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Home My WebLink About20061807.tiff Date: January 31, 2005 Job Name: Subsurface Exploration, Additional Test Hole information, Preliminary Geotechnical Recommendations for Proposed 140 Acre Subdivision @ SEC of SH 66 and CR 7 in Meade, Colorado: Job Number: 04-0085 Mr. Jerry Eckelberger Eckelberger and Jackson 7120 E. Orchard Road, Suite 450 Englewood, CO 80111 Dear Mr. Eckelberger, GROUND Engineering has previously submitted a subsurface exploration program ,.-. providing preliminary geotechnical recommendations for the proposed 140-acre subdivision located at the SEC of SH 66 and CR 7 in Meade, Colorado. In this study, GROUND drills .10 test holes out of the 14 originally budgeted for the project. GROUND Engineering felt at that time that the ten test holes were adequate to represent the site and to complete the preliminary study. The decrease in test holes was then credited to our Client in the amount of$900 dollars off of the signed proposal(proposal no. 0411-1539). At the request of the civil engineer, representing Eckelberger and Jackson, the remaining 4 test holes were completed and are identified as test holes TH-11, 12, 13, •and 14 on the Boring Logs. This submittal includes a revised test hole location plan (Figure 1), a complete set of the boring logs (Figures 2-4), and a revised legend (Figure.5). As a result of the additional soil bores, additional lab testing was performed and is attached in the revised Table 1. Based on the additional four test holes excavated on the southern side of the site, it appears that the depths to bedrock and groundwater levels were similar to the initial borings drilled on the north side of the site from east and west. Based on this information, the recommendations outlined in the original preliminary geotechnical report shall remain valid. ENGINEERING CONSULTRNTS, INC. 41 Inverness Drive East, Englewood,CO 80112.5412 Phone(303)289-1989 Fax(303)289-1886 www.groundeng.com Office Locations: Englewood Commerce City • Loveland • Granby • Gypsum 2006-1807 r Please do not hesitate to contact this office if you have any questions concerning these reports. Sincerely, GROUND EN NSULTANTS, INC. ct6)• Joseph Zorac , NM. '-` • r r1 1 1 2 --- Dirt • • • • • Form Road • 3 4 •5 I I • • Pond • 8 6 • • • • Farmhouse • 11 Oil/Gas j • Production i *14 • • 10 • Concrete Ditch 12 *13 • • Foster -Dirt Reservoir Farm Road l J L. W:J.\5 i�\ - 4- r GROUND 1 ENGINEERING CON51ll,TRNT5 /-..,/-.., N LOCATION OF TEST HOLES JOB NO. 040085 DRAWN BY: WW � • Indicates test hole number 1----_ FIGURE: 1 APPROVED BY: JZ ^ and approximate location. (Not Io Scale) --- CADFILE NAME: 0085SITE.DWG 1 Test Hole r"•;_,-st Hole Test Hole �;± N-l� s�st ur,:,„ 1I I____ .••••••0 '''":: ------.."P'l 2 3 4 5 \-----.. 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'1=411 50/12 ....A10,.00 "110ell:...::::.... 20 50/7 GROUND ENGINEERING CONSULTRNT5 /"-- LOGS OF TEST HOLES JOB NO. 04-0085 DRAWN BY: WW _~ FIGURE: 2 APPROVED BY: �J2 CAUFIL E NAME: 00854OO01.0WG Test Hole ^Test Hole Test Hole Hole Test Hole J 6 7 8 9 10 i. '---- I//, Trr.• ,,, I//..,..-1 //I /// //// /// //// ... 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JZ CADFIIE NAME: 0085-LOG02DWG - i 0 Test Hole Test Hole Test Hole j-Nt Hole 1 11 12 13 14 r__ t/..////. ,,, e.-..Test /,/ //// 1/// 1//// /// //// ///% //// /// ,/// ///! //// . - /// //// //J, r:///, /// ///1 //// ?,//A //, //// //// t/// /// ,/// //// 1//// /// //// //// /,/, -^ /7/ /// ,/// //// /// ///j 18/12 //,/ /,/, /// ,/// //// F//// -_ /// //// /.H //// ,,, 17112 ,,,, ///, ,,,/ /// //// /,/, ////- 71;2 /„ ,,,, /,/, ///r /// /,// /:,n-. - /,/, rJ ,// „// /// 9/12 - /„/ /„ 7/// 7 //.- /,/, /,. ,,,/ //„ ,,, „/ ,/„ //// /,,. /,, ,,,, ,,,, /„ /,// ,,,, 7/, //// //// /// ///, ,// — ,,,, /// /// ,,, — ,,,, /„ ,/,/ ,/, /,/71 /// ,,, ,,, 50/6 //// ,// ,,,. /// w ,,,/ ,,, ' ///, ,,, ;ell. Q ,,,, .. - • ,,,, - ,/, _ . . .■ 5012 _ 50/8 I 15 50/5 •" 20 � GROUMD ENGINEERING CONSULTRNTS ,^..' LOGS OF TEST HOLES JOB NO. 04-0085 DRAWN BY: WW __ FIGURE + APPROVED 8Y: JZ `- " CADFILE NAME: 0085-LOG03.OWG LEGEND: iK i Topsoil was variable in thickness and ranged from approximately 8 to 12 inches in depth. The topsoil L-\ was generally consisted of sandy clay, and was brown and humid. r7%' Native clay was sandy, fine to medium grained, medium plastic, soft to very stiff, moist to wet, and tan to brown in color and occasionally calcareous. Weathered Sandstone/Claystone was generally interbedded and ranged from sandy clay to clay sand. These materials were fine to medium grained, low to medium plastic,weathered, moist to very moist, light brown to gray with occasional iron staining. 2 Interbedded Sandstone/Claystone bedrock was ranged from sandy claystone to clayey sandstone. These materials were fine to medium grained, low to high plastic, hard to very hard, moist,light brown to gray with occasional iron staining. Drive sample, 2-inch l.D. California liner sample 23/12 Drive sample blow count, indicates 23 blows of a 140-pound hammer falling 30 inches were required to drive the sampler 12 inches. 0 Depth to water level and number of days after drilling that measurement was taken. NOTES: 1) Test holes were drilled on 11-10-04 and 1-22-05 with 4-inch diameter continuous flight power augers. 2) Locations of the test holes were measured approximately by pacing from features shown on the site plan provided. 3) Elevations of the test holes were not measured and the logs of the test holes are drawn to depth. 4) The test hole locations and elevations should be considered accurate only to the degree implied by the method used. 5) The lines between materials shown on the test hole logs represent the approximate boundaries between material types and the transitions may be gradual. 6) Groundwater level readings shown on the logs were made at the time and under the conditions indicated. Fluctuations in the water level may occur with time. GROUND ENGINEERING CONSULTRNTS LEGEND AND NOTES JOB NO. 04-0085 DRAWN BY: ww FIGURE; 5 APPROVED 8Y: JZ CADFILE NAME: 0085LEG.0WG ) ) ) ffOUHD ENGINEERING CONSULTRNTS TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Sample Locatiot Natural Natural Percent Atterberg Limits I Percent Unconfined Water Test Moisture Dry Passing Liquid Plasticity Swell Compressive Soluble Hole Depth Content Density No. 200 Limit index (1000 psf Strength Sulfates Soil or No feet 9', Oct), Sleve % (% Surchar a (psf) (%) Bedrock Type 1 5 7.8 110.5 25 22 9 0 5 Sandstone Bedrock J 2 4 15 8 105 7 73 36 i 17 1.2 0.18 Sand Clay 3 8 17.3 104.2 62 35 16 0.01 Weathered Claystone 4 3 19.9 99.8 69 I 38 1 17 1 2 I Sandy Clay 7 6 5 I 19 98.5 I 72 36 16 V I I Sandy Clay , 7 I 4 18/ 101.5 69 I 35 15 I I I Sandy Clay ,J 8 3 18.2 103.5 70 38 19 I Sandy Clay _J I 9 .,. 4 1 16.4 1,. 104.5 1 71 I . 