. The analytical tools which geotechnical engineers use are generally empirical and must be tempered by engineering judgment and experience. Therefore, the solutions or recommendations presented in any geotechnical evaluation should not be considered risk-free and, more importantly, are not a guarantee that the interaction between the soils and the proposed structures will perform as desired or intended. What the engineering recommendations presented in the preceding sections do constitute is our judgement of those measures that increase the chances for the structures and improvements performing satisfactorily. The Developer, Builder, and Owner must understand this concept of risk, as it is they who must ultimately decide what is an acceptable level of risk for the proposed development of the site. Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Page 12 15.0 LIMITATIONS We believe the professional judgments expressed in this report are consistent with that degree of skill and care ordinarily exercised by practicing design professionals performing similar design services in the same locality, at the same time, at the same site and under the same or similar circumstances and conditions. No other warranty, express or implied, is made. In the event that any changes in the nature, design or location of the facility are made, the conclusions and recommendations contained in this report should not be considered valid unless the changes are reviewed and the conclusions of this report are modified or verified in writing. Because of the constantly changing state of the practice in geotechnical engineering, and the potential for site changes after our field exploration, this report must not be relied upon after a period of three years without AGW being given the opportunity to review and, if necessary, revise our findings. The test borings drilled for this study were spaced to obtain an understanding of subsurface conditions for design purposes. Variations frequently occur from these conditions which are not indicated by the test borings. These variations are sometimes sufficient to necessitate modifications in the designs. If unexpected subsurface conditions are observed by any party during site development, we must be notified to review our recommendations. Our scope of services for this project did not include, either specifically or by implication, any research, identification, testing, or assessment relative to past or present contamination of the site by any source, including biological (i.e., mold, fungi, bacteria, etc.). If such contamination were present, it is likely that the exploration and testing conducted for this report would not reveal its existence. If the Client is concerned about the potential for such contamination or pollution, additional studies should be undertaken. We are available to discuss the scope of such studies with you. Our scope of services for this project did not include a local or global geological risk assessment. Therefore, issues such as mine subsidence, slope stability, faults, etc. were not researched or addressed as part of this study. If the Client is concerned about these issues, we are available to discuss the scope of such studies upon your request. Sincerely, A. G. Wassenaar, Inc. Reviewed by: Ashley A. McDaniels, P.E. Project Engineer Kathleen A. Noonan, M.S., P.E. Senior Geotechnical Engineer AAM/KAN/aam TB-1TB-2TB-3TB-4TB-5TB-6TB-7TB-8TB-9TB-10TB-11TB-12TB-13TB-14TB-15TB-160200400Scale in FeetNNOTES:1.TEST BORINGS ARE OVERLAID ON "REDWOOD - SUNIGA PLAN",PREPARED BY RIPLEY DESIGN, INC., DATED OCTOBER 17, 2019.2.ALL LOCATIONS ARE APPROXIMATE.OLD TOWN NORTHFORT COLLINS, COLORADONOT TO SCALEVICINITY MAPSITE PLANANDVICINITY MAPPROJECT NO. 201023FIGURE 1E. VINE DRREDWOOD ST N COLLEGE AVENUE CONIFER STLINDENMEIER RD L A K E C A N A L 