The URL can be used to link to this page

Home My WebLink AboutNEENAN OFFICE BUILDING - RC SITE PLAN REVIEW & MINOR SUBDIVISION - 5-96 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTlGeotechnical Engineering Exploration Terracon •1 The Neenan Company Project No. 20965009 Groundwater Conditions JGroundwater was encountered at approximate depths of 5 to 11-1/2 feet in the test borings at the time of field exploration. When checked 8 to 10 days after drilling, groundwater was Jmeasured at approximate depths of 9 to 11 feet in the majority of the test borings. These observations represent only current groundwater conditions, and may not be indicative of other times, or at other locations. Groundwater levels can be expected to fluctuate with varying seasonal and weather conditions. Based upon review of U.S. Geological Survey maps ('Hillier, et al, 1983), regional groundwater is expected to be encountered in unconsolidated alluvial deposits on the site, at depths ranging from 0 to 5 feet below the existing ground surface at the project site. Fluctuations in groundwater levels can best be determined by implementation of a groundwater monitoring plan. Such a plan would include installation of groundwater monitoring wells, and periodic measurement of groundwater levels over a sufficient period of time. The possibility of groundwater fluctuations should be considered when developing design and construction plans for the project. CONCLUSIONS AND RECOMMENDATIONS Geotechnical Considerations The site appears suitable for the proposed construction. Existing fill and debris will require particular attention in the design and construction. The following foundation systems were evaluated for use on the site: • straight shaft piers and grade beams drilled into bedrock; and • spread footings bearing on structural fill extended to the undisturbed soils. In view of the nature of the fill material encountered at the site, it is our opinion that slab -on - grade construction is not feasible without removal or reworking of at least the upper 3 feet of the existing fill below slabs or by scarifying and recompacting the existing fill and overlaying it by a minimum of 3 feet of select granular structural fill. 'Hillier, Donald E.; Schneider, Paul A., Jr.; and Hutchinson, E. Carter, 1983, Depth to Water Table (1979) in the Boulder -Fort Collins -Greeley Area, Front Range Urban Corridor, Colorado, United States Geological Survey, Map 1-855- 1. 5 Geotechnical Engineering Exploration The Neenan Company Project No. 20965009 Terracon surface. The bedrock is overlain by natural alluvial gravels of Pleistocene and/or Recent Age and fill. The area lies within the flood plain of the Cache La Poudre River. We understand the finished first floor of the building will be elevated above the 100-year flood plain of the stream. Mapping completed by the Colorado Geological Survey (Hart, 1972), indicates the site in an area of "Low Swell Potential." Potentially expansive materials mapped in this area include bedrock, weathered bedrock and colluvium (surficial units). Soil and Bedrock Conditions The following describes the characteristics of the primary soil strata in order of increasing depths: • Fill Material: A 1 to 14 foot layer of fill material was encountered in all borings drilled at the site. The fill consists of a mixture of silty sand with gravel and cobbles, sandy silt, washout concrete, chunks of concrete, brick, and minor amounts of wood and asphalt. The fill has been place in an excavated gravel pit and does not appear to have been uniformly or properly compacted. The fill is moist to wet, partially cemented and loose to extremely dense. • Well -Graded Gravel with Silt, Sand and Cobbles: This stratum underlies the fill in Borings 1, 3 and 5 through 14 and extends to the bedrock below and/or the depths explored. The well -graded gravel contains varying amounts of silt, sand and cobbles, is moist to wet and medium dense to dense. It is estimated the cobbles within the granular stratum are typically between 6 and 8 inches in diameter. • Siltstone-Claystone Bedrock: The bedrock was encountered in Borings 1 through 11 at depths of 13-1/2 to 18-1/2 feet and extends to greater depths. The upper 1 to 1- 1/2 feet of the bedrock is highly weathered; however, the underlying interbedded siltstone and claystone is hard. Field and Laboratory Test Results Field test results indicate the natural granular soils exhibit moderate bearing characteristics, and the bedrock exhibits very high bearing characteristics. The bedrock also exhibits low to moderate swell potential. 4 C J Terracon Geotechnical Engineering Exploration The Neenan Company Project No. 20965009 testing program was formulated to determine engineering properties of the subsurface Jmaterials. Boring logs were prepared and are presented in Appendix A. Selected soil and bedrock samples were tested for the following engineering properties: • Water content Plasticity Index JDry density Water soluble sulfate content • Grain size The significance and purpose of each laboratory test is described in Appendix C. Laboratory test results are presented in Appendix B, and were used for the geotechnical engineering analyses, and the development of foundation and earthwork recommendations. All laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards. SITE CONDITIONS JThe site is a vacant area vegetated with native grass, weeds, brush and trees. The area was previously mined for gravel and backfilled with construction debris including concrete Jand washout material from concrete mixer trucks. The area is relatively flat and has poor drainage. Several large piles of fill, 10 to 12 feet high, are scatted throughout the site along J with piles of waste concrete, asphalt and concrete washout material. Berms have been built along the east-northeast edge of the site. A bike path is located between