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HomeMy WebLinkAboutHORSETOOTH EAST BUSINESS PARK MINOR SUB - Filed SER-SUBSURFACE EXPLORATION REPORT -1 1 1 SUBSURFACE EXPLORATION REPORT PROPOSED CHRIS WELLS DEVELOPMENT FORT COLLINS, COLORADO EEC PROJECT 1942050 1 1 I 1 1 1 1 1 1 1 July 25, 1994 W.W. Reynolds EARTH ENGINEERING 4875 Pearl East Circle, #300 CONSULTANTS, INC. Boulder, Colorado 80301 Attn: Mr. Jerry Lee RE: Subsurface Exploration Report Proposed Chris Wells Development Timberline Road and Bighorn Drive Fort Collins, Colorado EEC Project No. 1942050 Mr. Lee: Enclosed, herewith, are the results of the subsurface exploration you requested for your proposed development south of Bighorn Drive and west of Timberline Road in Fort Collins. In summary, the subsurface soils at the site consist of stiff to soft cohesive soils, underlain by t medium dense granular materials. The overburden soils are underlain by weathered claystone bedrock. Groundwater was encountered at a depth of approximately 7 to 9 feet at the time of our exploration. Based on the subsurface materials encountered, it is our opinion light foundation loads could be supported using conventional footings. Drilled piers, driven piles or other deep foundation types should be considered for more heavily loaded foundations. Near surface floor slabs and pavements could be supported directly on the site soils. Geotechnical recommendations concerning design and construction of the foundations and support of floor slabs and pavements are presented in the text of the attached report. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we can be of further service to you in any other way, please do not hesitate to contact us. Very truly yours, Earth Engineering Consultants, Inc. wxumuu p Wks 4144 woo Lester itton, P.E. Curtiss L. Palin, P.E. Principal Engineer Principal cc: W.W. Reynolds - Fort Collins, Libby Glass Cityscape, Eldon Ward Vaught-Frye Arch., Frank Vaught 2600 Canton Ct, Suite A Fort Collins, CO 80525 303) 224-1522 FAX 224-4564 1 1 SUBSURFACE EXPLORATION REPORT PROPOSED CHRIS WELLS DEVELOPMENT FORT COLLINS, COLORADO EEC PROJECT NO. 1942050 1 INTRODUCTION h proposedChrisWells Development located south of BighornThesubsurfaceexplorationforteesg Drive and west of Timberline Road in Fort Collins, Colorado, has been completed. Eight (8) soil borings extending to depths ranging from approximately 5 to 20 feet below present site grades were advanced to develop information on existing subsurface conditions in the development area. Individual boring logs and a diagram indicating the approximate boring locations are included with this report. We understand the proposed Chris Wells Development will include an approximate 7,000 sq feet office building and an approximate 24,000 to 30,000 sq feet flex space unit. The approximate plan locations of those structures are indicated on the attached boring location diagram. The proposed office building will be a single story wood frame structure which will contain a full basement. The flex space unit will be a single-story, slab-on-grade structure, probably of steel frame construction. Foundation loads for the office building will be light with continuous wall loads less than 3 kips per lineal foot and column loads less than 50 kips. Higher foundation loads will be transmitted by the flex space building. Floor loads for both structure will be light, less than 100 psf. Paved drive and parking areas will be constructed in the vicinity of both buildings. Three to four feet of fill will be required in the office area to develop the final site grades. Small grade changes, involving cuts and fills less than 2 feet, are expected in the flex space area. The of this report is to describe the subsurface conditions encountered in the borings,purpose P g , analyze and evaluate the test data and provide geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements. 1 1 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 2 EXPLORATION AND TESTING PROCEDURES The boring locations were selected in the field by Earth Engineering Consultants, Inc. (EEC) personnel. Those field locations were established by pacing and estimating angles from the references indicated on the attached boring location diagram. The boring locations should be considered accurate only to the degree implied by the methods used to make the field measurements. The borings were performed using a truck mounted, rotary-type drill rig equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 4-inch nominal diameter continuous flight augers and samples of the subsurface materials encountered were obtained using thin-walled tube and split barrel sampling procedures in general accordance with ASTM Specifications D-1587 and D-1586, respectively. In the thin-walled tube sampling procedure, a seamless steel tube with a sharpened cutting edge is push into the ground with hydraulic pressure to obtain a relatively undisturbed sample of cohesive or moderately cohesive material. In the split barrel sampling procedure, a standard 2-inch O.D. split barrel spoon is driven into the ground by means of a 140 pound hammer falling a distance of 30 inches. The number of blows required to advance the split barrel sampler 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 materials. Additional bulk samples were obtained from the auger cuttings. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. Moisture content, and where appropriate, dry density and unconfined compressive strength tests were performed on representative portions of the discreet samples. In addition, Atterberg limits, washed sieve analysis, and swell/consolidation tests were performed on selected samples to evaluate the soil's tend to change volume with variation in moisture content. Hveem stabilometer R-value tests were also performed on a representative portion of one of the near surface bulk samples to provide subgrade strength information required for pavement design. Results of the outlined tests are indicated on the attached boring logs. 1 1 i Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 3 As a part of the testing program, all samples were examined in the laboratory by an engineer and classified in accordance with the attached General Notes and the Unified Soil Classification System, based on the soils 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. SITE AND SUBSURFACE CONDITIONS The proposed development site is located south of Bighorn Drive and west of Timberline Road in Fort Collins, Colorado. Site drainage is generally to the south with maximum difference in ground surface elevations across the site on the order of 5 feet. The site is presently vegetated and evidence of prior building construction was not observed at the site by EEC field personnel. An EEC field geologist was on site during drilling to evaluate the subsurface materials encountered and direct the drilling activities. Field logs were prepared by the EEC geologist based visual and tactual observation of disturbed samples and auger cuttings. Final boring logs included with this report may contain modifications to the field logs based on the results of laboratory testing and evaluation. Based on results of our field and laboratory services, subsurface conditions can be generalized as follows. Approximately 3 to 4 inches of vegetation and/or topsoil were encountered at the surface at the boring locations. The topsoil/vegetation was underlain by sandy lean clay which contained tvarying amounts of silt. Those soils were colored light brown to brown. The cohesive soils near ground surface were stiff and those materials became softer with depth. The cohesive soils extended to depths of approximately 10 to 15 feet. The cohesive soils at some locations were underlain by fine and fine to medium sand which contained varying amounts of silt, gravel and occasional cobbles. The granular soils were medium dense and extended to depths in the order of 13 to 18 feet. Below those depths, the subsurface materials consisted of highly weathered siltstone/claystone bedrock. The 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 4 111 siltstone/claystone was colored brown and was soft to moderately hard. Those materials were weathered near ground surface and became less weathered with depth. The stratification boundaries indicated on the boring logs represent the approximate location of changes in soil and rock types; in-situ, the transition of materials may be