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HomeMy WebLinkAboutBOARDWALK OFFICE BUILDING - PDP - PDP170032 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTGEOTECHNICAL EXPLORATION REPORT PROPOSED OFFICE BUILDING JFK PARKWAY AND EAST BOARDWALK DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162062 Prepared for: Michael Trinen 3003 E. Harmony Road, Suite #400 Fort Collins, Colorado 80528 Attn: Mr. Michael Trinen (Michael.trinen@rbc.com) Prepared by: Earth Engineering Consultants, LLC 4396 Greenfield Drive Windsor, Colorado 80550 4396 GREENFIELD DRIVE WINDSOR, COLORADO 80550 (970) 545-3908 FAX (970) 663-0282 www.earth-engineering.com July 12, 2016 Mr. Michael Trinen 3003 E. Harmony Road, Suite #400 Fort Collins, Colorado 80528 Attn: Mr. Michael Trinen (Michael.trinen@rbc.com) Re: Geotechnical Exploration Report Proposed Office Building JFK Parkway and East Boardwalk Drive Fort Collins, Colorado EEC Project No. 1162062 Mr. Trinen: Enclosed, herewith, are the results of the geotechnical subsurface exploration completed by Earth Engineering Consultants, LLC (EEC) personnel for the referenced project. In general, this project involves construction of a single story office building along with associated on-site pavement improvements on a vacant Lot, located at the northeast corner of JFK Parkway and East Boardwalk Drive in Fort Collins. To develop subsurface information for the proposed office building and associated site improvements, EEC personnel advanced five (5) soil borings on the site extending to depths of approximately 10 to 30 feet below present site grades. This exploration was completed in general accordance with our proposal dated June 16, 2016 (revised from June 10, 2016). In summary, subsurface conditions observed at the boring locations included dry, dense clayey sand subsoils to depths of approximately 2 to 4 feet below existing site grades underlain by a sandstone/siltstone bedrock with an occasional claystone zone. The siltstone/sandstone bedrock extended to the bottom of the borings at depths of approximately 10 to 30 feet below present site grades. Free groundwater was not observed in the test borings at the time of completion. GEOTECHNICAL EXPLORATION REPORT PROPOSED OFFICE BUILDING JFK PARKWAY AND EAST BOARDWALK DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162062 July 12, 2016 INTRODUCTION The geotechnical subsurface exploration for the proposed office building and associated on-site pavement improvements planned for construction at the northeast corner of JFK Parkway and East Boardwalk Drive in Fort Collins, Colorado, has been completed. Three (3) soil borings extended to depths of approximately 15 to 30 feet below present site grades were advanced within the proposed building area to develop information on existing subsurface conditions. Two (2) additional borings extending to depths of approximately 10 feet were advanced in proposed site drive and parking areas. Individual boring logs and diagram indicating the approximate boring locations are included with this report. We understand this project involves the construction of a single story office building at the approximate location as indicated on the enclosed boring location diagram. The new office building may contain a partial or full basement. We expect foundation loads for that structure will be light with continuous wall loads less than 3 kips per lineal foot and individual column loads less than 100 kips. Floor loads are also expected to be light. The site paved drive and parking areas are expected to carry low volumes of light vehicles with an occasional heavy truck. We anticipate small grade changes from existing grades will be required to develop the finish site grades for the proposed construction. The purpose of this report is to describe the subsurface conditions encountered in the test borings, analyze and evaluate developed data on site subsurface conditions and provide geotechnical recommendations concerning design and construction of the foundations and support of floor slabs, pavements and flatwork. EXPLORATION AND TESTING PROCEDURES The test boring locations were selected and established in the field by Earth Engineering Consultants, LLC (EEC) personnel by pacing and estimating angles from identifiable site features. The approximate boring locations are indicated on the attached boring location diagram. Those locations should be considered accurate only to the degree implied by the methods used to make the field measurements. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 2 The field borings were completed using a truck-mounted, CME-55 drill rig equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 4-inch nominal diameter continuous flight augers and samples of the subsurface materials encountered were obtained using split barrel and California barrel sampling procedures in general accordance with ASTM Specifications D1586 and D3550, respectively. In the split barrel and California barrel sampling procedures, standard sampling spoons are driven into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the split barrel and California barrel samplers 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 soils and hardness of weathered bedrock. All samples obtained in the field were sealed and returned to our laboratory for further examination, classification, and testing. In the California barrel sampling procedure, relatively