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7 Introduction This chapter provides a brief overview of the different types of commonly used trenchless renewal methods. The overview of each method includes a discussion of the generally accepted applicability of the method and limiting factors. A summary of the advantages and challenges associated with each method is included in Tables 1 and 2. Case studies are included in this chapter and are summarized in Tables 3 and 4. The information in this chapter provides back- ground for concepts and terminology needed in subsequent chapters. Definitions The trenchless renewal methods included in this synthesis generally follow the basic categories as outlined in Najafi (2016): ⢠Cured-in-place pipe (CIPP) ⢠Sliplining (SL) ⢠Modified sliplining (MSL) ⢠In-line replacement (ILR) ⢠Spray-in-place pipe (SIPP) ⢠Close-fit pipe (CFP) A discussion of a potential emergent method and some newer variations of currently com- monly used methods are included at the end of this chapter. Cured-in-Place Pipe CIPP consists of inserting a flexible, resin-impregnated fabric tube into the existing pipe, expanding (or inflating) the tube, and curing the resin using heat (e.g., hot water or steam) or ultraviolet light. The two common insertion methods are inversion and pull-in insertion. An example of the inversion method is shown in Figure 1. The pull-in method requires additional consideration of potential damage because the liner is dragged through the pipe. CIPP is commonly used for relining complete sections of a pipe (e.g., manhole to manhole, inlet to outlet, etc.) but can also be used for spot or localized repairs. Lengths of localized repair are commonly limited to between 3 and 15 ft with a maximum length of 50 ft (Najafi 2016). CIPP is suitable for the renewal of most structural defects and the small decrease in pipe cross-section does not typically reduce the hydraulic capacity. The method can accommodate a wide variety of diameters, typically up to about 108 in., although up to 120-in.-CIPP liners have been installed. Depending on pipe diameter, maximum reported installed lengths for CIPP are C H A P T E R 2 Trenchless Renewal Methods
8 The Renewal of Stormwater Systems Using Trenchless Technologies between 1,000 and 2,000 ft (Osborn 2010). CIPP can be used on pipes with circular, noncircular, and varying cross-sections. CIPP can also accommodate typical pipe bends. The flexibility of the fabric tube can result in larger defects and offsets being reflected in the final shape. During CIPP renewal, flow through the existing pipe must be bypassed, significant infiltration must be sealed, and a pre-liner is required where pipe is missing and only soil is exposed (Najafi 2016). The handling and disposal of styrene-contaminated cure water, which can be toxic to fish, is an important consideration when selecting CIPP for renewal of stormwater systems. Curing with ultraviolet light is one way to address the cure water handling and disposal. When considering CIPP, it is important to know the inside pipe dimensions and any variations in the pipe cross-section. Since the CIPP liner is typically manufactured specifically for each project and it is expanded to fit the inside surface of the pipe, the size and variation in pipe size and shape must be determined prior to the start of construction. Where access to the ends of the culvert is limited, the flexibility of the fabric CIPP liner is an advantage over more rigid renewal methods. The following case study is for a CIPP project completed in Wisconsin using a thermosetting resin-impregnated felt liner (Grams 2017). Problem The problem was freeze-and-thaw damage, including concrete spalling, exposed reinforcing steel, joint separation, and exfiltration of the existing 180-ft-long, 60-in.-diameter, reinforced concrete pipe (RCP). The exfiltration was identified as increasing the potential for soil piping, erosion, ground loss, and ultimately a sinkhole that could extend to the overlying highway. The maximum depth of cover over the pipe was about 25 ft. Limiting disruption to the motorists and property owners at the ends of the culvert was also considered. Design The primary design concern was restoring the hydraulic function of the culvert by sealing the joints and mitigating exfiltration. The secondary concern was addressing the spalling of the concrete liner. A CIPP liner with a 50-year design lift, consisting of six layers of thermosetting resin-impregnated felt, was selected to address the hydraulic and structural concerns. Figure 1. Installation of a 60-in.-diameter CIPP liner using the air inversion method (Courtesy: Michels Corporation).
