Rehabilitation of Culverts and Buried Storm Drain Pipes (2022)

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25   Representatives from four state transportation organizations that participated in the survey were interviewed to learn more about the factors that significantly affect the selection of cul- vert rehabilitation methods, maintenance programs, and implementation; the pros and cons of different rehabilitation methods; lessons learned; changes implemented; the rationale behind important decisions; and identification of information gaps and possible research to address those gaps for the implementation of promising methods and practices. The information pre- sented in the case examples documents further how the selected DOTs’ rehabilitation programs evolved and how they align with performance requirements for reasonable maintenance expec- tations. Agencies with established practices and experiences in the following areas were selected: • Relatively large number of rehabilitated culverts, • Specifications or guidance documents available to achieve specific performance objectives [e.g., Delaware DOT (2021), Maine DOT (Hartley, 2014), Oregon DOT (2014), and Wisconsin DOT (2018)], • Documentation and historical data on the rehabilitated culverts to demonstrate selected reha- bilitation applications, and • No major problems (e.g., associated with materials, construction, maintenance) observed in the field since the completion of rehabilitation of the culverts (more specifically, for those presented in this chapter). 4.1 Delaware DOT Rehabilitation Practices and Culvert Rehabilitation Guidance A new pipe inspection and rehabilitation manual was recently developed by the Delaware DOT (2021). This guide document provides a compilation of industry best practices, includ- ing post-installation inspection requirements for RCP, thermoplastic pipe, and CMP culverts. Various remediation procedures are also discussed. The document provides guidance and an action plan for potential common defects that may be observed during periodic inspections. For example, if joint separation is observed in an existing RCP, maximum allowable joint separa- tion is specified as the smaller value of the manufacturer’s recommendation and the following limit: 0.75 in. separation for RCP 12 to 36 in. in diameter, 1.25 in. for RCP 42 in. or larger in diameter, and 1.50 in. separation for all elliptical pipes. Similarly, if cracking is observed in an existing RCP, it is evaluated on the basis of the direction and width of the crack. The flowchart in Figure 4-1 can be used for crack analysis and remediation in an existing RCP. The state of Delaware defines structures with a pipe or hydraulic opening of 20 ft2 or larger as a bridge; thus such structures need to be maintained or replaced by the Delaware DOT. CMP bridges account for approximately 15% of the Delaware DOT’s inventory, but they account for C H A P T E R 4 Case Examples

26 Rehabilitation of Culverts and Buried Storm Drain Pipes Source: Delaware DOT, 2021. Figure 4-1. Delaware DOT flowchart for remediation and analysis of cracking observed in RCP.

Case Examples 27   approximately 72% of the structurally deficient bridges in the inventory. The bottom and end portions of CMP culverts tend to corrode and degrade or frequently fail along the water line. This may be caused by changes in water elevation or the presence of corrosive soil or corrosive water (e.g., in coastal regions or from agricultural farming runoff), which may include fertilizer or excrement from animal farming. Water elevation changes are typically created by tidal influ- ence, irrigation, or drought. Such deterioration of CMP culverts may eventually lead to loss of backfill soil materials, loss of structural capacity, or complete failure. Due to limited impact on the traveling public and on the environment, cementitious linings or spray-applied lining are commonly used (Figure 4-2). The Delaware DOT specifies requirements for installation of spray-applied structural liners using factory-blended portland cementitious or geopolymer cementitious materials. The system must be able to support all applicable design loads, assuming that the existing pipe carries no load and must provide a minimum 75-year ser- vice life for durability. The load rating of the spray liners is based on the load rating procedure required for the same deteriorated culvert. The specified cementitious pipe liner material must have less than 10% fly ash, must include nonmetallic fibers, and must include admixtures to enhance autogenous healing. The geopolymer pipe liner material must, at min imum, be com- posed of 70% pozzolanic material selected from a list of specified materials. Source: Delaware DOT, 2021. Figure 4-2. Before-and-after examples of culverts with spray-applied lining (top) and sliplining (bottom).

