Here’s why thousands of Cape Cod homeowners might need to replace their septic systems

State regulatory changes would require some homeowners to upgrade their septic systems to address water pollution.

Jonathan Wiggs/Globe Staff
The Barnstable Clean Water Coalition installed a KleanTu septic system in the Sandy Shores neighborhood around Shubael Pond in Marstons Mills. On Cape Cod and in many other places, poorly maintained and aging septic systems are a primary cause of the nitrogen pollution that plagues coastal ecosystems.

Thousands of Cape Cod homeowners may need to replace or upgrade their septic systems over the next few years, thanks to proposed state regulatory changes aimed at reducing nitrogen pollution in coastal areas. 

While that nitrogen can come from lawn fertilizer or agricultural and stormwater runoff, septic systems are a significant source, according to the Department of Environmental Protection (MassDEP).

In addition to amending Title 5, a regulation governing septic systems statewide, the agency is also looking to provide a watershed permitting approach to help control nitrogen and other pollutants entering bays and estuaries.

Expected to go into effect in early 2023, the initiative also targets Martha’s Vineyard, Nantucket, and parts of southeastern Massachusetts.

Why is nitrogen a problem?

“The problem really is nitrogen essentially is a fertilizer, and if you fertilize too much, you get too much growth. And in this case, we’re putting fertilizer into particularly our saltwater estuaries, and that’s causing rapid growth of algae,” explained Zenas “Zee” Crocker, executive director of Barnstable Clean Water Coalition, in an interview with Boston.com.

Cape Cod:

The result, he said, is a buildup of “muck” in the water.


The problem isn’t just cosmetic: When aquatic plants grow densely as a result of excess nutrients — a process called eutrophication — they can deprive existing plants and animals of oxygen and habitats needed to survive. 

“I think what it means is that recreationally, [Cape Cod’s water] becomes less attractive, and it becomes less attractive for year-round residents,” Crocker said. “It becomes less attractive for the blue economy — you know, visitors, tourists, the economy that really drives most of Cape Cod. And then besides that, it really is very, very damaging to things like our shellfish industry.”

What do the new regulations entail?

Crocker called current septic regulations imperfect, adding that Title 5-compliant systems don’t do much to reduce nitrogen and other nutrients in Cape Cod’s sandy soil. 

“It’s technology from the 1860s, 1870s in France,” he said. “It’s really, in my mind, only one step away from outhouses in the old days, and the technology that’s been used since the Egyptians: You dig a hole in the ground, and that’s where you put your waste, and then you forget about it. Well, that’s fine until you have the kind of density that we have now, the kind of populations that we have now.”


MassDEP’s initiative would create Nitrogen Sensitive Areas, places “where the discharge of nitrogen through a septic system would be detrimental to the environment or public health,” according to the agency’s explanation

All septic system owners in those areas would have to upgrade within five years, unless their community seeks a watershed permit. The 20-year permit is typically based on a community’s long-term plan to restore and protect water quality, according to MassDEP. 

Municipal sewer expansion could be part of a community’s plan, and BCWC is “bullish” on the idea, Crocker said.

“The problem is it takes decades … and most communities simply don’t have the money to put in the sewers,” he said. “By our estimates, it can cost anywhere from $100,0000 to $200,000 per parcel to expand and put in municipal treatment.”

Upgraded septic system technology can be faster to deploy and more cost-effective, Crocker explained. He estimated it will cost between $30,000 and $35,000 for a typical three-bedroom household to update or replace their system.

Financial assistance for septic system upgrades is available through the Community Septic Management Program, MassDEP noted.

What’s next?

MassDEP will hold three public hearings this week and next, with the first session scheduled for Wednesday at 6 p.m. The state will also accept written comments through 5 p.m. on Dec. 16. 


Crocker said he would like to see work start with the septic systems closest to the water’s edge, and he believes the regulations need to be revisited more frequently as technology improves.

Still, “perfect shouldn’t be the enemy of good,” he emphasized.

“These are good regulations; we think they need some tweaking to make them even more impactful and more timely, but we think it’s a step in the right direction,” Crocker said. 


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