UPPER SADDLE RIVER, NJ.- Har Shalom Cemetery was built on a hillside in Rockland County, New York, along a winding rural road a short walk from the border of New Jersey. Covering nearly 20 acres, it is expected to become the largest cemetery in the country reserved solely for ultra-Orthodox Jews.

Across the street, a sprawling facility where women will be able to immerse in a mikvah, a ritual Jewish bath, is under construction on land in New York that abuts backyards in Upper Saddle River, New Jersey.

The developments were approved by zoning and planning boards in New York, in part based on a federal law adopted in 2000 to safeguard religious entities from burdensome or discriminatory land-use regulations.

But neighbors in New Jersey and in New York who are now fighting to block, or scale back, the projects say the approval and oversight process has been blind to an arguably greater power: Mother Nature.

“We are observing an environmental train wreck in slow motion,” said Heather Federico, who lives in nearby Mahwah, New Jersey, and is a member of a community group opposed to both ventures.

The projects have separate developers but, according to opponents, present similar risks: overburdening the region’s already strained sewage pipes and jeopardizing the safety and availability of ground water in an area where most homes rely on wells for gardening, bathing, cooking and drinking.

Last week, Upper Saddle River officials said that they had hired a private lawyer to focus on residents’ environmental concerns and had scheduled meetings with state and federal leaders in New York and New Jersey.

The cemetery, in Airmont, New York, has been granted approval for more than 10,000 burials, or roughly 1,000 for each acre of land that has been cleared — a density Har Shalom’s manager, Michael Moskowitz, said would take decades to reach.

Still, neighbors are pressing for increased testing of well water, concerned that leachates from the large volume of decomposing matter could filter into wells and the nearby Saddle River, presenting a health threat.

The interments are considered green burials: no embalming fluids are used; bodies are placed in simple wooden caskets; and the graves are not lined with concrete vaults or lids, facilitating decomposition and the body’s return to the earth.

Moskowitz questioned whether the opposition had more to do with bias than with environmental safety.

“They are fighting every single Jewish project,” Moskowitz said. “What does it show? That you don’t like my existence.”

Two decades ago, a plan to build a yeshiva, housing and dormitory complex on the same rural property was similarly unpopular, as was a plan to construct a Christian church years before that.

Opponents acknowledge the inherent clash of cultures that exists between residents of one of the wealthiest regions of New Jersey and the tight-knit Orthodox religious community that holds fast to its traditions. But they insist that their objections are rooted in environmental concerns and frustration over what they consider a fast-tracked approval process weighted in favor of Rockland County’s thriving ultra-Orthodox Jewish community.

“It was designed as a shield,” William Spencer, of Upper Saddle River, said about the religious land-use statute, “but it’s been turned into a sword.”

There have been few burials at the cemetery, but a large funeral and graveside service last month for a popular Hasidic singer, Michoel Schnitzler, drew hundreds of mourners, leading traffic to back up along the narrow country road. After the service, several neighbors complained that a makeshift latrine had been dug at the edge of the cemetery after Har Shalom’s single portable toilet became overwhelmed by the crowd, Rockland County health department records show.

Last week, the projects became a focal point of a lengthy council meeting in Upper Saddle River.

Grace Clark urged the borough to begin collecting and comparing well-water testing data to create a baseline record of water quality.

“I’m very concerned about my water,” said Clark, of Upper Saddle River, adding that she lived beside a brook that was downhill from the cemetery. “My kids play in it all the time.”

The second project, the Hillside Mikvah, is being erected on land that once held two homes. It is slated to include more than 50 shower rooms and eight private pools, which, according to Orthodox custom, are used by women after their menstrual cycles and before marriage. Builders have already dug three wells but have not installed a new water line, which was discussed in an engineering report as a way to avoid the facility’s overreliance on well water and to fight fire, if needed, in a region with no hydrants.

A spokesperson for Veolia, the company that supplies water to the area, said that an application to install a new water main line was pending; representatives of the mikvah did not return calls or emails.

In granting approval for the mikvah, the planning board in Ramapo, New York, voted to overrule Rockland County officials, who had recommended denying the project because it exceeded some land-use guidelines.

“Applying those standards to this religious facility would impose an unreasonable burden and require a reduction in the size of the community mikvah and its ability to meet the demonstrated need of the religious community it will serve,” the Ramapo Planning Board wrote.

Gordon Wren, 75, was a firefighter for more than five decades and worked for 35 years as an emergency-services fire coordinator for Rockland County. He said he did not relish his role as an opponent of projects being built to serve his neighbors in the Orthodox Jewish community. But he said he was concerned about the safety and availability of a shared communal resource — water — and the volume of waste heading into pipes with a history of being pushed beyond their capacity.

“It’s beyond bad planning,” Wren, of Ramapo, said.

New York’s Department of Environmental Conservation has twice issued violations to the mikvah’s developer; last year, the department ordered all work to stop because of a missing permit. The problems were fixed, and DEC’s legal team is evaluating whether to issue fines that can exceed $37,500 for each of the days the project was out of compliance, a spokesperson said.

A spokesperson for New York State’s Division of Cemeteries said it does not regulate religious cemeteries and had no information about the risk of decomposed matter to well water.

There is little scientific research concerning the potential impact of cemeteries on human health and the environment, according to a recent report produced for the Baltimore County Department of Environmental Protection and Sustainability.

In 1998, the World Health Organization reviewed “the current state of knowledge” about the decomposition of human corpses in soil and the likelihood that bacteria and viruses, including polio, could seep into groundwater and spread waterborne diseases.

“If the cemetery is located in a porous soil type, such as sand or gravel, movement of seepage can be rapid and mix easily with the groundwater beneath the site,” the report found.

Other types of soil, however, can efficiently absorb and filter pathogens when bodies are buried above the water table, the report found. “The pollution potential from cemeteries is present, but in a well-managed cemetery with suitable soil conditions and drainage arrangements, the risk is probably slight,” the WHO found.

Caitlyn Hauke of the Green Burial Council, which advocates for simple, environmentally friendly burials, said that pathogens from cemeteries were unlikely to travel far if graves were dug at “an appropriate depth.”

“Soil is really a great filter,” said Hauke, an infectious disease microbiologist. “It clings onto a lot of the elements that get released during decomposition, so they’re not going to travel real far from where that body rests.”

As for the mikvah, Michael Specht, Ramapo’s supervisor, said that it was a permitted use for the area and that its owners had obtained all necessary permits. He acknowledged the frustration of New Jersey residents who might feel that they have limited tools to influence projects so close to the states’ shared border.

“Just as we have no say if it’s in New Jersey,” he said.

This article originally appeared in The New York Times.