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HomeMy WebLinkAboutB12-0042_Geotechnical Report_121511_11-05290ECHLEIN CONSULTING ENGINEEM4, INC. GEOTECHNICAL AND MATERIALS ENGINEERS GEOTECHNICAL REPORT PROPOSED EAST MALL PLAZA SHELTER EAST LIONSHEAD CIRCLE VAIL,,COLORADO Prepared for: Todd Oppenheimer Department of Public Works Town of Vail 1309 Elkhorn Drive Vail, CO 81657 T KCE Job No, 11 -052 December 15, 2011 DENVER: 12364 West Alameda Parkway •Suite 110 •Lakewood, CO 80228 • (303) 989 -1223 GRAND JUNCTION: 529 25112 Rd • Suite B -201 • Grand Junction, C081505 *(970)241-7700 December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers TABLE OF CONTENTS SCOPE 1 PROPOSED CONSTRUCTION 1 SITE CONDITIONS 2 SUBSURFACE EXPLORATION 2 SUBSURFACE CONDITIONS 3 EXCAVATIONS 3 SEISMICITY 4 FOUNDATIONS 4 SLABS -ON -GRADE 6 SURFACE DRAINAGE 7 COMPACTED FILL 7 LIMITATIONS 9 VICINITY MAP Fig. 1 LOCATIONS OF EXPLORATORY BORINGS Fig. 2 LOGS OF EXPLORATORY BORINGS Fig. 3 LEGEND OF EXPLORATORY BORINGS Fig. 4 GRADATION TEST RESULTS Fig. 5 December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers SCOPE This report presents the results of a subsurface exploration for the reconstruction of the East Mall Plaza shelter in Vail, Colorado. The approximate site location is shown on the Vicinity Map, Fig. 1. The purpose of this subsurface exploration was to evaluate the subsurface conditions at the site and to provide geotechnical recommendations for the proposed construction. This report includes descriptions of subsoil and ground water conditions encountered in the exploratory borings, recommended foundation systems, allowable soil bearing pressure, slabs -on -grade and recommended foundation design and construction criteria. This report was prepared from data developed during our field exploration, 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 proposed building being constructed. PROPOSED CONSTRUCTION We understand that an open shelter will be constructed on the subject site. We anticipate the proposed structure will be one story in height with no below grade level. We anticipate that the proposed structure will be of cast -in -place concrete, stone veneer and wood and steel -frame construction. We anticipated structural loads will be relatively light. 1 December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers SITE CONDITIONS The East Mall Plaza shelter to be reconstructed is located approximately 400 feet south of the intersection of East Lionshead Circle and the I -70 South Frontage Road. The site is bordered to the north by East Lionshead Circle. The area has been developed for commercial use with the East Lionshead Parking Structure located to the northeast. Vegetation to the sides and within the existing islands of the existing bus stop consists of grass and trees. SUBSURFACE EXPLORATION Subsurface conditions were explored at this site on June 13, 2011 by drilling two shallow borings with a 4 -inch diameter continuous flight power auger attached to a truck drill rig at the locations shown on the Locations of Exploratory Borings, Fig. 2. A representative from our office was on site to supervise the drilling of the borings and visually classify and document the subsurface soils and ground water conditions. Our personnel also obtained representative samples of the soils within the borings to be examined in our laboratory. A description of the subsurface soils encountered in the borings and a summary of laboratory test results are shown on the Logs of Exploratory Borings, Fig. 3; and on the Legend of Exploratory Borings, Fig. 4 Laboratory testing included visual classification by the project engineer and testing of the samples for moisture content, Atterberg limits, and gradation analysis properties. Results of the laboratory tests are presented on the Logs of Exploratory Borings, Fig. 3, and on the Gradation Test Results, Fig. 5. 