REHABILITATION OF THE LONG WHARF SEWER FORCE MAIN USING SLIPLINING METHODOLOGY IN NEWPORT, RHODE ISLAND

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1 North American Society for Trenchless Technology (NASTT) No-Dig Show 2011 Washington, D.C. March 27-31, 2011 Paper A-5-04 REHABILITATION OF THE LONG WHARF SEWER FORCE MAIN USING SLIPLINING METHODOLOGY IN NEWPORT, RHODE ISLAND Thomas Simbro 1 and Richard (Bo) Botteicher 2 1 Sr. Project Engineer, Wright-Pierce, Providence, RI 2 Sr. Product Engineer, Underground Solutions, Inc., Denver, CO ABSTRACT: In April 2009, a major structural failure was discovered on the Long Wharf Sewer Force Main in the City of Newport, Rhode Island. The existing 36 pre-stressed concrete cylinder pipe (PCCP) conveys 80% of the City s wastewater for processing and crosses beneath the historic as well as main tourist center of the City. A fulllength condition assessment revealed the existing 36 PCCP force main had major internal & external deterioration beyond the location of where the initial structural failure had occurred. Faced with making emergency repairs at the peak of tourist season, City officials, C. B. Utility and Wright-Pierce, the consulting engineer for the City, looked into trenchless options for pipeline replacement in Newport's downtown areas. After careful evaluation, structural slipline solutions with thermoplastic pipe were chosen as the most beneficial alternative. Maintaining maximum flow capacity was critical, so a sliplined pipe needed to provide the greatest inner diameter while fitting into the existing 36 force main. A 30 DR25 FPVC pipe demonstrated that flow capacity for the combined slipline and dig & replace sections could be maintained due to the higher flow coefficient of the smoother PVC versus the rougher surface of the degraded PCCP line. Sliplining operations commenced on August 17, 2009, near the end of the busy summer season and C.B. Utility maintained a tight schedule for the project. The new 30 line was grouted in place, pressure tested, and connected to the direct bury PVC bell-andspigot segment of the force main. The line was placed into service within schedule on October 28, INTRODUCTION If you are a utility manager in a tourist community, you know your worst nightmare is a utility failure that could disrupt the tourist season. That nightmare hit the City of Newport, Rhode Island (City) on April 7 th, 2009 when a leak was discovered in the City s Long Wharf Force Main (LWFM). The Long Wharf Pumping Station (LWPS), which feeds the LWFM, is the City s main pumping facility serving 80% of entire service area of Newport. In addition, the LWPS also receives the wastewater flow from Middletown's Wave Avenue pumping station. The LWFM is approximately 9,500 feet long and discharges directly to the Newport's Wastewater Treatment Facility located on JT Connell Hwy. Along the 36" force main route are five interconnections from bordering tributary sewer areas: the Dyre Street PS force main; the Navy Training Station PS force main; and three interconnections at the WWTP site namely the Coddington Point PS force main, the Coddington Cove pressure sewer and the Middletown Coddington Highway pressure sewer. The general layout of the existing LWFM is shown in Figure 1. Paper A

2 Figure 1. Existing LWFM alignment and major tie-in and appurtenance locations. The Long Wharf Pumping Station and these five interconnections account for the entire influent flow to the wastewater treatment facility making the 36" force main one of the City's most vital infrastructure components. The LWFM was constructed in the 1970s of pre-stressed concrete cylinder pipe (PCCP). The force main transports wastewater approximately 9,500 feet from the LWPS to the City s Treatment Facility. The original force main was constructed with no in-line isolation valves and no viable means of by-pass interconnection along its route. 2. ASSESSMENT OF THE PIPELINE The City and United Water hired C. B. Utility Company to install a temporary by-pass system and to make necessary repairs due to the discovered leak. The City retained Wright-Pierce to assist in the LWFM repair. To start, a hydraulic analysis was performed and recommendations were given to the LWFM repair contractor, C. B. Utility, for the large scale station by-pass pumping system. A first attempt at a limited by-pass in Long Wharf and America s Cup Ave. area could not be completed due to excessive groundwater inflow. After consultation with C. B. Utility and Wright-Pierce, the City authorized a complete by-pass of the 36" force main shown in Figure 2. The bypass consisted of three 18 polyethylene (PE) pipes, approximately 10,000 LF each, to circumvent the exiting alignment. The bypass ran along the railroad ROW and track, and the railroad was actually used to construct the line using a crane on a railcar to load PE pipe for fusion assembly of the lines. This complete by-pass allowed for a thorough inspection of the pipeline and for any and all necessary LWFM repairs. The City was aware that aging PCCP has a history of failure in both water and wastewater applications due to corrosion; including most recently and locally the Providence Water transmission main in Cranston and the Barrington / East Providence wastewater force main high profile failures. Paper A

