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HomeMy WebLinkAboutHILL POND ON SPRING CREEK - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT - (2)REPORT OF A SOILS AND FOUNDATION INVL STICATION FOR PHIL RIDDELL & ASSOCIATES FORT COLLINS, COLORADO PROJECT NO. •1034-71 BY EMPIRE LABORATORIES, INC. 214 NORTH HOWES STREET FORT COLLINS, COLORADO SJ521 TABLE OF CONTENTS Table of Contents Letter of Transmittal ii Report 1-5 Test Boring Location Plan 6 Key to Borings 7 Log of Borings 8=.9 Consolidation Test Data 13-1.1 Summary of Test Results 12-13 Appendix A 14-15 i- 1 Empire Laboratories, Inc. Materials and Foundation Engineers i 11 November 1971 i Phil Riddell and Associates, Inc. 217 West Magnolia Street Fort Collins, Colorado 81)521 Dear Mr. Riddell: We are pleased to submit our Report of a Soils and Foundation Investi- gation prepared for the proposed Hill Pond on Spring Creek Subdivision, First Tailing.. in southeast Fort Collins, Colorado, as requested. Eased upon our findings in the subsurface, we feel that the site is suitable for the proposed construction, providing the design criteria and recommendations as set forth in this report are met. The accompanying report presents our findings in the subsurface and our recommendations based upon these findings. Very truly yours. EMPIRE LAF3ORATORIES, INC. ed c e Neil R. Sherrod Secretary jai Reviewed by: 0 1 Chester C. Smith, P. E. 7 4803 Vice President Y- 4' ,' 91F OF GO\ w' e0RA• 0 P,,..aP N g 2 1 OFFICE AND LABORATORY-214 NORTH HOWES • P.O.BOX 149 • FORT COLUNB,COLORADO 80521 • TELEPHONE AREA 303/484-03.59 g' r,i REPORT OF A SOILS AND FOUNDATION INVESTIGATION SCOPE This report presents the results of a soils and foundation investigation prepared for the proposed subdivision located on South Melds Street south of Prospect Street in Fort Collins, Colorado. The investigation was carried out by means of test borings and laboratory testing of samples obtained from these borings. The objectives of this investigation were to (i) determine the suitability of the site for construction purposes, (2) make recommenda- tions regarding the design of the substructures, and (3) recommend certain precautions which should be taken because of adverse soil and/or groundwater conditions. SITE INVESTIGATION The field investigation, carried out on October 19, 1971,. con- sisted of drilling, logging, and sampling five (5) test borings. The locations of the test borings are shown on the Test Boring Location Plan included on page 6 of this report. Boring logs prepared from the field logs are shown on pages 8 and 9 . These logs show soils encountered, location of sampling, and groundwater at the tine of the investigation. All borings were advanced with a four-inch diameter, continuous- type, power-flight auger drill. During the drilling operations, an engineering geologist from Empire Laboratories, Inc. , was present and made a continuous visual inspection of the soils encountered. SITE LOCATION AND DESCRIPTION The proposed site is located just south of Spring Creek and east of South Shields Street in Southwest Fort Collins, Colorado. More particularly, the site is described as a parcel of land situate in the Northwest 1/4 of Section 23, Township 7 North, Range 69 West of the 6th P. 11I. , Larimer County, Colorado. The site consists of relatively flat irrigated pasture land. It is currently under vegetation and has good positive drainage to the north- east to Spring Creek which flows eastward along the north edge of the site. LADDRATORY TESTS AND EXAMINATION Samples obtained from the test borings were subjected to testing and inspection in the laboratory to provide a sound basis for deter- ruining the physical properties of the soils encountered. Moisture contents, dry unit weights, unconfined compressive strengths, water soluble sulfates, and the Atterbe rg Limits were determined. A summary of the test data is included on pages 12 and 13 . Consolidation characteristics were also determined, and curves showing this data are included on pages 10 and 11. SOIL AND GROUNDWATER: CONDITIONS The soil profile at the site consists of strata of materials arranged in different combinations. In order of increasing depths, they are as follows: 1) Silty Topsoil: The entire site is overlain by a one- foot layer of silty topsoil. The upper six inches of the topsoil have been penetrated by plant roots and organic matter and should not be used as backfill or as a bearing soil. - 2) Sandy, Silty Clay: This stratum underlies the topsoil in the western portion of the site in the area of Boring 1, 2, and 3 and extends to depths of three and one-half to five feet below the surface. The silty clay contains varying amounts of sand, is slightly plastic, non-expansive, and exhibits low bear- ing characteristics in its moist natural state. 3) Silty Clay: A layer of silty clay underlies the upper sandy silty clays and the topsoil and extends to depths of eight to fourteen feet below the surface. The silty clays are plastic, non-expansive, and exhibit low bearing characteristics in their moist natural state. When wetted, the clays' shearing strengths are reduced and they consolidate readily. 4) Sand and Gravel: A layer of sand and gravel underlies the upper clay strata and extends to depths of fourteen to greater than fifteen feet below the surface. The gravels are clean, well graded, and exhibit moderate bearing capacities in their loose to medium dense natural state. 5) Siltstone (Bedrock): The bedrock stratum underlies the gravels and extends to depths of greater than fifteen feet below the surface. The bedrock encountered at this depth is highly weathered, and exhibits moderate bearing characteristics. 2- a 7) Gr ound ater: At the time of the investigation, free groundwater was encountered at depths of three and one-half to five and one-half feet below the surface. It should be noted. that these levels are subject to change depending upon seasonal variations, irrigational demands on adjacent properties, and the flow in Spring Creek. RECOMMENDATIONS AND DISCUSSION Foundation It is our understanding that the proposed structures are to be patio houses with conventional, crawl-space or slab-on-grade type of construction. In view of this and the soil and groundwater conditions encountered at the site, it is recommended that the substructures be supported by conventional-type, continuous, spread footings. All footings should be founded on original, undisturbed soil a minimum of thirty inches below finished grade for frost protection. The undisturbed nature of the soil should be verified by a soils engineer prior to placement of any foundation concrete. Footings at the above level may be designed for a maximum allowable bearing capacity of one thousand pounds (1, 000 ) per square foot (dead load plus maximum live load). The predicted settlement under the above maximum loading should be less than J. 75 inche generally considered to be within an acceptable tolerance. All slabs on grade should be underlain by a minimum of four inches of gravel or crushed rock devoid of fines. The gravel layer will act as a capillary break and will help to distribute floor loads. • Fill material supporting slabs on grade should be a granular-type material compacted at optimum moisture to at least ninety percent 30%) of standard proctor density. (See Appendix A. ) All floor slabs should be reinforced with reinforcing running through the construction joints. To minimize and control shrinkage cracks in the concrete slabs, it Is suggested that control joints be placed every 15 to 20 feet and that the total slab area contained within these construction joints be not greater than four hundred square feet. Streets Soils were classified, and group indexes were determined at various locations within the proposed subdivision for the purpose of developing criteria for the pavement design. Group indexes of the upper soils at the site range from 1. 