2 December 15, 2011 KCE Job No. 11 -052 SUBSURFACE CONDITIONS Koechlein Consulting Engineers, Inc. ■ Geotechnical and Materials Engineers Subsurface conditions encountered in the borings (P -1 and P -2) were generally similar. The subsurface conditions consisted of two feet of sand with gravel and silt. Observation of the drilling indicated the material was likely medium dense. Below two feet, the material became more gravelly and appeared denser, based on drilling observations. This material extended to the maximum depth explored of 5 feet. At the time of drilling, ground water was not encountered in either of the borings to the maximum depth explored of 5 feet. EXCAVATIONS We anticipate that relatively shallow excavations will be required for the construction of the proposed structure. Based on the subsurface conditions encountered at the site, we anticipate that conventional construction equipment will be capable of completing the necessary excavations. Care needs to be exercised during construction so that the excavation slopes remain stable. In our opinion, the granular materials encountered at this site classify as Type C soils in accordance with OSHA classifications. The contractor's designated competent person should evaluate the soils during cutting to assess the appropriate classification at the time of construction. OSHA regulations should be followed in any excavations or cuts. 3 December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers SEISMICITY The subsurface soil and ground water conditions encountered at the site indicate that the soil profile classifies as a very dense soil and soft rock profile. Based on this classification and the International Building Code (IBC), it is our opinion that the subject site has a seismic site classification of Site Class C. FOUNDATIONS We anticipate that the subsurface conditions at the foundation elevation for the proposed shelter will consist of silty sand and gravel with nil to low potential swell. It is our opinion that the proposed shelter may be constructed using a spread footing foundation system constructed on the silty sand and gravel or properly moisture conditioned and compacted, non - expansive, structural fill with a low risk of movement. Since the borings for this project were not completed within the foot print of the structure, we must be contacted to observe the completed excavation and determine if the design criteria are valid. We recommend that spread footings be designed and constructed to meet the following criteria: 1. Footings should be constructed on the silty sand and gravel, or properly moisture conditioned and compacted, non - expansive structural fill, as described below in Items 2, 8, and 9. 2. Any topsoil or existing fill encountered beneath foundations must be removed in order to expose the natural sand and gravel. If necessary, properly moisture conditioned and compacted structural fill may be placed beneath the proposed foundations. Refer to the COMPACTED FILL section of this report for backfill requirements. Id December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers 3. Spread footings constructed on the silty sand and gravel, or properly moisture treated and compacted structural fill may be designed for a maximum allowable soil bearing pressure of 3,500 psf. 4. Spread footings constructed on the silty sand and gravel, or properly moisture conditioned and compacted structural fill should experience less than 1.0 -inch of differential movement between foundation elements. 5. Foundation systems should be designed to span a distance of at least 10 feet in order to account for anomalies in the soil. 6. 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 4 feet. 7. 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. 8. Pockets or layers of loose or soft soils or fill may be encountered in the bottom of the completed footing excavations. These materials should be removed to expose the undisturbed natural, sand and gravel. The foundations should be constructed on the natural sand and gravel; or properly moisture conditioned and compacted structural fill. Refer to the COMPACTED FILL section of this report for backfill requirements. 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 compaction of structural fill used in foundation construction during the placement process. It has been our experience that without engineering quality control, inappropriate construction techniques occur which result in unsatisfactory foundation performance. 