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Home My WebLink About1721 S. COLLEGE TOWNHOMES - PDP - PDP160042 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTSUBSURFACE EXPLORATION REPORT PROPOSED 10 UNIT TOWNHOME DEVELOPMENT 1721 CHOICE CENTER DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162091 Prepared for: Core Spaces 2234 West North Avenue Chicago, Illinois 60647 Attn: Mr. Mark Goehausen (markg@corespaces.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 October 27, 2016 Core Spaces 2234 West North Avenue Chicago, Illinois 60647 Attn: Mr. Mark Goehausen (markg@corespaces.com) Re: Subsurface Exploration Report Proposed 10 Unit Townhome Development 1721 Choice Center Drive Fort Collins, Colorado EEC Project No. 1162091 Mr. Goehausen: Enclosed, herewith, are the results of the subsurface exploration completed by Earth Engineering Consultants, LLC for the referenced project. As a part of this exploration, three (3) soil borings were drilled on September 28, 2016 within the proposed building/development area on the referenced site. The borings were extended to approximate depths 20 to 30-feet below existing site grades. This exploration was completed in general accordance with our proposal dated September 19, 2016. We understand this project involves the development of an infill property located west of College Avenue and south of Prospect Road at 1721 Choice Center Drive in Fort Collins, Colorado. We understand this project involves the construction of two (2) townhome buildings containing a total of 10 units. The buildings will be two-story, wood-frame, slab on-grade (no basement) buildings with “tuck-under” 2 car garages. Foundation loads for the structures are expected to be light with continuous wall loads less than 3 kips per lineal foot and individual column loads less than 50 kips. Floor loads are expected to be light. In summary, an approximate 9-foot layer of “undocumented” fill material was encountered at the surface of the borings. The fill materials consisted of either clay sand and/or sandy lean clay, and trace gravel, which extended to the native sandy lean clay subsoils below. The native cohesive soils extended to sands and gravels in two (2) of the borings and to the bedrock SUBSURFACE EXPLORATION REPORT PROPOSED 10 UNIT TOWNHOME DEVELOPMENT 1721 CHOICE CENTER DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162091 October 27, 2016 INTRODUCTION The geotechnical subsurface exploration for the proposed two (2) building/ten (10) unit townhome development project planned for construction at 1721 Choice Center Drive situated west of College Avenue and south of Prospect Road in Fort Collins, Colorado has been completed. For this exploration, three (3) soil borings were drilled on September 28, 2016 within the proposed building/development area at the site. Those borings were extended to approximate depths of approximately 20 to 30 feet below existing site grades. This exploration was completed in general accordance with our proposal dated September 19, 2016. We understand the proposed development will generally include the construction of two (2) townhome buildings each containing five (5) residential units. The proposed building layout is indicated on the attached boring location diagram. The buildings are planned as two-story, wood- frame, slab-on-grade (no basement) structures with “tuck-under” two car garages for each unit. Foundation loads for the structures are expected to be light with continuous wall loads less than 3 kips per lineal foot and individual column loads less than 50 kips. Floor loads are expected to be light. The paved drive for the development is expected to carry light traffic consisting predominately of private autos and light trucks. The purpose of this report is to described the subsurface conditions encountered in the test borings, analyze and evaluate the test data and provide geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements for the proposed site improvements. This report does not include recommendations for the development of a proposed retaining wall along the west side of the development site. Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 2 EXPLORATION AND TESTING PROCEDURES The test 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. 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 advanced 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. In the California barrel sampling procedure, relatively intact samples are obtained in removable brass liners. All samples obtained in the field were sealed and returned to our laboratory for further examination, classification and testing. Laboratory moisture content tests were completed on each of the recovered samples. Atterberg limits and washed sieve analysis tests were completed on selected samples to evaluate the quantity and plasticity of fines in the subgrade. Swell/consolidation tests were completed to evaluate the potential for the subgrade materials to change volume with variation in moisture and load. 