A CASE STUDY IN CURED-IN-PLACE PIPE (CIPP) FOR STORMWATER PIPE REPAIR. By John Featherstone, P.E

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1 A CASE STUDY IN CURED-IN-PLACE PIPE (CIPP) FOR STORMWATER PIPE REPAIR By John Featherstone, P.E The author has served the City of Shoreline, WA, as Surface Water Engineer since 2014 This paper will be presented in Stormwater Program Management Session P72 at Storm Con 2017 INTRODUCTION: The City of Shoreline (City), Washington, presents a case study in utilizing Cured-In-Place Pipe (CIPP) methods for stormwater pipe repair. While CIPP is more commonly used for sanitary sewer repair, it is also a valuable tool for stormwater managers to address the increasingly important problem of stormwater pipe structural deterioration and failure due to age. Apparently only a few municipalities in the greater Pacific Northwest region of the U.S. are currently implementing systematic pipe repair programs using CIPP lining to repair stormwater pipes. While CIPP stormwater pipe repair is not typically grouped within the broad collection of topics related to stormwater water quality, there are three notable areas where CIPP does overlap with stormwater water quality. First, CIPP can be used to remediate deficient pipe conditions which may be allowing entry of contaminants into stormwater. Secondly, concerns over potential water quality impacts from the styrene as a common component in CIPP resins may have excessively limited CIPP usage in stormwater system (discussed in further depth below). Finally, the cost savings of using CIPP for priority stormwater pipe repairs (relative to other comparable methods) may allow stormwater managers to allocate increased proportions of funding towards other purposes, including water quality and habitat improvements. Since 2014 the City of Shoreline has installed approximately 3,800 linear feet of CIPP in stormwater pipe under the Stormwater Pipe Repair and Replacement Program. The City has learned that special strategies are needed to accommodate unique conditions of the CIPP market and materials. Anticipating and understanding these special conditions helps to maximize the efficiency and overall success of pipe repairs. This paper relates the narrative of the City of Shoreline s experiences using Cured-in-Place Pipe (CIPP) to repair stormwater pipe. The background section explains the City of Shoreline s programs for systematic assessment of stormwater pipe condition and prioritizing pipe repairs, as well as why CIPP was selected as the preferred trenchless repair method. The results section summarizes the actual work completed and associated costs for multiple projects implemented since The conclusions section describes lessons learned, including recommended CIPP-specific contents for design and bid/construction documents, limitations and range of applicable conditions for use of CIPP, and strengths and advantages of CIPP. As a case study, the observations are anecdotally-based; some light data is presented related to CIPP used in City of Shoreline projects and CIPP in general, but objectives and conclusions are generally not data-driven.

2 BACKGROUND: The City of Shoreline owns and maintains approximately 140 miles of stormwater pipes in active use. A majority of these pipes were installed more than 50 years ago and are nearing or have already exceeded their original design lifespan. In order to address this aging stormwater infrastructure issue, the City has systematically assessed the condition of stormwater pipes (as grouped by drainage basins) since Condition assessments Stormwater pipe condition assessments are conducted using the NASSCO PACP methodology. Under the PACP system, observed pipe defects are cataloged by the CCTV technician into a pipe inspection software program, which automatically applies standard predetermined numerical ratings to each pipe defect. PACP scoring for each individual defect ranges from 0 to 5 in severity, 5 being the worst. The pipe inspection software creates a report for each discrete (structure-to-structure) pipe segment featuring aggregate scores to represent the general structural, maintenance, and overall conditions of the whole pipe. For assessing general pipe structural condition, the City uses QSR as the preferred aggregate score (compared to SPR or SPRI, which respectively sum or average the pipe s defect ratings); QSR is a 4- digit code representing the number of the two worst-scored defect types. Prioritizing pipe repairs Pipes identified having serious structural deficiencies likely need repair or replacement within a 20-year timeframe (which typically covers individual defects with PACP structural scores ranging from 3 to 5). The City prioritizes such pipes for repair and replacement based upon estimated likelihood of failure (based on PACP score) and potential consequences of failure (based on contextual elements of pipe location). Initially, pipe repair need is assessed shortly after CCTV inspection is completed. This work is most efficiently performed by an engineering technician or junior engineer reviewing batches of several pipe inspections as they are available. Each pipe inspection CCTV video is reviewed to confirm severity of pipe defects detected in inspection (per PACP scoring), and each pipe is additionally scored for prioritization using criticality criteria based on expected consequence of potential failure. This process will ultimately include hundreds of pipes in a typical basin-wide condition assessment effort. First-pass prioritization is used to determine the initial groupings of pipes to be potentially repaired, including whether trenchless repair methods are expected to be suitable. Typical groupings include a Priority Open Cut Repair set, a Priority Trenchless Repair set, and a Second Tier Repair set. These grouped repair sets are created for use in long-term programmatic stormwater pipe repair planning. Cases where pipes are found in very bad condition with high potential consequences of failure can also be elevated for immediate repair. The City of Shoreline s Stormwater Pipe Repair and Replacement Program addresses the prioritized structurally deficient stormwater pipes to proactively ensure public safety, reduce flooding, decrease maintenance demands, and protect critical infrastructure and public and private property. Secondary assessment and re-prioritization occurs as needed during design of the pipe repair bid package. Pipe inspection CCTV video results are revisited within the specific context of the pipe repair project locations, objectives, and limitations; pipes may be added to or dropped from the design set based on this more detailed, project-specific assessment of pipe condition and repair needs. Second-tier pipes may be added to a priority repair design if they are located in close proximity to a high priority repair 2

