HomeMy WebLinkAbout; Chinquapin Lift Station; Chinquapin Lift Station; 1999-05-21i KLEINFELDER
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A report prepared for:
Carlsbad Municipal Water District
5950 El Camino Real
Carlsbad, California 92008
Attn: Mr. Randy Klaahsen, Associate Engineer
LIMITED SOILS EXPLORATION
CHINQUAPIN LIFT STATION
CARLSBAD, CALIFORNIA
Kleinfelder Job No. 51-521902
Prepared by:
Kevin R. Wells
Staff Engineer
KLEINFELDER, INC.
5015ShorehamPlace
San Diego, California 92122
(619)320-2000
May 21, 1999
Rick E. Larson
Senior Engineer
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TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1
2.0 PROJECT DESCRIPTION 2
3.0 FIELD EXPLORATION 3
4.0 LABORATORY TESTING 4
5.0 SUBSURFACE CONDITIONS 5
6.0 CONCLUSIONS 6
7.0 RECOMMENDATIONS 7
7.1 SITE PREPARATION AND EARTHWORK 7
7.1.1 Subgrade Preparation 7
7.1.2 Subgrade Preparation - Below Grade Structures 7
7.1.3 Remedial Grading Requirements 8
7.2 REVIEW OF PROPOSED PAVEMENTS/PAVEMENT SUBGRADE
PREPARATION 8
7.3 CONSTRUCTION DEWATERING 9
7.4 EXCAVATIONS 10
7.4.1 Excavations and Stability 10
7.4.2 Buried Vault and Wetwell Excavation 11
7.4.3 Pipe Bedding for Utilities 11
7.4.4 Backfill 12
7.5 SHORING '. 12
7.5.1 General 12
7.5.2 Lagging 12
7.5.3 Active Earth Pressures 13
7.5.4 Surcharge Pressures 13
7.5.5 Lateral Resistance 13
7.5.6 Estimated Lateral Displacements 14
7.6 BUILDING FOUNDATIONS AND FLOOR SLABS 14
7.6.1 Wetwell and Utility Vault Foundations and Floor Slabs 14
7.6.2 Generator Enclosure Foundation and Floor Slab 15
7.6.3 Exterior Slabs 16
7.6.4 Foundations for Free Standing Posts 16
7.7 UNIFORM BUILDING CODE SEISMIC DESIGN PARAMETERS 16
7.8 LATERAL EARTH PRESSURES 17
7.8.1 Lateral Earth Pressures for Utility Vault and Wetwell 17
7.8.2 Lateral Earth Pressures for Above-Grade Retaining Walls 17
7.9 BURIED UTILITY PIPE SOIL PARAMETERS 19
8.0 LIMITATIONS 20
IP*
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TABLE OF CONTENTS (continued)
P, FIGURES
fa*Figure 1 - Vicinity Map
r Figure 2 - Boring Location Plan
APPENDICES
ry Appendix A - Boring Logs
Appendix B - Laboratory Testing
Appendix C - Suggested Guidelines for Earthwork ConstructionCAppendix D - ASFE Insert
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2.0 PROJECT DESCRIPTION
*-< We understand that the project will consists of a new lift station to be developed at an
unimproved site located at the west end of Chinquapin Avenue, adjacent to Carlsbad Boulevard.
*•« The new lift station will include an at-grade electrical generator enclosure (12 feet by 14 feet in
—« plan area), a valve and meter vault (10 feet deep and 8 feet by 8 feet in plan area), and a wetwell
— (16 feet deep and 8 feet in diameter). In addition, a new concrete driveway, paved parking, and
I-* associated hardscaped areas will be incorporated into the project.
«"• We anticipate that the generator enclosure will be constructed of cast-in-place concrete or
*" reinforced masonry block retaining walls set against an existing hillside in the northern part of
** the site. Wetwell and vault structures are expected to have sidewalls constructed of cast-in-place
ta concrete that are tied into a conventional slab-on-grade designs. The proposed finished grade
f elevation for the project is expected to be at an approximate elevation of 24 feet to 25 feet MSL.
The majority of the proposed plan area is relatively flat. An existing hillside, sloping downward
f into the proposed site area, exists within the northern edge of the site.
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3.0 FIELD EXPLORATION
M A single test boring was completed at the approximate location shown on Figure 2. We had
.-, intended to complete the boring to a depth of approximately 25 feet below the existing ground
— surface, but we encountered effective auger refusal at a depth of 14 feet in both locations we
_ attempted to drill. The test boring was advanced using an Ingersoll-Rand A-300 truck-mounted
*M drill equipped with an 8-inch hollow-stem auger. Soil samples were obtained at nominal 5-foot
•* intervals with a 3-inch outside diameter California sampler. The California sampler was lined
*«" with 2.5-inch diameter brass sleeves. The sampler was driven 18 inches using a 140-pound
m» hammer falling 30 inches.
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f» The number of blows required to drive each 6-inch increment was recorded, and the blow counts
^ for each foot of drive is reported on the boring log. In addition to the blow counts, the boring log
p» describes the earth materials encountered. The boundaries between soil layers shown on the log
•* are approximate because the transitions between different soil layers are likely to be gradual.
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I 4.0 LABORATORY TESTING
H The geotechnical laboratory program included tests for gradation, moisture content, and dry unit
_ weight. The gradation test results are included in Appendix B; the moisture content and unit
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weight test results are also included in Appendix B.
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5.0 SUBSURFACE CONDITIONS
AH The subsurface conditions encountered during our field exploration consisted of medium dense
p to dense, medium to coarse grained silty sands (SM) within the upper ten feet of subgrade.
Itf Below ten feet the subgrade primarily consists of dense, relatively clean, coarse-grained sands
(SP). These soils represent the dense to very dense terrace deposits exposed along the shore.
Effective auger refusal was encountered in very dense terrace deposits at 14 feet of drilling
depth. An identical refusal depth was achieved in a subsequent exploratory boring. We
anticipate these terrace deposits may be partially cemented to some degree.
No groundwater was encountered within 14 feet of the ground surface at the boring location.
However, based on known elevations of the local water table, we anticipate that the local
groundwater table should be at or below a depth of 18 feet (6 feet MSL), which is about 2 feet
below the bottom of the wetwell. If groundwater is encountered at a higher elevation, we
anticipate that it will likely be a light seepage from a localized strata within the terrace deposit.
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6.0 CONCLUSIONS
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if Based on limited exploration, the site appears generally suitable for the proposed projects from a
geotechnical standpoint. The project can be supported on conventional foundations and floor
slabs. The only anticipated impact to the construction of the project may be that the terrace
deposits found below a depth of 14 feet have the potential for difficult excavation. Use of a
jackhammer to break cemented portions of the terrace deposits may be required.
