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3656; Foxes Landing Lift Station Upgrade; Foxes Landing Lift Station Upgrade; 1999-05-18
LIMITED SOILS EXPLORATION FOXES LANDING LIFT STATION UPGRADE CARLSBAD, CALIFORNIA May 18, 1999 This document was prepared for use only by the client, only for the purposes stated, and within a reasonable time from issuance. Non- commercial, educational and scientific use of this report by regulatory agencies is regarded as a "fair use" and not a violation of copyright Regulatory agencies may make additional copies of this document for internal use. Copies may also be made available to the public as required by law. The reprint must acknowledge the copyright and indicate that permission to reprint has been received. 51-52190175119L197.doc Pageiofiii May 18,1999 Copyright 1999 KJeinfelder, Inc. KLEINFELDER TABLE OF CONTENTS Section Page 1.0 INTRODUCTION 1 2.0 PROJECT DESCRIPTION 2 3.0 FIELD EXPLORATION 3 4.0 LABORATORY TESTING 4 5.0 SUBSURFACE CONDITIONS 5 6.0 DISCUSSION OF POTENTIAL IMPACTS 6 7.0 RECOMMENDATIONS 7 7.1 SITE PREPARATION 7 7.2 CONSTRUCTION DEWATERING 7 7.3 EXCAVATIONS 9 7.3.1 Excavations and Stability 9 7.3.2 Buried Vault Excavation 9 7.3.3 Pipe Bedding for Utilities 10 7.3.4 Backfill 11 7.4 SHORING 11 7.4.1 General 11 7.4.2 Caving Potential 11 7.4.3 Lagging 12 7.4.4 Active Earth Pressures 12 7.4.5 Surcharge Pressures 12 7.4.6 Lateral Resistance 13 7.4.7 Estimated Lateral Displacements 13 7.5 BUILDING FOUNDATIONS AND FLOOR SLABS 14 7.5.1 Bypass Connection Vault Foundations and Floor Slabs 14 7.5.2 Generator Building Foundation and Floor Slab 15 7.6 UNIFORM BUILDING CODE SEISMIC DESIGN PARAMETERS 16 7.7 LATERAL EARTH PRESSURES FOR BYPASS CONNECTION VAULT 16 7.8 BURIED UTILITY PIPE SOIL PARAMETERS 17 7.9 RESTORED PAVEMENTS 17 8.0 LIMITATIONS 18 FIGURES Figure 1 - Vicinity Map Figure 2 - Boring Location Plan Figure 3 - July 1963 Boring for Existing Pump Station APPENDICES Appendix A - Boring Logs Appendix B - Laboratory Testing Appendix C - Suggested Guidelines for Earthwork Construction Appendix D - ASFE Insert 51-52190175119L197.doc Pageiiiofiii May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 1.0 INTRODUCTION At this time we have completed our Limited Soils Exploration for the Lift Station Upgrade at Foxes Landing, Carlsbad, California. The objective of this report is to provide the Carlsbad Municipal Water District with findings, conclusions, and recommendations regarding the geotechnical aspects of the proposed upgrade. The following sections describe our understanding of the project, the subsurface conditions encountered during our field exploration, and our recommendations regarding geotechnical design information. The recommendations contained in this report are subject to the limitations presented herein. Attention is directed to the limitations section of this report. In addition, a brochure prepared by the Association of Firms Practicing in the Geosciences (ASFE) has also been included (see attachments). We recommend that this report be reviewed in conjunction with this document. 51-521901/5119L197.doc Page 1 of 18 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 2.0 PROJECT DESCRIPTION We understand that the improvements to the existing lift station will include an at-grade electrical generator building (approximately 10 feet by 16 feet in plan area) and a bypass connection vault (approximately 8 feet by 8 feet in plan area and about 12 feet deep below the existing pavement grade). We anticipate that both structures will have sidewalls constructed of cast-in-place concrete and/or reinforced masonry block. The improvements will be located directly northwest of the existing lift station in an area that is relatively flat and paved with asphalt. The elevation at the top of the asphalt in the improvement vicinity is about 10.7 feet above mean sea level (MSL). Existing site drainage is toward the south. 51-521901/5119L197.doc Page2ofl8 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 3.0 FIELD EXPLORATION A single test boring was completed to a depth of approximately 26.5 feet below the existing pavement surface at the approximate location shown on Figure 2. The test boring was advanced using a CME-75 truck-mounted drill equipped with an 8-inch hollow-stem auger. Soil samples were obtained at nominal 5-foot intervals with a 3-inch outside diameter California sampler. The California sampler was lined with 2.5-inch diameter brass sleeves. The sampler was driven 18 inches using a 140-pound hammer falling 30 inches. The number of blows required to drive each 6-inch increment was recorded, and the blow counts for each foot of drive is reported on the boring log. In addition to the blow counts, the boring log describes the earth materials encountered. The boundaries between soil layers shown on the log are approximate because the transitions between different soil layers are likely to be gradual. 51-521901/5119L197.doc Page3ofl8 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 4.0 LABORATORY TESTING The geotechnical laboratory program included tests for gradation, moisture content, and dry unit weight. The gradation test results are included in Appendix B; the moisture content and unit weight test results are included on the boring logs in Appendix A. 51-521901/5119L197.doc Page4ofl8 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 5.0 SUBSURFACE CONDITIONS The log for the July 1963 test borings (shown as Boring No. 1 on Figure 3) completed for the original pump station indicates loose to soft alluvium (silts, sands, and clays) to a depth of 24 feet. Below 24 feet, compact sand was encountered to the maximum depth of the boring, 50 feet. We interpret this compact sand to be either older, more dense alluvium or a dense formational stratum. The subsurface conditions encountered during our field exploration for the new improvements consisted of an existing asphaltic concrete and aggregate base flexible pavement underlain by alluvial soils. The alluvium generally consists of medium-dense, medium-grained silty sands (SM) within the upper nine feet of subgrade. Below nine feet the alluvium consists of loose, relatively clean, medium-grained sands (SP) with generally less than 10% silt content to the bottom of our test boring at a depth of 26.5 feet. Groundwater was encountered within our exploratory boring at five feet below the ground surface at an approximate elevation of 5.7 feet MSL which is consistent with the water table elevation found in 1963 (+5 feet). 