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HomeMy WebLinkAboutHORSETOOTH COMMONS PUD - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -HORSETOOTH COMMONS REPORT OFA GEOTECHNICAL INVESTIGATION FOR WILLIAMSBURG P.U.D. FORT COLLINS, COLORADO MR. KENT L. GOODMAN FORT COLLINS, COLORADO PROJECT NO. 6809-86 BY EMPIRE LABORATORIES, INC. 301 NORTH HOWES STREET FORT COLLINS, COLORADO 80521 A TABLE OF CONTENTS Table of Contents Letter of Transmittal ii Report 1 Appendix A A-1 Test Boring Location Plan A-2 Key to Borings A-3 Log of Borings A-4 Appendix B B-1 Consolidation Test Data B-2 Hveem Stabilometer Data B-3 Summary of Test Results B-4 Appendix C C-1 Empire Laboratories, Inc. P O.Box 503 • (303)484.0359 GEOTECHNICAL ENGINEERING&MATERIALS TESTING 301 No.Howes • For1Collin ,Colorado 80522 December 31 , 1986 Mr. Kent L. Goodman P. 0. Box 9014 Fort Collins, Colorado 80522 Dear Mr. Goodman: We are pleased to submit our Report of a Geotechnical Investigation prepared for the proposed streets and the Phase III portion of Williamsburg P.U.D. located at the northwest corner of South Shields Street and Horsetooth Road in southwest Fort Collins, Colorado. Based upon our findings in the . subsurface, we feel that the site is suitable for the proposed construction, providing the design criteria and recommendations 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, j J`4 C r i •.Fs C`... i\,...\EICNTE f.0EMPIRELAB0RATOES, I C. /' . y 237.) .`e 1; I.." AG 1\iR.rrod rs;)Senior Engineering Geologist w,';,o s: -c`-•i OFC.; :• . -j Reviewed by: 11t1111t(Illl/!/!/ c.r eGISTE-••. /j,!. Qs H i Chester C. Smith, P.E. 6; _ President 4808 ,.ii •Ri t• N ram.. CIC 1` '.O cl. *t cc: ZVFK , Architects/Planneri rS'• . c 32`F iek iaqr Branch Offices n P.O.Box 1135 P.O.Box 1744ice.( P.O.Box 10076 a1 Longmont,Colorado 60502 Greeley.Colorado 80632 Cheyenne,Wyoming 82003L.\303)776.3921 303)351.0460 307)632.922a Member of Consulting Engineers Council REPORT OF A GEOTECHNICAL INVESTIGATION SCOPE This report presents the results of a geotechnical evaluation prepared for the proposed streets and the Phase III portion of Williamsburg P.U.D. located north of Horsetooth Road and west of South Shields Street in southwest Fort. Collins, Colorado. The investigation• included test borings and laboratory testing of samples obtained from these borings. The objectives of this study were to (1 ) evaluate the subsurface conditions at the site relative to the proposed construction, (2) make recommendations regarding the design of the substructures, (3) recommend certain precautions which should be taken because of adverse soil and/or ground water conditions, and (4) make recommendations regarding pavement types and thicknesses for the proposed streets to be constructed at the site. SITE EXPLORATION The field exploration, carried out on December 26, 1986, consisted of . drilling , logging, and sampling six (6) test borings. The locations of the test borings are shown on the Test Boring Location Plan included in Appendix A of this report. Boring logs prepared from the field logs are shown in Appendix A. These logs show soils encountered, location of sampling , and ground water at the time of the exploration. Field resistivity tests were performed in selected areas throughout the site exploration. The borings were advanced with a four-inch diameter, continuous- type, power-flight auger drill. During the drilling operations, a geotechnical engineer from Empire Laboratories, Inc. was present and made continuous observations of the soils encountered. 