Leftover water plant sludge, horse manure and mulched construction material discards don't sound like welcome additions to most South Florida backyards.
But they are allowed in rural pockets of Palm Beach County where there's a mix of homes, nurseries, crops and horses sharing land that allows both agriculture uses and residential development.
Lime sludge, horse manure and "recycled" construction materials referred to as RSM have been mixed in with soil and used as fill for land in areas such as The Acreage, west of Royal Palm Beach.
Concerns about potential effects on well water, due to what may leach out of this influx of fill material, has raised new questions in The Acreage.
How much of the fill material gets used, where it's applied and who keeps tabs on its use are among the issues that state and county regulators are being asked to address.
"It is an issue of concern," said Tanya Quickel, administrator of the Indian Trail Improvement District, which helps manage water supplies in The Acreage. "There are several types of materials … that are potential problems here."
County health department and state environmental regulators allow the use of these types of fill, with some limits on where and how much can be applied.
But local activist Patricia Curry, who lives in The Acreage, contends more attention needs to the potential harm that could come from what's being spread on the land and how it could affect the water supply.
"I consider the lime sludge material unacceptable," Curry said. "There are other materials being used as fill in the community as well. This has been an on-going story."
Lime sludge is a byproduct of treating groundwater to get it ready for the tap.
While "sewage sludge" from wastewater plants is considered too much of a pollution risk to spread untreated on land, Florida allows spreading lime sludge on property as an alternative to dumping it in a landfill.
Arsenic and barium are some of the potential contaminants from lime sludge, but testing has shown that they are not found in levels considered a significant threat to human health or a risk of groundwater contamination, according to the Florida Department of Environmental Protection.
"Lime sludge can be beneficially land applied without the need for additional analysis and without the need for specific approval by the Department," DEP spokeswoman Cristina Llorens said.
The Palm Beach County Health Department also doesn't object to properly applied lime sludge.
"There was nothing in it that would have an adverse effect," Health Department spokesman Tim O'Connor said about lime sludge. "It doesn't really pose any threat to (drinking) water."
Despite state assurances, the Indian Trail Improvement District in a letter this month to Palm Beach County commissioners raised concerns about "the potential for irresponsible and unregulated" use of sludge from county water plant treatment ending up on local properties.
"It goes without saying that this type of activity may pose a threat to public health and the environment," District Board President Michelle Damone wrote to the county.
The county maintains that its lime sludge "is a safe material that can be land applied," according to County Utilities Director Bevin Beaudet.
Excessive dumping of horse manure from nearby Wellington on land in Loxahatchee has been a problem through the years.
Enforcing restrictions on how much can be spread on land and where it can be applied remains a difficulty.
"The real concern is related to water quality because most of the homes are on wells," Quickel said.
RSM can include ground up wood, concrete, plastic and other construction material discards.
Florida allows adding RSM to soil in residential communities, as long as tests show it doesn't pose a health risk, according to the DEP.
The state Health Department in 2010 found no connection between fill materials used in The Acreage and a cancer cluster. The Health Department ultimately identified no cause for elevated rates of brain cancer among children between 2005 and 2007 in The Acreage.
"It was all factored in (and) there was no link," O'Connor said.
Curry still questions whether state and local regulators are giving enough scrutiny to what's allowed as fill material.
"Sometimes it feels, in numerous areas, as the county and state believe our area is a great dumping ground," Curry wrote to the DEP.