WELLFLEET — The state Dept. of Environmental Protection (DEP) is proposing major changes to Title 5 that, if adopted, could force home owners near sensitive bodies of water to upgrade their septic systems with nitrogen-reducing technology at their own expense or require towns to adopt nitrogen-reduction systems at taxpayer expense.

“It is a huge deal,” said Andrew Gottlieb, executive director of the Dennis-based Association to Preserve Cape Cod. “It finally gets to the core of the problem — that the standard Title 5 systems are the source of our problem.”

Septic systems are responsible for 82 percent of the nitrogen-polluted wastewater entering Cape Cod estuaries, according to a 2017 study by the Mass. Estuaries Project.

The proposed changes would create designated nitrogen sensitive areas (NSAs) wherever there exists “any watershed to an embayment or sub-embayment that is the subject of a nitrogen Total Maximum Daily Load (TMDL),” according to a fact sheet released by the DEP on June 1. A TMDL establishes the total amount of nitrogen that is allowed in a body of water before it fails to meet EPA-defined water quality standards.

For years, towns have been slowly working to come up with plans for reducing nitrogen pollution. A 2011 lawsuit by the Conservation Law Foundation, which sued the federal Environmental Protection Agency for inaction on pollution on the Cape, has not done much to help. In 2015, the Cape Cod Commission’s revised water management plan imposed legal requirements for each town, according to the Conservation Law Foundation.

Many Cape towns are now closer to executing nitrogen-reduction plans, but the proposed changes in the DEP rules would be real motivation to get the job done, Gottlieb said. Towns that have DEP-approved watershed permits can be exempted from new Title 5 septic system requirements.

Wellfleet’s Watershed Plan

The Wellfleet Select Board submitted the final draft of the town’s targeted watershed plan at its June 23 meeting. Four representatives of the DEP were present at the meeting, including Commissioner Martin Suuberg.

The plan will now be reviewed by the DEP and the Cape Cod Commission, and there will be a public comment period.

“I wish we had some fireworks going off,” said Chair Ryan Curley of the select board. “Just getting this far represents the culmination of 12 years of work.”

There are currently 30 watersheds on the Cape with EPA-approved nitrogen TMDLs. A draft TMDL for Wellfleet Harbor will soon be issued for public comment by the DEP.

“We ultimately have the responsibility to ensure that concrete actions are taken in a timely way to address nitrogen contamination and ensure that critical water resources meet water quality standards,” said Suuberg.

One proposed change to Title 5 would require any septic system within an NSA to be updated to include the “best available nitrogen-reducing technology” within five years of the NSA designation. The technology referred to is an alternative type of septic system certified by the DEP.

Towns with watershed permits will not need to replace all the septic systems within their NSAs. They will be given the opportunity to address water quality through other innovative approaches.

The watershed permit option “gives almost all the control to the towns,” said Gottlieb. “Watershed permits can be scaled and modified to meet the needs of individual towns. It gives us the ability to provide meaningful relief to our individual residents, and not impose septic burden upgrades on them.”

The watershed permit requires towns to monitor and report results of implemented strategies over a 20-year period. If those strategies do not meet nitrogen mitigation requirements, the towns must modify their plans.

Wellfleet’s draft plan includes strategies for reducing nitrogen in nine vulnerable sub-watersheds. Those strategies are consistent with the Cape’s 208 Plan, which was approved in 2015 to comply with the Clean Water Act.

Scott Horsley, a water resources consultant, presented two approaches for watershed management in Wellfleet’s plan at the June 23 meeting.

The first “hybrid” approach incorporates a variety of methods that would function throughout the town to reduce nitrogen pollution. They include installation of enhanced innovative and alternative septic systems and permeable reactive barriers, fertilizer mitigation, stormwater reduction, ecological restoration of Herring River and Mayo Creek, consideration of aquaculture and its natural ability to reduce nitrogen loads, and construction of a centralized sewage system that includes a collection and treatment plant at a location still to be determined.

In this approach, centralized sewering would encompass the affordable housing project at 95 Lawrence Road as well as the Harborside Trailer Park and a small portion of the town in the developed areas of Duck Creek and the Cove. The estimated cost of this hybrid approach is $106.6 million.

A second approach, referred to as “traditional,” incorporates innovative and alternative septic systems and construction of a centralized sewage system with a collection and treatment plant.

In this approach, centralized sewering would encompass 95 Lawrence Road, the Harborside Trailer Park, and a larger portion of the town in the areas of Duck Creek, the Cove, Drummer Cove and Blackfish Creek, Wellfleet Harbor, and Loagy Bay. The estimated cost of the “traditional” approach is $237.5 million.

“By having a balanced plan with a lot of different technologies, the town is extremely well served,” said Curt Felix, chair of the Wellfleet Clean Water Advisory Committee.

The Cape Cod Commission will review Wellfleet’s draft watershed plan to ensure consistency with the 208 Plan. Public feedback will be sought.