1- I SITE LOCATION AND DESCRIPTION The proposed site consists of an area located north of Horsetooth Road and west of South Shield Street in southwest Fort Collins, Colorado. More particularly, the site is described as a portion of Williamsburg P.U.D. , situate in the Southwest 1/4 of Section 27 , Township 7 North, Range 69 West of the Sixth P.M. , City of Fort Collins, Larimer County, Colorado. The site consists of an undeveloped field vegetated with grass and weeds. The property is relatively flat and has minor drainage to the northeast. Existing residences are located north of Richard Drive, which is gravel surfaced and has been partially constructed. Open fields are located east of the existing project area, and an existing subdivision is located northwest of the site. LABORATORY TESTS AND EVALUATION Samples obtained from the test borings were subjected to testing in the laboratory to provide a sound basis for evaluating the physical properties of the soils encountered. Moisture contents, dry unit weights , unconfined compressive strengths, water soluble sulfates, pH, swelling potentials, and the. Atterberg limits were determined. A summary of the test results is included in Appendix B. Consolidation and Hveem stabilometer characteristics were also determined, and curves showing this data are included in Appendix B. SOIL AND GROUND WATER 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 and Fill Material: The majority of the site is overlain by a six (6) inch layer of silty topsoil. The topsoil has been penetrated by root growth and organic matter and 2- should not be used as a hearing soil or as a fill and/or backfill material. A two (2) foot layer of fill material was- encountered at the surface of Boring 1 . The fill was placed in conjunction with the existing gravel road and/or utilities adjacent to Shields Street. The fill consists of a mixture of silty clay and sandy silty clay. 2) Silty and/or Gravelly Silty Clay: This stratum underlies the topsoil in Borings 2, 3 and 4 and extends to depths one and one-half (1-1 /2) to two and one-half (2-1/2) feet below the surface. The silty clay is plastic, contains minor amounts of gravel and exhibits generally moderate bearing characteristics in its damp in situ condition. When wetted, the clay stratum exhibits slight to moderate swell potential. 3) Sandy and/or Sandy Gravelly Silty Clay: A layer of red sandy silty clay underlies the upper brown silty clay and extends beyond the depths explored. The lower silty clay stratum contains varying amounts of sand and gravel, lenses of sand and gravel and exhibits generally moderate bearing characteristics in its damp natural condition. 4) Ground Water: At the time of the investigation, no free ground. water was encountered at the site to the depths explored. Water levels in this area are subject to change due to seasonal variations and irrigation demands on and/or adjacent to the site. RECOMMENDATIONS AND DISCUSSION It is our understanding that the. Phase Ill portion of Williamsburg P.U.D. is to be developed for single-family residential construction. In addition, Richmond Drive, which has been classified as a commercial or collector street, will be constructed through the project area. 3- Charlamagne Drive; which has been classified as a residential street, will be located south of the Phase III portion of the project. Site Grading and Utilities Specifications pertaining to site grading are included below and in Appendix C of this report. It is recommended that the upper six (6) inches of topsoil below building, filled and paved areas be stripped and stockpiled for reuse in planted areas. The upper six (6) inches of the• subgrade below building, paved and filled areas should be scarified and recompacted two percent (2%) wet of optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78. See Appendix C.) Fill should consist of the on-site soils or imported material approved by the geotechnical engineer. Fill should be placed in uniform six (6) to eight (8) inch lifts and mechanically compacted two percent (2%) wet of optimum moisture to at least ninety-five percent 95%) of Standard Proctor Density ASTM D 698-78. In computing earthwork quantities, an estimated shrinkage factor of eighteen percent (18%) to twenty-three percent (23%) may be used for the on-site clay soils compacted to the above-recommended density. Utility trenches dug four. (4) feet or more into the upper clay soils should be excavated on stable and safe slopes in accordance with OSHA regulations, or the excavations should be properly shored. Where utilities are excavated below ground water, dewatering will be needed during placement of pipe and backfilling for proper construction. All piping should be adequately bedded for proper load distribution. Backfill placed in utility trenches in open and planted areas should be compacted in uniform lifts at optimum moisture to at least ninety percent (90%) of Standard Proctor Density ASTM D 698-78 the full depth of the trench. The upper four (4) feet of backfill placed in utility trenches under roadways and paved areas should be compacted at or near optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78, and the lower portion of these trenches should be compacted to at least ninety percent (90%) of 4 Standard Proctor Density ASTM D 698-78. Addition of moisture to - and/or drying of the subsoils may be needed for proper compaction. Stripping , grubbing , subgrade preparation, and fill and backfill placement should be accomplished under continuous observation of the geotechnical engineer. Field density tests should be taken daily in the compacted subgrade, fill , and backfill under the direction of the geotechnical engineer. Resistivity tests performed in the field and pH and water soluble sulfate tests performed in the laboratory indicate that the subsoils at the site are noncorrosive, and protection of utility pipe will not, in our opinion, be required. Foundations In view of the loads transmitted by the proposed residential construction and the soil conditions encountered at the site, it is recommended that the structures be supported by conventional-type spread footings and/or grade beams. All footings and/or grade beams should be founded on the original, undisturbed soil or on a structural fill extended to the undisturbed soil a minimum of thirty (30) inches below finished grade for frost protection. The structural fill should be constructed in accordance with the recommendations discussed in the Site Grading and Utilities" section of this report. The structural integrity of the fill as well 'as the identification and undisturbed nature. of the soil should be verified by the geotechnical engineer prior to placement of any foundation concrete. Footings and/or grade beams founded at the above levels may be designed for a maximum allowable bearing capacity of one thousand five hundred (1500) pounds per square foot (dead load plus maximum live load) . To counteract swelling pressures which will develop if the subsoils become wetted, all footings and/or grade beams should be designed for a minimum dead load of five hundred (500) pounds per square foot. The predicted settlement under the above maximum loading, as determined by laboratory consolidation tests , should be less than 5- three-fourths (3/4) inch, generally considered to be within acceptable tolerances. Basements and Slabs on Grade Since no free ground water was encountered at the site to the depths explored , it is our opinion that basement construction is feasible at the site. Basement excavations should be dug on safe and stable slopes. Subgrade below slabs on grade should be prepared in accordance with the recommendations discussed in the "Site Grading and Utilities" section of this report. All slabs on grade should be underlain by a minimum of four (4) 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. It is recommended that all slabs on grade be designed structurally independent of bearing members. Due to the expansive nature of the upper brown silty clay soils at the site, it should be noted that slabs on grade founded on this stratum may be subject to movement if upper clay layer becomes wetted. To minimize and control shrinkage cracks which will develop in slabs on grade, it is suggested that control joints be placed every fifteen (15) to twenty (20) feet and that the total area contained within. these joints be no greater than four hundred (400) square feet. Pavement Flexible Pavement It is our opinion that flexible pavement is suitable for the proposed street construction at the site. A flexible pavement alternate should consist of asphaltic concrete underlain by crushed aggregate base course and subbase or asphaltic concrete underlain by plant mix bituminous base course. Using the City of Fort Collins "Design Criteria and Standards for Streets" dated July 1986, a serviceability index of 2.5, a regional factor of 1 , an "R" value of 5 as determined by laboratory test 6- I I results, a twenty (20) year design life, an eighteen (18) kip equivalent daily load application of 15 for Charlamagne Drive and 25 for Richmond Drive, and weighted structural numbers of 2.75 and 3.0, respectively, the following pavement thicknesses are recommended: Wit:,')=%t 7,£-har1areagne• Drive 1"? Asphaltic Concrete 3" Crushed Aggregate Base Course 4" Select Subbase 10" Total Pavement Thickness 17" Asphaltic Concrete 2" Plant Mix Bituminous Base Course 53" Total Pavement Thickness 71." Richmond Drive Asphaltic Concrete 4" Crushed Aggregate Base Course 6" Select Subbase 5" Total Pavement Thickness 15" Asphaltic Concrete 2" Plant Mix Bituminous Base Course 6" Total Pavement Thickness 8" The select subbase should meet City of Fort Collins . Class 1 specifications, and the crushed aggregate base course should meet City of Fort Collins Class 5 or 6 specifications. The subgrade below the proposed asphalt pavement should be prepared in accordance with the recommendations discussed in the "Site Grading and Utilities" section of this report. Upon proper preparation of the subgrade, the subbase and base course should be placed and compacted at optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78. (See Appendix C.) 7- It is recommended that the asphaltic concrete and/or plant mix bituminous base course be placed in two (2) to three (3) inch lifts. All. plant mix bituminous base course and asphaltic concrete shall meet City of Fort Collins specifications and should be placed in accordance with these specifications. All subbase material shall have an "R" value between 50 and 69 , the crushed aggregate base course shall have an "R" value between 78 and 83, the plant mix bituminous base course shall have an Rt value of 90 or greater, and the asphaltic concrete shall have an Rt value of 95 or greater. The "R" value of the pavement materials used should be verified by laboratory tests. Field density tests should be taken in the aggregate base course, bituminous base course, and asphaltic concrete under the direction of the geotechnical engineer. Rigid Pavement A feasible pavement alternate at the site would be rigid pavement. Using the eighteen (18) kip equivalent daily load application described above, a modulus of subgrade reaction of one hundred (100) pounds per square inch per inch based on an "R" value of 5 , a design life of twenty 20) years, and concrete designed with a modulus of rupture of six hundred (600) pounds per square inch, the following minimum pavement thicknesses are recommended: Charlamagne Drive Nonreinforced Concrete - 5" Richmond Drive Nonreinforced Concrete - 51" Subgrade below proposed streets should be prepared in accordance with the recommendations discussed in the "Site Grading and Utilities" section of this report. Concrete pavement should be placed directly on the subgrade that has been uniformly and properly prepared in accordance with the above recommendations. All concrete used in the paving shall meet. ASTM specifications, and all aggregate shall conform to ASTM C-33 specifications. The concrete should be designed with a minimum modulus 8- of rupture of six hundred (600) pounds per square inch in twenty-eight 28) days. It is recommended that laboratory mix designs be done to determine the proper proportions of aggregates, cement, and water necessary to meet these requirements. It is essential that the concrete have a low water-cement ratio, an adequate cement factor, and sufficient quantities of entrained air. Joints should be carefully designed and constructed in accordance with the City of Fort Collins "Design Criteria and Standards for Streets" to ensure good performance of the pavement. It is recommended that all concrete pavement be placed in accordance with City of Fort Collins specifications. If paving is done during cold weather, acceptable cold weather procedures as outlined in the City specifications should be utilized. The concrete pavement should be properly cured and protected in accordance with the above specifications. Concrete injured by frost should be removed and replaced. It is recommended that the pavement not be opened to traffic until a flexural strength of four hundred (400) pounds per square inch is obtained or a minimum of fourteen (14) days after the concrete has been placed. 