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CF-Fire Station 1-SY080402 G E Consulting Services, Inc. Geotechnical, Materials and Environmental Engineering G E Consulting Services, Inc. Geotechnical, Materials and Environmental Engineering 2530 Electronic Lane Suite 710 Dallas, Texas 75220 214.351.5633 FAX 214.351.5680 www.gmeconsult.com April 2, 2008 City of Coppell- Fire Administration 500 Southwestem Boulevard Coppell, Texas 75019 Attn: Mr. Eric Greaser Deputy Chief Subject: Geotechnical Exploration PROPOSED STORAGE BUILDING FIRE STATION NO.1 520 Southwestem Boulevard Coppell, Texas GME Project No. 08.04.0062 Dear Mr. Greaser: GME Consulting Services, Inc. (GME) has completed the authorized subsurface exploration and geotechnical engineering evaluation for the above referenced project. The attached report briefly reviews our understanding of the project, presents our exploration procedures, describes existing site and subsurface conditions, and presents our evaluations, conclusions, and recommendations conceming geotechnical aspects of the project. The principal geotechnical issue at the site is the need to design the foundations and floor slab of the new storage building for the potentially expansive soils that underlie the site. The most common method for addressing expansive soils is by constructing the new storage building supported on drilled and underreamed shaft foundations (similar to the foundations for the existing Fire Station building) with the floor slab system either suspended above the existing soils or suppolied on improved sub grade soils. We have enjoyed working with you on this project and are prepared to assist you with any further questions you may have during the design or construction of the project. It is our recommendation that once the design team has reviewed the recommendations and floor slab preparation approaches presented, that a meeting be held with GME to discllss our findings. The meeting will help reduce the potential for misapplication of our design recommendations. Additionally as recommended within Section 6.0 of the report, the geotechnical engineer must be retained to review the plans and specifications at the appropriate time during the latter stages of the design so that comments can be provided regarding the interpretations and implementation of the geotechnical recommendations into the contract documents. Additionally, once design is complete, it is suggested that GME stay involved in the construction monitoring (especially through earthwork construction and foundation installation) to assist in the implementation of the design recommendations. Please contact us at (214) 351-5633 if you have questions about this report or when we may be of further servIce. "'-'~"" --i OF T.e- '\ Sincerely ~ ~ ............ ...;~ 't , pi' 6-,;-" .. * ":-f~. GME Consultin 'f- .e~' c . c. ."\ tr .'" : . . ~ ~ : ...........\...1 ' G'P,'ZIOLKOWSKI ~ .O.~fl~.O........."'....'..~~~ ~ "J.'~' 7574 .'~~ Dou s . ZlOlk~-t:'9"",,~I,.It ~~ .'~.1 Senior Vice Presi. ",' '~~~ ',~,o;,A\.. ~- Copies submitted: Addr~~m ~ President Geotechnical Exploration PROPOSED STORAGE BUILDING FIRE STATION NO.1 520 Southwestern Boulevard Coppell, Texas GME Proiect No. 08.04.0062 EXECUTIVE SUMMARY The following information is a summary of the findings and recommendations presented in the attached report. The attached report must be read in its entirety prior to the implementation into design and construction of this project. I. GME performed two (2) soil test borings at the project site. Both test borings (Borings B- I and B-2) were performed within the proposed storage building limits and were extended to depths of 30 to 50 feet below the existing ground surface. 2. Within the test borings, variable clayey and sandy soils were encountered. It appears that some unmapped terrace deposit or alluvial soils are present at the site. No residual soils derived from weathering of the underlying shale bedrock were encountered. Underlying the clayey and sandy soils is gray shale bedrock of the Eagle Ford Shale Formation. The gray shale bedrock was encountered at a depth of approximately 41 feet below the existing ground surface within test boring B-1 and extends to the termination depth of 50 feet. 3. Groundwater seepage was observed on the drilling rods at depths varying from 23 to 24 feet beneath the ground surface in the two test borings. Both test borings were checked for groundwater at completion and groundwater levels varying from 24 to 25 feet beneath the surface were recorded. Provided drilled and underreamed shafts are installed to the recommended depths, no temporary casing is anticipated to be required. Casing will be required if straight-shaft piers are selected for the foundation system on this project. 4. Laboratory test results indicate that the clayey soils encountered are highly to very highly plastic and have a low to high potential to be expansive. Based on the laboratory data, and our experience performing geotechnical explorations on sites within the same geologic formation, it is estimated that a potential vertical movement (PVM) varying from less than 2 inches to in excess of 3 inches, could occur beneath the new storage building, flatwork and pavement areas, if construction takes place after a long dry season and if the building is constructed at or near existing grade. If drainage is not properly controlled and the soils beneath the new building become saturated, then estimated potential vertical movements in excess of 3 to 4 inches in localized areas could be experienced. Foundation and floor slab recommendations have been provided which consider the expansive characteristics of the soils. 5. We understand that the eXIstmg fire station building is supported on a drilled and underreamed shaft foundation system. Based on the soil, rock and groundwater conditions encountered in our test borings, it is GME's recommendation that the new storage building be supported on a similar drilled and underreamed shafts foundation system with the drilled shafts bearing within the sandy lean clay soil materials. The storage building should be supported on drilled and underreamed shafts bearing at IS to 17 feet below the existing ground surface elevation for bearing capacity purposes. The underreamed shafts should bear on the reddish brown and gray, sandy lean clay soils found at these depths. The foundations should be designed for a maximum allowable end bearing pressure of 6,000 pounds per square foot (psf). An uplift soil pressure of 1,500 psf should be used in design of the drilled shafts acting over the top 10 feet of the shaft. Uplift resistance can be achieved by underreaming (belling) the base of the shaft to 2.5 to 3 times the shaft diameter. Total settlement of foundation elements should be less than 0.5 inch. 6. GME has provided alternative recommendations for constructing the floor slab of the proposed storage building. The most positive method is to construct the building on a suspended (elevated) floor slab system supported on the drilled and underreamed shafts as described within Section 4.4. An alternative floor slab system would be to construct the floor slab on modified subgrade materials. In order to reduce the potential for vertical movements to a design level of I inch or less below the storage building floor slab, GME has provided only one method for modifying the subgrade soil conditions utilizing a 1.5- foot thick layer of special fill material over 10 feet of electrochemically treated soil as described within Section 4.5 of this report. 7. For standard duty traffic, a concrete pavement section consisting of 5 inches of reinforced concrete underlain by 6 inches properly compacted, lime stabilized subgrade is recommended. For heavy duty pavement design, a reinforced concrete pavement section consisting of 7 inches of concrete underlain by 6 inches of compacted lime stabilized sub grade is recommended. Recommendations pertaining to pavement design and pavement subgrade preparation are provided within Section 4.6. 8. Consideration should be given to electrochemically injecting those shallow expansive soils likely to remain beneath critical flatwork areas adjacent to the new building. The purpose of injecting these materials is to both reduce the magnitude of the potential vertical movements beneath these areas of the site and to reduce the differential movement between the building slab and adjacent flatwork. GME can provide additional recommendations for further reducing the potential movements in these areas upon request. These recommendations and other design and construction recommendations are discussed in more detail in the attached report. 11 TABLE OF CONTENTS EXECUTIVE SUMMARy....................................................................................................... i 1.0 INTRODUCTION.............................................................................................................. 1 1.1 Project Information ..................................................................................................1 1.2 Purpose of Exploration............................................................................................l 1.3 Scope of Exploration................................................................................................ 1 2.0 EXPLORATION PROCEDURES .......... '" .... .... ..... ............ ...... ........ ............... ................3 2.1 Site Reconnaissance.... ..... ..... ....... .................... ..... ........... ..... ................. ....... .... .......3 2.2 Field Exploration ........ ..... ..... ...... ........ .... ............ ......... ........... ... ................ ....... .......3 2.3 Laboratory Testing...................................................................................................4 3.0 SITE AND SUBSURFACE CONDITIONS ........... ................................ ...... ...... .............5 3.1 Site Description........................................................................................................5 3.2 Area and Site Geology........ ............... .............................. ................... ................. ....5 3.3 Subsurface Conditions.............................................................................................6 3.4 Frost Depth............................................................................................................... 7 4.0 DESIGN RECOMMENDATIONS ..... ........... ............. ...... .... ....... ........ ............ ................8 4.1 Proposed Construction............................................................................................. 8 4.2 General Considerations............................................................................................ 9 4.3 Drilled and Underreamed Shaft and Grade Beam Foundation System .................10 4.4 Suspended Floor Slab ................................ ........................................................... .12 4.5 Floor Slab on Modified Subgrade..........................................................................13 4.6 Pavement Subgrade Preparation and Pavement Design ........................................16 4.7 Expansive PotentiaL............... .............................................................................. ..18 4.8 Drainage................................................................................................................ .19 4.9 Exterior Flat-work................................................................................................. .19 5.0 CONSTRUCTION RECOMMENDATIONS ...... ............... ..........................................21 5.1 Site and Subgrade Preparation ...............................................................................21 5.2 Pier Excavations.................................................................................................... .21 5.3 Fill Placement and Compaction.............................................................................22 5.4 Difficult Excavation.............................................................................................. .24 5.5 Electrochemical Pressure Injection ..................................................................... ..24 5.6 Groundwater Conditions....................................................................................... .25 6.0 QUALIFICATION OF RECOMMENDATIONS ........................................................27 APPENDICIES APPENDIX A Text Figures Figure 1 - Site Vicinity and Topographic Map Figure 2 - Site Geologic Map Figure 3 - Boring Location Plan APPENDIX B Field Results Records of Subsurface Exploration Sheets (Test Borings B-1 and B-2) Key to Symbols and Classifications- Soil & Rock APPENDIX C Laboratory Results Table 1 - Summary of Free Swell Test Results APPENDIX D Construction Procedures General Notes for Excavation and Trench Safety Guideline Specifications for Electrochemical Pressure Injection GEOTECHNICAL EXPLORA nON PROPOSED STORAGE BUILDING FIRE STATION NO.1 520 Southwestern Boulevard Coppell, Texas GME Project No. 08.04.0062 1.0 INTRODUCTION 1.1 Project Information This report presents the findings of our subsurface exploration and geotechnical engineering evaluation for the proposed storage building to be constructed at the City of Coppell Fire Station No. 1 located at 520 Southwestern Boulevard in Coppell, Texas. The new storage building will be a single-story detached building used for storage of support vehicles and other related equipment. The new building will be located adjacent to the northwest corner of the existing fire station building. 1.2 Purpose of Exploration The objective of this exploration was to explore the general subsurface conditions at the site and to analyze these conditions as they relate to foundation and floor slab design and construction for the new storage building and the associated new parking and drive areas. 