3 pipe. Priority pipes may also be deferred to a future repair project, for a number of reasons such as insufficient access (lack of easement) or condition information (incomplete inspection). Selection of CIPP as a preferred repair method Cured-In-Place Pipe is a trenchless pipe repair method first developed in 1970s which rehabilitates damaged pipes using a flexible composite liner inserted through existing pipe end openings then quickly and permanently cured into a hard, durable composite material fully lining the complete pipe length. The City of Shoreline currently prefers CIPP over other trenchless methodologies due to: 1. Minimal impacts for installation (for example, compared to slip-lining or pipe bursting which require open cut excavation for insertion pits and to reconnect laterals); 2. Fits 12-inch diameter pipe (other trenchless methods such as spiral wound pipe and applied cementitious liners (shotcrete, etc.) are generally unavailable for the 12-inch diameter pipes which are the most common size in Shoreline s stormwater system); 3. Available in a competitive market (some trenchless technologies are not currently widely available in the Pacific Northwest region); and 4. Installation costs which are competitive with or lower than other comparable repair methods. CIPP installation s lack of excavation and other surface disturbance means that crews can work quickly and without lengthy impacts to traffic and neighbors. Potential impacts at a given location are typically limited to temporary traffic revisions (lasting one or two days), and some minor noise and odor associated with the steam-curing process (which lasts a few hours and dissipates immediately upon completion). Uncured CIPP resin as well as condensate and rinse water from the curing process are strictly controlled to minimize potential water quality impacts (via special provisions, discussed in further depth below). The CIPP pipe repair method provides optimal sustainability by extending the lifespan of the City s existing stormwater infrastructure without the expense and high level of disturbance that comes with extensive excavation. Design of CIPP repairs Design for CIPP stormwater pipe repairs mostly involves (1) confirming that damaged pipe is a suitable candidate for CIPP repair, (2) determining the optimal groupings of prioritized pipes for repair, and (3) ensuring that any potential obstacles to the CIPP installation process (such as protruding laterals, or difficult-to-access pipe ends) have been accounted for. Design for CIPP repair is much less intensive than design for open cut repair (which needs to account for removals, restoration, and any underground utilities which excavation might encounter). While CIPP lining does slightly reduce the effective diameter of the pipe, post-lining pipe capacity is usually equal to or better than pre-lining capacity due to increased pipe interior smoothness (as compared to worn concrete pipe or corroded corrugated metal pipe). Accordingly, the City s design process for CIPP repairs checks capacity only in select cases when a system may be suspected of having insufficient capacity. If such a capacity check reveals that the system would have significantly insufficient capacity following CIPP lining, the pipe repair is deferred for open cut up-sizing replacement. The City of Shoreline to date has relied upon consultant engineering to produce repair designs, but intends to shift to more in-house design for CIPP repairs as a means to improve cost efficiency. 3