33 I 14 2.5 1 I Sandy Clay 10 15 I 8.5 112.3 I 38 r 25 I 12 I 0.6 Sandstone Bedrock ,_ r , 1 11 I 9 I 16 6 109.2 I 49 5 29 1 6 I I I Interbedded Sandstone/Claystone Bedrock , , I 13 1 4.5 19.9 I , 99 l..9 67 1 31 1 16 L, 1,500 0.06 Sandy Clay I 14 I 4 20.4 I 95.9 1 65 I 35 15 I 1 l Sandy Clay I > Job N.).04-0;SS n s-� Subsurface Exploration Program Preliminary Geotechnical Recommendations Proposed 140 Acre Subdivision SEC of SH 66 and CR 7 Meade, Colorado Prepared for: Longs Peak Investors, LLC 7120 E. Orchard Road, Suite 450 Englewood, CO 80111 Attention: Mr. Jerry Eckelberger Job Number: 04-0085 November 22, 2004 �. GROUND ENGINEERING CONSULTRNTS 41 Inverness Drive East, Englewood, CO 80112-5412 Phone(303)289-1989 Fax (303)289-1686 www.groundeng.com Office Locations: Englewood • Commerce City • Loveland • Granby • Glenwood Springs TABLE OF CONTENTS Page Conclusions 1 Purpose and Scope of Study 2 Proposed Construction 2 Site Conditions 3 Geologic Setting 3 Subsurface Exploration 3 Laboratory Testing 4 Subsurface Conditions 4 Water Soluble Sulfates 5 Geologic Hazards and Considerations 6 Preliminary Geotechnical Recommendations 9 General Observations 9 Anticipated Foundation Systems 10 Anticipated Floor Systems 11 Exterior Flatwork 11 Underdrain Systems 12 Site Grading 12 Utility Installations 15 Excavation Considerations 17 Preliminary Pavement Recommendations 18 Closure and Limitations 19 Location of Test Holes Figure 1 Logs of Test Holes Figures 2 -3 Legend and Notes Figure 4 Summary of Laboratory Test Results Table 1 References Appendix A r"' Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 CONCLUSIONS The subsurface conditions encountered in the test holes generally consisted of topsoil overlying varying depths of natural clay. Weathered bedrock was encountered below the natural clay in most of the test holes ranging in depth from approximately 5.5 feet to 8 feet below existing grades. Competent bedrock was encountered below the native clay and weathered bedrock at depths of approximately 4.5 feet to 14 feet below existing grades and extended to the test hole termination depths ranging from 15 to 20 feet in depth. Groundwater was encountered in several test holes from 10 to 19 feet below existing grades at the time of drilling. When measured after 3 days the groundwater was observed to range from approximately 4.5 to 16 feet below existing grades. Groundwater may fluctuate however, in response to the onsite irrigation canals, applied irrigation after construction is complete, water elevations of the adjacent lake southeast of the site, and surface drainage. Site grading plans were not available at the time of this report preparation, however we anticipate a significant amount of grading will occur on the subject development. Based on the preliminary studies and the laboratory test data, GROUND anticipates that majority of the proposed structures in this development may be supported on spread footings bearing on undisturbed native soils or on properly moisture conditioned and compacted onsite materials. Floor systems consisting of slab on grade construction will likely be feasible for the proposed structures. Localized areas of moderate swell potential were encountered in the overburden clays and underlying bedrock materials. Foundation movements resulting from expansive soils of this nature can be reduced by overexcavation and replacement in a properly moisture-density treated state. Depths of overexcavation will depend upon the actual subsurface conditions encountered at each structure. A design-level subsurface exploration should be performed on a lot-by-lot basis after site grading has been complete to evaluate proposed foundation system for each structure. In addition areas of soft saturated overburden clays were encountered on the eastern lower-lying portions of the site. These soils may be unstable and require some stabilization during construction. To help provide more stabilization site-grading plans should provide as much fill placement as possible in these lower-lying unstable areas. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 1 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 Additional recommendations with respect to geologic conditions, foundations, floor slabs, water-soluble sulfates, excavation conditions, utility installation, exterior flatwork, preliminary pavement sections and drainage are contained herein. PURPOSE AND SCOPE OF STUDY This report presents the results of a subsurface exploration program performed by GROUND Engineering Consultants, Inc. (GROUND), to provide preliminary geotechnical recommendations for the Proposed 140-Acre Subdivision located at the SEC of SH66 and CR7 in the Town of Meade, Colorado. Our study was conducted in general accordance with GROUND's Proposal No. 0411-1539, dated November 1, 2004. A field exploration program was conducted to obtain information on subsurface conditions. Material samples obtained during the subsurface exploration were tested in the laboratory to provide data on the classification and engineering characteristics of the on-site soils. The results of the field and laboratory explorations are presented herein. This report has been prepared to summarize the data obtained and to present our conclusions and preliminary recommendations based on the proposed construction and the subsurface conditions encountered. Design parameters and a discussion of engineering considerations related to construction of the proposed development are included herein. PROPOSED CONSTRUCTION We understand that the proposed development is to include a residential subdivision with local streets, flatwork, and utilities. The single-family housing may or may not have below grade levels at this time. The site layout is depicted on Figure 1. If the proposed construction differs significantly from that described above, GROUND should be notified to re-evaluate the recommendations contained herein. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 2 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 SITE CONDITIONS The site is generally undeveloped with the exception of a farm house/garage located on the west side of the property. The farmhouse and adjacent pond will not be considered as a portion of the proposed subdivision. The western portion of the site is significantly higher in elevation then the eastern half. A small creek was observed to north of the site and Foster Reservoir was observed to the southeast. Site drainage generally propagates to the southeast in the direction of Foster Reservoir. The site is also bordered by CR 7 to the west and by SH 66 to the north. The majority of the site appeared to be used for agricultural purposes in which corn stalks were observed in the eastern fields and the western fields were tilled at this time. Site vegetation also consisted of weeds, grasses, deciduous trees adjacent to SH 66 and the old farmhouse. GEOLOGIC SETTING The project site lies within the Denver Basin complex located along the eastern flank of the Front Range of the Rocky Mountains. The site is depicted on published maps (e.g., Tweto, 1979) as underlain by Pleistocene eolian (wind-blown) deposits. These materials consist primarily of fine sands and silts with subordinate volumes of clays. Weathering commonly has resulted in alteration of feldspars these deposits to clays. The surficial soils are mapped as underlain by interbedded strata of the upper member of the Cretaceous Pierre Shale formation. The upper member of the Pierre Shale consists largely of expansive claystones and clay shales. Beds and lenses of sandstone are encountered locally. SUBSURFACE EXPLORATION Subsurface exploration for the project was conducted in November 10, 2004. A total of ten (10) test holes were drilled with a truck-mounted, continuous flight, power auger rig to evaluate subsurface conditions, including depths to groundwater and bedrock, as well as to retrieve samples for laboratory testing and analysis. A GROUND engineer directed subsurface exploration, logged the test holes in the field, and prepared the samples for transport to our laboratory. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 3 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 Samples of the subsurface materials were retrieved with a 2-inch I.D. "California" -type liner sampler. The sampler was driven into the substrata with blows from a 140-pound hammer falling 30 inches. This procedure is similar to the Standard Penetration Test described by ASTM Method D1586. Penetration resistance values (blows per distance driven, typically 12 inches), when properly evaluated, indicate the relative density or consistency of soils and bedrock. Depths at which the samples were obtained and associated penetration resistance values are shown on the test hole logs. The approximate locations of the test holes are shown on Figure 1. Logs of the exploratory test holes are presented on Figures 2 and 3. Explanatory notes and a legend are provided on Figure 4. LABORATORY TESTING Samples retrieved from our test holes were examined and visually classified in the laboratory by the project engineer. Laboratory testing of soil samples obtained from the subject site included standard property tests, such as natural moisture contents, dry unit weights, grain size analyses and liquid and plastic limits. Swell-consolidation tests were performed on selected samples of the soils. Water-soluble sulfate contents were determined for selected samples, as well. Laboratory tests were performed in general accordance with applicable ASTM protocols. Data from the laboratory testing program are summarized in Table 1. SUBSURFACE CONDITIONS The subsurface conditions encountered in the test holes generally consisted of topsoil overlying varying depths of natural clay. Weathered bedrock was encountered below the natural clay in most of the test holes ranging in depth from approximately 5.5 feet to 8 feet below grades. Competent bedrock was encountered below the native clay and weathered bedrock at depths of approximately 4.5 feet to 14 feet below existing grades and extended to the test hole termination depths ranging from 15 to 20 feet in depth. Topsoil was variable in thickness and ranged from approximately 8 to 12 inches in depth. The topsoil was generally consisted of sandy clay, and was brown and humic. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 4 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 Natural Clay was sandy, fine to medium grained, medium plastic, soft to stiff, moist to wet, and tan to brown in color and occasionally calcareous. Weathered Sandstone/Claystone was generally interbedded and ranged from sandy clay to clay sand. These materials were fine to medium grained, low to medium plastic, weathered, moist to very moist, light brown to gray with occasional iron staining. Interbedded Sandstone/Claystone bedrock was ranged from sandy claystone to clayey sandstone. These materials were fine to medium grained, low to high plastic, hard to very hard, moist, light brown to gray with occasional iron staining. Groundwater was encountered in several test holes from 10 to 19 feet below existing grades at the time of drilling. When measured after 3 days the groundwater was observed to range from 4.5 to 16 feet below existing grades. Groundwater may fluctuate however, in response to the onsite irrigation canals, applied irrigation after construction is complete, water elevations of the adjacent lake southeast of the site, and surface drainage. Swell-Consolidation Testing indicated low to occasionally moderate potentials for heave in the native clay soils and bedrock. Measured swells ranged from negligible to approximately 2.5 percent upon saturation against a 1,000 -pound per square foot (psf) surcharge load. (See Table 1.) WATER-SOLUBLE SULFATES The concentrations of water-soluble sulfates measured in selected samples retrieved from the test holes ranged up to 0.18 percent by weight. (See Table 1.) Such concentrations of soluble sulfates represent a moderate environment for sulfate attack on concrete exposed to these materials. Degrees of attack are based on the scale of 'negligible,' 'moderate,' 'severe' and 'very severe' as described in the "Design and Control of Concrete Mixtures," published by the Portland Cement Association. Additional soil samples should be taken for sulfate testing across the project site to provide an adequate representation of the site soils for final design requirements. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 5 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 Based on the available data to date, GROUND recommends use of Type II, Type IP(MS), Type IS(MS), Type P(MS), Type l(PM)(MS), or Type l(SM)(MS) sulfate-resistant cement in all concrete exposed to site soils. (Cement Type II is specified by ASTM C150. The other types and blends are specified by ASTM C595.) All concrete used should have a maximum water/cement ratio of 0.50 by weight. All concrete used should have a minimum compressive strength of 3,750 psi. Concrete mixes should be relatively rich and should be air entrained. GEOLOGIC HAZARDS Expansive Soils As noted above, the shallow earth materials underlying the site included clays and interbedded sandstone/claystone bedrock. Swelling clayey soils and bedrock change volume in response to changes in moisture content, which can occur seasonally, or in response to changes in land use, including development. Expansion potentials vary with moisture contents, density and details of the clay chemistry and mineralogy. The swell potential in any particular area can vary markedly both laterally and vertically due to the complex interbedding of the site soil and bedrock materials. Moisture changes also occur erratically, resulting in conditions which cannot always be predicted. Swell-consolidation testing indicated low to moderate potentials for heave in the more plastic site soils. (See Table 1.) Although there is a certain amount of risk involved where structures are placed on these types of soils, with appropriate geotechnical design, properly implemented during construction, the proposed development is feasible with regard to expansive earth materials. It is important that the soil conditions be reviewed on an individual structure basis when the site building layout is known. Collapsible Soils Certain surficial deposits, typically eolian (wind-blown) materials including loess, are known to be susceptible to local hydro-consolidation or "collapse." Hydro-consolidation consists of a significant volume loss due to re-structuring of the constituent grains of the soil to a more compact arrangement upon wetting under a surcharge load. Site surficial soils are interpreted to be, at least in part, weathered eolian materials. Some samples, particularly near the Foster Reservoir exhibited macroscopic voids. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 6 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 Tested samples of that material exhibited a low potential for consolidation. Similarly to expansive soils, there is a risk associated with construction on soils vulnerable to consolidation. Therefore, geotechnical evaluations of individual building sites should include an assessment of the possible presence of collapsible materials in the foundation soils, so that appropriate, remedial design and construction can be implemented, where appropriate. Radon Testing for the possible presence of radon gas prior to project development does not yield useful results regarding the potential accumulation of radon in completed structures. Radon accumulations most typically are found in basements or other enclosed portions of buildings built in areas underlain at relatively shallow depths by granitic crystalline rock. The likelihood of encountering radon in concentrations exceeding applicable health standards on the subject site, underlain by relatively deep soils and sedimentary bedrock, is significantly lower. GROUND recommends that radon testing be performed in each building on-site, after construction completed. Proper ventilation usually is sufficient to mitigate potential �-. radon accumulations. Building designs should accommodate such ventilation for all building areas. Seismic Activity/Faulting: Neither site reconnaissance nor review of available geologic maps indicated the trace of an active or potentially active fault traversing or immediately adjacent to the site. Therefore, the likelihood of surface fault rupture at the site is considered to be low. The closest documented active fault to the site is the Rocky Mountain Arsenal Fault, which is located approximately 16 miles to the southeast (Kirkham and Rogers, 1981). This fault is approximately 15 miles in length, trends generally northwest/southeast and is considered to be a right-lateral, strike-slip fault. The most recent significant seismic movements associated with the fault occurred in the 1960's, generating earthquakes up to magnitude 5.5. Research performed by the U.S. Geological Survey concluded that a strong correlation existed between the seismic activity of this fault and pressure injection of liquid waste into a disposal well located at the nearby Rocky Mountain Arsenal. Pressure injection in the disposal well was discontinued in 1966 and only minor seismic activity along the fault has been recorded since. The risk of this fault giving rise to Job No. 04-0085 Ground Engineering Consultants,Inc. Page 7 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 damaging, earthquake-induced ground motions at the site is considered to be relatively low given the low previously recorded seismic magnitudes. The project area falls within Seismic Performance Category A based on AASHTO guidelines, and is considered to have a low probability for large, damaging earthquakes. Compared with other regions of Colorado, recorded earthquake frequency in the project area is low. Slope Stability and Erosion: The topography of the site was generally gently rolling with a slope on the order of 3 percent down to the east. Geologic maps providing coverage of the site that were reviewed for this study did not depict landslide deposits on or adjacent to the subject site. During our preliminary reconnaissance of site area, no evidence was noted of mass- wasting processes associated with steep slopes, such as landslides, slumps or unusual soil creep. Therefore, the likelihood of project developments being affected by large scale, unanticipated slope instabilities is considered low. Development adjacent to the steeper slopes in the southwestern portion of the site should be evaluated on a site r specific basis, however. Preliminarily, we recommend that un-retained, permanent slope cuts be less than 10 feet in height and maintain a maximum 3:1 (horizontal : vertical) slope angle or less with proper erosion control measures implemented. Proper surface drainage controls to reduce the potential for erosional slope damage need to be implemented in the grading design to control runoff, which may be increased due to proposed pavement surfaces, structures and landscape irrigation. Re-vegetation or other means of protection should be used on graded slopes. Flooding The subject property was bordered to the west and north by an unnamed, ephemeral tributary to the Saint Vrain River. Foster reservoir sits to the southeast of the site at a lower elevation than the site. Therefore, the site does not appear to be vulnerable to flooding, with the exception of possible local, surface saturation during episodes of heavy rainfall and associated temporary ponding of run-off in areas of relatively slow surface drainage. Job No. 04-0085 Ground Engineering Consultants, Inc. Page 8 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 Wetlands Potential Somewhat marshy conditions, cattails and other phreatophytes were noted generally along the edge of Foster Reservoir, south and east of the project site. No other indications of conditions similar to jurisdictional wetlands were apparent during GROUND's site reconnaissance. However, during site development all regulations concerning wetland protection, as well as any other areas designated as wetlands by the Federal Wetlands Protection Act should be adhered to. Explicit designation of wetlands was not included as part of the scope of this study. Mining Activity and Subsidence Review of U.S. Geological Survey topographic maps covering the site (e.g., U.S.G.S. 1949, revised 1979) and Jones, and others (1978) and other available, published maps depicting areas of coal extraction, did not indicate past mining activities on or adjacent to the subject parcel. No indications of mining activities were apparent on the site during the site reconnaissance. Therefore, there appears to be little potential for surface subsidence associated with consolidation of former mine workings at depth. Published geologic maps do not indicate formations underlying the site at shallow ,.� depths which include evaporite (salt, gypsum, etc.) deposits, limestones or other materials vulnerable to subsurface dissolution. Therefore, the likelihood of subsidence or other mining-related hazards appears to be low. Based on the published information reviewed for the site and the findings of this preliminary assessment, the site appears to be feasible for development with respect to potential geologic hazards and general geotechnical design concerns. PRELIMINARY GEOTECHNICAL RECOMMENDATIONS General Observations Based on the information obtained from the test holes and our understanding of the proposed development, the geotechnical recommendations below may be used for initial site development and for planning purposes. The primary finding of this preliminary geotechnical study is that the shallow earth materials are composed largely of sandy clay and interbedded sandstone and claystone bedrock. Occasionally, grading operations and building foundation design will need to account for expansive soils and ,.� areas of soft and wet soils associated with the onsite soil characteristics, but in general, Job No. 04-0085 Ground Engineering Consultants,Inc. Page 9 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 conventional shallow foundations appear appropriate. Site-specific studies, particularly after overlot grading, will be needed to develop appropriate geotechnical recommendations for individual buildings, reaches of roadway, etc. Groundwater appears to be a significant factor in the development of the eastern portion of the site. Site grading should be carefully planned to reflect the shallow groundwater conditions. Anticipated Foundation Systems As noted above, the soils encountered at the site generally exhibited low swell potentials with localized areas of moderate swell. Based on existing site topography, we anticipate that there will be a significant amount of site grading to occur on the subject development including the possibility of import fill materials. Based on the preliminary studies and the laboratory test data, GROUND anticipates that majority of the proposed structures in this development may be supported on spread footings bearing on undisturbed native soils or on properly moisture conditioned and compacted onsite materials. Localized areas exhibiting moderate swell potential or