Subsurface Exploration and Geotechnical Evaluation New Church for Bateman Baptist Church FM 20, Bastrop County, Texas.

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1 Nicholas F. Kauffman, M.S., P.E. Principal Geotechnical Engineer Mobile: (512) Subsurface Exploration and Geotechnical Evaluation New Church for Bateman Baptist Church FM 20, Bastrop County, Texas Prepared for: Bateman Baptist Church P.O. Box 213 Red Rock, Texas Prepared by: Capital Geotechnical Services PLLC Cedar Park, Texas Texas Engineering Firm Registration # 9458 Capital Geotechnical Services Project # November 20, 2014

2 New Church Building for Capital Geotechnical Services Project # TABLE OF CONTENTS Page: SCOPE... 1 SUMMARY... 1 SITE LOCATION AND CONDITIONS... 2 LANDFILL LITERATURE REVIEW... 3 PLANNED CONSTRUCTION... 3 GEOLOGY AND SOIL MAPPING INFORMATION... 4 SUBSURFACE EXPLORATION... 4 LABORATORY TESTING... 5 SUBSURFACE CONDITIONS... 5 POTENTIAL MOVEMENT OF THE CLAY SOILS... 7 SITE PREPARATION AND EARTHWORK... 8 FOUNDATION SLAB TALL PERIMETER BEAMS SEISMIC DESIGN SURFACE DRAINAGE, VEGETATION, AND UTILITY CONNECTIONS POST-TENSIONING (IF USED) DRIVEWAY LIMITATIONS INSPECTIONS FIGURES: Figure 1: Vicinity Map Figure 2: Local Lot Plan Figure 3: Geology Map Figure 4: Approximate Locations of Exploratory Borings Figure 5 and Figure 6: Boring Logs Figure 7: Standard Reference Notes for Boring Logs Figure 8: Swell Test Results

3 SCOPE This report presents the results of a geotechnical evaluation for a new church building on the Bateman Baptist Church property in Bastrop County, Texas. This study was performed to evaluate subsurface conditions and to provide recommendations for the design and construction of the foundation system. Capital Geotechnical Services PLLC performed this subsurface exploration and geotechnical evaluation in accordance with our proposal # P authorized (signed) on October 9, The scope of services for this study included a site reconnaissance, the determination of subsurface conditions through field and laboratory testing, an evaluation of the subsurface conditions relative to the proposed construction, and the preparation of a geotechnical report. This report includes results, evaluations, and recommendations concerning earthwork, foundations, quality control testing, and other geotechnical related aspects of the project. A summary of our conclusions is presented in the following section of this report. More complete descriptions and findings of our field and laboratory testing are presented in the rest of the report. The scope of services did not include any environmental site assessments. SUMMARY The subsurface conditions encountered during our exploration and our geotechnical engineering evaluations and recommendations are summarized in the following paragraphs. This summary should not be considered apart from the entire text of this report. This report should be read and evaluated in its entirety prior to using our engineering recommendations for the preparation of design or construction documents. Details of our findings and recommendations are provided in subsequent sections of this report and in the attached figures. 1. Two (2) exploratory borings were drilled to evaluate soil conditions. The subsurface profile generally consists of a 4-ft thick surface stratum of light brown, reddish brown, and light yellowish brown highly plastic clay (CH) (expansive clay), overlying a 2-ft to 4-ft thick stratum of pale grayish brown, light yellowish brown, and pale yellowish brown lean clay with sand (CL) and clayey fine sand (SC), underlain by light gray, pale brownish gray, pale yellowish grayish brown, and pale yellowish brown medium dense silty to clayey fine sand (SC-SM) to a depth of 18 to 19 feet, overlying a small layer of light gray, light yellowish brown, medium gray, and orange-brown highly plastic clay (CH) to a depth of 20 to 21 feet, overlying light yellowish brown, light gray, and light brown silty fine sand (SM) and silty to clayey fine sand (SC-SM) with clay seams (CL) to a depth of at least 25 feet. Groundwater was not encountered during the drilling operation in October The maximum depth of exploration was 25 feet. 1

4 2. The TxDOT PVR index was calculated to be 2 ¾ inches at this site if no soil improvement is performed, essentially due to the presence of the surface stratum expansive clay. Potential vertical soil movement (design PVR) was calculated to be 4 inches if no soil improvement is performed and notable changes in moisture content occur within the 4-ft thick clay surface stratum. 3. Based on the available soil information, proposed construction, and assumed structural loads, a ground-supported stiffened slab (foundation slab) can be used to support the proposed building structure. Some soil improvement should be performed to reduce the design PVR to a level acceptable to the Owner, Architect, and Structural Engineer. Recommendations concerning the design and construction of the foundation slab are presented in this report. 4. Based on a finished floor elevation assumed to be just above highest exterior grade on the upslope side of the building, we estimate 4 inches to 48 inches of new fill will be required to reach planned slab subgrade elevation across the footprint, before consideration of soil improvement. Recommendations concerning earthwork are included in this report. 5. Surface drainage should be designed, constructed, and subsequently not adversely altered by the Owner, to provide rapid removal of water runoff away from all sides of the building. SITE LOCATION AND CONDITIONS The project site is within a 2.6-acre lot adjoining another 1.05 acre lot located on the south side of FM 20 in the Bateman and Red Rock community of Bastrop County, Texas (Figure 1 and Figure 2). The site was a relatively clear grass field west of the existing church buildings. The site slopes gently down toward the southeast. 2

