May 27, 2011 801 Glenneyre St. Suite F Laguna Beach CA 92651 (949) 494-2122 FAX (949) 497-0270 City of Laguna Beach Project No. 71478-02 505 Forest Avenue Report No. 10-6755 Laguna Beach, CA 92651 Attention: Ms. Lisa Penna Subject: Geotechnical Update Report for Storm Drain Outfall and Replacement of the Circle Way Beach Access Stairs Crescent Bay Beach Laguna Beach, California INTRODUCTION This update report presents results of a geotechnical investigation undertaken to relate geotechnical conditions to proposed replacement of the storm drain and beach access stairs located at the end of Circle Way in Laguna Beach, California. The purpose of this study is to evaluate the stability of the immediate area and provide geotechnical recommendations for the design and construction of the proposed improvements. Scope of Investigation The investigation included: 1. Review of the published and unpublished geotechnical reports and maps regarding the project area and adjacent properties. 2. Surface reconnaissance of the site and nearby areas, including the excavation, sampling, and downhole logging of one large diameter exploratory boring to determine the rock structure at the proposed storm drain and stair location. 3. Preparation of a topographic-geologic cross section relating site conditions to existing conditions and proposed construction. 4. Laboratory testing of representative materials to determine in situ moisture and density, Atterberg Limits, maximum density and optimum moisture, shear strength, and corrosivity characteristics. 5. Geotechnical stability analysis of site conditions and proposed design. 6. Preparation of this report and its illustrations.
Transcript
May 27, 2011
801 Glenneyre St. Suite F Laguna Beach CA 92651(949) 494-2122 FAX (949) 497-0270
City of Laguna Beach Project No. 71478-02 505 Forest Avenue Report No. 10-6755 Laguna Beach, CA 92651 Attention: Ms. Lisa Penna Subject: Geotechnical Update Report for Storm Drain Outfall
and Replacement of the Circle Way Beach Access Stairs Crescent Bay Beach Laguna Beach, California
INTRODUCTION This update report presents results of a geotechnical investigation undertaken to relate geotechnical conditions to proposed replacement of the storm drain and beach access stairs located at the end of Circle Way in Laguna Beach, California. The purpose of this study is to evaluate the stability of the immediate area and provide geotechnical recommendations for the design and construction of the proposed improvements. Scope of Investigation The investigation included:
1. Review of the published and unpublished geotechnical reports and maps regarding the project area and adjacent properties.
2. Surface reconnaissance of the site and nearby areas, including the excavation, sampling, and downhole logging of one large diameter exploratory boring to determine the rock structure at the proposed storm drain and stair location.
3. Preparation of a topographic-geologic cross section relating site conditions to existing conditions and proposed construction.
4. Laboratory testing of representative materials to determine in situ moisture and density, Atterberg Limits, maximum density and optimum moisture, shear strength, and corrosivity characteristics.
5. Geotechnical stability analysis of site conditions and proposed design.
6. Preparation of this report and its illustrations.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 2 Accompanying Illustrations and Appendices Appendix A - References Appendix B - Boring Log Appendix C - Field and Laboratory Test Data Appendix D - Standard Grading Specifications Appendix E - Trenching, Backfilling, and Compacting Specifications Appendix F - Slope Stability Analysis Figure 1 - USGS Geologic Site Location Map Figure 2 - Typical Retaining Wall Subdrain Detail Figure 3 - Updated Geotechnical Plot Plan Figure 4 - Updated Cross Section A-A' Proposed Construction Our understanding of the project is based on our review of the “City of Laguna Beach, Public Works Department, Circle Way Storm Drain and Stairs Repair”, sheets 1 to 25 of 25, undated, by Psomas. Based on these plans, the proposed improvements project generally includes the removal of existing infrastructure and the installation of a new 42-inch to 60-inch RCP storm drain with a beach level outlet, new 6-inch to 8-inch SDR sewer utilities, and the construction of new beach access stairs, site walls, landscaping, and asphalt pavement. The proposed project limits depict limited remedial grading extending onto 299 Crescent Bay Drive to the west. It is anticipated that the new stairs will be supported on caissons near the beach level and on grade upslope. The beach storm drain outlet structure will be supported on caissons constructed in bedrock. GEOTECHNICAL CONDITIONS Earth Materials The site is underlain at depth by bedrock strata assigned on the basis of regional geologic mapping to the Monterey Formation. To the south, the bedrock is overlain by 3 to 5+ feet of beach deposits in the vicinity of the lower stairs, and over the remainder of the alignment it is mantled with 6+ feet of fill. Based on the review of aerial photos, the bedrock surface is likely irregular and incised by the former drainage course that transected the alignment. Based upon exposures in the boring, the bedrock strata consist of grey-brown siltstone and yellow to orange-brown fine-grained sandstone. At depths below 9+ feet, the rock is fractured but moderately cemented and hard. Above 8+ feet, the clayey siltstone is soft, brecciated, and sheared.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 3 The beach deposits consist of medium to coarse-grained sand with scattered shell fragments. The beach deposits are loose, essentially cohesionless and are prone to caving. The fill deposits consist of silty sand to clay, that are variably soft to stiff. The relationship between subsurface materials and proposed improvements are depicted on the Geotechnical Cross-Section, Figure 4. Geologic Structure The proposed alignment is westerly adjacent to previous slope instability. Bedrock landsliding in this area is reported to have occurred initially in 1950 and reactivated in 1983, impacting properties at 287,297, and 299 Crescent Bay Drive. Based on the report by 2R Engineering Inc., the failures appeared to have been structurally controlled along south-dipping bedding planes within the weathered zone of the bedrock. Earthwork to buttress the bedrock was completed in 1983. The bedrock exposed in our exploratory boring revealed similar adverse structure, with weathered and brecciated bedding dipping west-southwest at moderate angles. In cross-section, the apparent dip is gently inclined out-of-slope toward the shoreline. Although this alignment is not within the former instability, this bedrock structure forms the basis for our stability analyses. Stability Analysis Engineering stability analyses were performed to evaluate the stability of the existing and proposed conditions under both static and seismic (pseudostatic) conditions. The analyses were performed on geometries depicted on Cross Section A-A’ using a computer program based upon the Simplified Janbu method. Strength parameters used for the analyses were based upon laboratory testing performed previously. The values determined are considered reasonable for the materials encountered. The analyses indicate that both the existing and proposed slope configurations have factors-of-safety below the normally accepted criteria of 1.5 for static and 1.1 for seismic conditions, as presented below. A caisson foundation system may be utilized to increase the factors-of -safety to meet the criteria. Our analyses indicate that a caisson foundation should provide at a minimum a resisting lateral force of 13,000 lbs per lineal foot. The piers should extend a minimum of 20 feet below proposed grades (10 feet minimum into bedrock). The results of the slope stability analyses are presented in the following table and in Appendix F.
