Pipelines 2023: Construction and Rehabilitation

Construction Manager at Risk (CMAR) contract mechanisms have been used for decades in other types of construction around the world. CMAR contracts are a relatively new concept in horizontal-directional drilling projects, but this type of construction with a high risk is suited for this type of contract instrument. This paper will cover the Bartram/US1 24″ Water Main project that consisted of three HDPE horizontal directional drills: one across I-95, one across Durbin Creek, and one across wetlands. The purpose of this project was to provide a dedicated fill line to the Bartram Repump Station. The current water supply source was also used as a distribution main for the surrounding area. When the station is filling, the existing main could not meet the demands of the surrounding area, which results in low water pressures within the grid. As development continues in the area, the duration of low water pressures would have continued to increase, further decreasing system reliability without this new 24″ water main. This required the line to be put in across a high-risk corridor utilizing three horizontal directional drills quickly before more low-pressure events happen and to meet the growth in the area. It was decided to use the CMAR with guaranteed maximum price (GMP) contract mechanism to shorten the procurement time for the construction contractor and to reduce the risks of the HDDs across sensitive infrastructure and waterways. An overview of the project phases with CMAR procurement and collaboration will be covered, as well as risk register development, GMP negotiations, project cost auditing, and final schedule and cost analysis.

The Sister Grove Regional Water Resource Recovery Facility (Sister Grove project) is a new wastewater treatment plant being constructed to accommodate the continued regional growth in North Texas Regional Water District’s (NTMWD’s) service area. Garney Construction is the Construction Manager At-Risk (CMAR) responsible for the entirety of the treatment plant and outfall pipeline construction, which includes preconstruction design services, coordination, scheduling, estimating, management, oversight, portions of construction, and cost management. The outfall pipeline was designed as a 96-in. gravity system that extends roughly 4 mi from the treatment facility to the discharge point. The project is in a geologic region where solid rock exists just feet below the surface. There are constructability challenges associated with large diameter pipeline installation in solid rock coupled with elevations of the pipeline requiring excavations in excess of 60 ft deep. The CMAR worked with the district’s engineering and operations teams along with the design team to optimize the construction methods to deliver this project. Using the CMAR’s experience, it was determined that a combination of trenchless installations and a traditional open-cut installation would be the best options for construction. The project’s scope ultimately included 9,453 linear feet (LF) of large diameter tunneling completed using a 123-in. tunnel boring machine and 12,071 LF of open-cut installation within mass excavations, vertical shoring, and employing both aggregate and controlled low strength material (CLSM) embedment around the pipeline. The CMAR delivery method engages a contractor early in the design phase unlike that of the traditional design-bid-build contracting method. For the Sister Grove project, the CMAR’s early engagement in the design process allowed for constructability reviews and suggestions, participation and input in public engagement and relations, construction sequencing to optimize schedule and efficiency, and development and procurement of the scope of work and material supply bid packages. In an environment where pricing on projects remains volatile, the CMAR’s early engagement afforded NTMWD the ability to secure pricing on materials, execute construction contracts, and procure long-lead items prior to the final design. This engagement ultimately provided NTMWD with the ability to overcome constraints in schedule and procurement that commonly exist without the involvement of a CMAR.

The City of Tacoma’s Jefferson Avenue and Hood Street Surface Water Interceptor Project will play a vital role in providing additional surface water capacity to alleviate flooding and increase capacity for growth in the downtown area. Project improvements included approximately 3,200 ft of new 48- and 60-in. surface water conveyance pipe; trenchless crossings of mainline railroad tracks; sound transit light rail tracks and a major city arterial; tie-ins to existing active pipelines; and a new marine outfall with adjoining shoreline improvements. The city elected to use the progressive design-build procurement method because of the alternative alignments available, the extensive permitting processes required, the railroad and light rail crossings, and the many stakeholders and downtown businesses impacted by the project. The paper will review the process for selection of alignment and project delivery method, which relied on a conceptual design to bring in a contractor partner to collaborate with the city in navigating challenging right-of-way crossings in difficult soil conditions.

The San Antonio Water System (SAWS) embarked on an ambitious plan in the early 2000s to address deficiencies in their wastewater collection system. The C_13 Broadway Corridor project addressed both condition and capacity in SAWS’ Central Sewershed, which collects wastewater from the central area of San Antonio (including downtown). The Broadway Corridor was the first full-scale application of polymer concrete hydraulic structures in the SAWS collection system. Two hydraulic structures were designed to convey wet weather flows to the parallel sewer system. In both applications, the pre-fabrication drawings ensured that the structures were manufactured to exact elevations and gradients for proper hydraulic operation once installed. This first application of polymer concrete hydraulic structures has been successful, providing multiple benefits, especially in a highly congested, restricted right-of-way and in complex hydraulic applications.

Extending the life of concrete structures within a wastewater collection and treatment system is a critical element to the life-cycle cost of the infrastructure assets. Many different types of concrete protection systems have been developed, one being epoxy coatings to provide a corrosion barrier to prevent wastewater gasses from corroding the structural concrete. The City of Pflugerville has recently completed construction of an expansion to the city’s Upper Gilleland Creek Wastewater Treatment Plant. The expansion included 12 wastewater manholes, an influent lift station, and headworks structure, and all were protected by an epoxy coating system. Each of the coating application steps is being evaluated in this paper, and some recommendations are provided. The two different epoxy systems (one being 100% solid epoxy sprayed with plural component spray equipment and the second being solvent cured epoxy sprayed with conventional spray equipment) are compared for constructability and efficiency of coating significant structures.

The Trinity River Authority of Texas (TRA) supports the City of Fort Worth by operating and maintaining the Walker-Calloway Interceptor system, a 4.7-mi major wastewater conveyance system constructed in 1970 of unlined reinforced concrete pipe (RCP). On June 4, 2022, a brief, intense rain event occurred within the Calloway branch of the collection system and led to a sudden increase in wastewater flow, causing surcharge. The surcharge event caused a portion of the unlined concrete pipe to become dislodged and collapse in the path of flow leading to an SSO immediately upstream from the blockage. Unseen from above grade, the pipe collapse had undermined a 25″ tall drainage channel embankment and the residential driveway above the collapsed pipe. During excavation for the repair of the pipe, a massive cavern was discovered and subsequently repaired. The collapsed pipe was uncovered and replaced along with the downstream section of pipe, which was also deteriorated to the point of collapse. A combination of open cut and pipe bursting was used in the repair, and flow was restored on July 1, 2022.

DC Water owns hundreds of miles long masonry sewer, typically in congested areas packed with many linear assets of different owners. The integrity management of such old masonry pipe mandates a unique mindset in condition and adjacent construction impact assessment, prior, during, and after adjacent construction. In July 2021, DC Water discovered damage to a 39″ × 56″ brick sewer. A DC Water team launched into emergency response action in steps to prevent such localized damage of “bottom fall-out” from becoming a cause of street sinkhole. (1) By collaborating with peer agencies, we convinced the owner of the hand tunnel to fill it solid with flowable fill; (2) By in-depth knowhow of masonry sewer, we deployed extended chemical grouting to solidify the compromised bedding; and (3) By hydraulic modeling, we clarified which structural rehabilitation solution would not cause surge in the sewer. With above mitigation, DC Water successfully achieved our goal and prevented a sinkhole from forming relating to the brick trunk sewer that was damaged by an adjacent construction by others. This case study will share a few critical knowhows for integrity management of buried masonry asset in congested street.