5 The USGS topographic map shows no indication of any potentially backfilled pre-existing pond, quarry pit, or landfill at the site at the time the map was made (see graphic). LANDFILL LITERATURE REVIEW The 2002 CAPCO (Capital Area Planning Council; now the Capital Area Council of Governments) Closed and Abandoned Landfill Inventory report (and the 2010 update) for Bastrop County was reviewed and there were no small landfills (dumps) identified at the subject property. PLANNED CONSTRUCTION The planned construction includes a one-story church building. The structure might consist of steel framing and metal roofing (i.e. metal building). A preliminary site plan was provided to Capital Geotechnical Services and was used for the boring location plan (Figure 4) although the planned footprint appears larger in another architectural plan. The planned construction is assumed to include a paved driveway to access the front of the building. Information concerning structural loads was not provided to Capital Geotechnical Services. We have assumed that structural loads will not exceed 75,000 lbs for any single column and 2,000 lbs per foot for any wall loads. Information concerning planned finished floor (FF) elevation was not provided to Capital Geotechnical Services by the time of this report but the conceptual sketches indicate the rear of the building will have exterior space that steps down to the adjacent grade. We have therefore assumed that planned finished floor elevation will be close to, but just above, highest existing grade on the upslope side of the building. We estimate 4 inches to 48 inches of fill will be required to reach planned slab subgrade elevation before consideration of any soil improvement. The thickest fill and tallest perimeter beam would be at the southeast corner of the footprint. We assume exterior grades will not be altered except for minor fine-grading for drainage design purposes. 3

6 If the planned construction varies from what is described in this report, Capital Geotechnical Services must be contacted to determine if revisions to our recommendations are required. GEOLOGY AND SOIL MAPPING INFORMATION According to the USDA Natural Resources Conservation Service shallow soil mapping information, the shallow soils of the local area may be a member of the Robco Loamy Fine Sand and Crockett Fine Sandy Loam soils series. The Robco series is stated to typically have a 2- ft thick surface stratum of sand soil (SM, SC) overlying mixed fine-grained soils (CL, SC), and the Crockett soil is indicated to commonly consist of a thin sandy topsoil layer overlying clay soils (CL, CH). We assume the clay soils encountered at the boring locations are of the Crockett soil series. According to available geology mapping information by the U.T. Bureau of Economic Geology, the site is located in the Gulf Coastal Plain geologic physiographic province and consists of fiengrained soils (clay, silt, fine sand), siltstone, and sandstone sedimentary deposits categorized as the Wilcox Group geologic formation. Lignite coal is also present in this formation. A geology map is provided in Figure 3. SUBSURFACE EXPLORATION Two (2) exploratory borings were drilled to evaluate soil conditions. The borings drilled in this exploration were located in the field by Capital Geotechnical Services by measurements from existing site features (trees; and building footprint corner stakes placed by others). The borings were drilled on October 22, 2014, to a depth of 25 feet below existing grade at the approximate locations indicated in Figure 4. Drilling was performed using a truck-mounted drill rig equipped with 4-inch diameter continuous flight solid stem augers and a split-spoon sampler. A hammer weighing 140 pounds falling 30 inches was used to drive the split-spoon sampler. Boreholes were backfilled with available auger cuttings and bentonite chips if needed. The soil samples were delivered to our laboratory where they were visually classified by a Geotechnical Engineer and selected samples were subjected to laboratory testing. Detailed boring logs are provided as Figures 5 and 6. 4

7 LABORATORY TESTING Representative soil samples were selected and tested to assist the visual classifications and to determine pertinent engineering and physical characteristics. Tests were performed in general accordance with applicable ASTM standards. Results of the laboratory tests are included on the boring logs. Specialized testing to determine the presence of chemicals in soil samples (e.g., sulfates, chlorides) was not requested. A Geotechnical Engineer classified each soil sample on the basis of texture and plasticity in accordance with the Unified Soil Classification System (USCS). The USCS group symbols for each soil type are indicated in parentheses following the soil descriptions on the boring logs. Expansive properties of 2 samples of clay soil were evaluated by performing swell tests. The test consists of placing a remolded specimen in a rigid ring at the as-sampled moisture content, applying a light seating load, allowing the sample to absorb water, and measuring the vertical heave of the sample while not allowing horizontal (lateral) strain. The results of such testing are used by the Geotechnical Engineer to help properly evaluate the clay mineralogy and the shrinkswell behavior of the clay soil. Soil samples that remain after testing will be kept for 3 weeks after the date of this report. Samples will then be discarded unless we receive instructions regarding their disposition. SUBSURFACE CONDITIONS Information from the exploratory borings indicates that the soil stratigraphy may generally consist of 5 distinguishable strata above a depth of 25 feet. The characteristics of these strata are summarized in the following paragraphs. Stratum A: Expansive Clay The upper 3 ½ feet to 4 feet of soil at this site appears to consist of reddish brown, light yellowish brown, and light brown highly plastic clay (CH). The clay was hard at the time of sampling, exhibiting pocket penetrometer (PP) measurements of 4.5+ tsf. Two samples were tested to determine plasticity (Atterberg limits) and yielded a liquid limit (LL) of 52% and 74%, and a plasticity index (PI) of 32 and 51. Two remolded specimens were subjected to swell testing and exhibited 15.9% and 17.1% vertical swell from initially hard (PP=4.5+ tsf) and low to moderate moisture condition (LI = to ) (Figure 8). Stratum B: Fine-Grained Soils The surface clay is underlain by an apparent 2-ft to 4-ft thick stratum of pale grayish brown clayey fine sand (SC) to light yellowish brown and pale yellowish brown lean clay with fine sand (CL). 5