51-521901/5119L197.doc PageSoflS May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 6.0 DISCUSSION OF POTENTIAL IMPACTS From a geotechnical standpoint, the site is generally suitable for the proposed lift station improvements with only a limited number of potential impacts. These potential impacts include the depth to groundwater with respect to the vault excavation, caving of the granular soils during the vault excavation, and seismic shaking. Excavation of the vault area below a depth of 5 feet will be affected by the groundwater table and will likely require temporary dewatering for placement of the vault walls and foundation. The granular soils will have a marked tendency to slough and cave, especially at depths greater than 5 feet. We anticipate that temporary shoring will be required to mitigate the soil caving potential. In general, the alluvium in our test boring consists of medium dense to loose, silty to relatively clean sand to a depth of at least 26.5 feet. Based on our analysis and field exploration, the soil has a medium to high potential for liquefaction during a major seismic event. The most likely impact as a result of the liquefaction would be the potential for seismic-induced settlement to occur. We anticipate that seismic-induced settlement on the order of 3 to 5 inches could occur following a large earthquake. However, since the structures are relatively small, we anticipate that they can be reasonably reinforced so that a complete collapse of the structures can be avoided in the event that liquefaction should occur. We recommend that flexibility be designed in the connections between the structures and incoming utilities to accommodate up to 3 to 5 inches of differential vertical movement should liquefaction occur. If this amount of vertical movement cannot be accommodated by flexible connections and the structures are to remain operational through a large earthquake, then we recommend the structures be supported on driven piling bearing below a minimum depth of 30 feet below the existing ground surface. 51-521901/5119L197.doc Page6ofl8 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.0 RECOMMENDATIONS 7.1 SITE PREPARATION We anticipate that site preparation will consist primarily of the sawcutting of the existing asphalt pavement and its removal from the site. This will be followed by the excavation of the bypass vault, construction of the bypass vault structure with appropriate backfilling, construction of the generator building, and replacement of any required pavement between the structures and the existing pavement. The anticipated site preparation is limited and will consist of scarifying and recompacting the upper 6 inches of subgrade to 90 percent of its ASTM D1557 maximum dry density prior to the placement of the floor slab for the generator building or the new aggregate base for the pavement repair. 7.2 CONSTRUCTION DEWATERING Excavations which extend below the site groundwater level (currently estimated to be at approximately 5 feet below existing grade, but subject to future variations) will need to be dewatered. To maintain stability of the excavation bottom, groundwater levels should be drawn down a minimum of two feet below the lowest portion of the excavation. The groundwater level should be maintained below the recommended level until the backfill has been completed to an elevation of at least five feet above the pre-dewatering elevation. Analysis of contractor dewatering needs or the design of contractor dewatering systems were not within the scope of our services. This work is best accomplished by a competent dewatering contractor. However, we have included some discussions of potential dewatering methods in the following paragraphs. There are two likely methods of dewatering which can be used. These include well points and sheet-pile cutoffs (in combination with sumps and vacuum well points). The method ultimately selected is dependent on a number of factors, e.g., quantity of groundwater to be removed, cone 51-521901/5119L197.doc Page7ofl8 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEIN FELDER of depression (zone of influence) of dewatering measures within the excavation, stability of the silty sands, the presence of potential seepage zones which will pipe water from distant sources after the groundwater table is lowered, and cost. Collection of groundwater and seepage in open or sheeted sumps without filters, while appearing less expensive perhaps, may have disadvantages which the contractor may have to address. Silty sand is sensitive to seepage pressures; slope instability and loss of strength in the bottom are likely with open pumping. Use of sheet piling to support the excavation walls can also be used to provide lateral cutoff, lower the amount of dewatering, and mitigate heave of the excavation bottom. Sheet piling should extend to at least a depth of 10 feet below the bottom of the excavation or the required depth for stability, whichever results in the greater depth of the embedment. Positive dewatering methods with well points at close intervals may still be required. Well points offer good flexibility as a dewatering method over a range of subsoils, but are limited to a suction lift limitation of 20 feet for single stages. This depth limitation may require multiple well point stages and/or placement of the system at the bottom of the excavation or partially up the excavation slope which may hamper construction operations and backfilling. Normal spacing for well points is on the order of 3 to 5 feet. Pumping rates are uncertain because no pump test data is available. The Regional Water Quality Control Board is likely to restrict the discharge of water pumped from excavations. Temporary construction dewatering will require an NPDES permit for discharge unless the water is discharged to a sanitary sewer system, which will still require approval from the City. Lowering the water table could induce settlements of the dewatered and underlying soils. If structures or utilities are located within the anticipated cone of depression, groundwater levels, settlement, and deflections at and near the structure or utility should be monitored during dewatering to observe if the groundwater level is changing and movement is occurring. Dewatering 51-521901/51 19L197.doc Page 8 of 18 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER should stop and appropriate corrective action should be taken if settlement or changes in groundwater levels are noted at these critical points. 7.3 EXCAVATIONS 7.3.1 Excavations and Stability All excavation work should comply with the current requirements of OSHA. The onsite soils are generally classified as the Type C soils for evaluating OSHA sloping or shoring requirements. All discussion in this section regarding stable excavation slopes assumes minimal equipment vibration and adequate setback of excavated materials and construction equipment from the foundation excavation. We recommend the minimum setback distance from the near edge of he excavation be equivalent to the adjacent excavation depth. If excavated materials are stockpiled adjacent to the excavation, the weight of this material should be considered as a surcharge load for lateral earth pressure calculations. Configuration values presented in the OSHA regulations assume that the soils in the cut face do not change in moisture content significantly. Slope configuration estimates should not be considered applicable for personnel safety. The contractor must determine slopes for safety of personnel and meet all regulations covering excavation stability and safety. 