Groundwater Groundwater was encountered in the exploratory excavation in the form of seepage at three feet below grade and standing water at 11 feet below grade. The groundwater level is anticipated to fluctuate within the project site under normal weather conditions. When present, groundwater will promote caving in excavations exposing beach sands or soft deposits. Groundwater also influences slope stability, and provisions should be made during storm drain construction to include a subdrain system so that groundwater rise is precluded. CONCLUSIONS 1. Proposed construction is considered feasible and safe from a geotechnical viewpoint
provided the recommendations of this report are followed during design, construction and maintenance of the subject property. Proposed development should not adversely affect adjacent properties.
2. The site is underlain at relatively shallow depth by bedrock, which is in turn overlain with fill or beach deposits. The upper weathered portion of the bedrock is sheared and brecciated. The beach deposits and portions of the fill are caving prone.
3. Temporary stability conditions are anticipated to be poor, with shallow perched water and caving prone soils. The gross and surficial stability of the existing condition and the proposed design do not meet normally accepted criteria. However, the factor-of-safety may be increased with proposed foundation caissons.
4. Shallow groundwater conditions will likely be encountered throughout the alignment. Designs and construction may also consider tidal and wave activity in the southern end of the alignment.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 5 5. The beach access stairs, storm drain, and retaining walls may be supported by competent
bedrock within the near-shore environment, and by compacted fill in upslope areas. RECOMMENDATIONS Our recommendations are considered to be generally consistent with the standards of practice. They are based on both analytical methods and empirical methods derived from experience with similar geotechnical conditions. These recommendations are considered the minimum necessary for the likely soil conditions and are not intended to supersede the design of the Structural Engineer or criteria of governing agencies. Site Preparation and Grading 1. General
All grading of the site should be performed in accordance with the Standard Grading Specifications of Appendix D. All excavations should be supervised and approved in writing by a representative of this firm. Storm drain excavations should be backfilled with properly moisture conditioned native soils which are free of trash, vegetation, construction debris and oversized rock fragments. The maximum allowable rock fragment size is 3 inches measured in the greatest dimension. All trenching, backfilling and soil compacting should be performed in general accordance with the Specifications presented in Appendix E. Overexcavation and recompaction of soils below the storm drain invert is not anticipated; however, if soft subgrades below the pipe are encountered, they should be bridged with crushed rock with a minimum thickness of one foot and overlain by geofabric. As an alternative, sand-cement slurry may be used as provided in Appendix E.
Excavations in fill or beach deposits should be laid back to 1:1 (horizontal:vertical). Shoring is required where space limitations preclude slope layback. Shoring should anticipate lagging between shoring elements where wet fill, beach deposits, and locally fractured bedrock will be exposed.
2. Removal of Existing Improvements
All deleterious materials, including demolition debris and concrete rubble, organic materials, and trash, should be removed and disposed of offsite.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 6 3. Compaction Standard
All onsite soils are anticipated to be suitable for use as compacted fill. All materials should be placed at or near optimum moisture content and compacted under the observation and testing of the soil engineer. The recommended minimum density for compacted material is 90 percent of the maximum density as determined by ASTM D 1557.
Sheeting, Shoring, and Bracing of Trenches
Trenches shall have sheeting, shoring, and bracing conforming to CAL/OSHA requirements. Lateral pressures for design of trench sheeting, shoring, and bracing shall be based on type of soil exposed in the trench, groundwater conditions, surcharge loads adjacent to the trench, and type of shoring what will be used in the trench. For preliminary design purposes, the following soil parameter values may be utilized for shoring designs; these may require modification to meet specific conditions at varying locations. Active Pressure Lateral Loading = 35 pounds per cubic foot equivalent fluid pressure Passive Pressure Lateral Resistance = 250 pounds per cubic foot equivalent fluid pressure Friction Coefficient = 0.35. Plans for shoring and bracing should be provided as a part of the plan submittal and should be reviewed by the geotechnical consultant and civil engineer. Structural Design of Foundations and Caissons It is anticipated that stair and wall foundations will bear in bedrock or compacted fill and will utilize caissons at the beach level and conventional footings upslope. The stairs and landings should be designed as structural elements where necessary to span areas of beach deposits and uncompacted fill material. Caissons and structural slabs should be designed by the structural engineer.
The following recommendations are based on the geotechnical data available and are subject to revision based on conditions actually encountered in the field. Earth materials to be exposed at the finish grades are anticipated to have a low expansion potential. Foundations and slabs should be designed for the intended use and loading by the Structural Engineer. Our recommendations are considered to be generally consistent with the standards of practice. They are based on both analytical methods and empirical methods derived from experience with
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 7 similar geotechnical conditions. These recommendations are considered the minimum necessary for the likely soil conditions and are not intended to supersede the design of the Structural Engineer or criteria of governing agencies. 1. Conventional Foundations Conventional spread footings embedded into competent bedrock or compacted fill may
be designed for allowable bearing values of 4000 and 2000 pounds per square foot, respectively. Footings should be designed with a minimum width of 12 inches and a minimum embedment of 12 inches below the lowest adjacent grade. Actual footing depth and width should be governed by CBC requirements and the structural engineering design. The design values may be increased one-third for short duration wind or seismic loading. Settlement due to footing loads is anticipated to be nil in bedrock, while settlement in fill may be on the order of ¾ inch.
