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HomeMy WebLinkAbout1ST CHOICE BANK OF FORT COLLINS (TEMPORARY FACILITY) - MINOR SUBDIVISION - 41-94 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORT1st Choice Bank Terracon ELI Project No. 20945096 This report is for the exclusive purpose of providing geotechnical engineering and/or testing information and recommendations. The scope of services for this project does not include, either specifically or by implication, any environmental assessment of the site or identification of contaminated or hazardous materials or conditions. If the owner is concerned about the potential i for such contamination, other studies should be undertaken. I� J E I] I I� II II II ORE 1st Choice Bank ELI Project No. 20945096 Terracon • Underground Utility Systems: All piping should be adequately bedded for proper load distribution. Temporary dewatering will be required where utilities are excavated below ground water. • Corrosion Protection: Results of soluble sulfate testing indicate that ASTM Type 1-II Portland cement is suitable for all concrete on and below grade. Foundation concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. GENERAL COMMENTS It is recommended that the Geotechnical Engineer be retained to provide a general review of final design plans and specifications in order to confirm that grading and foundation recommendations have been interpreted and implemented. In the event that any changes of the proposed project are planned, the conclusions and recommendations contained in this report should be reviewed and the report modified or supplemented as necessary. The Geotechnical Engineer should also. be retained to provide services during excavation, grading, foundation and construction phases of the work. Observation of footing excavations should be performed prior to placement of reinforcing and concrete to conform that satisfactory bearing materials are present and is considered a necessary part of continuing geotechnical engineering services for the project. Construction testing, including field and laboratory evaluation of fill; backfill, pavement materials, concrete and steel, should be performed to determine whether applicable project requirements have been met. It would be logical for Empire Laboratories, Inc. to provide these additional services since we are most qualified to determine consistency of field conditions with those data used in our analyses. The analyses and recommendations in this report are based in part upon data obtained from the field exploration. The nature and extent of variations beyond the location of test borings may not become evident until construction. If variations then appear evident, it may be necessary to ]; reevaluate the recommendations of this report. Our professional services were performed using that degree of care and skill ordinarily exercised, under similar circumstances, by reputable geotechnical engineers practicing in this or similar localities. No warranty, express or implied, is made. We prepared the report as an aid in design Jj of the proposed project. This report is not a bidding document. Any contractor reviewing this report must draw his own conclusions regarding site conditions and specific construction techniques to be used on this project. 19 1st Choice Bank ELI Project No. 20945096 Drainage: • Surface Drainage: Terracon 1. Positive drainage should be provided during construction and maintained throughout the life of the proposed facility. Infiltration of water into utility or foundation excavations must be prevented during construction. Planters and other surface features which could retain water in areas adjacent to the building or pavements should be sealed or eliminated. 2. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of approximately 10 percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of all construction debris to reduce the possibility of moisture infiltration. 3. Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when the ground surface beneath such features is not protected by exterior slabs or paving. 4. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent to the foundation system should be minimized or eliminated. Additional Design and Construction Considerations: • Exterior Slab Design and Construction: Exterior slabs -on -grade, exterior architectural features, and utilities founded on, or in backfill may experience some movement due to the volume change of the backfill. Potential movement could be reduced by: • minimizing moisture increases in the backfill • controlling moisture -density during placement of backfill • using designs which allow vertical movement between the exterior features and adjoining structural elements • placing effective control joints on relatively close centers • allowing vertical movements in utility connections 1s 1st Choice Bank ELI Project No. 20945096 Terracon 2. The face of all slopes should be compacted to the minimum specification for fill embankments. Alternately, fill slopes can be over -built and trimmed to compacted material. • Compliance: Recommendations for slabs -on -grade, foundations and pavement elements supported on compacted fills or prepared subgrade depend upon compliance with "Earthwork" recommendations. To assess compliance, observation and testing should be performed under the direction of the geotechnical engineer. • Excavation and Trench Construction: Excavations into the on -site soils will encounter a variety of conditions. Excavations into the clays and bedrock can be expected to stand on relatively steep temporary slopes during construction. However, caving soils and groundwater may also be encountered. In addition, well -cemented and densely cemented bedrock.encountered may be difficult to excavate as discussed in the "Excavation" section of this report. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottom. All excavations should be sloped or shored in the interest of safety following local, and federal regulations, including current OSHA excavation and trench safety standards. The soils to be penetrated by the proposed excavations may vary significantly across the site. The preliminary soil classifications are based solely on the materials encountered in widely spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions. As a safety measure, it is recommended that all vehicles and soil piles be kept to a minimum lateral distance from the crest of the slope equal to no less than the slope height. The exposed slope face should be protected against the elements. The contractor should retain a geotechnical engineer to monitor the soils exposed in all excavations and provide engineering services for slopes. This will provide an opportunity to monitor the soil types encountered and to modify the excavation slopes as necessary. It also offers an opportunity to verify the stability of the excavation slopes during construction. 17 1st Choice Bank ELI Project No. 20945096 Terracon 5. If a well defined maximum density curve cannot be generated by impact compaction in the laboratory for any fill type, engineered fill should be compacted to a minimum of 80 percent relative density by determined by ASTM D4253. 6. On -site clay soils should be compacted within a moisture content range of optimum moisture to 2 percent above optimum. On -site clay below pavement and on -site granular fill, bedrock and imported soils should be compacted within a moisture range of 2 percent below to 2 percent above optimum. • Shrinkage: For balancing grading plans, estimated shrink or swell of soils and bedrock when used as compacted fill following recommendations in this report are as follows: Material Estimated Shrink(-) Swell (+) Based on ASTM D698 On -site soils: Clays..................................... .15 to -20% On -site bedrock materials: Sandstone .................................. .10 to -15% • Slopes: 1. For permanent slopes in compacted fill areas, recommended maximum configurations for on -site materials are as follows: Material Maximum Slope Horizontal:Vertical Cohesive soils (clays) ........................... 2'h:1 Bedrock...................................... 1:1 Canal slopes .................................... 3:1 If steeper slopes are required for site development, stability analyses should be completed to design the grading plan. 16 1st Choice Bank ELI Project No. 20945096 7. Imported soils for use in the canal liner should conform to the following: Terracon • Canal Liner Material No.4 Sieve ............................................. 100 No.200 Sieve ........................................ 75(min) • Liquid Limit .......................................... 35 (min) • Plasticity Index ....................................... 15 (min) 8. Aggregate base should conform to Colorado Department of Transportation Class 5 or 6 specifications. • Placement and Compaction: 1. Place and compact fill in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. 2. Uncompacted fill lifts should not exceed 10 inches loose thickness. 3. No fill should be placed over frozen ground. 4. Materials should be compacted to the following: Material On -site soils: Minimum Percent Compaction IASTM D698) Beneath foundations ............................ ao Beneath slabs ................................. 95 Beneath pavements ............................ 95 Wetted perimeter of canal (clay) 95 Imported fill: Beneath foundations ............................ ao Beneath slabs ................................ 95 95 Beneath pavements ...........I ................. Wetted perimeter of canal (clay) ................... 95 Miscellaneous backfill................................ 90 15 1st Choice Bank ELI Project No. 20945096 Terracon Use of lime, fly ash, kiln dust, cement or geotextiles could also be considered as a stabilization technique. Laboratory evaluation is recommended to determine the . effect of chemical stabilization on subgrade soils prior to construction. • Fill Materials: 1. Clean on -site soils or approved imported materials may be used as fill material for the following: • general site grading • exterior slab areas • foundation areas • pavement areas • interior floor slab areas • foundation backfill 2. On -site bedrock materials are not recommended for use beneath structural ares of the site, or as backfill. Should bedrock materials be used for general site grading, placement in fills at non-structural locations on the site is recommended. 3. Select granular materials should be used as backfill behind walls which retain earth. 4. Frozen soils should not be used as fill or backfill. 5. Imported soils for structural fill and backfill (if required) should conform to the following: • Gradation (ASTM C136): percent finer by weight 6.. 