Rehabilitation of Culverts and Buried Storm Drain Pipes (2022)

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14 This chapter presents specific practices used by U.S. DOTs to maintain, repair, and reha- bilitate culverts and buried storm drain pipes. The agency-specific rehabilitation practices and experiences were compiled from a survey of the transportation agencies, their documented implementations, specifications, and guidance documents. 3.1 Survey Focus and Participation The synthesis survey questionnaire (see Appendix A) was received by engineers at 51 trans- portation agencies, including 50 state DOTs, and the District of Columbia. The web-based ques- tionnaire was developed by using an online survey tool in Qualtrics. Forty-two state DOTs responded to the survey, as shown in Figure 3-1. Four agencies (the Georgia, Iowa, Oklahoma, and South Carolina DOTs) reported that culverts and storm drain pipes are not rehabilitated in their respective states (i.e., their response was “No” to Question 4 in the questionnaire). As a result, analysis and discussion of the results for Questions 5 through 9 in this chapter are based on the responses received from 38 state DOTs. The goal of the questionnaire was to collect information on agency practices and experiences pertaining to the following topics: • Types of culverts or storm drain pipes that are rehabilitated by state DOTs, • Presence of a statewide rehabilitation program or established requirements, • Factors affecting the selection of rehabilitation methodology, • Repair and rehabilitation methodologies used, • Consideration of the existing structural capacity of the culvert, • In-house rehabilitation and maintenance, and • Quality assurance and quality control. For each topic area, the results of the questionnaire and practices of the state DOTs are pre- sented in this chapter. The detailed responses of all state DOTs are provided in Appendix B. 3.2 Culvert Types and Frequency of Rehabilitation Four major culvert types were investigated (see Question 2): corrugated metal, precast concrete three-sided or box, precast concrete pipe or arch, and thermoplastic pipe culverts. The responses of the 42 state DOTs about rehabilitation of these four general types of culverts and other culverts are summarized in Figures B-1 through B-4. Half of the 42 state DOTs that responded to the survey indicated that they frequently reha- bilitate corrugated metal culverts (Figure B-1). Figure B-1 shows that five state DOTs do not C H A P T E R 3 State of the Practice

State of the Practice 15   rehabilitate them. Of the 42 responding state DOTs, 30 (71%) reported that they rehabilitate precast concrete three-sided or box culverts infrequently, while seven state DOTs reported that they rehabilitate them frequently (Figure B-2). Responses were similar for the precast concrete pipe culverts, with two-thirds (28 of 42) of the state DOTs reporting infrequent rehabilitation of these types of culverts (Figure B-3). Eight state DOTs rehabilitate concrete pipes frequently. A majority (71%) of the transportation agencies do not use or rehabilitate thermoplastic pipes. Only one state DOT (Louisiana) frequently rehabilitates thermoplastic pipes, while nine state DOTs fix them infrequently (Figure B-4). In response to Question 2, several state DOTs reported on the status of the rehabilitation of culverts made of materials other than corrugated metal, precast concrete, or thermoplastic materials (Figure B-5). Caltrans reported rehabilitation of polyvinyl chloride pipe, the Florida DOT reported rehabilitation of clay pipe and fiber-reinforced concrete pipe (Hardy pipe), the Ohio DOT reported infrequent rehabilitation of masonry culverts, the Utah DOT reported infre- quent rehabilitation of structural steel plate culverts, and the Virginia DOT mentioned aluminum culverts. As shown in Figure 3-2, many state DOTs have statewide programs, published documents or specifications for materials, and installation requirements or practices after defects are identified in culverts. The respondents provided web links to their state DOT documents or specifications related to maintenance, rehabilitation, replacement, and life-cycle analysis. Of the 42 state DOTs responding to the survey, 25 (60%) have established culvert rehabilitation programs or require- ments, 19 (45%) have routine preventive maintenance or repair requirements or guidance, and 20 have established guidance for culvert replacement. Six of the 13 state DOTs reporting a statewide program or published document on expected service life and life-cycle costs (Florida, Figure 3-1. Response of state DOTs to the culvert rehabilitation questionnaire. Of the 42 state DOTs that responded to the survey, four answered “No” to Question 4 (i.e., no rehabilitation).

