EASTHAM — The town and a volunteer property owner, Peter Dobyns, are participating in a wastewater treatment experiment that could alter the finances of controlling nitrogen contamination.

The experimental Eastham site is the 15th “layer cake” leach field system to be permitted in a Mass. Dept. of Environmental Protection (DEP) pilot program, and the first of its kind on the Outer Cape.

The layer cake design involves layering sand and wood chips in a septic leaching area. The carbon found in wood chips is a vital component of the denitrification process. Across all the layered systems installed thus far in the pilot program, there has been a 72-percent nitrogen removal average, with some systems removing more than 90 percent.

The Cape Cod Area-Wide Water Quality Management Plan, known as the 208 Plan Update, requires all Cape Cod towns to document their actions to improve water quality and reduce pollution. In Eastham, all wastewater treatment takes place onsite in septic systems — there is no centralized town sewer system. As reported by the Independent last April, the layer-cake design is one of many projects Eastham has under way to reduce contaminants in the Nauset estuaries.

The fragile coastal ecosystems of the Outer Cape depend on clean water and nutrients. In excess, however, beneficial nutrients can pollute the area’s interconnected groundwater, ponds, and estuaries.

The Massachusetts Estuaries Project found that septic systems are responsible for 80 percent of the controllable nitrogen load on Cape Cod. The authors of a 2012 Barnstable County Dept. of Health and Environment report noted, “Cape Cod’s designation as a sole source aquifer means that all drinking water sources are part of a contiguous groundwater supply that hydraulically connects wastewater discharge sites to drinking water sources.”

The Association to Preserve Cape Cod’s 2020 State of the Waters project found that “most of the Cape’s coastal embayments and many freshwater ponds and lakes are suffering from water pollution.” Excess nitrogen in coastal waters and phosphorus in fresh water cause eutrophication, a process that depletes oxygen from water and leads to microscopic algae blooms. Eutrophication can harm or kill aquatic life.

The layered leach field was designed for the multi-unit Dobyns property at 999 State Highway Route 6 by J.C. Ellis Design and is being installed by Brundage Site Work. Both are Eastham-based companies.

“We are excited to be chosen for this,” said Corey Brundage. “This opportunity is huge. It could open options to allow this design to be accepted into the wastewater management DEP code and be able to be used routinely outside the pilot program.”

The town of Eastham is kicking in about $5,000 for monitoring and testing at the site. Dobyns, the property owner, is responsible for the cost of installation, estimated at $20,000 to $41,000. The layer cake is more cost-effective than other denitrification systems, said Dobyns, who lives in Duxbury. He was in the mountains of Colorado during the installation.

The town chose the site, said Jane Crowley, director of health and environment, in hopes of benefiting the Nauset estuary by reducing nitrogen. If it is successful, she said, they will try to use the model on a wider scale.

The layer-cake system, considered “innovative/alternative” (I/A) by the DEP, is not yet permitted for general use. Before any I/A system is approved, it must complete pilot and provisional phases.

Funded by a DEP grant, the Mass. Alternative Septic System Testing Center (MASSTC), a division of the Barnstable County Dept. of Health and Environment (DHE), began experimenting with layer-cake leach fields in 2014.

According to the Barnstable County Septic Management Program, there are 421 innovative and alternative septic systems installed on the Outer Cape. Besides being a research facility, MASSTC is also a third-party testing site for such systems.

State regulations for the installation, use, and maintenance of onsite septic systems under Title 5 do not address nitrogen removal. Many I/A systems designed to reduce nitrogen output are at various phases of DEP approval, but most are proprietary and come with a hefty price tag.

NitROE is one example of a patented I/A technology that, like the layer cake, uses wood chips to remove nitrogen. The NitROE tank supplements existing septic tanks and can cost anywhere from $18,750 to $55,000 for installation. NitROE is currently under provisional DEP permit status, which means it has completed the initial pilot stage of permitting but has not yet been granted a general-use permit.

If they work, layer cakes are a simple amendment to a standard septic system, said George Heufelder, project specialist at MASSTC and former director of DHE. Compared to other alternative systems, layer cakes are simple to install and have lower operating costs, he said. Because the layer-cake concept is not proprietary, you don’t have to go through a specific company for materials and installation. Unlike most I/A technologies, there are few mechanical parts. You can buy wood chips anywhere, you can get the parts at any hardware store, and you can get any installer, said Heufelder. He estimated the added cost of the layer cake at “about $1,500 beyond a standard Title 5.”

Loans are available through the county for home owners to replace failed septic systems with nitrogen reducing I/A systems.