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HomeMy WebLinkAboutDRB16-0339_Geotechnical Report Lots 9 - 12_1471292100.pdfKOECHLEIN CONSULTING ENGINEERS, INC. CONSULTING GEOTECHNICAL AND MATERIALS ENGINEERS DENVER: 12364 West Alameda Prkwy., Suite 115, Lakewood, CO 80228 (303) 989-1223 AVON/SILVERTHORNE: (970) 949-6009 GEOTECHNICAL INVESTIGATION PROPOSED HOTEL AND CONDOMINIUM BUILDING LOTS 9, 10, 11, AND 12 1783 NORTH FRONTAGE ROAD VAIL, COLORADO Prepared for: Greg Gastineau Timberline Commercial Real Estate 12 South Frontage Road Vail, Colorado 81657 Job No. 05-112 July 14, 2005 July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers TABLE OF CONTENTS SCOPE 1 EXECUTIVE SUMMARY 2 PROPOSED CONSTRUCTION 3 SITE CONDITIONS 4 INVESTIGATION 5 ADDITIONAL INVESTIGATION 6 SUBSURFACE CONDITIONS 6 GROUND WATER 7 EXISTING FOUNDATIONS AND UTILITIES 8 EXCAVATIONS 9 SHORING 10 SEISMICITY 10 RADON 11 MOLD 11 FOUNDATIONS 11 SLABS-ON-GRADE 13 FOUNDATION DRAINAGE 14 LATERAL WALL LOADS 15 RETAINING WALLS 16 SURFACE DRAINAGE 16 IRRIGATION 17 COMPACTED FILL 18 LIMITATIONS 19 VICINITY MAP Fig. 1 LOCATIONS OF EXPLORATORY BORINGS Fig. 2 LOGS OF EXPLORATORY BORINGS Figs. 3 and 4 LEGEND OF EXPLORATORY BORINGS Fig. 5 GRADATION TEST RESULTS Figs. 6 thru 9 TYPICAL WALL DRAIN DETAIL Fig. 10 TYPICAL RETAINING WALL DRAIN DETAIL Fig. 11 SUMMARY OF LABORATORY TEST RESULTS Table I July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers SCOPE This report presents the results of a geotechnical investigation for the proposed hotel and condominium building to be constructed on Lots 9, 10, 11, and 12 at 1783 North Frontage Road in Vail, Colorado. The approximate site location is shown on the Vicinity Map, Fig. 1. The purpose of this investigation was to evaluate the subsurface conditions at the site and to provide geotechnical recommendations for the proposed construction. The purpose of this report is to provide descriptions of subsurface soil and ground water conditions encountered in the exploratory borings, allowable soil bearing capacity, recommended foundation systems, and recommended foundation design and construction criteria for the proposed building. This report was prepared from data developed during the field investigation, our laboratory testing, and our experience with similar projects and subsurface conditions in the area. The recommendations presented in this report are based on the construction of the proposed building as described in the PROPOSED CONSTRUCTION section of this report. We should be contacted to review our recommendations when the final plans for the proposed building have been completed. A summary of our findings and conclusions is presented below. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 2 EXECUTIVE SUMMARY 1. Subsurface conditions encountered in exploratory borings were slightly variable across the site. The subsurface conditions consisted of asphalt, existing fill, or natural, very loose, sandy, gravelly silt overlying medium dense to very dense, cobbly, sand and gravel to the maximum depth explored of 28.0 feet. The existing fill was characterized by medium dense, sandy, gravelly silt with scattered cobbles. Practical drill rig refusal on boulders was encountered in all borings at depths varying from 11.0 to 28.0 feet. 2. Up to 8.0 feet of existing fill was encountered at this site. Greater depths of fill could be encountered during construction of the proposed building. All existing fill will need to be removed from below construction areas prior to construction. 3. No free ground water was encountered in any of the exploratory borings to the maximum depth explored of 28.0 feet. However, plans at the writing of this report are for excavation depth up to 50 feet. Ground water may be encountered below a depth of 28 feet. Refer to the GROUND WATER section of this report for additional details. 4. We anticipate that sand and gravel, or possibly cobbles and boulders, will be encountered at the proposed foundation elevations. In our opinion, the natural sand and gravel, or cobbles and boulders if encountered, will safely support spread footing foundations for the proposed building. Refer to the FOUNDATIONS section of this report for complete recommendations. 5. We anticipate that the soils at the potential floor slab elevation for the proposed building will consist of the natural sand and gravel or possibly cobbles and boulders. In our opinion, the natural sand and gravel, cobbles and boulders if encountered, or properly moisture conditioned and compacted structural fill will safely support slab-on-grade floors for the proposed building. Refer to the SLABS-ON-GRADE section of this report for complete recommendations. 