Trenchless Renewal Methods 9 Construction The construction was scheduled for December, a relatively dry month in Wisconsin, to miti- gate the potential need to bypass flows. The CIPP liner was installed using the inversion method and air (Figure 1). Steam was used to facilitate curing of the resin. The installation required an eight-person crew and took less than 1 full day to install. The cost, including mobilization and preparation of the existing pipe, was about $650 per foot. Summary The CIPP liner met the design requirements for addressing both the hydraulic and structural concerns associated with the existing culvert. Performing the installation in the winter addressed potential difficulties associated with flow bypassing, and the frozen ground reduced the con- struction traffic impacts at the staging area. Sliplining SL consists of inserting a new, smaller diameter pipe into the existing pipe. Common SL pipe types include polyethylene, high-density polyethylene (HDPE), and polyvinyl chloride (PVC). The insertion process consists of either pushing or pulling the new pipe from one end of the existing pipe to the other end (Figure 2). The annular space between the new and existing pipe is typically grouted. To prevent possible point loading of the new liner, the grout should fully encap- sulate the new pipe preventing it from resting on the invert of the existing pipe (Hartley 2014). The outside diameter of the new pipe is typically between 90% to 95% of the inside diameter of the existing pipe, which can result in significant loss in hydraulic capacity (Thornton et al. 2005). The method can accommodate diameters up to about 160 in. and lengths up to 1,000 ft. Both circular and noncircular pipelines can be sliplined. SL is usually performed with a constant cross-section diameter liner. SL is suitable for the structural renewal of existing pipes without large joint offsets or significant deformation and pipe bends less than about 6 degrees. During SL renewal, infiltration and flow in the existing pipe can typically be accommodated with the selection of the appropriate pipe material (Najafi 2016). When considering SL, it is important to know the inside pipe dimensions and any variations in the pipe cross-section to ensure that the new pipe and grout lines will fit. The new pipe is sized to fit in the smallest diameter located within the existing pipe (Thornton et al. 2005). Figure 2. Sliplining a culvert (Courtesy: Advanced Drainage Systems, Inc.).
10 The Renewal of Stormwater Systems Using Trenchless Technologies Access to both ends of the pipe is needed to facilitate installation and grouting of the annular space. Joining shorter sections of pipe together during insertion can reduce the amount of required space. In addition, pipe handling stresses and installation loading need to be monitored to prevent damage. Modified Sliplining MSL is suitable for renewal of personnel-accessible pipes and culverts with circular and non- circular cross-sections. MSL consists of assembling a new liner consisting of pipe segments, structural plate, panels, or strips, in the case of the spiral-wound method, within the existing pipe. Examples of spiral-wound liner installation are provided in Figures 3 and 4. Figure 3. Spiral-wound liner surface footprint (Courtesy: Contech Engineered Solutions LLC). Figure 4. Spiral-wound liner installation from within a manhole (Courtesy: Contech Engineered Solutions, LLC).
Trenchless Renewal Methods 11 The annular space between the new liner and existing pipe is typically grouted. The grout is required for a structural renewal. The reduction in hydraulic capacity associated with the use of MSL can be small. The method can accommodate the larger diameter stormwater pipes, generally greater than 48 in. and up to about 14 ft including varying cross-sections. The installation length for the spiral-wound method is limited to about 1,000 ft. Assuming sufficient access is avail- able, there is no installation length limit for the segment, plate, or panel methods. The size and shape flexibility of panels, segments, and strips facilitates the use of MSL in noncircular pipes and where access is limited. MSL can accommodate typical pipe bends and deformed pipe sections. During MSL renewal, infiltration and flow in the existing pipe can be accommodated, and access to both ends of the pipe is needed to facilitate grouting the annular space (Najafi 2016). The following case study is for an SL/MSL project completed in Tennessee in April 2016 using tunnel liner plate and steel-reinforced polyethylene pipe (Herbert and Hyma 2017). Problem The existing approximately 400-ft-long, 72-in.