Septic systems offer promise, perils for Bay
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More than 1.3 million homes in the Bay watershed have something of a nutrient bomb in their yards. It’s the septic system.
The systems are largely a success in dealing with their intended purpose — moving effluent away from homes and protecting people’s health. They’re also cheap, and — unlike public sewer systems — provide benefits such as recharging aquifers.
But they often do little to protect local groundwater, or the Bay, from nitrogen; they were never intended to do that.
“We only designed those systems to get the sewage out of the yard so the kids and the dogs didn’t play in it, and we didn’t smell it,” said Tom Miller of the Maryland Cooperative Extension Service. “We didn’t care what happened once it got into the ground; we didn’t know any better.”
Miller chaired a Maryland Tributary Team task force that spent much of the last year looking at the pros and cons of “on site” — or septic — systems. Its report lamented that while nutrients from wastewater treatment plants and agricultural land have been the target of major control efforts, “septic system discharges have received scant attention."
The Bay Program estimates that about 25 percent of the homes in the watershed have septic systems, and they contribute about 12 million pounds of nitrogen a year to the Chesapeake.
That’s only about 4 percent of all the nitrogen entering the Bay. But at a time when many major sources of nutrients are being pressed to control pollution, septic systems stick out as one of the fastest growing nitrogen sources in the watershed. Nitrogen from septic systems is estimated to have increased 19 percent from 1985 to 1996, and that trend is expected to grow even faster in the future.
But controlling nitrogen from septic systems is more than just an equity issue. In some areas, they can contaminate groundwater. In coastal areas, they contribute 30 percent of the nitrogen to local waters, according to a Bay Program report.
“In some areas, it’s probably the biggest contaminant to the water,” Miller said. “Small coves off a river body, old communities that have a lot of failing septic systems and are all on quarter-acre lots, communities that surround lakes, and stuff like that. In other areas, it’s not an issue at all.”
To deal with the problem in Maryland, Gov. Parris Glendening plans to produce legislation next year establishing “areas of special concern” where new septic systems designed to control nitrogen would be required.
Areas of special concern would include places with high water tables, which are likely to result in system failures; areas where failures have created a public health or environmental threat; areas near water supply reservoirs; or other areas where septic systems are most likely to cause an environmental or public health risk.
A special advisory committee made up of agency officials, local government representatives, builders and other groups is recommending that nitrogen-removing systems be required in areas of special concern for all new dwellings and to replace old septic systems as they fail and need repair, said Jim Dieter, program administrator for wastewater permits with the Maryland Department of the Environment. “Since all systems somewhere along the line will need repair or replacement, we will get to them all eventually, but it may take 20 years.”
The new systems will likely double the expense of installation, adding about $3,000 to $5,000 to the cost. As a result, financial assistance programs may need to be established to assist people whose systems have to be replaced, Dieter said.
No specific technologies are being recommended, but he said the state would most likely publish a list of system designs that would be acceptable. Typically, such “alternative” septic system designs can remove 60 percent or more of the nitrogen from the water before it enters the ground.
The only other state in the watershed with legislation dealing with septic system environmental (rather than just health) issues is Virginia, which requires regular pumpouts — at least once every five years — of systems in tidewater portions of the state, under its 1987 Chesapeake Bay Preservation Act.
“What we were addressing is the unique need in the tidewater type of land and soil environment that we have,” said Mike Clower, director of the state’s Chesapeake Bay Local Assistance Department. “We have typically higher water tables and obviously a much larger chance of contaminating the Bay through failures.”
Pennsylvania has no state law regarding pumpouts, although some local governments have ordinances that address the issue.
A traditional septic system usually consists of two parts. The first is a large tank, which is designed to hold about two days of wastewater. That allows grit and solids time to settle to the bottom, where bacteria and other organisms can digest solid wastes.
Then, the wastewater flows into the second part, the drainfield. That is a series of perforated pipes laid in underground trenches, surrounded with stone and covered with soil. The drainfield is designed to distribute wastewater so it can be slowly absorbed into the underlying soil.