7.3.2 Buried Vault Excavation Due to the anticipated soil disturbance during excavation, and in order to provide a suitable working surface on the bottom of the buried vault excavation, we recommend the bottom of the S vault area be overexcavated by at least 18 inches below the design elevation of the vault bottom. The bottom of the excavation should then be cleaned of any loose debris and backfilled with clean, crushed granular drain rock graded from a maximum particle size of 3/4-inch and with 0- 5% passing the No. 4 sieve. 51-521901/5119L197.doc Page 9 of 18 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEIN FELDER The aggregate base should be placed in two 9-inch thick loose lifts and compacted with three passes of a vibratory base plate compactor. The vibrating compactor should have a minimum ,*a, ^ weight of 200 pounds and a minimum vibrating frequency of 1,600 cycles per minute. The initial lift may be increased to 12 inches if "pumping" of the aggregate base occurs during initial compaction. Since the vault structure is to be constructed below the existing water table, hydrostatic uplift pressures on the order of 500 psf should be incorporated in to the design for a vault depth of 12 feet. Accordingly, design dead load factors should maintain a 1.3 minimum factor of safety against potential uplift pressures. •*&st 7.3.3 Pipe Bedding for Utilities «*»» Granular pipe bedding should be sand, gravel, or crushed aggregate with a sand equivalent of not — less than 30. Onsite materials are generally too silty to meet this requirement. Bedding should be ^ extended the full width of the trench to one foot above the top of the pipe. The pipe bedding should *, be densified to 90 percent relative compaction prior to backfilling. Densification of pipe bedding «, can be accomplished by either jetting with water or by mechanical compaction. If water jetting is <« permitted, the size and length of jet pipe, quantities of water, and jetting locations should be *, established in the field at the time of construction and should be sufficient to thoroughly saturate * and density the bedding material around the pipe. Jetting should be accomplished by use of a jet ,« pipe (1-1/2 inch minimum diameter pipe) to which a minimum 2-inch diameter hose is attached *» carrying a continuous supply of water under pressure. The bedding should be allowed to drain •* thoroughly until the surface of the bedding is in a firm and unyielding condition prior to •*> commencement of any subsequent improvements. The specifications should require the contractor <*• to provide an sump and pump to remove any accumulated water which remains. Compaction of the «*• pipe bedding by mechanical means is acceptable provided the specifications require compacting *• with pneumatic "powder puffs" and periodic density testing (which will require the contractor to ** provide special excavation for access and shoring). 51-52190175119L197.doc Page 10 of 18 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.3.4 Backfill The onsite soils can be used as backfill above the pipe zone; however, the soils excavated from below the water table may be too moist in their present condition to allow proper compaction within deep excavations without allowing them to dry out. If imported backfill is required, we recommend that it meet the following requirements: Liquid Limit: Less than 30% Plasticity Index: Less than or equal to 15% Percent Soil Passing No. 200 Sieve: Less than 30% Maximum Particle Dimension: Less than 3 inches UBC Expansion Index: Less than 30 Soluble Sulfates: Less than 0. 1 0% Trench backfill should be placed in uniform layers not exceeding 8 inches in loose thickness, moisture conditioned to within two percentage points of optimum, and mechanically compacted. The relative compaction should be to at least 90 percent. 7.4 SHORING 7.4.1 General Shoring may be required where space or other restrictions do not allow a sloped embankment. A conventional shoring system consisting of closely spaced soldier piles or sheet piles may be used. 7.4.2 Caving Potential The soils below five feet are likely to cave without support and/or drainage. If possible, wide- flange sections may be installed into pre-drilled holes surrounded by concrete. If caving of the 51-521901/5119L197.doc Page 11 of 18 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER drilled holes occurs, soldier piles may need to be driven to the required depth or a drilling slurry may be required. 7.4.3 Lagging Timber lagging may be used between the soldier piles to support loose or soft soils. If lagging is to be left in place, treated lumber should be used. Lagging should be designed for the full lateral pressure recommended below. If possible, structural walls should be cast directly against the shoring, eliminating the need for backfilling a narrow space. However, special provisions for wall drainage (such as the use of prefabricated composite drain) may be required where this type of construction is used. 7.4.4 Active Earth Pressures Cantilevered shoring systems should be designed to resist an active earth pressure equivalent to a fluid weighing 35 pounds per cubic foot (pcf). Braced excavations should be designed to resist a uniform horizontal soil pressure of 22H (in pounds per square foot, psf), where H is the wall height in feet. 7.4.5 Surcharge Pressures Thirty percent of any area surcharge placed adjacent to the shoring may be assumed to act as a uniform horizontal pressure against the shoring. Special cases such as combinations of sloping and shoring or other surcharge loads (not specified above) may require an increase in the design values recommended above. These conditions should be evaluated by the project geotechnical engineer on a case-by-case basis. The above pressures do not include hydrostatic pressures; it is assumed that temporary hydrostatic pressures will be relieved by dewatering outside the excavation or that drainage will be provided by weep holes or spaces in the lagging. 51-521901/5119L197.doc Pagel2ofl8 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.4.6 Lateral Resistance All soldier or sheet piles should extend to a sufficient depth below the excavation bottom to provide the required lateral resistance. We recommend required embedment depths be calculated using methods for evaluating sheet pile walls and based on the principles of force and moment equilibrium. For this method, the allowable passive pressure against soldier piles which extend below the level of excavation may be assumed to be equivalent to a fluid weighingv250y pcf above the groundwater table and 125 pcf below the groundwater table. To account for three- dimensional effects, the passive pressure may be assumed to act on an area two times the width of the embedded portion of the pile, provided adjacent piles are spaced at least three diameters, center-to-center. Additionally, we recommend a factor of safety of 1.2 to be applied to the calculated embedment depth and that the passive pressure be limited to 2,500 psf. Alternatively, lateral capacity of a soldier pile extending below the excavation bottom may be evaluated using the "Pole Formula" given in Section 1806.8 of the Uniform Building Code, 1997 edition. For this method, we recommend a lateral soil bearing pressure of 150 pounds per square foot of embedment may be used to estimate the required embedment depth. The 100 percent increase allowed by the Code for isolated poles (which are not adversely affected by a 1/2 inch horizontal deflection at the ground surface due to short-term lateral loads) may be used. 7.4.7 Estimated Lateral Displacements Lateral movement of a shored excavation will depend on the type and relative stiffness of the system used and other factors beyond the scope of this study. However, based on our experience with projects with similar shoring requirements, we anticipate maximum lateral movement of the shoring system should generally be less than two inches. 51-521901/5119L197.doc Page 13 of 18 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.5 BUILDING FOUNDATIONS AND FLOOR SLABS 7.5.1 Bypass Connection Vault Foundations and Floor Slabs Conventional spread footings supported on compacted aggregate base as recommended in Section 7.3.2 can be sized using a nominal bearing pressure of 1,500 psf. This value may be increased by one third for seismic or wind loads. The foundations should be a minimum of 12 inches wide. The allowable soil bearing pressure may be increased by 1/3 for wind and seismic loading. Unless the average applied load of the structure exceeds the weight of the displaced soil significantly, we do not anticipate static settlement in excess of 1/2 to one inch. We recommend that the footings be provided with at least minimal reinforcement consisting of four No. 4 reinforcing bars, two placed at the top and two at the bottom. Resistance to lateral loads on foundation footings may be calculated using a passive equivalent fluid unit weight of 250 pcf and a coefficient of friction of 0.35. Uplift resistance may be calculated using the dead weight of the structure plus the friction along the walls of the structure. An average value of 1 ,000 psf can be used to calculate frictional resistance to uplift. In actuality, the frictional resistance increases in a triangular fashion with depth to a critical point below which the frictional resistance is assumed to be constant. However, for general design purposes, the recommended average value can be used regardless of depth. The surface area of the upper two feet of the structure should be neglected in these calculations. We recommend the concrete floor slabs for buried structures be at least five inches thick and be reinforced with at least No. 3 steel reinforcing bars at 18-inch centers (both ways) or No. 4 steel reinforcing bars at 24-inch centers (both ways). These reinforcement guidelines should not supercede the reinforcement requirements calculated by the structural engineer. As described earlier under Section 6.0, there is a potential for 3 to 5 inches of dynamic settlement that could occur following a large earthquake as the result of liquefaction. If this amount of settlement following an earthquake is unacceptable, then we recommend supporting the structure on driven piles bearing below a depth of 30 feet. For calculating the allowable axial 51-521901/5119L197.doc Page 14 of 18 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER capacity of the pile, an allowable skin friction value of 500 psf can be used for the pile surface embedded below a minimum depth of 24 feet; no value should be allowed for the length of pile above a depth of 24 feet. The allowable passive pressure against piles can be assumed to be equivalent to a fluid weighing 125 pcf. To account for three dimensional effects, the passive pressure may be assumed to act on an area two times the width of the embedded portion of the pile, provided adjacent piles are spaced at least three diameters apart, center to center. 7.5.2 Generator Building Foundation and Floor Slab Conventional shallow spread footings may be used to support the intended foundation loads. Footings may be designed for support upon engineered fill using an allowable soil contact pressure of 1 ,500 pounds per square foot for dead load plus normal live load. This value may be increased by one third for seismic or wind loads. Resistance to lateral forces may be computed using lateral bearing and lateral sliding combined. Lateral bearing may be computed as 150 pounds per square foot per foot of depth below natural grade. Lateral sliding resistance can be obtained by multiplying 0.35 by the dead load. All footings should be trenched at least 1.5 feet below the lowest adjacent finished grade and should be a minimum of 1 foot in width. Reinforcement steel requirements for foundations should be designed by the structural engineer. As a minimum, we recommend that continuous footing reinforcement consist of at least two No. 4 bars placed at the top and two placed at the bottom of the foundation. These reinforcement guidelines should not supersede the reinforcement requirements calculated by the structural engineer. Total and differential static settlements are expected to be less than 1/2 inch for these loading conditions. We further expect that settlements will occur rather quickly as the loads are applied. Therefore, the majority of the settlement should occur during the construction phase when the loads on the structures often reach their average maximum. 51-521901/5119L197.doc PagelSoflS May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER If the potential for dynamic settlement of 3 to 5 inches as described under Section 6.0 is unacceptable, the generator building should be supported on driven piling as described for the bypass connection vault. The floor slab for the generator building should be supported on 6 inches of subgrade compacted to 90 percent of the ASTM D1557 maximum dry density. The concrete floor slab should be at least five inches thick and reinforced with at least No. 3 steel reinforcing bars at 18-inch centers (both ways) or No. 4 steel reinforcing bars at 24-inch centers (both ways). 7.6 UNIFORM BUILDING CODE SEISMIC DESIGN PARAMETERS Since this site is located in the seismically active Southern California region, we recommend that, as a minimum, the proposed development be designed in accordance with the requirements of the latest (1997) edition of the Uniform Building Code (UBC) for Seismic Zone 4. We recommend that a soil profile factor of SE be used with the UBC design procedure (Table 16-J). Near source seismic coefficients for acceleration and velocity, Na=1.0 and Nv=l.l (UBC Tables 16-S and 16-T), should be used in design. 7.7 LATERAL EARTH PRESSURES FOR BYPASS CONNECTION VAULT Lateral earth pressures acting against vault walls can be calculated assuming that the retained soils act as a fluid. The equivalent fluid weight (efw) for walls which are restrained at the top or are sensitive to movement and tilting should be designed for the at-rest efw. If on-site or imported non-expansive sandy soils with a Unified Soil Classification of SP, SM, or SC are used as backfill, an at-rest efw value of 60 pcf can be used above the water table and 90 pcf below the water table. Fifty and thirty percent of any uniform area surcharge placed at the top of the wall may be assumed to act as a uniform horizontal pressure over the entire wall. We should be contacted where point or live loads are expected so we can provide recommendations for additional wall 51-52190175119L197.doc Pagel6ofl8 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER stresses. Also, permanent walls should be designed for seismic loading. The resultant seismic force (in pounds) can be calculated as 13H2 where H is the height of the wall (in feet) above its base. The resultant seismic force acts at 0.6H above the wall base. For combined effects of static and seismic forces, a minimum factor of safety of 1.2 is recommended. 