If seepage is encountered in the bottom of the deeper excavations, we anticipate that the flows
will be low enough for use of conventional sumping. The bottom of the excavation is expected
to be founded in material that should not lose any significant stability if seepage is encountered.
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7.0 RECOMMENDATIONS
7.1 SITE PREPARATION AND EARTHWORK
Prior to site preparation, all surficial organic material and debris should be removed in general
accordance with the recommendations presented in Appendix C.
7.1.1 Subgrade Preparation
Subgrade preparation for the generator enclosure may be achieved by scarifying the top six
P inches of subgrade underlying the generator slab. Scarified soils should then be moisture
conditioned to within 1 percent below to 3 percent above optimum moisture content and
^* compacted to at least 90 percent of ASTM D1557. Any material encountered larger than 3
IM inches in diameter should be removed. Wall/retaining wall footings enclosing the generator pad
P may be excavated into the existing native subgrade without further improvement provided that
the excavated footing subgrade meets minimum bearing requirements. A Kleinfelder staff
P representative should be attained by the Contractor for inspection of the excavated footings.
P 7.1.2 Subgrade Preparation — Below Grade Structures
„, Foundation subgrades for below-grade structures (i.e., wetwell and utility vault) will not require
to any improvement to undisturbed soils immediately underlying the subgrade for footings and
P* concrete slab support. Subgrades for these structures should be excavated to proposed footing
to and slab elevations with little or no disturbance to the underlying native soil conditions. Any
p. excavation below these elevations should be recompacted with on-site soils in general
*• accordance with the recommendations contained in Appendix C. However, if groundwater is
resent that will not allow construction of a firm, stable foundation bottom, then the underlying
soils should be overexcavated to a depth of 18 inches below the foundation level. This 18 inches
of additional removal should be replaced with 3/4-inch crushed drain rock (5% maximum
passing the No. 4 sieve). The drain rock should be placed in two 9-inch thick lifts. Each lift
should be compacted with 3 passes of a vibratory baseplate compactor to seat the drain rock.
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7.1.3 Remedial Grading Requirements
Existing subgrades to receive fill should be scarified to a depth of 6 inches and recompacted to
90 percent of ASTM D1557. All subsequent placement of engineered fill should be placed in
loose horizontal lifts no greater than eight inches in thickness, moisture conditioned between 1
percent above to 3 percent above optimum moisture content, and compacted to a minimum of 90
t* percent relative compaction. The exposed faces of fill slopes should be constructed at a slope of 2
horizontal to 1 vertical or flatter. Free standing permanent cut slopes should be cut back at a slope
f* of 2 horizontal to 1 vertical, or flatter. Steeper cut slopes may require construction of retaining
walls and/or a specific case-by-case slope stability analysis.
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L When properly moisture conditioned, the on-site soils can be used as engineered fill. If import fill is
^ required, we recommend that it be a granular soil meeting the following requirements:
f* Liquid Limit: Less than 30
Plasticity Index: Less than or equal to 15
i Percent passing No. 200 sieve: Less than 30
b Maximum particle dimension: Less than three inches
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Proposed import fill should be submitted to the geotechnical engineer for review and testing to
verify conformance to these requirements. All imported fill should be compacted to the general
recommendations provided for engineered fill.
All site preparation and fill placement should be observed and tested by a representative of our firm.
This is especially true during the scarification process so that we cai
undesirable material or conditions are encountered in the construction area.
I This is especially true during the scarification process so that we can observe whether anyIw
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7.2 REVIEW OF PROPOSED PAVEMENTS/PAVEMENT SUBGRADE PREPARATION*»
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** The proposed pavement sections (4-inch asphaltic concrete over 6 inches Class 2 aggregate base
P as referenced in the Construction Plans for the Chinquapin Sewer Lift Station - Sheet No. 7)
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should be adequate to support wheel loads for driveway and parking areas provided that
subgrade soil are consistent with what we encountered in our test boring.
Pavement subgrades founded on native material or engineered fill soils should be processed to a
depth of 6 inches below grade and should consist of soils exhibiting a low expansion potential.
Subsequent compaction of subgrade soils should be placed in lifts no greater than eight-inch
uniform loose thickness and compacted to a minimum of 95 percent of ASTM D1557 maximum
dry density at a moisture content of 1 percent below to 3 percent above optimum.
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Asphalt concrete pavement and aggregate base materials used should conform to Section 02510,
IP Parts 2 and 3 of the standard specification referred in Section 1.4 of the Standard Specifications
for Construction of Public Works (Green Book), current edition.
7.3 CONSTRUCTION DEWATERING
Based on the information provided, the maximum depth of excavation for the wetwell is
I expected to be about 16 feet. Since we anticipate groundwater will be at or below a depth of 18
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feet we do not expect that groundwater should be a significant issue. Excavations which extend
i near or below the site groundwater level (currently estimated to be at approximately 18 feet to 19
feet below existing grade, but subject to future variations) may need to be dewatered in order to
f" . .i maintain the stability of the excavation bottom. If at the time of excavation of below-grade
structures the stability of the excavated bottom is compromised, groundwater levels should be
IP*f 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
f*»| completed to an elevation of at least five feet above the pre-dewatering elevation.
Analysis of contractor dewatering needs or the design of contractor dewatering systems were not
within the scope of our services. This work is best accomplished by a competent dewatering
contractor. However, we have included some discussions of potential dewatering methods in the
following paragraphs.
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The most common method of dewatering used in the removal of nuisance seepage water from
terrace deposits/formations is conventional sump pumping. 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, the presence of potential seepage zones which will pipe water from distant sources after
the groundwater table is lowered, and cost.
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.
L 7.4 EXCAVATIONS
i 7.4.1 Excavations and Stability
IP* All excavation work should comply with the current requirements of OSHA. The onsite soils are
•» generally classified as the Type B soils for evaluating OSHA sloping or shoring requirements.
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*• All discussion in this section regarding stable excavation slopes assumes minimal equipment
f« vibration and adequate setback of excavated materials and construction equipment from the
•* foundation excavation. We recommend the minimum setback distance from the near edge of he
excavation be equivalent to the adjacent excavation depth. If excavated materials are stockpiled
adjacent to the excavation, the weight of this material should be considered as a surcharge load
f* for lateral earth pressure calculations. Configuration values presented in the OSHA regulations
I** assume that the soils in the cut face do not change in moisture content significantly. Slope
f" 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.
