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HomeMy WebLinkAboutHAMPSHIRE POND EAST PUD PRELIMINARY AND FINAL - 44 93C - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTof maximum density and optimum moisture for these materials. Tests for this determination will be made using methods conforming to requirements of ASTM D698. Copies of the results of these tests will be furnished to the contractor. These test results shall be the basis of control for' compaction effort. D E N S I T Y T E S T S The density and moisture content_,,,of.each layer of compacted fill s_ wi11 be determined by the soils. engineer in accordance with ASTM D1556 or D2167. Any material found not to comply with the minimum specified density shall be recompacted until the required density is obtained. The, results of all density tests will be furnished to both the owner and the contractor by the soils engineer. 4 optimum compaction. The moisture shall be uniform throughout the fill. The contractor may be required to add necessary moisture to the backfill material in the excavation if, in the opinion of the soils engineer, it is not possible to obtain uniform moisture content by adding water'on the fill surface. If, in the opinion of the soils engineer, the material proposed for use in the compaction is too wet to permit adequate compaction, it shall be dried in an acceptable manner prior to placement and compaction. C O M P A C T I O N When an acceptable uniform moisture content is obtained, each layer shall be compacted by a method acceptable to the soils engineer and as specified in the foregoing report as determined by the standard Proctor test (ASTM D698). Compaction shall be performed by rolling with approved tamping rollers, pneumatic -tired rollers, three -wheel power rollers, or other approved equipment well -suited to the soil being compacted. If a sheepsfoot roller is used, it shall be provided with cleaner bars attached in a manner which would prevent the accumulation of material between the tamper feet. The roller should be so designed that the effective weight can be increased. M O I S T U R E- D E N S I T Y D E T E R M I N A T I O N Samples of representative fill materials to be placed shall be furnished by the contractor to the soils engineer for determination 3 P R E P A R A T I O N O F S U B G R A D E All topsoil and vegetation shall be removed to a depth satisfactory to the soils engineer before beginning preparation of the subgrade. The subgrade surface oC the area to be filled shall be scarified to a minimum depth of six (6) inches, moistened as necessary, and compacted in a manner specified below for the subsequent layers of fill. Fill shall not be placed `on frozen or muddy ground. P L A C I N G F I L L No sod, brush or frozen material or other deleterious or unsuitable material shall be placed in the fill. Distribution of material in the fill shall be such as to preclude the formation of lenses of material differing from the surrounding material. The materials shall be delivered and spread on the fill surface in such a manner as will result in a uniformly compacted fill. Prior to compacting, each layer shall have a maximum thickness of eight (8) inches and its upper surface shall be relatively horizontal. M O I S T U R E C O N T R O L The fill material in each layer, while being compacted, shall as nearly as practical contain the amount of moisture required for j 2 f APPENDIX A Suggested Specifications for Placement of Compacted Earth Fills and/or Backfills. G E N E R A L A soils engineer shall be the owner's representative to supervise and control all compacted fill and/or compacted backfill on the project. The soils engineer shall approve all earth materials prior to their use, the methods of placing, and the degree of compaction obtained. A certificate of approval from the soils engineer will be required prior to the owner's final acceptance of the filling operations. M A T E R I A L S The soils used for compacted fill beneath interior floor slabs and backfill around foundation walls shall be impervious and non - swelling for the depth shown on the drawings. No material shall be placed for fill which has a maximum dimension of six (6) inches or greater. All materials used in either compacted fill or compacted backfill shall be subject to the approval of the soils engineer. 