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Home My WebLink AboutTHE LODGE AT MIRAMONT PUD - PRELIMINARY - 54-87AP - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTSUBSURFACE EXPLORATION REPORT THE LODGE AT MIRAMONT FORT COLLINS, COLORADO EEC PROJECT NO. 1992107 -- — — , — --T ;��, b �, r, , . � �!'�.':SMs . ., � , . ..,. . . . L �� E EC �� EARTH ENGINEERING CONSULTANTS, INC. �� r i � � n,4. - ri , � � .y .,�y _; �.,._�"`';�: ;:._� c �:.�` EARTH ENGINEERING CONSULTANTS, INc. September 11, 1999 Sollenberger Development Corporation P.O. Box 272469 Fort Collins, Colorado 80527 Attn: Mr. Mike Sollenberger Re: Subsurface Exploration Report The Lodge at Miramont Fort Collins, Colorado EEC Project No. 1992107 Mr. Sollenberger: Enclosed, herewith, are the results of the subsurface exploration completed by Earth Engineering Consultants, Inc. personnel for the referenced project. In summary, the subsurface soils encountered in the test borings consisted of low plasticity lean clay with varying amounts of silt and sand underlain by granular and essentially granular soils and/or sandy claystone bedrock. Groundwater was encountered at depths of approximately 4 to 8 feet below present site grades. Based on the materials we observed at the boring locations and our understanding of the proposed construction, it is our opinion the proposed lightly loaded multi-family residential structures could be supported on conventional footing foundation bearing in newly placed and compacted fill or in the very near surface cohesive materials. The low plasticity cohesive soils or properly placed and compacted fill could also be used for direct support of floor slabs and pavements for the proposed development. CENTRE FOR ADVANCED TECHNOLOGY 2301 RESEARCH BOULEVARD, SUITE I O4 FORT COLLINS, COLOR.QDO 80526 (970) 224- I 522 (F,nx) 224-4564 EEC Project No. 1992107 September 11, 1999 Page 2 Earth Engineering Consultants, Inc. Geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements are presented in the text of the attached report. If you have any questions concerning the enclosed 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 En ineering Consultants, Inc. ��,�:,, � _ ��,. ��;; �.� �� i�":E u��,� ��.� �� j� � `r•`+N O+ ��. ± � �'ra,�,L ��J�% : �s M�'�.`;� • l'��'�— -`'''�� " cc Mary Harnett - TST, Inc. Consulting Engineers Lester L. Litton, P.E. Principal Engineer LLL/dmf � � � � � SUBSURFACE EXPLORATION REPORT TI� LODGE AT NIIRAMONT FORT COLLINS, COLORADO EEC PROJECT NO. 1992107 September 11, 1999 � Lrl � � � � � � � L.�-I � �I � INTRODUCTION The subsurface exploration for the proposed Lodge at Miramont multi-family residential development to be constructed northwest of the intersection of Lemay Avenue and Boardwalk Drive in Fort Collins, Colorado, has been completed. Eleven (11) soil borings extending to depths of approximately 15 feet below present site grades were advanced in the proposed development area to obtain information on existing subsurface conditions. Individual boring logs and a diagram indicating the approximate boring locations are included with this report. The proposed development will include eleven (11) residential condominium buildings on approximately seven acres with detached garage/carport structures. The residential structures will be two or three-story, wood frame, slab-on-grade buildings. Foundation loads for the proposed structures are expected to be light with continuous wall loads less than 3 kips per lineal foot and column loads less than 70 kips. Floor loads are expected to be less than 100 psf. Paved drive and parking areas will be constructed as a part of the development. Two to four feet of fill is expected � across the site to develop final 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 geotechnical recommendations concerning design and construction of foundations and support of floor slabs and pavements. EXPLORATION AND TESTING PROCEDiTRES The boring locations were selected and established in the field by Earth Engineering Consultants, Inc. (EEC) personnel. The �eld locations were established by estimating angles and distances , � � EEC Project No. 1992107 September 11, 1999 Page 2 Earth Engineering Consultants, Inc. ,� � � � � � � � � from identifiable site references. The locations of the borings 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 CME 45-drill rig equipped with a hydraulic head employed in drilling and sampling operations. The boreholes were advanced using 4-inch nominal diameter continuous flight augers. Samples of the subsurface materials encountered were obtained using split-barrel and California barrel sampling procedures in general accordance with ASTM Specification D-1586. In the split-barrel and California barrel sampling procedures, standard sampling spoons are driven into the ground by means of a 140-pound