3 Figure 2. Bypass alignment used for LWFM rehabilitation and replacement project. Due to these known PCCP concerns and with the full by-pass completed and in operation, an internal and external pipeline condition assessment was performed through test pits and CCTV inspection. Hammer testing at test pits along Long Wharf revealed early signs of exterior pipe corrosion from the pipe springline to the invert due to chlorides in the tidally influenced groundwater near the Narragansett Bay. The CCTV pipe interior inspection of nearly the entire force main length revealed concrete deterioration from hydrogen sulfide gas; the worst case conditions at high points where pitted areas had exposed the pipe's steel barrel, also in early stages of corrosion. In addition, the buried 36" pipe fittings and plug valve at the Long Wharf pumping station site appeared improperly restrained to handle the LWFM's operating pressures. After the conclusion of the pipeline assessment, and with the advantage of a full by-pass in place, the City decided to move forward with a proactive approach to fully replace the entire 9,500 foot force main. 3. SELECTION OF A REHABILITATION METHOD Based upon the results of the pipeline condition assessment and the pipeline's critical importance in the overall City infrastructure, the City requested that C. B. Utility, with Wright-Pierce engineering support, provide repair alternatives for the entire LWFM. Several options for pipeline replacement were evaluated. A key design consideration was to preserve the hydraulic capacity of the new replacement force main consistent with the City s CSO long-term control plan. Additionally, City officials were understandably concerned with the potential disruption that construction activities would have on its historic downtown during the height of tourist season. The following five alternatives were considered: Scenario 1. 36" Cured-In-Place Pipe (CIPP) Liner Scenario 2. 30" Sliplining Scenario 3. 36" Ductile Iron Pipe Dig & Replace Scenario 4. 36" PVC Pipe Dig & Replace Scenario 5. Hybrid 30" Sliplining (Downtown) and 36" PVC Dig & Replace (Railroad Right of Way and Cross-Country) Paper A

