CLEANING AND LINING WATER MAIN
PETERBOROUGH, NEW HAMPSHIRE

In the summer of 2008, as one of three large water improvement projects in the Town of Peterborough, NH, Dufresne Group (DG) provided the design and construction oversight for the cleaning and lining of over 5,000 lf of existing 10-inch and 12-inch unlined cast iron water main and the installation of 1,000 linear feet of new 12-inch ductile iron water main.

The 12 inch cast iron main is used to feed one of three water storage tanks in the Town of Peterborough. Coordination with the Town Water Department and other contractors was key to using alternative water mains to fill the water tank while the feed line was shut down for the cleaning and lining process.

At the intersection where the water tank water main interconnects with the high pressure water zone there were 9 valves within a 25 foot radius with no documentation of what the valves were connected to. By the end of the project 7 valves were removed, and piping was re-configured. The intersection now has 8 valves total which are clearly documented and easy to locate. This portion of the project was very important because for years the Peterborough Water Department has struggled to get efficient shut-downs from this intersection during emergency situations.

Key Project Features:

• Coordination with other contractors to install a Pressure Reducing Valve (PRV) vault to allow the alternative water mains to fill the water tank.
• Of the 4,500 linear feet of feedline to the tank, the last 1,000 linear feet of main was completely replaced by new 12-inch ductile iron pipe. The installation of this pipe also required coordination with the installation of the PRV vault (separate DG contract) on Route 101 in Peterborough.

Existing unlined cast iron water main with significant scale buildup.

Water flowing from water main during the cleaning process.