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HomeMy WebLinkAbout; Agua Hedionda Pump Station Soils Exploration; Agua Hedionda Pump Station Soils Exploration; 1999-08-25|jp| KLEINFELDER A report prepared for: Carlsbad Municipal Water District 5950 El Camino Real Carlsbad, California 92008 Attn: Mr. Randy Klaahsen, Associate Engineer SOILS EXPLORATION FOR THE PROPOSED SOUTH AGUA HEDIONDA WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA Kleinfelder Job No. 51-531401 Prepared by: Robert M. Gibbens, Senior Staff Engineer Rick E. Larson, G.E. 2027 Senior Engineer KLEINFELDER, INC. 5015ShorehamPlace San Diego, California 92122 (619)320-2000 August 25, 1999 51-53140175119R393.doc Copyright 1999 Kleinfelder, Inc. Page ii of iv August 25, 1999 KLEINFELDER TABLE OF CONTENTS Section Page 1. INTRODUCTION 1 2 . PROJECT DESCRIPTION 2 3 . FIELD EXPLORATION 3 4 . LABORATORY TESTING 4 5 . SUBSURFACE CONDITIONS 5 6 . DISCUSSION OF POTENTIAL IMPACTS 6 7. RECOMMENDATIONS 7 7.1 SEISMIC DESIGN 7 7.2 FAULTING AND SEISMICITY 7 7.3 SITE PREPARATION 8 7.3.1 Subgrade Preparation 8 7.3.3 Pipe Bedding for Utilities 9 7.3.4 Backfill 9 7.4 CONSTRUCTION DEWATERING 10 7.5 TEMPORARY EXCAVATIONS 12 7.5.1 General 12 7.6 ENGINEERED FILL 12 7.7 SHORING 13 7.7.1 General 13 7.7.2 Caving Potential 13 7.7.3 Lagging 13 7.7.4 Active Earth Pressures 14 7.7.5 Surcharge Pressures 14 7.7.6 Lateral Resistance 14 7.7.7 Estimated Lateral Displacements 15 7.8 BUILDING FOUNDATIONS AND FLOOR SLABS 15 7.8.1 Pump Station Foundation and Floor Slab 15 7.8.2 Generator/Electrical Control Building Foundation and Floor Slab 16 7.9 LATERAL EARTH PRESSURES FOR PUMP STATION VAULT 16 7.10CRIBRETAININGWALLS 17 7.10.1 Foundations 17 7.10.2 Lateral Earth Pressure 18 7.10.3 Wall Drainage 19 7.10.4 Backfill Placement 19 7.11 BURIED UTILITY PIPE SOIL PARAMETERS 19 7.12CORROSIVITY 20 7.13 FLEXIBLE PAVEMENT 20 7.13.1 Construction Consideration 21 8. LIMITATIONS 22 51-531401/5119R393.doc Pageiiiofiv August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER TABLE OF CONTENTS (Cont'd) FIGURES *•' Figure 1 - Vicinity Map iu Figure 2 - Boring Location Plan •" APPENDICES mi Appendix A - Boring Logs *" Appendix B - Laboratory Testing •w Appendix C - Suggested Guidelines for Earthwork Construction Appendix D - ASFE Insert 51-531401/5119R393.doc Pageivofiv August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 1. INTRODUCTION At this time we have completed our soils exploration for the Proposed South Agua Hedionda Wastewater Pump Station in 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 construction. 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. 51-531401/5119R393.doc Page 1 of 22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 2. PROJECT DESCRIPTION The project includes the construction of a pump station and a generator/electrical control building on a small, irregular-shaped parcel of ground (about 1.35 acres). The site is located between an existing unpaved access road and the transmission towers at the south end of the Agua Hedionda Lagoon just northeast of the Audubon Society Center and directly north of the proposed Cannon Road bridge (currently under construction) over Macario Canyon. The pump station will have a surface elevation of approximately elevation +24 (the adjacent access road is currently at about elevation +25) and a bottom slab elevation of about -15 for a total embedment depth below finished grade of about 39 feet. The pump station will be approximately 36 feet by 30 feet in plan area to house 4 pumps. The pump station will have both wet and dry pits. The generator/electrical control building will be one story above finished grade and will be of slump block masonry construction with conventional slab-on-grade and shallow foundations. The footprint of this building will be approximately 30 feet by 40 feet. The existing site grade is about 15 to 25 feet above the proposed grade. During site development, the grade will be lowered, and the existing slopes will be retained with conventional crib retaining walls. The remainder of the site uncovered by the proposed structures will be paved with asphalt. 51-531401/5119R393.doc Page2of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 3. FIELD EXPLORATION Two test borings were completed to depths of 50.5 feet below the existing unimproved road at the approximate locations shown on Figure 2, Boring Location Plan. The test borings were advanced using a CME-75 truck-mounted drill rig, equipped to drill with 8-inch hollow-stem augers. An engineer from our staff supervised the field operations and logged the borings. Selected bulk and drive samples were retrieved, sealed, and transported to our laboratory for further evaluation. Our typical sampling interval was every five feet for the total depth of the borings. A description of the field exploration, an Explanation to the Logs, and the Logs of Borings are presented in Appendix A. A California sampler was used to obtain drive samples of the soil encountered. This sampler consists of a 3-inch O.D., 2.4-inch I.D. split barrel shaft that is pushed or driven a total of 18 inches into the soil at the bottom of the boring. The soil was retained in six-inch long brass sleeves for geotechnical laboratory testing. An additional two inches of soil from each drive remained in the cutting shoe and was usually discarded after visually classifying the soil. The sampler was driven using a 140-pound hammer falling 30 inches. The total number of blows required to drive the sampler 12 inches is termed the blow count (N) and is recorded on the Logs of .Borings. Driving was stopped when greater than 50 blows per 6 inch increment was encountered and the blow count (N) is recorded as 50 blows per number of inches driven. The procedures we employed in the field are generally consistent with those described in ASTM Standard Test Method D-1586. 