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 No1162091 October 27, 2016 Page 3 SITE AND SUBSURFACE CONDITIONS The proposed townhome development will be located at 1721 Choice Center Drive, just west of College Avenue and south of Prospect Road. A former building was located at the site as indicated of the attached Figure 2 Google-Earth Aerial site diagram. The building was generally located on the west side of the site in the present gravel surfaced parking area extending west within the slope portion of the sites. Attached photographs 3 and 4 show a portion of the west wall of the building. The former structure apparently included lower level walk out to the west. The presence of the concrete parking pad to the east of the former building indicates that care should be exercised to insure that the foundations/basement walls were removed from the areas of the new west building. Based on results of the field borings and laboratory testing, subsurface conditions can be generalized as follows. Approximately 9 feet of undocumented fill materials were encountered at the surface of the borings. The fill materials generally consisted of clayey sand and/or sandy lean clay and variable gravel, with approximately 3 feet of pit-run gravel at the surface in boring B-3. Native sandy lean clay was encountered beneath the fill materials and extended to a sand and gravel layer at depths of approximately 18 to 20 feet in borings B-1 and B-3. Claystone/sandstone bedrock was encountered in borings B-1 and B-3 beneath the sands and gravels and beneath the sandy lean clay in boring B-2. The bedrock materials extended to the bottom of boring at depths of approximately 20 to 30 feet below present ground surface. The stratification boundaries indicated on the boring logs represent the approximate locations of changes in soil and bedrock types. In-situ, the transition of materials may be gradual and indistinct. The upper cohesive soil fills were generally soft to stiff in consistency. The soft fill soils suggest low compaction effect of the fill materials with resultant consolidation/settlement potential for overlying in pavements. The swell potentials of the lean surface soils are shown on the enclosed swell-consolidation curves presented in the Appendix of this report. Claystone/sandstone was tan/gray/rust in color, moderately hard and exhibited moderate to high bearing characteristics. The bedrock materials were weathered near surface; however, became less weathered and more competent with depth. Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 4 GROUNDWATER CONDITIONS Observations were made while drilling and after completion of the borings to detect the presence and depth to hydrostatic groundwater. At the time of drilling, free water was observed at approximate depths of 16 to 20 feet below site grades. The test borings were backfilled after completion of drilling and sampling; subsequent groundwater measurements are not available. 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. Longer term monitoring of water levels in cased wells, which are sealed from the influence of surface water would be required to more accurately evaluate fluctuations in groundwater levels at the site. We have typically noted deepest groundwater levels in late winter and shallowest groundwater levels in mid to late summer ANALYSIS AND RECOMMENDATIONS Swell – Consolidation Test Results The swell-consolidation test is performed to evaluate the swell or collapse potential of soils or bedrock to help determine foundation, floor slab and, pavement design criteria. In this test, relatively intact samples obtained directly from the ring barrel sampler are placed in a laboratory apparatus and inundated with water under a predetermined load. The samples are monitored for swell and/or consolidation. The swell-index is the resulting amount of swell or collapse after the inundation period, expressed as a percent of the sample’s initial thickness. After the inundation period additional incremental loads are applied to evaluate the swell pressure and consolidation. For this assessment, two (2) swell-consolidation tests were completed on the lean clay fill and sandy lean clay native soils. The swell index values for the samples analyzed revealed low swell characteristics ranging from approximately (+) 0.1 to (+) 2.1%. Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide uniformity in terminology between geotechnical engineers to provide a relative correlation of performance risk to measured swell. “The representative percent swell values are not necessarily Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 5 measured values; rather, they are a judgment of the swell of the soil and/or bedrock profile likely to influence slab performance.” Geotechnical engineers use this information to also evaluate the swell potential risks for foundation performance based on the risk categories. Recommended Representative Swell Potential Descriptions and Corresponding Slab Performance Risk Categories Slab Performance Risk Category Representative Percent Swell (500 psf Surcharge) Representative Percent Swell (1000 psf Surcharge) Low 0 to < 3 0 < 2 Moderate 3 to < 5 2 to < 4 High 5 to < 8 4 to < 6 Very High > 8 > 6 Based on the laboratory test results, the samples analyzed for this project were within the low range. Site Preparation Based on our understanding of the proposed development, it appears the “upper” level of the site is near design subgrade elevation. Up to 8 to 10 feet of fill will be required along the west edge of the site to develop subgrade elevations similar to the remainder of the site. We understand a retaining wall will be constructed along the west property boundary. At this time, we have not been provided details of that wall design; recommendations provided herein presume the wall design has been prepared to accommodate the loads imposed by the new structure near the top of the wall. All former/existing site improvements should be removed from the new building areas. Documentation of the complete removal of the prior site buildings should be requested and/or care should be taken to see that all elements of that structure were removed. Additionally, we recommend the site soft fill materials be removed to at least 2½ feet below foundation bearing. The over excavation material should be replaced with granular structural fill containing sufficient fines to prevent ponding of water in the fill materials if footing foundations are used for support. Sandy clay soils could be used if the buildings will be supported on post-tensioned slab-on-grade foundation systems. The over excavation should extend at least 1½ feet outside of the outside of the perimeter footings. Over excavation would not be required in the pavement areas although additional Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 6 settlement should be expected in these areas. We anticipate a portion of the removed lean clay fill materials could be placed in deeper fill positions along the west property boundary. Fill soils to develop the building, pavement/flatwork and site subgrades should consist of approved, low-volume-change materials, which are free from organic matter and debris. It is our opinion the on-site cohesive soils could be used as fill below the prescribed over excavation zone, provided adequate moisture treatment and compaction procedures are followed. If footing foundations are used for building support, granular structural fill should be used above the cohesive soil fills and in the over excavation zones to develop a granular structural fill envelope extending 2½ feet below foundation bearing below each of the buildings. Site cohesive soils could be used for fill in the over excavation zones if post-tension slabs are used. We recommend the fill soils be placed in loose lifts not to exceed 9 inches thick and adjusted in 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. The moisture content of the fill should be adjusted to be within ±2% of standard Proctor optimum at the time of compaction. If the site lean clay soils are used as fill material, care will be needed to maintain the recommended moisture content prior to and during construction of overlying improvements. Care should be exercised after preparation of the subgrades to avoid disturbing the subgrade materials. Positive drainage should be developed away from the structures and pavements to avoid wetting of subgrade materials. Subgrade materials becoming wet subsequent to construction of the site improvements can result in unacceptable performance. As presented on the enclosed boring logs and laboratory test results, soft in-place fill soils are present on this site. This report provides recommendations to help mitigate the effects of consolidation of the fill and settlement of the overlying buildings. Even if these procedures are followed, some movement and at least minor cracking in the structures should be anticipated. The severity of cracking and other cosmetic damage such as uneven floor slabs/exterior flatwork will probably increase if any modification of the site results in excessive wetting or drying of the site soils. Eliminating the risk of movement and cosmetic distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 7 during construction such as drilled pier foundations. We would be pleased to discuss other construction alternatives with you upon request. Areas of deeper fills may experience settlement from underlying native soils and within the placed fill materials. Settlement on the order of 1-inch or more per each 10 feet of fill depth would be estimated. The rate of settlement