GEOTECHNICAL STUDY RESIDENTIAL AND COMMERCIAL PROJECT th STREET OGDEN, UTAH

Transcription

1 GEOTECHNICAL STUDY RESIDENTIAL AND COMMERCIAL PROJECT th STREET OGDEN, UTAH Prepared For: Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue Ogden, Utah Prepared by: Summit Engineering Services A Division of Pangean-CMD Associates, Inc South 500 West Salt Lake City, Utah JOB NO. TC-0G MAY 2012

2 May 17, 2012 Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue. Ogden, Utah Subject: Project No.: Geotechnical Study Residential and Commercial Project th Street Ogden, Utah TC-0G Dear Mr. Parker: Summit Engineering Services (SES), a division of Pangean-CMD Associates, Inc, has completed a geotechnical study for the proposed Condominium Project to be located at th Street, Ogden, Utah. Details of findings and recommendations, along with the supporting field and laboratory data, are presented in the attached report. Five test holes terminating at depths of 21.5 to 51.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of approximately 1.5 feet of manmade fill capping the site underlain by interbedded native deposits of loose to medium dense silty, SAND (SM) and loose to medium dense SILT (ML) overlying soft to medium stiff, CLAY (CL) to the maximum depth explored of 51.5 feet. Groundwater was measured at a depth of 10 to 10.5 feet during drilling. SES appreciates the opportunity to be of service to you on this project. Please call us if you have any questions or need additional information. Sincerely, SUMMIT ENGINEERING SERVICES A Division of Pangean-CMD Associates, Inc. CURT STRIPEIKA Project Engineer DAVID A. SCHMIDT, P.E. Utah License Number: Vice President Environmental Engineering Geotechnical Engineering Construction Inspection Materials Testing 3640 South 500 West Salt Lake City, Utah Phone Fax

3 Geotechnical Study Page i th Street, Ogden, Weber County, Utah May 17, 2012 TABLE OF CONTENTS 1.0 INTRODUCTION PROPOSED CONSTRUCTION SITE CONDITIONS SUBSURFACE CONDITIONS SEISMIC SETTING Faulting Site Soil Classification Liquefaction LABORATORY PROGRAM SITE PREPARATION AND GRADING FOUNDATION RECOMMENDATIONS BELOW GRADE PARKING LEVEL SLAB BELOW GRADE WALLS BACKFILL AROUND THE BUILDING SURFACE DRAINAGE PAVEMENT DESIGN PLANS AND SPECIFICATIONS REVIEW CONSTRUCTION INSPECTION LIMITATIONS...9 APPENDIX A: FIELD EXPLORATION, VICINITY MAP, SITE PLAN, AND LOGS OF TEST HOLES Figure A-1 Vicinity Map Figure A-2 Test Hole Location Maps Figures A-3 through A-7 Logs of Test Holes Figure A-8 Key to Test Holes APPENDIX B: LABORATORY TEST PROCEDURES AND RESULTS Table B-1 Summary of Laboratory Test Data APPENDIX C: LIQUEFACTION ANALYSIS \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

4 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, INTRODUCTION Summit Engineering Services (SES) has completed the geotechnical study for the proposed Condominium Project to be located at th Street, Ogden, Utah. The purpose of this study was to provide information on subsurface conditions, general recommendations for foundation types and depths, soil bearing capacities, site preparation and grading, and other design and construction considerations influenced by the subsoil conditions. The study included site reconnaissance, subsurface exploration and soil sampling, laboratory testing, engineering analysis, client consultation, and preparation of this report. 2.0 PROPOSED CONSTRUCTION SES understands that the proposed development will consist of a square-in-plan building with nominal dimensions of approximately 250 by 250 feet. The building is to be configured with a partial below grade parking structure reserved for resident/visitor parking. Above the parking level are an additional three stories of living units. The parking portion of the building is anticipated to consist of poured in place reinforced concrete construction. The three levels of living units are anticipated to be wood framed. Final grade elevations were not available at the time of this report. Structural loads were not available at the time of this study; however, no unusually heavy loads are anticipated. 3.0 SITE CONDITIONS The site is currently a paved parking lot, is generally rectangular-in-plan and is approximately 1.5 acres in size. The site is located proximal to the northwest corner of 25 th Street and Jefferson Avenue. The site slopes slightly to the west. The surrounding properties consist of apartments to the north, a vacant building to the west, 25 th Street to the south and Jefferson Avenue to the east. Surface drainage appears to be fair. 4.0 SUBSURFACE CONDITIONS Five test holes terminating at depths of 21.5 to 51.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of approximately 1.5 feet of manmade fill capping the site underlain by interbedded native deposits of loose to medium dense silty, SAND (SM) and loose to medium dense SILT (ML) overlying soft to medium stiff, CLAY (CL) to the maximum depth explored of 51.5 feet. Groundwater was measured at a depth of 10 to 10.5 feet during drilling. Researching the State of Utah, Department of Environmental Quality, Division of Environmental Response and Remediation interactive map viewer for \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

5 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 leaking underground storage tank sites indicates historical groundwater seasonal fluctuations are on the order of 1 to 2 feet. A detailed description of the conditions encountered at each test hole location is presented on the Logs of Test Holes included in Appendix A. Please refer to Figures A-3 through A-7. Figure A-8 is the key to symbols and abbreviations used on the Test Hole Logs. 5.0 SEISMIC SETTING 5.1 Faulting Review of available literature for the Ogden area, indicates that no active faults traverse the property or immediately adjacent to the property. The closest known fault is the Wasatch fault approximately 1.5 miles to the east. 5.2 Site Soil Classification According to the 2006 International Building Code (IBC), it appears the soils are a seismic site class of E. This evaluation is not based upon a 100-foot deep boring as required by the IBC but an analysis of the N-values (blow counts) and soil types encountered along with a review of water well boring logs in the vicinity and available at the State of Utah, Division of Water Rights website. If needed for design, the building at this site can utilize an assumed critical earthquake of magnitude M = 7 and a peak ground acceleration of Specific parameters (such as S MS, S M1, S DS, S M1 ) for seismic design at this site (as defined by either latitude/longitude or Zip Code) for Site Class E and can be obtained from the United States Geological Survey (USGS) web site maps/ Liquefaction The Weber County liquefaction hazard map rates the site and adjoining area having a High liquefaction potential. It should be noted that this is a general classification applied to a relatively large geographic area and does not take into account any site-specific mitigating factors. High is defined as greater than a 50 percent probability of experiencing an earthquake of sufficient magnitude to cause liquefaction to occur in 100 years. Liquefaction can be generally defined as a condition that can develop in a saturated sandy soil resulting in a substantial reduction in soil strength and a significant decrease in soil volume (settlement). Liquefaction can cause serious building damage and is a hazard to building occupants. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

6 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 The following conditions are considered conducive to liquefaction occurring: 1. A seismic event (earthquake) of magnitude 7.0 generating a ground acceleration of 0.25g. 2. Deposits of loose to medium dense clean (SP, SP-SM) to silty (SM) sands and silts (ML, MH, OL) below the groundwater table within a depth of 30 feet from the ground surface. Liquefaction impacts generally decrease with increasing fines content (silts and silty sands are less susceptible to liquefaction than clean sands). Clays of the type found in the area are generally considered not subject to liquefaction. A review of subsurface conditions as identified by the test holes indicates the following sitespecific conditions related to liquefaction: 1. The sands encountered within the depth of exploration, are loose to medium dense, silty, and mainly fine grained, which are not as susceptible to liquefaction. 2. Groundwater was encountered at approximately 10 feet below existing site grades. Based on the test hole data, liquefaction induced settlement was determined to be approximately 2 inches during a major seismic event. This result does not include any static differential settlement discussed in Section 8. Results of SES s analysis are presented in Appendix C. The liquefaction-induced settlement is anticipated to occur differentially beneath the structure. Consideration should be given to conducting additional exploration using Cone Penetration Test (CPT) techniques to better define the thickness of potential liquefiable layers and anticipated liquefaction-induced settlements. 6.0 LABORATORY PROGRAM Representative samples obtained from field investigation were subjected to the following laboratory analyses: Test Sample Type Purpose of Test % By Weight Passing the #200 Sieve Moisture Content and Unit Dry Density Swell/Consolidation Native Soils Native Soils Native Soils Soil Classification In-Situ Soil Conditions Swell/Settlement Potential \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