-diameter, corrugated metal pipe (CMP) culvert was experiencing greater than anticipated loading and as a result was deforming and was identified to be at risk of failing. The maximum depth of cover over the pipe was 50 ft, which coincided with the area of the greatest pipe deformation. Design The engineer, with support from the manufacturer, identified a combination of SL and MSL as the preferred renewal methods. To mitigate the ongoing deformation and impending collapse, a structural MSL, consisting of 160 ft of 48-in. steel tunnel liner plate was proposed. For the remainder of the culvert, about 240 ft, SL with 60-in. steel-reinforced polyethylene pipe was proposed. A concrete invert liner was constructed within the 48-in. liner to improve the hydraulic efficiency and smooth the transition between the 60-in. and 48-in. liners. Construction The renewal process started with the MSL renewal of the length of pipe with the largest defor- mation. After the steel tunnel liner plate was installed, the ends bulk headed, and the annular space grouted, the contractor switched to SL renewal. The contractor used skid rails, blocking, and bracing to facilitate the alignment of the steel-reinforced polyethylene pipe. The welded pipe segments were installed from both ends and met at the previously completed section of steel tunnel liner plate. The annular space was grouted in multiple lifts (or stages) and monitoring was performed to verify that the required alignment was maintained. Summary The selected two-method solution maintained the required hydraulic capacity and provided two distinctly different levels of structural capacity. In-Line Replacement ILR is the process of replacing pipes along the existing alignment using pipe bursting or pipe removal methods. ILR generally consists of pulling or pushing tooling connected to the replacement pipe through and along the existing pipe alignment. With pipe bursting, the existing pipe is broken or split and pushed outward to make space for the new pipe. With pipe
12 The Renewal of Stormwater Systems Using Trenchless Technologies removal, the existing pipe is removed by (1) reaming or crushing the pipe into small pieces that are removed by circulating drilling mud or slurry or (2) by pulling or pushing the intact existing pipe out of the ground. Pipe bursting, which is mainly performed using polyethylene pipe, is typically limited to pipes 36 in. in diameter or smaller that are less than about 1,000 ft long. General guidelines for pipe bursting diameters and lengths provided by the International Pipe Bursting Association (2012) are also described with relation to the relative degree of difficulty. To assist with understanding the International Pipe Bursting Association guidelines the following terms are defined: ⢠âSize for sizeâ refers to replacing the existing pipe with the same size pipe. ⢠âUpsizeâ refers to the number of standard pipe sizes larger the new pipe is than the existing pipe. For example, pipe bursting an 18-in. pipe and installing a 20-in. pipe would be one upsize. Pipe removal includes three subcategories: pipe reaming, pipe eating, and pipe ejection. The general guidelines for pipe diameters and lengths for pipe reaming and pipe eating are generally the same as those for horizontal drilling and microtunneling, respectively. Infor- mation on the relative limitations of these methods is included in NCHRP Synthesis 242 (Iseley and Gokhale 1997). Limitations on the applicability of pipe ejection are a function of the thrust capacity of the existing pipe, whether the replacement is size for size or an upsize, the pipe diameter, length, and original backfill soils. The method can accommodate varying cross-sections. ILR is generally best suited for replac- ing brittle pipe types (e.g., vitrified clay, cast iron, plain concrete, asbestos concrete, and some plastics). Although more challenging, some successful replacement of RCP and CMP has also been accomplished using ILR. The use of pipe bursting to replace CMP has resulted in the final unburst sections being pulled out of the ground (Matthews et al. 2012 and Adamtey 2016). The last section of a pipe pulled out during pipe bursting is shown in Figure 5. ILR is suitable for the structural renewal of existing pipes with joint offsets and significant deformation and pipe bends less than about 20 degrees (Najafi 2016). Pipe bursting and pipe reaming can exaggerate existing grade problems by lowering sagged portions of the alignment. The steerable microtunneling machine used in conjunction with pipe eating allows the method to mitigate sags of about 4 in. or more (UNITRACC 2017). During ILR renewal, the presence of groundwater, soil types (e.g., expansive clay soils), and potential concrete encasement require additional consideration during design. For pipe bursting, the potential for damaging adjacent utilities and structures should also be considered. Figure 5. Completed pipe bursting of a CMP (Courtesy: HammerHead Trenchless Equipment).