51-531401/5119R393.doc Page3of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 4. LABORATORY TESTING As stated previously, laboratory testing was performed on selected bulk and drive samples to substantiate field classifications and to provide general engineering parameters for geotechnical design. Testing consisted of moisture content, unit weight, direct shear, and corrosion testing. A description of the laboratory tests and their results are presented in Appendix B. 51-531401/5119R393.doc Page4of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 5. SUBSURFACE CONDITIONS The subsurface conditions encountered during our field exploration for the proposed pump station consist of alluvial silty sands to sandy clays over formational sandy silts and silty sands. The alluvium, found in Boring 1, generally consists of medium-dense, fine-grained, silty sands and sandy clays within the upper eight feet. No alluvium was encountered in Boring 2. Below the alluvium in Boring 1 and from the ground surface in Boring 2, very dense, fine-grained, formational sandy silts and silty sands were encountered to depths of 50.5 feet. Groundwater was encountered just below the sandy silt layer at depths of 28.5 and 14.0 feet within Borings 1 and 2, respectively. The variation in groundwater levels between Borings 1 and 2 is likely due to the impermeability of the deeper, very dense sandy silt layer encountered in Boring 1. Boring 2 is likely to more accurately represent the actual depth to groundwater (14 feet) during construction. 51-531401/5119R393.doc Page5of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 6. DISCUSSION OF POTENTIAL IMPACTS From a geotechnical standpoint, the site is generally suitable for the proposed pump station construction with only a limited number of potential impacts. These potential impacts include the depth to groundwater with respect to the anticipated excavation, caving of the granular soils during excavation, and seismic shaking. Excavation of the vault area below a depth of 14 feet will be affected by the groundwater table and will likely require temporary dewatering for placement of the pump station walls and foundation. The granular and fine-grained soils observed within the upper 14 feet at the site may have a 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, alluvium was encountered at the site to depths of 8.5 feet. The soils observed below the water table generally consist of very dense formational sands and silts. Based on our analysis and field exploration, the very dense formational sands and silts have a relatively low potential for liquefaction or seismic settlement during a major seismic event. 51-531401/5119R393.doc Page6of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7. RECOMMENDATIONS 7.1 SEISMIC DESIGN 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 Sc 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 along with a seismic source type B (Table 16-V). 7.2 FAULTING AND SEISMICITY The site is located in the seismically active southern California region and is likely to be subjected to moderate seismic shaking during the design life of the project. The San Andreas fault system of California comprises a number of northwest trending, predominantly right-lateral strike-slip faults at the boundary between the Pacific and North American tectonic plates. As the Pacific plate moves northwestward relative to the adjacent North American plate, stress accumulates and is relieved by strain along the many known faults of the San Andreas system. In the general site area, these include the Elsinore, Newport-Inglewood, Rose Canyon, and La Nacion fault zones. The distance of these faults from the project site and their respective maximum probable magnitudes are given in the following table: 51-53140175119R393.doc Page7of22 August25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER LOCAL FAULTS Fault Name Rose Canyon La Nacion Elsinore Newport-Inglewood Approx. Distance and Direction From Site (miles) 10 16 22 16 Max. Probable Magnitude (Richter) 6.00 4.25 6.75 5.75 Peak Horizontal Ground Acceleration .126 .035 .104 .077 Listing peak site accelerations is a convenient method of categorizing and comparing earthquakes for geologic purposes. However, peak accelerations are generally poor indications of building performance during earthquakes. The duration of the shaking, the frequency of the motion, localized subsurface conditions, and the details of the structures involved are all important factors influencing building performance. The site is not located within a State of California designated Earthquake Fault-Rupture Hazard Zone (Hart and Bryant, 1997). 