100 3.. ................................................ 70-100 No.4 Sieve .......................................... 50-100 No.20O Sieve ....................................... 25(max) • Liquid Limit ......................................... 30 (max) • Plasticity Index ...................................... 15 (max) 14 1st Choice Bank ELI Project No. 20945096 • Excavation: Terracon 1. It is anticipated that excavations in the soil for the proposed construction can be accomplished with conventional earthmoving equipment. 2. Excavation penetrating the well -cemented and densely cemented bedrock may require the use of specialized heavy-duty equipment, together with drilling and blasting to facilitate rock break-up and removal. 3. Depending upon depth of excavation and seasonal conditions, groundwater may be encountered in excavations on the site. Pumpingfrom sumps may be utilized to control water within excavations. Well points may be required for significant groundwater flow, or where excavations penetrate groundwater to a significant depth. • Slab Sub -grade Preparation: 1. Where existing on -site clay soils will support floor slab, the soils should be scarified, moisture conditioned and compacted to a minimum depth of 8 inches. 2. A minimum 4-inch layer of clean -graded gravel should be placed beneath slabs. 3. A minimum 8-inch layer of free -draining gravel should be placed beneath basement floor slabs in conjunction with the underslab drainage system. • Pavement Subarade Preparation: 1. The subgrade should be scarified, moistened as required, and recompacted for a minimum depth of 8 inches prior to placement of fill and pavement materials. 2. On -site clay soils may be pumped or become unstable or unworkable at high water contents. Workability may be improved by scarifying and drying. Overexcavation of wet zones and replacement with granular materials may be necessary. Lightweight excavation equipment may be required to reduce subgrade pumping. 13 1st Choice Bank Terracon ELI Project No. 20945096 should be constructed when the ditch is dry. All channel slopes should be placed on a grade of J3:1 or flatter. Earthwork: • General Considerations: The conclusions contained in this report for the proposed construction are contingent upon compliance with recommendations presented in this section. Although fills or underground facilities such as septic tanks, cesspools, basements, and utilities were not observed during site reconnaissance, such features might be encountered during construction. • Site Clearing.: 1. Strip and remove existing vegetation, debris, and other deleterious materials from proposed building and pavement areas. All exposed surfaces should be free of mounds and depressions which could prevent uniform compaction. 2. Where existing fill and unexpected fills or underground facilities are encountered during site clearing, such features should be removed and the excavation thoroughly cleaned prior to backfill placement and/or construction. All excavations should be observed by the geotechnical engineer prior to backfill placement. 3. Stripped materials consisting of vegetation and organic materials should be wasted from the site, or used to revegetate exposed slopes after completion of grading operations. If it is necessary to dispose of organic materials on -site, they should be placed in non-structural areas, and in fill sections not exceeding 5 feet in height. 4. The site should be initially graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed building structures. 5. All materials derived from the demolition of existing concrete foundations and slabs should be removed from the site, and not be allowed for use in any on -site fills. 6. All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of eight inches, conditioned to near optimum moisture content, and compacted. 12 1st Choice Bank Terracon ELI Project No. 20945096 Since the clay soils on the site have shrink/swell characteristics, pavements could crack in the future primarily because of expansion of the soils when subjected to an increase in moisture content to the subgrade. The cracking, while not desirable, does not necessarily constitute structural failure of the pavement. The performance of all pavements can be enhanced by minimizing excess moisture which can reach the subgrade soils. The following recommendations should be considered at minimum: • Site grading at a minimum 2% grade away from the pavements; • Compaction of any utility trenches for landscaped areas to the same criteria as the pavement subgrade; • Sealing all landscaped areas in or adjacent to pavements to minimize or prevent moisture migration to subgrade soils; • Placing compacted backfill against the exterior side of curb and gutter; and, • Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of base course materials. Preventative maintenance should be planned and provided for through an on -going pavement management program in order to enhance future pavement performance. Preventative maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment. Preventative maintenance consists of both localized maintenance (e.g. crack sealing and patching) and global maintenance (e.g. surface sealing). Preventative maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements Recommended preventative maintenance