Channeling cleaner water
Last spring, Martin County, Fla., retrofitted the stormwater management system for a 157-acre subdivision to improve the water quality of nearby rivers and to alleviate flooding during heavy rains. The open roadside swales that previously carried stormwater directly from the neighborhood roads to two nearby creeks were supplemented with a collection system that captures runoff and routes it to detention ponds for treatment before it enters the creeks.
When the Golden Gate subdivision was built in Martin County in 1925, it did not have to meet any water quality or flood protection requirements. Builders simply designed ditches and canals to channel untreated stormwater into Willoughby and Crooked creeks, which flow into the St. Lucie River. As the area became urbanized, however, the water in the river degraded, in turn polluting the Indian River Lagoon, into which the river flows. Additionally, some houses in neighboring subdivision Port Sewall Harbor and Tennis Club, built in the 1970s — also before stormwater quality treatment requirements were devised — flooded during heavy rains.
In 1991, Martin County created a water quality office to improve stormwater management and surface water quality. The office began identifying areas that were prone to flooding and designing eight high-priority projects that would alleviate floods as well as improve water quality. Concurrently, a 1994 study by consultants under contract with the Indian River Lagoon National Estuary Program recommended several methods for improving water quality in the lagoon, including reducing stormwater runoff loads from nearby urban areas and retrofitting stormwater systems in developed urban areas.
In 2001, the county contracted with Stuart, Fla.-based Captec Engineering to design a stormwater retention system for the Golden Gate subdivision. The project called for turning vacant and abandoned neighborhood lots into stormwater detention and treatment areas. Stuart, Fla.-based Lucas Marine Construction began building the stormwater system in March 2002.
To supplement the swales and ditches that originally existed, the project called for the installation of baffle boxes to divert stormwater to detention areas that would clean pollutants from the water before discharging it to the creeks. Two dry detention areas, totaling 3 acres, were built to allow debris to settle out of the stormwater, after which it flows into one of two treatment areas, totaling 8.3 acres. Those marsh areas feature vegetation where pollutants, such as nitrogen and phosphorous, are filtered.
Completed in March 2004, the new stormwater treatment system has turned vacant lots into park-like marshes, complete with mulched walking trails. Native wildlife species, such as Roseate Spoonbills and nesting sandhill cranes, have found new homes in the marshes.
The system is designed to reduce the neighborhood’s stormwater pollutant load by 80 percent, and it has alleviated flooding for all homes in the area. In fact, no flooding was reported after two hurricanes swept through the county last fall.
One of eight similar projects in the county, the $2.8 million Golden Gate retrofit project cost approximately $16,000 per acre to complete. It was funded by ad valorem taxes; grants from the St. Lucie River Issues Team, Environmental Protection Agency and Florida Department of Environmental Protection (DEP); and DEP State Clean Water Revolving Fund loans. The county plans to begin another 18 stormwater retrofit projects in the future.
Martin County also is working with the University of Florida’s Institute of Food and Agricultural Sciences to promote the Florida Yards and Neighborhoods Program to Golden Gate homeowners. The program provides educational seminars at community facilities to teach residents landscape maintenance techniques for reducing non-point source pollution, such as the correct use of fertilizer and pest control substances.