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7.4.2 Buried Vault and Wetwell Excavation
Excavations made below a depth of 14 feet may be difficult for light to medium backhoes and
may require jacking or ripping. If wet or unstable subgrade conditions are encountered at the
bottom of the excavation, we recommend the bottom of the vault or wetwell area be
overexcavated by at least 18 inches below the design elevation of the bottom of the structure.
P The bottom of the excavation should then be cleaned of any loose debris and backfilled with
3/4-inch crushed aggregate drain rock as described earlier. The 3/4-inch drain rock should be
P placed in two 9-inch thick loose lifts and compacted with three passes of a vibratory base plate
compactor. The vibrating compactor should have a minimum weight of 200 pounds and a
P minimum vibrating frequency of 1,600 cycles per minute. The initial lift may be increased to 12
inches if "pumping" of the aggregate base occurs during initial compaction.
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7.4.3 Pipe Bedding for Utilities
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i» Granular pipe bedding should be sand, gravel, or crushed aggregate with a sand equivalent of not
p. less than 30. Onsite materials are generally too silty to meet this requirement. Bedding should be
i* extended the full width of the trench to one foot above the top of the pipe. The pipe bedding should
pi be densified to 90 percent relative compaction prior to backfilling. Densification of pipe bedding
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^ can be accomplished by either jetting with water or by mechanical compaction. If water jetting is
P» permitted, the size and length of jet pipe, quantities of water, and jetting locations should be
•• established in the field at the time of construction and should be sufficient to thoroughly saturate
P» and densify the bedding material around the pipe. Jetting should be accomplished by use of a jet
•* pipe (1-1/2 inch minimum diameter pipe) to which a minimum 2-inch diameter hose is attached
f» carrying a continuous supply of water under pressure. The bedding should be allowed to drain
•* thoroughly until the surface of the bedding is in a firm and unyielding condition prior to
commencement of any subsequent improvements. The specifications should require the contractor
to provide an sump and pump to remove any accumulated water which remains. Compaction of the
pipe bedding by mechanical means is acceptable provided the specifications require compacting
with pneumatic "powder puffs" and periodic density testing (which will require the contractor to
provide special excavation for access and shoring).
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7.4.4 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
f" within deep excavations without allowing them to dry out. If imported backfill is required, we
•w recommend that it meet the following requirements:
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Liquid Limit: Less than 30%
** Plasticity Index: Less than or equal to 15%
to Percent Soil Passing No. 200 Sieve: Less than 30%
f" Maximum Particle Dimension: Less than 3 inches
UBC Expansion Index: Less than 30
r Soluble Sulfates: Less than 0.10%
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P Trench backfill should be placed in uniform layers not exceeding 8 inches in loose thickness,
moisture conditioned to within two percentage points of optimum, and mechanically compacted.
f* The relative compaction should be to at least 90 percent.
f 7.5 SHORING
IP* 7.5.1 General
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Shoring may be required where space or other restrictions do not allow a sloped embankment. ArL conventional shoring system consisting of closely spaced soldier piles or sheet piles may be
used.
7.5.2 Lagging
f*L Timber lagging may be used between the soldier piles to support loose or soft soils. If lagging is to
f™ 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 wallc
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drainage (such as the use of prefabricated composite drain) may be required where this type of
construction is used.
7.5.3 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.
7.5.4 Surcharge Pressures
_. Thirty percent of any area surcharge placed adjacent to the shoring may be assumed to act as a
L uniform horizontal pressure against the shoring. Special cases such as combinations of sloping and
p» shoring or other surcharge loads (not specified above) may require an increase in the design values
ii» recommended above. These conditions should be evaluated by the project geotechnical engineer on
p. a case-by-case basis.
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P. 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.
P» 7.5.5 Lateral Resistance
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All soldier or sheet piles should extend to a sufficient depth below the excavation bottom torL 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 groundwater table. To account for three-
dimensional effects, the passive pressure may be assumed to act on an area two times the width
of the embedded portion of the pile, provided adjacent piles are spaced at least three diameters,
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center-to-center. Additionally, we recommend a factor of safety of 1.2 to be applied to the
calculated embedment depth and that the passive pressure be limited to 2,500 psf.
Alternatively, lateral capacity of a soldier pile extending below the excavation bottom may be
evaluated using the "Pole Formula" given in Section 1806.8 of the Uniform Building Code, 1997
edition. For this method, we recommend a lateral soil bearing pressure of 150 pounds per square
foot of embedment may be used to estimate the required embedment depth. The 100 percent
increase allowed by the Code for isolated poles (which are not adversely affected by a 1/2 inch
horizontal deflection at the ground surface due to short-term lateral loads) may be used.
7.5.6 Estimated Lateral Displacements
f* 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
f" with projects with similar shoring requirements, we anticipate maximum lateral movement of the
shoring system should generally be less than two inches.
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7.6 BUILDING FOUNDATIONS AND FLOOR SLABS
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J*» 7.6.1 Wetwell and Utility Vault Foundations and Floor Slabs
1 Conventional spread footings supported on native soils compacted as recommended in Section
7.3.2 can be sized using a nominal bearing pressure of 2,000 psf. This value may be increasedr[ 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.
i Unless the average applied load of the structure exceeds the weight of the displaced soil
significantly, we do not anticipate static settlement in excess of 1/2 to one inch. We recommend
that the footings be provided with at least minimal reinforcement consisting of four No. 4
reinforcing bars, two placed at the top and two at the bottom.
Resistance to lateral loads on foundation footings may be calculated using a passive equivalent
fluid unit weight of 250 pcf and a coefficient of friction of 0.35. Uplift resistance may be
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calculated using the dead weight of the structure plus the friction along the walls of the structure.
An average value of 500 psf can be used to calculate frictional resistance to uplift. In actuality,
the frictional resistance increases in a triangular fashion with depth to a critical point below
which the frictional resistance is assumed to be constant. However, for general design purposes,
the recommended average value can be used regardless of depth. The surface area of the upper
two feet of the structure should be neglected in these calculations. ,
We recommend the concrete floor slabs for buried structures be at least five inches thick and be
?*jy 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
L supercede the reinforcement requirements calculated by the structural engineer.
^ 7.6.2 Generator Enclosure Foundation and Floor Slab
', Conventional shallow spread footings may be used to support the intended foundation loads.
Footings and sidewalls for the north and east sides of the enclosure are expected to be of
F* retaining wall type. Footings may be designed for support upon engineered fill using an
allowable soil contact pressure of 2,000 pounds per square foot for dead load plus normal live
j load. This value may be increased by one third for seismic or wind loads. Resistance to lateral
forces may be computed using lateral bearing and lateral sliding combined. Lateral bearing may
| be computed as 150 pounds per square foot per foot of depth below natural grade. Lateral
sliding resistance can be obtained by multiplying 0.35 by the dead load.