7.8 BURIED UTILITY PIPE SOIL PARAMETERS We recommend the following soil parameters for use in buried utility pipe design: • Total soil unit weight, yt = • Modulus of soil reaction, E' = HOpcf 1,000 psi for pipe provided with gravel bedding (4 inch minimum thickness) and gravel pipe zone to one foot over pipe. 400 psi where the pipe is constructed on native fill without the gravel pipe zone and bedding. 7.9 RESTORED PAVEMENTS Subgrades for restored pavement areas should be scarified and recompacted to 90 percent relative compaction (ASTM D1557) by the contractor prior to the placement of the pavement section. It is recommended that the restored pavement section match existing pavements in the area (2-inch asphaltic concrete over 4 inches of Class 2 aggregate base). 51-521901/5119L197.doc Copyright 1999 Kleinfelder, Inc. Page 17 of 18 May 18, 1999 KLEINFELDER 8.0 LIMITATIONS Recommendations contained in this report are based on our literature research, field observations, data from the field exploration, laboratory tests, and our present knowledge of the proposed construction. It is possible that soil conditions could vary between or beyond the points explored. If soil conditions are encountered during construction which differ from those described herein, our firm should be notified immediately in order that a review may be made and any supplemental recommendations provided. If the scope of the proposed construction, including the proposed loads or structural locations, changes from that described in this report, we should also review our recommendations. Additionally, if information from this report is used in a way not described under the project description portion of this report, it is understood that it is being done at the designer's and owner's own risk. Our firm has prepared this report for the use of Carlsbad Municipal Water District, on this project in substantial accordance with the generally accepted geotechnical engineering practice as it exists in the site area at the time of our study. No warranty is made or intended. The recommendations provided in this report are based on the assumption that an adequate program of tests and observations will be conducted by our firm during the construction phase in order to evaluate compliance with our recommendations. This report may be used only by the client and only for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both on-site and offsite) or other factors may change over time, and additional work may be required with the passage of time. Based on the intended use of the report, Kleinfelder may require that additional work be performed and that an updated report be issued. Non-compliance with any of these requirements by the client or anyone else will release Kleinfelder from any liability resulting from the use of this report by any unauthorized party. 51-521901/5119L197.doc PagelSoflS May 18, 1999 Copyright 1999 Kleinfelder, Inc. VICINITY MAPKLEINFELDER 5015 SHOREHAM PLACE SAN DIEGO, CAUFORNIA 92122 FOXES LANDING LIFT STATION UPGRADE CARLSBAD, CALIFORNIACHECKED BY: DATE: 5/11/99PROJECT NO. 51-5219-01 B1 IMPROVEMENT AREA EXISTING PARKING AREA EXISTING FENCE EXISTING PUMP STATION APPROXIMATE BORING LOCATION APPROXIMATE PREVIOUS BORING LOCATION (JULY 1963)APPROXIMATE GRAPHIC SCALE (FEET) KLEINFELDER 5015 SHOREHAM PLACE SAN DIEGO, CALIFORNIA 92122 CHECKED BY: PROJECT NO. 51-5219-01 FN: 5219SITE DATE: 5/13/99 BORING LOCATION PLAN FOXES LANDING LIFT STATION UPGRADE CARLSBAD, CALIFORNIA FIGURE M.S.L* O -/O -ZO -3O -4O Uj /VOT TEST HOLE LOG BORM6 NO. 1 BORING NO. 2 0 CLEV. +6.9 0 / 3 4 6 9 44- 34 40 30 ?j BLOWS PER FT./.4 1.4 2JS 2.6 ZS /.4 /.4 /A M ? «»j !^ 3RL • " * > -.'{;•• T-i»~ •~:': :~.'.'^ / / // y/ // '/, // **$• fy. ">UN Loos* Orown Ffnf to medium Sand . BtocJe Organic Si/f • oLoose BrotvrtSand- /O Very Soft 6/u* <5rey -/o C/oyzg y Compact Grey f/nf ~ZO aft to Mfdiuifl Sand C/ay Layer -so 4O -40 Com/oacf Grry C/ay*y *0 Sand SCALE: /"-/o' D WATGR ELGV. + £ /A/ |f| KLEINFELDER F<£L, 5015 SHOREHAM PLACE SAN DIEGO, CALIFORNIA 92122 FOXFfi \_ 1 CHECKED BY: j^ FN: PROJECT NO. 51-5219-01 DATE: 5/13/99 6 /3 4O 30 - 80*t BLOWS PER FT.$/.4 /.4 /.4 1.4 (^ SAMPLE size~£r- / / Y^';- •€»••* I^Vgl /96 Lociff Brown Fin* - Peat /O Vary 5off '8/t/* Grey C/oy r^/nff Sand Grave/ Layer 30 Compact Fins fo Sand Grave/ Layer 4O SO 3 Y 1963 BORING 1 DATA EXISTING PUMP STATION <\NDING LIFT STATION UPGRADE 3ARLSBAD, CALIFORNIA / compact Medium FIGURE 3 APPENDIX A 71-5219-01 LOG OF BORING LEGEND SHEET 1 OF 1 DRILLINGEQU1PMENT PROJECT NAME FOXES LANDING LIFT STATION UPGRADE LOCATION TYPE OF BIT HAMMER DATA: WT.LBS. DROP INCHES TOP OF CASING ELEVATION STARTED: COMPLETED: BACKFILLED: DRILLING AGENCY LOGGED BY SURFACE CONDITIONS GROUNDWATER Fl FVATION DATE GEOLOGICLOGSOIL DESCRIPTION SAMPLE NO.BLOWCOUNTSMOISTURECONTENT(%)NOTES 4— oSs; 6— -7 8 9— 10— 11 — 12— 13 14— 15— 16— 17— 18— 19— 20— 21— 22— 23 24 25— 26— 27— 28— 29— 30- WELL-GRADED GRAVELS AND GRAVEL-SAND MIXTURES, LITTLE OR NO FINES POORLY GRADED GRAVELS AND GRAVEL-SAND MIXTURES, LITTLE OR NO FINES SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES WELL-GRADED SANDS AND GRAVELLY SANDS, LITTLE OR NO FINES POORLY GRADED SANDS AND GRAVELLY SANDS, LITTLE OR NO FINES SILTY SANDS, SAND-SILT MIXTURES CLAYEY SANDS, SAND-CLAY MIXTURES INORGANIC SILTS, VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SANDS OR SILTS, ELASTIC SILTS INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY PEAT, MUCK AND OTHER HIGHLY ORGANIC SOILS VATD WATER LEVEL AT TIME OF DRILLING -5 WATER LEVEL MEASURED IN WELL GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT BENTONITE CAVED AREA CEMENT CONCRETE NATURAL BACKFILL BENTONITE PACKER SAND BACKFILL SAND VOLCLAY GROUT PIPE SLOTTED PIPE CONTINUOUS SAMPLER GRAB SAMPLE CALIFORNIA SAMPLER MODIFIED CALIFORNIA SAMPLER NO RECOVERY PITCHER SAMPLER SHELBY TUBE SAMPLER STANDARD PENETRATION SAMPLER FN: 5219LOG v i eihjeei r^nnKLtllNrtLL/CK 5015 SHOREHAM PLACESAN DIEGO. CALIFORNIA 92122 FOJRF NO.A1 PROJECT NO. 51-5219-01 LOG OF BORING 1 SHEET "I OF DRILLINGEQUIPMENTIR A-300 PROJECT NAME FOXES LANDING LIFT STATION UPGRADE LOCATION SEE SITE PLAN TYPE OF BIT 8" HSA HAMMER DATA: WT. 1 40 LBS. DROP 30 INCHESSURFACE ELEVATION TOTAL DEPTH OF HOLE STARTED: 4/27/99 COMPLETED: 4/27/99 BACKFILLED: 4/27/99 DRILLING AGENCY SCOTT'S DRILLING LOGGED BY RMG SURFACE CONDITIONS 2" AC / 4" BASE GROUNDWATER DEPTH 7'DATE 5' 11727/99 11727/99 0 1 2— 3— 4— 5 CD LOG OF MATERIAL Inches asphalt concrete. 4 inches base SILTY SAND, dark gray, wet, medium dense, medium grained SM — Very loose with shell fragments 6-j ' • 22 7— 8— 9— SPSAND, brown, wet, very loose, some silt, (<10%), coarse grained 11—F-v •••••••• 4 12—; 13—- 14—: 15—1 No recovery ,- -, 17—I: 18—; 19—- 20—l.