7.3 SITE PREPARATION All site preparation and earthwork operations should be performed in accordance with applicable codes. All references to maximum dry density are established in accordance with ASTM Standard Test Method D 1557. Based on our interpretation of the geotechnical subsurface profile, we anticipate that the soils exposed during construction will consist primarily of fine- to medium-grained silty sands and sandy silts. 7.3.1 Subgrade Preparation The anticipated subgrade preparation is limited and will consist of scarifying and recompacting the upper 6 inches of subgrade to at least 90 percent of its ASTM D1557 maximum dry density 51-531401/5119R393.doc Copyright 1999 Kleinfelder, Inc. Page 8 of22 August 25, 1999 KLEINFELDER prior to placement of the floor slabs for the generator/electrical control building and pump station, as well as retaining wall foundations. The upper 12 inches of subgrade should be scarified and recompacted to at least 90 percent of its ASTM D1557 maximum dry density prior to the placement of aggregate base for pavements. 7.3.2 Excavation Conditions The borings at the site were drilled using a truck-mounted, hollow-stem auger drill rig. Drilling was completed with moderate effort through the existing native soils. Conventional earth moving equipment should be capable of performing the anticipated excavations required for site development. 7.3.3 Pipe Bedding for Utilities Pipe bedding should consist of sand or similar granular material having a minimum sand equivalent value of 30. The sand should be placed in a zone that extends a minimum of 6 inches below and 12 inches above the pipe for the full trench width. The bedding material should be compacted to a minimum of 90 percent of the maximum dry density. Trench backfill above pipe bedding may consist of approved, on-site or import soils placed in lifts no greater than 8 inches loose thickness and compacted to at least 90 percent of the maximum dry density. Jetting of pipe bedding or trench backfill materials is not permitted. In landscaped areas, the compaction requirements of backfill above the pipe zone may be reduced to at least 85 percent of maximum density. 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 percent Maximum Particle Dimension: Less than 3 inches 51-531401/5119R393.doc Page9of22 August25, 1999 Copyright 1999 Kleinfelder, Inc. KLEIN FELDER UBC Expansion Index: Soluble Sulfates: Less than 30 Less than 0.10 Trench backfill should be placed in uniform layers not exceeding eight 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 CONSTRUCTION DEWATERING Excavations which extend below the site groundwater level (currently estimated to be at approximately 14 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. For the conceptual design of a temporary dewatering system, the permeabilities presented below were estimated based on the grain size distribution of the various soils encountered. It should be noted these are general values typical to the soil types listed below. Actual permeabilities will vary; we recommend the dewatering contractor further evaluate the actual permeabilities directly by field pump studies or other methods prior to designing a dewatering system. Soil Description Medium-to-coarse grained SAND Fine-to-medium grained SAND with trace silt Fine-to-medium grained SAND with some silt Fine-to-medium grained silty SAND Silty SAND/sandy SILT Sandy SILT Clayey SILT/silty CLAY Unified Soil Classification SP SP SP/SM SM SM/ML ML ML/CL Permeability (cm/sec) 10-' io-2 io-3 io-4 io-5 10'6 io-7 It should be noted that the subsurface conditions at the site include layered and interbedded sands and silts. Permeability is likely to vary significantly with depth and location across site. 51-531401/5119R393.doc Copyright 1999 Kleinfelder, Inc. Page 10 of 22 August 25, 1999 KLEINFELDER 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 deep wells. The method ultimately selected is dependent on a number of factors, e.g., quantity of groundwater to be removed, cone of depression (zone of influence) of dewatering measures within the excavation, stability of the silty sands and sandy silts, the presence of potential seepage zones which will pipe water from distant sources after the groundwater table is lowered, and cost. 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 three to five feet. Deep wells with individual pumps are often selected where the yield per well is high and the total number of wells is expected to be low. These conditions tend to occur in deep excavations with limited site area where the bottom of the aquafier is well below the bottom of the excavation and the soils are reasonably free-draining. 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 groundwater 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 should stop and appropriate corrective action taken if settlement or changes in groundwater levels are noted at these critical points. 