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HomeMy WebLinkAboutTAPESTRY - FDP240016 - SUBMITTAL DOCUMENTS - ROUND 1 - Geotechnical (Soils) Report400 North Link Lane | Fort Collins, Colorado 80524 Telephone: 970-206-9455 Fax: 970-206-9441 GEOLOGIC AND PRELIMINARY GEOTECHNICAL INVESTIGATION ODELL TOWNHOMES FORT COLLINS, COLORADO Prepared For: HARTFORD HOMES 4801 Goodman Street Timnath, Colorado 80547 Attention: Landon Hoover Project No. FC09777-115 March 8, 2021 i TABLE OF CONTENTS SCOPE ....................................................................................................................... 1 SUMMARY OF CONCLUSIONS ............................................................................... 1 SITE DESCRIPTION ................................................................................................. 2 PROPOSED DEVELOPMENT .................................................................................. 3 SITE GEOLOGY ........................................................................................................ 3 GEOLOGIC HAZARDS ............................................................................................. 4 Beet Spoils ............................................................................................................. 4 Expansive Soils and Bedrock ................................................................................ 4 Groundwater ........................................................................................................... 5 Flooding .................................................................................................................. 6 Seismicity ............................................................................................................... 6 Radioactivity ........................................................................................................... 7 FIELD AND LA BORATORY INVESTIGATIONS ...................................................... 7 SUBSURFACE CONDITIONS .................................................................................. 8 Existing Beet Spoils Fill .......................................................................................... 9 Natural Clay and Sand ........................................................................................... 9 Bedrock ................................................................................................................ 10 DEVELOPMENT RECOMMENDATIONS ............................................................... 10 Over-Excavation ................................................................................................... 10 Site Grading ......................................................................................................... 11 Permanent Cut and Fill Slopes ............................................................................ 12 Utility Construction ............................................................................................... 12 Underdrain System .............................................................................................. 14 PRELIMINARY PAVEMENT RECOMMENDATIONS ............................................ 15 Subgrade Preparation .......................................................................................... 15 Preliminary Pavement Thickness Design ............................................................ 15 PRELIMINARY RECOMMENDATIONS FOR STRUCTURES ............................... 16 Foundations .......................................................................................................... 16 Monolithic Slab Foundations ................................................................................ 17 Below-Grade Construction ................................................................................... 17 Surface Drainage ................................................................................................. 18 General Design Considerations ........................................................................... 18 RECOMMENDED FUTURE INVESTIGATIONS .................................................... 19 LIMITATIONS .......................................................................................................... 20 ii TABLE OF CONTENTS cont’d FIGURE 1 – LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 – SUMMARY LOGS OF EXPLORATORY BORINGS FIGURES 3 THROUGH 7 – LABORATORY TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TESTING APPENDIX A – GUIDELINE SITE GRADING SPECIFICATIONS HARTFORD HOMES 1 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 SCOPE This report presents the results of our Geologic and Preliminary Geotechnical Investigation. The purpose of our investigation was to identify geologic hazards that may exist at the site and to evaluate the subsurface conditions to assist in planning and budgeting for the proposed development. The report includes descriptions of site geology, our analysis of the impact of geologic conditions on site development, a description of subsoil, 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 Project No. FC-21-0050) dated February 3, 2021. This report was prepared based upon our understanding of the development 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. No geologic or geotechnical conditions were identified which would preclude development of this site. Beet spoils, expansive soils, shallow groundwater, flooding, and regional issues of seismicity and radioactivity are the primary geologic concerns pertaining to the development of the site. 2. In general, the soils and bedrock encountered in our borings consisted of 7 to 9 feet of sandy clay over 13 to 15 feet of gravelly sand over claystone bedrock. Borings were drilled at the toe of a beet spoils mound and it is crucial that it is known that beet spoils exist above the borings drilled as observed the previous investigation, CTL|T Project HARTFORD HOMES 2 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 No. FC09775-125, dated February 11, 2021. Bedrock was encountered at depths ranging from 21 to 22 feet below the existing ground surface. 