intact samples are obtained in brass sampling sleeves. Laboratory moisture content tests were completed on each of the recovered samples along with dry density determination of appropriate California barrel samples. The unconfined strength of appropriate samples was estimated using a calibrated hand penetrometer. Washed sieve analysis and Atterberg limits tests were completed on selected samples to determine the quantity and plasticity of the fines in the subgrade materials. Swell/consolidation tests were also completed on select samples to evaluate the soil and bedrock tendency to change volume with variation in moisture content and load. Soluble sulfate tests were completed to evaluate possible sulfate attack on site cast concrete. Results of the outlined tests are indicated on the attached boring logs and summary sheets. As part of the testing program, all samples were examined in the laboratory and classified in general 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 Soil Classification System is indicated on the boring logs and a brief description of that classification system is included with this report. Classification of the bedrock was based on visual and tactual observation of disturbed samples and auger cuttings. Coring and/or petrographic analysis may reveal other rock types. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 3 SITE AND SUBSURFACE CONDITIONS The proposed development site is located at the northeast corner of JFK Parkway and East Boardwalk Drive in Fort Collins. An office park with several similar office buildings is located to the east of this building site. At present, the site shows surface drainage to the southwest with 5 to 10 feet of fall across the site. Based on results of the field borings and laboratory testing, subsurface conditions can be generalized as follows. Sparse vegetation was observed at the ground surface at the boring locations. The vegetation was underlain by sandy lean clay/clayey sand extending to depths ranging from approximately 2 to 4 feet. The moderately cohesive soils were stiff to dense and dry to very dry. The sandy lean clay/clayey sand soils were underlain by siltstone/sandstone bedrock. Some claystone layering was observed at some locations and zones of well cemented sandstone were encountered at some locations. The bedrock materials were generally moderately hard with low swell potential. Those materials extended to the bottom of the borings at depths of approximately 10 to 30 feet. The stratification boundaries indicated on the boring logs represent the approximate locations of changes in soil and rock types; in-situ, the transition of materials may be gradual and indistinct. GROUNDWATER CONDITIONS Observations were made while drilling and after completion of the borings, to detect the presence and depth to the hydrostatic groundwater table. Free water was not observed in any of the test borings at the time of drilling. The boreholes were backfilled upon completion of drilling and additional groundwater measurements were not obtained. Fluctuations in groundwater levels can occur over time depending on variations in hydrologic conditions, and other conditions not apparent at the time of this report. In addition, zones of perched and/or trapped water can be encountered in more permeable zones in the subgrade soils or in fractured or higher permeability zones interbedded within the bedrock. Perched water is commonly encountered in soils immediately above a low permeability bedrock layer such as the well cemented sandstone layers. The location and amount of perched/trapped water can also vary over time dependent on variations in hydrologic conditions and other conditions not apparent at the time of this report. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 4 ANALYSIS AND RECOMMENDATIONS Swell–Consolidation Test Results The swell-consolidation test is performed to evaluate the swell or collapse potential of soils to assist in determining foundation, floor slab and/or pavement design criteria. In this test, relatively intact samples obtained directly from the California barrel sampler are placed in a laboratory apparatus and inundated with water under a predetermined load. The swell-index is the resulting amount of swell or collapse after the inundation period expressed as a percent of the sample’s preload/initial thickness. After the inundation period, additional incremental loads are applied to evaluate the swell pressure and/or consolidation. For this assessment, we conducted four (4) swell-consolidation tests on soil samples obtained at various intervals/depths. Based on the laboratory test results, the in-situ samples analyzed for this project showed moderate swell for the dryer, higher density near surface essentially cohesive soils and low swell for the deeper bedrock materials. Site Preparation Preliminary grading plans were not provided to us prior to preparation of this subsurface exploration report. However, based on observed site conditions, it appears that small cuts or fills will be needed to achieve final site grades. All existing vegetation and/or topsoil should be removed from within the building and pavement foot prints or within site fill areas. In addition, close evaluation of the in-place materials will be required at the time of construction to monitor for unacceptable in-place fill materials, construction debris, and/or suitability of the in-place