6. Because practical drill rig refusal on boulders was encountered in the exploratory borings, we anticipate that heavy-duty excavation equipment will be necessary to complete the required excavations. Refer to the EXCAVATIONS section of this report for additional recommendations. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 3 7. Excavations were anticipated to be 20 feet in depth for this investigation and therefore, borings were advanced to a maximum depth of 28 feet. Plans at the writing of this report indicated excavation depth up to 50 feet. When plans are finalized and the actual depth is determined, additional investigation may be needed. 8. Due to the plans at the writing of this report indicating a depth of excavation up to 50 feet and the proximity of surrounding structures, property lines and streets, it may not be possible to slope all of the excavation sides as required by OSHA regulations. Therefore, a shoring system may be necessary. Refer to the SHORING section of this report for additional recommendations. 9. Based on the subsurface soil profile, this site has a seismic site classification of Site Class D. Refer to the SEISMICITY section of this report for additional recommendations 10. The potential for radon gas is a concern in the area. Refer to the RADON section of this report for additional recommendations. 11. The potential for mold is a concern. Refer to the MOLD section of this report for additional recommendations. 12. Drainage around the structure should be designed and constructed to provide for rapid removal of surface runoff and avoid concentration of water adjacent to foundation walls. Refer to the SURFACE DRAINAGE section of this report for additional recommendations. PROPOSED CONSTRUCTION Based on the most recent architectural plans provided by Gwathney/Pratt/Schultz Architects, P. C., we understand that a five-story hotel and condominium building with two levels of below grade parking will be constructed on the subject lots that are currently occupied by the Roost Lodge. The Roost Lodge and its associated buildings July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 4 will be demolished and the new structure constructed in its place. We anticipate that the two below grade levels will be of cast-in-place concrete construction while the five stories above grade will be of wood frame construction. The top of floor slab elevation for the lowest level of below grade parking under the hotel section, which is the southwest wing of the proposed building, will be EL. 7974. The top of floor slab elevation for the lowest level of below grade parking under the condominium section, which is the northeast wing of the proposed building, will be EL. 8007. In the northwest corner of the building, the lowest floor slab elevation will be EL. 7985. At the time this report was prepared, structural loads for the proposed building had not been determined. SITE CONDITIONS The proposed building will be constructed on Lots 9, 10, 11, and 12 at 1783 North Frontage Road in Vail, Colorado. Currently the lots are occupied by the Roost Lodge. The Roost Lodge consists of four two to three story, wood framed buildings and an enclosed, in-ground swimming pool. The area immediately to the southeast, south, and southwest of the existing buildings is paved with asphalt. The North Frontage Road borders the parking lot and access drives to the southeast. Meadow Road borders the site to the west. To the north of the site is a residential area. At the north end of the site, a cut approximately 20 feet deep has been made in the natural slope to accommodate the existing buildings, resulting in a slope down toward the south at a grade of approximately 54 percent. The existing parking lot at the south end of the site slopes down toward the July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 5 southwest at a grade of approximately 6 percent. Landscaping around the existing building consists of grass, aspen trees and pine trees. INVESTIGATION Subsurface conditions at this site were investigated on June 30, 2004 by drilling seven exploratory borings with a 4-inch diameter, continuous flight, solid stem power auger mounted on a rubber-tire ATV drill rig at the locations shown in the Locations of Exploratory Borings, Fig. 2. An engineer from our office was on site during our field investigation to supervise the drilling of the exploratory borings and to visually classify and document the subsurface soils and ground water conditions. Graphical logs of the subsurface conditions encountered within the exploratory borings are presented in the Logs of Exploratory Borings, Figs. 3 and 4; and in Legend of Exploratory Borings, Fig. 5. Soil samples obtained from the exploratory borings were tested in our laboratory to determine their natural moisture content, dry density, and gradation properties. The results of the laboratory testing are presented in the Logs of Exploratory Borings, Figs. 3 and 4; in the Legend of Exploratory Borings, Fig. 5; in the Gradation Test Results, Figs. 6 thru 9; and in the Summary of Laboratory Test Results, Table I. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 6 ADDITIONAL INVESTIGATION Based on the most recent architectural plans provided by Gwathney/Pratt/Schultz Architects, P.C., we anticipate excavations of up to 50 feet will be required for the proposed building. Our investigation was based on previous plans that indicated an approximate maximum depth of excavation of 20 feet. Therefore, borings were planned for depths of 20 to 30 feet and the borings drilled encountered drill rig refusal at depths varying from 11.0 feet to 28.0 feet. Due to the proposed depth of excavation and the fact that the borings were not advanced to depths greater than 50 feet, we recommend further investigation of this site when plans are finalized. The additional investigation should provide information on the subsurface conditions down to and below the base of the proposed excavation. This additional information will assist in designing any shoring systems that may be required and provide information on the subsurface ground water conditions. SUBSURFACE CONDITIONS Subsurface conditions encountered in exploratory borings were slightly variable across the site. The subsurface conditions encountered in exploratory borings TH-1 and TH-2 consisted of approximately 4.0 inches of asphalt overlying red, brown, white, dry to very moist, medium dense to very dense, sand and gravel to the maximum depths explored of 28.0 feet in boring TH-1 and 11.0 feet in boring TH-2. Subsurface conditions encountered in borings TH-2 and TH-4 consisted of approximately 4.0 inches July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 7 of asphalt overlying existing fill to depths of 8.0 feet in boring TH-2 and 6.0 feet in boring TH-4. The existing fill consisted of dark brown to black, moist to very moist, medium dense, sandy, gravelly silt with scattered cobbles. Underlying the existing fill to the maximum depths explored of 24.0 feet in boring TH-2 and 16.0 feet in boring TH-4, the subsurface conditions consisted of the medium dense to very dense sand and gravel. Subsurface conditions encountered in borings TH-6 and TH-7 consisted of red, brown, dry to very moist, very loose, sandy, gravelly silt to depths of 5.0 feet in boring TH-6 and 2.0 feet in boring TH-7. Underlying the sandy, gravelly silt to the maximum depths explored of 13.0 feet in boring TH-6 and 18.0 feet in boring TH-7, the subsurface conditions consisted of the medium dense to very dense, sand and gravel. Practical drill rig refusal on boulders was encountered in all borings at depths varying between 11.0 and 28.0 feet. No free ground water was encountered in any of the exploratory borings to the maximum depth explored of 28 feet at the time of drilling. GROUND WATER No free ground water was encountered in any of the exploratory borings to the maximum depth explored of 28.0 feet. However, plans at the writing of this report are for excavation depth up to 50 feet. Ground water may be encountered below a depth of 28 feet. As indicated in the ADDITIONAL INVESTIGATION section of this report, subsurface ground water conditions could be better defined with deeper borings. In July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 8 addition, our investigation was conducted during a dry time of year. Therefore, it is possible that ground water may be encountered during construction if the construction takes place during a wet time of the year. If ground water is encountered during construction, we should be contacted to provide specific recommendations at that time. EXISTING FOUNDATIONS AND UTILITIES We understand the existing buildings will be demolished prior to construction of the new building. We recommend that all foundations and existing fill from the existing structures be removed and, if necessary, replaced with properly moisture treated and compacted approved granular structural fill. Any utilities to the existing building should be removed and the associated fill should be replaced with approved structural fill. This includes, but is not limited to, fill in trenches for the various utilities that could be encountered during demolition of the existing building or during excavation for the new building. A representative from our office should observe the removal of the existing foundations and fill from utilities in order to verify that the fill and foundations have been removed prior to construction of the new building. New granular structural fill should be moisture conditioned and compacted as recommended in the COMPACTED FILL section of this report. A representative from our office should observe, test, and document all structural fill placed for the construction of the proposed commercial building. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 9 EXCAVATIONS Based on the most recent architectural plans provided by Gwathney/Pratt/Schultz Architects, P. C., we anticipate that excavations between approximately 20 to 50 feet in depth will be required for construction of the new building. The excavation in the southwest part of the site will be the shallowest at a depth of approximately 20 feet. The deepest excavation will be slightly east of the northwest corner of the proposed building, and will be approximately 50 feet deep. Based on the subsurface conditions encountered within the borings, we anticipate that these excavations will be in the natural sand and gravel. However, because practical drill rig refusal on boulders was encountered in the exploratory borings, we anticipate heavy-duty construction equipment will be necessary to complete the required excavations. Care needs to be exercised during construction so that the excavation slopes remain stable. In our opinion, existing fill and the natural sand and gravel classify as Type B soils in accordance with OSHA. OSHA regulations should be followed in any excavations or cuts. All existing foundations, fill, and soft soils beneath the proposed construction should be removed, and if necessary, replaced with properly moisture conditioned and compacted fill. All fill should be placed and compacted as recommended in the COMPACTED FILL section of this report. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 10 SHORING Due to the depth of excavation and proximity of surrounding structures, property lines and streets, it may not be possible to slope all of the excavation sides as required by OSHA regulations. Therefore, a shoring system may be necessary. Property boundaries may also limit how far the shoring system can extend beyond the excavation and intrude into the adjacent property. The ability to complete the excavation within the site constraints and the need for a shoring system, including the type of system, should be evaluated during the design phase of the project. Based on the subsurface conditions encountered during this investigation, the shoring system may be designed using the following engineering soil characteristics for the natural sand and gravel: φ' = 35°, γ = 135 psf, c = 0. We recommend a contractor specializing in shoring be contacted for design and construction of the shoring. SEISMICITY The subsurface soil and ground water conditions encountered within the exploratory borings indicate that the soil profile classifies as a dense soil and soft rock profile. Based on this classification and the 2003 International Building Code (IBC), it is our opinion that the subject site has a seismic site classification of Site Class D. A higher site class may be possible. Site specific seismic testing would be required to determine if a higher seismic site class could be assigned to this site. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 11 RADON In recent years, radon gas has become a concern. Radon gas is a colorless, odorless gas that is produced by the decay of minerals in soil and rock. The potential for radon gas in the subsurface strata is likely. Because the proposed building will be constructed with two below grade levels, we recommend that the building be constructed with a below grade ventilation system. MOLD In recent years mold has become an issue. Mold tends to grow in areas that are dark and damp, such as bathrooms and below grade areas. Recommendations for mold prevention, mitigation, or remediation is outside the scope of this investigation. We recommend that the owner contact a professional Industrial Hygienist to provide specific recommendations for the prevention and/or remediation of mold. FOUNDATIONS The subsurface material at the potential foundation elevation for the proposed hotel and condominium building will consist of natural sand and gravel and possibly cobbles and boulders. In our opinion, the natural sand and gravel or cobbles and boulders if encountered, will safely support a spread footing foundation system for the proposed building. We recommend that the spread footing foundation system be designed and constructed to meet the following criteria: July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 12 1. Footings should be supported by the undisturbed, natural sand and gravel, cobbles and boulders if encountered, or properly moisture conditioned and compacted fill, as described below in Items 7, 8, and 9. 