Lateral loads may be resisted by passive forces computed on the basis of equivalent fluid densities of 600 and 250 pounds per cubic foot for bedrock and fill, respectively. A coefficient of friction of 0.40 for bedrock and 0.35 for fill may be utilized in computing the frictional resistance.
2. Caissons Caissons utilized for foundation support should be a minimum 24-inch diameter and
embedded into competent bedrock a minimum depth of 10 feet. Caissons should be designed for lateral loading of 13 kips per lineal foot. Caissons may be designed for a dead plus live load end bearing value of 12,000 pounds per square foot for bedrock, respectively. These values may be increased by one-third for wind and seismic forces. A skin friction value of 600 pounds per square foot may also be used for bedrock. Settlement of caisson foundations in bedrock is anticipated to be negligible.
Lateral resistance may be computed utilizing 600 pounds per square foot per foot of depth
for competent bedrock. The lateral resistance value provided above for bedrock may act on a tributary area of twice the caisson diameter. No lateral resistance may be taken in the beach deposits, slope wash or fill material. An allowable coefficient of friction of 0.40 may be assumed for bedrock.
3. Slope Setback The base of all footings and caissons should be deepened as necessary to establish a
horizontal distance of 15-feet as measured from the bottom edge of the foundation to the slope face.
The apron keyway should be embedded a minimum of 24 inches into competent bedrock. Structural Design of Retaining Walls Lateral pressure forces acting on cantilevered shoring/retaining walls retaining level and 2:1 sloping granular onsite soil may be designed utilizing equivalent fluid pressures of 35 and 45 pounds per cubic foot, respectively. Wall rotation on the order of 0.1 percent of the wall height should be anticipated and considered in the design for active earth pressure walls. Restrained walls should be designed utilizing an equivalent fluid pressure of 60 pounds per cubic foot. Retaining wall and shoring design must consider topographic and structural surcharges from existing and adjacent improvements. Groundwater Groundwater elevations are anticipated to vary across the site with topography. Beach level groundwater will be generally consistent with tidal levels, and may reach elevation 8+ feet. Groundwater/seepage levels in the upslope areas may vary from 3 to 10 feet below grade. Subdrains The drainage schemes depicted on Figures 3 and 4, or geotechnically approved alternatives, should be used to reduce the potential for seepage forces behind retaining walls. Waterproofing of retaining walls should be applied in accordance with the architect’s specifications or those of a waterproofing consultant. Hardscaping Hardscaping elements should be designed for an allowable bearing value of 2000 pounds per square foot for terrace deposits or approved granular compacted fill. Allowable passive pressure forces may be computed using an equivalent fluid density of 250 pounds per cubic foot, and a coefficient of friction of 0.35. Slabs on grade should have a minimum thickness of 5-inches (actual), and be reinforced with No. 4 bars spaced 12-inches on center both ways. Slabs should be provided with weakened plane joints at maximum 6 feet intervals in order to control the location of cracks and reduce the possibility of developing randomly located irregular cracks. Concrete and Reinforcing Steel Laboratory test results indicate onsite derived soils have a negligible sulfate content. However, as the concrete is in a marine environment, a moderate sulfate exposure should be used for design
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 9 purposes. The concrete mix should be designed by a concrete expert in consideration of structural requirements and anticipated exposure. In lieu of a specific design, applicable recommendations as presented in the 2010 California Building Code, Section 1904.3 should be utilized, which refer to Tables 4.2.2 and 4.3.1 of ACI 318, which recommends Type II cement, a maximum water-cement ratio of 0.40, and a minimum design unconfined compressive strength of 5,000 psi, if exposed to sea water. The selection of reinforcing steel should also consider the corrosive environment. Either stainless steel (up to No. 8 bars) or epoxy coated steel is recommended. Finished Grade and Surface Drainage Finished grades should be designed and constructed to reduce the potential for ponding of water in the vicinity of footings, and to direct discharge from the site in a non-erosive manner. Drainage gradients should conform to California Building Code, Section 1803.3 requirements. Foundation Plan Review In order to help assure conformance with recommendations of this report and as a condition of the use of this report, the undersigned should review final foundation plans and specifications prior to submission of such to the building official for issuance of permits. Such review is to be performed only for the limited purpose of checking for conformance with the design concept and the information provided herein. This review shall not include review of the accuracy or completeness of details, such as quantities, dimensions, weights or gauges, fabrication processes, construction means or methods, coordination of the work with other trades or construction safety precautions, all of which are the sole responsibility of the Contractor. Geofirm’s review shall be conducted with reasonable promptness while allowing sufficient time in our judgment to permit adequate review. Review of a specific item shall not indicate that Geofirm has reviewed the entire system of which the item is a component. Geofirm shall not be responsible for any deviation from the Construction Documents not brought to our attention in writing by the Contractor. Geofirm shall not be required to review partial submissions or those for which submissions of correlated items have not been received. Monitoring Complete documentation of the pre- and post-construction conditions of existing and adjacent improvements should be undertaken. Such documentation should include: 1. A sufficient number of photographs to establish the existing condition of nearby structures.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 10 2. Establishment of a sufficient number of ground elevation control stations so that potential
subsidence associated with lateral movement can be detected. Monitoring of such points should be accomplished during shoring and excavation work and continued until retaining walls are backfilled.
In addition, monitoring of ground movement and construction vibrations should be made as an integral part of the construction. Several construction activities can produce ground vibrations that are potentially damaging to structures. Measurement of ground vibrations at or adjacent to a construction site is typically used to help the Contractor maintain activities below threshold values which could cause damage to adjacent property, or on-site. After construction is completed, the monitoring record may be used as evidence in the event of vibration-related damage claims. Pre-Construction Meeting A pre-construction meeting should be held with representatives of the owner, contractor, architect, civil engineer, geotechnical engineer, engineering geologist, and building official prior to grading and/or construction to clarify any questions relating to the incorporation of geotechnical recommendations into grading construction and work sequence.