gradual and indistinct. Classification of the bedrock was based on visual and tactual observation of disturbed samples and auger cuttings, as well as observation of drilling progress. Coring and/or petrographic analysis may reveal other rock types. WATER LEVEL OBSERVATIONS Observations were made while drilling and immediately after completion of the borings to detect the presence and depth to groundwater. At the time of drilling, free water was encountered at a depth of approximately 7 to 9 feet below ground surface. Similar water level depths were observed shortly after drilling activities were concluded. Based on those observed groundwater levels and on the moisture content of the subgrade soils, it is our opinion that the hydrostatic groundwater table was at a depth of approximately 7 to 9 feet at the time the subsurface exploration was performed. Fluctuations in groundwater levels can occur over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. In addition, zones of perched and/or trapped water may be encountered in more permeable zones in the subgrade soils and this condition is often encountered in the soils immediately over lying less permeable bedrock. The location and amount of perched water can also vary over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. 1 I 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 5 ANALYSIS AND RECOMMENDATIONS FOUNDATIONS Based on materials observed at the boring locations, it is our opinion the proposed lightly loaded foundations for the basement and non-basement portions of the office building could be 1 supported on conventional footing foundations. Deep foundation types may be necessary for more heavily loaded foundations as expected in the flex space building. Recommendations for these foundation types are provided below. Over excavation and backfill procedures could also be considered for light to moderate loads. We will provide additional recommendations concerning those alternatives, if desired. FOOTING FOUNDATIONS 1 We recommend the footing foundations extend through all existing vegetation and/or topsoil and bear in natural, stiff cohesive soils. We understand site grading will be such that non-basement footings will be supported at or very near existing ground surface elevations. Basement footing for the office building would extend to depths of approximately 6 to 7 feet below present ground surface. At those anticipated elevations and for footings bearing on natural, stiff cohesive soils, we recommend the foundations be designed using a net allowable total load soil bearing pressure not to exceed 1,500 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load refers to full dead and live loads. Exterior foundations and foundations in unheated areas should be located a minimum of 30 inches below final adjacent exterior grades to provide frost protection. We recommend formed continuous footings have a minimum width of 16 inches and isolated column foundations have a minimum width of 30 inches. Trenched foundations (grade beam foundations) could be used in soils similar to the near surface cohesive materials. If used, we recommend those trenched foundations have a minimum width of 12 inches. 1 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 6 In completing the excavations required for construction footings in the basement areas, some softer material zones may be encountered. The bearing soils should be closely observed and tested at the time of construction to see that footing foundations are not supported on or immediately above the soft cohesive materials. As a minimum, hand auger borings should be performed at random locations along continuous footing lines and should be completed at each column location. Soft or loose zones observed during construction would require removal and replacement prior to placement of the footings. The extent of the over excavation and backfill will vary with the consistency of the materials encountered and with the size of the footing. Those conditions can best be addressed during construction. Care should be taken to avoid disturbing the bearing materials. The soils at basement depth may be easily disturbed so that extra care will be needed. Soils which are loosened or disturbed by construction activities or materials which become dry and desiccated or wet and softened should be removed from the foundation excavations prior to placement of reinforcing steel and foundation concrete. We estimate the long-term settlement of lightly loaded footing foundations designed and constructed as recommend above would be small, less than 3/4-inch. Additional settlement could be caused by placement of overlot fill. We recommend overlot grading be completed as far in advance of building construction as possible. DRILLED PIER FOUNDATIONS For more heavily loaded foundations, consideration should be given to the use of deep foundations. Drilled pier foundations could be used for support of the proposed heavier column loads for the flex-space building. We recommend those drilled-pier foundations extend through the overburden soils to bear a minimum of 5 feet into the underlying bedrock. The 5 foot penetration is recommended so the drilled pier foundations extend through any soft, weathered materials near the surface of the bedrock. For design of drilled pier foundations bearing a minimum of 5 feet into the highly weathered to weathered bedrock, we recommend using a total load end bearing pressure not the exceed 20,000 psf. A friction value of 2000 psf could be used 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 7 for the portion of the drilled shaft extending greater than 5 feet into the site bedrock. The total load pressure includes both live and dead loads of the building, as well as deadload of the foundation. Exterior grade beams for the structure should be extended to at least 30 inches below adjacent exterior grade for frost protection. The near surface site soils have low expansion potential so that construction of a void space beneath the building grade beams would not be required. Soil and groundwater conditions vary at the boring locations; we anticipate temporary casing would be required to prevent an influx of soil and groundwater into the open bore holes. We recommend the drilled pier foundations have a minimum diameter of 12-inches. We estimate the long term settlement of drilled pier foundations designed and constructed as recommended above would be small less than 1/2-inch. 1 BELOW GRADE AREAS The below grade walls for the office building will be subjected to unbalanced lateral earth forces. We recommend the below grade area be designed with a perimeter drain to help remove surface infiltration water from adjacent to the below grade walls and help reduce the lateral loads on the walls. In general, a perimeter drain system would consist of perforated metal or plastic pipe placed at approximate foundation bearing level around the perimeter of the below grade areas. The drainline should allow for the free flow of water to a sump area where it can be removed without reverse flow into the system. The drainline should be surrounded by a minimum of six inches of appropriately sized permeable filter soil and either the granular filter soil or the drainline should be surrounded by an appropriate filter fabric to reduce potential for an influx of fines into the system. The exterior drain system should be tied into the underslab floor drain system (subsequently described in this report) at least two locations. Backfill placed above the drain system should consist of approved, low-volume change materials, free from organic matter and debris. The near surface cohesive site soils could be used as 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 8 backfill in these areas. However, soft/wet zones were noted in those materials and aeration drying of the soils would likely be required prior to use as backfill. We recommend the backfill materials be placed in loose lifts not to exceed 9-inches thick, adjusted in moisture content and compacted to at least 90 percent of the material's maximum dry density as determined in accordance with ASTM specifications D-698, the standard Proctor procedure. The moisture content of the reworked soils should be adjusted to be within the range of ±2% of standard Proctor optimum moisture. 