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HomeMy WebLinkAboutSoils Report 06.18.19American GeoServices Geotechnical Evaluation Report Aspen Glen Filing, Lot S9, Saddleback Rd, Garfield County, CO Date: June 18, 2018 Project No: 0238-CO18 1338 Grand Avenue #306 Glenwood Springs, CO 81601 Ph: (303) 325 3869 www.americangeoservices.com sma@americangeoservices.com Ph: (888) 276 4027 Fx: (877) 471 0369 Mailing: 191 University Blvd, #375 Denver, CO 80206 Ph: (303) 325 3869 GEOTECHNICAL & MATERIALS ENVIRONMENTAL STRUCTURAL CIVIL ENGINEERING AND SCIENCE 888-276-4027 June 18, 2018 PROJECT NO: 0238-CO18 CLIENTS: Mr. Jake Dewolfe Reference: Soil Testing / Lot-specific Geotechnical Evaluation, Lot S9, Saddleback Rd, Garfield County, 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. SCOPE 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. In June 2018, we performed one soil exploration (B1) at approximate location 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 14.5 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. Project No: 0238-CO18 June 18, 2018 Page No: 2 of 15 The Legend and Notes necessary to interpret our Exploration Logs are also included in an 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 an irregularly-shaped parcel of land bordered by roadways on the north and west sides as shown in Figure 2. Currently the site topography is gently sloping downwards to the north and east. At the time of our site visit, there was no visual indication of slope instability or landslides in the site vicinity. Our review of available geology maps and geologic hazards information did not reveal the presence of 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. In some cases, the stratigraphic boundaries shown on Exploration Logs represent transitions between soil types rather than distinct lithological boundaries. It 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 Conditions: Approximately 6 inches mixtures of topsoil, loam, sand, and root mass is present at the surface. Silty Sand to Sand with Gravel/Cobble (Alluvium): Site is primarily underlain by low-plasticity mixtures of sand, silt, clay, gravel, pebble, and some rock/cobble pieces (SM/GM) extending to a maximum depth of about 2 feet. These soils have a relative density of medium dense near the surface to mostly dense. Clayey Silt to Silty Clay (Colluvium): These soils appeared to have been derived from complete weathering and erosion of local calcareous sandstone and/or calcareous shale of the Eagle Valley Formation. Colluvium is know to extend to at least 7.5 feet in the site vicinity area where it is underlain by the local calcareous bedrock (Figure 3) which extends to several tens of feet. Refusal to angering was encountered at a depth of about 7.5 feet in offsets taken at the site for boreholes. Project No: 0238-CO18 June 18, 2018 Page No: 3 of 15 Groundwater: Groundwater was not encountered at the completion of our soil explorations. 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 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 Evaporite Sinkholes: Site is located in general vicinity of the Eagle Valley Evaporite. The evaporite between Carbondale and about 3 miles south of Glenwood Springs is part of the Roaring Fork diaper which meets with the Grand Hogback monocline. This marks the western limit of the Carbondale evaporite collapse center. The Carbondale evaporite collapse center is the western collapse center among the two in the western Colorado evaporite region. Up to a possible 4,000 feet of regional ground subsidence may have occurred during the past 10 million years resulting from dissolution and evaporite flowage from beneath the region. Data cannot show whether the regional subsidence and evaporite deformation along the Roaring Fork diaper are still an active geomorphic process or if the evaporite deformations have stopped. If the evaporite deformation is still active, current deformations are most probably occurring at rates similar to long-term rates of the past, between 1.0 and 2.0 inches per 100 years. Due to the slow or unmoving nature of the deformations, AGS does not consider them a risk to future developments at the project site. At the time of four site visit, we did not notice any visual evidence of sinkholes at the site or adjacent to site boundaries. The closest possible general sinkhole areas near the site may be an existing pond which is located at least 100-150 feet away from the site, and do not pose a concern at this time. Evaporite sinkholes in western Colorado are typically 10ft