16 Rehabilitation of Culverts and Buried Storm Drain Pipes Montana, New York, Oregon, Pennsylvania, and Tennessee) provided their documents for life- cycle analysis or service life prediction, as shown in Figure 3-2. Chapter 5 of the Oregon DOT’s Hydraulics Design Manual (2014) has the most detailed information on culvert service life pre- diction. No response was received from 13 state DOTs for Question 3. In response to the general question on the average age of culverts when they are rehabilitated (Question 4), many respondents commented that this very much depends on the type of culvert and other conditions. For example, Florida reported the lowest age (10 years) and commented that salt water is a critical factor for rehabilitation criteria in the next question of the survey. The reported average culvert rehabilitation age ranged from 10 to 100 years. As shown in Figure 3-3, eight state DOTs (of the 42 responding to the survey) reported an average age of 40 years or less for rehabilitation. A few state DOTs reported a very wide range (e.g., 25 to 75 years was reported by Oregon and 40 to 80 years by Ohio). It was commented that generally the age or service life was shorter for CMP culverts than reinforced concrete culverts. Specifically, a range of 20 to 50 years was reported as the average age for CMP culverts by four state DOTs: Arkansas (more than 40 years), Connecticut (40–50 years), Delaware (30 years), and Virginia (20–25 years). On the other hand, two of the same state DOTs reported much longer service lives for reinforced concrete culverts: Delaware (80–100 years) and Virginia (50 years). 3.3 Critical Factors Affecting the Rehabilitation Method The effects of several factors on the selection of rehabilitation methods are ranked by the state DOTs that responded to Question 5. The responses are presented in Figures B-6 through B-14 in Appendix B. Four state DOTs consider environmental factors, such as temperature and Figure 3-2. Number of state DOTs with established statewide programs for maintenance, rehabilitation, replacement, and life-cycle analysis (based on answers of 42 state DOTs to Question 3). Items in key correspond top to bottom with figure bars left to right.

State of the Practice 17   humidity, to be critical factors affecting the decisions for rehabilitation and construction (Fig- ure B-6). All other responding state DOTs consider environmental factors as either insignifi- cant or important but not critical. State DOTs with a rehabilitation program overwhelmingly consider hydraulics a critical factor (33 of 38 state DOTs, or 87%), as shown in Figure B-7. Of 38 state DOTs, only five consider hydraulics to be either an important (but not critical) factor or an insignificant factor. Materials are considered insignificant, important, and critical in the selection of rehabilitation method by 1, 21, and 16 responding state DOTs (out of 38), respec- tively, as shown in Figure B-8. Site conditions are considered critical by 16 state DOTs (42%) and important but not critical by 18 state DOTs (47%) (Figure B-9). Only three state DOTs consider the effect of site condi- tions to be insignificant with regard to the selection of rehabilitation method. The majority of the state DOTs consider site access to be a critical parameter for the decision-making process for culvert rehabilitation (Figure B-10). Only two state DOTs (Delaware and Missouri) described it as an insignificant factor. Impact on the traveling public is considered a critical parameter in the selection of rehabilitation method by 28 of the 38 respondents (74%); for the remaining 10 state DOTs, this is an important parameter (Figure B-11). Therefore, along with hydraulics, impact on the users of the roadway is one of the most important factors influencing the selec- tion of a culvert rehabilitation method. Of the 38 responding state DOTs, most [22 (58%)] consider the ability to perform the rehabil- itation work in-house to be an insignificant factor in the selection of the rehabilitation method (Figure B-12); only the Nebraska DOT considers it to be a critical factor. This indicates that most state DOTs work with contractors for culvert rehabilitation, which is consistent with the lack of response to Question 8 (about the ability of the state DOT to perform in-house rehabilitation) by a relatively large number of state DOTs. Expected service life and life-cycle costs are important, but not critical, for most of the 38 state DOTs [26 (68%)], while 10 (26%) consider these to be critical factors in the selection of rehabilitation method (Figure B-13). Figure B-14 shows that 30 of the 38 state DOTs (79%) did not report any factor other than the eight listed in Question 5 that might be affecting the selection of the rehabilitation method. Figure 3-3. Average age of culverts being rehabilitated as reported by the state DOTs. Items in key correspond top to bottom with figure bars left to right.