1 In the areas where the backfill materials will support floor slabs, pavements, steps, sidewalks or similar improvement, the backfill materials should be compacted to at least 95 percent of standard Proctor maximum dry density. The top 2 feet of material around the perimeter of the building should be an essential cohesive soil to help reduce surface infiltration. For design of below grade walls where appropriate steps have been taken to use low volume change materials and eliminate the buildup of hydrostatic loads, we recommend using an equivalent fluid pressure of 50 pounds per cubic foot. The equivalent fluid pressure is based on an at-rest stress distribution which assumes the walls have been restrained from lateral movement. Placement of the first floor of the structure should be considered to reduce the potential for displacement of the basement walls during backfilling. The recommended equivalent fluid pressure does not include an allowance for hydrostatic loading nor does it include a factor of safety. FLOOR SLAB SUBGRADES All existing vegetation and/or topsoil should be removed from beneath the floor slabs and pavements. After stripping and completing all cuts and prior to placement of any fill or floor slabs, we recommend the in-place soils be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95 percent of the material's maximum dry density as determined in accordance with ASTM Specification D-698, the standard Proctor procedure. The moisture content of the scarified soils should be adjusted to be within the range of ±2 percent of standard Proctor optimum moisture. Occasional zones of higher silt content soils 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 9 were encountered in the subgrades. The moisture content of those materials should be adjusted to develop a stable subgrade. Those moisture contents may be lower than recommended above. Scarification and recompaction of the subgrade soils in the basement areas would not be required. However, consideration should be given to installation of under-slab drain system in this area. For development of an underslab drain system, the in-place materials would be removed to a depth of 6 to 12 inches below subgrade elevation in the basement area. The soil subgrade at that elevation would be sloped to drained to perforated drain lines spaced periodically across the building. An interior perimeter drain line would also be installed at approximate foundation bearing level. The area around the drain lines and the over excavated zone beneath the floor slab should be backfilled with free draining granular fill. The entire system should be sloped to a sump area where water can be removed without reverse flow into the system. The drain line should also be tied to the exterior perimeter at least two locations as previously recommended. Fill required to develop floor slab or pavement subgrades should consist of approved, low- volume change material, free from organic matter and debris. Normally, soils with a liquid limit of 40 or less and plasticity index of 18 or less could be used as low volume change fill. The near surface site cohesive soils could be used as low volume change fill beneath the floor slabs and pavements. Fill materials in the floor slab and pavement areas should be placed in loose lifts not to exceed 9-inches thick, adjusted in moisture content as recommended for the sacrificed materials and compacted to at least 95 percent of the material's standard Proctor maximum dry density. materials, care should be taken toprevent disturbance of the preparedAfterplacementofthefill subgrades. Materials which are loosened or disturbed by construction activities, or materials which become dry and desiccated or wet and softened should be removed and replaced or reworked in place. I 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 10 PAVEMENTS A R-value of 8 was determined to be appropriate for the site materials based on laboratory testing of a near surface soil sample. Pavement sections have been evaluated for this project based on that R-value and the 1986 American Association of State Highway and Transportation Officials(AASHTO) "Guidelines for Design of Pavement Structures". Traffic in the paved drive and parking areas was assumed to consist of low volumes of light vehicles including mostly automobiles and light trucks. If the pavements are to be used on a regular basis by heavier vehicles, the pavement section recommendations provided in this report should be reevaluated. Alternatively, if the pavements will be used exclusively by automobiles, a lighter pavement section may be considered. Based on the consideration of the subgrade soils and anticipated traffic loadings, we recommend the site pavements consist of 3 inches of asphaltic concrete wearing surface overlying 6 inches of aggregate base course. The wearing surface should consist of asphaltic concrete consist with City of Fort Collins recommendations for SC-1 or SC-2 blends. Aggregate base course should be compatible with Colorado Department of Transportation (CDOT) recommendations for class 5 or 6 base. Stabilization of pavement subgrades could be considered to reduce the required pavement section and provide stronger, uniform subgrades. For this procedure, Class C fly ash or a similar material would be blended with the site soils to develop a stabilized subgrade. Each inch of stabilized subgrade would replace approximately 1 inch of aggregate base. We would be pleased to provide additional recommendations concerning subgrade stabilization, if desired. 1 OTHER CONSIDERATIONS Positive drainage should be developedawayfrom the proposed building and across and awayg t from pavement edges to avoid wetting of the bearing or subgrade materials. Bearing soils which are allowed to become wetted could result in unacceptable settlement of the site structure. 1 1 1 Earth Engineering Consultants, Inc. Proposed Chris Wells Development July 25, 1994 Page 11 Subgrade soils which are allowed to become wetted could result in premature failure of the pavement section. We recommend a minimum slope away from the structure of 1 inch per foot for the first 10 feet. In addition, roof drains should be designed to discharge at least 5 feet beyond the perimeter of the building. Lawn sprinkling system should also be installed at least 5 feet beyond the perimeter of the building and designed to avoid spraying water directly on the foundation walls. Plantings which are water intensive should not be planted immediately adjacent to the buildings. A detention pond will be constructed in the southeast corner of the site. Materials excavated from that area could likely be used as general site fill for the project. We anticipate groundwater at a relatively shallow depth in that area of the site. Fill materials will likely need to be dried prior to placement. Excavations extending near the groundwater table may be unstable and scrapers or similar heavy equipment may not be suitable for the excavations. GENERAL COMMENTS The analysis and recommendations presented in this report are based upon the data obtained from the soil borings performed at the indicated locations and from any other information discussed in this report. This report does not reflect any variations which may occur between borings or across the site. The nature and extent of such variations may not become evident until construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. 1 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. 1 I I Earth Engineering Consultants, Inc. 1 Proposed Chris Wells Development July 25, 1994 Page 12 This report has been prepared for the exclusive use of W.W. Reynolds 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. 1 I I 1 1 1 1 1 1 1 I 1 77 ri-N .. A1:QM; . T1ON'l l I i /i!, , i,!! 7 .illllilll , , III TI111111ii L 11 I 1 13 PARKING SPACES 1 I1 I 2.NJ 1v I I • L. N c > ( O p 9,, • I CC00 1 N i J 45,D 11 • ;I 1 1 = I IL WI ? k. . . 1r S. V J ji4 4 4 F I o 4 r4 4 4 E f 4 1 8..3 I h? r 7o 1 f 4 4 F 4 a 1 z I44444F \\ 4 I. f 4 4 4 4\ r'. 4 4 4 4 4 r 4 4Q 4 4 4 \\ I I I I 1`, v \ _ 1 II4t444 , 4 f` 45 PARKING SPACESt, 1I. f t 444Z4 4 4 4 IF fi: :4 4 G22o 4 4 4 IlIII 1 4. f L\ f 4 II 1 4 4 1 4 N a I, 4 (` t 4 4 F 4 i, N I444r4444- v n I V r ' • 4 4 0 f 4 t N _ I I o lr t 4 < r.4Z r 4 t 4 co •c08 I ei * 4 ` 7! 4 I '/I D `i , : -glitz') lii f 4 4= 4 ccJJ F A• 4 4 F n -r, 1 f f 4 f 4 4 F r f'1 // 1 1 f 4 4. t 4 a-s' l 4 4 4 4 4 4 1 4 4 Q-lo N TBiNE ROAD NOT TO SCALE I BORING LOCATION DIAGRAM CHRIS WELLS DEVELOPMENT FORT COLLINS, COLORADO IJULY 1994 PROJECT No: 1942050 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050. DATE JULY 1994 I LOG OF BORING B-1 SHEET 1 OF 1 RIG TYPE:TRACK RIG CME bi3.."'`3 :::<>': >.'"•:..' r;t::ti, ti '`;;;';i>ta•,`::+ iaSe :z`•': WATER DEPTH ELEV FOREMAN: SCK START DATE 7/8/94 WHILE DRILLING 8' NIA AUGER TYPE: 4"CFA FINISH DATE 718/94 AFTER DRILLING NIA NIA _ SPT HAMMER: MANUAL SURFACE ELEV NIA 24 HOUR NIA NIA ISOIL DESCRIPTION D N oU MC OD A-OMITS 200 SWELL TYPE (FEET) s( BLOWS/FT) (PSF)PCF) LL PI PRESSURE l%_41 500 PSF 12 16.0 35 15 79.9 SS I SANDY CLAY(CL) Medium brown Moist Medium stiff 3 22.0 wet SS 5 1 I SS 10 2 25.3 I I CLAYEY GRAVELLY SAND(SP) Brown Saturated Dense SS — 15 43 14.0 SANDY CLAY(CL) I Tanish brown Mottled Saturated-Soft HIGHLY WEATHERED CLAYSTONE/SHALE ITanish brown Mottled Slighty hard 1 Plastic SS 20 25 for 4" 20 2 BOTTOM OF BORING 20 FEET. 25 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLUNS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 1 RIG TYPE:TRACK RIG CME LOG OF BORING B-2 SHEET.'HEET 1 OF 1 T:<` '` IN:::•.:•:;, •z:,,,• ::,,,,,,z„WATER DEPTH ELEV FOREMAN: SCK START DATE 7I8194 WHILE DRILLING 9' NIA AUGER TYPE: 4'CFA FINISH DATE 7/8/94 AFTER DRILLING NIA N/A I SPT HAMMER: MANUAL SURFACE ELEV N/A 24 HOUR NIA NIA SOIL DESCRIPTION D N DU MC DD A•L00T3 200 SWELL TYPE (FEET) (BLOWS/FT) (PSF)MI (PCF) LL PI (%( PRESSURE %(I0 500 PSF 8 16.3 SS _ _ I SANDY CLAY(CL) Medium brown Moist I Medium stiff Wet SS 5 3 31.1 I i I SS 10 6 22.6 i SANDY LEAN CLAY(CL) I Soft Weathered Weathered SS _15 15 16.2 I GRAVELLY SAND(SP) Brownish red ISaturated-Medium dense HIGHLY WEATHERED CLAYSTONE/SHALE I Grayish brown Mottled Slightly hard 1 PlasticBOTTOMSS — 20 39 OF BORING 20 FEET. I I I 25 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 I LOG OF BORING B-3 SHEET 1 OF 1 RIG TYPE:TRACK RIG CME MUM.,5, .;::,:`:•v.:::::::t:.:•:::_0 :::.::s:sX:?':' :::::3`:':3:'::: :::':,>.:':::is :WATER l DEPTH ELEV FOREMAN: SCK START DATE 718194 WHILE DRILLING 9' NIA AUGER TYPE: 4"CFA FINISH DATE 7/8/94 AFTER DRILLING N/A NIA SPT HAMMER: MANUAL SURFACE ELEV WA 24 HOUR NIA NIA I SOIL DESCRIPTION D N I OU MC DO A-LIMwTS 200 SWELL TYPE (FEET) (SLOWS/FT)JII, (PSF)PCF) LL PI PRESSURE %f SOO PSF I SS _ _ 8 19.4 I SANDY CLAY(CL) Medium brown Moist IMedium stiff ST 5 500 NONE I I I SS 10 8 21.6 i I GRAVELLY CLAYEY SAND I Red Saturated SS 15 37 16.2 Dense I IHIGHLY WEATHERED CLAYSTONEISHALE _ _ Olive grayish brown I Mottled-Slightly hard-Plastic SS —20 39 19.6 BOTTOM OF BORING 20 FEET. I 1 I 25 Earth Engineering Consultants I CHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 I LOG OF BORING B- SHEET 1 OF 1 RIG TYPE:TRACK RIG CME t t`tti +iti ti\< LOG BORING fit; t'+`tx+ L}?3it 3%{^ o`. "? r WATER DEPTH ELEV FOREMAN: SGK START DATE 7/8194 WHILE DRILLING NONE N/A AUGER TYPE: 4"CFA FINISH DATE 718/94 AFTER DRILLING NIA N/A SPT HAMMER: MANUAL SURFACE ELEV NIA 24 HOUR N/A N/A I SOIL DESCRIPTION D N QU MC DO MLO DTS 200 SWELL TWfi (FEET) (BLOWS/FT) IPSF)PCF) LL %PRESSURE %B 500 PEP I SANDY CLAY(CL) 8 22.5 Medium brown SS — — I Moist Medium stiff to soft i ST 5 2 28.3 I BOTTOM OF BORING 51@ FEET. I 10 I 15 1 1 20 I 25 rEarth Engineering Consultants I CHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 1 LOG OF BORING B5 SHEET 1 OF_1 RIG TYPE:TRACK RIG CME K" :"0;3 5 F' I ..•vi.'Zt a? 3'#z?##i>; .`WATER DEPTH ELEV FOREMAN: SCK START DATE 718194 WHILE DRILLING NONE WA AUGER TYPE: 4"CFA FINISH DATE 718194 AFTER DRILLING WA NIA SPT HAMMER: MANUAL SURFACE ELEV WA 24 HOUR NIA WA I SOIL DESCRIPTION D N GU MC on A-LD9TS zoo SWELL TYPE (FEET) (BLOWS/FT) (PSF)PCF) LL PI PRESSURE %e 500 PSF I SANDY CLAY(CL) Dark brown SS _ _ 8 20.7 I Moist Soh ST 5 2 27.9 IBOTTOM OF BORING 51/2 FEET. 1 10 1 1 15 i I 20 I 25 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 I LOG OF BORING B SHEET 1 OF 1 RIG TYPE:TRACK RIG CME M.. i•:Ytiv\J V,'iv •.• .•:`\'tiitiiCu.;ti'Yiv.,+vv ti;;i<Ltii';i<•_'•:<;ti'7$`:3• r#### #zr## \E•sss ssrr>?+., ? #r,...rs.:s.:st ss.rs3.`•+:3. WATER DEPTH ELEV gINI FOREMAN: SCK START DATE 718194 WHILE DRILLING 9' NIA AUGER TYPE: 4'CFA FINISH DATE 718I94 AFTER DRILLING NIA N/A I SPT HAMMER: MANUAL SURFACE ELEV N/A 24 HOUR N/A N/A 801E DESCRIPTION D N ou MC OD A-UMrrS 200 SWELL TYPE (FEET) (BLOWS/FT) (PSF)PCF) LI. PI PRESSURE %5 See PSF I SS _ _ 12 16.9 39 16 78.8 I SANDY CLAY(CL) Medium brown Moist IMedium stiff to soft ST 5 3 19.9 1 SS _10 4 22.6 I SANDY LEAN CLAY(CL) Tan and Olive Mottled Saturated SS —15 12 14.4 Medium stiff to stilt GRAVELLY SAND Red-Saturated-Dense IHIGHLY WEATHERED CLAYSTONEISHALE Mottled Slightly hard IPlastic SS 20 34 20.9 BOTTOM OF BORING 201/2 FEET. 1 1 I 25 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLUNS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 I LOG OF BORING B-7 SHEET 1 OF 1 c•;:.;..;:: .;.: ,:1R ::.NIE§.,.<. .:•:..tip`,y tk*.jr •:R WATER J, DEPTH ELEVRIGTYPE:TRACK CME h••w`•r> '::\•h,:SEzx@:i h::.w•••• `.h\..±h+i••;r' FOREMAN: SCK START DATE 7/8194 WHILE DRILLING T NIA AUGER TYPE: 4'CFA FINISH DATE 718194 AFTER DRILLING NIA WA I SPT HAMMER: MANUAL SURFACE ELEV NIA 24 HOUR NIA NIA SOIL DESCRIPTION o N ou MC oo A.LmmS -200 SWELL TYPE (FEET) (BLOWS/FT) w ( PSF)PCF) v LL PI (%) PRESSURE % 500 PSF ISANDY GRAVELLY CLAY(CL) Medium brown Moist SS — _8 IMedium stiff SANDY CLAY(CL)ST 5 5 20.2 I Reddish brown Moist Medium stiff I ISS _- 10 4 21.3 I GRAVELLY SAND(SP) Red Saturated II Medium dense SANDY CLAY(CL) Gray 1 Saturated SS —15 19 7.9 Medium stiff BOTTOM OF BORING 15112 FEET. I 20 25 Earth Engineering Consultants ICHRIS WELLS DEVELOPMENT FORT COLLINS,COLORADO PROJECT NO:1942050 DATE: JULY 1994 LOG OF BORING B-8 SHEET 1 OF 1IRIGTYPETRACKRIGCME1:'r:;.3. y+:;R;tix? 2 ;k ;xM32;,2.`',`.`;`.•;`kc`,# i`aye#:3>;„ >;':§:g.;'WATER DEPTH i ELEV FOREMAN: SCK START DATE 718194 WHILE DRILLING 9' NIA AUGER TYPE: 4"CFA FINISH DATE 718194 AFTER DRILLING N/A NIA 1 SPT HAMMER: MANUAL SURFACE ELEV WA 24 HOUR NIA NIA SOIL DESCRIPTION D N QU MC 00 A.IAWTS 200 SWELL TYPE (FEET) (BLOWS/FT) (PSF)PCP) LL -__PI PRESSURE %(.500 PSF I I SANDY CLAY(CL) Medium brown Moist to saturated Medium stiff to softI 5 10 I SANDY GRAVEL(GP) Saturated Dense I HIGHLY WEATHERED CLAYSTONEISHALE _ _ I Slightly hard 15 Plastic I 20 BOTTOM OF BORING 20 FEET. I 25 Earth Engineering Consultants IDRILLING AND EXPLORATION DRILLING & SAMPLING SYMBOLS: I SS : Split Spoon - 13/4" 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" 0.D. unless otherwise noted. PA : Power Auger.FT : Fish Tail Bit I 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 DC : Dutch Cone IWB : 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. IWATER 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 1 indicated levels may reflect the location of groundwater. In low permeability soils, the accurate determination of groundwater levels is not possible with only short term observations. IDESCRIPTIVE SOIL CLASSIFICATION PHYSICAL PROPERTIES OF BEDROCK Soil Classification is based on the Unified Soil Classification DEGREE OF WEATHERING: system and the ASTM Designations D-2487 and D-2488. I Coarse Grained Soils have more than 50% of their dry Slight Slight decomposition of parent material on weight retained on a #200 sieve; they are described as: joints. May be color change. boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50%of their dry weight retained on a #200 sieve; Moderate Some decomposition and color change I they are described as: clays, if they are plastic, and silts if throughout. they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be High Rock highly decomposed, may be extremely added according to the relative proportions based on grain broken. I size. In addition to gradation, coarse grained soils are defined on the basis of their relative in-place density and HARDNESS AND DEGREE OF CEMENTATION: fine grained soils on the basis of their consistency. Limestone and Dolomite: Example: Lean clay with sand, trace gravel, stiff (CL); silty Hard Difficult to scratch with knife. I sand, trace gravel, medium dense (SM). Moderately Can be scratched easily with knife, CONSISTENCY OF FINE-GRAINED SOILS Hard Cannot be scratched with fingernail. IUnconfined Compressive Soft Can be scratched with fingernail. Strength, Qu, psf Consistency I Shale, Siltstone_and Claystone:. 500 Very Soft Hard Can be scratched easily with knife, cannot 500 - 1,000 Soft be scratched with fingernail. 