Ditching individual septic tanks for decentralized wastewater systems
By Diane McDilda
Since 1950, Minnesota license plates have boasted, “10,000 Lakes,” and Cedar Lake is just one of them. Situated in Rice County in southern Minnesota, Cedar Lake spans 804 acres and is surrounded by campgrounds, resorts, and both full-time and weekend getaway homes. As one of the state’s top fishing spots, the lake gives way to the annual Faribault Bass Challenge tournament, drawing 100 anglers or more to vie for the top catch and $2,000 in prize money. But the quality of life for the bass, pike, crappie, and blue gill that call the lake home may be in jeopardy.
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Impacts From Shoreline Septic Systems
Many lakes and water bodies across Minnesota were impacted by shoreline septic systems. A 2004 report to the legislature by the Minnesota Pollution Control Agency (MPCA) estimated that 535,000 homes, or 86% of resident population, are not connected to public wastewater treatment systems and rely on onsite systems, many of which include septic tanks. Of those systems, 144,000 are estimated to be failing with 64,000 imminent threats to public heath and safety.
Maintaining water quality in Minnesota not only protects sports fishing but also is vital to public health. A comparison between effluents from failing private or individual treatment systems to municipal wastewater treatment systems is summarized in Table 1. Immediate threats are bacteria and pathogens contained in untreated sewage, but excessive amounts of nutrients also encourage nitrification of lakes, which promotes algae growth on the surface and can limit clarity and impact other aquatic plants and animals. Closer to home, malfunctioning septic systems can cause sewage to back up into houses and pond in yards.
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Photo: Faribault Area Chamber of Commerce and Tourism |
| Minnesota faces the challenge of treating water at coastal sites with offsite cluster systems. |
In Minnesota, failures of individual sewage treatment systems (ISTSs) are often the result of a high water table, particularly in the spring when the snows have melted and plants have yet to use the excess water. A sufficient unsaturated zone is needed as the majority of treatment takes place in the soils below or beyond the septic tank, not in the tank itself, where microorganisms break down waste into less harmful materials. The quality of subsurface soils is also paramount to the ability to treat wastewater. Much of Minnesota is underlain by high-clay soils with low porosity. This limits the flow of water and proper aeration needed by the microbes.
The solution as Minnesota regulators saw it was to encourage individuals and groups to come together and construct their own treatment systems. This would solve the problem of impacted surface water and groundwater without financially burdening municipalities with construction of large centralized wastewater treatment plants. Community wastewater systems are also known as cluster systems, as they serve a cluster of homes, or decentralized systems, as they are separate from larger, more centralized wastewater treatment plants operated by municipalities. Cluster systems generally incorporate septic tanks and drainfields into their design. However, they are located offsite, away from shorelines and private residences.
Regulatory efforts to overhaul the septic problems in Minnesota started in 1974 with ISTS rules that provided advisory guidelines to local regulators. Since then, amendments have been made setting standards for ISTS professionals, requiring certification, and making local governments responsible for regulating ISTSs in their jurisdiction. Response has been good with only two of the 87 counties in Minnesota reticent to developing rules.
In some instances, counties rely on homeowners to take the initiative to repair or replace aging systems; however, that is not the case in Rice County. Direct enforcement isn’t generally used, but strict county ordinances tie properly functioning septic tanks to any home improvement or real estate transaction—a key to educating the public and improving septic systems.
“When a piece of property is transferred, a compliance inspection is done on the sewer system,” says Marilee DeGroot, the Rice County environmental health administrator. “If anyone wants to add a bedroom, they must have a compliance inspection. We believe it’s better to encourage and educate people. Compliance inspections give us the opportunity to help people realize the costs and benefits. The majority of the people are very open-minded.” As a result, Rice County has approximately 20 community, or cluster, systems, a large number compared to other counties.
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Photo: Faribault Area Chamber of Commerce and Tourism |
| The community had to agree on a cluster system to best meet specific residential wastewater treatment needs. |
Cluster systems, over individual residential units, have grown in popularity in Rice County as they free up space on lots that are often limited in size or by inadequate subsurface conditions. Lot size also becomes a factor when considering proximity of a septic system to a drinking-water well. Approximately 1 million Minnesotans get their drinking water from private wells. To avoid drinking-water contamination, state law requires wells and septic systems to be separated by no fewer than 50 feet.
Cedar Lake’s Solution
Between wanting to do their part to ensure lake quality and get out from under the onus of county ordinances, a group of residents decided to ditch their personal septic systems for a safer wastewater treatment alternative in 2001. And thus, the Cedar Lake Cluster Association was formed. But coming together as a group was just the first step. Next on the agenda was learning about and evaluating their options, reaching consensus, and constructing the project, a daunting task the citizens of Cedar Lake took seriously.
Norbert Malecha was chosen to lead the pack after he attended a county-sponsored meeting in Faribault on wastewater alternatives. “I gave my report at an association meeting. It just so happened that the president was resigning so I stepped in,” he says. As president of the cluster association, Malecha was the point man for dealing with the engineers and designers who submitted plans for the project. After reviewing proposals and design plans, the association elected to go with Ellingson Companies, a third-generation design-build company out of West Concord, MN.