to 50ft diameter, circular depressions at the ground surface that result from upward caving of a soil rubble pipe to the ground surface. The soil rubble pipe is formed by subsurface erosion (piping) of near surface soils into subsurface voids. Sinkhole development or reactivation in the area is still an active geomorphic process. Expansive Soils and Bedrock: The site is not underlain by highly expansive clayey soils or expansive clayey sedimentary bedrock materials. The site location is not near known swell hazard zones that pose a significant geotechnical concern. However, local pockets of expansive clayey materials can occur through the site and may cause heave in the flatwork around the site. This is typical of many areas in Colorado. Therefore, an open hole inspection by AGS (footing subgrade inspection) is highly recommended. Flooding: Our review of available flood hazards map and literature did not indicate that the site is susceptible to flooding due to river, and perennial and intermittent tributaries across the project Project No: 0238-CO18 June 18, 2018 Page No: 4 of 15 area. Notwithstanding, a detailed flood hazard evaluation was beyond our scope of services. We recommend hiring an experienced hydrologist to evaluate the flood hazards for the site, if necessary. 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. 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 landslides had occurred at the site or immediately adjacent to the site (Figure 4). Landslide deposits are not located within 500 feet of the site boundaries. 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. During our reconnaissance, there was no visual evidence of active global slope instability or active global landslides that would adversely impact site stability in the immediate site vicinity. 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 significant hazard. Ground accelerations in excess of 0.1g to -0.2g are not anticipated to occur at the site. Based on the results of our subsurface explorations and review of available literature (2009 International 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. Project No: 0238-CO18 June 18, 2018 Page No: 5 of 15 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. It 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 •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: •Over-excavate any boulders or large cobbles or expansive clay pockets within the foundation areas, then surficial compact the excavated surface, and then backfill (if necessary) 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 (non-rocky) subgrade” and to facilitate the placement of foundation drain. Over-excavation can 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 2,500 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. Isolated 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. Project No: 0238-CO18 June 18, 2018 Page No: 6 of 15 • Continuous foundation walls should be reinforced in the top and bottom to span an unsupported length of at least 8 feet to further aid in resisting differential movement. As a minimum, additional reinforcement as shown in Figure 5 should be placed. • Foundation/stem walls should be adequately designed as retaining walls and adequate drainage measures should be implemented as shown in Figure 4. 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. STRUCTURAL FLOOR & CRAWL 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. If 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. In 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 SPACE PERIMETER/UNDERDRAIN SYSTEM In 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 Project No: 0238-CO18 June 18, 2018 Page No: 7 of 15 should be properly designed and connected to the area underdrain system or a sump-pump system for suitable discharge from the lot. • Drainage recommendations illustrated in Figure 6 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. • 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. • 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. If recommended drain systems are used, the actual design/layout, outlets, locations, and construction means and methods should be observed by a representative of AGS. SLAB-ON-GRADE AND PERIMETER/UNDERDRAIN SYSTEM Groundwater is not expected to be at depths below the proposed foundation levels if excavation is performed during dry seasons. In order to assure proper slab-on-grade construction (if used), following recommendations should be strictly followed: • 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. • As a minimum, drainage recommendations illustrated in Figure 4 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 Project No: 0238-CO18 June 18, 2018 Page No: 8 of 15 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. • 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. If 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. Proper wetting of the subgrade to obtain soil moisture content in the range of 20-22% and/or moisture-conditioning and recompaction of onsite materials for upper 2 feet should reduce the risk of movement. If the owner is not willing to assume any risk, then a structural floor slab system option should be considered. 