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HomeMy WebLinkAboutSubsoil StudyAMERICAN CEOSERVICES Geotechnical Evaluation Report 1054 River Bend Way, Glenwood Springs, CO 81601 Date: August 26, 2019; Project No: 0464-WS19 AMERICAN CECSERVICES CFOTFCHNICAI, Ñ MATÊRIAI^S ENVIRONMENTAL STRUCTURAL CIVIL ENCINEERINC AND SCIENCE aaa276-402J August 26,2019 PROJECT N0:0464-WS19 CLIENTS: Mr. Gregg Sanders Reference: Soil Testing / Lot-specific Geotechnical Evaluation, 1054 River Bend Way, Glenwood Springs, CO At your request, we have completed the geotechnical evaluation for the referenced project in accordance with the American GeoServices, LLC (AGS) Proposal. Results of our evaluation and design recommendations are summarized below. PROJECT INFORMATION The site is located as shown in Figure 1 and Figure 2. The proposed development will consist of residential construction. We do not anticipate significant site grading for this project. We anticipate proposed structure will be constructed with light to moderate foundation loads. SGOPE OF WORK Our scope of services included the geologic literature review, soil explorations, geologic hazards evaluation, geotechnical evaluation, and the preparation of this report. Evaluation of any kind of existing structures on and adjacent to the site was beyond our scope of services. ln August 2019, we performed soil explorations (81 and B,2) at approximate locations shown in Figure 2 and collected soil/rock samples. Our soil exploration included logging of soils from soil boring. Our explorations extended to a maximum depth of 12.5 feet below existing ground surface (BGS). All soil/rock samples were identified in the field and were placed in sealed containers and transported to the laboratory for further testing and classification. Logs of all soil explorations showing details of subsurface soil conditions encountered at the site are included in an appendix. The Legend and Notes necessary to interpret our Exploration Logs are also included in an 1338 Grand Avenue #306 Glenwood Springs, CO 81601 Ph: (303) 325 3869 www,a mericangeoservices.com sma @americangeoservices.com Ph: (888) 276 4027 Fx: (877') 47L 0369 Mailing: 191 University Blvd, #375 Denver, CO 80206 Ph: (303) 32s 3869 appendix. Data obtained from site observations, subsurface exploration, laboratory evaluation, and previous experience in the area was used to perform engineering analyses. Results of engineering analyses were then used to reach conclusions and recommendations presented in this report. SURFACE CONDITIONS The site is roughly a rectangularly-shaped parcel of land as shown in Figure 2. Currently the site topography is gently sloping downwards to the east. At the time of our site visit, there was no visual indication of active slope instability or active landslides in the site vicinity. Our review of available geology maps and geologic hazards information did not reveal the presence of active geologic hazards at or immediately adjacent to the site. SUBSURFACE CONDITIONS Subsurface conditions encountered in our explorations and noted in our literature research are described in detail in the Exploration Logs provided in an Appendix and in the following paragraphs. Soil classification and identification is based on commonly accepted methods employed in the practice of geotechnical engineering. ln some cases, the stratigraphic boundaries shown on Exploration Logs represent transitions between soil types rather than distinct lithological boundaries. lt should be recognized that subsurface conditions often vary both with depth and laterally between individual exploration locations. The following is a summary of the subsurface conditions encountered at the site. Surface Gonditions: Approximately 8-10 inches of topsoil, loam, sand, silt and root mass is present at the surface. Sand-Silt-Clay Alluvium: Site is primarily underlain by generally loose or medium stiff to stiff mixtures of sand-silt-clay (SM, MK, CL) extending to a depth of about 6.5-7.5 feet. These soils exhibited low plasticity in the field and in the laboratory. These soils do not represent old debris flow deposit or ancient landslide deposit. Gravel-Sand-Silt Alluvium: Below about 6.5-7.5 feet, the site is generally underlain by medium dense to dense gravelly alluvium (GP, GM) extending to a maximum exploration depth of 12.5 feet. Groundwater: Groundwater was encountered during exploration or at the time of completion of our soil explorations at depths of 11-12 feet. This observation may not be indicative of other times or at locations other than the site. Some variations in the groundwater level may be experienced Project No: 0464-WS19 August 26, 2019 Page No: 2 of 1 9 in the future. The magnitude of the variation will largely depend upon the duration and intensity of precipitation, temperature and the surface and subsurface drainage characteristics of the surrounding area. GEOLOGIC HAZARDS EVALUATION Expansive/Collapsible Soils: The site is not underlain by highly expansive clayey soils or clayey sedimentary bedrock materials. The site location is not near known swell hazard zones that pose a significant geotechnical concern. However, local pockets of 'collapsible' soils/materials can occur through the site and may cause settlement in the foundations or flatwork around the site. This is typical of many areas along the Roaming Fork River corridor. Flooding: Proposed construction area is not located within 1O0-yearflood hazard zone, however, a flood hazard evaluation was beyond our scope of services. We recommend hiring an experienced hydrologist to evaluate the flood hazards for the site, or an in-depth evaluation of published flood hazard maps, considering the proximity of the site to the river. Debris Flow: Site is not located within alluvial fans or flood channels. Debris flow hazard at the site is minimal under normal site, topographic, geologic, and weather conditions. However, the site vicinity area may consist of ancient debris flow or ancient landslide deposit, which is currently inactive. Rockfall: Site is not located within rockfall hazard zone. Rockfall hazard at the site is minimal under normal site, topographic, geologic, and weather conditions. Landslides: Our review of available geologic maps and landslide hazard maps did not indicate that recent landslides or recent debris flow had occurred at the site or in the immediate proposed building area. During our site reconnaissance, we did not notice scarps, crevices, depressions, tension cracks in the ground surface, irregular slope toes, exposed surfaces of ruptures without vegetation, presence of distinct fast-growing vegetation, undrained depressions, etc., that are generally indicative of local active and/or inactive landslides or slope instability that would adversely impact the on-site structure at this time, however, a detailed landslide evaluation of any kind or slope stability evaluation under seismic conditions was beyond our scope of services. The site is not located within the mapped landslide hazard areas surrounding the site (Figure 6). There are potentially mapped landslides and/or ancient landslide deposits close to the site boundaries, within 750-1000 feet to the west. There is also moderate to high potential for the presence of dormant and/or unknown historic landslides, deep-seated ancient landslides, or Project No: 0464-WS 19 August 26, 20'19 Page No: 3 of 1 9 geologically-recently developed dormant landslides in the site vicinity close to the site, but not at the site. The site itself is not mapped as being situated within the existing active or ancient active landslide mass or an ancient active global landslide. However, the site vicinity area to the west is mapped as having landslide hazard (Figure 6). Considering these findings, the site topography, and site geologic conditions, it is our opinion that the immediate site vicinity area (but not the site) have 'site-specific landslide hazards' and has some 'inherent' risk associated with slope instability and structural impact from the movement of any global/ancient landslide and local slope movements. Moreover, historically, with construction in such areas, there is always an inherent risk associated with ground movement and/or settlements and related structural damage. The owner should understand these inherent risks related to site vicinity. lf the owner wants to better understand the risks and to eliminate the site-specific landslide hazard risks, then a detailed and comprehensive geotechnical evaluation including deep drilling, detailed slope stability modeling, and a detailed geologic hazards assessment (including global landslide hazards evaluation) should be performed in the site vicinity area to quantify the abovementioned risks and to provide detailed geotechnical design recommendations for comprehensive mitigation measures. Unless these recommended studies are performed, the owner is completely responsible for taking all risks associated with any future potentialfor instability at the site occurring due to landslide hazards in the site vicinity. lnitial Slope Stability Evaluation: Based on the results of our initial analyses (as discussed in following paragraphs), in our opinion, at present there are no slope instability hazards at the site provided site drainage is properly maintained during the design life of the structure. Using the results of geologic and soils literature review (as attached in the appendix) and site reconnaissance data, we analyzed on-site slopes by performing preliminary slope stability