hainmer falling a distance of 30 inches. The number of blows required to advance the samplers is recorded and is used to estunate the in-situ relative density of cohesionless soils and, to a lesser degree of accuracy, the consistency of cohesive soils and hardness of weathered bedrock. In the California barrel sampling procedure, relatively undisturbed samples are obtained in removable brass liners. All samples obtained in the field were sealed and returned to the laboratory for further examination, classification and testing. Moisture content tests were performed on each of the recovered samples. In addition, selected samples were tested for fine content and plasticity by washed sieve analysis and Atterberg limits � tests. Swell/consolidation tests were completed on selected samples to evaluate the subgrade materials tendency to change volume with variation in moisture content. Results of the outlined � tests are indicated on the attached boring logs and summary sheets. � 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 sample's texiure and plasticity. The estimated group symbol for the Unified '` Soil Classification System is shown on the boring logs and a brief description of that classification . system is included with this report. Classification of the bedrock was based on visual and tactual � observation of disturbed samples and auger cuttings. Coring and/or petrographic analysis may , reveal other rock types. 1 , � � � � � � � � � � �J � � � � � � � � EEC Project No. 1992107 September 11, 1999 Page 3 SITE AND SUBSURFACE CONDITIONS Earth Engineering Consultants, Inc. The development parcel is located north of Boardwalk Drive and west of Lemay Avenue in Fort Collins, Colorado. The project site is presently an undeveloped open field. Surface drainage at the site is generally towards the south and east with a maYimum difference of ground surface elevation across the site appearing to be on the order of 5 feet. Evidence of prior building construction was not observed at the project site by EEC field personnel. An EEC field engineer was on-site during drilling to direct the drilling activities and evaluate the subsurface materials encountered. Field descriptions of the materials encountered were based on visual and tactual observation of disturbed samples and auger cuttings. The boring logs included with this report may contain modifications to the field logs based on results of laboratory testing and engineering evaluation. Based on results of field and laboratory evaluation, subsurface conditions can be generalized as follows. Approximately 3 to 6 inches of vegetation and/or topsoil were encountered at the surface at the boring locations. The topsoil and/or vegetation were underlain by brown to light brown lean clay which contained varying amounts of silt, sand, and gravel. The cohesive soils were stiff to soft, exhibited low plasticity and extended to depths of approximately 3 to 11 feet. The cohesive materials were underlain in borings B-1, B-2, B-3, B-4 and B-9 by medium dense brown, granular to essentially granular materials with varying amounts of silt and clay. The granular materials included occasional zones of interbedded lean clay and sand. Those materials extended to depths of approximately 7 to 14 feet below present ground surface. Sandy claystone was encountered beneath the sandy lean clay and/or granular and essentially granular soils except in boring B-9 where the granular soils extended to the bottom of the boring. The claystone was soft to moderately hard and highly weathered to weathered. The borings were temunated at depths of approximately 15 feet in the sandy claystone bedrock. 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. � � � � � � � � I� � � � � � � � � � � , EEC Project No. 1992107 September 11, 1999 Page 4 GROUND WATER OBSERVATIONS Earth Engineering Consultants, Inc. Observations were made while drilling and after completion of the borings to detect the presence and level of free water. Free water was observed at depths ranging from approximately 12 to 14 feet when measured while and immediately after drilling. Based on those observations, previous data we have developed in this area and the moisiure content of the subgrade soils, we anticipate the measured water depths reflect the depth to hydrostatic groundwater at the time of drilling. Perched and/or trapped water may be encountered in more permeable zones in the subgrade soils at times throughout the year. Fluctuations in ground water levels and in the location and amount of perched water may occur over time depending on variations in hydrologic conditions, irrigation activities on surrounding properties, and other conditions not apparent at the time of this report. ANALYSIS AND RECOIVIMENDATIONS Site Preparation We understand 2 to 4 feet of fill will be placed over the entire site