26-D-00030 Ybor Pumping Station Force Main Repairs Design

Tampa Construction Specifications
RFQ 26-D-00030 Ybor Pumping Station Force Main Repairs Design
CITY OF TAMPA, FLORIDA
Supplemental Information for
RFQ 26-D-00030 Ybor Pumping Station Force Main Repairs Design
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Supplemental information should e-mail Contractadministration@tampagov.net.
City of Tampa
Contract Administration Department
Tampa Municipal Office Building
306 E Jackson Street #280A4N Fourth Floor
Tampa, Florida 33602

FINAL
Ybor Force Main Urgent Repairs
PHASE 2 - LONG-TERM RESOLUTION
ALTERNATIVES ANALYSIS
April 10, 2026

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TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................................................................... 5
1.1 Background ........................................................................................................................................ 5
1.2 Problem ............................................................................................................................................... 5
1.3 Scope of Services ............................................................................................................................... 6
2.0 ALTERNATIVES SOLUTIONS ................................................................................................................. 6
2.1 General ............................................................................................................................................... 6
2.2 Alternative A - Flow Diversion to allow Force Main Rehabilitation or Replacement ..................... 7
2.3 Alternative B - Hot Taps, Line Stops and Temporary Bypass Pipe ................................................. 9
2.4 Alternative C - Hot Taps, Line Stops and Permanent Bypass Pipe .................................................. 9
3.0 RECOMMENDATIONS........................................................................................................................... 9
3.1 Comparative Costs ............................................................................................................................. 9
3.2 Project Duration .............................................................................................................................. 10
3.3 Final Recommendation ................................................................................................................... 11
FIGURES
Figure 1-1 Typical Threaded Outlet in Embedded Cylinder Pipe ........................................................... 5
Figure 1-2 Embedded Cylinder Pipe Construction ................................................................................. 6
TABLES
Table 2-1 Conceptual Level Hydraulics .................................................................................................. 8
APPENDICES
Appendix A. Alternatives A , B and C
Appendix B. Breakdown of Comparable Costs
Appendix C. Ybor FM As-Built Drawings
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Acronyms
Table text
PCCP Prestressed Concrete Cylinder Pipe
DIP Ductile Iron Pipe
ARV Air Release Valve
SCADA Supervisory Control and Data Acquisition
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1.0 INTRODUCTION
1.1 Background
The Ybor Force Main, designated Division 4F1, was constructed in 1980. This sanitary force main is
comprised of 72-inch and 54-inch diameter prestressed concrete cylinder pipe (PCCP). The
downstream segment is 54-inch and the upstream segment is 72-inch. A second parallel
downstream segment was originally planned, but it is now apparent this segment will not be
required.
1.2 Problem
In 2025, one of the force main's air release valves (ARV) in 26th Street was found to be leaking.
Further investigations revealed the top mounted two-inch diameter threaded outlet in the 72-inch
force main was structurally compromised. This threaded outlet is mounted on a reinforcing band
attached to the steel cylinder of the PCCP. See Figure 1-1. It is evident that the pipe is deteriorated
by common crown corrosion from the accumulation of hydrogen sulfide gas that is reduced to
sulfuric acid. The PCCP is embedded cylinder pipe which means the corrosion has progressed
through the 1.75 inch thick interior concrete core and reached the steel cylinder. See Figure 1-2. The
steel cylinder functions as the waterproof membrane in PCCP since concrete is porous. This
deteriorated pipe would not be watertight under elevated pressures. Fortunately, the exterior
concrete core is approximately 3.75 inch thick. Optimistically, it will take some additional time for the
corrosion to progress through the exterior concrete core before it reaches the prestressing wires.
This pipe needs to be permanently replaced, repaired or rehabilitated before corrosion reaches the
wires. Historically, corroded prestressed wires result in rather catastrophic rupture failures in higher
pressure applications. Fortunately, this pipe normally operates at much lower pressures of around
10 to 20 psi. During significant storms resulting in higher flows, the City should use due care to avoid
operating this force main at higher pressures as much as is practicable until permanent repairs are
completed.