analysis. We used the software SLOPE/W to model on-site slopes, subsurface soil conditions, and the impact of existing construction on the stability of the site. We used several methods (Bishop, Janbu, Spencer, etc.) in order to obtain the lowest factor of safety against slope failures. The SLOPEM computer software calculates the most likely failure plane based on topography, subsurface conditions (including soil parameters), and groundwater conditions. The stability of this most likely failure plane is calculated as the factor of safety (FOS), which is a ratio of the resisting forces or shear strength to the driving forces or shear stress required for equilibrium of the slope. A FOS of 1.0 indicates the resistive forces and driving forces are equal. A FOS below 1.0 indicates the driving forces are greater and the landslide is active. A FOS above 1.0 indicates the resisting forces are greater and the slope is stable. Based on the engineering community and our experience, a factor of safety in the range of 1.3-2.0 is generally acceptable to assure slope stability in residential applications. Project No: 0464-WS19 August 26, 201 9 Page No: 4 of 19 Slope stability analysis was performed using various input soil parameters derived from the results of our subsurface exploration and laboratory evaluation, in order to properly evaluate the stability of a slope. Of particular importance were surface and subsurface profiles (slope geometry), soil strength parameters, and groundwater conditions. Based on our experience with past slope stability evaluations in similar geologic conditions, soil strength parameters can vary considerably. Notwithstanding, we used soil strength values typical of on-site soils and native soils/bedrock based on our experience with soil strength testing, as well as back-calculation of soil strength parameters for failed slopes in similar geologic conditions. For our "design" slope stability analysis, which was used as a basis for obtaining our recommended geotechnical parameters for initial site design, we assigned optimal range of soil parameters. We assumed the presence of perched groundwater and soil saturation in order to model possible broken drainage pipes in future. During slope stability analyses, both translational and circular failure surfaces were considered. A sensitivity analysis was also performed using various soil strength values, groundwater configurations and slip surface profiles. We analyzed a typical cross section using post-construction conditions in order to determine the FOS of the slope. Based on the results of our initial analyses (as discussed in following paragraphs), in our opinion, at present there are no slope instability hazards at the site provided site drainage is properly maintained during the design life of the structure. Based on the results of our slope stability analyses, we recommend a building setback of at least 40 feet from the edge of the riverbanks. lnherent Slope lnstability Risks: Historically, with construction in areas adjacent to riverbanks, there is an inherent risk associated with slope failures along the riverbanks. Although there was no active slope instability observed within the proposed building envelope or adjacent to the river banks, and the potential for future active slope failure is low, the owner is still responsible for taking any risks associated with any existing or future potential for instability at the site or in the river bank areas. Since this report and recommendations continued herein have been prepared in order to maintain a low degree of risk for future slope instability, all of our recommendations should be strictly followed. Earthquakes: Based on site geology, topography, and our preliminary evaluation, in our opinion, the site is generally not considered to be located within highly active seismic area. Therefore, anticipated ground motions in the region due to seismic activity are relatively low and do not pose a significanthazard. Ground accelerations in excess of 0.19 to -0.29 are not anticipated to occur at the site. Project No: 0464-WS19 August 26, 201 9 Page No: 5 of 19 Based on the results of our subsurface explorations and review of available literature (2009 lnternational Building Code), in our opinion, a site classification "C" may be used for this project. However, this site classification may be revised by performing a site-specific shear wave velocity study. Subsurface soil conditions at the site are not susceptible to liquefaction. Seismically induced slope instability may occur on a global scale impacting not just the site but also the surrounding area, however, such an evaluation was beyond our scope of services. A detailed seismic hazards evaluation of the site was beyond our scope of services. CONCLUSIONS AND RECOMMENDATIONS Based on the results of our geotechnical evaluation, in our opinion, the site is suitable for the proposed construction provided following recommendations are strictly followed. lt should be noted that our conclusions and recommendations are intended as design guidance. They are based on our interpretation of the geotechnical data obtained during our evaluation and following assumptions: . Proposed/Final site grades will not differ significantly from the current site grades; . Proposed foundations will be constructed on level ground; and a Structural loads will be static in nature Construction recommendations are provided to highlight aspects of construction that could affect the design of the project. Entities requiring information on various aspects of construction must make their own interpretation of the subsurface conditions to determine construction methods, cost, equipment, and work schedule. SHALLOW FOUNDATIONS We recommend that the proposed structure be supported on shallow spread footings designed and constructed in accordance with following criteria: Due to the presence of potential collapsible soils, over-excavate the collapsible soils from within the foundation areas to a depth of 24 inches below the bottom of footings, then surficial compact the excavated surface and call AGS for an open hole inspection. a Afterthe subgrades are approved byAGS, then install TENSAR 8X1100 geogríd tofurther stabilize the subgrades and to minimize the potential for differential movement due to potential presence of collapsible soils. The placement of the geogrid can be eliminated if the owner is Project No: 0464-WS19 August 26, 2019 Page No:6 of 19 a a a a a a a willing to assume a low risk of future differential settlements due to the presence of collapsible soils. Backfill with granular free-draining structural fill (or onsite sandy soils) compacted to at least 95% of ASTM D698 maximum dry density in order to achieve a "uniform subgrade" and to facilitate the placement of foundation drain. Over-excavation can also be minimized or eliminated based on the results of open-hole inspection or foundation subgrade inspection performed by AGS. Onsite materials may be used as structural fill, provided they are approved by AGS. Foundations bearing upon properly prepared and approved subgrade should be designed for a maximum allowable bearing pressure of 2,000 pounds per square foot (psf). Estimated final structural loads will dictate the final form and size of foundations to be constructed. However, as a minimum, we recommend bearing walls be supported by continuous footings of at least 18 inches in width. lsolated columns should be supported on pads with minimum dimensions of 24 inches square. Exterior footings and footings in unheated areas should extend below design/preferred frost depth of 36 inches. Continuous foundation walls should be reinforced in the top and bottom to span an unsupported length of at least I feet to further aid in resisting differential movement. As a minimum, additional reinforcement as shown in Figure 7 should be placed. Foundation/stem walls should be adequately designed as retaining walls and adequate drainage measures should be implemented as shown in Figure 8. We estimate total settlement for foundations designed and constructed as discussed in this section will be one inch or less, with differential settlements on the order of one-half to three- fourths of the total settlement. OpTlONllL: IIRILLED PIERS or DEEP FOUNÐATlCINS This option can be used if the owner wants to significantly reduce the risk of future differential settlements and related structural damage to a level of minimal to none, and to significantly increase the safety factors for foundation stability. Following recommendations are provided to highlight aspects of design and construction that could significantly affect the performance of the project. Entities requiring information on various aspects of design must make their own interpretation of the subsurface conditions. After the review of structural and architectural project plans and proposed loads and grading, we may recommend deeper soil borings to confirm or to modify following recommendations: Project No: 0464-WS19 August 26, 201 9 Page No: 7 of 19 a Piers should have a minimum design length of 20 feet below the bottom of foundation level The minimum pier diameter (D) will depend on the length (L) to diameter ratio (L/D). We recommend the L/D not exceed 30. A minimum pier diameter of 12 inches is recommended to facilitate proper cleaning and observation of the pier hole during construction. This recommendation can be modified after the discussions with your foundation contractor and/or structural engineer. Piers should be designed for an allowable