policies for asphalt and jointed concrete pavements, based upon type and severity of distress, are provided in Appendix D. Prior to implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventative maintenance. Channel Realignment: Where the existing canal is to be realigned, the channel should be lined with a minimum of 1 foot of on -site or imported clay material specified under fill material. The channel 11 1 st. Choice Bank Terracon ELI Project No. 20945096. base course should meet a particular gradation. Use of aggregates meeting Colorado Department of Transforation Grading G or C specifications is recommended. The mix design should be submitted prior to construction to verify it adequacy. The asphalt material should be placed in maximum 3-inch lifts, and should be compacted to a minimum of 95% Hveem density (ASTM D1561). Where rigid pavements are used, the concrete should be obtained from an approved mix design with the following minimum properties: • Modulus of Rupture @ 28 days ........................ 650 minimum • Strength Requirements ................................ ASTM C94 • Minimum Cement Content .......................... 5.5 sacks/cu. yd. • Cement Type .................................... Type I Portland • Entrained Air Content ................................... 6 to 8% • Concrete Aggregate ................. ASTM C33 and CDOT Section 703 • Aggregate Size ................................. 1 inch maximum • Maximum Water Content .. 0.49 lb/lb of cement • Maximum Allowable Slump ............................... 4 inches Concrete should be deposited by truck mixers or agitators and placed a maximum of 90 minutes from time the water is added to the mix. Other specifications outlined by the Colorado Department of Transportation should be followed. Longitudinal and transverse joints should be provided as needed in concrete pavements for expansion/contraction and isolation. The location and extent of joints should be based upon the final pavement geometry and should be placed (in feet), at roughly twice the slab thickness (in inches), on center in either direction. Sawed joints should be cut within 24-hours of concrete placement, and should be a minimum of 25% of slab thickness plus 1/4 inch. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. Where dowels cannot be used at joints accessible to wheel loads, pavement thickness -should be increased by 25 percent at the joints and tapered to regular thickness in 5 feet. Future performance of pavements constructed on the clay soils at this site will be dependent upon several factors, including: • maintaining stable moisture content of the subgrade soils; and, • providing for a planned program of preventative maintenance. 10 I J J I 1st Choice Bank Terracon ELI Project No. 20945096 Recommended Pavement Section Thickness (Inches) Traffic Area Alterna- tive Asphalt Concrete Aggregate Base Plant Mix Bituminous Portland Cement TOTAL Surface Course Base Course Concrete A 3„ 5„ 8„ B 2„ 2 yZ 4+/2 Automobile Parking C 5„ 5„ A 3" 8" 11" B 1 2" 4" 1 6" Drive Areas C 6„ 6„ Each alternative should be investigated with respect to current material availability and economic conditions. Rigid concrete pavement is recommended at the location of dumpsters where trash trucks will park and load. Aggregate base course (if used on the site) should consist of a blend of sand and gravel which meets strict specifications for quality and gradation.. Use of materials meeting Colorado Department of Transportation Class 5 or 6 specifications is recommended. Aggregate base course should be placed in lifts not exceeding six inches and should be compacted to a minimum of 95% Standard Proctor density (ASTM D698), within a moisture content range of 2 percent below to 2 percent above optimum. Where base course thickness exceeds 6 inches, the material should be placed and compacted in two or more lifts of equal thickness. Asphalt concrete should be obtained from an approved mix design stating the Hveem properties, optimum asphalt content, job mix formula, and recommended mixing and placing temperatures. Aggregate used in asphalt concrete should meet a particular gradation. Use of materials meeting Colorado Department of Transportation Grading C or CX specification is recommended. The mix design should be submitted prior to construction to verify its adequacy. The asphalt materials should be placed in maximum 3-inch lifts and should be compacted to a minimum of 95% Hveem density (ASTM D1561). Plant -mixed bituminous base course should be composed of a mixture of aggregate, filler and additives if required and approved bituminous material. The bituminous base should conform to an approved mix design stating the Hveem properties, optimum asphalt content, job mix formula, and recommended mixing and placing temperatures. Aggregate used in plant -mixed bituminous I 9 d I ] 1st Choice Bank Terracon ELI Project No. 20945096 7 general tolerance for normal slab -on -grade construction. To reduce any potential slab movements, the subgrade soils should be prepared as outlined in the "Earthwork" section of this report. For structural design of concrete slabs -on -grade, a modulus of subgrade reaction to 100 pounds J per cubic inch (pci) may be used for floors supported on existing soils or engineered fill consisting of on -site soils. A modulus of 150 pci may be used for floors