The City of Ensenada is located south of San Diego, approximately 75 mi from the international border, and has been a retirement community and summer retreat community. The city is also a tourist gateway into the wine country of Baja California. Its population of 350,000 doubles during the high season in the summer months. In August 2022, two significant breaks occurred in the main waterline to the town. These breaks caused the town to be without water for eight days. Following repair, additional breaks occurred, and it was established that there was significant corrosion along the entire 77 km alignment. Most of the breaks occurred in a 2-km stretch which was the high-pressure segment of the aqueduct. The governor of Baja California declared an emergency and directed the state director of public works to devise a replacement for the aqueduct. Recognizing the emergency, it was determined to go with a design-build of the 30 in. aqueduct. Constructora Makro (“Makro”) was awarded the Design-Build contract, and within eight weeks, the 2-km section was designed, pipe manufactured, and construction began. This was a great example of bi-national cooperation between businesses in the United States and Mexico.

During DC Water’s multiple-camera entry inspection for an in-depth condition assessment of the Northeast Boundary Trunk Sewer (NEBTS), an abnormal condition with severe invert heaving, crown sagging, longitudinal fracture, and up to 10% ovality in a century-old 72″ brick sewer trunk sewer triggered DC Water Engineering attention. DC Water engineers coordinated with DC Water’s permitting and construction management teams to conduct a thorough investigation and review all adjacent construction activities in the damaged area. The investigation found that a tieback from the recently completed building was placed too close to the invert of the brick sewer. The pressure grouting in the tiebacks heaved the brick invert causing the crown and invert to deform and crack. The risk assessment revealed that there was a potential high impact sinkhole in the narrow street congested with a gas line, two other sewer lines, two water lines, and multiple duct banks above the 72″ brick sewer. To prevent a catastrophic sinkhole, an immediate “no-dig” zone in these blocks was enforced, and DC Water engaged a sole source high confidence specialty contractor to perform carbon fiber reinforced pipe (CFRP) laminating to structurally replace the compromised brick sewer without compromising hydraulic capacity. This paper will present how DC Water performed every critical step to manage the risk and successfully averted a catastrophic failure, handled design and construction challenges, and lessons learned.

On March 18, 2021, the City of Baltimore DPW received notification of a water main leak inside a CSX Transportation tunnel that runs beneath Howard Street in Baltimore, Maryland. The city contacted EBA Engineering, Inc. (EBA), who already had a contract in place with the city to provide urgent need water engineering services. A visual inspection determined that the infiltration encompassed extensive dripping, seeping, and flowing water across roughly 200 ft of the tunnel. During a meeting with the entire response team, including the city, CSX, EBA, and the city’s on-call contractor, a decision was made to identify the source of the water leak and begin repairs immediately. Finding a water leak of unknown origin is not an easy task—finding one within the maze of utility lines and other structures located along Howard Street was akin to finding a needle in a haystack. After several weeks of aboveground inspections, followed by CCTV inspections and reviews, were unsuccessful, the city retained Pure Technologies, Ltd., to perform a SmartBall leak detection survey that identified three water main leaks from a 16-in. water main located under the Maryland Transportation Authority (MTA) Light RailLink tracks in Howard Street. With a size between 2 gallons per minute (gpm) and 10 gpm, one leak was significant, while the other two, at a size of less than 2 gpm, were suspected to be feature related. The city tasked EBA with design, permitting, and oversight of the leak repairs to avoid a catastrophic tunnel failure. During efforts to address the largest leak, the contractor discovered a 16-ft by 22-ft void under the MTA light rail tracks and extending down to the CSX tunnel. Repair of the two smaller leaks then required a challenging tunnel design and construction under the MTA light rail tracks. Despite multiple challenges, the city and its on-call design consultant and contractor fostered a strong collaboration to rapidly plan, design, and execute the repairs.

The City of Rocky Mount’s Beech Branch Outfall consists of 27-in. corrugated metal pipe (CMP) with a total length of approximately 25,000 linear feet. This gravity line was installed in 1978 and was well beyond the expected service life for a pipe of this material of construction used in sanitary sewer service. The pipe had experienced several failures, and a comprehensive program was undertaken, which included flow monitoring, modeling, data collection, review of historical data, and surveying, to develop and evaluate rehabilitation and replacement alternatives for this critical asset. Initial inspections performed revealed the CMP was lined with road tar-like material rather than a coal tar epoxy creating some unique challenges to be addressed during design. This paper will explore the data, decisions, findings, and recommendations that lead to successful rehabilitation of the pipe using the cured in place pipe method in 2020.

The City of Toronto’s Ashbridges Bay Treatment Plant Outfall (ABTPO) project will be the largest wastewater treatment plant effluent outfall in Canada. This paper discusses the design approach and construction efforts for the riser pipes on the ABTPO project, including construction sequencing. Base bid marine construction performance requirements and limitations, alongside contractor-specific construction methods for all riser installation steps, are presented in the paper. Finally, the paper includes consultant and owner perspectives on challenges encountered and solutions implemented to successfully perform marine construction for ABTPO.

The North Davis Sewer District (NDSD) collects and treats wastewater from the cities of Clearfield, Clinton, Layton, Roy, Sunset, Syracuse, West Point, and Kaysville. The current NDSD facilities treat up to 34 million gallons per day (MGD) prior to discharging into Farmington Bay of the Great Salt Lake (GSL). NDSD began investigating methods to meet stricter nutrient load requirements implemented by the state of Utah. By collaboratively working with the state, NDSD was able to invest in a capital improvement project consisting of a pump station and pipeline instead of a new treatment facility capable of meeting the state’s newly implemented technology-based phosphorus effluent limits (TBPELs). This approach results in treated effluent remaining in the GSL, a terminal water body in Utah that is experiencing historically low water levels, rather than being consumed by water reuse or evaporation. A four-year evaluation period included evaluating the long-term health of the GSL, including the water level of the lake; meeting the discharge requirements of Farmington Bay; limiting the growth of invasive phragmites; and maintaining wildlife habitat.

Placer County Water Agency (PCWA) operates the Middle Fork American River Project (MFP) that includes three powerhouses with above-ground penstocks nearing 60 years in age. PCWA is managing a plethora of penstock issues that have manifested themselves over the life of these penstocks. These issues include episodic ground movement at multiple saddles and one anchor block leading to associated movement in select penstock pipe sections and joints; local area slope instability and surface drainage inefficiencies; age-related degradation of linings and coatings; and unfavorable conditions at welds in sleeve-type mechanical couplings. This paper/presentation describes programs and projects PCWA has initiated and executed to monitor, mitigate, and address these issues focusing on replacing a slipping coupling with one having greater span to accommodate anchor block movement; conducting a program to test and replace unfavorable flash welds on middle rings of couplings susceptible to rupture.

This article presents an in-depth stress analysis of a large diameter wye fitting using finite element analysis (FEA). The analysis aims to investigate the effect of different parameters on deflection and stress distribution at critical points. The paper presents the nominal FEA settings needed to achieve most reasonable results. Additionally, the effects of different boundary conditions of the FEA as well as minimum required fitting length for handling are investigated. Moreover, limitations of the wye fitting stresses are examined against the ASCE MOP 79 Steel Penstocks, and the effects of wye design parameters such as pipe diameter-to-thickness ratio (D/t) and crotch plate length-to-thickness ratio (D_w/t) are investigated in an attempt to reduce the cost and ease of installation of wye fitting with crotch plates. Finally, wye fitting with pressure diameter value (PDV) values of 6,000−10,000 is investigated to evaluate their performance according to the ASCE MOP 79.