end bearing capacity of 20,000 psf and an allowable skin friction value of 1 ,500 psf for the minimum 10 feet embedded portion of the pier into the medium dense to dense material present below a depth of 10 feet. Where there will be tension loads or uplift on the piers, the tension loads should be resisted by skin friction of the pier embedded below 10 feet of existing ground surface. The skin friction value of 1,250 psf can be used to calculate uplift capacity. Some movement of drilled pier foundations should be anticipated to mobilize skin friction. We estimate the required movement will be on the order of 118 to 114 inch. Differential movement between adjacent piers may equalthe total movement. All axially loaded piers should have a minimum center-to-center spacing of at least three pier diameters (3D). All laterally loaded piers should have a minimum center-to-center spacing of at least six pier diameters (6D) in the direction parallel to pier loading, and 2.5 diameters (2.5D) in the direction perpendicular to pier loading. Piers placed closer than these values should be designed using the appropriate reduction factors to account for group action. For the final design, the exact geometry of the pier group should be submitted to us for review and approval so that appropriate modifications can be made to our recommendations. Piers should be adequately reinforced to their full length. Reinforcement should extend well into grade beams and walls. Steel to pier ratio of a minimum of 0.005 based on cross-sectional atea of pier is recommended. More reinforcement may be required from structural considerations. As a minimum, one #5 rebar per 18-inch pier diameter should be used to resist uplift tension generated by swelling soils. The project specifications should allow for modifications by geotechnical engineer during the pier installation. The contractor should mobilize proper equipment so that drilling in gravels/river rock or unanticipated hard materials can be achieved to required depths. The contractor should carefully review this report to account for all possibilities and extras in their bid to avoid high cost overruns. Project No: 0464-WS19 August 26, 201 9 Page No: I of '19 a a a a a a a a a a a a a The use of casing and dewatering equipment is anticipated. However, it is contractor's responsibility to make the determination regarding the use of casing and dewatering equipment. Mushrooming of the pier top should be avoided by not allowing the pier size to vary towards the ground surface. Drilled pier holes should be cleaned of loose material prior to concrete placement. Once the proper depth is achieved, the auger should be placed in the bottom of the hole and several high-speed revolutions should be made to clean the bottom. Loose cuttings should not remain in the bottom of the excavations prior to concrete placement. Concrete should be onsite and ready during drilling of piers. Concrete should be placed immediately after pier observations and measurements are made, and reinforcement is set within the hole. Groundwater was encountered during our investigation and is anticipated to be a significant factor during construction of the piers. Pier holes should not be left "open" overnight. Concrete to be placed in the piers should have a slump of 4 to 7 inches. lf more than 3 inches of water is present in the bottom of the pier hole, de-watering should be performed using a pump or tremie prior to concrete placement. lnstallation of drilled piers should be observed by a member of American GeoServices, LLC on a full-time basis to identify and confirm that subsurface conditions are consistent with those encountered in our soil borings, and to monitor construction procedures. Assuming that the pier length to diameter ratio (L/D) will be greater than 7, in our opinion, the Matlock and Reese method of analysis can be used for lateral load analyses. Therefore, the lateral soil-structure interaction of single shafts may be analyzed using the software application, LPILE developed by Ensoft, lnc (or equivalent such as COM624). This analysis procedure estimates the lateral load-displacement behavior based on elastic beam-column theory and soil reaction-displacement (p-y) curves. Deflection, bending moment and shear profiles at specified intervals along the length of the shaft are computed. For lateral load analysis, modulus of horizontal subgrade reaction values of 20 tcf and 35 tcf may be used for the overburden soils present in upper 10 feet and denser materials present below 10 feet, respectively. Resistance to lateral load in upper 5 feet should be neglected. As noted earlier, all laterally loaded piers should have a minimum center-to-center spacing of at least six pier diameters (6D) in the direction parallel to pier loading, and 2.5 diameters (2.5D) in the direction perpendicular to pier loading. Piers placed closer than these values should be designed using the appropriate reduction factors to account for group action. For the final design, the exact geometry of the pier group should be submitted to us for review and Project No: 0464-WS19 August 26, 201 9 Page No: 9 of 19 o approval so that appropriate modifications can be made to our recommendations. Total lateral load versus deflection graph for the pier group can be developed by adding the lateral load resistance of piers at selected deflections. a For a detailed LPILE analysis, we should be contacted to provide specific input soil parameters or to review input parameters and to participate in the pile design along with project structural en gineers. $TRUCTURAL FLOCIR & GRAWL SPACE We understand a structural/framed floor with crawl space may be used for this project. The grade beams (if used) and floor system should be physically isolated from the underlying soil materials with crawl-space type construction. The void or crawl space of minimum of 6 inches or whatever minimum current Uniform Building Code (UBC) requirement is. For crawl-space construction, various items should be considered in the design and construction that are beyond the scope of geotechnical scope of work for this project and require specialized expertise. Some of these include design considerations associated with clearance, ventilation, insulation, standard construction practice, and local building codes. lf not properly drained and constructed, there is the potential for moisture to develop in crawl-spaces through transpiration of the moisture/groundwater within native soils underlying the structure, water intrusion from snowmelt and precipitation, and surface runoff or infiltration of water through irrigation of lawns and landscaping. ln crawl space, excessive moisture or sustained elevated humidity can increase the potential for mold to develop on organic building materials. A qualified professional engineer in building systems should address moisture and humidity issues. CRAWL SPI\CE PERIMETER/UNDERDRAIN SYSTEM ln order for the crawl space to remain free of moisture, it is important that drainage recommendations are properly implemented, and adequate inspections are performed prior to the placement of concrete. As a minimum, subgrade beneath a structural floor system should be graded so that water does not pond. Perimeter drains and under-slab drains should be installed in conjunction with a sump pump system to eliminate the potential for ponding and any subsequent damage to foundation and slab elements. The lot-specific perimeter dewatering, and underdrain systems should be properly designed and connected to the area underdrain system or a sump-pump system for suitable discharge from the lot. a Project No: 0464-WS19 August 26, 201 9 Page No: 10 of 19 a Drainage recommendations illustrated in Figure 8 should be implemented. The subsurface drainage system should consist typically of 4-inch minimum diameter perforated rigid PVC or flexible pipe (rigid preferred due to depth of placement) surrounded by at least one pipe diameter of free draining gravel. The pipe should be wrapped in a geosynthetic to prevent fine soils from clogging the system in the future. The pipe should drain by gravity to a suitable all- weather outlet or a sump-pit. Surface cleanouts of the perimeter drain should be installed at minimum serviceability distances around the structure. A properly constructed drain system can result in a reduction of moisture infiltration of the subsurface soils. Drains which are improperly installed can introduce settlement or heave of the subsurface soils and could result in improper surface grading only compounding the potential issues. a The underdrain system should consist of adequate lateral drains and a main drain, regular clean out and inspection locations, and proper connections to the sump-pump system for discharge into suitable receptacles located away from the site. a The entire design and construction team should evaluate, within their respective field of expertise, the current and potential sources of water throughout the life of the structure and provide any design/construction criteria to alleviate the potential for moisture changes. lf recommended drain systems are used, the actual design/layout, outlets, locations, and construction means, and methods should be observed by a representative of AGS. S LAB.ON.G RADE AN D PERIMETERYU N DERDRAIN SYSTEM Groundwater is not expected to be at depths below the proposed foundation levels if excavation is performed during dry seasons. ln order to assure proper slab-on-grade construction (if used), following recommendations should be