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Home My WebLink AboutHEARTSIDE HILL COMMUNITY FACILITY - PDP230016 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTPRELIMINARY GEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED RESIDENTIAL DEVELOPMENT LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION 6501 BRITTANY STREET, FORT COLLINS, COLORADO SOILOGIC # 21-1239 August 13, 2021 Soilogic, Inc. 3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144 August 13, 2021 Highland Development Services, Inc. 6355 Fairgrounds Avenue, Suite 100 Windsor, Colorado 80550 Attn: Mr. Jason Claeys, P.E. Re: Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development Lots 1 and 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 Mr. Claeys: Soilogic, Inc. (Soilogic) personnel have completed the preliminary geotechnical subsurface exploration report you requested for the proposed residential development to be constructed on Lots 1 and 2 in the Heart of the Rockies Second Subdivision, located at 6501 Brittany Street in Fort Collins, Colorado. The results of our subsurface exploration and pertinent geotechnical engineering recommendations are included with this report. The subsurface materials encountered in the completed site borings were quite variable across the site, but generally consisted of a thin mantle of vegetation and topsoil underlain by brown/beige/rust lean clay with varying amounts of sand. A portion of the near-surface lean clay encountered at the location of boring B-2 extending to a depth of about 3 to 4 feet below ground surface was somewhat mottled in color, appeared to contain bedrock fragments and was identified as possible existing fill material which may have been placed to develop present site grade. In general, the lean clay varied from medium stiff to very stiff in terms of consistency, exhibited variable swell potential (ranging from none to very high) at current moisture and density conditions and extended to depths between 2½ to 18 feet below present site grade, where it was underlain by brown/olive/beige/gray/rust interbedded claystone/siltstone/sandstone bedrock of varying composition. The bedrock varied from weathered to very hard in terms of hardness, also exhibited variable swell potential (ranging from low to high) at in-situ moisture and density conditions and extended to the bottom of each boring at depths ranging from approximately 15 to 30 feet below present site grades. In general, we judge the bedrock unit underlying the site to possess moderate to high swell potential overall. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 and 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 2 Groundwater was measured in borings B-1, B-2, B-3 and B-6 at depths between about 13 and 27 feet below ground surface, but was not encountered in any of the remaining site borings to the depths explored when checked immediately after completion of drilling. When checked seven (7) days after drilling, groundwater was measured in all borings with the exception of boring B-3 at depths between about 5 and 15 feet below ground surface. The ground surface in the area of boring B-3 had been disturbed, such that subsequent groundwater level measurements could not be completed. Care will be needed across the development in order to maintain adequate separation distances between finish floor slab and crawl space subgrade elevations and the observed levels of groundwater. Typically, we recommend finish floor slab and/or crawl space subgrade elevations be established a minimum of three (3) feet above observed groundwater levels. Raising site grades across portions of the development property could be considered to facilitate full-basement construction in areas of the site. Due to the presence of very shallow groundwater in the vicinity of boring B-7 (approximately 5 feet below present site grade), use of crawl space or at-grade construction will likely be necessary unless this area of the site is raised considerably from existing grade through fill placement. Lowering site groundwater levels with an underdrain system could also be considered. Underdrain systems would require a suitable outfall. Expansive lean clay soils and interbedded bedrock of variable composition were encountered in all of the completed site borings except boring B-3 at this site at depths which could influence spread footing foundations and slab-on-grade floors. Where expansive soils and bedrock are identified near intended foundation bearing elevation, drilled pier foundations used in conjunction with structural flooring systems are recommended. As a higher risk option, sub-excavation/backfill procedures completed on a development-wide basis and extended to a minimum depth of 10 feet below intended foundation bearing elevation could be considered to develop support for the proposed lightly-loaded structure foundations and living area floor slabs in the expansive soil/ bedrock environment. Based on existing subsurface soil/bedrock stratigraphy and assuming grading cuts/fills on the order of five (5) feet or less, we estimate the proposed community building, all of the proposed single-family residences and all of the multi-family residences (with the possible exception of the two southeastern-most structures) to be constructed at this site would Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 and 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 3 likely require the use of drilled pier foundations and structurally-supported living area floors or higher risk deep sub-excavation/backfill procedures. Preliminary estimates regarding drilled pier foundation design are outlined in this report. Recommendations concerning sub-excavation procedures to redevelop low volume change (LVC) potential footing foundation and floor slab support are also included provided the risk of some foundation and floor slab movement and associated distress can be tolerated. Similar overexcavation/backfill procedures are recommended to develop low volume change (LVC) potential garage slab, pavement and exterior flatwork subgrade soils. Where lean clay soil with low swell potential is identified extending well below proposed foundation bearing elevation and adequate offset from expansive bedrock can be maintained, conventional spread footing foundation and slab-on-grade construction could be utilized. Based on results of the completed site borings, it is possible that the 2 southeastern-most multi-family residences to be constructed at this site could be constructed in this fashion. Several of the single-family residences constructed in the vicinity of boring B-7 in the northeastern portion of the property may also be able to be constructed in this fashion if crawl space construction is utilized and suitable offset from bedrock and groundwater is maintained. Five (5) feet of overexcavation/backfill (or offset from expansive lean clay and/or bedrock) could be planned for site drive and parking area pavements and completed at the time of site development prior to subsurface exploration for final pavement section design. The five (5) foot thick zone/offset could be developed through any combination of overexcavation/backfill and fill placement procedures. Based on the results of completed laboratory testing, the site lean clay and thoroughly-processed bedrock materials could be used as fill and overexcavation/backfill to develop the site, provided care is taken to thoroughly process bedrock material to a maximum nominal particle size of three (3) inches and to develop