8 One sample of the more clayey soil was tested to determine plasticity and yielded a LL of 37% and a PI of 20. Stratum C: Sand Soil A large stratum of light gray, pale yellowish grayish brown, pale brownish gray, and pale yellowish brown fine sand with some silt and clay content (SC-SM) was encountered starting at a depth of 6 to 8 feet and extended to a depth of approximately 18 to 19 feet. The sand was generally in a medium dense condition as evidenced by the SPT N-values of 20 blows per foot (bpf) to 32 bpf for the 5 tests performed. Stratum D: Clay Layer A small layer of light gray, light yellowish brown, medium gray, and orange-brown highly plastic clay (CH) was evident within the depth range of 18 to 21 feet. Stratum E: Sand Soil The soil beyond a depth of approximately 20 to 21 feet consisted of light yellowish brown and light gray silty to clayey fine sand (SC-SM) to silty fine sand (SM) that was in a dense condition, exhibiting SPT N-values of 43 bpf and 56 bpf for the two tests performed. The above descriptions are of a generalized nature to highlight the major soil stratification features and soil characteristics. The boring logs provided in the Appendix should be reviewed for specific information at each location. The stratification of the soil represents our interpretation of the subsurface conditions at the boring locations based on observations of the soil samples by a Geotechnical Engineer. Variations from the conditions shown on the boring logs could occur in areas in between borings or in areas around the borings. The stratification lines shown in the boring logs represent approximate boundaries between soil types and condition, and the transitions may be gradual rather than distinct. It is sometimes difficult to identify changes in stratification within narrow limits. It may also be difficult to distinguish between fill and discolored natural soil deposits if foreign substances are not present. Groundwater was not encountered in our exploratory borings at the time of drilling. Moisture contents were relatively low, indicating that groundwater was not present. Groundwater, however, can be temporary instead of perennial. Although groundwater was not encountered during the drilling and sampling operation, our experience requires us to emphasize that groundwater can still appear later. Groundwater levels may fluctuate seasonally in the project area due to variations in precipitation, runoff, evaporation, groundwater pumping, and other factors that affect groundwater recharge such as water levels in nearby creeks, ponds, lakes, and rivers. 6

9 POTENTIAL MOVEMENT OF THE CLAY SOILS The clay soils within the zone of seasonal moisture change (or within a potential active zone) will experience changes in condition due to changes in environmental conditions (rainfall quantities and frequency; temperature; evaporation; tree roots) and man-made conditions (leaking water lines; irrigation; poor drainage) that affect the moisture content of the clay soils. The clay soil near the surface may harden, shrink, and crack when subjected to drying, swell when subjected to wetting, and soften when subjected to saturation. The TxDOT Potential Vertical Rise (PVR) index (Tex-124-E) considering existing conditions and existing overburden pressure was calculated to be approximately 2 ¾ inches. It was assumed that the clay would be in an initially dry condition as defined by the method at the time of construction and that the thickness of the active zone is 8 feet at boring B-2 (4 feet of highly expansive clay, overlying 4 feet of lean clay with relatively low shrink-swell potential). Note that the TxDOT PVR method assumes limited wetting occurs and should only be used as an index tool for comparing sites. The TxDOT PVR value should not be considered an estimate of maximum potential vertical heave. Using reasonable estimates of relatively dry and relatively moist suction profiles or moisture content profiles and physical properties of the clay soil, the swelling potential of the clay soils within the active zone (assumed to be 8 feet deep) may be approximated as 4 inches if the moisture content changes between a relatively dry condition and a relatively moist condition. The design PVR does not consider absolute worst case moisture change conditions (i.e. 200-year to 500-year drought event or rainfall event, etc). The potential amount of total and differential heave or shrinkage is difficult to accurately predict because it will depend on the extent of impervious cover, seasonal changes in climate conditions, drainage conditions, presence of leaking water pipes, groundwater conditions, landscape watering, vegetation planting, thickness of clay soil affected, and varying physical characteristics and mineralogy of the clay soils. The PVR is not a static value because it depends on how the soil behavior and the boundary conditions are modeled such as what changes in moisture content to consider and what initial moisture condition to consider at the time of construction. 7

