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This article was published in Government Engineering Magazine's October 2005 issue.
You can click the image below to download the PDF.

To view a video and additional photos of the installation of vacuum sewers
in Virginia Beach go to our Large Municipal Project Gallery.

Lessons In Wastewater Collection

Vacuum technology helps Virginia Beach solve sewer problems.

An excellent way to learn is to follow the example of others who have gone before you. Cities that want to learn something about wastewater collection would do well to look at the example of Virginia Beach, VA.

This coastal city at the mouth of the Chesapeake Bay has sewer issues that are common to hundreds of seaside communities. Like many older communities, many of the homes in Virginia Beach in the early 1960s relied on septic tanks for the treatment of sewage. As most wastewater experts know, septic tank systems may fail over time and allow untreated sewage to leak into the groundwater.

The obvious solution was to eliminate the septic tanks in favor of a public sewer system. However, a high water table, sandy soil, flat terrain and densely populated neighborhoods created significant installation obstacles for a gravity sewer system. Deep trenches and lots of dewatering are necessary to bury the collection lines for gravity sewers, and numerous pumping stations are required in flat terrains to keep wastewater moving toward the treatment plant. The combination of these factors made for an expensive, highly disruptive wastewater project – the kind that civil engineers and taxpayers loathe.

There are no easy, inexpensive solutions to wastewater collection, especially for cities like Virginia Beach. But this historic town has discovered that there are alternatives to gravity flow sewers, alternatives that are cost effective, highly efficient and far less disruptive to install.

Virginia Beach was an early proponent of vacuum sewer technology. The city is currently installing its sixth vacuum station and collection system in an area known as Little Neck, an affluent area with lots of trees and narrow streets. The disruption caused by the installation of the new sewer is minimal and only one vacuum station will be needed to serve hundreds of homes. A gravity sewer system in the same area would have required three pumping stations.

“This project will eliminate the need for about 320 septic tanks,” said Mike McCarthy, P.E. McCarthy works for the Virginia Beach Department of Public Utilities and is project manager for the Little Neck sewer system installation. “Plus, vacuum sewers are much less disruptive to install. For this situation it was a perfect solution.”

400 YEARS IN THE MAKING
To say that Virginia Beach is an established community is, well, something of an understatement.

In 1607, Admiral Christopher Newport sent a landing party of 30 men ashore at what is now known as Virginia Beach, Virginia. They were the first Englishmen to set foot on North American soil. Shortly afterward the first English settlement in the New World was established on an island in the James River, just a few miles upriver from present-day Virginia Beach.

The early residents of Virginia Beach liked what they saw. One settler remarked, “Heaven and Earth never agreed better to frame a place for man’s habitations than Virginia.” The town became a busy seaport and grew steadily over the years. Today, more than 425,000 people call Virginia Beach “home.” Nearby cities such as Norfolk, Newport News, and Chesapeake also are thriving.

The beautiful environment around Virginia Beach remained unspoiled for decades. But as development and population growth occurred, the impact on Mother Nature became more apparent. People began to experience problems with septic tanks and see the effects caused by groundwater pollution. They also found that having septic tanks limited their growth and dampened property values.

“About 20 years ago the city council in Virginia Beach determined to do something about the sewer problems they had,” explained McCarthy. “Neighborhoods were divided into service areas. If 51 percent of a service area decided they wanted public sewers and funding was available, a new sewer project was initiated. The citizens of Virginia Beach realized that sewers would make their property more valuable and allow them to expand their homes more easily, which they could not easily do with a septic tank system. They also would be solving a potentially bad pollution problem. It was a big issue with this city.”

VACUUM ADVANTAGES
Any public utilities professional knows that installing sewers in developed communities is a difficult assignment, especially in a coastal community such as Virginia Beach. The various factors that made gravity sewers difficult to install led utility officials to seek a different solution, in this case vacuum sewer technology.

“A vacuum system is particularly attractive if you have high water tables like we have in Virginia Beach,” said Phil Hubbard, P.E., of the city’s Public Utilities Operation Division. “We can install vacuum lines at 3 to 7 feet deep, as opposed to 16 to 20 feet deep for a gravity line. You also eliminate a lot of pumping stations.”

Virginia Beach’s vacuum sewer systems have used technology developed by AIRVAC, Inc., of Rochester, Indiana. AIRVAC is a pioneer in vacuum sewer technology and has been a valuable partner to Virginia Beach for approximately 10 years.

In a vacuum sewer system, a central vacuum station maintains vacuum pressure within the sewer collection lines. Wastewater flows from each house by gravity to a vacuum valve pit nearby. Typically, two homes can be connected to a single valve pit, although as many as four can connect if conditions allow. Each valve pit is equipped with a vacuum interface valve that activates when wastewater in the lower sump reaches a predetermined level, typically ten gallons. When the valve activates, wastewater enters the collector line followed by a volume of air. The wastewater forms a slug that is driven by the air due to differential pressure. Operation of the valve pit is completely pneumatic, so external power is not required. The sewage moves so rapidly through the line that build-ups of grease or sludge are rare.

Virginia Beach public utilities officials have utilized vacuum technology for several years, so it was no surprise that the technology was the deciding factor when they were designing a new sewer for the Little Neck community.

“The Little Neck area is bordered on three sides by water, and property values are upwards of $500,000,” said Brad Law, P.E., the project’s senior manager. “A gravity sewer system was not a good idea here because of the lack of available land to build pumping stations. And the streets there are very narrow. Deep trenches would have required us to close streets for weeks at a time and reroute traffic.

“The nice thing about vacuum sewers is that they can serve a very large area, up to a 10,000 foot radius from the vacuum station,” Law continued. “A gravity system in this area would have required about three pumping stations. We didn’t have that much available land for multiple pumping stations.”

EASIER INSTALLATION
McCarthy explained that the installation went smoothly due to three factors: the system requires shallow lines, usually four feet deep or less; the crews were experienced with vacuum technology; and the support of AIRVAC.

“They’re great to work with,” said McCarthy of AIRVAC. “We’ve been very happy with the relationship.”

Among the best post-installation benefits of vacuum technology, according to Hubbard, is that vacuum sewers require little maintenance.

“There’s just a small amount of maintenance required for the vacuum pumps,” Hubbard explained. “We regularly change the oil and filters, things like that. Other than that, you really don’t have many issues with them. And the valve pits are easy as well. AIRVAC has pretty much gotten those down to a science. We have something like 1,200 valve pits in all our systems. Over the course of a year we may have to look at 35 to 40 of them, usually for some minor adjustment. It’s really very low maintenance.”

The vacuum sewers also hold up well during inclement weather. Hubbard noted that when Hurricane Isabelle came through two years ago, some 360 of the city’s 393 gravity-pumping stations were shut down due to lack of electrical power. All of the vacuum stations continued to function thanks to permanent back-up generators that are installed in every station.

Virginia Beach is an old town that has become wise with age. The city is converting large areas from troublesome septic tanks to efficient vacuum sewers that are environmentally friendly and very dependable.

“Vacuum systems are just very reliable,” said Law. “If they are operated the way they are designed to be operated, they are essentially trouble free.”

This article appeared in the October 2005 issue of Government Engineering. If you would like to read the entire story as it appeared in the magazine, you can download a pdf, or you may request hard copies. Additional information and photos of the installation of vacuum sewers in Virginia Beach can be found in our Large Municipal Project Gallery.

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