The Olmsted 102-in. diameter welded steel pipeline was originally constructed in the 1950s and conveys water to the 11 mega-watt Olmsted Hydroelectric Power Plant. As part of the rehabilitation and replacement of the Olmsted Power Plant in 2018, an in-place cement mortar lining was installed inside the pipeline in accordance with AWWA C602, Standard for Cement-Mortar Lining of Water Pipelines in Place—4 in. (100 mm) and Larger. It was decided during construction that the field-installed cement mortar lining would not require a finished troweled surface because of concerns related to the out-of-round and elliptical shape of the pipe. It was also assumed that the untroweled cement mortar lining would exhibit a hydraulic surface roughness similar to that of the surface of an orange, as suggested in AWWA C602. This paper will present the hydraulic capacity and roughness characteristics of the untroweled cement mortar lining along with the field-measured and calibrated roughness characteristics for this pipeline based on the original bare steel lining and subsequent field-installed epoxy lining used in the existing 102-in. diameter pipeline. The hydraulic roughness was determined by measuring free water surface elevations and installing manometers along the pipeline to collect hydraulic grade line data for flows between 100 and 400 cubic feet per second (cfs). The roughness and surface profile of the field cement mortar lining will also be presented based on collected samples of the lining once it was removed. The benefits of this paper will be a presentation of roughness coefficients for a large-diameter pipeline that utilized different lining systems, all field-measured and calibrated under similar flow and hydraulic conditions. The subject matter will be useful for pipeline designers and utility owners considering different options for the rehabilitation of linings in large-diameter pipelines.

CCTV can be a great tool for inspecting pipe interiors for problems. At about 30 days after construction, gross problems can be seen such as tools left in the pipe, poor lateral connections, extreme over-deflection or collapsed pipe, and large cracks. At one year, sags, infiltration stains, and joint offsets are more evident. Since the maximum earth load on the pipe does not occur until about 3 to 12 months after construction, excessive deformation and cracks may not be detected for several months. CCTV has its issues, however. Untrained camera operators and video reviewers find problems that do not exist. This may lead to unnecessary removal and replacement. Case histories, from snail trails to wicking in hairline cracks, will be cited to illustrate that proper techniques, procedures, and reporting are important. The accuracy of the interpretation of CCTV systems heavily relies on the experience levels of operators and the quality of the acquired images. It can also depend on how well the pipe has been cleaned. Representatives from the clay pipe and concrete pipe industries will add their experiences to the paper and the presentation.

The City of Phoenix (city) launched an assessment program for its force main assets in 2015. In 2020, as part of the city’s ongoing efforts to understand and minimize risk associated with buried infrastructure, Black & Veatch was hired to perform a comprehensive condition assessment of the force main associated with Lift Station 43 (LS 43). LS 43 Force Main is a triple barrel force main, with each barrel comprised of 1.5 mi of 24-in. ductile iron pipe DIP, referred to as Barrels 1, 2, and 3. Two of the three force main barrels were assessed (3.0 mi total). DIP tends to fail through corrosion, causing initiation and growth of localized defects. Based on the city’s objective of identifying the location and approximate depth of pitting in every foot of the inspected pipes, remote field electromagnetic (RFEM) technology was identified as the primary inspection technology. Barrel 1 was inspected first. During the inspection, a construction anomaly was identified, preventing the RFEM inspection tool from flowing freely through the pipeline and requiring extraction by excavation. The anomaly was assumed to be present throughout all force main barrels, and the RFEM inspection tool was subsequently modified to allow passage. Barrel 3 was then successfully inspected using the modified tool until the last 5 ft when the tool became stuck again. This document will review inspection planning, execution, and tool recovery. Significant operational challenges must be overcome to insert, track, retrieve, and obtain high-quality data when deploying the 22-in. outer diameter inspection tool through a 24-in. inner diameter pipe. Lessons learned from planning and executing the inspections will be discussed.

The general requirements for structural classification systems are defined in AWWA Manual M28. Currently, there is no specific protocol or procedure for development and testing of AWWA Class IV lining system. The steel composite lining system (SCL) has been developed, tested, and installed for over the past 13 years. This paper will describe the liner design methodology, the materials, component, and full-scale model testing for the SCL system, which documents the AWWA Class IV classification. Rigorous testing with innovative technology at three levels transformed the SCL system from original concept to a Class IV lining system. The data collected during each level is used to better understand the design and construction methodology and their impacts on system performance. Full-scale mockup and testing along with posttest digital twin computational modeling verifies the design approach and Class IV lining system performance. As an additional proof of performance, an instrumented installation was monitored for more than one year, in situ. The long-term measurement further verified material and system performance while in water delivery service. Not all SCL tests were successful on the path to becoming a Class IV system. The SCL story is indicative of the need for testing on all levels to make sure the system in its final form can be designed using industry standards, is constructible as designed, and provides the functionality required.

Trenchless pipeline technology is an emerging field in both new installation and the rehabilitation process of underground pipeline infrastructure. Polymeric spray applied pipe lining (SAPL) is a rehabilitation technology that is continuously developing to provide solutions for deteriorated pipelines’ design life extension. Polymeric SAPL can be used as a corrosion protection and also as a structural lining inside the host pipe. This research work aimed to develop a methodology and liner design practice for short-term hole-spanning internal hydrostatic pressure testing. The liner material used for this test was a fast-setting pure polyurea. The full-scale hole-spanning laboratory testing evaluated the hole-spanning capacity of pipes lined with polyurea under high-pressure (up to 500 psi) with breach sizes of 0.5, 1, and 2 in. The breaches in the pipe samples simulated the corrosion holes. The liner thickness was designed as class II semi-structural, interactive with the host pipe based on AWWA structural classification. The results of this testing determined the capacity of the liner to renew the high-pressure pipes with corrosion holes. The testing also provided design guidelines to determine the liner thickness when used as a semi-structural application.

Use of innovative composite systems for new pipeline construction as well as rehabilitation of existing pipes can open the door for extraordinary applications that would be too expensive or unfeasible to produce, transport, and install with conventional materials such as reinforced concrete and steel. This is more pronounced for supersize pipes over 10 ft in diameter. Once the diameter reaches above that level, production costs go up drastically mainly due to going above the typical size range of serial production with standard equipment. Another caveat is the high weight and large space these pipes take with conventional materials to an extent that it could be virtually impossible to load and transport them across the country due to roadway load restrictions in the itinerary, limited clearances under bridges, and truck bed size. As such, for super large pipes (e.g., 10 ft and above in diameter), the options are very limited. For rehabilitation, cast/cured in place systems or panels in lieu of 360-degree pipe liners are the more common options. Nevertheless, those methods have their limitations with respect to load bearing capacity, installation difficulties, as well as the need for bypassing the flow and drying out the pipe for cured-in-place components. This paper will discuss the design and production methods used to make large diameter pipes/liners utilizing a patented composite system that is comprised of glass, carbon fiber, and a proprietary core layer. Case studies including rehabilitation of a 17.5-ft sewer interceptor with a 16-ft diameter liner will be presented. At 16-ft internal diameter (ID), this is likely the largest polymeric pipe ever made as a monolithic piece.