the proper moisture content in those materials at the time of placement and compaction. Depending on the in-place moisture content of the pavement subgrade soils at the time of construction, stabilization of the subgrade soils may become necessary prior to surfacing in order to develop a suitable paving platform. Preliminary pavement section design estimates for site drive and parking area pavements are included with this report. Final pavement section design alternatives can be provided as part of a design-level geotechnical subsurface exploration to be completed once development plans have been finalized and the site has been developed to approximate finish grade. Other preliminary Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 and 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 4 opinions and recommendations concerning design criteria and construction details for the proposed site improvements are included with this report. We appreciate the opportunity to be of service to you on this project. If we can be of further service to you in any way or if you have any questions concerning the enclosed information, please do not hesitate to contact us. Very Truly Yours, Soilogic, Inc. Reviewed by: Darrel DiCarlo, P.E. Alec Kaljian, P.E. Senior Project Engineer Project Engineer 08/13/2021 08/13/2021 PRELIMINARY GEOTECHNICAL SUBSURFACE EXPLORATION REPORT PROPOSED RESIDENTIAL DEVELOPMENT LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION 6501 BRITTANY STREET, FORT COLLINS, COLORADO SOILOGIC # 21-1239 August 13, 2021 INTRODUCTION This report contains the results of the preliminary geotechnical subsurface exploration completed for the proposed residential development to be constructed on Lots 1 and 2 of the Heart of the Rockies Second Subdivision, located 6501 Brittany Street in Fort Collins, Colorado. The purpose of our exploration was to describe the subsurface conditions encountered in the completed site borings and develop preliminary recommendations concerning design and construction of residence foundations and support of floor slabs and site pavements. Recommendations concerning the installation of site utilities and preliminary pavement section design estimates are also included. The conclusions and recommendations outlined in this report are based on results of the completed field and laboratory testing and our experience with subsurface conditions in this area. PROPOSED CONSTRUCTION Lots 1 and 2 of the combined development parcel includes approximately 8.55 acres, which we understand will be developed as single and multi-family residential, with about 72 multi-family units, 10 single-family detached residences, 2 group homes and a shared multipurpose community center. We expect the proposed community center and multi- family residences will be lightly-loaded one to three-story wood-frame structures constructed as slab-on-grade or over crawl spaces, while the single-family residences would likely consist of one to two-story wood-frame structures constructed over crawl spaces or full-depth basements. Foundations loads for the structures are expected to be light, with continuous wall loads on the order of 3 to 4 kips per lineal foot and individual column loads less than 75 kips. Grading was unknown at the time of report development; however, we anticipate grade changes on the order of five (5) feet or less will be required to develop finish site grades. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 2 SITE DESCRIPTION The development parcel is identified as Lots 1 and 2 of the Heart of the Rockies Second Subdivision, located at 6501 Brittany Street in Fort Collins, Colorado. At the time of our exploration, Lot 1 of the property contained the Heart of the Rockies Christian Church building, several outbuildings and associated site drive and parking area pavement improvements, while the remainder of the property (Lot 2) was generally vacant and contained a moderate growth of native grasses. Numerous small diameter deciduous trees and shrubs/bushes were noted in the areas surrounding the existing improvements on Lot 1, along Brittany Street and in a landscaped area near the southeast corner of the property. The relative high point of the property was noted near the southwest corner of the site, with ground surface gently sloping downward to the east in general. The maximum difference in ground surface elevation across this proposed development property is estimated to be about 40 feet based on review of a preliminary site plan. SITE EXPLORATION Field Exploration To develop subsurface information across the development parcel, a total of seven (7) soil borings were extended to depths of approximately 15 to 30 feet below present site grades across the property. The boring locations were selected by Soilogic personnel based on preliminary site plan and established in the field by surveyors. A diagram indicating the approximate boring locations is included with this report. Graphic logs of each of the auger borings are also included. The test holes were advanced using 4-inch diameter continuous-flight auger, powered by a truck-mounted CME-45 drill rig. Samples of the subsurface materials were obtained at regular intervals using California barrel sampling procedures in general accordance with ASTM specification D-1586. As part of the D-1586 sampling procedure, the standard sampling barrel is driven into the substrata using a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the sampler a distance of 12 inches is recorded and helpful in estimating the consistency, relative density or hardness of the soils and/or bedrock encountered. In the California barrel sampling procedure, lesser Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 3 disturbed samples are obtained in removable brass liners. Samples of the subsurface materials obtained in the field were sealed and returned to the laboratory for further evaluation, classification and testing. Laboratory Testing The samples collected were tested in the laboratory to measure natural moisture content and visually classified in accordance with the Unified Soil Classification System (USCS). The USCS group symbols are indicated on the attached boring logs. An outline of the USCS classification system is included with this report. Classification of bedrock was completed through visual and tactual observation of disturbed samples. Other bedrock types could be revealed through petrographic analysis. As part of the laboratory testing, a calibrated hand penetrometer (CHP) was used to estimate the unconfined compressive strength of essentially-cohesive specimens. The CHP also provides a more reliable estimate of soil/bedrock consistency than tactual observation alone. Dry density, Atterberg limits, -200 wash and swell/consolidation tests were completed on selected samples to help establish specific soil/bedrock characteristics. Atterberg limits tests are used to determine soil/bedrock plasticity. The percent passing the #200 size sieve (-200 wash) test is used to determine the percentage of fine-grained materials (clay and silt) in a sample. Swell/consolidation tests are performed to evaluate soil/bedrock volume change potential with variation in moisture content. Results of the completed laboratory tests are outlined on the attached boring logs and swell/consolidation test summaries. Water Soluble Sulfate (WSS) tests are currently being completed on two (2) selected bedrock samples to evaluate corrosive soil characteristics with respect to buried concrete and results will be