Trenchless Renewal Methods 13 The following case study is for an ILR project completed in Ohio in June and July 2014 using pipe bursting (Adamtey 2016). Problem Pipe bursting has historically been largely limited to renewal of more brittle pipe types, and more ductile pipes, such as CMP culverts, have not been considered ideal candidates for pipe bursting. A study to evaluate pipe bursting of CMP culverts was undertaken at four locations. The locations were selected as being âlow riskâ and âlow impactâ culverts if pipe bursting was not successful. The diameters of the existing pipes ranged from 12 to 24 in. and the lengths ranged from 90 to 105 ft. The depth of cover ranged from 8 to 18 ft. Design The study looked at using pneumatic pipe bursting for one culvert and static pipe bursting for three culverts. Pipe bursting manufacturers were included in the study process and pro- vided the design of the bursting tools. HDPE pipe was selected as the new pipe for all four sites. The 12-in.-diameter culvert was upsized to 16 in. and the remaining culverts were replaced âsize for size.â Construction The reaction for the pipe bursting winch/rod pulling equipment was provided by a combina- tion of steel plates and driven steel I-beams. The setup and bursting using the pneumatic head took about 10 hours, with the actual bursting taking slightly over 2 hours. The setup and burst- ing using the static head at each of the three sites took between 12 to 14 hours, and the actual bursting took between 30 to 45 minutes. Both the pneumatic and static bursting resulted in the last approximately 10 to 20 ft of the culverts not being burst, but rather being pulled out of the ground. The estimated construction costs ranged from about $120 to almost $200 per linear foot. Additional Information The overcut associated with pulling the last section of deformed, unburst pipe out of the ground resulted in ground loss around the new pipe. This ground loss ultimately resulted in surface settlement and deformation of the road shoulder that required repair. The Ohio DOT anticipates that the inspection cycle for the culvert will be the same as for any other culvert, and they expect a 100-year service life. Summary Pipe bursting was successfully used to install the new HDPE pipe. The ground deformation associated with the unburst pipe was unanticipated and resulted in additional effort to repair. Spray-in-Place Pipe SIPP consists of spraying a cementitious or polymer coating on the inside of the existing pipe (Figure 6). For larger pipes and culverts, SIPP with incorporated fibers or applied over steel reinforcement can provide renewal of structural defects. The relatively small decrease in pipe cross-section, depending on the existing pipe size, does not typically reduce the hydraulic capacity. The method has been used on pipes with diameters between 3 and 276 in. and on pipes up to 1,476 ft long (Thornton et al. 2005). SIPP can be used on pipes with circular, noncircular, and varying cross-sections. SIPP can also accommodate typical pipe bends. During SIPP renewal,
14 The Renewal of Stormwater Systems Using Trenchless Technologies the inside of the existing pipe must be clean to promote proper adhesion of the coating, flow through the existing pipe must be bypassed, and infiltration must be sealed. The following case study is for an SIPP project completed in Indiana in September 2015 using a fiber-reinforced geopolymer resin (Keaffaber 2016). Problem The existing approximately 275-ft-long, 84-in.-diameter, CMP culvert is located under State Route 446 in Indiana, with the outlet directing flow to an unnamed tributary to Little Salt Creek. The depth of cover over the culvert is approximately 30 ft. A previous inspection identified through-going invert corrosion and groundwater leakage at over a dozen locations. Design The original plans specified a CIPP liner. The intent of the design was to address the infiltra- tion and exfiltration and mitigate the corrosion. A SIPP alternative consisting of centrifugally cast concrete pipe was proposed and accepted as a demonstration project. The expected service life is 50 years. Construction Spot repair was performed to fill the invert voids using hand spraying of the mortar. After the spot repair was completed (Figure 7), a 1.5-in.-thick SIPP liner was applied in two passes using a centrifugal spray unit that was pulled through the culvert. The construction equipment was delivered to the site in a 24-ft box truck, and the work was staged from the road shoulder. No lane closures were required. The work was completed in 7 days. The construction costs were about $1,125 per linear foot. Additional Information An inspection approximately 18 months after construction was completed noted that while most of the original leaks were sealed, a few spots were still leaking. The contractor has agreed to fix the leaks. Regular inspections will be once every 5 years. Figure 6. Example of cementitious SIPP liner (Courtesy: Centri-Pipe).
