Rehabilitation of Culverts and Buried Storm Drain Pipes (2022)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

3   1.1 Synthesis Scope During the implementation of asset management strategies, which are usually developed in response to federal and state initiatives, state departments of transportation (DOTs) aim to pre- serve assets during their intended service life, or, whenever possible, to increase their service- ability beyond the intended service life. Transportation agencies typically manage many aging culverts and buried storm drain pipes, which can be considered critical assets in their inven- tory. Effective and low-cost rehabilitation or repair methods can increase the service life of these assets significantly if they are applied in a timely manner. Waiting and applying expen- sive treatments to rehabilitate degrading assets or replacing them may not be a cost-effective option. Many facilities may be quickly and easily rehabilitated using both short-term and long-term rehabilitation or repair methods. This synthesis report summarizes the established and emerging rehabilitation and repair methods used by the state DOTs. The final report for NCHRP Project 14-26, “Culvert and Storm Drain System Inspection Manual” (Beaver and Richie, 2016), presents a detailed methodology to assess the condition of in-service culvert and storm drain systems to ensure system safety, functional performance, and the economical use of state DOT resources. The manual also provides a condition rating system and assessment criteria. Condition assessment criteria and implementation of methodologies in the NCHRP 14-26 report identify asset deficiencies and provide guidance to help state DOTs prioritize their maintenance needs. Many state DOTs develop their own criteria and rating systems. After the state DOTs identify degrading culverts and pipes on the basis of their criteria, they need to determine which rehabilitation method is economical and at the same time most effective to restore the function or extend the service life of the deficient assets. This report investigates the factors affecting the selection of repair and rehabilitation methods and identification of appropriate culvert rehabilitation methodologies on the basis of the level, type, and extent of deterioration and identified parameters. Within the context of the synthe- sis, factors affecting the selection and implementation of current and emerging rehabilitation methodologies are investigated for culverts and buried storm pipes. Challenges of monitoring (not doing anything), repair, rehabilitation, or replacement include, but are not limited to, (1) the type and level of deficiency observed in the culvert, including corrosion, cracking or spalling of concrete, and permanent deflections; (2) the likelihood for progression of observed deficiencies and potential consequences (e.g., collapse due to not being able to repair or rehabilitate) if no action is taken immediately or the observed deterioration or damage is not fixed within a certain time period; (3) financial constraints; and (4) the effectiveness of available rehabilitation methods. In this project, information was gathered through literature review, a survey of state DOT agencies, and follow-up interviews with four selected agencies for the development of case examples. This synthesis report identifies gaps in knowledge and the research that could address C H A P T E R 1 Introduction

4 Rehabilitation of Culverts and Buried Storm Drain Pipes those gaps. This synthesis work investigates the currently available and emerging repair and rehabilitation strategies and related factors. The study also investigates the methods for restoring the structural load-carrying capacity of the culvert system, considering both the structure and the surrounding soil. This synthesis shows whether and how frequently the repair and rehabilita- tion methods are used by the state DOTs, and best practices and limitations are also discussed. Information gathered in the report includes the following: • Impact of culvert material, size, condition, and other factors affecting the selection and imple- mentation of rehabilitation methodologies. • Current and emerging rehabilitation methodologies for culverts and buried storm drain pipes: – Factors affecting the selection criteria for the rehabilitation method, including environ- mental factors, materials, site geometry, impacts on the traveling public, current culvert condition, hydraulics, fish passage, and life-cycle costs; – Consideration of existing structural capacity of host pipe; – Suitability of rehabilitation methodologies for in-house maintenance installation; and – Quality assurance and quality control process of the installation. • Current and emerging methods for restoring the structural and hydraulic capacity of the soil– pipe system, including chemical or cementitious grouting, invert concrete paving, sliplining, and spray-applied structural lining. • Expected service life and long-term monitoring. The methodology used to collect the information includes (1) a literature review, (2) a web- based questionnaire to acquire information from state DOTs and document the state of culvert rehabilitation practices, and (3) case examples developed in collaboration with four state DOTs. 1.2 Synthesis Objectives The objective of this synthesis was to collect and summarize rehabilitation practices (including full and partial rehabilitation) used by the state DOTs for culverts and buried storm drain pipes. Results of the literature review, responses of the state DOTs to the survey, and case examples were used to achieve the following objectives: • Identification of factors affecting the decision in the selection of repair and rehabilitation methods, including both culvert materials and repair/rehabilitation materials, hydraulics, impact on the traveling public, aquatic organism or fish passage, cost, and expected service life; • Investigation of new or emerging culvert repair and rehabilitation methodologies (e.g., usage of FRPs for structural rehabilitation), designs to increase hydraulic capacity (e.g., usage of flared outlet diffuser), sliplining of arch or elliptical shaped culverts, and various designs to enable fish passage; • Investigation of factors influencing the implementation of repair and rehabilitation, including whether the structural capacity of the host culvert is considered, and ability to perform in-house rehabilitation; and • Investigation of whether and how frequently the currently available methods are used by dif- ferent state DOTs, identification of selected methods that are successfully and frequently used by some state DOTs, and identification of issues regarding installation and design for which guidance is needed. 1.3 Terminology Since culvert rehabilitation methods are associated with a variety of names, the following common terms and definitions are used in conjunction with the questionnaire and throughout the synthesis report.

Introduction 5   • Culvert: A culvert is a structure that is typically fully enclosed by soil or embankment. Some culverts are supported on spread footings, with the streambed serving as the bottom of the culvert. In this report, when pipes are mentioned, culverts are included. • Storm drain pipe: Tube or conduit structure used to convey runoff from a storm event. A pipe can be made from steel, concrete, polyethylene, or other materials. • Replacement: Removal or abandonment of the existing culvert and replacing it with a new culvert pipe. This can be done by either open-cut or trenchless construction methods. • Rehabilitation: The existing culvert or pipe is upgraded and returned to a condition similar to its original condition or better (e.g., sliplining or invert paving). • Repair: A corrective or maintenance procedure that keeps the existing culvert in a uniformly good and safe condition (e.g., joint repair). 1.4 Report Organization Chapter 2 documents the findings from the literature review. Current best practices reported in the literature and available culvert rehabilitation specifications, provisions, and guidelines developed by different state DOTs and other agencies or researchers are provided. Chapter 3 presents the results of the survey of state DOT practices. The results are organized into topic areas, including culvert types and materials used by DOTs; factors affecting the selection of rehabilitation methodology; rehabilitation methodologies used; consideration of existing hydraulic and structural capacity of the host pipe or culvert; in-house maintenance potential and implications; and quality assurance and quality control. Main results and critical points are presented in Chapter 3. The questionnaire and results are included in Appendices A and B, respectively. Case examples and interviews with representatives of the four selected state DOTs are pre- sented in Chapter 4. This chapter also documents how the selected state DOTs manage mainte- nance, repair, and rehabilitation issues and presents unique rehabilitation examples. The synthesis concludes with a summary of the overall findings and possible future research to advance the state of the practice. The summary of findings included in Chapter 5 is based on the results of the questionnaire and on case examples and associated interviews.