Directional Bore, Stormwater Treatment Technologies Solve Problems At Florida Lagoon

By W. Keith McCully, P.E. | June 2009 Vol. 64 No. 6

Many Floridians and other Americans may take for granted the lagoons that contribute to the nation’s ecosystems.

However, Florida’s Indian River County has found a solution using directional boring and water treatment technologies to rehabilitate the second most polluted section of the 154-mile-long Indian River Lagoon. The entire lagoon stretches along the eastern coast of Florida, from just north of New Smyrna Beach south to Fort Pierce.

Pollution of Indian River County’s portion of the lagoon began 80 years ago, when a vast canal system was created to drain more than 50,000 acres of marshland. The canal system now discharges huge quantities of stormwater runoff and groundwater seepage into the lagoon through three large relief canals. The canal system’s purpose was to make the county more attractive to farmers and other commercial ventures by making the land suitable for farming and development.

However, eight decades later, it is that very farming and development that is hurting the final drainage point for the canals – the Indian River Lagoon. The stormwater runoff and groundwater seepage is contaminated with nitrogen and phosphorus from fertilizers used on farms and residential developments. Those elements are washed off the land into the canals by rainfall runoff, fertilizing the aquatic plants growing in the canals. The canals eventually transport the freshwater plants into the lagoon where they die from the lagoon’s saline environment and fall to the bottom, creating muck deposits and hindering the growth of seagrass. The estimated toll of the over-fertilization is 25,000 tons of vegetative material that finds a way into the lagoon each year.

This process creates algae blooms in the Indian River Lagoon, which paired with suspended solids in the water, significantly reduce sunlight’s ability to penetrate the water column. That light is critical to the survival of seagrass in the area. Healthy seagrass coverage is a significant indicator of a healthy and diverse lagoon ecosystem.

One of Indian River County’s solutions was to remove as many of the pollutants as possible from the canal water with the creation of Egret Marsh Regional Stormwater Park.

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