3. Groundwater was encountered in all three borings during drilling at depths ranging from 13 ½ to 18 feet below the existing ground surface. When measured several days later, groundwater was measured in all three borings at depths ranging from 10 to 14 feet below existing ground surface. We recommend a 3-foot (preferably 5- foot) separation between foundation elements and groundwater. Basement level construction may be possible if foundation elevations are carefully planned to maintain the recommended separation or site grades are raised. 4. Swell-consolidation testing indicated swell potential in the sandy clay to be 0.8 to 6.4 percent. We understand monolithic slab foundations are desired for the proposed construction. The desired foundation type is inherently higher-risk than typical footing and crawlspace or slab-on-grade floor construction typical to local practice. We judge monolithic slab foundations may be used for the proposed multifamily building across the subject lots provided some risk movement and cracking is acceptable to the buyer. We recommend that beet spoils are completely removed. Additionally, the upper expansive clays will need to be removed or moisture treated. Moisture treatment should extend to the gravelly sands or to 5 feet below the foundation. 5. Pavement subgrade mitigation for swell is likely over the majority of the site. Mitigation may consist of moisture and/or chemical treatment of the subgrade soils. A minimum of 12 inches of chemical treatment (fly ash or lime) should be expected. Asphaltic pavement sections on the order of 5 to 6 inches for streets, parking areas, access drives are anticipated for preliminary planning purposes. Portland cement concrete with at least 6 inches in thickness should be considered for intersections, trash enclosures or areas of heavy turning. Pavement and concrete shall not be constructed on beet spoils. SITE DESCRIPTION The site is located along 3rd Street near Logan Street and 3rd Street in Fort Collins, Colorado as presented on Figure 1. The site is generally in a plains area and is primarily vegetated with grasses and weeds. At the time of our exploration the site was undeveloped with beet spoils existing on the eastern half of the build site. HARTFORD HOMES 3 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 The building site on the 8.57 +/- acre parcel has a gentle slope to the west. No water features or rock outcrops were noted onsite. PROPOSED DEVELOPMENT We understand the parcel is planned for development of multi-family housing. Preliminary plans indicate site grading will include the removal of 3 to 10 feet of beet spoils existing on the eastern half of the build site. We assume the structures will be 1 to 2-story, wood frame structures, with basements or crawl spaces. CTL|Thompson has performed a beet waste delineation for other portions of this development. These include CTL|T Project No. FC09775-125, dated February 11, 2021. The data generated from these studies was reviewed in preparation of this report. 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, 1978). Geology was further evaluated through review of conditions found in exploratory borings, and our experience in the area. According to the referenced mapping, the site is located within the Post-Piney Creek Alluvium. POST-PINEY CREEK ALLUVIUM (UPPER HOLOCENE) The alluvium is comprised of clay, sand, and gravel. Alluvium can be found in areas near flood plains, streams, and rivers. Alluvium was deposited from fluvial processes originating from the Cache La Poudre River. The materials encountered in our borings were in general agreeance with the referenced mapping. HARTFORD HOMES 4 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 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 geologic 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 beet spoils, expansive soils, shallow groundwater, flooding, 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. Beet Spoils Site development of areas underlain by beet spoils or soils mixed with beet spoils is problematic. Roadways constructed in these areas typically require stabilization. Roadways constructed over beet spoils without mitigation will result in poor pavement performance, differential settlement, and regular maintenance. Beet spoils do not have adequate support characteristics for even lightly loaded structures. Removal and replacement will be necessary below structures and roads. Other site improvements such as flat work, sidewalks, curb and gutter and grade critical wet utilities can also present challenges in areas underlain by beet spoils. Beet spoils shall be completely removed from the site. 