provided once they become available. SUBSURFACE CONDITIONS The subsurface materials encountered in the completed site borings were quite variable across the site, but generally consisted of a thin mantle of vegetation and topsoil underlain by brown/beige/rust lean clay with varying amounts of sand. A portion of the near-surface lean clay encountered at the location of boring B-2 extending to a depth of about 3 to 4 feet below ground surface was somewhat mottled in color, appeared to contain bedrock Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 4 fragments and was identified as possible existing fill material which may have been placed to develop present site grade. In general, the lean clay varied from medium stiff to very stiff in terms of consistency, exhibited variable swell potential (ranging from no to very high) at current moisture and density conditions and extended to depths between 2½ to 18 feet below present site grade, where it was underlain by brown/olive/beige/gray/rust interbedded claystone/siltstone/sandstone bedrock of varying composition. The bedrock varied from weathered to very hard in terms of hardness, also exhibited variable swell potential (ranging from low to high) at in-situ moisture and density conditions and extended to the bottom of each boring at depths ranging from approximately 15 to 30 feet below present site grades. In general, we judge the bedrock unit underlying the site to possess moderate to high swell potential overall. The stratigraphy indicated on the included boring logs represents the approximate location of changes in soil and bedrock types. Actual changes may be more gradual than those indicated. Groundwater was measured in borings B-1, B-2, B-3 and B-6 at depths between about 13 and 27 feet below ground surface, but was not encountered in any of the remaining site borings to the depths explored when checked immediately after completion of drilling. When checked seven (7) days after drilling, groundwater was measured in all borings with the exception of boring B-3 at depths between about 5 and 15 feet below ground surface. The ground surface in the area of boring B-3 had been disturbed, such that subsequent groundwater level measurements could not be completed. Groundwater level information is indicated in the upper right-hand corner of the attached boring logs. Groundwater levels will vary seasonally and over time based on weather conditions, site development, irrigation practices and other hydrologic conditions. Perched and/or trapped groundwater conditions may also be encountered at times throughout the year. Perched water is commonly encountered in soils overlying less permeable soil layers and/or bedrock. Trapped water is typically encountered within more permeable zones of layered soil and bedrock systems. The location and amount of perched/trapped water can also vary over time. Based on the subsurface stratigraphy identified in the borings completed at this site and measured levels of groundwater, we expect a perched groundwater condition is present or could develop over time in most areas of the site. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 5 ANALYSIS AND RECOMMENDATIONS General Expansive lean clay soil and interbedded bedrock of variable composition were encountered in all of the completed site borings at this site except for boring B-3 at depths which could influence spread footing foundations and slab-on-grade floors. Total and differential heaving and associated distress of site improvements supported directly on or immediately above expansive soils/bedrock would be expected as the subgrade soils increase in moisture content subsequent to construction. Based on the results of completed field and laboratory testing, anticipated cuts and fills and type of construction proposed, we expect deep foundation systems used in conjunction with structural floor systems will be required for the proposed community building and all of the proposed single and multi- family residences to be constructed at this site (with the possible exceptions of the 2 southeastern-most multi-family residences and several of the single-family residences constructed in the vicinity of boring B-7 in the northeastern portion of the property, provided crawl space construction is utilized and suitable offset from bedrock and groundwater can be maintained) in order to reduce the potential for post-construction heaving and associated distress to the proposed site residences. As a higher risk option, sub-excavation/backfill procedures completed on a development-wide basis and extended to a minimum depth of 10 feet below intended foundation bearing elevation and 5 feet laterally beyond the building footprints could be considered to develop support for the proposed lightly-loaded structure foundations and living area floor slabs in the expansive soil/bedrock environment. As part of site development, we recommend a minimum of five (5) feet of properly moisture conditioned and compacted fill and/or overexcavation/backfill or offset from expansive lean clay and/or bedrock be developed beneath the site roadways prior to drilling for final pavement section design. The five (5) foot thick zone/offset can be developed through any combination of overexcavation/backfill and fill placement procedures. It would be possible to leave roadway subgrade levels five (5) feet low and complete shallower utility excavations prior to backfilling up to finish roadway subgrade level with a five (5) foot thick low-volume-change (LVC) zone. The site lean clay and thoroughly- processed bedrock materials could be used as fill and overexcavation/backfill to develop Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 6 the site. Depending on the swell potential and in-place moisture content of the subgrade soils/bedrock identified at the time of drilling for final pavement section design, supplemental heave mitigation and/or stabilization of the pavement subgrade soils may become necessary after grading and prior to surfacing in order to develop a suitable paving platform with low volume change potential. A final pavement exploration would be necessary for design of public street improvements (if any) after overlot grading has been completed in accordance with the requirements of Larimer County Urban Area Street Standards (LCUASS) or other governing entities standards. As previously outlined, groundwater was measured 7 days after drilling in each of the completed site borings with the exception of boring B-3 at depths which could impact typical basement construction (between approximately 5 and 15 feet below present site grade). Care will be needed to establish finish floor slab and/or crawl space subgrade levels a minimum of three (3) feet above the observed levels of water. Raising finish site grades and/or lowering the groundwater table with an underdrain system could be considered to facilitate full-depth basement construction. Underdrain systems would require a suitable outfall. Due to the presence of very shallow groundwater in the vicinity of boring B-7 (approximately 5 feet below present site grade), use of crawl space or at-grade construction will likely be necessary unless this area of the site is raised considerably from existing grade through fill placement. Individual site explorations should be completed for each of the proposed residences and community building after overlot grading and infrastructure development of the site have been completed to help better define subsurface conditions at the specific building