1.3 Scope of Exploration Our scope of work included a site reconnaissance, soil test boring and sampling, laboratory testing, engineering evaluation of the field and laboratory data, and the preparation of this report. The services were provided in general accordance with our Proposal Number P08.04.0024 dated February 28, 2008 and was authorized by City of Coppell Purchase Order No. 08-0001685-000 dated March 3, 2008. Specifically, this report addresses the following: 1. Description of the existing site conditions. 2. A description of the area and site geologic and subsurface conditions. 3. Subsurface soil and rock stratigraphy and groundwater observations. 4. Recommendations for foundation design and construction including allowable capacities, estimated bearing levels, anticipated total and differential movement, and estimated potential vertical rise (PVR). Frost penetration depth is also provided. 5. Recommendations for support of floor slab systems on or above grade and recommended sub grade improvements to limit potential vertical movements to a desirable level of I-inch or less have been provided. 6. Recommendations for site preparation, earthwork, excavation bracing and/or sloping, sub grade stabilization, proofroIIing, groundwater control, difficult excavation etc., as required. This information includes a maximum plasticity index for select and non-select fill materials and analysis of the effect of weather and construction equipment on soil during construction. 7. Recommendations for pavement design and subgrade preparation for the anticipated traffic loads, including pavement sections. 8. Analysis of soils to ascertain presence of potentially expansive conditions. 2 2.0 EXPLORATION PROCEDURES 2.1 Site Reconnaissance The site and surrounding areas were visually evaluated by a senior geotechnical engineer from the GME office. His observations were used during the formulation of our recommendations to determine areas of special interest and to relate site conditions to known geologic conditions in the area. 2.2 Field Exploration Two (2) soil test borings were performed at the approximate locations shown on the Boring Location Plan (refer to Figure 3 in Appendix A). Both test borings (Borings B-1 and B-2) were performed within the proposed storage building limits and were extended to depths of 30 to 50 feet below the existing ground surface. Boring locations were determined by the GME senior geotechnical engineer and were established in the field by measuring distances and estimating right angles from existing site features. Existing overhead and subsurface utilities sometimes restrict boring locations; therefore, boring relocation is sometimes required. (Note: The test borings were drilled at the indicated positions on Figure 3 to avoid underground utility lines and to minimize damage to the property. No test borings were offset for this investigation). Representative undisturbed samples of the cohesive subsurface materials were obtained by hydraulically pressing 3-inch outside-diameter (O.D.) thin-wall tubes into the underlying soils at selected depths (ASTM D 1587). These samples were removed from the sampling tubes in the field and examined visually. One representative portion of each sample was sealed in a plastic bag for use in future visual examinations and testing in the laboratory. In addition, representative soil samples of the subsurface materials were obtained employing split-spoon sampling procedures (ASTM D 1586). Relatively disturbed samples were obtained at selected depths in the borings by driving a standard 2-inch O.D. split-spoon sampler 18 inches into the subsurface material using a 140-pound hammer falling 30 inches. The number of blows required to drive the split-spoon sampler the final 12 inches of penetration (N-Value) is recorded in the appropriate column on the logs. The underlying gray, sandy shale bedrock was tested using Texas Highway Department (THD) cone penetrometer test methods. The cone penetrometer test is performed by driving a three-inch diameter, 600 metal cone into the bedrock materials using an energy equivalent to 170-pound hammer falling 24 inches. The cone is driven with 100 blows of the hammer and the number of inches of penetration driven is then recorded. The THD values are provided on the boring logs provided within Appendix B. 3 The soil and rock descriptions and classifications are based on visual examination and should be considered approximate. Record of Subsurface Exploration Sheets (boring logs), which graphicaIly depict soil descriptions, penetration resistance, and observed groundwater levels, are included in Appendix B. 2.3 Laboratory Testing Natural moisture content tests (ASTM D 2216) and Atterberg limit tests (ASTM D 4318) were performed on selected samples to aid in classifying the subsurface materials and to determine the engineering characteristics of the materials. In addition, hand penetrometer and unconfined compression strength tests were performed on selected soil samples. Results of all laboratory tests described above are provided on the boring logs in Appendix B. Free SweIl Tests: The expansion properties of the upper clay layer were further analyzed by performing two free sweIl tests (ASTM D 4546). The free sweIl tests were performed by placing selected samples in consolidation machines with predetermined overburden pressures and all owing the samples to expand by absorbing water. When the samples exhibited very little tendency for further expansion, the final heights were recorded and the percent sweIl and total moisture gain calculated. The results of these tests are listed in Table 1 in Appendix C. Unconfined Compressive Strength Tests: Unconfined compressive strength tests (ASTM D 2166) were performed on selected soil samples in order to evaluate the potential allowable end bearing pressure design values. The results of these tests are listed on the appropriate boring logs provided in Appendix B. 4 3.0 SITE AND SUBSURFACE CONDITIONS 3.1 Site Description We understand that this project will consist of the design and construction of a new storage building. The building is to be constructed adjacent to the City of Coppell Fire Station No. 1 located at 520 Southwestern Boulevard in Coppell, Texas as shown on Figures 1 and 3 within Appendix A. The new storage building will be a single-story detached building used for storage of support vehicles and other related equipment. The storage building will be located adjacent to the northwest comer of the existing fire station building. We understand that the building will be approximately 4,900 square feet in size. The building will likely be constructed with steel framing and masonry veneer with either a suspended slab or a slab on modified sub grade. Some small new areas of pavement will also be constructed as part of the project and will connect into the existing pavements. At the time of the field investigation, the entire area where the new storage building is planned was found to be an open grass covered area. Some standing water was observed on the ground surface in a swaled area located to the north and west of the proposed building area. Based on the Site Vicinity and Topographic Map of the project area (refer to Figure 1 in Appendix A) and based on our visual observations, the site topography within the area of the new storage building is gently sloping downward from the southeast comer of the proposed building area to the north and to the west. It appears that the existing fire station building was graded to provide gentle positive drainage away from the building. Based on visual observations, there appears to be approximately 1 to 2 feet of gentle relief within the proposed building area. 3.2 Area and Site Geology According to regional geologic information, the project site is underlain by Cretaceous-age Eagle Ford Shale Geologic Formation (refer to Figure 2 in Appendix A). Within the test borings, variable highly plastic clayey soils and non-plastic sandy soils were encountered. It appears that some unmapped terrace deposit or alluvial soils are present at the site. The Eagle Ford Formation consists primarily of interbedded shales and clayey shales with thin limestone beds. It has a thickness of 200 to 300 feet and serves as a confining layer above the underlying water-bearing Woodbine Formation. The upper plastic soils encountered exhibit potentially moderately to highly expansive characteristics. The naturally developed soil profile maybe changed by erosion and/or grading activities, so that the upper, more weathered zones may be completely stripped away. Also, residual soils may be covered by washed-in alluvial soils, man-made fills, or both. In general, possible alluvial and terrace deposit clayey and sandy soil materials were encountered. 5 3.3 Subsurface Conditions Data from the soil test borings are shown on the Record of Subsurface Exploration Sheets (boring logs) included in Appendix B. A total of two (2) test borings were drilled at the approximate locations depicted on Figure 3 in Appendix A. The subsurface conditions discussed in the following paragraphs and those shown on the Record of Subsurface Exploration sheets are based on the soil test borings drilled at the site and represent an estimate of the subsurface conditions based on interpretation of the boring data using normally accepted geotechnical engineering judgements. We note that the transition between different soil strata is less distinct than those shown on the test boring records. 3.3.1 Clayey and Sandy Soils In general, fat clay and sandy lean clay materials were encountered from the existing ground surface down to depths of 18 to 19 feet. These materials are in turn underlain by variable, dense to very dense, fine to coarse sand seams, which extend down to the top of the underlying gray shale bedrock that is discussed in the following section. The upper clayey materials are primarily dark brown to brown to reddish brown and gray in color and are stiff to hard in consistency. The lower sandy materials are typically tan in color and exhibit a dense to very dense relative density. Again, the upper sandy and clayey soil strata appear to be unmapped alluvial or terrace deposit soils. The plasticity index (PI) of the clayey soils ranged from 34 to 54. The moisture contents of the soils tested ranged from 8 to 30 percent. The clayey soils tested had pocket penetrometer compressive strengths that ranged from 1.0 to over 4.5 tsf. The standard penetration test values for the sandy materials ranged from 43 to 57 blows for 12 inches penetration. 3.3.2 Shale Gray shale bedrock was encountered below the clayey and sandy soil materials. The depth to gray shale was approximately 41 feet beneath the existing ground surface within test boring B-1. The shale bedrock extends beyond the 50 feet depth explored in test boring B-1. The Texas Highway Department (THD) cone test of the shale bedrock indicated penetrations of 1.5 inches per 100 blows of the hammer. 3.3.3 Groundwater Standard continuous flight auger drilling techniques were used to advance the test borings. Groundwater seepage was observed on the drilling rods at depths varying from 23 to 24 feet beneath the ground surface in the two test borings. Both test borings were checked for groundwater at completion and groundwater levels varying from 24 to 25 feet beneath the surface were recorded. 6 It is our experience that groundwater seepage flow in this formation generally occurs through the pervious sand seams or along the interface of the shale bedrock layer. Groundwater may also be encountered flowing through joints or fractures in the clay strata or through more permeable seams within the shale bedrock. It should be noted that groundwater levels fluctuate seasonally depending on the amount of rainfall, prevailing weather conditions, and subsurface drainage characteristics, and may be different at other times. 3.4 Frost Depth The design frost depth in Dallas County, Texas is 12 inches. 7 4.0 DESIGN RECOMMENDATIONS The following design recommendations have been developed on the basis of the previously described project characteristics and subsurface conditions. If there is any change in the project criteria, a review should be made by this office to determine if any modifications in the recommendations will be required. 4.1 Proposed Construction We understand that this project will consist of the design and construction of a new storage building planned for construction at the City of Coppell Fire Station No. I located at 520 Southwestern Boulevard in Coppell, Texas. The new storage building will be a single- story detached building used for storage of support vehicles and other related equipment. This storage building will be located adjacent to the northwest comer of the existing fire station building. We understand that the building will be approximately 4,900 square feet in size. We anticipate that the building will be constructed with steel framing and masonry veneer with either a suspended slab or a slab on modified subgrade. Some small new areas of pavement will also be constructed as part of the project and will connect into the existing pavements. Based on the Site Vicinity and Topographic Map of the project area (refer to Figure 1 in Appendix A) and based on our visual observations, the site topography within the area of the new storage building is gently sloping downward from the southeast comer of the proposed building area to the north and to the west. It appears that the existing fire station building was graded to provide gentle positive drainage away from the building. Based on visual observations, there appears to be approximately 1 to 2 feet of gentle relief within the proposed building area. At the time this report was prepared, no information was provided to GME regarding the finished floor elevation of the proposed storage building. However, assuming the finished floor elevation of the new building will match the floor slab of the adjacent fire station building, then it is anticipated that less than 6 inches of cut and up to 2 feet of fill placement may be required to establish finish grades within the proposed storage building area. To confirm these assumptions and our related design recommendations, we recommend that GME be provided the proposed grading plan for our review and comment prior to issuing the final design documents for bidding purposes. The following conclusions and recommendations are based on our observations at the site, interpretation of the field and laboratory data obtained during this exploration, and our experience with similar subsurface conditions. Soil and bedrock penetration data, along with results of pocket penetrometer tests on the clays have been used to estimate allowable bearing pressures using previous correlations of penetration data and allowable foundation bearing pressures. Subsurface conditions in unexplored locations may vary somewhat from those encountered. If structure location, loadings or levels are changed 8 from the above understanding, we request that we be advised so that we may reevaluate our recommendations. 