-.-.v.-.-.•. Loose gray, medium grained 21—];:•.•:•:•:•:•:• 6 7 22-4 Very loose, brown, medium to coarse grained 23—: 24— 25—: 264....... | | 7 3 27 I Bottom @ 26.5' Water observed © 5'28—|Bottom of boring caved below 20 29—I Boring backfilled with soil cuttings and asphaltic concrete30- FW S9idirv BKI V \ C I k.1 C C I rkEO 5015 SHOREHAM PLACEFN: 5219LOG ••"• KLEINFELDER SAN DIEGO. CALIFORNIA 92122 SAMPLE NO. 1 3 21 LU) I— kp NOTES FIGURE NO.: A2 APPENDIX B KLEI NFELDER APPENDIX B LABORATORY TESTING Foxes Landing Lift Station Upgrade Carlsbad, California General Laboratory tests were performed on selected, representative samples as an aid in classifying the soils and to evaluate physical properties of the soils which may affect foundation design and construction procedures. A description of the laboratory testing program is presented below. Moisture and Density Moisture content and dry unit weight tests were performed on a number of samples recovered from the test borings. Moisture content and dry unit weight were evaluated in general accordance with ASTM Test Methods D2216 and D2937, respectively. Results of these tests are presented on the test boring logs in Appendix A. Sieve Analyses Sieve analyses were performed on thirteen samples of the materials encountered at the site to evaluate the gradation characteristics of the soils and to aid in their classification. Tests were performed in general accordance with ASTM Test Method D422. Results of these tests are presented on Figures Bl through B13. 51-521901/5119L197.doc PageB-1 May 18,1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER TABLE B-l MOISTURE CONTENT AND DRY UNIT WEIGHT ASTM D216 AND D2937 Sample B1-1C B1-4C Description Gray-Brown Sand with Little Silt (SP) Gray-Brown Sand with Little Silt (SP) Moisture (%) 10.5 16.8 Dry Density (pcf) 115.4 118.0 51-521901/5119L197.doc Copyright 1999 Kleinfelder, Inc. Page B-2 May 18, 1999 APPENDIX C KLEI NFELDER APPENDIX C SUGGESTED GUIDELINES FOR EARTHWORK CONSTRUCTION Foxes Landing Lift Station Upgrade Carlsbad, California 1.0 GENERAL 1.1 Scope - The work done under these specifications shall include clearing, stripping, removal of unsuitable material, excavation, installation of subsurface drainage, preparation of natural soils, placement and compaction of on-site and imported fill material, and placement and compaction of pavement materials. 1.2 Contractor's Responsibility - A geotechnical investigation was performed for the project by Kleinfelder and presented in a report dated May 18, 1999. The Contractor shall attentively examine the site in such a manner that he can correlate existing surface conditions with those presented in the geotechnical investigation report. He shall satisfy himself that the quality and quantity of exposed materials and subsurface soil or rock deposits have been satisfactorily represented by the Geotechnical Engineer's report and project drawings. Any discrepancy of prior knowledge to the Contractor or that is revealed through his investigations shall be made known to the Owner. It is the Contractor's responsibility to review the report prior to construction. The selection of equipment for use on the project and the order of work shall similarly be the Contractor's responsibility. The Contractor shall be responsible for providing equipment capable of completing the requirements included in following sections. 1.3 Geotechnical Engineer - The work covered by these specifications shall be observed and tested by Kleinfelder, the Geotechnical Engineer, who shall be 51-52190175119L197.doc Copyright 1999 Kleinfelder, Inc. Page C-l May 18, 1999 KLEINFELDER hired by the Owner. The Geotechnical Engineer will be present during the site preparation and grading to observe the work and to perform the tests necessary to evaluate material quality and compaction. The Geotechnical Engineer shall submit a report to the Owner, including a tabulation of tests performed. The costs of retesting unsuitable work installed by the Contractor shall be deducted by the Owner from the payments to the Contractor. 1.4 Standard Specifications - Where referred to in these specifications, "Standard Specifications" shall mean the current State of California Standard Specifications for Public Works Construction, 1994 Edition, with Regional Supplement Amendments. 1.5 Compaction Test Method - Where referred to herein, relative compaction shall mean the in-place dry density of soil expressed as a percentage of the maximum dry density of the same material, as determined by the ASTM D1557 Compaction Test Procedure. Optimum moisture content shall mean the moisture content at the maximum dry density determined above. 2.0 SITE PREPARATION 2.1 Clearing - Areas to be graded shall be cleared and grubbed of all vegetation and debris. These materials shall be removed from the site by the Contractor. 2.2 Stripping - Surface soils containing roots and organic matter shall be stripped from areas to be graded and stockpiled or discarded as directed by the Owner. In general, the depth of stripping of the topsoil will be approximately 6 inches. Deeper stripping, where required to remove weak soils or accumulations of organic matter, shall be performed when determined necessary by the Geotechnical Engineer. Stripped material shall 51-521901/5119L197.doc Page C-2 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEIN FELDER be removed from the site or stockpiled at a location designated by the Owner. Material should be evaluated for petroleum hydrocarbon impact. After such analyses, the material should be handled as directed by the regulating authority 2.3 Removal of Debris- Any existing, trash and debris encountered in the areas to be graded shall be removed prior to the placing of any compacted fill. Portions of any existing fills that are suitable for use in new compacted fill may be stockpiled for future use. All organic materials, topsoil, expansive soils, oversized rock, or other unsuitable material shall be removed from the site by the Contractor or disposed of at a location on-site, if so designated by the Owner. Material should be evaluated for petroleum hydrocarbon impact and handled as directed by the regulating authority after such evaluation. 2.4 Ground Surface - The ground surface exposed by stripping shall be scarified to a depth of 6 inches, moisture conditioned to the proper moisture content for compaction, and compacted as required for compacted fill. Ground surface preparation shall be approved by the Geotechnical Engineer prior to placing fill. 3.0 EXCAVATION 3.1 General - Excavations shall be made to the lines and grades indicated on the plans. The data presented in the Geotechnical Engineer's report is for information only and the Contractor shall make his own interpretation with regard to the methods and equipment necessary to perform the excavation and to obtain material suitable for fill. 51-521901/5119L197.doc Page C-3 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEIN FELDER 3.2 Materials - Soils which are removed and are unsuitable for fill shall be placed in nonstructural areas of the project, or in deeper fills at locations designated by the Geotechnical Engineer, provided the soils have been evaluated for petroleum hydrocarbon impact, and such soil is handled in accordance with the directions of the regulating authority. 