supported on non -expansive Jimported fill meeting the specifications outlined below. Additional floor slab design and construction recommendations are as follows: • Positive separations and/or isolation joints should be provided between slabs and all foundations, columns or utility lines to allow independent movement. • Contraction joints should be provided in slabs to control the location and extent of cracking. Maximum joint spacing of 15 to 20 feet in each direction is recommended. • Interior trench backf ill paced beneath slabs should be compacted in accordance with recommended specifications outlined below. • In areas subjected to normal loading, a minimum 4-inch layer of clean -graded gravel should be placed beneath interior slabs. • A minimum 8-inch layer of free -draining gravel should be placed beneath basement floor slabs in conjunction with the underslab drainage system. 1 • If moisture sensitive floor coverings are used on interior slabs, consideration should be given to the use of barriers to minimize potential vapor rise through the slab. • Floor slabs should not be constructed on frozen subgrade. • Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1 R are recommended. Pavement Design and Construction: The required total thickness for the pavement structure is dependent primarily upon the foundation soil or subgrade and upon traffic conditions. Based on the soil conditions encountered at the site, the type and volume of traffic and using a group index of 6 as the criterion for pavement design, the following minimum pavement thicknesses are recommended: 8 J� 1st Choice Bank Terracon ELI Project No. 20945096 Since the basement will be below groundwater, alternating pumps and an emergency generator should be provided in case of a mechanical or electrical failure. In addition, temporary dewatering will be required during construction for proper basement excavation and foundation placement. Lateral Earth Pressures: For soils above any free water surface, recommended equivalent fluid pressures for unrestrained foundation elements are: • Active: Cohesive soil backfill (on -site clay) .......................... 45 psf/ft • Passive: Cohesive soil backfill (on -site clay) ......................... 350 psf/ft • Coefficient of base friction (sandstone) ......................... 0.40 • Adhesion at base of footing (clay) .......................... 500 psf *The coefficient of base friction should be reduced to 0.30 when used in conjunction with passive pressure. Where the design includes restrained elements, the following equivalent fluid pressures are recommended: • At rest: Cohesive soil backfill (on -site clay) .......... .............. 65 psf/ft Fill against grade beams and retaining walls should be compacted to densities specified in "Earthwork" section of the report. Compaction of each lift adjacent to walls should be accomplished with hand -operated tampers or other lightweight compactors. Overcompaction may cause excessive lateral earth pressures which could result in wall movement. Seismic Considerations: The project site is located in Seismic Risk Zone I, of the Seismic Zone Map of the United States as indicated by the Uniform Building Code. Based upon the nature of the subsurface materials, a seismic site coefficient, "s" of 1.0 should be used for the design of structures for the proposed project (Uniform Building Code, Table No. 23-J). Floor Slab Design and Construction: Low -swelling natural soils or engineered fill will support the floor slab. Some differential movement of a slab -on -grade floor system is possible should the subgrade soils become elevated in moisture content. Such movements are considered within 7 J 1st Choice Bank ELI Project No. 20945096 Terracon Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, proper drainage should be provided in the final design and during construction. Foundations and masonry walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in masonry walls is recommended. Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required. Basement Construction: Groundwater was encountered on the site at depths of 6 to 10 feet below existing grade. In view of this and the proximity of the proposed building to the Larimer County No. 2 Canal, the proposed partial, full -depth basement construction is considered feasible only if a complete dewatering system is placed around the lower basement area. The drainage system should be constructed around the exterior perimeter of the basement foundation and slope at a minimum of 1 /8 inch per foot to a suitable outlet, such as a sump and pump system. The drainage system should consist of a properly sized perforated pipe, embedded in free -draining gravel, and placed in a trench at least 12 inches in width. Gravel should extend a minimum of 3 inches beneath the bottom of the pipe and at least 2 feet above the bottom of the foundation wall. The gravel should be covered with drainage fabric prior to placement of foundation backfill. The dewatering system should include an underslab gravel. drainage layer sloped to a suitable outlet, such as a sump and pump system. The underslab drainage layer should consist of a minimum 8-inch thickness of free -draining gravel meeting the specifications of AST C33, Size No. 57 or 67. Sizing of drainage pipe will be dependent upon groundwater flow into the dewatering system. Groundwater flow rates will fluctuate with permeability of the soils/bedrock to be dewatered and the depth to which groundwater may rise in the future. Pump tests to determine groundwater flow rates are recommended in order to properly design the system. Since the basement may be constructed several feet below groundwater level, consideration should be given to including vertical drainage against foundation walls to reduce hydrostatic forces. Use of drainage media discharging to the foundation dewatering system is recommended. 