Jobsite Safety Neither the professional activities of Geofirm, nor the presence of Geofirm’s employees and subconsultants at a construction/project site, shall relieve the General Contractor of its obligations, duties and responsibilities including, but not limited to, construction means, methods, sequence, techniques or procedures necessary for performing, superintending and coordination the work in accordance with the contract documents and any health or safety precautions required by any regulatory agencies. Geofirm and its personnel have no authority to exercise any control over any construction contractor or its employees in connection with their work or any health or safety programs or procedures. The General Contractor shall be solely responsible for jobsite safety. Observation and Testing The 2010 California Building Code requires geotechnical observation and testing during construction to verify proper removal of unsuitable materials, that foundation excavations are clean and founded in competent material, to test for proper moisture content and proper degree of compaction of fill, to test and observe placement of wall and trench backfill materials, and to confirm design assumptions. It is noted that the CBC requires continuous verification and testing during placement of fill, pile driving, and pier/caisson drilling.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 11 A Geofirm representative shall visit the site at intervals appropriate to the stage of construction, as notified by the Contractor, in order to observe the progress and quality of the work completed by the Contractor. Such visits and observation are not intended to be an exhaustive check or a detailed inspection of the Contractor’s work but rather are to allow Geofirm, as an experienced professional, to become generally familiar with the work in progress and to determine, in general, if the work is proceeding in accordance with the recommendations of this report. Geofirm shall not supervise, direct, or have control over the Contractor’s work nor have any responsibility for the construction means, methods, techniques, sequences, or procedures selected by the Contractor nor the Contractor’s safety precautions or programs in connection with the work. These rights and responsibilities are solely those of the Contractor. Geofirm shall not be responsible for any acts or omission of the Contractor, subcontractor, any entity performing any portion of the work, or any agents or employees of any of them. Geofirm does not guarantee the performance of the Contractor and shall not be responsible for the Contractor’s failure to perform its work in accordance with the Contractor documents or any applicable law, codes, rules or regulations. These observations are beyond the scope of this investigation and budget and are conducted on a time and material basis. The responsibility for timely notification of the start of construction and ongoing geotechnically involved phases of construction is that of the owner and his contractor. Typically, at least 24 hours notice is required. LIMITATIONS This investigation has been conducted in accordance with generally accepted practice in the engineering geologic and soils engineering field. No further warranty is offered or implied. Conclusions and recommendations presented are based on subsurface conditions encountered and are not meant to imply a control of nature. As site geotechnical conditions may alter with time, the recommendations presented herein are considered valid for a time period of one year from the report date. The recommendations are also specific to the current proposed development. Changes in proposed land use or development may require supplemental investigation or recommendations. Also, independent use of this report in any form cannot be approved unless specific written verification of the applicability of the recommendations is obtained from this firm.
May 27, 2011 Project No. 71478-02 Report No. 10-6755 Page No. 12 Thank you for this opportunity to be of service. If you have any questions, please contact this office. Sincerely, GEOFIRM Erik R. Hilde, P.G. Hannes H. Richter, P.E., G.E. 717 Engineering Geologist, C.E.G. 2303 Chief Geotechnical Engineer Registration Expires 10-31-11 Registration Expires 3-31-12 Date Signed: / / ERH/HHR:fp Distribution: (5) to Addressee
APPENDIX A
REFERENCES
APPENDIX A
REFERENCES
1. Bagahi Engineering, 1989, “Preliminary Geotechnical Investigation, Proposed Bluff Stabilization, 267, 279, 287, and 299 Crescent Bay Drive, and 1371 and 1367 Circle Way Drive, Laguna Beach, California”, Job No. 231-069-10, dated November 30.
2. California Building Code, 2001 Edition
3. California Division of Mines and Geology, 1976, “Geology of the Laguna Beach
Quadrangle, Orange County, California”; Special Report 127.
4. California Divisions of Mines and Geology, 1997, “Guidelines for Evaluating and Mitigating Seismic Hazards in California,” Special Publication 117.
5. California Division of Mines and Geology, 1998, “Seismic Hazards Zones Map,
Laguna Beach Quadrangle. 6. Geofirm, Inc. 1983, “Geotechnical Investigation, Retaining Wall Construction and
Slope Restoration, 1259 Cliff Drive, Laguna Beach, California”, Project No. 83-320, dated August 1.
7. Geofirm, Inc. 1990, “Geotechnical Review of Proposed Crescent Bay Bluff
Stabilization, Laguna Beach, California”, Project No. 389-3, dated February 5.
8. Geofirm, 2001, “Limited Geotechnical Investigation, Proposed Crescent Bay Restrooms, Barranca Street, Laguna Beach, California”, Project No: 71224-00, Report No. 01-3853, dated November 12.
9. Tetra Tech, Inc. 1989, “Crescent Bay Shore Defense System, Laguna Beach,
California, Revised Design Report”, TC 3717-03, dated July 31.
10. 2R Engineering, Inc., 1989, “Preliminary Geotechnical Investigation, Proposed Bluff Stabilization for 267, 279, 287 and 299 Crescent Bay Drive (Lots 28, 30, 31 and 33, Tract No. 707) and 1371 and 1367 Circle Way Drive (Lots 20 and 21, Tract No. 1087), Laguna Beach, California”, dated July 10, Project No. 89-1160-1.
Notes: This system consists of a geotextile fabric-wrapped gravel envelope. Collection is with a 4-inch diameter perforated plastic pipe embedded in the gravel envelope and tied to a 4-inch diameter non-perforated plastic pipe which discharges at convenient locations. The outlet pipe should be placed such that the flow gradient is not less than 2.0 percent. The geotextile fabric-wrapped gravel envelope should be placed at a similar gradient
All drain pipes should be Schedule 40 PVC or ABS SDR-35. Perforations may be either bored 1/4-inch diameter holes or 3/16-inch slots placed on the bottom one-third of the pipe perimeter. If the pipe is to be bored, a minimum of 10 holes should be uniformly placed per foot of length. If slots are made, they should not exceed 2-1/2 inches in length and should not be closer than 2 inches. Total length of slots should not be less than 50 percent of the pipe length and should be uniformly spaced.
The fabric pore spaces should not exceed equivalent 30 mesh openings or be less than equivalent 100 mesh openings. The fabric should be placed such that a minimum lap of 8-inches exists at all splices.