strictly followed: a A perimeter dewatering system should be installed to reduce the potential for groundwater entering slab-on-grade areas. The lot-specific perimeter dewatering should be properly designed and connected to the area underdrain system or a sump-pump system for suitable discharge from the lot. a As a minimum, drainage recommendations illustrated in Figure I should be implemented. The subsurface drainage system should consist typically of 4-inch minimum diameter perforated rigid PVC or flexible pipe (rigid preferred due to depth of placement) surrounded by at least one pipe diameter of free draining gravel. The pipe should be wrapped in a geosynthetic to prevent fine soils from clogging the system in the future. The pipe should drain by gravity to a suitable all-weather outlet or a sump-pit. Surface cleanouts of the perimeter drain should be installed at minimum serviceability distances around the structure. A properly constructed drain system can result in a reduction of moisture infiltration of the subsurface soils. Drains Project No: 0464-WS19 August 26, 201 9 Page No: 11 o'f 19 a which are improperly installed can introduce settlement or heave of the subsurface soils and could result in improper surface grading only compounding the potential issues. The entire design and construction team should evaluate, within their respective field of expertise, the current and potential sources of water throughout the life of the structure and provide any design/construction criteria to alleviate the potential for moisture changes. lf recommended drain systems are used, the actual design/layout, outlets, locations, and construction means, and methods should be observed by a representative of AGS. The "Slab Performance Risk" associated with native soils is "Low". Therefore, the slab can be constructed as a slab-on-grade provided the owner is aware that there is still potential risk of some slab movement due to presence of possibly collapsible soils. Proper wetting of the subgrade to obtain soil moisture content in the range of 2Q-22% and/or moisture-conditioning and recompaction of onsite materials for upper 2 feet should reduce the risk of movement. lf the owner is not willing to assume any risk, then a structural floor slab system option should be considered. Another option is to over-excavate the slab area and reinforce the subgrades using TENSAR 8X1100 geogrid as per the recommendations given for the over-excavation of the foundation areas. The actual slab movements that will occur on a particular project site are very difficult, if not impossible, to predict accurately because these movements depend on loads, evapo- transpiration cycles, surface and subsurface drainage, consolidation characteristics, swell index, swell pressures and soil suction values. The actual time of year during which the slab-on-grade is constructed has been found to have a large influence on future slab-on-grade movements. Slab heaves or settlements are normally defined in terms of "total" and "differential" movement. "Total" movement refers to the maximum amount of heave or settlement that the slab may experience as a whole. "Differential" movement refers to unequal heave or settlement that different points of the same slab may experience, sometimes over relatively short horizontal distances. Differential movements are arbitrarily determined to be one-half of the total movement in soils exhibiting Low Slab Performance Risk. Greater differential movements can occur in areas where expansive soils have been encountered and where the natural soils abruptly transition to fill material. For design of floor slabs, a modulus of subgrade reaction of 200 pounds per cubic inch (pci) may be used. Based on the results of our analyses, we believe that interior floor slabs designed as recommended above and constructed as recommended in following paragraphs could result in "total" movement of approximately up to 1-inch with "differential" movement on the order of half the total movement. Project No: 0464-WS19 August 26, 201 9 Page No: 12 ol 19 We recommend that the construction measures outlined in the following paragraphs be followed to reduce potential damage to floor slabs, should excessive wetting of the subsurface soils occur: o Design and construct the floor slab to move independently of bearing members (floating slab construction). Provide slip joints around exterior walls and interior columns to allow free vertical movement of the slabs. Frequent control joints should be provided at about 10 feet spacing in the floor slab to reduce problems with shrinkage and cracking according to ACI specifications. Controljoint spacing is a function of slab thickness, aggregate size, slump and curing conditions. The requirements for concrete slab thickness, joint spacing, and reinforcement should be established by the designer, based on experience, recognized design guidelines and the intended slab use. Placement and curing conditions will have a strong impact on the final concrete slab integrity. Floor slabs should be adequately reinforced with welded wire mesh andsteel rebar. Structural engineer should include steel rebar in addition to welded wire mesh in order to reduce the risk of differential movement due to bending over I feet of unsupported length. a a a The need for a vapor barrier will depend on the sensitivity of floor coverings to moisture. lf moisture sensitive floor coverings are proposed for portions of the proposed structure, a capillary break material, typically consisting of a "clean" gravel, should be considered. We can provide additional recommendations if this is the case. Provided gravel is desired below the slab, a layer of 4 to 6 inches can be used. Plumbing passing through slabs should be isolated from the slabs and provided with flexible connections to allow for movement. Under slab plumbing should be avoided if possible and should be brought above the slab as soon as possible. a lf slab-bearing partitions are used, they should be designed and constructed to allow for movement. A minimum of 2 inches of void space (as illustrated in Figure 3) should be maintained below or above partitions. lf the void is provided at the top of partitions, the connections between the interior, slab-supported partitions and exterior foundation supported walls should allow for differential movement. o Where mechanical equipment and HVAC equipment are supported on slabs, we recommend provision of a flexible connection between the furnace and ductwork with a minimum of 2 inches of vertical movement. RETAINING WALL Retaining walls for at-rest conditions can be designed to resist an equivalent fluid density of 55 pcf for on-site fill materials if needed only imported granular backfill meeting CDOT Class 1 structural backfill should be used. Retaining walls for unrestrained conditions (free lateral Project No: 0464-WS19 August 26, 201 9 Page No: 13 of 19 movement) can be designed to resist an equivalent fluid density of 35 pcf for on-site fill materials and 35 pcf for imported granular backfill or CDOT Class 1 structural backfill. For passive resistance of unrestrained walls, we recommend passive resistance of 300 psf per foot of wall height. A coefficient of friction value of 0.35 may be used for contact between the prepared soil surface and concrete base. The above recommended values do not include a factor of safety or allowances for surcharge loads such as adjacent foundations, sloping backfill, vehicle traffic, or hydrostatic pressure. We should be contacted to provide additional recommendations for any specific site retaining conditions. Retaining wall backfill should be placed in strict accordance with our earthwork recommendations given below and as illustrated in Figure 8. Backfill should not be over-compacted in order to minimize excessive lateral pressures on the walls. As a precautionary measure, a drainage collection system (drains or geosynthetic drains) should be included in the wall design in order to minimize hydrostatic pressures. A prefabricated drainage composite or drain board such as the MiraDrain 2000 or an engineer-approved equivalent may be installed along the backfilled side of the basement foundation wall. EARTHWORK CONSTRUCTION Site grading should be carefully planned so that positive drainage away from all structures is achieved. Following earthwork recommendations should be followed for all aspects of the project. Fill material should be placed in uniform horizontal layers (lifts) not exceeding I inches before compacting to the required density and before successive layers are placed. lf the contractor's equipment is not capable of properly moisture conditioning and compacting 8-inch lifts, then the lift thickness shall be reduced until satisfactory results are achieved. Clays or weathered sandstone/claystone bedrock (if encountered) should not be re-used onsite except in landscaped areas. lmport soils should be approved by AGS prior to placement. Fill placement obseryations and fill compaction tests should be performed by AGS Engineering in order to minimize the potential for future problems. Fill material should not be placed on frozen ground. Vegetation, roots, topsoil, the existing fill materials, and other deleterious material to depth of approximately 6 inches should be removed before new fill material is placed. On-site fill to be placed should be moisture treated to within 2 percent of optimum moisture content (OMC) for sand fill and from OMC to 3-4 percent above OMC for clay and weathered bedrock. Project No: 0464-WS19 