10 SITE PREPARATION AND EARTHWORK Stripping and Clearing All of the topsoil (soil with high organic content), tree roots, vegetation, deleterious forest materials (downwood, litter, duff), wet soils, and any soft or loose soils must be removed from the proposed building and driveway pavement areas. Deep stripping may be required to remove deep roots of mature trees. Disturbed (loose) subgrade within stump and root bulb removal areas must be compacted and proof-rolled before placing any overlying fill, slab materials, or pavement materials. Alternatively, the loose material can be removed and replaced with properly compacted select fill. Stripping should be observed and documented to record that unsuitable materials were removed prior to placement of fill, slab, or pavement materials. Soil Improvement in the Building Area The potential soil movement due to shrinkage and swelling can be reduced by using soil improvement techniques to change the characteristics and properties of the subgrade soils. For this scale of project and for the unique subsurface conditions of the site, we recommend for the building area considering removal and replacement with imported select fill. The thickness of removal and replacement will be selected by the Owner, Architect, Builder, and the Structural Engineer since multiple factors affect how much vertical movement can be tolerated by the structure (type of cosmetics used, flexibility of framing detailing and cosmetics, aversion to risk, stiffness of framing to resist wind loads, rigidity of slab, design deflection tolerance, etc). Design parameters for various thickness of soil improvement are provided in this report. Cut Grading and Subgrade Evaluation After stripping and soil improvement excavation have been completed, the exposed subgrade soils in building and pavement areas should be evaluated. Proof-rolling should be performed where possible with a heavy (minimum 20 ton) rubber-tired vehicle such as a loaded dump truck or water truck to provide a more thorough evaluation of the subgrade stiffness. Soils that are observed to rut or deflect excessively under the moving load should be under-cut, scarified, airdried, and compacted as necessary to achieve a stiff subgrade condition, or soft soil can be undercut and replaced with compacted select fill that meets the requirements of this report. All proofrolling and under-cutting activities should be observed, documented, and performed during periods of dry weather. 8

11 Subgrade inspections must be followed immediately by placement of select fill, pavement materials, or slab materials to protect the approved subgrade condition. Soil conditions change when exposed to environmental conditions and man-made disturbance so approvals of subgrade conditions are only valid for a short period of time. If rainfall events in particular occur before protecting the area, the subgrade inspection results are no longer valid and re-inspection and possible re-working and compaction of the subgrade will be required. Field observations and testing should be performed during the earthwork operation to verify and document proper construction. Field observation and inspection should include final approval of subgrades prior to placement of compacted fill, slabs, or pavement. Backfilling of Buried Utilities Unless all 4 feet of clay is removed, note that utility trenches within clay soils, backfilled with clean sand or gravel can function as post-construction conduits for water below the building. This can result in swelling of clay soils affected by the water along the trench and result in development of cracking and heaving in the pavement, slab and building near the trench. Capital Geotechnical Services recommends using fine-grained backfill such as on-site trench cuttings or imported low to medium plasticity clay (CL) or clayey sand (SC) to backfill utility trenches. The backfill must not be densely compacted (i.e. allow some soil compressibility within the trench). Alternatively, concrete cut-off collars or clay plugs should be included in the trench design to prevent water from entering sections of trench beneath slab and pavement areas. Fill Placement Select fill that is re-used or imported to the site for use under the slab should be classified according to the Unified Soil Classification System (USCS) as SM-SC, SC, GM-GC, or GC, and should meet the following criteria: Percent passing the No. 4 sieve: 50% to 100% (0% to 50% gravel) Percent passing the No. 200 sieve: 20% to 45% PI of soil passing the No. 40 sieve: 6 to 20 Maximum size of gravel or rock fragments: 3 inches in any dimension The compacted select fill pad (and soil improvement excavation) must extend horizontally beyond the edge of the foundation slab footprint a minimum distance equal to the thickness of the fill between the bottom of the perimeter beam and the bottom of the fill pad (i.e. if there is going to be approximately 2 feet of fill beneath the perimeter beam in one area, then the fill pad must extend horizontally at least 2 feet beyond the edge of the slab). The project team should also 9

12 consider extending the pad horizontally to include immediately adjacent flatwork. The soil improvement excavation can be stepped (shallow benches) to permit the installation of horizontal lifts of fill and prevent excessive excavation depth at the upslope side of the building. Select fill should be placed in horizontal loose lifts of not more than 6 to 8 inches in thickness depending on the size and weight of the compaction equipment. Select fill should be moisture treated and compacted to achieve a minimum relative compaction of 96% based on the maximum dry unit weight as determined by the Standard Proctor method (ASTM D 698). Moisture content of select fill material should be within -1 and +3 percentage points of the optimum moisture content at the time of compaction (-1% to +3%). Some wetting or drying might be required to produce the necessary moisture content at the time of compaction. The performance of foundations placed on new fill material is influenced by the quality of the compaction and quality of the materials selection of the fill material. Capital Geotechnical Services should be retained to perform quality control testing and inspection during selection, placement, and compaction of the fill material. Appropriate laboratory tests such as Proctor moisture-density tests should be performed on samples of fill material and pavement base course material. Field moisture-density tests and visual observation of lift thickness and material types should be performed during compaction operations to verify that the construction satisfies material and compaction requirements. In-place moisture-density tests and lift thickness checks must be performed on every lift of fill. Fill materials should not be placed on soils that have been recently subjected to precipitation or saturation. All wet soils should be removed, or reworked, or stabilized, or allowed to dry prior to continuation of fill placement operations. Fill soils must be free of wood debris (organics) such as large branches, thick roots, and wood chips since over time these organic materials will decay, causing localized settlement or creating voids. Water entering voids can eventually lead to collapse of the void and settlement under pavement or under a slab. If any problems are encountered during the earthwork operations, or if newly exposed soil and site conditions are different from those encountered during our subsurface exploration, the Geotechnical Engineer must be notified immediately to determine the effect on recommendations expressed in this report. If construction is performed during winter or spring seasons when the occurrence of rainfall is more frequent, to limit effects of wet weather, the building pad area can be initially graded high or crowned to protect the slab subgrade. The additional soil can be removed when slab 10

