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Home My WebLink AboutRENNAT SUBDIVISION - PDP190011 - SUBMITTAL DOCUMENTS - ROUND 2 - GEOTECHNICAL (SOILS) REPORTSUPPLEMENTAL SUBSURFACE EXPLORATION AND GROUNDWATER REPORT RENNAT PROPERTY NORTHWEST OF ROSEN ROAD AND TIMBERLINE DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1192061 Prepared for: Post Modern Development 144 North Mason, Suite 4 Fort Collins, Colorado 80524 Attn: Mr. J.D. Padilla (JD@postmoderndevelopment.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 August 16, 2019 Post Modern Development 144 North Mason, Suite 4 Fort Collins, Colorado 80524 Attn: Mr. J.D. Padilla (JD@postmoderndevelopment.com) Re: Supplementary Subsurface Exploration and Groundwater Evaluation Report Rennat Property Northwest of Rosen Road and Timberline Drive Fort Collins, Colorado EEC Project No. 1192061 Mr. Padilla: Enclosed, herewith, are the results of the supplementary subsurface exploration and groundwater evaluation completed by Earth Engineering Consultants, LLC personnel for the referenced project in Fort Collins, Colorado. This exploration/evaluation was completed as a supplementary groundwater study to the “Preliminary Subsurface Exploration Report” completed by our predecessors (EEC, Inc.) in February of 2012, Project No. 1122013. For this project, six (6) soil borings were drilled and hand/field slotted groundwater piezometers were installed, at the approximate locations as indicated on the enclosed Boring Location Diagram included with this report. The borings were extended to depths of approximately 15 to 20 feet below existing site grades. Individual boring logs, including groundwater observations, depth to bedrock, and results of laboratory testing are included as a part of the attached report. This exploration was completed in general accordance with our proposal dated July 10, 2019. In summary, the subsurface soils encountered in the preliminary test borings generally consisted of lean clay with varying amounts of sand soils. The lean clay soils were generally soft to very stiff becoming soft near the groundwater table and exhibited low to moderate swell potential at current moisture and density conditions. The lean clay soils extended to the depths explored at approximately 15 to 20 feet in a majority of the borings and to the underlying sand with varying amounts silt in boring PZ-3 at a depth of approximately 9 feet below the ground surface. The sand was generally loose to medium dense and extended to depths explored at approximately 15 feet below the ground surface. Groundwater was observed in the test borings at depths of approximately 5 to 15 feet below existing site grades at the time of drilling. Based on the materials observed within the preliminary borings and the anticipated foundation loads, we believe the proposed lightly loaded residential structures with potential basements, SUPPLEMENTAL SUBSURFACE EXPLORATION AND GROUNDWATER REPORT RENNAT PROPERTY NORTHWEST OF ROSEN ROAD AND TIMBERLINE DRIVE FORT COLLINS, COLORADO EEC PROJECT NO. 1192061 August 16, 2019 INTRODUCTION The supplemental subsurface exploration and groundwater evaluation for the Rennat Property located northwest of Rosen Road and Timberline Drive in Fort Collins, Colorado has been completed. This exploration/evaluation was completed as a supplementary groundwater study to the “Preliminary Subsurface Exploration Report” completed by our predecessors (EEC, Inc.) in February of 2012, Project No. 1122013. For this supplementary assessment, six (6) soil borings were drilled and hand/field slotted groundwater piezometers were installed on August 7, 2019 at the approximate locations as indicated on the enclosed Boring Location Diagram included with this report. The supplementary soil borings were advanced to depths of approximately 15 to 20 feet below existing site grades to obtain general information on existing subsurface and groundwater conditions. The individual boring logs and a site diagram indicating the approximate boring locations are included with this report. This The development property is located northwest of Rosen Road and Timberline Drive in Fort Collins, Colorado. The property, as we understand will most likely be developed for single family residential use with full-depth basements including associated interior roadways and infrastructure. Foundation loads for the proposed residential structures are anticipated to be light with continuous wall loads less than 2½ kips per lineal foot and individual column loads less than 35 kips. Floor loads are expected to be light. We anticipate maximum cuts and fills on the order of 5 feet (+/-) will be completed to develop the site grades. Overall site development will include construction of interior roadways designed in general accordance with the typical Larimer County Pavement Design Criteria. The purpose of this report is to describe the subsurface conditions encountered in the preliminary borings, analyze and evaluate the test data and provide supplementary/updated geotechnical recommendations concerning site development including foundations, floor slabs, an area underdrain system, and pavement sections. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 2 EXPLORATION AND TESTING PROCEDURES The boring locations were established in the field by a representative of Earth Engineering Consultants, LLC (EEC) by pacing and estimating angles from identifiable site features. Those locations should be considered accurate only to the degree implied by the methods used to make the field measurements. Photographs of the site taken at the time of drilling are provided with this report. The supplemental preliminary groundwater related borings were performed using a truck-mounted CME 75 drill rig equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 4¼-inch nominal ID hollow stem augers to maintain open boreholes for sampling and PVC piezometer/pipe installation. Samples of the subsurface materials encountered were obtained using split-barrel and California barrel sampling procedures in general accordance with ASTM Specifications D1586 and D3550, respectively. In the split-barrel and California barrel sampling procedures, standard sampling spoons are driven into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the 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 undisturbed samples are obtained in brass liners. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. After completing the drilling and sampling, and prior to removal of the hollow stem augers, a hand/field slotted 1-inch diameter PVC casing was installed in each borehole through the hollow stem auger. Laboratory moisture content tests were performed on each of the recovered samples. In addition, selected samples were tested for fines content and plasticity by washed sieve analysis and Atterberg limits tests. Swell/consolidation tests were completed on selected samples to evaluate the subgrade materials’ tendency to change volume with variation in moisture content and load. The quantity of water-soluble sulfates was determined on select samples to evaluate the risk of sulfate attack on site concrete. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 3 As a 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 sample's texture and plasticity. The estimated group symbol for the Unified Soil Classification System is shown 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. SITE AND SUBSURFACE CONDITIONS The development property is located northwest of Rosen Drive and Timberline Road in Fort Collins, Colorado. The project site is generally undeveloped with vegetation and topsoil at the surface of the borings. Surface water drainage across the site is generally to the southwest. Estimated relief across the site from northeast to southwest is approximately 20 to 35 feet (±). An EEC field engineer was on-site during drilling to direct the drilling activities and evaluate the subsurface materials encountered. Field descriptions of the materials encountered were based on visual and tactual observation of disturbed samples and auger cuttings. The boring logs included with this report may contain modifications to the field logs based on results of laboratory testing and engineering evaluation. Based on results of field and laboratory evaluation, subsurface conditions can be generalized as follows. Vegetation and topsoil were encountered at the surface of the borings. The topsoil and vegetation layers were underlain by lean clay with varying amounts of sand soils. The lean clay soils were generally soft to very stiff becoming soft near the groundwater table and exhibited low to moderate swell potential at current moisture and density conditions. The lean clay soils extended to the depths explored at approximately 15 to 20 feet in a majority of the borings and to the underlying sand with varying amounts silt in boring PZ-3 at a depth of approximately 9 feet below the ground surface. The sand was generally loose to medium dense and extended to depths explored at approximately 15 feet below the ground surface. The stratification boundaries indicated on the boring logs represent the approximate locations of changes in soil and rock types; in-situ, the transition of materials may be gradual and indistinct. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 4 GROUNDWATER OBSERVATIONS Observations were made while drilling and approximately 24 hours after drilling to detect the presence and level of groundwater. At the time of drilling and 24 hours after drilling, groundwater was observed in the preliminary test borings at depths ranging from approximately 5 to 15 feet below existing site grades. The measured depths to groundwater are recorded near the upper right- hand corner of each boring log included with this report. A groundwater contour diagram showing the approximate elevations of groundwater encountered across the site has been included with this report. Based on the existing groundwater conditions as presented herein, the groundwater piezometric flow is in the southeast direction. The groundwater measurements provided with this report are indicative of groundwater