In 2006 Killington Resort began to have leakage problems with a steel wastewater effluent transfer line, which had been installed in 1997. This transfer line moved treated wastewater from a treatment facility at the base of Killington Resort; over a mountain range to the base of Pico Resort; to finally discharge into a municipal system for final disposal. Over the next few years the frequency of these leakage problems increased, and Killington Resort owners made a decision to replace the entire welded steel line.
Find a piping system that: would satisfy the high pressures required; and if possible, would improve the longevity of the system, to reduce costly system installation at road crossings and alpine stream crossings. In addition to these crossings, sections of the pipe line passed through areas of constraint through the base area, and more than 75% of the line had to be installed in extremely rocky terrain.
Working with the Design Engineer, Marsh Engineering Services; Killington Resort selected the High Pressure MDRA Ductile Iron (DI) pipe system for several reasons:
- Longevity of this DI pipe was +3 times longer than steel pipe.
- MDRA lining contained alumina cement, which withstands highly toxic operating conditions, prevalent in wastewater applications.
- For the pipe size required, the lock restraint joint design of this High Pressure DI pipe system could operate continuously at pressures up to 100 bar (1450 psig).
- For the pipe size required, the lock restraint joint design did not require thrust blocks.
- The DUPLEX external coating, containing a zinc undercoat and a Polyurethane exterior coat, provides unique sacrificial repair for any surface damage which exposes bare metal. This repair characteristic was very important, to deal with the rocky terrain along ±75% of the entire pipeline.
- Simplicity of the lock restraint joint design made it easier and faster to install this pipe.
Tight constraints were encountered along sections of the entire pipeline, but especially in the area adjacent to the pump station and treatment facility, where subterranean utility and power systems existed. The road crossing had to occur at a specific location; and the stream crossing had to occur at a specific location. The specific locations of both crossings created unusual constraints along the pipeline, on either side of each crossing. Because of the rocky terrain along ±75% of the entire line, it was necessary for the new DI pipe to be installed in existing shallow burial trenching.
This project required more time than a normal installation for DN200 pipe, because it was necessary to remove existing welded steel piping before the new DI pipe could be installed. The rapid installation of the DI system was a key to being able to complete this project in a single phase.
Project Team Members:
CLIENT: Killington Resort
DESIGN ENGINEER: Marsh Engineering Services
DIP DESIGN/SALES/FIELD SERVICS: PNP Supply LLC
GENERAL CONTRACTOR: G.W. Tatro Construction, Inc