7 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 Refer to Appendix B of this report and the Boring Logs in Appendix A for laboratory test results. It is noted at the time this report was prepared, the swell/consolidations tests were not complete and will be submitted as an addendum to this report when they are complete. 7.0 SITE PREPARATION AND GRADING Any man-made fill underlying the site should be removed from the proposed building footprint and all other areas to be structurally loaded, and replaced with structural fill. Following site stripping, the native subgrade should be further excavated as required to establish the lowest bottom grade required for the foundation option selected for this project. The condition of the exposed native subgrade should then be evaluated by SES and stabilization efforts implemented if required as recommended below. The exposed native subgrade at this site may be soft and unstable and compaction by conventional methods/equipment to a firm unyielding condition prior to any required fill placement and/or construction activity may not be possible. Unstable subgrades (those that are soft or exhibit excessive pumping) may need to be undercut up to 18 inches or more and replaced with structural fill, select graded stabilization material, tamped-in-place cobble rock and/or a subgrade reinforcing geo-fabric/geo-grid. The subgrade stabilization method selected should be evaluated and approved by SES with additional recommendations provided by addendum as needed. Structural fill should be placed on and above a stable subgrade where fill is required to reach required foundation/slab grades. Some of the native soil deposits may be suitable for re-use as structural fill pending laboratory qualification testing and approval by SES. Structural fill should consist of SES-approved imported material placed in 8-inch maximum loose lifts, at the moisture content optimum for compaction, and compacted to at least 95 percent modified Proctor (ASTM D1557) maximum dry density. In general, imported fill should consist of well-graded sands and gravels containing 10 to 40 percent fines (material passing the No. 200 sieve, based on the minus ¾-inch fraction), and should have a maximum particle size of 4 inches. The plasticity index of the fines should not exceed 15. Compaction of fill lifts should be with equipment that will not negatively impact the foundations and structural integrity of any nearby structures including buildings, pavement, and below/above ground utilities. Utility trenches should be backfilled with compacted fill. The fill should be placed in lift thickness appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent modified Proctor (ASTM D1557) maximum dry density by mechanical means. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

8 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 All site grading and fill operations should be observed by a representative from SES to determine the adequacy of site preparation, the stability of exposed native subgrades, the suitability of fill materials, and compliance with compaction requirements. Further, the site should be inspected immediately after the completion of excavation operations to identify and provide mitigating recommendations if required for any unexpected subsurface conditions that may underlie the site. 8.0 FOUNDATION RECOMMENDATIONS SES has considered several options for the support of the proposed building at this site including shallow (spread footings) and intermediate (Geopier rammed aggregate pier systems) foundations. Shallow Foundations Subsurface soils have been determined to be liquefiable during a seismic event. If the anticipated settlement is unacceptable, consideration should be given to mitigate the liquefaction potential through compaction grouting, use of rammed aggregate piers or other methods to reduce the hazard. Alternatively, the building structure could be designed to resist potential liquefaction-induced differential settlements at the ground surface by stiffening the foundation with the use of grade beams between spread footings or use of rammed aggregate piers. Provided the owner is aware of the risks involved of using a conventional spread footing type foundation, the following recommendations can be used. 1. Spread footings founded on 2 feet of structural fill can be designed for a maximum net allowable bearing pressure of 2,000 psf. This pressure may be increased by one-third for short-term transient wind and seismic loads. Under these pressures the total footing settlement is expected to be less than about 1 inch. The differential settlement between adjacent spot footings or a 25 foot span of continuous wall footing should be about half this amount. 2. Continuous (wall) and individual (column) footings should be at least 18 and 24 inches wide, respectively, and should be placed a minimum of 2.5 feet below the lowest adjacent final grade for frost protection. 3. Continuous foundation walls should be adequately reinforced both top and bottom. As a guide, SES suggests an amount of steel equivalent to that required for a simply supported span of 12 feet. 4. Structural fill should extend a lateral distance beyond the footing at least one half equal to the nominal footing width. Intermediate Foundations A foundation option that may be particularly suited to this site is the Geopier rammed aggregate pier (RAP) system developed by the Geopier Foundation Company (GFC). The RAP system consists of a pre-augured borehole into which select graded high-quality aggregate is placed and tamped in lifts with a beveled rammer. Compaction \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

9 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 densifies the aggregate and increases lateral stress in the soil matrix. RAP lengths typically vary from 10 to 30 feet. Common RAP diameters are 30 and 36 inches. Considering site liquefaction potential, a RAP length of 20 to 25 feet is recommended. Geopier elements typically cover approximately 30 percent of the footing footprint area. The RAP system serves to reduce settlement by replacing the compressible native soils in the upper 10 to 30 feet below the footing with a stiffer composite soil matrix. Design bearing pressure improvements of up to 10 kips per square foot (ksf) with less than 1 inch of total settlement can be achieved. Installation rates of 30 to 60 piers per day are common and better than what can be typically achieved by installing piles. Project cost is usually significantly less than for a pile-supported foundation system. QA/QC efforts have pier performance evaluated prior to production installation of the piers with a full scale load test (Modulus Test) performed on a test pier located in an area suspected of having the worst site subsurface conditions in a manner similar to a pile load test. Each production pier subsequently installed then uses a Bottom Stabilization Test to assess the performance of the pier against the performance of the pier used for the Modulus test. Any production pier not meeting the standard set by the Modulus Test is re-installed. Other RAP foundation considerations and recommendations include: 1. Specifications for and a specific design of an aggregate pier foundation system at this site should be provided by GFC assisted by SES as required. 2. One demonstration pier should be installed with the contractor s standard procedures and then load-tested (Modulus Test). The load testing setup and procedures should be selected by the GFC and submitted for review to SES. The demonstration pier should be installed at the foundation grade level. 3. All of the Geopier element installation operations should be observed and documented by SES personnel. This inspection is conducted to reduce the potential for short Geopier element installations and excessive aggregate lift thicknesses. 4. After the foundation soils have been reinforced with Geopier elements, the treated ground surface should be cleared and cleaned to the satisfaction of SES, and shallow foundations installed at grade. 5. The design bearing pressure and expected settlement should be determined by GFC, assisted by SES as required. 6. Lateral resistance to backfill placed against footings and parking level walls should be evaluated by GFC, assisted by SES as required. RAP foundation systems have been installed in the Wasatch front area for subsurface conditions similar to those disclosed at this site. One specific example is the Weber State \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