materials for reuse as engineered fill. Unacceptable materials, soft/loose fill materials, and/or the in-situ near surface dry and dense soils should be removed from the building, pavement and flatwork areas. Based on the results of the test borings, we expect the in-place materials will need to be removed/reworked to depths of 2 to 4 feet below current site grades, depending on site location. After removal of all topsoil/vegetation or any other unacceptable materials within the planned development areas, including the dry/dense overburden soils, and prior to fill placement and/or site Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 5 improvements, the exposed subgrades should be scarified to a minimum depth of 9-inches, adjusted in moisture content to within +/- 2% of standard Proctor optimum moisture content and compacted to at least 95% of the material's standard Proctor maximum dry density as determined in accordance with ASTM Specification D698. Fill soils required for developing the building subgrades, including areas overexcavated to remove unacceptable in-place materials, should consist of approved, low-volume-change materials, which are free from organic matter and debris. Based on the testing completed, it appears the on-site lean clay soils could be used as general site fill provided adequate moisture treatment and compaction procedures are followed. Claystone bedrock materials should not be used for fill below site improvement areas although the sandstone/siltstone bedrock could be used provided it is thoroughly broken-up/processed prior to or during the fill placement process. Import materials similar to the site clayey sand subsoils or consisting of granular structural fill with sufficient fines to prevent ponding of water in the fill materials could be used. The site fill materials should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content to ±2% of optimum moisture content and compacted to at least 95% of the materials maximum dry density as determined in accordance with ASTM Specification D698, the standard Proctor procedure. Care will be needed after preparation of the subgrades to avoid disturbing the subgrade materials. Positive drainage should be developed away from site structures to avoid wetting of subgrade materials. Subgrade materials becoming wet subsequent to construction of the site improvements could result in unacceptable performance. Office Building Foundations Based on the results of our field borings and laboratory testing as outlined in this report, it is our opinion the proposed lightly loaded office building could be supported on conventional footing foundations bearing on the moderately hard weathered siltstone/sandstone bedrock. For design of footing foundations bearing on the native bedrock materials, we recommend using a net allowable total load soil bearing pressure not to exceed 4,000 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. The foundations should all bear on the underlying bedrock to reduce the potential for differential movement of dissimilar bearing materials. Close evaluation of the foundation bearing strata will be necessary during the construction phase. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 6 Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches below adjacent exterior grade to provide frost protection. We recommend formed continuous footings have a minimum width of 12 inches and isolated column foundations have a minimum width of 24 inches. Trenched and/or grade beam foundations should not be used in the near surface soils to allow for close observation of the bearing strata. Care should be taken during construction to see that the footing foundations as well as all floor slabs are supported on suitable strength subsoils and/or approved engineered fill materials. Extra care should be taken in evaluating the in-place soils for excessively dry and expansive in-place materials which would generally be unacceptable for future support of floor slabs and/or pavements. No unusual problems are anticipated in completing the excavations required for construction of the footing foundations. However, zones of well cemented sandstone were observed in the test borings and difficult excavation of these materials should be expected. Care should be taken during construction to avoid disturbing the foundation bearing materials. Materials which are loosened or disturbed by the construction activities or materials which become dry and desiccated or wet and softened should be removed and replaced prior to placement of foundation concrete. We anticipate settlement of the footing foundations designed and constructed as outlined above would be less than 1 inch. Below Grade Areas Perimeter drain systems should be constructed around all below grade areas to intercept any surface infiltration and reduce the potential to develop hydrostatic loads on the below grade walls. The perimeter drain systems would generally include perforated metal or plastic pipe placed near foundation bearing level and sloped uniformly to a sump area where the accumulated water can be removed without reverse flow into the system. The drain line should be surrounded by at least 6 inches of free draining granular soils and the drain line and/or granular bedding should be surrounded by a filter fabric to reduce the intrusion of fines into the drain system. Below grade building walls should be designed for at-rest