HomeMy WebLinkAbout3338; Agua Hedionda & Calavera Creek Dredging; Agua Hedionda Lift Station/Pedestrian Bridge; 2001-04-01Final Design Report
Engineering Design Services For
Agua Hedionda Lift Station Utility / Pedestrian Bridge
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Submitted to:
April, 2001
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Prepared for:
Krieger & Stewart, Inc.
3602 University Avenue
Riverside, CA. 92501
(909) 684-6900 FAX (909) 684-6986
Prepared hy:
W. Koo & Associates, Inc.
717 Pier View Way
Oceanside, CA. 92054
(760) 439-3073 FAX (760) 439-3360
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TABLE OF CONTENTS
PRELIMINARY DESIGN REPORT
AGUA HEDIONDA LIFT SATION UTILITY/PEDESTRIAN BRIDGE
PROJECT OVERVIEW 2
BACKGROUND 2
PROJECT REQUIREMENTS 2
EXISTING STRUCTURES 2
JOINT PEDESTRIAN USES ; 2
BRIDGE SITE 3
ENVIRONMENTAL ISSUES AND PERMITS : 3
HYDRAULICS '. 3
PROPOSED INTERCEPTOR SEWER PIPE 3
AESTHETICS 4
GEOTECHNICAL CONSIDERATION 4
MAINTENANCE ACCESS 4
DESIGN CRITERIA 4
CONCEPTUAL ALTERNATIVES 4
CAST-IN-PLACE (CIP) CONCRETE BOX GIRDERS SPAN 4
PRECAST CONCRETE GIRDERS 5
Delta girders 6
"Bathtub " Section 6
STEEL TRUSS SPAN 6
HYBRID ARCH STRUCTURE ? 7
CONSTRUCTION SEQUENCE 7
PRECAST CONCRETE GIRDER ALTERNATIVES 7
STEEL TRUSS SPAN 7
HYBRIDCONCRETE ARCH SPAN 7
COST COMPARISONS 8
SUMMARY 8
FIGURES
MARGINAL ESTIMATES
ARCHITECTURAL RENDERINGS
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PROJECT OVERVIEW
The Agua Hedionda Lift Station Upgrade project consists of an expansion of the existing lift station by
upgrade or replacement, and replacement of Reach VCl IB of the Vista/Carlsbad Interceptor Sewer. The
facilities are owned jointly by the City of Carlsbad and the City of Vista (C&V). The Agua Hedionda
Lift Station is operated and maintained by the Encina Wastewater Authority (EWA) under agreement
with C&V.
The preliminary design of the proposed upgrade to the Agua Hedionda Lift Station is presented in a
separate report entitled, "Preliminary Design Report for Agua Hedionda Sewer Lift Station Upgrade
(Project 99-101), dated March 7, 2000, by Krieger and Stewart, Inc. (K&S).
This report will address the replacement of Reach VCl IB of the existing 42" Vista/Carlsbad Interceptor
Sewer beginning on the north side of Agua Hedionda Lagoon and extending south to the Agua Hedionda
Lift Station within North County Transit District (NCTD) right-of-way. The interceptor sewer mns
easterly and parallel to the existing railroad tracks and crosses over the Agua Hedionda Lagoon,
supported by a wooden trestle. To increase lift station capacity from 23 MGD to 30 MGD, the existing
42" interceptor sewer will be replaced with a 54" diameter interceptor. The proposed bridge to support
the 54" interceptor sewer at the Lagoon crossing is to also be designed for the Lagoon crossing of the
Coastal Rail Trail, a proposed 14 feet 'wide pedestrian trail.
W. Koo & Associates (WKA), as a subconsultant to K&S, prepared the preliminary design for the
utility/pedestrian bridge at the Agua Hedionda Lagoon crossing. The proposed bridge structure will
cross the Agua Hedionda Lagoon at a physically constrained and environmentally sensitive location. The
location of the bridge structure is dictated by the alignment of the proposed interceptor sewer and the
requirement to maximize its separation from the NCTD railroad tracks. To minimize environmental
impacts to the Agua Hedionda Lagoon, the proposed bridge altematives will have a clear span over the
Lagoon (no intermediate piers inside the Agua Hedionda Lagoon channel). The proposed bridge
stmcture will span 210 feet over the Agua Hedionda Lagoon and be a minimum of 16 feet in width to
accommodate pedestrian and bicycle traffic. The report investigates three types bridge designs including
a concrete box girder, a steel tmss, and a concrete arch. Each of the proposed bridge altematives will
require some intmsion into the Agua Hedionda Lagoon during constmction. The degree of intmsion
varies with the aUematives. This report presents the advantages and disadvantages of each ahemative.
In addition, for each bridge altemative this report presents the required constmction sequences and
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
preliminary constmction cost estimates. Based on the evaluations contained in this report, it is recommended that the
Hybrid Arch Concrete Box Girder stmcture be used for final engineering and design because its aesthetic appearance,
relative constmction cost and future maintenance efforts.
BACKGROUND
The existing Vista/Carisbad Interceptor Sewer that parallels the NCTD railroad tracks and discharges to the Agua
Hedionda Lift Station is being replaced to provide increased capacity. The interceptor sewer is divided into pipeline
reaches. This project replaces interceptor sewer of Reach VCl IB. The existing sewer is a 42" diameter pipeline which
commences approximately 1,100' north ofthe Agua Hedionda Lagoon and crosses the Agua Hedionda Lagoon supported
by a wooden trestle constmcted in 1963.