10 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 University Hurst Center for Lifelong Learning, which is a 16,000 square foot building with column loads of up to 340 kips. GFC maintains an office in the Salt Lake Area. Additional information, project examples and/or consultation can be obtained from: David M. Plehn, P.E. Director of Design and Engineering Geopier Northwest 8188 S. Highland Drive, Suite D-3 Sandy, UT Office Phone dplehn@geopier.com 9.0 BELOW GRADE PARKING LEVEL SLAB The parking level slab will likely be placed on compacted/firm natural subgrade and/or structural fill. In addition, a minimum of six inches of gravel should be provided below the slab to provide a uniform subgrade condition and to break the rise of capillary water. The slab should also be provided with frequent joints to minimize damage due to shrinkage cracking, and should be adequately reinforced for the loading conditions imposed on the slab. Further, the slab should be separated from all bearing walls and partitions with a slip joint BELOW GRADE WALLS SES recommends using the following equivalent fluid pressures (EFP) and a triangular shaped pressure distribution for the design of any below grade walls resisting lateral loads: Wall Type Equiv. Active/At-Rest Fluid Pressure (psf/ft) Equiv. Passive Fluid Pressure (psf/ft) Basement floors, restrained at top 60 (At-Rest) 300 Retaining, unrestrained and free to rotate at top 35 (Active) 300 For seismic considerations, the combined static (P A ) and dynamic lateral forces (P E ) are combined such that P AE = P A + P E = ½(γ)H 2 K ao + 3/8(γ) H 2 K h where, γ = Wall backfill moist/total unit weight ~ 120 pcf for this project H = Wall height K ao = Active (unrestrained) or at rest (restrained) earth pressure coefficient. For this project, assume the active earth pressure coefficient ~ 0.3 and the at rest earth pressure coefficient ~ 0.5. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

11 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 K h = Horizontal ground acceleration in g s (0.25g to 0.3g has been along the Wasatch Front area for many years for an assumed critical earthquake with a magnitude of 7.0). The horizontal ground acceleration can also be specifically derived for the site from the Peak Ground Acceleration (PGA) determined for the Maximum Considered Earthquake (MCE). Local practice is to consider K h = PGA/2. P A, as is standard practice for equivalent fluid pressures, acts 1/3H up from the base of the wall; P E is assumed to act at 0.6H up from the base of the wall. The factor of safety for the combined effect of static and seismic loading is recommended to be in the range of 1.1 to 1.2. As an alternate method, lateral resistance can be calculated based on sliding resistance. For this case, a friction factor of 0.35 for concrete against soil may be used for design. If passive pressures and friction are used in combination, SES further recommends using a reduced coefficient of base friction equal to The above equivalent fluid pressure recommendations assume a level surface grade and a drained condition adjacent to the wall. EFP recommendations for sloping backfill conditions can be provided upon request. Backfill within four lateral feet of the back of the wall should consist of free-draining sand/gravel (less than 5% clay/silt fines) or an appropriate manufactured drainage product. Open-graded aggregates should be avoided unless enveloped in an SES approved geotextile filter fabric. Beyond 4 feet/drainage product, wall backfill can consist of any available soil material free of organics, large rocks or other deleterious materials or as required by the drainage product manufacturer/supplier. The top 2 feet of wall backfill should consist of an impervious clay cap (the on-site native lean clay is anticipated to be suitable). Wall backfill should be compacted to at least 88 percent but not more than 92 percent of modified Proctor maximum dry density. Relatively light manually propelled compactors should be used within 5 feet of walls. Compactors used beyond 5 feet should be limited in weight to 3,000 lbs. As a precaution, SES recommends that a positive draining, perforated pipe be placed behind the wall to serve as a drainage medium. The pipe should be enveloped with a minimum of 12 inches of gravel. Both the gravel and drainpipe should be wrapped with filter fabric to prevent soil intrusion. The drainpipe should be connected to a sump where water can be removed with a pump. A pump need not be purchased unless water conditions develop BACKFILL AROUND THE BUILDING The on-site native soils may be used as backfill around the building. The backfill should be free of organics and other deleterious materials and should be moistened, placed in maximum 6-inch loose lifts, and compacted to at least 88 percent of the maximum dry density as determined by ASTM D The negative impacts of using vibratory or heavy compactors on nearby existing structures should be carefully evaluated. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

12 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, SURFACE DRAINAGE Adequate surface drainage must be maintained during the course of construction and after construction has been completed. The ground surface surrounding the exterior of the building should be sloped to drain away from the building in all directions. SES recommends a minimum slope of 6 inches in the first 10 feet. Roof downspouts should discharge into splash blocks extended beyond the limits of all backfill. All sprinkler heads should be aimed away from and kept at least 2 feet from the foundation walls. Landscaping requiring extensive watering should not be allowed within 2 feet of the building PAVEMENT DESIGN SES does not anticipate significant pavement or drive areas for this project. Where necessary, SES recommends a pavement section consisting of 3 inches of asphaltic concrete, 8 inches of high quality base, over 12 inches of subbase. Three inches and 10 inches, respectively, are recommended in drives. This recommendation assumes the subgrade material below the base will consist of at least 12 inches of well-compacted gravelly, sand and/or sandy gravel subbase and assumes low volume, light vehicular loading. Compaction of the subbase should be to a minimum of 95 percent of modified Proctor maximum dry density PLANS AND SPECIFICATIONS REVIEW It is recommended that SES be provided the opportunity to review the final design and specifications in order to determine whether any change in concept may have had any affect on the validity of our recommendations, and whether those recommendations have been properly implemented in the design and specifications. Review of the final design and specifications will be noted in writing CONSTRUCTION INSPECTION All site grading operations should be observed by an SES representative to determine the adequacy of site preparation, removal of unsuitable material, compliance with compaction requirements, observe/ document ground improvement operations, and in general assure that the recommendations presented in this report are properly implemented during construction LIMITATIONS The analysis and recommendations submitted in this study are based upon the data obtained from the test holes drilled at the location of the proposed structure as indicated on Figure A-2. This study does not reflect any variations, which may occur between the test holes. The nature and extent of variations may not become evident until the course of construction and are sometimes \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

13 Geotechnical Study Page th Street, Ogden, Weber County, Utah May 17, 2012 sufficient to necessitate changes in the designs; thus, it is important that SES observes subsurface materials exposed in the excavations to take advantage of all opportunities to recognize differing conditions, which would affect the performance of the facility being planned. This study has been prepared in order to assist the architect and engineer in the design of this project. In the event that any changes are planned in the design, location, or elevation of the building as outlined in this study, the conclusions and recommendations contained in this study shall not be considered valid unless the changes are reviewed and conclusions of this study modified or approved in writing by the geotechnical engineer. SES also recommends that final plans and specifications be reviewed by our office to evaluate whether SES recommendations were properly understood and implemented. The study should be available to prospective contractors for information on technical data only as interpreted from the test holes and not as a warranty of subsurface conditions. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\550 25th Street\Final Report\TC-0G Report.doc

14 APPENDIX A Field Exploration, Vicinity Map, Site Plans, and Logs of Test Holes

15 FIELD EXPLORATION The field exploration consisted of the drilling, logging, and sampling of five (5), 21.5-foot to foot deep test holes. Undisturbed samples were taken at selected intervals, sealed and returned to the laboratory for classification and testing. A continuous log of the subsurface conditions as encountered in the test holes was kept during drilling. Mr. Curt Stripeika of SES supervised the drilling and sampling operations. The test holes were drilled by Earthcore, Inc., of Salt Lake City, Utah.

16 TC 0G FIGURE A 1

17 NO SCALE PROPOSED MULTI USE BUILDING th STREET OGDEN, UTAH TC 0G FIGURE A 2

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24 APPENDIX B Laboratory Test Procedures and Results

25 LABORATORY TESTING PROCEDURES The soil samples obtained from the exploration test holes were examined in the laboratory to confirm field classification. Laboratory tests conducted included natural moisture and density, sieve analysis and swell consolidation tests. All tests were conducted in accordance with ASTM standards unless otherwise noted.

