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HomeMy WebLinkAboutGATEWAY AT HARMONY ROAD PUD, TACO CABANA - PRELIMINARY & FINAL - 1-88H - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT SUBSURFACE EXPLORATION REPORT PROPOSED TACO CABANA FORT COLLINS, COLORADO EEC PROJECT NO. 1952036 1 tY ., • EARTH ENGINEERING CONSULTANTS, INC. It 1 June 7, 1995 E ,_ * , IEARTH ENGINEERING P.I.I. CONSULTANTS, INC. It 1318 Paragon Place Fort Collins, Colorado 80525 II. Attn: Mr. Larry Clark RE: Subsurface Exploration Report X Proposed Taco Cabana South College Avenue Fort Collins, Colorado II EEC Project No. 1952036 Mr. Clark: Enclosed, herewith, are the results of the subsurface exploration you requested for the referenced project. In summary, the subsurface materials encountered in the test borings consisted of low IIplasticity sandy silty clay with occasional zones of silty clayey sand. A portion of the near surface samples appeared to be fill materials. Based on the results of our field and laboratory testing, it II is our opinion the proposed lightly loaded structure could be supported on conventional footing foundations bearing on the natural site soils. It is our opinion the near surface materials would also be acceptable for support of floor slabs and pavements for the proposed development. II Geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements are presented in the text of the attached report. II We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the enclosed report, or if we can be of further service to you in any other way, please do not hesitate to contact us. IIVery truly yours, I Earth Engineering Consultants, Inc.t4„,,,,...,."„,,,t., Revie -.,- .• f II /ti',.4w„1:". - i:4 e0,i p : 2 r. • '. j �a • r " w" 27315 ,;'W �rYy: •� � ; J iffy " �� •��► Les-' -,,,, .. P.E. Curti - '.E. IIPrincipal Engineer Principal cc: Plaza Associates/Sergio Plaza U Ripply Associates/Linda Ripply Centre For Advanced Technology 2301 Research Boulevard,Suite 104 Fort Collins,CO 80526 II (970)224-1522 FAX 224-4564 U U SUBSURFACE EXPLORATION REPORT PROPOSED TACO CABANA SOUTH COLLEGE AVENUE FORT COLLINS, COLORADO EEC PROJECT NO. 1952036 U June 7, 1995 111 I INTRODUCTION The subsurface exploration for the proposed Taco Cabana Restaurant to be located on the west side of South College Avenue, nortli'"of Harmony Road, in Fort Collins, Colorado, has been completed. Two (2) soil borings extending to depths of approximately 15 feet below existing site grades were advanced in the proposed building area to develop information on existing subsurface conditions relative to foundation and floor slab support. Two (2) other borings were advanced to depths of approximately 5 feet below existing site grades in the parking areas to develop additional information on subsurface conditions relative to support of the proposed pavements. Individual boring logs and a diagram indicating the approximate boring locations are included with this report. U We understand the proposed Taco Cabana Restaurant will be a single story, slab-on-grade (non- '. basement) structure. The new building will be constructed north of Harmony Road (north of the existing McDonalds Restaurant) and west of South College Avenue. It is anticipated the new I building will have light foundation loads with continuous walls loads less than 3 kips per lineal foot and individual column loads less than 50 kips. Floor loads for the new restaurant will be light, less than 100 psf. Paved drive and parking areas will be constructed to the south of the new building and drive-thru facilities will be constructed on the north side of the structure. Cuts and fills of less than 2 feet will be required to develop the site grades. The purpose of this report is to describe the subsurface conditions encountered in the borings, analyze and evaluate the test data and provide geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements. U U I 111 Earth Engineering Consultants, Inc. Proposed Taco Cabana _ June 7, 1995 Page 2 EXPLORATION AND TESTING PROCEDURES The borings locations were determined and established in the field by Earth Engineering 1111 Consultants, Inc. (EEC) personnel. The field locations were established by pacing and estimating angles from the references indicated on the attached boring location diagram. The boring locations should be considered accurate only to the degree implied by the methods used to make 1111 the field measurements. IIThe borings were performed using a truck mounted, CME 45 drill rig, equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 111 continuous flight augers and samples of the subsurface materials encountered were obtained using split-barrel sampling procedures in general accordance with ASTM Specifications D-1586. In the split-barrel sampling procedure, a standard 2-inch O.D. split-barrel sampling spoon is driven into the ground by means of a 140 pound hammer falling a distance of 30 inches. The number of I blows required to advance the split barrel sampler is recorded and is used to estimate the in-situ relative density of cohesionless soils and, to a lesser degree of accuracy, the consistency of cohesive materials. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. UMoisture content tests were performed on each of the recovered samples. In addition, the unconfined strength of those samples was estimated using a calibrated hand penetrometer. Atterberg limits and washed sieve analysis tests were performed on selected samples to aid in soil classification and to determine the plasticity of the subgrade materials. Swells/consolidation tests were also performed on selected samples to evaluate the potential for the site materials to change volume with variation in moisture content. Results of the outlined tests are indicated on the attached boring logs and summary sheets. As a part of the testing program, all samples were examined in the laboratory by an engineer and classified in accordance with the attached General Notes and the Unified Soil Classification System, based on the soil's texture and plasticity. The estimated group symbol for