August 26, 201 9 Page No: 14 o'f 19 Fill to be placed in wall backfill areas and driveway areas and all other structural areas should be compacted to 95% of Standard Proctor (ASTM D 698) dry density or greater. Compaction in landscape areas should be 85% or greater. lmported structural fill should consist of sand or gravel material with a maximum particle size of 3 inches or less. ln addition, this materialshall have a liquid limit less than 30 and a plasticity index of 15 or less" Structural fill should also have a percent fine between 15 to 30 percent passing the No. 200 sieve. Structural fill should be moisture conditioned to within 2 percent of OMC and compacted to at least 95 percent of Standard Proctor (ASTM D698) dry density. ln our opinion, the materials encountered at this site may be excavated with conventional mechanical excavating equipment. For deeper excavations, heavier equipment with toothed bucket may be required. Although our soil explorations did not reveal "buried" foundation elements or other structures or debris within the building footprint, these materials may be encountered during excavation activities. Debris materials such as brick, wood, concrete, and abandoned utility lines, if encountered, should be removed from structural areas when encountered in excavations and either wasted from the site or placed in landscaped areas. Temporary excavations should comply with OSHA and other applicable federal, state, and local safety regulations. ln our opinion, OSHA Type B soils should be encountered at this site during excavation" OSHA recommends maximum allowable unbraced temporary excavation slopes of 1.25:1(H:V) for Type B soils for excavations up to 10 feet deep. Permanent cut and fill slopes are anticipated to be stable at slope ratios as steep as 2H:1V (horizontal to vertical) under dry conditions" New slopes should be revegetated as soon as possible after completion to minimize erosion. We recommend a minimum of 12feet of clearance between the top of excavation slopes and soil stockpiles or heavy equipment or adjacent structures. This setback recommendation may be revised by AGS once the project plans are available for review. lf braced excavations or shoring systems are to be used or needed, they should be reviewed and designed by AGS" lt should be noted that near-surface soils encountered at the site will be susceptible to some sloughing and excavations should be periodically monitored by AGS's representative. The proposed excavation should not adversely impact any existing structures. Proper shoring and/or underpinning should be used to maintain the stability of existing structure as well as the excavated faces of the new construction area. It should be noted that the above excavation recommendations are commonly provided by local consultants. The evaluation of site safety during construction, stability of excavated slopes and Project No: 0464-WS19 August 26, 201 9 Page No: l5 of 19 cuts, and overall stability of the adjacent areas during and after construction is beyond our scope of services. At your request, we can provide these services at an additional cost. During construction in wet or cold weather, grade the site such that surface water can drain readily away from the building areas. Promptly pump out or othenvise remove any water that may accumulate in excavations or on subgrade surfaces and allow these areas to dry before resuming construction. Berms, ditches and similar means may be used to prevent storm water from entering the work area and to convey any water off-site efficiently. lf earthwork is performed during the winter months when freezing is a factor, no grading fill, structural fill or other fill should be placed on frosted or frozen ground, nor should frozen material be placed as fill. Frozen ground should be allowed to thaw or be completely removed prior to placement of fill. A good practice is to cover the compacted fill with a "blanket" of loose fill to help prevent the compacted fill from freezing overnight. The "blanket" of loose fill should be removed the next morning prior to resuming fill placement. During cold weather, foundations, concrete slabs-on-grade, or other concrete elements should not be constructed on frozen soil. Frozen soil should be completely removed from beneath the concrete elements, or thawed, scarified and re-compacted. The amount of time passing between excavation or subgrade preparation and placing concrete should be minimized during freezing conditions to prevent the prepared soils from freezing. Blankets, soil cover or heating as required may be utilized to prevent the subgrade from freezing. GENERAL DRAINAGE Proper drainage is criticalfor achieving long-term stability and overall success. ln general, where interior floor elevations are situated at an elevation below proposed exterior grades, we recommend installation of a perimeter drains around the exterior grade beam and foundations as illustrated in Figure L ln addition, drain laterals that span the crawl space are recommended to prevent ponding of water within the crawlspace (if used). lf necessary, AGS can provide further recommendations for the exterior drain system and a typical drain detail. Groundwater was encountered at depth at the time of our explorations. However, based on the weather and surface water run-off conditions in the site vicinity area during construction, site may require pumping and other dewatering methods during construction. Proper surface drainage should be maintained at this site during and after completion of construction operations. The ground surface adjacent to buildings should be sloped to promote rapid run-off of surface water. We recommend a minimum slope of six inches in the first five Project No: 0464-WS19 August 26, 2019 Page No: 16 of 19 horizontal feet for landscaped or graveled areas. These slopes should be maintained during the service life of buildings. lf necessary, adequate interceptor drains should be installed on uphill sides to intercept any surface water run-off towards the site. Landscaping should be limited around building areas to either xeri-scaping, landscaping gravel, or plants with low moisture requirements. No trees should be planted or present within 15 feet of the foundations. lrrigation should be minimal and limited to maintain plants. Roof downspouts should discharge on splash-blocks or other impervious surfaces and directed away from the building. Ponding of water should not be allowed immediately adjacent to the building. It is important to follow these recommendations to minimize wetting or drying of the foundation elements throughout the life of the facility. Construction means and methods should also be utilized which minimize improper increases/decreases in the moisture contents of the soils during construction. Again, positive drainage away from the new structures is essential to the successful performance of foundations and flatwork and should be provided during the life of the structure. Paved areas and landscape areas within 10 feet of structures should slope at a minimum grade of 10H:1V away from foundations. Downspouts from all roof drains, if any, should cross all backfilled areas such that they discharge all water away from the backfill zones and structures. Drainage should be created such that water is diverted away from building sites and away from backfill areas of adjacent buildings. CONCRETE CONSTRUCTION Concrete sidewalks and any other exterior concrete flatwork around the proposed structure may experience some differential movement and cracking. While it is not likely that the exterior flatworks can be economically protected from distress, we recommend following techniques to reduce the potential long{erm movement: Scarify and re-compact at least 12 inches of subgrade material located immediately beneath structures. . Avoid landscape irrigation and moisture holding plants adjacent to structures. No trees should be planted or present within 15 feet of the foundations. . Thicken or structurally reinforce the structures. We recommend Type l-ll cement for all concrete in contact with the soil on this site. Calcium chloride should not be added. Concrete should not be placed on frost or frozen soil. Concrete must be protected from low temperatures and properly cured. Project No: 0464-WS19 August 26, 2019 Page No: 17 oÍ 19 a LIMITATIONS Recommendations contained in this report are based on our field observations and subsurface explorations, limited laboratory evaluation, and our present knowledge of the proposed construction. lt is possible that soil conditions could vary between or beyond the points explored. lf soil conditions are encountered during construction that differ from those described herein, we should be notified so that we can review and make any supplemental recommendations necessary. lf the scope of the proposed construction, including the proposed loads or structural locations, changes from that described in this report, our recommendations should also be reviewed and revised by AGS. Our Scope of Work for this project did not include research, testing, or assessment relative to past or present contamination of the site by any source. lf such contamination were present, it is very likely that the exploration and testing conducted for this report would not reveal its existence. lf the Owner is concerned about the potential for such contamination, additional studies should be undertaken. We are available to discuss the scope of such studies with you. No tests were performed to detect the existence