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 TEST BORING LOGS SEE FIGURE 5 FOR LEGEND AND NOTES TO TEST BORINGS FIGURE 2 CLIENT D R Horton PROJECT NAME Old Town North PROJECT LOCATION Fort Collins, ColoradoPROJECT NUMBER 201023 U:\PROJECT FILES\2 - GEOTECHNICAL\201023 OLD TOWN NORTH D R HORTON SD AAM\TO BE SAVED\GINT\201023S_GT2020-01-29 OLD TOWN NORTH SF.GPJ50 / 10 39 / 12 MC = 8 -#200 = 7 LL = NV PI = NP AS AS TEST BORING 1 ELEV. 4961 50 / 7 MC = 2 -#200 = 6 LL = NV PI = NP TEST BORING 2 ELEV. 4961 50 / 8 50 / 8 50 / 11 AS 50 / 2 MC = 25 -#200 = 61 LL = 44 PI = 25 TEST BORING 3 ELEV. 4959 50 / 6 MC = 2 -#200 = 6 LL = NV PI = NP 50 / 9 50 / 8 MC = 7 -#200 = 6 LL = NV PI = NP AS TEST BORING 4 ELEV. 4957 24 / 12 50 / 5 MC = 11 -#200 = 10 LL = NV PI = NP AS AS TEST BORING 5 ELEV. 4960 23 / 12 50 / 2 50 / 11 MC = 7 -#200 = 7 LL = NV PI = NP AS AS TEST BORING 6 ELEV. 4959 D E P T H I N F E E T D E P T H I N F E E T 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 TEST BORING LOGS SEE FIGURE 5 FOR LEGEND AND NOTES TO TEST BORINGS FIGURE 3 CLIENT D R Horton PROJECT NAME Old Town North PROJECT LOCATION Fort Collins, ColoradoPROJECT NUMBER 201023 U:\PROJECT FILES\2 - GEOTECHNICAL\201023 OLD TOWN NORTH D R HORTON SD AAM\TO BE SAVED\GINT\201023S_GT2020-01-29 OLD TOWN NORTH SF.GPJ50 / 10 50 / 5 MC = 7 -#200 = 8 LL = NV PI = NP AS AS TEST BORING 7 ELEV. 4958 8 / 12 MC = 21 -#200 = 51 LL = 28 PI = 12 36 / 12 AS 50 / 4 MC = 13 -#200 = 97 LL = 47 PI = 28 TEST BORING 8 ELEV. 4960 11 / 12 DD = 95 MC = 26 COM = 0.1 -#200 = 88 LL = 56 PI = 35 39 / 12 AS 50 / 6 DD = 120 MC = 14 SW = 3.6 50 / 5 TEST BORING 9 ELEV. 4959 20 / 12 50 / 8 AS AS TEST BORING 10 ELEV. 4958 11 / 12 MC = 7 -#200 = 19 LL = 22 PI = 4 50 / 7 AS 50 / 2 TEST BORING 11 ELEV. 4959 D E P T H I N F E E T D E P T H I N F E E T 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 TEST BORING LOGS SEE FIGURE 5 FOR LEGEND AND NOTES TO TEST BORINGS FIGURE 4 CLIENT D R Horton PROJECT NAME Old Town North PROJECT LOCATION Fort Collins, ColoradoPROJECT NUMBER 201023 U:\PROJECT FILES\2 - GEOTECHNICAL\201023 OLD TOWN NORTH D R HORTON SD AAM\TO BE SAVED\GINT\201023S_GT2020-01-29 OLD TOWN NORTH SF.GPJ21 / 12 25 / 12 MC = 6 -#200 = 6 LL = NV PI = NP AS TEST BORING 12 ELEV. 4958 7 / 12 DD = 98 MC = 26 COM = 0.4 50 / 10 50 / 9 MC = 7 -#200 = 5 LL = NV PI = NP AS TEST BORING 13 ELEV. 4961 8 / 12 DD = 101 MC = 20 COM = 0.7 -#200 = 64 LL = 33 PI = 15 41 / 12 AS AS TEST BORING 14 ELEV. 4959 10 / 10 40 / 12 22 / 12 AS AS TEST BORING 15 ELEV. 4962 8 / 12 DD = 101 MC = 20 COM = 0.3 -#200 = 83 LL = 43 PI = 24 36 / 12 MC = 1 -#200 = 10 LL = NV PI = NP 50 / 7 50 / 2 TEST BORING 16 ELEV. 4960 D E P T H I N F E E T D E P T H I N F E E T CLIENT D R Horton PROJECT NAME Old Town North PROJECT LOCATION Fort Collins, ColoradoPROJECT NUMBER 201023 FIGURE 5 LEGEND AND NOTES ABBREVIATIONSSOIL DESCRIPTIONS DD MC SW COM UC -#200 LL PI NP NV pH R WS CL x/y x/y SS C-x F-x FG NR Bounce B AS Dry density of sample in pounds per cubic foot (pcf) Moisture content as a percentage of dry weight of soil (%) Percent swell under a surcharge of 1000 pounds persquare foot (psf) upon wetting (%) Percent compression under a surcharge of 1000 poundsper square foot (psf) upon wetting (%) Unconfined compressive strength in pounds per squarefoot (psf) Percent passing the Number 200 sieve (%) Liquid Limit Plasticity Index Non-Plastic No Value Acidity or alkalinity of sample in pH units Resistivity in ohms.cm Water soluble sufates in parts per million (ppm) Chlorides in percent (%) X blows of a 140-pound hammer falling 30 inches were requiredto drive a 2.5-inch outside diameter sampler Y inches X blows of a 140-pound hammer falling 30 inches were requiredto drive a 2.0-inch outside diameter sampler Y inches Depth of cut to grade (rounded to the nearest foot) Depth of fill to grade (rounded to the nearest foot) Finished grade (rounded to the nearest foot) No sample recovered Sampler bounced during driving Bulk sample Auger sample Well to very well cemented layer Depth at which practical drilling refusal was encountered Water level at time of drilling Caved depth at time of drilling Water level 2 to 11 day(s) after drilling Caved depth 2 to 11 day(s) after drilling Notes: 1. Test borings were drilled January 22, 2020 . 