The existing sewer is not adequate in size to convey proposed peak flows of 30 MGD. To provide sufficient capacity, a
54" diameter pipeline is required to convey the proposed sewage flow. The existing wooden trestle is stmcturally
inadequate to support a large sewer. In addition, the existing trestle is reaching its useful life expectancy. Furthermore,
the City proposes to design a pedestrian trail parallel to the existing NCTD railroad tracks, and the bridge will need to
incorporate the requirements necessary to accommodate both a proposed 54" replacement sewer and pedestrian and .
bicycle traffic.
PROJECT REQUIREMENTS
Existing Structures
There are currently three bridge stmctures that cross the Lagoon in the same vicinity. Approximately 50' to the west of
the existing 42" interceptor sewer trestle is a single-track railroad facility owned and operated by NCTD. The railroad
stmcture is a timber trestle stmcture, supported on a series of timber pile bents in the Lagoon channel. Approximately
10' to the east ofthe existing 42" interceptor sewer trestle is a timber trestle bridge that carries a 12" high-pressure gas
pipe owned by San Diego Gas and Electric (SDG&E). The 12" gas line serves the SDG&E power plant south of the lift
station and much of the south coast area.
Joint Pedestrian Uses
In addition to supporting the new 54" interceptor sewer, the proposed bridge will carry pedestrians from the Coastal Rail
Trail. The proposed 44 mile long Coastal Rail Trail will commence in the City of Oceanside and travel southerly along
NCTD railroad right-of-way to San Diego. The Coastal Rail Trail will accommodate both bicycle and pedestrian traffic.
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Bridge Site
The proposed alignment of the new Interceptor sewer. Reach VCl IB, considered the location of all
existing bridge stmctures. The new bridge is proposed to mn parallel and westerly of the existing sewer
trestle. The preliminary bridge alignment has been reviewed with NCTD. NCTD has requested that the
proposed bridge be located as close as possible to the existing interceptor sewer trestle to provide
maximum clearance from the existing railroad trestle. The alignment shown on Figure 1 sets the
proposed bridge at 4 feet minimum clearance from the existing interceptor sewer trestle. This provides a
distance from the centeriine of the railroad tracks to the outside of the proposed bridge of 28 feet at the
south abutment and 42 feet at the north abutment, based on a 16-foot bridge width.
Environmental Issues and Permits
A preliminary biological assessment ofthe bridge site was performed on June 24, 1999, by Pacific
Southwest Biological Services, Inc. A report containing their finding is included as Appendix C in K&S
"Preliminary Design Report for Agua Hedionda Sewer Lift Station Upgrade", and is summarized as
follows:
The project site involves largely non-native plant growth.and some landscape plantings. There are no
sensitive plants or animals anticipated in the habitats on the site. However, there is a possibility that the
Califomia Least Tems (a state and federally listed endangered species) uses the Lagoon for foraging. If
so, the U.S. Fish and Wildlife Service (USF&WS) could restrict constmction activities during the bird's
presence in the area, typically from about March 1 to August 15. During this period, the use of noisy
equipment and significant amounts of human activity would be prohibited in areas near the Tems. The
limits of the affected areas would be determined by the USF&WS during final design as part of the
permit process.
Erection of the new bridge stmcture will require constmction along the northerly and southerly
shorelines of the Agua Hedionda Lagoon. The preliminary site field inspection indicates the presence of
plants along the shoreline that are indicator species of saltwater wetlands. During final design, a
biological assessment known as a wetland delineation report will be required. If the area proposed for
constmction is a wetland, a Section 10 Permit will be required from the U.S. Army Corps of Engineers
under the Rivers and Harbors Act. In addition, a 401 Certification will be required from the Califomia
Regional Water Quality Control Board, San Diego Region, for potential water quality impacts to the
Agua Hedionda Lagoon.
Due to the project's close proximity to the Agua Hedionda Lagoon, a Coastal Development Permit will be required from
the Califomia Coastal Commission. The Califomia Coastal Commission may establish architectural requirements for the
bridge stmcture and embankment landscaping.
A preliminary list of agencies from which permits or approvals will be required is as follows:
• U.S. Fish and Wildlife Service
U.S. Army Corps of Engineers
Califomia Regional Water Quality Control Board, San Diego Region
• Califomia Coastal Commission
Interceptor Sewer Hydraulics'
Proposed 54" Interceptor Sewer Reach VCl IB will be designed to convey 30 MGD peak flow and will match the slope
ofthe existing 42" sewer (i.e. 0.10%). At the Agua Hedionda Lagoon crossing, the invert elevations of the proposed 54"
sewer will be the same as the invert elevations of the existing sewer.
Sewage Spill Prevention
The proposed bridge stmcture will be located in an environmentally sensitive area. The bridge stmcture and supported
interceptor sewer will be designed to minimize the possibility of a sewage spill. The bridge will be designed to maintain
its stmctural integrity under all loading conditions, including seismic events. The sewer pipe will be provided with a
protective liner to prevent minor leaks due to the corrosive effects of raw sewage. The sewer pipe will be anchored
within the bridge and provided with mbber gasketed pressure joints, which is flex joint for longitudinal, vertical and
lateral movements, and will offer some degree of flexibility during earthquake motion.
To minimize the potential for pipe mpture outside the bridge, manholes will be constmcted directly adjacent to the bridge
abutments. Short sections of sewer with mbber gasketed joints will be provided between the manholes and the abutments
to accommodate ground movement due to differential settlement or earthquake motion.
Proposed Interceptor Sewer Pipe
The proposed interceptor sewer pipe will have a minimum inside diameter of 54". Proposed pipe types include
reinforced concrete pipe with PVC lining. Ifthe selected stmcture type requires a "sealed box" design, such as a precast
concrete box girder, the bridge joints will need to be restrained and sealed to prevent leakage using 360° PVC hner
Preliminary Design Report
Interceptor Vlll Bridge over Agua Hedionda
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welded all around. A leak detection system is recommended inside such the "sealed box" in order to
alert operators of a sewage leak. An emergency basin is also recommended for draining the leaked and
spilt sewage to prevent sewage spilling into the Lagoon.