1,001 - 2,000 Medium 2,001 - 4,000 Stiff Moderately Can be scratched with fingernail. I 4,001 - 8,000 Very Stiff Hard 8,001 - 16,000 Very Hard Soft Can be easily dented but not molded with RELATIVE DENSITY OF COARSE-GRAINED SOILS: fingers. IN-Blows/ft 0-3 Relative Density Very Loose Sandstone and Conglomerate: 4-9 Loose Well Capable of scratching a knife blade. 10-29 Medium Dense Cemented I 30-49 Dense 50-80 Very Dense Cemented Can be scratched with knife. 80 + Extremely Dense Poorly Can be broken apart easily with fingers. ICemented I IUNIFIED SOIL CLASSIFICATION SYSTEM Soil Classification I Criteria for Assigning Group Symbols end Group Names Using Laboratory Tests'Group Symbol Group Name' Coarse-Grained Gravels more than Clean Gravels Less Cu > 4 and 1 < Cc <3E GW Well graded gravel° Soils more than 50% of coarse than 5% fines° I 50% retained on No. 200 sieve fraction retained on No. 4 sieve Cu < 4 and/or 1 > Cc > 3E GP Poorly graded gravel' Gravels with Fines Fines classify as ML or MH GM Sky gravel,G,H more than 12% fines IFines classify as CL or CH GC Clayey gravelF•O•" Sands 50% or more Clean Sands Less Cu > 6 and 1 < Cc < 3E SW Well-graded sand' of coarse fraction than 5% finesE I passes No. 4 sieve Cu < 6 and/or 1 > Cc > 3E SP Poorly graded sand' Sands with Fines Fines classify as ML or MH SM Sitty sand°M' more than 12% fines° Fines Classify as CL or CH SC Clayey sand°•"•' I Fine-Grained Soils Silts and Clays inorganic PI > 7 and plots on or above "A line' CL Lean clay't•L•''' 50% or more Liquid limit less passes the than 50 PI < 4 or plots below "A"line ML Silt"' No. 200 sieve organic Liquid limp -oven dried Organic clay' 0.75 OL Liquid limit -not dried Organic saw" Silts and Clays inorganic PI plots on or above "A" line CH Fat clay' I Liquid limit 50 or more PI lots below "A"line MH Elastic Silt'-''' organic Liquid limit -oven dried Organic clay'-" 0.75 OH I Liquid limit -not dried Organic sihKu+.a Highly organic soils Primarily organic matter,dark in color, and organic odor PT Peat ABased on the material passing the 3-in. I If soil contains 15 to 29%plus No. 200, add 75-mm) sieve atv=Dc°/D10 Cc = (D10)with sand" or"with gravel", whichever is If field sample contained cobbles or D.o x Dopredominant. boulders, or both, add "with cobbles or Llf soil contains >30%plus No. 200 boulders, or both" to group name. predominantly sand, add "sandy" to group I CGravels with 5 to 12%fines require dual FIf soil contains > 15%sand, add "with name. symbols: sand" to group name. It soil contains >30%plus No. 200, GW-GM well-graded gravel with silt If fines classify as CL-ML, use dual symbol predominantly gravel, add "gravelly" to group GW-GC well-graded gravel with clay GC-GM, or SC-SM. name. I GP-GM poorly graded gravel with silt If fines are organic, add "with organic fines" "PI > 4 and plots on or above "A"line. GP-GC poorly graded gravel with clay to group name. PI < 4 or plots below "A"line. Sands with 5 to 12%fines require dual Ilf soil contains > 15% gravel, add "with PPI plots on or above "A"line. symbols: gravel" to group name. PI plots below "A"line. SW-SM well-graded sand with silt 1f Atterberg limits plot in shaded area, soil is I SW-SC well-graded sand with clay a CL-ML, silty clay. SP-SM poorly graded sand with silt SP-SC poorly graded sand with clay 60 I For classification of Ilns•grained soils and fine-grained fraction of coarse. IEigrainedsoils EOuation of"A"•line I \'Horizontal at PI - I to LL " 25.5.J i V I C then PI "0.73 iLL-201 O\ N I rP . I I 10.. Equation of-U"•Ilna et, -__ --r"—'i---— p Vertical at LL " 16 to PI "7. Z then PI "0.9 ILL•81 iC.,./i i iI F I I CO x° -- I —I o I -- r--i F— -- --- ii I pv I MH OR OH; Itof—r — 7 ® IMLoaOL I 1 I Iu_ 0 10 18 20 30 40 50 80 70 80 90 100 110 LIQUID LIMIT(LLI I 0 t.. f `(I ,.t .__ Oirl 1 1 1 1 1 1 PRELIMINARY SUBSURFACE EXPLORATION REPORT 1 HORSETOOTH EAST DEVELOPMENT-2ND FILING FORT COLLINS, COLORADO EEC PROJECT 1942051 1 1 1 i 1 1 1 1 1 1 1 1 1 I IJuly 25, 1994 1 `' IW.W. Reynolds EARTH ENGINEERING CONSULTANTS, INC. 4875 Pearl East Circle, #300 IBoulder, Colorado 80301 Attn: Mr. Jerry Lee IRE: Preliminary Subsurface Exploration Report Proposed Horsetooth East Development - 2nd Filing I Automation Way and Bighorn Drive Fort Collins, Colorado EEC Project No. 1942051 IMr. Lee: IEnclosed, with this letter are the results of the preliminary subsurface exploration you requested for the proposed Horsetooth East - 2nd Filing to be located south of Bighorn Drive and west of I Automation Way in Fort Collins, Colorado. In summary, the subsurface materials at the site consist of sandy, stiff to soft cohesive soils with occasional zones of medium dense granular materials which are underlain by weathered siltstone/claystone bedrock. Based on the results I of our exploration, it is our opinion the site soils could be used to support lightly loaded footing foundations. Deep foundations extending to the highly weathered to weathered bedrock should be considered for more heavily loaded foundations. Floor slabs and pavements could be I supported directly on the near surface site soils. Geotechnical recommendations concerning design and construction of the foundations and support of floor slabs and pavements are presented in the text of the attached report. IWe appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we can be of further service to you in any other way, please do not Ihesitate to contact us. Very truly yours, IEa g Consultants, Inc. 0 RECj a• Vie, 957 S 2 315 ;,i ILest- P.E. Curtiss . '1 in, P.E. Principal Engineer Principal I cc: W.W. Reynolds - Fort Collins, Libby Glassy Cityscape, Eldon Ward 1 2600 Canton Ct, Suite A Fort Collins, CO 80525 I 303) 224-1522 FAX 224-4564 1 PRELIMINARY SUBSURFACE EXPLORATION REPORT HORSETOOTH EAST DEVELOPMENT - 2ND FILING FORT COLLINS, COLORADO EEC PROJECT NO. 1942051 1 INTRODUCTION The subsurface exploration for the proposed 2nd Filingof the Horsetooth East Development toPPP be located south of Bighorn Drive and west of Automation Way in Fort Collins, Colorado, has been completed. Five (5) soil borings extending to depths of approximately 15 to 20 feet below present site grades were advanced to develop information on existing subsurface conditions in the development area. Individual boring logs and a diagram indicating the approximate boring locations are included with this report. We understand the proposed Horsetooth East - 2nd Filing will be developed south of Bighorn Drive and west of Automation Way in Fort Collins, Colorado. The specific buildings to be developed have not been identified at this time; however, are expected to be one or two story office/manufacturing buildings which may contain basement areas. Foundation loads are expected to be light to moderate; continuous wall loads of 3 to 5 kips per lineal foot and column loads of 50 to 100 kips. Floor loads are expected to be light. Paved drive areas will be developed although traffic loads are not presently known. Minor cuts and fills are expected to develop the site grades. The purpose of this report is to describe the subsurface conditions encountered in the borings, analyze and evaluate the test data and provide preliminary geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements. EXPLORATION AND TESTING PROCEDURES The boring locations were selected in the field by Earth Engineering Consultants, Inc. (EEC) personnel. The field locations were established by pacing and estimating angles from the references indicated on the attached boring location diagram. The boring locations should be considered accurate only to the degree implied by the methods used to make the field measurements. 1 1 I Earth Engineering Consultants, Inc. Horsetooth East Development- 2nd Filing July 25, 1994 Page 2 The borings were performed using a truck-mounted, CME-45 drill rig. The boreholes were advanced using 4-inch nominal diameter continuous flight augers and samples of the subsurface materials encountered were obtained using thin-walled tube and split barrel sampling procedures in general accordance with ASTM Specifications D-1587 and D-1586, respectively. In the thin- walled tube sampling procedure, a seamless steel tube with a sharpened cutting edge is push into the ground with hydraulic pressure to obtain a relatively undisturbed sample of cohesive or moderately cohesive material. In the split barrel sampling procedure, a standard 2-inch O.D. split barrel sampling spoon is driven into the ground by means of a 140-pound hammer falling a distance of 30 inches. The number of blows required to advance the split barrel sampler 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 materials. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. 1 Moisture content, and where appropriate, dry density and unconfined compressive strength tests were performed on representative portions of the recovered samples. In addition, Atterberg limits, washed sieve analysis, and swell/consolidation tests were performed on selected samples. Results of the outlined laboratory tests are shown on the attached boring logs. As a part of the testing program, all samples were examined in the laboratory by an engineer and classified in accordance with the attached General Notes and the Unified Soil Classification System, based on the materials' 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. SITE AND SUBSURFACE CONDITIONS The proposed development site is located south of Bighorn Drive and west of Automation Way in Fort Collins, Colorado. Site drainage is generally to the south with maximum difference in groun d surface elevations across the site on the order of 5 feet. The site is presently vegetated and evidence of prior building construction was not observed at the site by EEC field personnel. 1 1 I IEarth Engineering Consultants, Inc. 1 Horsetooth East Development- 2nd Filing July 25, 1994 Page 3 An EEC field geologist was on site during drilling to evaluate the subsurface materials encountered and direct the drilling activities. The field logs prepared by our field geologist were Ibased visual and tactual observation of disturbed samples and auger cuttings. Final boring logs included with this report may contain modifications to the field logs based on the results of I laboratory testing and evaluation. Based on results of our field and laboratory services, subsurface conditions can be generalized as follows. Approximately 3 to 4 inches of vegetation and/or topsoil was encountered at the surface at thePP _ _ . Y g P I boring locations. The topsoil/vegetation was underlain by sandy lean clay, which contained varying amounts of silt. Those soils were colored light brown to brown. The cohesive soils near ground surface were stiff and those materials became softer below depths of approximately I5 feet. The cohesive soils extended to depths of approximately 8 to 15 feet. 1 The cohesive soils at boring locations B-2, B-3, B-4 and B-5 were underlain by fine and fine to medium sand which contained varying amounts of silt, gravel and occasional cobbles. The Icobble zones were encountered deeper in the granular material. The sandy soils were medium dense and extended to depths on the order of 14 to 18 feet. Below those depths, the subsurface I materials consisted of highly weathered siltstone/claystone bedrock. The siltstone/claystone was colored brown and was soft to moderately hard. Those materials were weathered near ground 1 surface and became less weathered with depth. The stratification boundaries shown on the boring logs represent the approximate locations of Ichanges in soil and rock types; in-situ, the transition of materials may be gradual and indistinct. Classification of the bedrock was based on visual and tactual observation of disturbed samples Iand auger cuttings. Coring and/or petrographic analysis may reveal other rock types. 1 WATER LEVEL OBSERVATIONS I Observations were made while drilling and immediately after completion of the borings to detect the presence and depth to groundwater. At the time of drilling, free water was encountered at a depth of approximately 9 feet at each of the boring locations. Similar free water depths were 1 I 1 Earth Engineering Consultants, Inc. Horsetooth East Development - 2nd Filing July 25, 1994 Page 4 observed shortly after drilling activities were concluded. Based on those observed groundwater levels and on the moisture content of the subgrade soils, it is our opinion the hydrostatic groundwater tables was at a depth of approximately 7 to 9 feet at the time the subsurface exploration was performed. 1 Fluctuations in groundwater levels can occur over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. In addition, zones of perched and/or trapped water may be encountered in more permeable zones in the subgrade soils and perched conditions are often encountered in soils immediately overlying less permeable bedrock. The location and amount of perched water can also vary over time depending on variations in hydrologic conditions and other conditions not apparent at the time of this report. ANALYSIS AND RECOMMENDATIONS 1 FOUNDATIONS Based onthe soils observed at the boringlocations, it is our opinion lightly structures could beaPgY supported on conventional footing foundations. Heavier foundations loads may require alternative foundations. Overexcavation and backfill techniques or preloading of the site could 1 be considered for moderate foundation loads. These options would allow the use of footings. Deep foundations should be considered for heavily loaded foundations. Regarding conventional footings for light foundation loads, those foundations should extend through all existing vegetation and/or topsoil bear in the natural, stiff cohesive soils. The foundations should bear as near as possible to existing ground surface or should extend to basement depths. Intermediate footing depths would likely necessitate overexcavation and backfill procedures as zones of soft cohesive soils were observed in these areas. We expect those foundations could be designed using a net allowable total load soil bearing pressure on the order of 1,000 to 2,000 psf. The net bearing pressure refers to the pressure at foundation bearing level in excess of the minimum surrounding overburden pressure. Total load bearing pressure refers to full dead and live loads. 1 1 Earth Engineering Consultants, Inc. Horsetooth East Development - 2nd Filing July 25, 1994 Page 5 Preloading of the site may be considered for more heavily loaded foundations or to reduce the overexcavation potential for lightly loaded footings. Preloading would involve placement of a predetermined depth of fill over the building area to simulate the load expected from the building construction. After consolidation of the in-place materials occurs, the fill may be removed and the building constructed. For cohesive soils, the consolidation of the site materials my require 3 to 4 months. The required time period may be reduced by placing additional fill. The preload pressure required would depend on the building loads and design elevations as well as acceptable settlements. We expect bearing pressures in the range of those provided for conventional lightly loaded footings would be applicable. The bearing soils should be closely observed and tested at the time of construction to see that footing foundations are not supported on or immediately above soft soil zones. As a minimum, hand auger boring should be performed at random locations along continuous footing lines and should be completed at each column location. Soft or loose zones observed during construction would require removal and replacement prior to construction of the footings. The extent of the overexcavation and backfill required would vary with the consistency of the materials encountered at bearing level and with the size of the footings. Overexcavation and backfill techniques may be required to deal with soft or loose zones and could be considered to provide a higher bearing pressures for footing foundations. The depth of overexcavation required would vary with footing size/allowable bearing pressure. Typically overexcavations will extend to a depth below foundation bearing which is equal to one-half of the design footing width. For this site, we expect a design bearing pressure of 2000 to 3000 psf could be achieved using over excavation and backfill techniques. Overexcavation would extend laterally beyond the edges of the footings, varying with the footing width. For more heavily loaded foundations, consideration should be given to the use of deep foundations. Drilled piers could be considered. The drilled pier foundations should extend through the overburden soils to bear in the underlying bedrock. For design of drilled pier foundations we anticipate a total load end bearing pressure of 15,000 to 20,000 psf could be 1 1 1 Earth Engineering Consultants, Inc. Horsetooth East Development - 2nd Filing July 25, 1994 Page 6 used. The total load pressure includes both live and dead loads of the building, as