2. Location of the test borings were staked by others at locations chosen bythis firm. 3. The horizontal lines shown on the logs are to differentiate materials andrepresent the approximate boundaries between materials. The transitionsbetween materials may be gradual. 4. Elevations were obtained from staking provided by others and have beenrounded to the nearest foot. 5. Boring logs shown in this report are subject to the limitations, explanations,and conclusions of this report.U:\PROJECT FILES\2 - GEOTECHNICAL\201023 OLD TOWN NORTH D R HORTON SD AAM\TO BE SAVED\GINT\201023S_GT2020-01-29 OLD TOWN NORTH SF.GPJTopsoil, clay, sandy, organic Clay, medium stiff Clay, stiff to very stiff Sand, medium dense, silty, clayey Sand and gravel, medium dense to dense, silty Claystone (Bedrock), hard to very hard Sand and gravel, dense to very dense, silty CLIENT D R Horton PROJECT NAME Old Town North PROJECT LOCATION Fort Collins, ColoradoPROJECT NUMBER 201023 FIGURE 5 LEGEND AND NOTES ABBREVIATIONS DD MC SW COM UC -#200 LL PI NP NV pH R WS CL x/y x/y SS C-x F-x FG NR Bounce B AS Dry density of sample in pounds per cubic foot (pcf) Moisture content as a percentage of dry weight of soil (%) Percent swell under a surcharge of 1000 pounds persquare foot (psf) upon wetting (%) Percent compression under a surcharge of 1000 poundsper square foot (psf) upon wetting (%) Unconfined compressive strength in pounds per squarefoot (psf) Percent passing the Number 200 sieve (%) Liquid Limit Plasticity Index Non-Plastic No Value Acidity or alkalinity of sample in pH units Resistivity in ohms.cm Water soluble sufates in parts per million (ppm) Chlorides in percent (%) X blows of a 140-pound hammer falling 30 inches were requiredto drive a 2.5-inch outside diameter sampler Y inches X blows of a 140-pound hammer falling 30 inches were requiredto drive a 2.0-inch outside diameter sampler Y inches Depth of cut to grade (rounded to the nearest foot) Depth of fill to grade (rounded to the nearest foot) Finished grade (rounded to the nearest foot) No sample recovered Sampler bounced during driving Bulk sample Auger sample Moderately to well cemented layer Approximate depth of cut Depth at which practical drilling refusal was encountered Water level at time of drilling Caved depth at time of drilling Water level 2 to 11 day(s) after drilling Caved depth 2 to 11 day(s) after drilling Notes: 1. Test borings were drilled January 22, 2020 to January 24, 2020. 2. Location of the test borings were staked by others at locations chosen bythis firm. 3. The horizontal lines shown on the logs are to differentiate materials andrepresent the approximate boundaries between materials. The transitionsbetween materials may be gradual. 4. Elevations were obtained from staking provided by others and have beenrounded to the nearest foot. 5. Boring logs shown in this report are subject to the limitations, explanations,and conclusions of this report. SOIL DESCRIPTIONS U:\PROJECT FILES\2 - GEOTECHNICAL\201023 OLD TOWN NORTH D R HORTON SD AAM\TO BE SAVED\GINT\201023S_GT2020-01-29 OLD TOWN NORTH SF.GPJTopsoil, clay, sandy, organic Clay, medium stiff Clay, stiff to very stiff Sand, medium dense, silty, clayey Sand and gravel, medium dense to dense, silty Sand and gravel, dense to very dense, clayey Claystone (Bedrock), hard to very hard 1288644688121010(7)TB-1(3.5)TB-2(8)TB-3(7)TB-4(7.5)TB-5(8)TB-6(7.5)TB-7(8)TB-8(8.5)TB-9(8.5)TB-10(9)TB-11(7)TB-12(10)TB-13(10)TB-14(11.5)TB-15(12)TB-160200400Scale in FeetNOLD TOWN NORTHFORT COLLINS, COLORADOESTIMATED DEPTH TOGROUND WATERPROJECT NO. 201023FIGURE 6NOTES:1.TEST BORINGS ARE OVERLAID ON "REDWOOD - SUNIGA PLAN",PREPARED BY RIPLEY DESIGN, INC., DATED OCTOBER 17, 2019.2.ALL LOCATIONS ARE APPROXIMATE.3.GROUND WATER CONTOURS ARE BASED UPON THEEXTRAPOLATION OF DATA FROM WIDELY SPACED TESTBORINGS. LOCAL AND SIGNIFICANT VARIATIONS MAY OCCURBETWEEN BORINGS. THIS FIGURE REPRESENTS AN OPINIONWHICH IS ACCURATE ONLY TO THE DEGREE IMPLIED BY THEMETHOD USED.