1 5UMMAiR**� Or- T E6T 5 Table No. Unconfined Standard Sample Hole Depth Moisture Dry % paesing Liquid Plasticity Compreaetve Penetration Deed tion p No. (ft.Jp Content f7b) �mm Limit Index Strength Teat (PCF�y CPSF) 1 5-6 6.7 20/12 Clayey sand 2 2-3 8.4 112.3 --- Clayey sand 2 3-4 5.9 12/12 Clayey sand 2 7-8 5.9 11/12 Clayey sand 2 15-16 16.6 12/12 Clayey sand 3 3-4 4.7 6/12 Clayey sand 3 9-10 3.6 31/12 Gravelly sand 4 5-6 3.6 25/12 Clayey sand 5 2-3 4.7. 107.9 --- Sandy clay 5 3-4 5.7 14/12 Clayey sand 5 7-8 5.6 21/12 Clayey sand 5 15-16 15.5 15/12 Sandy clay 3 8-9 -2.3 9.4 np np Gravelly sand 4 1-3 --- 21 np np A-2-4(0) I FOUNDATION 4 SOILS ENGINEERING Project No. 1163-20-01-01 FIG. 6 4 r% ME G-3RA 1N 51 ZE D 15TR1 BUT I ON CURVE O we w M ae r a v a ♦ w yr aw r w r i am H re.uraw a� TEST HOLE NO. 4_ CURVE A DEPTH (Ft-) 1-4 SAMPLE OF CLAYEY SAND a to 0 TEST HOLE NO. 3 CURVE B DEPTH (F!J 8-9 SAMPLE OF GRAVELLY SAND FOUNDATION 4 SOILS ENGINEERING JOB NO. 1163-30-01-01 FIGURE NO. 5 100 w 8m 10 60 60 40 30 20 10 6 4 2 Project No. 1163-30-01-01 LOAD (.Per) 6mm WOO BOW Inundated Test Pole No. 2 Sample \ Depth (Ft,) 2-3 Sample of CLAYEY SAND Moisture Content (96) 8.4 Dry Density (PCF) 1123 LOAD (psi) 500 1000 5000 wwo Inundated Test Pole No. 5 Sample \ Depth Cfta 2-3 Sample of SANDY CLAY, sl. gravelly Moisture Content l90 4.1 Dry Density (PC7) 101.9 6WELL -CONSOLIDATION TEST FOUNDATION 4 SOILS ENGINEERING FIGURE NO. 4 Elevation 1m3 (Feet) 1 M Oi�f NC- LOCHS NO.1 NO2 NO3 NOA NOB Elevation (Feet) 105 II ♦ '�12 ri 31. 12 2 Y12 '2/12 / ,san g,--sT -Qravelly,s.mos, / stiff, brown "/t2 SAND with lenses of clay t gravel, al. to v. moist, mad. drilled 6/18/95 All soil and/or rock contacts shown are approximate. FOUNDATION 4 SOILS ENGINEERING JOB NO. 1163-30-01-01 FIGURE NO. 3 es as :" '15 LE�ENE) of 5�rM5OL5 l Fill materials Caravel Sand Stlt Clay Weathered bedrock S(Itstone Glaystone Sandstone Limestone Igneous * Metamorphic rocks Symbols may be combined to represent mixtures. N Shelby sample Standard Penetration Test sample f Caroundwa ter level f 6/12 indicates that 6 blows of a 1400 hammer falling 30' was required to penetrate 12' FOUNDATION 4 SOILS ENGINEERINCa Project No.--I63-2o of-ol �u�a �u¢ TII�cIN 9.op.00,mN W} ' I p i i ti 1: ih�' �wtirtt)to nr of :t --Ci• 9t �e� F z N J i i y p i � I F 1 orcr Golk1 w5 �-fGYJ 50FRING LOCATION MAF FOUNDATION 4 SOILS ENGINEERING FIGURE NO. I The test holes drilled were spaced to obtain a reasonably accurate 4 picture of subsurface conditions for design purposes. These variations are sometimes sufficient to necessitate modifications f in design. The methods used for the analysis and recommendations for construc- tion on soils is not an exact science. Engineering judgement and experience in addition to the laboratory and field analysis are used to make these recommendations. Therefore, the recommendations and solutions made in this report cannot be considered risk -free and are not a guarantee of the performance of the structures. The recommendations included in this report are our best estimates of the measures that are necessary to help the proposed structures perform in a satisfactory manner. The contractor and owners should understand the risks of construction at this site. The contractor and owners must decide what level of risks and measures are acceptable. :3 We recommend that construction be observed by a qualified soils technician trained and experienced in the field to take advantage of all opportunities to recognize some undetected condition which might affect the performance of the foundation systems and pavement structure. 14 �.i I the hot bituminous pavement (HBP) shall meet Grading C or CX of Colorado Department of Transportation Standards and have a R,-value of 95. The remaining HBP shall meet Grading G or better of CDOT Standards and have an Rt-value of 95. All work shall be done in accordance "with City of'Fort Collins standards. Addition stabilization techniques of the subgrade may be required if conventional moisture control/compaction techniques will not result in a non -yielding subgrade. A proof -roll with heavy equipment is recommended to determine if any soft, yielding areas exist. Stabilization recommendations such as fly ash, lime, or geotextiles can be made if needed. G E N E R A L I N F O R M A T I O N The data presented herein were collected to help develop designs and cost estimates for this project. Professional judgments on design alternatives and criteria are presented in this report. These are based on evaluation of technical information gathered, partly on our understanding of the characteristics of the structure proposed, and partly on our experience with subsurface conditions in the area. We do not guarantee the performance of the project in any respect, only that our engineering work and judgments rendered meet the standard of care of our profession. 