“I was the main contact with Ellingson,” says Malecha. “They were very friendly and easy to work with.” The company reviewed the submittals given to the association, listened to its concerns about what it wanted and didn’t want, and completed the design.
“Norbert [Malecha] put a lot of work into it,” explains Jeremy Ellingson of Ellingson Companies. “The group was determined to fix the problem. We went in and looked at the project, what needed to be designed, and the homeowners’ concerns.”
First and foremost, the homeowners wanted their individual septic tanks removed from their property. By eliminating their septic tanks, homeowners no longer needed to annually pump out their systems, and they gained more flexibility with their yards. Decks could be built or additions constructed without being limited by the location or condition of a septic tank. It was decided that treatment of the wastewater would be handled using two large septic tanks located on otherwise empty property. Some regulators are split on the efficacy of combining sewage flows prior to treatment. While it largely reduces the number of septic systems that need to be pumped, maintained, and inspected, the source of any problems can be hard to trace. In Rice County, however, the final decision is left with the homeowners.
Ultimately, the system selected by the cluster association and designed and installed by Ellingson Companies used technology developed and manufactured by Environment One (E/One), known as a pioneer in pressurized sewer systems. Historically, sewers across the country were designed based on gravity flow that relied on sufficient slope and velocity needed to convey liquids and solids and avoid settling. But the system developed by E/One incorporates a grinder pump to create slurry and move the sewage, eliminating the need for sloping pipes and lift stations. Because pipe slope wasn’t a controlling factor for the project at Cedar Lake, the contour of the land was followed and pipe was buried just below the frost line, approximately 6.5 feet to 7 feet deep.
Another plus in the construction was that conveyance pipe was installed using directional drilling. By cutting out the need for open trenches, there were no road closures and no needed repairs to landscaped and asphalt surfaces.
“We could install 1,500 feet to 2,000 feet of 3-inch pipe in one shot, without disrupting anything,” says Ellingson. “The total cost for directional drilling is no more than open cut. Open cut costs about $8 to $9 per foot, plus restoration. Directional drilling is about $9 to $11 per foot, but there are no restoration costs. And directional drilling is a lot safer than open-cut trenching too.”
Jerry Van Auker is the Great Lakes region sales representative for E/One and believes the company’s system has many advantages over both traditional individual septic systems and gravity-driven centralized wastewater systems, especially the smaller pipe. “Before you had large chunks in a bunch of water, the minimum sizes of pipe were 4 inches in diameter. With a grinder, it grinds down to a quarter of an inch and goes to a pump that pumps slurry though a 1.25-inch pipe,” says Van Auker.
Improvements with grinder pumps continue to be made. “The low-pressure systems are easy to install and require minimal maintenance,” Van Auker says. “The average time between service calls used to be seven to eight years now it’s 10. We’re working to improve and are aiming for a service time of 14 to 15 years. Homeowners are asked to put aside $50 a year so that when service is required they’ll have the money to repair or replace the pump.” Van Auker compares the service life of a grinder pump to that of any household appliance. “People don’t expect to require service calls for the refrigerator every three to five years; they shouldn’t for their pumps. Pumps are a home appliance,” he says.
Another bonus is that low-pressure sewer systems eliminate infiltration of groundwater and rainwater into the system. “A gravity system is open to the atmosphere and allows infiltration. Pipes in a pressurized system don’t need to be sized to handle the additional volume from infiltration,” Van Auker says. “On average a home produces approximately 190 to 220 gallons of wastewater a day. The EPA requires treatment of 400 gallons per day [gpd] because they require all potential infiltration from rain and groundwater to be captured. Now, some of the EPA writings for closed systems are being reviewed a little differently.”
System Details
The Cedar Lake cluster system components include one vertical grinder pump, model GP 2010, at each house, which grinds the solids into fine particles discharging at 11 gallons per minute and 40 pounds per square inch. This connects to a force main, with diameters ranging from 1.5 to 4 inches, depending on the flow in that part of the system. All the piping is HDPE SDR 11 fusible pipe, one of the main components that eliminate infiltration. Sewage is then carried through the force main to two 10,000-gallon septic tanks. From the septic tanks, effluent gravity flows to a 2,500-gallon pump tank where two Gould’s submersible 0.5-horsepower pumps evenly distribute flow to the drainfield, which is divided into four separate cells and is constructed of 7,514 feet of Prinsco 10-inch-diameter Goldline gravel-less leachbed pipe.
Malecha monitors the system on a monthly basis. It’s set on timers to allow controlled flow of water to each of the drainfield cells. The septic tanks are pumped out once a year by a contractor who is paid by individual contributions to the association. The same contractor also makes service calls if maintenance is needed on the system or at individual residences.
The system was sized for 10,000 gpd, just under the threshold requiring a state disposal system permit (SDS). Monitoring requirements for an SDS include collecting groundwater samples from wells located at the perimeter of the discharge area. Samples are then analyzed for drinking-water standards. While it’s thought that some designers intentionally develop systems that are sized just under the permitting threshold, Ellingson ensures that wasn’t the case with Cedar Lake.