UPDATED GEOTECHNICAL PLOT PLANCITY OF LAGUNA BEACH
CIRCLE WAY STORM DRAIN IMPROVEMENTSLAGUNA BEACH, CALIFORNIA
UPDATED GEOTECHNICAL CROSS SECTION A-A'CITY OF LAGUNA BEACH
CIRCLE WAY STORM DRAIN IMPROVEMENTSLAGUNA BEACH, CALIFORNIA
Project no.: Date: Figure:71478-02 MAY 2011 4
A'AE
LEV
ATI
ON
(FE
ET,
PE
R P
LAN
)
10
0
-10
-20
-30
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30
40
50
60
70
10
0
-10
-20
-30
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70
APPENDIX B BORING LOGS
Drop:
Date(s) Logged:
LOCATION:
Logged By:
B-1
71478-00Project No.: LOG OF BORING Figure No.:
B:N35W/22W
B:N30W/23E
24" Flight Auger
Pacific Drilling
30"
140 lbs
Depth
(fe
et)
Soil
Cla
ssific
ation
Weight(s):
Method of Drilling:
Drilling Company:ERH
Circle Way Beach Access Stairs; storm drain
easement
Blo
ws/6
"
Undis
turb
ed
Sam
ple
Bulk
Sam
ple
8/3/2004
Ground Elevation:
Depth
(fe
et)
Geologic
AttitudesDescription
BORING NO.:
Mois
ture
Conte
nt (%
)
In-p
lace D
ry
Density (
pcf)
0
1
2
3
4
5
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
31
32
33
34
35
36
37
38
39
40
0
1
2
3
4
5
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7
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9
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20
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23
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25
26
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28
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30
31
32
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39
40
Fill - Upper ~1' consists of loose, dry to damp, silty SAND, scattered rootlets, scattered gravel and cobbles, brown. Grades to CLAY, soft to stiff, very moist, dark greenish gray and dark brown; scattered large fragments of cemented siltstone.
21.2 99.64,8
@6.5': Bedrock: Monterey Formation - Generally highly jointed and fractured, weakly to moderately indurated clayey SILTSTONE, very moist, somewhat crumbly, brownish gray. Heavy seepage from shading gravel on northeast side of boring; from 6'-8'.13.0 112.5
19.9 107.5
15,28
14,20
Total Depth = 6'Groundwater @11.5'Backfilled with cuttings
@3': Seepage.
@5'-6': Soft zone, very wet, seepage.
@7.5'-8.4': Highly brecciated zone along bedding. Attitudes taken along base of brecciated bedding. Numerous polished partings with scattered vague striations.
@8.4': Silty fine SAND, very moist, olive to yellowish brown.
@9.5': Gradational change to highly fractured, moderately to strongly cemented siltstone, wet, light yellowish to orangish brown. Thin clay along fracture and joint surfaces.
@11.5': Very difficult to drill, possible concretion. Groundwater level after drilling.
Boring Log.xls 5/27/2011 Geofirm
APPENDIX C
FIELD EXPLORATION AND LABORATORY TESTING
APPENDIX C
FIELD EXPLORATION AND LABORATORY TESTING
I. Field Exploration Procedures
A. Field Exploration
A portable bucket auger drilling rig with a 24 -inch diameter auger was utilized to expose subsurface soils.
B. Sampling
1. Core Samples
Core samples of subsurface materials were obtained by driving a steel barrel drive sampler with an effective weight of 140 pounds that is raised and permitted to fall 30 inches. The sampler has an outside diameter of 3.0 inches and is lined with a series of 1-inch high brass rings having an inside diameter of 2.43 inches. A drive shoe is placed on the tip of the sampler to hold the liners in place during sampling.
The samples were removed from the sample barrel in the brass rings, placed in moisture tight containers and transported to the laboratory for testing. Records of the number of blows required to effect each 6 inches of penetration were made.
2. Disaggregated Samples
Bulk samples of typical soil types were bagged and transported to the laboratory for classification and physical testing.
II. Laboratory Testing Procedures
A. Moisture and Density Tests
Dry unit weights and field moisture contents were determined for core specimens obtained from the test sampler by measuring the volume and weight of the core specimens. Moisture determinations were made in accordance with ASTM test methods. The results are summarized on the Boring Logs in Appendix B.
B. Maximum Density-Optimum Moisture
A maximum density-optimum moisture determination was performed in accordance with ASTM test method D1557. The results of the test are tabulated below:
Sample Designation - Boring 1 @ 3-5’ Maximum Density - 129.0 pcf Optimum Moisture Content - 11.0%
D. Direct Shear Tests Direct shear tests were performed in general accordance with ASTM D 3080 on specimens of native material inundated before and during testing. The direct shear machine employed was a conventional single shear, strain controlled device. The shearing strength parameters were obtained by fitting a straight line through three points of peak shear strength versus total normal stress. The total normal stress range used was 1000 to 4000 pounds per square foot. Results from the tests are summarized below.
Atterberg limits determinations were performed in accordance with ASTM D 4318 on a specimen of onsite soil. Results from this test are summarized below.