2 1st Choice Bank Terracon ELI Project No. 20945096 CONCLUSIONS AND RECOMMENDATIONS Site Development Considerations: The site appears suitable for the proposed construction. Potentially expansive soils, bedrock depths and shallow groundwater will require particular attention in the design and construction. Excavation of well -cemented and densely cemented sandstone may be difficult. Because of variations in the engineering properties of the on -site soils, foundation bearing levels, structural loads, and possible final grades, the following foundation systems were evaluated for use on the site: • spread footings and/or grade beams bearing on undisturbed soils; and, • spread footings and/or grade beams bearing on engineered fill. Slab -on -grade construction is considered acceptable for use when subgrade soils consist of the on -site soils, provided that design and construction recommendations are followed. Foundation Systems: Due to the presence of low -swelling soils and bedrock on the site, spread footing and/or grade beam foundations bearing upon undisturbed subsoils and/or engineered fill are recommended for support for the proposed structure. The footings may be designed for a maximum bearing pressure of 2,000 psf. Footings extended to the bedrock stratum may be designed for a maximum bearing pressure of 5,000 psf. In addition, the footings should be sized to maintain a minimum dead -load pressure of 500 psf. Exterior footings should be placed a minimum of 30 inches below finished grade for frost protection. Existing fill on the site should not be used for support of foundations without removal and recompaction. This may require overexcavation below slabs and/or footings. Finished grade is the lowest adjacent grade for perimeter footings and floor level for interior footings. The design bearing capacities apply to dead loads plus design live load conditions. The design bearing capacity may be increased by one-third when considering total loads that include wind or seismic conditions. J Footings should be proportioned to minimize differential foundation movement. Proportioning on the basis of equal total settlement is recommended; however, proportioning to relative constant dead -load pressure will also reduce differential settlement between adjacent footings. Total or differential settlement resulting from the assumed structural loads are estimated to be on the order of 3/4 inch, provided that foundations are constructed as recommended. 5 I 1st Choice Bank Terracon ELI Project No. 20945096 Soil and Bedrock Conditions: As presented on the Logs of Boring, the subsurface soils were encountered in order of increasing depths as follow: • Fill Material: The site is overlain by a 1 to 5 foot layer of fill material. The fill consists of Jsilty sand with a trace of gravel and sandy lean clay. The fill is brown, dry to moist, medium dense and very stiff. • Sandy Lean Clay: This stratum underlies the fill except in Boring 6 and extends to the bedrock below. The sandy lean clay is moderately plastic, moist and stiff to hard in Jconsistency. 0 Sandstone Bedrock: The bedrock was encountered at depths of 1 to 8 feet below the surface and extends to the depths explored. The upper 1 Y2 to 4 feet of the bedrock is highly weathered; however, the underlying sandstone is well -cemented. A Y2 to 1 Yz foot lense of densely cemented sandstone was encountered within the sandstone stratum in Borings 3 and 4 at depths of 6 to 9 feet. Feld and Laboratory Test Results: Laboratory test results indicate the subsoils at shallow depth have low expansive potential. The bedrock exhibits low expansive potential. Field and laboratory tests indicate the soils exhibits moderate bearing characteristics, and the bedrock exhibits high to very high bearing characteristics. Groundwater Conditions: Groundwater was not observed in any test boring at the time of the field exploration. However, when checked one day after drilling, groundwater was measured at approximate depths of 6 to 10 feet. 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 and the flow in the Larimer County No. 2 Canal. W 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. 