Trenchless Renewal Methods 15 Summary The small size of the equipment limited the disturbance to traffic and a single product was used for both the spot repair and the new liner. While most of the leaks were mitigated, additional rehabilitation will be required to complete the mitigation. Close-Fit Pipe CFP consists of inserting a new, deformed (deformed and reformed [D&R]), or folded (fold and formed [F&F]) pipe into the existing pipe. After placement, the new pipe is expanded to its original size and shape to be tight against the inside of the existing pipe. An example of D&R pipe is shown in Figure 8. Because of the close fit, there is no annular space to grout. CFP is suit- able for the renewal of most structural defects and the small decrease in pipe cross-section does not typically reduce the hydraulic capacity. The CFP material typically consists of PVC, HDPE, or medium-density polyethylene. F&F pipe, typically consisting of PVC, is more commonly used for gravity pipelines than D&R pipe (Najafi 2016). The method can accommodate up to 30- and 60-in.-diameter renewal using F&F and D&R pipe, respectively. The maximum renewal length is about 2,500 ft, and the existing pipe needs to be circular and typically have a consistent cross-section. The F&F variant of CFP can accommodate pipe bends up to about 30 degrees (Thornton et al. 2005). The D&R variants of CFP are generally limited to pipe without bends. Typically during CFP renewal, flow through the existing pipe must be bypassed and infiltration must be sealed (Najafi 2016). Figure 7. Spot repair to fill invert voids prior to application around the complete perimeter with the centrifugal spray unit (Courtesy: Milliken Infrastructure Solutions, LLC).
16 The Renewal of Stormwater Systems Using Trenchless Technologies The following case study is for a CFP project completed in Colorado in fall 2012 by swage- lining a 27-in. steel-finished water main (Matthews and Randall 2014). Problem The existing approximately 2,500-ft-long, 27-in.-diameter, steel-finished water main was experiencing frequent corrosion-related leaks. The alignment transverses backyards in a primarily residential area and was located in an area with high groundwater. The depth of cover over the water main is about 5 to 6 ft. The potential neighborhood impacts and total construction costs for a replacement line led to rehabilitation being selected as the preferred alternative for addressing the leaks. Design Swagelining was selected to provide a continuous liner and maintain as much hydraulic capacity as possible. Swagelining also allows for the use of National Science Foundationâapproved HDPE pipe for potable water. The expected service life is more than 50 years. Construction The flow in the existing pipe was bypassed and CCTV was used to verify there were no pro- trusions into the existing pipe and that it was clean. The new pipe was fused into a single section prior to starting the pull. During the pull the new pipe was pulled through a reduction dye, which reduced the outside diameter of the new pipe to about 90% of the inside diameter of the existing pipe. Tension was maintained during the pull to prevent the HDPE pipe from reverting to the original diameter. The pulling of the 2,500 linear feet of liner was completed in 18 hours. The HDPE pipe reverted back to the original diameter about 24 hours after the tension on the pipe was released. The construction costs were about $365 per linear foot. Additional Information Lessons learned using swagelining on a curved, 1,400-ft-long, 24-in. RCP transmission main, where the HDPE pipe failed in tension during the pull, were applied to the 2,500-ft-long pull. These lessons included using a reinforced concrete anchor block to provide the resistance for the reduction dye and not using swagelining on a curved alignment. Figure 8. Deforming the HDPE pipe in a reduction dye (Courtesy: City of Fort Collins).
Trenchless Renewal Methods 17 Summary The successful renewal of the water transmission main using swagelining required deliberate preparation including bypassing the existing flow, CCTV to verify there were no obstructions and that the pipe was clean, and construction of reinforced concrete anchor block. Summary of Advantages and Challenges The following summary of the advantages and challenges (Tables 1 and 2) is based on Najafi (2016); Jin, Piratla, and Matthews (2015); Caltrans (2013); and Hollingshead and Tullis (2009). Emerging Technologies One goal of the literature review was to identify potential emerging technologies and also to identify if different methods are being used internationally. The Bibliography includes infor- mation on the international use of trenchless renewal, which is generally similar to the methods used in the United States. The literature search did reveal three potentially emergent methods used in the United States. A steel-reinforced composite system that is a variation on SIPP and CIPP was identified during the literature search. The steel-reinforced composite system includes continuously wrapped, Method Existing Pipe Type Advantages Challenges CIPP ⢠Concrete ⢠Steel ⢠Plastic ⢠Brick ⢠Small construction footprint. ⢠Excavation typically not required. ⢠Grouting not required. ⢠Minimal reduction in culvert size. ⢠No joints. ⢠Accommodates most bends. ⢠Noncircular and varying cross-sections. ⢠Flow bypass required. ⢠Typically manufactured specifically for each project. ⢠Toxic resins associated with some variants. ⢠Capture and disposal of cure water requires additional consideration. ⢠Relatively high volumes of steam and water required for some methods. SL ⢠Concrete ⢠Steel ⢠Plastic ⢠Brick ⢠Flow bypass not always required. ⢠Structural renewal. ⢠Can accommodate large radii bends. ⢠Large insertion pits and construction area typically required. Can be mitigated with use of segmental pipe. ⢠Limited to smallest diameter of existing pipe. ⢠Excavation may be required. ⢠Bulkheading and grouting of annulus requires additional considerations. MSL ⢠Concrete ⢠Steel ⢠Plastic ⢠Brick ⢠Flow bypass not always required. ⢠Structural renewal. ⢠Smaller construction footprint. ⢠Noncircular and varying cross-sections. ⢠Accommodates some bends. ⢠Grouting not always required. ⢠Specialized equipment needed for some products. ⢠Excavation may be required at some bends. ⢠Typically manufactured specifically for each project. Table 1. Summary of advantages and challenges of CIPP, SL, and MSL.