2. We recommend wall and column footings be designed for a maximum allowable soil bearing pressure of 5,000 psf for foundations constructed on the natural sand and gravel or cobbles and boulders. 3. Spread footings constructed entirely on the natural sand and gravel, cobbles and boulders, or properly moisture treated and compacted structural fill may experience up to 0.25 inch of differential movement between foundation elements. Because the soils are granular in nature, we anticipate that the majority of the differential settlement will occur during construction. 4. Wall footings and foundation walls should be designed to span a distance of at least 10.0 feet in order to account for anomalies in the soil or compacted fill. 5. The base of the exterior footings should be established at a minimum depth below the exterior ground surface, as required by the local building code. We believe that the depth for frost protection in the local building code in this area is 3.5 feet. 6. Column footings should have a minimum dimension of 24 inches square and continuous wall footings should have a minimum width of 16 inches. Footing widths may be greater to accommodate structural design loads. 7. We anticipate that cobbles and boulders will be encountered at the foundation elevation. Removal of the cobbles and boulders may result in depressions and rough bottoms in the excavation. The resulting depressions can be backfilled with compacted structural fill or lean concrete. Refer to the COMPACTED FILL section of this report for backfill requirements. 8. Pockets or layers of soft soils may be encountered in the bottom of the completed footing excavations. These materials should be removed to expose the undisturbed, natural sand and gravel or cobbles and boulders. The foundations should be constructed on the natural sand and gravel, cobbles and boulders, or new compacted structural fill. Refer to the COMPACTED FILL section of this report for backfill requirements. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 13 9. Fill should be placed and compacted as outlined in the COMPACTED FILL section of this report. We recommend that a representative of our office observe and test the placement and compaction of structural fill used in foundation construction. It has been our experience that without engineering quality control, inappropriate construction techniques occur which result in poor foundation performance. 10. We recommend that a representative of our office observe the completed foundation excavations. Variations from the conditions described in this report, which were not indicated by our borings can occur. The representative can observe the excavations to evaluate the exposed subsurface conditions. SLABS-ON-GRADE The subsurface soils at the anticipated floor slab elevations for the proposed hotel and condominium building will consist of the natural sand and gravel or possibly cobbles and boulders. In our opinion the natural sand and gravel or cobbles and boulders will support slabs-on-grade with a low risk of movement. We recommend the following precautions for the construction of slabs-on-grade: 1. Slabs should be placed on the natural sand and gravel, cobbles and boulders, or properly moisture conditioned and compacted structural fill. All existing fill or soft soils beneath slabs-on-grade should be removed and replaced with properly moisture treated and compacted structural fill prior to construction of slabs-on-grade. Existing fill may be used as structural fill if it is free of deleterious material. 2. A subgrade modulus of 300 pci may be used for design of slabs-on-grade on the sand and gravel, cobbles and boulders or new compacted structural fill. 3. Slabs should be separated from exterior walls and interior bearing members. Vertical movement of the slab should not be restricted. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 14 4. Exterior slabs should be separated from the building. These slabs should be reinforced to function as independent units. Movement of these slabs should not be transmitted directly to the foundations or walls of the structure. 5. Frequent control joints should be provided in all slabs to reduce problems associated with shrinkage of concrete. 