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 HARTFORD HOMES 5 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 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 wetting 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 will perform satisfactorily. The soils at this site include sandy clay in the upper 7 to 9 feet. The clay is expansive. There is risk that ground heave will damage pavements, slabs-on-grade, and foundations. We believe that risk is high. Engineered design of grading, pavements, foundations, over-excavation, monolithic slab foundations, and surface drainage can mitigate, but not eliminate, the effects of expansive soil. Problems associated with the existence of expansive materials are typically mitigated through currently utilized foundation and floor slab techniques. Individual soils and foundation investigations conducted for specific sites should address procedures for mitigating problems associated with expansive soils and bedrock. Groundwater Groundwater was encountered in all three borings during drilling at d epths ranging from 13 ½ to 18 feet below the existing ground surface. When measu red several days later, groundwater was measured in all three borings at depths ranging from 10 to 14 feet below existing ground surface. We recommend a 3-foot (preferably 5-foot) separation between foundation elements and groundwater. HARTFORD HOMES 6 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Basement level construction may be possible if foundation elevations are carefully planned to maintain the recommended separation or site grades are raised. Groundwater may rise due to site development and will likely occur during extended periods of flow in the nearby Cache La Poudre River. Perched water conditions may develop where residential construction and irrigation occur in low permeability soil areas. The depth to groundwater should be evaluated during Geotechnical Investigations at the site. In general, grading should be designed to raise the elevations in areas of shallow groundwater. Construction of underdrain systems with the sanitary sewer trenches is a commonly employed method to mitigate the accumulation of shallow groundwater after construction. A minimum separation of 3 feet, 5 feet is preferred, is desirable between the groundwater elevations and the lowest elevation of any below-grade structure. Flooding This site lies within Zone X as shown on Flood Insurance Rate Maps prepared by the Federal Emergency Management Agency found on the City of Fort Collins website. A Zone X 500-year or 100-year flood zone occurs across the entirety of the site. 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 of the past earthquake activity in Colorado is somewhat incomplete. HARTFORD HOMES 7 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Based on the subsurface conditions encountered in our borings and our understanding of the geology, the site classifies as a Seismic Site Class D (2015 International Building Code). Only minor dam age to relatively new, properly designed and built buildings would be expected. Wind loads, not seismic considerations, typically govern dynamic structural design in this area. 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 bed rock. Radon 222 gas is considered a health hazard and is one of several radioactive products in the chain of the natural decay of uranium into stable lead. Radioactive nuclides are common in the soils and sedimentary rocks underlying the subject site. Because these sources exist on most sites, there is potential for radon gas accumulation in poorly ventilated spaces. The amount of soil gas that can accumulate is a function of many factors, including the radio-nuclide activity of the soil and bedrock, construction methods and materials, pathways for soil gas and existence of poorly-ventilated accumulation areas. It is difficult to predict the concentration of radon gas in finished construction. We recommend testing to evaluate radon levels after constr uction is completed. If required, typical mitigation methods for residential construction may consist of sealing soil gas entry areas and periodic ventilation of below-grade spaces and perimeter drain systems. It is relatively economical to provide for ventilation of perimeter drain systems or underslab gravel layers at the time of construction, compared to retrofitting a structure after construction. 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 three exploratory HARTFORD HOMES 8 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 borings at the approximate locations shown on Figure 1. The borings were drilled using a truck-mounted drill rig and 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 in 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 and by collecting hand samples from auger cuttings. Samples recovered from the test holes were returned to our laboratory and visually classified by the geologist. Laboratory testing included determination of moisture content and dry density, swell-consolidation characteristics, and particle- size analysis. Laboratory test results are presented in Figures 3 through 7 and in Table 1. SUBSURFACE CONDITIONS The rear portion of the site is primarily beet waste (beet spoil) materials with a steep slope toward the street. Due to the slope, potential boring locations were limited to the front of the lots. Our borings were performed at the toe of this slope and likely represent the site subsurface conditions for the building area one the beet waste materials are removed from the site. A beet waste delineation effort was performed (CTL|T Project No. FC09775-125, dated February 11, 2021) and should be considered during the site planning for the proposed structures. Subsurface conditions encountered in the borings consisted of 7 to 9 feet of sandy clay over 13 to 15 feet of gravelly