4.2 General Considerations The upper clayey soils encountered at the new storage building site location are considered highly to very highly plastic and can be considered to have a low to high expansive potential. The site soils will experience vertical movements as a result of soil moisture content changes that will occur beneath areas of the site covered by the proposed building floor slab, flatwork and pavements. The soils currently have natural moisture contents near the plastic limit to wet of the plastic limit and are also stiff to hard in consistency. Based on the laboratory data, and our experience performing geotechnical explorations on sites within the same geologic formation, it is estimated that a potential vertical movement (PVM) varying from less than 2 inches to in excess of 3 inches, could occur beneath the new storage building, flatwork and pavement areas, if construction takes place after a long dry season and if the building is constructed at or near existing grade. If drainage is not properly controlled and the soils beneath the new building become saturated, then estimated potential vertical movements in excess of 3 to 4 inches in localized areas could be experienced. Similar soil related movements should be anticipated beneath flatwork, pavements and other covered elements of the project. In our opinion, we feel that a drilled and underreamed shaft foundation and grade beam foundation system with shafts bearing within the sandy lean clay soil layer is the most practical foundation system for the proposed storage building structure. We understand that the existing fire station building is supported on a drilled and underreamed foundation system. The new foundation system is anticipated to perform similarly to the existing building. Recommendations for a drilled and underreamed shaft foundation system are given in Section 4.3 of this report. As an alternative to utilizing drilled and underreamed shafts, the use of drilled straight shafts bearing within the shale bedrock were also initially considered. However due to the depth to the bearing strata, the sandy nature of the lower soils and the presence of groundwater, temporary casing would be required to install the drilled straight shafts. The use of steel casing would substantially increase the cost of foundation construction for the project. As such, this type of foundation system was not considered further by GME. If the client or design team desires recommendations for a straight shaft foundation system, GME would be glad to provide additional recommendations. Associated with the pier and beam foundation system, we considered two methods of floor system construction for the new storage building. These two methods of construction consist of utilizing one of the following floor slab systems: I) A structural or suspended floor slab system. 2) A ground-supported-floor slab constructed over modified subgrade. 9 A suspended floor slab involves structurally connecting grade beams directly beneath the floor slabs to the drilled shafts. These drilled shafts would therefore support the weight of the floor slab and the new building. Furthermore, the floor slab would not be in contact with the expansive clays, therefore, eliminating post construction movement due to such soils swelling. Recommendations for a suspended floor slab system are included in Section 4.4 of this report. A more economical method of constructing the floor slab system for the proposed storage building is to construct the floor slab system on a modified subgrade. By using a floor slab on modified subgrade alternate, the owner accepts risk of soil related movement beneath the floor slab. As stated previously, we anticipate that a potential vertical movement (PVM) varying from approximately 2 inches to approximately 3 inches could occur beneath the new structure. To reduce the adverse conditions due to swell potential of the soils beneath the proposed structure, special sub grade modifications must be performed beneath those areas to support the floor slab and critical flatwork. These modifications are intended to reduce the potential vertical movements to a design level of I-inch or less, with differential movements of75 percent of the total movement and provided that our recommendations for grading, backfill, and drainage are strictly followed. If these recommendations are not followed, then there is increased risk that greater than predicted movements and the associated distress may be experienced. One method of subgrade modification for slab on grade construction has been considered for this project. This method has been incorporated and discussed in Section 4.5 of this report. 4.3 Drilled and Underreamed Shaft and Grade Beam Foundation System Our findings indicate that the structural frame and walls for the proposed storage building can be supported by a system of drilled and underreamed shafts bearing in the sandy lean clay soil layer. Following are our recommendations for the design of drilled and underreamed shaft foundations bearing in sandy lean clay soil. 4.3.1 Vertical Downward Loads The shafts should be brought to bear in the reddish brown and gray sandy lean clay soils at depths of 15 to 17 feet below existing ground surface elevation (anticipated to be 15 to 18 feet below final grade) for bearing capacity purposes. Some field adjustment in the bearing depth may be required in order to properly construct the underream excavation (caving of sandy soil or seepage inflow could preclude satisfactory underreaming at some locations). Bell to shaft diameter ratios of 2.5 to 1 to 3 to 1 should be maintained for these drilled shaft excavations. The shafts should be dimensioned based on a net allowable end bearing pressure of 6,000 pounds per square foot. A minimum center to center spacing of 2 times the largest bell diameter is recommended for the piers. Construction of each drilled and underreamed shaft must proceed in a near continuous manner from constructing the underream portion of the shaft followed within 2 hours or less 10 by placement of the reinforcing cages and concrete in order to minimize the potential for groundwater accumulation and soil cave-in. Some field adjustment of the bearing depth of the underreamed piers may be required in order to properly construct the underream excavation. GME must be contacted if any revisions to the anticipated pier bearing depths are contemplated. Again, caving of soils or groundwater seepage at a depth shallower than anticipated could preclude satisfactory underreaming at some locations. Provided the shafts are designed as outlined above, total settlement beneath properly constructed foundation elements is estimated to be minor, generally less than 0.5 inch. Such settlement normally occurs as elastic deformation during construction. 4.3.2 Uplift Considerations Based on our understanding of the project and depending on the soil conditions below the proposed floor elevations, the drilled shafts will need to be designed to accommodate uplift pressures due to potentially expansive soil conditions. Swelling clay soils in contact with the shaft perimeters will cause such uplift pressures to develop in upward skin friction. The magnitude of uplift pressure due to soil swell along the shafts is estimated not to exceed 1,500 pounds per square foot. The soil swell pressure should generally act over the portion of the shaft bearing in the clayey soils to a maximum depth of 10 feet below the final exterior grade. All shafts should be adequately reinforced due to uplift pressures caused by either potential swelling soils and/or structural loading conditions. Reinforcing steel should extend the full length of the shaft. The uplift resistance for underreamed shafts bearing at the recommended bearing depth can be achieved by underreaming the bottom of the shafts. It is recommended that the underreamed portion be at least 2.5 to 3 times the diameter of the shaft. 4.3.3 Grade Beams During installation of the shafts, the cross-section of the shafts should not be allowed to increase at the ground level. A "mushroom" at the top of the shafts could create uplift pressures related to soil swelling which could be detrimental to the shafts at some locations. All grade beams constructed over clays should be formed with a nominal 10- inch void. If the sub grade modification recommended in Section 4.5 for beneath the floor slab is performed, the void box thickness can be decreased to 6 inches. This void is typically formed with rigid soil retainers on the sides, using cardboard box forms or other means for this purpose. The purpose of this void is to minimize uplift pressures on the grade beams from the underlying expansive soils. GME recommends against the use of trapezoidal void boxes on this project. 11 Clay soils (PI between 20 and 45) must be used to backfill around the exterior of perimeter grade beams shortly after removing concrete forms. If a suspended slab system is used, then within the interior of the structure, on-site native clayey soils can be used as grade beam backfill. If the subgrade modifications described within Section 4.5 are used, only electrochemically injected clay soils and special fill materials meeting the requirements specified in Section 5.3 must be used as backfill on the interior of the grade beams. The backfill of grade beams inside the building must be similar to the sub grade modifications with respect to thickness, location and required compaction as described within Section 4.5. It is recommended that grade beams extend at least 1 foot deeper than the special fill depth in order to provide adequate protection to the fill and prevent any possible lateral migration of water into the fill from the surface of the building exteriors once construction is complete. All grade beam backfill materials must be compacted to the recommended moisture and compaction ranges presented in Section 5.3 to prevent water from entering the void space during or after construction and inducing swelling of the underlying soils. Any rainwater, which accumulates within the grade beam excavations, must not be allowed to pond under or around the grade beams and must be removed as soon as possible by pumping or other methods. 4.3.4 Seismic Design A Class C site classification is recommended for this project based on IBC 2000 Table 1615.1.1 for seismic design. 4.4 Suspended Floor Slab A suspended floor slab involves structurally connecting grade beams directly beneath the floor slab to the drilled shafts. These drilled shafts would therefore support the weight of the floor slab, grade beams, and the proposed storage building. The floor slab would not be in contact with the expansive clays, therefore, eliminating post construction movement due to the swelling of such soils. Grading of the site could be accomplished using on site materials or moderate to high plasticity materials from on-site or off-site. Other than complying with the fill placement recommendations within Section 5.3 of this report and providing positive drainage beneath the building, no other special efforts for sub-slab preparation would be required if a suspended floor slab system is utilized. Two methods are available for constructing a suspended floor slab system. These include using pan and joist type construction and raising the floor slab well above the underlying expansive soils, or using cardboard carton forms to create a void. Pan and joist type construction can be used to suspend the slab using either concrete or steel beams. If this system is used, we recommend that the floor slab be suspended at least 36 inches, and preferably more, above final subgrade elevations. Future movements of soil-supported utility lines must be considered when designing connections, especially where these lines approach or enter the stationary structure. Provisions should be made for positive drainage of the under-floor space. Construction with metal beams and joists 12 must also contain sufficient ventilation to limit corrosIon of the metal components. Precast concrete floor systems may also be used. Cardboard carton forms may also be used to create the void beneath the slab. A minimum void box thickness of 10 inches is recommended. It must be understood that there is an inherent risk involved with this method in that the design intent may be comprised by improper construction methods as described within this paragraph. If cardboard void forms are used, extreme care must be taken during construction to preserve their structural integrity and ability to maintain a consistent void. V oid box systems must not be allowed to become wet or exposed to moisture or water prior to the placement of the overlying concrete. Any wet void boxes or void boxes whose structural performance has been compromised due to exposure to excessive moisture or which have been damaged during the placement of the rebar or concrete must be removed and replaced with competent void boxes prior to placing concrete. Inspection and monitoring of the void system prior to and during placement of the concrete are critical. A rigid layer, such as masonite or rigid cardboard, should be placed directly on the void box forms to prevent collapse or puncture by personnel during placement of the reinforcing steel or concrete. This rigid layer would also help reduce the potential for concrete to leak down between the cardboard forms during placement. Again, careful observation of the slab concrete is critical to aid in observing evidence of any collapse of void boxes during placement of the slab concrete. The contractor must carefully estimate and closely track the quantity of concrete placed during the slab pour to help confirm that the void forms did not collapse resulting in placement of larger than expected concrete quantities. Ultimately, construction and maintenance of the void system and placement of concrete is the responsibility of the contractor. 