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All footings should be trenched at least 12 inches below the lowest adjacent finished grade and
i should be a minimum of 1 foot in width. Reinforcement steel requirements for foundations
should be designed by the structural engineer. As a minimum, we recommend that continuous
[ footing reinforcement consist of at least two No. 4 bars placed at the top and two placed at the
bottom of the foundation. These reinforcement guidelines should not supersede the•»-»
[ reinforcement requirements calculated by the structural engineer.
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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.
The floor slab for the generator enclosure should be prepared in accordance with the
recommendations presented in Section 7.5.3.
y 7.6.3 Exterior Slabs
P Exterior concrete non-vehicular hardscape areas supported on select soil, as specified earlier in
this report, should be at least 5 inches thick and reinforced with No. 3 rebars at 18-inch spacing
f" in both directions. To reduce the effects of cracking, we recommend that expansion relief joints
be placed at maximum distances of approximately 15 feet in both directions in large sections
f" (such as courtyards), and every 5 feet for narrow sections (such as sidewalks). Use of a slab
h.underlay, as described above for interior slabs, would only be required if moisture-sensitive slab
I treatments are used.
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| 7.6.4 Foundations for Free Standing Posts
P« Construction employing posts or poles as columns embedded in earth or embedded in concrete
** footings in the earth to resist both axial and lateral loads (such as for light standards) can be
P" designed in general accordance with Section 1806.8 of the Uniform Building Code. However, we
l- recommend that a lateral soil-bearing pressure of 200 psf per foot of depth below natural grade be
p« used for parameter Si and 83 rather than one of the values given in Table 18-I-A. An allowable soil-
** bearing pressure of 2,500 psf may be used to support vertical loads.
^ 7.7 UNIFORM BUILDING CODE SEISMIC DESIGN PARAMETERS
^ Since this site is located in the seismically active Southern California region, we recommend
that, as a minimum, the proposed development be designed in accordance with the requirements
^ of the latest (1997) edition of the Uniform Building Code (UBC) for Seismic Zone 4. We
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recommend that a soil profile factor of SD be used with the UBC design procedure (Table 16-J).
Near source seismic coefficients for acceleration and velocity, Na=1.0 and Nv=l.l (UBC Tables
16-S and 16-T), should be used in design.
7.8 LATERAL EARTH PRESSURES
7.8.1 Lateral Earth Pressures for Utility Vault and WetwellL
_ Lateral earth pressures acting against buried walls can be calculated assuming that the retained
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IH soils act as a fluid. The equivalent fluid weight (efw) for walls which are restrained at the top or
p. are sensitive to movement and tilting should be designed for the at-rest efw. If on-site or
L imported non-expansive sandy soils with a Unified Soil Classification of SP, SM, or SC are used
p. as backfill, an at-rest efw value of 60 pcf can be used above the water table and 90 pcf below the
in water table (if encountered).
c«
*• Fifty and thirty percent of any uniform area surcharge placed at the top of the wall may be
_ assumed to act as a uniform horizontal pressure over the entire wall. We should be contactedi
*• 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 13H2 where H is the height of the wall (in feet) above its
P» 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.
r*
i
•* 7.8.2 Lateral Earth Pressures for Above-Grade Retaining Walls
For planning purposes, the following lateral earth pressures values for. level or sloping backfill
are provided for walls backfilled with drainage materials and imported nonexpansive soils.
51-52190275119R258.doc Pagel7of20 May 21, 1999
Copyright 1999 Kleinfelder, Inc.
KLEINFELDER
EQUIVALENT FLUID WEIGHT (pcf)
E
r
E
r
c
L
f*I
Conditions
Active
At-Rest
Passive (Fill Soils)
Passive
(Formational Materials)
'"'•"<' LeveP-'
35
55
300
(Maximum of 3 ksf)
400
(Maximum of 3 ksf)
2:1 Slope
50
70
150*
200*
3:1 Slope
45
65
200*
300*
Passive values for slope conditions are for a descending (sloping down) slope condition.
Unrestrained (yielding) cantilever walls should be designed for an active equivalent fluid weight
value provided above. In the design of restrained (nonyielding) walls where the top of the wall is
not expected to move laterally more than 0.001H, (where H is the unbalanced wall height), the
at-rest pressures should be used. The above values assume nonexpansive backfill and free-
draining conditions. The native silty sands should be suitable for wall backfill provided they
meet the general backfill requirements presented in Section 7.1.3.
All retaining wall structures should be provided with appropriate drainage. Since the design
retaining walls are to enclose the generator slab area, drainage design may incorporate the use of
a manufactured drain panel behind the retaining wall in addition to normal waterproofing. This
system generally consists of a drain panel lined with filter fabric. At the wall base, we
recommend that a minimum of the bottom 24 inches of the drain panel and the gravel
surrounding the perforated PVC drain be wrapped in filter cloth (Mirafi 140N or equivalent).
The pipe should be surrounded by approximately two cubic feet of clean gravel per foot of wall
length. The pipe should be sloped to drain to a suitable outlet or cleanouts should be provided at
appropriate intervals.
C Wall backfill should be compacted by mechanical methods to at least 90 percent relative
compaction in accordance with ASTM D1557.
L
C
Retaining walls that incorporate slab-on-grade support for the general enclosure may be designed
for support upon engineered fill using an allowable soil contact pressure of 2,000 pound per
square foot for dead load plus normal live load. This value may be increased by one third for
51-521902/5119R258.doc
Copyright 1999 Kleinfelder, Inc.
Page 18 of 20 May 21, 1999
pL
E
1
KLEINFELDER
seismic or wind loads. Resistance to lateral forces may be computed using lateral bearing and
lateral sliding combined. Lateral bearing may be computed as 150 pounds per square foot per
foot of depth below natural grade. Lateral sliding resistance can be obtained by multiplying 0.35
by the dead load.
i
E
E
C
p
Surcharge loading may be calculated according to the City of San Diego Building Inspection
Department Newsletter 23-3 or other equivalent methods. We should be contacted if unusual
surcharge loadings are anticipated. Wall footings should be designed in accordance with the
foundation design recommendations and reinforced in accordance with local codes and structure
considerations.
7.9 BURIED UTILITY PIPE SOIL PARAMETERS
We recommend the following soil parameters for use in buried utility pipe design:
Total soil unit weight, yt =
Modulus of soil reaction, E' =
HOpcf
1,000 psi for pipe provided with gravel bedding (4 inch
minimum thickness) and gravel pipe zone to one foot
over pipe.