locations. If higher-risk overexcavation/backfill procedures will be completed as part of mass grading to develop suitable low volume change potential spread footing/slab-on- grade support as subsequently outlined, lot-specific explorations should be performed after these procedures have been completed. Site Development All existing vegetation and topsoil should also be removed from within the areas of the proposed residences, community building, flatwork/pavement and any proposed fill areas. After stripping and completing all cuts and planned overexcavation and prior to placement Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 7 of any new fill, overexcavation/backfill, floor slab/flatwork concrete and site pavements, we recommend the exposed subgrade soils be scarified to a depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the materials standard Proctor maximum dry density. The moisture content of the scarified soils should be adjusted to be within the range of -1 to +3% of standard Proctor optimum moisture content at the time of compaction. Slopes steeper than 4:1 (H:V) expected to receive fill should be continuously and horizontally benched during fill placement. Soils used as site fill and overexcavation/backfill should consist of approved materials free from organic matter, debris and other objectionable materials. Based on the results of completed laboratory testing, it is our opinion, the site lean clay and thoroughly-processed bedrock materials could be used as fill and overexcavation/backfill to develop the site provided the proper moisture content is developed in those materials at the time of placement and compaction. Bedrock should be processed to less than three (3) inches in any dimension prior to use as fill and/or overexcavation/backfill. If it is necessary to import fill material to the site, those materials should have low potential for volume change and be relatively impervious. Typically soils with a liquid limit less than 40 and plasticity index less than 18 could be used as LVC fill. Essentially-granular structural fill materials should not be used as fill due to the high permeability and the ability of those materials to pond and transmit water. We recommend the site lean clay, thoroughly-processed bedrock and/or approved import LVC soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as recommended for the scarified materials above. At the high end of the above-recommended moisture content range, some pumping of the fill and overexcavation/backfill soils may be observed and would be expected. Care should be taken to avoid disturbing the prepared subgrade soils and placed fill materials prior to construction of any overlying improvements. Subgrade soils which are disturbed by construction activities or allowed to become wet and softened or dry and desiccated should be removed and replaced or reworked in place prior to placement of any fill or overlying improvements. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 8 Drilled Pier Foundations Lean clay and claystone/siltstone/sandstone bedrock with moderate to high swell potential were identified at depths which would affect conventional spread footing foundation and slab-on-grade construction at the locations of all of the test borings drilled on this site except for boring B-3. If/where moderately to highly expansive lean clay and/or claystone/ siltstone/sandstone bedrock are encountered within eight (8) feet of proposed foundation bearing elevation at the time of individual subsurface exploration, drilled pier foundations used in conjunction with structural flooring systems will likely be required in order to mitigate damage to the building foundations and floor slabs as a result of expansive soil/ bedrock uplift forces. Drilled piers would develop support capacity through a combination of end bearing and skin friction along the drilled shaft extended into bedrock underlying the site. Uplift forces developed on the drilled piers by the expansive lean clay and bedrock would be resisted by anchoring the piers into deeper-lying bedrock less likely to experience moisture-induced volume change subsequent to construction. Based on existing subsurface soil/bedrock stratigraphy and assuming grading cuts/fills on the order of five (5) feet or less, we estimate drilled pier and structural flooring systems (or higher risk deep sub- excavation procedures) would be required across most of property, with the possible exception of the two southeastern-most multi-family residences. Minimum bedrock penetration lengths on the order of 8 to 12 feet would be expected, with minimum overall pier lengths on the order of approximately 24 to 30 feet. Based on the depth to groundwater observed in the completed site borings, placement of pier concrete with a tremie will likely be required and casing may become necessary at some locations. Living Area Floors If/where drilled pier foundation systems will be employed, structural flooring systems should be used for living area floors in conjunction with the drilled shafts to allow for some movement of the subgrade soils/bedrock to occur without transmitting those forces to the overlying structures. If higher-risk deep sub-excavation (overexcavation/backfill procedures) as subsequently outlined below will be completed, the reconditioned materials could most likely be used for direct support of the community building, residence and garage floor slabs. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 9 Care should be taken to avoid disturbing floor slab subgrades prior to placement of the overlying improvements. Subgrade soils expected to receive flatwork concrete should be evaluated closely prior to surfacing. If areas of disturbed, wet and softened, or dry subgrade soils develop during construction, those materials should be removed and replaced or reworked in place prior to placement of the overlying improvements. Overexcavation/Backfill Procedures As a lower cost, higher risk alternative, deep sub-excavation (overexcavation/backfill procedures) could be considered beneath the community building and residence foundations and floor slabs in the moderately to very highly expansive lean clay and bedrock environment in order to reduce the potential for movement of those supported elements subsequent to construction and allow for conventional spread footing foundation and concrete slab-on-grade floor construction. Higher risk should be expected to include an increased risk of foundation and floor slab movement and possible distress to foundation and floor slab concrete. Similar overexcavation/backfill procedures should be anticipated for roadway pavements where expansive lean clay and/or bedrock are present within five (5) feet of finish pavement subgrade elevation. If this alternative is selected to provide suitable LVC spread footing/slab-on-grade support, we recommend overexcavation be performed as part of mass grading procedures and not on a lot-by-lot basis. Overexcavation would include the entire building envelopes and extend a depth of 10 feet below proposed foundation bearing elevation and at least five (5) feet laterally outside the building footprints in order to develop controlled and compacted low volume change potential (LVC) foundation bearing and floor slab support. Overexcavation/backfill procedures extended to five (5) feet below proposed roadway pavements and exterior flatwork should also be expected for areas of the site where expansive lean clay and/or claystone/siltstone/sandstone bedrock are expected to be