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: 0238-CO18 June 18, 2018 Page No: 9 of 15 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: • 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 (Figure 5). • 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. Control joint 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 and steel 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 8 feet of unsupported length. • The need for a vapor barrier will depend on the sensitivity of floor coverings to moisture. If 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. • If 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. If 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. • 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: 0238-CO18 June 18, 2018 Page No: 10 of 15 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 4. 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 8 inches before compacting to the required density and before successive layers are placed. If 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. Import soils should be approved by AGS prior to placement. Fill placement observations 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: 0238-CO18 June 18, 2018 Page No: 11 of 15 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. Imported structural fill should consist of sand or gravel material with a maximum particle size of 3 inches or less. In addition, this material shall 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. In 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. In 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 12 feet 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. If braced excavations or shoring systems are to be used or needed, they should be reviewed and designed by AGS. It 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: 0238-CO18 June 18, 2018 Page No: 12 of 15 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 otherwise 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. If 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 critical for achieving long-term stability and overall success. In 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 6. In addition, drain laterals that span the crawl space are recommended to prevent ponding of water within the crawlspace (if used). If necessary, AGS can provide further recommendations for the exterior drain system and a typical drain detail. Groundwater was not encountered 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 horizontal feet for landscaped or graveled areas. These slopes should be maintained during the Project No: 0238-CO18 June 18, 2018 Page No: 13 of 15 service life of buildings. If 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. Irrigation 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-term 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 I-II 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: 0238-CO18 June 18, 2018 Page No: 14 of 15 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. It is possible that soil conditions could vary between or beyond the points explored. If 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. If 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. If such contamination were present, it is very likely that the exploration and testing conducted for this report would not reveal its existence. If 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. In 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: 0238-CO18 June 18, 2018 Page No: 15 of 15 We appreciate the opportunity to be of service to you on this project. If we can provide additional assistance or observation and testing services during design and construction phases, please call us at 1 888 276 4027. Sincerely, Sam Adettiwar, MS, PE, GE, P.Eng, M.ASCE Senior Engineer Attachments FIGURES APPENDIX SAND to SILTY SAND with GRAVEL/ COBBLES, medium to fine grain, brown,dry to damp, medium dense to dense, (ALLUVIUM) End of Borehole. Groundwater was not encountered during or at the completion of drilling. At completion, borehole was backfilled with soil cuttings. 