Aesthetics
An important aspect of the conceptual design for the new bridge crossing is the aesthetics of each
alternative. The bridge will be part of the Coastal Rail Trail system of Northem San Diego County.
Therefore, the visual impact ofthe stmcture on its surroundings will be an important part of the bridge
selection process. Factors to be considered include bridge type, geometry, and architectural finishes.
The appearance of the stmcture from the pedestrian walkway, including the bridge deck, railing, and light
standards, is also important to the overall aesthetic impact of the stmcture. The appearance ofthe final,
stmcture, both on the pedestrian level and from the trail will be considered in the final selection of the
preferred stmcture altemative.
Geotechnical Considerations
As part of the design of the Vista/Carlsbad Interceptor Sewer and South Carlsbad Village Storm Drain
Project north of the Agua Hedionda Lagoon, Woodward Clyde Engineering conducted a number of
subsurface investigations with a combination of hollow-stem auger borings and CPT tests. At the south
end of the project (approximately 1000 feet north of the Agua Hedionda Lagoon the soil was found to be
predominately medium dense to very dense Terrace Deposit in the top 20 to 25 feet, underlain by
medium to very dense Santiago Formation. Due to the shallow groundwater, Woodward Clyde
investigated the liquefaction potential and its effects on the soil strength. It was concluded that at the
south end.of the project (north of the bridge) soil might liquefy during an earthquake. Prior to
commencing final design, a geotechnical investigation of the bridge site will be required. For the
purpose of developing conceptual level cost estimates for the various stmcture altematives, HP 14x87
steel driven piles were utilized and assumed to reach capacity of 70 tons at a depth of 40 feet.
Maintenance Access
All the altematives that were studied, except for the steel tmss section, are provided with inspection
catwalks mounted inside the girders. The catwalks will be a minimum of two feet wide and will be
placed at or below the pipe spring line level. The minimum headroom above the catwalk will be six feet.
Manhole covers will be provided in the bridge deck to allow access to the catwalks at each end of the
structure and at mid-span. At each location three feet diameter manholes will be placed on either side of
the pipe to allow full access to the sewer pipe.
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
Design Criteria
Bridge Material
• Steel - A5 8 8 Weathering Steel
• Prestressed and Reinforced Concrete
Width-14'-0" Clear
Span - 210' ± Clear Span, No Supports in Lagoon
Maximum Height - 16'-0"; Steel Tmss Girder, 10'-0"; Precast Concrete Girder
Decking Type - Reinforced Concrete Slab
Minimum Uniform Live Load - 100 pounds per sq. ft.
Minimum Concentrated Live Load - 24,000 pounds (equivalent to HI5-44 Tmck)
Maximum Utility Dead Load - 2,000 pounds per foot (54" reinforced concrete pipe filled with water)
Uses - Support
• 54" Interceptor Sewer
Pedestrian
Bicycle
Equestrian
• Constmction Constraints
• No Bridge Supports in Lagoon Channel
• Minimizing Disturbance to Lagoon
Provide Access to Sewer for Maintenance and Repair
. Safety
• Lighting
• Railings
• Detection System
Drainage to Emergency Basin
CONCEPTUAL ALTERNATIVES
Cast-In-Place (CIP) Concrete Box Girders Span
The first altemative consists of a single span box girder with one box cell to contain the sewer. The CIP box girder would
be post-tensioned to increase its efficiency. A single span CIP concrete box girder requires the erection of formwork to
form and support the concrete box girder section while under constmction. The concrete formwork will have to be
temporarily supported with falsework (shoring) undemeath to carry the stioicture weight during curing of the concrete. It
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is anticipated that the falsework will be supported over temporary piles, driven inside the lagoon. After
the concrete girder is cured inside the formwork, the girder will be prestressed and the formwork and
falsework will then be removed.
The advantages ofthis type of constmction are (1) ufilization of common constmction techniques, (2)
accommodates uses of .various architectural enhancements, and (3) cost effectiveness.
(1) The CIP box girder system involves one of the most common types of bridge constmction in
Califomia. Most bridge contractors have in-depth experience in formwork and falsework
constmctions. The familiarity of the constmction techniques enhances the quality of the
final product.
(2) CIP concrete stmctures can be cast with a variety of architectural finish on the exterior to
enhance the aesthetic value of the project.
(3) Because of the widely used constmction techniques, the CIP box girder bridge is often the
most economical to constmct. Most ofthe bridge contractors in the area have.stockpiles of
various formwork and falsework assemblies, which can be erected with relatively low costs.
The disadvantage of the CIP box girder system is the requirement for constmction of falsework within
the ecologically sensitive lagoon. Extensive falsework and a large number of temporary piles will need
to be placed inside the lagoon to support the stmcture during constmction. Temporary steel beams will
be used to span over the lagoon between the falsework bents (pile groups). The erection and subsequent
removal of the falsework towers and steel beams requires constmction activity inside the lagoon. These
activities will physically impact the lagoon, including the underlying lagoon bed.
Due to the degree of interference inside the lagoon, this altemative is deemed unacceptable. The CIP
concrete box girder system is therefore not recommended for further consideration.