26 TABLE B 1 SUMMARY OF LABORATORY TEST RESULTS Page 1 of 1 TEST PIT NO. DEPTH (FT.) NATURAL MOISTURE (%) NATURAL DRY DENSITY (PCF) (MC) (DD) GRAVEL > #4 GRAIN SIZE DISTRIBUTION (%) SAND SILT/ CLAY < #200 ATTERBERG LIMITS LIQUID LIMIT (LL) PLASTIC LIMIT (PL) HAND PENETROMETER STRENGTH (PP/TSF) SWELL (%) SWELL-CONSOLIDATION COLLAPSE (%) PRESS (KSF) SOIL TYPE ML ML ML SM SM CL SM SM ML CL

27 APPENDIX C Liquefaction Analysis

28 LIQUEFACTION ANALYSIS th Street, Ogden, Utah Hole No.=TH-1 Water Depth=6 ft Surface Elev.=4376 Magnitude=7 Acceleration=0.25g (ft) 0 Soil Description Fill Raw Unit Fines SPT Weight % Shear Stress Ratio Factor of Safety Settlement 0 (in.) 10 Silt silty SAND LiquefyPro CivilTech Software USA CLAY fs1=1 fs2=1.00 CRR CSR fs1 fs2 Shaded Zone has Liquefaction Potential S = 2.03 in. Saturated Unsaturat. CivilTech Corporation TC-0G2183 Plate A-1 Figure C-1

29 Table C Liquefaction Summary ***************************************************************************** LIQUEFACTION ANALYSIS SUMMARY Copyright by CivilTech Software ***************************************************************************** Font: Courier New, Regular, Size 8 is recommended for this report. Licensed to, 5/15/2012 1:26:43 PM Input File Name: E:\Liquefy5\550 25th Street.liq Title: th Street, Ogden, Utah Subtitle: TC-0G2183 Surface Elev.=4376 Hole No.=TH-1 Depth of Hole= ft Water Table during Earthquake= 6.00 ft Water Table during In-Situ Testing= ft Max. Acceleration= 0.25 g Earthquake Magnitude= 7.00 Input Data: Surface Elev.=4376 Hole No.=TH-1 Depth of Hole=30.00 ft Water Table during Earthquake= 6.00 ft Water Table during In-Situ Testing= ft Max. Acceleration=0.25 g Earthquake Magnitude=7.00 No-Liquefiable Soils: CL, OL are Non-Liq. Soil 1. SPT or BPT Calculation. 2. Settlement Analysis Method: Ishihara / Yoshimine 3. Fines Correction for Liquefaction: Idriss/Seed 4. Fine Correction for Settlement: During Liquefaction* 5. Settlement Calculation in: All zones* 6. Hammer Energy Ratio, Ce = 1 7. Borehole Diameter, Cb= 1 8. Sampling Method, Cs= 1 9. User request factor of safety (apply to CSR), User= 1 Plot two CSR (fs1=1, fs2=user) 10. Use Curve Smoothing: Yes* * Recommended Options In-Situ Test Data: Depth SPT gamma Fines ft pcf % Output Results: Settlement of Saturated Sands=2.03 in. Settlement of Unsaturated Sands=0.00 in. Total Settlement of Saturated and Unsaturated Sands=2.03 in. Differential Settlement=1.017 to in. Depth CRRm CSRfs F.S. S_sat. S_dry S_all ft in. in. in Page 1

30 Table C Liquefaction Summary Page 2

31 Table C Liquefaction Summary Page 3

32 Table C Liquefaction Summary Page 4

33 Table C Liquefaction Summary Page 5

34 Table C Liquefaction Summary * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Page 6

35 Table C Liquefaction Summary * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Page 7

36 Table C Liquefaction Summary * F.S.<1, Liquefaction Potential Zone (F.S. is limited to 5, CRR is limited to 2, CSR is limited to 2) Units: Unit: qc, fs, Stress or Pressure = atm (1.0581tsf); Unit Weight = pcf; Depth = ft; Settlement = in. 1 atm (atmosphere) = 1 tsf (ton/ft2) CRRm Cyclic resistance ratio from soils CSRsf Cyclic stress ratio induced by a given earthquake (with user request factor of safety) F.S. Factor of Safety against liquefaction, F.S.=CRRm/CSRsf Page 8

37 S_sat S_dry S_all NoLiq Table C Liquefaction Summary Settlement from saturated sands Settlement from Unsaturated Sands Total Settlement from Saturated and Unsaturated Sands No-Liquefy Soils Page 9

38 GEOTECHNICAL STUDY JEFFERSON COMMONS 2604 JEFFERSON AVENUE OGDEN, UTAH Prepared For: Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue Ogden, Utah Prepared by: Summit Engineering Services A Division of Pangean-CMD Associates, Inc South 500 West Salt Lake City, Utah JOB NO. TC-0G MAY 2012

39 May 17, 2012 Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue. Ogden, Utah Subject: Project No.: Geotechnical Study Jefferson Commons 2604 Jefferson Avenue Ogden, Utah TC-0G Dear Mr. Parker: Summit Engineering Services (SES), a division of Pangean-CMD Associates, Inc., has completed the geotechnical study for the proposed Jefferson Commons Project to be located at 2604 Jefferson Avenue, Ogden, Utah. Details of findings and recommendations, along with the supporting field and laboratory data, are presented in the attached report. Two test holes terminating at depths of 11.5 to 31.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of interbedded native deposits of loose to medium dense, SILT (ML) underlain by silty, SAND (SM) overlying soft to medium stiff, silty CLAY (CL-ML) and lean CLAY (CL) to the maximum depth explored of 31.5 feet. Groundwater was measured at a depth of 13.7 feet during drilling. SES appreciates the opportunity to be of service to you on this project. Please call us if you have any questions or need additional information. Sincerely, SUMMIT ENGINEERING SERVICES A Division of Pangean-CMD Associates, Inc. CURT STRIPEIKA Project Engineer DAVID A. SCHMIDT, P.E. Utah License Number: Vice President Environmental Engineering Geotechnical Engineering Construction Inspection Materials Testing 3640 South 500 West Salt Lake City, Utah Phone Fax

40 Geotechnical Study Page i Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, 2012 TABLE OF CONTENTS 1.0 INTRODUCTION PROPOSED CONSTRUCTION SITE CONDITIONS SUBSURFACE CONDITIONS SEISMIC SETTING Faulting Site Soil Classification Liquefaction LABORATORY PROGRAM SITE PREPARATION AND GRADING FOUNDATION RECOMMENDATIONS FLOOR SLAB BACKFILL AROUND THE BUILDING SURFACE DRAINAGE PAVEMENT DESIGN PLANS AND SPECIFICATIONS REVIEW CONSTRUCTION INSPECTION LIMITATIONS...6 APPENDIX A: FIELD EXPLORATION, VICINITY MAP, SITE PLAN, AND LOGS OF TEST HOLES Figure A-1 Vicinity Map Figure A-2 Test Hole Location Maps Figures A-3 through A-4 Logs of Test Holes Figure A-5 Key to Test Holes APPENDIX B: LABORATORY TEST PROCEDURES AND RESULTS Table B-1 Summary of Laboratory Test Data APPENDIX C: LIQUEFACTION ANALYSIS \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

41 Geotechnical Study Page 1 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, INTRODUCTION Summit Engineering Services (SES) has completed the geotechnical study for the proposed Jefferson Commons Project to be located at 2604 Jefferson Avenue, Ogden, Utah. The purpose of this study was to provide information on subsurface conditions, general recommendations for foundation types and depths, soil bearing capacities, site preparation and grading, and other design and construction considerations influenced by the subsoil conditions. The study included site reconnaissance, subsurface exploration and soil sampling, laboratory testing, engineering analysis, client consultation, and preparation of this report. 2.0 PROPOSED CONSTRUCTION SES understands that the proposed development will consist of a two story, wood framed building. The building will be 2,100 square feet in plan area with a slab on grade floor. Final grade elevations were not available at the time of this report. Structural loads were not available at the time of this study; however, no unusually heavy loads are anticipated. 3.0 SITE CONDITIONS The site currently is comprised of a vacant lot and a paved parking area. The property is approximately 0.25 acres in size and slopes to the north. The surrounding properties are mainly residential. Surface drainage appears to be fair. 4.0 SUBSURFACE CONDITIONS Two test holes terminating at depths of 11.5 to 31.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of interbedded native deposits of loose to medium dense, SILT (ML) underlain by silty, SAND (SM) overlying soft to medium stiff, silty CLAY (CL-ML) and lean CLAY (CL) to the maximum depth explored of 31.5 feet. Groundwater was measured at a depth of 13.7 feet during drilling. A detailed description of the conditions encountered at each test hole location is presented on the Logs of Test Holes included in Appendix A. Please refer to Figures A-3 through A-4. Figure A-5 is the key to symbols and abbreviations used on the Test Hole Logs. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