51-531401/5119R393.doc Pagellof22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.5 TEMPORARY EXCAVATIONS 7.5.1 General All excavation work should comply with the current requirements of OSHA. The onsite soils within the pump station excavation are generally classified as Type C soils for evaluating OSHA sloping or shoring requirements with the onsite soils within the retaining wall back-cut generally classified as Type A soils. All excavations should comply with applicable local, state, and federal safety regulations including the current OSHA Excavation and Trench Safety Standards. Construction site safety generally is the sole responsibility of the Contractor, who should also be solely responsible for the means, methods, and sequencing of construction operations. We are providing the information below solely as a service to our client. Under no circumstances should the information provided be interpreted to mean that Kleinfelder is assuming responsibility for construction site safety or the Contractor's activities; such responsibility is not being implied and should not be inferred. 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 the 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. 7.6 ENGINEERED FILL Engineered fill consisting of low expansion potential soils should be placed in lifts no greater than 8 inches thick, loose measurement, and should be compacted to at least 90 percent of the maximum dry density. The moisture content of the imported fill should be between one percent below and three percent above the optimum moisture content. The existing silty sand to sandy silt soils are acceptable as engineered fill. If imported fill is required, we recommend that it be a 51-53140175119R393.doc Pagel2of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER semi-impervious to impervious soil classified as either GM, GC, SM, or SC under the Unified Soil Classification System and also 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 0.10% All earthwork operations should be observed and tested by a representative of this office. 7.7 SHORING 7.7.1 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. 7.7.2 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 drilled holes occurs, soldier piles may need to be driven to the required depth or a drilling slurry may be required. 7.7.3 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. 51-531401/51 l9R393.doc Pagel3of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 7.7.4 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. 7.7.5 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. 7.7.6 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 weighing 250 pcf above the groundwater table and 125 pcf below the ground water 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 51-531401/5119R393.doc Pagel4of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 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. 7.7.7 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. 7.8 BUILDING FOUNDATIONS AND FLOOR SLABS 7.8.1 Pump Station Foundation and Floor Slab Conventional spread footings supported on recompacted native soils can be sized using a nominal bearing pressure of 2,500 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 buried structure exceeds the weight of the displaced soil significantly, we do not anticipate static settlement in excess of 1/2 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 350 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. Since the vault structure is to be constructed below the existing water table, hydrostatic uplift pressures on the order of 1,600 psf should be incorporated into the design for a vault depth of 39 feet. Accordingly, design dead load factors should maintain a 1.3 minimum factor of safety against potential uplift pressures. 51 -53140115119R393 .doc Page 15 of 22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER We recommend the concrete floor slabs for buried structures be at least 5 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. 7.8.2 Generator/Electrical Control 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 recompacted native soils using an allowable soil contact pressure of 2,500 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 a passive equivalent unit weight of 300 pcf and a coefficient of friction of 0.35. All footings should be trenched at least 1.5 feet below the lowest adjacent finished grade and should be a minimum of 12 inches wide. Reinforcement steel requirements for foundations should be designed by the structural engineer. We recommend that the footings be provided with at least minimal reinforcement consisting of 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. 7.9 LATERAL EARTH PRESSURES FOR PUMP STATION VAULT Lateral earth pressures acting against pump station 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 55 pcf can be used above the water table and 90 pcf below the water table. 51-531401/5119R393.doc Pagel6of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER Fifty 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 stresses. Also, permanent walls should be designed for seismic loading. The resultant seismic force (in pounds) can be calculated as 6H2 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. 