Starting Jan. 1, people renovating or building new houses near the Narrow River or the South County salt ponds will be required to install new septic systems at dramatically higher costs than in the past.

Also facing big new bills are homeowners throughout the state who must replace failed septic systems or cesspools on small lots that also have drinking water wells.

In a new effort to reduce the flow of household pollution into the groundwater, wells and nearby water bodies, the state Department of Environmental Management will require many homeowners to install new, high-tech septic systems that could cost $25,000 or more — or two and a half times the cost of conventional systems.

More homeowners will be affected, probably next summer, when the state’s new cesspool phase-out law goes into effect.

The cesspool act, starting on June 1, will require homeowners to replace cesspools that have failed, or those used for a commercial enterprise or multi-family dwelling, and those within 200 feet of tidal water, a public well or a reservoir.

While many of the cesspool owners will be able to install a conventional septic system at a cost of roughly $10,000, some of them will also be required to install more efficient systems that could cost two or three times more.

The DEM estimates there are 50,000 cesspools in use in Rhode Island and the new law will require about 3,000 to be replaced during the next five years. The law requires all cesspools to be replaced by 2013.

The new requirements are part of a statewide effort to reduce the flow of nitrogen into local waters. Communities have already spent millions to reduce outputs from sewage treatment plants and homes connected to sewers have faced steadily rising bills.

The good news is that most coastal communities have set up wastewater management districts that can loan state money to homeowners for septic system replacements at an interest rate of 2 percent.

In the last eight years, the state’s Clean Water Finance Agency has loaned $4 million to communities that in turn provided loans to homeowners replacing cesspools and septic systems. So far the loans have been available in Charlestown, Glocester, Block Island, North Kingstown, South Kingstown, Johnston, Jamestown, Narragansett and Tiverton.

Anthony B. Simeone, executive director of the agency, says he expects the demand for state loans to go up when the new regulations go into effect, so he is setting aside $2 million for next year. Governor Carcieri has pledged even more in a 2008 bond issue.

Communities must have waste water management districts to distribute the loans, and applicants must meet DEM standards, Simeone said. But there are no income guidelines.

“We focus on improving groundwater,” Simeone said. “Whether someone makes $20,000 or $100,000 is immaterial to us.”

With the new regulations, even the traditional nomenclature is changing. What most people would call a septic system, the DEM for years has called an individual sewage disposal system, or ISDS. But now the agency has a new title for the devices: onsite wastewater treatment systems, or OWTS.

During the last two decades DEM made many piecemeal changes to its septic-system regulations, but this year the agency completely rewrote the rules.

Last summer, the DEM held a series of hearings and workshops around the state to get public input on the new rules, but attendance was low — a few representatives of environmental groups, as well as those in the business of designing and installing septic systems. So the new changes may surprise many of those who will have to pay for them.

“I would say the changes are fairly comprehensive,” says Russell Chateauneuf, chief of the groundwater and wetlands protection programs at the DEM. “The last time we changed the rules to this level was probably 18 years ago.”

The DEM filed the new regulations with the secretary of state last week.

Chateauneuf said the biggest changes are designed to reduce the flow of nitrogen into the Narrow River and the South County salt ponds. Biologists have known for years that the river and the ponds have been receiving too much nitrogen from the cesspools and septic systems in the neighborhoods that crowd their shores.

One pond, Green Hill Pond, is closed to shellfishing because of the pollution. Study after study has shown that nitrogen of human origin has helped kill off valuable eelgrass beds, which support fish life, and grow more macro algae, which harm marine life, in all the ponds.

The problems have worsened as summer cottages were converted to year-round use, putting more pollution into the ground, where it flowed to the ponds.

Cesspools were commonly used for household waste in shoreline communities. In 1968, new cesspools were prohibited by the state. Cesspools are essentially tanks that hold waste and allow it to drain into the ground without any treatment.

Septic systems during the last several decades had two main components: a tank to hold waste and allow settling and some treatment by bacteria, and a leach field or galleys to disperse liquid waste into the ground, where bacteria provides more treatment.

In the last decade, the state has gradually allowed use of new, alternative septic systems that incorporate pumps, sand filters and other technology to more thoroughly treat household waste and remove more of the nitrogen. Some of the systems require regular maintenance to operate properly.

Chateauneuf says there are about 3,000 such advanced systems in use in Rhode Island and several companies are providing regular maintenance. They were largely used by owners of substandard lots where better treatment was necessary.

“Over the last 10 years we’ve been building capacity for these new systems,” Chateauneuf said. “Today, hundreds of people are licensed to design them. Five systems have been approved. Hundreds of installers are trained. And we actually have companies that came into existence in the last several years to maintain these systems —they have pumps and electrical controls and they require some cleaning.”

Chateauneuf said many of the alternative systems now in use were designed to overcome problems with small lots or nearby waters, so they have extra features, such as bottomless sand filters, that make them more expensive than basic denitrifying septic systems, and drive their costs up to $30,000 or $35,000.

He said he hopes the typical nitrogen-reducing systems will cost $20,000 to $25,000 and that prices might go down as there is more competition. Nearly all lots south of Route 1 will require the systems, but many areas just north of the highway will be affected too.

Currently the DEM issues permits for 2,500 new and replacement septic systems annually, Chateauneuf said. The agency said it expects the new rules to increase that total by about 10 percent each year.

For those who can’t afford the upgrades, the department will grant extensions of up to five years, or until a property is sold.

The cesspool phase-out law and the cost of the new systems have already become part of a battle in Portsmouth over DEM demands to clean up sewage in the Island Park, Portsmouth Park and Common Fence Point neighborhoods.

The DEM wants the town to provide sewers in the neighborhoods. Many residents were opposed to the costs. Some also objected that sewers would only invite more development. Some of the opposition waned, however, when it would became clear that at least 100 homes will be ordered to replace cesspools near the water and the costs of individual septic systems could be higher than the costs of providing sewers.

The new rules can be found at www.dem.ri.gov/pubs/regs/regs/water/owts08.pdf. Maps of South County areas where the stricter standards kick in can be found at the end of the document.

plord@projo.com