Precast Concrete Box Girders
A different concrete bridge system involves the use of precast concrete girders (see Figure 2). With this
type of constmction, girders are often prefabricated offsite, and transported to the site location. The
girders are then erected on the permanent supports by cranes. A precast girder system for this project
will require constmction of temporary erection bents because of the extraordinarily long span for a
precast girder. The normal length of precast girder is between 80 feet and 100 feet. The maximum
length of a precast girder that can be safely transported on highway is 120 feet long, and the maximum
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
weight is 100 Tons. However for the jumbo girder section satisfying the span over 200 feet, 50 to 55 feet is the
maximum shipping length allowed Therefore, the 210 feet long bridge using precast girders will require four or more
segments. These segments will need to be spliced in place after they are erected on site. Temporary erection bents will
be used to support the precast segments prior to prestressing and completion of the girder splice closure pours.
The advantages of a precast constmction are (1) temporary erection bents pose less impact to the lagoon than CIP
falsework; (2) constmction activity poses less impact to the lagoon, and (3) constmction time is significantly less than
CIP concrete constmction.
(1) As previously mentioned, the constmction of the bridge requires the placement of erection bents in the
lagoon for precast girder splicing operations. These bents will be constmcted and placed inside the channel
from the channel slopes, and no constmction equipment will be mobilized inside the lagoon.
(2) The precast concrete girder sections are completed prior to erection. Once the girders are on the erection
bents, minimum constmction activity will be required on the girders. This would minimize constmction
impact to the lagoon channel due to-reduced onsite constmction activity. . •
(3) The constmction time will be reduced with precast girders because the girders will be fabricated offsite,
concurrently with the onsite constmction activities(such as the abutment constmction). It is anticipated that
the precast girders will be completed within two week after the erection of the first girder segment.
The disadvantages ofthe precast construction are (1) higher cost than CIP girder altemative; (2) less architectural options
than a CIP girder altemative. , . . '
(1) Comparable stmctures using precast concrete system are normally more costly than CIP concrete stmctures.
Part ofthe reasons is explained in the CIP concrete girder section of the report. Most of the large precast
girders are fabricated outside Southem Califomia, in Phoenix, Arizona. The transportation and erection cost
is normally higher than the cost of falsework used for the CIP constmction.
(2) A precast girder is constmcted using prefabricated formwork in the casting yard. Special architectural
features are difficult to incorporate, and add significant cost to the precast girders.
There are two different precast girder systems available for this project, namely a "delta" section and a "bathtub"
section (see Figure 3). Specific discussions on these two types of girders are presented below.
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Delta girders
A "delta" girder contains a precast concrete trapezoidal box section with a deck that
sometimesoverhangs the edges of the box. A "delta" girder is normally reinforced with both
mild steel reinforcements and pretension strands. For the girders that are spliced, post-tensioning
ducts will be provided in the girder web sections. The girders are transported to the project
location, and they are erected following the constmction sequence discussed in the subsequent
section ofthis report. The precast girders will be spliced with "closure pours" between the
segments. Afterward, high strength steel strands will be threaded through all the segments
inside the post-tensioning ducts, and are prestressed. The sewer pipe will be inserted into the
section and secured with cradles and steel anchors after the girders are fully spliced, and
temporary erection bents are removed. Because there are very few steps required for the "delta"
girders, they can be constmcted in the least time, and with the least amount of onsite work.
"Bathtub" Section
A "bathtub" section requires the offsite fabrication of portion of the complete girder section; the
bottom slab and the two web stems. The top slab or bridge deck will be constmcted onsite after
the "bathtubs" are erected on the temporary erection bents. With the exception of the cast-in-
place top slab, the bathtub sections are constmcted following a similar sequence as discussed in
the "delta" girder section of this report.
The main advantage of the 'bathtub" section design is the reduced weight of the precast section
by 30% during girders transportation and erection. This would permit the erection of the girders
with smaller cranes, which can be maneuvered easier on the site. Secondly, the sewer pipe can
be dropped into the bathtub prior to forming the top slab, simplifying the placement of the sewer
pipe.
Steel Through Truss Span
The steel tmss span design requires the fabrication of two steel tmss girders. The tmss girders will be
tied together with a floor deck and a framed soffit. The tmsses will be designed as typical "Warren"
tmsses with four way intersection tmss members connected with gusset plates along the top and bottom
chords of the tmss (see Figure 4). The "through" tmss will be designed to clear span the 210' long
charmel, with an estimated depth of 16 feet at mid span. The pedestrian walkway deck will be
positioned 5 feet below the top chord of the tmss girders, which will provide 11 feet below the deck for
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
the sewer pipe and maintenance walkways (See Figure 5). Pedestrian railings will be placed along the inside of the tmss
girders in compliance with American with Disabilities Act (ADA) requirements. The tmss stmcture will be a prismatic
tmss design of constant depth. An altemative tmss type that could be considered during the final design is a tapered
tmss. A tapered tmss design is accomplished with either a linear tapering, or parabolic tapering along the top chord of
the tmss.
Constmction ofthe steel tmss is similar to the precast concrete alternative in many respects. The steel secfions will be
prefabricated and assembled to a reasonable length for transportation. The tmss sections will then be assembled onsite,
either when the segments are placed on the temporary erection bents, or onsite in a separate staging area. The erection of
the tmsses-can be accomplished either with lifting cranes, or by rolling the fully assembled tmsses onto the temporary
erection bents, and finally the bridge abutment. A more detailed description of the required constmction steps are
presented in the " Constmction Sequence" Section of this report.
The advantages of the steel tmss span are (1) relatively light weight design, which would result in smaller foundation and
substmctures; (2) constmction duration is reduced similar to the precast concrete option; and (3) tmss stmcture can be
provided with a variety of architectural features to provide an aesthetically pleasing stmcture.