well as deadload of the foundation. The near surface site soils have low expansion potential so that construction of a void space beneath the grade beams would not be required. Soil and groundwater conditions vary at the boring locations; we anticipate temporary casing would be required to prevent an influx of soil and groundwater into the open borings prior to placement of the drilled pier concrete. We estimate the long term settlement of drilled pier foundations would be less than 1/2-inch. The settlement of footings could vary depending on foundation loads and selected construction methods. We would be pleased to provide additional analysis after building types are selected. BELOW GRADE AREAS 1 The below grade walls for the site buildings will be subjected to unbalanced lateral forces. We recommend that the below grade area be designed with a perimeter drain to help remove surface infiltration from adjacent to below grade walls and to reduce the potential for water seepage into the below grade areas. In general, a perimeter drain system would consist of perforated metal or plastic pipe placed at approximate foundation bearing level around the perimeter of the below grade areas. The drainline should allow for the free flow of water to a sump area where it can be removed without reverse flow into the system. The drainline should be surrounded by a minimum of six inches of appropriately sized permeable filter soil and either the granular filter soil or the drainline should be surrounded by an appropriate filter fabric to reduce potential for an influx of fines into the system. SUBGRADES All existing vegetationPand/or topsoil should be removed from beneath the floor slabs and pavements. After stripping and completing all cuts and prior to placement of any fill or floor slabs, the in-place soils should be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95 percent of the material's maximum dry density as 1 tEarth Engineering Consultants, Inc. Horsetooth East Development- 2nd Filing July 25, 1994 Page 7 determined in accordance with ASTM Specification D-698, the standard Proctor procedure. The moisture content of the scarified soils should generally be adjusted to be with in the range of±2 percent of standard Proctor optimum moisture. Occasional zones of higher silt content soils were encountered in the subgrades. The moisture content of those materials should be adjusted to develop stable subgrades. Those moisture contents may be lower than 2 percent below standard Proctor optimum moisture. Scarification and recompaction of the soils in basement areas wouldpoud not be required. However, installation of an under slab drain system may be required, depending on the design elevation of the building. Fill required to develop slab or pavement subgrades should consist of approved, low-volume change material, free from organic matter and debris. Normally, soils with a liquid limit of 40 or less and plasticity index of 18 or less could be used as low volume change fill. The near surface site cohesive soils could be used as low volume change fill beneath the floor slabs and pavements. Fill materials in the floor slab and pavement areas should be placed in loose lifts not to exceed 9-inches thick, adjusted in moisture content as recommended for the sacrificed materials and compacted to at least 95 percent of the material's standard Proctor maximum dry density. After placement of the fill materials, care should be taken to prevent disturbance of the prepared subgrades. Materials which are loosened or disturbed by construction activities, or materials which become dry and desiccated or wet and softened should be removed and replaced or reworked in place prior to construction of the floor slabs. PAVEMENTS A R-value of 8 was determined to be appropriate for the site materials based on laboratory testing of a nearby, near surface soil sample. Pavement sections have been evaluated for this project based on that R-value and the 1986 AASHTO "Guidelines for Design of Pavement 1 1 Earth Engineering Consultants, Inc. Horsetooth East Development- 2nd Filing July 25, 1994 Page 8 Structures". Traffic in the paved drive and parking areas is assumed to consist of low volumes of light vehicles including automobiles and light trucks. If the pavements are to be used on a regular basis by heavier vehicles, pavement recommendations provided in this report should be reevaluated. 1 Based on the consideration of the subgrade soils and anticipated traffic loadings, we recommend the site pavements consist of 3 inches of asphaltic concrete wearing surface overlying 6 inches of aggregate base course. The wearing surface should consist of asphaltic concrete consist with City of Fort Collins recommendations for SC-1 or SC-2 blends. Aggregate base course should be compatible with Colorado Department of Transportation (CDOT) recommendations for class 5 or 6 base. Stabilization of pavement subgrades could be considered to reduce the required pavement section and provide stronger, uniform subgrades. For this option, Class C fly ash or similar material would be blended with the site soils to develop a stabilized subgrade. Each inch of stabilized subgrade would replace approximately 1 inch of aggregate base. We would be pleased to. provide additional recommendations concerning subgrade stabilization, if desired. 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 1 discussed in this report. This report does not reflect any variations which may occur between borings or across the site. The nature and extent of such variations may not become evident until construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. It is recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be made regarding the interpretation and implementation of our geotechnical recommendations in the design and specifications. It is further recommended 1 1 1 Earth Engineering Consultants, Inc. Horsetooth East Development- 2nd Filing July 25, 1994 Page 9 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 W.W. Reynolds 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. 111 1 I I 1 1 1 1 1 1 I I I RAILROAD II PUBLIC z I SERVICE o I Q I I o i i APPROXIMATE EXTENT QOFPROPERTYBOUNDARY I II BIG HORN DRIVE I B- 1B2 I I I MOUND OFII III DIRT N I III B-5 I 4-U II I III I II B-3 B-4 IL*1 I I I I I NOT TO SCALE BORING LOCATION DIAGRAM IHORSETOOTH EAST — 2°d FILING FORT COLLINS, COLORADO IJULY 1994 PROJECT No: 1942051 Earth Engineering Consultants I HORSETOOTH EAST-2nd FILING FORT COLLINS,COLORADO PROJECT NO:1942051 DATE: JULY 1994 LOG OF BORING B-1 SHEET 1 OF 1 I RIG TYPE:CME45 Lpsi`.:ny;:`2;4hi ti 0 B.:1•:? 3 w p: i?IE;;?WATER DEPTH ELEV FOREMAN: SCK START DATE 719194 WHILE DRILLING 9' AUGER TYPE: 4-CFA FINISH DATE 718194 AFTER DRILLING 9' SPT HAMMER: MANUAL SURFACE ELEV. 24 HOUR N/A 1 SOIL DESCRIPTION o N au TYPE MC 00 a Leans zoo SWELL FEET) (SLOWS/FT) - (PSF)PCF) U. P PRESSURE %g COO PSF 4 INCHES TOPSOILNEGETATION IMEDIUM BROWN SANDY CLAY(CL) moist,medium stiff ISS = - 8 17.7 36 16 70.1 500. NONE I 5 soft below 5 feet I SS _ _2 26A I I 10 I OLIVE BROWN SANDY CLAY(CL) I SS_ =5 24.3 wet,soft I 1 MOTTLED BROWN ORANGE OLIVE 15 ICLAYSTONEISILTSTONE I SS 31 20.5 slightly hard,plastic,highly weathered i LESS WEATHERED WITH DEPTH I I 20 SS _ _ 41 19.3 BOTTOM OF BORING 20 FEET 6 INCHES. I I I 25 Earth Engineering Consultants I HORSETOOTH EAST-2nd FILING FORT COLLINS,COLORADO PROJECT NO:1942051 DATE: JULY 1994 LOG OF BORING B-2 SHEET 1 OF I tt :R :? w:> iti? II:i i::fs;.',k<:•-+t•,Z2;.:i wM WATER _ DEPTH ELEVRIGTYPE:CME 45 yy ;:•:. r'.,•..,,. io ti:i ?2.:h`.,.,,...,•.v'..Sa:....v:tiSd+ ^Si4v?i•.w:i:j ii' FOREMAN: SCK START DATE 7/8194 WHILE DRIWNG 8' AUGER TYPE: 4"CFA FINISH DATE 718I94 AFTER DRILLING 8' SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR WA I SOIL DESCRIPTION o N nu MC DO a UNITS a) SWELL TYPE-(FEET) (BLOWS/FT) (PSF)PCF) LL PI (%) .PRESSURE %e 500 PSF 5 INCHES TOPSOILNEGETATION I MEDIUM BROWN SANDY CLAY(CL) moist,medium stiff SS _ _ 8 14.6 5 soft below 5 feet L—_ _ 2 23.2 30 14 62A <500 NONE I 10IOLIVEBROWNSANDYCLAY(CL) I SS _ _ 4 22.0 wet,soft I SAND AND GRAVEL WITH COBBLES ZONES — _ wet,medium dense MOTTLED BROWN ORANGE OLIVE 15 I CLAYSTONEISILTSTONE I SS — — 34 22.7 slightly hard,plastic,highly weathered LESS WEATHERED WITH DEPTH I 20 SS 46 20.1 BOTTOM OF BORING 20 FEET 6 INCHES. I 25 Earth Engineering Consultants I HORSETOOTH EAST-2nd FILING FORT COLLINS,COLORADO PROJECT NO:1942051 DATE: JULY 1994 LOG OF BORING B-3 SHEET 1 OF 1 RIG TYPE:CME 45 Q*i 3;# :•.M.:§i 3< i.3§§iiiiNgiiiii i>,3?:'.