Study: Septic tanks may be polluting groundwater

By Steve Miller, Journal staff | Wednesday, November 21, 2007

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As Piedmont residents continue to cope with wells polluted by an Aug. 17 flood, a new study is finding that septic systems could be contaminating groundwater throughout the east-central Black Hills area.

The government study, begun last year, won't be finished until next fall, but initial screening samples in observation wells have tested positive for elevated levels of nitrates, which can indicate the presence of other contaminants including fecal coliform and E. coli bacteria,  according to Larry Putnam, a hydrologist with the U.S. Geological Survey.

Some test samples also are showing direct evidence of fecal coliform and E. coli.

Fecal coliform and E. coli are found in the digestive tracts of humans and other warm-blooded animals.

The study areas include locations in the Minnekahta Limestone and other geologic formations on the edge of the Black Hills from about 10 miles south of Rapid City up to the Piedmont area, plus Rapid Valley, the Johnson Siding area, Hisega, Hill City and Silver City.

The study's results will be provided to the public and to local governments grappling with the effect of burgeoning residential development.

So far, samples from the 29 observation wells, some private wells and a few small public water supplies haven't detected much fecal coliform and E. coli, except in situations where there was heavy rain, such as at Piedmont, Putnam said.

The test wells were purposefully drilled downhill from dense housing areas to try to determine if septic systems are affecting groundwater, and, by extension, drinking water.

Putnam cautioned that the tests, so far, are preliminary, and a second phase of sampling is under way to test for more specific contaminants.

Septics are suspect

But the evidence so far is pointing to septic systems. Putnam explains that the test wells are showing nitrate levels well above those that would occur naturally and some even above the EPA standard for drinking water of 10 mg of nitrates per liter.

One test well near Berry Pine Road in west Rapid City showed high nitrate levels as well as fecal coliform.

With a septic system, all sewage from a home runs through a pipe to a septic tank outside, which catches solids, releasing only liquids into a drain field. The trench to the drain field and the drain field  itself are supposed to further filter impurities before the water evaporates or seeps down into the aquifer below.

Septic systems are used by virtually all area residents who are not on a municipal or other group-type sewer system. The Department of Environment and Natural Resources, which is collaborating with USGS on the new study, estimated that at least 9,000 septic systems were in use in the central Black Hills early this decade.

Several thousand more are being used along the Interstate 90 corridor between Rapid City and Spearfish.

The study is not testing public or private wells, but Putnam said if drinking-water wells are located near observation wells with high nitrate levels, they could be having problems.

Piedmont flood woes

The people of Piedmont already have experienced problems with their drinking water. Earlier testing programs have been finding contamination in Piedmont Valley wells since the late 1990s, but the Aug. 17 storm and flood worsened  existing problems with old septic systems built close to shallow wells, according to longtime residents such as Sonny Hemsher, who was elected Nov. 6 to the first    Piedmont Town Board.

The surging floodwaters flowed into septic systems and then into wells in Piedmont.

Hemsher said he put Clorox in his well to kill the contamination and is able to use his water now.

But many people in town are still drinking bottled water, even if they've treated their wells, Hemsher said.

"People I know are using Clorox in the dishwasher and using bottled water to drink."

Hemsher said it's likely some wells in Piedmont that tested positive for contamination after the flood would have tested positive before the flood.

He hopes the newly formed city can get state or federal help to build a sewer system.

Phil Anderson, another longtime Piedmont resident elected to the town board, said he and other residents have treated their polluted wells so they can use the water.

"When you know the cause, you dump the Clorox down and fix the well," Anderson said. But, he added, "It hides the potential longer-term problem."

He said the problem of ongoing contamination is still undetermined. "I think throughout the Hills that's everybody's concern."

Hard questions

Indeed, local governments want more information about whether septics pose a danger, especially when they're considering whether to approve a particular development project, according to Foster Sawyer, a hydrologist with the DENR.

"They all want to know, No. 1, is this a safe proposal that's before us; is it safe to have this many septic tanks? How many is too many? And how closely spaced is too closely spaced? Those aren't easy questions," Sawyer said.

Septic systems are not innately unsafe, some experts say. Properly installed and maintained, they are effective ways to dispose of and treat household sewage.

But not all septic systems were installed properly in past years. Some are older than the regulations that began imposing standards in the 1970s, Sawyer said.