Although some civil engineers may be aware of the general concept of tapping into and plugging a pipeline in order to accomplish repair or reconfiguration of piping systems while maintaining service, there are others that are unfamiliar with the process. This is because the information in public references and standards commonly used by civil engineers is usually limited to taps for small diameter service lines. More detailed information for larger diameter pipes relative to this procedure is confidential and particular to the relatively few industrial organizations that offer the fittings and tapping and plugging services. As a result, it is not uncommon for engineers to simply indicate a tap and plugging procedure in documents, or develop an incomplete or erroneous specification that could be detrimental to an efficient and economical execution of a project. This paper discusses tapping and plugging specifications; selection and design of appropriate fittings and their respective configurations for different pipe materials and pipeline product; fitting installation and testing; tapping and plugging procedures; options for addressing loads and thrusts developed during operations; plugging sequencing; withdrawal of equipment and closure of fittings in order to improve project effectivity.

The City of Houston was faced with a need to replace an approximately 50-year-old 42-in. PCCP line with a history of leaks, which carries water from a critical 96-in. transmission line with no redundancy to seven smaller partner cities to the south. This replacement required a new interconnection to the existing 96-in. line without impact to water service by maintaining an internal pressure of at least 55 psi throughout the work. To respond to this request, the design team performed two levels of evaluation, first considering the trade-off between risk, cost, and temporary service interruption for options including cut-in TEE, single full-diameter tap, multiple smaller taps connected to a header, and extending the new water line an additional 1.5 mi to enable a connection at an existing stub-out within the treatment plant. For the option with multiple hot taps, the required removal of prestressing wires and concrete outer core while the 96 in. line with unknown condition is in service warranted detailed analysis. Finite element modeling was performed to evaluate the safe maximum line pressure during the time the prestressing wires and concrete outer core are being removed for potential 24-in. or 30-in. taps.

Metro Vancouver’s Sperling Avenue Forcemain cuts right through environmentally sensitive Burnaby Lake Park. The 533 mm diameter steel force main was installed in 1962 and is a critical piece of Metro Vancouver’s wastewater system. In 2020, Metro Vancouver issued an RFP for condition assessment of the force main and selected Pure Technologies to execute a high-resolution condition assessment. Prior to the project, no previous condition assessments had been completed; however, the force main suffered from point failures in the past. In 2021, an inspection of the force main was completed with a high-resolution, free-swimming inspection technology. Challenges associated with the inspection included limited flow control ability and mobilizing and working during the COVID-19 pandemic. Analysis of the inspection data identified defects, which Metro Vancouver decided to repair. In September 2022, repairs were completed, increasing Metro Vancouver’s confidence the force main can continue to successfully operate in its unique in situ conditions.

Pipeline rehabilitation comes with a variety of inherent risks, ranging from system operations, extreme weather, and the installation process itself. While the budgetary effectiveness and socioeconomic benefits of trenchless rehabilitation remain ever present, understanding and planning for risk should be a key component of any rehabilitation program, the necessity of which becomes even more apparent when the risks associated with large diameter and complex rehabilitation work are evaluated. Working within existing in-service pipelines, which often form part of a much larger collection system, creates inherent risk for trenchless rehabilitation. As pipeline diameters increase, flow conveyance and asset criticality go up while redundancy within the system typically goes down. To quantify risk, a sufficient understanding of the existing system, flow regimes, and failure consequences is required. Rehabilitation technologies, similarly, have a range of characteristics which affect both installation and system risk during construction. Beyond long-term structural and operational performance characteristics, the selection of rehabilitation systems must also consider their imposed risk on the wider system during installation. This paper will address recommended planning activities and considerations for trenchless pipeline rehabilitation with a focus on large diameter and complex rehabilitation. Topics discussed include evaluating the existing system, assessing rehabilitation technologies, quantifying risk, tendering, and construction monitoring. Failure to undertake adequate planning can lead to unfortunate events, such as basement flooding, sewer overflows, or other third-party damage with potential costs well in excess of the contract value. Ultimately, the responsibility for risk mitigation falls to all parties involved, that is, the engineer, owner, and contractor. All three parties have a critical role in the process, and the paper delineates these responsibilities and provides recommendations for how risk mitigation can be implemented at all stages of the project. It is the authors’ hope that readers (from all facets of the rehabilitation process) will gain a better understanding of risk assessment process and its importance when planning and implementing trenchless pipeline rehabilitation projects.

Fiber reinforced polymers (FRP) have been gaining momentum in the last decade for structural pipeline rehabilitation in addition to other infrastructure. The advantages these systems provide include having the highest strength to weight ratio in the industry, corrosion resistance, and ability to install with minimal disruption, footprint, equipment, and greenhouse gas emissions. Another advantage FRP systems provide is the ability to install them externally on a pipe without the need for stopping the flow of disrupting service. Use of externally wrapping has been more common in the energy industry as well as in other manufacturing facilities where pressures and safety factors can be quite high. As such, there is more experience in the field of mechanical engineering than civil, and ASME’s PCC2—Repair of Pressure Equipment and Piping, Part 4 provides detailed guidance for designing carbon fiber reinforced polymer (CFRP) wrap on energy and other facility piping. This paper will discuss the design methods for FRP linings with respect to differences in external and internal applications. The internal pressure design equations included in PCC2/Part 4 and AWWA C305 will be reviewed, and differences will be outlined. Then case studies on pipeline rehabilitation by externally wrapping of pipes with FRP in the water and wastewater facilities will be presented. The design methods used in those case studies will be elaborated.

The deterioration of stormwater culverts placed into service 50 to 100 years ago includes reduced structural integrity, high rates of leakage, insufficient flow capacities due to partial collapses, and other types of issues. Spray applied pipe lining, grouting, and sliplining are viable trenchless rehabilitation methods to restore culvert pipes’ intended functionalities. The objective of this paper is to present a review of these rehabilitation processes. The renewal methods considered in this study are categorized into fully structural, semi-structural, and non-structural enhancements of deteriorating culverts. Technical features, application methods and conditions, and benefits and limitations of the rehabilitation technologies are presented. The result of this study will provide an overview on the implementation of these methods in various case scenarios.

Legacy pipelines experience damage associated with temperature fluctuations. Axial deformation and stress can be induced by pipe thermomechanical behavior. In legacy cast iron pipelines, movement induced by temperature fluctuations may be concentrated at weak joints or existing discontinuities. Successful installation of a rehabilitating internal pipe will affect thermal deformation of the host-repair system and must be designed to accommodate upper bound conditions. Here, an analytical approach is used to estimate potential levels of axial deformation. The assessment focuses on movement at a discontinuity, representative of a weak joint or circumferential crack in the host pipe, which is spanned by a rehabilitating internal pipe. Closed-form equations for induced force and crack opening displacement are derived. The analytical solution shows that crack opening displacement increases as initial crack width increases and the axial rigidity of the repair pipe decreases. The solutions at limiting cases compare favorably with previous work. These solutions provide a useful estimation of potential in-field displacements.

Seattle Public Utilities (SPU) selected HDR Engineering, Inc. (HDR) to rehabilitate approximately 2,600 linear feet (LF) of the 66-in. diameter concrete pipeline known as Tolt Pipeline No. 1 (TPL1), which traverses an active landslide area that has been slowly moving approximately 1 in. per year for the last 20 years. HDR initially performed a detailed condition assessment of TPL1 to determine if sliplining would be feasible to minimize open-cut installations within the slide area. The pipeline alignment and profile, pipe material design parameters, and slipline pipe pull forces were evaluated to determine the number of pit locations and maximum slipline lengths, resulting in a total of three slipline segments of a 54-in.-diameter high-density polyethylene (HDPE) DR-17 pipeline using four launch and retrieval shaft locations. The slipline segments included a pull length of 170 LF limited by appurtenances, a pull length of 1,100 LF, to a maximum pull length of 1,125 LF, resulting in the total slipline rehabilitation of 2,395 LF.