<5##§§§ii ii§§iii WATER DEPTH ELEVItr5hh: }.. FOREMAN: SCK START DATE 718194 WHILE DRILLING 9' AUGER TYPE: 4'CFA FINISH DATE 718194 AFTER DRILLING 8' SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR NIA SOIL DESCRIPTION D N CM MC Do •a UMITs zoo SWELL TYPE (FEET) (BLOWS/PT) (PSF)PCF) LL PI PRESSURE %IN 500 PSF 5 INCHES TOPSOILNEGETATION 1 MEDIUM BROWN SANDY CLAY(CL) moist to medium stiff 1 I SS _ _8 22.5 5 soft below 5 feet I SS _ —2 27.2 1 10 I BROWN/GRAY SANDY GRAVEL/GP) I ss — = 17 12.0 wet,medium dense to dense I MOTTLED BROWN ORANGE OLIVE 15 1 CLAYSTONEISILTSTONE 1 SS 32 8.5 slightly hard,plastic,highly weathered BOTTOM OF BORING 15 FEET 9 INCHES. I 1 20 I 1 1 25 Earth Engineering Consultants I HORSETOOTH EAST-2nd FILING FORT COLLINS,COLORADO PROJECT NO::1942051 DATE: JULY 1994 LOG OF BORING.B-4 SHEET 1 OF 1 I O :TRACK RIG CME x:::":: ':':;::::tiri:'`.;'•:#;'t,i# s.om :iex.:.`: ` .:,..... WATER DEPTH ELEVRI .TYPE FOREMAN: SCK START DATE -_.___718l94 WHILE DRILLING 9' AUGER TYPE: 4"CFA FINISH DATE 7!8l94 AFTER DRILLING 9' SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR N/A I SOIL DESCRIPTION o N nu MC DO A-LOb0TS 200 SWELL TYPE (FEET) (BLOWS/FT) (PSF)PCF) LL PI. .. .(%) - PRESSURE. R SUO PSF 4 INCHES TOPSOILNEOETATION MEDIUM BROWN SANDY CLAY(CL) moist medium stiff to soft ISS _ _ 6 19.8 I 5 soft below 5 feet 1.SS _ _ 2 25.9 I r I 10, I BROWNIGRAYSANDY GRAVEL(GP) [ SS _ _ 18 17.2 saturated,medium dense to dense I SS - - 30 15.0 BOTTOM OF BORING 14 FEET 6 INCHES. 15 1 r I I 20 I 1 I 25 Earth Engineering Consultants IHORSETOOTH EAST-2nd FILING FORT COLLINS,COLORADO PROJECT NO:1942051 DATE: JULY 1994 I RIG TYPE:CME 45 FOREMAN: SCK LOG OF BORING B-5 iiiligiMi.M.Mni:ii:§:a:MEMSki.:MW.:;iiiiiia:K,;:igiin WATER SHEET 1°F 1 START DATE 718194 WHILE DRILUNG _ ( DEPTH 9' ... ELEV AUGER TYPE: 4"CFA FINISH DATE 718194 AFTER DRILLING 9' SPT HAMMER: MANUAL SURFACE ELEV 24 HOUR N/A I SOIL DESCRIPTION D N CM MC DO A-LSOTS 200 SWELL TY1. .E (FEET) (BLOWS/FT) .,_. (PSF)PCF) LL PI PRESSURE %e SOO PSF MEDIUM BROWN SANDY CLAY(CL) moist medium stiff to soft I FS7' -6 16.8 18 18 72.5 <500 psf NONE I Soft below 5 feet 5 2 I I 10 II $S — _ 18 24.1 I BROWN/GRAY SANDY GRAVEL(GP) saturated,medium dense to dense I 30 27.8 I 15 OLIVE BROWN CLAYSTONEISILTSTONE I slightly hard,plastic lightly weathered I I BOTTOM OF BORING 20 FEET. 20 II I I 5 Earth Engineering Consultants 1 DRILLING AND EXPLORATION DRILLING & SAMPLING SYMBOLS: I SS : Split Spoon - 13/4" I.D., 2" 0.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" 0.D. unless otherwise noted. PA : Power Auger FT : Fish Tail Bit I 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 DC : Dutch Cone II WB : Wash Bore Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2-inch 0.D. split spoon, except where noted. HWATER LEVEL MEASUREMENT SYMBOLS: WL : Water Level WS : While Sampling WCI : Wet Cave in WD : While Drilling I 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 groundwater. In low permeability soils, the accurate determination of groundwater levels is not possible with only short term observations. 11 DESCRIPTIVE SOIL CLASSIFICATION PHYSICAL PROPERTIES OF BEDROCK Soil Classification is based on the Unified Soil Classification DEGREE OF WEATHERING: system and the ASTM Designations D-2487 and D-2488. H Coarse Grained Soils have more than 50% of their dry Slight Slight decomposition of parent material on weight retained on a #200 sieve; they are described as: joints. May be color change. boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; Moderate Some decomposition and color change I they are described as: clays, if they are plastic, and silts if throughout. they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be High Rock highly decomposed, may be extremely added according to the relative proportions based on grain broken. size. In addition to gradation, coarse grained soils are defined on the basis of their relative in-place density and HARDNESS AND DEGREE OF CEMENTATION: fine grained soils on the basis of their consistency. Limestone and Dolomite: Example: Lean clay with sand, trace gravel, stiff (CL); silty Hard Difficult to scratch with knife. a sand, trace gravel, medium dense (SM). Moderately Can be scratched easily with knife, CONSISTENCY OF FINE-GRAINED SOILS Hard Cannot be scratched with fingernail. HUnconfined Compressive Soft Can be scratched with fingernail. Strength, Qu, psf Consistency Shale, Siltstone__and Claystone: 500 Very Soft Hard Can be scratched easily with knife, cannot 500 - 1,000 Soft be scratched with fingernail. 1,001 - 2,000 Medium 2,001 - 4,000 Stiff Moderately Can be scratched with fingernail. I 4,001 - 8,000 Very Stiff Hard 8,001 - 16,000 Very Hard Soft Can be easily dented but not molded with RELATIVE DENSITY OF COARSE-GRAINED SOILS: fingers. IN-Blows/ft 0-3 Relative Density Very Loose Sandstone and Conglomerate: 4-9 Loose Well Capable of scratching a knife blade. 10-29 Medium Dense Cemented II 30-49 Dense 50-80 Very Dense Cemented Can be scratched with knife. 80 + Extremely Dense Poorly Can be broken apart easily with fingers. ICemented w i3=z ;a4:j' a 1 1 UNIFIED SOIL CLASSIFICATION SYSTEM Soil Classification Criteria for Assigning Group Symbols end Group Names Using Laboratory Testsa Group Symbol Group Name Coarse-Grained Gravels more than Clean Gravels Less Cu > 4 and 1 < Cc <36 GW Well-graded ravel`Soils more than 50% of coarse than 5% fines° g 1 50% retained on No. 200 sieve fraction retained on No.4 sieve Cu < 4 and/or 1 > Cc > 36 GP Poorly graded gravelr Gravels with Fines Fines classify as ML or MH GM Silty gravel,G,Hmorethan12% fines° 1 Fines classify as CL or CH GC Clayey graver" tSands 50% or more Clean Sands Less Cu > 6 and 1 < Cc < 3E SW Well-graded sand' t of coarse fraction than 5% finest 1 passes No. 4 sieve Cu < 6 and/or 1 > Cc > 31 SP Poorly graded sand' Sands with Fines Fines classify as ML or MH SM Silty sand°"•' more than 12% fines° Fines Classify as CL or CH SC Clayey sandq"•i 1 Fine-Grained Soils Silts and Clays inorganic PI > 7 and plots on or above "A lines CL Lean clayKL'r 50% or more Liquid limit less passes the than 50 PI < 4 or plots below "A"line ML Silt`LM No. 200 sieve organic Liquid limit •oven dried Organic clay'L Mhl 0.75 OL Liquid limit -not dried Organic silt'•Lm•° i Silts and Clays inorganic PI plots on or above "A"line CH Fat clayut i u I Liquid limit 50 or more PI lots below "A" line MH Elastic Siltw' organic Liquid limit -oven dried Organic clay".." 0.75 OH Liquid limit -not dried Organic sitt''— O Highly organic soils Primarily organic matter,dark in color, and organic odor PT Peat ABased on the material passing the 3-in. Llf soil contains 15 to 29%plus No. 200, add I I( 75-mm) sieve f field sample contained cobbles or Cu-Daq/Dio Cc . D(Dx Dco with sand" or "with gravel", whichever is predominant. boulders, or both, add "with cobbles or Llf soil contains > 30%plus No. 200 i boulders, or both" to group name, predominantly sand, add "sandy" to group Gravels with 5 to 12%fines require dual Elf soil contains > 15% sand, add "with name. I symbols: sand" to group name. Elf soil contains > 30%plus No. 200, I' GW-GM well-graded gravel with silt If fines classify as CL-ML, use dual symbol predominantly gravel, add "gravelly" to grouptGW-GC well-graded gravel with clay GC-GM, or SC-SM. name. iGP-GM poorly graded gravel with silt If fines are organic, add "with organic fines" 'PI > 4 and plots on or above "A" line. GP-GC poorly graded gravel with clay to group name. PI < 4 or plots below "A"line.11 Sands with 5 to 12% fines require dual 'If soil contains > 15% gravel, add "with PPI plots on or above "A"line. symbols: gravel" to group name. PI plots below "A"line. SW-SM well-graded sand with silt If Atterberg limits plot in shaded area, soil is SW-SC well-graded sand with clay a CL-ML, silty clay. SP-SM poorly graded sand with silt t SP-SC poorly graded sand with clay 1 4 60 r 1 I For classification of tine-grained soils e and fine-grained fraction of coarse. 50 grained sous Equation of•A"-line Horizontal at PI . e to LL . 25.5. I V Of. men PI .0.73(LL•20) J 0`I` ep; IL 40 ILEquation of"U"•line 0Q` '-- - ------------• p Vertical al LL . 18 to PI ), z then PI .0.e(LL•e) G F 1, _- O t a i, G>' MH OR OH i 1)"•- 7. GL.MLd14'- I ' i MLoROL I o 0 10 16 20 30 40 50 60 70 8° 90 100 110 LIQUID LIMIT(LL) ji aJ t INC. 1 1