6. Fill beneath slabs-on-grade may consist of on-site fill soils free of deleterious material or approved imported fill. Fill should be placed and compacted as recommended in the COMPACTED FILL section of this report. Placement and compaction of fill beneath slabs should be observed and tested by a representative of our office. FOUNDATION DRAINAGE Surface water tends to flow through relatively permeable backfill typically found adjacent to foundations. The water that flows through the fill collects on the surface of relatively impermeable soils occurring at the foundation elevation. Both this surface water and possible ground water can cause wet or moist below grade conditions after construction. Because the proposed building will be constructed with two below grade levels, we recommend that the structure be constructed with a foundation drain. The drain should consist of a 4-inch diameter perforated pipe encased in free draining gravel. The drainpipe should be sloped so that water flows to a sump where the water can be removed by pumping, or to a positive gravity outlet. Recommended details for a typical foundation wall drain are presented in the Typical Wall Drain Detail, Fig. 10. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 15 LATERAL WALL LOADS Due to the topography of the site and the proposed depths of excavation, walls that require lateral earth pressures for design will be constructed for this project. Lateral earth pressures depend on the type of backfill and the height and type of wall. Walls that are free to rotate sufficiently to mobilize the strength of the backfill should be designed to resist the "active" earth pressure condition. Walls that are restrained should be designed to resist the "at rest" earth pressure condition. The following table presents the lateral wall pressures that may be used for design. Earth Pressure Condition Equivalent Fluid Pressure1 (pcf) Active 35 At-rest 50 Passive 300 Notes: 1. Equivalent fluid pressures are for a horizontal backfill condition with no hydrostatic pressures or live loads. 2. A coefficient of friction of 0.4 may be used at the base of spread footings to resist lateral wall loads. Backfill placed behind or adjacent to foundation walls should be placed and compacted as recommended in the COMPACTED FILL section of this report. Placement and compaction of the fill should be observed and tested by a representative of our office. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 16 RETAINING WALLS Due to the topography of the site and the adjacent property, we anticipate that retaining walls may be constructed as part of the development of the site. Foundations for retaining walls may be designed and constructed as recommended in the FOUNDATIONS section of this report. Lateral earth loads for retaining wall designs are presented in the LATERAL WALL LOADS section of this report. In order to reduce the possibility of developing hydrostatic pressures behind retaining walls, a drain should be constructed adjacent to the wall. The drain may consist of a manufactured drain system and gravel. The gravel should have a maximum size of 1.5 inches and have a maximum of 3 percent passing the No. 200 sieve. Washed concrete aggregate will be satisfactory for the drainage layer. The manufactured drain should extend from the bottom of the retaining wall to within 2 feet of subgrade elevation. The water can be drained by a perforated pipe with collection of the water at the bottom of the wall leading to a positive gravity outlet. A typical detail for a retaining wall drain is presented in the Typical Retaining Wall Drain Detail, Fig. 11. SURFACE DRAINAGE Reducing the wetting of structural soils can be achieved by carefully planned and maintained surface drainage. We recommend the following precautions be observed during construction and maintained at all times during and after the construction is completed. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 17 1. Wetting or drying of the open foundation excavations should be minimized during construction. 2. All surface water should be directed away from the top and sides of the excavations during construction. 3. The ground surface surrounding the exterior of the proposed building should be sloped to drain away in all directions. We recommend a slope of at least 12 inches in the first 10 feet for landscaped areas adjacent to the proposed building. 4. Hardscape (concrete and asphalt) should be sloped to drain away from the building. We recommend a slope of at least 2 percent for all hardscape within 10 feet of the building. 5. Backfill, especially around foundation walls, must be placed and compacted as recommended in the COMPACTED FILL section of this report. 6. Roof drains should discharge at least 10 feet away from foundation walls with drainage directed away from the structure. 7. Surface drainage should be designed by a Professional Civil Engineer. IRRIGATION Irrigation systems installed next to foundation walls or sidewalks could cause consolidation of backfill below and adjacent to these areas. This can result in settling of exterior steps, patios and/or sidewalks if they are constructed on these soils. We recommend the following precautions be followed: 1. Do not install an irrigation system next to foundation walls or above retaining walls. The irrigation system should be at least 10 feet away from the building or face of retaining walls. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 18 2. Irrigation heads should be pointed away from the structure or in a manner that does not allow the spray to come within 5 feet of the building or face of retaining walls. 3. The landscape around the irrigation system should be sloped so that no ponding occurs at the irrigation heads. 4. Install landscaping geotextile fabrics to inhibit growth of weeds and to allow normal moisture evaporation. We do not recommend the use of a plastic membrane to inhibit the growth of weeds. 5. Control valve boxes for automatic irrigation systems should be located at least 10 feet away from the structure and periodically checked for leaks and flooding. COMPACTED FILL Structural fill for this project may consist of the on site soils or approved imported fill. The imported fill may consist of non-expansive silty or clayey sands or gravels with up to 25 percent passing the No. 200 sieve and a maximum plasticity index of 10. No gravel or cobbles larger than 10 inches should be placed in fill areas. Fill areas should be stripped of all vegetation, existing fill, and loose soils, and then scarified, moisture treated, and compacted. Fill should be placed in thin loose lifts; moisture treated, and compacted as shown in the following table. The recommended compaction varies for the given use of the fill, as indicated in the following table. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 19 Recommended Compaction Use of Fill Percentage of the Standard Proctor Maximum Dry Density (ASTM D-698) Percentage of the Modified Proctor Maximum Dry Density (ASTM D-1557) Below Foundations 98 95 Below Slabs-On-Grade 95 90 Utility Trench Backfill 95 90 Backfill (Non-Structural) 90 90 Notes: 1. For clay soils the moisture content should be 0 to +3 percent of the optimum moisture content. 2. For granular soils the moisture content should be –2 to +2 of the optimum moisture content. We recommend that a representative of our office observe and test the placement and compaction of each lift placed of structural fill. Fill below foundations, slab-on- grade floors, and exterior slabs-on-grade is considered structural. It has been our experience that without engineering quality control, inappropriate construction techniques can occur which result in poor foundation and slab-on-grade performance. LIMITATIONS Although the exploratory borings were located to obtain a reasonably accurate determination of foundation conditions, variations in the subsurface conditions are always possible. Any variations that exist beneath the site generally become evident during removal of the existing building and during excavation for the new structure. A representative from our office must observe the completed excavations to confirm that the soils are as indicated by the exploratory borings, to verify that all existing foundations and utilities have been removed, and to verify our foundation and slab-on-grade design July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 20 and construction recommendations. The placement and compaction of fill, as well as installation of foundations, should also be observed and/or tested. The design criteria and subsurface data presented in this report are valid for 3 years provided that a representative from our office observes the site at that time and confirms that the site conditions are similar to the conditions presented in the SITE CONDITIONS section of this report and that the recommendations presented in this report are still applicable. We recommend that final plans and specifications for proposed construction be submitted to our office for study, prior to beginning construction, to determine compliance with the recommendations presented in this report. July 14, 2005 KOECHLEIN CONSULTING ENGINEERS, INC. Job No. 05-112 Consulting Geotechnical Engineers 21 We appreciate the opportunity to provide this service. If we can be of further assistance in discussing the contents of this report or in analysis of the proposed structure from a geotechnical viewpoint, please contact our office. KOECHLEIN CONSULTING ENGINEERS, INC. Richard M. Wenzel III, P.E. Staff Engineer Reviewed by: William H. Koechlein, P.E. President (4 copies sent) 1 copy via email – Greg Gastineau, Timberline Commercial Real Estate TH-1 APP.EL. 8000.0 15/12WC=7-200=19 14/12WC=13DD=118-200=24 50/3WC=4-200=13 78/11 TH-2 APP.EL. 8000.0 7/12 38/12 18/12 TH-3 APP.EL. 7998.1 19/12 30/12 TH-4 APP.EL. 8003.4 11/12WC=18DD=99-200=62 50/5WC=5DD=113-200=9 WC=2-200=7 8005 