18 Rehabilitation of Culverts and Buried Storm Drain Pipes Caltrans listed the following as potential factors: health assessment score, waterway adequacy, shape, joints, and alignment condition. The Connecticut, Florida, and Nebraska DOTs men- tioned environmental permitting, saltwater, and costs, respectively, as other critical parameters. The Texas DOT noted that sliplining may be done as a temporary fix in cases where hydraulic requirements cannot be met and that the severity of the condition and the load rating will also be drivers on deciding if rehabilitation is pursued. The Utah and Vermont DOTs both mentioned aquatic organism passage and regulatory requirements for fish passage as additional factors that may affect their decision process in the selection of rehabilitation method. 3.4 Local and Joint Repair Methods Seven different local repair, spot patch, and joint repair and sealing methods were included in the first part of Question 6. Similarly, four concrete invert paving methods and eight general rehabilitation methods were listed in the second and third parts of Questions 6. The responding state DOTs indicated whether and how often they used these methods to restore the structural capacity of the culvert or storm drain pipe. As an example, Figure 3-4 shows the response rates for the first repair method, local injection of epoxy adhesive or flexible crack fillers in concrete walls. Figures B-15 through B-21 in Appendix B show detailed responses for all local and joint repair methods. As shown in Figure 3-4, 42% of the state DOTs with a rehabilitation program (16 of 38) rarely or sometimes use concrete crack fillers or local injection methods, which are briefly described in Section 2.3. Only the Florida and Louisiana DOTs use them frequently. Metal culverts are rarely or never coated or painted (Figure B-15). Only 8% of the responding DOTs—three states (Maryland, Washington, and West Virginia)—sometimes apply them. Of the 38 responding state DOTs, 18 (47%) reported using nonstructural chemical grouting, including gels and poly- urethane foams (as described in Section 2.3), only rarely, and 10 (26%) said they never used them; only the Florida DOT reported frequent use of this method (Figure B-16). In comparison, Figure 3-4. Reported usage and frequency of local injection methods by state DOTs responding to Question 6. Items in key correspond top to bottom with figure bars left to right.

State of the Practice 19   internal joint sealing systems (e.g., rubber membrane seals or backing plate, as discussed in Sec- tion 2.3) are used more often: 10 of the 38 responding state DOTs (26%) reported sometimes using this method and 11 (29%) said they never use it (Figure B-17). The cementitious grouting method is used more frequently than the other local repair or joint sealing methods included in the survey. All 38 responding state DOTs use cementitious grout- ing; five (13%) use it frequently and 15 (39%) use it sometimes, as shown in Figure B-18. The Kansas and New Jersey DOTs frequently combine structural repair methods by using cementi- tious, mortar, or epoxy materials and nonstructural repair materials, including chemical grout- ing or foam (Figure B-19). This combination approach is used sometimes by 11 state DOTs (29%) and rarely by 13 state DOTs (34%). Internal joint sealing with steel sleeves or bands combined with grout (Figure 2-2) is used frequently by the Virginia DOT, but 13 state DOTs (34%) never use it, as shown in Figure B-20. This viable method is infrequently used. Figure B-21 shows that only four state DOTs reported usage of any local repair or joint sealing method other than those listed in Question 6. The North Dakota DOT mentioned a private vendor (Sprayroq) for structural repair. 3.5 Invert Paving and Invert Lining Rehabilitation Methods Of the invert paving or invert lining methods described in Section 2.3, the most common method reported being used was concrete invert installed in CMP culverts (Figure 2-3). Steel armor plate invert in CMP (Figure 2-4) was the least-common method reported. Four different invert paving or lining methods were listed in Question 6. Figure B-22 shows that the New Jersey, Oregon, and Pennsylvania DOTs regularly use concrete invert pavement in concrete culverts, while 39% (15 of 38 state DOTs with rehabilitation programs) never use this method. As shown in Figure 3-5, CMP culverts are rehabilitated with concrete invert paving or lining by more than 90% of the responding state DOTs. Seven of 38 state DOTs (18%) frequently use it. The Texas and Wyoming DOTs never use concrete invert paving inside CMP culverts. Figure 3-5. Frequency of installation of concrete paving or lining in the invert of CMPs and culverts. Items in key correspond top to bottom with figure bars left to right.