(XX)GROUND WATER OR WET CAVE ENCOUNTERED AT A DEPTH OFXX FEET (4954)TB-1(4958)TB-2(4951)TB-3(4950)TB-4(4953)TB-5(4951)TB-6(4951)TB-7(4952)TB-8(4951)TB-9(4950)TB-10(4950)TB-11(4951)TB-12(4951)TB-13(4949)TB-14(4951)TB-15(4948)TB-16495449564956495849544952495249504950494849500200400Scale in FeetNOLD TOWN NORTHFORT COLLINS, COLORADOESTIMATED ELEVATIONOF GROUND WATERPROJECT NO. 201023FIGURE 7NOTES:1.TEST BORINGS ARE OVERLAID ON "REDWOOD - SUNIGA PLAN",PREPARED BY RIPLEY DESIGN, INC., DATED OCTOBER 17, 2019.2.ALL LOCATIONS ARE APPROXIMATE.3.GROUND WATER ELEVATION CONTOURS ARE BASED UPON THEEXTRAPOLATION OF DATA FROM WIDELY SPACED TESTBORINGS. LOCAL AND SIGNIFICANT VARIATIONS MAY OCCURBETWEEN BORINGS. THIS FIGURE REPRESENTS AN OPINIONWHICH IS ACCURATE ONLY TO THE DEGREE IMPLIED BY THEMETHOD USED.(XXXX)GROUND WATER OR WET CAVE ENCOUNTERED AT AN ELEVATIONOF XXXX FEET Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Appendix A APPENDIX A LABORATORY TEST RESULTS SUMMARY OF LABORATORY TEST RESULTS ...................................................... TABLE A-1 SWELL-CONSOLIDATION TEST RESULTS .............................. FIGURES A-1 THROUGH A-3 GRADATION/ATTERBERG TEST RESULTS ............................ FIGURES A-4 THROUGH A-12 TABLE A-1 SUMMARY OF LABORATORY TEST RESULTS February 25, 2020 Project Number 201023 Old Town North Fort Collins, Colorado 1 of 1 Liquid Limit LL Plasticity Index PI 1 9 Sand, gravelly, slightly silty 8 7 NV NP 2 4 Gravel, very sandy, slightly silty 2 6 NV NP 3 34 Claystone, very sandy 25 61 44 25 4 4 Gravel, very sandy, slightly silty 2 6 NV NP 4 14 Sand, very gravelly, slightly silty 7 6 NV NP 5 4 Sand, gravelly, slightly silty 7.9 4,296 <100 0.0010 5 9 Sand, gravelly, slightly silty 11 10 NV NP 6 14 Sand, very gravelly, slightly silty 7 7 NV NP 7 9 Sand, very gravelly, slightly silty 7 8 NV NP 8 4 Clay, very sandy, trace gravel 21 51 28 12 8 29 Claystone, trace sand 13 97 47 28 9 4 Clay, slightly sandy 95 26 -0.1 NA 88 56 35 9 24 Claystone, slightly sandy 120 14 3.6 12,600 11 4 Sand, gravelly, silty to clayey 7 19 22 4 12 4 Sand, gravelly, clayey 7.9 2,583 140 0.0011 12 9 Gravel, very sandy, slightly silty 6 6 NV NP 13 4 Clay, very sandy 98 26 -0.4 NA 13 14 Sand, very gravelly, slightly silty 7 5 NV NP 14 4 Clay, very sandy, trace gravel 101 20 -0.7 NA 64 33 15 15 4 Clay, sandy 7.9 1,753 200 0.0020 16 4 Clay, sandy, trace gravel 101 20 -0.3 NA 83 43 24 16 9 Sand, gravelly, slightly silty 1 10 NV NP NA - Not Applicable NV - No Value NP Nonplastic Chlorides (%) Swell Pressure (psf) Water Soluble Sulfates (ppm) % Passing #200 Sieve Atterberg pH Resistivity (ohm●cm) Swell / Consolidation (-) (%) 1 Test Boring Number Depth (feet)Soil Type Natural Dry Density (pcf) Natural Moisture (%) 1 Indicates percent swell or consolidation when wetted under a 1,000 psf load Notes: -5 -4 -3 -2 -1 0 1 2 3 4 5 100 1,000 10,000 105 Dry Unit Weight (pcf)95CONSOLIDATION - % - SWELLMoisture Content (%)26 Sample Location Test Boring No. 9 at a depth of 4 feet APPLIED PRESSURE - PSF Sample Description Clay, slightly sandy PROJECT NO. 201023 SWELL - CONSOLIDATION TEST RESULTS FIGURE A-1 -5 -4 -3 -2 -1 0 1 2 3 4 5 100 1,000 10,000 105 Dry Unit Weight (pcf)120CONSOLIDATION - % - SWELLMoisture Content (%)14 Sample Location Test Boring No. 9 at a depth of 24 