Sewer system backup has backup

Post date: May 02, 2009 6:21:30 PM

By HARRY G. PERKINS , Hub Regional Correspondent, May 2nd, 2009 Kearney HUB on line at: http://www.kearneyhub.com

JOHNSON LAKE — Just having its own sewer system makes Johnson Lake unique.

But the lake’s recently completed system has other features to talk about.

It’s ready after two years of construction at a cost of $16 million or more. It will be paid for by property owners with no federal or state grants to defray the cost.

Ken Gardner, the waste water operator, maintains the system 24 hours a day, seven days a week. He describes it as “a big-city system out in the middle of nowhere.”

The system is unique for several reasons and has attracted attention in the engineering profession and construction industry.

One reason is that it encircles a lake and, unlike a village or city, each of the more than 900 cabins and homes has an individual connection. The system includes a variety of safeguards that make it almost failproof.

The system’s backups have backups.

Critical components to the gravity system are the 11 pump stations that keep the sewage moving.

To guard against pump failure, each station has two pumps instead of one. If one pump breaks down, the other pump takes over, and to ensure that both operate properly, their use is routinely alternated.

If a pump station breaks down, there is another safeguard. Each is linked to communications equipment in Gardner’s office at the sewer improvement district’s maintenance building south of the lake.

A computerized map of the system displays each pump and backup pump. It immediately notifies Gardner on his cell phone of the problem and where it is.

“It calls me right away,” Gardner said with a smile. He has the same type of computer in his home.

“The first thing I do each morning is check my computer.” Even before he has breakfast, he will know if there is a problem and where it is.

Gardner has another full-time lake resident as a backup maintenance operator.

Because it is a gravity system, the sewage in the sewer lines flows from a high level to a lower depth. In certain areas, Gardner said, the sewage flows to such a depth that it must be pumped upward.

At these lift stations, sewage can be raised from depths of more than 20 feet to four feet below ground level, enabling gravity to again take over waste movement.

“The problem is, we’re so flat,” Gardner said of the area where the system flows. That is where engineering combined with construction makes the system work.

In connecting each cabin and home to the sewer main, the contractor had to know the precise degree of slope from the home to its sewer main. The system uses a drop of ¼ inch for every 10 feet on the service line for sewage to flow to the main at an appropriate speed.

Ten cabins were so low gravity could not be achieved. Those folks use grinder pumps and have purchased their own spare grinder pumps.

The construction of the system was interesting, Gardner said. Where the sewer mains cross the inlet and outlet canals on each side of the lake, the contractor bored the sewer line to 10 feet below the bottom of the canal.

“Directional boring is a science by itself,” Gardner said.

Special monitoring equipment in a boat was used to measure the depth and length of the sewer line as it was bored beneath the bottom of the canal. The line was bored downward 50 feet and back up the same distance to emerge at the opposite side of the canal.

During construction, 892 septic systems were filled with sand or removed altogether. So, too, were 27 outdoor privies.

Gardner’s job is not one to sit and wait for something to go wrong. He makes a physical inspection of each pumping station every week. The system has 230 manholes that he routinely opens for inspection.

Gardner has already had one memorable experience that involved another fail-safe element. In the dead of winter this past year, an eagle flew into a power line, shutting off electricity to the lake, including the pumps.

The SID has its own 80,000-kilowatt generator. Gardner towed the generator around to each of the pump stations to move sewage while Dawson Public Power repaired the break in the line.

The temperature was 10 degrees with winds up to 40 miles an hour.

“I hope I don’t have too many of those experiences,” he said with a smile.