2.5 5.0 7.5 10 7-10-16 19-20-34 80 80 SM/ GM CL/ ML Saddleback Rd, Lot S9, Garfield County, CO B1 Project Number 0238-CO18 Geologist/Engineer SMA Date Drilled 06-17-2018 Borehole Diameter 4 OD Inches Drill Rig: CME55 Solid Stem Auger, 4" Diameter Ground Elevation Moisture (%)See Figures Total Depth of Borehole 8 Feet Depth to Water Not Encountered Page 1Graphic LogDescription / Lithology Depth (feet)SampleCompletionDD (pcf)Recovery (%)Swell (%)SPT Blow CountLL (%), PL (%)25-28-54 50 SANDY CLAY to SILTY CLAY to CLAYEY SANDY SILT, fine to coarse grain, brown, some gravel or weathered rock pieces, very stiff to hard, damp to moist, low plasticity (COLLUVIUM) Residuum /Completely weathered Sandstone/ Shale (Possibly Eagle Valley Formation) UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART COARSE-GRAINED SOILS (more than 50% of material is larger than No. 200 sieve size.) GRAVELS More than 50% of coarse fraction larger than No. 4 sieve size SANDS 50% or more of coarse fraction smaller than No. 4 sieve size Clean Gravels (Less than 5% fines) GW GP Well-graded gravels, gravel-sand mixtures, little or no fines Poorly-graded gravels, gravel-sand mixtures, little or no fines Gravels with fines (More than 12% fines) GM GC Silty gravels, gravel-sand-silt mixtures Clayey gravels, gravel-sand-clay mixtures Clean Sands (Less than 5% fines) SW SP Well-graded sands, gravelly sands, little or no fines Poorly graded sands, gravelly sands, little or no fines Sands with fines More than 12% fines SM Silty sands, sand-silt mixtures SC Clayey sands, sand-clay mixtures FINE-GRAINED SOILS (50% or more of material is smaller than No. 200 sieve size.) SILTS AND CLAYS Liquid limit less than 50% SILTS AND CLAYS Liquid limit 50% or greater HIGHLY ORGANIC SOILS ML CL OL MH CH OH PT Inorganic silts and very fine sands, rock flour, silty of clayey fine sands or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts Inorganic clays of high plasticity, fat clays Organic clays of medium to high plasticity, organic silts Peat and other highly organic soils GW GP GM GC SW SP SM SC LABORATORY CLASSIFICATION CRITERIA cu D 50 D 30 = --greater than 4; Cc = between 1 and 3 D 10 010 x D50 Not meeting all gradation requirements for GW Atterberg limits below "A" Above "A" line with P.I. between line or P.I. less than 4 4 and 7 are borderline cases Atterberg limits above "A" requiring use of dual symbols line with P. I. greater than 7 cu D 50 D 30 = --greater than 4; Cc = between 1 and 3 D 10 01o xD60 Not meeting all gradation requirements for GW Atterberg limits below "A" Limits plotting in shaded zone line or P.I. less than 4 with P.I. between 4 and 7 are Atterberg limits above "A" borderline cases requiring use line with P. I. greater than 7 of dual symbols. Determine percentages of sand and gravel from grain-size curve. Depending on percentage of fines (fraction smaller than No. 200 sieve size), coarse-grained soils are classified as follows: Less than 5 percent .................................... GW, GP, SW, SP More than 12 percent .................................. GM, GC, SM, SC 5 to 12 percent ................... Borderline cases requiring dual symbols PLASTICITY CHART 60 ,,/ � � 50 � CH / / >< 40 V" ALINE: Vp1 = on(LL-20) � 30 >-CL ,,/ MHlOH 20 / j:: / 10 ...J CL+ML ./ ML&OL II.. 0 0 I 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT (LL) (%) DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION LABORATORY/FIELD TESTING DEFINITIONS FOR EXPLORATION LOGS DD = DRY DENSITY (PCF) WD = WET DENSITY (PCF) MC = MOISTURE CONTENT (%) PL = PLASTIC LIMIT (%) LL = LIQUID LIMIT (%) PI = PLASTICITY INDEX OC = ORGANIC CONTENT (%) S = SATURATION PERCENT (%) SG = SPECIFIC GRAVITY C = COHESION Ф = ANGLE OF INTERNAL FRICTION QU = UNCONFINED COMPRESSION STRENGTH #200 = PERCENT PASSING THE #200 SIEVE CBR = CALIFORNIA BEARING RATIO VS = VANE SHEAR PP = POCKET PENETROMETER DP = DRIVE PROBE SPT = STANDARD PENETRATION TEST BPF = BLOWS PER FOOT (N VALUE) SH = SHELBY TUBE SAMPLE GW = GROUND WATER RQD = ROCK QUALITY DESIDNATION TP = TEST PIT B = BORING HA = HAND AUGER GROUNDWATER LEVEL/SEEPAGE ENCOUNTERED DURING EXPLORATION STATIC GROUNDWATER LEVEL WITH DATE MEASURED CONSISTENCY OF COHESIVE SOILS CONSISTENCY STP (BPF) PP (TSF) VERY SOFT 0-1 LESS THAN 0.25 SOFT 2 - 4 0.25 - 0.5 MEDIUM STIFF 5 - 8 0.5 - 1.0 STIFF 9 - 15 1.0 - 2.0 VERY STIFF 16 - 30 2.0 - 4.0 HARD 30+ OVER 4.0 RELATIVE DENSITY OF COHESIONLESS SOILS DENSITY SPT (BPF) VERY LOOSE 0 – 4 LOOSE 5 – 10 MEDIUM DENSE 11 – 30 DENSE 31 – 50 VERY DENSE 50+ PARTICLE SIZE IDENTIFICATION NAME DIAMETER (INCHES) SIEVE NO. ROCK BLOCK >120 BOULDER 12-120 COBBLE 3-12 GRAVEL COURSE 3/4 - 3 FINE 1/4 – 3/4 NO. 4 SAND COARSE 4.75 MM NO. 10 MEDIUM 2.0MM NO. 40 FINE .425 MM NO. 200 SILT .075 MM CLAY <0.005 MM GRAIN SIZE FINE GRAINED <0.04 INCH FEW GRAINS ARE DISTINGUISHABLE IN THE FIELD OR WITH HAND LENS. MEDIUM GRAINED 0.04-0.2 INCH GRAINS ARE DISTINGUISHABLE WITH THE AID OF A HAND LENS. COARSE GRAINED 0.04-0.2 INCH MOST GRAINS ARE DISTINGUISHABLE WITH THE NAKED EYE. 