0 to 7. 3. Using this as criteria for pavement design, it is recommended that pavement thickness for this type of soil be as follows: 3_ Residential Streets: 713 inches minimum total thickness 54 inches of base course 2 inches of asphaltic concrete Arterial Streets: /3 inches of minimum total thickness 6 inches of base course 2 inches of asphaltic concrete. I 3 All topsoil, organic matter and other deletrious materials should be stripped and removed from the street subgrade prior to placing any fill material or base course. All base course and asphaltic concrete should meet City Specifications and should be placed in accor- dance with these specifications. GENERAL RECOMMENDATIONS 1) Laboratory test results indicate that water soluble sulfates in the soil are negligible, and a Type I cement may be used in all concrete. 2) Finished grade should be sloped away from the structures on all sides to give positive drainage. It is suggested that ten percent for the first ten feet away from the structures be provided. 3) Backfill around the outside perimeter of the structures should be mechanically compacted at optimum moisture to at least eighty-eight percent (88%) of standard proctor density. Puddling should not be permitted as a method of compaction. (See Appendix A. ) 4) Gutters and downspouts should be provided on the structures in such a manner that water from the roof area is discharged well beyond the backfill area. 5) All plumbing and utility trenches underlying slabs and paved areas should be backfilled with an approved material compacted to at least ninety percent (90%) of standard proctor density. Puddling should not be permitted as a method of compaction. (See Appendix A. ) 6) An attempt should be made to proportion footing sizes in such a manner that the unit loads applied to the soil are nearly equal in order that differential settle- ments will be minimized. 7) It is recommended that all compaction requirements specified herein be verified in the field with density tests performed under the supervision of an expetienced soils engineer. 4- y 1.>< U00 SeI:.•y^ y4tV t v tv T:-y ZL ti di 30 of 3'Zl:w ri I?,,aii'1 IQ r 31 I°I,0o.J I I,I 4,' o Jl yi c ' R1 p, U.S N , Cr I l U '';, U • Un J to of l'' Ioh;~ I•c iaI °`l rI o' oleo oI vi 0 m ? JN Ia nI O n;tl N l o' 1 l C 0. n; n v jh ZF y - N I I`,, ' 1? „ 1, 0[._Z 1 a s° it • s rii 0 r °ISI 8. 1 ' , ,, ay. U c c e" WI" L. 0 v Pn ' I ' r8 1 .i a; I ' NN alb. Q Z2 ,. ' 1 QJ oZ0 I00N n. If Di DI0o V UpJ0 O Nj r°, p u yv01 r. 1-31 0 CI ,Q 0 f al n1".01 , NQ Oz' t ZJ)a V 0 il 11 o0_ Z Q da0l aQQzZ 1 Qil Z QJl`tZ„N 4i 01f- Q2 I- 0 F Jai r V3 rye ©A 1 - '°•? o Ada N r` a, 1t a ;' y a, n. u `ire 1 .4 o x s 9 ® a s ® P- o'`d ' ,, .L t ce 4 u e log i91a wa ,' 1 c ° s 1\K 1 °a m; 1 d'1 , is -' a 2 - A. o ,® e . 0a gym a o® 1' ',,`©i .n ; na N u'SEI- 1. O ot°.o t 1 J Ngoo '°_ _r oo?z _ J " w r sz°. 1 eon..., P..DO T t, I r 1 t,,il „ °e p y 8 o °0 o®; 8 y xam m©° z W n MINI 2 om s tov o S.. .> LT 1 1 iPl 19 21 1 S S O'1'- II—I S r-I 1y11 0 S J ocs avd^-c-f2 ,.o.- J.. n .,. -- . _ n KEY TO BORING LOGS IMMO FILL 6 s GRAVEL igN SILT a aI SAND & GRAVEL CLAYEY SILT P>SILTY SAND & GRAVEL as cc. a SANDY SILT o COBBLES Pa CLAY C c SAND, GRAVEL & COBBLES Nommi iummnggSILTYCLAY WEATHERED BEDROCKswim m. A SANDY CLAY SILTSTONE BEDROCK SAND CLAYSTONE BEDROCK 1007 mrs SILTY SAND SANDSTONE BEDROCK irarmA as Eli MI02rCLAYEYSAND LIMESTONE. El I SHELBY TUBE SAMPLE STANDARD PENETRATION DRIVE SAMPLER0 y WATER TABLE 24 HOURS AFTER DRILLING 5/12 indicates that 5 blows of a 140 pound hammer falling 30 inches was required to penetrate 12 Inches. 