to develop site grades. All existing vegetation and/or topsoil should be removed from beneath fill, roadway or building subgrade areas. After stripping and completing all cuts and prior to placement of any fill, floor slabs or pavements, we recommend the exposed soils be scarified to a minimum depth of 9 inches, adjusted in moisture content and compacted to at least 95 % of the material's maximum dry density as determined in accordance with ASTM Specification D-698, the standard Proctor procedure. The moisture content of the scarified materials should be adjusted to be within the range of ±2 % of standard Proctor optimum moisture at the time of compaction. Fill soils required to develop the building areas or pavement subgrades should consist of approved, low-volume change materials which are free from organic maiter and debris. Normally, soils with a liquid limit of 40 or less and plasticity index of 18 or less could be used as low- volwne change fill. We recommend the fill soils contain sufficient fines to prevent ponding of water in the fill. Those fill soils should be placed in loose lifts not to exceed 9 inches thick, �� ' � � � � � � � � � � . a � � � � EEC Project No. 1992107 September 11, 1999 Page 5 Earth Engineering Consultanu, Inc. adjusted in moisture content as recommended for the scarified materials and compacted to at least 95 % of the material's standard Proctor maximum dry density. Care should taken after preparation of the subgrades to avoid disturbing the in-place materials. Positive drainage should be developed away from the structures and across and away from the pavement edges to avoid wetting of subgrade materials. Subgrade materials allowed to become wetted subsequent to construction of the residences and/or pavements can result in unacceptable performance of those improvements. Fill placement on this site will create settlement with consolidation of the underlying lean clay soils. The total settlement will vary with the depth of fill placed. We recommend fill placement occur well in advance of the construction of the structures or pavements to allow the settlement to occur prior to construction of the improvements. Footin� Foundations Based on materials observed at the boring locations, it is our opinion the proposed multi-family residences and garage structures could be supported on conventional footing foundations bearing on newly placed and compacted fill soils or stiff to very stiff natural sandy lean clay soils. For design of footing foundations bearing in acceptable natural site soils or newly placed and compacted fill as outlined above, we recommend 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 should include full dead and live loads. Soft zones were observed in the in-situ lean clay soils. Care should be taken during foundation construction to evaluate the anticipated bearing materials. If unacceptable materials are observed at that time, overexcavation and backfill. procedures may be necessary to develop acceptable foundation bearing. Those conditions can best be evaluated in the field during construction. � � � � � � � � � � � � � � � � � � � � � EF,C Project No. 1992107 3eptember 11, 1999 Page 6 Earth Engineering Consulrants, Inc. Exterior foundations and foundations in unheated areas should be located at least 30 inches below adjacent exterior grade to provide frost protection. We recommend formed continuous footings have a minimum width of 12 inches and isolated column foundations have a minimum width of 24 inches. Trenched foundations or grade beam foundations could be used in the near surface cohesive materials; however, the choice of fill soils may affect the suitability of these rypes of foundations. If used, we recommend trenched foundations have a minimum width of 12 inches and formed grade beam foundations have a minimum width of 8 inches. No unusual problems are anticipated in completing the excavations required for construction of the footing foundations. Care should be taken during construction to avoid disturbing the foundation bearing materials. Any materials which are loosened or disturbed by the construction activities or materials which become dry and desiccated or wet and softened should be removed and replaced or reworked in place prior to construction of the footing foundations. We estimate the long-term settlement of footing foundations designed and constructed as outlined above would be less than 1 inch. That estimate assumes fill placement well in advance of the building construction. Floor Slab Subgrades We recommend a11 existing vegetation/topsoil be removed from beneath the floor slab areas. After stripping and completing all cuts and prior to placement of any floor slabs or iill, the exposed subgrades should be scarified, adjusted in moisture content and recompacted as outlined in the "site development" section