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 concrete exposed to subsoils. Slabs on grade subjected to de-icing chemicals should be composed of a more durable concrete with low water-cement ratios and higher air contents. 2) Finished grade should be sloped away from the structures on all sides to give positive drainage. Ten percent (10%) for the first ten (10) feet away from the structures is the suggested slope. 3) Backfill around the outside perimeter of the structures should be mechanically compacted at optimum moisture to at least ninety percent (90%) of Standard Proctor Density ASTM D 698-78. See Appendix C.) Puddling should not be permitted as a method of compaction. 9- 4) Plumbing and utility trenches underlying slabs and paved areas should be backfilled with an approved material compacted to at least ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78. Puddling should not be permitted as a method of compaction. 5) Gutters and downspouts should be designed to carry roof runoff water well beyond the backfill area. 6) Underground sprinkling systems should be designed such that piping is placed a minimum of five (5) feet outside the backfill of the structures. Heads should be designed so that irrigation water is not sprayed onto the foundation walls. These recommendations should be taken into account in the landscape planning. 7) Footing and/or grade beam sizes should be proportioned to equalize the unit loads applied to the soil and thus minimize differential settlements. 8) It is recommended that compaction requirements specified herein be verified in the field with density tests performed under the direction of the geotechnical engineer. 9) It is recommended that a registered professional engineer design the substructures and that he take into account the findings and recommendations of this report. GENERAL COMMENTS This report has been prepared to aid in the evaluation of the property and to assist the architect and/or engineer in the design of this project. In the event that any changes in the design of the structures or their locations are planned, the conclusions and recommendations contained in this report will not be considered valid 10- unless. said changes are reviewed and conclusions of this report modified or approved in writing by Empire Laboratories, Inc. , the geotechnical engineer of record. Every effort was made to provide comprehensive site coverage through careful locations of the test borings, while keeping the site investigation economically viable. Variations in soil and ground water conditions between test borings may be encountered during construction. In order to permit correlation between the reported subsurface conditions and the actual conditions encountered during construction and to aid in carrying out the plans and specifications as originally contemplated , it is recommended that Empire Laboratories, Inc. be retained to perform continuous construction review during the excavation and foundation phases of the work. Empire Laboratories, Inc. assumes no responsibility for compliance with the recommendations included in this report unless they have been retained to perform adequate on-site construction review during the course of construction. 11- APPENDIX A. TEST BORING LOCATION PLAN a„ , 0_. __r AT Delve- JeLA H 4, / 1 4_ 1,- . -- c-focrPe4jP4 441 1-11 1 licar,l4c1, 43. L I1 , A-2 KEY TO BORING LOGS TOPSOIL Fl• GRAVEL FILL SAND & GRAVEL I SILT i•• SILTY SAND& GRAVEL i 1771 CLAYEY SILT eo COBBLES SANDY SILT a• SAND,GRAVEL& COBBLES CLAY WEATHERED BEDROCK SILTY CLAY SILTSTONE BEDROCK SANDY CLAY l l CLAYSTONE BEDROCK 1 SAND C SANDSTONE BEDROCK SILTY SAND LIMESTONE OEM CLAYEY SAND K x GRANITE d SANDY SILTY CLAY 1 SHELBY TUBE SAMPLE STANDARD PENETRATION DRIVE SAMPLER WATER TABLE 5 DAYS AFTER DRILLING C. HOLE CAVED T 5/12 Indicates that 5 blows of a 140 pound hammer.falling 30 inches was required to penetrate 12 inches. A-3 LOG OF BORINGS EvA1iod Lb . I 105 11/12 Jam° 3/12 29/12 100 J• 15/12 i ! i 3/12 22/12 i 95 13/12 • ' 5/12 r 90 8/12 • •___ 85 A-4 LOG OF BORINGS 1 T J F.lo.' do.5 1.17.