Warranty Inspection --
Supplement to the Pilot Project Report 

Executive Summary

Warranty Inspection Process

From 2002 to 2004, King County and local sewer agencies jointly sponsored 10 pilot projects to test methods of controlling infiltration and inflow (I/I) into sewers. These pilot projects, conducted as part of the County's Regional Infiltration and Inflow Program, included rehabilitation or replacement of public and private sewers within the service areas of the 12 local sewer agencies listed below.

The October 2004 Pilot Project Report describes how the pilot projects were conducted, including: selecting pilot project locations, rehabilitation technologies, implementing design, bidding, administration, and construction. The Pilot Project Report also provides an evaluation of the effectiveness of each pilot project and describes lessons learned.

This document supplements the Pilot Project Report and describes the results of warranty inspections conducted after the pilot projects were completed. By conducting warranty inspections, King County and the local agencies that hosted pilot projects determined whether the techniques used and products installed during the pilot projects performed according to manufacturers’ and contractors’ claims. Warranty inspection resulted in contractor repair of some defects or failures in the rehabilitation work. It also provided an opportunity to see if I/I occurred in parts of the system that were not rehabilitated, and whether water migrated along the exterior of rehabilitated pipes before entering through a defect in a section of the sewer system that was not rehabilitated.

The pilot project construction contracts included warranty periods of 12, 18, and 24 months for various types of rehabilitation techniques and products. Extended warranty periods were required because: (a) many of the techniques and products had not been used in the Pacific Northwest, and (b) it was desirable to ensure that warranty inspections were conducted during wet weather months. Those items that were repaired under the initial warranty had an extended warranty and were inspected again in the winter of 2006.

King County and local agencies worked together to identify which portions of the rehabilitated sewers would be inspected. In some cases, all installations of a product were inspected; in other cases, only a sample was inspected. In one case, the number of defects noted during the initial inspection led to inspection of the entire project. Warranty inspection was performed by King County’s consultant and a contractor equipped to inspect sewer pipes and manholes.

Defects discovered during warranty inspections were identified as either “product failure” or “product not performing as anticipated”. When product failures were observed during inspections, the County and local agency determined which failures required repair, then contacted the contractor to arrange for repair work. This report discusses how warranty repairs were made. Products that did not perform as anticipated were not repaired; these products are noted in this report.

Warranty Inspection Results

Very few warranty defects were identified during inspection. The results are summarized as follows:

• In general, sewers replaced by pipe bursting were almost defect-free. Defects were limited to connections made at welded saddles (where the lateral connects to the sewer main) or where mechanical couplings were used to connect the pipe to the manhole. These few defects could be attributed to backfill and compaction of the excavation, to a lapse in quality control by field personnel, or to the flexibility of high density polyethylene (HDPE) pipe.
• Work involving cured-in-place (CIP) products also showed few defects; however, more defects were observed than for pipe bursting. These defects could be attributed to the limited access available inside a pipe (most CIP work is done remotely using robotic equipment). Defects were noted in CIP liners of sewer mains and in the first project that used TOP HATs™, a product that seals the lateral-to-main connection.
• Only a few rehabilitated manholes had defects. Several manholes replaced during pipe bursting developed cracks in the bottom section above the connecting pipe. It is likely that this was due to settlement or compaction of the backfill around the manhole, or due to structural defects. Immediately after construction, King County crews found and repaired several CIP manhole liners that had separated from the manhole walls. During warranty inspection, these manhole CIP liners were in good condition.

The repairs made by contractors were accepted and are covered by an extended warranty. King County performed a second warranty inspection in the winter of 2006, before the extended warranties expired. The results of the second warranty inspection are also included in this report.

Table of Contents

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Warranty Inspection, issued August 2006
-- Supplement to the Pilot Project Report

Contents (19 KB)
Entire report (889 KB)

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