3.3 Treatment of Exposed Surface - The ground surface exposed by excavation shall be scarified to a depth of 6 inches, moisture conditioned to the proper moisture content for compaction, and compacted as required for compacted fill. Compaction shall be approved by the Geotechnical Engineer prior to placing fill. 3.4 Rock Excavation - Where solid rock is encountered in areas to be excavated, it shall be loosened and broken up so that no solid ribs, projections, or large fragments will be within 6 inches of the surface of the final subgrade. 4.0 COMPACTED FILL 4.1 Materials - Fill material shall consist of suitable on-site or imported soil. All materials used for structural fill shall be reasonably free of organic material, have a liquid limit less than 30, a plasticity index less than 15, 100% passing the 3 inch sieve and less than 30 percent passing the #200 sieve. 4.2 Placement - All fill materials shall be placed in layers of 8 inches or less in loose thickness and uniformly moisture conditioned. Each lift should then be compacted with a sheepsfoot roller or other approved compaction equipment to at least 90 percent relative compaction in areas under structures, utilities, roadways and parking areas, and to at least 85 percent in 51 -521901 /5119L197.doc Page C-4 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER undeveloped areas. No fill material shall be placed, spread, or rolled while it is frozen or thawing, or during unfavorable weather conditions. 4.3 Benching - Fill placed on slopes steeper than 5 horizontal to 1 vertical shall be keyed into firm, native soils or rock by a series of benches. Benching can be conducted simultaneously with placement of fill. However, the method and extent of benching shall be checked by the Geotechnical Engineer. 4.4 Compaction Equipment - The Contractor shall provide and use sufficient equipment of a type and weight suitable for the conditions encountered in the field. The equipment shall be capable of obtaining the required compaction in all areas. 4.5 Recompaction - When, in the judgment of the Geotechnical Engineer, sufficient compactive effort has not been used, or where the field density tests indicate that the required compaction or moisture content has not been obtained, or if pumping or other indications of instability are noted, the fill shall be reworked and recompacted as needed to obtain a stable fill at the required density and moisture content before additional fill is placed. 4.6 Responsibility - The Contractor shall be responsible for the maintenance and protection of all embankments and fills made during the contract period and shall bear the expense of replacing any portion which has become displaced due to carelessness, negligent work, or failure to take proper precautions. 5.0 UTILITY TRENCH BEDDING AND BACKFILL 5.1 Material - Pipe bedding shall be defined as all material within 4 inches of the perimeter and 12 inches over the top of the pipe. Material for use as 51-521901/5119L197.doc PageC-5 May 18, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER bedding shall be clean sand, gravel, crushed aggregate, or native free- draining material, having a Sand Equivalent of not less than 30. Backfill should be classified as all material within the remainder of the trench. Backfill shall meet the requirements set forth in Section 4.1 for compacted fill. 5.2 Placement and Compaction - Pipe bedding shall be placed in layers not exceeding 8 inches in loose thickness, conditioned to the proper moisture content for compaction, and compacted to at least 90 percent relative compaction. All other trench backfill shall be placed and compacted in accordance with Section 306-1.3.2 of the Standard Specifications for Mechanically Compacted Backfill. Backfill shall be compacted as required for adjacent fill. If not specified, backfill shall be compacted to at least 90 percent relative compaction in areas under structures, utilities, and concrete flatwork, to 85 percent relative compaction in undeveloped areas, and at least 95 percent relative compaction under roadways and pavements. 51-521901/5119L197.doc PageC-6 May 18, 1999 Copyright 1999 Kleinfelder, Inc. APPENDIX D IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL ENGINEERING REPORT As the client of a consulting geotechnical engineer, you should know that site subsurface conditions cause more construction problems than any other factor. ASFE/The Association of Engineering Firms Practicing in the Geosciences offers the following suggestions and observations to help you manage your risks. A GEOTECHNICAL ENGINEERING REPORT IS BASED ON A UNIQUE SET OF PROJECT-SPECIFIC FACTORS Your geotechnical engineering report is based on a subsurface exploration plan designed to consider a unique set of project-specific factors. These factors typically include: the general nature of the structure involved, its size, and configuration; the location of the structure on the site; other improvements, such as access roads, parking lots, and underground utilities; and the additional risk created by scope-of-service limitations imposed by the client. To help avoid costly problems, ask your geotechnical engineer to evaluate how factors that change subsequent to the date of the report may affect the report's recommendations. Unless your geotechnical engineer indicates otherwise, do not use your geotechnical engineering report: • when the nature of the proposed structure is changed, for example, if an office building will be erected instead of a parking garage, or a refrigerated warehouse will be built instead of an unrefrigerated one; • when the size, elevation, or configuration of the proposed structure is altered; • when the location or orientation of the proposed structure is modified; • when there is a change of ownership; or • for application to an adjacent site. Geotechnical engineers cannot accept responsibility for problems that may occur if they are not consulted after factors considered in their report's development have changed. SUBSURFACE CONDITIONS CAN CHANGE A geotechnical engineering report is based on condi- tions that existed at the time of subsurface exploration. Do not base construction decisions on a geotechnical engineering report whose adequacy may have been affected by time. Speak with your geotechnical consult- ant to learn if additional tests are advisable before construction starts.Note, too, that additional tests may be required when subsurface conditions are affected by construction operations at or adjacent to the site, or by natural events such as floods, earthquakes, or ground water fluctuations. Keep your geotechnical consultant apprised of any such events. MOST GEOTECHNICAL FINDINGS ARE PROFESSIONAL JUDGMENTS Site exploration identifies actual subsurface conditions only at those points where samples are taken. The data were extrapolated by your geotechnical engineer who then