GENERAL These Guidelines present the usual and minimum requirements for grading operations observed and tested by Geofirm, or its designated representative. No deviation from these guidelines will be allowed, except where specifically superseded in the geotechnical report signed by a registered geotechnical engineer. The placement, spreading, mixing, watering and compaction of the fills in strict accordance with these guidelines shall be the sole responsibility of the contractor. The construction, excavation, and placement of fill shall be under the direct observation of the geotechnical engineer or any person or persons employed by the licensed geotechnical engineer signing the soils report. If unsatisfactory soil-related conditions exist, the geotechnical engineer shall have the authority to reject the compacted fill ground and, if necessary, excavation equipment will be shut down to permit completion of compaction. Conformance with these specifications will be discussed in the final report issued by the geotechnical engineer. SITE PREPARATION All brush, vegetation and other deleterious material such as rubbish shall be collected, piled and removed from the site prior to placing fill, leaving the site clear and free from objectionable material. Soil, alluvium, or rock materials determined by the geotechnical engineer as being unsuitable for placement in compacted fills shall be removed from the site. Any material incorporated as part of a compacted fill must be approved by the geotechnical engineer. The surface shall then be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment used. After the area to receive fill has been cleared and scarified, it shall be diced or bladed by the contractor until it is uniform and free from large clods, brought to the proper moisture content, and compacted to minimum requirements. If the scarified zone is greater than 12 inches in depth, the excess shall be removed and placed in lifts restricted to 6 inches. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipe lines or others not located prior to grading are to be removed or treated in a manner prescribed by the geotechnical engineer. MATERIALS Materials for compacted fill shall consist of materials approved by the geotechnical engineer. These materials may be excavated from the cut area or imported from other approved sources, and soils from one or more sources may be blended. Fill soils shall be free from organic vegetable matter and other unsuitable substances. Normally, the material shall contain no rocks or hard lumps greater than 6 inches in size and shall contain at least 50 percent of material
smaller than 1/4-inch in size. Materials greater than 4 inches in size shall be placed so that they are completely surrounded by compacted fines; no nesting of rocks shall be permitted. No material of a perishable, spongy, or otherwise of an unsuitable nature shall be used in the fill soils. Representative samples of materials to be utilized as compacted fill shall be analyzed in the laboratory by the geotechnical engineer to determine their physical properties. If any material other than that previously tested is encountered during grading, the appropriate analysis of this material shall be conducted by the geotechnical engineer as soon as possible. PLACING, SPREADING, AND COMPACTING FILL MATERIAL The material used in the compacting process shall be evenly spread, watered, processed and compacted in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer. When the moisture content of the fill material is below that specified by the geotechnical engineer, water shall be added by the contractor until the moisture content is near optimum as specified. When the moisture content of the fill material is above that specified by the geotechnical engineer, the fill material shall be aerated by the contractor by blading, mixing, or other satisfactory methods until the moisture content is near optimum as specified. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to 90 percent of the maximum laboratory density in compliance with ASTM D: 1557 (five layers). Compaction shall be accomplished by sheepsfoot rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of acceptable compacting equipment. Equipment shall be of such design that it will be able to compact the fill to the specified density. Compaction shall be continuous over the entire area and the equipment shall make sufficient passes to obtain the desired density uniformly. A minimum relative compaction of 90 percent out to the finished slope face of all fill slopes will be required. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of 2 to 5 feet in elevation gain or by overbuilding and cutting back to the compacted inner core, or by any other procedure which produces the required compaction. GRADING OBSERVATIONS AND TESTING The geotechnical engineer shall observe and test the placement of fill during the grading process and will file a written report upon completion of grading stating his observations as to compliance with these specifications. One density test shall be required for each 2 vertical feet of fill placed, or one for each 1,000 cubic yards of fill, whichever requires the greater number of tests. Any cleanouts and processed ground to receive fill must be observed by the geotechnical engineer and/or engineering geologist prior to any fill placement. The contractor shall notify the geotechnical engineer when these areas are ready for observation.
PROTECTION OF WORK During the grading process and prior to the complete construction of permanent drainage controls, it shall be the responsibility of the contractor to provide good drainage and prevent ponding of water and damage to adjoining properties or to finished work on the site. After the geotechnical engineer has terminated his observations and tests of the completed grading, no further excavations and/or filling shall be performed without the approval of the geotechnical engineer, if it is to be subject to the recommendations of this report.
APPENDIX E
TRENCHING, BACKFILLING AND COMPACTING SPECIFICATIONS
APPENDIX E
TRENCHING, BACKFILLING AND COMPACTING SPECIFICATIONS PART 1 – GENERAL A. Description
This section describes materials, testing, and performance of trench excavation, backfilling, and compacting.
B. Submittals
1. Shop drawings shall be submitted showing excavation and shoring, bracing, or sloping for worker protection and protection of adjacent improvements in accordance with the General Provisions.
2. Six copies of a report from a testing laboratory shall be submitted verifying that
backfill material conform to the specified gradations or characteristics for pea gravel, granular material, imported sand, rock refill for foundation stabilization, and water.
C. Protection of Existing Utilities and Facilities
1. General: The contractor shall be responsible for the care and protection of all existing sewer pipelines, water pipelines, gas mains, storm drains, culverts, or other facilities and structures that may be encountered in or near the area of work.
2. Notification: It shall be the duty of the contractor to notify each agency or
jurisdiction and make arrangements for locating each agency’s facilities prior to beginning construction.
3. Damage: In the event of damage to any existing facilities during the progress of
the work due to the failure of the contractor to exercise the proper precautions, the contractor shall be responsible for the cost of all repairs and protection to said facilities. The contractor’s work may be stopped until repair operations are complete.
D. Protection of Landscaping
1. General: The contractor shall be responsible for the protection of all the trees,
shrubs, fences, and other landscape items adjacent to or within the work area, unless directed otherwise on the plans.
2. Restoration: After the completion of work in planted or improved areas within
public or private easements, the contractor shall restore such areas to original condition.
PART 2 - MATERIALS A. Definition of Zones
1. Pavement Zone: The pavement zone shall include the asphaltic concrete and aggregate base pavement section placed over the street zone.
2. Street Zone: The street zone shall consist of the top 18-inches of the trench
immediately below the pavement zone in paved areas or areas to be paved. 3. Trench Zone: The trench zone shall include the portion of the trench from the top
of the pipe zone to the bottom of the street zone in paved areas or to the existing surface in unpaved areas.
4. Pipe Zone: The pipe zone shall include the full width of trench 12 inches from
the bottom of the pipe to a horizontal level 12-inches above the top of the pipe. 5. Pipe Base: The pipe base shall be defined as a layer of material immediately
below the pipe zone and extending over the full trench width.
B. Native Earth Backfill -- Trench Zone Native earth backfill shall be excavated, fine-grained non-organic materials free from peat, roots, debris, and rocks larger than 3-inches, and which can be compacted to the specified relative compaction.
C. Backfill -- Pipe Base The pipe base backfill, up to an elevation of 12-inches above the pipe invert, shall be
imported gravel as specified herein. The material shall consist of gravel or crushed rock having the following gradation:
D. Imported Sand -- Pipe Zone Imported sand used in the pipe zone or for the pipe base shall have the following
gradation:
Percent Passing Sieve Size by Weight 3/8 – inch 100 No. 4 75 - 100 No. 30 12 - 50 No. 100 5 - 20 No. 200 0 - 15 Minimum sand equivalent shall be 30 per ASTM D 2419. E. Refill Material for Foundation Stabilization Refill material below the pipe shall be either material conforming to the 1 ½-inch size
requirement for gravel or crushed rock, or naturally occurring rock having the same gradation specified above for the Pipe Base backfill.