the property and the Cache La Poudre River, which is located to the north and east of the site. SUBSURFACE CONDITIONS l Geology J The proposed area is located within the Colorado Piedmont section of the Great Plains physiographic province. The Colorado Piedmont, formed during Late Tertiary and Early Quaternary time (approximately 2,000,000 years ago), is a broad, eresional trench which separates the Southern Rocky Mountains from the High Plains. Structurally, the site lies along the western flank of the Denver Basin. During the Late Mesozoic and Early Cenozoic Periods (approximately 70,000,000 years ago), intense tectonic activity occurred, causing l the uplifting of the Front Range and associated downwarping of the Denver Basin to the J east. Relatively flat uplands and broad valleys characterize the present-day topography of the Colorado Piedmont in this region. The site is underlain by the Cretaceous Pierre 1 Formation. The Pierre shale underlies the site at depths of 13-1/2 to 18-1/2 feet below the J 3 Geotechnical Engineering Exploration Terracon The Neenan Company Project No. 20965009 J SITE EXPLORATION The scope of the services performed for this project included site reconnaissance by an engineering geologist, a subsurface exploration program, laboratory testing and engineering analysis. Field Exploration A total of 14 test borings were drilled on January 22 and 24, 1996 to depths of 15 to 24-1/2 feet at the locations shown on the Site Plan, Figure 1. Eleven borings were drilled within the footprint of the proposed building, and three borings were drilled in the area of proposed pavements. All borings were advanced with a truck -mounted drilling rig, utilizing 4-inch diameter solid stem auger. The borings were located in the field by pacing from property lines and/or existing site features,. Elevations were taken at each boring location by measurements with an engineer's level from a temporary bench mark (TBM) shown on the Site Plan. The accuracy of boring locations and elevations should only be assumed to the level implied by the methods used. Continuous lithologic logs of each boring were recorded by the engineering geologist during the drilling operations. At selected intervals, samples of the subsurface materials were taken by driving split -spoon samplers. Penetration resistance measurements were obtained by driving the split -spoon into the subsurface materials with a 140-pound hammer falling 30 inches. The penetration resistance value is a useful index to the consistency, relative density or hardness of the materials encountered. Groundwater measurements were made in each boring at the time of site exploration, and 8 to 10 days after drilling. Laboratory Testing All samples retrieved during the field exploration were returned to the laboratory for observation by the project geotechnical engineer, and were classified in accordance with the Unified Soil Classification System described in Appendix C. Samples of bedrock were classified in accordance with the general notes for Bedrock Classification. At that time, the field descriptions were confirmed or modified as necessary and an applicable laboratory 2 GEOTECHNICAL ENGINEERING REPORT PROPOSED NEENAN OFFICE BUILDING SEVEN LAKES BUSINESS PARK FORT COLLINS, COLORADO Project No. 20965009 February 5, 1996 INTRODUCTION Terracon J This report contains the results of our geotechnical engineering exploration for the proposed Neenan office building to be located on Tract D of the Seven Lakes Business Park in east Fort Collins, Colorado. The site is located in the Southeast 1/4 of Section 17, Township 7 North, Range 68 West of the 6th Principal Meridian. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: l subsurface soil and bedrock conditions • groundwater conditions l foundation design and construction • lateral earth pressures • floor slab design and construction • pavement design and construction 1 earthwork • drainage J The conclusions and recommendations contained in this report are based upon the results of field and laboratory testing, engineering analyses, and experience with similar soil conditions, structures and our understanding of the proposed project. PROPOSED CONSTRUCTION Based on information provided by The Neenan Company, it is our understanding the + proposed structure is to a 43,000 square foot office building with associated parking. The 1 majority of the building will be a one-story structure with a partial story section. The finished first floor will be elevated several feet above existing grade. The building will have precast or site cast, tilt -up panel walls and interior steel columns. Anticipated wall and column loads are 3 kips per linear foot and 90 kips, respectively. 1 Geotechnical Engineering Exploration The Neenan Company Project No. 20965009 TABLE OF CONTENTS (cont'd) APPENDIX A Site Plan and Boring Location Diagram Logs of Borings APPENDIX B Laboratory Test Results APPENDIX C General Notes Terracon 2 Terracon TABLE OF CONTENTS Letter of TransmittalPage No. .............................................................................................................ii INTRODUCTION.................................................................................................................1 PROPOSED CONSTRUCTION..........................'..............................................................1 SITEEXPLORATION..........................................................................................................2 FieldExploration......................................................................................................2 LaboratoryTesting.................................................................................................. 2 SITECONDITIONS............................................................................................................. 