present within five (5) feet of finish subgrade elevation. Provided the site lean clay and bedrock materials are thoroughly processed and properly moisture conditioned and compacted, the reconditioned section would provide a zone of material immediately beneath the structure footing foundations/floor slabs and pavements which will have low potential for volume change subsequent to construction. The LVC mat and surcharge loads placed on the underlying soils/bedrock by the reconditioned mat will reduce the potential for total and Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 10 differential movement of the supported improvements subsequent to construction. The reconditioned zone also assists in distributing movement in the event that some swelling of those materials underlying the reconditioned zone occurs. The overexcavation/backfill procedures outlined above will reduce, but not eliminate, the potential for movement of the supported foundations and floor slabs subsequent to construction. The in-place materials below the moisture conditioned zone can increase in moisture content, creating some structural and floor slab movement. Inherent risks exist when building in areas expansive soils and/or bedrock. The risk of some movement cannot be eliminated. Some post-construction movement of residence footing foundations and floor slabs and associated distress should be expected. Moisture/density testing of the overexcavation/backfill soils will be required during placement and compaction. Overexcavation/backfill materials consisting of a blend of site lean clay and thoroughly-processed bedrock material should be placed and compacted as outlined above in the “Site Development” section of this report. Bedrock fragments should be processed to less than 3-inches in size in any dimension prior to placement and compaction. Care will be needed to thoroughly process/disk the processed bedrock materials to a uniform consistency and develop the proper moisture content in the materials at the time of placement and compaction. Groundwater was measured in all of the borings (except for boring B-3) at depths between about 5 and 15 feet below ground surface when checked seven (7) days after drilling. Based on subsurface stratigraphy, we expect perched/trapped water exists in areas of the site. Deep subexcavation procedures may encounter soft/unstable soils in some areas, requiring removal/replacement or other approved stabilization procedures prior to fill/backfill placement. Cuts below groundwater elevation will require dewatering to facilitate proper construction. We expect a majority of the dewatering procedures could be completed through open pumping procedures in sumps fed from ditches or sloped trench excavations. Care should be taken to maintain the proper moisture content in the bearing/subgrade soils prior to concrete placement and/or paving. The prepared structural mat should not be left exposed for extended periods of time. In the event that the reconditioned soils are allowed to dry out or if rain, snowmelt or water from any source is allowed to infiltrate the open Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 11 excavation, reworking of the subgrade soils or removal/replacement procedures may be required. It should be noted that the bedrock materials identified in the borings at this site typically exhibit moderate to high swell potential. Processing these materials to a soil-like consistency and recompacting them at or above optimum moisture content to significantly reduce swell potential may be difficult. Additionally, even if the sub-excavation procedures outlined in this report are performed properly, they are provided as a guideline in an attempt to reduce resultant swell potential. As such, LVC bearing condition suitable for direct support of spread footing foundations and conventional slab-on-grade floors may not result. If/where expansive overexcavation/ backfill materials are identified at the time of final geotechnical subsurface explorations (to be completed for each of the individual structures after mass grading), supplemental, more extensive overexcavation/backfill procedures or drilled pier foundations used in conjunction with structural flooring systems would be required. Footing Foundations Based on the subsurface conditions encountered in the completed site borings and results of field and laboratory testing, we expect the proposed lightly-loaded community building and residential structures could be constructed with conventional spread footing foundations and slab-on-grade floors bearing on overexcavation/backfill if higher risk deep sub-excavation procedures are completed. For design of footing foundations bearing on lean clay with low swell potential (if/where feasible) or a minimum ten (10) foot zone of properly placed and compacted fill and/or overexcavation/backfill developed as outlined above, maximum net allowable soil bearing pressures in the range of 1,000 to 2,000 psf appear usable, with minimum dead load pressures in the range of 350 to 650 psf. Individual site explorations should be completed for each of the proposed structures after overlot grading procedures have been completed to help better define subsurface conditions at the specific building locations and help ensure the proposed improvements will be supported on like materials with suitable strength and low volume change potential. If Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 12 higher-risk overexcavation/backfill procedures will be completed as part of mass grading to develop suitable low volume change potential spread footing/slab-on-grade support as previously outlined, lot-specific explorations should be performed after these procedures have been completed. Floor Slabs Based on the type of construction proposed and results of the completed field and laboratory testing, we expect the lightly-loaded building floor slabs could be supported on lean clay with low swell potential (if/where feasible) or a suitable zone of properly placed and compacted fill or overexcavation/backfill developed as outlined “Overexcavation/ Backfill Procedures” section of this report. Care should be taken to avoid disturbing floor slab subgrades prior to concrete placement. Subgrade soils expected to receive floor slab concrete should be evaluated closely prior to surfacing. If areas of disturbed, wet and softened, or dry subgrade soils develop during construction, those materials should be removed and replaced or reworked in place prior to placement of floor slab concrete. Below-Grade Construction We recommend perimeter drain systems be installed around all below-grade areas (including crawl spaces) to help reduce the potential for development of hydrostatic pressures behind below-grade walls and surface water infiltration into the crawl space and/or basement areas of the residences. Perimeter drain systems should consist of a 4-inch diameter, perforated drain pipe surrounded by a minimum of six (6) inches of free-draining gravel. A filter fabric should be considered around the free-draining gravel or perforated pipe to reduce the potential for an influx of fine-grained soils into the systems. The drain pipes should be placed at approximate foundation bearing level at the high point of the systems, run around interior or exterior perimeters of crawl space and/or basement voided structural floor areas and exterior perimeters of footing foundation basement areas with a minimum slope of ⅛-inch per foot to facilitate efficient water removal and be designed