soft subgrade conditions will require overexcavation below the footing elevations and replacement with either site soils or import fill materials in a properly moisture-density treated state. The depth of overexcavation below the shallow foundation (spread footings) will vary depending upon the actual soil conditions after initial site grading. Soft-unstable footing subgrades may require additional attention such as stabilization with crushed rock to provide adequate bearing capacity. The bearing capacity for the spread footing systems placed on undisturbed stiff natural clays, bedrock, or moisture density treated onsite or import fill materials will range from an allowable bearing pressure of 1,500 psf to 2,500 psf depending upon the actual subgrade conditions at each structure. As an alternative to overexcavation and replacement, post-tensioned slab foundations placed on site soils or a fill section of limited thickness may be suitable for some buildings. Groundwater will likely be a significant factor for the proposed construction. Installation of perimeter underdrains for each structure may be required and/or the installation of a site-wide underdrain system. Perimeter underdrains established for individual structures may be more beneficial due to the cohesive nature and low permeability of the site soils. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 10 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 ,^ Site specific recommendations will be provided in a final subsurface exploration after site grading has been complete to evaluate proposed foundation systems for each structure. Anticipated Floor Systems The overburden shallow clay materials generally exhibited low swell potentials with localized areas of moderate swell. Floor slabs present a very difficult problem where swelling materials are present near floor slab elevation because sufficient dead load cannot be imposed on them to resist the uplift pressure generated when the materials are wetted and expand. Depending on final site grading and the actual subsurface conditions encountered at each structure, we anticipate that slab-on-grade construction structures will generally be feasible. Where swell potentials are in the moderate range, we anticipate that slab-on- grade construction may be used if measures to reduce slab movement are utilized. A common and widely used alternate approach involves the removal of the underslab soils and replacement with properly moisture-density treated on-site materials and/or import structural backfill. This method of overexcavation and replacement has been used with varying degrees of success. The potential for slab movement will not be eliminated, but may tend to make movement more uniform and can reduce damage if movement does occur. Based on the preliminary data, the depth of excavation could range from a minimum of 1 to 3 feet, depending on site-specific conditions, site grading, floor slab movement tolerances, and finish floor elevations. EXTERIOR FLATWORK Exterior slab-on-grade construction including sidewalks, driveway, and patio present a difficult problem where swelling materials are present near slab elevation because sufficient dead load cannot be imposed on them to resist the uplift pressure generated when the materials are wetted and expands. At the current time, there is no economically feasible method to control movement of these slab-on-grade construction elements. Where moderate swell potentials are encountered, the Owner should take into consideration an overexcavation alternative as presented above for the floor slab section. The additional handling of these materials including the excavation and moisture-density conditioning typically results in higher initial costs. These costs may be Job No. 04-0085 Ground Engineering Consultants, Inc. Page 11 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 partially recaptured due to potential reduced future maintenance. Even so, the Owner should be aware that rigid hardscaping construction supported by localized on-site swelling materials may experience heave and cracking resulting in the potential for damage during the life of the structures. UNDERDRAIN SYSTEM Shallow groundwater was encountered in the test holes and varied from about 4.5 to 16 feet below existing grades across the site. Site grading plans were not available at the time of this report preparation, however based on shallow groundwater conditions located on the eastern portion of the site each structure may require the installation of an underdrain system. In addition it has been our experience that local, perched water conditions can develop at the interface between fill soils and the native-cohesive soils after development is complete and landscape irrigation starts. Typical underdrain systems should consist of perforated PVC drain pipe at least 4 inches in diameter, free-draining gravel, and filter fabric. The free-draining gravel should contain less than 5 percent passing the No. 200 Sieve and more than 50 percent retained on the No. 4 Sieve, and have a maximum particle size of 2 inches. Each drain pipe should be surrounded with 6 or more inches of free-draining gravel. The gravel surrounding the drain pipe and/or the pipe itself should be wrapped with filter fabric to reduce the migration of fines into the drain system. The placement location of the underdrains should be a function of the foundation type and should be based on the actual subsurface profile after site grading is complete. SITE GRADING Site grading plans were not available at the time of this report preparation, however we anticipate a significant amount of grading will occur on the subject. Grading operations performed in the lower-lying areas will likely encounter areas of subgrade instability associate with the existing soft-saturated clay materials. Groundwater was encountered as shallow as 4.5 feet in test hole TH-6 and groundwater elevations will likely remain shallow at lower-lying elevations and at locations adjacent to Foster Reservoir. To help provide more stabilization site grading plans should provide as much fill placement as possible in these lower-lying unstable areas. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 12 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 Site grading should be planned carefully to provide positive surface drainage away from the buildings, and all pavements, utility alignments, and flatwork. In proposed parking areas we suggest that surface diversion features be implemented to prevent surface runoff from flowing across the paved surfaces. Site soils free of deleterious materials are, in general, suitable for placement as compacted fill. Cobbles or rock fragments coarser than 6 inches in maximum dimension should not be incorporated into project fills. Care should be taken, however, with regard to achieving and maintaining proper moisture contents during placement and compaction. We anticipate that some on-site soils may exhibit significant pumping, rutting, and deflection at moisture contents near optimum and above. Potential earthwork contractors should be made aware that significant processing and reprocessing of the on-site materials will likely be required. The placement of on-site fill materials should be monitored on a full-time basis by a representative of the Geotechnical Engineer. Prior to earthwork construction, existing structures, vegetation, topsoil and other deleterious materials should be removed and disposed of off-site. Relic underground utilities should