7- EMPIRE LABORATORIES,. INC. LOG OF BORINGS ELEVAT/ON NO/ NO a 03 100 4/12 • 95 3:n20 3/12 ;)17 20/12 1 1.._. l 90 v. 4/120 5/12 1 V12 v: a 85 e '• 22/12 • 4, iD/i2 80 NOTE: Temporary Benchmark t Shields Street opposite Northwest property corner. EMPIRE LABORATORIES, INC. R- LOG OF BORINGS ELEVATION N0+ N0 5 100 95 T<, • 5/12 4/12 90 7/12 / 7/12 a 'd 85 4 17/12 19/12 - ' '• 80 EMPIRE LABORATORIES, INC. 9- CONSOLIDATION TEST Note: Sample taken from boring No. 4 __E • 0 ' o -- 58 o o. o .54 I _ 0 r i I 50 a 0.1 0.5 1 5 10 50 100 APPLIED PRESSURE --- KIPS/SQ. FT. E'APiPF I ABOI AI RIES, IN(- 10- CONSOLIDATION TEST Note: Sample taken from boring No. __._.______5 ? 3. 0 ' 74 0 0 Ix ' . 70 0 O 0 Eh 0.1 0.5 1 5 10 50 100 APPLIED PRESSURE - - KIPS/SQ. 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C) t\ c2 • a v rI t.r) M n O KC z • H O •zr az 0 x if E1 raI w A Nr-IrI NO H c ) . • • cis 001fl O H U] d' V r I d' O z • H O Cr) az 0 as o Ea • a M U) E o CO N cV rh H 1-- pCJ • • • V Cl) 00 'd'C) CO H U) l0 N r-I r-i M I Ei. z J) H • H w ao Ei O z r.4 as O Iv U) b o Cl) 4-1 H N H aa 0 a 0 U 'r-I H E•+ 'b Uw dU) a U) U1 RS H 4-I • w rr coao w •r- 4 off, aaa 0 H a W U) Ei Ei a r=C U 13 MINE lk e j APPENDIX A Suggested Specifications for Placement of Compacted Earth Fills and/or Backfills • GENERAL A soils engineer shall be the owner's representative to inspect and control all compacted fill and/or compacted backfill placed 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. MATERIALS Soils used for all compacted fill beneath interior floor slabs shall be a granular, non-expansive type. Compacted earth backfill placed adja- cent to foundation walls shall be an impervious, non-expansive material. No material having a maximum dimension of greater than six inches shall be placed in any fill. All materials proposed for use in com- pacted fill and/or compacted backfill shall be approved prior to their use by the soils engineer. PREPARATION OF SUBGRADE All topsoil and vegetation shall be removed to a depth satisfactory to the soils engineer before beginning preparation of the subgrade. The subgrade surface of the area to be filled shall be scarified to a minimum depth of six 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. PLACING FILL No sod, brush, frozen material or other deletrious 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 to 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 inches; and its upper surface shall be approximately horizontal. 14- MOISTURE CONTROL The fill material in each layer, while being compacted, shall as nearly as practical contain the amount of moisture required for optimum compaction; and 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 compacted fill is too wet to permit adequate compaction, it shall be dried in an acceptable manner prior to placement and compaction. COMPACTION 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 D698-70). 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 sheepfoot roller is used, it shall be pro- vided with cleaner bars so attached as to prevent the accumulation of material between the tamper feet. The rollers should be so designed that the effective weight can be increased. MOISTURE - DENSITY DETERMINATION Samples of representative fill materials to be placed shall be furnished by the contractor to the soils engineer for determination of maximum density and optimum moisture for these materials. Tests for this determination will be made using methods conforming to requirements of ASTM D698-70. 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. DENSITY TESTS The density and moisture content of each layer of compacted fill will be determined by the soils engineer in accordance with ASTM D1556-68, D2167-66, or D2922-71. Any material found to not 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. 15-