Figure 1-1
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Figure 1-2
The leaking ARV was stopped from leaking by the addition of an outlet saddle over the ARV and the
outlet was filled with concrete and capped. This ARV can no longer vent gases which means
corrosion will continue to progress. Since the steel cylinder is compromised, adding a new tap to
replace the ARV involves seating the outlet saddle gasket on an exposed surface of the corroded
cylinder which would likely fail and be very risky to chip away the exterior core to expose the surface
of the cylinder.
1.3 Scope of Services
Wade Trim has been authorized to provide recommendations to the City for mitigation of this
problem. The services are divided into two phases. Phase 1 includes more immediate external
strengthening of the most susceptible parts of the force main, While Phase 2 provides
recommendations for a long term solution. Phase 1 is addressed separately, while Phase 2 is
provided herein.
2.0 ALTERNATIVES SOLUTIONS
2.1 General
When large diameter pressure pipes have localized failures, it is common to employ line-stops
upstream and downstream of the failure in need of repair. If maintaining flow is required, the stops
have adjacent hot taps and a bypass around the failure. In the size range for this project, the line
stops and hot taps are approximately $250,000 each just for the specialized sub-contractor and four
are required. For this project the length of the level, high portion of pipe, according to design
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documents, is 1,090 linear feet. This section of pipe is located just south of Adamo Dr. (SR60) and
continues to the railroad tracks north of the Selmon Expressway. It is unfortunate that this
segment which is susceptible to gas accumulation and crown corrosion, along 26th Street, is so
long. 26th Street is a City of Tampa right- of-way. There is a likelihood that the gas accumulation will
be most prevalent in the downstream part, especially at the downturn which is 155 feet
downstream of the failed air release valve.
A temporary bypass approximately 42 to 48 inches in diameter could be laid above ground, but there
are five important business access driveways that would require sections of buried bypass pipe.
Below ground there are significant utilities that will make finding clear corridors difficult.
Three alternative solutions were developed for comparison, evaluation and cost comparison as
follows"
* Alternative A - includes diversion of flows from the pump station upstream of the force main
so the suspect portion of force main can be isolated and either rehabilitated or replaced.
* Alternative B - includes two linestops, two hot taps and a temporary bypass pipe so that the
suspect portion of force main can be rehabilitated or replaced.
* Alternative C - includes two linestops, two hot taps and a permanent buried bypass pipe so
that the suspect portion of force main can be abandoned and removed from service.
2.2 Alternative A - Flow Diversion to allow Force Main Rehabilitation or
Replacement
New facilities will be required to divert normal high flows from Ybor Pump Station estimated at 35
MGD following review of recent SCADA data. A new 36-inch force main would be constructed from
Ybor Pump Station approximately 4,205 linear feet east to the intersection of 34th Street and 3rd
Avenue where a hot tapped connection to the City's existing 48-inch diameter East Tampa Force
Main would be constructed. See Figure 2-1 in Appendix A. The route avoids parallel construction in
East 4th Avenue which is a County Road (CR 574). Two crossings of this county road will likely require
trenchless construction. A crossing of the Selmon Expressway Connector occurs where the roadway
is elevated thus a trenchless crossing is averted. This facility should allow approximately 22.5 MGD
of flow diversion. The East Tampa Force Main base flows are well below planned estimates leaving
ample capacity for the diversion flows. Hydraulic analysis will be needed to determine if the existing
station pumps can be used or if bypass pumps are needed
In addition, the City currently has an existing 36-inch reinforced concrete pipe (RCP) gravity sanitary
sewer that allows excess flows in the Main Outlet sewer to overflow into Ybor PS. With some
structure modifications, this connection could be modified to allow flow in the opposite direction
under low pressures. Using this existing facility averts the need for a connection to the Main Outlet
Sewer located in the median of Adamo Drive (State Road 60) This facility should allow approximately
12.5 MGD of flow diversion. See Figure 2-1 in Appendix A.
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Basic hydraulic calculations suggest both the East Tampa Force Main and the Main Outlet
sewer can accept these additional flows during normal high flow periods. See Table 2-1.
More detailed hydraulic calculations and review of historic SCADA information should be
performed if this alternative progresses to the final design stage.