20 Rehabilitation of Culverts and Buried Storm Drain Pipes Installation of steel armor plate inverts inside CMP culverts is not a common method. As shown in Figure B-23, half of the responding state DOTs never use this rehabilitation method. None of the respondents use it frequently. Only five state DOTs (13%) sometimes use it, and 12 (32%) rarely use it. FRP materials have been gaining popularity in recent years, especially to seal culvert walls to improve durability and prevent corrosion-related deterioration. Of the 38 state DOTs, 14 (37%) have never used FRP lining inside a precast concrete or CMP culvert, as shown in Figure B-24. Most of the responding state DOTs reported using it sometimes or rarely. The Kentucky Transportation Cabinet uses it frequently. Figure B-25 shows that only the Missouri and North Dakota DOTs reported using other invert lining or paving methods. The Missouri DOT reported rare use of concrete blanket. 3.6 System-Level Rehabilitation Methods Eight different general rehabilitation methods were included in Question 6. The results are presented in Figures 3-6 through 3-9 and Figures B-26 through B-30. Figure B-26 shows that sandblasting and recoating or painting is not a common method to remove corrosion or coat- ing damage and then improve the wall coating: 27 of the 38 responding state DOTs (71%) never use this method. Only the Ohio DOT uses it sometimes, and none of the state DOTs uses it frequently. This is comparable to the response shown in Figure B-15 for the coating or painting of metal culverts used for routine maintenance or local repair. CIPP is a relatively common method that involves installation by feeding a thermosetting resin–soaked sleeve through the host pipe and then expanding and heating to cure the resin, as described in Section 2.3. Figure 3-6 shows that of the 38 responding state DOTs, 8 (21%) fre- quently use the CIPP method and 14 (37%) sometimes use it. On the other end of the spectrum, nine state DOTs (24%) never use it. Centrifugally cast and spray-on liners and spray-on treatments, which involve pressurized spraying onto the culvert wall surface, are frequently used by four state DOTs (Colorado, Figure 3-6. Responses of state DOTs showing how often they use the CIPP method. Items in key correspond top to bottom with figure bars left to right.

State of the Practice 21   New Hampshire, Oregon, and Virginia). Eight of the 38 responding state DOTs (21%) some- times use spray-on liners, as shown in Figure B-27. Ten state DOTs (26%) never use this method. A majority of the 38 responding state DOTs [22 (59%)] report that they rarely use shotcreting or sprayed mortar as a structural rehabilitation method (Figure B-28). Six state DOTs use it more regularly: the Colorado, New Hampshire, and Virginia DOTs frequently use it, and the New York, Oregon, and Pennsylvania DOTs sometimes use it, as shown in Figure B-28. Seven of the respond- ing state DOTs (19%) never use it. One converging result of the survey is that all of the 38 state DOTs implementing culvert reha- bilitation programs use sliplining and other trenchless techniques to install a new internal pipe inside the existing culvert (Figure 3-7); 15 (39%) reported frequent use of sliplining methods. Figure B-29 shows that most of the state DOTs use methods to stabilize the surrounding backfill soil to fill in voids outside the envelope, mostly through a pressure-grouting operation or controlled injection. Only the Florida DOT frequently uses soil stabilization methods, and four state DOTs never use it. As shown in Figure 3-8, except for two state DOTs (Delaware and Nebraska), all responding state DOTs apply some kind of end treatment by rehabilitating or adding endwalls or wingwalls, or installing slope protection elements at culvert ends; of the 38 state DOTs, 15 (39%) frequently implement end treatment methods (Figure 2-5). Consider- ing that more state DOTs use end treatment methods sometimes, a best practices or guidance document could help state DOTs in their end treatment applications. As shown in Figure 3-9, most state DOTs use trenchless methods (e.g., pipe jacking, which may be accompanied by a boring operation) to replace existing pipes and culverts, although not frequently; two state DOTs, Montana and Nebraska, are the exception. Question 6 listed microtunneling, horizontal directional drilling, pipe swallowing, pipe crushing, pipe ramming, and pipe bursting as potential trenchless replacement methods. Five state DOTs never use these trenchless replacement applications. Figure B-30 indicates that, other than a few state DOTs, eight general rehabilitation methods listed in Question 6 are identified or applied by the state DOTs responding to the survey. Figure 3-7. Responses of state DOTs showing how often they use sliplining and other trenchless techniques. Items in key correspond top to bottom with figure bars left to right.