13 R-value of the Subgrade = 12.2 (MR = 7771) Serviceability Loss (Apsi) = 2.5 Design Life = 20 years Structural Coefficients Hot Bituminous Pavement (HBP) = 0.40 Aggregate Base Course (ABC) = 0.10 s Local (Water Blossom Lane) (DTN = 5, 18k ESAL = 36,500, Reliability Factor = 65%, Structural Number = 1.66) Option 1 Option 2 HBP 3" 5" ABC TOTAL 8" 5" All subgrade shall be scarified and recompacted to at least 95% of standard Proctor and recompacted at plus or minus two percent (+2%) of optimum moisture content. All Aggregate Base Course (ABC) shall meet Class 5 or 6 of Colorado Department of Transportation (CDOT) Standards and have an R-value of 72 or greater. All subbase shall meet Class 1 or better of CDOT Standards and have an R-value of 68 or greater. All subbase and aggregate base course shall be compacted to 95% of modified Proctor. The top two (2) inches of 12 I foundation walls should be well -cured, braced or subfloor installed __. prior to backfilling. Past experience has shown that severe damage could occur to the foundation walls if excessively expansive material is placed for backfill and allowed to become wet. The backfill placed immediately adjacent to the foundation walls, if not properly compacted, can be expected to settle with resulting damage to sidewalks, driveway aprons, and other exterior slabs -on - grade. To avoid settlement and disfigurement of the slabs in the event •that the backfill is not properly compacted, we recommend that. concrete slabs which must span the backfill be supported by the foundation walls. This is conventionally done by use of a brick ledge or haunch. Exterior slabs should not be dowelled to the foundation wall. The slab should be reinforced as necessary for the span involved. PAVEMENT RECOMMENDAT ION S It is our understanding that the roadway for the project will be paved utilizing a flexible pavement section. This pavement design was determined by using the 1990 Colorado Department of Transporta- tion's (CDOT) Roadway Design Manual and Pavement Analysis Software which utilizes the 1993 AASHTO "Guide for the Design of Pavement Structures." Other factors used for the design were based on City of Fort Collins criteria. The following criteria was used in the pavement section recommendations. 11 Finished grade should be sloped away from the structure on all sides to give positive drainage. A minimum of twelve (12) inches fall in the first ten (10) feet is recommended. Sprinkling systems should not be installed within ten (10) feet of the structure. Downspouts are recommended and should be arranged to carry drainage from the roof at least five (5) feet beyond. the foundation walls. 0 Plantings are not recommended around the perimeter of the founds- tions. However, if the owners are willing to accept the risks of foundation and slab movement, low water use plant (xeriscape) varieties could be used. A horizontal impervious membrane, such as polyethylene, should not be used next to the foundation wall. We recommend the use of a landscape fabric which will allow normal evaporation in lieu of a plastic membrane. All plants located next to the foundation should be hand watered only using the minimum amount of water. Backfill around the outside perimeter of the structure, except as noted above, should be compacted from optimum moisture to three percent (3$) above optimum moisture, and from eighty-five percent (85%) to ninety percent (90%) of Standard Proctor Density as determined by ASTM Standard Test D-698. The Backfill should be mechanically compacted in loose lifts not to exceed twelve (12) inches. Expansive soils and/or bedrock fragments should not be used for backfill materials. If imported material is used, the i soil should be relatively