18 The Renewal of Stormwater Systems Using Trenchless Technologies high strength, steel wires embedded in a spin-cast or spray-applied cementitious or polymeric matrix and sandwiched between two epoxy-impregnated, fiber-reinforced polymer sheets. The process as described in the literature requires personnel entry and starts with applying the fiber- reinforced polymer sheets to the inside of the existing pipe, installing the steel wire, applying the cementitious or polymeric matrix, and applying a second set of fiber-reinforced polymer sheets to covert the matrix. The method was developed for renewal of prestressed concrete cylinder pipes and designed to provide the original design capacity in the event of complete failure of prestressing wires. The method was used to renew a 54-in. pipe for Miami-Dade Water & Sewer Department (Aguiar, Pridmore, and Geraghty 2015). Two variations of ILR using pipe ramming, referred to as âpipe crushingâ and âpipe swal- lowing,â were identified as potential emerging technologies. These variations are similar to pipe eating in that the new pipe is larger than the existing pipe and the existing pipe is removed from within the new pipe after installation. For both pipe crushing and pipe swallowing, the new casing is rammed over the existing casing and along the existing alignment. With pipe crushing, angled steel wedges welded within the inner portion of the leading section of new casing crush the existing casing during the ramming process to facilitate removal. A view of the interior of the crushed existing pipe is shown in Figure 9. The crushed pipe can be removed as a single piece. With pipe swallowing, the existing casing is broken or crushed with a separate piece of equipment, such as auger, to facilitate removal. One relatively unique potential emergent method was identified during the literature search (Witter 2017). The method uses geosynthetic cementitious composite mats (GCCM) to reline personnel-accessible pipes. GCCM is similar but distinct from current definitions of CIPP. It is also similar to paved invert repair. GCCM includes a flexible cement impregnated cloth with a Method Existing Pipe Type Advantages Challenges ILR ⢠Unreinforced or lightly reinforced concrete ⢠Steel ⢠Plastic ⢠Structural renewal. ⢠Can upsize existing pipe size. ⢠Accommodates some bends. ⢠Flow bypass typically required. ⢠Larger construction footprint. ⢠Excavation may be required. ⢠Can damage adjacent structures and improvements. ⢠Not suitable for all soil conditions. ⢠Can exaggerate line and grade defects. SIPP ⢠Concrete ⢠Steel ⢠Brick ⢠Small construction footprint. ⢠Noncircular and varying cross-sections. ⢠Can incorporate reinforcement. ⢠Larger diameter can be accommodated. ⢠Protects against corrosion. ⢠Flow bypass required. ⢠Specialized equipment and training required. ⢠Surface preparation is critical. ⢠Can accommodate most bends. CFP ⢠Concrete ⢠Steel ⢠Plastic ⢠Brick ⢠Annular grouting not required. ⢠Structural renewal. ⢠Accommodates some bends. ⢠Flow bypass required. ⢠Larger construction footprint. ⢠Limited to circular cross- sections. Table 2. Summary of advantages and challenges of ILR, SIPP, and CFP.