42 Geotechnical Study Page 2 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, SEISMIC SETTING 5.1 Faulting Review of available literature for the Ogden area, indicates that no active faults traverse the property or immediately adjacent to the property. The closest known fault is the Wasatch fault approximately 1.5 miles to the east. 5.2 Site Soil Classification According to the 2006 International Building Code (IBC), it appears the soils are a seismic site class of E. This evaluation is not based upon a 100 foot deep boring as required by the IBC but an analysis of the N-values (blow counts) and soil types encountered along with a review of water well boring logs in the vicinity available at the State of Utah, Division of Water Rights website. If needed for design, the building at this site can utilize an assumed critical earthquake of magnitude M = 7 and a peak ground acceleration of Specific parameters (such as S MS, S M1, S DS, S M1 ) for seismic design at this site (as defined by either latitude/longitude or Zip Code) for Site Class E and can be obtained from the United States Geological Survey (USGS) web site maps/. 5.3 Liquefaction The Weber County liquefaction hazard map rates the site and adjoining area having a High liquefaction potential. It should be noted that this is a general classification applied to a relatively large geographic area and does not take into account any site-specific mitigating factors. High is defined as greater than a 50 percent probability of experiencing an earthquake of sufficient magnitude to cause liquefaction to occur in 100 years. Liquefaction can be generally defined as a condition that can develop in a saturated sandy soil resulting in a substantial reduction in soil strength and a significant decrease in soil volume (settlement). Liquefaction can cause serious building damage and a hazard to building occupants. The following conditions are considered conducive to liquefaction occurring: 1. A seismic event (earthquake) of magnitude 7.0 generating a ground acceleration of 0.25g. 2. Deposits of loose to medium dense clean (SP, SP-SM) to silty (SM) sands and silts (ML, MH, OL) below the groundwater table within a depth of 30 feet from the ground surface. Liquefaction impacts generally decrease with increasing fines content (silts and silty sands are less susceptible to liquefaction than clean sands). Clays of the type found in the area are generally considered not subject to liquefaction. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

43 Geotechnical Study Page 3 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, 2012 A review of subsurface conditions as identified by the test holes indicates the following sitespecific conditions related to liquefaction: 1. The sands encountered within the depth of exploration, are loose to medium dense, silty, and mainly fine grained, which are not as susceptible to liquefaction. 2. Groundwater was encountered at approximately 14 feet below existing site grades. Based on the test hole data, the liquefaction potential for this site is low. The results of SES s analysis are presented in Appendix C. 6.0 LABORATORY PROGRAM Representative samples obtained from field investigation were subjected to the following laboratory analyses: Test Sample Type Purpose of Test % By Weight Passing the #200 Sieve Moisture Content and Unit Dry Density Swell/Consolidation Native Soils Native Soils Native Soils Soil Classification In-Situ Soil Conditions Swell/Settlement Potential Refer to Appendix B of this report and the Boring Logs in Appendix A for laboratory test results. 7.0 SITE PREPARATION AND GRADING Any man-made fill underlying the site should be removed from the proposed building footprint and all other areas to be structurally loaded, and replaced with structural fill. Following site stripping, the native subgrade should be further excavated as required to establish the lowest bottom grade required for the foundation option selected for this project. The condition of the exposed native subgrade should then be evaluated by Summit Engineering Services (SES) and stabilization efforts implemented if required as recommended below. The exposed native subgrade at this site may be soft and unstable and compaction by conventional methods/equipment to a firm unyielding condition prior to any required fill placement and/or construction activity may not be possible. Unstable subgrades (those that are soft or exhibit excessive pumping) may need to be undercut up to 18 inches or more and \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

44 Geotechnical Study Page 4 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, 2012 replaced with structural fill, select graded stabilization material, tamped-in-place cobble rock and/or a subgrade reinforcing geo-fabric/geo-grid. The subgrade stabilization method selected should be evaluated and approved by SES with additional recommendations provided by addendum as needed. Structural fill should be placed on and above a stable subgrade where fill is required to reach required foundation/slab grades. Some of the native soil deposits may be suitable for re-use as structural fill pending laboratory qualification testing and approval by SES. Structural fill should consist of SES-approved imported material placed in 8-inch maximum loose lifts, at the moisture content optimum for compaction, and compacted to at least 95 percent modified Proctor (ASTM D1557) maximum dry density. In general, imported fill should consist of well-graded sands and gravels containing 10 to 40 percent fines (material passing the No. 200 sieve, based on the minus ¾-inch fraction), and should have a maximum particle size of 4 inches. The plasticity index of the fines should not exceed 15. Compaction of fill lifts should be with equipment that will not negatively impact the foundations and structural integrity of any nearby structures including buildings, pavement and below/above ground utilities. Utility trenches should be backfilled with compacted fill. The fill should be placed in lift thickness appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent modified Proctor (ASTM D1557) maximum dry density by mechanical means. All site grading and fill operations should be observed by a representative from SES to determine the adequacy of site preparation, the stability of exposed native subgrades, the suitability of fill materials, and compliance with compaction requirements. Further, the site should be inspected immediately after the completion of excavation operations to identify and provide mitigating recommendations if required for any unexpected subsurface conditions that may underlie the site. 8.0 FOUNDATION RECOMMENDATIONS Spread footings placed on scarified re-compacted native or structural fill should provide adequate support for the proposed building. The following design and construction details should be observed: 1. Spread footings founded on scarified and re-compacted native soils can be designed for a maximum net allowable bearing pressure of 2,000 psf. This pressure may be increased by one-third for short-term transient wind and seismic loads. Under these pressures the total footing settlement is expected to be less than about 1 inch. The \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

45 Geotechnical Study Page 5 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, 2012 differential settlement between adjacent spot footings or a 25 foot span of continuous wall footing should be about half this amount. 2. Continuous (wall) and individual (column) footings should be at least 18 and 24 inches wide, respectively, and should be placed a minimum of 2.5 feet below the lowest adjacent final grade for frost protection. 3. Continuous foundation walls should be adequately reinforced both top and bottom. As a guide, SES suggests an amount of steel equivalent to that required for a simply supported span of 12 feet. 9.0 FLOOR SLAB The floor slab will likely be placed on compacted/firm natural subgrade and/or structural fill. In addition, a minimum of four inches of gravel should be provided below the slab to provide a uniform subgrade condition and to break the rise of capillary water. The slab should also be provided with frequent joints to minimize damage due to shrinkage cracking, and should be adequately reinforced for the loading conditions imposed on the slab. Further, the slab should be separated from all bearing walls and partitions with a slip joint BACKFILL AROUND THE BUILDING The on-site native soils may be used as backfill around the building. The backfill should be free of organics and other deleterious materials and should be moistened, placed in maximum 6-inch loose lifts, and compacted to at least 88 percent of the maximum dry density as determined by ASTM D The negative impacts of using vibratory or heavy compactors on nearby existing structures should be carefully evaluated SURFACE DRAINAGE Adequate surface drainage must be maintained during the course of construction and after construction has been completed. The ground surface surrounding the exterior of the building should be sloped to drain away from the building in all directions. SES recommends a minimum slope of 6 inches in the first 10 feet. Roof downspouts should discharge into splash blocks extended beyond the limits of all backfill. All sprinkler heads should be aimed away from and kept at least 2 feet from the foundation walls. Landscaping requiring extensive watering should not be allowed within 2 feet of the building PAVEMENT DESIGN Where necessary, SES recommends a pavement section consisting of 3 inches of asphaltic concrete, 8 inches of high quality base, over 12 inches of subbase. 3 inches and 10 inches, respectively, are recommended in drives. This recommendation assumes the subgrade material \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