feet APPLIED PRESSURE - PSF Sample Description Claystone, slightly sandy Water Added Consolidation under constant pressure because of wetting Water Added Swell under constant pressure because of wetting -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 105 Dry Unit Weight (pcf)98CONSOLIDATION - % - SWELLMoisture Content (%)26 Sample Location Test Boring No. 13 at a depth of 4 feet APPLIED PRESSURE - PSF Sample Description Clay, very sandy PROJECT NO. 201023 SWELL - CONSOLIDATION TEST RESULTS FIGURE A-2 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 100 1,000 10,000 105 Dry Unit Weight (pcf)101CONSOLIDATION - % - SWELLMoisture Content (%)20 Sample Location Test Boring No. 14 at a depth of 4 feet APPLIED PRESSURE - PSF Sample Description Clay, very sandy, trace gravel Water Added Consolidation under constant pressure because of wetting Water Added Consolidation under constant pressure because of wetting -5 -4 -3 -2 -1 0 1 2 3 4 5 100 1,000 10,000 105 Dry Unit Weight (pcf)101CONSOLIDATION - % - SWELLMoisture Content (%)20 Sample Location Test Boring No. 16 at a depth of 4 feet APPLIED PRESSURE - PSF Sample Description Clay, sandy, trace gravel PROJECT NO. 201023 SWELL - CONSOLIDATION TEST RESULTS FIGURE A-3 Water Added Consolidation under constant pressure because of wetting 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)7 Sand (%)75 Gravel (%)18Sample Location Test Boring No. 1 at a depth of 9 feet Sample Description Sand, gravelly, slightly silty Classification A-1-b(0), WELL-GRADED SAND with SILT and GRAVEL(SW-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-4 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)6 Sand (%)37 Gravel (%)57Sample Location Test Boring No. 2 at a depth of 4 feet Sample Description Gravel, very sandy, slightly silty Classification A-1-a(0), POORLY GRADED GRAVEL with SILT and SAND(GP-GM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 44 Plasticity Index 25 Clay/Silt (%)61 Sand (%)39 Gravel (%)0Sample Location Test Boring No. 3 at a depth of 34 feet Sample Description Claystone, very sandy Classification A-7-6(13), SANDY LEAN CLAY(CL) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-5 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)6 Sand (%)41 Gravel (%)53Sample Location Test Boring No. 4 at a depth of 4 feet Sample Description Gravel, very sandy, slightly silty Classification A-1-a(0), POORLY GRADED GRAVEL with SILT and SAND(GP-GM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)6 Sand (%)52 Gravel (%)43Sample Location Test Boring No. 4 at a depth of 14 feet Sample Description Sand, very gravelly, slightly silty Classification A-1-a(0), POORLY GRADED SAND with SILT and GRAVEL(SP-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-6 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)10 Sand (%)64 Gravel (%)26Sample Location Test Boring No. 5 at a depth of 9 feet Sample Description Sand, gravelly, slightly silty Classification A-1-b(0), WELL-GRADED SAND with SILT and GRAVEL(SW-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)7 Sand (%)59 Gravel (%)34Sample Location Test Boring No. 6 at a depth of 14 feet Sample Description Sand, very gravelly, slightly silty Classification A-1-b(0), WELL-GRADED SAND with SILT and GRAVEL(SW-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-7 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)8 Sand (%)47 Gravel (%)45Sample Location Test Boring No. 7 at a depth of 9 feet Sample Description Sand, very gravelly, slightly silty Classification A-1-a(0), WELL-GRADED SAND with SILT and GRAVEL(SW-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 28 Plasticity Index 12 Clay/Silt (%)51 Sand (%)48 Gravel (%)1Sample Location Test Boring No. 8 at a depth of 4 feet Sample Description Clay, very sandy, trace gravel Classification A-6(3), SANDY LEAN CLAY(CL) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-8 