4.5 Floor Slab on Modified Subgrade We anticipate potential vertical movements varying from approximately 2 inches up to 3 inches could occur beneath the building, flatwork and pavement areas, if constructed at or near existing grades, and if construction takes place after a prolonged dry period as is currently occurring. If drainage is not properly controlled and the soils beneath the new building become saturated from external sources, then estimated potential vertical movements in excess of 3 to 4 inches in localized areas could be experienced. Therefore, if a slab-on-grade system is selected, then sub grade improvements and positive drainage management will be required to reduce the post-construction vertical movements to a tolerable design level of I-inch or less with differential movements of 75 percent of the total movement. If the owner elects to construct a floor slab on modified sub grade, the owner is accepting some inherent risk of future movement related distress to the slab supported elements of the new structure. This risk is increased if the recommendations for maintaining positive site drainage away from the new structure during and after construction and our recommendations regarding construction of slopes, landscaping planting and irrigation as described within Section 4.8 are not strictly followed. 13 Due to the relatively small confines of the building and concerns with excavating adjacent to the existing Fire Station building, GME only evaluated one method for reducing the potential vertical movements to a level of 1 inch or less below the proposed building assuming the floor slab is supported on a modified sub grade. This method of sub grade improvement consists cutting or filling within the building area with onsite clayey soils to a depth of 1.5 feet below finished grade elevation, electrochemically pressure injecting the resulting subgrade to a depth of 10 feet, and placing 1.5 feet of compacted special fill over the electrochemically pressure injected sub grade within the building footprint to obtain final grades. The following paragraphs of this section provide detailed recommendations for modifying the sub grade conditions beneath the new storage building using the method of sub grade improvement outlined above. Electrochemical Pressure Iniected Clays and Special Fill This method of sub grade improvement recommended beneath the new storage building involves a combination of electrochemical pressure injection and special fill beneath the proposed floor slab. Specifically, in order to reduce the total potential vertical movements to a desirable design level of 1 inch or less beneath the floor slab, the following sub grade improvements must be accomplished: All existing vegetation must be stripped from the sub grade within the proposed building pad and at least ten feet outside the structure limits (but to a distance no closer than 5 feet adjacent the existing Fire Station building). The building pad should then be undercut or filled with on-site clayey soils to establish the preliminary sub grade elevation within the building area at approximately 1.5 feet below the finished grade elevation. Prior to filling all low areas, the building pad area must be proofrolled as described in Section 5.1. All filling must be performed consistent with the recommendations for low or high plasticity clay soils as described in Section 5.3 of this report. After fill placement is complete, the exposed pad area and extending at least ten feet outside the structure limits (but to a distance no closer than 5 feet adjacent the existing Fire Station building) must then be electrochemically pressure injected to a total depth of 10 feet. The purpose of the electrochemical pressure injection is to stabilize the clay soils and thereby reduce the swell potential of the clays to an acceptable level. For this project, an average swell percent of no greater than 0.8 percent over a depth of 10 feet must be obtained after injection to reduce the swell potential to 1- inch or less after the special fill placement. We recommend that initially a minimum of at least three electrochemical pressure injection passes be performed over the building pad area. It is possible that additional passes of electrochemical pressure injection may be necessary, especially if construction proceeds during or just after dry seasonal periods. The success of the injection procedure depends upon the contractor's ability to inject the electrochemical solution under pressure into the seams and fissures in the otherwise impervious clay soils. The contract documents should require that the injection contractor provide a lump sum price to inject the site 14 sufficiently to obtain the specified performance criteria (acceptable average free swell percentage for the injected soils). Details conceming the injection depths, associated construction procedures and confirmation testing are described in Section 5.5 and in Appendix D of this report. It is recommended that GME be retained by the client to be involved throughout the chemical injection process. Initially, we should be included in a pre-injection meeting to review the project requirements with the contractor and his subcontractor. During injection we should be retained to perform periodic inspections of the injection procedures. Once injection is complete, GME must perform certain post-injection testing and analysis to confirm the proper completion of the injection phase(s) of the project. We also recommend that the contractor provide an as-built survey of the injected area to confirm the limits of the injected building and flatwork areas. This as-built survey must be provided to the owner as confirmation that the desired area has been injected and to provide for documentation and information regarding the injected area should future expansions be planned at this site. Upon satisfactory completion of the injection process, the upper six inches of the subgrade should be scarified to a depth of 6 inches and properly recompacted. Some reworking and/or drying of the surficial soils may be necessary to hasten the surface preparation prior to special fill placement. In an attempt to provide a uniform bearing material for the building floor slab and further reduce potential floor slab movements, then following sub grade preparation, a 1.5 feet layer of non-expansive special fill (meeting the requirement specified in Section 5.3) must be installed as described earlier to achieve the desired final design sub grade elevation within the building pad area. General If the above-recommended improvements are successfully performed, and drainage considerations described below are maintained, then the potential post construction moisture-induced movements below the floor slab should be limited to 1 inch or less. The horizontal limits of the special fill materials must be limited to those areas where a reduction in potential soil movements is desired. The special fill must not extend outside the limits of the building. Flatwork areas outside the building pad do not require any special fill placement. Additional recommendations regarding use of special fill below grade are provided in Section 5.3. Recommendations regarding the construction of exterior flatwork elements of the building are provided in Section 4.9. When constructing with special fill, care must be taken to avoid allowing water to pond in the fill layer. The presence of ponding water either during or following construction could cause post construction movements that exceed the estimated values. Care must be taken to prevent landscape watering, surface drainage, leaking utility lines or other sources of water from entering the fill. Again, it is recommended that grade beams extend to at least the I-foot deeper than the special fill in order to provide adequate protection to 15 the fill and prevent any possible lateral migration of water into the fill from the surface once construction is complete. Configuration of the sub grade preparation beneath areas to receive the building slab-on- grade is dependent upon the type of floor system the owner is constructing. For a conventional slab system, it is appropriate to place a thin sand cushion on the subgrade to provide uniform load distribution on the underside of the slab during construction. A high quality vapor retarder with a maximum perm rating of no more than 0.3 and puncture resistance of at least 475 grams is recommended to be placed directly beneath the concrete floor slab in those areas where floor coverings or painted floor surfaces will be applied with moisture-sensitive products or where moisture-sensitive equipment will be stored or installed. Care should be exercised during placement of the reinforcing steel and concrete to avoid damage or penetration of the vapor retarder. 4.6 Pavement Subgrade Preparation and Pavement Design Based on the test borings performed on the site, we anticipate that once the site grading is performed, that highly plastic clay soils will be exposed at the site surface. Because the clay soils exhibit a potential for shrinking and swelling, it is likely that pavements constructed on-site will be subject to movement from the soils below. The result of these movements causes distress within the pavement section, which typically leads to higher maintenance frequency and costs than for pavements constructed over non-expansive soils. Significant differential movement of the expansive sub grade soils should be anticipated once grading is completed and these areas are covered with pavement or flatwork. Therefore, the pavement surfaces should be finished and adequately sloped to insure positive drainage even after these anticipated movements have occurred. Good perimeter drainage around the pavements is also recommended. Both total and differential movements should be taken into consideration at locations where pavement systems transition into structures. Generally, it is common practice to lime stabilize the upper 6 to 8 inches of subgrade soil beneath the pavements within the Coppell, Texas area. The purpose of this stabilization is not to reduce the movements beneath the pavements, but instead to improve the bearing value of the pavement subgrade soils and provide uniform soil conditions on which to construct the pavements. To reduce the movements beneath the pavement areas generally requires additional pavement sub grade preparation in conjunction with the pavement design. For estimating purposes only, typically 10 percent lime is necessary for lime stabilization. We recommend performing a lime-series test based on ASTM D-6276 at or near the start of construction to determine the appropriate lime content required for proper stabilization results. The exposed surface of the soils should be scarified to a depth of at least 6 inches and mixed with hydrated lime (estimated to be 10% or approximately 45 pounds/per square 16 yard) in accordance with the procedures described in the Standard Specifications for Public Works Construction, North Central Texas, Item 4.6, prepared by the North Central Texas Council of Governments (NCTCOG). The sealed soil-lime mixture should be allowed to cure for a minimum of 48 hours, then be remixed. The remixing and pulverization operation, as described in NCTCOG Item 4.6, should proceed until the soil is uniformly broken down and meets the gradation limits provided in that specification. The resulting mixture should then be brought to near optimum (optimum to plus 3 percentage points) moisture conditioned and uniformly compacted to a minimum of 95 percent of Standard Proctor (ASTM D-698) density. The compacted material should then be covered immediately with the paving or kept moist until the paving is placed. In all areas where hydrated lime is used to stabilize the sub grade soils, routine gradation tests should be performed at a rate of one test every 10,000 square feet of paving area and at least one test per day. Specified gradation criteria outlined in NCTCOG Item 4.6 should be utilized. The gradation tests will confirm that the material has been adequately broken down. Should any areas be out of conformance on these tests, then additional lime or remixing must be performed to bring the soil into compliance for the 10,000 square feet area represented by the deficient tests. Field density testing should also be performed at the above-recommended frequency to confirm proper compaction. The following pavement sections have been developed based on assumed traffic conditions for consideration at this site. Reinforced Concrete Section Light Traffic (automobiles, occasional light trucks) 5.0 in. Reinforced concrete 6.0 in. Lime stabilized and compacted sub grade Heavy Traffic (fire lanes, service drives) 6.0 in. Reinforced concrete 6.0 in. Lime stabilized and compacted subgrade Heavy Traffic (dumpster pad, loaded tractor trailers) 7.0 in. Reinforced concrete 6.0 in. Lime stabilized and compacted subgrade Minimum Compressive Strength @ 28 days...............................................................3,600 psi Minimum Cement Content...... ........ ......................... ........... ....................................... 520 lbs/cy Air Content ................ ......... ........ ........ .............................. .......................................... ...... 4 _ 6% 17 General A relatively close joint spacing of 12.5 to 15 feet is preferred. Local area practice often includes the use of No.3 reinforcing steel bars in each direction at spacing of 12 to 24 inches, with an I8-inch spacing being commonly used. Control joints should be sawed as soon as the concrete will allow and prior to shrinkage cracking occurring. Expansion joints are typically placed on 60 to 80 foot centers however the placement of all joints is a factor of the pavement shape. The design civil engineer is best suited for determining the joint spacing and locations at the project site. We recommend that the main drive lanes and traffic lanes within the parking area be placed as separate pours from the parking spaces in order that the pours are linear and the contractor might best control the timing of the installation of the saw joints and control the cracking within the sawn joints and not randomly across the pavement surface. Additional details on this process can be provided upon request. A properly graded and drained pavement subgrade to minimize the trapping of water under the pavement must also be provided. Proper concrete finishing and curing practices must be employed. All paving materials should comply with the Texas Department of Transportation Standard Specifications for Construction of Highways, Streets and Bridges, Item 360, 1993. Loading (traffic) must not be allowed until the concrete has reached 75 percent of its design strength. The recommended pavement design sections are subject to successful completion of site drainage and subgrade preparation and fill placement as recommended in this report. A GME soil engineering technician working under the direction of a geotechnical engineer should observe placement and compaction of the grade raise fill and subgrade materials and perform soil density tests to confirm that the material has been placed in accordance with our recommendations. The pavement sections described above are considered suitable for general purpose usage for the anticipated sub grade conditions. A comprehensive analysis of the pavement system would include consideration of traffic loads, frequency, sub grade drainage, design life and the overall economics. In general, it is expected that the reinforced concrete pavement life could be increased with an aggressive maintenance program including seal coating of cracks and joints to help retard moisture migration into the sub grade soils. 4.7 Expansive Potential The site soils have a low to high expansive potential, as indicated by the free swell laboratory tests and the plasticity indices of the soil. Recommendations for addressing the expansive nature of the soil are addressed in Sections 4.3, 4.4, 4.5, and 4.7 of this report. 18 4.8 Drainage Positive surface drainage must be maintained during construction and following the completion of construction. Positive surface drainage must be incorporated into the final grading plan to reduce seasonal variations in moisture content of the foundation soils. All sidewalks must be sloped away from the proposed storage building to prevent ponding of water near the new structure. Final exterior grades must slope downward at least I foot (vertical) to 10 feet (horizontal) for a distance of at least 5 feet (but preferably 10 feet) away from the new building. We recommend that roof drainage be collected in a downspout collector system and piped to the underground storm water system and diverted off site thereby reducing the chances that surficial water can migrate beneath the surface or collect near the foundations and activate the in-situ soils. Flatwork located adjacent to the building foundation must be sloped sufficiently to allow for the slab movement associated with the anticipated soil PVR beneath these areas while maintaining positive site drainage away from the building. We recommend that exterior flatwork extend to the new building lines, if possible, rather than have planters or other open areas adjacent to the structure. If planters are located adjacent to the new building, they must be self-contained (including their own internal drainage systems) to eliminate a possible source of moisture gain or loss to the soils beneath the adjacent new building floor slab. All trees must be a minimum of one-half their mature height away from the new building or pavement edges to reduce potential moisture losses. Careful control of irrigation water within planters is essential. No water must be allowed to percolate down to any remaining underlying potentially active soils below the new storage building. Therefore, we recommend that the exposed backfill soils extending beyond the new building lines be capped with an 18-inch thick cover of well-compacted, impervious clay with a plasticity index between 20 and 45, or be covered with flatwork. The purpose of the clay cap or flatwork is to minimize potential moisture losses or gains beneath the proposed new building. If a suspended slab system with crawl space is used at the building, it is recommended that drainage of the area beneath the suspended floor slab system be performed to prevent water from accumulating within this area. The drainage must be collected and sent to a suitable outfall. 4.9 Exterior Flat-work Soil related movements on the order of those indicated with Section 4.2 of this report or greater should be anticipated beneath all covered areas of the site. These areas not only include any building floor slab on grade, but also covered flatwork areas outside of the building limits. Critical flatwork areas may be defined as those movement sensitive areas adjacent to the building foundation, which can tolerate either no greater movements than those for which the building slab was designed, or very limited movement to maintain 19 proper slope for drainage or to meet ADA accessibility requirements. Typically, these elements might include building entries, entry ramps, or other areas of the building exteriors. Those critical flatwork elements immediately adjacent to the building entries should be constructed as structural elements that are supported on drilled shafts with the slab areas suspended according to the recommendations in Sections 4.3 and 4.4 of this report. In less movement critical areas, but where slab movements approaching the total potential vertical movement may not be desirable, the new flatwork elements can be designed to bear on grade if sufficient modification of the underlying soils is performed. The soil modification is intended to reduce the movements below the slab. If the subgrade modifications within Section 4.5 are performed, then flatwork areas located within a horizontal distance of 10 feet from the new building will receive electrochemical injection to a depth of 10 feet. For those flatwork areas further than 10 feet from the building, it may also be desired to reduce potential future movements beneath the flatwork areas to within a similar order of magnitude. This movement objective needs to be evaluated and determined by the architect and civil engineer during the design, as it could adversely affect the drainage and accessibility requirements, should the estimated movement be realized beneath these areas. The extent of soil modification in these areas should be dictated by the design approach and detailing in these areas as well as the overall project economics. Should certain areas be tolerant of greater allowable movement as the distance away from the entries increases, then it is possible that the depth of electrochemical stabilization can be reduced. There is no requirement for special fill placement beneath any of these new flatwork portions of the site. GME can provide additional recommendations for addressing potential movements beneath the flatwork areas if requested by the project architect and civil engineer. During the design, it is recommended that GME be consulted to assist in defining the stabilization limits where structural elements transition from areas requiring deep injection (10 feet beneath the building addition area) to flatwork areas requiring shallower injection. If electrochemical stabilization is not performed below either the building or the exterior flatwork areas and a suspended floor slab system is utilized, then it should be anticipated that the potential for the full estimated movement beneath any on grade elements may occur. It is possible to reduce the differential component of the movement somewhat by over-excavating of the materials to a depth of 1 foot, then recompacting the materials to the moisture and density requirements for clayey fill materials described in Section 5.3. However, this will not significantly reduce the potential total movement beneath these areas, only make the movements somewhat more uniform. If the objective is only to achieve subgrade uniformity, then the moisture level must be maintained within the soils up to within a period of 24 hours prior to placing the concrete for these flatwork areas. Regardless as discussed in Section 4.8, the flatwork close to the perimeter of the new building addition must be adequately sloped to provide positive drainage away from the building. The degree of slope must take into consideration the rotation and vertical displacement expected to result from the total estimated movement of the underlying soils beneath these areas of the site. 20 5.0 CONSTRUCTION RECOMMENDATIONS 5.1 Site and Subgrade Preparation Before proceeding with construction, all vegetation, root systems, and other deleterious non-soil materials should be stripped from proposed construction areas. GME recommends that all plant roots greater than 2 inches in diameter be removed from the site. Some hand labor may be necessary to adequately remove the roots from the fill matrix. Additionally, organic material must not comprise more than 5 percent of the soil matrix used as structural fill. After clearing, stripping, and excavating areas intended to support new pavements, new fill, and foundations; these areas must be carefully evaluated by a geotechnical engineer. At that time, proofrolling of the sub grade with a 20- to 30-ton loaded truck or other pneumatic-tired vehicle of similar size and weight must be performed. The purpose of the proofrolling is to locate soft, weak, or excessively wet soils present at the time of construction. Any unsuitable materials observed during the evaluation and proofrolling operations must be undercut and replaced with compacted fill or stabilized in-place. The proofrolling operation must be performed under the observation of a qualified geotechnical engineer or his representative. The geotechnical engineer should also determine whether the existing subgrade is suitable for the proposed construction. Care must be exercised during the grading operations at the site. The traffic of heavy equipment, including heavy compaction equipment, may create a general deterioration of the shallower, clayey soils. Therefore, it should be anticipated that some construction difficulties could be encountered during periods when these soils are saturated and that it may be necessary to improve, remove or simply stay off of the saturated soils. 5.2 Pier and Foundation Excavations All drilled and underreamed pier excavations must be inspected under the direction of a qualified geotechnical engineer to confirm that foundations will bear on satisfactory material as described in Sections 4.3. Materials exposed in the bases of all satisfactory excavations should be protected against detrimental changes in condition. Surface runoff water should be drained away from the foundation excavations and not allowed to collect. All concrete for drilled shafts should be placed the same day the excavation is made and not more than 2 hours after completion of drilling or excavation as described below. All drilled shafts should be at least 1.5 feet in diameter to facilitate clean-out and proper inspection of the pier base. As stated in Section 3.3.3, groundwater seepage was encountered within both building test borings at depths of24 to 25 feet beneath the ground surface of the site. Provided that drilled and underreamed shafts for the new structures are designed and constructed to the depths described as recommended in Section 4.3, GME does not anticipate the need for casing the drilled shafts. GME recommends that the foundation specifications be 21 written such that drilling of the underream shaft is followed by placement of the shaft cage and then placement of concrete within less than 2 hours from completion of belling to prevent potential groundwater accumulation and soil cave-in from interrupting the shaft construction. If necessary, the shafts may need to be constructed by immediate placement of the shaft cage and pouring of concrete after the bell portion of the drilled shaft has been completed. Should excessive caving be experienced during construction, the contractor should be prepared to install a straight shaft pier system. GME would be glad to assist in providing design recommendations for a straight shaft pier system if requested. Again, GME must be contacted if any revisions to the anticipated pier bearing depths are contemplated. We also recommend that a tremie pipe be utilized during concrete placement to minimize segregation of aggregate from the concrete. During concrete placement for the drilled shafts, the use of spacers/rollers and bottom bolsters are recommended to maintain the pier reinforcing steel within the center of the drilled shafts and to lift the cage off of the bottom of the pier excavation. Bottoms of drilled shafts must be evaluated by a geotechnical engineer prior to placement of reinforcing steel and concrete to confirm that adequate bearing materials are present and that all debris, mud, and loose, frozen or water-softened soils are removed. Concrete placement must be completed in any shallow foundation excavations of any structural significance as soon as practical after the excavation is completed. Water must not be allowed to pond in any excavation. If an excavation is planned to be left open for an extended period, a thin mat of lean concrete must be placed over the bottom to minimize damage to the bearing surface from weather or construction activities. Foundation concrete must not be placed on frozen or saturated sub grade. 