7.10 CRIBRETAINING WALLS 7.10.1 Foundations Crib wall footings should be founded a minimum of 3 feet below grade. An allowable foundation pressure of 5000 psf may be used to design crib wall footings that bear on undisturbed, native formational materials provided the minimum width of the foundation is 6 feet and the minimum embedment is 3 feet. Total and differential static settlements are expected to be less than '/•> inch for these loading conditions. The following table outlines the soil parameters which can be used for foundation, retained, and crib fill soils 51-531401/5119R393.doc Pagel7of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER Foundation Soil Retained Soil Crib Fill Soil Phi Angle (degrees) 34 30* 30** Cohesion (pst) 500 0 0 Dry Unit Weight (psf) 120 110* 110** * Soil properties assume fill soils are compacted to at least 90 percent of ASTM D1557. ** Soil properties assume non-erodible (gravel preferred) granular fill soils, compacted to at least 90 percent of ASTM D1557. 7.10.2 Lateral Earth Pressure We understand that a crib type retaining wall will be utilized in this project. The retaining wall should be designed to resist the earth pressure exerted by the retained, compacted backfill plus any additional lateral force that will be applied to the wall due to surface loads placed at or near the wall. The following active earth pressure values for sloping backfill are provided for walls backfilled with drainage materials and imported nonexpansive soils. Equivalent Fluid Weight (pcf) Slope 2:1 1 '/2:1 1:1 Active Condition 50 65 95 Fifty percent of any uniform surcharge placed within a horizontal distance from the top of the wall equal to the wall height may be assumed to act as a uniform horizontal pressure over the entire height of the wall. Also, permanent walls should also be designed for seismic loading. The resultant seismic force (in pounds) for each linear foot of wall can be calculated as 6H2 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. 51-531401/5119R393.doc Copyright 1999 Kleinfelder, Inc. Page 18 of 22 August 25, 1999 KLEINFELDER 7.10.3 Wall Drainage The above-recommended values do not include lateral pressures due to hydrostatic water pressures generated by infiltrating surface water that may accumulate behind the walls. Therefore, wall backfill materials should be free draining and provisions should be made to collect and remove excess water that may accumulate behind earth retaining structures. Wall drainage may be provided by free-draining gravel surrounded by non-woven synthetic filter fabric or by prefabricated, synthetic drain panels. In either case, drainage should be collected by perforated pipes and directed to a sump, storm drain, weep hole(s), or other suitable location for disposal. We recommend that drainage gravel consist of durable stone having 100 percent passing the 1-inch sieve and zero percent passing the No. 4 sieve. Synthetic filter fabric should have an equivalent opening size (EOS), U.S. Standard Sieve, of between 40 and 70, a permeability of at least 0.02 centimeters per second, a minimum flow rate of 50 gallons per minute per square foot of fabric, and a minimum puncture strength of 50 pounds. 7.10.4 Backfill Placement All backfill should be placed and compacted in accordance with recommendations provided above for engineered fill. During grading and backfilling adjacent to any walls, heavy equipment should not be allowed to operate within a lateral distance of five feet from the wall, or within a lateral distance equal to the wall height, whichever is greater, to avoid overstressing of the wall. Within this zone, only hand operated equipment ("whackers", vibratory plates or pneumatic compactors) should be used to compact backfill soils. 7.11 BURIED UTILITY PIPE SOIL PARAMETERS We recommend the following soil parameters for use in buried utility pipe design: • Total soil unit weight, yt = 110 pcf • Modulus of soil reaction, E' = 1,300 psi for pipe with a minimum cover of 20 feet backfilled with native sand on gravel bedding. 51-531401/5119R393.doc Pagel9of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. |jp| KLEINFELDER 7.12 CORROSIVITY One selected sample of the near-surface soils encountered in the borings was subjected to preliminary chemical corrosion analysis. The test results indicate that soluble chloride and sulfate concentrations in the sample tested were moderate to low, respectively. These concentrations indicate that on-site soils of similar composition should not be aggressive towards concrete, and that Type II cement should be suitable for design of concrete elements. The minimum resistivity value obtained for the one sample tested was 354 ohm-centimeters, and therefore, representative of an environment that is probably highly corrosive to unprotected metals. Our corrosion tests are preliminary in nature. Additional sampling and testing should be performed after completion of grading. We recommend that a qualified corrosion engineer to evaluate the general corrosion potential with respect to construction materials at this site review the proposed design. The corrosion test results are included in Appendix B. 7.13 FLEXIBLE PAVEMENT We have provided a minimum pavement section for a traffic index of 4.0. The