Military Base Sewer System Upgraded With HDPE Pipe

November 2009 Vol. 64 No. 11
A section of Hancor SaniTite HDPE sanitary sewer pipe, part of the new system at Ft. Lewis.

Because of the size of the pipe, precast concrete manholes that are at least 72-inches in diameter at the bottom, and tapering to 48 inches at the top were used. Some larger 84 inch manholes were used to accommodate three pipes – two coming in and one out.

After the pipe was put into place, it took about 20 days to do all the tie ins.

“We started at the high side and worked down,” Sharp explained. “We would stop one stick short of the manhole, and didn’t tie into it. Then, we’d put in the whole line, go to the very bottom and stop one stick short again, excavate for the manhole, expose it and the pipe on both sides. The existing line would then be exposed and we brought in a system of 8 inch bypass pumps with triple bypass so we would have one workhorse and two back pumps. This was just in case one couldn’t keep up or broke down. We pumped the sewage around the tie in point, capped it off, cut the pipe open and installed the manhole.

“We used a channel manhole for that because it’s open at the bottom and could be slipped over the top of the pipe,” Sharp continued. “The crew did the grouting, got it all buttoned up, brought the new line into the manhole, took the plug out and connected to the pumps. We then did the same on the opposite side, and made sure everything was tested before we did that.”

The Hancor HDPE pipe is designed specifically for sanitary sewer systems which are usually buried deeper and subjected to greater water pressure than corrugated HDPE pipe used for storm sewer installations. According to Sheehy, two types of Hancor HDPE pipe were used – SantiTite Sanitary Sewer pipe and Low Head pipe. “Both provided the necessary water tight seal between pipe sections,” he explained.

Since 1917, Ft. Lewis has been serving the country. With the projected life expectancy of HDPE pipe listed at 100 years, the property will be at least 200 years old when it next might need a new sewer system.

FOR MORE INFORMATION:
Hancor, (888) 367-7473, www.hancor.com