28 Rehabilitation of Culverts and Buried Storm Drain Pipes One of the identified research gaps is related to the structural capacity of deteriorated CMP culverts. CMPs develop their strength through the interaction of the soil backfill with the metal structure. There is no analytical way to determine the remaining strength of the system, espe- cially after some of the soil backfill is lost through the joint opening or perforations created in the sides or bottom of the deteriorated culvert. The Delaware DOT’s Bridge Element Inspec- tion Manual (Delaware DOT, 2017) provides requirements for condition assessment of CMP culverts. If loss of backfill material is observed, closure of the culvert structure is required until temporary repair is made. Temporary repair may include installation of steel plates along the roadway to span the deficient culvert. Many culverts are close to the sea level in Delaware, and they are basically flat, with very low velocities or sitting water (Figure 4-3). Many other culverts also become submerged during hurricanes, tropical storms, or superstorms. As a result, the Delaware DOT started to use thermo- plastic pipes more frequently in the early 2000s. Inspection, rehabilitation, and replacement of submerged culverts pose additional challenges, including dewatering. Cofferdams, sheet piles, and other barriers are commonly needed to rehabilitate or replace submerged culverts (Figure 4-4). Source: Delaware DOT. Used with permission. Figure 4-3. Submerged HDPE pipes and CMP culvert with deterioration. Source: Delaware DOT. Used with permission. Figure 4-4. Sheet piles, barriers, and cofferdams used during rehabilitation or replacement of culverts.

Case Examples 29   4.2 Maine DOT Rehabilitation Practices and Culvert Rehabilitation Guidance e culvert rehabilitation guidance document published by the Maine DOT (Hartley, 2014) includes descriptions of sliplining, invert lining, CIPP, and spray-on treatment methods. e document also covers culvert evaluation, environmental and hydraulic considerations, and rehabilitation plan development. e guidance document presents examples and illustrates how each method is constructed, as shown in Figure 4-5. e advantages and disadvantages of each method are also discussed to help a designer to decide between dierent options. Section 502 of the Maine DOT’s Standard Specications also has special provisions for struc- tural concrete culvert invert lining using cast-in-place, shotcrete, and FRP composite methods (Maine DOT, 2020). Standard Specications also includes specic requirements for annular space grouting and structural concrete and HDPE sh weirs. Specications are also provided for sliplining of culverts (in Section 602). For example, bracing of the new pipe is required so that the new pipe will remain in place and not oat during grouting operations. A minimum 1 in. of grout between the new and existing culvert is also required. Bracing material must not signicantly impede grout ow into the annular space between the culverts. Maine DOT personnel indicated that they use invert lining of deteriorated or distorted CMP culverts and sliplining methods more than other rehabilitation methods. ey estimate the average age as 30–60 years for CMP culverts and ≥50 years for concrete culverts at the time of rehabilitation. They report that asphalt- or polymer-coated CMPs have a longer service life (i.e., it takes a little longer for water to reach under the coating material). In addition to hydraulic capacity and sh passage requirements, the depth of the culvert is mentioned as a factor driving the decision of whether to rehabilitate or replace the culvert. For culverts deeper than 10 , rehabilitation (typically sliplining) is preferred, considering the cost associated with removal of the existing culvert. For culverts with a diameter of 3  or larger and with limited deterioration or deciencies, local repair, small patches, grouting, or lling of holes is not unusual. If no erosion or piping is observed in host pipes, no structural capacity calcula- tions are made. Maine DOT maintenance crews generally do the sliplining. ey also sometimes do replacements in-house. e Maine DOT has conducted research, developed guidance, and presented a eld example involving the installation of FRP composite lining in a corroded CMP culvert in a technical report (Maine DOT, 2010). e construction and installation process for this rehabilitation project in Amherst, Maine, is illustrated in Figure 4-6. Source: Maine DOT (Hartley, 2014). Figure 4-5. Proper grout application (left) and incorrect grouting (middle) of sliplined pipes and FRP-lined pipe (right).

30 Rehabilitation of Culverts and Buried Storm Drain Pipes When fish passage is a critical factor for rehabilitation, FRP-lined culverts with combined weirs have been used as shown in Figures 4-6 and 4-7. Maine DOT personnel mentioned that their rehabilitation projects must meet strict state and federal requirements to protect the des- ignated critical habitat of Atlantic salmon. The Maine DOT recently applied a method to affordably increase the hydraulic capacity of the culverts by up to 40%. The flared culvert outlet diffusers are designed as described in Maine DOT Technical Report 14-17 (Mann, 2016). Testing of the culvert performance was accom- plished by the “drawdown method” developed at the Maine DOT, as described in the Technical Report 14-17. The culvert capacity is increased by using flared culvert outlet diffusers or bell inlets or both (Figure 4-8), which is typically much less expensive than replacing a deep pipe (Mann, 2020). This approach reduces the inlet water level, outlet velocity, and outlet scour. It is compatible with sliplined pipes, beneficial on undersized pipes, and most advantageous for undersized deep pipes. While at this point the Maine DOT recommends using diffusers on culverts with slopes less than 3%, diffusers have been used on closed-conduit spillways with very steep slopes. These hooded and re-entrant inlets and some bell inlets allow culverts to fill even on steep slopes. This method addresses the concerns many state DOTs may have related to the hydraulic capacity of the rehabilitated culvert, inlet water level, and outlet velocity typically associated with sliplined culverts; at the same time, this method maintains the benefits of reduc- tions in the cost, traffic disruption, and time necessary for the installation. The Maine DOT is Source: Maine DOT, 2010. Figure 4-6. Process of installation of FRP lining in a CMP in Amherst, Maine: corroded CMP (top left), patching applied to corroded areas in the invert (top middle), movement of FRP panel to mouth of culvert (top right), fastening of FRP panels to CMP (bottom left), progression of panel placement (bottom middle), and completed installation (bottom right).