the Unified I Earth Engineering Consultants, Inc. I Proposed Taco Cabana June 7, 1995 Page 3 Soil Classification System is shown in the appropriate column on the boring logs and a brief description of that classification system is included with this report. SITE AND SUBSURFACE CONDITIONS The proposed Taco Cabana site is located north of the existing McDonalds Restaurant (north of Harmony Road) and west of South College Avenue. The site is presently an undeveloped open field although topsoil and vegetation has been stripped from the site or fill materials have been placed on the site covering the topsoil and vegetation. Site drainage is to the south and east with maximum fall across the site on the order of 2 feet. Evidence of prior building construction was not observed at the site by EEC field personnel. An EEC field geologist was on site during drilling to evaluate the subsurface materials encountered and direct the drilling activities. Field logs prepared by EEC field personnel were based on visual and tactual observation of disturbed samples and auger cuttings. The final boring logs included with this report may contain modifications to those field logs based on results of laboratory testing and engineering evaluation. Based on the results of the field borings and laboratory testing, subsurface conditions can be generalized as follows. The soils observed at the test boring locations consisted of brown and light brown lean clay with varying amounts of sand. Occasional sandier zones were observed in the subgrade soils with at least a portion of the materials being described as silty clayey sand. The granular materials were loose to medium dense with cohesive soils being very stiff. The very near surface materials, 111 including the top 1 to 2 feet of material, are potentially recently placed fill materials. It is _ possible these materials are natural site soils which have been disturbed by site traffic. The borings were terminated at depths ranging from approximately 5 to 15 feet in very stiff cohesive materials. The stratification boundaries shown on the boring logs represent the approximate locations of changes in soil types; in-situ, the transition of materials may be gradual and indistinct. I I 111 Earth Engineering Consultants, Inc. Proposed Taco Cabana _ June 7, 1995 Page 4 WATER LEVEL OBSERVATIONS Observations were made while drilling and after completion of the borings to detect the presence . and depth to free water. Free water was not observed in any of the borings either during or immediately after their completion. The boreholes were backfilled immediately after completion so that longer term observation of ground water levels was not possible. The site cohesive soils have relatively low permeability so that longer term observations including the installation of piezometers or monitoring wells which are sealed from the influence of surface water would be • required to more accurately evaluate ground water levels. The depth to the ground water can fluctuate over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. Zones of perched and/or trapped water may also be encountered in more permeable zones in the subgrade soils at times throughout the year and the 111 location in the amount of perched water can also fluctuate depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. 111 ANALYSIS AND RECOMMENDATIONS 111 FOUNDATIONS Based on the materials observed at the test boring locations, it is our opinion the proposed lightly loaded structure could be supported on conventional footing foundations bearing in the natural, stiff to very stiff silty sandy lean clay. For design of footing foundations bearing in the natural, stiff to very stiff cohesive soils, we recommend using a net allowable total load soil bearing pressure not exceed 3000 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Swell tests on the site materials indicate a low potential for volume change with fluctuations in moisture content. Therefore, recommendations concerning a minimum dead load pressure for the footing foundations are not being provided. I I U Earth Engineering Consultants, Inc. Proposed Taco Cabana June 7, 1995 Page 5 Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches below adjacent exterior grade. We recommend formed continuous footings have a minimum width of 16 inches and isolated column foundations have a minimum width of 30 inches. Trenched foundations (grade-beam foundations) could be used in the near surface cohesive and dirty granular soils. If used, we recommend those trenched foundations have a minimum width of 12 inches. Care should be taken during construction to see that footing foundations extend to bear below any Ipreviously placed site fill materials. -.,In addition, care will be necessary to avoid disturbing the bearing materials. Materials which are loosened or disturbed during the construction activities, 111 or materials which become dry and desiccated or wet and softened should be removed and replaced beneath the footing foundations or the footing foundations should be extended to bear in underlying acceptable natural soils. 1111 We estimate the long-term settlement of footing foundations designed and constructed as outlined above would be small, less than 1/2 inch. 111 FLOOR SLAB AND PAVEMENT SUBGRADES 111 A portion of the near surface site materials may be recently placed fill. It is also possible these materials are natural site soils disturbed by vehicle traffic. To further evaluate the suitability of the near surface soils for support of the floor slabs and pavements, we recommend those soils be proofrolled prior to placement of any additional fill, floor slabs or pavements. Proofrolling should consist of several mutual perpendicular passes over the subgrade with heavy construction equipment, such as a fully loaded tandem axle dump truck weighing not less than 40,000 pounds. Proofrolling should be observed by qualified personnel. If soft or loose zones are observed during proofrolling, it may be necessary to remove and replace those materials with acceptable fill soils or it may be