flexible pavement design recommendations presented in Table 7.13-1 are based on the California Department of Transportation (Caltrans) design procedures. TABLE 7.13-1 RECOMMENDED MINIMUM PAVEMENT SECTIONS Traffic Index, Tl 4.0 Asphalt Concrete (inches) 3.0 Class 2 Aggregate Base (inches) 6.0 51-531401/5119R393.doc Page20of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER The flexible pavement should conform to, and be placed in accordance with, current Caltrans Standard Specifications. The aggregate base (Class 2) should comply with the specifications in Section 26. The aggregate base and the upper 6 inches of subgrade should be compacted to a minimum of 95 percent relative compaction as determined by the ASTM D 1557 test procedure. In addition, it is recommended that all pavement areas conform to the following criteria: 1. All trench backfill, including utility and sprinkler lines, should be properly placed and adequately compacted to provide a stable subgrade. 2. An adequate drainage system should be provided to prevent surface water or subsurface water from saturating the subgrade soil. 3. A periodic maintenance program should be incorporated to include sealing cracks and other measures. 4. All concrete curbs separating pavement and landscaped areas should extend below the bottom of adjacent aggregate base materials. 7.13.1 Construction Consideration If significant site grading is required, we recommend the final subgrade soil be tested to confirm the values used in design. A modified pavement section may be required if subgrade conditions vary from those assumed in design. In the event unstable (pumping) subgrade are encountered within planned pavement areas, we recommend a heavy, rubbed-tired vehicle (typically a loaded water truck) be used to test the load/deflection characteristics of the finished subgrade materials. We recommend this vehicle have a minimum rear axle load (at the time of testing) of 15,000 pounds with tires inflated to at less 65-psi pressure. If the tested surface shows a visible deflection extending more than six inches from the wheel track at the time of loading, or a visible crack remains after loading, corrective measures should be implemented. Such measures could include disking to aerate, chemical treatment, replacement with drier material, or other methods. We recommend Kleinfelder be retained to assist in developing which method (or methods) would be applicable for this project. 51-531401/5119R393.doc Page21of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 8. 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. gg 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 m owner's own risk. H pi Our firm has prepared this report for the use of Carlsbad Municipal Water District, on this Hi 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 I 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 P- change over time, and additional work may be required with the passage of time. Based on the Iv 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. 51-531401/5119R393.doc Page22of22 August 25, 1999 Copyright 1999 Kleinfelder, Inc. VI 1 VI VI II VI II • I II II • 1 • I II II II II II VI II ' CARNEGIE CT./ \Pacific Ocean NOT TO SCALE KLEINFELDER 5015 SHOREHAM PLACE SAN DIEGO. CALIFORNIA 92122 CHECKED BY: RMG |FN: 5314VIC PROJECT NO. 51-5314-01 [DATE: B/99 VICINITY MAP SOUTH AQUA HEDIONDA WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA FIGURE 1 r i i i r i i i f i r i r i r i r i r i r i • t i c i f i f i r i EXISTING UNIMPROVED ROAD APPROXIMATE PUMP STATION FACILITY LIMITS (PROPOSED) PROPOSED CANNON ROAD LEGEND: APPROXIMATE BORING LOCATION NOT TO SCALE KLEINFELDER 5015 SHOREHAM PLACE SAN DIEGO, CALIFORNIA 92122 CHECKED BY: RMG |FN: 5314SITE PROJECT NO. 51-5314-01 | DATE: 8/99 SITE PLAN SOUTH AGUA HEDIONDA WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA FIGURE T^ttjMa1 APPENDIX A DATE DRILLED: 7/22/99 DRILLED BY: Tri-County Drilling WATER DEPTH: 28.5 ft. DATE MEASURED: 7/22/99 DRILLING METHOD: CME-75 w/autohammer ELEVATION: 25.0 ft. LOGGED BY: R. Gibbens UL— ~ "J ££ f £ i o r" iL zp fr -> m uj Q ^ S— J C/3 ^UJ 00 •1 1jl -20 5— U 1 lN12~M~M-is 10— iy fl1J -10 15 — U 1 -5 20 — W -0 25— U --5 30— U £& olO g O£, CD 20 24 77 50/5" 50/5" 50/3" 50/5" O Ox1 CD nf\° ^ Vffirw/, RERERENCE DATUM: As per client SOIL DESCRIPTION AND CLASSIFICATION Sandy gravel road base (1") ALLUVIUM; SILTY SAND (SM), light gray, moist, medium dense, fine grained SANDY CLAY (CL/CH), light gray, moist, stiff, fine grained FORMATION; SILTY SAND (SM), gray with yellow brown, moist, very dense, fine to medium grained Gray Olive Light gray, wet, medium grained ra KLEINFELDER PROJECT NO. 51-5314-01 h- O UJ i o 1s a:Q 95 UJ? D^frt UJ oz-soo 28.0 a: UJ HUJ Q y v> CLLU ZUJa. SOUTH AGUA HEDIONDA FIGURE WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA A2a LOG OF BORING Bl L ' J. ELEVATION (ft.) 1§ DEPTH (feet) 1I I 1 1 1 1 1 1| | SAMPLE TYPE |ccUlm 11 T 9 * T -25 50 —.11 BLOW COUNTS 1(blows/foot) 150/5" 50/5" 50/4" 50/5"GRAPHIC LOG 1SOIL DESCRIPTION AND CLASSIFICATION (Continued From Previous Page) Yellow-brown SILTY SAND (SM), light gray, wet, very dense, medium grained Bottom of borehole @ 50.5 ft. Water observed @ 28.5 ft. No caving observed Borehole grouted upon completion DRY UNIT WEIGHT 1(pcf) 1MOISTURE 1CONTENT (%) 1POCKETPENETROMETER(tsf)mu SOUTH AGUA HEDIONDA FIGURE mR-m KLEINFELDER WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA A2b PROJECTNO. 