4 In addition to the pipeline alternatives above, each design alternative would include full replacement of the access man way & air release manholes and include in-line isolation valves, which were deficient in the existing LWFM alignment. Two trenchless methods were selected for consideration in order to address one of the primary concerns of the project, namely the impact that construction may have on the downtown area. One was sliplining and the other was CIPP. Sliplining is a very simple low-dig installation methodology, by where a new whole pipe or conduit is slipped into an existing pipe or conduit in need of rehabilitation. The benefits of the is installation methodology are that it provides a new pipeline, independent and fully structural regardless of the host pipe or the condition of the host pipe, and it utilizes the existing utility alignment, thus limiting the crowding of an existing utility corridor. The major downside of the methodology is that it requires that the new pipe be smaller than the original host pipe in terms of flow area. This can be offset by the relative smoothness of the new pipeline compared to the old host pipe, however, the reduction of the flow area must be considered in the design of the new line compared to the old. There are many pipe products for use with sliplining technology but for this size pipe and known alignment considerations on this project, Fusible PVC (FPVCP) provided the greatest inner diameter or flow area compared to the constrained outer diameter, thus providing the most flow area for a pipe that could reasonably be installed in the existing pipeline. Additionally, with the use of ductile iron pipe sizing standard materials, such as ductile iron fittings, pipe, and PVC pipe, connections were very simple and straightforward for the construction of the line. CIPP is a rehabilitation methodology in which a resin impregnated tube is inverted into an existing pipe or conduit, and then formed to the inside of the existing host pipe or conduit while it is cured. This creates a close-fit liner on the inside of the existing pipeline in need of rehabilitation. The benefits of CIPP technology is that it has a very small construction footprint, it provides a new corrosion resistant lining in the existing pipe, and has a shorter construction schedule window than other methods. The primary limitations of this technology are that it is still relies on the structural integrity of the host pipe, and it will not stop external corrosion. This second point was a major concern on this project. The City requested that Wright-Pierce perform a hydraulic evaluation of each repair alternative, excluding the CIPP method due to the exterior corrosion concern, in order to assess their potential impacts relative to CSO occurrences. Included in Table 1 is a summary of the proposed rehabilitated and replaced LWFM hydraulic analysis, for scenarios 2 through 5, not including scenario 1, CIPP. Table 1. Hydraulic analysis of the rehabilitation and repair scenarios. Existing Scenario No. 2 Scenario No. 3 Scenario No. 4 Scenario No. 5 Long Wharf Existing Conditions 30" FPVCP 36" DI Pipe 36" PVC Pipe Hybrid Pump Station 36" PCCP Sliplining Dig & Replace Dig & Replace 30" / 36" PVC Operation (C=100) (C=150) (C=130) (C=150) (C=150) 1 Pump 9.41 MGD 9.51 MGD 9.81 MGD 9.86 MGD 9.60 MGD 2 Pumps MGD MGD MGD MGD MGD Paper A

5 Figure 3. Hybrid Alternative Repair Plan including sliplining and dig and replace methods. Figure 4. Hybrid Alternative Repair Profile including sliplining and dig and replace methods. Paper A

6 Based upon the estimated construction costs, scheduling and hydraulic analysis, the most advantageous alternative appeared to be the Hybrid 30" Sliplining in the Downtown area and 36" PVC Dig & Replace in the railroad ROW and cross-country sections as shown in Figures 3 and 4. The hybrid LWFM alternative offered the following preferred features: 1. Greater hydraulic capacity over existing 36" PCCP. By using smooth pipe wall PVC pipe, the hybrid 30 FPVCP and 36 PVC force main replacement actually achieved a slightly better hydraulic capacity than the original 36 concrete pipe, while also providing superior corrosion resistance. 2. Reduced community and societal impacts. Sliplining in the downtown area would have less impact on residents and commercial properties than conventional dig & replace construction. 3. Reduced conflict possibility with existing utilities. Sliplining in the downtown area would greatly reduce the conflicts with adjacent underground utilities over conventional dig & replace construction. 4. Limited dewatering requirements. Sliplining in the downtown area would limit potential exposure to having to maintain and remediate construction dewatering operations. 5. Low cost. The hybrid alternative estimated construction costs were one of the lowest of the alternatives evaluated. 6. Compact schedule. The pipe and appurtenant materials were generally available in the shortest time period in respect to performing the work as quickly as possible. 4. SLIPLINE CONSTRUCTION The bypass piping, having been installed after the initiation event and through the assessment phase of the project, allowed full access to the existing 36 PCCP host pipe during the rehabilitation and replacement phase as well. Sliplining was chosen as a means to limit the excavation required along the alignment and in highly congested or critical areas, however direct bury, dig and replace methodology was also utilized where it made the most sense as part of the hybrid alternative selected. In the end, of the ~9,300 LF of pipe that was designated to be rehabilitated and/or replaced for the project, less than half of it, or ~3,890 LF was actually sliplined. Slipline methodology was mainly used in those areas of the highest congestion, where dig and replace methods would have had the biggest impact on the community and on the schedule. In the downtown area, the existing 36 PCCP was sliplined with 30 DR 25 FPVCP supplied by Underground Solutions. Construction excavation was reduced to just the sliplining entry and exit pits. The sliplined portions included a record 1/3-mile segment (1,810 LF) single pull for 30 FPVCP. The remaining 3,800 linear feet of force main was replaced with 36 DR25 PVC bell and spigot pipe utilizing conventional dig and replace methods along an existing railroad corridor, with a final connection at the wastewater treatment facility headworks. Sliplining and general project operations commenced August 17, 2009, near the end of the busy summer season. UGSI provided an on-site construction supervisor to assist C.B. Utility with planning and coordination in order to maintain the tight schedule in relation to fusion and installation. Fusion work began in earnest on August 18, The project was broken into roughly 13 segments, based on installation methodology and location along project. Of the 13 segments, 6 of these were slipline runs of FPVCP, and the rest of the piping was bell and spigot PVC, dig and replace installation. Table 2, illustrates the way the project was segregated based on actual installation of the segments described. This can be compared to Figure 4 for a graphic illustration of how the line was completed. Of note, while the downtown section was designated to be all slipline installation, certain sections were open cut due to existing alignment bends, appurtenances, and limitations of the project sites. Table 2. Segmentation of the project by installation method and lengths. All values are to the nearest 10 feet. Pipeline Segment Stations Installation method Approximate Length 1 Sta to Sta Open Cut 100 LF 2 Sta to Sta Slipline 100 LF 3 Sta to Sta Slipline 380 LF 4 Sta to Sta Open Cut 60 LF 5 Sta to Sta Slipline 640 LF Paper A