8000 7995 7990 7985 7980 7975 7970 7965ELEVATION FEET8005 8000 7995 7990 7985 7980 7975 7970 7965 ELEVATION FEETKOECHLEIN CONSULTING ENGINEERS, INC.Consulting Geotechnical Engineers LOGS OF EXPLORATORY BORINGS JOB NO. 05-112 FIG. 3 TH-5 APP.EL. 8009.5 22/12 TH-6 APP.EL. 8009.7 3/12WC=18DD=99-200=53 57/12WC=6-200=15 TH-7 APP.EL. 8030.0 18/12 8030 8025 8020 8015 8010 8005 8000 7995 7990ELEVATION FEET8030 8025 8020 8015 8010 8005 8000 7995 7990 ELEVATION FEETKOECHLEIN CONSULTING ENGINEERS, INC.Consulting Geotechnical Engineers LOGS OF EXPLORATORY BORINGS JOB NO. 05-112 FIG. 4 1. Exploratory borings were drilled on June 30, 2005 using a 4-inch diameter, continuous flight, solid stem auger mounted on a rubber tire ATV drill rig. 2. No free ground water was encountered at the time of drilling in any of the borings to the maximum depth explored of 28.0 feet. 3. The Boring Logs are subject to the explanations, limitations, and conclusions as contained in this report. 4. Laboratory Test Results: WC - Indicates natural moisture (%) DD - Indicates dry density (pcf) -200 - Indicates percent passing the No. 200 sieve (%) 5. Approximate elevations are based on boring TH-7 having an elevation of 8030.0 then measuring the elevation difference to each of the remaining borings with a Stanley Compulevel Elevation Measurement System. Notes: ASPHALT SAND and GRAVEL, Cobbly, Silty, Occasional boulders, Dry to very moist, Medium dense to very dense, Red, Brown, White. FILL, Silt, Sandy, Gravelly, Scattered cobbles, Moist to very moist, Medium dense, Dark brown, Black. Silt, Sandy, Gravelly, Dry to very moist, Very loose, Red, Brown. CAVING. Indicates depth at which soils caved while drilling. REFUSAL. Indicates practical drill rig refusal on boulders. CALIFORNIA DRIVE SAMPLE. The symbol 15/12 indicates that 15 blows of a 140 pound hammer falling 30 inches were required to drive a 2.5 inch O.D. sampler 12 inches. SPLIT SPOON DRIVE SAMPLE. The symbol 78/11 indicates that 78 blows of a 140 pound hammer falling 30 inches were required to drive a 2.0 inch O.D. sampler 11 inches. BULK SAMPLE. Obtained from the auger cuttings. No sample recovered. KOECHLEIN CONSULTING ENGINEERS, INC.Consulting Geotechnical EngineersLEGEND: LEGEND OF EXPLORATORY BORINGS JOB NO. 05-112 FIG. 5 Job No. %PLASTICITY INDEX %LIQUID LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of %PLASTICITY INDEX %LIQUD LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of KOECHLEIN CONSULTING ENGINEERS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 FIG.605-112 194.0 feetTH-1 3744 GRAVEL, Sandy, Silty GRADATION TEST RESULTS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 249.0 feetTH-1 5125SAND, Gravelly, Silty Job No. %PLASTICITY INDEX %LIQUID LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of %PLASTICITY INDEX %LIQUD LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of KOECHLEIN CONSULTING ENGINEERS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 FIG.705-112 1314.0 feetTH-1 5334 SAND, Gravelly, Silty GRADATION TEST RESULTS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 624.0 feetTH-4 362FILL, Silt, Sandy Job No. %PLASTICITY INDEX %LIQUID LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of %PLASTICITY INDEX %LIQUD LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of KOECHLEIN CONSULTING ENGINEERS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 FIG.805-112 99.0 feetTH-4 6922 SAND, Gravelly GRADATION TEST RESULTS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 714.0 feetTH-4 2964GRAVEL, Sandy Job No. %PLASTICITY INDEX %LIQUID LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of %PLASTICITY INDEX %LIQUD LIMIT%SILT & CLAYElev./DepthSample No.Source %SAND%GRAVELSample of KOECHLEIN CONSULTING ENGINEERS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 FIG.905-112 534.0 feetTH-6 461 SILT, Sandy GRADATION TEST RESULTS 10 90 20 80 30 70 40 60 50 50 60 40 70 30 80 20 90 10 0 100 100 0 PERCENT PASSINGPERCENT RETAINED100 10 1 0.1 0.01 0.001200DIAMETER OF PARTICLE IN MM COBBLES GRAVEL SAND SILT CLAY 6 in.3 in.2 in.1-1/2 in.1 in.3/4 in.1/2 in.3/8 in.#4 #10 #20 #30 #40 #60 #100 #140 #200 159.0 feetTH-6 5629SAND, Gravelly, Silty SUMMARY OF LABORATORY TEST RESULTS TABLE I LIQUID LIMIT (%) PLASTICITY INDEX (%) TH-1 4.0 7 19 GRAVEL, Sandy, Silty TH-1 9.0 13 118 24 SAND, Gravelly, Silty TH-1 14.0 4 13 SAND, Gravelly, Silty TH-4 4.0 18 99 62 FILL, Silt, Sandy TH-4 9.0 5 113 9 SAND, Gravelly TH-4 14.0 2 7 GRAVEL, Sandy TH-6 4.0 18 99 53 SILT, Sandy TH-6 9.0 6 15 SAND, Gravelly, Silty SOIL TYPEHOLE SAMPLE DEPTH (ft) NATURAL MOISTURE CONTENT (%) NATURAL DRY DENSITY (pcf) PERCENT SWELL AT 1,000 PSF (%) PASSING NO. 200 SIEVE (%) ATTERBERG LIMITS JOB NO. 05-112 KOECHLEIN CONSULTING ENGINEERS, INC.