will be dependent on the type of fill material placed and construction methods. Granular soils will consolidate essentially immediately upon placement of overlying loads. Cohesive soils will consolidate at a slower rate. Foundation Systems – General Considerations The following foundation systems were evaluated for use on the site:  Conventional spread footings  Post-Tensioned Slab Foundation System Conventional Spread Footing Foundations To reduce to potential for post-construction excessive differential settlement of the footings subsequent to construction, we recommend the in-place soils be removed to a depth of at least 2½ feet below foundation bearing and replaced as granular structural fill material. A similar depth of granular structural fill should be placed below the footings on the west side of the west building. The site lean clay soils could be used as backfill below the granular structural fill. The cohesive soils and granular structural fill should be moisture conditioned to ± 2% of the material’s standard Proctor optimum moisture content and mechanically compacted to at least 95% of standard Proctor maximum dry density, ASTM D698. Conventional type spread footings could be used to support the proposed slab-on-grade buildings provided the footings are placed on approved moisture/density controlled granular fill material and the maximum anticipated wall and column loads do not exceed those presented herein. If actual design loads exceed the assumed values as previously presented, we should be consulted to provide supplemental design criteria, possibly including alternative foundations. Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 8 Footings bearing on approved moisture/density conditioned soils could be designed for a maximum net allowable total load bearing pressure of 2,000 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load should include full dead and live loads. Footings should be proportioned to reduce differential foundation movement. We estimate the total long term settlement of footings designed as outlined above would be less than one-inch. However, the presence of undocumented fill materials below the buildings increased the risk that additional settlement could occur from undiscovered soft or loose zones in the fill materials. Design of the retaining wall along the west property boundary may also influence the settlement along the west line of the west building. The backfill soils adjacent to the foundations should be placed in loose lifts not to exceed 9 inches thick, moisture conditioned to ± 2% of the material’s standard Proctor optimum moisture content, and mechanically compacted to be at least 95% of standard Proctor maximum dry density, ASTM D698. After placement of the fill materials, for foundation support, care should be taken to avoid wetting or drying of those materials. Bearing 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 or reworked in place prior to construction of the overlying improvements. Exterior foundations and foundations in unheated areas should be located at least 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. Post-Tensioned Slab Foundation Systems The results of our field exploration and laboratory testing completed for this exploration indicate the upper cohesive fill soils exhibited soft subgrade conditions and consolidation potential. Based on the subsurface conditions encountered, the proposed 2 building/10 unit townhome development units/slab Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 9 on grade structures could be supported by post-tensioned slab-on-grade foundations that bear directly on approved fill material. While we still recommend the over excavation of the subgrades in the building areas, the backfill soils could consist of approved lean clay or sandy lean clay similar to the in- place fill materials. The lean clay fill soils should be placed and compacted as outlined for fill beneath the footing foundations. Post-tensioned slab construction can be considered as an alternate foundation system for the project. Outlined below are the post tensioned slab design criteria based on the subsurface conditions and information provided in the 3rd Edition of the Post-Tensioning Institutes design manual. Post- tensioned slabs, thickened or turn-down edges and/or interior beams should be designed and constructed in accordance with the design criteria outlined in the below table. PTS Edition 3rd Edition Maximum Allowable Bearing Pressure, psf 1500 Edge Moisture Variation Distance, em Center Lift Condition, ft. 8.2 Edge Lift Condition, ft. 4.2 Differential Soil Movement, ym Center Lift Condition, Inches 0.5 Edge Lift Condition, Inches 1.0 Slab-Subgrade friction coefficient,  on polyethelene sheeting 0.75 on cohesionless soils – (sands) 1.0 on cohesive soils – (clays) 2.0 Seismic The site soil conditions consist of approximately 15 to