51-5314-01 LOG OF BORING Bl DATE DRILLED: 7/22/99 WATER DEPTH: 14 ft. DRILLED BY: Tri-County Drilling DATE MEASURED: 7/22/99 DRILLING METHOD: CME-75 w/autohammer ELEVATION: 25.0 ft. LOGGED BY: R. Gibbens RERERENCE DATUM: As per client i£ "- U \££ ? £ |z £ P §O ..- UJ ZF £ ^ W 1 » liUJ U) *—j mm i -| -n -20 5— U 2 fl -15 10— U 3 fl 2 1 -10 15— U . -5 20— U 0 25 — U --5 30— U 7 BLOW COUNTS(blows/foot)71 89 50/4" 50/5" 50/5" 50/5" 50/4"GRAPHIC LOG^ ^ SOIL DESCRIPTION AND CLASSIFICATION - Sandy gravel road base (1 ") FORMATION: SILT (ML), with sand, gray with yellow brown, moist, hard, fine grained SILTY SAND (SM), yellow brown, moist, very dense, fine grained, moderately cemented SILT (ML), with sand, gray, moist, hard, fine grained SILTY SAND (SM), olive, wet, very dense, fine grained No recovery Gray Yellow brown, weakly cemented RY UNIT WEIGHT(pcf)O 23 MOISTURECONTENT (%)104.0 POCKET3ENETROMETER(tsf)Wn ^TrTTvrirrTr,iro SOUTH AGUA HEDIONDA FIGURE•9-B KLEIMI^ELDER WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA A3a PROJECTNO. 51-5314-01 LOG OF BORING B2 r ~ J ; ELEVATION (ft.)g DEPTH (feet)I I 1 1 I I 1 I| | SAMPLE TYPEir SAMPLE NUMBEg 9 -20 45^U10 -25 50 —.11 BLOW COUNTS(blows/foot)50/5" 50/4" 50/4" 50/5"GRAPHIC LOGSOIL DESCRIPTION AND CLASSIFICATION (Continued From Previous Page) SILTY SAND (SM), gray, wet, very dense, fine grained, not cemented SANDSTONE WITH SILT, dark gray, moderately cemented Olive Light gray Bottom of borehole @ 50.5 ft. Water observed @ 14 ft. No caving observed Borehole grouted upon completion DRY UNIT WEIGH!(pcf)28 MOISTURECONTENT (%)100.0 POCKETPENETROMETEF(tsf)__-_ SOUTH AGUA HEDIONDA FIGURE mSM KLEINFELDER WASTEWATER PUMP STATION CARLSBAD, CALIFORNIA A3b PROJECT NO. 51-5314-01 LOG OF BORING B2 APPENDIX B KLEINFELDER APPENDIX B LABORATORY TESTING South Agua Hedionda Wastewater Pump Station Carlsbad, California m GENERAL m Laboratory tests were performed on selected, representative samples as an aid in classifying the m 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. m * MOISTURE AND DENSITY y 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 aremm presented on the test boring logs in Appendix A. m m SIEVE ANALYSES f* Sieve analyses were performed on four samples of the materials encountered at the site to|g 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 t* presented on Figure B1. a* „. CORROSIVITY TESTS m A series of chemical tests were performed on one selected sample of the near surface soil to ** estimate pH, resistivity, sulfate, and chloride contents. The test results are presented in Table B-l. m DIRECT SHEAR m A direct shear test was performed on a relatively undisturbed sample to evaluate the drained Hi shear strength of the onsite soils. Samples were tested in a near-saturated condition in general accordance with ASTM Test Method D3080 (consolidated, drained). Results of this tests are^P> Ig presented on Table B2. *•* 51-531401/5119R393.doc PageB-1 August 25, 1999 *" Copyright 1999 Kleinfelder, Inc. KLEINFELDER TABLE B-l CORROSION TEST RESULTS Boring 1 Depth (ft) 7-12 ;;P%':^ 7.1 Sulfate (ppm) 220 Chloride (ppm) 590 Resistivity (ohm-cm) 354 TABLE B-2 DIRECT SHEAR TEST RESULTS Boring 1 V: '-.<?-.' "(TO' 3-3.5 Phi Angle 37° 51-53140175119R393.doc Copyright 1999 Kleinfelder, Inc. Page B-2 August 25, 1999 APPENDIX C KLEINFELDER APPENDIX C SUGGESTED GUIDELINES FOR EARTHWORK CONSTRUCTION South Agua Hedionda Wastevvater Pump Station Carlsbad, California 1.0 GENERAL m m 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 this report. 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. mi 1.3 Geotechnical Engineer - The work covered by these specifications shall be observed and tested by Kleinfelder, the Geotechnical Engineer, who shall be 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 51-531401/5119R393.doc Copyright 1999 Kleinfelder, Inc. PageC-1 August 25, 1999 m m m K~l K L E I N F E L D E R *• Engineer shall submit a report to the Owner, including a tabulation of tests „,. performed. The costs of retesting unsuitable work installed by the to Contractor shall be deducted by the Owner from the payments to the Contractor. M 1.4 Standard Specifications - Where referred to in these specifications, m "Standard Specifications" shall mean the current State of California Standard * Specifications for Public Works Construction, 1994 Edition, with Regional pi Supplement Amendments. tt 1.5 Compaction Test Method - Where referred to herein, relative compaction ^Wy 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 Dl557 Compaction Test Procedure. Optimum moisture content shall mean the moisture content at the maximum dry density determined above. m * 2.0 SITE PREPARATION IP* to 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 Removal of Debris- Any existing, trash and debris encountered in the areas ta 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 fc 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. P 2.3 Ground Surface - The ground surface exposed by excavation shall be M scarified to a depth of six inches, moisture conditioned to the proper m moisture content for compaction, and compacted as required for compacted 51-531401/5119R393.doc PageC-2 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 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. 