400 psi where the pipe is constructed on native fill
without the gravel pipe zone and bedding.
L
C
C
C
E
51-52190275119R258.doc
Copyright 1999 Kleinfelder, Inc.
Page 19 of 20 May 21, 1999
KLEINFELDER
E
I
I
E
8.0 LIMITATIONS
Recommendations contained in this report are based on our literature research, field
observations, data from the field exploration, laboratory tests, and our present knowledge of the
proposed construction. It is possible that soil conditions could vary between or beyond the
points explored. If soil conditions are encountered during construction which differ from those
described herein, our firm should be notified immediately in order that a review may be made
and any supplemental recommendations provided.
P» 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.
f» 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
P* owner's own risk.
IH
*•• Our firm has prepared this report for the use of Carlsbad Municipal Water District, on this
•" project in substantial accordance with the generally accepted geotechnical engineering practice
•• as it exists in the site area at the time of our study. No warranty is made or intended. The
recommendations provided in this report are based on the assumption that an adequate program
F« of tests and observations will be conducted by our firm during the construction phase in order to
evaluate compliance with our recommendations.
This report may be used only by the client and only for the purposes stated, within a reasonable
^* time from its issuance. Land use, site conditions (both on-site and offsite) or other factors may
change over time, and additional work may be required with the passage of time. Based on the
^ intended use of the report, Kleinfelder may require that additional work be performed and that an
updated report be issued. Non-compliance with any of these requirements by the client or
f* anyone else will release Kleinfelder from any liability resulting from the use of this report by any
unauthorized party.
f*L
L 51-521902/5119R258.doc Page20of20 May 21, 1999
Copyright 1999 Kleinfelder, Inc.
pi
M
m
it
p
li
P
III
Pacific
Ocean
AGUA HEDIONDA
LAGOON
PALOMAR
COLLEGE
BLVD
APPROXIMATE GRAPHIC SCALE
(FEET)
VICINITY MAPKLEINFELDEU
CHINQUAPIN SEWER LIFT STATION
CARLSBAD MUNICIPAL WATER DISTRICT
CARLSBAD, CALIFORNIA
5015 SHOREHAM PLACE
SAN DIEGO, CALIFORNIA 92122
CHECKED BY:
DATE: . 5/20/99PROJECT NO. 51-4219-01
i i f i ii r i f i f i r i r i i i n 'i n ri rt
GENERATOR
ENCLOSURE METER AND
VALVE VAULT
LIFT STATION
WET WELL
Carlsbad Blvd.
100 200
APPROXIMATE GRAPHIC SCALE
(FEET)
LEGEND:
B1 APPROXIMATE BORING LOCATION
KLEINFELDER
5015 SHOREHAM PLACE
SAN DIEGO, CALIFORNIA 92122
CHECKED BY:: 5219SITE-1
PROJECT NO. 51-5219-01 [DATE: 5/20/99
SITE PLAN
CHINQUAPIN SEWER LIFT STATION
CARLSBAD MUNICIPAL WATER DISTRICT
CARLSBAD, CALIFORNIA
FIGURE
c
APPENDIX A
PROJECT NO.
51-5219-01 LOG OF BORING LEGEND SHEET 1 OF 1
DRILLINGEQUIPMENT PROJECT NAME
PUMP STATION - CHINQUAPIN SITE
LOCATION
TYPE OF BIT HAMMER DATA: WT.LBS. DROP INCHES SURFACE
ELEVATION
TOP OF CASING
ELEVATION
STARTED:
COMPLETED:
BACKFILLED:
DRILLING AGENCY
LOGGED BY
SURFACE CONDITIONS
GROUNDWATER
ELEVATION DATE
SOIL DESCRIPTION SAMPLE
NO.imo oo
NOTES
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-
FN: 5219LOG
WELL-GRADED GRAVELS AND GRAVEL-SAND
MIXTURES, LITTLE OR NO FINES
POORLY GRADED GRAVELS AND GRAVEL-SAND
MIXTURES, LITTLE OR NO FINES
SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES
CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES
WELL-GRADED SANDS AND GRAVELLY SANDS,
LITTLE OR NO FINES
POORLY GRADED SANDS AND GRAVELLY SANDS,
LITTLE OR NO FINES
SILTY SANDS, SAND-SILT MIXTURES
CLAYEY SANDS, SAND-CLAY MIXTURES
INORGANIC SILTS, VERY FINE SANDS, ROCK
FLOUR, SILTY OR CLAYEY FINE SANDS
INORGANIC CLAYS OF LOW TO MEDIUM
PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS,
SILTY CLAYS, LEAN CLAYS
ORGANIC SILTS AND ORGANIC SILTY CLAYS
OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS
FINE SANDS OR SILTS, ELASTIC SILTS
INORGANIC CLAYS OF HIGH PLASTICITY,
FAT CLAYS
ORGANIC CLAYS OF MEDIUM TO
HIGH PLASTICITY
PEAT, MUCK AND OTHER HIGHLY
ORGANIC SOILS
\7ATD WATER LEVEL AT TIME OF DRILLING
•= - WATER LEVEL MEASURED IN WELL
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
BENTONITE
CAVED
AREA
CEMENT
CONCRETE
NATURAL
BACKFILL
BENTONITE
PACKER
SAND
BACKFILL
SAND
VOLCLAY
GROUT
PIPE
SLOTTED
PIPE
CONTINUOUS
SAMPLER
GRAB
SAMPLE
CALIFORNIA
I SAMPLER
MODIFIED
CALIFORNIA
SAMPLER
NO
RECOVERY
PITCHER
SAMPLER
SHELBY
TUBE
SAMPLER
STANDARD
PENETRATION
SAMPLER
KLEINFELDER 5015 SHOREHAM PLACE
SAN DIEGO, CALIFORNIA 92122 FIGURE NO.A1
PROJECT NO.