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 ADVANCEMENT AND SAMPLES ARE RETRIEVED FROM CUTTINGS. HAND AUGUR EXPLORATION: TESTING IS PREFORMED USING A 3.25” DIAMETER AUGUR TO ADVANCE INTO THE EARTH AND RETRIEVE SAMPLES. DRIVE PROBE EXPLORATIONS: THIS “RELATIVE DENSITY” EXPLORATION DEVICE IS USED TO DETERMINE THE DISTRIBUTION AND ESTIMATE STRENGTH OF THE SUBSURFACE SOIL AND DECOMPRESSED ROCK UNITS. THE RESISTANCE TO PENETRATION IS MEASURED IN BLOWS-PER-1/2 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 20-TON TRUCK. THE CONE RESISTANCE (QC) AND SLEEVE FRICTION (FS) ARE MEASURED AS THE PROBE WAS PUSHED INTO THE EARTH. THE VALUES OF QC AND FS (IN TSF) ARE NOTED AS THE LOCALIZED INDEX OF SOIL STRENGTH. ANGULARITY OF GRAVEL & COBBLES ANGULAR COARSE PARTICLES HAVE SHARP EDGES AND RELATIVELY PLANE SIDES WITH UNPOLISHED SURFACES. SUBANGULAR COARSE GRAINED PARTICLES ARE SIMILAR TO ANGULAR BUT HAVE ROUNDED EDGES. SUBROUNDED COARSE GRAINED PARTICLES HAVE NEARLY PLANE SIDES BUT HAVE WELL ROUNDED CORNERS AND EDGES. ROUNDED COARSE GRAINED PARTICLES HAVE SMOOTHLY CURVED SIDES AND NO EDGES. SOIL MOISTURE MODIFIER DRY ABSENCE OF MOISTURE; DUSTY, DRY TO TOUCH MOIST DAMP BUT NO VISIBLE WATER WET VISIBLE FREE WATER WEATHERED STATE FRESH NO VISIBLE SIGN OF ROCK MATERIAL WEATHERING; PERHAPS SLIGHT DISCOLORATION IN MAJOR DISCONTINUITY SURFACES. SLIGHTLY WEATHERED DISCOLORATION INDICATES WEATHERING OF ROCK MATERIAL AND DISCONTINUITY SURFACES. ALL THE ROCK MATERIAL MAY BE DISCOLORED BY WEATHERING AND MAY BE SOMEWHAT WEAKER EXTERNALLY THAN ITS FRESH CONDITION. MODERATELY WEATHERED 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. HIGHLY WEATHERED 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. 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 STRUCTURE AND MATERIAL FABRIC IS DESTROYED. THERE IS A LARGE CHANGE IN VOLUME, BUT THE SOIL HAS NOT BEEN SIGNIFICANTLY TRANSPORTED. DESCRIPTIVE TERMINOLOGY & SOIL CLASSIFICATION 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 GEOTECHNICAL ENG.NEERING REPORT IS BASED ON A UNIQUE SET OF PROJECT-SPECIFIC FACTORS Your geotechnical engineering report is based on a subsurface exploration plan designed to consider a unique set of project-specific 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. •when the nature of the proposed structure ischanged. for example, if an office building willbe erected instead of a parking garage, or arefrigerated warehouse will be built instead ofan unrefrigerated one;•when the size, elevation. or configuration of theproposed structure is altered;•when the location or orientation of the proposedstructure is modified;•when there is a change of ownership; or .forapplication to an adjacent site. 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. 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 SPECIFIC 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 otherwise, 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 ASFE 8811 Colesville Road/Suite G106/Silver Spring, MD 20910 Telephone: 301/565-2733 Facsimile: 301/589-2017 about the potential for hazardous materials existing at the site. The equipment, techniques, and personnel used to perform a geoenvironmental exploration differ substantially from those applied in geotechnical engineering. Contamination can create major risks. If 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. (If 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. In 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. It 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. Instead, 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. Subsurface Explorations Soil Testing Earthwork Monitoring Geotechnology Foundation Engineering Rock Mechanics Earthquake Engineering Geophysics Retaining Wall Design Geostrructural Design Pavement Design Drainage Evaluations Groundwater Studies Environmental Assets Building Assessments AmericanGeoServices.com