Often, the decision on whether selecting a structural over a non-structural pipe lining option during trenchless design is based on dead and live load requirements, which results only in differences in liner thickness. But other factors, like the proper liner material mechanical properties, are also important where pressure cycles, vibrations, and surge pressures play an important role. In general, the differences in material mechanical properties between structural and non-structural solutions are not considered during liner design. Therefore, the general liner design methodology can be improved when the often-unexplored material mechanical properties are considered. Data from tensile testing allow for interpretation of often unexplored advantages of liner materials made with different material formulations. The complete range of material characteristics discernible in tensile stress-strain curves is explained and discussed for different materials. The basis for a decision support system for liner design is presented.

There are two inevitable facts about the world we live in: buried water infrastructure continues to deteriorate and our population continues to grow. These diverging aspects create a challenging task of fully restoring critical assets while balancing the increasing needs of the entire water system. It is more important than ever to leverage the innovative technologies to provide cost-effective solutions. Some technologies are easier to see the cost savings and benefit; however, there are other technologies that are not as obvious. This presentation will highlight the true cost savings of water main rehabilitation techniques and even quantify the indirect costs that are avoided through improved construction techniques.

The City of Winnipeg (city) has undertaken a large-scale rehabilitation of their North End Sewage Treatment Plant. An integral component of this rehabilitation project was the in situ structural renewal of 1,640 LF (500 m) of in-service return activated sludge (RAS) process piping with several active leaks. The city engaged Kontzamanis Graumann Smith MacMillian Inc., Group (KGS Group) as the project’s engineering consultant to evaluate options for strengthening the RAS piping, which range in diameter from 12 in. (300 mm) to 36 in. (900 mm). The city and KGS Group selected external carbon fiber reinforced polymer (CFRP) as the rehabilitation method. The CFRP subcontractor, Pullman, mobilized to the project in April 2022 and worked collaboratively alongside the city, KGS, Simpson, Gumpertz and Heger (SGH), and the general contractor—Trotter and Morton. As was expected, the project details evolved frequently in response to as found condition. SGH utilized an in-field engineer and an iterative design process to minimize project delays. The collective team met frequently to resolve these RFIs in a timely fashion. The CFRP component of the project was completed on time with change orders accounting for less than 1% of contract value.

A leaking 80-year-old 60-in. diameter wastewater force main under the embankment of IH-35 near downtown Dallas presented a difficult challenge. With wastewater service and the freeway both in jeopardy, DWU collaborated with the engineer and contractor to devise an innovative in situ repair methodology. The team performed a forensic analysis that pointed to an original installation transition point near the suspected leak location. Running out of options and needing an internal rehabilitation construction option that could avoid surface impacts and excavation, the team investigated a carbon fiber reinforced polymer (CFRP) construction repair solution. CFRP offered an internal rehabilitation method unconstrained by pipe geometry or surface constraints and formed a pipe that is now capable of handling higher surface loads than its original design capacity. The collaborative approach between DWU, the engineer, and the contractor yielded a fast-track solution to a problem that had lingered for years but was completed in mere months.

Over the past 15 years, the Region of Peel in Southern Ontario has been developing an extensive condition assessment program for its large diameter prestressed concrete cylinder pipe feedermains. The proactive assessment and repair of critical feedermains helps assure that the Region can deliver safe and reliable drinking water to its customers every day. The Herridge 1,500-mm (60-in.) feedermain is approximately 6 km (3.7 mi) in length and was first assessed using electromagnetic inspection technology in conjunction with a visual and sounding inspection in 2011. This inspection identified a significantly higher-than-average degradation rate for prestressed concrete cylinder pipe (PCCP), with 6.2% of pipes exhibiting signs of broken prestressing wire wraps, particularly along a critical trucking route with heavy traffic loading and an adjacent rail corridor. From 2014 through 2016, the Region undertook an extensive repair program of the Herridge Feedermain, repairing 106 pipes throughout the length of the feedermain with carbon fiber reinforced polymer (CFRP). Repairs were completed before the introduction of American Water Works Association C305 standard and included both composite and stand-alone designs to reinforce distressed pipes. A follow-up electromagnetic and visual and sounding inspection in 2021 also included a detailed inspection of the CFRP repairs to assess their long-term durability. The electromagnetic inspection confirmed continued high rates of degradation, with 6.2% of all pipes exhibiting signs of broken prestressing wire wraps in 2011, and an additional 2.8% exhibiting signs of broken prestressing wire wraps in 2021. Inspection of the CFRP repairs concluded that the stand-alone designs had held up well; however, structural issues were found in several composite repaired pipes as well as new pipes. This led to upgrades in 2022 for the damaged and most at-risk composite pipes to the stand-alone design to increase the expected lifespan of the repairs. Additionally new repairs were completed for a handful of pipes that had experienced new or growing amounts of broken prestressing wires since 2011. The 2021 condition assessment also featured the addition of inspection and maintenance on all in-line butterfly valves in the feedermain, including entering the pipe where possible to inspect the valve gaskets and seats. The valve maintenance program ensured that valves are operable in an emergency and was completed at a fraction of the price of valve replacement. The Region’s long-term management of the Herridge Feedermain, including electromagnetic inspections, planned CFRP repairs during future outages, and valve maintenance program is helping to achieve system reliability and honor the commitment to customers of delivering clean, safe drinking water.

Many power plants and utilities implement a condition assessment program for their pipelines to identify distressed pipes and repair them as necessary based on the condition of the pipes. Based on the result of the condition assessment (including electromagnetic or visual and sounding inspections), a failure margin analysis is conducted to prioritize the distressed pipes for repairs. Generally, the condition assessment and repairs of highly distressed pipes must be completed within the limited duration of a shutdown. This paper presents an approach of preparing a pipe degradation ranking (ranking of distressed pipes in need of repairs) to assist the pipeline owners in planning and prioritizing the pipe repairs in the current and future shutdowns. It describes the criteria for considering the condition assessment results for ranking the distressed pipes and prioritizes them for repairs. It also discusses the phased repair solutions when the shutdown duration does not allow complete repairs for all distressed pipes.

The 42 in. diameter prestressed concrete cylinder pipe (PCCP), lined cylinder (LCP) type, is a sewer force main that was constructed in 1976. Condition assessment of the pipeline using electromagnetic technology was performed in 2019. Based on the results of the condition assessment, the owner selected nine pipes to repair in 2022. The repair pipes are located on a shallow bend along the shore of a reservoir. The owner elected to repair the pipes with externally applied carbon fiber-reinforced polymer (CFRP) while the line remained in operation. The CFRP was designed following AWWA Standard C305—CFRP Renewal and Strengthening of PCCP. The CFRP was installed to lengths of pipe in phases to allow the line to remain in operation while providing full circumference access and limiting the potential for vertical and horizontal movements from longitudinal forces. Initial condition inspection identified that much of the pipe’s mortar coating and corroded prestressing wires spalled off during excavation, exposing the LCP steel cylinder. As excavation proceeded, spalling of mortar coating resulted in very short periods of minor leakage through the exposed and corroded steel cylinder, which was quickly contained and mitigated. Assessing the condition of the pipes, the owner elected to replace two pipe segments with ductile iron replacement pieces and to limit the continuous length of pipe exposed at one time. Field engineering support was provided throughout the CFRP repair construction. Based on the field conditions, surface preparation requirements and details at exposed steel cylinder and terminations were updated, and a phased excavation and pipe support strategy was implemented. This paper describes the approach to evaluating pipes based on the external conditions of the pipe, different methods utilized to stop the leaks in the active line, factors for surface preparations to consider for deteriorated steel, phased excavation and pipe support approach, and overall repair construction of the pipes.