sand over claystone bedrock. Bedrock was encountered at depths ranging from 21 to 22 feet below the existing ground surface. Groundwater was encountered in all three borings during drilling at depths ranging from 13 ½ to 18 feet below the existing ground surface. When measured several days later, groundwater was measured in all three borings at depths ranging from 10 HARTFORD HOMES 9 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 to 14 feet below existing ground surface. We recommend a 3-foot (preferably 5-foot) separation between foundation elements and groundwater. Basement level construction may be possible if foundation elevations are carefully planned to maintain the recommended separation or site grades are raised. Groundwater may rise due to site development and will likely occur during extended periods of flow in the nearby Cache La Poudre River. Perched water conditions may develop where residential construction and irrigation occur in shallow bedrock areas. A more detailed description of the subsurface conditions is presented in our boring logs and laboratory testing. Measured depth to groundwater and bedrock maps are presented on Figure 2 of this report. Existing Beet Spoils Fill The borings drilled during this investigation were drilled at the toe of a beet spoils mound that exists on the eastern half of the build site. Beet spoils are white to light brown in color and are primarily comprised of calcium carbonate (chalk). Thickness of beet spoils will range from 3 to 10 feet based on elevatio ns of the beet spoils mound as observed in the previous investigation, CTL|T Project No. FC09775-125, dated February 11, 2021. Site development of areas underlain by beet spoils or soils mixed with beet spoils is problematic. Roadways constructed in these areas typically require extensive stabilization. Roadways constructed over beet spoils without mitigation will result in poor pavement performance, differential settlement, and regular maintenance. Beet spoils do not have adequate support characteristics for even lightly loaded structures. Removal and replacement will be necessary below structures and roads. Other site improvements such as flat work, sidewalks, curb and gutter and grade critical wet utilities can also present challenges in areas underlain by beet spoils. Beet spoils shall be completely removed from the site. Natural Clay and Sand The soils encountered on this site included sandy clay and gravelly sand. HARTFORD HOMES 10 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 The thickness of soil was variable across the site, ranging from about 21 feet to 22 feet. The soils encountered in our borings consisted of 7 to 9 feet of sandy clay over 13 to 15 feet of gravelly sand. Field penetration resistance tests indicated the sandy clay was stiff to very stiff. Field penetration resistance tests indicated the gravelly sand was dense to very dense. As observed in the field, the gravelly sand is susceptible to 10 to 15 feet of cave. The gravelly sand does not pose a risk of swell. 3 samples of sandy clay were selected for swell-consolidation testing. The results indicated 0.8 to 6.4 percent swell after wetting under a 500-psf load. We anticipate most of the site will be considered to have high risk of swell. It is recommended that the sandy clay be moisture treated down to the gravelly sands or to a minimum 5- foot below foundations. Bedrock Bedrock was encountered in all three test holes. Bedrock was encountered 21 to 22 feet below the existing ground surface. The bedrock encountered was predominately claystone. Due to caving gravelly sand, only hand samples of claystone bedrock were collected from two of three borings . Hand samples of bedrock are highly disturbed and therefore, laboratory testing was not performed on bedrock. We do not anticipate the bedrock will impact planned construction. DEVELOPMENT RECOMMENDATIONS Over-Excavation Over-excavation consists of removal of expansive clay and reworking these soils as fill compacted in a controlled manner. Areas where expansive clay is present should be further delineated during design level investigations. Excavation observations and density testing are commonly recommended for sites such as this in addition to a design level geotechnical investigation. Complete removal of beet spoil fill and an over-excavation of the upper 5 feet of sandy clay soil is expected to sufficiently combat high swelling clay soils. Clay soils were observed in the upper 7 HARTFORD HOMES 11 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 to 9 feet at the toe of the beet spoil fill mound. Over-excavation slopes will need to be sloped as a minimum according to Occupational Safety and Health Administration (OSHA) criteria for the appropriate soil type (refer to Utility Construction section). When plans are available, we are available to consult with your design/construction team as they develop a sub- excavation grading plan. A detailed plan is recommended to incorporate details of building locations and elevations, and also allow documentation by surveyors and be as explicit and efficient as possible for the contractor. 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 additional cuts and fill may be needed. Site grading will likely affect the proposed development. 