4 3 J 1st Choice Bank ELI Project No. 20945096 • Water content • Dry density • Consolidation • Compressive strength Terracon • Expansion • Plasticity • Soluble sulfate content 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 analysis, 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 The site is vegetated with grass and weeds and trees in the eastern portion of the property. The area is relatively flat and has poor surface drainage. The site is bordered on the north by Horsetooth Road, on the west by College Avenue, on the south by the Larimer County No. 2 canal and on the east by an existing parking lot and two-story office building. Several concrete slabs and foundations are located in the eastern portion of the site. SUBSURFACE CONDITIONS Geology: The project 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, erosional 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 the uplifting of the Front Range and associated downwarping of the Denver Basin to the 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 Formation. The Pierre shale is overlain by residual soils of Pleistocene and/or Recent Age. Mapping completed by the Colorado Geological Survey ('Hart, 1972), indicates the site in an area of "Moderate Swell Potential". Potentially expansive materials mapped in this area include bedrock, weathered bedrock and colluvium (surficial units). 'Hart, Stephen S., 1972, Potentially Swelling Soil and Rock in the Front Range Urban Corridor, Colorado, Colorado Geological Survey, Environmental Geology No. 7. 3 1st Choice Bank Terracon ELI Project No. 20945096 SITE EXPLORATION The scope of the services performed for this project included a site reconnaissance by an engineering geologist, a subsurface exploration program, laboratory testing and engineering analysis. Field Exploration: A total of eight test borings were drilled on May 25, 1994 to depths of 9'/z to 15 feet at the locations shown on the Site Plan, Figure 1. The borings were drilled within the footprint of the proposed building and drive -up facility, and four borings were drilled in the area J of proposed parking and/or channel relocation. All borings were advanced with a truck -mounted drilling rig, utilizing 4-inch diameter solid stem auger. JThe borings were located in the field by measurements from property lines and existing site features. Elevations were taken at each boring location by measurements with an engineer's level 7 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 to determine each. 7 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 7 means of pushing thin -walled Shelby tubes, or 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 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 one day 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, an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials. 07 Selected soil and bedrock samples were tested for the following engineering properties: 2 GEOTECHNICAL ENGINEERING REPORT 1ST CHOICE BANK COLLEGE AVENUE AND HORSETOOTH ROAD FORT COLLINS, COLORADO ELI PROJECT NO. 20945096 JUNE 7, 1994 INTRODUCTION This report contains the results of our geotechnical engineering exploration for the proposed project to be located at the southeast corner of South College Avenue and Horsetooth Road in south Fort Collins, Colorado. The site is located in the Northwest 1 /4 of Section 36, Township 7 North, Range 69 West of the 6th Principal Meridian. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: 0 subsurface soil and bedrock conditions • groundwater conditions • foundation design and construction • basement construction • lateral earth pressures • floor slab design and construction • pavement design and construction • earthwork • drainage The conclusions and recommendations contained in this report are based upon the results of field and laboratory testing, engineering analysis, and experience with similar soil and structural conditions. PROPOSED CONSTRUCTION The project as we understand it will be to construct a two-story, steel frame structure having slab - on -grade construction and a partial full -depth basement. Anticipated column loads are approximately 50 kips. Minor amounts of site grading with maximum fills of 1 to 2 feet are anticipated. The building will have a drive -up facility on the northeast side with parking surrounding the structure on the west, north and east. Portions of the Larimer County No. 2 canal may be relocated along the south property line. 1st Choice Bank ELI Project No. 20945096 TABLE OF CONTENTS (Cont'd) Terracon Page No. Corrosion Protection ....................................... 19 GENERAL COMMENTS ............................................... 19 APPENDIX A Figure No. SITEPLAN ......................................................... 1 Logsof Borings .......................................... Al thru A8 APPENDIX B Consolidation Test .............................................. B1 Summary of Test Results .......................................... B2 APPENDIX C: GENERAL NOTES Drilling & Exploration ............................................ C1 Unified Soil Classification .......................................... C2 Bedrock Classification, Sedimentary Bedrock ............................ C3 Laboratory Testing, Significance and Purpose ........................... C4 ReportTerminology ............................................. C5 APPENDIX D Recommended Preventative Maintenance -Asphalt Concrete Pavements ......... D1 Recommended Preventative Maintenance -Jointed Concrete Pavements ......... D2 1st Choice Bank Terracon i ELI Project No. 20945096 J TABLE OF CONTENTS Page No. -y Letter of Transmittal ................................................... ii 1 INTRODUCTION..................................................... 1 PROPOSED CONSTRUCTION ........................................... 1 SITEEXPLORATION .................................................. 2 Field Exploration .............................................. 