Systems typically “fail” when the drainfield becomes clogged. That can be caused by natural buildups of scum in the drainfields; by solids which enter the tanks over the years; outside intrusions, such as tree roots; or the collapse of pipes crushed by above-ground activity.
Failures can force raw sewage to back up out of the tank, or force it up through the ground. Either way, it creates a health hazard. Such failures usually have to be corrected with the installation of a new system.
While this “hydraulic” failure is a health issue, it has no real impact on nitrogen discharges unless the system is adjacent to a waterway.
What alarms some officials, though, is how poorly traditional septic systems are maintained — despite the fact that replacing a failed system can cost thousands of dollars.
Maintenance for a conventional system means having the tanks pumped out every few years to remove the buildup of grit, sand and other solids, and having periodic inspections to make sure water is properly flowing through the tank. But studies show that people are woefully ignorant about their septic systems and how to maintain them.
A survey by a nonprofit research organization, the Center for Watershed Protection, found that in the Bay watershed, 46 percent of those polled had not had their septic systems pumped out in the past three years. And 12 percent of the people who had systems didn’t even know where they were.
That lack of care has important implications for systems that remove nitrogen because they require more maintenance. Such systems typically move effluent through chambers containing different kinds of microbes, which remove the nitrogen. To do that, the systems often have pumps, moving parts, electrical connections and other components that need to be inspected every year or two, or the system can back up, spewing effluent and creating health problems.
“If it functions improperly, it could be worse than if it were just a septic tank,” said Jay Prager, MDE’s chief of On-Site Sewage and Water Supply.
Therefore, officials say that a move toward more high-tech systems must be accompanied with a maintenance program that can be tracked. Whether that would be done by local governments, private contractors or other means is yet to be determined.
“Maintenance is a big issue,” Dieter said. “Everyone recognizes that if you put these systems in, they need active work on them.”
That would also add about $200 to $300 a year to the cost of the system. Costs, and concerns over proper maintenance, were the main reasons both the tributary teams task force and the advisory committee recommended that alternative technologies only be required in “areas of special concern” — those most likely to suffer problems.
Conventional septic systems can release surprisingly high amounts of nutrients — anywhere from 8 to 11 pounds of nitrogen per person — into the ground each year. A septic system serving a house on an acre lot with two or more people can produce more nitrogen than an acre of cropland, according to Bay Program figures.
If it makes its way to the Bay, the nitrogen can spur algae blooms, which cloud the water, blocking sunlight from reaching important underwater plants that provide food and habitat for many species. When the algae die, they sink to the bottom and decompose, creating an oxygen-starved “dead zone” unusable by most species.
(Phosphorus, another nutrient of concern for the Bay and freshwater streams, is less of a concern from septic systems: It typically binds to soil particles before it reaches the water.)
In some areas, nitrogen from septic systems can cause groundwater to exceed EPA standards for drinking water. Excess nitrogen in drinking water can contribute to health problems, such as “blue baby” syndrome.
But the amount of nitrogen that leaves the drainfield and makes it into the groundwater — and eventually local streams — can vary widely.
In some areas, discharges from septic tanks essentially go into a deep underground ditch, rather than a drainfield. Such systems, Miller said, basically “inject” nitrogen straight into the groundwater. But drainfields that run through soils with high levels of microbial activity can remove large amounts of nitrogen.
It’s a delicate tradeoff — while shallower drainfields can remove more nutrients, deeper drainfields tend to have better hydrology and offer less risk of sewage rising to the surface to create a health problem.
After the nitrogen leaves the drainfield and enters the groundwater, there is also potential for some additional removal if the groundwater passes through a wetland or vegetated buffer en route to a stream.
In Maryland, the Office of Planning has calculated that — on average — 65 percent of the nitrogen that leaves a septic drainfield reaches the groundwater, and that 75 percent of the nitrogen reaching the groundwater ultimately reaches surface water.
