Small-Water-InversionA successful rehabilitation installation involves, quite simply, preparing and implementing a plan. Although easy to say, it’s not quite that simple when dealing with all the moving parts of an actual project. As a result, NASSCO has developed some tips for completing a quality rehabilitation project.

Although these tips focus on cured-in-place pipe (CIPP), many of these principles can be applied to other rehabilitation products. Depending on the nature of the contract, some of the following items can be performed by the owner, some by the engineer and some by the contractor.

1. Determine the rehabilitation requirements. The purpose can be structural rehabilitation, reducing infiltration, addressing corrosion in concrete sewers or a combination of requirements.

2. Select the correct technology. Based on the project requirements and expected results, select the correct technology. This may involve some research of product technical information. The product design, application, location and access should also be considered when selecting a technology.

3. Prepare the design to meet rehabilitation requirements. For CIPP, design often means calculating the minimum wall thickness required based on the physical properties of the technology selected, the design parameters and the purpose of the project. Design also includes selecting the proper materials for the project and the appropriate installation approach. For example, a 72-in. pipeline rehabilitation project may require that the wet-out and installation be performed at the field installation location. The engineer may designate a specific location for access. Because of the distance between manholes, an on-site wet out may need to be accommodated in the design.

4. Prepare detailed technical specifications. The technical specifications of the contract documents are the instructions for the contractor to furnish a specified product or completed project that meets the contract requirements. The technical specifications also instruct the inspector as to what needs to be observed, inspected, measured, tested and documented to ensure that the product meets the contract requirements.

Performance specifications where the contractor defines the means and methods for installation of the work are preferred. Performance specifications allow the contractor to use innovative means which are at his or her disposal to deliver the specified product at a defined level of quality, at the lowest cost for the owner. A well written specification defines:

a. Existing conditions
b. The selected rehabilitation product
c. Work required by the contractor and the inspector
d. Submittal requirements
e. The product quality level required
f. Required quality controls, including specific ASTM requirements
g. Required quality assurance practices during construction
h. The required measurements through inspection and testing
i. The warranty inspection procedure

An example Performance Specification Guideline, for CIPP, is available from NASSCO at nassco.org under “Publications & Specifications.”

5. Bid and award the project to the best qualified and most responsible bidder with the lowest competitive price. In some cases contractor pre-qualifications are required to bid the work.

6. Performance Work Statement (PWS). As a part of the submittal process, the contractor prepares a detailed PWS outlining the installation plan including the proposed means and methods to be employed, by the contractor, to complete the project. The PWS provides information that the inspector can reference throughout the project. Examples of what may be included in the PWS include:

a. Statement of product conformance to the contract documents
b. Installation to manufacturer’s recommended standards
c. Detailed installation plan
d. Statement of contractor experience and description of lead personnel
e. CIPP wall thickness design
f. Manufacturers’ technical data
g. Listing of redundant tools and equipment
h. Proposed public notification program
i. Safety plan
j. Quality plan
k. Odor control plan
l. Recommended CIPP repair and replacement procedures, if required
m. Others

7. Inspection. Have a technology-trained inspector onsite to observe, measure, inspect, document and test the materials provided and confirm the quality of the delivered product. This includes all measureable requirements described in the contract documents. The inspector also ensures that the contractor’s submitted means and methods are implemented.

8. Develop a warranty inspection checklist. The inspector prepares a warranty checklist typically consisting of 10 to 15 percent of the installed product. The checklist represents work quality issues observed and documented during installation.

9. Perform warranty inspections. Pipelines on the checklist should be re-inspected at least one month before the end of the warranty period. The inspection should be by the owner or a third-party contractor. If deficiencies are found, the amount of sewers to be re-inspected can be increased, if necessary. Extended warranties may be applied for portions of the project that have not met the requirements of the contract, are defective or have been repaired.

10. Make repairs if applicable. Any necessary repairs are made in accordance with the CIPP repair or replacement procedures submitted with the PWS.

A key element of a successful project is to achieve a quality installed product. To help ensure this, have a trained, knowledgeable inspector on the jobsite. In order to define the inspector’s role and authority, quality controls and assurances must be outlined in the contract documents and all submittals, specification requirements and referenced standards are available to the inspector. The following are suggested quality checks before, during and after installation.

1. Inspections and quality checks before and during installation:


a. Materials, including the tube and resin, as specified. Manufacturers’ technical information and testing data, including shipping, storage and handling recommendations, are reviewed. Safety Data Sheets (SDS) are received and reviewed.

b. Amount of resin required for tube wet out as supplied by the tube manufacturer. Resin quantity, per unit length for each size tube on the project, is determined through information supplied by the manufacturer. Each wet out tube is checked for the proper amount of resin by reviewing the tube wet out sheet and comparing the amount of resin used to the manufacturer’s required amount.

c. Condition of host pipe just prior to installation. The host pipe is inspected, typically through CCTV using the Pipeline Assessment and Certification Program (PACP), just prior to installing the liner. The inspector should be knowledgeable on the different conditions that can occur in a sewer and should be able to determine if a sewer can be rehabilitated to specified standards, or if it must first be cleaned and/or repaired.

d. CIPP curing schedule. Since the cured resin forms the body of the CIPP, correct curing is very important. The cure schedule is based on the manufacturer’s requirements and contractor performance for different field conditions. Cure is monitored and compared to the submitted manufacturer’s recommended schedule.

e. Workmanship of lateral connections. The inspector verifies that the contractor leaves a clean, smooth opening within tolerance, meeting the contract-specified requirements.

2. Inspections and quality checks after CIPP installation:


a. Visual inspection. Inspection of the final product, typically by CCTV, verifies a defect-free and functionally operating system. The CIPP should be continuous over the entire length of the installation run and free of dry spots, lifts, delamination and other defects. Any defects located are repaired in accordance with the contract documents and PWS.

b. Physical properties. The physical properties of the installed CIPP are determined through independent testing by the owner and compared to the values specified or submitted for wall thickness design. The contract documents should define a remedy if the test results are below specified requirements.

c. CIPP thickness. Wall thickness is measured and compared to the approved design for each installed CIPP. The contract documents should define a remedy to be used if the tested thicknesses are below approved thickness.

d. Chemical resistance. Resistance to corrosive agents in the waste stream is typically certified by the resin manufacturer in accordance with ASTM requirements.

e. Water tightness. Leakage is tested as specified in the contract documents. Testing options include an exfiltration test, low pressure air test and a visual inspection for infiltration.

Detailed planning by the engineer and the contractor, followed by execution of the plan, is required for a successful pipe rehabilitation installation. In order to ensure quality product installation, quality control and quality assurance, requirements should be specified in the contract documents. The contractor installs the products in accordance with the contract documents and the submitted PWS and a trained and knowledgeable inspector then observes, inspects, measures, tests and documents before and during product installation and then assures final product quality once the product is installed.
Lynn Osborn is techical director and Gerry Muenchmeyer is past technical director at NASSCO.

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