Case Examples 31   Source: Maine DOT. Used with permission. Figure 4-7. FRP-lined CMP culverts enabling fish passage in Maine. Source: Maine DOT. Used with permission. Figure 4-8. Flared culvert outlet diffuser projects completed in Maine.

32 Rehabilitation of Culverts and Buried Storm Drain Pipes working with the University of Maine’s Advanced Composites Center to develop a process of three-dimensional manufacturing and installation of flared outlet diffusers. Most state DOTs consider the reduced hydraulic capacity to be a significant factor and use trenchless methods such as directional drilling, pipe bursting, pipe swallowing/pipe ramming (Figure 3-9), or other expensive replacement methods. In many of these cases, a diffuser outlet can be a cost-effective alternative to increasing hydraulic capacity. The Maine DOT provided contract requirements and project details for several sliplining projects completed in Maine. In a project completed in Skowhegan, Maine, a CMP culvert 89 ft long and 36 in. in diameter was replaced with a 28-in.-diameter HDPE pipe, according to the requirements in Section 603 of the Standard Specifications (Maine DOT, 2020), as shown in Fig- ure 4-9. A corroded CMP, which was an extension for a concrete box culvert, was replaced with a 96-in.-diameter, 42-ft-long HDPE pipe. The HDPE pipe weighed 87 lb/ft and was grouted into the existing concrete culvert, as shown in Figure 4-10. Pressure-rated polyethylene resin and 80 ksi steel reinforcement provide strength and durability to the HDPE pipe with a smooth inner wall. 4.3 Oregon DOT Rehabilitation Practices and Culvert Rehabilitation Guidance The Oregon Standard Specifications for Construction (Oregon DOT, 2021) has chapters includ- ing special provisions for pipe bursting and sliplining, CIPP lining, spray-applied pipe structural lining, and video inspection of pipes. Chapter 5 of Oregon’s Hydraulics Design Manual (Oregon DOT, 2014) includes culvert material selection and connection design requirements and major Source: Maine DOT. Used with permission. Dra Figure 4-9. Sample cross sections of sliplining project completed in Skowhegan, Maine.

Case Examples 33   factors affecting the service life. Connection design options and issues related to service life and durability are not typically covered or considered in best practices or specification documents of other state DOTs. Although 13 state DOTs indicated that they consider life-cycle costs (Figure 3-2), they did not provide references for implementation. The Oregon DOT (2014) assigns a design life for new culverts of between 15 and 75 years, depending on the geometry, location, materials, and type of facility or structure. Culverts with spans of less than 72 in. are required to have 75 years of service life when they are installed under freeways. The assigned expected service life of concrete pipes is ≥75 years, and that of corrugated polypropylene pipe is 75 years if water and soil pH is between 4.5 and 10.0 and soil resistivity is more than 1,500 ohm-cm. Similar to the other interviewed state DOTs, installation of thermoplastic pipes is relatively recent in Oregon. Fire has been a concern for plastic pipes or any other flammable materials. While thin-walled pipes are easier to transport, there may be serviceability issues. Thicker-walled pipes (e.g., HDPE) have been performing well, considering that durability is a major concern for culverts. Coastal environments may include corrosive materials that affect both metal and concrete culverts. The Oregon DOT frequently rehabilitates CMP and concrete culverts. Concrete invert pave- ment, CIPP, and spray-on liners are frequently used. The Oregon DOT has an established design procedure that uses rebar-reinforced concrete for invert pavement of CMP culvert. As shown in Source: Maine DOT. Used with permission. Figure 4-10. Replacement of a deteriorated CMP with a 42-ft-long HDPE pipe in Warren, Maine.