of mold or other environmental hazards as it was beyond Scope of Work. Local regulations regarding land or facility use, on and off-site conditions, or other factors may change over time, and additional work may be required with the passage of time. Based on the intended use of the report within one year from the date of report preparation, AGS may recommend additional work and report updates. Non-compliance with any of these requirements by the client or anyone else will release AGS from any liability resulting from the use of this report by any unauthorized party. Client agrees to defend, indemnify, and hold harmless AGS from any claim or liability associated with such unauthorized use or non-compliance. ln this report, we have presented judgments based partly on our understanding of the proposed construction and partly on the data we have obtained. This report meets professional standards expected for reports of this type in this area. Our company is not responsible for the conclusions, opinions or recommendations made by others based on the data we have presented. Refer to American Society of Foundation Engineers (ASFE) general conditions included in an appendix. This report has been prepared exclusively for the client, its' engineers and subcontractors for the purpose of design and construction of the proposed structure. No other engineer, consultant, or contractor shall be entitled to rely on information, conclusions or recommendations presented in this document without the prior written approval of AGS. Project No: 0464-WS19 August 26, 201 9 Page No: 18 of 19 We appreciate the opportunity to be of service to you on this project. lf we can provide additional assistance or observation and testing services during design and construction phases, please call usat 1 8882764027. Sincerely, Sam Adettiwar, MS, PE, GE, P.Eng, M.ASCE Senior Engineer Attachments Project No: 0464-WS19 August 26, 201 9 Page No: 19 of 19 FIGURES ! Ê€rÉiéroÞ'td 9--' êsPe-tlqittld I tq¡ ft¡*çer¡ Mrsntsll ¡ls¡¡* {t ',fJffi"giå$ç '%. \. -2t' :'{i,z:?:,r:æ SF Ìqlql comadf ñ i ànd Ì8Ê 6ffi,ùni Y Ès\*, ðtÐðþ" *q. ':& Ë Éo6é' ,f rrET"* €+*-:\n tL* ¿ ?*tø L ç E} $.nosrin¿,Èo*itø**r $ v*e¡aocøa su¡ply &ffif vÈát!eå"tÍ $Þfrrfì¡ãlÞi rhnr t"ærtúanett Ç liEir @ LOCATION '4â. ö 1 Eg @ EI Vã0ey-für¡t Gled{ood Sûrin!û å- I o'À filirr3€.'gr4tPll-9 æ.. i -'' -- " --*- : 1 9t :: z FIGURE 1: SITE LOCATION MAP !'i'"ï..Itø:m l I 5rü! IEFERENCE: ìOOGLE MAPS rE MËRlt'tl.¡ üEüSËEYICË5 N lô^ô T^n^^n^nut^ tt^nô ***üFåTet*tt . ilr*dm¡çr$r*È*ûnt NOTE: SCHEMATIC PLAN TO SHOWAPPROXIMATE SUBSURFACE EXPLORATION LOCATION ONLY;NOT SURVEYED. LBGEND:f\ Y DESTcNATES suBsuRFAcE EXpLoRATToN LocATroN, ByAMERTcAN cEosERVrcES, LLc. , Aucusr 2019 sEE EXPLORATION LOG IN APPENDIX FOR FURTHER DETAILS. AMERICAN CEOSERVICES 888.276,4027 " ¡ñericârgeoserlics.com N REFERENCE: PITKIN COUNTY COLORADO GIS -*/FIGURE 2: SCHEMATIC SITE PLAN -l.'ì t.\*aa :5 663 REFERENCE: U.S. GEOLOGICAL MAPS Åtu1 Ëtt tüÅ N ü Ltsþ-flv tc Ës ftrn loungr ilthrlr.ll*n dofirrli[r {}lo}¡cene} Strtnn¡,ch¡nnel. ll¡od.fl¡ln¡ ¡rd l¡1' ferrrrce rlepnrllt {Hülûrðn€ ¡¡n.l låre f lr}lsroc.rs} i ! I \ 1 \ ,l i iI ¡I LEGEND ary ûe at l'o0r¡ger i€frãß* rrlluvlüm ûâlt flú¡s¡oefäül Cr¡llurlum {Holocono enrl lrte Pbl*lrrena) ilrtlfirsl l¡ll {lstert }}tlor!nú¡ Odf' N Qlo', I 1:It" lâ tl \ a J 'l{* "ìq'r it¡nQdfY :-,. - "'îi'r -., - i¡ I It I '"'élr È*l¡ ¿;t¡l¡Éi " r¡r$i¡e.aÉ.1r]¡s¡ri¡<¡rry¡FIGURE 3: GEOLOGIC MAP LEGEND syr,nboN Mãþ tlrrit Èlarnte , ¡"ll_rn Ã.()l t I't |Hm¡r loam, 1" to, t 12 percent slopes Totals for Area of 4rI Intefest Å,M ÉRlü¡\N ü ÉÕS L,ttV ¡tES As.p€il'Gytrsurn Areq, Çoloqado, Fal.ts of Eagler, Garfietrd, and trïtkin"Ëounties (Ct¡655 ) Aspen-Gypsurï'r Area, Colorado, Parts of @ Eagle, Garfield, and Pitkin Counties {cÐqF5), 6 P€reent ,'.l¡f ÂÐI Ifrü.ts/Ð4.2 N REFERENCE: WEB SOIL SURVEY f Ëlåi4,li¡E - ¡mricgl'âäl¡'*r#tren FIGURE 4: SOIL SURVEY MAP <tr,Y I ^-^,--J cJt*ps* * ¡*-selis-ç",i tl¡ fu iEe ker' W-34' Éparir:E Fqrk.€i,rpí t *;rrîd*r *+liar,zi*4e zç'.1 i(J- i 4 tt*,¡ân l$Jr ft c-Ðls,Æ:*' j geos9i19 EG-14 ú¡¿;tæ artá. *be¡;s earzé. depçxí3* æ EG- I d Cr+ta¿eous ¡nd Tentie ry Fa"nrsl,on-. Ø Fb- lq t'.rËFi}r ie f,frÍ13ÌlÐns SL¿úe hitlz.aade"tzl -* lìich : i54II A,\,IER ICÅN CIÛSü RVIC ffi ÐL*rå.: N IEFERENCE: )OLORADO GEOLOGICAL iURVEY 8$-&21 ¡t.ú.ë - øzì* sFw*icw FIGURE 5: COLLAPSIBLE SOILS MAP -* :a:.:,. :t- .'PÆJ¡TG V',I €t|,å ,77 sa Ê .a: rY'É Ê ç^sr r¡irrçeta'i ç-LOCATION 4"u,",!3Þl¡tlqþ a '4."^. ,¡* Cdtle Gæk u þa 2 :7 4. 'Y' :: ": ìi 'lr. -..+V. Cj\t!* v'- ,.d IEFERENCE: )OLORADO LANDSLIDE {VENTORY ,.ç Cclgradq*l ándsf ide,i nvÊntÕ ry-n,ff¡r trGmP ìËd-lar+dEridel-irom 24K-maps : eüm p ;+d-l ancj si'd e-t-f rum-.!Ë- i üC' (-rnepsr cempiî*d: .lgnd sëådeE-tr'æm- HB 1 Û'4 ? -æa'psI rG * od ag:c{3a.r åds I n dÊ-x E Å['t[Kle/\N úgtsûllV tCfS N 4r-'éèat"¿3 L.4:. t - rëekq\Á{4r*íf$ffi FIGURE 6: LANDSLIDE HAZARD MAP NOTES: A. ADDITIONAL REINFORCEMENT, #4 CONTINUOUS BAR, BOTTOM OF FOOTING. B. ADDITIONAL REINFORCEMENT, #4 AT 48' C/C, TOP OF FOOTING. G. REINFORCEMENT AS PER STRUCTURAL ENGINEER'S DESIGN. AS A MINIMUM, USE #4 AT 48" CIC. RETAINING WALL DIMENSIONS AND REINFORCEMENT TO BE DONE BY PROJECT STRUCTURAL ENGINEER BASED ON GEOTECHN ICAL RECOMMENDATIONS. CONCRETE FOOTING TO BE DIMENSIONED BY PROJECT STRUCTURAL ENGINEER BASED ON GEOTECHNICAL RECOMMENDATIONS ADDITIONAL FOOTING REINFORCEMENT DETAIL AMERICAN CEOSERVICES 888.2?6..$2? - nmericangeos€nies.com FIGURE 7: TYPICAL DETAILS FLEXIBLE ADH ESIVE EQUIVALENT, 4'ABOVE GROUND; MAINTAIN LEAK-FREE COMPACTED EARTH BACKFILUSOIL CAP (DO NOT USE rF STEM WALL rS DESIGNED AS A RETAINING WALL. IN CASE OF RETAINING WALL, USE FREE-DRAINING CRUSHED ROCK FILL TO AVOI D HYSROSTATIC PRESSURE. LEAK-FREE AND ADEQUATE CAPACITY DOWNSPOUTS 4" MINIMUM 3" THICK DECORATIVE GRAVEL, ROCK OR BARK LAYER AT LEAST 4 FT LONG 20 MIL THICK POLY SHEET LINER AT LEAST 4FT LONG; EXTEND 4' ABOVE GROUND & 36" BELOW GROUND DOWNSPOUT & MOISTURE BARRIER DETAIL * EXTEND DOWNSPOUT BEYOND DECORATIVE LAYER, 10H:1V GRADE; WITHOUT CAUSING ADVERSE IMPACT ON ADJACENT PROPERTIES; DISCHARGE ONTO SPLASH BLOCKS. FOUNDATION/STEM WALL - POLYETHYLENE FILM GLUED TO FOUNDATION WALL AND EXTENDED BELOW THE DRAIN AS SHOWN MIRAFI 140 N FILTER FABRIC OR EQUIVALENT f- 12'MlN r I-SLAB-ON-GRADE WITH EXPANSTON JOTNTS OR CRAWL-SPACEI 6" MIN OVER-EXCAVATION (sEE NOTE B)EXCAVATED TRENCH, NEAR VERTICAL TO 0.5H:1VFREE-DRAINING CLEAN CRUSHED ROC}IGRAVEL \-,SUBGRADE, IN-SITU SOITì (sEE NOTE C) PERIMETER OR FOUNDATION DRAIN DETAIL NOTES:4.4-INCH DIAMETER PERFORATED PIPE PLACED 2" ABOVE DRAIN SUBGRADE EMBEDDED lN FREE-DRAINING GRAVEL OR CRUSHED ROCK ENVELOPE WITH2Yo GRADE TO SUMP PIT OR DISCHARGED TO A SUITABLE RECEPTACLE SUCH THATON-SITEAS WELL AS OFF-SITE STABILITY IS NOT ADVERSELY IMPACTED. B. DEPTH BASED ON OPEN HOLE INSPECTION, FOR SHALLOW FOUNDATION OPTION. C. ALL FOUNDATION OR OVER-EXCAVATED SUBGRADES MUST BE INSPECTED AND APPROVED BY A AMERICAN CEOSERVICES 6"MlN J* OFFSET FORANY SPRINKLER HEADS; PART CIRCLE SPRAYING AWAY FROM BUILDING SLOPE TO DRAIN AWAY FROM STRUCTURE, 10H:1V (sEE DOWNSPOUT DETATL) GEOTECHNICAL ENGINEER. 'fl/8S8.2?ó,402?- {melihgoserricc$com FIGURE 8: DRAINAGE DETAILS APPENDIX B1 1054 River Bend way,Glenwood Springs CO 81601 Project Number 0464-WS19 Drill Rig: SoilAuger & Wllliamson Drive Probe Geologist/Engineer SMA Ground Elevation See Figures Date Drilled 08-28-19 Total Depth of Exploration 12.5 Feet Borehole Diameter 4 OD lnches Depth to Water !2 Feet ct)oJ .9 o. ct (9 Description / Lithology oo o.oo -9 CL E G' U' tr oo =o m t-o- U' E Þo ooo É. s E =.2o = oo. oo s J o- s JJ s oìU' ço Io. Eoo 0 u $ D 0 SM ML/ CL GP/ GM SILTY SAND, brown to tan, fine to medium grained, loose to medium dense, dry SILTY SANDY CLAY TO CLAYEY SANDY SILT, tan, fine to medium grained, loose to medium dense, dry SANDY to SILTY GRAVEL, tan, fine to coarse grained, medium dense to dense, moist to wet End of Borehole at 12.5 feet. Groundwater seepage was not encountered during or at the completion of drilling. Soil description based on exploration, soils and geologic maps reviews, and localexperience. See figures and appendix for more information. -2.5- -5.0- J.5- 10.0- V îru 2-3-3 3-3-3 4-5-6 8-17-21 50+ 30 2C -0.9 o/c @ 1000 psf 4l/ åY åï::*)*cjosERV ICES Page 1 82 1054 River Bend way,Glenwood Springs CO 81601 Proiect Number 0464-WS19 Drill Rig: SoilAuger & Wllliamson Drive Probe GeologisUEngineer SMA Ground Elevation See Figures Date Drilled 0B-28-1 9 Total Depth of Exploration 12.5 Feet Borehole Diameter 4 OD lnches Depth to Water 11.0 Feet ctoJ .9 CLg o Description / Lithology oo .C o.oo -9 CL E (E(t, q o C) ìo m t-À Ø E Ðo ooo É, s o .9o = oo. oo s J o- s JJ s oì U, co -9 CL Eoo SM ML/ CL 0 þ û ûi û U G GM 0 0 o* ü SILTY SAND, brown to tan, fine to medium grained, loose to medium dense, dry SILTY SANDY CLAY TO CLAYEY SANDY SILT, tan, fine to medium grained, loose to medium dense, dry .5- .0- SANDY to SILTY GRAVEL, tan, fine to coarse grained, medium dense to dense, moist to wet E 0.0- End of Borehole at 12.5 feet. Groundwater seepage was not encountered during or at the completion of drilling. Soil description based on exploration, soils and geologic maps reviews, and localexperience. See figures and appendix for more information. V t 12.5 2-3-4 3-4-3 3-5-5 17-18-22 50+ 32,21 -0.6 o/o@ 1 000 psf ¿41 -z AMERICAN CEOSERVICES " l7 888.276.402? - añcdcrngmscr{ic.