51-5219-01 LOG OF BORING 1 SHEET 1 OF
DRILLINGEQUIPMENTIR A-300
PROJECT NAME
PUMP STATION - CHINQUAPIN SITE
LOCATION
SEE SITE PUN
TYPE OF BIT 8" HSA HAMMER DATA: WT. 1 40 LBS. DROP 30 INCHES SURFACE
ELEVATION -24.5'TOTAL DEPTH
OF HOLE 14'
STARTED: 4/27/99
COMPLETED: 4/27/99
BACKFILLED: 4/27/99
DRILLING AGENCY SCOTT'S DRILLING
LOGGED BY RMG
SURFACE CONDITIONS
BARE GOUND
GROUNDWATER
DEPTH DATE
OmI
-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-
FN: 5219LOG
LOG OF MATERIAL
SAMPLE
NO.m oo
LJ|
co 2:-:00
NOTES
SILTY SAND, brown, moist, dense, medium to
coarse grained
SM
52
Medium dense, medium grained 31
SAND, yellow brown, moist, dense, with trace
gravel, coarse grained
Hard drilling noted @ 13 ft. (grinding on auger)
SP 45
Bottom of borehole @ 14' (refusal)
No free water observed
No caving observed
Boring backfilled with soil cuttings
KLEINFELDER 5015 SHOREHAM PLACE
SAN DIEGO, CALIFORNIA 92122 FIGURE NO.: A2
KLEINFELDER
APPENDIX B
LABORATORY TESTING
Chinquapin Lift Station
Carlsbad, California
GENERAL
Laboratory tests were performed on selected, representative samples as an aid in classifying the
soils and to evaluate physical properties of the soils which may affect foundation design and
construction procedures. A description of the laboratory testing program is presented below.
MOISTURE AND DENSITY
Moisture content and dry unit weight tests were performed on a number of samples recovered
from the test borings. Moisture content and dry unit weight were evaluated in general
accordance with ASTM Test Methods D2216 and D2937, respectively. Results of these tests are
presented on the test boring logs in Appendix A.
SIEVE ANALYSES
Sieve analyses were performed on thirteen samples of the materials encountered at the site to
evaluate the gradation characteristics of the soils and to aid in their classification. Tests were
performed in general accordance with ASTM Test Method D422. Results of these tests are
presented on Figures Bl through B13.
51-521902/5119R258.doc PageB-1 May 21,1999
Copyright 1999 Kleinfelder, Inc.
KLEINFELDER
TABLE B-l
MOISTURE CONTENT AND DRY UNIT WEIGHT
ASTM D216 AND D2937
Sample
B1-1C
Description
Tan Silty Sand
Moisture (%)
13.9
Dry Density (pcf)
110.0
51-521902/5119R258.doc
Copyright 1999 Kleinfelder, Inc.
Page B-2 May 21,1999
PERCENT FINER BY WEIGHT |•
•
]
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS I HYDROMETER
6 4 3 2 1.5 1 3/4 1/23/8 3 4. 6 810 14 16 20 30 40 50 60 100140200
I I
\
!
-^
^\i
\
1
\
\
\
\
\
\
1
'
\\
\
\
\V.1
100 10 1 0.1 0.01
GRAIN SIZE IN MILLIMETERS
COBBLES GRAVEL
coarse fine
SAND
coarse medium fine SILT OR CLAY
Sample ID Depth
B1 8.0
Sample ID Depth
B1 8.0
Classification
BROWN, MEDIUM GRAINED SAND (SP-SM)
D100
4.75
D60
0.398
D30
0.258
••_• Kiel nfelder, Inc.
HdfH 5015 Shoreham Place
•>m-™ San Diego, CA 92122
Telephone: (619)320-2000
Fax: (619)320-2001
D10
0.152
LL PL
%Gravel %Sand
0.0 94.3
PI Cc
1.11
%Silt
0.001
Cu
2.63
%Clay
5.6
GRAIN SIZE DISTRIBUTION
CHINQUAPIN SEWER LIFT STATION FIGURE
CARLSBAD, CALIFORNIA _.
PROJECT NUMBER: 51-5219-02
KLEINFELDER
APPENDIX C
SUGGESTED GUIDELINES FOR EARTHWORK CONSTRUCTION
Chinquapin Lift Station
Carlsbad, California
1.0 GENERAL
1.1 Scope - The work done under these specifications shall include clearing,
stripping, removal of unsuitable material, excavation, installation of
subsurface drainage, preparation of natural soils, placement and compaction
of on-site and imported fill material, and placement and compaction of
pavement materials.
1.2 Contractor's Responsibility - A geotechnical investigation was performed for
the project by Kleinfelder and presented in a report dated May 21, 1999.
The Contractor shall attentively examine the site in such a manner that he
can correlate existing surface conditions with those presented in the
geotechnical investigation report. He shall satisfy himself that the quality
and quantity of exposed materials and subsurface soil or rock deposits have
been satisfactorily represented by the Geotechnical Engineer's report and
project drawings. Any discrepancy of prior knowledge to the Contractor or
that is revealed through his investigations shall be made known to the
Owner. It is the Contractor's responsibility to review the report prior to
construction. The selection of equipment for use on the project and the order
of work shall similarly be the Contractor's responsibility. The Contractor
shall be responsible for providing equipment capable of completing the
requirements included hi following sections.
1.3 Geotechnical Engineer - The work covered by these specifications shall be
observed and tested by Kleinfelder, the Geotechnical Engineer, who shall be
hired by the Owner. The Geotechnical Engineer will be present during the
51-521902/5119R258.doc
Copyright 1999 Kleinfelder, Inc.
PageC-1 May 21, 1999
KLEINFELDER
site preparation and grading to observe the work and to perform the tests
necessary to evaluate material quality and compaction. The Geotechnical
Engineer shall submit a report to the Owner, including a tabulation of tests
performed. The costs of retesting unsuitable work installed by the
Contractor shall be deducted by the Owner from the payments to the
Contractor.
1.4 Standard Specifications - Where referred to in these specifications, "Standard
Specifications" shall mean the current State of California Standard
Specifications for Public Works Construction, 1994 Edition, with Regional
Supplement Amendments.
1.5 Compaction Test Method - Where referred to herein, relative compaction
shall mean the in-place dry density of soil expressed as a percentage of the
maximum dry density of the same material, as determined by the ASTM
D1557 Compaction Test Procedure. Optimum moisture content shall mean
the moisture content at the maximum dry density determined above.
2.0 SITE PREPARATION
2.1 Clearing - Areas to be graded shall be cleared and grubbed of all vegetation
and debris. These materials shall be removed from the site by the
Contractor.
2.2 Stripping - Surface soils containing roots and organic matter shall be stripped
from areas to be graded and stockpiled or discarded as directed by the
Owner. In general, the depth of stripping of the topsoil will be
approximately 6 inches. Deeper stripping, where required to remove weak
soils or accumulations of organic matter, shall be performed when
determined necessary by the Geotechnical Engineer. Stripped material shall
be removed from the site or stockpiled at a location designated by the
51-521902/5119R258.doc Page C-2 May 21, 1999
Copyright 1999 Kleinfelder, Inc.
KLEINFELDER
Owner. Material should be evaluated for petroleum hydrocarbon impact.
After such analyses, the material should be handled as directed by the
regulating authority.