34 Rehabilitation of Culverts and Buried Storm Drain Pipes Figure 4-11, the 346-ft-long, 8-ft-diameter deteriorated culvert under Van Dine Creek in Oregon was rehabilitated with reinforced pavement and spray-on geopolymer mortar, and a fish passage design was implemented. The 146-ft-long, 14-ft-diameter culvert shown in Figure 4-12 is located on Oak Point Creek in Oregon. In the rehabilitation design of this deteriorated CMP, fish pas- sage rocks were anchored to the reinforced invert pavement. Figure 4-13 shows the reinforced invert pavement of a 350-ft-long, 6-ft-diameter CMP culvert on Senecal Creek in Oregon. This rehabilitation project includes three unique aspects: 1. Due to the extent of corrosion and deterioration, the concrete paving or lining was extended well above the water line or mid-height of the culvert; 2. In addition to the welded steel wire mesh, three longitudinal deformed bars were welded to shear studs that were welded on each ridge of the corrugations on each side of the CMP; and 3. Concrete was placed with equipment used for spray-applied structural liners. As discussed in Section 2.3, shotcrete, cementitious grouting, spray-applied lining, and invert paving methods can be similar, depending on the cementitious or concrete materials used and the application process and equipment. Source: Oregon DOT. Used with permission. Figure 4-11. Invert pavement with reinforcement and design for fish passage.

Case Examples 35   Source: Oregon DOT. Used with permission. Figure 4-12. Fish passage design and reinforced invert pavement in a deteriorated CMP. For spray-applied structural liner, the Oregon DOT (2021) specifies a cementitious or geo- polymer mortar material that meets the minimum physical property requirements. The mini- mum liner thickness, independent of design for all structural applications, is required to be 1.0 in. for all pipes of less than 48 in. diameter or equivalent and 1.5 in. for all pipes of greater than 48 in. diameter or equivalent. Figure 4-14 shows an example of CIPP application for the rehabilitation of an arch CMP culvert in Oregon. CIPP is frequently used by the Oregon DOT (Figure 3-6). 4.4 Wisconsin DOT Rehabilitation Practices and Culvert Rehabilitation Guidance A majority of significant culvert rehabilitation projects in Wisconsin are slipliners, according to a standardized special provision. The biggest issue observed with these installations is during grouting. Excessive pressure applied during grouting has caused floating, joint separation, and deformation in some cases. Because of this, about 3 years ago, the Wisconsin DOT revised the standardized special provision to change the grout mix to a leaner, more fluid mix, and the agency is currently requiring a grouting and bracing plan from the contractor. Since then, the Wisconsin DOT has still encountered challenges. Ready-mix plants prefer to supply much stiffer mixes, and getting a complete grouting and bracing plan from contractors has been a challenge in some cases. Wisconsin DOT engineers still feel this is necessary for many reasons, such as aquatic organism passage and floodplain hydraulics. It is essential that these liners be installed as intended. The Wisconsin DOT provides guidance on culvert rehabilitation and trenchless construc- tion in its facilities manual (Wisconsin DOT, 2018) and provides examples (see Figure 4-14). One unique aspect of best practices at the Wisconsin DOT is effective sliplining of elliptical or arch-shaped culverts, as shown in Figure 4-15. For unique liner projects, the Wisconsin DOT tends to use a smoothed-lined, polywrapped CMP pipe, as these can be pressed into arched

36 Rehabilitation of Culverts and Buried Storm Drain Pipes Source: Oregon DOT. Used with permission. Figure 4-13. Reinforced invert pavement of deteriorated CMP. shapes. Because of hydraulics, round liners are discouraged in elliptical or arched host pipes. The specification is written specifically for each individual project as a special provision, as they are often unique, but a template is provided for the designer to complete. The Wisconsin DOT has largely had success with these products, but a recent issue with flotation and damage by a contractor on one installation was a reminder that preparing and following the installation and grouting plan is critical for larger and more complicated installations. The Wisconsin DOT also tries to develop a standard method to create inlet bevels on these liners to improve hydraulics. The best approach appears to be installation of a headwall if one was not previously in place. On large steel plate culverts installed without a headwall, this also helps to reduce the likelihood of the end of the pipe becoming buoyant and bending during a flood event. Often these steel plate structures are installed with mitered ends, and they can lift in some cases. CIPP is used less commonly but has been becoming more popular. The Wisconsin DOT has been developing a standardized special provision for CIPP based on best practices from other state DOTs and the industry. There is an ASTM design process for sizing these liners (ASTM F1216, 2016), but the Wisconsin DOT still encourages designers to do some preliminary sizing to determine hydraulic impacts.