2 Laboratory Testing 2 JSITE CONDITIONS ...............................:................... 3 SUBSURFACE CONDITIONS ............................................ 3 Geology....................................... 3 Soil and Bedrock Conditions 4 Field and Laboratory Test Results .................................... 4 Groundwater Conditions .......................................... 4 CONCLUSIONS AND RECOMMENDATIONS ................................. 5 Site Development Considerations .................................... 5 l Foundation Systems ............................................. 5 J Basement Construction 6. Lateral Earth Pressures ........................................... 7 l Seismic Considerations ........................................... 7 j Floor Slab Design and Construction 7 Pavement Design and Construction ............................... .. 8 Channel Realignment ............................................ 11 : Earthwork 12 General Considerations ..................................... 12 J Site Clearing ............................................. 12 Excavation 13 Slab Subgrade Preparation .................................... 13 Pavement Subgrade Preparation ... : .............. : .......:... 13 Fill Materials ' 14 Placement and Compaction .................................. 15 Shrinkage ............................................... 16 Slopes 16 Compliance............................................. 17 Excavation and Trench Construction :::::::::: : :::::::::: : :::::: 17 Drainage 18 SurfaceDrainage ......................................... 18 Additional Design and Construction Considerations 18 Exterior Slab Design and Construction .......................... 18 Underground Utility Systems ................................. 19 1st Choice Bank ELI Project No. 20945096 Terracon We have appreciated being of service to you in the geotechnical engineering phase of this project, and are prepared to assist you during the construction phases as well. If you have any questions concerning this report or any of our testing, inspection, design and consulting services, please do not hesitate to contact us. Sincerely, EMPIRE LABORATORIES, INC. A Division of The Terracon Companies, Inc Nei R. S err d ej Senior Engineering Geologist Reviewed by: Larry G. O'Dell, P.E. Office Manager NRS/LGO/cic ` = AIPG i Copies to: Addressee (2) Hillhouse Architects - Mr. Jim Hillhouse (1) Empire Laboratories, Inc. A Division of The Terracon Companies, Inc. P.O. Box 503 • 301 No. Howes Fort Collins, Colorado 80522 (303) 484-0359 FAX No. (303) 484-0454 Chester C. Smith, PE. Neil R. Sherrod, C.P.G. June 7, 1994 1 st Choice Bank 2164 35th Avenue Greeley, Colorado 80634 Attn: Mr. Darrell McAllister Re: Geotechnical Engineering Report, 1st Choice Bank College Avenue and Harmony Road, Fort Collins, Colorado ELI Project No. 20945096 Empire Laboratories, Inc. (ELI) has completed a geotechnical engineering exploration for the proposed project to be located at the intersection of College Avenue and Harmony Road in south Fort Collins, Colorado. This study was performed in general accordance with our proposal number D2094156 dated April 28, 1994. 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 subsurface soils at the site consisted of silty sand and sandy lean clay fill underlain by sandy lean clay and sandstone bedrock. Groundwater was encountered at approximate depths of 6'/z to 10 feet below the surface. The information obtained by the results of field exploration and laboratory testing completed for this study indicates that the soils and bedrock at the site have low expansive potential. The soils at anticipated foundation bearing depth have moderate load bearing capability, and the bedrock has high to very high load bearing capacity. Based on the geotechnical engineering analyses, subsurface exploration and laboratory test results, we recommend that the proposed building be supported on a spread footing foundation system. Slab -on -grade may be utilized for the interior floor system provided that care is taken 'in the placement and compaction of the subgrade soil. In view of the shallow depth to groundwater, basement construction is not feasible without construction of a complete dewatering system. Other design and construction details, based upon geotechnical conditions, are presented in the report. Offices of The Terracon Companies, Inc. Geotechnical, Environmental and Materials Engineers r Arizona: Tucson ■ Colorado: Colorado Springs, Denver, Ft. Collins, Greeley, Longmont ■ Idaho: Boise ■ Illinois: Bloomington, Chicago, Rock Island ■ Iowa: Cedar Falls, Cedai Rapids, Davenport, Des Moines, Storm Lake ■ Kansas: Lenexa, Topeka, Wichita ■ Minnesota: St. Paul ■ Missouri: Kansas City ■ Nebraska: Lincoln, Omaha ■ Nevada: Las Vegas ■ Oklahoma: Oklahoma City, Tulsa ■ Texas: Dallas, Fort Worth ■ Utah: Salt Lake City ■ Wyoming: Cheyenne QUALITY ENGINEERING SINCE 1965 GEOTECHNICAL ENGINEERING REPORT 1ST CHOICE BANK COLLEGE AVENUE AND HORSETOOTH ROAD FORT COLLINS, COLORADO ELI PROJECT NO. 20945096 Prepared for. 1ST CHOICE BANK 2164 35TH AVENUE GREELEY, COLORADO 80634 ATTN: MR. DARRELL MCALLISTER G Empire Laboratories, Inc. A Division of the Terracon Companies, Inc. l GEOTECHNICAL ENGINEERING REPORT 1ST CHOICE BANK COLLEGE AVENUE AND HORSETOOTH ROAD FORT COLLINS, COLORADO ELI PROJECT NO. 20945096 I A Division of The Terracon Companies, Inc.