46 Geotechnical Study Page 6 Jefferson Commons, 2604 Jefferson Avenue, Ogden, Weber County, Utah May 17, 2012 below the base will consist of at least 12 inches of well-compacted gravelly, sand and/or sandy gravel subbase and assumes low volume, light vehicular loading. Compaction of the subbase should be to a minimum of 95 percent of modified Proctor maximum dry density PLANS AND SPECIFICATIONS REVIEW It is recommended that SES be provided the opportunity to review the final design and specifications in order to determine whether any change in concept may have had any affect on the validity of SES s recommendations, and whether those recommendations have been properly implemented in the design and specifications. Review of the final design and specifications will be noted in writing CONSTRUCTION INSPECTION All site grading operations should be observed by an SES representative to determine the adequacy of site preparation, removal of unsuitable material, compliance with compaction requirements, observe/ document ground improvement operations, and in general assure that the recommendations presented in this report are properly implemented during construction LIMITATIONS The analysis and recommendations submitted in this study are based upon the data obtained from the test holes drilled at the location of the proposed structure as indicated on Figure A-2. This study does not reflect any variations, which may occur between the test holes. The nature and extent of variations may not become evident until the course of construction and are sometimes sufficient to necessitate changes in the designs; thus, it is important that SES observes subsurface materials exposed in the excavations to take advantage of all opportunities to recognize differing conditions, which would affect the performance of the facility being planned. This study has been prepared in order to assist the architect and engineer in the design of this project. In the event that any changes are planned in the design, location or elevation of the building as outlined in this study, the conclusions and recommendations contained in this study shall not be considered valid unless the changes are reviewed and conclusions of this study modified or approved in writing by the geotechnical engineer. SES also recommends that final plans and specifications be reviewed by our office to evaluate whether SES s recommendations were properly understood and implemented. The study should be available to prospective contractors for information on technical data only as interpreted from the test holes and not as a warranty of subsurface conditions. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\2604 Jefferson Street\Final Report\TC-0G Report.doc

47 APPENDIX A Field Exploration, Vicinity Map, Site Plans, and Logs of Test Holes

48 FIELD EXPLORATION The field exploration consisted of the drilling, logging, and sampling of five (5), 21.5-foot to foot deep test holes. Undisturbed samples were taken at selected intervals, sealed and returned to the laboratory for classification and testing. A continuous log of the subsurface conditions as encountered in the test holes was kept during drilling. Mr. Curt Stripeika of SES supervised the drilling and sampling operations. The test holes were drilled by Earthcore, Inc., of Salt Lake City, Utah.

49 TC 0G FIGURE A 1

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51

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54 APPENDIX B Laboratory Test Procedures and Results

55 LABORATORY TESTING PROCEDURES The soil samples obtained from the exploration test holes were examined in the laboratory to confirm field classification. Laboratory tests conducted included natural moisture and density, sieve analysis and swell consolidation tests. All tests were conducted in accordance with ASTM standards unless otherwise noted.

56 TABLE B 1 SUMMARY OF LABORATORY TEST RESULTS Page 1 of 1 TEST PIT NO. DEPTH (FT.) NATURAL MOISTURE (%) NATURAL DRY DENSITY (PCF) (MC) (DD) GRAVEL > #4 GRAIN SIZE DISTRIBUTION (%) SAND SILT/ CLAY < #200 ATTERBERG LIMITS LIQUID LIMIT (LL) PLASTIC LIMIT (PL) HAND PENETROMETER STRENGTH (PP/TSF) SWELL (%) SWELL-CONSOLIDATION COLLAPSE (%) PRESS (KSF) SOIL TYPE ML ML SM CL-ML CL-ML CL CL CL

57 APPENDIX C Liquefaction Analysis

58 LIQUEFACTION ANALYSIS 2604 Jefferson Ave Hole No.=TH-1 Water Depth=8 ft Surface Elev.=4374 Magnitude=7 Acceleration=.25g (ft) 0 Soil Description FILL Raw Unit Fines SPT Weight % Shear Stress Ratio Factor of Safety Settlement 0 (in.) 1 SILT SAND silty CLAY NoLq NoLq 20 CLAY NoLq NoLq LiquefyPro CivilTech Software USA fs1=1 fs2=1.00 CRR CSR fs1 fs2 Shaded Zone has Liquefaction Potential S = 0.07 in. Saturated Unsaturat. CivilTech Corporation TC-0G2183 Plate A-1 Figure C-1

59 Table C Liquefaction Summary ******************************************************************************* LIQUEFACTION ANALYSIS SUMMARY Copyright by CivilTech Software ******************************************************************************* Font: Courier New, Regular, Size 8 is recommended for this report. Licensed to, 5/15/2012 4:41:18 PM Input File Name: E:\Liquefy5\2604 Jefferson Ave.liq Title: 2604 Jefferson Ave Subtitle: TC-0G2183 Surface Elev.=4374 Hole No.=TH-1 Depth of Hole= ft Water Table during Earthquake= 8.00 ft Water Table during In-Situ Testing= ft Max. Acceleration= 0.25 g Earthquake Magnitude= 7.00 Input Data: Surface Elev.=4374 Hole No.=TH-1 Depth of Hole=30.00 ft Water Table during Earthquake= 8.00 ft Water Table during In-Situ Testing= ft Max. Acceleration=0.25 g Earthquake Magnitude=7.00 No-Liquefiable Soils: CL, OL are Non-Liq. Soil 1. SPT or BPT Calculation. 2. Settlement Analysis Method: Ishihara / Yoshimine 3. Fines Correction for Liquefaction: Stark/Olson et al.* 4. Fine Correction for Settlement: Post Liquefaction 5. Settlement Calculation in: All zones* 6. Hammer Energy Ratio, Ce = 1 7. Borehole Diameter, Cb= 1 8. Sampling Method, Cs= 1 9. User request factor of safety (apply to CSR), User= 1 Plot two CSR (fs1=1, fs2=user) 10. Use Curve Smoothing: Yes* * Recommended Options In-Situ Test Data: Depth SPT gamma Fines ft pcf % NoLiq NoLiq NoLiq NoLiq Output Results: Settlement of Saturated Sands=0.05 in. Settlement of Unsaturated Sands=0.02 in. Total Settlement of Saturated and Unsaturated Sands=0.07 in. Differential Settlement=0.033 to in. Depth CRRm CSRfs F.S. S_sat. S_dry S_all ft in. in. in. Page 1

60 Table C Liquefaction Summary Page 2

61 Table C Liquefaction Summary Page 3

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65 Table C Liquefaction Summary Page 7

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67 Table C Liquefaction Summary Page 9

68 Table C Liquefaction Summary * F.S.<1, Liquefaction Potential Zone (F.S. is limited to 5, CRR is limited to 2, CSR is limited to 2) Units: Unit: qc, fs, Stress or Pressure = atm (1.0581tsf); Unit Weight = pcf; Depth = ft; Settlement = in. 1 atm (atmosphere) = 1 tsf (ton/ft2) CRRm Cyclic resistance ratio from soils CSRsf Cyclic stress ratio induced by a given earthquake (with user request factor of safety) F.S. Factor of Safety against liquefaction, F.S.=CRRm/CSRsf S_sat Settlement from saturated sands S_dry Settlement from Unsaturated Sands S_all Total Settlement from Saturated and Unsaturated Sands NoLiq No-Liquefy Soils Page 10