5.3 Fill Placement and Compaction All soil materials used as fill must be free of decomposable or otherwise deleterious material. Engineered fill material must be free of significant organic matter or debris, have a low to moderate plasticity and have a uniform composition. The suitability of specific soils as fill material would be based on results from classification and compaction tests and subject to the approval of the geotechnical engineer. Special fIll Materials This report section provides recommendations for testing and placement of materials that can be used as special fill below the desired sections of the new storage building floor slab. The special fill material recommended for this project consists of flexible base material comprised of recycled concrete road mix meeting TxDOT Item 247, Type D, 3/8 inch screening material. This material (which has to be imported) can provide a good quality, low plasticity, fill. This material must be compacted in 6-inch thick lifts with the initial 2 lifts compacted to a minimum 95 percent Standard Proctor and the final surface lift 22 compacted to a mInImUm 100 percent Standard Proctor. The moisture of the material should be at or within 3 percentage points above or below optimum moisture. Additionally, the material must have a plasticity index between 3 and 10. High Plasticity Clayey Fill Materials All on-site soils with a plasticity index greater than 20 can also be used as grade-raise fill beneath building, pavement and landscape areas. All high plasticity clay soils must be compacted to a dry density of at least 93 percent of Standard Proctor and not exceeding 98 percent. The compacted moisture content of the clays during placement must be between 2 and 7 percentage points above optimum moisture content. Low Plasticity Clayey and Sandy Fill Materials All on-site clayey and sandy soils with a plasticity index less than 20 can also be used as grade-raise fill beneath building, pavement and landscape areas. All low plasticity clay soils and sandy soils must be compacted to a dry density of at least 95 percent of Standard Proctor and not exceeding 100 percent. The compacted moisture content of the low plasticity clays and sandy soils clays during placement must be between minus 3 to plus 3 percentage points of the optimum moisture content. General Guidelines Compaction of any fill by flooding must not be permitted. During wet and rainy periods, aeration is generally necessary to bring the fill materials to the required moisture condition. During dry periods, the addition of water may be necessary to reach the proper soil moisture content for compaction. Compaction must be accomplished by placing the fill in either 6-inch lifts for the special fill, select fill and limestone fill or 8-inch thick loose lifts for the clayey soils, and compacting each lift to at least the specified minimum dry density. It is imperative that the fill particle size be less than four inches in diameter as they are placed in the fill lift prior to compaction. If larger clods or rock fragments are encountered during grading, then these clods or rock fragments must be broken down prior to final placement in the fill. This may require placement of the material, an initial compactive effort to break the clods down, scarifying, wetting and recompacting. For this project, it is necessary that the contractor be required to provide equipment specifically designed for fill compaction. Walking in clayey fill or compacting the fill with track type equipment by itself, such as bulldozers or front-end loaders, should not be considered acceptable compaction methods or equipment. Typically, two or four wheel, smooth steel drum vibratory compactors and smooth tire compactors must be utilized for compacting all 3/8-inch screenings special fill material. For on-site clayey fill materials, two or four wheel, steel drum, self-propelled or tractor-pulled, sheepsfoot compactors must be utilized for compacting We have found that this type of equipment is best for breaking down any large clods, kneading the clayey soils to provide more uniformity in 23 the resulting compacted fill, and tying the clay fill, or special fill material layers together into a well compacted, homogeneous material. Additionally, a water truck should be available to provide adequate moisture to the fill as it is placed. In order for the fill materials to perform as intended, the fill material must be placed in a manner which produces a good uniform fill compacted within the density and moisture ranges outlined in the preceding paragraphs. Density testing must be performed on fill soils to confirm this performance as construction progresses. For the proposed structure, we recommend that each lift be tested at a frequency of no less than 2 tests per lift per each 5,000 square feet. In remaining areas on-site, a testing frequency of at least 1 test per lift per each 10,000 square feet should be sufficient. The testing frequency for utility trench backfill should no less than one density test for each 1 foot of compacted fill depth (2 lifts) and each 150 lineal feet of trench. Testing of grade beam backfill should be performed at a frequency of 1 test per compacted lift for every 100 to 150 If of grade beam. Depending upon the type of compaction equipment used for backfill compaction in utility trenches and behind grade beams, it may be necessary to reduce the fill lift thickness and maximum particle size to about one-half of the above recommended dimensions in order to achieve properly compacted backfill. 5.4 Difficult Excavation No difficulty is anticipated in the construction of drilled and underreamed shaft foundations or during the grading operations for this project. Due to the presence of possible presence of thin limestone seams as often encountered in the Eagle Ford Shale Formation, field operations such as straight shaft excavations (if utilized) could encounter difficult conditions especially upon initial penetration into the shale layers. Therefore, the contractor should be prepared to handle these difficulties with special rock removal and drilling equipment. Blasting is not anticipated to be necessary, nor is blasting standard practice in the Coppell, Texas area. 5.5 Electrochemical Pressure Injection After excavation to 1.5 feet below finished grade and proofrolling or filling is completed within the storage building area, the proposed building pad and to 10 feet outside the building limits but within a distance no closer than 5 feet of the existing fire station building should be pressure injected with an electrochemical solution to a minimum depth of 10 feet. The injection should also be extended to the limits any sidewalks abutting the building if these sidewalks extend a distance greater than the recommended 10 feet from the new building. The purpose of this procedure is to introduce an electrochemical solution that will aid in controlling natural variations in moisture content of the clayey soils by altering the molecular nature of the soils. Satisfactory completion of the injection process will have been achieved when the desired free swell potential (average of 0.8 percent over a depth of 10 24 feet, and no individual test greater than 1.6 percent) has been reached, based on results of additional field and laboratory soil tests. We recommend initially that three electrochemical pressure injection passes be made. No water passes will be allowed prior to injection unless prior approval is given by the design geotechnical engineer. The number of additional electrochemical pressure injection passes required to achieve the desired average free swell percentage will depend upon the condition of the clayey soils prior to injection and the tendency of the soils to absorb the injected materials. If construction of the foundation slab is initiated after a prolonged dry period or if harder more highly consolidated materials are encountered, as many as two more electrochemical pressure injections may need to be performed. Soil samples must be obtained from test holes taken during this procedure to confirm that a satisfactory free swell level is achieved. We note that there is some risk that the injection process may not reduce the free swell percentage of the soils to the proper level. Additional re-injections would then be necessary to achieve the design potential vertical rise of I inch or less below the floor slab area. The subgrade surface must not be allowed to dry during or following the injection process. Guideline construction specifications for the electrochemical injection process are provided in Appendix D. Immediately following successful completion of the injection process, the subgrade must be scarified to a depth of 6 inches, brought to proper moisture content and compacted. A uniform thickness of 1.5 feet of special fill must then be installed within the building limits to achieve the finished floor sub grade elevation. Specific recommendations on placement, compaction and extent of the special fill are described in Sections 4.5 and 5.3. Special fill must comply with the recommendations outlined in Section 5.3 for recycled concrete 3/8- inch screenings special fill materials. 5.6 Groundwater Conditions Based on the groundwater conditions encountered in our borings, the use of temporary casing during the construction of the drilled and underreamed shafts bearing within the clay soil strata is not expected to be necessary provided the shafts are constructed in a manner as described in Sections 4.3 and 5.2. It is recommended that the reinforcing steel cage and concrete be placed in the underreamed shafts within 2 hours upon final cleaning prior to groundwater accumulating in the excavation. Additionally, it is our experience that to install the piers correctly, the reinforcing steel cage and concrete must be ready to install in the shafts immediately upon final cleaning and prior to groundwater accumulating in the excavation. Drainage ditches or trenches or pumping from small sumps may be used for temporary dewatering of surface runoff that occurs onsite and within the proposed excavations prior to filling. 25 Positive drainage away from the building pad should be maintained throughout construction. Rainwater and runoff, must not be all owed to accumulate in grade beam, shaIlow foundation and utility excavations. Any incidental water that does accumulate in these areas must be removed immediately by pumping from smaIl sumps within the excavations. Groundwater levels are subject to seasonal, climatic and other variations and may be different at other times and locations than those stated in this report. During construction, it is very critical to the slab and flatwork performance that a site drainage plan be implemented and maintained at all times by the contractor to redirect all site drainage away from the limits of the building and site feature elements and avoid accumulation of water within any areas of the site to support movement sensitive elements of the project. 26 6.0 QUALIFICATION OF RECOMMENDATIONS The recommendations in this report were developed from the information obtained from the test borings which depict subsurface conditions only at the specified locations and at the times indicated on the boring logs. Additionally, the laboratory test results for selected soil and rock samples relate only to the samples tested. Soil and rock conditions at other locations may vary from the indicated conditions and the nature and extent of such variations may not become evident until the course of construction. If variations then appear evident, it will be necessary to re-evaluate the recommendations of this report after noting the characteristics of such variation. Additionally, if there are any changes in the proposed construction, including the location of the new building on site, GME must be contacted of the proposed revisions, we must be allowed to review the revisions and we must be allowed to provide revisions to our recommendations if necessary to achieve the same design criteria. The estimated soil movements (PVM) referenced within this report are based upon the conditions observed at the time this investigation was performed and the assumption that all of our design recommendations will be followed precisely. If for any reason the user of this report chooses not to follow all of the recommendations precisely, then prior to fmal design development, GME must be contacted for further consultation. This report is intended for the sole use of City of Coppell. The scope-of-services performed in execution of this investigation may not be appropriate to satisfy the needs of other users, and any use or re-use of this document or its findings, conclusions, or recommendations is at the risk of said user. GME Consulting Services, Inc. is not responsible for conclusions, opinions, or recommendations made by others based on this information. It is additionally recommended that the geotechnical engineer be retained to review the plans and specifications so that comments can be provided regarding the interpretations and implementation of the geotechnical recommendations into the contract documents. It is further recommended that the geotechnical engineer be retained for testing and observations during the foundation construction and earthwork phases of the proposed construction. Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties either expressed or implied. This report shall not be reproduced except in its entirety and with the express written permission of GME Consulting Services, Inc. 27 APPENDIX A- TEXT FIGURES Figure 1 Figure 2 Figure 3 Site Vicinity and Topographic Map Site Geologic Map Boring Location Plan ~., lie! II L " i /~" \~(, ,.:::11 '/ II, . \. : ',:"'-,', "'!I " ,'/ ',:.\>~ ~'"'---::.:--'!- -' _ 1 \. "', ~ 81 .-- -;;\ ( '. / I . "ROAD "'II 518 '. ) , ! /' '--. (/-'\ '\.;::" .. ." \ ( o ;' ('/ , " ,=/\,' \ ) / \~ I / ( ) I "r- I I c ROA ~"', 'li>.. , CO'~ '., ~A"\, "- -"._~::~, (~"fi "oP' i \ -<~ 'Q., \ l~" \ I CORP ~DY i , . '\ \ L_______~-- l~ \ ,""'~ \ _.!-~ I~ i ' \, \ \ I ,,-, liliF-il ~\ \ 'i 'I~ """ I ~ I~ . ~ 08 \.-----... I I"',, , '0 <t-~~ \ t~~~ \ ~ 'vfi), \ I ~ .---___ // />\ \ I ~ - ~ \ I ,< '\ \ .____~5.2F-- '\~\ '\%,\ ~("!\ "~~\ ".:'-' \'''''' '\%\ "j ''\,,<> \ ..- ''t)\f<'\ ~ . ,l\ ~ " I , ,) ~ ( /! ,1-' J --,""J I{~ c.f iLt !I- //' \ ~ Project: Proposed Storage Building Fire Station No. I 520 Southwestern Blvd. -- Coppell, Texas Scale: 1 :24,000 Project Number: 08.04.0062 Date: March 28, 2008 Figure 1 Site Vicinity and Topographic Map I : 1]\ ~., .- c~./ I: '. . .~.~'''~~~'-' :- I Oall \ ' - _ ',.......;,.. k 1lI__ I.. ( "I "2-,l1lm.1.nok :-r;- ,'/ J~.l " \ '. ,..i0-~' J l~ !J -"'i , . u /, ~ . 0 0 0S' ;:L WJ; ~ I ~ ~. ~~ 9! ~~ \. ~. . .~ ~ ~ t"J , i t"' ~ 1 ~_ ~ 1 tri> ! \ ~- ~ ~ j\] ~ "- ;)fflm . lJ ~ ~\ r ~x '~au ..... p ~ z I~, [X 'A ~. _ "'lA~."V ~"~ r ~/ N'" l<g~ )~ ~ ~~ ,A ~BIL ~~~ 1i j I ~ 2.. 5 r'i=t7?, I~ 1 ,h\(~~ ~ -:f _~ :. ~_ I,P/ ~~ -'l J>~ ., '':. ~Yk:' L'1g ~f v ')0)\1 ( ) ~:l- '-"- _ -:!.-) I. is; r ~, 550 ~ ): , ITO- kCQ~'-~ ;..~:~S" ~NT.y -..., '-, '=. .. , c;. J (l'nQ ~ ~ ..I:::t, )~ bl rJ ~ . '11 1lJf. """'''"r. ~~ . , ~ ~-..t - ~ 'fl, . ,_~ ' ~!l~ ~ . ,.-<a"1" . I~, .'~~ ',. .~~\~ r ',~~i-i ,"Jd~~ ;. ~~Ji~"S I-~~ :~.~. ' - ~/""f" ~. IQ ':ti( '7.'. '::T . ~. , ' I ~ ~,,:r'\) - ';.>, ~ "", JDa~' ..'FO~"'~~ ~ .~, \S' \;,~ '1 ' ~ nter'n' iongl:Arrpo ,.. ~ ~ J ~.. '. 44 ~,[,""l.~.';.;""." _~~" '~~ ~ ~~~ '(' ;'T ~ "i~:.p" . ~. ,,--, ''IN .,'.., '/,. ,~ t . 'tS (f z.P"'~ 'J~~ .-:,#- ~ .' . lf~J~~!.s ipg; ? L'o' J\.'W---~ 7' ':~~f' ~J1,~ ~~11.1.1 0~,:+Cll~. ' :' -~ ~:-'I')L 1:J,~~ ,r-: '" """')'t,;. ~ ~~~"~!~ '0 .,~ S~\J ~~ 'A~f--;~::,: >- 08t ~. ~ / 'UA'JJ -eat (.!bAt ~~ , ~,~~. ~l/~ -~I( _ rt ",,' -'%, "-. ~ C \UI' . ~, 11zt-' L:>-.. A.~ :?V ~'" I r :.&lJII ~ ~ 1-, w ceo, ,/,,' l l^,' ,,~ [" -'/ ~ ...~ ~. J1~ alla~ , ./ ~ . """-, lOl~ ~",? _).; (H~~?)' ;, '.. /1/....."1- tJ '{ Ie '495 ", r ,....." J I} < .'p "... · ~ ~~ J' g,'; '-.. ~{', . " 'A~ on'hi'~\1 t1' ~i~ .~~ t , ,~\ '~~~I~ ~I~ ~:4~'~ etf ''? W~-\I [~":.. . u ~., ,,' .;;[ . J_ \ ~ ) t /~. ~.,.~.'."".' _" .'~~I.J~: Qt ;, v ,," ~~ .,. I /II ,....r-r , . ~. 811 - V'~).J\ ,'<K~mr:-;\I ~~ : '~85~ F . >'/1'1 ~., ,. 'I .:t<J... iii. '" -~- S / / r,. ~ .-, ~' ~i Geolol!ic Formation Ko- Ozan Formation Kau- Austin Chalk Formation Kef- Eagle Ford Formation Kwb- Woodbine Formation Kgm- Grayson Marl and Main Street Limestone Undivided Kpw- Pawpaw Formation Qal- Alluvium Deposits Qu- Quaternary Terrace Deposits Qt- FluviatileTerrace Deposits Project: Proposed Storage Building Fire Station No. I 520 Southwestern Blvd. -- Coppell, Texas Scale: 1:250,000 Project Number: 08.04.0062 Date: March 28, 2008 Figure 2 Site Geologic Map Railroad Tracks t_t+t-HtH++++-H-H++-H-++H-H++-H+++++\++l+I,~'-'-~r-~--' ~_;_.l ! l_T_.~_~\--1-t--i-+--1-+t1++-++-1--1--1-~-rl-l-t-l-\-T+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- Legend: ~ \ \ B-2 Water Tower Proposed Storage Building ~ B-1 \ Fire Station No 1 520 Southwestern B~ulevard I -./ --~--------------./ ---~---- SOUTHWESTERN BOULEVARD Approximate Soil Boring Location I";;;~'~~~ -d Project: Proposed Storn e B .. . 520 Southwest g uIldmg-Flfe Station No I em Boulevard Coppell, Texas I Scale: I" 50':f: Project Number: 08.04.0062 Date: April 2, 2008 Figure 3 t 1 Boring Location Plan APPENDIX B- FIELD RESULTS Records of Subsurface Exploration Sheets (Test Borings B-1 and B-2) Key to Symbols and Classifications - Soil & Rock <Xl ~ ~ l- e C) N W z ::i w ::;; C) ,g cill RECORD OF SUBSURFACE EXPLORATION ,I Gr.1E1 I Client: CITY OF COPPELL Boring No.: B-1 Page 1 of 1 Project: PROPOSED STORAGE BUILDING Project No.: 08.04.0062 FIRE STATION NO.1 Approved By: D. ZIOLKOWSKI, P.E. 520 SOUTHWESTERN BOULEVARD COPPELL, TEXAS FIELD DATA LABORATORY DATA Date Started: 3/13/08 Date Completed: 3/13/08 W ATTERBERG > LIMITS Drilling Co.: TEETS DRILLING CO. in Vl ~ C Drilling Method(s): Boring advanced using continuous W >< a: I- W W flight auger drilling equipment l1. Z 0 > a: 0 :IE W I- :!: W W 0 0 l- I- ~ in m a: I- :r U I- Z ~ ~ ..J W >= U ~ll.: 0 :; Cl Groundwater Information: Groundwater seepage :IE I- U. 0 ~ Cl 0 l1. a: :!: u :; U N ~ ::J U. 0 w:ru. _::J U ~ encountered at 23' during drilling. Water at 25' upon m Z W in Vl in :!:I-O VlU W 0 1= 1= 0 :IE W > := in := fficn a: :5 Vl Vl !!:. completion. )0 W 0 U.ClVl Z ..J ..J ZZ- ::J ~ ~ :r Vl U 0 Z 0 o~ I- 0 Vl ..J l1. l1. W ..J 0 ..J owVl Vl :; l1. l1. ::J l- e :IE :IE a: m I- m ua:z )o::J e Z l1. <( <( :Z 0.: ZI-o a:o ~ W D~~H DESCRIPTION OF STRATUM Vl Vl Vl <f. .:.: ::)U)C 0l1. :IE LL PL PI 0 - Dark brown, stiff, fat CLAY (CH) ~i P: 1.0 24 - - - - P: 1.3 28 68 23 45 - - - brown below 4.0' - -5 ~ P: 1.5 28 66 26 40 5- - - - P: 1.8 27 78 24 54 - - . very stiff below 8.0' - - ~~ P: 2.8 2.3 92.4 27 - -10 10- - 12.0 - - ------------- - - Reddish brown and gray, very stiff to hard, ~. I I-- - - SANDY lean CLAY (CL) 6 P:4.5 3.8 111.1 22 - I-- 15 ~ I-- 15- I- - I- 18.0 ~. - '- ------------- - I- Tan. dense, fine to coarse SAND (SW) ......X 7 N:43 8 - I-- 20 20- I- - ~ - - very dense below 23.0' ......X - I- 8 N: 54 14 - I-L 25 25- I- - I- - - - - ::::::X 9 N:53 13 - -30 - flowing sand encountered below 30.0' 30- - - - - - - - :::::: I 10 - -35 35- - - - - - - - ::::::. - -40 11 40- 41.0 - ~------------ '. ...." - I- Gray SANDY SHALE "':~~' - I- .......:-... - I- /.;:}. 12 - t-- 45 45- '1- :'~.:?: - I- .--:"""""..... - I- ....,,:....~ - - '+:7':" .... 13 T: 100/1.5" - ~- '1- Bottom of Test Boring at 50.0' - 'Sl.- WATER INITIAL rsJ NO RECOVERY IJ BAG SAMPLE N . STANDARD PENETRATION TEST .Y. WATER FINAL rn ROCK CORE ~ TEXAS CONE PENETROMETER P . HAND PENETROMETER [(] CUTTINGS . SHELBY TUBE SAMPLES [8J DRIVEN SPLIT SPOON T - TEXAS CONE PENETROMETER .., D- C) N to o o .. o <Xl o ~ Vl W ::;; C) '" ~ ;;; RECORD OF SUBSURFACE EXPLORA liON ,1l1'1IDl, Client: CITY OF COPPELL Boring No.: B-2 Page 1 of 1 Project: PROPOSED STORAGE BUILDING Project No.: 08.04.0062 FIRE STATION NO.1 Approved By: D. ZIOLKOWSKI, P.E. 520 SOUTHWESTERN BOULEVARD COPPELL, TEXAS FIELD DATA LABORATORY DATA Date Started: 3/13/08 Date Completed: 3/13/08 W ATTERBERG > LIMITS Drilling Co.: TEETS DRILLING CO. iii ~ Vl >': Drilling Method(s): Boring advanced using continuous W x 0:: f- W W flight auger drilling equipment 0.. Z C > 0:: C :;; W f- ~ W W a 0 f- f- i iii III 0:: f- J: 0 f- Z i ~ Groundwater Information: ..J W :;; ): 0 ~u, 0 ::; 0 Groundwater seepage 0 0.. f- IL ~ c 1=' 0 ::; u 0 ~ ::l 0:: IL a WJ:IL _::l 0 N 1=' encountered at 24' during drilling. Water at 24' upon III Z W Ui Vl Ui ~f-a VlO W C j:: j:: ci :;; > ;: Ui ;: ffiU5 0:: 5 Vl Vl !!:. completion. >- W W 0 "-elVl ::l :5 :5 Z Vl ..J ..J 0 0 Z 0 ZZ- c~ f- a Vl Z ..J 0.. 0.. W ..J 0 ..J owVl Vl ::; 0.. 0.. ::l f- a :;; :;; 0:: III f- III oo::z >-::l a Z 0.. <C <C Z a.: ~ Zf-o 0::0 i W D~~H DESCRIPTION OF STRATUM Vl Vl Vl ~ ::lVlC co.. :;; LL PL PI c - Dark brown, stiff, fat CLAY (CH) ~~ P: 1.0 23 - - - I- ~~ P: 1.3 30 59 25 34 - I- - brown below 4.0' - I-- 5 ~ P: 1.5 28 72 23 49 5- c- ~4 - - P: 1.8 28 78 26 52 - f- - very stiff below 8.0' ~ - - c- 5 P: 2.0 2.3 44.2 28 - I-- 10 - 10- f- ~ - c- - ------------- 13.0 '\: - - ~ - Reddish brown and gray, very stiff to hard, P: 2.3 2.0 94.9 22 - SANDY lean CLAY (Cl) -15 ~. 15- - - - ~ - - - - f-------_______ 19.0 0 - Tan, dense, fine to coarse SAND (SW) '" IX 7 N:45 9 I-- 20 20- c- - t- - t- - ~ ......X 8 N:49 13 - I-- 25 25- - - - - very dense below 27.0' - - - - ......X 9 N: 57 10 - -- -^ - Bottom of Test Boring at 30.0' - - - - - - - '5l- WATER INITIAL [SJ NO RECOVERY IJ BAG SAMPLE N - STANDARD PENETRATION TEST Y WATER FINAL CD ROCK CORE ~ TEXAS CONE PENETROMETER P - HAND PENETROMETER [J] CUTTINGS . SHELBY TUBE SAMPLES o DRIVEN SPLIT SPOON T - TEXAS CONE PENETROMETER .... o CJ N W Z ::; w ::! CJ ..., a. CJ N co o o ... o '" o N o .... Ul w ::! Cl CLASSIFICATION OF SUBSURFACE MATERIALS - SOIL Soil descriptions noted on Records of Subsurface Exploration (boring logs) are based on Standard Penetration Test results, visual/manual examination of soil samples, previous experience with similar soil types in the area, and the results of field and laboratory testing on selected soil samples. This classification sheet is based in part on ASTM D 2487- 92 and ASTM D 2488-90. The criteria, descriptive terms and definitions used are as follows: TYPICAL DESCRIPTIONS · Dark gray, hard, fat CLAY (CH) with trace fine sand. · Tan and light gray, hard, lean CLAY (CL) with calcareous nodules. · Tan, dense, fine SILTY SAND (SM) with trace fine gravel. DENSITY OR CONSISTENCY Ve Loose Loose Medium Dense Dense Ve Dense Penetration resistance determined in the field by Standard Penetration Test (SPT, ASTM D 1586): Number of blows required to drive a standard 2.0-inch outside diameter split-spoon sampler 12 inches into undisturbed soil by means of a 140-poound weight falling freely through a vertical distance of 30 inches. The sampler is normally driven in three successive 6-inch increments. The total number of blows required to drive the sampler over second and third 6-inch increments of penetration is the Standard Penetration Resistance, N. Ve soft Soft Medium Stiff Stiff Ve Stiff Hard Less than .25 .25 to .50 .50 to 1.00 1.00 to 2.00 2.00 to 4.00 Over 4.00 o to 2 2 to 4 4 to 8 8to 15 15 to 30 Over 30 2 Determined in the field by Soil Test pocket penetrometer test or in lab by unconfined compression test. 3 Determined in the field by Standard Penetration when no other strength test data is available. COLOR Dark gray, brown, tan, etc. a COMPONENT DEFINITIONS BY GRADATION Material passing though the 3" sieve & retained on the Fine 0/." NO.4 NO.4 sieve Sand Material passing Coarse NO.4 NO.1 0 the NO.4 sieve and retained on the No. Medium NO.1 0 No. 40 200 sieve. Fine No. 40 No. 200 Silt Material passing the No. 200 sieve which is also non- plastic in character and exhibits little or no strength when dried Clay Material passing the No. 200 sieve which can also be made to exhibit plasticity within a certain range of water contents and which exhibits considerable strength when air dried. No. 200 No. 200 COMPONENTS Major soil components: Upper case letters Secondary components: Adjective used (if .:: 30% plus No. 200 for fine-grained soils; if> 12% minus No. 200 for coarse- grained soils Third components: "with" used (if third component comprises 15% to 29% plus No. 200 for fine-grained soils; > 12% to 15% of total for coarse-grained soils Other components: "trace" to "little" used sometimes (if 1 % to 15% of total) OTHER DESCRIPTIVE TERMS The soils are also classified by the criteria of the Unified Soil Classification System (USCS), with the appropriate group symbol indicated in parentheses for each soil description. Fill: Soils indicated to have been recently placed by man Probable fill: Soils indicated to most likely be filled on the basis of stratigraphy, presence of foreign matter, etc. Possible fill: Soils which could possible be filled on the basis of visual soil texture, stratigraphy, etc. CLASSIFICATION OF SUBSURFACE MATERIALS - ROCK Rock descriptions noted on Records of Subsurface Exploration (boring logs) are based on visual/manual examination of rock samples, previous experience with similar rock types in the area, and the results of laboratory testing on selected rock core samples. This classification was modified for this project based in part on ISRM "Rock Characterization Testing and Monitoring." The criteria, descriptive terms and definitions used are as follows: TYPICAL DESCRIPTIONS · Gray, unweathered SHALE, calcareous with occasional fossils. · Tan, argillaceous LIMESTONE with clay layers. WEA THE RING Unweathered Fresh; few fractures, possibly with light staining. Very Severe "Rock" fabric discernible, but mass effectively reduced to "soil"; often discolored or stained. Moderate Significant portions of rock show discoloration and weathering effects. Rock has dull sound under hammer and shows significant loss of strength compared with fresh rock. Complete Rock reduced to "soil." "Rock" fabric tvpicallv not discernible. COLOR Gray, dark gray, light gray, etc. LITHOLOGY LIMESTONE, SHALE, MARL, CLAY LAYER, etc. Descriptive terms for limy shale visually determined by color and field hardness. Marl Limy shale. Limy Evidence of CaC03 cementing (typically reacts on contact with weak acid solution). Clay Layer Seam or layer of )1.," to 8"+ thickness typically consisting of hard, tan or gray shaly clay Shale Gray, typically soft, dominant clay and silt percentage, 'subdues" fissility typically observed on drying. a FRACTURES Surfaces representing discontinuities of breaks separating the rock in to discrete units. Bedding Plane Parting A separation between bedding planes. Joint A simple fracture along which no shear displacement has occurred. Mav form ioint sets. Remains or traces of animals or plants which have been naturally preserved (other than historical organisms). Fossil Shear A fracture along which differential movement has occurred parallel to the surface with sickensides, striations or polishing. Attitude Horizontal: Low Angle: High Angle: Vertical: o to 5 degrees 5 to 45 degrees 45 to 85 degrees 85 to 90 deorees ROD Rock Quality Designation (RQD) is defined as the sum in inches of all pieces of moderately weathered or less weathered rock core 4 inches in length and longer, divided by the length in inches of the core run, expressed as a percentage. If the core is broken by handling or drilling procedures, the pieces are fit together and counted as one piece, providing they constitute the required 4 inch length. The iength determination is measured down the centerline of the core and is calculated for each core run. FIELD TEST, THD Texas Highway Department (THO, now TxDOT) Cone Penetrometer Test. Conducted by a 3" diameter, 50 degree cone driven with energy equivalent of a 17o-pound hammer falling 24 inches. In relatively soft materials, the number of blows required to drive the cone over 12 inches of penetration is recorded for each 5-inch penetration interval. In hard materials, the penetration of the cone resulting from 1 DO-pound blows of the hammer is recorded for each 50-blow interval. GENERAL NOTES: 1. Records of Subsurface Explorations (boring logs) depict subsurface soil, rock and water conditions only at the specific locations and on the dates indicated. Soil and rock conditions and water levels at other locations may differ from conditions and levels occurring at the subsurface exploration locations. Also, the passage of time may result in a change in the conditions and water levels at the subsurface exploration locations. 