4 RESULTS Since 2014 the City has worked closely with consulting engineers and specialty contractors to repair over 3,800 linear feet of structurally deficient stormwater pipe using CIPP lining was the initial year of the Stormwater Pipe Repair and Replacement Program. The initial 2014 bid package combined CIPP and open cut sites and received two bids; however both bids were mandatorily rejected due to neither bidder satisfying the supplemental qualifications for CIPP installers. A re-bid set was assembled with the CIPP supplemental qualifications moved to the Division 7 special provisions as construction submittals. The re-bid package received two bids from the same previous bidders, and was successfully awarded to low bidder. Construction repaired 13 pipes at locations within the Storm Creek and Boeing Creek Basins, which included installing 784 linear feet (LF) of CIPP repairs at nine locations, and 86 LF of open cut-replaced pipe at four locations. Of the 784 LF of CIPP liner installed, 70 LF was 24 diameter pipe, and the remaining 714 LF was 12 diameter pipe. Complete actual costs for CIPP lining installed during the 2014 Stormwater Pipe Repair and Replacement Project totaled approximately $243,000, including $25,000 for City staff time (mostly project management with some construction management services), $83,000 for the engineering consultant effort, and $135,000 for construction. The bid item for CIPP liner installation was approximately $90/LF for 12-inch diameter and $250/LF for 24-inch diameter; gross per LF average for all costs associated with completing pipe repair (including all project-related staff and consultant time, but excluding initial condition assessment CCTV inspection) was around $310/LF. In 2015 the City solicited bids for a stormwater pipe repair project which combined 2,349 LF of CIPP liner installations at 16 locations with open cut repairs at four locations. This bid package received no bids, and prospective bidders were contacted to determine why no bids were made. Following this investigation, the combined work items were split into separate open cut-only and CIPP-only contracts. The open cut project was successfully re-bid and completed by early The re-packaged CIPP work was successfully re-bid in early 2016, in a set which included nearly 700 LF of additional CIPP pipe repairs. The 2016 CIPP Stormwater Pipe Repair Project repaired 3,020 linear feet (LF) of failing stormwater pipes, comprising of 39 pipes distributed over 21 separate locations. Of the 3,020 LF of CIPP liner installed, 860 LF was 18 diameter pipe, and the remaining 2,160 LF was 12 diameter pipe. Complete actual costs for the 2016 CIPP Stormwater Pipe Repair Project totaled approximately $467,000, including $18,000 for City staff time (mostly project management with some construction management services), $88,000 for the engineering consultant effort, and $361,000 for construction. The bid item for CIPP liner installation was approximately $80/LF for 12-inch diameter and $110/LF for 18- inch diameter; gross per LF average for all costs associated with completing pipe repair (including all project-related staff and consultant time, but excluding initial condition assessment CCTV inspection) was around $150/LF. To date, the City has been focused on implementing the initial projects under the Stormwater Pipe Repair and Replacement program, and learning from these experiences. Efficiency of pipe repair planning and design processes are expected to increase going forward as repair methods are better understood and higher quantities of pipe repairs are included in each bid package, leading to lowered unit costs for those processes as well as for construction. 4

5 Shoreline expects to complete the initial condition assessment for all stormwater pipes in the City in the near future, and is currently about halfway to this goal. There is a large backlog of pipes to be repaired and the City is currently undergoing a Surface Water Master Plan update (scheduled for 2017 completion) which will include recommendations for the optimal programmatic approaches to satisfy long-term infrastructure needs. Table 1 Summary comparisons of actual completed and estimated/targeted future costs for City of Shoreline CIPP and Open Cut Stormwater Pipe Repair Projects These repair packages consist of a 70% or greater aggregate length of 12-inch diameter stormwater pipe, with lesser proportions of 18- to 24-inch diameter stormwater pipe. Project Info CIPP Liner Repair Open Cut Repair/Replacement Actual Target Actual Estimated Construction year Total Cost $243,000 $467,000 $437,500 $155,831 $224,418 $366,000 Total LF installed 784 3,020 3, Total Cost $/LF $310 $150 $125 $2,120 $706 $676 -Construction $/LF $172 $115 $110 $1,464 $457 $581 -Consulting $/LF $107 $28 $0 $505 $204 $60 -City staff $/LF $32 $6 $15 $151 $44 $35 Total pipes fixed Total Cost $/pipe $27,020 $11,960 $9,730 $38,960 $11,810 $32,690 -Construct. $/pipe $14,960 $9,240 $8,560 $26,900 $7,650 $28,150 -Consulting $/pipe $9,290 $2,260 $0 $9,290 $3,420 $2,850 -City staff $/pipe $2,770 $460 $1,170 $2,770 $740 $1,690 Figure 1- CIPP liner insertion (2016) 5