69 GEOTECHNICAL STUDY 27 th STREET APARTMENTS th STREET OGDEN, UTAH Prepared For: Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue Ogden, Utah Prepared by: Summit Engineering Services A Division of Pangean-CMD Associates, Inc South 500 West Salt Lake City, Utah JOB NO. TC-0G MAY 2012

70 May 17, 2012 Mr. Chris Parker Ogden Community Investment Group 2604 Jefferson Avenue. Ogden, Utah Subject: Geotechnical Study 27th Street Apartments th Street Ogden, Utah Project No.: TC-0G Dear Mr. Parker: Summit Engineering Services (SES), a division of Pangean-CMD Associates, Inc., has completed the geotechnical study for the proposed 27th Street Apartments Project to be located at th Street, Ogden, Utah. Details of findings and recommendations, along with the supporting field and laboratory data, are presented in the attached report. Two test holes terminating at depths of 16.5 to 31.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of interbedded native deposits of loose to medium dense silty, SAND (SM) and loose to medium dense SILT (ML) overlying soft to medium stiff, CLAY (CL) to the maximum depth explored of 31.5 feet. Groundwater was measured at a depth of 15 feet during drilling. SES appreciates the opportunity to be of service to you on this project. Please call if you have any questions or need additional information. Sincerely, SUMMIT ENGINEERING SERVICES A Division of Pangean-CMD Associates, Inc. CURT STRIPEIKA Project Engineer DAVID A. SCHMIDT, P.E. Utah License Number: Vice President Environmental Engineering Geotechnical Engineering Construction Inspection Materials Testing 3640 South 500 West Salt Lake City, Utah Phone Fax

71 Geotechnical Study Page i 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, 2012 TABLE OF CONTENTS 1.0 INTRODUCTION PROPOSED CONSTRUCTION SITE CONDITIONS SUBSURFACE CONDITIONS SEISMIC SETTING Faulting Site Soil Classification Liquefaction LABORATORY PROGRAM SITE PREPARATION AND GRADING FOUNDATION RECOMMENDATIONS FLOOR SLAB BACKFILL AROUND THE BUILDING SURFACE DRAINAGE PAVEMENT DESIGN PLANS AND SPECIFICATIONS REVIEW CONSTRUCTION INSPECTION LIMITATIONS...7 APPENDIX A: FIELD EXPLORATION, VICINITY MAP, SITE PLAN, AND LOGS OF TEST HOLES Figure A-1 Vicinity Map Figure A-2 Test Hole Location Maps Figures A-3 through A-4 Logs of Test Holes Figure A-5 Key to Test Holes APPENDIX B: LABORATORY TEST PROCEDURES AND RESULTS Table B-1 Summary of Laboratory Test Data APPENDIX C: LIQUEFACTION ANALYSIS \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

72 Geotechnical Study Page 1 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, INTRODUCTION Summit Engineering Services (SES) has completed the geotechnical study for the proposed 27 th Street Apartments Project to be located at th Street, Ogden, Utah. The purpose of this study was to provide information on subsurface conditions, general recommendations for foundation types and depths, soil bearing capacities, site preparation and grading, and other design and construction considerations influenced by the subsoil conditions. The study included site reconnaissance, subsurface exploration and soil sampling, laboratory testing, engineering analysis, client consultation, and preparation of this report. 2.0 PROPOSED CONSTRUCTION SES understands that the proposed development will consist of a two story, wood framed building. The building will be 4,230 square feet in plan area with a slab on grade floor. Final grade elevations were not available at the time of this report. Structural loads were not available at the time of this study; however, no unusually heavy loads are anticipated. 3.0 SITE CONDITIONS The site currently is comprised of a vacant lot on the west side and a vacant home on the east side. The property is 0.37 acres in size and is generally flat. The surrounding properties consist of 27th Street to the north, a church to the west, residential property to the south and east. Surface drainage appears to be fair. 4.0 SUBSURFACE CONDITIONS Two test holes terminating at depths of 16.5 to 31.5 feet were drilled at this site. The subsoils correlated well between the test holes and generally consisted of interbedded native deposits of loose to medium dense silty, SAND (SM) and loose to medium dense SILT (ML) overlying soft to medium stiff, CLAY (CL) to the maximum depth explored of 31.5 feet. Groundwater was measured at a depth of 15 feet during drilling. A detailed description of the conditions encountered at each test hole location is presented on our Logs of Test Holes included in Appendix A. Please refer to Figures A-3 through A-4. Figure A-5 is the key to symbols and abbreviations used on the Test Hole Logs. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

73 Geotechnical Study Page 2 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, SEISMIC SETTING 5.1 Faulting Review of available literature for the Ogden area, indicates that no active faults traverse the property or immediately adjacent to the property. The closest known fault is the Wasatch fault approximately 1.5 miles to the east. 5.2 Site Soil Classification According to the 2006 International Building Code (IBC), it appears the soils are a seismic site class of E. This evaluation is not based upon a 100-foot deep boring as required by the IBC but an analysis of the N-values (blow counts) and soil types encountered along with a review of water well boring logs in the vicinity available at the State of Utah, Division of Water Rights website. If needed for design, the building at this site can utilize an assumed critical earthquake of magnitude M = 7 and a peak ground acceleration of Specific parameters (such as S MS, S M1, S DS, S M1 ) for seismic design at this site (as defined by either latitude/longitude or Zip Code) for Site Class E and can be obtained from the United States Geological Survey (USGS) web site maps/ Liquefaction The Weber County liquefaction hazard map rates the site and adjoining area having a High liquefaction potential. It should be noted that this is a general classification applied to a relatively large geographic area and does not take into account any site-specific mitigating factors. High is defined as greater than a 50 percent probability of experiencing an earthquake of sufficient magnitude to cause liquefaction to occur in 100 years. Liquefaction can be generally defined as a condition that can develop in a saturated sandy soil resulting in a substantial reduction in soil strength and a significant decrease in soil volume (settlement). Liquefaction can cause serious building damage and is a hazard to building occupants. The following conditions are considered conducive to liquefaction occurring: 1. A seismic event (earthquake) of magnitude 7.0 generating a ground acceleration of 0.25g. 2. Deposits of loose to medium dense clean (SP, SP-SM) to silty (SM) sands and silts (ML, MH, OL) below the groundwater table within a depth of 30 feet from the ground surface. Liquefaction impacts generally decrease with increasing fines content (silts and silty \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

74 Geotechnical Study Page 3 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, 2012 sands are less susceptible to liquefaction than clean sands). Clays of the type found in the area are generally considered not subject to liquefaction. A review of subsurface conditions as identified by the test holes indicates the following sitespecific conditions related to liquefaction: 1. The sands encountered within the depth of exploration, are loose to medium dense, silty, and mainly fine grained, which are not as susceptible to liquefaction. 2. Groundwater was encountered at approximately 10 feet below existing site grades. Based on the test hole data, liquefaction induced settlement was determined to be approximately 2 inches during a major seismic event. This result does not include any static differential settlement discussed in Section 8. The results of our analysis are presented in Appendix C. The liquefaction-induced settlement is anticipated to occur differentially beneath the structure. Consideration should be given to conducting additional exploration using Cone Penetration Test (CPT) techniques to better define the thickness of potential liquefiable layers and anticipated liquefaction-induced settlements. 6.0 LABORATORY PROGRAM Representative samples obtained from field investigation were subjected to the following laboratory analyses: Test Sample Type Purpose of Test % By Weight Passing the #200 Sieve Moisture Content and Unit Dry Density Native Soils Native Soils Soil Classification In-Situ Soil Conditions Atterberg Limits Native Soils Soil Classification Swell/Consolidation Native Soils Swell/Settlement Potential Refer to Appendix B of this report and the Boring Logs in Appendix A for laboratory test results. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