levels at the location and at the time the measurements were completed. Perched and/or trapped water may be encountered in more permeable zones in the subgrade soils at times throughout the year. Perched water is commonly encountered in soils immediately overlying less permeable bedrock materials. Fluctuations in ground water levels and in the location and amount of perched water may occur over time depending on variations in hydrologic conditions, irrigation activities on surrounding properties and other conditions not apparent at the time of this report. ANALYSIS AND RECOMMENDATIONS Swell/Consolidation Test Results Swell/consolidation testing is performed to evaluate the swell or collapse potential of soil or bedrock to assist in determining/evaluating foundation, floor slab and/or pavement design criteria. In the swell/consolidation test, relatively undisturbed samples obtained directly from the California barrel sampler are placed in a laboratory apparatus and inundated with water under a pre-established load. The swell-index is the resulting amount of swell or collapse under the initial loading condition expressed as a percent of the sample’s initial thickness. After the inundation period, additional incremental loads are applied to evaluate swell pressure and/or consolidation. For this assessment, we conducted five (5) swell-consolidation tests on relatively undisturbed soil samples obtained at various intervals/depths on the site. The swell index values for the in-situ soil samples analyzed revealed low swell characteristics and a tendency to consolidate upon loading as indicated on the attached swell test summaries. The (+) test results indicate the soil materials swell Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 5 potential characteristics while the (-) test results indicate the soils materials collapse/consolidation potential characteristics when inundated with water. Results of the laboratory swell tests are indicated in Table I below as well as on attached boring logs and the enclosed summary sheets. TABLE I – Summary of Swell Test Results Boring No. Depth (ft) Material Type Swell Consolidation Test Results Dry Density, (pcf) In-Situ Moisture Content (%) Inundation Pressure (psf) Swell Index (%) Swell Pressure (psf) 1 4 Lean Clay with Sand (CL) 103.8 19.5 500 (+) 0.0 < 500 2 9 Lean Clay with Sand (CL) 109.4 13.2 500 (+) 1.5 1700 4 4 Lean Clay (CL) 103.5 22.2 500 (+) 0.0 < 500 5 2 Lean Clay with Sand (CL) 94.9 7.9 150 (+) 3.5 600 6 9 Lean Clay with Sand (CL) 107.6 21.8 150 (-) 0.3 < 150 The Colorado Association of Geotechnical Engineers (CAGE) uses the following information to provide uniformity in terminology between geotechnical engineers to provide a relative correlation risk performance to measured swell. “The representative percent swell values are not necessarily 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. TABLE II: 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 of overburden soils analyzed exhibited generally low to moderate swell potential conditions within the lean clay nearing the ground table. The swell potential for the sample from boring/piezometer PZ-5 exhibited a swell potential greater than the maximum allowable 2% for pavement design, therefore a swell mitigation procedure may be necessary for pavement subgrades. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 6 General Considerations The swell potential of the site soils was generally low to moderate. Additionally, dry clay soils with moderate plasticity were observed near the surface in borings/piezometers PZ-2, PZ-5, and PZ-6. Care will be needed to see that the site improvements are not placed directly on or immediately above moderately swelling soils. Based on the observed swells, mitigation of the swell potential will likely be required as a part of the pavement subgrade preparation. Care should also be taken to avoid placing higher plasticity site soils as fill in any structure or flatwork areas. Subsurface conditions should be evaluated individually for each residence. If lower level construction or full-depth basements are being considered for the site, we would suggest that the lower level subgrade(s) be placed a minimum of 3 feet above the maximum anticipated rise in groundwater levels and a combination exterior and interior perimeter drainage system(s) be installed in areas with shallow groundwater, as shown on the attached diagram. Also, consideration could be given to 1) either designing and installing an area underdrain system to lower the groundwater levels provided a gravity discharge point can be established. If a gravity outlet/system cannot be designed another consideration would be to design and install a mechanical sump pump system to discharge the collected groundwater within the underdrain system, or 2) elevate/raise the site grades to establish the minimum suggested 3-foot separation to the maximum anticipated rise in groundwater. Foundations for buildings that are constructed with no basement should also be placed a minimum of 3 feet above the maximum anticipated rise in groundwater levels. During our subsurface exploration groundwater was found at depths as shallow as 5 feet in some areas, as shown on the attached groundwater contour diagram. Consideration should be given to the implementing a drainage or grading plan, as listed above, in these areas. Site Preparation All existing vegetation and/or topsoil should be removed from beneath site fills, roadways or building subgrade areas. Stripping depths should be expected to vary, depending, in part, on past agricultural activities. In addition, any soft/loose native soils or any existing fill materials without documentation of controlled fill placement should be removed from improvement and/or new fill areas. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 7 After stripping and completing all cuts, and prior to placement of any fill, floor slabs or pavements, we recommend the exposed soils be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95% of the material's maximum dry density as determined in accordance with ASTM Specification D698, the standard Proctor procedure. The moisture content of the scarified materials should be adjusted to be within a range of 2% of standard Proctor optimum moisture at the time of compaction. We expect mitigation for moderate swell cohesive soils will be required in flatwork, floor slab (non- basement), and pavement areas in portions of the site. That mitigation would commonly include removal of dry and hard materials, increasing the moisture in the clay soils and replacing the moisture conditioned soils as controlled density fill. Mitigation could be done on an individual residence/roadway basis; however, care should be taken during overlot grading to avoid placing fill above the dry, dense soils which would require future removal and reworking. In general, fill materials required to develop the building areas or site pavement subgrades should consist of approved, low-volume change materials which are free from organic matter and debris. The near surface lean clay, underlying sand, and/or approved imported structural fill could be used as fill in these areas. If granular imported structural fill is used, it should be similar to CDOT Class 5, 6 or 7 base course material with sufficient fines to prevent ponding of water in the fill. We recommend the fill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted to at least 95% of the material’s maximum dry density as determined in accordance with the standard Proctor procedure. The moisture content of cohesive soils should be adjusted to be within the range of ±2% of optimum moisture content at the time of placement. Granular soil should be adjusted to a workable moisture content. Specific explorations should be completed for each building/individual residential lot to develop recommendations specific to the proposed structure and owner/builder and for specific pavement sections. Areas of slight hydro-compaction prone subsoils and loose/compressible soils encountered within the lean clay soils nearing the ground water table will require particular attention in the development of each lot. Care should be taken to carefully evaluate the materials during the specific explorations for individual lots as well as during construction, to determine whether ground stabilization measures will be necessary below footings. Care should be taken after preparation of the subgrades to avoid disturbing the subgrade materials. Positive drainage should be developed away from structures and across and away from pavement Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 8 edges to avoid wetting of subgrade materials. Subgrade materials allowed to become wetted subsequent to construction of the residences and/or pavements can result in unacceptable performance of those improvements. Areas of greater fills overlying areas with loose/compressible subsoils, especially within the deeper utility alignments, may experience settlement due to the loose/compressible subsoils below and within the zone of 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. Preloading and/or surcharging the fill areas could be considered to induce additional settlement in these areas prior to construction of improvements in or on the fills. Unless positive steps are taken to pre-consolidate the fill materials and/or underlying loose/compressible subgrades, special care will be needed for construction of improvements supported on or within these areas. Foundation Systems – General Considerations The cohesive subsoils will require particular attention in the design and construction to reduce the amount of movement due to moderate to the in-situ soft/compressible characteristics. Groundwater was also encountered at relatively shallow depths which will require special attention in the overall design and construction of the project. As previously mentioned, consideration could be given to the installation of an area underdrain system. Conventional type spread footings bearing on native subsoils or engineered controlled fill material were evaluated for use on the site; however final subsurface explorations should be performed after building footprints and elevations have been better defined and actual design loads determined. Preliminary Spread Footing Foundation Recommendations We anticipate use of conventional footing foundations could be considered for lightly loaded structures at this site. We expect footing foundations would be supported either on the native soils or on newly placed and compacted fills. Some of the lean clay materials exhibited soft/compressible conditions especially nearing the groundwater table; therefore, care should be taken to see that foundations are not supported directly on soft/compressible materials. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 9 In areas where the soils exhibited compressible conditions and/or where relatively low SPT N- Blows/ft were recorded, we would expect these zones could require particular attention/ground modification procedures to develop increased support capacity characteristics below foundations. We expect enhancing/stiffening of the subgrade/bearing soils could be accomplished by incorporating into the soft/compressible subsoils a layer granular rock (i.e., 1-½ inches minus crushed concrete aggregate) into the top 12 to 18 inches (+/-) of the subgrades as an initial means and method. Depending on the proximity to groundwater and/or severity of the loose/compressible soils, over excavation and backfill with an approved fill material placed and compacted as outlined herein could also be considered. After completing a site-specific/lot-specific geotechnical exploration study, a thorough “open- hole/foundation excavation” observation should be performed prior to foundation formwork placement to determine the extent of any possible over excavation and replacement procedures for loose/compressible areas. In general, the over excavation area would extend 8 inches laterally beyond the building perimeter for every 12 inches of overexcavation depth. Backfill materials should be placed as described in the section Site Preparation. For design of footing foundations bearing on approved native subsoils or on properly placed and compacted fill materials as outlined above, maximum net allowable total load soil bearing pressures on the order of 1,500 to 2,500 psf could be considered depending upon the specific backfill material used. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load would include full dead and live loads. Exterior foundations and foundations in unheated areas are typically located at least 30 inches below adjacent exterior grade to provide frost protection. Formed continuous footings would have minimum widths of 12 to 16 inches and isolated column foundations would have a minimum width of 24 to 30 inches. Care should be taken to avoid placement of structures partly on native soils and partly on newly placed fill materials to avoid differential settlement. In these areas, mitigation approaches could include surcharging of the fill materials or overexcavation of the native soils. Mitigation approaches may vary between structures depending, in part, on the extent and depth of new fill placement. Specific approaches could be established at the time of exploration for the individual structures. Care should be taken on the site to fully document the horizontal and vertical extent of fill placement on the site, including benching the fill into native slopes. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 10 Preliminary Basement Design and Construction Groundwater was encountered across the site within the preliminary soil borings at approximate depths of 5 to 15 feet below existing site grades. If lower level construction for either garden-level or full-depth basements is being considered for the site, we would suggest that the lower level subgrade(s) be placed a minimum of 3 feet above maximum anticipated rise in groundwater levels, or a combination exterior and interior perimeter drainage system(s) be installed in areas with shallow groundwater. Consideration could be given to 1) either designing and installing an area underdrain system to lower the groundwater levels provided a gravity discharge point can be established. If a gravity outlet/system cannot be designed another consideration would be to design and install a mechanical sump pump system to discharge the collected groundwater within the underdrain system, or 2) elevate/raise the site grades to establish the minimum required 3-foot separation to the maximum anticipated rise in groundwater EEC is available to assist in the underdrain design if requested. For each individual building with a garden level or full-depth basement located less than 3 feet above maximum groundwater levels, the dewatering system should, at a minimum, include an under- slab gravel drainage layer sloped to an interior perimeter drainage system. Considerations for the preliminary design of the combination exterior and interior perimeter drainage system are as follows: The under-slab drainage system should consist of a properly sized perforated pipe, embedded in free-draining