possible to rework those materials in place prior to placement of overlying fill, floor slabs or pavements. U N Earth Engineering Consultants, Inc. Proposed Taco Cabana June 7, 1995 Page 6 I After proofrolling, we recommend the exposed subgrades be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the materials' maximum dry density as determined in accordance with ASTM Specification D-698, the standard Proctor procedure. The moisture content of the scarified soils should be adjusted to be within the range of ±2 percent of standard Proctor optimum moisture. A portion of the near surface soils may contain high silt contents and exhibit instability and strength loss when wetted to 2% over standard Proctor optimum moisture. For these soils, in a lower moisture content may be necessary to maintain stability in the subgrades. Fill materials required to develop the floor slab or pavement subgrades should consist of approved, low-volume change materials, free from organic matter and debris. Soils similar to the near surface silty sandy clays or silty clayey sand could be used as low volume change fill. If off site granular materials are used, we recommend those materials contain sufficient fines to prevent ponding of water in these materials. Normally, low volume change materials have a liquid limit of 40 or less and plasticity index of 18 or less. Fill materials in floor slab and pavement subgrade areas should be placed in loose lifts not to Iexceed 9-inches thick, adjusted in moisture content as recommended for the scarified soils and compacted to at least 95% of the materials' maximum dry density as determined in accordance with the standard Proctor procedure. In landscape areas of the site, the compaction of the fill materials could be reduced to 90% of standard Proctor maximum dry density. U After completion of the subgrades, care should be taken to avoid disturbing the in-place materials. Materials which are loosened or disturbed by the construction activities or materials which become dry and desiccated or wet and softened should be reworked in place or removed and replaced prior 111 to placement of the overlying pavements or floor slabs. Positive drainage should be developed across the pavements and away from the pavement edges to reduce potential for wetting of the subgrades. Subgrades allowed to become wetted could result U I I Earth Engineering Consultants, Inc. Proposed Taco Cabana June 7, 1995 Page 7 U in premature failure of the pavement sections. Positive drainage should also be developed away 111 from the structure to avoid wetting of the floor slab subgrades and bearing materials. PAVEMENTS Based on previous experience with similar facilities and subgrade conditions, we recommend the 111 pavement section for the Taco Cabana Restaurant consist of 3 inches of hot bituminous pavement overlying 6 inches of aggregate base. The hot bituminous pavement should be compatible with City of Fort Collins standard criteria fQr SC-1 or SC-2 materials. The aggregate based should be compatible with Colorado Department of Transportation requirements for Class 5 or Class 6 materials. The higher silt contents soils observed on the site may be subject to instability and strength loss when wetted. Consideration could be given to stabilization of the pavement subgrades to reduce the potential for instability during construction and to reduce the required aggregate and/or asphalt pavement sections. We would be pleased to provide additional information concerning subgrade stabilization, if requested. In areas which are designated as automobile parking only, a reduction in the pavement section Ucould be considered. Likewise, in areas where heavy truck traffic is expected, such as the area for trash service, consideration should be given to construction of a thicker pavement section. U The recommended pavement section is minimum and, as such, periodic maintenance should be 111 expected. The pavement section is based on light to moderate volumes of a vehicle mix consisting almost exclusively of automobiles and light trucks. Occasional delivery trucks or similar type vehicles are expected although repeated loadings of heavy trucks, such as a trash truck, may cause pavement distress. U ■ I • Earth Engineering Consultants, Inc. Proposed Taco Cabana June 7, 1995 Page 8 111 GENERAL COMMENTS The analysis and recommendations presented in this report are based upon the data obtained from I the soil borings performed at the indicated locations and from any other information discussed in this report. This report does not reflect any variations which may occur between borings or across the site. The nature and extent of such variations may not become evident until 111 construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. • �. It is recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. It is further recommended that the geotechnical engineer be retained for testing and observations during earthwork and foundation construction phases to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of P.I.I. for specific application to the project . discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranty, express or implied, is made. In the event that any changes in the nature, design or location of the project as outlined in this report are planned, the conclusions and ._ recommendations contained in this report shall not be considered valid unless the changes are reviewed and the conclusions of this report modified or verified in writing by the geotechnical engineer. I I 111 1111 ,-7,y- '4 b' 79-7 707 kJ, ,C j r , • 1 06 H 1 III o --2 1 , i—+-1. I i �J III ,, 1„,,,..dok , e) 412 ritipattinia m __. arocio•41. , , . a/c CT- 111 - /-----/ f 1 I • 7 cO'N- 1 N ; / A . ....4%' ,A I•II i I,//INi ,i. t *aP"- ----r.41,t.,i4,.Abt,4s.,eft1244 '1 .2e., 1 ,♦ 4 iOrl III .11 -PA?). .it`.• _ - es,....$ 7--- --,. /-:.',1, L.. Q (.44 k •, , %.166-.4 ; . -i-: \NJ::_ cn ),,:. ® ..------------ . II ---' . , NOT TO SCALE ® TEST BORING LOCATION DIAGRAM TACO CABANA ® FORT COLLINS, COLORADO JUNE 1995 IIPROJECT No: 1952036 Earth Engineering Consultant: