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HomeMy WebLinkAboutSTONERIDGE PUD, THIRD FILING FINAL - 21 92G - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTM GEOTECHNICAL ENGINEERING REPORT STONE RIDGE VILLAGE P.U.D. 2ND, 3RD AND 4TH FILINGS FORT COLLINS, COLORADO ELI PROJECT NO. 20945023 A Division of The Terracon Companies, Inc. Terracon The Kaplan Company ELI Project No. 20945023 • Fill Material. A 1'/2 to 3'/2 foot layer of fill material was encountered at the surface of test borings 1 through 4. It is our understanding that this area has been overlot graded .and controlled fill placement activities were observed. The fill material consists of a homogeneous mixture of a sandy lean clay with gravel. • Topsoil. The area tested is Filing 4 is overlain by an approximate 6-inch layer of silty topsoil. The topsoil has been penetrated by root growth and organic matter and should not be used as a fill, backfill or bearing soil. • Lean Clay with Sand. This stratum underlies the fill material encountered in test boring Nos. 1 through 4, beneath the topsoil encountered in test borings drilled in Filing 4 and was encountered at the surface in test borings drilled in Filing 3. This clay stratum extends to the underlying soils encountered at depths of 2 Yz to 7 Y2 feet below the surface. The lean clay is brown, moist, moderate plastic and contains varying amounts of sand. • Sandy Lean Clay. This red, tan, cohesive clay stratum underlies the upper soils and extends to the gravel stratum encountered below and/or beyond the depths explored. The sandy lean clay material is moist to wet and moderate plastic and contains trace amounts of fine gravel. • Well Graded Sand with Gravel. This stratum was encountered in all test borings with the exception of Nos. 1 and 11 at depths of 10Yz to 14Y2 feet below the surface and extends beyond the depths explored. The gravel stratum varies from a silty sand with gravel to a relatively well graded sand with gravel with intermittent cobbles ranging in size up to 3 to 6 inches in diameter, is moist to wet and dense to very dense in -situ. Field and Laboratory Test Results: Field test results indicate that the clay soils vary from a medium stiff to stiff material in consistency. The sand soils vary from a medium dense to dense in relative density. The soils at anticipated foundation bearing depth have a moderate load bearing capability. Laboratory test results indicate that the clay subsoils at shallow depths have a low to moderate expansive potential. When water is added to compacted near -surface soils, the materials exhibit a low to moderate expansion potential. Groundwater Conditions: Groundwater was encountered at depths of 11 Ys to 14'/z feet in the majority of the test borings at the time of the field exploration. When checked 6 days after drilling, groundwater was measured at depths of 11 to 13Y2 feet. Three test borings were cased with 3-inch diameter PVC casing to allow for future groundwater monitoring. These observations n Terracon The Kaplan Company ELI Project No. 20945023 represent only current groundwater conditions, and may not be indicative of other times, or at other locations. Groundwater levels can be expected to fluctuate with varying seasonal and weather conditions. Based upon review of U.S. Geological Survey maps ('Hillier, et al, 1983), regional groundwater is expected to be encountered in unconsolidated alluvial deposits on the site, at depths ranging from 10 to 20 feet below the existing ground surface at the project site. Fluctuations in groundwater levels can best be determined by implementation of a groundwater monitoring plan. Such a plan would include installation of groundwater monitoring wells, and periodic measurement of groundwater levels over a sufficient period of time. The possibility of groundwater fluctuations should be considered when developing design and construction plans for the project. ICONCLUSIONS AND RECOMMENDATIONS General Considerations: Because of variations in the engineering properties of the on -site soils, foundation bearing levels, structural loads, and possible final grades, the following foundation systems were evaluated for use on the site: • conventional -type spread footings and/or continuous grade beams bearing on undisturbed soils; • conventional -type spread footings and/or continuous grade. beams bearing on .—, engineered fill. Design and construction recommendations for foundation systems and other earth connected phases of the project are outlined below. Foundation Systems: Due to the presence of low to moderate expansive soils on the site, conventional -type spread footing and/or continuous grade foundation systems bearing upon undisturbed soils and/or engineered fill material are recommended for support of the residential structures. The footings may be designed for a maximum bearing pressure of 2,000 pounds per square foot (psf). In addition, the footings the footings should be size to maintain a minimum dead 'Hillier, Donald E.; Schneider, Paul A., Jr.; and Hutchinson, E. Carter, 1983, Depth to Water Table (1976-1977) in the Greater Denver Area, Front Range Urban Corridor Colorado, United States Geological survey, Map 1-856-K. 5 1 Terracon The Kaplan Company ELI Project No. 20945023 0 load pressures of 500 psf. Exterior footing should be placed a minimum of 30 inches below finished grade for frost protection. Interior footings should bear a minimum of 12 inches above finished grade. Footings should be proportioned to minimize differential foundation movement. Proportioning on the basis of equal total settlement is recommended; however, proportioning to relative constant dead -load pressure will also reduce differential settlement between adjacent footings. Total or differential settlement resulting from the assumed structural loads are estimated to be on the order of % inch or less, provided that foundations are constructed as recommended. Additional foundation movements could occur if water from any source infiltrates the foundation soils; therefore, proper drainage should be provided in the final design and during construction. Footings, foundations, and masonry walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in masonry walls is recommended. Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantlyfrom those presented in this report, supplemental recommendations will be required. Basement Construction: Groundwater was encountered on the site at depths of 11 to 13'/z feet below the surface. Full -depth basement construction is considered feasible on the site provided recommendations in this section are followed. In view of the high moisture contents encountered at proposed basement depths and to reduce the potential for groundwater to enter the basement of the structures, it is recommended that a perimeter drain be installed around the lower basement area. The perimeter drain (dewatering system) should be constructed around the exterior of the basement foundation, and sloped at a minimum '/a -inch per foot to a suitable outlet, such as a sump and pump system. The drainage system should consist of a properly sized perforated pipe, embedded in free -draining gravel, placed in a trench at least 12-inches in width. Gravel should extend a minimum of 3-inches beneath the bottom of the pipe, and at least 2 feet above the bottom of the foundation wall. The gravel should be covered with drainage fabric prior to placement of foundation backfill. The underslab drainage layer should consist of a minimum 8-inch thickness of free -draining gravel meeting the specifications of ASTM C33, Size No. 57 or 67. R, Terracon The Kaplan Company ELI Project No. 20945023 Floor Slab Design and Construction: Low to moderately expansive subsurface soils with support the floor slab. Some differential movement of a slab -on -grade floor system is possible should the subgrade soils become elevated in moisture content. Such movements are considered within general tolerance for normal slab -on -grade construction. To reduce any potential slab movements, the subgrade soils should be prepared as outlined in the earthwork section of this report. Additional floor slab design and construction recommendations are as follows: • Positive separations and/or isolation joints should be provided between slabs and all foundations, columns or utility lines to allow independent movement. • Contraction joints should be provided in slabs to control the location and extent of cracking. Maximum joint spacing of 15 to 20 feet in each direction is recommended. • Interior trench backfill paced beneath slabs should be compacted in accordance with recommended specifications outlined below. • In areas subjected to normal loading, a minimum 4-inch layer of clean -graded gravel or crushed rock devoid of fines should be placed beneath interior slabs. • A minimum 8-inch layer of free -draining gravel should be placed beneath basement floor slabs in conjunction with the underslab drainage system for those residences where basement slabs are placed within a minimum of 3 feet or less above groundwater table. • Floor slabs should not be constructed on frozen subgrade. • Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1 R are recommended. Pavement Design and Construction: Traffic criteria for pavement thickness design for light traffic residential streets and cul-de-sacs include equivalent single -axle loads of 36,500. At the time of the site exploration, traffic data was not available for the proposed streets to be located within the fourth filing of the subdivision. When traffic data becomes available, additional pavement sections will be provided in an addendum to this report. 7 Terracon The Kaplan Company ELI Project No. 20945023 Design of pavements for the project have been based on the procedures outlined in the 1986 Guideline for Design of Pavement Structures by the American Association of State Highway and Transportation Officials (AASHTO). Areas within proposed pavements on the site will be divided into two categories based upon anticipated traffic and usage. Based upon AASHTO criteria, Colorado is located within Climatic Region VI of the United States. This region is characterized as being dry, with hard ground freeze and spring thaw. The spring thaw condition typically results in saturated or near -saturated subgrade soil moisture conditions. The AASHTO criteria suggests that these moisture conditions are prevalent for approximately 12- 1 /2% of the annual moisture variation cycle. Local drainage characteristics of proposed pavements areas are considered to be fair to good depending upon location on the site. For purposes of this design analysis, fair drainage characteristics are considered to control the design. These characteristics, coupled with the approximate duration of saturated subgrade conditions, results in a design drainage coefficient of 1.0 when applying the AASHTO criteria for design. For flexible pavement design of low volume traffic streets, a terminal serviceability index of 2.0 was utilized along with an inherit reliability of 70%. Using the correlated design R-value of 5.7, appropriate ESAL/day, environmental criteria and other factors, the structural numbers (SN) of the pavement sections were determined on the basis of the 1986 AASHTO design equation. In addition to the flexible pavement design analyses, a rigid pavement design analysis was completed, based upon AASHTO design procedures. Rigid pavement design is based on an evaluation of the Modulus of Subgrade Reaction of the soils (K-value), the Modulus of Rupture of the concrete, and other factors previously outlined. The design K-value of 100 for the subgrade soil was determined by correlation to the laboratory tests results. A modulus of rupture of 650 psi (working stress 488 psi) was used for pavement concrete. The rigid pavement thicknesses for each traffic category were determined on the basis of the AASHTO design equation. Recommended alternatives for flexible and rigid pavements for low volume, residential streets and cul-de-sacs are as follows: K i Terracon The Kaplan Company ELI Project No. 20945023 Recommended Pavement Section Thickness (inches) Asphalt Aggregate Plant - Mixed Portland Traffic Area (Light Alternative Traffic) Concrete Base Bituminous Cement Total Surface Course Base Concrete Low Volume A 3 8 11 B 2 4 6 Residential Streets & Cul-De-Sacs C 6 6 Each alternative should be investigated with respect to current material availability and economic conditions. In view of the subgrade soil conditions, and projected traffic, either full -depth asphalt or rigid concrete pavement sections should be considered in areas of main traffic corridors, drive bays or truck access. Rigid concrete pavement is recommended at the location of dumpsters where trash trucks will park and load. Aggregate base course (if used on the site) should consist of a blend of sand and gravel which meets strict specifications for quality and gradation. Use of materials meeting Colorado Department of Transportation Class 5 or 6 specifications is recommended. In addition, the base course material should be moisture stable. Moisture stability is determined by R-value testing which shows a maximum 12 point difference in R-values between exudation �. pressures of 300 psi and 100 psi. Aggregate base course material should be tested to determined compliance with these specifications prior to importation to the site. 4 Aggregate base course should be placed in lifts not exceeding six inches and should be compacted -� to a minimum of 95% Standard Proctor density (ASTM D698), within a moisture content range of 2 percent below, to 2 percent above optimum. Where base course thickness exceeds 6 inches, ® the material should be placed and compacted in two or more lifts of equal thickness. Asphalt concrete should be obtained from an approved mix design stating the Marshall or Hveem properties, optimum asphalt content, job mix formula, and recommended mixing and placing temperatures. Aggregate used in asphalt concrete should meet a particular gradation. Use of materials meeting Colorado Department of Transportation Grading C or CX specification is _1 recommended. The mix design should be submitted prior to construction to verify its adequacy. The asphalt materials should be placed in maximum 3-inch lifts, and should be compacted to a minimum of 95% Marshall or Hveem density (ASTM D1559). II 0 Terracon The Kaplan Company ELI Project No. 20945023 Plant -mixed bituminous base course should be composed of a mixture of aggregate, filler and additives if required, and approved bituminous material. The bituminous base should conform to an approved mix design stating the Marshall or Hveem properties, optimum asphalt content, job mix formula, and recommended mixing and placing temperatures. Aggregate used in plant -mixed bituminous base course should meet a particular gradation. Use of aggregates meeting Colorado Department of Transforation Grading G or C specifications is recommended. The mix design should be submitted prior to construction to verify it adequacy. The asphalt material should be placed in maximum 3-inch lifts, and should be compacted to a minimum of 95% Marshall or Hveem density (ASTM D1559). Where rigid pavements are used, the concrete should be obtained from an approved mix design with the following minimum properties: • Compressive Strength @ 28 days ................... 3750 psi minimum • Modulus of Rupture @ 28 days ........................ 650 minimum • Strength Requirements ................................ ASTM C94 • Minimum Cement Content ......................... 5.5 sacks/cu. yd. • Cement Type .................................... Type I Portland • Entrained Air Content ................................... 6 to 8% • Concrete Aggregate .................. ASTM C33 and CDOT Section 703 • Aggregate Size ................................. 1 inch maximum • Maximum Water Content ....................... 0.49 lb/lb of cement • Maximum Allowable Slump ............................... 4 inches Concrete should be deposited by truck mixers or agitators and placed a maximum of 90 minutes from time the water is added to the mix. Other specifications outlined by the Colorado Department of Transportation should be followed. Longitudinal and transverse joints should be provided as needed in concrete pavements for expansion/contraction and isolation. The location and extent of joints should be based upon the final pavement geometry and should be placed (in feet), at roughly twice the slab thickness (in inches), on center in either direction. Sawed joints should be cut within 24-hours of concrete placement, and should be a minimum of 25% of slab thickness plus 1/4 inch. All joints should be sealed to prevent entry of foreign material and dowelled where necessary for load transfer. Where dowels cannot be used at joints accessible to wheel loads, pavement thickness should be increased by 25 percent at the joints and tapered to regular thickness in 5 feet. 10 Terracon The Kaplan Company ELI Project No. 20945023 Future performance of pavements constructed on the clay soils at this site will be dependent upon several factors, including: • maintaining stable moisture content of the subgrade soils; and, • providing for a planned program of preventative maintenance. Since the clay soils on the site have shrink/swell characteristics, pavements could crack in the future primarily because of expansion of the soils when subjected to an increase in moisture content to the subgrade. The cracking, while not desirable, does not necessarily constitute structural failure of the pavement. The performance of all pavements, but in particular the recommended asphalt sections, can be enhanced by minimizing excess moisture which can reach the subgrade soils. The following recommendations should be considered at minimum: • Site grading at a minimum 2% grade away from the pavements; • Compaction of any utility trenches for lands aped areas to the same criteria as the pavement subgrade; • Sealing all landscaped areas in, or adjacent to pavements to minimize or prevent moisture migration to subgrade soils; • Placing compacted backfill against the exterior side of curb and gutter; and, • Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of base course materials. Preventative maintenance should be planned and provided for through an on -going pavement management program in order to enhance future pavement performance. Preventative maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment. Preventative maintenance consists of both localized maintenance (e.g. crack sealing and patching) and global maintenance (e.g. surface sealing). Preventative maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. 11 Terracon The Kaplan Company ELI Project No. 20945023 Recommended preventative maintenance policies for asphalt and jointed concrete pavements, based upon type and severity of distress, are provided in Appendix D. Prior to implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventative maintenance. Earthwork: • General Considerations: The conclusions contained in this report for the proposed construction are contingent upon compliance with recommendations presented in this section. Although underground facilities such as septic tanks, cesspools, basements, and utilities were not observed during site reconnaissance, such features might be encountered during construction. A 1'/2 to 3 foot layer of fill material was encountered in filing No. 2 in test borings 1 through 4. The fill material consists of a brown, sandy lean clay with gravel and is considered controlled structural fill material. • Site Clearing: 1. Strip and remove existing vegetation, debris, and other deleterious materials from proposed building and pavement areas. All exposed surfaces should be free of mounds and depressions which could prevent uniform compaction. 2. If unexpected fills or underground facilities are encountered during site clearing, such features should be removed and the excavation thoroughly leaned prior to backf ill placement and/or construction. All excavations should be observed by the geotechnical engineer prior to backfill placement. 3. Stripped materials consisting of vegetation and organic materials should be wasted from the site, or used to revegetate exposed slopes after completion of grading operations. 4. The site should be initially graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed building structures. 12 Terracon The Kaplan Company ELI Project No. 20945023 5. All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 12 inches, conditioned to near optimum ,moisture content, and compacted. • Excavation: 1. It is anticipated that excavations for the proposed construction can be accomplished cI with conventional earthmoving equipment. 2. Depending upon depth of excavation and seasonal conditions, groundwater may be encountered in excavations on the site. Pumping from sumps may be utilized to control water within excavations. Well points may be required for significant groundwater flow, or where excavations penetrate groundwater to a significant depth. • Slab Subarade Preparation: 1 . Where existing on -site clay soils will support floor slab, the soils should be scarified, moisture conditioned and compacted to a minimum depth of 12 inches. 2. A minimum 4-inch layer of clean -graded gravel or crushed rock devoid of fines should be placed beneath slabs. 3. A minimum 8-inch layer of free -draining gravel should be placed beneath basement floor slabs in conjunction with the underslab drainage system. • Pavement Subarade Preparation: 1. The subgrade should be scarified, moistened as required, and recompacted for a minimum depth of 12 inches prior to placement of fill and pavement materials. 2.. Due to the plastic nature of the subsoils, a need for subgrade stabilization is anticipated. On -site clay soils may pump or become unstable or unworkable at high water contents. Workability may be improved by scarifying and drying. Overexcavation of wet zones and replacement with granular materials may be necessary. Lightweight excavation equipment may be required to reduce subgrade pumping. 13 GEOTECHNICAL ENGINEERING REPORT STONE RIDGE VILLAGE P.U.D. 2ND, 3RD AND 4TH FILINGS FORT COLLINS, COLORADO ELI PROJECT NO. 20945023 Prepared for. THE KAPLAN COMPANY, INC. 1060 SAILORS REEF FORT COLLINS, COLORADO 80525 ATTN: MR. LES KAPLAN Empire Laboratories, Inc. 1 _ A Division of the Terracon Companies, Inc. Terracon The Kaplan Company ELI Project No. 20945023 3. Use of lime, fly ash, kiln dust, cement or geotextiles could also be considered as a stabilization technique. Laboratory evaluation is recommended to determine the affect of chemical stabilization on subgrade soils prior to construction. Lightweight excavation equipment may be required to reduce subgrade pumping. • Fill Materials: 1. Clean on -site soils or approved imported materials may be used as fill material for the following: • general site grading • exterior slab areas • foundation areas • pavement areas • interior floor slab areas • foundation backfill 2. Frozen soils should not be used as fill or backfill. 