(o 7-.7-• 24/12 . ." r 105 23/12 V(./.•/.34/12 117/12 . ; 4/12 r 54/ J/ • S 18/12 > 100 T 19/12 9 ' 28/12 7 i• ./. G 24/12 i 95 4'.. 11/12 • •„ 1-- r 20 1-2. i/ 2::.4 90 85 A-5 APPENDIX B. CONSOLIDATION TEST pp..). 6839 360 BORING NO. : 6 DEPTH: 7 .064n DRY DENSITY: 1D1 .7 PCF MOc • • 21 .9TURE.62A 8nn 98n 56n 1.3 540 52 L71 9nn 460 A. 1 171. "5 n 9 1 . 0 APPLIED PRESSURE - TSF 4 . L-1.1 2 117.1 71 t74-11 J 8 A A 0.7.5 A 5 n APPLIED PRESSURE - TSF EMPIRE LFIBc)RATI,PIES INC . 3-2 CONSOLIDATION TEST PRO. 6809 E:ORING NO. : F 64n DEPTH: 7 .0 DRY DENSITY: 1 B 1 .7 PCF 2 t MOISTURE: 21 .911 600 58n li 561_1 5413 520 n. 1 0. 25 0. 5 1 . 0 5 10 APPLIED PRESSURE - TSF 4 .0 J I W 2 .0 F-1 1... A -4 .t_t H l n. 1 . 0.25 0. 5 1 .t_, 5 In APPLIED PRESSURE - TSF Er-1FIRE LAE;0R19T0RIE5 INC . B-2 RESISTANCE R—VALUE AND EXPANSION PRESSURE OF COMPACTED SOIL ASTM — D 2844 CLIENT: KENT GOODMAN PROJECT: WILLIAMSBURG PUD LOCATION OF SAMPLE: BORING 4 COMPOSITE @ 0. 5'-2. 5' SAMPLE DATA TEST SPECIMEN 1 2 3 COMPACTION PRESSURE — PSI 50 80 110 DENSITY — PCF 107. 6 109. 8 113. 6 MOISTURE — 19. 6 17. 7 16. 6 EXPANSION PRESSURE — PSI 0. 00 0. 00 0. 00 HORIZONTAL PRESSURE @ 160 psi 160 141 138 SAMPLE HEIGHT — ire. 2. 50 2. 50 2. 39 EXUD.ATIOIN PRESSURE — PSI 291 458 589 UNCORRECTED R—VALUE 0.0 7. 1 8. 5 CORRECTED R-:VALUE 0. 0 7. 1 8. 1 R—VALUE AT 300 PSI EXUDATION PRESSURE = . 7 100 l W6 n e J U:. 4 1_1 —a 2 —........._...... -:r.::: 11710• 200 001 4100 500 600 71010 1100 EXUDATION PRESSURE — psi EMPIRE LAE;ORATORIE5 INC. B-3 RESISTANCE R-VALUE AND EXPANSION PRESSURE OF COMPACTED SOIL ASTM — D 2844 CLIENT: TENT GOODMAN PROJECT: WILLIAMSBURG PUD LOCATION OF SAMPLE: BORING 4 COMPOSITE 0 0. 5'-2. 5' SAMPLE DATA TEST SPECIMEN 1 2COMPACTIONPRESSURE - PSI 50 80 110DENSITY - PCF 107. 6 109. 8 113. 6MOISTURE - % 19. 6 17. 7EXPANSIONPRESSURE -- PSI16. 0 0. 00 0. 00 0. 00HORIZONTALPRESSURE0160psi160141138SAMPLEHEIGHT - in. 2. 50 2.50EXUDATIONPRESSURE - PSI2. 39 UNCORRECTED R-VALUE 2914587. 1 589 0. CORRECTED R-VALUE0. 0 0 8. 0. 0 7. 1 8. 11 R-VALUE AT 300 PSI EXUDATION PRESSURE = . 7 100 80 60 J S h• U' 40 =......... ..... .. 20 100 8600 300 400 500 600 700 800 EXUDATION PRESSURE — psi EMPIRE LAEORATOF'IES INC . B-3 cr) el w O ONi O CO00Z7 co Iv 2 0 p 0 -0 0 . D to O40 D N I,4- J. O t0 A N /--•0 1A N r-+t0 A N 1-+O t0 A N -• tl1 O C) .O O CD CD CD O CD CD CD01 O O CDO —01I111I1IIIIIIIIIIIT-,,,N I-. 01 W N 4-4 (J1 W N I--. V1 W N N I-. 0, W N CDO CD O CD O CD O CD O O O O •CDCDCDOO J N) I-+ N N IJ §—. )--a 1-. 1-'' _ r-+ I.-,.3l00I--' CO O tp O 1-•O V N N 01 co• 0 N o soO1 N (i A O N to.) A W I. •• C...) N CO t0 (Ti ; f c m CD CD CD0 nwvVAOW11.7..t t0 01 0 O to o Ca t0 Ol t0 t0 N A 9COC) CT ma' O OD O CO C) `z-. m I—, 0 fn 3 • N Tc C O 2t m g r D coOp O c oOE. CDDOo„.cr CW1OlmT O r m Nm1^ V I 01 1' n l0 rn C. r IrN01rrCI) A CDg3•c w) 01 A a N IN) ii- 1) A COt0 7 N 11,a A Co Co A CO zO Ol t0 Com x-p I D1III 1IVVC) O1 01 1 1)47 CD« 1- I-. y_7ATiIo i P e r Si p.,iD N Co O Ti 3 y. 0 3 , N N r- N m a Co A W W (r.) 1-. T1 t71 t0 N o mCoO (.J N f. 0 a m rn to z o CD P 5' rD m 0 CD t A 00 V A (,,) t-•A CO V .A W t-+ S D O O O O O O O O O O O O _p s I I I I I I 1 I I I I I m m O F-• t0 co CT A N - lO Co Cn A N '•a 0- O O O O CD O O O O O D CD O a to Cu I- 3 Df O, I-- V O TAA C t-• -• A .ice N o- A A N.) V N I--'tO 'O V GO t--• CO v c m O Av O n„2 m<K f) N 0 N m•7 rho mT N N V) m O CD y: f C Tc 1 30• g Dm D CO) •< CO o O e W 0. O D a.m M O m 0 m N m v) V 77 z I m n Cl) C a v 2 IAo. x C T O o.oo x O n Dd CDCN y n=fl p o. 3 Clem f-' I--.I--'N.) N N.) 1 Lao m.1-• VD V APPENDIX C. I APPENDIX C. Suggested Specifications for Placement of Compacted Earth Fill and/or Backfills. GENERAL A geotechnical engineer shall be on-site to provide continuous observation during filling and grading operations and shall be the owner's representative to inspect placement of all compacted fill and/or backfill on the project. The geotechnical engineer shall