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 advance of surface construction as possible. It is our experience that fill compacted in accordance with the compaction recommendations in this report may settle about 1 percent of its height under its own weight. Most of this settlement usually occurs during and soon after construction. Some additional settlement is possible after development and landscape 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 fills is recommended. The existing on-site beet spoil fill is not suitable for re-use as fill material. However, the existing on-site clay soils are suitable for re-use as fill material HARTFORD HOMES 12 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 provided debris or deleterious organic materials are removed and the soil is carefully moisture conditioned. Gravelly sand should be avoided as fill material because it is too coarse and rounded to compact efficiently. Prior to fill placement, all trash and debris should be removed from fill areas and properly disposed. Imp ort fill should generally have similar or better engineering properties as the ons ite materials and should be approved by CTL. 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 compacted as recommended be low. 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. Compaction and moisture requirements are presented in Appendix A. The placement and compaction of fill should be observed and density tested during construction. Guideline site grading specifications are presented in Appendix A. 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 as shown on Figure 4. 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 steeper slopes. Utility Construction We believe excavations for utility installation in the overburden soils can be performed with conventional heavy-duty trenchers or large backhoes. Groundwater HARTFORD HOMES 13 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 is not anticipated in excavations. 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 clayey soils classify as Type B soil and gravelly sand soils classify as Type C soil based on OSHA standards. Excavation slopes specified by OSHA are dependent upon soil types and groundwater conditions encountered. Seepage and groundwater conditions in trenches may downgrade the soil type. Contractors should identify the soils encountered in the excavation and refer to OSHA standards to determine appropriate slopes. Excavations deeper than 20 feet should be designed by a professional engineer. The width of the top of an excavation may be limited in some areas. Bracing or “trench box” construction may be necessary. Bracing systems include sheet piling, braced sheeting and others. Lateral loads on bracing depend on the depth of excavation, slope of excavation above the bracing, surface loads, hydrostatic pressures, and allowable movement. For trench boxes and bracing allowed to move enough to mobilize the strength of the 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 rest” earth pressure condition, assuming level backfill. These pressures do not include allowances for surcharge loading or for hydrostatic conditions. We are available to assist further with bracing design if desired. Water and sewer lines are usually constructed 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 moisture conditioned to between optimum and 3 percent above optimum content for HARTFORD HOMES 14 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 clay soils and within 2 percent of optimum moisture content for sand. Trench backfill should be compacted to at least 95 percent of maximum dry density (ASTM D 698). The placement and compaction of fill and backfill should be observed and tested by our firm during construction. If deep excavations are necessary for planned utilities, the compaction requirements provided in Appendix C should be considered. Underdrain System The use of underdrain systems below sewer mains and services is a common method to control groundwater in response to development. We recommend an underdrain system be incorporated into sanitary sewer and sewer collection systems. Underdrains should also be installed below sewer service lines to each residence planned in this area with connection to residence foundation drains. The underdrain should consist of free-draining gravel surrounding a rigid PVC pipe. The pipe should be sized for anticipated flow. Guidelines for underdrain sizing are shown in Table A. The line should consist of smooth, perforated or slotted rigid PVC pipe laid at a grade of at least 0.5 percent. A gravel cross-section of at least 2 square feet should be placed around the pipe. A sewer underdrain detail is shown on Figure 5. A positive cutoff collar (concrete) should be constructed around the sewer pipe and underdrain pipe immediately downstream of the point the underdrain pipe leaves the sewer trench. Solid pipe should be used down gradient of this collar to the daylight point. Clean-outs should be provided along the system. The entity responsible for maintenance should be identified and guidelines developed f or maintenance. The underdrain should be designed to discharge to a gravity outfall provided with a permanent concrete headwall and trash rack, or to a storm sewer with a check valve to control water backing up into the underdrain system. The underdrain system should be designed by a professional engineer that is licensed in the State of Colorado. HARTFORD HOMES 15 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 TABLE B UNDERDRAIN SIZING Slope = 0.005 (0.5 percent) Pipe Size (inches) 4 6 8 Maximum Number of Residences 50 100 200 Slope = 0.01 (1.0 percent) Pipe Size (inches) 4 6 8 Maximum Number of Residences 75 150 300 Slope = 0.02 (2.0 percent) Pipe Size (inches) 4 6 Maximum Number of Residences 100 300 Note: Minimum slopes of the