\com Page 1 4VåY"'H[$ë.' DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION UNIFIED SOIL CLASSIFICATION SYSTEM UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART LABORATORY CLASSIFIGATION CRITERIA COARSE-GRAINED SOILS (more than 507o of material is larger than No. 200 sieve size.) GW Well-g raded gravels, g ravel-sand mixtures, little or no fines C,, = Doo qreater than 4:C^ = Dso between 1 and 3" D1o ' Dlo xDeo --GW GP Poorly-graded gravels, gravel-sand mixtures, little or no fines GP Not meeting all gradation requirements for GW Atterberg line or P.l.GM limits below "A" less than 4GMSilty gravels, gravel-sand-silt mixtures GC Clean Gravels than 57o Gravels with fines than 12o/ofi GRAVELS More than 507o of coarse fraction larger than No. 4 sieve size Clayey g ravels, gravel-sand-clay mixtures GC Atterberg limits above "A line with P.l. greater than Above "4" line with P.l. between 4 and 7 are borderline cases requiring use of dual symbols "" = + sreater than 4;Cc =E:fu between 1 and 3 SWSWWell-graded sands, gravelly sands, little or no fines SP Poorly graded sands, gravelly sands, little or no fines Sp Not meeting all gradation requirements for GW SM Silty sands, sand-silt mixtures SM Atterberg limits below "A" line or Pl. less than 4 SC Clean Sands than 5% SANDS 507o or more of coarse fraction smaller than No. 4 sieve size Clayey sands, sand-clay mixtures SC Atterberg limits above "4" line with P.l. greater than 7 Limits plotting in shaded zone with Pl. between 4 andT are borderline cases requiring use of dual symbols. FINE-GRAINED SOILS (50% or more of material is smaller than No. 200 sieve size.) ML lnorganic silts and very fine sands, rock flour, silty of clayey fine sands or clayey silts with sl¡ght plasticity Determine percentages ofsand and gravel from grain-size curve. Depending on percentage of flnes (fraction smaller than No. 200 sieve size), coarse-grained soils are classifìed as follows: Less than 5 percent ¡¡ore inan tä þercent ... ....'. 5 to 12 percent GW GP, SW SP GM, GC, SM, SC Borderline cases requiring dual symbols CL lnorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays PLASTICITY GHART SILTS AND CLAYS Liquid limit less than SOYo OL Organic silts and organic silty clays of low plasticity MH lnorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts CH lnorganic clays of high plasticity, fat clays SILTS AND CLAYS Liquid limit 50% or greater OH Organic clays of medium to high plasticity, organic silts HIGHLY ORGANIC sorLs PT Peat and other highly organic soils 60 s:50 E- x40 lrJcl =30t-özo trøt J o- CH . ALINE; | = 0,73(Ll.-20) CL MH.,OH 'vlabl I 0 10 20 30 40 50 60 70 80 90 100 LTQUTD LrMrr (LL) (%) 0 DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION LABORATORY/FIELD TESÏING DEFINITIONS FOR EXPLORATION LOGS CONSISTENCY OF COHESIVE SOILS NCY sTP (BPF) VERY STIFF HARD -- RELATIVE DENSITY OF COHESIONLESS SOILS DENSITY VE.RVtóóSí_- DD WD MC PL LL PI oc S SG c o QU DRY DENSTTY (PCF) wET DENSTTY (PCF) MOTSTURE CONTENT (%) PTASTTC LrMrT (%) LTQUTD LrMrT (%) PLASTICIry INDEX oRGANTC CONTENT (%) SATURATTON PERCENT (%) SPECIFIC GRAVIry COHESION ANGLE OF INTERNAL FRICTION UNCONFINED COMPRESSION STRENGTH PERCENT PASSING THE #2OO SIEVE CALIFORNIA BEARING RATIO VANE SHEAR POCKET PENETROMETER DRIVE PROBE STANDARD PENETRATION TEST BLOWS PER FOOT (N VALUE) SHELBY TUBE SAMPLE GROUNDWATER ROCK QUALITY DESIDNATION TEST PIT BORING HANDAUGER LOOSE -- MEúú.i¡ ó.ÈñSE -- DENSE PARTICLE SIZE IDENTI FICATION NAME PP (TSF) LESS THAN 0.25 0.25 - 0.5 0.5 - 1.0 1.0 - 2.0 2.O - 4.0 OVER 4.0 sPT (BPF) 0-4 5-10 11-30 31 -50 50+ '#2O0 = CBR = VS= PP= DP= SPT = BPF = SH= GW= RQD = TP= $= HA= DIAMETER (rNcHES) SIEVE NO. ROCK BLOCK BOULDER COBBLE CLAY GRAIN SIZE FINE GRAINED ME DIUM GRAINED NS ARE DISTINGUISHABLE IN THE FIELD OR WITH HAND LENS RAINS ARE DISTINGUISHABLE WITH THE AID OF A HAND LENS. MOST GRAINS ARE DISTINGUISHABLE WITH THE NAKED EYE. Væ GROUNDWATERLEVEUSEEPAGE ENCOUNTERED DURING EXPLORATION Y - STATIc GRoUNDWATER LEVELWITH DATE MEASURED VERY SOFT STIFF SOFT MEDIUM STIFF 30+ 5-8 0-1 2-4 9-15 16 - 30 >'120 GRAVEL COURSE- --"ÈiñE NO.4 NO. 10 12-'120 s-iz" " - -' 314-3 1t4 - 3t4 NO.40MEDIUM FINE SAND*--ec;ARsE--**- .425MM NO. 200 075 MM <0.005 MM COARSE GRAINED 0.04-0.2 tNcH -6.ott:oi.l1iñicn" DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION SPT EXPLORATIONS STANDARD PENETRATION TESTING IS PERFORMED BY DRIVING A 2 - INCH O.D. SPLIT. SPOON INTO THE UNDISTURBED FORMATION AT THE BOTTOM OF THE BORING WITH REPEATED BLOWS OF A 140 - POUND PIN GUIDED HAMMER FALLING 30 INCHES. NUMBER OF BLOWS (N VALUE) REQUIRED TO DRIVE THE SAMPLER A GIVEN DISTANCE WAS CONSIDERED A MEASURE OF SOIL CONSISTENCY. SH SAMPLING SHELBY TUBE SAMPLING IS PERFORMED WITH A THIN WALLED SAMPLER PUSHED INTO THE UNDISTURBED SOIL TO SAMPLE 2.0 FEET OF SOIL. AIR TRACK EXPLORATION TESTING IS PERFORMED BY MEASURING RATE OF ADVANCEMENTAND SAMPLES ARE RETRIEVED FROM CUTTINGS. HAND AUGUR EXPLORATION: TESTING IS PREFORMED USING ¡.3.25" DIAMETER AUGUR TO ADVANCE INTO THE EARTH AND RETRIEVE SAMPLES. DRIVE PROBE EXPLORATIONS: THIS'RELATIVE DENSIry" EXPLORATION DEVICE IS USED TO DETERMINE THE DISTRIBUTION AND ESTIMATE STRENGTH OF ÏHE SUBSURFACE SOIL AND DECOMPRESSED ROCK UNITS. THE RESISTANCE TO PENETRATION IS MEASURED IN BLOWS-PER-1 12 FOOT OF AN 11-POUND HAMMER WHICH FREE FALLS ROUGHLY 3.5 FEET DRIVING THE 0.5 INCH DIAMETER PIPE INTO THE GROUND. FOR A MORE DETAILED DESCRIPTION OF THIS GEOTECHNICAL EXPLORATION METHOD, THE SLOPE STABILITY REFERENCE GUIDE FOR NATIONAL FORESTS IN THE UNITED STATES, VOLUME I, UNITED STATES DEPARTMENT OF AGRICULTURE, EM-7170-13, AUGUST 1994, P.317- 321. CPT EXPLORATION CONE PENETROMETER EXPLORATIONS CONSIST OF PUSHING A PROBE CONE INTO THE EARTH USING THE REACTION OF A 2O.TON TRUCK. THE coNE RESTSTANCE (OC) AND SLEEVE FR|CT|ON (FS) ARE MEASURED AS THE PROBE WAS PUSHED INTO THE EARTH. THE VALUES OF QC AND FS (tN TSF) ARE NOTED AS THE LOCALTZED INDEX OF SOIL STRENGTH. ANGULARITY OF GRAVEL & COBBLES ANGULAR SUBANGULAR SúeRóúñoEo COARSE PARTICLES HAVE SHARP EDGES AND RELATIVELY PLANE SIDES WITH UNPOLISHED SURFACES. COARSE GRAINED PARTICLES ARE SIMILAR TO ANGULAR BUT HAVE ROUNDED EDGES. COARSE GRAINED PARTICLES HAVE NEARLY PLANE SIDES BUT HAVE WELL ROUNDED CORNERS AND EDGES. ROUNDED SOIL MOISTURE MODIFIER GRAINED PARTICLES HAVE SMOOTHLY CURVED SIDES AND NO EDGES. DRY MOIST WET WEATHERED STATE FRESH StfctirtY --- WEATHERED WEATHERED ABSENCE OF MOISTURE; DUSTY, DRY TO TOUCH DAMP BUT NO VISIBLE WATER WATER NO VISIBLE SIGN OF ROCK MA WEATHERING; PERHAPS SLIGHT DISCOLORATION IN MAJOR DISCONTINUITY SURFACES. INDICATES WEATHERING OF ROCK MATERIAL AND DISCONTINUIry SURFACES. ALL THE ROCK MATERIAL MAY BE DISCOLORED BY WEATHERING AND MAY BE SOMEWHAT WEAKER EXTERNALLY THAN ITS FRESH CONDITION. LESS THAN HALF OF THE ROCK MATERIAL IS DECOMPOSED AND/OR DISINTEGRATED TO SOIL. FRESH OR DISCOLORED ROCK IS PRESENT EITHER AS A CONTINUOUS FRAMEWORK OR AS CORE STONES. MORE THAN HALF OF THE ROCK MATERIAL IS DECOMPOSED AND/OR DISINTEGRATED TO SOIL. FRESH OR DISCOLORED ROCK IS PRESENT EITHER AS DISCONTINUOUS FRAMEWORK OR AS CORE STONE. HIGHLY WEATHERED COMPLETELY WEATHERED ALL ROCK MATERIAL IS DECOMPOSED AND/OR DISINTEGRATED TO SOIL. THE ORIGINAL MASS STRUCTURE IS STILL LARGELY INTACT, RESIDUAL SOIL ALL ROCK MATERIAL IS CONVERTED TO SOIL, THE MASS STRUCTUREAND MATERIAL FABRIC IS DESTROYED. THERE IS A LARGE CHANGE IN VOLUME, BUT THE SOIL HAS NOT BEEN SIGNIFICANTLY TRANSPORTED. Map Unit Description: Almy loam, 1 to l2 percent slopes---Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitk¡n Counties Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties 6-Almy Ioam, 1 to 12 percent slopes Map Unit Setting National map unit symbol: jq6l Elevation: 6,000 to 7,800 feet Mean annual precipitation: 12to 14 inches Mean annual air temperature: 42 to 46 degrees F Frost-free period: 85 to 105 days F a rm I a n d cl assifi c ation: Farm land of statewide importa nce Map Unit Composition Almy and similar soils: B0 percent Minor components: 20 percent Estimates are based on obseruations, descriptions, and transects of the mapunit. Description of Almy Setting Landform : Alluvial fans, hills Landform position (two-dimensional) : Footslope Down-slope shape: Linear Across-s/ope shape: Linear Parent material: Alluvium derived from calcareous sandstone and/or alluvium derived from calcareous shale Typical profile H1 -0toBinches: loam H2 - B to 26 inches; fine sandy loam H3 - 26 to 60 inches; sandy clay loam Properties and qualities S/ope; 1 lo 12 percent Depth to restrictive feature: More than B0 inches Natural drainage c/ass; Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 2.00 in/hr) Depth to water table: More than B0 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 8.6 inches) Interpretive groups Land capability classification (irrigated): 4e Land capability classification (nonirrigated): 4e Hydrologic Soil Group: B Ecological sife; Rolling Loam (R048AY29BCO) Othervegetative classificafion: ROLLING LOAM (null 20) USDA - Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8t26t20't9 Pagel o12 Map Unit Description: Almy loam, 1 to 12 percent slopes---Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Hydric soil rating: No Minor Gomponents Other soils Percent of map unit: 20 percent Hydric so/ rafing: No Data Source Information Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Version 9, Sep 10,2018 Soil Survey Area: Pitkin Counties Survey Area Data: USDÁY Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8t26t2019 Page2 ot 2 IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL ENGINEERING REPORT As the client of a consulting geotechnical engineer, you should know that site subsurface conditions cause