“We counted the number of houses that wanted to be on the system, and the numbers shook out to be less than 10,000 gallons,” says Ellingson.
Initially, not everyone living on Cedar Lake wanted a piece of the action. Of about 100 homes in the area, only about 40 joined the association. The system is considered closed, even though there is still volume available. Malecha explains that because Cedar Lakes does not have capacity available for everyone wanting to connect to the system, the association won’t allow any one individual to connect. While the system could be expanded, Malecha feels that the association constructed the system needed at the time and that’s that.
Other community cluster systems allow for expansion but charge a higher rate for those who join after the fact. “We suggest that anyone who doesn’t commit and connect initially be charged an extra $10,000,” DeGroot says. “There will always be fence sitters who eventually have a change of heart, and $10,000 can still be cheaper than putting in a new system of their own.”
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Photo: Faribault Area Chamber of Commerce and Tourism |
| Samples are taken to be analyzed to ensure that water meets the criteria set forth by drinking-water standards. |
Ready Money
When it came to paying for the system, the homeowners took care of it themselves. Each initially anteed up $100 so the association knew exactly who was in and who was out and could use this count to determine system capacity. Fifty percent of the total cost was paid prior to construction with the rest paid on completion. Each homeowner was assigned a cost calculated according to the distance between his house and the main line. The average cost to each homeowner came out to about $9,800.
“Being able to fund the project privately made it a lot more cost-effective. When groups go with federal or state funding they have to have the system designed and then they have to bid out construction,” says Ellingson. “Going through design-bid can add anywhere from $30,000 to $100,000 to the cost of a project.” Ellingson also believes that design-build is more efficient when compared to engineering design and construction. Because design-build contractors are in the field installing systems, they have a better understanding of what’s constructible.
Funding can be complicated by a variety of issues, including the value of the home and property, the complexity of the design, and the cost of construction of a cluster system. While there are state and federal loans available, they can complicate matters.
“Some communities want to stay away from government fixes and low-interest loans,” says Doug Malchow, an educator with the University of Minnesota (UM) Extension office. “It costs as much or more to use the funds, and there are so many hurdles. When you have an area where the median cost of a home is $100,000 to $120,000 and some of the homes are only $40,000, it can make it difficult to bring people together.” As an educator, Malchow recommends that communities go for the simplest thing first, with respect to both technology and money, and believes that the state needs to expand all options—not just treatment but funding too.
Malchow travels the state helping groups identify their goals and learn their options and stresses the importance of water quality. Although optimistic, he admits that many groups aren’t limited just by funding but by mindset too. He applauds the Cedar Lake Cluster Association for working together to improve its situation.
“It can be a problem getting people to work together. Kudos to them,” says Malchow. “Some people believe that because they’ve handled their wastewater in the same way for 70 years, they don’t need to change anything. I have to explain that spending money on their wastewater could ultimately improve the quality of the nearby creek. Where they only have suckers and crappie now, they could have bass or trout.”
While Malchow maintains he’s an educator, he admits his role as a facilitator is growing. Facilitators can often recommend different options for certain neighborhoods. Their recommendations are considered objective in that they have no connection with designers, suppliers, contractors, or regulators. Facilitators not only help associations decide on design; they have ample information on available funding and can help evaluate whether or not it’s worth it to borrow. The use of facilitators can reduce the anxiety in implementing a new system, thereby increasing the potential for more associations and neighborhoods to address septic problems and install decentralized treatment systems. The UM Extension office has contact information for facilitators in Minnesota. Facilitators are currently paid by the state, but the contract has to be renewed every three years. Malchow and others are working to make the payment of facilitators a permanent line item in the state’s budget.
Van Auker has seen the increase in the number of low-pressure decentralized systems installed that’s been spurred not just by success stories, like Cedar Lake, but by a change in heart of many regulators. In the 1980s engineers and regulators were slow to overcome the prospect of pumping sewage and using smaller decentralized systems. By the late 1980s the EPA saw the importance of cluster systems and began publishing voluntary guidelines for communities to follow when improving wastewater treatment. In 2005, the EPA reported that 25% of households in the US rely on septic systems to treat their sewage and that 10% to 20% are likely malfunctioning.
Jeff Mogush is the pump division manager for Northern Water Works Supply, a company that distributes E/One systems. “After World War II the demand for housing jumped. Septic systems were easy to install,” says Mogush. “Then they became popular with vacation homes. Now the systems are starting to fail. There has been some skepticism about decentralized systems, but that’s typical when people are resistant to change.”
The EPA considers that with effective management, decentralized systems can be “a cost-effective and long-term option for meeting public health and water-quality goals, particularly for small, suburban, and rural areas.”
Van Auker, a former firefighter, gets somewhat philosophical when he sees the benefits of decentralized or cluster systems firsthand. “We’ve seen sites where the sewer was being discharged to ditches. Not only does it look horrible and smell; the family dog runs through it, and then the kids play with the dog. Then after startup of the system, the problem is all gone. I may not have rescued someone from a fire, but I feel good and I know why I’m here.”
Diane McDilda is an environmental engineer and a technical writer in Florida.
OW- November/December 2007
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