22 Rehabilitation of Culverts and Buried Storm Drain Pipes Figure 3-9. How frequently culverts are replaced by trenchless installation. 3.7 Structural Capacity, In-house Rehabilitation, and Quality Assurance Half of the state DOTs responding to the survey indicated that they would not include the structural capacity of the host pipe when the culvert is rehabilitated (Figure 3-10). Several state DOTs provided brief explanation of why they consider the existing structural capacity or not. For example, the Oregon DOT stated that for invert paving and repairs, the existing capacity of the Figure 3-8. Frequency of implementation of end treatment by state DOTs. Items in key correspond top to bottom with figure bars left to right.

State of the Practice 23   host pipe is included; however, for CIPP and spray-applied pipe lining rehabilitation projects, the Oregon DOT assumes and uses full deterioration of the host pipe. The Texas DOT commented that inclusion of the structural capacity of the host pipe depends on the specifics of the culvert. According to the Wisconsin DOT, for CIPP liners, the ASTM F1216 (2016) design method is used, assuming full deterioration unless the liner is being installed at the first signs of corrosion or installed just for joint separation on RCP (Wisconsin DOT, 2018). Similarly, the Michigan DOT refers to ASTM F1216 to determine the additional struc- tural capacity provided by liners. State DOT responses to the survey suggest that the consider- ation of host pipe capacity in rehabilitation applications highly depends on the level of actual deterioration observed. Half of the state DOTs reported that they do not consider the existing structural capacity. Figure 3-11 summarizes the responses of state DOTs regarding the question of factors affect ing the decision to perform in-house rehabilitation. Half of the responding state DOTs (or 19 out of 38) indicated that their in-house rehabilitation depends on the availability of inter- nal expertise and experience (Figure 3-11). Similarly, availability of equipment and in-house versus contractor costs are listed as critical factors by 15 (39%) and 16 (42%), respectively, of the 38 responding state DOTs. Four state DOTs (11%) listed laws and regulations as critical factors. Few state DOTs (e.g., Colorado and Michigan) stated that their maintenance forces can do some of the routine maintenance and basic culvert pipe repairs. The Oregon DOT mentioned that its in-house work is limited to sliplining and invert paving and repairs. Lack of full-time positions for crews was mentioned as a limitation for in-house implementation of repair and maintenance. The Wisconsin DOT reported that the design is done in-house or by consultants and that installation is primarily by contractor for bid-let projects or individually contracted maintenance projects. In-house maintenance at the Wisconsin DOT is handled by contracts with county highway departments. The Wisconsin DOT mentioned that not much in-house work is done besides limited sliplining, some invert paving, and patching. Figure 3-10. Consideration of existing structural capacity of host pipe in rehabilitation by the state DOTs responding to Question 7. Items in key correspond top to bottom with figure bars left to right.

24 Rehabilitation of Culverts and Buried Storm Drain Pipes Two-thirds of the state DOTs have requirements for quality assurance and quality control of the rehabilitation and installation (Figure 3-12). In addition to standard specifications, the Florida DOT has additional video inspection requirements. The Texas DOT stated that controls are implemented on contracted work through construction inspection. The Wisconsin DOT has contractual requirements for materials, installation, and testing (e.g., liner specifications require a contractor quality assurance and quality control plan for grouting). Most other rehabilitation projects, such as CIPP, are handled by special provisions. Figure 3-11. Factors affecting the decision to perform in-house rehabilitation (in response to Question 8). Items in key correspond top to bottom with figure bars left to right. Figure 3-12. Presence of requirements for quality assurance and quality control of rehabilitation or installation in state DOT documents (Question 9). Items in key correspond top to bottom with figure bars left to right.