of this report. Fill soils required to develop the floor slab subgrades should consist of approved, low-volume change materials which are free from organic matter and debris. The near surface cohesive soils or similar borrow materials could be used for fill beneath floor slabs. Normally, low-volume change materials would have a liquid limit of 40 or less and plasticity index of 18 or less. Those materials should contain sufficient fines, material passing a#200 sieve, to prevent ponding of water in the fill. � � EEC Project No. 1992107 September 11, 1999 Page 7 Earth Engineering Consultants, Inc. � � � � Care should be taken after development of the floor slab subgrades to prevent disturbance of the in-place materials. Care will also be needed to maintain the moisture levels in the subgrades prior to floor slab construction. Materials which are loosened or disturbed by construction activities or materials which become wet and softened or dry and desiccated should be reworked prior to placement of the overlying floor slabs. Pavement Sub�rades All existing vegetation and/or topsoil should be removed from pavement areas. After stripping � and completing all cuts and prior to placement of any fill or pavements, we recommend the exposed soils be scarified to a minimum depth of 9 inches, adjusted in moisture content and � compacted to at least 95 % of the material's maximum dry density as determined in accordance with the standard Proctor procedure. The moisture content of the scarified soils should be � '�J � � � � � � adjusted to be within the range of ±2 % of standard Proctor optimum moisture. Fill materials required to develop the pavement subgrades should consist of approved, l�w-volume change materials, free from organic matter and debris. We recommend those fill soils be placed in loose lifts not to exceed 9 inches thick, adjusted in moisture content and compacted to at least 95 % of the material's standard Proctor maximum dry density. After completion of the pavement subgrades, care should be taken to prevent disturbance of those materials prior to placement of the overlying pavements. Soils which are disturbed by construction activities should be reworked in-place or, if necessary, removed and replaced prior to placement of overlying fill or pavements. Pavements We expect the site pavements will be used by low to moderate volumes of light vehicles, predominately automobiles and light trucks. The on-site lean clay subgrade soils have relatively low support capacity for pavements with "R" values in the range of 5 to 8 based on other testing � � � � � � � � � � � � � � � � � � � EEC Project No. 1992107 September 11, 1999 Page 8 Earth Engineering Consultants, Inc. we have completed nearby. The support capacity of bonow materials will vary with the material selected. For this analysis we have assumed materials similar to the site sandy lean clay. For the expected site soil conditions and anticipated traffic, we recommend the site pavement include 3 inches of hot bituminous pavement (HBP) overlying 6 inches of aggregate base coarse. The HBP should be consistent with City of Fort Collins requirements for grading C or CX materials. The aggregate base should be consistent with Class 5 or Class 6 materials. Other pavement sections could be considered and we would be pleased to provide alternate recommendations at your request. Thicker pavement sections would be needed in areas of heavy truck traffic such as trash truck routes and loading areas. Thinner sections may be possible with carefiil selection of off-site borrow. GENERAI. COMMENTS The analysis and recommendations presented in this report are based upon the data obtained from the soil borings performed at the indicated locations and from any other information discussed in this report. This report does not reflect any variations which may occur between borings or across the site. The nature and extent of such variations may not become evident until construction. If variations appear evident, it will be necessary to re-evaluate the recommendations of this report. It is recommended that the geotechnical engineer be retained to review the plans and specifications so 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 deterxnine that the design requirements are fulfilled. This report has been prepared for the exclusive use of the Sollenberger Development Corporation 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, . � � � EEC Project No. 1992107 September 11, 1999 . Page 9 Earth Engineering Consulrants, Inc. .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. � � ■ � � ■ � , � � , � , � L�--J � , . . � � . . . . . . � � . . � . . r . . s i � w � z w > Q � a � w J . BORING LOCATION DIAGRAM - THE LODGE @ MIRAMONT P.U.D. - LARIMER COUNTY, COLORADO . PROJECT N0:1992107 DATE: SEPTEMBER 1999 . EARTH ENGINEERING CONSULTANTS