F. Sand-Cement Slurry Refill Material for Foundation Stabilization in Pipe Base and Pipe Zone Sand-Cement slurry shall consist of one sack (94 pounds) of portland cement per cubic
yard of sand and sufficient moisture for workability. G. Pea Gravel Pea gravel shall be defined as gravel, uniformly graded from coarse to fine with less than
10% passing a No. 200 sieve, less than 50% passing a No. 4 sieve, and having a maximum particle size of ¾ - inch.
H. Water for Compaction Water used in compaction shall have a maximum chloride concentration of 500 mg/l, a
maximum sulfate concentration of 500 mg/l, and shall have a pH of 7.0 to 9.0. Water shall be free of acid, alkali, or organic materials injurious to the pipe coating.
PART 3 – EXECUTION
A. Testing for Compaction
1. Methods: The density of soil shall be determined in place by the sand cone method, ASTM D 1556, or by the nuclear method, ASTM D 2922 or D 3017.
2. Soil Moisture-Density Relationship: The laboratory moisture-density relations of
soils shall be determined per ASTM D 1557. 3. Cohesionless Materials: The relative density of cohesionless materials shall be
determined by ASTM D 4253 and D 4254.
4. Sampling: Backfill materials shall be sampled per ASTM D 75.
5. Relative Compaction: “Relative compaction” shall be expressed as the ratio, expressed as a percentage, of the in place dry density to the laboratory maximum dry density.
6. Compaction Compliance: Compaction shall be deemed to comply with the
specifications when none of the tests falls below the specified relative compaction. The contractor shall notify the City 24-hours in advance of when backfill lifts are ready for testing, and shall pay the costs of any retesting of work not conforming to the specifications.
B. Compaction Requirements
Unless otherwise shown on the drawing or otherwise described in the specifications for the particular type of pipe installed, relative compaction in pipe trenches shall be as follows:
1. Pipe Base and Pipe Zone: Pipe base and pipe zone - - 90% relative compaction.
2. Trench Zone: Backfill in trench zone - - 90% relative compaction. 3. Street Zone: Backfill in street zone in paved areas - -95% relative compaction. 4. Foundation Stabilization: Rock refill materials for foundation stabilization - -
90% relative density. 5. Overexcavation: Rock refill for overexcavation - - 90% relative density. 6. Material Testing: All imported or native materials shall be tested before the start
of compaction operations to determine the moisture density relationships. Variation on imported or native earth materials may require a number of base curves of the moisture-density relationship.
7. Testing Intervals: Unless noted otherwise, compaction tests shall be performed at
random depths and at 100-foot intervals, and as directed by the City’s Representative.
C. Materials Replacement
Trenching and backfilling material which does not meet the specifications shall be removed and replaced at no additional expense to the City.
D. Sheeting, Shoring, and Bracing of Trenches Trenches shall have sheeting, shoring, and bracing conforming to CAL/OSHA requirements and General Provisions. Lateral pressures for design of trench sheeting, shoring, and bracing shall be based on type of soil exposed in the trench, groundwater
conditions, surcharge loads adjacent to the trench, and type of shoring what will be used in the trench. For preliminary design purposes, the following soil parameter values may be utilized for shoring designs; these may require modification to meet specific conditions at varying locations. Active Pressure Lateral Loading = 35 pounds per cubic foot equivalent fluid pressure Passive Pressure Lateral Resistance = 250 pounds per cubic foot equivalent fluid pressure Friction Coefficient = 0.35 Plans for shoring and bracing should be provided as a part of the plan submittal and should be reviewed by the geotechnical consultant and civil engineer.
E. Grade Trenches shall be excavated to the lines and grades shown on the drawings with allowance for pipe thickness and for pipe base. If the trench is excavated below the required grade, the portion of the trench excavated below the grade shall be refilled with refill materials at no additional cost to the City. The refill material shall be placed over the full width of trench in compacted layers not exceeding 6-inches deep to the required grade with allowance for the pipe base. Hard spots that would prevent a uniform thickness of pipe base shall be checked with a straight edge and any irregularities corrected. The trench bottom shall form a continuous and uniform bearing and support for the pipe at every point.
F. Pipe Base Thickness
Thickness of the pipe base shall be as shown on the drawings or as otherwise described in the specifications for the particular type of pipe installed, but in no cases shall the thickness be less than 4 – inches.
G. Dewatering
1. Means and Devices: Suitable means and devices shall be provided and maintained to continuously remove and dispose of all water entering the trench excavation during the time the trench is being prepared for the pipe laying, during the laying of the pipe, and until the backfill at the pipe zone has been completed. These provisions shall apply during the noon hour as well as overnight. Water shall be disposed of in a manner to prevent damage to adjacent property. Trench water shall not be drained through the pipeline under construction. Groundwater shall not be allowed to rise around the pipe until jointing compound has firmly set.
2. Notification: The City shall be notified 48 hours prior to commencement of
dewatering. The contractor is responsible for obtaining and complying with NPDES dewatering permits, as required.
H. Storage of Excavated Material During trench excavation, excavated material shall be stored only within the working
area. Roadways or streets shall not be obstructed. The safe loading of trenches with excavated material shall conform to federal, state, and local codes.
I. Length of Open Trench
The length of open trench shall be limited to 200 feet in advance of pipe laying or amount of pipe installed in one working day. Backfilling and temporary or first layer paving shall be completed so that not more than 200 feet of trench is open in the rear of pipe laying. Sidewalks, driveways and other traveled ways shall be backfilled or adequately bridged to provide safe access and egress at the completion of each days work.