2.3 Removal of Debris- Any existing, trash and debris encountered in the areas
to be graded shall be removed prior to the placing of any compacted fill.
Portions of any existing fills that are suitable for use in new compacted fill
may be stockpiled for future use. All organic materials, topsoil, expansive
soils, oversized rock, or other unsuitable material shall be removed from the
site by the Contractor or disposed of at a location on-site, if so designated by
the Owner. Material should be evaluated for petroleum hydrocarbon impact
and handled as directed by the regulating authority after such evaluation.
2.4 Ground Surface - The ground surface exposed by stripping shall be scarified
to a depth of 6 inches, moisture conditioned to the proper moisture content
for compaction, and compacted as required for compacted fill. Ground
surface preparation shall be approved by the Geotechnical Engineer prior to
placing fill.
3.0 EXCAVATION
3.1 General - Excavations shall be made to the lines and grades indicated on the
plans.
The data presented in the Geotechnical Engineer's report is for information
only and the Contractor shall make his own interpretation with regard to the
methods and equipment necessary to perform the excavation and to obtain
material suitable for fill.
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
51 -521902/5119R258.doc Page C-3 May 21,1999
Copyright 1999 Kleinfelder, Inc.
KLEINFELDER
designated by the Geotechnical Engineer, provided the soils have been
evaluated for petroleum hydrocarbon impact, and such soil is handled in
accordance with the directions of the regulating authority.
3.3 Treatment of Exposed Surface - The ground surface exposed by excavation
shall be scarified to a depth of 6 inches, moisture conditioned to the proper
moisture content for compaction, and compacted as required for compacted
fill. Compaction shall be approved by the Geotechnical Engineer prior to
placing fill.
3.4 Rock Excavation - Where solid rock is encountered in areas to be excavated,
it shall be loosened and broken up so that no solid ribs, projections, or large
fragments will be within 6 inches of the surface of the final subgrade.
4.0 COMPACTED FILL
4.1 Materials - Fill material shall consist of suitable on-site or imported soil. All
materials used for structural fill shall be reasonably free of organic material,
have a liquid limit less than 30, a plasticity index less than 15, 100% passing
the 3 inch sieve and less than 30 percent passing the #200 sieve.
4.2 Placement - All fill materials shall be placed in layers of 8 inches or less in
loose thickness and uniformly moisture conditioned. Each lift should then
be compacted with a sheepsfoot roller or other approved compaction
equipment to at least 90 percent relative compaction in areas under
structures, utilities, roadways and parking areas, and to at least 85 percent in
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
51-521902/5119R258.doc Page C-4 May 21,1999
Copyright 1999 Kleinfelder, Inc.
** Ml KLEI NFELDERm
be conducted simultaneously with placement of fill. However, the methodm
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.m
4.5 Recompaction - When, in the judgment of the Geotechnical Engineer,
sufficient compactive effort has not been used, or where the field density
Pi
,y 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
pn
j^ shall be reworked and recompacted as needed to obtain a stable fill at the
required density and moisture content before additional fill is placed.P*
4.6 Responsibility - The Contractor shall be responsible for the maintenance and
M
• protection of all embankments and fills made during the contract period and
shall bear the expense of replacing any portion which has become displaced
ta due to carelessness, negligent work, or failure to take proper precautions.
ta 5.0 UTILITY TRENCH BEDDING AND BACKFILL
m 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
m shall be clean sand, gravel, crushed aggregate, or native free-draining
material, having a Sand Equivalent of not less than 30.
•
m Backfill should be classified as all material within the remainder of the
M trench. Backfill shall meet the requirements set forth in Section 4.1 for
_ compacted fill.
51-521902/5119R258.doc PageC-5 May 21, 1999
Copyright 1999 Kleinfeider, Inc.
KLEI NFELDER
V 5.2 Placement and Compaction - Pipe bedding shall be placed in layers not
exceeding 8 inches in loose thickness, conditioned to the proper moisture
p*content for compaction, and compacted to at least 90 percent relative
compaction. All other trench backfill shall be placed and compacted in
pi
accordance with Section 306-1.3.2 of the Standard Specifications forM V
Mechanically Compacted Backfill. Backfill shall be compacted as required
m
for adjacent fill. If not specified, backfill shall be compacted to at least 90
percent relative compaction in areas under structures, utilities, and concrete
m
flatwork, to 85 percent relative compaction in undeveloped areas, and at least
95 percent relative compaction under roadways and pavements.
51-521902/5119R258.doc PageC-6 May 21, 1999
Copyright 1999 Kleinfelder, Inc.
APPENDIX D
I
I IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL
ENGINEERING REPORT
As the client of a consulting geotechnical engineer, you
should know that site subsurface conditions cause more
construction problems than any other factor. ASFE/The
Association of Engineering Firms Practicing in the
Geosciences offers the following suggestions and
observations to help you manage your risks.
A GEOTECHNICAL ENGINEERING REPORT IS BASED
ON A UNIQUE SET OF PROJECT-SPECIFIC FACTORS
Your geotechnical engineering report is based on a
subsurface exploration plan designed to consider a
unique set of project-specific factors. These factors
typically include: the general nature of the structure
involved, its size, and configuration; the location of the
structure on the site; other improvements, such as
access roads, parking lots, and underground utilities;
and the additional risk created by scope-of-service
limitations imposed by the client. To help avoid costly
problems, ask your geotechnical engineer to evaluate
how factors that change subsequent to the date of the
report may affect the report's recommendations.
Unless your geotechnical engineer indicates otherwise,
do not use your geotechnical engineering report:
when the nature of the proposed structure is
changed, for example, if an office building will be
erected instead of a parking garage, or a refrigerated
warehouse will be built instead of an unrefrigerated
one;
when the size, elevation, or configuration of the
proposed structure is altered;
when the location or orientation of the proposed
structure is modified;
when there is a change of ownership; or
for application to an adjacent site.
Geotechnical engineers cannot accept responsibility for
problems that may occur if they are not consulted after
factors considered in their report's development have
changed.
SUBSURFACE CONDITIONS CAN CHANGE
A geotechnical engineering report is based on condi-
tions that existed at the time of subsurface exploration.
Do not base construction decisions on a geotechnical
engineering report whose adequacy may have been
affected by time. Speak with your geotechnical consult-
ant to learn if additional tests are advisable before
construction starts.Note, too, that additional tests may
be required when subsurface conditions are affected by
construction operations at or adjacent to the site, or by
natural events such as floods, earthquakes, or ground
water fluctuations. Keep your geotechnical consultant
apprised of any such events.