6 Figure 2 - CIPP curing process, insertion end (2016) Figure 3- CIPP liner passing through a catch basin, to be cut after curing (2016) 6

7 Figure 4 - CIPP curing process, steam venting end (2014) CONCLUSIONS The City s experiences with multiple CIPP pipe repair projects have led to a better understanding of some peculiarities of CIPP including limitations, environmental concerns, and strengths. Understanding these nuances of utilizing CIPP lining within stormwater systems helps to maximize the efficiency and overall success of pipe repairs. Limitations and other considerations Supplemental qualifications: The initial 2014 bid documents included Supplemental Bidder Responsibility Criteria related to CIPP work, which both bidders failed to meet leading to mandatory rejection of both bids. For the re-bid set approximately one month later, these CIPP supplemental qualifications were moved to the Division 7 special provisions as construction submittals, where they have stayed for subsequent CIPP repair bid documents. 7

8 Mixing CIPP specialty work with general contractor-type work: 2014 bid package combined CIPP pipe repair at nine sites and open cut pipe repair at four other sites, and received two bids. In 2015 the City issued another bid package combined CIPP repair (at 16 locations) and open cut repair (at four sites, including one with both CIPP and open cut repairs) and received no bids. The follow-up investigation revealed (among other factors) that bid package s combination of open cut conventional pipe repairs and CIPP repairs was unappealing to both general contractors and the CIPP specialty contractors. The combined package was split into separate open cut-only and CIPP-only contracts, both of which were successfully constructed following receiving multiple bids each. For the 2016 CIPP work, the City made sure that any small general work items related to pipe end access such as locating buried or paved-over catch basins, and vegetation management were taken care of by City maintenance crews prior to CIPP installation. CIPP submittals: 2014 project special provisions called for submittals covering a total of 35 CIPPrelated items. There were multiple iterations of CIPP submittals and the contractor(s) appeared to make a concerted effort: 16 items related to CIPP planning, qualifications, and quality assurance were submitted and generally accepted; however, at time of physical completion, 15 of the 19 remaining items related to CIPP design in particular had not been submitted. The 2016 CIPP project documents made a concerted effort to reduce the number of CIPP-related submittal items from 35 to 23 by eliminating redundancies and streamlining requirements; the contractor was able to successfully meet submittal requirements. Future design sets will look at further streamlining submittal requirements. CCTV warranty inspections: In 2016, the City attempted to include a CCTV inspection to be done 11 months after CIPP liner installation to identify any potential problematic installations before the end of the 1-year warranty period. However, the contractor balked at this requirement due to contracting implications and accordingly these inspections were dropped. Pre- and post-cipp installation inspection CCTV video quality: Some 2016 CIPP repair project video inspections as provided were in a low-resolution video file format, which made it difficult to see pipe conditions well enough to confirm pre- and post-installation conditions. For future work, specifications will be updated to specifically require minimum video resolution high enough to prevent this problem. Confirming suitability of CIPP repair: CIPP can only address certain types of damaged pipes, and cannot repair the most heavily damaged pipes. It is best suited for moderately damaged concrete pipe, exhibiting common deficiencies such as cracks, fractures, breaks, small holes, moderate joint displacements, and surface damage. CIPP is also suitable for fixing a similar array of defects in corrugated metal pipe (protruding metal edges must be removed prior to CIPP insertion). The 2016 contractor informed the City that CIPP is typically not suitable for thin-walled plastic pipes such as corrugated polyethylene which can deform under the heat and pressure of the CIPP curing process, and smooth interior pipes, such as PVC, HDPE, or ductile iron, which may offer insufficient surface roughness and/or joints for the CIPP liner to mechanically lock into. Pipes with severe structural damage, such as large holes or missing pieces, major deformation, collapse, or obstructions, or large joint displacements must be repaired by conventional open cut methods. Limited shelf life of pre-installed CIPP material: It is important to either (1) confirm with the contractor that pipes are suitable for CIPP repair prior to the contractor ordering CIPP liner, or (2) very specifically establish in the contract documents that it is the contractor s responsibility to verify these conditions prior to ordering the CIPP liner and that any unused liner must be disposed of at the contractor s expense. During the 2016 CIPP repair project, the City wound up paying for (relatively small quantities 8