2. Water levels noted on the logs were monitored at the times and under the conditions noted. In test borings, these water levels could have been affected by the introduction of water into the boring during drilling, extraction of tools or other procedures and thus may not reflect the actual groundwater level at the test boring location. It should be noted that fluctuations in groundwater levels normally occur due to variations in precipitation, temperature, season, adjacent construction activity, and pumping of water supply at wells and construction dewatering systems. APPENDIX C- LABORA TORY RESULTS Table 1- Summary of Free Swell Test Results rJ'j Eo-- S rJ'j ~ Eo-- rJ'j ~ Eo-- ~ ....~ ~~ ~rJ'j ~~ ~ ~ o >- ~ ~ ~ rJ'j C'l 1.000 00 00 '<:tt::! 0'- 00t2 Or') .. o z ..... CJ ~ ..... ~ e ~ ~Q o Z en ro c :>< .~ Q) ~~ .... ..... ~ ~1 t:J ~ 0 .. > ~ U .. C: QJ :.0'0 rl\ :-;:::> ..., .J ;:j ...... o:lo:l OJ) ~ E = :::: Cd 2 .. g I-. en ...... g. 0 Q) ~= 0 U5 ::: U'O-B II:) 4-0 Q) ;:j = 0 en 0 ?: 8 r./J o ..... 00 U ..... I-. C'l Uo...V) ~ ~~ ~O . t:J = ~ .. = ..... 0 CJ .- .~ ~ o CJ l-. 0 ~...:l - ~ ~ r./J~ ~ ~ l-. r... ..... = ~ = o U ~ l-. = ..... ~ .- o ~ ~ ..... 's J b1I l-. ~ ,.Q l-. ~ ..... ..... ~ = ~ ~ c.. l-. = ,.Q l-. ~ ~ o ..... ~ ~ ..cf ..... c.. ~ Q b1I = .... 0 ~ z ~ ~ ~ - ~ = fi: ":!? c ~ - ~ .- ..... 'a - - ~ ~ ~ ...:l ...:l oj' l-. = ~ ~ ~ l-. ~ I I 0\ V) o 0 o C'l r') 0\ 0\ C'l V) '<:t r') C'l 00 1.0 V) ."f .- .- '<:t I C'l .- I o:l r- o r') r') 0\ C'l 0\ '<:t r') C'l C'l r- '<:t r') .- .- 1.0 I '<:t C'l I o:l APPENDIX D- CONSTRUCTION PROCEDURES General Notes for Excavation and Trench Safety Guideline Specifications for Electrochemical Pressure Injection Geotechnical Exploration PROPOSED STORAGE BUILDING FIRE STATION NO.1 520 Southwestern Boulevard Coppell, Texas GME Proiect No. 08.04.0062 GENERAL NOTES FOR EXCA VA TION AND TRENCH SAFETY 1. Contractor shall follow all applicable OSHA requirements regarding excavations including the revised regulation - Occupation Safety and Health Standards _ Excavations 29 CFR Part 1926 as printed in the Federal RegisterNol. 54 No. 209/Tuesday, October 31, 1989. 2. Contractor shall employ a supervisor full time experienced and qualified to recognized non-compliance with the trench safety design and soil conditions and shall notify GME for further directions. 3. Prior to opening an excavation, effort shall be made to determine whether underground installations; i.e., sewer, telephone, water, fuel, electric lines, etc., will be encountered and if so, where such underground installations are located. When the excavation approaches the estimated location of such an installation, the exact location shall be determined and when it is uncovered, proper supports shall be provided for the existing installation. Utility companies shall be contacted and advised of proposed work prior to the start of actual excavation. 4. Trees, boulders, and other surface encumbrances, located so as to create a hazard to employees involved in excavation work or in the vicinity thereof at any time during operations shall be removed or made safe before excavating is begun. 5. Trenches and excavations shall be inspected by the contractor supervisors after each rain shower for compliance with trench safety designs before proceeding. If dangerous ground movements are apparent, such as subsidence or tension cracks, all work in the excavation must be stopped until GME Engineers have been notified. 6. Diversion dikes and ditches or other suitable means shall be used to prevent surface water from entering an excavation and to provide adequate drainage of the area adjacent to the excavation. Geoteclmical Exploration PROPOSED STORAGE BUILDING FIRE STATION NO.1 520 Southwestern Boulevard Coppell, Texas GME Proiect No. 08.04.0062 GUIDELINE SPECIFICATIONS FOR ELECTROCHEMICAL PRESSURE INJECTION WITH IONIC SOIL STABILIZER (Minimum of Three Electrochemical Injection Passes) A. SCOPE OF WORK The purpose of this work is to obtain a relatively uniform, properly chemically- stabilized zone of soil beneath the building floor slab of the storage building and below certain critical exterior flatwork portions of the project. Due to the wide variation in qualifications of injection subcontractors, electrochemical pressure injection is not recommended as a stabilization teclmique unless an inspector, under the supervision of a professional geoteclmical engineer, is retained on a part time basis. The work covered by this specification consists of furnishing all labor, equipment and materials and performing all operations in connection with the injection of an approved electrochemical fluid as specified below. The application of depth and injector spacing should be the sub grade to depths of 10 feet, as described in the report, all on three-foot centers and to ten feet (or edge of the sidewalks) outside the construction limits. B. QUALIFICATIONS FOR INJECTION The Contractor shall submit that his Subcontractor is competent in injecting an approved electrochemical fluid. The Contractor will insure that his Subcontractors have sufficient, competent personnel to carry out the operations specified and such personnel shall have experience in chemical injection. In particular, an injection specialist employed by the Contractor or Subcontractor shall be used to control the composition, mixing and application of the electrochemical. To be considered an approved electrochemical fluid, performance of a chemical must be analyzed and documented under a study performed by a major U.S. University or by the research arm of a US/State governmental agency. The qualified study shall state that the chemical will reduce the swell characteristics of the inplace clays to meet the project specifications. The study shall clearly state that the chemical not only reduces the negative charge of the clay particles but also changes the clay structure from an expanding crystalline lattice to a noncrystalline amorphous structure. The study will also qualify further the injection dilution rates and/or the required chemical per unit volume of soil in order to achieve proper stabilization. All injection at the site will be performed at the dilution rate upon which the conclusions in the university study are based. C. SITE PREPARATION Prior to the start of injection stabilization, the building floor slab area should be brought to approximately 1.5 feet below finish grade elevation and staked out to accurately mark the areas to be injected. The injection process must be extended ten feet outside the structure area or to the limits of the sidewalks. Allowance should be made for surface swelling that may occur as a result of the injection process depending on soil properties and in-situ moisture (generally 1 to 6 inches). Regrading may be required after injecting the soils to allow for the slab construction. D. MA TERIALS/EXECUTION 1. Chemical a. Approved Electrochemical Stabilizer The Contractor shall provide a certificate from the manufacturer on each shipment of electrochemical material certifying that it is an approved material. b. ElectrochemicallWater Mixture The ElectrochemicaVwater solution must be proportioned to a proportion rate documented within the university study to be effective as outlined in Section B of these guideline specifications and must be kept at this proportion for the first injection pass or injected in sufficient quantity to achieve uniform distribution of the required chemical per unit volume of injected soil as outlined in the supporting documentation of the university study. The total quantity of electrochemical solution (in gallons) and the total quantity of water used (in gallons) and then injected into the soil must be confirmed from the electrochemical tank and the water meters installed at the site. Batch tickets of the amount of chemical and water used each day along with the area of site injected must be submitted to the general contractor, who in turn must provide a copy to the GME representative on-site on a daily basis. Review of the injected area for acceptance will not proceed with receipt of these daily submittals by GME. 2. Water The water shall be clean, fresh, and contain no materials deleterious to the soil electrochemical reactions such as high acidity, high sulfate content, etc. 3. Injection Depth The injection depth shall be to minimum depths of 10 feet as described in the report. Injection time shall be until either refusal has occurred or until a minimum of 15 seconds or a maximum of 45 seconds has elapsed at each interval. Injections are to be made in 12" to 18" intervals down to the total depth. Inject at each interval to "refusal" (i.e., until the maximum quantity of solution has been injected into the soil and the electrochemical solution is running freely at the surface, from areas where the surface soils have fractured) or to the maximum interval time as specified. 4. Injection Pressure The injection pressure shall be adjusted to inject the greatest quantity of fluid possible (depending upon site conditions) at a constant flow and within a constant pressure range of 225 to 275 psi. Pressures shall be adjusted based on field conditions to assure solution penetration into soil fractures rather than returning to the surface around the injector pipe. 5. Equipment The injection vehicle should be capable of forcing injection rods into the soil with minimum lateral movement to prevent excessive blowback and loss of electrochemical solution around the injection rods. The injection should be track mounted and with a minimum weight of 10 tons. The lower portion of the injection rods should be of hardened material to insure maximum penetration. The hole pattern should allow for 3600 dispersion but not on the lower portion of the rod, which would tend to blow a path for the injection rod. E. Subsequent Electrochemical Injection Passes 1. After waiting approximately 24 hours from the time an area is first injected, the building area must should be injected at least two additional passes to hasten the dispersion process. The injection holes on additional passes shall be orthogonally offset 1.5 feet from the previous injection pass. The dilution rates must be at the same rate of proportions as performed within the documented university study. Also the quantities of chemicals injected and process must be pre-approved by the geotechnical engineer prior to initiating any injection at the site. F. INSPECTION AND TESTING An inspector working under the supervision of a professional geotechnical engineer will be retained by the Owner to periodically observe the injection operations. The GME representative must be scheduled by the contractor and be on site periodically during the electrochemical injection. His duties will include recording quantities of materials used (as supplied on batch tickets of chemical usage supplied from the contractor) and to observe the injection passes to watch for refusal of the chemical solution and time spent per each probe injection spacing. The contractor will be responsible for coordinating testing of the injected area(s) a minimum of 72 hours in advance of requiring drilling rigs and testing equipment for confirmation testing of the injected materials. After a minimum curing time of 72 hours upon completion of the electrochemical injection pass, the injected area will be tested as required to determine if any additional injections are necessary. Tests will include free swell, and other tests, as required, on samples obtained from soil borings drilled in representative injected areas. Test borings should be performed to minimum depths of 10 feet (or refusal) at a spacing of one boring per every 2,500 square feet of building pad area injected. Samples should be obtained at 2-foot intervals and tested at the same interval (minimum 5 free swell tests per boring) in accordance with general practice for electrochemical injection-treated soils. The design geotechnical engineer (GME) must be involved from the beginning of the electrochemical injection through subsequent electrochemical injection passes and testing to evaluate the soil stabilization process. An average of laboratory free swell tests of 0.8 percent within the la-foot deep injected areas with no swell test exceeding 1.6 percent will be considered as satisfactory injection within any injected area.