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 47 Plasticity Index 28 Clay/Silt (%)97 Sand (%)3 Gravel (%)0Sample Location Test Boring No. 8 at a depth of 29 feet Sample Description Claystone, trace sand Classification A-7-6(29), LEAN CLAY(CL) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 56 Plasticity Index 35 Clay/Silt (%)88 Sand (%)12 Gravel (%)0Sample Location Test Boring No. 9 at a depth of 4 feet Sample Description Clay, slightly sandy Classification A-7-6(33), FAT CLAY(CH) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-9 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 22 Plasticity Index 4 Clay/Silt (%)19 Sand (%)60 Gravel (%)21Sample Location Test Boring No. 11 at a depth of 4 feet Sample Description Sand, gravelly, silty to clayey Classification A-1-b(0), SILTY, CLAYEY SAND with GRAVEL(SC-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)6 Sand (%)33 Gravel (%)61Sample Location Test Boring No. 12 at a depth of 9 feet Sample Description Gravel, very sandy, slightly silty Classification A-1-a(0), WELL-GRADED GRAVEL with SILT and SAND(GW-GM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-10 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)5 Sand (%)56 Gravel (%)39Sample Location Test Boring No. 13 at a depth of 14 feet Sample Description Sand, very gravelly, slightly silty Classification A-1-a(0), POORLY GRADED SAND with SILT and GRAVEL(SP-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 33 Plasticity Index 15 Clay/Silt (%)64 Sand (%)35 Gravel (%)1Sample Location Test Boring No. 14 at a depth of 4 feet Sample Description Clay, very sandy, trace gravel Classification A-6(7), SANDY LEAN CLAY(CL) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-11 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit 43 Plasticity Index 24 Clay/Silt (%)83 Sand (%)15 Gravel (%)1Sample Location Test Boring No. 16 at a depth of 4 feet Sample Description Clay, sandy, trace gravel Classification A-7-6(20), LEAN CLAY with SAND(CL) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) 0 10 20 30 40 50 60 70 80 90 100 0.0010.010.1110100 0 10 20 30 40 50 60 70 80 90 100 Cobbles Liquid Limit NV Plasticity Index NP Clay/Silt (%)10 Sand (%)63 Gravel (%)27Sample Location Test Boring No. 16 at a depth of 9 feet Sample Description Sand, gravelly, slightly silty Classification A-1-b(0), WELL-GRADED SAND with SILT and GRAVEL(SW-SM) Silt (Non-Plastic) to Clay (Plastic)fine Sand mediumcoarse Gravel finecoarse PERCENT PASSING (%)PARTICLE SIZE (MM) GRADATION AND ATTERBERG TEST RESULTS PROJECT NO. 201023FIGURE A-12 Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Appendix B APPENDIX B SPECIFICATIONS FOR PLACEMENT OF FILL Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Appendix B APPENDIX B SPECIFICATIONS FOR PLACEMENT OF FILL General AGW, as the Client's representative, should observe fill placement and conduct tests to determine if the materials placed, methods of placement, and compaction are in reasonable conformance with these specifications. Specifications presented in this Appendix are general in nature. They should be used for construction except where specifically superseded by those presented in the attendant geotechnical study. For the purpose of this specification, structural areas include those areas that will support constructed appurtenances (e.g., foundations, slabs, flatwork, pavements, etc.) and fill embankments or slopes that support significant fills or constructed appurtenances. Structural areas will be as defined by AGW. Fill Material Fill material should consist of on or off-site soils which are relatively free of vegetable matter and rubble. Off-site materials should be evaluated by AGW prior to importation. No organic, frozen, perishable, rock greater than 6 inches, or other unsuitable material should be placed in the