Table 2-1
Once in place, these diversion facilities will allow the existing 72-inch force main to be removed from
service to allow either replacement or rehabilitation. The most cost effective rehabilitation technique
would be to slip line the 72-inch inside diameter PCCP with 54-inch diameter high density
polyethylene pipe. This pipe could be iron pipe size DR 26, 80 psi, inside diameter of 49.6" and a
wall thickness of 2.08" or DR 21, 100 psi inside diameter of 48.55" and a wall thickness of 2.57",
Grouting the annulus is imperative. Fortunately, the long, level section of pipe is favorable for
inserting the liner pipe. Insertion pits would be required at each end and likely two or three more in
between. This rehabilitation could be performed significantly more quickly than removal and
replacement. It also avoids disrupting the five critical business access driveways.
There is a discrepancy in the 72-inch PCCP record drawings on the south side of Adamo Drive (State
Road 60). The plan view shows casing pipe but the profile does not and includes vertical points of
deflection which are very difficult to encase. The record drawings state that the information is
incomplete. A thorough sub-surface utility investigation will be required here before final design. This
investigation is also required for the other alternatives
Perhaps most importantly, the aforementioned proposed diversion facilities are not a sunk cost.
These facilities could be available long after this project is completed, providing more flexibility and
resiliency for the next challenges or hurricanes. This alternative avoids the cost and risks associated
with 72-inch diameter hot taps and linestops potentially on corroded pipe. There is a risk that
extreme weather conditions could occur during implementation of this project which could
overwhelm the diversion capacity resulting in a sanitary sewer overflow. It is recommended that
construction should occur during the dry season (December to June).
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2.3 Alternative B - Hot Taps, Line Stops and Temporary Bypass Pipe
A pair of hot taps and line stops would be required just south of Adamo Drive (State Road 60).
Another pair would be required just north of the active CSX railroad on the north side of the Selmon
Expressway. See Figure 2-2 in Appendix A. Fortunately, the right-of-way is City and not County or
State. The line stop and hot taps near the CSX railway will be required on pipe that according to
design documents is sloped at 4.25 degrees. This slope is not ideal for vertical oriented line stops,
but acceptable. To mitigate the risk of inadequate sealing due to potential corrosion, final design
should include detailed pipe condition verification and evaluate the use of a horizontal line stop
configuration to limit the seal to a known, sound section of pipe.
As mentioned in the preceding section of this report, sub-surface utility investigations will be required
to properly locate the line stop and hot tap just south of Adamo Drive. A temporary alignment of the
42 or 48-inch bypass pipe could utilize sidewalk along the west side of the road as the roadway
pavement is underlain with numerous utilities. Some sections of bypass pipe may require bury to
maintain access to businesses. Business accesses on the west side include two driveways to IKEA.
Business accesses on the east side include three or four driveways to I Storage, cruise parking and
an Industrial office building with multiple tenants.
The time required to perform this option is difficult to predict accurately since the suspect pipe must
be replaced or repaired. Again, it is our opinion that slip lining would be faster and less costly than
replacement with 54-inch pipe such as ceramic epoxy lined ductile iron pipe (DIP). Transition from
PCCP to slip line pipe (54-inch HDPE) will require long lead time PCCP adaptor fittings/reducers, but
are not particularly difficult to construct.
2.4 Alternative C - Hot Taps, Line Stops and Permanent Bypass Pipe
As with Alternate B, A pair of hot taps and line stops would be required just south of Adamo Drive
(State Road 60). Another pair would be required just north of the active CSX railroad on the north
side of the Selmon Expressway. See Figure 2-3 in Appendix A. Ideally a rigorous utility investigation
and careful pipe alignment design could produce a corridor for the buried, permanent 48 or 54-inch
bypass pipe without requiring excessive relocations of existing parallel utilities including drainage, up
to 15-inch sanitary sewers, telephone cables, and power poles with mostly aerial wires. Crossing
utilities include gas and buried electrical transmission (two at 66 KV). Minimizing business disruption
will likely require some trenchless construction. New easements are not recommended.
3.0 RECOMMENDATIONS
3.1 Comparative Costs
Without significant effort to advance design past the conceptual stage, it is difficult to prepare
accurate project cost estimates that include administration, engineering, construction and regulatory
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