Florida's freshwater ecosystems protected with WaStop

High Water Levels
Tidal Water

(Article Published in World Water July/August 2016)

Location:  Marsh Landing, Florida USA

Customer: Genesis Group

Problem:  Marsh Landing, an elegant residential community in Ponte Vedra Beach, Florida, United States, uniquely integrates natural beauty and luxurious housing through careful land planning. Concern for nature and the environment has always been foremost in the community design of more than 1,000 single-family homes. Building and infrastructure in coastal areas with natural elevations that range a mere 1 to 2 meters above sea level, however, possess challenges for stormwater management systems using ponds and wetlands; Marsh Landing is no exception.

Successfully maintaining a natural environment that contains wetlands and ponds woven into an active, vibrant community requires careful consideration. Nearly 100 inter- connected retention ponds drain into the Intracoastal Waterway and tidal tributaries. These ponds function as an integrated system to protect the community from stormwater flooding and limit the rate of drainage discharge, further protecting downstream property and watershed quality.

Salinity levels must be controlled to ensure that the ponds function as intended. Only a small increase in water salinity can cause a significant loss of biodiversity and alter the ways that the ecosystem functions. At high tide, the Intracoastal Waterway can fill these ponds with brackish water and reduce their intended design storage capacity, thus increasing the chance of community flood damage.

Additionally, salt water harms freshwater ecosystems surrounding these ponds and further shortens the life of reinforced concrete culverts and control structures. Salt water contains magnesium chloride, sulfate ions, and hydrogen carbonation ions that will essentially attack concrete to a certain degree, but what really starts to corrode in a concrete structure is its inner steel sub- structure. Because concrete is a type of porous material, oxygen and humidity can be present where the salt water comes into contact with the film that surrounds the reinforcing steel inside the concrete, initiating the corrosion process of the steel.

In their juvenile stages, fish are least tolerant to salinity, which potentially inhibits the reproduction of existing populations, and salt-averse species may be replaced by salt-tolerant species such as the three- and ten-spined stickleback in highly saline lakes. Macrophyte diversity may also decrease due to difficulties in plant germination, along with the success of a small number of salt-tolerant species.

Solution:  Major infrastructure improvements have been made over the past few years, and new projects for continuous improvement are being carried out, including a substantial investment to refurbish drainage and pump systems. These projects are being implemented to ensure that the ponds retain their usefulness as stormwater retention structures and also as wetland breeding grounds.

Genesis Group, a US-based civil engineering, landscape architecture, and urban design consultancy, hired the US contractor CS3 to install approximately 100 WaStop inline check valves in order to protect these ponds and wetlands from brackish floodwaters.

Structures including outfall culverts, control works, pump discharge lines, and sluice gate controls have been put in place to control the outlet of the ponds to maintain water quality. Together, these structures maintain the freshwater ecosystems by preventing tidal inflow. WaStop inline check valves have been implemented within many of these structures as a backflow prevention device to ensure that flow can exit the ponds to maintain water levels. Additionally, the inline check valves prevent salt water from entering the ponds to ensure that salinity levels are also maintained.

Partner: CS3 Florida

 

 

Many of the WaStop installations in Marsh Landing are being retrofitted into existing structures. The WaStop inline check valve can be fitted horizontally or vertically and at either an inlet or an outlet of a structure; the valves are customized for easy installation without the need to rebuild the structures.

WaStop inline check valves are market leaders in low head loss, which means that the ponds can quickly drain water out to the canals during periods of high rainfall. This feature ensures that there is no upstream flooding, which in turn protects the surrounding residential properties, gardens, golf course, and other properties.

The valve works on differential pressure; it is completely closed and vapor-tight in its natural state. Flow in the right direction causes a pressure build-up against the membrane, which opens just enough to allow the liquid to flow unhindered. If the flow is reversed, the membrane fills with water or gas and acts as a stopper, blocking all backflow. When 100 percent closed, the valve stops all flow, thereby ensuring no area for growth of shellfish, which normally thrive in the transitional zone between salt water, brackish water, and fresh water. Consequently, the valves significantly lower maintenance costs and improve the system’s reliability.