Trenchless Renewal Methods 19 PVC backing that is mechanically fastened in strips to the inside of the existing pipe. A sealant is used along the seams of the overlapped strips to help prevent infiltration. GCCM is like CIPP in that the process consists of a flexible rolled cloth used to line an existing pipe. However, unlike CIPP, it is hand-placed in strips around the inside of the existing pipe to create a continuous liner and uses cement rather than resin. The following case study is for a GCCM project completed in Washington in September 2015 (Conrad 2016). Problem A portion of the existing 240-ft-long, 60-in.-diameter CMP culvert had been replaced in 2005. During a yearly inspection, corrosion, including through-going corrosion and pitting, was observed along the older 180-ft length of culvert. The maximum depth of cover was about 20 to 25 ft, and Tacoma Waterâs water supply pipeline crosses over the top of the culvert. Initial estimates to replace the culvert were in the $250,000 to $300,000 range. Given the relatively low cost of the GCCM materials, Tacoma Water elected to try the installation themselves. Design The design consisted of two 3.5-ft-wide strips of 0.3-in.-thick GCCM with a 4-in. overlap mechanically fastened. A moisture-cured sealant and a tar sealant were called for along the overlap and edge, respectively. The GCCM included a PVC backing to provide additional waterproofing. Construction The construction took an eight-person crew two 8-hour days to complete. Grout was placed to fill the pitted areas of the culvert. The GCCM was delivered to the site on roll and was unspooled as it was pulled into the culvert. The mats were placed longitudinally along the invert in 50- to 60-ft strips. Installation included fastening the GCCM with self-tapping screws with washers on an 8-in. pattern including along the overlap. The joints and edges were sealed. The mat was hydrated after installation. The cost of the materials and the estimated installation costs by Tacoma Waterâs crew was about $20,000. Figure 9. Interior of existing CMP culvert during the pipe crushing (Courtesy: HammerHead Trenchless Equipment).
20 The Renewal of Stormwater Systems Using Trenchless Technologies Additional Information No discernable change in the GCCM was observed during a 9-month, post-construction review of the installation. Tacoma Water continues to perform regular inspections of the culvert and is hopeful that they will achieve an additional 15 to 20 years of life from the renewed culvert. Summary The owner is very satisfied with the relative ease of installation and the additional anticipated service life. Case Example Summary A summary of the case studies is provided in Tables 3 and 4. The summary includes the trenchless renewal methods, project location, existing pipe type and dimensions, date of renewal, expected service life, planned inspection schedule, and project cost. Method(s) CIPP ILR (Pipe Bursting) SL/MSL Product Thermoset Resin- Impregnated Felt Liner HDPE Pipe Steel-Reinforced Polyethylene and Tunnel Liner Plate Location Wisconsin Ohio Tennessee Existing Pipe Type RCP CMP CMP Existing Pipe Length (feet) 180 90, 105, 100, and 105 400 Existing Pipe Diameter (inches) 60 12, 18, 24, and 24 72 Final Pipe Diameter (inches) 60 16, 18, 24, and 24 48 and 60 Date December 2016 June/July 2014 April 2016 Expected Service Life 50 years 100 years Not Available Inspection Schedule Same as other culverts Same as new construction Not Available Approximate Cost per Linear Foot $650 $120 to $200 Not Available Table 3. Case example summary for CIPP, ILR, and SL/MSL. Method(s) SIPP GCCM CFP Product Fiber-Reinforced Geopolymer Mortar Geosynthetic Cementitious Composite Mat HDPE Pipe Location Indiana Washington Colorado Existing Pipe Type CMP CMP Steel Existing Pipe Length (feet) 275 240 2,500 Existing Pipe Diameter (inches) 84 60 27 inside diameter Final Pipe Diameter (inches) 81 60 27 outside diameter Date September 2015 September 2015 Fall 2012 Expected Service Life 50 years 15 to 20 years Greater than 50 years Inspection Schedule Every 5 years Same as other culverts Not Available Approximate Cost per Linear Foot $1,125 $83 $365 Table 4. Case study summary for SIPP, GCCM, and CFP.
Trenchless Renewal Methods 21 Chapter Summary This chapter provides a brief overview of CIPP, SL, MSL, ILR, SIPP, and CFP trenchless renewal methods. The generally accepted applicability of the methods and limiting factors are included in the overview. The advantages and disadvantages of these methods are provided in Tables 1 and 2. Potential emergent methods, including a steel-reinforced composite system that is a variation on SIPP and CIPP, the use of GCCM for culvert renewal, and two variations of ILR are also discussed. Case studies for projects using CIPP, SIPP, SL, MSL, CFP, and ILR (pipe bursting) are summarized in Tables 3 and 4.