75 Geotechnical Study Page 4 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, SITE PREPARATION AND GRADING Any man-made fill underlying the site should be removed from the proposed building footprint and all other areas to be structurally loaded, and replaced with structural fill. Following site stripping, the native subgrade should be further excavated as required to establish the lowest bottom grade required for the foundation option selected for this project. The condition of the exposed native subgrade should then be evaluated by SES and stabilization efforts implemented if required as recommended below. The exposed native subgrade at this site may be soft and unstable and compaction by conventional methods/equipment to a firm unyielding condition prior to any required fill placement and/or construction activity may not be possible. Unstable subgrades (those that are soft or exhibit excessive pumping) may need to be undercut up to 18 inches or more and replaced with structural fill, select graded stabilization material, tamped-in-place cobble rock and/or a subgrade reinforcing geo-fabric/geo-grid. The subgrade stabilization method selected should be evaluated and approved by SES with additional recommendations provided by addendum as needed. Structural fill should be placed on and above a stable subgrade where fill is required to reach required foundation/slab grades. Some of the native soil deposits may be suitable for re-use as structural fill pending laboratory qualification testing and approval by SES. Structural fill should consist of SES-approved imported material placed in 8-inch maximum loose lifts, at the moisture content optimum for compaction, and compacted to at least 95 percent modified Proctor (ASTM D1557) maximum dry density. In general, imported fill should consist of well-graded sands and gravels containing 10 to 40 percent fines (material passing the No. 200 sieve, based on the minus ¾-inch fraction), and should have a maximum particle size of 4 inches. The plasticity index of the fines should not exceed 15. Compaction of fill lifts should be with equipment that will not negatively impact the foundations and structural integrity of any nearby structures including buildings, pavement and below/above ground utilities. Utility trenches should be backfilled with compacted fill. The fill should be placed in lift thickness appropriate to the type of compaction equipment utilized and compacted to a minimum degree of compaction of 90 percent modified Proctor (ASTM D1557) maximum dry density by mechanical means. All site grading and fill operations should be observed by a representative from SES to determine the adequacy of site preparation, the stability of exposed native subgrades, the suitability of fill materials, and compliance with compaction requirements. Further, the site \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

76 Geotechnical Study Page 5 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, 2012 should be inspected immediately after the completion of excavation operations to identify and provide mitigating recommendations if required for any unexpected subsurface conditions that may underlie the site. 8.0 FOUNDATION RECOMMENDATIONS Subsurface soils have been determined to be liquefiable during a seismic event. If the anticipated settlement is unacceptable, consideration should be given to mitigate the liquefaction potential through compaction grouting, use of rammed aggregate piers or other methods to reduce the hazard. Alternatively, the building structure could be designed to resist potential liquefaction-induced differential settlements at the ground surface by stiffening the foundation with the use of grade beams between spread footings or use of rammed aggregate piers. Provided the owner is aware of the risks involved of using a conventional spread footing type foundation, the following recommendations can be used. 1. Spread footings founded on scarified and recompacted native soil can be designed for a maximum net allowable bearing pressure of 2,000 psf. This pressure may be increased by one-third for short-term transient wind and seismic loads. Under these pressures the total footing settlement is expected to be less than about 1 inch. The differential settlement between adjacent spot footings or a 25 foot span of continuous wall footing should be about half this amount. 2. Continuous (wall) and individual (column) footings should be at least 18 and 24 inches wide, respectively, and should be placed a minimum of 2.5 feet below the lowest adjacent final grade for frost protection. 3. Continuous foundation walls should be adequately reinforced both top and bottom. As a guide, we suggest an amount of steel equivalent to that required for a simply supported span of 12 feet. 4. Structural fill should extend a lateral distance beyond the footing at least one half equal to the nominal footing width. 9.0 FLOOR SLAB The floor slab will likely be placed on compacted/firm natural subgrade and/or structural fill. In addition, a minimum of four inches of gravel should be provided below the slab to provide a uniform subgrade condition and to break the rise of capillary water. The slab should also be provided with frequent joints to minimize damage due to shrinkage cracking, and should be adequately reinforced for the loading conditions imposed on the slab. Further, the slab should be separated from all bearing walls and partitions with a slip joint. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

77 Geotechnical Study Page 6 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, BACKFILL AROUND THE BUILDING The on-site native soils may be used as backfill around the building. The backfill should be free of organics and other deleterious materials and should be moistened, placed in maximum 6-inch loose lifts, and compacted to at least 88 percent of the maximum dry density as determined by ASTM D1557. The negative impacts of using vibratory or heavy compactors on nearby existing structures should be carefully evaluated SURFACE DRAINAGE Adequate surface drainage must be maintained during the course of construction and after construction has been completed. The ground surface surrounding the exterior of the building should be sloped to drain away from the building in all directions. SES recommends a minimum slope of 6 inches in the first 10 feet. Roof downspouts should discharge into splash blocks extended beyond the limits of all backfill. All sprinkler heads should be aimed away from and kept at least 2 feet from the foundation walls. Landscaping requiring extensive watering should not be allowed within 2 feet of the building PAVEMENT DESIGN Where necessary, we recommend a pavement section consisting of 3 inches of asphaltic concrete, 8 inches of high quality base, over 12 inches of subbase. 3 inches and 10 inches, respectively, are recommended in drives. This recommendation assumes the subgrade material below the base will consist of at least 12 inches of well-compacted gravelly, sand and/or sandy gravel subbase and assumes low volume, light vehicular loading. Compaction of the subbase should be to a minimum of 95 percent of modified Proctor maximum dry density PLANS AND SPECIFICATIONS REVIEW It is recommended that SES be provided the opportunity to review the final design and specifications in order to determine whether any change in concept may have had any affect on the validity of our recommendations, and whether those recommendations have been properly implemented in the design and specifications. Review of the final design and specifications will be noted in writing. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

78 Geotechnical Study Page 7 27 th Street Apartments, th Street, Ogden, Weber County, Utah May 16, CONSTRUCTION INSPECTION All site grading operations should be observed by our representative to determine the adequacy of site preparation, removal of unsuitable material, compliance with compaction requirements, observe/document ground improvement operations, and in general assure that the recommendations presented in this report are properly implemented during construction LIMITATIONS The analysis and recommendations submitted in this study are based upon the data obtained from the test holes drilled at the location of the proposed structure as indicated on Figure A-2. This study does not reflect any variations, which may occur between the test holes. The nature and extent of variations may not become evident until the course of construction and are sometimes sufficient to necessitate changes in the designs; thus, it is important that SES observes subsurface materials exposed in the excavations to take advantage of all opportunities to recognize differing conditions, which would affect the performance of the facility being planned. This study has been prepared in order to assist the architect and engineer in the design of this project. In the event that any changes are planned in the design, location or elevation of the building as outlined in this study, the conclusions and recommendations contained in this study shall not be considered valid unless the changes are reviewed and conclusions of this study modified or approved in writing by the geotechnical engineer. SES also recommends that final plans and specifications be reviewed by our office to evaluate whether our recommendations were properly understood and implemented. The study should be available to prospective contractors for information on technical data only as interpreted from the test holes and not as a warranty of subsurface conditions. \\tserver\public\ses\geo Projects\TC-0G Ogden Community Inv. Group\661 27th Street\Final Report\TC-0G Report.doc

79 APPENDIX A Field Exploration, Vicinity Map, Site Plans, and Logs of Test Holes

80 FIELD EXPLORATION The field exploration consisted of the drilling, logging, and sampling of five (5), 21.5-foot to foot deep test holes. Undisturbed samples were taken at selected intervals, sealed and returned to the laboratory for classification and testing. A continuous log of the subsurface conditions as encountered in the test holes was kept during drilling. Mr. Curt Stripeika of SES supervised the drilling and sampling operations. The test holes were drilled by Earthcore, Inc., of Salt Lake City, Utah.

81 TC 0G FIGURE A 1