October 25, 2015
Research: Septic systems ‘primary’ source of river, reef pollution
By Tyler Treadway
Septic systems are a primary source of St. Lucie River pollution, according to a soon-to-be-released study Martin County-commissioned from the Florida Atlantic University’s Harbor Branch Oceanographic Institute.
The finding refutes an opinion popular with some local officials and environmentalists that Lake Okeechobee discharges and fertilizer in agricultural runoff are the primary sources.
“We’re not saying there are no pollutants from (agriculture); there are,” said Brian Lapointe, a Harbor Branch research professor and study team leader. “But sewage from septic tanks is a significant contributor, in fact a primary contributor, to nutrients damaging the estuary and the reefs offshore. And it’s not just nutrients: (Septic systems) also contribute bacteria that contaminate the water.”
Final data will be available when Lapointe presents his findings at the Martin County Commission’s Nov. 3 meeting. Also at the meeting, county staff will propose a $30.7 million project to switch 2,145 residences from septic to sewer.
Hitting ‘hot spots’
Along the 156-mile lagoon, septic systems dump more than 4.4 million pounds of nitrogen each year, Lapointe said. That’s the weight of the Space Shuttle — fully loaded with its external tanks, solid rocket boosters, crew and cargo.
The Martin County study focuses on two suspected pollution “hot spots”: Old Palm City and the Golden Gate neighborhood, both areas with a high concentration of aging septic systems.
Two other sites where homes are hooked to sewer systems — in Jensen Beach and northern Palm City — were monitored for a comparison.
The researchers looked for:
- Nitrates and phosphates, nutrients that in high concentrations spur algae blooms, which sometimes are toxic and can lead to fish kills.
- The artificial sweetener Sucralose, which indicates a human rather than animal source of fecal contamination.
- The researchers collected algae from ditches, the estuary and reefs outside the St. Lucie Inlet using chemical properties known as “tracers” to determine if the samples were fed by nutrients from farm fertilizers, residential fertilizers or septic systems.
From tanks to reefs
“We confirmed that the areas with a high concentration of septic systems had nitrates and phosphates in the groundwater and in the ditches leading to the St. Lucie,” Lapointe said. “Then we found that sewage is getting into the estuary and being taken by tides out to the reefs, where it’s causing a chain reaction that’s literally killing the reefs.”
Lapointe explained the “chain reaction” as nitrates and phosphates causing algae to grow on reefs. “The more algae grows, the more you get things that eat algae, and the things that eat the things that eat algae.”
The reefs are now home to several types of sponges and sea urchins, as well as bright orange patches of “boring sponge,” Lapointe said, “that you never saw 20 or 30 years ago.”
Making the switch
A 2001 study found 13 high priority areas in the county’s service area where septic systems should be eliminated, including Old Palm City and Golden Gate. Since then, the county helped homeowners switch about 450 septic systems to sewers in the Seagate Harbor and Lighthouse Point area of Palm City and about the same number in North River Shores.
The area served by the Martin County Utilities and Solid Waste Department still has about 16,000 septic tanks, said director John Polley. Stuart has another 1,450 or so septic systems, said David Peters, the city’s assistant director of public works.
The county’s proposed septic-to-sewer project would include 1,078 residences in Old Palm City, 775 in Golden Gate and 292 in North River Shores.
The utility department would pay 30 percent of the cost; property owners would pay 70 percent, about $11,750 per parcel.
“The fix is expensive,” Lapointe said, “but living in paradise ain’t cheap.”
IF YOU GO
Brian Lapointe, a research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute at Fort Pierce, will talk about his team’s study on the impact of septic systems on the St. Lucie River estuary and nearshore reefs.
What: Martin County Commission meeting
When: 9 a.m. Nov. 3
Where: Commission Chambers, 2401 S.E. Monterey Road, Stuart
About Tyler Treadway:
Tyler is an environmental and lead Indian River Lagoon reporter at Treasure Coast Newspapers.