7 6 Sta to Sta Open Cut 180 LF 7 Sta to Sta Slipline 840 LF 8 Sta to Sta Open Cut 360 LF 9 Sta to Sta Slipline 1,810 LF 10 Sta to Sta Open Cut 360 LF* 11 Sta to Sta Open Cut 570 LF 12 Sta to Sta Slipline 120 LF 13 Sta to Sta Open Cut 3,780 LF Slipline Total 3,890 LF Open Cut Total 5,410 LF *Segment 10 was an alternate alignment section and is an estimate on actual pipe length per the stationing, not actual distance. The following section describes the slipline segments that were performed. Descriptions can be referred to Table 2, and Figures 3 and 4. Segment 1 tied into the Long Wharf Pumping Station and the force main piping there. It utilized dig and replace methods. Segments 2 and 3 where slipline installations from a single insertion pit, pulling each length of the pipe in opposite directions. Pipe was fused and staged along Long Wharf drive in the vicinity of the Newport Marriott. Construction progressed with the cooperation of the Newport Marriott facility, allowing limited and temporary closure to several of the accesses to the property while the pipe was fused, staged, and then installed. Figure 5 shows the fusion and staging of several runs near the Newport Marriott. Figure 6 shows insertion of one of the slipline runs at this location. Figure 5. Fusion and staging, as well as insertion pit construction near the Newport Marriott on Long Wharf Drive. Paper A

8 Segment 4 was an angled vertical crossing under a major sewer tunnel which then crosses a portion of America s Cup Ave. before turning North in America s Cup Ave. This area utilized the dig and replace method due to the bends in the existing alignment. Segment 5 was a 640 LF slipline installation in the northbound inside lane of traffic of America s Cup Ave. This section was fused on the shoulder of the roadway in the diagonal parking area prior to insertion. Segment 6 was 120 LF of open cut which crossed from northbound inner to southbound outer lanes and back again in America s Cup Ave as it changes direction. Dig and replace was used here due to the bends in the existing alignment. Slipline installation methodology was used in segment 7 for a total of 840 LF. Fusion and installation took place in America s Cup Ave., as pipe was fused in one lane of traffic and then installed. It was staged in 3 pipe strings of approximately 280 LF each and then intermediate fusion joining was performed during the insertion. Segment 8 was an open cut, dig and replace segment along the road curve of America s Cup Ave. into Farewell St. for a total length of 360 LF. Bends in the existing alignment and then the turn to go North on Farewell St. made it easier to open cut than slipline. Figure 6. Slipline insertion near the Newport Marriott on Long Wharf Drive. The longest stretch of slipline installation came in segment 9. A total of 1,820 LF of pipe was installed along Farewell St., a very busy thoroughfare and highly congested roadway. This stretch of construction also included approximately 200 LF of additional sliplining, which extended the pipeline beyond an existing bend and past a busy ramp exchange with Highway 183 and Farewell St. 36 PVC bell and spigot piping was installed at this location through the intersection and beyond, prior to the sliplining activity. This allowed what was originally designed as a ~1,620 LF slipline to stretch to ~1,810 LF in one shot. This also marked an alignment change for the original pipeline, as this moved the alignment North along Farewell St. prior to the new alignment jog that was created over to JT Connell Hwy before it connected back to the existing pipeline as it crosses under Highway 138 and runs north along the JT Connell Hwy. The pipe was fused into 6 segments averaging 240 to 360 LF, which then required 5 intermediate fusion joints to be performed upon installation. These length restrictions were due to limited laydown area along the side of Farewell St. A section of the existing pipe was also exhumed and cut at the high point in this section to install an access and air release valve assembly. The ~1,800 LF pipe string was cut at those locations twice to allow for those installs. The 30 pipe was cut and opened up to allow the insertion of the gate valves, access man way tees, and ductile iron pipe pup pieces before being recoupled. Paper A