be abandoned in accordance with applicable regulations, removed as necessary, and capped at the margins of the property. Topsoils should not be incorporated into common fill placed on the site. Instead, topsoils should be stockpiled during initial grading operations for placement in areas to be landscaped or for other approved uses. Grading Swell/Shrinkage Factors: In review of our laboratory data, the onsite soils will change in volume during the construction process from undisturbed native material to moisture-density treated fill. Based on compaction efforts ranging from 95 to 100 percent (assume 97 % average) of the maximum standard proctor density, we believe that an average change in dry density will be minimal. We estimate that the total site grading will result in a net shrink of 0 to 10 percent based on available data. Import materials used as common fill should be free of topsoils, organic material, claystone and other deleterious materials. Imported material should have less than 75 percent passing the No. 200 Sieve and should have a liquid limit less than 40 and a Job No. 04-0085 Ground Engineering Consultants,Inc. Page 13 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 PeN plasticity index of less than 20. In addition, the import fill should be relatively non- expansive when placed as properly moisture conditioned and compacted fill. These soils should exhibit a swell potential of less than 1.0 percent when remolded at optimum moisture content at approximately 95 percent of the maximum dry density in general accordance with ASTM D698. Select, granular materials imported for use as structural fill should meet the criteria for CDOT Class 1 Structure Backfill as tabulated below. All imported soils should be tested and approved by the Geotechnical Engineer prior to transport to the site. CDOT CLASS 1 STRUCTURE BACKFILL Sieve Size or Acceptable Range Parameter 2-inch 100% passing No.4 30%to 100%passing No. 50 10%to 60% passing No.200 5%to 20%passing Liquid Limit <35 Plasticity Index < 6 Base of Fill: the top 12 inches of in-place materials on which fill soils will be placed should be scarified, moisture conditioned and properly compacted to provide a uniform base for fill placement. Site soils that generally classify as CL, CH, ML or MH (cohesive soils) and should be compacted to 95 percent of the maximum standard Proctor density at moisture contents from 1 percent below to 3 percent above the optimum as determined by ASTM D698. Where site soils classify as SM or SC in accordance with the USCS classification system (granular materials), these materials should be compacted to 98 or more percent of the maximum standard Proctor dry density at moisture contents within 2 percent of optimum moisture content as determined by ASTM D698. If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material, additional material should be excavated, or other measures taken, to establish a firm platform for filling. Overlot and Embankment Fill: Fill materials should be thoroughly mixed to achieve a uniform moisture content, placed in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted to the recommendations stated above for base of fill. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 14 r Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 However, in areas where fill depths will be greater than 12 feet, onsite material which will be more than 12 feet below final grades should be compacted to higher relative compactions in order to reduce subsequent settlements: CL, CH, ML and MH soils should be compacted to at least 98 percent of the maximum standard Proctor density at moisture contents from 2 percent below to 2 percent above the optimum as determined by ASTM D698; SM or SC soils should be compacted to 100 or more percent of the maximum standard Proctor dry density at moisture contents within 2 percent of optimum moisture content as determined by ASTM D698. No fill materials should be placed, worked, rolled while they are frozen, thawing, or during poor/inclement weather conditions. The materials testing firm should provide a written declaration stating that the project site, including all building pad areas, was filled with acceptable materials and was placed in accordance with the specifications outlined in this report. The Geotechnical Engineer should observe the exposed excavation surface prior to placement of fill, and observe earthwork operations and test the soils. Permanent site slopes supported by on-site soils up to 10 feet in height should be constructed no steeper than 3:1 (horizontal : vertical). Minor raveling or surficial sloughing should be anticipated on slopes cut at this angle until vegetation is well re- established. Surface drainage should be designed to direct water away from slope faces. UTILITY INSTALLATION Recommendations regarding utility trench excavation are provided in the Excavation Considerations section of this report. On-site soils excavated from trenches are suitable, in general, for use as trench backfill. Backfill soils should be free of vegetation, debris and other deleterious materials. Cobbles coarser than 6 inches in maximum dimension should not be incorporated into trench backfills. Trench backfill materials should be conditioned to a uniform moisture content, placed in uniform lifts not exceeding 6 inches in loose thickness, and properly compacted. Onsite backfill materials should placed in general accordance with the recommendations outlined in the site grading section of this report. Bedding should be brought up uniformly on both sides of the pipe to reduce differential loadings. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 15 �-, Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 The Contractor should take adequate measures to achieve proper compaction in the utility trench backfills, particularly in the lower portions of the excavations. Some settlement of trench backfill materials should be anticipated, even where materials are placed and compacted correctly. The Contractor should take particular care to achieve and maintain adequate compaction of the backfill soils around manholes, valve risers and other vertical pipeline elements where greater settlements commonly are observed. Use of "flowable fill," i.e., a lean, sand-cement slurry, or a similar material should be considered in lieu of compacted soil backfill for areas with low tolerances for surface settlements. Placement of flowable fill in the lower portions of the excavations and around risers, etc., likely will yield a superior backfill, although at an increased cost. Pipe bedding materials, placement and compaction should meet the specifications of the pipe manufacturer and applicable municipal standards. The Contractor should not anticipate that significant quantities of materials excavated on-site will be suitable for use where relatively free-draining bedding materials are called for. Imported materials should be tested and approved by the Geotechnical Engineer prior to transport to the site. We assume that surface drainage will direct water away from utility trench alignments. Where topography, site constraints or other factors limit or preclude adequate surface drainage, the granular bedding materials should be surrounded by non-woven filter fabric (e.g., Mirafi® 140N or the equivalent) to reduce migration of fines into the bedding which can result in severe, local settlements. Development of site grading plans should consider the subsurface transfer of water in utility trenches and the pipe bedding. Sandy