to discharge to sump pit and pump systems, underdrain system or free outfalls. If free outfalls Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 13 will be considered, measures to help reduce the potential for reverse flow and animal access into the systems should be considered. Backfill placed adjacent to the below-grade walls should consist of LVC potential and relatively impervious soils which are free from organic matter, debris and other objectionable materials. The site lean clay, thoroughly-processed bedrock and/or approved LVC fill could be used as backfill in these areas. The site lean clay, thoroughly-processed bedrock and/or LVC fill materials should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as previously outlined in the “Site Development” section of this report. Excessive lateral stress can be imposed on below-grade walls when using heavier mechanical compaction equipment. We recommend compaction of unbalanced basement wall backfill be completed using light mechanical or hand compaction equipment. Utility Installation Bedding around utility pipelines should be placed in accordance with recommendations from the pipeline designer. Backfill soils placed above pipelines should consist of approved materials which are free from organic matter, debris and other objectionable materials. The site lean clay and thoroughly processed bedrock materials could be used as pipeline backfill. Pipeline backfill should be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted as previously outlined in the “Site Development” section of this report. At current moisture contents, we expect the site soils/ bedrock will require moisture adjustment to achieve proper moisture content prior to placement as utility backfill. Care will be needed to ensure utilities are not placed on or above disturbed or sloughed materials. Utility excavations will likely expose the lean clay overburden and underlying interbedded bedrock. Care will also be needed to develop stable side slopes in pipeline trenches. As such, we expect temporary shoring, bracing, or cutting of shallow slopes may be necessary in deeper excavations. Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards. As a safety measure, it is recommended that vehicles and soil Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 14 stockpiles be kept to a minimum lateral distance from the crest of the slope equal to no less than the slope height. Groundwater was measured in all of the borings (except for boring B-3 which had been destroyed) at depths between about 5 and 15 feet below ground surface when checked seven (7) days after drilling. Cuts below groundwater elevation will require dewatering to facilitate proper construction. We expect a majority of the dewatering procedures could be completed through open pumping procedures in sumps fed from ditches or sloped trench excavations. Site Roadways We expect the site pavement subgrades will consist of natural, undisturbed lean clay and processed lean clay and claystone/siltstone/sandstone bedrock overexcavation/backfill with low swell potential. Based on results of completed laboratory testing, overexcavation/ backfill procedures extended to a depth of five (5) feet below finish pavement subgrade elevation should be expected in areas of the site where expansive lean clay and/or claystone/siltstone/sandstone bedrock are identified within five (5) feet of finish roadway subgrade elevation. The 5-foot LVC zone beneath flatwork and site pavements could be developed through any combination of overexcavation/backfill procedures, subgrade reconditioning and new fill placement. Pavement subgrades should be developed as outlined in the “Site Development” section of this report. A final subgrade evaluation and pavement section design report will be necessary for public roadways (if any) once overlot grading has been completed and roadways are developed to approximate finish grade in accordance with requirements of LCUASS. For preliminary design estimates, a pavement section consisting of 4 to 5 inches of asphaltic concrete overlying 6 to 8 inches of aggregate base course could be used for local residential roadways and private site drives and parking area pavements. The site lean clay and thoroughly-processed claystone/siltstone/sandstone bedrock overexcavation/backfill would be particularly susceptible to strength loss and instability when elevated in moisture content with a tendency to rut and pump when wetted. Depending on the time of year when construction occurs and other hydrologic conditions, stabilization of site pavement subgrades may become necessary to develop a suitable Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 15 paving platform. If required, we recommend consideration be given to stabilization of the pavement subgrades with Class “C” fly ash. Chemical stabilization can also eliminate some of the uncertainty associated with attempting to pave during periods of inclement weather. In addition, it may be possible to reduce the required thicknesses of asphaltic concrete and aggregate base course with the increase in subgrade strength developed through the chemical stabilization procedures. Drainage Positive drainage is imperative for satisfactory long-term performance of the proposed site structures and associated site improvements. We recommend positive drainage be developed away from all site structures and pavement areas to reduce the potential for wetting of the subgrade and bearing materials. Water which is allowed to pond adjacent to site improvements can result in unsatisfactory performance of those improvements over time. Water which is allowed to pond adjacent to site roadways can result in a loss of subgrade support and premature failure of the roadway pavement sections. LIMITATIONS This report was prepared based upon the data obtained from the completed site exploration, laboratory testing, engineering analysis and any other information discussed. The completed borings provide an indication of subsurface conditions at the boring locations only. Variations in subsurface conditions can occur in relatively short distances away from the borings. This report does not reflect any variations which may occur across the site or away from the borings. If variations in the subsurface conditions anticipated become evident, the geotechnical engineer should be notified immediately so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any biological or environmental assessment of the site or identification or prevention of pollutants or hazardous materials or conditions. Other studies should be completed if concerns over the potential of such contamination or pollution exist. Preliminary Geotechnical Subsurface Exploration Report Proposed Residential Development – Lots 1 & 2, Heart of the Rockies Second Subdivision 6501 Brittany Street, Fort Collins, Colorado Soilogic # 21-1239 16 The geotechnical engineer should be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. The geotechnical engineer should also be retained to provide testing and observation services during construction to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with the generally accepted standard of care for the profession. No warranties express or implied, are made. The conclusions and recommendations contained in this report should not be considered valid in the event that any changes in the nature, design or location of the project as outlined in this report are planned, unless those changes are reviewed and the conclusions of this report modified and