9 of) unused CIPP liners because two pipes from the bid documents were unsuitable to CIPP repair. The contractor stated that because the CIPP liners cannot be re-used for another project due to limited shelf life once the liner is infused with resin, that the City was obligated to pay for the material costs of the unused liners. Reconnecting stormwater laterals: For the 2016 CIPP repair design, the City assumed that reconnecting laterals to CIPP-lined stormwater pipes would require top hat connections, which reinforce the lateral s junction with the main pipe and install a small length of CIPP up the lateral pipe (the 2014 CIPP design omitted pipes with laterals to avoid having to deal with reconnections). In the contract these top hat lateral connections had a bid price around $4,300 each. However, during the project the City learned that a number of these laterals were unsuitable for top hatting (due to size/material), and that the general integrity of the CIPP liner in the larger stormwater pipe did not require top hatting. Upon receiving this information, the City and contractor agreed to drop all six top hats called for in the design. Environmental concerns The most-documented environmental concern for CIPP lining is related to styrene, commonly used in CIPP resins. These concerns are generally understood to have originated with a 2007 Virginia Department of Transportation (VDOT) report (Winter, Ken; Styrene Resin Used in Cured in Place Pipe Rehabilitation May have a Significant Localized Ecotoxic, Despite Fast General Biodegradation ) linking styrene released to downstream waterbodies during a poorly-implemented CIPP repair installed within a culvert as having adverse impacts to aquatic life. The City reviewed subsequent research related to this issue and seemed to find a general consensus supporting the concept that potential environmental impacts from styrene could be effectively eliminated by requiring construction practices to (1) prevent pre-cured resin spills/leaks/drips, (2) rinse the CIPP lining after curing, and (3) capture curing condensate and rinsewater to prevent discharge to the storm system. The 2012 Caltrans report (Penders, Sean, and Melendrez, David; Environmental Effects of Cured-In-Place Pipe Repairs) is one such source indicating that release of styrene was caused by poor CIPP installation practices, and implementing new specifications could eliminate these problems. These requirements (partially taken from recommended CIPP specifications provided by VDOT), are written into the City s special provision section for CIPP, including a bid item for Post-CIPP Installation Rinse to highlight this requirement. The 2014 CIPP project special provision prohibited styrene-based resin; however contractor submitted a styrene-based resin noting that non-styrene resins were more difficult to work with and said that other clients had considered the water quality issue and determined styrene was not a major concern, provided problem handling and installation practices were observed. One such former client, the Oregon Department of Transportation (ODOT), was contacted to confirm the latter statement. Styrene-based resins were accepted for use in the 2014 project. Modifications were made to the 2016 CIPP project specifications to help further ensure that all procedures for proper handling, installation, bypass, and cleanup were followed by the contractor. Regardless of stringency of specifications, contractor practices in the field must be closely monitored to ensure compliance and protection of water quality. The 2016 CIPP project contractor noted that his company was working hard on developing styrene-free CIPP resins which would be more cost-effective and easier to work with then the current non-styrene CIPP products. Providers of UV-cured CIPP systems claim that styrene contamination is a much lesser 9