(1) Tmss girders will be constmcted with standard rolled shaped steel members. The entire weight of the two
required tmss girders will be less than 50% of the comparable precast concrete bridge. The lighter-weight
bridge will reduce foundation and substmcture sizes. A smaller bridge foundation will reduce the project
impact and disturbance to the lagoon embankments.
(2) Constmction duration will be significantly reduced from the CIP concrete girder altemative. Because the
tmss stmcture requires a smaller foundation (as previously mentioned), a trass stmcture can be constmcted
in less time than a precast concrete altemative.
(3) A tmss stmcture can be provided with architectural features, such as architectural railing and fencing, to
enhance the architectural appearance of the completed stmcture. The tmss stmcture will be relatively
andless physically imposing than the concrete stmcture altematives.
The disadvantages ofthe steel tmss span are (1) higher maintenance requirements and (2) higher costs.
(1) Steel stmctures will require regular inspection and maintenance of protective coatings. In the coastal marine
environmental, high corrosion resistance steel will be used in the tmss to reduce stmctural corrosion. A
regular inspection program will need to be implemented and protective coatings will need to be maintained
for the life of the stmcture.
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(2) A steel bridge stmcture is traditionally more costly than a concrete bridge stmcture in
Califomia. The fabrication of a trass stracture requires a large number of bolted connections
and extensive welding. Corrosion resistant steel is also more costly than standard mill
steel. The high level of fabrication would require a more rigorous QA/QC process, which
further increases the cost of the project.
Hybrid Arch Box Girder Structure
To increase the aesthetics of the precast concrete altemative a concrete arch extends upward from the
footings to the center of the girders giving the appearance of an arch supported the bridge. This is
accomplished by adding a pair of precast concrete arch ribs below the overhang deck on both sides of the
P/C girder. (See Figure 6). In order to configure pleasant geometry, the arch rib will be set on a parabolic
curve and the abutment foundations at the end of the arches will be dropped to approximately sea level at
elevation of zero.
The arch ribs are non-stmctural elements supported on the abutment foundation at their lower ends. The
stmctural system consists of single span precast concrete girders supported on abutments. Each concrete
arch only carries its own weight and receives no load from the bridge spans. Bolts embedded in the P/C
girder stems at midspan connect the arch crown, to the superstmcture, stabilizing the top of the arch. (See
Figure 7). A concrete closure pour encases the bolted joint at the arch crown to complete the appearance
of an arch supported stmcture. A reveal is also added along the length of the arch rib sides to further
enhance the final appearance.
The advantage ofthe hybrid arch bridge stmcture is to provide an additional architectural feature to the
simple box stmcture.
The disadvantage of the hybrid arch stmctures is added cost to the precast concrete altemative. Since the
ribs are purely architectural, the cost associated with the design and constmction of the P/C girder
altemative remains unchanged. The erection of the arch ribs further complicates the precast girder
altemative since they can be launched in only two segments after the precast girders are in place. These
segments will be set in place from both the channel embankments and from top of the finished bridge
deck. Also, additional costs stem from dropping the abutment foundation which generates a larger
substmcture that consequently requires more excavation and more concrete casting.
CONSTRUCTION SEQUENCE
Constmction sequences for each of the three altemative stmctures vastly differ and are cmcial to the total stmcture
cost. A brief constmction sequencing narrative of each altemative is described herein.
Precast Concrete Box Girder Alternatives, Figure 8
As previously discussed, the precast girder altemative requires the erection of temporary bents because the girders
have to be spliced together after they are set in place. Because of limited access and site constraints at the south
embankment, the maj or constmction operations have to be executed from north embankment of the Agua Hedionda
Lagoon. In order to haul the girder sections, which has approximate self weight of 80 tons each, over the Agua
Hedionda lagoon channel, a crawler cranes are required. The crawler cranes will span over and be supported by the
temporary bents. The temporary bents consist of temporary piles driven with pile driving equipment located at the
top ofthe lagoon embankments, followed by installation of the crawler platform. The constmction sequence requires
erection ofthe girder segments first, followed by the post-tensioning of the complete bridge girder. This avoids the
need for a crane inside the lagoon. To reduce costs, the transportation of the precast girders may be feasible from the
NCTD tracks. Use of the tracks will be discussed with NCTD officials during the final design phase.
Steel Through Truss Span, Figure 9
The steel tmss is erected on temporary bents similar to the precast concrete girder altemative. The steel tmss is pre-
buih in three segments of which the two end segments are placed first, followed by the mid-segment. Another
optional method for the steel tmss span is by way of "rolling" the trass girder in place. With this option, the steel;,
tmsses are brought to the job site, and fully assembled on site. The completed girders are then rolled in place with
steel rollers undemeath the trasses. The rollers require temporary bents in the lagoon similar to the precast concrete
girder altemative. Due to less self-weight of the steel trass, comparing with the precast concrete girder, a lighter
crawler crane or a conventional lift crane will be acceptable. The rolling operation is relatively quick after the trass
girders are assembled.
Hybrid Arch Concrete Box Span, Figure 10
The concrete arch span is constmcted of precast girders with precast concrete arch rib beams on both sides of the
bridge. Precast concrete arch ribs are placed by erecting two pairs of arch rib beams from either end of the bridge
span. The constmction sequence begins the same as the P/C girder altemative. The arch rib erection is executed
after the P/C girder system is complete.
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
Page 7
COST COMPARISONS
The estimated constmction cost for the three bridge aUematives are listed per Table below. Detail
information of the estimation is illustrated in the Marginal Estimates in the Report Appendix.