greater than 20-feet of overburden soils overlying moderately hard/cemented bedrock. For those site conditions, the International Building Code indicates a Seismic Site Classification of D. Floor Slabs Slab-on-grade construction is feasible for the site provided certain precautions are adhered to. To reduce floor slab movement, we recommend the proposed floor slab on grade bear upon a properly placed and compacted granular structural fill material as outlined under “Site Preparation”. It is our Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 10 opinion the on-site cohesive soils could be used as fill below the granular zone, provided adequate moisture treatment and compaction procedures are followed. If the site lean clay soils are used as fill material, care will be needed to maintain the recommended moisture content prior to and during construction of overlying improvements. This procedure will not fully eliminate the possibilities of slab movement; but movements should be reduced and tend to be more uniform. For structural design of concrete slabs-on-grade, a modulus of subgrade reaction of 200 pounds per cubic inch (pci) may be used for floors supported on granular structural fill placed and compacted as outlined in this report. 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.  Control joints should be provided in slabs to control the location and extent of cracking.  Interior trench backfill placed beneath slabs should be compacted in a similar manner as previously described for imported structural fill material.  Floor slabs should not be constructed on frozen subgrade.  Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1R are recommended. Pavements We expect the site pavements will carry low volume automobile traffic. Proofrolling and recompacting the subgrade is recommended immediately prior to placement of the aggregate road base section or concrete 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 Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 11 subsurface conditions encountered at the site, and the laboratory test results, it is recommended the on-site private drives and parking areas be designed using an R-value of 5. Hot Mix Asphalt (HMA) underlain by crushed aggregate base course and non-reinforced concrete pavement are feasible alternatives for the proposed on-site paved sections. 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 significantly more expensive 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. Recommended pavement sections are provided below in TABLE I. The hot bituminous pavement (HBP) could be grading SX (75) or S (75) with PG 58-28 oil. The aggregate base should be Class 5 or Class 6 base. Portland cement concrete should be a high quality pavement mix with a minimum 28-day compressive strength of 4,000 psi and should be air entrained. TABLE I – RECOMMENDED PAVEMENT SECTIONS Automobile Parking EDLA Reliability Resilient Modulus PSI Loss 5 75% 3025 2.5 Design Structure Number 2.48 Composite Hot Bituminous Pavement Aggregate Base (Design Structural Data) 4" 6" (2.42) PCC (Non-reinforced) 5″ Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 12 The recommended pavement sections are minimums and periodic maintenance should be expected. 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 ACI recommendations. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. 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. Other Considerations Positive drainage should be developed away from the structures 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, (if required), adjacent to the building to avoid features which would pond water adjacent to the foundations or stemwalls. 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. Irrigation systems should not be placed within 5 feet of the perimeter of the buildings and parking areas. Spray heads should be designed not to spray water on or immediately adjacent to the structures or site pavements. Roof drains should be designed to discharge at least 5 feet away from the structures and away from the pavement areas. Excavations into the on-site clays can be expected to stand on relatively steep temporary slopes during construction. However, if excavations extend into the underlying groundwater, caving soils may be encountered. 