applied judgment to render an opinion about overall subsurface conditions. The actual interface between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled may differ from those predicted in your report. While nothing can be done to prevent such situations, you and your geotechnical engineer can work together to help minimize their impact. Retaining your geotechnical engineer to observe construction can be particularly beneficial in this respect. A REPORT'S RECOMMENDATIONS CAN ONLY BE PRELIMINARY The construction recommendations included in your geotechnical engineer's report are preliminary, because they must be based on the assumption that conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Because actual subsurface conditions can be discerned only during earthwork, you should retain your geo- technical engineer to observe actual conditions and to finalize recommendations. Only the geotechnical engineer who prepared the report is fully familiar with the background information needed to determine whether or not the report's recommendations are valid and whether or not the contractor is abiding by appli- cable recommendations. The geotechnical engineer who developed your report cannot assume responsibility or liability for the adequacy of the report's recommenda- tions if another party is retained to observe construction. GEOTECHNICAL SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND PERSONS Consulting geotechnical engineers prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated otherwise, your geotechnical engineer prepared your report expressly for you and expressly for purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the geotechnical engineer. No party should apply this report for any purpose other than that originally contemplated without first conferring with the geotechnical engineer. GEOENVIRONMENTAL CONCERNS ARE NOT AT ISSUE Your geotechnical engineering report is not likely to relate any findings, conclusions, or recommendations about the potential for hazardous materials existing at the site. The equipment, techniques, and personnel used to perform a geoenvironmental exploration differ substantially from those applied in geotechnical engineering. Contamination can create major risks. If you have no information about the potential for your site being contaminated, you are advised to speak with your geotechnical consultant for information relating to geoenvironmental issues. A GEOTECHNICAL ENGINEERING REPORT IS SUBJECT TO MISINTERPRETATION Costly problems can occur when other design profes- sionals develop their plans based on misinterpretations of a geotechnical engineering report. To help avoid misinterpretations, retain your geotechnical engineer to work with other project design professionals who are affected by the geotechnical report. Have your geotech- nical engineer explain report implications to design professionals affected by them, and then review those design professionals' plans and specifications to see how they have incorporated geotechnical factors. Although certain other design professionals may be fam- iliar with geotechnical concerns, none knows as much about them as a competent geotechnical engineer. BORING LOGS SHOULD NOT BE SEPARATED FROM THE REPORT Geotechnical engineers develop final boring logs based upon their interpretation of the field logs (assembled by site personnel) and laboratory evaluation of field samples. Geotechnical engineers customarily include only final boring logs in their reports. Final boring logs should not under any circumstances be redrawn for inclusion in architectural or other design drawings, because drafters may commit errors or omissions in the transfer process. Although photographic reproduction eliminates this problem, it does nothing to minimize the possibility of contractors misinterpreting the logs during bid preparation. When this occurs, delays, disputes, and unanticipated costs are the all-too-frequent result. To minimize the likelihood of boring log misinterpreta- tion, give contractors ready access to the complete geotechnical engineering report prepared or authorized for their use. (If access is provided only to the report prepared for you, you should advise contractors of the report's limitations, assuming that a contractor was not one of the specific persons for whom the report was prepared and that developing construction cost esti- mates was not one of the specific purposes for which it was prepared. In other words, while a contractor may gain important knowledge from a report prepared for another party, the contractor would be well-advised to discuss the report with your geotechnical engineer and to perform the additional or alternative work that the contractor believes may be needed to obtain the data specifically appropriate for construction cost estimating purposes.) Some clients believe that it is unwise or unnecessary to give contractors access to their geo- technical engineering reports because they hold the mistaken impression that simply disclaiming responsi- bility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly construction problems. It also helps reduce the adversarial attitudes that can aggravate problems to disproportionate scale. READ RESPONSIBILITY CLAUSES CLOSELY Because geotechnical engineering is based extensively on judgment and opinion, it is far less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against geotechnical engineers. To help prevent this problem, geotechnical engineers have developed a number of clauses for use in their contracts, reports, and other documents. Responsi- bility clauses are not exculpatory clauses designed to transfer geotechnical engineers' liabilities to other parties. Instead, they are definitive clauses that identify where geotechnical engineers' responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take appropriate action. Some of these definitive clauses are likely to appear in your geotechnical engineering report. Read them closely. Your geotechnical engineer will be pleased to give full and frank answers to any questions. RELY ON THE GEOTECHNICAL ENGINEER FOR ADDITIONAL ASSISTANCE Most ASFE-member consulting geotechnical engineer- ing firms are familiar with a variety of techniques and approaches that can be used to help reduce risks for all parties to a construction project, from design through construction. Speak with your geotechnical engineer not only about geotechnical issues, but others as well, to learn about approaches that may be of genuine benefit. You may also wish to obtain certain ASFE publications. Contact a member of ASFE or ASFE for a complimentary directory of ASFE publications. PROFESSIONAL FIRMS PRACTICINGIN THE GEOSCIENCES COLESVILLE ROAD/SUITE G106/S1LVER SPRING, MD 20910 TELEPHONE: 301/565-2733 FACSIMILE: 301/589-2017 Copyright 1992 by ASFE, Inc. Unless ASFE grants specific permission to do so, duplication of this document by any means whatsoever is expressly prohibited Re-use of the wording in this document, in whole or in part, also is expressly prohibited, and may be done only with the express permission of ASFE or for purposes of review or scholarly research IIGR0294