The University of Alberta’s cooling plant (CP) uses the North Saskatchewan River (NSR) water to produce chilled water used to meet the university’s cooling needs. The river water is supplied to the plant via two concrete intake structures located on the bed of the river, each connected to a wet well by a “1980 built 54-in. diameter steel pipe,” which runs under the riverbed perpendicularly to the river flow. Inspection and condition assessment efforts completed in 2020 on the 320 ft long west intake pipe revealed significant tuberculation build-up, scale deposits, multiple pinhole, and weeping leaks. The rehabilitation program started with evaluation of the technical viability and overall suitability of various rehabilitation methodologies with consideration given to all applicable characteristics of the pipe and the anticipated service life extension. Composite liner system (combining CFRP and GFRP) emerged as the most technically viable option. The rehabilitation activities were completed successfully in September 2022 to design, specifications, schedule, and budget with no safety incident.

Cured-in-place pipe (CIPP) is the most widely used trenchless technology for gravity-flow sewer and pressure pipe applications. As a composite material, CIPP consists of a formulated thermosetting resin and a textile carrier tube (liner) constructed from woven, non-woven or reinforcement material, or combination thereof. Reinforcement such as fiberglass or carbon fiber can provide enhanced performance and mechanical properties to resist internal and external pressures. Conventional CIPP liners are downsized relative to the host pipe inside dimensions and designed to expand under pressure and increasing temperature to compress and form tightly against the inner surface of the existing pipe. The degree of downsizing is dependent on the liner characteristics, host pipe geometry, application, installation process, and curing method. Reinforced CIPP designed for uniform, radial expansion is analogous to prestressing as the reinforcement material is in tension during installation, and then transitions into compression after cure and cool down while offsetting residual thermal stresses in the thermosetting resin. This paper discusses how prestressing concepts impact mechanical properties, performance, and structural classification of CIPP utilized for pressure pipe applications.

The District of Columbia Water and Sewer Authority (DC Water) is repairing 6,200 linear feet of clay sewers constructed more than a century ago. The project is in Soapstone Valley, part of Rock Creek Park. The sewer system will be rehabilitated using hot water curing and a styrene-free resin. In July 2021, DC Water proactively issued a Supplementary Standard Specification for CIPP adding requirements for air emissions. In June 2022, during the construction phase, local elected officials passed a resolution urging the Department of Energy and Environment (DOEE) to require DC Water to obtain an air quality permit for the CIPP work. DOEE required DC Water to submit an Air Quality Monitoring and Testing Plan (AQMP). A third-party contractor via the Water Research Foundation (WRF) will implement the Air Quality Monitoring Plan during CIPP installation. This study addresses worker safety, community safety, and the potential for air emissions during CIPP. According to the safety data sheets (SDS), the resin material contains no volatile organic compounds (VOCs). However, based on the review of the activator SDS, cumene and acetophenone are anticipated. Baseline samples will be collected. The research team will document the field conditions during air monitoring—daily activities, site maps, corrective actions taken, and unusual field situations, which may impact samples or sampling. An action level response plan was prepared, including clear protocols in the event concentrations in the ambient air, or lateral sewers exceed acceptable levels. Daily results will be reported to DOEE and shared with the community. The final report of air quality monitoring will be used to inform future construction approaches and data gathering efforts. Eventually, the project will generate data for DOEE to evaluate the effectiveness of monitoring and mitigation measures in the district. With the implementation of the AQMP, DC Water hopes to ensure the project is carried out in accordance with best practices aimed at mitigating environmental risks. Ultimately, the results of the study will provide broad value to utilities across the USA. This paper and presentation will focus on the regulatory framework that led to the AQMP and the air quality results.

Subaqueous horizontal directional drills (HDDs) require butt-fusion welding of the pipe joints to fuse the sections of piping together prior to pulling it into place. The fused joints are often stated by manufacturers to be stronger at these locations than the overall sections of piping, further reducing the potential of leaking at the joints. HDDs are typically pressure tested above ground but can also be pressure tested once pulled into place or pressured tested both times. Pressure testing of the HDDs should occur after the piping is pulled into place for final acceptance and assurances that no issues occurred during the installation process. What if an HDD passed the required pressure testing for clearance, was placed into operation, and subsequently was identified to be leaking? Further, what if this HDD was a subaqueous HDD for which the leaks could not readily be accessed due to the depth of installation and the inability to dig down and repair them with conventional open cut methods? This paper will discuss how an innovative trenchless liner was used to rehabilitate a leaking subaqueous HDD, present the construction considerations, and provide key items to review prior to project implementation.

The Kildonan-Redwood Feeder Main is a 600 mm (24 in.) diameter steel pressure pipe crossing of the Red River, adjacent to the Harry Lazarenko Bridge in Winnipeg, Manitoba, Canada. The feeder main was inspected in March 2019 as part of the city’s High Risk River Crossings (HRRC) program. The inspection consisted of an electromagnetic (EM) assessment using remote field testing (RFT) technology and multiple leakage tests. The EM inspections revealed that the steel crossing pipe was in relatively good condition structurally (e.g., it had full hoop strength); however, the leakage tests confirmed that its hydrostatic integrity was compromised, and the feeder main was removed from service to preclude direct discharge of chlorinated water to the river. The crossing was originally constructed in 1955, is 238 m (780 ft) long, and was constructed using a complex balance of tunneling on its west side, through a 16 m (52 ft) deep vertical shaft through a 90 degree to a horizontal tunnel section and then transitioning to shallow open-cut construction across the river and up its east side, using coffer dams to facilitate installation through the channel. Replacement of the crossing using new installation trenchless techniques was also deemed to be prohibitively expensive ($7−10 million). In 2019/2020, an AWWA Class III lining solution was designed and tendered using a reinforced CIPP for potable pressure service. However, the configuration was deemed to have excessive installation risk, and no bids were received. In 2020/2021, the use of FFRP, which was discarded in the initial predesign, was further investigated. It was found to have acceptable hydraulic impacts in review of the overall system, and its installation and long-term operational risk was deemed to be acceptable as well. In 2022, the project was tendered and successfully constructed for a cost of approximately $1.2 million or about 15% of the capital cost of a new installation with a comparable anticipated design life. This paper provides an overview of the long journey of the Kildonan-Redwood Feeder Main through its complex beginnings, modern assessment, and eventual rehabilitation to achieve a new design life.

The City of Garland (the city) needed to rehabilitate or replace the Rowlett Creek Wastewater Treatment Plant (WWTP) onsite 54-in. sanitary sewer pipe. The 750 linear feet (LF) of sewer was severely corroded and in need of immediate repair. During the preliminary analysis in 2020, the city stated an additional desire to be able to send influent flow from the Rowlett Creek WWTP to the city’s second WWTP, Duck Creek WWTP, via an existing transfer pump station. Rehabilitation and improvements to bypass and transfer flow were recommended to address both the critical infrastructure issues and operational requests. Coordination and communication between the design team, the city, and the contractor was essential to successfully complete the project and on an expedited schedule. The project was completed in fast-track design production, contracted via BuyBoard, and successfully constructed in 2021.