impervious and non -expansive. The 10 '7 1 ( slabs should be constructed using a sulfate resistant concrete f containing a Type I/II cement. S I T E G R A.D I N G A N D U T I L I T I E S Specifications pertaining to site grading are included below and in Appendix A of this report. It is recommended that the upper ten (10) inches of the subgrade below paved and filled areas be stripped and stockpiled for reuse in planted areas. The upper six (6) inches of the subgrade below paved and filled areas should be scarified and recompacted plus or minus two percent (±2%) of optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D-698-78 (See Appendix A of this report). Additional fill should consist of the onsite soil or imported materials approved by the geotechnical engineer. Fill should be placed in uniform six to eight (6-8) inch lifts and mechanically compacted plus or minus two percent (±2%) of optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D-698-78. L A N D S C A P I N G A N D D R A I N A G E Every precaution should be taken to prevent wetting of the subsoils and percolation of water down along the foundation elements. 9 4 The foundation walls and other structural elements should be designed by a qualified structural engineer for the appropriate loading conditions. All footings or pads should be placed below any topsoil or fill unless the fill has specifically been placed 1 and compacted for support of footings or pads. All exterior footings, pads, and grade beams should be placed below frost depth (thirty (30) inches in this area) to provide adequate cover for frost protection. F L O O R S L A B S Soils at proposed foundation elevations are stable at their natural moisture condition. However, should moisture contents of the upper F i clays increase, slight heaving may result. This phenomenon can result in heaving and/or cracking of the slabs -on -grade. With the above in mind, construction of the structure, as much as possible, should be done to accommodate movement of the slabs without damage. Slabs should be constructed "free-floating", isolated from all bearing members, reinforced with wire mesh (or equivalent), and jointed frequently. Slabs -on -grade in habitable or storage areas should be underlain with a four (4) inch layer of clean gravel or crushed rock to help distribute floor loads and provide a capillary break. Positive drainage should be provided for the gravel underlayment to prevent pooling of water beneath the slab. All 0 { 1. All footings, pads, and\or grade beams should be below frost r depth. Frost depth in this area is considered to be thirty (30) inches. 2. Foundation walls should be reinforced with rebar to span an unsupported length of ten (10) feet or between each pad. Rebar should be run continuously around corners and be properly spliced. Foundations should be designed by a Registered Engineer for the conditions described in this report. 3. Bearing walls should be omitted in the basement. Partitions - located over slabs -on -grade should be hung from the floor joists and beams supported by adjustable steel columns. A one (1) inch void should be constructed under all partition walls located over slabs. 4. All footings, pads, and/or grade beams should bear on similar strata. 5. We recommend the performance of an excavation inspection for each lot to make a final determination on foundation type. 6. All concrete shall be composed of Type I/II sulfate resistant cement. 7 F O U N D A T I O N R E C O M M E N D A T I O N S Spread Footings and/or Grade Beams Based upon conditions observed in the field, laboratory tests and the anticipated loading of the structure, we feel that the structure. should be supported by a continuous balanced spread footing and/or grade beam foundation. The footings and/or grade beams should be placed on the natural, undisturbed clays or sands. The footings should be designed for a maximum allowable bearing capacity of 1500 pounds per square foot (dead load plus 112 live load). If isolated areas of loose or soft soils are exposed during final footing excavation and open hole inspection, these soil areas should be removed down to undisturbed, acceptable soils prior to placement of the footings. Footings can then be placed directly upon the acceptable soil, or the excavation can be backfilled up to the