gravel, placed in a trench at least 12 inches in width. The trench should be inset from the interior edge of the nearest foundation a minimum of 12 inches. In addition, the trench should be located such that an imaginary line extending downward at a 45-degree angle from the foundation does not intersect the nearest edge of the trench. Gravel should extend a minimum of 3 inches beneath the bottom of the pipe. The underslab drainage system should be sloped at a minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system. The underslab drainage layer should consist of a minimum 6-inch thickness of free-draining gravel meeting the specifications of ASTM C33, Size No. 57 or 67 or equivalent. Cross-connecting drainage pipes should be provided beneath the slab at minimum 15-foot intervals and should discharge to the perimeter drainage system. Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 11 Sizing of drainage pipe will be dependent upon groundwater flow into the dewatering system. Groundwater flow rates will fluctuate with permeability of the soils to be dewatered and the depth to which groundwater may rise in the future. Pump tests to determine groundwater flow rates are recommended in order to properly design the system. For preliminary design purposes, the drainage pipe, sump and pump system should be sized for a projected flow of 0.5 x 10-3 cubic feet per second (cfs) per lineal foot of drainage pipe. Additional recommendations can be provided upon request and should be presented in final subsurface exploration reports for each residential/commercial lot. The exterior drainage system should be constructed around the exterior perimeter of the lower level/below grade foundation system and sloped at a minimum 1/8 inch per foot to a suitable outlet, such as a sump and pump system. The exterior drainage system should consist of a properly sized perforated pipe, embedded in free- draining gravel, placed in a trench at least 12 inches in width. Gravel should extend a minimum of 3 inches beneath the bottom of the pipe, and at least 2 feet above the bottom of the foundation wall. The system should be underlain with a polyethylene moisture barrier, sealed to the foundation walls, and extended at least to the edge of the backfill zone. The gravel should be covered with drainage fabric prior to placement of foundation backfill. Preliminary Floor Slab/Exterior Flatwork Subgrades Based on the observed subsurface conditions, we believe the native lean clay soils with low swell potential and/or properly placed structural fill material could be used for direct support of floor slabs. Floor slab and exterior flatwork subgrades should be prepared as outlined in the section Site Preparation. Preliminary Pavement Subgrades Based on the current subsurface conditions, we believe a swell mitigation plan will likely be required for pavements, this would likely consist of moisture conditioning and reworking a zone of the dry near surface clay material. Pavement subgrades should be prepared as described in the section site preparation. After completion of the pavement subgrades, care should be taken to prevent disturbance of those materials prior to placement of the overlying pavements. Soils which are disturbed by construction Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 12 activities should be reworked in-place or, if necessary, removed and replaced prior to placement of overlying fill or pavements. Depending on final site grading and/or weather conditions at the time of pavement construction, stabilization of a portion of the site pavement subgrades may be required to develop suitable pavement subgrades. The site clay soils could be subject to instability at higher moisture contents. Stabilization could also be considered as part of the pavement design, although prior to finalizing those sections, a stabilization mix design would be required. Preliminary Site Pavements Pavement sections are based on traffic volumes and subgrade strength characteristics. An assumed R-Value of 10 was used for the preliminary pavement design. Suggested preliminary pavement sections for the local residential and minor collector roadways are provided below in Table III. Thicker pavement sections may be required for roadways classified as major collectors. A final pavement design thickness evaluation will be determined when a pavement design exploration is completed (after subgrades are developed to ± 6 inches of design and wet utilities installed in the roadways). The projected traffic may vary from the traffic assumed from the roadway classification based on a site-specific traffic study. TABLE III – PRELIMINARY PAVEMENT SECTIONS Local Residential Roadways Minor Collectors Roadways EDLA – assume local residential roadways Reliability Resilient Modulus PSI Loss – (Initial 4.5, Terminal 2.0 and 2.5 respectively) 10 80% 3562 2.5 25 80% 3562 2.2 Design Structure Number 2.67 3.11 Composite Section without Fly Ash – Alternative A Hot Mix Asphalt (HMA) Grading S (75) PG 58-28 Aggregate Base Course ABC – CDOT Class 5 or 6 Design Structure Number 4ʺ 9ʺ (2.75) 5ʺ 9ʺ (3.19) Composite Section with Fly Ash – Alternative B Hot Mix Asphalt (HMA) Grading S (75) PG 58-28 Aggregate Base Course ABC – CDOT Class 5 or 6 Fly Ash Treated Subgrade Design Structure Number 4ʺ 6 ʺ 12″ (2.92) 4ʺ 7ʺ 12ʺ Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 13 Asphalt surfacing should consist of grading S-75 or SX-75 hot bituminous pavement with PG 64-22 or PG 58-28 binder in accordance with Larimer County requirements. Aggregate base should be consistent with CDOT requirements for Class 5 or Class 6 aggregate base. As previously mentioned, a final subgrade investigation and pavement design should be performed in general accordance with the Larimer County Pavement Design Criteria prior to placement of any pavement sections, to determine the required pavement section after design configurations, roadway utilities have been installed and roadway have been prepared to “rough” subgrade elevations have been completed. Underground Utility Systems All piping should be adequately bedded for proper load distribution. It is suggested that clean, graded gravel compacted to 70 percent of Relative Density ASTM D4253 be used as bedding. Where utilities are excavated below groundwater, temporary dewatering will be required during excavation, pipe placement and backfilling operations for proper construction. Utility trenches should be excavated on safe and stable slopes in accordance with OSHA regulations as further discussed herein. Backfill should consist of the on-site soils or approved imported materials. The pipe backfill should be compacted to a minimum of 95 percent of Standard Proctor Density ASTM D698. Other Considerations and Recommendations Although evidence of fills or underground facilities such as septic tanks, cesspools, basements, and utilities was not observed during the site reconnaissance, such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction. Excavations into the on-site soils will encounter a variety of conditions. Excavations into the essentially cohesive soils and bedrock can be expected to stand on relatively steep temporary slopes during construction; however, caving soils may also be encountered especially in close proximity to the groundwater table. Groundwater seepage should also be anticipated for utility excavations. Pumping from sumps may be utilized to control water within the excavations. Well points may be required for significant groundwater flow, or where excavations penetrate groundwater to a significant depth. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation Earth Engineering Consultants, LLC EEC Project No. 1192061 August 16, 2019 Page 14 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. 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 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. Site specific explorations will be necessary for the proposed site buildings. It is recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. It is further recommended that the geotechnical engineer be retained for testing and observations during earthwork and foundation construction phases to help determine that the design requirements are fulfilled. This report has been prepared for the exclusive use of Post Modern Development for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranty, express or implied, is made. In the event that any changes in the nature, design or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed, and the conclusions of this report modified or verified in writing by the geotechnical engineer. 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 2 1 1 2 Piezometer Location Diagram Rennat Property - Fort Collins, Colorado EEC Project Number: 1192061 August 2019 EARTH ENGINEERING CONSULTANTS, LLC -1 tru -: Approimate Locations o Preliminary orings Completed in Feb 2012 Legend P-1 tru P-6: Approimate Locations or 6 Groundater Piezometers 1 Site Potos Potos taen in approimate location, in direction o arro 1 2 1 2 2 1 2 Groundwater Contour Diagram Rennat Property - Fort Collins, Colorado EEC Project Number: 1192061 August 2019 EARTH ENGINEERING CONSULTANTS, LLC Legend P-1 tru P-6: Approimate Locations or 6 Groundwater Pieometers 29Ground Surace Eleation Groundwater 29Eleation Approimate Groundwater Contours Groundwater Directional Flow RENNAT PROPERTY FORT COLLINS, COLORADO EEC PROJECT NO. 1192061 AUGUST 2019 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 VEGETATION & TOPSOIL _ _ 1 LEAN CLAY with SAND (CL) _ _ brown 2 soft _ _ with organics 3 _ _ 4 _ _ CS 5 5 2500 19.5 97.9 37 23 73.6 < 500 psf None _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 5 31.9 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ CS 15 4 27.2 BOTTOM OF BORING DEPTH 15.0' _ _ 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION & TOPSOIL _ _ 1 LEAN CLAY with SAND (CL) _ _ brown 2 very stiff to soft _ _ with calcareous deposits CS 3 22 9000+ 8.6 104.7 _ _ 4 _ _ SS 5 12 9000+ 9.8 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ CS 10 13 3500 13.2 102.9 35 20 78.6 1700 psf 1.5% _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 