verified in writing by the geotechnical engineer. LOG OF BORING B-1 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 CL LEAN CLAY with varying - amounts of SAND 2 brown, rust - 4941.0 3 - 4 - 5 CS 50/9 8.8 110.5 9000+5.7%6400 --- - 6 - 7 - 8 - 9 - 10 CS 50/6 11.8 ------- - 11 Interbedded - CLAYSTONE/SILTSTONE/SANDSTONE 12 of varying composition - brown, olive, beige, gray, rust 13 hard to very hard - 14 - 15 CS 50/6 13.9 111.6 9000+2.1% @ 1000 3100 --- - 16 - 17 - 18 - 19 - 20 CS 50/8 15.5 111.5 9000+----- - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - BOTTOM OF BORING @ 30.0'30 CS 50/3 13.4 -9000+----- US C S Sa m p l e r Atterberg Limits Surface Elev.4944.0'Field Personnel:7 Days After Drilling 15.0' Finish Date 7/29/2021 Hammer Type:After Drilling 27.0' Sheet Drilling Rig:Water Depth Information Start Date 7/29/2021 Auger Type:During Drilling 27.0' LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 LOG OF BORING B-2 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 POSSIBLE EXISTING FILL MATERIAL;- CL LEAN CLAY with BEDROCK fragments 2 brown, beige, gray, rust - very stiff 3 CS 19 9.9 117.2 9000+8.3%7100 34 17 55.0% - 4 - 5 CS 22 13.9 102.1 9000+5.7%6200 --- - 6 - 7 CL LEAN CLAY with varying - amounts of SAND 8 brown, beige, rust - medium stiff to very stiff 9 - 10 CS 7 22.6 101.2 5000 None <500 --- - 11 - 12 - 4916.3 13 CLAYSTONE/SILTSTONE/SANDSTONE - brown, olive, beige, gray, rust 14 medium hard - 15 CS 50/11 17.5 113.1 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling 13.0' Start Date 7/29/2021 Auger Type:During Drilling 13.0' 7 Days After Drilling 11.0' US C S Sa m p l e r Atterberg Limits Surface Elev.4929.3'Field Personnel: LOG OF BORING B-3 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 - 2 - 3 - 4 - 5 CS 13 21.2 103.5 5000 0.4%1100 --- - 6 - 7 - 8 CL LEAN CLAY with varying - amounts of SAND 9 brown, beige, rust - medium stiff to stiff 10 CS 14 21.4 103.6 6000 None <500 --- - 11 - 12 - 13 - 14 - 15 CS 8 23.6 101.6 4000 ----- - 16 - 17 - 4897.3 18 - 19 - 20 CS 50/4 16.5 114.0 9000+----- - 21 - 22 - Interbedded 23 CLAYSTONE/SILTSTONE/SANDSTONE - of varying composition 24 brown, olive, beige, gray, rust - very hard 25 - 26 - 27 - 28 - 29 - BOTTOM OF BORING @ 30.0'30 CS 50/3 14.0 117.5 9000+----- Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling 17.0' Start Date 7/29/2021 Auger Type:During Drilling 17.0' 7 Days After Drilling Destroyed US C S Sa m p l e r Atterberg Limits Surface Elev.4915.3'Field Personnel: LOG OF BORING B-4 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 CL LEAN CLAY with SAND - brown, rust 2 very stiff - 3 CS 23 10.6 120.4 9000+7.2%9800 --- 4918.3 - 4 - 5 CS 50/11 11.2 111.6 9000+5.5%7100 --- - 6 - 7 - 8 Interbedded - CLAYSTONE/SILTSTONE/SANDSTONE 9 of varying composition - brown, olive, beige, gray, rust 10 CS 50/6 12.9 115.3 9000+4.0%4900 --- medium hard to very hard - 11 - 12 - 13 - 14 - 15 CS 50/6 7.7 127.1 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling None Start Date 7/29/2021 Auger Type:During Drilling None 7 Days After Drilling 10.0' US C S Sa m p l e r Atterberg Limits Surface Elev.4921.8'Field Personnel: LOG OF BORING B-5 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - CL LEAN CLAY with SAND 1 brown, beige, rust - very stiff 2 4933.2 - 3 CS 27 9.2 114.4 9000+7.3%7400 --- - 4 - 5 CS 50 15.4 106.4 9000+0.8%1000 --- - 6 - 7 Interbedded - CLAYSTONE/SILTSTONE/SANDSTONE 8 of varying composition - brown, olive, beige, gray, rust 9 medium hard to very hard - 10 CS 50/9 13.0 119.6 9000+----- - 11 - 12 - 13 - 14 - 15 CS 50/5 14.4 119.0 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling None Start Date 7/29/2021 Auger Type:During Drilling None 7 Days After Drilling Wci @ 13.5' US C S Sa m p l e r Atterberg Limits Surface Elev.4935.7'Field Personnel: LOG OF BORING B-6 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 - CL LEAN CLAY with varying 2 amounts of SAND - brown, beige, rust 3 very stiff - 4 - 4923.5 5 CS 34 16.9 117.3 9000+1.2%1400 --- - 6 - 7 - 8 - 9 - 10 CS 50/8 15.1 112.5 9000+2.0%2000 --- - 11 - 12 - 13 - 14 - Interbedded 15 CS 50/6 12.9 115.4 9000+1.1% @ 1000 3000 --- CLAYSTONE/SILTSTONE/SANDSTONE - of varying composition 16 brown, olive, beige, gray, rust - hard to very hard 17 - 18 - 19 - 20 CS 50/5 15.3 118.1 9000+----- - 21 - 22 - 23 - 24 - 25 - 26 - 27 - 28 - 29 - BOTTOM OF BORING @ 30.0'30 CS 50/3 20.4 105.4 5500 ----- Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling 21.0' Start Date 7/29/2021 Auger Type:During Drilling 21.0' 7 Days After Drilling 12.0' US C S Sa m p l e r Atterberg Limits Surface Elev.4928.5'Field Personnel: LOG OF BORING B-7 1/1 CME 45 4" CFA Automatic HM / BM Estimated Swell % Passing SOIL DESCRIPTION Depth "N"MC DD qu % Swell @ Pressure # 200 Sieve (ft)(%)(pcf)(psf)500 psf (psf)LL PI (%) 4 - 6" VEGETATION & TOPSOIL - 1 - 2 - 3 CS 13 8.9 ------- - CL LEAN CLAY with varying 4 amounts of SAND - brown, beige, rust 5 CS 10 26.1 97.9 4000 None <500 37 23 75.5% very stiff - 6 - 7 - 8 - 4902.7 9 - 10 CS 19 23.0 102.4 9000+0.1%700 --- - Interbedded 11 CLAYSTONE/SILTSTONE/SANDSTONE - of varying composition 12 brown, olive, beige, gray, rust - weathered to hard 13 - 14 - 15 CS 50/7 13.0 119.6 9000+----- BOTTOM OF BORING @ 15.0'- 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 Sheet Drilling Rig:Water Depth Information LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Finish Date 7/29/2021 Hammer Type:After Drilling None Start Date 7/29/2021 Auger Type:During Drilling None 7 Days After Drilling 5.0' US C S Sa m p l e r Atterberg Limits Surface Elev.4911.7'Field Personnel: Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)110.5 500 Final Moisture 11.6% % Swell @ 500 psf 5.7% Swell Pressure (psf)6,400 Sample ID: B-1 @ 4 Initial Moisture 8.8% Sample Description: Gray/Beige/Rust Claystone/Siltstone SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)111.6 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 13.9% Sample ID: B-1 @ 14 Sample Description: Gray/Olive/Beige/Rust Claystone/Siltstone 1000 Final Moisture 21.9% % Swell @ 1,000 psf 2.1% Swell Pressure (psf)3,100 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit 34 Plasticity Index 17 % Passing #200 55.0% Dry Density (pcf)117.2 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 9.9% Sample ID: B-2 @ 2 Sample Description: Possible Existing Fill; Brown/Beige/Rust Lean Clay with Bedrock fragments (CL) 500 Final Moisture 22.1% % Swell @ 500 psf 8.3% Swell Pressure (psf)7,100 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)102.1 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 13.9% Sample ID: B-2 @ 4 Sample Description: Brown/Rust Lean Clay with Sand (CL) 500 Final Moisture 23.6% % Swell @ 500 psf 5.7% Swell Pressure (psf)6,200 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)101.2 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 22.6% Sample ID: B-2 @ 9 Sample Description: Dark Brown Lean Clay with Sand (CL) 500 Final Moisture 24.9% % Swell @ 500 psf None Swell Pressure (psf)<500 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)103.5 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 21.2% Sample ID: B-3 @ 4 Sample Description: Brown/Rust Lean Clay with Sand (CL) 500 Final Moisture 23.4% % Swell @ 500 psf 0.4% Swell Pressure (psf)1,100 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)103.6 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 21.4% Sample ID: B-3 @ 9 Sample Description: Dark Brown Lean Clay with Sand (CL) 500 Final Moisture 22.8% % Swell @ 500 psf None Swell Pressure (psf)<500 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)120.4 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 10.6% Sample ID: B-4 @ 2 Sample Description: Brown/Beige Lean Clay with Sand (CL) 500 Final Moisture 16.6% % Swell @ 500 psf 7.2% Swell Pressure (psf)9,800 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)111.6 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 11.2% Sample ID: B-4 @ 4 Sample Description: Gray/Brown/Olive/Rust Claystone/Siltstone 500 Final Moisture 23.3% % Swell @ 500 psf 5.5% Swell Pressure (psf)7,100 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)115.3 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 12.9% Sample ID: B-4 @ 9 Sample Description: Gray/Brown/Olive/Rust Siltstone/Claystone 500 Final Moisture 19.8% % Swell @ 500 psf 4.0% Swell Pressure (psf)4,900 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)114.4 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 9.2% Sample ID: B-5 @ 2 Sample Description: Brown/Gray/Rust Lean Clay (CL) to Claystone/Siltstone 500 Final Moisture 20.7% % Swell @ 500 psf 7.3% Swell Pressure (psf)7,400 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)106.4 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 15.4% Sample ID: B-5 @ 4 Sample Description: Gray/Brown/Olive/Rust Claystone/Siltstone/Sandstone 500 Final Moisture 22.4% % Swell @ 500 psf 0.8% Swell Pressure (psf)1,000 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)117.3 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 16.9% Sample ID: B-6 @ 4 Sample Description: Gray/Brown/Olive/Rust Claystone/Siltstone/Sandstone 500 Final Moisture 23.1% % Swell @ 500 psf 1.2% Swell Pressure (psf)1,400 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)112.5 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 15.1% Sample ID: B-6 @ 9 Sample Description: Gray/Brown/Olive/Rust Siltstone/Claystone 500 Final Moisture 21.6% % Swell @ 500 psf 2.0% Swell Pressure (psf)2,000 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)115.4 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 12.9% Sample ID: B-6 @ 14 Sample Description: Gray/Brown/Olive/Rust Claystone/Siltstone/Sandstone 1000 Final Moisture 21.6% % Swell @ 1,000 psf 1.1% Swell Pressure (psf)3,000 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit 37 Plasticity Index 23 % Passing #200 75.5% Dry Density (pcf)97.9 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 26.1% Sample ID: B-7 @ 4 Sample Description: Dark Brown Lean to Fat Clay with Sand (CL-CH) 500 Final Moisture 26.1% % Swell @ 500 psf None Swell Pressure (psf)<500 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) Liquid Limit - Plasticity Index - % Passing #200 - Dry Density (pcf)102.4 SWELL/CONSOLIDATION TEST SUMMARY LOTS 1 AND 2, HEART OF THE ROCKIES SECOND SUBDIVISION PRELIMINARY 6501 BRITTANY STREET, FORT COLLINS, COLORADO Project # 21-1239 August 2021 Initial Moisture 23.0% Sample ID: B-7 @ 9 Sample Description: Gray/Brown/Rust Claystone/Siltstone/Sandstone 500 Final Moisture 24.6% % Swell @ 500 psf 0.1% Swell Pressure (psf)700 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 10 100 1000 10000 100000 --------- Applied Load (psf) UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification Group Symbol Group NameB Cu ! 4 and 1 " Cc " 3E GW Well graded gravelF Clean Gravels Less than 5% finesC Cu < 4 and/or 1 > Cc > 3E GP Poorly graded gravelF Fines classify as ML or MH GM Silty gravelF,G, H Coarse Grained Soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Gravels with Fines More than 12% finesC Fines classify as CL or CH GC Clayey gravelF,G,H Cu ! 6 and 1 " Cc " 3E SW Well graded sandI Clean Sands Less than 5% finesD Cu < 6 and/or 1 > Cc > 3E SP Poorly graded sandI Fines classify as ML or MH SM Silty sandG,H,I Sands 50% or more of coarse fraction passes No. 4 sieve Sands with Fines More than 12% finesD Fines classify as CL or CH SC Clayey sandG,H,I PI > 7 and plots on or above “A” lineJ CL Lean clayK,L,M Silts and Clays Liquid limit less than 50 Inorganic PI < 4 or plots below “A” lineJ ML SiltK,L,M Liquid limit - oven dried Organic clayK,L,M,N Fine-Grained Soils 50% or more passes the No. 200 sieve Organic Liquid limit - not dried < 0.75 OL Organic siltK,L,M,O Inorganic PI plots on or above “A” line CH Fat clayK,L,M Silts and Clays Liquid limit 50 or more PI plots below “A” line MH Elastic siltK,L,M Liquid limit - oven dried Organic clayK,L,M,P Organic Liquid limit - not dried < 0.75 OH Organic siltK,L,M,Q Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well graded gravel with silt, GW-GC well graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: 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 E Cu = D60/D10 Cc = F If soil contains ! 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. HIf fines are organic, add “with organic fines” to group name. I If soil contains ! 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains ! 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains ! 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI ! 4 and plots on or above “A” line. O PI < 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. GENERAL NOTES DRILLING & SAMPLING SYMBOLS: SS: Split Spoon - 1⅜" I.D., 2" O.D., unless otherwise noted HS: Hollow Stem Auger ST: Thin-Walled Tube – 2.5" O.D., unless otherwise noted PA: Power Auger RS: Ring Sampler - 2.42" I.D., 3" O.D., unless otherwise noted HA: Hand Auger CS: California Barrel - 1.92" I.D., 2.5" O.D., unless otherwise noted RB: Rock Bit BS: Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary The number of blows required to advance a standard 2-inch O.D. split-spoon sampler (SS) the last 12 inches of the total 18-inch penetration with a 140-pound hammer falling 30 inches is considered the “Standard Penetration” or “N-value”. For 2.5” O.D. California Barrel samplers (CB) the penetration value is reported as the number of blows required to advance the sampler 12 inches using a 140-pound hammer falling 30 inches, reported as “blows per inch,” and is not considered equivalent to the “Standard Penetration” or “N-value”. 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 Casing Removal Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater. In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations. DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally 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 in-place relative density and fine-grained soils on the basis of their consistency. FINE-GRAINED SOILS COARSE-GRAINED SOILS BEDROCK (CB) Blows/Ft. (SS) Blows/Ft. Consistency (CB) Blows/Ft. (SS) Blows/Ft. Relative Density (CB) Blows/Ft. (SS) Blows/Ft. Consistency < 3 0-2 Very Soft 0-5 < 3 Very Loose < 24 < 20 Weathered 3-5 3-4 Soft 6-14 4-9 Loose 24-35 20-29 Firm 6-10 5-8 Medium Stiff 15-46 10-29 Medium Dense 36-60 30-49 Medium Hard 11-18 9-15 Stiff 47-79 30-50 Dense 61-96 50-79 Hard 19-36 16-30 Very Stiff > 79 > 50 Very Dense > 96 > 79 Very Hard > 36 > 30 Hard RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY Descriptive Terms of Other Constituents Percent of Dry Weight Major Component of Sample Particle Size Trace < 15 Boulders Over 12 in. (300mm) With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm) Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand Silt or Clay #4 to #200 sieve (4.75mm to 0.075mm) Passing #200 Sieve (0.075mm) RELATIVE PROPORTIONS OF FINES PLASTICITY DESCRIPTION Descriptive Terms of Other Constituents Percent of Dry Weight Term Plasticity Index Trace With Modifiers < 5 5 – 12 > 12 Non-plastic Low Medium High 0 1-10 11-30 30+