lateral earth pressures. Site retaining walls or similar structures could be designed on the basis of active lateral pressure acknowledging that some rotation can occur. Coefficient values for backfill with anticipated types of soils for calculation of active, at rest and passive earth pressures are provided in Table I below. Equivalent Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 7 fluid pressure is equal to the coefficient times the appropriate soil unit weight. As appropriate, buoyant weights and hydrostatic pressures should be considered. The outlined coefficient values are based on horizontal backfill with backfill soils consisting of essentially granular materials with a friction angle of 35 degrees or low volume change cohesive soils, assuming a friction angle of at least 28 degrees. The assumed values should be verified with the material supplier or through laboratory testing. For the at-rest and active earth pressures, slopes away from the structure would result in reduced driving forces with slopes up away from the structures resulting in greater forces on the walls. The passive resistance would be reduced with slopes away from the wall. The top 30-inches of soil on the passive resistance side of walls could be used as a surcharge load; however, should not be used as a part of the passive resistance value. Frictional resistance is equal to the tangent of the friction angle times the normal force. Table I: Lateral Earth Pressure Values Soil Type On-Site Low Plasticity Cohesive Imported Medium Dense Granular Wet Unit Weight 120 135 Saturated Unit Weight 130 140 Friction Angle () – (assumed) 28° 35° Active Pressure Coefficient 0.36 0.27 At-rest Pressure Coefficient 0.53 0.42 Passive Pressure Coefficient 2.77 3.70 Surcharge loads or point loads placed in the backfill can also create additional loads on below grade walls. Those lateral pressures should be evaluated on an individual basis. The outlined lateral earth values do not include factors of safety nor allowances for hydrostatic loads. Care should be taken to develop appropriate drainage systems behind below grade walls to eliminate potential for hydrostatic loads developing on the walls. Those systems would likely include perimeter drain systems extending to sump areas or free outfall where reverse flow cannot occur into the system. Where necessary, appropriate hydrostatic load values should be used for design. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 8 Floor Slab Design and Construction All existing vegetation and/or topsoil should be removed from beneath the new floor slabs. Soft or loose in-place soils, any wet and softened or dry and desiccated soils encountered within the proposed building areas including the dry, dense near surface lean clays or any unacceptable in- place fill soils should be removed from the floor areas. Overexcavations extending 2 to 4 feet below current ground surface should be anticipated to remove the dry, dense in-situ soils. After stripping, completing all cuts and removal of any unacceptable materials and prior to placement of any new fill or floor slabs, the in-place soils should be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95% of maximum dry density as determined in accordance with ASTM Specification D698, the standard Proctor procedure. The moisture content of the scarified materials should be adjusted to be within the range of 2% of standard Proctor optimum moisture at the time of compaction. Scarification and compaction of the basement floor subgrades would not be required. Fill materials required to develop the floor slab subgrades should consist of approved, low-volume change materials which are free from organic matter and debris. We recommend the fill materials contain sufficient fines to prevent ponding of water in the subgrade subsequent to construction. The on-site sandy clay materials and properly processed sandstone/siltstone bedrock are acceptable for use as fill in the floor slab subgrade areas; any claystone bedrock should not be used for fill. Fill materials beneath the floor slabs should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content as recommended for the scarified materials and compacted to at least 95% of the material's standard Proctor maximum dry density. After preparation of the subgrades, care should be taken to avoid disturbing the subgrade materials. Materials which are loosened or disturbed by the construction activities will require removal and replacement or reworking in place prior to placement of the overlying floor slabs. Positive drainage should be developed away from the proposed building to avoid wetting the subgrade or bearing materials. Subgrade or bearing materials allowed to become wetted subsequent to construction could result in unacceptable performance of the improvements. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 9 Pavements We expect the site pavements will include areas designated for low volume automobile traffic/parking and areas of heavier/higher volume traffic. For heavier traffic areas, we are using an assumed equivalent daily load axle (EDLA) rating of 15 and in automobile/parking areas we are using an EDLA of 5. Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the pavements. Soft or weak areas delineated by the proofrolling operations should be undercut or stabilized in-place to achieve the appropriate subgrade support. Based on the subsurface conditions encountered at the site and the results of the laboratory testing, it is recommended the on-site private drives and parking areas be designed using an R-value of 10. Due to the moderately expansive characteristics of the overburden site fill soils, a swell mitigation plan will be necessary to reduce the potential for movement within the pavement section. As presented in the “Site Preparation” section of this report, we recommended overexcavating the in-place fill soils and the replacement of these soils as moisture conditioned/engineered fill material beneath pavement areas. Pumping conditions could develop within a moisture treatment process of on-site cohesive soils. Subgrade stabilization may be needed to develop a stable subgrade for paving. If needed, stabilization could include incorporating at least 12 percent (by weight) Class C fly ash into the upper 12 inches of subgrade. Eliminating the risk of movement within the proposed pavement section may not be feasible due to the characteristics of the subsurface materials; but it may be possible to further reduce the risk of movement if more extensive subgrade stabilization measures are used during construction. We would be pleased to discuss other construction alternatives with you upon request. Pavement design methods are intended to provide structural sections with adequate thickness over a particular subgrade such that wheel loads are reduced to a level the subgrade can support. The support characteristics of the subgrade for pavement design do not account for shrink/swell movements of an expansive clay subgrade or consolidation of a wetted subgrade. Thus, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade. It is, therefore, important to minimize moisture changes in the subgrade to reduce shrink/swell movements. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 10 Recommended pavement sections are provided below in Table II. If selected, Portland cement concrete should be an exterior pavement design mix with a minimum 28-day compressive strength of 4,000 psi and should be air entrained. Hot bituminous pavement should consist of S-75 or SX-75 with performance graded PG 58-28 or 64-22 binder, compacted to be within the range of 92 to 96% of maximum theoretical specific gravity (Rice). In the drive lanes for the coffee kiosk and/or areas subject to heavier truck loads or truck turning movements, (including trash truck routes and load/unload areas) consideration should be given to use of Portland cement concrete for the pavements. The recommended pavement sections are minimums and periodic maintenance should be expected. Table II. Recommended Minimum Pavement Sections Automobile Parking Heavy Duty Areas 18-kip EDLA 18-kip ESAL’s Reliability Resilient Modulus PSI Loss 5 36,500 75% 3562 psi 2.5 15 109,500 85% 3562 psi 2.0 Design Structure Number 2.34 3.00 (A) Composite Hot Bituminous Pavement Aggregate Base (Design Structural Number) 4" 6" (2.42) 5" 8" (3.08) (B) Composite with Fly Ash Treated Subgrade Hot Bituminous Pavement Aggregate Base Fly Ash Treated Subgrade (Design Structure Number) 3" 6" 12" (2.58) 4" 6" 12" (3.02) (C) PCC (Non-reinforced) 5" 6" 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. Sawed joints should be cut in accordance with ACPA or ACI recommendations. All joints should be sealed to prevent entry of foreign material and dowelled or tied where necessary and appropriate for load transfer. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 11 The collection and diversion of surface drainage away from paved areas is critical to the satisfactory performance of the pavement. Drainage design should provide for the removal of water from paved areas in order to reduce the potential for wetting of the subgrade soils. Long-term pavement performance will be dependent upon several factors, including maintaining subgrade moisture levels and providing for preventive maintenance. The following recommendations should be considered the minimum:  The subgrade and the pavement surface should be adequately sloped to promote proper surface drainage.  Install pavement drainage surrounding areas anticipated for frequent wetting (e.g. garden centers, landscaped islands)  Install joint sealant and seal cracks immediately.  Seal all landscaped areas in, or adjacent to pavements to minimize or prevent moisture migration to subgrade soils.  Place compacted, low permeability backfill against the exterior side of curb and gutter; and place curb, gutter, and/or sidewalk directly on approved proof rolled subgrade soils. Preventive maintenance should be planned and provided for an on-going pavement management program. Preventive maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment. Preventive maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventive maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Prior to implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventive maintenance. Site grading is generally accomplished early in the construction phase. However, as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or rainfall. As a result, the pavement subgrade may not be suitable for pavement construction and corrective action will be required. The subgrade should be carefully evaluated at the time of pavement construction for signs of disturbance, such as but not limited to drying, or excessive rutting. If disturbance has occurred, pavement subgrade areas should be reworked, moisture conditioned, and properly compacted to the recommendations in this report immediately prior to paving. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 12 Note that if during or after placement of the stabilization or initial lift of pavement, the area is observed to be yielding under vehicle traffic or construction equipment, it is recommended that EEC be contacted for additional alternative methods of stabilization, or a change in the pavement section. Water Soluble Sulfates – (SO4) The water soluble sulfate (SO4) testing of the on-site subgrade materials taken during our subsurface exploration are provided in the table below. TABLE III - Water Soluble Sulfate Test Results Sample Location Description Soluble Sulfate Content (mg/kg) Soluble Sulfate Content (%) B-2, S-2 @ 4' Clayey Sand 180 0.02 Based on the results as presented in table above, ACI 318, Section 4.2 indicates the site overburden soils have a low risk of sulfate attack on Portland cement concrete. Therefore, Class 0 (Type I/II cement with or without the use of fly ash) could be used for concrete on and below site grades within the overburden soils and extending into the underlying bedrock formation. Foundation concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. These results are being compared to the following table. TABLE IV Requirements to Protect Against Damage to Concrete by Sulfate Attack from External Sources of Sulfate Severity of Sulfate exposure Water-soluble sulfate (SO4) in dry soil, percent Water-cement ratio, maximum Cementitious material Requirements Class 0 0.00 to 0.10% 0.45 Class 0 Class 1 0.11 to 0.20% 0.45 Class 1 Class 2 0.21 to 2.00% 0.45 Class 2 Class 3 2.01 of greater 0.45 Class 3 Other Considerations Positive drainage should be developed away from the structure and pavement areas with a minimum slope of 1 inch per foot for the first 10 feet away from the improvements in landscape areas. Care should be taken in planning of landscaping adjacent to the building and parking and drive areas to avoid features which would pond water adjacent to the pavement, foundations or stemwalls. Earth Engineering Consultants, LLC EEC Project No. 1162062 July 12, 2016 Page 13 Placement of plants which require irrigation systems or could result in fluctuations of the moisture content of the subgrade material should be avoided adjacent to site improvements. Lawn watering systems should not be placed within 5 feet of the perimeter of the building and parking areas. Spray heads should be designed not to spray water on or immediately adjacent to the structure or site pavements. Roof drains should be designed to discharge at least 5 feet away from the structure and away from the pavement areas. Excavations into the on-site lean clay subsoils and underlying bedrock should be relatively stable for short term construction activities depending, in part, upon the depth of excavation and excavation side slopes. 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 following local and federal regulations, including current OSHA excavation and trench safety standards. GENERAL COMMENTS The analysis and recommendations presented in this report are based upon the data obtained from 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 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 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 Mr. Michael Trinen 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 are modified or verified in writing by the geotechnical engineer. Earth Engineering Consultants, LLC DRILLING AND EXPLORATION DRILLING & SAMPLING SYMBOLS: SS: Split Spoon ‐ 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample ST: Thin‐Walled Tube ‐ 2" O.D., unless otherwise noted WS: Wash Sample R: Ring Barrel Sampler ‐ 2.42" I.D., 3" O.D. unless otherwise noted PA: Power Auger FT: Fish Tail Bit HA: Hand Auger RB: Rock Bit DB: Diamond Bit = 4", N, B BS: Bulk Sample AS: Auger Sample PM: Pressure Meter HS: Hollow Stem Auger WB: Wash Bore Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2‐inch O.D. split spoon, except where noted. WATER LEVEL MEASUREMENT SYMBOLS: WL : Water Level WS : While Sampling WCI: Wet Cave in WD : While Drilling DCI: Dry Cave in BCR: Before Casing Removal AB : After Boring ACR: After Casting Removal Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not possible with only short term observations. DESCRIPTIVE SOIL CLASSIFICATION Soil Classification is based on the Unified Soil Classification system and the ASTM Designations D‐2488. Coarse Grained Soils have move than 50% of their dry weight retained on a #200 sieve; they are described as: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are described as : clays, if they are plastic, and silts if they are slightly plastic or non‐plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse grained soils are defined on the basis of their relative in‐ place density and fine grained soils on the basis of their consistency. Example: Lean clay with sand, trace gravel, stiff (CL); silty sand, trace gravel, medium dense (SM). CONSISTENCY OF FINE‐GRAINED SOILS Unconfined Compressive Strength, Qu, psf Consistency < 500 Very Soft 500 ‐ 1,000 Soft 1,001 ‐ 2,000 Medium 2,001 ‐ 4,000 Stiff 4,001 ‐ 8,000 Very Stiff 8,001 ‐ 16,000 Very Hard RELATIVE DENSITY OF COARSE‐GRAINED SOILS: N‐Blows/ft Relative Density 0‐3 Very Loose 4‐9 Loose 10‐29 Medium Dense 30‐49 Dense 50‐80 Very Dense 80 + Extremely