The system costs significantly less to install and operate than a gravity system and requires less maintenance. "The Athens abandonment project has been operational for more than two years. There have been virtually no problems and little service or maintenance required," said Davis.

Pump station records verify that 700,000 fewer gallons were eliminated from wet weather spike flows in the first year after installation. In 2003 there were 500,000 gallons of water overflow from nine events; in 2007 there were zero gallons and zero events.

"Our records also indicate a reduced flow through the pump station to our treatment plant of 27.5 million gallons per year, with a yearly savings of $89,212 in treatment cost alone. Eliminating overflow levels, which are state violations, helps our standing with state regulatory officials," said Harrison.

"The construction savings by choosing the pressure sewer system was 25 to 35 percent. The actual cost included abandonment of the old gravity main, which would have been required regardless of the technology chosen."

"The low-pressure system has needed little time or attention and savings from reduction of wastewater infiltration and inflow through the treatment plant is significant. Pump run time is also greatly reduced. Maintenance time for stopping to clean the system has diminished and less overtime will likely produce additional savings," said Davis.

Marion, Massachusetts

Rocky soils, sandy soils, high groundwater, variable terrain sloping and draining toward the waterfront create significant geo-technical challenges that make conventional wastewater disposal methods obsolete. With small lots built to capacity and packed tightly together, the coastal town of Marion, Mass., needed a solution that created maximum density for wastewater infrastructure.

In 2004, when Marion undertook an expansion of its sewer systems, it selected a low-pressure sewer over a traditional gravity system. With only shallow trenching required and no inflow, LPS was a good option. The challenges of the terrain helped steer the decision toward LPS, along with ease of design, installation and lower-cost operation and maintenance (O&M). Since Marion had 455 homes in three shoreline neighborhoods, this project became the largest single-contract LPS system in New England.

Residents, however, were concerned with the cost of installation and O&M and had some mixed history with earlier systems. The design and installation firm, Earth Tech Inc. from Long Beach, Calif., thoroughly involved the community through ongoing town meetings, communications and consultations. The residents were treated as stakeholders in the project. The proposed LPS system was widely accepted, so a proposal was presented that the town purchase, install and maintain the pumps for the entire project. This proposal included a five-year manufacturer's warranty and a ten-year service contract from the town for all private property installations. The voters accepted the proposal.

The manufacturer of the specified grinder pumps and its Rockland, Mass., representative, F.R. Mahony & Associates, negotiated with the town of Marion and provided a favorable warranty and service agreement. The manufacturer would provide free repairs onsite and free required maintenance during the warranty period.

The project was completed in October 2006. Servicing the 455 homes saved more than 40 percent compared to the gravity alternative. The project was completed in half the time of the gravity proposal and resulted in more than 22 percent savings over what was planned in the construction budget. With only minimal non-startup service calls since installation, Marion considers this a successful project.

Conclusion

Hundreds of thousands of successful installations worldwide show that what was once considered a sewer alternative is now a sewer choice, especially in communities that have flat, hilly, rocky or wet terrain. With municipal budgets challenged more than ever and sensitivity toward carbon footprint increasing, the grinder pump-driven pressure sewer is a lean and green option.

Pumps & Systems, October 2009

George A. Vorsheim, Jr. is the director of marketing communications at Environment One Corporation, 2773 Balltown Road, Niskayuna, NY 12309.

Tags: October 2009 Issue , Pumps , Vertical Turbine Pumps

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