J. Foundation Stabilization After the required excavation has been completed, the City Representative shall inspect
the exposed trench subgrade to determine the need for any additional excavation. It is the intent that additional excavation shall be conducted in all areas within the influences of the pipeline where unacceptable materials exist at the exposed subgrade. Overexcavation shall include the removal of all such unacceptable material that exists directly beneath the pipe base and to the depth required. The presence of unacceptable material may require excavating a wider trench. The width and depth of known areas to be overexcavated shall be shown on the drawings. The overexcavated portion of the trench shall be backfilled to the subgrade of the pipe base with refill material for foundation stabilization. Foundation stabilization material shall be place over the full width of the excavation and compacted in layers not exceeding 6-inches in depth, to the required grade.
K. Trench Backfilling and Compaction 1. General: Trench backfill shall conform to the following requirements.
2. Pipe Base: The specified thickness of pipe base material shall be place over the full width of trench. The top of the pipe base shall be graded ahead of the pipe laying to provide firm, uniform support along the full length of pipe.
3. Pipe Zone: After the pipe has been bedded, pipe zone material shall be placed
simultaneously on both sides of the pipe, keeping the level of backfill the same on each side. Material shall be carefully placed around the pipe so that the pipe barrel is completely supported and that no voids or uncompacted areas are left beneath the pipe. Particular care shall be taken in placing material on the underside of the pipe to prevent lateral movement during subsequent backfilling. Material placed within the pipe zone shall be compacted by hand tamping only.
4. Trench Zone: Backfill material shall be carefully deposited onto the backfill previously placed in the pipe zone. Free fall of the material shall not be permitted until at least 2 feet of cover is provided over the top of the pipe. Sharp, heavy pieces of material shall not be dropped directly into the pipe of the tamped material around the pipe.
5. Trench Backfill: Trench backfill shall be compacted to the specified relative
compaction. Compaction shall be performed by using mechanical compaction of hand tamping equipment. Unless specified otherwise, consolidation by jetting or flooding shall not be permitted. High impact hammer-type equipment shall not be used except where the pipe manufacturer warrants in writing that such use will not damage the pipe.
6. Equipment: Axle-driven or tractor-drawn compaction equipment shall not be
used within 5 feet of walls and structures. 7. Street Zone Backfill: Street zone backfill shall be done in accordance with the
requirement and to the satisfaction of the City. 8. Pavement Zone: The pavement shall be replaced in kind, consisting of 4 to 7
inches full depth asphalt concrete.
L. Import or Export of Backfill Material
1. Excess Material: Excess excavated soil material shall be removed and disposed of off the project site at no additional expense to the City. Excess soil material shall be disposed of in accordance with local regulations.
2. Imported Material: Any additional backfill material necessary to return all grades
to plus or minus 0.2 feet form the grade encountered at the beginning of construction or as shown on the contract drawings shall be imported, placed, and compacted at no additional cost to the City.
M. Moisture Content of Backfill Material During the compacting operations, the optimum moisture content required for
compaction purposes shall be maintained in each lift of the backfill material. Moisture content throughout the lift shall be maintained at a uniform level. If placement is discontinued and proper moisture content not maintained, the upper layer shall be brought back to proper moisture content by sprinkling, cultivating and rolling the backfill material before placing new material. At the time of compaction, the water content of the material shall be at optimum water content to plus two percentage points. Material which contains excessive moisture shall not be worked to obtain the required compaction. Material having excessive moisture content may be dried by blading, discing, or harrowing to hasten the drying process.
APPENDIX F
SLOPE STABILITY ANALYSIS
APPENDIX F
ENGINEERING STABILITY ANALYSES
GENERAL Engineering stability analyses were performed to assess the minimum Factors of Safety (FS) against future movement of the slope located within the subject property. The analyses were performed with the actual geologic conditions. The “GSTABL7” slope stability program (developed by Gary H. Gregory, P.E. of Gregory Geotechnical Software) in conjunction with STEDwin (a graphical User Interface developed by Harald W. Van Aller, P.E.) were utilized for the stability analyses of the slope mass. The computer program utilizes the limit equilibrium theory for the calculation of the minimum Factory of Safety (FS). SHEAR STRENGTH PARAMETERS The shear strength parameters utilized in our stability analyses are presented in Table F-1, below. These values were based on local experience in similar soils and engineering judgment, upon laboratory testing performed herein and laboratory test results summarized by Bagahi Engineering, Inc., and are considered reasonable and representative of the on-site materials.
TABLE F-1 SUMMARY OF STRENGTH PARAMETERS
Pseudostatic &
Static Condition Material Type
Bulk Densityγm (pcf)
Bulk Densityγs (pcf) Cohesion
c (psf)
Friction Angle φ (deg)
Fill – Af Montery Formation Bedrock – Tm - Across Bedding Montery Formation Bedrock – Tm - Along Bedding
120
120
120
125
125
125
0
450 0
32
40
18
ANALYSES Slope stability analyses were performed for the slope located within the property using Cross Section A-A’. Based on our analyses, we recommend that a pier system providing a resisting lateral force of 2,000 lbs per lineal foot be constructed at the site. The piers should extend a minimum of 20 feet below proposed subgrade (10 feet minimum into bedrock). Analyses were made with the proposed grades. The required factors of safety (FS) were achieved with the inclusion of the pier system. The Factor of Safety (FS) criteria adopted for verifying the adequacy of the stability of the slope for the final design are as follows: Static Conditions – FS>1.5 Pseudostatic Conditions – FS>1.1
Assumed Lateral Force (Seismic) – 0.15g The results of the analyses are presented in Table F-2 and Figures F-1 to F-3. Any revisions to the grading plans may require additional analyses and revisions to the recommendations presented herein.
TABLE F-2 SUMMARY OF STABILITY ANALYSES
Section Static FOS
Seismic FOS
File name
Figure No. Comments
A-A’ 1.42
0.86
71284es1
71284ep1
F-1.1
F-1.2 Block mode. Existing Grades.
A-A’ 1.46
0.87
71284ps1
71284pp1
F-2.1
F-2.2 Block mode. Proposed Grades.
A-A’ 1.53
1.11
71478-1
71478-1s
F-3.1
F-3.2
Block mode. The analyses were made with the inclusion of a pier system, extend a minimum of 20 feet below proposed subgrade (10 feet minimum into bedrock), providing a resisting lateral force of 13,000 lbs per lineal foot.