10. A representative of our office must observe the completed foundation excavation. Variations from the conditions described in this report, which were not indicated by our borings, can occur. The representative can observe the excavation to evaluate the exposed subsurface conditions and make the necessary recommendations. Z December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers SLABS -ON -GRADE We anticipate that the subsurface conditions at the approximate slab -on -grade elevation will consist of silty and gravelly sand, or new structural fill with a low risk of movement. Any topsoil or existing fill beneath slabs -on -grade must be removed and if necessary, replaced with properly moisture treated and compacted, non - expansive structural fill. We recommend that slabs -on -grade be designed and constructed to meet the following criteria: 1. Slabs -on -grade may be constructed on the natural sand and gravel, or properly compacted non - expansive fill, as described below in Items 2 and 6. 2. Any topsoil or existing fill below the slabs -on -grade should be removed and if necessary, replaced with properly compacted and moisture treated, non - expansive structural fill. Refer to the COMPACTED FILL section of this report for backfill requirements. 3. Slabs -on -grade constructed on structural fill or the existing granular materials may be designed using a modulus of subgrade reaction of 150 pci. 4. Slabs -on -grade 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 the concrete. 6. Structural fill beneath slabs -on -grade may consist of the existing on -site soils free of all organics and deleterious materials, or approved imported, non - expansive fill. Structural 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 each lift of structural fill used in slab -on -grade construction. It has been our experience that without engineering quality control, inappropriate construction techniques can occur which result in unsatisfactory slab performance. December 15, 2011 KCE Job No. 11 -052 SURFACE DRAINAGE Koechlein Consulting Engineers, Inc. ■ Geotechnical and Materials Engineers 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 after the proposed construction has been completed. 1. Wetting or drying of the open excavations should be minimized during construction. 2. All surface water should be directed away from the top and sides of the excavation during construction. 3. The ground surface surrounding the exterior of the proposed structure should be sloped to drain away from the structure in all directions. We recommend a slope of at least 12 inches in the first 10 feet in landscaped areas. 4. Hardscape (concrete and asphalt) should be sloped to drain away from the structure. We recommend a slope of at least 2 percent for all hardscape within 10 feet of the structure. 5. Backfill, especially around foundation walls, should 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 for this site should be designed by a Professional Civil Engineer. COMPACTED FILL Structural fill for this project may consist of on -site, natural, granular materials, or approved imported, non - expansive structural fill. Any topsoil or existing fill should be 7 December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers removed prior to construction. Topsoil with organics or other deleterious material may be used in landscaped areas. The imported fill may consist of non - expansive silty or clayey sands or gravels with up to 10 percent passing the No. 200 sieve with a maximum plasticity index of 10. No gravel or cobbles larger than 6 inches should be placed in fill areas. Fill areas should be stripped of all vegetation, topsoil, and existing fill, and then scarified. Fill should be placed and compacted in thin loose lifts, moisture conditioned and compacted to the recommended compaction shown in the following table. The recommended compaction varies for the given use of the fill. We recommend that a representative of our office observe and test the placement and compaction of each lift placed for structural fill. Fill placed below foundations, slabs- on- grade, and behind retaining walls is considered structural. It has been our experience that without engineering quality control, inappropriate construction techniques can occur which result in unsatisfactory foundation and slab -on -grade performance. E Recommended Compaction Percentage of the Standard Percentage of the Modified Use of Fill Proctor Maximum Proctor Maximum Dry Density Dry Density (ASTM D 698) (ASTM D 1557) Below Structure Foundations 98 95 Below Slabs -on -Grade 95 90 Utility Trench Backfill 95 90 Backfill (Non- Structural) 90 90 Notes: 1. For granular soils, the moisture content should be —2 to +2 percent of the optimum moisture