Some are not maintained well or at all.

The Environmental Protection Agency estimates that 10 to 20 percent of all septic systems in the country are failing.

With well over 10,000 septic systems in the Black Hills, more than 1,000 septic systems could be leaking contaminants into the aquifers that provide drinking water for the region.

Sawyer cautions that the aquifers, as a whole, are not contaminated but are being affected, particularly in areas downhill from dense clusters of septic systems.

Earlier studies in the Hills have found evidence that the aquifers underneath are susceptible to contamination, partly because the aquifers are so interconnected.

A South Dakota School of Mines & Technology study a few years ago found human and animal fecal pollution in Spring Creek, which feeds the Madison Aquifer, the source of much of Rapid City's drinking water.

Sawyer notes that nitrates found in the current study can come from a variety of sources, including fecal matter and lawn fertilizer. The study will try to determine which is the culprit, Sawyer said, but regardless of the source, it is having a negative effect.

"In the larger picture, nitrate is nitrate, no matter where it comes from. It's not good for our water quality," he said.

Safe septics solutions

DENR supports local requirements to inspect and maintain septic systems.

Meade County Commission Chairman Bob Mallow of Black Hawk said there is definitely a problem, particularly in the Piedmont area, where many of the wells are shallow.

He said the whole Piedmont valley needs water and sewer systems.

County governments now do the inspections for new septic systems, which must meet state standards when they are installed.

Mallow said Meade County also is requiring new developments to have sewer systems. But he said the commission is reluctant to require inspections for existing septic systems.

Piedmont residents are reluctant to talk about their septics because they fear they will be forced to make costly improvements, Hemsher said.

In Pennington County, officials are getting tougher on septic standards in new developments, commission Chairman Jim Kjerstad said.

The county required the new Canyon Springs development off Nemo Road to cluster its septics and perform regular inspection and maintenance.

The Pennington County Commission also is beginning plans for a broad water-quality study of both groundwater and surface water.

The county in 2002 rejected mandatory inspections of existing systems after residents complained of the cost.

Kjerstad said the commission might revisit the inspection issue, but he wants to see how the city of Rapid City's new inspection requirement works.

Rapid City in 2006 began inspecting the almost 3,000 septic systems within the city limits and is finding that most of those checked so far are working well, according to Louie Arguello, who coordinates the program for the city Public Works Department.

The city requires all septics to be pumped out and inspected every three years. If problems are found, the homeowner must get the system repaired. The requirement also applies to homes within one mile of city limits.

Some residents don't know how their septics work and how to maintain them, Arguello said.

Gene and Audrey Solseth own Hills Septic, one of the companies in town that pump out septic tanks. Hills Septic also repairs problems.

Gene Solseth said septic systems work just fine when properly installed and maintained.

But if they're installed incorrectly or in the wrong location, they're bound to fail.

Caring about septics

Solseth, like DENR's Sawyer, said septics and drain fields built on fractured rock up in the Black Hills just don't do the job. Solseth's house sits on such a formation.

As much as he believes in septic systems, Solseth said if a city sewer line came to his neighborhood, he'd be the first one to hook up.

He said the city's inspection requirement hasn't meant any more business for him.

But Solseth is one businessman who wants more government regulation. As his crew worked to fix a septic system in Black Hawk on Wednesday, he said, "We should have an inspector here when we start, and another visit when we're halfway through and another when we finish."

Too many homeowners don't care about how their septic systems work as long as the water goes somewhere, he said.

"If you really care about groundwater, you have to have regulation," Solseth said.

A few miles away, Putnam and an assistant began collecting water samples from a test well next to Stagebarn Elementary School. Earlier samples from the well found nitrate    levels approaching the federal threshold for unsafe drinking water.

The next samples will test for more contaminants, including fecal coliform, other bacteria and viruses.

The test well is drilled 150 feet into the Minnekahta Aquifer. A few hundred feet to the west, homes dot the ridge where the Minnekahta limestone emerges. They all have septic tanks and drain fields.

To some, the study may seem like an academic exercise.

But for residents of Piedmont, who live below the Minnekahta outcrop, the situation is all too real. "Everybody gets nervous about coliform in the wells," Phil Anderson said. "We're all worried, and that's why we're trying to fix the problem."

Contact Steve Miller at 394-8417 or steve.miller@rapidcityjournal.com