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. Earth Engineering Consultants, LLC EEC Project No1162091 October 27, 2016 Page 13 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 phases to help determine that the design requirements are fulfilled. Site-specific explorations should be completed to develop site- specific recommendations for each of the site buildings. This report has been prepared for the exclusive use of Core Spaces, 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 1 2 B-1 B-2 B-3 Figure 1: Boring Location Diagram 10 Unit Townhome Development - 1721 Choice Center Drive Fort Collins, Colorado EEC Project Number: 1162091 Date: September 2016 EARTH ENGINEERING CONSULTANTS, LLC Approximate Boring Locations 1 Legend Site Photos (Photos taken in approximate location, in direction of arrow) Figure 2: Google Earth Image from 2012 10 Unit Townhome Development - 1721 Choice Center Drive Fort Collins, Colorado EEC Project Number: 1162091 Date: September 2016 EARTH ENGINEERING CONSULTANTS, LLC Approximate Location of Proposed Building 1721 CHOICE CENTER DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162088 SEPTEMBER 2016 1721 CHOICE CENTER DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1162088 SEPTEMBER 2016 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 BASE / GRAVEL - 6" _ _ 1 SANDY LEAN CLAY - FILL MATERIAL _ _ brown 2 soft to stiff _ _ mottled 3 _ _ 4 _ _ * classified as CLAYEY SAND CS 5 4 1000 15.6 111.9 29 15 42.2 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SANDY LEAN CLAY (CL) SS 10 12 7500 14.7 light brown to reddish brown _ _ stiff 11 _ _ 12 _ _ 13 _ _ 14 brown / grey / rust _ _ CS 15 7 2000 22.9 106.6 _ _ 16 _ _ 17 _ _ 18 _ _ SAND & GRAVEL (SP/GP) 19 medium dense _ _ SS 20 19 -- 10.0 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ SANDSTONE, brown / rust CS 25 45 -- 25.6 BOTTOM OF BORING DEPTH 25.0' _ _ Earth Engineering Consultants, LLC 10 UNIT TOWNHOME DEVELOPMENT 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 ASPHALT - 3.25" _ _ ABC - 7" 1 _ _ SANDY LEAN CLAY with Gravel - FILL MATERIAL 2 brown / dark brown / rust _ _ stiff CS 3 9 8000 15.4 112.5 33 16 51.4 600 psf 0.1% mottled _ _ 4 _ _ SS 5 14 5500 10.6 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SANDY LEAN CLAY (CL) CS 10 6 8500 16.4 107.1 light brown to reddish brown _ _ stiff to very stiff 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 20 3000 13.2 SANDSTONE _ _ brown / rust 16 poorly cemented to cemented _ _ 17 _ _ 18 _ _ 19 _ _ CS 20 50/7" 8000 17.1 106.0 BOTTOM OF BORING DEPTH 20.0' _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC 10 UNIT TOWNHOME DEVELOPMENT 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 _ _ GRAVEL PIT RUN (GP) - FILL MATERIAL 1 with cobbles _ _ 2 _ _ 3 CLAYEY SAND with GRAVEL - FILL MATERIAL _ _ brown / mottled 4 medium dense _ _ CS 5 6 7500 7.3 108.4 36 20 29.5 2.1% _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SANDY LEAN CLAY (CL) SS 10 10 7000 14.5 light brown to reddish brown _ _ stiff to medium stiff 11 _ _ 12 _ _ 13 _ _ 14 _ _ CS 15 6 3000 19.9 107.0 _ _ 16 increase in sand with depth _ _ 17 _ _ 18 _ _ 19 _ _ SS 20 12 2000 25.4 _ _ SAND & GRAVEL (SP/GP) 21 brown _ _ medium dense 22 _ _ 23 _ _ 24 _ _ CS 25 9 Continued on Sheet 2 of 2 _ _ Earth Engineering Consultants, LLC 10 UNIT TOWNHOME DEVELOPMENT 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 27 brown / rust / grey _ _ poorly cemented to cemented 28 _ _ 29 _ _ SS 30 50/3" 4000 17.0 _ _ 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 10 UNIT TOWNHOME DEVELOPMENT FORT COLLINS, COLORADO Project: Location: Project #: Date: SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown / Dark Brown / Rust SANDY LEAN CLAY (CL) - Fill Material Sample Location: Boring 2, Sample 1, Depth 2' Liquid Limit: 33 Plasticity Index: 16 % Passing #200: 51.4% Beginning Moisture: 15.4% Dry Density: 113.5 pcf Ending Moisture: 19.7% Swell Pressure: 600 psf % Swell @ 500: 0.1% 10 Unit Townhome Development Fort Collins, Colorado 1162091 October 2016 -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: SWELL / CONSOLIDATION TEST RESULTS Material Description: CLAYEY SAND / SANDY LEAN CLAY (CL) - Fill Material Sample Location: Boring 3, Sample 1, Depth 4' Liquid Limit: 36 Plasticity Index: 20 % Passing #200: 29.5% Beginning Moisture: 7.3% Dry Density: 119.7 pcf Ending Moisture: 20.1% Swell Pressure: % Swell @ 500: 2.1% 10 Unit Townhome Development Fort Collins, Colorado 1162091 October 2016 -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 NO: 1162091 LOG OF BORING B-3 OCTOBER 2016 SHEET 2 OF 2 WATER DEPTH START DATE 9/28/2016 WHILE DRILLING 19.5' 9/28/2016 AFTER DRILLING N/A SURFACE ELEV 24 HOUR N/A FINISH DATE A-LIMITS SWELL N/A FORT COLLINS, COLORADO PROJECT NO: 1162091 LOG OF BORING B-3 OCTOBER 2016 SHEET 1 OF 2 WATER DEPTH START DATE 9/28/2016 WHILE DRILLING 19.5' SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 9/28/2016 AFTER DRILLING N/A A-LIMITS SWELL FORT COLLINS, COLORADO PROJECT NO: 1162091 LOG OF BORING B-2 OCTOBER 2016 SHEET 1 OF 1 WATER DEPTH START DATE 9/28/2016 WHILE DRILLING 18' SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 9/28/2016 AFTER DRILLING N/A A-LIMITS SWELL FORT COLLINS, COLORADO PROJECT NO: 1162091 LOG OF BORING B-1 OCTOBER 2016 SHEET 1 OF 1 WATER DEPTH START DATE 9/28/2016 WHILE DRILLING 15.5' SURFACE ELEV N/A 24 HOUR N/A FINISH DATE 9/28/2016 AFTER DRILLING N/A A-LIMITS SWELL 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