Ironically, despite all the concerns, septic systems are in many respects better for the environment than public sewer systems, especially if nitrogen is controlled. Septic fields allow water to slowly drain back into the soil, replenishing aquifers — something that can be especially important during times of drought.
Sewer systems collect large amounts of water and pour it directly into the river; that not only changes the hydrology of the river, but also raises nutrient levels at the point of discharge.
Septic systems are cheaper to build and maintain than sewer systems. Wastewater treatment systems have to be tied together with a maze of underground pipelines leading from homes and businesses to the treatment plant. Maintaining an aging system can be hugely expensive: In some cities, sewer authorities pay more for road work than highway agencies.
“Every time you have to replace a pipe you have to tear up a road,” said Danielle Lucid, director of the Maryland Department of Natural Resources Tributary Strategies Program, and an author of the tributary team’s report.
And, some nutrient-removing systems can outperform wastewater treatment plants in nitrogen reduction. “If you have a good on-site sewage disposal system, you can reduce nutrients to almost negligible amounts,” she said.
While some see septic systems as promoting sprawl, the use of new systems with nitrogen-control technology could actually help control growth, Lucid said. Historically, much of the large lot zoning in the watershed was based on the amount of land needed to absorb the waste from a septic system, or to “perc.”
New designs can allow homes to be built closer together with a shared septic system, conserving open space. “You could put 50 homes in one small development instead of everybody having a 3-acre lot, and save all this open land,” Miller said.
In some cases, Lucid said, clustered homes with a community septic system, which could control pollution to a higher degree than a wastewater treatment plant, while still returning water to the groundwater. “This is kind of a new way of thinking about it,” Lucid said. “You can even build on marginal lands and save the good land for agriculture.”
Over time, septic systems — with the targeted use of alternative systems — may be seen as a benefit to the Bay, rather than a buried nutrient bomb.
“On-site systems are not evil, and they’re not bad, and they might be preferential,” Miller said. “They’re certainly more affordable than running sewer lines, and they’re recharging the groundwater. If we can just remove the nitrogen from them, they’re great. They’re the best thing we could have.”
Copies of the Tributary Team report, “Reducing the Environmental Impacts from On-Site Sewage Disposal Systems,” are available by calling the Maryland DNR’s Tributary Strategies Program at 410-260-8708 or at the DNR web site: www.dnr.stat.md.us/bay
Septic System Maintenance Tips
- Keep roof drains, basement sump pump drains and other rainwater or surface water drainage away from the absorption field. Flooding the absorption field will keep the soil from naturally cleansing the wastewater, which can lead to groundwater and/or nearby surface water pollution.
- Conserve water to avoid overloading the septic system. Repair any leaky faucets or toilets. Use low-flow fixtures.
- Don’t use caustic drain cleaners for clogged drains; they can harm the bacteria that decompose wastes. Use boiling water or a drain snake to open clogs.
- Don’t use septic tank additives, commercial septic tank cleansers, yeast, sugar, etc. These products are not necessary and may be harmful to your system.
- Use commercial bathroom cleaners and laundry detergents in moderation. Many people prefer to clean their toilets, sinks, showers, and tubs with a mild detergent or baking soda.
- Check with your local regulatory agency if you have a garbage disposal unit to ensure that your septic system can accommodate the added waste.
- A septic system is not a trash can. Don’t put grease, diapers, sanitary napkins, tampons, condoms, paper towels, plastics, cat litter, latex paint, pesticides or hazardous chemicals into your system.
- Keep records of repairs, pumping, inspections, permits issued and other maintenance activities.
- Locate your septic system. Keep a sketch of it handy with your maintenance record for service visits.
- Have your septic system inspected every 1–2 years, and pumped periodically (usually every 3–5 years) by a licensed inspector/contractor.
- Plant only grass over and near your septic system. Roots from trees or shrubs may clog and damage the absorption field.
- Don’t drive or park over any part of your septic system. This can compact the soil and crush your system.
From the National Small Flows Clearinghouse at West Virginia University. For information about septic systems, visit its web site at: www.nsfc.wvu.edu
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