content. We recommend that a representative of our office observe and test the placement and compaction of each lift placed for structural fill. Fill placed below foundations, slabs- on- grade, and behind retaining walls is considered structural. It has been our experience that without engineering quality control, inappropriate construction techniques can occur which result in unsatisfactory foundation and slab -on -grade performance. E December 15, 2011 Koechlein Consulting Engineers, Inc. KCE Job No. 11 -052 Geotechnical and Materials Engineers LIMITATIONS The exploratory borings were originally located to obtain a reasonably accurate determination of conditions at the subject site for paving of the bus loop, with one boring relatively close to the proposed structure. Variations in the subsurface conditions are always possible. Any variations that exist beneath the site generally become evident during excavations for the proposed structure. A representative from our office must observe the completed excavation to confirm that the soils are as indicated by the exploratory borings and to verify our foundation, slab -on- grade, and general design and construction recommendations. The placement and compaction of fill, as well as installation of foundations, should also be observed and tested. The design criteria and subsurface data presented in this report are valid for 3 years from the date of this report. 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 existing or proposed pavements from a geotechnical viewpoint, please contact our office. KOECHLEIN CONSULTING ENGINEERS, INC. Timothy A. Mitchell, P.E. Senior Engineer (4 copies sent) KOECHLEIN CONSULTING ENGINEERS, INC. Geotechnical and Materials Engineers Potato Patch O^ 1 N f1omage Pd W .... Q SITE ore Greek 08av�r_ Dam Forest Pa _ Rcc .+'Wge Po, NOT TO SCALE VICINITY MAP JOB NO. 11 -052 FIG. 1 /eaor azv, EXISTING SHELTER KOECHLEIN CONSULTING ENGINEERS, INC. Geotechnical and Materials Engineers PROPOSED SHELTER DRAINAGE EASEMENT (HATCHED AREA) SCALE: 1 in = 80 ft LOCATIONS OF EXPLORATORY BORINGS JOB NO. 11 -052 FIG. 2 a� a� C s CL m D N 2 4 [.1 10 12 14 Mv JOB NO. 11 -052 P -1 WC =2.3 - 200 =9.9 LL =NV P1 =NP KOECHLEIN CONSULTING ENGINEERS, INC. Geotechnical and Materials Engineers P -2 WC =3.0 - 200 =12 LL =NV P1 =NP LOGS OF EXPLORATORY BORINGS N 2 4 [.1 v rt $ s. c� c� rt 10 12 14 16 Fig. 3 KOECHLEIN CONSULTING ENGINEERS, INC. Geotechnical and Material Engineers LEGEND: 10 SAND, Gravelly, Silty, Medium dense, Slightly moist, Brown Q SAND and GRAVEL, Silty, Dense, Slightly moist, a° Brown NBULK SAMPLE. Obtained from auger cuttings. Notes: 1. Borings were drilled on 6 -13 -11 using a 4 -inch diameter continuous flight power auger mounted on a truck drill rig. 2. Borings were originally drilled for East Lionshead Circle Bus Stop, KCE Job No. 11 -025 3. No free ground water was encountered at the time of drilling in any of the pavement borings to the maximum depth explored of 5 feet. 4. The Boring Logs are subject to the explanations, limitations, and conclusions as contained in this report. 5. Laboratory Test Results: WC - Indicates natural moisture ( %) -200- Indicates percent passing the No. 200 sieve ( %) LL - Indicates liquid limit ( %) PI - Indicates plasticity index ( %) LEGEND OF EXPLORATORY BORINGS JOB NO. 11 -052 Fig. 4 KOECHLEIN CONSULTING ENGINEERS 100 0 100 0 90 90 10 10 80 80 20 20 70 (D 70 (D z ISL 30 Z U) � so m A n 60 cn 50 W 40 m a C 40 W a 60 Z m 30 z 50 50 w 20 80 10 Of 40 W 0 60 z m a 200 100 10 1 0.1 0.01 0.001 DIAMETER OF PARTICLE IN MM +75 MM GRAVEL SAND SILT CLAY 30 70 20 80 10 90 0 100 200 100 10 1 0.1 0.01 0.001 DIAMETER OF PARTICLE IN MM +75 MM GRAVEL SAND SILT CLAY Sample of Poorly Graded GRAVEL with Silt and Sand (GP -GM) GRAVEL 50 % SAND 40 % Source P -1 Sample No. Elev. /Depth 0.5 to 5 Feet SILT & CLAY 10 % LIQUID LIMIT NV % PLASTICITY INDEX NP % 6 in. 3 in. 2 M.A. in. 1 in. /4 in. 112 in 10 920 #30 #40 #60 #100 140 AZOO 100 0 90 10 80 20 70 (D z ISL 30 m X � so ao m z 50 W 50 -m D C 40 W a 60 Z m 30 70 20 80 10 90 0 100 200 100 10 1 0.1 0.01 0.001 DIAMETER OF PARTICLE IN MM +75 MM GRAVEL SAND SILT CLAY Sample of Poorly Graded SAND With Silt and Gravel (SP -SM) GRAVEL 44 Source P -2 Sample No. Elev. /Depth 0.5 to 5 Feet SILT & CLAY 12 PLASTICITY INDEX GRADATION TEST RESULTS • SAND 44 % • LIQUID LIMIT NV % NP % Job No. 11 -052 Fig. 5