13 construction can begin. Note that during periods of cold weather, frozen soils cannot be used as fill or backfill. Certain construction practices can reduce the magnitude of problems associated with moisture content increases of subgrade soil for pavement, slabs, and areas to receive compacted fill. If rainfall appears imminent, the contractor should seal exposed subgrade areas at the end of the work day with a smooth drum roller to reduce the potential for infiltration of water into the subgrade. If asphalt paving is used, pavement base course should preferably consist of well graded crushed stone material and not open-graded aggregate, but should conform to any locally developed guidelines. Site grading should be continuously evaluated to assure that surface runoff will drain away from pavement, slab, and fill areas. Final grading of the subgrade along the driveway alignment must be carefully controlled so that low spots in the subgrade that could trap water in the base course or under a concrete joint are eliminated. FOUNDATION SLAB Based on the subsurface conditions encountered and our experience with similar construction, the proposed building structure can be constructed on a ground-supported stiffened slab foundation system. Recommendations concerning the design and construction of the foundation slab are presented in the following paragraphs. 1. The metal building structure can be supported on a rigid, monolithically-cast, grid-type grade beam and slab foundation system (foundation slab). When placed on expansive soils, subgrade improvement should be performed to reduce potential soil and foundation movement to levels acceptable to the Owner, Architect, and Structural Engineer. 2. The rigidity of a stiffened slab will limit the effects of differential soil movement caused by swelling and shrinkage of clay soils and compression of soils due to structural loads. However, discernible cracking in brittle construction materials may still occur. This type of slab should be designed with perimeter grade beams and interior stiffening grade beams adequate to provide sufficient rigidity to the slab element. The foundation slab can be designed considering an allowable bearing pressure of 2,500 psf across the grade beam contact area if all grade beams are placed on properly compacted select fill and/or firm native soil. 3. Perimeter grade beams should extend at least 12 inches below final adjacent exterior grade and have a minimum width of 10 inches. The grade beam width and depth will be determined by the project Structural Engineer. Grade beams may be thickened and widened at column or load bearing wall locations to support concentrated load areas. The 11

14 grade beam details must specify minimum beam height and minimum beam penetration below exterior grade (ground surface) (i.e. emphasize that a uniform total beam height is not expected if the perimeter grade varies due to sloping topography, so some stepped trenching will be required). 4. Floor coverings (carpet, tile, wood, laminate, vinyl) can be damaged or subject to mold growth by moisture penetrating the slab, therefore a moisture vapor barrier (i.e. 10 mil thick geosynthetic geomembrane) should be placed on top of the fill and properly sealed to limit the migration of moisture to and through the slab, and to serve as a separator between the fill and concrete. The moisture barrier can be placed after the grade beams are formed. We recommend lapping the sheets of vapor barrier 12 inches and taping the joints/laps. Since many field crews do not force membranes down to make continuous contact with the trench walls and bottom to maintain proper rectangular beam cross section, if a single sheet of geomembrane is placed across a trench, we recommend cutting the membrane at the bottom of the grade beam trench to prevent the poured cross section area from being reduced (prevent bridging at bottom corners), and installing a separate strip of vapor barrier along the bottom to overlap the cut membrane on either side of the trench. 5. The foundation slab can be post-tensioned or conventionally reinforced. The foundation slab should be designed using the PTI, WRI, or BRAB soil-related design parameter values provided in the subsequent paragraphs. 6. Guidelines for the design of a conventionally reinforced foundation slab are provided by resources such as the Wire Reinforcement Institute (WRI), the International Building Code (IBC), the 1968 FHA BRAB report, and ACI 360R. 7. We recommend the parameter values in Table 1 when designing a conventionally reinforced stiffened slab using traditional BRAB or WRI guidelines. We do not recommend designing and constructing a foundation slab on soil conditions with a design PVR greater than 2 inches. Parameter values for a design PVR greater than 2 inches are provided for illustration purposes only. 12

15 Table 1: Do nothing Soil Improvement Condition Design PVR Design PI BRAB Support Index C 1-C WRI Cantilever Length 4 inches ¼ feet lc Under-cut 1 foot of clay and replace with properly compacted select fill * Under-cut 2 feet of clay and replace with properly compacted select fill * Under-cut 3 feet of clay and replace with properly compacted select fill * Under-cut 4 feet of clay and replace with properly compacted select fill * 3 ¼ inches ¼ feet 2 ¼ inches ¾ feet 1 ¼ inches ½ feet < 1 inch ¾ feet *: Under-cut is from existing grade. Clay must be replaced with properly compacted select fill to support interior grade beams and, depending on depth of improvement, the perimeter grade beams. For foundation slabs designed using the BRAB or WRI type methods, long term deflection of flexural beams resulting from creep and shrinkage of concrete under sustained loading can be determined using ACI Guidelines for the design of post-tensioned slab-on-grade can be found in the PTI manual Design of Post-tensioned Slabs-on-ground (2 nd Edition 1996 or 3 rd Edition 2004) and the PTI manual Standard Requirements for Design and Analysis of Shallow Post-Tensioned Concrete Foundations on Expansive Soils (2012). We recommend the soil-related parameter values in Table 2 if using a PTI method of design. We do not recommend designing and constructing a foundation slab on soil conditions with a design PVR greater than 2 inches. Parameter values for a design PVR greater than 2 inches are provided for illustration purposes only. 13

