Liquid-only sewers (also known as effluent sewers) have proven to be a cost-effective solution for municipalities, new subdivisions and a variety of other areas in need of sewer. They use small-diameter, shallowly buried mainlines that follow the contour of the land and are easily installed with light-duty equipment, minimizing disturbance to the surrounding area.
Liquid-only sewers have been installed by hundreds of communities over the past several decades. Many of these sewers have now been providing reliable service for more than 35 years.
The following case studies provide examples that illustrate the benefits of liquid-only sewers.
Glide, Oregon: Liquid-only sewer sets new standard
In the late 1960s, onsite septic tank and drainfield failures were common in the unincorporated community of Glide, Oregon. One after another, three different engineering firms attempted – and failed – to find an affordable solution. In 1973, the county health department enacted a moratorium on any further development in the area.
For the next couple of years, the county’s Department of Public Works studied several options and compared both upfront and long-term costs for a system designed to serve about 2,300 equivalent dwelling units. The county researched gravity sewers, vacuum sewers and pressure sewers, including both grinder and liquid-only sewers.
When the evaluations were done, the department proposed a liquid-only sewer that could eventually serve 7,000 residents. It would be the largest of its kind in North America and would set a standard for innovative design by demonstrating that small communities have more wastewater options than traditional wisdom dictated.
Lacey, Washington: Unique hybrid collections system fills niche
The City of Lacey, Washington, grew rapidly between 1980 and 2000. The city needed an affordable wastewater solution to support construction in the Urban Growth Area it shares with neighboring communities. Lacey chose an Orenco System liquid-only sewer, which discharges into the city's gravity sewer lines, creating a hybrid collection system. Now, more than 25 years later, the system successfully serves about 14,000 gravity sewer connections and roughly 4,600 liquid-only sewer connections.
Thomas Faye, senior maintenance technician (collections) for the City of Lacey, describes some of the benefits of this hybrid sewer system. “Lacey has approximately 70 miles of liquid-only sewer lines and they don’t require lift stations. With liquid-only sewers, you get to dictate the shortest route to wherever you want it to go. I’ve been working with these systems for 15 years and they're very simple: economical to maintain, economical to install.”
Vero Beach, Florida: Affordable liquid-only sewer helps clean lagoon waters
Along the Indian River Lagoon adjacent to Vero Beach, Florida, both residents and government officials were becoming increasingly concerned about excessive nutrient loads and pollution. About 1,500 homes in Vero Beach had septic systems, many of which were antiquated and failing.
The City of Vero Beach installed an Orenco liquid-only sewer consisting of directionally drilled, small-diameter mainlines and individual septic tank effluent pump (STEP) packages. Replacement of failed septic systems will result in fewer pollutants ending up in the lagoon. At full buildout, with an estimated 1,500 residences connected to the city’s liquid-only sewer, water quality in the Indian River Lagoon is expected to improve considerably. Local officials are confident this will be a boon to the dolphins, manatees and other animals that make their home in these vital waters.
Orenco Systems has designed and built decentralized wastewater systems since 1981. Orenco’s technologies are based on sound scientific principles of chemistry, biology, mechanical structure and hydraulics. As a result, the company’s research appears in numerous publications, and its engineers are regularly asked to give workshops and trainings.
800-348-9843 | www.orenco.com