pipe bedding materials can function as efficient conduits for re-distribution of natural and applied waters in the subsurface. Cut- off walls in utility trenches or other water-stopping measures should be implemented to reduce the rates and volumes of water transmitted along utility alignments and toward buildings, pavements and other structures where excessive wetting of the underlying soils will be damaging. Incorporation of water cut-offs and/or outlet mechanisms for saturated bedding materials into development plans could be beneficial to the project. These measures also will reduce the risk of loss of fine-grained backfill soils into the bedding material with resultant surface settlement. Job No. 04-0085 Ground Engineering Consultants, Inc. Page 16 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC ofSH66 and CR7 EXCAVATION CONSIDERATIONS Test holes for subsurface exploration were advanced to the depths indicated on the test hole logs by means of truck-mounted, flight auger equipment. Hard to very hard claystone and sandstone bedrock was encountered at depth across the site, however we anticipate no unusual excavation difficulties for the proposed construction in these materials with conventional, medium- to heavy-duty excavating equipment in good working condition. Groundwater was encountered in several test holes from 4.5 to 16 feet below existing grades. Based on existing grades, groundwater will be a significant factor in excavations on the eastern portion of the site where groundwater elevations are relatively shallow. We recommend that temporary, un-shored excavation slopes up to 12 feet in height be cut no steeper than 1.5:1 (horizontal : vertical) in the cohesive native and fill soils in the absence of seepage and no steeper than 2 (horizontal) : 1 (vertical) in areas where seepage is encountered. Some surficial sloughing may occur on slope faces cut at this re" angle. Local conditions encountered during construction, such as loose, dry sand, or soft or wet materials, or seepage will require flatter slopes. Stockpiling of materials should not be permitted closer to the tops of temporary slopes than 5 feet or a distance equal to the depth of the excavation, which ever is greater. Deeper excavations such as sewer trenches will likely encounter groundwater. A properly designed and installed de-watering system may be required during the construction in these sections of trench. The risk of slope instability will be significantly increased in areas of seepage along the excavation slopes and may require flatter slopes and the addition of temporary shoring. Where seepage is encountered during construction, such excavations should be observed by the Geotechnical Engineer to verify actual conditions and provide additional recommendations if appropriate. Should site constraints prohibit the use of the recommended slope angles, then temporary shoring should be used. Actual shoring system(s) should be designed for the Contractor by a registered engineer. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 17 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 Good surface drainage should be provided around temporary excavation slopes to direct surface runoff away from the slope faces. A properly designed drainage swale should be provided at the top of the excavations. In no case should water be allowed to pond at the site. Slopes should also be protected against erosion. Erosion along the slopes will result in sloughing and could lead to a slope failure. Excavations in which personnel will be working must comply with all OSHA Standards and Regulations particularly CFR 29 Part 1926, OSHA Standards-Excavations, adopted March 5, 1990. PRELIMINARY PAVEMENT RECOMMENDATIONS A pavement section is a layered system designed to distribute concentrated traffic loads to the subgrade. Performance of the pavement structure is directly related to the physical properties of the subgrade soils and traffic loadings. Pavement design of public streets should be in accordance with the applicable municipal requirements and procedures at the time of design and construction. Private pavements should meet the requirements of the individual owners/users. Subgrade Materials The majority of site soils are A-6 and A-7-6 soils, based on the AASHTO classification system which are anticipated to provide relatively poor pavement support. Preliminary Pavement Section Based on the classification of the onsite soil, assumed traffic ESAL values for the local roadways, and our experience the following pavement sections were provided. This pavement section is very preliminary and should not be used in any final project plans as the pavement section. Based on the preliminary pavement calculations, GROUND anticipates that a flexible pavement section ranging from 4 to 5 inches asphalt overlying 6 to 10 inches of aggregate base course could be used. As an alternate, a full depth section on the order of 6 to 7 inches will likely be required. The pavement section subgrades may require overexcavation and replacement in a properly moisture-density treated state, depending on the proposed site. Based on current data and areas of soft-unstable subgrade located on the eastern portion of the site moisture density treatment on the order of 1 to 3 feet may be required. In areas Job No. 04-0085 Ground Engineering Consultants,Inc. Page 18 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 / , which are not easily stabilized by moisture density treatment chemical stabilization of the subgrade materials may be required. Chemical stabilization could consist of lime treatment or fly-ash depending upon actual subgrade conditions. The collection and diversion of surface drainage away from paved areas is extremely important to satisfactory performance of the pavement. The surface drainage system should be carefully designed to ensure removal of all water from paved areas. The long-term performance of the pavement will be greatly influence by the proper backfill and compaction behind curb, gutter, and sidewalk. Routine maintenance programs should be scheduled to seal cracks, repair distressed areas, and perform thin overlays to achieve proper pavement life. CLOSURE Geotechnical Review The poor performance of many pavements, foundations and subsurface structures has been directly attributed to inadequate geotechnical review and earthwork quality control. Therefore, project plans and specifications should be reviewed by the Geotechnical Engineer to evaluate whether they comply with the intent of the recommendations in this report. This review should be reported in writing. Project earthwork construction operations should be observed by the Geotechnical Engineer. All excavations should be observed by the Geotechnical Engineer prior to placement of fill or backfill soils, installation of shoring, or foundation construction. Placement of fill/backfill soils should be observed by the Geotechnical Engineer, and the soils tested. The geotechnical recommendations presented in this report are highly contingent upon observation and testing of project earthworks by representatives of GROUND. If another geotechnical consultant is selected to provide construction observation and quality control, then that consultant must assume all responsibility for the geotechnical aspects of the project by concurring in writing with the recommendations in this report, or by providing alternative recommendations. Limitations This report has been prepared for Longs Peak Investors, LLC as it pertains