approve all earth materials prior to their use, the methods of placing, and the degree of compaction obtained. MATERIALS Soils used for all compacted fill and backfill shall be approved by the geotechnical engineer prior to their use. The upper two (2) feet of compacted earth backfill placed adjacent to exterior foundation walls shall be an impervious, nonexpansive material. No material, including rock, having a maximum dimension greater than six (6) inches shall be placed in any fill. Any fill containing rock should be carefully mixed to avoid nesting and creation of voids. In no case shall frozen material be used as a fill and/or backfill material. PREPARATION OF SUBGRADE All topsoil, vegetation (including trees and brush) , timber, debris, rubbish, and other unsuitable material shall be removed to a depth satisfactory to the geotechnical engineer and disposed of by suitable means before beginning preparation of the subgrade. The subgrade surface of the area to be filled shall be scarified 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. C-2 r PLACING FILL No sod, brush, frozen or thawing material, or other unsuitable material shall be placed in the fill, and no fill shall be placed during unfavorable. weather conditions. All clods shall be broken into small pieces, and 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 a manner which will result in a uniformly compacted fill. Each layer shall be thoroughly blade mixed during spreading to ensure uniformity of material and moisture in each layer. Prior to compacting, each layer shall have a maximum thickness of eight (8) inches, and its upper surface shall be approximately horizontal. Each successive 6" to 8" lift of fill being placed on slopes or hillsides should be benched into the existing slopes, providing good bond between the fill and existing ground. MOISTURE CONTROL While being compacted , the fill material in each layer shall as nearly as practical contain the amount of moisture required for optimum compaction or as specified, and the moisture shall be uniform throughout the fill. The contractor may be required to add •necessary moisture to the fill material and to uniformly mix the water with the fill material if, in the opinion of the geotechnical engineer, it is not possible to obtain uniform moisture content by adding water on the fill surface. If,' in the opinion of the geotechnical 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 geotechnical engineer and as specified in the foregoing report as determined by applicable standards. Compaction shall be performed by rolling with approved tamping rollers, C-3 r pneumatic-tired rollers, three-wheel power rollers, vibratory compactors, or other approved equipment well-suited to the soil being compacted. If a sheepfoot roller is used, it shall be provided with cleaner bars attached in a manner which will prevent the accumulation of material between the tamper feet. The rollers should be designed so that effective weight can be increased. MOISTURE-DENSITY DETERMINATION Samples of representative fill materials to be placed shall be furnished by the contractor to the geotechnical engineer for determination of maximum density and optimum moisture or percent of Relative Density for these materials. Tests for this determination will be made using methods conforming to requirements of ASTM D 698, ASTM D 1557, or ASTM D 2049. Copies of the results of these tests will be furnished to the owner, the, project engineer, and the contractor. These test results shall be the basis of control for all compaction effort. i DENSITY TESTS The density and moisture content of each layer of compacted fill will be determined by the geotechnical engineer in accordance with ASTM D 1556, ASTM D 2167, or ASTM D 2922. Any material found not to comply with the minimum specified density shall be recompacted until the required density is obtained. Sufficient density tests shall be made and submitted to support the geotechnical engineer's recommendations. The results of density tests will also be furnished to the owner, the project engineer, and the contractor by the geotechnical engineer. C-4.•