desired footing bearing elevation. The fill should extend a minimum of three (3) feet beyond each side of any footings, pads or grade beams. All fill should be placed and compacted in accordance with the recommendations contained in the Section "Site Grading and Utilities", and Appendix A of this report. All fill shall be tested and approved by the Engineer. The following recommendations should be followed in the design of the foundation system: 6 s E. E S U B S U R F A C E C O N D I T I O N S Generally, a thin layer of sandy clay overlies sands with clay and gravel lenses to the depths explored. Free groundwater was not ' encountered in the borings. Clays' containing moderate amounts of sand and slight amounts of gravel were encountered in the upper one to two (1 - 2) feet of the borings. These deposits are of low plasticity, exhibiting low to moderate bearing capacities with little to no swelling when wetted. Sands containing lenses of clay and gravel were encountered from _._ below the upper, clays to the depths explored. These deposits exhibit low to moderate bearing capacities with no swell potential when wetted. Groundwater observations were made as the borings were being advanced and immediately after completion of the drilling opera- tion. At the time of our field investigation, groundwater was not encountered. The groundwater table can be expected to fluctuate throughout the year depending upon variations in precipitation, surface irrigation and runoff on the site. The ambient groundwater table at the site is not expected to rise to a level which would affect basement level construction unless a source of water not presently contributing becomes available. 5 stability characteristics. These include swelling, compres- sibility, collapse and shear strength of the soil and/or rock. One dimensional consolidation -swell tests were performed on selected samples to evaluate the expansive, compressive and collapsing nature of the soils and/or bedrock stratum. In the consolidation -swell test, a trimmed specimen is placed in a one- dimensional confinement ring and -a vertical load is applied. After seating, the sample is inundated with water and the height change of the specimen is recorded. The confining load is then incremen- tally increased until the specimen is compressed to its original volume. Results of those tests are presented at the end of this -- report. A calibrated hand penetrometer was used to estimate the approximate unconfined compressive strength of selected samples. The calibra- ted hand penetrometer has been correlated with unconfined compres- sion tests and provides a better estimate of soil consistency than visual examination alone. As part of the testing program, an R-value, Atterberg Limits and gradation analyses were conducted on selected samples to determine the plasticity and texture of the soils and to classify the soil in accordance with AASHTO Classification. n standard penetration tests are shown on each boring log. The transition between different strata can be and most often is gradual. An index of soils relative density and consistency was obtained by use of the standard penetration test, ASTM Standard Test D-1586. The penetration test result listed on the log is the number of blows required to drive the two (2) inch split -spoon sampler twelve (12) inches (or as shown) into undisturbed soil by a one hundred and forty (140) pound hammer dropped thirty (30) inches. Undisturbed samples for use in the laboratory were taken in three (3) inch O.D. thin wall samplers (Shelby), pushed hydraulically into the soil in accordance with ASTM D-1587. in this sampling procedure, a seamless steel tube with a beveled cutting edge is pushed hydraulically into the ground to obtain a relatively undisturbed sample of cohesive or moderately cohesive soil. All samples were sealed in the field and preserved at natural moisture content until time of test. L A B O R A T O R Y T E S T I N G P R O C E D U R E S The recovered samples were tested in the laboratory to measure their dry unit weights, natural water contents, and for classifica- tion purposes. Selected samples were tested for strength and 3 F I E L D I N V E S T I G A T I O N The field investigation consisted of five (5) borings at selected locations on the site. Distances.between borings are