3 28.3 _ _ 16 _ _ 17 _ _ 18 _ _ 19 brown / tan _ _ SS 20 3 25.4 _ _ BOTTOM OF BORING DEPTH 20.5' 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION & TOPSOIL _ _ 1 LEAN CLAY with SAND (CL) _ _ brown / tan 2 soft _ _ 3 _ _ 4 _ _ CS 5 5 1500 27.5 93.1 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SAND with SILT (SP - SM) SS 10 14 17.1 11.9 brown / rust _ _ medium dense to loose 11 with gravels _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 6 1000 21.8 _ _ BOTTOM OF BORING DEPTH 15.5' 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION & TOPSOIL _ _ 1 LEAN CLAY with SAND (CL) _ _ brown 2 medium stiff to soft _ _ 3 _ _ 4 _ _ CS 5 6 3500 22.2 98.3 41 26 68.2 < 500 psf None _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ SS 10 2 1500 22.3 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 7 1500 21.7 _ _ BOTTOM OF BORING DEPTH 15.5' 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION & TOPSOIL _ _ 1 SANDY LEAN CLAY (CL) _ _ brown 2 stiff to soft _ _ % @ 150 psf CS 3 14 9000+ 7.9 97.9 33 18 59.1 600 psf 3.5% _ _ 4 _ _ SS 5 6 7500 13.1 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ CS 10 1 2500 14.1 92.5 _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 3 1000 24.0 _ _ BOTTOM OF BORING DEPTH 15.5' 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL DATE: RIG TYPE: CME55 FOREMAN: DG AUGER TYPE: 4" CFA SPT HAMMER: AUTOMATIC SOIL DESCRIPTION D N QU MC DD -200 TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF VEGETATION & TOPSOIL _ _ 1 LEAN CLAY with SAND (CL) _ _ brown 2 very stiff to soft _ _ CS 3 20 9000+ 8.8 106.2 _ _ 4 _ _ SS 5 12 9000+ 16.1 _ _ 6 _ _ 7 _ _ 8 _ _ 9 _ _ CS 10 4 1000 21.8 102.7 < 500 psf None _ _ 11 _ _ 12 _ _ 13 _ _ 14 _ _ SS 15 1 500 24.3 _ _ BOTTOM OF BORING DEPTH 15.5' 16 _ _ 17 _ _ 18 _ _ 19 _ _ 20 _ _ 21 _ _ 22 _ _ 23 _ _ 24 _ _ 25 _ _ Earth Engineering Consultants, LLC A-LIMITS SWELL Project: Location: Project #: Date: Rennant Property Fort Collins, Colorado 1192061 August 2019 Beginning Moisture: 19.5% Dry Density: 103.8 pcf Ending Moisture: 21.1% Swell Pressure: < 500 psf % Swell @ 500: None Sample Location: Boring PZ-1, Sample 1, Depth 4' Liquid Limit: 37 Plasticity Index: 23 % Passing #200: 73.6% SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown Lean Clay with Sand (CL) -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: Rennant Property Fort Collins, Colorado 1192061 August 2019 Beginning Moisture: 13.2% Dry Density: 109.4 pcf Ending Moisture: 20.1% Swell Pressure: 1700 psf % Swell @ 500: 1.5% Sample Location: Boring PZ-2, Sample 3, Depth 9' Liquid Limit: 35 Plasticity Index: 20 % Passing #200: 78.6% SWELL / CONSOLIDATION TEST RESULTS Material Description: Brown Lean Clay with Sand (CL) -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: Brown Lean Clay with Sand (CL) Sample Location: Boring PZ-4, Sample 1, Depth 4' Liquid Limit: 41 Plasticity Index: 26 % Passing #200: 68.2% Beginning Moisture: 22.2% Dry Density: 103.5 pcf Ending Moisture: 22.1% Swell Pressure: < 500 psf % Swell @ 500: None Rennant Property Fort Collins, Colorado 1192061 August 2019 -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: Brown Sandy Lean Clay (CL) Sample Location: Boring PZ-5, Sample 1, Depth 2' Liquid Limit: 33 Plasticity Index: 18 % Passing #200: 59.1% Beginning Moisture: 7.9% Dry Density: 94.9 pcf Ending Moisture: 25.8% Swell Pressure: 600 psf % Swell @ 150: 3.5% Rennant Property Fort Collins, Colorado 1192061 August 2019 -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: Brown Lean Clay with Sand (CL) Sample Location: Boring PZ-6, Sample 3, Depth 9' Liquid Limit: - - Plasticity Index: - - % Passing #200: - - Beginning Moisture: 21.8% Dry Density: 107.6 pcf Ending Moisture: 21.2% Swell Pressure: < 500 psf % Swell @ 150: None Rennant Property Fort Collins, Colorado 1192061 August 2019 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 0.01 0.1 1 10 Percent Movement Load (TSF) Consolidatio Swell Water Added SURFACE ELEV N/A 24 HOUR 9.1' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 11.0' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-6 AUGUST 2019 SURFACE ELEV N/A 24 HOUR 12.7' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 12.5' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-5 AUGUST 2019 SURFACE ELEV N/A 24 HOUR 10.1' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 9.0' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-4 AUGUST 2019 SURFACE ELEV N/A 24 HOUR 6.1' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 5.0' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-3 AUGUST 2019 SURFACE ELEV N/A 24 HOUR 14.1' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 15.0' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-2 AUGUST 2019 SURFACE ELEV N/A 24 HOUR 6.3' FINISH DATE 8/7/2019 AFTER DRILLING N/A SHEET 1 OF 1 WATER DEPTH START DATE 8/7/2019 WHILE DRILLING 8.0' RENNANT PROPERTY FORT COLLINS, COLORADO PROJECT NO: 1192061 LOG OF BORING PZ-1 AUGUST 2019 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 (3.04) PCC (Non-reinforced) – placed on an approved subgrade 6″ 6½″