Dense PHYSICAL PROPERTIES OF BEDROCK DEGREE OF WEATHERING: Slight Slight decomposition of parent material on joints. May be color change. Moderate Some decomposition and color change throughout. High Rock highly decomposed, may be extremely broken. Group Symbol Group Name Cu≥4 and 1<Cc≤3 E GW Well-graded gravel F Cu<4 and/or 1>Cc>3 E GP Poorly-graded gravel F Fines classify as ML or MH GM Silty gravel G,H Fines Classify as CL or CH GC Clayey Gravel F,G,H Cu≥6 and 1<Cc≤3 E SW Well-graded sand I Cu<6 and/or 1>Cc>3 E SP Poorly-graded sand I Fines classify as ML or MH SM Silty sand G,H,I Fines classify as CL or CH SC Clayey sand G,H,I inorganic PI>7 and plots on or above "A" Line CL Lean clay K,L,M PI<4 or plots below "A" Line ML Silt K,L,M organic Liquid Limit - oven dried Organic clay K,L,M,N Liquid Limit - not dried Organic silt K,L,M,O inorganic PI plots on or above "A" Line CH Fat clay K,L,M PI plots below "A" Line MH Elastic Silt K,L,M organic Liquid Limit - oven dried Organic clay K,L,M,P Liquid Limit - not dried Organic silt K,L,M,O Highly organic soils PT Peat (D30)2 D10 x D60 GW-GM well graded gravel with silt NPI≥4 and plots on or above "A" line. GW-GC well-graded gravel with clay OPI≤4 or plots below "A" line. GP-GM poorly-graded gravel with silt PPI plots on or above "A" line. GP-GC poorly-graded gravel with clay QPI plots below "A" line. SW-SM well-graded sand with silt SW-SC well-graded sand with clay SP-SM poorly graded sand with silt SP-SC poorly graded sand with clay Earth Engineering Consultants, LLC IIf soil contains >15% gravel, add "with gravel" to group name JIf Atterberg limits plots shaded area, soil is a CL- ML, Silty clay Unified Soil Classification System BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO EEC PROJECT NO. 1162062 JUNE 2016 1 2 B-4 B-5 B-3 B-1 B-2 Boring Location Diagram Boardwalk Office Building Fort Collins, Colorado EEC Project Number: 1162062 Date: July 2016 EARTH ENGINEERING CONSULTANTS, LLC Approximate Boring Locations 1 Legend Site Photos (Photos taken in approximate location, in direction of arrow) DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF SPARSE VEGETATION _ _ 1 SANDSTONE / SILTSTONE _ _ brown / rust / grey 2 with calcareous deposits _ _ 3 _ _ 4 _ _ * classified as CLAYEY SAND CS 5 50/10" 9000+ 6.1 119.0 34 13 49.3 1300 psf 0.9% _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SANDSTONE / SILTSTONE / CLAYSTONE SS 10 50/10" 9000+ 9.6 brown / rust / grey _ _ moderately hard to hard 11 _ _ 12 _ _ 13 _ _ 14 _ _ CS 15 50/5" 9000+ 5.8 116.2 _ _ 16 _ _ 17 _ _ 18 with intermittent cemented lenses _ _ 19 _ _ SS 20 Bounce -- 4.3 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ CS 25 50/6" 9000+ 13.7 113.0 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF Continued from Sheet 1 of 2 26 _ _ SANDSTONE / SILTSTONE / CLAYSTONE 27 brown / rust / grey _ _ moderately hard to hard 28 _ _ 29 _ _ SS 30 50/6" _ _ BOTTOM OF BORING DEPTH 30.5' 31 _ _ 32 _ _ 33 _ _ 34 _ _ 35 _ _ 36 _ _ 37 _ _ 38 _ _ 39 _ _ 40 _ _ 41 _ _ 42 _ _ 43 _ _ 44 _ _ 45 _ _ 46 _ _ 47 _ _ 48 _ _ 49 _ _ 50 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL N/A DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF SPARSE VEGETATION _ _ 1 CLAYEY SAND (SC) _ _ tan / brown 2 very stiff/dense _ _ % @ 150 psf with calcareous deposits CS 3 34 9000+ 5.3 113.9 33 14 44.5 960 psf 4.4% _ _ 4 _ _ SS 5 41 7000 9.0 SANDSTONE / SILTSTONE _ _ brown / rust / tan 6 moderately hard to hard _ _ 7 _ _ 8 _ _ 9 _ _ CS 10 50/6" 9000+ 9.3 109.0 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 50/6" 3000 11.6 _ _ BOTTOM OF BORING DEPTH 15.5' 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF SPARSE VEGETATION _ _ 1 SANDSTONE / SILTSTONE / CLAYSTONE _ _ brown / grey / rust 2 weathered to moderately hard to hard with depth _ _ 3 _ _ 4 _ _ CS 5 50/" 9000+ 8.6 116.4 1400 psf 1.3% _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 50/6" 1500 11.4 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ CS 15 50/6" 9000+ 12.5 105.0 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ SS 20 50/6" 4000 13.4 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ CS 25 50/5" 8500 13.4 107.8 BOTTOM OF BORING DEPTH 25.0' _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF SPARSE VEGETATION _ _ 1 CLAYEY SAND (SC) _ _ brown / olive 2 very stiff / dense _ _ with calcareous deposits CS 3 34 6500 7.0 100.4 _ _ 4 *intermittent CAPROCK / WELL-CEMENTED _ _ SANDSTONE lens (Approx. 1 to 2' thick) SS 5 50/0.25" -- 2.6 _ _ SANDSTONE / SILTSTONE Bedrock 6 brown/gray/rust/olive _ _ moderately hard to hard 7 _ _ 8 _ _ 9 _ _ SS 10 50/8" 2000 13.8 _ _ BOTTOM OF BORING DEPTH 10.5' 11 _ _ 12 _ _ 13 _ _ 14 _ _ 15 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF SPARSE VEGETATION _ _ 1 SANDSTONE / SILTSTONE _ _ brown / tan 2 poorly cemented, with calcareous deposits _ _ % @ 150 psf CS 3 32 9000+ 7.0 115.2 29 5 46.1 1200 psf 3.9% *classified as CLAYEY SAND _ _ 4 _ _ SANDSTONE / SILTSTONE / CLAYSTONE SS 5 50 9000+ 11.5 brown / grey / rust _ _ moderately hard to hard 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 50/10" 6000 13.1 _ _ BOTTOM OF BORING DEPTH 10.5' 11 _ _ 12 _ _ 13 _ _ 14 _ _ 15 _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL Project: Location: Project #: Date: Boardwalk Office Building Fort Collins, Colorado 1162062 July 2016 Beginning Moisture: 6.1% Dry Density: 113.3 pcf Ending Moisture: 22.1% Swell Pressure: 1300 psf % Swell @ 500: 0.9% Sample Location: Boring 1, Sample 1, Depth 4' Liquid Limit: 34 Plasticity Index: 13 % Passing #200: 49.3% SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown / Rust / Grey Sandstone / Siltstone (CLAYEY SAND - SC) -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 0.01 0.1 1 10 Percent Movement Load (TSF) Consolidatio Swell Water Added Project: Location: Project #: Date: Boardwalk Office Building Fort Collins, Colorado 1162062 July 2016 Beginning Moisture: 5.3% Dry Density: 106 pcf Ending Moisture: 23.6% Swell Pressure: 960 psf % Swell @ 150: 4.4% Sample Location: Boring 2, Sample 1, Depth 2' Liquid Limit: 33 Plasticity Index: 14 % Passing #200: 44.5% SWELL / CONSOLIDATION TEST RESULTS Material Description: Tan / Brown CLAYEY SAND (SC) -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 0.01 0.1 1 10 Percent Movement Load (TSF) Consolidatio Swell Water Added Project: Location: Project #: Date: Boardwalk Office Building Fort Collins, Colorado 1162062 July 2016 Beginning Moisture: 8.6% Dry Density: 117.7 pcf Ending Moisture: 18.1% Swell Pressure: 1400 psf % Swell @ 500: 1.3% Sample Location: Boring 3, Sample 1, Depth 4' Liquid Limit: - - Plasticity Index: - - % Passing #200: - - SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown / Grey / Rust Sandstone / Siltstone / Claystone -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 0.01 0.1 1 10 Percent Movement Load (TSF) Consolidatio Swell Water Added Project: Location: Project #: Date: Boardwalk Office Building Fort Collins, Colorado 1162062 July 2016 Beginning Moisture: 7.0% Dry Density: 119.9 pcf Ending Moisture: 16.5% Swell Pressure: 1200 psf % Swell @ 150: 3.9% Sample Location: Boring 5, Sample 1, Depth 2' Liquid Limit: 29 Plasticity Index: 5 % Passing #200: 46.1% SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown / Tan Sandstone / Siltstone - classified as CLAYEY SAND - SC -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 0.01 0.1 1 10 Percent Movement Load (TSF) Consolidatio Swell Water Added SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 6/27/2016 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-5 JULY 2016 SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 6/27/2016 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-4 JULY 2016 SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 6/27/2016 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-3 JULY 2016 SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 6/27/2016 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-2 JULY 2016 6/27/2016 AFTER DRILLING N/A SURFACE ELEV 24 HOUR N/A FINISH DATE SHEET 2 OF 2 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-1 JULY 2016 SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 6/27/2016 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 6/27/2016 WHILE DRILLING None BOARDWALK OFFICE BUILDING FORT COLLINS, COLORADO PROJECT NO: 1162062 LOG OF BORING B-1 JULY 2016 Soil Classification Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Sands 50% or more coarse fraction passes No. 4 sieve Fine-Grained Soils 50% or more passes the No. 200 sieve <0.75 OL Gravels with Fines more than 12% fines Clean Sands Less than 5% fines Sands with Fines more than 12% fines Clean Gravels Less than 5% fines Gravels more than 50% of coarse fraction retained on No. 4 sieve Coarse - Grained Soils more than 50% retained on No. 200 sieve CGravels with 5 to 12% fines required dual symbols: Kif soil contains 15 to 29% plus No. 200, add "with sand" or "with gravel", whichever is predominant. <0.75 OH Primarily organic matter, dark in color, and organic odor ABased on the material passing the 3-in. (75-mm) sieve ECu=D60/D10 Cc= HIf fines are organic, add "with organic fines" to group name LIf soil contains ≥ 30% plus No. 200 predominantly sand, add "sandy" to group name. MIf soil contains ≥30% plus No. 200 predominantly gravel, add "gravelly" to group name. DSands with 5 to 12% fines require dual symbols: BIf field sample contained cobbles or boulders, or both, add "with cobbles or boulders, or both" to group name. FIf soil contains ≥15% sand, add "with sand" to GIf fines classify as CL-ML, use dual symbol GC- CM, or SC-SM. Silts and Clays Liquid Limit less than 50 Silts and Clays Liquid Limit 50 or more 0 10 20 30 40 50 60 0 10 20 30 40 50 60 70 80 90 100 110 PLASTICITY INDEX (PI) LIQUID LIMIT (LL) ML OR OL MH OR OH For Classification of fine-grained soils and fine-grained fraction of coarse-grained soils. Equation of "A"-line Horizontal at PI=4 to LL=25.5 then PI-0.73 (LL-20) Equation of "U"-line Vertical at LL=16 to PI-7, then PI=0.9 (LL-8) CL-ML HARDNESS AND DEGREE OF CEMENTATION: Limestone and Dolomite: Hard Difficult to scratch with knife. Moderately Can be scratched easily with knife. Hard Cannot be scratched with fingernail. Soft Can be scratched with fingernail. Shale, Siltstone and Claystone: Hard Can be scratched easily with knife, cannot be scratched with fingernail. Moderately Can be scratched with fingernail. Hard Soft Can be easily dented but not molded with fingers. Sandstone and Conglomerate: Well Capable of scratching a knife blade. Cemented Cemented Can be scratched with knife. Poorly Can be broken apart easily with fingers. Cemented Since the cohesive soils on the site have some shrink/swell potential, pavements could crack in the future primarily because of the volume change 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.