The Bird Creek Interceptor is one of the primary wastewater gravity pipelines serving the City of Temple (City). Built over 60 years ago, this 5.3-mi portion of the interceptor constructed of vitrified clay and brick manholes has experienced numerous overflows in recent years due to excessive infiltration/inflow (I/I), lack of capacity, and aging conditions. The interceptor passes through private property, public parks and golf courses, crosses TXDOT infrastructure and BASF rail lines, and is lain within easements and right-of-way. Carter Burgess, contracted in 2007 to assist the City of Temple to identify sanitary sewer overflows (SSOs), underwent an effort to evaluate the system, flow monitor, and prepare a hydraulic model to identify the exact problems that exist within the interceptor and recommend improvements necessary to properly convey the peak wastewater flows to the Brazos River Authority (BRA) Temple-Belton Regional Sanitary Sewer (TBRSS) Lift Station.

As part of Toronto Water’s proactive asset management program, numerous sewers are planned to be rehabilitated using trenchless technologies. The City of Toronto opted to bundle projects to include two or more site locations. These bundled projects included rehabilitation of sanitary trunk sewers (STS) of a variety of pipe sizes and materials, each with unique project site challenges. Due to individual site constraints, the bundled projects would be delivered over multiple years, sequentially. This paper discusses each of the bundled projects of Mendota STS, Queensway STS, and Long Branch STS, which was tendered in fall 2019 with anticipated completion at the end of 2021. This project experienced unanticipated benefits and challenges due to the COVID-19 pandemic and extreme weather events, such as lower traffic and transit volumes and material shortages. Construction began in 2020 and was completed in 2022.

A deteriorated pipe can lead to a community out of service and an operations group on standby for repairs. Hence, rehabilitation methods are vital in keeping a pipe in service, more so for a 30″ ductile iron effluent force main for the largest lift station in the San Antonio Water Systems (SAWS). Analysis of the main in preparation for a hot tap revealed up to 90% loss of its wall thickness. Given the corrosion, the hot tap was not completed. Given the high potential of failure, SAWS pursued improvements to the lift station to mitigate risk and increase operational redundancy for the critical lift station. The lift station is in an “environmentally sensitive” area within the San Antonio Missions National Historical Park, which is designated as a United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site, owned by the San Antonio River Authority (SARA), and managed by the National Park Service (NPS). As a result, a plan was developed to have archeological monitoring to occur during the construction effort to collect archaeological materials should they be encountered. Given the criticality and location of the lift station, various improvements to the effluent force main were analyzed to improve the redundancy in the system. Cured-in-place pipe (CIPP), pipe bursting rehabilitation, and open cut replacement were analyzed to determine the feasibility of restoring the force main. Cost, lead time, feasibility, and materials were all considered as part of the analysis. Additionally, a parallel force main alignment with a future bypass connection was studied to improve the resiliency of the lift station. Rehabilitation methods were ruled out due to work zone availability and regulation requirements. HDPE, PVC, and ductile iron pipe materials were analyzed for both parallel and replacement force mains. Based on maintenance, cost, and lead time, HDPE was selected as the preferred pipe material. Availability of large diameter plug valves was determined to have an impact in replacing the force main. Thus, plug valve procurement was initiated during the design phase. Knife gate valves and swing check valve replacements were also necessary inside the lift station to avoid future maintenance.

Starting in the spring of 2022, Macomb County Public Works Office (MCPWO) engineering staff evaluated the rehabilitation of approximately 800 lineal feet of an 84-in. diameter reinforced concrete pipe sanitary sewer interceptor. The pipe segment under evaluation is in a high traffic area, is densely populated, and is under typical moderately high dry weather flows with sizeable cross connections that would require extensive bypass operations. To minimize socioeconomic impacts to the surrounding community, reducing construction footprint to coordinate with other construction projects in the area along with keeping costs in check, MCPW engineering staff reviewed multiple solutions to accomplish all these goals. Typical rehabilitation techniques utilized by MCPWO historically include standard slip lining and the use of cured-in-place pipe. Unfortunately, with the depth of the pipe and access location for an insertion pit in a primary intersection, slip lining was deemed unfeasible due to traffic impact. The need for full bypass, size of bag and shipping logistics, along with overall construction footprint, cured-in-place pipe was eliminated as a solution also. With the improvements made for cross bracing of spiral wound pipe (SPR) and the ability to install under flow along with minimal footprint, MCPW elected to move forward with SPR as the solution under a pilot program. This paper will focus on evaluation of rehabilitation techniques and how to avoid trying to incorporate technologies purely due to familiarity and forcing a square peg into a round hole. Another major challenge is overcoming acceptance of a new technology that has not been widely accepted in a certain geographic region. Lessons learned along with project results will be included, demonstrating the success of thorough vetting of rehabilitation solutions, and determining the correct fit.

The City of Modesto, California, is currently constructing a realignment of its River Trunk wastewater interceptor system due to the fact that the existing interceptor is significantly corroded from high levels of hydrogen sulfide gas. This project includes 2.5 mi (13,200 ft) of 48-in. to 60-in. gravity sanitary sewer pipeline at depths from 20 ft to 30 ft below ground surface. Several pipeline materials were evaluated during preliminary design, and the city selected fiberglass pipe with a vinyl ester lining to mitigate potential corrosion impacts from the very high levels of hydrogen sulfide gas. The project alignment is through a narrow, two-lane residential neighborhood. Trenchless construction and open-cut construction were evaluated with several metrics, and open-cut construction was ultimately selected by the city. During bidding, the contractor was required to identify the fiberglass pipeline manufacturer. However, once construction started, the pipeline manufacturer was not able to supply the pipe material due to supply chain shortages. The contractor requested an “or equal” manufacturer, and the pipeline was supplied by Future Pipe Industries manufactured in Abu Dhabi, United Arab Emirates. The city allowed the pipeline contingent on factory inspection by the Engineer of Record prior to shipment to the United States. Additional challenges included approving an engineered shoring system for the deep trench, preventing pipeline floatation with a slurry bedding, and compaction immediately above the pipeline. This paper summarizes the design analysis and decisions, pipeline material approval and inspection, construction challenges, and related recommendations for future projects.

A significant percentage of the sewer pipelines in the United States were installed in the early to mid-20th century, and many still in service have exceeded their intended design life. Other sewers installed in the late 1800s also present major challenges where modernization has resulted in other major types of infrastructure, typically installed above deep sewer systems. As a result, there is an increasing need for sewer line rehabilitation or renewal. This paper focuses on informed decision-making and risk analysis for various pipeline rehabilitation options. This evaluation can be further modified based on rehabilitation option availability and market price fluctuations. This paper describes the basis and methodology used for evaluating the design methods and is intended to assist owners and engineers in making better-informed decisions.