3 lSUBSURFACE CONDITIONS............................................................................................ 3 JGeology................................................................................................................... 3 Soil and Bedrock Conditions................................................................................... 4 Field and Laboratory Test Results........................................................................... 4 Groundwater Conditions.......................................................................................... 5 CONCLUSIONS AND RECOMMENDATIONS.................................................................... 5 Geotechnical Considerations................................................................................... 5 FoundationSystems................................................................................................6 ShallowFoundation Systems.................................................................................. 7 Lateral Earth Pressures...........................................................................................8 Seismic Considerations...........................................................................................9 Floor Slab Design and Construction........-.............................................................. 9 Pavement Design and Construction........................................................................10 Earthwork................................................................................................................ 13 Site Clearing and Subgrade Preparation.....................................................13 Excavation...................................................................................................14 Placement and Compaction.........................................................................15 Shrinkage.....................................................................................................16 Compliance..................................................................................................16 Excavation and Trench Construction...........................................................16 Drainage..................................................................................................................17 Surface Drainage.........................................................................................17 Subsurface Drainage...................................................................................17 Additional Design a; d Construction Considerations................................................18 Exterior Slab Design and Construction........................................................18 Underground Utility Systems........................................................................18 Corrosion Protection....................................................................................19 GENERALCOMMENTS.....................................................................................................19 1 February 5, 1996 The.,Neenan Company P. O. Box 2127 Fort Collins, Colorado 80522 Attn: Mr. Kent Norwood Irerracon CONSULTANTS WESTERN, INC. EMPIRE DIVISION P.O. Box 503 • 301 N. Howes Fort Collins, Colorado 80522 (970)484-0359 Fax (970) 484-0454 Larry G. O'Dell, P.E. Neil.R. Sherrod, C.P.G. Re: Geotechnical Engineering Report, Proposed Neenan Office Building Seven Lakes Business Park, Fort Collins, Colorado Project No. 20965009 Terracon Consultants Western, Inc., Empire Division has completed a geotechnical engineering exploration for the proposed office building to be located in the Seven Lakes Business Park on East Prospect Road, Fort Collins, Colorado. This study was performed in general accordance with our proposal number D2096010 dated January 18, 1996. The results of our engineering study, including the boring location diagram, laboratory test results, test boring records, and the geotechnical recommendations needed to aid in the design and construction of foundations and other earth connected phases of this project are attached. The subsoils at the site consist of granular fill material containing concrete and debris underlain by natural gravels and siltstone-claystone bedrock. In view of the anticipated loads of the proposed office building and the subsurface conditions, it is recommended the structure be supported by a drilled pier foundation system or by conventional spread footings placed on structural fill extended to the undisturbed soil. Overexcavation of a portion of the existing fill material is recommended for slab -on -grade construction. Further details are provided in this report. We appreciate the opportunity to be of service to you on this phase of your project. If you have any questions concerning this report, or if we may be of further service to you, please do not hesitate to contact us. Sincerely, TERRACON CONSULTANTS WESTERN, INC. Empire Division Prepared by: �\,.U�FOCA►EO �'/�y Reviewed by: � 5 •.••• 0Q �B ••, �� Q l) rr s : �� 2575 �gg AEPG 76 ell d �� y '., illiam J. Attwoollq tP* �. 47,° Senior Engineering Geolo a >.F�! R••••••q ns Office Manager Mana op,_ SHER•. .. g Copies to: Addressee (3) 90008 { ° 400 Offices of The Terracon Companies, Inc. Geotechnical, Environmental and Materials Engineers Arizona ■ Arkansas ■ Colorado ■ Idaho ■ Illinois ■ Iowa ■ Kansas ■ Minnesota Missoud ■ Montana ■ Nebraska ■ Nevada ■ Oklahoma IN Texas ■ Utah ■ Wyoming QUALITY ENGINEERING SINCE 1965 GEOTECHNICAL ENGINEERING REPORT PROPOSED NEENAN OFFICE BUILDING SEVEN LAKES BUSINESS PARK FORT COLLINS, COLORADO PROJECT NO. 20965009 February 5, 1996 Prepared for. THE NEENAN COMPANY P. O. BOX 2127 FORT COLLINS, COLORADO 80522 ATTN: MR. KENT NORWOOD PROJECT ARCHITECT Prepared by. Terracon Consultants Western, Inc. Empire Division 301 North Howes Street Fort Collins, Colorado 80521 I lrerracon