MOST GEOTECHNICAL FINDINGS ARE
PROFESSIONAL JUDGMENTS
Site exploration identifies actual subsurface conditions
only at those points where samples are taken. The data
were extrapolated by your geotechnical engineer who
then applied judgment to render an opinion about
overall subsurface conditions. The actual interface
between materials may be far more gradual or abrupt
than your report indicates. Actual conditions in areas
not sampled may differ from those predicted in your
report. While nothing can be done to prevent such
situations, you and your geotechnical engineer can work
together to help minimize their impact. Retaining your
geotechnical engineer to observe construction can be
particularly beneficial in this respect.
A REPORT'S RECOMMENDATIONS
CAN ONLY BE PRELIMINARY
The construction recommendations included in your
geotechnical engineer's report are preliminary, because
they must be based on the assumption that conditions
revealed through selective exploratory sampling are
indicative of actual conditions throughout a site.
Because actual subsurface conditions can be discerned
only during earthwork, you should retain your geo-
technical engineer to observe actual conditions and to
finalize recommendations. Only the geotechnical
engineer who prepared the report is fully familiar with
the background information needed to determine
whether or not the report's recommendations are valid
and whether or not the contractor is abiding by appli-
cable recommendations. The geotechnical engineer who
developed your report cannot assume responsibility or
liability for the adequacy of the report's recommenda-
tions if another party is retained to observe construction.
GEOTECHNICAL SERVICES ARE PERFORMED
FOR SPECIFIC PURPOSES AND PERSONS
Consulting geotechnical engineers prepare reports to
meet the specific needs of specific individuals. A report
prepared for a civil engineer may not be adequate for a
construction contractor or even another civil engineer.
Unless indicated otherwise, your geotechnical engineer
prepared your report expressly for you and expressly for
purposes you indicated. No one other than you should
apply this report for its intended purpose without first
conferring with the geotechnical engineer. No party
should apply this report for any purpose other than that
originally contemplated without first conferring with the
geotechnical engineer.
GEOENVIRONMENTAL CONCERNS
ARE NOT AT ISSUE
Your geotechnical engineering report is not likely to
relate any findings, conclusions, or recommendations
about the potential for hazardous materials existing at
the site. The equipment, techniques; and personnel
used to perform a geoenvironmental exploration differ
substantially from those applied in geotechnical
engineering. Contamination can create major risks. If
you have no information about the potential for your
site being contaminated, you are advised to speak with
your geotechnical consultant for information relating to
geoenvironmental issues.
A GEOTECHNICAL ENGINEERING REPORT IS
SUBJECT TO MISINTERPRETATION
Costly problems can occur when other design profes-
sionals develop their plans based on misinterpretations
of a geotechnical engineering report. To help avoid
misinterpretations, retain your geotechnical engineer to
work with other project design professionals who are
affected by the geotechnical report. Have your geotech-
nical engineer explain report implications to design
professionals affected by them, and then review those
design professionals' plans and specifications to see
how they have incorporated geotechnical factors.
Although certain other design professionals may be fam-
iliar with geotechnical concerns, none knows as much
about them as a competent geotechnical engineer.
BORING LOGS SHOULD NOT BE SEPARATED
FROM THE REPORT
Geotechnical engineers develop final boring logs based
upon their interpretation of the field logs (assembled by
site personnel) and laboratory evaluation of field
samples. Geotechnical engineers customarily include
only final boring logs in their reports. Final boring logs
should not under any circumstances be redrawn for
inclusion in architectural or other design drawings,
because drafters may commit errors or omissions in the
transfer process. Although photographic reproduction
eliminates this problem, it does nothing to minimize the
possibility of contractors misinterpreting the logs during
bid preparation. When this occurs, delays, disputes, and
unanticipated costs are the all-too-frequent result.
To minimize the likelihood of boring log misinterpreta-
tion, give contractors ready access to the complete
geotechnical engineering report prepared or authorized
for their use. (If access is provided only to the report
prepared for you, you should advise contractors of the
report's limitations, assuming that a contractor was not
one of the specific persons for whom the report was
prepared and that developing construction cost esti-
mates was not one of the specific purposes for which it
was prepared. In other words, while a contractor may
gain important knowledge from a report prepared for
another party, the contractor would be well-advised to
discuss the report with your geotechnical engineer and
to perform the additional or alternative work that the
contractor believes may be needed to obtain the data
specifically appropriate for construction cost estimating
purposes.) Some clients believe that it is unwise or
unnecessary to give contractors access to their geo-
technical engineering reports because they hold the
mistaken impression that simply disclaiming responsi-
bility for the accuracy of subsurface information always
insulates them from attendant liability. Providing the
best available information to contractors helps prevent
costly construction problems. It also helps reduce the
adversarial attitudes that can aggravate problems to
disproportionate scale.
READ RESPONSIBILITY CLAUSES CLOSELY
Because geotechnical engineering is based extensively
on judgment and opinion, it is far less exact than other
design disciplines. This situation has resulted in wholly
unwarranted claims being lodged against geotechnical
engineers. To help prevent this problem, geotechnical
engineers have developed a number of clauses for use in
their contracts, reports, and other documents. Responsi-
bility clauses are not exculpatory clauses designed to
transfer geotechnical engineers' liabilities to other
parties. Instead, they are definitive clauses that identify
where geotechnical engineers' responsibilities begin and
end. Their use helps all parties involved recognize their
individual responsibilities and take appropriate action.
Some of these definitive clauses are likely to appear in
your geotechnical engineering report. Read them
closely. Your geotechnical engineer will be pleased to
give full and frank answers to any questions.
RELY ON THE GEOTECHNICAL ENGINEER
FOR ADDITIONAL ASSISTANCE
Most ASFE-member consulting geotechnical engineer-
ing firms are familiar with a variety of techniques and
approaches that can be used to help reduce risks for all
parties to a construction project, from design through
construction. Speak with your geotechnical engineer not
only about geotechnical issues, but others as well, to
learn about approaches that may be of genuine benefit.
You may also wish to obtain certain ASFE publications.
Contact a member of ASFE or ASFE fora complimentary
directory of ASFE publications.
PROFESSIONAL
FIRMS PRACTICING
IN THE GEOSCIENCES
8811 COLESVILLE ROAD/SUITE G106/SILVER SPRING, MD 20910
TELEPHONE: 301/565-2733 FACSIMILE: 301/589-2017
Copyright 1992 by ASFE, Inc. Unless ASFE grants specific permission to do so, duplication of this document by any means whatsoever is expressly prohibited.
Re-use of the wording in this document, in whole or in part, also is expressly prohibited, and may be done only with the express permission of ASFE or for purposes
of review or scholarly research.
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