fill. For the purpose of this specification, cohesive soil is defined as a mixture of clay, sand, and silt with more than 35% passing a U. S. Standard #200 sieve and a Plasticity Index of at least 11. These materials will classify as an A-6 or A-7 by the AASHTO Classification system. Granular soils are all materials which do not classify as cohesive. Preparation of Fill Subgrade Vegetation, organic topsoil, and any other deleterious materials should be removed from the fill area. The area to be filled should then be scarified, moistened or dried as necessary, and compacted to the moisture content and compaction level specified below prior to placement of subsequent layers of fill. Placement of Fill Material The materials should be delivered to the fill in a manner which will permit a well and uniformly compacted fill. Before compacting, the fill material should be properly broken down, mixed, and spread in approximately horizontal layers not greater than 8 inches in loose thickness. Moisture Control The material must contain uniformly distributed moisture for proper compaction. The Contractor will be required to add moisture to the materials if, in the opinion of AGW, sufficient and uniform moisture is not present in the fill. If the fill materials are too wet for proper compaction, aerating and/or mixing with drier materials will be required. Moisture content should be controlled as a percentage deviation from optimum. Optimum moisture content is defined as the moisture content corresponding to the maximum density of a laboratory compacted sample performed according to ASTM D698 for cohesive soils or ASTM D1557 for granular soils. The moisture content specifications for the various areas are as follows: Cohesive Soils Granular Soils 1.Beneath Structural Areas: 0 to +4%−2 to +2% 2.Beneath Non-Structural Areas:−3 to +3%−3 to +3% Geotechnical Site Development Study D R Horton Old Town North February 25, 2020 AGW Project Number 201023 Appendix B Compaction When the moisture content and conditions of each layer spread are satisfactory, the fill should be compacted. Laboratory moisture-density tests should be performed on typical fill materials to determine the maximum density. Field density tests must then be made to determine fill compaction. The compaction standard to be utilized in determining the maximum density is ASTM D698 for cohesive soils or ASTM D1557 for granular soils. The following compaction specifications should be followed for each area: 1.Beneath Structural Areas:95% of Maximum Dry Density 2.Beneath Non-Structural Areas:90% of Maximum Dry Density If the fill contains less than 10% passing the No. 200 sieve, it may be necessary to control compaction based on relative density (ASTM D2049). If this is the case, then compaction around the structures and beneath walkway or other slabs should be to at least 70% relative density, and compaction beneath foundations and vehicle supporting should be to at least 80% relative density. Responsibility Any mention of essentially full-time testing and observation does not mean AGW will accept responsibility for future fill performance. AGW shall not be responsible for constant or exhaustive inspection of the work, the means and methods of construction or the safety procedures employed by Client's contractor. Performance of construction observation services does not constitute a warranty or guarantee of any type, since even with diligent observation, some construction defects, deficiencies or omissions in the Contractor's work may occur undetected. Client shall hold its contractor solely responsible for the quality and completion of the project, including construction in accordance with the construction documents. Any duty hereunder is for the sole benefit of the Client and not for any third party, including the contractor or any subcontractor.