16 Table 2: Soil Improvement Condition Do nothing Design PVR PTI Differential Movement (ym) Center Lift Edge Lift Edge Moisture Variation Distance (em) Center Lift Edge Lift 4 inches 2 ¾ inches 4 inches 5 feet 3 feet Under-cut 1 foot of clay and replace with properly compacted select fill * Under-cut 2 feet of clay and replace with properly compacted select fill * Under-cut 3 feet of clay and replace with properly compacted select fill * Under-cut 4 feet of clay and replace with properly compacted select fill * 3 ¼ inches 2 ¼ inches 3 ¼ inches 5 feet 3 feet 2 ¼ inches 1 ½ inches 2 ¼ inches 5 feet 3 feet 1 ¼ inches 1 inch 1 ¼ inches 5 feet 3 feet < 1 inch ¾ inch ¾ inch 5 feet 3 feet *: Under-cut is from existing grade. Clay must be replaced with properly compacted select fill to support interior grade beams and, depending on depth of improvement, the perimeter grade beams. The vertical modulus of elasticity (E s) of immediate subgrade under slab for use in determination of the PTI beta parameter value can be selected to be 100 tsf (1,389 psi). The PTI partition load slab stress coefficient (C p) (3 rd Edition PTI manual) can be selected to be 1.10 for k s = 180 pci (compacted select fill). 9. Although the ground-supported foundation slab can be designed for vertical soil movement greater than 1 inch, the cosmetic elements of the building might not be able to tolerate the associated slab deflection. The building occupants might perceive excessive movement when they see cracking in brittle elements such as drywall, hard tile, and any exterior brittle veneer. The acceptable design slab deflection must be carefully selected. The foundation slab can be designed for a PVR greater than 1 inch if an acceptable slab deflection can be achieved by the design. Potential tilting and angular distortion, however, cannot be avoided, and the effects are uncertain. The Owner must compare the risks of tilting and associated consequences, with the costs of more robust soil improvement associated with a lower risk of tilt and angular distortion. 10. If the slab will be post-tensioned, the General Contractor may consider using a subcontractor installer who is PTI certified to help ensure the quality of the construction. 11. Exposure to the environment may weaken the soils at the grade beam bearing level if the foundation excavations remain open for an extended duration. Foundation slab concrete should be placed within 2 weeks of the completion of trench excavations and the moisture 14

17 barrier should be installed before any notable rainfall event. If the bearing soils are softened by surface water intrusion or disturbance, the softened soils must be removed from the foundation excavation bottom prior to concrete placement. 12. Grade beam dimensions and reinforcing steel should be observed and documented asbuilt ( pre-pour inspection by the Structural Engineer; or by the Geotechnical Engineer if needed). 13. Prior to installation of reinforcing steel (or tendons) and the moisture-vapor barrier, Capital Geotechnical Services should be retained to observe and test the grade beam subgrade to determine if the foundations are being placed on suitable materials and to document that loose material has been removed. Dynamic Cone Penetrometer (DCP) tests can be performed to help evaluate subgrade condition. In areas where the subgrade is soft or loose, the soil should be removed and foundations lowered to bear on firm soil or foundation subgrade elevations can be restored using flowable fill approved by the Structural Engineer. 14. Concrete material should be sampled and tested for compressive strength, and placement operations should be monitored to record concrete slump, temperature, and age at time of placement. Concrete batch tickets should be provided by the supplier and collected by the General Contractor to permit inspection and documentation of water-cement ratio, cement content, and other mix design ingredients. 15. Perimeter grade beams can be designed to transfer horizontal column reactions into the soil. Passive resistance from the upper 1 foot of soil however should be ignored because of the potential to have poorly placed backfill along the perimeter beam or because of the potential for future excavation, erosion, or saturation. Beams penetrating into the properly compacted select fill within the soil improvement excavation can consider a passive earth pressure coefficient (k p) of 3.0 or an equivalent fluid unit weight of 360 psf. 16. We recommend that a slab surface elevation survey be performed within 2 weeks after the concrete is poured to document the initial condition of the slab. Such information will be useful if future soil and slab movement is suspected and must be compared with the initial elevation differences. Capital Geotechnical Services can be retained to perform a slab surface elevation survey upon request. 15

18 TALL PERIMETER BEAMS The planned construction includes tall perimeter beams on the downslope side of the building. The wall is anticipated to retain properly compacted select fill. The wall can be designed considering an equivalent fluid unit weight of 55 pcf for at-rest earth pressure. The wall design should account for any surcharge loads within a 45 degree angle from the base of the wall. The fill pad is anticipated to drain into the deeper fill used for soil improvement purposes. SEISMIC DESIGN The subject site is located in a region of low seismicity. The region has relatively low spectral response acceleration and can be assigned to Seismic Design Category A according to ASCE 7-05 and Section 1613 of the 2012 IBC guidelines. The subject site can be categorized as a Class D site for determination of design soil shear wave velocities. SURFACE DRAINAGE, VEGETATION, AND UTILITY CONNECTIONS We recommend the following precautions be implemented during construction: A. Unless 4 feet of clay is removed and replaced, utility structures that connect to the building should be designed to be flexible enough to tolerate some differential soil movement. Water supply pipes and sanitary sewer pipes beneath the slab should be placed in long sections with as few joints (leak-prone) as possible and should be of durable size and material. Utilities that project through the foundation slab should be designed with either some degree of flexibility or with sleeves in order to prevent damage or leaking should vertical movement occur (i.e. sanitary sewer drain penetrations). Water supply and sanitary sewer systems should be leak tested after installation. Telescoping joint or swivel joint pipe fittings can be considered. B. The ground surface around the building should be sloped away from the building to provide positive drainage away from the building perimeter. A minimum drop of 6 inches over the first 10 feet from the edge of the foundation is recommended (IBC 2012: ). C. Roof drains should be designed and placed to discharge stormwater at least five feet away from the building. Roof drain downspouts should also be concentrated on the downslope side of the building. D. Unless notable soil improvement is performed, if concrete root barriers are not installed, trees or deep-rooted bushes should not be planted or allowed to exist adjacent to the 16