as indicated on the attached test boring location map, Figure 1. The borings were advanced using a four (4) inch diameter continuous flight power auger. All borings were continued to depths considered sufficient for the purposes of this report as set forth in the scope. The borings were laid out by Foundation & Soils Engineering, Inc. personnel based on a sketch provided by the client. Distances from the referenced features to the boring locations, as indicated on the attached diagram, are approximate and were made by pacing. Angles for locating the borings were estimated. Elevations of the borings are approximate and were obtained using a level and rod. The elevations were referenced to an assumed elevation of one hundred (100) feet using Test Hole No. 1. The approximate location of the benchmark is shown on the attached boring location map, Figure 1. The locations and elevations of the borings should be considered only to the degree implied by the methods used to make those measurements. Complete logs of the boring operations were compiled by a represen- tative of our firm as the borings were advanced. The approximate location of soil and rock contacts, free groundwater levels, and 2 S C 0 P E The following report presents the results of our subsurface investigation on Hampshire Ponds East P.U.D., Fort Collins, Colorado. This investigation was performed for Bret Larimer, Ltd. at the request of Mr. Bret Larimer. We understand the site is to be developed into multi -family townhomes. Construction is to be typical wood frame type and brick veneer and as such, should generate only light loading, on the order of 1,000 to 2,000 PLF. Concentrated loads, if any, should not exceed 15 to 20 KIPS. The purpose of this investigation is to identify subsurface condi- tions and to obtain test data to properly design and construct the foundation systems, floor slabs, and roadway pavement. The conclusions and recommendations presented in this report are based upon the acquired field and laboratory data and previous experience with similar subsurface conditions in the area. 1_ S I T E D E S C R I P T I O N The site is located in west Fort Collins, south of Drake Road on water Blossom Lane. The 3+ acre site is relatively flat and is vegetated with grasses and weeds. 1 TABLE OF CONTENTS Letter of Transmittal i Scope 1 Site Description 1 Field Investigation 2 Laboratory Testing Procedures 3 Subsurface Conditions 5 Foundation Recommendations 6 Floor Slabs 8 Site Grading and Utilities 9 Landscaping and Drainage 9 Pavement Recommendations 11 General Information 13 Test Boring Location Map Figure 1. Legend of Soil Symbols Figure 2 ' Boring Logs Figure 3 Consolidation Swell Tests Figure 4 Grain Size Distribution Curve Figure 5 Summary of Test Results Figure 6 Suggested Specifications for Placement Appendix A of Compacted Earth Fills and/or Backfills FOUNDATION Engineering, AND SOILS II Inc. l August 22, 1995 ,. commission No.: 1663-30-01-01 Bret Larimer, Ltd. 1600 Horsetooth Road Fort Collins, Colorado 80526 I Gentlemen: The enclosed report presents the results of a subsurface investigation for Hampshire Pond East P.U.D., Larimer County, Colorado. In summary, non -swelling soils were encountered in the borings. Although the site soils and/or rock are suitable for support of the proposed structures, care will be needed in both the design and construction of the buildings to minimize the potential for foundation and floor slab movement. The attached geotechnical report presents the results of our investigation and recommendations concerning design and construc- tion of the foundation system and support of floor slabs. We appreciate the opportunity to be of service to you on this project. If you have any questions, please feel free to call. Respectfully, Thomas W. Finley, Engineering Geologist Reviewed by: Kevin W. erson, '. FOUNDATION & SOILS E, TWF/jlb 2;�Eil�'f 100 East 3rd Street 9 Loveland, Colorado 80537 • (970) 663-0138 t i firm ✓.T' i}U >-: a ��� F " 7 t a !n'r�%' SUBSURFACE;INVESTIGATION FOR HAMPSHIRE POND EAST P.U.D. FORT COLLINS, COLORADO Prepared for Bret Larimer, Ltd. 1600 Horsetooth Road Fort Collins, Colorado 80526 August 22, 1995 Commission No.: 1163-30-01-01 Prepared By FOUNDATION & SOILS ENGINEERING, INC. CONSULTING ENGINEERS 100 East Third Street Loveland, CO 80537