Precast Concrete Girder Steel Thm Trass Hybrid Arch Concrete Box
$1,609,000 $1,902,000 $1,744,000
SUMMARY
The proposed overcrossing stracture is part of the Agua Hedionda Lift Station Upgrade project. The
bridge rans 210 feet, spanning over the Agua Hedionda Lagoon, providing support ofthe proposed 54"
diameter Vista/Carlsbad Interceptor Sewer, as well as carrying pedestrians/bicyclists traffic from the
Coastal Rail Trail.
To minimize the environmental impact to the Agua Hedionda Lagoon, three bridge altematives are
proposed, all of which have a clear span over the lagoon. Temporary intmsions into the Agua Hedionda
Lagoon during constmction will be required to a different degree, varying with the altematives.
Due to the environmentally sensitive project site, several recommendations are proposed to prevent
potential sewage spill and leakage due to corrosion or pipe mpture caused by seismic events. These
recommendations include: l)Utilizing RCP with PVC lining and mbber gasketed flex joints,
2)Constmcting manhole directly adjacent to the bridge abutment and using rabber gasketed flex joint for
relative movemenL 3) Providing "seal box" or steel casing to drain the sewer into an emergency basin if a
spill occurs, and 4)Installing detection system to alert the operator of the sewage leak or spill.
Architecturally designed safety fencing, railing and lighting are proposed to enhance the bridge
appearance viewing from bridge deck level. To further enhance the aesthetics of the global setting ofthe
bridge, a tapered trass girder for the Steel Through Trass and precast concrete arch for the Precast Concrete Box girder is
added.
A manhole on the concrete box girder and a catwalk inside the box and the steel trass bridge are recommended for future
access and maintenance. Geotechnical investigation and recommendations will be required prior to commencing the final
bridge design.
Advantages and disadvantages of each ahemative are recapped per the followings:
Precast Concrete Box Steel Through Tmss Hybrid Arch Concrete
Box
Aesthetics Fair Good Best
Future Maintenance Minimum Life Time Minimum
Disturbance to Lagoon
(Constmction)
less Least less
Constmction Duration Fair Short Longer
Constmction Cost High Highest Higher
All the three proposed bridge altematives avoid the permanent interference into the Agua Hedionda Lagoon. The
concrete constmction altematives eliminate the future maintenance concems. The Hybrid Arch Concrete Girder provides
an aesthetically pleasing stmcture. Based on the aforementioned factors, it is our recommendation that the Hybrid Arch
Concrete Box girder be chosen stracture for the final engineering and design.
Preliminary Design Report
Interceptor VIII Bridge over Agua Hedionda
Pages
^ G 0 0 N
AGUA HEDIONDA LIFT STATION UTILITY / PEDESTRIAN BRIDGE SITE PLAN
SCALE: r
FIGURE 1
INV. ELEV = 20.37' <t MANHOLE TYP-
IvtANHOLE
MIN COVER
^^ /-t SEWER
ABUTMENT ABUTMENT
P/C CONCRETE BOX GIRDER
ELEVATiON
r - 20'
FIGURE 2
t BRIDGE ? BRIDGE
P/C DELTA GIRDER
CROSS SECTION
3/S- = r-0"
P/C BATHTUB GIRDER
CROSS SECTION
3/8" = I'-O"
FIGURE 3
I
INVERT ELEV = 20.18
INVERT ELEV =
20.37
STEEL THROUGH TRUSS BRIDGE
20'
FIGURE 4
^ BRIDGE
CORRUGATED
STEEL CATWALK, TYP
STEEL THROUGH TRUSS GIRDER
CROSS SECTION
NO SCALE
FIGURE 6
BRIDGE DECK
INV. ELEV = 20.37'
MANHOLE TYP-
- SAFETY RAILING
WITH FENCE ONE MANHOLE
PER END, TYP-
RETAINING WALL
WINGWALL, TYP
MANHOLE
PILE, TYP
ABUTMENT ABUTMENT
HYBRID ARCH CONCRETE BOX GIRDER
ELEVATION
1" = 20"
FIGURE 6
S BRIDGE
PRECAST ARCH RIB
BOLTED TO GIRDER
ON BOTH SIDES-
P/C CONCRETE BOX GIRDER WITH P/C CONCRETE ARCH
CROSS SECTION
3/8" = I'-O"
FIGURE 7
CIP CONC ABUTMENT
APPROX OG
P/C CONCRETE BOX GIRDER
ERECTION SEQUENCE
STEP 1 - CAST FOUNDATION AND SUBSTRUCTURE
APPROX OG
aP CONC ABUTMENT
55'-0
ABUTMENT
ABUTMENT
2 @ 50'-0" = 100'-0" 55'-0'
j—1
:RAWLER CRANE
-TEMPORARY
CONSTRUCTION SUPPORT
STEP 2 - CONSTRUCT ERECTION TOWER ANO LIFT /
ROLL IN GIRDER SEGNENTS
DROP P/C CONC
GIRDER SEGMENT
SPLICE P/C CONC
GIRDER SEGMENT
REMOVE TEMPORARY SUPPORT
STEP 4 - CONCRETE ABUTMENT AND
AND REMOVE ERECTION TOWERS
POST TENSION
P/C GIRDER
ABUTMENT
CAST ABUTMENT
BACKWALL it BACKRLL. TYP
FIGURE 8
STEEL THROUGH TRUSS GIRDER
ERECTION SEQUENCE
STEP 1 - CAST FOUNDATION AND SUBSTRUCTURE
tSAME STEP 1, AS P/C CONCRETE GIRDER!