underdrains will govern pipe sizes and maximum number of residences serviced. PRELIMINARY PAVEMENT RECOMMENDATIONS Subgrade Preparation Based on the borings, the near surface soils on this site will consist of sandy clay or beet spoil fill. The beet spoil fill shall be completely removed. These sandy clay soil will range from lean to highly plastic and will provide relatively poor subgrade support below the pavements. Lime or fly ash stabilization of these soils will improve their subgrade support characteristics, in addition to enhancing the workability of the clays and reducing water infiltration into the underlying subgrade and the potential movements under the pavements. Preliminary Pavement Thickness Design Plans for this site were not provided prior to this report; we have provided only general recommendations here. Preliminary guidelines for pavement systems on this site are provided. Final pavement sections should be determined based a HARTFORD HOMES 16 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 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. We anticipate HMA pavement sections for this site will be on the order of 4 to 6 inches thick overlying 6 to 8 inches of ABC. Portland cement concrete (PCC) pavement is recommended in areas subject to any heavy truck traffic such as garbage pickup and/or dumpster trucks and any heavy delivery trucks. We anticipate the use of 6 inches of PCC for general area pavements which are not subject to truck traffic. A minimum 6-inch-thick section is anticipated in main drives and any areas subject to some moderately heavy truck traffic. Any areas subject to frequent heavy trucks should be designed based on frequency and wheel loads. PCC pavements in this area are typically 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, multi-family construction. The following discussions are preliminary and are not intended for design or construction. After grading is completed, a detailed soils and foundation investigation should be performed. Due to the preliminary nature of this project, subdivision organization or site grading plans have not been prepared, and therefore not available for review in conjunction with this subsurface exploration program. Therefore, recommendations provided here are general and for planning purposes only. Foundations Our geologic and preliminary geotechnical investigation for this site indicates HARTFORD HOMES 17 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 structures may be founded on a shallow foundation constructed on a 5-foot over- excavation. A design level geotechnical investigation may identify potential hazards for specified areas not indicated by our borings which may suggest the need for a deeper foundation system. Soft soils may require stabilization. Existing beet spoil fill should be completely removed. Existing sandy clay soils should be removed, moisture treated and recompacted below improvements. Sub-excavation should be anticipated for areas where collapse-prone soils are encountered. Monolithic Slab Foundations The use of monolithic slab foundation should be used in areas where beet spoil fill has been completely removed and a minimum 5-foot over-excavation has been performed in the sandy clay soils to combat high swelling clay. Sandy clay should be removed and reworked in a controlled manor as to compact the fill and achieve optimum density. Once beet spoil is removed and a 5-foot over-excavation is performed in the sandy clay we believe most of the lots will be rated with low risk of poor slab performance. Basement level construction is not recommended for this site unless the grade can be raised permanently to maintain a 3-foot separation from groundwater or if garden-level foundations with a maximum excavation of 5 feet are utilized. Sub-excavation should be anticipated on many of the lots to mitigate risk associated with collapse-prone soils if excavations are anticipated in the gravelly sand. Below-Grade Construction Groundwater was encountered at 10 to 14 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. Being near the Cache La Poudre River, groundwater levels are expected to fluctuate significantly. Groundwater levels higher than levels measured during this investigation are expected. To reduce the risk of hydrostatic pressure developing on foundation walls, foundation drains will be necessary around all bel ow-grade areas. HARTFORD HOMES 18 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 We suggest foundation drains be tied to the sewer underdrain system. They may also discharge to sumps where water can be removed by pumping. In our opinion, underdrain systems offer more comprehensive control of ground water and 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 should 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 sh ould 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 to prevent HARTFORD HOMES 19 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 possible ponding, particularly next to the bu ilding due to soil movement. Positive grades away from the buildings should be used for sidewalks and flatwork around the perimeter of the buildings in order to reduce the possibility of lifting of this flatwork, resulting in ponding next to the structures. Where movement of the flatwork is objectionable, procedures recommended for on-grade floor slabs should be considered. Joints next to buildings should be thoroughly sealed to prevent the infiltration of surface water. Where concrete pavement is used, joints should also be sealed to reduce the infiltration