19 building within a distance equal to half of their mature height because of the root penetration and moisture demand that will dry the underlying clay soils. E. If concrete root barriers are not installed, large tree species or bushes should not be planted or allowed to exist near the foundation within a horizontal distance equal to half of their mature height because of the root penetration and moisture demand that will dry underlying clay soils. F. Plants placed close to the foundation should be limited to those with low moisture requirements. G. Air conditioner condensation outlet pipes should not discharge immediately adjacent to the foundation slab (perimeter beam). The pipes should be extended and/or buried to discharge water at least 3 feet away from the foundation slab and preferably on the downslope side of the building. H. If shrubs must be placed adjacent to the building, the landscape beds or planters should not be recessed (place at grade or elevate above grade and drain properly to prevent ponding adjacent to the foundation slab). POST-TENSIONING (IF USED) Post-tensioning cables (tendons) and accessories need to be accurately placed, protected, and correctly installed. Utility penetrations through the slab must be planned in conjunction with the placement of post-tensioning cables. The Structural Engineer, or the Geotechnical Engineer if needed, should be retained to perform a pre-pour inspection to observe and document grade beam dimensions and proper cable installation. Pulling (tensioning) of cables should be performed by experienced personnel because of the danger involved during the pulling and lock-off operation. Cable ends must be properly covered or coated to prevent corrosion that can allow long term relaxation and reduction of design strength, and potential excessive movement in isolated areas of the slab. Tendon tails should not be cut until the tensioning (stressing) test data is approved by the project Structural Engineer. The posttensioning stressing operation should be observed by the Structural Engineer (or by the Geotechnical Engineer if needed) to document proper construction. Observations should include obtaining a copy of the calibration sheet correlating force and hydraulic pressure of the jack being used. Each tendon elongation should be measured and compared to specification requirements. Results can then be provided to the project Structural Engineer for approval. 17

20 DRIVEWAY The upper 4 feet of soils encountered on the subject site are highly plastic and susceptible to volume changes due to variations in moisture content. To reduce the amount of progressive damage to the driveway, Capital Geotechnical Services recommends designing site drainage to guide water away from driveway and prevent ponding along and around the driveway. Soil improvement can be performed under the driveway alignment if the Owner will be sensitive to cracking and heaving in the pavement (i.e. 2 feet remove and replace). If the driveway will consist of concrete, the pavement should include full-depth joints every 10 feet (maximum spacing) or closer to isolate shrinkage cracking and limit or prevent intermediate cracking due to concrete shrinkage, deflection, and soil movement, and prevent the associated negative effect on aesthetic quality. The concrete (i.e. 5 inches thick) must be reinforced (i.e. #3 bars tied at 18-inch spacing in both directions) and steel must not cross through the joints and negatively affect the intended function of the joints. Joints must be doweled, however, (i.e. 18- inch long, ¾ inch diameter, smooth steel bars with greased or sleeved end for freedom of horizontal movement) to prevent joint faulting (bumps, tripping hazard). LIMITATIONS This report is subject to the limitations and assumptions presented in the report. Should conditions change or if assumptions are not accurate, we must be contacted to review our recommendations. Borings were spaced to obtain a reasonable indication of subsurface conditions. The data from the borings is only accurate at the exact boring locations. Variations in the subsurface conditions not indicated by our borings are possible. The recommendations in this report were developed considering conditions exposed in the exploratory borings and our understanding of the type of structure planned. We believe that the geotechnical services for this project were performed with a level of skill and care ordinarily used by geotechnical engineers practicing in this area at this time. No warranty, express or implied, is made. Capital Geotechnical Services should be retained to review plans and specifications related to geotechnical elements of the construction to check that our recommendations have been properly interpreted. Capital Geotechnical Services cannot be responsible for incorrect 18

21 interpretations of our recommendations, particularly if we are not retained to review plans and specifications. This report is valid until site conditions change due to disturbance (cut and fill grading) or changes to nearby drainage conditions, or for 3 years from the date of this report, whichever occurs first. Beyond this expiration date, Capital Geotechnical Services shall not accept any liability associated with the engineering recommendations in the report, particularly if the site conditions have changed. If this report is desired for use for design purposes beyond this expiration date, we recommend drilling additional borings so that we can verify the subsurface condtions and validate the recommendations in this report. INSPECTIONS Capital Geotechnical should be retained to perform the field observations, field testing, and laboratory testing recommended in this report because of our familiarity with the project and site conditions. Quality control (QC) inspections by Capital Geotechnical Services can include: Inspect the soil improvement excavation. Inspect proof-rolling of subgrade before placing fill, slab formwork, or pavement materials. Sampling and lab testing of proposed fill material to check and document classification. Testing of compacted fill in place to check and document proper compaction and moisture-conditioning. Pre-pour inspection to check and document grade beam dimensions, subgrade condition, reinforcing steel installation, and moisture vapor barrier installation (if not performed by Structural Engineer). Pre-pour inspection of post-tension cable installation (if applicable) (if not performed by Structural Engineer). Concrete sampling and testing to document as-built condition of wet concrete and to document that the supplier provided an adquate mixture to the site. 19