Washington, DC, is a small but historic city with old and abandoned infrastructure. There is also a lot of construction with older buildings being renovated and modernized, capital improvement projects throughout the city, and some new buildings being constructed. Most of this construction will require new underground utilities and abandonment of old ones. Given the small size of the city at 68 mi² and all the construction being performed, one of the many challenges you will face when performing construction work, particularly excavation, is utility congestion. Many times, other utilities or infrastructure conflicts with the utility you are trying to repair. When the utilities are above and in the way of the utility you are trying to repair, you’ll have to get creative with your repair approach. Such was the case at 529 14th St. NW, where there was no direct access to a broken 10″ lateral servicing the National Press Building due to several utilities in the way and little clearance between them. The 10″ lateral was 19 ft deep, meaning that with all the utilities in the way and little clearance, traditional excavation and shoring would have been very challenging. DC Water first reached out to the owners of the utilities in conflict to see if they can be moved to allow easy access for excavation. After being unsuccessful with contacting some of the utility owners and getting others to temporarily relocate their utility, DC Water directed its contractor, Spiniello Companies, to hand-excavate and expose the utilities. During excavation, Spiniello uncovered even more unmarked utilities, again, with little spacing between them. DC Water had Spiniello backfill the excavation knowing that it will be difficult to excavate deeper and practically no avenue to install shoring. The next approach was to excavate adjacent to the initial hole and then dig toward the broken lateral. Again, Spiniello encountered more utilities. Ultimately, DC Water decided to have Spiniello backfill the second excavation and seek other options. Knowing that performing traditional excavation would require a large footprint on a busy arterial roadway and a complicated shoring system, DC Water decided to look for other alternatives. One of those options, box-tunneling, became attractive because the broken lateral terminated at a manhole about 10 ft from where the lateral was broken. DC Water’s other contractor, Anchor Construction, dug a 3 ft by 5 ft box-tunnel from inside the manhole using hand tools, shoring along the way, until they reached the broken pipe. Anchor was able to make repairs to the sewer lateral, rebuild the manhole wall, and fill the tunnel with flowable fill. This time and cost saving approach required no restoration. Since all work was performed from inside the manhole, the work zone was small and the impact to traffic was minimal. Box tunneling truly saved the day.

The City of Boulder, Colorado, is in need of a new 2.5-mi sewer transmission main to convey the majority of the city’s wastewater flows to the Boulder Water Resource Recovery Facility. On the upstream end of this project, a 2,000-ft section of the proposed pipeline was planned to be constructed via open cut methods beneath a major arterial road and adjacent to several rural residential properties. The project team investigated the impacts of open cut pipeline construction in the area. Key areas of the investigation included: (1) hydrogeologic modeling of the construction dewatering and its influence on existing domestic wells; and (2) construction phasing requirements needed to limit traffic disturbances, adhere to work hour limitations, and maintain access to the residences. After the team analyzed the cost, schedule, and public impacts of open cut construction, the design team developed a trenchless alternative for comparison. The trenchless alternative is further complicated by the likely presence of boulders, potential mixed-face conditions, and the possibility of a basalt dike along the pipeline alignment. Ultimately, the team pivoted the design philosophy toward the trenchless option and focused on gathering additional field data and refining the vertical alignment to mitigate risks associated with tunneling this section of the project. This case study reviews how the team weighed multiple approaches to mitigate the unique design challenges for this project, ultimately leading to the design of a three-shaft trenchless installation that includes a nearly 1,500-ft long continuous section. The presentation includes a description of the constructability methods reviewed and implemented that ultimately provided value to the project.

In 2018, as part of a conventional design, bid, build project two circular shafts were started for a trenchless crossing of a United States Army Corps of Engineers (USACE) controlled body of water. After four years, the seal slab was finally installed on the second shaft, resulting in two shafts for launching and receiving the proposed tunneling machine. The project was a performance-based design and had specific requirements for this crossing that were different from all other trenchless crossings included on the project. With continued support and work by multiple consultants, contractors, and subcontractors, the work has reached a stage that tunneling will finally start and hopefully be completed in the near future. The risk associated with underground crossings can vary, and careful consideration is needed to ensure success. This paper will dive into details and issues impacting the design, bid, and construction process for this challenging shaft and provide risk mitigation methods for municipalities hoping to decrease risk inherently associated with underground trenchless crossings as part of performance-based design, bid, build projects.

The San Antonio Metropolitan area has experienced sustained growth for decades, putting increased pressure on existing wastewater infrastructure. In June 2013, the San Antonio Water System (SAWS) approved a settlement agreement with the USEPA in conjunction with a consent decree that requires significant improvements to the SAWS wastewater system over a 10-year period to reduce sanitary sewer overflows (SSOs). This work includes the targeted replacement and rehabilitation of an aging infrastructure system that consists of over 5,200 mi of sewer pipe. One of the critical projects that evolved from the consent decree was the W-6 Upper Segment Tunnel project to reduce sanitary sewer overflows on an existing sewer main running through Lackland Airforce Base. The replacement project consisted of a new tunnel nearly 29,190 LF of primarily 104″ FRP gravity sanitary sewer pipe. The project also includes nine shafts and multiple trenchless crossings to make near surface connections to the new works. This unique paper will focus on the related, yet contrasting, perspectives and key challenges faced by the overall project team: owner, design engineer, contractor, and construction manager. As the largest capital improvement project undertaken by the utility, this project was bid at the start of the COVID-19 pandemic and endured the severe Texas winter snowstorm of 2021 and an estimated 50-year flash flood event the following summer. Even with those challenges, the tunnel excavation was completed nearly six months ahead of schedule and under budget. This project utilized fiberglass reinforced pipe (FRP) and polymer concrete shaft structures to combat the severe, harsh environment associated with wastewater systems. This project was designed and constructed to last 100 years or more. Substantial completion was completed toward the end of the first quarter of 2023. This project is expected to serve the greater San Antonio community for generations to come.

The devastating flooding associated with Hurricane Harvey left the City of Beaumont, Texas (city), without water service for nearly a week. The flood waters inundated the city’s existing raw water pump station and cut off the city’s primary source of raw water. For resiliency, the city elected to design and construct a new pump station, the Collier’s Ferry Pump Station. The city primarily obtains water from an intake upstream of the Neches River saltwater barrier. This required the new pump station to tie into the forebay of the existing pump station. The new pump station had to be constructed on higher ground, while also avoiding wetlands, but the nearest suitable location was located nearly a half mile away. Therefore, a key part of the new pump station was a 48″ diameter gravity pipeline from the existing forebay. Microtunneling was specified for construction of the pipeline through alluvial soils beneath the groundwater table along the Neches River while minimizing surficial construction adjacent to existing wetlands. This paper and presentation will describe a case study for utilizing microtunneling in a unique application to allow the city to provide a more resilient water supply system, while minimizing impacts to wetlands and the need for additional improvements.

The Northeast Transmission Line (NETL) is part of an initiative to meet the Harris-Galveston Subsidence District’s (HGSD) mandate to restrict the use of groundwater. This mandate was put into place to substantially alleviate surface subsidence throughout southeastern Texas from years of withdrawal of oil and water from the ground. The landmark NETL construction of the City of Houston Public Works is a $450 million undertaking, consisting of nearly 17 mi of large diameter pipeline that ranges in diameters of 54-in. through 120-in., with the majority being 108-in. This is the third paper in a series that discusses various aspects of the NETL project’s design and construction. Although the majority of pipe was installed using open cut, this paper will focus specifically on tunneling applications with its greater risk that produced most of the program’s significant problematic issues. There were 55 tunnels on this project in total. After discussing specifications and manufacture of the steel casing pipes and related QA/QC issues, attention is given to challenges faced in tunneled sections due to soil conditions, unconventional tunneling methods, challenges with broken TBMs underneath bayous, encountering unforeseen buried obstacles underground, and a number of other topics. It is hoped that these discussions will help the design processes and how designers can better incorporate construction considerations, as well as how contractors can better prepare for projects of this magnitude.