CIP CONC ABUTMENT
STEP 2 - DROP PREFABRICATED TRUSS GIRDER SEGMENT
DROP PRE-FABRICATED
TRUSS SEGMENT IN PLACE
CIP CONC ABUTMENT
DROP PRE-FABRICATED
TRUSS SEGMENT IN PLACE
STEP 3 - ERECT TRUSS SEGMENT
^CAST BRIDGE
( DECK IN PLACE
DROP PRE-FABRICATED
TRUSS SEGMENT IN PLACE
STEP 4 - CAST BRIDGE DECK AND
REMOVE ERECTION TOWER
FIGURE 9
P/C CONCRETE BOX GIRDER BRIDGE
WITH P/C CONCRETE ARCH
-LIMIT OF
EXCAVATION, TYP
ABUTMENT STEP 1 • COMPLETE P/C GIRDER BRIDGE ABUTMENT
ABUTMENT STEP 2 - ERECT P/C ARCH RIB ABUTMENT
-LIMIT OF
BACKFILL, TYP
ABUTMENT STEP 3 - CLOSURE POUR AND BACKFILL ABUTMENT
FIGURE 10
DEPARTMENT OF TRANSPORTATION
STRUCTURAL QUANTITY SURVEY AND MARGINAL ESTIMATE
DPD-OSD-D19 (REV.1/78)
W. Koo & Associates
•( •""^ ^''y p^'''^^^y ^^^f- su'te 310
-if^icjOL ' Orange, CA 92868
CHARGE BR. NO. N/A
BRIDGE AGUA HEDIONDA LAGON UTILITY/PEDESTRIAN OC (PRECAST CONCRETE BOX) TYPE CONCRETE
DISTRICT |COUNTY| SD ROUTE KP N/A
LENGTH (ft) 210.00 WIDTH (FT) 16.00 DEPTH • 16.0 LL
LONGSPANI 210.0 FT |SPANS| 1 SKEW 0.000
DESIGN SECTIONI PC/PS CONCRETE BOX
Rec'd Est Group By
Quantity By
Cheeked By
T.J. Chou
Wei Koo
Revised By T. J. Chou
Date
Date
Date
Date
4/10/01
4/10/01
4/10/01
CODE CONTRACT ITEMS UNIT SUPERSTRUCTURE SU BSTRUCTURE OTHER ELEMENTS TOTAL PRICE AMOUNT CODE CONTRACT ITEMS UNIT
QUANTITY CHECK USE QUANTITY CHECK USE QUANTITY CHECK USE USE
PRICE AMOUNT
BRIDGE REMOVAL LS 1 1 1 $20,000.00 $20,000
STRUCTURE EXCAVATION (BRIDGE) CY 2h5 285 $50.00 $14,250
STRUCTURE BACKFILL (BRIDGE) CY 1505 635 $75.00 $47,625
FURNISH STEEL PILE (HP14x89) FT 2400 2400 $30.00 $72,000
DRIVE STEEL PILE (HP14x89) EA 1 U 60 $3,000.00 $180,000
ERECT FALSEWORK TOWER EA 2 2 $20,000.00 $40,000
STRUCTURE CONCRETE (BRIDGE ABUTMENT) CY 96 96 $520.00 $49,920
STRUCTURE CONCRETE (BRIDGE DECK) CY 42 42 $600.00 $25,200
SAFETY RAILING FT 420 420 $120.00 $50,400
FURNISH, ERECT AND POST-TENSION P/C CONCRETE GIRDER * EA 1 1 $695,000.00 $695,000
BAR REINFORCING STEEL (BRIDGE) LBS 26600 26600 $0.90 $23,940
* INCLUDE $400,000 ESTIMATE FOR THE MOBILIZATION AND DEMOBILIZATION OF Revision
SUB TOTAL $1,218,335
* INCLUDE $400,000 ESTIMATE FOR THE MOBILIZATION AND DEMOBILIZATION OF Revision MOBILIZATION @ 10% $121,834
LARGE CRAWLER CRANE Mar ginal Est. By T.J. Chou SUB TOTAL CONTRACT ITEMS $1,340,169 LARGE CRAWLER CRANE Mar
Date 4/10/01 CONTINGENCIES @ 20% $268,034
LARGE CRAWLER CRANE Mar
Cost Index 1999 1999 TOTAL $ 478.87 /FT2 $1,608,202
LARGE CRAWLER CRANE Mar
FOR BUDGET PURPOSES - SAY $1,609,000
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DEPARTMENT OF TRANSPORTATION
STRUCTURAL QUANTITY SURVEY AND MARGINAL ESTIMATE
DPD-0SD-D19 (REV.1/78)
" "'"^v W. Koo & Associates
y^^^^ 600 The City Parkway West, Suite 310
^fiU'S-tijSf Orange, CA 92868
CHARGE BR. NO. N/A
BRIDGE AGUA HEDIONDA LAGON UTILITY/PEDESTRIAN OC (STEEL THROUGH TRUSS) TYPE STEEL
DISTRICT ICOUNTYI SD ROUTE KP N/A Rec'd Est Group By Date
LENGTH (ft) 210.00 WIDTH (FT) 16.00 DEPTH 16.0 LL Quantity By T.J Chou Date 4/10/01
LONGSPANI 210,0 FT |SPANS| 1 SKEW 0.000 Checked By Wei Koo Date 4/10/01
DESIGN SECTIONI STEEL THRU TRUSS Revised By T.J. Chou Date 4/10/01
CODE CONTRACT ITEMS UNIT SUPERSTRUCTURE SUBSTRUCTURE OTHER ELEMENTS TOTAL PRICE AMOUNT
QUANTITY CHECK USE QUANTITY CHECK USE QUANTITY CHECK USE USE
BRIDGE REMOVAL LS 1 1 1 $20,000.00 $20,000
STRUCTURE EXCAVATION (BRIDGE) CY 285 285 $50.00 $14,250