9 Segment 10 is the open cut installation of this new stretch of pipeline, approximated at 360 LF based on the existing pipeline stationing. Segment 11 crossed underneath Hwy 138 to get to the ramp crossing and segment 12 was a slipline installation under the ramp. There was a casing location here, and in-pit fusion was utilized to install the pipe, as there was no room for layout of a pipe string. The 120 LF long installation was completed 20 LF at a time, as sections of pipe were lowered into the fusion machine in the pit, fused, and then pushed through the fusion machine and into the alignment. This completed the slipline portions of the project, roughly at station ~55+20 then the rest of the project was dig and replace construction utilizing 36 PVC bell and spigot piping. All of the sliplined sections utilized an 800 G Grundoburst pipe bursting hydraulic ram (800 G) to perform the insertions and pull the pipe into place. A 10 ton TT Technologies, Inc. Grundowinch was also used to pull the pipe bursting rods for the 800 G into the existing alignment, which is faster and less work than pushing them into place with the 800 G. The new sliplined 30 sections were grouted in place by the Elastizell Corporation, using a cellular type grout mix, which is a highly flowable, highly air-entrained grout that is ideal for pumping longer distances and filling the annulus between the existing LWFM and the new pipe. The sliplined sections were also hydrostatically pressure tested to 100 psi after installation and then connected to the direct bury PVC bell-and-spigot segments of the force main. Aside from tie-in connections, the only other appurtenances installed on the pipeline were air release valves, combination air release and vacuum valves, and access man way tees, which allowed manned entry into the new pipeline if required. Each of these assemblies was similar in scope and installation. Sections of the pipeline were assembled using ductile iron pup pieces, a tee to facilitate the appurtenance, and gate valves on either side. These gate valves then tied into the PVC piping in the alignment. In total, there was one air release assembly, one combination air release and vacuum assembly and three access man way tee assemblies used in the sliplined section of the project. Scheduling was critical on the project and in the end construction of the 9,500 force main replacement was completed on schedule on October 28, 2009 when the new pipeline was commissioned and placed into service. 5. SUMMARY In April 2009, a leak prompted the discovery of major structural problems with the Long Wharf Sewer Force Main in the City of Newport, Rhode Island. This primary conduit is absolutely essential for the operations of the City s wastewater infrastructure and it would need to be replaced. Faced with constructing this emergency project at the peak of the tourist season, City officials, C. B. Utility and Wright-Pierce, the consulting engineer for the City, looked into trenchless options for pipeline replacement in Newport's downtown areas and ultimately selected a structural slipline solution with FPVCP to maintain required flow and provide a new pipeline. Sliplining operations commenced on August 17, 2009, near the end of the busy summer season and C.B. Utility maintained a tight schedule for the project. The new 30 line was grouted in place, pressure tested, and connected to the direct bury PVC bell-and-spigot segments of the force main. The line was placed into service on schedule on October 28, Paper A