3. Imported soils (if required) should conform to the following: • Gradation (ASTM C136): percent finer by weight J' 6.. ........................................ 100 3.. ................................................ 70-100 No.4 Sieve I....................50-100 ..................... No. 200 Sieve ....................................... 35 (max) • Liquid Limit ......................................... 35 (max) • Plasticity Index ...................................... 15 (max) • Minimum R-value........................................... 6 4. Aggregate base should conform to Colorado Department of Transportation Class 5 or 6 specifications. • Placement and Compaction: J 1. Place and compact fill in horizontal lifts, using equipment and procedures that will y produce recommended moisture contents and densities throughout the lift. J. 14 i The Kaplan Company ELI Project No. 20945023 2. Uncompacted fill lifts should not exceed 10 inches loose thickness. 3. No fill should be placed over frozen ground. 4. Materials should be compacted to the following: Material On -site soils: Terracon Minimum Percent Compaction (ASTM D698) Beneath foundations .......................... I . 95 Beneath slabs ................................ 95 Beneath pavements ............................ 95 Utility construction ............................. 95 Utility construction in open sections ................. 90 Imported fill: Beneath foundations ............................ Ub Beneath slabs ................................ 95 Beneath pavements ............................ 95 Utility construction ............................. 95 Utility construction in open sections ................. 90 Miscellaneous backfill .................................. 90 5. If a well defined maximum density curve cannot be generated by impact compaction in the laboratory for any fill type, engineered fill should be compacted to a minimum of 80 percent relative density by determined by ASTM D4253. 6. On -site clay soils in foundation areas should be compacted within a moisture content range of optimum moisture to 2 percent above optimum. Imported soils should be compacted within a moisture content range of 2 percent below to 2 percent above optimum. In pavement sections, on -site clay soils should be compacted within a moisture content range of 2 percent below to 2 percent above optimum. 15 Terracon The Kaplan Company ELI Project No. 20945023 • Slopes: 1. For permanent slopes in compacted fill areas, recommended maximum configurations for on -site materials are as follows: Material Maximum Slope Horizontal:Vertical Cohesive soils (on -site clays) ........................ 2.1 Cohesionless soils ............................... 3:1 If steeper slopes are required for site development, stability analyses should be completed to design the grading plan. 2. The face of all slopes should be compacted to the minimum specification for fill embankments. Alternately, fill slopes can be over -built and trimmed to compacted material. • Compliance: Recommendations for slabs -on -grade, foundations and pavement elements supported on compacted fills or prepared subgrade depend upon compliance with "Earthwork" recommendations. To assess compliance, observation and testing should be performed under the direction of the geotechnical engineer. • Excavation and Trench Construction: Excavations into the on -site soils will encounter a variety of conditions. Excavations into the clays and bedrock can be expected to stand on relatively steep temporary slopes during construction. However, caving soils may also be encountered. The individual contractor(s) should be made responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottom. All excavations should be sloped or shored in the interest of safety following local, and federal regulations, including current OSHA excavation and trench safety standards. The soils to be penetrated by the proposed excavations may vary significantly across the site. The preliminary soil classifications are based solely on the materials encountered in widely spaced exploratory test borings. The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions. 16 The Kaplan Company Terracon ELI Project No. 20945023 As a safety measure, it is recommended that all vehicles and soil piles be kept to a minimum lateral distance from the crest of the slope equal to no less than the slope height. The exposed slope face should be protected against the elements. The contractor should retain a geotechnical engineer to monitor the soils exposed in all excavations and provide engineering services for slopes. This will provide an opportunity to monitor the soil types encountered and to modify the excavation slopes as necessary. It also offers an opportunity to verify the stability of the excavation slopes during construction. Drainage: J• Surface Drainage: 1. Positive drainage should be provided during construction and maintained throughout the life of the proposed project. Infiltration of water into utility or foundation excavations must be prevented during construction. Planters and other surface features which could retain water in areas adjacent to the building or pavements should be sealed or eliminated. 2. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of 7 approximately 10 percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of all construction debris to reduce the possibility of moisture infiltration. 3. Downspouts, roof drains or scuppers should discharge into splash blocks or extensions when the ground surface beneath such features is not protected by exterior slabs or paving. 4. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent to the foundation system should be minimized or 7 eliminated. • Subsurface Drainage: Free -draining, granular soils containing less than five percent fines (by weight) passing a No. 200 sieve should be placed adjacent to walls which retain earth. A drainage system consisting of either weep holes or perforated drain lines (placed near the base of the wall) should be used to intercept and discharge water which would tend to 17 Terracon The Kaplan Company ELI Project No. 20945023 saturate the backfill. Where used, drain lines should be embedded in a uniformly graded filter material and provided with adequate clean -outs for periodic maintenance. An impervious soil should be used in the upper layer of backfill to reduce the potential for water infiltration. Additional Design and Construction Considerations: • Exterior Slab Design and Construction: Exterior slabs -on -grade, exterior architectural features, and utilities founded on, or in backfill may experience some movement due to the volume change of the backfill. Potential movement could be .reduced by: • minimizing moisture increases in the backfill • controlling moisture -density during placement of backfill • using designs which allow vertical movement between the exterior features and adjoining structural elements • placing effective control joints on relatively close centers • allowing vertical movements in utility connections • Corrosion Protection: Results of soluble sulfate testing indicate that ASTM Type I Portland cement is suitable for all concrete on and below grade. However, if. there is no, or minimal cost differential, use of ASTM Type II Portland cement is recommended for additional sulfate resistance of construction concrete. Foundation concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 4. GENERAL COMMENTS It is recommended that the Geotechnical Engineer be retained to provide a general review of final design plans and specifications in order to confirm that grading and foundation recommendations have been interpreted and implemented. In the event that any changes of the proposed project are planned, the conclusions and recommendations contained in this report should be reviewed ,J and the report modified or supplemented as necessary. The Geotechnical Engineer should also be retained to provide services during excavation, grading, foundation and construction phases of the work. Observation of footing excavations should be performed prior to placement of reinforcing and concrete to conform that satisfactory bearing materials are present and is considered a necessary part of continuing geotechnical engineering services for the project. Construction testing, including field and laboratory evaluation of fill, backfill, pavement materials, concrete and steel should be performed to determine whether 18 Terracon The Kaplan Company ELI Project No. 20945023 applicable project requirements have been met. It would be logical for Empire Laboratories, Inc. to provide these additional services since we are most qualified to determine consistency of field conditions with those data used in our analyses. The analyses and recommendations in this report are based in part upon data obtained from the field exploration. The nature and extent of variations beyond the location of test borings may not become evident until construction. If variations then appear evident, it may be necessary to re- evaluate the recommendations of this report. Our professional services were performed using that degree of care and skill ordinarily exercised, under similar circumstances, by reputable geotechnical engineers practicing in this or similar localities. No warranty, express or implied, is made. We prepared the report as an aid in design of the proposed project. This report is not a bidding document. Any contractor reviewing this report must draw his own conclusions regarding site conditions and specific construction techniques to be used on this project. This report is for the exclusive purpose of providing geotechnical engineering and/or testing information and recommendations. The scope of services for this project does not include, either specifically or by implication, any environmental assessment of the site or identification of contaminated or hazardous materials or conditions. If the owner is concerned about the potential for such contamination, other studies should be undertaken. 19 A v.3 ANo.S s - Li :P.2 194o,4 0 EIL'W� T. V 647 o. vM, 13 S�aLE I'i = 3or�1 Empire Laboratories, Inc. A Division of The Terracon Companies, Inc. — Empire Laboratories, Inc. A Division of The Terracon Companies, Inc. P.O. Box 503 • 301 No. Howes Fort Collins, Colorado 80522 (303) 484-0359 FAX No. (303) 484-0454 Chester C. Smith, P.E. Neil R. Sherrod. C.P.G. February 17, 1994 The Kaplan Company, Inc. 1060 Sailors Reef Fort Collins, CO 80525 Attn: Mr. Les Kaplan Re: Geotechnical Engineering Report, Stone Ridge Village P.U.D. 2nd, 3rd and 4th Filings, Fort Collins, Colorado ELI Project No. 20945023 Empire Laboratories, Inc. (ELI) has completed a geotechnical engineering exploration for the proposed Stone Ridge Village P.U.D., 2nd, 3rd and 4th Filings to be located north of Horsetooth Road and east of County Road No. 9 in southeast Fort Collins, Colorado. This study was performed in general accordance with our proposal number D20942028 dated February 8, 1994. The results of our engineering study, including the boring location diagram, laboratory test results, test boring records, and the geotechnical recommendations needed to aid in the design and construction of foundations and other earth connected phases of this project are attached. The subsurface exploration indicated conditions which