to design of the development as described herein. It may not contain sufficient information for other parties or other purposes. The geotechnical recommendations in t Job No. 04-0085 Ground Engineering Consultants, Inc. Page 19 Preliminary Geotechnical Report Proposed 140-Acre Subdivision SEC of SH 66 and CR 7 this report are preliminary. Additional subsurface exploration testing and analysis are necessary to develop geotechnical recommendations to support foundation, slab, wall, and pavement designs. In addition, GROUND has assumed that project construction will commence by Fall, 2005. Changes in project plans or schedule should be brought to the attention of the Geotechnical Engineer, in order that the geotechnical recommendations may be re-evaluated and, as necessary, modified. The geotechnical conclusions and recommendations in this report relied upon subsurface exploration at a limited number of exploration points, as shown on Figure 1. Subsurface conditions were interpolated between and extrapolated beyond these locations. Findings were dependent on the limited amount of direct evidence obtained at the time of this geotechnical evaluation. Our recommendations were developed for site conditions as described above. Actual conditions exposed during construction may be anticipated to differ, somewhat, from those encountered during site exploration. If during construction, surface, soil, bedrock, or groundwater conditions appear to be at variance with those described herein, the Geotechnical Engineer should be advised at once, so that re-evaluation of the recommendations may be made in a timely manner. This report was prepared in accordance with generally accepted soil and foundation engineering practice in the Weld County Area, at the date of preparation. GROUND makes no other warranties, either express or implied, as to the professional data, opinions or recommendations contained herein. Sincerely, Ground Engineering Consultants, Inc. " warnrwnnrnn ii -o• :�_ Joseph Zorack, P.E. Reviewed by Brian Reck, C.E.G. Job No. 04-0085 Ground Engineering Consultants,Inc. Page 20 te""3/4, el\ 1 2 Dirt • • • • Farm Road • 3 •4 5 Pond 9 7 6 • 8 • • • Farmhouse Oil/Gas Production 10 • Concrete\ Ditch Foster -- Dirt - Reservoir Farm Road GROUND ENGINEERING CONSULTRNTS LOCATION OF TEST HOLES 1 JOB NO. 04-0085 DRAWN BY: WW a Indicates test hole number FIGURE: 1 APPROVED BY: JZ and approximate location. (Not to Scale) CADFILE NAME: 0085SITE.DWG Test Holerest Hole Test Hole .st Hole Test Hole 1 2 3 4 5 0 ,/„ /,,, ,,,, ,,,, ',,,, F,,, /,,, ,,,, ,,,, „/, /,,, ,,,, ,,,, //// ///, - ///, //// ,//, ,,,, •',/// ,/, /,/, /,,, ,/„ mg.- .... ,,,, ,„/ ,„/ „/, ,//, ,,,, ,,,, //„ ,//, ,,,, ,,,, ,,,, ,,,, /// ,/„ ,,,/ //„ //..,. ... ,//0 5/12 ,,,, ,,,, ,,,, ',,,, mi in, ......,/, ...,/, /..... 6112 ,,,1 ,,,, ,,,, ,,,, .,,,, ,,,, //„ /„/ /,,, ,,,, /,,, ,,,, ,,,/ 11/12 /„/ ,,,, ,//, „ ,/„ ,/ // / , ///, /,,, ///, ///, //// 50/9 /„/ ,//, ,,,, _ ,//, /,,, 3 ,/„ „/, ,/„ //,/ ,,,, „/, ,/„ //„ ,,, ,/,/ .iii"/"ti.I.V... //// / //// /,,, ,,,,/„ /,// //// //// /„/ ot 17/12 l.. /w0:........ //// el 22/12 10 50/12 iiii 0 • 35/12 I & 50/10 15 .#! ••• t it4. son — • Y 0 50/12• • 20 son GROUND ENGINEERING CONSULTANTS ek LOGS OF TEST HOLES JOB NO. 04-0085 DRAWN BY: WW FIGURE: 2 APPROVED BY: JZ CADFILE NAME: 0085-LOG0I.DWG Test Hole Test Hole Test Hole ' st Hole Test Hole 6 7 8 9 10- nn 0 \ \---, � \----. /,// ../. ,,,, ./.. ./.l .... //// //// ///l //// ///l - //// //// ///l //// //// //// //// //// //// //// //// //// //// //// //// //// //// //// //// '//// //// //// //// .///, //// //// //// /// //// //// /,// 8/12 iii/ /nn /// ,,,/ „// /// ///, „/l //„ //// //// „n /„/ //./ //// //// //./ //// //// //// //// - //// //, 7/12 7/12 //// //./ 13/12 '//// 3 ,/////.///,/////// //// //// ./// /..l ...1 - /„/ //// ,/// //// ,/// - ,/// //// //// ,//l //// 5 ////a 5/12 ,/„ //l///... // //// //// //// ///l ///l //// ///l //// ///l //// //// ././ //// ///l //// //// //// /,// ./,/, ,,,/ - /,/, //// ///, ,,,/ ,,,1 //// ,,,, ,,,, .,,// /../ ,,,, ,,,l nn ,/„ / / „/, // ,,,/ nn ,,,, ......, „„ .._ , ,,,,, w - = t 10 / 25/12 9 o _ # 50/6 0 0 ..-: . 15 35/12 _ 50/9 - 50/8 20 ...:. . 50/7 GROUND ENGINEERING CONSULTANTS LOGS OF TEST HOLES JOB NO. 04-0085 DRAWN BY: WW FIGURE: 3 APPROVED BY: JZ CADFILE NAME: 0085-LOG02.DWG t "--.., LEGEND: Topsoil was variable in thickness and ranged from approximately 8 to 12 inches in depth. The topsoil was generally consisted of sandy clay, and was brown and humic. :n Native clay was sandy, fine to medium grained, medium plastic, soft to stiff, moist to wet, and tan to "' brown in color and occasionally calcareous. ® Weathered Sandstone/Claystone was generally interbedded and ranged from sandy clay to clay sand. These materials were fine to medium grained, low to medium plastic,weathered, moist to very moist, light brown to gray with occasional iron staining. 2 Interbedded Sandstone/Claystone bedrock was ranged from sandy claystone to clayey sandstone. These materials were fine to medium grained, low to high plastic, hard to very hard, moist, light brown to gray with occasional iron staining. lDrive sample, 2-inch I.D. California liner sample 23/12 Drive sample blow count, indicates 23 blows of a 140-pound hammer falling 30 inches were required to drive the sampler 12 inches. 0 Depth to water level and number of days after drilling that measurement was taken. NOTES: 1) Test holes were drilled on 11-10-04 with 4-inch diameter continuous flight power augers. 2) Locations of the test holes were measured approximately by pacing from features shown on the site plan provided. 3) Elevations of the test holes were not measured and the logs of the test holes are drawn to depth. 4) The test hole locations and elevations should be considered accurate only to the degree implied by the method used. 5) The lines between materials shown on the test hole logs represent the approximate boundaries between material types and the transitions may be gradual. 6) Groundwater level readings shown on the logs were made at the time and under the conditions indicated. Fluctuations in the water level may occur with time. GROUND ENGINEERING CONSULTANTS LEGEND AND NOTES JOB NO. 04-0085 DRAWN BY: ww FIGURE: 4 APPROVED BY: JZ CADFILE NAME: 0085LEG.DWG ) ) GROUND ENGINEERING CONSULTRNTS TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Sample Location Natural Natural Percent Atterber9 Limits Percent Water Test Moisture Dry Passing Liquid Plasticity Swell/Consol. Soluble Hole Depth Content Density No. 200 Limit index (1000 psf Sulfates Soil or No. (feet) (%) (pcf) Sieve (%) (%) Surcharge) (%) Bedrock Type 1 5 110.5 7.8 25 22 9 0.5 Sandstone Bedrock 2 4 105.7 15.8 73 36 17 1 1.2 0.18 Sandy Clay 3 8 L104.2 17.3 62 35 16 + 0.01 Weathered Claystone 4 3 99.8 19.9 I 69 38 17 -1.2 Sandy Clay 6 5 98.5 19.7 72 36 16 1 Sandy Clay 7 4 101.5 18.7 69 35 15 Sandy Clay 8 3 103.5 18.2 70 38 19 I Sandy Clay 9 4 104.5 16.4 71 33 14 _ 2.5 I Sandy Clay 1 10 15 112.3 8.5 38 25 12 0.6 Sandstone/Claystone Job No.04-0085 APPENDIX A REFERENCES r r REFERENCES: Jones, D.C., J.E. Schultz and D.K. Murray, 1978, Coal Resources and Development Map of Colorado, Colorado Geological Survey, Map Series 9. Kirkham, R.M., and W. P. Rogers, 1981, Earthquake Potential in Colorado, A Preliminary Evaluation, Colorado Geological Survey, Bulletin 43. Tweto, O., 1979, Geologic Map of Colorado, U.S. Geological Survey. U.S. Geological Survey, 1960 (revised 1984) 7.5 Minute Series (Topographic), Gowanda Quadrangle, Colorado. Hello