TRURO — Out West, the saying goes that “Whisky’s for drinkin’, and water’s for fightin’.” In Truro’s ongoing debate about affordable housing at the Cloverleaf parcel, the water is for drinking, and the wastewater is for fighting.

On Monday, 77 residents who live near the Cloverleaf site on Highland Road sent a letter to the zoning board of appeals, outlining their concern that the development will increase nitrogen levels in local drinking water to dangerous levels. Attached to the letter is a 40-page report by Docs for Truro Safe Water, a group of seven M.D.s and holders of doctorate degrees in various specialties. (The group includes two medical doctors, an epidemiologist, a biology professor, two engineers, and a doctor of social work.) The report focuses on the danger of nitrogen in drinking water and argues for a tighter standard for nitrates than that used by the Environmental Protection Agency.

With conflicting estimates of the adequacy of wastewater treatment systems being advanced by the developer, town staff, outside engineers, and supporters and opponents of the project, the Independent spoke with several experts on water and wastewater in order to better understand the claims being made.

What’s Being Measured?

Tim Pasakarnis, a water resources analyst at the Cape Cod Commission, said that it is crucial to focus not just on numbers, but on what those numbers are measuring. “There’s a lot of milligram-per-liter [mg/L] numbers being thrown around,” said Pasakarnis, “and they don’t necessarily represent the same thing. So, for instance, you have the effluent nitrogen concentration — that’s what is coming out of a treatment system. That number is assumed to be 35 mg/L for a traditional septic system.

“Then you have site-wide nitrogen loading at a development site — that’s the effluent, plus nitrogen from fertilizer and storm runoff, divided by the volume of recharge that comes from rainwater on the site, and modified by the surface coverage of the proposed development,” Pasakarnis continued. Five mg/L is the Cape Cod Commission’s development standard, according to Pasakarnis. Standards for nitrogen in tap water are different, and not regulated by the commission, he said.

The ZBA ordered an independent review of the design for the Cloverleaf’s wastewater treatment system by the Horsley Witten Group, which found it adequate. Horsley Witten’s Mark Nelson said the system should reduce nitrogen to 5 mg/L.

What can be confusing is that these three kinds of measurements — effluent, site-wide loading, and water samples — are expressed in the same units, and in very similar numeric ranges. So, for instance, the developer says that a BioMicrobics system can produce effluent in a leaching field between 5 and 10 mg/L. The Cape Cod Commission’s site-wide loading standard for development projects is 5 mg/L. And the Docs for Truro Safe Water argue that the correct threshold for safe drinking water in a well is 5 mg/L.

Despite all three of those values being 5 mg/L, they refer to three different things measured in three very different places.

The Bar for Drinking Water

This could confuse anyone. One of the doctors told the ZBA, “We are trying to understand why the Cape Cod Commission recommends no more than 5 ppm, and the EPA accepts a standard of 10 ppm.”

Pasakarnis pinpointed the source of that confusion. The commission’s standard of 5 mg/L applies to site-wide nitrogen loading, he said, while 10 mg/L is the EPA’s standard for public drinking water coming from a tap.

One place where the Docs for Truro Safe Water and the water experts the Independent consulted were in clear agreement was on older septic and pre-septic systems as likely causes of nitrogen contamination.

“Truro is estimated to still have about 210 cesspools in operation,” says the Docs report — “about 10 percent of Truro homes…. Cesspools lack the ability to filter waste and the sewage eventually contaminates the surrounding soil. For this reason, cesspools are outdated and illegal.”

Brian Baumgaertel is director of the Mass. Alternative Septic System Test Center, located in Mashpee and managed by Barnstable County. He specializes in all kinds of septic systems.

“The current rules were put in place in 1995 — that’s Title 5 septic systems,” said Baumgaertel. “Before that, it’s an older protocol called Code-78, passed in 1978. Before that, it’s cesspools and cesspits. There’s still a lot of those out there. They should be pumped out every three to five years, but there’s no pumping requirements in the state code.” Baumgaertel said he does not know of any local pumping regulations on the Cape.

“People will claim, ‘I’ve got by 50 years without a pump-out!’ ” Baumgaertel said, when, in reality, “the system has failed, and they don’t know it.”

Because septic upgrades cost between $12,000 and $50,000, according to Baumgaertel, the only time an upgrade is required is when a property is sold. That’s when the gains of appreciation are being reaped, so it’s the least painful time to require such a large, unglamorous investment.

Passing on a property within a family doesn’t trigger an inspection and upgrade, however. That’s how cesspools are effectively “grandfathered in.”

Nor is there a testing regime to discover failed systems, said Baumgaertel. That’s because, if an inspection were to discover a failed system, the home owner immediately becomes obligated to bring it up to current codes. Health departments hesitate to check on older systems when findings could cost individual home owners tens of thousands of dollars.

“I’m on the Mashpee Board of Health,” said Baumgaertel. “We can require any home owner to get an inspection at any time. That’s a power that I can say is very lightly used. I’m not aware of any Cape town that’s doing residential inspections on any kind of schedule.”

The benchmark number for a properly operating Title 5 residential septic system is 35 mg/L of nitrates going into the tank, and 26.25 mg/L of nitrates discharged in the leaching field, said Baumgaertel. In reality, he said, what’s going into the tank is more like 60 mg/L, a number the state D.E.P. confirmed is typical. “We’ve found numbers as high as 120 mg/L in test sites,” he added.

That means undetected failed cesspools are likely dumping large amounts of nitrates into the aquifer — possibly 80 mg/L or more. A few failed cesspools could contribute more nitrates than the entire Cloverleaf development.

Failed systems aren’t easy to solve, said Baumgaertel. “The county has a loan program to help people replace their failed septic systems. It’s a 20-year loan at 5 percent.” That helps spread out the pain, but it’s still an expensive undertaking. (For more information on that program, see barnstablecountysepticloan.org.)

A 5 mg/L Standard?

When the Docs for Truro Safe Water report argues for a 5 mg/L nitrogen limit for well water, it is setting a standard that would be difficult for Truro to meet.

To arrive at their standard, they draw on a variety of studies on cancer incidence as associated with nitrates in drinking water. Emerging science, they say, suggests a new standard is needed.

Their report, however, doesn’t cite any jurisdiction anywhere that currently has a 5 mg/L standard for drinking water. The Independent attempted to contact the Docs for Truro Safe Water, but did not receive a response by press time.

The World Health Organization and the European Environment Agency use a standard slightly higher than the EPA’s 10 mg/L. So does New Zealand. Canada uses the 10 mg/L standard. The Independent could not identify any jurisdictions with a 5 mg/L standard.

There may be such jurisdictions. Or maybe Truro will be the first.

To really clean up the water, though, someone’s going to need to dive into the cesspool problem.