are typical of soils commonly found in the southeast Fort Collins area. The subsurface soils at the site consisted predominately of a lean clay with sand underlain by a sandy lean clay. The information obtained by the results of our field exploration and laboratory testing completed for this study, indicate that the soils at the site have a low to moderate expansive potential. The soils at anticipated foundation bearing depth have a moderate load bearing capability. Based on the geotechnical engineering analyses, subsurface exploration and laboratory test results, ces be supported on s is recommended that the proposed continuous grade bleam foe-familundat y resideonnsystems. Slab on gradenmay be utilized spread footings and/or co Wed that care is taken in the placement and compaction oft e for the interior floor system prov subgrade soil. Other design and construction details, based upon geotechnical conditions, are presented in the report. Geotechnlcal, Environmental and Materials Engineers Offices of The Terracon Companies, Inc. g Illinois: Bloomington, Arizona: Tucson ■ Colorado: Colorado Springs, Denver, Ft. Collins, Greeley.Lon moot ■ Idaho: BoisKanss: Lenexa, Topeka, Chicago, Rock Island ■ Iowa: Cedar Falls, Cedar Rapids, Davenport. Des Nebraska eLincoln, Omaha s, Storm Lake ■■ Nevada: Las Vegas Wichita ■ Minnesota: St. Paul ■ Missouri: Kansas City ■ Utah: Salt Lake City ■ Wyoming: Cheyenne ■ Oklahoma: Oklahoma City, Tulsa las N QUA ENGINEERING IEERING SINCE 1965 The Kaplan Company ELI Project No. 20945023 We have appreciated being of service to you in the geotechnical engineering phase of this project, and are prepared to assist you during the construction phases as well. If you have any questions concerning this report or any of our testing, inspection, design and consulting services, please feel free to contact us. Sincerely, EMPIRE LABORATORIES, INC. A Division of The Terracon Companies, Inc. , David A. Richer, P.E. Geotechnical Engineer �S'�irR C Reviewed by Chester C. Smith, P.E. Division Manager DAR/CCS/dmf Copies to: The Kaplan Company (3) RBD, Inc. (1) The Kaplan Company ELI Project No. 20945023 TABLE OF CONTENTS Page No. Letter of Transmittal................................................... i INTRODUCTION..................................................... 1 PROPOSED CONSTRUCTION ........................................... 1 SITEEXPLORATION .................................................. 2 2 Field Exploration ............................................... 2 Laboratory Testing 3 SITECONDITIONS ................................................... SUBSURFACE CONDITIONS ............................................ 3 3 Soil Conditions ..................:............................... 4 Field and Laboratory Test Results . 4 Groundwater Conditions .......................................... CONCLUSIONS AND RECOMMENDATIONS ................................. 5 General Considerations ........................................... 5 Foundation Systems ............................................. 5 Basement Construction ........................................... 6 Floor Slab Design and Construction .................................. 7 Pavement Design and Construction .................................. 7 Earthwork................................................... 12 General Considerations ..................................... 12 SiteClearing ............................................ 12 Excavation .............................................. 13 Slab Subgrade Preparation ................................... 13 Pavement Subgrade Preparation ............................... 13 Fill Materials ............................................ 14 Placement and Compaction .................................. 14 Slopes................................................. 16 Compliance............................................. 16 Excavation and Trench Construction ............................ 16 Drainage.................................................... 17 SurfaceDrainage ......................................... 17 SubsurfaceDrainage ....................................... 17 Additional Design and Construction Considerations ...................... 18 Exterior Slab Design and Construction .......................... 18 Corrosion Protection ....................................... 18 GENERAL COMMENTS ............................................... 18 The Kaplan Company ELI Project No. 20945023 TABLE OF CONTENTS (Cont'd) APPENDIX A Site Plan .............................................. Figure No. 1 Logs of Borings ......................................... Al thru A14 APPENDIX B R-Value....................................................... 131 Consolidation Test ...................................... 6 .. B2 thru 5 Summary of Test Results ................................... B6 thru B9 APPENDIX C: GENERAL NOTES Drilling & Exploration ............................................ C1 Unified Soil Classification ......................................... C2 Laboratory Testing, Significance and Purpose ........................... C3 Report Terminology ............................................. C4 APPENDIX D Recommended Preventative Maintenance -Asphalt Concrete Pavements ......... D1 Recommended Preventative Maintenance -Jointed Concrete Pavements ......... D2 in J GEOTECHNICAL ENGINEERING REPORT STONE RIDGE VILLAGE P.U.D. J 2ND, 3RD, 4TH FILINGS FORT COLLINS, COLORADO J ELI Project No. 20945023 INTRODUCTION This report contains the results of our geotechnical engineering exploration prepared for the proposed Stone Ridge Village P.U.D., 2nd, 3rd and 4th Filings, situate north of Horsetooth Road and east of County Road 9. The site is located in the south half of Section 21, Township 7 North, Range 68 West of the 6th Principal Meridian. J The purpose of these services is to provide information and geotechnical engineering recommendations relative to: • subsurface soil conditions • groundwater conditions • foundation design and construction • basement construction • floor slab design and construction • pavement design and construction • earthwork • drainage The conclusions and recommendations contained in this report are based upon the results of field and laboratory testing, engineering analyses, and experience with similar soil and structural conditions. PROPOSED CONSTRUCTION Based on information provided concerning construction at the site, it is our understanding the property is to be developed for single-family residential structures having conventional basement 1 construction. Final site grading plans were not available prior to preparation of this report. Ground floor level is anticipate at or slightly above existing site grades. Other major site development will include the construction of interior residential streets and cul-de- sacs. Design and construction of streets with residential and lightweight traffic designation in accordance with City of Fort Collins requirements are anticipated. J Terracon The Kaplan Company ELI Project No. 20945023 SITE EXPLORATION The scope of the services performed for .this project included a site reconnaissance by a geotechnical engineer, a subsurface exploration program, laboratory testing and engineering analyses. Field Exploration: A total of 14 test borings were drilled on February 1 1, 1994 to depths of 15 feet below the surface at the locations shown on the Site Plan, Figure 1. Twelve test borings were drilled in the center of proposed residential lots and two of the test borings were drilled in the area of the proposed cul-de-sac and residential street construction. All borings were advanced with a truck -mounted drilling rig, utilizing 4-inch diameter continuous -type power flight auger drills. It should be noted that two previous geotechnical engineering reports for proposed pavement sections for Stone Ridge Filing 2 and 3 were prepared by ELI in February, 1993 (ELI Project No. 20935030) and for filing No. 3, November, 1993 (ELI Project No. 20935273). The location of borings were positioned in the field by measurements from property lines and existing site features. Elevations were taken of the ground surface at each boring location by interpolation from contours intervals on the topographic maps supplied by REID, Inc. dated April 1993 and February 1994. The accuracy of boring locations and elevations should only be assumed to the level implied by the methods used to determine each. Continuous lithologic logs of each boring were recorded by the geotechnical engineer during the drilling operations. At selected intervals, samples of the subsurface materials were taken by means of pushing thin -walled Shelby tubes, or by driving split -spoon samplers. Representative bulk samples of subsurface materials were obtained from pavement borings. Penetration resistance measurements were taken with each sampling with the split -spoon by driving the sampler with a 140-pound hammer falling 30 inches. When properly interpreted, the penetration resistance is a useful index to the consistency, relative density or hardness of the materials encountered. Groundwater conditions were evaluated in each boring at the time of site exploration, and six days after drilling. Laboratory Testing: All samples retrieved during the field exploration were returned to the laboratory for evaluation by the project geotechnical engineer, and were classified in accordance with the Unified Soil Classification System described in Appendix C. At that time, the field descriptions were confirmed or modified as necessary, final boring logs prepared, and an applicable 2 Terracon The Kaplan Company ELI Project No. 20945023 laboratory testing program was formulated to determine engineering properties of the subsurface materials. Boring Logs for the project are presented in Appendix A. Selected soil samples were tested for the following engineering properties: • Water content • Expansion • Dry density • Plasticity • Consolidation • R-Value • Unconfined compressive strength • Soluble sulfate content The significance and purpose of each laboratory test is described in Appendix C. Laboratory test results are presented in Appendix B, and were used for the geotechnical engineering analyses, and the development of foundation and earthwork recommendations. All laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards. SITE CONDITIONS The site for the proposed development is divided into three filings. The second filing is presently under construction with single-family residential structures occupying a few of the lots and with residential streets presently in place. Filing No. 3 is currently under construction with site grading activities taking place. The area of filing No. 4 is presently a vacant tract of land vegetated with native grasses, weeds and sagebrush. The entire property is relatively flat and exhibits positive surface drainage in the east to northeast directions. Situate north of the site is the CSU Agronomy property consisting of pasture/grazing land. East of the property is County Road 9 and at the northeast portion the property is a detention pond. South of the site is Horsetooth Road with the English Ranch subdivision located beyond. West of the site is the Dakota Ridge residential subdivision with the new Fort Collins High School property beyond. SUBSURFACE CONDITIONS Soil Conditions: As presently on the Logs of Borings included in Appendix A, the subsurface soils encountered at the site are described in order of increasing depths. K]