more construction problems than any other factor. ASFE/the Association of Engineering Firms Practicing in the Geosciences offers the following suggestions and observations to help you manage your risks. A GEOTEGHNICAL ENG.NEERING REPORT IS BASED ON A UNIQUE SET OF PROJECT. SPECIFIC FAGTORS Your geotechnical engineering report is based on a subsurface exploration plan designed to consider a unique set of projectspecific factors. These factors typically include: the general nature of the structure involved, its size, and configuration; the location of the structure on the site; other improvements, such as access roads, parking lots, and underground utilities; and the additional risk created by scope- of-service limitations imposed by the client. To help avoid costly problems, ask your geotechnical engineer to evaluate how factors that change subsequent to the date of the report may affect the report's recommendations. Unless your geotechnical engineer indicates otherwise, do not use your geotechnical engineering report: MOST GEOTECHNICAL FINDINGS ARE PROFESSIONAL JUDGMENTS Site exploration identifies actual subsurface conditions only at those points where samples are taken. The data were extrapolated by your geotechnical engineer who then applied judgment to render an opinion about overall subsurface conditions. The actual interface between materials may be far more gradual or abrupt than your report indicates, Actual conditions in areas not sampled may differ from those predicted in your report. While nothing can be done to prevent such situations. you and your geotechnical engineer can work together to help minimize their impact. Retaining your geotechnical engineer to observe construction can be particularly beneficial in this respect. o when the nature of the proposed structure is changed. for example, if an office building will be erected instead of a parking garage, or a refrigerated warehouse will be built instead of an unrefrigerated one; o when the size, elevation. or configuration of the proposed structure is altered; ¡ when the location or orientation of the proposed structure is modified;. when there is a change of ownership; or .for application to an adjacent site. A REPORT'S RECOMMENDATIONS CAN ONLY BE PRELIMINARY The construction recommendations included in your geotechnical engineer's report are preliminary, because they must be based on the assumption that conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Because actual subsurface conditions can be discerned only during earthwork, you should retain your geo- technical engineer to observe actual conditions and to finalize recommendations. Only the geotechnical engineer who prepared the report is fully familiar with the background information needed to determine whether or not the report's recommendations are valid and whether or not the contractor is abiding by applicable recommendations. The geotechnical engineer who developed your report cannot assume responsibility or liability for the adequacy of the report's recommendations if another party is retained to observe construction. SUBSURFACE CONDITIONS CAN CHANGE A geotechnical engineering report is based on condi- tions that existed at the time of subsurface exploration. Do not base construction decisions on a geotechnical engineering report whose adequacy may have been affected by time. Speak with your geotechnical consult- ant to learn if additional tests are advisable before construction starts. Note, too, that additional tests may be required when subsurface conditions are affected by construction operations at or adjacent to the site, or by natural events such as floods, earthquakes, or ground water fluctuations. Keep your geotechnical consultant apprised of any such events. GEOTECHNICAL SERVICES ARE PERFORMED FOR SPECIFIG PURPOSES AND PERSONS Consulting geotechnical engineers prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated othenvise, your geotechnical engineer prepared your report expressly for you and expressly for purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the geotechnical engineer. No party should apply this report for any purpose other than that originally contemplated without first conferring with the geotechnical engineer. GEOENVIRONMENTAL CONCERNS ARE NOT AT ISSUE Your geotechnical engineering report is not likely to relate any findings, conclusions, or recommendations Geotechnical engineers cannot accept responsibility for problems that may occur if they are not consulted after factors considered in their report's development have changed. about the potential for hazardous materials existing at the site. The equipment, techniques, and personnel used to perform a geoe from nvironmental exploration differ substantially those applied in geotechnical engineering. Contamination can create major risks. lf you have no information about the potential for your site being contaminated. you are advised to speak with your geotechnical consultant for information relating to geoenvironmental issues. A GEOTECHNICAL ENGINEERING REPORT IS SUBJECT TO MISINTERPRETATION Costly problems can occur when other design profes- sionals develop their plans based on misinterpretations of a geotechnical engineering report. To help avoid misinterpretations, retain your geotechnical engineer to work with other project design professionals who are affected by the geotechnical report. Have your geotechnical engineer explain report implications to design professionals affected by them. and then review those design professionals' plans and specifications to see how they have incorporated geotechnical factors. Although certain other design professionals may be fam- iliar with geotechnical concerns, none knows 'as much about them as a competent geotechnical engineer. BORING LOGS SHOULD NOT BE SEPARATED FROM THE REPORT Geotechnical engineers develop final boring logs based upon their interpretation of the field logs (assembled by site personnel)and laboratory evaluation of field samples. Geotechnical engineers customarily include only final boring logs in their reports. Final boring logs should not under any circumstances be redrawn for inclusion in architectural or other design drawings. because drafters may commit errors or omissions in the transfer process. Although photographic reproduction eliminates this problem, it does nothing to minimize the possibility of contractors misinterpreting the logs during bid preparation. When this occurs. delays. disputes. and unanticipated costs ara the all-too-frequent result. To minimize the likelihood of boring log misinterpretation, give contractors ready access to the complete geotechnical engineering report prepared or authorized for their use. (lf access is provided only to the report prepared for you, you should advise contractors of the report's limitations. assuming that a contractor was not one of the specific persons for whom the report was prepared and that developing construction cost estimates was not one of the specific purposes for which it was prepared. ln other words. while a contractor may gain important knowledge from a report prepared for another party, the contractor would be well-advised to discuss the report with your geotechnical engineer and to perform the additional or alternative work that the contractor believes may be needed to obtain the data specifically appropriate for construction cost estimating purposes.) Some clients believe that it is unwise or unnecessary to give contractors access to their geo- technical engineering reports because they hold the mistaken impression that simply disclaiming responsibility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly construction problems. lt also helps reduce the adversarial attitudes that can aggravate problems to disproportionate scale. READ RESPONSIBILITY CLAUSES CLOSELY Because geotechnical engineering is based extensively on judgment and opinion, it is far less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against geotechnical engineers. To help prevent this problem, geotechnical engineers have developed a number of clauses for use in their contracts, reports, and other documents. Responsibility clauses are not exculpatory clauses designed to transfer geotechnical engineers' liabilities to other parties. lnstead, they are definitive clauses that identify where geotechnical engineers' responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take appropriate action. Some of these definitive clauses are likely to appear in your geotechnical engineering report. Read them closely. Your geotechnical engineer will be pleased to give full and frank answers to any questions. RELY ON THE GEOTECHNICAL ENGINEER FOR ADDITIONAL ASSISTANCE Most ASFE-member consulting geotechnical engineering firms are familiar with a variety of techniques and approaches that can be used to help reduce risks for all parties to a construction project, from design through construction. Speak with your geotechnical engineer not only about geotechnical issues, but others as well, to learn about approaches that may be of genuine benefit. You may also wish to obtain certain ASFE publications. Contact a member of ASFE of ASFE for a complimentary directory of ASFE publications. ASFE 8811 Colesville Road/Suite G106/Silver Spring, MD 20910 Telephone: 301 1565-2733 Facsimile: 301/589-2017 Subsurfoce Explorolions Soil Tesling Eorthwork Geolech Roek Me keE ,6eoph Retuining clu esrgn Pqvement Design Droinoge Evoluolions Groundwoler Sludies [nvironmentol Assels Building Assessmenls AMERI CANCEOSERVI CES. COM