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 six 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 six 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 51-531401/5119R393.doc PageC-3 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER percent 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 eight 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 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. 51-531401/5119R393.doc Page C-4 August 25, 1999 Copyright 1999 Kleinfelder, Inc. KLEINFELDER 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 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 4.0 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. 51-531401/5119R393.doc PageC-5 August 25, 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 KLEINFELDER An employee owned company April 25, 2000 ProjectNo. 51-531401 RECEIVED Mr. Randy Klaahsen APR 2 7 2000 Associate Engineer Carlsbad Municipal Water District ENGINEERING 5950 El Camino Real DEPARTMENT Carlsbad, California 92008 Subject: Clarification on Geotechnical Report Items South Agua Hedionda Pump Station Reference Report: "Soils Exploration for the Proposed South Agua Hedionda Wastewater Pump Station, Carlsbad, California", Kleinfelder Project No. 51-531401, dated August 25,1999 Dear Mr. Klaahsen: The purpose of this letter is to follow up some items we discussed with Mr. Wain Cooper of COM Engineering on April 6, 2000 regarding the reference soils report for the South Agua Hedionda Wastewater Pumpstation. The items we discussed and clarified are as follows: 1. Section 7.6 Engineered Fill. This section was included in the report as part of the general site grading since we did not have any grading plans at the time the report was completed. If no engineered fill will be placed as part of general site grading, this section can be ignored. 2. Site Elevation (Section 2 Project Description). At the time we proposed on the project we were told the elevation of the existing adjacent access road was currently at about elevation +25 and that the pump station would be designed with a surface elevation about 1 foot below the existing adjacent access road. Based on our conversation with Mr. Cooper of CDM Engineering, we understand that the existing adjacent access road where we completed our test borings is not at elevation +25. We clarified with Mr. Cooper that our test borings were taken in the center of the access roadways at about the locations shown on Figure 2 of the report. All elevations in the report are referenced to the relative elevations of the roadways at the two boring locations as being elevation +25 feet. If topographic information is currently available which indicates the existing roadway elevations are not at elevation +25 as we were informed, then the designer will need to make adjustments to the elevations referenced in our report accordingly. 51-531401/5110L203.doc Page 1 of 2 April 25, 2000 Copyright 2000 Kleinfelder, Inc. KLEINFELDER 5015 Shoreham Place, San Diego, CA 921 22 (858)320-2000 (858) 320-2001 fax 3. 7.3.4 Backfill and 7.9 Lateral Earth Pressures for Pump Station Vault. The onsite soils can be used to backfill the pump station vault for the lateral earth pressures provided in the report. However, the civil designer and contractor are cautioned that soils removed from the excavation are anticipated to be moist to saturated and are likely to require drying prior to placement. Also, depending on the size of the space of the void to be backfilled, the contractor will need to determine how he intends to compact the silty sands and sandy silts within the wet environment. On some projects, the specifications simply state minimum requirements for backfill materials (similar to Section 7.3.4) and state the minimum degree of compaction (generally 90%); the source of the material and the manner to accomplish the compaction are left in the hands of the contractor. On other projects, the designer sets up the specifications so that the contractor is required to build the pump station tightly against the shoring, and the shoring is left in place. Others have specified a select import aggregate for backfill and a method specification for placement. We have no objection to either of the three methods as long as the responsibility of the contractor is clearly identified in the specifications to avoid change orders or disagreement during construction. The lateral earth pressures of 7.9 can be used for all 3 cases. Please contact our office should you have any questions with regard to this correspondence. Sincerely, KLEINFELDER, INC. Rick E. Larson, GE 2027 Senior Engineer cc.: Mr. Wain Cooper, CDM Engineering REL:rl 51-531401/5110L203.doc Page 2 of 2 April 25, 2000 Copyright 2000 Kleinfelder, Inc. KLEINFELDER 501 5 Shoreham Place, San Diego, CA 921 22 (858)320-2000 (858) 320-2001 fax