of water. Since some post construction movement of pavement and flatwork may occur, joints around the buildings should be periodically observed and resealed where necessary. Roof drains should be discharged well away from the structures, preferably by closed pipe systems. Where roof drains are allowed to discharge on concrete flatwork or pavement areas next to the structures, care should be taken to insure the area is as water tight as practical to eliminate the infiltration of this water next to the buildings. RECOMMENDED FUTURE INVESTIGATIONS Based on the results of this investigation and the proposed development, we recommend the following investigations be performed: 1. Review of final site grading plans by our firm; 2. Construction testing and observation for site development; 3. Subgrade investigation and pavement design after site grading is complete; 4. Design-level soils and foundation investigations after grading; 5. Construction testing and observation for residential building construction and paving. HARTFORD HOMES 20 ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 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 possible. We believe this investigation was conducted in a manner consistent with that level of skill and care ordinarily used by members of the profession currently practicing under similar conditions 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 understanding 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. Kyle Poisson R.B. "Chip" Leadbetter, III, P.E. Staff Geologist KCP:RBL Senior Geotechnical Engineer UT I L I T Y ST O R A G E UT I L I T Y ST O R A G E UT I L I T Y STO R A G E UT I L I T Y STO R A G E UP UP FO Y E R 1-C A R GA R A G E 1-C A R GAR G E 2-C A R GA R A G E ME C H . 1-C A R GA R A G E 2-C A R GA R A G E 2-C A R GA R A G E 1-C A R GA R G E 1-C A R GAR A G E FO Y E R UP FO Y E R 1-C A R GA R A G E 1-C A R GA R G E 2-C A R GA R A G E MEC H . 1-C A R GAR A G E 2-C A R GA R A G E 2-C A R GA R A G E 1-C A R GA R G E 1-C A R GA R A G E FO Y E R UP UP FO Y E R 1-C A R GAR A G E 1-C A R GA R G E 2-C A R GA R A G E ME C H . 1-C A R GA R A G E 2-C A R GAR A G E 2-C A R GA R A G E 1-C A R GA R G E 1-C A R GA R A G E FO Y E R UP UP FO Y E R 1-C A R GAR A G E 1-C A R GA R G E 2-C A R GA R A G E ME C H . 1-C A R GA R A G E 2-C A R GAR A G E 2-C A R GAR A G E 1-C A R GAR G E 1-C A R GA R A G E FO Y E R UP ME C H . MEC H . O.E . UP UP O.E . KIT C H E N MAS T E R BE D W.I. C . BA T H 2 FO Y E R HA L L DIN I N G UP UP MA S T E R BE D W.I . C . M. B A T H BE D 2 LIV I N G CO V E R E D EN T R Y LIV I N G CO V E R E D EN T R Y CO V E R E D EN T R Y LIV I N G BED 2 M. B A T H W.I. C . W.I . C . M. B A T H BED 2 LIV I N G CO V E R E D EN T R Y LIV I N G MA S T E R BED CO V E R E D EN T R Y CO V E R E D EN T R Y LIV I N G BE D 2 M. B A T H W.I . C . W.I. C . M. B A T H BE D 2 LIV I N G CO V E R E D EN T R Y LIV I N G DIN I N G DIN I N G FO Y E R FO Y E R HA L L HA L L DIN I N G UP UP MA S T E R BE D CO V E R E D EN T R Y CO V E R E D EN T R Y LIV I N G BE D 2 M. B A T H W.I. C . W.I . C . M. B A T H BE D 2 LIV I N G CO V E R E D EN T R Y LIV I N G DIN I N G DIN I N G BA T H 2 MA S T E R BE D KIT C H E N KIT C H E N MA S T E R BE D BA T H 2 FO Y E R FO Y E R FO Y E R HAL L HA L L DIN I N G UP UP MA S T E R BE D CO V E R E D EN T R Y CO V E R E D EN T R Y LIV I N G BED 2 M. B A T H W.I. C . DIN I N G DIN I N G KIT C H E N W.I. C . BAT H 2 MA S T E R BE D UP O.E . KIT C H E N KIT C H E N MA S T E R BE D BA T H 2 FO Y E R FO Y E R FO Y E R HA L L HA L L DIN I N G UP UP DIN I N G DIN I N G KIT C H E N W.I . C . BA T H 2 MA S T E R BED O.E . BAT H O.E . UP UP UP O.E . KIT C H E N KIT C H E N MA S T E R BE D BA T H 2 FO Y E R FO Y E R FO Y E R HA L L KIT C H E N W.I . C . BA T H 2 MA S T E R BE D ME C H . BA T H ME C H . O.E . O.E . UP UP UP O.E . KIT C H E N KIT C H E N ME C H . BA T H ME C H . O.E . O.E . UP UP UP ME C H . BA T H ME C H . O.E . CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y CO V E R E D EN T R Y LAUN. LAUN. LAUN. LAUN. S. L E M A Y A V E . E. LINCOLN AVE. BUCKINGHAM ST. 3R D S T . 2N D S T . 1S T S T . N. L E M A Y A V E . LIN D E N S T CACHE LA POUDRE RIVER RIVE R S I D E A V E . SITE LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING TH-1 HARTFORD HOMES ODELL TOWNHOMES CTL I T PROJECT NO. FC09777-115 FIGURE 1 Locations of Exploratory Borings VICINITY MAP (FORT COLLINS, COLORADO AREA) NOT TO SCALE 3r d S t r e e t 100'50' APPROXIMATE SCALE: 1" = 100' 0' TH-3 TH-2 TH-1 Buckingham Street Logan Street DRIVE SAMPLE. THE SYMBOL 34/12 INDICATES 34 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES. ND INDICATES NO DRIVE. BULK SAMPLE FROM AUGER CUTTINGS. CLAYSTONE, SANDY, MOIST, GRAY SAND, GRAVELLY, MOIST TO WET, DENSE TO VERY DENSE, BROWN (SP, SW) Borings NOTES: INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER APPROXIMATE OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES UNCONFINED COMPRESSIVE STRENGTH (psf). INDICATES SOLUBLE SULFATE CONTENT (%). CLAY, SANDY, MOIST, STIFF TO VERY STIFF, DARK BROWN, BROWN (CL) LEGEND: THE BORINGS WERE DRILLED ON FEBRUARY 18, 2021 USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. WATER LEVEL MEASURED AT TIME OF DRILLING. WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING. INDICATES DEPTH WHERE HOLE CAVED. 1. Exploratory Summary Logs of FIGURE 2 WC DD SW -200 LL PI UC SS - - - - - - - - 3. 2. THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 34/12 48/12 ND WC=15.1DD=117SW=6.4 WC=15.1DD=117SW=6.4 TH-1 13/12 50/10 50/9 WC=16.4DD=108SW=0.8 -200=5 -200=5 WC=16.4DD=108SW=0.8 -200=5 -200=5 TH-2 18/12 37/12 ND WC=12.8DD=113SW=5.9 -200=4 WC=12.8DD=113SW=5.9 -200=4 TH-3 DE P T H - F E E T DE P T H - F E E T Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=117 PCF From TH - 1 AT 4 FEET MOISTURE CONTENT=15.1 % HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 APPLIED PRESSURE -KSF CO M P R E S S I O N % E X P A N S I O N Swell Consolidation Test Results FIGURE 3 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=108 PCF From TH - 2 AT 4 FEET MOISTURE CONTENT=16.4 % HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 APPLIED PRESSURE -KSF CO M P R E S S I O N % E X P A N S I O N Swell Consolidation Test Results FIGURE 4 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of CLAY, SANDY (CL) DRY UNIT WEIGHT=113 PCF From TH - 3 AT 4 FEET MOISTURE CONTENT=12.8 % HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 APPLIED PRESSURE -KSF CO M P R E S S I O N % E X P A N S I O N Swell Consolidation Test Results FIGURE 5 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 EXPANSION UNDER CONSTANT PRESSURE DUE TO WETTING 0.1 1.0 10 100 Sample of SAND (SP)GRAVEL 32 %SAND 63 % From TH - 2 AT 9 FEET SILT & CLAY 5 %LIQUID LIMIT % PLASTICITY INDEX % Sample of SAND (SW)GRAVEL 35 %SAND 60 % From TH - 2 AT 14 FEET SILT & CLAY 5 %LIQUID LIMIT % PLASTICITY INDEX % HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 FIGURE 6 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 PE R C E N T P A S S I N G 0 10 20 30 50 60 70 80 90 100 PE R C E N T R E T A I N ED 40 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 PE R C E N T P A S S I N G PE R C E N T R E T A I N E D 0 10 20 30 40 50 60 70 80 90 100 Sample of SAND (SP)GRAVEL 43 %SAND 53 % From TH - 3 AT 9 FEET SILT & CLAY 4 %LIQUID LIMIT % PLASTICITY INDEX % Sample of GRAVEL %SAND % From SILT & CLAY %LIQUID LIMIT % PLASTICITY INDEX % HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 FIGURE 7 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 PE R C E N T P A S S I N G 0 10 20 30 50 60 70 80 90 100 PE R C E N T R E T A I N ED 40 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 PE R C E N T P A S S I N G PE R C E N T R E T A I N E D 0 10 20 30 40 50 60 70 80 90 100 PASSING MOISTURE DRY APPLIED SWELL NO. 200 DEPTH CONTENT DENSITY SWELL*PRESSURE PRESSURE SIEVE BORING (FEET)(%)(PCF)(%)(PSF)(PSF)(%)DESCRIPTION TH-1 4 15.1 117 6.4 500 16,000 CLAY, SANDY (CL) TH-2 4 16.4 108 0.8 500 1,200 CLAY, SANDY (CL) TH-2 9 5 SAND (SP) TH-2 14 5 SAND (SW) TH-3 4 12.8 113 5.9 500 9,200 CLAY, SANDY (CL) TH-3 9 4 SAND (SP) SWELL TEST RESULTS* TABLE I SUMMARY OF LABORATORY TESTING Page 1 of 1 * NEGATIVE VALUE INDICATES COMPRESSION. HARTFORD HOMES ODELL TOWNHOMES CTL|T PROJECT NO. FC09777-115 APPENDIX A GUIDELINE SITE GRADING SPECIFICATIONS HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Appendix A-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) HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Appendix A-2 inches. Fill materials shall be obtained from cut areas shown on the plans or staked in the field by the Engineer. 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 HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Appendix A-3 work on that section of the fill shall be delayed until the material has been allowed to dry to the required moisture content. The Contractor will be permitted to rework wet material in an approved manner to hasten its drying. 8. COMPACTION OF FILL AREAS Selected fill material shall be placed and mixed in evenly spread layers. After each fill layer has been placed, it shall be uniformly compacted to not less than the specified percentage of maximum density. Fill shall be compacted to the criteria above. At the option of the Soils Engineer, soils classifying as SW, GP, GC, or GM may be compacted to 95 percent of maximum density as determined in accordance with ASTM D 1557 or 70 percent relative density for cohesionless sand soils. Fill materials shall be placed such that the thickness of loose materials does not exceed 12 inches and the compacted lift thickness does not exceed 6 inches. Compaction as specified above, shall be obtained by the use of sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other equipment approved by the Engineer for soils classifying as CL, CH, or SC. Granular fill shall be compacted using vibratory equipment or other equipment approved by the Soils Engineer. Compaction shall be accomplished while the fill material is at the specified moisture content. Compaction of each layer shall be continuous over the entire area. Compaction equipment shall make sufficient trips to ensure that the required density is obtained. 9. COMPACTION OF SLOPES Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction operations shall be continued until slopes are stable, but not too dense for planting, and there is not appreciable amount of loose soils on the slopes. Compaction of slopes may be done progressively in increments of three to five feet (3' to 5') in height or after the fill is brought to its total height. Permanent fill slopes shall not exceed 3:1 (horizontal to vertical). 10. PLACEMENT OF FILL ON NATURAL SLOPES Where natural slopes are steeper than 20 percent in grade and the placement of fill is required, benches shall be cut at the rate of one bench for each 5 feet in height (minimum of two benches). 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 HARTFORD HOMES ODELL TOWNHOMES CTL | T PROJECT NO. FC09777-115 Appendix A-4 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. 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.