A new 16-acre stormwater treatment area beside Taylor Creek is designed to reduce the amount of nutrients and other pollutants reaching the Indian River Lagoon from two St. Lucie County communities.
The Sheraton Plaza Stormwater Treatment Area received final acceptance from the St. Lucie County Board of County Commissioners on Sept. 15. The facility includes multiple treatment cells, wetlands and dry detention areas designed to hold and treat stormwater before it reaches the lagoon.
The project began after the South Florida Water Management District approached St. Lucie County about replacing outdated pipes that were contributing to stormwater discharges near Taylor Creek.
But the county decided replacing the pipes alone would not address the broader water quality issue, said Jim Lappert, the county's Water Quality Division director.
"We decided not just to replace the pipe, but we decided to build this STA, this stormwater treatment area, so that as the water leaves these older communities, it doesn't just discharge directly into the C-25 and then to the Indian River Lagoon. It actually is held in this new STA. The water is cleaned, which will improve water quality downstream in the IRL," he said.
The treatment area serves the Sheraton Plaza community and also captures some runoff from Harmony Heights. The project is located about 1.5 miles west of the Taylor Creek spillway, which discharges into the Indian River Lagoon near the St. Lucie Inlet.
The size of the facility was driven in part by the amount of water coming from the surrounding communities, Lappert said.
"By making it this large, this 16 acre facility, not only catch stormwater from the Sheridan Plaza community, we actually catch a little bit of water from the Harmony Heights community also. So we're keeping a lot of dirty water out of the Indian River Lagoon and we felt like the size of it was important because there's a lot of water draining from the communities," he said.
The wetlands and detention areas are intended to slow the movement of stormwater and give vegetation time to absorb nutrients such as nitrogen and phosphorus before the water leaves the treatment area.
"Rather than that dirty water directly discharging to the C-25 or the Taylor Creek into the Indian River Lagoon, those nutrients kind of get held back and the plants in the STA will help us by absorbing those nutrients. And so you know, that's the key factor here is that when the water eventually discharges to the Indian River Lagoon, it's much cleaner," he said.
The county estimates the STA will reduce phosphorus by 77 pounds per year and nitrogen by 498 pounds per year.
Finding land suitable for a project of this type can be difficult, but the Taylor Creek property provided a direct connection between the surrounding drainage areas and the waterway, Lappert said.
"In this day and age, it's hard to find good property to do these kind of projects and this one was ideal because the water drains from these older communities can be held right next to the C-25 and so it does a really effective job at holding back that water before it has the negative influence," he said.
The project also replaced outdated outfall pipes with a new 72-inch pipe at the request of the South Florida Water Management District.
The district will monitor and test the area to determine whether the treatment system affects water quality downstream.
"We will be watching that and seeing if this project has had an influence on the downstream water quality. We suspect it will. Now keep in mind when the water hits that inland area down by the Indian River, you have a lot of other influences. You have daily tides coming in, high tide, low tide. You have water running up and down the Indian River Lagoon. So we don't expect that this one project will clean up the whole Indian River, but we certainly feel like it'll be a positive step in the right direction," he said.
The project was funded through a partnership with the Indian River Lagoon National Estuary Program and $2.23 million from the American Rescue Plan Act of 2021. Construction was completed under budget, with $172,448.90 remaining, according to the county.
The STA was one of multiple stormwater and water quality projects funded through $19 million in federal funding awarded to the county. Other projects have included improvements in White City and River Park, as well as work in Indrio Savannahs, Ten Mile Creek and Hog Pen Slough.
Lappert said the county is considering additional projects, including baffle boxes and drainage improvements.