22 Post-tension cable stressing inspection (if applicable) (if not performed by Structural Engineer). Pre-pour inspection of concrete driveway contruction (reinforcing steel, joint layout, joint doweling, thickness). 20

23 Site Area Vicinity Map New Building for Bateman Baptist Church Bateman / Red Rock Bastrop County, Texas Prepared By: NFK Base Map By: TxDOT Capital Geotechnical Services PLLC Cedar Park, Texas Scale: - Date: October 2014 Project #: Figure #: 1

24 Subject Lot Local Lot Plan New Building for Bateman Baptist Church Bateman / Red Rock Bastrop County, Texas Prepared By: NFK Base Plan By: Bastrop County Capital Geotechnical Services PLLC Cedar Park, Texas Scale: - Date: October 2014 Project #: Figure #: 2

25 Site Area Ewi : Fine-grained soils, siltstone, sandstone, and lignite sedimentary deposits categorized as the Wilcox Group geologic formation. Geology Map New Building for Bateman Baptist Church Bateman / Red Rock Bastrop County, Texas Prepared By: NFK Base Map By: U.T. Bureau of Econ. G. Capital Geotechnical Services PLLC Cedar Park, Texas Scale: - Date: October 2014 Project #: Figure #: 3

26 B-1 B-2 Approximate Locations of Exploratory Borings New Building for Bateman Baptist Church Bateman / Red Rock Bastrop County, Texas Prepared By: NFK Base Plan By: Barbee Architects Capital Geotechnical Services PLLC Cedar Park, Texas Scale: - Date: October 2014 Project #: Figure #: 4

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29 Capital Geotechnical Services PLLC I. Sampling & Testing Symbols: STANDARD REFERENCE NOTES FOR BORING LOGS Shelby Tube Split-Spoon ST SS RC Rock core A Auger GT Sampler Geoprobe tube II. Correlations of Penetration Resistance to Soil Properties: III. Relative Density of Sand and Sandy Silt Consistency of Clay and Clayey Silt Relative Density SPT N-value Consistency SPT N-value (qualitative measure) Unconfined Compressive Strength (tsf) Very loose 0 to 4 Very soft 0 to 3 Under 0.25 Loose 5 to 10 Soft 4 or Medium dense 11 to 30 Medium stiff 6 to Dense 31 to 50 Stiff 11 to Very Dense > 50 Very stiff 16 to Hard > Unified Soil Classification Symbols: GP - Poorly Graded Gravel SP - Poorly Graded Sand ML - Low Plasticity Silt GW - Well Graded Gravel SW - Well Graded Sand MH - High Plasticity Silt GM - Silty Gravel SM - Silty Sand CL - Low to Medium Plasticity Clay GC - Clayey Gravel SC - Clayey Sand CH - High Plasticity Clay OH - High Plasticity Organics OL - Low Plasticity Organics IV. Rock Quality Designation index (RQD): V. Natural moisture content: Dry No apparent moisture, crumbles easily RQD: Description of Rock Quality: Moist Damp but no visible water (if all natural fractures) Wet Visible water 0-25 % Very poor % Poor % Fair % Good % Excellent VI. Grain size terminology: VIII. Descriptive terms or symbols: Cobble: 3-inches to 12-inches Mottled : occasional/spotted presence of that color Gravel: #4 sieve size (4.75 mm) to 3-inches - [ ] : identifies change in soil characteristics Coarse sand: #10 to #4 sieve size LL: Liquid Limit (moisture content as % of dry weight) Medium sand: #40 to #10 sieve size PL: Plastic Limit (moisture content as % of dry weight) Fine sand: #200 to #40 sieve size WOH: Weight of hammer Silt or clay: smaller than #200 sieve size with [ ] : item identified within that sample only VII. Descriptive terms for soil composition: IX. Plasticity of cohesive soil: (function of PI and clay mineral types) Capital Geotechnical Services PLLC * Cedar Park, Texas * Fax: (512) Trace to 9% Plasticity Index (PI): Plasticity: Some to 29% 0 to 20 Low (with suffix y, e.g. sandy, clayey ) to 49% 20 to 30 Medium 30 + High Fig. 7

30 Vertical Swell (%) Vertical Swell (%) Swell Test Results Net vertical swell due to wetting under constant load 17.1% Rebound from remolding compaction = 2.3% Vertical Pressure (ksf) Light brown clay Dry unit weight = 108 pcf Remolded specimen Initial moisture content = 14 % B-1 at 2 to 3.5 feet (PP= 4.5+ tsf) Final moisture content = 32 % Initial liquidity index (LI): Days soaking: Net vertical swell due to wetting under constant load: 15.9% Elastic rebound from remolding compaction: 1.4% Vertical Pressure (ksf) Reddish brown and light brown Dry unit weight = 104 pcf Remolded specimen Initial moisture content = 16 % B-2 at 0 to 1.5 feet (PP=4.5+ tsf) Final moisture content = 37 % Initial liquidity index (LI): Days soaking: 5 Bateman Baptist Church Site, Bastrop County, Texas Capital Geotechnical Services Project # Figure 8