STRUCTURE BACKFILL (BRIDGE) CY 1505 635 $75.00 $47,625
FURNISH STEEL PILE (HP14x89) FT 17( 1) 1760 $30.00 $52,800
DRIVE STEEL PILE (HP14x89) EA 11 44 , $3,000.00 $132,000
ERECT FALSEWORK TOWER EA 2 2 $20,000.00 $40,000
STRUCTURE CONCRETE (BRIDGE ABUTMENT) CY 96 96 $520.00 $49,920
STRUCTURE CONCRETE (BRIDGE DECK) CY 95 95 $600.00 $57,000
SAFETY RAILING FT 420 420 $120.00 $50,400
METAL DECKING (BRIDGE) SF 3360 3360 $2.50 $8,400
FURNISH STRUCTURAL STEEL (BRIDGE) LBS 232000 232000 $2.00 $464,000
ERECT STRUCTURAL STEEL (BRIDGE) * LS 1 .1 $430,000.00 $430,000
CLEAN AND PAINT STRUCTURAL STEEL LS 1 1 $50,000.00 $50,000
BAR REINFORCING STEEL (BRIDGE) LBS 26600 26600 $0.90 $23,940
SUB TOTAL $1,440,335
INCLUDE $200,000 ESTIMATE FOR THE MOBILIZATION AND DEMOBILIZATION OF Revision MOBILIZATION @ 10% $144,034
UKAWLbR/LIFT CRANE Marginal Est. By T.J. Chou SUB TOTAL CONTRACT ITEMS $1,584,369
Date 4/10/01 CONTINGENCIES @ 20% $316,874
Cost Index 1999 1999 TOTAL $ 566.07 /FT2 $1,901,242
FOR BUDGET PURPOSES -SAY $1,902,000
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DEPARTMENT OF TRANSPORTATION
STRUCTURAL QUANTITY SURVEY AND MARGINAL ESTIMATE
DPD-OSD-D19 (REV.1/78)
W. Koo & Associates
^ '"''^ C/iy Parkway Vi/est, Suite 310
5jSri«Aif Orange, CA 92868
CHARGE BR. NO. N/A
BRIDGE AGUA HEDIONDA LAGON UTILITY/PEDESTRIAN OC (HYBRID ARCH CONCRETE BOX) TYPE CONCRETE
DISTRICT ICOUNTYj SD ROUTE KP N/A Rec'd Est GrouD Bv Date
LENGTH (ft) 210.00 WIDTH (FT) 16.00 DEPTH 16.0 LL Quantity By
Checked By
T.J Chou Date 4/10/01
LONGSPANI 210.0 FT |SPANS| 1 SKEW 0.000
Quantity By
Checked By Wei Koo Date 4/10/01
DESIGN SECTIONI PC/PS CONCRETE BOX Revised By T. J. Chou Date 4/10/01
CODE CONTRACT ITEMS UNIT SUPERSTRUCTURE SUBSTRUCTURE OTHER ELEMENTS TOTAL PRICE AMOUNT
QUANTITY CHECK USE QUANTITY CHECK USE QUANTITY CHECK USE USE
BRIDGE REMOVAL LS 1 1 1 $20,000.00 $20,000
STRUCTURE EXCAVATION (BRIDGE) CY 285 325 $50.00 $16,250
STRUCTURE BACKFILL (BRIDGE) CY 1505 646 $75.00 $48,450
FURNISH STEEL PILE (HP14x89) FT 2400 2400 $30.00 $72,000
DRIVE STEEL PILE (HP14x89) EA 60 $3,000.00 $.180,000
ERECT FALSEWORK TOWER EA > 2 $20,000.00 $40,000
STRUCTURE CONCRETE (BRIDGE ABUTMENT) CY 96 96 $520.00 $49,920
STRUCTURE CONCRETE (BRIDGE DECK) CY 42 42 $600.00 $25,200
SAFETY RAILING FT 420 420 $120.00 $50,400
FURNISH, ERECT AND POST-TENSION P/C CONCRETE GIRDER * EA 1 1 $695,000.00 $695,000
FURNISH AND ERECT PRECAST CONCRETE ARCH EA 4 4 $25,000.00 $100,000
BAR REINFORCING STEEL (BRIDGE) LB 26600 26600 $0.90 $23,940
$0
•ic SUB TOTAL $1,321,160
iNULUUb MUO,0UO ESTIMATE FOR THE MOBILIZATION AND DEMOBILIZATION OF Revision MOBILIZATION @ 10% $132,116
LAK(ib CKAWLER CRANE Marginal Est By T.J. Chou SUB TOTAL CONTRACT ITEMS $1,453,276
Date 4/10/01 CONTINGENCIES @ 20% $290,655
Cost Index 1999 1999 TOTAL $ 519.05 /FT2 $1,743,931
FOR BUDGET PURPOSES -SAY $1,744,000
Existing Condition
f 0 C U S 3 6 0
.'I li ) ' I- I • I; I
( T; 111 m 11 r i I ,1 : i ,;-| r- i Agua Hedionda
P/C Concrete Box Girder
f 0 C U S 3 B 0
(• (j m m ;i n i r" ,1 • i .fl n -
VI t . 1 i . i« la 0 s
Agua Hedionda
steel Through Truss Bridge
f D C U S 3 B 0
f I h i ' I' I : i: ;
C 0 iTi rn 11 n i c ,i • i .;; r .
"> •> 0 . z ^ 4 , n a o s
Agua Hedionda
Hybrid Arch Concrete Box Girder
f D C U S 3 B D
• ll '. :.i III.;':
'-' '"i IV J f i (1 i ; IJ '-
'> J '.> . 2 .1 . (I a I) II
Agua Hedionda