Last month, we introduced the dilemma of dying septic systems pushing the fragile ecology of Peach Lake to the brink. After two separate State Environmental Quality Reviews were performed, two sewer proposals were considered—either a gravity/low-pressure hybrid with eight pump stations or a low-pressure sewer system employing grinder pumps at each home.
BUILDING THE LPS
“The gravity system would have the disadvantages of needing land in several associations for pump stations, as well as requiring deeper excavations, more blasting, greater infiltration and inflow and more attention to groundwater disposal during construction,” says Sarah Cwikla, an engineer with G.H.D. of Middletown, Connecticut, which designed the project. “The low-pressure sewer system would be less expensive to construct but required individual (grinder) pumps.”
Unlike septic, LPS is environmentally safe. LPS construction costs can be 50-percent lower than a conventional gravity system, partly because it eliminates lift stations which in the United States can run about $350,000 to $500,000 each.
Cwikla’s team recommended grinder pumps manufactured by Environment One Corporation in Niskayuna, New York, about 125 miles north of Peach Lake. It has assembled around 500,000 grinder pumps at its facility which comprise the largest installed base of pressure sewers in the world. E/One’s waterfront LPS projects include Martha’s Vineyard, Baja California (Mexico), and Hawaii.
“I did talk to some other communities in Pennsylvania and around the U.S. down south and they were using the grinder pumps, specifically E/One, and I talked to them about what they saw and most of them were happy with the units,” says Lucas of his due diligence.
GRINDER PUMPS IN THE LPS
An LPS begins at the grinder pump which accepts wastewater, grinds its contents into fine slurry, and transports it through small-diameter 2 inch to 4 inch PVC pipes buried just beneath the frost line to roadside force mains.
Most installations around the lake consist of a rugged E/One DH071 grinder pump station, the company’s most popular model, incorporating a 1 horsepower pump in a 70-gallon tank.
The grinder pump is automatically activated and runs for very short periods. Electrical consumption of the grinder pump is low—a household that uses 250 gallons of water per day should use less than 10 kWh per month to run the pump.
As with thousands of other installations, E/One’s grinder pumps were set in the footprint of an old Peach Lake septic tank or just adjacent to it making the installations far less environmentally disruptive to private landscapes.
“It is rare that a district take on the responsibility of installing grinder pumps on private property,” says Cwikla. “This required extensive planning with each resident and coordination of septic pump outs and grinder pump installations.”
Whereas about thirty of North Salem’s homes are close together with only a few feet between them, “most of them are on at least a quarter-of-an-acre or so, if not more,” says Lucas.
EFFECTIVE AND EFFICIENT
A gravity system to service these far-flung residences distributed on roller coaster elevations was cost-prohibitive. With LPS, the wastewater can be propelled uphill from the homes and around contours. It is effective for distances at more than a mile from force mains or water treatment facility.
“From (G.H.D.’s) point of view there were several reasons why they thought (LPS) was more appropriate based on how the homes were laid out in communities, and this is on the lake,” says Lucas. “So it’s kind of hard at least for a large number of homes to gravity feed without the grinder pumps. The grinder pumps are actually lifting the effluent, the sewage, up to the lines,” Lucas adds.
“I obviously have a bunch of homes right around the lake and so you’re not going to gravity feed out of those,” Lucas says. “It’s just not going to happen.”
The E/One grinder pump addresses this with a progressing cavity pump—rather than a centrifugal pump—which produces a nearly constant discharge rate over a wide range of head conditions, including negative head conditions.
“The one thing that did impress me, because I was very concerned about these things being able to push against the head, you know, a static head in the line,” says Lucas. “This is a rolling hill topology so you have people that are 30 to 40 feet higher in some areas than others closer to the lake so those pumps have to pump it up at high pressure basically to put the stuff into the line. And there’s been no issues at all in terms of capacity or volume issues with these pumps. They have no problem working correctly handling the volumes and stuff or pushing against the pressures of the line.”
A HISTORY OF SUCCESS
Even though LPS technology has been refined for more than forty-five years, many like Lucas remain unfamiliar with its capabilities. While satisfied E/One’s grinder pumps could sufficiently service single-family homes, he fretted over the large, almost nightly events his town’s facilities host during the summer.
“I have large lake community buildings—we call them pavilions—where you have 300 to 400 people in a building when they have a party or something,” says Lucas. “I did have a concern up front about their ability to actually pump the volumes but there’s been no problems at all. So it does service those.”
Reliability and low operation and maintenance costs are inherent with grinder pumps.
A recent study analyzing a ten-year-old E/One grinder pump installation found them not only dependable but cost effective: Mean time between service calls (MTBSC) was approximately twenty-eight years; O&M costs were about $37/year/home (excluding power).
If service is required, the unique, one-piece core eliminates the need for in-field troubleshooting and servicing—the pump core can be quickly pulled out and replaced, meaning minimal maintenance costs and inconvenience for the homeowner.
“Based on what’s needed for the community and how it’s working here, it works really good,” says Lucas. “You just don’t have the breaks in the lines and you don’t have those kinds of problems. There’s no catastrophic problems with the low-pressure system.”
Septic debacles polluted Peach Lake for nearly a century but the switch to a hospitable LPS means there’s now more than just a fiery sunset burnishing the horizon.
A BRIGHT FUTURE
Peach Lake’s collection system and treatment plant were completed in 2012 and the final grinder pumps installed in 2013. Until the new LPS was online, concerns about deteriorating septic made it almost impossible to obtain a building permit for expanding homes and adding bedrooms.
With the transition from decentralized, independent septic schemes to a centralized low-pressure sewer system, real estate values in the project area are increasing in tandem with improvement in lake quality.
Homeowners are free to build additions and convert demure abodes to comfortable year-round residences. Some obsolete housing stock is being replaced with entirely new structures. In one case, a property owner erected a modular home so it would be ready for occupancy as soon as a grinder pump hook-up was available.
Just before the system’s inauguration, a member of the North Salem Town Board asked Cwikla the $30 million question everyone wanted answered about their investment: “When will the lake be really clean?”
“You won’t see an immediate effect,” Cwikla responds. “In five or six years you’ll begin to see major changes. In ten years there will be a significant change.” ◆
For More Information
With corporate headquarters in New York and regional offices and distribution throughout the industrialized world, Environment One Corporation (E/One) is a manufacturer and provider of products and services for the disposal of residential sanitary waste and utility systems for the protection and performance optimization of electric utility assets. For more information, visit www.eone.com.
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MODERN PUMPING TODAY, November 2015 Buyers Guide
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Peach Lake Finds a Solution for a Dying Septic System: Part 2 of 2