Source: Oregon DOT. Used with permission. Figure 4-14. Rehabilitation of an arch culvert by using CIPP. Source: Wisconsin DOT, 2018. Figure 4-15. Rehabilitation of circular CMP using plastic sliplining (left) and arch CMP sliplined with smooth polymer-coated CMP (right).

38 Rehabilitation of Culverts and Buried Storm Drain Pipes Spray lining is not encouraged and is restricted by the Wisconsin DOT to a diameter of 48 in. or less. The main concern is that manufacturers have been apprehensive about sharing propri- etary design methodologies for these materials, and there is a lack of national standards. As design methodologies become more standardized, the Wisconsin DOT is considering easing its restric- tions, but the preference would still be for larger pipes, so that a finite element analysis could be performed. Two unique projects that have been done in the last few years are included here. 4.4.1 Tunnel Liner on State Highway 53 The feasibility of rehabilitation was analyzed for a 6- by 6-ft box culvert on State Highway 53 in Trempealeau County, Wisconsin. Replacement would have involved open cutting very large embankments (in one case, close to more than 60 feet). This was in the coulee region near the Mississippi River, and it was thought that stabilization of the site would be difficult and that ongoing maintenance efforts would be necessary. After the hydraulics were evaluated, the boxes were found to be oversized and, due to the steep terrain, any impacts to the headwaters were minimal and limited to the immediate area of the culvert. These were not active waterways, but there were flash events because of the steep terrain. Ultimately, a tunnel-lining product was specified, as the culvert handled the deep fills and allowed for assembly within the pipe to serve as shoring during construction. Prior to the liner installation, the floor of the culvert was repaired to allow for better installation of the liner and to ensure the soil–structure interface was established (Figure 4-16). An energy dissipater was also installed to reduce exit velocity, so as to address erosion issues at the outlet. The Wisconsin DOT estimated that this approach Source: Wisconsin DOT. Used with permission. Figure 4-16. Rehabilitation of a deficient concrete box culvert by using tunnel liner plates.

Case Examples 39   saved approximately $300,000 to $500,000 and unknown future maintenance costs. Use of this approach also significantly reduced the Wisconsin DOT’s environmental risk at this site from both construction erosion and other unforeseen site conditions, such as hazardous materials. Construction went smoothly, and the contractor’s only comment was that it wished it had ordered longer tunnel plate sections to speed assembly. This approach was effective; however, it is limited to few sites because of hydraulic constraints. 4.4.2 Smooth Lined CMP Liners on State Highway 54 Two large steel plate vertical ellipse culverts (84 in. equivalent and 92 in. equivalent) required replacement. There were perforations along the invert and at the flowline (Figure 4-17). These were deep structures, and removing and replacing them would have required open cutting of the roadway, which would have caused severe disruption to traffic, as the road would have had to be closed and a detour would be extensive. The culverts were lined with smooth polymer-coated CMP pipes that were slightly ellipsed to fit the host pipes. This provided a structural rehabilita- tion that met the hydraulic needs of the site. The project received a state design award for this Source: Wisconsin DOT. Used with permission. Figure 4-17. Sliplining of CMP culverts with polycoated CMP pipes.

40 Rehabilitation of Culverts and Buried Storm Drain Pipes and other noteworthy design elements. Also, on this project, the invert of a 72-in. cattle pass structure was paved, as shown in Figure 4-17. The Wisconsin DOT also has a detailed inventory and maintenance program called the Culvert Asset Management Program (CAMP). After reviewing more than 50,000 culvert pipes through CAMP, the Wisconsin DOT found 3.55% of the existing culverts had pipe liners and another 1.05% were recommended to be lined as a maintenance action. Table 4-1 shows the current data on culvert lining projects in Wisconsin. As part of the CAMP process, the following maintenance actions can be selected as part of the culvert inspection: brushing, clean end treatment, clean pipe, ditching, extend pipe, increase inspection frequency, line pipe, and other. Rehabilitation actions may include remove pipe, repair embankment washout, repair endwall, repair extension, repair inlet ring, repair joint separation, repair pipe connection, repair scour, replace casting, replace endwall, replace pipe, retie endwall, and tuck-point inlet. Source: Wisconsin DOT. Used with permission. Note: Detail may not add to total because of rounding. Pipes That Are Lined Region Corrugated Steel/Aluminum Reinforced Concrete Corrugated Polyethylene Total NC NE NW SE SW 219 102 498 67 390 Total 1,276 57 22 87 34 101 301 16 2 4 182 43 247 0.48%0.59%2.49% 292 126 589 283 534 1,824 3.55% Table 4-1. Details of lined culverts in the Wisconsin DOT’s current inventory.