10 potential issue compared to the more conventional steam- and water-cured CIPP systems. The City has not yet researched UV-cured CIPP as a possibly preferable alternative to steam-cured CIPP, but intends to do so when designing the next CIPP pipe repair set. A secondary environmental impact of styrene in CIPP resins is a distinctive odor which could be a potential indoor air quality issue in the rare case that a homeowner has an interior drain connected to the storm drain. Because most stormwater systems are not connected to the interiors of residences, this is not expected to be a major issue for stormwater repairs, and accordingly, the odor of styrene is generally more of a transient outdoor air quality nuisance. For 2016 CIPP repair, the City included an Odor Control Response bid item, to be paid by force account; however, there were no odor complaints and so this item was not used. Strengths Lower cost than open cut: Per Table 1 above, the costs for CIPP repair are, at worst, roughly equivalent to the costs for an open cut repair; at best it is three to ten times more economical for cost per linear foot or cost per each pipe repaired (acknowledging that it may be somewhat difficult to show this as a direct apples-to-apples comparison using the data from Table 1). Durability: A 2011 article on durability published by the EPA ( found no evidence of durability concerns for CIPP: The pilot testing used CIPP samples from both large and small diameter sewers in two cities that were in excellent condition after being in use for 25, 23, 21, and 5 years, respectively Three of the liners had already been in service for nearly half of their originally expected service life, but overall, there is no reason to anticipate that the liners evaluated will not last for their intended lifetime of 50 years and perhaps beyond. Less disturbance than open cut: CIPP installation s lack of excavation and other surface disturbance means that crews can work quickly and without lengthy impacts to traffic and neighbors. Repair of moderate defects in concrete and corrugated metal pipes: CIPP is optimal for repairs of certain types of defects, mostly within concrete pipe and corrugated metal pipe (CMP) materials. The City of Shoreline has used CIPP to repair concrete pipe damage including cracks, fractures, breaks, small holes, moderate joint displacements, root intrusions, and surface damage; corrugated metal pipe damage including small holes (protruding metal edges must be removed prior to CIPP insertion), root intrusions, and corrosion; and problematic transitions between dissimilar pipe materials. See photos below for multiple examples of repairs completed by City of Shoreline CIPP projects in 2014 and

11 Figure 5 - Concrete pipe, fracture repair Figure 6 - Concrete pipe, fracture repair Figure 7 - Concrete pipe, hole repair 11

12 Figure 8 - Concrete pipe, break repair Figure 9 - Concrete pipe, break repair Figure 10- Concrete pipe, break repair 12

13 Figure 11 - Concrete pipe, joint offset repair Figure 12 - Concrete pipe. Open cut repair implemented prior to CIPP installation to address major pipe displacement at short section of pipe (replacing concrete pipe with ductile iron section), followed by CIPP repair of cracks and fractures throughout remaining pipe length. Figure 13 - CIPP used to repair dissimilar material transitions (between concrete and corrugated metal pipe) 13

14 Figure 14 Corrugated metal pipe, corrosion and hole repair Figure 15 Corrugated metal pipe, corrosion and hole repair Figure 16 Corrugated metal pipe, corrosion and hole repair (sharp edges must be trimmed prior to CIPP installation) 14

15 Figure 17 Corrugated metal pipe, hole repair (any sharp edges must be trimmed prior to CIPP installation) Figure 18 Corrugated metal pipe, root intrusion repair Figure 19 Concrete pipe, root intrusion repair (showing initial condition with roots, pre-lining, and post-lining) 15

16 Figure 20 Concrete pipe, root intrusion repair (showing initial condition with roots, pre-lining, and post-lining) AUTHOR BIO: John Featherstone is a Washington State-licensed Professional Engineer in Civil Engineering. After 10 years doing civil stormwater engineering design work in the private consulting sector, John came to the City of Shoreline as the City s surface water engineer in April At City of Shoreline he has been responsible for providing project management, program management, engineering and other technical support for the City s Surface Water Utility; notable efforts include the Stormwater Pipe Repair and Replacement Program, 25th Avenue NE Flood Reduction Project, Hidden Lake Dam Removal and Boeing Creek Restoration Projects, Greenworks bioretention projects, and the McAleer Creek and Lyon Creek Basin Plans. Contact info - jfeatherstone@shorelinewa.gov Phone: (206) Address: Midvale Ave N, Shoreline, WA